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Simulation and economic analysis of indirect coal-to-liquid technology coupling CCS Li Zhou, Wenying Chen, Xiliang Zhang, and Tianyu Qi Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie301748m • Publication Date (Web): 18 Jun 2013 Downloaded from http://pubs.acs.org on June 19, 2013
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Industrial & Engineering Chemistry Research
Simulation and economic analysis of indirect coal-to-liquid technology coupling CCS Li ZHOU*, Wen-Ying CHEN, Xi-Liang ZHANG, Tian-Yu QI Institute of Energy, Environment and Economy, Tsinghua University, Beijing 100084, China Abstract Because the liquid fuel market in China is growing rapidly compared to the capacity for liquid fuel production, interest of coal-to-liquid technology is growing for producing liquid fuel. Several processes have not yet been industrialized. Among these, the Fischer-Tropsch (FT) process for fuel production from coal was chosen for simulation and analysis. We consider carbon capture and storage (CCS) technology because of the importance of CO2 emissions in climate change. Systems with and without CCS coupling were simulated using Aspen Plus software. We used the simulation results to estimate costs, investment per unit of product, net present value, internal rate of return, and the static investment recovery period as economic indicators. The economic benefits of CCS technology were estimated in terms of CO2 emission reductions cost and the cost for CO2 capture. We also performed a price sensitivity analysis. The results reveal that CCS coupling to indirect coal liquefaction is economically feasible. With the pressure to limit CO2 emissions, CCS coupling systems for FT fuel production are expected to be competitive. Keywords: coal to liquid; carbon capture and storage; economic analysis Corresponding author. Tel.: +86-10-62784829; Fax: +86-10-62772759. E-mail:
[email protected] 1. Introduction Although petroleum and natural gas production has recently increased, the energy resource structure for China still involves plentiful coal, inadequate oil, and less gas. The pattern in which coal is the main energy source remains unchanged. At present, discovered coal reserves can be exploited for hundreds of years; more than 1000 billion tons of coal resources are reserved for future exploration and development. These plentiful coal reserves provide powerful assurance of sufficient energy resources for economic and industrial development in China. With the increase in energy demands, petroleum consumption has increased accordingly and China is now the second largest petroleum consumer in the world after the USA, and the main petroleum-importing country. Predicted data indicate that the Chinese dependence on petroleum imports is expected to increase further[1]. The country’s position as an oil consumer, as well as its national and economic security, is confronted with great challenges, considering the recent discoveries of shale gas. One of the important responses to the crisis lies in establishing a multi-source and diversified petroleum supply system, excellent implementation of a coal-to-liquid (CTL) strategy, and positive development of a crude oil substitute. CTL could be a clean coal utilization technology in which coal is processed to produce various oil and other petrochemical products, such as diesel oil, gasoline, and aviation kerosene, if it is well implemented. This strategy represents an intelligent choice for resolving the petroleum security problem in China. It is also considered one of
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possible decisions in strategic adjustments of the energy supply structure. However, one major problem facing the CTL industry is serious environmental pollution, in particular CO2 emissions. How to assure sufficient CO2 emission reductions for coal utilization in a low-carbon economy is an important issue regarding the development of CTL technology. CCS technology could be an important choice for future clean energy production and climate change alleviation. Therefore, CTL coupled to CCS technology is an obvious choice to assure economic benefits as a petroleum substitute and reduce CO2 emissions. China has resource strengths and research and development abilities in the CTL field. Therefore, research into the feasibility and economics of different CTL and CCS combinations has both theoretical value and important practical significance. CTL technology is divided into two methods: indirect liquefaction by coal gasification and direct liquefaction. Here we discuss the feasibility and economic benefits of indirect coal liquefaction coupled to CCS technology. Figures 1 and 2 show the two possibilities for indirect coal liquefaction: once-through synthesis of syngas; and recycled synthesis of unreacted syngas. Each route can be considered with and without coupling to CCS technology. Several processes have not been industrialized yet, so it is necessary to perform simulations, especially for coal gasification and other processes, to assess FT fuel, methanol and dimethyl ether as replacements for traditional liquid fuel. Here we focus on FT production of fuel from coal.
Fig. 1 Indirect liquefaction via once-through synthesis. The broken lines denote the option with or without CCS technology.
Fig. 2 Indirect liquefaction via recycled synthesis. The broken lines denote the option with or without CCS technology.
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Industrial & Engineering Chemistry Research
2 Modular flowchart and simulation The technical route considered here has not been industrialized yet so we could not obtain relevant details. Therefore, it was necessary to obtain data through software simulation. We chose Aspen Plus for our study[2,3,4]. All the systems are divided into subsystems that include the air separation unit (ASU), gasification, the water gas shift (WGS), syngas cleaning, synthesis and distillation, flue-gas cleaning, and power generation. For each unit, different commercial or advanced technologies are discussed, compared, and selected. The models for each part are semi-mechanistic and based on selected technologies. For validation, the simulation data need to be compared with literature data. The relative error for each parameter should be
