CFBB External Heat Exchanger Hot-State Experimental Study

Contemporary social development faces the two main themes: Energy and Environment. China is a large energy consumption, and its pollution is not optimistic, So the Clean Combustion Technology that have high efficiency, low pollution should be attended. Circulating Fluidized Bed (CFB) with itselfe characteristics adapt to this development trend, and become a new generation of international of the Clean Combustion Technology. Now, with China's rapid economic and social development, our country's power resources is increased. Objectively, promote the development of the large power station CFB boilers in China. External Heat Exchanger (EHE) solve some problems that encountered in CFB boiler larger process. For example, coal suitability, load regulating range, super-heater not enough space layout and wearing problem. So EHE become growing concern.In order to slove this task, a power plant 300 MW CFB boiler equipped with EHE be used for the industrial model, and a similar principle make the theoretical basis. According Glicksman and other scholars concluded the CFB similar criteria, make geometric ratio of 1 : 28 physics modeling. EHE match with the hot state CFB experiment equipment. The EHE heat transfer coefficient distribution and influenced factors were researched. We observed the directional flow phenomenon in EHE, and research that the directional flow phenomenon impact the heat transfer coefficient and the temperature deviation of the inmersde tube in EHE.The purpose of the cold experiment study is that study the fluidization characteristics of fine particles. Experimental results show: fine particles have good fluidization quality, donot happened poor fluidized status—blocking , channeling, and so on.The purpose of hot experimental study in the following several aspects:①With the same external heat exchanger condition, the cycle ash amount of CFB experimental equipment effect on the external heat exchanger heat transfer characteristics;②With the same air flow conditions of CFB experimental equipmen(ttemperature, fluidized air velocity, etc), the external heat exchanger changes in the status of external heat exchanger heat transfer characteristics;③The particle size effect on the external heat exchanger heat transfer characteristics;④The temperature distribute in EHE;⑤Amended Veedendery empirical correlation, joined the flow of wind chamber of the dimensionless number of criteria external heat exchanger gray side Nu number of factors, make it suitable for external heat exchanger heat transfer coefficient.During this pilot study, the following main conclusions:①In cold experimental condition, the flow of the characteristic curve and the classic characteristics of the flow curve have the same trends. As external 2 and 3 compartment occur the stages of the formation of the flow phenomena, the characteristic curve in EHE is special. So experimental conditions obtained in the range of its full flow stage.②Under the same particle size and EHE condition, when the wind speed increases, heat transfer coefficient will increase slightly.③Under the same furnace a wind condition, the bed material finer particle size, the greater the heat transfer coefficient. Tally with Update Particle Group Theory.④Under the same particle size and quantity of recyclable materials circumstances, with the the wind speed in EHE increased, the heat transfer coefficient increased first, and then increase slightly. The heat transfer coefficient exhibits a maximum.⑤For this experiment bench, EHE inside the warehouse Room intermediate have a good fluid effect. But because of the wall effect the hybrid gas-solid flow that is near the wall is far less intensity among regions. Therefore the central heat transfer coefficient is obviously larger than that on both sides of the heat transfer coefficient.⑥The directional flow occur in the EHE and affect the recycling ash temperature.⑦From the experimental results analysis,the heat transfer coefficient have been the directional flow little impact. And the heat transfer quantity is decreased.⑧The particle size, the particle concentration in EHE, the speed of wind, the location of tube and the heating surface area effect the average heat transfer coefficient of horizontal immersed tube.⑨The furnace air flow conditions remain unchanged, comparation the heat transfer coefficient that we count based on Experimental data and Calculated data from the empirical correlation. One based on bubbling bed, the other based on circulating fluidized bed dense-phase. The error is within the permissible range (±20% between).⑩In cycle ash amount change, and to ensure that external heat exchanger for the status quo. At this time calculated and empirical correlation errors. So we intrduce correction factor to amend the empirical correlation of Veedendery. The error that amended calculated number and experimental number is within the permissible range (±20% between).