Coupling mechanism of activated carbon mixed with dust for flue gas desulfurization and denitrification

To clarify the effect of coking dust, sintering dust and fly ash on the activity of activated carbon for various industrial flue gas desulfurization and denitrification, the coupling mechanism of the mixed activated carbon and dust was investigated to provide theoretical reference for the stable operation. The results show that coking dust had 34% desulfurization efficiency and 10% denitrification efficiency; correspondingly, sintering dust and fly ash had no obvious desulfurization and denitrification activities. For the mixture of activated carbon and dust, the coking dust reduced the desulfurization and denitrification efficiencies by blocking the pores of activated carbon, and its inhibiting effect on activated carbon was larger than its own desulfurization and denitrification activity. The sintering dust also reduced the desulfurization efficiency on the activated carbon while enhancing the denitrification efficiency. Fly ash blocked the pores of activated carbon and reduced its reaction activity. The reaction activity of coking dust mainly came from the surface functional groups, similar to that of activated carbon. The reaction activity of sintering dust mainly came from the oxidative property of Fe₂O₃, which oxidized NO to NO₂ and promoted the fast selectively catalytic reduction (SCR) of NO to form N₂. Sintering dust was activated by the joint action of activated carbon, and both had a coupling function. Sintering dust enhanced the adsorption and oxidation of NO, and activated carbon further promoted the reduction of NO_x by NH₃; thus, the denitrification efficiency increased by 5%-7% on the activated carbon.     

Study on the denitrification performance of FexLayOz/activated coke for NH3-SCR and the effect of CO escaped from activated coke at mid-high temperature on catalytic activity

Currently, activated coke is widely used in the removal of multiple pollutants from industrial flue gas. In this paper, a series of novel Fe_xLa_yO_z/AC catalysts was prepared by the incipient wetness impregnation for NH₃-SCR denitrification reaction. The introduction of Fe-La bimetal oxides significantly improved the denitrification performance of activated coke at mid-high temperature, and 4% Fe_0.3La_0.7O_1.5/AC exhibited a superior NO_x conversion efficiency of 90.1% at 400 °C. The catalysts were further characterized by BET, SEM, XRD, Raman, EPR, XPS, FTIR, NH₃-TPD, H₂-TPR, et al., whose results showed that the perovskite-type oxide of LaFeO₃ and oxygen vacancies were produced on the catalysts’ surfaces during roasting. Fe-La doping enhanced the amount of acid sites (mainly Lewis and other stronger acid sites) and the content of multifarious oxygen species, which were beneficial for NO_x removal at mid-high temperature. Moreover, it was investigated that the effect of released CO from activated coke at mid-high temperature on the NO_x removal through the lifetime test, in which it was found that a large amount of CO produced by pyrolysis of activated coke could promote the NO_x removal, and long-term escaping of CO on the activated coke carrier did not have a significant negative impact on catalytic performance. The results of the TG-IR test showed that volatile matter is released from the activated coke while TG results showed that the weight loss rate of 4% Fe_0.3La_0.7O_1.5/AC only was 0.0015~0.007%/min at 300–400 °C. Hence, 4% Fe_0.3La_0.7O_1.5/AC had excellent thermal stability and denitrification performance to be continuously used at mid-high temperature. Finally, the mechanisms were proposed on the basis of experiments and characterization results.

     

Multi-process and multi-pollutant control technology for ultra-low emissions in the iron and steel industry

The iron and steel industry is not only an important foundation of the national economy, but also the largest source of industrial air pollution. Due to the current status of emissions in the iron and steel industry, ultra-low pollutant emission control technology has been researched and developed. Liquid-phase proportion control technology has been developed for magnesian fluxed pellets, and a blast furnace smelting demonstration project has been established to use a high proportion of fluxed pellets (80%) for the first time in China to realize source emission reduction of SO₂ and NO_x. Based on the characteristics of high NO_x concentrations and the coexistence of multiple pollutants in coke oven flue gas, low-NO_x combustion coupled with multi-pollutant cooperative control technology with activated carbon was developed to achieve efficient removal of multiple pollutants and resource utilization of sulfur. Based on the characteristics of co-existing multiple pollutants in pellet flue gas, selective non-catalytic reduction (SNCR) coupled with ozone oxidation and spray drying adsorption (SDA) was developed, which significantly reduces the operating cost of the system. In the light of the high humidity and high alkalinity in flue gas, filter materials with high humidity resistance and corrosion resistance were manufactured, and an integrated pre-charged bag dust collector device was developed, which realized ultra-low emission of fine particles and reduced filtration resistance and energy consumption in the system. Through source emission reduction, process control and end-treatment technologies, five demonstration projects were built, providing a full set of technical solutions for ultra-low emissions of dust, SO₂, NO_x, SO₃, mercury and other pollutants, and offering technical support for the green development of the iron and steel industry.     

Carbon consumption and adsorption-regeneration of H2S on activated carbon for coke oven flue gas purification

Environmental Science and Pollution Research - Carbon consumption of activated carbon varies with sulfur-containing products. In this work, differential thermogravimetric (DTG), electron...     

碳酸盐岩对Fe2+生物氧化及铁矿物合成的影响

利用从高硫煤矸石堆场浸出液中培养驯化获得的氧化亚铁硫杆菌（Acidithiobacillus ferrooxidans,A.f）,通过静态实验,探讨添加不同量的碳酸盐岩对酸性硫酸盐体系中Fe²⁺生物氧化速率及次生铁矿物合成的影响.结果表明：添加10 g和30 g碳酸盐岩不会对体系中pH、氧化还原电位（ORP）和Fe²⁺生物氧化速率产生明显影响,但总铁（TFe）的去除率可从37%分别提高到55%和62%,矿物生成量也从8.17 g·L^-1分别增加到12.03 g·L^-1和13.69 g·L^-1;同时,体系中合成的次生铁矿物相与不加碳酸盐岩时无明显变化,主要为黄铁矾和施氏矿物的混合物.随着碳酸盐岩添加量增至50、70和90 g时,体系pH快速上升,Fe²⁺生物氧化速率受到抑制,并产生大量结晶程度较好的硫酸钙,形成的铁矿物主要为纤铁矿或针铁矿.而适量的碳酸盐岩添加可使体系中产生Ca²⁺和Mg²⁺,从而影响次生铁矿物的合成.因此,在以碳酸盐岩为反应介质的酸性矿山废水处理工艺设计中,可通过添加A.f菌并控制碳酸盐岩投加量,强化系统中Fe²⁺生物氧化及次生矿物的合成,从而进一步提高反应系统对TFe的去除效果.     

新型高效H2-SCR尖晶石型NiFe2O4催化还原NO

采用柠檬酸配位溶胶-凝胶法制备尖晶石型复合金属氧化物NiFe2O4,以H2为还原剂,在固定床反应器中考察了该催化剂催化还原NO的性能,并借助X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、比表面积测定(BET)、程序升温还原(TPR)和程序升温脱附(TPD)等方法对样品的晶体结构、形貌等特性进行了表征.结果表明.在空速4500 h-1,H2/NO浓度比为1,温度为400℃下,H2催化还原NO的效率可达97.8%,高H2/NO浓度比对NO转化率提升不大,高空速对其催化活性无明显影响.所制备的NiFe2O4催化剂具有典型的尖晶石结构,颗粒不规则,粒径大约为30—150 nm,并且具有良好的双官能团氧化还原性质.     

Adsorption and desorption of SO2, NO and chlorobenzene on activated carbon

Activated carbon (AC) is very effective for multi-pollutant removal; however, the complicated components in flue gas can influence each other''s adsorption. A series of adsorption experiments for multicomponents, including SO₂, NO, chlorobenzene and H₂O, on AC were performed in a fixed-bed reactor. For single-component adsorption, the adsorption amount for chlorobenzene was larger than for SO₂ and NO on the AC. In the multi-component atmosphere, the adsorption amount decreased by 27.6% for chlorobenzene and decreased by 95.6% for NO, whereas it increased by a factor of two for SO₂, demonstrating that a complex atmosphere is unfavorable for chlorobenzene adsorption and inhibits NO adsorption. In contrast, it is very beneficial for SO₂ adsorption. The temperature-programmed desorption (TPD) results indicated that the binding strength between the gas adsorbates and the AC follows the order of SO₂ > chlorobenzene > NO. The adsorption amount is independent of the binding strength. The presence of H₂O enhanced the component effects, while it weakened the binding force between the gas adsorbates and the AC. AC oxygen functional groups were analyzed using TPD and X-ray photoelectron spectroscopy (XPS) measurements. The results reveal the reason why the chlorobenzene adsorption is less affected by the presence of other components. Lactone groups partly transform into carbonyl and quinone groups after chlorobenzene desorption. The chlorobenzene adsorption increases the number of C = O groups, which explains the positive effect of chlorobenzene on SO₂ adsorption and the strong NO adsorption.     

基于空间插值的西安市重空气污染期间主要污染物时空变化特征及相关性分析

西安市是我国承东启西、连接南北的战略性枢纽城市,但其长期受到重空气污染的影响.基于2018年11月24日-12月3日西安市及其周边7个地级市共38个环境质量监测站点的逐时数据,利用空间插值、趋势分析和相关性分析方法,研究了西安市一次重空气污染期间六大污染物（PM_2.5、PM₁₀、CO、NO₂、SO₂和O₃）的质量浓度时空变化及彼此间的相关关系.结果表明:①IDW（inverse distance weighting,反距加权插值法）和OKri（ordinary Kriging,普通克里格插值法）均能较好地获得西安市空气污染物的时空变化情况,但IDW的插值精度优于OKri,距离指数为7的IDW可以满足西安市空气污染物时空变化模拟的要求.②研究期间,西安市首要污染物为PM_2.5和PM₁₀,二者分别是中度-重度污染及严重-"爆表"污染天气的首要贡献因子.③ρ（PM_2.5）、ρ（PM₁₀）、ρ（CO）、ρ（NO₂）和ρ（SO₂）均呈中部高、两边低,北部高、南部低的空间分布特点,而ρ（O₃）则相反;PM_2.5、PM₁₀、O₃污染程度日趋严重,NO₂污染程度逐渐缓解.④ρ（PM_2.5）、ρ（NO₂）、ρ（CO）之间呈中等正相关,三者在时空变化上具有较高的一致性;ρ（SO₂）与ρ（PM_2.5）、ρ（NO₂）、ρ（CO）均呈弱正相关;ρ（O₃）与ρ（NO₂）、ρ（CO）均呈弱负相关.受扬尘天气和特殊风向及地形共同影响,西安市PM₁₀出现"爆表"现象,导致ρ（PM₁₀）与其他污染物质量浓度之间的相关性不明显.研究显示,距离指数为7的IDW适合西安市空气污染情况时空变化的模拟,重污染天气条件下,西安市ρ（PM_2.5）、ρ（NO₂）、ρ（CO）之间具有较高的同源性,但各污染物间时空变化和相关性关系较复杂.      

基于环境污染责任保险的环境风险评估研究进展

环境风险评估是环境污染责任保险制度实施和应用的重要环节,是一种为投保人和承保人量化环境风险的方法,量化结果是保险公司厘定保费的重要参考依据。随着环境污染责任保险的发展和推广,构建适用于环境污染责任保险的环境风险评估体系逐渐成为当前的研究热点之一,但目前针对环境污染责任保险环境风险评估缺乏深入系统的研究与总结。在已有研究基础上,本文进一步明确环境污染责任保险环境风险评估内涵及特征,并对其评估体系进行科学界定,简要评述当前环境污染责任保险环境风险评估的相关研究主题,并在已有模型和方法基础上构建环境污染责任保险环境风险评估的理论框架,最后在总结当前研究不足的前提下,探讨未来环境污染责任保险环境风险评估的研究趋势,为环境污染责任保险的实施和应用提供思路和参考。     

A review of the catalysts used in the reduction of NO by CO for gas purification

The reduction of NO by the CO produced by incomplete combustion in the flue gas can remove CO and NO simultaneously and economically. However, there are some problems and challenges in the industrial application which limit the application of this process. In this work, noble metal catalysts and transition metal catalysts used in the reduction of NO by CO in recent years are systematically reviewed, emphasizing the research progress on Ir-based catalysts and Cu-based catalysts with prospective applications. The effects of catalyst support, additives, pretreatment methods, and physicochemical properties of catalysts on catalytic activity are summarized. In addition, the effects of atmosphere conditions on the catalytic activity are discussed. Several kinds of reaction mechanisms are proposed for noble metal catalysts and transition metal catalysts. Ir-based catalysts have an excellent activity for NO reduction by CO in the presence of O₂. Cu-based bimetallic catalysts show better catalytic performance in the absence of O₂, in that the adsorption and dissociation of NO can occur on both oxygen vacancies and metal sites. Finally, the potential problems existing in the application of the reduction of NO by CO in industrial flue gas are analyzed and some promising solutions are put forward through this review.