A condensing steam turbine is a type of steam turbine in which, after the steam expands and does work within the turbine, virtually all of the steam—except for a small amount that leaks through the shaft seals—is directed into the condenser, where it condenses into water. In practice, to enhance the thermal efficiency of a condensing steam turbine and reduce the diameter of the turbine’s exhaust cylinder, part of the steam that has already done some work is extracted and sent to a regenerative heater to preheat the boiler feedwater. Such unregulated extraction-type turbines are also generally referred to as condensing steam turbines. They are commonly used in thermal power plants for electricity generation. The condensation equipment mainly consists of a condenser, a circulating water pump, a condensate pump, and an air ejector. After entering the condenser, the steam from the condensing turbine is cooled by circulating water and condensed into water, which is then pumped out by the condensate pump, heated through various stages of heaters, and finally delivered as feedwater to the boiler.

　　When the exhaust steam from a condensing steam turbine condenses into water in the condenser, its volume suddenly shrinks, creating a vacuum in the enclosed space previously filled with steam. This reduces the pressure of the turbine exhaust and increases the ideal enthalpy drop of the steam, thereby improving the thermal efficiency of the plant. Non-condensable gases (primarily air) in a condensing steam turbine are extracted by an ejector to maintain the necessary vacuum level.

　　The condenser commonly used in condensing steam turbines is of the surface type. The cooling water, after being discharged into a cooling pond or cooling tower to reduce its temperature, is then recycled for further use. For power plants located near rivers, lakes, and other bodies of water, if water resources are abundant, the discharged cooling water can be directly released into these water bodies—a method known as runoff cooling. However, this approach may cause thermal pollution of rivers and lakes. In regions experiencing severe water shortages, power plants may adopt air-cooling systems. Yet, such systems have bulky structures and consume large amounts of metallic materials. With the exception of mobile power stations mounted on trains, air-cooling systems are rarely employed in conventional power plants. Some older power plants once utilized hybrid condensers, in which the condensing steam turbine was directly mixed with cooling water for cooling purposes. However, since the condensate from the exhaust steam becomes contaminated by the cooling water, it must undergo treatment before it can be reused as boiler feedwater; thus, this method is now seldom used.

　　Operating Characteristics of Condensing Steam Turbines

　　Exhaust pressure has a significant impact on operational economy. The primary factors affecting vacuum levels are the inlet temperature of cooling water and the cooling rate. The former is influenced by the region where the power plant is located, the season, and the method of water supply; the latter refers to the ratio between the designed flow rate of cooling water and the steam exhaust from the turbine. A higher cooling rate can achieve a higher vacuum level. However, increasing the cooling rate also leads to higher electricity consumption by circulating pumps and greater capital investment in equipment. Typically, the surface condenser design is set at a cooling rate ranging from 60 to 120. Given that condensing turbines have high cooling water requirements, water source conditions have become one of the key factors in selecting a site for a power plant.

　　Ideally, the temperature of the condensate should be the same as that of the exhaust steam, and the heat carried away by the cooling water would correspond solely to the latent heat of vaporization of the exhaust steam. However, in actual operation, due to flow resistance in the exhaust steam and the presence of non-condensable gases, the temperature of the condensate is lower than that of the exhaust steam. The temperature difference between the two is referred to as subcooling. Improper arrangement of cooling water pipes, high condensate levels during operation, and immersion of cooling water pipes in water can all increase the degree of subcooling. In general, the subcooling should not exceed 1–2°C.

　　For specific materials, fluidized-bed jet mills can be used for both crushing and classification. When high-purity requirements are involved, inert gas-protected crushers and classifiers can be employed to prevent oxidation, and oxygen can be isolated to enable closed-loop production.