| With the widely use of fossil energy,its resources are becoming increasingly exhausted.Due to its advantages of renewable,universal,and huge resources,biomass has attracted attentions of many countries around the world.Biomass densified technology is one of the main ways of effective utilization of biomass.It can process loose biomass raw materials to high-value fuels with a certain shape,higher density,higher heating value,and low emissions in burning.Therefore,it has important practical significance for the efficient use of biomass with studying the biomass densified technology and equipment.Firstly,the paper studied influencing factors of the ram compression molding machine,which analyzed the effects of extraction treatment,pressure,compression speed and compression frequency on the quality of densified biofuel.The results showed that with the removal of extractives,the combustion performance of densified biofuel was significantly improved,and it would be easier to ignite and burn out.The density was also increased,reaching 1250kg/m~3.However,there was no clearly evidence showed that the removal of extractives can effectively improve the diametric compressive strength.While increasing the pressure,the density,diametric compressive strength and specific energy consumption will increase together.As the compression speed increases,it has little effect on the density,diametric compressive strength and specific energy consumption.It was also concluded that the density increases first and then stabilizes with the increase of compression frequency.Different from the density,the diametric compressive strength was increases first and then decreases.But they both has the small change.Orthogonal experiments showed that pressure was the most important factor affecting density and diametric compressive strength,followed by compression speed,and the effect of compression frequency was the weakest.The optimal molding combination obtained were the pressure of 7 k N,compression speed of 40 mm/min and two compression frequencies.Secondly,combining with the problems of the exist molding machine,we delivered a new ram compression molding machine on the basis of the numerical control pressure device.The prototype was also assembled.The machine adopts a switched reluctance motor which has high starting torque and can stop/start frequent as a power source.The machine also takes the characteristics that flywheel can accumulate energy.While working,the motor first accelerates the ram to a set-speed,and then the molding was completed under the combined action of the ram gravitational potential energy and the energy accumulated by the flywheel.Hence,the motor does not need to be work all the time.The mold consists of three parts,and each part is an independent structure.In order to evaluate the feasibility of this molding machine,three typical biomass(corn straw,pine sawdust,and peanut shell)were selected as raw materials,and a molding test was performed.The density,durability and combustion performance of the densified biofuel were analyzed.In order to make the evaluation objective,a comparative experiment was performed with the densified biofuel produced by the pellet mill with horizontal and ring type die.The results as follows:(1)The densities of corn stalks,pine sawdust,and peanut shells were 1273 kg/m~3,1262kg/m~3,and 1196 kg/m~3,respectively,all of which meet the requirements for transportation and use,and beyond the density of ring-molding fuel;(2)All the durability of stamping fuels was beyond 95%,and significantly higher than that of ring molding fuel;(3)The heating value of corn stalks,pine sawdust,and peanut shells were 28.393 MJ/kg,29.937 MJ/kg and 32.397 MJ/kg,respectively,and were significantly higher than those of ring die forming fuels;(4)The combustion process and kinetic analysis results showed that the stamping fuel does not perform better than the ring molding fuel.The reason may be that the test was based on thermal analysis and the experimental material is less. |
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