Thermoneutral tri-reforming of flue gases from coal- and gas-fired power stations

The treatment of flue gases from fossil fuel fired power stations by tri-reforming with natural gas or by coal gasification could become an attractive approach for converting the CO₂, H₂O, O₂, and N₂ contained in these flue gases via syngas processing into useful products, such as methanol, hydrogen, ammonia, or urea. The present study determines the constraints for achieving such thermochemical reactions under conditions of thermoneutrality, by reacting the flue gases with water, air, and natural gas or coal at 1000–1200 K. The implications of such reactions are examined in terms of CO₂ emission avoidance, fuel saving, economic viability, and exergy efficiency.     

Separation and enrichment of carbon dioxide by capillary membrane module with permeation of carrier solution

A novel facilitated transport membrane for gas separation using a capillary membrane module is proposed in which a carrier solution is forced to permeate the membrane. Both a feed gas and a carrier solution are supplied to the lumen side (high pressure side, feed side) of the capillary ultrafiltration membrane and flow upward. Most of the carrier solution which contains dissolved solute gas, CO₂ in the present case, permeates the membrane to the permeate side (low pressure side, shell side), where the solution liberates dissolved gas to form a lean solution. The lean solution is circulated to the lumen side. This type of capillary membrane module was applied to the separation of CO₂ from model flue gases consisting of CO₂ and N₂. Monoethanolamine (MEA), diethanolamine (DEA) and 2-amino-2-methyl-1-propanol (AMP) were used as carriers or absorbents of CO₂. The feed side pressure was atmospheric and the permeate side was evacuated at about 10 kPa. CO₂ in the feed gas was successfully concentrated from 5–15% to more than 98%. The CO₂ permeance was as high as 2.7×10⁻⁴ mol m⁻² s⁻¹ kPa⁻¹ (8.0×10⁻⁴ cm³ cm⁻² s⁻¹ cmHg⁻¹) when the CO₂ mole fraction in the feed was 0.1 and temperature was 333 K. The selectivity of CO₂ over N₂ was in the range from 430 to 1790. The membrane was very stable over a discontinuous one-month testing period.     

Spectroscopic analysis of carbon dioxide and nitrogen mixed gas hydrates in silica gel for CO2 separation

In this study solid-state NMR spectroscopy was used to identify structure and guest distribution of the mixed N₂ + CO₂ hydrates. These results show that it is possible to recover CO₂ from flue gas by forming a mixed hydrate that removes CO₂ preferentially from CO₂/N₂ gas mixture. Hydrate phase equilibria for the ternary CO₂–N₂–water system in silica gel pores were measured, which show that the three-phase H–L_w–V equilibrium curves were shifted to higher pressures at a specific temperature when the concentration of CO₂ in the vapor phase decreased. ¹³C cross-polarization (CP) NMR spectra of the mixed hydrates at gas compositions of more than 10 mol% CO₂ with the balance N₂ identified that the crystal structure of mixed hydrates as structure I, and that the CO₂ molecules occupy mainly the abundant 5¹²6² cages. This makes it possible to achieve concentrations of more than 96 mol% CO₂ gas in the product after three cycles of hydrate formation and dissociation.     

普通小球藻固定模拟烟气中CO2的实验研究

大气中CO₂浓度增加造成的全球变暖已成为一个严峻的环境问题,利用微藻生物固碳法减排CO₂正成为研究热点.本文以普通小球藻(Chlorella vulgaris,FACHB-1227)为研究对象,采用SE无碳培养基,在沿程曝气型套管式光生物反应器中通入含不同体积分数CO₂(5%、10%、15%和20%)的模拟烟气培养小球藻,培养周期为17天,以细胞密度和平均固碳速率为检测指标,研究模拟烟气下普通小球藻生长情况及固碳能力.实验结果表明:当模拟烟气中CO₂体积分数为10%时,普通小球藻的细胞密度达到最大值8.76×10⁶cells/mL,相比于5%组、15%组和20%组分别提高了54.23%、66.86%和76.97%;其平均固碳速率达最大值30.18mg/(L·d),较5%组、15%组和20%组分别提高了57.27%、70.89%和81.91%.可见,在模拟烟气中CO₂体积分数为10%时,普通小球藻的生长情况和固碳性能最好.     

CO2 absorption performance in a rotating disk reactor using DBU-glycerol as solvent

Gas–liquid mass transfer of rotating disk reactor was studied in CO_2 absorption using 1,8-diazabicyclo-[5.4.0]-undec-7-ene(DBU)-glycerol solution as solvent. Effects of the rotating disk structure and various operation parameters on the CO_2 absorption rate and CO_2 removal efficiency were investigated. The rotating disk with optimal holes is conducive to mass transfer of CO_2 and the formation of thin liquid film at the opening increases the gas–liquid contact area. With the increase of rotating speed, the liquid flow pattern on the rotating disk surface changes from thin film flow to separated streams and creates extra liquid lines attached to the rim of the disk,which leads to a very complicated change on the CO_2 absorption rate and CO_2 removal efficiency. The overall gas-phase mass transfer coefficient increases 138% as the rotating speed increasing from 250 to 1400 r·min~(-1).Increasing temperature from 298 to 338 K can enhance the CO_2 absorption rate due to lowering the viscosity of the solvent. The rate-determined step for the absorption is focused on the gas side. The rotating disk reactor can effectively enhance the absorption of CO_2 with viscous DBU-glycerol solvents.     

Exploring aramid as emerging contender for CO2 capture

To prevent CO_2 accumulation in the atmosphere generated from scorching of fossil fuels, carbon capture and sequestration(CCS) technology is considered as a potential route to mitigate the emissions of CO_2 from reaching the atmosphere. Power generation from sources such as gas, coal and biomass can fulfill the energy demand more readily than many other sources of electricity production. Thus these sources may be retained as important alternative option in the global energy cycle. In order to curtail CO_2, porous aramid network was fabricated by the condensation of 1,3,5-benzenetricarbonyl trichloride and 1,3-phenylenediamine in 1,4-dioxane solvent. Aramid was characterized for various analyses including FTIR, XRD, TGA, BET surface area and pore size analysis, FESEM and CO_2 adsorption measurements. Excellent thermal stability was provided by strong amide linkages in the polymer backbone. Optimum CO_2 uptake of aramid was achieved to be 23.14 mg·g~(-1) at 273 K at 0.1 MPa. The basic amide groups of network structure showed greater affinity for CO_2.Excellent thermal stability of aramid makes it a promising sorbent for CO_2 capture in adverse conditions.     

酸性气体脱除单元副产二氧化碳中夹带甲醇的去除方案研究

酸性气体脱除单元副产的二氧化碳可作为粉煤气化装置载气循环利用,但其夹带微量甲醇,需经过处理才能达标排放。以某二氧化碳需求量为20000 m³/h的粉煤气化装置为例,分析对比了压缩机段间洗涤和压缩前洗涤两种水洗法脱除二氧化碳中微量甲醇的方案,结果发现水洗法脱除甲醇的方案可行,且压缩机段间洗涤方案较压缩前洗涤方案安全性更高,设备费用更低,能耗低15.5%,每小时可省操作费用105.1元。初步探讨了吸附法用于脱除二氧化碳中微量甲醇的可行性。     

煤/生物质流态化富氧燃烧的CO2富集特性

流化床富氧燃烧是具有重要应用前景的燃烧中碳捕集技术。为更深入认识固体燃料的流态化富氧燃烧行为,构建了微型流态化反应-质谱联用实验系统,反应器直径10 mm,燃烧温度700～900℃,探索了基于在线质谱分析的流态化燃烧过程特性表征方法,以烟煤和花梨木为对象,研究了煤、生物质及其混合物在富氧气氛和流态化条件下的燃烧行为,重点考察了氧浓度、燃烧温度、煤与生物质质量比对CO₂谱峰曲线形态、反应总时间、起始反应时刻、烟气中富集CO₂体积分数、颗粒燃烧产生CO₂量、CO₂相对生成率等特性的影响。结果表明,在O₂/CO₂燃烧气氛下,随着氧体积分数增加,燃烧总反应时间缩短,颗粒燃烧产生的CO₂量和生成速率均增加,但烟气中富集的CO₂体积分数减小;提高燃烧温度,缩短了燃烧过程所需的时间,可以促进CO₂的富集,烟气中CO₂浓度、颗粒燃烧产生的CO₂量和生成速率均增加;生物质比例增大,起始反应时间提前,燃烧反应所需总时间减少,烟气中富集的CO₂浓度和颗粒燃烧产生的CO₂均减少,但CO₂生成速率增加。     

富氧燃烧烟气净化工艺研究进展

随着工业的快速发展,化石燃料消耗与日俱增,造成了大量温室气体CO₂的排放,全球气候变化形势不容乐观。为了减少CO₂排放,需要对高浓度CO₂进行捕获、利用与封存,而富氧燃烧技术能有效实现碳捕集,是目前最具潜力的碳减排技术之一。富氧燃烧过程中,SO_x、NO_x、Hg等污染物以及惰性气体的存在不利于碳的捕集与封存。烟气中各成分浓度会对管道运输、地质储存和提高采收率(EOR)产生影响,介绍了烟气中CO₂及各种杂质浓度的不同标准,系统综述了国内外脱硫、脱硝、脱汞和惰性气体脱除以及联合脱除技术的研究进展。脱硫部分除介绍传统脱硫技术外,重点描述了富氧燃烧烟气中CO₂气氛对SO_x脱除的影响以及加压条件下SO₂的转化与去除。发现CO₂气氛下SO₂的吸收速率相比N2气氛有所降低,且SO₂吸收过程中临界pH发生变化。脱硝部分重点描述了氧化吸收法脱硝技术以及加压条件下NO的氧化机理,并对高压下NO的氧化动力学进行阐述。随着压力的增加,NO氧化速率常数呈先下降后上升的趋势,且证明了反应器压力对液体夹带率的影响比较显著。总结了Hg脱除技术中不同烟气成分对Hg氧化的影响,HCl与Cl2起到了明显的促进作用。对活性炭进行改性,增加孔结构比表面积以及吸附剂表面的活性位点,提高Hg的脱除效率。介绍了惰性气体的净化技术,主要采用变压吸附方法来吸附和解吸附,降低了CO₂气流中惰性气体去除的成本,实现一部分惰性气体再次循环回到锅炉中,提高CO₂的捕获。重点讨论了在烟气压缩液化系统中的联合脱除技术,有效利用压缩过程条件将SO_x、NO_x、Hg分别以硫酸、硝酸、Hg(NO₃)₂形式协同去除,随着压力的增加,SO_x与NO_x去除效率提高,有利于SO₄^-2、NO₃^-、HADS和HAMS(N-S化合物)的生成,同时也导致了N2O生成量增多。证明了Hg与NO₂是气相反应,提出了高压下NO₂与Hg反应产物的不确定性。简单介绍了低温碳捕集技术,有潜力取代洗涤器和其他烟气处理方法,但目前还缺乏可行性的研究。未来需对不同压力下NO氧化速率常数的变化趋势进行解释,高压下NO_x与SO_x联合脱除的产物以及NO₂与Hg的反应产物进行分析。     

Performance of CO2 absorption in a diameter-varying spray tower

The application of spray towers for CO₂ capture is a development trend in recent years. However, most of the previous jobs were conducted in a cylindrical tower by using a single spray nozzle, whose configuration and performance is not good enough for industrial application. To solve this problem, the present work proposed a diameter-varying spray tower and a new spray mode of dual-nozzle opposed impinging spray to enhance the heat and mass transfer of CO₂ absorption process. Experiments were performed to investigate the mass transfer performance (in terms of the CO₂ removal rate (η) and the overall mass transfer coefficient (K_Ga_e2 are major factors, which affect the absorption performance and the maximums of η and K_Ga_e that are 94.0% and 0.574 kmol·m^-3·h^-1·kPa^-1, respectively, under the experimental conditions. Furthermore, new correlations to predict the mass transfer coefficient of the proposed spray tower are developed in various CO₂ concentrations with a Pearson Correlation Coefficient over 90%.     

Blautia coccoidesGA-1的传代培养及其同化H2/CO2产乙酸特征

为了解同型产乙酸菌异养代谢与自养代谢的相互作用与机制,并为快速获得具有较强自养代谢能力的菌体细胞提供培养方法,以H₂/CO₂和(或)葡萄糖为碳源,考察了Blautia coccoidesGA-1在连续传代培养中的代谢特征。结果表明,以H₂/CO₂作为唯一碳源进行连续传代培养时,菌株GA-1长势较弱,其子代的自养代谢能力也逐渐下降;在葡萄糖培养基中,菌株GA-1增殖旺盛,但高浓度的葡萄糖对其自养代谢能力有显著抑制作用,这种抑制作用可能是自养代谢和异养代谢对辅酶A和ATP的竞争、酸性环境造成的代谢抑制以及辅酶I的氧化还原平衡调节等综合作用的结果。以体积比为4:1的H₂/CO₂混合气为气相条件,用200mg·L^-1葡萄糖培养基对菌株GA-1进行传代培养,不仅可获得稳定的子代培养物,而且可以将其利用H₂/CO₂产乙酸的能力维持在2.16g乙酸·(g干细胞)^-1的水平。     

富氧燃烧烟气压缩净化及高浓度CO2制备工艺研究

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、NO_x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NO_x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。     

SOLUBILITY OF CARBON DIOXIDE IN AQUEOUS AND ANHYDROUS MIXTURES OF METHYLDIETHANOLAMINE AND TRIETHYLENE GLYCOL MONOMETHYL ETHER

Mixed solvents are a combination of chemical and physical solvents and are used for the removal of acid gases from gas streams. The solubility of CO₂ in a mixed nonaqueous solution of methyldiethanolamine (MDEA) (50 wt.%) and triethylene glycol monomethj'l ether (TEGMME) (50 wt.%) has been measured at 40°C. The data are compared with solubility data of CO₂ in pure TEGMME. The solubility of CO₂ has been measured at 40°C and 100°C in an aqueous mixed solvent consisting of MDEA (40 wt.%) and TEGMME (40 wt. %) and water (20 wt.%) at partial pressures of CO₂ up to 12 MPa. The solubility results were compared with the solubility in the nonaqueous mixed solvent and previously reported data of aqueous MDEA. The solubility model of Deshmukh and Mather was used to correlate the data.     

典型现代煤化工过程的二氧化碳排放比较

基于低碳经济发展的要求,对几种典型煤化工过程中的CO₂排放情况进行了分析,提出科学比较现代煤化工过程的CO₂排放量。对于煤制烯烃、煤制乙二醇等煤基化学品而言,使用单位热值CO₂排放量作为评价指标并不合适。基于煤基燃料产品和化学品的不同特点,结合我国碳排放强度的控制目标,本文探索采用单位产值CO₂排放量和单位工业增加值CO₂排放量作为补充指标,用以比较研究不同现代煤化工过程的低碳水平和碳排放强度。研究结果表明,用不同的指标来衡量比较现代煤化工过程的CO₂排放量,得到的结果不同。煤制甲醇、煤制二甲醚的吨产品CO₂排放量虽然较低,分别为3.85t和5.0t,但单位热值CO₂排放量较高,分别为0.159t/GJ和0.160t/GJ。在80美元/bbl和40美元/bbl的原油价格体系下,煤制天然气和煤制甲醇的单位产值和单位工业增加值CO₂排放量均高于其他现代煤化工产品。     

On-stream modification of MFI zeolite membranes for enhancing hydrogen separation at high temperature

-Alumina-supported MFI zeolite membranes were modified by on-stream catalytic thermal cracking of methyldiethoxysilane (MDES) molecules inside the zeolitic channels during the separation of H₂/CO₂ gas mixture at 450 °C and atmospheric pressure. The MDES vapor was carried by the H₂/CO₂ feed gas and the effect of modification was monitored continuously through online analysis of the permeate stream. The modified membrane exhibited a significant increase in H₂ selectivity over CO₂ with a moderate decrease in H₂ permeance. At 450 °C, the modified MFI membrane obtained a H₂/CO₂ permselectivity of 17.5 with H₂ single gas permeance of 1.86 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ as compared to a permselectivity of 2.78 and permeance of 2.75 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ for the membrane before modification. The modified membrane also showed good performance and stability in separation of H₂/CO₂ gas mixture containing up to 28.4% water vapor at 450 °C and atmospheric pressure.     

面向二氧化碳捕集的过程强化技术进展

化石能源的大量燃烧在推进人类工业化进程的同时也使当今世界面临愈发严峻的气候变化和环境问题。为降低大气中日益增长的CO₂浓度并实现《巴黎协定》所设定的2℃目标,CO₂捕集技术得到了越来越广泛的关注和研究,其中部分技术已实现了小规模工业化。在持续推进节能减排的背景下,通过CO₂捕集对现有工业过程进行强化是CO₂捕集技术发展的一个新兴方向,如此不但可提高原有过程的效率和产品品质,还可大幅减少其碳排放,是具有应用前景的技术路线。本文从CO₂捕集的主流技术出发,介绍了面向CO₂捕集的过程强化技术,重点介绍CO₂捕集强化的蒸汽重整制氢过程、水气变换过程和生物质气化过程,以及耦合CO₂捕集的CO₂加氢过程、CH₄干重整过程和化学链燃烧过程,最后还对捕集后CO₂的利用与转化技术进行了简介。     

CO2 Removal from Biogas by Water Washing System

CO2 removal from biogas by water washing system was investigated with various parameters, including liquid/gas ratio, pressure, temperature, and CO2 content. The results indicate that CO2 removal ratio...     

温度对载氧体还原过程中汞的析出特性及形态分布的影响

化学链燃烧是近年来提出的一种具有高效、内分离CO₂特点的新型燃烧方式。本文在立式管式炉实验装置上研究了温度对基于Fe₂O₃载氧体的煤化学链燃烧载氧体还原过程中汞析出特性的影响,探讨了不同燃烧温度下燃料反应器（FR）出口烟气组分的变化及其对汞迁移变化的影响。结果表明：在高温条件下（≥ 800℃）,煤中的汞在载氧体还原过程中基本全部析出,180s时基本达到90%,并且随着温度升高而增加;FR出口烟气中的汞主要以单质态（Hg⁰）形式存在,各工况下的单质态汞占烟气中气态总汞比例都在88%以上,随着温度的升高,烟气中Hg⁰/Hg^T略有降低;温度对烟气组分具有影响,随着温度的升高,CO、NO和SO₂浓度上升;对于汞而言,SO₂会抑制Cl及Cl₂的形成从而抑制Hg⁰向Hg²⁺转化,NO会直接或间接促进汞的氧化过程,FR烟气中以CO为主的还原性气氛不利于汞的氧化。     

Low-Temperature Coupling of Methane

Methane is the main component of natural gas and its utilization amounts to ca. 1.7 × 10⁹ tons of oil equivalent per year [1]. Since the present reserve of methane is located in remote places, its transportation is a major problem. Methane coupling to form C₂₊ hydrocarbons is, therefore, of a primary importance because before transportation methane should be converted into hydrocarbons with higher boiling points, such as ethane, propane, etc. The catalytic conversion of methane can be carried out in several ways which have excellently been reviewed in Refs. 1 and 2. Basically, three routes exist: (i) the indirect route in which methane is first converted into syngas in presence of water (steam reforming), CO₂ (carbon dioxide reforming), or oxygen (partial oxidation) and the resultant syngas can be utilized in the traditional way; (ii) direct coupling in the presence of oxygen (oxidative coupling of methane, OCM) or hydrogen (two-step polymerization); and (iii) direct conversion in the presence of oxygen to oxygenates (CH₃OH, HCOH), in the presence of Cl₂, HCI to methane chlorides, in the presence of ammonia to HCN, etc.