| In recent years,with the increase of grain yield,the yield of straw is increasing.How to realize the comprehensive utilization of crop straw stalk is an urgent problem to be solved.According to the incomplete statistics,the amount of burnt and abandoned crop straw in the field reaches 2.15~ 3.14 million tons in China.It not only causes a great waste of resources,but leads to the pollution of the environment and the generation of haze weather.Therefore,it is extremely essential to realize the comprehensive utilization of crop straw,reduce the damage to the environment from burning straw,and promote fiber manufacturing enterprises in long-term form of wood as the main material turning into sustainable development form of straw as the main material accompanied by wood.This paper was supported by “Study on the Technology and Equipment of Straw Plant Fiber Film” No.2010BAD32B02-5.Based on the principle of pollution-free,clean,and efficient production of crops straw fiber,optimization design and test was taken in view of the straw fiber production technology and device pilot experiments platform.With the actual operation situation and technological process of D200 straw fiber product pilot production system,it could be divided into material crushing pretreatment system,raw material cleaning and soaking supply system,forced feeding system,and clean producing system.However,there is little in depth reports in the fiber production system,and cooperate relation between each subsystem is not clear enough.Therefore,this study,taken the continuous stability,high efficiency and clean production of straw fiber as the breakthrough point,adopted theoretical modeling,kinematics analysis,mechanical analysis and other methods to analyze the existing problems in pilot production system.And based on the theoretical analysis,discussion of D200 straw fiber product pilot production system and its subsystems was conducted through experimental investigations.In order to find out the best working parameters of key components of the fiber production system,improve the technological process,and unroll the cooperate relationship between each key component and the influence of system parameters on fiber evaluation index,this article launched the research from the following six aspects.The main research contents were as following:(1)Optimization design and existing problems analysis of straw fiber pilot production systemThe D200 straw fiber extruder,developed by Northeast Agricultural University,is used mainly in fiber processing for getting crop straw expanded utilizing physical extrusion method,which realizes clean,efficient and high value utilization of crop straw.The crop straw,getting through a series of physical and chemical reaction with steam blasting in straw fiber extruder,eventually met the requirement of plant straw fiber mulch production.Combined with the technology of single screw extruder,following the principle of reasonable economy,strong operability,convenient utilization,low cost and energy consumption,no pollution,easy maintenance,durable and high degree of automation,optimization design of straw fiber pilot production system was conducted.(2)Crushing pretreatment parameter optimization of rice strawIn order to meet the needs of rice straw material of D200 straw fiber extruder quickly and efficiently and solve the problems such as great toughness of rice straw itself and not easy to crush,optimization improvement was carried out for 9QR20-60 type straw rubbing-cutting machine and a series of investigations were conducted on the improved straw rubbing-cutting machine.The results showed that: 1)moisture content of rice straw and spindle speed of the rubbing-cutting machine had an extremely significant effect on the crushed straw length(P<0.01).Moisture content of rice straw had a significant effect on rubbing-cutting degree of straw(P<0.05),spindle speed of the rubbing-cutting machine had an extremely significant effect on rubbing-cutting degree of straw(P<0.01).2)Rice straw materials with length in the rage of 100~140 mm and rubbing-cutting degree surpassed 80% could be produced by the parameter combination of feed amount at 1000 kg/h,moisture content of rice straw within 17~22% and spindle speed of the rubbing-cutting machine within 1800~1850 r/min.(3)Optimization design and experiment for raw material supply system of D200 straw fiber extruderDue to a relatively small number of both special studies of crop straw fish and conveyer machine and the pretreatment technology of raw material supply for the purpose to meet the straw fiber extruder.Therefore,a test apparatus of raw material supplement matching D200 straw fiber extruder was designed to realize the efficient and clean production.In order to improve the efficiency in soaking,cleaning,continuously and stable conveying of crop straw materials and solve the problems of strong labor intensity when artificial feeding and nonuniform feeding,the development of a matched raw material supply device is absolutely necessary.This supply device mainly consisted of soaking device,stirring device and fishing conveyor device in which the fishing conveyor device functions as a critical component.Based on analysis of the cooperating relationship among three systems(referring to soaking,stirring and fishing systems),a fishing rake was selected as research object to establish a mathematical model of fishing amount by analyzing the kinematic process between harrow tooth and straw.The results showed that: 1)belt linear velocity,harrow tooth number and rotating speed of agitator had very significant effect on fishing efficiency(P<0.01);belt linear velocity had very significant effect on variation coefficient of fishing efficiency(P<0.01).2)The optimal combination of parameters occurred with a line speed of conveyor line at 0.6 m/s,rotation speed of stirring paddle at 40 r/min and harrow tooth number of rake at 8 for the raw material supplementary system of the D200 straw fiber extender.With the investigation condition above,fishing amount per unit time was 1111.2 kg/h and variable coefficient was 0.124.It could achieve continuous stability of rice straw raw material supply on the premise of ensuring the production efficiency of D200 straw fiber extruder no less than 1000 kg/h.(4)Optimization design and study on the forced feeding systemIn the process of crop straw processing by D200 straw fiber extruder,feeding continued stability of the feeding device is one of the most key technologies.As an important part of the fiber producing pilot system,the uniformity and controllability of feeding device directly affected the stability of the system,the accuracy and repeatability of the test results and then affected the processing quality of straw fiber.Therefore,by referring to design and theory of general screw conveyor and combining the cooperate relationship between the forced feeding device and fiber machine and the cooperate relationship between forced feeding device and feeding port,the radius of principal axis of forced feeding screw was calculated at 0.03 m,the outside diameter of principal axis was 0.064 m,the screw pitch was 0.12 m,the rotate speed was 417 r/min.And the variable coefficient of the mass flow rate of 3 measurements was 0.1398,0.1436 and 0.1412,respectively,which met the production demand of fiber producing machine.(5)Process parameters optimization of rice straw fiberIn order to achieve the clean and efficient making of the crop straw fiber,this study explored the optimal technological parameter of rice straw fiber to ensure the fiber meet the manufacturing requirements of plant fiber mulch.The single factor tests were conducted by using the D200 straw fiber extruder for the process the rice straw with the method of continuous steam blasting.To determine the scope of testing factors,the influence rule that feed rate,rotate speed of the straw fiber extruder and the diameter of the pressure regulating die head had on burst pressure and consumed power of the extruder was analyzed.The optimal process parameters meeting the demand of straw fiber extruder by the orthogonal experiment were principal axis rotate speed of the extruder was 110 r/min,feed rate was 1100~1200 kg/h,cavity gap of the regulating outer ring and the regulating inner ring was 3 mm.Under the condition of optimal process parameter,length-width ratio of the fiber was 44.5,fiber receiving rate was 81%,initial beating degree of fiber was 24.6 °SR and tensile index was 7.1 N /g·m.(6)Tensile strength prediction model for plant fiber mulchIn the actual production,plant fiber mulch was processed with different papermaking technology parameters to meet the various kinds of requirements of agriculture.However,there existed large deviation in the control of technological parameter of the plant fiber manufacture for the majority of enterprises and the lack of an on-line monitoring instrument of tensile strength.The destructive tests were inevitable,which not only improved the production cost,but caused the waste of straw raw material.Therefore,based on the particle swarm optimization to optimize support vector machine regression combine with the orthogonal test method L25(56),the beating degree of fiber,dosage of wet strength agent,dosage of wet strength agent,mulch quantitative and mixture ratio were taken as the input parameters,and the tension strength of plant fiber mulch was taken as the output to simulation and prediction.The results showed that according to the different manufacture paper parameters in the production process,prediction model of the tension strength of plant fiber mulch was established.The mean square error,coefficient of determination and root-mean-square error could reach 0.117,0.915 and 0.342.This model could provide a reference for the prediction and laid a good foundation for the further realization of on-line monitoring of tensile strength of the plant fiber mulch.(7)Technical and economic analysis of straw fiber production systemBased on the principles and methods of engineering economics,the feasibility and economic benefit analysis of straw fiber pilot production system are analyzed,to predict the feasibility of straw fiber technology.The results showed that: the fixed investment is 2 million 270 thousand Yuan,the annual operating cost is $1 million 259 thousand and 500,an annual output of straw fiber up to 1814.4 tons,net present value is $3 million 276 thousand and 500,the internal rate of return is 74%,the investment recovery period is 1.2 years,cumulative net present value is 16 million 603 thousand and 280 Yuan.The project is economically viable. |
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