A method for efficiently capturing carbon oxides in flue gas from steel sources using aluminum waste

Abstract

The present invention discloses a method for efficiently capturing carbon oxides in flue gas from steel sources by using aluminum waste, belonging to the technical field of resource utilization of aluminum waste. This method involves covering the surface of aluminum waste with molten salt and melting it under an inert atmosphere to obtain a melt. After removing nitrogen and oxygen from the flue gas from steel sources, it is introduced into the interior of the melt. The carbon oxides in the flue gas from steel sources are used to selectively oxidize the aluminum in the melt into aluminum trioxide, which migrates to the molten salt layer on the surface of the melt to form aluminum-rich slag. The aluminum-rich slag is separated from aluminum trioxide by water leaching. This method makes full use of the activity differences between metallic aluminum and other impurity components in aluminum waste, selectively oxidizes aluminum while capturing flue gas, and then realizes the separation of aluminum from impurity components such as silicon, copper, and iron. The aluminum-rich slag can be obtained high-purity aluminum trioxide through simple treatment, having both economic and environmental benefits and meeting the development requirements of the steel industry and the secondary aluminum industry.

Description

Technical Field

[0001] The present invention relates to a method for treating aluminum waste, specifically to a method for efficiently capturing carbon oxides in steel source flue gas by using aluminum waste, and belongs 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 for aluminum waste such as contaminated aluminum generated during the recycling of aluminum products, directly using it for smelting will introduce a large number of impurity components, affecting the smelting efficiency and increasing production costs. Aluminum oxide has a porous structure, with characteristics of high specific surface area, good thermal stability and chemical stability. It is widely used as a catalyst support and also has certain catalytic properties, and is used in fields such as hydrocarbon cracking and dehydration of alcohols to ethers. If aluminum-containing waste can be used to prepare aluminum oxide products with higher added value, the resource utilization efficiency of aluminum waste can be greatly improved. Chinese Patent (Publication No.: CN105253905B) discloses a method for extracting aluminum from aluminum-containing waste. In this method, the aluminum-containing waste, activated carbon and alkali metal chloride are first subjected to chlorination roasting, the chlorinated volatiles are absorbed by dilute hydrochloric acid, and then after preliminary silicon removal by heating and filtration, the pH value of the filtrate is adjusted to hydrolyze aluminum into soluble salts, while other impurity metals are hydrolyzed into precipitates, thereby completing the enrichment of aluminum, and then further extracting aluminum and its compounds from the solution enriched with aluminum. Although this method can make aluminum oxide products from aluminum waste, its operation process is long, the impurity removal process is complex, it consumes a large amount of acids and alkalis, and the cost is high. Summary of the Invention

[0003] Aiming at the technical problem of the difficult resource utilization of aluminum waste 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 by using aluminum waste. While efficiently capturing and fixing carbon monoxide and carbon dioxide in the steel source flue gas by using aluminum waste, this method realizes the efficient separation of metallic aluminum from other impurities in the aluminum waste, achieving the flue gas treatment in the steel industry and the resource recovery of aluminum waste, and having important environmental protection value and economic value.

[0004] To achieve the above technical purpose, the present invention provides a method for efficiently capturing carbon oxides in steel source flue gas by using aluminum waste. In this method, the surface of the aluminum waste is covered with molten salt and smelted in an inert atmosphere to obtain a melt. After removing nitrogen and oxygen from the steel source flue gas, it is introduced into the interior of the melt. The carbon oxides in the steel source flue gas are used to selectively oxidize the aluminum in the melt into aluminum oxide and migrate it to the molten salt layer on the surface of the melt to form an aluminum-rich slag. The aluminum-rich slag is separated by water leaching to obtain aluminum oxide.

[0005] The key to the technical solution of the present invention lies in: on the one hand, making full use of the chemical activity difference between aluminum and impurity components, and using carbon oxides with weak oxidizing properties at high temperatures to selectively oxidize metallic aluminum into aluminum oxide preferably; on the other hand, taking advantage of the characteristics that the physical properties such as density of aluminum oxide are different from those of impurities, aluminum oxide can migrate directionally to the molten salt layer on the upper part of the melt; on the third hand, taking advantage of the catalytic property of the 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 passes the steel-source flue gas, after simply removing oxygen and nitrogen, into the melt formed by aluminum scraps, and the following chemical reactions mainly occur: 2Al + 3CO → Al2O3 + 3C, 4Al + 3CO2 → 2Al2O3 + 3C; aluminum is selectively oxidized into aluminum oxide, while carbon oxides are reduced to carbon and are effectively fixed.

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

[0008] As a preferred solution, the mass content of metallic aluminum in the aluminum scraps is not less than 50%. The main impurities in the aluminum scraps include iron, silicon, copper, etc. The aluminum scraps include, but are not limited to, aluminum contaminated by impurities generated during the waste use process of aluminum products, wherein the content of metallic aluminum is not less than 50%. Metallic aluminum is the active component for capturing carbon oxides in flue gas. If the content is too low, it will lead to too high smelting energy consumption, increased capture cost, and it is difficult to separate aluminum from impurities during the smelting process, increasing the treatment difficulty.

[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, etc. are all important sources of steel-source flue gas, and the flue gas generated in these processes all 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 components by mass percentage: 45% - 70% sodium chloride and 30% - 55% potassium chloride. The functions of the molten salt are as follows: on the one hand, after melting, the molten salt can serve as a protective layer to reduce the influence of the external environment on the alloy melt, such as oxidation; on the other hand, by using the molten salt to capture aluminum oxide products, the directional enrichment of aluminum oxide in the upper molten salt layer can be achieved, which helps to separate metallic aluminum. As a more preferred solution, the mass of the molten salt is 10% - 80% of the mass of the aluminum scrap. The addition amount of the molten salt on the surface of the aluminum scrap is determined according to the aluminum content in the aluminum scrap. When the aluminum content is low, the addition amount is relatively small; when the aluminum content is high, the addition amount 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 removing nitrogen and oxygen 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%. The main components of the steel source flue gas are carbon monoxide and carbon dioxide, and at the same time, it contains a small amount of oxygen and nitrogen. Excessive oxygen and nitrogen contents will react with aluminum in the melt to form aluminum nitride or aluminum oxide preferentially during the capture process, resulting in poor capture effect of carbon oxides by the melt. The specific reaction equations are 4Al + 3O2 → 2Al2O3 and 2Al + N2 → 2AlN. Therefore, it is necessary to remove nitrogen and oxygen from the steel source flue gas.

[0012] As a preferred solution, the temperature of the melt is 700°C - 800°C. If the temperature is too high, the energy consumption will increase; if the temperature is too low, the aluminum scrap will not melt completely, the separation effect will be poor, and it will also affect the capture rate of carbon oxides.

[0013] As a preferred solution, the steel source flue gas is introduced into the interior of the melt at a height of 1 / 4 - 1 / 5 from the bottom of the melt. If the steel source flue gas is mainly introduced into the upper part of the melt, it will cause insufficient capture of carbon oxides by the bottom melt, and the effective capture distance of carbon oxides by the melt will be shortened, affecting the capture efficiency. At the same time, the steel source flue gas plays a role in gas stirring, and the closer the introduction position is to the bottom of the melt, the more beneficial it is.

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

[0015] The method for removing nitrogen and oxygen from the steel source flue gas in the present invention is to use molecular sieve means. The means of molecular sieve adsorbing nitrogen and oxygen are common techniques in the prior art, such as using carbon molecular sieve to adsorb oxygen and using zeolite molecular sieve to remove nitrogen.

[0016] Beneficial technical effects brought by the technical solution of the present invention compared with the prior art:

[0017] (1) The present invention utilizes carbon oxides in the flue gas from the steel source to selectively oxidize metallic aluminum in the alumina waste, while converting the carbon oxides into fixed carbon. Impurities such as iron, silicon, and copper are not oxidized, and the generated aluminum oxide migrates directionally to the upper salt slag layer. Subsequently, through water leaching treatment, high-purity aluminum oxide can be obtained by purification. This not only realizes the capture of nitrogen oxides in the flue gas from the steel source but also realizes the resource utilization of aluminum waste, producing high-purity aluminum oxide, providing a new approach for carbon capture from the flue gas of the steel source and the resource recovery of aluminum waste.

[0018] (2) The equipment used in the present invention is a melting furnace widely used in the secondary aluminum industry, without the need for new equipment, and solves the problem of difficult separation of aluminum and impurity components such as iron, silicon, and copper in aluminum waste, while realizing the capture of carbon oxides in the flue gas from the steel source.

[0019] (3) The present invention makes full use of the chemical activity differences between aluminum and impurity components, enabling the selective oxidation of aluminum, while realizing the directional enrichment of aluminum oxide in the molten salt layer, and enhancing the flue gas capture effect by utilizing the catalytic activity of the in-situ generated aluminum oxide during the capture process. Specific embodiments

[0020] The following examples are intended to further illustrate the content of the present invention rather than limit the protection scope 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 contents of the main impurities are: copper content 3.1%, silicon content 4.5%, and iron content 35.9%.

[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 melting is insufficient, resulting in incomplete reaction of some metallic aluminum. After the reaction is completed, the upper aluminum-rich salt slag is separated, and the aluminum-rich salt slag is subjected to water leaching treatment. First, the carbon layer floating on the water surface is removed, and then solid-liquid separation is carried out to obtain 282.02 g of high-purity aluminum oxide. The capture efficiency of carbon oxides in the 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 by molecular sieve. The proportion of carbon monoxide is about 2.6%, the proportion of carbon dioxide is about 83.1%, the proportion of oxygen is about 4%, and the proportion of nitrogen is about 10%.

[0027] Due to the high content of oxygen and nitrogen 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-layer aluminum-rich salt slag is separated, and the aluminum-rich salt slag is subjected to water leaching treatment. First, the carbon layer floating on the upper layer of the water is removed, and then solid-liquid separation is carried out to obtain 572.63 g of high-purity aluminum oxide. The carbon oxide capture efficiency of the 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] Due to the too low capture temperature, the flue gas capture effect is poor.

[0032] Due to the relatively low melting temperature, the conversion of metallic aluminum is incomplete. After the reaction is completed, the upper-layer aluminum-rich salt slag is separated, and the aluminum-rich salt slag is subjected to water leaching treatment. First, the carbon layer floating on the upper layer of the water is removed, and then solid-liquid separation is carried out to obtain 567.02 g of high-purity aluminum oxide. The carbon oxide capture efficiency of the 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 the sintering flue gas treated by molecular sieve is introduced into the melt at a distance of about 1 / 2 of the melt distance from the bottom of the molten pool.

[0035] Due to the too far distance from the bottom of the molten pool where the sintering flue gas is introduced, the sintering flue gas capture effect is poor.

[0036] Since the sintering flue gas is introduced from the middle of the melt, the carbon oxides at the bottom of the melt are not sufficiently captured, and the effective carbon oxide capture distance of the melt is shortened, affecting the capture efficiency. After the reaction is completed, the upper-layer aluminum-rich salt slag is separated, and the aluminum-rich salt slag is subjected to water leaching treatment. First, the carbon layer floating on the upper layer of the water is removed, and then solid-liquid separation is carried out to obtain 639.91 g of high-purity aluminum oxide. The carbon oxide capture efficiency of the 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] Using 500 g of a certain aluminum waste (with a metal aluminum content of 84.8%, copper content of 2.4%, silicon content of 3.1%, and iron content of 5.6%) as the capture raw material, in an argon atmosphere, add 30% of the mass of the alloy waste as molten salt (sodium chloride accounts for 50% and potassium chloride accounts for 50%), melt at 800 °C, and introduce sintering flue gas (carbon monoxide accounts for about 3.1%, carbon dioxide accounts for about 96.2%, oxygen accounts for about 0.2%, and nitrogen accounts for about 0.3%) that has been treated with molecular sieves (carbon molecular sieve removes oxygen and zeolite molecular sieve removes nitrogen) at a melt distance of about 1 / 5 from the bottom of the molten pool. The input amount of the sintering flue gas is measured according to the molar amount of complete oxidation of metallic aluminum. After the reaction is completed, separate the upper aluminum-rich salt slag, perform water leaching treatment on the aluminum-rich salt slag, first remove the carbon layer floating on the upper layer of the water, and then perform solid-liquid separation to obtain 756.86 g of high-purity aluminum oxide. The capture efficiency of carbon oxides in the sintering flue gas is 80.2%. After calculation, the aluminum oxide in the salt slag is 94.5% of the theoretical recovery rate.

[0039] Example 2

[0040] Using 500 g of a certain aluminum waste (with a metal aluminum content of 74.8%, copper content of 2.5%, silicon content of 1.9%, and iron content of 5.4%) as the capture raw material, in an argon atmosphere, add 30% of the mass of the alloy waste as molten salt (sodium chloride accounts for 50% and potassium chloride accounts for 50%), melt at 750 °C, and introduce sintering flue gas (carbon monoxide accounts for about 4.6%, carbon dioxide accounts for about 94.1%, oxygen accounts for about 0.2%, and nitrogen accounts for about 0.3%) that has been treated with molecular sieves (carbon molecular sieve removes oxygen and zeolite molecular sieve removes nitrogen) at a melt distance of about 1 / 5 from the bottom of the molten pool. The input amount of the sintering flue gas is measured according to the molar amount of complete oxidation of metallic aluminum. After the reaction is completed, separate the upper aluminum-rich salt slag, perform water leaching treatment on the aluminum-rich salt slag, first remove the carbon layer floating on the upper layer of the water, and then perform solid-liquid separation to obtain 661.25 g of high-purity aluminum oxide. The capture efficiency of carbon oxides in the sintering flue gas is 82.9%. After calculation, the aluminum oxide in the salt slag is 93.6% of the theoretical recovery rate.

[0041] Example 3

[0042] Using 500 g of a certain aluminum waste (with 69.2% metallic aluminum content, 2.7% copper content, 3.6% silicon content, and 8.9% iron content) as the capture raw material, under an argon atmosphere, adding 30% of the mass of the alloy waste as molten salt (50% sodium chloride and 50% potassium chloride), melting at 800 °C, introducing blast furnace gas (with approximately 50.2% carbon monoxide, 48.8% carbon dioxide, 0.1% oxygen, and 0.1% nitrogen) that has been treated by molecular sieves (carbon molecular sieve to remove oxygen and zeolite molecular sieve to remove nitrogen) at a melt distance of about 1 / 4 from the bottom of the molten pool. The input amount of the blast furnace gas is measured according to the molar amount of complete oxidation of metallic aluminum. After the reaction is completed, the upper-layer aluminum-rich salt slag is separated, and the aluminum-rich salt slag is subjected to water leaching treatment. First, the carbon layer floating on the upper layer of the water is removed, and then solid-liquid separation is carried out to obtain 616.97 g of high-purity aluminum oxide. The capture efficiency of carbon oxides in the blast furnace gas is 83.2%. After calculation, the aluminum oxide in the salt slag is 94.4% of the theoretical recovery rate.

[0043] Example 4

[0044] Using 500 g of a certain aluminum waste (with 70.5% metallic aluminum content, 3.0% copper content, 2.9% silicon content, and 8.1% iron content) as the capture raw material, under an argon atmosphere, adding 40% of the mass of the alloy waste as molten salt (60% sodium chloride and 40% potassium chloride), melting at 760 °C, introducing steelmaking gas (with approximately 68.4% carbon monoxide, 31.1% carbon dioxide, 0.2% oxygen, and 0.1% nitrogen) that has been treated by molecular sieves (carbon molecular sieve to remove oxygen and zeolite molecular sieve to remove nitrogen) at a melt distance of about 1 / 5 from the bottom of the molten pool. The input amount of the steelmaking gas is measured according to the molar amount of complete oxidation of metallic aluminum. After the reaction is completed, the upper-layer aluminum-rich salt slag is separated, and the aluminum-rich salt slag is subjected to water leaching treatment. First, the carbon layer floating on the upper layer of the water is removed, and then solid-liquid separation is carried out to obtain 626.56 g of high-purity aluminum oxide. The capture efficiency of carbon oxides in the steelmaking gas is 85.9%. After calculation, the aluminum oxide in the salt slag is 94.1% of the theoretical recovery rate.

Claims

1. A method for efficiently capturing carbon oxides in flue gas from iron and steel sources using aluminum waste, characterized in that: Cover the surface of aluminum waste with molten salt and carry out smelting in an inert atmosphere to obtain a melt. Remove nitrogen and oxygen from the steel source flue gas and introduce it into the interior of the melt. Use the carbon oxides in the steel source flue gas to selectively oxidize the aluminum in the melt into aluminum trioxide and migrate it to the molten salt layer on the surface of the melt to form aluminum-rich slag. The aluminum-rich slag is separated by water leaching to obtain aluminum trioxide.

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

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

5. A 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 by mass percentage: 45% - 70% sodium chloride, 30% - 55% potassium chloride.

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

7. A method for efficiently capturing carbon oxides in steel source flue gas using aluminum waste according to claim 1 or 3, characterized in that: After removing nitrogen and oxygen 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%.

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

9. A 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 interior of the melt at a height of 1 / 4 - 1 / 5 from the bottom of the melt.

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