Study On Coal Feeding Uniformity Of 600MW Super-Critical Circulating Fluidized Bed Boiler

Circulating Fluidized Bed(CFB) combustion engineering is one clean coal technology which has a lot of advantages, it would make a big difference to the clean and efficient utilization of Chinese fault coal. In order to acquire higher generating efficiency and lower pollutant emission, CFB utility boilers are moving forward to large-scale level constantly, it's also faced with some difficult technical problems which needs to be solved as soon as possible in the meantime.This article depends on CAS priority strategy science and technology project, combining the theory and practice, the author has deeply discussed 600 MW super-critical CFB boiler coal feeding uniformity and other related issues by field measurement and correlative calculation, on the basis of the secondary coal feeding system optimization and heat balance in dense phase zone perspective, which gets an important relationship of large-scale CFB boiler between the coal feeding uniformity and furnace structure plus operating characteristics. It provides valuable references for coal feeding system design and operation of super-critical and ultra-supercritical CFB boilers in the future.The main study contents and related conclusions include:(1) On the basis of 600 MW super-critical CFB boiler coal feeding uniformity and coal feeding delay at varying load working condition, analyzed the specific reasons,that is the secondary coal feeding system arrangement characteristics.(2) For large-scale CFB boilers which use the side wall secondary coal feeding system, the author presented an improvement project of annular coal feeding method and accuracy control the coal quantity of each feeding point, also presented a new technical route that considers the regularities of coal quantity distribution which has involved with recycle material heat balance at furnace dense phase zone for the first time, it could ensure the uniformity of combustion in the furnace and bed temperature distribution, it is also suited to coal feeding system of all large-scale CFB boilers.(3) On account of related researchers' experimental results, established heat balance calculation and acquired 600 MW super-critical CFB boiler's corresponding relation of coal quantity at three different furnace areas change with the boiler load, it provides theoretical basis for 600 MW super-critical CFB boiler follow-up operation optimization. The results showed that, coal feeding quality reaches the minimum at front wall area and maximum at middle area under 100% boiler load condition; while coal feeding quality increases from front wall to rear wall in sequence under 80% boiler load condition and 60% boiler load condition. Meanwhile, with the boiler steam parameter changes from super-critical to sub-critical, the gas and solid material distribution has changed, the heat absorption fraction of heating surfaces in external heat exchangers has also changed markedly, the combined influence leads to the coal feeding distributing characteristics presented a different variation trend.