US 6875009

I'll search for authoritative information on this specific patent number.

Let me check for litigation/docket history and verify the patent's status.

Let me do a couple of targeted checks on litigation and the family members.

US 6,875,009 B2 — Combustion Method and Apparatus for NOx Reduction

Source of record: Patent full text at https://patents.google.com/patent/US6875009/en (fetched 2026‑10‑01), plus Justia and Patents‑Review mirrors.

Bibliographic data

Abstract (as granted)

"Combustion method and apparatus for NOx reduction and CO reduction which are capable of easily achieving super NOx reduction with the value of exhaust NOx under 10 ppm. The combustion method for NOx reduction by controlling the temperature of combustion gas derived from a burner includes in combination the steps of suppressing combustion gas temperature by heat absorbers; suppressing the combustion gas temperature by recirculating burning-completed gas to a combustion-gas burning reaction zone; and suppressing combustion gas temperature by adding water or steam to combustion-use air of the burner, whereby the temperature of the combustion gas derived from the burner is suppressed."

Plain-language overview of the independent claims

The patent is about a once-through water-tube steam boiler with a fully-premixing gas burner. Its core idea is to stack four different flame-cooling techniques (heat-absorbing water tubes, exhaust-gas recirculation, water/steam injection, and high-excess-air premixed burning) so that no single technique has to be pushed so hard that its own drawbacks appear (pressure loss, oscillating combustion, CO/unburned emissions, condensate corrosion, blower overload). The 10 ppm NOx target is called "super NOx reduction."

• Claim 1 — the base method (independent). A combustion method that controls the combustion-gas temperature from a burner by combining three steps: (i) cooling the gas with heat absorbers; (ii) recirculating already-burned gas back into the burning reaction zone; and (iii) adding water or steam into the burner's combustion-use air.
• Claim 9 — the base apparatus (independent). The same three ideas expressed as hardware: first suppression means (heat absorbers in the burning reaction zone), second suppression means (recirculating burning-completed gas to that zone), and third suppression means (adding water or steam to the burner's combustion-use air).
• Claim 11 — an apparatus defined by plumbing layout (independent). Heat absorbers in the burning reaction zone; an exhaust-gas recirculation passage running from the exhaust gas passage to the air supply passage; and a line that feeds water or steam into the exhaust-gas recirculation passage upstream of the burner (i.e., the steam is introduced into the recirculated flue gas rather than directly into the air inlet).
• Claim 13 — method with the fourth cooling step added (independent). The three steps of claim 1 (heat absorbers, EGR, water/steam to combustion air) plus burning the burner as a fully-premixing type burner at a high excess air ratio, with the result that NOx is held to 10 ppm or less at 0% O2 in the exhaust gas, dry basis — the first claim to recite the numeric target as a result limitation.
• Claim 14 — method framed around the NOx outcome (independent). Burning fuel to produce combustion gases and exhaust gases while maintaining NOx in the exhaust gases at no more than 10 ppm or less at 0% O2, dry basis, where that maintaining step comprises the same three sub-steps (heat-absorber cooling, burning-completed gas recirculation, water/steam addition to combustion air).

Representative dependent claims: 2 (adds fully-premixing burner at high excess air ratio), 3 (holds the high excess air ratio substantially constant independent of outside air temperature), 4 (inject water/steam upstream of the blower), 5 (add water/steam into the recirculated gas), 6 (water/steam into the recirculated gas upstream of the blower), 7 and 8 (recite the ≤10 ppm at 0% O2 dry basis result), 10 (adds fourth suppression means as apparatus), 12 (blower in the EGR/water-steam apparatus path), 15 (adds high-excess-air fully-premixing burning), 16 (water/steam added to the recirculated gas and mixed with combustion air).

Litigation / docket check — important caveat

• I could not verify any Court of Appeals for the Federal Circuit 2026 docket activity for US 6,875,009, and I found no district-court or PTAB proceeding naming this patent. My searches returned no matching case. This may reflect search coverage, not the absence of litigation; treat it as unverified, not as a negative finding.
• The Google Patents record carries the banner "Family has litigation — First worldwide family litigation filed," with a Darts‑ip link for family ID 31190313. That banner is generated from a third-party litigation database and Google expressly states assignee/legal-status data "may be inaccurate" and that legal status is an assumption, not a legal conclusion. No case number, court, party, or outcome is given, so I cannot report specifics.
• One search hit referenced an IPR final written decision on US 9,006,483 B2 (Daicel) in which "Miura" appears as a prior-art reference cited against the claims. That is a different patent and a different context; it is not this patent and I am not treating it as related.

Related-art framing (useful for context)

• The patent expressly builds on the applicant's own earlier work: JP HEI 11‑132404 / US 6,029,614, incorporated by reference, which combined water-tube cooling and EGR but achieved only about 25 ppm NOx.
• Later documents cite US 6,875,009 as prior art, e.g. US 7,473,095 (Siddhartha Gaur, NOx emissions reduction process and apparatus) and US 8,549,862 (Lean Flame, Inc.).

Caution on the identifier

Interpreted literally, "6875009" also designates an unrelated Japanese patent, JP 6875009 B2 (特許第6875009号; Catalyst and use thereof — anatase titanium oxide electrochemical catalyst; registered 2021‑04‑26, issued 2021‑05‑19; applicant National Institute of Advanced Industrial Science and Technology / Kyushu University inventors; PCT/JP2017/008360). That is a completely different document from US 6,875,009. Do not conflate the two — the coincidence of numerals is not a family relationship.

Uncertainty disclosure

Bibliographic fields above are taken from the granted US text and are high-confidence. Litigation status and any 2026 CAFC involvement are not confirmed; I have no authoritative source for those, and I will not infer a case from the Darts‑ip banner alone.

I'll research litigation involving US Patent 6,875,009 across patent litigation sources.

Let me search more targeted litigation sources.

The Google Patents page indicated this family has litigation (Darts-IP family 31190313). Let me dig deeper.

Findings: Litigation involving US Patent 6,875,009

Short answer: I could not identify any confirmed litigation — in U.S. district courts, the CAFC, PACER, or Unified Patents' litigation database — that specifically names U.S. Patent No. 6,875,009 ("Combustion method and apparatus for NOx reduction," Miura Co., Ltd.; inventors Kayahara and Takubo; filed 2003‑07‑21; granted 2005‑04‑05; status Expired – Fee Related).

What I searched

• Google Patents page for US6875009 (authoritative full text provided).
• General web searches for "6875009 litigation," "6,875,009 / 6875009" patent infringement/lawsuit/defendant, and Miura Co. boiler/NOx patent litigation.
• Attempted searches (which returned no usable results before I reached my search limit) for the Darts‑IP family ID, CA/Darts‑IP records, and the family members CA2435525C and KR20040012525A.

What I did find (and important caveats)

1. A litigation flag on the Google Patents family page — unverified. The Google Patents record for US6875009 contains a "Family has litigation / First worldwide family litigation filed" indicator, hyperlinked to Darts‑IP family ID 31190313 (https://patents.darts-ip.com/?family=31190313). This suggests some litigation may be associated with the patent family in the Darts‑IP database. However:

   • I could not retrieve the underlying record (no plaintiff, defendant, forum, case number, filing date, or outcome was obtainable).
   • I cannot confirm that any such litigation actually asserts US 6,875,009 (as opposed to another family member or an unrelated matter), so I will not represent it as confirmed litigation against this patent.

2. No U.S. court filings found. I found no PACER/district‑court docket, no CAFC appeal, and no Unified Patents case‑list entry involving US 6,875,009.

Distractor to avoid

A prominent search hit is JP 6875009 B2 — a Japanese patent owned by the Japan Science and Technology Agency (JST) (National University Corporation Kyushu University), directed to an electrochemical/anatase titanium‑oxide catalyst for alcohol synthesis. This is a completely different patent with a coincidentally similar number and has no relationship to U.S. 6,875,009 or to Miura Co. Ltd. It should not be treated as the same patent or conflated with the U.S. patent.

Bottom line

Based on the sources I could access, no public litigation is known against US Patent 6,875,009. The only litigation‑related signal is the unverified Darts‑IP "family has litigation" flag on the Google Patents page, which I could not substantiate. Because the patent expired (anticipated expiration 2023‑07‑21; status "Expired – Fee Related"), and because I was unable to complete searches of the Darts‑IP record and the CA/KR family members, I recommend verifying directly against:

• PACER / CourtListener (docket search by patent number),
• Unified Patents litigation portal (portal.unifiedpatents.com/litigation),
• Darts‑IP family 31190313, and
• USPTO Assignment / Patent Center and the CAFC docket.

I have stated this explicitly rather than inferring details: I do not have high confidence that any litigation exists, and I am not fabricating plaintiff/defendant/case‑number data that I could not verify.

I'll verify the structured data ("no AIA trial proceedings on file") against public sources before finalizing.

Let me run a few more targeted checks on equivalent identifiers and the patent owner's PTAB history.

One more check for post-grant alternatives (reexam, CBM) and any docket-tracked challenge.

PTAB proceedings on file — US 6,875,009

Verification of the structured record: The "PTAB proceedings on file" block for this prompt states that the USPTO Open Data Portal (ODP) API returns no AIA trial proceedings for US 6,875,009. I re-checked the public record out of caution. Nothing contradicts the structured data. I found no IPR, PGR, CBM, or ex parte reexamination record naming US 6,875,009.

Two things I surfaced during searching are distractors, and I flag them so nobody downstream conflates them with this patent:

1. JP 6875009 B2 — a Japanese patent owned by the Japan Science and Technology Agency (JST) / Kyushu University, directed to an anatase titanium‑oxide electrochemical catalyst for alcohol synthesis. Coincidentally similar number; unrelated to US 6,875,009 or Miura Co., Ltd. (This matches the distractor already flagged in the earlier litigation section — no contradiction.)
2. "Miura" references in unrelated IPRs — e.g., NV5 v. … (IPR2021‑01510), Daicel (IPR2019‑00313), and catalyst/engine petitions. These cite a prior‑art reference named "Miura" or name a different Miura entity. They are not PTAB proceedings involving US 6,875,009 or Miura Co., Ltd. as patent owner.

The only proceeding‑adjacent artifacts I could retrieve were noise from unrelated technology (semiconductors, telematics, pharma). None mention this patent, its inventors (Kayahara / Takubo), or its claims.

Proceedings overview

Total AIA trial proceedings on file for US 6,875,009: 0 (0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denials). There is nothing in the PTAB record to point a defendant toward — the defensive posture is not "the patent has been tested and narrowed," but rather "the patent has never been subjected to an AIA validity challenge at all," and because it expired for fee‑related reasons on the 2023‑07‑21 anticipated‑expiration date, it is now an expired patent whose claims cannot support a forward‑looking infringement injunction (though past‑damages assertions for pre‑expiration conduct remain theoretically possible within the § 286 six‑year lookback).

The absence of any proceeding means the "claims canceled via IPR" defensive shortcut does not exist here. Anyone facing this patent must build validity contentions from scratch — and should note the earlier litigation section's warning that even the Darts‑IP "family has litigation" flag could not be substantiated, so there is no known court case generating PTAB‑type estoppel either.

Per‑proceeding detail

None available. There is no proceeding number, petitioner, patent owner, panel, institution decision, Final Written Decision, settlement, or Federal Circuit appeal to report for US 6,875,009. I will not invent one. The reasons this is likely (not certain):

• Expiry. The patent's legal status is "Expired – Fee Related," with anticipated expiration 2023‑07‑21. Expired claims are a low‑value IPR target, since the primary benefit — knocking out live claims to defeat an injunction — largely evaporates.
• Narrow, niche field. This is a small‑capacity water‑tube/once‑through boiler NOx method (LP HEI 11‑132404 / US 6,029,614 is the cited predecessor). The likely assertion targets are boiler manufacturers, a concentrated industry where settlement or design‑around often beats a costly IPR.
• Filing‑date caveat. The application was filed 2003‑07‑21, after the AIA's 2012‑09‑16 effective date? No — it predates it, so any challenge would have been an IPR (not PGR) and CBM was legally unavailable for this technology class (a combustion method is not a "financial product or service," so § 18 CBM eligibility was never a fit — no CBM proceeding could have been brought here as a matter of law).

Strategic summary

Claim status. All 16 claims of US 6,875,009 — independent claims 1, 9, 11, 13, and 14, and dependents 2–8, 10, 12, and 15–16 — are UNTESTED. None were canceled, none were confirmed, none were construed by the Board. There is no FWD, no institution decision, and therefore no claim‑level survivorship map to work from. I state this at claim‑level granularity precisely because the record is empty: do not represent any claim as "surviving IPR" or "invalidated by the PTAB."

Estoppel landscape. With zero PTAB trials, there is no § 315(e)(2) estoppel binding anyone. No petitioner is barred from any ground, and — symmetrically — a defendant gains no benefit from someone else's prior petition. Every § 102/§ 103 ground a defendant wants to raise is presumptively available, subject only to the normal one‑year bars of § 315(b) and any Fintiv/discretionary‑denial risk if a parallel district‑court case exists. Note the interplay with the earlier litigation section: because the only litigation signal is an unverified Darts‑IP family flag, I cannot confirm a parallel case that would trigger § 315(b) or Fintiv; verify that first.

Pattern signals. No repeat petitioners (no petitioners at all), no patent‑owner PTAB appeals, no defensive aggregator (Unified Patents or similar) in the chain. This patent simply never entered the PTAB system — a signal consistent with a low‑assertion, niche, now‑expired boiler patent rather than a troll‑driven campaign. Contrast the patents in the search results that do show patterns (multiple VW IPRs against Neo Wireless patents; Ford follow‑on petitions) — 6,875,009 shows none of that.

Recommended next steps

1. If you are a defendant and were hoping for invalidated claims to point to — there are none. There is no FWD to link or quote. Ground your defense in district court, not in a prior PTAB disposition (there isn't one).
2. Take the expiry seriously. With anticipated expiration 2023‑07‑21 and status "Expired – Fee Related," confirm the legal‑status date directly in Patent Center (https://patentcenter.uspto.gov) and check for any § 41(c) petition to accept late payment / reinstatement in the file history. If the patent genuinely lapsed, the exposure collapses to past damages within the § 286 six‑year window — frame your damages defense around that.
3. Run the definitive negative confirmations yourself (my web reach is limited and the ODP block is the canonical source but is only as fresh as its ingest):
   • PTAB E2E / PTAB Decisions: search patent number 6,875,009 — https://developer.uspto.gov/ptab-api and https://ptacts.uspto.gov.
   • USPTO Patent Center "Proceedings" tab for the application (10/622,489) to catch any ex parte reexam (which is not an AIA trial and would not appear in the ODP AIA‑proceedings list).
   • CourtListener / RECAP and Docket Alarm for any district‑court or CAFC activity — https://www.courtlistener.com.
   • Unified Patents litigation portal: https://portal.unifiedpatents.com/litigation.
4. Resolve the litigation open item. The earlier section flagged an unverified Darts‑IP family‑31190313 "has litigation" indicator (https://patents.darts-ip.com/?family=31190313). If a live or past case existed, that is where a § 315(b) bar or estoppel could theoretically originate — but since no PTAB proceeding was ever filed, even a confirmed litigation history would produce no PTAB estoppel. Confirm it for completeness, not because it changes the PTAB analysis.
5. Do not cite JP 6875009 B2 or unrelated "Miura" IPRs. If a colleague or an AI‑assisted research tool hands you either, treat it as a false positive.

Bottom line: The honest, non‑fabricated answer is that the PTAB record for US 6,875,009 is empty — zero AIA trials, ever. That absence is itself the signal: this is an expired, niche boiler‑NOx patent that never attracted an invalidity challenge, so a defendant gets neither a free "claims already canceled" win nor a hardened "survived IPR" obstacle. The fight, if any, is a district‑court limitations‑and‑damages fight, not a PTAB one.

I'll research the assignment record for US 6,875,009 across USPTO sources and cross-reference ownership signals.

Let me dig deeper into the specific assignment records and legal events.

I've completed my research. Note on method: I attempted to pull the USPTO Assignment Center record (reel/frame and correspondent) directly and to verify against Google Patents legal events, PEDS/ODP, SEC filings, and the RPX/Unified asserter directories, but I hit my search limit before retrieving the Assignment Center detail page. I flag below exactly what is verified versus unretrieved rather than filling gaps with plausible-looking numbers.

Inventors

• Both inventors list Matsuyama, Ehime-ken as their residence — the same city as the assignee's headquarters (Miura Co., Ltd., Ehime-ken). Together with the fact that the application was assigned to Miura on the filing date, the natural inference is that both were Miura employees at filing. This is an inference from address + same-day assignment, not a directly documented employment record; treat it as high-likelihood, not confirmed.
• The inventors also appear as the assignors on the sole recorded conveyance (see timeline), which is the ordinary inventor-to-employer assignment that accompanies a corporate-filed application.
• No unusual departure pattern. There is no evidence that either inventor left the assignee within 12 months of filing, and no "all inventors departed" signal. Because there is no post-issuance assignment chain and no litigation, there is no basis to support (or refute) a fire-sale narrative.

Original assignee

• Entity on the issued patent: Miura Co., Ltd., Ehime-ken, Japan (per the USPTO Official Gazette entry for US 6,875,009 B2).
• Primary line of business: Manufacture, sale, and maintenance of small once-through boilers and other water-tube boilers, plus water-treatment equipment, food-processing equipment, medical equipment, marine equipment, environmental products, and chemicals. Miura is a publicly traded operating company — Tokyo Stock Exchange Prime Market, stock code 6005, HQ Matsuyama, Ehime, founded 1927 (Miura Co., Ltd. established 1959), ~6,000 employees across 24 countries.
• Did they ship a product embodying the claims? Yes — strong evidence. The specification is written as a working example of a once-through steam boiler (Miura's core product line), with concrete dimensions ("longitudinally 60 cm, laterally 18 cm sized rectangular-shaped burner"), tube outer diameters (60.5 mm), test fuel (LPG), and measured performance (NOx ≈10 ppm at 5.8–6.25% O₂). This is a production-oriented disclosure, not a paper design, and the later Miura filings (US 2006/0177784, US 2006/0204912, US 2006/0214015, US 2009/0025655) show the company continuing to build on this boiler platform.
• Current status: Operating. Miura remains an independent listed company. Material recent corporate events:
  • 2024-05-15 — Miura completed the acquisition of CBE Enterprises, Inc. (parent of Cleaver-Brooks, Inc.) from Harbour Group for ~US$774 million (per Miura press releases dated 2024-03-29 and 2024-05-17). This is Miura as acquirer, not as target.
  • 2024-05-30 — Daikin Industries and Miura entered a capital/business partnership; Daikin took 4.67% of Miura and Miura took 49% of Daikin Applied Systems. A minority stake, not an acquisition.
• No bankruptcy, dissolution, or fire-sale. No Chapter 7/11 event involving Miura was found.

Assignment timeline

Finding up front: The record shows only one assignment — the original inventor-to-employer conveyance at filing. There are no post-issuance assignments (no transfer to any IP-holding LLC, no securitization, no reassignment of record). That is itself a finding: the original operating assignee has retained title for the life of the patent.

• 2003-07-21 (executed on/around the filing date) / recorded 2003-07-21 — Reel/Frame not retrieved (see caveat)
  • Conveyance: ASSIGNMENT OF ASSIGNORS' INTEREST (SEE DOCUMENT FOR DETAILS)
  • Assignor: Kayahara, Toshihiro; Takubo, Noboru
  • Assignee: Miura Co., Ltd., Ehime-ken, Japan
  • Correspondent: Not retrieved. Because this is a single, same-day inventor-to-employer assignment on a Japanese-origin filing, the correspondent of record would ordinarily be the U.S. associate attorney who filed the original application (there is no later attorney/firm switch to compare against, so the "repeat correspondent" tell cannot be run — there is no chain for a correspondent to recur across).
  • Context: Original employment assignment at filing — not an acquisition, fire-sale, securitization, or transfer-to-asserter.

No further recordings follow. Google Patents' legal-events panel for US 6,875,009 terminates after the 2003-07-21 assignment and shows only prosecution/publication/expiry events (publication 2004-04-15; grant 2005-04-05; anticipated expiration 2023-07-21; status "Expired – Fee Related"). There is no assignment event after 2003.

Caveat on the reel/frame and correspondent (do not treat as fabricated): I could not retrieve the specific reel/frame number or the correspondent of record from the USPTO Assignment Center detail page for this patent within my search budget — my attempt to load that page returned no data before my step limit. The single-assignment finding rests on the Google Patents legal-events record (which enumerates the one "reassignment" event) and on my inability to surface any later recording. To nail down the exact reel/frame and correspondent, query the USPTO Assignment Center by patent number 6,875,009 directly.

Timeline diagram

timeline
    title Ownership of US 6875009
    2002 : Priority JP 2002-219397
    2003 : Priority JP 2003-141253
         : Filed by Miura Co Ltd
         : Inventors assign to Miura
    2004 : Application published
    2005 : Patent granted
    2023 : Anticipated expiration
    2024 : Miura acquires Cleaver-Brooks

NPE / troll-pattern signals

Corroborating negative signal: the Google Patents banner "Family has litigation — First worldwide family litigation filed" points to a Darts-IP family ID and provides no case number, court, party, or outcome. I could not substantiate any actual proceeding. Per the earlier litigation section, treat that flag as unverified — it is derived from a third-party database and Google disclaims the accuracy of its legal-status fields.

Verdict

Insufficient data — but affirmatively no NPE pattern. The record contains only the original inventor-to-employer assignment (Kayahara/Takubo → Miura Co., Ltd., executed and recorded 2003-07-21), with no post-issuance transfer of any kind; title remained with Mira through the 2023-07-21 anticipated expiration. Because the enumerated verdict options reserve "Operating-company assertion" for a current assignee that is both shipping products and suing competitors, and no competitor suit naming this patent could be confirmed, the strict-category answer is Insufficient data (only the original assignment) — notwithstanding that the evidence points clearly away from any NPE/assertion pattern and toward a large operating company (Miura Co., Ltd.) simply holding its own patent.

Verify at: https://assignmentcenter.uspto.gov/ — search by patent number 6,875,009 (or application 10/622,489) to obtain the exact reel/frame and correspondent of record for the 2003-07-21 assignment, which I was unable to retrieve. Cross-check the absence of later recordings against the Google Patents legal-events history and USPTO PEDS/ODP.

I'll search for the USPTO record and the cited prior art for US 6,875,009.

Let me try to retrieve the actual "References Cited" (backward citations) list for this specific patent.

Prior-Art Analysis for US Patent 6,875,009 (application 10/622,489)

1. Identity of the searched number — confirmed, literally

A USPTO-record search for "6875009" resolves to US 6,875,009 B2, "Combustion method and apparatus for NOx reduction," Miura Co., Ltd., inventors Kayahara & Takubo, app. 10/622,489, filed 2003‑07‑21, granted 2005‑04‑05, 16 claims (independent: 1, 9, 11, 13, 14). Source of record: https://patents.google.com/patent/US6875009/en. I have not substituted any nearby number (e.g., the unrelated Japanese JP 6875009 B2, or the Miura siblings US 6,792,895 and US 6,823,821, which are different documents — see §5).

2. Critical data-availability caveat (read before the table)

The granted front page's "(56) References Cited / U.S. Patent Documents" block for US 6,875,009 was not captured in the authoritative text supplied to me, and my searches could not retrieve that block. What the Google Patents record did supply under "Citation" is:

• The "Cited By (19)" list — i.e., forward citations (later documents citing this patent). Those are not prior art to 6,875,009 (all have post‑2003 priority dates) and are addressed in §4.
• "Prior art keywords" (combustion, gas, burner, burning, steam) — a text index, not a citation list.

Because I will not fabricate an examiner's citation list, the references below are reconstructed from two verifiable anchors:

1. References the 6,875,009 specification expressly identifies or incorporates by reference; and
2. The "(56) References Cited" list published on the closely related, same-applicant/same-technology Miura patent US 6,823,821 ("Combustion method and apparatus for NOx reduction"), retrieved from FreePatentsOnline (https://www.freepatentsonline.com/[6823821](/patent/6823821).html).

Inference flag: anchor (2) is a sibling Miura filing, not US 6,875,009 itself. The overlap is likely high (same applicant, same inventors, same problem statement) but is not guaranteed to be identical. Every item below should be confirmed against the official front page at USPTO Patent Public Search (ppubs.uspto.gov) or PatentCenter before being relied on.

3. Candidate prior-art references

Filing dates for these references were not recovered in this search; only publication/grant dates are shown. Filing dates matter for pre‑AIA §102(e)/(g) and must be verified.

4. Claim-by-claim §102 assessment under 35 U.S.C. § 102

The controlling point is that every independent claim requires the combination of all three suppression techniques (and claims 13–15 add the fourth). No reference identified above discloses that combination:

• Claims 1, 9, 13, 14 and their dependents — no anticipation. Each requires, in combination, (i) heat-absorber cooling + (ii) recirculation of burning-completed gas + (iii) water/steam addition to the burner's combustion air. US 6,029,614 supplies (i)+(ii) but not (iii); JP H07‑103411 supplies (ii)+(iii) but not (i). Neither, alone, discloses the full method or apparatus. Claim 13 additionally requires burning as a fully-premixing burner at high excess-air ratio and the ≤10 ppm result; claim 14 frames the same three sub‑steps around the ≤10 ppm outcome. Nothing found discloses these.
• Claim 11 — no anticipation. It is drafted around a specific plumbing layout: heat absorbers in the burning reaction zone plus an exhaust-gas recirculation passage connected to the air supply passage plus a line feeding water/steam into the EGR passage upstream of the burner. That specific steam-into-EGR injection point was not found in any single reference.
• Dependent claims 2–8, 10, 12, 15, 16 — no anticipation. Each incorporates all elements of its parent independent claim, so the combination requirement is not met.

Bottom line for §102: on the evidence available, none of the identified references anticipates any claim of US 6,875,009. Their significance is as §103 obviousness art — particularly US 6,029,614 (heat absorbers + EGR) combined with JP H07‑103411 (EGR + steam jet), which together would cover each element of claim 1 if a motivation to combine could be shown. The fact that the claims issued over this art is consistent with the combination/results limitations carrying the patentability weight.

5. Items to explicitly NOT treat as prior art

• The "Cited By (19)" list (e.g., US 2006/0177784 A1, US 2006/0204912 A1, US 2006/0214015 A1, US 2009/0025655 A1 — all Miura; US 2006/0246385 A1 and US 2008/0115773 A1 — Siddhartha Gaur; US 2008/0092544 A1 and US 8,549,862 B2 — Lean Flame; US 7,473,095 — Gaur) are forward citations with priority dates of 2005–2013. They cannot be §102 prior art against a patent with a 2002‑07‑29 priority date. Do not confuse "cited by" with "cited."
• US 6,823,821 (app. 10/730,092, filed 2003‑12‑09) and US 6,792,895 are same-applicant, same-family Miura siblings with the same title and overlapping specification. Because their U.S. filing dates post-date 6,875,009's 2003‑07‑21 filing (and because they share common ownership/priority), they are not §102(e) prior art against 6,875,009. I explicitly did not treat them as prior art.
• JP 6875009 B2 (特許第6875009号, anatase titanium-oxide electrochemical catalyst; registered 2021) is a numerically coincidental, unrelated document. As flagged in the prior sections, it must not be conflated with US 6,875,009.

6. Date caveat for US 6,558,153

US 6,558,153 issued 2003‑05‑06 — after the 2002‑07‑29 JP priority date but before the 2003‑07‑21 US filing. Under pre‑AIA §102, whether it qualifies as prior art depends on its own filing/priority date (§102(e)) and on whether the applicant can swear behind under §102(a)/(e) using the JP §119 priority (which cannot be used to overcome §102(b), whose critical date is 2002‑07‑21). Its precise status cannot be resolved without its filing date, which I did not retrieve.

7. Recommended verification steps (before relying on this list)

1. USPTO Patent Public Search / PatentCenter — pull the granted front page of US 6,875,009 and read the (56) References Cited block directly. This is the single authoritative fix for the gap in §2.
2. USPTO Global Dossier / EPO — obtain the JP counterpart (JP 2004‑125379 A) file wrapper, which usually prints the examiner's cited references.
3. Verify filing dates for each reference in the table to run the pre‑AIA §102(a)/(b)/(e)/(g) analysis properly.

Confidence statement: The identification of 6875009 as US 6,875,009 B2 and the three‑way claim structure are high confidence (drawn from the granted text). The reference list in §3 is reconstructed by inference and is medium-to-low confidence as to completeness; I have stated this openly rather than presenting an invented examiner citation list. On the record available, no reference anticipates any claim — the relevant analysis is §103.

I'll ground this analysis in the actual prior-art record for US 6,875,009 before building the §103 combinations.

Good — I now have the actual "Referenced Cited" record. Let me pull details on those specific references and confirm the full list.

Obviousness Analysis — US 6,875,009 B2 under 35 U.S.C. § 103

Builds on the bibliographic and litigation sections already generated. That material is not repeated here.

0. A note on what "the Prior Art section of this page" actually contains

The Google Patents HTML supplied in this record has a "Prior art keywords: combustion, gas, burner, burning, steam" field and a "Prior art date: 2002‑07‑29" field, plus a "Cited By (19)" table. Critically, the supplied HTML does not contain a "References Cited" (backward-citation) block, and the "(19)" table is forward citations — documents that cite this patent, which are not § 102/§ 103 art against a 2002/2003 priority date (they are, at most, evidence of the state of the art later).

To get the actual cited-art record I used the Justia mirror of the same file (https://patents.justia.com/patent/6875009), which reproduces the "Referenced Cited" list. I flag this substitution explicitly rather than pretending the Google page supplied it.

Cited-art list retrieved (U.S. patents):

Admitted prior art in the patent's own Background: two-stage combustion, thick/thin fuel combustion, exhaust-gas-recirculate combustion, water-addition combustion, steam-jet combustion, and flame-cooling with water-tube groups — all recited as known per se techniques. The specification also incorporates US 6,029,614 / JP HEI 11‑132404 by reference as the starting point, and concedes that that technique reached only ~25 ppm NOx.

Two caveats I will not paper over: (i) the Justia snippet was truncated, so the cited-art list may be longer than the five rows above; (ii) US 6,705,855 issued after the 2002‑07‑29 priority date, so it is only available as art via its § 102(e) filing date, which I have not verified.

Governing law. Priority is 2002‑07‑29 / 2003‑05‑20, so pre-AIA § 103 applies (post-KSR analytical framework; the patent actually issued in 2005 under the stricter TSM regime — a point worth noting, since it survived an examiner applying In re Vaeck‑era law but would face a materially easier rejection today under KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007)).

PHOSITA. A mechanical or chemical engineer with ~3–5 years in industrial burner/package-boiler design, familiar with the Zeldovich thermal-NOx mechanism and with the menu of NOx-control techniques the patent itself lists as known.

1. Independent claim 1 and claim 9 — the core three-way combination

Claim 1 = method: (a) cool combustion gas with heat absorbers + (b) recirculate burning-completed gas into the burning reaction zone + (c) add water/steam to the burner's combustion-use air.
Claim 9 = the same three elements as apparatus "means."

Primary combination: Kayahara US 6,029,614 + Lang US 6,383,461.

• US 6,029,614 discloses a water-tube boiler in which a plurality of water tubes is arranged in the burning-reaction zone/flame zone (its stated zone: burning-reaction gas above ~900 °C, ideally 900–1300 °C) together with exhaust-gas re-circulation equipment feeding part of the exhaust gas back to the burner. That is elements (a) and (b) in a single reference, and it is the applicant's own admitted starting point. (https://patents.justia.com/patent/6029614; https://patentimages.storage.googleapis.com/48/ea/12/032090bfca14c0/CA2226202C.pdf)
• US 6,383,461 (Lang) discloses recirculating flue gas into the burner and then injecting steam into the flue-gas conduit (steam inlet conduit 46, flow-control valve 48, feeding the flue-gas/fuel mixing circuit upstream of the burner). Lang expressly reports: "When steam injection into the flue gases is utilized … a flue gas nitrogen oxide content of from 8 to 14 parts per million can be achieved," versus 20–26 ppm without it. (https://uspto.report/patent/grant/6383461)

Why a PHOSITA would combine them (motivation, articulated and not hindsight-based):

1. Same field, same problem, same mechanism. Both address thermal-NOx suppression in gas-fired combustion equipment by lowering peak flame temperature. Kayahara '614's own text invokes the Zeldovich mechanism and targets the ~1400 °C thermal-NOx threshold; Lang independently states that the steam "dilutes the fuel, reduces the flame temperature and reduces the content of nitrogen oxides." The two references operate on the same principle, which is the paradigm case for a predictable combination.
2. The problem the patent admits was unsolved is solved in the art. The specification concedes Kayahara '614 topped out at ~25 ppm and that no practical <10 ppm technique existed. Lang supplies the missing step and reports 8–14 ppm using steam + EGR. A PHOSITA seeking "super NOx reduction" would not merely have been permitted to add steam; the art handed them that exact improvement with a measured result.
3. Finite, identified, predictable solutions. The patent's own Background enumerates six known NOx-reduction techniques, all temperature- or oxygen-partial-pressure-based. KSR holds that where there are "a finite number of identified, predictable solutions," a PHOSITA has good reason to pursue the known options — here, simply using two of the admitted options together at moderate levels instead of one at an extreme level.
4. Design incentive / regulatory demand. The Background recites increasingly strict NOx regulation for small boilers; that market pressure is a textbook KSR motivation.
5. No unexpected interaction. Cooling by water tubes, by EGR, and by water/steam injection are additive heat-capacity/dilution effects on the same flame. Nothing in the record suggests a synergy that would defeat predictability.

Result: claims 1 and 9 are obvious over Kayahara '614 + Lang. (No single reference anticipates both — Lang lacks heat absorbers in the burning zone, Kayahara '614 lacks water/steam addition — so this is a combination, not anticipation case.)

2. Independent claims 11 and 12 — the steam-into-EGR plumbing

Claim 11 requires: heat absorbers in the burning reaction zone; an EGR passage from the exhaust passage to the air supply passage; and a line feeding water/steam into the EGR passage upstream of the burner. Claim 12 adds a blower upstream of the injection point.

This is the claim most exposed to § 103, because Lang's Fig. 4 literally shows a steam conduit attached to the flue-gas conduit upstream of the burner/mixing chamber (https://uspto.report/patent/grant/6383461). Combining Lang's steam-injection-into-the-recirculated-gas line with Kayahara '614's water-tube boiler produces precisely the claimed arrangement. The only arguable difference is where the recirculated gas is joined (Lang joins flue gas to fuel gas; claim 11 says the EGR passage runs to an air supply passage). That is a change in the destination of a conduit in a known recirculation loop, with no alleged and no apparent change in function — the KSR "mere rearrangement of parts" / predictable-variation rationale, reinforced by the patent's own statement that the water/steam addition "may be carried out in the exhaust-gas recirculation passage in another embodiment."

Result: claims 11 and 12 obvious over Kayahara '614 + Lang.

3. Claims 2, 7, 13, 15 (and apparatus claim 10) — fully-premixing burner at high excess air

These add (i) a fully-premixing burner burned at high excess air ratio, and (ii)/(iii) the ≤10 ppm at 0 % O₂, dry result.

Combination: Kayahara '614 + Lang '461 + one lean-premix reference — Johnson US 5,201,650 and/or Nagayama US 6,705,855.

• US 5,201,650 (Johnson) teaches exactly the element the patent calls the "fourth suppression means": a burner fed a fuel-lean premixed fuel/air mixture (equivalence ratio < 1), with the mixture optionally including recycled flue gas, and with the high-velocity fuel streams diluted with a non-reactive thermal ballast selected from steam, water, recycled or recirculated flue gas, or mixtures thereof — and claim 1(d) recites "flue gases … contain less than about 10 ppm NOx." (https://patents.google.com/patent/US5201650; http://www.everypatent.com/comp/pat5201650.html)
• Johnson also identifies the very limitations the patent later claims to overcome: it notes that the "air is supplied in two stages" method and the "exhaust circulated at an increased rate" method fail, the latter because increased recirculation "will impair steady combustion." That is a specific teaching that combining dilution techniques at moderate levels — rather than pushing EGR alone — is the workable path, which is the patent's own stated insight.

Motivation is again direct and non-hindsight: Johnson discloses the lean-premix + recirculated-flue-gas + steam/water ballast stack and the sub-10 ppm outcome; Nagayama '855 (a Miura document) shows the premixing burner hardware. A PHOSITA adding a fully-premixing burner and operating it lean to a water-tube/EGR boiler of the Kayahara '614 type is doing no more than applying a known technique to a known device with a predictable result.

On the numeric result limitations (claims 7, 8, 13, 14, 15): a "whereby NOx ≤ 10 ppm" clause is a result limitation and carries patentable weight only if it reflects an unexpected result. It does not: Johnson '650 already recites flue gases containing "less than about 10 ppm NOx." The 10 ppm target was therefore known to be attainable in this art, and the claims cannot be rescued by the number alone. Note also that the 5.8 % O₂ / 6.25 % O₂ set points are nowhere in the claims — they live only in the working example, so no "critical range" argument is available at the claim level.

Result: claims 2, 7, 8, 10, 13, 14, 15 are obvious; claims 13/14 in particular reduce to claim 1 (or claim 9/10 equivalents) plus a known and previously-reported result.

4. Claims 4, 5, 6, 16 — where the water/steam is introduced

• Claims 5, 6, 16 (add water/steam to the recirculated gas, and mix it with combustion air): taught squarely by Lang '461 (steam into the flue-gas conduit before the mixture reaches the burner), and independently by US 5,224,851, "Low NOx burner" — which describes using steam as the motive fluid to induce flue gas and discharging condensate water as a fine spray into the induced-flue-gas/fuel mixture to lower flame temperature and NOx (https://companyprofiles.justatic.com/patent/5224851). This is a two-reference-plus-common-knowledge showing.
• Claim 4 (inject upstream of the blower): the placement of an additive injector upstream vs. downstream of a fan is a routine engineering choice with well-known, predictable trade-offs — upstream gives better mixing but adds blower load and condensation/corrosion risk; downstream spares the blower. That trade-off is recited in the patent's own specification as the justification for its alternative embodiments, i.e., it was within the ordinary skill level. Under KSR, "the improvement is the product of ordinary creativity, not invention."

Result: claims 4, 5, 6, 16 obvious.

5. Claim 3 — high excess air ratio held "substantially constant independent of outside air temperature"

Claim 3 requires maintaining the high excess-air ratio constant despite outside-air-temperature variation. This is oxygen-trim / closed-loop excess-air control, a long-established boiler control practice: sense exhaust O₂ (or intake-air temperature) and modulate blower speed (inverter) or a damper to hold the set point. The record's cited art does not include a dedicated O₂-trim reference, so I am less confident here than on claims 1/9/11/13 — but the concept is notorious in the boiler art, the applicant's own later filings (e.g., US 2009/0025655, assigned to Miura) treat air-ratio sensing and adjustment as conventional, and the claim recites the result ("substantially constant") rather than any particular control algorithm or structure. Absent evidence of unexpected behavior of the control loop, claim 3 is likely obvious over the primary combination further combined with ordinary-skill excess-air control (plus, e.g., the air-ratio control teachings of Nagayama '855). I flag this as the weakest-grounded conclusion in this memo.

6. The general KSR motivation synthesis (applies across all claims)

The last row deserves emphasis: the patent's central argument for nonobviousness — that pushing any one suppression means to its limit creates its own problem (pressure loss, oscillating combustion, CO/unburnts, condensate corrosion, blower load) — is not a teaching away and does not help. Johnson '650 identifies the same EGR-instability problem a decade earlier and prescribes the same class of solution (dilute with a thermal ballast). A reference that identifies a problem and points to the claimed remedy is the strongest possible motivation evidence, not a bar to combination.

7. What the applicant would argue, and how it fares

1. No reference discloses all three elements in one boiler — true, but irrelevant; § 103 permits combination. Every granted claim here survived on that basis, which is exactly why the KSR frame matters.
2. Unexpected result (<10 ppm) — defeated by Johnson '650's express "<10 ppm NOx."
3. Teaching away / "each technique must be used moderately" — not a teaching away; it is the motivation.
4. Long-felt need + commercial success (Miura is a real commercial boiler maker) — the strongest genuine nonobviousness argument. A long-felt, unmet need for practical <10 ppm NOx boilers is recited in the patent and echoed in the sibling US 6,792,895. To carry weight, however, the applicant would need nexus evidence (i.e., that the commercial success is attributable to the claimed combination rather than to price, service network, regulatory mandate, or unrelated features), which this record does not contain. I note this argument is potentially available but unproven.
5. Criticality of the O₂ set points — unavailable; the numeric set points are unclaimed.

8. Bottom line and confidence

Explicit uncertainties: (a) the cited-art list I used comes from the Justia mirror, truncated — a complete OF‑/USPTO "References Cited" pull could add references and strengthen the rejections; (b) US 6,705,855's § 102(e) date is unverified; (c) claim 3's obviousness rests on the notoriousness of excess-air/oxygen-trim control rather than on a specific cited reference; (d) I did not obtain the examiner's actual § 103 rejections, which are not in this record. I have not invented any reference, date, or passage.