稻壳灰-电石渣复合吸收剂的脱硫脱硝性能

SO₂和NO_x是水泥窑炉尾气中主要的大气污染物,减少其排放已经成为控制大气污染的主要途径。本工作尝试采用农业废渣稻壳灰和工业废渣电石渣配制复合吸收剂,在水泥熟料形成过程中实现脱硫脱硝。本工作研究了稻壳灰和电石渣掺配比(2∶5~18∶5,质量比)、反应温度(500~900 ℃)、氧气浓度(0%~3%)对复合吸收剂脱硫脱硝效率的影响。结果表明,稻壳灰和电石渣的配比为6∶5,掺入水泥生料中,在900 ℃、1%的氧气浓度条件下,脱硝率达到97%,脱硫率达99%。利用稻壳灰和电石渣这两种废渣配制复合吸收剂可以在水泥分解炉中有效脱除SO₂和NO_x。     

膜吸收法烟气同时脱硫脱硝试验研究

采用自行研制的新型错流式气-液膜接触器,以NaClO2海水溶液为吸收液,分别以NaHCO3/Ca(OH)2/Ca(ClO)2为添加剂,对电厂燃煤烟气开展膜吸收法烟气同时脱硫脱硝现场试验研究.考察了吸收液流量、浓度、活化时间、初始pH以及烟气流量、SO2浓度等因素对脱硫脱硝效果的影响.试验表明:增大吸收液流量和浓度,NOx和SO2脱除率升高;延长吸收液活化时间,增大烟气流量,脱硫脱硝率略有降低;吸收液初始pH升高,脱硫率几乎不变,而脱硝率却略有降低;随着SO2浓度增大,脱硝率出现极值点;另外,添加剂NaHCO3/Ca(OH)2/Ca(ClO)2对NaClO2氧化吸收NOx和SO2均有增强作用.采用膜气体吸收技术,可实现烟气同时脱硫脱硝,具有一定应用潜力.     

醋酸钙/飞灰复合脱硫脱硝剂热解性能实验研究

为了提高脱硫脱硝效率同时合理利用火电厂产生的飞灰,研究了醋酸钙中加入飞灰制备的复合脱硫脱硝剂的热解性能。对不同条件下制得的醋酸钙/飞灰复合脱硫脱硝剂的热重特性、X射线衍射图谱、比表面积、扫描电镜结果等进行了分析,结果表明:利用醋酸钙和飞灰水合制备的脱硫脱硝剂具有比单纯的醋酸钙和飞灰更大的比表面积;经过900℃煅烧后脱硫脱硝剂孔隙结构最好;脱硫脱硝剂经过900℃煅烧后的热解产物(SiO2、Al2O3、Fe2O3和CaO)有助于脱除烟气中的硫氧化物和氮氧化物。     

FGD吸收塔系统调试方法与措施

Flue gas desulfurization,简称FGD,是石灰石-石膏湿法烟气脱硫系统的简称.目前目前世界上燃煤或燃油电站所采用的脱硫工艺多种多样,常见为石灰石-石膏湿法、千法、半干法、电子束法、氨法、镁法等.其中石灰石-石膏湿法是应用最为广泛和成熟的脱硫技术,具有脱硫效率高(95%以上),吸收剂利用率高,对煤种变化的适应性强,吸收剂资源丰富、价格便宜,脱硫副产物便于综合利用等优点.本文主要结合亲身经历介绍了FGD吸收塔系统的调试方法及措施,以期对从事相关工作的朋友有所帮助.     

论火力发电厂的脱硝技术

火电厂燃煤中排放的氮氧化物是造成大气污染的主要成分之一,如何经济有效地控制燃煤中氮氧化物的排放量是我国乃至世界节能减排领域中急需解决的关键问题。文章综述了国内外火电厂脱硝技术的应用和发展、脱硝脱硫一体化技术的发展趋势,着重介绍了世界上主要脱硝技术的技术特点、分类和应用,包括联合脱硫脱硝、同时脱硫脱硝在内的脱硫脱硝一体化原理、应用前景和特点,对火力发电厂脱具有一定的参考价值。     

浮法玻璃熔窑烟气治理和利用

本文阐述了浮法玻璃熔窑的运行特点和烟气特性,对国内应用的烟气脱硫、脱硝技术进行了分析比较,结合浮法玻璃熔窑工艺特点,提出了几种适合浮法玻璃生产线的脱硫脱硝除尘余热发电一体化工艺方案和相关建议。     

气-液膜接触器法烟气脱硫脱硝的研究进展

气-液膜接触器以其比表面积大、体积小、模块化设计与安装和规模易于放大等优点,有望替代传统的湿法烟气脱硫脱硝装置.本文对气-液膜接触器法烟气脱硫脱硝的研究进行了综述,指出选择与开发高性能的吸收剂、构造合理的气-液膜接触器的结构、优化膜法烟气脱硫脱硝的操作工艺和烟气中同时脱硫脱硝等方面,是气-液膜接触器法烟气脱硫脱硝领域的主要研究方向.     

活性炭法脱硫脱硝的自动控制

烧结烟气活性炭法脱硫脱硝技术成功解决了烧结烟气量大、SO2浓度低、成份复杂等脱硫脱硝工艺技术的难题,在烧结脱硫脱硝领域取得了重大突破,其自动控制系统的成功开发与应用使工艺系统得以安全、高效、稳定运行.     

超声波辅助氧化改性钙基吸收剂的制备及性能研究

通过超声波辅助溶液浸渍的方法,将K2 S2 O8、Ca(ClO)2、(NH4)4 Ce(SO4)4及K2 Cr2 O7等氧化剂分别浸渍在钙基吸收剂表面,形成具有氧化性的活性位点,即氧化位点,改善钙基吸收剂脱除NOx的效果.通过正交实验,在不同超声波功率、浸渍时间和浸渍温度下,按照一定掺杂比例,利用氧化剂对钙基吸收剂进行化学调质.将改性后钙基吸收剂在固定床反应器上进行了同时脱硫脱硝实验,选择污染物的平均脱除率作为评价指标.正交实验结果表明:以Ca(ClO)2作为氧化剂进行超声波浸渍改性效果最好,最优改性工艺参数为氧化剂掺杂比例20％(质量分数,下同)、超声波功率100％、浸渍时间1.5 h、浸渍温度70℃.同时,基于晶相结构(XRD)分析和扫描电镜(SEM)显微形貌观测,可知超声波辅助氧化改性的方法能有效改善钙基吸收剂表面形貌,表面上形成了氧化位点,该氧化位点不仅能够增大吸收剂与SO2和NOx的接触,还能促进NO氧化为NO2,进一步提高SO2和NOx的脱除率.     

不同结构聚丙烯中紫外线吸收剂的迁移

目的探究温度、时间、食品模拟物、材料结构及添加剂分子等对聚丙烯中3种紫外线吸收剂迁移的影响。方法建立3种紫外线吸收剂(UV-P,UV-531,UV-327)的高效液相色谱检测方法。再在20,40,70°C下,研究添加剂向5种食品模拟物的迁移。结果添加剂在0.1~20μg/m L内线性良好(R0.99),检出限为0.03~0.05μg/m L。加标含量为每克塑料中添加20,80,200μg紫外线吸收剂时,回收率为81.6%~99.8%,相对标准偏差为2.3%~7.7%。在体积分数为10%的乙醇和质量分数为3%的乙酸溶液中,未检出添加剂;在体积分数为20%的乙醇溶液中,只检测到UV-P;在体积分数为50%的乙醇溶液和异辛烷中,3种紫外线吸收剂均被检测到。结论升高温度、延长时间,紫外线吸收剂迁移量逐渐增加直到平衡;紫外线吸收剂易于向异辛烷和乙醇溶液迁移,乙醇溶液中,随着乙醇含量的增加,发生迁移的添加剂种类和质量也随之增加;紫外线吸收剂的迁移量随着聚丙烯材料结晶度的增加而减小;添加剂的分子量越大、结构越复杂,越不容易发生迁移。     

Effect of curing conditions and ionic additives on properties of fly ash-lime compacts

In the present work the reaction between fly ash and lime in fly ash-lime compacts under water curing and steam curing conditions was studied thoroughly in relation to the processing conditions. Fly ash from different sources were collected, characterized, mixed with lime in different ratios and compacted. The compacts were cured with water and steam separately. The reduction in the free CaO content in these compacts was measured as a function of curing time and curing process. Role of two ionic additives, FeCl₃ and MgCl₂, on the reaction between fly ash and lime was also investigated by measuring the free CaO content. Kinetics of these reactions was studied by determining the reaction order and rate constants with respect to the free CaO content and it was observed that the curing conditions and additives affected the reaction kinetics significantly.     

Equilibrium and kinetic mechanism for Reactive Black 5 sorption onto high lime Soma fly ash

Batch adsorption studies were carried out for the sorption of C.I. Reactive Black 5, a reactive dye, onto high lime fly ash, obtained from Soma Thermal Power Plant (Turkey), to be low cost adsorbent. The effect of various experimental parameters such as contact time, adsorbent dose and initial dye concentration were investigated. Determination of the adsorption equilibrium concentrations was determined by UV-vis spectrophotometry analytical method. Equilibrium data were fitted to the Freundlich and Langmuir isotherm equations and the equilibrium data were found to be well represented by the Freundlich isotherm equation. The adsorption kinetics of C.I. Reactive Black 5 onto high lime fly ash were also studied to characterize of the surface complexation reaction. A pseudo-second-order mechanism has been developed to predict the rate constant of the adsorption, the equilibrium capacity and initial adsorption rate with the effect of initial concentration. A single-stage batch adsorber design of the adsorption of C.I. Reactive Black 5 onto high lime fly ash has been studied based on the Freundlich isotherm equation.     

Suppression of solidification of calcium-rich incinerator fly ash during thermal treatment for decomposition/detoxification of dioxins

Dioxins and dioxin-like compounds released from municipal and industrial solid waste incinerators have been a serious problem from the viewpoint of environmental pollution control. Since these compounds are concentrated especially on fly ash, supplemental treatment systems to decompose/detoxify them are required after collecting the fly ash either by a bag filter or an electrostatic precipitator. The present work is aimed at developing a heat treatment technique for fly ash, which contains a large amount of calcium (Ca) derived from hydrated lime, at a temperature higher than 500°C by adding chemical additives to prevent the solidification of Ca-rich fly ash. As calcium hydroxychloride (CaClOH) in the Ca-rich fly ash was found to cause solidification of fly ash at high temperatures, sodium hydroxide, mullite and coal fly ash were added as additives prior to the heat treatment. As a result, the additives studied in the present work are effective for decomposing CaClOH and therefore suppressing the solidification of fly ash, and yet they promoted the decomposition/detoxification of dioxins.     

Environmental behavior of cement-based stabilized foundry sludge products incorporating additives

A series of experiments were conducted to stabilize the inorganic and organic pollutants in a foundry sludge from a cast iron activity using Portland cement as binder and three different types of additives, organophilic bentonite, lime and coal fly ash. Ecotoxicological and chemical behavior of stabilized mixes of foundry sludge were analyzed to assess the feasibility to immobilize both types of contaminants, all determined on the basis of compliance leaching tests. The incorporation of lime reduces the ecotoxicity of stabilized mixes and enhances stabilization of organic pollutants obtaining better results when a 50% of cement is replaced by lime. However, the alkalinity of lime increases slightly the leached zinc up to concentrations above the limit set under neutral conditions by the European regulations. The addition of organophilic bentonite and coal fly ash can immobilize the phenolic compounds but are inefficient to reduce the ecotoxicity and mobility of zinc of final products.     

Evaluation of blends of high and low calcium fly ashes for use as supplementary cementing materials

The present paper outlines the results of a research attempt aimed at developing and evaluating the performance of ternary blended cements, incorporating mixtures of two different types of fly ash (of high and low calcium content). The main target of this study was to investigate whether and by what means, the introduction of a certain type of fly ash into a fly ash–cement (FC) matrix containing a different type of ash, can improve the performance of the initial binary system. For achieving this, new pozzolans were prepared by mixing, in selected proportions, a high lime fly ash with an ash of lower calcium content. The efficiency of the new materials was examined in terms of active silica content, pozzolanic activity potential, strength development, k-values and progress of the pozzolanic action by means of fixed lime capabilities. The results obtained demonstrated that the mixtures containing equal amounts of each fly ash were the most effective for moderate cement substitution, whilst for higher replacements the intermixture possessing the highest active silica content shows supremacy at almost all hydration ages. The superior performance of the ternary fly ash blends was mainly attributed to synergistic effects detected for all the ashes utilized. These were quantified in each case and almost linear correlations were obtained with the k-values of the most efficient ternary mixes.     

IMMOBILIZATION OF ARSENIC IN COAL COMBUSTION FLY ASH LEACHATES

Characterization of baghouse fly ash produced from lignite in fluidized-bed combustion tests indicated that the presence of arsenic in the ash leachate was an environmental concern. The capacity of three chemical additives (lime, calcium sulfate, and nitric acid) to immobilize the arsenic in the fly ash was evaluated. Lime was judged to be the preferred means of arsenic immobilization because it required the lowest weight percent addition to significantly reduce the arsenic concentration in the leachate. Calcium arsenate solution chemistry and various arsenic immobilization mechanisms are also discussed.     

Transition Criteria for Fluidized Beds Revisited

ABSTRACT

Characterization of baghouse fly ash produced from lignite in fluidized-bed combustion tests indicated that the presence of arsenic in the ash leachate was an environmental concern. The capacity of three chemical additives (lime, calcium sulfate, and nitric acid) to immobilize the arsenic in the fly ash was evaluated. Lime was judged to be the preferred means of arsenic immobilization because it required the lowest weight percent addition to significantly reduce the arsenic concentration in the leachate. Calcium arsenate solution chemistry and various arsenic immobilization mechanisms are also discussed.     

Investigation of reactions in high-alumina fly ash and lime pastes

By-product fly ash from coal combustion generally contains a high percentage of active silica and smaller amounts of alumina, although some coals can have higher alumina contents (30 to 40%). During our experimental tests on the utilization f fly ash in road and highway foundation sheets, we have found a fly ash poor in silica, having an exceptionally high alumina content. This material has shown a good reactivity towards lime paste, giving hardened mixtures with high mechanical properties.     

制革污泥及其固化块的微观结构研究

采用扫描电镜-能谱分析(SEM-EDS)对制革污泥及其固化块的微观结构进行研究。结果表明每千克污泥掺加石灰、粉煤灰和煤渣分别为0.12、0.02和0.08kg,经过6、8、10、15、20d自然条件养护后,污泥固化块污泥致密性及抗压强度均随养护时间的增加而增强。污泥固化块经过20d养护后通过5000倍扫描电镜观察,发现污泥固化块内部出现明显的针状结构。污泥固化块的抗压强度主要来源于石灰和活性硅酸盐料(粉煤灰、煤渣)与水反应生成的钙矾石,养护时间的延长也是制革污泥固化块抗压强度增大的主要原因。     

Microconcrete with partial replacement of Portland cement by fly ash and hydrated lime addition

The reduction in Portland cement consumption means lower CO₂ emissions. Partial replacement of Portland cement by pozzolans such as fly ash has its limitations due to the quantity of calcium hydroxide generated in the mix. In this work we have studied the contribution of the addition of hydrated lime to Portland cement + fly ash systems. We have also studied several levels of cement replacement, ranging from 15% to 75%.The best mechanical results were obtained replacing 50% of Portland cement by the same amount of fly ash plus the addition of hydrated lime (20% respect to the amount of fly ash). In these systems, an acid-base self-neutralization of the matrix has occurred through a pozzolanic reaction of fly ash with portlandite liberated in the hydration of Portland cement and the added hydrated lime. It has been identified for these mixtures a significant amount of hydrated gehlenite, typical reaction product from rich-alumina pozzolans.