A method for producing super-high basicity sinter for improving slagging, dephosphorization and reducing splashing in a converter

Abstract

The present application belongs to the technical field of sinter production, and particularly relates to a production method of ultra-high basicity sinter for improving converter slagging, dephosphorization and reducing in-furnace spattering, which comprises the following steps: mixing 65% limonite powder, 20% magnetite powder and 15% blast furnace return fines, proportionally mixing 64% sintered mixture, 30% flux, 6% coke powder and 10% sintered internal return to prepare sintered mixed material, mixing and granulating under mist water according to a ratio of 7:3, and sintering under the condition that the thickness of the material layer is controlled to be 850 mm. The composition of the obtained ultra-high basicity sinter is as follows: CaO: 20% to 25%; SiO2: 5.5% to 6.6%; TFe: greater than or equal to 45%; basicity: 3.2 to 3.5; and drum strength: greater than or equal to 68. The micro-phase composition of the ultra-high basicity sinter is as follows: calcium ferrite: greater than or equal to 35%; dicalcium ferrite: 15% to 20%; dicalcium silicate: 10% to 20%; and iron oxide: less than or equal to 25%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sinter production, and particularly relates to a production method of ultra-high-alkalinity sinter for improving converter slagging, dephosphorization and reducing in-furnace spitting. BACKGROUND

[0002] As an important burden structure for blast furnace smelting, the sinter has an alkalinity generally controlled at 1.70-2.10, TFe greater than or equal to 54%, and mainly includes iron oxide, a small amount of calcium ferrite, glass phase and the like. During the blast furnace smelting process, most of the gangue phase and harmful elements in the sinter can be removed, but the dephosphorization effect is poor during normal smelting, and a high phosphorus content in the molten iron increases the dephosphorization load of the converter steelmaking, resulting in an increased cost.

[0003] During the converter smelting process, part of the active lime lump is usually added as a dephosphorization agent, and part of the blast furnace return ore is added as a slagging agent. A high proportion of return ore addition is easy to form spitting in the converter.

[0004] The dephosphorization step of the converter smelting process mainly includes: (1) the phosphorus in the molten metal reacts with FeO in the liquid slag to generate P2O5, (2) P2O5 reacts with CaO in the liquid slag to generate 3CaO·P2O5, and (3) 3CaO·P2O5 in the slag combines with 2CaO·SiO2 in the slag to generate 2CaO·SiO2-3CaO·P2O5 solid phase. The first step is to remove the phosphorus in the molten steel, and the last two steps are to solidify the removed phosphorus in the slag. In the early stage of the converter smelting, due to the low temperature of the molten pool, it is the rapid dephosphorization period, and by adding low-melting-point substances to reduce the melting point of the slag, liquid slag is quickly formed, and the slag has a high content of calcium oxide and dicalcium silicate phase, which is most beneficial to dephosphorization. The calcium ferrite substance with a melting temperature of 1250℃ has a good slagging effect, the calcium ferrite has a good dephosphorization effect, the dicalcium silicate has a good phosphorus solidification effect, and the substance with a small amount of iron oxide content can reduce the occurrence of spitting during the converter smelting.

[0005] As an important flux for sinter production, lime has a high CaO content, and the generated Ca(OH)2 colloid has a large specific surface area after digestion, which is beneficial to the mixing and granulation of sinter and helps to improve the yield and quality of sinter production. The proportion of flux for ultra-high-alkalinity sinter production is large, and the proportion of lime and limestone powder is very important for the stability of the ultra-high-alkalinity sinter production process and the stability of the production quality.

[0006] Studies have shown that when the sinter alkalinity exceeds 2.8, the glass phase content of the sinter increases significantly, which has a great impact on the drum strength of the sinter, the sinter return rate increases, the final temperature decreases, the negative pressure increases, the waste gas temperature decreases, and the composition of the sinter fluctuates greatly, which affects the stable production of ultra-high-alkalinity sinter. SUMMARY

[0007] In order to solve the above technical problems, the present application aims to provide a production method of super-high basicity sinter, more particularly, a production method of super-high basicity sinter for improving converter slagging, dephosphorization and reducing in-furnace spitting.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0009] A production method of super-high basicity sinter for improving converter slagging, dephosphorization and reducing in-furnace spitting, comprising the following steps:

[0010] (1) batching: preparing sintering mixture by mixing the proportion of 65% limonite powder, 20% magnetite powder and 15% blast furnace return ore in the mixing yard; preparing sintering mixed material by batching the sintering mixture, flux, coke powder and sintering internal return according to a certain proportion, wherein the proportion of sintering mixture in the sintering mixed material is 64%, the proportion of coke powder is 6%, the proportion of flux is 30%, and the proportion of sintering internal return is 10%; wherein the proportion of quicklime in the flux is 1% to 5%, and the proportion of limestone is 25% to 29%; preferably, the proportion of quicklime in the flux is 5%, and the proportion of limestone is 25%;

[0011] (2) mixing and granulating: transporting the sintering mixed material in step (1) to a one-two mixing drum mixer by a belt conveyor for mixing and granulating, the mixing and granulating time is 10 minutes, the mixed material is wetted by mist water, the moisture content of the mixed material is 7.0%, and the water addition amount of one mixing is 7:3 of that of two mixing;

[0012] (3) distributing: the sintering mixed material after mixing and granulating is transported to a shuttle distributor by a belt conveyor and is uniformly added to a sintering mixed material chute, the sintering mixed material is uniformly distributed to a sintering machine trolley by a circular roller distributor and a nine-roller distributor, and the overall layer thickness is 850 mm;

[0013] (4) igniting: the sintering mixed material in step (3) is distributed to the sintering machine table surface for ignition and sintering, in order to avoid the problem of the decrease of the overall layer permeability caused by the over-melting and solidification of the surface sinter layer after the high proportion of flux is added, the ignition temperature is controlled at 950℃, the ignition negative pressure is 7 to 9 kPa, and the ignition time is 2 minutes;

[0014] (5) sintering: after the ignition is completed, air is drawn for sintering, the sintering machine speed is adjusted, the sintering air bellow temperature reaches the highest temperature, and the position where the highest temperature appears is the second last air bellow, and the sintering process is ended;

[0015] (6) crushing: the sintered cake obtained by the above sintering is crushed by a single-roller crusher;

[0016] (7) Screening: the crushed sinter is transported to the screening system by a belt conveyor for size screening, and sinter with a particle size greater than 5mm is obtained as a finished sinter, and sinter with a particle size less than 5mm is obtained as a sinter internal return ore and is matched into the sinter mixing material circulation for matching.

[0017] The sinter mixing material TFe: 50%~52%, SiO2: 6.0%~6.8%, CaO: 20%~25%, MgO: 1.2%~1.6%, Al2O3: 1.8%~2.2%, basicity: 3.20~3.50.

[0018] The sinter process parameter control standard: end point temperature ≥ 420℃, negative pressure -13.5~-15.5kPa, waste gas temperature 135~150℃, sinter internal return rate 10~14%, end point position controlled at the second last air bellow.

[0019] The sinter control standard, basicity: 3.2~3.5; CaO: 20%~25%; SiO2: 5.5%~6.6%; TFe ≥ 45%, drum strength ≥ 68.

[0020] The total proportion of calcium ferrite system phases in the sinter micro phase composition is ≥ 35%, the overall micro phase is more calcium ferrite system, containing 15%~20% dicalcium ferrite, 10%~20% dicalcium silicate, ≤ 25% iron oxide, a small amount of unmelted lime, and a higher content of calcium ferrite system is conducive to converter slagging, a certain amount of dicalcium ferrite and dicalcium silicate is conducive to dephosphorization, and a small amount of iron oxide is conducive to reducing in-furnace spattering.

[0021] The beneficial effects of the present application are:

[0022] The present application provides a production method of an ultra-high basicity sinter capable of improving converter slagging and dephosphorization capacity, the main components, micro phase structure and sinter process parameters of the sinter all meet the control standard requirements; the sinter process parameters are: end point temperature ≥ 420℃, negative pressure -13.5~-15.5kPa, waste gas temperature 135~150℃, sinter internal return rate 10~14%, end point position controlled at the second last air bellow, and drum strength ≥ 68. The main process control points required for stable production of conventional basicity sinter, such as end point position, end point temperature, waste gas temperature, negative pressure and internal return rate, can be realized at the same level. The ultra-high basicity sinter provided by the present application can provide high-quality sinter raw material for fast slagging, effective dephosphorization and spattering reduction in converter steelmaking; can make up for poor dephosphorization effect in the ironmaking process, promote the digestion of high-phosphorus hot metal in steelmaking, and reduce the cost of dephosphorization; at the same time, such raw fuel and important process index control standard can greatly improve the stability of the sintering process with a basicity greater than 3.0, and provide effective support for stable production of ultra-high basicity sinter with a basicity greater than 3.0. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described in detail below. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of the present application.

[0024] Embodiment 1

[0025] 1. A sintering mixture is prepared by mixing the raw materials in a proportion of 65% limonite powder, 20% magnetite powder and 15% blast furnace return fines in a mixing yard; the sintering mixture is mixed with flux, coke powder and sintering internal return fines in a certain proportion to prepare sintering mixed material, wherein the proportion of the sintering mixture in the sintering mixed material is 64%, the proportion of coke powder is 6%, the proportion of quicklime in the flux is 1%, the proportion of limestone is 29% and the proportion of sintering internal return fines is 10%;

[0026] 2. The sintering mixed material is transported by a belt conveyor to a 1-2 mixing cylinder mixer for mixing and granulating, the mixing and granulating time is 10 minutes, the mixed material is wetted by mist water, the moisture content of the mixed material is 7.0%, and the water addition amount of the 1st mixing is 7:3 of that of the 2nd mixing;

[0027] 3. The sintering mixed material after mixing and granulating is transported by a belt conveyor to a shuttle feeder and uniformly fed into a sintering mixed material tank, and then uniformly distributed on the sintering machine trolley by a circular roller feeder and a nine-roller feeder, and the total layer thickness is 850 mm;

[0028] 4. The sintering mixed material is ignited and sintered on the sintering machine trolley, in order to avoid the problem of decreased permeability of the overall layer due to over-melting and solidification of the surface layer of the sinter after adding a high proportion of flux, the ignition temperature is controlled at 950℃, the ignition negative pressure is 7-9 kPa, and the ignition time is 2 minutes;

[0029] 5. After ignition, the sintering is carried out by air draft, the sintering machine speed is adjusted so that the sintering air bellow temperature reaches the highest temperature, and the highest temperature appears at the second last air bellow, and the sintering process is ended;

[0030] 6. The sintered cake obtained by the above sintering is crushed by a single-roller crusher;

[0031] 7. Screening: the crushed sinter is transported by a belt conveyor to a screening system for granulation and screening, and the sinter with a particle size greater than 5 mm is obtained as finished sinter, and the sinter with a particle size less than 5 mm is used as sintering internal return fines and is added into the sintering mixed material for circulation and use;

[0032] 8. The finished sinter with a particle size greater than 5 mm is sampled and tested for sinter composition and drum strength, and the proportion of calcium ferrite in the microstructure, and the results are shown in Table 1.

[0033] Embodiment 2

[0034] 1. Sintering mixture is prepared by mixing raw materials in a proportion of 65% limonite powder, 20% magnetite powder, and 15% blast furnace return fines in a mixing yard; the sintering mixture is mixed with flux, coke powder, and sintering return fines in a certain proportion to prepare sintering mixed material, wherein the proportion of sintering mixture in the sintering mixed material is 64%, the proportion of coke powder is 6%, the proportion of quicklime in the flux is 3%, the proportion of limestone is 27%, and the proportion of sintering return fines is 10%;

[0035] 2. The sintering mixed material is transported by a belt conveyor to a first-second mixing cylinder mixer for mixing and granulating, the mixing and granulating time is 10 minutes, the mixed material is wetted by mist water, the moisture content of the mixed material is 7.0%, and the water addition amount of the first mixing is 7:3 of the water addition amount of the second mixing;

[0036] 3. The sintering mixed material after mixing and granulating is transported by a belt conveyor to a shuttle feeder and uniformly added to a sintering mixed material tank, the sintering mixed material is uniformly distributed on a sintering machine trolley by a circular roller feeder and a nine-roller feeder, and the total material layer thickness is 850 mm;

[0037] 4. The sintering mixed material is ignited and sintered after being distributed on the sintering machine table, in order to avoid the problem of decreased permeability of the overall material layer caused by over-melting and solidification of the surface layer of sinter after adding a high proportion of flux, the ignition temperature is controlled at 950°C, the ignition negative pressure is 7-9 kPa, and the ignition time is 2 minutes;

[0038] 5. After ignition, the sintering is carried out by air draft, the sintering machine speed is adjusted so that the sintering air bellow temperature reaches the highest temperature, and the highest temperature appears at the second last air bellow, and the sintering process is completed;

[0039] 6. The sintered cake obtained by the above sintering is crushed by a single-roller crusher;

[0040] 7. Screening: the crushed sinter is transported by a belt conveyor to a screening system for granulation and screening, the sinter with a particle size greater than 5 mm is obtained as finished sinter, and the sinter with a particle size less than 5 mm is used as sintering return fines and is added to the sintering mixed material for circulation and use;

[0041] 8. The finished sinter with a particle size greater than 5 mm is sampled and tested for sinter composition and drum strength, and the proportion of calcium ferrite in the microstructure, and the results are shown in Table 1.

[0042] Example 3

[0043] 1. Sintering mixture is prepared by mixing raw materials in a proportion of 65% limonite powder, 20% magnetite powder, and 15% blast furnace return fines in a mixing yard; the sintering mixture is mixed with flux, coke powder, and sintering return fines in a certain proportion to prepare sintering mixed material, wherein the proportion of sintering mixture in the sintering mixed material is 64%, the proportion of coke powder is 6%, the proportion of quicklime in the flux is 5%, the proportion of limestone is 25%, and the proportion of sintering return fines is 10%;

[0044] 2. The sintered mixed material is transported by a belt conveyor to a first mixing cylinder for mixing and granulation, the mixing and granulation time is 10 minutes, the mixed material is wetted by mist water, the moisture content of the mixed material is 7.0%, the water addition amount of the first mixing is 7:3 of the second mixing;

[0045] 3. The mixed and granulated sintered mixed material is transported by a belt conveyor to a shuttle feeder and uniformly added to a sintering mixed material tank, the sintered mixed material is uniformly distributed on the sintering machine trolley by a circular roller feeder and a nine-roller feeder, and the total material layer thickness is 850mm;

[0046] 4. The sintered mixed material is ignited and sintered, in order to avoid the problem of over-melting and solidification of the surface layer of the sintered ore layer after adding a high proportion of flux, the ignition temperature is controlled at 950°C, the ignition negative pressure is 7-9kPa, and the ignition time is 2min;

[0047] 5. After ignition, the sintering is carried out by air draft, the sintering machine speed is adjusted to make the sintering air bellow temperature reach the highest temperature, and the highest temperature appears at the second last air bellow, and the sintering process is completed;

[0048] 6. The sintered cake obtained by the above sintering is crushed by a single-roller crusher;

[0049] 7. Screening: the crushed sintered ore is transported by a belt conveyor to a screening system for granulation and screening, the product sintered ore with a particle size greater than 5mm is obtained as a finished product, and the sintered ore with a particle size less than 5mm is used as a sintered internal return ore and is added to the sintered mixed material for circulation and use;

[0050] 8. The finished product sintered ore with a particle size greater than 5mm is sampled and tested for sintered ore composition and drum strength, and the calcium ferrite system proportion of the microstructure, the results are shown in Table 1.

[0051] Table 1. Main components and microstructure of the finished product sintered ore of Examples 1-3

[0052]

[0053] Table 2. Actual parameters of the sintering process of Examples 1-3

[0054]

Claims

1. A method for producing ultra-high basicity sinter for improving slag formation in a converter, dephosphorization and reducing in-furnace spitting, characterized in that: (1) batching: a sintering mixture is prepared by mixing a brown iron ore powder, a magnetite powder and a blast furnace return ore in a proportion of 65%, 20% and 15% respectively on a mixing yard; the sintering mixture is mixed with fluxes and coke powder, and 10% of sintering return ore by weight is added to prepare a sintering mixed material; the sintering mixed material contains 64% of the sintering mixture, 6% of coke powder and 30% of fluxes; the fluxes contain 1%-5% of quicklime and 25%-29% of limestone; (2) mixing and granulating: the sintering mixed material is transported to a first and second mixing drum mixer by a belt conveyor for mixing and granulating, the mixing and granulating time is 10 minutes, the mixed material is wetted by mist water, the moisture content of the mixed material is 7.0%, and the water addition amount of the first and second mixing is 7:3; (3) distributing: the overall layer thickness is 850 mm; (4) ignition: ignition sintering is performed on a sintering machine, the ignition temperature is controlled at 950℃, the ignition negative pressure is 7-9 kPa, and the ignition time is 2 minutes; (5) sintering: air draft sintering is performed, the sintering machine speed is adjusted to make the sintering air box temperature reach the maximum temperature, and the maximum temperature appears at the second last air box, the sintering process is completed, and a sinter cake is obtained; (6) crushing and screening: the sinter cake obtained by sintering is crushed by a crusher; the crushed sinter is conveyed to a screening system by a belt conveyor for granulating and screening, and the product sinter with a particle size greater than 5 mm is obtained, and the sinter with a particle size less than 5 mm is used as sintering return ore and is added to the sintering mixed material for circulation. The sintering mixed material contains TFe: 50%-52%, SiO2: 6.0%-6.8%, CaO: 20%-25%, MgO: 1.2%-1.6%, Al2O3: 1.8%-2.2%, and basicity: 3.20-3.

50. The sintering stable production process parameters are as follows: final temperature ≥420℃, waste gas temperature: 135-150℃, sintering negative pressure: 13.5-15.5 kPa, sintering return rate: 10-14%, and sintering end position at the second last air box. The control standards of the ultra-high basicity sinter for improving slag formation in a converter, dephosphorization and reducing in-furnace spitting are as follows: CaO: 20%-25%, SiO2: 5.5%-6.6%, TFe ≥45%, basicity: 3.2-3.5, and drum strength ≥68. The micro phase composition of the ultra-high basicity sinter for improving slag formation in a converter, dephosphorization and reducing in-furnace spitting is as follows: calcium ferrite system ≥35%, dicalcium ferrite 15-20%, dicalcium silicate 10-20%, and iron oxide ≤25%. ​ ​ ​ ​ ​ ​ 2. The process for producing ultra-high basicity sinter according to claim 1, wherein: ​ 3. The process for producing ultra-high basicity sinter according to claim 1, wherein: ​ 4. The process for producing ultra-high basicity sinter according to claim 1, wherein: ​ 5. The process for producing ultra-high basicity sinter according to claim 1, wherein: ​

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