Steam Utilization

             Heat of evaporation is given by steam to the process and in turn steam gets condensed Heat transfer coefficients during condensation are highest and thus saturated steam at exact pressureshould be used for process heating.

The most common use for steam that is put to work in process or heating plants is a coil heated vessel.

The vessel is filled with the product to be heated, and steam is admitted to the coil. The steam then gives up its
enthalpy of evaporation to the metal wall of the coil which transfers it to the product. Hot water is formed as the steam condenses, and runs down to the bottom of the coil. This condensate, as it is properly known, must be then recovered for further use.

The correct steam pressure for heating process

Steam should be always used at the lowest possible pressure. At low pressure, heat content ( enthalpy of evaporation ) is high and heat transfer would be efficient. Less steam would be consumed in the process making it economical. For example, if final product temperature of 110 ^oC is to be attained in a coil reactor, considering the suitable temperature difference across the reactor, say 15 ^oC, the required steam temperature is 125 ^oC. Then the corresponding steam pressure is 2.5 to 3.0 bar g.

Steam traps

During the heating process the steam is converted into condensate. Steam Traps will allow this condensate to pass through it into the condensate return lines and at the same time will hold back the steam within the heat exchanger or whatever the steam is applied to, such as a steam main drainage application.

There are three points, which are fundamental about the use of steam traps:

selection of the best type
choosing of the correct size
the right installation

It can be claimed that the majority of steam traps will "work" on any application ( provided that the operation conditions fall within the pressure range and condensate discharge capacity of the trap). However, we do not just want steam traps which "work" moderately well. We must aim to achieve maximum output and efficiency from all steam using plants. This means selecting the best trap to suit each particular job.

The benefits of selecting the best type of steam trap for a given application will be wasted if the trap is not sized correctly. It is a bad practice to choose a 20 mm trap simply because it has to go on a 20 mm drain pipe.

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