Conventional Power

Challenge

When a deaerator is installed inside a boiler house, it is usually located on the top floor so as to generate the required NPSH for the Boiler Feed Water Pump. The NPSH is calculated using the water level in the storage tank. The required height of the boiler house is therefore determined by the total height of the deaerator. For a Stork Spray Type deaerator with its single tank design, the total height is a number of meters less compared to that of a spray-tray-type deaerator. Consequently the required height of the boiler house can be a number of meters lower, thereby allowing for considerable savings on investment costs.
The Stork deaerator design accommodates steam turbine bypass (trip) operation.

Solution

The most extreme condition for the deaerator is when the steam turbine suddenly trips. In this case the inlet temperature of the condensate is continuously lowered to the outlet temperature value of the condenser because the preheaters do not receive any more steam from the turbine. At the same time the steam supply from the turbine to the deaerator is cut-off. In this situation a large amount of steam is produced from the water volume in the deaerator. After a certain period of time the plant control system directs steam to the deaerator from the boiler, in most cases this is steam from the cold reheat line.
As the Stork type deaerator is a one tank design equipped with a large steam volume there is enough space to transport this large amount of steam to the sprayer(s). The full preheating of the condensate takes place in the sprayer section.

Benefits

A deaerator has to be designed for the maximum possible steam flow. When this maximum flow is determined by exceptional circumstances such as bypass conditions of preheaters, this will result in off-design situations at normal loads. In a Stork Spray type deaerator, the rangeability of the steam distribution system is very high and also additional heat sources can be combined to deliver sufficient heat under (exceptional) bypass conditions. When required separate steam distribution systems can be installed, each optimally designed for specific operating conditions.

Location: Germany

Fuel type: Coal

Output: 500 MW

Features: Used for district heating

Deaerator size: Total length 39000 mm x Dia 4100 mm

Year of delivery: 2010

Outlet flow: 616 kg/s

Operating pressure: 11.14 Barg

Gross volume: 303 m3

Total weight: 174 tons

Performance: 7 ppb

Design code: EN13445, PED