acid dewpoint

As expected, firing with low excess air reduced acid dewpoint formation.

Acid dewpoint is primarily dependent upon the concentration of water vapour and Sulphurtrioxide in the gas.

However, SO3 and acid dewpoint consistently dropped to low values when excess air was reduced below 1% oxygen in the flue gas.

(1967) concluded that when firing high sulphur coals, relationship among sulphur content, SO3 level, acid dewpoint and corrosion potential becomes unpredictable.

Further work on acid dewpoint by various researchers, conveniently summarized by Lisle and Sensenbaugh (1965), called into question the reliability of dewpoints as determined by dewpoint meter.

Therefore when combusted it emits neither SO2 nor SO3 , has no sulphur-related high-temperature corrosion problems, and having no problems with acid dewpoint, is amenable to high-efficiency condensing heat recovery.

In cold-end or low-temperature corrosion, i.e., at temperatures below acid dewpoint, H2SO4 formed from fuel sulphur is the primary agent although in some circumstances HCl and H2CO3 may play some role.

Goksøyr and K. Ross."The Relationship Between Acid Dewpoint and Sulphur Trioxide Content of Flue Gases."Thornton Research Center, Shell Research Ltd., 1962.

Figures 4 and 5 respectively show SO3 and acid dewpoint for coal with 6.3% S. Figure 6 shows the relationship of SO3 to acid dewpoint, compared with the calculated data of Müeller.

Then, by varying the temperature of the SO3 condenser and measuring SO3 captured vs. SO3 passing through the condenser, it was possible to establish the temperature at which a given concentration of SO3 saturated the flue gas i.e., the acid dewpoint.

In the vicinity of the coalwalled furnace, any soot which forms is likely to be deposited on the walls and, being sticky and porous, becomes a condensation site for H2 SO4 formed when chilling effect of the walls drop SO3 below the acid dewpoint.