Technical method and mixer for roasting aluminum electrolysis anode by using natural gas and hydrogen mixed fuel

Abstract

The invention provides a technical method for using natural gas and hydrogen mixed fuel for aluminum electrolysis anode roasting and a mixer, and belongs to the technical field of anode roasting. The invention relates to the technical field of natural gas mixing. According to the method, hydrogen in a certain proportion is mixed into natural gas through the mixer, the mixed gas serves as fuel to roast the aluminum electrolysis anode green block, the production process requirement is met, and the curve is matched with an original roasting temperature rise curve. According to the method, carbon emission in the production process can be reduced, climate changes can be coped, the combustion efficiency of natural gas can be improved, and energy waste in the production process is reduced. And the compression strength and the specific resistance of the aluminum electrolysis prebaked anode prepared from the fuel are equivalent to those of an aluminum electrolysis prebaked anode obtained by calcining natural gas.

Description

Technical Field

[0001] The invention relates to the technical field of anode baking, and in particular to a technical method for using a mixed fuel of natural gas and hydrogen for aluminum electrolysis anode baking. Background Art

[0002] In the production process of aluminum electrolytic anodes, natural gas (mainly methane) is used to roast the green blocks for a long time to meet the performance requirements of electrolytic production. However, a large amount of greenhouse gas CO2 is generated during the combustion process, which requires a large investment to capture. If not properly handled, it will cause environmental pollution. At the same time, the lean combustion limit of natural gas is relatively narrow. In the case of a lean mixture, it may not be able to burn stably, affecting the combustion efficiency, and a small amount of unburned fuel will be discharged, resulting in a waste of resources.

[0003] As a highly potential energy source, hydrogen has the advantages of being clean, environmentally friendly, and efficient. At the same time, hydrogen has a wider ignition limit and lean combustion limit, and the explosion limit is 4.0% to 75.6% (volume concentration), which means that if the volume concentration of hydrogen in the air is within this range, it may explode when encountering a fire source. Therefore, it is rarely used in the industrial field, especially in the production process of prebaked anodes for electrolytic aluminum. If hydrogen is used in the industrial field through corresponding technical research and development, compared with traditional natural gas combustion, it can reduce carbon emissions generated during natural gas combustion to a certain extent, thereby achieving green production and sustainable development.

[0004] Traditional aluminum electrolysis green anode roasting uses natural gas combustion to provide heat, which has the disadvantages of high production cost, incomplete fuel combustion, and large CO2 emissions. Reducing the CO2 pollution generated when roasting anodes with natural gas, and the problem that the current natural gas roasting process cannot burn stably due to the relatively narrow lean combustion limit, affecting the combustion efficiency and causing waste of resources are the main technical problems to be solved. Summary of the invention

[0005] In view of this, the present invention provides a technical method for using a mixed fuel of natural gas and hydrogen for roasting aluminum electrolytic anodes. The method of the present invention mixes a certain proportion of hydrogen into natural gas through a mixer, and the mixed gas is used as fuel to roast aluminum electrolytic anode green blocks. This can not only reduce carbon emissions in the production process and help address climate change, but also improve the combustion efficiency of natural gas and reduce energy waste in the production process.

[0006] The technical method of using natural gas and hydrogen mixed fuel for aluminum electrolysis anode baking in the present invention comprises the following steps:

[0007] S1: mixing hydrogen and natural gas to obtain a mixed gas;

[0008] S2: using the mixed gas to bake the raw anode for aluminum electrolysis to obtain a prebaked anode for aluminum electrolysis;

[0009] In the mixed gas in step S1, the volume ratio of hydrogen is 5-20%.

[0010] Preferably, the temperature of the hydrogen in step S1 is ≤28°C.

[0011] Preferably, the preparation method of the aluminum electrolytic raw anode in step S2 is: 70-75% of calcined coke, 10-15% of residual anode, and 12-18% of modified asphalt are mixed, and then pressed and molded at 150° C. and 10-15 MPa to obtain the aluminum electrolytic raw anode.

[0012] Preferably, the roasting in step S2 comprises the following steps:

[0013] S2-1: heating the aluminum electrolytic anode to 270-690°C at a heating rate of 8-15°C / h;

[0014] S2-2: heating to 880-1080°C at a heating rate of 5-10°C / h;

[0015] S2-3: Heat to 1160±5℃ at a rate of 5-10℃ / h and keep warm for 28h.

[0016] Another object of the present invention is to provide a mixer for the natural gas and hydrogen mixed fuel, comprising a natural gas inlet (1), a hydrogen inlet (2), a natural gas pressure reducing valve (4), a natural gas flow meter (5), a gas mixer (6), a chromatograph (7), a mixed gas outlet (8), a hydrogen pressure reducing valve (9), a hydrogen flow meter (10) and a mixed gas flow meter (11);

[0017] The natural gas inlet (1) is connected to the natural gas pressure reducing valve (4) via a valve (3), and then enters the gas mixer (6) via a natural gas flow meter (5);

[0018] The hydrogen inlet (2) is connected to the hydrogen pressure reducing valve (9) via a valve (12), and then enters the gas mixer (6) via a hydrogen flow meter (10);

[0019] The gas mixer (6) is connected to the chromatographic analyzer (7) via a mixed gas flow meter (11); the chromatographic analyzer (7) is connected to the mixed gas outlet (8) via a valve (13).

[0020] Preferably, the natural gas pressure reducing valve (4) adjusts the natural gas pressure to 0.08-0.1 MPa.

[0021] Preferably, the hydrogen pressure reducing valve (9) adjusts the hydrogen pressure to 0.08-0.012 MPa.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention mixes a certain proportion of hydrogen into natural gas through a mixer, and the mixed gas is used as fuel to bake the aluminum electrolysis anode green blocks, which meets the production process requirements and is consistent with the original baking temperature rise curve. This method can not only reduce carbon emissions in the production process and help to cope with climate change, but also improve the combustion efficiency of natural gas and reduce energy waste in the production process. The compressive strength and resistivity of the aluminum electrolysis prebaked anode prepared using the fuel are comparable to those of the aluminum electrolysis prebaked anode obtained by calcining natural gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic structural diagram of a mixer for the natural gas and hydrogen mixed fuel of the present invention;

[0025] In the figure, 1 is the natural gas inlet, 3 is the valve, 2 is the hydrogen inlet, 4 is the natural gas pressure reducing valve, 5 is the natural gas flow meter, 6 is the gas mixer, 7 is the chromatograph, 8 is the mixed gas outlet, 9 is the hydrogen pressure reducing valve, 10 is the hydrogen flow meter, 11 is the mixed gas flow meter, 12 is the valve, and 13 is the valve. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the embodiments.

[0027] The present invention provides a technical method for using a mixed fuel of natural gas and hydrogen for aluminum electrolysis anode baking, the steps of which are as follows:

[0028] S1: mixing hydrogen and natural gas to obtain a mixed gas;

[0029] S2: using the mixed gas to bake the raw anode for aluminum electrolysis to obtain a prebaked anode for aluminum electrolysis;

[0030] In the mixed gas in step S1, the volume ratio of hydrogen is 5-20%.

[0031] Preferably, the temperature of the hydrogen in step S1 is ≤28°C.

[0032] Preferably, the preparation method of the aluminum electrolytic raw anode in step S2 is: 72% of calcined coke, 12.5% ​​of residual anode, and 15.5% of modified asphalt are mixed, and then pressed and molded at 150° C. and 13 MPa to obtain the aluminum electrolytic raw anode;

[0033] In a specific embodiment of the present invention, the electrolyte crust on the surface of the buttom is removed by conventional methods, and then the buttom particles with a particle size of 1.2-8 mm are obtained by crushing and screening, and then mixed with calcined coke and modified asphalt;

[0034] In a specific embodiment of the present invention, the modified asphalt is conventionally purchased on the market and meets the requirements of the YB / T5194-2015 industry standard.

[0035] Preferably, the roasting in step S2 comprises the following steps:

[0036] S2-1: heating the aluminum electrolytic anode to 270-690°C at a heating rate of 8-15°C / h;

[0037] S2-2: heating to 880-1080°C at a heating rate of 5-10°C / h;

[0038] S2-3: Heat to 1160±5℃ at a rate of 5-10℃ / h and keep warm for 28h.

[0039] The present invention also provides a mixer for the natural gas and hydrogen mixed fuel, comprising a natural gas inlet (1), a hydrogen inlet (2), a natural gas pressure reducing valve (4), a natural gas flow meter (5), a gas mixer (6), a chromatograph (7), a mixed gas outlet (8), a hydrogen pressure reducing valve (9), a hydrogen flow meter (10) and a mixed gas flow meter (11);

[0040] The natural gas inlet (1) is connected to the natural gas pressure reducing valve (4) via a valve (3), and then enters the gas mixer (6) via a natural gas flow meter (5);

[0041] The hydrogen inlet (2) is connected to the hydrogen pressure reducing valve (9) via a valve (12), and then enters the gas mixer (6) via a hydrogen flow meter (10);

[0042] The gas mixer (6) is connected to the chromatographic analyzer (7) via a mixed gas flow meter (11); the chromatographic analyzer (7) is connected to the mixed gas outlet (8) via a valve (13).

[0043] In a specific embodiment of the present invention, the mixer is used to mix hydrogen and natural gas, and the specific process is as follows:

[0044] The natural gas enters the pipeline from the natural gas inlet (1), and enters the gas mixer (6) through the valve (3), the natural gas pressure reducing valve (4), and the natural gas flow meter (5) in sequence; the valve (3) can cut off the gas supply, and the natural gas pressure reducing valve (4) adjusts the natural gas pressure to 0.08-0.1 MPa, and then the natural gas, as an active gas source with stable pressure, enters the gas mixer (6) after the flow is measured by the natural gas flow meter (5);

[0045] The hydrogen supplied from the hydrogen production system is controlled at a temperature below 28° C., enters the pipeline from the hydrogen inlet (2), passes through the valve (12), the hydrogen pressure reducing valve (9) and the hydrogen flow meter (10) in sequence, and enters the gas mixer (6); after the pressure is adjusted to 0.08-0.012 MPa by the hydrogen pressure reducing valve (9), it is used as a mixing gas source, passes through the hydrogen flow meter (10), and enters the gas mixer (6);

[0046] Then, the two gases mixed by the gas mixer (6) are metered by the mixed gas flow meter (11) and enter the chromatograph (7). According to the set value of the mixed hydrogen, the chromatograph 7 performs online real-time analysis on the ratio of the mixed gas to the hydrogen, and at the same time feeds back the structure to the valve (12) to perform real-time online adjustment of the hydrogen flow rate, thereby achieving the target mixing accuracy and controlling the mixing accuracy to about one thousandth. After passing through the valve (13), the mixed gas is output from the mixed gas outlet (8) for industrial baking of prebaked green anodes for aluminum electrolysis.

[0047] The schematic diagram of the mixer structure for the natural gas and hydrogen mixed fuel is as follows Figure 1 .

[0048] Example 1

[0049] A technical method for using a mixed fuel of natural gas and hydrogen for aluminum electrolysis anode baking, the steps are as follows:

[0050] S1: using the mixer of the natural gas and hydrogen mixed fuel to mix hydrogen and natural gas to obtain a mixed gas, in which the volume ratio of hydrogen is 12%, the temperature of the hydrogen is 10°C, the hydrogen pressure is 0.12MPa, and the natural gas pressure is 0.09MPa;

[0051] S2: Using the mixed gas for roasting raw anodes for aluminum electrolysis, comprising the following steps:

[0052] S2-1: heating the aluminum electrolytic anode to 270-590°C at a heating rate of 8-15°C / h;

[0053] S2-2: heating to 880-1080°C at a heating rate of 5-10°C / h;

[0054] S2-3: heating to 1160±5°C at a heating rate of 5-10°C / h, and keeping the temperature for 28h to obtain a prebaked anode for aluminum electrolysis;

[0055] The preparation method of the aluminum electrolysis raw anode is as follows: 72% of calcined coke, 12.5% ​​of residual anode and 15.5% of modified asphalt are mixed, and then pressed and molded at 150° C. and 13 MPa to obtain the aluminum electrolysis raw anode.

[0056] In the experiment, 9 fire channels were used for calcination, including fire channels 1 to 9. Material boxes were placed between the fire channels, among which No. 1 material box was placed between fire channels 1 and 2, No. 2 material box was placed between fire channels 2 and 3, No. 3 material box was placed between fire channels 3 and 4, and so on. The heating rates for different heating stages are shown in Table 1, and the specific temperature change processes of different fire channels are shown in Table 2.

[0057] Table 1

[0058]

[0059] Table 2

[0060]

[0061] It can be seen that the present invention roasts the raw anode for 28 hours, the combustion process is smooth, the airflow is stable, and the temperature of the roasting furnace is measured during the process, wherein the high temperature reaches 1160°C, the secondary temperature is 1080-1160°C, and the medium temperature is 870-1080°C, which meets the production process requirements and is consistent with the original roasting temperature rise curve.

[0062] The prebaked anodes obtained from different bins in Example 1 were selected for performance testing. The results are shown in Table 3. 。

[0063] Table 3

[0064]

[0065] Embodiment 2-4

[0066] By adjusting the natural gas flow rate and the hydrogen flow rate to change the ratio of hydrogen to natural gas, the same roasting process as in Example 1 is adopted to obtain the actual high temperature under different hydrogen ratios as shown in Table 4.

[0067] Table 4

[0068]

[0069] Comparative Example 1

[0070] According to the method of Example 1, natural gas aluminum electrolysis anode roasting was adopted, 9 fire channels were used for calcination, and the heating rate was set as in Example 1. The specific temperature change process of different fire channels was as shown in Table 5.

[0071] Table 5

[0072]

[0073]

[0074] The prebaked anodes obtained from different material boxes in Comparative Example 1 were selected for performance testing. The results are shown in Table 6.

[0075] Table 6

[0076]

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A technical method for using a mixed fuel of natural gas and hydrogen for aluminum electrolysis anode baking, characterized in that: The following steps are involved: S1: mixing hydrogen and natural gas to obtain a mixed gas; S2: using the mixed gas to bake raw anodes for aluminum electrolysis to obtain prebaked anodes for aluminum electrolysis; In the mixed gas in step S1, the volume ratio of hydrogen is 5-20%.

2. The technical method of using natural gas and hydrogen mixed fuel for aluminum electrolysis anode baking according to claim 1 is characterized in that: The temperature of the hydrogen in step S1 is ≤28°C.

3. The technical method of using natural gas and hydrogen mixed fuel for aluminum electrolysis anode baking according to claim 1 is characterized in that: The preparation method of the aluminum electrolytic raw anode in step S2 is: 70-75% of calcined coke, 10-15% of residual anode, and 12-18% of modified asphalt are mixed, and then pressed and molded at 150° C. and 10-15 MPa to obtain the aluminum electrolytic raw anode.

4. The technical method of using natural gas and hydrogen mixed fuel for aluminum electrolysis anode baking according to claim 1 is characterized in that: The roasting in step S2 comprises the following steps: S2-1: heating the aluminum electrolytic anode to 270-690°C at a heating rate of 8-15°C / h; S2-2: heating to 880-1080°C at a heating rate of 5-10°C / h; S2-3: Heat to 1160±5℃ at a rate of 5-10℃ / h and keep warm for 28h.

5. A mixer for the natural gas and hydrogen mixed fuel, characterized in that: It comprises a natural gas inlet (1), a hydrogen inlet (2), a natural gas pressure reducing valve (4), a natural gas flow meter (5), a gas mixer (6), a chromatograph (7), a mixed gas outlet (8), a hydrogen pressure reducing valve (9), a hydrogen flow meter (10) and a mixed gas flow meter (11); The natural gas inlet (1) is connected to the natural gas pressure reducing valve (4) via a valve (3), and then enters the gas mixer (6) via a natural gas flow meter (5); The hydrogen inlet (2) is connected to the hydrogen pressure reducing valve (9) via a valve (12), and then enters the gas mixer (6) via a hydrogen flow meter (10); The gas mixer (6) is connected to the chromatographic analyzer (7) via a mixed gas flow meter (11); the chromatographic analyzer (7) is connected to the mixed gas outlet (8) via a valve (13).

6. The mixer for natural gas and hydrogen mixed fuel according to claim 5, characterized in that: The natural gas pressure reducing valve (4) adjusts the natural gas pressure to 0.08-0.1 MPa.

7. The mixer for natural gas and hydrogen mixed fuel according to claim 5, characterized in that: The hydrogen pressure reducing valve (9) adjusts the hydrogen pressure to 0.08-0.012 MPa.

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