| There is a huge amount of fertilizer used in agricultural production in our country,but the utilization rate of traditional fertilizer is low,which will pollute the environment.At the same time,our country produces a large number of agricultural and forestry waste each year,but many of them are abandoned or burned,which not only waste resources,but also pollute the environment.The biochar can be obtained by heating the biomass under certain conditions.In addition,biochar and ordinary fertilizer in accordance with a certain process can be prepared biochar-based fertilizer.Biochar-based fertilizer can improve the utilization rate of fertilizer,reduce the pollution of the environment.It has obvious advantages,when compared with the traditional fertilizer.This not only provides a new way for the utilization of agricultural waste,but also helps to overcome the drawbacks of traditional fertilizer.Therefore biochar-based fertilizer has a wide development prospects.But biochar-based fertilizer currently obtains mainly by means of the direct mixing,without forming,which is not conducive to the transport,storage,mechanized application,large-scale promotion and industrial development for biochar-based fertilizer.And there are many problems in the current forming equipment.So the development of biochar-based fertilizer forming equipment and the relevant experimental research are of great significance.In this paper,the study on extrusion forming experiment was carried out to obtain the best combination of material ratio factors.And based on the proportion,the forming material used for subsequent forming machine test was made.The properties of the forming material were tested.On this basis,a columnar biochar-based fertilizer forming machine was designed and developed.Then,the forming effect test and performance test were carried out.The main research contents and conclusions were summarized as follows:(1)Extrusion forming test was carried out.The single factor test and orthogonal test were carried out on the experimental platform,which was made of the self-made extrusion die and universal testing machine.In the experiment,the water resistance,compressive strength,and density were selected as the comprehensive evaluation indexes of the forming quality.In addition,the binder type,biochar content,and binder addition were selected as the test factors.The results of single factor test showed that the effect of binder type on water resistance,density and compressive strength was very significant(P<0.01).And that the effect of binder addition on water resistance and compressive strength was significant(P<0.05),while it was not significant for density(P>0.05).And that the effect of biochar content on water resistance and compressive strength were not significant(P>0.05),while it was significant for density(P<0.05).The results of orthogonal test showed that when biochar content is 60%,soluble starch is as the binder,and the amount of binder was 15%,the comprehensive performance of the forming quality is the best.At this time,the compressive strength is 206.27 N,the density is 1.004g/cm3,and the water resistance is 52.45 min.(2)The physical properties of the material to be molded were tested.The loose density,the angle of repose and the coefficient of static friction between the material and the steel plate were determined,which provided the basis for the design of the structural parameters of the molding machine.The test results showed that the bulk density of the material to be molded is 0.57g/cm3,the static friction coefficient is 0.31,and the natural angle of repose is 35.33 °.In addition,the fluidity of the material is in general.(3)A columnar biochar-based fertilizer forming machine was designed and the finite element analysis of important working parts was carried out.The transmission scheme of the extrusion part and the pelletizing part of the molding machine was determined.The overall structural design of the molding machine was carried out and the main technical parameters were determined.The structural parameters of the key components were designed.The static structure analysis of the screw was done by utilizing ANSYS Workbench software.Then,it that the screw is safe enough can be gotten.The modal analysis of the screw is carried out,and it is found that the resonance will not occur when the screw is working.It can avoid the structural damage caused by the resonance.Finally,based on the principle of screw extrusion,a columnar biochar-based fertilizer forming machine mainly consisting of extruding device,forming device and pelletizing system was designed,which can complete the process of conveying,extruding,forming and granulating.(4)Experimental study on forming machine was carried out.The single factor test,orthogonal test and molding machine performance test were carried out by using the forming machine designed and manufactured.In the experiment,the screw speed,the cutting speed of the pellet shaft and the opening rate of the hole board were selected as the test factors,and the qualified rate,yield and hardness were taken as the judging indexes of forming effect.The results of single factor experiment showed that there was a great relationship between the qualified rate and the matching degree of the screw speed and the cutting speed of the pellet shaft.And that with the increase of screw speed,the cutting speed of the pellet shaft and the opening rate,the grain yield can be increased.And that the cutting speed of the pellet shaft had no effect on the hardness,while with the increase of the screw speed and the opening rate,the hardness reduced.The results of orthogonal test showed that for the qualified rate,the influence of the cutting speed of the pellet shaft and the interaction between it and the screw speed were very significant(P<0.01),while the screw speed was significant(P<0.05),and the other was not significant(P>0.05).For the yield,the influence of the screw speed was very significant(P<0.01),while the opening rate of the hole board and the cutting speed of the pellet shaft were significant(P<0.05),and the other was not significant(P>0.05).For the hardness,the influence of the screw speed and the opening rate of the hole board were very significant(P<0.01),while the other was not significant(P>0.05).When the screw speed is 45r/min,the cutting speed is 185r/min,and the opening rate of the hole board is 10%,the best forming effect was gotten.Under this condition,the qualified rate is 86%,the yield is 32.27kg/h,and the hardness is 2.56 kg.The performance test results showed that the forming rate of particles was 96.2%,the density of particles was 0.92g/cm3,the moisture content of the particles was 1.61%,which was consistent with the relevant forming requirements,and can meet the needs of production. |
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