基于尿素/NaClO2溶液湿法烟气同时脱硫脱硝的研究

结合燃煤电厂实际工况条件,基于尿素/NaClO2溶液进行了同时脱硫脱硝试验研究,探索尿素/NaClO2湿法同时脱硫脱硝的主要影响因素和优化工艺条件,并分析其反应机理.结果表明:纯尿素溶液可有效脱除烟气中的SO2,但对NO脱除效果较差,NaClO2的添加可有效改善NO的脱除效果;液气比和NaClO2质量分数增大有利于提高尿素/NaClO2溶液的脱硫脱硝效果,其中NaClO2质量分数对NO脱除效率的影响比对SO2脱除效率的影响明显;空塔气速和NO初始质量浓度与系统脱硫、脱硝效率成负相关关系.NaClO2的添加对尿素溶液脱硫效果影响较小,SO2被吸收后生成的SO32-主要被烟气中溶于水的O2氧化成SO42-;难溶于水的NO被NaClO2氧化为NO2和NO2-等,进而被尿素溶液有效吸收,NOx最终多数以N2形式排放.     

基于尿素/NaClO_2溶液湿法烟气同时脱硫脱硝的研究

结合燃煤电厂实际工况条件,基于尿素/NaClO2溶液进行了同时脱硫脱硝试验研究,探索尿素/NaClO2湿法同时脱硫脱硝的主要影响因素和优化工艺条件,并分析其反应机理.结果表明:纯尿素溶液可有效脱除烟气中的SO2,但对NO脱除效果较差,NaClO2的添加可有效改善NO的脱除效果;液气比和NaClO2质量分数增大有利于提高尿素/NaClO2溶液的脱硫脱硝效果,其中NaClO2质量分数对NO脱除效率的影响比对SO2脱除效率的影响明显;空塔气速和NO初始质量浓度与系统脱硫、脱硝效率成负相关关系.NaClO2的添加对尿素溶液脱硫效果影响较小,SO2被吸收后生成的SO2-3主要被烟气中溶于水的O2氧化成SO2-4;难溶于水的NO被NaClO2氧化为NO2和NO-2等,进而被尿素溶液有效吸收,NOx最终多数以N2形式排放.     

酸性NaClO_2溶液同时脱硫、脱硝的试验研究

以NaClO2溶液为吸收剂,在自行设计的小型鼓泡反应器中进行了烟气同时脱硫、脱硝的实验研究,分析了影响脱除效率的各种因素及规律.试验发现,NaClO2初始浓度、吸收溶液初始pH值、吸收液温度、SO2和NO初始浓度等对脱除效率影响较大;在确定的最佳试验条件下,脱硫、脱硝效率分别达到100%和95.2%.另外还利用光化学方法分析了脱硫、脱硝产物,结果表明:脱硫产物主要为SO24-,脱硝产物主要为NO3;在此基础上,提出了酸性NaClO2溶液脱硫、脱硝的反应机理.     

基于臭氧前置氧化的新型喷淋散射技术同时脱硫脱硝实验研究

采用喷淋散射技术结合臭氧前置氧化进行同时脱硫脱硝实验,探究了O_3与NO物质的量比、SO_2初始体积分数、液气体积比、浸没深度等对脱除效率(脱硫和脱硝效率)的影响。结果表明:喷淋散射技术的脱除效率均高于只喷淋或只鼓泡方式;随着O_3与NO物质的量比和SO_2初始体积分数的增大,脱硝效率不断提高,脱硫效率基本未受影响;脱除效率随液气体积比和浸没深度的增大而提高;与只喷淋方式、液气体积比较大的条件相比,采用喷淋散射技术、液气体积比较小时的脱除效率更高;与只鼓泡方式、浸没深度较大的条件相比,采用喷淋散射技术、浸没深度较小时的脱除效率更高。     

氧化亚铁硫杆菌烟气脱硫实验研究

研究利用氧化亚铁硫杆菌和Fe离子协同脱除烟气中的SO2,考察了液气比、反应温度、初始Fe2＋浓度等因素对脱硫率的影响。研究表明氧化亚铁硫杆菌和Fe3＋体系对SO2具有循环催化氧化吸收的作用,并且提高初始Fe2＋浓度,保持适宜的温度（30～40℃）,有利于维持此循环效果而得到持久高效的脱硫率。     

氧活性粒子注入烟道中脱除SO2的研究

为解决目前石灰石-石膏湿法烟气脱硫(FGD)存在的投资和运行费用高、占地面积大、产生大量污水及低质硫酸钙等问题,将小流量高浓度氧活性粒子和HO2-引发剂分别注入烟道中,与烟气中水反应生成·OH,并在无吸收剂、催化剂及其他技术协同作用下,利用·OH氧化脱除大流量烟气量中的微量SO2并生成H2SO4.结果表明:氧活性粒子与SO2的物质的量比n=4时,SO2脱除率达到94.6%,回收酸液中SO42-回收率达到28.8%;烟气温度每升高10 K,脱硫率降低5%左右;O2体积分数成倍变化对脱硫率影响甚微;当H2O体积分数大于9%时基本满足了脱硫要求.     

臭氧氧化烟气脱硝制硝酸的试验研究

将含NO的模拟烟气用臭氧氧化后进行洗气,在脱硝过程中制得硝酸.在100～160℃模拟烟气温度范围内,O3与NO3浓度是影响气液反应HNO3生成的重要因素.臭氧与NO的物质的量比(O3/NO)在1.5以上为宜.高的O3/NO物质的量比和低的模拟烟气温度,利于反应生成NO3和提供较高体积分数的O3进行气液反应,促进HNO3的生成,抑制亚硝酸的生成.试验中在模拟烟气温度120℃下,O3/NO物质的量比为1.5和2时,硝酸产率分别为70.5%和88%.随着在气相反应器中停留时间的延长,O3与NO3的浓度降低,HNO3产率下降,HNO2生成上升.吸收液的酸度对HNO3生成的影响并不明显,在pH值1.5～2.5时,硝酸的产率比pH值等于7时降低3%～4%.     

烟气循环方式对SO_3生成的影响

基于化学反应动力学计算方法研究了富氧燃烧中不同循环方式对SO3生成的影响.结果表明:富氧燃烧方式下SO3体积分数急剧增大,其中湿烟气循环方式下的SO3体积分数最大;增大初始O2、SO2和H2O体积分数,增加了燃烧过程O、OH和HOSO2等自由基的浓度,促进了SO3的生成;SO3生成率随初始SO2体积分数的增大而减小,随初始O2体积分数和初始H2O体积分数的增大而增大;富氧燃烧导致烟气酸露点普遍升高,其中湿烟气循环方式下烟气酸露点最高,对烟气进行脱硫或者脱水处理,能够有效降低烟气酸露点.     

吸附协同等离子体作用的顺序式锅炉烟气脱硫脱硝工艺

针对锅炉（烟厂用锅炉等）烟气，提出了一种具有高脱除率和低能耗的顺序式烟气脱硫脱硝工艺。即在吸附剂颗粒表面利用活性N原子还原NO产生的活性0原子来继续氧化二氧化硫生成SO3，并通过化学反应动力学模拟研究了该工艺的可行性。NO／SO2/N2系统等离子体脱硫脱硝的模拟结果显示：NO有显著的脱除效果，SO2有少量转化为SO3，SO2脱除率随停留时间增加而增加。研究结果表明顺序式烟气脱硫脱硝是可行的，关键在于选用合适吸附剂来控制其表面的O2浓度和停留时间。     

基于喷淋散射技术的臭氧前置氧化氨法同时脱硫脱硝特性研究

基于喷淋散射技术采用前置臭氧氧化结合氨水吸收的方法,开展了烟气同时脱硫脱硝实验研究,测试了O_3与NO物质的量比、SO_2质量浓度、NO质量浓度、液气比和浸液深度等对脱硫脱硝效率的影响,建立了喷淋散射传质面积计算模型。结果表明:O_3与NO物质的量比增大可明显提高脱硝效率;SO_2质量浓度增大会促进NO_2的吸收;液气比和浸液深度的增大均会使总传质面积增大,从而提高脱硫脱硝效率;在O_3与NO物质的量比为1、液气比为6 L/m~3的工况下,浸液深度为50 mm、氨水质量分数为0.06%时,采用喷淋散射技术后脱硫效率和脱硝效率分别可达99.6%和82.5%,均高于同参数下仅喷淋技术和仅鼓泡技术。     

Photocatalytic H2 production over RuO2@ZnS and RuO2@CuS nanostructures

Photocatalytic hydrogen production is a promising approach of sustainable economy, because a use of sunlight and water to produce a fuel will solve a problem of fossil fuels depletion. Metal sulfides are well known photocatalysts in water splitting process, but in absence of sacrificial electron donor they undergo a photocorrosion. In this paper we studied a possible strategy to protect the sulfide photocatalysts and to improve its photostability by a deposition of small amount of ruthenium oxide at surface of sulfides. Nanocrystalline zinc sulfide and copper sulfide were prepared in a hydrothermal way and have been functionalized by RuO₂. As prepared photocatalysts showed good activity towards hydrogen formation. Modification of sulfides with ruthenium oxide had a few positive effects: it expanded a light absorption range by photocatalysts, enhanced the photocatalytic activity towards H₂ formation, improved a photostability in comparison with neat ZnS and CuS as well as protected from the electronic and structural changes within semiconductors due to irradiation.     

Evaluation of in-situ formed La2O3–TiO2–La2O2CO3 nanocomposite photocatalyst for H2 production

The photocatalytic evolution of H₂ over La₂O₃ decorated TiO₂ catalyst was examined under solar light. It was observed that during the course of the reaction, the transformation of La₂O₃/TiO₂ into La₂O₃–TiO₂–La₂O₂CO₃ occurred and these species effectively suppressed electron-hole pair recombination by forming electron trapping centres on the surface, resulting in an increased visible light absorption and improved H₂ yield. The 2 wt%La₂O₃/TiO₂ nanocomposite demonstrated better H₂ yield (～8.76 mmol (g_cat)^?1) than the bare TiO₂ (～1.1 mmol (g_cat)^?1). The catalyst was stable even after several consecutive recycles with no substantial loss of hydrogen production rate. The H₂ rates were correlated with the physicochemical characteristics of the catalysts examined by BET–SA, H₂-TPR, XRD, UV-DRS, Raman spectroscopy, FTIR, HRTEM, EPR and PL spectroscopy.     

Numerical study of the O2/CO2, O2/CO2/N2, and O2/N2-syngas MILD combustion: Effects of oxidant temperature,O2 mole fraction,and fuel blends

Moderate or Intense Low-oxygen Dilution (MILD) combustion of a syngas fuel under air-fuel, oxygen-enhanced, and oxy-fuel condition are numerically studied with using counterflow diffusion flame. Fuel composition, temperature of oxidant (T_ox), and oxygen mole fraction (X_O2) are selected as the main parameters. Fake species (FCO₂) with the same CO₂ physical properties is used for separation the physical and chemical effects of replacing CO₂ with N₂. According to the results, under the high preheating temperatures, the chemical effect of changing the oxidant composition from N₂ to CO₂ is the main reason of the changes in flame structure, ignition delay time (IDT) and heat release rate (HRR) while physical differences play a more prominent role in the low preheating temperature MILD combustion. In all X_O2, the physical and chemical effects of replacing CO₂ with N₂ have almost the same role on the maximum flame temperature. The results of IDT expressed that chemical discrepancies of CO₂ and N₂ play a key role on IDT enhancement by increasing CO₂ in the oxidant composition. The sensitivity analysis of CH₂O for variations of T_ox and X_O2 shows that reactions R54, R56, R58, and R101 are the main responsible of lower HRR and higher IDT by moving from air-syngas to oxy-fuel MILD combustion.     

保护气氛烧结炉

介绍了HIC封装管壳中玻璃绝缘子网带烧结炉的特殊机械结构、氮氢保护气氛系统和电气保护措施。确立了网带炉低速爬行力学模型及炉内合理的气氛流向。     

New gas chromatographic packing ZIF-67@NH2–SiO2 for separation of hydrogen isotope H2/D2

ZIF-67@NH₂–SiO₂ composites were prepared by loading the metal-organic frameworks ZIF-67 on amino modified SiO₂ gel particles (NH₂–SiO₂, 80–100 mesh) through layer-by-layer self-assembly method. Systematic investigation on the effects of ZIF-67 loading amounts on NH₂–SiO₂ packed stainless steel chromatographic column (specification 1.0 m×2.0 mm I.D.), the flow rate of He as carrier gas and the injection amount of mixed gas (H₂/D₂) on the hydrogen isotope H₂/D₂ separation performance at liquid nitrogen temperature, unraveled the optimal conditions for H₂/D₂ isotope separation. The results showed that the optimal stationary phase materials under the optimized conditions can effectively separate H₂ and D₂ with separation resolution R = 1.52 and the separation time t = 10.15 min. The superior performance of the ZIF-67 is tentatively thought to be due to kinetic quantum sieving (pore size 3.3 Å) effect and chemical affinity sieving effect of Co ion in ZIF-67.     

Photocatalytic reduction of CO2 with H2O on CuO/TiO2 catalysts

Carbon dioxide was photocatalytically reduced to produce methanol and ethanol in the presence of CuO-loaded titania powders suspended in water containing Na₂SO₃ as the hole scavenger. The photocatalysts were synthesized by an impregnation method using P25 (Degussa) as support. At the optimum amount of copper oxide loading (3 wt%), the methanol and ethanol yields were 12.5 and 27.1 μmol/g-catal., respectively, following 6 h of UV illumination. The redistribution of photogenerated charge carriers in CuO/TiO₂ facilitates electron trapping and prohibits the recombination of electrons and holes, which significantly increases photoefficiency. The addition of Na₂SO₃ promotes the formation of ethanol.     

Photocatalytic reduction of CO2 using TiO2 powders in supercritical fluid CO2

The photocatalytic reduction of CO₂ was investigated using TiO₂ powders in supercritical fluid CO₂. These were irradiated in a stainless steel vessel at 9.0 MPa and 35°C. After reducing the CO₂ pressure to the ordinary state, pure water was added to the vessel while avoiding air contamination. No gaseous reduction products were observed. Formic acid was obtained only in aqueous solution. The optimal irradiation time for the production of formic acid was 5 h. Addition of acidic solutions rather than pure water was preferable for formic acid formation. Formic acid seems to be produced through the protonation of reaction intermediates on TiO₂ powders in solutions. The CO₂-reduction system described here may be of practical value for efficient CO₂-conversion and fixation, storage of solar energy, and production of raw materials for the photochemical industry.     

Effects of CO2 addition on flame structure in counterflow diffusion flame of H2/CO2/N2 fuel

Numerical analysis on flame structure in a counterflow diffusion flame has been conducted for understanding the effects of CO₂ addition to fuel, systematically varying initial concentration of CO₂ and axial velocity gradient. The effects of CO₂ addition to fuel side in a counterflow diffusion flame are globally divided into two categories: diluent effects due to the relative reduction in the concentrations of the reactive species, and direct chemical effects caused by the breakdown of CO₂ through the reactions of third‐body collision and thermal dissociation. The deflection of CO₂ mole fraction profile with mixture fraction clarifies that the converted CO quantity from CO₂ is not negligible at low axial velocity gradients. It is also known that the addition of CO₂ does not alter the basic skeleton of the H₂–O₂ reaction mechanism, but contributes to the formation and destruction of hydrocarbon products such as HCO. At high axial velocity gradients the CO converted reaction is suppressed and then CO₂ plays the role of a diluent at these conditions. Copyright © 2001 John Wiley & Sons, Ltd.