Abstract
Hydro-conversion of coal hydroliquefaction residue obtained from a 6t/day pilot plant of Shenhua Group in Shanghai was carried out under the hydrotreating condition. The coal hydroliquefaction residue and its product were extracted in sequence with n-hexane, toluene and tetrahydrofuran in a Soxhlet apparatus. The n-hexane soluble fractions increased with the increase of reaction temperature and time. Its amount increased from 14.14% to a maximum of 40.86% under the conditions of 470 °C and 30 min, which meant that moderate extension of coal residence time in the coal hydroliquefaction reactor is beneficial to the increase of oil yield. A 4-lumped kinetic model of coal hydroliquefaction residue hydro-conversion was performed using solubility-based lumped fractions. In the model, the tetrahydrofuran insoluble fractions were classified into two parts: easily reactive part and unreactive part. The kinetic parameters were estimated by a fourth-order Runge-Kutta method and a nonlinear least squares method, and the apparent activation energies were calculated according to the Arrhenius Equation. A large quantity of total catalyst consisting of remained liquefaction catalyst, part of the mineral from raw coal and additive Fe-based catalyst could considerably reduce the apparent activation energy of hydro-conversion for the toluene insoluble/tetrahydrofuran insoluble fractions to 36.79 kJ•mol-1. The calculated values of the model coincided well with the experimental values.
Highlights
Due to the growing global energy demand and rising oil prices, coal hydroliquefaction (CHL) as a kind of clean coal technology which could replace crude oil imports by converting coal to liquids, has attracted increasing interest around the world, especially in China
In order to figure out the possibilities and advantages of recycled coal hydroliquefaction residues (CHLR) as a co-reactant in CHL, the hydro-conversion behavior of CHLR was studied under moderate hydrotreating conditions and a kinetic model of this process was proposed using a 4-lumped kinetic model, considering the similarities and dissimilarities between CHL and CHLR hydro-conversion
The composition of the CHLR sample obtained by the sequential extraction is 14.14% n-hexane soluble fraction (HS), 35.00% n-hexane insoluble/toluene soluble fractions (A), 14.63% toluene insoluble/tetrahydrofuran soluble fractions (PA) and 36.23% tetrahydrofuran insoluble fraction (THFIS)
Summary
Due to the growing global energy demand and rising oil prices, coal hydroliquefaction (CHL) as a kind of clean coal technology which could replace crude oil imports by converting coal to liquids, has attracted increasing interest around the world, especially in China. Coal hydroliquefaction residues (CHLR), a by-product, usually account for 20%–30%, while the oil is just about 55% in a typical product distribution. The minerals from raw coal and the catalyst used in the hydroliquefaction process with their large content in inorganic matter are beneficial for optimizing. CHL technology if CHLR is recycled as a CHL co-reactant, so it is absolutely necessary to study the liquefaction behavior of CHLR and its kinetics before designing any CHLR recycle process. In order to figure out the possibilities and advantages of recycled CHLR as a co-reactant in CHL, the hydro-conversion behavior of CHLR was studied under moderate hydrotreating conditions and a kinetic model of this process was proposed using a 4-lumped kinetic model, considering the similarities and dissimilarities between CHL and CHLR hydro-conversion
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