Recovery of sulfides from tannery waste liquor

In an apparatus for the removal and recovery of sulfides from tannery waste liquor, a close vessel, means for introducing waste tannery liquor containing sulfide into said vessel, means for reducing the pH of said liquor to a value below 5.5, agitating and conveying means disposed in said vessel for conveying and agitating said liquor, said agitating and conveying means comprising a rotatable shaft and a plurality of conveying discs mounted on said shaft, means for maintaining the liquor in said vessel at a level beneath the upper extremities of said discs, so that the upper portions of said discs are exposed, rotation of said shaft acting to agitate and convey said liquor to release hydrogen sulfide gas from said liquor and coagulate proteinaceous material in said liquor, discharge means for discharging the liquor from said vessel, and means in said vessel for converting said hydrogen sulfide gas to sulfhydrate and/or sulfide.

A process for treating waste sulfide liquor from a hide tanning operation, comprising the steps of introducing a hide tanning sulfide liquor into a first zone of a closed vessel, adjusting the pH of the liquor to a value less than 5.5 in said first zone, passing the liquor at said pH through a second zone of said vessel to effect release of hydrogen sulfide gas, spraying an aqueous alkali metal hydroxide solution into contact with the hydrogen sulfide gas in a third zone of said vessel to convert said hydrogen sulfide to alkali metal sulfhydrate and/or alkali metal sulfide, collecting the sprayed solution in a trough in said third zone, agitating the solution in said trough to aid in conversion to said alkali metal sulfhydrate and/or alkali metal sulfide, and discharging the alkali metal sulfhydrate and/or alkali metal sulfide from the vessel.

An apparatus for treating waste sulfide liquor from a hide tanning operation, comprising a closed vessel including a first zone, a second zone, and a third zone, means for introducing tannery waste liquor containing sulfide into said first zone, means or reducing the pH of said liquor in said first zone to a value below 5.5, means for discharging the liquor from said first zone to said second zone, means for continuously advancing the liquor through said second zone to a discharge end of said second to to coagulate proteinaceous materials in said liquor and release hydrogen sulfide to said third zone, said advancing means comprising rotatable conveyor means including a conveyor shaft and a plurality of conveyor discs, said discs being constructed and arranged to convey said liquor towards said discharge end and to agitate said liquor in said second zone, means for discharging said liquor from said discharge end of said second zone, means for contacting said released hydrogen sulfide gas with an alkaline hydroxide solution in said third zone to produce alkaline sulfhydrate and/or alkaline sulfide, and means for discharging said sulfhydrate and/or sulfide from third zone.

A process for treating waste sulfide liquor from a hide tanning operation, comprising the steps of introducing a tannery waste sulfide liquor into a first zone, adjusting the pH of the liquor in said first zone to a value less than 5.5, transferring the liquor from said first zone to a second zone, engaging the liquor in said second zone with a plurality of rotating conveyor discs to agitate and advance said liquor in a downstream direction in said second zone and effect release of hydrogen sulfide gas, maintaining the liquor in said second zone at a predetermined level beneath the upper extremities of said conveyor discs so that the upper portions of said discs are exposed, contacting the released hydrogen sulfide gas in a third zone with an aqueous alkaline solution to form alkali metal sulfhydrate and or alkali metal sulfide, and discharging the alkali metal sulfhydrate and/or alkali metal sulfide from said third zone.

An apparatus for treating waste sulfide liquor from a hide tanning operation, comprising a closed vessel including a first zone, a second zone, and a third zone, means for introducing tannery waste liquor containing sulfide into said first zone, means for reducing the pH of said liquor in said first zone to a value below 5.5, means for discharging the liquor from said first zone to said second zone, means for continuously advancing the liquor through said second zone to a discharge end of said second zone to coagulate proteinaceous materials in said liquor and release hydrogen sulfide to said third zone, means for discharging said liquor from the discharge end of said second zone, spray means for spraying an alkaline hydroxide solution into the flow path of said hydrogen sulfide gas in said third zone to produce alkaline sulfhydrate and/or alkaline sulfide trough means disposed in said third zone and disposed to collect the solution being sprayed from said spray means, and means for discharging said sulfhydrate and/or sulfide from said third zone.