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Licensed for the sole use of the purchaser.See license agreement penalties for distribution. CGA G-1,8-2017 COMPRESSED CAS ASSOCIATION, INC. PAGE 3 The calcium carbide used in this process is manufactured by the reduction of high-quality quicklime (calcium oxide)with carbon from selected cokes at high temperatures of the carbide electric furnacing process.The acet- ylene manufacturing process produces a consistent quality hydrated lime with chemical properties that vary slightly depending on the calcium carbide source and production conditions. Carbide lime has a chemical analysis comparable to high-grade hydrated lime (see CGA G-1.5, Carbide Lime: Its Value and Uses) [4]. Carbide lime has a fine particle size and a characteristic grayish tint due to finely divided carbon and ferrosilicon. Small quantities of acetylenic impurities give carbide lime a characteristic odor, which quickly dissipates when exposed to air. Measuring the pH of carbide lime is a highly temperature-dependent endeavor and should be done under controlled laboratory conditions (see 5.1 for further information on carbide lime i Lime slurry from a wet generating process is generally processed to increase the solids content through lime ponds, decanting, membrane filtration, mechanical thickeners, and mixing with quicklime. Lime ponds, which also function as a storage facility, are usually excavations with earthen dike perimeters, Inactive lime ponds usually form a crusty surface when dry. This is due to the natural reaction of atmospheric carbon dioxide with calcium hydroxide to form calcium carbonate. However, calcium hydroxide remains stable several inches below the carbonate surface of the pond. 4.2 Lime uses Carbide lime is a versatile material that can often substitute for commercial hydrated lime. It is used in many chemical and industrial processes for neutralization, coagulation, precipitation, hydrolysis, chemical reactions, and numerous other applications. It is also used in agriculture for soil sweetening and for soil stabilization in highways, airfields, and other structural projects. Many environmentally beneficial uses include wastewater pH adjustment, lime precipitation of sewage effluent, sewage sludge stabilization, water purification and softening, neutralization of acidic waste streams, flue gas desulfurization of power plants, and stabilization of hazardous waste before disposal. It is also used to close hazardous waste sites. See CGA G-1.5 for a further description of carbide lime applications [4]. 5 Regulatory issues for carbide lime 5.1 Carbide lirrfe—a co-product Carbide lime is a co-product resulting from the manufacture of acetylene gas from reacting calcium carbide with water. Carbide lime is sold for many uses including but not limited to those identified in 4.2. In many cases, the lime meets American Society for Testing and Materials(ASTM) purity standards before use [5]. As long as the lime is being marketed actively, it is considered a product and not a solid waste. Due to the beneficial properties of lime in land application as described in 4.2, closure of lime ponds in strict accordance with solid waste regulatory requirements can be unnecessary and unwarranted. In this publication, CGA has identified responsible best practices to safely operate and close lime ponds while mitigating potential adverse environmental impacts. Carbide lime that can be classified as a solid waste is not considered a hazardous waste according to U.S. regulations. On November 13, 1979, EPA removed calcium hydroxide from the hazardous substance list under Section 311 of the Clean Water Act since it does not exceed the acute toxicity criterion when discharged to the environment[6]. Further, on May 19, 1980, EPA finalized regulations that adjusted the upper pH limit to 12.5 for hazardous waste under the characteristic of corrosivity. EPA established this upper pH limit principally so it would not inhibit lime use for beneficial processes such as waste stabilization. Finally, on April 5, 1995, EPA issued a regulation establishing a temperature range of 24°C to 26 IC (75 °F to 79 'F) to use when analyzing the pH of materials for the corrosivity characteristic when the material has a pH greater than 12. Since carbide lime cannot have a pH greater than or equal to 12.5 under these laboratory conditions, carbide lime is not a hazardous waste under the corrosivity characteristic[7]. This document licensed for the sole use of the purchaser. It may not be shared with any other person or used after the expiration date without the express written permission of the CGA_ Any unauthorized use. reproduction, distribution, or modification of this printed page will result in a$5,000 liquidated damages fee plus loss of access to CGA publications for one year for your company.