Method and a system for producing hydrochloric acid from flue gases

Patent metadata

Field	Value
Publication number	US-2021354076-A1
Application number	US-201917273640-A
Country	US
Kind code	A1
Filing date	Sep 24, 2019
Priority date	Sep 24, 2018
Publication date	Nov 18, 2021
Grant date	—

Abstract

A method for producing aqueous hydrochloric acid from flue gases is provided. The method comprises conveying water to a first scrubber (102, 202, 302, 402, 502, 602, 702) or to a line (112b, 212b, 312b, 412b, 512b, 712b, 712c) to use the water in a scrubbing liquid of the first scrubber. The method also comprises providing flue gas containing chlorides into the first scrubber (102, 202, 302, 402, 502, 602, 702) and scrubbing the flue gas containing chlorides with the scrubbing liquid by contacting the flue gas with the scrubbing liquid in the first scrubber (102, 202, 302, 402, 502, 602, 702). Dilute hydrochloric acid and a flue gas derivate (104, 204, 304, 404, 504, 704) are produced. The method comprises letting out at least some of the dilute hydrochloric acid from the first scrubber (102, 202, 302, 402, 502, 602, 702) as a scrubber bleed, separating solids suspended by the scrubber bleed in a solids separator (192, 592, 692), conveying the scrubber bleed from the solids separator (192, 592, 692) into an evaporation vessel (194, 594, 694) and concentrating the scrubber bleed in the evaporation vessel (194, 594, 694) to produce hydrochloric acid vapor having a concentration of 5-22 wt-%. A corresponding system is also provided.

First claim

1 . A method for producing aqueous hydrochloric acid from flue gases, the method comprising the steps of:
conveying water to a first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ) or to a line ( 112 b , 212 b , 312 b , 412 b , 512 b , 712 b , 712 c ) to use the water in a scrubbing liquid of the first scrubber, the scrubbing liquid being aqueous hydrochloric acid or water, providing flue gas containing chlorides into the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ), scrubbing the flue gas containing chlorides with the scrubbing liquid by contacting the flue gas with the scrubbing liquid in the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ), thereby producing dilute hydrochloric acid and a flue gas derivate ( 104 , 204 , 304 , 404 , 504 , 704 ), the dilute hydrochloric acid being an aqueous solution of hydrochloric acid, wherein a content of hydrochloric acid is at most 20 wt-%, letting out at least some of the dilute hydrochloric acid from the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ) as a scrubber bleed, separating solids suspended by the scrubber bleed in a solids separator ( 192 , 592 , 692 ), conveying the scrubber bleed from the solids separator ( 192 , 592 , 692 ) into an evaporation vessel ( 194 , 594 , 694 ), and concentrating the scrubber bleed in the evaporation vessel ( 194 , 594 , 694 ) to produce hydrochloric acid vapor having a concentration of 5-22 wt-%.

2 . The method according to claim 1 , further comprising the step of:
circulating the scrubbing liquid within the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ) by spraying the circulated scrubbing liquid onto the flue gas containing chlorides.

3 . The method according to claim 1 , wherein:
the water comprises at most 1 wt-% impurities; and preferably the scrubbing liquid comprises at most 1 wt-% other compounds than water and hydrochloric acid.

4 . The method according to claim 1 , further comprising the step of:
maintaining a level of the scrubbing liquid in the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ) by controlling an amount of the water conveyed to the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ).

5 . The method according to claim 1 , further comprising the steps of:
introducing the hydrochloric acid vapor from the evaporation vessel ( 194 , 594 , 694 ) into a concentrator ( 540 ), and concentrating the hydrochloric acid vapor in the concentrator ( 540 ), to produce hydrochloric acid having a concentration of over 30 wt-%.

6 . The method according to claim 1 , further comprising the step of:
prior to providing the flue gas containing chlorides into the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ), cooling the flue gas with a heat exchanger ( 653 ) and removing particles from the cooled flue gas using a particle separating unit ( 654 ).

7 . The method according to claim 1 , further comprising the step of:
removing catalytically nitrogen oxide and/or nitrogen oxides from the flue gas containing chlorides; wherein the removing step preferably occurs before cooling of the flue gas containing chlorides with a heat exchanger ( 653 ).

8 . The method according to claim 1 , further comprising the steps of:
introducing the flue gas derivate ( 104 , 204 , 304 , 404 , 504 , 704 ) from the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ) into a second scrubber ( 313 ); and removing at least sulphur oxide and/or sulphur oxides from the flue gas derivate ( 104 , 204 , 304 , 404 , 504 , 704 ) in the second scrubber ( 313 ).

9 . The method according to claim 1 , further comprising the step of:
burning fuel ( 650 ) to produce the flue gas containing chlorides, wherein the fuel ( 650 ) comprises at least one of the following: biomass, coal, and waste; preferably the fuel ( 650 ) comprises coal and biomass-based compound.

10 . The method according to claim 1 , further comprising the steps of:
prior to scrubbing, recovering heat from the flue gas containing chlorides to a heat exchange medium, such as water and/or steam, and producing electricity using the heat of the heat exchange medium.

11 . The method according to claim 1 , wherein the flue gas containing chlorides is scrubbed with at least one scrubbing liquid by contacting the flue gas with the scrubbing liquid(s) in at least two washing stages; preferably the scrubber bleed is taken from a first washing stage, which is arranged upstream from all other washing stages in the direction of flow of the flue gas.

12 . The method according to claim 1 , comprising further the steps of:
contacting the flue gas comprising chlorides with a first scrubbing liquid in a first washing stage to scrub the flue gas comprising chlorides, conveying the scrubbed flue gas from the first washing stage to a second washing stage, and contacting the flue gas comprising chlorides with a second scrubbing liquid in the second washing stage to scrub the flue gas comprising chlorides, wherein:
the first scrubbing liquid has a first content of hydrochloric acid,
the second scrubbing liquid has a second content of hydrochloric acid, and
the first content of hydrochloric acid is greater than the second content of hydrochloric acid; preferably the scrubber bleed is taken from the first washing stage and the first washing stage is arranged upstream from all other washing stages in the direction of flow of the flue gas.

13 . A system ( 100 , 300 , 500 , 600 ) arranged to produce aqueous hydrochloric acid from flue gases, the system comprising:
a first conduit ( 101 , 201 , 301 , 401 , 501 , 601 , 701 ) configured to feed flue gas containing chlorides into a first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ), a second conduit ( 103 , 203 , 303 , 403 , 503 , 703 ) configured to convey water to be used in a scrubbing liquid of the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 703 ), a line ( 112 b , 212 b , 312 b , 412 b , 512 b , 712 b ) configured to convey scrubbing liquid comprising the water into the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ) and a first line ( 105 , 205 , 305 , 405 , 505 , 705 ) for expelling dilute hydrochloric acid as a scrubber bleed from the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ), wherein:
the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ) is configured to scrub the flue gas containing chlorides with the scrubbing liquid, the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ) thereby being configured to produce the scrubber bleed and a flue gas derivate ( 104 , 204 , 304 , 404 , 504 , 704 ), and
the system further comprises:
a solids separator ( 192 , 592 , 692 ) for separating solids suspended by the scrubber bleed,
an evaporation vessel ( 194 , 594 , 694 ) comprising a heater ( 197 ) for heating the scrubber bleed from which the solids have been separated, and
a second line ( 193 , 593 ) for conveying the scrubber bleed from the solids separator ( 192 , 592 , 692 ) into the evaporation vessel ( 194 , 594 , 694 ),
the evaporation vessel ( 194 , 594 , 694 ) being configured to concentrate the scrubber bleed to produce hydrochloric acid vapor having a concentration of 5-22 wt-%.

14 . The system according to claim 13 , further comprising:
a first sensor ( 430 ) for determining a concentration of the dilute hydrochloric acid in the first scrubber ( 102 , 202 , 302 , 402 , 502 , 602 , 702 ), a first

Assignees

• Valmet Technologies Oy

Inventors

• Hämäläinen Risto
• Korhonen Tarja
• Chenna Naveen
• Kokko Lauri

Classifications

• B01D53/1456 Primary

  Removing acid components · CPC title

• B01J2208/00106

  by indirect heat exchange · CPC title

• B01D53/1418 Primary

  Recovery of products · CPC title

• B01D2257/2045

  Hydrochloric acid · CPC title

• B01D53/68

  Halogens or halogen compounds · CPC title