Industrial Furnace & Kiln Patents: Who Leads, Where the Gaps Are 2026
- Filing has cooled since 2023. The peak year so far is 2023 at 88 families; the 2022 midpoint of 75 shows growth has flattened rather than accelerated.
- Two IPC subclasses dominate the corpus. F27D (furnace details & accessories, 913 records) and F27B (furnaces & kilns, 851) between them cover most of the filing activity, dwarfing burner-specific F23D at 55.
- China receives more than double the next office. 640 records were filed at the Chinese office versus 187 at the USPTO, 84 at the JPO and 78 at the EPO — filing strategy here is regionally lopsided.
What this dataset covers
This landscape draws on 1,329 patent families published between 2015 and the 2026 data cut-off, matched against a search string combining industrial furnace, rotary kiln and reheating furnace terminology with refractory lining, burner control, heat recovery, temperature uniformity and electrification-of-heat concepts. Coverage spans IPC classes F27B (furnaces and kilns), F27D (furnace details and accessories) and F23D (burners), plus adjacent classes for ceramics, drying and metal extraction. Publication lags filing by roughly eighteen months, so the 2026 figure of 13 records is a partial year and understates true filing activity.
The picture that emerges is a mature, densely claimed field rather than an emerging one. Filing volume climbed steadily through the late 2010s, peaked in 2023, and has since eased — a pattern more consistent with a technology whose core mechanical and thermal claims are largely staked out than with one still being defined.
Filing trend and technology composition
Two views of the same 1,329-family corpus: how filing volume has moved year over year, and how that volume splits across IPC subclasses.
Filings rose to a 2023 peak, then eased
From 40 families in 2017, filings built steadily to 88 in 2023 before declining. The 2022 midpoint of 75 sits close to the peak, meaning most of the growth in this window happened in a compressed few years rather than gradually across the whole decade. The 2026 count of 13 is a partial year under the 18-month publication lag and should not be read as a collapse.
F27D and F27B carry the corpus
Furnace details and accessories (F27D, 913) and furnaces and kilns proper (F27B, 851) account for the bulk of filings, with ceramics and refractories (C04B, 178) a distant third. Burner-specific claims under F23D (55) and drying under F26B (58) are comparatively thin, which is one indicator of where claim density is lighter relative to the core mechanical furnace and kiln structures.
Shares are the percentage of the 1,329 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Industrial Furnace and Kiln Technology with Eureka
This page is one run against one query. Ask Eureka your own question about industrial furnace and kiln technology and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited records and a representative filing
EP0004756A3 — Mixer block and refractory lining for rotary kilns
A mixer block for use in a rotary kiln for mixing, drying, cooling, heating or calcining solid materials such as gravel, stone or fluxes. It has a base surface and two converging side surfaces forming a generally triangular cross-section, with one side acting as a leading surface and the other as a trailing surface during rotation. The angles between the base and each side surface are set within ten degrees of the material's angle of repose, which produces a more uniform product.Filed by Bethlehem Steel Corporation, dated 1979-10-31 — one of the earlier mechanical solutions to temperature and material uniformity inside a rotating kiln, well before the modern refractory and burner-control filings in this corpus.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US6210154B1 | Treatment of exhaust gases from kilns | 64 |
| 2 | US4639217A | Countercurrent heat transfer device for solid particle streams | 46 |
| 3 | US4551051A | Apparatus for charging a rotary kiln with pneumatic tires | 43 |
| 4 | US5103743A | Method and apparatus for drying solid material | 40 |
| 5 | US4248639A | Method of calcining sinterable materials to form cement clinker or the like | 40 |
| 6 | JP2006029667A | Shell cooling device and shell cooling method for rotary kiln, and exhaust heat recovery method for rotary ki… | 38 |
| 7 | US6213764B1 | Disposal of waste tires | 38 |
| 8 | US5989017A | Disposal of waste tires | 38 |
| 9 | US4381916A | Method and apparatus for roasting fine grained ores | 37 |
| 10 | US6183242B1 | Rotary kiln for forming lightweight aggregate from flyash and sewage sludge | 36 |
Citation counts inside a searched corpus favour older records with more time to accumulate citations; treat them as a signal of influence on the field, not of current commercial relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Three readings of the corpus that matter for anyone deciding where to file next or where to expect resistance.
Growth has flattened, not accelerated
The corpus grew from 40 families in 2017 to a peak of 88 in 2023, with the 2022 midpoint already at 75. That trajectory — a fast climb followed by a plateau — is typical of a field where the core mechanical and refractory claims are staked out and remaining filings are incremental.
China is the dominant filing venue
China's receiving office accounts for 640 of the tracked records, more than three times the US total of 187 and well ahead of Japan (84), the EPO (78) and the UK (69). Anyone assessing freedom to operate should weight Chinese prior art heavily, not treat it as a secondary check.
Furnace structure is dense, burner control is thin
F27D and F27B together account for the great majority of records, while F23D (burners) sits at only 55 and F26B (drying) at 58. Structural and refractory-side claims are heavily contested; burner-control and drying claims are comparatively open.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to industrial furnace and kiln technology, with the prior art for and against each one.
Who is filing, and where they have gone quiet
Ten identified co-assignee pairs point to a handful of joint development relationships, but recent-year momentum data shows the most visible historical filers have gone silent in the latest tracked year.
One partnership dominates joint filing
The pairing of Cadence Environmental Energy and Ash Grove Cement accounts for 36 shared filings, far ahead of the next strongest pairs. Sumitomo Heavy Industries appears in two separate pairings — with JFE Metal Materials (8) and with Sumitomo Metal Industries (5) — suggesting an internal group filing pattern rather than external partnering.
Historical leaders show no latest-year filings
F L Smidth, Cadence Environmental Energy, Ash Grove Cement, Blue Circle Industries, Metso Minerals and Sumitomo Heavy Industries all show zero filings in the most recent tracked year. That does not necessarily mean exit from the field — the 18-month publication lag means recent filings from these assignees may simply not have published yet.
A broad base with concentrated pairs
Across 1,329 families the identified collaborative filing is limited to ten co-assignee pairs, implying most assignees in this corpus file independently rather than jointly. That favours single-owner freedom-to-operate checks over consortium-style clearance work.
| Assignee | Recent year | YoY |
|---|---|---|
| FLSmidth | 0 | — |
| Cadence Environmental Energy, Inc. | 0 | — |
| Ash Grove Cement Company | 0 | — |
| Blue Circle Industries Ltd. | 0 | — |
| Metso Minerals Corporation | 0 | — |
| Sumitomo Heavy Industries, Ltd. | 0 | — |
| PPG Industries, Inc. | 0 | — |
| Italcementi S.p.A. | 0 | — |
Where to take this next
The dataset points to specific follow-up work rather than a single conclusion.
Check freedom to operate against the Chinese filing base
With 640 of 1,329 records filed at the Chinese receiving office, any clearance search that stops at USPTO and EPO records is checking less than a fifth of the relevant prior art.
Run a freedom-to-operate search in EurekaMap the burner-control and drying claim space
F23D and F26B carry a fraction of the filing density of F27B and F27D, which is where a first claim is more likely to clear prior art rather than collide with it.
Explore white space in EurekaWatch for a publication-lag rebound
The apparent 2024–2026 decline may partly reverse as recent filings from quiet historical assignees work through the 18-month publication pipeline.
Track filing trends in EurekaCommon questions about this landscape
The corpus shows a mix of cement and heavy-industry specialists rather than a single dominant player, with co-assignee data showing Cadence Environmental Energy and Ash Grove Cement as the strongest collaborative pair at 36 shared filings. Sumitomo Heavy Industries appears in multiple internal-group pairings, pointing to a Japanese conglomerate filing strategy. However, recent-year momentum data shows these same historically active assignees recording zero filings in the latest tracked year, which may reflect either reduced activity or the normal 18-month lag between filing and publication.
Filing activity rose from 40 families in 2017 to a peak of 88 in 2023, then declined toward 13 in 2026, but the most recent years are understated because publication lags filing by roughly 18 months. Part of the apparent drop is a data artefact rather than a genuine slowdown. That said, the plateau visible from 2022 (75 families) through the 2023 peak suggests the core mechanical and refractory claim space was already becoming saturated before the most recent partial years.
F27D (furnace details and accessories) and F27B (furnaces and kilns) are by far the largest classes in this corpus, with 913 and 851 records respectively, together covering the great majority of filings. C04B (ceramics, cement and refractories) follows at 178. Burner-specific claims under F23D total only 55 records, making it a comparatively lighter-claimed adjacent class worth checking for open filing space.
The densest claim territory sits in furnace structural details, refractory lining and core kiln mechanics under F27B and F27D, where 1,329 families concentrate the bulk of their filings. Burner control (F23D, 55 records), drying-stage heat recovery (F26B, 58 records) and waste-gas incineration integration (F23G, 62 records) carry substantially less filing density. A first claim targeting burner-control algorithms or electrification-of-heat retrofit paths is more likely to find open space than one targeting refractory lining geometry.
Yes, by a clear margin. China's receiving office recorded 640 of the 1,329 tracked records, more than three times the 187 filed at the USPTO and well ahead of Japan (84), the EPO (78), the UK (69) and Canada (50). Any competitive or freedom-to-operate analysis in this field that does not weight Chinese-language prior art heavily is missing the largest single filing venue in the dataset.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.