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1.
膜法捕集CO2是现役燃煤电厂碳减排的重要手段之一,在实际应用中膜法捕集系统通常适合安装在湿法脱硫系统下游,鉴于脱硫净烟气中的颗粒物及气态污染物难以完全脱除,同时水汽接近饱和状态,气相中的共存杂质以及吸收液组分与膜及膜材料相互作用,会对膜法捕集CO2性能造成严重影响。本文综述了烟气中共存气态、颗粒物组分及液相吸收剂对膜分离、膜吸收宏观性能、膜微结构及材质的影响,以及燃煤脱硫净烟气环境下膜法捕集CO2长期运行性能及变化规律的研究现状,指出了抑制膜失效的技术方法,以期为突破膜法捕集CO2技术发展的瓶颈,实现膜的稳定高效运行提供参考。 相似文献
2.
石灰石-石膏湿法烟气脱硫(wet flue gas desulfurization,WFGD)工艺具有吸收剂来源广、成本低、脱硫效率高等优点,成为应用最广泛的烟气脱硫工艺。湿法脱硫过程中,燃煤烟气在喷淋浆液的洗涤作用下不仅能高效脱除SO2而且可以协同去除细颗粒物,但同时存在石灰浆液夹带导致出口颗粒物浓度增加的问题。本文首先综述了湿法脱硫的应用现状,对比了湿法脱硫系统前后细颗粒物物性变化,然后概述了应用于湿法脱硫协同去除细颗粒物的新方法,包括脱硫塔内部结构调整以及促进细颗粒物凝聚长大,同时分析了湿法脱硫工艺中采用荷电细水雾吸附细颗粒物并增益脱除SO2的可行性,以期为燃煤电厂细颗粒物排放控制提供借鉴。最后指出未来湿法脱硫技术不仅要实现高脱硫效率,而且能有效脱除未被静电除尘器脱除的细颗粒物,湿法脱硫技术的发展趋势是多种技术耦合实现多污染物的协同脱除。 相似文献
3.
燃煤烟气中的SO3会对机组运行及大气环境造成不利影响。为研究燃煤电厂SO3排放特征,本文采取异丙醇吸收法对某300MW超低排放机组污染物控制装置进出口SO3采样,以分析SO3在燃煤机组中的迁移及脱除特性。结果表明:炉膛燃烧过程以及选择性催化还原装置(selective catalytic reduction,SCR)均将部分SO2转化为SO3,炉膛燃烧生成SO3的质量浓度为SO2的0.86%,SCR内SO2/SO3转化率为0.45%。烟气经过空气预热器,SO3浓度降低了5.7%;静电除尘器(electrostatic precipitator,ESP)脱除SO3效果较差,主要由于ESP内烟温在110℃以上,H2SO4酸雾凝结量较少;双级湿法脱硫装置(wet flue gas desulfurization,WFGD)对SO3脱除效率达到81.3%,比国内单级脱硫装置SO3脱除效果高30%~50%;湿式静电除尘器(wet electrostatic precipitator,WESP)脱除SO3效率为23.0%。机组烟囱排放SO3质量浓度为2.025mg/m3(标准),SO3排放因子EF为0.034kg/t。 相似文献
4.
利用湿壁塔实验台对燃煤烟气中SO2对氨水溶液[1%~7%(质量)]吸收CO2的影响进行了实验研究,具体分析了不同反应温度(20~80℃)和CO2体积分数(5%~20%)条件下,CO2传质通量及传质系数随SO2浓度和SO2负载量的变化规律。结果表明, SO2浓度由0增至11428 mg·m-3,CO2传质通量及传质系数均有一半左右降幅,而SO2负载量[0.1~0.4 mol SO2·(mol NH3)-1]的增加,同样导致CO2传质通量及传质系数明显减小。氨水浓度及反应温度增加可有效提高CO2传质通量和传质系数,相对降低SO2对CO2传质的影响。CO2浓度的增加可明显提高其传质通量,但是CO2的传质系数有所降低。 相似文献
5.
燃煤锅炉污染物超低排放标准对电厂脱硫和脱硝系统提出了更高的要求。CaO作为脱硫剂可以实现循环流化床锅炉烟气中SO2的高效脱除,焦炭作为还原剂直接还原NO,同时CaO的存在对焦炭还原NO起催化作用,可以实现燃煤烟气中SO2/NO的联合脱除。为了探究连续温度变化对CaO/生物质焦联合脱硫脱硝性能的影响,在钙循环捕集CO2技术背景下,研究了等速升温流态化下CaO/生物质焦的SO2/NO联合脱除特性。探究了烟气中O2和CO2对CaO/椰壳焦脱除SO2/NO的影响。结果表明,O2通过对椰壳焦表面碳原子的活化作用降低了异相还原NO温度,在300~950℃等速升温过程中CaO/椰壳焦的NO脱除效率逐渐增加,780℃以上能实现100%脱硝。O2也提高了CaO/椰壳焦的脱硫效率。CO2与CaO的碳酸化反应以及与椰壳焦的气化反应对同时脱除SO2/NO有明显抑制作用。O2和CO2共同作用下,在500~800℃内CaO/椰壳焦的脱硝效率随温度升高而增加,脱硫效率先降低后升高。NO促进了CaO/椰壳焦脱除SO2,而SO2对脱硝有抑制作用。800℃时CaO/椰壳焦同时脱除SO2和NO的效率分别为97.7%和93.9%。 相似文献
6.
利用聚丙烯中空纤维双层曝气式膜接触器,对膜曝气-膜吸收耦合式海水烟气脱硫过程开展实验研究,考察了烟气流量、海水流量、海水pH以及曝气量等因素对烟气脱硫参数的影响。结果表明,曝气式膜吸收过程具有更高的脱硫效率和传质性能,相较于非曝气过程,SO2吸收率可提高12.4%。提高烟气流量,使SO2吸收率降低,总传质系数先增大再减小;提高吸收剂流量、pH和曝气量,SO2吸收率和总传质系数均会提高,海水pH较高条件下加入曝气更能有效加强吸收效果;烟气中SO2的吸收通量均随海水pH和曝气量的增加而增加。扫描电镜及接触角测量显示在使用一个月后的膜丝仍具有较高的疏水性能和使用性能。 相似文献
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8.
在使用膜吸收装置脱除燃煤电厂尾气中二氧化碳的实际应用中,膜吸收二氧化碳系统装配于湿法烟气脱硫系统(WFGD)出口是最适宜的选择。经过湿法脱硫的烟气中含有一定量的细颗粒物,这些颗粒物可能会影响膜的性能,因此有必要揭示细颗粒物对膜吸收二氧化碳的影响。本文采用模拟实验装置,选取飞灰、硫酸钙、硫酸铵3种颗粒物,考察了它们对聚丙烯(PP)中空纤维膜吸收二氧化碳的影响。结果表明:3种颗粒物通过膜组件时,均会在膜表面沉积,导致二氧化碳脱除效率下降;膜吸收二氧化碳的性能与颗粒物沉积程度呈负相关;3种颗粒物对膜吸收二氧化碳的影响程度从大到小依次为硫酸钙、硫酸铵、飞灰;颗粒物在膜表面沉积后很难被气体反吹,这会使膜基本失效。 相似文献
9.
采用臭氧氧化结合湿法喷淋硫代硫酸钠溶液的方法开展模拟烟气同时脱硫脱硝实验研究。结果表明,采用臭氧氧化结合Na2S2O3-NaOH溶液湿法喷淋可以实现NOx和SO2协同脱除:在O3/NO摩尔比为1.1~1.2时,溶液中Na2S2O3浓度的增加会提高系统的NOx脱除效率,烟气中SO2的存在会促进NOx的脱除,当SO2浓度为1030 mg·m-3、2.0%Na2S2O3溶液作为喷淋液时可实现较高的SO2脱除效率,同时NOx脱除效率可达70%以上;喷淋液pH在2.5~9范围内变化时提高浆液pH有利于NOx的脱除,当pH 9时脱硝效率可达75%。180 min连续同时脱硫脱硝实验结果表明,硫代硫酸钠可有效促进NOx的脱除,并实现SO2较高的脱除效率,同时可实现系统同时脱硫脱硝连续稳定运行,喷淋吸收后烟气中NOx的主要转化产物为NO2-, 该方法作为一种有效的同时脱硫脱硝技术,具有一定的工业应用推广前景。 相似文献
10.
富氧燃烧技术是目前最有可能大规模推广和商业应用的碳捕集与封存技术之一,其中,烟气压缩净化及CO2提纯对于整个富氧燃烧系统至关重要。然而,目前研究多聚焦于富氧燃烧后烟气压缩净化的工艺验证,而对烟气压缩纯化各单元运行特性的研究仍不深入,特别是烟气压缩净化过程杂质污染组分的迁移转化、系统运行参数与污染物脱除效率的关联仍不明确。且现有研究对净化后烟气的深度提纯及高浓度CO2制备的关注也相对较少,直接关系到富氧燃烧系统运行经济性。因此,针对富氧燃烧烟气净化及CO2提纯需求,系统探究了富氧燃烧烟气压缩纯化过程SO2、NOx吸收脱除以及CO2深度提纯等各子系统的运行特性,其中SO2与NOx脱除采用压缩-酸液吸收,CO2深度提纯采用低温精馏。结果表明:通过烟气净化可实现SO2脱除效率达100%,NO脱除效率达99%,同时实现纯度为99.99%的食品级液态CO2制备。烟气净化过程中,气相反应占据主导,提高压力可缩短反应时间;当SO2吸收塔运行压力超过0.8 MPa时,SO2脱除效率可达100%;当NO吸收塔运行压力超过3.0 MPa时,NO排放浓度可达超低排放标准。CO2提纯过程中,提高压力会降低液体CO2纯度。SO2吸收塔运行压力为1.6 MPa、NO吸收塔运行压力为3.0 MPa、CO2提纯塔运行压力为3.8 MPa时,系统整体功耗最低,为0.37 MJ/kg。 相似文献
11.
Linjun Yang Jingjing Bao Jinpei Yan Jinhui Liu Shijuan Song Fengxian Fan 《Chemical engineering journal (Lausanne, Switzerland : 1996)》2010,156(1):25-32
A novel process to remove fine particles with high efficiency by heterogeneous condensation in a wet flue gas desulfurization (WFGD) system is presented. A supersaturated vapor phase, necessary for condensational growth of fine particles, was achieved in the SO2 absorption zone and at the top of the wet FGD scrubber by adding steam in the gas inlet and above the scrubbing liquid inlet of the scrubber, respectively. The condensational grown droplets were then removed by the scrubbing liquid and a high-efficiency demister. The results show that the effectiveness of the WFGD system for removal of fine particles is related to the SO2 absorbent employed. When using CaCO3 and NH3·H2O to remove SO2 from flue gas, the fine particle removal efficiencies are lower than those for Na2CO3 and water, and the morphology and elemental composition of fine particles are changed. This effect can be attributed to the formation of aerosol particles in the limestone and ammonia-based FGD processes. The performance of the WFGD system for removal of fine particles can be significantly improved for both steam addition cases, for which the removal efficiency increases with increasing amount of added steam. A high liquid to gas ratio is beneficial for efficient removal of fine particles by heterogeneous condensation of water vapor. 相似文献
12.
A water‐swollen thin‐film composite membrane, which was a reverse osmosis membrane with a thin polyamide layer, was used to separate a model mixture of N2, CO2, and SO2. The polyamide swells with water, and thus, becomes more permeable to polar gases. The flue gas contains water vapor, which must be removed before it is subjected to SO2 removal. Here moisture is employed to keep the membrane swollen. Using the model mixture, the humidified feed stream is brought to the membrane, where it is cooled below the dew point, so that water condenses on the membrane to keep the polyamide swollen. The membrane showed high CO2 and SO2 permeance, but low selectivity, so it could be applied to separate these two gases from N2, and thus, is suitable for flue gas purification. 相似文献
13.
《Gas Separation & Purification》1994,8(2):107-114
Studies were made on the membrane absorption of CO2 and/or SO2 using hydrophobic microporous hollow-fibre (HF) membrane modules. The absorbent liquids used were aqueous solutions of NaOH, K2CO3, alkanolamines and Na2SO3, flowing on the lumen side of the HF in laminar flow. A semi-empirical correlation was derived for the gas-phase mass-transfer coefficient on the shell side, by including geometrical factors of the HFs and the shell tube in the general correlation for mass transfer. It was found that the CO2 absorption rate in various aqueous solutions of alkalis and alkanolamines is successfully described by a model based on gas diffusion through the membrane pores subsequent to gas absorption accompanied by chemical reaction. The simultaneous membrane absorption of SO2 and CO2 was also studied using aqueous Na2SO3 solution, the selective removal of SO2 to CO2 being successfully achieved when both the liquid flow rate and solute concentration are low. This suggests that this membrane absorption method provides an energy saving process for SO2 removal from flue gases. 相似文献
14.
In the CO2 capture process from coal-derived flue gas where amine solvents are used, the flue gas can entrain small liquid droplets into the gas stream leading to emission of the amine solvent. The entrained drops, or mist, will lead to high solvent losses and cause decreased CO2 capture performance. In order to reduce the emissions of the fine amine droplets from CO2 absorber, a novel method using charged colloidal gas aphron (CGA) generated by an anionic surfactant was developed. The CGA absorption process for MEA emission reduction was optimized by investigating the surfactant concentration, stirring speed of the CGA generator, and capture temperature. The results show a significant reduction of MEA emissions of over 50% in the flue gas stream exiting the absorber column of a pilot scale CO2 capture unit. 相似文献
15.
Removal of fine particles by heterogeneous condensation in the double-alkali desulfurization process
Jingjing BaoLinjun Yang Weidi SunJunfeng Geng Jinpei YanXianglin Shen 《Chemical Engineering and Processing: Process Intensification》2011,50(8):828-835
Removal of fine particles by heterogeneous condensation in the rotating-stream-tray scrubber was investigated experimentally for the double-alkali desulfurization process in this paper. A supersaturated vapor phase, necessary for condensational growth of fine particles, was achieved in the SO2 absorption zone and at the top of the scrubber by adding steam in the gas inlet, between the pieces of rotating-stream-tray and above the desulfurization liquid inlet of the scrubber, respectively. Fine particles grew in size by vapor heterogeneous condensation with the particles acting as nucleation centers. Then the condensational grown droplets were removed efficiently by the desulfurization liquid and a high-efficiency demister. In order to optimize the removal process, the influences of temperature of inlet flue gas and desulfurization liquid, steam addition method and amount of steam added on the particle removal efficiency were presented. The results show that a few fine particles could be removed in the rotating-stream-tray scrubber. The removal efficiency can be significantly improved for various steam addition cases, and the improve performance is related to the method and the amount of steam addition. Particle removal efficiency with steam added between the pieces of rotating-stream-tray is higher than that of else steam addition cases. 相似文献
16.
《Fuel》2003,82(15-17):2153-2159
A membrane-based gas–liquid contacting process was evaluated in this work for CO2 removal from flue gases. The absorption of CO2 from a CO2–N2 mixture was investigated using a commercial hollow fiber membrane contactor and water or diethanolamine as absorbing solvents. Significant CO2 removal (up to 75%) was achieved even with the use of pure water as absorbent. By using aqueous amine solutions and chemical absorption, mass transfer improved, and CO2 removal was nearly complete (∼99%). A mathematical model was developed to simulate the process and it was validated with experimental data. Results show that membrane contactors are significantly more efficient and compact than conventional absorption towers for acid gas removal. 相似文献
17.
J. R. Jensen L. B. Nielsen C. Schultz-Møller S. Wedel H. Livbjerg 《Aerosol science and technology》2013,47(6):490-509
The formation of particles during cooling of a synthetic flue gas with vapors of sodium and potassium species is studied in a laboratory tubular reactor with laminar flow. It is shown to agree well with a theoretical model for the process. The kinetics of homogeneous nucleation of the pure chloride vapors is described by the classical nucleation theory, adapted to include the participation of stable dimer as well as monomer vapor molecules. The Tolman equation is used to describe the curvature-dependence of the surface tension of small nuclei. The values of the Tolman parameter for NaCl and KCl are determined from the measurements. The homogeneous nucleation of the pure chlorides is suppressed by even relatively small concentrations of foreign seed particles and is therefore unlikely to contribute to the creation of new particles in real flue gases. The addition of SO2 to the chloride vapor feed, in the presence of oxygen and water vapor, increases the number concentration of effluent particles significantly and affects their composition to include sulphate in addition to chloride. The sulphate content is independent of the peak temperatures of the flue gas but increases with increasing content of oxygen and SO2. The study proves that the alkali sulphates are formed by the sulphation of vapor phase rather than solid, alkali chloride. The sulphate vapors are formed in high supersaturation and show a pronounced tendency towards homogeneous nucleation, which is identified as the likely source of the submicron particles formed in alkali rich flue gases. 相似文献
18.
Parametric experiments were carried out to study the interactions of mercury, SO3, and injected activated carbon (AC) in a coal flue gas stream. The levels of SO3 vapor in flue gas were altered by individually varying flue gas temperature, moisture, or sodium fume injection in the flue gas. Meanwhile, mercury emissions with AC injection (ACI) upstream of an electrostatic precipitator (ESP) were evaluated under varied SO3 concentrations. SO3 measurements using a condensation method indicated that low temperature, high moisture content, and sodium fume injection in flue gas shifted SO3 partitioning from the vapor to particulate phase, subsequently improving mercury capture with ACI. 0.08 g/m3 of DARCO® Hg-LH injection only provided approximately 20% mercury reduction across the ESP in a bituminous coal flue gas containing 28 ppm SO3, but mercury capture was increased to 80% when the SO3 vapor concentration was lowered less than 2 ppm. Experimental data clearly demonstrate that elevated SO3 vapor is the key factor that impedes mercury adsorption on AC, mainly because SO3 directly competes against mercury for the same binding sites and overwhelmingly consumes all binding sites. 相似文献
19.
Removal of elemental mercury from simulated coal-combustion flue gas using a SiO2–TiO2 nanocomposite
A novel silica–titania (SiO2–TiO2) nanocomposite has been developed to effectively capture elemental mercury (Hg0) under UV irradiation. Previous studies under room conditions showed over 99% Hg0 removal efficiency using this nanocomposite. In this work, the performance of the nanocomposite on Hg0 removal was tested in simulated coal-fired power plant flue gas, where water vapor concentration is much higher and various acid gases, such as HCl, SO2, and NOx, are present. Experiments were carried out in a fix-bed reactor operated at 135 °C with a baseline gas mixture containing 4% O2, 12% CO2, and 8% H2O balanced with N2. Results of Hg speciation data at the reactor outlet demonstrated that Hg0 was photocatalytically oxidized and captured on the nanocomposite. The removal efficiency of Hg0 was found to be significantly affected by the flue gas components. Increased water vapor concentration inhibited Hg0 capture, due to the competitive adsorption of water vapor. Both HCl and SO2 promoted the oxidation of Hg0 to Hg(II), resulting in higher removal efficiencies. NO was found to have a dramatic inhibitory effect on Hg0 removal, very likely due to the scavenging of hydroxyl radicals by NO. The effect of NO2 was found to be insignificant. Hg removal in flue gases simulating low rank coal combustion products was found to be less than that from high rank coals, possibly due to the higher H2O concentration and lower HCl and SO2 concentrations of the low rank coals. It is essential, however, to minimize the adverse effect of NO to improve the overall performance of the SiO2–TiO2 nanocomposite. 相似文献