煤催化气化过程中钾催化剂回收的实验研究

对内蒙平庄煤-蒸汽催化气化过程残渣中KOH催化剂的回收进行了实验研究,考察了时间、温度、水渣比和洗涤次数等条件对钾催化剂回收率的影响。实验结果表明,水蒸气催化气化过程中,催化剂的流失可忽略不计。水洗法回收可溶钾占总钾量的80%,回收所得催化剂的有效成分为K2CO3和KOH,占总回收钾量的90%以上。钾收率随时间的增长而快速提高,一般洗涤4 h即可达到预期的收率;升高温度和增大水渣比能明显提高催化剂的收率;水洗洗涤3次,能回收90%左右的可溶钾。     

煤／煤焦—水蒸气的催化气化理论基础

本文以文献为基础,阐述了以碱金属、碱土金属及复合化合物为催化剂的煤/煤焦-水蒸气催化气化机理及功力学模型,为深入开展这一方面的研究、开发提供了理论基础。     

煤催化气化技术进展

煤气化是发展现代煤化工最重要和最广泛的关键技术之一。煤催化气化技术由于反应温度低,反应过程热效率高、煤气中甲烷含量高而被认为是用于煤制气的第三代煤气化技术。主要介绍了煤催化气化工艺技术的研究现状、EXXON催化煤气化的主要工艺路线、主要工艺影响因素及催化剂的类型,并提出催化气化技术应在高效、低成本、低污染、低腐蚀的新型催化剂的开发、催化剂回收工艺的优化、煤质与气化炉匹配等方面加大研究力度以促进其工业化应用进度。     

催化气化(一步法)煤制天然气催化剂研究进展

概述了煤制天然气工艺的研究现状,综述了煤-水蒸气催化气化制天然气(一步法煤制天然气)催化剂的最新研究进展,包括催化剂的分类、不同催化剂对煤催化气化碳转化率及产品气体组成的影响、各类催化剂在活性经济性等方面的优缺点等,并分析了导致催化剂失活的原因以及回收的方法。指出了一步法煤制天然气催化剂的研究方向。     

煤催化气化研究进展与煤-纸浆黑液共气化

论述了煤催化气化研究领域中催化剂种类,催化气化反应机理及其反应动力学的现状,发展方向以及存在的主要问题。在此基础上结合纸浆黑液组成特性和处理现状,提出煤－纸浆黑液共气化设想。     

煤催化气化技术的研究现状与展望

煤催化气化由于可以大幅度降低操作条件,实现定向转化,目前正受到国内外重视。本文综述了碱金属、碱土金属、过渡金属催化剂与复合催化剂在煤催化气化过程中的活性、优缺点、反应机理等。对影响煤催化气化的各类因素如煤阶、矿物质、催化剂添加方式、添加量、气化条件等进行了分析。介绍了当前催化气化工业化进程以及合成天然气甲烷和催化气化制氢两种工艺。当前研究的难点是兼顾催化剂的效率与经济性,煤催化气化未来将以开发高活性、易回收且廉价的催化剂为研究方向。     

煤无氧气化催化剂和气化机理研究进展

文章综述了碱金属、碱土金属和过渡金属等催化剂对煤无氧气化的催化活性以及催化剂的添加方式对催铊效果的影响。同时,重点分析了不同金属作为催化剂时煤无氧偻化气化的反应机理。     

煤温和气化研究及应用

对煤温和气化工艺条件,催化剂选择和实际应用进行了系统的阐述,重点介绍了影响温和气化过程的温度,煤种等因素,并对不同煤种下的硫分布进行了汇总。     

Low-temperature catalytic conversion of lignite: 2. Recovery and reuse of potassium carbonate supported on perovskite oxide in steam gasification

Catalytic recovery after repeated uses of unsupported K₂CO₃ or K₂CO₃ supported on 3 kinds of perovskites (LaMn_0.8Cu_0.2O₃, LaMn_0.8Cu_0.2O₃/γ-alumina, and La_0.9K_0.1MnO₃) was investigated during steam gasification of an Indonesian lignite (Adaro) at 700 °C. Perovskite supports effectively retained K₂CO₃ and maintained higher catalytic activity than K₂CO₃ alone. The supported catalysts were recovered from the ash after gasification based on their size and ferromagnetism. Quartz and alumina accumulation on the catalyst poisoned the ash due to reactivity with potassium. Catalytic activity as high as 90% carbon conversion was maintained up to seven cycles, and separation from the ash after gasification regenerated the activity.     

恩德粉煤气化炉的气化工艺及应用

煤气化技术对于促进煤炭的综合利用、改善当前资源紧缺状况并减少环境污染具有重要的意义。对恩德粉煤气化炉的特点和气化工艺流程、工艺操作进行了分析,并以景德镇市焦化煤气总厂应用恩德粉煤气化炉实现煤气化的工程实例,分析了恩德粉煤气化技术的运行指标和投资效益。     

Eutectic salt catalysts for graphite and coal char gasification

Low melting binary and ternary eutectics of the alkali metal halides, carbonates and sulphates have been found to be more effective low temperature catalysts for the CO₂ and steam gasification of graphite and coal chars than the pure salt components. The reduced melting points of the eutectic phase facilitate contact between the catalyst and the carbonaceous substrate.     

Effectiveness and mobility of catalysts for gasification of bitumen coke

The compounds K₂CO₃, KCl, Na₂CO₃, CaCO₃, CaO, and MgO were tested as catalysts for steam gasification of coke from oil sands bitumen at atmospheric pressure and 600-800 °C. Catalysts were added to liquid vacuum residue prior to coke formation and directly to the coke solids. K₂CO₃ and Na₂CO₃ were most effective, giving nearly complete conversion at 800 °C in 30 min, regardless of whether they were added before or after coke formation. Ca and Mg compounds did not promote catalytic reactions, nor did they interact physically with the coke based on SEM and EDX analyses. KCl was effective, to a lower extent than K₂CO₃ and Na₂CO₃ only at higher temperatures (800 °C). The alkali metal compounds showed high mobility within the coke phase, which was consistent with their catalytic activities.     

Modeling of catalytic gasification kinetics of coal char and carbon

Calcium- and potassium-catalyzed gasification reactions of coal char and carbon by CO₂ are conducted, and the common theoretical kinetic models for gas-carbon (or char) reaction are reviewed. The obtained experimental reactivities as a function of conversion are compared with those calculated based on the random pore model (RPM), and great deviations are found at low or high conversion levels as predicted by theory. Namely, calcium-catalyzed gasification shows enhanced reactivity at low conversion levels of <0.4, whereas potassium-catalyzed gasification indicated a peculiarity that the reactivity increases with conversion. CO₂ chemisorption analysis received satisfactory successes in both interpreting catalytic effects and correlating the gasification reactivity with irreversible CO₂ chemical uptakes (CCU_ir) of char and carbon at 300 °C. In details, calcium and potassium additions led to significant increases in CCU_ir and correspondent high reactivities of the char and carbon. Furthermore, CCU_ir of char and carbon decreased with conversion for calcium-catalyzed reaction but increased for potassium-catalyzed one, corresponded to the tendency of their reactivity. The RPM is extended and applied to these catalytic gasification systems. It is found that the extended RPM predicts the experimental reactivity satisfactorily. The most important finding of this paper is that the empirical constants in the extended RPM correlate well with catalyst loadings on coal.     

Catalytic gasification of char from co-pyrolysis of coal and biomass

The catalytic gasification of char from co-pyrolysis of coal and wheat straw was studied. Alkali metal salts, especially potassium salts, are considered as effective catalysts for carbon gasification by steam and CO₂, while too expensive for industry application. The herbaceous type of biomass, which has a high content of potassium, may be used as an inexpensive source of catalyst by co-processing with coal. The reactivity of chars from co-pyrolysis of coal and straw was experimentally examined. The chars were prepared in a spout-entrained reactor with different ratios of coal to straw. The gasification characteristics of chars were measured by thermogravimetric analysis (TGA). The co-pyrolysis chars revealed higher gasification reactivity than that of char from coal, especially at high level of carbon conversion. The influence of the alkali in the char and the pyrolysis temperature on the reactivity of co-pyrolysis char was investigated. The experimental results show that the co-pyrolysis char prepared at 750 °C have the highest alkali concentration and reactivity.     

Application of catalysts to coal gasification processes. Incentives and perspectives

There are several processes used for coal gasification, but these have three characteristic types of reactors — moving-bed, fluidized-bed and entrained phase. Design and comparison of different processes and reactors is possible if kinetic data relevant to technical performance of processes are available. The state of reaction kinetics of the non-catalysed and catalysed steam-carbon reaction as the basic coal gasification reaction is discussed. Catalysts only have effects on gasification rates in the temperature range of chemical reaction or pore diffusion control. Furthermore the increase in reaction rates by catalysts can also be reached without using catalysts. Therefore the application of catalysts seems not to be attractive in conventional gasification processes because the advantages (less coal and oxygen consumption and lower heat losses) are compensated by their disadvantages (additional costs, side effects). Only such processes in which a temperature increase is limited for different reasons does the application of catalysts have significant advantages. Such processes are the allothermal gasification using nuclear heat and processes leading to synthetic natural gas (SNG).     

Exxon catalytic coal gasification process: Fundamentals to flowsheets

This Paper reviews basic features of the reaction kinetics of potassium-catalysed coal gasification and describes how small-scale data were used for the conceptual design of large fluidized-bed gasifiers. It shows how potassium was chosen from among the alkali metals, the importance of the methanation reaction, and of steam conversion.     

气流床煤气化的技术现状和发展趋势

气流床煤气化是煤高效洁净利用的关键技术。综述了具有代表性的气流床煤气化技术的应用现状,探讨了影响水煤浆气化的主要因素,如烧嘴、耐火砖、激冷环等,分析了干煤粉气化的技术优势和存在的问题,并阐述了发展趋势。水煤浆气化已积累丰富经验,而干煤粉气化的实践较少,应用于化工领域还有待工程检验。基于国内煤气化技术的研究开发现状和工业运行情况的分析,提出了发展我国煤气化技术的战略。