RU2294406C1 - Anode gases effectively after-burning apparatus to aluminum cell - Google Patents

Abstract

FIELD: electrolytic production of aluminum in cells with self-firing anode, namely anode gases after-burning apparatuses.

SUBSTANCE: apparatus for after-burning anode gases of aluminum cell includes torch with counter-current heat exchanger and gas duct system. Torch has upper cylindrical and lower cone portions. Torch is mounted with gap on inner surface of cup arranged on lug of gas collecting bell for forming pre-combustion chamber between lower portion of said cup and torch. Lower edge of torch has triangular teeth. Counter-current heat exchanger is mounted on outer surface of cup.

EFFECT: improved efficiency of thermal neutralizing of anode gas due to enhanced quality of mixing anode gas and heated air, highly stable operation of torch at minimal degree of maintenance.

2 cl, 1 dwg, 1 tbl

Description

The invention relates to the electrolytic production of aluminum in electrolytic cells with a self-baking anode, in particular to devices for afterburning anode gases.

In the electrolytic production of aluminum in electrolyzers with a self-burning anode, anode gases are formed containing toxic tarry substances and carbon monoxide. The neutralization of the components of the anode gases is carried out in burner devices.

A device is known for afterburning the anode gases of an aluminum electrolyzer, including a burner with slots installed on a gas collecting bell tide, a direct-flow heat exchanger for heating air and reducing heat losses of the burner body, and a gas duct system [patent RU No. 2104337, IPC C 25 C 3/22, BI No. 4 , 1998]. The presence of a heat exchanger makes it possible to heat air with heat from the lower part of the burner body and reduce heat loss by radiation through openings for air intake. However, the direct-flow heat exchanger does not insulate the top of the burner. In addition, the mixture of anode gases and heated air is not intense enough, and dust and soot emissions from the air inlet openings clog the gap between the heat exchanger and the burner body, obstructing the movement of air, thereby creating the need for frequent burner cleanings.

Closest to the proposed invention in terms of the set of essential features and the achieved result is a device comprising a burner with countercurrent heat exchanger mounted on a gas collecting bell tide and a gas duct system [USSR author's certificate No. 783368, IPC С 25 С 3/22, 1980]. The burner is made in the form of a pipe, vertically mounted inside a large diameter pipe, acting as a counterflow heat exchanger. A washer with openings for air intake is freely mounted on the end of the pipe. A hatch for cleaning the burner is made in the middle part of the pipe.

The disadvantage of this device is the remoteness of the lower cut of the burner body from the landing ring of the tidal section of the gas collection bell. As a result, the anode gases are cooled before mixing with heated air. 30% of the height of the heat exchanger is not used for air heating. The mixing of air with the anode gas is not effective enough, because it occurs only on the lower edge of the burner. The hatch for cleaning the burner from dust deposits is leaky, as made on the lateral cylindrical surface of the heat exchanger, as a result of which suction of cold air is possible. Finally, the suspension of the combustion chamber on the flange of the duct during long-term operation leads to its deviation from the vertical axis and, as a result, to a deterioration of heat transfer processes and the effectiveness of thermal neutralization.

The objective of the invention is to develop a device for afterburning the anode gases of an aluminum electrolyzer, which improves the efficiency of thermal neutralization of the anode gas by improving the quality of mixing of the anode gas and heated air. Another objective is to increase the stability of the burner with a minimum of maintenance.

The achievement of the above task is ensured by the fact that in the inventive device for afterburning the anode gases of an aluminum electrolyzer, including a gas collection bell, a burner with a counter-flow heat exchanger and a gas duct system, according to the invention, a bowl is mounted on the tide of the gas collection bell with the formation of a prechamber between the bowl and the lower part of the burner body. The burner is made of upper cylindrical and lower conical parts and is fixed with a gap on the inner surface of the bowl. The lower edge of the burner is gear. The counterflow heat exchanger is fixed on the outer surface of the bowl.

The invention complements a particular distinguishing feature, also aimed at solving the tasks.

The lower edge of the burner is made in the form of triangles.

In relation to the prototype of the proposed device has the following distinctive features. The burner and heat exchanger rest on the bottom of the bowl mounted on the tide of the gas collection bell. In this case, a prechamber is formed between the lower part of the burner body and the bowl, which intensifies the process of mixing the anode gas and heated air and the combustion of the mixture inside the burner. The heated air flow between the teeth of the lower edge of the burner is as close as possible to the flow of hot anode gas exiting from the bore hole of the corner section.

Between the distinguishing features and the object of the invention there is the following connection. Air in countercurrent movement in the annular gap of the heat exchanger enters the prechamber, where it is additionally heated, partially mixed with the anode gas and ignited, while the combustion process in the burner volume is intensified. Due to the supply of heated air between the teeth of the lower edge of the burner, the combustion zone is as close as possible to its base, which increases the stability of the device, the efficiency of the burning of CO and resinous substances.

The developed gear surface of the lower edge of the burner allows you to split the flow of gas and air, intensifying the process of mixing and sustainable combustion. The narrowed conical shape of the lower part of the burner provides high speeds of the jets of the gas-air flow entering the burner, which turbulizes the flow and improves the quality of mixing.

The burnup efficiency of the combustible components of the anode gas is also increased due to the fact that carbon particles that do not fall into the stream of flue gases removed from the burner hit the end cover of the burner, settle in the stream and are re-burned.

The drawing shows a device for afterburning the anode gases of an aluminum electrolyzer. The device includes a burner, consisting of an upper cylindrical 1 and lower conical 2 parts with a serrated lower edge in the form of triangles with gaps 3, for supplying heated air. The burner is supported by tides 4 with a gap on the inner surface of the bowl 5. The bowl 5 is mounted on the tide of the gas collection bell 6. The heat exchanger 7 covers the burner with a gap and rests on the bottom of the bowl 5 from the outside. Between the conical lower part of the burner 2 and the bowl 5 there is a prechamber in the form of a gap 8. In the bowl there is a hatch 9 closed by an inclined pivoting cover 10. The horizontal nozzle of the burner for removing flue gases 11 is connected to the exhaust system 12.

The device operates as follows. Anode gases enter the conical part of burner 2. The air required for combustion is supplied countercurrently from above through the gap between the cylindrical part of burner 1 and the heat exchanger 7. The air is heated by contact with the surface of the burner and dispersed into the conical part of burner 2 through toothed gaps of the lower edge in the form triangles 3. Part of the heated air is mixed with the anode gas in the prechamber 8, the mixture ignites, intensifying the process of heat transfer, combustion inside the burner and burning out harmful substances ulation anode gas. The heat exchanger 7 is simultaneously a screen that reduces heat loss by the radiation of the burner. Preheating the air and shielding the burner increase the temperature level in the burner, which also helps to increase the efficiency of thermal neutralization of the harmful components of the anode gas. To enable cleaning of the inner surface of the burner, the bowl 5 is equipped with a sealed hatch 9 with an inclined pivoting lid 10. The stability of the burner and the efficiency of burning out harmful impurities are increased due to the possibility of cleaning the burner through a sealed hatch, which is necessary in conditions of high dusty gas flow when the baths are automatically fed with alumina .

The results of pilot industrial thermotechnical tests conducted at the Krasnoyarsk aluminum smelter showed the advantage of the proposed device compared to the prototype. The test results are presented in the table.

Test results for half-link burners Parameters of afterburning of the anode gas in the combined gas duct Prototype The inventive device Temperature ° C 144 132 Mass flow, kg / h: Carbon monoxide 31.71 9.27 Resinous substances 0.87 0,07 Benz (a) pyrene 0.0058 0,0006

Compared with the prototype, the claimed device according to the data of pilot tests allows to reduce the content of CO in the products of afterburning of the anode gas by 3.4 times, and resinous substances and benzo (a) pyrene by about 10 times.

Claims (2)

1. A device for afterburning the anode gases of an aluminum electrolyzer, including a gas collection bell, a burner with a counterflow heat exchanger and a gas duct system, characterized in that it is equipped with a bowl mounted on the gas collecting bell rush to form a pre-chamber between the bowl and the lower part of the burner body in the form of a gap, burner consists of an upper cylindrical and lower conical parts, which is made with a serrated lower edge, and is fixed on the inner surface of the bowl, and the counter-current heat exchanger covers Azores burner and simply supported at the bottom of the cup from the outside. 2. The device according to claim 1, characterized in that the lower gear edge of the burner is made in the form of triangles.