Iron-containing calcium-based flue gas desulfurizer and method for preparing the same

Abstract

The application provides a preparation method of a calcium-based flue gas desulfurizer containing iron, and is characterized in that the method comprises the following steps: 1) ball milling calcium oxide or a substance containing calcium oxide to 100-200 meshes to obtain a powder containing calcium oxide; 2) taking 5-50 parts of an iron-containing active additive, 5-10 parts of a forming additive and 3-10 parts of a reinforcing agent by weight, respectively, mixing them thoroughly, then adding water into the mixture, and kneading and stirring thoroughly to obtain a mixture; 3) taking 50-90 parts of the powder containing calcium oxide, mixing it with the mixture in batches, waiting for 1-2 hours for gradual digestion, and obtaining a mud; 4) controlling the final humidity of the mud, extruding the mud into a strip by using a powerful extruder, cutting the mud into mud sections by using a rotary cutter, and waiting for drying to complete the preparation. The desulfurizer has a high specific surface area and a large saturated sulfur capacity, can effectively remove sulfur dioxide in flue gas, and can achieve the purpose of waste reutilization due to the use of industrial solid waste, and has a great green significance for the environment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental governance technology, and particularly relates to a kind of iron-containing calcium-based flue gas desulfurizer and its preparation method. BACKGROUND

[0002] The current SO2 removal method mainly includes wet desulfurization, semi-dry desulfurization and dry desulfurization. Dry flue gas desulfurization technology refers to the application of powdery or granular absorbent, adsorbent or catalyst to remove sulfur-containing components in flue gas. It is metal oxide dry desulfurization technology and calcium injection desulfurization technology in the furnace. Dry desulfurization does not produce waste acid and waste water, and has less corrosion to equipment, higher flue gas temperature after desulfurization and less heat loss; but it has low desulfurization efficiency and slow reaction speed. Semi-dry flue gas desulfurization technology includes circulating suspension type semi-dry flue gas desulfurization technology, NID semi-dry desulfurization process, active coke desulfurization process, etc. This technology generally combines desulfurization with dust removal. Compared with dry desulfurization technology, this process has higher desulfurization efficiency. Wet desulfurization technology includes limestone-gypsum wet desulfurization process, supergravity desulfurization process, ionic liquid desulfurization process, etc. Wet desulfurization technology has good desulfurization effect, but has the disadvantages of high equipment investment and operation and maintenance cost, and is suitable for removing flue gas with high sulfur content. The calcium-based desulfurizer currently used in industry usually adds various active substances to improve the saturated sulfur capacity and desulfurization reaction rate of the desulfurizer, such as sodium, iron, manganese, strontium, etc. metal oxides, and NaCl, KCl, etc. These active substances can change the pore structure of the desulfurizer while improving the activity of the calcium-based catalyst to enhance the adsorption capacity of sulfur dioxide.

[0003] Patent CN201310528591.5 proposes a calcium-based desulfurizer using municipal sewage sludge as active substance, which has important environmental protection significance. Patent CN201810676553.7 proposes a calcium-based desulfurizer using humic acid as active substance. Patent CN200910264210.0 proposes a preparation method of calcium hydroxide with high specific surface area for dry desulfurization. Patent CN200910044305.1 mentions a calcium-based desulfurizer using fly ash as active substance; CN201910793246.1 proposes a mixed calcium-based desulfurization and denitrification agent using calcium carbonate, ferrous oxide and potassium permanganate as active components; CN202010263135.2 proposes a calcium-based desulfurizer using carbide slag and manganese ore waste residue as additives.

[0004] The calcium-based desulfurizer currently used in industry often has various shortcomings in the process of flue gas desulfurization, such as poor desulfurization activity at low temperature, low saturated sulfur capacity, complex preparation process, high cost, etc. Therefore, the development of low-cost, simple-to-prepare high-sulfur-capacity calcium-based desulfurizer has become the development direction of industrial flue gas desulfurization. SUMMARY

[0005] The technical problem this invention aims to solve is to address the high modification cost and low sulfur capacity of existing calcium hydroxide desulfurizers by providing an iron-containing calcium-based desulfurizer and its preparation method. This invention uses ferric hydroxide and galvanized iron sludge and titanium dioxide production waste iron sludge containing ferric hydroxide as active additives, and high-alumina cement and alumina sol as binders, with calcium oxide directly digested to prepare a desulfurizer with calcium hydroxide as the main component. This calcium hydroxide desulfurizer has a high specific surface area and a large saturated sulfur capacity, effectively removing sulfur dioxide from flue gas. Since it uses industrial solid waste, it also achieves waste recycling, which has significant environmental benefits.

[0006] The objective of this invention and the technical problem it solves are achieved by the following technical solutions.

[0007] This invention provides a method for preparing an iron-calcium-based flue gas desulfurizer, the method comprising the following steps:

[0008] 1) Ball mill calcium oxide or substances containing calcium oxide to 100-200 mesh to obtain calcium oxide powder;

[0009] 2) According to the weight, take 5-50 parts of iron-containing active additive, 5-10 parts of molding aid and 3-10 parts of reinforcing agent and mix them thoroughly. Then add water to the mixture and knead and stir thoroughly to obtain the mixture.

[0010] 3) Take 50-90 parts of calcium oxide powder and mix it with the above mixture in batches. Wait for it to gradually digest for 1-2 hours until the reaction is complete to obtain mud.

[0011] 4) Control the final moisture content of the mud material so that it can be extruded into strips using a high-power extruder and cut into mud segments by rotary cutting. After drying, the preparation is complete, and an iron-calcium-based flue gas desulfurizer is obtained.

[0012] Preferably, the calcium oxide-containing substance mentioned in step 1) includes calcined limestone, calcined dolomite, or calcined carbide slag.

[0013] Preferably, the iron-containing active additive in step 2) includes ferric hydroxide or zinc-plated iron sludge, titanium dioxide sludge, or alumina red mud containing ferric hydroxide; wherein the particle diameter is less than 100 mesh and the moisture content is less than 70%.

[0014] Preferably, the galvanized iron sludge is a solid waste material obtained after chemical precipitation of acidic wastewater during the hot-dip galvanizing process.

[0015] Preferably, the titanium dioxide iron sludge is a solid fertilizer obtained by alkali precipitation of iron salts during the production of titanium dioxide using the sulfuric acid process or the chloride process.

[0016] Preferably, the alumina red mud is a basic iron-containing solid waste separated in the process of producing alumina by the Bayer method.

[0017] Preferably, the forming aid in step 2) comprises a binder, a dispersant and a reinforcing agent; wherein the binder comprises a silica-alumina sol, high-alumina cement and polyethylene oxide; the dispersant comprises an alcohol amine compound and oligomeric ethylene glycol; and the reinforcing agent comprises glass short fibers, aluminum silicate or alumina ceramic fibers.

[0018] Preferably, the reinforcing agent in step 2) comprises glass short fibers, aluminum silicate or alumina ceramic fibers.

[0019] Preferably, the moisture content of the mud in step 4) is controlled to be 15-30%.

[0020] Preferably, the drying temperature in step 4) is 60-150°C, and the drying time is 5-20h.

[0021] The present application has the following beneficial effects:

[0022] (1) The loading of iron has a promoting effect on the desulfurization performance of calcium hydroxide, which has been confirmed by researchers. Usually, after loading the soluble iron salt on the calcium hydroxide and drying and calcining decomposition, the doped iron oxide calcium hydroxide desulfurizer is realized. However, the promoting effect of iron hydroxide-hydroxyl iron oxide on the desulfurization of calcium hydroxide has not been studied by predecessors. This substance has been used as an adsorption and removal material for reduced sulfur (hydrogen sulfide), but it has no effect on SO2 removal. However, the present application has found that the substance has a strong promoting effect on the desulfurization of calcium hydroxide in a wide temperature range, and can be used as an active substance added to the calcium-based desulfurizer.

[0023] (2) In industrial production, a large amount of industrial solid waste is usually generated, such as zinc plating slag generated in the galvanizing process, iron mud produced as a byproduct in the process of producing titanium dioxide from titanium concentrate / high-titanium slag, and red mud discarded in the process of producing alumina by the Bayer method, etc. These wastes contain a large amount of hydroxyl iron oxide, alkaline components and free water. If these wastes cannot be recycled, they will be discarded, which not only makes it difficult to handle and causes damage to the environment, but also ignores the high reuse potential of the material itself. The present application adds the waste as an active component to the calcium-based desulfurizer, which is beneficial to the environment and develops the reuse value of the iron oxide-containing waste, achieving both purposes at once.

[0024] (3) The present application proposes a new type of flue gas desulfurizer using calcium hydroxide as raw material and hydroxyl iron oxide and industrial solid waste containing iron oxide (zinc-plated iron slag, titanium white iron mud) as active substance to solve the problems of high modification cost and small sulfur capacity of existing calcium hydroxide desulfurizer. The process greatly reduces the development cost of high-performance calcium-based desulfurizer, improves the adsorption capacity of the desulfurizer to sulfur dioxide, and has good flue gas desulfurization activity in low temperature zone and high saturated sulfur capacity.

[0025] (4) The present application uses hydroxyl iron oxide or waste containing the same as active additive, calcium oxide and calcium-containing quicklime or calcined dolomite as main component. During the digestion reaction of calcium oxide and water, water is continuously taken from the iron-containing mud as a reactant for digestion reaction, and under the action of organic additive, the digestion reaction rate of calcium oxide is effectively controlled, the specific surface area and pore volume of the desulfurizer are increased, and the sulfur capacity of the desulfurizer is improved. At the same time, the presence of hydroxyl iron oxide has weight loss at 150-400℃, the generated iron oxide catalyzes the removal of SO2, and the generated pores provide a channel for the diffusion of SO2 in gas phase, thereby improving the reaction efficiency of the prepared desulfurizer to SO2 and increasing the sulfur capacity.

[0026] (5) In addition to the catalytic effect of iron oxide, the present application also makes full use of the following advantages of iron oxide: 1) Hydroxyl iron oxide has decomposition weight loss in the range of 100-400℃, which generates pores for the diffusion of SO2 in the pores in the flue gas, thereby expanding the sulfur capacity of Ca(OH)2 reaction; 2) Ca(OH)2 is generated by hydration and digestion reaction of CaO, and the digestion process uses iron oxide hydroxyl mud containing water and iron oxide powder to gradually knead, which effectively controls the digestion reaction rate of CaO by gradually taking water from the water-containing iron oxide hydroxyl mud, thereby realizing large specific surface area and pore volume. The prepared desulfurizer has high desulfurization efficiency. In addition, the use of hydroxyl iron oxide in industrial solid waste to prepare calcium-based desulfurizer not only reduces the pollution and cost generated by solid waste treatment, but also provides a new outlet for resource recycling. Especially after being applied to steel hot blast furnace, the desulfurization waste can be directly applied in the rotary hearth furnace, thereby realizing iron recycling.

[0027] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, and to implement the content of the description, the following will be described in detail with reference to the preferred embodiments of the present application and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Desulfurization effect curve of iron-containing calcium-based flue gas desulfurizer obtained according to Example 1 of the present application and pure calcium hydroxide, and a certain commercial calcium hydroxide. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application and the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0030] Example 1: (1) The calcium oxide is ball milled to 100-200 mesh to obtain a calcium oxide-containing powder. According to weight parts, 30 parts of galvanized iron mud, 5 parts of high-aluminum cement and 5 parts of aluminum silicate are respectively taken and fully mixed, and then water is added to the mixture and fully kneaded and stirred to obtain a mixture. The calcium oxide-containing powder is taken in batches and mixed with the above mixture, and the reaction is allowed to proceed for 1-2 hours until it is completed, to obtain a mud. The final humidity of the mud is controlled so that the moisture content is 23%, so that the mud can be extruded into a strip by using a powerful extruder, and the mud segment is cut by rotation, and after drying at 105°C for 23 hours, the preparation is completed to obtain an iron-calcium-based flue gas desulfurizer.

[0031] Example 2: (2) The calcined limestone is ball milled to 100-200 mesh to obtain a calcium oxide-containing powder. According to weight parts, 40 parts of titanium white iron mud, 5 parts of polyethylene oxide and 5 parts of aluminum silicate are respectively taken and fully mixed, and then water is added to the mixture and fully kneaded and stirred to obtain a mixture. The calcium oxide-containing powder is taken in batches and mixed with the above mixture, and the reaction is allowed to proceed for 1-2 hours until it is completed, to obtain a mud. The final humidity of the mud is controlled so that the moisture content is 15%, so that the mud can be extruded into a strip by using a powerful extruder, and the mud segment is cut by rotation, and after drying at 150°C for 5 hours, the preparation is completed to obtain an iron-calcium-based flue gas desulfurizer.

[0032] Example 3: The calcined calcium carbide slag is ball milled to 100-200 mesh to obtain a calcium oxide-containing powder. According to weight parts, 5 parts of alumina red mud, 5 parts of high-aluminum cement and 5 parts of glass short fibers are respectively taken and fully mixed, and then water is added to the mixture and fully kneaded and stirred to obtain a mixture. The calcium oxide-containing powder is taken in batches and mixed with the above mixture, and the reaction is allowed to proceed for 1-2 hours until it is completed, to obtain a mud. The final humidity of the mud is controlled so that the moisture content is 30%, so that the mud can be extruded into a strip by using a powerful extruder, and the mud segment is cut by rotation, and after drying at 60°C for 20 hours, the preparation is completed to obtain an iron-calcium-based flue gas desulfurizer.

[0033] Comparative Example 1

[0034] The catalyst is prepared according to the following weight percentage: uranium oxide 5 kg, zirconium oxide 5 kg, exciter 15 kg, carbide slag 40 kg, manganese ore waste residue 35 kg, wherein the exciter uses molten salt furnace waste residue. The above catalyst is added to industrial-grade calcium hydroxide (calcium hydroxide mesh number ~ 260, content > 75%) at a proportion of 1%, stirred uniformly, then water is added, and the mud is placed in an extruder for extrusion and dried into a shape.

[0035] Test Example 1: Desulfurization effect of the desulfurizer on SO2

[0036] Test objects: iron-containing calcium-based flue gas desulfurizer of Example 1, pure calcium hydroxide, and a certain commercial calcium hydroxide.

[0037] Test conditions: SO2: 0.1%, H2O: 10%, O2: 6%, gas flow rate 200 ml / min, desulfurizer dosage: 1 g.

[0038] Test method (steps): The desulfurizer is placed in a fixed bed quartz reactor, and after being raised to 150°C, the residual gas in the gas path is purged using N2, the reaction water vapor is obtained by flowing out of the laminar pump and being preheated in a heating band, the heating band temperature is set at 200°C, and SO2, H2O, and O2 are used for the reaction, which are supplied from gas cylinders. After the water is removed using a gas washing bottle at the end of the reactor, the gas concentration is measured using a flue gas analyzer (Gasmate DX4000, Finland), and the conversion rate is calculated according to the following formula:

[0039] ;

[0040] The experimental results are shown in the accompanying Figure 1 From the Figure 1 It can be seen that the desulfurization efficiency of the iron-containing calcium-based flue gas desulfurizer of Example 1 of the present application remains at about 85 min, which is much higher than that of pure calcium hydroxide and a certain commercial calcium hydroxide. This shows that Example 1 of the present application has superior desulfurization activity and can effectively remove SO2 in flue gas.

[0041] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and scope of the claims are intended to be included in the present application.

Claims

1. A process for the preparation of an iron-containing calcium-based flue gas desulfurizer, characterized in that, The method comprises the following steps: 1) Ball-milling calcium oxide or a substance containing calcium oxide to 100-200 mesh to obtain a calcium oxide-containing powder; 2) Taking 5-50 parts of an iron-containing active additive, 5-10 parts of a molding additive, and 3-10 parts of a reinforcing agent by weight, respectively, and mixing them thoroughly, then adding water to the mixture and kneading and stirring thoroughly to obtain a mixture; 3) Taking 50-90 parts of the calcium oxide-containing powder and mixing it with the above mixture in batches, waiting for it to gradually digest for 1-2 hours until the reaction is complete to obtain a paste; 4) Controlling the final humidity of the paste so that it can be extruded into a strip using a powerful extruder, and cutting the paste into sections using a rotary cutter, waiting for it to dry to complete the preparation to obtain an iron-containing calcium-based flue gas desulfurizer; The iron-containing active additive in step 2) includes iron hydroxide or galvanized iron mud containing iron hydroxide, titanium white iron mud, and alumina red mud; wherein the particle diameter is less than 100 mesh and the moisture content is less than 70%. The iron-containing calcium-based flue gas desulfurizer is used for removing sulfur dioxide.

2. The production method according to claim 1, characterized by, The substance containing calcium oxide in step 1) includes calcined limestone, calcined dolomite, or calcined calcium carbide slag.

3. The preparation method according to claim 1, characterized in that, The galvanized iron mud is a solid waste material obtained by chemical precipitation of acidic wastewater in a hot-dip galvanizing process.

4. The production method according to claim 1, characterized by, The titanium white iron mud is a solid fertilizer obtained by alkaline precipitation of iron salt in the production process of sulfuric acid method titanium white or chlorination method titanium white.

5. The method of claim 1, wherein, The alumina red mud is an alkaline iron-containing solid waste separated during the production of alumina by the Bayer process.

6. The method of claim 1, wherein, The molding additive in step 2) includes a binder, a dispersant, and a reinforcing agent; wherein the binder includes silica sol, high-aluminum cement, and polyethylene oxide; the dispersant includes an alcohol amine compound and an oligomeric ethylene glycol; and the reinforcing agent includes glass short fibers, aluminum silicate, or alumina ceramic fibers.

7. The preparation method according to claim 1, characterized in that, The reinforcing agent in step 2) includes glass short fibers, aluminum silicate, or alumina ceramic fibers.

8. The method of claim 1, wherein, The humidity of the paste in step 4) is controlled to have a moisture content of 15-30%.

9. The method of claim 1, wherein, The drying temperature in step 4) is between 60-150°C, and the drying time is 5-20 hours.

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