CN112501429B - SO in sintering process 2 、NO x Synergistic emission reduction method - Google Patents

Abstract

The invention provides a method for collaborative emission reduction of SO2 and NOx during the sintering process, which belongs to the technical field of pollutant emission reduction during the sintering process. During the preparation process of sintering raw materials, multi-layer composite pellets are added. The multi-layer composite pellets include inner pellets and a wrapping layer arranged outside the inner pellets; ammonia is added during the preparation process of the inner pellets to inhibit agent and inner layer pelletizing material. The ammonia inhibitor can release ammonia gas after thermal decomposition. The N element content in the ammonia inhibitor accounts for 0.02-0.15% of the inner layer pellet mass; then use the outer layer pelletizing material to The outer coating layer of the inner layer pellets; the present invention can effectively improve the SO ₂ , NOx and dioxin emission reduction efficiency by adding multi-layer composite pellets to the sintering process.

Description

A method for collaborative emission reduction of SO2 and NOx during sintering process

Technical field

The present invention relates to the technical field of pollutant emission reduction during the sintering process, and more specifically, to a method for collaborative emission reduction of SO2 and NOx during the sintering process.

Background technique

As environmental problems become increasingly serious and people's awareness of environmental protection gradually increases, the steel industry, as a major pollutant emission source, has attracted more and more attention from national environmental protection departments. In 2019, five ministries and commissions including the Ministry of Ecology and Environment of China jointly issued the "Opinions on Promoting the Implementation of Ultra-Low Emissions in the Steel Industry" requiring steel companies across the country to significantly reduce pollutant emission levels and set the pollutant emission standards for the sintering/pelletizing process as particulate matter, SO ₂ ^The emission ^{limits of ,} _NO Policy controls are becoming more and more stringent, and environmental protection pressure on enterprises has increased, and they have begun to vigorously develop desulfurization, denitrification, and dioxin removal technologies. Existing flue gas pollutant emission reduction technologies generally use terminal treatment. Although the emission reduction effect is good, it requires a large investment, may produce secondary pollution, and it is difficult to achieve coordinated emission reduction of multiple pollutants.

Long Hongming of Anhui University of Technology and others innovatively proposed adding urea in a specific material layer height interval in the sintering mixture, rationally utilizing the thermodynamic and kinetic conditions of the sintering process itself, and establishing the levels of SO ₂ , NO _X and dioxins. Emission barrier, the reaction products neither enter the sinter nor the flue gas, but are concentrated and discharged with dust in the wind box at a specific position of the sintering machine. The urea method has good SO ₂ and dioxin removal effects, ammonia additives come from a wide range of sources, and the reaction products have no secondary pollution problems. It is one of the effective ways for steel enterprises to reduce emissions in the future. _{However ,} the effect _of this technology in removing _NO , but the input costs and operating costs are huge, which increases the burden of emission reduction on enterprises. The SNCR process is a non-catalyst in-furnace injection process and is used in coal-fired boilers. The SNCR process does not require the addition of a catalyst. It injects reducing agents such as NH ₃ , ammonia and urea directly into the high-temperature area of the furnace to react with NO _X. , the denitrification rate of this method can generally reach 30-50%. The denitrification process of the SNCR process needs to control the temperature within the range of 850-1100°C. However, in actual production, the sintering flue gas temperature is generally below 200°C, which does not meet the reaction temperature requirements of ammonia spray denitrification. In summary, there is an urgent need to seek appropriate solutions from a technical and economic perspective to achieve coordinated emission reduction of SO ₂ , _NO

After a patent search, some relevant technical solutions have been disclosed. For example: a method and system for synergistic emission reduction of SO ₂ and dioxin in the sintering process (CN104962732B), and a method and system for synergistic emission reduction of SO ₂ and dioxin in the sintering process based on the addition of solid inhibitors (CN105861816B). Relevant technical solutions for online SO ₂ emission reduction during the sintering process are disclosed: a desulfurization method for iron ore sintering process based on adding inhibitors (CN201110022407.0), an online desulfurization method for the sintering process (CN103834800B); Relevant technical solutions for reducing dioxin emissions are disclosed: a method for reducing dioxin emissions during the sintering process of iron ore (CN102847419A), and a method and device for adding inhibitors that reduce the generation of dioxin during the sintering process (CN105316480B). The above-mentioned disclosed technical solution proposes three adding schemes of ammonia inhibitors: (1) Mix all the ammonia inhibitors and add them to the sintered material layer; (2) Add the ammonia inhibitors to a certain part of the sintered material layer. At the height, (3) spray ammonia inhibitor on the sintered mixture layer. Although the above technical solution can achieve online emission reduction of _{SO 2} and dioxin pollutants _during the sintering process, it does not have a good inhibitory effect on _NO

Contents of the invention

1.Problems to be solved

The present invention is aimed at the problems of adding ammonia inhibitors to the sintering material in the prior art, which will lead to poor online emission reduction effects of pollutants such as SO ₂ , _NO Provides a method for synergistic emission reduction of SO ₂ and NOx during the sintering process. By adding multi-layer composite pellets to the sintering process, the multi-layer composite pellets wrap ammonia inhibitors in them, which can effectively slow down the pellets at high sintering temperatures. The NH ₃ generated at a lower release rate allows it to fully react with the pollutants generated by sintering, thereby achieving the purpose of collaborative emission reduction.

2.Technical solutions

In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

A method for collaborative emission reduction of SO2 and NOx during the sintering process. During the preparation process of sintering raw materials, multi-layer composite pellets are added. The multi-layer composite pellets include inner layer pellets and a wrapping layer arranged outside the inner layer pellets; During the preparation process of the inner layer pellets, an ammonia inhibitor and an inner layer pelletizing material are added. The ammonia inhibitor can release ammonia gas when decomposed by heat. The N element content in the ammonia inhibitor accounts for 0.02 of the mass of the inner layer pellets. -0.15%; then use the outer layer of pelletizing material to coat the outer layer of the inner layer of pellets.

Preferably, the specific steps are:

Step 1: Pour the prepared sintering raw materials and water into the cylinder mixer in sequence for primary mixing, and then perform secondary mixing without adding water; after the granulation is completed, add the multi-layer composite pellets evenly into the sintered raw materials and mix evenly to form composite sintered raw materials;

Step 2: First lay a base material layer on the lower part of the sintering cup device; then spread the mixed and granulated composite sintering raw materials and fill the sintering cup body; finally, ignite and sinter;

Step 3: After ignition, exhaust sintering is performed, and NO _X , SO ₂ , NH ₃ and dioxins in the flue gas are measured online.

Preferably, the sintering raw materials include domestic concentrate, King's ore, Russian concentrate, Roy Mountain ore, iron oxide scale, Ba mixed ore, blast furnace return ore, dust removal ash, internal return ore, as well as dolomite and quicklime as flux and coke powder as fuel.

Preferably, the outer layer of pelletizing material has a particle size of -0.149mm particle size and a mass percentage content of ≥95%; the inner layer of pelletizing material has a particle size of -0.074mm particle size and a mass percentage content of ≥95%.

Preferably, the ammonia inhibitor is urea, the particle size of which reaches -0.074mm particle size and the mass percentage content is ≥95%.

Preferably, the particle size of the inner pellets is 3-5mm;

And/or the moisture content of the multi-layer composite pellets is 8.0-8.5%, and the particle size is 12-16 mm.

Preferably, a casing is attached outside the wrapping layer; the casing includes SCR spent catalyst.

Preferably, the particle size of the pellets containing the shell is 14-18 mm.

Preferably, the specific steps are:

Step 1: Pour the prepared sintering raw materials into the cylindrical mixer one by one for mixing, add an appropriate amount of water to the air press, and then spray it into the mixer through the atomizer to mix with the sintering raw materials. The "first mixing" time is controlled at 6 minutes. After the first mixing is completed, the second mixing is carried out. No water is added for the second mixing. The "second mixing" time is controlled at 3 minutes. The moisture content of the mixture is controlled at 7.0%. After the granulation is completed, it will be finished. The multi-layer composite pellets are evenly added to the sintered raw materials, and then mixed for 30 seconds to form a composite sintered raw material;

Step two:

A) Pave a 2kg base material layer at the lower part of the sintering cup device;

B) Directly spread the mixed and granulated composite sintering raw materials, fill the sintering cup, then lightly compact it with a special round cake, and spread a small amount of finer-grained sintering raw materials into the depressions;

C) Ignition and sintering. Start the exhaust fan under the sintering cup, rotate the ignition (device) cover to the top of the sintering cup, control the negative pressure at 7kPa by adjusting the air inlet valve and the relief valve, carry out ignition, and control the amount of air and gas opening, so that The ignition temperature is maintained at around 1150°C, and the sintering timer starts. After 2 minutes of ignition, remove and close the ignition cover, adjust the negative pressure to 14kPa, and start the computer in the central control room to automatically collect the sintering temperature and exhaust negative pressure. When the sintering flue gas temperature reaches the highest value and then begins to decrease, it is the sintering end point, and the timing time t is a complete sintering time. After sintering is completed, adjust the exhaust negative pressure to 7kPa. When the exhaust gas temperature cools to 300°C, pour out the sinter;

Step 3: After ignition, exhaust sintering is performed. During the sintering process of the sintering machine, the oil-free vacuum pump is used to take out the sintering flue gas from the sampling port. The gas pipeline is connected in parallel to take the gas and transport the gas to MCA 10m infrared flue gas analysis. In the instrument, NO _X , SO ₂ , NH ₃ and dioxins in the flue gas are measured online.

Preferably, the size of the cylindrical mixer is: Φ600×1200mm, power 8.5kw, and loading capacity 120k;

And/or the specifications of the sintering cup operating platform are: 4.0m×3.0m, the inner diameter of the sintering cup is Φ200, the effective height is 800mm, the cup body is cast from Cr-containing cast iron, and the charging capacity is 50kg.

3. Beneficial effects

Compared with the existing technology, the beneficial effects of the present invention are:

(1) A method for synergistic emission reduction of SO2 and NOx during the sintering process of the present invention. During the preparation process of sintering raw materials, multi-layer composite pellets are added. The multi-layer composite pellets include inner layer pellets and pellets arranged in the inner layer. The outer wrapping layer; during the preparation process of the inner layer pellets, an ammonia inhibitor and an inner layer pelletizing material are added. The ammonia inhibitor can release ammonia gas by thermal decomposition. The N element content in the ammonia inhibitor accounts for 0.02-0.15% of the mass of the inner layer pellets; then use the outer layer pelletizing material to coat the outer layer of the inner layer pellets; the outer layer of the pellet can slow down the release rate of NH ₃ , making it Concentrated _and stable release at 600-800°C, while _NO Reduce it below the dioxin synthesis temperature to improve SO ₂ and dioxin emission reduction efficiency.

(2) A method of synergistic emission reduction of SO2 and NOx during the sintering process of the present invention. A shell is attached outside the wrapping layer. The shell includes SCR waste catalyst. The particle size of the pellets containing the shell is 14-18 mm. Utilizing the activity of V and Ti substances in the residual part of the SCR spent catalyst waste promotes _the selective reduction of _NO It is consistent with the emission window period of SO ₂ , NO _X and dioxin in flue gas, thereby effectively improving emission reduction efficiency.

(3) A method of synergistic emission reduction of SO2 and NOx in the sintering process of the present invention. The particle size of the outer layer pelletizing material reaches -0.149mm and the particle mass percentage content is ≥95%; the particle size of the inner layer pelletizing material reaches -0.074 The mass percentage content of mm particle size is ≥95%; on the one hand, this is conducive to the full mixing of the raw materials, so that the bonding effect can be fully exerted when dispersed in the pellets, and at the same time, the decomposable substances in the binder bentonite can be made high-temperature After decomposition, the adverse impact on the strength of the pellets is reduced to a minimum, thereby achieving the purpose of improving emission reduction efficiency.

(4) A method of synergistic emission reduction of SO2 and NOx in the sintering process of the present invention uses urea, a common and low-priced material, as the main pelletizing raw material. The raw materials for its preparation have wide sources, low prices, and high flue gas emission reduction efficiency. The technology is reasonable, the economic benefits are significant, and it has broad application prospects.

Description of the drawings

Figure 1 is a schematic flow chart of a method for collaborative emission reduction of SO2 and NOx in the sintering process of the present invention;

Figure 2 is a schematic diagram of the preparation effect of pellets containing inner pellets and wrapping layers according to the present invention;

Figure 3 is a schematic diagram of the preparation effect of the pellet containing the inner pellet, the wrapping layer and the outer shell of the present invention.

Label description in the schematic diagram:

100. Inner layer of pellets; 200. Wrapping layer; 300. Shell;

Detailed ways

In order to better understand the content of the present invention, the present invention will be further described below in conjunction with examples.

Example 1

As shown in Figure 1, in this embodiment, a method for collaborative emission reduction of SO2 and NOx during the sintering process, during the preparation process of sintering raw materials, multi-layer composite pellets are added. The multi-layer composite pellets include inner layer pellets 100 and a set of The wrapping layer 200 outside the inner pellet 100; ammonia inhibitors and inner pelletizing materials are added during the preparation process of the inner pellets 100. The ammonia inhibitor can release ammonia gas when decomposed by heat, and ammonia inhibits The N element content in the agent accounts for 0.02-0.15% of the mass of the inner layer pellets, in this embodiment it is 0.047%, and the mass ratio converted into urea is 0.1%; then the outer layer pelletizing material is used to make the inner layer pellets 100 The outer coating layer 200; the outer layer pelletizing material particle size reaches -0.149mm particle size mass percentage content ≥ 95%; the inner layer pelletizing material particle size reaches -0.074mm particle size mass percentage content ≥ 95%; The particle size of the inner layer pellets 100 is 3-5mm; the moisture content of the pellets is 8.0-8.5%, and the particle size is 12-16mm;

In this embodiment, the inner layer pelletizing material and the outer layer pelletizing material are both prepared by mixing domestic concentrate and bentonite as a binder. The specific content ratio is as follows:

Table 1. Ingredient list of pelletizing materials

type National essence Bentonite Adding amount(g) 2940 60

In order to verify the emission reduction performance of the pellets in this embodiment, they were added during the sintering process of the sintered material, and the performance advantages of the pellets were analyzed by detecting the changes in the contents of SO ₂ , NO _X and dioxin in the sintering flue gas. Poor, the specific implementation steps are as follows:

Step 1: Preparation of pellets.

(A) Preparation of pelletizing materials: Weigh the inner layer pelletizing materials and outer layer pelletizing materials according to weight percentage, add appropriate moisture, control the moisture content to 8.0%, mix evenly and put it into the lubricant together with 5kg steel balls. The mill is set to 40 minutes for grinding pretreatment, and particle size screening is performed after the grinding is completed;

It should be noted that in this embodiment, the outer layer pelletizing material has a particle size of -0.149mm particle size and the mass percentage content is ≥95%, the inner layer pelletizing material has a particle size of -0.074mm particle size and the mass percentage content is ≥95%, and the ammonia content is ≥95%. The particle size of the inhibitors reaches -0.074mm and the particle mass percentage content is ≥95%; this is conducive to the full mixing of the raw materials, so that the bonding effect can be fully exerted when dispersed in the pellets, and at the same time, the adhesive can be The high-temperature decomposition of decomposable substances in the binder bentonite will minimize the adverse effects on the pellet strength, thereby achieving the purpose of improving emission reduction efficiency;

(B) Prepare ammonia inhibitor solution: Mix an appropriate amount of ammonia inhibitor with water and stir to fully dissolve;

(C) Preparing the inner layer pellets 100: Add the inner layer pelletizing material into a disc pelletizing machine, and add an ammonia inhibitor solution for mixing and pelletizing to prepare the inner layer pellets 100;

It should be noted that in this step, the ammonia inhibitor solution is added by first placing it in a special ammonia inhibitor solution storage device, and then spraying it through a pipeline during the preparation of the core, and the ammonia is The inhibitor solution storage device includes a storage box, an aluminum pipe with a diameter of 15mm, and a 4-hole nozzle; spraying urea in the form of a solution into the disc pelletizing machine can effectively increase its contact with the inner pelletizing material The contact area between them increases the bonding strength of the inner pellet 100 itself to avoid damage during the subsequent granulation or sintering process, thereby achieving the purpose of improving the utilization rate of urea;

(D) Attached wrapping layer 200: Continue to add the outer layer of pelletizing material to the disc pelletizing machine, add moisture to make it grow into balls, and finally obtain the pellets.

Step 2: Pre-granulation.

Pour the prepared sintered materials into the cylindrical mixer one by one and mix them once. Add an appropriate amount of water to the air pressurizer, and then spray it into the mixer through the atomizer to mix with the sintered materials. "One-time mixing" "The time is controlled at 6 minutes. After the primary mixing is completed, secondary mixing is performed. No water is added for the secondary mixing. The "second mixing" time is controlled at 3 minutes. The moisture content of the mixture is controlled at 7.0%. After the granulation is completed, add the pellets made in step 1 evenly to the sintered material, and mix for 30 seconds to form a composite sintered raw material.

The sinter materials used in this embodiment include domestic concentrates, king ores, Russian concentrates, Royshan ores, iron oxide scales, Ba mixed ores, blast furnace return ores, dust removal ash and internal return ores, and the fluxes used include dolomite and Quicklime and solid fuel are coke powder. The chemical composition of each raw material is shown in Table 2. The proportion of each component of the composite sintering raw material is shown in Table 3. It should be noted that the table does not list all the components of various types of raw materials. , the part whose composition does not add up to 100% is other impurities;

Table 2. Chemical composition of sintered materials (%, ω)

Table 3. Sintering raw material ratio/%

Step 3: Sinter the fabric

(A) Pave a 2kg base material layer at the lower part of the sintering cup device;

(B) Directly spread the mixed and granulated composite sintering raw materials, fill the sintering cup, then lightly compact it with a special round cake, and spread a small amount of finer-grained mixture into the depression;

(C) Ignition and sintering. Start the exhaust fan under the sintering cup, rotate the ignition (device) cover to the top of the sintering cup, control the negative pressure at 7kPa by adjusting the air inlet valve and the relief valve, carry out ignition, and control the amount of air and gas opening, so that The ignition temperature is maintained at around 1150°C, and the sintering timer starts. After 2 minutes of ignition, remove and close the ignition cover, adjust the negative pressure to 14kPa, and start the computer in the central control room to automatically collect the sintering temperature and exhaust negative pressure. When the sintering flue gas temperature reaches the highest value and then begins to decrease, it is the sintering end point, and the timing time t is a complete sintering time. After sintering is completed, adjust the exhaust negative pressure to 7kPa. When the exhaust gas temperature cools to 300°C, pour out the sinter.

Step 4: Smoke detection

After ignition, exhaust sintering is performed. During the exhaust sintering process of the sintering machine, an oil-free vacuum pump is used to take out the sintering flue gas from the sampling port. The gas pipeline takes the gas in parallel and transports the gas to the MCA 10m infrared flue gas analyzer. The _NOx , _SO2 , _NH3 and dioxins in the flue gas were measured online and the emission reduction efficiency was calculated. The test results are shown in Table 4.

Example 2

The preparation method of the pellets and the sintering emission reduction method of this embodiment are basically the same as those of Embodiment 1. The difference is that the N element content of the ammonia inhibitor in this embodiment accounts for 0.038% of the 100 mass of the inner pellets. The mass ratio converted into urea is 0.08%. The concentration of SO ₂ , _NO

Example 3

The preparation method of the pellets and the sintering emission reduction method of this embodiment are basically the same as those of Example 1. The difference is that the N element content of the ammonia inhibitor in this embodiment accounts for 0.071% of the 100 mass of the inner layer pellets. The mass ratio converted into urea is 0.15%. The concentration of SO ₂ , _NO

Example 4

The preparation method of the pellets and the sintering emission reduction method of this embodiment are basically the same as those of Example 1. The difference is that the N element content of the ammonia inhibitor in this embodiment accounts for 0.094% of the 100 mass of the inner layer pellets. The mass ratio converted into urea is 0.20%. The concentration of SO ₂ , _NO

Comparative example 1

This comparative example is used as a benchmark experiment. The sintering process of this comparative example is the same as that of Example 1. The difference is that this comparative example does not add urea, and the mixed sintering material is directly added to the sintering device for sintering cup testing. After sintering begins, the concentrations of SO ₂ , _NO

Comparative example 2

The sintering process of this comparative example is roughly the same as that of Example 1. The difference is that this comparative example adopts the adding method of urea in the traditional urea method: the mixture mixed with urea is paved into a specific area in the sintered material layer. , where a specific area refers to distributing the mixture in the sintering material at 70-200mm on the sintering trolley, and the rest of the mixture is used for the sintering cup test without adding urea. After sintering begins, the concentrations of SO ₂ , NO _X and dioxin in the flue gas during the sintering process are measured and the emission reduction efficiency is calculated. The records are shown in Table 4.

Table 4. Concentrations and emission reduction efficiencies of SO ₂ , _NO

Through the experimental results of Comparative Example 1, Comparative Example 2 and Example 1, it can be found that in Example 1, urea is added to the inner layer pellets 100 to prepare pellets containing the coating layer 200, and then mixed with the sintering raw materials and added to During the sintering process, compared with the benchmark experiment without adding urea in Comparative Example 1 and the sintering test in which urea was directly paved on a specific material layer in Comparative Example 2, the SO ₂ , NO _X and dioxin emission reduction efficiencies were all higher. improved;

It can be found that compared with Comparative Example 1, the amount of sintering smoke released in Comparative Example 1 without any addition is extremely large, and the pollution caused to the environment is also extremely large; while under the action of the urea-containing pellets of Example 1, the sintering smoke The emissions of gas SO ₂ , _NO

Compared with Comparative Example ₂ , after adding urea to a specific material layer, the _{NO At} 1250 _° ^C , ammonia cannot effectively ^contact with _NO ^, the emission reduction efficiency ^{reached 80.67} %; _NO ^3. The emission reduction efficiency reaches 81.17%. It achieves a breakthrough in online coordinated emission reduction of SO ₂ , NO _X and dioxin during the sintering process, overcoming this major technical bottleneck.

This is because the outer wrapping layer 200 of the pellets can prevent the release of NH _3. Under high-temperature sintering, the outer wrapping layer 200 delays the release rate of NH ₃ , allowing it to be released concentratedly and stably at 600-800°C. _{NO _} Improve _SO2 and dioxin emission reduction efficiency.

By comparing Examples 1, 2, 3 and 4, it can be found that the emission reduction efficiency of SO ₂ , _NO , the improvement of emission reduction efficiency becomes gradually slow, and the benefits are not high. Therefore, from the perspective of efficiency and economy, it is best to choose 0.10% urea addition amount.

The present invention is described in detail above in conjunction with specific exemplary embodiments. However, it is to be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description and drawings are to be regarded as illustrative only and not restrictive, and if any such modifications and variations are made, they will fall within the scope of the invention described herein. In addition, the background art is intended to illustrate the research and development status and significance of the present technology, and is not intended to limit the present invention or the application and application fields of the present invention.

More specifically, although exemplary embodiments of the present invention have been described herein, the present invention is not limited to these embodiments, but includes modifications, omissions, modifications, omissions, modifications, omissions, modifications, omissions, modifications, omissions, etc. Any and all embodiments may be combined, adapted, and/or substituted (eg, between embodiments), and embodiments of the invention may be combined as desired. The limitations in the claims may be construed broadly depending on the language used in the claims and are not limited to the examples described in the foregoing detailed description or during the prosecution of this application, which examples are to be considered non-exclusive. Any steps recited in any method or process claim may be performed in any order and are not limited to the order presented in the claim. Accordingly, the scope of the invention should be determined only by the appended claims and their legal equivalents, and not by the description and examples given above.

Claims (7)

1. The method for reducing emission by synergy of SO2 and NOx in the sintering process is characterized in that a plurality of layers of composite pellets are added in the preparation process of sintering raw materials, and the plurality of layers of composite pellets comprise inner pellets (100), a wrapping layer (200) arranged outside the inner pellets (100) and a shell (300) wrapped outside the inner pellets (100); the ammonia inhibitor and the inner pellet forming material are added in the preparation process of the inner pellet (100), the ammonia inhibitor is decomposed by heating to release ammonia, the content of N element in the ammonia inhibitor is 0.02-0.15% of the mass of the inner pellet, and the particle size of the inner pellet is controlled to be 3-5mm; then coating a wrapping layer (200) on the outer part of the inner pellet (100) by using an outer pellet forming material, wherein the particle size of the obtained pellet is 12-16mm; finally, wrapping the outer part of the wrapping layer (200) by using an SCR waste catalyst, wherein the particle size of the formed pellets is 14-18mm;

specifically, the emission reduction method comprises the following steps:

step one: pouring the prepared sintering raw materials and water into a cylinder mixer in sequence for primary mixing, and then carrying out secondary mixing without adding water; after granulating, uniformly adding the produced multilayer composite pellets into a sintering raw material, and uniformly mixing to form a composite sintering raw material; more specifically, the prepared sintering raw materials are sequentially poured into a cylinder mixer for primary mixing, a proper amount of water is added into an air pressurizing machine, and then sprayed into the mixer through an atomizer to be mixed with the sintering raw materials, wherein the primary mixing time is controlled to be 6min, secondary mixing is performed after the primary mixing is finished, water is not added during the secondary mixing, the secondary mixing time is controlled to be 3min, and the water content of the mixture is controlled to be 7.0%; after granulating, uniformly adding the manufactured multilayer composite pellets into the sintering raw materials, and uniformly mixing for 30 seconds to form the composite sintering raw materials;

step two: firstly, paving a primer layer at the lower part of a sintering cup device; paving the mixed and granulated composite sintering raw materials and filling the sintering cup body; finally, ignition and sintering are carried out;

step three: after ignition, carrying out induced draft sintering to NO in the flue gas _X 、SO ₂ 、NH ₃ And dioxin on-line measurement.

2. The method for reducing emission of SO2 and NOx in a sintering process according to claim 1, wherein the sintering raw materials comprise domestic concentrate, king ore, russian fine powder, luo Yishan ore, iron scale, bamixed ore, blast furnace return ore, fly ash, internal return ore, dolomite as a flux, quicklime and coke powder as fuel.

3. The method for reducing emission by synergy of SO2 and NOx in a sintering process according to claim 1, wherein the particle size of the outer layer pelleting material reaches-0.149 mm, and the mass percentage content of the particle size fraction is more than or equal to 95%; the particle size of the inner layer pelletizing material reaches-0.074 mm, and the mass percentage content of the particle size is more than or equal to 95%.

4. The method for reducing emission of SO2 and NOx in a synergistic manner in a sintering process according to claim 1, wherein the ammonia inhibitor is urea, and the mass percentage content of the ammonia inhibitor reaches-0.074 mm particle size fraction and is more than or equal to 95%.

5. The method for reducing emission of SO2 and NOx in a sintering process according to claim 1, wherein the water content of the multi-layer composite pellets is 8.0-8.5%.

6. A method for reducing emission of SO2 and NOx in a sintering process according to any one of claims 1 to 5, wherein,

in the second step, the specific steps are as follows:

a) Paving 2kg of base material layer at the lower part of the sintering cup device;

b) Directly paving the uniformly mixed and granulated composite sintering raw materials, filling the sintering cup body, lightly compacting by using a special round cake, and distributing a small amount of sintering raw materials with finer granularity in the concave part;

c) Firing and sintering: starting an exhaust fan below the sintering cup, rotating an ignition (device) cover to the position above the sintering cup body, controlling negative pressure to 7kPa through adjusting an air inlet valve and a relief valve, igniting, controlling the air inlet amount and the gas opening, keeping the ignition temperature at about 1150 ℃, and starting timing of sintering; after ignition for 2min, removing and closing an ignition (device) cover, adjusting the negative pressure to 14kPa, and starting a computer in a central control room to automatically collect sintering temperature and exhaust negative pressure; when the temperature of the sintering flue gas reaches the highest value, the temperature starts to drop to be the sintering end point moment, and the timing time t is the once complete sintering time; after sintering, adjusting the negative suction pressure to 7kPa, and pouring out the sinter when the temperature of the waste gas is cooled to 300 ℃;

in the third step, the specific steps are as follows: the sintering process includes igniting, exhausting sintering, taking out sintering fume from the sampling port with oil-free vacuum pump, taking gas via parallel gas pipeline, conveying the gas to MCA10m infrared fume analyzer, and eliminating NO in fume _X 、SO ₂ 、NH ₃ And dioxin on-line measurement.

7. The method for synergistic SO2 and NOx emission reduction in sintering process according to claim 6, wherein the dimensions of the cylinder mixer are: phi 600 multiplied by 1200mm, power 8.5kw, and charge 120k;

and/or the specification of the sintering cup operation platform is as follows: 4.0mX3.0m, the inner diameter phi 200 of the sintering cup and the effective height 800mm, the cup body is cast by Cr-containing cast iron, and the charging amount is 50kg.