Process for producing sulfuric acid with low levels of niter

1. A process for producing sulfuric acid with reduced levels of niter, comprising:

a) providing an absorption tower wherein sulfur trioxide is absorbed in a sulfuric acid feed having a first sulfuric acid solution to produce a sulfuric acid effluent having i) a second sulfuric acid solution which has a higher concentration than the first sulfuric acid solution, ii) a niter concentration greater than about 5 ppm (as NO 3 ), and iii) a temperature greater than 100° C.; and

b) contacting a first purifying agent comprising sulfamic acid and a second purifying agent comprising hydrogen peroxide with the sulfuric acid effluent to form a treated sulfuric acid effluent, the treated sulfuric acid effluent being maintained at a temperature of greater than 100° C. for a maintenance period of at least about 1 minute;

wherein the first purifying agent and the second purifying agent are added to the sub-surface of the sulfuric acid effluent.

2. The process of claim 1 wherein both the amount of sulfamic acid and the amount of hydrogen peroxide added to the sulfuric acid effluent are at least the stoichiometric amount.

3. The process of claim 1 wherein both the amount of sulfamic acid and the amount of hydrogen peroxide added to the sulfuric acid effluent are at least about twice the stoichiometric amount.

4. The process of claim 1 wherein the first purifying agent is added to the sulfuric acid effluent no later than the addition of the second purifying agent.

5. The process of claim 1 wherein the first purifying agent and the second purifying agent are mixed, and the resulting mixture is contacted with the sulfuric acid effluent.

6. The process of claim 1 wherein the first purifying agent and the second purifying agent are contacted with the sulfuric acid effluent with a temperature greater than 100° C.

7. The process of claim 1 wherein the treated sulfuric acid effluent is maintained at a temperature of from about 105° C. to about 150° C.

8. The process of claim 1 wherein the treated sulfuric acid effluent has a niter concentration of no more than about 5 ppm (as NO 3 ).

9. A process for producing sulfuric acid with reduced levels of niter, comprising:

a) providing an absorption tower wherein sulfur trioxide is absorbed in a sulfuric acid feed having a first sulfuric acid solution to produce a sulfuric acid effluent having i) a second sulfuric acid solution which has a higher concentration than the first sulfuric acid solution, ii) a niter concentration greater than about 5 ppm (as NO 3 ), and iii) a temperature greater than 100° C.; and

b) contacting a first purifying agent comprising sulfamic acid and a second purifying agent comprising hydrogen peroxide with the sulfuric acid effluent to form a treated sulfuric acid effluent, the treated sulfuric acid effluent being maintained at a temperature of greater than 100° C. for a maintenance period of at least about 1 minute;

wherein the sulfuric acid effluent and the purifying agents are introduced into a treatment vessel, the treated sulfuric acid effluent exits the treatment vessel after the maintenance period, and at least a portion of the treated sulfuric acid effluent is recycled to the treatment vessel.

10. The process of claim 9 wherein both the amount of sulfamic acid and the amount of hydrogen peroxide added to the sulfuric acid effluent are at least the stoichiometric amount.

11. The process of claim 9 wherein the first purifying agent is added to the sulfuric acid effluent no later than the addition of the second purifying agent.

12. The process of claim 9 wherein the first purifying agent and the second purifying agent are mixed, and the resulting mixture is contacted with the sulfuric acid effluent.

13. The process of claim 9 wherein the treated sulfuric acid effluent is maintained at a temperature of from about 105° C. to about 150° C.

14. The process of claim 9 wherein the treated sulfuric acid effluent has a niter concentration of no more than about 5 ppm (as NO 3 ).

15. A process for producing sulfuric acid with reduced levels of niter, comprising:

a) providing an absorption tower wherein sulfur trioxide is absorbed in a sulfuric acid feed having a first sulfuric acid solution to produce a sulfuric acid effluent having i) a second sulfuric acid solution which has a higher concentration than the first sulfuric acid solution, ii) a niter concentration greater than about 5 ppm (as NO 3 ), and iii) a temperature greater than 100° C.; and

b) contacting a first purifying agent comprising sulfamic acid and a second purifying agent comprising hydrogen peroxide with the sulfuric acid effluent to form a treated sulfuric acid effluent, the treated sulfuric acid effluent being maintained at a temperature of greater than 100° C. for a maintenance period of at least about 1 minute;

wherein the first sulfuric acid solution has a concentration of at least about 93 wt %.

16. The process of claim 15 wherein both the amount of sulfamic acid and the amount of hydrogen peroxide added to the sulfuric acid effluent are at least the stoichiometric amount.

17. The process of claim 15 wherein the first purifying agent is added to the sulfuric acid effluent no later than the addition of the second purifying agent.

18. The process of claim 15 wherein the first purifying agent and the second purifying agent are mixed, and the resulting mixture is contacted with the sulfuric acid effluent.

19. The process of claim 15 wherein the treated sulfuric acid effluent is maintained at a temperature of from about 105° C. to about 150° C.

20. The process of claim 15 wherein the treated sulfuric acid effluent has a niter concentration of no more than about 5 ppm (as NO 3 ).

21. A process for producing sulfuric acid with reduced levels of niter, comprising:

a) providing an absorption tower wherein sulfur trioxide is absorbed in a sulfuric acid feed having a first sulfuric acid solution to produce a sulfuric acid effluent having i) a second sulfuric acid solution which has a higher concentration than the first sulfuric acid solution, ii) a niter concentration greater than about 5 ppm (as NO 3 ), and iii) a temperature greater than 100° C.; and

b) contacting a first purifying agent comprising sulfamic acid and a second purifying agent comprising hydrogen peroxide with the sulfuric acid effluent to form a treated sulfuric acid effluent, the treated sulfuric acid effluent being maintained at a temperature of greater than 100° C. for a maintenance period of at least about 1 minute;

wherein the second sulfuric acid solution has a concentration of at least about 98 wt %.

22. The process of claim 21 wherein both the amount of sulfamic acid and the amount of hydrogen peroxide added to the sulfuric acid effluent are at least the stoichiometric amount.

23. The process of claim 21 wherein the first purifying agent is added to the sulfuric acid effluent no later than the addition of the second purifying agent.

24. The process of claim 21 wherein the first purifying agent and the second purifying agent are mixed, and the resulting mixture is contacted with the sulfuric acid effluent.

25. The process of claim 21 wherein the treated sulfuric acid effluent is maintained at a temperature of from about 105° C. to about 150° C.

26. The process of claim 21 wherein the treated sulfuric acid effluent has a niter concentration of no more than about 5 ppm (as NO 3 ).