Numerical Simulation of Pressurized Spouted Fluidized Bed for Coal Semi-Gasification

Numerical simulation study is conducted for a pressurized spouted fluidized bed coal carbonizer, in which hydrodynamics of pressurized spouted fluidized bed, chemical reactions and energy balance are taken into account. The effect of operating conditions such as bed pressure, air and steam mass flow ratio, temperature on product compositions in the bed is investigated. According to the calculated results, bed pressure and bed temperature have the key effects on coal semi gasification.

A critical review on direct catalytic hydrogasification of coal into CH_(4):catalysis process configurations,evaluations,and prospects

Coal catalytic hydrogasification(CCHG)is a straightforward approach for producing CH_(4),which shows advantages over the mature coal-to-CH_(4) technologies from the perspectives of CH_(4) yield,thermal efficiency,and CO_(2) emission.The core of CCHG is to make carbon in coal convert into CH_(4) efficiently with a catalyst.In the past decades,intensive research has been devoted to catalytic hydrogasification of model carbon(pitch coke,activated carbon,coal char).However,the chemical process of CCHG is still not well understood because the coal structure is more complicated,and CCHG is a combination of coal catalytic hydropyrolysis and coal char catalytic hydrogasification.This review seeks to shed light on the catalytic process of raw coal during CCHG.The configuration of suitable catalysts,operating conditions,and feedstocks for tailoring CH_(4) formation were identified,and the underlying mechanisms were elucidated.Based on these results,the CCHG process was evaluated,emphasizing pollutant emissions,energy efficiency,and reactor design.Furthermore,the opportunities and strategic approaches for CCHG under the restraint of carbon neutrality were highlighted by considering the penetration of“green”H2,biomass,and CO_(2) into CCHG.Preliminary investigations from our laboratories demonstrated that the integrated CCHG and biomass/CO_(2) hydrogenation process could perform as an emerging pathway for boosting CH_(4) production by consuming fewer fossil fuels,fulfilling the context of green manufacturing.This work not only provides systematic knowledge of CCHG but also helps to guide the efficient hydrogenation of other carbonaceous resources such as biomass,CO_(2),and coal-derived wastes.

Integrated vacuum pressure swing adsorption and Rectisol process for CO_(2) capture from underground coal gasification syngas

An integrated vacuum pressure swing adsorption(VPSA) and Rectisol process is proposed for CO_(2) capture from underground coal gasification(UCG) syngas. A ten-bed VPSA process with silica gel adsorbent is firstly designed to pre-separate and capture 74.57% CO_(2) with a CO_(2) purity of 98.35% from UCG syngas(CH_(4)/CO/CO_(2)/H_(2)/N_(2)= 30.77%/6.15%/44.10%/18.46%/0.52%, mole fraction, from Shaar Lake Mine Field,Xinjiang Province, China) with a feed pressure of 3.5 MPa. Subsequently, the Rectisol process is constructed to furtherly remove and capture the residual CO_(2)remained in light product gas from the VPSA process using cryogenic methanol(233.15 K, 100%(mass)) as absorbent. A final purified gas with CO_(2) concentration lower than 3% and a regenerated CO_(2) product with CO_(2) purity higher than 95% were achieved by using the Rectisol process. Comparisons indicate that the energy consumption is deceased from 2.143 MJ·kg^(-1) of the single Rectisol process to 1.008 MJ·kg^(-1) of the integrated VPSA & Rectisol process, which demonstrated that the deployed VPSA was an energy conservation process for CO_(2) capture from UCG syngas. Additionally, the high-value gas(e.g., CH_(4)) loss can be decreased and the effects of key operating parameters on the process performances were detailed.

Thermal performance analysis of advanced partial gasification combined cycle

This paper presents the thermodynamic performance analysis and comparison of four kinds of advanced pressurized fluidized bed combustion combined cycle (APFBC-CC) system schemes, two based on pressurized fluidized bed (PFB) combustion and the other two based on atmospheric circulating fluidized bed (CFB) combustion. The results show that the first scheme avoids high temperature gas filter, but has the lower cycle efficiency and syngas heating value. The second scheme can gain the highest cycle efficiency, however it is better to now lower the filter operating temperature. The third and fourth schemes, based on CFB, have lower efficiencies than the second one. But the fourth one, with preheating air/steam for gasification, can obtain the highest heating value of syngas and gain higher efficiency than the third one.

Effect of operating parameters on coal gasification

Coal combustion and gasification are the processes to utilize coal for production of electricity and many other applications. Global energy demand is increasing day by day. Coal is an abundant source of energy but not a reliable source as it results into high CO2 emissions. Energy industries are expected to decrease the CO2 emission to prevent global warming. Coal gasification is a process that reduces the CO2 emission and emerges as a clean coal technology. Coal gasification process is regulated by several operating parameters. A Number of investigations have been carried out in this direction. A critical review of the work done by several researchers in the field of coal gasification has been compiled in this paper. The effect of several operating parameters such as coal rank, temperature, pressure, porosity, reaction time and catalyst on gasification has been presented here.

Hydrogen Production by Coal Gasification Coupled with <i>in Situ</i>CO₂Capture

CO2 adsorption enhanced gasification process is a prospective technology to be used in hydrogen production with nearly zero CO2 emission. In this paper, a gasification kinetics steady state model is developed based on the chemical kinetics mechanism with the condition of fluidization. It is used to predict the parameters of gas phase and solid phase for a continuous flow reactor with steady state. The variation of components distribution with gasification temperature and pressure are determined, from which the optimal operation parameters of gasifier can be obtained.

Intrinsic kinetics and external diffusion of catalytic steam gasification of fine coal char particles under pressurized and fluidized conditions

Catalytic steam gasification of fine coal char particles was carried out using a self-made laboratory reactor to determine the intrinsic kinetics and external diffusion under varying pressures (0.1-0.5 MPa) and superficial gas flow velocities (GF Vs) of 13.8- 68.8 cm· s^-1. In order to estimate the in-situ gas release rate at a low GFV, the transported effect of effluent gas on the temporal gasification rate pattern was simulated by the Fluent computation and verified experimentally. The external mass transfer coefficients(kmam) and the effectiveness factors were determined at lower GF Vs, based on the intrinsic gasification rate obtained at a high GFV of 55.0 cm·s^-1. The kmamwas found to be almost invariable in a wider carbon conversion of 0.2-0.7. The variations of kmam at a median carbon conversion with GFV, temperature and pressure were found to follow a modified Chilton-Colburn correlation:Sh=0.311Re^2.83Sc1/3(P/P0)^-2.07 (0.04<Re<0.19), where P is total pressure and Po is atmospheric pressure. An intrinsic kinetics/extemal diffusion integrating model could well describe the gasification rate as a function of GFV, temperature and pressure over a whole gasification process.

基于Aspen Plus的煤部分气化氢电联产系统模拟

为了提高煤制氢系统的能源利用效率,减少碳排放,构建了4种以煤部分气化为基础的新型氢电联产系统.基于Aspen Plus软件,采用系统效率、制氢效率作为评价标准,对各系统进行模拟与对比分析.结果表明:存在不同氧煤比与碳转化率使得系统效率达到最高,系统1~4分别在碳转化率为60%、85%、65%、60%时达到最高系统效率;各系统效率与气化效率随着气化温度的提高,呈先迅速增长后趋于平稳趋势;各系统效率与气化效率随着气化压力的提高,呈先迅速减少后趋于平稳趋势;在氧煤比为0.33,气化压力为2 MPa,气化温度为1000℃工况下系统1~4效率分别为59.12%、66.13%、62.21%和58.57%;采用CO_(2)与O_(2)作为气化剂,且CO_(2)与O_(2)的质量比为4∶1的煤部分气化加压富氧燃烧循环系统(系统2)在各项标准下具有优势,为最佳氢电联产系统.

生态环境视域下基层医院医疗废物处理研究

医疗废物含有大量的病毒、致病微生物以及化学药剂等,若直接排放对生态环境污染性大。因此,文章研究一种生态环境视域下基层医院医疗废物处理方法。该方法采用高温高压蒸汽灭菌与热解气化联合技术,对医疗废物进行前处理和深度处理。通过此法,废物中的病毒、致病微生物及化学药剂得到有效消减。研究结果表明,处理后二噁英含量显著降低,符合国家标准,杀菌率高达90%以上。这不仅验证了联合处理技术的有效性,也显示了对生态环境的保护作用。此方法为基层医院处理医疗废物提供了新的解决方案,有助于减少环境污染,促进生态平衡。

Effect of pressure on gasification reactivity of three Chinese coals with different ranks

The gasification reactivities of three kinds of different coal ranks(Huolinhe lignite,Shenmu bituminous coal,and Jincheng anthracite)with CO_(2) and H_(2)O was carried out on a self-made pressurized fixed-bed reactor at increased pressures(up to 1.0 MPa).The physicochemical characteristics of the chars at various levels of carbon conversion were studied via scanning electron microscopy(SEM),X-ray diffraction(XRD),and BET surface area.Results show that the char gasification reactivity increases with increasing partial pressure.The gasification reaction is controlled by pore diffusion,the rate decreases with increasing total system pressure,and under chemical kinetic control there is no pressure dependence.In general,gasification rates decrease for coals of progressively higher rank.The experimental results could be well described by the shrinking core model for three chars during steam and CO_(2) gasification.The values of reaction order n with steam were 0.49,0.46,0.43,respectively.Meanwhile,the values of reaction order n with CO_(2) were 0.31,0.28,0.26,respectively.With the coal rank increasing,the pressure order m is higher,the activation energies increase slightly with steam,and the activation energy with CO_(2) increases noticeably.As the carbon conversion increases,the degree of graphitization is enhanced.The surface area of the gasified char increases rapidly with the progress of gasification and peaks at about 40%of char gasification.

西湾煤焦在加压条件下的气化反应特性研究

为阐明加压、多种气化剂共存条件下西湾煤焦的气化反应规律,考察了不同热解制焦与气化条件对煤焦气化过程中碳转化率与气体组分的影响,以指导接近工业化热解-气化一体化反应器的设计与优化,研究了不同热解温度(600℃~900℃)、升温速率(10℃/min~40℃/min)、停留时间(10 min~40 min)及气化温度(900℃~1100℃)、气化压力(常压到4.0 MPa)、气氛(100%(体积分数,下同)CO_(2),50%CO_(2)+50%H2O,100%H2O等)对西湾煤焦加压气化反应特性的影响。结果表明:在升温速率为20℃/min、气化温度为1000℃、反应气氛为100%CO_(2)条件下,加压可以降低煤焦中挥发分的析出与扩散速率,煤焦中自由基分子相互作用发生缩聚、交联等反应能够降低气化反应速率;增大气化剂体积分数可增加气化剂与煤焦表面碳分子的碰撞概率,从而提高气化反应活性,使西湾煤焦的碳转化率由常压下的95.15%减小至4.0 MPa下的78.22%;较高水蒸气分压可抑制煤焦石墨化进程与提升气化反应速率,使加压条件下水蒸气气氛下煤焦气化活性高于二氧化碳气氛下煤焦气化活性。100%H_(2)O气氛下煤焦的碳转化率最大,达到95.12%,较100%CO_(2)气氛下煤焦的碳转化率增加约13.5%。

碎煤加压气化固态排渣系统工艺技术分析比较

固定床碎煤加压气化是一种重要的煤气化技术,根据其灰渣特性采取适当排渣技术是一个重要环节,目前主要有水力湿法排渣、水冷干法排渣及风冷干法排渣等排渣方式。从灰渣收集、冷却方式、综合利用、节水节能等方面对三种排渣方式进行了分析比较,认为水力湿法排渣技术成熟,但已相对落后,水冷干法排渣技术介于风冷干法和水力湿法排渣两者之间,风冷干法排渣技术具有诸多优势,但目前没有在碎煤加压气化系统的应用业绩,煤化工项目在碎煤加压气化排渣技术选择中,应综合考虑各种因素,选择与项目匹配的排渣技术。

固定床加压熔渣气化过程的仿真模拟

为研究固定床加压熔渣气化炉气化反应过程及最优工艺参数,利用Aspen Plus软件建立固定床加压熔渣气化炉的动力学模型,并利用该模型对内蒙某固定床加压熔渣气化炉进行模拟计算,计算结果与实际生产数据的误差<5%,从而验证该模型的准确性。在该模型的基础上探讨固定床熔渣气化炉内的组分和温度分布,以及不同操作参数对气化炉性能的影响。结果表明:炉内最高温度为2019℃,在蒸氧喷嘴附近;炉内各反应层所占高度的比例为燃烧层占15%,气化层占25%,干馏+干燥层占60%;随着蒸氧比(蒸汽质量流量∶氧气体积流量)的增加,碳转化率增加,蒸汽分解率下降,当蒸氧比为0.95—1.0时,气化炉性能最优;随着氧煤比(氧气质量流量∶煤质量流量)的增加,碳转化率增加,蒸汽分解率先增加后降低,当氧煤比为0.45—0.46时,气化炉性能也最优。研究结果可为固定床加压熔渣气化炉的设计和操作提供一定的理论依据。

兰炭在固定床碎煤加压气化炉的应用分析与探讨

晋控金石园区分公司采用固定床碎煤加压气化技术生产合成氨、甲醇,气化炉原料煤为无烟块煤。为进一步拓展气化炉原料煤种,公司开展了掺烧兰炭的试烧试验。介绍了兰炭掺烧比例为20%、30%、50%、100%等不同条件下的气化炉运行工况、煤气组分、吨氨消耗、煤气水产量变化情况,分析了气化炉掺烧兰炭的经济性,试烧数据可为同类型企业的原料煤结构调整提供实践指导。

水煤浆气化烧嘴喷口和炉砖烧蚀性的优化及应用

水煤浆加压气化工艺中工艺烧嘴的设计需与煤浆投料负荷相匹配。国内某公司6.5 MPa水煤浆加压气化装置原工艺烧嘴设计煤浆处理量73 m3/h,因下游合成气的需求变化使装置负荷需大幅改变,新方案烧嘴要求能满足75%~125%范围的负荷调节。为了评估极端负荷工况对气化装置造成的影响,针对该厂运行工况,对原烧嘴和新方案烧嘴进行了气化炉全炉燃烧数值模拟。计算结果表明:新方案优化了烧嘴在低负荷下的端面烧蚀和高负荷下的冲蚀问题,改善了高负荷下炉砖筒体和锥底的温度分布,有利于缓解炉砖的冲蚀速率。新方案实际投用后兼顾了较高的气化生产效率和宽广的负荷变化范围,验证了计算的正确性。

碎煤加压气化炉配套煤气水分离装置优化改造

煤制天然气项目配套煤气水分离装置在运行中出现煤气水贮槽排污管线排料困难、余热回收器堵塞、外送重芳烃水含量高等问题。针对存在问题经过多次研究分析,通过采取煤气水贮槽技术改造、余热回收器前增加煤气水尘分离器、新增2台重芳烃分液罐等有效措施,保证了煤气水分离装置安全、稳定、长周期运行。

流化床气化旋流—过滤复合除尘设备的功能耦合研究

流化床气化出炉合成气中含尘量高,通常采用多级旋风分离器+颗粒床过滤的方式进行气固分离,工艺流程较长。本文提出一种耦合旋流分离与过滤分离功能的新型旋流-过滤复合除尘设备,可缩短除尘工序工艺流程。通过冷模实验考察了复合除尘设备的分离性能,采用正交实验方法确定了各因素的影响程度,采用单因素实验获得了除尘器性能的变化规律。研究结果表明,旋流分离可去除大部分粒径>1μm的粉尘颗粒,颗粒床过滤几乎可以捕集<1μm的大部分微细粉尘,复合除尘设备的整体分离效率稳定在99.9%以上。

热解压力及气氛对神府煤焦气化反应活性的影响

利用加压热重分析仪研究了热解压力和气氛对神府煤焦CO2气化反应活性的影响。实验表明,在氮气中,加压热解导致焦油发生再沉积和再聚合反应,即焦油的二次反应,在煤焦颗粒表面上形成二次反应产物层,其活性很差,覆盖煤焦微孔的开孔,影响煤焦的初期气化反应性。氢气中热解,氢气与煤焦中的碳发生加氢气化反应,生成甲烷和其他碳氢化合物,在煤焦颗粒上产生活性位,对煤焦起到活化作用,高压加氢热解有利于加氢气化反应和提高产物煤焦的气化反应活性。加氢气化反应可以在一定程度上消除焦油二次反应的负面影响,并活化煤焦。

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%。

煤焦与水蒸气的气化实验及表观反应动力学分析

在Thermax500型热重分析仪上对褐煤煤焦与水蒸气的气化反应进行了实验研究,并采用n级速率方程和Langmuir-Hinshelwood(L-H)速率方程考察了反应气体分压的影响。实验系统压力为0.1和0.6MPa,其中0.1MPa下水蒸气浓度分别为5%,10%和20%,0.6MPa下的水蒸气浓度为20%。气化反应在恒温条件下进行,温度分别为850、875、900、925、950和1000℃。实验发现,反应速率随温度和压力的增大而加快,900℃以下为化学反应控制区,不同压力下的表观活化能数值接近,而900℃以上由于受到扩散阻力的作用,表观活化能不同程度降低。采用n级速率方程计算得到褐煤煤焦与水蒸气的反应级数n为0.34,活化能E为153.7kJ·mol-1,采用L-H方程得到活化能为207.1kJ·mol-1,其速率方程可更精确地描述水蒸气压力的影响。