PTAB

IPR2020-00928

NRG Energy Inc v. MidWest Energy EMiSSIons Corp

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1. Case Identification

2. Patent Overview

  • Title: Method for Mercury Emissions Capture from a Gas
  • Brief Description: The ’147 patent relates to methods for removing mercury from flue gas, such as from coal-fired power plants. The purported invention involves improving mercury capture by using exceptionally reactive, halogen-promoted carbon sorbents created by treating the carbon with a bromide promoter.

3. Grounds for Unpatentability

Ground 1: Obviousness over Lissianski-Presentation and Olson-646 - Claims 18-19 are obvious over Lissianski-Presentation in view of Olson-646.

  • Prior Art Relied Upon: Lissianski-Presentation (a January 2006 conference presentation on mercury control) and Olson-646 (Application # 2006/0048646).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Lissianski-Presentation taught a method for separating mercury from a mercury-containing gas in a coal plant. The reference disclosed a system that separately injected a bromine-containing promoter and an activated carbon sorbent into the flue gas to "trim Hg emissions," followed by particulate removal using an electrostatic precipitator (ESP) and a fabric filter. Olson-646, which taught the use of the same commercial "Darco FGD" sorbent, provided the underlying chemical theory. Olson-646 explained that bromine reacts with activated carbon at "carbene species on the edge of the graphene sheet structures" to form a promoted brominated sorbent, which includes a carbocation paired with a bromide anion that is highly effective for oxidizing and capturing elemental mercury.
    • Motivation to Combine (for §103 grounds): A person of ordinary skill in the art (POSITA) would combine Lissianski-Presentation’s practical system with Olson-646’s detailed chemical explanation to understand and optimize a known process. Both references addressed the identical technical problem of mercury removal from flue gas using the same key components (bromine and activated carbon), making their combination a matter of applying known principles to a known system.
    • Expectation of Success (for §103 grounds): A POSITA would have had a high expectation of success because Olson-646 did not propose a new process but rather provided a scientific explanation for the well-known and effective mercury capture process described in Lissianski-Presentation.

Ground 2: Obviousness over Sjostrom and Olson-646 - Claims 18-19 are obvious over Sjostrom in view of Olson-646.

  • Prior Art Relied Upon: Sjostrom (a January 2005 conference presentation on mercury removal) and Olson-646 (Application # 2006/0048646).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Sjostrom taught enhancing mercury removal from coal-fired power plants by injecting halogens (including bromine) and an activated carbon sorbent. Sjostrom's diagrams showed flexibility in injection points, including injecting bromine into the boiler (combustion chamber) and injecting the sorbent downstream into the flue gas, prior to an ESP or fabric filter. This constitutes separate injection into a mercury-containing gas stream. As in Ground 1, Olson-646 provided the scientific basis, explaining the promotion reaction between bromine and the activated carbon's surface structure to enhance mercury capture.
    • Motivation to Combine (for §103 grounds): The motivation was identical to that in Ground 1. A POSITA reviewing the successful mercury removal system in Sjostrom would have been motivated to consult a reference like Olson-646 to understand the underlying chemical mechanisms, particularly how bromine promotes the activated carbon sorbent.
    • Expectation of Success (for §103 grounds): Success was reasonably expected because Sjostrom demonstrated high mercury removal rates (over 70%), and Olson-646 merely provided the accepted chemical theory explaining that success, making the combination a confirmation of known principles.

4. Key Technical Contentions (Beyond Claim Construction)

  • Priority Date Challenge: A central argument of the petition was that claims 18-19 were not entitled to the priority date of the 2004 provisional application. Petitioner argued that the claims require separately injecting a sorbent and a bromine promoter into a mercury-containing gas to cause an in-flight reaction. According to the Petitioner, the parent applications in the priority chain failed to provide written description support for this specific process. Instead, they allegedly disclosed either co-injection of the promoter and sorbent together or pre-treating the sorbent in a transport line that did not contain mercury before injection into the flue gas. Therefore, Petitioner contended the effective priority date for claims 18-19 is no earlier than April 6, 2009, the filing date of the application that led to the ’147 patent, which makes the Sjostrom (2005) and Lissianski-Presentation (2006) references available as prior art.

5. Arguments Regarding Discretionary Denial

  • Petitioner argued that the Board should not exercise discretionary denial.
    • §314(a) (Fintiv Factors): Denial under Fintiv was argued to be inappropriate because the related district court litigation was in its earliest stages. At the time of filing, motions to dismiss were pending, no answer had been filed, no trial schedule was set, and discovery had not commenced.
    • §325(d): Denial was also argued to be improper because the primary references relied upon—Sjostrom and Lissianski-Presentation—are conference presentations that were never before the Examiner during the original prosecution of the ’147 patent. The petition therefore raised new art and arguments that had not been previously considered by the USPTO.

6. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 18 and 19 of the ’147 patent as unpatentable.