Investigation into Operating Conditions of a Dry Mechanical Draft Cooling Tower at the TETs-12 Cogeneration Power Station of PAO Mosenergo

Abstract

The results of the comprehensive investigation into operation of a dry mechanical draft cooling tower (DMDCT) of a PGU-220 power unit at the TETs-12 cogeneration power station of PAO Mosenergo are presented. Thermal performance of the main and auxiliary DMDCTs and their individual sections is examined. To determine the cooling-air flowrate, a rake consisting of 11 velocity transducers and thermocouples was installed at the fan outlet above the fan diffuser of the examined section. The DMDCT heat balances calculated on the basis of water- and cooling-air conditions agree with each other with a maximum error of 8%. The overall thermal performance indices of the main and auxiliary DMDCTs were lower than those specified by the supplier. Performance of DMDCT fans was investigated at different blade angles α. According to our calculations, the effect of better fan performance in terms of an increase in the power of a steam turbine in a combined-cycle unit at α > 15° does not compensate for an increase in the power consumption of fan motors and even reduces the amount of delivered power. Therefore, the range of α = 10°–15° for the fans of the main DMDCT may be considered optimal. As to the auxiliary cooling tower, an increase in the air flow at α = 17° can offer a wider operation range for the fans at high ambient air temperatures, which is important considering limitations on the supply temperature (below 35°С) of the auxiliary equipment cooling water. The investigation of DMDCT operation during the cold season yielded the dependence of the minimum heat load of DMDCT, required for its safe operation, on the ambient air temperature. The study into the performance of the humidification system revealed that its efficiency is inadequate. The best solution to this problem is to replace the normal humidification nozzles with nozzles with smaller diameter holes to improve water dispersion that will prevent the water drops from falling onto the ground and improve the efficiency of the humidification system while decreasing the water flow to the humidification nozzles.