Co-processing method of waste activated carbon and hot rolling sludge

Abstract

This invention discloses a method for the co-processing of waste activated carbon and hot-rolled sludge, comprising the following steps: taking hot-rolled sludge, solvent, and concentrated sulfuric acid, adding them to a mixing tank, mixing, and stirring to break the emulsion for 5-10 minutes; adding waste activated carbon to the mixture after the emulsification treatment, and continuing to stir for 30-45 minutes; sending the stirred mixture to an aging tank, and aging and settling for 60-90 minutes; separating the activated carbon from the upper layer of the aging tank to obtain recycled activated carbon, drying the recycled activated carbon, and using it for blast furnace pulverized coal injection; filtering the remaining mixture to obtain filtrate and filter residue, collecting the filter residue, and re-sintering for use; the filter residue is iron oxide scale. This invention is simple and practical, requiring only simple process facilities and existing process equipment in the main process of a steel plant to achieve the co-processing of multiple solid and hazardous wastes from steel plants. It is lower in cost than treating and utilizing each type of solid and hazardous waste separately, has better technical and economic efficiency, and offers advantages such as low cost, simple recycling method, and environmental friendliness.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically to a method for the co-processing of waste activated carbon and hot-rolled sludge. Background Technology

[0002] Steel companies typically use sintering activated carbon desulfurization to treat sintering flue gas. However, the waste activated carbon produced by the sintering activated carbon desulfurization process and the hot rolling sludge produced by the hot rolling circulating water are both hazardous solid wastes controlled by the national hazardous waste list and cannot be disposed of arbitrarily. The disposal of these two types of solid wastes requires a lot of costs and consumes a lot of resources.

[0003] Waste activated carbon (mainly carbon-containing) can be recycled as fuel for blast furnace pulverized coal injection, but it suffers from low combustion activity and requires processing; direct recycling negatively impacts pulverized coal combustion. Adding a catalytic combustion aid to waste activated carbon may improve its combustion efficiency. Chinese invention patent CN103013616B discloses a catalytic combustion aid for blast furnace pulverized coal injection and its application method. This method involves finely grinding and mixing dicyclopentadienyl iron or potassium permanganate, lanthanum oxide, persimmon oxide, calcium peroxide, and magnesium peroxide, and then using this mixture in blast furnace pulverized coal injection to promote the early release of coal chemical energy and improve pulverized coal combustion. However, this method requires the addition of precious metal materials, resulting in high catalytic costs.

[0004] Hot-rolled sludge contains a large amount of iron oxide scale (including iron oxides such as Fe2O3 and Fe3O4), which can theoretically be recycled for sintering. However, the presence of a certain amount of oil hinders the mixing of iron ore powder and negatively impacts sintering production. Current technology primarily treats hot-rolled sludge using air flotation for degreasing. Patent application CN106809912A provides an air flotation degreasing system and method for hot-rolled sludge, including a sludge hopper, screw feeder, mixing tank, water pump, air flotation tank, and oil skimmer, separating oily wastewater and iron sludge. However, both the iron sludge and oily wastewater require further treatment, resulting in a long hot-rolled sludge recycling process and correspondingly high recycling costs.

[0005] In view of the current problems of high recycling costs in the treatment of waste activated carbon and complex and costly methods for the resource utilization of hot-rolled sludge, there is an urgent need to provide an environmentally friendly and simple method for the disposal of waste activated carbon and hot-rolled sludge, so as to achieve the purpose of harmless treatment and resource utilization of solid and hazardous waste and reduce costs. Summary of the Invention

[0006] To overcome the shortcomings of the above-mentioned technologies, the purpose of this invention is to provide a method for the co-processing of waste activated carbon and hot-rolled sludge, which solves the problems of high recycling costs in the treatment of waste activated carbon and complex and costly methods for the resource utilization of hot-rolled sludge. This method achieves the harmless disposal of hazardous solid waste and recovers and utilizes ferrite and fuel resources to replace conventional raw materials and fuels, and has the advantages of being environmentally friendly and having low processing costs.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for the co-processing of waste activated carbon and hot-rolled sludge includes the following steps:

[0009] 1) Take hot-rolled sludge, solvent, and concentrated sulfuric acid, add them to a mixing tank, mix, and stir to break the emulsion for 5-10 minutes;

[0010] 2) Add waste activated carbon to the mixture after demulsification treatment and continue stirring for 30-45 minutes;

[0011] 3) Transfer the stirred mixture into an aging tank and allow it to stand for 60–90 minutes.

[0012] 4) Separate the activated carbon from the upper layer of the aging tank to obtain recycled activated carbon;

[0013] 5) The recovered activated carbon is dried and then used for pulverized coal injection in the blast furnace;

[0014] 6) Filter the remaining mixture to obtain filtrate and filter residue. Collect the filter residue and return it to the steel sintering process.

[0015] Preferably, the amount of each raw material used, by mass, is: 10 parts hot-rolled sludge, 200-250 parts solvent, 2-4 parts concentrated sulfuric acid, and 20-30 parts waste activated carbon.

[0016] Preferably, the hot-rolled sludge is waste discharged from the hot-rolling turbid water process of a steel plant, comprising solid iron oxide scale, oil, and water, with a water content of 10-20%, an oil content of 5-10%, and a solid content of 70-85%. The solid phase chemical composition of the hot-rolled sludge is: TFe ≥ 70.0%, C ≤ 3.0%, MnO ≤ 0.5%, CaO ≤ 1.0%, MgO ≤ 0.5%, SiO2 ≤ 2.0%, Al2O3 ≤ 0.2%, Cl ≤ 0.2%, S ≤ 0.1%, P ≤ 0.1%, with the balance being O element combined with Fe and other unavoidable impurities. The solid phase particle size characteristics of the hot-rolled sludge are: particle content of 0.3-2 mm ≥ 50%, and particle content of less than 0.075 mm ≤ 5%.

[0017] Preferably, the solvent is water; the concentrated sulfuric acid is industrial concentrated sulfuric acid with a mass fraction of 98%.

[0018] Preferably, the waste activated carbon is activated carbon discarded from the flue gas desulfurization process of a steel plant, and its chemical composition is: C≥92.0%, with the remainder being water and other unavoidable impurities; the content of particles with a particle size of 0.5-2mm in the waste activated carbon is greater than 90%.

[0019] Preferably, in step 4), the separation of the activated carbon in the upper layer of the aging tank is achieved by a slag remover.

[0020] Preferably, in step 5), before using the recycled activated carbon for blast furnace pulverized coal injection, the recycled activated carbon is first mixed with anthracite and ground; the moisture content of the recycled activated carbon is 10-15%; and the moisture content of the anthracite is ≤1.0%.

[0021] Preferably, the mass ratio of the recovered activated carbon to anthracite is 2-5:100.

[0022] Preferably, in step 6), the filter residue is iron oxide scale with an oil content ≤1.0%.

[0023] Preferably, the method further includes the following steps: using the filtrate filtered in step 6) as a solvent for the next round of co-processing of waste activated carbon and hot-rolled sludge, and supplementing with water when the amount of filtrate is insufficient.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] Compared with existing methods such as oil steaming and air flotation, the method of this invention utilizes waste activated carbon adsorption for oil removal, saving energy consumption in the hot-rolled sludge treatment process. Simultaneously, this invention transfers the oil from the hot-rolled sludge to a blast furnace for combustion, providing additional heat to the blast furnace, directly eliminating secondary pollution and pollutants in hazardous waste, and significantly reducing the oil content of the iron oxide scale.

[0026] The method of this invention dissolves the ferrite in the iron oxide scale and loads it onto the waste activated carbon, making it a catalyst for pulverized coal injection. This improves the combustion efficiency of the waste activated carbon and facilitates its resource utilization without the need for additional resource purchases.

[0027] The method of this invention is simple and practical. It only requires simple process facilities and existing process equipment in the main process of steel plants to achieve the co-processing of various solid and hazardous wastes in steel plants. It is less costly than the separate treatment and utilization of each solid and hazardous waste and has better technical and economic efficiency.

[0028] Within the formulation range of this invention, the sulfuric acid in the recovered filtrate has been completely reacted with no residue, the water resources can be recycled and reused without further treatment, and it does not affect the next formulation, thus achieving resource conservation. Attached Figure Description

[0029] Figure 1This is a schematic diagram of a method for the co-processing of waste activated carbon and hot-rolled sludge according to the present invention. Detailed Implementation

[0030] To better explain the present invention, the main contents of the present invention are further illustrated below with reference to specific embodiments, but the contents of the present invention are not limited to the following embodiments.

[0031] The main principle of the co-treatment method for waste activated carbon and hot-rolled sludge provided by this invention is as follows:

[0032] The activated carbon method for flue gas desulfurization and denitrification mainly utilizes the porosity and catalytic ability of activated carbon to catalytically transform pollutants in flue gas. After a period of use, the catalytic activity decreases, and its performance becomes insufficient to meet the requirements of flue gas purification reactions, necessitating replacement with new activated carbon. The replaced waste activated carbon needs to be disposed of. Although the catalytic activity of this waste activated carbon decreases, it still retains a large number of internal pore structures, exhibiting good affinity and adsorption properties for oily substances.

[0033] Hot-rolled sludge originates from the hot-rolled circulating water process. A small amount of mill oil used for lubrication enters the circulating water, forming a three-phase structure of oil, water, and solid together with the iron oxide scale generated during processes such as descaling. Hot-rolled sludge contains a large amount of ferrite and theoretically can be directly recycled for sintering without further treatment. However, due to its oil content, it affects the uniformity of sintering batching and the quality of sinter in practice, making it difficult to implement.

[0034] Blast furnace pulverized coal (PFC) utilizes anthracite as fuel to provide heat to the blast furnace. While spent activated carbon is combustible, its combustion performance is weaker than conventional anthracite. Therefore, its performance in blast furnace PFC is inferior to that of anthracite, and direct use of it can negatively impact the combustion efficiency. Numerous studies have shown that Fe... 3+ It has a beneficial effect on catalytic coal combustion, such as the ability to convert Fe... 3+ Loading waste activated carbon can improve its combustion performance and reduce the impact of waste activated carbon replacing anthracite on blast furnace production.

[0035] Therefore, the principle of this invention is to utilize the characteristics of waste activated carbon and hot-rolled sludge. Waste activated carbon particles adsorb the oil in the hot-rolled sludge, making it easier for the sintering and reuse. Simultaneously, some of the ferrite in the hot-rolled sludge is loaded onto the waste activated carbon, improving its combustion efficiency, thus achieving synergistic treatment and utilization of both. Using a stirred tank as the reaction vessel, sulfuric acid is added to demulsify the oil, suspending it on the water surface, and to react with iron oxide scale, allowing iron ions to enter the water. Both the oil and iron ions are adsorbed by the waste activated carbon.

[0036] The present invention provides a method for the co-processing of waste activated carbon and hot-rolled sludge, which specifically includes the following steps:

[0037] 1) Add 10 parts by weight of hot-rolled sludge, 200-250 parts by weight of water, and 2-4 parts by weight of concentrated sulfuric acid to a mixing tank and stir to break the emulsion for 5-10 minutes;

[0038] 2) Add 20-30 parts by weight of the waste activated carbon to the mixing tank and continue stirring for 30-45 minutes;

[0039] 3) Transfer the mixture in the mixing tank into the aging tank and let it stand for 60-90 minutes to allow the waste activated carbon to float on the water surface and solids such as iron oxide scale to settle to the bottom.

[0040] 4) Use a slag remover to remove the activated carbon from the top of the aging tank to obtain recycled activated carbon, and then send it to the stockpile to dry.

[0041] 5) The recovered activated carbon and anthracite are fed into a coal mill together, ground, and then used for pulverized coal injection in the blast furnace; wherein the mass ratio of recovered activated carbon to anthracite is 2-5:100.

[0042] 6) After the upper layer of waste activated carbon is discharged from the aging tank, the mixture in the aging tank is filtered. The filter residue is iron oxide scale, which is returned to sintering for reuse. The filtrate is recycled and sent to the mixing tank, and hot-rolled sludge, concentrated sulfuric acid and water are added again in appropriate proportions to continue the next cycle.

[0043] In the above scheme, in step 1), the hot-rolled sludge is a waste product discharged from the hot-rolled turbid circulating water process of steel plants. It is mainly composed of solid iron oxide scale, oil, and water, with a water content of 10-20%, an oil content of 5-10%, and a solid content of 70-85%. Its solid phase chemical composition is as follows: TFe ≥ 70.0%, C ≤ 3.0%, MnO ≤ 0.5%, CaO ≤ 1.0%, MgO ≤ 0.5%, SiO2 ≤ 2.0%, Al2O3 ≤ 0.2%, Cl ≤ 0.2%, S ≤ 0.1%, P ≤ 0.1%, and the balance being O element combined with Fe and other unavoidable impurities. Its solid phase particle size is as follows: the content of particles with a diameter of 0.3-2 mm is ≥ 50%, and the content of particles with a diameter less than 0.075 mm is ≤ 5%.

[0044] In the above scheme, in step 1), the concentrated sulfuric acid is industrial concentrated sulfuric acid with a mass fraction of 98%;

[0045] In the above scheme, in step 2), the waste activated carbon is activated carbon discarded from the flue gas desulfurization process of a steel plant; its chemical composition characteristics are: C≥92.0%, with the remainder being water and other unavoidable impurities; its size characteristics are: the content of particles with a particle size of 0.5~2mm is greater than 90%;

[0046] In the above scheme, in step 5), the moisture content of the dried waste activated carbon is 10-15%; the moisture content of the anthracite is ≤1.0%.

[0047] In the above scheme, in step 6), the oil content of the filtered iron oxide scale is ≤1.0%.

[0048] The process method of the present invention will be further described below with reference to Examples 1-3.

[0049] Example 1:

[0050] A method for the co-processing of waste activated carbon and hot-rolled sludge includes the following steps:

[0051] 1) Add 1 ton of hot-rolled sludge, 21 tons of water, and 0.2 tons of concentrated sulfuric acid to a mixing tank and stir to break the emulsion for 10 minutes;

[0052] 2) Add 2 tons of waste activated carbon to the mixing tank and continue mixing for 30 minutes;

[0053] 3) Transfer the mixture in the mixing tank into the aging tank and let it stand for 60 minutes to allow the waste activated carbon to float on the water surface and solids such as iron oxide scale to settle at the bottom.

[0054] 4) Use a slag remover to remove the activated carbon from the top of the aging tank to obtain recycled activated carbon, and then send it to the stockpile to dry.

[0055] 5) After drying, the moisture content of the recovered activated carbon was found to be 11%, and the weight was 2.1 tons. The recovered activated carbon was then fed into a coal mill with 100 tons of anthracite to be ground into a mixed fuel of recovered activated carbon for use in blast furnace pulverization.

[0056] 6) After the upper layer of waste activated carbon is discharged from the aging tank, the mixture in the aging tank is filtered. The filter residue is iron oxide scale, and the oil content is 0.6%, which can be reused for sintering. The filtrate is recovered and sent to the mixing tank for the next use.

[0057] Example 2:

[0058] A method for the co-processing of waste activated carbon and hot-rolled sludge includes the following steps:

[0059] 1) The amount of filtrate recovered in Example 1 was 19 tons. 1 ton of hot-rolled sludge, 4 tons of water, and 0.3 tons of concentrated sulfuric acid were added to it, and the mixture was stirred to break the emulsion for 7 minutes.

[0060] 2) Add 2.5 tons of waste activated carbon to the mixing tank and continue mixing for 38 minutes;

[0061] 3) Transfer the mixture in the mixing tank into the aging tank and let it stand for 75 minutes to allow the waste activated carbon to float on the water surface and solids such as iron oxide scale to settle at the bottom.

[0062] 4) Use a slag remover to remove the waste activated carbon from the top of the aging tank to obtain recycled activated carbon, and then send it to the stockpile to dry.

[0063] 5) After drying, the moisture content of the recovered activated carbon was found to be 14.6%, and the weight was 2.8 tons. The recovered activated carbon was fed into a coal mill with 70 tons of anthracite to be ground to produce a mixed fuel of recovered activated carbon for use in blast furnace pulverization.

[0064] 6) After the upper layer of waste activated carbon is discharged from the aging tank, the mixture in the aging tank is filtered. The filter residue is iron oxide scale, and the oil content is 0.4%, which can be reused for sintering. The filtrate is recovered and sent to the mixing tank for the next use.

[0065] Example 3:

[0066] A method for the co-processing of waste activated carbon and hot-rolled sludge includes the following steps:

[0067] 1) The amount of filtrate recovered in Example 2 was 22 tons. 1 ton of hot-rolled sludge, 2 tons of water, and 0.4 tons of concentrated sulfuric acid were added to it, and the mixture was stirred to break the emulsion for 10 minutes.

[0068] 2) Add 3 tons of waste activated carbon to the mixing tank and continue mixing for 45 minutes;

[0069] 3) Transfer the mixture in the mixing tank into the aging tank and let it stand for 90 minutes to allow the waste activated carbon to float on the water surface and solids such as iron oxide scale to settle at the bottom.

[0070] 4) Use a slag remover to remove the waste activated carbon from the top of the aging tank to obtain recycled activated carbon, and then send it to the stockpile to dry.

[0071] 5) After drying, the moisture content of the recovered activated carbon was found to be 13.1%, and the weight was 3.3 tons. The recovered activated carbon was fed into a coal mill with 70 tons of anthracite to be ground into waste activated carbon mixed fuel for use in blast furnace pulverization.

[0072] 6) After the upper layer of waste activated carbon is discharged from the aging tank, the mixture in the aging tank is filtered. The filter residue is iron oxide scale, and the oil content is 0.7%, which can be reused for sintering. The filtrate is recovered and sent to the mixing tank for the next use.

[0073] Thermogravimetric analysis was conducted on the above-mentioned anthracite for blast furnace pulverized coal injection, the original waste activated carbon that was not treated by the present invention, and the mixed fuel of recycled activated carbon in each embodiment. The combustion performance was evaluated as shown in Table 1.

[0074] As shown in Table 1, the initial weight loss temperature (ignition point), final weight loss temperature (burnout point), and combustion temperature range of untreated waste activated carbon are all higher than those of anthracite, indicating that anthracite is more flammable than untreated waste activated carbon. In contrast, the initial weight loss temperature (ignition point), final weight loss temperature (burnout point), and combustion temperature range of each embodiment are lower than those of anthracite, indicating that the combustion performance of the treated recycled activated carbon mixed fuel shows no deterioration compared to anthracite. Furthermore, the use of recycled activated carbon has no impact on the normal production of blast furnace pulverized coal injection. Therefore, this invention has beneficial technical effects.

[0075] Table 1: Combustion performance test results of the recovered activated carbon mixed fuels in Examples 1-3

[0076]

[0077] This invention relates to a method for the synergistic utilization of hot-rolled sludge and spent activated carbon, which has significantly different technical features compared with existing technologies and has obvious technical and economic value. The above-described embodiments are merely illustrative of several implementations of the invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this invention, and these all fall within the scope of protection of this invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

[0078] All other unspecified parts belong to the prior art.

Claims

1. A method for the co-processing of waste activated carbon and hot-rolled sludge, characterized in that: Includes the following steps: 1) Take hot-rolled sludge, solvent, and concentrated sulfuric acid, add them to a mixing tank, mix, and stir to break the emulsion for 5-10 minutes; 2) Add waste activated carbon to the mixture after demulsification treatment and continue stirring for 30-45 minutes; 3) Transfer the stirred mixture into an aging tank and let it stand for 60-90 minutes; 4) Separate the activated carbon from the upper layer of the aging tank to obtain recycled activated carbon; 5) The recovered activated carbon is dried and then used for pulverized coal injection in the blast furnace; 6) Filter the remaining mixture to obtain filtrate and filter residue. Collect the filter residue and return it to the steel sintering process. The hot-rolled sludge is a waste product discharged from the hot-rolling turbid water process in steel plants, comprising solid iron oxide scale, oil, and water, with a water content of 10-20%, an oil content of 5-10%, and a solid content of 70-85%. The solid phase chemical composition of the hot-rolled sludge is: TFe ≥ 70.0%, C ≤ 3.0%, MnO ≤ 0.5%, CaO ≤ 1.0%, MgO ≤ 0.5%, SiO2 ≤ 2.0%, Al2O3 ≤ 0.2%, Cl ≤ 0.2%, S ≤ 0.1%, P ≤ 0.1%, with the balance being O element combined with Fe and other unavoidable impurities. The solid phase particle size characteristics of the hot-rolled sludge are: particle size of 0.3-2 mm ≥ 50%, and particle size of less than 0.075 mm ≤ 5%. The waste activated carbon is activated carbon discarded from the flue gas desulfurization process of a steel plant. Its chemical composition is: C≥92.0%, with the remainder being water and other unavoidable impurities; the content of particles with a particle size of 0.5~2mm in the waste activated carbon is greater than 90%. In step 5), before using the recycled activated carbon for blast furnace pulverized coal injection, the recycled activated carbon is first mixed with anthracite and ground; the moisture content of the recycled activated carbon is 10~15%; the moisture content of the anthracite is ≤1.0%; and the mass ratio of the recycled activated carbon to the anthracite is 2~5:

100.

2. The collaborative processing method according to claim 1, characterized in that: The usage of each raw material, by mass, is as follows: 10 parts hot-rolled sludge, 200-250 parts solvent, 2-4 parts concentrated sulfuric acid, and 20-30 parts waste activated carbon.

3. The collaborative processing method according to claim 1, characterized in that: The solvent is water; the concentrated sulfuric acid is industrial concentrated sulfuric acid with a mass fraction of 98%.

4. The collaborative processing method according to claim 1, characterized in that: In step 4), the separation of activated carbon in the upper layer of the aging tank is achieved by a slag remover.

5. The collaborative processing method according to any one of claims 1-4, characterized in that: In step 6), the filter residue is iron oxide scale with an oil content of ≤1.0%.

6. The collaborative processing method according to claim 5, characterized in that: It also includes the following steps: The filtrate obtained from the filtration in step 6) is used as a solvent for the next round of co-processing of waste activated carbon and hot-rolled sludge. Water is used to supplement the filtrate if the amount is insufficient.

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