Optimization and renovation of energy complementary intra-plant/inter-plant integrated heat exchanger networks for waste heat recovery in the calcium carbide industry

The calcium carbide industry, characterized by its energy and emissions intensity, faces pressing sustainability demands in the “double-carbon” era. This study identifies substantial energy-saving opportunities within heat exchange networks. An optimization method is proposed that combines intra-/inter-plant heat integration to retrofit carbide plant heat exchange networks for energy efficiency. This approach is primarily based on pinch technology, where the heat exchange was first reconstructed within subsystems to minimize utility consumption. Results indicate that the intra-plant heat integration yields energy savings of 31.49 % for subsystem 1 and 28.79 % for subsystem 2. Subsequently, excess heat and cooling loads from the optimized subsystems were extracted as new heat exchange streams, facilitating heat exchange matching between subsystems. Thus, excess heat from subsystem 1 serves as heat source, while the excess cold from subsystem 2 acts as heat sink in inter-plant integration, creating a synergistic energy-saving mechanism to achieve inter-plant heat integration. The total energy from inter-plant heat integration reaches 10.83 MW, contributing to an overall heat recovery potential of 38.55 MW, ultimately achieving a remarkable total energy saving rate while minimizing the heat exchange units in this case. This research underscores the importance of multi-energy complementarity in advancing energy efficiency for future carbide industry.