Condenser exhausting involves the removal of air and other non-condensable gases from the steam space of power plant condensers. The purpose of removing these gases is to maintain the lowest possible turbine backpressure. The equipment used for this application is crucial to the efficient operation of thermal and nuclear power plants.
Geothermal Gas Removal
Similar in application to condenser exhausting, geothermal gas removal involves the removal of air and other non-condensable gases from the steam space of the condensers. However, in geothermal power plants, the steam used to drive the turbine is extracted from the earth and contains large amounts of corrosive gases. The gases must be removed from the condenser in the most efficient manner possible.
In this application, vacuum pumps are used to maintain a siphon in power plant cooling water systems. Maintaining a siphon allows cooling water circulating pumps to maintain design cooling water flows with minimum power consumption. Single stage liquid ring pump packages, often supplied with priming valves, are ideal for this application because they prevent ingesting of water slugs into the pumps.
Fly Ash Conveying
This application consists of pneumatically conveying fly ash from the precipitator hoppers to a central dry collection point under vacuum. The main advantage of this type of conveying system is that since the ash is being conveyed under vacuum, any leakage is of air inward, and not ash outward.
Flue Gas Desulphurization
When flue gas is scrubbed to remove sulfur compounds, an aqueous slurry results. It is advantageous to remove the water from the slurry and handle only the solid material. This is done using vacuum filters.
Turbine Gland Exhausting
Steam turbines employ a gland to seal the shaft against inward air leakage. These glands are sealed with steam. In order for them to function as designed, excess steam and condensate must continuously be removed.
Boiler makeup must be deaerated prior to being introduced into the system. This is sometimes done in a vessel called a deaerator. A vacuum is pulled on the vessel and the makeup water is passed through it to remove all dissolved gases prior to introducing it to the system.
Condenser Initial Evacuation (Hogging)
In order to start a thermal power plant, a condenser must be brought from atmospheric pressure to vacuum. In some systems, requirements preclude the use of the condenser exhauster to perform this job. In these cases, a separate vacuum device is used.