煤气化工艺的发展趋势之一：—两段气化法

如果仔细观察近年来国外开发的和正在开发的各种煤气化工艺,不难发现采用两段气化工艺的愈来愈多,这种气化方法既保持了气流床气化的碳效率高、生产能力大的特点,又吸取了逆流气化的优点,将高温煤气显热用于煤气化反应,使煤气出口温度下降,煤气夹带的熔融液渣固化,因此使气流床气化工艺更趋完善。     

Application of K2CO3 catalysts in the coal gasification process using nuclear heat

Conventional gasification processes use coal not only as feedstock to be gasified but also for supply of energy for reaction heat, steam production, and other purposes. With a nuclear high temperature reactor (HTR) as a source for process heat, it is possible to transform the whole of the coal feed into gas. This concept offers advantages over existing gasification processes: saving of coal, as more gas can be produced from coal; less emission of pollutants, as the HTR is used for the production of steam and electricity instead of a coal-fired boiler; and a lower production cost for the gas. However, the process has the disadvantage that the temperature is limited to the outlet temperature (950 °C max) of the helium cooling gas of the HTR. Therefore the possibility of catalytic steam gasification was examined. Model calculations based on experimental results show that use of 3–4 wt% relative to coal of K²CO³ catalyst increases the throughput of a large scale nuclear gasification plant by ≈65%, while gas production costs decrease by ≈15%. Corrosion by catalysts is not significant at low concentration (< 5 wt%) and low temperature (< 900 °C).     

浆态床反应器流体力学行为研究及工业应用

浆态床是一种重要的气-液-固三相反应器,具有结构简单,传热、传质性能好以及催化剂可在线补加和更换等优点,在学术研究和工业应用上备受关注。对浆态床反应器的流型、气含率、气泡行为、传质、传热等研究进行了总结,并对温度、压力、液体性质等参数对于流体力学性质的影响进行了分析。介绍了多级浆态床和构件式浆态床新型反应器,对浆态床在大化工、精细化工及环保等重要过程中的工业应用进行了总结,并对浆态床反应器的应用前景和研究趋势进行了展望。     

Coal Gasification in Moving Bed Reactor with a Draft Tube

1 INTRODUCTIONMany different types of reactors,for example,fixed bed,moving bed,fluidized bed and spoutedbed,have been used in industrial production and laboratory in research studies.Althougheach of these coal gasifiers has its own specific advantages,there exists,generally speaking,certainwaste gas in product gas because of the direct burning of coal with oxygen or air to provide heatneeded in the endothermic process of coal gasification in gasifiers.A new type of moving bed     

两种加压煤气化工艺的比较

介绍了加压气流床煤气化工艺和加压固定床煤气化工艺固有的优点和缺点。分析了加压气流床煤气高温显热的利用率,探讨了加压固定床蒸汽消耗高、废水处理成本高和气化工艺氧耗低的原因。认为煤制天然气选择加压固定床煤气化工艺具有更多的优点。     

低阶煤热解-气化-燃烧TBCFB系统模拟及优化

三塔式循环流化床（TBCFB）是基于低阶煤分质转化利用理念开发的新型工艺系统,包含热解、气化及燃烧三个主反应器。提出了采用半焦颗粒代替石英砂作为循环热载体的新工艺,并使用Aspen Plus建立了基于半焦颗粒的TBCFB系统模拟流程,寻求系统内物料转化和能量利用的适宜操作条件。结果表明,只需燃烧40%的热解半焦,即可满足低阶煤在600℃热解和60%的热解半焦在800.9℃进行水蒸气气化所需热量;与石英砂或高温灰相比,利用热容较高的半焦颗粒作为循环介质可以显著降低热载体循环量,与原煤质量比仅为5.5。综合气化产物组成、低热值和冷煤气效率等指标,适宜的水蒸气与反应半焦质量比为1.5。上述模拟结果对半焦循环TBCFB新技术的工业应用具有一定指导意义。     

Lower emission plant using processed low-rank coals

Low-rank coals can be processed into non-fouling coal, ultra-low ash coal, and coals containing catalysts. Systematic studies of the action of acid to reduce ash in a number of low-rank coals have shown total ash reduction varied from 96% to 30%; the extent of ash reduction was limited by the nature of minerals, which may be removed using various acids, including HF, to produce ultra-low ash coal. A commercial process must operate at elevated temperatures, but this must not produce toxic wastewater; data are provided to show that wastewater may be treated and water recycled without polluting the environment. The addition of effective catalysts results in enhanced reactivity of the coal to oxygen and steam; experimental data show high yield of H₂ from char and steam, and accompanying post-gasification chemistry. Development of catalytic steam gasification requires an understanding of aqua-chemistry and the thermal transformations of inorganics as the coal is heated. The scientific basis exists for processing low-rank coals, but commercial application requires: (i) high production rates, (ii) treating wastewater produced from coal treatment plant, (iii) catalysts that increase the yield of H₂ from steam gasification, and (iv) plant that achieves high power and thermal efficiencies. Modelling studies for super-critical plant, and for direct coal-fuelled turbine in combined cycle, illustrate the potential for lower-emission technology; catalytic steam gasification offers the cleanest option for future coal-fuelled plant.     

煤催化气化催化剂发展现状及研究展望

煤与气化剂(如水蒸气、CO2、H2和O2)之间的气化反应最有效的催化剂主要为碱金属、碱土金属以及过渡金属的盐类,根据其组成,详细论述了煤催化气化催化剂的特性。据研究,在气化反应中碱金属催化剂如Na、K等易与煤中矿物质如Si或Al反应致使催化剂失活,同时过渡金属易被煤中S毒化,这在一定程度上制约了煤催化气化工业化进程。论述了煤催化气化催化剂的研究方向,认为开发新型高效、低廉且易回收催化剂是有必要的。     

Steam gasification of coal char catalyzed by K2CO3 for enhanced production of hydrogen without formation of methane

Steam gasification of coal char catalyzed by potassium carbonate was investigated on a laboratory fixed-bed reactor to examine the catalytic effects not only on the reaction rate but also on the reaction selectivity, and non-catalytic gasification of coal char was performed by way of contrast. It was observed that the catalytic gasification of coal char with steam occurred significantly in a temperature range of 700-750 °C, producing a hydrogen-rich gas with slight formation of carbon monoxide and virtually no formation of methane. An oxygen transfer and intermediate hybrid mechanism of the catalytic char gasification with steam is proposed for understanding of the experimental data regarding both the kinetic behaviors and reaction selectivity. The study has highlighted the advantages of the catalytic gasification of coal char over the conventional coal gasification with respect to the reaction selectivity. The catalytic steam gasification of coal char makes it possible to eliminate or simplify the methane reforming and water-gas shift processes in the traditional gas-to-hydrogen purification system.     

生物质热解和气化制取富氢气体的研究现状

随着世界能源和环境问题的发展,洁净的氢能源成为备受关注的新能源。目前,生物质热化学法作为制取富氢气体的有效方法而被广泛研究。本文系统地介绍了国内外通过生物质热解和气化制取富氢气体的研究现状,包括热解气化工艺、物料特性、热源类型、反应条件、气化剂及催化剂等对制取富氢气体的影响。重点介绍了不同类型催化剂在生物质热解和气化反应中的应用,以及催化剂在制取富氢气体方面的优势及其作用机理。提出生物质热解和气化制取富氢气体所面临的主要问题是寻求既高效又寿命长的新型或混合型催化剂,或者从工艺、反应器的改进入手,改善催化剂的催化环境,从而解决其失效问题。     

Resistance to Coking Determination by Temperature Programmed Reaction of n-Butane with Steam

Resistance to coking is one of the most important characteristics of nickel catalysts used for steam reforming of hydrocarbons, CO₂ reforming or methanation of carbon oxides. Microbalance reactors have for a long time played an important role in catalyst deactivation studies, providing coking and coke gasification rates. However, conventional thermogravimetric microbalances have a number of limitations. The aim of this paper is to compare initial temperatures of coking of Ni and Ni-Mo catalysts (with different resistance to coking) obtained in the temperature-programmed reaction of _n-butane with steam with the results of coking rates obtained by the traditional thermogravimetric method. The investigations showed great agreement of the results.     

Thermophoresis effects on gas-particle phases flow behaviors in entrained flow coal gasifier using Eulerian model

A numerical model based on the Eulerian–Eulerian two-fluid approach is used to simulate the gasification of coal char inside an entrained flow gasifier. In this model, effects of thermophoresis of coal char particles are thoroughly investigated. The thermophoresis is due to the gas temperature gradient caused by absorpted heat of coal char gasification. This work, firstly, calculates the gas temperature gradient and thermophoretic force at1100 °C,1200 °C,1300 °C and 1400 °C wall temperatures. Then, the changes of particle volume fraction and velocity in the gasifier are studied in the simulation with thermophoresis or not. The results indicate that considering the particle thermophoresis has some effects on the calculation of particle volume fraction in the gasifier, especially at wall temperature of 1400 °C, and the maximum particle volume fraction variance ratio reaches up to 1.38% on wall surface of the gasifier. These effects are mainly caused by large gas temperature gradient along the radial direction of the gasifier. For the particle velocity, the changes are small but can be observable along radial direction of the gasifier, which has good agreement with the distributions of radial gas temperature gradient and thermophoretic force. These changes above may have certain effects on gasification reaction rates in this Eulerian model. So the change of gasification reaction rates in the simulation with thermophoresis or not is studied finally.     

Simulated moving bed technology applied to coal gasification

An alternative technology to conventional coal gasification is discussed in order to improve the performances of the existing processes. The concept of simulated moving bed (SMB) is applied to coal gasification: a number of fixed-bed reactors are connected in series and a suitable switching policy is applied so that each fixed-bed is cyclically operated both as a combustion and a gasification reactor.     

Design of laboratory reactors for the measurement of catalytic carbon and coal gasification kinetics

A great deal of conflicting experimental kinetics results have appeared for catalytic carbon and coal gasification by water and carbon dioxide. The reason for this can in large part be attributed to inhibition of these reactions by their products and the influence of this product inhibition on the measured kinetics in different laboratory reactor systems. The measurement of differential rates and the determination of true kinetic values requires the use of feed streams with an excess of water and hydrogen for the catalytic CH₂O reaction and an excess of carbon dioxide and carbon monoxide for the catalytic CCO₂ reaction. Recommendations are put forward for the design of laboratory reactors for the measurement of catalytic carbon and coal gasification kinetics.     

On the intrinsic reaction rate of biomass char gasification with carbon dioxide and steam

The gasification of beech wood char and oil palm shell char with carbon dioxide and steam was studied. To avoid heat and mass transport limitations during gasification, the amount of char, particle size and flow rate were varied in isothermal experiments. A rate expression of the Langmuir–Hinshelwood-type was applied to match the experimental data at different partial pressures and reaction temperatures in the intrinsic regime. Furthermore, the reactive surface area (RSA) of the biomass chars was determined as a function of the degree of conversion by the temperature-programmed desorption technique (TPD). The results show that the reaction rate is in general proportional to the RSA. The surface related reaction rates for the studied biomass chars are comparable to surface related reaction rates for coal chars at similar reaction temperatures.     

The catalytic steam gasification of one Australian and three Japanese coals using potassium and sodium carbonates

The catalytic steam gasification of four different coals using potassium and sodium carbonates as catalysts was carried out in a semi-flow type fixed-bed reactor. The coal was gasified with or without the catalyst under a steam—argon atmosphere at a heating rate of 50°C/s at 700–800°C. The catalytic activity of carbonates for gasification was remarkable for Japanese high-volatile coals (Miike and Takashima coals), and moderate for Australian medium-volatile coal (New Lithgow coal); however, the carbonates had little effect on gasification of Japanese lignite (Taiheiyo coal). It is assumed that Miike and Takashima coals soften and melt during the heating process to make the contact between char and catalyst better. New Lithgow and Taiheiyo coals do not have this property. Gasification was promoted significantly at lower temperatures when the catalyst was used. In both catalyzed and uncatalyzed runs the main products were hydrogen and carbon dioxide; the reaction temperature did not affect the composition of the gases much. A water—gas shift reaction occurred during gasification resulting in a large amount of carbon dioxide under a large excess of steam flow.     

Kinetik der Kohlen-Pyrolyse als Grundlage für die Auslegung technischer Reaktoren

Kinetics of coal pyrolysis as a foundation for the design of technical reactors . The pyrolysis of coal is understood to mean its thermal decomposition at temperatures above 300°C, affording tar and char. It is the basic process underlying coking and the starting reaction of combustion, gasification, and hydrogenation. In addition, pyrolysis offers a means of converting coal into gases and liquids in a ?third way”? besides gasification and hydrogenation. In order to establish a basis for the design of relevant technical reactors, the kinetics of coal pyrolysis has been investigated as a function of temperature and rate of heating and recently of pressure under inert gases and hydrogen. In particular, the rates of formation and the yields of liquid and gaseous products and the alteration of the solid matter have been examined under pressures ranging from 1 to 100 bar and at rates of heating between 0.05 and 1 000 K/s. It is shown how product formation can be controlled by these parameters and how the experimental data can be applied to reactor design.     

大型射流流化床混沌特性的研究

1 INTRODUCTIONJetting fluidized beds have been widely applied in suchprocesses as catalytic and flame reactions,combustionand gasification of coal,treatment of waste,cleaningof dusty gases,coating and granulation.The flowcharacteristics of jetting fluidized beds are relevant tothe stable gas jet and the high rates of heat transfer     

聚乙烯技术新进展

评述了双峰聚乙烯技术,茂金属催化剂和采用液态冷凝技术的乙烯气相聚合工艺的新进展。介绍了生产双峰聚乙烯产品的各种双反应器工艺和单反应器工艺,指出双反应器工艺是目前国际上采用最广泛的工艺,而单反应器工艺目前仍处于开发试验中,是生产双峰聚乙烯产品未来发展方向。液态冷凝气相聚乙烯工艺利用冷凝液体的蒸发潜热及时移走反应热,极大地缓和了反应器散热问题,使得反应器单位体积的聚乙烯产量得到大幅度提高。将液态冷凝技术与超高活性的茂金属催化剂配合使用是当今研究的一个热点。     

科林高压干粉煤气化工艺技术分析

介绍了科林高压干粉煤气化的工艺流程、工艺特点.对该气化技术的可操作性进行了分析,并与国内应用的2种煤气化工艺(干粉煤废锅气化工艺和水煤浆加压气化工艺)数据进行了简单对比.科林高压干粉煤气化工艺具有设备结构简单、煤种适用性更宽、消耗低和设备国产化程度高的特点.