Union Electric Co v. MES Inc

1. Case Identification

• Case #: IPR2025-01324
• Patent #: 10,933,370
• Filed: July 18, 2025
• Petitioner(s): Union Electric Company
• Patent Owner(s): Birchtech Corporation
• Challenged Claims: 1-6, 8, 11, 14-15

2. Patent Overview

• Title: Method for Separating Mercury from Gas
• Brief Description: The ’370 patent relates to a method for removing mercury from flue gas generated by coal combustion. The method involves combusting a mixture of coal and a halogen-based additive, followed by adding a particulate sorbent like activated carbon into the resulting mercury-containing gas to capture the mercury.

3. Grounds for Unpatentability

Ground 1: Obviousness over Downs and Nelson - Claims 1-6, 8, 11, 14-15 are obvious over Downs in view of Nelson, or Downs in view of Altman and Nelson.

• Prior Art Relied Upon: Downs (Application # US 2008/0107579), Nelson (Application # US 2004/0003716), and Altman (Patent 5,827,352).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Downs taught the core concept of claim 1(a): adding a bromine-containing additive (e.g., calcium bromide) to coal before or during combustion to enhance mercury oxidation. Downs also disclosed the subsequent use of a powdered activated carbon (PAC) sorbent injection system downstream to capture the oxidized mercury, meeting the requirements of claims 1(b), 1(d), and 1(e). Nelson and Altman were cited as providing specific, well-known details for the sorbent injection step, such as injection rates and system configurations for activated carbon, which Downs described more generally.
  • Motivation to Combine: A POSITA would combine Downs with Nelson or Altman because all references address the same problem of mercury removal from coal flue gas. Downs taught the benefit of pre-combustion halogen addition, while Nelson and Altman provided established methods for post-combustion sorbent injection. A POSITA would have been motivated to combine these known, complementary techniques to create a more effective, multi-stage mercury capture system.
  • Expectation of Success: The combination involved applying known technologies (halogen additives, sorbent injection) in their expected manner to achieve the predictable result of improved mercury capture. Petitioner contended a POSITA would have a high expectation of success.
  • Key Aspects: The argument for the weight ratio of claim 1(c) was met by combining the additive concentration taught in Downs (e.g., 375 ppm calcium bromide) with the sorbent injection rate taught in Nelson (e.g., 7 lbs PAC/MMacf), which Petitioner calculated to fall within the claimed range of 1:100 to 30:100.

Ground 2: Anticipation by Pollack - Claims 1-6, 8, 11, 14-15 are anticipated by Pollack.

• Prior Art Relied Upon: Pollack (Application # US 2011/025011).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that Pollack disclosed every element of the challenged claims in a single reference. Pollack explicitly described a method of removing mercury by applying a halogen precursor (such as an aqueous solution of calcium bromide or sodium bromide) directly onto the fuel source (coal) before combustion. Pollack also explicitly taught injecting a sorbent material, such as activated carbon, into the exhaust stream downstream of the combustion chamber to capture mercury, followed by collecting the mercury-laden sorbent in a baghouse or electrostatic precipitator.
  • Key Aspects: Pollack’s disclosure of spraying a liquid halogen precursor onto coal before combustion was argued to directly teach the limitations of claims 2, 3, and 4. Further, Petitioner calculated that the exemplary additive and sorbent rates disclosed in Pollack resulted in a weight ratio (approx. 25:100) that falls squarely within the range recited in claim 1(c), thus anticipating that element as well.

Ground 3: Obviousness over Vosteen and Nelson - Claims 1-6, 8, 11, 14-15 are obvious over Vosteen in view of Nelson, or Vosteen in view of Altman and Nelson.

• Prior Art Relied Upon: Vosteen (Application # US 2004/0013589), Nelson (Application # US 2004/0003716), and Altman (Patent 5,827,352).

• Core Argument for this Ground:

  • Prior Art Mapping: This ground presented Vosteen as an alternative to Downs for the pre-combustion additive step. Petitioner argued Vosteen taught adding bromine compounds (e.g., sodium bromide) to the furnace or upstream to the coal to cause "substantial, essentially complete, oxidation of the mercury." This teaching was then combined with the post-combustion activated carbon injection systems of Nelson or Altman, similar to the logic presented in Ground 1.
  • Motivation to Combine: The motivation was identical to Ground 1: combining a known pre-combustion oxidation step (from Vosteen) with a known post-combustion capture step (from Nelson/Altman) to achieve a well-understood and effective mercury removal process.
  • Expectation of Success: A POSITA would have expected success for the same reasons as in Ground 1, as it involved the combination of known, complementary elements for their intended purpose.

• Additional Grounds: Petitioner asserted an additional obviousness challenge (Ground 4) based on combinations of Pollack with Nelson or Pollack with Olson-235 (Patent 8,652,235), relying on similar combination rationales to bolster the primary arguments.

4. Key Technical Contentions (Beyond Claim Construction)

• Invalid Priority Claim: A central contention of the petition was that the ’370 patent is not entitled to its claimed priority date of 2004. Petitioner argued that the parent applications in the priority chain lack written description support for the key limitation of adding a halogen additive directly to the coal or into the combustion chamber. The priority applications allegedly only described creating a pre-promoted sorbent outside the flue gas stream and then injecting that promoted sorbent into the flue gas post-combustion. Because this critical element was first disclosed in the application that matured into the ’370 patent, Petitioner argued its effective filing date is in 2018, making references like Downs, Vosteen, and Pollack qualifying prior art.

5. Arguments Regarding Discretionary Denial

• Petitioner argued against discretionary denial under §314(a) and §325(d). It contended that the parallel district court litigation is at a very early stage, having been consolidated into an MDL proceeding with no depositions taken and a Markman brief not due until late 2025, meaning a Final Written Decision would issue well before any trial. Petitioner also argued that the Examiner did not consider the most relevant prior art, Pollack, during prosecution, and that other cited references (Downs, Olson-235) were only mentioned in passing and not used in any substantive rejection, making Board review appropriate.

6. Relief Requested

• Petitioner requested institution of an inter partes review and cancellation of claims 1-6, 8, 11, 14, and 15 of the ’370 patent as unpatentable.