Medium-Btu gasification

Major Technical Issues Facing Low and Medium Btu Gasification... 

In particular, the subject today is the barriers to commercialization of coal gasification. There will be a couple of points where it will apply to liquefaction, but the concentration will be on gasification. I will talk mostly about high Btu coal gasification (i.e., pipeline gasification) as compared with industrial gasification (i.e., low/medium Btu gasification). 

Rensfelt, E., Blomkuist, G., Ekstrom, S., Espenas, B.G. Liinanki, L. (1978). Basic gasification studies for development of biomass medium-btu gasification processes. Energy from Biomass and Wastes, IGT, 14-18 August 1978. Paper No. 27, pp. 466-494. 

Elliott, D. C. Analysis of Medium-BTU Gasification Condensates June 1985 - June 1986, PNL-5979, Pacific Northwest Laboratory Richland, WA, 1987. 

During the late seventies and early eighties, when oil prices rose after the 1973 war, extensive research was done to change coal to liquid hydrocarbons. However, coal-derived hydrocarbons were more expensive than crude oils. Another way to use coal is through gasification to a fuel gas mixture of CO and H2 (medium Btu gas). This gas mixture could be used as a fuel or as a synthesis gas mixture for the production of fuels and chemicals via a Fischer Tropsch synthesis route. This process is... 

Chaudhari, S.T., Ferdous, D., Dalai, A.K, Bej, S.K, Thring, R.W., and Bakhshi, N.N. (2000). Pyrolysis and Steam Gasification of Westvaco Kraft Lignin for the Production of Hydrogen and Medium Btu Gas, Abstracts Progress in Thermochemical Biomass Conversion, Tyrol, Austria, 17-22 September. 

This paper touches on the chemistry of coal gasification and liquefaction comments on the current status of conversion processes and the influence of coal properties on coal performance in such processes and examines the contributions which coal conversion could make towards attainment of Canadian energy self-sufficiency. Particular attention is directed to a possible role for the medium-btu gas in long-term supply of fuel gas to residential and industrial consumers to linkages between partial conversion and thermal generation of electric energy and to coproduction of certain petrochemicals, fuel gas and liquid hydrocarbons by carbon monoxide hydrogenation. 

While on the subject of coal gasification, we should remember that low- and medium-Btu gas from coal should be considered as lower cost alternatives to pipeline quality high-Btu gas. For one thing, the capital investment for low-Btu gas plants is lower than the high-Btu gas plants as shown below ... 

As a result of this sudden about-face by the Carter Administration and their new found religion in switching to natural gas, it shouldn t surprise anyone to find there will be little incentive for anyone to keep working very hard on coal gasification whether it be for low-Btu, high-Btu or medium-Btu gas or any combination of them. 

Another important consideration is that Medium-Btu plants require oxygen. If an oxygen plant must be built with the gasification unit, the economics of scale dictate that plants of larger than 30 billion Btu/day output would be necessary. A plant of 50 billion Btu/day is estimated to cost about 200 million. The cost of the clean gas produced at the gate has been estimated to be 3.75 - 4.50/MM Btu depending on cost of coal, capital and other factors. 

High-BTU Coal Gasification (Advanced Technology) Medium-BTU Coal Gasification... 

This process produces low or medium Btu gases from wood and wood wastes, agricultural residues and MSW. Processing these synthetic gases with water can produce ammonia, methanol, or hydrogen. Commercial gasification systems exist, but their widespread use has been limited by hauling distances for the feedstock. 

The most widespread approach to gasification is the anaerobic digestion of manures and land-based aquatic biomass. This conversion process produces either a medium-Btu gas. which can be used on-site, or in some cases, upgraded to a substitute natural gas (SNG). 

The objective of this paper is to present experimental data on effects of operating parameters, including the catalytic effects of wood ash, calcium oxide, and calcium carbonate, on wood gasification in a continuous reactor. These results will be utilized to guide operation of a multi-solid fluid-bed (MSFB) wood gasification process which is being developed by Battelle to improve the economics of producing a medium-Btu gas or synthesis gas from wood and other biomass (2). 

Producer Gas - Low or medium Btu content gas, composed mainly of carbon monoxide, nitrogen(2), and hydrogen(2) made by the gasification of wood or coal. 

All of the major operations associated with low-, medium-, and high-Btu gasification technology (coal prelrealment, gasification, raw gas cleaning, and gas benefidation) can produce potentially hazardous air anissions. Auxiliary operations, such as sulfur recovery and combustion of fuel for electricity and steam generation, could account for a major portion of the emissions from a gasification plant. 

It should also be pointed out that gasifiers operated at steam to oxygen ratios as low as possible provide the thermally most efficient and lowest cost route to the production of medium BTU gas (1). The co-production of pipeline gas in the gasification step improves the overall thermal efficiency of various liquefaction processes (Flscher-Tropsch, Methanol, Mobils MTG route) by 13 to 18 % (2). 

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