Carbon-calcium composite conversion of calcium carbide-acetylene system: On the imperative roles of carbon capture and solid waste recycling

As an important national basic industry in China, the production of calcium carbide faced with huge pressure on energy conservation and emission reduction because of the CO₂ emission and solid waste carbide slag. Therefore, it is necessary to realize the recycling of carbon and calcium in the production process of calcium carbide. A novel system of carbon-calcium compound conversion for calcium carbide-acetylene production was proposed in this work, which combines two-stage carbon capture and calcium carbide waste slag reuse processes to achieve CO₂ enrichment and calcium cycle. Based on the simulation data, the proposed system was comprehensively evaluated by material conversion, exergy and exergoeconomic analyses. It was found that the improved process performed better with an effective C, H, Ca atomic conversion rate for carbide furnace of 85.41% and CO₂ capture efficiency of 90.35%, compared with the referenced process of 64.51% and 0, respectively. The exergoeconomic analysis results suggested that more focus should be put on carbide furnace, acetylene reactor, re-carbonization furnace, gasifier and calciner since they are the top five of capital investments and exergy destruction. Besides, the carbide furnace, acetylene reactor, re-carbonization furnace and gasifier have relatively lower exergoeconomic factor (f_k) values of 1.00%, 0.93%, 2.27% and 3.07%, respectively, indicating that exergy destruction costs of these components can be decreased with the improvement of system thermodynamic and equipment performance. Furthermore, the calcium looping process formed based on the improved oxy-thermal method (OTM) process, using the captured CO₂ to mineralize carbide slag to form another calcification cycle for the production of calcium carbide-acetylene, has a higher exergy efficiency of 48.97% than the referenced process of 47.85%, and also achieves the lowest carbon emissions and the obvious reduction in CaO input. Results revealed that the proposed calcium looping system with high-efficiency, low-carbon and clean for calcium carbide-acetylene production, could be a promising process for carbon emission reduction in practical applications.