Calcination Of Raw Materials Research Articles

Application of green hydrogen for decarbonization of cement manufacturing process: A technical review

Rising carbon dioxide (CO2) levels in the atmosphere have a direct effect on the weather, climate events, and global temperature that leads to adverse impacts on the environment and human beings. Industrial sectors are the major source of carbon footprint and contribute more than 30% of global CO2 emissions in global cement industries being the second largest after the steel industry i.e., 7% contribution. Raw material preparation, clinker burning, and cement grinding are the three major processes involved in cement manufacturing. The CO2 emissions throughout these phases are split into two categories: direct emissions (90%), mostly from the burning of fossil fuels and the breakdown of limestone (CaCO3) during the calcination of raw materials; and indirect emissions (2–10%), primarily from the use of electricity. Fossil fuel combustion is the major source of energy in cement manufacturing processes, accounting for 35% of cement’s CO2 emissions. In this study, the various pathways of decarbonization of the cement industry have been extensively reviewed. This research has revealed that hydrogen may be an appropriate substitute for carbon-intensive fuels in kilns. It can be concluded that the usage of hydrogen as a source of process heat, can present a potential for comparatively smooth integration into, or replacement of, process heat systems based on fossil fuels.

Improved microstructure and optical properties of Nd:YAG ceramics by hot isostatic pressing

Hot isostatic pressing (HIP) has unique advantages in the preparation of high-density, fine-grained ceramics. In this work, 1.0 at.% neodymium-doped yttrium aluminum garnet (Nd:YAG) powders were prepared via solid-state reaction (SSR) and co-precipitation (CP) methods, and differences in their microstructure after being subjected to the same sintering process were compared. After calcination of raw materials at different temperatures, there was significant phase change at 800 °C-1400 °C for SSR powders. However, this process did not occur for CP powders. Average grain size of Nd:YAG ceramics prepared via CP method was smaller than that of ceramics prepared via SSR method. HIP provided significant improvement in both microstructure and in-line transmittance of ceramics. Ceramics pre-fired under vacuum at 1700 °C showed slight increase in grain size after HIP, with densities close to 100%, and clean, narrow grain boundaries. Moreover, in-line transmittance of ceramics increased from 69.91% to 80.37% (at 1064 nm) via HIP.

The effect of in-situ formed layered hBN on the machinability and mechanical properties of SPS sintered SiC

In this study, the relationship between machinability, mechanical properties and microstructure of hBN-SiC composites was investigated. Manufacturing of the composites started with the calcination of raw materials at 850 °C for 16 h under a nitrogen atmosphere prior to mixing with 5 wt% of Al 2 O 3 :Y 2 O 3 sintering additives and then powder mixtures were spark plasma sintered at 1850 °C for 17 min by applying 50 MPa pressure. Characterizations of the samples were carried out with FTIR, XRD, SEM and TEM methods. The physical and mechanical properties of the samples were determined with density measurement, Vickers hardness, Young's modulus, three-point bending, fracture toughness and drill test methods. The amount of in-situ formed hBN phase within the sintered composites was calculated by using the Rietveld method. The physical, mechanical and machinability properties of the composite were evaluated according to the calculated amount of hBN. The highest drilling speed during the test was obtained as 34.24 mm/min for the sample containing 29 wt% of hBN. Increasing the drill load from 19.61 N to 49.03 N resulted in 4.33 times increase in the drilling rate. TEM and STEM studies which were carried out for the microstructural investigations showed the internal defects as delamination bands within hBN phase formed during sintering. In addition to these analyses, novel precession electron diffraction method in TEM was utilized for orientation mapping to investigate any possible orientation relationship between SiC and in-situ synthesized hBN phase.

Influence of calcination process on the formation of selected air pollutants

The subject of the study is to analyze the phenomena of thermal flow in the precalcinator chamber of the exchanger's furnace tower including the combustion of coal dust and decarbonisation of raw lime powder. During the research were provided development of a mathematical model of particulate solid fuels combustion, calcining the raw material, NO x and CO x formation. Moreover conducting the number for the current and the upgraded design of the precalcinator and analysis of the results. In this study, a mathematical model based on Euler's method to describe the motion of the gas phase and the Lagrange method to describe the motion of particles [1-4]. In the calculations there were assumed fractional particles raw material and fuel, and the following processes: flow of exhaust gases from the rotary kiln through the precalcinator chamber, heat exchange between the particles of raw material and exhaust gases, the additional fuel combustion in the precalcinator, the process of raw material calcination, transformation of gaseous substances, effect of the additional (tertiary) air delivery on the processes in the chamber.

Assessment of greenhouse CO2 emissions associated with the cement manufacturing process

ABSTRACTThe goal of the present work was to identify the impact of carbon dioxide (CO2) emissions on a cement plant's workplace environment and its surrounding area. The concentration levels of CO2 over the study domain were investigated by means of the Weather Research and Forecasting/California Puff Model (WRF/CALPUFF) integrated modeling system (TRC Environmental Corporation, Windsor, CT, USA). Two sources were modeled for the current study: CO2 resulting from the calcination of raw materials and fuel consumption in three kilns and power plant emissions, which were treated as point sources, and vehicular-based CO2 emissions, emitted during the transportation of raw materials from the quarry to the crusher, which was modeled as a line source and calculated using the activity data collected from the cement plant and the emission factors as described by various environmental agencies. A comparison between the predicted results and the allowable limits of CO2 were made to investigate the environmental quality in the study area. The results of the study revealed that the CO2 contributions due to line source emissions were higher within and outside the plant than those from the point sources during the selected winter days. On the other hand, the individual contributions made by the point sources in the selected summer days exceeded the line source contributions, even though the combined contribution of CO2 (from both types of sources in the workplace and nearby areas) was at its height during the chosen winter days. Furthermore, maximum average concentrations, as predicted by CALPUFF for a standard period of 1 hr, were at higher than permissible levels during the selected days in both winter and summer. Within an average 24-hr period, the maximum modeled concentrations of CO2 were at the higher end of allowable limits during the designated winter days and at the lower end throughout the summer days.

Eco innovation strategies for promoting cleaner cement manufacturing

Carbon dioxide (CO2) emissions in cement plants are generated by the decarbonation of raw materials and fuel combustion in the cement kiln during the cement clinker production process and account for 8% of global emissions. This paper presents a mixed integer linear programming (MILP) by considering various mitigation measures, such as co-processing of fuels, kiln improvements and carbon capture and storage (CCS) yields, that can have substantial benefits. The benefits include cleaner cement production with minimum production costs, while satisfying the quality standard, carbon reduction target, and fuels substitution rate. The developed model is applied to a case study in order to demonstrate the applicability of the model. For the base case, the optimal cost for clinker production is USD 90.21/t clinker while CO2 emissions generated from both calcination of raw materials and fuels combustion is 531.68 kg CO2/t clinker and 325.00 kg CO2/t clinker. It was found that the highest possible CO2 emissions reduction that can be achieved by a combination of co-processing, kiln improvements and CCS technology is 79%, with an increment cost of USD 136.46/t clinker.

Scenarios for sewage sludge reduction and reuse in clinker production towards regional eco-industrial development: a comparative emergy-based assessment

The synergic treatment benefit of reducing the amount of raw material and fuel and its contribution to the Greenhouse Gas (GHG) total emissions are of great interest for cement manufacturing. Additionally, it should be considered that the major sources of GHG in clinker production are CO2 from the calcination of raw materials and CO2 from fossil fuel combustion. Calcination CO2 can be reduced by the substitution of raw materials with noncarbonated calcium sources. Taking into account its potential reduction effect, a comprehensive research in the use of sewage sludge as a raw material alternative in clinker production, is required and is likely to provide valuable improvement. An emergy analysis to evaluate the synergic reduction effect of urban sewage sludge use as alternative raw material or fuel in clinker production was carried out. The main steps of the synergic treatment process, namely (1) sewage sludge treatment and (2) its transport to clinker production, were assessed by means of the emergy accounting approach. This evaluation aimed to assess the environmental resource demand in terms of equivalent solar energy, extending the energy quality hierarchy principle from ecosystems to eco-industrial process. The achievable synergic reduction effects, in terms of alternative raw material or fuel and recycling process, due to four different scenarios of sludge treatment and energy recycling, are analyzed in this study. The resulting unit emergy values of cement were compared with previous emergy assessments in order to highlight how emergy analysis is sensitive to local context and reference system's boundaries. Emergy Yield Ratio (EYR) with and without accounting for additional emergy investment due to damages caused by the process were calculated and discussed as comprehensive indicators of process sustainability. Results show that if the environmental impact is accounted for, the EYR drops significantly, thus suggesting that polluting emissions greatly increase the system's demand for additional resources from outside to repair damage and replace lost natural and human-made capital (the latter amounting to about 10% of the total emergy investment). The use of emergy accounting and LCA provides indices that allow a quantitative metrics of eco-industrial sustainability and environmental impact reduction.

Optimization of the Effective Parameters on the Synthesis of the Mn-Zn Ferrite Powder with a High Saturation Magnetization Using Different Iranian Routs of Iron Oxide

Mn-Zn ferrites with chemical formula (Mn-Zn) Fe2O4 have widespread applications in the electrical and electronics industries. These ferrites are synthesized generally by conventional method. This method, which contains calcination of raw materials, is affected by several parameters such as composition and purity of the raw materials and temperature, time and atmosphere of the process. Optimization of these parameters is very important because these parameters affect the magnetic and electrical properties of the material. In this work, the ratio of the different Iranian routs of the raw materials for production of high Ms ferrite powder has been optimized and the effects of calcination conditions have been investigated using XRD, DTA/TGA techniques. The magnetic properties have also been measured.

Effect of attritor milling on the densification of magnesium aluminate spinel

Densification of magnesium aluminate spinel was studied with both the single stage and double stage sintering processes using attritor mill for the reduction of particle size. Presynthesized spinel and a stoichiometric mixture of calcined magnesia and alumina were used for the study. Presynthesization of spinel and calcination of raw materials were done at 1400 and 1600°C. Milling was done for 2, 4 and 6 h. Extent of milling was characterised by measuring the specific surface area of the milled powders. Densification was found to be greatly influenced by milling. A maximum 99.5% densification was obtained.