Modeling of Two-Stage Coal Coprocessing Process

Abstract

Coal coprocessing can be done either in a single-stage or in a multistage process. It has been found that multistage processing offers some advantages over single-stage processing. In this study, a two-stage process was selected for coal liquefaction. In the first stage (solvent production stage), the waste materials were liquefied at milder conditions to obtain a suitable solvent for the coal liquefaction. In the second stage, the liquid product obtained from the first stage was used as solvent for coal. The two-stage liquefaction process was carried out in the absence of externally added catalysts. The reactions were carried out in a tubing bomb microreactor at temperatures of 350−450 °C and 1250 psig of cold hydrogen pressure for reaction times of 15−120 min at 10% coal loading. Total conversion, and conversion to asphaltenes, oils, etc., were monitored. A model for coal liquefaction has been developed as part of this study. A rigorous parameter estimation method was used to estimate the model parameters. The predictions for the coal conversions were found to be within ±3% of the observed values. Total conversion as high as 99% and oil conversion up to 90% were obtained in two-stage processing. Two-stage processing leads to higher coal conversion and oil yield compared to single-stage processing. The model parameters for the single-stage and two-stage processes were compared.