Improved SO.sub.x, NO.sub.x, and particulate removal system

• US 5,540,897 A
• Filed: 02/27/1995
• Issued: 07/30/1996
• Est. Priority Date: 07/25/1988
• Status: Expired due to Term

• Current Assignee: Babcock & Wilcox Power Generation Group Incorporated (Babcock International Group PLC)
• Original Assignee: Babcock & Wilcox Company (Babcock International Group PLC)
• Inventors: Chu, Paul, Doyle, John B., Downs, William, Smith, Peter V.
• Primary Examiner(s): Warden, Robert
• Assistant Examiner(s): TRAN, HIEN THI
• Application Number:
  US08/394,980
• Time in Patent Office: 519 Days
• Field of Search: 422/171, 422/172, 422/177, 422/180, 422/197, 422/178, 422/222, 422/223, 95/280, 423/239.1, 423/244.01, 423/244.07, 423/235, 502/439, 502/527, 55/302, 55/341.1, 55/341.7, 55/378, 55/379
• US Class Current: 422/177
• CPC Class Codes: B01D 53/8637 Simultaneously removing sulfur oxides and nitrogen oxides

Abstract

A method and apparatus for controlling emissions of a fossil fuel fired boiler including a high temperature fabric filter house with an SCR catalyst situated therein for receiving flue gases along with an injected ammoniacal compound and sorbent. The sorbent reacts with the SO_x while the ammoniacal compound reduces the NO_x in the presence of the SCR catalyst inside the high temperature fabric filter house. Both the SO_x and the particulates are removed upstream of the SCR catalyst to diminish the problems of SO₂ or SO₃ poisoning of the catalyst and erosion and fouling of the catalyst with the fly ash. Since the sulfur oxides and particulates are removed prior to the heat recovery system, the fouling and corrosion potential are substantially decreased thus allowing the heat recovery system to be operated at a lower outlet flue gas temperature which yields an incremental improvement in energy recovery.

Claims

1. An apparatus for controlling emissions of a fossil fuel fired boiler which produces flue gases containing SO_x, NO_x and particulates, comprising:

a flue gas duct constructed so as to carry flue gases from a boiler to a stack for discharge;

a high-temperature pulse jet fabric filter house connected along the flue gas duct between the boiler and the stack, said filter house constructed so as to remove particulate from the flue gas passing along the flue gas duct, said fabric filter house having a plurality of fabric filter bags contained therein with each of said fabric filter bags having a bag retainer situated therein;

a selective catalytic reduction catalyst positioned inside the bag retainer of each of said fabric filter bags in said filter house, said selective catalytic reduction catalyst being coated on wedge-shaped metal plates;

means for recovering heat connected along the flue gas duct downstream of said fabric filter house, said heat recovering means constructed so as to be heated by the flue gases in the flue gas duct;

means for injecting an ammoniacal compound into the flue gas duct upstream of said filter house; and

means for injecting sorbent into the flue gas duct upstream of the filter house whereby the sorbent reacts with SO_x from the flue gas, the particulates are removed in said fabric filter house, thus protecting the selective catalytic reduction catalyst from fly ash erosion and SO_x poisoning.

2. An apparatus for controlling emissions of a fossil fuel fired boiler which produces flue gases containing SO_x, NO_x, and particulates, comprising:

a flue gas duct constructed so as to carry flue gases from a boiler to a stack for discharge;

a high-temperature pulse jet fabric filter house connected along the flue gas duct between the boiler and the stack, said filter house constructed so as to remove particulate from the flue gas passing along the flue gas duct, said fabric filter house having a plurality of fabric filter bags contained therein with each of said fabric filter bags having a bag retainer situated therein;

a selective catalytic reduction catalyst positioned inside the bag retainer of each of said fabric filter bags in said filter house, said selective catalytic reduction catalyst being situated in an upper portion of said bag retainer in said fabric filter bag, said selective catalytic reduction catalyst further having a plurality of passages defining a honeycomb shape, said selective catalytic reduction catalyst further including a blow-back tube extending therethrough for periodically cleaning said fabric filter bag;

means for recovering heat connected along the flue gas duct downstream of said fabric filter house, said heat recovering means constructed so as to be heated by the flue gases in the flue gas duct;

means for injecting an ammoniacal compound into the flue gas duct upstream of said filter house; and

means for injecting sorbent into the flue gas duct upstream of the filter house whereby the sorbent reacts with SO_x from the flue gas, the particulates are removed in said fabric filter house, thus protecting the selective catalytic reduction catalyst from fly ash erosion and SO_x poisoning.

3. An apparatus for controlling emissions of a fossil fuel fired boiler which produces flue gases containing SO_x, NO_x, and particulates, comprising:

a flue gas duct constructed so as to carry flue gases from a boiler to a stack for discharge;

a high-temperature pulse jet fabric filter house connected along the flue gas duct between the boiler and the stack, said filter house constructed so as to remove particulate from the flue gas passing along the flue gas duct, said fabric filter house having a plurality of fabric filter bags contained therein with each of said fabric filter bags having a bag retainer situated therein;

a selective catalytic reduction catalyst positioned inside the bag retainer of each of said fabric filter bags in said filter house, said selective catalytic reduction catalyst being a catalyst bed situated in a first cylinder that is surrounded coaxially by a second cylinder with both of said cylinders being constructed of a porous material;

means for recovering heat connected along the flue gas duct downstream of said fabric filter house, said heat recovering means constructed so as to be heated by the flue gases in the flue gas duct;

means for injecting an ammoniacal compound into the flue gas duct upstream of said filter house; and

means for injecting sorbent into the flue gas duct upstream of the filter house whereby the sorbent reacts with SO_x from the flue gas, the particulates are removed in said fabric filter house, thus protecting the selective catalytic reduction catalyst from fly ash erosion and SO_x poisoning.

4. A catalytic fabric filter house, comprising:

a fabric filter house constructed to receive a flue gas and to remove particulate therefrom, said fabric filter house having at least one fabric filter bag contained therein with each of the at least one fabric filter bag having a bag retainer situated therein; and

a selective catalytic reduction catalyst positioned inside the bag retainer of the at least one fabric filter bag in said fabric filter house for reducing nitrogen oxides with ammonia in the flue gas said selective catalytic reduction catalyst having a plurality of passages and being positioned to allow the flue gas to pass therethrough.

5. A catalytic fabric filter house as recited in claim 4, wherein said selective catalytic reduction catalyst is honeycomb in shape.

6. A catalytic fabric filter house as recited in claim 4, wherein said selective catalytic reduction catalyst includes a blow-back tube centrally located therein and extending therethrough.

7. A catalytic fabric filter house as recited in claim 4, wherein said selective catalytic reduction catalyst passages include wedge-shaped passages.

8. A catalytic fabric filter house as recited in claim 7, wherein said selective catalytic reduction catalyst is coated on metal plates.

9. A catalytic fabric filter house, comprising:

a fabric filter house constructed to receive a flue gas and to remove particulate therefrom., said fabric filter house having at least one fabric filter bag contained therein with each of the at least one fabric filter bag having a bag retainer situated therein; and

a selective catalytic reduction catalyst bed for reducing nitrogen oxides with ammonia in the flue gas stream, said selective catalytic reduction catalyst positioned between said bag retainer of the at least one fabric filter bag and an inner concentric cylinder, both said bag retainer and said inner cylinder being constructed of a porous material, said bag retainer and inner cylinder with said catalyst bed being constructed to be positioned inside the at least one fabric filter bag.

10. A catalytic fabric filter house, comprising:

a fabric filter house constructed to receive a flue gas and to remove particulate therefrom, said fabric filter house having at least one fabric filter bag contained therein with each of the at least one fabric filter bag having a bag retainer situated therein; and

a selective catalytic reduction catalyst bed for reducing nitrogen oxides with ammonia in the flue gas stream, said selective catalytic reduction catalyst bed positioned inside a cylinder surrounded concentrically by said bag retainer of the at least one fabric filter bag with both said cylinder and said bag retainer being constructed of a porous material and being constructed to be positioned inside the at least one fabric filter bag.