Study On Combustion Characteristic And Life Cycle Assessment Of Straw Building Material

With the development of market economy and the expansion of urban, a large number ofwood resources are used for furniture industry and economy construction, so the forest isseriously damaged. In such condition there is a good future for the development of strawbuilding material in China. Besides, straw building material is a green material and perfectlymatches the requirement of environmental protection from the government and the public.Therefore, straw building material can be the good resource for furniture and constructionindustries, and straw building material industry is one of the main forces of comprehensiveutilization of agricultural straw.The thermogravimetric characteristics, kinetic parameters, gases emissions andenvironmental impacts of straw tile and straw board were studied using thermogravimetricinstrument, tube reactor flue gas analyzer and life cycle assessment method in this paper. Thecombustion characteristics and the environmental impact assessment of straw buildingmaterial were compared with straw and other ordinary building material. The study resultswill provide the reference and instruction for the healthy development of straw buildingmaterial industry.The combustion of rice straw, straw tile and straw board in two atmospheres （80N₂/20O₂,90N₂/10O₂） at30℃/min was analyzed thermogravimetrically. The oxygen concentration hasno obvious effect on the ignition temperature, but influenced the residual mass obviously andmake more complete combustion. The subsequence of the corresponding of maximum weightloss rate is straw board＞straw tile＞rice straw, and the subsequence of maximum weightloss rate is rice straw＞straw tile＞straw board. It is more difficult to ignite two strawbuilding materials than rice straw. The ignition temperature of straw board is bigger than ricestraw, straw tile and wood, indicating the non-flammability of straw board. The ignition timeof straw board exceeds10min, and longer than that of straw by3min under the atmospherewith20vol%oxygen concentration. Therefore, the straw board has good fire-safe capability.The pyrolysis and combustion of straw tile, asbestos sound-absorbing panel, gypsumboard, mineral fIber ceiling, three-ply wood board and PVC board in two atmospheres（100N₂/20O₂,0N₂/10O₂） at10℃/min,20℃/min and30℃/min were analyzedthermogravimetrically. In air at20℃/min, the weight loss curve of straw tile is similar to PVCboard. The subsequence of maximum weight loss rate is three-ply wood board＞straw tile＞PVC board＞gypsum board＞mineral fIber ceiling＞asbestos sound-absorbing panel. The subsequence of the corresponding of maximum weight loss rate is asbestos sound-absorbingpanel＞three-ply wood board＞straw tile＞PVC board＞mineral fIber ceiling＞gypsumboard. The subsequence of residual mass is asbestos sound-absorbing panel＞gypsum board＞mineral fIber ceiling＞PVC board＞straw tile＞three-ply wood board. The subsequence ofcomprehensive combustion characteristic index is asbestos three-ply wood board＞straw tile＞PVC board＞gypsum board＞mineral fIber ceiling＞asbestos sound-absorbing panel. Thecomprehensive combustion characteristic indexs of straw tile, PVC board and gypsum boardare an order of magnitude. For three-ply wood board, gypsum board, straw tile and PVCboard, the increment of heating rate make their curves shifting to a higher temperature rangeand increase the maximum weight loss rate, and the effects of heating rate on ignition timeand comprehensive combustion characteristic index are bigger. At10℃/min or20℃/min,straw tile cann’t be ignited in10min, and it helps people escape.Based on weight loss curves, the kinetic parameters of straw tile and five buildingmaterials were calculated using first order reactions model. In air at20℃/min, thesubsequence of apparent activation energy is Asbestos sound-absorbing panel＞Gypsumboard＞Mineral fIber ceiling＞Three-ply wood board. For straw tile and PVC board, thevalues of the apparent activation energies of three reactions vary very much, and the value oftheir second reaction is the smallest. The value of the first two reactions of straw tile issmaller than that of PVC board, but the value of the third reaction of straw tile is litter bigger.The values of the apparent activation energies of straw tile are slightly lower under theatmosphere with higher oxygen concentration, indicating the increment of oxygenconcentration can promote the reaction to a certain extent.The gases emissions from rice straw and straw tile combustion at five temperatures in atube reactor were analyzed by a flue gas analyzer. The effect of temperature on CO₂peakconcentration of rice straw and straw tile is small, but their CO₂peak concentration increaseswith decreasing oxygen concentration in the atmosphere. The variation of CO, SO₂and NO_xpeak concentrations with temperature is related to the atmosphere, materiel type, and gasemission type. It is only when the temperature is high that the decrease of oxygenconcentration increases CO emission and the combustion is deteriorated. At the sametemperature, the NO_xpeak concentration decreases with decreasing oxygen concentration. Atlower temperature, SO₂peak concentration is highest at air, while at higher temperatures SO₂peak concentration is highest under terrible oxygen deprivation atmosphere. Under the same atmosphere, straw tile has lower CO₂and NO_xconcentrations but higher CO and SO₂concentrations than rice straw.A straw manboard project with the capacity of50000m³per year was analyzed using lifecycle assessment （LCA） method. The results show212.58kg standard coal and0.16kg oilare consumed to produce1m³straw manboard. The resource consumption coefficient and theweighted environmental potentials for1m³straw manboard are2.18mPR90and15.03PET2010. The sum energy consumption for1m³straw manboard is6228.56MJ and coal is themain consumption energy. The life cycle of straw manboard project exerts the worst influenceover acid and has a nonnegligible bad effect on dusk and eutrophication, while strawmanboard project has a good effect on global warming.