Patent ID: 8580224

Claim:
A method of increasing the sulfuric acid concentration of a first aqueous sulfuric acid solution with a sulfuric acid concentration of 82-89% to a concentrated sulfuric acid solution with a sulfuric acid concentration of at least 90%, the method comprising: evaporating water from the first aqueous sulfuric acid solution in an evaporator vessel to the concentrated sulfuric acid solution; and pumping around a mixture of the first aqueous sulfuric acid solution, part of the concentrated sulfuric acid solution, a second aqueous sulfuric acid solution, and hydrogen peroxide through an enameled piping system comprising the evaporator vessel and one or more heaters and pumps, wherein the piping system is operating at a temperature of at least 180° C., and the sulfuric acid concentration of the second aqueous sulfuric acid solution is at least 90%.