CIESC Journal ›› 2020, Vol. 71 ›› Issue (12): 5754-5762.DOI: 10.11949/0438-1157.20200360

• Energy and environmental engineering • Previous Articles     Next Articles

Energy efficiency analysis of natural gas hydrates production method

WANG Xiaohui(),XU Qiang,ZHENG Huaxing,SUN Changyu,CHEN Guangjin()   

  1. State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China
  • Received:2020-04-07 Revised:2020-06-22 Online:2020-12-05 Published:2020-12-05
  • Contact: CHEN Guangjin

天然气水合物置换开采的能源效率研究

王晓辉(),许强,郑华星,孙长宇,陈光进()   

  1. 中国石油大学(北京)重质油国家重点实验室,北京 102249
  • 通讯作者: 陈光进
  • 作者简介:王晓辉(1987—),男,博士,讲师,xh.wang@cup.edu.cn
  • 基金资助:
    国家自然科学基金项目(21908243);中国石油大学(北京)科研基金项目(2462018YJRC010)

Abstract:

The decomposition of natural gas hydrates is a phase change process, which involves the consumption and conversion of various forms of energy, such as electrical energy, chemical energy, and thermal energy. In order to evaluate the economy capacity of natural gas hydrates exploitation, an exergy model was established to calculate the energy efficiency ratio (EER) of hydrate production method. The CO2 replacement method is taken as a case study to introduce the calculation equation and flow chart of energy efficiency ratio in any production period. The amount of CO2 injection, gas production and mole fraction of methane in produced gas are three key parameters in the process of CO2 replacement. The ratio between the amount of gas production and CO2 injection is defined as production injection ratio to eliminate the influence of deposit size. This work studied the influence of production injection ratio and the mole fraction of methane in produced gas on EER. The results show that the EER of gas hydrates production by CO2 replacement is between 0.31 and 6.4 under the set conditions, and it increases with the increase of production injection ratio. In addition, increasing the mole fraction of methane in produced gas can reduce the energy consumption for gas separation and increase EER. Therefore, there are two effective ways to increase EER of CO2 replacement through controlling the amount of gas production and the mole fraction of methane in produced gas. The EER model is established to provide guidance for the optimization of gas hydrate mining process.

Key words: hydrate, production, energy efficiency, exergy, model, CO2 replacement

摘要:

天然气水合物分解是一个相变过程,开采时涉及各种形式能量的消耗和转化,如电能、化学能、热能等。为了科学地评价天然气水合物开采技术的经济性,建立了以有效能()为核心的能源效率计算方程,并以CO2置换法开采天然气水合物为例,介绍任意生产周期内能源效率的计算方法和流程框图。在CO2置换开采天然气水合物的工艺过程中,注气量、产气量和产气中甲烷含量是三个关键参数,将产气量与注气量之比定义为采注比,分析采注比及产气中甲烷含量对能源效率的影响。结果表明:在设定条件下CO2置换开采天然气水合物的整体能源效率介于0.31~6.4之间;增大采注比,有利于提高能源效率;产气中甲烷的摩尔分率越高,气体分离的能耗越低,能源效率也可显著提高。因此,调控产气量和产气中甲烷摩尔分率是提高CO2置换法能源效率的主要途径。通过所建立的能效计算方程为天然气水合物开采工艺的优化提供指导。

关键词: 水合物, 生产, 能源效率, 模型, CO2置换

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