Study On Solar-High Temperature Combined Drying Of Pinus Massoniana

Wood drying is an indispensable part of the forest product production process,and it is also the most energy-intensive and polluting part of the entire production process.Although the overall level of wood drying in my country is already very high,the most commonly used process in actual production is conventional drying,which leads to a long drying cycle and high production costs in this link.Most factories do not have purification and absorption treatment equipment for the exhaust gas during the drying process.The volatile organic compounds and VOCs produced by wood drying are directly discharged into the atmosphere,and some of the harmful substances are discharged seriously exceeding the standard,which will cause irreversible damage to the atmosphere and the operators.Since our country began to ban commercial logging of natural forests,plantation forests have become an important substitute for wooden raw materials.At present,our country's plantation forests mainly use Pinus Massoniana,Larix gmelini,Chinese fir,etc.As pioneer species.Because of its fast-growing characteristics,it can better meet the rapid social and economic development,and there is still a lot of room for future development of plantation forests.Taking Pinus Massoniana sawn timber as the research object,first use Baidu test method to study its drying characteristics,and formulate conventional drying standards suitable for local conditions;adopt conventional drying,high-temperature drying,solar drying,solar-conventional combined drying,and solar-high-temperature combined drying,etc.Five different drying processes,to study the drying characteristics of Pinus Massoniana wood,especially the evaluation of drying quality and comparative analysis of energy consumption,and to study the release law of VOCs during conventional drying and high-temperature drying,and explore the most energy-efficient and efficient Green drying process.The main findings are as follows:1.The conventional drying of masson pine sawn timber takes 134 h in total,and the high-temperature drying takes 21 h in total.In terms of time cost,high-temperature drying saves 84.3% compared with conventional drying.The total drying speed of conventional drying is 0.6%/h,and the total drying speed of high-temperature drying is 4.0%/h,which is6.4 times that of conventional drying.Conventional drying reaches the third level of drying quality,and high-temperature drying reaches the second level of drying quality.The dry quality of the test material after high temperature drying is better,the visible defects are very few,and the dimensional stability is strong.The whole process of solar drying takes 202h;the solar-conventional combined drying takes 80h;the solar-high temperature combined drying takes 65 h.The total speed of solar drying and drying is 0.4%/h,the total speed of solar-conventional combined drying is1.1%/h,which is 175% higher than solar drying speed,and the total speed of solar-high temperature combined drying is 1.3%/h,which is higher than solar drying Up 225%.After solar drying,many indicators of masson pine sawn timber are below the third level of drying quality;the comprehensive level of solar-conventional combined drying has reached the second level of drying quality;the comprehensive level of solar-high temperature combined drying has reached the second level of drying quality.2.Conventional drying consumes a total energy of 450.500 kw·h/m~3,equivalent to214.9786 yuan/m~3,and high-temperature drying consumes a total of 143.667kw·h/m~3,equivalent to 68.5579yuan/m~3,which is the ratio of energy consumption per cubic meter of masson pine high-temperature drying Conventional energy consumption can be saved by68.1%,and the energy saving effect is remarkable.The total energy consumption of solar drying is 26.651 kw·h/m~3,equivalent to12.7177yuan/m~3,and the energy consumption of solar-conventional combined drying is87.106 kw·h/m~3,equivalent to 41.5669yuan/m~3,which consumes more masson pine per cubic meter than solar drying.Energy 226.8%,solar-high temperature combined drying consumes 20.911 kw·h/m~3,equivalent to 9.9789yuan/m~3.Masson pine is 21.5% more energy-saving than solar drying and 2.7388yuan/m~3 per cubic meter,which is higher than solar-conventional combined drying.Energy saving is 76.0%,saving 31.5880yuan/m~3.3.A total of 25 aldehydes,terpenes and other volatiles were detected in the exhaust gas from the drying process of masson pine sawn timber.Among them,the aldehydes volatiles include formaldehyde,n-propionaldehyde,acetaldehyde/acetaldehyde dimethyl acetal,and n-butyl.There are 9 kinds of aldehydes,acrolein/acrolein dimethyl acetal,n-hexanal,benzaldehyde,isovaleraldehyde and n-valeraldehyde;terpene volatiles include?-pinene,camphene,myrcene,?-piene,?-phellandrene,limonene,r-terpinene,1-heptene and 2-cyclohexenone,9 kinds in total;n-heptane,2-4 dimethyl hexane and hexamethyl cyclotrisiloxane There are three kinds of alkane volatiles: carbon tetrachloride,benzene,propylbenzene and 2-ethylfuran,a total of 25 kinds of volatiles.The release of conventional drying VOCs is mainly concentrated in the middle stage of drying,and the release of VOCs in the high-temperature drying process is mainly concentrated in the early stage of drying.4.The amount of formaldehyde released under the two drying processes of conventional drying and high-temperature drying does not exceed the standard.The total amount of benzene released under conventional drying is 2.5503mg/m~3,which is 2.6 times the amount specified in the Beijing Comprehensive Air Pollutant Emission Standard;the total amount of non-methane total hydrocarbons released is 287.9120mg/m~3,which is the amount specified in the standard.2.9 times.Under high temperature and dry conditions,the total release of benzene is 8.8705mg/m~3,which is 3.5 times the conventional dry benzene release,and 8.9 times the standard release;the total release of non-methane total hydrocarbons is 2283.1332mg/m~3,which is The release of conventional dry non-methane total hydrocarbons is 7.9 times,which is 22.8 times the release of standard regulations.The above research results show that for the drying of masson pine sawn timber,solar-high temperature combined drying is the most energy-saving,most efficient and greenest drying technology.The centralized collection of VOCs in the early stage of drying can effectively reduce the pollution in the wood drying industry.Pollution caused by the atmospheric environment.