Advanced Oxidation to Reduce Emissions in Foundries from Coal Pyrolysis
نویسندگان
چکیده
Foundries employ green sand molds, which contain coal, silica sand, clay, water, and core binders. This represents one of the largest non-combustion users of coal. When the coal experiences high temperature during the metal casting process, it undergoes pyrolysis reactions and can generate significant amounts of volatile organic compounds. Some of the compounds are released as hazardous air pollutants, while others that are released from the coal that is closest to the molten metal, will re-attach to clay surfaces that are further away from metal via chemical deposition. This carbon on the clay surface hampers the clay’s ability to exhibit compressive strength, and hence more clay must be added. This carbon coating can be removed by an innovative advanced oxidation (AO) system [1], which has shown promising results in several U. S. foundries. This AO process diminishes air pollutants by 30 to 70% [2][3]; and this process has also diminished the clay and coal consumption by 20-40% [4][5]. This represents an important portion of costs in the foundries. The AO systems treat the water that is used in the green sand molding process by coupling ozone, hydrogen peroxide, ultrasonics, and underwater plasma. This generates advanced oxidants that react with the green sand in a manner that removes carbon from clay surfaces that had deposited following coal pyrolysis. As a consequence, full-scale foundries have found that they can achieve the same green compressive strength with 20-40% less clay additions when AO treatment is used [5]. The main objectives of this paper are: 1. To gain a better fundamental knowledge of how advanced oxidation affects green sand physicochemical properties. 2. To evaluate the effects of AO treatment on emissions via bench-scale analytical techniques;
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