膜法氨水吸收脱除烟气中CO2的研究

以氨水为吸收剂,对聚丙烯中空纤维膜分离烟气中CO2进行了实验研究.结果表明:随着气体流量和入口CO2浓度的增加,CO2去除率下降而传质速率增加;随着氨水浓度和氨水流量的增加,CO2去除率和传质速率均显著增加,但当氨水浓度大于2.5 mol·L-1,吸收液流量大于80m L·min-1后,膜接触器对CO2去除率和传质速率基本保持不变;膜接触器连续运行15 d后其吸收性能显著下降,CO2去除率、传质速率、总传质系数均下降约40%~50%.接触角测量、SEM及XPS表征结果表明:随着操作的进行,聚丙烯膜在吸收液环境中接触角逐渐降低,疏水性减弱,造成膜孔润湿;同时碳酸盐在膜孔形成结晶,堵塞膜孔,使得传质阻力进一步增加,从而造成膜接触器吸收性能的下降.     

KrBr*准分子灯直接光解一甲胺气体

研究了正弦电源驱动的207 nm KrBr*准分子灯光解气相中的一甲胺(MA).考察了降解的影响因素(气体流速、初始浓度、输入功率),测定了灯的输入功率和辐射光谱.为了评价光解过程,对去除效率、能率、碳平衡和CO2的选择性这4个参数进行了研究.结果表明,去除率随着灯的输入功率升高、气体流速的降低以及气体初始浓度的升高而升高.能率与一甲胺初始浓度呈正相关性,输入功率为65.1 W时能率最高.输入功率升高,气体流速下降,碳平衡和CO2选择性都略有升高.当灯的输入功率为79.8 W,气体流速9.0 m3·h-1,初始浓度为2 897 mg·m-3,一甲胺去除率为56.8%,能率为185.6g·(kW·h)-1,相应的碳平衡和CO2选择性为16.8%和10.3%.最后,利用气质联用仪测定了一甲胺降解的产物,结合一甲胺的吸收光谱,推测了一甲胺的光解机制.     

基于碳捕集的富氧燃煤烟气联合脱硫脱硝试验研究

富氧燃煤烟气压缩液化CO2的高压低温工况为NO氧化为易溶于水的NO2提供了十分有利的条件.基于小型高压吸收试验装置,采用配制的富氧燃煤模拟烟气,在高压常温下进行了NO、SO2、O2与H2O的吸收反应试验.根据反应前后的气液产物分析,测定了不同组分比例与不同压力下混合气体中NO与SO2的转化率.NO氧化与吸收试验表明,NO转化为HNO3的比率随压力升高而增加,在0.5 ～2 MPa之间增加很快,在2 ～3 MPa之间增速趋丁平缓,压力达3 MPa以上时,90％以上的NO均转化为稀硝酸,且初始NO浓度越高,NO的转化率越大.混合气体中同时存在5O2与NO的联合吸收试验发现,只有少量的NO转化成了NO3-,SO2向H2SO4的转化率随压力升高而增加,初始SO2浓度越大,转化率越高.分析表明,SO2与NO同时存在时SO2先行转化为SO3,NO充当了催化剂,但SO2转化为SO3的一次转化率小于35％,反应酸液产物的多次循环能使SO2的转化率达到90％以上.建议的工艺流程中需采用两座吸收反应塔顺序脱除SO2与NO并回收稀酸溶液,有望在富氧燃煤发电捕集CO2系统中降低脱硫脱硝成本,部分地弥补富氧燃烧机组发电成本的增加.     

Vaporization reduction characteristics of aqueous ammonia solutions by the addition of ethylene glycol, glycerol and glycine to the CO2 absorption process

Aqueous ammonia (NH₃) solution can be used as an alternative absorption for the control of CO₂ emitted from flue gases due to its high absorption capacity, fast absorption rate and low corrosion problem. The emission of CO₂ from iron and steel plants requires much attention, as they are higher than those emitted from power plants at a single point source. In the present work, low concentration ammonia liquor, 9 wt.%, was used with various additives to obtain the kinetic properties using the blast furnace gas model. Although a solution with a high ammonia concentration enables high CO₂ absorption efficiency, ammonium ions are lost as ammonia vapor, resulting in reduced CO₂ absorption due to the lower concentration of the ammonia absorbent. To decrease the vaporization of ammonia, ethylene glycol, glycerol and glycine, which contain more than one hydroxyl radical, were chosen. The experiments were conducted at 313 K similar to the CO₂ absorption conditions for the blast furnace gas model.     

电晕放电与络合催化联合同时去除烟气中SO_2、NO实验研究

采用电晕放电与液相络合催化协同同时去除烟气中SO2和NO,电压、水流量、乙二胺合钴浓度、pH、SO2和NO初始浓度以及气流量对同时去除SO2和NO效率的影响进行了实验研究.结果表明:NO去除率随着放电电压、水流量、乙二胺合钴浓度、pH的增加而增加,而随SO2和NO初始浓度、烟气流量的增大而减小;SO2去除率也随放电电压,水流量的增加而增加,随烟气流量的增加而下降,但溶液pH,SO2和NO初始浓度和乙二胺合钴浓度对其影响很小.溶液中加入Mn2+和尿素能分别增强SO2和NO的去除效果.最佳条件为:电压25 kV、水流量80 L·h-1,乙二胺合钴浓度0.02 mol·L-1,烟气流量1.0 m3·h-1、尿素浓度0.02 mol·L-1,Mn2+浓度为0.02 mol·L-1时,NO和SO2去除率分别可达68%和94%,对应能量消耗分别为22.2 g·k Wh-1和75.2 g·k Wh-1.     

The oxycoal process with cryogenic oxygen supply

Due to its large reserves, coal is expected to continue to play an important role in the future. However, specific and absolute CO₂ emissions are among the highest when burning coal for power generation. Therefore, the capture of CO₂ from power plants may contribute significantly in reducing global CO₂ emissions. This review deals with the oxyfuel process, where pure oxygen is used for burning coal, resulting in a flue gas with high CO₂ concentrations. After further conditioning, the highly concentrated CO₂ is compressed and transported in the liquid state to, for example, geological storages. The enormous oxygen demand is generated in an air-separation unit by a cryogenic process, which is the only available state-of-the-art technology. The generation of oxygen and the purification and liquefaction of the CO₂-enriched flue gas consumes significant auxiliary power. Therefore, the overall net efficiency is expected to be lowered by 8 to 12 percentage points, corresponding to a 21 to 36% increase in fuel consumption. Oxygen combustion is associated with higher temperatures compared with conventional air combustion. Both the fuel properties as well as limitations of steam and metal temperatures of the various heat exchanger sections of the steam generator require a moderation of the temperatures during combustion and in the subsequent heat-transfer sections. This is done by means of flue gas recirculation. The interdependencies among fuel properties, the amount and the temperature of the recycled flue gas, and the resulting oxygen concentration in the combustion atmosphere are investigated. Expected effects of the modified flue gas composition in comparison with the air-fired case are studied theoretically and experimentally. The different atmosphere resulting from oxygen-fired combustion gives rise to various questions related to firing, in particular, with regard to the combustion mechanism, pollutant reduction, the risk of corrosion, and the properties of the fly ash or the deposits that form. In particular, detailed nitrogen and sulphur chemistry was investigated by combustion tests in a laboratory-scale facility. Oxidant staging, in order to reduce NO formation, turned out to work with similar effectiveness as for conventional air combustion. With regard to sulphur, a considerable increase in the SO₂ concentration was found, as expected. However, the H₂S concentration in the combustion atmosphere increased as well. Further results were achieved with a pilot-scale test facility, where acid dew points were measured and deposition probes were exposed to the combustion environment. Besides CO₂ and water vapour, the flue gas contains impurities like sulphur species, nitrogen oxides, argon, nitrogen, and oxygen. The CO₂ liquefaction is strongly affected by these impurities in terms of the auxiliary power requirement and the CO₂ capture rate. Furthermore, the impurity of the liquefied CO₂ is affected as well. Since the requirements on the liquid CO₂ with regard to geological storage or enhanced oil recovery are currently undefined, the effects of possible flue gas treatment and the design of the liquefaction plant are studied over a wide range.     

A novel gas purification system for biologically produced gases

A novel gas purification system employing membrane contactors with dense membranes in the absorption as well as the desorption unit has been tested concerning the separation efficiency of CO₂. The separation efficiency of potassium carbonate (K₂CO₃) promoted by piperazine (PZ) as absorption medium has been tested in the absorption unit. Since the absorbent will be regenerated in the desorption unit, the influence of temperature, sweep flow rate and absorbent type (0.5 M K₂CO₃ and 0.5 M K₂CO₃/0.5 M PZ) on the separation efficiency of CO₂ in the desorption unit has been investigated. Desorption by vacuum has been considered as well.In addition experimental results of the coupling of a bioreactor producing hydrogen by anoxygenic photosynthesis (low and fluctuating product gas flow rates and fluctuating compositions) with a membrane contactor for gas purification are reported. This was done in order to show the applicability of this system to processes producing biogases.     

CO2 capture performance of bi-functional activated bleaching earth modified with basic-alcoholic solution and functionalization with monoethanolamine: isotherms, kinetics and thermodynamics

CO_2 capture performance of bifunctional activated bleaching earth(ABE) was investigated at atmospheric pressure. The sorbents were characterized by means of X-ray diffraction(XRD), Brunauer–Emmett–Teller(BET), Caron-Hydrogen-Nitrogen analysis(CHN), Fourier transform infrared(FT-IR) and thermal gravimetric analysis(TGA). The CO_2 capacity was enhanced via basic-modification and monoethanolamine(MEA) loading of the ABE sorbent to obtain a bifunctional surface property. Here, basic-modified calcined ABE with a 30 wt.%MEA loading(SAB-30) showed the highest CO_2 capture capacity, but this was decreased with excess MEA loading( 30 wt.%). At a 10%(V/V) initial CO_2 concentration feed, the maximum capacity of SAB-30 increased from 2.71 mmol/g at 30℃(without adding moisture to the feed) to 3.3 mmol/g at 50℃ when adding 10%(V/V) moisture to the feed. Increasing the moisture concentration further reduced the maximum CO_2 capacity due to the blocking effect of the excess moisture on the sorbent surface. However, SAB-30 could completely capture CO_2 even in a 100%(V/V) initial CO_2 concentration feed. A maximum CO_2 capacity of5.7 mmol/g for SAB-30 was achieved at 30℃. Varying the ratio of sorbent weight to total flow rate of the gas stream had no discernible effect on the equilibrium CO_2 capture capacity. Avrami's equation and Toth's isotherm model provided a good fitting for the data and suggested the presence of more than one reaction pathway in the CO_2 capture process and the heterogeneous adsorption surface of SAB-30. Thermodynamics studies revealed that CO_2 capture on the bifunctional SAB-30 is feasible, spontaneous and exothermic in nature.     

低温等离子体-生物耦合系统对复合CVOCs的降解

采用低温等离子体-生物耦合系统降解氯苯和二氯乙烷混合气体,考察频率为10 000 Hz,能量密度(specific input energy,SIE)为6 111 J·L-1时进气浓度和气体流速对目标污染物降解的影响,并通过对产物与SIE之间关系以及生物滴滤塔中生物量和生物多样性的分析,更进一步揭示等离子-生物耦合系统的优势.结果表明,当SIE和气体流速一定时,增加初始浓度会降低混合气体的去除率;从经济效益考虑,气体流速宜采用0.71 L·min~(-1).经产物分析发现,在二氯乙烷和氯苯的浓度均为500 mg·m-3,气体流速为0.71 L·min~(-1)的条件下,二氧化碳的生成量以及选择性均随着SIE的增大而增大;在同样的条件下氯离子浓度随着SIE的增加而逐渐变大;生物滴滤塔中蛋白质含量随着反应器运行逐渐增加最后趋于稳定,下层的生物量高于上层;通过高通量测序分析,结果显示生物滴滤塔中的生物保有丰富的群落及物种多样性的特点.     

Toluene decomposition performance and NOx by-product formation during a DBD-catalyst process

Characteristics of toluene decomposition and formation of nitrogen oxide (NOx) by-products were investigated in a dielectric barrier discharge (DBD) reactor with/without catalyst at room temperature and atmospheric pressure. Four kinds of metal oxides, i.e., manganese oxide (MnOx), iron oxide (FeOx), cobalt oxide (CoOx) and copper oxide (CuO), supported on Al₂O₃/nickel foam, were used as catalysts. It was found that introducing catalysts could improve toluene removal efficiency, promote decomposition of by-product ozone and enhance CO₂ selectivity. In addition, NOx was suppressed with the decrease of specific energy density (SED) and the increase of humidity, gas flow rate and toluene concentration, or catalyst introduction. Among the four kinds of catalysts, the CuO catalyst showed the best performance in NOx suppression. The MnOx catalyst exhibited the lowest concentration of O₃ and highest CO₂ selectivity but the highest concentration of NOx. A possible pathway for NOx production in DBD was discussed. The contributions of oxygen active species and hydroxyl radicals are dominant in NOx suppression.     

Fe/Zn-TMS体系吸收去除催化裂化干气中H2S的性能

本研究采用FeCl3·6H2O、ZnCl2和环丁砜(TMS)复配形成的Fe/Zn-TMS体系脱除催化裂化(FCC)干气中的H2S,并用30%H2O2氧化再生Fe/Zn-TMS体系.同时,研究了各活性成分比例、吸收液体积浓度、吸收液pH值等对脱硫效率的影响,以及H2O2用量、吸收富液pH值对Fe2+氧化率的影响.结果表明,n(FeCl3·6H2O)∶n(ZnCl2)∶n(TMS)为0.45∶0.55∶1,吸收液pH为0.75,体积浓度(W)为50%的条件下能长时间高效脱硫,最高脱硫率达99.9%;在n(Fe2+)∶n(H2O2)为2∶1,吸收富液pH为0.65的条件下,Fe2+氧化率达96.7%.体系可循环使用3次,且能耗低、操作简单.     

多针-水膜电极电晕放电脱硫研究

采用不锈钢多针作为高压电极系统,水膜为低压电极.负直流高压电源供电,含二氧化硫(SO2)的污染气体从高压电极系统的轴向进入,沿着电晕放电电场从水膜上方通过,在电晕放电等离子体和水吸收共同作用下,生成硫酸使SO2得到脱除.主要研究了放电电压、气体中SO2初始浓度和气体在电极系统的停留时间对脱硫效果的影响,并测试了水中SO32-和SI42-离子浓度,分析SO2脱除机制.结果表明,电晕放电和水吸收对SO2脱除具有很好的协同作用,脱硫效果明显升高,SO2转变生成硫酸量的体积分数提高;脱硫效果随电压增加和停留时间的增加而增加,初始浓度对脱硫效果有影响.当SO2初始浓度(体积分数)为430×10-6,施加电压为14.5 kV,停留时间为7.5 s时,脱硫效率达90%以上.     

Microalgae: a promising tool for carbon sequestration

Increasing trends in global warming already evident, the likelihood of further rise continuing, and their impacts give urgency to addressing carbon sequestration technologies more coherently and effectively. Carbon dioxide (CO₂) is responsible for over half the warming potential of all greenhouse gases (GHG), due to the dependence of world economies on fossil fuels. The processes involving CO₂ capture and storage (CCS) are gaining attention as an alternative for reducing CO₂ concentration in the ambient air. However, these technologies are considered as short-term solutions, as there are still concerns about the environmental sustainability of these processes. A promising technology could be the biological capture of CO₂ using microalgae due to its unmatched advantages over higher plants and ocean fertilization. Microalgae are phototrophic microorganisms with simple nutritional requirements, and comprising the major primary producers on this planet. Specific pathways include autotrophic production via both open pond or closed photobioreactor (PBR) systems. Photosynthetic efficiency of microalgae ranged from 10?C20 % in comparison with 1?C2 % of most terrestrial plants. Some algal species, during their exponential growth, can double their biomass in periods as short as 3.5 hours. Moreover, advantage of being tolerant of high concentration of CO₂ (flue gas), low light intensity requirements, environmentally sustainable, and co-producing added value products put these as the favoured organisms. Advantages of microalgae in comparison with other sequestration methodologies are discussed, which includes the cultivation systems, the key process parameters, wastewater treatment, harvesting and the novel bio-products produced by microalgal biomass.     

Effect of light supply on CO2 capture from atmosphere by Chlorella vulgaris and Pseudokirchneriella subcapitata

Carbon dioxide (CO₂) is one of the primary greenhouse gases that contribute to climate change. Consequently, emission reduction technologies will be needed to reduce CO₂ atmospheric concentration. Microalgae may have an important role in this context. They are photosynthetic microorganisms that are able to fix atmospheric CO₂ using solar energy with efficiency ten times higher than terrestrial plants. The objectives of this study were: (i) to analyse the effect of light supply on the growth of Chlorella vulgaris and Pseudokirchneriella subcapitata; (ii) to assess the atmospheric CO₂ capture by these microalgae; and (iii) to determine the parameters of the Monod model that describe the influence of irradiance on the growth of the selected microalgae. Both microalgae presented higher growth rates with high irradiance values and discontinuous light supply. The continuous supply of light at the highest irradiance value was not beneficial for C. vulgaris due to photooxidation. Additionally, C. vulgaris achieved the highest CO₂ fixation rate with the value of 0.305 g-CO₂ L^?1 d^?1. The parameters of the Monod model demonstrated that C. vulgaris can achieve higher specific growth rates (and higher CO₂ fixation rates) if cultivated under higher irradiances than the studied values. The presented results showed that microalgal culture is a promising strategy for CO₂ capture from atmosphere.     

Toluene decomposition performance and NOx by-product formation during a DBD-catalyst process

Characteristics of toluene decomposition and formation of nitrogen oxide (NO_x) by-products were investigated in a dielectric barrier discharge (DBD) reactor with/without catalyst at room temperature and atmospheric pressure. Four kinds of metal oxides, i.e., manganese oxide (MnOx), iron oxide (FeOx), cobalt oxide (CoOx) and copper oxide (CuO), supported on Al₂O₃/nickel foam, were used as catalysts. It was found that introducing catalysts could improve toluene removal efficiency, promote decomposition of by-product ozone and enhance CO₂ selectivity. In addition,NO_xwas suppressedwith the decrease of specific energy density (SED) and the increase of humidity, gas flow rate and toluene concentration, or catalyst introduction. Among the four kinds of catalysts, the CuO catalyst showed the best performance in NO_x suppression. The MnOx catalyst exhibited the lowest concentration of O₃ and highest CO₂ selectivity but the highest concentration of NOx. A possible pathway for NOx production in DBD was discussed. The contributions of oxygen active species and hydroxyl radicals are dominant in NOx suppression.     

准分子灯光照降解水相中烷基酚的动力学

准分子灯辐射的206 nm紫外光可以直接光解4-壬基酚(4-NP)和4-辛基酚(4-OP),但不能使之完全氧化为CO2.相同光照条件下,4-OP的去除率高于4-NP.采用拟一级动力学模型和修正的动力学模型对光解过程进行拟合,得到两种烷基酚206 nm直接光解的速率常数.结果表明,烷基酚初始浓度越低,光解速率常数越高.两种动力学模型对低浓度烷基酚直接光解都具有一定的适用性,但修正的模型不适合高浓度4-OP直接光解.UV/H2O2体系中,烷基酚的降解速率明显提高,但只有当H2O2加入量很高时,TOC去除才比较明显.最后,推导出4-OP直接光解的速率常数kd为0.0328 min-1,4-OP与H2O2反应的速率常数kpH为17.4520 L·(mol·min)-1.     

次氯酸钠湿法烟气脱硝及同时脱硫脱硝技术研究

采用NaClO作氧化吸收剂,在鼓泡反应装置进行了湿法烟气脱硝实验研究,考察了NaIO、NO浓度、液相温度、气体流量、pH对脱硝效率的影响以及SO2对同时脱硫脱硝效率的影响,并结合液相产物分析探讨了同时脱硫脱硝反应机理.研究结果表明,pH值是影响活性成分HClO存在形式的重要因素,同时也是影响氧化吸收的关键因素;在一定范...     

Simultaneous removal of CO2, NOx and SOx using single stage absorption column

Capturing flue gases often require multiple stages of scrubbing, increasing the capital and operating costs. So far, no attempt has been made to study the absorption characteristics of all the three gases (NO, SO₂ and CO₂) in a single stage absorption unit at alkaline pH conditions. We have attempted to capture all the three gases with a single wet scrubbing column. The absorption of all three gases with sodium carbonate solution promoted with oxidizers was investigated in a tall absorption column. The absorbance was found to be 100% for CO₂, 30% for NO and 95% for SO₂ respectively. The capture efficiency of sodium carbonate solution was increased by 40% for CO₂ loading, with the addition of oxidizer. Absorption kinetics and reaction pathways of all the three gases were discussed individually in detail.     

树脂基固态胺吸附剂室温下对低浓度CO2的吸附性能研究

以大孔甲基丙烯酸酯吸附树脂为载体,聚乙烯亚胺(PEI)为有机胺,采用液相浸渍法制备出固态胺吸附剂,并研究了其在室温下对低浓度CO2的吸附行为.同时,利用氮气吸附、热重分析和扫描电镜表征了材料的物理化学性质,并采用热重法和固定床吸附法考察了材料的CO2吸附性能.结果表明,大孔树脂担载50%PEI(质量分数)时吸附性能最佳,对纯CO2的最大吸附量为175 mg·g-1;CO2的吸附行为由扩散动力学与吸附热力学共同决定,低温有利于提高吸附容量;吸附剂对400 ppm~15%浓度的CO2都具有优异的动态吸附性能,其中对400 ppm CO2的吸附量达到86 mg·g-1,对15%CO2的吸附量达到150 mg·g-1;湿度对吸附起促进作用,相对湿度为10%时,对400 ppm CO2的吸附量提高至139mg·g-1;吸附剂具有优异的循环性能,具有直接空气捕集CO2的潜力.     

Carbon dioxide capture using polyethylenimine-loaded mesoporous carbons

A high efficiency sorbent for CO2 capture was developed by loading polyethylenimine (PEI) on mesoporous carbons which possessed well-developed mesoporous structures and large pore volume. The physicochemical properties of the sorbent were characterized by N2 adsorption/desorption, scanning electron microscopy (SEM), thermal gravimetric analysis (TG) and Fourier transform infrared spectroscopy (FT-IR) techniques followed by testing for CO2 capture. Factors that affected the sorption capacity of the sorbent were studied. The sorbent exhibited extraordinary capture capacity with CO2 concentration ranging from 5% to 80%. The optimal PEI loading was determined to be 65 wt.% with a CO2 sorption capacity of 4.82 mmol-CO2 /g-sorbent in 15% CO2 /N2 at 75°C, owing to low mass-transfer resistance and a high utilization ratio of the amine compound (63%). Moisture had a promoting effect on the sorption separation of CO2 . In addition, the developed sorbent could be regenerated easily at 100°C, and it exhibited excellent regenerability and stability. These results indicate that this PEI-loaded mesoporous carbon sorbent should have a good potential for CO2 capture in the future.