Clay Calcination Patents: Top Companies & Filing Trends 2026
- Filing has cooled since 2018. The peak year was 2018 at 19 records, and by 2026 (partial) annual filings had dropped to 2 — a flat-to-declining trend since the 2022 midpoint of 9.
- Five companies hold two-thirds of the field. The top 5 assignees account for 86 of the 128 records in scope, or 67.2% — filing new claims here means designing around a small, concentrated group.
- Furnace and battery-materials classes are thinner than the core. F27B furnace/kiln claims sit at 14.1% of records and H01M battery-cell claims at 11.7%, well below the 63.3% concentration in C04B ceramics and cement.
Filing growth compares 2021 (5 records) with 2024 (6) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 128 records in scope (CR5), not by the ranked leaders only.
What clay calcination patenting actually covers
Clay calcination patents cluster around three problems: controlling the dehydroxylation temperature window so kaolinite converts to reactive metakaolin without overheating into inert phases, managing colour and iron reduction during firing, and reducing rotary residence time or replacing rotary kilns with flash calciners for throughput and fuel efficiency. A growing slice of filings ties calcined clay reactivity to battery and cathode material applications rather than cement alone, which is why H01M appears alongside the core ceramics classes.
The dataset spans 2015 through the 2026 cut-off. Because publication typically lags filing by around 18 months, the last one to two years understate real filing activity and should be read as provisional.
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Filing trend and technology composition
The 128 records in scope span nine receiving offices and eight IPC subclasses, with activity concentrated in a small set of classes and a filing curve that peaked in 2018.
A curve that peaked and has not recovered
Filings ran 16 in 2017, peaked at 19 in 2018, sat at 9 by the 2022 midpoint, and had fallen to 2 by 2026 (a partial year). This is a mature, slowing filing curve rather than an emerging one, though the most recent one to two years are undercounted due to publication lag.
Where the claims sit
C04B (ceramics, cement and refractories) covers 63.3% of the 128 records, by far the densest class. B01J (chemical/physical processes) and C01F (alkaline-earth and aluminium compounds) each sit above 30%, while F27B (furnaces and kilns) at 14.1% and H01M (batteries) at 11.7% are comparatively thin given how central kiln equipment and downstream battery-material use are to the field.
Shares are the percentage of the 128 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Clay Calcination Process and Equipment with Eureka
This page is one run against one query. Ask Eureka your own question about clay calcination process and equipment and every answer comes back with the patent numbers behind it.
Try EurekaThe most-cited prior art and the most recent filing
EP4733698A1 — Clay calcination colour control method
The filing describes a rotary kiln fed through staged fuel inlets — natural gas for ignition, then conventional fossil fuel and RDF for calcination heat — with kiln-tail flue gas cooled to 70-80°C before recirculating into a cooler that treats the exiting high-temperature material. The structure targets colour control during clay calcination through staged combustion and heat recovery rather than through additive chemistry.Filed by CBMI Construction Co., Ltd., dated 2026-04-29 — near the data cut-off, so its examination status is still early.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US5423891A | Method for direct gasification of solid waste materials | 105 |
| 2 | US5049198A | Calcium sulfate process for the coproduction of Portland cement clinker and concentrated sulfur dioxide adequ… | 57 |
| 3 | WO2014085538A1 | System for the production of fine lime | 43 |
| 4 | WO2012145802A2 | Reactor system and method for thermally activating minerals | 37 |
| 5 | US5919038A | Method for the calcination of calcium carbonate bearing materials | 29 |
| 6 | WO2016077863A1 | Process and apparatus for manufacture of calcined compounds for the production of calcined products | 23 |
| 7 | WO2018076073A1 | A flash calciner | 19 |
| 8 | US20170320774A1 | Process and apparatus for manufacture of calcined compounds for the production of calcined products | 17 |
| 9 | US4128392A | Calciner for fine limestone | 17 |
| 10 | US20190275485A1 | A flash calciner | 15 |
Citation counts favour older filings simply because they have had longer to accumulate citations within this searched corpus — read them as a signal of influence, not of current relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Browse MCP servers →What the numbers mean for a filing decision
Three patterns matter more than any single ranking: how concentrated ownership is, how the technology classes split, and how filing momentum has moved over the past decade.
A short list controls most of the claim space
The top 5 assignees combined account for 86 of the 128 records in scope. That is not a crowded field of small filers; it is a small group holding most of the position, which raises the freedom-to-operate bar for anyone entering fresh.
Materials claims dominate; equipment claims are thinner
Ceramics and cement composition claims (C04B) cover nearly two-thirds of records, while furnace and kiln equipment claims (F27B) sit at just 14.1%. Process and equipment innovation looks comparatively open next to the dense composition space.
Filing has been declining since 2018
Annual filings peaked at 19 in 2018, sat at 9 by the 2022 midpoint, and had fallen to 2 by the 2026 cut-off. Even allowing for publication lag understating the most recent years, the multi-year trajectory is downward, not flat.
Filing is spread across offices, not concentrated in one
The United States leads with 24 filings, Europe (EPO) follows with 20, and India with 18 — with the UK, WIPO/PCT and Australia all also represented. No single office dominates the way the top assignees dominate ownership.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to clay calcination process and equipment, with the prior art for and against each one.
Who holds the position, and where the field is still open
Ownership is concentrated at the top with a long tail of single- or few-filing entrants below tenth place, where counts fall to single digits.
A clear filing leader
The top-ranked assignee holds 47 of the 128 records in scope, well ahead of fifth place at 8 records — a gap that marks this out as a leader-and-field structure rather than an even spread.
A long tail below the top ten
By tenth place, filing counts have dropped to 3 records, and the ranking runs to 30 companies total. Most of that list holds only a handful of records each, which is where opportunistic or defensive filing shows up rather than sustained programmes.
No leading assignee filed in the most recent year
Every assignee tracked for recent-year momentum, including the field leader and the sector's largest cement producers, shows zero filings in the latest year, with one recording a full year-on-year drop. Read this alongside publication lag before concluding activity has stopped outright.
| Assignee | Recent year | YoY |
|---|---|---|
| Calix Ltd | 0 | — |
| Heidelberg Materials AG | 0 | — |
| Origen Power Ltd | 0 | — |
| Fuller Co | 0 | — |
| CEMENTOS ARGOS | 0 | -100% |
| Alstom Technology Ltd | 0 | — |
| Evonik Operations GmbH | 0 | — |
| Mississippi Lime Co | 0 | — |
Where to take this from here
The dataset points to a mature, concentrated field with specific gaps rather than an open frontier. The next step is turning that reading into a filing or freedom-to-operate decision.
Map freedom-to-operate against the top 5
With 67.2% of records held by five assignees, any new filing needs a claim-by-claim check against that group before drafting, not just a general prior-art search.
Run a freedom-to-operate check in EurekaWatch the equipment classes, not just materials
F27B and F27D claims are thinner than the C04B core, which is where process and equipment differentiation is more likely to clear.
Explore equipment-class filings in EurekaTrack the 2026 filings as they publish
Publication lag means the last one to two years of filings are still arriving; revisit the trend once later 2025-2026 records clear examination.
Set up monitoring in EurekaCommon questions on clay calcination patents
Filing in this field is concentrated: the top-ranked assignee alone holds 47 of the 128 records in scope, and the top 5 combined account for 67.2% of all records. That leaves a long tail of 30 companies overall, most holding only a handful of filings each. Anyone assessing competitive position should weight the leader and the next four heavily rather than treating the field as evenly spread.
No — filings peaked at 19 in 2018, had fallen to 9 by the 2022 midpoint, and dropped to 2 by the 2026 partial year. That is a declining multi-year trend, not a plateau. The most recent one to two years are understated because publication typically lags filing by around 18 months, but the multi-year direction is still downward.
Both terms appear directly in the search scope used for this dataset, alongside dehydroxylation temperature window, colour control, and fuel switching as the recurring technical themes. Rotary calcination filings tend to focus on residence time and fuel-inlet staging inside a kiln, while flash calcination filings focus on throughput and heat transfer in shorter-residence equipment. The representative EP4733698A1 filing, for example, addresses colour control through staged fuel inlets in a rotary kiln design.
C04B (ceramics, cement and refractories) is by far the densest class at 63.3% of the 128 records, covering material composition and processing claims. Furnace and kiln equipment sits in F27B at 14.1% of records and F27D at 6.3%, both considerably thinner than the materials core. That gap suggests equipment and process-engineering claims face less prior art than composition claims do.
H01M (batteries, cells and fuel cells) appears in 11.7% of the 128 records, reflecting filings that link calcined clay reactivity to cathode or electrode material applications rather than cement alone. This crossover shows up because reactivity control — one of the core technical themes in the search scope — matters for both binder chemistry and battery-material precursor performance. It is a smaller share than the ceramics and cement core, but it is a distinct and growing thread worth tracking separately.
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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.