Study On Direct Pyrolysis Technology Parameters Experiment Of Cotton Stalk

Staw waste, produced in the process of production, gathering, processing, transportation and energy conversion of straw, has a direct or indirect impact on the ecological environment. Hence the study aims to convert cotton stalk into green energy--biochar by applying dispersed pyrolytic carbonization technology, which will utilize cotton stalk resource effectively and alleviate the environmental pollution. Having reviewed studies about pyrolytic carbonization of waste biomass materials at home and abroad, it applies a mode of dispersed pyrolysis carbonization in cotton stalks: experiments are conducted on carbonization mode, carbonizing device and carbonization process to achieve on-site treatment on biomass straw materials and realize economic benefits. The study is on cotton stalk. By conducting pyrolytic carbonization directly and utilizing dispersed pyrolytic carbonizing furnace, the paper, making solid biomass char as the target product, studied the factors of direct pyrolytic carbonization and the qualities of target product, providing theoretical support for effective utilization of biomass materials.The main findings are as follows.(1) Tests on mechanical properties of cotton stalks, elemental analysis and thermogravimetric analysis are conducted. Based on the relationship between the component of raw material and thermal weight loss, it analyzes the factors of the yield of direct pyrolytic solid product of cotton stalks and points out the parameters of direct pyrolysis of cotton stalk: the minimum temperature is higher than300℃, the maximum temperature is lower than600℃, and heating rate not suitable too high.(2) Study on the pyrolysis products of crushed cotton stalks pyrolysis experiments in the different equipment. The effects of three factors (pyrolysis temperature, pyrolysis heating rate and pyrolysis holding time) were investigated by using the mass of the products yield as the indexes. Through direct pyrolysis experiments on cotton stalks, the changes of raw material mass and the relationship between pyrolysis parameters and pyrolytic products are found. In the process of pyrolysis, the mass of pyrolytic solid product decreases as the reaction temperature increases; when the pyrolysis temperature is higher than400℃, fixed carbon(FC)content in solid product begins to decrease as reaction temperature increases. In order to determine the optimum technological parameter of pyrolysis, an orthogonal experiment is conducted. The maximum product yield of49.98%is obtained with5℃/min of heating rates,400℃of optimum pyrolysis temperature, and2h of holding time. Box-Benhnken design (BBD) and response surface methodology (RSM) are adopted to obtain the optimum parameters on the basis of results of single-factor experiments. The results indicate that the optimum parameters is ratio of raw material of carbonization chamber and combustion chamber2:1, maximum product yield of50%.(3) Temperature field on the biomass carbonization furnace is simulated and analyzed by the software, Ansys. Because of the gas flow in the pyrolysis furnace, temperature has not been evenly spread, and there is a large temperature difference. In order to meet the pyrolysis temperature, it must have had enough holding time, let the charring materials carbonize fully; it should increase the chimney and carbonized material contact area of pyrolysis furnace to increase the temperature of vents through stack draft; Through even arrangement of heat transfer around the coking furnace, use the heat transfer tablet to transfer heat to the bottom and sides, to achieve even distribution of temperature field.(4) With the development of the pyrolysis reaction, it changes the distribution proportion of solid products and elements. T he solid residues were analyzed by elemental analyzers, scanning electron microscopy (SEM), FTIR and thermogravimetric analyzer. When the temperature rises, the element in solid products gradually increase or decrease; fixed carbon(FC) content is maximum when the temperature is500℃. Study on the physicochemical properties of a solid product obtained after pyrolysis of cotton stalk found that calorific value of cotton stalk is30MJ/kg, moisture content10.125%, ash9%, volatile30%, fixed carbon content of32%, bulk density421kg/m3, Accumulated angle58.16°, friction coefficient0.45-0.60, flow property69.1. The results show Cotton carbon formed easily and is not so easy to flow with high calorific value.(5) This part is about prediction analysis about the application of dispersed pyrolytic carbonization furnace. To predict the applicability of carbonization furnace, it analyzes the raw material adaptability, energy conversion efficiency, dispersed pyrolytic carbonization and centralized plant carbonization, and the cost and benefits of straw compression. It is found that carbonization furnace could be applied not only to cotton stalk but also to most crop straw and agricultural and forestry waste. The enterprise production cost of plants with electricity as energy is higher than plants using oil and burning produced by pyrolysis carbonization furnace. By comparison with dispersed on-site carbonization, centralized plant carbonization and straw compression, it turns out that dispersed carbonization has low cost and high benefit.Biomass pyrolysis is a very complex process.Pyrolysis is not only relative to the raw material and environment., but also has intimate correlation to process parameters and pyrolysis equipmeng. Only part of the work of this paper, study of a raw material.It is verified by simulations and experimental.