Research On New Bed Material Of Coal Washery Sludge Circulating Fluidized Bed Boiler

The high density fluidized bed combustion technology makes the coal washery sludge combust steadily and efficiently in the fluidized bed boiler. In the real operational process, the quartz sand is usually regarded as the high density fluidized bed material, but they can be fretted into some tiny kernels by the violent state in the circulating fluidized bed, which arouses elutriation and carrying phenomenon to influence regular fluid. Moreover, because the high hardness of the quartz sand can seriously wear off the buried tube in the process of the bubbling fluidization in the boiler, so that doing research on the new bed material of the fluidized bed boiler to take the place of the quartz sand is a pressing mission.The washing gangue takes the place of the quartz sand as the bed material of the high density fluidized bed performs inefficiently on desulfurizing. Analyzing the respective advantages and disadvantages of the limestone and the washing gangue, the author finds that the former is more valuable to take the place of the quartz sand as the bed material of the high density fluidized bed. To compare the technical parameters of the limestone and the quartz sand firstly: Although the density of the limestone is lower than the quartz sand's, but is over twice higher than the dry coal sludge's, which can meet the demand for the bed material of the high density fluidized bed combustion technology in theory. If the bulky grains of the limestone can prevent the deposition of the coal-water mixture agglomeration in the calcinatory process, and keep on the normal fluidization of the fluidized bed boiler, so there is a new bed material which is inexpensive and can efficiently desulphate for the high density fluidized bed. However, because the calcinatory reaction of the limestone happens in the furnace cavity, the thermal equilibration of the boiler will be changed. So the model of the calcinations of the limestone needs to be established to simulate the calcinatory process in the fluidized bed boiler, which can know the calcinatory property of the bulky grains of the limestone. this text makes further hypothesis on the classical shrinking core model, and introduces a concept named calcinatory degree to reflect the process of the calcinations of the limestone, and solves the relationship of the calcinatory degree varying with the time in the calcinations of the limestone. The author uses the finite difference method to solve the unsteady state heat conduction equation, and programs to run iterative computations with the MATLAB software. The author does experiment on the test bed of the fluidized bed subsequently. After roasting the limestone by 3,5,10,15,20minutes separately, the author records the variety of the calcinatory degree to compare with the analog value, and analyses the reason that may cause the inaccuracy.Moreover, this article also summarizes the principle of the high density fluidized bed, and introduces the auxiliary system of the 75t/h coal washery sludge fluidized bed boiler in some thermal power plant. Using the coal washery sludge property list,the chemical composition of the limestone list and the technical parameter list of the 75t/h high density fluidized bed boiler, This text computes the consumption of the limestone and does devulcanized calculation. Aiming at the application of substituting the limestone for the quartz sand as the new bed material in coal washery sludge circulating fluidized bed boiler, we put forward proposal to remodify the shed of the limestone,the receiving hopper,the scraper conveyor,the storage hopper of the limestone and the feeding engine in front of the boiler.