TWI772835B - Method for dry recovery of lime from by-products of iron or steelmaking processes - Google Patents

Abstract

A method for dry recovery of lime from by-products of iron-making or steel-making processes comprises a preparatory step, a feeding step, and a screening step. In this preliminary step, a lime recovery device is prepared, which includes a material distribution unit, a screening unit connected to the material distribution unit, a negative pressure unit, and a heating unit. In the feeding step, the filter material to be screened is dried through the heating unit, and the filter material to be screened is driven by the air flow through the negative pressure unit to pass through the material distribution unit for screening. In this screening step, the screened out fines are further screened. Through the aforesaid steps, particles below 150 microns containing a large amount of calcium oxide can be sieved from the reduced slag, the desulfurized slag or the mixture of the two to obtain high-calcareous materials and improve the recovery efficiency.

Description

Method for dry recovery of lime from by-products of iron- or steel-making processes

The present invention relates to a method for dry recovery, in particular to a method for dry recovery of lime from reduction slag, desulfurization slag or a mixture thereof.

Generally, scrap iron recycling steelmaking plants mainly use electric arc furnaces to make steel, and the steelmaking process can be divided into three stages: melting, oxidation and reduction according to its chemical reaction. In the reduction period, after the slag formation is completed and the scum is removed, in order to fully react with the oxides to avoid excess oxygen remaining in the molten steel, a large amount of secondary raw materials such as limestone and carbon powder will be added. There is still a lot of lime remaining in the reduction slag and desulfurization slag. If the lime with strong alkalinity is not recovered and disposed of together with the reduction slag or desulfurization slag, it will cause impact and damage to the environment. Under the situation of increasing rising, it is imperative to effectively recover lime (CaO) from reduction slag and desulfurization slag, but unfortunately, my country has not yet seen any related treatment methods, which is undoubtedly for green and sustainable development. A big hit. In addition, after lime recovery, stabilization treatment is generally required to avoid the problem of excessive expansion rate, which is inconvenient and requires many procedures.

According to the sieve analysis, the proportion of the sieved particle size in the reduced slag is roughly as follows: the larger material accounts for 30~40% by weight of the particles passing through, and those passing through No. The sieve (about 75 microns) accounts for about 28% by weight of the particles, and the composition of calcium oxide in the composition below 75 microns is as high as 54% by weight, and the composition of calcium oxide in the composition of 300 microns to 75 microns is also up to 52% by weight. Therefore, if the particles below 300 microns can be separated from the reducing slag, lime with a total weight percentage of more than 50% can be obtained. Similarly, the ratio of the sieving particle size in the desulfurization slag is roughly: the larger material accounts for the particle passing weight. Percentage of 30~40%, passing through No. 48 sieve (about 300 microns) accounts for about 50% by weight of particles, and passing through No. 200 sieve (about 75 microns) accounts for about 35% of particles passing by weight. Separated from the reduced slag, lime with a total weight percentage of more than 55% can be obtained.

If a screen is used for the recovery method of sieving, the particles below 300 microns are too small and are easily scattered in the external environment during screening, resulting in low recovery efficiency and environmental pollution, which is contrary to the original recovery of lime to prevent environmental impact. The present invention can not only overcome the aforementioned problems of screen recycling, but also has high recycling efficiency, can effectively reduce the waste of steel plants and greatly reduce environmental pollution.

In addition, at present, common steel mills (including Yihuanhua steel mills or electric furnace steel mills) will use water cooling to cool down when they discharge slag during operation. Therefore, most of the above-mentioned recovery methods adopt wet treatment (steam, slag in water pits), so there is no dry treatment technology on the market at present.

Therefore, the object of the present invention is to provide a method for efficiently dry recovery of lime in reduced slag, desulfurized slag or a mixture thereof.

Therefore, the method for dry recovery of lime from by-products of iron-making or steel-making processes of the present invention includes a preparatory step, a feeding step, and a screening step. In this preliminary step, a lime recovery device is prepared, the lime recovery device includes a material distribution unit, a screening unit connected to the material distribution unit, a filter unit for extracting gas from the material distribution unit and the screening unit The negative pressure unit, and a heating unit. In the feeding step, the negative pressure unit and the heating unit are turned on, so that the air flow passes through the material distributing unit and the screening unit in sequence and then is discharged to the outside. The material to be screened of the mixture is placed in the material distribution unit, and the air flow is heated through the heating unit to dry the material to be screened, and the material to be screened will be preliminarily screened into the larger particle size in the material distribution unit. Coarse material and fine material with smaller particle size. In the screening step, the air flow drives the fine materials in the material to be screened, and makes the fine materials pass through the screening unit to be further screened, and the fine materials passing through the screening unit are collected to complete the recovery. The fine material contains more than 50% by weight of lime.

The effect of the present invention is: the air flow generated by the negative pressure unit can drive the fine materials with smaller particle size in the material to be screened to be further collected after being screened, and the material distribution unit and the screening unit can accept the first screen The filter material can prevent it from being scattered to the outside world, and the particles below 300 microns are driven by the air flow to pass through the sieving unit and be led to the outside for collection. Because the particles below 300 microns containing a large amount of calcium oxide can be separated from the filter material to be sieved, Therefore, the efficiency of lime recovery can be greatly improved, and the pollution caused by the scattering of fine particles in the external environment can be avoided. In addition, the heating unit can bake the filter material to be screened during the feeding process to remove the moisture contained in the filter material to be screened. Carbon dioxide can react with the lime in the material to be screened to form calcium carbonate, which can improve the stability of the recovered fine material and reduce the expansion rate to achieve the effect of stable recovery.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are designated by the same reference numerals.

Referring to FIG. 1 and FIG. 2 , a first embodiment of a method for dry recovery of lime from by-products of iron-making or steel-making processes of the present invention includes a preparatory step, a feeding step, and a sieving step. In this preparation step, a lime recovery device 1 is prepared. The lime recovery device 1 includes a material distribution unit 2 , a screening unit 3 connected to the material distribution unit 2 , a negative pressure unit 4 connected to the screening unit 3 , and a heating unit 5 . The distributing unit 2 includes an outer wall 21 defining an inner space 210 , a screening mechanism 22 disposed in the inner space 210 , and a crusher 23 . The outer wall 21 forms a feed port 211 that communicates with the top of the inner space 210 and faces upward, a communication port 212 that is located below the feed port 211 and opens laterally (ie horizontally) and communicates with the interior space 210 , a communication port 212 located at the bottom of the feed port 211 Below the communication port 212 and communicates with the collection port 213 at the bottom of the inner space 210 , and an air inlet 214 located below the feed port 211 and above the collection port 213 and opened laterally. In the first embodiment, the air inlet 214 extends obliquely from top to bottom to connect with the inner space 210 . The screening mechanism 22 is located between the feeding port 211 and the collecting port 213 in the up-down direction, and has a plurality of supporting plates 221 fixed to the inner surface of the outer wall 21 at intervals in the up-down direction. Each support plate 221 extends obliquely, wherein the higher end extends toward the feed port 211 , and the lower end extends toward the communication port 212 . The crusher 23 can be a jaw crusher, a centrifugal crusher, or a roller crusher.

The screening unit 3 includes an outer casing 31 defining a filter space 310 , and a filter material 32 disposed in the filter space 310 of the outer casing 31 . The outer casing 31 forms a port 311 opened laterally to communicate with the filter space 310 and the communication port 212 of the material distribution unit 2 , and a discharge port 312 located below the port 311 and communicated with the bottom of the filter space 310 . The filter material 32 has a plurality of filter bags 321 fixed on the inner surface of the outer casing 31 and located above the discharge port 312. It should be noted that, in addition to the filter bags 321, the filter material 32 can also be a multi-layer filter mesh or Other filter elements are not limited to this. The negative pressure unit 4 includes an exhaust fan 41 that communicates with the discharge port 312 and can extract air from the discharge port 312 and can control the wind power. The heating unit 5 includes a combustion heater 51 disposed in the air inlet 214 and located opposite the support plates 221 . The number of the combustion heaters 51 can also be configured in multiples according to actual needs, which is not limited to this. .

In the feeding step, the exhaust fan 41 and the combustion heater 51 are turned on, so that the air is drawn out from the inner space 210 and the filter space 310, enters from the air inlet 214, and passes through the communication port 212 and the filter space 310. The interface 311 finally passes through the filter bags 321 and discharges the airflow from the outlet 312 , and the combustion heater 51 heats the airflow entering through the air inlet 214 . The to-be-screened filter material 6 formed from the reduced slag, the desulfurized slag, or the mixture 5 of the two will be fed into the inner space 210 from the feeding port 211, and the downwardly-dropped to-be-screened filter material 6 will first hit the uppermost support. The plate 221, which contains the components to be screened 6 with different particle sizes and weights, will be initially screened as shown in FIG. The coarse material 61 and the fine material 62 that are lifted and scattered due to the smaller particle size (lighter weight), the coarse material 61 that falls down will fall down into the collection port 213 and be collected. The supporting plate 221 located below will be hit again to perform screening again, and the arrangement of the plurality of supporting plates 221 can ensure that the to-be-screened filter material 6 can hit the supporting plates 221 when falling. In addition, the general reducing slag contains 0-5% by weight of moisture, and the desulfurization slag contains 10-12% by weight of moisture. In the above process, the combustion heater 51 can be used to heat the airflow to treat the sieve. The filter material 6 is heated and dried, and then removes the moisture in the filter material 6 to be screened. The combustion heater 51 can be switched on and off depending on the water content of the filter material to be screened 6. When it is detected that the water content of the filter material to be screened 6 is sufficiently low , the combustion heater 51 can also be turned off to save energy. It should be noted that the coarse material 61 collected by the collection port 213 not only falls due to the large particle size, but also has a heavy weight due to high water content. The coarse material 61 is firstly crushed by the crusher 23, and then sent to the feeding port 211 again, so that the coarse material 61 can be dried and dehydrated again, so that the coarse material 61 with a heavier weight due to the high water content, After circulating dehydration and drying, it becomes the fine material 62 to improve the recovery rate.

In the screening step, since the aforementioned fine material 62 is light in weight, it will be driven by the air flow guided by the exhaust fan 41 to pass through the communication port 212 and the interface 311 and enter the filter space 310 middle. The fine material 62 entering the filter space 310 is continuously driven by the air flow, and then passes through the filter bags 321 for further sieving, and the particles with larger particle size in the fine material 62 are retained in the filter bags 321 , and the particles with smaller particle size will be recovered by sieving and guided by the airflow to the discharge port 312 at the bottom. The particle size of the recovered particles is mostly below 300 microns, which are by-products of the iron-making or steel-making process. The high calcareous material recovered in the medium contains extremely high calcium oxide, which can achieve the effect of recovering more than 55% by weight of lime (CaO). love affair. In addition, the combustion heater 51 can not only remove the moisture in the material 6 to be screened, thereby obtaining a high-calcareous material containing dry lime, and during the combustion and heating process of the combustion heater 51, the carbon dioxide discharged can be mixed with the material to be sifted. The lime in the sieve filter material 6 reacts to form calcium carbonate, which improves the stability of the high-lime material and reduces the expansion rate, and reduces the process and time of subsequent processing.

It should be noted that the particles recovered through the first embodiment, since the total content of calcium oxide and magnesium oxide exceeds 60% by weight, they are quite suitable as sintering ingredients and slag-forming agents. At the same time, due to the content of calcium oxide If it exceeds 50% by weight, it can meet the requirements of cement raw meal, so it can replace the limestone powder used in mining, which can also save the power consumption caused by raw meal grinding. It is a very environmentally friendly green material. In addition, due to the high alkalinity of the recovered particles, it can also be used to neutralize the acidity in wastewater to replace slaked lime, or to provide alkalinity for the reaction of the basalt material to be used as a curing agent. Helps reduce the impact on the ecology.

Referring to FIG. 3 and FIG. 4, it is a second embodiment of a method for dry recovery of lime from by-products of iron-making or steel-making process of the present invention. The second embodiment is substantially the same as the first embodiment, except that the The point is: in the preparatory step, the screening mechanism 22 of the distributing unit 2 has a space between the feeding port 211 and the collecting port 213 in the up-down direction, and the communication port 212 is arranged in the inner space 210 correspondingly Centrifuge 222 in . The centrifuge 222 has a plurality of fan blades 223 which are arranged in an annular shape and whose rotating shafts are parallel to the vertical direction. The air inlet 214 extends obliquely from bottom to top to connect with the inner space 210 .

In this feeding step, when the material to be screened 6 falls, it will be hit by the fan blades 223 or blown away by the surrounding wind as shown in FIG. 4 , so that the material to be screened 6 can be screened The coarse material 61 that falls down to the collection port 213 due to the weight, and the fine material 62 that is scattered and raised, and the coarse material 61 in the collection port 213 will also be crushed by the crusher 23 and then fed into the feed port again. 211, so the second embodiment performs preliminary screening through centrifugal separation, which is different from the gravity separation in the first embodiment, and provides another screening method for users to choose, improving versatility and selectivity. . The screening mechanism 22 may also have a plurality of centrifuges 222 arranged at intervals in the up-down direction, so as to further screen the fallen coarse material 61 to improve the recovery rate. In addition, the airflow heated by the combustion heater 51 is also rolled up by the fans 223 to dry and heat the filter material 6 to be screened.

To sum up, the present invention can initially screen the reduced slag, desulfurization slag or their mixtures into fine materials 62 and coarse materials 61 through the screening mechanism 22 , and the fine materials can be driven by the airflow guided by the exhaust fan 41 . 62 through these filter bags 321 to continue filtering, through the drying and dehydration of the combustion heater 51, the moisture in the to-be-screened filter material 6 and the coarse material 61 can be further removed, so as to filter the high-density particles with a particle size below 300 microns. The calcareous material can effectively increase the content of the recovered lime, and can prevent the particles with smaller particle size from floating in the external environment, reduce the pollution and impact on the environment, and effectively reduce the waste of the iron and steel plant. The above-mentioned dry lime recovery method can achieve the highest recovery rate by repeatedly drying and dropping the material through continuous circulation, so it can indeed achieve the purpose of the present invention.

However, the above are only examples of the present invention, and should not limit the scope of the present invention. Any simple equivalent changes and modifications made according to the scope of the application for patent of the present invention and the content of the patent specification are still within the scope of the present invention. within the scope of the invention patent.

1: Lime recovery device 2: material distribution unit 21: outer wall 210: Interior Space 211: Feeding port 212: Connecting port 213: Collection port 214: air inlet 22: Screening mechanism 221: Bearing plate 222: Centrifuge 223: fan blade 23: Crusher 3: Sieve unit 31: Outer shell 310: Filter Space 311: interface 312: discharge port 32: filter material 321: filter bag 4: Negative pressure unit 41: Exhaust fan 5: Heating unit 51: Combustion heater 6: reduction slag 61: Coarse material 62: fine material

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: 1 is a schematic diagram illustrating a first embodiment of one of the methods for dry recovery of lime from iron-making or steel-making process by-products of the present invention; FIG. 2 is an incomplete schematic diagram illustrating a situation in which a screening mechanism performs material distribution in the first embodiment; Fig. 3 is a schematic diagram illustrating a second embodiment of a method for dry recovery of lime from iron-making or steel-making process by-products of the present invention; and FIG. 4 is an incomplete schematic diagram illustrating the situation in which the sieving mechanism performs material distribution in the second embodiment.

1: Lime recovery device

2: material distribution unit

21: outer wall

210: Interior Space

211: Feeding port

212: Connecting port

213: Collection port

214: air inlet

22: Screening mechanism

221: Bearing plate

23: Crusher

3: Sieve unit

31: Outer shell

310: Filter Space

311: interface

312: discharge port

32: filter material

321: filter bag

4: Negative pressure unit

41: Exhaust fan

5: Heating unit

51: Combustion heater

Claims (6)

A method for dry recovery of lime from by-products of iron-making or steel-making process, comprising: a preparatory step, preparing a lime recovery device, the lime recovery device comprising a material distribution unit, a screening unit connected to the material distribution unit, A negative pressure unit for extracting gas from the material distribution unit and the screening unit, and a heating unit, the material distribution unit includes an outer wall defining an inner space, and the outer wall forms a material inlet, a A communication port located below the feed port and communicated with the screening unit, a collection port located below the communication port and communicated with the bottom of the interior space, and a communication port connected to the interior space and located between the feed port and the collection port The heating unit is arranged in the air inlet, and the screening unit includes an outer casing that defines a filter space, and a filter material disposed in the filter space. The outer casing forms a continuous The interface through the communication port and the filter space, and a discharge port connected with the filter space, the negative pressure unit includes an exhaust fan connected with the discharge port, and the heating unit includes at least one switchably disposed in the inlet port. The combustion heater in the tuyere; in a feeding step, the negative pressure unit and the heating unit are turned on, so that the air flow enters the inner space from the air inlet, and then passes through the material distribution unit and the screening unit in sequence and then flows to the Then, the filter material to be screened selected from reducing slag, desulfurization residue, or a mixture thereof is placed in the material distribution unit, and the air flow is heated through the heating unit to dry the filter material to be screened, and the filter material to be screened It will be initially screened into coarse material with larger particle size and fine material with smaller particle size in the material distribution unit; and a screening step, the air flow drives the fine material in the material to be screened and makes the fine material It is further screened through the filter material, and the fine material passing through the screening unit is output from the discharge port and collected to complete the recovery. The recovered fine material contains more than 50% by weight of lime. The method for dry recovery of lime from iron-making or steel-making by-products according to claim 1, wherein, in the preliminary step, the material distributing unit further comprises a screening mechanism disposed in the inner space, The screening mechanism has at least one supporting plate located between the feeding port and the collecting port along the up-down direction and inclined and arranged, and two ends of the at least one supporting plate are respectively extended toward the feeding port and the communication port. In the feeding step, the material to be screened is fed into the inner space from the feeding port, and then hits the at least one support plate to be screened into coarse material and fine material, and the coarse material will fall down and enter the inner space. The collection port, the fine material is driven by the air flow and enters the screening unit through the communication port. The method for dry recovery of lime from by-products of an iron-making or steel-making process as claimed in claim 1, wherein, in the preliminary step, the material distributing unit further comprises a screening mechanism disposed in the inner space, the screen The sub-mechanism has at least one centrifuge located between the feeding port and the collecting port along the up-down direction. The at least one centrifuge has a plurality of fan blades arranged in a ring shape and the rotating shaft is parallel to the up-down direction. In the feeding step, The material to be screened is fed into the inner space from the feeding port, and then hits the at least one centrifuge to be screened into coarse material and fine material. The coarse material will fall down and enter the collection port, while the fine material will be After being driven by the airflow and passing through the communication port, it enters the screening unit. The method for dry recovery of lime from by-products of ironmaking or steelmaking as claimed in claim 1, wherein the filter material of the screening unit has a plurality of filter bags fixed on the inner surface of the outer casing and located in the filter space. The method for dry recovery of lime from iron-making or steel-making by-products according to claim 1, wherein, in the feeding step, the coarse material dropped into the collecting port is introduced into the feeding port for drying again and sieving. The method for dry recovery of lime from iron-making or steel-making by-products according to claim 1, wherein, in the preliminary step, the material distributing unit further comprises a crusher, and in the feeding step, the collection The coarse material exported from the mouth is firstly crushed by the crusher.

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