Fluid Bed Dryer and Ethanol Content

We are having trouble getting the ethanol in our product. We use etbanol, api and povidone as granulating solution. After we used a new starch batch, final product after test failed ethanol content 5000 ppm. And others have high ethanol content. Our product seems to be normal endpoint is 28 deg exhaust temp. We have a chiller to control humidity. What can we do to improve? Is the starch contributing to the problem

It is more likely your analytical method! Ethanol will be absorbed by the starch. Thus, you will need a distillation or head-space (GC-HS) step in your analytical method.

Yes we used a head space gc to test. We dried the product to dryness that was validated. We run 65 batches. Then we changed lot of starch. Looks like the new starch has more than 1% moisture compared than the previous. But does the ethanol is trapped in the granules? Even if we dry for three hours and the exhaust temp is reached and not changing still the product ethanol content is 4000 to 5000 ppm. On the high limit. Granule moisture endpoint with moisture analysis between 5% and 3.5% then we stop drying and mill the product

Try raising the temperature in your head space analyzer. Ethanol will cause the starch to swell when it is absorbed. Water in the starch used to do this. You may have to reformulate for this dried starch by adding water to your mix before drying.

What is your milling or drying temperature?

Fbd drying temp is 35deg. Milling is done twice at ambient temp. Then the 2 parts of batch are combined in the blender and mixed. The final product then is tested for ethanol.

When you say absorb by starch, you mean the ethanol molecule are getting in the molecule of water in the moisture? Or just adsorbed as in the surface.

Will try to inc temp for headspace


A starch particle actually will swell as it absorbs water. Instead of water it would use Ethanol. No chemical reaction occurs. Remember, many chemicals occur as hydrates in nature. Thus, only a sample in an oven at 105 Celcius overnight will have this bond broken. Ethanol may form a similar bond and require a higher temperature (less than 105C) in order to be released.

Interesting. Thanks.