Preparation of feed grade calcium formate from calcium carbide residue

Calcium carbide residue is generated from the reaction of CaC₂ (calcium carbide) and water in the production of acetylene in the chlor-alkali industry. The main component contained in calcium carbide residue is Ca(OH)₂ (calcium hydroxide). At present, great amounts of calcium carbide residue in China are disposed by land stockpiling or landfilling. These disposal practices cause serious environmental pollution and lead to resource wastage. Effective disposal methods by recycling and reusing the calcium carbide residue are urgently needed. In this paper, a novel method for producing feed grade calcium formate from calcium carbide residue is introduced. The calcium carbide residue and CO (carbon monoxide) are utilized as raw materials to prepare Ca(HCOO)₂ (calcium formate) through the carbonylation synthesis route. The optimal reaction conditions (reaction temperature = 200 °C, reaction pressure = 6 MPa, reaction time = 22.5 min, and slurry concentration = 0.125 g/mL) have been obtained through pilot-scale experimental studies with the aim of producing high-quality feed grade calcium formate product. Data from the continuous pilot plant are used to evaluate the economic feasibility of the production method. In addition, CO, which is acquired from industrial exhausts, is innovatively used as a reactant to produce calcium formate instead of being treated as a waste material, reducing carbon dioxide emissions significantly. Therefore, the proposed method is a very promising clean and green chemical technology that turns calcium carbide residue and industrial exhaust gas into a useful product, promoting the development of industrial waste recycling in China.