Pilot-Scale Continuous Conveyor Diffusion Extraction System for Sweet Sorghum

Abstract

The purpose of this paper is to present preliminary results from testing a pilot-scale sweet sorghum diffusion extractor that was designed to extract the juice from sweet sorghum stalks while simultaneously filtrating the extracted juice. The ultimate use of the juice is fuel grade ethanol. In essence, the system is a large coffee percolator that works by running shredded sorghum through a conveyor with recirculating hot water running over the crop to extract the sugar through diffusion. The current system spans 10 m in length, is 1m wide, and 0.6 m high. The sorghum is harvested with a forage chopper, and discharged at a constant rate into the trough. The sorghum moves at a rate of 0.2 m per minute, so the sorghum is in the diffusion system for 20 minutes. The water/juice is sprayed over the chopped stalks and is kept at a target temperature of 660C. A roller fixture located at the end of the trough helps squeeze out some of the remaining juice. The pilot scale sweet sorghum diffusion system continuously extracts the sugar at a rate of 3 metric tons (mt) of sorghum an hour with a minimum sugar extraction of 60%. During our pilot testing phase we were able to process 0.65 mt of material per hour with a resultant brix of 6%. The system was halted several times to adjust the heating system, so we are confident that with further testing we can process at least 3 mt per hour of material. The conversion from the conventional harvesting and roller press of the sorghum stalk to this method could resulted in a 66% reduction in energy to harvest and extract the juice.