Economic Feasibility Analyses 



3507 



STEAM 

 H2Q i 



H2SO4 

 WOOD ^ ~,V-i ► 



CHIPPER 



i f 



BOILER 



LIGNIN 



LIME 



HYDRO- 

 LYZER 



nil. 



t-Jj Hflash 



-WFILTER 



NEUTRALIZER 



EVAPORATOR 

 14- 



HOLD 



FILTER 



4.5% 



SUGAR 



SOLUTION 



C^ 



< STEAM 



15.9% SUGAR SOLUTION 



-► TO FERMENTATION 



STEAM 

 15.9 7o SUGAR ^ ^cv^ STERILIZATION 



r^ 



NUTRIENTS 



CO2 



FERMENTOR 

 AIR — 



fe 



DISTILLATION UNIT 



4.9% BEER 



HOLD 



i 



YEAST 

 RECOVERY 



rCENTRIFUGE 



YEAST 



STEAM 



-m 



6.5% 

 PENTOSE 



H2SO4 , 



STEAM 



95% ETHANOL 



•FURFURAL 



-►WASTE 



FURFURAL UNIT 



Figure 28-5. — (Top) Wood sugars production using dilute-acid hydrolysis. (Bottom) 

 Processing wood sugars to ethanol, yeast, and furfural. (Drawings after Karchesy 

 1981.) 



ethanol and pentose sugars are converted to furfural by acid catalyzed dehydra- 

 tion after ethanol recovery (fig. 28-5 bottom). Lignin residue from hydrolysis 

 and 36 percent of the wood feed are burned to meet process steam requirements. 

 Product yield per ton of hardwood chips is shown in figure 28-6. In order to 

 obtain a 30 percent pretax return on investment, it is found necessary to sell 

 ethanol produced for $6.87/gallon. Projected sale price of furfural is $0.55/ 

 pound and that of yeast $0.25/pound. 



