Design and examples of Plate & Shell Heat Exchangers in Power Plant use

Vahterus Plate & Shell Heat Exchanger can be used for certain applications within a power plant.

Hot water – thermal-oil heaters

Hot water boilers are used to heat a district heating network or other source of heat. Typically, a boiler heats either hot pressure water or thermal oil. The Heat exchanger is then used to separate the boiler circuit from the heating network.

Design temperatures and pressures:

- 0 / 350°C

- 0 – 40 bar(g)

High pressure preheaters

High pressure preheaters are used in conventional power plants to pre-heat the condensate before entering the boiler. High pressure steam taken from the bleed of the high pressure turbine is used for heating the water. In large coal powered plants the design pressures for these units are typically over 200 bar(g), but in biopower plants the design conditions are suitable for PSHE.

Design temperatures and pressures:

- 0 / 350°C

- 0 – 150 bar(g)

Low pressure preheaters

Low pressure preheaters are used on conventional power plants to pre-heat the condensate before entering into the feedwater tank. Bleed steam from the low pressure turbine is used for heating. In most cases, these positions are very suitable for PSHE.

Design temperatures and pressures:

- 0 / 250°C

- 0 – 10 bar(g)

District heating condenser

A District heating condenser has similar design to a low pressure pre-heater. Condensing steam from the rear of the turbine or from bleed is used to heat the district heating water. In many power plants, district heating units are connected in series. District heating water is heated up in several condensers by using higher pressure steam in each condenser.

Design temperatures and pressures:

- 0 / 150°C

- 0 – 25 bar(g)

Turbine by-pass condensers

Turbine by-pass condensers are used to condense the steam in cases when the process or the steam turbine process is suddenly stopped. This steam is condensed either with district heating water or cold raw water. It is typical that this unit is only used 100 hours per year. Steam entering the unit is typically high pressure and has a very large degree of superheat. Over 100K superheat is typical.

Design temperatures and pressures:

- 0 / 400°C

- 0 – 40 bar(g)

Condensers convert steam into liquid. Steam condenses on the surface which is colder than the saturation temperature of the steam. In a plate heat exchanger, condensing is film condensing. This means that the condensing liquid creates a film where the steam condenses. Also, direct condensing on the plate surface occurs occasionally.