Biomass Integrated Gasification Combined Cycle Systems at Corn Ethanol Plants

Abstract

Biomass Integrated Gasification Combined Cycle (BIGCC) systems were employed to provide heat and electricity to a 190 million liter (50 million gallon) per year corn ethanol plant using co-products and biomass residues as fuels. Different fuel combinations (corn stover and syrup, and corn stover alone) and fuel input rates (105 to 120 MW) were simulated using Aspen Plus software. Also, the effect of two levels of synthesis gas pressure for the gas turbine (10 bar with 2 stage compression, and 20 bar with 3 stage compression) was studied. A fuel input rate of 110 MW (10 bar with 2 stage compression and 20 bar with 3 stage compression) met heat and power needs of the ethanol plant, and provided approximately 23 to 25 MW electricity to the grid. The system thermal efficiencies ranged from 71 to 73%, and power generation efficiency ranged from 29 to 31%. The above systems used steam tube dryers for drying ethanol co-products and fuel. We also studied the impact of substituting a superheated steam dryer for a steam tube dryer. Compared to the steam tube dryer, the superheated steam dryer reduced the heat demand for drying and allowed recovery of the water removed in drying, which reduced the water requirement for the ethanol process. However, including the superheated steam dryer in the BIGCC-ethanol system also reduced the amount of electricity that could be generated and sent to the grid because total process steam requirements were reduced and BIGCC gas compression power requirements were increased.