Experimental Research On Cement Clinker Calcination With Coal Gangue As Argillaceous Material

China is a major coal production and consumption country. Coal mining and processing is accompanied by a mass of coal gangue, which has presently become the largest emission and stock of industrial solid waste in China. Coal refuse piles, not only pollutes the surrounding environment, but also takes up much of arable land. In cement production, the current silicon aluminum material commonly uses clay. But due to its higher reaction activation energy, it needs excessive energy consumption during the process of calcinations, furthermore, clay mining destroys vegetation and farmland, therefore clay has been banned by many developed countries for cement production. Most of the coal gangue ash has similar composition with clay, so that it can be used as a substitute of clay. Mixing Coal gangue instead of argillaceous material into cement compound will not only make us be free of lack of clay resources, but will also make full use of energy and resource of coal gangue, which is a way that doubles the benefits.Based on the geographic characteristic distribution of coal gangue in China, we have taken some representative coal gangue sample from several typical mining areas in our country, and analyzed their physicochemical property. According to analysis results, we found that coal gangue has the similar mineral composition and chemical ingredient with the common argillaceous materials used in cement production, also coal gangue contains lots of oxygen-rich minerals and trace elements which play a positive mineralization role in clinker calcination. So we can assume that the coal gangue can be used in cement industry to substitute the conventional argillaceous materials. Besides, coal gangue itself has certain calories, so that it can bring heat into the calcination process to save energy consumption in cement industry.Grinding tests have researched on the relationship between the coal gangue granularity and grinding time, compared the grindability of coal gangue, sandstone and shale, and analyzed the grinding performance of the cement raw meal with three different coal gangue replacement ratio of clay. Results indicate that: coal gangue is relatively difficult to grind compared with argillaceous material when both are seperately grinded. Under the same conditions, coal gangue must be grinded about 5 to 10min more to satisfy the cement production requirements of granularity; In comparison, for compound-grinding, because the argillaceous material is in a lower content in the cement production, even if all of the argillaceous material is substituted by the coal gangue, there is no strong influence on grinding fineness of cement raw meal, the raw meal fineness requirement also can be generally satisfied.In the experiment, we simulated the calcination process of Pre-calcining Kiln. Firstly, we set the three modulus KH=1.01, SM=2.8, IM=1.4, and adopted Degression Making-up Method to optimize the formulation. According the chemical analysis of raw material, we prepared cement raw meal and calcined it to be clinker. Considering the influence of calcination temperature on burnability of raw meal, the experiment adopted 1250℃, 1300℃, 1350℃, 1400℃and 1450℃as its calcination temperature. The experimental results showed that when the temperature reached 1400℃, large quantity of liquid phase appeared and the color of the clinker became darker, and the lab clinker had the same appearance with the industry clinker. At the same time, the contents of f-CaO in cement clinker decreased dramatically below 2%, cement clinker is successfully calcined basically. By XRD analysis, we can obviously get that the mineral composition of the lab clinkers had a reasonable proportion which didn't change with temperature rising after the calcination temperature reached 1400℃.Taking into account the influential factors on burnability of raw mea are not only the temperature, but also the quality of limestone and additional tailing. With the chemical and XRD analysis on the clinker, we can find that burnability of raw meal is related to the quality of limestone, the lower grade of limestone, the better burnability of raw meal. But no matter what kinds of limestone, matching coal gangue can guarantee the quality of clinker. In addition, when coal gangue practical formulation is added with tailings, the burnability of raw meal can be improved further. In other words, combined admixture of coal gangue and mineralizing agent has a better effect upon clinker.Then we took compression strength tests to determine whether the clinker can be strong enough to meet the construction requirement. Based on the tests, we found the compression strength had already possessed the same or exceeded the standard currently produced in cement industry. So we are sure that cement clinker with coal gangue as argillaceous material is calcined successfully.At last we made an industrial experiment in 2500t/d pre-calcining rotary kiln production line. The results show that coal gangue raw meal can not only greatly reduce energy consumption, but also effectively improve the quality of the clinker, which brings enterprises considerable economic benefit, as well as significant social and environmental benefits.