Appeal No. 1997-0664
Application No. 08/280,945
pickling acid from said pickling bath at least one
compound which contains nitrogen which will react
with said molecular chlorine and said nitrogen
oxides to regenerate said hydrochloric acid and
produce molecular nitrogen.
25. In a process for the regeneration of
hydrochloric acid used as a pickling acid in a
pickling bath, wherein iron chloride is produced in
said pickling bath and wherein said regeneration
process includes the thermal decomposition of said
iron chloride in the spent pickling acid from said
pickling bath into iron oxide and gaseous
hydrochloric acid and molecular chlorine and further
including the formation of nitrogen oxides, the
improvement comprising admixing with the spent
pickling acid from said pickling bath at least one
compound which contains nitrogen having a low
oxidation number and selected from the group
consisting of ammonium compounds, ammonia, urea, and
amides.
The subject matter on appeal generally relates to a
process for regenerating hydrochloric acid from pickling
plants, in which iron chloride in the spent pickling acid is
thermally decomposed into iron oxide and gaseous hydrochloric
acid (brief, page 3). According to the appellants, the
process of pickling steel products with hydrochloric acid (or
mixtures containing hydrochloric acid) dissolves mill scale
layers that are formed on the steel surface by preceding
processes such as rolling or annealing, according to the
following reaction:
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