PTAB

IPR2025-01323

Union Electric Co v. MES Inc

Key Events

Petition

petition

Title: Method for Mercury Removal from Flue Gas
Brief Description: The ’225 patent relates to methods for removing mercury from flue gas generated by coal combustion. The claimed method involves combusting a mixture that includes coal and a bromide-based additive, and subsequently adding an activated carbon sorbent into the resulting mercury-containing gas.

Prior Art Relied Upon: Downs (Application # US 2008/0107579).
Core Argument for this Ground:
- Prior Art Mapping: Petitioner argued that Downs discloses every limitation of the challenged claims. Downs teaches a method for removing mercury from coal combustion flue gas by adding a "bromine-containing reagent," which includes HBr, Br2, and bromide compounds like calcium bromide, directly to the coal or into the combustion furnace. This mixture is then combusted. Downs further discloses the subsequent injection of a powdered activated carbon (PAC) sorbent downstream to adsorb the mercury, which is then removed by particulate collectors like fabric filters or electrostatic precipitators (ESPs).

Prior Art Relied Upon: Downs (Application # US 2008/0107579) and Altman (Patent 5,827,352).
Core Argument for this Ground:
- Prior Art Mapping: Petitioner asserted that Downs teaches the pre-combustion addition of a bromide additive to enhance mercury oxidation, and Altman teaches a well-known and effective post-combustion sorbent injection and collection system. Altman discloses injecting activated carbon sorbent into flue gas and using a downstream particulate control device (a wet ESP) to collect the sorbent and captured mercury.
- Motivation to Combine: A POSITA would combine Downs's pre-combustion chemical treatment with Altman's post-combustion physical capture system to create a more effective, two-step mercury removal process. Combining an oxidation-enhancing step with a known adsorption method was a predictable strategy to improve overall capture efficiency.
- Expectation of Success: A POSITA would have a reasonable expectation of success, as the combination leverages complementary and well-understood technologies to address the same technical problem.

Prior Art Relied Upon: Blankinship (Power Engineering, Vol. 113, Issue 6, Jan. 6, 2009).
Core Argument for this Ground:
- Prior Art Mapping: Petitioner argued that Blankinship, a trade journal article, describes a commercial two-step mercury removal process by Alstom that meets all limitations of the independent claims. Blankinship discloses using a bromide compound (KNX™ calcium bromide solution) added pre-combustion "to the boiler or to the coal." It further describes a post-combustion activated carbon sorbent injection system (MER-CURE™) to capture the oxidized mercury "upstream of a particulate control device." The article's reported 80-90% mercury removal rate also meets the quantitative limitation of dependent claim 5.

Prior Art Relied Upon: Blankinship (Power Engineering, Vol. 113, Issue 6, Jan. 6, 2009) and Vosteen (Application # US 2004/0013589).
Core Argument for this Ground:
- Prior Art Mapping: Blankinship teaches the two-step process of adding a bromide compound pre-combustion and injecting activated carbon post-combustion. Vosteen teaches continuously measuring the mercury content of the flue gas and controlling the amount of bromine additive fed into the system based on that measurement to optimize performance.
- Motivation to Combine: A POSITA would be motivated to incorporate Vosteen’s process controls into the system described by Blankinship. This would allow for optimization of chemical additive usage, reducing operational costs and ensuring consistent compliance with emissions regulations—a primary goal in the field.
- Expectation of Success: Implementing feedback control is a fundamental engineering principle. A POSITA would reasonably expect to successfully apply Vosteen's monitoring-and-adjustment method to the process in Blankinship to achieve predictable improvements in efficiency and cost-effectiveness.
Additional Grounds: Petitioner asserted additional obviousness challenges based on Vosteen in view of Altman, as well as combinations including Nelson and Olson-235, but relied on similar theories of combining known pre-combustion oxidation with post-combustion sorbent injection and capture.

Petitioner’s primary technical contention, central to all grounds, was that the ’225 patent is not entitled to its claimed priority date earlier than its filing date of May 14, 2015. Petitioner argued that the parent applications fail to provide written description support for the key claimed step of adding a promoter (e.g., HBr, bromide compound) to the coal or combustor. The parent applications allegedly only describe preparing a promoted sorbent and injecting that promoted sorbent downstream. Petitioner contended this lack of support breaks the priority chain, making the asserted prior art references timely and rendering the claims unpatentable.

Petitioner argued against discretionary denial under 35 U.S.C. §314(a) based on Fintiv factors, stating that the co-pending district court litigation is in a very early stage. The case had been consolidated into a multi-district litigation (MDL) proceeding with a trial date years away, ensuring a Final Written Decision (FWD) from the Board would issue well before any trial.
Petitioner also argued against denial under §325(d), asserting that the Examiner did not consider the Blankinship reference during prosecution. While other key references were cited in the patent, Petitioner contended they were not applied in any substantive rejection, and the Examiner never made findings on the critical priority date issue.

Petitioner requests institution of an inter partes review (IPR) and cancellation of claims 1-2, 5-15, 17-20, and 22-29 of Patent 10,589,225 as unpatentable.