4. I.G. CLAUS PROCESS FOR RECOVERY OF SULPHUR FROM H2S
The I.G. Claus process is a method for converting gaseous hydrogen sulfide into molten elementary sulfur. This process is often used as a supplementary process in connection with the Alkazid H2S removal process. The reaction basis of the Claus process is shown by the following equations:
2H2S+3O2 2H2O+2SO2
2H2S+SO2 2H2O+3S
Drawing Ze 1416-2 in the appendix of this report presents a flowsheet of the process. In this flowsheet the H2S comes from Gasometer Unit 14 through a blower to the two Claus "kessels" in parallel. Here it is partially burned with a controlled amount of air to yield a ratio of SO2 to H2S of 1:2.) This mixture then passes over the bauxite catalyst in the first Claus "ofen" at a temperature of the about 300º to 400º where the second reaction takes place. The gas from the first "ofen" passes through an "aufhiter" where fuel gas is burned to heat the gases further before they pass through the second Claus "ofen" to complete the second reaction. Molten sulfur is drawn from the bottom of each the second reaction. Molten sulfur is drawn from the bottom of each "ofen". The tail gases from the second "ofen" consist principally of nitrogen, water vapor, and carbon dioxide (from hydrocarbon gases) with about 3.5.g/m3 of unreacted SO2 and H2S. This is gas passes through a cyclone or electrostatic separator to remove entrained elemental sulphur, then to the "Nachbrennungsofen" where a pilot flame burns to remaining H2S over bauxite before passage to the atmosphere.
Drawings FZAlb and FZA4-a show the Claus ofen and Nachbvebrennungsofen respectively. A catalyst bed of 3m diamter and 7m high will produce about 6 tons of sulfur per day at 80% recovery. The inlet H2S content can vary from 40% to 100%. Drawing 4A34210 shows the arrangement of equipment and piping.
The catalyst life is indefinte unless overheating causes sintering in which case only the upper layer is ordinarily affected. When this happens, the upper layer of catalyst is replaced.
The equilibria, experimental and calculated, are presented in an "Aktennotiz" dated July 11, 1941 by Dr. Orlick under the title "Untersuchen uber die Lago des chemischen Gleichgewichtes bein Clausprozess."
Complete operating data for the Leuna Plant are presented in a translation "Claus Ofen Operation" in the appendix.