Sodium-based dry desulfurizer and its preparation method and use

Abstract

The present invention relates to a sodium-based dry desulfurizer for flue gas, and a preparation method and use thereof, and belongs to the field of chemical technology. The sodium-based dry desulfurizer of the present invention comprises secondary particles with a particle size of 1 to 10 mm composed of primary particles of sodium salt with a particle size of less than 10 μm; the sodium salt is sodium carbonate. The desulfurizer of the present invention has high desulfurization activity, can stably meet national emission indicators and has a wider engineering operation margin; the desulfurization process has lower requirements on flue gas temperature, can be used for flue gas desulfurization at lower temperatures, and broadens the application temperature range of sodium dry desulfurization; in actual use, the excess coefficient can be reduced by 10 to 30%, and the cost of desulfurization agents can be reduced by more than 20%; the preparation method of the present invention is simple, and the workload of the mill of the dry desulfurization system is greatly reduced when it is used, and the mill only plays a role in dispersing and fluidizing the desulfurizer, reducing the operating electricity cost of the desulfurization system and extending the service life of the mill of the dry desulfurization system.

Description

Technical Field

[0001] The invention relates to a sodium-based dry desulfurizing agent for flue gas and a preparation method and application thereof, belonging to the technical field of chemical industry. Background Art

[0002] In the coking, sintering, refractory materials, waste incineration, gas boiler and other industries, the dry desulfurization process has excellent industry adaptability. In the coking industry, the dry desulfurization process can keep the chimney hot and safe; in the refractory industry, it can operate reliably without wastewater discharge; in the waste incineration industry, it is a bottom-line measure to meet emission standards; in the coal-fired power generation industry, it can effectively remove SO before denitrification. 3 ; In the gas boiler industry, it has efficient desulfurization, no corrosion, and no wastewater discharge.

[0003] There are many types of flue gas dry desulfurization agents. Compared with other dry desulfurization agents (such as calcium, magnesium, etc.), sodium bicarbonate is currently the most efficient dry desulfurization agent and is generally accepted by various industries, forming a wide application of sodium bicarbonate dry desulfurization process. The optimal pyrolysis reaction temperature condition of sodium bicarbonate dry desulfurization process is: 120 ~ 180 ℃. Under high temperature conditions, sodium bicarbonate pyrolysis expands, the surface is modified, and the reaction interface is greatly increased. Practice has proved that when sodium bicarbonate is used as a desulfurization agent, the purified flue gas SO 2 The content is affected by the original flue gas SO 2 The content fluctuation has little impact and can be stably controlled at the emission level set by the system. However, the use of other desulfurizers, such as calcium hydroxide, is limited by the low reaction efficiency of calcium salts, and the SO 2 The content is affected by the original flue gas SO 2 The content fluctuates and cannot stably control SO 2 emission levels.

[0004] Compared with calcium and magnesium desulfurizers, sodium bicarbonate is expensive and has only one sodium atom in its molecule, so its desulfurization equivalent is low and its cost of use is high. Industrial-grade sodium bicarbonate is in the form of flakes with large particle size, which limits its desulfurization efficiency. It needs to be processed and ground during desulfurization. The grinding equipment has a large load and high energy consumption, which is a vulnerable point of the dry desulfurization system and is where system failures often occur. The particle size of sodium bicarbonate is still large after grinding. When a non-desulfurizer circulating desulfurization system is used, the excess coefficient is above 120%, the utilization rate is low, and the cost is further increased. In addition, efficient desulfurization of sodium bicarbonate requires a high-temperature pyrolysis process of flue gas. Only after the specific surface area is doubled can the gas-solid reaction to remove SO be more effective. 2 Since sodium bicarbonate dry desulfurization undergoes a high-temperature (130°C and above) pyrolysis process, it has strict requirements on the flue gas temperature. It must be above 130°C for pyrolysis and expansion. If the desulfurization is below 100°C, the pyrolysis process is not sufficient, the desulfurization effect becomes poor, it is difficult to ensure that the emission meets the standard, and the utilization rate of the desulfurizer is seriously reduced.

[0005] Sodium carbonate molecules have 2 sodium atoms, and their desulfurization equivalent (SO removed by complete reaction per unit mass of desulfurizer) 2 The amount of sodium carbonate (in tons) is 1.585 times that of sodium bicarbonate, and its market price is also comparable to that of sodium bicarbonate, making it a more economical sodium-based desulfurizer. However, since sodium carbonate itself does not have the property of pyrolysis and expansion in high-temperature flue gas, it is impossible to use the pyrolysis process to increase the specific surface area and strengthen the desulfurization gas-solid reaction. Therefore, the effect of using it for dry desulfurization is very poor, and it is currently only used as a wet or semi-dry desulfurizer. However, in the application of wet and semi-dry desulfurization, the economy of sodium carbonate is lower than that of alternative calcium-based and magnesium-based desulfurizers. If sodium carbonate is deeply crushed to form submicron ultrafine particles of 5 microns or less, it will seriously stick to pipes and mills and cannot be directly applied to existing dry desulfurization systems.

[0006] In addition, dry desulfurization is limited by the inefficient characteristics of gas-solid reaction. To achieve higher and higher emission targets, higher requirements must be placed on the reactivity of the desulfurizer itself. The relevant use and technical service industries are in urgent need of finding dry desulfurization agents with higher activity and lower cost.

[0007] Lin Guangcheng, Zhao Hongchao, Du Zaiwang, et al. 2 CO 3 Application of dry desulfurization technology[J]. Gansu Metallurgy, 2018, v.40; No.176(03):101-102. A method for desulfurization using sodium carbonate is disclosed, which converts SO 2 The reaction with atomized sodium carbonate aqueous solution essentially requires SO 2 After absorbing with water, 2 CO 3 Reaction, which belongs to the principle of wet desulfurization. Since a large amount of aqueous solution still needs to be sprayed during the desulfurization process, it is essentially a semi-dry desulfurization process, and it causes a large drop in flue gas temperature. It is not suitable for many industries that require dry desulfurization or have requirements on flue gas temperature, and it is impossible to use it in the existing dry desulfurization systems that have been built and actually operated. Summary of the invention

[0008] The first problem to be solved by the present invention is to provide a new sodium-based dry desulfurization agent.

[0009] To solve the first technical problem of the present invention, the sodium-based dry desulfurizer comprises secondary particles with a particle size of 1 to 10 mm composed of primary particles of sodium salt with a particle size of less than 10 μm; the sodium salt is sodium carbonate.

[0010] In a specific embodiment, the particle size of the sodium salt primary particles is less than 5 μm.

[0011] In a specific embodiment, the particle size of the sodium salt primary particles is 0.1 to 3 μm.

[0012] In a specific embodiment, the particle size of the sodium salt primary particles is 0.1 to 1 μm.

[0013] The preparation method of the sodium salt primary particles includes but is not limited to: obtaining the sodium salt by high-speed airflow pulverization equipment. The preparation method of the sodium salt primary particles includes but is not limited to: obtaining the sodium salt by spraying the aqueous solution of the sodium salt or sodium salt mixture into high-temperature air and drying.

[0014] In a specific embodiment, the secondary particles have a particle size of 3 to 5 mm.

[0015] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned sodium-based dry desulfurization agent coarse particles.

[0016] To solve the second technical problem of the present invention, the method for preparing sodium-based dry desulfurization agent coarse particles comprises: granulating the sodium salt primary particles with a particle size of less than 10 μm to obtain secondary coarse particles with a particle size of 1 to 10 mm.

[0017] For example, sodium salt fine particles with a particle size of 0.1 to 5 μm can be extruded into secondary coarse particles with a particle size of 1 to 10 mm. Figure 5 .

[0018] For example, sodium salt fine particles with a particle size of 0.1 to 5 μm are passed through a rolling granulation device to obtain secondary coarse particles with a particle size of 1 to 10 mm.

[0019] In a specific embodiment, the particle size of the sodium salt primary particles is less than 5 μm, preferably 0.1 to 3 μm, and more preferably 0.1 to 1 μm.

[0020] The preparation method of the sodium salt primary fine particles includes various ultrafine grinding methods such as spray drying, ultrafine grinding and high-speed air flow grinding. Regardless of the physical and / or chemical method used to obtain the primary fine powder, if it is further subjected to secondary granulation molding, it is within the scope of protection of this patent.

[0021] The third technical problem to be solved by the present invention is to provide an application method of a sodium-based dry desulfurization agent.

[0022] To solve the third technical problem of the present invention, the method described comprises using the above-mentioned sodium-based dry desulfurization agent or the sodium-based dry desulfurization agent prepared by the above-mentioned method for dry desulfurization.

[0023] In a specific embodiment, the temperature of the dry desulfurization is T≥80°C, preferably 80°C≤T<100°C. Compared with the existing dry desulfurization with sodium-based desulfurizers, which requires flue gas to reach a high temperature of more than 130°C, it has a wider temperature application range.

[0024] Beneficial effects:

[0025] (1) The desulfurizing agent of the present invention has high desulfurization activity, can stably meet national emission targets and has a wide engineering operation margin.

[0026] (2) The desulfurizer of the present invention has low requirements on flue gas temperature and can be applied to flue gas as low as 80°C. The desulfurizer has a wider application range. Compared with the existing desulfurizers that have strict requirements on flue gas temperature, it can save a lot of flue gas heating costs in low-temperature flue gas desulfurization applications. At the same time, there is no need to worry about the impact of flue gas temperature fluctuations on the desulfurization effect. The desulfurization system runs more smoothly and is easy to operate and control.

[0027] (3) Improve the utilization rate of desulfurizer and reduce the excess coefficient by 10-30% in actual use.

[0028] (4) Low cost. Compared with the existing dry desulfurization using sodium bicarbonate, the desulfurization agent of the present invention reduces the direct cost by more than 20%, and has better economic performance than the existing mainstream dry desulfurization agents.

[0029] (5) The preparation method of the present invention is simple. When used, the workload of the mill in the dry desulfurization system is greatly reduced. The mill only plays a role in dispersion and fluidization, which can save electricity costs for the operation of the desulfurization system and extend the service life of the mill in the dry desulfurization system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a 1000 times magnified SEM image of the existing 800 mesh ground sodium bicarbonate desulfurizer;

[0031] Figure 2 This is a 2000-fold magnified SEM image of the primary particles of the desulfurizer prepared in Example 1 of the present invention;

[0032] Figure 3 This is a 5000 times magnified SEM image of the existing 800-mesh ground sodium bicarbonate desulfurizer;

[0033] Figure 4 This is a 20,000-fold magnified SEM image of the primary particles of the desulfurizer prepared in Example 1 of the present invention;

[0034] Figure 5 These are the desulfurizer secondary particles prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] To solve the first technical problem of the present invention, the sodium-based dry desulfurizer comprises secondary particles with a particle size of 1 to 10 mm composed of primary particles of sodium salt with a particle size of less than 10 μm; the sodium salt is sodium carbonate.

[0036] In a specific embodiment, the particle size of the sodium salt primary particles is less than 5 μm.

[0037] In a specific embodiment, the particle size of the sodium salt primary particles is 0.1 to 3 μm.

[0038] In a specific embodiment, the particle size of the sodium salt primary particles is 0.1 to 1 μm.

[0039] The preparation method of the sodium salt primary particles includes but is not limited to: obtaining the sodium salt by high-speed airflow pulverization equipment. The preparation method of the sodium salt primary particles includes but is not limited to: obtaining the sodium salt by spraying the aqueous solution of the sodium salt or sodium salt mixture into high-temperature air and drying.

[0040] In a specific embodiment, the secondary particles have a particle size of 3 to 5 mm.

[0041] To solve the second technical problem of the present invention, the preparation method of the sodium-based dry desulfurizer comprises: granulating the primary sodium salt particles with a particle size of less than 10 μm to obtain secondary coarse particles with a particle size of 1 to 10 mm.

[0042] The granulation method may be an existing conventional granulation method, such as extrusion granulation, rolling granulation, etc.

[0043] For example, sodium salt fine particles with a particle size of 0.1 to 5 μm can be extruded into secondary coarse particles with a particle size of 1 to 10 mm. Figure 5 .

[0044] For example, sodium salt fine particles with a particle size of 0.1 to 5 μm are passed through a rolling granulation device to obtain secondary coarse particles with a particle size of 1 to 10 mm.

[0045] In a specific embodiment, the particle size of the sodium salt primary particles is less than 5 μm, preferably 0.1 to 3 μm, and more preferably 0.1 to 1 μm.

[0046] In a specific embodiment, the method for preparing the sodium salt powder comprises: obtaining the sodium salt aqueous solution by spray drying.

[0047] The preparation method of the sodium salt primary fine particles includes various ultrafine grinding methods such as spray drying, ultrafine grinding and high-speed air flow grinding. Regardless of the physical and / or chemical method used to obtain the primary fine powder, if it is further subjected to secondary granulation molding, it is within the scope of protection of this patent.

[0048] To solve the third technical problem of the present invention, the method described comprises using the above-mentioned sodium-based dry desulfurization agent or the sodium-based dry desulfurization agent prepared by the above-mentioned method for dry desulfurization.

[0049] In a specific embodiment, the temperature of the dry desulfurization can be as low as T≥80°C, preferably 80°C≤T<100°C.

[0050] The working temperature of the desulfurizer of the present invention can be the same as that of the existing sodium bicarbonate, or can be a lower desulfurization temperature than the existing one, 80°C≤T<100°C. The desulfurizer has a wider application range, saves the flue gas heating cost of some low-temperature flue gas dry desulfurization, and does not worry about the influence of flue gas temperature fluctuation on the desulfurization effect.

[0051] The specific implementation modes of the present invention are further described below in conjunction with embodiments, but the present invention is not limited to the scope of the embodiments.

[0052] Example 1

[0053] Preparation of primary fine particles of desulfurizer: prepare sodium carbonate into a saturated solution, add anti-agglomeration components, spray into hot air to obtain powder with a particle size of 0.1 to 3 μm. Extrude and granulate the obtained powder to obtain a desulfurizer with a particle size of 1 to 10 mm.

[0054] The SEM image of the prepared desulfurizer primary particles is as follows: Figure 2 and 4 As shown, the SEM image of the existing sodium bicarbonate desulfurizer is as follows Figure 1 and 3 As shown in the figure, it can be seen that the microstructure sphericity of the desulfurizer of the present invention is better, while the existing sodium bicarbonate desulfurizer is a larger flaky particle.

[0055] Desulfurization agent secondary particles prepared by extrusion granulation such as Figure 5 shown.

[0056] The secondary particle desulfurizer of Example 1 and the existing 800-mesh sodium bicarbonate desulfurizer were used for desulfurization of coking flue gas in a steel plant. Desulfurized flue gas volume: 600,000 Nm 3 , flue gas temperature 100~120℃, sulfur content in flue gas 150~260mg / Nm 3 , control the SO at the outlet of desulfurization 2 ≤30mg / Nm 3 The comparison of desulfurizer dosage is shown in Table 1 below:

[0057] Table 1 Desulfurization agent dosage comparison

[0058]

[0059] The desulfurizer of Example 1 and the existing 800-mesh desulfurizer (sodium bicarbonate) were used for desulfurization of coking flue gas in a steel plant.

[0060] The desulfurizer prepared in Example 1 was used to desulfurize 600,000 Nm 3Flue gas, sulfur content in flue gas 150~260mg / Nm 3 , flue gas temperature 100 ~ 120 ℃, control the outlet SO 2 ≤30mg / Nm 3 The desulfurization effects of different dosages of desulfurizer are shown in Table 2:

[0061] Table 2 Desulfurization effect of different dosages of desulfurizer

[0062]

Claims

1. Flue gas sodium-based dry SO2 desulfurizer, characterized in that: The sodium-based dry SO2 desulfurizer comprises secondary particles with a particle size of 1 to 10 mm composed of primary particles of sodium salt with a particle size of less than 10 μm; the sodium salt is sodium carbonate; The method for preparing the sodium salt primary particles comprises: ultrafine grinding, high-speed airflow pulverization and / or spray drying; The preparation method of the sodium-based dry SO2 desulfurizer comprises: granulating the primary sodium salt particles with a particle size of less than 10 μm to obtain secondary coarse particles with a particle size of 1 to 10 mm; the granulation method is extrusion granulation or rolling granulation.

2. The sodium-based dry SO2 desulfurization agent according to claim 1, characterized in that: The particle size of the sodium salt primary particles is less than 5 μm.

3. The sodium-based dry SO2 desulfurization agent according to claim 1 or 2, characterized in that: The particle size of the sodium salt primary particles is 0.1 to 3 μm.

4. The sodium-based dry SO2 desulfurization agent according to claim 1 or 2, characterized in that: The particle size of the sodium salt primary particles is 0.1 to 1 μm.

5. The sodium-based dry SO2 desulfurization agent according to claim 1 or 2, characterized in that: The particle size of the secondary particles is 3 to 5 mm.

6. The method for preparing a sodium-based dry SO2 desulfurization agent according to any one of claims 1 to 5, characterized in that: The method comprises: granulating primary sodium salt particles with a particle size of less than 10 μm to obtain secondary coarse particles with a particle size of 1 to 10 mm; the granulation method is extrusion granulation or rolling granulation.

7. The method for preparing a sodium-based dry-process SO2 desulfurization agent according to claim 6, characterized in that: The particle size of the sodium salt primary particles is less than 5 μm.

8. The method for preparing a sodium-based dry-process SO2 desulfurization agent according to claim 6, characterized in that: The particle size of the sodium salt primary particles is 0.1 to 3 μm.

9. The method for preparing a sodium-based dry-process SO2 desulfurizer according to claim 6, characterized in that: The particle size of the sodium salt primary particles is 0.1 to 1 μm.

10. Use of the sodium-based dry-process SO2 desulfurizer prepared by the preparation method of the sodium-based dry-process SO2 desulfurizer as claimed in any one of claims 1 to 6 or the sodium-based dry-process SO2 desulfurizer as claimed in any one of claims 7 to 9 in dry-process SO2 removal.

11. Use of the sodium-based dry SO2 desulfurizer according to claim 10 in dry SO2 removal, characterized in that: The application temperature T of the dry SO2 removal is ≥80°C.

12. Use of the sodium-based dry SO2 desulfurizer according to claim 10 in dry SO2 removal, characterized in that: The application temperature of the dry SO2 removal is 100°C≤T<130°C.

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