Demonstration plants, coal gasification

In this study detailed fault trees with probability and failure rate calculations were generated for the events (1) Fatality due to Explosion, Fire, Toxic Release or Asphyxiation at the Process Development Unit (PDU) Coal Gasification Process and (2) Loss of Availability of the PDU. The fault trees for the PDU were synthesized by Design Sciences, Inc., and then subjected to multiple reviews by Combustion Engineering. The steps involved in hazard identification and evaluation, fault tree generation, probability assessment, and design alteration are presented in the main body of this report. The fault trees, cut sets, failure rate data and unavailability calculations are included as attachments to this report. Although both safety and reliability trees have been constructed for the PDU, the verification and analysis of these trees were not completed as a result of the curtailment of the demonstration plant project. Certain items not completed for the PDU risk and reliability assessment are listed. 

Coalcon A coal gasification process using a fluidized bed operated with hydrogen. Developed by Union Carbide Corporation and the Chemical Construction Company, based on work on liquid-phase hydrogenation completed by Union Carbide in the 1950s. A 20-ton per day pilot plant was operated in the 1960s, but a planned larger demonstration plant was abandoned because of cost. 

The MHI gasification technology has been tested in Nakoso (Japan) in two pilot-scale gasifiers. A new IGCC project has been started that is a 250 MW air-blown IGCC demonstration plant located in Nakoso, where the former pilot plants were based, and will process up to 1500 ton/day of coal, which is about nine times more than the former 200 ton/day... 

The 168 ton coal/day demonstration plant was commissioned in 1996 and has since undergone a series of tests in standalone and in IGCC mode, operating for a total of 1200 hours until the year 2000. The plant is designed for the gasification of Indian coals with a high ash content of up to 42%. 

Daramend was used to treat approximately 100 m of PAH-contaminated soil at the Pacific Place Coal Gasification Plant in Vancouver, British Columbia, Canada. According to the vendor, the costs for this demonstration were approximately 95 per ton (D10085W, pp. 18-20). 

According to the vendor, landfarming was used to treat 10 yd of soil contaminated with PAH from a coal gasification plant in Connecticut. The cost of this pilot-scale demonstration was approximately 80/yd (D213718, p. 6). 

A search of the recent literature indicates identifiable plans for 19 high Btu coal gasification, 10 medium and low Btu gas, and 15 liquefaction projects. These range from laboratory scale, through seeking funds for feasibility studies, to the construction of commercial scale demonstration plants. The implied coal input in Table V is based on extrapolations to commercial size of those projects which are sufficiently advanced to provide data on input and/or output, site, and time frame. Other projects may be included later but they could not make a contribution before the mid-1990 s. 

Field demonstration of an aerated soil cell was conducted with soil contaminated by PAH originating from a coal gasification plant (Taddeo et al., 1989). After 78 days of compost treatment, total PAH concentrations were reduced from 6330 to 370 mg/kg compost. However, 5-ring PAHs including benzo[ pyrene were not degraded within this time period. 

It will be noted Ihm there are a number of similarities in the various designs. Although several designs may be required to satisfy varying compositions of coal feed, it would appear that ultimately coal gasification processes will he fewer in number in the future, once the demonstration plants complete their tests. 

The COGAS Process (4) was presented by the senior author from the Illinois Coal Gasification Group, the prime contractor for the DOE demonstration plant program. Economics for the conceptual commercial plant were presented in mid-1978 dollars. 

A tube-wall reactor, in which the catalyst is coated on the tube wall, is conceptually ideally suited for highly exothermic and equilibrium-limited reactions because the heat generated at the wall can be rapidly taken away by the coolant. Previous work (1) has numerically demonstrated that for highly exothermic selectivity reactions, the optimized tube-wall reactor is superior from both steady state production and dynamic points of view to the fixed-bed reactor. Also, the tube-wall reactor is being advanced as a possible reactor for carrying out methanation in coal gasification plants (2). From a reaction engineering point of view, it therefore seems appropriate to analyze the reactor for the analytically resolvable case of complex first-order isothermal reactions. 

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