我国华东地区污染土壤异位热脱附修复碳排放及减排策略

Carbon emissions and emission reduction strategy for remediation of contaminated soil by ex-situ thermal desorption in East China

为探索我国污染土壤异位热脱附修复的碳减排路径,采用生命周期评价方法理论,确定污染土壤异位热脱附修复碳排放核算系统边界和清单。将异位热脱附修复划分为土壤开挖、运输、预处理、主处理、尾气处理、最终处置6个过程,基于华东区域5个典型工程的能源及物料调研数据,核算了异位热脱附修复过程碳排放水平,识别出碳排放的主要影响因素,提出针对性的减排策略。结果表明,异位热脱附修复1 m^(3)污染土壤全过程碳排放为212.22 kgCO_(2eq),碳排放集中在预处理、主处理和尾气处理3个过程,尾气处理过程最高,占比为54%。从碳排放源上看,主要为间接碳排放,占比达62%。生石灰、天然气、NaOH碱性溶液等物料投入量是碳排放的主要影响因素。同时,修复后土壤外运距离超过300 km后,将会对全过程碳排放产生较大影响,应提高物料使用率、控制土壤外运距离,以实现修复过程碳减排。本研究结果可为污染土壤异位热脱附修复技术的低碳应用提供参考。

To explore the carbon emission reduction path of ex-situ thermal desorption remediation of contaminated soil in China,the boundary and list of carbon emission accounting system of the process were determined based on the life cycle assessment theory.Ex-situ thermal desorption was divided into six processes:soil excavation,transportation,pretreatment,main treatment,tail gas treatment and final disposal.Based on the energy and material research data of five typical projects in East China,the carbon emission levels in the process of ex-situ thermal desorption were calculated.The main influencing factors of carbon emissions were analyzed and identified.Based on the analysis above,emission reduction strategies were put forward directing at the key processes and factors of carbon emission.The results showed that the carbon emission of 1 m^(3) contaminated soil remediation by ex-situ thermal desorption was 212.22 kgCO_(2eq).Carbon emissions were concentrated in three processes:pretreatment,main treatment and tail gas treatment.The carbon emission of tail gas treatment was the highest,accounting for 54%.From the perspective of carbon emission sources,it was mainly indirect carbon emissions,accounting for 62%.The input of quicklime,natural gas,alkaline solution prepared by NaOH and other materials was the main influencing factor of carbon emission.Meanwhile,the transportation distance of post-remediation soil beyond 300 kilometers will have a great impact on the whole process of carbon emissions.The utilization rate of materials should be improved and the outward transportation distance of soil should be controlled to achieve carbon emission reduction in the remediation process.The research results provide a theoretical reference for the low-carbon application of ex-situ thermal desorption technology.