Effective communication is the backbone of any successful organization. It ensures that information flows seamlessly across all levels – facilitating understanding, decision-making, and collaboration. Clear communication reduces ambiguity, minimizes conflicts, and promotes transparency.

Impact on Team Dynamics and Company Vision

Accountability:

When expectations, goals, and responsibilities are communicated clearly, each team member knows what is expected of them. Regular feedback and updates keep everyone answerable for their roles and actions. As well as clear all the doubts and facilitate fast and correct decision making.

Energy and Motivation:

Open communication boosts morale by giving employees a voice. When people feel heard and informed, they are more engaged, enthusiastic, and willing to contribute. Also, this promotes emotional bonding with the organization which is a very critical attribute for the maximum productivity and quality output.

Alignment with Vision:

Consistent communication about the organization’s mission, goals, and progress ensures that all teams are moving in the same direction. It fosters unity and shared purpose, which is vital for strategic execution. When employees have clear vision of the organization, they can also visualize their growth trajectory. This reduces the employee attrition rate. Apart from above, this help to develop strategic thinking among employees, which expedite the mission to achieve company’s vision.

Strategy to Foster an Effective Communication Environment

Below can be the initiatives we can pursue to build effective communication environment in the organization:

• Establish Clear Communication Channels be it is verbal, written or in presence. Define formal and informal channels for different types of communication.
• Promote a Two-Way Culture, in this encourage listening and feedback at all levels, which is very important. One side communication has no meaning.
• Train Managers and Leaders to equip them with skills like active listening, empathy, and clarity.
• Leverage of the technology that use collaboration tools like Slack, Teams, or Trello. Below is the summary of various tools:

• Ensure transparency by sharing company goals, updates, and challenges regularly.
• Celebrate Success and Acknowledge efforts of the team members. In this initiative we can use communication, rewards or certification to recognize and motivate.

Action Plan

Below is tentative action plan which can be rolled out to meet the objective “to develop the effective communication environment”.

Conclusion

Effective communication is not just a tool but a culture that drives accountability, energizes teams, and ensures alignment with organizational goals. With deliberate strategy and consistent action, organizations can create a communication-rich environment that fuels growth and success.

Thank for reading…

The post Importance of Effective Communication within an Organization appeared first on ChemEnggHelp.

With over 25 years of experience in chemical plant design, process optimization, and digitalization, I have witnessed firsthand how expert consulting can bridge the gap between technology and profitability. Let’s explore the key responsibilities and value additions that a consultant brings to chemical process industries.

1. Feasibility Studies & Conceptual Design

A successful project begins with a robust feasibility study. This involves:

• Process Selection: Evaluating raw materials, reaction pathways, and technology options. So that capex investment is safe and provide highest possible returns to the investors.
• Techno-Economic Analysis: Assessing CAPEX, OPEX, and ROI to determine economic viability. Selecting best possible technology in terms of initial capital requirement. Choosing contemporary technology which is providing highest product yield, lowest cost of manufacturing and generating low waste which is not toxic and hazardous.
• Process Flow Development: Creating initial Process Flow Diagrams (PFDs) and performing mass & energy balances. This will help to understand the process at macro level to the stockholders and enables to estimate cost of production data for financial feasibility study.
• Risk Analysis: Identifying potential challenges related to safety, sustainability, and regulatory compliance. Assessment of the safety equipment requirement, process controls, material handling, selection of effluent treatment, required provision during plant design & engineering.

2. Process Design & Engineering

Once feasibility is established, the consultant plays a pivotal role in detailed process design:

• PFDs & P&IDs: Developing block flow and process flow diagram, carryout the material and energy balance for the process. Subsequently designing of process control system with process and instrumentation diagrams.
• Equipment Sizing & Selection: Designing and preparation of specification sheets of unit operation such as reactors, distillation columns, heat exchangers, pumps, and separators.
• Process Simulations: Using advanced tools like ChemCad, HYSYS, and other simulators to optimize process conditions. The detailed design of heat exchangers, distillation & absorber columns.
• Safety Considerations: Conducting HAZOP studies, SIL assessments, and relief system design to mitigate risks.

3. Detailed Engineering & Project Support

A chemical process consultant collaborates with multidisciplinary teams to ensure smooth project execution:

• Material & Equipment Specification: Providing detailed guidelines and equipment specification data sheets for procurement and fabrication. This includes all the required details including equipment operating parameters (i.e., flow rate, capacity, pressure, temperature), design parameters and material of construction, applicable codes & standards for equipment design and testing, sketch of the equipment with nozzle schedule, site conditions, etc.
• Process Control & Automation: Defining instrumentation requirements, control schemes, and digital monitoring solutions. After detailed study of the chemical process, we design a control philosophy for the smooth and efficient plant operation. In this course of work we take into consideration emergency plant shutdown requirements to avoid any hazardous conditions.
• Vendor & Licensor Evaluations: Analysing technology proposals for proprietary processes, identify optimal solutions, assess technological options to minimize variable production costs, and study effluent generation, treatment methods, and environmental impact.

4. Process Optimization & Troubleshooting

Even well-designed plants require continuous optimization and this is imperative for businesses to remain competitive. To meet this objective, a consultant applies tools like Six Sigma & Lean and can provide solutions for:

• Energy & Yield Optimization: Applying DMAIC & Lean methodology, Implementing heat integration, advanced process controls, and AI-driven analytics.
• Debottlenecking & Capacity Expansion: By process mapping and using Lean methodology to Identify the constraints or debottleneck stages. This way improving throughput without major capital investment.
• Operational Issues: Analysing process data using six sigma tools and troubleshooting quality, yield, or equipment performance problems.

5. Sustainability & Green Chemistry

With increasing regulatory pressure and environmental concerns, sustainability is at the core of modern plant design. To meet this objective we need to work upon below line items:

• Waste Reduction & Byproduct Recovery: Enhancing material efficiency to minimize waste. Finding the possibilities of recycling & reusing the effluent streams inside the plant. Working upon options to convert the waste into wealth so that final product can more economical and sustainable.
• Carbon Capture & Green Energy Integration: Exploring alternative energy sources and emission control strategies. We can study the process and work upon the methods to recover waste heat available from heat of reaction, distillation column condensers, high temperature streams and flue gases. This way we can reduce the overall energy requirement for the plant and can reduce the carbon foot prints.
• Eco-Friendly Processes: To design a sustainable and green process, evaluation of renewable feedstocks, green solvents, and low-carbon production methods.

6. Commissioning & Startup Support

Consultants play a hands-on role in plant commissioning and startup. Since he or she has complete knowledge of process technology and plant, therefore can anticipate the possible hurdles and problems during commissioning. Also, previous experience gives hands of solutions to resolve the issues which helps to expedite the plant start up:

• Pre-Startup Safety Reviews (PSSR): Ensuring that the plant meets all design and safety criteria. This step help to avoid any unforeseen issues which can lead to accident or equipment breakdown before commissioning. This includes to check the issues like missing of gaskets, bolts, welding joint failure, electric motor direction, any blind availability, NRV fitting, strainer or filter chocking, safety valves, vents & drain provisions, etc.
• Operator Training: Conducting workshops on plant operation, troubleshooting, and digital tools. This is an important step before plant handover to the production team. Also, preparation and review of the plant standard operating procedures before actual plant commissioning is very crucial.
• Performance Validation: Analysing startup data to confirm that the plant is operating as per design expectations. In case there is any gap in plant performance then conducting brainstorming to fix the problems so that design parameters can be achieved.

7. Compliance & Regulatory Support

Navigating the complex landscape of industry regulations is another critical aspect:

• Environmental & Safety Regulations: Ensuring compliance with OSHA, EPA, REACH, and other global standards.
• Documentation & Permitting: Preparing necessary reports and technical documentation for regulatory approvals.
• Risk Management: Conducting safety audits and implementing best practices for chemical handling.

How a Consultant Adds Value

• Independent & Unbiased Perspective: Unlike in-house teams, consultants provide objective insights.
• Cost Savings: Optimizing CAPEX & OPEX through smarter engineering and technology choices.
• Innovation & Digitalization: Leveraging real-time analytics, AI, and machine learning for better plant control.
• Risk Mitigation: Proactively identifying and resolving potential failures.

Conclusion

In an industry where margins are tight and efficiency is key, the right consulting expertise can mean the difference between success and failure. Whether you are planning a new project, troubleshooting an existing plant, or looking for digital transformation solutions, expert consulting can help unlock new levels of productivity and sustainability.

If you are looking for a consultant with deep experience in chemical plant design, process improvement, and digital transformation, feel free to reach out. Let’s work together to build the future of chemical manufacturing!

Thanks for reading,

Kailash Mehra

The post The Role of a Chemical Process and Plant Design Consultant appeared first on ChemEnggHelp.

There are many advantages in using a liquid jet pump for certain applications, where fluid viscosity is low, fluid is not highly volatile, not very erosive in nature, has no sticky or polymerizing tendency, etc. The benefits of liquid jet pump use in such applications can be like, no moving parts, in line mixing, no or low maintenance and comparatively simple system.  

Principle of Liquid Jet Pump

In operation a high velocity jet of pressurised liquid discharged from the motive nozzle produces a region of low pressure in the suction chamber that entrains the secondary liquid or fluidised solid. The two streams then thoroughly mix in the throat before the resulting mixture flows through the diverging cone to regain some pressure to overcome system discharge heads.

Liquid jet pumps, utilize the pressure energy of a high-pressure fluid stream to boost the pressure and/or flow of a low-pressure fluid stream.

Ejectors are generally inefficient devices. However, their simplicity and lack of moving parts make them worthy of consideration, particularly where a high-pressure fluid stream is already available. This way we can use the available waste energy and can save energy cost for the process.

Performance of the Liquid Jet Pump

Let us refer the below simple liquid-liquid jet pump sketch.

Let us assume at Section-1, two fluids are mixing Stream-1 having mass flow rate W1 (kg/s) and Stream-2 with mass flow rate W2 (kg/s). The flow area for Stream-1, for Stream-2 is S2 (m2) and at Section-2 flow area is S3 (m2).

Mass Balance for the System

Here we can write the mass balance at steady state between Section-1 and Section-2,

W1 + W2 = W3                (here W3 (kg/s) is the mass flow rate at Section-2)

ρ1*V1*S1 + ρ2*V2*S2 = ρ3*V3*S3         -Eq.1     (i.e., rate of mass in at Section-1 = rate of mass out at Section-2)

since this is a liquid and can be assumed as an incompressible fluid hence, ρ1= ρ2= ρ3= ρ

Also, from geometry we can have, S1 + S2 = S3                 -Eq-2

Therefore, we can rewrite above Eq.1 with the help of Eq.2 and above assumptions:

V1*S1 + V2*S2 = V3*(S1 + S2)

(S2/S1) = [(V1 -V3)/(V3 – V2)]              -Eq.3

Momentum Balance for the System

Assuming negligible friction, the momentum balance can be written as below:

Rate of momentum in – Rate of momentum out = 0         (for steady state flow)

W1*V1 + W2*V2 – W3*V3 + P1*S1 + P2*S2 – P3*S3 = 0              

We can solve the above equation for discharge pressure,

P3 = (W1*V1 + W2*V2 – W3*V3 + P1*S1 + P2*S2)/S3                   -Eq.4

Hence, using above equations we can estimate the inlet pressure and flow rates to meet the required discharge flow rate and pressure requirements.

Various Applications of Liquid Jet Pump

We can find various industrial application of Liquid Jet Pumps as below:

• Eductors Inside as Storage Tank for mixing the liquid inside. In many cases such as dilution of incoming feed into the tank or when there are multiple streams are coming into the tank with different composition. In such cases Eductors can be very helpful and below figure shows the typical installation.

Here, the pump provides high pressure liquid stream which passes through the jet pump or eductor nozzle and pumps the tank liquid to make it a homogeneous mixture. This way we can avoid the installation of large size agitators and motor power consumption.

• Second application we can see for inline dilution of some concentrated solution. Many times, we use dilute NaOH solution for our process requirements and available is of 48% concentration. So, in such cases we can use an inline liquid-liquid ejector to get the desired dilute caustic solution. The typical installation in such cases can be as shown in below figure.

So, this way we can avoid a mixing vessel and can get continuous feed of dilute caustic solution.

• Another use we can see to pump the liquid using available high-pressure liquid. This way we can use available waste energy and can save power bill for the process. This type of arrangement we can understand by below figure.

As we can see in above figure, the primary fluid is passed through a nozzle where the pressure energy is converted into kinetic energy. The high-velocity jet entrains the secondary fluid. The two streams mix in the mixing tube, leading to pressure recovery. Further static pressure is recovered in a narrow-angle diffuser downstream of the mixing tube.

• High pressure liquid jet generates a vacuum, which we can use to diffuse the gas into the mixing chamber. As the gas/liquid mixture enters the diffuser, the static pressure begins to recover. This way gas is compressed as it approaches into the discharge. This way, we can see the Liquid Ejector works as an evacuator as well as a compressor also.

Conclusion

Liquid Jet Pumps/Ejectors are available in stainless steel, carbon steel, duplex steel, Hastelloy, titanium, rubber lined, PP, PTFE and PVDF. Liquid jet ejectors are jet pumps, which uses high pressure liquid as motive fluid. They use the kinetic energy of the pressurized liquid to entrain liquid, gases or vapours. Moreover, these can be used for pumping slurries and other liquids or granular solids. These devices discharge the resultant mixture against a higher pressure.

We should look into the plant and should find the applications of liquid jet pumps. As this will save the power bill required for pumping or generating vacuum. Also, this is the idea of creating wealth from waste energy, where we have high pressure liquid stream available.

Thanks for reading..

The post <strong>Liquid Jet Pumps</strong> appeared first on ChemEnggHelp.

Different Types of Structured Packings

For example, Mellapak 250Y is a less denser structured packing and mostly used where we are looking for highest vapour or gas throughput rates and low theoretical plates per meter of packed height. While, Mellapak 750Y or gauge packing like BX & CY are used where we are looking for highest number of theoretical stages in per meter of packed height. Here, we can get around 8-10 stages. But these packing packings are good for low liquid flow rates and gas throughput rates.

Once we get the superficial velocity through column for a given structured packing, using the velocity and volumetric flow rate we can calculate column diameter.

Flow Area (m2) = Volumetric Flow Rate (m3/s)/ Superficial Velocity (m/s)

Diameter (mm) = 1128.4*(Flow Area^0.5)

Superficial Velocities for Different Structured Packings

In below table there are the values of superficial velocities which we can use to estimate the packed column diameter for given vapour load. In my experience I found these values are very close to actual plant operation. These values are good for atmospheric column operation. For vacuum operation we can use higher superficial velocities than this, around 3-4 times of the given values.

Conclusion

Column diameter depends on vapor or gas volumetric flow rate through the column. And, volumetric flow rate is the function of column pressure. At higher pressure, vapour density will be higher and volumetric flow rates will be lesser. On other hand, in vacuum while density is low therefore we can afford higher superficial velocities through the column. In summary, we can say if we operate a column in vacuum, which was designed for atmospheric conditions, the capacity of that column will reduce. As, at higher gas velocities column will lead to flooding conditions.

Thanks,

The post Packed Column Diameter Estimation appeared first on ChemEnggHelp.

What is Six Sigma?

When we talk about six sigma, it means our process efficiency is 99.99966%. In other words, we can say there will be only 3.4 defects generation per 1000000 opportunities. Therefore, our process sigma level is directly related with product quality and product cost. Below matrix gives us a clear picture sigma level and cost of quality for our product manufacturing.

So, you can see it is evident being better is cheaper for any company. Now we will dive into step-by-step process to understand the DMAIC methodology. DMAIC is the short form of Define, Measure, Analyse, Improve and Control phases. First, let us talk about Define phase.

Define Phase

Define is the first and very important phase for any improvement project. This is the foundation of any successful project. You should understand a project will be successful or fail mostly depends on this phase.

The objective of this step is to recognise and understand the need of our stakeholders. Whether this project is important or not for them. Your stakeholders can be external or internal. External stakeholders are such as suppliers, customers, local administration, pollution control body, society, shareholders, etc. When we talk about internal stakeholders, it means those who are directly concerned with your project. They can be like, your manager, business head, plant manager, site head, etc.

Various activities in this phase are as below:

Identification of Project CTQ’s

CTQ is the abbreviation for Critical to Quality. For a project this is a characteristic of a product or a service that satisfies a customer requirement or process requirement. In a project there can be more than one CTQs. You can think various examples for CTQs in a business such as cost of product, numbers of customer complaints, employee attrition rate, % sales growth per year, etc.

Therefore, we can see the CTQ is the VOC (voice of customer) or VOB (voice of business), which is the pain area or need of a customer or a business. Let’s understand the CTQ identification exercise with an example VOC for Product Variable Cost reduction by 10%, which the need of your customer.

CTQ Identification for Product VC Reduction

Here we have taken a hypothetical product case, in which we are using two raw materials Chemical A & B. Other than this we are using Steam and Power as utilities. Moreover, other overhead cost includes like packaging cost, logistics cost and employee cost. This we can see in below figure.

In above exercise we can see there are total 7 nos of CTQs, which leads to the customers need through drivers. Therefore, if we address these CTQs then our customer or stakeholder will be satisfied.

Project ‘Y’

Now, these 7 CTQs will lead us to Project ‘Y’. This is the actual project on which we will work to improve the project CTQs. In our example these are as in below table:

So here we got seven projects, in reality it is not possible to take up all the projects simultaneously. Because every project needs resources which are limited such as man, machine and money. Therefore, it is necessary to prioritise your projects. It means you must take up high impact projects first and subsequently you can work upon other projects as well.

To prioritize the projects, we can use Pareto analysis of Prioritization Matrix. Here we will use Pareto Analysis, it says our 80% of benefits comes from 20% of work. We will make Pareto chart for our all CTQs based on their contribution in the product variable cost.

Pareto Chart

This is a statistical tool developed by Vifredo Pareto in 1896 and used for decision making. This is also known as 80:20 rule also. In our example contribution of various CTQs are in below table.

You can prepare Pareto chart in excel first put the contribution cost in descending order. And, add one more column showing cumulative contribution.

From above you can see if you focus on first 2 CTQs, that will address over 70% total variable cost of the product. Therefore, working on these two CTQs related projects will lead you towards major impact on product cost reduction.

Project Baselining

After freezing the CTQs and the Project ‘Ys’, you should collect the data for Project ‘Y’. In our case this is consumption norm of chemical ‘A’ and ‘B’. It is better we collect data for one year of consistent plant operation. Because in a year you can see the impact of seasonal change also. After collection of one year of data for the norms, just draw a Run Chart. This chart will give us the behaviour of our process over the year. In case there are any shutdown or breakdown we can see it in run chart. Remove these data points and estimate the mean as a baseline for your project.

When data are not normal then we should consider median as the baseline of our project. Because in that case mean will not give us a realistic representation of the operating process.

SIPOC (Supplier Input Process Output Customer)

In Lean Six Sigma we use SIPOC to identify the relationship between response (outputs) and independent variables (inputs) or in other words Y = f(X). Here, we try to recognize the suppliers which provides inputs to the process and customers who uses outputs from the process. You need to prepare a SIPOC for your project in the define phase of the six sigma project.

Let us consider the example for reducing steam consumption norm for a distillation column. For this below can be a typical SIPOC Diagram:

Benefits of SIPOC are mainly two, first it gives us understanding of the process from highest level. And, second it helps us to draw the scope of the project.

Project Charter

We need to understand this clearly that any Six Sigma project is a team work. Basis of six sigma is to develop cultural change in the organization for continuous improvement with sustenance. A Project Charter is a written document and which is an agreement between management and project team, about the project scope of work and goal. This project can be a new plant project, existing plant de-bottlenecking, process improvement initiative, plant maintenance work, new product development or plant digital transformation campaign, etc.

Below is the typical format of a project charter and this a very important deliverable of Define phase of six sigma project. It is very important to get signoff this project charter from all the stake holders named in this document.

Stakeholder Analysis

Whoever is affected directly or indirectly by the business operation are considered its stakeholders. These can be like, suppliers, customers, company management, its employees, families of employees, people living in vicinity, government, financers, shareholders, etc.

The stakeholder support is very critical for the success of any business. During the project cycle we need support from many stakeholders at various levels. So, it is necessary for you to carryout stakeholder analysis to understand and evaluate their support requirement. Subsequently you need to prepare a strategy to getting their support for the overall success of the project. When we talk about overall success it means working with man & machine both at the same time.

For this purpose, you can use RACI Matrix, which stands for Responsible, Accountable, Consulted & Informed. Example of RACI Matrix for a Six Sigma project can be as below:

In a Six Sigma project we need a cross functional team as we may need different functional inputs to solve the problem. A Six Sigma team is formed to include respective domain knowledge experts, as we need this expertise to find out the solution. For example, if we are looking to reduce steam consumption norm in distillation column, we need to include a Chemical Engineer (from Process Design Department). Similarly for procurement lead time reduction we require purchase manager in our team. For recruitment time reduction project, we need Human Resource Manager as a team member.

Communication Strategy

A proper communication plan is very important for the overall success of the project and it is must to prepare a communication strategy in define phase of six sigma project itself. This will eliminate the confusions & surprises during project. A good communication plan includes following things:

• Who will communicate?
• What to communicate?
• When & at what frequency communication will be done?
• It is important to mention the reason of communication.
• Who will be the recipient of the communication and what will be the mode of communication? Like written, verbal or meeting.

Conclusion

So, end of the define phase we should have performed following things typically:

• We have conducted first meeting with the project team and discussed about the goal of the project. Team members and their roles are clear with timebound deliverables.
• High level project schedule is ready with measure Milestones.
• Cost benefit analysis of the project is completed.
• Data collection is completed for the project CTQ with Run chart preparation. Project baseline is frozen.
• Project charter is ready and signed off with all the stakeholders.
• Stakeholder analysis is done and a communication plant is ready with us.

Once Define phase is completed, we are ready to move towards the next phase of our Six Sigma project which Measure phase.

Thanks for reading…

The post Six Sigma Methodology – Define Phase appeared first on ChemEnggHelp.

So, in this article we will try to understand about heat pump and its possible use in a distillation column. First, let us understand, what is a Heat Pump?

What is a Heat Pump?

Fundamentally, as we know heat flows spontaneously from high temperature to low temperature. So, using a heat pump we can transfer heat from low temperature to higher temperature. Or in other words, we can convert energy at lower temperature into higher temperature energy.

You can see the utility of a heat pumps in our surroundings, which includes heating of houses and offices during winters and cooling in summers. The examples of heat pumps in our homes are air conditioners and refrigerators. In these appliances refrigerant is used, which evaporated in outside air and reject heat. This is the heat which refrigerant absorbs at lower temperature (i.e., temperature which is maintained inside the AC room and refrigerator) than atmosphere.

During winter heat pump absorbs heat from atmosphere and rejects into the office or building to maintain the temperature higher than outside atmosphere. In this process the flow of refrigerant is in reverse direction than a refrigerator or air conditioner system.

Apart from this we can see another example of a heat pump in our industry is a thermo-compressor. Where we compress the low pressure & temperature steam to convert into high pressure & temperature steam. This objective we can achieve using a thermo vapour compressors (TVR) or a mechanical vapour compressor (MVR).

Heat Engine, Refrigerator & Heat Pump

All three are cyclically operating devices. Heat engine absorbs energy from high temperature reservoir, generates work and rejects balance energy into a low temperature reservoir. While refrigerator and heat pump are the reverse cycle of a heat engine. Here, it absorbs heat from low temperature and work is applied to reject heat into high temperature reservoir. Performance or efficiency of these cyclic devices, we can estimate using below equations:

1. Heat Engine Efficiency:                 η = |W|/|Q_H|

• COP of Refrigerator:                     COP_R = |Q_L|/|W|

• Heat Pump COP:                            COP_HP = |Q_H|/|W|

Below is the schematically representation of the heat engine, refrigerator and heat pump.

A thermal power plant is the example of a heat engine. While refrigerator and heat pump are the reverse of a heat engine. Both these devices, refrigerator and heat pump absorb heat from low temperature reservoir and use work, which is applied by a compressor and reject heat at higher temperature reservoir. Please clear in your mind refrigerator is also a heat pump.

Various Possible Ways to Use a Heat Pump in Distillation Column

So, we discussed about the heat pump in above section. Now, we will look into the application of heat pumps in a distillation column. In a distillation column this heat pump is a compressor. In this compressor, vapour from distillation column goes into the compressor and adiabatic compression takes place. Because, we are note removing any heat of compression temperature of the outlet vapour rises. Subsequently, this high temperature vapour we can use into column reboiler to supply the heat in place of steam.

So, thermodynamically we can see in a distillation column, we absorb heat from column top/condenser (i.e., a low temperature reservoir) and work upon it using compressor and reject this heat in column bottom/reboiler (i.e., a high temperature reservoir).

There can be below three type of configurations which we can use to install a heat pump in a distillation column.

Direct Vapour Compression

In this setup, column vapour directly enters into a compressor and after adiabatic or polytropic compression superheated vapour reject heat in column reboiler. Subsequently condensed vapour goes for column reflux and product draw.

External Vapour Compression

Here one buffer fluid is used in column condenser which evaporates and converts into the vapour. Subsequently, this vapour enters into the compressor and after adiabatic or polytropic compression gets superheated. High temperature vapour enters into the column reboiler and reduce equivalent steam consumption. This type of installation is recommended where compression of direct vapour is hazardous or fluid is very corrosive in nature.

Bottom Flashing

Third possible way for heat pump installation can be for the column where we are using direct steam. In other words, there is no reboiler, this bottom goes into the condenser and converts into the vapour. Subsequently, this vapour from condenser enters into the compressor. After adiabatic compression vapour temperature increases and we can use this heat in column bottom.

Now, to understand the heat pump use in a distillation column we will consider an example in subsequent section. 

Example of Heat Pump in Distillation

Let us consider a distillation column to distil the ethanol-water mixture. In this column feed contains Ethanol: 50 wt.% and Water: 50 wt.%. The feed flow rate is 5000 kg/h and feed temperature is 40 ⁰C. This is an atmospheric distillation column, top product is the azeotropic composition of ethanol & water, contains 95 wt.% ethanol and remaining is water. The bottom product from this column is aqueous waste contains traces of ethanol (around <100 ppm). You can refer below figure to understand the distillation setup for our case.

Distillate rate, D = 5000*(50/100)*(100/95) = 2632 kg/h (considering ethanol in bottom negligible)

Reflux rate, R = D*3 = 7896 kg/h (Reflux ratio is 1:3)

Vapour rate from column top, V = R + D = 10528 kg/h

Latent heat of top vapour, LH1 = 221 kcal/kg

Feed specific heat, Cp1 = 0.81 kcal/kg-C

Column bottom temp, T2 = 105 ⁰C

Feed temperature, T1 = 40 ⁰C

Steam Enthalpy, H1 = 517 kcal/kg (@ 3.0 bar saturated steam)

Reboiler duty, Q1 = 5000*0.81*(105 – 40) + 10528*221 = 2,326,688 kcal/h

Steam requirement, MS = Q1/H1 = 5003 kg/h

Cooling water requirement, MC = 10528*221/6 = 387,781 kg/h (@ 6 ⁰C ∆T)

Equivalent power for cooling water, 40m discharge pressure, PE = MC*9.81*40/3600/0.8/0.9 + 17500 (Watt for cooling tower fan) = 76.21 kWh

Therefore, total estimated utility cost for above distillation will be, C1 = MS*1.1 + PE*7.5 = 6075 Rs/h. (@ Steam Cost 1100 Rs/MT & Power Cost 7.50 Rs/kWh). Which is 6075*8000/100000 = Rs. 486 Lacs.

Distillation with Heat Pump

Now, let us consider the above example with using heat pump. To understand this, you can refer below figure.

So, in above figure we can see, this a direct vapour compression heat pump system. Here, column vapour directly enters into the compressor and after polytropic/adiabatic compression heats up (i.e., at outlet pressure is 3.0 bar the adiabatic temperature rise will be 144 ⁰C). This hot vapour goes into the reboiler and provide heat to the column and condense @ 108 ⁰C. Subsequently, this hot condensed liquid goes into a feed preheater and cools down to around 75 ⁰C. The cold liquid from feed preheater partly goes for reflux into the column and partly we recover as a distillate or product.

Moreover, there is one more reboiler with steam, which supplies balance heat to the column and ensures stable column operation.

We have vapour rate from the column is, V = 10528 kg/h (this enters into the compressor).

After compression at 3.0 bar pressure temperature increases from 78 to 144 ⁰C (Here, we are considering adiabatic compression). This vapour condenses at 108 ⁰C and 3.0 bar, to supply heat to the column through reboiler. Total power consumption in compressor with 75% efficiency is, PE1 = 306 kWh. (Please note theses data are based on CHEMCAD simulation).

Additional steam consumption is zero here. So, distillation column operating cost with heat pump will be as below:

C2 = PE1*7.50*8000/100000 = Rs. 183.6 Lacs/annum

Therefore, savings in operating cost by using heat pump will be = C1 – C2 = 486.0 – 183.6 = Rs. 302.4 Lacs/annum.

Apart from above saving there will be no requirements for the cooling water and condenser also. However, we need to provide a condenser as a standby provision, this is in case of any problems in heat pump operation. This will ensure the stable column operation.

Conclusion

Finally, when we plan for a heat pump in a distillation column, first we need to evaluate its technical feasibility. If, it is technically feasible then second question comes to work out the financial feasibility. Any economic advantage of a heat pump depends on the cost of electricity in comparison with the cost of steam. As a thumb rule if difference between distillation column top and bottom temperature is around 20 – 25⁰C or less, using heat pump will be a feasible option. Because for higher temperature differences you need to compress column vapour more and require more electric power.

Also, there should be around 30 ⁰C temperature difference between compressed hot vapour and column bottom temperature. Otherwise, required surface area for reboiler will be higher side and increases initial capital investment.

As a process engineer you need to see, where you can use this heat pump in your plant. Because this is a huge opportunity to save energy and our blue planet as well.

Thanks for reading.

The post Heat Pump in Distillation Column appeared first on ChemEnggHelp.

So, let us understand the fundamentals behind a VAHP working as below.

What is Vapour Absorption Refrigeration Cycle?

As we discussed above VAHP works upon vapour absorption refrigeration cycle. In this process there are two working fluids – one is refrigerant and other is absorbent. So, to generate chilled water @ 7.0 ⁰C we use LiBr (lithium bromide) as an absorbent and water as refrigerant. And, to generate chilled brine, we use ammonia and water working fluids. Where, ammonia is refrigerant and water is absorbent.

The below are two important properties which are the basis for working a VAHP (with LiBr and water working fluids):

• Boiling point of water is the function of pressure, as we reduce the pressure its boiling point reduces. So, we can see at 6 mmHg absolute pressure water boils at 3.7 ⁰C.
• Second important property is the Lithium Bromide affinity towards water. So, this concentrated LiBr aqueous solution can absorb water vapours.  

Now, we will see how above two properties works in absorption refrigeration cycle. You can refer the below figure to understand this principle.

Various Part of a VAHP and their Function

A vapour absorption heat pump or VAHP has different sections as we can see in above figure. There is evaporator, absorber, regenerator, condenser, circulation pumps and vacuum pump. The utility of each part we can understand as given below:

Evaporator

In evaporator we maintain vacuum around at 6 mmHg absolute and chilled water provide the heat to this water (refrigerant) for evaporation at 3.7 ⁰C. After supplying heat chilled water cool down to around 7.0 ⁰C. The chilled water inlet temperature to evaporator is around 13.0 ⁰C. These vapour at 3.7 ⁰C from evaporator goes into the absorber section.

Absorber

Where concentrated solution of LiBr (absorbent) absorbs this water vapour. This concentrated solution of absorbent we get from regenerator. And the lean solution of absorbent from absorber goes back into the regeneration section. For circulation of this absorbent, we use absorbent circulation pump.

Regenerator

In regenerator we regenerate lean LiBr solution, by evaporating excess water. For this purpose, we use waste heat, which is a low-pressure steam @ 2.0 kg/cm²g. Here, water evaporates and vapour goes into a condenser, while concentrated absorbent solution goes into the absorber. Other than steam many VAHP operates at hot water also, in that case this regenerator will operates under vacuum. This way we can evaporate water from the lean LiBr solution at low temperatures also. Moreover, VAHP can be double effect type, where we need steam supply at higher pressures. For your clarification the above figure is for a single effect VAHP, having LiBr and water as a working fluid.

Condenser

So, we need a condenser which is a shell & tube type heat exchanger to condense the water vapour generating from regenerator. Here this water is our refrigerant and we use cooling water to condense it. After condensation this refrigerant goes into the evaporator again, which is operating at vacuum of 6 mmHg absolute. This way this refrigeration cycle keeps on working.

We can find the fundamental difference between a vapour compression and vapour absorption is a compressor. In compression refrigeration cycle we use a compressor to compress the refrigerant vapour. While in absorption cycle, we use absorbent to condense/absorb the vapours.

In summary, we supply heat to regenerator using steam and remove heat in evaporator from circulating chilled water. And, remove heat from condenser using cooling water. This way our VAHP generates chilled water at around 7.0 ⁰C temperature. This chilled water temperature depends on the evaporator section vacuum, if vacuum reduces chilled water supply temperature will increase. Simultaneously, condenser cooling water supply temperature is also important. Because condensed refrigerant (i.e., water) temperature will depend on cooling water temperature.

Types of Vapour Absorption Heat Pump

In our industries we can find two types of VAHP first is single effect which require low pressure steam (i.e., around 2.0 kg/cm²g). While second type is double effect VAHP, which operates at higher pressure around 5.0 – 8.0 kg/cm²g steam supply pressure.

In double effect VAHP there are two generators while in single effect we have one generator. So, water vapour generating from first regenerator goes into the second regenerator. This way we can achieve low steam consumption to evaporate the same amount of water from lean LiBr solution.

So, benefit of two effect VAHP over single effect is the specific steam consumption to generate same TR. The specific steam consumption in single effect VAHP is 7.5 – 8.0 kg/TR, while for double effect this as low as 4.5 – 5.0 kg/TR. Therefore, double effect VAHP gives advantage of around 35 – 40% lower steam consumption.  

Coefficient of Performance (COP) of a VAHP

We can measure the performance of a refrigeration machine by estimating it’s COP or coefficient of performance. The COP for a VAHP we can estimate using below relationship:

If we designate the Q₁ = Heat supplied by steam in regenerator or heat added from source at T₁ and Q₃ = Heat supplied by chilled water in evaporator or heat absorbed for refrigeration at T₃. And, T₂ is the ambient temperature. Then, we can rewrite above relationship as below:

So, if our VAHP is operating at 2.0 kg/cm²g and has regenerator temperature 100 ⁰C (373 K) and evaporator temperature is 4 ⁰C (277 K). Considering ambient temperature 35 ⁰C (308 K), COP will be = [277*(373 – 308)]/[373*(308 – 277)] = 1.56.

Cost Benefit Analysis Vapour Absorption v/s Vapour Refrigeration System

Ideally a VAHP is advantageous when we have waste heat available in our plants. When we talk about waste heat is means, we are rejecting this heat into our cooling towers or atmosphere. Moreover, there are conditions where power cost is very high in comparison with steam cost, then use of VAHP is a cost-effective option.

So, to understand the economic feasibility let’s consider a plant where we require 100 TR refrigeration in terms of chilled water. We have option to go for a vapour compressor refrigeration unit or a single effect VAHP. Below table is the working to understand this comparison which can help us to take better decision.

We have made following assumptions for our estimation:

• Power consumption in refrigeration compression system 0.7 kWh/TR
• Steam consumption is VAHP 5.0 kg/TR
• Power cost @ 6.5 Rs/kWh and steam cost @ 0.5 Rs/kg
• Plant operating hours = 8000 hrs/annum
• All other overhead cost is same in both cases

Therefore, from above analysis we can see, by selecting VAHP over refrigeration compressor is preferable. As, there will be annual savings in operating cost around Rs.16.40 lacs. However, investment requirement for VAHP is higher by Rs.10 Lacs (35 -25 = 10). The simple pay back period for the differential investment will be =10*12/16.4 = 7.3 months. 

Conclusion

Finally, in this article we discussed about vapour absorption refrigeration system based on LiBr-Water working fluids. This can provide refrigeration requirement up to 7.0 ⁰C. For refrigeration requirements at lower temperature say (-) 18 ⁰C, we use NH3-Water as working fluids. This VAHP operates under pressure to condense the ammonia vapours coming out from regenerator. Subsequently, liquid ammonia is throttled into the evaporator to generate chilled brine utility. From evaporator ammonia gas goes into the absorber, where water is used to absorb the ammonia gas.

So, we should explore the avenues of waste heat available in our plants. Various possible sources can be such as reactor outlet hot gases or heat of reaction, condensate flash steam, hot process streams, hot flue gases, etc. This waste heat we can use to generate low pressure steam or hot water and can use in VAHP refrigeration system. These VAHP refrigeration machines will help us to stop our refrigeration compressor, which are one the major power consumers in our plants. This way we can reduce the overall power consumption, which is ultimately a reduction in variable cost of the product.

Moreover, using VAHP is good for our environment sustenance, where we are not using any harmful refrigerants. Simultaneously, it encourages the use of waste heat available inside the plants to generate low-cost refrigeration. Consequently, which is the effort towards reduce carbon foot prints.

Thanks for reading and looking forward for your comments!!!

The post Vapour Absorption Refrigeration Cycle in VAHP appeared first on ChemEnggHelp.

Generally, it is observed in our batch plants, plant operates in manual control mode. In other words, if a process parameter deviated from desired value, plant operator takes necessary action to restore it.

This manual control causes huge variation in the process parameters. In result this deviation is source of many inefficiencies and losses in the process. Like, high batch cycle time, low product yield and in some cases where process is very sensitive, we face total batch failure also. So, we can see all these are cost to the business.

So, in this article we will discuss the automation and controls of a thermic fluid heating system for a batch reactor. For this purpose, we will take an example of bulk chlorination reaction for methyl-pyridine. 

Process Details

To understand the process, you can refer below figure. Here, we have one glass lined jacketed reactor with agitator. This is a batch process and reaction take place in a solvent base having normal boiling point around 208 ⁰C. First, we charge organic solvent into the reactor and heat up the reactor mass. Subsequently, we charge methyl-pyridine and heat up the reaction mass to 180 ⁰C. This we do by circulation of hot thermic fluid in reactor jacket. After achieving reaction temperature chlorine gas purging starts under agitated condition. Our requirement is to maintain the reaction temperature around 185 ±2 ⁰C, this is atmospheric pressure reaction.

In above system you can see hot oil circulation pump circulates thermic fluid via thermic fluid heater coil. In heater coil this thermic fluid absorbs heat from the firing of fuel (i.e., FO, NG, Electricity or Coal). After heating up, this hot oil supply heat to the reactor and outlet of reactor jacket goes into the expansion tank. From expansion tank this colder oil again feed into the thermic fluid heater coil. This way this system continues to work.

Parts of Thermic Fluid System

In above figure you can see the various parts of a thermic fluid heater. We will discuss these parts one by one as follows:

Heater or Furnace

This is the main component of a thermic fluid heating system. Here we supply heat to the circulating thermic fluid. This heat we can supply through electric heaters or direct firing of fuels in a furnace.

Electrical Heaters

In case of electric heater thermic fluid remain in shell side and tubes contains electric heating elements. When we supply electricity to these heating elements they heat-up and supply heat to the circulating thermic fluid inside the shell. This type of heater provides neat and clean service for the plants. Moreover, operation is also very easy in comparison with direct fired furnace. But in this case operating cost is high and huge electricity supply is required. Therefore, this is a good alternative for small capacity heating requirements say around < 1000 kW.

Direct Fired Heater

In direct fired heater we fire fuel inside the furnace body and heat is absorbed by the circulating thermic fluid inside the furnace coils. This fluid can be furnace oil, natural gas or coal. However, natural gas is the cleanest fuel among all three options. In comparison with electric heater, direct fired heater require lots of controls for efficient of safe operation of the furnace. These controls include fuel flow control, combustion air control, stake temperature and excess air control etc. When we compare this with electrical heater, there we have one control which cuts the electricity supply if hot oil supply temperature goes beyond set point. To understand direct fired heater operation and controls you can refer to the figure in Process Details section.

Hot Oil Tank

In thermic fluid system hot oil tank is required for thermic fluid storage and dumping. When I say dumping it means during plant shutdown or in case of any leakage, we need to drain complete thermic fluid from the system. This we do for the maintenance or repair work.

Hot oil tanks should be provided with a proper size vent. And the vent of this tank we should connect to a hot oil vent condenser. You must take care the expansion of thermic fluid during finalizing the volume of hot oil tank. For example, if you take 1 m3 volume of thermic fluid at atmosphere temperature then at 250 ⁰C it will expand by around 20%.

Furthermore, we should provide proper insulation to the tank. When we dump the oil, it is very hot, so for personal safety insulation is must.

Hot Oil Expansion Tank

As you can see from name itself, the service of this equipment is to take care the expansion of thermic inside the system. We install this equipment at highest level inside the plant. We should ensure that the elevation difference between expansion tank and the highest-level consumer is minimum 3 meters.

When we do start-up of the thermic fluid system, heating is done slowly. This we do to vent off the moisture and non-condensable present in the fresh thermic fluid. Therefore, being at the top most level, expansion tank vent takes care for this requirement.

Also, expansion tank level indicator tells us about the level of thermic fluid into the system. In case of any leakage in the system, expansion tank level will come down and we will get an alarm to take appropriate action. 

Circulation Pump

Thermic fluid circulation pump operates at high temperature (i.e., 260 – 380 ⁰C) and pressure around 11.0 bar. Therefore, pump should follow API 610 latest standards to avoid any process failure and hazardous.

Pump installation should be in such a way that it is free from connecting piping thermal expansion stresses. Otherwise, it will create misalignment in mechanical assembly and may cause frequent seal failure and leakages.

Thermic Fluid

If pump is the heart then, thermic fluid is the blood for a thermic fluid heating system. Based on the process heating requirement we select suitable thermic fluid. A heat transfer fluid is a eutectic mixture of two organic compounds or a single organic compound as mentioned in below table. These in case of mixture, compounds have practically the same vapor pressures, so the mixture can be handled as if it were a single compound. Below table can guide you to understand various types of thermic fluids.

Why Automation is Required?

So, we have discussed our process setup and thermic fluid heating system also. Now we will develop automation and controls for the reactor heating system. First, we need to understand the importance of reactor temperature control. As we know all reactions are temperature dependent. And, to achieve optimum selectivity and yield, we need to maintain the reaction temperature in optimum range.

In the absence of the efficient automation & controls we will observe huge variation in reactor temperature. When temperature is lower side conversion will be lower and by-products will form. Moreover, at higher temperatures then optimum, we will get tar formation and high boiling unwanted compounds. Below is the control charts for reactor temperature variation with and without automation for your reference.

From above control charts and table, we can see the impact of the manual control & process automation. When we control reactor temperature manually, we observe huge variation (i.e., Temp1 variable). Reactor temperature oscillates between the range 178 – 192 ⁰C and standard deviation is also high 4.01 ⁰C.  

When we provide proper automation and controls to maintain the reactor temperature. Now manual intervention is not there in reactor operation. The difference is evident, you can variation is very low (i.e., range is 182 – 187 ⁰C and standard deviation also reduced from 4.01 to 1.43 ⁰C).

Therefore, we can see the impact of auto-control on reactor performance. This reduction in temperature variation will result in higher reactor yield. Moreover, reactor productivity will increase due to low batch cycle time. Because when reactor temperature oscillates too much, we stop the feed and wait till the temperature return back to normal state. And, this increases the overall batch cycle time of the process.

Automation & Controls for Batch Reactor Heating System

So, to understand the automation and controls for a batch reactor system, you can refer to the below figures. We can divide our control system in two parts. First is for thermic fluid system and second is for our batch reactor temperature.

Automation & Controls for Thermic Fluid Heater

In below figure we see the various automation and controls for the smooth operation of a thermic fluid heater. 

To control fuel flow rate, we use FCV in fuel feed line. Apart from this the fuel flow rate should be in cascade control to maintain the thermic fluid outlet temperature from the furnace. We should provide a ratio control between fuel feed flow and combustion air flow. This will adjust the combustion air flow automatically in case there is any variation in fuel feed flow.

Combustion air flow control require a control valve in vent line at the discharge of combustion air fan. This controller is very important for efficient and safe furnace operation.

Other important controls are stake temperature and excess air control. If these values go beyond set point combustion air flow control valve will take action to control them. To measure excess air in flue gas we provide oxygen analyser in furnace stack.  Other instruments like PT gives the back-pressure indication at furnace inlet. Various temperatures transmitters we need to monitor the radiant section, tube skin, convection section temperatures. These parameters are very critical for the furnace safety.

Automation & Controls for Reactor Temperature

To understand the reactor temperature control & automation you can refer below figure. While thermic fluid heater control and automation will take care to supply the thermic fluid at a stable temperature with minimum variation. So, to control the reactor temperature variation we need to control the hot oil supply flow rate and temperature both.

First, we need to understand the sources of temperature variation in a batch reactor. Since this reactor is semi-batch type process, where we have charged one raw material and chlorine gas we are feeding continuously. Therefore, any variation in chlorine feed rate will affect the reaction rate and subsequently heat balance. When chlorine gas flow rate is at lower side reactor temperature will go down as reaction rate will decrease. On other side at higher chlorine gas flow rate than set point value, reaction rate will increase and reaction mass temperature will go up.

Other than this variation in temperature of circulating thermic fluid in reactor jacket is another source of reactor temperature variation. For this we have already discussed control and automation for thermic fluid heater in previous section.

Details of Control Strategy

 So, we need automation & controls to deal with reactor temperature variations. We can provide various controls and automation as follows:

• Flow control valve in chlorine feed gas line, this will ensure chlorine gas flow control to the reactor. This flow control will be in cascade control with the reactor temperature also. In case of reactor temperature variation chlorine gas flow will change accordingly.
• To control the reactor temperature, we provide a temperature control valve in the hot oil cooler by-pass line. In case when reactor temperature goes below set point value, this valve will open to increase the hot oil supply temperature. And for the situation when reactor temperature goes up this by-pass TCV will close down to decrease the hot oil inlet temperature to the reactor jacket.
• Hot oil cooler uses cooling water for cooling the oil. We install a manual valve at hot oil cooler outlet to provide sufficient back pressure for the efficient operation of TCV.
• A pressure control valve (PCV) at expansion tank vent control the system pressure according to circulating thermic fluid temperature.
• Level indicators for Hot Oil Tank and Expansion Tank to monitor the levels.

Conclusion

So, we got the idea for automation and control for a batch reactor heating system. This way you can provide automation and controls to batch reactor and thermic fluid heating system. This will ensure the stable reactor operation with minimum variation in the reactor operating temperature.

We can also look into the feed forward control option for reactor temperature control. Any variation in chlorine gas flow will be taken as input to the hot oil inlet temperature control (TCV). This way TCV will take appropriate action in advance to mitigate the reactor temperature variation. For this purpose, we need to develop a correlation matrix between chlorine gas flow rate and reactor temperature.

This way you can implement smart control strategies, which will eliminate the human interventions in process. In result process will be stable with minimum variation in operating parameters. Moreover, variable cost of production will come down and we will get consistent product quality and production capacity.

Thanks for reading and looking forward for your feedbacks.

The post Automation and Controls for Batch Reactor appeared first on ChemEnggHelp.

Below are two commonly seen designs of furnace for most process services. First is Vertical Cylindrical Furnace which we use for low heat duty around less than 100 MBtu/hr. Second one is Horizontal Tube Cabin Type Furnace; this we use for higher duties say in the range around 100 – 450 MBtu/hr.

Various Heat Supply Systems

As I mentioned above, in chemical industries we can supply heat to the process using steam from boilers, thermic fluid heater, molten salt system and fired heater mainly. For selection, we take into consideration the design parameters such as temperature levels, heat transfer efficiency, pumping power and operational life. We need to look into the performance of the fluid and operating expenses. Also, we can’t overlook other factors like safety parameters such as pressure build-up, flashpoint, flammability and toxicity. With these concerns in mind, you can select better option among various alternatives as mentioned above. Let us discuss all of them one by one.

Boilers

Boilers are used in almost all process industries as a source of heating utility. Boiler generates steam which we use to supply heat to reboilers, evaporators, heaters etc. In case of steam, as heating temperature increases required operating pressure of the boiler and process equipment goes up.

For example, if we want to supply heat at 150 ⁰C to a distillation column through reboiler. The require steam pressure is around 16 bar (as we need steam temperature between 190 – 200 ⁰C). Therefore, for higher process temperature say 230 ⁰C, we need much higher pressure (i.e., around 50 bar pressure saturated steam). For this pressure, we require higher thickness of shell, tube-sheet, flanges, tubes, nozzles, piping, etc. This will increase equipment cost and moreover possibility of hazardous will be too high.

Therefore, for heating up to 170 ⁰C, steam is used in our industries (as required steam pressure is around 16 bar). And, for higher temperature heating requirements, it is better to use thermic fluid system from economy and safety point of view.

Thermic Fluid Heating System

In case of heating requirements between 170 – 360 ⁰C, we generally use thermic fluid system. Based on the operating temperature requirement, we decide the types of thermic fluid. Below table can give you the details based on the temperature requirement. For heat supply to thermic fluid, we use furnace oil, natural gas, electric heater or coal.

Molten Salt Heating System

For the temperature services higher than 360 ⁰C, we can use molten salt heating system. As thermic fluid degrades rapidly and we need regular replacement to maintain its properties. Therefore, heating with thermic fluid becomes uneconomical. In this case we can use molten salt heaters for heating requirements, which is suitable up to 500 ⁰C. One of the most commonly used molten salts is a eutectic mixture of sodium nitrate and potassium nitrate.

You need to provide proper heat tracing to avoid molten salt solidification problem.

Furnace or Fired Heater

Fired heater in process industries can supply heat at highest possible temperature requirements. This temperature depends on the maximum operating temperature limits of the material of construction. For example, in case of Ketene Furnace, acetic acid cracking takes place @ 740 ⁰C. In ketene furnace we use tube material as Inconel, which has high melting points (i.e., > 1200 ⁰C).

In a fired heater we can use different type of fuels like furnace oil, natural gas, coal etc. The process fluid enters into tube side of the furnace and fuel combustion takes place in furnace chamber. To minimize heat loss from furnace, we provide refractory lining inside and insulation outside of the furnace body.

In this article we will discuss furnace calculations in detail. Furthermore, we will discuss the automation and control for efficient and safe furnace operation. For this purpose, we will consider a furnace for air heating at 620 ⁰C. This hot air we need for the reactor pre-heating and we will use furnace oil as a fuel.

Process Details for Furnace

You can refer to below figure to understand the process. Here we are feeding process air for compressor to the furnace coil at inlet temperature 110 ⁰C. This air first goes into the convection section and exchange heat with out going hot flue gases. After preheating air goes into the radiant section coils/tubes. The outlet temperature of hot process air from furnace is maintained at 620 ⁰C. In furnace chamber bottom there are burners in which we feed furnace oil and combustion air. This mixture burns and supply heat to the process air, which is flowing through furnace coils.

Furnace Calculations

So, now we will do the calculations for furnace, which includes design basis, heat duty, theoretical air requirement, furnace efficiency, adiabatic flame temperature, etc.

Design Basis

Flow rate of process ai                                              : 6000 kg/h

Compressor discharge pressure                             : 3.0 bar

Inlet temperature of air to the furnace                 : 110 ⁰C

Heat capacity of process air                                      : 0.25 kcal/kg-⁰C

Air discharge temperature from furnace               : 620 ⁰C

Flue gas discharge temperature                               : 285 ⁰C

Flue gas heat capacity                                               : 0.33 kcal/kg-⁰C

Furnace oil composition (% wt/wt)

Carbon               : 85.8

H2                        : 12.4

N2                        : 0.5

S                           : 0.5

Gross Calorific Value                                                 : 10800 kcal/kg

Net Calorific Value                                                     : 10197 kcal/kg

Furnace thermal efficiency                                       : 80%

Heat Load on Furnace

You can calculate heat load on furnace from the heating requirement of process air.

Q = Air flow rate*Heat Capacity*(620 – 110)

Q = 6000*0.25*(620 – 110) = 765,000 kcal/h

Considering 5% heat loss from furnace actual heat requirement will be Q’ = 765,000*1.05 = 803,250 kcal/h.

Furnace Oil Requirement, Mf = Heat load on furnace/(FO Net Calorific Value*Furnace Efficiency)

Mf = 803,250/(10197*(80/100)) = 98.5 kg/h

Theoretical Air Requirement

Now we can calculate the theoretical air required for Mf = 98.5 kg/h furnace oil firing, using furnace oil composition. Below are combustion equations for various fuel constituents.

C + O₂ = CO₂

H₂ + 0.5O₂ = H₂O

S + O₂ = SO₂

A_th = [(C/12)*32 + (H2/2)*0.5*32 + (S/32)*32]/0.23

A_th = [(98.5*0.858/12)*32 + (98.5*0.124/2)*0.5*32 + (98.5*0.05/32)*32]/0.23 = 1426 kg/h

Taking 20% excess air, actual air for combustion will be, Aa = 1426*1.20 = 1711 kg/h

Furnace Efficiency Estimation

Since, we have furnace oil feed rate, net calorific value and combustion air flow rate with us. Assuming 100% burner efficiency.

So, generation of heat from furnace oil firing, Q1 = 98.5*10197 = 1,004,404 kcal/h

Heat loss from insulation to the surrounding (which is 5%), L1 = Q1*5/100 = 50,220 kcal/h

Heat loss with furnace flue gases, L2 = (1711 + 98.5)*0.33*(285 – 35) = 149,284 kcal/h

(here we have assumed combustion air supply temperature 35 ⁰C and total flue gas flow is furnace oils flow rate + actual air flow rate)

So, Furnace Efficiency, Eff = (Q1 – L1 – L2)*100/Q1 = (1,004,404-50,220-149,284)*100/1,004,404 = 80%

Adiabatic Flame Temperature Calculation

Since you have fuel burning rate and actual combustion air flow, so adiabatic flame temperature can be estimated as follows:

Adiabatic Flame Temperature, Taf = 35 + FO feed rate*FO NCV/(Flue gas flow rate*Heat Capacity)

Adiabatic Flame Temperature, Taf = 35 + 98.5*10197/((1711+98.5)*0.33) = 35 + 1682 = 1717 ⁰C

In furnace around 45% of total heat is comprises by radiative heat, therefore heat absorbed by process air in radiant section will be, Qr = Q1*0.45 = 1,004,404*0.45 = 451,982 kcal/h

Now balance heat going into convection section will be, Qc = Q1 – Qr = 552,422 kcal/h

Now we can calculate the flue gas temperature leaving from the radiant section of the furnace as below,

Flue gas temperature at convection section inlet, Tci = Taf – Qr/(Flue gas flow rate*Heat Capacity)

Flue gas temperature at convection section inlet, Tci = 1717 – 451,982/((1711-98.5)*0.33) = 868 ⁰C In summary we can see that, in radiant section of furnace around 451,982 kcal/h heat is absorbed by process air. Before entering into the radiant section process air pre-heat in convection section by exchanging heat from flue gases. In other words, hot flue gas cools down from 868 ⁰C to 285 ⁰C to pre-heat the process air.

Fired Heater Instrumentation & Control

Hence, from above discussion you could have understand that, to operate a furnace efficiently and safely we need proper instrumentation and controls. Otherwise in the absence of automation furnace efficiency will be reducing and may lead to possible process hazard also. When we talk about process hazardous it means like, furnace backfire, explosion in body, flare at furnace stack outlet, burning of furnace tubes, etc.

So, you can refer below figure to understand various instrumentation and controls for a safe and efficient furnace operation.

To control furnace oil flow rate, we use FCV in furnace oil feed bypass line. Apart from this the fuel flow rate should be in cascade control to maintain the furnace process air outlet temperature. Moreover, level transmitter shows us the furnace oil inventory in feed tank.

Combustion air flow control require a control valve in vent line at the discharge of combustion air fan. This controller is very important for efficient and safe furnace operation. We should provide a ratio control with the fuel feed flow. If there is change in fuel flow the combustion air flow will change accordingly.

Other important controls are stake temperature and excess air control. If these values go beyond set point combustion air flow control valve will take action to control them. To measure excess air in flue gas we provide oxygen analyser in furnace stack. 

Other instruments like PT gives the back-pressure indication at furnace inlet. Various temperatures transmitters we need to monitor the radiant section, tube skin, convection section temperatures. These parameters are very critical for the furnace safety.   

Discussion

In this article we discussed about various heat supply sources in our industries. Also, we did comparative study of all the options. Subsequently, we did process calculation for a process air pre-heating furnace. Furthermore, we discussed required instrumentation and process controls for the furnace.

Finally, I suggest you should look into the digital transformation of the fired heater also. In our industry furnace or fired heater is one of the highest energy consuming unit operation. Therefore, precise process control will be the key for cost effective and safe operation.

Digital transformation of the furnace will enable us to analyze the real time furnace parameters. Realtime monitoring of various critical parameters like stake temperature, oxygen % in furnace stack, process outlet temperature, furnace temperature, will give us insight in the furnace process. We can use this real time analysis to take timely decision to control the various parameters. This way we can maintain sustained efficiency at highest possible level.

We can also look into machine learning model to predict the furnace coil fouling or chocking problems. Moreover, in many processes frequent furnace tube failure takes place. In such cases we can use real time analytics and machine learning to predict the tube failure/leakages. This way, it will help us to take preventive steps to avoid furnace breakdowns. These sudden breakdowns cause plant shutdown, which is a huge revenue loss for any organization.  

Thanks for reading and looking forward for your feedback and comments.

The post Fired Heater Process Calculations and Automation appeared first on ChemEnggHelp.

If we go in past we can see time to time many industrial revolutions took place. After 18th century manufacturing shifted from batch mode to continuous mode. Now, there was abundance of product in the market. Moreover, continuous process was superior over batch process in terms of lower production cost and better consistent quality. Therefore, advent of continuous process in chemical manufacturing started stiff competition in the market. So, in the changed market scenario customer is the boss. Today customer has options to go to that supplier who can provide the material of best quality with lowest cost.

Same thing happened in case of fine & specialty chemical business also. Here, coming of too many manufacturers created market competition. So, those manufacturers who can make product with minimum cost and best quality. They will capture lion share in the markets. While, others will be losing their business because of non-cost competitiveness.   

Relationship between Profit and Waste

For both type of processes, whether continuous or batch below is the model which shows cost and profit relationship.

From above model it is evident that Product Price is fixed by stiff market competition. Moreover, Raw Material and Energy cost is also governed by the market. In case of energy we can see the cost of power, coal, natural gas or fuel oil is not in our hands. Therefore, for any industry to beat this competition remaining focus area is Waste reduction.

So, what is waste? In a process any excess consumption of material, efforts and other services for which our customer does not pay we are not paid or we don’t get any value addition is a waste. In other words, we can say, our product cost is bearing the cost of waste also, which is a loss for us. So, reducing waste from process will increase our profit, which we can see in above generalize relationship also.

Sources and Type of Wastes

In chemical plants first main source of waste generation is the Reactor. You just imagine a theoretical process where you can achieve 100% conversion, 100% selectivity and 100% recovery. This will give you 100% yield without recovery and recycles involved in the process. Moreover, no by-products and residue will be generated.

When we talk about this ideal process, our energy consumption is lowest possible which will eliminate the waste of different fuels consumed. Moreover, it will reduce environment pollution and will make our Blue Planet more beautiful and safer for future generations.

In actual our reactors are operating at lower conversion and yield. For batch plants yield can be somewhere in the range of 55 to 80%, while for continuous plant it can be around between 70 to 95%. 

So, it is very important for us to look into the area of efficient and innovative reaction technologies. Like micro-reactors, advanced flow reactors and use of membrane technologies in reactors. In these type of reactors very precise control of operating parameters is possible. This efficient control can give us highest possible conversion and yield.

In those processes, where we are operating with batch reactors should be replaced with flow reactors. This will improve the yield and reduce wastage of input material and energy consumption as well.

Second source of waste generation is the neutralization process in chemical plants. This process generates huge amount of aqueous waste. This aqueous effluent contains inorganic salts or organic chemicals, many times it can be mixture or both also. This effluent waste is very harmful for the environmental sustainability. Therefore, we need to treat this effluent in incinerators or spray dryers. These effluent treatment setups are the huge consumers of energy, which is again the source of fossil fuel wastage and environment pollution.

Types of Wastes in our Processes

There are many other forms of wastes in chemical plants. We can categorize them in seven types as per the LEAN methodology. These are Defects, Overproduction, Transportation, Waiting, Inventory, Motion and Over Processing.

Defects

in any process are the results of variation in parameters beyond the specified limits. In a process there are three types of variations. (1) Input variable variation, (2) Process variable variations, and (3) Output variable variation. Out of these, input and process variable variation are independent, while output variable variation depends on previous two. Therefore, to minimize the defects in our process we need precise control over input and process variables.

 For example, in a batch reactor process we can understand these different types of variables as below:

Input Variables

Examples for input variables can be such as, variation in quantities added and purity of input raw materials. Variation in heat addition or heat removal rate to and from the reactor. Variation in the addition rate of the input materials into the reactor. There is variation in stage wise batch cycle time, etc.

Process Variables

In a batch reactor, process variable are its parameters like temperature, pressure, agitator RPM, pH levels, conversion rate, etc.

Output Variables

The examples of output variable in a batch reactor are such as, yield, product quality, batch cycle time, etc. 

Overproduction

In an industry overproduction is a type of waste, which is the result of poor coordination and wrong demand forecasting. Overproduction increases the finished good inventory which is a source of negative cash flow for any organization.

Transportation

This loss occurs during material and energy transfer from one equipment to another equipment. To understand this, we can visualize the leakages from pipeline and fittings this will increase wastage of material. Moreover, in case of steam transfer from boiler to plant heat loss to the surrounding is wastage of energy.

Waiting

An example of waiting loss inside plant can be the delay of raw materials supply. Everything is ready but absence of input material is a wastage of time and production capacity. This can be because of poor co-ordination and planning. Other case of waiting can be the holding of batch for quality control lab clearance. There is common inconsistency in the reporting time for QC lab report. So, this is the wastage of time and unnecessarily increase in overall batch cycle time and lower production per batch.

Inventory

This type of waste is very common in plants. We can see excess inventory of consumables, raw material, work in process and finished good in most of the plants. This excess inventory generates because of non-availability of data in time and poor decision making. This inventory carrying cost is big waste for our industries.

Motion

Unnecessary movement of man, machine and material is a type of waste for which we do not receive any money from customer or any other value addition to the product. The major source of this waste is absence of timely & effective information sharing among the team members. Like, wrong information will cause for the supply of wrong material. And then it will be return back and in second time we will receive desired material. This is the example of motion waste for efforts, material & machinery.

Over processing

This is the type of waste, where we are putting additional material, energy and efforts. For which we are not going to receive any additional value. Suppose if customer need 95% purity of a product. And, we are giving him 99% purity material. Here we are generating waste in our process in terms of material, energy and efforts.

Possible Strategies to Reduce Waste

Therefore, we can see in our plants above all types of wastes are there. And, which is eating away our profit knowingly or unknowingly. So, to increase our cost competitiveness and robust quality, elimination of this waste from the process is most important. To do this I thing following strategies should be implemented: –

Process innovation and intensification

This is most important action on which we must focus on priority. Because, we can see in most of the industries we are still using batch processes and old technologies for reaction and separation. We should use efficient and low waste generating technologies. Such as, advance flow reactors, membranes, etc. Industries should collaborate with research institutes and academic establishments to facilitate this objective. For long term success, investment in this area should not be looked from the immediate return perspective.

Automation and Robotics

We must look into make our plants fully auto control. Using instruments and control systems can minimize human intervention in our process. Moreover, wherever manual operation is there possibilities of using robots should be look into. For example, solid loading into the reactor, solid waste handling, product packaging and staking can use robots. Full automation and use of robotics in our process will reduce the human intervention. This will further reduce the variations in our process. And, plant operation will be more consistent and robust. In result defect and waste generation from plant will reduce significantly.

Digital Transformation

For quick, efficient and effective decision-making digital transformation will be very helpful. After getting real-time data form the value chain an analytical platform can be developed. This platform will have machine learning algorithms to give intelligent insight. These machine learning algorithms will provide artificial intelligence to us, which will enable to take quick and efficient decisions. This will help us to eliminate those types of wastes, which generates because of poor and untimely decision making. Digitalization will empower us to do better demand forecasting, efficient production planning, timely availability of material with required quantity and timely logistics management. Moreover, process control will become smarter and more intelligent with the use of artificial intelligence. This smart control will reduce raw material and energy consumption norms and as well as minimize the waste generation from plant also.

Conclusions

In this article we discussed about waste and the value of waste which we are losing every moment. This waste can be material, energy, efforts and machine occupancy times. Afterwards, we discussed all types of wastes in our plant and their sources. And, finally we chalked out a strategy to reducing waste from our processes. It is very necessary to understand reducing waste is not only important from the profitability point of view. But also, it is required to save our blue planet and this is a top most responsibility for all of us.

For our earth and Industries elimination of the waste is more beneficiary than its treatment, recycle and reuse.

Thanks,

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