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NASH condenser exhauster packages are used in steam cycle plants to efficiently remove inward air leakage from the condenser. The effect is to provide lower turbine backpressure, improve heat rates, and reduce generating costs.
The packages typically consist of a liquid ring vacuum pump (either a two-stage vacuum pump or a single stage vacuum pump with air ejector), air-liquid discharge separator, heat exchanger, and associated controls.
NASH condenser exhauster packages perform reliably, operate automatically, and hold the condenser at the best possible vacuum during unexpected transients of air leakage.
Hogging: Initial evacuation of the condenser to a pressure of 200 to 400 mbar abs. (6" to 12" Hg abs.) within a defined period of time before applying steam to the condenser.
Holding: Continuous exhausting of the air leakage into the condenser during normal operation in order to optimize the efficiency of the power generation.
To realize a low absolute pressure, two stage liquid ring vacuum pumps are the perfect solution. They offer a low absolute pressure with a small and compact system design. Two stage vacuum pumps work best with water cooled condensers.
Capacity Bonus: You get more capacity and save energy when water vapor is condensed ahead of the NASH liquid ring vacuum pump. This performance bonus is made possible by NASH conical porting.
Since more than two-thirds of the gas drawn from the condenser is water vapor, the NASH conical ported design is ideal for handling this air-vapor mixture. Spray water condenses a substantial portion of the vapor ahead of the pump and, as that condensate passes through the pump as a liquid, pumping capacity is increased and energy saved. This “NASH capacity bonus” is not possible with other pump designs.
Power plants sometimes use the plant's secondary cooling water for cooling the condenser exhauster system. This means that the cooling water temperature of the condenser exhauster system is higher than the cooling water temperature of the main condenser cooling water, which limits the pump performance. As a solution, an air ejector is added as a first stage to the vacuum pump. Single-stage vacuum pump systems with air ejectors can reach very low pressures, irrespective of the cooling water temperature.
The operating pressure of an air-cooled condenser is a function of the air temperature, not the cooling water temperature. The performance characteristics of the liquid ring pump and air-jet package allow it to track the condenser pressure over the entire range of cooling water temperatures.
Power plants continue to struggle with the changing demand for electric power. When the plant runs at low load, ordinary liquid ring pumps are prone to damage from cavitation, resulting in higher operating costs and shorter pump life.
The upgraded line of NASH TC pumps offers an innovative, patent-pending design that extends pump life by reducing the potential for cavitation damage without affecting capacity or performance. The new design is available on all TC models, and as an aftermarket upgrade to existing NASH TC pumps. Aftermarket upgrades can be performed in any Nash factory service center. The upgraded pump design offers the same fit as your original NASH TC, with only minimal piping changes to your NASH system. External connections are unchanged.
