Obviousness

Obviousness Analysis under 35 U.S.C. § 103

A patent claim is obvious if "the differences between the claimed invention and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art" (35 U.S.C. § 103). This analysis will identify potential combinations of prior art references that would render the claims of US10933370B2 obvious.

Person Having Ordinary Skill in the Art (POSA)

A POSA in this field would likely have a Master's degree or equivalent experience in chemical engineering, environmental engineering, or a related discipline, with a focus on air pollution control, specifically mercury emissions from industrial sources like coal-fired power plants or incinerators. They would be familiar with various sorbent technologies, flue gas treatment systems, and methods for pollutant removal and sorbent regeneration.

Potential Obviousness Combinations

The core of US10933370B2 lies in the use of halogen/halide-promoted activated carbon for mercury removal, particularly its high initial reactivity, regenerability, and methods for in-flight preparation and controlling injection rates. Several prior art references point towards the individual elements of this invention, suggesting that their combination could be considered obvious to a POSA.

Combination 1: Halogen/Halide Promoted Activated Carbon (Claim 1 and 12)

• US10933370B2 teaches: A promoted carbon sorbent comprising a base activated carbon reacted with a halogen, halide, or combination thereof, effective for mercury removal (Claim 1), and a method of preparing it by reacting granular activated carbon with such a promoter (Claim 12).
• Prior Art:
  • US 5,891,324 (Nelson): Describes activated carbon containing an acid (HCl, H2SO4, or H3PO4) for removing mercury from a liquid phase. While it focuses on liquid phase and acids, it establishes the concept of modifying activated carbon for mercury removal. The patent explicitly states that it lacks features like "in-flight bromine treatment" and "regeneration, recycling, or reuse", indicating these were known or desirable concepts at the time.
  • JP 49-43197 and JP 50-6438: Describe using metal iodide salts on a support or resin impregnated with metal iodide for treating Hg-contaminated electrolysis cell gas. These show the concept of using halide compounds for mercury removal, albeit in different forms and applications. The current patent distinguishes itself by claiming a "carbon bromide compound" which these Japanese patents do not appear to represent.
  • General knowledge in the art: The patent itself mentions that "Halogen treatment resulted in higher-activity carbons because the halide anions (especially bromide and iodide) were effective in promoting the oxidation by stabilizing the developing positive charge on the mercury in the transition state for oxidation." This statement indicates that the enhancing effect of halogens, particularly bromide and iodide, on activated carbon for mercury oxidation was recognized in the field. Also, activated carbon can be modified, e.g., by sulfur or halogen impregnation, to increase its mercury adsorption capacity for flue gas treatment. Activated carbons chemically modified with bromine compounds are known to be effective at sequestering vapor phase mercury from industrial flue gas streams.
• Motivation for Combination: A POSA, observing the known efficacy of activated carbon for mercury removal and the documented benefits of halide compounds (specifically iodide and bromide) in promoting mercury oxidation, would have been motivated to combine these elements to enhance the performance of activated carbon. The Nelson patent's acknowledgment of the lack of "in-flight bromine treatment" and "regeneration, recycling, or reuse" in its own system implies that these were recognized as desirable improvements in the art. Furthermore, the general knowledge that activated carbons can be chemically modified with halogens to enhance mercury adsorption capacity would lead a POSA to explore such modifications. The specific use of bromine, with its highly polarizable electrons, for enhanced reactivity would be a logical choice given the understanding of halide anion promotion effects on mercury oxidation.

Combination 2: Regenerable Sorbents and Reuse (Claim 22, 27)

• US10933370B2 teaches: A method for reducing mercury in flue gas by injecting sorbent, collecting >70% mercury, and substantially recovering the sorbent (Claim 22). Also, using larger sorbent particles (>40 micrometers) for separation from ash and re-injection after regeneration (Claim 27).
• Prior Art:
  • PCT/US04/12828 (Process for Regenerating a Spent Sorbent, incorporated by reference in US10933370B2): This prior art explicitly describes a "process and system for regenerating spent sorbents, or enhancing fresh sorbents" for mercury and other pollutant removal from flue gas. It mentions that the invention provides a cost-effective way to capture pollutants by utilizing a process to regenerate the reactivity and capacity of the sorbent. The abstract of US10933370B2 also states that the sorbents are "regenerable".
  • US 2002/0150516: Describes injecting manganese oxide sorbent particles, with regeneration claimed by rinsing with dilute aqueous acid.
  • US 5,607,496: Teaches oxidation of mercury on a metal oxide sorbent bed and subsequent absorption, but notes challenges with regeneration due to sulfate formation.
  • US 2001/0003116: Describes regeneration of transition metal oxide plate or honeycomb material for mercury sorption, involving heating in a reducing gas and impregnation with a complex-forming reagent.
  • US 6,136,072: Mentions amalgamating noble metals on a support that can be regenerated by microwave heating.
  • US 5,928,617: Describes a process for removing mercury from gas using elemental sulfur as a medium, and a further object of the invention is to provide for a process for mercury recovery from a spent sulfur pastille filter medium which also allows recycle of the sulfur.
  • "Comparing Permanent vs. Regenerable Mercury Adsorbents": Discusses both permanent and regenerable mercury adsorbents, outlining their characteristics and applications, indicating that regenerable systems are a known alternative for certain applications and offer lifecycle cost reductions.
  • "Novel Regenerable Sorbent for Mercury Capture from Flue Gases of Coal-Fired Power Plant": Discusses a natural chabazite-based silver nanocomposite (AgMC) that shows higher mercury capture capacity and can be regenerated by simple heating at 400 °C, retaining its performance over multiple cycles.
  • General Activated Carbon Regeneration: Activated carbon in mercury guard beds can be regenerated, extending service life and minimizing waste. The regeneration of spent granular activated carbon (GAC) is a known technique. Supercritical CO2 extraction has also been investigated for sorbent regeneration.
  • US 7,214,254 B2: Discusses regeneration of carbon sorbents through hot-gas vaporization.
• Motivation for Combination: The prior art clearly demonstrates a strong motivation for developing regenerable mercury sorbents due to cost savings, waste reduction, and sustainability. A POSA would have been motivated to combine the known benefits of activated carbon's mercury capture capabilities with existing regeneration techniques to develop a more economical and environmentally friendly solution. The explicit mention of regeneration in PCT/US04/12828, which is cross-referenced in the current patent, highlights the contemporary relevance of this aspect. Furthermore, the problem of separating fine sorbent particles from fly ash, which the current patent addresses with larger particles, was a recognized challenge in the field (as indicated by the "Standard AC sorbents generally are of fine size...separation of the two is difficult" statement in the patent). The combination of a regenerable sorbent with a larger particle size to facilitate physical separation would be an obvious solution to this known problem.

Combination 3: In-flight Preparation and Control (Method of Use Claims)

• US10933370B2 teaches: In-flight preparation of sorbent by reacting activated carbon and a promoter within a pneumatic transport line before injection into the flue gas. Also, monitoring mercury content of cleaned flue gas to control sorbent injection rate and composition.
• Prior Art:
  • General Activated Carbon Injection (ACI): Activated carbon injection (ACI) systems for mercury removal are well-established. ACI involves injecting powdered activated carbon into the flue gas stream.
  • US10933370B2 itself (Definitions): States, "New methods for in-flight preparation, introduction, and control of the active sorbent into the mercury contaminated gas stream are described." It further details that the "halogen promoted carbon sorbent can be readily produced 'in-flight'. This is accomplished by, for example, contacting the vapors of any combination of halogens and optionally a second component, in-flight, with very fine carbon particles."
  • US 5,569,436 and CA 2,114,331: Describe removing toxic metals, including mercury, from incinerator flue gases by contact with dry alkaline material and dry activated carbon, followed by solids separation. While not explicitly "in-flight preparation" of a promoted carbon, it demonstrates the concept of injecting materials into a flue gas stream for contaminant removal.
  • US 7,060,233 B1: Describes a process for removing sulfur and mercury, where elemental mercury reacts with sulfur to form HgS, which is removed by condensation. While not direct sorbent injection, it shows simultaneous removal and reaction within the gas stream.
  • US 10,343,114 B2: Describes in-flight preparation, introduction, and control of the sorbent, promoter, and promoted sorbent into the mercury contaminated gas stream.
  • Control Systems in Pollution Abatement: Continuous Emission Monitors (CEMs) for mercury are a known technology for monitoring emissions. Feedback control systems are common in industrial processes, including pollution control, to optimize reagent addition based on measured pollutant levels. The patent explicitly states that flow controllers can be adjusted "according to control algorithms well known in the art."
• Motivation for Combination: Given the existing practice of injecting activated carbon into flue gas streams for mercury removal, a POSA would be motivated to improve the efficiency and reactivity of this process. The idea of preparing the sorbent "in-flight" would stem from a desire to maximize reactivity by ensuring fresh reaction product at the point of injection, especially considering the known issue of existing sorbents being initially unreactive and requiring "seasoning" in flue gas. The patent's own description of "in-flight" preparation as a "very simple to implement" technology that "results in a great cost savings" reinforces its obviousness. Combining this with continuous mercury monitoring to dynamically adjust injection rates is a standard engineering approach to optimize performance and minimize costs in pollution control systems.

Combination 4: Co-injection of Alkaline Material (Method of Use Claims)

• US10933370B2 teaches: Co-injecting an optional alkaline material to improve mercury capture efficiency by capturing oxidized mercury and/or gaseous components that reduce sorbent capacity.
• Prior Art:
  • US 5,569,436 and CA 2,114,331: Teach removing mercury from incinerator flue gases by contact with dry alkaline material and dry activated carbon. These patents explicitly disclose the simultaneous use of activated carbon and alkaline material for mercury removal.
  • "IPM Model – Updates to Cost and Performance for APC Technologies Mercury Control Cost Development Methodology": States that "alkali reagent injection (typically Trona) before the mercury sorbent injection system can reduce the SO3 concentration and facilitate easier mercury capture." This clearly articulates the benefit of alkali injection in conjunction with mercury sorbents to address flue gas constituents that can hinder mercury capture.
  • US10933370B2 (Definitions): States, "an optional alkaline material, including without limitation alkaline and alkaline earth components, to improve the efficiency of mercury capture by capturing oxidized mercury and/or capturing gaseous components that might otherwise reduce sorbent capacity." This directly acknowledges the known function of alkaline materials in flue gas treatment.
  • US 10,596,517 B2: Describes co-injection of an optional alkali component with promoted carbon sorbent into a flue gas stream for mercury reduction.
  • "Mercury Removal from Flue Gas by Aqueous Precipitation": Notes that while the CMAP process (using sodium hydroxide) has low elemental mercury removal efficiency, it can remove oxidized mercury with more than 90% efficiency.
• Motivation for Combination: A POSA would be motivated to co-inject alkaline materials with activated carbon sorbents to address known challenges in flue gas mercury control. Specifically, the prior art highlights that alkaline materials can effectively capture oxidized mercury and mitigate the detrimental effects of acid gases like SO3 on sorbent capacity. The explicit mention in US 5,569,436 and CA 2,114,331 of combining dry alkaline material and dry activated carbon for mercury removal directly suggests this combination. The knowledge that different mercury species (elemental vs. oxidized) might be preferentially captured by different agents would further motivate the use of a multi-component system.

Conclusion on Obviousness

The identified prior art references, individually and in combination, disclose many key aspects of US10933370B2. A person having ordinary skill in the art, motivated by the ongoing challenges of efficient and cost-effective mercury removal from flue gases, would have found it obvious to combine these known elements. The drive for improved sorbent reactivity, regenerability, reduced waste, and optimized injection strategies would have naturally led a POSA to:

1. Promote activated carbon with halogens/halides: Given the known enhancing effects of halides on mercury oxidation and the existing use of modified activated carbons for mercury removal.
2. Develop regenerable sorbents and reuse strategies: Driven by economic and environmental concerns, and the established techniques for sorbent regeneration in various contexts.
3. Implement in-flight preparation and feedback control: To maximize sorbent efficacy and optimize resource utilization, building on existing ACI systems and general principles of process control.
4. Co-inject alkaline materials: To address specific challenges with oxidized mercury capture and interference from other flue gas constituents.

While US10933370B2 presents a comprehensive system, the individual components and the motivations for combining them appear to be present in the prior art, rendering the claims, particularly the independent claims 1, 12, 22, and 27, potentially obvious under 35 U.S.C. § 103.