Comparative Study Of Devolatilization Characteristics About Biomass Pyrolysis

Recently, the development and utilization of biomass energy is concerned by the domestic and abroad governments and research institutes, not only involved in the agriculture and rural economy, but also related to the energy security. On the one hand, developing and using biomass energy is the strategic measures to develop new energy sources and alleviate the contradiction between the energy supply and demand in China. On the other hand, it is the important task to solve the "three rural" issue for the sustainable development of Chinese-socio-economic. With the implementation of joint action to pay for the greenhouse gas emissions of the world by the international community, the vigorous development of biomass energy resources is of great significance to improve our energy structure based on fossil fuel, especially to provide clean and convenient energy for the rural areas in local conditions.In this paper, the importance of biomass energy development is described firstly. Then, the research status of biomass energy conversion and utilization technologies and the concepts and features focused on biomass resources are introduced in this paper. From the macro and micro aspects, the necessity and significance of the biomass energy resources development and the biomass energy utilization technologies are discussed. At last, the main direction and research method of this study is stated. This study is of the important practical significance to the further research in biomass research field.In this paper, based on a large amount of literature and experimental studies, two methods are used to study the volatilization characteristics and reaction mechanism of slow and fast pyrolysis of biomass respectively. The differences between slow and fast biomass pyrolysis are compared in the end.In this study, using the WCT-1C type differential thermal analyzer, the slow pyrolysis experiments of corn stalks, peanut shells and cotton stalks particles under different heating rates (5℃/min,10℃/min,15℃/min and 20℃/min) were conducted. The curves of the percentage of pyrolysis volatilization and the rate of weight loss with the time at different heating rates in slow pyrolysis experiments were determined. The curves indicated that, in the temperature programmed conditions, pyrolysis of biomass is mainly affected by heating rate. As the heating rate increased, the time of percentage of maximum pyrolysis volatilization gradually advanced, and the rate of weight loss also increased.In this study, the fast pyrolysis device, laminar entrained flow reactor, was improved by extending the length of the reaction tube in order to extend the reaction time of the biomass. The extended tube was heated by an electric heater and controlled by a PID controller, so that the reaction tube temperature could keep consistent as much as possible. More thermocouples were used to realize the real-time monitoring of temperature in the reaction tube. At the same time, the feeder was re-designed and the feeding rate and its uniformity were improved. We obtained a suitable parameter of feeding volume. Corn stalk was used to conduct the fast pyrolysis experiments at different temperatures and different collection distance based on the above improvement and optimization of the device in this study. By the fast pyrolysis experiments, the devolatilization characteristics of biomass fast pyrolysis were studied, and the final percentage of the devolatilization was determined. It will validate and optimize the previous proposed model of the devolatilization characteristics of biomass fast pyrolysis. We measured the final volatilization percentage of corn stalk and came to the conclusion of 85%.In this study, based on two experiments in the above, the volatile characteristics and reaction mechanism of the slow pyrolysis and fast pyrolysis of biomass in different conditions was compared. The experimental results showed that, under the conditions of slow pyrolysis, the pyrolysis of biomass is mainly affected by the heating rate. The higher heating rate is accompanied by the greater rate of weight loss and the shorter time of maximum volatilization percentage. When the heating rate increased to a certain value, the pyrolysis of biomass volatilization rate will tend to reach a constant value, too. This value is named as the final volatilization percentage of biomass. The fast pyrolysis of biomass is under a very high heating rates, and the experimental results showed that, in the fast pyrolysis of biomass under the conditions of the high heating rate, the volatile characteristics is no longer affected by the heating rate any more, but only be related to the type of biomass. Different types of biomass will have the different final evaporation percentage.