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Nitrogen oxide emissions have attracted much attention due to their impact on the atmospheric environment and human health. Combined with NO removal in the cement production process, coal gasification slag was used to prepare denitrification materials to decompose NO in cement kilns without the addition of reducing agents. Denitrification materials were synthesized by a chemical precipitation method at different pH. The denitrification mechanism was proposed in this study. The results indicated that the denitrification material prepared at a pH of 7 exhibited the best denitrification performance. The NO decomposition rate first increased and then decreased below 400°C, and then increased as the temperature increased, reaching over 97% above 700°C. In the low-temperature range, Fe(II) was assumed to be active species, and the absorbed NO on the Fe(II) site obtained an electron, which promoted the decomposition of NO. In the high-temperature range, besides the active element Fe, the residual carbon in the coal gasification slag was prone to oxidation-reduction reactions, reducing nitric oxide to nitrogen. A new waste-to-value concept is introduced in this study, which promotes green technology for sustainable development. [ABSTRACT FROM AUTHOR]

NOx emission from the cement industry have received much attention. In order to reduce the NOx emission in cement kilns, nickel slag was used to prepare the non-ammonia denitrification material, and a denitrification mechanism was proposed in this study. The results showed that the denitrification material prepared at pH 7 exhibited the best denitrification performance. At low temperature, the highest denitrification performance was achieved between 200 and 300 °C with a NO decomposition rate of approximately 40%. Then, the NO decomposition rate increased as the temperature increased, reaching over 95% above 700 °C. The physicochemical characteristics showed that the material had the highest specific surface area and the highest relative Fe content, which benefited the denitrification performance. The divalent iron of the denitrification material was considered the active site for the reaction, and trivalent iron was not conducive to denitrification performance at a low temperature range. After the denitrification reaction, the Fe3+/Fe2+ increased from 0.89 to 1.31. The proposed denitrification mechanism was the redox process between divalent iron and trivalent iron. This study not only recycles industrial waste to reduce solid waste pollution but also efficiently removes nitrogen oxides from cement kilns without ammonia. [ABSTRACT FROM AUTHOR]

Ca(OH)2, a widely available and low-cost calcium-based desulfurizer, needs further improvement in calcium utilization in flue gas desulfurization. In this experiment, Ca(OH)2 crystals with different morphologies were prepared by doping impurity ions including SO42− and SiO32− by precipitation method, which played directing role in the process of crystal growth. The prepared Ca(OH)2 crystals were applied to cement kiln flue gas desulfurization environment to investigate the effect of crystal morphology on flue gas desulfurization. The observed results illustrated that Ca(OH)2 prepared by SO42− as impurity ion in hexagonal plate shape presents the best desulfurization performance with desulfurization efficiency up to 93%. The structural characterization of Ca(OH)2 crystals by XRD and SEM, and the investigation of the reasons for desulfurization by BET, EDS, and XPS showed that the hexagonal plate-shaped Ca(OH)2 crystals increased the specific surface area and had the highest elemental sulfur content of 5.04% on the (100) crystal plane, and the high surface energy on the (100) plane led to the high reactivity. This confirms the guiding significance of hexagonal plate-like morphology for improving the desulfurization performance of Ca(OH)2. [ABSTRACT FROM AUTHOR]

Nitrogen oxide (NOx) emissions have attracted much attention for increasing concern on the quality of the atmospheric environment. In view of NO decomposition in the cement production process, the preparation of Cu-Al/SiO2 porous material and its effect on NO decomposition were studied, and the denitrification mechanism was proposed in this paper. The NO decomposition performance of the Cu-Al/SiO2 porous material was tested via the experimental setup and infrared spectrometer and micro gas chromatography (GC). The result shows that the Cu-Al/SiO2 porous material with the template of cetyltrimethylammonium bromide (CTAB) had a better NO decomposition rate than materials with other templates when the temperature was above 500 °C, and NO decomposition rate could approach 100% at high temperatures above 750 °C. Structure analysis indicates that the prepared Cu-Al/SiO2 material structure was a mesoporous structure. The X-Ray Diffraction (XRD) and Ultraviolet–visible spectrophotometry (UV–Vis) results of the denitrification product show that the Cu-Al/SiO2 material mainly decomposed to Cu2O and Si2O, and the CuO decomposed to Cu2O and O2 at high temperature. The Cu(I)O was considered as the active phase. The redox process between Cu(II)O and Cu(I)O was thought to be the denitrification mechanism of the Cu-Al/SiO2 porous material. [ABSTRACT FROM AUTHOR]

Abstract: To make clear the environmental damages and potential improvements of Chinese cement industry, the detailed life cycle inventory (LCI) of cement manufacture with direct input and output in the boundary of cement plant as well as corresponded transport is conducted. The functional units are 1 t of Portland Ordinary cement and 1 t of clinker. The input data contain not only the traditional items such as raw materials (limestone, sandstone, ferrous tailings and gypsums), energy (coal and electricity), and admixtures (fly ash and furnace slag), but also fresh water which is not paid attention in other literature. The output data contain not only greenhouse gas (CO2) and primary pollution (NO x , PM, SO2), but also the hazardous air pollutants (HCl, NMVOC, PCDD/Fs, PAHs and fluoride) as well as noise and heavy metal emissions (As, Cd, Cr, Hg, Ni, Pb, Zn, Cu) which are usually neglected by others. The data were measured on-site. The applications of reducing pollutants and waste heat recovery technologies, and AFRs usage in cement industry are evaluated. The three steps of developments of LCI study for China cement industry are discussed. [Copyright &y& Elsevier]