System and process for collecting effluents from an electrolytic cell

Abstract

The invention provides a system and a process for collecting effluents produced by an electrolytic cell intended for the production of aluminium and for drawing said effluents away from the cell in a flow of gas. The system comprising a hooding to confine the effluents, at least one outlet channel to collect said flow of gas and suction means to draw said flow of gas away from the cell. The hooding includes removable hoods and, optionally, at least one door to get access to the inside of the hooding. The system further comprises at least one pipe for blowing pressurized air within the outlet channel so as to increase the rate of said flow of gas. Pressurized air supply is activated at a specified pressure Po so as to obtain a specified flow rate Ro.

1 . System for collecting effluents produced by an electrolytic cell intended for the production of aluminium and for drawing said effluents away from the cell in a flow of gas, said system comprising a hooding to confine the effluents, at least one outlet channel to collect said flow of gas and suction means to draw said flow of gas away from the cell through said at least one outlet channel, said hooding including removable hoods, to get access to the inside of the hooding, wherein said system further comprises at least one pipe comprising:
 a first end that is directly or indirectly connected to a pressurized air supply; and   a second end that is located inside said at least one outlet channel includes at least one aperture and is oriented so that pressurized air can be projected through said aperture in a manner that increases the rate of said flow of gas within said at least one outlet channel.   
     
     
         2 . System according to  claim 1 , wherein said second end is oriented so that pressurized air can be projected substantially along the direction of said flow of gas. 
     
     
         3 . System according to  claim 1 , wherein said second end is fitted with a nozzle that forms said aperture. 
     
     
         4 . System according to  claim 1 , wherein the dimension of said at least one said aperture is between 5 mm 2  and 1300 m 2 . 
     
     
         5 . System according to  claim 1 , wherein the dimension of said at least one aperture is between 300 mm 2  and 1000 mm 2 . 
     
     
         6 . System according to  claim 1 , wherein said at least one pipe is connected to said pressurized air supply through a valve. 
     
     
         7 . System according to  claim 6 , wherein said valve is selected from electrically controlled valves and pneumatically controlled valves. 
     
     
         8 . System according to  claim 6 , wherein said valve is coupled to a regulation system. 
     
     
         9 . System according to  claim 1 , wherein said pressurized air supply can supply pressurized air at a specified pressure and a specified flow rate. 
     
     
         10 . System according to  claim 9 , wherein the specified flow rate is between 5 and 15% of said gas flow rate. 
     
     
         11 . System according to  claim 9 , wherein the specified pressure is smaller than 5 bars. 
     
     
         12 . System according to  claim 9 , wherein the specified pressure is comprised between 30 and 300 kPa. 
     
     
         13 . System according to  claim 9 , wherein the specified pressure is comprised between 70 and 120 kPa. 
     
     
         14 . System according to  claim 1 , wherein a pressure reducer is inserted between said at least one pipe and said pressurized air supply so as to make it possible to reduce the pressure to a specified value. 
     
     
         15 . System according to  claim 1 , wherein said pressurized air supply includes a blower that provides pressurized air directly at a specified pressure value. 
     
     
         16 . System according to  claim 1 , wherein said at least one outlet channel includes a length of duct with an internal cross section that varies along said length and wherein said second end is located within said length of duct. 
     
     
         17 . System according to  claim 16 , wherein said length of duct has an inlet and an outlet and includes a constriction between said inlet and outlet. 
     
     
         18 . System according to  claim 17 , wherein said second end is located in the vicinity of said constrictions. 
     
     
         19 . System according to  claim 17 , wherein said second end is located upstream of a plane where the section of said constriction is narrowest. 
     
     
         20 . System according to  claim 1 , wherein the suction means include at least one fan. 
     
     
         21 . System according to  claim 1 , wherein said suction means include a conduit that is common to at least two electrolytic cells and is connected to at least one common fan. 
     
     
         22 . System according to  claim 21 , wherein said fan is located in an installation for the treatment of said effluents or downstream thereof. 
     
     
         23 . System according to  claim 1 , wherein said system further includes at least one adjustable or removable flow balancing means located in said at least one outlet channel or downstream thereof. 
     
     
         24 . System according to  claim 23 , wherein said flow balancing means is selected from the group comprising diaphragms, shutters and flaps. 
     
     
         25 . Process for collecting effluents produced by an electrolytic cell intended for the production of aluminium and for drawing said effluents away from the cell in a flow of gas circulating in at least one outlet channel, wherein said process comprises:
 providing the cell with a system according to  claim 1 ,   connecting said at least one pipe to a pressurized air supply,   activating said suction means so as to create a flow rate in said at least one outlet channel,   supplying pressurized air in said at least one pipe at a specified flow rate so as to increase the rate of said flow of gas within said at least one outlet channel.   
     
     
         26 . Process according to  claim 25 , wherein the supply of pressurized air in said at least one pipe is activated manually or automatically, or a combination thereof. 
     
     
         27 . Process according to  claim 25 , wherein pressurized air is supplied in said at least one pipe when at least one hood is removed from the cell. 
     
     
         28 . Process according to  claim 25 , wherein the hooding is further provided with at least one door to get access to the inside of the hooding, and wherein pressurized air is supplied in said at least one pipe when said doors is opened. 
     
     
         29 . Process according to  claim 25 , wherein the hooding is further provided with at least one door to get access to the inside of the hooding, and wherein pressurized air is supplied in said at least one pipe at a first specified flow rate when at least one hood is removed from the cell and at a second specified flow rate when said doors is opened. 
     
     
         30 . Process according to  claim 25 , wherein pressurized air is supplied in said at least one pipe when said cell is being started up. 
     
     
         31 . Process according to  claim 25 , wherein the ratio Po/P between the pressure Po inside said at least one pipe and the pressure P inside said at least one outlet channel where the second end of said at least one pipe is located is selected so as to avoid shock waves. 
     
     
         32 . Process according to  claim 25 , wherein the specified flow rate is between 5 and 15% of said gas flow rate. 
     
     
         33 . Process according to  claim 25 , wherein, said system is further provided with at least one adjustable or removable flow balancing means located in said at least one outlet channel or downstream thereof, and said process includes opening or removing said flow balancing means so as to ease the flow of gas and thereby further increase the throughput in said at least one outlet channel.