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WO2022260526A1 - A system for removing ammonia from an ammonia-containing gas and a method for removing ammonia from an ammonia-containing gas - Google Patents

A system for removing ammonia from an ammonia-containing gas and a method for removing ammonia from an ammonia-containing gas Download PDF

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Publication number
WO2022260526A1
WO2022260526A1 PCT/NO2021/050144 NO2021050144W WO2022260526A1 WO 2022260526 A1 WO2022260526 A1 WO 2022260526A1 NO 2021050144 W NO2021050144 W NO 2021050144W WO 2022260526 A1 WO2022260526 A1 WO 2022260526A1
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WO
WIPO (PCT)
Prior art keywords
ammonia
scrubber
inlet
gas
outlet
Prior art date
Application number
PCT/NO2021/050144
Other languages
French (fr)
Inventor
Odd Ivar LINDLØV
Lars Grønnæss
Leidulf Dyrland
Original Assignee
Wärtsilä Gas Solutions Norway AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Wärtsilä Gas Solutions Norway AS filed Critical Wärtsilä Gas Solutions Norway AS
Priority to PCT/NO2021/050144 priority Critical patent/WO2022260526A1/en
Publication of WO2022260526A1 publication Critical patent/WO2022260526A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1425—Regeneration of liquid absorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/54—Nitrogen compounds
    • B01D53/58—Ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/96—Regeneration, reactivation or recycling of reactants
    • B01D53/965—Regeneration, reactivation or recycling of reactants including an electrochemical process step
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/04—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of inorganic compounds, e.g. ammonia
    • C01B3/047—Decomposition of ammonia
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C1/00—Ammonia; Compounds thereof
    • C01C1/02—Preparation, purification or separation of ammonia
    • C01C1/12—Separation of ammonia from gases and vapours
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/02—Hydrogen or oxygen
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B15/00—Operating or servicing cells
    • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
    • C25B15/081—Supplying products to non-electrochemical reactors that are combined with the electrochemical cell, e.g. Sabatier reactor
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B15/00—Operating or servicing cells
    • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
    • C25B15/087—Recycling of electrolyte to electrochemical cell
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/07—Common duct cells
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/40—Nitrogen compounds
    • B01D2257/406—Ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0208—Other waste gases from fuel cells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0283—Flue gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2259/00—Type of treatment
    • B01D2259/45—Gas separation or purification devices adapted for specific applications
    • B01D2259/4566—Gas separation or purification devices adapted for specific applications for use in transportation means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/002—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by condensation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8634—Ammonia
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B43/00—Engines characterised by operating on gaseous fuels; Plants including such engines
    • F02B43/10—Engines or plants characterised by use of other specific gases, e.g. acetylene, oxyhydrogen

Definitions

  • the present disclosure relates to a system for removing ammonia from an ammonia- containing gas and a method for removing ammonia from an ammonia-containing gas. More specifically, the disclosure relates to a system for removing ammonia from an ammonia- containing gas and a method for removing ammonia from an ammonia-containing gas as defined in the introductory parts of claim 1 and claim 10.
  • Ammonia is considered a promising candidate for carbon free fuels for deep-sea voyage to reach future CO2 emission targets.
  • ammonia As fuel, there is a general concern about releases due to the toxic nature of ammonia and the strong smell that could cause panic on a passenger vessel.
  • Ammonia scrubbers also referred to as wet scrubbers or acid scrubbers, have been identified as a possible solution for the treatment of operational and emergency releases of ammonia.
  • Ammonia scrubbers are used in the onshore industry for the treatment of gases or air containing ammonia.
  • An ammonia scrubber is specifically designed to remove harmful ammonia and particulates from industrial exhaust streams.
  • Ammonia scrubbers may incorporate a variety of gas-liquid contacting techniques, including i.a., packed beds, spray chambers, and water jets.
  • An Ammonia scrubber works by leading ammonia-containing gas from the bottom and up through the scrubber, and inside the scrubber a scrubber liquid is brought into contact with the gas to remove ammonia.
  • Purified gas leaves the scrubber from the top, and the scrubber liquid used in the gas scrubbing leaves from the bottom of the scrubber.
  • Open loop scrubbers with water can be used, but released water will contain dissolved ammonia and will in general not be accepted for operational ammonia releases.
  • acid is used to neutralize the dissolved ammonia in a closed loop scrubber system.
  • the resulting mixture of water, acid and ammonia is normally a dissolved salt that can be used as a component in fertilizers.
  • a system for removing ammonia from an ammonia-containing gas comprising: an ammonia scrubber, the ammonia scrubber containing an inlet for ammonia-containing gas, a scrubber liquid inlet, a treated gas outlet and a scrubber liquid outlet connected in a closed loop to at least one pump, an electrolytic cell for regeneration of scrubber liquid, and the scrubber liquid inlet, the electrolytic cell comprising a scrubber liquid inlet, at least one anode and at least one cathode connected to at least one power source, and a scrubber liquid outlet.
  • the electrolytic cell further comprises at least one gas outlet.
  • the system comprises a second scrubber liquid outlet from the scrubber, a pump and a second scrubber liquid inlet into the scrubber.
  • the electrolytic cell is configured to split produced hydrogen and nitrogen gas by a separating wall in the electrolytic cell.
  • the electrolytic cell comprises two gas outlets.
  • the system comprises an ammonia combustion engine with a fuel inlet pipe connected to a fuel return pipe, configured to receiving ammonia through the fuel inlet pipe and returning ammonia through the fuel return pipe, and further configured to receiving nitrogen gas through the fuel inlet pipe for purging the fuel inlet and return pipes, said fuel return pipe being connected to a separation tank having an inlet, a vapour outlet, and a liquid ammonia outlet, and during the fuel piping purging operation said inlet receiving nitrogen/ammonia mixture from the fuel return pipe, and the ammonia scrubber having an inlet for receiving the nitrogen/ammonia vapour mixture from the separation tank.
  • the system comprises an ammonia combustion unit having an air inlet, an ammonia inlet and a gas inlet for gas supplied from the treated gas outlet in the ammonia scrubber and from the gas outlet in the electrolytic cell, an exhaust outlet, the ammonia combustion unit being connected to an ammonia cracker having an exhaust inlet, an ammonia inlet from a heat exchanger, an exhaust outlet to the heat exchanger and an outlet for hydrogen, nitrogen and unconverted ammonia for return via the heat exchanger to the ammonia scrubber through an inlet.
  • the scrubber liquid is an acid solution.
  • the acid solution is based on citric acid.
  • a method for removing ammonia from an ammonia-containing gas comprising feeding ammonia-containing gas into an ammonia scrubber through a gas inlet and scrubbing the ammonia-containing gas with scrubber liquid in the scrubber, removing treated gas from the scrubber through a gas outlet, in a closed loop passing scrubber liquid from a scrubber liquid outlet into an electrolytic cell, performing ammonia electrolysis in the electrolytic cell, and returning the scrubber liquid from the electrolytic cell to the scrubber via a scrubber liquid inlet.
  • the method comprises removing hydrogen and nitrogen gas through at least one gas outlet from the electrolytic cell.
  • the method comprises passing part of the scrubber liquid from the scrubber through a second scrubber liquid outlet and returning said scrubber liquid through a pump to the scrubber through a second scrubber liquid inlet.
  • the method comprises splitting the hydrogen and the nitrogen gas in the electrolytic cell.
  • the method comprises removing the hydrogen and nitrogen gas from the electrolytic cell through two separate gas outlets.
  • an ammonia combustion engine receives ammonia through a fuel inlet pipe connected to a fuel injection system and a fuel return pipe and said ammonia combustion engine further receives nitrogen gas for a fuel piping purging operation through the fuel inlet pipe and passing the nitrogen/ammonia mixture from the fuel return pipe through an inlet to a separation tank, passing nitrogen/ammonia vapour mixture from the separation tank through an outlet to an inlet to the ammonia scrubber, and passing liquid ammonia from the separation tank through an outlet.
  • the method comprises feeding treated gas leaving the ammonia scrubber through the gas outlet and gas from the gas outlet in the electrolytic cell into an ammonia combustion unit through an inlet together with air through an inlet and ammonia through an inlet, exhaust leaving the ammonia combustion unit through an outlet and entering an ammonia cracker through an inlet, cracking ammonia in the ammonia cracker, and passing hydrogen, nitrogen and unconverted ammonia through an outlet from the ammonia cracker through a heat exchanger and feeding ammonia containing gas from the heat exchanger to the ammonia scrubber through an inlet for removal of ammonia.
  • scrubbing liquid is to be interpreted as the liquid used in the ammonia scrubber for scrubbing gas or vapour containing ammonia. It might also be denoted “scrubbing liquid”, “acid solution”, “acid/water solution”.
  • Figure 1 shows an ammonia scrubber and electrolytic cell with regeneration of scrubber liquid in a closed loop according to an embodiment of the present disclosure.
  • Figure 2 shows an alternative configuration of the closed loop ammonia scrubber and electrolytic cell with regeneration of scrubber liquid according to an embodiment of the present disclosure.
  • Figure 3 shows an alternative configuration of the closed loop ammonia scrubber and electrolytic cell with regeneration of scrubber liquid according to an embodiment of the present disclosure.
  • Figure 4 shows an ammonia electrolytic cell according to an embodiment of the present disclosure.
  • Figure 5 shows an alternative ammonia electrolytic cell according to an embodiment of the present disclosure.
  • Figure 6 shows removal of ammonia during purging operation of fuel piping and ammonia combustion engine using closed loop ammonia scrubber and electrolytic cell with regeneration of scrubber liquid according to an embodiment of the present disclosure.
  • Figure 7 shows an application of an ammonia scrubber and electrolytic cell with regeneration of scrubber liquid with an ammonia combustion unit and an ammonia cracker according to an embodiment of the present disclosure.
  • the present disclosure includes a system comprising an ammonia scrubber for the treatment of operational releases of ammonia on board ships in closed loop with an electrolytic cell to regenerate scrubber liquid back to the scrubber to avoid the storage/handling issues in prior art solutions.
  • Examples of applications for the system comprising a closed loop ammonia scrubber and electrolytic cell with regeneration of scrubber liquid according to the invention are for example in the treatment of purge gas mixture of ammonia and nitrogen from fuel pipe and/or engine purging operation, treatment of exhaust gas from fuel cell, engine, boiler or gas combustion unit, and treatment of product stream from ammonia cracker (removal and conversion of unconverted ammonia).
  • the hydrogen that is produced in the electrolysis may be utilized as fuel on board the ship.
  • the first aspect of this disclosure shows a system for removing ammonia from an ammonia-containing gas, the system comprising: an ammonia scrubber 10, the ammonia scrubber 10 containing an inlet 101 for ammonia-containing gas, a scrubber liquid inlet 102, a treated gas outlet 103 and a scrubber liquid outlet 104 connected in a closed loop to at least one pump 11, an electrolytic cell 12 for regeneration of scrubber liquid, and the scrubber liquid inlet 102, the electrolytic cell 12 comprising a scrubber liquid inlet 105, at least one anode 13 and at least one cathode 14 connected to at least one power source 15, and a scrubber liquid outlet 106.
  • the electrolytic cell 12 may further comprises at least one gas outlet 107.
  • Figure 1 shows a system according to an embodiment of the present invention with a closed loop ammonia scrubber 10 and electrolytic cell 12.
  • Ammonia-containing gas enters the ammonia scrubber 10 through an inlet 101
  • scrubber liquid is regenerated to the ammonia scrubber 10 through a scrubber liquid inlet 102
  • treated gas leaves the ammonia scrubber 10 through a treated gas outlet 103
  • scrubber liquid is led from the ammonia scrubber 10 from a scrubber liquid outlet 104 through a pump 11 through an inlet 105 to an electrolytic cell 12.
  • the pump 11 is illustrated upstream the electrolytic cell 12. In another embodiment of the invention, not illustrated, the pump 11 may also be placed downstream the electrolytic cell 12. It is also possible to have more than one pump.
  • the electrolytic cell 12 In the electrolytic cell 12, scrubber liquid is regenerated by electrolysis.
  • the electrolytic cell 12 comprises an anode 13, a cathode 14 and a power source 15. Hydrogen gas and nitrogen gas formed in the electrolysis are removed through an outlet 107.
  • the regenerated scrubber liquid leaves the electrolytic cell 12 through an outlet 106 and is returned to the ammonia scrubber 10 through scrubber liquid inlet 102.
  • the system may comprise a second scrubber liquid outlet 108 from the scrubber 10, a pump 16 and a scrubber liquid inlet 109 into the scrubber 10.
  • FIG 2 shows an alternative configuration of the present invention where the ammonia scrubber 10 is connected to the electrolytic cell 12 in a closed loop as described for Figure 1, and in addition, the system comprises a second scrubber liquid outlet 108 from the scrubber 10, a pump 16 and a second scrubber liquid inlet 109 into the scrubber 10.
  • the system comprises a second scrubber liquid outlet 108 from the scrubber 10, a pump 16 and a second scrubber liquid inlet 109 into the scrubber 10.
  • FIG 3 shows an alternative configuration of the present invention where an additional regeneration circulation tank 17 has been added to the configuration disclosed in Figure 2, for enabling isolated circulation of the scrubber liquid regeneration.
  • the regeneration circulation tank 17 is located upstream the pump 11, and downstream the electrolytic cell 12.
  • the regeneration circulation tank 17 is located parallel to the scrubber 10 in the scrubber liquid regeneration flow circuit.
  • This configuration can be operated as follows: When valves 18 and 19 are open, and valves 20 and 21 are closed, the circulation of scrubber liquid through the electrolytic cell 12 happens as in the configuration in Figure 2. With valves 19 and 21 closed, and valves 18 and 20 open while the pump 11 is running, the regeneration circulation tank 17 is filled with the scrubber liquid up to a desired level.
  • the scrubber liquid can be regenerated in the electrolytic cell 12 in a loop that is isolated from the scrubber 10 operation. Then, by opening valve 19 and closing valve 20, while valve 18 is still closed, a desired amount of regenerated scrubber liquid can be returned from the regeneration circulation tank 17 into the scrubber 10.
  • ammonia scrubber used in the present invention is not limited to a specific type, any suitable type of commercially available ammonia scrubber may be used, such as for example ammonia acrubbers with spray nozzles or ammonia acrubbers with packed bed.
  • Figure 4 shows an ammonia electrolytic cell 12 comprising an anode 13, a cathode 14, a power source 15 and a gas outlet 107. Scrubber liquid regeneration with electrolysis removes dissolved ammonia and produces hydrogen and nitrogen.
  • the overall electrolysis reaction is:
  • the electrode reactions are:
  • the electrolytic cell 12 may be placed outside the ammonia scrubber 10 as shown in figures 1 - 3, or may be integrated inside the ammonia scrubber 10. In both embodiments, the scrubber 10 and the electrolytic cell 12 are in a closed loop with regeneration of scrubber liquid back into the scrubber 10.
  • the electrolytic cell used in the present invention is not limited to a certain type, any suitable type of commercially available electrolytic cell may be used.
  • Electrode material can for example be graphite. More expensive/advanced electrode material might provide higher efficiency, such as for example Pt, Ti/Pb0 2 , Ti/I r0 2 , Ti/Ru0 2 , etc.
  • the electrolytic cell 12 is configured to split produced hydrogen and nitrogen gas by a separating wall 22 in the electrolytic cell 12.
  • FIG. 5 shows such alternative configuration of an ammonia electrolytic cell 12 comprising an anode 13, a cathode 14 and a power source 15.
  • a separating wall 22 separates the produced hydrogen and nitrogen gases.
  • the electrolytic cell 12 may comprise two gas outlets 110, 111.
  • the electrolytic cell 12 shown in Figure 5 comprises two gas outlets 110,111, one for hydrogen and one for nitrogen. This might be relevant for applications for example where hydrogen is utilized as fuel.
  • Figure 6 shows the removal of ammonia with closed loop ammonia scrubber 10 and electrolytic cell 12 and regeneration of scrubber liquid to the ammonia scrubber 10 during purging operation of fuel piping and ammonia combustion engine 23.
  • the system comprises an ammonia combustion engine 23 with a fuel inlet pipe 112 connected to a fuel return pipe 113, configured to receiving ammonia through the fuel inlet pipe 112 and returning ammonia through the fuel return pipe 113, and further configured to receiving nitrogen gas through the fuel inlet pipe 112 for purging the fuel inlet and return pipes 112,
  • said fuel return pipe 113 being connected to a separation tank 24 having an inlet 115, a vapour outlet 116, and a liquid ammonia outlet 117, and during the fuel piping purging operation said inlet 115 receiving nitrogen/ammonia mixture from the fuel return pipe 113, and the ammonia scrubber 10 having an inlet 118 for receiving the nitrogen/ammonia vapour mixture from the separation tank 24.
  • the ammonia combustion engine 23 includes a fuel injection system configured to receiving ammonia fuel in normal engine running condition.
  • the engine fuel injection system is connected to a fuel piping for receiving ammonia fuel from a supply source via the fuel inlet pipe 112.
  • the fuel piping also contains the fuel return pipe 113 from the engine injection system for returning a portion of the fuel to the fuel supply source, and a bypass pipe 114 from the fuel inlet pipe 112 to the fuel outlet pipe 113 for bypassing the engine fuel injection system.
  • An engine designed to run on ammonia as fuel might require purging of the fuel piping with nitrogen as part of the normal operation.
  • the piping is configured to receiving nitrogen through the fuel inlet pipe 112 and leading the nitrogen via the bypass pipe 114 to the fuel return pipe 113, the nitrogen thereby flushing remains of ammonia in the piping and creating a nitrogen/ammonia vapour mixture.
  • the fuel return pipe 113 is connected to a separation tank 24, said separation tank 24 having an inlet 115 for receiving nitrogen/ammonia mixture, a nitrogen/ammonia vapour mixture outlet 116, a liquid ammonia outlet 117, the ammonia scrubber 10 having an inlet 118 for receiving the nitrogen/ammonia vapour mixture from the separation tank 24.
  • pressurized nitrogen is supplied into the fuel inlet pipe 112.
  • the system comprises an ammonia combustion unit 25 having an air inlet 119, an ammonia inlet 120 and a gas inlet 121 for gas supplied from the treated gas outlet 103 in the ammonia scrubber 10 and from the gas outlet 107 in the electrolytic cell 12, an exhaust outlet 122, the ammonia combustion unit 25 being connected to an ammonia cracker 26 having an exhaust inlet 123, an ammonia inlet 124 from a heat exchanger 27, an exhaust outlet 125 to the heat exchanger 27 and an outlet 126 for hydrogen, nitrogen and unconverted ammonia for return via the heat exchanger 27 to the ammonia scrubber 10 through inlet 127.
  • ammonia is decomposed (cracked) over a catalyst to produce hydrogen (H2) and nitrogen (N2).
  • An ammonia cracker producing hydrogen from ammonia may need high temperature and large volumes and retention time for complete conversion of ammonia to hydrogen.
  • the produced hydrogen/nitrogen mixture may be treated with an ammonia scrubber with electrolysis to remove ammonia from the product. Hydrogen produced in the electrolysis can be added to the product or used as fuel for the ammonia cracker.
  • ammonia cracker used in the present invention is not limited to a certain type, any suitable type of commercially available ammonia cracker may be used.
  • the scrubber liquid may be an acid solution.
  • the acid solution may be based on citric acid.
  • Scrubber liquid in the ammonia scrubber is brought into contact with the ammonia- containing gas to remove ammonia.
  • Acid solution may be used as the scrubber liquid in the ammonia scrubber to neutralize the ammonia (ammonia is alkaline) as the vapour pressure of ammonia (fraction that cannot be dissolved in acid/water solution) depends on pH and therefore effects the scrubber efficiency. At pH below 7 vapour pressure of ammonia is neglectable.
  • An example of a suitable acid is citric acid as this acid is relatively weak and thus less harmful than stronger acids, but have good buffer properties (small change of pH when adding alkaline component). It is also possible to add salt in addition to acid to improve the efficiency of the acid/electrolyte solution further.
  • the system according to the present invention with an ammonia scrubber and electrolytic cell in a closed loop with regeneration of scrubber liquid may be connected to an ammonia fuelled engine or gas combustion unit, which may be run in rich fuel condition to reduce NOx emissions.
  • an ammonia fuelled engine or gas combustion unit which may be run in rich fuel condition to reduce NOx emissions.
  • an ammonia fuelled engine or gas combustion unit which may be run in rich fuel condition to reduce NOx emissions.
  • some unburned fuel/ammonia can be expected in the exhaust gas.
  • Exhaust gas can be treated with ammonia scrubber/electrolysis and produced hydrogen can be utilised in combustion. Water produced in combustion may be condensed and treated with electrolysis to remove ammonia.
  • the second aspect of this disclosure shows a method for removing ammonia from an ammonia-containing gas, the method comprising feeding ammonia-containing gas into an ammonia scrubber 10 through a gas inlet 101 and scrubbing the ammonia-containing gas with scrubber liquid in the scrubber 10, removing treated gas from the scrubber 10 through a gas outlet 103, in a closed loop passing scrubber liquid from a scrubber liquid outlet 104 into an electrolytic cell 12, performing ammonia electrolysis in the electrolytic cell 12, and returning the scrubber liquid from the electrolytic cell 12 to the scrubber 10 via a scrubber liquid inlet 102.
  • the scrubber liquid may be passed from the scrubber liquid outlet 104 via a pump 11 to the electrolytic cell 12.
  • the pump 11 may be placed downstream the electrolytic cell 12. If necessary, more than one pump may be used.
  • the method comprises removing hydrogen and nitrogen gas through at least one gas outlet 107 from the electrolytic cell 12.
  • the method comprises passing part of the scrubber liquid from the scrubber 10 through a second scrubber liquid outlet 108 and returning said scrubber liquid through a pump 16 to the scrubber 10 through a second scrubber liquid inlet 109.
  • the method comprises splitting the hydrogen and the nitrogen gas in the electrolytic cell 12.
  • the method comprises removing the hydrogen and nitrogen gas from the electrolytic cell 12 through two separate gas outlets 110,111.
  • an ammonia combustion engine 23 receives ammonia through a fuel inlet pipe 112 connected to a fuel injection system and a fuel return pipe 113 and said ammonia combustion engine 23 further receives nitrogen gas through the fuel inlet pipe 112 for purging the fuel inlet and return pipes 112, 113 and passing the nitrogen/ammonia mixture from the fuel return pipe 113 through an inlet 115 to a separation tank 24, passing nitrogen/ammonia vapour mixture from the separation tank 24 through an outlet 116 to an inlet 118 to the ammonia scrubber 10, and passing liquid ammonia from the separation tank 24 through an outlet 117.
  • treated gas leaving the ammonia scrubber 10 through the gas outlet 103 and gas from the gas outlet 107 in the electrolytic cell 12 are fed into an ammonia combustion unit 25 through an inlet 121 together with air through an inlet 119 and ammonia through an inlet 120, exhaust is leaving the ammonia combustion unit 25 through an outlet 122 and entering an ammonia cracker 26 through an inlet 123, cracking ammonia in the ammonia cracker 26, and passing hydrogen, nitrogen and unconverted ammonia through an outlet 126 from the ammonia cracker 26 through a heat exchanger 27 and feeding ammonia containing gas from the heat exchanger 27 to the ammonia scrubber 10 through inlet 127 for removal of ammonia.
  • the system and method according to the present invention might be used both onshore and offshore.
  • the system and method according to the present invention are particularly suited for use on offshore installations, such as for example on board ships.
  • the person skilled in the art realizes that the present disclosure is not limited to the preferred embodiments described above.
  • the person skilled in the art further realizes that modifications and variations are possible within the scope of the appended claims. Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed disclosure, from a study of the drawings, the disclosure, and the appended claims.

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Abstract

The disclosure relates to a system for removing ammonia from an ammonia-containing gas, the system comprising: an ammonia scrubber (10), the ammonia scrubber (10) containing an inlet (101) for ammonia-containing gas, a scrubber liquid inlet (102), a treated gas outlet (103) and at least one scrubber liquid outlet (104) connected in a closed loop to at least one pump (11), an electrolytic cell (12) for regeneration of scrubber liquid, and the scrubber liquid inlet (102), the electrolytic cell (12) comprising a scrubber liquid inlet (105), at least one anode (13) and at least one cathode (14) connected to at least one power source (15), and a scrubber liquid outlet (106). The disclosure further relates to a method for removing ammonia from an ammonia-containing gas.

Description

A system for removing ammonia from an ammonia-containing gas and a method for removing ammonia from an ammonia-containing gas
Technical field
The present disclosure relates to a system for removing ammonia from an ammonia- containing gas and a method for removing ammonia from an ammonia-containing gas. More specifically, the disclosure relates to a system for removing ammonia from an ammonia- containing gas and a method for removing ammonia from an ammonia-containing gas as defined in the introductory parts of claim 1 and claim 10.
Background art
Ammonia is considered a promising candidate for carbon free fuels for deep-sea voyage to reach future CO2 emission targets. For ships using ammonia as fuel, there is a general concern about releases due to the toxic nature of ammonia and the strong smell that could cause panic on a passenger vessel.
Ammonia scrubbers, also referred to as wet scrubbers or acid scrubbers, have been identified as a possible solution for the treatment of operational and emergency releases of ammonia. Ammonia scrubbers are used in the onshore industry for the treatment of gases or air containing ammonia. An ammonia scrubber is specifically designed to remove harmful ammonia and particulates from industrial exhaust streams. Ammonia scrubbers may incorporate a variety of gas-liquid contacting techniques, including i.a., packed beds, spray chambers, and water jets. An Ammonia scrubber works by leading ammonia-containing gas from the bottom and up through the scrubber, and inside the scrubber a scrubber liquid is brought into contact with the gas to remove ammonia. Purified gas leaves the scrubber from the top, and the scrubber liquid used in the gas scrubbing leaves from the bottom of the scrubber. Open loop scrubbers with water can be used, but released water will contain dissolved ammonia and will in general not be accepted for operational ammonia releases. For operational ammonia releases in the onshore industry, acid is used to neutralize the dissolved ammonia in a closed loop scrubber system. The resulting mixture of water, acid and ammonia is normally a dissolved salt that can be used as a component in fertilizers.
The application of closed loop scrubbers with acid to neutralize ammonia on board a ship for handling of operational releases of ammonia has the main drawback of acid storage/handling as well as storage/handling of used acid/ammonia mixture. There is thus a need for an improved system and method for the handling of operational releases of ammonia, particularly on offshore installations.
Summary
It is an object of the present disclosure to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages in the prior art and solve at least the above-mentioned problem.
According to a first aspect there is provided a system for removing ammonia from an ammonia-containing gas, the system comprising: an ammonia scrubber, the ammonia scrubber containing an inlet for ammonia-containing gas, a scrubber liquid inlet, a treated gas outlet and a scrubber liquid outlet connected in a closed loop to at least one pump, an electrolytic cell for regeneration of scrubber liquid, and the scrubber liquid inlet, the electrolytic cell comprising a scrubber liquid inlet, at least one anode and at least one cathode connected to at least one power source, and a scrubber liquid outlet.
According to some embodiments, the electrolytic cell further comprises at least one gas outlet.
According to some embodiments, the system comprises a second scrubber liquid outlet from the scrubber, a pump and a second scrubber liquid inlet into the scrubber.
According to some embodiments, the electrolytic cell is configured to split produced hydrogen and nitrogen gas by a separating wall in the electrolytic cell.
According to some embodiments, the electrolytic cell comprises two gas outlets.
According to some embodiments, the system comprises an ammonia combustion engine with a fuel inlet pipe connected to a fuel return pipe, configured to receiving ammonia through the fuel inlet pipe and returning ammonia through the fuel return pipe, and further configured to receiving nitrogen gas through the fuel inlet pipe for purging the fuel inlet and return pipes, said fuel return pipe being connected to a separation tank having an inlet, a vapour outlet, and a liquid ammonia outlet, and during the fuel piping purging operation said inlet receiving nitrogen/ammonia mixture from the fuel return pipe, and the ammonia scrubber having an inlet for receiving the nitrogen/ammonia vapour mixture from the separation tank. According to some embodiments, the system comprises an ammonia combustion unit having an air inlet, an ammonia inlet and a gas inlet for gas supplied from the treated gas outlet in the ammonia scrubber and from the gas outlet in the electrolytic cell, an exhaust outlet, the ammonia combustion unit being connected to an ammonia cracker having an exhaust inlet, an ammonia inlet from a heat exchanger, an exhaust outlet to the heat exchanger and an outlet for hydrogen, nitrogen and unconverted ammonia for return via the heat exchanger to the ammonia scrubber through an inlet.
According to some embodiments, the scrubber liquid is an acid solution.
According to some embodiments, the acid solution is based on citric acid.
According to a second aspect there is provided a method for removing ammonia from an ammonia-containing gas, the method comprising feeding ammonia-containing gas into an ammonia scrubber through a gas inlet and scrubbing the ammonia-containing gas with scrubber liquid in the scrubber, removing treated gas from the scrubber through a gas outlet, in a closed loop passing scrubber liquid from a scrubber liquid outlet into an electrolytic cell, performing ammonia electrolysis in the electrolytic cell, and returning the scrubber liquid from the electrolytic cell to the scrubber via a scrubber liquid inlet.
According to some embodiments, the method comprises removing hydrogen and nitrogen gas through at least one gas outlet from the electrolytic cell.
According to some embodiments, the method comprises passing part of the scrubber liquid from the scrubber through a second scrubber liquid outlet and returning said scrubber liquid through a pump to the scrubber through a second scrubber liquid inlet.
According to some embodiments, the method comprises splitting the hydrogen and the nitrogen gas in the electrolytic cell.
According to some embodiments, the method comprises removing the hydrogen and nitrogen gas from the electrolytic cell through two separate gas outlets.
According to some embodiments of the method, an ammonia combustion engine receives ammonia through a fuel inlet pipe connected to a fuel injection system and a fuel return pipe and said ammonia combustion engine further receives nitrogen gas for a fuel piping purging operation through the fuel inlet pipe and passing the nitrogen/ammonia mixture from the fuel return pipe through an inlet to a separation tank, passing nitrogen/ammonia vapour mixture from the separation tank through an outlet to an inlet to the ammonia scrubber, and passing liquid ammonia from the separation tank through an outlet.
According to some embodiments, the method comprises feeding treated gas leaving the ammonia scrubber through the gas outlet and gas from the gas outlet in the electrolytic cell into an ammonia combustion unit through an inlet together with air through an inlet and ammonia through an inlet, exhaust leaving the ammonia combustion unit through an outlet and entering an ammonia cracker through an inlet, cracking ammonia in the ammonia cracker, and passing hydrogen, nitrogen and unconverted ammonia through an outlet from the ammonia cracker through a heat exchanger and feeding ammonia containing gas from the heat exchanger to the ammonia scrubber through an inlet for removal of ammonia.
Effects and features of the second aspect are largely analogous to those described above in connection with the first aspect. Embodiments mentioned in relation to the first aspect are largely compatible with the second aspect.
The present disclosure will become apparent from the detailed description given below. The detailed description and specific examples disclose preferred embodiments of the disclosure by way of illustration only. Those skilled in the art understand from guidance in the detailed description that changes and modifications may be made within the scope of the disclosure.
Hence, it is to be understood that the herein disclosed disclosure is not limited to the particular component parts of the device described or steps of the methods described since such device and method may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It should be noted that, as used in the specification and the appended claim, the articles "a", "an", "the", and "said" are intended to mean that there are one or more of the elements unless the context explicitly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like. Furthermore, the words "comprising", "including", "containing" and similar wordings does not exclude other elements or steps.
The term "scrubber liquid" is to be interpreted as the liquid used in the ammonia scrubber for scrubbing gas or vapour containing ammonia. It might also be denoted "scrubbing liquid", "acid solution", "acid/water solution". Brief descriptions of the drawings
The above objects, as well as additional objects, features and advantages of the present disclosure will be more fully appreciated by reference to the following illustrative and non-limiting detailed description of example embodiments of the present disclosure, when taken in conjunction with the accompanying drawings.
Figure 1 shows an ammonia scrubber and electrolytic cell with regeneration of scrubber liquid in a closed loop according to an embodiment of the present disclosure.
Figure 2 shows an alternative configuration of the closed loop ammonia scrubber and electrolytic cell with regeneration of scrubber liquid according to an embodiment of the present disclosure.
Figure 3 shows an alternative configuration of the closed loop ammonia scrubber and electrolytic cell with regeneration of scrubber liquid according to an embodiment of the present disclosure.
Figure 4 shows an ammonia electrolytic cell according to an embodiment of the present disclosure.
Figure 5 shows an alternative ammonia electrolytic cell according to an embodiment of the present disclosure.
Figure 6 shows removal of ammonia during purging operation of fuel piping and ammonia combustion engine using closed loop ammonia scrubber and electrolytic cell with regeneration of scrubber liquid according to an embodiment of the present disclosure.
Figure 7 shows an application of an ammonia scrubber and electrolytic cell with regeneration of scrubber liquid with an ammonia combustion unit and an ammonia cracker according to an embodiment of the present disclosure.
Detailed description
The present disclosure will now be described with reference to the accompanying drawings, in which preferred example embodiments of the disclosure are shown. The disclosure may, however, be embodied in other forms and should not be construed as limited to the herein disclosed embodiments. The disclosed embodiments are provided to fully convey the scope of the disclosure to the skilled person. The present invention includes a system comprising an ammonia scrubber for the treatment of operational releases of ammonia on board ships in closed loop with an electrolytic cell to regenerate scrubber liquid back to the scrubber to avoid the storage/handling issues in prior art solutions.
It was surprisingly found that a combination of an ammonia scrubber with an electrolytic cell in a closed loop with regeneration of scrubber liquid to the scrubber according to the present invention provided an improved handling of operational releases of ammonia than what is known in the art.
Examples of applications for the system comprising a closed loop ammonia scrubber and electrolytic cell with regeneration of scrubber liquid according to the invention are for example in the treatment of purge gas mixture of ammonia and nitrogen from fuel pipe and/or engine purging operation, treatment of exhaust gas from fuel cell, engine, boiler or gas combustion unit, and treatment of product stream from ammonia cracker (removal and conversion of unconverted ammonia). The hydrogen that is produced in the electrolysis may be utilized as fuel on board the ship.
The first aspect of this disclosure shows a system for removing ammonia from an ammonia-containing gas, the system comprising: an ammonia scrubber 10, the ammonia scrubber 10 containing an inlet 101 for ammonia-containing gas, a scrubber liquid inlet 102, a treated gas outlet 103 and a scrubber liquid outlet 104 connected in a closed loop to at least one pump 11, an electrolytic cell 12 for regeneration of scrubber liquid, and the scrubber liquid inlet 102, the electrolytic cell 12 comprising a scrubber liquid inlet 105, at least one anode 13 and at least one cathode 14 connected to at least one power source 15, and a scrubber liquid outlet 106.
The electrolytic cell 12 may further comprises at least one gas outlet 107.
Figure 1 shows a system according to an embodiment of the present invention with a closed loop ammonia scrubber 10 and electrolytic cell 12. Ammonia-containing gas enters the ammonia scrubber 10 through an inlet 101, scrubber liquid is regenerated to the ammonia scrubber 10 through a scrubber liquid inlet 102, treated gas leaves the ammonia scrubber 10 through a treated gas outlet 103, scrubber liquid is led from the ammonia scrubber 10 from a scrubber liquid outlet 104 through a pump 11 through an inlet 105 to an electrolytic cell 12. In figure 1, the pump 11 is illustrated upstream the electrolytic cell 12. In another embodiment of the invention, not illustrated, the pump 11 may also be placed downstream the electrolytic cell 12. It is also possible to have more than one pump. In the electrolytic cell 12, scrubber liquid is regenerated by electrolysis. The electrolytic cell 12 comprises an anode 13, a cathode 14 and a power source 15. Hydrogen gas and nitrogen gas formed in the electrolysis are removed through an outlet 107. The regenerated scrubber liquid leaves the electrolytic cell 12 through an outlet 106 and is returned to the ammonia scrubber 10 through scrubber liquid inlet 102.
In an embodiment, the system may comprise a second scrubber liquid outlet 108 from the scrubber 10, a pump 16 and a scrubber liquid inlet 109 into the scrubber 10.
Figure 2 shows an alternative configuration of the present invention where the ammonia scrubber 10 is connected to the electrolytic cell 12 in a closed loop as described for Figure 1, and in addition, the system comprises a second scrubber liquid outlet 108 from the scrubber 10, a pump 16 and a second scrubber liquid inlet 109 into the scrubber 10. Thus, there is a recirculation of scrubber liquid in the ammonia scrubber 10.
Figure 3 shows an alternative configuration of the present invention where an additional regeneration circulation tank 17 has been added to the configuration disclosed in Figure 2, for enabling isolated circulation of the scrubber liquid regeneration. The regeneration circulation tank 17 is located upstream the pump 11, and downstream the electrolytic cell 12. In other words, the regeneration circulation tank 17 is located parallel to the scrubber 10 in the scrubber liquid regeneration flow circuit. This configuration can be operated as follows: When valves 18 and 19 are open, and valves 20 and 21 are closed, the circulation of scrubber liquid through the electrolytic cell 12 happens as in the configuration in Figure 2. With valves 19 and 21 closed, and valves 18 and 20 open while the pump 11 is running, the regeneration circulation tank 17 is filled with the scrubber liquid up to a desired level. After the filling operation of the regeneration circulation tank 17, by having the valves 18 and 19 closed, while valves 20 and 21 are open and the pump 11 is running, the scrubber liquid can be regenerated in the electrolytic cell 12 in a loop that is isolated from the scrubber 10 operation. Then, by opening valve 19 and closing valve 20, while valve 18 is still closed, a desired amount of regenerated scrubber liquid can be returned from the regeneration circulation tank 17 into the scrubber 10.
The ammonia scrubber used in the present invention is not limited to a specific type, any suitable type of commercially available ammonia scrubber may be used, such as for example ammonia acrubbers with spray nozzles or ammonia acrubbers with packed bed. Figure 4 shows an ammonia electrolytic cell 12 comprising an anode 13, a cathode 14, a power source 15 and a gas outlet 107. Scrubber liquid regeneration with electrolysis removes dissolved ammonia and produces hydrogen and nitrogen.
The overall electrolysis reaction is:
2NH3(aq) -> N2(g) + 3H2(g)
The electrode reactions are:
Anode: NH3(aq) + 20H -> N2(g) + 6H20 + 6e
Cathode: 6H20 + 6e -> 3H2(g) + 60H
Other ions in the scrubber liquid solution may be involved in intermediate reaction steps, but this will not change the overall reaction.
The electrolytic cell 12 may be placed outside the ammonia scrubber 10 as shown in figures 1 - 3, or may be integrated inside the ammonia scrubber 10. In both embodiments, the scrubber 10 and the electrolytic cell 12 are in a closed loop with regeneration of scrubber liquid back into the scrubber 10.
The electrolytic cell used in the present invention is not limited to a certain type, any suitable type of commercially available electrolytic cell may be used.
Electrode material can for example be graphite. More expensive/advanced electrode material might provide higher efficiency, such as for example Pt, Ti/Pb02, Ti/I r02, Ti/Ru02, etc.
In an embodiment of the invention, the electrolytic cell 12 is configured to split produced hydrogen and nitrogen gas by a separating wall 22 in the electrolytic cell 12.
Figure 5 shows such alternative configuration of an ammonia electrolytic cell 12 comprising an anode 13, a cathode 14 and a power source 15. In the electrolytic cell 12 shown in Figure 5, a separating wall 22 separates the produced hydrogen and nitrogen gases. Further, the electrolytic cell 12 may comprise two gas outlets 110, 111. The electrolytic cell 12 shown in Figure 5 comprises two gas outlets 110,111, one for hydrogen and one for nitrogen. This might be relevant for applications for example where hydrogen is utilized as fuel.
Figure 6 shows the removal of ammonia with closed loop ammonia scrubber 10 and electrolytic cell 12 and regeneration of scrubber liquid to the ammonia scrubber 10 during purging operation of fuel piping and ammonia combustion engine 23. In an embodiment of the present invention, as illustrated in Figure 6, the system comprises an ammonia combustion engine 23 with a fuel inlet pipe 112 connected to a fuel return pipe 113, configured to receiving ammonia through the fuel inlet pipe 112 and returning ammonia through the fuel return pipe 113, and further configured to receiving nitrogen gas through the fuel inlet pipe 112 for purging the fuel inlet and return pipes 112,
113, said fuel return pipe 113 being connected to a separation tank 24 having an inlet 115, a vapour outlet 116, and a liquid ammonia outlet 117, and during the fuel piping purging operation said inlet 115 receiving nitrogen/ammonia mixture from the fuel return pipe 113, and the ammonia scrubber 10 having an inlet 118 for receiving the nitrogen/ammonia vapour mixture from the separation tank 24.
In an embodiment of the present invention, the ammonia combustion engine 23 includes a fuel injection system configured to receiving ammonia fuel in normal engine running condition. The engine fuel injection system is connected to a fuel piping for receiving ammonia fuel from a supply source via the fuel inlet pipe 112. The fuel piping also contains the fuel return pipe 113 from the engine injection system for returning a portion of the fuel to the fuel supply source, and a bypass pipe 114 from the fuel inlet pipe 112 to the fuel outlet pipe 113 for bypassing the engine fuel injection system.
An engine designed to run on ammonia as fuel might require purging of the fuel piping with nitrogen as part of the normal operation. In order to purge the engine fuel piping, the piping is configured to receiving nitrogen through the fuel inlet pipe 112 and leading the nitrogen via the bypass pipe 114 to the fuel return pipe 113, the nitrogen thereby flushing remains of ammonia in the piping and creating a nitrogen/ammonia vapour mixture. The fuel return pipe 113 is connected to a separation tank 24, said separation tank 24 having an inlet 115 for receiving nitrogen/ammonia mixture, a nitrogen/ammonia vapour mixture outlet 116, a liquid ammonia outlet 117, the ammonia scrubber 10 having an inlet 118 for receiving the nitrogen/ammonia vapour mixture from the separation tank 24.
During the fuel piping purging operation pressurized nitrogen is supplied into the fuel inlet pipe 112.
In an embodiment of the present invention, as shown in Figure 7, the system comprises an ammonia combustion unit 25 having an air inlet 119, an ammonia inlet 120 and a gas inlet 121 for gas supplied from the treated gas outlet 103 in the ammonia scrubber 10 and from the gas outlet 107 in the electrolytic cell 12, an exhaust outlet 122, the ammonia combustion unit 25 being connected to an ammonia cracker 26 having an exhaust inlet 123, an ammonia inlet 124 from a heat exchanger 27, an exhaust outlet 125 to the heat exchanger 27 and an outlet 126 for hydrogen, nitrogen and unconverted ammonia for return via the heat exchanger 27 to the ammonia scrubber 10 through inlet 127.
In an ammonia cracker, ammonia is decomposed (cracked) over a catalyst to produce hydrogen (H2) and nitrogen (N2). An ammonia cracker producing hydrogen from ammonia may need high temperature and large volumes and retention time for complete conversion of ammonia to hydrogen. The produced hydrogen/nitrogen mixture may be treated with an ammonia scrubber with electrolysis to remove ammonia from the product. Hydrogen produced in the electrolysis can be added to the product or used as fuel for the ammonia cracker.
The ammonia cracker used in the present invention is not limited to a certain type, any suitable type of commercially available ammonia cracker may be used.
In embodiments of the present invention, the scrubber liquid may be an acid solution. The acid solution may be based on citric acid.
Scrubber liquid in the ammonia scrubber is brought into contact with the ammonia- containing gas to remove ammonia. Acid solution may be used as the scrubber liquid in the ammonia scrubber to neutralize the ammonia (ammonia is alkaline) as the vapour pressure of ammonia (fraction that cannot be dissolved in acid/water solution) depends on pH and therefore effects the scrubber efficiency. At pH below 7 vapour pressure of ammonia is neglectable. An example of a suitable acid is citric acid as this acid is relatively weak and thus less harmful than stronger acids, but have good buffer properties (small change of pH when adding alkaline component). It is also possible to add salt in addition to acid to improve the efficiency of the acid/electrolyte solution further.
The system according to the present invention with an ammonia scrubber and electrolytic cell in a closed loop with regeneration of scrubber liquid may be connected to an ammonia fuelled engine or gas combustion unit, which may be run in rich fuel condition to reduce NOx emissions. When running combustion in rich fuel condition, some unburned fuel/ammonia can be expected in the exhaust gas. Exhaust gas can be treated with ammonia scrubber/electrolysis and produced hydrogen can be utilised in combustion. Water produced in combustion may be condensed and treated with electrolysis to remove ammonia.
The second aspect of this disclosure shows a method for removing ammonia from an ammonia-containing gas, the method comprising feeding ammonia-containing gas into an ammonia scrubber 10 through a gas inlet 101 and scrubbing the ammonia-containing gas with scrubber liquid in the scrubber 10, removing treated gas from the scrubber 10 through a gas outlet 103, in a closed loop passing scrubber liquid from a scrubber liquid outlet 104 into an electrolytic cell 12, performing ammonia electrolysis in the electrolytic cell 12, and returning the scrubber liquid from the electrolytic cell 12 to the scrubber 10 via a scrubber liquid inlet 102.
The scrubber liquid may be passed from the scrubber liquid outlet 104 via a pump 11 to the electrolytic cell 12. In some embodiments, the pump 11 may be placed downstream the electrolytic cell 12. If necessary, more than one pump may be used.
In an embodiment of the present invention, the method comprises removing hydrogen and nitrogen gas through at least one gas outlet 107 from the electrolytic cell 12.
In an embodiment of the present invention, the method comprises passing part of the scrubber liquid from the scrubber 10 through a second scrubber liquid outlet 108 and returning said scrubber liquid through a pump 16 to the scrubber 10 through a second scrubber liquid inlet 109.
In an embodiment of the present invention, the method comprises splitting the hydrogen and the nitrogen gas in the electrolytic cell 12.
In an embodiment of the present invention, the method comprises removing the hydrogen and nitrogen gas from the electrolytic cell 12 through two separate gas outlets 110,111.
In an embodiment of the method according to the present invention, an ammonia combustion engine 23 receives ammonia through a fuel inlet pipe 112 connected to a fuel injection system and a fuel return pipe 113 and said ammonia combustion engine 23 further receives nitrogen gas through the fuel inlet pipe 112 for purging the fuel inlet and return pipes 112, 113 and passing the nitrogen/ammonia mixture from the fuel return pipe 113 through an inlet 115 to a separation tank 24, passing nitrogen/ammonia vapour mixture from the separation tank 24 through an outlet 116 to an inlet 118 to the ammonia scrubber 10, and passing liquid ammonia from the separation tank 24 through an outlet 117.
In an embodiment of the method according to the present invention, treated gas leaving the ammonia scrubber 10 through the gas outlet 103 and gas from the gas outlet 107 in the electrolytic cell 12 are fed into an ammonia combustion unit 25 through an inlet 121 together with air through an inlet 119 and ammonia through an inlet 120, exhaust is leaving the ammonia combustion unit 25 through an outlet 122 and entering an ammonia cracker 26 through an inlet 123, cracking ammonia in the ammonia cracker 26, and passing hydrogen, nitrogen and unconverted ammonia through an outlet 126 from the ammonia cracker 26 through a heat exchanger 27 and feeding ammonia containing gas from the heat exchanger 27 to the ammonia scrubber 10 through inlet 127 for removal of ammonia.
The system and method according to the present invention might be used both onshore and offshore. The system and method according to the present invention are particularly suited for use on offshore installations, such as for example on board ships. The person skilled in the art realizes that the present disclosure is not limited to the preferred embodiments described above. The person skilled in the art further realizes that modifications and variations are possible within the scope of the appended claims. Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed disclosure, from a study of the drawings, the disclosure, and the appended claims.

Claims

1. A system for removing ammonia from an ammonia-containing gas, the system comprising: an ammonia scrubber (10), the ammonia scrubber (10) containing an inlet (101) for ammonia-containing gas, a scrubber liquid inlet (102), a treated gas outlet (103) and at least one scrubber liquid outlet (104) connected in a closed loop to at least one pump (11), an electrolytic cell (12) for regeneration of scrubber liquid, and the scrubber liquid inlet (102), the electrolytic cell (12) comprising a scrubber liquid inlet (105), at least one anode (13) and at least one cathode (14) connected to at least one power source (15), and a scrubber liquid outlet (106).
2. The system according to claim 1, wherein the electrolytic cell (12) further comprises at least one gas outlet (107).
3. The system according to claim 1 or claim 2, wherein the system comprises a second scrubber liquid outlet (108) from the scrubber (10), a pump (16) and a scrubber liquid inlet (109) into the scrubber (10).
4. The system according to any of the preceding claims, wherein the electrolytic cell (12) is configured to split produced hydrogen and nitrogen gas by a separating wall (22) in the electrolytic cell (12).
5. The system according to claim 4, wherein the electrolytic cell (12) comprises two gas outlets (110, 111).
6. The system according to any one of the preceding claims, wherein the system comprises an ammonia combustion engine (23) with a fuel inlet pipe (112) connected to a fuel return pipe (113), configured to receiving ammonia through the fuel inlet pipe (112) and returning ammonia through the fuel return pipe (113), and further configured to receiving nitrogen gas through the fuel inlet pipe (112) for purging the fuel inlet and return pipes (112, 113), said fuel return pipe (113) being connected to a separation tank (24) having an inlet (115), a vapour outlet (116), and a liquid ammonia outlet (117), and during the fuel piping purging operation said inlet (115) receiving nitrogen/ammonia mixture from the fuel return pipe (113), and the ammonia scrubber (10) having an inlet (118) for receiving the nitrogen/ammonia vapour mixture from the separation tank (24).
7. The system according to any one of claims 1 to 5, comprising an ammonia combustion unit (25) having an air inlet (119), an ammonia inlet (120) and a gas inlet (121) for gas supplied from the treated gas outlet (103) in the ammonia scrubber (10) and from the gas outlet (107) in the electrolytic cell (12), an exhaust outlet (122), the ammonia combustion unit (25) being connected to an ammonia cracker (26) having an exhaust inlet (123), an ammonia inlet (124) from a heat exchanger (27), an exhaust outlet (125) to the heat exchanger (27) and an outlet (126) for hydrogen, nitrogen and unconverted ammonia for return via the heat exchanger (27) to the ammonia scrubber (10) through inlet (127).
8. The system according to any one of the preceding claims, wherein the scrubber liquid is an acid solution.
9. The system according to claim 8, wherein the acid solution is based on citric acid.
10. A method for removing ammonia from an ammonia-containing gas, the method comprising feeding ammonia-containing gas into an ammonia scrubber (10) through a gas inlet (101) and scrubbing the ammonia-containing gas with scrubber liquid in the scrubber (10), removing treated gas from the scrubber (10) through a gas outlet (103), in a closed loop passing scrubber liquid from a scrubber liquid outlet (104) into an electrolytic cell (12), performing ammonia electrolysis in the electrolytic cell (12), and returning the scrubber liquid from the electrolytic cell (12) to the scrubber (10) via a scrubber liquid inlet (102).
11. The method according to claim 10, comprising removing hydrogen and nitrogen gas through at least one gas outlet (107) from the electrolytic cell (12).
12. The method according to any of claims 10 or 11, comprising passing part of the scrubber liquid from the scrubber (10) through a second scrubber liquid outlet (108) and returning said scrubber liquid through a pump (16) to the scrubber (10) through a scrubber liquid inlet (109).
13. The method according to any one of claims 10 to 12, comprising splitting the hydrogen and the nitrogen gas in the electrolytic cell (12).
14. The method according to claim 13, comprising removing the hydrogen and nitrogen gas from the electrolytic cell (12) through two separate gas outlets (110,111).
15. The method according to any one of the claims 10 to 14, wherein an ammonia combustion engine (23) receives ammonia through a fuel inlet pipe (112) connected to a fuel injection system and a fuel return pipe (113) and said ammonia combustion engine (23) further receives nitrogen gas through the fuel inlet pipe (112) for purging the fuel inlet and return pipes (112, 113) and passing the nitrogen/ammonia mixture from the fuel return pipe (113) through an inlet (115) to a separation tank (24), passing nitrogen/ammonia vapour mixture from the separation tank (24) through an outlet (116) to an inlet (118) to the ammonia scrubber (10), and passing liquid ammonia from the separation tank (24) through an outlet (117).
16. The method according to any one of the claims 10 to 14, wherein treated gas leaving the ammonia scrubber (10) through the gas outlet (103) and gas from the gas outlet (107) in the electrolytic cell (12) are fed into an ammonia combustion unit (25) through an inlet (121) together with air through an inlet (119) and ammonia through an inlet (120), exhaust is leaving the ammonia combustion unit (25) through an outlet (122) and entering an ammonia cracker (26) through an inlet (123), cracking ammonia in the ammonia cracker (26), and passing hydrogen, nitrogen and unconverted ammonia through an outlet (126) from the ammonia cracker (26) through a heat exchanger (27) and feeding ammonia containing gas from the heat exchanger (27) to the ammonia scrubber (10) through inlet (127) for removal of ammonia.
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GB2635309A (en) * 2023-09-14 2025-05-14 Lge Ip Man Company Limited Method and system for recovering fuel from an engine

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