PLANT FOR REMOVING FLUOR CONTAINING WASTE GASES

Abstract: Plant for decentralized dry cleaning by removing fluor containing waste gases from the reduction process in several electrolytic cells for aluminium, the plant comprising a storing place (2) for aluminium oxide from which a piping system (3) distributes aluminium oxide to the decentralized cleaning plant (1), each cleaning plant (1) comprising an exhaust fan (5) and storing tanks for aluminium oxide before and after use in the plant, and the exhaust fan (5) and the storing tanks being integrated with the top filter part (4) of the plant.

Description: Plant for Removing Fluor containing Waste Gases The present invention is related to a plant for decentralized dry cleaning by removing flour containing waste gases from the reduction process in electrolytic cells for aluminium. Known embodiments of plants for dry cleaning of waste gases developed during electrolytic processing of aluminium, are centralized plants servicing one or several halls comprising ovens with cells whereby each hall may comprise between 70 and 150 electrolytic cells or ovens, and which are arranged centrally between the halls or outside. The plant is connected with each of the cells by means of a comprehensive and costly effluent channel . The aluminium oxide used as adsorbent during the cleaning process is stored in separate silos before or after use in the cleaning process and thereafter is transported back to each cell by means of transportation vehicles, cranes or other transportation systems for aluminium, such as a system for transportation in a compact phase. With the device according to the present invention for cleaning of waste gases from the reduction process of aluminium, substantial savings are achieved as to the volume or area needed, as well as savings in the equipment and time savings during the process and the building. This is achieved with the plant according to the present invention as described with the features stated in the claims. By using a decentralized plant according to the present invention major parts of the traditional stores and transpor- tation systems for aluminium oxide as can be found in known plants for dry cleaning, are eliminated. Likewise a substantial part of the channel system for waste gases as well as the connection channels between the cleaning plant and the main chimney is made redundant. Even the need for main fans for waste gas is eliminated. With the present invention a substantial reduction on the space requirement is achieved, furthermore the processing time is reduced and a much more simpler construction and operation is achieved. There is no demand for a storing silo for treated aluminium oxide and likewise the demands for fundamen- tations are substantially reduced. As opposed to known embodiments of plants, no chimney is required furthermore no silos and no lifting devices. Furthermore large flexibility is achieved as s to starting up the operation and there is a short distance between the places for storing of the aluminium oxide and the ovens. The method of storing and the place of storing for the aluminium oxide may be chosen depending on local conditions and suitability. With the present invention suitable groups of o between 5 and 40 electrolytic cells may be served in each plant, preferably between 10 and 20. The present invention provides further substantial reduced energy consumption and thereby connected substantial cost savings. As a result of the simplified plant, the need for spare s parts also is substantially reduced. Outlet dumpers for the filters are not necessary and there also is no need for a compressor room as the case is with known plants. The installation time is strongly reduced and the design well adapted for adjustment to specific products. o The drawing discloses chematically a plant according to the present invention where figure 1 discloses a section 2-2 in figure 2 and figure 2 discloses a ground view of a plant according to the invention. Fresh aluminium oxide is transported in a compact form 5 from a central tank 2 to each decentralized cleaning plant 1 by a transportation system, such as a piping system 3. Further storing of aluminium oxide before or after use in the plant 3 is made in storing tanks integrated in the filter portion 4 of the cleaning plant. The waste gas fan 5 which is serving each o cleaning plant 1, is integrated with the top filter part and make the traditional outlet dampers on top of the filter redundant. The new embodiment enables recirculation of fluorides and other raw materials from a specific group of cells, in return to the same cells. 5 The modules for removing impurities as well as S0 2 also can be integrated in a very simple way as part of the decentralized plant 1 for dry cleaning, possibly at a later time.

Claims: Patent claims 1. Plant for decentralized dry cleaning by removing s fluor containing waste gases from the reduction process in several electrolytic cells for aluminium, CHARACTERIZED IN the plant comprising a storing place ( 2 ) for aluminium oxide from which a piping system ( 3 ) distributes aluminium oxide to the decentralized cleaning plant ( 1 ) , each cleaning plant ( 1 ) o comprising an exhaust fan ( 5 ) and storing tanks for aluminium oxide before and after use in the plant, and the exhaust fan (5) and the storing tanks being integrated with the top filter part (4) of the plant. 2. Plant according to preceding claim, CHARACTERIZED IN s each cleaning plant ( 1 ) being adapted to serve groups of between 5 and 40 electrolytic cells, preferably between 10 and 20. 0 5 0

Inventors: WEDDE GEIR, WEDDE, GEIR
Applicants: FLAEKT AB, WEDDE GEIR, ABB FLAEKT AB, WEDDE, GEIR
Application year: 1998
Main classification: C25C3
IPC codes: B01D53, C25C3