Method for producing blue ammonia

Abstract

The present invention provides a method and system for producing blue ammonia that provides a higher percentage of carbon recovery. The method and system of the present invention can be used in any ammonia plant.

Description

Technical Field

[0001] The present invention provides a method and system for producing blue ammonia that provides a higher percentage of carbon recovery. The method and system of the present invention can be used in any ammonia plant.

Background Art

[0002] Blue ammonia is a fossil fuel-based product produced while minimizing CO emissions into the atmosphere. It is considered a transitional product between conventional fossil fuel-based ammonia and green ammonia produced from green or renewable electricity and air. The CO produced from blue ammonia production must be permanently stored or converted into other chemicals. The main steps for producing blue ammonia are essentially the same as those for producing conventional fossil fuel-based ammonia, the difference being that much of the carbon derived from carbon fuels is recovered, which presents the possibility of further processing. 2 2 2 Here, it is important that blue ammonia does not emit carbon dioxide when used as a fertilizer or burned. Current available technologies trap almost all of the CO produced during the conversion process, making this fuel the first choice for a carbon-free fuel for large-scale use. Blue ammonia is considered an environmentally friendly product that can be used until sufficient renewable or green electricity becomes available to produce green ammonia.

[0003] 2 2 2

[0004] Document WO2018 / 149641 (Patent Document 1) discloses a method for the synthesis of ammonia from natural gas, which involves converting a charge of desulfurized natural gas and steam into synthesis gas (11) together with oxygen-enriched air or oxygen, and treating the synthesis gas (11) by a shift reaction and decarbonization. A part of the synthesis gas depleted in CO obtained after decarbonization is separated and used as a fuel fraction for one or more furnaces in the conversion section, and the remaining part of the gas is used to produce ammonia. 2 It discloses a method in which a part of the synthesis gas depleted in CO is separated and used as a fuel fraction for one or more furnaces in the conversion section, and the remaining part of the gas is used to produce ammonia.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] According to the method of the present invention, off-gases from different process steps are utilized as fuel in a preheating system including several combustion preheaters for preheating a hydrocarbon feedstock, together with carbon recovery from at least one preheater, thereby enabling the use of a more carbon-depleted fuel and achieving a high carbon recovery rate (over 98%) compared to the prior art, which is different from the method disclosed in the above document.

[0007] Summary of the Invention The present invention provides a method, system and plant for producing ammonia with a high percentage of carbon recovery, preferably over 98% carbon recovery, compared to a standard method in which carbon recovery of optimally between about 90 - 93% is achieved.

[0008] The method of the present invention offers the following advantages: - Applicable to general plants and as an improvement - For complete CO 2 recovery, in the ammonia process, the CO already available2 Utilize the removal step; - Enable CO2 recovery of over 98%; - Lower the adiabatic flame temperature, thus reducing NOx formation and thereby reducing NOx emissions to the atmosphere; The above advantages are provided by a series of features including: - Reduce the combustion of natural gas used in the pilot burner; - Carbon-depleted gas used as fuel in the fuel system, mainly H 2 and N 2 ; - Off-gas containing over 60% methane and / or CO is redirected back to the reforming section or desulfurization section as additional feedstock gas.

[0009] Description of the Invention CO 2 Reducing the emission of is an issue to be solved in the chemical industry. The production of ammonia using hydrocarbons as feedstock inevitably results in formation, which typically results in at least two CO 2 containing process streams, namely one nearly pure CO 2 stream (1) extracted from the syngas cleaning section and one or more flue gas streams (2). The CO 2 stream (1) can be utilized for further chemical processing or stored. The CO 2 in the flue gas stream (2) needs to be recovered until it can find a similar use. The flue gas recovery process is costly in terms of operation and capital. Therefore, it is advantageous to limit the CO 2 content in the flue gas. 2 By using carbon-free fuel, the CO in the flue gas

[0010] 2 ​It is well known that it can be avoided. Generally, hydrocarbons such as natural gas and carbon-containing off-gases derived from the process are used as fuels. The advantages of the present invention are that a major part of these fuels is replaced by an internal hydrogen-rich stream and that the inevitable off-gases are recycled to the process. By applying the present invention, the CO 2 content in the flue gas stream can be reduced by 90% to a very low level. If a pure CO 2 stream (1) is utilized or stored, the resulting ammonia is considered blue.

[0011] Definitions Blue ammonia is ammonia produced from the use of fossil fuels, where at least 90% of the carbon in the fossil fuel is recovered and used in other products and processes or stored.

[0012] A pollutant means an undesirable substance or element. In the context of the present invention, pollutants include catalyst poisons.

[0013] Flash gas means an intermediate gas stream obtained during the desorption of CO 2 in the solvent-based CO 2 removal step.

[0014] Green ammonia is ammonia produced by using green electricity, water and air.

[0015] Green electricity is electricity generated from renewable resources such as wind power, solar power, hydropower, or geothermal energy.

[0016] The fuel system includes a tubular reformer and / or a combustion heater and / or an auxiliary boiler and / or a fuel system for supplying fuel to the combustion side of a gas turbine. These systems are equipped with one or more burners where the incoming fuel stream is combusted with air at variable temperatures and pressures.

[0017] High-pressure electrolysis (HPE) is the electrolysis of water by passing electricity through water at elevated pressures, typically above 10 bar, to decompose water (H 2 2O) into oxygen (O 2 2) and hydrogen gas (H 2 2).

[0018] PSA means pressure swing adsorption.

[0019] Preferred Embodiment 1. The following steps: a) Preheating a hydrocarbon feedstock in a fuel system; b) Removing sulfur and other contaminants from the preheated hydrocarbon feedstock; c) Reforming the preheated hydrocarbon feedstock from step b) to obtain synthesis gas containing CO, CO 2 2, H 2 2, H 2 2O and CH 4 4; d) Passing the synthesis gas from step c) through a shift reaction step to reduce the CO content; e) Sending the gas from step d) to a CO 2 2 removal step, wherein the gas is split into at least a CO 2 -rich stream and a hydrogen-rich stream, optionally and a flash gas; f) Passing the hydrogen-rich stream from step e) through the following: i) H 2 2O, CO, CO 2 2, CH 4 4 are removed to an off-gas stream to obtain a purified hydrogen stream, and nitrogen is added to obtain an ammonia synthesis gas stream containing nitrogen and hydrogen; or ii) A PSA that provides a hydrogen stream containing more than 99.5% hydrogen, wherein nitrogen is added to obtain a syngas stream containing nitrogen and hydrogen and an offgas stream; or iii) CO and CO 2 are converted together with hydrogen to CH 4 and H 2 O to obtain a syngas stream containing nitrogen, hydrogen, and an inert substance containing CH 4 ; methanation g) Passing a portion of the syngas stream from step f) through an ammonia synthesis section to convert said portion to ammonia and sending another portion of said syngas stream to a preheating system; A method for producing ammonia, comprising The preheating system includes at least two separate combustion heaters, at least one of the combustion heaters is equipped with a unit for removing 80% or more of CO2 from the generated flue gas, and the combustion heaters use the offgas from step f), the flash gas from step e), and in the case of f)iii) the offgas from step g) as fuel. The method.

[0020] 2. The method according to embodiment 1, wherein the reforming step c) is carried out in an autothermal reformer, or in a tubular reformer followed by steps in an autothermal reformer, or in a tubular reformer and a subsequent air flown secondary reformer.

[0021] 3. The method according to embodiment 1 or 2, wherein a hydrocarbon fuel, the flash gas from step e), the offgas from step f), and a portion of the syngas stream from step f) are premixed or separately supplied to the fuel system.

[0022] 4. The adiabatic pre-reforming step c of the hydrocarbon stream from step b 0The method according to any one of the above embodiments, comprising

[0023] 5. In step f) i), hydrogen purification and nitrogen addition are carried out by sending the hydrogen-rich stream to PSA and then adding nitrogen to the resulting hydrogen stream, and at least a part of the resulting off-gas stream is sent to the preheating in step a), the method according to any one of the above embodiments.

[0024] 6. In the methanation step f) iii), CO, CO 2 and hydrogen are converted to CH 4 and H 2 O, and a purge gas stream containing CH 4 from ammonia synthesis is added, the method according to any one of the above embodiments.

[0025] 7. In the hydrogen recovery unit, by recovering CH 4 from the stream of unreacted components from the ammonia synthesis section, a stream containing more than 99% hydrogen is provided, which is sent to the ammonia synthesis section in step g) and / or the preheating system in step a), and an off-gas containing a CH 4 content of more than 95% in the synthesis gas stream to the ammonia synthesis section in step g) is provided, which is used as fuel in one or more combustion heaters equipped with a flue gas CO2 removal unit, the method according to embodiment 8.

[0026] 8. The amount of air to the air-blown secondary reformer is adjusted so that a molar ratio of N 2 to H 2 between 1:2.5 and 1:3.5 is obtained in the stream from methanation in step f iii), the method according to embodiment 2.

[0027] 9. The synthesis gas stream obtained from step f) is N 2 and H 2The method according to the above embodiment, containing the following at a ratio between 1:2.9 and 3.1.

[0028] 10. A system for producing ammonia according to the method of Embodiments 1-9, comprising: a) A preheating unit b) A desulfurization unit; c) A reforming unit; d) A shift unit; e) CO 2 Removal unit; f) A nitrogen washing unit or a pressure swing adsorption unit or a methanation unit, g) An ammonia synthesis section; and h) A fuel system for supplying fuel to at least two or more separate heaters in the preheating unit, wherein at least one heater comprises a combustion system with a unit for removing 80% or more of CO2 from the generated flue gas.

[0029] 11. The system according to Embodiment 10, wherein the pre-reforming unit is arranged upstream of the reforming unit c).

[0030] 12. The system according to Embodiment 10 or 11, wherein the reforming unit c) comprises an autothermal reformer, or a tubular reformer following the autothermal reformer, or a tubular reformer following an air-blown secondary reformer.

[0031] 13. The system according to Embodiment 10 or 11, wherein the reforming unit c) comprises an autothermal reformer, and f) is a CO 2 and H 2 O dryer.

[0032] 14. The system according to Embodiment 10 or 11, wherein the reforming unit c) comprises an autothermal reformer, and f) is a PSA.

[0033] 15. The system according to Embodiment 10 or 11, wherein the reforming unit c) comprises a tubular steam reformer following an autothermal reformer, and f) is a CO 2 and H 2The system according to embodiment 10 or 11, which is a dryer.

[0034] 16. The system according to embodiment 10 or 11, wherein the reforming unit c) includes a tubular steam reformer followed by an autothermal reformer, and f) is PSA.

[0035] 17. The system according to embodiment 10 or 11, wherein the reforming unit c) includes a tubular steam reformer followed by an air blown secondary reformer, and f) is a methanation unit.

Brief Description of the Drawings

[0036] Figure 1 shows an overview for producing ammonia by a prior art method. a) Desulfurization b 0 ) Pre-reforming b) Reforming (SMR) b) Secondary reformer (air blown ATR) c) Shift section d) CO 2 Removal section e) Methanation f) Ammonia synthesis g) Fuel system(s) i) Ammonia recovery Stream (9) Hydrogen-rich fuel containing nitrogen (replacing the use of natural gas as fuel) Stream (2) Flash gas from CO2 removal

[0037] Figure 2 shows an overview of a method for producing ammonia using the Topsoe SynCOR ammonia 商標 process: a) Desulfurization b 0 ) Pre-reforming b) Reforming (ATR) c) Shift section d) CO2 removal e) Nitrogen washing or PSA f) Ammonia synthesis g) Fuel system(s) Stream (4,8) recycle off-gas stream Stream (5,7) hydrogen-rich fuel containing nitrogen (replacing the use of natural gas as fuel) Stream 2 flash gas from CO2 removal

[0038] Figure 3 shows an overview for producing ammonia using a steam reformer followed by an autothermal reformer in syngas production: a) Desulfurization b) Pre-reforming b) Reforming (SMR) b) Reforming (ATR) c) Shift section d) CO 2 Removal e) Nitrogen washing or PSA f) Ammonia synthesis g) Fuel system(s) Stream (4,8) recycle off-gas stream Stream (5,7) hydrogen-rich fuel containing nitrogen (replacing the use of natural gas as fuel) Stream (2) flash gas from CO 2 Removal

[0039] Figure 4 is an exploded view of the fuel system(s) g): FH) Combustion heater CCU) Flue gas carbon recovery unit Stream (2,4,8) flash gas from CO 2 Removal in unit d), and recycle off-gas stream from unit e) Stream (5,7,9) hydrogen-rich fuel containing nitrogen split stream

[0040] The references used to represent the different steps in the method of the present invention are as follows: a) Desulfurization b 0 ) Pre-reforming b) Reforming (SMR) b) Reforming (ATR) b) Reforming (Air Blown Secondary Reformer) c) Shift d) CO 2 Removal e) Nitrogen Wash or PSA or Methanation f) Ammonia Synthesis g) Fuel System(s) i) Ammonia Recovery Stream (4, 8, 10): Recycle Offgas Stream Stream (9): Hydrogen Rich Fuel (Replaces the use of natural gas as fuel) Stream (5, 7): Hydrogen Rich Fuel (Replaces the use of natural gas as fuel) Stream (2): Flash Gas from CO 2 Removal

Examples

[0041] Example 1 Table 1 shows the advantages of the proposed layout in the present invention from the viewpoint of carbon recovery rate (%).

[0042] Traditional ammonia production involves the utilization of natural gas as a supplementary main fuel for combustion heaters / process furnaces for offgases from ammonia recovery and syngas preparation steps. This results in carbon emissions from the flue gas stack, which could be partially recovered by solution-based carbon recovery technologies. The recovery rate (including carbon recovery from flue gas) for such plants does not exceed 90% and is a capital-intensive process. Using the proposed layout that includes the combustion of hydrogen rich fuel and the use of offgases in the main process results in a significant reduction in carbon emissions, i.e., a recovery rate of over 98%. This process is significantly less expensive, requires a minimum number of steps, and has a lower footprint on the plot. By recycling at least a portion of Streams (4, 8) to reforming step b, a recovery rate better than 99% can be obtained.

[0043]

Table 1

Claims

1. The following steps: a) Preheating a hydrocarbon feedstock in a fuel system; b) Removing sulfur and other contaminants from the preheated hydrocarbon feedstock; c) reforming the preheated hydrocarbon feedstock from step b) to obtain a synthesis gas containing CO, CO ２ , H ２ , H ２ O and CH ４ ; d) Passing the syngas from step c) through a shift reaction step to reduce the CO content; e) A step of sending the gas from step d) to a CO ２ removal step, wherein the gas is at least CO ２ rich stream and a hydrogen-rich stream, and optionally split into a flash gas; f) Passing the hydrogen-rich stream from step e) through: i) H ２ O, CO, CO ２ , CH ４ are removed from the off-gas stream to obtain a purified hydrogen stream, and nitrogen is added to obtain an ammonia synthesis gas stream containing nitrogen and hydrogen, hydrogen purification and nitrogen washing; or ii) A PSA that provides a hydrogen stream containing more than 99.5% hydrogen, wherein nitrogen is added to the hydrogen stream to obtain a syngas stream containing nitrogen and hydrogen and an offgas stream; or iii) Methanation of CO and CO ２ together with hydrogen to CH ４ and H ２ O to obtain a syngas stream containing nitrogen, hydrogen, and CH ４ including inert substances; g) Passing a portion of the syngas stream from step f) through an ammonia synthesis section to convert the portion to ammonia and sending another portion of the syngas stream to a preheating system; A method for producing ammonia, comprising: The fuel system includes at least two separate combustion heaters, at least one of the combustion heaters is equipped with a unit for removing 80% or more of CO2 from the generated flue gas, and the combustion heaters use the offgas from step f), the flash gas from step e), and, in the case of f) iii), the offgas from step g) as fuel; The method.

2. The method according to claim 1, wherein the reforming step c) is carried out in an autothermal reformer, or in a tubular reformer followed by steps in an autothermal reformer, or in a tubular reformer and a subsequent air-blown secondary reformer.

3. The method according to claim 1 or 2, wherein the hydrocarbon fuel, the flash gas from step e), the offgas from step f), and a portion of the syngas stream from step f) are premixed or separately supplied to the fuel system.

4. Adiabatic pre-reforming step c of the hydrocarbon stream from step b ０ The method according to any one of claims 1 to 3, comprising

5. In step f) i), hydrogen purification and nitrogen addition are carried out by sending the hydrogen-rich stream to a PSA and then adding nitrogen to the obtained hydrogen stream, and at least a portion of the obtained offgas stream is sent to the preheating in step a). The method according to any one of claims 1 to 4.

6. In the methanation step f) iii), CO, CO ２ and hydrogen are converted to CH ４ and H ２ O, and a purge gas stream containing CH ４ from ammonia synthesis is added, the method according to any one of claims 1 to 5.

7. In the hydrogen recovery unit, CH is recovered from the stream of unreacted components from the ammonia synthesis section ４ to result in a stream containing more than 99% hydrogen, which is sent to the ammonia synthesis section in step g) and / or the preheating system in step a), and an off-gas containing a CH content of more than 95% in the synthesis gas stream to the ammonia synthesis section in step g), which is used as fuel in one or more combustion heaters equipped with a flue gas CO2 removal unit, the method according to claim 6. ４ ​

8. The amount of air to the air-blowing secondary reformer is adjusted so that the molar ratio of N to H in the stream from the methanation in step f iii) is between 1:2.5 and 1:3.

5. The method according to claim 2. ２ and H ２ The method according to claim 2, wherein the molar ratio of N to H is obtained.

9. The synthesis gas stream obtained from step f) contains N ２ and H ２ in a ratio between 1:2.9 and 3.1, the method according to any one of claims 1 to 8.

10. The following: a) A preheating unit b) A desulfurization unit; c) A reforming unit; d) A shift unit; e) CO ２ Removal unit; f) a nitrogen washing unit, a pressure swing adsorption unit or a methanation unit, g) an ammonia synthesis section; and h) a fuel system(s) for supplying fuel to at least two or more separate heaters in the preheating unit, wherein at least one heater comprises a combustion system(s) equipped with a unit for removing 80% or more of CO2 from the resulting flue gas, A system for producing ammonia according to the method of claims 1 to 9, comprising.

11. The system according to claim 10, wherein the pre-reforming unit is arranged upstream of the reforming unit c).

12. The system according to claim 10 or 11, wherein the reforming unit c) comprises an autothermal reformer, or a tubular reformer following an autothermal reformer, or a tubular reformer following an air-blown secondary reformer.

13. The reforming unit c) includes an autothermal reformer, and f) is a CO ２ and H ２ and an H2O dryer followed by a nitrogen purging unit, according to claim 10 or 11.

14. The system according to claim 10 or 11, wherein the reforming unit c) comprises an autothermal reformer and f) is PSA.

15. The reforming unit c) includes a tubular steam reformer followed by an autothermal reformer, and f) is a CO and H ２ O dryer following nitrogen washing, the system according to claim 10 or 11. ２ and H ２ ２ O dryer, the system according to claim 10 or 11.

16. The system according to claim 10 or 11, wherein the reforming unit c) comprises a tubular steam reformer following an autothermal reformer and f) is PSA.

17. The system according to claim 10 or 11, wherein the reforming unit c) comprises a tubular steam reformer following an air-blown secondary reformer and f) is a methanation unit.

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