Cold Model Experimental Research On Bottom Ash Separate And Elutriate Character Of Mixed-flow Fluidized Bed Bottom Ash Cooler

In consideration of the coal account for the majority of energy structure in our country at present, and new state of coal quality becoming worse and worse, the circulating fluidization bed boiler (short title CFB) combustion technology which derived from the 80s last century have had a rapid expansion in China. Our country is the maximum state for CFB install and total capacity, with about 30 CFB units for 300MW put into operation, the first maximum supercritical 600MWCFB in process of constructing Baima model plant in Sichuan province. Under the background of coal quality getting worse and worse, especially, along with large-scale CFB, effective boiler bottom ash cooling and fine ash recovery become very important. Traditional ash cooler can do the things, but they can't be satisfactory frequently, so to speak, almost all the CFB have undesirable operating conditions more or less. On the base of absorbing multitudinous merit of traditional fluidized bed ash cooler, Clean Coal Combustion Technology Laboratory develops a kind of mixed-fluid fluidized bed ash cooler, and has obtained state inventive patent. This product has been put into operation on 150CFB and 300MWCFB units, and the effect was very well as a whole. However, it's necessary to do some research about particle separation and fine ash recovery. The author did series test on a semi-industrial visual test-bed.The author adopted as test materials boiler bottom ash out of rotary ash cooler running in Baima 300MW plant. Primarily, test and verify bare board resistance of two cabins; then, confirm the critical fluidized air velocity, get through fluidization characteristics curve, do plentiful test study, such as, separation and returning materials character in different air velocity and different partition height of sorted cabin, returning materials character in different air velocity, different static state bed height and different test time of bubble cabin, and returning materials character when two cabins are running at the same time; besides, counter returning materials react on the particle size distribution of furnace, apply mathematical model to make some calculation and analysis; at last, make brief analysis for mixed-flow fluidized bed bottom ash industrial application. The test results and analysis are as follows:①Through checking, the test-bed design was reasonable, and could reach all the test demands;②Both efficiency of separation and scale efficiency of separation of sorting cabin increased with air velocity, but decreased with partition height rise. At 700mm partition and 5m/s air velocity, efficiency of separation is the best and reached to 50%(ideal value is 70%), and scale efficiency of separation of particle under 1mm more than 60%;③Sorting rate of sorting cabin magnified with air velocity improvement, and when air velocity exceeded to 4m/s, it decreased with partition height rise. Similarly, at 700mm partition and 5m/s air velocity, Sorting rate is the best and reached to 4.5t/h; in sorting cabin, more than 90% particle were less than 4mm, which was good for micro-bubbling;④The returning material quantity of two cabins increased with air velocity increase; the returning material quantity of sorting cabin decreased with partition height rise; the returning material quantity of bubbling cabin increased with static bed-height rise, and sharply increased within 4th minutes to 12th minutes; when the two cabins were running simultaneously, the returning material rate of sorting cabin became greater;⑤Two cabins'returning material size distribution were in the range of circulating ash of boiler(0～0.38mm). What's more, the returning material of sorting cabin was more fine relatively speaking, more than 90% under 0.15mm; for this, two cabins running simultaneously, the returning material size distribution was close to sorting cabin;⑥Adopting mixed-fluid fluidized bed ash cooler, returning material could reverse fine particle decreasing tendency in furnace in short time, which had an prominent improvement on the fine particle in furnace;⑦Industrial application of mixed-flow fluidized bed ash cooler indicated that: the ash cooler sorted effect is favorable ,could effectively avoid ash cooler cooking, blocking and other common troubles, it has much stronger adaptability to big bottom ash compared with traditional fluidized bed ash cooler.