Method for preparing iron-carbon pellets by using cold rolling sludge and use thereof

Abstract

The application discloses a method and use for preparing iron-carbon pellets from cold rolling oil sludge, and comprises the following steps: S1, stirring and uniformly mixing the dilute oil sludge generated in the cold rolling process with lime at a mass ratio of 1:(0.5-1) to obtain a mixture with a water content of less than 15%; S2, uniformly mixing the mixture obtained in S1 with undersize coke powder, steelmaking OG sludge, steel rolling mill scale, bentonite and polyacrylamide solution to obtain a uniformly mixed material; S3, feeding the uniformly mixed material obtained in S2 into a pair roller ball machine for cold consolidation forming, and the forming pressure is 20-30 MPa, so as to obtain cold-pressed pellets; and S4, drying the cold-pressed pellets obtained in S3 to obtain iron-carbon pellets. The application realizes the resource utilization of waste oil sludge. The cold rolling oil sludge contains iron and oil resources, and the mixing of the cold rolling oil sludge with other solid waste resources of a steel enterprise can not only recover the iron resources, but also fully utilize the oil in the oil sludge to replace the original fuel, so that the fuel consumption is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil sludge resource utilization, and particularly relates to a method for preparing iron-carbon pellets from cold rolling oil sludge and application. BACKGROUND

[0002] The rolling oil sludge is mainly the rolling oil sludge containing a large amount of iron-containing dust sludge generated in the recycling process of the emulsion cooling and lubricating the rolling mill and the steel strip, and has been listed in the National Hazardous Waste List (HW08). The main components of the oil sludge are water content of 27.62%, oil content (30.76%), TFe 63.32% (burning base), and calcium oxide, silicon dioxide residue (3.5%) and other mixtures. The emulsion wastewater is generally filtered through a magnetic filter, and the filter material iron powder and oil sludge are disposed of as hazardous waste, which is high in cost and cannot be disposed of in time in the factory, thus bringing great pressure on the environmental protection of the enterprise. At present, the cold rolling oil sludge is treated as hazardous waste in industry, and the main way is incineration disposal, residue landfill, blending with other solid substances or high-temperature carbonization of the sludge to achieve utilization. However, the above treatments all have negative effects on the environment: 1) During the incineration process of the oil sludge, dioxins or polycyclic aromatic hydrocarbons may be generated, which pollute the atmosphere. Due to the problems of temperature, residence time and process control in the incineration process, a large amount of organic waste gas will be generated. Based on the de novo synthesis reaction, the oil sludge will inevitably generate the de novo formation reaction of dioxins and furans during the incineration disposal process, resulting in air pollution. 2) Oil sludge solidification landfill. The oil sludge solidification landfill has a large disposal amount, but based on the current scarcity of suitable land resources, the cost is high, and there may be seepage pollution to the soil or groundwater. 3) Resource waste: the cold rolling oil sludge contains a large amount of oil and iron resources, and simple disposal not only pollutes the environment but also causes resource waste. Based on the existing background, therefore, it is the key to solve the above problems to find a method for disposing the cold rolling oil sludge at low cost, without secondary pollution, and realizing the recovery of oil and the utilization of iron resources, so as to realize the comprehensive utilization of the cold rolling oil sludge. SUMMARY

[0003] The purpose of the present application is to solve the problems in the background art, and to provide an iron-carbon pellet preparation method and application for the comprehensive utilization of cold rolling oil sludge at low disposal cost and without secondary pollution.

[0004] The technical scheme of the present application is as follows: a method for preparing iron-carbon pellets from cold rolling oil sludge, characterized in that it comprises the following steps,

[0005] S1, stirring and mixing the dilute oil sludge generated in the cold rolling process with lime at a mass ratio of 1:(0.5-1) to obtain a mixture with a water content of <15%;

[0006] S2, mix the mixture obtained in step S1 with under-screen coke powder, steelmaking OG mud, rolled steel millscale, bentonite and polyacrylamide solution to obtain a mixed material, the mass percentage of each component in the mixed material being: 10-15% of the mixture, 10-20% of the under-screen coke powder, 30-45% of the steelmaking OG mud, 30-40% of the rolled steel millscale, 1-5% of the bentonite and 1-6% of the polyacrylamide solution, the mass percentage of each component being 100%;

[0007] S3, send the mixed material obtained in step S2 into a roller press balling machine for cold consolidation forming, the forming pressure being 20-30 MPa, to obtain cold-pressed pellets;

[0008] S4, dry the cold-pressed pellets obtained in step S3 to obtain iron-carbon pellets.

[0009] Preferably, in step S2, the moisture content of the mixed material is controlled to be 6-10%.

[0010] Preferably, in step S2, the carbon content of the under-screen coke powder is 75-85% and the moisture content is <8%.

[0011] Preferably, in step S2, the TFe of the steelmaking OG mud is 50-60% and the moisture content is 12-15%.

[0012] Preferably, in step S2, the TFe of the rolled steel millscale is 70-80% and the moisture content is <5%.

[0013] Preferably, in step S2, the polyacrylamide solution is cationic, the molecular weight is >5 million and the mass concentration is 0.1-0.2%.

[0014] Preferably, in step S2, the bentonite is calcium bentonite, the water absorption rate (2h) is ≥200%, the blue absorption is ≥30 g / 100 g, the swelling index is ≥5 ml / 2 g, the screening rate (75 μm) is ≥95% and the moisture content is 9-13%.

[0015] Preferably, in step S3, the vibration screen is used after forming to obtain cold-pressed pellets with a particle size of 25-50 mm, the cold-pressed pellets being circular or elliptical.

[0016] Preferably, in step S4, the cold-pressed pellets are dried at 100-120°C, the drying time being 5-10 h, and the heat source can be selected to be 0.1-0.2 MPa residual steam.

[0017] Preferably, in step S4, the heat source in the drying chamber can be selected to be low-pressure saturated steam with a pressure of 0.1-0.2 MPa.

[0018] Preferably, in step S4, the obtained iron-carbon pellets satisfy green ball drop strength ≥ 6, dry ball compressive strength ≥ 2500N, and TFe > 40%.

[0019] In the above scheme, TFe is total iron content, carbon content, moisture content, and TFe are all in terms of weight percentage, and the steelmaking OG mud specifically refers to the sludge generated by the wet dust removal system (OG) of the converter gas of a steelmaking plant.

[0020] The application also provides an iron-carbon pellet prepared by any of the above methods for preparing iron-carbon pellets from cold rolling oil sludge. The iron-carbon pellet satisfies green ball drop strength ≥ 6, dry ball compressive strength ≥ 2500N, and TFe > 40%.

[0021] The application also provides an application of an iron-carbon pellet. The iron-carbon pellet is used for steelmaking coolant, torpedo iron-carbon pellet, or sintered pellet.

[0022] In the application, the mixing of the thin oil sludge and lime has the following effects: on the one hand, it is beneficial to the analysis of water in the oil sludge and the reaction with lime, thereby reducing the moisture content of the oil sludge; on the other hand, lime is also a binder, which has the effects of desulfurization and dephosphorization, and the control of the moisture content of the mixed material < 15% is to not only improve the binding capacity of the material, but also maintain a high strength after drying. The effects of the components in the mixed material are as follows: the undersize coke powder is to provide the carbon content required for the metallization rate, and too high or too low is not conducive to the completion of the metallization rate; the steelmaking OG mud is to provide the iron content required for the pellet, and part of the raw material is also beneficial to slag making; the rolling steel scale contains the highest iron content and is the main source of iron; the bentonite is mainly used as an inorganic binder, and the cationic polyacrylamide solution is used as an organic binder. The advantages of the combination of the components are to not only provide the iron content required for the pellet, but also to be beneficial to the pelletizing performance and improve the drop and compressive strength of the pellet.

[0023] The mixed material needs to be controlled to have a moisture content of 6-10%, which is to ensure the pelletizing performance of the green briquette, and the appropriate moisture can improve the capillary force between the materials, and also improve the drop and compressive strength of the briquette.

[0024] The application has the following beneficial effects:

[0025] 1. The resource utilization of waste oil sludge is realized. The cold rolling oil sludge contains iron and oil resources, and the mixing of the cold rolling oil sludge and other solid waste resources of a steel plant can not only recover the iron resource, but also fully utilize the oil in the oil sludge to replace the original fuel and reduce fuel consumption. At the same time, since the pellet is prepared from the oil sludge and other solid waste, the oil fume generated in the process of direct incineration of the oil sludge is reduced, and the pollution to the fan rotor and the environment is reduced. It is an effective resource utilization method, which has obvious environmental and economic benefits.

[0026] 2. The obtained iron-carbon pellets have a drop strength of ≥6 pellets, a dry pellet compressive strength of ≥2500N, and a ferrite content of greater than 40%. Therefore, the iron-carbon pellets have excellent properties of high drop strength and compressive strength, which can be used as a converter coolant to promote converter slag formation. They can also be used in torpedo ladles and blast furnace iron-carbon pellets, which not only meet the self-reduction requirements but also reduce smelting costs and realize the resource utilization of metallurgical solid waste. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of the preparation method of this application. Detailed Implementation

[0028] The following specific embodiments further illustrate the invention in detail. The raw materials used in the following embodiments are: coke powder with a carbon content of 75-85% and a moisture content of less than 8%; steelmaking sludge with a TFe content of 50%-60% and a moisture content of 12-15%; rolled iron oxide scale with a TFe content of 70%-80% and a moisture content of less than 5%; calcium-modified bentonite with a water absorption rate (2h) ≥200%, blue absorption capacity ≥30g / 100g, expansion index ≥5ml / 2g, sieve pass rate (75μm) ≥95%, and a moisture content of 9-13%; and cationic polyacrylamide solution with a molecular weight greater than 5 million and a concentration of 0.1%-0.2%.

[0029] Example 1

[0030] like Figure 1 As shown, the present invention provides a method for preparing iron-carbon pellets using cold-rolled sludge, comprising the following steps:

[0031] S1. First, the sludge produced in the cold rolling process is fed into a mixer. Then, lime is added to the mixer and stirred until homogeneous. The mass ratio of lime to sludge is 1:1. The moisture content of this batch of mixture is measured to be 9.8%.

[0032] S2. Continue to add undersize coke powder, steelmaking OG sludge, steel rolling mill iron oxide scale, bentonite, and 0.2% cationic polyacrylamide solution to the mixer and mix to obtain a homogenized material. The mass percentage of each component in the homogenized material is as follows: 10% homogenized material, 15% undersize coke powder, 40% steelmaking OG sludge, 30% steel rolling mill iron oxide scale, 1% bentonite, and 4% cationic polyacrylamide solution. The moisture content of the final homogenized material after mixing is controlled at 8.7%.

[0033] S3. The mixture is fed into a roller briquetting machine for cold solidification and molding. The molding pressure is 20MPa, and the mixture is vibrated and screened to obtain cold-pressed pellets with a particle size of 25-50mm.

[0034] S4. Then, place the formed cold-pressed pellets in a drying chamber at 105℃ for 5 hours to obtain iron-carbon pellets.

[0035] The green ball drop strength of the iron-carbon pellet is 7, the average dry ball compression strength is 2500N, and the TFe content is 45.2%.

[0036] Example 2

[0037] As shown in the Figure 1 The application provides a method for preparing iron-carbon pellets from cold rolling oil sludge, which comprises the following steps:

[0038] S1, first, the oil sludge generated in the cold rolling process is sent into a mixing mill, then lime is added into the mixing mill, and stirring and mixing are performed, wherein the ratio of lime to dilute oil sludge is 0.75:1, and the moisture of the batch of mixed materials is 12.3%.

[0039] S2, continue to add undersize coke powder, steelmaking OG sludge, rolled steel oxide scale, bentonite and a cationic polyacrylamide solution with a mass concentration of 0.2% into the mixing mill, and mix to obtain mixed materials, wherein the mass percentage of each component in the mixed materials is: 10% of the mixed materials, 10% of the undersize coke powder, 45% of the steelmaking OG sludge, 30% of the rolled steel oxide scale, 2.5% of the bentonite and 2.5% of the cationic polyacrylamide solution, and the moisture of the final mixed materials is controlled at 6.4% after mixing.

[0040] S3, the mixed materials are sent into a pair roller pelletizer for cold consolidation and forming, the forming pressure is 25MPa, and the vibration screen is divided to obtain cold pressed pellets with a particle size of 25-50mm;

[0041] S4, then, the formed cold pressed pellets are placed in a drying room at 105℃ for 7.5h to obtain iron-carbon pellets.

[0042] The green ball drop strength of the iron-carbon pellet is 7, the average dry ball compression strength is 2500N, and the TFe content is 45.2%.

[0043] Example 3

[0044] As shown in the Figure 1 The application provides a method for preparing iron-carbon pellets from cold rolling oil sludge, which comprises the following steps:

[0045] S1, first, the oil sludge generated in the cold rolling process is sent into a mixing mill, then lime is added into the mixing mill, and stirring and mixing are performed, wherein the ratio of lime to dilute oil sludge is 0.75:1, and the moisture of the batch of mixed materials is 12.3%.

[0046] S2, continue to add undersize coke powder, steelmaking OG mud, rolling steel oxide scale, bentonite and 0.2% cationic polyacrylamide solution to the mixer, mix to obtain mixed material, the mass percentage of each component in the mixed material is: 20% undersize coke powder, 30% steelmaking OG mud, 35% rolling steel oxide scale, 4% bentonite and 1% cationic polyacrylamide solution, and the moisture of the final mixed material is controlled at 8% after mixing.

[0047] S3, send the mixed material into a pair of roller ball press to perform cold consolidation forming, the forming pressure is 30 MPa, and the vibration sieve is divided to obtain cold pressed pellets with a particle size of 25-50 mm;

[0048] S4, then place the formed cold pressed pellets in a 105℃ drying room for 10 h to obtain iron-carbon pellets.

[0049] It is determined that the green ball drop strength of the iron-carbon pellets is 10, the average dry ball compression strength is 3560 N, and the TFe content is 53.7%.

[0050] Example 4

[0051] As shown in Figure 1 , the present application provides a method for preparing iron-carbon pellets from cold rolling oil mud, comprising the following steps:

[0052] S1, first send the oil mud generated in the cold rolling process into a mixer, then add lime into the mixer, stir and mix, wherein the ratio of lime to thin oil mud is 0.5:1, and the moisture of the mixed material is measured to be 14%.

[0053] S2, continue to add undersize coke powder, steelmaking OG mud, rolling steel oxide scale, bentonite and 0.2% cationic polyacrylamide solution to the mixer, mix to obtain mixed material, the mass percentage of each component in the mixed material is: 20% undersize coke powder, 30% steelmaking OG mud, 35% rolling steel oxide scale, 4% bentonite and 1% cationic polyacrylamide solution, and the moisture of the final mixed material is controlled at 8% after mixing.

[0054] S3, send the mixed material into a pair of roller ball press to perform cold consolidation forming, the forming pressure is 30 MPa, and the vibration sieve is divided to obtain cold pressed pellets with a particle size of 25-50 mm;

[0055] S4, then place the formed cold pressed pellets in a 105℃ drying room for 10 h to obtain iron-carbon pellets.

[0056] It is determined that the green ball drop strength of the iron-carbon pellets is 10, the average dry ball compression strength is 3560 N, and the TFe content is 53.7%.

[0057] The iron-carbon pellets prepared in the above examples 1-4 can be used as steelmaking coolant, iron-carbon pellets for torpedoes or sintered pellets.

Claims

1. A method for preparing iron-carbon pellets using cold-rolled sludge, characterized in that, Includes the following steps, S1. Mix the thin oily sludge produced in the cold rolling process with lime at a mass ratio of 1:(0.5~1) to obtain a mixture with a moisture content of <15%; S2. The mixture obtained in step S1 is mixed with undersized coke powder, steelmaking OG sludge, rolling mill iron oxide scale, bentonite, and polyacrylamide solution to obtain a homogenized material. The mass percentage of each component in the homogenized material is as follows: mixture 10%–15%, undersized coke powder 10%–20%, steelmaking OG sludge 30%–45%, rolling mill iron oxide scale 30%–40%, bentonite 1%–5%, and polyacrylamide solution 1%–6%. The total mass percentage of all the above components is 100%. The moisture content of the mixed material is controlled at 6-10%, the carbon content of the undersize coke powder is 75-85%, and the moisture content is <8%, the TFe content of the steelmaking OG sludge is 50-60%, and the moisture content is 12-15%, the TFe content of the rolled iron oxide scale is 70%-80%, and the moisture content is <5%, and the polyacrylamide solution is cationic, with a molecular weight >5 million and a mass concentration of 0.1%-0.2%. S3. The mixed material obtained in step S2 is fed into a double roller briquetting machine for cold solidification molding. The molding pressure is 20-30MPa to obtain cold-pressed briquettes. S4. Dry the cold-pressed pellets obtained in step S3 to obtain iron-carbon pellets.

2. The method for preparing cold-rolled sludge pellets as described in claim 1, characterized in that, In step S4, the cold-pressed pellets are dried at 100-120°C for 5-10 hours.

3. The method for preparing cold-rolled sludge pellets as described in claim 1, characterized in that, In step S4, the obtained iron-carbon pellets meet the following requirements: green pellet drop strength ≥ 6, dry pellet compressive strength ≥ 2500N, and TFe > 40%.

4. An iron-carbon pellet, characterized in that, It is prepared by any of the methods for preparing iron-carbon pellets using cold-rolled sludge as described in claims 1 to 3.

5. An application of the iron-carbon pellets as described in claim 4, characterized in that, Used as a coolant in steelmaking, and as iron-carbon pellets or sintered pellets for torpedoes.

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