Abstract:

Production of SNG from a waste incineration power plant-power to gas hybrid system can reduce greenhouse gas emissions and storage renewable energy on a massive scale. However, an optimization of this process is still needed due to the low efficiencies of waste incineration power plants and poor waste heat utilization. In this paper, an integrated process was modeled by using Aspen Plus software. Based on energy balance analysis, an innovative way was proposed to improve the efficiency of a waste incineration power plant by recovering the methanation reaction heat. A two-stage methanation process was designed where an adiabatic fixed bed reactor and a low-temperature fluidized bed reactor connected in series. Energy recovered from the hot gas flow at the outlet of the fixed bed reactor was used to improve steam parameters and optimize the steam cycle, and the power generation efficiency was increased from 22.05% to 31.72%. The low-temperature fluidized bed reactor ensured the quality of synthetic natural gas. Moreover, the type of flue gas recirculation in the waste oxy-combustion process had an impact on the overall process efficiency. And the energy conversion efficiency was higher with dry flue gas recirculation. The above results have some guidance for improving process economy and competitiveness.

Key words: waste incineration power plant, power to gas, methanation, power generation efficiency

摘要：

垃圾焚烧发电耦合电转气技术制备合成天然气工艺可同时实现温室气体减排和大规模储能。由于垃圾发电效率低和甲烷化反应热利用效率不高，此工艺能效偏低。为了提升工艺能效，本文采用Aspen Plus软件对垃圾焚烧发电耦合电转气制备合成天然气过程进行了全流程模拟，基于能量平衡分析，提出了一种利用甲烷化反应热优化垃圾焚烧发电过程的工艺集成方法。针对这个优化过程，设计了一套由一级绝热固定床反应器和一级低温流化床反应器串联组成的甲烷化工艺。借助绝热固定床反应器出口高温气体提升主蒸汽参数、优化蒸汽循环过程，可将发电效率从22.05%提升至31.72%。流化床反应器低温操作有利于提升合成天然气品质，其内置换热管束作为补充蒸发受热面。此外，还考察了垃圾焚烧炉烟气再循环方式对整体工艺的影响，结果表明采用烟气干循环工艺时能效较高。以上结果对于提升工艺经济性和竞争力具有一定指导意义。

关键词: 垃圾焚烧发电, 电转气, 甲烷化, 发电效率