THE CHEMICAL WORLD THIS WEEK
OCEAN MINING:
Continuous Dredging
on butadiene) from C 4 fraction feedstock. At Nagoya, Toray's two-step process will first convert Mitsubishi-supplied cyclododecane to cyclododecane oxime in a light-catalyzed nitrosation step. Lauryl lactam (azacyclotridecan-2-one) is then produced by Beckmann rearrangement. West Germany's Chemische Werke Huels, also a contender in the Japanese market, goes from cyclododecane to lauryl lactam in a four-step synthesis. Last month Huels formed a 50-50 joint venture with Japan's Daicel, Ltd., to build a 2000 metric-ton-a-year nylon 12 unit at Daicel's Aboshi plant. In France, meanwhile, Aquitaine-Organico is building a lauryl lactam plant using its own photonitrosation technology (C&EN, Nov. 10, 1969, page 14).
SULFUR DIOXIDE:
Riddance by the Sea A Berkeley, Calif., chemical engineer has proposed and tested what may well prove to be the simplest and least expensive method yet for reducing sulfur dioxide content of flue gases. University of California's Leroy A. Bromley has conducted experiments at the Bodega Marine Laboratory of the University of California in which he eliminates as much as 99.9% SOo from stack gas by scrubbing the gas with untreated sea water. His experiments, funded for three
months by California's Project Clean Air (C&EN, March 30, page 3 3 ) , are designed to investigate possible use of sea water for S 0 2 removal from stack gases of plants located near a convenient sea water source. The most attractive economic feature of the method, Dr. Bromley asserts, is to combine scrubbing of SOo by sea water with a desalination pretreatment facility. Dr. Bromley's group is currently studying use of S 0 2 instead of the sulfuric acid now needed to prevent alkaline scale in conversion units in pretreatment of sea water. Sulfuric acid could represent from 5 to 10% of the cost of converted sea water in large facilities. By Dr. Bromley's calculations, stack gas pollution control could be paid for by a desalination plant from the savings in sulfuric acid treatment costs. The Berkeley professor, with the help of chemical engineer Stanley Read, has built and tested several modifications of the unit. In one experiment cool air containing about 900 p.p.m. S 0 2 by volume passes countercurrent to sea water sprayed through a 6-inch-diameter, 1-foot-long single-stage absorber. This simple process removes 90% of the S 0 2 . By going to a 5-foot-long absorption tower packed with ceramic berl saddles, it's possible to strip 99.9% of the S 0 2 , Dr. Bromley claims. He estimates, in the case of a single-stage absorber, that the amount of sea water needed to cope with effluent gases coming from a typical power plant burning fuel is about 25 pounds of sea water per pound of stack gas. That's equivalent to the amount of cooling water used by power companies in condensers, Dr. Bromley notes. The sea water requirement may be reduced to one fifth, he says, by using several countercurrent absorbing stages or plates, or a packed or fluidized bed absorption tower. But the brine produced will have a pH between 2 and 3 and will require neutralization by a carbonate (or hydroxide). Alternatively, it could simply be diluted with additional sea water either before or after aeration and then returned to the sea. On the other hand, the resultant brine effluent from the single-stage absorber has a pH near 6 when the ratio of water to gas flow is 25 or more. In a preliminary estimate, Dr. Bromley calculates that scrubbing stack gases by sea water would cost about 16 cents per barrel of fuel oil burned. This is 7 cents less than the 23 cents per barrel figure for the dolomite-injection, wet-scrubbing process. These costs, he adds, apply to an 800Mw. generating plant.
Ocean mining was still largely just an idea in mid-July, when Deepsea Miner sailed out of Charleston, S.C., headed for Blake Plateau some 170 miles off the Georgia/Florida coast. The research vessel's mission has changed all that. During 26 days of tests, the ship and its equipment performed the first continuous dredging of the deep sea. Success of the tests marks a major step in the development program of Deepsea Ventures, Inc. The company is an oceanographic subsidiary of Tenneco, set up to develop the technology needed to mine from the ocean floor, process, and market metals found in what are loosely called manganese nodules. These nodules contain manganese, copper, nickel, and cobalt in varying amounts. Dredging has previously been carried out in shallow water (less than 600 feet) and in batch operations in the deep sea. Deepsea Ventures' tests with the prototype vessel were performed at about 2500 feet. In the mining system, a dredge collects nodules, which are carried up to the ship in conduit pipe by fluid flow. Air injected into the pipe lowers density of the water, and pressure differences cause it to flow up, carrying the nodules to a separator tank on the ship. Other major components are a hinged boom which helps the dredge negotiate varying water depths, and a dump valve which empties the pipe of solids if flow stops. Deepsea Ventures expects actual full-scale mining operations to be in the Pacific, where there are greater amounts of nodules and assay of metals is higher. The mining system will operate there at 12,000 to 20,000 feet. Action also continues on aspects of the program other than the mining technology. Deepsea Ventures expects to have a pilot plant on stream at its Gloucester Point, Va., headquarters by the end of the year processing nodules from a prime site in the Pacific. On another front, Tenneco is actively negotiating with a number of companies in different countries to join in a consortium with it and announced partner Metallgesellschaft, A.G., of Frankfurt, West Germany. Deepsea Ventures president John E. Flipse says Japanese companies are included. Tenneco hopes to have the consortium put together by early 1971. On the basis of the current tests, the company has narrowed its earlier $100 to $200 million investment estimate to $150 to $200 million for a 1 million ton-per-year operation. If all goes well, the company says, a commercial operation could get under way by the end of 1974. AUG. 31, 1970 C&EN 13
