(57) A fluid which is to be heated by a gas (in 17) containing sulfur oxides and water
vapour is passed through the inner tube(s) (25) of a multi-pipe heat exchanger (21)
and recovered from the outermost tube (26) thereof at such a temperature thatthe outer
surface temperture of the outermosttube (26) is always above the acid dew point, thereby
avoiding acid corrosion of the outermost tube (26) of the heat exchanger (21).
In an embodiment, the heat exchanger (21) is of the double pipe type, but whichever
type is employed, the heat transfer characteristics and/or sizes of the tubes of the
heat exchanger (21) are selected to provide an outer surface temperature exceeding
the acid dew point for reasonable and/or acceptable ranges of fluid flow rates and
pressure drops therethrough.
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