Steam Turbine Condenser

Introduction

This is a 3D model of a steam turbine surface condenser.

3D Model Annotations

Surface Condenser

There are two types of condenser use in power plants, the direct contact type, and surface type. This 3D model shows a surface type condenser. Direct contact condensers spray water directly into the condenser to cool and condense the steam. Surface condensers use cooling water to cool the steam, but the two mediums do not come into direct contact with each other. Cooling water supplied to the condenser is taken from a heat sink (usually a cooling tower reservoir, lake, or river).

Extraction Piping

Extraction steam enters the condenser through this piping. Exhaust steam from the boiler feedwater pumps is discharged to the condenser also.

Steam Inlet

Steam from the low-pressure steam turbine is discharged to the condenser. The condenser is held at vacuum in order to provide a low back pressure for the turbine exhaust, which increases the overall plant efficiency.

Shell

The shell houses the internals of the condenser, including the tube support plates, tubes, hot well (lower part of condenser) and extraction piping; it is usually manufactured from heavy steel plates that are welded into one piece. Tubes are spaced away from the shell to allow steam to access all parts of the tube, thus increasing the condenser’s efficiency.

Waterbox

Cooling water flows through the waterboxes, which are installed at opposite ends of the condenser. One end of the condenser forms the inlet, whilst the other forms the discharge. Depending upon the size of the unit, a condenser may have one or more inlets and discharges (more than two is unusual). It is essential the waterboxes remain fully primed with cooling water to ensure water is adequately distributed to the tubes and that no overheating occurs. Waterboxes should have a protective corrosive resistant lining covering all water-side surfaces.

Nozzle

The large shape of a waterbox nozzle is designed to keep water velocities low.

Hotwell

The hotwell forms the lower part of the condenser. Condensed steam forms condensate, which gathers in the hotwell and is then discharged through piping at the base of the hotwell.

Condensate Sump

Condensate is discharged through this pipe. As condensate (water) has a much smaller volume than steam (1600:1), the discharge pipe is much smaller than the main steam inlet.

Instrumentation

Sensors are fitted to several areas of the condenser. Each sensor records operational data relating to flow, pressure, and temperature. All data is then fed to a monitoring system in real time. Alarms and shutdown are triggered based upon the data received from the installed sensors.

Low-Pressure Feedwater Heaters

Large power stations often install low-pressure feedwater heaters in the neck of the condenser. There are two main reasons for this, space, and cost. Removing a feedwater heater tube bundle requires a lot of space, this space adds cost to the building construction, which is not desired. Installing the feedwater heater within the neck of the condenser reduces the amount of extraction steam piping needed, which reduces the number of hangers, joints, valves etc. required, and it reduces the extraction steam pressure drop (yielding an increase in system efficiency).

Tubes

Cooling water flows into the condenser via waterboxes, then through the tube stack. The tube stack comprises of a series of tubes mounted to tubesheets. Tubesheets are mounted at opposite ends of the tubes; they hold the tubes in position and lend mechanical strength to the tubes. Each tube is rolled and expanded into the associated tubesheet. Turbulators are often installed within the tubes to promote turbulent flow, which increases the heat transfer capability of the tubes and thus the overall efficiency of the condenser.

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