Outline - ydhermawan's blog · 2017/01/05 · Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY The production cycle for three batches each of Product 1 and Product 2. The batches have

Chemical Plant Design – 1210384 Chapter-5

Department of Chemical Engineering - UPN “Veteran” Yogyakarta Page 1 of 21

Dr.Eng. Yulius Deddy HermawanDepartment of Chemical EngineeringUPN “Veteran” Yogyakarta

VBATCH PROCESS

Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Outline1. Introduction to Batch Processes2. Batch Reactor3. Batch Separation4. Gantt Chart5. Production Schedules for Single Products6. Production Schedules for Multiple Products7. Equipment Cleaning and Material Transfer




V.1INTRODUCTION TOBATCH PROCESSES


Batch and Continuous Processes(Smith, R, 2005)

• However, not all processes operate continuously.• In a batch process, the main steps operate discontinuously.• In contrast with a continuous process, a batch process does

not deliver its product continuously but in discrete amounts.This means that heat, mass, temperature, concentration andother properties vary with time.

• In practice, most batch processes are made up of a series ofbatch and semicontinuous steps.

• A semicontinuous step runs continuously with periodic start-ups and shutdowns.




Various modes of operation for batch and semibatch reactors.(Smith, R, 2005)


Batch Processes:(R. Smith)

• are economical for small volumes;• are flexible in accommodating changes in product formulation;• are flexible in changing production rate by changing the

number of batches made in any period of time;• allow the use of standardized multipurpose equipment for the

production of a variety of products from the same plant;• are best if equipment needs regular cleaning because of fouling

or needs regular sterilization;• are amenable to direct scale-up from the laboratory and• allow product identification.




Batch Processes:(R. Smith)

One of the major problems with batch processing is batch to-batch conformity.

• Minor changes to the operation can mean slight changesin the product from batch to batch.

• Fine and specialty chemicals are usually manufactured inbatch processes. Yet, these products often have very tighttolerances for impurities in the final product and demandbatch-to-batch variation being minimized.


Batch Processes:(James M. Dauglas)

Select batch, if:1. Production rate

a. Sometimes batch if less than 10million lb/yearb. Usually batch if 1million lb/yearc. Multiproduct plant

2. Market forces:a. Seasonal productionb. Short product lifetime

3. Scale up problems:a. Very long reaction timesb. Handling slurries at low flowratesc. Rapidly fouling materials




V.2.BATCH REACTOR


Example of parallel reaction

Minimize Byproduct:If a2 > a1 and b2 > b1: The concentration of both feeds should be minimizedand each added progressively as the reaction proceeds. Predilution of the feedsmight be considered.If a2 > a1 and b2 < b1: The concentration of FEED1 should be minimized bycharging FEED2 at the beginning of the batch and adding FEED1 progressivelyas the reaction proceeds. Predilution of FEED1 might be considered.If a2 < a1 and b2 > b1: The concentration of FEED2 should be minimized bycharging FEED1 at the beginning of the batch and adding FEED2 progressivelyas the reaction proceeds. Predilution of FEED2 might be considered.If a2 < a1 and b2 < b1: The concentration of FEED1 and FEED2 should bemaximized by rapid addition and mixing.

Ratio:




A temporal superstructure for a well-mixed batch reactor.(Smith, R., 2005)

The greater the number of the time intervals, the closer themodel approaches the batch reactor modeled.


A temporal superstructure for a multiphase well-mixed batch reactor(Smith, R., 2005)




Some examples of mixing compartment networks to represent agitatedvessels.




V.3.BATCH SEPARATION


Batch Distillation

Find other examples ofbatch separation!

Advantages Disadvantages

The same equipment can be used to processmany different feeds and produce differentproducts

High purity products require the carefulcontrol of the column because of its dynamicstate

There is flexibility to meet different productspecifications

The mixture is exposed to a high temperaturefor extended periods

One distillation column can separate amulticomponent mixture into relatively pureproducts

Energy requirements are generally higher.

Simple distillation from a batch pot




V.4.GANTT CHART


Gantt Chart for a simple batch process




Overlapping batches allows the batch cycle time to bedecreased


Example 5.4.1: determine reactor capacity

Filling time = 0.25 hReaction time = 2.5 hReactor emptying = 0.25 h

Cycle time = 3 h

Production capacity = 3000 ton/year (active: 330 day/year)

h

kg8.378

h24300tonkg

10003000rateProduction

1 kg of FEED produces 0.8 of main product

kg5.1420h3h8.0

kg8.378capacityReactor




Single Step – Single Reactor

1

timeSTEP Hour

FILLING 0.25REACTION 2.50

EMPTYING 0.25total 3.00


Single Step – 3 Parallel Reactors

1

2

3

time

1

2

3

time

1

2

3

time

STEP HourFILLING 0.25REACTION 2.50EMPTYING 0.25

total 3.00




V.5.PRODUCTION

SCHEDULE FORSINGLE PRODUCTS


Production schedules for a three-step process.




Subsequent batches are only started once the previous batchhas been completely finished. For this sequential productionschedule, the cycle time is 20 h. This clearly leads to very poorutilization of equipment.


It has already been noted that overlapping batches can reduce the cycle time. Subsequent batches are started as soon as the appropriate equipment becomes

available. Cycle time decreases to 10 h for overlapping batches (the length of thelongest step).

If a specified volume of production needs to be achieved over a given period oftime, then the equipment in the process that uses overlapping batches in Figure(b) can in principle be half the size of the equipment for sequential production inFigure (a).




There are two items of equipment operating Step A, but in parallel. This allows both Step B and Step C to be carried out with complete utilization. If the sizes of the equipment are compared to the sequential production schedule,

then each of the two Steps A1 and A2 in Figure (c) can in principle be one-quarterthe size of the equipment for Step A for sequential production in Figure (a).

The size of the equipment for Steps B and C in Figure (c) will also be one-quarterthe size of those in the sequential production schedule in Figure (a).


The final option shown in Figure (d) is to use intermediate storage for the limitingstep.

Material from Step A is sent to storage, from which Step B draws its feed. Materialis still passed directly from Step B to Step C. Now all three steps are fully utilized.

For the same rate of production over a period of time, the size of Step A can inprinciple be half that relative to the sequential production in Figure (a) and thesizes of Steps B and C can in principle be one-quarter those for sequentialproduction. However, this is at the cost of introducing intermediate storage.




V.6.PRODUCTION

SCHEDULE FORMULTIPLE PRODUCTS


Production schedule for two products with athree-step process.




Figure (a) shows a production cycle involving a sequentialproduction schedule. Production alternates between Product 1 and Product 2. The cycle time to produce a batch each of Product 1 and 2 is

30 h.


The first thing that can be considered in order to reduce thecycle time and increase equipment utilization is to overlap thebatches as shown in Figure (b). This reduces the cycle time to 18 h.




All of the schedules considered so far involved transferring material from one stepto another, from a step to storage or from storage to a step without any timedelay. This is known as zero-wait transfer.

An alternative is to exploit the equipment in which a production step has takenplace to provide hold-up.

In this situation, material is held in the equipment until it is required by theproduction schedule. A schedule using equipment hold-up is shown in Figure (c).This reduces the cycle time to 15 h.


Finally, Figure (d) shows the use of intermediate storage. The use of storage is only necessary for Product 2. Use of intermediate storage in this way reduces the cycle timeto14 h.




Single versus mixed-product campaigns forthree batches each of two products.


The production cycle for three batches each of Product 1 and Product 2. The batches have been overlapped to increase equipment utilization. In order to produce three products each of Product 1 and Product 2, the

schedule involves single-product campaigns. Three batches of Product 1 and three batches of Product 2 follow directly

from each other. The cycle time is 47 h. The total time required to produce a given number of batches, in this case

three batches of each Product 1 and Product 2, is known as themakespan, it is 53 h.




An alternative production schedule can be suggested byfollowing a mixed-product campaign. Alternating between batches of Product 1 and Product 2 in

allows the cycle time to be reduced to 45 h and the makespanto be reduced to 51 h.




V.7.EQUPIMENT CLEANING

ANDMATERIAL TRANSFER


Cleaning between product changes extends the cycle times.

Once cleaning is introduced, themixed-product campaigns areseen to be less efficient than

single-product campaigns




Transfer times extend the cycle times.

Compare to the theschedule withouttransfer time,Cycle time increasesfrom 10 h to 12 h.

Compare to the theschedule withouttransfer time,Cycle time increasesfrom 20 h to 24 h.


Good luck

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Outline - ydhermawan's blog · 2017/01/05 · Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY The production cycle for three batches each of Product 1 and Product 2. The batches have