Source: World Dredging & Marine Construction
An aragonite production facility near Bimini, the Bahamas requires the pumping of the mineral slurry to a close coupled barge and then through 6,000 feet of line to a dewatering plant on Ocean Cay, a nearby artificial island.
The Marcona Ocean Industries operation uses the 24-inch Ellicott® cutter suction dredge “Allan Judith”. The dredge conveys the slurry to the barge “Guthrie III”, where the tramp and oversize are screened, then enters a densifying tank and is transported in a 30 to 35 percent slurry.
Aragonite is a pure form of calcium carbonate (CaCO3) which is competitive with U.S. domestic limestone. It occurs in billions of tons of the Grand Bahamas Bank, and is formed by precipitation out of ocean waters. It is used for such purposes as production of cement, manufacture of glass, agricultural liming and for neutralization of acid wastes by chemical companies. The material has a consistent, round, small grain structure and is very low in iron and other impurities.
Marcona is mining a deposit which is 22 miles long, two miles wide and ten to 25 feet thick in the shallow waters near Bimini.
Formed from two other cays, or islands, using the cutter dredges “Allan Judith” and the “Western Warrior”, the Ocean Cay reclamation took one year to create 65 acres. It has since been expanded to approximately 90 acres. The Ellicott® dredge has served reliably as the primary excavating tool for the mine for over 20 years.
The processing plant on the island consists of 12 cyclone separators and 12 vibrating screens which reduce water content to 20 percent. The aragonite is then moved by yard belt to single wing stackers, which deposit it over a live tunnel feeding onto a ship-loading belt. The material is loaded into ships at a rate of 3,400 tons per hour.
The company uses a 70,000 DWT belt-self-loading vessel to ship much of the material. This ship can unload at a rate of 4,000 tons per hour. For shorter journeys, an oceangoing barge and time charter vessels are used to ship the material.
Marcona Ocean Industries has a long term lease with the Bahamas government to exploit all the aragonite and other calcerous material in four major areas of deposit — Bimini, Joulter’s Cay, Tongue of the Ocean and Schooner’s Cay. The deposit is 55 miles east of Miami, Florida, and the product is shipped to East Coast and Gulf Coast markets.
Reprinted from World Dredging & Marine Construction