Performance Calculation, Analysis And Evaluation Of Coal-fired Power Station Combined Calcium Carbide Multi-generation System

Coal-based power and chemicals multi-generation is a crucial way of high utilization of coal and clean power generation. Coal-fired power generation occupies a considerable proportion on various generation forms and has mature technology in consequence of China’s rich coal resource. Integrating the thought of multi-generation into coal-fired power station is not only a breakthrough in multi-generation technology and traditional operation mode of power station, but also a new mentality for reasonable conversion coal and energy cascade utilization. So it is of great significance to energy sustainable development.Coal-fired power station combined calcium carbide is a new kind of multi-generation system which integrates oxygen-fuel calcium carbide production with generation technology. Oxygen-fuel calcium carbide reactor is in tandem with boiler, and lime feeding device and air separation unit are added. Dry pulverized coal, lime and oxygen are used as materials to produce calcium carbide. By-products flue gas and fly ash with unburned carbon are injected into furnace to release heat and combust, which can recovery their thermal and chemical energy.This paper takes 350 MW supercritical coal-fired unit combined 0.3Mt/a calcium carbide multi-generation system as research object. Firstly, chemical reactions in calcium carbide are modeling and calculating based on thermodynamic theory. The results show that calcium carbide which produced by pulverized coal and oxygen-fuel method has 65.97% purity. Producing 1t Ca C2, consumption of pulverized coal, lime and oxygen are 1747.08 kg, 980.5kg and 1285.25Nm3, power consumption is 554.28 k W·h. When improving oxygen purity, each parameter changes little but power consumption of oxygen-making increases greatly. While using different pulverized coal, each parameter varies significantly. Then, using exergy analysis theory calculates exergy loss of multi-generation system and each component. Calculation shows that exergy efficiency of system overall is 49.89%, exergy loss is 583.18 MW. Boiler is the weakest component in system for the lowest exergy efficiency and highest exergy loss, which exergy loss rate is 71.79%. Neither changing calcium carbide output nor unit capacity could improve the condition. Finally, relative energy saving ratio, cost of co-production and CO₂ emission per ten thousand RMB output value are used as three indicators to evaluate the performance of multi-generation system from energy, economy and environment aspects respectively. It can be found that comparing with the standalone system of both power generation and calcium carbide production, relative energy saving ratio of multi-generation system is 18.58%. Calcium carbide cost is 721.6RMB/t, power supply cost is 0.328RMB/k W·h. Both of them are lower than calcium carbide sales price and local network price. CO₂ emission per ten thousand RMB output value is 19.83 t, which decreases 17.29% than conventional coal-fired power unit. In conclusion, coal-fired power station combined calcium carbide multi-generation system has prominent energy utilization, economic and environmental superiorities.