High-efficiency condenser of steam from a steam–gas mixture

Resumo

The design of a module for a high-efficiency condenser of steam with a high content (up to 15%) of noncondensable gases (NCGs) with a nearly constant steam–gas mixture (SGM) velocity during the condensation of steam has been developed. This module provides the possibility to estimate the operational efficiency of six condenser zones during the motion of steam from the inlet to the SGM suction point. Some results of the experimental tests of the pilot high-efficiency condenser module are presented. The dependence of the average heat transfer coefficient k̄ on the volumetric NCG concentration v̄ has been derived. It is shown that the high-efficiency condenser module can provide a moderate decrease in k̄ from 4400–4600 to 2600–2800 W/(m² K) at v̄ ≈ 0.5–9.0%. The heat transfer coefficient distribution over different module zones at a heat duty close to its nominal value has been obtained. From this distribution, it can be seen that the average heat transfer coefficient decreases to 2600 W/(m² K) at an NCG concentration v̄ = 7.5%, but the first condenser sections (1–3) retain high values of k̄ at a level of no lower than 3200 W/(m² K), and the last sections operate less well, having k̄ at a level of 1700 W/(m² K). The dependence of the average heat transfer coefficient on the water velocity in condenser tubes has been obtained at a nearly nominal duty such that the extrapolation of this dependence to the water velocity of 2 m/s may be expected to give k̄ = 5000 W/(m² K) for relatively pure steam, but an increase in k̄ at v̄ = 8% will be smaller. The effect of the gas removal device characteristic on the operation of the high-efficiency condenser module is described. The design developed for the steam condenser of a gas-turbine plant with a power of 25 MW, a steam flow rate of 40.2 t/h, and a CO₂ concentration of up to 12% with consideration for the results of performed studies is presented.