The Research On Rice Straw Hot Press Molding Experiment And Thermogravimetric Experiment Of Pellets

As one of renewable energies, biomass energy has the characteristics of zero pollution and zero emissions. Rice straw cold press process had been done early by the team and the result showed that the fuel consumption of pellets was high and the quality was bad. To improve the quality of rice straw pellets, this paper carried on the following work:(1) Using loose density and some durability indexes as judgment criteria, rice straw hot-press forming was carried out to get the general law and range of each parameter. The confirmed best process parameters were as follows: particle size 0-2mm, temperature 70-100?, compressive forces 8.89-40 MPa, moisture content 12%-25%. Compared with the cold press molding, pressure decreased greatly and size range of raw material particle became wide. That the temperature considered at the same time made the range of moisture content expanding, which could reduce the cost of production, and providing data support for the parameters selection in practical production.(2)In order to increase the quality of rice straw pellets, some wood chips were added to the rice straw materials forming the mixed raw material.With rice straw raw material, wood raw material and mixing raw material as the research object, hot-pressing forming experiment was carried out respectively. The results showed that mixing raw material pellets had better physical properties than pure rice straw pellets. Compared with traditional methods, the processes of this method were much simpler, and do not increased the ash content and lower calorific value of pallets.(3)Because of the structural feature of wood chips material, the 1:1 blends of rice straw and wood chips material pellets were more weaker than rice straw and wood chips materials pellets in the respects of water resistance physical property. Therefore, a set of orthogonal hot pressing forming experiment were used to respectively get the most significant effect factors and the reasonable combination of three parameters for each physical property respectively and the result would be testified by test. The results indicated that each process parameter had different impact extent to various physical properties. Indexes of loose density, shatter resistance and compressive strength were strongly correlated with compressive force, and the mixing ratio had massive effect on the index of water resistance. The reasonable parameter combination for water resistance and compressive strength: the mixing ratio was 1.5:1 and the temperature was 90 ?and compressive strength was 31.11 MPa. The reasonable parameter combination(mixing ratio, temperature and compressive forces) for loose density was 0.5:1×70 ×31.11 MPa, and for shatter resistance was 2:1×110 ×31.11 MPa. On the basis of the above tests, a set of surface response texts were conducted. Selection of mixing ratio, temperature and pressure as variables, loose density as response value, obtained the mathematical model of loose density and the model was significant. The optimum technological parameters were predicted by the software: 32 Mpa compressive forces, mixing ratio 1.83:1, loose density 0.9958g·cm-3. The predictive value was verified in the range of error.(4)With pellets of rice straw and wood chips as the research object, by studying the pyrolytic process under argon atmosphere, we got that: Rice straw briquette fuel pyrolytic process was divided into three important phases namely preheating solution, fast pyrolysis and slow pyrolysis stage; Pyrolysis maximum rate would increase with the rising of pyrolysis heating rate, which was beneficial to pyrolysis, but could cause such problems as incomplete reaction, so the temperature rise rate should not too high. By comparing the performance of the two kinds of pellets, sawdust pellet stability was better than that of rice straw briquette fuel; Through calculating kinetic parameters of the rice straw pellets pyrolysis, activation energy and referred to the former factor increases with the rising of heating rate, and linear fitting coefficients were all above 0.99, showing that the main reaction stage were in line with the first order reaction model.