A dry process for the whole process of steel slag treatment and system

Abstract

The present invention discloses a dry process for the whole process of steel slag treatment, belonging to the technical field of steel slag treatment. It includes: S1. Roller pressing process, where the liquid steel slag is roller pressed and crushed, and during this process, it is cooled by air cooling to solidify the liquid steel slag; S2. Cooling process, where the steel slag obtained in step S1 is cooled to below 100 °C by a non-air cooling method; S3. Grinding process; S4. Sorting process; S5. Waste heat recovery process, where the heat released by the steel slag in the roller pressing process and the cooling process is recovered and utilized. The present invention also discloses a dry treatment system for the whole process of steel slag. Through reasonable design, the present invention enables the roller pressing process and the cooling process to form a gradient cooling, and at the same time recovers the heat released by the steel slag in these two processes, solving the problem of low waste heat recovery rate in steel slag treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of steel slag treatment, and particularly relates to a dry treatment process and system for the whole process of steel slag. Technical Background

[0002] Steel slag is a waste generated in steelmaking production. In order to reduce the environmental pollution in steel mills, it is necessary to treat it and ensure that the steel slag treatment meets the principles of "less input, fast output, maximum benefit, and increased steel recycling rate". Steel slag includes carbon steel slag, stainless steel slag, etc. Compared with the treatment process of carbon steel slag, the treatment process of stainless steel slag has the following characteristics: ① High calcium oxide content, volume expansion after absorbing water, resulting in pulverization; polymorphic transformation of dicalcium silicate occurs at about 600 °C, volume expansion causes pulverization, and dust is difficult to control; ② Powder materials are prone to agglomeration when encountering water, affecting the magnetic separation and dust removal effects; ③ 300-series slag has no magnetism, and conventional magnetic separation methods cannot select steel blocks in it in time, resulting in hard steel blocks (alloys) being prone to damaging crushing equipment.

[0003] The treatment process of stainless steel slag generally adopts the wet process. The wet process has a large water consumption, sewage flowing everywhere on site, and muddy tail slag yards, seriously not meeting the requirements of clean production. Therefore, the wet process will be gradually phased out, and the dry process will become the mainstream process for stainless steel slag treatment.

[0004] Chinese Patent CN114939591B discloses a dry separation process for stainless steel slag, which consists of four process sections: stainless steel molten slag casting slag jaw crushing, electric furnace slag ball milling separation, AOD slag dry rapid cooling ball milling separation, and AOD slag dry balanced cooling slow cooling pulverization separation. The products of electric furnace slag ball milling separation are lump steel, granular steel, steel fine powder, and electric furnace slag fine powder. The products of AOD slag dry rapid cooling ball milling separation are lump steel, granular steel, steel fine powder, and β-C2S phase fine slag powder. The products of AOD slag dry balanced cooling pulverization separation are lump steel, granular steel, steel fine powder, and γ-C2S phase fine slag powder. The lump steel and granular steel are returned to the steelmaking process for recycling, the steel fine powder is used as a sintering raw material, and the electric furnace slag fine powder, γ-C2S phase fine slag powder, and β-C2S phase fine slag powder are used as auxiliary materials for cement production. Although this patent adopts a dry separation process, it does not recover and utilize the waste heat generated during the treatment process. On the one hand, it causes a large amount of resource waste and does not meet the principle of maximum benefit. On the other hand, the existence of waste heat increases the load of the treatment system and the maintenance cost of the equipment.

[0005] Chinese Patent CN115522001A discloses a dry treatment method for stainless steel slag. The specific operation steps of this method are as follows: Step 1: Hot crushing. The molten stainless steel slag is condensed into a flat plate by a flat plate casting machine, and then the stainless steel refining slag is broken into pieces by a single-roll crusher. Step 2: The pieces obtained in Step 1 are added to a dry cooler, where a phase change occurs, and at the same time, hot air at a temperature higher than 300 °C is generated at a rate of 3000 m 3 / ton, and the waste heat is used for drying, steam generation or power generation. Step 3: Dry crushing. The steel slag obtained in Step 2 is crushed by a rod mill, and then fed into a roller press by a hoist to be extruded into a cake. After the crushed steel slag passes through a blower, the metal that cannot be crushed is separated from the steel slag by gravity, realizing the recovery of the metal in the stainless steel slag, and at the same time obtaining the first steel slag powder. Step 4: The steel slag ultrafine powder extrusion and combined grinding system includes a roller press and an ultrafine ball mill. The roller press forms a closed circuit with an air classifier, and the ball mill is in an open circuit. The first steel slag powder is fed into a constant flow weighing bin by a belt conveyor and an automatic iron remover through a hoist. The material in the bin is extruded into a cake by the roller press and then fed into the air classifier by the hoist for sorting. The coarse powder separated is returned to the roller press for re-extrusion, and the fine powder separated is fed into the ball mill for grinding. The material discharged from the mill obtains the second steel slag powder. Although this patent includes waste heat recovery and utilization, it only recovers the heat generated by the dry cooler and does not recover the heat in the hot crushing step. Therefore, the waste heat recovery rate is still relatively low. Summary of the Invention

[0006] In view of the above problems, the present invention provides a dry treatment process for the whole process of steel slag. Through reasonable design, a gradient temperature drop is formed between the rolling process and the cooling process, and at the same time, the heat released by the steel slag in these two processes is recovered, solving the problem of low waste heat recovery rate in steel slag treatment.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A dry treatment process for the whole process of steel slag includes:

[0009] S1. Rolling process. The liquid steel slag is rolled and crushed, and during this process, air cooling is used to cool down the liquid steel slag to make it solidify.

[0010] S2. Cooling process. The steel slag obtained in Step S1 is cooled to below 100 °C by a non-air-cooling method; this non-air-cooling method is also a non-wet cooling method.

[0011] S3. Grinding process;

[0012] S4. Sorting process;

[0013] S5. Waste heat recovery process. The heat released by the steel slag in the rolling process and the cooling process is recovered and processed for steam generation.

[0014] Compared with the wet treatment process, there is a problem that the pulverization of steel slag leads to difficult heat recovery, resulting in a large amount of waste of waste heat resources. The full-process dry process of the present invention adopts gradient cooling. Among them, the temperature of the roll pressing process is high, and the air cooling method is used for cooling, with high heat exchange efficiency; the cooling process adopts a non-air cooling method for cooling, avoiding the influence of steel slag pulverization on the air cooling method, and at the same time avoiding the risk of metal oxidation. Therefore, during the entire heat recovery process, the influence of steel slag pulverization is very small, realizing the recovery of the heat generated during the steel slag treatment and reducing resource waste; on the other hand, discharging the heat from the equipment in the roll pressing process and the cooling process in a timely manner can greatly reduce the load of the equipment and ensure that the cooling can proceed smoothly.

[0015] Preferably, in step S1, the cooling medium of the air cooling method is the tail gas discharged from the waste heat recovery process. By blowing the tail gas discharged after the waste heat recovery and utilization back into the roll pressing process for recycling, on the one hand, the tail gas discharged after the waste heat recovery treatment is recycled, improving the resource recovery utilization rate, and at the same time, it can also reduce the load of the waste heat recovery system; on the other hand, since this cooling medium has reacted with the steel slag and has the characteristic of reduced oxygen content, using it as the cooling medium reduces the possibility of the steel slag being oxidized, thereby improving the recovery rate of metallic iron.

[0016] Preferably, the temperature of the tail gas is 130 - 180 °C.

[0017] Preferably, the controlled wind speed of the cooling medium is 5 - 30 m / s.

[0018] Preferably, the controlled wind speed of the cooling medium is 10 - 20 m / s.

[0019] Preferably, in step S1, the temperature of the steel slag after roll pressing is 800 - 1000 °C.

[0020] Preferably, in step S1, the roll pressing time is 5 - 30 min.

[0021] The speed of the wind and the temperature of the steel slag after roll pressing have certain effects on the roll pressing time, the particle size of the steel slag after roll pressing and crushing, the final metal recovery rate, the waste heat recovery rate, and even the output of the entire steel slag treatment. The present invention selects an appropriate wind speed and controls the temperature of the steel slag after roll pressing within a reasonable range, which can obtain a high metal recovery rate and waste heat recovery rate, and keep the output of the steel slag treatment at a high level.

[0022] Preferably, in step S1, the temperature of the liquid steel slag before roll pressing and crushing is 1300 - 1600 °C.

[0023] Preferably, in step S1, the particle size of the rolled steel slag is less than 50 mm. Since the film cooler has a higher waste heat recovery efficiency, transferring the steel slag with a sufficiently high temperature into the film cooler as soon as possible can obtain a higher waste heat recovery rate; and controlling the particle size of the rolled steel slag to be less than 50 mm is beneficial to the smooth progress of subsequent processes.

[0024] Preferably, in step S2, the cooling equipment with non-air-cooling method is a film cooler. When the processing amount of steel slag is relatively large, a two-stage film cooler can be used for cooling to improve the cooling efficiency. There are cooling water pipes inside the film cooler, which can quickly cool the steel slag. At the same time, the cooling water in the cooling water pipes is heated and can directly generate high-temperature and high-pressure water.

[0025] Preferably, in step S2, the cooling rate is 10 - 25 °C / min.

[0026] Preferably, in step S5, the waste heat recovery process uses a waste heat boiler to recover heat, and the heat recovered by the waste heat boiler is used to generate steam.

[0027] Preferably, it further includes a flash evaporation process to flash the high-temperature and high-pressure water generated by the film cooler to obtain saturated steam, and send the saturated steam into the waste heat boiler. Sending the saturated steam into the waste heat boiler can increase the temperature and pressure of the steam generated by the waste heat boiler, and further improve the waste heat recovery rate.

[0028] Preferably, the grinding process includes rod mill treatment and ball mill treatment. The purpose of rod mill treatment is rough grinding and fine crushing. Since the energy consumption of ball mill is relatively high and multi-breaking and less grinding is more energy-saving, combining rod mill treatment and ball mill treatment can improve the grinding efficiency and reduce the energy consumption at the same time.

[0029] Preferably, the sorting process includes magnetic separation treatment and air separation treatment. According to the chemical composition and physical properties of steel slag, in steel slag, the 300 series generally does not show magnetism; while the 200 series and 400 series show magnetism; therefore, the sorting of steel adopts a combination of magnetic separation and air separation as needed. Through such a treatment method, the useful components in steel slag can be recovered more effectively, and it also helps to reduce environmental pollution.

[0030] The present invention also provides a dry full-process treatment system for steel slag, including a rolling equipment, a cooling equipment, a waste heat recovery system, a grinding system, and a sorting system; the rolling equipment is connected to the cooling equipment through a conveyor; the flue gas inlet of the waste heat recovery system is connected to the rolling equipment and the cooling equipment for recovering the heat released by the steel slag in the rolling process and the cooling equipment; the tail gas outlet of the waste heat recovery system is connected to the rolling equipment to blow the discharged tail gas back into the rolling equipment.

[0031] Preferably, the cooling equipment is a film cooler.

[0032] Preferably, it further includes a flash evaporation device, which is connected to the water outlet of the cooling device to flash the high-temperature and high-pressure water of the cooling device to obtain saturated steam.

[0033] Preferably, the waste heat recovery system includes a waste heat boiler with a superheater inside. The steam outlet of the flash evaporation device is connected to the superheater of the waste heat boiler to deliver saturated steam to the waste heat boiler.

[0034] Preferably, the waste heat recovery system further includes a dust removal device and a circulation fan. The waste heat boiler is connected to the roll pressing device and the cooling device through pipelines to collect the heat generated by the roll pressing device and the cooling device for generating steam. The dust removal device is connected to the waste heat boiler through a pipeline to remove dust from the tail gas discharged after the waste heat boiler is utilized. The circulation fan is respectively connected to the dust removal device and the roll pressing device through pipelines to blow the dust-removed tail gas back into the roll pressing device for cooling the toothed rolls and steel slag.

[0035] Preferably, the roll pressing device is arranged in a closed space, and the slag pot tipping is carried out in this closed space to prevent fresh air from entering. After the steel slag is dumped, the slag pot exits, the door of the closed space is closed, and then the cooling medium air is introduced to avoid sucking in fresh air. On the one hand, it can keep the wind speed and temperature stable in the closed space, thus ensuring the stability of the steam in the waste heat boiler. On the other hand, it further avoids the influence of high environmental oxygen content on metal oxidation.

[0036] Preferably, the grinding system includes a rod mill device and a ball mill device.

[0037] Preferably, the sorting system includes a magnetic separation device and a wind separation device.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The present invention is applicable to the treatment of stainless steel slag, but is not limited to stainless steel slag, and is also applicable to the treatment of other types of steel slag, such as plain carbon steel slag, stainless steel slag, high-temperature smelting gold slag, etc. First, the full-process dry process of the present invention takes heat from the roll pressing process for the first time, combined with taking heat from the cooling process, greatly improving the waste heat recovery rate. Second, the present invention adopts gradient cooling. Among them, the roll pressing process is cooled by air cooling while recovering heat, improving the thermal recovery efficiency of the overall process; the cooling process is cooled by a non-air cooling method, avoiding the influence of steel slag pulverization on the air cooling method and the risk of metal oxidation. During the entire heat recovery process, the influence of steel slag pulverization is very small, realizing the efficient recovery of heat and metal in the steel slag treatment, reducing resource waste; on the other hand, discharging the heat from the equipment in the roll pressing process and the cooling process in a timely manner can greatly reduce the load of the equipment and ensure the smooth progress of cooling.

[0040] (2) By blowing the tail gas discharged from the waste heat recovery treatment back into the roller pressing process for recycling, on the one hand, the tail gas discharged after the waste heat recovery treatment is recycled, improving the resource recovery utilization rate; on the other hand, the cooling medium has the characteristic that its oxygen content is lower than that of fresh air. Using it as the cooling medium reduces the possibility of the metal in the steel slag being oxidized, thereby improving the recovery rate of metallic iron.

[0041] (3) The present invention uses a film cooler as the cooling equipment for the non-air-cooling method. There are cooling water pipes inside it to cool the steel slag. The film cooler has a higher thermal efficiency than the waste heat boiler. The cooling water in the cooling water pipes of the cooler is heated to directly generate high-temperature and high-pressure water, and then saturated steam can be obtained through flash evaporation. The saturated steam is sent to the superheater of the waste heat boiler, which can increase the temperature and pressure of the steam generated by the waste heat boiler, further improving the waste heat recovery utilization rate.

[0042] (4) The present invention selects an appropriate wind speed and controls the temperature of the steel slag after roller pressing within a reasonable range, which can obtain an ideal particle size of the steel slag, thereby obtaining a higher metal recovery rate and waste heat recovery rate, and keeping the steel slag treatment output at a relatively high level.

[0043] (5) The present invention combines rod milling treatment and ball milling treatment, which can improve the grinding efficiency and reduce energy consumption at the same time.

[0044] (6) The present invention combines magnetic separation treatment and air separation treatment, which can more effectively recover the useful components in the steel slag and also help reduce environmental pollution. Description of the Drawings

[0045] Figure 1 It is a schematic flow chart of treating steel slag by using the full-process dry treatment process of the present invention. Detailed Embodiments

[0046] To better present the present invention, it is illustrated through specific implementation cases. These implementation cases belong to the protection scope of the present invention but do not limit the protection scope of the present invention.

[0047] Example 1

[0048] A dry treatment system for the whole process of steel slag, including a roll pressing device, a film cooler, a flash evaporation device, a waste heat boiler, a dust removal device, a circulation fan, a rod mill device, a ball mill device, a magnetic separation device and a wind separation device; the roll pressing device is connected to the film cooler through a conveying device; the flue gas inlet of the waste heat boiler is connected to the roll pressing device and the cooling device through a pipeline to collect the heat released by the steel slag in the roll pressing device and the cooling device. There is a superheater in the waste heat boiler for generating steam; the inlet of the dust removal device is connected to the flue gas outlet of the waste heat boiler to remove dust from the flue gas discharged after the waste heat boiler is utilized; the circulation fan is respectively connected to the outlet of the dust removal device and the roll pressing device through pipelines, and blows the dedusted tail gas back into the roll pressing device for cooling the toothed rollers and the steel slag; there are cooling water pipes in the film cooler, and the water outlet of the cooling water pipes is connected to the inlet of the flash evaporation device. The flash evaporation device flashes the high-temperature and high-pressure water in the cooling water pipes to obtain saturated steam, and the steam outlet of the flash evaporation device is connected to the superheater of the waste heat boiler to supply saturated steam to the superheater of the waste heat boiler; the roll pressing device is arranged in a closed space, and the slag tank tilts inside the closed space to prevent fresh air from entering. After the steel slag is poured, the slag tank exits, the door of the closed space is closed, and then the cooling medium air is introduced to avoid sucking in fresh air.

[0049] A dry treatment process for the whole process of steel slag, which applies the above treatment system, including:

[0050] S1. Roll pressing process: Use a roll pressing device to roll and crush the liquid steel slag at 1300 - 1600 °C for 5 - 30 minutes. During this process, use air cooling to cool down and solidify the liquid steel slag; the cooling medium of the air cooling method comes from the tail gas discharged in the waste heat recovery process in step S5, and the wind speed is controlled at 5 - 30 m / s.

[0051] S2. Cooling process: Use a film cooler to cool the steel slag obtained in step S1 to below 100 °C, and the cooling rate is 10 - 25 °C / min; the cooling water in the cooling water pipes in the film cooler is heated to obtain high-temperature and high-pressure water.

[0052] S3. Grinding process: Control the particle size of the steel slag cooled by the film cooler, and then sequentially enter the rod mill device and the ball mill device for rod milling and ball milling.

[0053] S4. Separation process: The ground steel slag sequentially enters the magnetic separation device and the wind separation device for magnetic separation and wind separation.

[0054] S5. Waste heat recovery process: The waste heat boiler recovers the heat released by the steel slag in the roll pressing equipment and the film cooler to generate steam. The flue gas temperature after being utilized by the waste heat boiler is 130 - 180°C. The dust removal equipment conducts dust removal on it, and then the circulating fan introduces the tail gas after dust removal into the roll pressing equipment as the cooling medium for cooling the steel slag in the roll pressing equipment.

[0055] S6. Flash evaporation process: The flash evaporation equipment conducts flash evaporation on the high-temperature and high-pressure water generated by the film cooler to obtain saturated steam, and sends the saturated steam into the superheater of the waste heat boiler to increase the temperature and pressure of the steam generated by the waste heat boiler.

[0056] In this embodiment, referring to the full-process dry treatment process of steel slag provided above, with the wind speed of the cooling medium in the roll pressing equipment and the temperature of the steel slag after roll pressing as variables, different treatment groups are set (as shown in Table 1) to investigate the influence of these variables on the treatment effect of steel slag.

[0057] Table 1 Settings of each treatment group in Example 1

[0058] Group Wind speed of cooling medium / m / s Temperature of steel slag after roll pressing / °C Treatment 1 20 900 Treatment 2 30 800 Treatment 3 5 1000 Treatment 4 10 950 Treatment 5 3 1000 Treatment 6 35 800 Treatment 7 5 1100 Treatment 8 30 700

[0059] Example 2

[0060] It is basically the same as the full-process dry treatment process of steel slag provided in Example 1, and is treated with reference to the settings of Treatment 1. The only difference is that the high-temperature and high-pressure water in the film cooler is not flash-evaporated to obtain saturated steam and is not sent into the superheater of the waste heat boiler.

[0061] Example 3

[0062] It is basically the same as the full-process dry treatment process of steel slag provided in Example 1, and is treated with reference to the settings of Treatment 1. The only difference is that the tail gas discharged from the waste heat recovery treatment is not introduced into the roll pressing equipment for recycling, but fresh air is used as the cooling medium with the wind speed unchanged.

[0063] Comparative Example 1

[0064] The treatment method of Patent CN115522001A.

[0065] Effect comparison experiment

[0066] 1. Install a flow meter and a pressure gauge on the steam pipeline, read the flow and pressure values of the steam, and respectively obtain the amount and pressure of the steam generated by each treatment group in Example 1, Example 2, and Example 3, and compare them with Comparative Example 1. The results are shown in Table 2.

[0067] Table 2 Steam production and pressure conditions of each treatment group in Example 1, Example 2, Example 3, and Comparative Example 1

[0068] Group Steam output / kg / ton Steam pressure / MPa Treatment 1 300 1.8 Treatment 2 280 1.5 Treatment 3 290 1.6 Treatment 4 295 1.6 Treatment 5 275 1.4 Treatment 6 265 1.3 Treatment 7 270 1.4 Treatment 8 260 1.3 Example 2 250 1.2 Example 3 270 1.3 Comparative Example 1 200～240 0.8～1

[0069] As can be seen from Table 2:

[0070] (1) In Example 1 of the present invention, a gradient temperature drop is formed between the rolling equipment and the film cooler in Treatments 1 to 4, and the heat generated by the rolling equipment and the film cooler is recovered. The amount of steam generated per ton of steel slag is above 280 kg, reaching a maximum of 300 kg, and the steam pressure is as high as 1.5 - 1.8 MPa, achieving a high waste heat recovery utilization rate. In Example 2, the saturated steam generated by flashing the water discharged from the film cooler is not sent to the superheater of the waste heat boiler, so the steam pressure also decreases accordingly; in Example 3, on the basis that the wind speed and the temperature of the steel slag after rolling are the same as those in Treatment 1, fresh air is used as the cooling medium. Although the large temperature difference between the fresh air and the steel slag helps to quickly cool the steel slag, it also leads to a large loss of heat during the heat exchange process between the steel slag and the cooling medium, thereby reducing the efficiency of the waste heat boiler and affecting the overall waste heat recovery utilization rate; in Comparative Example 1, only the heat generated during the treatment of steel slag by the dry cooler is recovered. The amount of steam generated per ton of steel slag is only 200 - 240 kg, and the pressure is only 0.8 - 1 MPa, which is lower than that in Example 2 and significantly lower than that in Treatments 1 to 4.

[0071] (2) Compared with Treatment 3, the wind speed in Treatment 5 is too slow, which means that it takes a longer rolling time to cool the steel slag to 1000 °C, affecting the processing capacity and output of the rolling equipment; and the longer the rolling time, the larger the total air volume, and the overall air temperature decreases, thus affecting the normal operation of the waste heat boiler and the overall waste heat recovery rate also decreases accordingly.

[0072] (3) Compared with Treatment 2, the wind speed in Treatment 6 is too fast, which means that it can reach 800 °C in a shorter rolling time. However, the shorter rolling time results in an inability to obtain the ideal steel slag particle size. When the steel slag with too large a particle size enters the cooling process, the heat dissipation is slow, and the heat cannot be quickly and effectively removed, thus reducing the waste heat recovery rate.

[0073] (4) Compared with Treatment 3, at the same wind speed, the temperature of the steel slag after rolling in Treatment 7 is on the high side, and the rolling is also ended in a shorter time. There is a situation where the ideal steel slag particle size cannot be obtained, resulting in a reduction in the waste heat recovery rate; on the other hand, the steel slag with a high temperature is not completely solidified and will re - adhere into large blocks, affecting the normal operation of the film cooler and thus affecting the waste heat recovery rate; moreover, the too high temperature will also damage the film cooler, reduce the service life of the film cooler, and is prone to safety accidents.

[0074] (5) Compared with Treatment 2, at the same wind speed, the temperature of the steel slag after rolling in Treatment 8 is relatively low, which means a longer rolling time and more heat is transferred to the cooling medium of the rolling equipment. The temperature of the steel slag entering the finned tube cooler is relatively low, greatly reducing the waste heat recovery rate of the finned tube cooler. However, in fact, the heat recovery efficiency of the finned tube cooler is higher than that of the waste heat boiler. Therefore, the temperature of the steel slag after roll crushing is too low, which does not meet the target requirement of quickly transferring the steel slag with a high enough temperature into the finned tube cooler for efficient heat extraction in the present invention.

[0075] 2. Refer to the method for determining the metallic iron content in "GBT 38812.2-2020 Determination of metallic iron content in direct reduced iron - Potassium dichromate titration method after decomposition with ferric chloride" to determine the metallic iron content in each treatment group of Example 1 and the steel slag before and after treatment in Example 3, and calculate the metallic iron residue rate. Among them, the average metallic iron content of the liquid steel slag to be treated is 8%. The metallic iron residue rate (%) = metallic iron content in the tail slag / metallic iron content in the liquid steel slag * 100%. The results are shown in Table 3.

[0076] Table 3 Metallic iron content and metallic iron residue rate of the tail slag in each treatment group of Example 1 and Example 3

[0077]

[0078]

[0079] As can be seen from Table 3:

[0080] (1) Under the treatment process of the present invention, the metallic iron content in the tail slag of Treatments 1 to 4 in Example 1 is all below 0.1%, and the metal residue rate is relatively low, indicating that the treatment process of the present invention has reached a relatively high level of metal recovery rate.

[0081] (2) In Example 3, fresh air is used instead of the tail air discharged from waste heat recovery treatment as the cooling medium to cool the steel slag in the rolling equipment, and the metal recovery rate is greatly affected. The reason is that the oxygen content in fresh air is higher than that in the tail air discharged from waste heat recovery treatment, and it is easy to oxidize the metal in the steel slag under high temperature conditions, resulting in a decrease in the metal recovery rate.

[0082] (3) In Processes 5 and 8, if the wind speed of the cooling medium is too low or the temperature of the steel slag after roll pressing is too low, it means that the roll pressing time is too long, increasing the possibility of metal oxidation at high temperatures, thus reducing the metal recovery rate to a certain extent and also reducing the processing capacity and output of the roll pressing and crushing process. In Process 6, if the wind speed of the cooling medium is too fast, since the temperature in the roll pressing equipment is very high and a large amount of tail wind blows the steel slag at high temperatures, it will also accelerate the oxidation of metallic iron in the steel slag, thereby affecting the metal recovery rate. In Process 7, the steel slag ends roll pressing at a relatively high temperature, indicating that the roll pressing time is relatively short. Even at an appropriate wind speed, it will result in an inability to obtain the ideal particle size of the steel slag, and even the steel slag is not completely solidified. The cooling effect of the subsequent film cooler is greatly affected, and the grinding and sorting effects are also affected, thus indirectly affecting the metal recovery rate.

[0083] In summary, the reason why the present invention adopts the two-stage heat extraction method of the roll pressing process and the cooling process lies in: 1. By reasonably controlling the wind speed and roll pressing time of the roll pressing process, reducing the contact time between the wind and the steel slag, and avoiding metal oxidation, thereby improving the metal recovery rate; 2. By reasonably controlling the wind speed and roll pressing time of the roll pressing process, solidifying the steel slag and transferring the steel slag with a sufficiently high temperature into the film cooler as soon as possible, because the film cooler has a higher waste heat recovery efficiency, thus improving the overall waste heat recovery rate; 3. The roll pressing process uses the tail wind after dust removal and purification to blow and cool the steel slag, making full use of the heat of the tail wind, further improving the waste heat recovery rate, and making the whole process more environmentally friendly.

[0084] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several alternatives or modifications can be made to these described embodiments, and these alternative or modified forms should be regarded as belonging to the protection scope of the present invention.

Claims

1. A full-process dry treatment process for steel slag, characterized in that: include: S1. Rolling process, the liquid slag is crushed by rolling, during which the liquid slag is cooled by air cooling to solidify the liquid slag; S2. A cooling step, wherein the slag obtained in step S1 is cooled to below 100°C by a non-air cooling method; S3. Grinding process; S4. Sorting process; S5. Waste heat recovery process, recycling the heat released by the slag in the rolling process and the cooling process; In step S1, the cooling medium of the air cooling method is the tail air discharged from the waste heat recovery process; The wind speed of the cooling medium is 5 to 30 m / s; In step S1, the temperature of the steel slag after roller crushing is 800-1000°C, the rolling time is 5-30 minutes, and the particle size of the steel slag after roller crushing is less than 50 mm.

2. The full-process dry treatment process of steel slag according to claim 1 is characterized in that: In step S2, the cooling device used in the non-air cooling method is a film cooler.

3. The full-process dry treatment process of steel slag according to claim 2 is characterized in that: In step S5, the waste heat recovery process uses a waste heat boiler to recover heat.

4. The full-process dry treatment process for steel slag according to claim 3 is characterized in that: The method also includes a flash evaporation process, in which high-temperature and high-pressure water generated by the membrane cooler is flashed to obtain saturated steam, and the saturated steam is sent to the waste heat boiler.

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