A two-stage heating process with low energy consumption for treatment of preliminary desalinated impregnation effluent to produce xylose

Abstract

Production of xylose from preliminary desalinated impregnation effluent (PDSIE) containing hemicellulose is an economical way of the effluent treatment. However, due to the high alkali and salt contents in PDSIE, its resource utilization is limited in the developed treatment process for pulp-impregnated effluent that has been deeply desalted. In this study, based on analysis of reaction rate and kinetic characteristics of pre-hydrolysis, a two-stage pre-hydrolysis heating process including heating at a high temperature for a short time followed by slow cooling to enzymatic hydrolysis temperature (HCP) with low energy consumption was developed for PDSIE. The heating time was shortened from 2 h to 0.5 h, the inhibition of conversion from hemicellulose to xylose by the high alkali and salt contents in PDSIE was alleviated, and the loss of xylose was reduced by HCP, compared to those under the constant temperature heating conditions. The heating cost based on coal consumption was reduced by 75.54% in HCP according to the preliminary economic analysis. Based on xylose yield and energy-saving results, the temperature in the first stage of HCP was determined to be 120 °C, and the cooling time in the second stage was determined to be 6 h.