A method and device for collaboratively treating waste plastic oil bottles and iron-zinc dust sludge

Abstract

The present invention discloses a method and device for the coordinated treatment of waste plastic oil cans and iron-zinc dust sludge, wherein the device for the coordinated treatment of waste plastic oil cans and iron-zinc dust sludge comprises a washing device, a crushing device, a first screening device, a strong mixer, a briquetting machine, a drying device, a rotary hearth furnace, a flue gas quenching tower and a dust collector; the present invention uses waste plastic oil cans to replace part of the coke as a reducing agent, and utilizes a rotary hearth furnace and the iron-zinc dust sludge for coordinated treatment, which can not only achieve efficient recovery of iron and zinc, but also solve the pollution problem of waste plastic oil cans in steel plants to a certain extent, save energy and raw materials, and further reduce the cost of the coordinated treatment of the rotary hearth furnace.

Description

Technical Field

[0001] The invention belongs to the technical field of comprehensive utilization of solid waste, and relates to a method and a device for collaboratively treating waste plastic oil bottles and iron-zinc dust sludge. Background Art

[0002] my country's steel industry typically generates dust accounting for 8% to 12% of steel production, a massive output of approximately 7 million tons. Major steel mills are increasing their environmental protection efforts and promoting the resource utilization of solid waste, specifically the recovery of valuable metals and the elimination of solid waste. Currently, the use of rotary hearth furnaces (RHFs) for the co-disposal of steel mill solid waste is emerging as a new trend. The RHF process primarily processes zinc-containing metallurgical dust through direct reduction, recovering both Fe and Zn, thereby achieving harmless disposal of metallurgical solid waste.

[0003] The packaging containers used in steel enterprises will also become solid waste after they have completed or lost their original value and use value of holding the contents. Therefore, waste plastic oil cans in steel plants have become another common solid waste in steel plants. Waste plastic oil cans are mainly made of polypropylene and polyvinyl chloride. From the chemical composition point of view, there is almost no difference between plastic and oil. At the same time, there is a small amount of residual waste oil, which poses a greater risk of environmental damage. The temperature for complete decomposition of waste plastic oil cans is not high, generally 500°C; the calorific value of polyethylene, polystyrene, and polypropylene can reach about 44,000 kJ / kg, which is close to industrial fuel oil. The remaining part after incineration is easy to decompose;

[0004] In view of the above situation, if waste plastic oil bottles are used as reducing agents instead of carbon powder or coke powder, and are treated in conjunction with zinc-containing metallurgical dust in a rotary hearth furnace, it will not only save the use of other energy and raw materials, but also achieve the comprehensive utilization of waste plastic oil bottles, thereby avoiding a series of environmental problems caused by the large-scale storage of the two. Summary of the Invention

[0005] In view of the above-mentioned defects in the prior art, the purpose of the present invention is to provide a method and a treatment device for the coordinated treatment of waste plastic oil cans and iron-zinc dust sludge, using waste plastic oil cans to replace part of the coke as a reducing agent, and utilizing a rotary hearth furnace to coordinate the treatment with the iron-zinc dust sludge, which can not only achieve efficient recovery of iron and zinc, but also solve the pollution problem of waste plastic oil cans in steel mills to a certain extent, save energy and raw materials, and further reduce the cost of coordinated treatment in the rotary hearth furnace.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a device for the coordinated treatment of waste plastic oil bottles and iron-zinc dust sludge, comprising a washing device, a crushing device, a first screening device, a high-pressure mixer, a briquetting machine, a drying device, a rotary hearth furnace, a flue gas quenching tower, and a dust collector;

[0008] The washing equipment, crushing equipment, first screening equipment, strong mixer, pelletizing machine, drying equipment and rotary hearth furnace are connected in sequence through a transfer belt;

[0009] The powerful mixer is used to evenly mix the waste plastic oil can powder obtained after being processed by the crushing equipment and the first screening equipment with the iron-zinc dust mud, the binder and water. The powerful mixer is equipped with a plastic powder bin, a dust mud bin and a binder bin;

[0010] The rotary hearth furnace is used to reduce the dried pellets processed by the drying equipment. The feed port of the rotary hearth furnace is provided with a vibrating distributor for distributing the pellets. The flue gas outlet of the rotary hearth furnace is connected to the flue gas inlet of the flue gas quenching tower through a flue gas duct. The discharge port of the rotary hearth furnace is provided with a discharge device.

[0011] The flue gas quenching tower is used to quickly cool the zinc-containing flue gas coming out of the rotary hearth furnace and recover waste heat; the flue gas outlet of the flue gas quenching tower is connected to the dust collector through a pipeline;

[0012] The dust collector is used to remove dust from the zinc-containing flue gas cooled by the flue gas quenching tower and obtain zinc oxide powder.

[0013] Preferably, the rotary hearth furnace is provided with a heating zone, a first reduction zone, a second reduction zone, a third reduction zone, a fourth reduction zone and a fifth reduction zone in sequence; and the flue gas outlet of the rotary hearth furnace is provided in the reduction zone.

[0014] Preferably, the device for co-processing waste plastic oil bottles and iron-zinc dust and mud further includes a cooling cylinder connected to the discharging device and a second screening device; the cooling cylinder and the second screening device are connected via a transfer belt.

[0015] A second aspect of the present invention provides a method for the coordinated treatment of waste plastic oil cans and iron-zinc dust sludge, using the device for the coordinated treatment of waste plastic oil cans and iron-zinc dust sludge described in the first aspect of the present invention; the method for the coordinated treatment of waste plastic oil cans and iron-zinc dust sludge comprises the following steps:

[0016] S1, raw material pretreatment, waste plastic oil cans are washed to recover waste oil, and then crushed and sieved to obtain waste plastic oil can powder;

[0017] S2, pelletizing, mixing the waste plastic oil can powder with iron-zinc dust, a binder and water, and forming green pellets through a pelletizing process;

[0018] S3, reduction in a rotary hearth furnace, drying the green pellets to obtain dried pellets, and sending the dried pellets into a rotary hearth furnace for reduction roasting, whereby zinc in the iron-zinc dust is reduced and enters the zinc-containing flue gas, and iron oxides in the iron-zinc dust are reduced to metallized pellets at high temperature;

[0019] S4, flue gas treatment, the zinc-containing flue gas enters a flue gas quenching tower for cooling treatment, and then undergoes dust removal treatment to obtain zinc oxide powder.

[0020] Preferably, in step S1, the content of particles with a diameter of 0.2 to 0.5 mm in the waste plastic oil can powder is 75 to 85 wt%.

[0021] Preferably, in step S2:

[0022] The mass fraction of the iron-zinc dust is 100 parts, the mass fraction of the binder is 1 to 4 parts, the mass fraction of the waste plastic oil can powder is 0 to 4 parts, and the mass fraction of the water is 10 to 15 parts; and / or

[0023] The iron-zinc dust mud has a total iron content of ≥45wt% and a zinc content of ≥1wt%; and / or

[0024] The binder is corn starch; and / or

[0025] The moisture content of the green pellets is 10-15 wt % and the drop strength is greater than 4 times / 1 m.

[0026] Preferably, in step S3:

[0027] The moisture content of the dried pellets is less than 5wt%, and the drop strength is greater than 9 times / 1m; and / or

[0028] The thickness of the material layer on the rotating hearth of the rotary hearth furnace is 1 to 3 layers; and / or

[0029] During the reduction process in the rotary hearth furnace, the temperature in the rotary hearth furnace is 1230-1300° C., and the time for the rotary hearth furnace to rotate one circle is 25-30 minutes; and / or

[0030] The metallization rate of the metallized pellets is ≥90%; and / or

[0031] The metallized pellets are discharged from the rotary hearth furnace and then enter a cooling drum to be cooled to below 200°C. They are then screened and sent to a finished product bin.

[0032] Preferably, in step S4, the temperature of the zinc-containing flue gas is reduced to below 200° C. within 1 second after entering the flue gas quenching tower.

[0033] Preferably, in step S4, the zinc grade of the zinc oxide powder is greater than 65%.

[0034] The method and device for collaboratively treating waste plastic oil bottles and iron-zinc dust sludge provided by the present invention also have the following beneficial effects:

[0035] 1. The method and apparatus for the coordinated treatment of waste plastic oil jugs and iron-zinc dust sludge of the present invention use waste plastic oil jugs instead of part of the coke as a reducing agent, and utilize a rotary hearth furnace for coordinated treatment of the waste plastic oil jugs and iron-zinc dust sludge. This not only achieves efficient recovery of iron and zinc, but also, to a certain extent, solves the pollution problem of waste plastic oil jugs in steel mills, saves energy and raw materials, and further reduces the cost of the rotary hearth furnace coordinated treatment.

[0036] 2. The waste plastic oil cans used in the present invention have a combustion calorific value of up to 44,000 kJ / kg, which is close to that of industrial fuel oil. They can replace part of carbon powder or coke powder as a reducing agent, reducing the amount of reducing carbon powder added during the batching process and appropriately reducing the amount of coal gas used. By using a rotary hearth furnace and coordinating the treatment with iron-zinc dust and sludge, production efficiency can be improved and production costs can be reduced while the amount of waste to be treated remains the same.

[0037] 3. Waste plastic oil bottles are hazardous wastes. Conventional landfill and incineration treatments are difficult to effectively render them harmless. In the direct reduction process of the rotary hearth furnace of the present invention, the reduction temperature is about 1300°C (the decomposition temperature of waste plastic oil bottles is about 500°C). The atmosphere and temperature of the rotary hearth furnace can be used to decompose the waste plastic oil bottles, effectively avoiding the formation of dioxins. At the same time, using the waste plastic oil bottles as a reducing agent can achieve their harmlessness and resource utilization.

[0038] 4. The method and device for the coordinated treatment of waste plastic oil cans and iron-zinc dust sludge of the present invention include gas collection and treatment processes. During the coordinated treatment of waste plastic oil cans, not only can the secondary pollution to the environment caused by harmful gases generated during the reduction process of the rotary hearth furnace be effectively prevented, but the organic components in the waste plastic oil cans can also be reasonably and effectively utilized, further realizing the resource utilization of the waste plastic oil cans. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0040] Figure 1 This is a schematic structural diagram of a device for co-processing waste plastic oil bottles and iron-zinc dust sludge according to the present invention;

[0041] Figure 2 The figure is a schematic flow chart of the method for co-processing waste plastic oil bottles and iron-zinc dust sludge according to the present invention. DETAILED DESCRIPTION

[0042] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below with reference to embodiments.

[0043] Combine Figure 1As shown, the present invention provides a coordinated processing device for waste plastic oil bottles and iron-zinc dust and sludge. The device comprises a washing device 1, a crushing device 2, a first screening device 3, a high-pressure mixer 4, a briquetting machine 5, a drying device 6, a rotary hearth furnace 7, a flue gas quenching tower 8, and a dust collector 9. The washing device 1, crushing device 2, first screening device 3, high-pressure mixer 4, briquetting machine 5, drying device 6, and rotary hearth furnace 7 are sequentially connected by a transfer belt. The washing device 1 is used to clean the waste plastic oil bottles and recover the waste oil. The crushing device 2 and first screening device 3 are used to crush and screen the cleaned waste plastic oil bottles to obtain waste plastic oil bottle powder of appropriate size. The high-pressure mixer 4 is used to uniformly mix the waste plastic oil bottle powder obtained after treatment by the crushing device 2 and first screening device 3 with iron-zinc dust and sludge, a binder, and water. The high-pressure mixer 4 is equipped with a plastic powder bin, a dust and sludge bin, and a binder bin. The high-pressure mixer 4 is also equipped with a water supply device. The pelletizing machine 5 is used to press the material mixed by the high-pressure mixer 4 into green pellets. The drying equipment 6 is used to dry the green pellets. The rotary hearth furnace 7 is used to reduce the dried pellets processed by the drying equipment 6. The high-temperature zinc-containing flue gas obtained after the reduction treatment enters the flue gas rapid cooling tower 8 through the flue gas duct for treatment; wherein the feed port of the rotary hearth furnace 7 is provided with a vibrating distributor for distribution, so as to evenly distribute the dried pellets on the rotating hearth of the rotary hearth furnace 7, such as evenly distributing 1 to 3 layers of furnace charge on the rotating hearth; the flue gas outlet of the rotary hearth furnace 7 is connected to the flue gas inlet of the flue gas rapid cooling tower 8 through the flue gas duct, and the discharge port of the rotary hearth furnace 7 is provided with a discharge device, such as a spiral discharger. Flue gas quenching tower 8 is used to rapidly cool the zinc-containing flue gas from the rotary hearth furnace 7 and recover waste heat. The flue gas outlet of flue gas quenching tower 8 is connected to dust collector 9 via a pipeline. Since the zinc-containing flue gas from the rotary hearth furnace 7 is prone to re-formation of dioxins during the cooling process (300-500°C), the zinc-containing flue gas must be cooled to below 200°C within 1 second to prevent dioxin re-formation during the cooling process. Dust collector 9 removes dust from the zinc-containing flue gas cooled by flue gas quenching tower 8 and produces zinc oxide powder. After the zinc-containing flue gas has been dedusted and meets the standards, it is discharged through the chimney.

[0044] In a specific embodiment, a heating zone, a reduction zone 1, a reduction zone 2, a reduction zone 3, a reduction zone 4 and a reduction zone 5 are sequentially provided in the rotary hearth furnace 7. Since the dried pellets pass through the heating zone, the reduction zone 1, the reduction zone 2, the reduction zone 3, the reduction zone 4 and the treatment zone 5 in sequence, a large amount of zinc-containing flue gas will be generated when the dried pellets are subjected to reduction treatment in the rotary hearth furnace 7. The direction of the flue gas is opposite to the rotation direction of the rotary hearth furnace. Therefore, the flue gas outlet of the rotary hearth furnace 7 is arranged in the heating zone.

[0045] Combine Figure 1As shown, in order to further reduce the temperature of the metallized pellets after they come out of the rotary hearth furnace 7 and to screen out the powder that falls off during the reduction process, the device for co-processing waste plastic oil bottles and iron-zinc dust and mud also includes a cooling cylinder 10 connected to the discharge device and a second screening device 11; the cooling cylinder 10 and the second screening device 11 are connected by a transfer belt.

[0046] Combine Figure 2 As shown, the method for co-processing waste plastic oil bottles and iron-zinc dust mud of the present invention comprises the following steps:

[0047] S1, raw material pretreatment, waste plastic oil cans are washed to recover waste oil, and then crushed and sieved to obtain waste plastic oil can powder;

[0048] Specifically, waste plastic oil cans collected from steel mills are placed in a washing device for washing and the waste oil therein is recovered. The cleaned waste plastic oil cans are then sent to a crushing device for crushing, and then screened using a first screening device to obtain waste plastic oil can powder. In a further specific embodiment, the content of particles with a diameter of 0.2 to 0.5 mm in the waste plastic oil can powder is 75 to 85 wt%. Under this particle size distribution condition, the waste plastic oil can powder has similar combustion and gasification characteristics to coal powder, which can effectively ensure its reduction effect on iron-zinc dust and sludge. If the particle size of the waste plastic oil can powder is large, its reduction effect is poor, resulting in waste of resources and greatly affecting product quality. If the particle size of the waste plastic oil can powder is small, the waste plastic oil can powder will suffer greater burnout, which also results in waste of resources. At the same time, the energy consumption required for crushing is also large, which increases the process operation cost.

[0049] S2, pelletizing, mixing the waste plastic oil can powder with iron-zinc dust, a binder and water, and forming green pellets through a pelletizing process;

[0050] Specifically, waste plastic oil can powder is evenly mixed with iron-zinc dust, a binder, and water in a high-pressure mixer in a certain proportion, and then pressed into green pellets using a pelletizing process using a pelletizing machine. The raw materials are: 100 parts by weight of the iron-zinc dust (on a dry basis), 1 to 4 parts by weight of the binder, 0 to 4 parts by weight of the waste plastic oil can powder, and 10 to 15 parts by weight of water. The iron-zinc dust has a total iron content of ≥45wt%, and a zinc content of ≥1wt%. Corn starch is used as the binder. The green pellets prepared above have a moisture content of 10 to 15wt%, and a drop strength of >4 times / 1m.

[0051] S3, reduction in a rotary hearth furnace, drying the green pellets to obtain dried pellets, which are then fed into a rotary hearth furnace for reduction roasting. Zinc in the iron-zinc dust is reduced and enters the zinc-containing flue gas, and iron oxides in the iron-zinc dust are reduced at high temperature to form metallized pellets (DRI pellets);

[0052] Specifically, green pellets are fed into a drying device for drying to produce dried pellets, which are then transported to the inlet of a rotary hearth furnace via a conveyor belt. The dried pellets are evenly distributed on the rotary hearth of the rotary hearth furnace by a vibrating distributor, wherein the material layer (dried pellets) on the rotary hearth can be 1 to 3 layers thick. The dried pellets enter the rotary hearth furnace and undergo reduction roasting as the rotary hearth rotates. The dried pellets sequentially pass through a heating zone, a first reduction zone, a second reduction zone, a third reduction zone, a fourth reduction zone, and a fifth reduction zone, thereby being fully reduced within the rotary hearth furnace. During the reduction roasting process, waste plastic oil can powder replaces coke as a reducing agent, reducing zinc in the iron-zinc dust sludge and entering the zinc-containing flue gas. The iron oxides in the iron-zinc dust sludge are then reduced to metallized pellets at high temperature. The dried pellets have a moisture content of less than 5wt% and a drop strength of more than 9 times / 1m. During the reduction process in the rotary hearth furnace, the temperature in the rotary hearth furnace is 1230-1300°C, and the rotary hearth furnace rotates once every 25-30 minutes. The metallization rate of the metallized pellets is ≥90%. After the reduced metallized pellets are discharged from the discharging device of the rotary hearth furnace, they enter a cooling drum and are cooled to below 200°C. After screening by a second screening device to remove the powder, the metallized pellets are sent to a finished product bin.

[0053] S4, flue gas treatment, the zinc-containing flue gas enters a flue gas quenching tower for cooling treatment, and then undergoes dust removal treatment to obtain zinc oxide powder.

[0054] Specifically, the high-temperature zinc-containing flue gas enters a flue gas quenching tower for rapid cooling. The flue gas quenching tower is a key piece of equipment in the coordinated treatment of waste plastic oil cans and iron-zinc dust sludge. Since the zinc-containing flue gas generated by the rotary hearth furnace (300-500°C) is prone to re-formation of dioxins during the cooling process, the zinc-containing flue gas enters the flue gas quenching tower and is cooled to below 200°C within 1 second, effectively controlling the re-formation of dioxins. The flue gas quenching tower consists of a tower body, insulation, liquid and gas lines, piping, detection components, and a control system. Connected to the rotary hearth furnace flue gas system, the flue gas quenching tower rapidly cools the flue gas discharged from the rotary hearth furnace, effectively preventing the formation of dioxins. The flue gas treated in the flue gas quenching tower then passes through a dust collector for dust removal, producing zinc oxide powder with a zinc grade greater than 65%. The treated flue gas, once meeting standards, is discharged through a chimney.

[0055] The following is a further introduction to the method and device for collaboratively treating waste plastic oil bottles and iron-zinc dust sludge of the present invention with reference to specific examples.

[0056] Example 1

[0057] The method for co-processing waste plastic oil cans and iron-zinc dust sludge in this embodiment is as follows:

[0058] The iron-zinc dust (dry basis) contains TFe: 48.69%, Zn: 3.21%, C: 5%, Na: 1.44%, and K: 0.47%.

[0059] (1) Raw material pretreatment: waste plastic oil cans from steel mills are washed to recover waste oil, and then crushed and screened to obtain waste plastic oil can powder of appropriate size. The content of waste plastic oil can powder with a particle size of -50 mesh is 93%, of which the content of powder with a particle size of 0.2mm to 0.5mm is 80%;

[0060] (2) batching and mixing: the waste plastic oil can powder in step (1) is batched with iron-zinc dust, a binder, and water in proportion and then mixed; wherein 100 parts of iron-zinc dust (dry basis), 3 parts of binder, 2.8 parts of waste plastic oil can, and 13 parts of water are taken;

[0061] (3) pelletizing: the material mixed in step (2) is pelletized into green pellets by a pelletizing process. At this time, the green pellets have a moisture content of 13%, a particle size of 20 mm, and a drop strength of 4.3 times / 1 m;

[0062] (4) drying the green pellets, drying and dehydrating the green pellets in step (3), wherein the moisture content of the dried pellets is 4.3% and the drop strength is 9.1 times / m;

[0063] (5) direct reduction in a rotary hearth furnace, wherein the dried pellets obtained in step (4) are evenly distributed on the annular hearth of the rotary hearth furnace by a vibrating distributor, and the thickness of the furnace bottom material layer is 2 layers. During the rotation of the rotary hearth furnace body, the material must pass through the heating zone, the reduction zone 1, the reduction zone 2, the reduction zone 3, the reduction zone 4, and the reduction zone 5 in sequence, so that the pellets are fully reduced in the rotary hearth furnace; wherein during the reduction process in the rotary hearth furnace, the reduction temperature is 1230-1280° C., the highest reduction temperature is 1280° C., and the material stays in the rotary hearth furnace for 25 minutes;

[0064] (6) Finished product cooling: the metallized pellets obtained in step (5) are discharged through a screw discharger and then enter a cooling drum to be cooled to below 200° C. After screening, they are sent to the finished product bin; the metallization rate of the metallized pellets is 95.3%, and the zinc removal rate of the iron-zinc dust is 96.2%;

[0065] (7) Flue gas treatment and collection: The high-temperature zinc-containing flue gas discharged from the rotary hearth furnace passes through the flue gas quenching device, where the temperature is reduced to ~200°C. It then enters the rotary hearth furnace flue gas dust collector to obtain zinc oxide powder. The cooled flue gas (~120°C) is dusted, desulfurized, and denitrified before being discharged to meet standards. The zinc oxide powder is then packaged and recovered in the rotary hearth furnace flue gas dust collector. The grade of the zinc oxide powder is 69.8%.

[0066] Example 2

[0067] The method for co-processing waste plastic oil cans and iron-zinc dust sludge in this embodiment is as follows:

[0068] The iron-zinc dust (dry basis) contains TFe: 46.66%, Zn: 2.65%, C: 6.3%, Na: 1.22%, and K: 0.46%.

[0069] (1) Raw material pretreatment: waste plastic oil cans from steel mills are washed to recover waste oil, and then crushed and screened to obtain waste plastic oil can powder of appropriate size. The content of waste plastic oil can powder with a particle size of -50 mesh is 90%, and the content of powder with a particle size of 0.2mm to 0.5mm is 78%;

[0070] (2) batching and mixing: the waste plastic oil can powder in step (1) is batched with iron-zinc dust, a binder, and water in proportion and then mixed; wherein 100 parts of iron-zinc dust (dry basis), 3 parts of binder, 3 parts of waste plastic oil can, and 12.6 parts of water are taken;

[0071] (3) pelletizing, wherein the material mixed in step (2) is pelletized into green pellets by a pelletizing process, wherein the green pellets have a moisture content of 12.6%, a particle size of 20 mm, and a drop strength of 4.6 times / m;

[0072] (4) drying the green pellets, drying and dehydrating the green pellets obtained in step (3), wherein the dried pellets have a moisture content of 4.0% and a drop strength of 9.7 times / m;

[0073] (5) direct reduction in a rotary hearth furnace, wherein the dried pellets obtained in step (4) are evenly distributed on the annular hearth of the rotary hearth furnace by a vibrating distributor, and the thickness of the furnace bottom material layer is 2 layers. During the rotation of the rotary hearth furnace body, the material must pass through the heating zone, the reduction zone 1, the reduction zone 2, the reduction zone 3, the reduction zone 4, and the reduction zone 5 in sequence, so that the pellets are fully reduced in the rotary hearth furnace; wherein during the reduction process in the rotary hearth furnace, the reduction temperature is 1230-1280° C., the maximum reduction temperature of the rotary hearth furnace is 1280° C., and the material stays in the rotary hearth furnace for 25 minutes;

[0074] (6) Finished product cooling: the metallized pellets obtained in step (5) are discharged through a screw discharger and then enter a cooling drum to be cooled to below 200° C. After screening, they are sent to the finished product bin; the metallization rate of the metallized pellets is 94.7%, and the zinc removal rate of the iron-zinc dust is 95.9%;

[0075] (7) Flue gas treatment and collection: The high-temperature zinc-containing flue gas discharged from the rotary hearth furnace passes through the flue gas quenching device, where the temperature is reduced to ~200°C. It then enters the rotary hearth furnace flue gas dust collector to obtain zinc oxide powder. The cooled flue gas (~120°C) is dusted, desulfurized, and denitrified before being discharged to meet standards. The zinc oxide powder is then packaged and recovered in the rotary hearth furnace flue gas dust collector. The grade of the zinc oxide powder is 68.3%.

[0076] Example 3

[0077] The method for co-processing waste plastic oil cans and iron-zinc dust sludge in this embodiment is as follows:

[0078] The iron-zinc dust (dry basis) contains TFe: 48.09%, Zn: 3.94%, C: 5.54%, Na: 1.74%, and K: 0.43%.

[0079] (1) Raw material pretreatment: waste plastic oil cans from steel mills are washed to recover waste oil, and then crushed and screened to obtain waste plastic oil can powder of appropriate size. The content of waste plastic oil can powder with a particle size of -50 mesh is 95%, and the content of powder with a particle size of 0.2mm to 0.5mm is 82%;

[0080] (2) batching and mixing: the waste plastic oil can powder obtained in step (1) is batched with iron-zinc dust, a binder, and water in proportion and then mixed; wherein 100 parts of iron-zinc dust (dry basis), 3 parts of binder, 3 parts of waste plastic oil can, and 13.3 parts of water are taken;

[0081] (3) pelletizing, wherein the mixed material in step (2) is pelletized into green pellets by a pelletizing process, wherein the green pellets have a moisture content of 13.3%, a particle size of 20 mm, and a drop strength of 5.3 times / m;

[0082] (4) drying the green pellets, drying and dehydrating the green pellets obtained in step (3), wherein the moisture content of the dried pellets is 4.7% and the drop strength is 10.0 times / 1m;

[0083] (5) direct reduction in a rotary hearth furnace, wherein the dried pellets obtained in step (4) are evenly distributed on the annular hearth of the rotary hearth furnace by a vibrating distributor, and the thickness of the furnace bottom material layer is 2 layers. During the rotation of the rotary hearth furnace body, the material must pass through the heating zone, the reduction zone 1, the reduction zone 2, the reduction zone 3, the reduction zone 4, and the reduction zone 5 in sequence, so that the pellets are fully reduced in the rotary hearth furnace; wherein during the reduction process in the rotary hearth furnace, the reduction temperature is 1230-1280° C., the maximum reduction temperature of the rotary hearth furnace is 1280° C., and the material stays in the rotary hearth furnace for 25 minutes;

[0084] (6) Finished product cooling: the metallized pellets obtained in step (5) are discharged through a screw discharger and then enter a cooling drum to be cooled to below 200° C. After screening, they are respectively sent to the finished product bin; the metallization rate of the metallized pellets is 96.8%, and the zinc removal rate of the iron-zinc dust is 97.5%;

[0085] (7) Flue gas treatment and collection: The high-temperature flue gas discharged from the rotary hearth furnace passes through the flue gas quenching device, where the temperature is reduced to ~200°C. It then enters the rotary hearth furnace flue gas dust collector to obtain zinc oxide powder. The cooled flue gas (~120°C) is dusted, desulfurized, and denitrified before being discharged to meet standards. The zinc oxide powder is then packaged and recovered in the rotary hearth furnace flue gas dust collector. The zinc powder grade of the zinc oxide powder is 71.0%.

[0086] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present invention and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for the coordinated treatment of waste plastic oil bottles and iron-zinc dust sludge, characterized in that: The waste plastic oil can and iron-zinc dust sludge collaborative treatment device is used to implement the waste plastic oil can and iron-zinc dust sludge collaborative treatment method. The device for co-processing waste plastic oil bottles and iron-zinc dust sludge comprises a washing device, a crushing device, a first screening device, a strong mixer, a briquetting machine, a drying device, a rotary hearth furnace, a flue gas quenching tower and a dust collector; The washing equipment, crushing equipment, first screening equipment, strong mixer, pelletizing machine, drying equipment and rotary hearth furnace are connected in sequence through a transfer belt; The powerful mixer is used to evenly mix the waste plastic oil can powder obtained after being processed by the crushing equipment and the first screening equipment with the iron-zinc dust mud, the binder and water. The powerful mixer is equipped with a plastic powder bin, a dust mud bin and a binder bin; The rotary hearth furnace is used to reduce the dried pellets processed by the drying equipment. The feed port of the rotary hearth furnace is provided with a vibrating distributor for distributing the pellets. The flue gas outlet of the rotary hearth furnace is connected to the flue gas inlet of the flue gas quenching tower through a flue gas duct. The discharge port of the rotary hearth furnace is provided with a discharge device. The flue gas quenching tower is used to quickly cool the zinc-containing flue gas coming out of the rotary hearth furnace and recover waste heat; the flue gas outlet of the flue gas quenching tower is connected to the dust collector through a pipeline; The dust collector is used to remove dust from the zinc-containing flue gas cooled by the flue gas quenching tower and obtain zinc oxide powder. The method for co-processing waste plastic oil bottles and iron-zinc dust mud comprises the following steps: S1, raw material pretreatment, waste plastic oil cans are washed to recover waste oil, and then crushed and sieved to obtain waste plastic oil can powder; S2, pelletizing, mixing the waste plastic oil can powder with iron-zinc dust, a binder and water, and forming green pellets through a pelletizing process; S3, reduction in a rotary hearth furnace, drying the green pellets to obtain dried pellets, and sending the dried pellets into a rotary hearth furnace for reduction roasting, whereby zinc in the iron-zinc dust is reduced and enters the zinc-containing flue gas, and iron oxides in the iron-zinc dust are reduced to metallized pellets at high temperature; S4, flue gas treatment, the zinc-containing flue gas enters the flue gas quenching tower for cooling treatment, and then undergoes dust removal treatment to obtain zinc oxide powder, In the step S1: The content of particles with a diameter of 0.2 to 0.5 mm in the waste plastic oil can powder is 75 to 85 wt%. In the step S2: The mass fraction of the iron-zinc dust is 100 parts, the mass fraction of the binder is 1 to 4 parts, the mass fraction of the waste plastic oil can powder is 0 to 4 parts, and the mass fraction of the water is 10 to 15 parts; The iron-zinc dust mud has a total iron content of ≥45wt% and a zinc content of ≥1wt%; The binder is corn starch; The moisture content of the green pellets is 10-15 wt % and the drop strength is greater than 4 times / 1 m.

2. The method for co-processing waste plastic oil bottles and iron-zinc dust sludge according to claim 1, characterized in that: The rotary hearth furnace is provided with a heating zone, a first reduction zone, a second reduction zone, a third reduction zone, a fourth reduction zone and a fifth reduction zone in sequence; the smoke outlet of the rotary hearth furnace is arranged in the heating zone.

3. The method for co-processing waste plastic oil bottles and iron-zinc dust according to claim 1, characterized in that: The device for co-processing waste plastic oil bottles and iron-zinc dust and mud also includes a cooling cylinder connected to the discharging device and a second screening device; the cooling cylinder and the second screening device are connected via a transfer belt.

4. The method for co-processing waste plastic oil bottles and iron-zinc dust according to claim 3, characterized in that: In the step S3: The moisture content of the dried pellets is less than 5wt% and the drop strength is greater than 9 times / 1m; The thickness of the material layer on the rotating hearth of the rotary hearth furnace is 1 to 3 layers; During the reduction process in the rotary hearth furnace, the temperature in the rotary hearth furnace is 1230-1300° C., and the time for the rotary hearth furnace to rotate one circle is 25-30 minutes. The metallization rate of the metallized pellets is ≥90%; The metallized pellets are discharged from the rotary hearth furnace and then enter a cooling drum to be cooled to below 200°C. They are then screened and sent to a finished product bin.

5. The method for co-processing waste plastic oil bottles and iron-zinc dust sludge according to claim 1, characterized in that: In the step S4, the temperature of the zinc-containing flue gas entering the flue gas quenching tower is reduced to below 200° C. within 1 second.

6. The method for co-processing waste plastic oil bottles and iron-zinc dust sludge according to claim 1, characterized in that: In the step S4, the zinc grade of the zinc oxide powder is greater than 65%.

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