Process design and optimization play a vital role in creating and improving the manufacturing processes for chemicals and related products. Chemical process design includes several stages, including conceptual design, process development, detailed design, construction, and operation. The ultimate goal of chemical process design is to develop a cost-effective and safe process that can produce high-quality products at a high yield.
Thus, it necessitates understanding to understanding chemical reaction mechanisms, design effective plants or refineries for optimal production, and fine-tune processing conditions to enhance overall efficiency. Moreover, optimization involves analyzing and improving an existing process to make it more efficient, cost-effective, and environmentally sustainable.
Creating of manufacturing process in cost effective and safe manner involves several steps including basic engineering package, detailed engineering packages, construction and operation. Process engineers are professional who play a vital role to design a process which can produce high quality products efficiently.
Basic Engineering Design (BED) or Front-End Engineering Design (FEED) services is most important engineering design activity for working on any Greenfield or Brownfield projects. BED will establish the specific set of process operating conditions and equipment necessary to achieve the level of reliability, efficiency, and safety required. This design phase sets the direction for the rest of the project. At the completion of this phase, a cost estimate of +40%/-20% can typically be developed for the project. BED puts great emphasis on the development of the Design Basis at the initiation of design. When the design basis is complete, we typically have the following information defined:
Once the design basis is in place, and agreed upon with the client, process engineer works to create, analyze, and optimize the many aspects of the plant design. The end result is process documentation that clearly defines the process.Typical Process Engineering Deliverables for BED package can include the following or a smaller subset of these items:
Let us assume a homogeneous liquid phase non-catalytic reaction. In this reaction two organic raw materials, chemical ‘A’ and chemical ‘B’ reacts to form chemical ‘C’. This is an exothermic reaction and raw material ‘A’ is limiting reactant. Chemical ‘B’ consumption is 1.25 times of reactant ‘A’. Heat of reaction is 150 kcal/kg of reacted ‘A’.
In this process equilibrium conversion of the reaction is 85% on the mass basis for reactant ‘A’. This reaction takes place at 85 °C and atmospheric conditions. Selectivity of the reaction is 95% on mass basis. And remaining 5% of reacted ‘A’ converts into high boiling tar like material. This residue composition is as below which is sent for incineration. The calorific value for residue is 7500 kcal/kg approximately.
Sr. No. | Component | Composition (wt%) |
---|---|---|
1 | Chemical A | 1% |
2 | Chemical B | 2% |
3 | Chemical C | 2% |
4 | Heavies | 95% |
For our batch reactor process calculations, we need physical and chemical properties for the chemicals are in below table.
Sr. No. | Component | Normal Boiling Point (℃) | Heat Capacity (kcal/kg℃) | Density (kg/m3) | Heat of Vapourization (kcal/kg) |
---|---|---|---|---|---|
1 | Chemical A | 70 | 0.35 | 900 | 100 |
2 | Chemical B | 90 | 0.35 | 900 | 100 |
3 | Chemical C | 100 | 0.35 | 1000 | 90 |
4 | Heavies | 120 | 0.35 | 1000 | - |
A (liq.) + B (liq.) —-> C (liq.) at 85 °C and atmospheric pressure
Here,
RM – Raw Material
CWS – Cooling Water Supply
CWR – Cooling Water Return
Cond. – Steam Condensate
This process includes two steps first is reaction and second is batch distillation. The material balance for per batch will be as below.
The recovered quantities from distillation based on 90% recovery will be as below
Total production of product – C will be = product in crude – loss in intercut – loss in residue = 3633 – 22 – 3.82 = 3607.2 kg/batch.
Total RM – A consumed = Charged – Recovered = 2000 – 270 = 1730 kg/batch
Total RM – B consumed = 2500 – 337.5 = 2162.5 kg/batch
Heating utility for our process is 3.5 bar steam at saturated conditions. The temperature of the steam is 139 °C and latent heat is 513.5 kcal/kg.
Heat load for reaction mass heating after charging of RM – B will be Q1 = mass RM-B * Cp * (initial temp – final temp) = 2500*0.35*(80-35) = 39375 kcal/batch. Hence steam requirement will be m1 = Q1/513.5 = 76.7 kg/batch.
Heat load and steam requirement in distillation will as follows:
For recovery of RM – A, heat load will be Q2 = mass recovered * (1 + reflux ratio) * latent heat = 270*(1 + 5) *100 = 162000 kcal/batch. Steam requirement will be m2 = Q2/513.5 = 162000/513.5 = 315.5 kg/batch.
Similarly, for RM – B recovery Q3 = 337.5*(1 + 10)*100 = 371250 kcal/batch. Steam requirement will be m3 = Q3/513.5 = 723.0 kg/batch.
For product recovery Q4 = 3269.7*(1 + 10)*90 = 3237003 kcal/batch. Steam requirement will be m4 = Q4/513.5 = 3237003/513.5 = 6303.8 kg/batch.
For first intercut Q5 = 44.5*(1 + 25)*100 = 115700 kcal/batch. Steam required will be m5 = Q5/513.5 = 225.3 kg/batch.
Heat load for second intercut Q6 = 44.0*(1 + 40)*100 = 180400 kcal/batch. Hence steam requirement will be m6 = Q6/513.5 = 351.3 kg/batch.
Therefore, total steam requirement for total batch processing will be Q = Q1 + Q2 + Q3 + Q4 + Q5 + Q6 = 76.7+315.5+723.0+6303.8+225.3+351.3 = 7995.6 kg/batch. Considering 5% steam loss actual steam requirement will be Q’ = 1.05*Q = 8395 kg/batch.
Cooling water flow rate requirement will be based on when our reaction is going on and pure product draw is going on. As this will be maximum requirement any point of time during the process.