Underground gasification of coal and lignite

The underground gasification of coal and lignite is of interest when traditional coal extraction is impossible or unprofitable and also with increasing demand for thermal and/or electric power. In the Soviet Union, at six industrial Podzemgaz stations, beginning in the 1930s, more than 15 million t of coal was processed to obtain more than 50 billion m³ of gas. The South Abinsk station operated from 1955 to 1996, while the Angren station has been operating since 1963. Research on the underground gasification of coal has been largely theoretical, without close connection to industrial practice, and the results are based on mathematical modeling and data from 50–70 years ago. Obviously, Russia’s leading position in the underground gasification of coal has been lost. Russia now lags a number of countries that are making significant investments in the process. Note that, in Russia, despite the obvious benefits of underground gasification of coal, interest in the process has waned, on account of its significant deficiencies: the possibility of gas filtration to the surface; insufficient controllability of coal-bed preparation and thermal processing; the relatively low heat of combustion of the gas produced; and considerable losses of gas and coal underground. Note also the environmental impact of the underground gasification of coal, associated with the deformation of rock, its thermal, chemical, and hydrogeological changes, increase in its temperature, and active chemical pollution of groundwater. An obstacle to the adoption of the underground gasification of coal is the lack of clear ideas regarding the preparation and use of fuel gas. Recommendations for improving the process focus on the design of the underground gas generator and the gasification of the coal bed, without addressing the technology of the underground system, whose cost accounts for ~75% of the total equipment costs. The method proposed in the present work for the preparation of fuel gas from coal challenges the notion that the gas produced in underground gasification of coal should be divided into two products: gas and the tar (hydrocarbons) that forms in the preparation of the gas for combustion. If the specified temperatures are maintained, no condensation of hydrocarbons in the equipment and gas lines is observed, and dry dust removal from the gas may be employed, without complex processing of wastewater and of explosive and toxic materials. That significantly improves the economic and environmental characteristics of the process, Analysis of the results shows that the proposed approach to purifying the fuel gas produced by underground gasification of coal and lignite reduces capital costs in construction of the system by almost half; and the costs of gas production by a factor of 1.7. The time to recoup the initial investment is shortened by 41%; the yield of thermal energy is increased by 10.5%; and annual power output is increased by 151296 MW-h.     

Noncatalytic coal char gasification

A simple particle model is used to interpret differential thermogravimetric data taken on the gasification of coal/char with CO₂, H₂ and H₂O. The model takes into account the major physical factors which influence the gasification rate, viz., the changing magnitudes of surface area, porosity, activation energy and effective diffusivity during gasification. Specific reaction rate constants based on surface area and activation energies are extracted from the data. Practical criteria for regimes of reaction rate and diffusion control and for particle isothermality are developed. For isothermal particles at low classical Thiele moduli, the data can be correlated with only one parameter, which has a simple physical interpretation.     

煤气化技术进展

介绍近年来国内外开发的几种先进煤气化技术以及变压吸附制氧工艺在富氧气化炉上的应用情况。     

Fluidized bed gasification of coal

Gasification of high ash India coal has been studied in a laboratory-scale, atmospheric fluidized bed gasifier using steam and air as fluidizing media. A one-dimensional analysis of the gasification process has been presented incorporating a two-phase theory of fluidization, char gasification, volatile release and an overall system energy balance. Results are presented on the variation of product gas composiiton, bed temperature, calorific value and carbon conversion with oxygen and steam feed. Comparison between predicted and experimental data has been presented, and the predictions show similar trends as in the experiments.     

煤气化工艺的比较

我国以油为原料的氮肥企业不能满负荷生产,很多厂在做“以煤代油”的方案研究。目前世界上技术成熟的煤气化工艺主要有以下5种:德士古水煤浆气化(Texaco)、谢尔干煤粉气化(Shell)、鲁奇公司循环流化床技术(CFB)、鲁奇公司块煤加压气化技术(Lurgi)、固定层常压气化(UGI)。各种气化工艺各有特色,对不同煤种各有优缺点,所以选择不同的气化工艺适应煤的不同性质,是工艺方案选择的原则,以达到投资最低、操作费用最少、生产成本最低的目的。1　各气化工艺特点1.1　德士古水煤浆气化技术德士古水煤浆气化技术属于气流床气化技术,是将粗煤磨碎,…     

油气化与煤气化的区别及经济性分析

基于GE煤气化和油气化技术,介绍了GE水煤气化和油气化的工艺技术特点及国内的应用业绩,并从工艺流程、工艺配置、主要工艺参数、经济性等方面进行了对比分析,详细说明水煤浆气化和油气化的区别、优劣,为业主选择气化原料及确定工艺流程配置提供基础依据。研究表明:相比GE煤气化工艺,GE油气化具有原料输送和储存流程简单,集渣、捞渣系统简单,黑水闪蒸流程简单;耐火砖使用寿命长,气化装置连续运行时间较长;原料消耗低,比氧耗低,粗煤气中有效气含量高,氢碳比高;公用工程消耗低;固定资产投资低等优点。煤气化的合成气单位生产成本受原料价格变动更为敏感。     

现代煤气化技术及其煤种的适应性分析

结合国内外煤气化技术发展现状与趋势,讨论了煤质特性对气化过程的影响及其在不同气化炉型中的适应性。分析表明,煤种的多样性及气化工艺的选择促进了煤气化技术的快速发展,气流床和流化床代替固定床是煤气化技术发展的必然所趋。在充分认识各类煤气化技术优缺点的基础上,应发挥优势,针对煤种选用炉型,开发具有单炉生产能力高、煤种适应性强、气体成分可调等优势的加压气化技术以及可有效利用煤气高温显热的两段或多段式气化技术。     

Texaco水煤浆气化装置配煤模型及其优化

优化配煤对Texaco水煤浆加压气化装置的优化运行具有重要的意义。针对Texaco水煤浆气化装置优化配煤问题,建立了一个管理决策级视角下的配煤优化模型。模型综合考虑了混煤指标、库存成本、市场价格、操作成本、堆存和转运消耗。采用预交叉差分进化粒子群优化算法对模型进行求解,算法将粒子群和差分进化相结合,避免算法早熟,提高了全局搜索能力和收敛精度。最后,以某化肥厂水煤浆配煤优化过程为研究实例进行仿真,计算结果验证了模型和算法的可行性。     

废弃矿井地下气化大直径排气钻孔过老空区技术实践

在当今全球倡导低碳经济的环境下,利用煤炭地下气化技术对已闭坑矿井遗留的煤炭资源进行二次回采在全球多地已取得成效。煤炭地下气化施工过程中存在大直径排气钻孔经过采空区时很难施工的难题,很大程度上对工程进度和安全生产都造成影响。基于此,工程技术人员经过合理论证及施工组织,采取水泥浆堵漏,充填裂隙,多次钻进、扫孔、纠斜、规则孔径等方法措施,成功解决该项难题,取得了很好的经济效益和社会效益。     

煤气化技术的应用与发展

介绍了国内外煤气化技术的发展概况和发展趋势,重点对几种典型煤气化技术的应用与发展进行了研究,并对Lurgi炉、BGL炉、GE气化炉、多喷嘴炉、清华炉、Shell炉、GSP炉、两段炉、航天炉等典型煤气化炉的结构、性能进行了对比分析。从8个方面分析了煤气化技术的选择需要注意的问题。提出了煤气化技术创新建议,指出未来煤炭的清洁高效转化利用将以大型、先进的煤气化技术为核心,以电、化、热等多联产为方向进行技术集成。     

新河烟煤地下气化模型

为了探索烟煤地下气化过程的基本规律,为新河“煤炭地下气化发电示范工程”制定合理的工艺参数,测定了新河烟煤反应活性,并进行了富氧-水蒸气地下气化模型实验;研究了不同工艺条件下,出口煤气有效组分含量、热值的变化规律.实验结果表明,气化初期因煤层中含水,纯氧直接气化,可获得合格的煤气;在保持汽氧比在1.5∶1～2∶1之间时,新河烟煤采用富氧-水蒸气正向供风、辅助孔供风和反向供风连续气化可获得有效气体组分在70%、热值在10 MJ·m^-3左右的煤气;新河烟煤的产气率平均为1950 m³·t^-1,煤层气化率可达到74.6%.     

燃煤反烧制气技术及反义型煤气炉的应用

介绍了反火型煤气炉的原理、制气技术及应用情况。     

煤气化化学与技术进展

阐述了煤气化化学及气化过程,说明煤气化过程主要包括煤的热裂解、部分氧化燃烧、炭的气化、炉渣的生成和排出4个转化步骤。论述了固定床气化技术、流化床气化技术、气流床气化技术3种煤气化技术的工艺、设备、优缺点和适用范围。从煤灰液渣对耐火衬里的腐蚀机理、煤灰化学组成、灰熔融性和灰熔融温度、液渣黏度四方面分析了气流床灰/渣特性。最后阐述了美国煤气化技术进展及发展方向,提出应重点开展IGCC煤气化、低阶煤(褐煤和次烟煤)气化技术研究,开展以提高气化炉可靠性、气化效率和煤种适应性为目标的气化炉优化研究,控制多种污染物排放至极低水平的合成气净化技术研究,低成本高效率的O2分离技术及H2和CO2的分离技术研究等。     

GSP气化炉内多相湍流反应流动模拟研究

采用涡耗散概念(EDC)模型,对某化工厂的GSP气化炉内多相反应流场进行了数值模拟研究.计算中采用Realizable k-ε湍流模型对雷诺平均后的N-S方程进行封闭;采用离散相随机轨道模型来模拟气化炉内煤颗粒的弥散运动;采用P1模型对燃烧的辐射传热进行模拟.计算结果表明:气化炉内为强旋射流流场,颗粒在气化炉顶部回流区...     

Effects of alkaline metal on coal gasification at pyrolysis and gasification phases

A Chinese high-rank coal was acid-washed and ion-exchanged with Na and K to prepare the H-form, Na-form and K-form coals. After pyrolysis, H-form, Na-form and K-form chars and two additional H-form chars (acid washed Na-form and K-form chars) were prepared to investigate the effects of alkaline metal (AM) on coal gasification at the pyrolysis and gasification phases. The H-form char had the highest pryolysis rate; the H-form char had a relative low gasification rate. The AM loaded coals exhibited relative low pyrolysis rate, while the corresponding chars had high gasification reactivity. Acid-washing reduced the reactivities of Na-form and K-form chars. AM inhibited the progress of graphitization of the base carbon resulting in a more reactive char of less ordered crystalline carbon structure. A kinetic model incorporating AM-catalyzed gasification and non-catalytic gasification was developed to describe the gasification rate changes in the char conversion for AM-catalyzed gasification of chars.     

浅议煤气化技术的选择

原化集团有限责任公司在已有80kt/a合成氨和40kt/a串联醇及60kt/a并联醇的基础上，计划再上一套100kt/a低压并联醇项目。为使低压并联醇项目达到高技术水平，拟采用4．5～5MPa压力等级，接在高压机4段出口，既降低原料气压缩机能耗，又降低循环机能耗。由于甲醇生产要求造气供含氮很低的水煤气(最好CO≥40％，H2≥50％)，     

压力对煤气化反应的影响

为了提高煤气化效率,分析了影响产能的重要因素——压力。研究了压力对煤热解过程、煤焦燃烧速度及煤焦气化反应的影响。研究发现:加压热解情况下,挥发分和焦油产率均下降,但煤气产量增加,推测是因为焦油发生二次反应造成的。随着压力的增大,煤焦明显膨胀且比表面积下降。但过高的压力下,膨胀度减弱,易生成孔隙率高、薄壁的煤焦颗粒。提高O2分压,煤燃烧速度加快且生成的小颗粒较多。提高气化剂分压,煤气化速度加快,且蒸汽分解速度大于CO2还原速度,但生成的煤气对气化反应有抑制作用。     

气化对煤质的要求

介绍了气流床气化对煤质的要求,论述了煤的水分、反应活性、粒度和灰分对气化的影响。研究表明,煤的内水含量是决定煤浆性能的主要因素,灰渣的黏温曲线比灰熔点对气化炉的操作更具指导意义,选择在操作温度区间灰渣黏度变化平缓的煤种有利于气化炉的安全、平稳运行。     

煤气化技术发展趋势

介绍了固定床、移动床、流化床和气流床等煤气化的各种方式以及各种气化方式适用的煤种,并对煤气化的发展趋势及方向做了简要概述。