Study of Performance of an Atmospheric Bubbling Fluidized Bed Combuster Using Rice Waste

Abstract

Rice is cultivated in all the main regions of world. The worldwide annual rice production is 666 million tons for year 2008. Rice husk, rice straw and rice bran are three types of rice crop waste materials available today. Of these, rice husk and rice straw are the only types of rice waste which could be incinerated in fluidized bed combustors. The total rice waste generated is comprised of 20% rice husk, 70-80% rice straw and 2-3% rice bran. Rice straw is burned in open fields, ploughed in fields, used in compost, cattle house flooring and about 10-15% of total rice straw is available for direct combustion in commercial fluidized bed combustors in Punjab state. The available 10-15% rice straw for combustion in fluidized bed combustors is also dependent on region/area. Due to higher collection cost of rice straw it was not used in many of commercial fluidized bed combustors in the state. Rice husk being easily bought from rice mill owners is easily available for most of the commercial fluidized bed combustors. The study presented here is mainly focused on rice husk, which is abundantly available in this region. The combustion of rice husk/rice straw in fluidized bed combustors is an attractive possibility of future for power generation, the solution of waste disposal problems and the reduction of greenhouse gases. As paddy plants consume carbon dioxide emissions during photosynthesis process, the overall carbon dioxide emissions during combustion of rice husk/rice straw can be offset, which is fundamental advantage of extracting energy from rice husk/rice straw through combustion and gasification process in the perspective of sustainability. Rice husk characterized by having high ash content, low bulk density and poor flow characteristics makes it difficult for energy conversion. Where as rice straw is having low ash content as compared to rice husk, but when available for combustion it creates feeding and agglomeration problems more predominantly as compared to rice husk.