Method for efficiently trapping oxycarbide in steel source flue gas by using aluminum scrap

Abstract

The invention discloses a method for efficiently trapping oxycarbide in flue gas of a steel source by using aluminum wastes, and belongs to the technical field of resource utilization of the aluminum wastes. The method comprises the steps that the surface of the aluminum waste is covered with fused salt, smelting is carried out in an inert atmosphere to obtain a melt, steel source flue gas is introduced into the melt after nitrogen and oxygen are removed, aluminum in the melt is selectively oxidized into aluminum oxide through oxycarbide in the steel source flue gas, the aluminum oxide is migrated into a fused salt layer on the surface of the melt, and aluminum-rich salt slag is formed; and the aluminum-rich salt slag is subjected to water leaching to separate aluminum oxide. According to the method, the activity difference between metal aluminum and other impurity components in the aluminum waste is fully utilized, aluminum is selectively oxidized while smoke is captured, then aluminum is separated from silicon, copper, iron and other impurity components, high-purity aluminum oxide can be obtained through simple treatment of the aluminum-rich salt slag, economic benefits and environmental protection benefits are both achieved, and the method is suitable for industrial production. The development requirements of the steel industry and the secondary aluminum industry are met.

Description

Technical Field

[0001] The invention relates to a method for treating aluminum waste, and in particular to a method for efficiently capturing carbon oxides in steel source flue gas by using aluminum waste, belonging to the technical field of resource utilization of aluminum waste. Background Art

[0002] The aluminum industry faces the challenge of resource utilization of aluminum waste, especially aluminum waste such as impure aluminum generated during the recycling process of aluminum products. Direct use of aluminum waste for smelting will introduce a large number of impurity components, affect smelting efficiency, and increase production costs. Aluminum oxide has a porous structure, high specific surface area, good thermal stability and chemical stability. It is widely used as a catalyst carrier and has certain catalytic properties. It is used in hydrocarbon cracking, alcohol dehydration and ether production. If aluminum-containing waste can be used to prepare aluminum oxide products with high added value, the resource utilization efficiency of aluminum waste can be greatly improved. A Chinese patent (publication number: CN105253905B) discloses a method for extracting aluminum from aluminum-containing waste. The method first chlorinates and roasts aluminum-containing waste, activated carbon and alkali metal chloride, absorbs chlorinated volatiles with dilute hydrochloric acid, and then removes silicon by heating and filtering. The pH value of the filtrate is adjusted to hydrolyze aluminum into soluble salts, and other impurity metals are hydrolyzed into precipitates, thereby completing the enrichment of aluminum, and then further extracting aluminum and its compounds from the aluminum-enriched solution. Although this method can convert aluminum waste into aluminum oxide products, its operation process is long, the impurity removal process is complicated, it consumes a large amount of acid and alkali, and the cost is high. Summary of the invention

[0003] In view of the technical problem that the resource utilization of aluminum waste is difficult in the prior art, the purpose of the present invention is to provide a method for efficiently capturing carbon oxides in steel-source flue gas using aluminum waste. This method can efficiently capture and fix carbon monoxide and carbon dioxide in steel-source flue gas using aluminum waste, while achieving efficient separation of metallic aluminum and other impurities in the aluminum waste, thereby realizing flue gas treatment in the steel industry and resource recovery of aluminum waste, and has important environmental and economic value.

[0004] In order to achieve the above technical objectives, the present invention provides a method for efficiently capturing carbon oxides in steel-source flue gas using aluminum scrap, the method comprising: covering the surface of the aluminum scrap with molten salt and smelting the scrap in an inert atmosphere to obtain a melt, removing nitrogen and oxygen from the steel-source flue gas and then passing the melt into the melt, utilizing the carbon oxides in the steel-source flue gas to selectively oxidize the aluminum in the melt into aluminum oxide and migrate the aluminum to the molten salt layer on the surface of the melt to form aluminum-rich salt slag, and separating the aluminum oxide from the aluminum-rich salt slag through water leaching.

[0005] The key to the technical solution of the present invention lies in: on the one hand, making full use of the difference in chemical activity between aluminum and impurity components, and utilizing carbon oxides with weak oxidizing properties at high temperature to selectively oxidize metallic aluminum into aluminum oxide; on the other hand, utilizing the characteristics of aluminum oxide such as density being different from those of impurities, aluminum oxide can be directionally migrated to the molten salt layer above the melt; on the third hand, utilizing the catalytic properties of in-situ generated aluminum oxide to further strengthen the oxidation reaction between carbon oxides and metallic aluminum and improve the flue gas capture effect.

[0006] The present invention introduces the steel source flue gas into the melt formed by aluminum waste after simply removing oxygen and nitrogen, and the following chemical reactions mainly occur: 2Al+3CO→Al2O3+3C, 4Al+3CO2→2Al2O3+3C; aluminum is selectively oxidized to aluminum oxide, and carbon oxides are reduced to carbon and effectively fixed.

[0007] The aluminum-rich salt slag of the present invention can achieve separation of molten salt from aluminum oxide and carbon products through simple water immersion treatment, the aluminum oxide sinks to the bottom of the water, the molten salt dissolves in the water, and the carbon floats on the water surface.

[0008] As a preferred solution, the mass content of metallic aluminum in the aluminum waste is not less than 50%. The main impurities in the aluminum waste include iron, silicon, copper, etc. Aluminum waste includes but is not limited to impurity-contaminated aluminum generated during the use and disposal of aluminum products, wherein the content of metallic aluminum is not less than 50%. Metallic aluminum is an active component for capturing carbon oxides in flue gas. Too low a content will lead to excessive smelting energy consumption, increased capture costs, and difficulty in separating aluminum from impurities during the smelting process, making the processing more difficult.

[0009] As a preferred solution, the steel source flue gas includes at least one of coking flue gas, sintering flue gas, blast furnace flue gas and steelmaking flue gas. Coking, sintering, blast furnace and the like are all important sources of steel source flue gas, and the flue gas generated in these processes contains carbon oxides such as carbon monoxide and carbon dioxide.

[0010] As a preferred solution, the molten salt includes potassium chloride and sodium chloride. As a more preferred solution, the molten salt is composed of the following mass percentage components: 45%~70% sodium chloride, 30%~55% potassium chloride. The role of molten salt: on the one hand, after melting, the molten salt can be used as a protective layer to reduce the impact of the external environment on the alloy melt, such as oxidation; on the other hand, the use of molten salt to capture aluminum oxide products can achieve directional enrichment of aluminum oxide in the upper molten salt layer, which is helpful to achieve the separation of metallic aluminum. As a more preferred solution, the mass of the molten salt is 10%~80% of the mass of the aluminum scrap. The amount of molten salt added to the surface of the aluminum scrap is determined according to the aluminum content in the aluminum scrap. When the aluminum content is low, the amount added is relatively small, and when the aluminum content is high, the amount added is relatively high. The mass of the molten salt is further preferably 20%~50% of the mass of the aluminum scrap.

[0011] As a preferred solution, after nitrogen and oxygen are removed from the steel source flue gas, its oxygen volume content is not higher than 0.5%, and its nitrogen volume content is not higher than 0.5%. The main components of steel source flue gas are carbon monoxide and carbon dioxide, and it also contains a small amount of oxygen and nitrogen. Excessive oxygen and nitrogen content will preferentially react with aluminum in the melt to form aluminum nitride or aluminum oxide during the capture process, resulting in poor capture effect of the melt on carbon oxides. The specific reaction equation is 4Al+3O2→2Al2O3, 2Al + N2→2AlN. Therefore, nitrogen and oxygen need to be removed from the steel source flue gas.

[0012] As a preferred solution, the temperature of the melt is 700° C. to 800° C. If the temperature is too high, energy consumption will increase, and if the temperature is too low, the aluminum scrap will not be completely melted, the separation effect will be poor, and the carbon oxide capture rate will be affected.

[0013] As a preferred solution, the steel source flue gas is introduced into the melt from a height of 1 / 4 to 1 / 5 of the bottom of the melt. If the steel source flue gas is mainly introduced into the upper part of the melt, the bottom melt will not be able to capture carbon oxides sufficiently, and the distance for the melt to effectively capture carbon oxides will be shortened, affecting the capture efficiency. At the same time, the steel source flue gas plays a gas stirring role, and the closer the distance of the introduction position is to the bottom of the melt, the more favorable it is.

[0014] As a preferred solution, the amount of the steel source flue gas introduced is measured based on the total molar amount of carbon oxides required to oxidize all the metallic aluminum in the melt into aluminum oxide.

[0015] The present invention removes nitrogen and oxygen from steel source flue gas by using molecular sieves. The molecular sieves adsorb nitrogen and oxygen using a common technology in the prior art, such as using carbon molecular sieves to adsorb oxygen and using zeolite molecular sieves to remove nitrogen.

[0016] Compared with the prior art, the technical solution of the present invention brings the following beneficial technical effects:

[0017] (1) The present invention utilizes carbon oxides in steel source flue gas to selectively oxidize metallic aluminum in aluminum waste, and at the same time converts carbon oxides into fixed carbon. Impurities such as iron, silicon, and copper are not oxidized, and the generated aluminum oxide is directed to migrate to the upper salt slag layer, and then purified by water immersion treatment to obtain high-purity aluminum oxide. This not only achieves the capture of nitrogen oxides in steel source flue gas, but also realizes the resource utilization of aluminum waste, produces high-purity aluminum oxide, and provides a new way for carbon capture of steel source flue gas and resource recovery of aluminum waste.

[0018] (2) The equipment used in the present invention is a smelting furnace widely used in the recycled aluminum industry. No new equipment is required, and the problem of difficulty in separating aluminum and impurity components such as iron, silicon, and copper in aluminum waste is solved. At the same time, the carbon oxides in the flue gas from the steel source are captured.

[0019] (3) The present invention makes full use of the difference in chemical activity between aluminum and impurity components to achieve selective oxidation of aluminum, while achieving directional enrichment of aluminum oxide in the molten salt layer, and utilizing the catalytic activity of aluminum oxide generated in situ during the capture process to enhance the flue gas capture effect. DETAILED DESCRIPTION

[0020] The following examples are intended to further illustrate the present invention, rather than to limit the scope of protection of the claims of the present invention.

[0021] Comparative Example 1

[0022] Compared with Example 1, the only difference is that the composition of the aluminum waste used is different. The mass content of metallic aluminum is 45.8%, and the mass content of major impurities is 3.1% copper, 4.5% silicon and 35.9% iron.

[0023] Due to the low content of metallic aluminum, the flue gas capture effect is poor.

[0024] Due to the high iron content in the aluminum waste, the melt is not fully melted, and thus some of the metallic aluminum reacts incompletely. After the reaction is completed, the upper aluminum-rich salt slag is separated and the aluminum-rich salt slag is immersed in water to first remove the carbon layer floating on the water layer, and then the solid-liquid separation is performed to obtain 282.02g of high-purity aluminum oxide. The capture efficiency of carbon oxides in sintering flue gas is 55.7%. After calculation, the aluminum oxide in the salt slag is only 65.2% of the theoretical recovery rate.

[0025] Comparative Example 2

[0026] Compared with Example 1, the only difference is that the sintering flue gas is not treated with molecular sieves, and its carbon monoxide accounts for about 2.6%, carbon dioxide accounts for about 83.1%, oxygen accounts for about 4%, and nitrogen accounts for about 10%.

[0027] Due to the high oxygen and nitrogen content in the flue gas, the carbon oxide capture effect is poor.

[0028] Due to the high nitrogen content in the sintering flue gas, part of the aluminum is converted into aluminum nitride. After the reaction is completed, the upper aluminum-rich salt slag is separated and the aluminum-rich salt slag is immersed in water to first remove the carbon layer floating on the water layer, and then the solid-liquid separation is performed to obtain 572.63g of high-purity aluminum oxide. The capture efficiency of carbon oxides in sintering flue gas is 45.8%. After calculation, the aluminum oxide in the salt slag is only 71.5% of the theoretical recovery rate.

[0029] Comparative Example 3

[0030] Compared with Example 1, the only difference is that the melting temperature is 650°C.

[0031] Since the capture temperature is too low, the flue gas capture effect is poor.

[0032] Due to the low smelting temperature, the conversion of metallic aluminum is incomplete. After the reaction is completed, the upper aluminum-rich salt slag is separated and immersed in water to remove the carbon layer floating on the water. Then, the solid-liquid separation is performed to obtain 567.02g of high-purity aluminum oxide. The capture efficiency of carbon oxides in blast furnace flue gas is 51.3%. After calculation, the aluminum oxide in the salt slag is only 70.8% of the theoretical recovery rate.

[0033] Comparative Example 4

[0034] Compared with Example 1, the only difference is that sintering flue gas treated with molecular sieve is introduced at a distance of about 1 / 2 of the melt from the bottom of the molten pool.

[0035] Since the sintering fume inlet point is too far from the bottom of the molten pool, the sintering fume capture effect is poor.

[0036] Since the sintering flue gas is introduced from the middle of the melt, the bottom melt cannot capture carbon oxides fully, and the distance for the melt to effectively capture carbon oxides is shortened, affecting the capture efficiency. After the reaction is completed, the upper aluminum-rich salt slag is separated and the aluminum-rich salt slag is immersed in water to first remove the carbon layer floating on the water layer, and then separate the solid and liquid to obtain 639.91g of high-purity aluminum oxide. The capture efficiency of carbon oxides in sintering flue gas is 59.8%. After calculation, the aluminum oxide in the salt slag is only 79.9% of the theoretical recovery rate.

[0037] Example 1

[0038] 500g of aluminum scrap (metal aluminum content of 84.8%, copper content of 2.4%, silicon content of 3.1%, iron content of 5.6%) was used as the capture raw material. In an argon atmosphere, molten salt (sodium chloride accounts for 50%, potassium chloride accounts for 50%) of the mass of the alloy scrap was added, and smelted at 800℃. The sintering flue gas (carbon monoxide accounts for about 3.1%, distilled water accounts for about 1.5% and sintered oil accounts for about 2.5%) treated with molecular sieves (carbon molecular sieves remove oxygen and zeolite molecular sieves remove nitrogen) was introduced at a distance of about 1 / 5 from the bottom of the molten pool. Carbon oxide accounts for about 96.2%, oxygen accounts for about 0.2%, and nitrogen accounts for about 0.3%). The amount of sintering flue gas introduced is measured according to the molar amount of complete oxidation of metallic aluminum. After the reaction is completed, the upper aluminum-rich salt slag is separated, and the aluminum-rich salt slag is immersed in water to first remove the carbon layer floating on the water layer, and then separate the solid and liquid to obtain 756.86g of high-purity aluminum oxide. The capture efficiency of carbon oxides in sintering flue gas is 80.2%. After calculation, the theoretical recovery rate of aluminum oxide in the salt slag is 94.5%.

[0039] Example 2

[0040] 500g of aluminum scrap (metal aluminum content of 74.8%, copper content of 2.5%, silicon content of 1.9%, iron content of 5.4%) was used as the capture raw material. In an argon atmosphere, molten salt (sodium chloride accounts for 50%, potassium chloride accounts for 50%) of the alloy scrap weight was added, and smelted at 750℃. The sintering flue gas (carbon monoxide accounts for about 4.6%, distilled water accounts for about 1.5% and sintered oil accounts for about 2.5%) after molecular sieve treatment (carbon molecular sieve removes oxygen and zeolite molecular sieve removes nitrogen) was introduced at a distance of about 1 / 5 from the bottom of the molten pool. Carbon oxides account for about 94.1%, oxygen accounts for about 0.2%, and nitrogen accounts for about 0.3%). The amount of sintering flue gas introduced is measured according to the molar amount of complete oxidation of metallic aluminum. After the reaction is completed, the upper aluminum-rich salt slag is separated, and the aluminum-rich salt slag is immersed in water to first remove the carbon layer floating on the water layer, and then separate the solid and liquid to obtain 661.25g of high-purity aluminum oxide. The capture efficiency of carbon oxides in sintering flue gas is 82.9%. After calculation, the theoretical recovery rate of aluminum oxide in the salt slag is 93.6%.

[0041] Example 3

[0042] 500g of aluminum scrap (metal aluminum content of 69.2%, copper content of 2.7%, silicon content of 3.6%, iron content of 8.9%) was used as the capture raw material. In an argon atmosphere, molten salt (sodium chloride accounts for 50%, potassium chloride accounts for 50%) of the mass of the alloy scrap was added, and smelted at 800℃. Blast furnace flue gas (carbon monoxide accounts for about 50.2%, distilled water accounts for about 10.5%) treated with molecular sieves (carbon molecular sieves to remove oxygen and zeolite molecular sieves to remove nitrogen) was introduced at a distance of about 1 / 4 of the melt from the bottom of the molten pool. Carbon oxide accounts for about 48.8%, oxygen accounts for about 0.1%, and nitrogen accounts for about 0.1%). The amount of blast furnace flue gas introduced is measured according to the molar amount of complete oxidation of metallic aluminum. After the reaction is completed, the upper aluminum-rich salt slag is separated, and the aluminum-rich salt slag is immersed in water to first remove the carbon layer floating on the water layer, and then separate the solid and liquid to obtain 616.97g of high-purity aluminum oxide. The capture efficiency of carbon oxides in blast furnace flue gas is 83.2%. After calculation, the theoretical recovery rate of aluminum oxide in the salt slag is 94.4%.

[0043] Example 4

[0044] 500g of aluminum scrap (metal aluminum content of 70.5%, copper content of 3.0%, silicon content of 2.9%, iron content of 8.1%) was used as the capture raw material. In an argon atmosphere, molten salt (sodium chloride accounted for 60%, potassium chloride accounted for 40%) of the mass of the alloy scrap was added. The steelmaking fume (carbon monoxide accounted for about 68.4%, distilled water accounted for about 10% of the mass of the alloy scrap) was introduced into the steelmaking fume (carbon monoxide accounted for about 68.4%, potassium chloride accounted for about 40%) at a melt distance of about 1 / 5 from the bottom of the molten pool. Carbon oxide accounts for about 31.1%, oxygen accounts for about 0.2%, and nitrogen accounts for about 0.1%). The amount of steelmaking flue gas introduced is measured according to the molar amount of complete oxidation of metallic aluminum. After the reaction is completed, the upper aluminum-rich salt slag is separated, and the aluminum-rich salt slag is immersed in water to first remove the carbon layer floating on the water layer, and then separate the solid and liquid to obtain 626.56g of high-purity aluminum oxide. The capture efficiency of carbon oxides in steelmaking flue gas is 85.9%. After calculation, the theoretical recovery rate of aluminum oxide in the salt slag is 94.1%.

Claims

1. A method for efficiently capturing carbon oxides in steel source flue gas using aluminum waste, characterized in that: The surface of aluminum waste is covered with molten salt and smelted in an inert atmosphere to obtain a melt, and the steel source flue gas is passed into the melt after nitrogen and oxygen are removed, and the aluminum in the melt is selectively oxidized into aluminum oxide by carbon oxides in the steel source flue gas and migrated to the molten salt layer on the surface of the melt to form aluminum-rich salt slag, and the aluminum oxide is separated from the aluminum salt slag through water leaching.

2. The method for efficiently capturing carbon oxides in steel source flue gas using aluminum waste according to claim 1, characterized in that: The mass content of metallic aluminum in the aluminum scrap is not less than 50%.

3. The method for efficiently capturing carbon oxides in steel source flue gas using aluminum waste according to claim 1, characterized in that: The steel source flue gas includes at least one of coking flue gas, sintering flue gas, blast furnace flue gas and steelmaking flue gas.

4. The method for efficiently capturing carbon oxides in steel source flue gas using aluminum waste according to claim 1, characterized in that: The molten salt includes potassium chloride and sodium chloride.

5. The method for efficiently capturing carbon oxides in steel source flue gas using aluminum waste according to claim 4, characterized in that: The molten salt is composed of the following components in mass percentage: 45% to 70% sodium chloride and 30% to 55% potassium chloride.

6. A method for efficiently capturing carbon oxides in steel source flue gas using aluminum scrap according to claim 1, 4 or 5, characterized in that: The mass of the molten salt is 10% to 80% of the mass of the aluminum scrap.

7. A method for efficiently capturing carbon oxides in steel source flue gas using aluminum scrap according to claim 1 or 3, characterized in that: After nitrogen and oxygen are removed from the steel source flue gas, the volume content of oxygen is not higher than 0.5%, and the volume content of nitrogen is not higher than 0.5%.

8. The method for efficiently capturing carbon oxides in steel source flue gas using aluminum scrap according to claim 1, characterized in that: The temperature of the melt is 700°C to 800°C.

9. The method for efficiently capturing carbon oxides in steel source flue gas using aluminum waste according to claim 1, characterized in that: The steel source flue gas is introduced into the melt from a height of 1 / 4 to 1 / 5 of the bottom of the melt.

10. A method for efficiently capturing carbon oxides in steel source flue gas using aluminum waste according to claim 1 or 8, characterized in that: The amount of the steel source flue gas introduced is measured based on the total molar amount of carbon oxides required to oxidize all the metallic aluminum in the melt into aluminum oxide.