Feed temperature increase into the drum, decrease the feed pipe and between the drum wall temperature difference, thermal stress drop, so that the steam drum wall is helpful to prolong the service life of the drum. Before other, into the evaporating heating surface water is heated in the economizer, reduced the water absorption of heat in the heat of evaporation surface, this is equivalent to replacing the evaporation part with economizer heating surface. Economizer heating surface much more than the evaporating heating surface of low cost, therefore, from the manufacturing boiler efficiency, the economizer is economical.
