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Fossil Fuels
Effect of Carbonization Temperature on the Product Distributions and Characteristics for Integrated Mild Liquefaction and Carbonization of Low Rank Coals Sheng Huang, Xuhui Zhou, Shiyong Wu, Youqing Wu, and Jinsheng Gao Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b04142 • Publication Date (Web): 27 Mar 2018 Downloaded from http://pubs.acs.org on March 27, 2018
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Energy & Fuels
Effect of Carbonization Temperature on the Product Distributions and Characteristics for Integrated Mild Liquefaction and Carbonization of Low Rank Coals Sheng Huang†,‡, Xuhui Zhou†, Shiyong Wu*,†,‡, Youqing Wu*,†,‡, Jinsheng Gao†,‡ †
Department of Chemical Engineering for Energy Resources, East China University of Science and
Technology, Shanghai 200237, China ‡
Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education,
East China University of Science and Technology, Shanghai 200237, China ABSTRACT: In order to realize the efficient conversion of low rank coals, an integrated mild liquefaction and carbonization (IMLC) technology was proposed, and the effect of carbonization temperature (CT) on the product distributions and characteristics from the simulated IMLC technology was investigated. Results show that about 30.34-40.02% of liquid products (LPs) and 40.64-56.25% of semi-cokes (SCs) can be obtained from the IMLC process at the CT of 410-600 ℃. The adopted carbonization process is an effective measure to separate the solid and liquid products from coal liquefaction process, and the obtained SCs contain no n-hexane soluble fractions (HSs). The LPs present a quite high HS content (82.20-90.80%) and a small quantity of asphaltenes (ASs) and preasphaltenes (PAs), and the HSs are predominantly abundant with aliphatics, alkyl benzenes and alkyl naphthalenes, indicating that the LPs are potentially suitable for utilization to produce liquid fuels by further refining. The obtained SCs could be used as a binder to reduce the use of high-coking coals in the coke-making of coal blends or as fuel of boiler to substitute for anthracite, depending on the conditions of the carbonization process. The proposed IMLC process could realize the economic and efficient conversion of low-rank coals into LPs and SCs under mild conditions.
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1. INTRODUCTION Low-rank coals (included lignite and sub-bituminous coal) are abundant fossil resources, which account for 50% of the global total coal reserves.1-3 With high volatile content which are abundant in aliphatic -C-O- and -C-C- structures, low-rank coals present high reactivity during the thermo-chemical conversions. However, high water and oxygen contents and low calorific value severely limit low-rank coals application in traditional utilization technologies, such as combustion and gasification.3-5 In light of this, more attention has been paid to develop a reasonable method for the efficient utilization of low-rank coals. Direct coal liquefaction (DCL) technology, which have been available since the first half of the last century, is regarded as one of the feasible technologies which can realize the efficient conversion of low rank coals.6-10 In order to obtain high oil yield and coal conversion, severe liquefaction conditions are generally required that included high temperature (440-470 °C), high pressure (17-30 MPa), good hydrogen donor solvent, and effective hydrogenation catalyst for the traditional liquefaction technologies, such as NEDOL, IGOR, and Shenhua technologies. However, the traditional DCL technologies possess the disadvantages of high requirement of installation, high capital and operating cost, and high H2 consumption due to severe liquefaction conditions.8-12 Therefore, the severe liquefaction conditions make the liquid fuels from DCL economically uncompetitive compared with crude oil.11,12 Besides, the residues from traditional coal liquefaction (DCLR) processes present the characteristics of high ash and sulfur contents and low organic matter content due to the fully conversion of organic matter in coal during the severe liquefaction process, leading to the obtained DCLR are mainly used as inferior fuels for gasification or combustion.13-18 The high-value utilization of DCLR is an important goal in helping to make the coal liquefaction technology both commercially viable and environmentally acceptable. Furthermore, about 30-50%
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Energy & Fuels
heavy liquids, which are composed of oils, asphaltenes, and preasphaltenes, was retained in the DCLR for the convenient discharge from the system, leading to the relatively low oil yield of the traditional liquefaction processes.13-20 Therefore, it is necessary to develop an efficient coal liquefaction technology for low rank coals conversion. In view of the characteristics of low-rank coal, a novel coal liquefaction technology, integrated mild liquefaction and carbonization (IMLC) technology, was proposed and patented.21 Figure 1 displays the schematic diagram of the proposed IMLC technology. The main characteristics of the proposed technology is as follows. The mild hydroliquefaction conditions with relatively low liquefaction temperature (≤430 ℃) and pressure (
