Steam for Process Heating
Steam is largely used for the purpose of process heating. Using steam for processing heating offers multiple benefits over other heating media. Numerous benefits, simplicity of the system and high efficiency and reliability make steam the first choice for process heating.
Steam can be used either for direct heating or indirect heating.
a. Direct Heating
In direct heating, steam is directly injected in the substance which is to be heated. Care should be taken that proper mixing takes place to ensure uniform heating. It is also essential to take care that no temperature overshoots are observed. Sparge pipes should be used to ensure that steam does not escape to the environment without heating the product.
In pharmaceutical or food and beverages industry, steam of highest purity (safe to be consumed by humans) should always be used for direct heating purposes.
b. Indirect Heating
The indirect method of heating uses steam to heat the product with the help of heat exchangers so that the product does not come physically in contact with steam. The indirect heating can be done through use of various heating equipment such as cookers, jacketed vessels, plate type or shell and tube type heat exchangers etc.
Steam for Atomization
The process of atomization ensures a better combustion of fuels. The word atomization literally means breaking in to tiny particles. In burners, steam is used for the purpose of atomizing the fuel. This ensures a larger surface area of the fuel available for the combustion.
As a result of atomization, soot formation is minimized and overall efficiency of combustion goes up.
Steam for Power Generation
The very first commercial central electrical generating stations in New York and London, in 1882, also used reciprocating steam engines
For decades, steam is being used for the purpose of power generation in form of electricity. The steam power plants work on the Rankine Cycle. In Rankine cycle, superheated steam is generated and then taken to steam turbine. The steam drives the turbine which in turn generates the electricity. The used steam is again converted in to water using a condenser. This recovered water is again fed back to the boiler to generate steam.
The efficiency of the power plant is directly dependent on difference between pressure and temperature of steam at the inlet and outlet of turbine. Hence, use of high temperature and high pressure steam is advisable. Hence, power generation plants are most efficient when superheated steam is used. As high pressure is involved, water tube boilers are used for steam generation.
Steam for Humidification
Maintaining humidity is a crucial aspect of HVAC systems as humidity lower or higher than desired has adverse effects on humans, machines and materials. Humidity lower than desired might lead to drying of mucus membranes which ultimately results in respiratory distress.
Low humidity also leads to increased static electricity problems which might damage the costly equipment.
Steam can be used for the purpose of humidification. Using steam for the purpose of humidification offers added advantages over other media. There are different types of humidifiers from evaporating humidifiers to ultrasonic ones to suit different applications.
Steam for Drying
Product drying is another application of steam where steam is used to remove moisture from the product. Conventionally, hot air is used for product drying. Using steam to dry makes the system simple, easy to control drying rates and compact. The overall capital investment is also low.
On the other hand, use of steam is cheaper on operational basis compared to hot air. It is also a safer alternative. The use of steam for drying purpose also ensures a better product quality when compared with hot air.
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