N. Nagle et al., A process economic approach to develop a dilute-acid cellulose hydrolysis process to produce ethanol from biomass, APPL BIOC B, 77-9, 1999, pp. 595-607
Successful deployment of a bioethanol process depends on the integration of
technologies that can be economically commercialized. Pretreatment and fer
mentation operations of the traditional enzymatic bioethanol-production pro
cess constitute the largest portion of the capital and operating costs. Cos
t reduction in these areas, through improved reactions and reduced capital,
will improve the economic feasibility of a large-scale plant.
A technoeconomic model was developed using the ASPEN Plus(TM) modeling soft
ware package. This model included a two-stage pretreatment operation with a
co-current first stage and countercurrent second stage, a lignin adsorptio
n unit, and a cofermentation unit. Data from kinetic modeling of the pretre
atment reactions, verified by bench-scale experiments, were used to create
the ASPEN Plus base model. Results from the initial pretreatment and fermen
tation yields of the two-stage system correlated well to the performance ta
rgets established by the model. The ASPEN Plus model determined mass and en
ergy-balance information, which was supplied to an economic module to deter
mine the required selling price of the ethanol. Several pretreatment proces
s variables such as glucose yield, liquid: solid ratio, additional pretreat
ment stages, and lignin adsorption were varied to determine which parameter
s had the greatest effect on the process economics. Optimized values for th
ese key variables became target values for the bench-scale research, either
to achieve or identify as potential obstacles in the future commercializat
ion process. Results from this modeling and experimentation sequence have l
ed to the design of an advanced two-stage engineering-scale reactor for a d
ilute-acid hydrolysis process.