Catalytic activity of coal minerals in water vapour gasification of coal

Possible catalytic influences of coal minerals during water vapour gasification of coal have been studied by kinetic measurements and microanalytical methods. A bituminous coal without and with various pretreatments and also model chars synthesized from PVC and PVC-sulphur mixtures were used as raw materials. Kinetic measurements were performed in a fixed-bed flow reactor at pressures between 0.2 and 2 MPa and temperatures from 880 to 1010 °C using hydrogen/water vapour mixtures as gasification agents. It was found that coal gasification at and beyond 880 °C can be decisively catalysed by the iron as constituent of mineral matter. Preconditions are elimination of inorganic sulphur and reducing atmosphere to stabilize elemental iron. The optimum pressure is in the range of 0.5 to 1 MPa. Scanning electron microscopy and electron probe microanalysis confirm that catalytic gasification starts as soon as the iron is free of sulphur. The organic sulphur of coal does not prevent but lowers the catalytic activity of iron.     

Coal gasification using a molten iron bath

A coal gasification process using a molten iron bath as reactor has been developed by Sumitomo Metals. Pulverized coal is blown onto this molten iron together with oxygen and steam as gasification agents. Tests using a pilot plant having a capacity of 60 t (coal) day^?1, has shown that a sulphur-free carbon monoxide and hydrogen-rich gas can be generated at high coal conversion efficiency.     

等离子体煤热解与气化工艺的研究进展

介绍了煤在热等离子体中转化为小分子化合物的2个重要过程,即等离子体煤热解和气化的基本原理、应用及发展状况。在非氧化性气氛中,煤热解生成的气体产物主要是乙炔、氢气、一氧化碳,此外还有甲烷和乙烯等小分子烃,乙炔的收率与煤种、粉煤粒度、反应器结构、粉煤进料方式、进料速度及操作条件密切相关,等离子体中氢的存在有利于乙炔的产生;在氧化性气氛中,煤气化产物主要是一氧化碳和氢气,煤中碳的转化率达95%,合成气体积分数约85%,二氧化碳体积分数低于5%。指出等离子体应用于煤转化过程是煤洁净利用的有效方式,具有潜在的工业化应用前景。     

Catalytic activity of potassium halides in water vapour gasification of graphite

The catalytic activity of potassium halides in water vapour gasification of graphite was studied at 900 ° C and pressures up to 2 MPa. The initial step is the hydrolysis of the potassium halide which controls the catalytic activity: KF >KCl >KBr. Main steps of the catalysed gasification reaction are in good agreement with an oxygen transfer mechanism. The following general reaction scheme is proposed not only for the potassium halides, but also for K₂CO₃ and KNO₃. Initial reactions: K₂CO₃ + H₂O → 2KOH + CO₂; KNO₃ + H₂O → KOH + NO_x; KX + H₂O → KOH + HX. Intermediate step: KOH + C, H₂ → K + CO, H₂O. K-catalysed gasification reactions: K + H₂O → K(O) + H₂; K(O) + C → K + CO; K(O) + CO → K + CO₂.     

Coal gasification in a jet-spouted bed

Coal gasification has been studied for the production of synthesis gas by use of a laboratory-scale, two-stage, jet-spouted bed reactor. Tests were conducted in the dry ash mode with oxygen-steam mixtures. The effects of operating conditions on the gasification performance were investigated at atmospheric pressure and temperatures up to 1150°C. Carbon conversions of 75% to 97% and cold gas thermal efficiencies of 62 to 78% were obtained for Taiheiyo coal. Both the carbon conversion and thermal efficiency were mainly affected by the oxygen/coal ratio. The product gases contained 36-41% hydrogen and 30-43% carbon monoxide.     

水煤浆气化装置操作优化技术及其应用

针对水煤浆气化装置操作优化问题,提出了一种多种群竞争型协同文化差分进化算法(MCCDE),算法中建立了基于差分进化算法的竞争型协同策略及竞争适应度评判方法,并引入了文化算法的部分思想。同时,建立了德士古气化炉操作优化模型,将MCCDE算法用于优化模型的求解。采用某化工厂气化系统实际运行数据进行仿真,经过操作优化计算,能够获得优化的控制参数,并提高气化炉有效气产率。最后,开发了水煤浆气化操作优化系统应用软件,能够实现将建模、控制、优化技术应用于实际生产中,以提高装置的经济效益。     

煤质对PKM加压气化工艺的影响

煤质对PKM气化工艺的影响，并详细阐述了其对一些工艺参数的要求。     

Catalytic activity of iron in the water vapour gasification of sulphur-containing cokes

The influence of sulphur on the catalytic activity of iron in gasification with H₂-H₂O mixtures at different total pressures and temperatures was studied with model cokes of various sulphur contents, prepared by copyrolysis of PVC and elemental sulphur at 600 °C. Sulphur represents a strong poison which may completely inhibit the catalytic activity of iron, owing to the presence of extremely stable sulphur surface compounds. The inhibition may partly be compensated by increase of pressure or temperature. The beneficial effect of pressure results from hydrodesulphurization of the cokes in the early stages of gasification, especially at low water vapour partial pressures. High temperatures effect a reduction of the sulphur surface compounds. A general reaction scheme is proposed and it is concluded that gradual inhibition of the catalytic activity of iron is caused by partial blocking of active centres on the iron surfac.     

Coal gasification at pressure by mixtures of carbon dioxide and oxygen

This Paper discusses results obtained from experiments on coal gasification by mixtures of carbon dioxide and oxygen under pressure. This research was carried out at the INIEX pilot station as part of the Belgian-German programme for the development of underground gasification. Tests were carried out to study the influence of the ratio of carbon dioxide to injected oxygen on the composition and the heating value of the gas obtained, the gasification efficiency and the consumption of the gasification medium. The experimental results can be satisfactorily explained by means of a model based on thermodynamic equilibria, assuming that gasification is brought about by an internal gasification agent formed by the volatile components of the coal and by an external gasification agent consisting of injected carbon dioxide and oxygen.     

煤气废水好氧-缺氧-好氧生物处理研究

煤气废水生物处理目前遇到的主要问题是系统运行不稳定及氨氮去除率低,针对这些问题开发出好氧-缺氧-好氧生物处理工艺.实验表明,新工艺在入水COD较高的条件下可以稳定运行,系统中一级好氧白土-活性污泥单元作用较大.系统在平均入水COD为2 204mg/L、氨氮为244mg/L的条件下,COD和氨氮去除率分别可达87.6%和80%,HRT的降低对系统COD去除率影响不大,但使氨氮去除率降低到67%,主要是由于一级好氧单元硝化作用减弱所致.该工艺提高了煤气废水生物处理的功效,特别是在去除氨氮方面具有很大的优势,为后续深度处理奠定了基础.     

煤气化技术在中国:回顾与展望

系统回顾了煤气化技术在中国150多年的发展历史,从新中国建立前、新中国建立到改革开放前、改革开放后3个阶段,分别介绍了我国引进各类煤气化技术的过程及其应用情况;以改革开放前和改革开放后2个阶段,重点概括了我国煤气化技术领域的艰难探索、系统深入研究和技术示范与应用过程中取得的重要进展与成果;对我国自主开发的主要煤气化技术的研发历程、技术特点、应用情况及最新进展进行概要阐述,并对地下气化、催化气化、加氢气化、超临界水气化、等离子体气化等新型气化技术的国内研发进展进行简要述评;总结了我国煤气化技术引进、自主研究与工程应用经验,从降低装置投资、提高系统效率、实现环境友好、协同处理液/固有机废物、融合信息化技术、开发新技术、保护知识产权等方面对煤气化技术的未来发展进行了展望。     

流化床-气流床耦合反应器中煤气化特性

利用化工动力学软件CHEMKIN建立了流化床-气流床耦合反应器等效网络模型,在φ300 mm反应器中的煤气化实验结果基础上,充分考虑耦合反应器不同区域物料间两相流动、传质传热,对耦合反应器各部分流体力学特征以及耦合反应器中不同区域的化学反应进行了分析。利用模型对飞灰的碳转化率、耦合反应器的碳转化率、耦合反应器内温分布及物料停留时间进行计算,结果表明,流化床耦合气流床反应器后,气流床可将出口飞灰碳转化64.1%,实现了耦合反应器对飞灰的再气化;耦合反应器煤气化系统的碳转化率由单独流化床的84.9%提高到92.2%。     

Oxygen-steam gasification of coals in a spouted bed

A bituminous and a sub-bituminous coal from Western Canada have been gasified in oxygen-steam and air-steam mixtures in a 0.30-m diameter, 50 kg coal/h continuous spouted bed reactor. Results are presented to show the effects of the blast composition and reactor temperature on gas heating value and carbon conversion. Operation in the ash agglomeration mode is illustrated, and the role of K₂CO₃ as catalyst explored. Results from a wide range of experimental gasification conditions are compared with predictions of an equilibrium model.     

煤气化废水的超临界水氧化处理实验

对煤气化废水的超临界水氧化处理效果开展了探索性实验研究,以污水、污泥处理达标为目标,对过程中的工艺条件及有害物质的去除效果进行了研究和评价,结果表明,优化条件下无需经过预处理及后续深度处理,出水主要指标即可达到国家《污水综合排放标准》(GB 8978—1996)一级排放标准,并可实现废水的无害化处理和污泥的无害化减量。在此基础上,创新性地提出了碎煤加压气化-超临界水氧化组合工艺方案。     

Fluidized-bed gasification of some Western Canadian coals

Three Western Canadian coals were gasified with air and steam in a fluidized bed of 0.73 mm sand and coal, at atmospheric pressure and temperatures of 1023–1175K to produce a low-calorific-value gas. One non-caking and two caking coals were tested. The effects of temperature, coal feed rate, $\text{air}\text{coal}$ ratio, $\text{steam}\text{coal}$ ratio, coal quality, coal particle size and bed depth on gas composition, gas calorific value and operating stability of the gasifier were established. Results are compared with those previously obtained for the same three coals when gasified in essentially the same equipment, but operated as a spouted bed.     

褐煤制气化水煤浆实验研究

为提高褐煤制气化水煤浆的制浆浓度,采用传统制浆工艺与分级研磨制浆工艺分别对某化工企业提供的3种煤样进行水煤浆成浆性实验,并在此基础上进行配煤制浆实验。结果表明:东明煤、扎赉诺尔煤、宝矿提质煤传统制浆工艺的最高浓度分别为48.54%、51.76%、56.08%,分级研磨制浆最高浓度分别为51.72%、54.82%、59.21%,3种煤样分级研磨制浆工艺水煤浆浓度提高3%以上。按照东明煤、扎赉诺尔煤质量比1∶1或东明煤、宝矿提质煤质量比2∶1配煤时所制水煤浆浓度分别为53.12%、54.21%,满足水煤浆浓度设计要求。     

煤等离子气化反应器的(火用)分析

等离子煤气化技术是煤气化的潜在技术,降低煤等离子气化反应器的能耗是该反应器系统优化的重要方面。文中给出了煤等离子气化的工艺过程及煤等离子气化反应器装置的结构形式,通过进行煤等离子气化反应器系统的热力学分析,得出该反应器系统的火用分析模型,分析火用损失产生的原因,提出降低火用损失的措施,改进后的反应器系统采用顺、逆流多级热传递及原料预热等热量利用方式。实验结果表明,改进后的反应器系统的火用损失由改进前的629.4 kJ/kg下降为472.3 kJ/kg,减少了24.9%,为系统优化提供依据。     

XRD物相分析研究煤炭气化炉内固硫特性

主要通过粉末X-射线衍射(XRD)技术对常压固定床气化炉内固硫机理进行研究,并与化学法测定结果进行对照验证。结果表明所得结果一致,两者可以相互印证。     

Coal pyrolysis and gasification in a fluidized bed thermogravimetric analyzer

The kinetics and modelling of coal gasification were studied in the newly developed fluidized bed thermogravimetric analyzer. The total weight loss obtained from the fluidized bed reactor and the total gas product are in general agreement. The presented model for the micro‐fluidized bed reactor encompasses the kinetics of coal pyrolysis as well as the gasification reactions. For coal pyrolysis, the resulting activation energies for the individual gases were 34.7 to 59.8 kcal/mol. These values are 19 to 21 % lower than those found in the literature for similar coals. This decrease of the activation energies of the endothermic pyrolysis reactions is attributed to a gradient of temperature of 185 to 209 °C. The obtained activation energy for the CO shift reaction is 46.6 kcal/mol, increasing by 20 % from the one used in the literature. This increase of the activation energy of such a mildly exothermic reaction represents an equivalent of 170 °C gradient of temperature. The effects of temperature on the yield and the composition of the gas product are studied. Experimental results and equilibrium data are also compared. The model shows reasonably good agreement with the experimental results, except for the water gas shift reaction.

     

Catalysis of lignite char gasification by exchangeable calcium and magnesium

A Montana lignite was pretreated in either HCI—HF or ammonium acetate. The former treatment replaced cations associated with carboxyl groups by hydrogen, as well as removing essentially all mineral matter. The latter treatment replaced cations by ammonium ions but left the mineral matter intact. The pretreated lignites were then loaded with varying amounts of Ca and Mg, separately or jointly, by ion exchange. Reactivities of chars produced from these exchanged lignites, as well as the raw and pretreated lignites, were determined in air, CO₂ and steam. Gasification of exchanged lignites was strongly catalysed by Ca; its activity was not affected by the presence of Mg on the char. At a comparable Ca loading, gasification rates of the 1273 K raw lignite char in the various atmospheres was higher than that of the acid treated 1273 K char but lower than that of the ammonium acetate treated 1273 K char. The former finding is attributed to chlorine retention in the lignite and char; the latter, to enhanced sulphur release during lignite pyrolysis.