Study On Drying Characteristics And Energy Consumption Of Three Kinds Of Wood

Wood drying has always been a very energy-consuming and irreplaceable wood processing production link.China’s wood drying industry still has problems such as high drying energy consumption,serious energy waste,long drying cycle and low drying quality.The analysis of energy consumption in the drying process under different conditions can better predict the energy consumption of wood,and at the same time reasonably formulate a drying benchmark to reduce some energy consumption and drying cycle.With the implementation of China’s environmental protection and energy conservation policies and measures,the use of solar energy,a clean energy source,combined with conventional steam drying can achieve the goals of energy conservation and efficient use of resources.In this study,the basic drying characteristics of three kinds of sawn timber,Pinus sylvestris var.mongolica,Populus alba and Ulmus pumila,were studied by Baidu test method,and the drying schedule was formulated and improved.The energy efficiency of three kinds of sawn timber was studied from three different angles by using the optimized drying benchmark,including the energy efficiency of different wood species(coniferous wood,soft broad-leaved wood,hard broad-leaved wood),the energy efficiency of Pinus sylvestris var.mongolica with different thickness,and the energy efficiency of Pinus sylvestris var.mongolica with different initial moisture content.By optimizing the solar-conventional combined drying process,the conversion drying moisture content nodes of solar pre-drying and conventional drying were determined,and the drying quality in the study was guaranteed to meet the national sawn timber quality level 2 or above.The main results are as follows:(1)The basic drying characteristics of Pinus sylvestris var.mongolica,Populus bolleana and Ulmus pumila were studied by Baidu test method.The results showed that the initial cracking,internal cracking,section deformation,distortion and drying rate of Pinus sylvestris var.mongolica,Populus bolleana and Ulmus pumila were 1,1,1,2 and 1,respectively.2,4,1,3,1;3,2,2,3,2.According to the results of drying characteristics,the drying benchmark of three kinds of sawn timber was preliminarily established.(2)The total drying rate of Pinus sylvestris var.mongolica with 20 mm thickness was 1.19%/h,and the total drying rate of Pinus sylvestris var.mongolica with 40 mm thickness was 0.62%/h.The drying rate of Pinus sylvestris var.mongolica with 20 mm thickness was 1.9 times that of Pinus sylvestris var.mongolica with 40 mm thickness.The drying quality of Pinus sylvestris var.mongolica with two thicknesses reached the national secondary standard of sawn timber quality.By adjusting the temperature and humidity of the actual drying conditions of the sawn timber,a more reasonable conventional drying schedule for Pinus sylvestris was developed.The power consumption of 40 mm thick Pinus sylvestris is 1.9 times that of 20 mm,and the heat loss rate of the drying system is 57.4%.The steam loss rate of 20 mm thick Pinus sylvestris was 34.3%,and the steam loss rate of 40 mm thick Pinus sylvestris was 36.5%.Conventional steam drying requires about 544.08 kg of steam to dry 1m~3Pinus sylvestris.(3)The total drying rate of poplar was 2.50%/h,the total drying rate of elm was1%/h,and the total drying rate of Pinus sylvestris was 1.19%.The drying rate of poplar is the fastest,and the drying rate of elm is the slowest.The drying quality is in line with the national sawn timber quality level 2 or above standards.The electric energy consumed by elm is 4.3 times that of Pinus sylvestris and 1.4 times that of poplar.A more reasonable conventional drying schedule for poplar and elm was developed.The heat loss rate of the dried poplar wood pile system is 41.2%,and the heat loss rate of the dried elm wood pile system is 58%.The steam loss rate of dried poplar was 18.0%,and the steam loss rate of dried elm was 39.8%.Every 1m~3dried poplar needs to consume 869.44 kg of steam.Every 1m~3dried elm needs to consume 897.2 kg of steam.(4)The power consumption of Pinus sylvestris with initial moisture content of89.6%was 3.71 times that of Pinus sylvestris with initial moisture content of 30.2%.The steam loss rate of Pinus sylvestris lumber with initial moisture content of 30.2%was16.3%,which was 20.2%lower than that of Pinus sylvestris lumber with initial moisture content of 89.60%.(5)The drying rate and drying quality of complete solar drying were studied,and the moisture content of 28%was determined as the joint drying conversion node.The overall drying rate of complete solar drying is 1.88%/h,and the total drying rate of solar-conventional combined drying is 2.51%/h,which is 0.63%/h faster than that of complete solar drying,and the speed is increased by 33.5%.Solar drying consumes33.33 k Wh/m~3,and solar-conventional combined drying consumes 133.6 k Wh/m~3.Compared with conventional drying,the energy saving rate is 83.4%.The total steam consumption of solar-conventional combined drying was 411.67 kg/m~3,and the saving rate was 43.1%compared with conventional drying.The drying quality of solar-conventional combined drying reached the second grade standard of national sawn timber quality.