Design Of A 160 MW OTEC Plantship For Production of Methanol

Abstract

The use of OTEC plantships at their full potential to produce synfuels and energy intensive products would energy greatly exceeding present world demands. Methanol is a particularly attractive OTEC product because it can replace unleaded gasoline as a motor vehicle fuel and is a preferred feedstock for high efficiency fuel cells designed far electric power generation. Preliminary analyses indicate that OTEC methanol would be a more economical motor vehicle fuel than unleaded gasoline at present prices. ~ make the tropical oceans a resource which could supply OTEC methanol is produced in a process which involves reaction of oxygen, produced by water electrolysis on the OTEC ship, with coal to form carbon monoxide, which is then catalytically combined with hydrogen, produced in the same electrolysis process, to form methanol. Coal is transported to the plantship by bulk carrier and the methanol product is returned to shore by tanker.A preliminary description is presented in the paper of the process requirements, and projected output and costs of a 160 MW (nominal) OTEC methanol plantship. The design is based on scale-up of the 1980 APL design of a 40 MW ammonia plantship, with substitution of a methanol plant for the ammonia plant and readjustment of the ship system to accommodate the larger process and equipment space required.Three industrial organizations have participated in the design study. Brown and Root Development, Inc. (BARDI) performed the initial shipboard methanol plant design study and performance analysis benefiting from the detailed engineering design and cost information which BARDI had assembled for a barge mounted methanolfrom-natural-gas plant, and drawing on design, cost and operating information for the TVA ammonia-from-coal pilot plant, employing the Texaco gasifier, which was designed and built by BARDI. Information on a molten carbonate gasifier developed by Rockwell International, and ship integration and methanol synthesis data provided by Ebasco Services, Inc., are providing the basis for a second iteration of the plantship design and costs.Initial APL study of the molten carbonate gasifier process on a 160 MW plantship showed a significant increase in production over the initial shipboard methanol plant design study, to 1450 metric tonslday of fuel grade methanol, and a "first-cut'' estimated delivered cost at U.S. ports of $0.45 to $0.60 per gallon.

Vision of the U.S. Biofuel Future: A Case for Hydrogen-Enriched Biomass Gasification

“…We can envision a hypothetical modification of TRI gasification technology that takes advantage of its various unique features (low weight, low footprint, low environmental impact, need for water, need for low biomass contaminants, and so on) for use with seabed harvesting of algae technology. The Ocean Thermal Electric Conversion (OTEC) technology can provide electricity on site, and the sunlight and some drying of algae along with FTS water byproduct can provide direct energy and desalted water feedstock in the photoelectrochemical water splitting concept of generating H 2 fuel (such as that being planned by Coastal Hydrogen Energy, Inc., at a cost of less than $1/kg) at the plant site as co-located with the biorefining of algae. The oil tankers can make periodic visits to load up on the clean Fischer−Tropsch liquids to take to the large land-based oil refineries.…”