A method for preparing cement kiln flue gas purifier from aluminum ash

Abstract

This patent discloses a method for preparing cement kiln flue gas purifier from aluminum ash, wherein calcium source and sodium source are added to aluminum ash and mixed evenly, and then calcined in a nitrider to obtain the flue gas purifier. This method has low production cost and high efficiency, and realizes high-quality recycling of resources.

Description

Technical Field

[0001] The invention relates to the field of resource utilization of non-ferrous solid waste, and in particular to the application of aluminum ash in preparing a cement kiln flue gas purifier. The flue gas purifier prepared from the aluminum ash can be used for removing nitrogen oxides in cement kiln flue gas. Background Art

[0002] Aluminum ash is a product of the aluminum smelting process. Depending on the raw materials used for aluminum smelting and the purpose of production, the composition and content of aluminum ash will vary greatly. Aluminum ash produced by using electrolytic aluminum liquid to produce remelted aluminum ingots accounts for about 1.1% of the ingot output. Its composition is relatively simple and stable. It is mainly composed of metallic aluminum, aluminum oxide, aluminum nitride, chloride salts (sodium chloride, potassium chloride) and electrolytes (sodium fluoride, calcium fluoride, cryolite, etc.), of which aluminum accounts for about 40%-50% and aluminum oxide accounts for about 30%-40%. In the aluminum ash produced by the production of aluminum alloy products, in addition to metallic aluminum, aluminum oxide, aluminum nitride, chloride salts and electrolytes, there are also other elements and oxides of varying amounts and types [Liu Zhansheng, Liang Xuemin, Lu Zhifeng. A brief analysis of the formation and evolution of each component in aluminum ash [J]. Hunan Nonferrous Metals, 2019, 35 (5): 58-60].

[0003] The aluminum particles contained in aluminum ash have the characteristics of large surface area and high activity. They are easy to react and produce hydrogen when they come into contact with water or in a humid environment. The aluminum nitride in aluminum ash produces ammonia when it comes into contact with water. Hydrogen and ammonia are both reducing gases. They are prone to explosion when they come into contact with oxygen and open flames. Ammonia has a pungent odor, which is one of the main reasons why aluminum ash is environmentally harmful. In addition to being reactive, the leaching toxicity test found that the dissolved fluoride ions in the aluminum ash samples tested exceeded the standard. Excessive discharge of fluoride ions has serious harm to water bodies, soil, animals and plants. The removal and harmless disposal of fluorine are the key problems that need to be solved in the comprehensive disposal technology of aluminum ash [Jiao Zhiwei, Liu Wei, Zhang Tao, et al. Research on the identification of solid waste properties of aluminum ash in aluminum smelting enterprises [J]. Modern Metallurgy, 2019, 47 (4): 19-21].

[0004] Generally, aluminum ash can be divided into primary aluminum ash and secondary aluminum ash according to the different aluminum content in it. The aluminum slag scraped out from the smelting furnace is called primary aluminum ash. It is grayish white in appearance and is mainly a mixture of aluminum and aluminum oxide. The aluminum content can reach 15%-70%. It is also called "white aluminum ash". Secondary aluminum ash is the waste after the extraction of aluminum from primary aluminum ash. Its main components are aluminum oxide, aluminum nitride, aluminum, salts and other components. Because it is solidified into a block, it is also called "salt cake" [Li Shuai, Liu Wanchao, Liu Zhongkai, et al. Current status and prospects of aluminum ash treatment technology [J]. Nonferrous Metals (Smelting Part), 2018, (10): 25-29].

[0005] The aluminum ash used in this patent is secondary aluminum ash after metallic aluminum is extracted from primary aluminum ash. In view of the problem that secondary aluminum ash cannot be utilized at a high value, this patent provides a method for preparing cement kiln flue gas purifier from aluminum ash to promote the high value utilization of aluminum ash. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a method for preparing a cement kiln flue gas purifier from aluminum ash. Compared with the existing technical solutions, the method can increase the added value of products, realize resource recycling, and has significant economic and social benefits.

[0007] A method for preparing a cement kiln flue gas purifier from aluminum ash comprises the following steps: adding a calcium source and a sodium source to the aluminum ash and mixing them evenly, and calcining in a nitrider to obtain the flue gas purifier.

[0008] The calcium source is one of limestone, carbide slag and marble powder, and the added amount is 10-30% of the mass of the aluminum ash.

[0009] The sodium source is one of Glauber's salt and saltpeter, and the added amount is 10-30% of the mass of the aluminum ash.

[0010] The nitrider is a suspension calcining furnace.

[0011] The calcination temperature is 800-1100°C.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] The calcium source is one of limestone, carbide slag, and marble powder. During the calcination process, the calcium source decomposes into calcium oxide, which can react with aluminum oxide in aluminum ash to form calcium aluminate, thereby breaking the aluminum oxide film wrapped on the surface of the metal aluminum, which is beneficial to the nitridation of the metal aluminum to form aluminum nitride.

[0014] The sodium source is one of Glauber's salt and saltpeter. During the calcination process, the sodium source can also react with the alumina in the aluminum ash to form sodium aluminate, so that the alumina film wrapped on the surface of the metal aluminum breaks, and promotes the nitridation of the metal aluminum to form aluminum nitride. The nitrider is a suspension calciner, which consists of a preheater and a fluidized bed furnace, and has the characteristics of high thermal efficiency and low investment. The number of stages of the preheater is 2-6, and it is designed according to the principle of the preheater commonly used in the pre-decomposition cement kiln. The principle of the fluidized bed furnace is a columnar turbulent bed, which is a column unit with a constriction. The ratio of the inner diameter of the column unit to the inner diameter of the constriction is 1.1:1-1.8:1, and the ratio of the height of the column unit to the inner diameter of the column is 1:1-4:1. The fuel for calcination is one of waste oil, coal, and waste plastics, and the materials in the fluidized bed furnace are indirectly heated. Using waste oil and waste plastics as fuel can realize resource recycling. The gas in contact with the material in the nitrider is nitrogen, which is separated from the air. The oxygen separated from the air is used for fuel combustion, which is beneficial to increase the flue gas temperature. The flue gas produced is mainly carbon dioxide, which is conducive to recycling.

[0015] The main phases of the obtained flue gas purifier are aluminum nitride and calcium aluminate. Water is added to the flue gas purifier, and water reacts with aluminum nitride to release ammonia; calcium aluminate reacts with water to release calcium hydroxide, which promotes the reaction of aluminum nitride with water and the release of ammonia from the aqueous solution. The generated ammonia is used for denitrification of cement kiln flue gas and eliminates nitrogen oxides in the flue gas. In addition, the sodium source in the flue gas purifier can be used as a catalyst for the reaction of aluminum nitride with water, and the reaction rate of this reaction is 100%. The precipitate produced by the reaction of the flue gas purifier with water can be used as a raw material for cement, realizing full utilization of resources. The flue gas purifier is solid and easy to transport. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below in conjunction with specific embodiments.

[0017] Calcium source and sodium source are added to aluminum ash and mixed evenly, and then calcined in a nitrider to obtain a flue gas purifier. The formula of calcium source and sodium source and calcination temperature are shown in Table 1.

[0018] Table 1

[0019]

[0020] The metallic aluminum in the aluminum ash is converted into aluminum nitride, and the aluminum oxide is converted into calcium aluminate, and the conversion rate is 100%; the embodiments of the present invention can be implemented and achieve the purpose of the invention. The present invention is not limited to these embodiments.

Claims

1. A method for preparing a cement kiln flue gas purifier from aluminum ash, characterized in that: The following steps are involved: A calcium source and a sodium source are added to the aluminum ash and mixed evenly, and the mixture is calcined in a nitrider to obtain a flue gas purifier; wherein the calcium source is one of limestone, carbide slag and marble powder, and the added amount is 10-30% of the mass of the aluminum ash; the sodium source is one of sodium sulfate and saltpeter, and the added amount is 10-30% of the mass of the aluminum ash; the nitrider is a suspension calcining furnace, which is composed of a preheater and a boiling furnace; the calcining fuel is one of waste engine oil, coal and waste plastics, the material in the boiling furnace is indirectly heated, oxygen is used for fuel combustion, and the calcining temperature is 800-1100°C; the gas in contact with the material in the nitrider is nitrogen.

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