Study Of Key Technologies On The Process Scheme Of Biomass High-temperature Cyclone Staging Pyrolysis And Gasification

Biomass gasification converts solid biomass to gas fuel by thermal chemical reactions. The gas product of which can be used for gas supply, power generation, as well as central heating. There are some barriers to conversional biomass gasification technology, such as high content of biomass tar and effluent disposal etc.. In particular, high content of biomass tar in gas product is the primary issue. The paper proposes a process scheme of using cyclone furnace for biomass high-temperature staging pyrolysis and gasification, which is intended to solve the above problems by significantly reducing the content of tar in gas product through biomass cyclone staging pyrolysis and gasification at high temperature. The paper studied on the key technical problems in techniques of biomass high-temperature cyclone staging pyrolysis and gasification, including work in the following aspects:A process model by Aspen Plus was built for the scheme of biomass high-temperature cyclone staging pyrolysis and gasification. Process simulation of rice husk steam gasification was carried out for validation of the feasibility of the above scheme. 15.4%-20.5% of the total gas production was used for combustion could achieve heat self-sufficiency of biomass high-temperature cyclone staging pyrolysis and gasification.Based RSM model, simulation and structure optimization were carried out for single phase flow field of the biomass high-temperature cyclone staging pyrolysis and gasification furnace, which was verified by cold experiment. The furnace entrance of high-temperature cyclone staging pyrolysis and gasification was determined by bisymmetry inlets with 30° angle and the exhaust pipe without inserting into the cyclone.Bio-char was prepared by using a lift furnace, and the effects of char preparation temperature, heating rate and reaction time on char yield, as well as analyzing the topographic and pore characteristics of bio-char by SEM and surface area analyzer. The surface area of biomass raw material is small, whose absorption characteristics is also poor, and the surface area of bio-char rises rapidly along with the increasing of bio-char preparation temperature, and the surface area of husk char and sawdust char is respectively 315.59m2/g and 590.41m2/g prepared at 1000°C.The characteristics of bio-char high-temperature steam gasification reaction have been studied. A steam gasification reaction model was built to an alyze the effects of temperature, steam flow rate, reaction time and char preparation temperature on the conversion rate and gas composition, as well as the reaction kinetics. Temperature is the main factors affecting the conversion rate and gas composition, and temperature will contribute to improve the conversion rate of bio-char and hydrogen ratio, the surface reaction control in condensation reaction model can describe steam gasification reaction characteristics of rice husk char and sawdust char.A numerical simulation has been carried out for single particle bio-char gasification and gasification process in gasifier, which has studied the effects of temperature, pressure, particle size on single particle bio-char steam gasification and gasification process in gasifier. With the decreasing of the particle size as well as the increasing of temperature and steam partial pressure, the conversion rate and heating value will correspondingly increase; the boundary temperature of particle and external environment will be in a quasi-static convection, whose heat was conducted from outside to inside and as the temperature drops, the gas reaction will reach equilibrium.