Surface condensers leakage

The gas that accumulates inside the surface condenser is called the noncondensable load to the steam jets. Some of the noncondensable load consists of C02 accidentally produced when the boiler feedwater is vaporized into steam. Air leaks through piping flanges and valves are other sources of noncondensable vapors. But the largest source of noncondensable vapors is often air drawn into the turbine case, through the shaft s mechanical seals. To minimize this source of leaks, 2 or 3 psig of steam pressure is ordinarily maintained around the seals. However, as the turbine s shaft seals deteriorate, air in-leakage problems can overwhelm the jet capacity. This will cause a loss of vacuum in the surface condenser. 

The curve in Fig. 18.4 also represents the best possible vacuum that can be obtained in any surface condenser. The majority of surface condensers I have seen do operate right on the curve. Condensers operating below the curve are typically suffering from air in-leakage through the turbine shaft seals. 

Two SJEs are installed in parallel on the surface condenser (Figure 11.10), mainly to remove air leakage and uncondensed gases/vapour (50 kg/h of dry air and 373 kg/h of water vapour). The two ejectors require 1254.7 kg/h of MP steam, which after use is condensed by... 

The solubility of inlet gas oxygen in the Stretford liquor is a function of the oxygen partial pressure and the process temperature. Absorbed oxygen is undesirable since it initiates the oxidation of hydrosulfide ions to sulfate and thiosulfate. Some geothermal noncondensable gas may contain over 10 vol% of oxygen as a result of excessive air leakage into the turbine surface condenser, which is operated under vacuum. In this extreme situation, it has been reported that soda ash consumption is two to three times greater than normal. 

Control. It is necessary to have some over-surface and to have a proper baffling to allow for pressure control during process swings, variable leakage of inerts, etc. One designer adds 50% to the calculated length for the oversurface. The condenser must be considered part of the control system (similar to extra trays in a fractionator to allow for process swings not controlled by conventional instrumentation). 

A small leakage current flows from the aluminum plate at its contact with the surface of the electrolyte, but this can be reduced to a negligible amount by making the surface line very short and insulating the aluminum plate where it enters the liquid. When so constructed the cell forms a very good condenser. The film acts as the di-... 

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