Distillation: processes – separatory – Distilling to separate or remove only water – From nitric acid
Patent
1989-04-17
1990-10-30
Manoharan, Virginia
Distillation: processes, separatory
Distilling to separate or remove only water
From nitric acid
159 21, 159 471, 159DIG19, 159DIG22, 159DIG23, 203 22, 203 27, 203 35, 203 78, 203 80, 203 88, 203 94, 203 98, 203DIG8, 203DIG9, 423390, B01D 334
Patent
active
049662767
ABSTRACT:
An integrated continuous processes for concentrating "weak" nitric acid and concurrently reconcentrating the spent dehydrating agent used to break the nitric acid azeotrope to obtain "strong" nitric acid, the processes involving direct coupling of the nitric acid concentration with the reconcentration of the spent dehydrating agent so that less energy input is required. The major proportion of the feed "weak" nitric acid is vaporized before being fed countercurrently into a column to contact a large volume of the dehydrating agent, this vaporization being one of the two major sources of energy input, the second being through the reboiler at the bottom of the column. Energy input is balanced by energy rejection through condensation of strong nitric acid vapor and water vapor. The nitric acid vapor injected into the lower part of the column is subsequently contacted in succession with a mixture of nitric acid and a portion of the dehydrating agent to further increase the strength of the nitric acid vapor, then with a third portion of the dehydrating agent and finally a small reflux of concentrated "strong" nitric acid to remove further water and residual dehydrating agent from the concentrated "strong" nitric acid vapor in the upper part of the column. The spent dehydrating agent is reconcentrated by flashing under vacuum or alternatively through evaporative cooling with air without further substantial energy input, and is recycled back to the nitric acid concentration column without being cooled, avoiding consequent rejection of energy. The preferred dehydrating agents are aqueous solutions of sulfuric acid and of magnesium nitrate.
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Dietrich Gericke, "Concentration of Nitric Acid by Sulphuric Acid", Schott, pp. 894-899.
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