# What is acid dew point temperature?

## What is acid dew point temperature?

The acid dew point (also acid dewpoint) of a flue gas (i.e., a combustion product gas) is the temperature, at a given pressure, at which any gaseous acid in the flue gas will start to condense into liquid acid.

### What is the dew point of flue gas?

The acid dew point temperature depends on the levels of reactants present in the flue gas. It generally lies in the range 100-150°C.

Does sulfur in the fuel change the dew point?

During the combustion process, the sulfur contained in fuel undergoes oxidation. This leads to acid dew point, which is the highest level of temperature where acid deposition can take place.

How do you find the dew point temperature of a flue gas?

To perform the Acid Dew Point calculation the engineer needs to input the following data which he can get from a combustion analysis program:

1. Total Pressure of the Flue Gas: Ptotal (in Hg) = Pbar + Pgage
2. Percent of Water Vapor in the Wet Flue Gas Volume Basis:
3. Percent of Acid Gas in the Wet Flue Gas Volume Basis:

## What is the dew point of sulfuric acid?

Since all fuels contain some amount of sulfur, sulfuric and sulfurous acid dewpoint corrosion can occur if the metal temperatures are below the dewpoint. The dewpoint of sulfuric acid depends on the concentration of sulfur trioxide in the flue gas, but is typically about 280°F (138°C).

### What should the sulfur dew point be for HRSG?

Most do not do this. For HRSG’s burning fuel gas with 10ppm sulphur acid dewpoint is 81C, with 100ppm sulphur acid dewpoint is 93C. Between these points interpolate on a log10 scale for sulphur and a linear scale for temperature. Athomas, the use of the two points with interpolation in between seems a nice way to go.

How is the dew point of a fuel determined?

The concentration of contaminants (sulfur and chlorides) in the fuel and the operating temperature of flue gas metal surfaces determine the likelihood and severity of dew point corrosion. Since all fuels contain some amount of sulfur, sulfuric and sulfurous acid dewpoint corrosion can occur if the metal temperatures are below the dewpoint.

How does flue gas stay above the sulfur dew point?

In general, with sulfur bearing fuels, the flue gas in steam boilers is kept above the 300-350F range to stay above the sulfur dew point. The heat transfer equipment could get it much lower, but the sulfur won’t allow it.