In situ gas scrubbing method and system for odor and corrosion control in wastewater collection systems

• US 6,365,099 B1
• Filed: 11/12/1998
• Issued: 04/02/2002
• Est. Priority Date: 11/12/1998
• Status: Expired due to Term

• Current Assignee: PeroxyChem LLC (Rag-Stiftung)
• Original Assignee: FMC Corporation
• Inventors: Castrantas, Harry M., Duggan, Scott W.
• Primary Examiner(s): MCKANE, ELIZABETH L
• Application Number:
  US09/190,532
• Time in Patent Office: 1,237 Days
• Field of Search: 422/4, 422/5, 422/123, 422/306, 951/49, 952/35, 962/43, 423/220, 423/242.1, 423/243.01, 423/243.08, 423/243.06, 423/232
• US Class Current: 422/5
• CPC Class Codes: A61L 2209/22 Treatment by sorption, e.g. absorption, adsorption, chemisorption, scrubbing, wet cleaning
• CPC Class Codes: A61L 9/145 air-liquid contact processes, e.g. scrubbing
• CPC Class Codes: B01D 53/52 Hydrogen sulfide

Abstract

A process and system for reducing the concentration of odorous contaminants, primarily hydrogen sulfide, in the vapor spaces of sewage handling and treatment systems, primarily the vapor spaces of sewage trunk lines, by injecting a fine spray, mist or fog of a dilute solution of hydrogen peroxide and a base selected from a group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide and sodium carbonate to mix intimately with the vapor flow. The peroxide and base solutions may be pre-mixed and diluted with water and injected through atomizing nozzles utilizing compressed air as an atomizing fluid. The system may also provide for separate storage of the peroxide and base solutions, mixing of the peroxide and base solutions with dilution water with in-line mixing devices and direct injection with or without compressed air atomization into the vapor space. Sewage trunk lines, in particular, are treated at a substantial distance upstream of the sewage treatment facility to allow for adequate reaction time to reduce the concentration of the contaminant and reduce loading and corrosion on sewage treatment and foul air handling and scrubbing equipment.

Claims

1. A process for reducing odorous contaminant concentration comprising hydrogen sulfide in a vapor space of a sewage conduit through which a flow of vapor including said hydrogen sulfide is being induced and through which liquid sewage is flowing toward a sewage treatment plant, comprising the steps of:

providing a system including at least one spray nozzle connected to conduit means for conducting an alkaline-peroxide reagent comprising a first solution of base selected from a group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide and sodium carbonate and a second solution comprising hydrogen peroxide for injection into said vapor space;

placing said spray nozzle in said vapor space above a surface of said liquid flowing through said sewage conduit at a point upstream of a point of inducing said flow of vapor through said vapor space such as to provide a spray pattern extending substantially across the cross sectional area of said vapor space above said surface of said liquid; and

injecting said first solution and said second solution into said vapor space through said spray nozzle in a fine spray to provide intimate contact between said solutions and said odorous contaminant to oxidize said odorous contaminant and to contact a wall of said sewage conduit delimiting said vapor space to reduce corrosion thereof.

2. The process set forth in claim 1 wherein:

said second solution is provided as a solution of hydrogen peroxide in a minimum mole ratio to hydrogen sulfide of 4;

1 and said first solution comprising said base is provided in a minimum mole ratio to hydrogen peroxide of 2;

1.

3. The process set forth in claim 2 including the step of:

providing said second solution as a diluted solution of hydrogen peroxide in a concentration of one percent to five percent by weight.

4. The process set forth in claim 2 including the step of:

providing said first solution as a diluted solution in a concentration of said base of one percent to three percent by weight.

5. The process set forth in claim 1 including the step of:

providing said system comprising;

a source of said base;

a metering pump operably connected to said source of said base and to said conduit means for conducting a metered flow of said solution of said base to said spray nozzle;

a source of said hydrogen peroxide;

a metering pump operably connected to said source of hydrogen peroxide and to said conduit means for conducting a metered flow of said solution of hydrogen peroxide to said spray nozzle;

a metering pump operably connected to a source of water and to said conduit means for conducting dilution water to mix with said base and said hydrogen peroxide prior to injection through said spray nozzle into said vapor space;

a mixer for mixing water with said hydrogen peroxide and said base to provide a dilute mixed solution of said alkaline-peroxide reagent for injection through said conduit means and said spray nozzle into said vapor space; and

a source of pressure air connected to said spray nozzle for atomizing said solution of alkaline-peroxide reagent to form said spray pattern.

6. The process set forth in claim 5 including the step of:

providing said mixer comprising a first mixer for receiving a solution of water and one of said base and said hydrogen peroxide and a second mixer for receiving a mixed solution of said water and said one of said base and hydrogen peroxide and for mixing the other of said base and said hydrogen peroxide with said mixed solution prior to injection of said alkaline-peroxide reagent into said vapor space.

7. The process set forth in claim 5 including the step of:

providing said system with shutoff valve means interposed in respective conduits between said metering pumps and said sources of said base and said hydrogen peroxide, respectively, for controlling the flow of said base and said hydrogen peroxide through said conduit means and said spray nozzle.

8. A process for reducing odorous contaminant concentration comprising at least one of hydrogen sulfide, mercaptans, sulfur dioxide, amines and aldehydes in a vapor space of a sewage conduit through which a flow of vapor including said odorous contaminant is being induced and through which liquid sewage is flowing toward a sewage treatment plant, comprising the steps of:

providing a system including at least one spray nozzle connected to a conduit for conducting an alkaline-peroxide reagent therethrough and adapted to be inserted into said vapor space of said sewage conduit, said system further comprising a source of a base in solution and selected from a group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide and sodium carbonate, a metering pump operably connected to said source of said base and to said conduit for conducting a metered flow of said solution of said base to said spray nozzle, a source of said hydrogen peroxide, a metering pump operably connected to said source of hydrogen peroxide and to said conduit for conducting a metered flow of solution of hydrogen peroxide to said spray nozzle, a metering pump operably connected to a source of water and to said conduit for conducting dilution water to mix with said base and said hydrogen peroxide prior to injection through said spray nozzle into said vapor space, a mixer for mixing water with said hydrogen peroxide and said base to provide a dilute mixed solution of said alkaline-peroxide reagent for injection through said conduit and said spray nozzle into said vapor space, and a source of pressure air connected to said spray nozzle for atomizing said solution of alkaline-peroxide reagent to form a spray pattern extending substantially across the cross sectional area of said vapor space above a surface of said liquid in said sewage conduit;

placing said spray nozzle in said vapor space above said surface of said liquid in said sewage conduit at a point such that said spray pattern extends substantially across the cross sectional area of said vapor space above said surface of said liquid to provide intimate contact between said solutions and said odorous contaminant and to contact a wall of said sewage conduit delimiting said vapor space to reduce corrosion thereof; and

injecting said solutions into said vapor space through said spray nozzle in a fine spray to provide said intimate contact between said solutions and said odorous contaminant to oxidize said odorous contaminant and to contact said wall to reduce corrosion thereof.

9. A system for injecting an alkaline-peroxide reagent into a vapor space of a sewage handling conduit contaminated with hydrogen sulfide at a point upstream of a sewage treatment plant, said system including:

a substantially rigid fluid conducting conduit for insertion through a manway into said sewage handling conduit and supporting at least one spray nozzle for disposition in said vapor space of said sewage handling conduit, said conduit and said nozzle being configured for injecting a spray of said alkaline-peroxide reagent into said vapor space in a spray pattern extending substantially across the cross-section of said vapor space and to contact a wall of said sewage handling conduit defining said vapor space for mixing said alkaline-peroxide reagent with hydrogen sulfide contaminated vapor flowing through said vapor space and for reducing corrosion of said wall;

a source of a base selected from a group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide and sodium carbonate;

a metering pump operably connected to said source of said base and said rigid conduit for conducting a metered flow of a solution of said base to said nozzle;

a source of hydrogen peroxide;

a metering pump operably connected to said source of hydrogen peroxide and to said rigid conduit for conducting a metered flow of a solution of hydrogen peroxide to said nozzle;

a metering pump operably connected to a source of water and to said rigid conduit for conducting dilution water to mix with said base and said hydrogen peroxide prior to injection through said nozzle into said vapor space; and

an arrangement of fluid mixers for mixing said water with said hydrogen peroxide and said base to provide a dilute mixed solution of alkaline-peroxide reagent for injection into said vapor space through said nozzle.

10. The system set forth in claim 9, including:

a source of pressure air connected to said nozzle for atomizing said solution of alkaline-peroxide reagent to form said spray pattern in said vapor space.

11. The system set forth in claim 9, wherein:

said arrangement of mixers comprises a first mixer for receiving a solution of water and one of said base and hydrogen peroxide and a second mixer for receiving a mixed solution of water and said one of said base and hydrogen peroxide and for mixing the other of said base and hydrogen peroxide with said mixed solution prior to injection of said alkaline-peroxide reagent into said vapor space.

12. The system set forth in claim 9, including:

shut-off valves interposed in respective conduits between said metering pumps and said sources of said base and said hydrogen peroxide, respectively, for controlling the flow of said base and said hydrogen peroxide through said system.