基于CO_(2)减排重塑合成氨工艺流程方案研究

Research on reshaping the synthetic ammonia process plan based on carbon dioxide emission reduction

本文针对传统合成氨工艺存在物耗、能耗较高、污染严重及CO_(2)排放量高的问题,将CH_(4)干重整(DRM)、水煤气变换(WGS)、CO_(2)甲烷化(MCD)、CH_(4)部分氧化(POM)过程与传统合成氨过程进行有机耦合,以改善现有合成氨的工艺面貌,并借助流程模拟手段对设计的耦合工艺进行初步研究与分析,探索碳中和发展背景下重塑合成氨工艺的可能性。本文按照“降低CO_(2)排放-降低废水排放及新鲜水用量-降低天然气消耗-降低能耗”的思路演变构建合成氨耦合工艺方案,依次形成DRM-SynNH_(3)、“DRM+WGS”-SynNH_(3)、“DRM+WGS+MCD”-SynNH_(3)、“POM+WGS+MCD”-SynNH_(3)四个耦合工艺,研究结果表明:CO产品、合成气产品的获取均来源于CH_(4)的消耗,故各方案的天然气消耗量均相对较高;当耦合体系要消纳外界CO_(2)时,由于DRM与MCD本身较强的热效应导致二者单独或同时存在时,任何一种合成氨耦合工艺的能耗均不会低于传统工艺。但未来随着催化剂的研发与应用进展,DRM与MCD可能实现质量、能量的高效双重耦合,从而将大幅降低物耗与能耗。然而,如综合考虑CO_(2)消纳效应、CO_(2)减排效果以及合成气等化工产品的联产所带来的综合效益,尤其在未来碳指标稀缺、碳税高企情形下,上述工艺均可能具备一定竞争力。

This work focuses on the issues of high feed consumption,high energy consumption,severe pollution,and high carbon dioxide emissions in traditional ammonia synthesis processes.The processes of dry reforming of methane(DRM),water gas shift(WGS),methanation of carbon dioxide(MCD),and partial oxidation of methane(POM)are organically coupled with traditional ammonia synthesis processes to improve the appearance of existing ammonia synthesis process.Preliminary research and analysis of the designed coupling processes are carried out by using process simulation method in order to explore the possibility of reshaping the synthetic ammonia process in the context of carbon neutrality development.This work evolves to construct the coupling process for synthetic ammonia based on the idea of"reducing CO_(2)emissions-reducing wastewater emissions and fresh water usage-reducing natural gas consumption-reducing energy consumption",and sequentially forms four coupling processes,that is DRM-SynNH_(3),"DRM+WGS"-SynNH_(3),"DRM+WGS+MCD"-SynNH_(3),and"POM+WGS+MCD"-SynNH_(3).The research results indicate that the acquisition of CO and synthetic gas products all come from the consumption of methane,so the natural gas consumption of each scheme is inevitable relatively high.When the coupling system needs to consume external CO_(2),due to the strong thermal effect of DRM and MCD reaction systems,the energy consumption of coupling process will not be lower than that of traditional schemes,when DRM and MCD exist alone or simultaneously.But in the future,with the development and application of catalysts,DRM and MCD may achieve efficient dual coupling by mass and energy,which will significantly reduce feed and energy consumption.However,when considering the CO_(2)consumption effect,CO_(2)emission reduction effect,and the comprehensive benefits brought by the co production of chemical products such as synthetic gas,especially in the future where carbon emissions indexes are scarce and carbon taxes are high,the above processes may have certain competitiveness.