Chemical Looping Gasification Of Biomass And Reaction Kinetics Of Biomass Char With Oxygen Carrier

With the consumption of fossil fuels and other non renewable energy sources increasingly tense, it is important to seek a kind of renewable energy to alleviate the pressure caused by the lack fossil energy, biomass energy has the advantages of abundant reserves and is a kind of renewable energy, so it will become the main energy source in the future, among the numerous biomass utilization technologies, biomass gasification has great potential for use. The traditional ways of gasification have many drawbacks, such as high-cost and low purity of the syngas produced, chemical looping gasification, however, can reduce the cost of gasification, and can effectively control the content of CO2 and H2 O to get a high purity fule. At present some scholar have research on chemical looping gasification of biomass, but most attention was paid to study the performance of oxygen carrier, a little research on thermodynamic characteristics and the gasification characteristics of components about chemical looping gasification, especially, the reaction characteristics and dynamic characteristics of oxygen carrier with biomass char, however, the reaction mechanism and reaction characteristics of biomass char with oxygen oxygen carrier is important to chemical looping gasification of biomass. Therefore based on above analysis this the research is about chemical looping gasification of biomass, it will have the practical significance and academic significance.Firstly, this paper use theoretical calculation to study the thermodynamic characteristics of chemical looping gasification of walnut shell, for optimizing the reaction conditions, provide the basis for the experimental conditions that; Secondly, using the fixed bed, TG-FTIR, scanning electron microscope to study the walnut shell, Ca SO4, water vapor chemical looping co gasification characteristics and coking characteristics, to get the key factors influencing the reaction time of oxygen carrier with biomass; Finally, based on the kinetic mechanism of solid-phase pyrolysis, to study the reaction characteristics of walnut shell char with oxygen carrier and kinetic characteristics and model. The results show that.(1) The study found that, the molar ratio of walnut shell with Ca SO4, temperature can promote the chemical gasification of walnut shell, but the increasing of the pressure is not conducive to chemical looping gasification of the walnut shell,and integrating gasification and the degree of the negative reaction which produce Ca O, to get optimization of reaction conditions: The most suitable reaction ratio for Ca SO4/CH4 is 0.11, temperture could affect chemical looping gasification of biomass, and the most suitable temperture for the reation between Ca SO4 and biomass is 1000 ℃; The increasing of the pressure is not conducive to the chemical looping gasification for synthesis gas; The optimum temperature of reaction between Ca S and air in the air reactor is 950℃.(2) Through optimization conditions, this paper sets the experimental reaction conditions of the fixed bed, the characteristics of chemical looping gasification of walnut shell show out, the ratio of walnut shell / Ca SO4 and temperature has impact on, when the mass ratio of biomass is 0.4, CO can reach the maximum value; High temperature can improve the carbon conversion rate, and H2 and CO can increase gradually; Water vapor has great effect on the gasification components, and it can improve the conversion rate of biomass, with the increase of the concentration of water vapor, the calorific value of gas reduces gradually.(3) Through thermo-gravimetric analyzer coupled with fourier transform infrared spectroscopy(TG-FTIR) and scanning electron microscocpy to get reaction parameters and characteristics, the study found, the appropriate ratio of the oxygen carrier and the temperature increase can improve the reaction rate of walnut shell char with oxygen carrier, and shorten the reaction time. There is a loss peak about 950 ℃ in the chemical looping gasification process, and CO2,CO,COS,SO2 are founded in the reaction product, we can get that the appropriate proportion can enhance the reactivity of biomass char/Ca SO4 from the study on different ratio, the appropriate proportion is propitious to chemical looping gasification of biomass, temperature has a great influence on the walnut shell coke structure, the increase of temperature can enhance effect of walnut shell char.(4) The kinetic results from methods of Ozawa,Coats-Redfern and Malek show that: with the increase of the conversion rate, the activation energy is decreasing, what’s more, the shrinking cylinder model with surface reaction is the best model which agrees well with the experiment data.This study enriches the research results of chemical looping gasification, to a certain extent, the chemical looping gasification provides the experimental basis and theoretical basis.