A kind of carbon dioxide adsorbent and preparation method thereof

Abstract

The present invention discloses a carbon dioxide adsorbent and a preparation method thereof. By heat treating secondary aluminum ash and carbide slag, a calcium oxide / calcium aluminate composite is prepared. The composite is used as a carbon dioxide adsorbent and has a high adsorption capacity and stability. The adsorbent can be regenerated or used for other purposes. The method of the present invention can not only achieve the detoxification and resource conversion of hazardous / solid wastes, but also the obtained calcium-based composite can be used for carbon dioxide capture and solidification, showing great environmental benefits and application prospects.

Description

Technical field:

[0001] The present invention relates to the technical field of carbon capture and solid waste resource utilization, and in particular to a carbon dioxide adsorbent and a preparation method thereof. Background technology:

[0002] With the development of society, the carbon dioxide content in the environment has gradually increased, posing a serious threat to the climate. With the proposal of my country's "carbon peak and carbon neutrality" strategic goals, how to save energy and reduce emissions and achieve efficient capture, utilization and storage of carbon dioxide is crucial. At present, calcium-based adsorbents have shown obvious advantages in carbon dioxide capture, such as their wide source, low cost, non-toxicity to the environment, and the ability to cyclically capture carbon dioxide through the adsorption and desorption process of carbonation / calcination. However, calcium-based adsorbents also have certain shortcomings. During the cyclic adsorption process, their adsorption performance will drop sharply due to sintering, and it will also consume natural limestone resources. Further improving the sintering resistance and stability of calcium-based adsorbents and reducing resource consumption are of great significance for the efficient capture of carbon dioxide.

[0003] The smelting, refining, and casting processes of aluminum and recycled aluminum will produce a large amount of aluminum ash slag. In addition to aluminum oxide and metallic aluminum, it also contains toxic substances such as aluminum nitride and fluoride. It has been defined as a hazardous waste in the "National List of Hazardous Wastes (2021 Edition)". If improperly handled, it will cause harm to the environment. The annual amount of aluminum ash produced in my country has exceeded 3 million tons. Together with the aluminum ash stockpiled in the early stage, the total amount is more than 20 million tons. Calcium carbide slag is a solid waste produced by the reaction of calcium carbide and water to prepare acetylene. Its main component is calcium hydroxide. The polyvinyl chloride industry emits 18 million tons of calcium carbide slag each year. The development of harmless and resource-based disposal methods for secondary aluminum ash and calcium carbide slag is also of great significance to environmental protection and green development.

[0004] Patent CN101362048B discloses a method for preparing a carbon dioxide absorbent by dissolving carbide slag in ammonium formate. Patent CN102527225B discloses calcining carbide slag to obtain calcium oxide for absorbing carbon dioxide in flue gas, and calcining and replenishing new carbide slag to achieve cyclic adsorption of carbon dioxide. Patent CN106179172B discloses using snail shells as raw materials to produce calcium carbonate, which is modified with a flavonoid-rich ginkgo extract and microorganisms, then coated with an aluminum source and calcined at high temperature to obtain an alumina-coated calcium oxide adsorbent, which increases the heat resistance of calcium oxide and improves the adsorption capacity of carbon dioxide. Patent CN107961757B discloses a composite calcium-based carbon dioxide absorbent made from limestone, water-soluble aluminum salts, etc., and cotton wool as a template, which has good cyclic stability.

[0005] It can be seen that the calcium-based carbon dioxide adsorbent currently obtained using carbide slag as raw material has the disadvantages of low adsorption capacity and poor cyclic stability. By modifying the calcium oxide-based adsorbent, its performance can be improved to a certain extent, but the current modification method has cumbersome steps, complex procedures, and large additional investment. Summary of the invention:

[0006] To overcome the shortcomings of the prior art, the present invention provides a carbon dioxide adsorbent and a method for its preparation. By heat-treating hazardous waste (secondary aluminum ash) and solid waste (calcium carbide slag), a calcium oxide / calcium aluminate composite is produced. This composite, used as a carbon dioxide adsorbent, exhibits high adsorption capacity and stability, and is regenerable or reusable for other uses. This method not only detoxifies and recycles hazardous / solid waste, but also enables the resulting calcium-based composite to be used for carbon dioxide capture and solidification, demonstrating significant environmental benefits and promising applications.

[0007] The technical solutions of the present invention are as follows:

[0008] Secondary aluminum ash and carbide slag in a mass ratio of 1:0.2 to 1:9 are evenly mixed, heat-treated at 700 to 1600° C. in air for 0.5 to 5 hours, and then cooled to obtain a carbon dioxide adsorbent, which is a calcium-based complex, specifically a calcium oxide / calcium aluminate complex, wherein the molar ratio of calcium oxide to calcium aluminate is 1:1 to 1:5. The adsorption capacity of the obtained adsorbent for a mixed gas containing carbon dioxide at 20 to 800° C. reaches 0.2 to 0.6 grams of carbon dioxide per gram of adsorbent.

[0009] Compared with the prior art, the present invention has the following advantages:

[0010] The coordinated disposal of aluminum ash and carbide slag to prepare calcium-aluminum complexes can not only detoxify and harmlessly treat both hazardous / solid wastes at the same time, realizing green development of related industries, but the resulting calcium-aluminum complex carbon dioxide adsorbent has a high adsorption capacity, assisting in carbon dioxide capture and carbon neutrality.

[0011] The adsorbent has good stability at high temperatures. Calcium aluminate as a dispersion medium can effectively inhibit or alleviate the sintering between calcium oxide grains and improve the cyclic stability of the absorbent.

[0012] The adsorbent can be used again to adsorb carbon dioxide after high-temperature regeneration, and the high-purity carbon dioxide produced during the regeneration process can be directly used for conversion or storage; alternatively, the adsorbent is converted into a calcium carbonate / calcium aluminate complex after adsorbing carbon dioxide, which can be used as building materials, cement, etc., to achieve a permanent carbon fixation effect. Specific implementation method:

[0013] The present invention will be further described below in conjunction with specific embodiments. These embodiments should be understood as merely illustrative of the present invention and not intended to limit the scope of protection of the present invention. After reading the contents described herein, various modifications or alterations made to the present invention based on the principles of the present invention also fall within the scope defined by the claims of the present invention.

[0014] Example 1

[0015] 1g of secondary aluminum ash is evenly mixed with 1g of carbide slag, heat-treated at 1100℃ in air for 2h, and then cooled to obtain a calcium oxide / calcium aluminate complex, whose adsorption capacity for 0.1MPa flue gas at 700℃ reaches 0.4g of carbon dioxide per gram of adsorbent.

[0016] Example 2

[0017] 1g of secondary aluminum ash is evenly mixed with 2g of carbide slag, heat-treated at 1300℃ in air for 3h, and then cooled to obtain a calcium oxide / calcium aluminate complex, whose adsorption capacity for 0.1MPa flue gas at 200℃ reaches 0.3g of carbon dioxide per gram of adsorbent.

Claims

1. A method for preparing a carbon dioxide adsorbent, characterized in that: The following steps are involved: Step 1: Evenly mix secondary aluminum ash and carbide slag in a mass ratio of 1:0.2 to 1:9; Step 2, placing the mixture in air and heat treating it at 700-1600° C. for 0.5-5 h, and then cooling it to obtain a carbon dioxide adsorbent; The adsorbent is a calcium-based composite, specifically a calcium oxide / calcium aluminate composite, wherein the molar ratio of calcium oxide to calcium aluminate is 1:1 to 1:5; The adsorption capacity of the adsorbent for the mixed gas containing carbon dioxide is 0.2 to 0.6 grams of carbon dioxide per gram of adsorbent at 20 to 800°C; The adsorbent is used again to adsorb carbon dioxide after high-temperature regeneration and can be recycled 5 to 20 times without significant reduction in adsorption capacity; The adsorbent is converted into a calcium carbonate / calcium aluminate complex after absorbing carbon dioxide, and is used as a building material and cement additive to achieve a permanent carbon fixation effect.