RU2448200C1 - Recovery method of exit gases from aluminium electrolysis unit - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: recovery method of exit gases from aluminium electrolysis unit equipped with gas-collecting bell hung along the perimetre of anode shell and connected to gas ducts of centralised gas removal system involves gas combustion in under-bell space of gas-collecting bell by air supply under gas-collecting bell and removal of exit gases. Removal of gases during operational treatments of electrolysis unit and anode effects is performed by creation of negative pressure in under-bell space by injection in the flow direction of exit gases in gas discharge connection pipes. Injectors are built into gas discharge connection pipes installed on longitudinal sides of gas-collecting bell. Compressed air is supplied under pressure of 1÷4 atm.

EFFECT: invention allows increasing negative pressure in under-bell space, operating efficiency of system of bell gas suction at operational treatments of electrolysis unit and anode effects.

2 cl, 3 dwg

Description

The invention relates to non-ferrous metallurgy, in particular to the production of aluminum by an electrolytic method, and can be used to remove exhaust gases from aluminum electrolytic cells with a self-burning anode.

The system of bell gas suction existing on electrolyzers with a self-burning anode and top current supply does not provide the required efficiency of collecting and evacuating gases coming from under the anode sole, especially during operational processing of the electrolyzer and during anode effects.

The efficiency of the bell gas exhaust pump currently in operation is, on average, 75-85%, which is not enough to achieve the maximum allowable emissions established for the Russian aluminum smelters. And during operating processing of the electrolyzer, the efficiency of the gas suction pump drops to 30-40%. With anode effects, intense release of surface active hydrocarbons (PAHs) occurs - (fluorene, phenanthrene, anthracene, fluorantene, pyrene, benz (a) anthracene, chrysene, benz (e) peren, benzo (e) fluorantene, benzo (k) fluoranten benz (a) pyrene, dibenz (a, h) anthracene, benzyl (g, h, i) pyrene, indeno (1,2,3-s, d) pyrene) from under the anode sole and knocking these gases out from under bell space in the working area of the cell.

In this regard, the search for technical solutions to improve the efficiency of the bell gas exhaust during operations on the electrolyzer and when anode effects occur is relevant.

A known method of afterburning of anode gases in a gas collection bell (HSC) of an aluminum electrolyzer. The gas exhaust system creates a constant vacuum in the combustion chamber. Gases from under the bell space constantly flow into the combustion chamber. The air is heated due to the heat lost by the surface of the anode, and enters the combustion chamber (ed. St. USSR No. 1023005, microliter C25C 3/22, 1983).

The disadvantage of this method is the impossibility of cleaning the combustion chamber of the gas collector from deposits of dust and resinous substances and reducing the service life of the gas collector. In addition, the known method does not allow to effectively remove the anode gases during operations and anode effects.

The closest in technical essence to the claimed method is a method of removing exhaust gases from an aluminum electrolyzer, including preliminary combustion under a gas collector by supplying additional air with alumina and afterburning of gas. Gas afterburning is carried out by additional supply of heated compressed air through the ejector to the burner device (RF patent No. 1702717, microliter C25C 3/12, 1996). In an aluminum electrolyzer, the gas collector is hung around the perimeter of the anode casing. The belt of the anode casing is equipped with a channel for supplying compressed air under the gas collector and an alumina feed chamber. The channel connects the compressed air network and with the ejector. Under the gas collector, air is simultaneously supplied with alumina in the ratio of the volume of air to the volume of electrolysis gases equal to 0.8-1 - 1.5-1. At the same time, preheated air is supplied to the burner device.

The disadvantage of the prototype method is that the supply of compressed air to the bell-shaped space will not allow creating a vacuum to prevent knocking out of the anode gases during operations and anode effects, as well as during partial depressurization of the gas collection bell. The proposed method does not allow effective removal of anode gases, because the supply of compressed air together with alumina to the podkolokolnoy space will lead to the intensification of dust formation, as a result of the gas ducts will be clogged with particles of alumina, and the removal of gases will not be effective even in the interoperation period.

The objective of the invention is to increase the efficiency of the system for removing gases from the cell during operational treatments of the cell and anode effects.

The technical result consists in increasing the amount of rarefaction in the podkolokolnom space of the gas collection bell of an aluminum electrolyzer.

The problem is solved in that in a method for capturing exhaust gases from an aluminum electrolysis cell equipped with a gas collection bell hung around the perimeter of the anode casing and connected to the gas ducts of a central gas removal system, including burning gas in a bell-shaped space by supplying air under the gas collecting bell and removing exhaust gas, according to the claimed invention, the removal of gases during the execution of operational treatments of the cell and anode effects is carried out by creating a discharge Nia Podkolokolny space in the direction of travel by the injection of exhaust gases in the hot gas flow nozzles mounted on the longitudinal sides of the gas-collection bell, via built injectors.

The injection is carried out at a pressure of 1 ÷ 4 atm.

The proposed method differs from the prototype in that the removal of exhaust gases from an aluminum electrolysis cell is carried out by increasing the vacuum in the bells by injecting a stream of exhaust gases. Injectors are mounted in the exhaust pipes, which allow to increase the vacuum under the HSC during operational treatments of the electrolyzer and anode effects.

Neither from the patent nor from the scientific and technical literature is it known to use these distinguishing features in order to increase the efficiency of removal of anode gases during surgical treatments of the electrolyzer and anode effects.

This allows us to conclude that the proposed technical solution meets the criteria of "novelty" and "significant differences".

The method of gas removal is illustrated by drawings, where figure 1 shows a General view of the gas removal system of an aluminum electrolyzer; figure 2 shows a sketch of the insertion of the injector into the exhaust pipe; figure 3 shows a rarefaction diagram showing the distribution of the vacuum under the HSC at a pressure value of compressed air P = 1 ATM.

A system for removing gases from an aluminum electrolyzer (FIG. 1) includes a gas collection bell 1, gas ducts 2 and injectors 3 mounted on gas outlet pipes 4 (FIG. 2).

The invention consists in the following.

Compressed air is supplied through pressure injectors through injectors integrated in the gas outlet pipes and directed along the axis of the pipes in the direction of movement of the gas stream. As a result, under the action of a stream of compressed air, the discharge of the gas stream increases. Energy is transferred from one stream to another by turbulent mixing.

The invention is as follows.

In the process of operation of the aluminum electrolysis cell, anode gases are released, which enter the bell of the gas collecting bell of the electrolyzer, are burned and removed through the gas ducts under the influence of the vacuum created by the smoke exhausts of the gas treatment plants. When performing operational work, the gas collection bell is depressurized. To prevent knocking out of the anode gases into the housing in the podkolokolnoy space, the vacuum increases by supplying compressed air under pressure to the exhaust pipes through the injectors.

To confirm the increase in rarefaction in the annular space by means of a directed supply of compressed air to the exhaust system, a series of calculations of the current design of the exhaust system by the present method was carried out.

The results of mathematical modeling performed in the StarCD program showed that when the pressure of compressed air P = 1 ÷ 4 atm supplied to the injectors, the pressure in the gas collection bell of the electrolyzer increases by 1.5-2.7 times, reaching P = - 25 Pa (figure 3).

Claims (2)

1. The method of trapping exhaust gas from an aluminum electrolysis cell equipped with a gas collection bell hung around the perimeter of the anode casing and connected to the gas ducts of the central gas removal system, including burning gas in the under-bell space by supplying air under the gas collection bell and removing the exhaust gas, characterized in that the exhaust gas is carried out by creating a vacuum in the podkolokolnogo space by injection in the direction of movement of the exhaust gas flow in the exhaust bkah installed on the longitudinal sides of the gas collection bells, through the built-injectors. 2. The method according to claim 1, characterized in that the injection is carried out at a pressure of 1 ÷ 4 atm.

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