This study presents the mass concentrations of PM（2.5）,O3,SO2 and NOxat one urban,one suburban and two rural locations in the Changchun region from September 25 to October 272013. Major chemical components of PM（2....This study presents the mass concentrations of PM（2.5）,O3,SO2 and NOxat one urban,one suburban and two rural locations in the Changchun region from September 25 to October 272013. Major chemical components of PM（2.5）at the four sites were daily sampled and analyzed. Most of daily concentrations of SO2（7–82 μg/m^3）,O3（27–171 μg/m^3） and NOx（14–213 μg/m^3） were below the limits of the National Ambient Air Quality Standard（NAAQS）in China. However,PM（2.5）concentrations（143–168 μg/m^3） were 2-fold higher than NAAQS.Higher PM（2.5）concentrations（~ 150 μg/m^3） were measured during the pre-harvest and harvest at the urban site,while PM（2.5）concentrations significantly increased from 250 to400 μg m^（-3） at suburban and rural sites with widespread biomass burning. At all sites,PM（2.5）components were dominated by organic carbon（OC） and followed by soluble component sulfate（SO4^（2-））,ammonium（NH4~＋） and nitrate（NO3^-）. Compared with rural sites,urban site had a higher mineral contribution and lower potassium（K~＋and K） contribution to PM（2.5）.Severe atmospheric haze events that occurred from October 21 to 23 were attributed to strong source emissions（e.g.,biomass burning） and unfavorable air diffusion conditions.Furthermore,coal burning originating from winter heating supply beginning on October 18 increased the atmospheric pollutant emissions. For entire crop harvest period,the Positive Matrix Factorization（PMF） analysis indicated five important emission contributors in the Changchun region,as follows： secondary aerosol（39%）,biomass burning（20%）,supply heating（18%）,soil/road dust（14%） and traffic（9%）.展开更多
农作物秸秆类生物质水分含量高、能量密度低、资源分散,因此储存运输成本高,而且可磨性差不易制粉用于煤粉锅炉或气化炉的混合燃烧与气化。生物质低温预处理技术是一种能够解决上述问题的温和热解方法,它能够显著改善生物质的特性。选...农作物秸秆类生物质水分含量高、能量密度低、资源分散,因此储存运输成本高,而且可磨性差不易制粉用于煤粉锅炉或气化炉的混合燃烧与气化。生物质低温预处理技术是一种能够解决上述问题的温和热解方法,它能够显著改善生物质的特性。选取棉花秆和小麦秆在固定床实验台上N2氛围下分别升温至200℃、250℃、300℃热解,加热时间均为30 m in。制得的生物质半焦能量密度显著提高,对比原始的生物质其可磨性得到明显改善,并且具有了疏水性,便于储存运输或制粉用于气流床气化。最后根据实验结果进行预处理技术的可行性分析,推荐预处理条件为250℃、30 m in。展开更多
Agricultural biomass has some drawbacks such as high moisture content,low energy density and wide distribution and as a result,the cost of transport and storage are high.Moreover,raw biomass has poor grindability so i...Agricultural biomass has some drawbacks such as high moisture content,low energy density and wide distribution and as a result,the cost of transport and storage are high.Moreover,raw biomass has poor grindability so its use in a pulverized boiler or entrained flow gasifier is difficult.Torrefaction is a mild pyrolysis process carried out at temperatures ranging from 200°C to 300°C to deal with these problems.The cotton stalk and wheat straw were torrefied in a fix-bed reactor at moderate temperatures (200°C,230°C,250°C,270°C and 300°C) under N 2 for 30min.The biomass chars after torrefaction had higher energy density and improved grindability characteristics compared with raw biomass and they also showed hydrophobic characteristics.The volatiles consist of a condensable fraction and a non-condensable fraction.The former mainly contained water and tar (organic products but mainly acetic acid).The non-condensable products are typically comprised of CO 2,CO and a small amount of CH 4 and even trace H 2.The volatiles increased with an increase in the torrefaction temperature but the solid yield and the energy yield decreased.However,the grindability and energy density of the biomass char showed great improvement.A kinetic study on the generation of the main non-condensable gases was undertaken and we conclude that the gases are formed by parallel independent first-order reactions.Characteristic kinetic parameters for the generation of each gas were determined.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.41205106,41275158)
文摘This study presents the mass concentrations of PM（2.5）,O3,SO2 and NOxat one urban,one suburban and two rural locations in the Changchun region from September 25 to October 272013. Major chemical components of PM（2.5）at the four sites were daily sampled and analyzed. Most of daily concentrations of SO2（7–82 μg/m^3）,O3（27–171 μg/m^3） and NOx（14–213 μg/m^3） were below the limits of the National Ambient Air Quality Standard（NAAQS）in China. However,PM（2.5）concentrations（143–168 μg/m^3） were 2-fold higher than NAAQS.Higher PM（2.5）concentrations（~ 150 μg/m^3） were measured during the pre-harvest and harvest at the urban site,while PM（2.5）concentrations significantly increased from 250 to400 μg m^（-3） at suburban and rural sites with widespread biomass burning. At all sites,PM（2.5）components were dominated by organic carbon（OC） and followed by soluble component sulfate（SO4^（2-））,ammonium（NH4~＋） and nitrate（NO3^-）. Compared with rural sites,urban site had a higher mineral contribution and lower potassium（K~＋and K） contribution to PM（2.5）.Severe atmospheric haze events that occurred from October 21 to 23 were attributed to strong source emissions（e.g.,biomass burning） and unfavorable air diffusion conditions.Furthermore,coal burning originating from winter heating supply beginning on October 18 increased the atmospheric pollutant emissions. For entire crop harvest period,the Positive Matrix Factorization（PMF） analysis indicated five important emission contributors in the Changchun region,as follows： secondary aerosol（39%）,biomass burning（20%）,supply heating（18%）,soil/road dust（14%） and traffic（9%）.
文摘农作物秸秆类生物质水分含量高、能量密度低、资源分散,因此储存运输成本高,而且可磨性差不易制粉用于煤粉锅炉或气化炉的混合燃烧与气化。生物质低温预处理技术是一种能够解决上述问题的温和热解方法,它能够显著改善生物质的特性。选取棉花秆和小麦秆在固定床实验台上N2氛围下分别升温至200℃、250℃、300℃热解,加热时间均为30 m in。制得的生物质半焦能量密度显著提高,对比原始的生物质其可磨性得到明显改善,并且具有了疏水性,便于储存运输或制粉用于气流床气化。最后根据实验结果进行预处理技术的可行性分析,推荐预处理条件为250℃、30 m in。
文摘Agricultural biomass has some drawbacks such as high moisture content,low energy density and wide distribution and as a result,the cost of transport and storage are high.Moreover,raw biomass has poor grindability so its use in a pulverized boiler or entrained flow gasifier is difficult.Torrefaction is a mild pyrolysis process carried out at temperatures ranging from 200°C to 300°C to deal with these problems.The cotton stalk and wheat straw were torrefied in a fix-bed reactor at moderate temperatures (200°C,230°C,250°C,270°C and 300°C) under N 2 for 30min.The biomass chars after torrefaction had higher energy density and improved grindability characteristics compared with raw biomass and they also showed hydrophobic characteristics.The volatiles consist of a condensable fraction and a non-condensable fraction.The former mainly contained water and tar (organic products but mainly acetic acid).The non-condensable products are typically comprised of CO 2,CO and a small amount of CH 4 and even trace H 2.The volatiles increased with an increase in the torrefaction temperature but the solid yield and the energy yield decreased.However,the grindability and energy density of the biomass char showed great improvement.A kinetic study on the generation of the main non-condensable gases was undertaken and we conclude that the gases are formed by parallel independent first-order reactions.Characteristic kinetic parameters for the generation of each gas were determined.
