CN1040065A - The method of terminating anode effects when producing aluminium - Google Patents

Abstract

Eliminate during electrolyzing fused salt system aluminium or the method for terminating anode effects.Comprise salic ionogen and a plurality of carbon anodes that is dipped in the ionogen in this electrolyzer.By the inventive method at least 25% anode is divided into adjacent group, be arranged in the vertical different sites of electrolyzer, at least one group of anode promoted and all the other each group landing to stir electrolyzer, promote in the vertical and the anode group motion of landing hockets, and add aluminum oxide.Each anode is retracted into its origin operation position.If anode effect fails to eliminate, each organizes anode once more by identical or reverse mode motion.Can reach very high elimination efficient whereby, and the fused electrolyte surface changes minimum.

Description

The method of terminating anode effects when producing aluminium

Eliminate when the present invention relates to electrolysis of aluminum oxide for producing aluminum or " anode effect " method (anodeeffect) of termination.

The electrolytic reduction of aluminum oxide generally carries out in the Hall-Heroult electrolyzer, comprising a kiver that extends, and lining with electro-conductive material such as carbonaceous as negative electrode.Filling fused electrolyte in this container, generally is to contain 2-6%(weight) sodium aluminum fluoride of aluminum oxide of fusion.And a plurality of carbon anodes are immersed in the ionogen by top.When direct current passes through electrolyzer, generate molten aluminum and also be sunken at the bottom of the pond, form a cathode pool at this.The oxygen oxidizable carbon anode of Shi Fanging and generate carbonic acid gas/or carbon monoxide in addition.Because anode consumes gradually, and palpus holding anode and cloudy interpolar spacing, therefore need provide a lifting gear, so that anode is risen, lands and last the displacement on electrolyzer top.

In being called the electrolyzer of Soderberg, only use a big anode, it almost all covers the pond face.In the electrolyzer of another kind of Prebake, provide a plurality of anodes, and with in length and breadth to arranging as the positive plate district.The anode that generally has two rows vertically to arrange, and along the electrolyzer Y in each limit symmetry arrangement.Be considered as central road along the positive interpolar of axial two rows of electrolyzer space.It is big or small and different that horizontal anode number is pressed electrolyzer, but generally be 15 at the most, normally eight-15.Each anode spacing generally is identical in this arrangement.

During cell operation, electrolyte temperature remains in 950-980 ℃, to keep the molten state of the tall and aluminium of electrolysis.Lower at the electrolyte meter surface temperature, so be frozen into solid-state shell.Also lower near pool wall place temperature, ionogen also may solidify.In electrolytic process, alumina concentration reduces in the ionogen, and the shell that need periodically break certain position is added aluminum oxide from top.

Descend the most rapidly near the alumina concentration in the ionogen of anode bottom, and when the density loss at this position about 2%(weight extremely) or when lower, anode effect can take place.At this moment voltage raises (can reach 40 volts), and produces the fluorine carbide in the anode gas.The antianode effect has detailed description in following document, i.e. " Aluminium Electrolysis Fundamentals of the Hall-Heroult Process ", second edition, work such as K.Grjotheim, Aluminium Verlage, 1982, the 264-283 page or leaf; " Aluminium Smelter Technology, second edition, K.Grjotheim and B.J.Welch work, Aluminium Verlag, 116-118 page or leaf.Above-mentioned document is included in this specification sheets as a reference.The known shortcoming cause of antianode effect has detailed description in above-mentioned document, needs usually to eliminate as soon as possible or terminating anode effects.

The method of eliminating is normally: (a) break shell, aluminum oxide is added in the electrolyzer; (b) vigorous agitation ionogen by influenced anode bottom purge gas, also helps aluminum oxide is dispersed in the whole electrolyzer by adding the position whereby.Wooden rod commonly used or gas ejector pipe stir the ionogen under the anode.But the more effective automatic technology of development and application in recent years.For example the Canadian Patent 1,148, No. 892 (June 28 nineteen eighty-three) of Saksvikronning etc. is relevant Soderberg type electrolyzer, wherein discloses with verting and swinging single anodic method to clear away ionogen in unwanted gas and the mixing pond.But this method not exclusively is applicable to the Prebake electrolyzer, and this is because too small being difficult to of a plurality of anode spacings in the type electrolyzer verts and swing, but also needs complex apparatus.

In the prebake electrolyzer, once used a kind of " twitch " mode, be about to the whole positive plate segment distance that lands, and then with its lifting.The shortcoming of this method is, when positive plate lands, can cause that ionogen penetrates shell, bath surface is risen and spills.Need design for this reason and increase cost with the negative electrode of dark cavity.Elimination efficient by this method anode effect generally is in the 70-90%(cell operation, the ratio of the anode number that effect is successfully eliminated and the anode sum of lifting), efficient depends on that to a great extent the positive plate landing allows to greatest extent.Obtain more high-level efficiency such as 90-95%, then need the cathode of electrolytic tank of tool degree of depth cavity.

Our United States Patent (USP) 4,414 formerly, 070(Spence, November 8 nineteen eighty-three) in, disclose a kind of to prebake electrolyzer method that be suitable for and that need not degree of depth negative electrode cavity.In the described equipment, anode is promoted individually or land.Also address in this patent when one group of anode promotes, another group anode can land with twitch electrolyzer composition, and can not influence the fused electrolyte surface.Propose in the above-mentioned patent, vertical all anodes of row promote simultaneously in the electrolyzer, another vertical all anodes of row then land (pressing the electrolyzer Y); Or all anodes of electrolyzer one end promote, and all anodes of another opposite end then land (press the electrolyzer X) simultaneously, or the anode on an orientation promotes the while, the anode on its diagonal orientation then land (being called the diagonal angle line style).When these methods told on, anode effect was eliminated efficient not as desirable, generally reaches 80-90%.

Thereby the object of the present invention is to provide a kind of the elimination or the method for terminating anode effects, and improve its efficient whereby.

By the anode movement of the disclosed application apparatus of Spence is further studied, can find if a plurality of groups anode that will scatter mutually on electrolyzer is vertical moves in the opposite direction, eliminating efficient so can improve, and has realized the present invention based on above-mentioned discovery.

According to the present invention, a kind of method of terminating anode effects when producing aluminium in electrolyzer can be provided, comprise salic fused electrolyte in this electrolyzer, and a plurality of carbonaceous anodes, each anode arrangement is at least two vertical rows and at least three horizontally-arrangeds, thus the composition positive plate.Described method comprises: aluminum oxide is added in the ionogen; The anode that accounts for anode sum 25% is divided into adjacent group, and is positioned at electrolyzer different positions longitudinally, each the group comprise at least two anodes, but no more than anode sum 1/3rd.At least a described group begins to move in first vertical direction from the origin operation position, and all the other each groups are moved in opposite vertical direction from the origin operation position.Wherein said one or more group anode is in described first movement in vertical direction, and described one or more groups are in described opposite movement in vertical direction, and presses vertically alternating motion mutually of electrolyzer.Described anode is retracted on its origin operation position, repeats described motion or does reverse described moving, till described anode effect is eliminated.

According to motor pattern of the presently claimed invention, can guarantee to have only group that fewer adjacent anode becomes, motion simultaneously in the same direction in certain zone of electrolyzer, contiguous simultaneously group anode does not move or motion in the opposite direction fully.Its advantage is, because the ionogen shell does not stand to move up and down widely thrust, and makes its fracture possibility drop to minimum.On the other hand, also can guarantee the effect of twitching to greatest extent according to the present invention, this is owing on each position of electrolyzer anode movement is arranged all, and vertically go up the motion of contiguous group anodic reverse direction can be effectively with the aluminum oxide and the ionogen mixing that add.Composition in the also available induction stirring electrolyzer is identical with the anode movement effect.

According to the present invention,, can provide up to 99% anode effect and eliminate efficient, and can inwardly eliminate anode effect, as be less than 1 minute in short-term at least by its optimal way.Additional advantages of the present invention are consumed energy few (as be equivalent to each anode effect day be the 10-20 millivolt).In addition, the change of pond face can be reduced to bottom line or be eliminated together.

As follows by designed anode group arrangement of the present invention and anode movement mode illustrations.Each group should comprise two adjacent anode at least and preferably include no more than six adjacent anode.Preferably the adjacent anode of each group is formed one or more full horizontally-arrangeds (but and inessential like this).When each group is made up of full horizontally-arranged, the adjacent anode in each limit of the longitudinal cenlerline of electrolyzer can make the fracture of central area shell reduce to bottom line all in same direction motion like this.The fracture of shell can produce fragment and sink in the ionogen, and generates sludge and produce unnecessary heat consume on cathode layer.

During other group was discharged to, what begin to promote respectively organized anode between two groups of beginning to land, or vice versa, the end of electrolyzer anode then except.Certainly, when making when being less than 100% anode movement, actionless anode can be by telling " lifting " group in " landing " group, and at least in electrolyzer part be like this.

Though can only make 25% anode movement (promoting or landing), better have 40% anode movement at least, and preferably make all anode movement.

The anode group can be moved simultaneously, or continuous, substep ground motion in order.The anode number of Ti Shenging can equate with the anode number of landing within a certain period of time, and move distance is identical, thereby bath surface can not change.Yet this is also nonessential, no matter because of anodic promotes or the subtle change of the bath surface that landing causes is all permitted, and still is useful in some cases.Obviously the anode movement pattern should not cause bath surface to produce undue change.If anode movement causes the change of bath surface certain degree, the anode group of chosen lifter motion preferably at first makes its motion to avoid ionogen to overflow.

All " lifting " anode groups can promote simultaneously, can land at the same time or subsequently and own " landing " group.Also different " lifting " groups can be promoted (for example can produce waveform in electrolyzer moves up and down) in different time in addition, and different " landing " group can be landed by the same manner.

As mentioned above, each anode serially or stage by stage (is promptly having the dead time between the short period of time motion rapidly) and is promoting or landing.If segment movement, all anodic segment movement can be synchronous or fully independently.

Concerning these professional those skilled in the art, the lifting of antianode or landing all have the ultimate range of allowing, anode movement can not surpass this limit.The distance of landing often can surpass the point (Short-out point) of stopping, because of stop in some cases (shorting) is desirable (promptly thoroughly eliminate anode effect, but do not have respective associated with the inventive method).On the other hand, anode can not promote and move apart ionogen, especially should not make anode dialysis shell.Otherwise make by other anodic current excessive, and cause overheated so that the blast.

When anode movement to the permission ultimate range of its lifting or landing, each anode retreats to its origin operation position (promptly occur anode effect before position).Each anode can be same but with reciprocal pattern, and the speed that equates when leaving its origin operation position retreat to original position (for example as they to begin be to move with segmented mode, then can segmented mode return).In addition, each anode also can be return by different motion pattern and/or friction-motion speed.

If still fail to eliminate anode effect through a round-robin anode movement, can repeat one or many until the effect that reaches elimination.And next round-robin anode movement pattern can circulate identical or opposite with the first time.Promptly " lifting " anode can or opposite way motion identical with former direction of motion with " landing " anode in first circulation.

Though electrode movement situation normal opposite (promptly beginning the group by the work point lifting, can be the group of landing, or vice versa) with above-mentioned pattern.Sometimes need guarantee not make the electrode of electrolyzer longitudinal end by its origin operation position landing.This is the ionogen possibility " cohesion " owing to end wall, and its solid-state ionogen can partly stretch to the electrode bottom, so electrode landing motion may damage electrode itself or electrode supporting structure.

Can aluminum oxide be added electrolyzer by common method, as by shell being broken (be) and aluminum oxide is added the ionogen fused solution at cell center line position.The anodic agitaion can promptly be scattered in aluminum oxide whole electrolyzer.The add-on of aluminum oxide is consumption adding routinely also.The adding of aluminum oxide need not and must carry out simultaneously with the beginning of anode movement.For example, can before anode movement, add in the short period of time, also can be after 10-20 second or longer time motion anode.In general, add aluminum oxide more soon, the elimination effect begins to carry out soon more so.

Anode movement speed is not particularly important to successful implementation the present invention; Speed does not need the longer time to implement the elimination effect slowly, therefore the most handy fast speeds.Yet movement velocity also should not be too fast, in order to avoid destroy shell or ionogen is overflowed.

The inventive method needs anode support structure, and this structure can make the anode of different groups move simultaneously or in order in different directions.In the U.S. Pat 4,414 of Spence, 070(is incorporated into this specification sheets document for referencial use) in, described equipment is applicable to the object of the invention, because of this equipment can provide motion to all anodes.Yet, also can use easier equipment, it can be connected each single group electrode, maybe will own " lifting " group and " landing " and organize to get up continuously and motion simultaneously.

Can use computer to control the ultimate range of anode movement pattern and anode movement, especially in using above-mentioned patent during equipment used, computer control is easier to use by row.

As follows with reference to accompanying drawing to the preferred implementation of the present invention.

Accompanying drawing 1-3 is expression electrolyzer plane diagram, the positive column wherein is described and press arrow and shade shown in first motion.

Motion preference as shown in Figure 1, anode arrangement in the electrolyzer becomes two vertical row and 12 horizontally-arrangeds, and be divided into and comprise four anodes and six anodic groups (illustrate one positive column, as these professional those of skill in the art as can be known, wherein constitute an anode) in transversely both.As shown in the figure, when anode effect took place, the group of being made up of four anodes began to promote from its work point, and begins landing by the group that six anodes are formed.After each anode reached its lifting or the ultimate range of landing on the direction, each anode was with reversing motion, and each anode returns on its origin operation position.In this process, along the shell hole adding aluminum oxide in cell center road.If fail anode effect is eliminated satisfactorily through above-mentioned anode movement, but the repeating motion process, anode can identical direction move by as shown in the figure with beginning the time, or with its reverse direction motion, each anode returns on the origin operation position more then.Described process can repeat arbitrary number of times and eliminate satisfactorily up to anode effect.

The anode (being 1-2,6-7 and 11-12 row's anode) that belongs to three " lifting " groups can move or simultaneously by smooth alternating motion (producing wavy in electrolyzer).Anode movement can be successive or sectional, is promptly undertaken by the mode of going forward one by one.Each " landing " group anode (being 3-4-5 and 8-9-10 row anode) is also pressed the same manner motion.Each " lifting " or " landing " group can be moved or motion in order simultaneously.

In any specified time, promote and the anode quantity of landing preferably equates, can make bath surface remain in the level of electrode when being positioned at original work point like this.The subtle change of bath surface permits that therefore in fact as long as each anode begins to move in this way, any successive or sequenced anode movement pattern all can adopt yet as mentioned above.

Pattern can be turned as shown in Figure 1, and promptly " lifting " group becomes " landing " group, and vice versa.

Accompanying drawing 2 illustrates another anode movement pattern of electrolyzer as shown in Figure 1.The preferred movement pattern in nine horizontally-arranged anode electrolysis of accompanying drawing 3 explanation tools pond.In addition, anode movement can be continuous or sectional type, can carry out simultaneously or carry out in order.And the setting in motion direction is also adjustable changes into oppositely.

Effect of the present invention can illustrate by following example.

Example

In a Hall-Heroult electrolyzer (Apex electrolyzer), to be with two vertical row's anode and 12 horizontally-arranged anodes, and to be provided with the superstructure that can make each anode movement, this electrolyzer is operated up to producing anode effect by normal method.Set about then by certain anode movement mode adding aluminum oxide at the same time to eliminate anode effect.

The result as shown in the following Table 1.Can illustrate that by table 1 compare by the inventive method gained result and alternate manner, obtained effect is very significant.

Table 1

The plant experiment result that the automatization anode effect is eliminated

The successful anode of the influenced elimination of method is imitated the flat every pond-Ri Yang of high-voltage

% should on average all the time polar effect be suitable for anode sum quantity

Time (S) voltage (S) is average

Apportioning cost (mV) *

All sun 389 295 75.8 402 180 28

Utmost point landing

One side anode voltage drop

Fall and the other side

Anode promotes 135 113 83.8 246 84 23

By the present invention

Accompanying drawing 1 mode 3 92 389 99.3 120 60 13

* the fate that does not comprise no anode effect in the mean value.

When making electrolyzer all anodes landing on one side, and all anodes of the other side are when promoting, and the problem of its generation is not only that to eliminate efficient low, and in 17% elimination running, the shell of center trace sinks in the electrolyzer.

Claims (12)

1, the method of terminating anode effects when in electrolyzer, producing aluminium, comprise salic fused electrolyte in this electrolyzer, and a plurality of carbon anodes, described anode is arranged in two vertical rows at least and forms the positive plate district with at least three horizontally-arrangeds, aluminum oxide is added in the ionogen, and with described different group anodes liftings or landing, the aluminum oxide that is added is scattered in the described ionogen, described method feature is, at least the anode that accounts for anode sum 25% is divided into adjacent group, and being positioned at the different positions of electrolyzer on vertically, each group comprises at least two anodes, but can not be more than 1/3rd of anode sum;

At least one group of described group, at first from the origin operation position in first movement in vertical direction;

All the other group anodes from the origin operation position with opposite movement in vertical direction; Wherein said one or more group anode is in described first movement in vertical direction, and described one or more group anodes are in described opposite movement in vertical direction, and presses vertically alternating motion mutually of electrolyzer;

Described anode is got back on its origin operation position, and

Described motion repeats or eliminates to be reversed until described anode effect.

2, by the method for claim 1, it is characterized in that each anode group comprises no more than six anodes.

3, by the method for claim 1, it is characterized in that each anode group comprises no more than four anodes.

4,, it is characterized in that described anode group forms 40% the group that accounts for the anode sum at least by the method for claim 1,2 or 3.

5, by each method of aforesaid right requirement, it is characterized in that described all anodes are divided into described rank.

6,, it is characterized in that described all groups move simultaneously by each method of aforesaid right requirement.

7,, it is characterized in that described anode group moves in order by each the method for claim 1-5.

8, by each method of aforesaid right requirement, it is characterized in that described aluminum oxide be substantially with described group setting in motion in add.

9,, it is characterized in that described aluminum oxide is adding described group setting in motion after by each method of claim 1-7.

10, by claim 1,2 or 3 method, it is characterized in that being divided into even horizontally-arranged anode, described anode is divided into and comprises four anodic groups and comprise six anodic groups, described each group is pressed electrolyzer and is vertically alternately arranged, and wherein said all comprise that four anodic groups begin to move upward in described first party, and described all comprise that six anodic groups move on described reverse direction.

11, by claim 1,2 or 3 method, it is characterized in that being divided into even horizontally-arranged anode, described anode is divided into two groups at the electrolyzer longitudinal end, and between described longitudinal end four groups, and wherein said two groups and alternately four groups begin to move upward in described first party, remaining four groups at first move upward in described second party.

12, by claim 1,2 or 3 method is characterized in that being divided into the horizontally-arranged anode of odd number, and anode is divided into and comprises one anode row, wherein electrolyzer end anode group and therebetween the alternative group begin in the motion of described first direction, and described second party of all the other each group beginnings move upward.