Cold rolling waste acid recovery system and method

Abstract

The invention relates to the technical field of cold rolled steel production, and provides a cold rolling waste acid recovery system and method.The cold rolling waste acid recovery system comprises pickling equipment, a free acid adsorption mechanism, a low-temperature vacuum evaporation device and a freezing crystallization device; the free acid adsorption mechanism is connected with the pickling equipment, and is used for adsorbing free acid ions in a waste acid mixed solution containing ferrous ions discharged by the pickling equipment, and washing out the adsorbed acid ions through deionized water to form a recycled acid solution to be fed into the pickling equipment again; the low-temperature vacuum evaporation device is connected with the free acid adsorption mechanism and is used for evaporating the ferrous chloride solution which is discharged by the free acid adsorption mechanism and is subjected to free acid ion adsorption to remove water in the ferrous chloride solution, and a saturated ferrous chloride solution is obtained; the freezing crystallization device is connected with the low-temperature vacuum evaporation device and is used for separating out ferrous chloride crystals from the saturated ferrous chloride solution through freezing crystallization treatment and returning the solution from which the ferrous chloride crystals are separated out to the low-temperature vacuum evaporation device again for treatment; the method reduces environmental pollution caused by waste acid discharge, realizes high-purity recovery of acid and ferrous chloride, and saves cost.

Description

Technical Field

[0001] The invention relates to the technical field of cold-rolled steel production, and in particular to a cold-rolled waste acid recovery system and method. Background Art

[0002] The method of using acid solution to remove oxide scale and rust on the surface of steel is called pickling. In the production process of cold rolling and other steel surface treatments, a large amount of pickling waste liquid will be generated. The pickling waste liquid generally contains H+ and Fe2+. Due to its severe corrosiveness, the direct discharge of this type of waste liquid not only seriously pollutes the environment, but also causes great waste.

[0003] At present, hydrochloric acid pickling waste liquid is mainly composed of three substances: hydrogen chloride, water and ferrous chloride. The traditional treatment method generally adopts neutralization method or direct roasting method. Among them, the neutralization method uses calcium hydroxide for neutralization. Although the pH value can meet the requirements after neutralization, it is difficult to meet the standards for other indicators. In addition, the generated sludge is difficult to dehydrate, dry and post-process. In most cases, it is piled up for treatment, occupying a large amount of land and causing secondary pollution. At the same time, this method wastes a lot of acid and iron resources. The direct roasting method is to oxidize and hydrolyze ferrous salts with waste acid under high temperature conditions, and evaporate the water to obtain iron oxide. However, a part of the hydrogen chloride gas evaporates at the same time, which is then adsorbed by deionized water spray to form recovered acid liquid, which is reused in the pickling production. In addition, the purity of the iron oxide is not high, and its utilization value is not high. If the purity needs to be improved, a silicon removal system needs to be built, and the entire treatment process consumes a lot of energy. Summary of the invention

[0004] The invention provides a cold rolling waste acid recovery system and method, which are used to solve the problems of high cost of treating pickling waste liquid and poor recovery effect in the prior art.

[0005] In a first aspect, the present invention provides a cold rolling waste acid recovery system, comprising: Pickling equipment, used to treat the oxidation and rust on the surface of the strip steel plate; A free acid adsorption mechanism is connected to the pickling equipment and is used to adsorb free acid ions in the waste acid mixed solution containing ferrous ions discharged from the pickling equipment, and to rinse out the adsorbed acid ions with deionized water to form a recovered acid solution and re-send it to the pickling equipment; A low-temperature vacuum evaporation device is connected to the free acid adsorption mechanism, and is used to remove water from the ferrous chloride solution discharged from the free acid adsorption mechanism after adsorbing free acid ions, and obtain a saturated ferrous chloride solution; The freezing crystallization device is connected to the low-temperature vacuum evaporation device and is used to treat the saturated ferrous chloride solution by freezing crystallization to precipitate ferrous chloride crystals, and to return the solution after the ferrous chloride crystals are precipitated to the low-temperature vacuum evaporation device for treatment again.

[0006] The cold rolling waste acid recovery system provided by the present invention also includes an incinerator, which is connected to the freezing crystallization device and is used to burn the precipitated ferrous chloride crystals into iron-containing oxides; the incinerator includes a furnace body, a blower, an air duct and a feeding mechanism, the feeding mechanism is arranged on the outside of the furnace body, and is used to deliver the ferrous chloride crystals to the inlet of the furnace body, one end of the air duct is connected to the air outlet of the blower, and the other end of the air duct is arranged at the top inlet of the furnace body, so as to blow the ferrous chloride crystals delivered to the inlet of the furnace body into the furnace body.

[0007] According to the cold rolling waste acid recovery system provided by the present invention, the free acid adsorption mechanism comprises: A waste acid sedimentation tank, the inlet of which is connected to the pickling equipment through a pipeline, and is used to settle solid impurities in the waste acid mixed solution containing ferrous ions discharged from the pickling equipment to the bottom to form acid sludge by gravity; A first temporary storage tank, the inlet of which is connected to the outlet of the waste acid sedimentation tank through a pipeline, and is used to store the filtered waste acid mixed liquid; A filtering device, the inlet of which is connected to the outlet of the waste acid settling tank through a pipeline, for filtering the waste acid mixed solution containing ferrous ions and for returning the backwash liquid to the inlet of the waste acid settling tank; An adsorption resin bed, one end of which is connected to the outlet of the filtration device through a pipeline, for introducing the filtered waste acid mixture and adsorbing free acid in the waste acid mixture, and the other end of which is used to introduce deionized water to flush out the free acid adsorbed in the adsorption resin bed to form a recovered acid solution; A second temporary storage tank, the inlet of which is connected to the liquid outlet of the adsorption resin bed through a pipeline, and is used to store the ferrous chloride solution after free acid removal, and the outlet of which is connected to the low-temperature vacuum evaporation device through a pipeline.

[0008] The cold rolling waste acid recovery system provided by the present invention also includes a third temporary storage tank, the inlet of the third temporary storage tank is connected to the acid outlet of the adsorption resin bed through a pipeline, and is used to store the recovered acid liquid; the outlet of the third temporary storage tank is connected to the pickling equipment through a pipeline, and is used to send the recovered acid liquid to the pickling equipment for reuse.

[0009] According to the cold rolling waste acid recovery system provided by the present invention, the filtering device includes a first filter and a second filter connected in series, the inlet of the first filter is connected to the outlet of the waste acid sedimentation tank through a pipeline, and the outlet of the second filter is connected to the adsorption resin bed through a pipeline.

[0010] According to the cold rolling waste acid recovery system provided by the present invention, the waste acid sedimentation tank includes a tank body, a water distributor and a plurality of inclined plate layers, the plurality of inclined plate layers are arranged at intervals at the top of the tank body, the water distributor is arranged in the tank body and is located below the plurality of inclined plate layers, and a water outlet is arranged at the top of the tank body.

[0011] According to the cold rolling waste acid recovery system provided by the present invention, the low-temperature vacuum evaporation device comprises: a distillation kettle, wherein the inlet of the distillation kettle is connected to the outlet of the second temporary storage tank through a pipeline; An evaporator, the inlet of the evaporator is connected to the outlet of the distillation kettle through a pipeline, and is used to transport the ferrous chloride solution to the evaporator to be heated and evaporate the water therein; A vacuum pump connected to the evaporator and used to reduce the pressure inside the evaporator to reduce the boiling point of the ferrous chloride solution; An eddy current separator, the inlet of which is connected to the outlet of the evaporator through a pipeline, and is used to separate the steam generated by the evaporator from the concentrated ferrous chloride solution; A liquid discharge pump, the liquid discharge pump is connected to the liquid outlet of the eddy current separator through a pipeline, and is used to pump the concentrated ferrous chloride solution in the eddy current separator into the freezing crystallization device; a condenser, the inlet of the condenser being connected to the outlet of the eddy current separator, and being used for cooling and liquefying the steam separated by the eddy current separator; A compressor, wherein the inlet of the compressor is connected to the outlet of the condenser, and is used for compressing the liquid vapor discharged from the condenser to increase its pressure and temperature; and the outlet of the compressor is connected to the distillation kettle, and is used for feeding the compressed liquid vapor into the distillation kettle.

[0012] According to the cold rolling waste acid recovery system provided by the present invention, the first filter is a fiber filter, the second filter includes a filter element, a shell, a first partition, a second partition, a water inlet and a water outlet, the first partition and the second partition are horizontally spaced apart and arranged in the shell, the first partition and the second partition are respectively provided with mounting holes, the filter element is vertically arranged, and the top end of the filter element is sealed and connected to the mounting hole of the first partition, the bottom end of the filter element is sealed and connected to the mounting hole of the second partition, the water inlet is arranged on one side of the shell and communicated with the space between the first partition and the second partition, and the water outlet is arranged at the top end of the shell.

[0013] According to the cold rolling waste acid recovery system provided by the present invention, the first partition plate and the second partition plate are both provided with a plurality of through holes.

[0014] In a second aspect, the present invention further provides a method for recovering cold rolling waste acid, which is applied to the above-mentioned cold rolling waste acid recovery system and comprises the following steps: The waste acid mixed solution containing ferrous ions after pickling is subjected to adsorption treatment to recover free acid ions in the waste acid mixed solution; The adsorbed acid ions are rinsed out with deionized water to form a recovered acid solution, and the strip steel plate is further pickled; The ferrous chloride solution after adsorbing the free acid ions is subjected to low-temperature vacuum evaporation treatment to remove the water therein to obtain a saturated ferrous chloride solution; The saturated ferrous chloride solution is subjected to a freeze crystallization treatment to precipitate ferrous chloride crystals, and the solution after the precipitated ferrous chloride crystals is subjected to a low-temperature vacuum evaporation treatment again; The precipitated ferrous chloride crystals are burned to form iron-containing oxides, and the iron-containing oxides are recovered.

[0015] The cold rolling waste acid recovery system provided by the present invention comprises: pickling equipment, free acid adsorption mechanism, low-temperature vacuum evaporation device and freezing crystallization device; the present invention effectively recovers free acid ions from the waste acid mixed liquid through the free acid adsorption mechanism, and converts the free acid ions into recovered acid liquid and sends them back to the pickling equipment, thereby reducing the consumption of new acid, improving resource utilization and reducing the cost of raw materials; the ferrous chloride solution is treated by the low-temperature vacuum evaporation device to obtain a saturated ferrous chloride solution. Compared with normal pressure evaporation, the device operates under lower temperature and vacuum conditions, which can reduce energy consumption, effectively evaporate water, concentrate the ferrous chloride solution, and perform evaporation treatment at a lower temperature. The method can cooperate well with freezing crystallization to help save energy and reduce consumption, and can improve the recovery purity of ferrous chloride; the ferrous chloride crystals precipitated by the freezing crystallization device are of high purity, and no additional impurity removal device is required, thereby realizing the recovery of metal ions in the waste acid mixed solution, and these pure crystals can produce high-value-added high-purity soft magnetic iron oxide materials, thereby realizing high-value-added recycling of resources; compared with the neutralization, discharge or landfill methods that may be involved in the waste acid treatment in the traditional technology, the present invention significantly reduces the pollution of the environment caused by the discharge of waste acid, and realizes the high-purity recovery of acid and ferrous chloride to produce high-value-added high-purity soft magnetic iron oxide materials, thereby saving costs and improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a structural schematic diagram of a cold rolling waste acid recovery system provided by an embodiment of the present invention.

[0018] Figure 2 It is a schematic diagram of the structure of the free acid adsorption mechanism provided in an embodiment of the present invention.

[0019] Figure 3 It is a schematic diagram of the structure of an adsorption resin bed provided in an embodiment of the present invention.

[0020] Figure 4 It is a schematic diagram of the structure of the second filter provided in an embodiment of the present invention.

[0021] Figure 5 It is a schematic structural diagram of a first partition provided in an embodiment of the present invention.

[0022] Figure 6 It is a schematic flow chart of a method for recovering cold rolling waste acid provided in an embodiment of the present invention.

[0023] Reference numerals: 1. Free acid adsorption mechanism; 2. Low temperature vacuum evaporation device; 3. Freezing crystallization device; 4. Waste acid sedimentation tank; 41. Tank body; 42. Water distributor; 43. Inclined plate layer; 5. First temporary storage tank; 6. Filter device; 61. Second filter; 611. Filter element; 612. Housing; 613. First partition; 6131. ​​Through hole; 614. Second partition; 615. Water inlet; 616. Water outlet; 617. Cover; 618. Hoisting rod; 7. adsorption resin bed; 71. resin tank; 72. first water distribution device; 73. second water distribution device; 8. The third temporary storage tank; 9. The first pickling tank; 10. The second pickling tank; 11. The third pickling tank. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Combine the following Figure 1-Figure 5 The invention describes a system and method for recovering waste acid from cold rolling.

[0026] An embodiment of the present invention provides a cold rolling waste acid recovery system, comprising: a pickling device, a free acid adsorption mechanism 1, a low-temperature vacuum evaporation device 2 and a freezing crystallization device 3.

[0027] The pickling equipment uses hydrochloric acid to treat the oxidized rust on the surface of the strip steel plate; the free acid adsorption mechanism 1 is connected to the pickling equipment, and is used to adsorb the free acid ions in the waste acid mixture containing ferrous ions discharged from the pickling equipment, and is used to rinse the adsorbed acid ions out with deionized water to form a recovered acid solution and re-send it to the pickling equipment; the low-temperature vacuum evaporation device 2 is connected to the free acid adsorption mechanism 1, and is used to remove the water in the ferrous chloride solution discharged by the free acid adsorption mechanism 1 after the free acid ions are adsorbed, and obtain a saturated ferrous chloride solution, wherein the low-temperature evaporation refers to evaporating the ferrous chloride solution at -94 to -97 KPa and 30 to 50 ° C; the freezing crystallization device 3 is connected to the low-temperature vacuum evaporation device 2, and is used to remove the water in the ferrous chloride solution after the free acid ions are adsorbed, and obtain a saturated ferrous chloride solution. The saturated ferrous chloride solution is treated by freezing and crystallizing to separate out ferrous chloride crystals, and the solution after the ferrous chloride crystals are separated out is returned to the low-temperature vacuum evaporator 2 for treatment. That is to say, the ferrous chloride solution is circulated through the freezing and crystallizing device 3 and the low-temperature vacuum evaporator 2. On the one hand, the saturated ferrous chloride solution obtained by the low-temperature vacuum evaporator 2 enters the freezing and crystallizing device 3 to separate out ferrous chloride crystals, so that the ferrous chloride solution is recovered. On the other hand, the ferrous chloride solution after the ferrous chloride crystals are separated out cannot reach a saturated state. By returning the ferrous chloride solution to the low-temperature vacuum evaporator 2 for treatment again, a saturated ferrous chloride solution can be obtained. This goes back and forth, and the purity of the recovery of ferrous chloride from the solution is improved by utilizing the freezing purification principle.

[0028] It can be seen from the above scheme that the present invention effectively recovers free acid ions from the waste acid mixture through the free acid adsorption mechanism 1, and converts it into recovered acid solution and sends it back to the pickling equipment, thereby reducing the consumption of new acid, improving resource utilization, and reducing the cost of raw materials; the ferrous chloride solution is treated by the low-temperature vacuum evaporation device 2 to obtain a saturated ferrous chloride solution. Compared with normal pressure evaporation, this device operates under lower temperature and vacuum conditions, which can reduce energy consumption, effectively evaporate water, and concentrate the ferrous chloride solution. In addition, the evaporation treatment at a lower temperature can cooperate well with freezing crystallization, which is conducive to energy saving and consumption reduction. The recovery purity of ferrous chloride can be improved; the purity of ferrous chloride crystals precipitated by the freezing crystallization device is high, and no additional impurity removal device is required, so the recovery of metal ions in the waste acid mixed solution is realized, and these pure crystals can produce high-value-added high-purity soft magnetic iron oxide materials, thereby realizing high-value-added recycling of resources; compared with the neutralization, discharge or landfill methods that may be involved in the waste acid treatment in the traditional technology, the present invention significantly reduces the pollution of the environment caused by the discharge of waste acid, and realizes the high-purity recovery of acid and ferrous chloride to produce high-value-added high-purity soft magnetic iron oxide materials, thereby saving costs and improving economic benefits.

[0029] In this embodiment, an incinerator is also included, which is connected to the freezing crystallization device 3 and is used to burn the precipitated ferrous chloride crystals into iron-containing oxides. In this way, the iron-containing oxides have a wide range of application values ​​in the fields of anti-corrosion materials, soft magnetic oxide material manufacturing, etc., thereby achieving deep utilization of recycled resources.

[0030] Preferably, the incinerator comprises a furnace body, a blower, an air duct and a feeding mechanism, wherein the incinerator belongs to a product in the prior art, and the improvement of the present invention is that the original liquid nozzle system is cancelled at the top of the furnace body, the blower is a device of the incinerator's own blowing system, and a feeding mechanism is arranged on the outside of the furnace body to deliver ferrous chloride crystals to the entrance of the furnace body, one end of the air duct is connected to the air outlet of the blower, and the other end of the air duct is arranged at the top entrance of the furnace body, so that the ferrous chloride crystals delivered to the entrance of the furnace body can be blown into the furnace body; that is, on the basis of the original structure, an air duct is led out by the blower to the entrance of the furnace body, when the feeding mechanism such as a chain loader lifts the solid ferrous chloride crystals to the entrance of the furnace top, the blower provides power, and the gas blown out through the air duct throws the ferrous chloride crystals into the furnace body.

[0031] In this way, by improving the existing structure, the inlet for injecting acid is transformed into a throwing port, and the solid ferrous chloride crystals are thrown into the incinerator through the throwing port under the action of the blast. The blast not only provides the power for throwing, but also helps to evenly distribute the crystals in the furnace, which is conducive to achieving sufficient combustion.

[0032] It should be noted that the pickling equipment, low-temperature vacuum evaporation device 2 and freezing crystallization device 3 are all products in the prior art. Their structure and principle are not the focus of this article and will not be elaborated here.

[0033] In this embodiment, the free acid adsorption mechanism 1 includes a waste acid sedimentation tank 4, a first temporary storage tank 5, a filtering device 6, an adsorption resin bed 7 and a second temporary storage tank.

[0034] like Figure 1-Figure 2 As shown, specifically, the inlet of the waste acid sedimentation tank 4 is connected to the waste acid discharge storage tank of the pickling equipment through a pipeline, which is used to settle the solid impurities in the waste acid mixture containing ferrous ions discharged from the pickling equipment to the bottom to form acid sludge by gravity. The acid sludge is treated together with the acid sludge from the cold rolling mill wastewater treatment. For example, larger solid particles in the waste acid mixture, such as metal chips, oxides, etc., can be effectively removed to prevent these particles from entering subsequent processing units, thereby reducing equipment wear and clogging risks.

[0035] The inlet of the first temporary storage tank 5 is connected to the outlet of the waste acid sedimentation tank 4 through a pipeline, and is used to store the filtered waste acid mixture; in this way, the temporary storage tank can balance the flow fluctuations upstream and downstream, ensure the stable feed of the subsequent treatment unit, and avoid uneven treatment due to sudden changes in flow; and the temporary storage tank can also provide a certain residence time, so that some smaller particles have more opportunities to precipitate, further improving the initial purification effect of the waste acid mixture.

[0036] The inlet of the filter device 6 is connected to the outlet of the waste acid sedimentation tank 4 through a pipeline, which is used to filter the waste acid mixed liquid containing ferrous ions and to return the backwash liquid to the inlet of the waste acid sedimentation tank 4; in this way, the filter device 6 can remove small particles and suspended matter that cannot be completely removed by the waste acid sedimentation tank 4, ensure that the waste acid liquid entering the adsorption resin bed 7 is as pure as possible, and reduce the risk of pollution and clogging of the resin bed.

[0037] One end of the adsorption resin bed 7 is connected to the outlet of the filtering device 6 through a pipeline, which is used to introduce the filtered waste acid mixture and adsorb the free acid in the waste acid mixture. The other end of the adsorption resin bed 7 is used to introduce deionized water to rinse out the free acid adsorbed in the adsorption resin bed 7 to form a recovered acid solution; the inlet of the second temporary storage tank is connected to the liquid outlet of the adsorption resin bed 7 through a pipeline, which is used to store the ferrous chloride solution after the free acid is removed, and the outlet of the second temporary storage tank is connected to the low-temperature vacuum evaporation device 2 through a pipeline.

[0038] With such arrangement, solid impurities, suspended matter and free acid in the waste acid are gradually removed through multi-stage treatment of the waste acid settling tank 4, the filtering device 6 and the adsorption resin bed 7, thereby ensuring the quality and purity of the final product; the adsorption resin bed 7 not only purifies the waste acid, but also recovers valuable acid liquid through the desorption process, thereby realizing the recycling of the acid and reducing the operating cost of the enterprise; the design of the temporary storage tank provides a guarantee for the stable operation of the system and avoids uneven treatment due to flow fluctuations or equipment failures.

[0039] In a further embodiment, the free acid adsorption mechanism 1 also includes a third temporary storage tank 8, the inlet of the third temporary storage tank 8 is connected to the acid outlet of the adsorption resin bed 7 through a pipeline, and is used to store the recovered acid liquid, and the outlet of the third temporary storage tank 8 is connected to the pickling equipment through a pipeline, and is used to send the recovered acid liquid to the pickling equipment for reuse.

[0040] In some specific embodiments, Figure 3As shown, the adsorption resin bed 7 includes: a resin tank 71, a first water distribution device 72 and a second water distribution device 73, wherein the first water distribution device 72 and the second water distribution device 73 have the same structure and are symmetrically connected at both ends of the resin tank 71; the resin tank 71 is filled with an adsorption resin capable of adsorbing acid ions in a compacted state, and the particle size of the adsorption resin is 0.1-0.3 mm, which is about 20% smaller than the resin in the traditional ion exchange system. The smaller particles allow a larger number of resin particles to be accommodated in a unit volume, thereby providing a larger total surface area and improving the adsorption effect and adsorption efficiency; by utilizing the "acid hysteresis" characteristic of the adsorption resin, the free acid in the acid solution is adsorbed on the resin particles by the adsorption resin, and at the same time, salts and other impurities flow out of the resin tank because they cannot be adsorbed on the resin particles, thereby realizing the separation of the free acid from the metal ions or other impurities, and being able to recover hydrochloric acid ions in the waste acid solution containing heavy metal ions and remove the heavy metal ions therein.

[0041] The bottom of the resin tank 71 is connected to a first water distribution device 72, which is provided with a first liquid inlet pipe, and the first liquid inlet pipe is used to supply the acid liquid axially upward into the resin tank 71; the top of the resin tank 71 is connected to a second water distribution device 73, which is provided with a second liquid inlet pipe, and the second liquid inlet pipe is used to supply flushing water axially downward into the resin tank 71, and buffer fillers are provided inside the two water distribution devices to reduce and balance the liquid flow rate.

[0042] In some embodiments, the filtering device 6 includes a first filter and a second filter 61 connected in series, the inlet of the first filter is connected to the outlet of the spent acid settling tank 4 through a pipeline, and the outlet of the second filter 61 is connected to the adsorption resin bed 7 through a pipeline.

[0043] Optionally, the first filter is used as primary filtration, and the second filter 61 is used as precision filtration, wherein the first filter is a fiber filter, and the filter material is an acid- and alkali-resistant fiber filter material; Figure 4As shown, the second filter 61 includes a filter element 611, a housing 612, a first partition 613, a second partition 614, a water inlet 615 and a water outlet 616. The filter element 611 is a cylindrical structure. The filter element 611 can be made of polypropylene PP, modified polyethersulfone PES, modified nylon Nylon and other materials. The first partition 613 and the second partition 614 are horizontally spaced and arranged in the housing 612. The first partition 613 and the second partition 614 are respectively provided with mounting holes. The filter element 611 is vertically arranged, and The top end of the filter element 611 is sealed and connected to the mounting hole of the first partition 613, the bottom end of the filter element 611 is sealed and connected to the mounting hole of the second partition 614, the water inlet 615 is arranged on one side of the shell 612 and is connected to the space between the first partition 613 and the second partition 614, and the water outlet 616 is arranged at the top end of the shell 612. That is to say, the liquid enters the shell 612 through the water inlet 615, and the liquid passes through the filtering effect of the filter element 611 from bottom to top, and is finally discharged from the water outlet 616 at the top.

[0044] In addition, the shell 612 is detachably connected to a cover 617 , and the water outlet 616 is arranged on the cover 617 . A lifting rod 618 is also arranged on one side of the shell 612 for opening the cover 617 to facilitate replacement of the filter element 611 in the shell 612 .

[0045] like Figure 5 As shown, in this embodiment, the shell 612 is cylindrical, the first partition 613 and the second partition 614 are both circular plates, and a plurality of through holes 6131 are provided on the first partition 613 and the second partition 614, wherein a filter element support is provided at the unopened portion of the first partition 613, and a sealing structure can be provided in the support for sealingly connecting with the bottom end of the filter element 611; the through hole 6131 of the second partition 614 is adapted to the top of the filter element 611, and a sealing sleeve can be provided at the through hole 6131 of the second partition 614 for sealingly connecting with the top of the filter element 611, and the liquid enters the shell 612 from the water inlet 615, passes through the filter element After being filtered by 611, the liquid enters the filter element 611, goes up along the axial direction of the filter element 611, and finally flows out from the water outlet 616; in this way, by setting a through hole on the first partition plate 613, the liquid entering the shell 612 can fall into the space between the first partition plate 613 and the bottom of the shell 612, and the liquid level gradually increases from low to high, so that the solution can be evenly distributed in the outer space of the shell 612 before entering the filter element 611, preventing larger impurities or particles from directly impacting the filter element 611, playing a role of preliminary screening, reducing the impact force on the filter element 611, thereby avoiding excessive local filtration load and extending the service life of the filter element 611.

[0046] In some embodiments, the waste acid settling tank 4 includes a tank body 41, a water distributor 42 and a plurality of inclined plate layers 43, wherein the plurality of inclined plate layers 43 are arranged at intervals at the top of the tank body 41, the water distributor 42 is arranged in the tank body 41 and below the plurality of inclined plate layers 43, and a water outlet 616 is arranged at the top of the tank body 41, and each of the inclined plate layers 43 includes a plurality of inclined plates or inclined tubes arranged in parallel; Figure 2 As shown, the bottom of the trough body 41 is a conical structure, which is conducive to the sedimentation to gather at the bottom. The water distributor 42 includes an inlet pipe and a plurality of water distribution holes evenly distributed on the inlet pipe. Its working principle is mainly to use the water distribution holes to evenly disperse the water flow so that the area around each water distribution hole can get water flow; by setting a plurality of inclined plate layers 43, when the waste acid mixture passes through the inclined plate or inclined tube from bottom to top, due to the inclined setting of the inclined plate or inclined tube, it has a blocking effect on the solid impurities and suspended matter in the solution. After the waste acid mixture enters the multi-layer inclined plate area, due to the inclination angle of the inclined plate and the flow rate difference, the impurities and suspended matter will continue to accumulate, and gradually form an increasingly thick suspension layer. The suspension layer can continuously strengthen the interception and adsorption effect on small particle flocs, and the floc particles continuously collide, condense and settle in the suspension layer, thereby improving the sedimentation efficiency, so that the suspended matter and impurities in the solution can be effectively removed.

[0047] In this embodiment, the low-temperature vacuum evaporation device 2 includes a still, a vacuum pump, an evaporator, an eddy current separator, a condenser, a compressor and a drainage pump; wherein the inlet of the still is connected to the outlet of the second temporary storage tank by a pipeline, the outlet of the still is connected to the inlet of the evaporator, and is used to transport the ferrous chloride solution to the evaporator for heating and evaporating the water therein, the vacuum pump is connected to the evaporator, and is used to reduce the pressure inside the evaporator to reduce the boiling point of the ferrous chloride solution; the inlet of the eddy current separator is connected to the outlet of the evaporator, and is used to separate the steam generated by the evaporator from the concentrated solution, and the drainage pump is connected to the liquid outlet of the eddy current separator by a pipeline, and is used to pump the concentrated ferrous chloride solution in the eddy current separator into the freezing crystallization device 3.

[0048] The inlet of the condenser is connected to the outlet of the eddy current separator, which is used to cool and liquefy the steam separated by the eddy current separator; the inlet of the compressor is connected to the outlet of the condenser, which is used to compress the liquid steam discharged from the condenser to increase its pressure and temperature; the outlet of the compressor is connected to the distillation kettle, which is used to send the compressed liquid steam into the distillation kettle.

[0049] like Figure 1As shown, in this embodiment, the pickling equipment at least includes a first pickling tank 9, a second pickling tank 10 and a third pickling tank 11. The first pickling tank 9, the second pickling tank 10 and the third pickling tank 11 are connected in sequence along a first direction, and the strip steel plate passes through the above pickling tanks in sequence along the first direction; and the third pickling tank 11 is connected to the inlet of the waste acid sedimentation tank 4 through a pipeline, and the first pickling tank 9 is connected to the outlet of the third temporary storage tank 8 through a pipeline.

[0050] In a further embodiment, a grinder is also included, which is used to grind the iron-containing oxide. After the iron-containing oxide is ground into powder, it can be used as an inorganic pigment in industrial production, and can also be used as a colorant for rubber, artificial marble, and floor terrazzo, and a colorant and filler for plastics, asbestos, artificial leather, etc.

[0051] The present invention can realize the recycling of more than 95% of free acid by treating the pickling waste liquid, purify FeCl2 crystals by low-temperature vacuum evaporation combined with freezing crystallization technology, and directly incinerate the FeCl2 crystals in an incinerator to produce high-quality iron oxide powder with a purity of up to 99.8%. At the same time, it reduces energy consumption, saves costs, and meets the waste liquid discharge standard.

[0052] Figure 6 Schematic diagram of a cold rolling waste acid recovery method provided by an embodiment of the present invention, which is applied to the above-mentioned cold rolling waste acid recovery system, such as Figure 6 As shown, the method comprises the following steps: Step 1: Pickling the surface of the strip steel plate.

[0053] Step 2: subjecting the waste acid mixture containing ferrous ions after the pickling treatment to adsorption treatment to recover free acid ions in the waste acid mixture.

[0054] Step 3: The adsorbed acid ions are rinsed out with deionized water to form a recovered acid solution, and the strip steel plate is continued to be pickled.

[0055] Step 4: subjecting the ferrous chloride solution after adsorbing the free acid ions to low-temperature vacuum evaporation to remove the water therein to obtain a saturated ferrous chloride solution.

[0056] Step 5: The saturated ferrous chloride solution is subjected to freeze crystallization treatment to precipitate ferrous chloride crystals, and the solution after the precipitated ferrous chloride crystals is subjected to low-temperature vacuum evaporation treatment again.

[0057] Furthermore, step 6 is further included after step 5: burning the precipitated ferrous chloride crystals into iron-containing oxides, and recovering the iron-containing oxides.

[0058] The present invention combines waste acid treatment with resource recovery, and realizes resource recycling by recovering free acid ions and ferrous chloride in the waste acid, thereby reducing environmental pollution and production costs. Meanwhile, iron-containing oxides obtained by burning ferrous chloride crystals can also be reused as resources, thereby improving economic benefits.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cold rolling waste acid recovery system, characterized in that: include: Pickling equipment, used to treat the oxidation and rust on the surface of the strip steel plate; A free acid adsorption mechanism (1) is connected to the pickling equipment and is used to adsorb free acid ions in the waste acid mixed solution containing ferrous ions discharged from the pickling equipment, and to rinse out the adsorbed acid ions with deionized water to form a recovered acid solution which is then fed back into the pickling equipment; A low-temperature vacuum evaporation device (2) is connected to the free acid adsorption mechanism (1) and is used to remove water from the ferrous chloride solution discharged from the free acid adsorption mechanism (1) after adsorbing free acid ions, by evaporation, and obtain a saturated ferrous chloride solution; The freezing crystallization device (3) is connected to the low-temperature vacuum evaporation device (2) and is used to treat the saturated ferrous chloride solution by freezing crystallization to precipitate ferrous chloride crystals, and to return the solution after the ferrous chloride crystals are precipitated to the low-temperature vacuum evaporation device (2) for further treatment.

2. The cold rolling waste acid recovery system according to claim 1, characterized in that: It also includes an incinerator, which is connected to the freezing crystallization device (3) and is used to burn the precipitated ferrous chloride crystals into iron-containing oxides; the incinerator includes a furnace body, a blower, an air duct and a feeding mechanism, the feeding mechanism is arranged on the outside of the furnace body and is used to feed the ferrous chloride crystals into the inlet of the furnace body, one end of the air duct is connected to the air outlet of the blower, and the other end of the air duct is arranged at the top inlet of the furnace body, so as to be able to blow the ferrous chloride crystals fed to the inlet of the furnace body into the furnace body.

3. The cold rolling waste acid recovery system according to claim 1, characterized in that: The free acid adsorption mechanism (1) comprises: A waste acid sedimentation tank (4), the inlet of which is connected to the pickling equipment via a pipeline, and is used to sediment solid impurities in the waste acid mixed liquid containing ferrous ions discharged from the pickling equipment to the bottom to form acid sludge by gravity; A first temporary storage tank (5), the inlet of which is connected to the outlet of the waste acid sedimentation tank (4) via a pipeline, and is used to store the filtered waste acid mixed liquid; A filtering device (6), the inlet of the filtering device (6) being connected to the outlet of the waste acid settling tank (4) via a pipeline, and being used for filtering the waste acid mixed liquid containing ferrous ions, and for returning the backwash liquid to the inlet of the waste acid settling tank (4); an adsorption resin bed (7), one end of the adsorption resin bed (7) being connected to the outlet of the filtering device (6) via a pipeline, and being used for introducing the filtered waste acid mixed liquid and adsorbing the free acid in the waste acid mixed liquid, and the other end of the adsorption resin bed (7) being used for introducing deionized water to flush out the free acid adsorbed in the adsorption resin bed (7) to form a recovered acid solution; A second temporary storage tank, the inlet of which is connected to the liquid outlet of the adsorption resin bed (7) via a pipeline, and is used to store the ferrous chloride solution after the free acid has been removed, and the outlet of which is connected to the low-temperature vacuum evaporation device (2) via a pipeline.

4. The cold rolling waste acid recovery system according to claim 3 is characterized in that: It also includes a third temporary storage tank (8), the inlet of the third temporary storage tank (8) is connected to the acid outlet of the adsorption resin bed (7) through a pipeline, and is used to store the recovered acid solution; the outlet of the third temporary storage tank (8) is connected to the pickling equipment through a pipeline, and is used to send the recovered acid solution to the pickling equipment for reuse.

5. The cold rolling waste acid recovery system according to claim 3 is characterized in that: The filtering device (6) comprises a first filter and a second filter (61) connected in series, wherein the inlet of the first filter is connected to the outlet of the spent acid sedimentation tank (4) via a pipeline, and the outlet of the second filter (61) is connected to the adsorption resin bed (7) via a pipeline.

6. The cold rolling waste acid recovery system according to claim 3 is characterized in that: The waste acid sedimentation tank (4) comprises a tank body (41), a water distributor (42) and a plurality of inclined plate layers (43), wherein the plurality of inclined plate layers (43) are arranged at intervals at the top of the tank body (41), the water distributor (42) is arranged in the tank body (41) and below the plurality of inclined plate layers (43), and a water outlet (616) is arranged at the top of the tank body (41).

7. The cold rolling waste acid recovery system according to claim 3, characterized in that: The low-temperature vacuum evaporation device (2) comprises: a distillation kettle, wherein the inlet of the distillation kettle is connected to the outlet of the second temporary storage tank through a pipeline; An evaporator, the inlet of the evaporator is connected to the outlet of the distillation kettle through a pipeline, and is used to transport the ferrous chloride solution to the evaporator to be heated and evaporate the water therein; A vacuum pump connected to the evaporator and used to reduce the pressure inside the evaporator to reduce the boiling point of the ferrous chloride solution; An eddy current separator, the inlet of which is connected to the outlet of the evaporator through a pipeline, and is used to separate the steam generated by the evaporator from the concentrated ferrous chloride solution; a liquid discharge pump, the liquid discharge pump being connected to the liquid outlet of the eddy current separator via a pipeline and being used for pumping the concentrated ferrous chloride solution in the eddy current separator into the freezing crystallization device (3); a condenser, the inlet of the condenser being connected to the outlet of the eddy current separator, and being used for cooling and liquefying the steam separated by the eddy current separator; A compressor, wherein the inlet of the compressor is connected to the outlet of the condenser, and is used for compressing the liquid vapor discharged from the condenser to increase its pressure and temperature; and the outlet of the compressor is connected to the distillation kettle, and is used for feeding the compressed liquid vapor into the distillation kettle.

8. The cold rolling waste acid recovery system according to claim 5, characterized in that: The first filter is a fiber filter, and the second filter (61) comprises a filter element (611), a shell (612), a first partition (613), a second partition (614), a water inlet (615) and a water outlet (616); the first partition (613) and the second partition (614) are arranged horizontally in the shell (612) at intervals; the first partition (613) and the second partition (614) are respectively provided with mounting holes; the filter element (611) is arranged vertically, and the top end of the filter element (611) is sealed and connected to the mounting hole of the first partition (613); the bottom end of the filter element (611) is sealed and connected to the mounting hole of the second partition (614); the water inlet (615) is arranged on one side of the shell (612) and communicates with the space between the first partition (613) and the second partition (614); and the water outlet (616) is arranged at the top end of the shell (612).

9. The cold rolling waste acid recovery system according to claim 8, characterized in that: The first partition plate (613) and the second partition plate (614) are both provided with a plurality of through holes (6131).

10. A method for recovering waste acid from cold rolling, applied to the waste acid recovery system from cold rolling according to any one of claims 2 to 9, characterized in that: The steps include: The waste acid mixed solution containing ferrous ions after pickling is subjected to adsorption treatment to recover free acid ions in the waste acid mixed solution; The adsorbed acid ions are rinsed out with deionized water to form a recovered acid solution, and the strip steel plate is continuously pickled; The ferrous chloride solution after adsorbing the free acid ions is subjected to low-temperature vacuum evaporation treatment to remove the water therein to obtain a saturated ferrous chloride solution; The saturated ferrous chloride solution is subjected to a freeze crystallization treatment to precipitate ferrous chloride crystals, and the solution after the precipitated ferrous chloride crystals is subjected to a low-temperature vacuum evaporation treatment again; The precipitated ferrous chloride crystals are burned to form iron-containing oxides, and the iron-containing oxides are recovered.

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