Pilot Development of Polygeneration Process of Circulating Fluidized Bed Combustion combined with Coal Pyrolysis

A pilot polygeneration process of a 75 t h^–1 circulating fluidized bed (CFB) boiler combined with a moving bed coal pyrolyzer was developed based on laboratory‐scale experimental results. The process operation showed good consistency and integration between boiler and pyrolyzer. Some critical operating parameters such as hot ash split flow from the CFB boiler to the pyrolyzer, mixing of hot ash and coal particles, control of pyrolysis temperature and solid inventory in the pyrolyzer, and pyrolysis gas clean‐up were investigated. Yields of 6.0 wt‐% tar and 8.0 wt‐% gas with a heating value of about 26 MJ m^–3 at 600 °C were obtained. Particulate content in tar was restrained less than 4.0 wt‐% by using a granular filter of the moving bed. Operation results showed that this pilot polygeneration process was successfully scaled up.     

Process characteristics investigation of simulated circulating fluidized bed combustion combined with coal pyrolysis

A poly-generation process of simulated circulating fluidized bed (CFB) combustion combined with coal pyrolysis was developed in a laboratory scale. Pyrolysis characteristics of three bituminous coals with high volatile contents were investigated in a fixed bed with capacity of 10 kg solid samples. The effects of initial temperature of solid heat carrier, pyrolysis holding time, blending (ash/coal) ratio and coal particle size on gas and tar yields were studied experimentally. The results indicate that the initial temperature of the heat carrier is the key factor that affects the gas and tar yield, and the gas composition. Most of the gas and the tar are released during the first few minutes of the pyrolysis holding time. For caking coal, the amount of char agglomerating on the pyrolyzer inner wall is reduced by enhancing the blending ratio. The experimental results may provide basic engineering data or information for the process design of CFB combustion combined with coal pyrolysis in a large scale.     

热分解气氛对流化床煤热解制油的影响

在循环流化床锅炉上耦合流化床热解反应器既可提供电力又副产热解油,明显提高煤的利用价值。在这个过程中,热解反应器通常利用自身产生的热解气作为流化介质。本文考察了模拟热解气反应气氛对流化床煤热解拔头制取热解油产率的影响,并利用TG-FTIR分析了焦油官能团组成及随TG温度的变化。针对锅炉用烟煤的实验结果表明：采用热解气作为反应气氛时焦油产率最大,相对无水无灰基煤达13%。反应气氛中H₂和CO₂的存在不利于焦油生成,但CO 和CH₄的加入提高了焦油产率;H₂的加入有利于焦油中酚羟基、羧基类化合物生成,同时也促进了脂肪族化合物的裂解;CH₄的存在可以提高焦油中单环芳烃、脂肪族及酚羟基类化合物的含量。     

Gasification of coal and PET in fluidized bed reactor

Blended fuel comprising 23 wt.% polyethyleneterephthalate (PET) and 77 wt.% brown coal was gasified in an atmospheric fluidized bed gasifier of laboratory-scale. The gasification agent was composed of 10 vol.% O₂ in bulk of nitrogen. Thermal and texture analyses were carried out to determine the basic properties of the fuel components. The influence of experimental conditions, such as the fluidized bed and freeboard temperatures on major and minor gas components and tar content, as well as features of the blended fuel gasification in comparison with the single coal gasification, were studied. In the case of coal with PET gasification, only the fluidized bed temperature showed significant influence on CO, CO₂, CH₄ and H₂ content in the producer gas, whereas the effect of the freeboard temperature was insignificant. In single coal gasification both temperatures had considerable and almost the same influence. The content of minor components, such as ethane, ethylene, acetylene and benzene, was found to be more dependent on the freeboard temperature than on the fluidized bed temperature. It was observed that the higher the freeboard temperatures get, the lower is the concentration of the minor components, with the exception of acetylene. The absolute contents of almost all minor and tar components were approximately three times higher in blended fuel gasification than that in single coal gasification. Finally, partition of carbon (char) and selected metals into bottom and cyclone ash in gasification of both fuels is discussed.     

下行床煤拔头工艺的产品产率分布和液体组成

基于循环流化床锅炉燃烧技术和下行床技术相结合,在处理能力为8 kg/h的煤拔头工艺热态实验装置上,以内蒙古霍林河褐煤为原料,普通河砂为固体热载体,考察了反应温度和煤粉粒径对气液固产品产率分布和液体组成的影响规律. 结果表明,在实验温度范围内,随着温度的升高,气体和液体产品的产率增加;液体产率随粒径的增大而降低. 当反应温度为660℃、煤粉粒径小于0.28 mm、加料率为4.7 kg/h时,轻质焦油(焦油中的正己烷可溶物)的产率可达7.5%(干煤基,w),其中酚类占57.1%,粗汽油(脂肪烃类)占12.9%,芳香烃占21.4%,极性组分和其他组分占8.6%. 实验表明,下行床由于气固沿重力场并流向下流动的特点,是适合煤拔头工艺的比较理想的反应器.     

氧化钙催化活性在焦油裂解过程中的变化规律

在以循环床锅炉循环灰为热载体、部分气化产生的半焦为锅炉燃料的煤的部分气化技术中，循环灰中的氧化钙对降低焦油产率、提高煤气产率是有利的。以焦油中的苯和甲苯为对象，用固定床反应器实验研究了焦油裂解过程中反应对氧化钙催化活性的影响，测定了失活系数，探讨了失活机理。实验结果表明，随着积碳量的增加，氧化钙颗粒的比表面积和空隙率减小，裂解反应速率下降，裂解产物中碳的总产率增加。     

Co-pyrolysis of bituminous coal and biomass in a pressured fluidized bed

An experimental study on co-pyrolysis of bituminous coal and biomass was performed in a pressured fluidized bed reactor. The blend ratio of biomass in the mixture was varied between 0 and 100 wt%, and the temperature was over a range of 550–650 °C under 1.0 MPa pressure with different atmospheres. On the basis of the individual pyrolysis behavior of bituminous coal and biomass, the influences of the biomass blending ratio, temperature, pressure and atmosphere on the product distribution were investigated. The results indicated that there existed a synergetic effect in the co-pyrolysis of bituminous coal and biomass in this pressured fluidized bed reactor, especially when the condition of bituminous coal and biomass blend ratio of 70:30(w/w), 600 °C, and 0.3 MPa was applied. The addition of biomass influenced the tar and char yields and gas and tar composition during co-pyrolysis. The tar yields were higher than the calculated values from individual pyrolysis of each fuel, and consequently the char yields were lower.The experimental results showed that the composition of the gaseous products was not in accordance with those of their individual fuel. The improvement of composition in tar also indicated synergistic effect in the co-pyrolysis.     

Nickel-catalysed gasification of brown coal in a fluidized bed reactor at atmospheric pressure

Pyrolysis and steam gasification of nickel-loaded Yallourn coal were carried out in a fluidized bed reactor at ambient pressure. The pyrolysis mode was influenced by the addition of nickel catalyst. The yield of total volatile matter decreased whereas the gas yield markedly increased, when compared with uncatalysed pyrolysis. This is considered to result from tar decomposing on the catalyst and being converted to gases and deposited carbon. For the catalysed steam gasification, ≈ 80 wt% of coal conversion was achieved at 873 K and the gas yield was twelve times as much as that for the uncatalysed reaction. The homogeneous equilibrium in the gas phase controlled the composition of the product gas. The product gas contained little tarry material and a negligible amount of hydrogen sulphide. Nickel was efficiently recovered from the residue by an ammonia-leaching method.     

循环流化床锅炉浅床运行技术及大型化分析研究

对小容量循环流化床（CFB）锅炉浅床运行技术进行了分析总结,浅床运行方式适合于燃用褐煤及高挥发分烟煤的CFB锅炉,可降低一次风机压头和风机电耗。对于中等容量CFB锅炉,浅床运行可能会导致密相区结焦及燃烧效率降低等问题,为降低飞灰及底渣可燃物含量,需要维持足够的床层高度或风室压力。对浅床运行模式的大型化问题进行了技术分析。     

昭通褐煤气化扩大试验研究

针对昭通褐煤的特点 ,在气化煤量为 0 .3t/h的焦载热流化床气化扩大试验装置上进行了试验研究 .研究结果表明 ,煤气中焦油量很小 ,有利于煤气生产的后期处理 ;与移动床气化和普通流化床气化相比 ,煤气热值和气化产率都有较大增加 ,煤气热值已接近城市煤气的要求 ;加大气化煤量可增加提升段燃烧的易燃成分 ,从而提高了燃烧温度和气化温度 ;气化煤量的变化对褐煤气化产率和产量的影响较大 .对于开发昭通褐煤资源来说 ,采用本工艺技术生产城市煤气是一个较佳的方案 .     

高铝矾土改性对稻草热解与气化特性的影响

在固定床中研究了高铝矾土改性剂及其浓度和反应温度对稻草热解产气特性的影响,选取固定床中最佳实验条件,在流化床中研究了改性高铝矾土床料对稻草气化特性及焦油产率的影响。结果表明,不同物质改性的高铝矾土对稻草热解产气特性的影响不同,4种物质提高稻草热解产气能力的顺序为CaCl2相似文献   

灰融聚CAGG流化床粉煤气化技术述评

灰融聚CAGG流化床粉煤气化技术是我国具有自主知识产权的新型煤气化技术.介绍了该技术的气化原理、技术特点以及CAGG气化炉的结构特点;分别阐述了常压和加压灰融聚煤气化装置的工艺流程、气化指标、"三废"排放处理和装置投资情况;结果表明,新型CAGG灰融聚流化床粉煤气化技术适宜于中小型化肥、化工装置的气头改造以及燃料气、焦...     

复合流化床低阶煤热解制备兰炭的工艺条件

以不同粒径范围的新疆准东煤为原料,在耦合下部流化床和上部输送床的复合流化床中热解制备兰炭,考察了热解温度、过量氧气系数、气化温度、煤颗粒停留时间等对热解产物分布和热解半焦性质的影响. 结果表明,随过量氧气系数、气化温度和颗粒平均停留时间增加,气体产率升高,半焦和焦油产率降低;半焦的比表面积随气化温度升高而增大,而随过量氧气系数增大先增大后减小. 当煤从下部流化床进料时,在过量氧气系数0.11、流化床气化温度850℃、输送床热解温度750℃、流化床内煤颗粒停留时间90 s的操作条件下,可制备出固定碳含量超过83%(w)、挥发分含量低于9%(w)的兰炭.     

不同热解方式下长焰煤的热解特性研究比较

为提高长焰煤热解转化率,研究其热解过程和机理,采用格金干馏设备、固定床和间歇蒸气流化床3种不同热解装置,分别进行长焰煤的低温热解实验。研究结果表明,格金干馏实验中液体产率较高;在固定床低温热解装置中,煤颗粒达到完全热解需要的时间长,热解气体产物中氢气的产率高;在间歇蒸气流化床中,煤颗粒的热解反应速度快,但受热解过程中流化气吹损的影响,半焦产率低;热解气体的组成和分布也随热解气氛而改变,在水蒸气气氛条件下,水蒸气可能参与大分子烃类物质的部分反应,热解气体中CH4和C2以上小分子烃类物质CmHn总含量降低,CO2和CO含量增高。     

Factors affecting steam gasification rate of low rank coal char in a pressurized fluidized bed

A high-pressure bubbling fluidized bed reactor was used to study the steam gasification of coal char under pressure. Indonesian sub-bituminous coal char (Adaro) and Australian lignite char (Loy Yang) were gasified with steam in the reactor at temperatures below 1173 K and at total pressures ranging from 0.1 to 0.5 MPa. The steam gasification rates of the coal chars were determined by analysis of the gaseous products. Activation energies for the steam gasification of the chars were as high as about 250 kJ/mol, which suggests that the temperature dependence of the gasification was substantial. The apparent gasification rates under the study conditions were described by a Langmuir–Hinshelwood (L–H)-type equation. Analysis of the reaction kinetics on the basis of the L–H equation indicated that increasing steam pressure effectively increased the gasification rate.     

Simulation of a Lignite‐Based Polygeneration System Coproducing Electricity and Tar with Carbon Capture

Lignite‐based polygeneration systems for coproducing tar and electricity with and without carbon capture and storage (CCS) were proposed and simulated. Predried lignite was pyrolyzed into coal gas, tar, and char. Coal gas was fired in a gas turbine after the cleanup process, while char was combusted in circulating fluidized‐bed (CFB) boilers. The polygeneration plant without CCS turned out to be more efficient than the conventional CFB power plant, suggesting that the former is a promising and efficient option to utilize lignite resources. Moreover, the performance and emissions of polygeneration plants with and without CCS were compared. It was shown that the more CO₂ is captured, the larger energy penalty it will cost. Therefore, a trade‐off should be made between low emissions and high efficiency.     

An Eulerian modeling approach of wood gasification in a bubbling fluidized bed reactor using char as bed material

We present an Eulerian multiphase approach for modeling the gasification of wood in fluidized beds. The kinetic theory of granular material is used to evaluate constitutive properties of the dispersed solid phase. Comprehensive models for wood pyrolysis, char gasification and homogeneous gas phase reactions are taken into account. The dispersed solid phase within the reactor is modeled as three continuous phases, i.e., one phase representing wood and two char phases with different diameters. In contrast to most other studies we investigate a fluidized bed which consists of wood and char particles without additional inert particles such as limestone or olivine. 2D simulation results for a lab-scale bubbling fluidized bed reactor are presented and compared with experimental data for product gas and tar concentrations and temperature. We investigate the influence of two different classes of parameters on product gas concentrations and temperature: (i) operating conditions such as initial bed height, wood feeding rate, and reactor throughput and (ii) model parameters like thermal boundary conditions, primary pyrolysis kinetics, and secondary pyrolysis model. Two different pyrolysis models are implemented and are compared against each other. The numerical results indicate (i) a relatively low influence of the investigated operating conditions on the main product gas components, (ii) a high sensitivity of main product gas components CO and CO₂ on the thermal boundary condition, and (iii) a very strong influence of operating conditions and model parameters on the tar content in the product gas.     

The effect of hydrothermal pretreatment on the structure and fast pyrolysis behaviors of ShengLi lignite

The structure and composition of coal determine its fast pyrolysis characteristics,and the study of the relationship between them can play an important role in the efficient and clean utilization of coal.So,in this work,hydrothermal pretreatment was used to artificially change the structure and composition of ShengLi (SL) lignite,which was used to investigate the influence of structural changes on pyrolysis.The physicochemical structure and composition of samples were characterized by X-ray diffraction,specific surface area and porosity analyzer,solid-state 13C nuclear magnetic resonance,Fourier transform infrared spectroscopy,and elemental analyzer.Pyrolysis experiments were carried out in a powder-particle fluidized bed reactor,and the distribution and composition of the pyrolysis products were ana-lyzed.The gasification activity of char was investigated by thermogravimetric analysis with a CO2 atmo-sphere.The results show that hydrothermal pretreatment (HTP) can destroy the cross-linking structure of SL lignite,and affect its aromaticity,pore structure,functional group,and carbon structure to change the distribution and composition of pyrolysis products of SL lignite,especially the composition of tar.Finally,the structure-activity relationship between the structure,composition,and pyrolysis characteristics of coal was comprehensively studied.     

气体停留时间对煤温和气化的影响

在鼓泡流化床反应器中进行了神木煤添加ＣａＯ的煤温和气化研究。在常压、７５０℃,高纯氮载气及反应器内停留时间８．５ｓ～３４ｓ范围内,总挥发分产率随停留时间增加而增加。本试验条件下,停留时间８．５ｓ时,焦油产率出现最大值,达４．５４％（质量分数）,至１８．２ｓ时,下降为约１％,下降了７８％。随气体停留时间的增加,气态产率的提高和液态产率的减少与半焦中残留挥发分的降低呈对应关系。通过适当降低载气流量,控制气体停留时间,可以更合理地分配煤中有机质     

CO2 gasification of Thai coal chars: Kinetics and reactivity studies

Two sized fractions (<75 μm and 150–250 μm) of Ban Pu lignite A and Lampang subbituminous B coals were pyrolyzed in a drop tube fixed bed reactor under nitrogen atmosphere at 500–900 °C. Gasification of coal chars with excess carbon dioxide was then performed at 900–1,100 °C. The result was analyzed in terms of reactivity index, reaction rate and activation energy. It was found that chars at lower pyrolysis temperature had highest carbon conversion, and for chars of the same sized fraction and at the same pyrolysis temperature, reactivity indices increased with gasification temperature. The lower rank Ban Pu lignite A had higher R _s values than higher rank Lampang subbituminous B coals. Smaller chars from both coals had higher R _s values, due to the higher ash content. At present, it can be concluded that, within the gasification temperature range studied, gasification rates of chars obtained at various pyrolysis temperatures showed a linear correlation with temperature. However, additional experiment is needed to verify the correlation.