Design And Experiment Of Biochar Extrusion Molding Machine

With the economic development,human demand for energy is growing and the traditional fossil energy gradually is depleted.In this background,governments are paying more and more attentions to the development and utilization of renewable resources,especially the use of biomass resources.China is a large agricultural country,and is rich in biomass resources.Because of the distribution of scattered,low energy density,transportation and storage costs are high,most of these resources are directly burned or abandoned,failed to be fully effective used.If these biomass were charred and shaped to bio-carbon blocks,the energy density and combustion characteristics would be improved,and it is easy to be transported and storaged.However,the reports about bio-carbon molding research are few,so this subject is to develop a bio-carbon extrusion molding prototype,and test its performance,aim to provide reference for biochar molding technology and molding process.The main contents of this research are as follows:(1)The mechanism of biomass molding was analyzed.The biomass constituents were analyzed and their influence on biomass molding were analyzed.The mechanism of biomass molding was analyzed from both macro and micro aspects and several factors influencing biomass molding were analyzed.Compared to the advantages and disadvantages of two kinds of bio-carbon molding process,molding process after first carbonization was selected.(2)The compression of biochar was carried out.The compression molding of biochar was tested by universal testing machine and self-designed extrusion molding and mainly studied the effect of pressure on biochar compressibility The density and bulk modulus of biochar formed by fitting were all exponentially related to the pressure.The results showed that when the pressure was 1 MPa~3 MPa,the density of biochar was 1.0 g/cm3~1.2 g/cm3,and the compressibility was good.At the same time,the effect of moisture content and binder addition on the performance of biochar compression was studied.Through fitting the mathematical model of the influence of the moisture content and the amount of the binder on the compressive strength and the anti-drop resistance after the molding of biochar was obtained When the water content was 22%~40%,the binder addition was 15%~40%,the performance of biochar compression was relatively good.(3)A bio-carbon spiral extrusion molding prototype was developed.This paper designed a biochar molding prototype which depended on the principle of spiral extrusion,and then elaborated its working process.It included: designing the main structure and key components of the prototype,and determining the feeding device,the transmission device,the extrusion device,discharge and other key components of the structural parameters.(4)The single factor test was carried out on the forming performance of the extruded prototype.Based on the pre-experiment of the extruded prototype,the single factor test about three main factors: the extrusion screw type,the amount of the binder and the moisture content was carried out.The compressive strength and the anti-drop resistance were evaluated.The results showed: for compressive strength of molded sample,the type of extruded screw,the amount of binder added,the moisture content factor were very significant(P<0.01);for anti-drop resistance of the molded sample,the amount of binder added was very significant(P<0.01),the type of the extruded screw and the water content were significant(P<0.05).(5)The orthogonal test was carried out on the forming performance of the extruded prototype.On the basis of single factor test,the orthogonal test was carried out at the level of good performance.Through intuitive analysis,the order of influence on the compressive strength was determined: the type of extrusion screw,the addition of binder,the moisture content;The order of the influence on the anti-drop resistance was determined: the addition of binder,the type of extrusion screw,the moisture content.Through the integrated balance method,the optimum structural parameters and the level of the molding process were determined: the equidistant unequal extrusion screw with a moisture content of 35±1% and a binder addition of 25.0±0.5%.(6)The performance of the prototype was tested.After determining the optimum structural parameters and he level of the molding process,the performance of the prototype was tested.The test results showed that the molding prototype productivity is 215 kg/h,the molding density is 1.06 g/cm3,the compressive strength of the molded article is 0.16 MPa,and the anti-drop resistance is above 98%,which meets the requirements of biochar molding.