Method for treating aqueous feed by dissolved gas flotation

Patent metadata

Field	Value
Publication number	US-11629459-B2
Application number	US-201816766718-A
Country	US
Kind code	B2
Filing date	Dec 14, 2018
Priority date	Dec 15, 2017
Publication date	Apr 18, 2023
Grant date	Apr 18, 2023

Abstract

A method is disclosed for treating aqueous feed by dissolved gas flotation. The aqueous feed originates from industrial processing of fibrous material, where the aqueous feed includes an aqueous phase and solid particulate material suspended in the aqueous phase. The method includes bringing a flocculant in contact with the aqueous feed, flocculating suspended solid particulate material into flocs and contacting formed flocs with gas bubbles and inducing their flotation in a flotation basin. The flocculant includes a polymer composition having a charge density of at the most 1.7 meq/g dry and the polymer composition includes a cationic synthetic first polymer having a charge density at least 1.0 meq/g dry at pH 2.8, and at least one second polymer obtained by polymerization of (meth)acrylamide, the second polymer being polymerized in presence of the cationic first polymer, where the first polymer has a higher charge density than the second polymer.

First claim

The invention claimed is:

1. A method for treating an aqueous feed by dissolved gas flotation, the aqueous feed originating from an industrial processing of fibrous material of cellulosic origin, wherein the aqueous feed comprises an aqueous phase and a solid particulate material suspended in the aqueous phase, wherein the method comprises:
bringing a flocculant in contact with the aqueous feed and flocculating the suspended solid particulate material into flocs through interaction of the flocculant and the suspended solid particulate material,
contacting formed flocs with gas bubbles and inducing their flotation in a flotation basin,

wherein
the flocculant, which is used for flocculating the suspended solid particulate material, comprises a polymer composition having a charge density of at the most 1.7 meq/g dry, and the polymer composition comprises: comprising:
a cationic synthetic first polymer, which has a charge density of at least 1.0 meq/g dry at pH 2.8,
at least one cationic second polymer, which is a polymer obtained by polymerization of (meth)acrylamide and at least one cationic second monomer in presence of the cationic first polymer, an amount of the second monomer being 0.2-19 weight-%, calculated from total dry polymeric material weight of the polymer composition, and
wherein the cationic synthetic first polymer has a higher charge density than the at least one second cationic polymer.

2. The method according to claim 1 , wherein the cationic synthetic first polymer has charge density in a range of 1-12 meq/g dry, at pH 2.8.

3. The method according to claim 1 , wherein the cationic synthetic first polymer is selected from polyamines; homopolymers of cationic first monomer, obtained by radical polymerization; copolymers of acrylamide and a cationic first monomer, obtained by radical polymerization; or any combinations thereof.

4. The method according to claim 3 , wherein the cationic synthetic first polymer is polyamine selected from copolymers of epichlorohydrin and dimethylamine, copolymers of epichlorohydrin, dimethylamine and ethylenediamine, and linear or cross-linked polyamidoamines.

5. The method according to claim 3 , wherein the cationic synthetic first polymer is a homopolymer of cationic first monomer selected from group consisting of 2-(dimethylamino)ethyl acrylate (ADAM), [2-(acryloyloxy)ethyl] trimethylammonium chloride (ADAM-Cl), 2-(dimethylamino)ethyl acrylate benzylchloride, 2-(dimethylamino)ethyl acrylate dimethylsulphate, 2-dimethylaminoethyl methacrylate (MADAM), [2-(methacryloyloxy)ethyl] trimethylammonium chloride (MADAM-Cl), 2-dimethylaminoethyl methacrylate dimethylsulphate, [3-(acryloylamino)propyl] trimethylammonium chloride (APTAC), [3-(methacryloylamino)propyl] trimethylammonium chloride (MAPTAC), and diallyldimethyl-ammonium chloride (DADMAC).

6. The method according to claim 1 , wherein the polymer composition comprises cationic synthetic first polymer in amount of 0.5-35 weight-%, calculated from the dry polymeric material weight of the polymer composition.

7. The method according to claim 1 , wherein the cationic first polymer has a weight average molecular weight MW<500 000 g/mol.

8. The method according to claim 1 , wherein the second polymer is cationic and the second monomer is selected from group consisting of 2-(dimethylamino)ethyl acrylate (ADAM), [2-(acryloyloxy)ethyl] trimethylammonium chloride (ADAM-Cl), 2-(dimethylamino)ethyl acrylate benzylchloride, 2-(dimethylamino)ethyl acrylate dimethylsulphate, 2-dimethylaminoethyl methacrylate (MADAM), [2-(methacryloyloxy)ethyl] trimethylammonium chloride (MADAM-Cl), 2-dimethylaminoethyl methacrylate dimethylsulphate, [3-(acryloylamino)propyl] trimethylammonium chloride (APTAC), [3-(methacryloylamino)propyl] trimethylammonium chloride (MAPTAC), and diallyldimethyl-ammonium chloride (DADMAC).

9. The method according to claim 1 , wherein the second polymer is obtained by using adiabatic gel polymerization.

10. The method according to claim 1 , wherein the polymer composition has a standard viscosity in a range of 3-6 mPas.

11. The method according to claim 1 , wherein the polymer composition has an intrinsic viscosity in a range of 4- 20 dl/g.

12. The method according to claim 1 , wherein the aqueous feed comprises suspended solid particulate material in total amount of less than 6000 mg/l.

13. The method according to claim 1 , wherein the aqueous feed has a conductivity in a range of 0.2-10 mS/cm.

14. The method according to claim 1 , wherein the aqueous feed has a cationic demand value in a range of 20-3000 μeq/l.

15. The method according to claim 1 , wherein the pH of the aqueous feed is in a range of 4-9.5.

16. The method according to claim 1 , wherein the suspended solid particulate material comprises inorganic mineral particles and cellulosic fibres and/or fibrils.

17. The method according to claim 1 , wherein the flocculant comprising the polymer composition is used in amount of 0.1-10 mg/l, given as dry polymer composition per aqueous feed volume.

18. The method according to claim 1 , wherein a coagulant is introduced to the aqueous feed before the aqueous feed is brought in contact with the flocculant.

Assignees

• Kemira Oyj

Inventors

• Hietaniemi Matti
• Välimäki Jyri
• Likander Joonas
• Carceller Rosa

Classifications

• D21B1/322

  coated with synthetic materials · CPC title

• D21C5/027 Primary

  Chemicals therefor · CPC title

• D21C11/0042

  Fractionating or concentration of spent liquors by special methods (concentration by evaporation D21C11/10) · CPC title

• C02F1/56

  Macromolecular compounds · CPC title

• D21B1/327

  using flotation devices · CPC title