CO2资源化利用的现状及前景

介绍了CO2分离捕集最新工艺——电化学法、膜法、化学循环燃烧法的研究进展。评述分析了CO2的各种资源化应用前景：CO2气体用作生物碳源、辅助注射成型剂及有机物（如氨基甲酸酯、表面活性剂）合成原料等;液态CO2用于人造金刚石、热泵干燥、超临界CO2萃取及固体干冰冷喷射清洗等。CO2作为一种潜在的丰富碳源,应不断研发其新的应用领域,加快其工业化应用。     

燃煤烟气中CO_2脱除方法的分析与探讨

作为主要的温室气体,CO2减排问题引起全球范围的广泛关注。阐述了燃煤烟气中CO2脱除的多种方法,分析比较了CO2的吸收法、吸附法、膜分离法等的特点及各自的优缺点,侧重介绍了有机胺和氨水脱除的技术进展,并介绍了氨水烟气脱碳的部分试验结果。     

钙基固定剂对制氢和污染性气体减排的影响

在未来相当长的一段时间内,煤气化仍是大规模制取氢气的主要途径。目前,常规煤气化过程得到的是H2、CO和CO2为主的混合气,需要通过净化、变换和分离工艺才能得到洁净的氢气,工艺过程复杂。采用连续式超临界水反应装置,以质量分数为20%的水煤浆为反应原料,考察了Ca/C摩尔比和温度对褐煤制氢系统的影响。试验结果表明：Ca（OH）2不仅可以很好地固定气相中的CO2和硫化物,而且对煤气化过程也表现出较好的催化作用。反应温度600℃,压力为25MPa的条件下,与未加Ca（OH）2相比,Ca/C摩尔比为0.45时,气体中CO2的体积分数由50.7%降至1.0%,趋于完全固定;硫化物浓度由10 878mg/m3降至807mg/m3;H2的体积分数由32.4%增至73.3%。Ca（OH）2对煤气化的催化作用在高温下更加明显。     

金属有机骨架材料Cu2(BTC)3对CO2的吸附

采用溶剂热法,以均苯三甲酸(H3BTC)为有机配体与硝酸铜进行反应合成了Cu2(BTC).通过XRD和SEM等方法对Cu2(BTC)3进行了表征.实验结果表明,Cu2(BTC)3是一种典型的金属有机骨架(MOFs)材料,呈现规整的八面体晶状结构,晶粒大小为2～20 μm.相同条件下Cu2(BTC)3对CO2的吸附量高于活性炭和活性碳纤维,且随着吸附压力的升高吸附量明显增大,随着吸附温度的降低吸附量也增大.在0.4 MPa、25℃的条件下,用Cu2(BTC)3作吸附剂可以很好地分离CO2体积分数为5％和20％的CO2-甲烷混合气体,且对CO2含量低的混合气体分离效果更好.     

国外动态

超临界水热分解煤制 H2 和 CH4资源环境对策 ,2 0 0 0 ,3 6(10 ) :5 1　　日本工技院资源综合利用研究所和煤炭利用综合中心共同开发成功用超临界水热分解煤等有机物制造 80 % H2 和 2 0 % CH4 气体的新技术。每克煤可生成 2～ 3L气体 ,煤中碳或氢几乎可全部按理论量进行反应 ,生成的气体中不含硫化物。同时氢气生成时能和副反应生成的 CO2 分离 ,使 H2 能高质量浓缩 ,用作燃料。新工艺产生的氯化物、氮化物、硫化物等都能以无害化形式被分离。　　该技术除煤以外 ,还可用于分解其他有机物 (碳源 ) ,如生活垃圾、家畜粪尿、动植物残体、…     

超临界水热分解煤制H2和CH4

资源环境对策,2000,36(10):51 日本工技院资源综合利用研究所和煤炭利用综合中心共同开发成功用超临界水热分解煤等有机物制造80%H2和20%CH4气体的新技术.每克煤可生成2～3 L气体,煤中碳或氢几乎可全部按理论量进行反应,生成的气体中不含硫化物.同时氢气生成时能和副反应生成的CO2分离,使H2能高质量浓缩,用作燃料.新工艺产生的氯化物、氮化物、硫化物等都能以无害化形式被分离. 该技术除煤以外,还可用于分解其他有机物(碳源),如生活垃圾、家畜粪尿、动植物残体、废纸、废木材、废塑料等,生成H2和CH4,用作燃料.     

用生物体制高质量的燃料气

未来能源公司开发出一种被称作 Silva Gas的生物体气化法 ,已在一座每天可将 2 0 0～ 30 0 t生物体转化成 50 0 Btu/英尺3 燃料气的装置上进行了 30个月的示范试验 ,并计划将其推向市场生物体进入循环流化床气化器 ,在常压下与热沙 (约 1 80 0 )混合 ,并注入蒸汽以强化混合。生物体被转化成一种含 H2 1 8%、CO50 %、CH4 1 6%、CO2 9%、乙烯 6%及残炭的气体。残炭及沙子经旋风分离器与气体分离后进入燃烧室 ,残炭燃烧为气化过程提供热能 ,沙子被重新加热后返回气化器。产生的气体在大多数情况下可用于代替天然气用生物体制高质量的燃料…     

变压吸附技术分离模拟油田火驱尾气中的CO_2

采用变压吸附技术分离模拟油田火驱尾气(CO_2-N_2-CH_4混合体系)中的CO_2。考察了吸附压力、吸附温度和气体流量对吸附效果的影响。实验结果表明:在吸附温度为25℃、吸附压力为0.6 MPa、气体流量为2 000m L/min、初始CO_2体积分数为13.01%的条件下,CO_2的穿透吸附量为60.34 m L/g,CO_2吸附率为78.92%,碳分子筛对CO_2的分离因子为8.233;在床层利用率为0.523的条件下进行降压解吸,当吸附压力降至0.1 MPa时,出口CO_2体积分数约为80%,CO_2的回收率可达96.38%。     

低碳经济下燃煤电厂CO_2捕集技术

随着中国经济发展,温室气体排放量大幅增加。温室气体中,CO2的排放对气候的负面影响十分巨大,CO2排放已成为燃煤发展的瓶颈问题之一。针对电力工业CO2排放状况,介绍了几种火电厂CO2排放捕集措施：燃烧前脱碳、富氧燃烧以及燃烧后脱碳技术,分析了各项技术的优势和可行性;指出了低碳经济下火电厂的CO2减排方向。     

O2/CO2气氛下醋酸钙再燃脱硝机理分析

在O2/CO2气氛下对醋酸钙再燃脱硝性能进行了试验研究，并建立由112种物质和677步基元反应组成的机理模型，对反应机理进行了探讨。试验结果表明，醋酸钙再燃脱硝效率随温度的升高呈先提高后降低的趋势，高浓度的CO2对脱硝反应有促进作用。醋酸钙分解产生丙酮，丙酮高温热解主要气体产物为CO、CH4、C2 H4、H2、C2 H2和C2 H6，这些碳氢气体能够与OH反应生成碳氢自由基和HCCO，进而与NO反应实现脱硝，高浓度的CO2对碳氢自由基的生成有促进作用。     

Gasification of refuse derived fuel in a fixed bed reactor for syngas production

Steam gasification of two different refuse derived fuels (RDFs), differing slightly in composition as well as thermal stability, was carried out in a fixed-bed reactor at atmospheric pressure. The proximate and ultimate analyses reveal that carbon and hydrogen are the major components in RDFs. The thermal analysis indicates the presence of cellulose and plastic based materials in RDFs. H2 and CO are found to be the major products, along with CO2 and hydrocarbons resulting from gasification of RDFs. The effect of gasification temperature on H2 and CO selectivities was studied, and the optimum temperature for better H2 and CO selectivity was determined to be 725 degrees C. The calorific value of product gas produced at lower gasification temperature is significantly higher than that of gas produced at higher process temperature. Also, the composition of RDF plays an important role in distribution of products gas. The RDF with more C and H content is found to produce more amounts of CO and H2 under similar experimental conditions. The steam/waste ratio showed a notable effect on the selectivity of syngas as well as calorific value of the resulting product gas. The flow rate of carrier gas did not show any significant effect on products yield or their distribution.     

Prediction of syngas quality for two-stage gasification of selected waste feedstocks

This paper compares the syngas produced from methane with the syngas obtained from the gasification, in a two-stage reactor, of various waste feedstocks. The syngas composition and the gasification conditions were simulated using a simple thermodynamic model. The waste feedstocks considered are: landfill gas, waste oil, municipal solid waste (MSW) typical of a low-income country, the same MSW blended with landfill gas, refuse derived fuel (RDF) made from the same MSW, the same RDF blended with waste oil and a MSW typical of a high-income country. Energy content, the sum of H2 and CO gas percentages, and the ratio of H2 to CO are considered as measures of syngas quality. The simulation shows that landfill gas gives the best results in terms of both H2+CO and H2/CO, and that the MSW of low-income countries can be expected to provide inferior syngas on all three quality measures. Co-gasification of the MSW from low-income countries with landfill gas, and the mixture of waste oil with RDF from low-income MSW are considered as options to improve gas quality.     

Catalytic gasification of tars from a dumping site

The work deals with catalytic gasification, pyrolysis and non-catalytic gasification of tar from an industrial dumping site. All experiments were carried out in a vertical stainless steel gasification reactor at 800 °C. Crushed calcined dolomite was used as the gasification catalyst. Parameters such as addition of water and air, and the influence of the catalyst in regard to the composition of the process gas were investigated. The catalytic gasification experiment in the steady state produced process gas with the composition: 56 % of H₂, 9 % of CO, 11 % of CH₄ and 12 % of CO₂ (mol.%). Concentration of the C₂ fraction was lower than 1 mol.%. Volume flow of air was later changed from 120 to 230 ml min^?1 reducing the amount of hydrogen to 51 mol.% and that of methane to 10 mol.%. Process gas created in a non-catalytic gasification process contained 26–30 mol.% of methane, 13–15 mol.% of carbon monoxide and 15–17 mol.% of the C₂ fraction and lower amounts of hydrogen (20 mol.%) and carbon dioxide (2–3 mol.%). The highest apparent conversion of tar was reached in the catalytic gasification processes. A higher rate of catalyst deactivation can be observed when water or air is not added.     

Gasification characteristics of sewage sludge combined with wood biomass

The gas products from gasification processes have been considered to have some limitations in gas composition and heating value from the previous studies. Gasification characteristics of sewage sludge and wood mixture were investigated using different mixing ratios with the purpose of better quality of gas product suitable for energy/power generation. The gasification experiment was performed by an indirectly heated fluidized bed reactor. As reaction temperature increased from 600 to 900 °C, the yield of gas product increased with higher generation of CO, H₂ and CH₄ by more activated gas conversion reactions. As the equivalence ratio increased from 0.2 to 0.4, composition ratio of CO₂ increased while CO, CH₄, H₂ decreased as expected. Several operating variables including mixing ratio of wood with dried sludge were also tested. From this initial stage of experiment, optimal operating conditions for the bubbling fluidized bed gasifier, could be considered 900 °C in temperature; 0.2 in equivalence ratio and 40 % in wood mixing ratio within test variables range. These results will be more thoroughly investigated for the application to the larger scale pilot system.     

Adsorption removal of pollutants by active cokes produced from sludge in the energy recycle process of wastes

This study proposes a recycling system of sludge into active cokes and the fundamental examinations for the application were carried out. In the system, active cokes were produced by carbonizing pellets of sludge in a steam stream. Pyrolysis gas yielded by carbonization can be available to a fuel for a steam generation boiler. The exhaust heat from the boiler is used sequentially for drying of sludge. The active cokes are applied to the adsorbent for dioxin removal in exhaust gas from incinerators of wastes, or for purification of gas obtained in a gasification process of wastes, particularly removal of H2S. The used adsorbent is not recycled, but incinerated in the furnace without a desorption process to decompose adsorbed dioxin or to oxidize H2S for a sequential desulfurization process of SO2. Dry pellets of sludge were carbonized in a quartz tube reactor under various atmospheres. The micro pore structure and the adsorption performance of the cokes produced without activation process were examined. The micro pore structure was influenced by the temperature, the sort of flow gas (N2, CO2 and steam) and carbonization time, and the active cokes produced under the condition of the temperature 823 K for 60 min in the steam atmosphere had a largest specific surface area in the diameter less than 5 nm. The amount of benzene adsorption as an alternative substance of dioxin into the active cokes had a similar quality to a commercial active char produced from coal if it was evaluated by adsorption per a unit specific surface area. This fundamental knowledge must be reflected to an optimum design for development of a simple continuous process to produce the active cokes by a fluidized bed type of the carbonization furnace.     

鼓泡式反应器高径比对氨法烟气脱碳性能的影响

以N2和CO2混合气模拟燃烧烟气，研究了鼓泡反应器的高径比以及反应条件对氨法烟气脱碳性能的影响。实验结果表明:在相同高径比的条件下，CO2吸收率随氨水质量分数的增加、反应温度的升高而逐渐增大，随进气CO2体积分数和模拟烟气流量的增加而逐渐减小;CO2吸收率随高径比的增加而增大，在高径比为3.98、氨水质量分数为28%、进气CO2体积分数为10%、模拟烟气流量为1.0L/min、反应温度为40℃的条件下，CO2吸收率最高可达100%。     

DeepBlow – a Lagrangian Plume Model for Deep Water Blowouts

This paper presents a sub-sea blowout model designed with special emphasis on deep-water conditions. The model is an integral plume model based on a Lagrangian concept. This concept is applied to multiphase discharges in the formation of water, oil and gas in a stratified water column with variable currents. The gas may be converted to hydrate in combination with seawater, dissolved into the plume water, or leaking out of the plume due to the slip between rising gas bubbles and the plume trajectory. Non-ideal behaviour of the gas is accounted for by the introduction of pressure- and temperature-dependent compressibility z-factor in the equation of state. A number of case studies are presented in the paper. One of the cases (blowout from 100 m depth) is compared with observations from a field experiment conducted in Norwegian waters in June 1996. The model results are found to compare favourably with the field observations when dissolution of gas into seawater is accounted in the model. For discharges at intermediate to shallow depths (100–250 m), the two major processes limiting plume rise will be: (a) dissolution of gas into ambient water, or (b) bubbles rising out of the inclined plume. These processes tend to be self-enforcing, i.e., when a gas is lost by either of these processes, plume rise tends to slow down and more time will be available for dissolution. For discharges in deep waters (700–1500 m depth), hydrate formation is found to be a dominating process in limiting plume rise.     

Effect of fly ash addition on the removal of hydrogen sulfide from biogas and air on sewage sludge-based composite adsorbents

Desulfurization adsorbents were prepared from the mixtures of various compositions of New York City sewage sludge and fly ashes from SASOL, South Africa, by pyrolysis at 950 degrees C. The resulting materials were used as adsorbents of hydrogen sulfide from simulated dry digester gas mixture or moist air. The adsorbents before and after H(2)S removal were characterized using adsorption of nitrogen, elemental analysis, pH measurements, XRF, XRD, and thermal analysis. It was found that the addition of fly ash decreases the desulfurization capacity in comparison with the sewage sludge-based materials. The extent of this decrease depends on the type of ash, its content and the composition of challenging gas. Although the presence of CO(2) deactivates some adsorption sites to various degrees depending on the sample composition, the addition of ashes has a more detrimental effect when the adsorbents are used to remove hydrogen sulfide from air. This is likely the result of hydrophobicity of ashes since the H(2)S removal capacity was found to be strongly dependent on the reactivity towards water/water adsorption. On the other hand, the addition of ashes strongly decreases the porosity of materials where sulfur, as a product of hydrogen sulfide oxidation, can be stored.     

Influences of chemical activators on incinerator bottom ash

This research has applied different chemical activators to mechanically and thermally treated fine fraction (<14 mm) of incinerator bottom ash (IBA), in order to investigate the influences of chemical activators on this new pozzolanic material. IBA has been milled and thermally treated at 800 degrees C (TIBA). The TIBA produced was blended with Ca(OH)(2) and evaluated for setting time, reactivity and compressive strength after the addition of 0.0565 mole of Na(2)SO(4), K(2)SO(4), Na(2)CO(3), K(2)CO(3), NaOH, KOH and CaCl(2) into 100g of binder (TIBA+Ca(OH)(2)). The microstructures of activated IBA and hydrated samples have been characterized by X-ray diffraction (XRD) and thermogravimetry (TG) analysis. Thermal treatment is found to produce gehlenite (Ca(2)Al(2)SiO(7)), wollastonite (CaSiO(3)) and mayenite (Ca(12)Al(14)O(33)) phases. The thermally treated IBA samples are significantly more reactive than the milled IBA. The addition of Na(2)CO(3) can increase the compressive strength and calcium hydroxide consumption at 28-day curing ages. However, the addition of Na(2)SO(4), K(2)SO(4), K(2)CO(3), NaOH and KOH reduces the strength and hydration reaction. Moreover, these chemicals produce more porous samples due to increased generation of hydrogen gas. The addition of CaCl(2) has a negative effect on the hydration of TIBA samples. Calcium aluminium oxide carbonate sulphide hydrate (Ca(4)Al(2)O(6)(CO(3))(0.67)(SO(3))(0.33)(H(2)O)(11)) is the main hydration product in the samples with activated IBA, except for the sample containing CaCl(2).