The mutual effect between dual thermal power units under the advanced configuration of two units sharing one dry cooling tower and the energy-efficient and low-emission operation strategy

Abstract

For a thermal power plant configuration of two power units sharing one dry cooling tower, a comprehensive computational framework was developed to reveal the mutual effect between dual units via analyzing the competition between the air-cooled radiators which are owned by two units and coupled by the shared tower, under various environmental factors and unit power load schemes. Results showed that an increase in crosswind speed vcw aggravates the uneven performance distribution among radiators, but variations in ambient temperature ta have little impact. Each growth of 10 °C in ta results in a drop of ∼1.4% in power cycle efficiency ηe for both units operating at rated load, corresponding to increases of ∼9 g/(kW·h) and ∼26 g/(kW·h) in coal consumption and CO2 emission rates. ηe of the unit with its radiators facing towards ambient crosswind is 0.3% higher than ηe of the other unit as vcw exceeds 8 m/s. When both units operate with equal power load rate Np, a decline in Np aggravates the unevenness of air inflow among radiators and amplifies the predominance of air intake of windward radiators for the shared tower. An increase in Np causes a growth in ηe for both units, but this growth becomes slight as Np exceeds 75%. For both units operating with different Np, ηe declines more sharply with vcw for the unit with a higher Np, especially when radiators of the other unit face towards ambient crosswind. To maximize the overall operation economic efficiency, load difference between dual units should be minimized and radiators owned by the unit with a higher Np should be positioned against ambient crosswind. For dual units operating at a total Np = 150% on a strong-wind summer day with ta = 32.5 °C and vcw = 12 m/s, a maximum saving of 87.9 t standard-coal can be achieved by applying the optimal operating strategy, reducing daily CO2 emission by 250.3 t.