Abstract
A coal-based coproduction process of liquefied natural gas (LNG) and methanol (CTLNG-M) is developed and key units are simulated in this paper. The goal is to find improvements of the low-earning coal to synthesis natural gas (CTSNG) process using the same raw material but producing a low-margin, single synthesis natural gas (SNG) product. In the CTLNG-M process, there are two innovative aspects. Firstly, the process can co-generate high value-added products of LNG and methanol, in which CH4 is separated from the syngas to obtain liquefied natural gas (LNG) through a cryogenic separation unit, while the remaining lean-methane syngas is then used for methanol synthesis. Secondly, CO2 separated from the acid gas removal unit is partially reused for methanol synthesis reaction, which consequently increases the carbon element utilization efficiency and reduces the CO2 emission. In this paper, the process is designed with the output products of 642,000 tons/a LNG and 1,367,800 tons/a methanol. The simulation results show that the CTLNG-M process can obtain a carbon utilization efficiency of 39.6%, bringing about a reduction of CO2 emission by 130,000 tons/a compared to the CTSNG process. However, the energy consumption of the new process is increased by 9.3% after detailed analysis of energy consumption. The results indicate that although electricity consumption is higher than that of the conventional CTSNG process, the new CTLNG-M process is still economically feasible. In terms of the economic benefits, the investment is remarkably decreased by 17.8% and an increase in internal rate of return (IRR) by 6% is also achieved, contrasting to the standalone CTSNG process. It is; therefore, considered as a feasible scheme for the efficient utilization of coal by Lurgi gasification technology and production planning for existing CTSNG plants.
Highlights
China is the main source of global energy growth as well as the largest energy consumer in the past 20 years [1]
The results indicate that electricity consumption is higher than that of the conventional conduct synthetic natural gas (CTSNG) process, the new CTLNG-M process is still economically feasible
In terms of the economic benefits, the investment is remarkably decreased by 17.8% and an increase in internal rate of return (IRR) by 6% is achieved, contrasting to the standalone CTSNG process
Summary
China is the main source of global energy growth as well as the largest energy consumer in the past 20 years [1]. In 2016, China’s natural gas production was 148.7 billion Nm3 , with a yearly rate increase of 8.5%. The total imports are 92 billion m3 , with an annual growth rate of 27.6%. The total yearly gas consumption is 237.3 billion m3 , which is 15.3% higher than that of. If keeping with the same growth rates, the natural gas will be in insufficient supply in the near future. To alleviate such an energy shortage, the Chinese government encourages the build and operate (B&O) development of coal to conduct synthetic natural gas (CTSNG) projects.
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