A method and system for comprehensive utilization of high-value steel plant dust sludge

Abstract

The application discloses a steel plant dust mud high-value comprehensive utilization method and system, which compounding sintering machine head ash and lead-containing iron waste, and adopting combined roasting technology to realize enrichment, separation and recovery of various valuable metals, which can effectively utilize components of the sintering machine head ash, realize recovery of iron, lead, gold, silver, potassium, sodium, chlorine and other elements, solve problems of difficulty in direct reuse of the sintering machine head ash and low comprehensive utilization value, and cooperatively process the lead-containing iron waste, and has practical significance for development of secondary resource comprehensive utilization technology.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization of solid waste and metallurgical technology, and relates to a method and system for high-value comprehensive utilization of dust and sludge from steel plants. Background Technology

[0002] Sintering machine head dust (hereinafter referred to as "head dust") is the dust collected by the electrostatic precipitator for flue gas during the iron ore sintering process, accounting for approximately 2-4% of the total sinter production. In China, the iron and steel industry generates 15 kg of sintering dust for every 1 ton of sintered ore. Sintering dust contains a certain amount of iron, which has recycling value, but it also contains high levels of alkali metals and heavy metals such as lead, zinc, and copper.

[0003] Because sintering ash has a high alkali metal content, simply adding it to the sintering mixture and returning it to the sintering process will lead to equipment corrosion, nodule formation, and the enrichment of elements such as potassium, sodium, and chlorine in the system, while also causing a decrease in the grade of the finished ore. To ensure that "solid waste does not leave the factory," steel companies choose to use pyrometallurgical or hydrometallurgical methods to remove elements such as potassium, sodium, and chlorine from the ash before returning it to the sintering process for recycling. Among these methods, the pyrometallurgical method mainly involves the rotary kiln / rotary hearth furnace reduction process, while the hydrometallurgical method involves water washing. However, using these methods, valuable metals such as lead and precious metals in the ash cannot be recovered and reused, and the resource value is not fully realized.

[0004] Currently, the mining and smelting of precious metals are very energy-intensive. Moreover, with the increasing scarcity of natural resources on Earth, mining precious metals will increase investment costs and cause more serious pollution. Therefore, the secondary recycling of precious metals can effectively reduce costs, reduce unnecessary procedures, realize resource utilization, effectively reduce energy consumption, and achieve the goal of protecting the environment.

[0005] In view of the above, there is an urgent need to develop a method and system for high-value recycling of steel plant dust and sludge. This would be of practical significance for the development of technologies that separate and recycle valuable elements such as Fe, Pb, K, Na, and Cl from steel plant dust and sludge and utilize them as secondary resources. Summary of the Invention

[0006] To address the aforementioned deficiencies in existing technologies, the purpose of this invention is to provide a method and system for the high-value comprehensive utilization of dust and sludge from steel plants. This method combines sintering machine head ash with lead-containing iron waste and employs a combined roasting technology to achieve the enrichment, separation, and recovery of various valuable metals. This solves the problems of difficulty in directly reusing sintering machine head ash and low comprehensive utilization value, and has practical significance for the development of secondary resource comprehensive utilization technology.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The first aspect of this invention provides a method for the comprehensive utilization of high-value dust and sludge from steel plants, comprising the following steps:

[0009] S1, Batching: Mix lead-containing iron waste with a particle size ≤4mm with sintering machine head ash to obtain a homogeneous mixture;

[0010] S2, combined roasting: The mixed material is spread evenly on the bottom of the combined roasting furnace. During the rotation of the furnace body, it passes through the preheating zone, chlorination roasting zone, reduction roasting zone 1, reduction roasting zone 2 and discharge zone in sequence. The chlorides in the mixture volatilize into chloride flue gas in the chlorination roasting zone, and then are reduced in reduction roasting zone 1 and reduction roasting zone 2 to obtain reduced iron powder.

[0011] S3, Magnetic separation: After the reduced iron powder is cooled to below 200°C in a cooling cylinder, it is subjected to strong magnetic roughing and strong magnetic scavenging to obtain iron concentrate and magnetic tailings.

[0012] S4, flue gas treatment, high-chlorine dust is obtained from chloride flue gas through waste heat recovery and flue gas dust removal collection;

[0013] S5, water washing, the high-chlorine dust is washed and dehydrated to obtain lead mud.

[0014] Preferably, in step S1, the lead-containing iron waste with a particle size ≤4mm is obtained through a pretreatment process: the lead-containing iron solid waste is crushed, screened and dried to obtain lead-containing iron waste with a particle size ≤4mm and a moisture content ≤0.8%.

[0015] Preferably, in step S1:

[0016] The lead-containing iron waste contains Pb at a grade of 5–15 wt% and Fe at a grade of 10–30 wt%; and / or

[0017] The sintering machine head ash contains 10–40 wt% Fe, 3–25 wt% Pb, 5–18 wt% K, 5–20 wt% Cl, 1–4 wt% Na, ≥5 g / t Au, and ≥300 g / t Ag; and / or

[0018] The mixture contains 20-40 wt% Fe, 8-15 wt% Pb, ≤3 wt% K, 4-8 wt% Ca, 8-15 wt% Cl, 2-4 wt% Na, ≥2 g / t Au, and ≥100 g / t Ag.

[0019] Preferably, in step S2: the bottom of the combined roasting furnace is provided with a preheating zone, a chlorination roasting zone, a reduction roasting zone one, a reduction roasting zone two, and a discharge zone in sequence; a flue gas outlet is provided on the furnace top between the preheating zone and the chlorination roasting zone, and a carbon injection device is provided in the reduction roasting zone one or the reduction roasting zone two.

[0020] Preferably, in step S2: in the reduction roasting zone, pulverized coal is injected, and the amount of pulverized coal injected is 5-8 wt% of the total amount of the mixture.

[0021] Preferably, in step S2: the temperature of the preheating zone is 600-800℃, the temperature of the chlorination roasting zone is 900-1050℃, the temperature of the first reduction roasting zone is 1050-1150℃, the temperature of the second reduction roasting zone is 1100-1200℃, and the temperature of the discharge zone is 900-1000℃; the combined roasting time is 80-100 min.

[0022] Preferably, in step S3: the iron concentrate is dehydrated to obtain dehydrated iron concentrate, in which the TFe content is ≥78% and the MFe content is ≥70wt%; the magnetic separation tailings are returned to step S2 as ingredients.

[0023] Preferably, in step S5:

[0024] The wastewater generated during the washing and dehydration process is used to extract salt through a potassium salt recovery system.

[0025] The lead mud contains 60-70 wt% Pb, 10-15 wt% Zn, ≤1 wt% Na, ≤1 wt% K, ≤2 wt% Cl, 30-70 g / t Au, and ≥1000 g / t Ag.

[0026] The second aspect of the present invention provides a comprehensive system for the high-value utilization of dust and sludge from steel plants, including a raw material pretreatment device, a mixer, a combined roasting furnace, a cooling cylinder, a magnetic separation device, a flue gas treatment device, a water washing device, and a filter press.

[0027] The raw material pretreatment device includes crushing equipment, grinding equipment, screening equipment and drying equipment, which are used to pretreat lead-containing iron solid waste to obtain lead-containing iron waste.

[0028] The mixer is connected to the lead-containing iron waste bin and the ash bin respectively. The mixer is used to mix the lead-containing iron waste with the ash from the sintering machine head to obtain a homogeneous mixture.

[0029] The combined roasting furnace is connected to the mixer via a belt. The furnace chamber of the combined roasting furnace is sequentially provided with a preheating zone, a chlorination roasting zone, a reduction roasting zone one, a reduction roasting zone two, and a discharge zone. A flue gas outlet is provided on the furnace top between the preheating zone and the chlorination roasting zone. A carbon injection device is provided in the reduction roasting zone one or the reduction roasting zone two.

[0030] The cooling cylinder is connected to the discharge area of ​​the combined roasting furnace, and the outlet of the cooling cylinder is connected to the magnetic separator.

[0031] The magnetic separation device includes a high-intensity magnetic rougher and a high-intensity magnetic scavenger. The magnetic separation device obtains iron concentrate and magnetic tailings through magnetic separation.

[0032] The flue gas treatment device includes a waste heat boiler connected to the flue gas outlet of the combined roasting furnace and a flue gas dust collector connected to the flue gas outlet of the waste heat boiler.

[0033] The water washing equipment is connected to the flue gas dust collector, and the water washing equipment is used to wash the high-chlorine dust collected by the flue gas dust collector.

[0034] The filter press is connected to the washing equipment, and the filter press is used to dehydrate the solids after the washing equipment has been processed.

[0035] The steel plant dust and sludge high-value comprehensive utilization system is used to implement the steel plant dust and sludge high-value comprehensive utilization method as described in the first aspect of the present invention.

[0036] Preferably, the angle occupied by the reduction roasting zone one and the reduction roasting zone two in the combined roasting furnace is 40±2°.

[0037] Preferably, a material feeder and a material discharger are provided between the preheating zone and the discharge zone. The material feeder is located close to the preheating zone, and the material discharger is located close to the discharge zone. The angle occupied by the preheating zone in the combined roasting furnace is 25±2°, and the sum of the angles occupied by the material feeder, the material discharger, and the discharge zone in the combined roasting furnace is 40±2°.

[0038] Preferably, it also includes a potassium salt recovery system connected to the wastewater outlets of the washing equipment and the filter press, respectively.

[0039] The present invention has the following beneficial effects:

[0040] 1. This invention employs a combined roasting-magnetic separation process, which can effectively utilize alkali metals and chloride salts (NaCl, KCl) in the sintering machine head ash to separate various valuable metals (Pb, K, Na, Cl, Au, Ag, etc.), maximizing their value, and the process is environmentally friendly.

[0041] 2. This invention can collaboratively process solid waste containing Pb and Fe from other industrial enterprises in the city, not only ensuring that the steel plant's solid waste does not leave the factory, but also realizing the integration of industry and city and solving the problem of urban solid waste;

[0042] 3. The steel plant dust and sludge high-value utilization system of the present invention adopts a combined roasting furnace, in which a chlorination roasting zone is set up to make full use of the chloride salts in the sintering machine head ash. Compared with the traditional chlorination roasting process, it saves chloride salt costs, realizes continuous process, and saves energy consumption and equipment consumption in high-temperature transfer process compared with step-by-step process.

[0043] 4. The high-value utilization system for steel plant dust and sludge of the present invention is equipped with a combined roasting furnace and a magnetic separation system, which can not only effectively utilize chloride salts in sintering machine head ash, but also increase the iron content in the product, thereby realizing the high-value utilization of steel plant dust and sludge. Attached Figure Description

[0044] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0045] Figure 1 This is a schematic diagram of the process for the comprehensive utilization of high-value dust and sludge from steel plants according to the present invention.

[0046] Figure 2 This is a schematic diagram of the structure of the steel plant dust and sludge high-value comprehensive utilization system of the present invention;

[0047] Figure 3 This is a schematic diagram of the combined roasting furnace of the present invention. Detailed Implementation

[0048] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with embodiments.

[0049] This invention provides a method for the comprehensive utilization of high-value dust and sludge from steel plants. It employs a combined roasting technology. First, the chloride salts in the raw materials are roasted under certain temperature conditions to volatilize valuable metals such as Pb, K, Na, Cl, Au, and Ag. Then, reduction roasting is performed to reduce Fe3O4, Fe2O3, and FeO in the raw materials to Fe and FeO, effectively achieving the enrichment, separation, and recovery of various valuable metals.

[0050] Combination Figure 1 As shown, the method for high-value comprehensive utilization of steel plant dust and sludge of the present invention includes the following steps:

[0051] S1, Batching: Mix lead-containing iron waste with a particle size ≤4mm with sintering machine head ash to obtain a homogeneous mixture;

[0052] Specifically, the process begins by obtaining lead-containing iron waste with a particle size ≤4mm. Based on the particle size and moisture content of the lead-containing iron waste, pretreatment methods such as crushing, screening, and drying are performed to obtain lead-containing iron waste with a particle size ≤4mm and a moisture content ≤0.8%, ensuring that the particle size of the raw materials used in batching is ≤4mm. The lead-containing iron waste refers to lead-containing iron solid waste generated by steel plants or other industrial enterprises in the city; its source, particle size, and moisture content are not limited. In the lead-containing iron waste, the Pb grade is 5–15 wt%, and the Fe grade is 10–30 wt%.

[0053] The sintering machine head ash contains 10–40 wt% Fe, 3–25 wt% Pb, 5–18 wt% K, 5–20 wt% Cl, 1–4 wt% Na, ≥5 g / t Au, and ≥300 g / t Ag.

[0054] Lead-containing iron waste with a particle size ≤4mm is mixed with sintering machine head ash in a certain proportion to obtain a homogeneous material. The mass ratio of lead-containing iron waste to sintering machine head ash is adjusted according to the composition of the raw materials. The general principle of batching is as follows: After batching, the main components of the homogeneous material are as shown in Table 1, namely, Fe content is 20-40wt%, Pb content is 8-15wt%, K content is ≤3wt%, Ca content is 4-8wt%, Cl content is 8-15wt%, Na content is 2-4wt%, Au content is ≥2g / t, and Ag content is ≥100g / t.

[0055] Table 1 Main components of the mixture

[0056] content 20～40 8～15 ≤3 4～8 8～15 2～4 ≥2 ≥100

[0057] S2, combined roasting, the mixed material is spread evenly on the bottom of the combined roasting furnace by a material distributor. During the rotation of the furnace body, it passes through the preheating zone, chlorination roasting zone, reduction roasting zone 1, reduction roasting zone 2 and discharge zone in sequence. The chlorides in the mixture volatilize into chloride flue gas in the chlorination roasting zone, and then are reduced in reduction roasting zone 1 and reduction roasting zone 2 to obtain reduced iron powder.

[0058] Combination Figure 3 As shown, the bottom of the combined roasting furnace 6 is provided with a preheating zone, a chlorination roasting zone, a reduction roasting zone 1, a reduction roasting zone 2, and a discharge zone in sequence; a flue gas outlet 61 is provided on the furnace top between the preheating zone and the chlorination roasting zone, and a carbon injection device is provided in the reduction roasting zone 1.

[0059] The homogenized material obtained in step S1 is spread evenly on the bottom of the combined roasting furnace by a material distributor. The thickness of the material layer at the bottom of the furnace is 3-5 cm. During the rotation of the furnace, the homogenized material passes through the preheating zone, chlorination roasting zone, reduction roasting zone 1, reduction roasting zone 2, and discharge zone. During this process, the homogenized material first volatilizes metal chlorides such as K, Na, Pb, Au, and Ag in the chlorination roasting zone. The chloride flue gas enters the flue gas system through the flue gas outlet. Subsequently, in the reduction roasting zone 1 and reduction roasting zone 2, Fe3O4, Fe2O3, FeO, etc. in the homogenized material are reduced to obtain reduced iron powder, which is discharged by the discharge screw.

[0060] In the aforementioned combined roasting process, the temperature of the preheating zone is 600–800℃, the temperature of the chlorination roasting zone is 900–1050℃, the temperature of the first reduction roasting zone is 1050–1150℃, the temperature of the second reduction roasting zone is 1100–1200℃, and the temperature of the discharge zone is 900–1000℃. The furnace bottom of the combined roasting furnace has an adjustable rotation speed, and the combined roasting time is 80–100 minutes. A carbon injection device is provided in either the first or second reduction roasting zone (in the preferred embodiment, the carbon injection device is located in the first reduction roasting zone). The carbon content of the mixed material is low. To ensure reduction efficiency, an appropriate amount of pulverized coal can be injected, with the amount of pulverized coal being 5–8 wt% of the total amount of the mixed material.

[0061] S3, magnetic separation: After the reduced iron powder is cooled to below 200°C in the cooling cylinder, it is subjected to strong magnetic roughing and strong magnetic scavenging to obtain iron concentrate and magnetic tailings.

[0062] Specifically, the reduced iron powder obtained in step S2 is fed into a cooling cylinder and cooled to below 200°C, then sent to a magnetic separator. Through two processes—strong magnetic roughing and strong magnetic scavenging—the strong magnetic roughing process yields magnetically separated ore and iron concentrate. The magnetically separated ore is then subjected to strong magnetic scavenging to obtain magnetically separated tailings and iron concentrate. Through the above process, iron concentrate and magnetic separation tailings are finally obtained. The iron concentrate is dehydrated to obtain dehydrated iron concentrate, which is packaged and sold. This dehydrated iron concentrate contains ≥78% TFe (total iron) and ≥70wt% MFe (magnetic iron). The magnetic separation tailings are returned to step S2 as feedstock.

[0063] S4, flue gas treatment, high-chlorine dust is obtained from chloride flue gas through waste heat recovery and flue gas dust removal collection;

[0064] Specifically, the chloride flue gas volatilized in step S2 is discharged from the combined roasting furnace, and after the waste heat is recovered by the waste heat boiler, the temperature is reduced to ≤200℃. Then it enters the flue gas dust collector and is collected to obtain high-chlorine dust. The flue gas after dust removal (its temperature is ≤120℃) is discharged through the chimney after desulfurization and denitrification.

[0065] S5, water washing, high chlorine dust is washed and dehydrated to obtain lead mud.

[0066] The high-chlorine dust collected in step S4 is directly sent to the washing device via a chain conveyor. After washing, a solid phase is obtained. The solid phase is dewatered by a filter press to obtain lead mud, which can be sold directly as a product. The salt-rich wastewater generated during the washing and dewatering process is used to extract salt (potassium salt, sodium salt, rubidium chloride, cesium chloride) through a potassium salt recovery system.

[0067] The lead mud obtained above contains 60-70 wt% Pb, 10-15 wt% Zn, ≤1 wt% Na, ≤1 wt% K, ≤2 wt% Cl, 30-70 g / t Au, and ≥1000 g / t Ag.

[0068] Combination Figure 2 As shown, this invention also provides a comprehensive system for the high-value utilization of dust and sludge from steel plants, including a raw material pretreatment device, a mixer 5, a combined roasting furnace 6, a cooling cylinder 7, a magnetic separation device, a flue gas treatment device, a water washing device 12, and a filter press 13. The raw material pretreatment device includes a crushing device 1, a grinding device 2, a screening device 3, and a drying device 4, used to pretreat lead-containing iron solid waste to obtain lead-containing iron waste. The mixer 5 is connected to the lead-containing iron waste bin and the ash bin, respectively, and is used to mix the lead-containing iron waste with the sintering machine head ash to obtain a homogeneous material. The combined roasting furnace 6 is connected to the mixer 5 via a belt conveyor. The furnace chamber of the combined roasting furnace 6 is sequentially equipped with a preheating zone, a chlorination roasting zone, a reduction roasting zone one, a reduction roasting zone two, and a discharge zone; a flue gas outlet 61 is provided on the furnace top between the preheating zone and the chlorination roasting zone, and a carbon injection device is provided in the reduction roasting zone one. Cooling cylinder 7 is connected to the discharge area of ​​the combined roasting furnace 6, and its outlet is connected to a magnetic separator. The magnetic separator includes a high-intensity magnetic rougher 8 and a high-intensity magnetic sweeper 9, which obtain iron concentrate and tailings through magnetic separation. The flue gas treatment device includes a waste heat boiler 10 connected to the flue gas outlet of the combined roasting furnace 6 and a flue gas dust collector 11 connected to the flue gas outlet of the waste heat boiler 10. A washing device 12 is connected to the flue gas dust collector 13, used to wash the high-chlorine dust collected by the flue gas dust collector 11. A filter press 13 is connected to the washing device 12, used to dehydrate the solids processed by the washing device 12.

[0069] Combination Figure 3 As shown, the angle occupied by reduction roasting zone one and reduction roasting zone two in the combined roasting furnace is 40±2°. A material feeder 62 and a material discharger 63 are provided between the preheating zone and the discharge zone. The material feeder 62 is located closer to the preheating zone, and the material discharger 63 is located closer to the discharge zone. The angle occupied by the preheating zone in the combined roasting furnace is 25±2°. The sum of the angles occupied by the material feeder 62, the material discharger 63, and the discharge zone in the combined roasting furnace is 40±2°.

[0070] Combination Figure 2As shown, the comprehensive utilization system for high-value utilization of dust and sludge in steel plants also includes a potassium salt recovery system 14, which is connected to the wastewater outlets of the washing equipment 12 and the filter press 13, respectively.

[0071] The following describes a method and system for the comprehensive utilization of high-value dust and sludge from steel plants according to the present invention, with specific examples. The composition of the sintering machine head ash used in Examples 1 and 2 is as follows: Fe content is 10-40wt%, Pb content is 3-25wt%, K content is 5-18wt%, Cl content is 5-20wt%, Na content is 1-4wt%, Au content is ≥5g / t, and Ag content is ≥300g / t.

[0072] Example 1

[0073] The method for high-value comprehensive utilization of dust and sludge from steel plants in this embodiment adopts... Figure 2 The apparatus shown specifically includes the following steps:

[0074] (1) Raw material pretreatment: lead slag reverberatory furnace flue dust (hereinafter referred to as: flue dust) is selected. Its moisture content is <0.5% and the particle size is <4mm. No pretreatment is required. It can be directly used as lead-containing iron waste for batching. The main components are Pb: 23.33%, Fe: 10.70%, Zn: 1.02%, Na: 0.98%, K: 0.27%, Cl: 1.03%, Si: 4.15%, Ca: 3.17%.

[0075] (2) Batching and mixing: The flue dust and sintering machine head ash from step (1) are batched and mixed in proportion to obtain a homogeneous material; the raw material ratio in the homogeneous material is shown in Table 2; the homogeneous material contains Fe: 46.86%, Pb: 16.40%, Zn: 2.90%, C: 4.12%, Na: 1.02%, K: 8.30%, Cl: 15.30%, Ca: 4.62%, Au: 15.03g / t, and Ag: 521.32g / t.

[0076] Table 2. Raw material ratios in the mixture of Example 1

[0077] Ratio / % 20 80

[0078] (3) Combined roasting: The mixed material from step (2) is evenly spread to the bottom of the combined roasting furnace by a material spreader. The bottom material layer thickness is 3cm. During the rotation of the furnace, the mixed material passes through the preheating zone, chlorination roasting zone, reduction roasting zone 1, reduction roasting zone 2 and discharge section. The mixed material first volatilizes chloride flue gas, including metal chlorides such as K, Na, Pb, Au, and Ag, in the chlorination roasting zone, which is collected as high-chlorine dust by the dust collection system. Then, in the reduction roasting zone 1 and reduction roasting zone 2, Fe3O4, Fe2O3, and FeO in the raw material are reduced to reduced iron powder, which is discharged by the discharge screw and sent to the cooling system. The temperature of the preheating zone is 800℃, the temperature of the chlorination roasting zone is 1000℃, the temperature of the reduction roasting zone 1 is 1070℃, the temperature of the reduction roasting zone 2 is 1200℃, the temperature of the discharge section is 1000℃, the furnace bottom rotation speed is 4° / min, and the combined roasting time is 90min.

[0079] (4) Magnetic separation of reduced iron powder: The reduced iron powder mentioned in step (3) is cooled to below 200°C in a cooling cylinder and then enters a magnetic separation device, which includes three processes: grinding, strong magnetic roughing and strong magnetic scavenging, to finally obtain iron concentrate and magnetic tailings; the iron concentrate is dehydrated to obtain dehydrated iron concentrate, which can be directly packaged and sold; the magnetic tailings are returned to step (2) as raw materials; the dehydrated iron concentrate has TFe: 78.02% and MFe: 71.74%.

[0080] (5) Flue gas treatment and collection: High-temperature flue gas is discharged from the combined roasting furnace body and passes through the waste heat boiler. The temperature is reduced to ≤200℃ and then enters the flue gas dust collector for flue gas dust removal. After cooling, the flue gas (≤120℃) is discharged through the chimney after dust removal, desulfurization and denitrification to meet the standards. High-chlorine dust is collected at the flue gas dust collector.

[0081] (6) High-chlorine dust washing: The high-chlorine dust mentioned in step (5) is directly sent to the washing device via a chain conveyor. After washing, a solid phase is obtained. The solid phase is dewatered by a filter press to obtain lead sludge, which is sold directly as a product. The salt-rich wastewater treated by washing and dewatering is further used to extract salts (potassium salt, sodium salt, rubidium chloride, cesium chloride). The lead sludge contains Pb: 62.33%, Zn: 10.02%, Na: 0.08%, K: 0.10%, Cl: 0.13%, Au: 69.17 g / t, and Ag: 2734.42 g / t.

[0082] Example 2

[0083] The method for high-value comprehensive utilization of dust and sludge from steel plants in this embodiment adopts... Figure 2 The apparatus shown specifically includes the following steps:

[0084] (1) Raw material pretreatment: In this embodiment, electroplating sludge from a steel plant is selected as lead-containing iron solid waste. Its moisture content is 22.5%. After pretreatment, pretreated electroplating sludge with a moisture content of 0.8% and a particle size of <4mm is obtained. The pretreated electroplating sludge can be used as lead-containing waste. Its main components are Pb: 15.49%, Fe: 20.83%, Zn: 4.14%, Cu: 10.57%, Na: 0.54%, Mg: 0.35%, Ca: 5.75%.

[0085] (2) Batching and mixing: The pretreated electroplating sludge and sintering machine head ash in step (1) are mixed in proportion to obtain a homogeneous material; the raw material ratio in the homogeneous material is shown in Table 2; the homogeneous material contains Fe: 40.59%, Pb: 21.40%, Zn: 4.13%, C: 5.69%, Na: 1.02%, K: 9.94%, Cl: 13.22%, Ca: 3.56%, Au: 8.36g / t, and Ag: 437.03g / t.

[0086] Table 3. Raw material ratios in the mixed material of Example 2

[0087] Ratio / % 16 84

[0088] (4) Combined roasting: The mixed material from step (2) is evenly spread to the bottom of the combined roasting furnace by a material distributor. The bottom material layer thickness is 3.8 cm. During the rotation of the furnace, the mixed material passes through the preheating zone, chlorination roasting zone, reduction roasting zone 1, reduction roasting zone 2 and discharge section. The mixed material first volatilizes chloride flue gas, including metal chlorides such as K, Na, Pb, Au, and Ag, in the chlorination roasting zone, which is collected as high-chlorine dust by the dust collection system. Then, in the reduction roasting zone, Fe3O4, Fe2O3, and FeO in the raw material are reduced to obtain reduced iron powder, which is discharged by the discharge screw and sent to the cooling system. The temperature of the preheating zone is 840℃, the temperature of the chlorination roasting zone is 1050℃, the temperature of the reduction roasting zone 1 is 1100℃, the temperature of the reduction roasting zone 2 is 1190℃, the temperature of the discharge section is 1050℃, the furnace bottom rotation speed is 3.5° / min, and the combined roasting time is 103 min.

[0089] (4) Magnetic separation of reduced iron powder: The reduced iron powder described in step (3) is cooled to below 200°C in a cooling cylinder and then enters a magnetic separation device, which includes three processes: grinding, strong magnetic roughing and strong magnetic scavenging, to finally obtain iron concentrate and magnetic separation tailings; the iron concentrate is dehydrated to obtain dehydrated iron concentrate, which can be directly packaged and sold; the magnetic separation tailings are returned to step (2) as raw materials; the dehydrated iron concentrate has TFe: 82.10% and MFe: 73.96%.

[0090] (5) Flue gas treatment and collection: High-temperature chloride flue gas is discharged from the combined roasting furnace body and passes through the waste heat boiler. The temperature is reduced to ≤200℃ and then enters the flue gas dust collector for flue gas dust removal. After cooling, the flue gas (≤120℃) is discharged through the chimney after dust removal, desulfurization and denitrification to meet the standards. High-chlorine dust is collected at the flue gas dust collector.

[0091] (6) High-chlorine dust washing: The high-chlorine dust mentioned in step (5) is directly sent to the washing system via a chain conveyor. After washing, a solid phase is obtained. The solid phase is dewatered by a filter press to obtain lead sludge, which is sold directly as a product. The salt-rich wastewater treated by washing and dewatering is further used to extract salts (potassium salt, sodium salt, rubidium chloride, cesium chloride). The lead sludge contains Pb: 69.58%, Zn: 14.90%, Na: 0.22%, K: 0.34%, Cl: 0.21%, Au: 30.16 g / t, and Ag: 1776.59 g / t.

[0092] In summary, this invention employs a combined roasting technology. First, it utilizes the chloride salts in the raw materials, roasting them at a certain temperature to volatilize valuable metals such as Pb, K, Na, Cl, Au, and Ag. Then, it uses reduction roasting to reduce Fe3O4, Fe2O3, and FeO in the raw materials to reduced iron powders such as Fe and FeO. This effectively achieves the enrichment, separation, and recovery of various valuable metals, solving problems such as the difficulty of directly reusing sintering machine head ash and its low comprehensive utilization value. It not only ensures that "solid waste does not leave the steel plant" but also achieves industrial-urban integration, solving urban solid waste issues.

[0093] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A method for the high-value comprehensive utilization of dust and sludge from steel plants, characterized in that, Includes the following steps: S1, Batching: Lead-containing iron waste with a particle size ≤4mm is mixed with sintering machine head ash to obtain a homogeneous mixture. The lead-containing iron waste with a particle size ≤4mm is obtained through a pretreatment process: the lead-containing iron solid waste is crushed, screened and dried to obtain lead-containing iron waste with a particle size ≤4mm and a moisture content ≤0.8%. In the lead-containing iron waste, the Pb grade is 5-15 wt%, and the Fe grade is 10-30 wt%. The sintering machine head ash contains 10-40 wt% Fe, 3-25 wt% Pb, 5-18 wt% K, 5-20 wt% Cl, 1-4 wt% Na, ≥5 g / t Au, and ≥300 g / t Ag. The mixture contains 20-40 wt% Fe, 8-15 wt% Pb, ≤3 wt% K, 4-8 wt% Ca, 8-15 wt% Cl, 2-4 wt% Na, ≥2 g / t Au, and ≥100 g / t Ag. S2, Combined roasting: The mixed material is spread evenly on the bottom of the combined roasting furnace. During the rotation of the furnace, it sequentially passes through the preheating zone, chlorination roasting zone, reduction roasting zone one, reduction roasting zone two, and discharge zone. Chlorides in the mixture volatilize into chloride fumes in the chlorination roasting zone, and then undergo reduction in reduction roasting zone one and reduction roasting zone two. Fe3O4, Fe2O3, and FeO in the mixed material are reduced to obtain reduced iron powder. The combined roasting furnace has a preheating zone, a chlorination roasting zone, a reduction roasting zone one, a reduction roasting zone two, and a discharge zone arranged sequentially at its bottom. A flue gas outlet is located on the furnace top between the preheating zone and the chlorination roasting zone. A carbon injection device is installed in the reduction roasting zone one. In the reduction roasting zone, pulverized coal is injected at a rate of 5-8 wt% of the total amount of the mixture. S3, Magnetic separation: After the reduced iron powder is cooled to below 200°C in a cooling cylinder, it undergoes strong magnetic roughing and strong magnetic scavenging to obtain iron concentrate and magnetic tailings. The iron concentrate is dehydrated to obtain dehydrated iron concentrate, wherein the TFe content is ≥78% and the MFe content is ≥70wt%; S4, flue gas treatment, high-chlorine dust is obtained from chloride flue gas through waste heat recovery and flue gas dust removal collection; S5, water washing: The high-chlorine dust is washed and dehydrated to obtain lead sludge. The lead mud contains 60-70 wt% Pb, 10-15 wt% Zn, ≤1 wt% Na, ≤1 wt% K, ≤2 wt% Cl, 30-70 g / t Au, and ≥1000 g / t Ag. In step S2: the temperature of the preheating zone is 600-800℃, the temperature of the chlorination roasting zone is 900-1050℃, the temperature of the first reduction roasting zone is 1050-1150℃, the temperature of the second reduction roasting zone is 1100-1200℃, and the temperature of the discharge zone is 900-1000℃; the combined roasting time is 80-100 min.

2. The method for high-value comprehensive utilization of steel plant dust and sludge according to claim 1, characterized in that, In step S1, the lead-containing iron waste with a particle size ≤4mm is obtained through a pretreatment process: the lead-containing iron solid waste is crushed, screened and dried to obtain lead-containing iron waste with a particle size ≤4mm and a moisture content ≤0.8%.

3. The method for high-value comprehensive utilization of steel plant dust and sludge according to claim 1, characterized in that, In step S3: the magnetic separation tailings are returned to step S2 as ingredients.

4. The method for high-value comprehensive utilization of steel plant dust and sludge according to claim 1, characterized in that, In step S5: The salt-rich wastewater generated during the washing and dehydration process is treated with a potassium salt recovery system to extract salt.

5. The method for high-value comprehensive utilization of steel plant dust and sludge according to claim 1, characterized in that, The rotary hearth furnace treatment system for metallurgical dust and sludge includes a raw material pretreatment device, a mixer, a combined roasting furnace, a cooling cylinder, a magnetic separator, a flue gas treatment device, a water washing device, and a filter press. The raw material pretreatment device includes crushing equipment, grinding equipment, screening equipment and drying equipment, which are used to pretreat lead-containing iron solid waste to obtain lead-containing iron waste. The mixer is connected to the lead-containing iron waste bin and the ash bin respectively. The mixer is used to mix the lead-containing iron waste with the ash from the sintering machine head to obtain a homogeneous mixture. The combined roasting furnace is connected to the mixer via a belt. The furnace chamber of the combined roasting furnace is sequentially provided with a preheating zone, a chlorination roasting zone, a reduction roasting zone one, a reduction roasting zone two, and a discharge zone. A flue gas outlet is provided on the furnace top between the preheating zone and the chlorination roasting zone. A carbon injection device is provided in the reduction roasting zone one or the reduction roasting zone two. The cooling cylinder is connected to the discharge area of ​​the combined roasting furnace, and the outlet of the cooling cylinder is connected to the magnetic separator. The magnetic separation device includes a high-intensity magnetic rougher and a high-intensity magnetic scavenger. The magnetic separation device obtains iron concentrate and magnetic tailings through magnetic separation. The flue gas treatment device includes a waste heat boiler connected to the flue gas outlet of the combined roasting furnace and a flue gas dust collector connected to the flue gas outlet of the waste heat boiler. The water washing equipment is connected to the flue gas dust collector, and the water washing equipment is used to wash the high-chlorine dust collected by the flue gas dust collector. The filter press is connected to the washing equipment and is used to dehydrate the solids processed by the washing equipment.

6. The method for high-value comprehensive utilization of steel plant dust and sludge according to claim 5, characterized in that, The angle occupied by the reduction roasting zone one and the reduction roasting zone two in the combined roasting furnace is 40±2°.

7. The method for high-value comprehensive utilization of steel plant dust and sludge according to claim 5, characterized in that, A material feeder and a material discharger are provided between the preheating zone and the discharge zone. The material feeder is located close to the preheating zone, and the material discharger is located close to the discharge zone. The angle occupied by the preheating zone in the combined roasting furnace is 25±2°, and the sum of the angles occupied by the material feeder, the material discharger, and the discharge zone in the combined roasting furnace is 40±2°.

8. The method for high-value comprehensive utilization of steel plant dust and sludge according to claim 5, characterized in that, It also includes a potassium salt recovery system that is connected to the wastewater outlets of the washing equipment and the filter press, respectively.

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