The Sulfacid® process has been especially developed to meet the dual objectives of SO2 removal from waste gases generated by chemical and metallurgical processes and transformation into industrial grade sulfuric acid. It lends itself particularly well to applications where sulfuric acid can be directly used, for example copper or fertilizer industry, titanium dioxide production or similar sulfuric acid based processes. Additionally, the fixed activated carbon bed is able to remove heavy metals (such as Hg and Cd) from the waste gas.

Typical waste gas inlet parameters:

SO2 content up to 1 vol.%
Hg content 150 µg/Nm³ dry
O2 content min. 7 vol.%
Temperature up to 80°C
Dust content

< 30 mg/m³ STP (all data refers to dry gas)

Typical clean gas outlet parameters:

SO2 content ≤ 50 mg/Nm3 dry
Hg content 25 µg/Nm³ dry

The raw gas to be treated flows through an activated carbon catalyst fixed bed inside the reactor. The SO2 is converted to sulfuric acid by wet catalysis in the presence of oxygen and water.

The water-saturated clean gas discharges to atmosphere via a stack. The sulfuric acid collected in the pores and on the surface of the catalyst is intermittently washed out by spraying water over the catalyst. Clear industrial grade sulfuric acid of up to 60 wt.% strength flows into a buffer tank. The conversion of sulfur dioxide to sulfuric acid on the catalyst works according to the following reaction equation:

SO2 + ½ O2 + n H2O ⇒ H2SO4 · (n-1) H2O + heat

The first Sulfacid® plant was started-up in 1968; now a few hundred plants are in operation worldwide.

Typical features of the Sulfacid® process are: simple reaction control, minimum maintenance requirements and operator attendance, low specific energy costs and the use of mature, equipment-optimised technology & equipment.

When testing is required, a mobile pilot plant is available to verify the suitability of the Sulfacid® process directly on site and allow optimal scale-up to commercial operation.

One stage Sulfacid<sup>®</sup> plant

Single stage (first generation) Sulfacid® plant