Boiler Flue-Gas Measurements Using a Dewpoint Meter

Abstract

Corrosion and fouling of low temperature heat-transfer equipment poses one of the major obstacles to the achievement of maximum boiler operating efficiency. The first consideration in controlling or eliminating a problem of this nature is determination of its causes. Dewpoint-meter investigations for this purpose were performed on units fired by coal, oil, and various fuel combinations. The context of this paper presents a review of those factors thus revealed by these investigations as major contributors to plugging and corrosion processes in air preheaters installed on oil-fired boilers. These tests disclosed that corrosion potential of boiler flue gases is directly effected by the degree of boiler slagging. They have established that flue gas corrosion potential can be substantially reduced by decreasing the level of excess air employed in operation. The results of this study also indicate that maximum rate of condensation (peak rate, or PR) and the temperature of its occurrence (peak rate temperature, or PRT) are more reliable indicators of corrosion potential than the dewpoint.