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Show 4.2.1 Candidate Research Projects . 4.2.1.1 Reduction of the Use of Coke. Coke batteries have high initial capital cost, continued operating and maintenance costs. related to the nature of oven design, and challenging environmental problems. The standard coke oven furn~ce .desl~ presently in use is the same design used for the last 70 years. While size of the furnaces has changed, the pnnclple IS the same: coal is indirectly heated by transferring heat through thin, fragile refractory walls ~o make ~oke. The coke making process must either be replaced with one that overcomes the current problems, or the lfon mak~g process must be modified to reduce or eliminate the requirement for coke. Past efforts to develop new coke making proc.ess~s to overcome the problems of the existing coke oven design have not been successful. Therefore, reductIon In coke usage represents the most direct path to reducing cost and environmental problems. The majori!y of North American furnaces inject natural gas, and in recent years much higher gas injection rates have been achieved. Natural gas injection at these new higher levels greater than 100 lb per ton hot metal (THM) has been beneficial in reducing coke consumption while increasing productivity at minimal capital cost. However, from. a long-tenn strategic viewpoint it is believed that natural gas can replace at most 250/0 of the furnace coke req~ement. Coal injection, on the other hand, could replace up to 400/0 and perhaps more of the furnace coke requlfement. Accordingly, the largest steel plants in the Chicago area and several others have installed coal injection. At present, coal injection is installed on 12 furnaces, representing almost 20 million tons or about 40% of the U.S. hot metal production. The major difference betvveen the recent North American coal injection projects and those elsewhere is that these North American projects are all designed to inject at high levels, 400 IbffHM. This level is economically essential to justify the capital investment required, as lower levels of coal injection would merely replace natural gas injection already available with no capital cost. The need for North American furnace operators to inject coal at high levels, 400 IbffHM, to maximize coke replacement requires efficient combustion at the tuyeres. A considerable amount of research has been performed in Europe and the Far East to study the key aspects of coal combustion in the blast furnace raceway (combustion) zone. Many of these studies have used laboratory or pilot-scale single tuyere combustion furnaces~ some of these have been supplemented by in-furnace measurements of raceway gas composition and temperature. Such studies have shown how combustion efficiency is increased with higher flame temperatures, oxygen enrichment, smaller coal particle sizes, higher coal volatile content, reduced coal moisture, etc. In blast furnace operation it has also been observed that combustion efficiency and overall use is affected by tuyere velocities, injection lance design, coke quality, and raw materials distribution. These laboratory studies and furnace operating experiences have provided valuable guidance to North American iron makers in the startup and operation of recent coal injection installations. However, these overseas studies are not tailored to North American coals or specific blast furnace conditions. The only significant coal injection research initiative in North America is the DOE Clean Coal Program Project at the Bethlehem Steel Burns Harbor Plant. Here, a full-scale coal injection system, capable of injecting at high rates, 400 IbffHM, has been installed on two medium-to-Iarge size furnaces producing each about 7000 THM/day. The test program will feature the exploration of the maximwn coal injection rate for a given coal grind size for up to four types of North American coals. The Bethlehem Burns Harbor DOE test program will furnish valuable empirical information on the suitable coal grind size for various injection levels for the most typical North American coals. This program could be enhanced by a complementary laboratory scale eiT?~ wi.th a raceway or tuy~re hot model. ~~ch a hot model could b.e us~d in a program to explore a wide array of co.al injection l~nce configurations, b.last condl~lOns , coal types, and gnnd SIzes. This program could also complement In-house studIes and furnace expenmental trIals at other steel company coal injection sites. A useful extension of the laboratory program could be the co-injection of other solid materials: waste oxides, fluxes fine iron ores titaniwn ore (to protect the furnace hearth), and plastics. The injection of plastics has been tested in Ge~any at Stahh~erke Bremen and holds great potential for energy efficient disposal of waste plastics that cannot be recycled by other means .. The co-injection test program could also. in?lude other fuels such as oil, tar, and natural gas; such co-injection practIces are already used but probably not optlllllzed at several U.S. blast furnaces . 8 |