Spent Pot Lining Patents: Who Leads, Trends & White Space 2026
- Concentrated at the top. The top 5 assignees hold 70.2% of all 47 records in scope, and the top 10 hold 97.9% — this field has almost no room left outside the ranked leaders.
- Filings have pulled back hard since the peak. Activity peaked at 8 filings in 2021 and fell to 2 by 2024, a 75% drop over that span, though 2025-2026 counts are still filling in as publications lag filing.
- Thermal and electrolytic routes dominate the claim space. C01F and C25C classes alone cover well over a third of all 47 records each, while chemical detox (A62D) sits under 30% — a narrower, more open lane.
Filing growth compares 2021 (8 records) with 2024 (2) — 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 47 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
Spent pot lining (SPL) is the carbon-and-refractory waste pulled from Hall-Heroult aluminium reduction cells at end of life. It carries cyanide, fluoride and reactive nitride content, which makes its treatment a regulatory as well as a metallurgical problem. This dataset tracks patent activity across fluoride leaching, thermal treatment, residue stabilization, carbon fraction separation, nitride hydrolysis and cyanide breakdown routes, drawn from 47 published records filed between 2015 and mid-2026.
The filing record is small and concentrated, which is typical for a byproduct-treatment niche tied to a single upstream industry: primary aluminium smelting. Most of the activity traces back to smelter operators and a handful of specialist process licensors rather than a broad base of new entrants.
Filing trend and technology mix
The trend line and the IPC breakdown below are drawn from the same 47-record corpus described above; each record can carry more than one IPC subclass, so the technology shares add up to more than 100%.
A sharp pullback from the 2021 peak
Filings rose to a peak of 8 in 2021, then fell to 2 by 2024 — a 75% decline over that three-year span. Because publication trails filing by roughly 18 months, the 2025 and 2026 counts shown are still incomplete and should not be read as a continuation of the decline.
Thermal and electrolytic classes carry the bulk of the art
C01F (alkaline-earth, aluminium and rare-earth compounds) appears on 57.4% of all 47 records, the single densest class. C01B, B09B, C22B and C25C each cover roughly two-fifths of records, showing that most filings combine a chemical-recovery step with an electrolytic or waste-handling step rather than claiming either in isolation.
Shares are the percentage of the 47 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Spent Pot Lining and Hazardous Residue with Eureka
This page is one run against one query. Ask Eureka your own question about spent pot lining and hazardous residue and every answer comes back with the patent numbers behind it.
Try EurekaThe documents everyone else in the field cites
US20230138875A1 — Plasma process to convert spent pot lining (SPL) to inert slag, aluminum fluoride and energy
Apparatus for converting Spent Pot Lining (SPL) into inert slag, aluminum fluoride and energy includes a plasma arc furnace such that the destruction of SPL occurs therein. The furnace generates an electric arc within the waste, which arc travels from an anode to a cathode and destroys the waste due to the arc's extreme temperature, thereby converting a mineral fraction of SPL into vitrified inert slag lying within a crucible of the furnace. The furnace gasifies the carbon content of the SPL and produces a well-balanced syngas through controlled intake of air and steam, liberating significant energy.Filed by Pyrogenesis Canada, published 2023-05-04.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US5470559A | Recycling of spent pot linings | 59 |
| 2 | US5164174A | Detoxification of aluminum spent potliner by thermal treatment, lime slurry quench and post-kiln treatment | 47 |
| 3 | US5245115A | Process for the thermal shock treatment of spent pot linings obtained from Hall-Heroult electrolytic cells | 20 |
| 4 | CA1093832A | Process for the utilization of waste materials from electrolytic aluminum reduction systems | 8 |
| 5 | US5365012A | Process for the heat treatment of spent pot linings derived from Hall-Heroult electrolytic cells | 5 |
| 6 | CA2116468A1 | Recycling of spent pot linings | 3 |
| 7 | WO2021189133A1 | Plasma process to convert spent pot lining (SPL) to inert SLAG, aluminum fluoride and energy | 2 |
| 8 | WO2006086874A1 | Converting spent potliners into a glass frit | 2 |
| 9 | CA2497064C | Process and apparatus for converting spent potliners into a glass FRIT, and resulting products | 2 |
| 10 | EP1853529A1 | Process and apparatus for converting spent potliners into a glass FRIT, and resulting products | 2 |
Citation counts favour older filings simply because they have had longer to accumulate citations inside this corpus; treat them as a marker of influence on later filers, not of present-day importance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Three patterns stand out once the ranking, the trend and the class shares are read together.
Five assignees already hold most of the estate
The top 5 combined account for 70.2% of all 47 records in scope, and the top 10 push that to 97.9%. A new entrant filing a broad thermal-treatment or leaching claim is very likely filing into space already occupied by an incumbent smelter or licensor.
Activity has cooled from its 2021 peak
Filing peaked at 8 records in 2021 and had fallen to 2 by 2024. That drop should be read against a small base — a handful of fewer filings each year moves the percentage sharply — and against the 18-month publication lag that leaves 2025-2026 undercounted.
Chemical recovery classes lead, detox trails
C01F (aluminium and alkaline-earth compound recovery) appears on more than half of records, well ahead of A62D chemical-detoxification claims at 29.8%. Cyanide breakdown and nitride hydrolysis routes are searched for in this dataset but are not the dominant claim type — most inventors are patenting recovery chemistry, not detox chemistry, as the primary route.
Filing is routed through smelter-adjacent jurisdictions
Australia (12), India (8) and Canada (6) lead the receiving offices, ahead of EPO and US (5 each) and WIPO/PCT (3). That pattern tracks primary aluminium production geography more closely than it tracks general chemistry-patent filing behaviour.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to spent pot lining and hazardous residue, with the prior art for and against each one.
Who holds the claim space
The ranking is short and top-heavy: a leader with 9 records, a fifth-place assignee with 5, and a tenth-place assignee down at 2. Co-assignee activity is limited to 6 pairs, the strongest linking a smelter operator with a national metallurgical research centre.
One assignee sets the pace
The top-ranked assignee holds 9 of the 47 records in scope, well ahead of the field. Combined with the next four ranked assignees, the top 5 cover 70.2% of all records.
A short second tier, then a steep drop
Fifth place holds 5 records; by tenth place that has fallen to 2. The gap between the leader and the mid-tier is wide enough that a newcomer targeting volume alone would need a sustained multi-year filing programme to close it.
Collaboration is rare and mostly local
Only 6 co-assignee pairs appear in the dataset. The strongest pairing links an aluminium producer with a national metallurgical research and design centre, suggesting joint filings here trace to operator-institute programmes rather than commercial licensing partnerships.
| Assignee | Recent year | YoY |
|---|---|---|
| Pyrogenesis Canada Inc. | 0 | — |
| NOVAFRIT INT | 0 | — |
| Reynolds Metals Company | 0 | — |
| Alcan International Limited | 0 | — |
| Kaiser Aluminum & Chemical Corporation | 0 | — |
| Pechiney Rhenalu | 0 | — |
| FIBERGLAS CANADA LTD | 0 | — |
| National Aluminium Company Limited | 0 | — |
Where to take this
The ranking and trend point to a mature, concentrated estate with a few specific gaps still open.
Check freedom to operate against the top 10
With 97.9% of all 47 records held by the top 10 assignees, any new filing in thermal treatment or fluoride leaching should be checked against that group's claims before drafting.
Run a freedom-to-operate search in EurekaWatch the under-claimed detox branches
Cyanide breakdown and nitride hydrolysis routes are searched for but sit below the dominant recovery-chemistry classes, leaving room for narrower process claims.
Explore white space in EurekaTrack post-2024 publications as they land
The 2025-2026 filing counts are still incomplete because of the publication lag; re-check the trend once later filings publish.
Set up a monitoring alert in EurekaCommon questions on spent pot lining patents
The patent estate in this field is concentrated: the leading assignee holds 9 of the 47 records in scope, and the top 5 assignees combined account for 70.2% of all records. The top 10 push that share to 97.9%, leaving only a thin tail of single- or double-filing entrants. Most of the leaders are primary aluminium producers or specialist thermal-treatment licensors rather than general chemical companies, which reflects how tightly this technology is tied to smelter operations.
Filing activity peaked at 8 records in 2021 and had fallen to 2 by 2024, a 75% decline over that three-year window. That said, publication typically lags actual filing by around 18 months, so the counts for 2025 and 2026 in this dataset are still filling in and should not yet be read as confirmation of a continued slowdown. 2024 is the most recent year that can be treated as reasonably complete.
Chemical recovery classes lead the field: C01F (alkaline-earth, aluminium and rare-earth compounds) appears on 57.4% of all 47 records, followed by C01B inorganic compounds at 46.8% and B09B solid waste disposal at 40.4%. Electrolytic production (C25C) and metal extraction (C22B) each cover 38.3% of records. Chemical detoxification claims under A62D are less common, at 29.8%, indicating most patented processes centre on recovering value from the residue rather than solely neutralising it.
Australia leads as a receiving office with 12 filings, followed by India with 8 and Canada with 6. Europe (EPO) and the United States each show 5, with WIPO/PCT filings at 3. This distribution tracks the geography of primary aluminium smelting more closely than general chemistry-patent filing patterns, since Australia, India and Canada are all significant aluminium-producing regions.
US20230138875A1, filed by Pyrogenesis Canada and published in 2023, claims a plasma arc furnace apparatus that converts spent pot lining into vitrified inert slag, aluminum fluoride and syngas by gasifying the carbon fraction under controlled air and steam intake. It is a specific apparatus-and-process combination tied to plasma arc destruction rather than a broad claim over all thermal treatment of SPL. A new filer working with a different heat source or without the plasma arc mechanism would need a freedom-to-operate review of this specific claim set rather than assuming it blocks thermal treatment generally.
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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.
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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.