Obviousness

To assess the obviousness of US patent 11286168 under 35 U.S.C. § 103, we need to consider whether the claimed invention as a whole would have been obvious to a person having ordinary skill in the art (PHOSITA) at the time the invention was made, given the scope and content of the prior art. A PHOSITA is a hypothetical person with normal skills and knowledge in the relevant technical field, possessing ordinary creativity, but not a genius. The analysis requires identifying differences between the claimed invention and the prior art, and then determining if there would have been a motivation to combine or modify prior art references to arrive at the claimed invention.

The patent US11286168 focuses on reducing CO2 emissions in ammonia synthesis by using a CO2-depleted synthesis gas as fuel for furnaces in the conversion section, and by using oxygen-enriched air or oxygen in the reforming step.

Level of Ordinary Skill in the Art

In the field of ammonia synthesis, a person of ordinary skill in the art would likely possess:

• A strong understanding of chemical engineering principles, particularly thermodynamics, reaction kinetics, and mass transfer.
• Knowledge of various reforming technologies (e.g., steam methane reforming, autothermal reforming, partial oxidation) and their operational parameters.
• Familiarity with gas purification processes, including CO2 removal techniques (e.g., amine scrubbing), methanation, and hydrogen recovery units (HRU).
• Experience with process integration and optimization in industrial chemical plants, especially regarding energy efficiency and emissions control.
• Awareness of common catalysts used in ammonia synthesis and associated upstream processes.
• An understanding of the economic drivers and environmental regulations impacting ammonia production, such as the need to reduce CO2 emissions.

Obviousness Analysis of Claims

The patent text itself acknowledges that many individual steps of the process, such as reforming, shift reaction, CO2 removal, and methanation, are known in the prior art. The novelty lies in the specific integration and utilization of certain streams to achieve low CO2 emissions.

Independent Claim 1: Process for synthesis of ammonia from natural gas

Claim 1 describes:

1. Conversion of desulphurized natural gas and steam with oxygen-enriched air or oxygen into synthesis gas.
2. Treatment of synthesis gas with shift reaction and CO2 separation, yielding CO2-depleted synthesis gas and a CO2-rich flow.
3. Separation of a part of the CO2-depleted synthesis gas as a fuel fraction, fed to at least one furnace.
4. The separation involves splitting the CO2-depleted synthesis gas into two streams of the same composition: one as fuel, one for ammonia synthesis.

Prior Art Considerations:
The patent explicitly states that "the reforming process, in a common type of plant, comprises primary steam reforming and a subsequent catalytic air-fired secondary reforming" and mentions "autothermal reformer (ATR) preceded by a furnace for heating the charge" as other configurations. It also notes that processes for capturing CO2 from fumes are known, but costly. The patent distinguishes itself by deliberately allocating a significant portion of the CO2-depleted synthesis gas as fuel, a practice it states is different from the prior art that only allocates "purge streams derived from purification processes and containing methane."

Motivation to Combine/Modify:
A PHOSITA, at the time of the invention, would have been aware of the environmental pressure to reduce CO2 emissions from industrial processes, including ammonia synthesis. The patent itself highlights this problem, stating that existing ammonia plants "result in significant emissions of CO2 into the atmosphere" and that "it is required to minimize the CO2 emissions from the fumes of the NH3 plants."

Given the desire to reduce CO2 emissions, a PHOSITA would have been motivated to explore alternative fuels for the furnaces. The recognition that hydrogen combustion does not produce CO2 would naturally lead to considering hydrogen-rich streams as fuel. While the prior art might have used small purge streams with reduced CO2, the idea of using a larger, deliberately separated, CO2-depleted synthesis gas stream as primary furnace fuel, where hydrogen is the main combustible component, represents a significant departure from conventional practices of burning natural gas directly or using methane-rich purge streams.

The challenge for obviousness would be to find prior art that not only describes the individual steps but also suggests or teaches the combination of:

• Using oxygen-enriched air/oxygen for reforming to produce a specific synthesis gas composition.
• Performing CO2 removal.
• Then intentionally diverting a substantial portion (e.g., 10-40% as claimed) of this CO2-depleted synthesis gas as fuel for the plant's furnaces.
• And, crucially, doing so with the explicit motivation of drastically reducing CO2 emissions, even if it requires producing a larger overall quantity of synthesis gas.

If prior art existed that demonstrated the use of a CO2-depleted, hydrogen-rich synthesis gas as a primary fuel for ammonia plant furnaces, with the understanding that this would substantially reduce CO2 emissions, and if it taught splitting a main process stream for this purpose, then Claim 1 could be rendered obvious. However, the patent emphasizes that the prior art "teaches only allocating as fuel any purge streams derived from purification processes and containing methane." If this distinction holds true in the available prior art, then the deliberate large-scale diversion of CO2-depleted synthesis gas as furnace fuel would likely be non-obvious.

Independent Claim 11: Revamping method for an existing ammonia plant

Claim 11 describes a revamping method for an existing plant with a primary steam reformer and an air-fired secondary reformer, including:

1. Providing and using oxygen-enriched air or oxygen as an oxidant for the secondary reformer instead of air.
2. Separating a part of the synthesis gas downstream of decarbonation.
3. Feeding this separated, reduced-CO2 synthesis gas as fuel for at least one furnace of the plant.

Prior Art Considerations:
The patent indicates that conventional plants use air-fired secondary reformers. The replacement of air with oxygen-enriched air or oxygen in reformers is a known technique in various industrial processes to improve efficiency or control. The patent notes that "the advantages of a high oxygen content in the enriched air are as follows: greater calorific power of the synthesis gas; smaller flow of flue discharge gas; smaller volumetric flow through the apparatus of the conversion section and, consequently, smaller apparatus." These are known benefits of using enriched air or oxygen in combustion and reforming.

Motivation to Combine/Modify:
A PHOSITA seeking to revamp an existing plant to reduce CO2 emissions would consider several options. The motivation to replace air with oxygen-enriched air in the secondary reformer would be driven by known benefits like increased efficiency and calorific power, as stated in the patent. This change alone might not be sufficient to render the entire claim obvious.

The core of Claim 11's non-obviousness, similar to Claim 1, lies in the specific use of the separated CO2-depleted synthesis gas as fuel for the plant's furnaces. If a PHOSITA, motivated by CO2 reduction, would consider replacing natural gas furnace fuel with a hydrogen-rich stream, and prior art supported extracting a large, CO2-depleted portion of the synthesis gas after decarbonation for this purpose, then the combination might be obvious. The "revamping procedure" described in the patent (installing ASU, modifying secondary reformer, increasing natural gas for process, revamping desulphurization and CDR) suggests a comprehensive set of modifications.

If prior art discusses revamping existing ammonia plants to reduce CO2 emissions by replacing air with oxygen-enriched air in secondary reformers and simultaneously proposes utilizing a significant portion of the decarbonated synthesis gas as furnace fuel, then Claim 11 would be obvious. Absent such a combined teaching or strong suggestion, particularly regarding the large-scale diversion of decarbonated synthesis gas as fuel, the claim could be considered non-obvious.

Independent Claim 17: Process for producing ammonia with low CO2 emissions using ATR

Claim 17 describes:

1. Converting natural gas into synthesis gas using a catalytic autothermal reformer (ATR) (optionally with a pre-reformer) and oxygen-enriched air or oxygen.
2. Shift reaction of CO to CO2 and subsequent CO2 removal, producing CO2-depleted synthesis gas and a CO2-rich flow.
3. Separation of a part of the CO2-depleted synthesis gas as a fuel fraction, fed to a furnace for pre-heating the gas prior to ATR.
4. The remaining CO2-depleted gas is used for ammonia synthesis.

Prior Art Considerations:
The use of ATR in ammonia synthesis is a known technology. The patent itself mentions "autothermal reformer (ATR) preceded by a furnace for heating the charge" as a known configuration. The advantages of ATR, such as lower heat requirement compared to primary reformer/ATR combinations, are also noted.

Motivation to Combine/Modify:
The motivation to use ATR (with or without a pre-reformer) would stem from its known efficiencies and potentially smaller footprint. The use of oxygen-enriched air or oxygen with ATR is also a known optimization for reformer operation.

The key element for obviousness in Claim 17, again, is the diversion of a portion of the CO2-depleted synthesis gas to fuel the pre-heating furnace for the ATR. If a PHOSITA, seeking to minimize CO2 emissions from an ATR-based ammonia plant, would readily identify the pre-heating furnace as a source of CO2 emissions and would then consider replacing its conventional fuel (e.g., natural gas) with the hydrogen-rich, CO2-depleted synthesis gas produced within the same plant, then this claim could be obvious. The patent explicitly states that using the fuel fraction from the synthesis gas for the furnace (like AUX in the figures) instead of natural gas drastically reduces CO2 emissions.

If prior art demonstrates or strongly suggests using the product of the synthesis gas generation (after CO2 removal) to fuel the same synthesis gas generation process's pre-heaters (e.g., for an ATR), specifically to mitigate CO2 emissions, then Claim 17 would be obvious. The patent emphasizes that this approach results in a "smaller heat requirement of the furnace" and a "smaller fuel fraction of the synthesis gas," leading to "lower CO2 flue emissions." If these advantages were already known or predictable from existing technologies, and the combination of elements was straightforward for a PHOSITA, then it could be considered obvious.

Conclusion on Obviousness

To successfully argue obviousness for US11286168, specific prior art references would need to be identified that, either individually or in combination, teach or suggest the core inventive concept: utilizing a significant, deliberately separated portion of the CO2-depleted synthesis gas as primary fuel for the furnaces within the ammonia synthesis plant, particularly to achieve substantial reductions in CO2 emissions. The critical aspect is not merely the existence of the individual steps (reforming, shift, CO2 removal, burning fuel in a furnace), but the motivation and teaching to combine them in this specific way for the stated purpose of drastically reducing CO2 emissions, even if it entails producing an "additional quantity of synthesis gas" to account for the diverted fuel.

The patent explicitly states that the prior art "teaches only allocating as fuel any purge streams derived from purification processes and containing methane," differentiating its approach of deliberately allocating a non-negligible portion of synthesis gas to fuel. If this distinction is accurate and not contradicted by the identified prior art, the claims could stand against an obviousness challenge. However, if prior art exists that describes using significant, hydrogen-rich, CO2-depleted process streams as primary fuel sources within an ammonia plant for environmental benefits, then the claims would face a stronger obviousness challenge. The examiner would need to provide an explicit rationale, avoiding conclusory statements, for why a PHOSITA would have been motivated to combine the prior art elements in the manner claimed.