Steam Utilisation Concept



                                        
             
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 pressure should 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.

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