A method for internal short-process resource utilization of hot-rolled oily sludge

Abstract

The application discloses a kind of short process resource utilization methods of hot rolling oily sludge inside, belong to resource comprehensive utilization field.It includes the following steps: one, the iron oxide scale generated by cyclonic sedimentation tank is dried and then screened, and the screened iron oxide scale is sent to the bunker;Two, the hot rolling oily sludge generated by horizontal flow sedimentation tank is sent to the hopper after dewatering treatment, and the oily wastewater generated during the dewatering process is returned to the turbid circulating water treatment system for recycling;Three, the iron oxide scale and hot rolling oily sludge treated in step one and step two are mixed with quicklime powder according to the set proportion, and then stirred, the mixed material obtained by stirring is sent to the ball press to be pressed into balls, and then the qualified mixed material balls are returned to steelmaking as cooling agent.The application adds the treatment of hot rolling oily sludge on the basis of the original hot rolling turbid circulating water treatment system, and combines the original steelmaking production process, to realize the short process resource recycling utilization of hot rolling oily sludge in steelmaking production.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive resource utilization technology, and more specifically, relates to a short-process resource utilization method for hot-rolled oily sludge. Background Technology

[0002] Oily sludge from hot rolling mills in steel enterprises is the sludge settled in the horizontal flow tank of the hot rolling mill's turbid circulating water system. It appears as a thick, brownish-black mud containing water, oil, and slag. Compared to other oily sludge, hot rolling sludge has a higher density and finer granular structure due to the presence of iron oxide particles, making it prone to forming "oil sludge clumps." Its dry-basis iron content exceeds 60%. The water content of the oily sludge after sedimentation in the horizontal flow tank exceeds 60%, with an oil content of 1-5%. The oil content varies depending on the rolling mill's production operation and the oil removal efficiency of the turbid circulating water treatment system. Due to its high oil content, dewatering treatment using belt filter presses and plate and frame filter presses is not only ineffective but also prone to clogging of filter bags and cloths, affecting operation. Therefore, hot rolling oily sludge is difficult to directly recycle within steel enterprises due to its high water and oil content.

[0003] Chinese patent application number CN202210580593.8, published on August 26, 2022, discloses a method for drying and resource utilization of oily hot-rolled sludge. This method primarily uses a high-pressure pressing system to dewater the hot-rolled sludge, resulting in a sludge moisture content of less than 20% and an oil content of less than 1%. The sludge is then crushed to below 10mm and reused in sintering. While this method reduces sludge moisture content through high-pressure filtration, relying solely on filtration is insufficient to guarantee effective oil removal. If the oil content of the sludge after filtration is too high, reuse in sintering not only affects the granulation effect of the sintered mixture but also risks some of the oily substances volatilizing into the flue gas during the low-temperature sintering stage, impacting the dust removal system. Furthermore, this method does not address the treatment of oily wastewater after filtration.

[0004] A Chinese patent application, CN202111273918.X, published on December 31, 2021, discloses a system and process for the co-utilization of rolling mill sludge and chromium-containing dust. The system involves mixing rolling mill sludge and chromium-containing dust in a specific ratio, with the addition of a small amount of coke powder during the mixing stage. The mixture is then fed into a decoupled pyrolysis reactor for pyrolysis and polymerization. The resulting combustible organic gases are combusted in a combustion reactor, and the flue gas is treated for desulfurization and denitrification to meet emission standards. The solid products from the pyrolysis reactor are cooled, briquetted, and used as raw materials in a steel plant converter, or fed into a melting reactor where specific elements are added to form steel products. However, this scheme primarily considers the co-processing of rolling mill sludge and chromium-containing dust, involving a relatively long process flow and high energy consumption.

[0005] Chinese patent application number CN201610119952.4, published on June 22, 2016, discloses a self-reduction utilization process for oily sludge from steel rolling mills and blast furnace gas ash. The process involves mixing limestone powder, blast furnace gas ash, and oily sludge from steel rolling mills in a mass ratio of 10:75:15 using a conventional vertical mixer. After uniform mixing, the mixture is pressed into pellets with a diameter of 30-50 mm using a double-roll cold-pressing briquetting machine. During the converter slag removal process, these pellets are added to the slag pot along with the steel slag, or added from the top of a slag pot containing liquid steel slag, with a mass ratio of pellets to steel slag of 1:10. After the pellets are added, the slag pot is allowed to stand for 60±20 minutes, and then the steel slag is processed according to the normal hot slag quenching process. This scheme involves mixing rolling mill sludge with blast furnace gas ash and limestone powder, briquetting the mixture, and then adding it to hot steel slag. The hot steel slag provides the temperature conditions to reduce iron oxides in the mixture by carbon. However, the briquetting product is added to a slag pot, where the heat of the slag pot is used to achieve the reduction reaction between carbon in the blast furnace gas ash and iron oxides in the material. Since the metallic iron after the reaction exists in the steel slag, the subsequent recycling process still requires multiple crushing, grinding, and magnetic separation processes, resulting in low resource utilization efficiency.

[0006] Chinese patent application number CN202210534687.1, published on August 12, 2022, discloses a method and system for treating oily sludge water from steel rolling in a rotary hearth furnace. The system includes an oil-water separator, a mixer, a roller briquetting machine, a drying device, a rotary hearth furnace, a waste heat boiler, and a baghouse dust collector. This solution suffers from overly complex processes and high costs.

[0007] This invention fully considers the characteristics of hot-rolled oily sludge generation in steel enterprises, its own physicochemical properties, and the characteristics of internal steelmaking processes. It proposes a method for the internal resource utilization of hot-rolled oily sludge in steel enterprises. The method involves mixing the iron oxide scale generated during the hot-rolled circulating water treatment process with the oily sludge in a certain proportion by controlling its moisture content, pressing it into balls, and returning it to the steelmaking process as a coolant for recycling. At the same time, the oily wastewater generated from the dehydration of the oily sludge is returned to the hot-rolled circulating water treatment system for recycling and utilization, thereby realizing the full resource utilization of hot-rolled oily sludge within the steel enterprise. Summary of the Invention

[0008] 1. The problem to be solved

[0009] In view of the high water and oil content of hot-rolled oily sludge in steelmaking production, which makes direct internal recycling difficult and existing technologies are unable to solve this problem perfectly, this invention provides a short-process resource utilization method for hot-rolled oily sludge. Based on the original hot-rolled turbid circulating water treatment system, the treatment of hot-rolled oily sludge is added. Combined with the original steelmaking production process, the short-process resource recycling of hot-rolled oily sludge in steelmaking production is realized.

[0010] 2. Technical Solution

[0011] To solve the above problems, the present invention adopts the following technical solution.

[0012] A method for short-process internal resource utilization of hot-rolled oily sludge includes the following steps:

[0013] 1. After drying the iron oxide scale produced in the cyclone sedimentation tank of the hot rolling turbid circulating water treatment system, the iron oxide scale is screened and then sent to the silo.

[0014] 2. The hot-rolled oily sludge generated in the horizontal sedimentation tank of the hot-rolled turbid circulating water treatment system is dewatered and then sent to the hopper. The oily wastewater generated during the dewatering process is returned to the turbid circulating water treatment system for recycling.

[0015] 3. The iron oxide scale and hot-rolled oily sludge processed in steps 1 and 2 are mixed with quicklime powder according to a set ratio. The resulting mixture is then fed into a briquetting machine to be pressed into balls. The qualified briquetting balls are then returned to the steelmaking plant as a coolant.

[0016] As a further improvement to the technical solution, in step three, the pressed mixed balls are screened using a roller screen with a gap of 10mm. After screening, the undersize portion enters the return material silo for later use, while the oversize portion is returned to steelmaking as a finished product.

[0017] As a further improvement to the technical solution, in step three, the briquette return material is added and stirred together before mixing. The mass percentage of various materials in the mixture is as follows: iron oxide scale: 30-45%, hot-rolled oily sludge: 40-55%, quicklime powder: 0-5%, and briquette return material: 0-10%.

[0018] As a further improvement to the technical solution, in step one, the moisture content of the dried iron oxide scale is ≤4%.

[0019] As a further improvement to the technical solution, in one step, the moisture content of the dried iron oxide scale is 2.9% to 4%.

[0020] As a further improvement to the technical solution, in step two, the moisture content of the dehydrated hot-rolled oily sludge is ≤8%.

[0021] As a further improvement to the technical solution, in step two, the moisture content of the dehydrated hot-rolled oily sludge is 5.9% to 8%.

[0022] As a further improvement to the technical solution, in step three, the quicklime powder needs to meet the following conditions: CaO content not less than 85% and particle size not greater than 200 mesh.

[0023] As a further improvement to the technical solution, in the briquetting process of step three, the pre-pressing frequency of the briquetting machine is 30-35Hz, and the frequency of the main motor is 15-20Hz.

[0024] As a further improvement to the technical solution, in step three, qualified mixed pellets need to meet the following conditions: TFe≧55%, moisture content≦5.5%, and 2m drop strength≧5 times.

[0025] 3. Beneficial effects

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) The present invention provides a short-process resource utilization method for hot-rolled oily sludge. Based on the original hot-rolled turbid circulating water treatment system, it adds creative treatment measures for hot-rolled oily sludge. It mixes iron oxide scale and hot-rolled oily sludge, which are high-iron solid wastes, with corresponding ingredients and directly presses them into balls. The high-grade balls are directly returned to steelmaking as coolant. This not only solves the problem of difficult solid waste treatment, but also realizes the short-process full-quantity recycling of hot-rolled oily sludge. The process is simple and efficient. In particular, through the unique treatment research of the raw materials of the mixed balls, the method makes the iron oxide scale and hot-rolled oily sludge exactly in the same moisture content range and maintains a unique ratio range with the other ingredients. Thus, without increasing time and production costs, the final mixed balls have extremely high quality, which greatly improves the effectiveness of the method.

[0028] (2) The present invention provides a short-process resource utilization method for hot-rolled oily sludge, which utilizes the strong oil content and viscosity of iron oxide scale and oily sludge as a binder for briquetting. This not only avoids the problem of oil volatilization in the low-temperature zone affecting the flue gas dust removal system in the traditional oily sludge return sintering utilization, but also reduces the use of binders in the traditional briquetting process.

[0029] (3) The present invention provides a short-process resource utilization method for hot-rolled oily sludge. By utilizing the oil removal capacity of the turbid circulating water treatment system, the oily wastewater generated by the dewatering treatment of hot-rolled oily sludge produced in the horizontal flow tank is returned to the horizontal flow sedimentation tank of the turbid circulating water system for treatment, thereby realizing the treatment and recycling of wastewater. Attached Figure Description

[0030] Figure 1This diagram illustrates the internal short-process resource utilization technology for hot-rolled oily sludge. The solid line represents the typical hot-rolled turbid water treatment and recycling system in steel enterprises, while the dashed line represents the internal short-process resource utilization technology for hot-rolled oily sludge of this invention. Detailed Implementation

[0031] Exemplary embodiments of the present invention are described in detail below. While these exemplary embodiments have been described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be implemented and various changes may be made to the invention without departing from its spirit and scope. The more detailed description of embodiments of the invention below is not intended to limit the scope of the claimed invention, but is merely illustrative and does not limit the description of the features and characteristics of the invention, in order to suggest the best mode for carrying out the invention and to enable those skilled in the art to practice it. Therefore, the scope of the invention is defined only by the appended claims.

[0032] like Figure 1 As shown, a short-process resource utilization method for hot-rolled oily sludge is proposed. Based on the original hot-rolled turbid circulating water treatment system, the treatment of hot-rolled oily sludge is added. Combined with the original steelmaking production process, the short-process resource recycling of hot-rolled oily sludge in steelmaking production is realized. The specific steps and technical effects are described in detail below.

[0033] The method includes the following steps:

[0034] 1. After the iron oxide scale produced in the cyclone sedimentation tank of the hot rolling turbid circulating water treatment system is naturally dried, it is screened through a 10mm vibrating screen. The portion above the screen is conveyed by belt to a crusher for further crushing and then screened again. The portion below the screen is sent to a silo for later use. The moisture content of the dried iron oxide scale should be ≤4%, with an optimal range of 2.9% to 4%.

[0035] 2. The hot-rolled oily sludge generated in the horizontal flow sedimentation tank of the hot-rolled turbid circulating water treatment system is dewatered and then sent to the hopper. The oily wastewater generated during the dewatering process is recycled into the system through the horizontal flow sedimentation tank. The moisture content of the dewatered hot-rolled oily sludge should be ≤8%, with an optimal range of 5.9%–8%. Dewatering can be achieved using belt filter press or plate and frame filter press followed by natural drying, or direct hydraulic filter press. After dewatering, the proportion of sludge particles ≤5mm after spiral agitation should be no less than 80%.

[0036] 3. The iron oxide scale and hot-rolled oily sludge processed in steps one and two are mixed with quicklime powder according to a set ratio. The resulting mixture is then fed into a briquetting machine to be pressed into briquettes. Qualified briquettes are then returned to the steelmaking plant for use as a coolant. The quicklime powder must meet the following conditions: CaO content not less than 85%, particle size not greater than 200 mesh. During briquetting, the pre-pressing frequency of the briquetting machine is 30–35 Hz, and the main motor frequency is 15–20 Hz.

[0037] The pressed mixture briquettes are screened using a roller screen with a 10mm gap. After screening, the undersize portion enters the return material silo for later use, while the oversize portion is returned to steelmaking as finished product. Simultaneously, during continuous production, the returned briquettes are also incorporated into the briquette forming process in step three. Specifically, before mixing, iron oxide scale, hot-rolled oily sludge, quicklime powder, and returned briquettes are proportioned as follows: iron oxide scale: 30-45%, hot-rolled oily sludge: 40-55%, quicklime powder: 0-5%, returned briquettes: 0-10%.

[0038] The final qualified mixed pellets must meet the following conditions: TFe ≥ 55%, moisture content ≤ 5.5%, and drop strength ≥ 5 times from 2m (i.e., they will not break within 5 drops). Based on actual smelting needs, the amount of returned qualified mixed pellets used is 5 kg to 20 kg per ton of steel.

[0039] This method adds innovative treatment measures for hot-rolled oily sludge to the existing hot-rolled turbid water treatment system. It mixes high-iron-content solid wastes such as iron oxide scale and hot-rolled oily sludge with appropriate ingredients and directly presses them into pellets. The resulting high-grade pellets are directly returned to steelmaking as a coolant. This not only solves the problem of difficult solid waste treatment but also achieves short-process, full-scale recycling of hot-rolled oily sludge. The process is simple and efficient. In particular, through unique research on the raw materials of the mixed pellets, this method ensures that the iron oxide scale and hot-rolled oily sludge are within a specific moisture content range and maintain a unique ratio with the other ingredients. This results in extremely high-quality mixed pellets without increasing time or production costs, greatly improving the effectiveness of the method.

[0040] Furthermore, this method utilizes the inherent oiliness and viscosity of iron oxide scale and oily sludge as a binder for briquetting. This not only avoids the problem of oil volatilization at low temperatures affecting the flue gas dust removal system, which is present in traditional oily sludge recycling processes, but also reduces the amount of binder used in traditional briquetting. Simultaneously, leveraging the oil removal capacity of the circulating water treatment system, the oily wastewater generated from the dewatering of hot-rolled oily sludge in the horizontal flow tank is returned to the horizontal flow sedimentation tank of the circulating water system for further treatment, achieving wastewater treatment and recycling.

[0041] The following examples from specific production processes provide further details.

[0042] Example 1

[0043] The iron oxide scale produced by the cyclone sedimentation tank of the hot rolling turbid circulating water treatment system is naturally dried to a moisture content of 3.6%. It is then screened through a 10mm vibrating screen. The portion above the screen is conveyed by belt to a crusher for further crushing and then screened again. The portion below the screen is sent to a silo for later use. The oil content is 0.4% after sampling and testing.

[0044] The hot-rolled oily sludge generated in the horizontal flow sedimentation tank of the hot-rolled turbid circulating water treatment system is dewatered by hydraulic pressure filtration, with a moisture content of 6.8%. After being dispersed by a screw, it is transported to the sludge hopper for later use. The sludge particle size is less than 5mm, accounting for 85.1%. The oil content is 3.5% after sampling and testing. The oily wastewater generated by pressure filtration enters the system for recycling through the horizontal flow sedimentation tank of the turbid circulating water treatment system.

[0045] Iron oxide scale, hot-rolled oily sludge, quicklime powder, and briquetting return material were mixed in a ratio of 40:48:3:9 and then fed into a high-pressure mixer for thorough mixing. The mixture was then pressed into briquettes using a high-pressure roller briquetting machine with a pre-pressing frequency of 30Hz and a main motor frequency of 15Hz. After sieving, the undersize portion was sent to a return material silo for later use, while the oversize portion was tested and found to have a TFe content of 65.5%, a moisture content of 4.9%, and a 2m drop strength of 11 times.

[0046] The finished balls are returned to the converter for steelmaking and added at a rate of 8.5 kg per ton of steel after about 8 minutes of oxygen blowing in the converter.

[0047] Example 2

[0048] The iron oxide scale produced by the cyclone sedimentation tank of the hot rolling turbid circulating water treatment system is naturally dried to a moisture content of 2.9%. It is then screened through a 10mm vibrating screen. The portion above the screen is conveyed by belt to a crusher for further crushing and then screened again. The portion below the screen is sent to a silo for later use. The oil content is 0.4% after sampling and testing.

[0049] The hot-rolled oily sludge generated in the horizontal sedimentation tank of the hot-rolled turbid circulating water treatment system is dewatered by hydraulic pressure filtration, with a moisture content of 5.9%. After being dispersed by a screw conveyor, the sludge is sent to the sludge hopper for later use. 82.3% of the sludge particles are less than 5mm in size. The oil content was found to be 3.8% after sampling and testing. The oily wastewater generated by pressure filtration is recycled into the system through the horizontal sedimentation tank of the turbid circulating water treatment system.

[0050] Iron oxide scale, hot-rolled oily sludge, quicklime powder, and briquetting return material were mixed in a ratio of 35:50:5:10 and fed into a high-pressure mixer for thorough mixing. The mixture was then pressed into briquettes using a high-pressure roller briquetting machine with a pre-pressing frequency of 33Hz and a main motor frequency of 18Hz. After sieving, the undersize portion was sent to a return material silo for later use, while the oversize portion was tested and found to have a TFe content of 63.4%, a moisture content of 5.3%, and a drop strength of 9 times at 2m.

[0051] The finished balls are returned to the converter for steelmaking and added at a rate of 7 kg per ton of steel after about 8 minutes of oxygen blowing in the converter.

[0052] Example 3

[0053] The iron oxide scale produced by the cyclone sedimentation tank of the hot rolling turbid circulating water treatment system is naturally dried to a moisture content of 3.3%. It is then screened through a 10mm vibrating screen. The portion above the screen is conveyed by belt to a crusher for further crushing and then screened again. The portion below the screen is sent to a silo for later use. The oil content is 0.4% after sampling and testing.

[0054] The hot-rolled oily sludge generated in the horizontal flow sedimentation tank of the hot-rolled turbid circulating water treatment system is dewatered by hydraulic pressure filter, with a moisture content of 6.2%. After being dispersed by a screw, it is transported to the sludge hopper for later use. The sludge particle size is less than 5mm, accounting for 86.1%. The oil content is 4.1% after sampling and testing. The oily wastewater generated by pressure filter enters the system for recycling through the horizontal flow sedimentation tank of the turbid circulating water treatment system.

[0055] Iron oxide scale, hot-rolled oily sludge, quicklime powder, and briquetting return material were mixed in a ratio of 33:55:2:10 and fed into a high-pressure mixer for thorough mixing. The mixture was then pressed into briquettes using a high-pressure roller briquetting machine with a pre-pressing frequency of 35Hz and a main motor frequency of 18Hz. After sieving, the undersize portion was sent to a return material silo for later use, while the oversize portion was tested and found to have a TFe content of 62.5%, a moisture content of 5.1%, and a 2m drop strength of 14 times.

[0056] The finished balls are returned to the converter for steelmaking and added at a rate of 13 kg per ton of steel after about 8 minutes of oxygen blowing in the converter.

[0057] The examples described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. A method for the internal short-process resource utilization of hot-rolled oily sludge, characterized in that: Includes the following steps:

1. After drying the iron oxide scale produced in the cyclone sedimentation tank of the hot rolling turbid circulating water treatment system, the iron oxide scale is screened and then sent to the silo.

2. The hot-rolled oily sludge generated in the horizontal sedimentation tank of the hot-rolled turbid circulating water treatment system is dewatered and then sent to the hopper. The oily wastewater generated during the dewatering process is returned to the turbid circulating water treatment system for recycling.

3. The iron oxide scale and hot-rolled oily sludge processed in steps 1 and 2 are mixed with quicklime powder according to the set ratio. The resulting mixture is then fed into a briquetting machine to be pressed into balls. The qualified briquetting balls are then returned to the steelmaking plant as a coolant. In step one, the moisture content of the dried iron oxide scale is 2.9%~4%; In step two, the moisture content of the dehydrated hot-rolled oily sludge is 5.9%~8%; In step three, the briquette return material is added and stirred together before mixing. The mass percentage of each material in the mixture is as follows: iron oxide scale: 30-45%, hot-rolled oily sludge: 40-55%, quicklime powder: 0-5%, briquette return material: 0-10%.

2. The method for short-process internal resource utilization of hot-rolled oily sludge according to claim 1, characterized in that: In step three, the pressed mixture balls are screened using a roller screen with a gap of 10mm. After screening, the undersize portion enters the return material silo for later use, while the oversize portion is returned to steelmaking as finished product.

3. A method for short-process internal resource utilization of hot-rolled oily sludge according to claim 1 or 2, characterized in that: In step three, the quicklime powder needs to meet the following conditions: CaO content not less than 85%, and particle size not greater than 200 mesh.

4. A method for short-process internal resource utilization of hot-rolled oily sludge according to claim 1 or 2, characterized in that: During the briquetting process in step three, the briquetting machine has a pre-pressing frequency of 30~35Hz and a main motor frequency of 15~20Hz.

5. A method for short-process internal resource utilization of hot-rolled oily sludge according to claim 1 or 2, characterized in that: In step three, qualified mixed pellets need to meet the following conditions: TFe ≥ 55%, moisture content ≤ 5.5%, and drop strength ≥ 5 times at 2m.

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