Analysis of the Operational Characteristics and Performance Comparison of Steam Screw Pressure Matcher Based on Twin-Screw Expander

Abstract

To address the discrepancy between the steam parameters extracted by pure condensing units/combined heat and power units and those required by users, this paper introduces the design of a steam screw pressure matcher(SSPM) and determines its optimal steam supply scheme. The SSPM primarily comprises a twin-screw expander (TSE), twin-screw compressor(TSC), electric motor, and generator. Initially, models were developed for a 300-MW subcritical intermediate reheat condensing steam turbine unit, an SSPM, and a desuperheater and pressure reducer(DPR). Subsequently, these models are incorporated into the Ebsilon Professional software to simulate the operational characteristics of the SSPM. The performance parameters of the two options are then compared and analyzed. Simulation results reveal that the operational characteristics of the SSPM closely correlate with the mass flow rate of the TSE. As the TSE mass flow rate varies from 47 to 91 t/h, the efficiency of the TSE declines from 66.3% to 65.3%, while the power performed by the SSPM increases from −2457.978 to 1558.469 kW. Under identical operating conditions, the SSPM scheme exhibits a 6.2%–12.4% improvement in efficiency compared to the DPR scheme. Building upon the aforementioned analysis, the SSPM demonstrates effective cascade utilization of heat steam energy and exhibits favorable regulation characteristics under variable operating conditions. Contrasted with traditional DPR, the SSPM notably mitigates constraints on steam extraction by boilers and enhances the maximum generation efficiency of a single unit.