Tail gas treatment and waste heat recovery device for electrolytic aluminum process

Abstract

The utility model discloses a tail gas treatment and waste heat recovery device for an electrolytic aluminum process, which comprises a cleaning chamber which comprises an electrolytic aluminum flue gas heat exchanger, a heat exchanger outlet flue, a gravity chamber, a stock bin, a gas purification chamber, a dust remover, an ash bucket, a discharge pipe, a discharge ball valve, a cage ladder stand and a fan. The utility model belongs to the technical field of waste gas treatment and waste heat recovery in the aluminum electrolysis industry, and achieves the technical effects that the device is simple in structure, convenient to install and capable of controlling the temperature of a gas purification unit, so that the temperature control effect of the whole system is good; the flue gas waste heat recovery device has the advantages that the waste heat of the flue gas is recovered, the recovery efficiency is high, the cooled flue gas is not easy to damage the purification chamber, the pressure entering different purification chambers can be well balanced, the purification system is stabilized, powder blockage and scaling are not easy to occur, the mounting is convenient, the occupied area is small, the purification absorption rate is greatly improved, and the discharged flue gas stably reaches the national emission standard.

Description

Technical Field

[0001] The utility model relates to the technical field of waste gas treatment and waste heat recovery in the aluminum electrolysis industry, and particularly relates to a device for treating tail gas and recovering waste heat in the electrolytic aluminum process. Background Art

[0002] The flue gas discharged from the electrolytic cell mainly contains fluorine, sulfur dioxide and dust. According to the principle of toxicant toxicity grading in the current national standard of China, "Classification of the Degree of Hazard of Occupational Exposure to Toxicants", fluoride is of grade II and belongs to highly hazardous substances. Therefore, reducing and preventing the harm of hydrogen fluoride gas and dust generated in the aluminum electrolysis production process to humans and nature, and realizing the harmonious development of economy and nature have become the key problems to be solved in the waste gas treatment of the aluminum electrolysis industry.

[0003] The new "Emission Standards for Pollutants in the Aluminum Industry" stipulates the emission limits for aluminum electrolysis waste gas as follows:

[0004]

[0005] The tail gas of the electrolytic aluminum process is introduced into the flue gas purification system through a gas collection device to remove fluorine and dust, and then discharged through a chimney. The uncollected flue gas is discharged to the roof skylight of the electrolysis workshop. A dust separation facility is installed at the skylight, and a gas collecting pipe is installed at the upper part to collect the escaping gas again. The uncollected part of the flue gas is discharged without organization through the skylight. The gas collection efficiency of the electrolytic cell gas hood determines the total emission of fluorides. In actual production, the factors affecting the gas collection efficiency of the electrolytic cell include: the process operation control of the electrolytic cell, the structural design of the gas hood, the process design of the purification system, the operation performance of the purification system, etc., that is, all aspects of the aluminum electrolysis flue gas purification system. Therefore, if the good operation of all aspects of the aluminum electrolysis flue gas purification system cannot be strictly ensured, it is difficult to achieve the efficient and stable operation result with a gas collection efficiency of over 98%, and the emission of fluorides will seriously exceed the standard.

[0006] Among them, the temperature of the flue gas entering the gas treatment center plays an important role in determining the washing efficiency of the gas treatment center. When the temperature of the kiln gas exceeds 115 °C, the fluoride emissions in the chimney of the gas treatment center increase. For smelters located in hot climate conditions, this is always a major challenge. The hydrogen fluoride emission level in the gas treatment center is closely related to the temperature of the kiln gas. Above the temperature level of 110 - 115 °C, the hydrogen fluoride emissions increase sharply, and may double for every 10 °C increase.

[0007] The flue gas is cooled by diluting it with ambient temperature air upstream of the gas purification device. The thermal energy of the flue gas from electrolytic aluminum production has not been utilized on a large scale yet. For the treatment of flue gas from aluminum electrolysis cells, dry purification technology is adopted. This method uses a gas hood installed above the electrolysis cell to capture the flue gas and send it into the purification facility. In the purification facility, alumina, the raw material for electrolysis, is used to adsorb hydrogen fluoride in the flue gas. Then, a bag filter is used to achieve gas-solid separation, so as to purify the flue gas and remove gaseous and solid fluorides simultaneously. The purified clean flue gas is discharged into the atmosphere through a chimney. The alumina after adsorbing fluorine is returned to the electrolysis cell as a raw material for electrolytic production. The fluorine adsorbed by the alumina replenishes the fluoride electrolyte required in the electrolysis process, without generating waste or secondary pollution, and effectively recovering and utilizing fluorides. To improve the adsorption efficiency of alumina for hydrogen fluoride, a part of the fluorinated alumina is returned to the purification system for reuse before entering the production raw material conveying system.

[0008] Currently, the process with significant advantages is the new two-stage countercurrent dry purification. However, the devices with this process flow on the market still have the following technical problems:

[0009] Due to the presence of particulate matter and corrosive gases in the tail gas, especially a hard layer will form on the surface of the heat exchanger due to particulate deposition, condensation of corrosive acids, and scaling reactions;

[0010] Due to various reasons, the heat utilization rate is low during the heat recovery of the flue gas;

[0011] The resistance of the tail gas pipeline cannot be well balanced;

[0012] There is air leakage in the tail gas pipeline, and cryolite (sodium hexafluoroaluminate) and dust accumulate inside the device;

[0013] It fails to consider maintaining the stable operation of the electrolysis cell during the unsteady operation process of the electrolysis cell;

[0014] Temperature control of the tail gas entering the treatment system;

[0015] In hot climate conditions, it has a great impact on fluoride emissions. Utility Model Content

[0016] Therefore, the present utility model provides a device for treating tail gas and recovering waste heat in the electrolytic aluminum process to solve the above problems in the prior art.

[0017] To achieve the above purpose, the present utility model provides the following technical solutions:

[0018] According to the first aspect of the present utility model, a device for treating tail gas and recovering waste heat in the electrolytic aluminum process includes:

[0019] Cleaning room, comprising: electrolytic aluminum flue gas heat exchanger, heat exchanger outlet flue, gravity chamber, silo, clean gas chamber, dust collector, ash hopper, discharge pipe, discharge ball valve, protective cage ladder, fan, wherein:

[0020] The tube box of the electrolytic aluminum flue gas heat exchanger is vertically connected to one end of the heat exchanger outlet flue, the heat exchanger outlet flue is vertically connected to one side of the gravity chamber, the gravity chamber is vertically connected to one side of the silo, and the heat exchange tubes arranged inside the electrolytic aluminum flue gas heat exchanger are vertically connected to the internal space of the heat exchanger outlet flue and the gravity chamber;

[0021] The gravity chamber is horizontally connected to the ash hopper, the flue gas is connected to the upper notch of the ash hopper through the gravity chamber, part of the alumina powder passes through the lower notch of the gravity chamber and the ash hopper, and most of the powder flows out through the lower end outlet of the ash hopper;

[0022] The ash hopper is vertically connected to the dust collector, the dust collector is vertically connected to the clean gas chamber, and the internal space of the ash hopper, the dust collector and the clean gas chamber is vertically connected; the purified flue gas is extracted by the fan, the fan is installed on the upper part of the silo, the silo and the gravity chamber are vertically installed, and the internal parts of the silo and the gravity chamber are not connected;

[0023] The silo is connected to the dust collector through a discharge pipe, and a discharge ball valve is installed on the discharge pipe.

[0024] Furthermore, pleated filter bags are installed inside the dust collector, and a perforated plate is welded to one side of the dust collector.

[0025] Furthermore, the pleated filter bags are arranged in parallel and welded and fixed to one side of the perforated plate.

[0026] Furthermore, the cleaning room is provided with an inlet and a first inlet manifold for dividing the main raw material gas flow flowing through it into a plurality of separate sub-raw material gas flows before reaching the inlet of the cleaning room.

[0027] Furthermore, each of the electrolytic aluminum flue gas heat exchangers is located downstream of the first inlet manifold and is used for exchanging heat with the corresponding part of the original gas flow entering the corresponding cleaning room.

[0028] The utility model has the following advantages:

[0029] The utility model has the advantages of simple structure, convenient installation, controllability of the temperature of the gas purification unit, good temperature control effect of the overall system; high heat recovery efficiency for the flue gas, the cooled flue gas is not easy to damage the purification chamber, can well balance the pressure entering different purification chambers, stabilize the purification system, not easy to block powder and scale, convenient installation, small floor area, greatly improved purification absorption rate, and the discharged flue gas stably meets the national emission standards. Description of the Drawings

[0030] Figure 1System diagram of the device for electrolytic aluminum process tail gas treatment and waste heat recovery provided by the present utility model.

[0031] Figure 2 Front view of the device for electrolytic aluminum process tail gas treatment and waste heat recovery provided by the present utility model.

[0032] Figure 3 Front view of the electrolytic aluminum flue gas heat exchanger of the device for electrolytic aluminum process tail gas treatment and waste heat recovery provided by some embodiments of the present utility model.

[0033] Figure 4 Operation flow chart of the device for electrolytic aluminum process tail gas treatment and waste heat recovery provided by the present utility model.

[0034] In the figure: 1, support; 2, electrolytic aluminum flue gas heat exchanger; 3, heat exchanger outlet flue; 4, gravity chamber; 5, silo; 6, first top railing; 7, second top railing; 8, clean gas chamber; 9, perforated plate; 10, corrugated cloth bag; 11, dust collector; 12, ash hopper; 13, discharge pipe; 14, discharge ball valve; 15, cage ladder; 16, fan; 17, heat exchange tube; 18, first inlet and outlet; 19, first tube sheet; 20, heat exchanger housing; 21, second inlet and outlet; 22, second tube sheet; 23, blowdown port; 24, first inlet manifold; 25, second inlet manifold; 26, outlet manifold; 27, gas cleaning chamber; 28, output air damper. Detailed implementation manners

[0035] The following specific embodiments illustrate the implementation manners of the present utility model. Those skilled in the art can easily understand other advantages and effects of the present utility model from the content disclosed in this specification. Obviously, the described embodiments are some, but not all, of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0036] As Figures 1 to 4 shown, a device for electrolytic aluminum process tail gas treatment and waste heat recovery in the first aspect embodiment of the present utility model includes a plurality of cleaning chambers 27a-c. The flue gas passes through the first inlet manifold 24, is distributed into the second inlet manifolds 25a-c of the electrolytic aluminum flue gas heat exchanger 2, flows through a plurality of electrolytic aluminum flue gas heat exchangers 2a-c. Each electrolytic aluminum flue gas heat exchanger 2a-c is located downstream of the inlet manifold 24 and is used to exchange heat with a part of the original air flow entering the corresponding cleaning chambers 27a-c. It is extracted by the fan 16 through the output air dampers 28a-c of the cleaning chamber 27 and converges to the outlet manifold 26 for discharge, as Figure 1 shown.

[0037] As Figure 2As shown in the figure, a single clean room 27 includes a support 1, an electrolytic aluminum flue gas heat exchanger 2, a heat exchanger outlet flue 3, a gravity chamber 4, a silo 5, a first top railing 6, a second top railing 7, a clean gas chamber 8, a dust collector 11, a hopper 12, a discharge pipe 13, a discharge ball valve 14, a cage ladder 15, and a fan 16.

[0038] As Figure 3 shown, the electrolytic aluminum flue gas heat exchanger 2 is provided with multiple groups of heat exchange tubes 17 arranged in parallel. The heat exchange tubes 17 are conical pit heat exchange tubes. The formed tube bundle is vertically welded and fixed by a first tube sheet 19 and a second tube sheet 22. The first tube sheet 19 and the second tube sheet 22 separate the fluid in the heat exchanger housing 20 from the flue gas in the heat exchange tubes 17. The first tube sheet 19, the second tube sheet 22 and the housing 20 are welded and fixed. The housing 20 is provided with a first inlet / outlet 18, a second inlet / outlet 21 for the cooling fluid and a blowdown port 23.

[0039] The tube box of the electrolytic aluminum flue gas heat exchanger 2 is vertically welded and connected to the heat exchanger outlet flue 3. The heat exchanger outlet flue 3 is vertically welded and connected to the gravity chamber 4. The gravity chamber 4 is vertically welded and connected to the silo 5, so that the internal spaces of the heat exchange tubes 17 in the electrolytic aluminum flue gas heat exchanger 2, the heat exchanger outlet flue 3 and the gravity chamber 4 are vertically connected. The gravity chamber 4 is horizontally welded and connected to the hopper 12. The flue gas is connected through the upper notch of the gravity chamber 4 and the hopper 12. Part of the alumina powder passes through the lower notch of the gravity chamber 4 and the hopper 12, and most of the powder flows out through the lower end outlet of the hopper 12. The hopper 12 is vertically welded and connected to the dust collector 11. The dust collector 11 is vertically welded and connected to the clean gas chamber 8, so that the internal spaces of the hopper 12, the dust collector 11 and the clean gas chamber 8 are vertically connected. Thus, the flue gas of the entire device is connected together, and the purified flue gas is extracted by the fan 16. The fan 16 is installed on the upper part of the silo 5. The silo 5 is vertically welded and installed with the gravity chamber 4, but they are not internally connected. The silo 5 is connected to the dust collector 11 through the discharge pipe 13, and a discharge ball valve 14 is installed on the discharge pipe 13. The dust collector 11 is equipped with corrugated filter bags 10. The corrugated filter bags 10 are arranged in parallel and welded and fixed to the flower plate 9. The flower plate 9 is welded to the cylinder body of the dust collector 11. The flue gas enters the clean gas chamber 8 through the corrugated filter bags 10. The overall device is supported and fixed by the support 1. The top space of the device is provided with a first top railing 6 and a second top railing 7.

[0040] The waste heat and catalyst recovery equipment system for electrolytic aluminum includes multiple cleaning chambers 27 and multiple electrolytic aluminum flue gas heat exchangers 2. Each cleaning chamber 27 is provided with an inlet, and a first inlet manifold 24 for dividing the main raw material gas flow passing through it into multiple separate sub-raw material gas flows before flowing to the inlet of the cleaning chamber 27. Each electrolytic aluminum flue gas heat exchanger 2 is located downstream of the first inlet manifold 24 and is used to exchange heat with the corresponding part of the original gas flow entering the corresponding cleaning chamber 27. Each electrolytic aluminum flue gas heat exchanger 2 has a certain pressure drop, which can make the main raw material gas flow more evenly shared among the cleaning chambers 27; the pressure drop across the electrolytic aluminum flue gas heat exchanger 2 compensates to a certain extent for any changes in the pressure drop across the individual cleaning chambers 27 relative to other cleaning chambers 27, which makes the gas purification process more stable and reliable and avoids damage to the cleaning chambers 27.

[0041] Each electrolytic aluminum flue gas heat exchanger 2 is arranged to directly discharge the unpurified gas into the inlet in the corresponding clean gas chamber 8. Therefore, due to the pressure drop across each electrolytic aluminum flue gas heat exchanger 2, the gas velocity distribution across the entire outlet area of the electrolytic aluminum flue gas heat exchanger 2 tends to be uniform, so a more uniform spatial distribution of the flow of each individual split original gas flow entering the corresponding clean gas chamber 8 can be obtained.

[0042] Each electrolytic aluminum flue gas heat exchanger 2 is composed of multiple groups of cone-pit heat exchange tubes arranged in parallel and spaced apart, which can achieve high efficiency and low resistance, can slow down the ash accumulation and scaling inside and outside the tubes and can effectively reduce wear; thus obtaining a low degree of scaling and improving the waste heat recovery efficiency of the flue gas. In addition, the unpurified gas heat exchange cooling tubes are vertically erected; so there are fewer dead corners formed near any horizontal surface where dust may accumulate. In addition, the flue gas temperature is reduced below the maximum temperature rating of the filter bag, thereby increasing the absorption rate of fluorides in the electrolytic aluminum flue gas and enabling the flue gas to stably meet the national flue gas emission standards.

[0043] The utility model has the advantages of simple structure, convenient installation, can control the temperature of the gas purification unit, and has a good overall system temperature control effect. The waste heat of the flue gas is recovered with high efficiency, and the cooled flue gas is not easy to damage the cleaning chamber 27, can well balance the pressure entering different cleaning chambers 27, stabilize the purification system, is not easy to block powder and scale, is convenient to install, has a small floor area, greatly improves the purification absorption rate, and the discharged flue gas stably meets the national emission standards.

Claims

1. An apparatus for treating tail gas and recovering waste heat in an electrolytic aluminum process, characterized in that, Comprising: A clean room (27), which includes: an electrolytic aluminum flue gas heat exchanger (2), a heat exchanger outlet flue (3), a gravity chamber (4), a bin (5), a clean gas chamber (8), a dust collector (11), a hopper (12), a discharge pipe (13), a discharge ball valve (14), a cage ladder (15), a fan (16), wherein: The tube box of the electrolytic aluminum flue gas heat exchanger (2) is vertically connected to one end of the heat exchanger outlet flue (3), the heat exchanger outlet flue (3) is vertically connected to one side of the gravity chamber (4), the gravity chamber (4) is vertically connected to one side of the bin (5), and the heat exchange tubes (17) arranged inside the electrolytic aluminum flue gas heat exchanger (2) are vertically communicated with the internal spaces of the heat exchanger outlet flue (3) and the gravity chamber (4); The gravity chamber (4) is horizontally connected to the hopper (12) transversely, the flue gas is communicated through the upper notch of the gravity chamber (4) and the hopper (12), part of the alumina powder passes through the lower notch of the gravity chamber (4) and the hopper (12), and most of the powder flows out through the lower end outlet of the hopper (12); The hopper (12) is vertically connected to the dust collector (11), the dust collector (11) is vertically connected to the clean gas chamber (8), and the internal spaces of the hopper (12), the dust collector (11) and the clean gas chamber (8) are vertically communicated; the purified flue gas is extracted by the fan (16), the fan (16) is installed on the upper part of the bin (5), the bin (5) and the gravity chamber (4) are vertically installed, and the internal spaces of the bin (5) and the gravity chamber (4) are not communicated; The bin (5) is connected to the dust collector (11) through the discharge pipe (13), and the discharge ball valve (14) is installed on the discharge pipe (13).

2. The device for treating tail gas and recovering waste heat in an electrolytic aluminum process according to claim 1, characterized in that, The dust collector (11) is equipped with corrugated filter bags (10), and a perforated plate (9) is welded to one side of the dust collector (11).

3. The device for electrolytic aluminum process tail gas treatment and waste heat recovery according to claim 2, characterized in that, The corrugated filter bags (10) are welded and fixed in parallel on one side of the perforated plate (9).

4. The device for treating tail gas and recovering waste heat in an electrolytic aluminum process according to claim 1, characterized in that, The clean room (27) is provided with an inlet, a first inlet manifold (24) for dividing the main raw material gas flow flowing through it into a plurality of separate sub-raw material gas flows before reaching the inlet of the clean room (27).

5. The device for electrolytic aluminum process tail gas treatment and waste heat recovery according to claim 4, characterized in that, Each of the electrolytic aluminum flue gas heat exchangers (2) is located downstream of the first inlet manifold (24) for exchanging heat with the corresponding part of the raw gas flow entering the corresponding clean room (27).

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