Study Of Methods On Evaluating Char Combustion Characters Under The Circumstance Of The Precalciner Of Cement Kiln

Coal is the main fuel used in the cement industries. With the reduction of high quality coal, the inert coal is used more and more, however, the change of the coal quality will certainly influence the stable of the kiln's condition. In order to well know the combustion characteristics of coal in precalciners, in this article, the methods of evaluating the combustion characteristics of different quality of coal were studied, aiming to find one or more scientific and reliable methods for guiding the design and operating of cement kiln, which have important real significance.Using the graphics software programming platform LabVIEW invented by American NI corporation, two data acquisition softwares, the Thermobalance Mass / Temperature collect software and the Thermobalance / CO₂ Gas concentration collect software, were wrote with many functions such as high speed acquisition and automatic storage. Also other functions can be added whenever need.According to the theory of non-critical catching fire, defining the point where dT/dt≠0 and d²T/dt²=0 as the moment of catching fire, the kindling point of char, with the char temperature rising along with the furnace and with the char injected into the furnace at high temperature, is obtained respectively. By using thermobalance and coal comprehensive test instrument, the coal ignition information of both the kindling point and the burning time were studied. The results show that these methods have good reproducibility, the more ash the char contains, the kindling point is higher and the time for ignition is longer. Although there are similar kindling point and industrial analysis value of two kinds of chars, the time for ignition is different, illustrating that it is unscientific to evaluate coal quality only by the industrial analysis.The studying on combustion mechanism of char particles by using the thermobalance indicates that by observing the time which from the moment of the sample injected to the furnace to the moment of fast rate of loss of char weight via changing the thermobalance temperature and the gas flow rate, we could estimated whether the combustion mechanism is controlled by the diffusion combustion process or the dynamics combustion process or the both two.By using the CFD software FLUENT a set of coal suspension combustion implement was designed with the CO2 concentration collected by a certain software wrote by the graphics software programming platform LabVIEW. Through the experiments on five kinds of char, we know wherther the char is hard or easy to combust under the suspension combustion, combiningthe industrial analysis data it can be seen that under dynamic combustion conditions, there are widely different combustion results between different kinds of char although their industrial analysis data are very similar. Also the influence of the gas flow rate on the burnout degree of different char were discussed, showing that when the gas flow rate increases the burnout degree of some char fall, while some others increase firstly and then fall.The characteristic of this thesis are as follows: one one hand, by using the graphics software programming platform Lab VIEW, the multifunctional data-acquisition softwares were wrote and by the CFD software Fluent a set of coal suspension combustion implement was design;On the other hand, by modeling both the temperature and the gas flow circumstance in the precalciner of cement kiln, the initial research about the char combustion characters under suspension condition is processed.