| Corn stalk is an important biomass resource with abundant annual production in China.The key to its utilization is how to improve its value.Corn stalk is composed of rind,pith and leaf,which physical properties and nutrients are different,direct utilization of the whole corn stalk leads to poor performance,leaf and pith contain rich crude protein and crude fat,can be good animal feed,and can also be used as basic material and the brewing materials,rind of corn stalk is of high lignin and cellulose content,can be used for papermaking and man-made board and so on.Therefore,it is very important to separate the rind,pith and leaf of corn stalk effectively so as to realize high value utilization of corn stalk.In this paper,based on the study of basic mechanical properties of rind,pith and leaf of corn stalk,a rind-pith-leaf separation device for corn stalk was designed,and the separation device was theoretically analyzed and experimentally studied.The main research contents and conclusions are as follows:(1)Study on the basic mechanical characteristics related to the rind-pith-leaf separation of corn stalk.By means of universal testing machine and self-made clamping apparatus,the mechanical properties of rind,pith and leaf of corn stalk were studied with the change of joint position and water content.The tensile force between stalk and leaf based on conseq uent,vertical and reverse direction increases gradually from the root to the top with the node position.The maximum tensile force and binding strength between stalk and leaf increased first an d then decreased with the increase of water content.The variation law of tensile force and binding strength of stalk and leaf with joint position and water content during three-way stretching is as follows: consequent tensile > vertical tensile >reverse tensile.The reverse tensile failure is tear failure,and the consequent tensile failure is pull failure.With the increase of joint position,both the tensile strength and shear strength of the rind decreased and reached the maximum value at the root.The tensile strength and shear strength of the rind gradually incr eased with the increase of moisture content.With the increase of joint,both the tensile strength and shear strength of the pith decreased.The tensile strength and shear strength of the pith i ncreased first and then decreased with the increase of moisture content.(2)Separation performance test of stalk-leaf.By means of striking and rubbing,a combination model of fixed leaf-stripping tooth plate and movable leaf-stripping tooth plate was put forward.A stalk-leaf separation test bench was designed.The stalk-leaf separation mechanism and the stress of stalk and leaf were analyzed.The finite element analysis of the fixed tooth plate of leaf-stripping mechanism was carried out with ANSYS software.The experimental results show that the mechanical properties of the selected material are within a reasonable range under the working load.With the leaf-stripping rate as the evaluation index,the spring wire diameter,linear speed of feed roller and speed of leaf-stripping roller as the test factors.Three factors and three levels orthogonal tests were carried out on the stalk-leaf separation performance of corn stalk.The results show that linear speed of feed roller and speed of leaf-stripping roller have great influence,spring wire diameter has significant influence.The optimal parameters combination: spring wire diameter is 1.4 mm,linear speed of feed roller is 1 m/s,speed of leaf-stripping roller is 700 r/min.(3)Separation performance test of rind-pith.Combining the principle of cutting and throwing,a kind of pith-stripping mechanism was designed.The rind-pith separation mechanism and the stress of corn stalk were analyzed.The main factors affecting the length of the pith are the rotation ratio between the speed of compaction roller and the speed of pith-stripping roller,and the number of cutters.According to the track analysis of pith throwing and the bending characteristics of the rind,it is concluded that the axial distance between the rind output rollers and the pith-stripping roller should be less than 350 mm,the pith can fall into the designated collection area and the rind can be successfully exported.The finite element analysis of the cutter of the rind-pith separation mechanism was carried out with ANSYS software.The results show that the mecha nical properties of the selected material are within a reasonable range under the working load.Selecting pith residue rate and rind damage rate as the evaluation index,cutter angle,number of cutter,clearance between roof and cutter and speed of pith-stripping roller as test factors,four factors and three levels orthogonal tests were carried out.The experimental results showed that for the pith residue rate: number of cutter and the clearance has great influence,speed of pith-stripping roller has significant influence,cutter angle has less influence.For rind damage rate: cutter angle and the clearance has great influence,number of cutter has significant influence,speed of pith-stripping roller has significant influence,the optimal paramrters combi nation: cutter angle,number of cutter,clearance between roof and cutter and speed of pith-stripping roller respectively 45 °,6,1.8 mm,780 r/min.(4)Design and test of corn stalk rind-pith-leaf separation equipment.On the basis of the above research,corn stalk rind-pith-leaf separation equipment was designed.The modal analysis of the rack using ANSYS software shows that the frequency of the excitation source does not coincide with the natural frequency of the rack,and the rack does not produce resonanc e.According to the above optimization parameters,a verification test was carried out by the rind-pith-leaf separation equipment of corn stalk.The test showed that the leaf-stripping rate was97.7%,the pith residue rate was 2.5%,and the rind damage rat e was 2.7%.The verification test shows that the rind-pith-leaf separation equipment of corn stalk runs normally and has stable performance,which meets the performance requirements of separatin g corn stalk. |
