Steam Generation for Distillation Process
The steam required for the distillation of cellulosic ethanol is generated in a boiler by burning solid biomass wastes. According to the NREL cellulosic ethanol process design technical report, extra steam generated in the boiler can be used to produce electricity using a turbogenerator [4]. This NREL technical report gives steam generation requirements and operating conditions for a corn stover cellulosic ethanol plant with a capacity of 2,205 dry US ton/day.
The purpose of the combustor, boiler, and turbogenerator subsystem is to burn various organic byproduct streams to produce steam and electricity. Combustible byproducts include all of the lignin and the unconverted cellulose and hemicellulose from the feedstock, biogas from anaerobic digestion, and biomass sludge from waste water treatment. Burning these byproduct streams to generate steam and electricity allows the plant to be self-sufficient in energy, reduces solid waste disposal costs, and generates additional revenue through sale of excess electricity.