Experimental Research On Slagging Property Of Circulating Fluidized Bed Boiler Slag Cooler

In the increasingly serious energy crisis, the circulating fluidized bed combustion technology as a new generation of clean and efficient combustion technology developed rapidly in China. The circulating fluidized bed boiler burn the gangue as the fuel which contains a high proportion of slag, and much more heat will be lost when the slag is discharged. With the development of large-scale circulating fluidized bed boiler, this problem is more and more serious. In the past, the wet slag cooling system was used on the boiler which waste a lot of heat power. Then the dry slag cooling system came out. In the slag cooling system, slag cooler is the most important equipment which can recycle the high-grade waste heat of boiler slag, improve boiler efficiency and ensure the stable operation of boiler.Fist of all, various types of circulating fluidized bed boiler slag coolers are analyzed. In our country, air-water combined slag cooler is the earliest one which was used in circulating fluidized bed boiler. However, after many years’running of air-water combined slag cooler, there are so many problems that they are almost completely replaced by rolling-cylinder type slag-cooler.However, compared with rolling-cylinder type slag-cooler, air-water combined slag cooler has many advantages which cannot be replaced, such as higher heat transfer coefficient, high-grade heat recycling and so on. Therefore, solving the problems of air-water combined slag cooler has great significance to the energy saving. The air-water combined slag cooler has many problems, such as coking, wearing, blockage and so on. Among these problems, the most serious and fundamental problem is the coking.According to the mechanism of coking, the reason of coking is the slag continues burning in the environment with a high temperature. If slag combustion is not happen, the temperature is not high enough to coking. Therefore, as long as the combustion is prevented, the problem of coking will be solved. And then we put forward that a part of the air in the air-water combined slag cooler will be replaced by flue gas which can prevent the combustion.In this paper, through the theoretical analysis and coking experiment, we can conclude that the reason of agglomeration is the continued burning of slag. And in the air environment, the agglomeration will be more serious with a higher slag temperature or higher carbon content. But in the flue gas environment with a hypoxic environment, the combustion will be prevented and the coking will be prevented too.Finally, a very innovative solution to the coking is put forward. In the air-water combined slag cooler transformation, a part of the air is substituted by the flue gas, and the new slag cooler is called flue gas slag cooler. Through the calculation of the fluidization characteristics and heat transfer characteristics of the air-water combined slag cooler and the flue gas slag cooler, the feasibility of the transformation is verified.