ABSTRACT
Commercialization ............................................................................. 39 2.4.3 General Aspects of Gasification ........................................................ 40 2.4.4 Gasification Processes........................................................................ 41
2.4.4.1 Lurgi Gasification ............................................................... 41 2.4.4.1.1 Lurgi Dry-Ash Gasifier .................................... 42 2.4.4.1.2 Slagging Lurgi Gasifier .................................... 44
2.4.4.2 Koppers-Totzek Gasification .............................................. 44 2.4.4.2.1 Koppers-Totzek Gasifier................................... 45 2.4.4.2.2 Features of the Koppers-Totzek Process.......... 46 2.4.4.2.3 Process Description of Koppers-Totzek
Gasification....................................................... 47 2.4.4.3 Shell Gasification................................................................ 49 2.4.4.4 Texaco Gasification ............................................................ 50 2.4.4.5
In Situ
Gasification ............................................................. 51 2.4.4.5.1 Potential Possibility of Using Microbial
Processes for
In Situ
Gasification .................... 53 2.4.4.5.2 Underground Gasification System ................... 53 2.4.4.5.3 Methods for Underground Gasification ........... 55 2.4.4.5.4 Potential Problem Areas with
In Situ
Gasification....................................................... 56
2.4.4.5.5 Monitoring of Underground Processes ............ 57 2.4.4.5.6 Criteria for an Ideal Underground
Gasification System.......................................... 57 2.4.4.6 Winkler Process .................................................................. 57
2.4.4.6.1 Process Description .......................................... 58 2.4.4.6.2 Gasifier (Gas Generator) .................................. 58 2.4.4.6.3 Features of the Winkler Process ...................... 59
2.4.4.7 Wellman-Galusha Process .................................................. 61 2.4.4.8 The U-GAS Process ........................................................... 62 2.4.4.9 Catalytic Coal Gasification................................................. 64 2.4.4.10 Molten Media Gasification................................................. 68
2.4.4.10.1 Kellogg Molten Salt Process............................ 68 2.4.4.10.2 Atgas Molten Iron Coal Gasification............... 70
2.4.4.11 Plasma Gasification ............................................................ 70 2.5 Mathematical Modeling of Coal Gasifiers .................................................... 72 2.6 Future of Coal Gasification ........................................................................... 76 References................................................................................................................ 76
Conversion of coal by any of the processes to produce a mixture of combustible gases is termed
coal gasification
, even though a large number of chemical reactions other than so-called gasification reactions are involved. Even though the product gases of coal gasification involve combustible chemical species, the purpose of gasification is not limited to generation of gaseous fuel, because the product gas can be easily processed to generate other valuable chemical and petrochemical feedstock. Commercial gasification of coal generally entails the controlled partial oxidation of the coal to convert it into desired gaseous products. The coal can be heated either directly by combustion or indirectly by another heat source. A gasifying medium is typically passed over (or through) the heated coal to provide intimate molecular contact for chemical reaction. The gaseous reactants react with carbonaceous matters of coal (i.e., coal hydrocarbons) or with other primary decomposition products of coal to produce gaseous products. Not all the gaseous products generated by such processes are desirable from the standpoints of fuel quality, further processing, and environmental issues. Therefore, coal gasification is always performed in connection with downstream processes, not only for final applications but also for gas-cleaning purposes. The primary emphases of coal gasification may be on electricity generation via
integrated gasification combined cycle
(IGCC) types, on syngas production for pipeline applications, on
hydrogen production
, or on synthesis of
liquid fuels
and petrochemicals as alternative sources of raw materials. With the advent of a hydrogen economy, the role of coal gasification in generation of hydrogen may become even more important.
