Applied Research On Cassava Dreg And Stalk Pyrolysis Dynamics And Gasification Process Simulation

This paper analyzed the current situation of Guangxi’s agricultural and forestry wastes like cassava dreg and stalk, bagasse and others, knowing that these agricultural and forestry wastes have large volume, or is difficult to dispose of, and are affecting the surrounding environment, turned to restrict the Guangxi cassava starch industry and sugar industry’s rapid development. The paper proposes using the pyrolysis and gasification technology for recycling the agricultural and forestry wastes.The thermogravimetric analysis of cassava dreg at three various heating rates of10,30,50℃/min was studied. Results showed that the process of cassava dreg pyrolysis could be divided into four stages of40to100℃,110to220℃,220to360℃and400to730℃, and the most effective pyrolysis interval ranged from220to360℃.In cassava dreg’s most effective pyrolysis interval, with the increase of heating rate β, the the absolute value of peak release rate|Dmax|, the weight loss peak θmax and starting temperature of the most effective pyrolysis interval Ts increased. The minimum value of FWHM temperature interval△T1/2appeared at△=30℃/min, and the characteristics parameter of volatile emission reached to maximun at β=30℃/min, indicating that cassava residue was more susceptible to pyrolysis at this value of heating rate.In cassava stalk’s most effective pyrolysis interval, With the increase of heating rate β, the the absolute value of peak release rate|Dmax|,the weight loss peak θmax and starting temperature of the most effective pyrolysis interval Ts, the minimum value of FWHM temperature interval A△T1/2and the characteristics parameter of volatile emission increased.The Coats-Redfern equation was used to evaluate the linear fitting of pyrolysis characteristics in the the most effective pyrolysis interval of cassava dreg and stalk by substituting different temperatures and conversion rates, as the41kinds of common mechanism functions were substituted into the Coats-Redfern equation, the best fetting results were three-dimensional diffusion cylindrical symmetry and two-dimensional diffusion mechanism model, as well as their pyrolysis rate equations were and,respectively.Higher heating rate was more conductive to the cassava dreg and stalk’s gasification reaction with CO2, but lower heating rate made the reaction more concentrated. At constant temperature800℃, the cassava stalk was much easier than the cassava dreg in reacting with CO2.Modeling of biomass steam gasification has been investigated taking into account both mass balance and chemical equilibrium. This model was to simulate the steam gasification operated with bagasse, and good agreement was gained between prediction and measurements for the producer gas.And took the cassava dreg and bagasse as example to study the feature of this model, and from the model the best S/B ratio could reached0.3kg/kg and0.2kg/kg, respectively. As the temperature rised, the volumes of H2and CO increased. As the S/B ratio rised, the total volume of gasified gases and the gas yield increased significantly. The rise in temperature was helpful to the gasification reactions.This article design a set pyrolysis and gasification system, after installation and debugging, the system could start up for many times to carry on nomal pyrolysis and gasification process. Its processing capacity is1000kg/h, and gas production is1600m3/h. This system could treat many kinds of material, particle size of which is0.1-10mm, and it dosen’t require much about the feeding material, thus it has a wide rang of appilication. The CO, H2and CH4in the gasified gases account most(excceding70%) and less non-combustible components(less than30%), everage LHV of which is10.13MJ/Nm3.