Obviousness

The obviousness analysis under 35 U.S.C. § 103 for US patent 10589225 requires identifying combinations of prior art references that would have made the claimed invention obvious to a person having ordinary skill in the art (POSITA) as of the patent's priority date, August 30, 2004. The analysis also requires explaining the motivation for combining these references.

The independent claims of US10589225 focus on a promoted carbon sorbent (Claim 1), methods for its preparation (Claim 13), methods for mercury reduction with sorbent recovery and optional regeneration (Claim 22), and methods for mercury reduction utilizing sorbent particle size separation (Claim 35).

Prior Art Landscape (Pre-August 30, 2004)

Before the priority date, the following was generally known in the field of mercury removal from flue gas:

• Activated Carbon for Mercury Removal: Activated carbon injection (ACI) was a recognized method for capturing mercury from flue gas, including from coal combustion.
• Enhancement with Halogens/Halides: The use of halogens, particularly bromine and iodine, to enhance the mercury adsorption capacity of activated carbon was actively researched and demonstrated. This included both elemental halogens and halide compounds. Specifically, brominated activated carbon was identified as a strong performer. Methods for treating carbon with bromine-containing gases or solutions were known.
• Sorbent Regeneration: The concept of developing and using regenerable sorbents for mercury removal from flue gas was known, driven by cost and waste disposal concerns.
• Particle Size Effects: The impact of sorbent particle size on mercury capture efficiency was understood, with smaller particles generally offering better performance.
• Co-injection of Alkali Materials: The co-injection of alkaline materials in flue gas treatment systems, sometimes alongside carbon sorbents, was practiced for various purposes, including capturing oxidized mercury or other gaseous components that might reduce sorbent capacity.
• In-flight/In-situ Sorbent Treatment: The idea of preparing or activating sorbents in-situ or in-flight within the gas stream prior to mercury capture was also present in the art.

Obviousness Analysis

Independent Claim 1: Promoted Carbon Sorbent

• Claim Language: A promoted carbon sorbent for removing mercury from a gas stream, comprising a base activated carbon that has reacted with a promoter selected from the group consisting of halides, halogens, and combinations thereof, such that the reaction product is effective for the removal of mercury from a gas stream.
• Combination:
  • Reference 12 (Review article, published 2007 but reflects earlier knowledge): States that "brominated activated carbon appears to be the best-performing mercury sorbent."
  • Reference 9 (EP1509629B1, priority 2003-08-29): Teaches preparing a mercury sorbent by treating a carbonaceous substrate with an "effective amount of a bromine-containing gas, especially one containing elemental bromine or hydrogen bromide, for a time sufficient to increase the ability of the carbonaceous substrate to adsorb mercury." It explicitly notes that "the combination of carbon and gaseous bromine produces an inexpensive sorbent material that can be simply injected into the ductwork of a power plant." It also describes treating PAC with gaseous Br2 or HBr.
  • Reference 18 (Review article, published 2005 but covers prior studies): Mentions that "halogen-embedded activated carbon has been found to be an effective sorbent for elemental mercury capture" and that "previous experimental studies have shown that chemically embedded activated carbon has a higher elemental mercury removal capacity than thermally activated carbon."
• Reasoning: A POSITA, seeking highly effective mercury removal, would be motivated to utilize the acknowledged "best-performing" brominated activated carbon, as indicated by review articles. Reference provides a clear method for producing such a sorbent by reacting activated carbon with bromine-containing gases, resulting in an enhanced sorbent for mercury adsorption from combustion gases. The patent's claim of a "new modified carbon form containing a reactive compound produced by the reaction of bromine (or halide or other halogen) with the carbon" is addressed by's teaching of treating carbon with bromine to increase adsorption ability and's discussion of "chemically embedded activated carbon." The general concept of reacting carbon with halogens/halides to improve mercury capture was known, and the specific chemical details of the reaction product would be considered a matter of degree or routine investigation for a POSITA.

Independent Claim 13: Method of Preparation

• Claim Language: A method comprising providing a granular activated carbon; reacting the activated carbon with a promoter selected from the group consisting of halogens, halides, and combinations thereof, such that the reaction product comprises a promoted carbon sorbent effective for removal of mercury from a gas stream. (Further claims specify promoter amount, particle size for separation, and gas phase/solvent reaction).
• Combination:
  • Reference 9 (EP1509629B1): Describes treating a carbonaceous substrate with a bromine-containing gas (Br2 or HBr) to increase mercury adsorption. It mentions delivering halogens to heated PAC substrates as gases.
  • Reference 1 (Patent, inactive publication 2007-10-11, but covers prior art methods): Teaches preparing an impregnated activated carbon sorbent by spraying untreated sorbent with aqueous solutions of metal halides (KBr or KI).
  • General Knowledge (pre-2004): Granular activated carbon (GAC) was a common form of activated carbon used in adsorption processes. The idea of varying promoter concentration would be a routine optimization.
• Reasoning: Given the known benefits of halogen-promoted activated carbon for mercury removal (as discussed for Claim 1), a POSITA would be motivated to prepare such sorbents. References and disclose methods for reacting activated carbon with halogens or halides, whether in gaseous form or in solution. Since GAC was a standard form of activated carbon, selecting granular activated carbon as the "base activated carbon" would be an obvious choice for a POSITA when considering different physical forms. The specified range of "1 to about 30 grams promoter per 100 grams activated carbon" would represent routine optimization of known halogenation processes, as various concentrations were tested in prior art (e.g., 2% or 5% KBr/KI in, 1% or 10% KBr in).

Independent Claim 22: Method of Mercury Reduction with Recovery/Regeneration

• Claim Language: A method for reducing mercury in flue gas comprising providing a sorbent, injecting the sorbent into a mercury-containing flue gas stream, collecting greater than 70 wt-% of the mercury in the flue gas on the sorbent to produce a cleaned flue gas, and substantially recovering the sorbent from the cleaned flue gas. (Further claims specify monitoring and control, and reduced carbon requirements).
• Combination:
  • Reference 11 ("Removal of Mercury from Flue Gas using Activated Carbon" article): States that "Activated Carbon is very effective in the removal of mercury" and "removal efficiency of mercury can reach to over 90%." It also discusses "injection of activated carbon into the flue gas."
  • Reference 5 (US6719828B1, issued 2004-04-13): Discloses "A high-capacity regenerable sorbent for removal of mercury from flue gas." It discusses the economic and environmental problems of spent sorbent mixed with ash.
  • General knowledge: The economic imperative to reduce costs and waste would motivate regeneration.
• Reasoning: A POSITA would readily combine the known effectiveness of injecting activated carbon for high mercury capture efficiency (e.g., >70% or even >90% as noted in) with the known desire and feasibility of using regenerable sorbents for flue gas mercury removal as taught by. The patent's own background section highlights the cost and disposal problems with existing carbon injection systems that cannot be easily separated for regeneration and reuse. [Patent text] Therefore, the motivation to inject a sorbent, collect mercury, and then recover the sorbent for regeneration would be obvious to reduce costs and mitigate environmental impact. The achievement of "greater than 70 wt-%" removal is a performance target that could be met or exceeded by known ACI technologies, especially with enhanced sorbents.

Independent Claim 35: Method of Mercury Reduction with Size Separation

• Claim Language: A method for reducing the mercury content of a mercury and ash containing gas stream wherein particulate activated carbon sorbent with a mass mean size greater than 40 μm is injected into the gas stream, mercury is removed from the gas by the sorbent particles, the sorbent particles are separated from the ash particles on the basis of size, and the sorbent particles are re-injected to the gas stream.
• Combination:
  • Reference 11 ("Removal of Mercury from Flue Gas using Activated Carbon" article): Teaches activated carbon injection into flue gas for mercury removal.
  • Reference 24 (Article, published 2001): Investigates activated carbon particle sizes (e.g., 4-44 microns) and their effect on mercury capture, noting that smaller particles generally improve capture.
  • General engineering principles (pre-2004): Methods for separating particulate matter based on size (e.g., sieving, cyclone separators, air classification) were well-established in many industrial processes.
  • Motivation for regeneration (from Claim 22 analysis): The strong economic and environmental motivation to regenerate and reuse sorbents for mercury removal.
• Reasoning: While suggests smaller particles for improved mercury capture, the fundamental problem of separating activated carbon from much finer fly ash for regeneration was a known challenge, as implicitly acknowledged in the patent's background. [Patent text] Given the strong motivation to recover and reuse sorbents (as in Claim 22), a POSITA would find it obvious to modify the physical properties of the sorbent to facilitate its separation from ash. Using activated carbon particles with a "mass mean size greater than 40 μm" to enable size-based separation from finer fly ash particles is a straightforward engineering solution using known principles of particle separation. This would allow for recovery and re-injection of the sorbent. While there might be a trade-off in initial mercury capture efficiency with larger particles compared to very fine particles, this compromise would be deemed acceptable and obvious to achieve the significant benefits of sorbent reuse and reduced disposal costs.

In conclusion, key aspects of the US10589225 patent, including the use of halogen-promoted activated carbon, the regeneration and reuse of sorbents, and methods involving particle size manipulation for separation, appear to have been anticipated or rendered obvious by various combinations of prior art available before the patent's priority date of August 30, 2004.