CN109251779B - NOx emission reduction method based on modified fuel iron ore sintering process - Google Patents
NOx emission reduction method based on modified fuel iron ore sintering process Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L9/00—Treating solid fuels to improve their combustion
- C10L9/10—Treating solid fuels to improve their combustion by using additives
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L10/00—Use of additives to fuels or fires for particular purposes
- C10L10/02—Use of additives to fuels or fires for particular purposes for reducing smoke development
Abstract
The invention discloses a method for reducing NOx emission in an iron ore sintering process based on modified fuel, and relates to the technical field of emission reduction of sintering pollutants. Firstly, finely grinding sintered ores to obtain sintered ore fine materials, then adding the sintered ore fine materials into fuel under the condition of no water addition for dry mixing to obtain modified fuel, mixing the modified fuel with iron-containing raw materials and a flux, granulating to obtain a mixture, paving the mixture on a trolley, and igniting and exhausting the mixture for sintering; the fine sinter and the fuel are fully dry-mixed, so that the fine sinter and the fuel are loosely distributed around the fuel; NOx can be generated in the fuel combustion process, and the loosely distributed fine sinter materials can efficiently catalyze the reduction process of the NOx, so that the efficient emission reduction of the NOx in the iron ore sintering process is realized.
Description
Technical Field
The invention relates to the technical field of emission reduction of sintering pollutants, in particular to a method for reducing NOx emission in an iron ore sintering process based on modified fuel.
Background
Steel is the most used metal material for human beings at present, the global steel yield is continuously increased, and the global crude steel yield reaches 16.9 hundred million tons in 2017. However, while the global steel yield is increasing continuously, the harm to the environment in the steel production process is not negligible, and the current state of the NOx emission of the steel industry is particularly severe. The emission of a large amount of NOx is an important reason for the formation of photochemical smog and acid rain, and causes serious harm to the ecological environment and the physical health of the people. According to statistics, the emission of NOx gas in the steel industry accounts for about 10% of the total emission of the industry, and the sintering process is one of the main sources for generating NOx and accounts for about 50% of the total emission of the NOx.
At present, the emission reduction method of NOx in the sintering process at home and abroad is mainly used for carrying out tail end treatment on sintering flue gas, and the method mainly comprises an active coke flue gas purification technology, an SCR denitration technology (selective catalytic reduction method) and an SNCR denitration technology (selective non-catalytic reduction method). The NOx removal rate of the activated coke flue gas purification technology is high, but the investment and operation cost are high, a certain sintering plant reduces emission in the mode, the cost reaches 10 yuan/ton of sinter, and the treatment mode causes steel production enterprises to bear heavy burden; for the SCR denitration technology, the applicable temperature (320-450 ℃) of SCR denitration is usually not matched with the temperature (120-180 ℃) of sintering flue gas, and in addition, the sintering flue gas contains substances capable of reducing the activity of a catalyst, so that the NOx emission reduction rate of the technology is very limited; for the SNCR denitration technology, on one hand, the application temperature (850-. Sintering-related scholars and enterprises research sintering NOx process control-related technologies, process control investment and operation cost are low, implementation is easy, and denitration efficiency is relatively low.
Through retrieval, the invention has the name: a raw material preparation and sintering method for reducing NOx emission in iron ore sintering (application No. 201710422217.5, application date: 2017.06.07) comprises the following steps: step 1, weighing iron ore powder, fuel and flux according to mass ratio; dividing iron ore powder into iron ore powder I and iron ore powder II according to the mass ratio; 2, pelletizing the first iron ore powder to prepare a first mother ball; step 3, uniformly mixing iron ore powder II and a flux to prepare adhesive powder; step 4, pelletizing the adhering powder and the first mother ball in a disc pelletizer to prepare a second mother ball; step 5, uniformly mixing the coke powder and the mother ball II to obtain a raw material for reducing the emission of NOx in iron ore sintering; this application utilizes calcium ferrite and Fe2O3The method has the advantages that the NOx is subjected to catalytic reduction, so that the NOx emission reduction in iron ore sintering is realized, but the main source of NOx in the sintering process is the combustion process of fuel, and the application does not specifically treat NOx released by the fuel, so that the NOx emission reduction effect is greatly limited. The invention provides the following: a NOx control method based on inhibition of fuel nitrogen conversion during iron ore sintering (application No. 201610071111.0, filing date: 2016.02.01); the application discloses a NOx control method based on fuel nitrogen conversion inhibition in the iron ore sintering process, which comprises the steps of screening out particles smaller than 1mm in sintering return ores, then proportioning-1 mm sintering return ores, fine-grain hematite, quicklime, sintering fuel and hydrocarbon with a bonding effect, performing granulation in a cylindrical mixer, and granulating the obtained mixture, the rest iron-containing raw materials, flux and sintering return ores; then distributing, igniting and burning the mixtureKnot formation; the calcium ferrite generated in the application has the effect of catalyzing and reducing emission of NOx in the sintering process, but the granulation mode deteriorates the NOx emission reduction environment to a certain extent and limits the NOx emission reduction effect.
Disclosure of Invention
1. Technical problem to be solved by the invention
The invention aims to provide a method for reducing the emission of NOx in the sintering process of iron ore based on modified fuel, aiming at solving the problem of lower emission reduction efficiency of nitrogen oxide in the sintering process in the prior art; the invention prepares the modified fuel by dry mixing the crushed sintering ore and the fuel, and the modified fuel is mixed into the sintering mixture to effectively reduce the NOx emission.
2. Technical scheme
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the invention discloses a modified fuel iron ore sintering process-based NOx emission reduction method, which comprises the following steps:
fine grinding of sinter
Crushing the sinter to obtain sinter fine materials;
fuel reforming treatment
Adding the fine sinter into the fuel without adding water for dry mixing to prepare modified fuel;
preparation of the mixture
Mixing and granulating an iron-containing raw material, a fusing agent and a modified fuel to obtain a mixture;
air draft sintering
And (3) loading and paving the mixture on a trolley, and igniting and exhausting air for sintering the mixture.
Preferably, the sintered ore with the grain size larger than 5mm is selected and then is finely ground to obtain the sintered ore fine material.
Preferably, the addition amount of the sinter fines is 0.5 to 5% of the total mass of the fuel.
Preferably, the grain size of the sinter fines is not more than 0.5 mm.
Preferably, the mass content of H in the fuel is less than 0.5%.
Preferably, the sintered ore is 1 or more of blast furnace return ores, finished sintered ores or sintering bedding materials.
Preferably, the addition amount of the sinter fines is 1 to 2% of the total mass of the fuel.
Preferably, the sinter/sinter fines are dried and then dry blended with the fuel without adding water to produce the modified fuel.
Preferably, the dried sinter fines are added to the fuel during the fuel crushing process, and the fuel is dry blended with the sinter fines during the crushing process to produce the modified fuel.
Preferably, the modified fuel is prepared by adding the sinter fines and the quicklime to the fuel without adding water and performing dry mixing.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following remarkable effects:
(1) the invention relates to a method for reducing NOx emission in an iron ore sintering process based on modified fuel, which comprises the steps of firstly, finely grinding sintered ore to prepare fine sintered ore, then adding the fine sintered ore into fuel without adding water for dry mixing to prepare modified fuel, mixing the modified fuel with an iron-containing raw material and a fusing agent, granulating to obtain a mixture, paving the mixture on a trolley, igniting the mixture, and sintering the mixture by air draft; by dry mixing the sinter fines with the fuel sufficiently that they are loosely distributed around the fuel; because NOx is generated in the fuel combustion process, the sintering ore fine materials which are loosely distributed can efficiently catalyze the reduction process of the NOx, and further, the efficient emission reduction of the NOx in the iron ore sintering process is realized.
(2) According to the method for reducing the NOx emission in the iron ore sintering process based on the modified fuel, the addition amount of the fine sintered ore is 0.5-5% of the total mass of the fuel, and the fine sintered ore and the fuel are fully and dryly mixed and are loosely distributed around the fuel, so that the combustion process of the fuel is prevented from being hindered, the effective reduction of the nitrogen oxide generated by combustion is promoted, and meanwhile, the fine sintered ore can efficiently catalyze the reduction process of the nitrogen oxide generated by the fuel.
(3) According to the NOx emission reduction method based on the modified fuel iron ore sintering process, the sintered ore with the granularity larger than 5mm is selected, and then the sintered ore is crushed and finely ground; thereby ensuring that the used sintering ore contains enough calcium ferrite and further improving the catalytic effect on the NOx reduction process.
(4) According to the method for reducing the NOx emission in the iron ore sintering process based on the modified fuel, the particle size of the fine sinter is not larger than 0.5mm, the specific surface area of the fine sinter can be increased due to the particle size, the contact chance of calcium ferrite and NOx in the fine sinter is increased, and the catalytic efficiency in the NOx reduction process is improved.
Drawings
Fig. 1 is a flow chart of a NOx abatement process based on a modified fuel iron ore sintering process in accordance with the present invention.
Detailed Description
The detailed description and the exemplary embodiments of the present invention can be better understood with reference to the accompanying drawings.
Example 1
As shown in fig. 1, the method for reducing NOx emission based on the modified fuel iron ore sintering process of the invention comprises the following steps:
(1) fine grinding of sinter
Finely grinding the sintered ore to obtain a sintered ore fine material; the method comprises the following specific steps: selecting a sintering ore with the granularity of more than 5mm, adding the sintering ore into a crusher for crushing, and finely grinding the sintering ore after crushing is finished to ensure that the granularity of the finely ground sintering ore is less than 0.5 mm;
(2) fuel reforming treatment
Adding the fine sinter into the fuel without adding water for dry mixing to prepare modified fuel; the method comprises the following specific steps: under the dry condition, adding fuel into a mixer, adding the fine sintered ore into the fuel, and dry-mixing the fine sintered ore and the fuel, wherein the mass of the fine sintered ore is 0.5 percent of the total mass of the fuel, and the fuel in the embodiment is coke powder; here, it is noted that if the mixer is wet, the mixer needs to be dried;
(3) mixing and granulating an iron-containing raw material, a fusing agent and a modified fuel to obtain a mixture; the iron-containing raw materials can include iron ore powder, return fines, blast furnace dust, OG mud and other iron-containing dust and mud in steel works, and the specific raw material proportion of the embodiment is shown in Table 1; the raw materials in table 1 are added into a mixer according to the raw material proportion for mixing, and water is added in the mixing process, so that the sintering raw materials are mixed and granulated to obtain a sintering mixture.
TABLE 1 sintering raw material proportioning table
(4) Air draft sintering
The mixture is loaded and spread on a trolley, the mixture is ignited and air draft sintered, and NO of sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2. The sintering index was measured and recorded as shown in Table 3.
Example 2
The basic content of this example is the same as example 1, except that the sintered ore with a grain size of more than 8mm is selected for fine grinding, and the sintered ore used in this example is +8mm blast furnace return fines.
The mixture is loaded and spread on a trolley, the mixture is ignited and air draft sintered, and NO of sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2.
Example 3
The basic content of this example is the same as that of example 1, except that the sintered ore having a particle size of more than 15mm is selected for fine grinding, and the sintered ore used in this example is a sintering bed material.
The mixture is loaded and spread on a trolley, the mixture is ignited and air draft sintered, and NO of sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2.
Example 4
The basic content of this example is the same as example 1, except that the sintered ore with a particle size of more than 20mm is selected for fine grinding of the sintered ore, and the sintered ore used in this example is the finished sintered ore.
The mixture is loaded and spread on a trolley, the mixture is ignited and air draft sintered, and NO of sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2.
Example 5
The basic content of this example is the same as example 1, except that the fuel is added to a crusher for crushing, the dried sinter ore or sinter ore fines are added to the fuel during the crushing of the fuel, and the fuel is dry-mixed with the sinter ore fines during the crushing to prepare a modified fuel; the mixture of the iron-containing raw material, the flux and the modified fuel is loaded and spread on a trolley, the mixture is ignited and subjected to air draft sintering, and NO of the sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2.
Example 6
The basic content of this example is the same as example 1 except that the amount of the fine agglomerate grains added is 1% of the total mass of the fuel. Then the mixture of the iron-containing raw material, the flux and the modified fuel is loaded and spread on a trolley, the mixture is ignited and subjected to air draft sintering, and NO of the sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2. The sintering index was measured and recorded as shown in Table 3.
Example 7
The basic content of this example is the same as example 1 except that the amount of the fine agglomerate grains added is 2% of the total mass of the fuel. Then the mixture of the iron-containing raw material, the flux and the modified fuel is loaded and spread on a trolley, the mixture is ignited and subjected to air draft sintering, and NO of the sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2. The sintering index was measured and recorded as shown in Table 3.
Example 8
The true bookThe basic contents of the example are the same as example 1 except that the amount of the fine sinter ore added is 5% of the total mass of the fuel. Then the mixture of the iron-containing raw material, the flux and the modified fuel is loaded and spread on a trolley, the mixture is ignited and subjected to air draft sintering, and NO of the sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2. The sintering index was measured and recorded as shown in Table 3.
Example 9
The basic contents of this example are the same as example 1 except that the grain size of the sintered ore fines is not more than 0.25 mm. The mixture of the iron-containing raw material, the flux and the modified fuel is loaded and spread on a trolley, the mixture is ignited and subjected to air draft sintering, and NO of the sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2.
Example 10
The basic contents of this example are the same as example 1 except that the grain size of the sintered ore fines is not more than 0.10 mm. The mixture of the iron-containing raw material, the flux and the modified fuel is loaded and spread on a trolley, the mixture is ignited and subjected to air draft sintering, and NO of the sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2.
Example 11
The basic content of this example is the same as example 1, except that, after the fine grinding of the sintered ore to obtain the fine sintered ore, the dry quicklime is added to the fine sintered ore to be dry-mixed to obtain the composite fine sintered ore; adding the composite sinter fine material into the fuel for dry mixing to prepare a modified fuel; then the mixture of the iron-containing raw material, the flux and the modified fuel is loaded and spread on a trolley, the mixture is ignited and subjected to air draft sintering, and NO of the sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2.
Comparative example 1
The basic contents of this example are the same as example 1, except that the fuel is not modified, the mixture of the iron-containing raw material, the flux and the modified fuel is directly loaded on the bogie, and the mixture is subjected to the modification treatmentIgniting, exhausting and sintering, and detecting NO of sintering flue gas in main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2.
Comparative example 2
The basic content of this example is the same as example 1, except that the modified fuel is prepared by taking sintered ore with the same mass as the fuel and adopting a conventional granulation method. The specific process of the technology is as follows: adding water into the sintered ore and the fuel, mixing and granulating in advance to perform pre-granulation on the sintered ore and the fuel, wherein in order to improve the pre-granulation effect, a binder with the mass of 0.5% of the fuel is added in the embodiment; and mixing the fuel after the pre-granulation of the sintered ore with other raw materials for granulation.
The mixture of the iron-containing raw material, the flux and the modified fuel is loaded and spread on a trolley, the mixture is ignited and subjected to air draft sintering, and NO of the sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2. The sintering index was measured and recorded as shown in Table 3.
Comparative example 3
The basic content of this example is the same as example 1, except that the modified fuel was prepared by taking sintered ore 1.5 times the mass of the fuel and adopting a conventional granulation method. The specific process of the technology is as follows: adding water into the sintered ore and the fuel, mixing and granulating in advance to perform pre-granulation on the sintered ore and the fuel, wherein in order to improve the pre-granulation effect, a binder with the mass of 0.5% of the fuel is added in the embodiment; and mixing the fuel after the pre-granulation of the sintered ore with other raw materials for granulation.
The mixture of the iron-containing raw material, the flux and the modified fuel is loaded and spread on a trolley, the mixture is ignited and subjected to air draft sintering, and NO of the sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2. The sintering index was measured and recorded as shown in Table 3.
Comparative example 4
The basic contents of this example are the same as example 1, except that the sintered ore used in this example has a grain size of < 8 mm; then preparing and roastingAfter the mixture is combined, the mixture is loaded and spread on a trolley, the mixture is ignited and air draft sintered, and NO of sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2.
Comparative example 5
The basic contents of this example are the same as example 1, except that the sintered ore used in this example has a grain size of < 5 mm; then, after preparing the sintering mixture, the mixture is loaded and spread on a trolley, the mixture is ignited and drafted for sintering, and NO of sintering flue gas is detected in a main sintering flue gas pipelineXThe contents were measured and recorded as shown in Table 2.
TABLE 2 comparison table of emission reduction rate of experiment
TABLE 3 comparison table of sintering indexes
The following results can be obtained by performing comparative analysis on the above data,
(1) comparing example 1 with comparative example 1, it can be seen from table 2 that NO in the sintering flue gas can be made by modifying the fuelXThe concentration of (C) was determined from 260mg · m of comparative example 1 (experiment without fuel modification)-3Reducing the emission to 231 mg.m-3Thereby obviously reducing NO in the sintering flue gasXThe content of (a) and has a remarkable emission reduction effect; meanwhile, the data of the sintering indexes in the proportional table 3 show that the embodiment 1 not only achieves better emission reduction effect, but also enables the sintering indexes in the sintering process to be basically unchanged, and can achieve better NO on the premise of ensuring the quality of sintered mineral productsXAnd (5) emission reduction effect.
(2) Comparing example 1 with comparative examples 1 to 3, it can be found that NO emission reduction can be achieved by either fuel modification according to the present invention or pre-granulation of the fuelXThe thick effect of (2); however, it is worth analyzing that only 0.5% of sinter needs to be added to modify the NO during the fuel modification processXThe emission reduction efficiency of the fuel reaches 11.15 percent, and NO is not generated when the sintered ore with the same mass as the fuel is added to the fuel in the comparative example 2 for pre-granulating the fuelXThe emission reduction efficiency is only 5.38 percent, and NO is added into the sintered ore which is 1.5 times of the fuel mass in the comparative example 3 when the fuel is pre-granulatedXThe emission reduction efficiency of (a) is only 8.85%. The applicant has a lot of thought about this problem and demonstrates it by conducting many internal seminars, and the possible causes thereof will be described next.
Before introducing the reasons for the difference between the two emission reduction methods, the difference between the two emission reduction methods needs to be mainly introduced:
1) mode of addition of sintered ore
In the comparative example 2 (pre-granulation), the sintering ore and the fuel are pre-granulated, so that the sintering ore and the fuel are tightly combined, and the NOx released in the fuel combustion process is promoted to be catalytically reduced by calcium ferrite in the sintering ore, so that the emission reduction of the NOx in the sintering process is realized. In order to improve the granulation effect of the pre-granules, water needs to be continuously added in the process of pre-granulating to promote granulation. In contrast, the fuel modification method of example 1 of the present invention particularly requires that the fuel modification treatment be carried out by adding the sinter fines to the fuel under dry conditions for dry blending.
2) Addition amount of sinter
Meanwhile, comparative example 2 (pre-granulation) in order to allow the fuel in the post-granulation modified fuel to sufficiently contact the fine agglomerate grains, a large amount of fine agglomerate grains were added during the pre-granulation process; if only the fine sinter ore in an amount of 0.5% by mass of the fuel is added during the pre-pelletization process for modification, the fine sinter ore in the modified fuel after the pre-pelletization cannot be brought into sufficient contact with the fuel, so that the addition amount of the fine sinter ore is relatively large when the comparative example 2 (pre-pelletization) is used, and thus the addition amount of the fine sinter ore in the comparative example 2 (pre-pelletization) is 1 time and 1.5 times the mass of the fuel, respectively. In contrast, the fuel modification technology of embodiment 1 of the present invention aims to modify fuel, rather than pelletize the fuel, to achieve the effect of emission reduction, so that the fuel modification technology of the present invention only needs to add relatively less fine sinter material to achieve the effect of emission reduction, and the addition amount of the sinter material in embodiment 1 is 0.5% of the fuel mass.
Next, the reason why the emission reduction effect of comparative example 2 (pre-granulation) is inferior to that of example 1 is that:
first, comparative example 2 (pre-granulation) after pre-granulation, the pre-granulation mode prevents part of the fuel from contacting with external O to some extent, so that the reaction of part of the fuel to generate reducing gas such as CO is inhibited, and the reduction process of NOx can only depend on solid C as a reducing agent for reduction; in the process of modifying the fuel, the sintered ore fine fuel is fully contacted with the fuel, and meanwhile, the fuel is not completely isolated from O, so that the effective contact of the fuel and the O is ensured, the fuel can be smoothly combusted in the combustion process, the fuel is incompletely combusted to form a relatively large amount of CO reducing gas, the CO can reduce NOx generated by the combustion of the fuel, and a reaction interface of NOx reduction is changed; at this time, the reaction interface between NOx and CO is a gas-gas phase reaction interface, and the reaction rate of the reaction at the gas-gas phase reaction interface is faster and the reaction is more sufficient than that at the gas-solid phase reaction interface. In addition, in the process of reducing NOx by CO, calcium ferrite in the sintered ore can more easily fully catalyze gas-phase reactants, so that the reduction catalysis process of NOx is greatly promoted, and the emission reduction rate of NOx is obviously improved.
Secondly, in the using process of the comparative example 2 (precasting), because the combustion process of the fuel is blocked, the fuel is difficult to burn quickly, and the combustion temperature of the fuel is lower, because the temperature in the combustion process of the fuel is lower, and because the reaction of NOx needs to be carried out under the high-temperature condition, and because the surface temperature of the fuel is lower, the reduction effect of the NOx is insufficient; in the process of modifying the fuel in the embodiment 1, the modified fuel is loose, so that fuel particles in the modified fuel can fully contact with external O, so that effective combustion reaction is carried out, the effective combustion temperature is effectively increased, high temperature can promote effective reduction reaction of NOx and CO, the fluidity of calcium ferrite in the fine sintered ore can be improved, the emission reduction efficiency of the calcium ferrite on NOx is improved, and the efficient emission reduction of the NOx in the sintering process is realized.
Third, in the use of comparative example 2 (pre-granulation), modified fuel was produced by using the pre-granulation method, when NOx was produced by burning the fuel, as mentioned above, the reduction of NOx was mainly performed by solid C, and the pre-granulation method resulted in the close contact between particles, which resulted in the reduction of NOx being concentrated in a limited area and the catalytic reduction reaction area of NOx being small. Whereas example 1 in the course of modifying the fuel, since the modified fuel is relatively loose and NOx is reduced mainly by gaseous CO as mentioned above, NOx can be sufficiently reduced in a relatively large area, and calcium ferrite in the sintered ore fine material has a relatively large catalytic reduction reaction area for NOx.
From the above analysis, it can be seen that the fuel modification technique in example 1 has a better NOx reduction effect than the pre-granulation technique used in comparative example 2.
(3) Comparative example 2 and comparative example 3 were compared while examples 1, 7, 8 and 9 were compared; comparing the comparative example 2 with the comparative example 3, it is found that the emission reduction effect of the fine sintered ore added with 1.5 times of the fuel mass in the pre-granulation technology is better than that of the fine sintered ore added with 5% of the fuel mass, and the reason for this is probably that the more the fine sintered ore is added, the more the fine sintered ore is fully contacted with the fuel in the granulation process of the fine sintered ore and the fuel, and the better the emission reduction effect of the pre-granulation technology is; before comparative examples 2 and 3, the applicant also specially experimented with the addition of 5% of fine sinter ore and fuel for pre-granulation, but because the addition amount of the fine sinter ore is too small, the effect of emission reduction is not achieved basically after pre-granulation, and therefore no special experimental data are recorded.
However, for the modified fuel technology of the present invention, when comparing examples 1, 7, 8 and 9, it is found that if it is seen from the aspect of NOx reduction by sintering alone, as can be seen from table 2, the more sinter fines are added during the modification of the fuel, the higher the NOx reduction rate during sintering; however, as can be seen from table 3, the more the amount of the fine sinter ore is added, the lower the utilization coefficient of the sintering process and the higher the solid energy consumption, so that it can be expected that if too much fine sinter ore is added, the larger fluctuation of the sintering index will be caused, which is not favorable for sintering production. It can be concluded that the more the sinter fines are not added, the better the fuel modification.
(4) Comparing the example 1 with the comparative example 1, and then comparing the sintering indexes of the comparative examples 2, 3 and 1, the sintering index is found to be deteriorated by the 1-pregranulation technology of the comparative example 2, while the sintering index of the example 1 of the invention is basically equivalent to that of the comparative example 1, and the emission reduction of NOx is realized on the premise of ensuring the quality of sintered minerals.
(5) Comparing comparative example 4, comparative example 5, example 2, example 3 and example 4, it was found that the larger the particle size of the sintered ore used, the higher the NOx reduction rate of the modified fuel produced using the sintered ore fines milled from the sintered ore due to the higher calcium ferrite content in the sintered ore having the larger initial particle size, and therefore, the better the catalytic reduction effect of the sintered ore on NOx in the fuel.
(6) Comparing example 1, example 9 and example 10, it was found that the smaller the particle size of the added sinter fines, the higher the NOx abatement efficiency, due to: during sintering, NOx is reduced mainly by CO; if the particle size of the sinter ore fine material in the modified fuel is smaller, the specific surface area of the sinter ore fine material is larger, the sinter ore fine material is more contacted with gaseous NOx and CO, and therefore calcium ferrite in the sinter ore fine material can be fully contacted with the gaseous NOx and CO, and the calcium ferrite can efficiently catalyze the reduction process of the NOx; in addition, the smaller the particle size of the fine sinter is, the easier the fine sinter is adhered to and filled among fuel particles, and the contact chance between the fine sinter and gaseous NOx and CO is increased, so that the catalytic reduction of the NOx is fully performed, and the emission reduction rate of the NOx is improved.
(7) Comparing example 5 with example 1, it was found that the NOx reduction rate of example 5 was higher than that of example 1 because: in example 5, the dried fine sintered ore was added to the fuel during the fuel crushing process, and the fuel was dry-mixed with the fine sintered ore during the crushing process to obtain a modified fuel, which was crushed mechanically by a crusher. On one hand, the sintering ore fine materials can be promoted to be fully mixed with the fuel due to the violent vibration of the fuel in the crushing process of the fuel, and the sintering ore fine materials are promoted to be fully contacted with the surface of the fuel and fully filled among fuel particles in the subsequent mixing process; on the other hand, the addition of the fine sinter ore materials into the crusher can further promote the granularity refinement of the fine sinter ore materials, and is also beneficial to the emission reduction of NOx in the sintering process of the modified fuel.
(8) Comparing example 11 with example 1, it was found that the NOx reduction rate of example 11 was higher than that of example 1 because: after quicklime and sinter fines are added into fuel and dry-mixed, on one hand, the quicklime can catalyze and reduce NOx generated by fuel combustion; on the other hand, the quick lime can react with the iron oxide contained in the fine sinter and the sinter mixture to generate new calcium ferrite, and then the NOx generated by fuel combustion is catalytically reduced, so that the NOx emission reduction rate in the sintering process is improved.
Example 12
This embodiment is basically the same as embodiment 1 except that: drying the fine sinter, adding the dried fine sinter into the fuel without adding water, and dry-mixing to obtain the modified fuel. The fine sinter material has better dispersibility in the fuel, can be uniformly distributed in the modified fuel, and improves the catalytic reduction effect of the fine sinter material on NOx in the fuel.
Example 13
This embodiment is basically the same as embodiment 1 except that: in the embodiment, the ratio of the fine sintered ore with the granularity smaller than 300 meshes in the fine sintered ore is more than 80 percent by finely grinding the fine sintered ore; the results, in comparison with example 1, show an increase in the NOx abatement efficiency of 8%. The reason for this is that: the fine sinter ore with the particle size of less than 300 meshes is easy to form a very thin adhesion layer on the surface of fuel particles, and the fine sinter ore in the adhesion layer can be easily and fully contacted with NOx, so that calcium ferrite in the fine sinter ore can more efficiently catalyze and reduce the NOx, and further the effective emission reduction of the NOx is realized.
Example 14
This embodiment is basically the same as embodiment 1 except that: in the embodiment, 0.3 to 3 percent of CaCl is added in the fuel modification treatment process2In this example, CaCl 0.5% of the fuel mass was added during the fuel modification treatment2Grinding the mixture and mixing the ground mixture in the fuel modification process; the results, in comparison with example 1, show a 6.7% increase in the NOx abatement efficiency.
Example 15
This embodiment is basically the same as embodiment 1 except that: in the embodiment, 0.3-3% of potassium permanganate is added in the fuel modification treatment process, and in the embodiment, 0.5% of fuel by mass is added in the fuel modification treatment process, and the finely ground fuel is simultaneously mixed in the fuel modification treatment process; compared with example 1, the result shows that the NOx emission reduction efficiency is improved by 5.1%.
Example 16
This embodiment is basically the same as embodiment 1 except that: in the embodiment, 0.3-3% of steel slag is added in the fuel modification treatment process, and in the embodiment, the steel slag with the fuel mass of 0.5% is added in the fuel modification treatment process, and is mixed in the fuel modification treatment process after being levigated; compared with example 1, the result shows that the NOx emission reduction efficiency is improved by 8.3%. The reason for this is that: the steel slag contains CaO and iron oxide, and in addition, because the steel slag has a porous structure and a large specific surface area, the contained catalyst can fully catalyze and reduce NOx.
Example 17
This embodiment is basically the same as embodiment 1 except that: in the embodiment, steel slag with the fuel mass of 0.5 percent, potassium permanganate with the fuel mass of 0.5 percent and CaCl with the fuel mass of 0.5 percent are added in the fuel modification treatment process2Grinding the mixture and mixing the ground mixture in the fuel modification process; the results, in comparison with example 1, show a 9.7% improvement in NOx abatement efficiency.
Example 18
This embodiment is basically the same as embodiment 1 except that: in the embodiment, 0.3 to 3 percent of K is added in the fuel modification treatment process2CO3In the embodiment, 0.5% is added, so that the emission reduction efficiency of nitrogen oxides is improved by 5% compared with that in embodiment 1. The reason for this is that: k2CO3On one hand, the catalyst can play a role in catalyzing the reduction process of NOx by alkali metal; in addition K2CO3Part of CO decomposed2And gas-phase CO is generated with the solid C, so that the reduction and emission reduction of NOx are further promoted.
Example 19
This example is substantially the same as example 1, except that 0.3% -3% CaCO was added during the fuel modification treatment3In the embodiment, 0.5% is added, so that the emission reduction efficiency of nitrogen oxides is improved by 7% compared with that in the embodiment 1. CaCO3Decomposition to CaO and CO2On one hand, CaO can play a role in catalyzing the reduction process of NOx by alkali metal; another part of CO2And gas-phase CO is generated with the solid C, so that the reduction and emission reduction of NOx are further promoted.
Example 20
This embodiment is basically the same as embodiment 1 except that: the fuel used in this embodiment is national trade coal powder, which contains 0.92% of N element and 2.09% of H element, and is made into modified fuel, and then the mixture of iron-containing raw material, flux and modified fuel is loaded on a trolley, the mixture is ignited, air draft sintered, and NO of the sintering flue gas is detected in the main sintering flue gas pipelineXThe average emission concentration was recorded as shown in table 4.
Example 21
This embodiment is basically the same as embodiment 1 except that: the fuel used in the embodiment is Xindu source coal powder, the content of N element of the coal powder is 0.90%, the content of H element is 1.39%, the coal powder is made into modified fuel, then the mixture of iron-containing raw material, flux and modified fuel is loaded on a trolley, the mixture is ignited and subjected to air draft sintering, and NO of sintering flue gas is detected in a main sintering flue gas pipelineXThe average emission concentration was recorded as shown in table 4.
Example 22
This embodiment is basically the same as embodiment 1 except that: the fuel used in the embodiment is wind melt coal powder, the content of N element in the coal powder is 0.84%, the content of H element is 0.54%, the coal powder is made into modified fuel, then the mixture of iron-containing raw material, flux and modified fuel is loaded on a trolley, the mixture is ignited and air draft sintered, and NO of the sintering flue gas is detected in the main sintering flue gas pipelineXThe average emission concentration was recorded as shown in table 4.
Example 23
This embodiment is basically the same as embodiment 1 except that: the fuel used in this example is coked coke powder with an N element content of 1.03% and an H element content of 0.28%, which is made into a modified fuel, and then the mixture of the iron-containing raw material, the flux and the modified fuel is loaded on a trolley, the mixture is ignited and sintered by air draft, and NO of the sintering flue gas is detected in the main sintering flue gas pipelineXThe average emission concentration was recorded as shown in table 4.
Example 24
This embodiment is basically the same as embodiment 1 except that: the fuel used in this example is iron-making coke powder with an N element content of 0.89% and an H element content of 0.27%, which is made into a modified fuel, and then the mixture of the iron-containing raw material, the flux and the modified fuel is loaded on a trolley, the mixture is ignited and sintered by air draft, and NO of the sintering flue gas is detected in the main sintering flue gas pipelineXThe average emission concentration was recorded as shown in table 4.
Example 25
This embodiment is basically the same as embodiment 1 except that: the fuel used in this example is aviation cinnamon coke powder, the coke powder contains 0.80% of N element and 0.29% of H element, and is made into modified fuel, and then the mixture of iron-containing raw material, flux and modified fuel is loaded on a trolley, the mixture is ignited, air draft sintered, and NO of the sintering flue gas is detected in the main sintering flue gas pipelineXThe average emission concentration was recorded as shown in table 4.
When fuel types with different H content are used, the emission situation of nitrogen oxides is different, and the content of H, N in different types of fuel and the emission concentration of nitrogen oxides are shown in the table 4.
TABLE 4 content of H, N in different kinds of fuel and concentration of nitrogen oxide emission
As can be seen from the data of table 4, it has a tendency to lower the concentration of nitrogen oxides emitted as a whole, the less the H element in the fuel; for N element in the fuel, the content of the N element in the coking coke powder is higher than that of the coal powder, but the emission concentration of nitrogen oxide is far lower than that of the coal powder, and the content of the H element in the coking coke powder is found to be lower due to the fact that the content of the N element in the coking coke powder is lower.
At present, researchers researching nitrogen oxides in the sintering process generally think that in the aspect of source control, the emission of the nitrogen oxides can be effectively controlled by controlling the content of N element in fuel. However, it is found from the above data that the content of H element has a larger influence on the emission concentration of nitrogen oxides in fuel than the content of N element, and plays an even more important role than N element, and by studying the formation mechanism of nitrogen oxides, the process of converting N in fuel into NOx is found as follows:
N+H+C＝HCN
HCN+O＝NCO+H
NCO+O＝NO+CO
therefore, the existence of H in the fuel plays a role of a catalyst for the conversion of N to NO, so that the reduction of the content of H in the fuel can realize the emission reduction of nitrogen oxides in the sintering process to a certain extent.
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.
Claims (5)
1. A modified fuel-based method for reducing NOx emission in the iron ore sintering process is characterized by comprising the following steps: the method comprises the following steps:
fine grinding of sinter
Finely grinding the sintered ore to obtain a sintered ore fine material, and adding dry quicklime into the sintered ore fine material for dry mixing to obtain a composite sintered ore fine material; the grain size of the sinter fine material is not more than 0.5 mm;
fuel reforming treatment
Adding the composite sinter fine material into fuel for dry mixing under the condition of no water addition, wherein the mass content of H in the fuel is 0.27-0.54%, and preparing the modified fuel;
preparation of the mixture
Mixing and granulating an iron-containing raw material, a fusing agent and a modified fuel to obtain a mixture;
air draft sintering
And (3) loading and paving the mixture on a trolley, and igniting and exhausting air for sintering the mixture.
2. The method for reducing NOx emission in the iron ore sintering process based on the modified fuel according to claim 1, wherein the method comprises the following steps:
selecting sintered ore with the granularity of more than 5mm, and then finely grinding the sintered ore to obtain the fine sintered ore material.
3. The method for reducing NOx emission in the iron ore sintering process based on the modified fuel according to claim 1, wherein the method comprises the following steps:
the addition amount of the fine sinter materials is 0.5-5% of the total mass of the fuel.
4. The method for reducing NOx emission in the iron ore sintering process based on the modified fuel according to claim 2, wherein the method comprises the following steps:
the sintered ore is 1 or more of blast furnace return ores, finished sintered ores or sintering bedding materials.
5. The method for reducing NOx emission in the iron ore sintering process based on the modified fuel according to claim 1, wherein the method comprises the following steps:
the addition amount of the fine sinter materials is 1-2% of the total mass of the fuel.
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