Performance and Economic Analysis of a High-Efficiency Wide-Working Load Distillation System with Combined Ejector

A distillation system with an ejector for secondary steam utilization can effectively improve energy efficiency. However, the poor performance of the ejector under varying operating conditions makes it difficult for the distillation system to adapt to wide-range operational requirements. To address this challenge, a distillation system using a combined ejector with staged and continuous adjustment is proposed, and its performance and economic feasibility under wide load conditions is analyzed. The results show that when a combined ejector is used—composed of four fixed-structure ejectors with capacities of 6.25%, 12.5%, 25%, and 50%, along with a nozzle needle-adjustable ejector with a capacity range of 0–6.25%—the distillation system can combine the advantages of both staged and continuous adjustment. This system can utilize secondary steam across a load range of 2.53–100%, whereas a distillation system with a single continuously adjustable ejector can only utilize secondary steam within a load range of 40.5–100%. As the load varies from 0 to 100%, the proposed system achieves an average entrainment ratio of 0.525, with an efficiency not less than 50% of the design value over 95.23% of the range. In contrast, the conventional single continuously adjustable ejector has an average entrainment ratio of 0.177, and the distillation system efficiency remains above 50% of the design value for only 25.32% of the range. In a solar-assisted distillation system, the combined ejector improves the coefficient of performance (COP) by over 30%, with a payback period of less than one year. The findings highlight the system’s superior adaptability, efficiency, and economic viability for applications with unstable energy supply.