Method for removing mercury from washer suspensions

Patent metadata

Field	Value
Publication number	US-10280104-B2
Application number	US-201615091989-A
Country	US
Kind code	B2
Filing date	Apr 6, 2016
Priority date	Apr 15, 2015
Publication date	May 7, 2019
Grant date	May 7, 2019

Abstract

A method for removing mercury from flue gas in a flue gas desulfurization plant, in which the mercury concentration in the FGD gypsum is reduced without increasing the size of the waste water treatment plant, by increasing the volume-related mercury concentration in the wash wastewater and feeding this more concentrated flow of waste water to the waste water treatment plant.

First claim

The invention claimed is:

1. A method for removing mercury in a gypsum suspension ( 1 ) produced in a scrubber ( 10 ) of a wet flue gas scrubbing plant, comprising:
thickening said suspension ( 1 ) by at least one gypsum hydrocyclone ( 11 );
discharging the thickened suspension from the gypsum hydrocyclone ( 11 ) as underflow ( 3 );
discharging a first overflow waste water containing solids including mercury attached to fine material, from the gypsum hydrocyclone ( 11 ) and feeding said discharged first overflow waste water to at least one waste water cyclone ( 12 ), where solids are recovered and second overflow waste water ( 5 ) containing mercury attached to fine material is discharged;
feeding the discharged second overflow wastewater containing a concentration of mercury attached to fine material, into a mercury concentrator ( 14 ) where water ( 8 ) is separated and the mercury concentration is thereby increased in a third flow of wastewater;
delivering the third flow of wastewater with increased mercury concentration ( 7 ) to a water treatment plant ( 13 ), wherein the water ( 8 ) separated during concentration is fed to the scrubber ( 10 ).

2. The method according to claim 1 wherein water is fed to the gypsum hydrocyclone ( 11 ) through a dedicated feed pipe in addition to the gypsum suspension ( 1 ), thus resulting in fine material depletion in the underflow ( 3 ) in relation to the suspension volume.

3. The method according to claim 2 , wherein the gypsum is washed in two-stage gypsum dewatering with intermediate dilution using process water.

4. The method according to claim 2 wherein the concentration of the second overflow waste water ( 5 ) containing mercury is increased by one of a centrifuge, a sedimenter, or by flotation.

5. The method according to claim 1 wherein the gypsum is washed in two-stage gypsum dewatering with intermediate dilution using process water.

6. The method according to claim 1 wherein the concentration of the second overflow waste water ( 5 ) containing mercury is increased by one of a centrifuge, a sedimenter, or by flotation.

7. The method according to claim 1 wherein water is fed to the gypsum hydrocyclone ( 11 ) through a dedicated feed pipe in addition to the gypsum suspension ( 1 ), thus resulting in fine material depletion in the underflow ( 3 ) in relation to the suspension volume.

8. The method according to claim 1 , wherein the gypsum is washed in two-stage gypsum dewatering with intermediate dilution using process water.

9. The method according to claim 1 , wherein the concentration of the second overflow waste water ( 5 ) containing mercury is increased by one of a centrifuge, a sedimenter, or by flotation.

10. The method of claim 1 ,
water is fed to the gypsum hydrocyclone ( 11 ) through a dedicated feed pipe in addition to the gypsum suspension ( 1 ), thus resulting in fine material depletion in the underflow ( 3 ) in relation to the suspension volume;
the gypsum is washed in two-stage gypsum dewatering with intermediate dilution using process water; and
the concentration of the overflow waste water ( 5 ) containing mercury is increased by one of a centrifuge, a sedimenter, or by flotation.

Assignees

• Andritz Ag Maschf

Inventors

• Kramer Michael
• Reissner Harald

Classifications

• C02F9/00 Primary

  Multistage treatment of water, waste water or sewage · CPC title

• C02F1/24

  by flotation (C02F1/465 takes precedence) · CPC title

• C02F2101/20

  Heavy metals or heavy metal compounds · CPC title

• C02F2103/18

  from the purification of gaseous effluents · CPC title

• B01D53/64 Primary

  Heavy metals or compounds thereof, e.g. mercury · CPC title