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

NG Demand and Supply in China and Economic and Technical Analysis of Coal Gasification Technology

我国天然气消费市场持续增长,2008年天然气消费量达807×108m3,比上年增长10.1%;2020年天然气需求将增至2500×108m3,供应缺口达1000×108m3。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10×108m3(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。

China＇s natural gas market has been expanding continuously.In 2008,China＇s natural gas sumption reached 807×10^8m3,up 10.1% from the previous year.In 2020,China＇s natural gas demand is coI1- ex- pected to rise to 2500×10^8m3 and the country＇s natural gas shortage is expected to hit 1000×10^8m3.Compared with international natural gas prices,China＇s domestic natural gas prices are still too low.Coal-derived natural gas can be used as a substitute for liquefied petroleum gas and conventional natural gas to ease natural gas supply shortfall.The competitiveness of coal-derived natural gas lies in the use of low-price,low-quality coal and technologies needed are coal gasification and methane production techniques.High-water,high-ash and low-calorific value lignite is relatively more suitable for gasification in pressurized fixed beds or fluidized beds.Lurgi＇s coal gasification technology is the best option for coal gasification projects.Other technologies available include fluidized bed gasification furnace technology and BGL lump/fine coal slag gasification tech- nology.The Lurgi methanation technology is the world＇s first commercialized coal gasification technology.Other similar technologies include Topsoe＇s Recycle Methanation Process and Davy＇s methanation technology.Take a 10×10^8m3 coal gasification project for an example.Its rate of returns on investment would be 16.16% （on av- erage）,internal rate of returns on total investment would be 16.21% （after income tax） and investment would be recovered in 7.72 years.Such a project would be economically viable.Some local governments and enter- prises are not fully aware of the risks involved in coal gasification projects.Prior to launching a coal gasifi-＇ cation project ,the investor should first evaluate the energy efficiency and carbon dioxide emission level of the project.It would not be objective to overemphasize and exaggerate the high energy efficiency of a coal gasifi- cation project itself.It must be noted that the prices of feedstock coal and finished products are the most significant determinants for developing a coal gasification project.In addition,such project has relatively low product mix consistency and is subject to limitations associated with the construction and regulation of natural gas pipeline