Rights: The University of Waikato Published 1 February 2007 Download

Scientists at Plant & Food Research have to consider all sorts of problems with scale and quantity when shifting processing of a vegetable material from the laboratory bench to the production plant. What problems have they faced? Why can't they just use a big sieve?


Rebecca Abbot, Plant & Food Research When scaling up vegetable flour production from laboratory scale to pilot scale, there are a few things that we need to look at. For example, the equipment we use in the laboratory tends to have much higher specifications than equipment that we can use in the pilot plant or the production facility.

You need to look at things like how the material will handle in the plant, so the pumping of it, and whether you need to dilute the extraction mix. You also need to look at the centrifugation. The centrifuges in the lab can pull much higher RPMs [revolutions per minute] than in the plant.

Lyall Simmons, Plant & Food Research Scaling-up presents quite a number of difficulties. It is often difficult to reproduce precisely the process mechanically that you can easily achieve by hand or on a small scale.

We have encountered difficulties in making sure that the filtration system, or the sieving system, is exactly matched. We have had some difficulties in reproducing that on a large scale. For example, sieving material in the lab is simple and straight forward, but we have had problems with the trommel washer that we use to do that on a large scale. The action isn't precisely identical.

Why can't we use a big sieve? Part of it is economics. It is much easier to use existing machinery, and adapt it for use rather than build machinery at reasonably high expense to exactly recreate an action.

Rebecca Abbot, Plant & Food Research The problems we’ve faced with the processing of the particular raw material that I have been looking at is that the extraction mix that we have used in the laboratory has been far too thick to be used in the plant. So we have had to dilute that quite significantly, which if course has implications on cost because you've then got to get rid of the water.

Lyall Simmons, Plant & Food Research Economics is an important factor in scaling up.

Rebecca Abbot, Plant & Food ResearchTo decide whether a process is cost efficient for large scale production, we need to look at firstly a pilot run. From that pilot run we get some information about how it behaves and what sort of cost we are looking at for things like utilities - steam, water, and power. We also look at equipment costs at that point.

The other big one is the cost of waste, so whatever waste streams you have got that has been treated before it can be released into any waterways. And that can be a significant cost.