CN114369716B

CN114369716B - Preparation and direct reduction iron-making method of honeycomb diversion material block for enhancing mass transfer and heat transfer

Info

Publication number: CN114369716B
Application number: CN202111555596.8A
Authority: CN
Inventors: 程树森; 李世旺; 张丽英; 程晓曼; 胡铮; 王亮
Original assignee: Beijing Beike Shenzhou Yili Metallurgical Materials Research Institute; University of Science and Technology Beijing USTB
Current assignee: Beijing Beike Shenzhou Yili Metallurgical Materials Research Institute; University of Science and Technology Beijing USTB
Priority date: 2021-12-17
Filing date: 2021-12-17
Publication date: 2022-11-18
Anticipated expiration: 2041-12-17
Also published as: CN114369716A

Abstract

The invention discloses a preparation method of a honeycomb-shaped guide material block for strengthening mass transfer and heat transfer and a direct reduction ironmaking method, belonging to the technical field of direct reduction ironmaking in ferrous metallurgy. The method comprises the following steps: uniformly mixing an iron-containing material, a carbonaceous reducing agent, a composite binder and water to form a mixed material; fully kneading and briquetting the mixed material to obtain a honeycomb-shaped guide material block; sending the mixture into a trolley type roasting reduction device for processing to obtain initial reduction furnace charge; directly hot-charging the first part of the initial reduced furnace charge to an electric arc furnace for melting and separating to be used as raw materials for electric arc furnace steelmaking, carrying out magnetic separation on the second part of the initial reduced furnace charge to obtain a metalized furnace charge and other impurities mainly comprising carbon residue, further crushing and screening the obtained metalized furnace charge, and carrying out magnetic separation to obtain high-purity iron powder and tailings. The invention obviously improves the dynamic condition of the reaction of the materials and the high-temperature reducing gas in the direct reduction process of the iron ore, greatly improves the metallization rate of the reduction product and shortens the reduction time.

Description

Preparation and direct reduction iron-making method of honeycomb diversion material block for enhancing mass transfer and heat transfer

Technical Field

The invention belongs to the technical field of direct reduction ironmaking in ferrous metallurgy, and particularly relates to a preparation method of a honeycomb-shaped guide material block for strengthening mass transfer and heat transfer and a direct reduction ironmaking method.

Background

The blast furnace iron-making process is a foundation stone of the modern steel industry and plays a very important role in the whole steel industry. The main process of blast furnace iron making comprises coking and agglomeration (sintering)And pellets), blast furnace smelting and the like, but all the procedures have strong dependence on resources and have great pollution to the environment. Blast furnace iron making has strict requirements on raw fuel entering a furnace, high-grade iron ore with a certain size fraction is required to be used, some lean ore or fine ore is required to be further treated by ore dressing and agglomeration processes, the requirement on metallurgical coke is increased in the process, but the storage capacity of high-quality coking coal is limited, so that the cost of blast furnace iron making is greatly increased. In addition, a large amount of substances harmful to the environment are generated in the processes of ore dressing, agglomeration, coking and blast furnace ironmaking. In the long-flow production mainly comprising coking, sintering, blast furnace and converter, nearly 60 percent of energy consumption, 70 percent of cost per ton of steel and 90 percent of pollutant emission are concentrated in the coking, sintering and blast furnace ironmaking processes. At present, the average coke ratio of a large blast furnace in China can reach 450kg/t, about 1.6 tons of ore are needed for smelting each ton of pig iron, the percentage of sintered ore in the burden structure in China is about 75%, 11 million tons of ore powder need to be sintered into blocks calculated by 9 million tons of pig iron capacity in China in 2020, about 128 million tons of smoke and dust are generated in the whole blast furnace ironmaking process every year, and SO is generated ₂ About 205 million tons of gas produce about 77 million tons of nitrogen oxides. These varieties indicate that blast furnace ironmaking is not a long standing strategy. Meanwhile, in order to respond to the national call of 'carbon peak reaching and carbon neutralization', the development of a non-blast furnace iron making method which does not depend on coking coal and high-grade iron ore and is economic and environment-friendly is urgently needed.

The non-blast furnace ironmaking process takes non-coking coal as a main energy source, does not need procedures such as ore dressing, agglomeration and the like, has better requirements and adaptability to raw fuel than the traditional blast furnace ironmaking process, thereby greatly shortening the production flow and having the characteristics of strong controllability, low cost, little pollution and low emission. Direct reduction processes are divided into gas-based direct reduction and coal-based direct reduction according to the use of a reducing agent, and a reducing gas mainly composed of natural gas, hydrogen or carbon monoxide widely used in a gas-based direct reduction method also has a pressure in terms of resource supply. China is also a large-coal-storage country and has abundant coal resources. Therefore, the development of the coal-based direct reduction process is the central importance of the future development of non-blast furnace ironmaking technology in China.

The process for producing direct reduced iron by using a coal-based tunnel kiln, which is also called a Herganas coal-based tunnel kiln direct reduction method, is introduced into Herganas corporation in Sweden, is originally and widely applied to the field of powder metallurgy in China, and occupies a leading position in the industry. In recent years, with the development of a coal-based direct reduction process, china starts to apply the process to the field of steelmaking direct reduced iron and makes great progress, which has important significance for relieving the supply contradiction of high-quality scrap steel for steelmaking in China. In the raw material preparation stage, the current mainstream practice includes two methods, namely directly charging iron ore powder into a container, and pressing the raw material into pellets or other shapes. In a process of low-temperature reduction of iron ore, normal-temperature slag iron separation and electric furnace steel making, granular pellets, iron ore and carbon residue are used as raw materials for reduction reaction and are loaded into a rotary kiln; in the direct reduction process of the carbon-blending porous block in the iron ore powder mentioned in patent CN 104195276A, raw materials such as iron ore, reducing agent and the like are mixed to prepare a material block. In the former case, although the forming process is omitted, the mass and heat transfer during the reaction process are very limiting factors due to the characteristics of the materials. Meanwhile, the phenomenon of local reflow agglomeration caused by overlong contact time of local materials and high-temperature furnace gas is easily caused due to uneven mass and heat transfer. In addition, the treatment process of the powdery material is complicated and continuous large-scale production is not easy to realize. In the latter case, the quality of the final product is often affected by the degree of density of the material block, the manner of heat supply, the degree of uniformity of heat supply, and other factors.

In any method for treating the raw materials, the heating speed of the surface of the raw materials is far higher than the heat conduction speed of the interior of the raw materials, so that the condition that the surface of the raw materials is initially melted and the interior of the raw materials does not reach the temperature required by the reaction necessarily occurs, and the reaction speed, the reduction rate and the metallization rate of the reduction products are all affected adversely. Under such conditions, the quality of the product can only be maintained by prolonging the time of the high-temperature reduction reaction, with the consequent higher costs. Therefore, how to improve the mass and heat transfer conditions of the materials in the direct reduction process and increase the mass and heat transfer speed, the reaction interface, the product metallization rate and the overall reduction efficiency becomes urgent. On the basis of this, the prior art proposes to treat the material into pieces with holes, and the prior art mentions a checker brick for hot blast stoves with gas passages, but there is little mention of the specific opening characteristics of the pieces and the detailed treatment of the surfaces of the pieces. In addition, the selection problem of the reduction process is also a problem to be solved urgently, and the gas-based direct reduction process is widely applied as the existing mature non-blast furnace ironmaking process, but is always limited by resources. The traditional coal-based direct reduction process is limited to small-scale production and part of the production process is still imperfect.

Disclosure of Invention

Therefore, in order to solve the problems, on one hand, the invention designs a honeycomb material block which has a flow guide effect and can strengthen mass and heat transfer to the maximum extent by combining the design concept of the checker bricks of the hot blast stove and the synergistic theory of three fields of a speed field, a temperature field and a concentration field. On the other hand, the preparation method of the honeycomb-shaped guide material block for strengthening mass and heat transfer and the direct reduction iron-making method are provided on the basis of the traditional coal-based direct reduction method by combining the working principle of a sintering trolley and a belt type roasting machine. Therefore, the invention aims at overcoming the defects in the prior art and solves the technical problems of poor reaction kinetic conditions of materials and reducing substances, insufficient mass and heat transfer, long reaction time, low reduction efficiency, low metallization rate and the like in the direct reduction iron-making process. The preparation of the honeycomb-shaped guide material block for strengthening the mass transfer and heat transfer chemical reaction and the direct reduction ironmaking process obviously improve the dynamic condition of the reaction of materials and high-temperature reducing gas in the direct reduction process of the iron ore, greatly improve the metallization rate of a reduction product and shorten the reduction time.

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

according to the technical scheme of the invention, a method for preparing a honeycomb-shaped guide material block for enhancing mass and heat transfer and directly reducing iron making is provided, and is characterized by comprising the following steps:

step 1, uniformly mixing an iron-containing material, a carbonaceous reducing agent, a composite binder and water to form a mixed material;

step 2, fully kneading and briquetting the mixed material to obtain a honeycomb-shaped guide material block;

step 3, sending the honeycomb-shaped guide material block into a trolley type roasting reduction device for treatment to obtain an initial reduction furnace charge;

and 4, directly hot-charging the first part of the initial reduced furnace burden to an electric arc furnace for melting and separating to obtain raw materials for electric arc furnace steelmaking, carrying out magnetic separation on the second part of the initial reduced furnace burden to obtain a metalized furnace burden and other impurities mainly comprising carbon residue, further crushing and screening the obtained metalized furnace burden, and carrying out magnetic separation to obtain high-purity iron powder and tailings.

The ratio of the first fraction to the second fraction depends on the individual case, and if only required in the first aspect, all the initial reduced charge can be used for the "first fraction", and so on.

Further, in the step 1, the mixture ratio of the iron-containing material, the carbonaceous reducing agent, the composite binder and the water is calculated by weight ratio, and the mass ratio is as follows: 100:15 to 20:2 to 4:12 to 18.

Further, in step 1, the iron-containing materials include, but are not limited to, iron ore (magnetite, hematite, limonite, vanadium titano-magnetite, ilmenite, high-silicon iron concentrate, paragenetic ore, etc.), refractory low-grade fine iron ore, blast furnace sack dust, converter scale dust, sinter fly ash, and the like.

Further, in the step 1, the carbonaceous reducing agent is selected from one or more of semi coke, low-rank coal powder, carbon-containing dust and metallurgical coke powder.

Further, in the step 1, the selection of the composite binder comprises an inorganic binder (bentonite, slaked lime, water glass) and an organic binder (sodium carboxymethyl cellulose, calcium lignosulfonate).

Further, in the step 1, in order to improve the blocking performance and the reduction efficiency of the finished material block when the materials are mixed, at least 50% of the iron-containing materials are required to pass through a 200-mesh sieve, and 55% of the carbonaceous reducing agent is required to pass through a 100-mesh sieve.

Furthermore, in step 2, a plurality of oval through holes are formed in the honeycomb-shaped flow guide material block, the oval through holes penetrate through the front end face and the back end face of the honeycomb-shaped flow guide material block, and meanwhile, a plurality of semicircular flow guide grooves for guiding gas and a circular flow converging groove for exchanging and converging air flows are formed in at least one end face of the honeycomb-shaped flow guide material block.

Furthermore, according to the difference of the aperture of the oval through holes, the honeycomb-shaped guide material blocks comprise large-aperture material blocks and small-aperture material blocks.

Furthermore, during material distribution, the laying mode of the large-aperture-size material blocks and the small-aperture-size material blocks is as follows:

a first layer: paving any one of the large-aperture material blocks or the small-aperture material blocks on the bottommost layer;

a second layer: the material blocks of another type are laid on the material blocks in a way that the long axis direction of the oval through holes of the material blocks is parallel to the long axis of the through holes of the material blocks of the lower layer, so that the laying method can achieve the same effect as that of a zoom tube, and the airflow generates radial flow vertical to the main flow direction when flowing through a channel formed by the two material blocks;

and a third layer: the third layer is paved with the material blocks with the same aperture size as the second layer, and the third layer material blocks are paved in a way that the long axes of the through holes of the third layer material blocks are vertical to the long axes of the through holes of the second layer material blocks, so that the paving method can play the same effect as a local flattening pipe and a cross elliptical pipe, and the airflow generates vortex secondary flow vertical to the main flow direction when flowing through a channel formed by the two layers of material blocks;

a fourth layer: the fourth layer is paved with the material blocks with different aperture sizes from the third layer, and the fourth layer material blocks are paved in a way that the long axes of the through holes of the fourth layer material blocks are parallel to the long axes of the through holes of the third layer material blocks, so that the gas also generates radial flow when flowing through the channel formed by the two layer material blocks;

the four layers of material blocks are paved in a cycle until the height of the material layer reaches 800 mm-1000 mm.

Further, the shape of the honeycomb-shaped guide material block includes but is not limited to a cylinder, a cuboid, a cube and a regular polygon prism.

Furthermore, the honeycomb-shaped guide material block is provided with 4 semicircular guide grooves, one ends of the 4 semicircular guide grooves respectively penetrate through the middle point of the side wall of the material block, and the other ends of the 4 semicircular guide grooves are gathered in a circular convergence groove which takes the center of the face of the end face of the material block as the center of a circle.

Furthermore, the positive and negative two terminal surfaces of honeycomb water conservancy diversion material piece all seted up semi-circular water conservancy diversion recess just semi-circular water conservancy diversion recess and circular groove of converging have the same degree of depth.

Furthermore, each side wall of the honeycomb-shaped guide material block is provided with a plurality of semicircular fixing grooves which penetrate through the upper end surface and the lower end surface, so that the purposes of stabilizing the material layer and facilitating the laying are achieved.

Furthermore, 21 oval through holes are formed in the surface of the honeycomb-shaped flow guide block.

Further, the inner surface of a channel formed by the oval through hole is carved with a spiral groove.

Further, the step 3 specifically includes: and paving the honeycomb-shaped guide material blocks on a trolley, sending the honeycomb-shaped guide material blocks into a trolley type roasting reduction device, starting to slowly heat the material blocks in a drying section and a preheating section in the roasting furnace under the action of high-temperature smoke generated after the material blocks are reacted in the high-temperature reduction section, carrying out high-temperature reduction roasting on the dried and preheated material blocks in the high-temperature reduction section, and discharging to obtain initial reduction furnace burden.

Further, in the step 3, the cart-type roasting reduction apparatus includes: car-type roasting machine, top-burning hot-blast stove, electric arc furnace and dust collecting equipment.

Further, the trolley type roasting machine comprises a trolley, wherein a sealed smoke hood is mounted on the trolley, and a conveying device is arranged in the smoke hood.

Further, the trolley comprises a drying section, a preheating section and a high-temperature reduction section.

Furthermore, air boxes are arranged between the drying section and the preheating section and between the preheating section and the high-temperature reduction section.

Furthermore, in the high-temperature reduction section of the trolley, two groups of combustion chambers which are arranged in parallel are arranged right above the smoke hood.

Further, a secondary air inlet pipe is arranged on the combustion chamber.

Furthermore, two side cavities in the combustion chamber are respectively provided with retaining walls in opposite directions, and each side cavity side wall is provided with a turbulent flow nozzle inserted into the nozzle brick.

Furthermore, the main body of the turbulent flow nozzle as a whole comprises a coal powder injection pipe, a burner coaxially arranged with the coal powder injection pipe, a primary air inlet pipe, an oxygen-enriched pipe and a spoiler.

Further, a part of biomass fuel is used for replacing a part of coal dust and is injected together with the coal dust through a coal dust injection pipe.

Further, the biomass fuels include, but are not limited to: agricultural wastes such as corn, rice and sorghum straws; woody organisms including trees (forestry waste); bagasse, oil dregs, husks, etc. (processing waste); ginkgo biloba (Ginkgo biloba, ginkgo biloba family, among all deciduous trees). The invention preferably selects sorghum straws and ginkgo leaves, and the mass ratio of the sorghum straws to the ginkgo leaves is as follows: 7:3, the heat replacement ratio is 75 percent, and the biomass fuel replaces 15 percent of coal powder.

Further, in order to increase the fixed carbon content of the biomass fuel, the biomass raw material is heated to different temperatures in stages at different heating rates under the condition of nitrogen, and then naturally cooled to room temperature, so that the specific surface area, the reactivity and the fixed carbon content of the biomass fuel are increased through the pretreatment process.

Furthermore, the pulverized coal injection pipe comprises an inlet pipe section with a smaller pipe diameter and a flared pipe section far away from the inlet pipe section, a flow dividing pipe which is distributed coaxially with the inlet pipe section is arranged in the flared pipe section, an inner air duct is formed between the flow dividing pipe and the combustor, an annular flow passage is formed between the flow dividing pipe and the flared pipe section, and spoilers with slightly different swirl angles are respectively arranged at the tail part of the inner air duct; an outer air channel is formed between the flared pipe section of the pulverized coal injection pipe and the inner wall of the nozzle brick into which the turbulent flow nozzle is inserted, and the outer air channel is communicated with the primary air inlet pipe and the oxygen enrichment pipe.

Furthermore, high-temperature reducing gas sprayed out by the turbulence nozzles firstly enters a side cavity of the combustion chamber, further reacts in the side cavity and realizes voltage-sharing and flow-equalizing under the action of a retaining wall, finally the reducing gas in the side cavities on two sides simultaneously enters a main cavity of the combustion chamber and passes through stacked material layers under the action of an exhaust fan to complete the high-temperature reduction process, high-temperature flue gas after the reaction of the high-temperature reduction section sequentially passes through a preheating section and a drying section through a flue gas circulation system to complete the preheating and drying of material blocks, finally dust is removed through dust removal equipment under the action of a fan, the dust is removed and then blown into a top combustion type hot blast stove together with air blown in by an air fan, and generated hot air enters the turbulence nozzles through a primary air inlet pipe.

Further, the combustion chamber is communicated with the storage bin through a sealing device.

Further, the sealing device is in communication with an electric arc furnace.

Furthermore, the regular hexagon grate with the circular through holes is placed on the grate of the trolley type roasting machine, and the size of the regular hexagon grate is sequentially reduced along the directions of the drying section, the preheating section and the high-temperature reduction section, so that the speed of high-temperature flue gas pumped down along the drying section, the preheating section and the high-temperature reduction section is gradually increased, and the pre-reaction of the material blocks of the drying section and the preheating section is more complete.

Further, in the step 3, the top combustion stove is communicated with the combustion chamber and the air fan.

Furthermore, one end of the dust removing device is communicated with the drying section of the trolley, and the other end of the dust removing device is communicated with the top combustion type hot blast stove through an exhaust fan.

Further, in the step 4, the first part of the initial reduction products are directly hot-charged and sent into an electric arc furnace to be melted and separated to be used as a raw material for electric furnace steelmaking, the second part of the initial reduction products is subjected to primary magnetic separation to obtain residues containing carbon residues, the residues are returned to the material mixing stage for recycling, the metalized materials obtained through the primary magnetic separation are crushed and screened, then secondary magnetic separation is carried out, the obtained tailings are returned to the material mixing stage for recycling, the obtained metalized materials are ground to enable the granularity of more than 90% to reach 200 meshes, the final product high-purity iron powder is obtained, and the obtained high-purity iron powder can be directly used for a converter.

The invention has the beneficial effects that:

1. the honeycomb-shaped flow guide material block for strengthening mass and heat transfer related to the method obviously improves the mass and heat transfer efficiency and the heat transfer uniformity of the inner part and the outer part of the material block by arranging a certain number of elliptical through holes and various flow grooves and simultaneously utilizing the three-field synergy theory, has larger specific surface area compared with the traditional porous block, and can arrange more through holes without worrying about unsmooth air path caused by too many arranged through holes. Meanwhile, the material blocks have the enhanced mass and heat transfer capacity, and can be piled to 800-1000 mm during material piling, so that the problem of small charge per unit volume of a single material block caused by more open pores is solved to a certain extent. Can realize large-scale efficient reduction.

2. The trolley type roasting reduction device provided by the method promotes the full progress of combustion reaction through the reasonable configuration of the combustion chamber structure and the nozzle structure, improves the combustion efficiency and the uniformity of the temperature and pressure of airflow on the surface of the material block, avoids the local over-burning and light burning phenomena of the material block, and greatly improves the quality of products.

3. The method of the invention is simple and easy to implement, simple in required equipment, small in investment, large in production scale, small in requirement on raw fuel, small in pollution, low in emission and easy to popularize.

Drawings

In order to more clearly illustrate the patented embodiments or prior art solutions of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below.

FIG. 1 is a schematic view of the main structure of the present invention.

FIG. 2 is a schematic view showing the arrangement of combustion chambers in the bogie hearth type roasting reduction apparatus.

FIG. 3 is a schematic view of the main structure of the combustion chamber.

FIG. 4 is a schematic view of a turbulent nozzle structure for a bogie type roasting reduction apparatus.

Fig. 5 is a top view of the honeycomb-shaped guide material block for enhancing mass and heat transfer proposed by the process of the present invention.

Fig. 6 is a cross-sectional view of the honeycomb-shaped guide material block for enhancing mass and heat transfer proposed by the process of the invention.

Fig. 7 is a schematic view of gas passages formed between blocks after stacking in a particular manner.

Fig. 8 is a schematic view of the main structure of the car-type roasting machine.

Description of reference numerals: in the figure: 1. a feeding bin; 2. a trolley; 3. a smoke hood; 4. a conveying device; 5. a combustion chamber; 6. a secondary air inlet pipe; 7. a trolley charge level sealing device; 8. a storage bin; 9. a bellows; 10. a dust removal device; 11. an exhaust fan; 12. an electric arc furnace; 13. an air blower; 14. a turbulent flow nozzle; 15. a secondary air inlet swirler; 16. retaining walls; 17. a burner; 18. a pulverized coal injection pipe; 19. a primary air inlet pipe; 20. an oxygen enrichment pipe; 21. an inner air duct; 22. a circulation channel; 23. a spoiler; 24. an outer air duct; 25. a material block body; 26. an elliptical through hole; 27. a semicircular groove; 28. a flow guide groove; 29. a sink groove; 30. a helical groove; 31 a nozzle brick; 32. a shunt tube; 33. a top-fired hot blast stove; 34. a grate.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

The invention provides a preparation of a honeycomb-shaped guide material block for strengthening mass transfer and heat transfer and a direct reduction iron-making process, which belong to the components of raw materials and devices for directly reducing iron ore powder.

The invention relates to a preparation and direct reduction iron-making process of a honeycomb-shaped guide material block for strengthening mass and heat transfer. Based on three field synergistic theories of a speed field, a temperature field and a concentration field, raw materials such as an iron-containing material, a carbonaceous reducing agent, a composite binder and the like are uniformly mixed, kneaded and pressed into a special honeycomb-shaped flow guide material block according to a certain weight ratio, the material block is provided with an elliptical through hole and a groove for gas flow guide and collection, the material block has a larger specific surface area compared with the traditional material block, a spiral groove engraved in the through hole can play a role in turbulence enhancement, and the generation of secondary flow in the through hole is promoted by a unique laying method so as to enhance heat transfer. The obtained material blocks are sent into the trolley type roasting reduction device disclosed by the invention after being dried to be used as a raw material for direct reduction iron making for smelting. According to the invention, the materials are molded into a special material block and a special reduction device is used for assisting, so that the reduction production efficiency, the iron-containing grade and the metallization rate of the final product are greatly improved, and the energy consumption and the emission are reduced. In addition, the method has the advantages of simple process, small equipment investment, short flow and small pollution, has the capacity of batch production, simultaneously considers the recycling of resources, accords with the strategic targets of carbon peak reaching and carbon neutralization advocated by the state, is a short-flow non-blast furnace iron making technology with a good application prospect, and has the potential of replacing the traditional long-flow blast furnace iron making process.

As shown in figure 1, the preparation and direct reduction iron-making process of the honeycomb-shaped guide material block for strengthening the mass transfer and heat transfer chemical reaction comprises the steps of material mixing, briquetting, drying, reduction and the like. Wherein:

the mixing steps of the materials are as follows: uniformly mixing iron-containing materials, carbonaceous reducing agents, composite binders, water and the like, wherein the corresponding mass ratio is 100: 15-20: 2 to 4:12 to 18. The mass of the iron-bearing material is calculated as the mass of total iron therein.

The compression molding step is as follows: the materials after being proportioned and mixed are put into a pre-designed mould, and are pressed and processed into a preset shape by a press, and the density of a material block is kept at 2.4g/cm ² ～2.8g/cm ² In the meantime. Therefore, the density of the powder after compression molding is increased, reducing gas generated in the material block in the reaction process is not easy to dissipate, and the thorough reduction reaction is facilitated.

The mixed materials are pressed into blocks, 21 oval through holes with long axes of 20-30 mm and short axes of 13-20 mm are formed in the obtained pressing blocks, the oval through holes are arranged along the axial direction of the material blocks and penetrate through the upper end face and the lower end face of the material blocks, four semicircular flow guide grooves for gas circulation and a circular convergence groove for gas alternating current convergence are formed in the two end faces, one end of each flow guide groove is located at the middle point of the side wall of the material block, and the other end of each flow guide groove converges in the convergence groove with the center of the end face of the material block as the circle center. The width of the flow guide groove is 20-30 mm and is consistent with the long axis of the oval through hole, the radius of the confluence groove is 10-25 mm, and the same depth of the flow guide groove and the confluence groove is 2-20 mm. The thickness of the material block is between 80mm and 100 mm. The shape of the block includes, but is not limited to, a cylinder, a cuboid, a cube, a regular polygon prism, and preferably a cuboid herein. In addition, a spiral groove is carved inside the oval through hole.

Compared with the prior raw material processing technology, the honeycomb-shaped flow guide material block for strengthening mass and heat transfer has the advantages that the material block has a large specific surface area by arranging the through holes on the material block, the contact area of reducing substances and materials is increased, the mass and heat transfer efficiency inside and outside the porous block is obviously improved, in addition, the confluence groove and the plurality of flow guide grooves are arranged on the end surface and are mutually communicated, the material exchange and the heat exchange rate of air flow at the end surface of the single material block are accelerated, and the pressure-equalizing and flow-equalizing effects of the whole material pile are improved. In addition, according to the theory of synergy of the convection heat transfer field, the effect of heat transfer enhancement can be achieved by improving the synergy of the velocity field, the temperature field and the concentration field in different degrees. If the through holes of the stacked blocks are regarded as a pipe type heat exchanger, the radial temperature gradient is much larger than the axial temperature gradient in the pipe in view of the fact that the fluid flow always occurs in the direction of the larger temperature gradient, i.e. the temperature gradient in the pipe is mainly concentrated in the radial direction. For laminar flow, the heat exchange can be significantly affected by small speed generated in the radial direction in the pipe, the laminar heat exchange in the pipe can be obviously enhanced by secondary flow generated by rotating or zooming, and for turbulent heat exchange in the pipe, the field enhancement is also applicable, but the temperature gradient is mainly generated in the radial direction near the wall surface, which is different from the laminar flow. Therefore, mass transfer and heat exchange can be enhanced to the maximum extent by simultaneously adopting wall surface protrusion turbulent flow enhancement, extended surface enhancement and field cooperative enhancement. The invention stacks the material blocks with different elliptical through hole apertures in a crossed manner and carves the spiral grooves in the through holes, and simultaneously generates rotating flow, radial flow and vortex flow in the pipes, so that the fluid is strongly mixed in the radial direction with larger temperature gradient, the temperature of the fluid in the main flow area is homogenized and the temperature gradient at the wall surface is increased, and the mass transfer and heat transfer enhancement in a larger degree is realized. And the axial sectional area change of the oval through holes in the cross arrangement is small, so that the flow resistance of the heat exchange plate is increased less than that of the traditional circular through holes while the heat exchange is enhanced. Meanwhile, the introduced flow guide groove offsets resistance increase caused by enhanced heat transfer to a certain extent.

The drying and reducing steps of the materials are as follows: the briquette is charged into a car-type roasting furnace provided by the present invention, the main body of which comprises a trolley having rails, a hood sealed on the trolley, and a combustion system disposed directly above the high-temperature reduction section. The material blocks are stacked on the trolley to 800-1000 mm and then move forwards along the track at a preset speed until the material blocks move to a high-temperature reduction section, a large amount of high-temperature flue gas sprayed into the combustion chamber by the turbulent flow nozzle carries reformed coke oven gas entering from the second air inlet together, the high-temperature flue gas and the reformed coke oven gas flow into the smoke hood and penetrate through the whole material layer under the action of the exhaust fan, the material blocks are reduced gradually along with the movement of the trolley, and the reduced material blocks are discharged from the tail part of the trolley and enter a storage bin with micro-positive pressure reducing atmosphere.

Furthermore, the whole hearth is divided into two relatively independent parts by using the smoke hood, so that the material block can be prevented from being directly heated at the first time, the reduction smoke after full reaction is controlled by a valve enters the reaction chamber filled with the material block from the combustion chamber, in the continuous reaction process, the heat energy of the combustion chamber is close to the balance of the heat energy of the reaction chamber, and the material block is provided with a through hole and a flow groove, so that the heating degrees of the material block at all positions are very close, and the temperature difference between the inside and the outside of the material block can be controlled within a reasonable range.

Furthermore, the retaining walls with opposite directions are respectively arranged in the side cavities at the two sides of the combustion chamber, so that the front impact of high-temperature reducing gas blown into the main cavity of the combustion chamber from the side cavities is avoided, and the phenomena of unsmooth discharge of flue gas of the combustion chamber, low combustion efficiency, local high-temperature and low-temperature areas formed in the smoke hood, local over-burning and light burning of blocks and the like which are possibly caused by the front impact are avoided.

Furthermore, the turbulator arranged in the turbulator nozzle can strengthen the mixing between gases and form a rotational flow, continuously entrainment is performed while the high-temperature reduction flue gas is sprayed, so that a small part of the reduction flue gas can flow back, the problems of fire release and tempering caused by the fact that the speed of the fuel gas spraying from the nozzle is not matched with the combustion speed of the fuel in the initial stage of reaction can be solved to a great extent, and the safety and the stability of the reaction process are improved.

As shown in FIG. 5, the shape of the honeycomb-shaped flow guide material block for enhancing mass and heat transfer proposed by the process of the present invention is preferably rectangular, 21 oval through holes 26 with a major axis of 20 mm-30 mm and a minor axis of 13 mm-20 mm are opened on a material block body 25, and the material block is divided into two types A and B according to the difference of the aperture of the opened through holes. Two semicircular grooves 27 are respectively formed in the positions of 1/4 and 3/4 of the four side surfaces of the material block body 25, and the diameters of the semicircular grooves 27 are selected to be consistent with the major axis of the oval through hole. When a plurality of material blocks are stacked in layers along the axial direction of the oval through hole 26, the semicircular grooves of the adjacent material blocks can be spliced into a complete circular airflow channel, so that the through hole rate and the mass and heat transfer efficiency of the whole material layer are further increased. Meanwhile, the material block is also provided with a flow guide groove 28 and a confluence groove 29, the width of the flow guide groove 28 is 20-30 mm and is consistent with the major axis of the oval through hole, the depth is 2-20 mm, and one end of the flow guide groove is converged at the midpoint of the side wall of the material block and the other end is converged in the confluence groove 29. The converging groove 29 is a circular groove with the center of the end face of the material block body 25 as the center and the radius of 20 mm-50 mm, and the depth of the circular groove is also 2 mm-20 mm.

Therefore, when the gas flows through the material block, the gas can flow in the channels for gas exchange and collection in a criss-cross mode, and the ventilation rate and the mass and heat transfer efficiency of the whole material layer are improved. Meanwhile, the heat exchange efficiency and the pressure-equalizing and flow-equalizing effects of the single material block are accelerated.

Specifically, as shown in fig. 7, in the stacking manner of the material layers, firstly, any one of the a-type material and the B-type material is laid on the bottommost layer, and then the material block of the other type is laid on the material block in a manner that the long axis direction of the oval through hole of the material block is parallel to the long axis of the through hole of the material block at the lower layer. The laying method can achieve the same effect as a zoom tube, so that the airflow generates radial flow perpendicular to the main flow direction when flowing through the channel formed by the two layers of blocks. And then, paving the material blocks with the same type and number as those of the second layer on the third layer, wherein the difference is that the material blocks of the third layer are paved in a way that the long axes of the through holes of the material blocks of the third layer are vertical to the long axes of the through holes of the material blocks of the second layer. The laying method has the same effect as a local flattening pipe and a cross elliptical pipe, so that airflow generates vortex secondary flow perpendicular to the main flow direction when flowing through a channel formed by the two layers of blocks. Finally, a different type of block from the third layer is laid on it with its long axes parallel, so that the gas also produces a radial flow as it flows through the channel formed by the two layers of blocks. The four layers of blocks are laid in a cycle until the height of the material layer reaches 800 mm-1000 mm.

Specifically, as shown in fig. 6, a spiral groove 30 is engraved on the inner surface of the oval through hole, and when the gas flows through the passage formed by the block through holes, a rotational flow perpendicular to the main flow direction is generated. The heat and mass transfer efficiency in the reaction process can be greatly enhanced by the method, so that the product quality is improved.

The drying and reducing step: the material block after the pressing forming is sent into a feeding bin 1 and then sent to a trolley 2 through the feeding bin 1, a smoke hood 3 is hermetically arranged on the trolley 2, and a combustion chamber 5 is arranged right above a high-temperature reduction section of the smoke hood 3. Install the barricade 16 towards different in the side chamber in the combustion chamber 5, barricade 16's effect reduces the atmospheric pressure in 5 side chamber exits of combustion chamber, is favorable to 5 main chambeies in the combustion chamber to react and fully goes on, has improved combustion efficiency, can optimize the air current trend in combustion chamber 5 and the petticoat pipe 3 simultaneously, improves the homogeneity of material piece surface air flow distribution and temperature, avoids the local phenomenon that produces light burning or overburning of material piece.

When the formal production is started, 70% of low-rank coal dust which is sieved and ground and passes through 200 meshes is sprayed from a coal dust injection pipe 18, high-temperature hot air output by a top combustion type hot blast stove is blown in from a primary air inlet pipe 19, and a small part of oxygen is blown in from an oxygen-enriched pipe 20 to support combustion according to the intensity of the combustion reaction. The generated coal gas is sprayed into the combustion chamber 5 by the turbulent burner 14 and is further mixed fully with the blast furnace gas sprayed by the secondary air inlet pipe 6, then the high-temperature flue gas is sprayed out from the outlet of the combustion chamber 5 and enters the smoke hood 3 with the material block, and passes through the tiled material layer under the action of negative pressure generated by the exhaust fan 11 at the bottom of the trolley 2, and the material block is reduced after the high-temperature flue gas passes through the tiled material layer. The trolley 2 filled with the material blocks advances along the center line of the roasting furnace at a certain speed and sequentially passes through the drying section, the preheating section and the reduction section until the whole process is completed.

Different from the symmetrical arrangement of the combustion chambers of the traditional roasting machine, the retaining walls 16 with different orientations are arranged in the side cavities of the combustion chambers 5 of the trolley-type roasting furnace, the front impact of high-temperature flue gas flow sprayed from the combustion chambers 5 and opposite air flow is avoided after the high-temperature flue gas flow leaves the nozzles of the combustion chambers 5, the air flow is fully developed, the back pressure at the outlets of the combustion chambers 5 is reduced, the full combustion reaction in the combustion chambers 5 is facilitated, and the combustion efficiency is improved. In addition, the high-temperature airflow sprayed out from the outlet of the combustion chamber 5 benefits from the arrangement of the retaining wall 16 to avoid the frontal impact in a narrow space, so that the airflow flow state is more reasonable, the high-temperature airflow can be uniformly filled in the whole smoke hood 3, the excessive burning and incomplete burning of the material block caused by the local high-temperature area and low-temperature area formed on the surface of the material layer are avoided, the overall reduction efficiency of the material layer is improved, and the product quality is improved.

As shown in fig. 2 to 4, a turbulent nozzle 14 is installed on a side wall of the chamber on the side of the combustion chamber 5. The turbulent flow nozzle 14 as a whole comprises a main body including a pulverized coal injection pipe 18, a burner 17, a nozzle brick 31, a primary air inlet pipe 19, an oxygen enrichment pipe 20 and a turbulence generator 23. Wherein the pulverized coal injection lance 18 is provided as an inlet section with a relatively small pipe diameter and as a flared section remote from said inlet section. In addition, the division pipe 32 which is distributed coaxially with the division pipe is arranged in the flared pipe section, at this time, an inner air duct 21 which can also be called an inner annular flow passage is formed between the division pipe 32 and the combustor 17, and an outer annular flow passage 22 which can also be called an outer annular flow passage is formed between the division pipe 32 and the flared pipe section. The vortex generators 23 with slightly different vortex angles are respectively arranged at the tail parts of the inner and outer annular flow channels. Meanwhile, an outer air duct 24 is formed between the flared section of the pulverized coal injection pipe 18 and the inner wall of the nozzle brick 31 into which the turbulent nozzle 14 is inserted, and the outer air duct 24 is communicated with the primary air inlet pipe 19 and the oxygen enrichment pipe 20.

After the reduction product comes out from the high-temperature reduction section, the reduction product is prevented from being oxidized secondarily under the protection of a trolley charge level sealing device 7, then the reduction product enters a storage bin 8 with a micro-positive pressure reduction atmosphere, one part of initial reduction furnace charge is directly hot-charged into an electric arc furnace to be melted and separated to be used as a raw material for electric furnace steelmaking, the other part of initial reduction furnace charge is subjected to magnetic separation twice and crushing and screening once, obtained impurities and tailings which mainly comprise carbon residue are returned to the feeding bin 1 for recycling, and the obtained high-purity iron powder can be directly used for converter steelmaking.

In the whole reduction process, high-temperature reduction flue gas after reacting with a high-temperature reduction section material layer sequentially enters a preheating section and a drying section through a flue gas circulating system to preheat and dry the material block at the position, then the flue gas is dusted through dust removal equipment 10 and is blown into a top combustion type hot air furnace together with air blown out by an air fan, and high-temperature hot air generated by the hot air furnace is blown into a turbulence nozzle through a primary air inlet pipe. The dust filtered by the dust removal device 10 is returned to the feed bin 1 as raw material for the briquettes. Therefore, the byproducts generated by the reaction are fully utilized, thereby achieving the purposes of saving energy, reducing cost and reducing emission.

As shown in fig. 8, the regular hexagonal grates with circular through holes are placed on the grate 34 of the car-type roasting furnace, and the sizes of the regular hexagonal grates are sequentially decreased along the directions of the drying section, the preheating section and the high-temperature reduction section, so that the speed of the high-temperature flue gas extracted along the drying section, the preheating section and the high-temperature reduction section is gradually increased, and the pre-reaction of the material blocks of the drying section and the preheating section is more complete.

Example 1

The process of example 1 comprises the following steps: mixing vanadium titano-magnetite, low-rank coal powder, bentonite, sodium carboxymethylcellulose and water according to a mass ratio of 100:15:3.5:0.5:15, mixing uniformly, wherein the mass of the vanadium titano-magnetite is calculated by total iron. The vanadium titano-magnetite contains 54% of total iron, and in order to ensure the agglomeration performance of the material, the particle size of the vanadium titano-magnetite is controlled to be 80% and sieved by a 200-mesh sieve, and the particle size of the low-rank coal powder is controlled to be 70% and sieved by a 100-mesh sieve. And then the mixture is put into a brick press to be pressed into a cuboid material block with the specification size of 200mm & ltx & gt 100mm, then a special mould is used for punching 21 oval through holes on the material block, the oval major axis of the A-shaped material block is 20mm, the minor axis of the A-shaped material block is 15mm, the width of the flow guide groove and the diameter of the semicircular groove are 20mm, the radius of the confluence groove is 15mm, and the depths of the flow guide groove and the confluence groove are 4mm. The elliptical long axis of the B-type material block is 15mm, the short axis of the B-type material block is 10mm, and the other parameters are consistent with those of the A-type material block. In the laying mode, the second layer in each group forms an included angle of 90 degrees with the long axis of the third layer of the material block. Loading the material blocks into a trolley type roasting furnace, wherein the thickness of the material layer is 800mm, reacting in the trolley type roasting furnace for 40min at the reduction temperature of 1200 ℃ to obtain metalized material blocks, and discharging the metalized material blocks by adopting nitrogen to protect the metalized material blocks and further cooling. After crushing, screening and magnetic separation, the metallization rate of the reduced metallized material block is detected to be 80%.

Example 2

The process of example 2 comprises the following steps: magnetite concentrate, low-rank coal powder, bentonite, carboxymethyl cellulose calcium and water are mixed according to a mass ratio of 100:13:2.5:1.0:13, uniformly mixing, wherein the mass of the magnetite concentrate is calculated by total iron, the total iron content in the magnetite concentrate is 60%, and in order to ensure the blocking performance of the materials, the granularity of the magnetite concentrate is controlled to be 70% and sieved by a 200-mesh sieve, and the granularity of the low-rank coal powder is controlled to be 70% and sieved by a 100-mesh sieve. And then the mixture is put into a brick press to be pressed into a cuboid material block with the specification size of 200mm 100mm, then a special mould is used for punching 21 oval through holes on the material feeding block, the oval major axis of the A-shaped material block is 20mm, the minor axis of the A-shaped material block is 15mm, the width of the flow guide groove and the diameter of the semicircular groove are 20mm, the radius of the confluence groove is 15mm, and the depth of the flow guide groove and the confluence groove is 4mm. The elliptical long axis of the B-type material block is 15mm, the short axis of the B-type material block is 10mm, and the other parameters are consistent with those of the A-type material block. In the laying mode, the second layer and the third layer of the material blocks in each group form an included angle of 60 degrees with the long axis of the material blocks. The material blocks are loaded into a trolley type roasting furnace, the thickness of the material layer is 900mm, the material blocks react in the trolley type roasting furnace for 60min at the reduction temperature of 1250 ℃ to obtain metalized material blocks, and the metalized material blocks are protected by nitrogen and further cooled when discharged. After crushing, screening and magnetic separation, the metallization rate of the reduced metalized material block is detected to be 84%.

Example 3

The process of example 3 comprises the following steps: limonite concentrate, low-rank coal powder, bentonite, polyvinyl alcohol resin and water are mixed according to the mass ratio of 100:12:2.0:1.5:12, uniformly mixing, wherein the total iron content in the limonite concentrate is 48% by mass of the limonite concentrate calculated as total iron, and in order to ensure the caking performance of the material, the granularity of the limonite concentrate is controlled to be 65% and sieved by a 200-mesh sieve, and the granularity of the low-rank coal powder is controlled to be 60% and sieved by a 100-mesh sieve. And then the mixture is put into a brick press to be pressed into a cuboid material block with the specification size of 200mm & ltx & gt 100mm, then a special mould is used for punching 21 oval through holes on the material block, the oval major axis of the A-shaped material block is 20mm, the minor axis of the A-shaped material block is 15mm, the width of the flow guide groove and the diameter of the semicircular groove are 20mm, the radius of the confluence groove is 15mm, and the depths of the flow guide groove and the confluence groove are 4mm. The elliptical long axis of the B-type material block is 15mm, the short axis of the B-type material block is 10mm, and the other parameters are consistent with those of the A-type material block. In the laying mode, the second layer and the long axis of the third layer of the material blocks in each group form an included angle of 45 degrees. The material blocks are loaded into a trolley type roasting furnace, the thickness of the material layer is 1000mm, the material blocks react in the trolley type roasting furnace for 70min at the reduction temperature of 1300 ℃ to obtain metalized material blocks, and the metalized material blocks are protected by nitrogen and further cooled when discharged. After crushing, screening and magnetic separation, the metallization rate of the reduced metalized material block is detected to be 72%.

While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A direct reduction iron making method for strengthening mass and heat transfer is characterized by comprising the following steps:

step 2, fully kneading and briquetting the mixed material to obtain a honeycomb-shaped guide material block, wherein a plurality of oval through holes are formed in the honeycomb-shaped guide material block, the oval through holes penetrate through the front end face and the back end face of the honeycomb-shaped guide material block, and a plurality of semicircular guide grooves for gas guide and circular convergence grooves for gas flow exchange and convergence are formed in at least one end face of the honeycomb-shaped guide material block;

2. The direct reduction iron making method according to claim 1, wherein the honeycomb-shaped guide blocks comprise large-aperture-size blocks and small-aperture-size blocks according to the size of the elliptical through holes.

3. The direct reduction iron making method according to claim 2, wherein the laying manner of the large-aperture sized briquettes and the small-aperture sized briquettes in the distribution is as follows:

a second layer: paving the material blocks of another type on the material blocks in a manner that the long axis direction of the oval through holes of the material blocks is parallel to the long axis of the through holes of the material blocks on the lower layer;

and a third layer: paving material blocks with the same aperture size as the second layer on the third layer, and paving the material blocks of the third layer in a mode that the long axes of the through holes of the material blocks of the third layer are vertical to the long axes of the through holes of the material blocks of the second layer;

the four layers of blocks are paved in a cycle until the height of the material layer reaches 800mm to 1000mm.

4. The direct reduction iron making method according to claim 1, wherein the honeycomb-shaped guide material block has 4 semicircular guide grooves, one end of each of the 4 semicircular guide grooves penetrates through the middle point of the side wall of the material block, and the other end of each of the 4 semicircular guide grooves converges into a circular convergence groove centered on the center of the end face of the material block.

5. The direct reduction iron-making method according to claim 4, wherein the semicircular diversion grooves are formed on both front and back end surfaces of the honeycomb-shaped diversion material block, and the semicircular diversion grooves and the circular confluence grooves have the same depth.

6. The direct reduction ironmaking process according to claim 1, wherein each sidewall of the cellular deflector block is provided with a plurality of semicircular fixing grooves penetrating through upper and lower end surfaces to achieve the purposes of stabilizing the material layer and facilitating the laying.

7. The direct reduction ironmaking process according to claim 1, characterized in that step 3 specifically comprises: and paving the honeycomb-shaped guide material blocks on a trolley, sending the honeycomb-shaped guide material blocks into a trolley type roasting reduction device, starting to slowly heat the material blocks in a drying section and a preheating section in the roasting furnace under the action of high-temperature smoke generated after the material blocks are reacted in the high-temperature reduction section, carrying out high-temperature reduction roasting on the dried and preheated material blocks in the high-temperature reduction section, and discharging to obtain initial reduction furnace burden.

8. A direct reduction iron making method according to claim 7, wherein in said step 3, said car type roasting reduction apparatus comprises: car-type roasting machine, top-burning hot-blast stove, electric arc furnace and dust collecting equipment.

9. The direct reduction ironmaking process according to claim 1, characterized in that step 4 specifically comprises:

the first part of initial reduction products are directly hot-charged and sent into an electric arc furnace to be melted and separated to be used as raw materials for electric furnace steel making, the second part of the initial reduction products are subjected to primary magnetic separation to obtain residues containing carbon residues, the residues are returned to the material mixing stage to be recycled, the metalized materials obtained through the primary magnetic separation are crushed, screened and subjected to secondary magnetic separation, the obtained tailings are returned to the material mixing stage to be recycled, the obtained metalized materials are ground to enable the granularity of more than 90 percent to reach 200 meshes, the final product high-purity iron powder is obtained, and the obtained high-purity iron powder can be directly used in a converter.