Scale-up

4. Scale-Up Procedure

Now that you have calculated the raw materials, product output, and operating costs of the lab fermentor, you need to scale up these values and calculate their costs in the large manufacturing process. Not only that, but you must determine the capital costs of the process. This will let you know how economically feasible the process is.

How many fermentors do we need to reach our goal? How many batches would each of these fermentors need to make?

It's not a cut and dry solution. The basic procedure is to pick a volume for the fermentor (that is proportional in dimensions and operation to the lab fermentor). Then, calculate the income of ethanol this size fermentor produces, the raw material costs, and operating costs. This is to be done until the ethanol produced satisfies the objective we defined Step 1.

The Iterative Procedure:

1. Pick a volume from 500 - 1000 cu. meters.

2. Using this volume, calculate:

The amount of ethanol made in one year by one reactor.
The raw material, operating costs, and capital costs at this volume. Click here for instructions on scaled-up operating cost and capital cost calculations.

If not enough ethanol is produced to meet our goal or if the cost of making ethanol is greater than its present price per gallon, then calculate how many reactors of that volume working in the same time sequence will yield the adequate result.

If it takes more than five reactors (more than that is unreasonable) or if it is still too expensive to make the ethanol, go to Step 1 and choose a larger volume Then, repeat Step 2.

3. If still not enough ethanol can be made or if it is too expensive to produce, then this means that another production method using fermentation must be explored.

IMPORTANT NOTE: We highly suggest you try to run this iteration on a spreadsheet like MS Excel or Lotus 1-2-3. Make a spreadsheet that does the calculations based on the vaolume that you choose. In that way you'll only have to look at the results of the calculations when you do the iterations. You could also write a computer program to determine the feasibility of the process, but that would take much longer because of compiling times.

Check your answers by clicking here

When you have determined the feasibility of the batch process, click here to follow the steps for designing a continuous process.

Homepage by Charles P. Armesto, MIT Chem Eng '97
Graphics by CyclopsX Inc.