Apparatus and process for separation of liquid from a gas
View Patent ↗A pickling process for descaling metal includes a two-stage filtering process to remove pickling liquor fog, mist, and/or vapors from a gas collected during the descaling process. The process includes a two-stage filtering arrangement that includes a first stage filter, which is arranged to remove a liquid phase of the pickling liquor from the gas, and a second stage filter, which is arranged to remove a gaseous phase of the pickling liquor the said gas. The recovered pickling liquor can advantageously be recycled for reuse because it is recovered in a relatively higher concentration that has heretofore been possible.
1. A filtering process for removing a pickling liquor from a gas including a two-stage filtering process having:
a two-stage filtering arrangement for removing the pickling liquor from a gas, present in a fog or mist form as well as in aerosol solution said filtering arrangement comprising:
a first stage candle filter arranged to remove a liquid phase of said pickling liquor from said gas; and
a second stage tray filter arranged to remove a gaseous phase of said pickling liquor from said gas;
the steps comprising:
collecting the gas containing quantities of pickling liquor from a pickling process;
passing said gas through said first stage candle filter;
passing said gas through said second stage tray filter after passing said gas through said sail first stage candle filter;
collecting said pickling liquor from said two-stage filter arrangement;
returning said collected pickling liquor to said process.
2. A two-stage filtering arrangement for removing a pickling liquor from a gas, the pickling liquor being present in a fog or mist form as well as in aerosol solution in the gas, the filtering arrangement comprising:
a first stage candle filter arranged to remove a liquid phase of said pickling liquor from said gas; and
a second stage tray filter disposed in series downstream from said first stage candle filter and arranged to remove a gaseous phase of said pickling liquor from said gas.
3. The two-stage filtering arrangement of claim 2 , wherein the first stage filter contains at least one candle filter element operating to separate pickling liquor droplets from the gas such that said droplets coagulate and collect at a bottom portion of said first stage filter.
4. The two-stage filtering arrangement of claim 2 wherein said second stage filter contains two or more sieve trays disposed sequentially along the filter, and wherein a spray of water trickles down the filter over the two or more sieve trays absorbing pickling, liquor vapors from the gas.
5. The two-stage filtering arrangement of claim 4 , wherein a supply of water is provided to the second stage filter, and wherein the supply of water is substantially less than a corresponding supply of water in a known single-stage filtering arrangement having a tray filter.
6. The two-stage filtering arrangement of claim 4 wherein the water supplied to the second stage tray filter is supplied at about two and one half gallons per minute (2.5 gal./min.).
7. The two-stage filtering arrangement of any of claims 2 to 6 wherein said pickling liquor comprises a concentrate of hydrochloric acid in water.
8. The two-stage filter arrangement of claim 7 wherein the concentration of hydrochloric acid is about 6%.