Process for the removal of soot from a sulfurous gas stream

Abstract

In a process for the removal of soot from a sulfurous gas stream, a process gas containing O.sub.2 and more than 500 ppm SO.sub.2 and/or SO.sub.3 together with soot is brought into contact with a VK type catalyst in a reactor, said catalyst comprising vanadium pentoxide (V.sub.2O.sub.5), sulfur in the form of sulfate, pyrosulfate, tri- or tetrasulfate and one or more alkali metals, such as Na, K, Rb or Cs, on a porous carrier, preferably a silicon dioxide carrier.

Claims

1. A process for the removal of soot comprising >90 wt % C from a sulfurous gas stream, wherein a process gas containing O.sub.2 and more than 500 ppm SO.sub.2 and/or SO.sub.3 and a soot concentration of >2 mg/Nm.sup.3/h is brought into contact with a catalyst in a reactor, said catalyst comprising vanadium pentoxide (V.sub.2O.sub.5), sulfur in the form of sulfate, pyrosulfate, tri- or tetrasulfate and one or more alkali metals on a porous carrier.

2. Process according to claim 1, wherein the porous carrier of the catalyst is silicon dioxide (SiO.sub.2).

3. Process according to claim 2, wherein the porous carrier of the catalyst is SiO.sub.2 with <10 wt % of alumina.

4. Process according to claim 3, wherein the porous carrier of the catalyst is SiO.sub.2 with <2 wt % of alumina.

5. Process according to claim 3, wherein the porous carrier of catalyst is SiO.sub.2 with <1 wt % of alumina.

6. Process according to claim 1, wherein the alkali metal content of the catalyst is 2-25 wt %.

7. Process according to claim 1, wherein the catalyst contains 1-15 wt % V.sub.2O.sub.5.

8. Process according to claim 7, wherein the catalyst contains 2-12 wt % V.sub.2O.sub.5.

9. Process according to claim 1, wherein the catalyst contains 1-25 wt % sulfur in the form of sulfate, pyrosulfate, tri- or tetrasulfate.

10. Process according to claim 9, wherein the catalyst contains 2-20 wt % sulfur in the form of sulfate, pyrosulfate, tri- or tetrasulfate.

11. Process according to claim 10, wherein the catalyst contains 4-16 wt % sulfur in the form of sulfate, pyrosulfate, tri- or tetrasulfate.

12. Process according to claim 1, wherein the catalyst temperature is 250-700? C.

13. Process according to claim 12, wherein the catalyst temperature is 300-650? C.

14. Process according to claim 1, wherein the process gas has a soot concentration of >5 mg/Nm.sup.3/h.

15. Process according to claim 14, wherein the process gas has a soot concentration of >20 mg/Nm.sup.3/h.

16. Process according to claim 14, wherein the process gas has a soot concentration of >50 mg/Nm.sup.3/h.

17. Process according to claim 1, wherein the process gas contains more than 1000 ppm SO.sub.2 and/or SO.sub.3.

18. Process according to claim 17, wherein the process gas contains more than 5000 ppm SO.sub.2 and/or SO.sub.3.

19. Process according to claim 1, wherein the soot in the process gas has a composition comprising >95 wt % C.

20. Process according to claim 1, wherein the soot is carbon black.

21. Process according to claim 1, wherein the alkali metal content of the catalyst is 8-16 wt %.

22. Process according to claim 1, wherein the process gas contains more than 2500 ppm SO.sub.2 and/or SO.sub.3.

Description

EXAMPLE

(1) The ability of the VK-WSA catalyst to remove soot at 400? C. was tested by covering the surface of the catalyst with carbon black of the type Printex U and exposing the soot-covered catalyst to a gas in a reactor. The gas contained 10 vol % SO.sub.2 and 10 vol % O.sub.2.

(2) A comparative study of the thermal oxidation of carbon black in air at 400? C. showed a considerably lower removal of soot. The results are shown in Table 2 below.

(3) TABLE-US-00002 TABLE 2 Thermal oxidation VK-WSA Treatment at 400? C. at 400? C. Soot removal, wt % 47 >99