Comparative analysis of the consumption of energy of two wood pulping processes

Equations are presented for the cumulative energy analysis of a process wit h numerous recycle streams and multiple products. The equations enable a qu antitative assessment for alternative processes in the production of a part icular product. This method was applied to the production of chemical pulp from wood by the Kraft process and a proposed alcohol extraction process. T he Kraft process was found to be superior to the alcohol extraction process in terms of specific cumulative energy consumption for the production of c hemical pulp (50% consistency) as the only useful product: 14.5 vs. 19.9 MJ /kg. However, if by products of the alcohol extraction process are consider ed as useful products, the specific cumulative energy consumption of the ch emical pulp is reduced to 12.3 MJ/kg, which is below that of the Kraft proc ess. Cogeneration of steam and electricity decreases the specific energy co nsumption for pulp production significantly for both processes. Various cog eneration strategies will be presented for the two processes. (C) 2000 Else vier Science Ltd. All rights reserved.