December 29, 2008
Gasification has garnered significant interest as an efficient way to convert domestic feedstocks such as coal, petroleum coke, or biomass into an intermediate synthesis gas (syngas), which can then be used to produce power in an integrated gasification combined cycle (IGCC) power plant, or chemicals and fuels in other downstream processes.
ConocoPhillips (Houston, TX) is pursuing a gasification unit at its Sweeny Refinery in Brazorta County, TX. The Sweeny Refinery complex currently processes 247 million bbl/d of crude oil, and produces about 5,000 tons/d of petroleum coke; the neighboring petrochemical complex (owned jointly with Chevron Phillips Chemical Co.) processes 115,000 bbl/d of natural gas liquids to produce 5.4 billion Ib/yr of ethylene and propylene.
Two related scenarios are being considered. One option would produce substitute natural gas (SNG; essentially methane), plus hydrogen and CO2, via a methanation unit, with the SNG used at the facility and sold into the Texas Gulf Coast natural-gas pipeline system. The other option would produce electricity via an IGCC power plant, plus hydrogen and CO2. Final selection is expected in 2009, with startup anticipated in 2014-2015.
The project will use ConocoPhilllps's proprietary ?-Gas technology, which utilizes slurry-fed, oxygen-blown, entrained-flow gasification. Engineering studies are under way to evaluate several local CO2 storage and enhanced oil recovery (EOR) options. "The ability to recover CO2 at elevated pressures in a gasification process helps to reduce the cost per unit to recover and compress the gas, which makes gasification an attractive clean-coal technology choice," says Michael Culligan, manager of the Sweeny Gasification Project Development.
Meanwhile, despite recent setbacks in the proposed use of IGCC power generation (Sept., pp. 8-14 and Oct., p. 6, and pp. 12-13), several such facilities continue to move forward. Among the most promising for the short term are Duke Energy's 632-MW Edwardsport IGCC Facility in Knox County, IN, which has a target 2012 in-service date, and Excelsior Energy's 600-MW Mesaba Energy Project near Taconite, MN, slated to start up in 2014.
The Mesaba facility will represent the first commercial-scale, multi-train (two) installation of the ConocoPhillips' gas gasification technology, and will be designed to handle sub-bituminous coal, bituminous coal, and blends of sub-bituminous coal and petcoke. As for carbon capture and sequestration (CCS), Excelsior's design will use proven amine scrubbing, dehydration and compression technology, but no water-gas shift process at this point. The system is being designed to initially capture 30% of the CO2 from the syngas prior to combustion in anticipation of CCS becoming economically justified or required by law, and plans are being developed to sequester the captured CO2 via EOR, according to Richard Stone, senior vice president of development and engineering for Excelsior.
Source: Chemical Engineering Progress
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