TW202104085A - Method for dry recovery of lime from by-products of ironmaking or steelmaking process including a preparation step, a feeding step, and a sieving step - Google Patents

Abstract

A method for dry recovery of lime from by-products of ironmaking or steelmaking processes, which includes a preparation step, a feeding step, and a sieving step. In the preparation step, a lime recovery device is prepared, the lime recovery device includes a distributing unit, a sieving unit connected to the distributing unit, a negative pressure unit, and a heating unit. In the feeding step, a to-be-sieved material is dried through the heating unit, and the to-be-sieved material is driven by an airflow through the negative pressure unit to pass through the distributing unit for sieving. In the sieving step, the sieved fine material is further sieved. Through the aforementioned steps, particles having a particle size of 150 microns or less and containing a large amount of calcium oxide can be screened out from reduced slags, desulfurized slags, or a mixture of the two to obtain a high-calcareous material and improve recovery efficiency.

Description

Method for dry recovery of lime from by-product of self-ironmaking or steelmaking process

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, steelmaking plants for scrap iron recycling 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 reactions. In the reduction period, after the slagging is completed and the scum is poured out, in order to fully react with the oxides to avoid excessive oxygen remaining in the molten steel, a large amount of auxiliary materials such as limestone and carbon powder are added. However, after the reaction, it is often There is still a lot of lime left in the reduction slag and desulfurization slag. If the lime with strong alkalinity is discarded together with the reduction slag or desulfurization slag without being recycled, it will cause impact and damage to the environment. Under the situation of increasing growth, it is imperative to effectively recover lime (CaO) from reduction slag and desulfurization slag, but unfortunately, China has not yet seen any relevant treatment methods, which is undoubtedly for green and sustainable development. It's a big blow. In addition, after the lime is recovered, stability treatment is generally required to avoid the problem of excessive expansion rate, which is inconvenient to handle and requires more procedures.

According to the sieve analysis, the proportion of the sieved particle size in the reduction slag is roughly as follows: the larger material accounts for 30-40% of the particle passing weight, the 48th sieve (about 300 microns) accounts for about 40% of the particle passing weight, and the 200th The sieve (approximately 75 microns) accounts for about 28% by weight of the particles. Among them, the content of calcium oxide in components below 75 microns is as high as 54% by weight, and the content of calcium oxide in components from 300 to 75 microns is also as high as 52% by weight. Therefore, if the particles below 300 microns can be separated from the reduction slag, more than 50% of the total weight percentage of lime can be obtained. Similarly, the proportion of the sieved particle size in the desulfurization slag is roughly: the larger material accounts for the weight of the particles. Percentage of 30-40%, passing through the No. 48 sieve (about 300 microns) accounts for about 50% by weight of the particles, passing through the No. 200 sieve (about 75 microns), accounting for about 35% by weight of the particles, if the particles below 300 microns can be removed Separating from the reduction slag, more than 55% lime by weight can be obtained.

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

In addition, the current common steel plants (including Yiguanhua Steel Plant or Electric Furnace Steelmaking Plant) will use water cooling to cool down the slag during operation, so these slags will be shipped with a total weight percentage of 10 to 20. % Moisture, so most of the aforementioned recovery methods use wet treatment (steam, puddle slag removal), so there is no dry treatment technology currently on the market.

Therefore, the object of the present invention is to provide a method for efficiently and dry recovery of lime in reduction slag, desulfurization slag or their mixture.

Therefore, the method for dry recovery of lime from the by-products of the ironmaking or steelmaking process of the present invention includes a preliminary step, a feeding step, and a sieving step. In this preliminary step, a lime recovery device is prepared. The lime recovery device includes a distributing unit, a sieving unit connected to the distributing unit, and a unit for extracting gas from the distributing unit and the sieving unit The negative pressure unit, and a heating unit. In the feeding step, the negative pressure unit and the heating unit are turned on, and the airflow is sequentially passed through the distributing unit and the screening unit and then discharged outward, and then selected from the reduction slag, desulfurization slag, or the like The material to be sieved of the mixture is placed in the material separation unit, and the airflow is heated by the heating unit to dry the material to be sieved, and the material to be sieved will be preliminarily sieved into the material with a larger particle size in the material separation unit. Coarse materials and fine materials with smaller particle size. In the sieving step, the airflow drives the fine material in the material to be sieved, and the fine material passes through the sieving unit to be further sieved. The fine material passing through the sieving unit is collected to complete the recovery, and the recovered The fine material contains more than 50% lime by weight.

The effect of the present invention is that the airflow generated by the negative pressure unit can drive the fine material with a smaller particle size in the material to be sieved to be collected after further passing through the sieving unit, and receiving the sieve through the separating unit and the sieving unit. The filter material can prevent it from drifting to the outside, and the particles below 300 microns are driven by the airflow to pass through the filter unit and be guided 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 screened, Therefore, the efficiency of lime recovery can be greatly improved, and pollution caused by fine particles floating in the external environment can be avoided. In addition, the heating unit can bake the material to be sieved during the feeding process to remove the moisture contained in the material to be sieved, which is a method of dry recovery of lime that has not been seen in the market, and the heating unit produces 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 denoted by the same numbers.

1 and 2, a first embodiment of the method for dry recovery of lime from the by-products of the ironmaking or steelmaking process of the present invention includes a preliminary step, a feeding step, and a filtering step. In this preparation step, a lime recovery device 1 is prepared. The lime recovery device 1 includes a dividing unit 2, a screening unit 3 connected to the dividing unit 2, a negative pressure unit 4 connected to the screening unit 3, and a heating unit 5. The material dividing unit 2 includes an outer wall 21 defining an inner space 210, a screening mechanism 22 arranged in the inner space 210, and a crusher 23. The outer wall 21 forms an inlet 211 connected to the top of the internal space 210 and facing upward, a communicating port 212 located below the inlet 211 and opened laterally (i.e. horizontally) and connected to the internal space 210, and a communicating port 212 located at Below the communication port 212 and communicates with the collection port 213 at the bottom of the internal 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 to the internal space 210. The screening mechanism 22 is located between the inlet 211 and the collection port 213 in the vertical direction, and has a plurality of supporting plates 221 fixed to the inner surface of the outer wall 21 at intervals in the vertical direction. Each supporting plate 221 extends obliquely, wherein the higher end extends toward the inlet 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 filtering unit 3 includes an outer casing 31 defining a filtering space 310 and a filter material 32 disposed in the filtering space 310 of the outer casing 31. The outer shell 31 forms an interface 311 opened sideways to communicate with the filter space 310 and the communication port 212 of the distributing unit 2, and a discharge port 312 located below the interface 311 and communicates 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 shell 31 and located above the discharge port 312. It should be noted that in addition to the filter bags 321, the filter material 32 may also be a multi-layer filter screen or Other filter elements are not limited to this. The negative pressure unit 4 includes an exhaust fan 41 that is connected to the discharge port 312 to draw air out of the discharge port 312 and can regulate the wind power. The heating unit 5 includes a combustion heater 51 disposed in the air inlet 214 and located relatively above the supporting plates 221. The combustion heater 51 can also be arranged in multiples according to actual needs, and is not limited to this. .

In the feeding step, the exhaust fan 41 and the combustion heater 51 are turned on, so that air is drawn from the internal space 210 and the filter space 310 to form the air inlet 214 and pass through the communication port 212 and the The interface 311 finally passes through the filter bags 321 and the air flow discharged from the discharge port 312, and the combustion heater 51 heats the air flow entering from the air inlet 214. The filter material 6 to be sieved formed from the reduction slag, desulfurization slag, or the mixture of the two 5 will be fed into the internal space 210 from the inlet 211, and the material to be sieved 6 falling downwards will first hit the uppermost bearing Plate 221, the material to be sieved 6 containing components of different particle sizes and weights, will be preliminarily sieved as shown in Figure 2 and will fall down along the bearing plate 221 due to the larger particle size (heavier weight) The coarse material 61, and the fine material 62 that is raised and scattered due to the small particle size (lighter weight), the coarse material 61 falling downward will fall down into the collection port 213 and be collected, and some It will hit the supporting plate 221 located below again to perform screening again, and the arrangement of multiple supporting plates 221 can ensure that the filter material 6 to be screened can hit the supporting plates 221 when the filter material 6 is dropped. In addition, the general reduction slag contains 0 to 5% of the total weight of moisture, and the desulfurization slag contains 10% to 12% of the total weight of moisture. In the above process, the combustion heater 51 can heat the airflow to be sieved. The filter material 6 is heated and dried to remove the moisture in the filter material 6 to be screened. The combustion heater 51 can be switched on and off according to the water content of the filter material 6 to be screened. When it is detected that the water content of the filter material 6 to be screened is sufficiently low At this time, 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 may fall due to the large particle size, and sometimes it is caused by the high water content which makes the weight heavier. Therefore, the coarse material 61 collected in the collection port 213 may be heavy. The coarse material 61 is first crushed by the crusher 23 and then sent to the inlet 211 again, so that the coarse material 61 can be dried and dewatered again, so that the coarse material 61 with a heavier weight due to higher water content can be used. After cyclic dehydration and drying, it becomes fine material 62, which improves the recovery rate.

In the sieving step, since the weight of the fine material 62 that is sieved out is relatively light, it will be driven by the airflow guided by the exhaust fan 41 to pass through the communication port 212 and the interface 311, and enter the filter space 310 in. The fine material 62 entering the filtering space 310 is continuously driven by the airflow, and then passes through the filter bags 321 to be further sieved. The particles with larger particle size in the fine material 62 will be retained in the filter bags 321 , And particles with a 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 is a by-product of the ironmaking or steelmaking process. The high-lime-quality material recycled in the medium contains extremely high content of calcium oxide, which can achieve the effect of recycling more than 55% by weight of lime (CaO), with high recycling efficiency and avoiding pollution caused by dust escape to the external environment Love affairs. In addition, the combustion heater 51 can not only remove the moisture in the material to be screened 6 to obtain a high-lime material containing dry lime, and during the combustion and heating process of the combustion heater 51, the carbon dioxide discharged can be combined with the material to be filtered. The lime in the sieving material 6 reacts to form calcium carbonate, which improves the stability of the high-calcareous material and reduces the expansion rate, reducing subsequent processing procedures and time.

It should be particularly noted that the particles recovered through the first embodiment, because the total content of calcium oxide and magnesium oxide exceeds 60% by weight, they are quite suitable as sintering ingredients and slagging agents. At the same time, due to the content of calcium oxide It is more than 50% by weight and can meet the requirements of cement raw material. Therefore, it can replace the limestone powder from Kaishan mining. This 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 instead of slaked lime, or to provide alkalinity for the reaction of boszulan materials as a solidifying agent ingredient. The application level is very wide and has a wide range of applications. Help reduce the impact on the ecology.

Referring to Figures 3 and 4, there is a second embodiment of the method for dry recovery of lime from the by-products of the self-ironmaking or steelmaking process of the present invention. The second embodiment is substantially the same as the first embodiment, with the difference The point is: in the preliminary step, the sieving mechanism 22 of the distributing unit 2 has an up-and-down direction between the inlet 211 and the collection port 213, and the communication port 212 is provided in the internal space 210. In the centrifuge 222. The centrifuge 222 has a plurality of fan blades 223 arranged in a ring shape and the rotating shafts are parallel to the vertical direction. The air inlet 214 extends obliquely from bottom to top to connect to the internal space 210.

In the feeding step, when the filter material 6 to be screened falls, it will be impacted by the fan blades 223 or blown away by the surrounding wind as shown in FIG. 4, so that the filter material 6 to be screened can be sieved The coarse material 61 falling downwards to the collecting port 213 due to the weight, and the fine material 62 floating up, and the coarse material 61 in the collecting port 213 will also be crushed by the crusher 23 and then sent to the inlet again In 211, the second embodiment performs preliminary screening through centrifugal separation, which is different from the gravity separation of the first embodiment. It provides another screening method for users to choose, which improves versatility and selectivity. . The screening mechanism 22 may also have a plurality of centrifuges 222 arranged at intervals in the vertical direction to further screen the fallen coarse material 61 and improve the recovery rate. In addition, the air flow 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 preliminarily screen the reduced slag, desulfurization slag or their mixture into fine material 62 and coarse material 61 through the screening mechanism 22, and the air flow guided by the exhaust fan 41 can drive the fine material 62 through the filter bags 321 for continuous filtration. Through the drying and dehydration of the combustion heater 51, the moisture in the material 6 to be sieved and the coarse material 61 can be further removed, so as to filter a high particle diameter below 300 microns. Lime-based materials can effectively increase the content of recycled lime, and can prevent particles with smaller particle diameters from being scattered in the external environment, reduce environmental pollution and impact, and effectively reduce waste in steel plants. The present invention belongs to the market. See the dry lime recovery method, and the material is repeatedly dried and dropped and screened through continuous circulation, which can achieve the highest recovery rate, so it can indeed achieve the purpose of the invention.

However, the above are only examples of the present invention. When the scope of implementation of the present invention cannot be limited by this, all simple equivalent changes and modifications made in accordance with the scope of the patent application of the present invention and the content of the patent specification still belong to This invention patent covers the scope.

1: Lime recovery device 2: Distribution unit 21: Outer Wall 210: internal space 211: Inlet 212: Connecting port 213: Collection Port 214: air inlet 22: Screening mechanism 221: Shelf 222: Centrifuge 223: Fan Blade 23: Crusher 3: Screening unit 31: Outer shell 310: filter space 311: Interface 312: Outlet 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, in which: Figure 1 is a schematic diagram illustrating a first embodiment of the method for dry recovery of lime from the by-products of the self-ironmaking or steelmaking process of the present invention; Figure 2 is an incomplete schematic diagram illustrating the situation in which a screening mechanism performs material distribution in the first embodiment; 3 is a schematic diagram illustrating a second embodiment of the method for dry recovery of lime from the by-products of the self-ironmaking or steelmaking process of the present invention; and Figure 4 is an incomplete schematic diagram illustrating how the screening mechanism performs material separation in the second embodiment.

1: Lime recovery device

2: Distribution unit

21: Outer Wall

210: internal space

211: Inlet

212: Connecting port

213: Collection Port

214: air inlet

22: Screening mechanism

221: Shelf

23: Crusher

3: Screening unit

31: Outer shell

310: filter space

311: Interface

312: Outlet

32: filter material

321: filter bag

4: Negative pressure unit

41: Exhaust fan

5: Heating unit

51: Combustion heater

Claims (10)

A method for dry recovery of lime from by-products of self-ironmaking or steelmaking processes, comprising: A preliminary step is to prepare a lime recovery device. The lime recovery device includes a distributing unit, a screening unit connected to the distributing unit, and a negative electrode for extracting gas from the distributing unit and the screening unit. Pressure unit, and a heating unit; In a feeding step, the negative pressure unit and the heating unit are turned on, the airflow is passed through the material separation unit and the screening unit in sequence, and then discharged to the outside. Then, the selected from the reduction slag, desulfurization slag, or a mixture thereof The filter material to be sieved is placed in the material separation unit, and the airflow is heated by the heating unit to dry the material to be sieved, and the filter material to be sieved will be preliminarily sieved into coarse materials with larger particle diameters in the material separation unit. Fine materials with smaller particle size; and In a sieving step, the airflow drives the fine material in the material to be sieved, and makes the fine material pass through the sieving unit to be further sieved. The fine material passing through the sieving unit is collected to complete the recovery, and the recovered fine material It contains more than 50% lime by weight. The method for dry recovery of lime from the by-products of iron-making or steel-making processes as described in claim 1, wherein, in the preliminary step, the splitting unit includes an outer wall defining an internal space, and a For the screening mechanism in the internal space, the outer wall forms an inlet, a communication port located below the inlet and communicating with the screening unit, and a collection port located below the communicating port and communicating with the bottom of the internal space , The screening mechanism has at least one supporting plate located between the inlet and the collection opening in an up-and-down direction and arranged obliquely, and two ends of the at least one supporting plate respectively extend toward the inlet and the communicating opening, In the feeding step, the material to be screened is fed into the internal space from the inlet, and then hits the at least one supporting plate to be sieved into coarse material and fine material. The coarse material will fall down and enter At the collection port, the fine material is driven by the airflow and enters the screening unit through the communication port. The method for dry recovery of lime from the by-products of ironmaking or steelmaking process according to claim 1, wherein, in the preliminary step, the dividing unit includes an outer wall defining an inner space, and an inner wall For the screening mechanism in the space, the outer wall forms an inlet, a communication port located below the inlet and communicating with the screening unit, and a collection port located below the communicating port and communicating with the bottom of the internal space, the The screening mechanism has at least one centrifuge located between the inlet and the collection port along the vertical direction, and the at least one centrifuge has a plurality of fan blades arranged in a ring shape and rotating shafts parallel to the vertical direction. In the feeding step , The filter material to be screened is sent into the internal space from the inlet, and then hits the at least one centrifuge to be sieved into coarse material and fine material. The coarse material will fall down and enter the collection port. Then, it enters the filtering unit after being driven by the airflow and passing through the communication port. According to claim 2 or 3, the method for dry recovery of lime from the by-products of ironmaking or steelmaking processes, wherein, in the preliminary step, the filtering unit includes an outer shell defining a filtering space, and a set For the filter material in the filtering space of the outer shell, the outer shell forms an interface connecting the communication port of the distributing unit and the filter space, and an outlet connecting the filter space. In the filtering step, the airflow The fine material is driven to pass through the filter material for sieving, and the fine material passing through the filter material is output from the discharge port and collected. According to claim 4, the method for dry recovery of lime from by-products of ironmaking or steelmaking processes, wherein, in the preliminary step, the negative pressure unit includes an exhaust fan connected to the discharge port of the screening unit. According to claim 4, the method for dry recovery of lime from by-products of ironmaking or steelmaking processes, wherein the filter material of the filter unit has a plurality of filter bags fixed on the inner surface of the housing and located in the filter space. The method for dry recovery of lime from the by-products of ironmaking or steelmaking processes as described in claim 2 or 3, wherein, in the feeding step, the coarse material that has fallen into the collection port is introduced into the feeding port to perform the process again Drying and screening. According to claim 2 or 3, the method for dry recovery of lime from by-products of ironmaking or steelmaking processes, wherein, in the preliminary step, the outer wall of the dividing unit also forms a space communicating with the internal space and located in the feed material The heating unit is arranged in the air inlet between the air inlet and the collecting opening. In the feeding step, the air flows into the internal space from the air inlet, and then sequentially passes through the sub-division. The material unit and the filtering unit are then discharged to the outside. The method for dry recovery of lime from the by-products of ironmaking or steelmaking process according to claim 8, wherein, in the preliminary step, the heating unit includes at least one combustion heater switchably arranged in the air inlet. The method for dry recovery of lime from the by-products of ironmaking or steelmaking process according to claim 7, wherein, in the preliminary step, the dividing unit further includes a crusher, and in the feeding step, the collecting The coarse material exported from the mouth is first crushed by the crusher.

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