CN108588411B

CN108588411B - Preparation method of high-carbon-content metallized briquette for blast furnace

Info

Publication number: CN108588411B
Application number: CN201810390991.7A
Authority: CN
Inventors: 唐惠庆; 柳仕宏; 贠志伟; 薛庆国; 王劲松
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2018-04-27
Filing date: 2018-04-27
Publication date: 2020-02-07
Anticipated expiration: 2038-04-27
Also published as: CN108588411A

Abstract

A preparation method of high carbon-containing metallized briquette for a blast furnace, belonging to the technical field of iron making. The raw materials consist of superfine iron ore concentrate powder, anthracite powder and weakly caking bituminous coal powder, wherein the average particle size of the iron ore powder is 1-5 mu m, and the average particle size of the mixed coal powder is 50-100 mu m. After the raw materials are fully and uniformly mixed, organic binder and water with a certain proportion are added, and then the mixture is pressed into green blocks by a ball press. Then isolating the air or N₂And roasting according to a certain temperature system under the protection condition to prepare the high carbon content metallized briquette. The high carbon content metallized briquette of the invention has the carbon content of 20-40 wt%, and has good cold strength, crushing strength after reaction and good CO₂And (4) reactivity. In the production of the blast furnace, the high carbon-containing metallized briquette with proper proportion is added into the iron-containing mineral material layer, which is favorable for reducing the coke ratio and the energy consumption of the blast furnace and simultaneously does not influence the air permeability of the blast furnace. Because the carbon source of the high-carbon-content metallized briquette is from weakly caking bituminous coal and anthracite, the method is favorable for expanding the use of non-coking coal in blast furnace ironmaking and reducing the dependence of the blast furnace ironmaking on coke.

Description

Preparation method of high-carbon-content metallized briquette for blast furnace

Technical Field

The invention belongs to the field of ferrous metallurgy, and relates to a preparation method of high-carbon-content metallized briquette for blast furnace ironmaking.

Background

Blast furnace ironmaking is the major molten iron production process in the world. Coke is the most important raw material of blast furnaces in terms of improving the operating efficiency of the blast furnaces and controlling the quality of molten iron. Coke constitutes a major part of the cost of molten iron production. Because of the lack of coking coal resources and the high pollution industry of coking, the low coke ratio iron-making technology is always an important research content of blast furnace iron-making.

In blast furnace iron making, coke has three functions, namely: a thermal function, as a fuel, to provide heat for chemical reactions and molten iron and slag; a chemical function of providing a reducing gas as a reducing agent for reducing the iron-containing minerals; the mechanical function, as a framework, provides support for the iron-containing burden, so that liquid and gas can smoothly pass through the furnace, especially the lower part of the blast furnace. During the coke falling in the blast furnace, the coke is violentExposed to extreme reaction conditions. When the temperature is raised to about 800 ℃, the coke and carbon dioxide generated by the reduction of iron minerals have carbon dissolution reaction; when the temperature rises to 1200 ℃, the coke is mixed with liquid FeO and SiO₂Reaction and carburizing of molten iron; when the temperature is higher than 1500 ℃, the coke is subjected to combustion reaction with oxygen in hot air in the vicinity of a blast furnace convolution zone. During the last decades, much research has been done on low coke ratio blast furnace ironmaking techniques. The main technology in this aspect is blast furnace coal injection, and the consumption of coke in the raceway is replaced by non-coking coal by adopting the blast furnace coal injection technology. At present, the coal injection quantity per ton of iron can reach 200kg by using pulverized coal combustion catalyst, oxygen-enriched air blast, high air temperature and other technologies. Further increases in the amount of coal injection per ton of iron face a number of difficulties, for example, further increases in the amount of coal injection per ton of iron significantly affect the permeability and gas flow behavior in the lower part of the blast furnace. In the blast furnace shaft zone at temperatures of 800-. There are fewer techniques for reducing coke consumption in this area. Some researchers have proposed slowing down coke gasification by applying a passivating agent to the coke, but the effect of the passivating agent is not significant. Some researchers have proposed that highly gasified iron coke is used to suppress coke gasification, but some strong-caking coke coal still needs to be mixed in the process of producing iron coke itself (chinese patent CN 102827624B, chinese patent CN 104119939B). Therefore, the technology of saving coke in the temperature range of 800-.

Metallized briquettes (metallized pellets) have now partially replaced conventional blast furnace iron-containing charges consisting of lump ore, sinter ore and pellets. The main purpose of adding a part of the metallized lumps into the iron-containing burden of the blast furnace is to increase the productivity of the blast furnace. The metallized briquette is typically prepared by direct reduction of a cold-consolidated carbon internally-fitted briquette. The carbon content in the current metallized pellets (pellets) is about 2.0-4.0 wt%. If the carbon content of the metallized briquette can be greatly increased without damaging the strength of the metallized briquette, the carbon in the metallized briquette can be gasified in the coke dissolution reaction zone (800 ℃ C. and 1200 ℃ C.) of the blast furnace. Thus, the high carbon-containing metallized pellets can further have the function of iron coke, and the purposes of improving the CO component of blast furnace gas and promoting the reduction of iron-containing furnace burden are realized. In addition, because the high carbon content metallized briquette has low carbon content, when the briquette descends to a reflow zone along with iron mineral furnace burden, most of the carbon in the briquette is gasified, and the carbon content of the briquette is reduced to the level of the carbon content of the common metallized briquette, so that the briquette can not bring residual carbon particles into the lower area of the blast furnace, namely the ventilation performance of the lower part of the blast furnace is not influenced.

Disclosure of Invention

The invention aims to provide a preparation method of high-carbon metallized briquette for blast furnace ironmaking. The invention aims to adopt the technical route of preparing green agglomerates by using superfine iron ore powder and non-coking coal powder and insulating air or roasting in inert atmosphere. In the present invention, the high mechanical strength and high gasification performance of the high carbon-containing metallized briquette are achieved by controlling the particle size of the raw material and controlling the firing temperature and atmosphere. The prepared metallized briquette has higher strength in the blast furnace and can maintain the air permeability of furnace charge in the blast furnace.

The technical scheme of the invention is that the preparation method of the high carbon-containing metallized briquette for the blast furnace comprises the steps of raw material preparation and briquette roasting. The preparation method comprises the following steps:

a method of making a high carbon metallization briquette for a blast furnace, the method comprising the steps of:

step one, preparing superfine iron ore powder: crushing iron ore and fully and finely grinding the iron ore into iron ore powder by using a ball mill;

step two, coal powder preparation: preparing the selected coal sample into coal powder;

step three, mixing and briquetting raw materials: fully mixing the superfine iron ore powder and the coal powder according to a preset proportion, adding a certain proportion of organic binder and water, and pressing to obtain green blocks at the pressure of 300-400kg/cm²Cold press molding to obtain wet blocks of phi (15-20) mm multiplied by 15-20 mm;

step four, drying the raw blocks: fully drying the prepared raw blocks;

step five, roasting the green blocks: and roasting the dried agglomerate under a certain atmosphere and a certain temperature system.

Further, in the first step, the total iron content of the iron ore is more than 60 wt%, and the average particle size of the ore powder is 1-5 μm.

Further, in the second step, the coal is a mixture of weakly caking bituminous coal and anthracite, the average particle size of the coal powder is 50-100 μm, the fixed carbon content of the coal powder is 65-75%, the volatile matter is 18-25%, and the ash content is lower than 10%.

Further, in the third step, when the mineral powder and the coal powder are mixed, the mass ratio of the mineral powder to the coal powder is 1.5-2.0.

Further, in the third step, the amount of the organic binder used in the process of pressing the briquette is not more than 2% of the mass of the mixture, the water content is not more than 10%, and the organic binder comprises cellulose and waste paper pulp.

Further, in the fourth step, the drying temperature of the green briquette is 100-.

Further, in the fifth step, the atmosphere is N₂Atmosphere or air exclusion; the temperature system is that the furnace temperature is increased from the room temperature to 900-1000 ℃ at the temperature rising speed of 5-10 ℃/min, and the furnace is naturally cooled to the room temperature after the furnace is insulated for 30-60min at the temperature of 900-1000 ℃.

Hereinafter, the preferable technical effects of the technical means of the present invention will be described in detail.

The high carbon metallized briquette proposed by the present invention can be utilized as a superior raw material in blast furnace iron making, and has the following advantages.

(1) During the roasting process, the iron ore powder particles in the green agglomerates are reduced into ultra-fine metallic iron powder by the coal dust. These metallic iron powders are distributed in the voids between the carbon particles in a highly dispersed state and are closely adhered to the surfaces of the carbon particles. Therefore, the ultrafine metallic iron powder has a consolidation effect on carbon particles having a large particle size from both the mechanical action and the chemical action. Therefore, the high carbon-containing metallized briquette has good mechanical strength and meets the requirement of blast furnace iron-making on the strength of charging materials.

(2) Iron in the high carbon content metallized briquette is dispersed and distributed in the carbon matrix of the briquette,since metallic iron has a catalytic effect on the gasification reaction of carbon, it turns out that metallic iron powder forms many catalytically active sites on the surface of carbon particles. The carbon in the high carbon containing metallized briquette has higher CO than the carbon in the coke₂And (4) reactivity. CO produced by reduction of iron ore when charged into the blast furnace in admixture with iron-containing charge material of the blast furnace in an appropriate ratio₂The carbon in the metallized briquette is quickly converted into CO, so the metallized briquette with high carbon content can improve the reduction condition of iron mineral and improve the utilization rate of blast furnace gas.

(3) CO produced by reduction of iron minerals₂The carbon gasification reaction is firstly carried out with the carbon in the metallized briquette, so the high carbon-containing metallized briquette mixed with the iron-containing mineral layer also has the protection effect on the layered large coke, the large coke entering the central coke layer has larger granularity and strength, and the air permeability and liquid permeability of the hearth and the area nearby the hearth are improved.

(4) When the high carbon containing metallized briquette descends to the vicinity of the reflow zone, because most of the carbon therein is gasified, the briquette is left with mainly metallic iron and a small amount of gangue, and no or few residual carbon particles are present. Therefore, the melting of the soft melting belt has no influence on the air permeability of the blast furnace soft melting belt.

(5) The production process of the high-carbon-content metallized briquette completely uses the non-coking coal, and has good effects on measures for coal resource and strengthening environmental protection measures of iron works.

(6) The green briquette is cold pressed to form and has low cost and less environmental pollution. Meanwhile, the production process is simple, and has wide industrial application prospect.

Drawings

Fig. 1 is a diagram of a process for the preparation of a high carbon containing metallized briquette for a blast furnace according to the present invention.

FIG. 2 is an XRD pattern of a sample obtained in the first example of the present invention.

FIG. 3(a) is a micro-topography of a sample obtained in a first example of the present invention; fig. 3(b) is a microscopic morphology of iron particles (white) and carbon particles (gray) in the resulting sample.

FIG. 4(a) is a microscopic morphology of a metallized pellet in a first embodiment of the present invention after high temperature reaction; FIG. 4(b) is a microscopic morphology of iron particles (white) and carbon particles (gray) in the metallized agglomerates after high temperature reaction.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to fig. 1-4 and the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. On the contrary, the invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, certain specific details are set forth in order to provide a better understanding of the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details.

As shown in fig. 1, a method for preparing a high carbon-containing metallized briquette for a blast furnace specifically comprises the following steps:

step one, preparation of superfine iron ore powder: the iron ore concentrate raw material with the total iron content of more than 60 wt% is adopted, and after the iron ore concentrate is crushed and fully ball-milled, the average particle size of the obtained ore powder is 1-5 mu m.

Step two, coal powder preparation: the method takes weakly caking coal and anthracite as raw materials, and the average particle size of the obtained mixed coal powder is 50-100 mu m after a coal sample is crushed, ball-milled and fully mixed by a crusher and a ball mill.

Step three, mixing and briquetting raw materials: mixing the prepared superfine iron ore powder and coal powder according to a certain proportion, adding a certain proportion of organic binder and water into the uniformly mixed material, and pressing the uniformly mixed material into a briquette with the size of phi (15-20mm) multiplied by 15-20mm by using a double-roller ball press, wherein the binder is organic binder, the amount of the organic binder used in the ball making process is not more than 2%, and the content of water used is not more than 10%.

In the step, when the mineral powder and the coal powder are mixed, the mass ratio of the mineral powder to the coal powder is 1.5-2.0.

Step four, drying the raw blocks: in order to ensure the drying degree of the green pellets, the pellets can be dried naturally for 24 hours and then further dried at the temperature of 100 ℃ and 200 ℃ for 1-2 hours to achieve sufficient drying.

Step five, roasting the green blocks: and roasting the dried blocks under a certain temperature system and a certain atmosphere.

In the step, the temperature system for roasting the green agglomerates is that the furnace temperature is raised from the room temperature to 900-plus-1000 ℃ at the temperature raising rate of 5-10 ℃, and after the furnace temperature is kept at the temperature of 900-plus-1000 ℃ for 30-60min, the furnace temperature is naturally cooled to the room temperature. During the roasting process, the atmosphere is protected by air or inert gas. The carbon content of the resulting metallized agglomerates is 20-40 wt%. In the slow roasting process, the superfine iron oxide powder in the agglomerates is fully reduced in the roasting process, and the reaction between the iron ore powder and the coal powder particles cannot cause the agglomerates to deform or the surfaces of the agglomerates to generate cracks due to too violent reaction. The main phases in the agglomerates are metallic iron and carbon (as shown in figure 2). Since the fine particle size of the iron ore powder used is extremely fine, the fine-grained metallic iron particles in the agglomerates after calcination are distributed in a highly dispersed manner in the carbon matrix (as shown in fig. 3 (a)). Meanwhile, as can be seen from fig. 3(b), the size of these fine-grained metallic iron particles is less than 10 μ, much smaller than the grain size of the carbon particles; the shape of the metal iron powder is irregular particle shape, sawtooth shape sheet shape and fiber shape, and the metal iron powder is closely attached to the surface of the carbon particle. Microscopically, the strength of the agglomerates results from the interface where the iron particles are in intimate contact with the coke particles. On the interface, the surface of the coke particles is uneven, and a plurality of micropores and cracks exist; the surface of the metallic iron particles is also provided with a plurality of fine (nano-scale) iron whiskers. The fine iron whiskers can be embedded into pits and micropores on the surface of the coke particles, good conditions are provided for mechanical twisting and bonding of the interface of the coke particles and the metallic iron particles, and the metallic iron particles can be anchored on the surface of the coke particles. Meanwhile, atomic diffusion occurs at the interface between the coke particles and the iron particles during the high-temperature calcination process to form compounds such as Fe₃And C, partial fusion exists between the coke particle surface and the surface of the metallic iron, namely, the bonding force of chemical bonds between iron and carbon atoms also exists on the interface. These poles are for adjacent coke particlesThe fine-grained metallic iron powder essentially plays a role of binding. The single iron particles have very weak binding power to the coke particles, but the iron particles which are dispersed in the whole block and have huge number have very considerable binding power to the coke particles, thereby effectively improving the strength and toughness of the whole block.

If the high carbon-containing metallized briquette is used as the blast furnace burden, the cold strength and the crushing strength after screening must meet the requirements of the blast furnace on the burden. In the simulated high-temperature area environment of the blast furnace (temperature: 1100 ℃, atmosphere: CO)₂4:1, gas flow rate: 1m/s) was used, the microstructure of the metallized briquette was as shown in FIG. 4(a), and a comparison of FIG. 3(a) and FIG. 4(a) revealed that the iron particles in the briquette after the reaction had significantly increased in size. FIG. 4(b) is the microscopic morphology of the carbon particles and metallic iron in the agglomerates after the reaction, and it can be seen that the metallic iron particles are polymerized on the surface of the carbon particles, indicating that a metallic iron network structure is gradually formed in the agglomerates during the reaction. The aggregation and the network formation of the metallic iron particles effectively improve the crushing strength of the agglomerates after reaction, so that the agglomerates cannot generate the pulverization phenomenon in the high-temperature area of the blast furnace.

The process of the present invention is further described in detail below with reference to specific examples, in which the chemical composition of the iron ore concentrate used is shown in table 1, the coal samples used are shown in tables 2-3, and table 4 shows the composition of the comparative coke.

TABLE 1 iron concentrate chemical composition (wt%)

TABLE 2 Industrial analysis of weakly caking bituminous coal (Shenhua bituminous coal) (wt%)

TABLE 3 Industrial analysis of anthracite (Coke as anthracite) (wt%)

TABLE 4 Industrial analysis (wt%) of comparative ordinary metallurgical coke

Example one

[1] Preparing superfine iron ore powder: the results of chemical analysis of the iron concentrate used are shown in table 1. Taking 600g of iron ore concentrate, crushing and fully ball-milling the iron ore concentrate sample to obtain the mineral powder with the average particle size of 2.88 mu m.

[2] Preparation of coal dust: the results of the industrial analysis of the bituminous coal used are shown in table 2 and the results of the industrial analysis of the anthracite coal used are shown in table 3. 150g of the above-mentioned bituminous coal sample and 150g of the above-mentioned smokeless coal sample were sampled. The two coal samples are crushed, ball-milled and mixed uniformly, and the average particle size of the obtained mixed coal powder is 60 mu m.

[3] Mixing and briquetting of raw materials: the iron ore powder and the mixed coal powder are fully and uniformly mixed. The uniformly mixed materials are made into blocks with the diameter of phi 15mm multiplied by 15 mm. The mass of each mass was 5-6 g. The pelletizing adhesive is 2.0% cellulose.

[4] Drying the raw briquette: the green pellets were naturally dried for 24 hours and then further dried at 100 ℃ for 1 hour.

[5]Green briquette roasting: adopting a tube furnace, and roasting under the following conditions: the furnace temperature is increased to 1000 ℃ from room temperature at the heating rate of 5 ℃/min; keeping the temperature at 1000 ℃ for 30min, and cooling to room temperature. N is introduced into the furnace at a volume flow rate of 500ml/min during the roasting process₂. The carbon content of the high carbon containing metallized agglomerates obtained was 25 wt%.

The cold strength of the obtained metallized block is 2000N/block according to the test of national standard GB/T14201-93. In the simulated high-temperature area environment (temperature: 1100 ℃, atmosphere: CO) in the blast furnace₂4:1, gas flow rate: 1m/s), the crushing strength after reaction of a 100g lump sample after 1 hour was 2500N/piece. In the environment of a simulated high-temperature area of the blast furnace (temperature: 1100 ℃, atmosphere: CO)₂4:1, gas flow rate: 1m/s) of the carbon in a 100g mass sample after 1 hour of reactionThe ratio was 70%. For comparison, the carbon gasification rate of 100g of ordinary coke (composition shown in Table 4) having the same average particle size was 10% under the same reaction conditions.

Example two

[1] Preparing superfine iron ore powder: the results of chemical analysis of the iron concentrate used are shown in table 1. 600g of iron ore concentrate is taken, and after the iron ore concentrate is subjected to primary crushing and full ball milling, the average particle size of the obtained iron ore powder is 3.56 mu m.

[2] Preparation of coal dust: the results of the industrial analysis of the bituminous coal used are shown in table 2 and the results of the industrial analysis of the anthracite coal used are shown in table 3. 200g of the above-mentioned bituminous coal sample and 200g of the above-mentioned smokeless coal sample were sampled. The two coal samples are crushed, ball-milled and mixed uniformly, and the average particle size of the obtained mixed coal powder is 60 mu m.

[3] Mixing and briquetting of raw materials: the iron ore powder and the mixed coal powder are fully and uniformly mixed. Pressing the uniformly mixed materials into blocks with the diameter of 15mm multiplied by 15 mm. The mass of each mass was 5-6 g. The pelletizing adhesive is 2.0% cellulose.

[4] Drying the raw briquette: the green pellets were naturally dried for 24 hours and then further dried at 100 ℃ for 2 hours.

[5]Green briquette roasting: adopting a tube furnace, and roasting under the following conditions: the temperature of the furnace is raised to 1000 ℃ at the heating rate of 10 ℃/min; preserving the heat at 1000 ℃ for 60min, and naturally cooling to room temperature. N is introduced into the furnace at a volume flow rate of 500ml/min during the roasting process₂. The carbon content of the resulting metallized pellet was 33.0 wt%.

The cold strength of the alloy is 1500N/piece according to the standard test of national standard GB/T14201-93. In the simulated high-temperature area environment (temperature: 1100 ℃, atmosphere: CO) in the blast furnace₂4:1, gas flow rate: 1m/s), the crushing strength after reaction of 100g of the lump sample after 1 hour was 2000N/piece. In the environment of a simulated high-temperature area of the blast furnace (temperature: 1100 ℃, atmosphere: CO)₂4:1, gas flow rate: 1m/s), the rate of carbon gasification of 100g of the briquette sample after 1 hour of reaction was 60%. For comparison, the carbon vaporization rate in 100g of ordinary coke (composition shown in Table 4) having the same average particle size was 10% under the same reaction conditions.

EXAMPLE III

[1] Preparing superfine iron ore powder: the results of chemical analysis of the iron concentrate used are shown in table 1. Taking 600g of iron concentrate sample. After the iron ore concentrate sample is crushed and fully ball-milled, the average particle size of the obtained iron ore powder is 4.82 mu m.

[2] Preparation of coal dust: the results of the industrial analysis of the bituminous coal used are shown in table 2 and the results of the industrial analysis of the anthracite coal used are shown in table 3. 150g of the above-mentioned bituminous coal sample and 150g of the above-mentioned smokeless coal sample were sampled. After the two coal samples are crushed, ball-milled and uniformly mixed, the average particle size of the obtained mixed coal powder is 100 mu m.

[3] Mixing and briquetting of raw materials: the iron ore powder and the mixed coal powder are fully and uniformly mixed. Pressing the uniformly mixed materials into blocks with the diameter of 20mm multiplied by 20 mm. The mass of each mass was 9-11 g. The ball-making binder adopts 2.0 percent of waste paper pulp.

[4] Drying the raw briquette: the green pellets were naturally dried for 24 hours and then further dried at 200 ℃ for 1 hour.

[5] Green briquette roasting: adopting a tube furnace, and roasting under the following conditions: the temperature of the furnace is raised to 1000 ℃ at the heating rate of 10 ℃/min; preserving the heat at 1000 ℃ for 30min, and naturally cooling to room temperature. And air is isolated in the furnace during the roasting process. The carbon content of the resulting metallized pellets was 24 wt%.

The cold strength of the alloy is 1500N/piece according to the standard test of national standard GB/T14201-93. In the simulated high-temperature area environment (temperature: 1100 ℃, atmosphere: CO) in the blast furnace₂4:1, gas flow rate: 1m/s), 100g of the lump sample had a post-reaction crushing strength of 3000N/piece after 1 hour of reaction. In the simulated high-temperature area environment (temperature: 1100 ℃, atmosphere: CO) in the blast furnace₂4:1, gas flow rate: 1m/s), the rate of carbon gasification of 100g of the briquette sample after 1 hour of reaction was 65%. For comparison, under the same reaction conditions, the gasification rate of ordinary coke (composition shown in Table 4) having the same average particle size was 8%.

Example four

[1] Preparing superfine iron ore powder: the results of chemical analysis of the iron concentrate used are shown in table 2. Taking 600g of iron ore concentrate sample, crushing and fully ball-milling the iron ore concentrate sample to obtain the iron ore powder with the average particle size of 1.50 mu m.

[2] Preparation of coal dust: the results of the industrial analysis of the bituminous coal used are shown in table 2 and the results of the industrial analysis of the anthracite coal used are shown in table 3. 200g of the smokeless coal sample and 200g of the bituminous coal sample are taken. After the two coal samples are crushed, ball-milled and uniformly mixed, the average particle size of the obtained mixed coal powder is 80 μm.

[3] Mixing and briquetting of raw materials: the iron ore powder and the mixed coal powder are fully and uniformly mixed. Pressing the uniformly mixed materials into blocks with the diameter phi of 20mm multiplied by 20 mm. The mass of each mass was 9-11 g. The ball-making binder adopts 2.0 percent of waste paper pulp.

[5]Green briquette roasting: roasting in a tubular furnace under the following conditions: the furnace temperature is increased to 900 ℃ at the temperature rising rate of 5 ℃/min; preserving the temperature at 900 ℃ for 30min, and naturally cooling to room temperature. N is introduced into the furnace at a volume flow rate of 500ml/min during the roasting process₂. The carbon content of the resulting metallized pellets was 37 wt%.

The cold strength of the briquettes was 1900N/briquette, tested according to the national standard GB/T14201-93. In the simulated high-temperature area environment (temperature: 1100 ℃, atmosphere: CO) in the blast furnace₂4:1, gas flow rate: 1m/s), the crushing strength after reaction of 100g of the lump sample after 1 hour was 2900N/piece. In the simulated high-temperature area environment (temperature: 1100 ℃, atmosphere: CO) in the blast furnace₂4:1, gas flow rate: 1m/s), the carbon gasification rate of 100g of the briquette after 1 hour of reaction was 80%, and as a comparison, the carbon gasification rate of ordinary coke (composition shown in Table 4) having the same average particle size under the same reaction conditions was 8%.

Example five (comparative example)

[1] Preparing superfine iron ore powder: no iron ore powder is added.

[2] Preparation of coal dust: the results of the industrial analysis of the bituminous coal used are shown in table 2 and the results of the industrial analysis of the anthracite coal used are shown in table 3. 250g of the above-mentioned bituminous coal sample and 250g of the above-mentioned smokeless coal sample were sampled. After the two coal samples are crushed, ball-milled and uniformly mixed, the average particle size of the obtained mixed coal powder is 60 mu m.

[3] Mixing and briquetting of raw materials: pressing the uniformly mixed materials into blocks with the diameter of 15mm multiplied by 15mm, wherein the mass of each block is 5-6 g. 2.0% of waste paper pulp is used as the binder.

[4] Drying the raw briquette: the green pellets were naturally dried for 24 hours and then further dried at 200 ℃ for 2 hours.

[5]Green briquette roasting: adopting a tube furnace, and roasting under the following conditions: the temperature of the furnace is raised to 1000 ℃ at the temperature rise rate of 5 ℃/min; preserving the heat at 1000 ℃ for 30min, and naturally cooling to room temperature. N is introduced into the furnace at the flow rate of 500ml/min in the roasting process₂And (4) qi. The carbon content of the obtained briquette was 91 wt%.

The cold strength of the alloy is 2200N/piece according to the test of national standard GB/T14201-93. In the simulated high-temperature area environment (temperature: 1100 ℃, atmosphere: CO) in the blast furnace₂4:1, gas flow rate: 1m/s) of the specimen 100g had a crushing strength of 300N/specimen after 1 hour of reaction. The mechanical strength of the alloy can not meet the requirement of blast furnace ironmaking.

EXAMPLE six (COMPARATIVE EXAMPLE)

[1] Preparing superfine iron ore powder: the results of chemical analysis of the iron concentrate used are shown in table 2. 300g of iron ore concentrate sample is taken, and after the iron ore concentrate is crushed and fully ball-milled, the average particle size of the obtained iron ore powder is 2.88 mu m.

[2] Preparation of coal dust: the results of the industrial analysis of the bituminous coal used are shown in table 2 and the results of the industrial analysis of the anthracite coal used are shown in table 3. 150g of the above-mentioned bituminous coal sample and 150g of the above-mentioned non-coal sample were sampled. After primary crushing, ball milling and uniform mixing, the average particle size of the obtained mixed coal powder is 60 mu m.

[3] Mixing and briquetting of raw materials: pressing the uniformly mixed materials into blocks with the diameter of phi 15mm multiplied by 15 mm. The mass of each mass was 5-6 g. 2.0% of waste paper pulp is used as the binder.

[5]Green briquette roasting: adopting a tube furnace, and roasting under the following conditions: the temperature of the furnace is raised to 1000 ℃ at the temperature rise rate of 5 ℃/min; preserving the heat at 1000 ℃ for 30min, and naturally cooling to room temperature. 500ml/mi into the furnace during the roasting processN is introduced at a volume flow rate of N₂. The carbon content of the resulting briquette was 47 wt%.

The cold strength of the block sample was 500N/block as tested according to the national standard GB/T14201-93. In the simulated high-temperature area environment (temperature: 1100 ℃, atmosphere: CO) in the blast furnace₂4:1, gas flow rate: 1m/s), the crushing strength after reaction of 100g of the briquette after 1 hour was 300N/briquette. The strength of the alloy can not meet the requirement of blast furnace ironmaking.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A preparation method of high carbon-containing metallized briquette for blast furnace is characterized by comprising the following steps: the method comprises the following steps:

step three, mixing and briquetting raw materials: fully mixing the superfine iron ore powder and the coal powder according to a preset proportion, adding a certain proportion of organic binder and water, and pressing to obtain green blocks at the pressure of 300-400kg/cm²Cold press molding to obtain wet block of phi (15-20) mm x (15-20) mm;

step four, drying the raw blocks: fully drying the prepared raw blocks;

step five, roasting the green blocks: roasting the dried agglomerate in a certain atmosphere and under a certain temperature system, wherein in the process of slow roasting, the atmosphere is protected by isolated air or inert gas, and the carbon content of the metallized agglomerate obtained by roasting is 20-40 wt%; testing according to the national standard GB/T14201-93, wherein the cold strength of the obtained blocks is more than 1500N/block; the carbon gasification rate of the obtained briquette is more than 60 percent after the briquette reacts for 1 hour under the condition of simulating the high-temperature environment in the blast furnace, and the briquette has strong shatter resistanceThe temperature is more than 2000N/piece, and the simulated high-temperature environmental conditions in the blast furnace are as follows: 1100 ℃, atmosphere: CO-CO₂4:1, gas flow rate: 1 m/s.

In the first step, the total iron content of the iron ore is more than 60 wt%, and the average particle size of the superfine iron ore powder is 1-5 μm;

in the second step, the pulverized coal is a mixture of weakly caking bituminous coal and anthracite; the average particle size of the coal powder mixture is 50-100 mu m; the fixed carbon content of the coal powder mixture is 65-75 wt%, the volatile component is 18-25 wt%, and the ash content is lower than 10 wt%;

when the mineral powder and the coal powder are mixed, the mass ratio of the mineral powder to the coal powder is 1.5-2.0;

in the third step, the amount of the organic binder used in the process of pressing the briquette is not more than 2 percent of the mass of the mixture, the water content is not more than 10 percent, and the organic binder is cellulose or waste paper pulp;

in the fifth step, the atmosphere is N₂Atmosphere or air exclusion; the temperature system is that the furnace temperature is increased to 900-; secondly, the surface of the coke particles is uneven, and a plurality of micropores and cracks exist; the surface of the metal iron particle also has a plurality of fine nano-scale iron whiskers, the fine iron whiskers can be embedded into pits and micropores on the surface of the coke particle, the metal iron particle can be anchored on the surface of the coke particle, and meanwhile, atomic diffusion can occur on the interface of the coke particle and the iron particle in the high-temperature roasting process to form a compound.

2. The method for preparing high carbon content metallized briquette for blast furnace as claimed in claim 1, wherein in the fourth step, the drying temperature of the green briquette is 100-200 ℃ and the drying time is 1-2 h.