| 摘要 |
A method of preventing corrosion in boiler plant equipment when cooling flue gases originating from a combustion plant, such as flue gases containing sulphur oxide or organic acids, to a temperature beneath which sulfuric acid condenses (sulfuric acid dew point temperature) and a further temperature defined as an upper permitted wall-temperature of the stainless steel. The upper permitted wall temperature is with respect to the stainless steel material from which the walls are made and the prevailing partial pressure of water vapor present in the gases. This limiting temperature is specific to each stainless steel. The heat exchange is by means of a coolant, suitably water, located on the other, i.e. cold, side of the heat-exchanger wall; the coolant temperature is either at a set temperature or has a downwardly decreasing temperature gradient; condensation at dew point of acid is carefully controlled based on the respective temperature of the combustion gases, the specific upper permitted wall temperature, and the temperature on the hot side of heat transfer surface. An increase in the partial pressure of the water vapor increases the upper permitted wall temperature; this temperature limit can be increased by applying one of the following steps: supplying water or hydrogen-containing compounds to the combustion process, adding water to the gases, or cooling the gases at elevated pressures; a laminar flow region for the gases below the acid dew point "extends" the upper permitted wall temperature near the acid dew point temperature. |
