The Research And Development Of Coal-fired Industrial CFB Boiler With Recycled Solid Heat Exchanger

Because coal play a main role in the energy structure of our country and coal quality is worse gradually, the Cycle Fluidized Bed (CFB) combustion technology has become an important direction of coal-fired industrial boiler, which can burning various inferior fuel and is an environment-friendly and highly efficient technology. However, the basic theories and experimental study are unsatisfactory, which lead to some problems of industrial CFB boiler for a long time, such as low thermal efficiency, wear of buried pipes, complex structure, high cost and so on. When the quality of coal degenerates, the problems will be more serious. The poor quality of coal mainly reflected in decrease of calorific value, increase of ash content and raise of sulfur content. In order to meet the new requirements of industrial coal-fired CFB boiler, a new scheme was first proposed by the author and his colleagues and had already applied for a nation invention patent. The research was based on sufficient survey on middle and small size industrial CFB boiler. The 11t/h industrial CFB boiler with the new scheme of the structure arrangement had been put into operation in 2009.Through a series of industrial tests, the basic rules of industrial CFB boiler with recycled solid heat exchanger in structural arrangement, gas-solid flow, combustion and heat transfer, the material and energy balance were obtained. By numerical simulation, the gas-solids flow characteristics could be known in the fine particles heat exchanger. The results of the study mainly included that:①The industrial CFB boiler with recycled solid heat exchanger reached the expected design parameters and its scheme of the structure arrangement was available.②The rational use of fine particles heat exchanger was the key to lessening the furnace size of boiler and reducing consumption of metals.③The ignition efficiency was increased through calling off buried pipes of furnace and moving them to the fine particles heat exchanger. At the same time, wear of buried pipes was also substantially reduced.④It was effective to improve load-following capability through carefully considering the problems of combustion efficiency and material balance.⑤Through numerical simulation in software Fluent, the gas-solids flow characteristics could be reflected in the fine particles heat exchanger. ⑥When the fluidization velocity of air was 0.5m/s and the initial bed height was 1200mm, the fluid state of gas-solids was best in the fine particles heat exchanger.