1. Sequential Batch Processing
CH EN 5253 – Process Design II
Sequential Batch Processing
March 12, 2018

2. Books
Product and Process Design Principles: Synthesis, Analysis and Evaluation
by J. D. Seader, Warren D. Seider and Daniel R. Lewin
Chapter 22 (4th Edition)
Analysis, Synthesis and Design of Chemical Processes
by R. Turton,‎ R. C. Bailie,‎ W. B. Whiting,‎ J. A. Shaeiwitz,‎ D. Bhattacharyya
Chapter 3 (4th Edition)

3. Topics Design of reactor-separator processes
Covered in the previous class
Design of single/multiproduct processing sequences
Overview in the previous class

4. Topics Recipe/Bottle Neck/Cycle Time/Makespan/ Gantt chart
Batch Processes-
Flowshop
Jobshop
Single Product Batch Plants
Multiple Product Batch Plants
Transfer Policies
Zero Wait (ZW)
No Intermediate Storage (NIS)
Unlimited Intermediate Storage (UIS)
Preparing Gantt Chart

5. Recipe Cycle Time (CT) Makespan Bottleneck unit
Series of processing steps ( reaction, mixing, separation etc.) to manufacture a product
Cycle Time (CT)
Time between the completions of batches
Makespan
Total time required to produce a given number of batches.
Not always equal to multiplication of cycle time
Bottleneck unit
Unit having the longest batch unit

6. Multiple Product Batch Plants
FLOWSHOP (or multiproduct) plants
All products require all stages following the same sequence of operations
JOBSHOP (or multipurpose) plants
Not all products require all stages and/or follow the same sequence.
The greater the similarity in the products being produced, the closer a real plant will approach a flowshop, and vice versa-the more dissimilar, the more it will approach a jobshop.

7. Single Product Batch Plants
Processing Steps (RECIPE)
1.- Mix A + B, heat to 80 ºC, react to form C. Total 4 hours
2.- Mix with solvent D for 1 hour at 20 ºC
3.- Centrifuge to separate the product C for 2 hours
4.- Dry in a tray for 1 hour at 60 OC.

8. Non-overlapping Operation (with Zero Wait)
Cycle time (CT) = = 8 hrs,
Makespan (2 batches) =16 hrs.

9. Overlapping Operation (with Zero Wait)

10. Overlapping Operation (with Zero Wait)
Cycle time (CT) = max {4,1,2,1}=4 hrs,
Makespan (2 batches)= 12 hrs ( it’s not equal to 2X4)

11. Multiple Product Batch Plants
Calculate Cycle time and makespan for 2 batches of A and B
Single Product Campaigns (SPC)
Cycle time A = 5 hrs,
Cycle time B = 4 hrs
CTA+B = 9 hrs (To repeat AABB)
Makespan (2 batches) = 20 hrs

12. Multiple Product Batch Plants
Mixed Product Campaigns (MPC)
CTA+B = 7 hrs (To repeat ABAB).
Makespan (2 batches) = 18 hrs.

13. Multiple Product Batch Plants
Mixed Product Campaigns (MPC) with change over time
CTA+B = 9 hrs (To repeat ABAB).
Makespan (2 batches) = 21 hrs.

14. Transfer Policies Zero-wait strategy (ZW)
No intermediate storage or wait in unit
Content transferred immediately to next unit
No Intermediate storage (NIS)
Need not transfer immediately, can store in unit
Unlimited Intermediate storage (UIS)
Unlimited storage between units
In practice, plants will normally have a mixture of the three transfer policies.

15. Another Example
Production of the same number of batches of each product using a sequence ABAB

16. Zero Wait Transfer Policy
CTA+B = (slack) = 11 hrs (To repeat ABAB)
Makespan (2 batches) =26 hrs.

17. No Intermediate storage (NIS) Policy
CTA+B = (slack) = 10 hrs (To repeat ABAB)
Makespan (2 batches) =25 hrs.

18. Unlimited Intermediate storage (UIS) Policy
CTA+B = 6+3 = 9 hrs (To repeat ABAB)
Makespan (2 batches) =24 hrs.

19. How many intermediate storage tanks are required?