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

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)

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

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

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

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.

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.

Non-overlapping Operation (with Zero Wait) Cycle time (CT) = 4+1+2+1 = 8 hrs, Makespan (2 batches) =16 hrs.

Overlapping Operation (with Zero Wait)

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)

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

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

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

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.

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

Zero Wait Transfer Policy CTA+B = 6+3+2 (slack) = 11 hrs (To repeat ABAB) Makespan (2 batches) =26 hrs.

No Intermediate storage (NIS) Policy CTA+B = 6+3+1 (slack) = 10 hrs (To repeat ABAB) Makespan (2 batches) =25 hrs.

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

How many intermediate storage tanks are required?