life cycle assessment of energy consumption and GHG emissions of olefins production from alternative resources in China

Significance Statement

Olefins are generally produced by naphtha cracking process. However, the fossil energy reserves of China are characterized by richness in coal, while scarcity in oil and natural gas. Many studies focus on developing alternative olefins production technology. The representatives of them are UOP/Hydro MTO, DMTO developed by Dalian Institute of Chemical Physics of Chinese Academy of Science, SMTO by Sinopec, Lurgi MTP, and FMTP by Tsinghua University. A coal-to-olefins (CTO) plant based on the technology was built by Shenhua Group of China and successfully put into commercial production on January 2011. However, the research on process modeling, techno-economic and environmental performance analysis of the olefins production is relative scarce. Therefore, our group employed multi-disciplinary knowledge to establish models of olefins production processes, conduct techno-economic analysis and life cycle assessment for policy making. In this paper, life cycle assessment methodology is used to analyse advantages and disadvantages of alternative olefins production. Results show that the life cycle performance of the natural gas based methanol-to-olefins is roughly equivalent to those of the oil-to-olefins (OTO). While the CTO process suffers from serious GHG emissions. Our studies also propose several concept designs of coal and natural gas-to-olefins, and coal and coke-oven gas-to-olefins, CTO with CO2 capture for improving energy efficiency and decreasing GHG emissions of conventional CTO process. These studies have been published on some famous international journal, i.e. Applied Energy, Industrial & Engineering Chemistry Research, Chemical Engineering Journal, Energy Conversion and Management, and Computers & Chemical Engineering, et al, as showing in the following references. The two co-feed systems ensure great reduction of CO2 emissions and significant improving energy efficiency. They should be actively developed in regions with rich coal and gas. The effect of carbon capture on life cycle performance of alternative olefins production is investigated. The development of CTO with moderate carbon capture should be vigorously encouraged. However, emissions from upstream industries account for about 50% GHG emissions of the CTO. The huge upstream emissions could not be reduced by CCS of the CTO system. Therefore, upstream emissions should be monitored and strictly reduced to contribute to an equivalent GHG emissions of the CTO with the OTO. The framework for life cycle assessment involves determining the overall objectives and boundaries of olefins production, collecting energy consumption data and GHG emissions factors, calculating life cycle energy consumption and GHG emissions, evaluating each route to support policy making of olefins production pathways, and proposing several suggestions for energy conservation and GHG emissions reduction of the CTO process.

Our recent related works

  1. Yang SY; Yang QC, Man Y, Xiang D, Qian Y, Conceptual design and analysis of a nature gas assisted coal-to-olefins process for CO2 Ind. Eng. Chem. Res., 2013, 52: 14406-14414.
  2. Qian Y, Yang SY, Jia XP, Li XX, Li HC. Life cycle assessment and sustainability of energy and chemical processes. CIESC J., 2013, 64(1): 133-147 (in Chinese).
  3. Xiang D, Peng LJ, Yang SY, Qian Y. A review of oil-based and coal-based processes for olefins production. Ind. End. Prog., 2013, 32 (5): 959-970 (in Chinese).
  4. Xiang D, Qian Y, Man Y, Yang SY. Techno-economic analysis of the coal-to-olefins process in comparison with the oil-to-olefins process. Applied Energy, 2014, 113: 639-647.
  5. Xiang D, Liu X, Mai ZH, Yang SY, Qian Y. Techno-economic performance of the coal-to-olefins process with CCS. Eng. J., 2014, 240: 45-54.
  6. Man Y, Yang SY, Zhang J, Qian Y. Conceptual design of coke-oven gas assisted coal to olefins process for high energy efficiency and low CO2 Appl. energy, 2014, 133: 197-205.
  7. Xiang D, Yang SY, Li XX, Qian Y. Life cycle energy consumption and GHG emissions of olefins production from alternative resources in China. Energy Convers. Manage., 2015, 90: 12-20.
  8. Qian Y, Man Y, Peng LJ, Zhou HR, An integrated process of coke oven gas reforming and coal gasification to methanol with better carbon utilization, Eng. Chem. Res., 2015, 54, 2519-2525.
  9. Xiang D, Yang SY, Mai ZH, Qian Y, Comparative study of coal, natural gas, and coke-oven gas based methanol to olefins processes in China, Chem. Eng., 2015. DOI

life cycle assessment of energy consumption and GHG emissions of olefins production from alternative resources in China. Renewable Energy Global Innovations

Journal Reference

Dong Xiang1, Siyu Yang1, Xiuxi Li1, Yu Qian1, 2. Energy Conversion and Management.Volume 90, 2015, Pages 12–20.

Show Affiliations

1 School of Chemical Engineering, South China University of Technology, Guangzhou 510640, PR China.

2 State Key Lab for Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, PR China. 

 

Abstract

Olefins are important platform chemicals widely used in industry. In terms of the short supply of oil resources, natural gas and coal are two significant alternative feedstocks. In this paper, energy consumption and GHG emissions of olefins production are analysed with life cycle assessment methods. Results showed the energy consumption and GHG emissions of natural gas-to-olefins are roughly equivalent to those of oil-to-olefins, while coal-to-olefins suffers from higher energy consumption and serious GHG emissions, including 5793 kg eq. CO2/t olefins of direct emissions and 5714 kg eq. CO2/t olefins of indirect emissions. To address the problem, the effect of carbon capture on coal-to-olefins is investigated. In comprehensive consideration of energy utilization, environmental impact, and economic benefit, the coal-to-olefins with 80% CO2 capture of the direct emissions is found to be an appropriate choice. With this carbon capture configuration, the direct emissions of the coal-to-olefins are reduced to 1161 kg eq. CO2/t olefins. However, the indirect emissions are still not captured, which should be strictly monitored and significantly reduced. Finally, a scenario analysis is conducted to estimate resource utilization and GHG emissions of olefins production of China in 2020. Several suggestions are also proposed for policy making on the sustainable development of olefins industry.

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