Experimental Research Of Inert Paticle Effect On Low Concentration Methane Combustion Characteristics In A Fluidized Bed

Low concentration methane such as coal mine methane is difficult to utilize withregular technologies due to its low methane concentration and large variation, therefore,it is usually emitted to atmosphere without any treatment, which not only causes energywaste, but also exacerbates greenhouse effect and air pollutions. Fluidized bedcombustion technology gets more and more attention for its remarkable performance inlow concentration methane clean and effcient utilization. At present, the research aboutgas fuel combustion in fluidized bed mostly focuses on high concentration methane andlean methane catalytic combustion at low temperature. Few studies have been done onlow concentration methane combustion in fluidized bed with inert particles. Theinfluence of quartz sand particles, which is widely used as bed material, on methanecombustion in fluidized bed and explanation to its reaction mechanism also requirefurther study. Therefore, it has an important academic significance and application valueto research combustion characteristics of low concentration methane over inert particlesin fluidized bed.Research is carried out experimentally in a bubbling fluidized bed reactor systemwith quartz sand particles as bed material, the flow and combustion characteristics oflow concentration methane in fluidized bed are studied. Effects of bed temperature,fluidized velocity, inlet methane concentration and properties of bed material are studiedto determine low concentration methane conversion, combustion products and axialprofile of combustion products. The influence of inert particles on low concentrationmethane combustion is specially researched in a fixed bed reactor and reactionmechanism is given to explain the results.The results show that methane conversion increases and dimensionless methaneconcentration decreases with the increase of bed temperature, and combustion reactionmoves towards bed bottom. Methane conversion decreases and combustion reactionmoves towards bed top when fluidized velocity and inlet methane concentrationincrease. Methane conversion increases and dimensionless methane concentrationdecreases with the increase of particle diameter and bed height, and combustion reactionzone moves towards bed bottom.Methane combustion over inert particles also produces a little CO in combustionproducts. As bed temperature increases, CO concentration increases when bed temperature increases, and then decreases, CO concentration gets maximum peak at850℃. The results show that inert particles considerably inhibit methane combustion,the free radical adsorption and destruction on the inert particle surfaces, especially theOH radical destruction, is the main factor of combustion inhibition.