CN114737050A - Production process of pellet roasted at low temperature by microwave and without carbon - Google Patents

Production process of pellet roasted at low temperature by microwave and without carbon Download PDF

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Publication number
CN114737050A
CN114737050A CN202210460496.5A CN202210460496A CN114737050A CN 114737050 A CN114737050 A CN 114737050A CN 202210460496 A CN202210460496 A CN 202210460496A CN 114737050 A CN114737050 A CN 114737050A
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pellet
microwave
cooling
roasting
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CN114737050B (en
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甘敏
范晓慧
吕浩
季志云
孙增青
陈许玲
黄晓贤
刘卓奇
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Central South University
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/16—Sintering; Agglomerating
    • C22B1/20—Sintering; Agglomerating in sintering machines with movable grates
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/24—Binding; Briquetting ; Granulating
    • C22B1/2406—Binding; Briquetting ; Granulating pelletizing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/24—Binding; Briquetting ; Granulating
    • C22B1/242—Binding; Briquetting ; Granulating with binders
    • C22B1/243—Binding; Briquetting ; Granulating with binders inorganic
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/24—Binding; Briquetting ; Granulating
    • C22B1/242—Binding; Briquetting ; Granulating with binders
    • C22B1/244—Binding; Briquetting ; Granulating with binders organic
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

The invention discloses a pellet production process by microwave low-temperature carbon-free roasting, which is characterized in that pellet materials are placed on a mobile trolley and sequentially processed by a blast drying section, an air draft drying section, a preheating I section, a preheating II section, a roasting section, a cooling I section, a cooling II section and a cooling III section to obtain finished pellets, and the main improvement point is that the roasting section directly supplies heat through a microwave device. The process uniformly heats the pellet materials in a microwave direct heating mode, promotes the pellet materials in a roasting section to be fully consolidated, improves the pellet quality, reduces the roasting temperature, and meanwhile replaces the heat supply mode mainly based on carbon-based fuel combustion in the prior art with the heat supply mode of microwave direct heating, thereby realizing 'zero carbon emission' in the pellet production process and greatly reducing NOxAnd SO2And (4) discharging.

Description

Production process of pellet roasted at low temperature by microwave and without carbon
Technical Field
The invention relates to a pellet production process, in particular to a pellet production process of microwave low-temperature carbon-free roasting, and belongs to the technical field of energy conservation and emission reduction of iron ore pellets.
Background
The pellet ore is a high-quality blast furnace iron-making raw material, and compared with sintered ore, the pellet ore has the advantages of high iron grade and good metallurgical performance, and the process energy consumption and pollutant emission in the pellet production process are also lower. In addition, the current situation of iron ore resources mainly comprising concentrate in China is also more suitable for the development of pellet ore. In recent years, with the development of the steel industry, the pellet yield is gradually increased. Therefore, the pellet process is promoted to progress and develop, the energy-saving and emission-reducing technology of the pellet production process is further developed, and the pellet production process is an effective measure for assisting the carbon peak reaching and carbon emission reduction in the steel industry.
At present, the production process of pellet ore mainly comprises a grate-rotary kiln and a belt type roasting machine, and the proportion of the grate-rotary kiln and the belt type roasting machine is more than 90 percent. The grate-rotary kiln process or the belt type roasting machine process mainly uses heat generated by burning fuels such as anthracite or coal gas and the like to roast the pellet materials in a heat conduction mode. On one hand, the energy consumption of the pelletizing process is mainly concentrated in the roasting section, the existing pelletizing production process is mainly mixed iron concentrate pellets prepared from magnetite and hematite, the economical efficiency and the good product quality are achieved, the roasting temperature is mostly 1250-1280 ℃, and if the roasting temperature can be reduced to below 1250 ℃, the energy consumption of the pelletizing process is greatly reduced. On the other hand, when the pellet is roasted by heat conduction and heat supply, the problem of uneven temperature field in the pellet exists, and the uniformity of the quality of the pellet is influenced. For example, the over-burning or under-burning of part of the pellets can be caused by the over-high or over-low temperature of local flame in the chain grate-rotary kiln; the belt type roasting machine roasts the pellet material layer through air flow heat conduction, and the pellet minerals of 'over-burnt upper layer and under-burnt lower layer' existUneven quantity; for a single pellet, the heating mode of heat conduction from outside to inside also has the problems of low heating speed and uneven internal and external consolidation. This all makes further reduction of pellet firing temperatures desirable and possible. In addition, carbon-based fuels such as anthracite and coal gas can generate a large amount of CO in the combustion process2、NOxAnd SO2And the like. According to statistics, about 63kgCO is discharged per 1t of pellet ore produced2、0.35kg NOxSo that the pellet production faces a certain environmental protection pressure.
Therefore, it is necessary to develop a new pellet roasting process to replace the existing pellet roasting mode mainly based on carbon-based fuel combustion and heat conduction heat supply, improve the uniformity of the temperature field in the pellet roasting process, reduce the roasting temperature, reduce the energy consumption and pollutant emission of pellet production from the source, reduce the production cost of the pellet process, and assist the green development of the steel industry.
Disclosure of Invention
Aiming at the problems of high roasting temperature, high energy consumption, nonuniform roasting of pellets, over-burning or under-burning of partial pellets, carbon emission and smoke pollutant emission in a roasting mode mainly based on carbon-based fuel combustion and heat conduction heat supply in the prior art, the invention aims to provide a microwave low-temperature carbon-free roasting iron ore oxidized pellet production processxAnd SO2And (4) discharging. Under the condition of ensuring the quality of pellet ore, the energy conservation and emission reduction in the pellet production process are realized.
In order to achieve the technical purpose, the invention provides a pellet production process of microwave low-temperature carbon-free roasting, wherein a pellet material is placed on a mobile trolley and sequentially passes through a blast drying section, an air draft drying section, a preheating I section, a preheating II section, a roasting section, a cooling I section, a cooling II section and a cooling III section to be treated, and a finished pellet product is obtained; the key improvement points are as follows: the roasting section directly supplies heat through a microwave device; the microwave device is of a cavity structure, and microwave generators are arranged on the upper surface and the lower surface of the inner part of the cavity.
The key of the technical scheme of the invention is that a microwave direct heating mode is adopted in the pellet roasting process, and compared with a fuel heating mode in the prior art, on one hand, the invention can greatly reduce NO caused by adopting fossil fuel from the sourcexAnd SO2Discharging, and realizing 'zero carbon discharge' in the pellet production process; on the other hand, the microwave heating mode and the fuel combustion heating mode realize heating by completely different action principles, the microwave heating mainly realizes internal friction heat generation through the actions of ion conduction, dipole rotation and the like, can quickly and uniformly heat up, and the material layer heating process is not influenced by the actions of heat conduction and the like of common combustion heat supply, so that the sintering temperature of the pellet material can be effectively reduced, and the fuel combustion heating process inevitably generates temperature gradient due to the heat conduction action, so that higher sintering efficiency is obtained, and the fuel sintering needs higher sintering temperature; the third aspect, microwave heating mode itself has the fast and even characteristics of being heated of intensification, and through setting up special microwave device, adopt cavity formula microwave heating device, and all set up microwave generating device at bed of material upper and lower surface, can make the pelletizing bed of material be heated more evenly from top to bottom, effectively avoid pellet sintering process to appear local overheated, the inhomogeneous technical problem of sintering to can guarantee under the condition of certain pellet thickness, make pellet temperature field more even, improve pellet quality homogeneity. In conclusion, the pellet is directly heated by microwaves, so that the pellet can be uniformly heated, the pellet is fully consolidated in a roasting section, the quality of the pellet is improved, the roasting temperature is reduced, and compared with the prior art in which fuel combustion is a heat supply mode, the method realizes 'zero carbon emission' in the pellet production process, and greatly reduces NO (nitric oxide)xAnd SO2The emission of the pellet realizes energy conservation and emission reduction in the pellet production process under the condition of ensuring the quality of the pellet.
Preferably, the cavity structure is a rectangular cavity structure. And the movable trolley passes through the center of the cavity, so that the whole material layer of the pellet material can be uniformly heated up under the action of microwaves.
As a preferable scheme, the working frequency of the microwave generator is 915-2450 MHz, and the pellet material is heated to 1180-1250 ℃. The conventional fuel burning roasting temperature is mostly over 1250-1280 ℃, and the roasting temperature can be effectively reduced to be below 1250 ℃ by adopting a high-frequency microwave heating mode, so that the pellet sintering energy consumption is greatly reduced. The temperature of the pellet material can be effectively regulated and controlled by controlling the working frequency of the high-frequency microwave.
As a preferable scheme, the material distribution thickness of the pellet material on the movable trolley is 100-200 mm, and the particle size of the pellet material is 8-13 mm. By utilizing the characteristics of microwave integral heating and the mode of microwave heating of the upper and lower layers of pellet materials simultaneously, the temperature field of the pellet materials can be more uniform under the condition of ensuring higher thickness of the pellet materials, and the quality uniformity of the pellet ores is improved. Meanwhile, the granularity of the pellet and the cloth thickness thereof are controlled within a proper range, so that the microwave can fully penetrate through the pellet to heat.
As a preferred solution, the hot exhaust gas from the cooling stage I is recycled to the preheating stage II. Further preferably, the oxygen content in the hot waste gas generated in the cooling I section is not lower than 18%, and the temperature is 1050-1150 ℃. As a preferred solution, the hot exhaust gas from the cooling stage II is recycled to the preheating stage I. Further preferably, the oxygen content in the hot waste gas generated in the cooling II section is not lower than 18%, and the temperature is 800-1000 ℃. Before microwave heating is adopted for roasting, a two-stage preheating process is adopted, the two-stage preheating process can ensure that most chemical reactions such as oxidation, desulfurization, carbonate decomposition, primary micro crystallization and the like can be completed before microwave roasting by strictly controlling the oxygen content and the temperature, if pellet materials pass through a preheating II stage, the FeO content in the pellet materials is less than or equal to 3 percent, the removal rate of sulfur in the pellet materials is more than or equal to 85 percent, favorable conditions are provided for the microwave quick roasting process, pellet consolidation of the microwave roasting stage can be strengthened, because the microwave roasting stage needs to be in a relatively closed and independent space to prevent microwave leakage to realize quick heating and reach the required sintering temperature, and the relatively closed and independent space can influence the processes such as oxidation and the like of the pellet materials, most chemical reaction processes such as oxidation, desulfurization, carbonate decomposition, primary micro crystallization and the like can be completed through the two-stage preheating, the relative independence of the microwave roasting section is possible, and the two-section preheating process is beneficial to improving the microwave roasting effect. Furthermore, the energy circulation can be achieved for the hot exhaust gases of the preheating stage II and the preheating stage I from the cooling stage I and the cooling stage II, respectively.
As a preferred solution, the hot exhaust gases from said cooling III stage are recycled to the forced air drying stage. Further preferably, the temperature of hot waste gas generated in the cooling section III is 250-350 ℃. As a preferred scheme, the hot waste gas generated in the preheating II section is circulated to the air draft drying section. Further preferably, the temperature of hot waste gas generated in the preheating II section is 400-500 ℃. The hot waste gas generated in the cooling section III and the preheating section II respectively meets the drying and dehydration requirements of the pellet materials in the blowing drying section and the air draft drying section.
As a preferable scheme, the retention time of the pellet in the air blowing drying section is 2-3 min, the retention time in the air suction drying section is 4-5 min, the retention time in the preheating I section is 6-10 min, the retention time in the preheating II section is 6-10 min, and the retention time in the roasting section is 8-12 min.
As a preferable scheme, after the pellet material is preheated in the II section, the content of FeO in the pellet material is controlled to be less than or equal to 3 percent, and the removal rate of sulfur in the pellet material is controlled to be more than or equal to 85 percent.
As a preferable scheme, the pellet materials are cooled in a cooling I section, a cooling II section and a cooling III section at the speed of 50-80 ℃/min, and the temperature of the final finished pellet is controlled to be lower than 150 ℃.
As a preferable scheme, the pellet material of the invention is a common iron ore sintering pellet material, and mainly comprises iron-containing minerals, a binder, an additive and the like. Iron-containing minerals such as magnetite, hematite, vanadium titano-magnetite, etc., binders such as bentonite and organic binders (sodium carboxymethyl cellulose, starches, polyvinyl alcohol, humic acids, etc.), additives such as calcium-containing additives and magnesium-containing additives. These are common pellet materials in iron ore sintering processes.
In the pellet production process, the microwave generators are respectively arranged on the upper surface and the lower surface inside the cavity of the microwave device, the fire-resistant layers are arranged on the outer sides of the microwave generators to protect the microwave generators, and the microwave shielding plates are arranged on the upper surface and the lower surface inside the cavity to prevent microwave leakage.
In the pellet production process, the blast drying section, the draft drying section, the preheating I section, the preheating II section, the microwave roasting section, the cooling I section, the cooling II section and the cooling III section are separated by the fireproof baffle plates, so that air blowby is prevented.
The invention relates to a pellet production process, in particular to a device with a grate bed or a grate bed, wherein a moving bed is a chain grate.
Compared with the prior art, the invention has the advantages that:
(1) the invention utilizes the characteristic of microwave 'integral heating', adopts a microwave device with a cavity structure, realizes the simultaneous microwave direct heating of the upper layer and the lower layer of the pellet by arranging the microwave generators on the upper surface and the lower surface of the inner part of the cavity, and replaces the traditional hot air conduction heating mode to ensure that the temperature fields of the upper layer and the lower layer of the pellet and the inner and outer layers of the pellet are more uniform, thereby improving the quality of the pellet, reducing the temperature of a roasting section to be below 1250 ℃ under the condition of unchanged product quality, preventing the pellet from being over-burnt and reducing the energy consumption of the pellet.
(2) The invention completes most of oxidation, primary micro crystallization, desulfurization and carbonate decomposition of the pellet material in the preheating I section and the preheating II section through two-section preheating. On one hand, the full oxidation and the primary micro-crystallization are beneficial to strengthening the consolidation of the pellets in the microwave roasting section. On the other hand, the requirements of relevant reactions of the pellet materials in the microwave roasting section can be reduced, so that the microwave roasting section can be relatively independent, and meanwhile, the risk of microwave leakage can be reduced by means of arranging a microwave shielding plate and the like in the cavity of the microwave device.
(3) According to the invention, the high-temperature high-oxygen waste gas in the cooling I section and the cooling II section is respectively circulated to the preheating II section and the preheating I section, and the hot waste gas in the cooling III section is circulated to the blast drying section and the hot waste gas in the preheating II section is circulated to the draft drying section, so that the heat utilization rate can be improved, and the heat loss can be reduced.
(4) The invention adopts microwave heating in the roasting section, does not use carbon-based fuels such as anthracite, coal gas and the like for heat supply, can effectively reduce the emission of smoke pollutants in the pellet production process, can realize 'zero carbon emission' in the pellet production process, and greatly reduces NOxAnd SO2The emission of (2) and the reduction of the environmental protection operation cost.
In conclusion, the invention utilizes the characteristic of microwave integral heating, directly heats the pellet materials by microwave in the roasting section, combines the two-section reinforced preheating and hot waste gas circulation methods, develops the production process of the iron ore oxidized pellet without carbon at low temperature, can further reduce the energy consumption of pellet production, and reduces the carbon emission and the smoke pollutant emission in the pellet process.
Drawings
FIG. 1 is a flow chart of the microwave-based low-temperature carbon-free pellet roasting production process of the present invention; wherein, 1: pelletizing; 2: a forced air drying section; 3: an air draft drying section; 4: preheating the I section; 5: preheating a II section; 6: a roasting section; 7: cooling the section I; 8: cooling the II section; 9: cooling the section III; 10: a smoke hood; 11: a microwave generator; 12: a fan; 13: an air box; 14: a flue gas treatment tower.
Detailed Description
In order to further illustrate the present invention, the following examples are given in more detail, but the scope of the present invention is not limited to the following examples.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
The schematic diagram of the pellet production process of the present invention is shown in fig. 1. The roasting process is mainly carried out in a microwave device, the microwave device is provided with a cavity structure, the cross section of the cavity structure is rectangular, microwave generators are arranged on the upper surface and the lower surface of the inner part of the cavity, microwave shielding plates are arranged on the upper surface and the lower surface of the inner part of the cavity to prevent microwaves from leaking, and fire-resistant layers are arranged on the upper surface and the lower surface of the outer part of the cavity to mainly protect the microwave generators. The drying grate loading pellet material in the pellet roasting process passes through the center of the cavity of the microwave device, so that the whole material layer of the pellet material can be uniformly heated under the action of microwave and the temperature of the whole material layer can be rapidly raised. The hot waste gas generated in the cooling section I in the pellet production process is circulated to the preheating section II; the hot waste gas generated in the cooling II section is circulated to the preheating I section; circulating hot waste gas generated in the cooling section III to a forced air drying section; and hot waste gas generated in the preheating II section circulates to the air draft drying section. In the pellet production process, the blast drying section, the air draft drying section, the preheating section I, the preheating section II, the microwave roasting section, the cooling section I, the cooling section II and the cooling section III are separated by a fire-resistant baffle to prevent air blow by.
Comparative example 1
Aiming at the production process of the grate-rotary kiln-circular cooler iron ore oxidized pellet, 98.8 percent of magnetic and hematite mixed iron ore concentrate raw material (magnetite: hematite is 7:3) is added with 1.2 percent of bentonite to prepare the acid pellet. In the process, the thickness of the pellet is 180mm, the pellet size is 8-16 mm, and the finished pellet is obtained under the thermal regulation of blowing drying at 250 ℃ for 2min, air draft drying at 400 ℃ for 5min, transitional preheating at 650 ℃ for 3min, preheating at 950 ℃ for 8min, roasting at 1250 ℃ for 10min, and cooling speed of 60 ℃/min. Pellet index, carbon emission and NO in pellet production processxThe emissions are shown in table 1.
Comparative example 2
Aiming at the production process of the iron ore oxidized pellet of the belt type roasting machine, 92.4 percent of magnetic and hematite mixed iron ore concentrate raw material (magnetite: hematite is 7:3) is adopted, and 1.2 percent of bentonite, 2.0 percent of magnesium oxide powder and 4.4 percent of limestone are added to prepare the magnesium fluxed pellet (the alkalinity is 0.4, and the MgO content is 2.0). In the process, the thickness of the pellet is 400mm, the pellet size is 8-16 mm, and the finished pellet is obtained under the thermal regulation of blowing drying at 300 ℃ for 3min, exhausting drying at 400 ℃ for 7min, preheating and heating rate of 50 ℃/min, preheating and heating time of 18min, and roasting at 1275 ℃ for 10 min. Pellet index, carbon emission and NO in pellet production processxThe emissions are shown in Table 1.
Comparative example 3
Acid pellets are prepared by using 98.8% of magnetic and hematite mixed iron concentrate raw material (magnetite: hematite: 7:3) and adding 1.2% of bentonite. In the process, the thickness of the pellet is 200mm, the pellet granularity is 8-13 mm, the microwave frequency is 2450MHz, under the thermal regulation of blowing and drying at 350 ℃ for 2min, exhausting and drying at 500 ℃ for 4min, preheating at 650 ℃ for 3min and preheating at 950 ℃ for 8min, the FeO content in the preheated pellet is 6.7%, and the desulfurization rate of the pellet is 71.3%; roasting at 1200 deg.c for 8min and cooling at 80 deg.c/min to obtain pellet product. Pellet index, carbon emission and NO in pellet production processxThe emissions are shown in Table 1.
Example 1
Aiming at the process for roasting the pellets at low temperature without carbon based on microwave, 98.8 percent of magnetic and hematite mixed iron ore concentrate raw material (magnetite: hematite is 7:3) is added with 1.2 percent of bentonite to prepare the acid pellets. In the process, the thickness of the pellet is 200mm, the pellet granularity is 8-13 mm, the microwave frequency is 2450MHz, under the thermal regulation of blowing and drying at 350 ℃ for 2min, exhausting and drying at 500 ℃ for 4min, preheating at 800 ℃ for 6min and preheating at 1050 ℃ for 10min, the FeO content in the preheated pellet is 2.2%, and the desulfurization rate of the pellet is 92.3%; roasting at 1180 deg.c for 8min, and cooling at 80 deg.c/min to obtain pellet product. Pellet index, carbon emission and NO in pellet production processxThe emissions are shown in Table 1.
Example 2
Aiming at the low-temperature non-carbon pellet roasting process based on microwave, the magnesian fluxed pellets (with the alkalinity of 0.4 and the MgO content of 2.0) are prepared by adopting 91.2 percent of magnetic and hematite mixed iron concentrate and adding 0.5 percent of organic binder (CMC), 3.8 percent of magnesite and 4.5 percent of limestone. In the process, the thickness of the pellet is 200mm, the pellet granularity is 8-13 mm, the microwave frequency is 915MHz, under the thermal regulation of blowing and drying at 300 ℃ for 3min, exhausting and drying at 450 ℃ for 5min, preheating at 1000 ℃ for 8min and preheating at 1150 ℃ for 8min, the FeO content in the preheated pellet is 1.8%, and the desulfurization rate of the pellet is 88.3%; roasting at 1250 deg.c for 10min and cooling at 50 deg.c/min to obtain pellet product. Pellet index, carbon emission in pellet production process,NOxThe emissions are shown in Table 1.
Example 3
Aiming at the process for roasting the pellets at low temperature without carbon based on microwave, the magnesium vanadium titanium pellets (with MgO content of 2.0%) are prepared by adopting 96.3% of vanadium titano-magnetite, adding 1.6% of bentonite and 2.1% of magnesium oxide powder. In the process, the thickness of the pellet is 100mm, the pellet granularity is 8-13 mm, the microwave frequency is 2450MHz, under the thermal regulation of blowing and drying at 250 ℃ for 3min, exhausting and drying at 400 ℃ for 5min, preheating at 1000 ℃ for 10min and preheating at 1150 ℃ for 6min, the FeO content in the preheated pellet is 2.7%, and the desulfurization rate of the pellet is 89.5%; roasting at 1230 ℃ for 12min, and obtaining finished pellets under a thermal regulation with a cooling speed of 50 ℃/min. Pellet strength index, carbon emission and NO in pellet production processxThe emissions are shown in table 1.
Table 1 strength index of pellets produced by carrying out the process of the present invention
Figure BDA0003622003320000081

Claims (10)

1. The utility model provides a pellet production technology of microwave low temperature carbonless calcination, will pellet arrange the pellet material in and carry out the processing of forced air drying section, convulsions drying section, preheating I section, preheating II section, calcination section, cooling I section, cooling II section and cooling III section in proper order on the travelling car, obtain finished product pellet, its characterized in that: the roasting section directly supplies heat through a microwave device; the microwave device is of a cavity structure, and microwave generators are arranged on the upper surface and the lower surface of the inner part of the cavity.
2. The production process of the pellets by microwave low-temperature carbon-free roasting as claimed in claim 1, is characterized in that: the working frequency of the microwave generator is 915-2450 MHz, and the pellet material is heated to 1180-1250 ℃;
the material distribution thickness of the pellet on the movable trolley is 100-200 mm, and the particle size of the pellet is 8-13 mm.
3. The microwave low-temperature carbon-free roasting pellet production process as claimed in claim 1 or 2, wherein the microwave low-temperature carbon-free roasting pellet production process comprises the following steps:
the hot waste gas generated in the cooling I section is circulated to the preheating II section;
the hot waste gas generated in the cooling II section is circulated to the preheating I section;
hot waste gas generated in the cooling III section is circulated to the forced air drying section;
and hot waste gas generated in the preheating II section circulates to the air draft drying section.
4. The microwave low-temperature carbon-free roasting pellet production process as claimed in claim 3, is characterized in that: the oxygen content in the hot waste gas generated in the cooling I section is not lower than 18%, and the temperature is 1050-1150 ℃.
5. The microwave low-temperature carbon-free roasting pellet production process as claimed in claim 3, is characterized in that: the oxygen content in the hot waste gas generated in the cooling II section is not lower than 18%, and the temperature is 800-1000 ℃.
6. The microwave low-temperature carbon-free roasting pellet production process as claimed in claim 3, is characterized in that: the temperature of hot waste gas generated in the preheating II section is 400-500 ℃.
7. The production process of the microwave low-temperature carbon-free roasted pellets as claimed in claim 3, wherein the production process comprises the following steps: and the temperature of hot waste gas generated in the cooling III section is 250-350 ℃.
8. The process for producing pellets by microwave low-temperature carbon-free roasting according to claim 1 or 2, characterized in that: the retention time of the pellet materials in the blast drying section is 2-3 min, the retention time in the induced draft drying section is 4-5 min, the retention time in the preheating I section is 6-10 min, the retention time in the preheating II section is 6-10 min, and the retention time in the roasting section is 8-12 min.
9. The production process of the microwave low-temperature carbon-free roasted pellets according to claim 8 is characterized in that: after the pellet material is preheated in the II section, the FeO content in the pellet material is controlled to be less than or equal to 3 percent, and the removal rate of sulfur in the pellet material is controlled to be more than or equal to 85 percent.
10. The microwave low-temperature carbon-free roasting pellet production process as claimed in claim 1 or 2, wherein the microwave low-temperature carbon-free roasting pellet production process comprises the following steps: and cooling the pellet materials in a cooling I section, a cooling II section and a cooling III section at the speed of 50-80 ℃/min, and controlling the temperature of the final finished pellet to be lower than 150 ℃.
CN202210460496.5A 2022-04-28 2022-04-28 Pellet production process for microwave low-temperature carbonless roasting Active CN114737050B (en)

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