Analysis And Prediction Of Flue Gas Pollutants Emission From WTE Plants In China

Waste-to-Energy（WTE）is the key technology of municipal solid waste（MSW）treatment in China,accounting for 50.29%of the total treatment capacity in 2019.WTE plants will emit secondary pollutants such as dioxins and heavy metals（HMs）.However,most of the existing emission inventories in China are based on literature research and can not reflect the real emission status.Building a high-precision emission inventory is particularly important for MSW management and pollution prevention and control.This study investigated the pollutant emission and air pollutants control devices（APCDs）data of 510 WTE plants in China,divided them into three regions:East,middle and West,2 incinerator types:moving grate furnace（MG）,circulating fluidized bed（CFB）,and 4 kinds of single furnace treatment capacity:0-250 t/d,250-500 t/d,500-750 t/d and 750-1,000 t/d.And analyzed the different impacts of above elements on the typical flue gas pollutant emission factors.The emission inventory was constructed and its relationship with the local socio-economic level was explored.The artificial neural network（ANN）was used to construct the prediction models of WTE capacity and total pollutant emission in city level.The main conclusions are as follows:（1）In 2020,the emission factors（EFs）and uncertainty intervals in China of NO_x,SO₂,HCl,PM,CO,dioxins,Hg,Cd+Tl,Sb+As+Pb+Cr+Co+Cu+Mn+Ni are 137.56±0.18 mg/m³,18.09±0.06 mg/m³,11.88±0.04 mg/m³,4.03±0.01 mg/m³,10.31±0.05mg/m³,231.24±2.35×10^-4 ng-TEQ/m³,389.46±3.32×10^-5 mg/m³,48.18±2.59×10^-4 mg/m³,490.26±4.42×10^-4 mg/m³ respectively;Emission inventory and its uncertainty interval are 113572±136 t/y,14867±37 t/y,9712±97 t/y,3192±28 t/y,8173±82 t/y,14.07±0.23 g/y,3.29±0.09 t/y,7.87±0.44 t/y and 37.84±0.36 t/y respectively.Flue gas volume and operation time of incinerator are the main sources of uncertainty.（2）The EFs of SO₂ and Hg in CFB are 20%and 27%lower than those in MG.PM,NO_x,HCl,CO,dioxin,Cd+Tl,Sb+As+Pb+Cr+Co+Cu+Mn+Ni are 78%,8%,29%,354%,73%,71%and 97%higher than those of MG.The EFs of PM,NO_x,SO₂,CO,HCl,Cd+Tl,and Sb+As+Pb+Cr+Co+Cu+Mn+Ni decrease with the increase of the single incinerator treatment capacity,which is contrary with the EFs of Hg.There is little difference in the emission factors of dioxins among different capacity.The acid gas EF of"semi dry process+wet process"is the lowest（4.55 mg/m³）,and the NO_x EF of"SNCR+SCR"denitration process combination is the lowest（97.16 mg/m³）.（3）The EFs of PM,NO_x,SO₂,HCl,CO and Cd+Tl in the Eastern region are lower than those in the Mid and Western regions by 14-18%,15-18%,18-22%,14-14%,25-26%and 83-92%.The EF of Hg in the Mid region is the lowest,and the EF of dioxins and Sb+As+Pb+Cr+Co+Cu+Mn+Ni in the Western region are the lowest.（4）There is a significant positive correlation between the MSW incineration capacity,the total emission of pollutants and the socio-economic parameters.For the ANN prediction models with the MSW incineration activity levels and 9 flue gas pollutants total emissions as prediction variables,the mean square errors（MSE）are0.00-0.19,and the F value is 9.47-229.41,which meets the significance test requirements of the model.Among them,the models of the total incineration treatment capacity,NO_x,SO₂,dioxins and Cd+Tl have high accuracy.