Injection Nozzle for Ultraviolet Light-Enhanced H2O2 Oxidation of Air Pollutants in Flue Gas

Injecting aqueous solutions of hydrogen peroxide (H2O2) into hot flue gases can split the peroxide into OH and HO2 radicals. These reactive radicals readily oxidize air pollutants such as CO, VOCs, NO, mercury, and others. H2O2 is thermally “activated” (split into free radicals) rapidly at temperatures of 500°C and above. At lower temperatures, such as found in boiler exhaust flue gases, ultraviolet (UV) light can be used to activate the peroxide molecules. However, placing the UV lamps directly in the flue gases can lead to operating and maintenance problems, and “dilutes” the UV energy due to absorption by other gases. A “UV nozzle” has been developed that produces H2O2 radicals and delivers them into a flowing stream of boiler flue gases. Using a previously constructed pilot scale system at NASA's Kennedy Space Center, experiments were run to prove the concept of the nozzle, measuring the oxidation of NO as an indicator of radical formation and delivery. Data were taken at three temperatures, with none, one, or two UV lamps on, and with various injection rates of peroxide. Flue gas temperatures ranged from 85 to 304°C (186 to 580°F), and the molar ratios (inlet peroxide to inlet NOx) ranged from about 1.5 to over 15. Conversions of NO varied from 0% (at the lowest temperature tested) to above 50% (at highest temperature). Although increasing temperature had a marked effect on conversion, the activation of hydrogen peroxide by UV light was demonstrated in the temperature range of final flue gas exhaust gases (290–350°F). These results indicate that radicals can be created from hydrogen peroxide at reasonable temperatures using UV light, and that the radicals can be delivered into a flue gas stream where they can oxidize pollutants.     

Pilot-Scale Evaluation of H2O2 Injection to Control NOx Emissions

Nitric oxide (NO) in combustion flue gasses can be converted to higher oxidation states by the injection of aqueous solutions of hydrogen peroxide (H2O2) into the hot flue gases. The NO is oxidized to NO2, HNO2, and HNO3, which can then be removed in a wet scrubber. A pilot plant system that was designed, constructed, and operated at Kennedy Space Center confirmed previous results that H2O2 is very effective at oxidizing NO; conversions of NO above 90% were obtained at temperatures of about 500°C (930°F) using mole ratios of H2O2:NOx slightly above 1.0. The mole ratios of H2O2∕NOx needed to obtain high conversions of NO were significantly lower in the pilot plant that they had been in previous laboratory studies, demonstrating that this process can be an economically feasible method for NOx control. The position of the injector and the type of atomization were very important to the efficient utilization of peroxide. When SO2 was present in the flue gas, both NO and SO2 were oxidized without increasing the demand for peroxide.     

Kinetic Modeling of the Gas-Phase Oxidation of Nitric Oxide Using Hydrogen Peroxide

The use of hydrogen peroxide (H2O2) to enhance the oxidation of nitric oxide (NO) under postflame conditions in the presence or absence of sulfur dioxide (SO2) has been studied by means of chemical kinetic modeling and compared with pilot-scale experimental data. The experimental results were obtained from a nonisothermal reactor at atmospheric pressure with inlet temperatures in the range of 770–790?K. The CHEMKIN-II model with a kinetic mechanism from the literature was employed for this work. At the temperatures studied, H2O2 produces OH and HO2 radicals which enhance the oxidation of NO. The OH radical also helps oxidize SO2. The modeling results confirmed an optimum temperature of about 775?K where the NO conversion reached about 90% with an H2O2:NO molar ratio of 1:1. Conversion of NO2 to HNO3 was found to occur to a slight extent. Finally, the presence of SO2 was found to promote slightly the oxidation of NO to NO2.     

Simultaneous sulfur dioxide and nitrogen dioxide removal by calcium hydroxide and calcium silicate solids

At conditions typical of a bag filter exposed to a coal-fired flue gas that has been adiabatically cooled with water, calcium hydroxide and calcium silicate solids were exposed to a dilute, humidified gas stream of nitrogen dioxide (NO2) and sulfur dioxide (SO2) in a packed-bed reactor. A prior study found that NO2 reacted readily with surface water of alkaline and non-alkaline solids to produce nitrate, nitrite, and nitric oxide (NO). With SO2 present in the gas stream, NO2 also reacted with S(IV), a product of SO2 removal, on the exterior of an alkaline solid. The oxidation of S(IV) to S(VI) by oxygen reduced the availability of S(IV) and lowered removal of NO2. Subsequent acidification of the sorbent by the removal of NO2 and SO2 facilitated the production of NO. However, the conversion of nitrous acid to sulfur-nitrogen compounds reduced NO production and enhanced SO2 removal. A reactor model based on empirical and semi-empirical rate expressions predicted rates of SO2 removal, NO2 removal, and NO production by calcium silicate solids. Rate expressions from the reactor model were inserted into a second program, which predicted the removal of SO2 and NOx by a continuous process, such as the collection of alkaline solids in a baghouse. The continuous process model, depending upon inlet conditions, predicted 30-40% removal for NOx and 50-90% removal for SO2. These results are relevant to dry scrubbing technology for combined SO2 and NOx removal that first oxidizes NO to NO2 by the addition of methanol into the flue duct.     

Plasma-Assisted Process for Removing NO/NOx from Gas Streams with C2H4 as Additive

NOx removal from gas streams via dielectric barrier discharges (DBDs) has been experimentally evaluated. This paper investigates the effect of injecting C2H4 as an additive with respect to the De–NOx chemistry and the effect of gas composition on NO/NOx removal efficiencies. Experimental results indicate that both removal efficiencies of NO and NOx are enhanced with increasing applied voltage, gas temperature, and water vapor. Water vapor in gas streams has a distinct influence on NOx removal by generating OH radicals to convert NO2 to form HNO3. NOx removal decreases with increasing oxygen content although NO removal increases with increasing oxygen content. As high as 100% of NO and 57% of NOx are removed at 140°C for the gas stream containing [NO]:[C2H4]:[H2O(g)]:[O2]:[N2] = 0.05:0.2:3.0:5.0:91.75. Major mechanisms for NO and NOx removals in DBD processing with C2H4 as an additive are described in the text.     

烧结矿催化还原NO的实验研究

摘要：《钢铁企业超低排放改造工作方案（征求意见稿）》中，计划将烧结烟气中NOx排放质量浓度控制在50mg/m3以内，烧结烟气NOx减排势在必行。因此，旨在利用烧结矿本身作为脱硝催化剂，以烧结过程产生的还原性气体CO为还原剂，系统地研究了烧结矿粒径、焙烧温度、空速比、CO/NO物质的量之比和O2体积分数对烧结矿催化脱硝效果的影响。结果表明，O2体积分数对烧结矿催化还原NO的转化率影响较大，当CO体积分数为3%、O2体积分数为1.04%时，NO的转化率为68.83%；O2体积分数降低至0.90%以下时，NO的转化率可达95%以上。无O2条件下，烧结矿粒径为0.2～1.0mm、焙烧温度为500℃、空速比为3000h-1、CO/NO物质的量之比为6时，NO的转化率可达99.58%。以烧结矿为催化剂能有效地促进CO对NO的还原，具有十分重要的环保意义和经济应用前景。     

双氧水脱硫技术在倾动炉的应用实践

双氧水脱硫技术在各行业被广泛应用,该技术被应用在贵溪冶炼厂倾动炉杂铜冶炼烟气中SO2治理,烟气经文丘里洗涤器降温、除尘后进入脱硫塔,利用双氧水强氧化性将烟气中的SO2在脱硫塔内与稀释的双氧水发生化学反应达到脱除的目的,含酸雾烟气经电除雾脱除酸雾后达标排放。该工艺具有流程短、脱硫效率高、精确控制、阻力小等优点,同时产生的稀酸可回收利用,无二次污染。     

废水处理石膏工序离心机给液方式的探索

介绍了废水处理石膏工序原有的离心机高位槽给液方式,并根据实际生产情况对其存在的问题和弊端进行了分析。为了提高离心机给液效率,结合已有经验加装2台离心泵输送石膏浆液,用于替代原有的高位槽给液方式,其控制模式也进行了相应调整。投入运行后取得了良好的效果,解决了原系统存在的效率低、管线复杂、管道易堵塞、能耗高等缺点。     

低温氧化法用于烧结烟气脱硝的可行性探析

烧结烟气中氮氧化物（NOx）是危害人体健康和生态环境的主要污染物之一。鉴于大部分钢铁厂烧结生产线都还没配置烟气脱硝设施，烧结烟气NOx治理迫在眉睫。然而，烧结烟气具有温度低、SO2含量高、NOx含量低等特点，不适宜采用燃煤电厂常用的选择性催化还原（SCR）或非催化还原（SNCR）脱硝方法。介绍了几种低温氧化脱硝技术，分别采用氯酸、亚氯酸钠、高锰酸钾、过氧化氢和臭氧等氧化剂，并详细阐述其氧化原理及技术特点。还对低温脱硝技术应用于烧结烟气NOx治理进行可行性分析，认为过氧化氢法、臭氧法和和黄磷乳浊液法等氧化脱硝技术具有一定的市场前景。     

Emission Control of NO and SO2 for the High-Temperature and Low O2 Concentration Combustion of Coke by Urea and NH4HCO3

Urea and NH4HCO3 were used to control the emission of NO and SO2 from the combustion of coke at high-temperature and low oxygen concentration. Urea and NH4HCO3 could control NO emission only under 1100°C. Their effects disappeared above 1100°C even though the increase of urea and NH4HCO3 content from 10?to?50?wt?%. However, they showed good desulfurization effect on the emission of SO2 at all combustion temperatures and their effects showed remarkable results even at 1500°C. Only 10?wt?% of urea or NH4HCO3 could control the emission of SO2 effectively at 1400 and 1500°C. This effect was caused by ?NH and ?NH2 from the thermal decomposition of reducing agents at high temperature. Low O2 concentration showed little effect on the removal of SO2. Ammonia slip from the thermal decomposition of reducing chemical was not a considerable level.     

铁矿烧结烟气氧化- 氨法协同脱硫脱硝

铁矿烧结是钢铁行业SO2和NOx的主要排放源,采用氧化- 氨法工艺对铁矿烧结烟气进行协同脱硫脱硝研究。结果表明,预先氧化烧结烟气、提高吸收液中SO2-3初始质量浓度、pH值和增大液气比均有利于提高脱硫率和脱硝率,而烟气温度及烟气中NO质量浓度和SO2质量浓度的升高,均不利于烟气同时脱硫脱硝。在适宜的条件下,脱硫率和脱硝率分别达到97.95%和47.54%,烟气被氧化后进行氨法脱硫脱硝,最终脱硝产物为N2和NO-3。     

柳钢烧结烟气氨法脱硫体系脱硝机理

为了揭示氨法脱硫体系中的脱硝行为,以柳钢265 m2烧结机和 360 m2烧结机为研究对象,测定并评估柳钢烧结烟气氨法脱硫系统的脱硝效率,并对吸收液进行检测,分析脱硝产物的走向。结果表明,烧结烟气中NOx主要以NO的形式存在,烧结烟气氨法脱硫体系具有一定的脱硝能力,平均脱硫率为94.30%,平均脱硝率为24.37%。在氨法脱硫体系下,主要脱硝反应为NOx被(NH4)2SO3还原为N2,其次是NOx被吸收液吸收转化为NO-3。由于NO分子的极性很弱,难溶于水,将NO转化为易溶于水的NO2是提高氨法脱硫体系脱硝率的关键。     

烧结烟气臭氧氧化 半干法吸收脱硫脱硝实践

以梅钢7×105 m3/h烧结机烟气的脱硫脱硝为背景,研究了实际工程应用中臭氧对烟气的氧化和半干法对氧化产物(NOx和SO2)的吸收等问题。结果表明,臭氧喷入点位置对烟道内NOx氧化影响不大,喷射格栅保证了臭氧和烟气的均匀混合。吸收塔出口烟气温度对脱硝影响显著,NOx的吸收效率会随着温度的升高而降低,当温度高于95 ℃时,脱硝效率为0;而脱硫塔出口烟气温度变化对SO2吸收几乎没有影响。优化后的烧结烟气脱硫脱硝系统连续运行数据表明,出口SO2质量浓度均值为16.83 mg/m3,出口NOx质量浓度均值为72.33 mg/m3,均达到了系统设计要求。系统运行成本为10～11元/t,与活性炭烟气净化技术、循环流化床＋SCR工艺技术相比,臭氧氧化 半干法吸收协同脱硫脱硝工艺具有明显的优势。     

SO2 poisoning and regeneration of Mn-Ce/TiO2 catalyst for low temperature NOx reduction with NH_3

SO2 poisoning and regeneration of Mn-Ce/TiO2 catalyst prepared by a novel co-precipitation method for low temperature selective catalytic reduction (SCR) of NOx with ammonia were investigated in this study. When 700 ppm SO2 was fed in, the Mn-Ce/TiO2 catalyst had good resistance to SO2, but the deactivation of Mn-Ce/TiO2 poisoned by SO2 still occurred. The NO conversion of Mn-Ce/TiO2 (the molar ra-tio of Ce to Ti is 0.075) catalyst decreased from 92.5% to 34.6% in 13 h. Characterizations of fresh and SO2-poisoned Mn-Ce/TiO2 catalysts were carried out by Brunauer-Emmett-Teller method (BET), ion chromatography (IC), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The characterized results indicated that the deposition of sulfates and nitrates on the surface made the catalyst deactivated. Water washing, thermal regeneration and reductive regeneration were used to regenerate the deactivated Mn-Ce/TiO2. And water washing showed best performance on the regeneration of poisoned catalysts, especially with ultrasonic vibration. The Mn-Ce/TiO2 catalyst showed high stability under a series of deactivation-regeneration experiments for ten cycles.     

烟气脱硫脱硝一体化技术的研究现状

SO2和NOx主要来源于烟气,它们给环境带来严重的破坏,发展烟气净化技术势在必行.为此,本文着重讨论了近年来蓬勃发展的几种烟气脱硫脱硝一体化工艺,并分别分析了它们的机理、特点、应用及存在的问题.     

基于测试的烟气循环烧结工艺

在正常生产情况下,以新钢8号360m2烧结机为研究对象,提出基于测试的烟气循环烧结工艺思路。采用风箱支管开孔取样的测试方法,通过选择合理的测定位置和测点,测试烧结烟气温度、O2体积分数以及SO2和NOx体积分数,探索其变化规律并制定适宜的内、外循环工艺方案。研究结果表明,烧结机前段风箱烟气中O2体积分数较低,在18号风箱之后O2体积分数逐步上升;烧结烟气密度随温度升高而变小,流速相应增大,但其标况流量相当;烧结循环烟气O2体积分数越高,烧结机漏风率越低,烟气循环率越高;内、外循环工艺都能降低固体燃料消耗,清洁烧结生产,前者兼顾增产功效,适合新建项目,后者兼顾减排功效,适合改造项目。     

氧化球团烟气中SO2和H2O(g)对SCR脱硝的影响

选择性催化还原(SCR)具有效率高、技术成熟的优势,但处理球团烟气需要加热才能达到SCR脱硝的反应温度,导致能耗和运行成本高.氧化球团预热Ⅱ段(PH段)烟气温度在300℃以上,满足SCR反应所需温度,但是烟气中含有的SO2和H2O(g),会对催化剂的脱硝性能产生影响.研究了 PH段烟气中SO2和H2O(g)对V/Ti催...     

Thermal Analysis of Cover Systems in Municipal Solid Waste Landfills

Cover temperature variations were determined at four municipal solid waste landfills located in different climatic regions in North America: Michigan, New Mexico, Alaska, and British Columbia. Cover temperatures varied seasonally similarly to air temperatures and demonstrated amplitude decrement and phase lag with depth. Elevated temperatures in the underlying wastes resulted in warmer temperatures and low frost penetration in the covers compared to surrounding subgrade soils. The ranges of measured temperatures decreased and average temperatures generally increased (approximately 2°C/m) with depth. The ranges of measured temperatures (Tmax?Tmin) were 18–30°C and 13–21°C and the average temperatures were 13–18°C and 14–23°C at 1 and 2?m depths, respectively. For soil and geosynthetic barrier materials around 1?m depth, the maximum and minimum temperatures were 22–25°C and 3–4°C, respectively. Frost depths were determined to be approximately 50% of those for soils at ambient conditions. The main direction of heat flow in the covers was upward (negative gradients). The cover gradients varied between ?18 and 14°C/m, with averages of ?7?to?1°C/m. The gradients for soil and geosynthetic barrier materials around 1?m depth varied between ?11 and 9°C/m with an average of ?2°C/m. Cover thawing n-factors ranged between 1.0 and 1.4 and the cover freezing n-factor was 0.6. Design charts and guidelines are provided for cover thermal analyses for variable climatic conditions.     

Liquid-Impregnated Clay Solid Sorbents for CO2 Removal from Postcombustion Gas Streams

A novel liquid-impregnated clay sorbent [R. V. Siriwardane, U.S. Patent No. 6,908,497 B1 (2003)] was developed for carbon dioxide (CO2) removal in the temperature range of ambient to 60°C for both fixed-bed and fluidized-bed reactor applications. The sorbent is regenerable at 80–100°C. A 20-cycle test conducted in an atmospheric reactor with simulated flue gas with moisture demonstrated that the sorbent retains its CO2 sorption capacity with CO2 removal efficiency of about 99% during the cyclic tests. The sorbents suitable for fluidized-bed reactor operations showed required delta CO2 capacity requirements for sorption of CO2 at 40°C and regeneration at 100°C. The parameters such as rate of sorption, heat of sorption, minimum fluidization velocities, and attrition resistance data that are necessary for the design of a reactor suitable for capture and regeneration were also determined for the sorbent. A 20-cycle test conducted in the presence of flue-gas pollutant sulfur dioxide—SO2 (20 parts per million)—indicated that the sorbent performance was not affected by the presence of SO2.     

Analysis of flue gas emission law in sintering process of iron mine

In order to study the emission law of COx in the sintering flue gas, firstly, the fuel combustion behavior in the sintering process was studied and the generation mechanism of COx was analyzed. Then, the sintering process in the production site was simulated. Sintering flue gas was detected by the flue gas analyzer. Flue gas temperature, negative pressure, and flue gas composition were analyzed. The correlation between the change of flue gas parameters and the state of sinter bed was analyzed. The experimental results can be concluded that the main factor affecting the mass concentration of CO in the sintered flue gas is temperature. The changes of CO, CO2 and NOx mass concentrations are consistent and negatively correlated with the changes of O2 gas volume fraction.CO, SO2 and NOx concentrations have the same extreme time, and the flue gas temperature reaches the fastest rising period. The golden stage of staged treatment of CO in flue gas is from the end of sintering ignition to the rise of flue gas temperature.