An energy-saving re-use strategy for the treatment of lignocellulosic biomass applied to the production of levulinc acid

Abstract

A strategy for the re-use of spent liquors during the batch dilute acid treatment of lignocellulosic biomass was evaluated as an alternative to reduce the consumption of water and energy. Using the same spent liquor in the successive treatments of new biomass portions, instead of using fresh liquor, implies the concentration of the hemicellulose-rich liquor. It was compared with the operation without re-use and its effect in the process economy was pointed out for a particular case study, namely, levulinic acid production from pine sawdust hemicellulose fraction. In the studied scheme, extractive-free pine sawdust was treated by dilute acid hydrolysis, and the resulting liquid is first concentrated and then sent to a catalytic reactor in which hemicelluloses are converted to levulinic acid. The effect of liquor re-use on the treatment performance was experimentally evaluated to consider its feasibility. Experimental results showed that the hydrolysis and decomposition rates and yields were only slightly affected by the liquor re-use. The techno-economic analysis showed that energy consumption can be reduced by 45% when the spent liquor is re-used twice, as compared with no re-use. The total energy requirement was covered by burning the residual solid; the production cost can be reduced by 78% when the spent liquor is re-used three times, as compared with no re-use. In these conditions, an internal rate of return of 19.5% was achieved for a production capacity of 156,000 t/year.