Preparation Of Porous Ceramic Balls With Catalyst And Flowing Characteristics In A Fluidized Bed Reactor

Using biomass pyrolysis technology, agricultural and forest residues can be converted into bio-oil which is high energy density, renewable and easy to transport through a series of thermal chemical reaction. Some factors in the process of biomass pyrolysis such as the pyrolysic temperature, bed pressure,catalyst, heat carrier and effect of fluidization can also affect the quality and yield of bio-oil greatly.When dolomite is used as the catalyst in the process of biomass pyrolysis reaction, the reaction conditions can be morderated and product yield and quality can be improved. However, bed materials will encounter intensive collision and friction during the pyrolysis process, plain dolomite particles will be broken and crushed into fine particles due to its insufficient strength and get out of the fluidized bed by gases, resulting in the loss of catalyst. In order to solve this problem, putting forward combining dolomite with ceramic ball heat carrier into porous ceramic ball catalyst carrier was proposed in this study. Dolomite and quartz sand were used as aggregate, carbon powder was used as pore-forming agent, and carboxymethyl cellulose was used as adhesives. Firstly,porous ceramic ball catalyst carriers were prepared with different particle size and porosity by adding pore-forming agent technology. Secondly, the influence of porosity on the ceramic ball thermodynamic performance was studied. Finally,the flow characteristics of porous ceramic balls in the fluidized bed were analyzed using partical image velocimetry(PIV) technology.A set of visual cold fluidized bed testing equipment was design, fabricated and installed for studying the flow of porous ceramic balls in the fluidized bed.Preliminary orous ceramic balls flow experiments were conducted in the the fluidized bed. The experimental results showed that the design of this test-bed was reasonable and reliable, the experimental data were in agreement with the theoretic analysis.The performance of porous ceramic ball was measured and the flow characteristics of porous ceramic ball in the fluidized bed test bench were investigated. Experimental results showed that the porosity of porous ceramic ball had a greater influence on its compressive strength, thermal shock resistance,thermal conductivity and thermal expansion coefficient.The ceramic ball size and porosity had a significant influence on the flow characteristics. Within the scope of the test, with increase of porosity the bulk density of porous ceramic ball was reduced, compressive strength and thermal shock resistance reduced as well, the fluidization effect was improved.Wheresa the fluidization effect was getting worse and bed height was reduced with the increase of ceramic ball size. With the increase of static bed layer height there emerges an intensification of the ceramic ball fluidization effect in the fluidized bed. By comprehensive comparison and analysis, it is concluded that the best fluidization effect could be achieved inside the fluidized bed when ceramic ball size is 1 mm, porosity is 56.5%, static bed height is 120 mm. These studies would provide a experimental support for further research of biomass pyrolysis and multicomponent mixture flow process in fluidized bed.