CN102698714B - Preparation method of adsorbent for separating CO2 in biogas pressure swing adsorption - Google Patents

Abstract

A method for preparing an adsorbent for separating _CO in biogas pressure swing adsorption. After blending and mixing coal according to the mass ratio of peat: lignite = 30-40%: 70-60%, pulverize, sieve, and contact with air, Add denatured tapioca starch and coal tar to shape, then carbonize, impregnate to activate and expand pores, and activate with water vapor after drying to obtain an adsorbent with relatively uniform micropores. The adsorbent coal-type molecular sieve obtained by the method of the present invention has uniform pore diameters of 2.7-3.2 mm in centralized distribution, and the pore area of the adsorbent reaches 80%. Among the adsorbents used as biogas pressure swing adsorption to separate _CO2 , the high performance, large capacity, renewability and long life of the adsorbent are realized.

Description

Preparation method of adsorbent for separating CO2 in biogas pressure swing adsorption

technical field

The invention belongs to a method for preparing an adsorbent for separating _CO2 in biogas pressure swing adsorption.

Background technique:

Carbon molecules are a carbonaceous adsorbent with a uniform micron structure, and carbon molecular sieves (CMS) have micropores in a wedge-shaped slit state close to the diameter of the adsorbed object. With the development of science and technology, using CMS as the adsorbent, applying the mechanism of kinetic effect and equilibrium effect, the means of gas separation using pressure swing adsorption (PSA) has been continuously improved. PSA-CMS has begun to be used in biogas, coal mines, petrochemical , Natural gas, sewage treatment, rock formation gas and other fields began to be popularized and applied. the

In industrialization, there are many raw materials that can be used to manufacture CMS, including natural products, synthetic polymers, etc. Generally, the raw materials that can be used include: coal, wood, coconut shell, petroleum coke, carbon fiber, etc. Due to the wide source of coal, cheap price, relatively simple preparation process and wide application. The main component of coal is carbon, the surface is chemically active, the pore size is high, the specific surface area is large, and its abundant sub-pores are conducive to making highly active adsorption materials. the

In the pressure swing adsorption (PSA) gas separation process, the performance of the CMS adsorbent is one of the key factors for the success of this technology application. The effect of gas separation and purification depends on the performance of CMS, especially when adsorbing and separating CO ₂ in biogas, the biogas contains a small amount of impurity gases such as moisture and hydrogen sulfide, which will greatly reduce the performance of CMS adsorbent, resulting in the pressure change of biogas The effect of adsorption _CO2 separation is not ideal. Therefore, the research on the preparation of CMS adsorbent has become the focus of the research on the use of PSA separation technology in the process of biogas adsorption and separation.

Due to the many advantages of coal, the research of scientific and technical personnel on the preparation of carbon molecular sieves from coal is increasing. Among them, in foreign countries, bituminous coal and anthracite are mostly used as raw materials to prepare carbon molecular sieves. The main control procedures are pre-gas oxidation, bond breaking, and activation. In China, lignite and peat have become the focus of research, and the main control process is carbonization. the

Lignite and peat have the following characteristics respectively:

①Lignite is the coal material with the lowest degree of coalification, also known as firewood coal, and its English name is lignite, brown coal; lignite; brown coal. Low carbon content (60-70%) and high oxygen content (15-30)%. The appearance is brown, the luster is dull, and it contains high internal moisture and different amounts of humus. Because it is rich in volatile matter (>40%), it is easy to be weathered and broken in the air; it is easy to burn and smoke, and it has a wide range of sources and is cheap. The structure of lignite is loose and has a relatively developed pore structure; it has no cohesion and high oxygen content. Under certain carbonization conditions, its carbon skeleton structure tends to change towards an amorphous carbon structure with more pores that is conducive to adsorption and separation. . At present, lignite is mostly used to make molecular sieves in China. the

② Peat, (PEAT). Peat is also known as peat or peat. It is a product of natural swamps formed over thousands of years. In the absence of air in the water, a relatively stable accumulation of organic matter formed after the death of plants. The content of nitrogen and ash elements in peat is low, slightly acidic or strongly acidic, the pH value is 5.0-4.5, the water content is relatively high, generally 70-80%, and the ventilation rate is 27-29%. Lightweight, hydrated, breathable and organic. The substance is mainly composed of incompletely decomposed plant residues and complete humus, as well as minerals. In addition, peat has a certain degree of stickiness, and the addition of peat is conducive to the uniform mixing of lignite powder and coal tar, and is conducive to the mechanical strength of high adsorbent and better porosity. the

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing an adsorbent for separating _CO2 in biogas pressure swing adsorption by using lignite and peat as raw materials.

The present invention solves the above technical problems with the following technical solutions:

The process steps for preparing an adsorbent for separating _CO in biogas pressure swing adsorption using lignite and peat as raw materials are:

⑴ Coal blending, crushing, and sieving: According to the mass ratio of peat: lignite = 30-40%: 70-60%, the coal is blended and mixed, crushed, sieved through 250-300 mesh to obtain coal powder, and the coal powder is dispersed Open the shop and put it in contact with the air for 24 hours, avoid direct sunlight;

⑵ Molding: Add denatured tapioca starch and coal tar to the coal powder and mix well; the mass ratio of denatured tapioca starch: coal tar: coal powder is (4～5):(16～17):(80～78); molding specifications Diameter 2~4mm, length 4~5mm;

(3) Carbonization: heating rate 4-6°C/min; when the temperature is 200°C, keep the temperature constant for 2 hours; when the temperature is 400°C, keep the temperature constant for 2 hours; the final carbonization temperature is 780-820°C, and the final temperature constant temperature time is 35-40 minutes;

⑷ Activation and reaming: impregnate with a mixed aqueous solution containing 15-20% (m) hydrochloric acid and 5% (m) zinc chloride, the immersion temperature is 80°C, and keep for 24h; after the filtered product is dried, place it at 280-300°C , Activated with water vapor for 24h, the adsorbent with relatively uniform micropores was obtained. the

The laying thickness of the pulverized coal layer in step 1 is 5-8mm. the

The adsorbent coal-type molecular sieve obtained by the method of the present invention has uniform pore diameters of 2.7-3.2 mm in centralized distribution, and the pore area of the adsorbent reaches 80%. Among the adsorbents used as biogas pressure swing adsorption to separate _CO2 , the high performance, large capacity, renewability and long life of the adsorbent are realized.

Description of drawings

Figure 1 is a flow chart of the process for preparing an adsorbent for _CO2 separation in biogas pressure swing adsorption using lignite and peat as raw materials.

Detailed ways:

The quality of raw coal used to prepare carbon molecular sieves is different, and the selected preparation methods are also different. However, experiments have shown that the following three aspects must be considered: the raw coal itself has a high porosity reduction rate; the ash content of the coal is low; and the fixed carbon content is high. High-quality coal-type molecular sieves must have large absorption capacity, uniform distribution of pore particles, long service life, multiple regenerations, and high mechanical strength. the

Below to the present invention preparation biogas pressure swing adsorption separation _CO The process steps of the adsorbent are further described as follows:

⑴ Coal blending, crushing and sieving: coal blending according to the mass ratio of peat: lignite = 30-40%: 70-60%, the particle size of the coal should be reduced as much as possible, the finer the crushing, the better; usually pass through the particle size A 250-300-mesh sieve is appropriate; then spread out and expose to the air for 24 hours. But avoid direct sunlight. The laying thickness of the pulverized coal layer is 5-8mm. the

(2) Forming: The purpose of forming is to increase the regularity and mechanical strength of the adsorbent. The molding specifications are 2-4mm in diameter and 4-5mm in length. The binders used are denatured tapioca starch and coal tar, and the mass ratio of denatured tapioca starch: coal tar: coal powder is 4-5:16-17:80-78. the

⑶ Carbonization: Carbonization control mainly includes heating rate, carbonization final temperature, constant temperature time, etc. Through experimental comparison, it is determined that the better carbonization conditions are: heating rate 4-6°C/min; when the temperature is 200°C, keep the temperature constant for 2 hours; when the temperature is 400°C, keep the temperature constant for 2 hours; 35～40min. the

⑷ Activation and reaming: In order to activate the carbon element on the surface and edge of the carbonaceous substrate after carbonization at 780-820°C, measures are taken to make the closed pores open or form multiple void channels; the method is to use 15-20% (m) Immersion in a mixed aqueous solution of hydrochloric acid and 5% (m) zinc chloride. The immersion temperature is 80°C, keep it for 24h, filter the obtained product and dry it, place it at 280-300°C, and activate it with water vapor for 24h. Thus, an adsorbent with relatively uniform micropores is obtained. the

Example 1:

⑴ Coal blending, crushing, and sieving: blend coal according to the mass ratio of peat: lignite = 30:70, mix the peat and lignite completely, then crush them, and pass through a 250-mesh sieve to obtain the under-sieve, and then spread them out Expose to air for 24 hours in a cool place, layer thickness 5-6 mm, avoid direct sunlight. the

(2) Molding: Add denatured tapioca starch and coal tar to the undersieve obtained in step (1) to make it bonded and formed, and use a molding machine to make granules with a diameter of 2 mm and a length of 4 mm. The mass ratio of denatured tapioca starch: coal tar: coal powder is 5:15:80. the

(3) Carbonization: carbonize the shaped particles obtained in step (2), and control its heating rate to 4°C/min. When the temperature is 200°C, keep the temperature constant for 2 hours; . the

⑷ Activation and reaming: In order to activate the carbon elements on the surface and edge of the carbonaceous substrate carbonized at 780-820°C, make the closed pores open or form multiple void channels, use 15% (m) hydrochloric acid and 5% (m) Impregnation with zinc chloride mixed aqueous solution. The immersion temperature is 80°C, keep it for 24h, filter the obtained product to dry, place it at 280-300°C, and activate it with water vapor for 24h to obtain an adsorbent with relatively uniform micropores. the

Example 2

According to the mass ratio of peat: lignite = 40:60, the coal is blended, crushed and passed through a 300-mesh sieve, the diameter of the formed particles is 3mm, the length is 4.5mm, the carbonization heating rate is 5°C/min, the final carbonization temperature is 800°C, and the temperature is constant. The time is 37min, using 18% (m) hydrochloric acid and 5% (m) zinc chloride mixed aqueous solution for impregnation; the rest are the same as in Example 1. the

Example 3

According to the mass ratio of peat: lignite = 36:64, the coal is blended, crushed and passed through a 300-mesh sieve, the diameter of the formed particles is 4mm, the length is 5mm, the carbonization heating rate is 6°C/min, the final carbonization temperature is 820°C, and the constant temperature time For 40 minutes, use 20% (m) hydrochloric acid and 5% (m) zinc chloride mixed aqueous solution for impregnation, and the rest are the same as in Example 1. the

Claims (1)

1. prepare separation of C O in biogas pressure-variable adsorption for one kind ₂the method of adsorbent, processing step is:

(1) coal blending, pulverize, sieve, dry;

(2) to coal dust, add bonding agent moulding:

(3) the charing of heating;

(4) activate reaming: first with impregnating agent dipping, rear with steam activation;

It is characterized in that:

Adopt the quality of mud coal ︰ brown coal=30～40% ︰ 70～60% than coal blending, and mix rear pulverizing, cross 250～300 mesh sieves and obtain coal dust, by the coal dust lay ingress of air 24h that scatters, avoid direct sunlight;

Bonding agent is modified tapioca starch and coal tar, and the mass ratio of Bian Mu Shu Dian Fen ︰ Mei Jiao You ︰ coal dust is 5:15:80; Moulding format diameter 2～4mm, length 4～5mm;

4～6 ℃/min of programming rate of charing; When temperature is 200 ℃, constant temperature 2h; In the time of 400 ℃, constant temperature 2h; 780～820 ℃ of charing final temperatures, final temperature constant temperature time 35～40min;

With mass ratio 15-20% hydrochloric acid and 5% zinc chloride mixed aqueous solution dipping, 80 ℃ of dipping temperatures, keep 24h; After filtration gained article dry, be placed at 280～300 ℃, use steam activation 24h, obtain and there is the adsorbent compared with uniform micro.

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