CN112725616A - Method for reducing emission of sintering flue gas pollutants by using pellets containing SCR waste catalyst - Google Patents

Abstract

The invention discloses a method for reducing emission of sintering flue gas pollutants by using pellets containing SCR waste catalyst, and belongs to the technical field of pollutant emission reduction in a sintering process. Adding sintered pellets in the preparation process of a sintering raw material, wherein the sintered pellets are sequentially provided with an inner layer pellet, an outer layer pellet and a catalyst layer from inside to outside; the inner layer pellets comprise ammonia inhibitors, and the ammonia inhibitors can release ammonia gas after being heated and decomposed; the outer layer pellets comprise pore-forming agents, and the pore-forming agents enable the outer layer pellets to be internally perforated in the sintering process; the catalyst layer comprises an SCR catalyst and vanadium-titanium blast furnace slag. The pore-forming agent in the sintered pellet is heated and decomposed to generate pores, thereby delaying the decomposition of ammonia inhibitors such as urea, NH₃With NO_XThe emission window period of the fuel is consistent, and NO is reduced_XDischarging and realizing SO in a breakthrough manner under the action of a catalyst₂、NO_XAnd the dioxin is synergistically reduced.

Description

Method for reducing emission of sintering flue gas pollutants by using pellets containing SCR waste catalyst

Technical Field

The invention relates to the technical field of pollutant emission reduction in a sintering process, in particular to a method for reducing emission of sintering flue gas pollutants by using pellets containing SCR waste catalyst.

Background

The sintering/pelletizing process is an important pollution link in the steel industry, the existing flue gas pollutant emission reduction technology generally adopts terminal treatment, although the emission reduction effect is good, the required investment is large, secondary pollution is possibly generated, and the multi-pollutant synergistic emission reduction is difficult to realize.

Innovative proposals such as Longhongming, Anhui university of industry, etc. add urea in a certain specific material layer height interval in a sintering mixture, reasonably utilize own thermodynamic and kinetic conditions of the sintering process, and establish SO₂、NO_XAnd a dioxin discharge barrier, wherein reaction products do not enter sinter ores or flue gas, but are intensively discharged along with dust at a specific position of the sintering machine. SO removal by urea method₂Good dioxin removing effect, wide source of ammonia additives and no secondary pollution of reaction products, and is a future oneOne of the effective ways for reducing emission of iron and steel enterprises. However, this technique removes NO_XThe effect is not ideal, resulting in NO in the sintering flue gas_XThe emission does not conform to the existing national emission standard, and a few enterprises adopt SCR process or active carbon method to treat NO_XThe process is to flue gas NO_XThe control effect is very obvious, but the investment cost and the operation cost are huge, and the emission reduction burden of enterprises is increased. The SNCR process belongs to a non-catalytic in-furnace spraying process, is applied to a coal-fired boiler, does not need to add a catalyst, and is implemented by adding NH₃Reducing agents such as ammonia water and urea are directly sprayed into a high-temperature area of a hearth and NO_XThe reaction is carried out, and the denitration rate of the method can reach 30-50 percent generally. The temperature of the SNCR process needs to be controlled within the range of 850-1100 ℃, and the sintering flue gas temperature in the actual production is generally below 200 ℃, which does not meet the reaction temperature requirement of ammonia injection denitration. In view of the above, there is an urgent need to find a suitable solution from the technical and economic point of view to realize the sintering process SO₂、NO_XAnd the dioxin is synergistically reduced, so that the purposes of ultralow emission and low-cost treatment are achieved.

Through patent search, a part of related technical schemes are disclosed. Such as: sintering process SO₂Dioxin synergistic emission reduction method and system (CN104962732B), namely sintering process SO based on addition of solid inhibitor₂And a dioxin synergetic emission reduction method (CN 105861816B). With respect to SO during sintering₂The related technical scheme of online emission reduction is disclosed as follows: iron ore sintering process desulfurization method based on addition of inhibitors (CN201110022407.0), an on-line desulfurization method for sintering process (CN 103834800B); the related technical scheme about dioxin emission reduction in the sintering process is disclosed as follows: a method for reducing dioxin emission in the iron ore sintering process (CN102847419A), and a method and a device for adding an inhibitor for reducing dioxin generation in the sintering process (CN 105316480B). The disclosed technical proposal provides three adding schemes of the ammonia inhibitor, (1) the ammonia inhibitor is completely mixed and added into the sinter layer, (2) the ammonia inhibitor is added at a certain height of the sinter layer, and (3) the ammonia inhibitor is sprayed on the sinter mixture layer. The technical proposal can realize the sinteringIn-process SO₂And dioxin on-line abatement of pollutants, but for NO_XNo good inhibition effect on emission, and difficult realization of SO₂、NO_XAnd the emission reduction is coordinated with the dioxin.

Disclosure of Invention

1. Problems to be solved

The invention aims at the problem that the ammonia inhibitor in the prior art is added into the sintering material mainly in a mode of direct paving or direct mixing granulation, and NH generated by decomposition of the ammonia inhibitor can be caused due to the rapid decomposition of the ammonia inhibitor caused by solid heat transfer between the ammonia inhibitor and the sintering material₃With SO produced by sintering₂、NO_XInconsistent with the period of a dioxin emission window, the emission reduction efficiency is reduced; the method for reducing emission of sintering flue gas pollutants by using pellets containing SCR waste catalyst is characterized in that porous structure pellets containing ammonia inhibitors are designed at a specific temperature, so that the ammonia inhibitors are slowly heated, and the generated NH₃With SO₂、NO_XThe period of the emission window is consistent with that of dioxin emission, and the emission reduction efficiency is improved.

2. Technical scheme

In order to solve the problems, the technical scheme adopted by the invention is as follows:

a method for reducing emission of sintering flue gas pollutants by using pellets containing SCR waste catalysts is characterized in that sintering pellets are added in the preparation process of sintering raw materials, and the sintering pellets are sequentially provided with inner layer pellets, outer layer pellets and a catalyst layer from inside to outside; the inner layer pellets comprise ammonia inhibitors, and the ammonia inhibitors can release ammonia gas after being heated and decomposed; the outer layer pellets comprise pore-forming agents, and the pore-forming agents enable the outer layer pellets to be internally perforated in the sintering process; the catalyst layer comprises an SCR catalyst and vanadium-titanium blast furnace slag.

Preferably, the specific steps are as follows:

the method comprises the following steps: pouring the prepared sintering raw materials and water into a cylindrical mixer in sequence for primary mixing, and then carrying out secondary mixing without adding water; after the granulation is finished, uniformly adding the prepared sintered pellets into the sintering raw material, and uniformly mixing to form a composite sintering raw material;

step two: firstly, paving a primer layer at the lower part of a sintering cup device; then the evenly mixed and granulated composite sintering raw materials are paved and the sintering cup body is filled; finally, firing and sintering;

step three: after ignition, air draft sintering is carried out to remove NO in the flue gas_X、SO₂、NH₃And dioxins are measured on-line.

Preferably, the sintering raw materials comprise domestic concentrate, king ore, Russian fine powder, Roehan ore, iron scale, Bapug ore, blast furnace return mine, fly ash, internal return mine, dolomite serving as a fusing agent, quicklime and coke powder serving as a fuel.

Preferably, the SCR catalyst comprises V2O5 and TiO 2; the vanadium-titanium blast furnace slag comprises CaO, SiO2, V element and Ti element.

Preferably, the mass percentage content of the granularity of the outer-layer pelletizing material reaching-0.149 mm is more than or equal to 95 percent; the granularity of the inner layer pelletizing material reaches-0.074 mm, and the mass percentage content of the grain size is more than or equal to 95 percent. The average particle size of the outer layer balling material is larger than that of the inner layer balling material, so that the gaps among the mineral powder particles on the outer layer are enlarged, and the ammonium bicarbonate is favorably released by heating.

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

and/or the thickness of the outer layer pellets is 9-11 mm;

and/or the mass percentage content of the ammonia inhibitor and the pore-forming agent reaches-0.074 mm size fraction is more than or equal to 95 percent.

Preferably, the ammonia inhibitor is urea, wherein the content of N element accounts for 0.02-0.15% of the mass of the inner layer pellet; the pore-forming agent is ammonium bicarbonate, and the molar ratio of the urea to the ammonium bicarbonate is (4: 1) - (1: 4).

Preferably, the water content of the sintered pellets is 8.0-8.5%, and the particle size is 14-18 mm.

Preferably, the specific steps are as follows:

the method comprises the following steps: pouring the prepared sintering raw materials into a cylindrical mixer in sequence for primary mixing, adding a proper amount of water into an air pressurizing machine, spraying the mixture into the mixer through an atomizer to mix with the sintering raw materials, wherein the primary mixing time is controlled to be 6min, secondary mixing is carried out 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 mixed materials is controlled to be 7.0%; after the granulation is finished, uniformly adding the prepared sintered pellets into the sintering raw material, and uniformly mixing for 30 seconds to form a composite sintering raw material;

step two:

A) paving a 2kg bottom material layer on 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 little sintering raw material with fine granularity in the concave part;

C) and (5) igniting and sintering. Starting an exhaust fan below the sintering cup, rotating an ignition cover to the upper part of the sintering cup body, controlling the negative pressure at 7kPa by adjusting an air inlet valve and a relief valve, igniting, controlling the air inlet amount and the gas opening degree, keeping the ignition temperature at about 1150 ℃, and starting sintering timing. And (3) after ignition for 2min, moving away and closing an igniter cover, adjusting the negative pressure to 14kPa, and starting a central control room computer to automatically collect the sintering temperature and the air draft negative pressure. And when the temperature of the sintering flue gas reaches the maximum value, the temperature begins to drop, namely the sintering end point moment, and the timing time t is the one-time complete sintering time. After sintering, adjusting the negative pressure of air draft to 7kPa, and pouring out the sinter when the temperature of the waste gas is cooled to 300 ℃;

step three: performing air draft sintering after ignition, taking out sintering flue gas from a sampling port by using an oil-free vacuum pump in the air draft sintering process of the sintering machine, taking gas by a gas pipeline in a parallel connection mode, conveying the gas into an MCA 10m infrared flue gas analyzer, and carrying out NO treatment on the flue gas_X、SO₂、NH₃And dioxins are measured on-line.

Preferably, the dimensions of the cylindrical blender are: phi 600 multiplied by 1200mm, power 8.5kw, charge amount 120 k;

and/or the specification of the sintering cup operating platform is as follows: 4.0m is multiplied by 3.0m, the inner diameter phi of the sintering cup is 200, the effective height is 800mm, the cup body is cast by cast iron containing Cr, and the charging amount is 50 kg.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the method for reducing emission of sintering flue gas pollutants by using the pellets containing the SCR waste catalyst, the sintering pellets are added in the preparation process of sintering raw materials, and the sintering pellets are sequentially provided with the inner layer pellets, the outer layer pellets and the catalyst layer from inside to outside; the inner layer pellets comprise ammonia inhibitors, and the ammonia inhibitors can release ammonia gas after being heated and decomposed; the outer layer pellets comprise pore-forming agents, and the pore-forming agents enable the outer layer pellets to be internally perforated in the sintering process; the catalyst layer comprises an SCR catalyst and vanadium-titanium blast furnace slag. The pore-forming agent in the sintered pellets applied by the emission reduction method generates holes after being heated and decomposed, and the porous structure effectively delays the decomposition of ammonia inhibitors such as urea and NH₃With NO_XThe emission window period of the fuel is consistent, and NO is reduced_XDischarging; the activity of a portion of the V, Ti material in the catalyst may promote selective reduction of NO by urea_XFurther improve denitration efficiency, the separation effect of catalyst layer simultaneously can play the same role of delaying NH₃The purpose of the release is to make it react with SO in the flue gas₂、NO_XAnd the period of a dioxin discharge window is consistent, thereby realizing SO in a breakthrough manner₂、NO_XAnd the dioxin is synergistically reduced, the normal production of the sintering operation is ensured, the technical defect of single pollutant end treatment in the prior art is overcome, the pollutant reduction cost in the sintering process is greatly reduced, and the emission reduction burden of iron and steel enterprises is reduced.

(2) According to the method for reducing emission of sintering flue gas pollutants by using the pellets containing the SCR waste catalyst, the particle size of the ammonia inhibitor and the pore-forming agent reaches-0.074 mm, and the mass percentage content of the particle size is more than or equal to 95%. On the one hand, the raw materials are uniformly and fully mixed, so that the adhesive effect can be fully exerted when the raw materials are dispersed in the pellets, and meanwhile, the adverse effect of decomposable substances in the bentonite as the adhesive on the strength of the pellets after pyrolysis is reduced to the minimum, and the aim of improving the emission reduction efficiency is fulfilled.

(3) The method for reducing emission of sintering flue gas pollutants by using the pellets containing the SCR waste catalyst takes two common and low-price materials, namely urea and ammonium bicarbonate, as main pelletizing raw materials, and has the advantages of wide sources of preparation raw materials, low price, high flue gas emission reduction efficiency, reasonable technology, remarkable economic benefit and wide application prospect.

Drawings

FIG. 1 is a schematic flow diagram of a method for reducing emission of sintering flue gas pollutants using SCR-containing spent catalyst pellets according to the present invention;

FIG. 2 is a schematic view of sintered pellets containing inner pellets and outer pellets used in the present invention;

fig. 3 is a schematic view of sintered pellets containing inner pellets, outer pellets and a catalyst layer used in the present invention.

The reference numerals in the schematic drawings illustrate:

100. inner layer pellets; 200. pelletizing the outer layer; 300. a catalyst layer.

Detailed Description

The invention is further described with reference to specific examples.

Example 1

As shown in fig. 1, in the method for reducing emission of sintering flue gas pollutants by using pellets containing SCR waste catalyst in this embodiment, during the preparation of sintering raw materials, sintering pellets are added, and the sintering pellets are sequentially provided with an inner layer pellet 100, an outer layer pellet 200, and a catalyst layer 300 from inside to outside; the inner layer pellet 100 comprises an ammonia inhibitor, and the ammonia inhibitor can release ammonia gas after being heated and decomposed; the outer layer pellets 200 comprise pore-forming agents, and the pore-forming agents enable pores to be formed in the outer layer pellets 200 in the sintering process; the catalyst layer 300 comprises an SCR catalyst and vanadium-titanium blast furnace slag, in this embodiment, the thickness of the catalyst layer 300 is 2mm, and the mass ratio of the SCR catalyst to the vanadium-titanium blast furnace slag in the catalyst layer 300 is 1: 1; the SCR catalyst comprises V2O5 and TiO 2; the vanadium-titanium blast furnace slag comprises CaO, SiO2, V elements and Ti elements; the inner layer pelletizing material comprises domestic concentrate, and the mass percentage content of the granularity of which reaches-0.149 mm is more than or equal to 95 percent; the outer layer pelletizing material comprises domestic concentrate, and the mass percentage content of the granularity of the concentrate reaches-0.074 mm and is more than or equal to 95 percent; the particle size of the inner layer pellet 100 is 3-5 mm; the water content of the sintered pellets is 8.0-8.5%, and the particle size is 12-16 mm;

in this example, the ammonia inhibitor is urea, the decomposition temperature of the pore-forming agent is below 160 ℃, and ammonium bicarbonate with a decomposition temperature of 60-70 ℃ is selected, and the molar ratio of urea to ammonium bicarbonate is 3: 2; in addition, the content of the N element in the urea accounts for 0.047 percent of the mass of 100 percent of the inner layer pellet, and the mass ratio of the N element converted into the urea is 0.1 percent; in this embodiment, the inner layer ball-making material and the outer layer ball-making material are prepared by mixing domestic concentrate and bentonite as a binder, and the specific contents are as follows:

TABLE 1 pelletizing materials compounding table

Species of	Guojing medicine	Bentonite clay
			Added amount (g)	2940	60

In order to verify the advantages and disadvantages of the emission reduction method in the sintering process of the embodiment, SO in the sintering flue gas is detected₂、NO_XAnd analyzing the performance of the sintered pellets according to the content change of the dioxin, wherein the specific implementation steps are as follows:

the method comprises the following steps: and (4) preparing sintered pellets.

(A) Preparing raw materials: weighing and proportioning the inner-layer ball-making material and the outer-layer ball-making material according to weight percentage, adding proper water, controlling the water content to be 8.0%, uniformly mixing, then loading the mixture and 5kg of steel balls into a wet grinding machine, setting for 40min for wet grinding pretreatment, and screening the granules after the wet grinding is finished; taking a proper amount of ammonia inhibitor and pore-forming agent, and grinding to fine fraction; mixing a proper amount of ammonia inhibitor with water, and stirring to fully dissolve the ammonia inhibitor to obtain an ammonia inhibitor solution;

it should be noted that the particle size of the ammonia inhibitor and the pore-forming agent in this example reaches-0.074 mm, and the mass percentage content of the particle size is more than or equal to 95%; on the one hand, the raw materials are uniformly and fully mixed, so that the bonding effect can be fully exerted when the raw materials are dispersed in the pellets, and meanwhile, the adverse effect on the pellet strength after the decomposable substances in the binder bentonite are decomposed at high temperature is reduced to the minimum, and the purpose of improving the emission reduction efficiency is achieved;

(B) preparing inner layer pellets 100: adding the inner-layer pelletizing material into a disc pelletizer, and adding an ammonia inhibitor solution for mixing and pelletizing to prepare inner-layer pellets 100;

it should be noted that the ammonia inhibitor solution is added in this step by placing it in a specially-made ammonia inhibitor solution storage device, and spraying it through a pipe during the process of preparing the inner core, wherein the ammonia inhibitor solution storage device comprises a storage box, an aluminum pipe with a diameter of 15mm, and a 4-hole spray head; the urea is sprayed into the disc pelletizer in the form of solution, so that the contact area between the urea and the inner-layer pelletizing material can be effectively increased, the bonding strength of the inner-layer pellets 100 is improved, the urea is prevented from being damaged in the subsequent pelletizing or sintering process, and the purpose of improving the utilization rate of the urea is achieved;

(C) adhering outer layer pellets 200: continuously adding a common balling material and a pore-forming agent into the disc balling machine, and supplementing water to grow into balls;

(D) preparation of the catalyst layer 300: and continuously adding vanadium-titanium blast furnace slag and an SCR catalyst into the disc pelletizer to grow up, and finally obtaining the sintered pellets.

Step two: and (5) performing granulation.

The prepared sintering materials are poured into a cylindrical mixer in sequence for primary mixing, a proper amount of water is added into an air pressurizing machine and sprayed into the mixer through an atomizer to be mixed with the sintering materials, the 'primary mixing' time is controlled to be 6min, secondary mixing is carried out after the primary mixing is finished, no water is added in the secondary mixing, the 'secondary mixing' time is controlled to be 3min, and the water content of the mixed materials is controlled to be 7.0%. And (3) after the granulation is finished, uniformly adding the sintered pellets prepared in the step one into a sintering material, and uniformly mixing for 30 seconds to form the composite sintering raw material.

The sintering material used in this example includes domestic concentrate, king ore, russian fine powder, reunite ore, scale, batched ore, blast furnace return mine, fly ash and return mine, the used flux includes dolomite and quicklime, the solid fuel is coke powder, the chemical components of each raw material are shown in table 2, the mixture ratio of each component of the composite sintering raw material is shown in table 3, it should be noted that all the components of each kind of raw material are not listed in the table, and the part with the composition less than 100% is other impurities;

TABLE 2 chemical composition of sinter (%, ω)

TABLE 3 sintering raw material ratio%

Step three: sintered cloth

(A) Paving a 2kg bottom material layer on 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 little of mixture with fine granularity in the concave part;

(C) and (5) igniting and sintering. Starting an exhaust fan below the sintering cup, rotating an ignition cover to the upper part of the sintering cup body, controlling the negative pressure at 7kPa by adjusting an air inlet valve and a relief valve, igniting, controlling the air inlet amount and the gas opening degree, keeping the ignition temperature at about 1150 ℃, and starting sintering timing. And (3) after ignition for 2min, moving away and closing an igniter cover, adjusting the negative pressure to 14kPa, and starting a central control room computer to automatically collect the sintering temperature and the air draft negative pressure. And when the temperature of the sintering flue gas reaches the maximum value, the temperature begins to drop, namely the sintering end point moment, and the timing time t is the one-time complete sintering time. And after sintering, adjusting the negative pressure of air draft to 7kPa, and pouring out the sintered ore when the temperature of the waste gas is cooled to 300 ℃.

Step four: flue gas detection

Performing air draft sintering after ignition, taking out sintering flue gas from a sampling port by using an oil-free vacuum pump in the air draft sintering process of the sintering machine, taking gas by a gas pipeline in a parallel connection mode, conveying the gas into an MCA 10m infrared flue gas analyzer, and carrying out NO treatment on the flue gas_X、SO₂、NH₃And dioxin were measured on line and emission reduction efficiency was calculated, and the detection results are shown in table 4.

Example 2

The sintered pellets and the sintering emission reduction method in this example are basically the same as those in example 1, except that: this example was carried out by measuring SO while maintaining the thickness of the catalyst layer 300 at 1mm in example 1₂、NO_XAnd the generation concentration of dioxin are recorded as shown in table 4, and the desulfurization and denitrification rate and the emission reduction efficiency of dioxin are calculated.

Example 3

The sintered pellets and the sintering emission reduction method in this example are basically the same as those in example 1, except that: this example was carried out by measuring SO while maintaining the thickness of the catalyst layer 300 at 3mm in example 1₂、NO_XAnd the generation concentration of dioxin are recorded as shown in table 4, and the desulfurization and denitrification rate and the emission reduction efficiency of dioxin are calculated.

Example 4

The sintered pellets and the sintering emission reduction method in this example are basically the same as those in example 1, except that: this example was carried out by measuring SO while maintaining the thickness of the catalyst layer 300 at 4mm in example 1₂、NO_XAnd the generation concentration of dioxin are recorded as shown in table 4, and the desulfurization and denitrification rate and the emission reduction efficiency of dioxin are calculated.

By comparing the emission reduction efficiency of the sintered pellets of catalyst layers 300 of different thicknesses, it can be seen that between 1-3mm, SO₂And of dioxinsThe emission reduction efficiency is basically unchanged, and when the thickness is increased to 4mm, SO is added₂、NO_XAnd the reduction efficiency of dioxin is obviously reduced, which probably is because the release of ammonia in urea is influenced by the excessive wrapping of the catalyst. NO when the catalyst layer 300 has a thickness of 2mm_XThe efficiency is highest, and the thickness is optimal from the viewpoint of high efficiency and economy.

Comparative example 1

This comparative example is used as a reference experiment, and the sintering process of this comparative example is the same as example 1 except that: in the comparative example, urea is not added, and the uniformly mixed sintering material is directly added into a sintering device for sintering cup test. After the sintering is started, measuring SO of flue gas in the sintering process₂、NO_XAnd the concentration of dioxin, calculating the emission reduction efficiency, and recording the emission reduction efficiency as shown in table 4, wherein the emission reduction efficiency is used as the standard of later experiments.

Comparative example 2

The sintering process of this comparative example was substantially the same as example 1, except that: the comparative example adopts the mode of adding urea in the traditional urea method: and paving the mixture mixed with the urea in a certain specific area in the sinter bed, wherein the certain specific area is that the mixture is distributed in the sinter at the position of 70-200mm on the sintering trolley, and the rest part adopts the mixture without the urea for carrying out the sinter pot test. After the sintering is started, measuring SO of flue gas in the sintering process₂、NO_XAnd dioxin concentration and emission reduction efficiency were calculated and recorded as shown in table 4.

Through the experimental results of the comparative examples 1, 2 and 1, it can be found that the urea/ammonium bicarbonate in the example 1 is layered and pelletized, and then is uniformly mixed with the sintering raw material and added into the sintering process, compared with the standard experiment in which no urea is added in the comparative example 1 and the standard experiment in which urea is directly paved on a specific material layer in the comparative example 2, the SO is used for sintering experiment₂、NO_XThe emission reduction efficiency of dioxin is improved;

compared with the comparative example 1, the sintering smoke release amount of the comparative example 1 without any addition is extremely large, and the pollution to the environment is also extremely large; under the action of the sintered pellets prepared by mixing urea and ammonium bicarbonate in example 1, smoke was sinteredGas SO₂、NO_XAnd dioxin is effectively reduced, so the superiority of the technical scheme of preparing the sintered pellets by mixing urea and ammonium bicarbonate is reflected;

compared with the comparative example 2, after urea is added into a specific material layer, NO in the sintering flue gas_XThe emission is basically unchanged because the temperature of ammonia released by urea pyrolysis is 160 ℃, and NO is_XThe discharge temperature is 850-1250 ℃, and ammonia gas cannot be mixed with NO_XEffective contact can leave with the flue gas quickly, and NO is difficult to realize_XEfficient emission reduction; SO in flue gas in example 1₂The discharge amount is 151155mg/m³Reduced to 98458mg/m³The emission reduction efficiency reaches 83.11%; NO_XThe discharge amount is 160428mg/m³Reduced to 115468mg/m³The emission reduction efficiency reaches 28.73%; the discharge amount of dioxin is 422pg-TEQ/m³Reduced to 356pg-TEQ/m³The emission reduction efficiency reaches 81.07 percent, and the on-line SO in the sintering process is realized in a breakthrough manner₂、NO_XAnd the cooperative emission reduction of dioxin, so that the major technical bottleneck is overcome.

This is because the outer pellets 200 and the catalyst layer 300 can effectively slow down NH₃Time of release of NO with_XThe emission window period of the fuel is consistent, and NO is reduced_XThe discharged ammonia gas is not stable enough, furthermore, because the outer layer ammonium bicarbonate particles are decomposed at 60 ℃ to form porous spheres, the heat insulation effect of the porous spheres enables the urea to release NH₃The rate of the (A) is effectively reduced, so that the (A) is intensively and stably released at the temperature of 600-800 ℃, and NO is_XWill be discharged at 650 ℃ with NH₃The release temperature intervals are consistent, so that the release temperature intervals react with each other; meanwhile, the generation of dioxin can be inhibited in the process of cooling until the temperature of sintering flue gas is reduced to be lower than the synthesis temperature of dioxin, SO that SO is increased₂And dioxin emission reduction efficiency.

Comparative example 3

The sintered pellets and the sintering emission reduction method of the comparative example are basically the same as those of example 1, except that: the sintered pellet of this comparative example has no catalyst layer 300, and SO was detected₂、NO_XAnd the generation concentration of dioxin are recorded as shown in table 4, and the desulfurization and denitrification rate and the emission reduction efficiency of dioxin are calculated.

By comparing example 1 with comparative example 3, it can be found that the emission reduction efficiency of SO2 in the flue gas of comparative example 3 is improved from 75.66% to 83.11%, and NO is increased_XThe emission reduction efficiency is improved from 17.45% to 28.73%, and the emission reduction efficiency of the dioxin emission is improved from 79.73% to 81.07%. This is because the catalyst layer 300 is wrapped outside the outer pellet 200, and the activity of part V, Ti substance in the catalyst promotes urea to selectively reduce NO_XThe denitration efficiency is further improved; the blocking function of the catalyst layer 300 may also serve to retard NH₃The purpose of the release is to make it react with SO in the flue gas₂、NO_XThe period of a dioxin discharge window is consistent, so that the emission reduction efficiency is effectively improved; therefore, in the case of not including the catalyst layer 300, the emission reduction efficiency of the sintered pellets of the present comparative example may be greatly reduced.

Comparative example 4

The sintered pellets and the sintering emission reduction method of the comparative example are basically the same as those of example 1, except that: the catalyst layer 300 of this comparative example was tested for SO without adding vanadium-titanium blast furnace slag₂、NO_XAnd the generation concentration of dioxin are recorded as shown in table 4, and the desulfurization and denitrification rate and the emission reduction efficiency of dioxin are calculated.

By comparing example 1 with comparative example 4, it can be seen that SO2 and NO in the flue gas of comparative example 4_XAnd the emission reduction efficiency of dioxin are both reduced, because the catalyst layer 300 of the comparative example lacks the synergistic effect of the vanadium-titanium blast furnace slag and the SCR catalyst, compared with the comparative example 3, the emission reduction efficiency of the flue gas in the comparative example 4 is obviously improved, which shows that the existence of the catalyst can effectively improve the emission reduction efficiency of the flue gas.

TABLE 4 SO in the flue gas of the sintering test₂、NO_XAnd concentration and emission reduction efficiency of dioxin

The invention has been described in detail hereinabove with reference to specific exemplary embodiments thereof. It will, however, be understood that various modifications and changes may be made without departing from the scope of the invention as defined in the appended claims. The detailed description and drawings are to be regarded as illustrative rather than restrictive, and any such modifications and variations are intended to be included within the scope of the present invention as described herein. Furthermore, the background is intended to be illustrative of the state of the art as developed and the meaning of the present technology and is not intended to limit the scope of the invention or the application and field of application of the invention.

More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, combined (e.g., between various embodiments), adapted and/or substituted as would be recognized by those skilled in the art from the foregoing detailed description, and which may be combined as desired. The limitations in the claims are to be interpreted broadly based the language employed in the claims and not limited to examples described in the foregoing detailed description or during the prosecution of the application, which examples are to be construed as non-exclusive. Any steps recited in any method or process claims may be executed in any order and are not limited to the order presented in the claims. The scope of the invention should, therefore, be determined only by the appended claims and their legal equivalents, rather than by the descriptions and examples given above.

Claims (10)

1. A method for reducing emission of sintering flue gas pollutants by using pellets containing SCR waste catalysts is characterized in that sintering pellets are added in a sintering raw material preparation process, and the sintering pellets are sequentially provided with inner layer pellets (100), outer layer pellets (200) and a catalyst layer (300) from inside to outside; the inner layer pellet (100) comprises an ammonia inhibitor, and the ammonia inhibitor can release ammonia gas after being heated and decomposed; the outer layer pellets (200) comprise pore-forming agents, and the pore-forming agents enable pores to be formed in the outer layer pellets (200) in the sintering process; the catalyst layer (300) includes an SCR catalyst and vanadium-titanium blast furnace slag.

2. The method for reducing emission of sintering flue gas pollutants by using pellets containing SCR waste catalyst as claimed in claim 1, which comprises the following specific steps:

the method comprises the following steps: pouring the prepared sintering raw materials and water into a cylindrical mixer in sequence for primary mixing, and then carrying out secondary mixing without adding water; after the granulation is finished, uniformly adding the prepared sintered pellets into the sintering raw material, and uniformly mixing to form a composite sintering raw material;

step two: firstly, paving a primer layer at the lower part of a sintering cup device; then the evenly mixed and granulated composite sintering raw materials are paved and the sintering cup body is filled; finally, firing and sintering;

step three: after ignition, air draft sintering is carried out to remove NO in the flue gas_X、SO₂、NH₃And dioxins are measured on-line.

3. The method of claim 2, wherein the sintering raw materials comprise domestic concentrate, king ore, russian fine powder, reunite ore, scale, Bapug ore, blast furnace return ore, fly ash, internal return ore, dolomite as a flux, quicklime and coke powder as a fuel.

4. The method for reducing emission of sintering flue gas pollutants using SCR-containing spent catalyst pellets as claimed in claim 1, wherein the SCR catalyst comprises V2O5 and TiO 2; the vanadium-titanium blast furnace slag comprises CaO, SiO2, V element and Ti element.

5. The method for reducing emission of sintering flue gas pollutants by using pellets containing SCR waste catalyst as claimed in claim 1, wherein the outer layer pelletizing material has a grain size of-0.149 mm and a mass percentage content of more than or equal to 95%; the granularity of the inner layer pelletizing material reaches-0.074 mm, and the mass percentage content of the grain size is more than or equal to 95 percent.

6. The method for reducing emission of sintering flue gas pollutants by using pellets containing SCR waste catalyst as claimed in claim 1, wherein the particle size of the inner layer pellets (100) is 3-5 mm;

and/or the thickness of the outer layer pellets (200) is 9-11 mm;

and/or the mass percentage content of the ammonia inhibitor and the pore-forming agent reaches-0.074 mm size fraction is more than or equal to 95 percent.

7. The method for reducing emission of pollutants in sintering flue gas by using pellets containing SCR waste catalyst as claimed in claim 1, wherein the ammonia inhibitor is urea, wherein the content of N element is 0.02-0.15% of the mass of the pellets in the inner layer; the pore-forming agent is ammonium bicarbonate, and the molar ratio of the urea to the ammonium bicarbonate is (4: 1) - (1: 4).

8. The method for reducing emission of sintering flue gas pollutants by using pellets containing the SCR waste catalyst as claimed in claim 1, wherein the sintered pellets have a water content of 8.0-8.5% and a particle size of 14-18 mm.

9. The method for reducing emission of sintering flue gas pollutants by using SCR-containing waste catalyst pellets according to any one of claims 1 to 8, comprising the following specific steps:

the method comprises the following steps: pouring the prepared sintering raw materials into a cylindrical mixer in sequence for primary mixing, adding a proper amount of water into an air pressurizing machine, spraying the mixture into the mixer through an atomizer to mix with the sintering raw materials, wherein the primary mixing time is controlled to be 6min, secondary mixing is carried out 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 mixed materials is controlled to be 7.0%; after the granulation is finished, uniformly adding the prepared sintered pellets into the sintering raw material, and uniformly mixing for 30 seconds to form a composite sintering raw material;

step two:

A) paving a 2kg bottom material layer on 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 little sintering raw material with fine granularity in the concave part;

C) and (5) igniting and sintering. Starting an exhaust fan below the sintering cup, rotating an ignition cover to the upper part of the sintering cup body, controlling the negative pressure at 7kPa by adjusting an air inlet valve and a relief valve, igniting, controlling the air inlet amount and the gas opening degree, keeping the ignition temperature at about 1150 ℃, and starting sintering timing. And (3) after ignition for 2min, moving away and closing an igniter cover, adjusting the negative pressure to 14kPa, and starting a central control room computer to automatically collect the sintering temperature and the air draft negative pressure. And when the temperature of the sintering flue gas reaches the maximum value, the temperature begins to drop, namely the sintering end point moment, and the timing time t is the one-time complete sintering time. After sintering, adjusting the negative pressure of air draft to 7kPa, and pouring out the sinter when the temperature of the waste gas is cooled to 300 ℃;

step three: performing air draft sintering after ignition, taking out sintering flue gas from a sampling port by using an oil-free vacuum pump in the air draft sintering process of the sintering machine, taking gas by a gas pipeline in a parallel connection mode, conveying the gas into an MCA 10m infrared flue gas analyzer, and carrying out NO treatment on the flue gas_X、SO₂、NH₃And dioxins are measured on-line.

10. The method for reducing emission of sintering flue gas pollutants by using SCR-containing waste catalyst pellets as claimed in claim 9, wherein the cylindrical blender mixer has the dimensions: phi 600 multiplied by 1200mm, power 8.5kw, charge amount 120 k;

and/or the specification of the sintering cup operating platform is as follows: 4.0m is multiplied by 3.0m, the inner diameter phi of the sintering cup is 200, the effective height is 800mm, the cup body is cast by cast iron containing Cr, and the charging amount is 50 kg.

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