Linking laboratory data with pilot scale entrained flow coal gasification performance. Part 2: Pilot scale testing

By exploring the links between laboratory-scale gasification data (e.g. slag viscosity measurements, char reactivity considerations) and the performance of the same coals under realistic pilot-scale conditions, we are provided with a dataset that allow us to refine coal test procedures for entrained flow gasification, understand the entrained flow gasification process in significantly more detail than previously, and gain some new insight into how coal reactivity and slag viscosity properties interact to define operating envelopes for specific gasification technologies. The first paper in this two-part series presented a detailed characterisation of a suite of Australian coals using laboratory-scale gasification facilities. This paper presents gasification data obtained from pilot-scale testing of these same coals, and explores the links between laboratory data, coal assessments made using these data, and the performance of the coals under realistic conditions. The results demonstrate a high degree of consistency between laboratory indications of coal reactivity and coal gasification behaviour at pilot scale. This work also demonstrates the impact of interactions between coal conversion properties and slag formation and flow behaviour, and how these interactions dictate operational parameters for the gasifier.     

Gasification behaviour of Australian coals at high temperature and pressure

This paper presents gasification conversion data generated for a suite of Australian coals reacting with oxygen/nitrogen mixtures at 2.0 MPa pressure and at temperatures up to 1773 K, as part of a wider investigation into the gasification behaviour of Australian coals. The effects of O:C ratio, residence time and coal type on conversion levels and product gas composition were investigated under conditions relevant to those present in entrained-flow gasification systems. At higher temperatures, coal conversion levels are, as expected, higher, whilst product gas compositions continue to reflect the relevant gas phase equilibrium conditions. These gas phase equilibrium concentrations show strong dependence on the amount of carbon in the gas phase (i.e. coal conversion). The increased conversion achieved at high temperatures allows the contribution of coal-specific properties such as char structure and reactivity to be investigated in more detail than previously possible. Furthermore, at higher conversion levels the effects of coal type on product gas composition are more apparent than at lower conversion levels. These high temperature, high pressure gasification conversion data have been reconciled with high pressure bench-scale pyrolysis and char reactivity measurements, highlighting the significance of coal-specific effects of key gasification parameters.     

Determination of pneumatic transport capabilities of dry pulverised coal suitable for entrained flow processes

The use of pulverised coal in integrated gasification combined cycle (IGCC) power plant is currently under development. The results of a project to determine the suitability of Chinese coals for dry feed to the entrained flow gasifier that forms part of the above cycle are presented. This paper also includes some basic material characterisation of the pulverised coal.Pneumatic conveying test rigs were used in conjunction with a mathematical model to generate conveying characteristics for coal at high back pressures. The overall strategy was to test both coal and surrogate at atmospheric back pressure to compare the two materials' performance, under similar conveying conditions; and to test the surrogate material at elevated back pressure, and use this data to validate a mathematical model. The similarity of behaviours of the two materials then allowed the model to be applied to the data measured for coal and so generate conveying characteristics at conditions typical of entrained flow.The mathematical model used to scale the results to high back pressures, which characterise entrained flow processes, is based on the assumption that the influence of the pressure drop due to solids is independent of the back pressure, in the range of conditions considered. Conveying characteristics were generated at a variety of back pressures ranging from 1 to 25 bar. A brief analysis of the minimum conveying velocity is also presented.     

CO2 gasification rate analysis of coal char in entrained flow coal gasifier

Coal chars of four coal types were gasified with carbon dioxide using a PDTF or TGA at high temperature and pressure. Test conditions of temperature and partial pressure of the gasifying agent were determined to simulate the conditions in air-blown or oxygen-blown entrained flow coal gasifiers. Coal chars were produced by rapid pyrolysis of pulverized bituminous coals using a DTF with a nitrogen gas flow at 1670 K. In gasification tests with the PDTF, gasification temperatures were 1670 K or below and partial pressures of carbon dioxide were 0.7 MPa or below. Carbon monoxide of 0.6 MPa or below was supplied for the gasification tests with the TGA.As a result, coal types showed a large difference in the char gasification rate with carbon dioxide, and this difference remained large without decreasing even in the high-temperature area when the gasification rate was controlled by pore diffusion the same as in entrained flow gasifiers. Inhibition of the gasification reaction by carbon monoxide was also observed. Reaction rate equations of both the nth order and Langmuir-Hinshelwood type were applied to the char gasification reaction with the random pore model and the effectiveness factor, and the applicability of these rate equations to air-blown and oxygen-blown entrained flow gasifiers evaluated. Gasification rate equations and kinetic parameters applicable to a pore diffusion zone at high temperature were obtained for each coal.     

A three-dimensional numerical study of the combustion of coal blends in blast furnace

The practice of blending coals for pulverized coal combustion is widely used in ironmaking blast furnace. It is desirable to characterize the combustion behaviour of coal blends and their component coals. A three-dimensional numerical model is described to simulate the flow and combustion of binary coal blends under simplified blast furnace conditions. The model is validated against the experimental results from a pilot-scale combustion test rig for a range of conditions, which features an inclined co-axial lance. The overall performance of coal blend and the individual behaviours of their component coals are analysed, with special reference to the influences of particle size and coal type. The synergistic effect of coal blending on overall burnout is examined. The results show that the interactions between component coals, in terms of particle temperature and volatile content, are responsible for the synergistic effect. Such synergistic effect can be optimized by adjusting the blending fraction. The model provides an effective tool for the design of coal blends.     

煤气化工艺清洁生产及环境保护分析

简要介绍了固定床气化、流化床气化、气流床气化等主要煤气化工艺,对不同煤气化工艺的清洁生产及环境保护水平进行了对比分析,指出确定煤气化工艺时,在考虑煤种适应性和合成气用途的同时,还应兼顾建设地区资源、能源以及环境承载能力等因素,注重生产过程资源回收利用和污染物控制,在提高生产效率的同时,提高煤炭资源的利用率,以实现经济最优化和清洁生产。     

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.     

神经网络预测煤焦高温气化反应速率研究

神华大柳塔煤和兖州北宿煤都是气流床气化的优良煤种.通过三种算法的比较,采用BP神经网络的L-M算法,分析煤的制焦终温与制焦升温速率、气化反应温度、Vdaf和煤焦H/C原子比等不同因子对煤焦气化反应速率模型预测精度的影响,建立了基于Matlab下神华大柳塔单煤种四因子和神华-兖州双煤种五因子煤焦高温气化反应速率神经网络预测模型,得到比较满意的结果,其相对误差分别是0.167和0.264.     

普伦弗洛(PRENFLO)粉煤气化技术

PRENFL O气化属于粉煤气化技术 ,与 Shell粉煤气化相似 ,同属气流床气化技术。本文介绍了PRENFL O气化技术的来源、特色及进展     

Design and characterization of an apparatus for agglomeration testing during flash pyrolysis in entrained flow reactors

A small scale test apparatus is developed to measure the relative tendencies of different coals to agglomerate in dilute phase reactors with entrained flow and under conditions of flash pyrolysis. The important variables influencing agglomeration for a given coal are its feed rate and the temperature of pyrolysis. Changes in the method for collecting and measuring agglomerate were not significant at feed rates of dry coal greater than 2.5 g min^?1.     

Studies related to the structure and reactivity of coals : 18. The chemical structures of products from reactions of a suite of higher rank Australian coals

The structure of the oils, asphaltenes and residues obtained by the thermal reactions of a suite of Australian higher rank coals under hydrogen or nitrogen have been studied by chemical and spectroscopic methods. The host-guest model that has been used to describe the structure of Australian brown coals cannot be applied directly to the higher rank coals. Evidence is provided that suggests that a modified version of the model may be of use in describing the structure of some subbituminous coals. The methodology has proved to be useful in the understanding of structural features of coals which are often not rank dependent, e.g. Callide coal (ABL2), a subbituminous coal, has been shown to have characteristics of both very high and also low rank coals.     

新型气流床粉煤加压气化技术

气流床粉煤加压气化技术具有原料消耗低,碳转化率高,热效率高,煤种适应性强等优势。我国具有自主知识产权的气流床粉煤加压气化技术中试装置在兖矿鲁南化肥厂运行成功,各项技术指标分别为:有效气体积分数89%～93%,碳转化率98%～99%,比氧耗0.30～0.32m3/m3,比煤耗0.53～0.54kg/m3,冷煤气效率≥84%。     

Viscosity measurements and empirical predictions for fluxed Australian bituminous coal ashes

Recent interest in the suitability of Australian bituminous coals for use in integrated gasification-combined cycle (IGCC) technologies has provided the opportunity to determine viscosity data for a range of coal ashes slags fluxed with limestone at the tapping temperatures of entrained flow gasifiers. Experimental viscosity measurements have been made over a range of slag compositions covering the anorthite region at the 0–2.5, 2.5–5, 5–7.5 and 7.5–10 wt% FeO levels of the quaternary SiO₂–Al₂O₃–CaO–FeO system. Contour plots of viscosities at 1450°C for the four FeO ranges are presented as an example for predicting slag behaviour in entrained flow gasifiers. The viscosity measurements have also been fitted empirically using a modified Urbain treatment to give separate models for the four FeO levels. Polynomial expressions are given for the evaluation of viscosities covering the temperature range 1400–1550°C for slags within the compositional range used in the derivation.     

干法进料气流床煤气化技术的现状与发展

煤气化按煤的粒度和气化炉内的气体流速等可分为固定床、流化床、气流床3种。其中干煤粉气流床加压气化具有易大规模化、煤种适应范围广、碳转化率高等特点,近年来得到大规模的应用。详细介绍了以干煤粉为原料的Shell、Prenflo、Simens GSP和西安热工院的两段式气化技术。     

Slagging gasification of coal under addition of flux agents

Despite a general trend towards higher reaction temperatures with coal gasification processes of the second generation, process and material considerations also make it desirable to limit temperatures to a maximum of about 1500°C to 1600°C. For coal gasifiers to be operated under slagging conditions this means that feed coals with high ash melting points, as they are available on the market, have to be mixed with special flux agents to ensure trouble-free operation. Limestone is a suitable flux agent whose use and effect on the gasification behaviour of a German high volatile bituminous coal with a high ash fluid point is reported in this paper.     

Entrained‐flow gasifier fuel blending studies at pilot scale

For the foreseeable future, coal and petroleum‐based materials, such as petroleum Coke, residuals, and high‐sulphur fuel oil, are being adopted as the feedstocks of choice for gasification projects. Of particular interest from a Canadian perspective is Coke generated from the thermal cracking of the oil sands in Western Canada. Oil sand Coke contains high sulphur (5–6%), and also typically has a low volatile content, and lower reactivity than most coals. Experimental runs have recently been conducted on the pilot‐scale entrained‐flow gasifier at CETC‐Ottawa, blending oil sand Coke with sub‐bituminous and lignite coals, to try and enhance the gasification potential of these materials. Blending Genesee sub‐bituminous coal with the delayed oil sands Coke was found to alleviate problems encountered with slag plugging the reactor when running with Genesee coal alone. Blends of Genesee sub‐bituminous and Boundary Dam lignite coals with Coke achieved higher carbon conversions and cold gas efficiencies than runs completed with the Coke by itself. While using CO₂ as the conveying gas into the gasifier was not found to significantly affect the conversion obtained, steam addition was found to have a marked effect on CO and H₂ concentrations in the syngas.     

Characterization of coals for Lurgi pressure gasification and other moving bed processes: A method for reactivity parameter estimation from bench scale experiments

A method has been developed which yields global reactivity parameters of coals under conditions pertinent to gasification in moving bed reactors, in particular to the Lurgi process. The experimental procedure uses a bench scale pressure apparatus which allows the determination of other coal properties, besides reactivity, significant for gasification in moving bed reactors, like particle disintegration behaviour etc.. Herein, a coal sample of about 2 kg can be exposed subsequently to the conditions in the drying, pyrolysis and gasification zones of the moving bed gasifier. The data analysis procedure for the determination of reactivity parameters comprises a nonlinear fit of carbon gasification rate data by means of a first order kinetic model. As an example, results from a gasification experiment with North Dakota lignite related to the Lurgi process are presented. Pre-exponential factor and activation energy are estimated as global reactivity parameters from the data. They are intended to serve as coal-specific input data for kinetic models of commercial scale gasification reactors, thus widening the range of application of such models in reactor design and optimization.     

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。     

High‐temperature pyrolysis and CO2 gasification of Victorian brown coal and Rhenish lignite in an entrained flow reactor

The low rank coals from Victoria, Australia, and Rhineland, Germany are of interest for use in entrained flow gasification applications. Therefore, a high temperature, electrically heated, entrained flow apparatus has been designed to address the shortage of fundamental data. A Victorian brown coal and a Rhenish lignite were subjected to rapid, entrained flow pyrolysis between 1100 and 1400°C to generate high surface area chars, which were subsequently gasified at the same temperatures under CO₂ in N₂ between 10 and 80 vol %. The Victorian coal was more reactive than the Rhenish coal, and peak char reactivity was observed at 1200°C. Char conversion and syngas yield increased with increasing temperature and plateaued at high CO₂ concentration. Ammonia and tar species were negligible and HCN and H₂S were present in parts per million (volume) concentrations in the cooled, filtered syngas. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2101–2111, 2016     

Partial gasification of coal in a fluidized bed reactor: Comparison of a laboratory and pilot scale reactors

A 0.1 MW_th lab-scale and 2 MW_th pilot-scale experimental rigs were constructed to demonstrate the technical feasibility of a new process. The aim of the lab-scale study is to optimize coal partial gasification reactions operating conditions, which were applied in the pilot-scale tests. A comparison between the laboratory and pilot scale experimental results is presented in this paper in order to provide valuable information for scaling-up of the PFB coal partial reactor to industrial applications. The results show that trends and phenomena obtained in the laboratory reactor are confirmed in a pilot plant operating at similar conditions. However, many differences are observed in the two reactors. The higher heat loss in the lab-scale reactor is responsible for higher equivalence ratio (ER) and lower gas heating value at the similar reactor temperature. With respect to the pilot-scale reactor, mass transfer limitation between bubbles and emulsion phase may become important. Hence, longer contact time is required to achieve the same conversions as in the lab-scale reactor. This difference is explained by a significant change of the hydrodynamic conditions due to the formation of larger bubbles.