Analysis Of Pollution Emission Characteristics And Emission Reduction Potential Of Civil Clean Coal Combustion Heating

Residential coal-fired heating produces lots of pollutants,which has caused harm to the ambient air quality and human health.Clean coals and clean stoves can reduce the emission of raw coal combustion pollutants to a certain extent,but the research on its pollution emission characteristics and emission reduction effect is insufficient.In order to improve the environmental pollution caused by raw coal combustion heating and find new clean coal and clean stoves with low cost and low emissions,further clarify the pollution emission reduction effect and economy of clean coal compared with raw coal combustion heating,and systematically evaluate the feasibility of its promotion in rural areas.The pollution emissions from the combustion of raw coal and two new types of clean coals（clean coal balls and square honeycomb briquettes）are studied through a combination of field tests and laboratory tests.At the same time,its influencing factors are analyzed,and the emission reduction effect and economy are evaluated.The results show that the real-time emission characteristics of pollutants from the combustion of civil raw coal and clean briquette are influenced by the operating modes of the user’s stoves.The emission concentrations of the pollutants have obvious changes at different combustion stages,and the emission trend of the same combustion stage is more consistent.In the residential coal combustion heating field survey and testing found that because of the influence of residents’operating habits,the operation period of using water heating stoves to burn raw coal to seal fire is longer,and the amount of coal added in a single time is more.As a result,the combustion efficiency of raw coal in water heating stove is low,and the emission of various pollutants is relatively high.There is a significant PM_2.5 emission during the coal-adding and smoldering stages when the water heating stove burns raw coal,and the PM_2.5emission factors are 6.46±3.49 g/kg and 5.86±2.85 g/kg,respectively.The use of clean briquettes can effectively reduce the emission of pollutants from raw coal combustion,and fuel properties,stove combustion mode and structural design have an important impact on the pollutant emission reduction effect.The laboratory test results show that clean coal balls compared with raw coal burning in the updraft stove,the emission reduction rate of Non-Methane Hydro Carbons（NMHCs）and PM_2.5can reach 44.72%and 93.84%,and the emission reduction effect of NMHCs（P=0.025,<0.05）and PM_2.5(P=9.63×10^-5,<0.05)is significant.The downdraft stove can reduce PM_2.5 and NMHCs emissions due to its reasonable design of the flue and can prolong the residence time of volatiles,especially for PM_2.5 emission reduction effect of raw coal with high volatile content is more significant（P=0.005,<0.05）.Compared with the updraft stove,the downdraft stove can reduce the NMHCs and PM_2.5emissions by 80.14%and 75.13%for raw coal,but the CO emissions of the clean coal balls have been increased to a certain extent.The field test results show that due to the low volatile content and porous structure of square honeycomb briquettes,as well as the feeding mode and reasonable design of the internal structure of the special stove,which make the square honeycomb briquette burn stably and have high combustion efficiency.The use of square honeycomb briquettes can reduce PM_2.5,CO,and NOx emissions by 88.94%,87.06%,and 55.94%,respectively,PM_2.5(P=8.25×10^-5,<0.05)and CO（P=0.001,<0.05）emission reduction effect is more significant.From an economic standpoint,the production cost of square honeycomb briquette is relatively low,and residents using this heating method in each heating season is 1390～2502 yuan/household,which is 1～1.2 times the operating cost of raw coal heating,and the operating cost of the two heating forms is not much different.The findings of this study illustrate that"good coal+good stove"cannot achieve the emission reduction of all pollutants.When choosing a clean heating method,the performance of the stove and the properties of the fuel should be considered comprehensively,and"fuel adaptation of stoves"is important to reduce pollutants.The new type of civil square honeycomb briquettes combustion heating not only reduces the emission of various pollutants,but also greatly reduces the user’s heating expenditure in winter,providing a low-cost and low-emission technical path for coal-fired clean heating in underdeveloped rural areas in China.