Spent Pot-Lining (SPL) is a by-product of aluminum smelting electrolysis during production. The electric reduction of aluminum oxide, alumina, to the metal is done in the presence of sodium fluoride. The pots this is done in are lined with a refractory ceramic layer, and then a hard high carbon pitch layer. After several months this lining breaks down, and the resulting mess is stripped out. It's grey-brown and can be as tiny as fine dust or come out in big chunks.
Each year, 1.6 million tonnes of SPL is produced world-wide, at a rate of 25 kg per tonne of aluminum produced. Canada is the world's fourth-largest aluminum producer, with companies making progress in extending production cell lifespan thereby reducing the amount of SPL produced by 30%. Cement, steel and mineral wool production can potentially all use recycled SPL as a feedstock. As a last resort, it can be sent to landfill, albeit with leachable toxic contents - fluorides and cyanide - so attention must be paid to landfill lining and leachate management. It has a shipping name of ‘’UN 3170, ALUMINUM SMELTING BY_PRODUCTS (Spent Potlining), Class 4.3, Packing Group III’’. Here's a view of the removal of SPL from an aluminum cell cathode:
SPL FROM NORTHERN QUEBEC
Rio Tinto (formerly ALCAN) has a SPL treatment facility in Jonquiere, QC using a process pioneered by its research department. Low Caustic Leaching & Liming, in use since 2008, reducing the need to landfill about 20,000 to 30,000 tons per year. The facility was also expected to handle SPL from Kitimat, BC and other smelters in Quebec, up to 60,000 tons per year in 530 carloads. As a result, no SPL container cars seem to be coming from the Arvida area along with the usual aluminum ingots on RTAX or HPJX flat cars.
I briefly traced such a car on May 15, 1997- VTTX 97660. Observed eastbound on CN No 306, it arrived in Mont-Joli, QC on Montreal-Moncton CN train No 312. Then it travelled to Baie-Comeau on "00121" on May 22, where it spent a month. Arriving in Matane, QC on June 22 on "00122" thence Montreal on No 311, CN train No 395 took the car west along the Kingston Sub on June 24 on its way to interchange with Union Pacific at Chicago thence Gum Springs, AR.
In the late-90's, cars used in SPL container service were TrailerTrain flat cars witih ATTX, TTCX or VTTX reporting marks and CN 89-foot flat cars. CN and TTCX cars were heading to Gum Spring, the site of a longtime Alcoa SPL waste treatment facility - Elemental Environmental Services - five miles south of Arkdadelphia, AR. (Reminds me of the recent Tragically Hip release of Saskadelphia!) Here, the SPL is processed and buried. This site was bought last year by Veolia North America, to take that side business off Alcoa's hands, and fold it in with their expanding hazardous materials disposal business. Googlemaps view of the ALCOA Primary Metals site showing flat cars and containers:
Without car tracing, online reports suggest the cars currently seen here on the CN Kingston Sub come from Aluminerie Alouette at Pointe Noire/Sept-Iles or Aluminerie Alcoa de Baie-Comeau. Rail service to both sites crosses the lower St Lawrence via CN's COGEMA rail ferry service from Matane.
In 2019, Aluminerie Alouette, which began production in 1992, generated 20,000 tons of SPL. Just over 15,000 tons were buried in authorized sites, the remainder recycled or valorized. There are three main car fleets in this service that I see here. In 2019, Aluminerie Alcoa de Baie-Comeau had its SPL pre-treated and buried.
FLAT CARS IN SPL SERVICE
In the last few years, an interesting collection of leasing-company flat cars have been used to carry SPL containers. There are three main fleets that have been in SPL container service since 2014:
- AEQX 60-foot blue flat car (3 containers) of ATEL Capital Group. The cars were formerly owned by Southern Pacific.
- HESX 43 89-foot flat car (4 containers) of Heritage Environmental Services, built by Trenton Works in 2000 and formerly owned by Florida East Coast.
- SOXX black 89-foot flat car (4 containers). SOXX is SMBC Rail Services, formerly AWXX owned by Utah's East Carbon Development Company. Steve Boyko blogged about these cars in Winnipeg.
- 8/12/97 TTCX 98120 on CN No 395 Dest. Gum Springs, AR
- 14/2/98 CN 639331 on No 395 Dest. Gum Springs, AR.
- 15/5/98 VTTX 97660 on No 306 Dest. Baie Comeau, QC
- 15/7/98 TTCX 90265 on No 395
- 18/9/98 FEC 2891, TTCX 90524 on No 301
- 12/9/98 VTTX 92636 and 97698, TTCX 98033 on No 306
- 13/11/98 VTTX 97513 on No 301
- 20/9/99 TTCX 90521 on No 306
- 27/9/99 VTTX 92206 and 91968 on No 306 Dest. Riviere du Loup/Chemin de fer Baie des Chaleurs (CBC)
- 9/7/00 CP 251095, ATTX 91114 on No 310 Dest. Baie Comeau (CBC)
- 31/8/03 CN 638078 on No 369
- 2/11/03 ATTX 97597 on No 306
- 5/7/04 ATTX 95169 on No 306 (below):
- 27/3/10 VTTX 93385 on No 309
- 12/3/11 VTTX 91956 and ATTX 92635 on No 309
- 8/10/16 AEQX 242 wih container PLRU 02320 and HESX 54 with Pic Leasing container PLRU 023056 on No 306
- 11/8/2017 SOXX 20515 (top photo) with 20411 and 20291 (MHF Services MHFU containers) on No 369
- 30/9/17 AEQX 160 on No 368:
- 15/5/18 AEQX 220 on No 306
- 6/11/19 SOXX 20516 and 20188 on No 369 (below), plus AEQX 243 empty on No 368:
- 12/4/20 AEQX 262 on No 368
- 5/6/20 AEQX 204 and 242 with VTTX 97574 on No 305:
- 19/6/20 SOXX 20522, 20533, 20529, 20525, 20275, 20420 on No 368:
- 18/7/20 SOXX 20541 and 20222, AEQX 160, 204 and 213, and HESX 45 on No 306:
- 27/10/20 AEQX 141 and HESX 43 on No 369:
- 27/10/20 HESX 60