Texaco Gasification Process
TEXACO INC.
(Texaco Gasification Process)
TECHNOLOGY DESCRIPTION:
The Texaco Gasification Process (TGP) is an entrained-bed, noncatalytic, partial oxidation process in which carbonaceous substances react at elevated temperatures and pressures, producing a gas containing mainly carbon monoxide and hydrogen (see figure below). This product, called synthesis gas, can be used to produce other chemicals or burned as fuel. Inorganic materials in the feed melt and are removed as a glass-like slag. This technology is an extension of Texaco's conventional gasification technology, which has operated commercially for over 40 years with feedstocks such as natural gas, heavy oil, coal, and petroleum coke.
The TGP treats waste material at pressures above 20 atmospheres and temperatures between 2,200 and 2,800 °F.
Slurried wastes are pumped to a specially designed burner mounted at the top of the refractory-lined gasifier. The waste feed, oxygen, and an auxiliary fuel such as coal react and flow downward through the gasifier to a quench chamber that collects the slag. The slag is eventually removed through a lockhopper. A scrubber further cools and cleans the synthesis gas. Fine particulate matter removed by the scrubber may be recycled to the gasifier; a sulfur recovery system may also be added.
After the TGP converts organic materials into synthesis gas, the cooled, water-scrubbed product gas, consisting mainly of hydrogen and carbon monoxide, should contain no hydro-carbons heavier than methane. Metals and other ash constituents become part of the glassy slag.
Texaco is designing a transportable system to treat about 100 tons of hazardous waste per day.
This system would produce about 6 million stan-dard cubic feet of usable synthesis gas per day with a heat content of approximately 250 British thermal units per standard cubic foot.
WASTE APPLICABILITY:
The TGP can treat the following wastes:
· Contaminated soils, sludges, and sediments that contain both organic and inorganic constituents
· Chemical wastes
· Petroleum residues
Solids in the feed must be ground and pumped in a slurry containing 40 to 70 percent solids by weight and 30 to 60 percent liquid, usually water.
Texaco has demonstrated gasification of coal liquefaction residues, petroleum production tank bottoms, municipal sewage sludge, and surrogate contaminated soil. Texaco is building a gasification power facility at its El Dorado, Kansas refinery that will convert about 170 tons per day of petroleum coke and Resource Conservation and Recovery Act-listed refinery wastes into usable synthesis gas.
STATUS:
The TGP was accepted into the SITE Demon-stration Program in July 1991. A demonstration was conducted in January 1994 at Texaco's Montebello Research Laboratory in California using a mixture of clean soil, coal, and soil from the Purity Oil Sales Superfund site, located in Fresno, California. The mixture was slurried and spiked with lead, barium, and chloro-benzene. Forty tons of slurry was treated in preparation for and during three demonstration runs. The Technology Capsule (EPA/540/R-94/514a) is available from EPA. Detailed demonstration results will be published in late 1995.
DEMONSTRATION RESULTS:
Preliminary findings from the demonstration are summarized below:
· The average composition of the dry synthesis gas product from the TGP consisted of 37 percent hydrogen, 36 percent carbon monoxide, and 21 percent carbon dioxide. The only remaining organic contaminant greater than 0.1 part per million (ppm) was methane at 55 ppm.
· The destruction and removal efficiency for the volatile organic spike (chlorobenzene) was greater than the 99.99 percent goal.
· Samples of the primary TGP solid product, coarse slag, averaged below the toxicity characteristic leaching procedure (TCLP) limits for lead (5 milligrams per liter [mg/L]) and barium (100 mg/L). Volatile heavy metals tended to partition to and concentrate in the secondary TGP solid products, fine slag and clarifier solids. These secondary products were above the TCLP limit for lead.
FOR FURTHER INFORMATION:
EPA PROJECT MANAGER:
Marta K. Richards
U.S. EPA
National Risk Management Research
Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7692
Fax: 513-569-7549
TECHNOLOGY DEVELOPER CONTACT:
Richard B. Zang
Alternate Energy and Resources Department
Texaco Inc.
2000 Westchester Avenue
White Plains, NY 10650
914-253-4047
Fax: 914-253-7744