碳化对焚烧飞灰“减污降碳”协同处置潜力研究

Potential of Carbonization for Co-Disposal of Pollution and Carbon Reduction of Incineration Fly Ash

为探究我国不同地区生活垃圾焚烧飞灰“减污降碳”协同处置潜力,选取我国8个典型地区的飞灰为研究对象,采用加速碳化试验模拟飞灰长期填埋场景,通过重金属浸出试验探究碳化前后其重金属浸出浓度的变化情况,通过热重分析研究其对CO_(2)的实际吸收能力,同时基于Steinour方程研究2009—2021年我国飞灰对CO_(2)的理论吸收能力.结果表明:通过浸出试验得知加速碳化后飞灰中重金属Zn、Cd的浸出浓度分别下降了10%~18%和9%~30%,其中上海市和河南省飞灰样品中Zn的浸出浓度已低于生活垃圾填埋场入场要求.《生活垃圾焚烧污染控制标准》(GB 18485—2014)的发布实施导致飞灰中碱性成分占比上升,使得飞灰对CO_(2)的吸收潜能增至标准发布之前的约1.38倍.以贵州省、上海市、山东省、北京市、广东省、辽宁省、河南省、天津市8个不同地区的飞灰样品为例,通过Steinour方程推算得到2020年我国飞灰对CO_(2)的理论吸收量达339.93×10^(4)t,约占2020年我国碳排放总量的0.034%.对上海市、北京市及河南省3个飞灰样品进行加速碳化试验,通过热重曲线得到飞灰在碳化前后CaCO_(3)分解段的失重率,进一步推算出2020年我国飞灰对CO_(2)的实际吸收量达16.34×10^(4)t,占其理论吸收量的4.8%,飞灰对CO_(2)的实际吸收量小于其理论吸收量的主要原因是,在加速碳化过程中产生的碳酸钙及其他聚合物包裹飞灰,使外部CO_(2)难以进入飞灰内部.研究显示,加速碳化对飞灰“减污”效果明显,但“降碳”效果仍需对碳化场景以及预处理过程的工艺参数进行优化,以期最大限度地提高飞灰对CO_(2)的实际吸收能力.

In order to investigate the co-disposal potential of‘pollution and carbon reduction’of incineration fly ash in different regions of China,fly ash from eight typical regions of China was chosen as the research object.The accelerated carbonation test was used to simulate the long-term landfill of fly ash.The actual CO_(2) absorption capacity was studied by thermogravimetric analysis,and the theoretical CO_(2) adsorption capacity of fly ash in China from 2009 to 2021 was also investigated using the Steinour equation.The results showed that the leaching concentration of Zn and Cd in fly ash decreased by 10%-18%and 9%-30%,respectively,after accelerated carbonization,and the leaching concentration of Zn in fly ash samples from Shanghai and Henan Province was already lower than the admission requirement of domestic waste landfill.The implementation of China′s Domestic Waste Incineration Pollution Control Standard(GB 18485-2014)resulted in an increase in the content of alkaline components in fly ash,increasing the CO_(2) absorption potential of fly ash to about 1.38 times that before the standard′s release.Taking fly ash samples from eight different regions in Guizhou,Shanghai,Shandong,Beijing,Guangdong,Liaoning,Henan,and Tianjin as examples,the theoretical absorption of CO_(2) by fly ash in China in 2020 was calculated by the Steinour equation to be 339.93×10^(4)t,accounting for approximately 0.034%of China′s total carbon emissions in 2020.Three fly ash samples from Shanghai,Beijing and Henan were subjected to accelerated carbonization experiments,and the weight loss due to the CaCO_(3) decomposition of fly ash before and after carbonization was obtained through thermogravimetric curves.It was,further deduced that the actual amount of CO_(2) absorption by fly ash in China in 2020 was 16.34×104 t,accounting for 4.8%of the theoretical absorption.The main reason why the actual absorption of CO_(2) by fly ash is less than the theoretical absorption is that the calcium carbonate and other polymers produced in the accelerated carbonization process encapsulate the fly ash,making it difficult for external CO_(2) to enter the fly ash.The study shows that the accelerated carbonization has obvious‘pollution reduction’effect for fly ash,but the‘carbon reduction’still need to optimize the carbonization scenario and the pretreatment process parameters to maximize the actual absorption capacity of fly ash for CO_(2).