engleski

Decrease of High-Carbon-Ash Landfilling by Its Co- firing inside a Cement Calciner

At present, large amounts of high-carbon-ash (HCA), a waste by-product from chemical industry, are landfilled each year across China. Because of its small particulate size, HCA particles from open landfills are easily suspended in air and are a major source of air particulate pollution. Soil and ground water contamination with heavy metals is the second negative effect of HCA landfilling. As inappropriate disposal of the HCA may lead to serious environmental and human health impacts, alternative ways for its safe disposal are studied. One of the options is the co-firing of HCA and coal in a cement calciner. Energy recovery of HCA in cement combustion units has two major advantages over landfilling. First one is that after the carbon content in HCA is combusted the leftover ash, reach in silica, reacts with the raw material and exits the rotary kiln as clinker, so there is no solid residue to contend with. The second benefit from using HCA in existing pulverized coal cement combustion units is the preservation of space in existing landfills. However, due to different fuel properties, HCA has a direct impact on the performance of existing pulverized coal fired furnaces. Therefore, special care needs to be taken into account when such waste fuel is used. The aim of this paper is to present a numerical analysis of co- firing HCA and pulverized coal inside a cement calciner. Numerical model of pulverized HCA combustion was developed and implemented into a commercial computational fluid dynamics (CFD) code AVL FIRE®, which was then used for the analysis. To benchmark the HCA combustion numerical model, drop tube tests were performed. The drop tube tests datum together with the experimental analysis of HCA properties is also given in this paper. A real industrial cement calciner geometry was used for the numerical analysis. Four cases of which three different co-firing cases were analysed. As different co-firing modes have a different effect on the cement calciner’s performance, where the rate of calcium carbonate decomposition is an important indicator for evaluating the performance of a cement calciner, this study brings added value to the investigations related to HCA use as an alternative fuel inside a cement calciner.

Cement calciner ; Co-firing ; Drop tube test ; High-carbon-ash

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