What air flow is best for drying pellets in a kiln?

Question

I have built a kiln which will hold around 1 cubic metre of sheep manure pellets I have extruded. The kiln is similar in design to those used to dry malt in a malthouse. The air is heated and then forced through the product from below. Will the pellets dry faster with very hot air at a low volume or with air not as hot but with a greatly increased air flow? In a Malthouse, the stack valve closes as does the draught door to recirculate hot air to the kiln, where does the moisure escape to in a closed circuit like this? As yet I have not fabricated a stack valve or a draught door as I am not sure if there would be a need for these in order to dry manure down to 15% moisture or less. This is only a hobby of mine not a commercial enterprise.

Answer 1

IT is best to dry extruded pellets slowly. Too rapid a drying leads to a skin formation that will reduce diffusion of moisture from the centre of the pellet to the outside. Vapour pressure inside increases leading to cracks.

In bulk production a multistage belt dryer with humidity control is used. If yours is not a commercial venture and the rate of production small, a good alternative can be solar drying. You can make a low cost solar dryer using UV stabilized polyethylene film. The pellets being dark in colour will absorb solar energy directly without any need for a collector.

http://solarcooking.org/drying/Whitfield...

http://www.epsea.org/dry.html

http://www.areed.org/training/technology...

http://practicalactionconsulting.org/doc...

http://www.knowledgehound.com/topics/sol...