The Research On Continuous Microwave Pyrolysis Technology And Equipment Of Rice Straw

With the increase of fossil energy consumption and the environmental problems year by year,more and more scholars paid attention on clean and renewable energy.The biomass resources,especially crop straw has become a research hotspot in recent years because it’s abundant reserves and nearly zero carbon emissions.Pyrolysis is one of the most important technique for biomass energy conversion,which can transform biomass into bio-oil,bio-char and bio-gas,and achieve the efficient utilization of biomass.However,the traditional pyrolysis technique has high requirements on biomass and requires pretreatment,thus it will increase the energy consumption for recycling crop straw.Microwave pyrolysis could ignore the pretreatments and get higher quality products since it has the characteristics of rapid,uniform,and penetrable heating.Therefore,the pyrolysis process of rice straw was studied in this paper,and the characteristics and the distribution of products of rice straw microwave pyrolysis were also explored.Based on the rice straw microwave pyrolysis characteristics,a continuous biomass microwave pyrolysis equipment was designed and manufactured.And the gas carbon co-production process was also explored on this continuous microwave pyrolysis equipment.The main research contents and conclusions are as follows:The pyrolysis characteristic and kinetic of rice straw were analyzed by using the thermo-gravimetric analyzer.The influence of heating rates,rice straw size,and the additives on the pyrolysis process and kinetic were studied.According to the results,the process of rice straw contained 4 stages:drying stage,pre-pyrolysis stage,main pyrolysis stage and calcination stage.With the increase of heating rate,the main pyrolysis stage of straw shifted to higher temperature zone;all additives could promote the pyrolysis process:the main pyrolysis stage of straw was shifted to lower temperature zone.The effects of NaOH and Na2CO3 are more significant.The same conclusion is reached by the thermodynamic research.To promote the pyrolysis of rice straw,additives could be added in raw materials while using the pyrolysis technology to dispose rice straw.The process of rice straw microwave pyrolysis and the influence of material size,loading rate,and microwave power on the process and products of rice straw microwave pyrolysis were explored.The results showed that,it also contained 4 stages of rice straw microwave pyrolysis process,and main product is fuel gas.Microwave power and loading rate had significant influence on the pyrolysis process.Material size has no significant effect on the pyrolysis process and product yields.Based on the characteristic and products distribution of rice straw microwave pyrolysis,the technical indexes were obtained.And a continuous biomass microwave pyrolysis equipment was designed and manufactured.The key parts of this equipment were designed or selected,the structure of control system was built,and the human-computer interaction interfaces were also designed.The results showed that,this continuous biomass microwave pyrolysis equipment was safety,easy to operate,and basically met the requirements.The characteristic of grainy rice straw microwave pyrolysis was researched by using the continuous biomass microwave pyrolysis equipment.And the rice straw pyrolysis process also contained 4 stages.The main product was solid product,then was gas product,liquid product yield was the lowest.The main component of gas product was CO2.The main component of solid product was biochar,which had great adsorption property.Microwave power and pressure had significant influence on the pyrolysis process,product distribution and products characteristics.Holding time had significant influence on the biochar adsorption.Pressure had little influence on the process.If use the calorific value of gas product Q as index,the optimum conditions to produce gas were as follows:microwave power 28.87 kW,pressure 0.08kPa,and the Q was 5553.69 kJ/kg.If use the adsorption capacity of biochar Abs as index,the optimum conditions to produce biochar were as follows:microwave power 26.45 kW,holding time 20.96 min,pressure 0.04 kPa,and the Abs was 50.83 g/kg.If use the comprehensive score S as index,the optimum process conditions for gas carbon co-production were as follows:microwave power 26.79 kW,holding time 20.85 min,pressure-0.01 kPa,and the S was 22.98.