Papers by Keyword: Cement Kiln

Abstract: In order to deal with the pollution of NO in cement kiln exhaust, the study of NO catalytic decomposition catalyst obtained much more attention. The effect of silica-alumina ratio on NO decomposition rate in cement kiln without other reductant was studied. The NO decomposition rate of catalysts with different silica-alumina ratio was determined by infrared spectrometer. And pore structures and the microstructure of the catalyst were characterized separately by BET surface area, nitrogen adsorption-desorption and XRD. The results show that silica-alumina ratio of catalyst was preferred to be 50 with the best NO decomposition rate when the temperature was below 300 °C. The catalyst with silica-alumina ratio of 60 has the higher catalytic activity when the temperature was higher than 300 °C, and the decomposition rate achieved 70% at 600 °C. XRD results shows the crystallinity of catalysts increased as the silica-alumina ratio increased. BET surface area and the cumulative pore volume of catalysts gradually increased, and the average pore diameter gradually reduced with the increase of silica-alumina ratio.

Abstract: Many studies have indicated that carbon can be reduced to nitric oxide. This paper reports an experimental study of NO reduction by mixed materials of biochar or active carbon with cement raw meal. The proportion of mixed materials was 95 wt.% cement raw meal and 5 wt.% biochar or active carbon. A mixture loading amount and gas flow rate study quantifying the effect of carbon amount and gas residence on the reduction of nitric oxide was carried out. The experiment was performed in a fixed bed reactor at the temperature of 800°C, with O₂ concentration of 1%. The inlet NO concentration was 1000 ppm. The characterization of structure and properties of biochar and active carbon was conducted by SEM-EDS, BET. The results show that different carbon materials have different NO reduction effect. The NO conversion rate increases with the increase of the amount of mixture loading. This method of removing NO is practically feasible.

Abstract: Using cement kiln dispose sludge from sewage plants can achieve the sludge stabilization, harmless, reduction and resource comprehensive utilization purposes. This is Not only to solve the problem of sludge treatment which is difficult to solve by sewage treatment plant, but also to make full use of the sewage treatment plant sludge to replace part of cement clinker production materials. And it makes full use of sludge incineration emitted in the process of low calorific value. Municipal sludge contains more moisture. It is necessary to dry the sludge outside the kiln before entering kiln process. As cement kiln co-processing, it should be combined with the characteristics of NSP clinker production, it is necessary to not only consider the total energy consumption of the drying process, but also the re-use of dried sludge heat value, as well as consider the total of water into the kiln by drying sludge affecting the whole clinker production process. In this paper, with the initial solid content 20%, dry heating value 3400 cal/g sludge as a research object, the moisture morphology, thermal characteristics, drying technological parameters and composition of water after drying in sludge were analysed. This issue combines sludge drying with cement kiln disposal, which can not only solve the heat and odor problem during the individual sludge drying process, but also provide a theoretical basis for cement kilns co-disposal of municipal sewage sludge to achieve the purposes of sludge stabilization, harmless, minimization and resource utilization.

Abstract: Cement industry is one of the highest contributor in carbon dioxide (CO₂) emissions. With that, this paper proposes the development of a systematic optimization model where minimized production cost is anticipated within the CO₂ reduction target and fuels mixture. The optimization models consider co-processing measures which replaces parts of carbon rich fuels with lower carbon fuels in order to achieve lower carbon emissions. The proposed models are executed using General Algebraic Modeling System (GAMS). With highest carbon reduction of 3.2%, the minimum manufacturing cost went from €59.748/t clinker for a 0% carbon reduction target to €65.737/t clinker.

Abstract: Polymer resin and glass fiber are the main wastes during the production process of glass-fiber reinforced plastics (GRP). With GRP products used widely in many fields, GRP wastes also got a large increase and the disposal of GRP wastes became a serious environmental problem. In this paper, the combustion characteristic of GRP wastes was tested by the thermal analysis and contrasted to that of powdered coal. In the full-scale test of GRP wastes co-processing in the cement kiln, the efficiency of coal-saving, the influence on chemical components of the product and the CO₂ emission were investigated to evaluate the feasibility of this technology.

Abstract: While conducting research for dioxin emission factor for stationary source emission, it is found that some factors come from overestimation. The cause of discrepancy for estimating process comes often from lacking understanding of the process. The result of this study for secondary aluminum refining emission factors indicates that if raw materials are scraps, the factors averaged at 541 ng I-TEQ/Ton-raw materials. If waste aluminum is used as the raw material, factors averaged at 1338 ng I-TEQ/Ton-raw material. The factors based on site sampling for coal-fired power generation process is 24.84-549.62 ng I-TEQ/Ton-fuel. It varies according to coal sources. Emission factor for cement producing process is 95.4-102.66 ng I-TEQ/Ton-raw material. Due to fewer differences in operating traits, raw materials and fuel application for cement producing process, emission factors have smaller differences. The reliability for emission variables is relatively higher.

Abstract: Increased use of alternative fuels in cement kilns is a trend in the world. However, replacing fossil fuels like coal with different alternative fuels will give various impacts on the overall kiln process due to the fuel characteristics. Hence, it is important to know to what extent the fossil fuels can be replaced by different alternative fuels without severely changing process conditions, product quality or emissions. In the present study, a mass and energy balance for the combustion of different alternative fuels in a cement rotary kiln was developed. First, the impact of different fuel characteristics on kiln gas temperature, kiln gas flow rate and air requirement were observed by using coal (reference case), meat and bone meal (MBM), two different wood types, refuse derived fuel and a mixture of saw dust and solid hazardous waste as the primary fuel. It was found that the key process parameters depend largely on the chemical characteristics of the fuel. It appears that MBM shows quite different results from other alternative fuels investigated. Next, simulation of combustion of a mixture of coal and MBM in the main burner was carried out in three steps. The first step was combustion of replacing part of coal energy with MBM, and a reduction in kiln exhaust gas temperature compared to the coal reference case was found. In the second step, the fuel feed rate was increased in order to raise the kiln gas temperature to that of the reference case. In the third step, the fuel feed rate and the clinker production rate were changed in order to have not only the same kiln gas temperature but also to obtain the same volumetric flow rate of total exhaust gas from the precalciner as in the reference case. Around 7% of reduction in clinker production rate could be observed when replacing 48% of the coal energy input. Results from a full-scale test using the same mixture of coal and MBM verified the simulation results.

Abstract: The paper first discusses the relativity between alternative combustion andNOx emissions by a test in dry cement kiln, and a lot of case on fuel alternative The main findings of the study are that the use of RDF in cement kilns instead of coal or coke offers environmental benefits and reduce NOx emission. The conclusion is that the NOx generation can probably be lower because of lower flame temperatures or lower air excess and low nitrogen content in comparison with fossil fuels also is impartment reason., another a fact that most of the nitrogen (N) in biomass is released as ammonia (NH3) which acts as a reducing agent with NOx to form nitrogen (N2).

Abstract: The efficiency and problem of SNCR in cement are explained by case study .Catalyst also is discussed by the research. And this paper presents and discusses the technical feasibility issues related to implementing SCR technology at cement plant. Some pilot plant trial and scale-full plant are also discussed and the result show that SCR can reduce NOx emissions from cement kilns by greater than 90% and achieve less than 100 mg/Nm3 NOx emissions. The fact suggests that it is a more effective and proven technology to reduce nitrogen oxide emissions from cement kilns.

Abstract: Power generation using waste heat from cement kiln can not only bring economic benefits to the enterprise, but also play an important role in environment protection. Constantly researches have proved that there is still large energy saving potential in its operation. In this paper, the waste heat power generation system was divided into several subsystems, and the exergy calculation model of each subsystem unit was established. Finally, the weakest part in energy use was found according to the results. It provides a scientific basis for performance improvement and energy saving transformation of waste heat power generation.