Method for treating acid water containing metallic values

Claim 2

The method of claim 2 in which the alkali of step (a) is high calcium lime.

Claim 3

The method of claim 2 in which said portion of the sludge of step (c) contains at least about 20 pounds of solids per pound of solids precipitated in the second reactor.

Claim 4

The method of claim 2 in which the time of mixing of step (d) is not less than 1 second.

Claim 5

The method of claim 2 in which the time of mixing in step (e) is about 5 minutes to about 20 minutes.

Claim 6

The method of claim 2 in which the acid water is neutralized to a pH of about 7.0 and to about 9.0 with a preferred range of about 7.0 to about 8.0 in step (e).

Claim 7

The method of claim 2 wherein the acid water is waste acid pickle liquor from a steel plant.

Claim 8

In a method for treating acid water containing iron values in the form of ferric iron and compounds taken from the group consisting of aluminum, calcium, magnesium, silicon and zinc, the compounds being sulfates and/or chlorides, wherein the acidity of the water is neutralized and substantially all of the ferric iron values and a substantial portion of the other metallic values are precipitated as solids, which solids settle-out to produce a densified sludge containing at least about 15 percent solids, the method comprising: a. mixing water and at least one alkali taken from the group consisting of high calcium lime, magnesia, dolomitic lime and sodium hydroxide to form a slurry thereof, b. passing the slurry of step (a) to a first reactor, c. recycling a portion of the densified sludge formed in step (f) to the first reactor, d. mixing the slurry of step (a) and the portion of the densified sludge of step (c) for a time to obtain a uniform mix consisting essentially of said slurry and said densified sludge portion, e. thereafter mixing the mix of step (d) with the acid water in a second reactor to neutralize the acidity of the water and to precipitate the metallic values as solids, f. passing the materials of step (e) to a separating means wherein the precipitated solids settle-out to form a densified sludge containing at least about 15 percent solids and clarified neutralized water, and g. drawing off the clarified neutralized water as an overflow from the separating means and passing a portion of the densified sludge to waste.

Claim 9

In a method for treating acid water containing metallic values in the form of ferrous and ferric iron and compounds taken from the group consisting of aluminum, calcium, magnesium, silicon, and zinc, said compounds being sulfates and/or chlorides, wherein the acidity of the water is neutralized and substantially all the ferrous and ferric iron values and a substantial portion of the other metallic values are precipitated as solids, which solids settle-out to produce a densified sludge containing about 15 percent to about 50 percent solids, the method comprising: a. mixing high calcium lime and water to form a slurry of about 1 percent to about 10 percent high calcium lime, b. passing the slurry to a first reactor, c. passing a portion of sludge formed in step (f) to the first reactor, said portion containing about 20 pounds to about 30 pounds of solids for each pound of metallic values precipitated in step (e), d. mixing the slurry of step (a) and the portion of sludge of step (c) for a time between about one second and about 20 minutes to form a mix consisting essentially of said slurry and said sludge portion, e. thereafter mixing the mix of step (d) with the acid water in a second reactor for about 5 minutes to about 20 minutes in the presence of air to neutralize the acidity of the water to a pH of about 7.0 to about 9.0, with a preferred range of about 7.0 to about 8.0, and to oxidize substantially all the ferrous iron and to precipitate substantially all the iron values and a substantial portion of the other metallic values as solids, f. passing the mixture of step (e) to a thickener wherein the precipitated solids settle-out to form a sludge containing about 15 percent to about 50 percent solids and to obtain clarified neutralized water, and g. drawing off the clarified neutralized water as an overflow from the thickener and passing sludge to waste.

Claim 10

In a method for treating acid water containing metallic values in the form of ferric iron and compounds taken from the group consisting of aluminum, calcium, magnesium, silicon, and zinc, said compounds being sulfates and/or chlorides, wherein the acidity of the water is neutralized and substantially all the ferric iron values and a substantial portion of the other metallic values are precipitated as solids, which solids settle-out to produce a densified sludge containing at least about 15 percent solids, the method comprising: a. mixing high calcium lime and water to form a slurry of about 1 percent to about 10 percent high calcium lime, b. passing the slurry to a first reactor, c. passing a portion of sludge formed in step (f) to the first reactor, said portion containing about 20 pounds to about 30 pounds of solids for each pound of metallic values precipitated in step (e), d. mixing the slurry of step (a) and the portIon of sludge of step (c) for a time between about one second and about 20 minutes to form a mix consisting essentially of said slurry and said sludge portion, e. thereafter mixing the mix of step (d) with the acid water in a second reactor for about 5 minutes to about 20 minutes to neutralize the acidity of water to a pH of about 7.0 to about 9.0 with a preferred range of about 7.0 to about 8.0, and to precipitate substantially all the iron values and a substantial portion of the other metallic values as solids, f. passing the mixture of step (e) to a thickener wherein the precipitated solids settle-out to form a sludge containing at least about 15 percent solids and to obtain clarified neutralized water, and g. drawing off the clarified neutralized water as an overflow from the thickener and passing sludge to waste.

Claim 11

In a method for treating acid water containing metallic values in the form of ferrous iron and compounds taken from the group consisting of aluminum, calcium, magnesium, silicon and zinc, said compounds being sulfates and/or chlorides, wherein the acidity of the water is neutralized and substantially all the ferrous iron values and a substantial portion of the other metallic values are precipitated as solids, which solids settle-out to produce a densified sludge containing about 50 percent solids, the method comprising: a. mixing water and at least one alkali taken from the group consisting of high calcium lime, magnesia, dolomitic lime, and sodium hydroxide to form a slurry thereof, b. passing the slurry of step (a) to a first reactor, c. recycling a portion of the densified sludge formed in step (f) to the first reactor, d. mixing the slurry of step (a) and the portion of the densified sludge of step (c) for a time to obtain a uniform mix consisting essentially of said slurry and said densified sludge portion, (e) thereafter mixing the mix of step (d) with the acid water in a second reactor to neutralize the acidity of the water and to precipitate the metallic values as solids, f. passing the materials of step (e) to a separating means wherein the precipitated solids settle-out to form a densified sludge containing about 50 percent solids and clarified neutralized water, and g. drawing off the clarified neutralized water as an overflow from the separating means and passing a portion of the densified sludge to waste.

Claim 12

In a method for treating acid water containing metallic values in the form of ferrous iron and compounds taken from the group consisting of aluminum, calcium, magnesium, silicon and zinc, which compounds are sulfates and/or chlorides wherein the acidity of the water is neutralized and substantially all the ferrous iron and a substantial portion of the other metallic values are precipitated as solids, which solids settle-out to form a densified sludge containing about 50 percent solids, the method comprising: a. mixing high calcium lime and water to form a slurry of about 1 percent to about 10 percent high calcium lime, b. passing the slurry to a first reactor, c. passing a portion of densified sludge formed in step (f) to the first reactor, the portion of densified sludge containing about 20 pounds to about 30 pounds of solids for each pound of metallic values precipitated in step (e), d. mixing the slurry of step (a) and the portion of densified sludge of step (c) for about one second to about 20 minutes to obtain a uniform mix consisting essentially of said slurry and said densified sludge portion, e. thereafter mixing the mix of step (d) with the acid water in a second reactor for about 5 minutes to about 20 minutes to neutralize the acidity of the acid water to a pH of about 7.0 to about 9.0 with a preferred range of about 7.0 to about 8.0 and to precipitate substantially all the ferrous iron values and a substantial portiOn of the metallic values as solids, f. passing the mixture of step (e) to a thickener wherein the precipitated solids settle-out to form a densified sludge containing about 50 percent solids and to obtain clarified neutralized water, and g. drawing off the clarified neutralized water as an overflow from the thickener and passing a portion of the densified sludge to waste.