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Reversing the Gas Crisis: The Methane Hydrate Solution

 

Commercialization of methane recovery from coastal deposits of methane hydrates could head off an impending gas shortage.

Fortnightly Magazine - January 2005

between 2000 and 2025 was predicted, requiring an additional 6.9 Tcf/yr of natural gas at an average load factor of 50 percent. Also, the predicted increase in coal-fired power generation was only from 311 GW to 376 GW between 2000 and 2025, compared with an increase from 311 GW to 412 GW between 2001 and 2025 in the [12]. This ongoing renaissance of coal-fired power generation is spearheaded by American Electric Power (AEP), which is planning to build a 1,000 MW Integrated Coal Gasification - Combined-Cycle (IGCC) clean coal unit by 2010, although it has a substantially higher investment cost than conventional steam-electric plants-on the order of $1350/kW [26]. However, in addition to higher thermal efficiencies, IGCC plants have negligible conventional pollutant emissions and can be modified to produce hydrogen instead of synthesis gas-an objective of the DOE $2 billion FutureGen Project.

But so far only two 250 to 300 MW IGCC plants have been built with DOE support. Jeff Johnson writes: "If IGCC installations grow worldwide, and if ongoing R&D projects to sequester CO 2 turn out to be feasible, IGCC could knock coal from this current position as the world's dirtiest fuel and biggest contributor to global warming" [26]. This refers to the use of a modified IGCC Process in which the raw synthesis gas produced by the initial high-pressure, high-temperature steam-oxygen gasification of the coal is converted with more steam by the well-known catalytic water gas shift reaction (CO+H 2O t CO 2+H2) to a hydrogen-CO 2 mixture (either before or after removal of the hydrogen sulfide formed from the sulfur content of the coal depending on the sulfur resistance of the water-gas-shift catalyst), and the CO 2 is then removed by one of the commercial processes and sequestered in suitable underground reservoirs. The remaining high-pressure product hydrogen then can be used for emission-free central power generation, or as a regional source of fuel for distributed generation and, eventually, high-efficiency electromotive surface transport with proton exchange membrane (PEM) fuel cells using high-pressure on-board hydrogen storage. However, a recent estimate of the investment cost of such a modified IGCC process, excluding the cost of CO 2 sequestration, was $1,642/kW [19]. The author has advocated this approach to a pollutant and carbon-emission-free coal-based power generation method in several recent publications [20].

Another use of clean synthesis gas produced by the IGCC process is the production of synthetic liquid fuels such as naphtha and diesel oil by the Fischer-Tropsch Process. Houston-based DKRW Energy is working on a $2.76 billion project to build such a plant in Medicine Bow, Wyo., which would produce 26,200 barrels/day of these synthetic premium liquid fuels and 1,000 MW of power [21,22]. However, this would not allow elimination of CO 2 emissions by catalytic water gas shift and CO 2 sequestration.

In view of evidence of tightening U.S. gas supplies and the competition between the majority of gas consumers and electric utilities for the supplies that are available, it seems that a concentrated effort should be made to demonstrate the feasibility of producing methane