我国天然气供需现状及煤制天然气工艺技术和经济性分析

我国天然气消费市场持续增长,2008年天然气消费量达807×10^8m3,比上年增长10．1％;2020年天然气需求将增至2500×10^8m3,供应缺口达1000×10^8m3。与国际天然气价格相比,我国天然气价格水平仍然偏低。煤制天然气可以作为液化石油气和常规天然气的替代和补充,缓解我国天然气供应缺口。其竞争力主要源于可采用低价劣质煤．需要选择的主要是煤气化及甲烷化技术。含水含灰高、低热值的褐煤比较适于碎煤加压固定床或流化床气化。鲁奇煤气化工艺是煤制天然气项目首选的煤气化技术,此外还有流化床气化炉技术、BGL块／碎煤熔渣气化技术。鲁奇甲烷化技术是世界上首个商业化业绩,此外还有托普索公司甲烷化循环工艺技术和Davy甲烷化技术。以某年产10×10^8m3（标准）煤制天然气项目为例,其投资利润率16．16％（平均）,全部投资内部收益率16．21％（所得税后）,投资回收期7．72年,在经济上是可行的。目前一些地方和企业对煤制天然气项目的风险认识不足,首先应正确评价煤制天然气的能源效率和CO2排放,过分强调和夸大煤制天然气这个单一过程的高能源效率是不客观的：其次应认识到原料煤及产品价格是制约煤制天然气项目的关键因素;同时此类项目产品关联度低,并会受到天然气管网建设和管理的制约。     

煤气化工艺

煤气化工艺是生产合成气产品的主要途径之一,通过气化过程将固态的煤转化成气态的合成气,同时副产蒸汽、焦油（个别气化技术）、灰渣等副产品。煤气化工艺技术分为：固定床气化技术、流化床气化技术、气流床气化技术三大类。a）固定床气化技术。碎煤固定层加压气化采用的原料煤粒度为6 mm～50 mm,气化剂采用水蒸汽与纯氧作为气化剂。该技术氧耗量较低,原料适应性广,可以气化变质程度较低的煤种（如褐煤、泥煤等），得到各种有价值的焦油、轻质油及粗酚等多种副产品。该技术的典型代表是鲁奇加压气化技术和BGL碎煤熔渣气化技术。     

鲁奇FBDB煤气化技术及其最新进展

上世纪30年代,德国鲁奇公司开发出碎煤固定床加压气化技术,应用于煤气化项目,其关键设备为FBDB(固定床干底)气化炉,俗称鲁奇炉.几十年来,先后开发出四代鲁奇炉；同时,为实现气体和废水的达标排放,相继开发出煤气化的尾气处理和废水处理新技术.鲁奇FBDB煤气化技术成熟可靠,在无任何备用的情况下,单台气化炉年运转率超过93％,气化岛年运转率大于98％.由于采用碎煤进料方式,相对气流床干粉或水煤浆进料方式,备煤系统简单,投资及运行费用大为降低,同等规模下,气化岛加上配套空分的投资,约比水煤浆气化低20％.煤种适应范围广,除强黏结性焦煤外,从褐煤到无烟煤均可气化,包括水分、灰分较高的劣质煤；可副产焦油、轻质油及酚等多种高价值产品.新一代Mk+鲁奇气化炉,具有高产低耗、合成气中CH4含量高等特点,且环境友好,可以实现废水的零排放.     

煤制天然气的竞争力分析

通过煤炭气化将部分煤炭转化成天然气是我国一项重要的战略选择.煤制天然气项目的经济性要考虑多方面因素.煤制天然气的热值高于国家质量标准17.8%-21%,其他指标也高于或满足国家标准.对不同工艺煤制天然气生产成本的分析表明,生产成本中原材料和燃料动力费用所占比例高达60%左右,折旧和修理费用所占比例约为22%-30%,说明煤炭价格是影响天然气生产成本的最敏感因素,投资对生产成本的影响也较大.再考虑到管道输送等因素,建议煤制天然气项目应重点布局在新疆、内蒙古东部等地区.但无论是在新疆、内蒙古或其他地区的煤制天然气项目都难以与西气东输一线和陕京线国产天然气相竞争.新疆煤制天然气的竞争力高于土库曼斯坦进口天然气.内蒙古、山东的煤制天然气项目可与西气东输二线进口天然气竞争.此外,新疆、内蒙古和山东等地区的煤制天然气可与新增进口LNG(石油价格在80美元/bbl时)相竞争.从新疆到达华南地区的煤制天然气竞争力强于进口LPG.     

国家重点工程小湾电站首台机组正式投产发电

新奥集团股份有限公司年产60万吨甲醇／40万吨二甲醚项目在内蒙古鄂尔多斯市建成投产。目前装置运行平稳,生产负荷已达到70％以上。该项目采用水煤浆加压气化技术、耐硫变换及低温甲醇洗、净化技术、低压甲醇合成技术和新奥节能型二甲醚合成技术,以国内设备为主,建成国内最大的单系列煤基二甲醚装置。项目的建成投产为我国大型煤制二甲醚示范装置的建设提供经验,具有重要的借鉴意义。     

无须甲烷化制天然气技术

煤制天然气必须经过甲烷化,但甲烷化投资通常高达百亿元人民币。生物质项目受运距制约规模不大,甲烷化不适用于生物质项目,国内外无生物质制天然气先例。而"二元反应"法制天然气无须甲烷化,使合成天然气比"费托反应"法节省投资70%,降低运行成本55%。它使生物质合成天然气总投资几千万元就可以生产出合格天然气,热利用率由垃圾发电的13%提高到48%,由秸秆直燃发电的17%提高到74%,经济效益好,投资回收期为3~4年,而且高温焚烧无烟囱,无二噁英,不产生NOx和SO_2,焦油比现有气化技术约低1万倍。     

“正名”与去从

将煤制气称为煤制甲烷可能更为妥贴,在我国天然气供需形势将逐渐转变为供大于求,国产气生产、进口气合同需要优先保证前提下,煤制甲烷产能将受到严峻挑战。     

WSA硫回收工艺在生产中的应用

正中煤龙化哈尔滨煤化工有限公司40万吨/年甲醇装置,以块煤为原料,采用鲁奇纯氧连续气化技术制取粗煤气,粗煤气经中温变换、低温甲醇洗处理,得到净化煤气。低温甲醇洗分离出来的富含硫化氢的酸气去克劳斯硫回收装置副     

煤制气

以煤为原料经过加压气化后,脱硫提纯制得的含有可燃组分的气体。根据加工方法、煤气性质和用途分为：煤气化得到的是水煤气、半水煤气、空气煤气（或称发生炉煤气）,这些煤气的发热值较低,故又统称为低热值煤气;煤干馏法中焦化得到的气体称为焦炉煤气,属于中热值煤气,可供城市作民用燃料。     

煤制气

<正>以煤为原料经过加压气化后,脱硫提纯制得的含有可燃组分的气体。根据加工方法、煤气性质和用途分为:煤气化得到的是水煤气、半水煤气、空气煤气(或称发生炉煤气),这些煤气的发热值较低,故又统称为低热值煤气;煤干馏法中焦化得到的气体称为焦炉煤气,属于中热值煤气,可供城市作民用燃料。煤气中的CO     

对Texaco气化工艺的认识及炉温度的控制

Texaco水煤浆加压气化技术是目前工业化运行较好的第二代煤气化技术。由于在同样的工程条件下所表现出的工艺结果复杂多样,为此通过对气化炉中所发生的化学反应、流体力学分布和温度场以及传热过程进行分析,加深对水煤浆加压气化工艺的认识。气化炉温度的控制是工艺操作的关键,控制的原则是控制灰渣黏度达到25～40Pa·s,而实质是控制氧碳原子比。根据企业操作数据分析,气化炉温度的控制参数为：进料的O/C比一般应控制在0.9～0.95之间;气化炉压差应控制在0.05～0.06MPa;CH4含量控制在0.0008～0.001（体积分率）,CO2控制在18%～20%（体积分数）;6mm左右理想尺寸的渣应占20%～30%（质量分数）,且为圆形玻璃体;破渣机的压力指示值为2%～3%。在这些条件下,可达到合适的气化炉温度,获得高的有效气产率,并保证稳定运行。     

煤的气化技术及其应用

煤气化技术是环境友好的现代煤化丁的关键技术。介绍了当今世界主要的煤气化技术,着重介绍了已工业化生产的鲁奇、Transport、壳牌、德士古、康菲气化炉及我国自主开发的华东理工大学气化炉等技术,并且介绍了煤气化技术在煤气化联合循环发电和在煤化丁的合成油、合成氨、合成甲醇、合成烯烃等方面的应用。重点介绍了我国煤化工发展的具体情况。     

煤质对固定床气化炉气化性能影响的工业试验研究

在使用烟煤作为设计气化燃料的Lurgi固态排渣气化炉上,进行了褐煤气化实验,获得了褐煤固定床气化的工业实验数据。通过优化实验,确定了煤质改变条件下的Lurgi固定床气化炉的最佳工艺参数,并获得了褐煤的最佳气化指标。研究表明,针对煤质的特殊性采取一些针对性措施,可以在使用烟煤的固定床气化炉上完成褐煤气化,为设计褐煤固定床气化提供有力的参考。     

Method of gasification in IGCC system

A coal gasifier is designed to operate at the temperature range of 1200–1300 °C. The 1200 °C sets the lower limit to the carbon reforming efficiency of the high temperature reformer, and the 1300 °C is the lower limit of the fluid temperature of coal slags, below which they may be collected as non-fluid slag. The gasifier is connected to two syngas burners where a portion of product syngas is combusted with O₂ gas and produce ultra hot H₂O and CO₂ gases, these two gases enter into the gasifier and maintain the gasifier temperature at above 1200 °C and reform carbon into syngas. The temperature of the gasifier is controlled by the flow of O₂ gas into the syngas burner, where O₂ gas is completely consumed and none left to enter into the gasifier. This removes any possibility of forming oxidated products, and compressed CO₂ gas spray coal powder into the gasifier column and non-fluid slag is collected at the bottom. A higher level integration of oxidation–reduction cycle is shown for a IGCC system, wherein the exhaust gas of syngas turbine drives the reduction reaction of coal gasification.

A smooth and uniform temperature control within the gasifier assures high efficiency of carbon reforming and quality of product syngas. Conventional Lurgi gasifier relies on its large heat capacity and accumulating coal slag along the inner walls of the gasifier has made the gasifier bigger, lately as large as a three story building. The gasifier of the present design is constructed much smaller in its size, but with greater reforming efficiency.     

Underground coal gasification: From fundamentals to applications

Underground coal gasification (UCG) is a promising option for the future use of un-worked coal. UCG permits coal to be gasified in situ within the coal seam, via a matrix of wells. The coal is ignited and air is injected underground to sustain a fire, which is essentially used to “mine” the coal and produce a combustible synthetic gas which can be used for industrial heating, power generation or the manufacture of hydrogen, synthetic natural gas or diesel fuel. As compared with conventional mining and surface gasification, UCG promises lower capital/operating costs and also has other advantages, such as no human labor underground. In addition, UCG has the potential to be linked with carbon capture and sequestration. The increasing demand for energy, depletion of oil, and gas resources, and threat of global climate change have lead to growing interest in UCG throughout the world. The potential for UCG to access low grade, inaccessible coal resources and convert them commercially and competitively into syngas is enormous, with potential applications in power, fuel, and chemical production. This article reviews the literature on UCG and research contributions are reported UCG with main emphasis given to the chemical and physical characteristic of feedstock, process chemistry, gasifier designs, and operating conditions. This is done to provide a general background and allow the reader to understand the influence of operating variables on UCG. Thermodynamic studies of UCG with emphasis on gasifier operation optimization based on thermodynamics, biomass gasification reaction engineering and particularly recently developed kinetic models, advantages and the technical challenges for UCG, and finally, the future prospects for UCG technology are also reviewed.     

基于旋风渣膜气化炉的潞安烟煤煤气化特性实验研究

气流床气化技术是当前主流的煤气化技术,而已有的气流床气化炉一般采用悬浮气化,气化强度难以继续提高.通过在自主设计的旋风渣膜气化炉实验系统上,对潞安烟煤的旋风渣膜气化特性进行了实验研究,主要研究了运行负荷、蒸汽煤比对气化炉的气化温度、冷煤气效率、碳转化率等气化特性参数的影响规律.实验结果表明:潞安烟煤在旋风渣膜气化炉中具...     

Exergetic evaluation of biomass gasification

Biomass has great potential as a clean, renewable feedstock for producing modern energy carriers. This paper focuses on the process of biomass gasification, where the synthesis gas may subsequently be used for the production of electricity, fuels and chemicals. The gasifier is one of the least-efficient unit operations in the whole biomass-to-energy technology chain and an analysis of the efficiency of the gasifier alone can substantially contribute to the efficiency improvement of this chain. The purpose of this paper is to compare different types of biofuels for their gasification efficiency and benchmark this against gasification of coal. In order to quantify the real value of the gasification process exergy-based efficiencies, defined as the ratio of chemical and physical exergy of the synthesis gas to chemical exergy of a biofuel, are proposed in this paper. Biofuels considered include various types of wood, vegetable oil, sludge, and manure. In this study, exergetic efficiencies are evaluated for an idealized gasifier in which chemical equilibrium is reached, ashes are not considered and heat losses are neglected. The gasification efficiencies are evaluated at the carbon-boundary point, where exactly enough air is added to avoid carbon formation and achieve complete gasification. The cold-gas efficiency of biofuels was found to be comparable to that of coal. It is shown that the exergy efficiencies of biofuels are lower than the corresponding energetic efficiencies. For liquid biofuels, such as sludge and manure, gasification at the optimum point is not possible, and exergy efficiency can be improved by drying the biomass using the enthalpy of synthesis gas.