CAMPFORTS, Mieke (WAversebaan 1, Heverlee, B-3001, BE)
VAN CAMP, Maurits (Pansgatelaan 40, Mortsel, B-2640, BE)
VERSCHEURE, Karel (Oudenaardestraat 2, Vichte, B-8570, BE)
CAMPFORTS, Mieke (WAversebaan 1, Heverlee, B-3001, BE)
VAN CAMP, Maurits (Pansgatelaan 40, Mortsel, B-2640, BE)
| Claims 1. Process for the recovery of Ni and/or Co from electric or hybrid vehicle batteries, comprising the steps of: - providing a bath furnace equipped with means for 02 injection; - providing a metallurgical charge comprising CaO as a slag former, and said batteries, the fraction of batteries, expressed as weight % of the metallurgical charge, is at least equal to 40%; - feeding said metallurgical charge to the furnace while injecting 02, whereby at least part of the Ni and/or Co is reduced and collected in a metallic phase; - separating the slag from the metallic phase by tapping; characterized in that said bath furnace is operated so as to provide freeze lining of the slag. 2. Process for the recovery of metals according to claim 1, whereby the frozen slag layer lining the furnace, as measured at the surface of the molten slag, has a thickness of at least 10 mm, preferably at least 20 mm. 3. Process for the recovery of metals according to claims 1 or 2, characterized in that, in the step of feeding said metallurgical charge, a reducing agent is fed to the furnace. 4. Process for the recovery of metals according to claims 1 or 2, whereby said metals comprise Co and said vehicle batteries comprise Li-ion batteries also containing Al and C, comprising the steps of: - providing a bath furnace equipped with means for 02 injection; - providing a metallurgical charge comprising CaO as a slag former, and Li-ion batteries; - feeding said metallurgical charge to the furnace while injecting 02, whereby at least part of the Co is reduced and collected in a metallic phase; - separating the slag from the metallic phase by tapping; characterized in that the fraction of Li-ion batteries, expressed as weight % of the metallurgical charge, is at least equal to 153% - 3.5 (Al% + 0.6 C%), Al% and C% being the weight % of Al and C in the batteries. |
The disclosed invention concerns a recycling process for recovery of metals from HEV (hybrid electric vehicles) or EV (electric vehicles) batteries.
HEV and EV rely on high performance rechargeable batteries. While NiMH batteries (nickel-metal hydrides) have dominated until today, it is generally expected that Li-ion batteries will prevail in the near future. This is especially true for electric vehicles (EV), where a high gravimetric energy density of the embarked batteries is key to success.
It is therefore projected that considerable quantities of (H)EV batteries will hit the recycling market in the coming years. These could be both worn-out batteries and manufacturing rejects. Such batteries contain valuable metals, such as Cu, Ni, Mn and Co, which are worthwhile to recycle both from an economic and an ecologic point of view. The transition metals Ni, Mn and Co are normally present in an oxidized form in Li-ion batteries, while oxidized Ni is present in NiMH batteries.
At present, the best available technology for (H)EV battery recycling is the cupola packed-bed technology, where batteries together with fluxes and cokes are molten in a shaft to form a molten slag and Co-bullion. This process, described in EP-A-1589121, ensures a high metals recovery of more than 97% for Co, Ni and Cu. Its main advantage is that undismantled cells can be safely treated : as the heating rate in the shaft is low, the gasses evolving inside the cells can slowly escape, thereby avoiding any explosive release of gasses. Battery explosions are indeed a considerable threat for vehicular batteries, as the individual cells can be much larger than the cells commonly found in portable electronics.
This cupola process has however also a number of drawbacks. The coke consumption is very high, amounting to 30-40% of the feed. This amount of coke is needed to carry out the reduction, and also to keep the packed bed sufficiently porous. Size segregation in the shaft is furthermore difficult to avoid, which leads to an increased pressure drop over the packed bed. Large quantities of fines are also carried over with the gasses, resulting in problems at the bag house. The objective of the present invention is to overcome these problems by using a bath smelting process where the feed is directly introduced into a molten bath . The invented process is particularly adapted for treating metallurgical charges mainly constituted by Li-ion and/or NiMH batteries of the type used in electric vehicles and hybrids. The invention concerns a process for the recovery of Ni and/or Co from such batteries, comprising the steps of:
- providing a bath furnace equipped with means for 0 2 injection;
- providing a metallurgical charge comprising CaO, and preferably Si0 2 , as slag formers, and said batteries, the fraction of batteries, expressed as weight % of the metallurgical charge, is at least equal to 40%;
- feeding said metallurgical charge to the furnace while injecting 0 2 , whereby at least part of the Ni and/or Co is reduced and collected in a metallic phase;
- separating the slag from the metallic phase by tapping;
characterized in that said bath furnace is equipped with means to provide freeze lining of the slag.
In a preferred embodiment, the frozen slag layer lining the furnace, as measured at the level of the surface of the molten slag, has a thickness of at least 10 mm, preferably at least 20 mm.
Additional fuel or reducing agents may be needed in this case. The invented process is also particularly adapted for treating metallurgical charges mainly constituted by Li-ion batteries. This embodiment concerns an autogenous process for the recovery of Co, which is present in an oxidized form, from Li-ion batteries also containing Al and C, which is present as graphite or in organic matter, comprising the steps of:
- providing a bath furnace equipped with means for 0 2 injection;
- providing a metallurgical charge comprising CaO, and preferably Si0 2 , as slag formers, and Li-ion batteries;
- feeding said metallurgical charge to the furnace while injecting 0 2 , whereby at least part of the Co is reduced and collected in a metallic phase;
- separating the slag from the metallic phase by tapping; characterized in that the fraction of Li-ion batteries, expressed as weight % of the metallurgical charge, is at least equal to 153% - 3.5 (Al% + 0.6 C%), Al% and C% being the weight % of Al and C in the batteries. No additional reducing agent or fuel is needed in this particular embodiment.
A bath furnace requires only a basic charge preparation as the morphology of the feed is far less critical than with a shaft furnace. Also, the burden of gas cleaning is considerably lightened as no additional plasma torch is needed for the post combustion of the exhaust gasses with secondary air. When combining this with the known principle of post- combustion of the CO above the bath, the energy efficiency of the process is even further enhanced.
Batteries such as those found in portable devices can be fed as such to the furnace, i.e. without dismantling or shredding. The risk of explosion is then mitigated as the individual cells are sufficiently small. However, directly feeding large (H)EV batteries or battery packs requires additional protection measures in the furnace, in particular when the relative amount of batteries in the charge exceeds about 40% by weight. The use of freeze lining then becomes necessary from an economic point of view. Freeze lining is known for protecting the fire-bricks of furnaces against chemical attack. It however also appears suitable to protect against the mechanical attack from exploding batteries, thanks to its regenerating nature.
According to the invention, (H)EV batteries are thus directly fed to a bath smelter. The batteries do not need to be shredded in a preliminary process. Such batteries typically contain large cells, which are susceptible to explode violently when undergoing a rapid heating cycle. This can be detrimental to the lining of the furnace, unless special precautionary measures are taken. It appears that combining a bath smelter with freeze lining at the bath level, i.e. where the batteries contact the bath and tend to float for some time, is essential in protecting the lining.
In the particular embodiment concerning autogenous smelting, the excellent reduction kinetics and yields that are achieved are believed to be due to the proximity of metallic Al and oxidized metallic elements (such as Co, Ni and Mn) within the Li-batteries themselves. This characteristic is preserved, even if the batteries are pre-processed, such as by shredding and lixiviation, as long as the Al and the oxidized metals retain their proximity.
The invented process results in the reduction of Ni and/or Co, which, together with the Cu that is most of the time also present in such charges, forms a metallic bullion. This bullion can then be further processed according to known ways for the separation and recovery of the metals. Mn is mostly sent to the slag. Li is partially fumed and partially slagged. Li could be recovered from slag or fume using known processes, especially if the economic value of Li would rise further to its increased world consumption.
In Li-ion batteries, Al is generally present in its metallic form; C is typically present in the inorganic graphite anode, but also in the organic material in and around the cells. Organic C participates to the reduction and to the enthalpy in a similar way as graphite, allowing the total amount of C to be considered for applying the formula.
When applying the formula defining the minimum fraction of batteries needed to sustain energy-efficient processing, a result of more than 100% is obviously to be considered as unfeasible. In such a case, batteries containing more Al and/or more C have to be selected. Supplementing with additional gas and oxygen is another possibility. This could be natural gas injected through an oxy-gas burner.
By "oxidized form" is meant not only oxides but also compounds wherein the metal is an electron donor. By "metallurgical charge comprising a fraction of Li-ion batteries" is meant a charge comprising the said relative amount of batteries, either as such, or after physical processing, such as after dismantling, shredding, and selection by floatation. It is however clear that the invented process is specially adapted for processing charges containing sealed cells, as only such cells are susceptible to explode violently when heated.
"Batteries" may be actual cells, packs of cells, or assemblies.
A more detailed description of the process is now presented. A batch consisting of unprocessed Li batteries, fluxes and other raw materials containing valuable metals is fed in a bath smelting furnace. The furnace consists of three zones, the gas zone, the slag zone and the alloy zone. Oxygen is injected in the slag zone.
The charge falls under gravity in the molten slag bath, which is at about 1450 °C. As a result, the Li batteries are rapidly heated, detonate, and the residues react rapidly thanks to the good contact between reduction agents (such as the electrolyte, the plastics and the Al), and the oxides (such as LiCo0 2 ) in the batteries. The submerged injection leads to vigorous stirring of the bath which in turn also leads to fast reaction kinetics.
Only a minor part of the reduction agents is lost by evaporation or pyrolysis, the energy content of the batteries being efficiently employed for the reduction and as heat source. However, the detonating batteries are susceptible to spall pieces of refractory. Therefore, the furnace wall is cooled in the slag zone to form a freeze lining. A freeze lining consists of solidified process material, in this case mostly slag. This freeze lining is self regenerating. Thus, as a part of the freeze lining is deteriorated by explosions, fresh layers are rapidly grown.
In the gas zone, all CO, H 2 , and volatilized plastics and electrolyte are post combusted with the secondary air entering through the feed port. As a result, the formation of dioxins is prevented. The off gases are further treated with a classical gas cleaning system.
Al, Si, Ca and some Fe and Mn collect in the slag, while most Co and Ni (more than 90% of the input), and a large part of the Fe (more than 60%) collect in the alloy. Both slag and alloy are tapped, whereupon a new batch is processed. Typically, the process can treat all types of Li batteries, and, depending on the required Li battery content, also other types of raw materials that contain valuable metals like Co and Ni or their scrap. CaO, and preferably also Si0 2 , are added to flux the Al 2 0 3 , in order to obtain a liquid slag. Example 1
The Li-ion based charge shown in Table 1 is smelted according to the invention in a small furnace with a diameter of 1.5 m lined with chrome-magnesia bricks, the lining having a thickness of 300 mm.
As an essential part of the metallurgical charge, HEV batteries and battery packs weighing up to 50 kg are dropped into the molten bath from a height of 8 m. The furnace is operated in a mode allowing for freeze lining. Freeze lining is established by applying intensive cooling in of the slag zone, using water-cooled copper blocks according to known ways. Essentially no degradation of the refractory over time is observed.
This feed corresponds to an amount of batteries that is markedly higher than 40%. This means that freeze-lining is necessary to insure the economic viability of the furnace lining.
The weighted mean Al and C content of the Li-ion fraction can be calculated as respectively 9.4 and 32.3% by weight. According to the preferred formula, which is applicable when a relatively small furnace is used or when the furnace has high thermal losses, a minimum of 62.9% of Li-ion material is needed to sustain the autogenous combustion of the charge in this case.
The feed comprises 64.4% by weight of Li-ion material. This being slightly higher than the minimum required, the process indeed appears to be autogenous indeed. A bath temperature of 1450 °C is obtained without additional cokes or gas. 0 2 is blown through a submerged tuyere at a rate of 265 Nm3/h.
According to Table 1, excellent recovery of the metals Co, Ni, Cu and Fe is observed with no added energy requirements. Table 1 : Feed and products for autogenous process according tot the invention
Comparative example 2
A furnace similar to the furnace of Example 1 is used in continuous service.
However, a classical mode of operation is established, namely without freeze-lining. Hitherto, the water-cooled copper blocks are replaced by common chrome-magnesia bricks.
In this classic mode of operation, the degradation of the refractory is observed to be about 12 mm/day. This corresponds to an economically unviable situation, as the masonry would have to be refurbished about monthly.
It is assumed that the degradation of the refractory can be partly attributed to chemical erosion and, mainly, to mechanical erosion due to the lumps of material scraping against the walls and to the impact of the exploding cells.
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