Calcium carbide slag is used to prepare raw materials for calcium carbide production, thereby yielding calcium carbide

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Calcium oxide is produced as a raw material for calcium carbide (taken from Baidu). The AirReduction Plant in Louisville, Kentucky, United States, realized early on the urgency of dealing with calcium carbide sludge. In 1948, a test facility for producing 60 tons of quicklime per day was built. Two 330 t/a quicklime production units were built between 1959 and 1962. Operation is safe, with nearly 350 operating days per year. Process for producing lime from calcium carbide: After dehydration, calcium carbide waste with a solid content of 60% is obtained; it is conveyed using a screw conveyor and distributed evenly within the granulator at three-quarters of its length. Granulation takes place to form spheres of various sizes ranging from 5 to 20 mm. These spheres are then dried in a pneumatic dryer at 350°C, and finally calcined in a rotary furnace at 900–1000°C. The drying of the material inside the dryer is achieved using the hot exhaust gas from the rotary furnace. The calcined recycled lime flows into the discharge hopper and is loaded onto vehicles for transport to the calcium carbide plant as raw material for calcium carbide production. Specifications of lime products: CaO content of not less than 86%, CO2 content of not less than 1.0%, moisture content of 0.5%. Impurities such as Fe2O3, H2, and SiO3 should be at no more than 13%. Particle size ranges from 5 to 20 mm. Raw materials and energy requirements (for producing 1 ton of lime): 1.33 tons of calcium carbide slag, 8 m3 of water, 37 Kwh of electricity, 0.16 tons of coal powder, 0.111 tons of nitrogen, 3 m3 of fuel gas, and 0.001 tons of fuel oil. This technical approach is feasible; it represents the best method for producing lime. The reason for this is that, first, the investment required for producing lime is less than one-tenth of that needed for producing cement ； Second, lime is a raw material for the production of calcium carbide, so there is no issue of finding an alternative market; a closed-loop cycle of calcium carbide waste – lime – calcium carbide – calcium carbide waste can be achieved using calcium as a carrier ； Third, by reducing the factors that constrain it, the calcium carbide process for PVC can be scaled up further to enhance competitiveness; at the same time, it also helps to preserve limestone resources. The economic and social benefits generated by using new methods to convert calcium carbide waste into lime are far superior to those of other treatment methods. However, it consumes a lot of energy, and the recycled lime used as raw material for calcium carbide can only be incorporated in 20% of the calcium carbide mixture – not in larger amounts – because the recycled lime contains many sulfur and phosphorus impurities, which can affect the quality of the calcium carbide.