Plate Heat Exchanger Generator Hydrogen Cooling System

The hydrogen gas inside the large hydrogen cooled steam turbine generator takes away the operating heat of the stator and rotor, and the plate heat exchanger is used for secondary water water heat exchange in the hydrogen cooling circuit. The generator body is equipped with a hydrogen cooler to transfer the heat to the closed desalinated water, and the plate heat exchanger then uses circulating cooling water to cool the closed desalinated water and send it back to the generator hydrogen cooler for circulation, achieving closed-loop temperature control.

Workflow

1. The high-temperature hydrogen gas inside the generator is cooled by the main hydrogen cooler, and the heat is transferred to the closed desalinated water (hot side);

2. Hot desalinated water enters one side of the plate heat exchanger;

3. The other side is connected to the circulating cooling water (cold side) of the power plant for counter current heat exchange;

4. The cooled desalinated water is returned to the hydrogen cooler of the generator for circulation; Cooling water carries away heat to the cooling tower.

Typical operating conditions: Closed desalinated water 45 → 38 ℃; Circulating water 30 → 36 ℃; The operating pressure is generally 1.0-1.6MPa, and the medium is clean desalinated water+circulating water.

The advantages of using plate heat exchangers for hydrogen cooled secondary heat exchange

1. * * High heat transfer coefficient * *, small temperature difference at the end, and high temperature cooling water conditions in summer, the temperature of the desalinated water can still be pressurized to the design value, ensuring that the generator can operate at full capacity without reducing output.

2. * * Compact size * *, occupying only about one-third of the space of the shell and tube type, with obvious advantages when the space between the steam turbine auxiliary equipment is tight.

3. The board can be disassembled for easy cleaning of scale on the circulating water side; The heat exchange area can be increased or decreased to adapt to the expansion and renovation of the unit.

4. Sensitive temperature control is beneficial for stabilizing hydrogen temperature and ensuring stable hydrogen purity.

##Shortcomings and risk points

1. Due to the limitation of the gasket, the upper limit of pressure and temperature resistance is lower than that of the shell and tube type, and it is not suitable to directly use hydrogen gas; It is strictly prohibited to use ordinary gasket plates for direct heat exchange between hydrogen and gas, as there is a risk of hydrogen permeation and explosion.

2. The narrow flow channel makes it easy for the circulating water to scale and block when the water quality is poor, which requires high water quality for the circulating water.

3. Rubber gaskets have an aging cycle and need to be replaced regularly, which is a periodic maintenance component.

Key considerations for selection (hydrogen cooling system specific)

1. * Media and Materials*

-Plate: 316L stainless steel; Select titanium plate when circulating water has high chloride ions;

-Gasket: EPDM (for hot water conditions in power plants), ordinary NBR is strictly prohibited; Select aging resistant gaskets according to the lifespan requirements of the power plant.

2. * Pressure and pressure drop*

Strictly match the design pressure of the closed water system; Control the allowable pressure drop on both sides, as excessive pressure drop can increase the energy consumption of the closed water pump.

3. * Reserve redundancy in heat exchange area*

Considering the scaling coefficient, a margin of 15-25% should be reserved in the area to prevent excessive hydrogen temperature caused by insufficient heat exchange after several years of operation.

4. * Mandatory requirements for water quality*

Circulating cooling water must be filtered and scaled properly; If the water quality is poor, priority should be given to shell and tube or pre filter.

5. * Safety and Standards*

Plate type only performs * * secondary water water heat exchange * *; The hydrogen side body cooler still uses a shell and tube hydrogen cooler; The equipment shall undergo pressure testing and non-destructive testing in accordance with the pressure vessel specifications of the power plant.