Microporous steel slag carbon-based composite desulfurization and denitrification catalyst and preparation method thereof

Abstract

The invention belongs to the field of flue gas comprehensive treatment and solid waste resource utilization in atmospheric pollution treatment, and discloses a microporous steel slag carbon-based composite desulfurization and denitrification catalyst and a preparation method thereof. The invention aims to overcome the defects of low sulfur capacity, easy ignition and high production cost of the conventional desulfurization and denitrification catalyst, and fully utilizes the solid waste steel slag of the steel plant, the prepared catalyst retains the catalytic action of activated carbon / coke, and the sulfur capacity of the catalyst is improved by utilizing the alkaline component in the modified steel slag. The steel slag carbon-based composite desulfurization and denitrification catalyst with micropores (the pore diameter is smaller than 2nm) as a main component is obtained by adopting a chemical modification and high-temperature roasting activation process under an anaerobic condition.

Description

Technical Field

[0001] The invention belongs to the field of comprehensive flue gas treatment and solid waste resource utilization in air pollution control, and relates to a microporous steel slag carbon-based composite desulfurization and denitrification catalyst and a preparation method thereof. Background Art

[0002] In recent years, as the country pays more and more attention to the atmospheric environment, the emission of various flue gases has become the focus of governance, and many industries have proposed ultra-low emission indicators and countermeasures. Desulfurization and denitrification are the focus of flue gas treatment. Among the many desulfurization and denitrification technologies, dry desulfurization and denitrification technology has been widely used in the comprehensive treatment of industrial flue gas pollutants due to its advantages of not generating new solid waste, saving water, and resource utilization of by-products. Catalysts used for dry desulfurization and denitrification have also been greatly developed. In particular, activated carbon / coke as a desulfurization and denitrification catalyst has been widely used in flue gas treatment.

[0003] However, in actual application, activated carbon / coke desulfurization and denitrification catalysts have some shortcomings that need to be improved: first, activated carbon / coke is combustible, and when the flue gas temperature is high, it is very easy to cause the bed temperature to rise rapidly or even catch fire; secondly, the space velocity and sulfur capacity of activated carbon / coke are very low, resulting in a large equipment scale, affecting the promotion of technology; thirdly, the production cost of activated carbon / coke is high, which leads to increased operating costs.

[0004] Steel slag is the most common solid waste in steel enterprises. Except for a part of it used in road paving and building materials industry, a large amount of steel slag is not used and forms slag mountains, which seriously affects the ecological environment. Especially with the restriction of steel slag use in the cement industry, the problem of steel slag treatment has become increasingly serious. Therefore, developing and exploring new ways to recycle steel slag has become a top priority for solid waste management in steel plants.

[0005] The chemical composition of steel slag is mainly CaO, MgO, FeO, SiO 2 、Al 2 O 3 It is composed of minerals such as tricalcium silicate (C3S), dicalcium silicate (C2S), RO phase and free CaO. Although steel slag contains many alkaline chemical components, it is difficult to guarantee the desulfurization and denitrification effect directly without activation because it forms a stable structure.

[0006] In a shaped activated carbon for flue gas desulfurization and denitrification based on metallurgical solid waste and its preparation method (CN201810517997), the raw materials used are 65-80% powdered activated carbon and 20-35% shaping agent, wherein the shaping agent is compounded by steel slag powder, slag powder and desulfurization ash; the mass percentages thereof include: 22-35% steel slag powder, 60-70% slag powder, and 4-8% desulfurization ash. The preparation method is: the weighed steel slag, slag, and desulfurization ash are mixed and ground evenly, mixed with the weighed powdered activated carbon by a mixer, then water is added, stirred, poured into a mold, pressed and molded, demolded, and cured to obtain the shaped activated carbon.

[0007] A composite solid waste-based activated carbon for flue gas desulfurization and denitrification and its preparation method (201910274278.0), the raw materials can be: solid waste composite (mixture of steel slag and coal gangue) 10-15%, high-efficiency grinding aid (mixture of ethylene glycol, triethanolamine and anhydrous ethanol) 0.1-0.3%, anhydrous ethanol 20-30%, hydrochloric acid 1-3%, activated carbon 15-25%, water 30%-53%. Its manufacturing method is to mix the solid waste composite and the high-efficiency grinding aid, grind them into powder, disperse them ultrasonically, dry them and roast them at 200-400℃.

[0008] Both of the above patents use molded activated carbon as raw material, and the production process is basically just a simple grinding and mixing process. The steel slag has not been modified, and the molded product has not been reduced at high temperature, so the active ingredients in the steel slag cannot be fully utilized. Moreover, both are laboratory synthesis methods, which are still a long way from industrial application. Summary of the invention

[0009] The purpose of the present invention is to solve the shortcomings of conventional desulfurization and denitration catalysts, such as low sulfur capacity, easy ignition, and high production cost, and to make full use of the solid waste steel slag of steel plants. The present invention provides a microporous steel slag carbon-based composite desulfurization and denitration catalyst and a preparation method. The prepared catalyst retains the catalytic effect of activated carbon / coke, and utilizes the alkaline components in the modified steel slag to increase the sulfur capacity of the catalyst. A chemical modification and high-temperature calcination activation process under anaerobic conditions is adopted to obtain a steel slag carbon-based composite desulfurization and denitration catalyst with micropores (pore size less than 2nm) as the main component.

[0010] The above object of the present invention is achieved through the following technical solutions:

[0011] A microporous steel slag carbon-based composite desulfurization and denitrification catalyst, the raw materials include: carbon-based material, steel slag, modifier and binder. The mass composition of the raw materials is: carbon-based material 25-70wt%, steel slag (weight after iron removal) 20-50wt%, modifier 4-10wt%, binder 2-7wt%.

[0012] The finished product of the microporous steel slag carbon-based composite desulfurization and denitrification catalyst has the following characteristics: particle size: 3-10 mm; carbon content: 20-60 wt%; proportion of micropore volume to total pore volume: ≥70%; sulfur capacity ≥25 wt%.

[0013] The carbon-based material is any one of coal, coking coal, coke powder, coke, and lignite, or a mixture of two or more thereof.

[0014] Preferably, the carbon-based material is coking coal.

[0015] Steel slag is solid waste from steel plants, and there is no special requirement for the steel slag used in the present invention. In order to improve the degree of resource utilization, the iron in the steel slag is recycled through magnetic separation as much as possible. The steel slag after magnetic separation is weighed and measured.

[0016] The present invention adopts a chemical modifier as the modifier for modification. The modifier used is an alkaline modifier, and the alkaline modifier includes sodium hydroxide, potassium hydroxide, sodium bicarbonate, etc. (any one or a mixture of two or more).

[0017] Preferably, the modifier is industrial grade flaky potassium hydroxide.

[0018] The binder used in the present invention is asphalt, medium-temperature coal tar, coal tar or other organic binders.

[0019] Preferably, the binder is medium-temperature coal tar.

[0020] The preparation method of the above-mentioned microporous steel slag carbon-based composite desulfurization and denitrification catalyst comprises the following specific steps:

[0021] (1) Magnetic separation and mixing: The steel slag powder obtained after the steel slag is magnetically separated to recover iron is weighed, and the carbon-based material and the modifier are weighed separately and then mixed;

[0022] (2) Grinding: The mixture is ground into fine powder with a particle size of 100 to 300 mesh by a grinding machine, and the grinding time is not less than 2 hours;

[0023] (3) Mixing and kneading: After weighing the binder, add it to the fine powder and mix it. After mixing and kneading, it is extruded by an extruder to form a strip, column or clover shape with an equivalent diameter of 3 to 10 mm.

[0024] (4) Drying and activation: After forming and drying, the mold is placed in an activation furnace and calcined and activated under nitrogen protection and air isolation. The activation temperature is 800±50℃;

[0025] (5) Water washing: After cooling, the activated particles are washed with water until the pH value is less than 8 to form active micropores;

[0026] (6) Drying and finished product: After drying, the finished catalyst is obtained.

[0027] The present invention also seeks to protect the use of the microporous steel slag carbon-based composite desulfurization and denitrification catalyst prepared by the above preparation method in desulfurization and denitrification.

[0028] The beneficial effects of the present invention compared with the prior art are:

[0029] (1) Since steel slag is formed in a high-temperature process, the alkaline active substances in the steel slag are all in a solid solution state, and some are in a glassy state. These substances are difficult to play their due role in the desulfurization process. By adding an activator, utilizing the strong alkalinity of the activator and the reducing property of carbon in the carbon-based material, these desulfurization active substances are released from the solid solution and glassy state after grinding and high-temperature calcination activation, thereby increasing the sulfur capacity of the catalyst.

[0030] (2) Through chemical activation, a porous structure mainly composed of micropores is formed in the catalyst, which greatly increases the specific surface area of ​​the catalyst and improves the adsorption activity and reaction activity of the catalyst.

[0031] (3) The carbon-based material in the molded catalyst plays an adsorption and chemical catalytic role, removing SO from the flue gas. 2 Chemical adsorption converts it into sulfuric acid. Since sulfuric acid is in liquid form at flue gas temperature, it is easy for the active sites to be covered by liquid. At the same time, due to capillary phenomena, some micropores will be blocked by liquid sulfuric acid, resulting in a reduction in active sites. The alkaline substances in the activated slag can react with sulfuric acid to convert sulfuric acid into sulfate, and liquid sulfuric acid into solid sulfate and water. The evaporation of water will reopen the micropores, thereby releasing the active sites of the carbon-based substances and improving the reaction activity and sulfur capacity of the catalyst.

[0032] (4) Steel slag is non-combustible, and some of its components have flame retardant effects, such as aluminates, Al 2 O 3 Etc., thereby increasing the ignition point temperature of the product and ensuring the safety of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a flow chart of a method for preparing a microporous steel slag carbon-based composite desulfurization and denitrification catalyst. DETAILED DESCRIPTION

[0034] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0035] Example 1

[0036] The preparation method of microporous steel slag carbon-based composite desulfurization and denitrification catalyst comprises the following specific steps:

[0037] (1) Magnetic separation and mixing: The steel slag powder obtained after the steel slag is magnetically separated to recover iron is weighed, and the carbon-based material and the modifier are weighed separately and then mixed;

[0038] (2) Grinding: The mixture is ground into fine powder with a particle size of 100 to 300 mesh by a grinding machine, and the grinding time is not less than 2 hours;

[0039] (3) Mixing and kneading: After weighing the binder, add it to the fine powder and mix it. After mixing and kneading, it is extruded by an extruder to form a strip, column or clover shape with an equivalent diameter of 3 to 10 mm.

[0040] (4) Drying and activation: After forming and drying, the mold is placed in an activation furnace and calcined and activated under nitrogen protection and air isolation. The activation temperature is 800±50℃;

[0041] (5) Water washing: After cooling, the activated particles are washed with water until the pH value is less than 8 to form active micropores;

[0042] (6) Drying and finished product: After drying, the finished catalyst is obtained.

[0043] The raw material composition and ratio as well as the product composition are shown in Table 1.

[0044] Example 2

[0045] The raw material composition and proportion as well as the product composition are shown in Table 1. Others are the same as in Example 1.

[0046] Example 3

[0047] The raw material composition and proportion as well as the product composition are shown in Table 1. Others are the same as in Example 1.

[0048] Example 4

[0049] The raw material composition and proportion as well as the product composition are shown in Table 1. Others are the same as in Example 1.

[0050] Example 5

[0051] The raw material composition and proportion as well as the product composition are shown in Table 1. Others are the same as in Example 1.

[0052] Table 1 Raw material composition and finished product composition

[0053]

[0054] Table 2 is a comparison of some indicators of various embodiments and comparative examples. Comparative example 1 is a self-produced desulfurization and denitrification activated coke catalyst, and comparative example 2 is a commercially available desulfurization and denitrification activated coke catalyst produced by other manufacturers.

[0055] Table 2 Some indicators of examples and comparative examples

[0056]

[0057] Note 1: The method for determining the saturated sulfur capacity is as follows: refer to the determination method in GB / T30202.4-2013 Test method for coal-based granular activated carbon for desulfurization and denitrification Part 4: Desulfurization value. However, after adsorption saturation, no thermal regeneration is performed. Instead, the total sulfur content in the catalyst sample before and after desulfurization is measured. The saturated sulfur capacity (in terms of SO 2 mass meter).

[0058] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A microporous steel slag carbon-based composite desulfurization and denitrification catalyst, characterized in that: The raw materials include: carbon-based materials, steel slag, modifiers and binders; the mass composition of the raw materials is: 25-70wt% of carbon-based materials, 20-50wt% of steel slag, 4-10wt% of modifiers, and 2-7wt% of binders.

2. The microporous steel slag carbon-based composite desulfurization and denitrification catalyst according to claim 1, characterized in that: The finished product of the microporous steel slag carbon-based composite desulfurization and denitrification catalyst has the following characteristics: particle size: 3-10 mm; carbon content: 20-60 wt%; proportion of micropore volume to total pore volume: ≥70%; sulfur capacity ≥25 wt%.

3. The microporous steel slag carbon-based composite desulfurization and denitrification catalyst according to claim 1, characterized in that: The carbon-based material is any one of coal, coking coal, coke powder, coke, and lignite, or a mixture of two or more thereof.

4. The microporous steel slag carbon-based composite desulfurization and denitrification catalyst according to claim 1, characterized in that: The alkaline modifier is any one of sodium hydroxide, potassium hydroxide, and sodium bicarbonate, or a mixture of two or more thereof.

5. The microporous steel slag carbon-based composite desulfurization and denitrification catalyst according to claim 1, characterized in that: The binder is asphalt, medium-temperature coal tar, coal tar, and organic binder.

6. The method for preparing the microporous steel slag carbon-based composite desulfurization and denitrification catalyst is characterized by: The specific steps are as follows: (1) Magnetic separation and mixing: The steel slag powder obtained after the steel slag is magnetically separated to recover iron is weighed, and the carbon-based material and the modifier are weighed separately and then mixed; (2) Grinding: The mixture is ground into fine powder with a particle size of 100 to 300 mesh by a grinding machine, and the grinding time is not less than 2 hours; (3) Mixing and kneading: After weighing the binder, add it to the fine powder and mix it. After mixing and kneading, it is extruded by an extruder to form a strip, column or clover shape with an equivalent diameter of 3 to 10 mm. (4) Drying and activation: After forming and drying, the mold is placed in an activation furnace and calcined and activated under nitrogen protection and air isolation. The activation temperature is 800±50℃; (5) Water washing: After cooling, the activated particles are washed with water until the pH value is less than 8 to form active micropores; (6) Drying and finished product: After drying, the finished catalyst is obtained.

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