Research To Gas Emission Produced From Daxing'an Ling Forest Fuel Combustion

This article has taken the Daxing'anling in Heilongjiang Province as research area, by the method of field investigation and laboratory condition control burning experiments, in different burning stage this research analyzed the release of CO₂, CO, CxHy, NO, SO₂, and the gas emission mechanism of different forest fuels. Then from the perspective of release speed have analyzed the burning characteristics of different forest fuels, main content and results are as below:(1)This research systematically introduced the thermal decomposition and gas production mechanism of cellulose, hemicellulose and lignin in different temperature condition and different burning stages of different kinds of forest fuels. We also constructed methods for collecting, measuring and analyzing trace gases.(2)This research measured CO₂, CO, CxHy, NO, SO₂ capacity of each main species of arbor, bush and grass. The results showed that during the fuel burning process, CO₂ was the dominating gas released, CO released much longer than other kinds of gas, and it also took the shortest time to reach the peak value. The mean CO₂, CxHy, NO of burning arbor, bush and grass had significant difference, CO, SO₂ release capacity made little difference. The lasting time and the time of max value of CO release produced from arbor,bush and herbaceous are different significantly.(3)Considering arbor's physical and chemical characteristics(igniting point, heat of combustion, ash content, carbon content, air-dry moisture and dry moisture) , this research used the Multi-regression Analysis to find out the relationship between fuel physical-chemical property and gases release capacity and release speed during the burning process. The results showed that within 9 kinds of arbor , there is positive relationship between SO₂ release capacity and ash content;CO release time had a relation with the air-dry moisture, the higher the moisture the longer CO released, CxHy releasing time had a significant negative relationship with the dry moisture content.(4)This research measured burning process gas emission from different places of five kinds of arbor(Larch, Pinus sylvestris var.mongolica Litvin, Populus davidiana, Birch and Quercus mongolica), and also used t-test to evaluate the gas emission differences between different species and different parts. We used the Lowest Significance Difference (LSD)method to measure the gas emission differences between each species and different parts. The results showed that as for Larch, Populus davidiana, Birch and Quercus mongolica, the CO2 emission capacity, carbon containing gas content and five kinds of gas general content between branch, bark and bole made little differences, while Pinus sylvestris var.mongolica Litvin had a significant difference between bark and the other two parts;the NO emission capacity from different parts of Pinus sylvestris var.mongolica Litvin are similar, the other four kinds of arbor bole emission are the least, while branch released the largest capacity. The carbon containing gas emission capacity from branch of different kinds of arbor made little differences, while from bark and bole the differences are significant;within the burning production of bark, CO2 emission capacity, SO2 emission capacity, carbon containing gases, five kinds of gas general content of needle-leaved trees are higher than that of the broad-leaved trees.(5)Separately this research measured gas emission capacity from grass, dead wood and semi-decomposed layer of Larch stand, Pinus sylvestris var.mongolica Litvin stand and Populus-Birch stand. Results showed that during the burning processes of three layers in three different kinds of forest type, CO2 emission capacity, carbon containing gas general content and five kinds of gas general content are different significantly between three forest types. CO, CxHy, NO and SO2 made little differences. Needle-leaved stands (Larch stand, Pinus sylvestris var.mongolica Litvin stand) had more CO2 emission from dead branches than that of the broad-leaved stands(Populus-Birch stand), but in semi-decomposed layer Larch released more CO2 than the other two kinds of forest type, also, within Larch stand three different layers had different CO2 emission, carbon containing gas content and five kinds of gas general content. The other four kinds of gas made little differences.(6)This research measured gas emission of different moisture content (totally dry 5% 10%, 10% ²0%, 20% -30%), granularity (ï¿¡0, 60), fuel weight (3g, 5g> 8g) and environmental calefaction temperature (340 °C, 390°C, 440 °C, 490°C). Results showed that: Fuel moisture, to some degree, can accelerate the burning process, consequently the venomousness and harm gases capacity increased. The smaller the fuel granularity, the more CO2> NO, SO2 released, and the less CO and CxHy released, burning time moved up, and burning efficiency increased. The higher the environmental heating temperature, the more scorching the burning process, burning time moved up and flame burning process extended, and the less the residual left.Theoretically forest fuel and coal had the similar characteristics that high emission, high O and H content, less ash content and almost no S. From the perspective of forest fuel moisturecontent, granularity, environmental heating temperature effects on gas emission, forest fuel and coal had significant differences. So, this research took the gas emission from different species, parts, diameter, forest types, physical-chemical characteristic and heating temperature to estimate forest fire gas emission capacity, also to estimate the effects of forest fire on the atmosphere climate. This research can serve as important experimental data and theoretically foundation for forest fuel management and raw material fuel exploitation. It also can fill up some gaps in the forest fuel burning gas emission research, complete and develop the Forest Burning research content, at the same time, has a significant realistic importance for the forest fire control, melioration of atmosphere environment and the actualization of sustainable development stratagem.