Scale-up and scale-down of chemical processes

Special Topics in Industrial ChemistrySeppo Karrila

November 2014

Executive summary

• In scale-up, product and process development tend to move in small steps– Lab scale to bench scale, then to pilot scale, finally

to production scale– This reduces the risk with the larger investments

in the next step• Scale-down is mainly for troubleshooting or

development of processes used in ongoing production

My “Definitions”• Laboratory scale (OK at university)– Done in test tubes etc., some grams of product

• Bench scale (OK at university)– Device fits in a normal room, kilograms

• Pilot scale (almost never at university)– A “small industrial machine” that requires several men

to operate it, possibly has its own building, tens of kilgrams to tons of product

• Industry scale, machinery may occupy the area of a university campus

These are the steps to industrial production!

• Lab scale: prove that a product can be made from raw materials (“Proof of concept study”)

• Bench: make enough product to test its properties, learn about fundamentals of processing, improve formulation

• Pilot: Try small scale production before bigger investment at high risk. Critical points? Problems? Automation? Space and power requirements? Help in designing a factory or plant!

Use of pilot plant

• Check alternatives before designing full scale production– For example: which types of pumps, separators, heat

exchangers, mixers, dryers, etc. – Handling interruptions in production: emptying

reactors or tanks, cleaning, shut-down and start-up procedures

• When full-scale production is ongoing– Solve problems without interrupting production, take

the problems to the pilot machine

Further uses of pilot plant

• Check the product again! Demonstrations in lab and bench scale are not enough.– Food product: sensory, chemical, and microbiological

qualities; shelf-life; test marketing– Improvements in formulation and processing

• Note that the pilot results can discourage or prevent going to full scale– This is not a failure despite losses, this is part of the reasons

why pilot testing is done. The useful result is that a risk is avoided and the production plant will not be constructed, then failing with a large investment.

You simply can NOT

• Design a full-scale plant based on test tube experiments– The designer will not know what to do, without

some testing of alternatives– The risk of failure is too high, especially with the

big investment required: you can not get the money (by loaning or by selling shares)

Many decisions needed

• Mixing– Type of mixer, power or mixing speed used

• Heating or cooling– What rate of heating (cooling) is good or

desirable? – How long should we “hold” a high temperature?

• Each unit operation requires several choices– These can not be decided without pilot equipment

Full scale production decisions needed for design

• How much should be produced?– What is the market demand, what is the forecast for it?– The demand depends on price, and production costs

depend on amount produced… – What is availability of raw materials? Cost, supply,

price forecasts, … • Do we expect to increase production capacity?

Which effects of such increase need consideration in initial design?

What is down-scaling?

• The production process needs decisions– Troubleshooting: Solve problems that are causing

losses (poor quality, interruptions in production, …)– Improve productivity or product quality– Assess lower cost raw materials, additives,

consumables, unit operations• Some of this is fit for the pilot plant– Test new raw materials, test new mixer, heater,

sensor, or control system …

Down-scaling to bench scale• Benefits– Small material costs, while pilot would need tons of

raw materials– Can test conditions that are not possible with

process equipment (higher temperatures, pressures, …), or such that might damage the pilot machine

– Pilot is designed to be similar to actual production, just smaller. Bench scale should be designed to enable experiments, observations and measurements.

Bench-scale downsides

• Not similar to actual process operation– Often slower, smaller, batch instead of continuous– Results may not be correct– The decisions suggested by bench-scale need

checking in pilot scale, before going to production plant

Making paper (lab scale)

• You can make single sheets of paper in the lab with a “handsheet mold”

• It is just a standard size and shape gravity filtering device (small vacuum from water column)

Bench-scale papermaking

• Fiber suspension is sprayed inside a rotating drum onto a filter

• The water is centrifuged out

• Drum about similar size as in a washing machine

A pilot paper machine

A “real” paper machine

Goals for each• Real machine

– Designed to produce as quickly as possible product of sufficient quality, beat competitors on market

• Pilot– Help sell the real machine by demonstrating it to buyers, help

develop next real machine, troubleshoot production problems. Imitate several real designs when possible.

• Bench– Inspect one unit operation at a low cost for some decisions

about raw materials, additives, process parameters. Designed for experiments and observation. Duplicate key phenomena of real process, not the process itself.

• Lab– Nothing to do with the actual process. Demonstrate a

reaction, or a composite material, etc. Characterize raw materials and their quality variations or differences.

Scale-down

Scale-up

Summary• Scale-up– Moving from lower cost and smaller scale, to higher cost

and larger scale• Scale-down, opposite of scale-up– Most often about trouble-shooting or further

development of a large scale process that need experiments in smaller scale

– Sometimes scale-down of a product, in the extreme this is miniaturization• More customers for lower cost smaller size product• Drones vs. airplanes is one example