Surface condenser and its Effects of tube side fouling

Surface condensers are water-cooled shell-and-tube heat exchangers used to condense waste steam from steam turbines in thermal power stations.These condensers are heat exchangers that convert vapor from a gaseous state to a liquid state at subatmospheric pressure.Where the supply of cooling water is insufficient, air-cooled condensers are often used.However, air-cooled condensers are much more expensive and cannot achieve the same low turbine discharge pressures (and temperatures) as water-cooled surface condensers.Surface condensers are also used in applications and industries other than power plant turbine exhaust condensation.

Purpose

In a thermal power plant, the role of the surface condenser is to condense the exhaust steam of the steam turbine for maximum efficiency, and convert the exhaust steam of the steam turbine into pure water (referred to as condensed water) for reuse in steam generators or boilers as boilers give water.The steam turbine itself is a device that converts the heat in steam into mechanical energy. The difference between the heat per unit mass of steam at the turbine inlet and the heat per unit mass of steam at the turbine outlet represents the heat converted to mechanical energy.Therefore, the more heat per pound or kilogram of steam that is converted into mechanical energy in the turbine, the more efficient it will be.By condensing the turbine's exhaust steam at a pressure below atmospheric pressure, the vapor pressure drop between the turbine's inlet and exhaust is increased, which increases the amount of heat available for conversion into mechanical energy.Most of the heat released due to the condensation of the exhaust steam is carried away by the cooling medium (water or air) used by the surface condenser.

Effects of tube side fouling

As one would expect, with millions of gallons of circulating water flowing through the condenser tubes from sea or fresh water, any material contained in the water passing through the tubes may end up on the condenser tube sheets (discussed earlier ) or the tubing itself.Tubeside fouling of surface condensers falls into five main categories; particulate fouling, such as sludge and sediment, biofouling, such as slime and biofilm, scaling and crystallization, such as calcium carbonate, and macrofouling, which includes anything from can Zebra mussels growing on tube sheets, to wood or other debris clogging pipes, and finally corrosion products (discussed earlier).Depending on the degree of fouling, the ability of the condenser to condense the exhaust from the turbine can be quite severely affected.As dirt builds up in the pipes, there is an insulating effect and the heat transfer characteristics of the pipes are reduced, often requiring the turbine to be slowed down to the point where the condenser can handle the exhaust gas produced.Often, this can come at a considerable cost to the power plant in the form of reduced output, increased fuel consumption and increased CO2 emissions. This "derating" of the turbine to accommodate fouled or clogged piping in the condenser is an indication that the plant needs to clean the piping to restore the turbine to its nameplate capacity.Multiple cleaning methods are available, including in-line and off-line options, depending on specific conditions at the plant site.