Abstract: In a process for thermally cracking waste sulphuric acid, a combustible material is mixed with such acid and the mixture is supplied to a burner to which a flow of atomizing air is also supplied. A flow of secondary air which is enriched to about 23-40% by volume of oxygen is injected into a flame generated by burning said waste sulphuric acid-combustible material mixture to thereby thermally crack such acid while reducing the production of by-product sulphur trioxide.

Abstract: In a process for producing nitric acid, a mixture of oxygen, nitrogen, nitric oxide, nitrogen dioxide, and dinitrogen tetroxide is introduced into an absorption column into which cold oxygen (below 0.degree. C.) is introduced. H.sub.2 O is introduced into the upper reaches of the column and reacts with the nitrogen dioxide and dinitrogen tetroxide to form nitric acid. The low oxygen temperature helps to shift the equilibrium between nitric oxide and oxygen to dinitrogen tetroxide and in favor of reacting the latter with water to form nitric acid.

Abstract: An improved process for the manufacture of nitric acid involving catalytic oxidation of ammonia and passage of the resulting nitric oxide through columnar absorption zones, the improvement particularly comprising oxygen-enrichment of that gas passing through the absorption zones at one or more regions of the zones wherein the absorption reaction is from 50 to 90% complete. Further, the invention contemplates the oxygen-enrichment of bleaching air and a reduction in the rate at which bleaching air or other air is taken to form secondary air. The invention results in improved production rates of nitric acid and reductions in the concentration of nitrogen oxides in vent gas.