Chemical fixation of desulfurization residues

Claim 2

Method for the chemical fixation of industrial desulfurization residues containing calcium and sulfur which result from the sulfur constituent removal treatment of gaseous effluent of basic manufacturing processes which comprises: admixing said desulfurization residues with an alkaline argillaceous and calcarious calcination stack dust and adjusting the pH of the resulting admixture with an inorganic acid to a value in the acid pH range below 7 in the presence of sufficient water to provide a mass of workable consistency, and; drying the pH adjusted mass to constant weight to produce an enviornmentally stable and leach resistant hardened solid product.

Claim 3

Method according to claim 1 wherein said stack dust is a calcium and silicate containing cement kiln dust.

Claim 4

Method according to claim 1 wherein said desulfurization residue is a flue gas desulfurization sludge.

Claim 5

Method according to claim 1 wherein said acid is sulfuric acid.

Claim 6

Method according to claim 1 wherein said acid is phosphoric acid.

Claim 7

Method according to claim 1 wherein said acid is an inorganic acid selected from the group consisting of sulfuric, phosphoric, hydrochloric and nitric acids.

Claim 8

Method according to claim 1 wherein said drying is carried out by ambient air drying for about 1 to 2 weeks.

Claim 9

Method according to claim 1 wherein the pH is adjusted to a value in the acid range of from below 7 down to about 5.

Claim 10

Method according to claim 1 wherein said desulfurization residue and said dust are present in the weight ratio range of about 80:20 to 50:50.

Claim 11

Method according to claim 1 wherein said desulfurization residue and said dust are present in the weight ratio of about 50:50.

Claim 12

Method according to claim 1 wherein said water is present in an amount of about 10 to 95% by weight based on the combined weight of said desulfurization residue and dust.

Claim 13

Method according to claim 1 wherein said acid is about 10 Normal in concentration.

Claim 14

Method according to claim 1 wherein said dust and water are alternately added to said desulfurization residue in successive increments with agitation, and thereafter said acid is added thereto.

Claim 15

Method according to claim 1 wherein said desulfurization residue is in the form of a water-containing sludge and said dust is added thereto in successive increments with agitation, and thereafter said acid is added thereto.

Claim 16

Method according to claim 1 wherein the pH is adjusted by adding said acid to the premixed mass of said desulfurization residue, dust and water, in successive increments with agitation.

Claim 17

Method according to claim 1 wherein the pH is adjusted by adding sulfuric acid in an amount of about 12 to 20% by weight H 2 SO 4 based on the combined weight of said desulfurization residue and dust.

Claim 18

Method according to claim 1 wherein the pH is adjusted by adding phosphoric acid in an amount of about 2 to 7% by weight H 3 PO 4 based on the combined weight of said desulfurization residue and dust.

Claim 19

Method according to claim 1 wherein the pH adjusted mass is formed into a shaped article prior to said drying.

Claim 20

Method according to claim 1 for chemical fixation of industrial desulfurization residues which consists essentially of: intimately admixing a flue gas desulfurization sludge containing calcium and sulfur constituents, which results from treatment of sulfur constituent containing gaseous effluent of basic manufacturing processes with alkaline material correspondingly to remove such sulfur constituents from such gaseous effluent, with an alkaline calcium and silicate containing cement kiln dust in the presence of sufficient water to form a mixed solids alkaline mass of workable consistency in which the desulfurization sludge and kiln dust are in the weight ratio range of about 80:20 to 50:50, adjusting the pH of the resulting alkaline mass to a value in the acid range of from below 7 down to about 5 by adding to the mass in successive increments with agitation an acid selected from the group consisting of sulfuric acid and phosphoric acid, forming the pH adjusted mass into a shaped article, and drying the pH adjusted shaped article to constant weight to produce an enviornmentally stable and leach-resistant hardened solid cement-like product.

Claim 21

Method according to claim 19 wherein said drying is carried out by ambient air drying for about 1 to 2 weeks.

Claim 22

Method according to claim 20 wherein said dust and water are alternately added to said desulfurization residue in successive increments with agitation, and the pH is adjusted by adding said acid to the resulting mass in successive increments with agitation.

Claim 23

Method according to claim 20 wherein said desulfurization residue is in the form of a water-containing sludge, and said dust and acid are alternately added thereto in successive increments with agitation to form and adjust the pH of the mass incrementally.

Claim 24

Method according to claim 20 wherein said desulfurization residue and dust are present in the weight ratio of about 50:50, and the pH is adjusted by adding sulfuric acid in an amount of about 12 to 20% by weight H 2 SO 4 based on the combined weight of said desulfurization residue and dust.

Claim 25

Method according to claim 20 wherein said desulfurization residue and dust are present in the weight ratio of about 50:50, and the pH is adjusted by adding phosphoric acid in an amount of about 2 to 7% by weight H 3 PO 4 based on the combined weight of said desulfurization residue and dust.

Claim 26

Product produced according to the method of claim 1.

Claim 27

Product produced according to the method of claim 2.

Claim 28

Product produced according to the method of claim 3.

Claim 29

Product produced according to the method of claim 4.

Claim 30

Product produced according to the method of claim 5.

Claim 31

Product produced according to the method of claim 8.

Claim 32

Product produced according to the method of claim 9.

Claim 33

Product produced according to the method of claim 18.

Claim 34

Product produced according to the method of claim 19.

Claim 35

Product produced according to the method of claim 23.

Claim 36

Product produced according to the method of claim 24.