Cold rolling waste acid recovery system

Abstract

The utility model provides a cold rolling waste acid recovery system which 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; according to the utility model, the environmental pollution caused by the discharge of waste acid is reduced, the high-purity recovery of acid and ferrous chloride is realized, and the cost is saved.

Description

Technical Field

[0001] This utility model relates to the field of cold-rolled steel production technology, and in particular to a cold-rolled waste acid recovery system. Background Technology

[0002] Pickling is a method of removing scale and rust from the surface of steel using acid solutions. During the production process of cold rolling and other steel surface treatments, a large amount of pickling waste liquid is generated. 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] Currently, hydrochloric acid pickling waste liquid is mainly composed of three substances: hydrogen chloride, water, and ferrous chloride. Traditional treatment methods generally employ neutralization or direct roasting. 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 other indicators. Moreover, the generated sludge is difficult to dewater, difficult to dry, and difficult to post-process. In most cases, it is piled up and awaits 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.

[0004] The direct roasting method involves oxidizing and hydrolyzing ferrous salts in waste acid at high temperatures and evaporating the water to obtain iron oxide. However, some hydrogen chloride gas is also evaporated at the same time. After being adsorbed by deionized water spray, it forms a recycled acid solution that is reused in pickling production. Furthermore, the purity of the iron oxide is not high, and its utilization value is not high. If the purity is improved, a silicon removal system needs to be built. The entire process consumes a huge amount of energy. Utility Model Content

[0005] This invention provides a cold rolling waste acid recovery system to solve the problems of high cost and poor recovery effect in the treatment of pickling waste liquid in the prior art.

[0006] This utility model provides a cold rolling waste acid recovery system, including:

[0007] Pickling equipment is used to treat oxides and rust on the surface of steel strips;

[0008] The free acid adsorption mechanism is connected to the pickling equipment and is used to adsorb free acid ions in the waste acid mixture containing ferrous ions discharged from the pickling equipment. It is also used to rinse the adsorbed acid ions with deionized water to form a recycled acid solution that is then sent back into the pickling equipment.

[0009] 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 by evaporation, and obtain a saturated ferrous chloride solution.

[0010] A freeze crystallization apparatus, connected to the low-temperature vacuum evaporation apparatus, is used to precipitate ferrous chloride crystals from a saturated ferrous chloride solution through freeze crystallization, and to return the solution after precipitating ferrous chloride crystals to the low-temperature vacuum evaporation apparatus for further processing.

[0011] The cold-rolled waste acid recovery system provided by this utility model also includes an incinerator, which is connected to the freeze crystallization device and is used to burn the precipitated ferrous chloride crystals into iron oxides.

[0012] According to the cold rolling waste acid recovery system provided by this utility model, the free acid adsorption mechanism includes:

[0013] Waste acid settling tank, the inlet of which is connected to the pickling equipment via a pipeline, is used to settle solid impurities in the waste acid mixture containing ferrous ions discharged from the pickling equipment to the bottom to form acid sludge by gravity.

[0014] The first temporary storage tank, whose inlet is connected to the outlet of the waste acid settling tank via a pipeline, is used to store the filtered waste acid mixture.

[0015] A filtration device, the inlet of which is connected to the outlet of the waste acid settling tank via a pipeline, is used to filter the waste acid mixture containing ferrous ions and to return the backwash liquid to the inlet of the waste acid settling tank.

[0016] An adsorption resin bed is provided, with one end connected to the outlet of the filtration device via a pipeline for introducing the filtered waste acid mixture and adsorbing the free acid in the waste acid mixture. The other end of the adsorption resin bed is used to introduce deionized water to wash out the free acid adsorbed in the adsorption resin bed and form a recovered acid solution.

[0017] The second temporary storage tank, whose inlet is connected to the outlet of the adsorption resin bed via a pipeline, is used to store the ferrous chloride solution after the removal of free acid. The outlet of the second temporary storage tank is connected to the low-temperature vacuum evaporation device via a pipeline.

[0018] The cold rolling waste acid recovery system provided by this utility model 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 for storing the recovered acid solution. The outlet of the third temporary storage tank is connected to the pickling equipment through a pipeline for sending the recovered acid solution into the pickling equipment for reuse.

[0019] According to the cold rolling waste acid recovery system provided by this utility model, the filtration 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 settling tank through a pipeline, and the outlet of the second filter is connected to the adsorption resin bed through a pipeline.

[0020] According to the cold-rolled waste acid recovery system provided by this utility model, the waste acid settling tank includes a tank body, a water distributor and multiple inclined plate layers. The multiple inclined plate layers are spaced apart at the top of the tank body. The water distributor is located in the tank body and below the multiple inclined plate layers. The top of the tank body is provided with a water outlet.

[0021] According to the cold rolling waste acid recovery system provided by this utility model, the low-temperature vacuum evaporation device includes:

[0022] A distillation vessel, the inlet of which is connected to the outlet of a second temporary storage tank via a pipeline;

[0023] An evaporator, the inlet of which is connected to the outlet of the distillation vessel via a pipeline, is used to transport a ferrous chloride solution to the evaporator for heating and evaporation of the water therein;

[0024] A vacuum pump, connected to the evaporator, is used to reduce the pressure inside the evaporator to lower the boiling point of the ferrous chloride solution.

[0025] A vortex separator, the inlet of which is connected to the outlet of the evaporator via a pipeline, is used to separate the steam generated by the evaporator from the concentrated ferrous chloride solution;

[0026] A drain pump, which is connected to the outlet of the vortex separator via a pipeline, is used to pump the concentrated ferrous chloride solution in the vortex separator into the freeze crystallization device;

[0027] A condenser, the inlet of which is connected to the outlet of the vortex separator, is used to cool and liquefy the steam separated by the vortex separator.

[0028] The compressor has its inlet connected to the outlet of the condenser for compressing the liquid vapor discharged from the condenser to increase its pressure and temperature. The outlet of the compressor is connected to the distillation vessel for feeding the compressed liquid vapor into the distillation vessel.

[0029] According to the cold rolling waste acid recovery system provided by this utility model, the incinerator includes a furnace body, a blower, an air duct, and a feeding mechanism. The feeding mechanism is located on the outside of the furnace body and is used to feed 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 located at the top inlet of the furnace body, which can blow the ferrous chloride crystals fed to the furnace body inlet into the furnace body.

[0030] According to the cold-rolled waste acid recovery system provided by this utility model, the first filter is a fiber filter, and the second filter includes a filter element, a housing, a first partition, a second partition, an inlet, and an outlet. The first partition and the second partition are horizontally spaced apart in the housing, and 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 to the mounting hole of the first partition, and the bottom end of the filter element is sealed to the mounting hole of the second partition. The inlet is located on one side of the housing and communicates with the space between the first partition and the second partition. The outlet is located at the top of the housing.

[0031] According to the cold rolling waste acid recovery system provided by this utility model, both the first partition and the second partition are provided with multiple through holes.

[0032] This utility model provides a cold-rolling waste acid recovery system, comprising: pickling equipment, a free acid adsorption mechanism, a low-temperature vacuum evaporation device, and a freeze crystallization device. The free acid adsorption mechanism effectively recovers free acid ions from the waste acid mixture and converts them into recycled acid solution, which is then returned to the pickling equipment. This reduces the consumption of new acid, improves resource utilization, and lowers raw material costs. The ferrous chloride solution, after being processed by the low-temperature vacuum evaporation device, yields a saturated ferrous chloride solution. Compared to atmospheric pressure evaporation, this device operates under lower temperature and vacuum conditions, reducing energy consumption and effectively evaporating moisture and concentrating the ferrous chloride solution. Furthermore, the evaporation process is carried out at a lower temperature. The combination of physical energy recovery and freeze crystallization helps to save energy and reduce consumption, and can improve the purity of ferrous chloride recovery. The ferrous chloride crystals precipitated by the freeze crystallization device are of high purity, eliminating the need for additional impurity removal devices, and realizing the recovery of metal ions in the waste acid mixture. These pure crystals can be used to produce high-purity soft magnetic iron oxide materials with high added value, realizing the high-value-added reuse of resources. Compared with traditional technologies that may involve neutralization, discharge or landfill in waste acid treatment, this utility model significantly reduces the pollution of the environment caused by waste acid discharge, and realizes the high-purity recovery of acid and ferrous chloride to produce high-purity soft magnetic iron oxide materials with high added value, saving costs and improving economic benefits. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the structure of a cold-rolling waste acid recovery system provided in an embodiment of this utility model.

[0035] Figure 2 This is a schematic diagram of the free acid adsorption mechanism provided in an embodiment of this utility model.

[0036] Figure 3 This is a schematic diagram of the structure of the adsorption resin bed provided in an embodiment of the present invention.

[0037] Figure 4 This is a schematic diagram of the structure of the second filter provided in an embodiment of the present invention.

[0038] Figure 5 This is a schematic diagram of the structure of the first partition provided in an embodiment of the present utility model.

[0039] Figure label:

[0040] 1. Free acid adsorption mechanism; 2. Low-temperature vacuum evaporation device; 3. Freeze crystallization device;

[0041] 4. Waste acid settling tank; 41. Tank body; 42. Water distributor; 43. Inclined plate layer;

[0042] 5. First temporary storage tank; 6. Filtration device; 61. Second filter; 611. Filter element; 612. Housing; 613. First partition; 6131. ​​Through hole; 614. Second partition; 615. Inlet; 616. Outlet; 617. Cover; 618. Lifting rod;

[0043] 7. Adsorption resin bed; 71. Resin tank; 72. First water distribution device; 73. Second water distribution device;

[0044] 8. Third temporary storage tank; 9. First pickling tank; 10. Second pickling tank; 11. Third pickling tank. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0046] The following is combined Figures 1-5 This invention describes a cold-rolling waste acid recovery system and method.

[0047] This utility model provides a cold rolling waste acid recovery system, including: pickling equipment, free acid adsorption mechanism 1, low temperature vacuum evaporation device 2, and freeze crystallization device 3.

[0048] The pickling equipment uses hydrochloric acid to treat the oxide and rust on the surface of the steel strip; the free acid adsorption unit 1 is connected to the pickling equipment and is used to adsorb free acid ions in the waste acid mixture containing ferrous ions discharged from the pickling equipment, and to rinse the adsorbed acid ions with deionized water to form a recycled acid solution that is then fed back into the pickling equipment; the low-temperature vacuum evaporation unit 2 is connected to the free acid adsorption unit 1 and is used to evaporate the ferrous chloride solution discharged from the free acid adsorption unit 1 after the adsorption of free acid ions to remove the water and obtain a saturated ferrous chloride solution. Low-temperature evaporation refers to evaporating the ferrous chloride solution at -94 to -97 kPa and 30 to 50°C; the freeze crystallization unit 3 is connected to the low-temperature vacuum evaporation unit 2 and uses... The saturated ferrous chloride solution is subjected to freeze crystallization to precipitate ferrous chloride crystals. The solution after precipitating ferrous chloride crystals is then returned to the low-temperature vacuum evaporation unit 2 for further processing. In other words, the ferrous chloride solution is recycled through the freeze crystallization unit 3 and the low-temperature vacuum evaporation unit 2. On the one hand, the saturated ferrous chloride solution obtained after processing by the low-temperature vacuum evaporation unit 2 enters the freeze crystallization unit 3 to precipitate ferrous chloride crystals, thus recovering it. On the other hand, the ferrous chloride solution after precipitating ferrous chloride crystals cannot reach saturation. By returning it to the low-temperature vacuum evaporation unit 2 for further processing, a saturated ferrous chloride solution can be obtained again. This process is repeated, and the purity of ferrous chloride recovered from the solution is improved by utilizing the principle of freeze purification.

[0049] As can be seen from the above scheme, this utility model effectively recovers free acid ions from the waste acid mixture through the free acid adsorption mechanism 1, and converts them into recycled acid solution to be sent back to the pickling equipment, reducing the consumption of new acid, improving resource utilization, and reducing raw material costs. The ferrous chloride solution, after being treated by the low-temperature vacuum evaporation device 2, can obtain a saturated ferrous chloride solution. Compared with atmospheric pressure evaporation, this device operates under lower temperature and vacuum conditions, which can reduce energy consumption, effectively evaporate moisture, concentrate the ferrous chloride solution, and the lower temperature evaporation treatment can be well combined with freeze crystallization, contributing to energy saving and consumption reduction. This invention improves the purity of ferrous chloride recovery; the high purity ferrous chloride crystals precipitated by the freeze crystallization device eliminate the need for additional impurity removal equipment, achieving the recovery of metal ions from waste acid mixtures. These pure crystals can be used to produce high-purity soft magnetic iron oxide materials with high added value, realizing high-value-added resource reuse. Compared with traditional technologies that may involve neutralization, discharge, or landfill in waste acid treatment, this invention significantly reduces the environmental pollution caused by waste acid discharge and achieves high-purity recovery of acid and ferrous chloride to produce high-purity soft magnetic iron oxide materials with high added value, saving costs and improving economic efficiency.

[0050] This embodiment also includes an incinerator connected to the freeze crystallization device 3, used to burn the precipitated ferrous chloride crystals into iron oxides. With this configuration, the iron oxides have wide applications in fields such as corrosion-resistant materials and the manufacture of soft magnetic oxide materials, thus achieving deep utilization of recycled resources.

[0051] Preferably, the incinerator includes a furnace body, a blower, an air duct, and a feeding mechanism. The incinerator is a product of the prior art. The improvement of this utility model is that the original liquid spray head system at the top of the furnace body is eliminated, and the blower is a device of the incinerator's own air blowing system. By setting the feeding mechanism on the outside of the furnace body, ferrous chloride crystals are sent into the furnace body inlet. One end of the air duct is connected to the air outlet of the blower, and the other end of the air duct is set at the top inlet of the furnace body, which can blow the ferrous chloride crystals sent to the furnace body inlet into the furnace body. That is to say, by extending an air duct from the blower to the furnace body inlet based on the original structure, when the feeding mechanism, such as the chain feeder, lifts the solid ferrous chloride crystals to the furnace top inlet, the blower provides power and blows gas through the air duct to scatter the ferrous chloride crystals into the furnace body.

[0052] With this setup, the inlet used for injecting acid is modified into a spray port by improving the existing structure. Solid ferrous chloride crystals are sprayed into the incinerator through the spray port under the action of the blower. The blower not only provides the power for spraying, but also helps the crystals to be evenly distributed in the furnace, which is conducive to achieving complete combustion.

[0053] It should be noted that the pickling equipment, the low-temperature vacuum evaporation device 2, and the freeze crystallization device 3 are all products of existing technology. Their structure and principle are not the focus of this article and will not be elaborated here.

[0054] In this embodiment, the free acid adsorption mechanism 1 includes a waste acid settling tank 4, a first temporary storage tank 5, a filter device 6, an adsorption resin bed 7, and a second temporary storage tank.

[0055] like Figures 1-2 As shown, specifically, the inlet of the waste acid settling tank 4 is connected to the waste acid discharge storage tank of the pickling equipment through a pipeline. This is used to settle 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, it can effectively remove larger solid particles in the waste acid mixture, such as metal shavings and oxides, preventing these particles from entering subsequent treatment units and reducing the risk of equipment wear and blockage.

[0056] The inlet of the first temporary storage tank 5 is connected to the outlet of the waste acid settling tank 4 via a pipeline, and is used to store the filtered waste acid mixture. In this way, the temporary storage tank can balance the flow fluctuations of the upstream and downstream, ensure the stable feeding of the subsequent processing units, and avoid uneven treatment caused by sudden changes in flow. In addition, the temporary storage tank can also provide a certain residence time, allowing some smaller particles to have more opportunities to settle, further improving the initial purification effect of the waste acid mixture.

[0057] The inlet of the filter device 6 is connected to the outlet of the waste acid settling tank 4 via a pipeline. It is used to filter the waste acid mixture containing ferrous ions and to return the backwash liquid to the inlet of the waste acid settling tank 4. In this way, the filter device 6 can remove small particles and suspended solids that the waste acid settling tank 4 could not completely remove, ensuring that the waste acid liquid entering the adsorption resin bed 7 is as pure as possible, and reducing the risk of contamination and blockage of the resin bed.

[0058] One end of the adsorption resin bed 7 is connected to the outlet of the filter device 6 via a pipeline 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 wash out the free acid adsorbed in the adsorption resin bed 7 and form a recovered acid solution. The inlet of the second temporary storage tank is connected to the outlet of the adsorption resin bed 7 via a pipeline to store the ferrous chloride solution after the removal of free acid. The outlet of the second temporary storage tank is connected to the low-temperature vacuum evaporation device 2 via a pipeline.

[0059] This setup, through multi-stage treatment via waste acid settling tank 4, filtration device 6, and adsorption resin bed 7, gradually removes solid impurities, suspended solids, and free acid from the waste acid, ensuring the quality and purity of the final product. Adsorption resin bed 7 not only purifies the waste acid but also recovers valuable acid liquid through the desorption process, realizing acid recycling and reducing the company's operating costs. The design of the temporary storage tank ensures the stable operation of the system and avoids uneven treatment caused by flow fluctuations or equipment failures.

[0060] 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 for storing the recovered acid solution. The outlet of the third temporary storage tank 8 is connected to the pickling equipment through a pipeline for sending the recovered acid solution into the pickling equipment for reuse.

[0061] In some specific embodiments, such as Figure 3 As shown, the adsorption resin bed 7 includes: a resin tank 71, a first water distribution device 72, and a second water distribution device 73. The first water distribution device 72 and the second water distribution device 73 have the same structure and are symmetrically connected to both ends of the resin tank 71. The resin tank 71 is filled with adsorption resin capable of adsorbing acid ions in a compacted state. The particle size of the adsorption resin is 0.1-0.3 mm, which is about 20% smaller than the resin in traditional ion exchange systems. The smaller particles allow a larger number of resin particles to be contained in a unit volume, thereby providing a larger total surface area and improving the adsorption effect and adsorption efficiency. By utilizing the "acid retardation" characteristic of the adsorption resin, the free acid in the acid solution is adsorbed onto the resin particles. At the same time, salts and other impurities flow out of the resin tank because they cannot be adsorbed onto the resin particles, thus achieving the separation of free acid from metal ions or other impurities. It can recover hydrochloric acid ions from waste acid solutions containing heavy metal ions and remove heavy metal ions from them.

[0062] 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 for supplying acid solution upward along the axial direction 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 for supplying rinsing water downward along the axial direction into the resin tank 71. Both water distribution devices are equipped with buffer packing to reduce and balance the liquid flow rate.

[0063] In some embodiments, the filtration 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 waste acid settling tank 4 via a pipeline, and the outlet of the second filter 61 is connected to the adsorption resin bed 7 via a pipeline.

[0064] Optionally, the first filter serves as primary filtration, and the second filter 61 serves as precision filtration. The first filter is a fiber filter, and the filter media is made of acid- and alkali-resistant fiber media. Figure 4 As shown, the second filter 61 includes a filter element 611, a housing 612, a first partition 613, a second partition 614, an inlet 615, and an outlet 616. The filter element 611 has a cylindrical structure and can be made of materials such as polypropylene (PP), modified polyethersulfone (PES), or modified nylon. The first partition 613 and the second partition 614 are horizontally spaced within the housing 612, and each partition has a corresponding mounting hole. The filter element 611 is vertically positioned, and... The top of the filter element 611 is sealed to the mounting hole of the first partition 613, and the bottom of the filter element 611 is sealed to the mounting hole of the second partition 614. The inlet 615 is located on one side of the housing 612 and communicates with the space between the first partition 613 and the second partition 614. The outlet 616 is located at the top of the housing 612. That is to say, the liquid enters the housing 612 through the inlet 615, and the liquid flows from bottom to top through the filtration effect of the filter element 611 and is finally discharged from the outlet 616 at the top.

[0065] In addition, the housing 612 is detachably connected to a cover 617, and the water outlet 616 is set on the cover 617. A lifting rod 618 is also provided on one side of the housing 612 for opening the cover 617 to facilitate the replacement of the filter element 611 inside the housing 612.

[0066] like Figure 5 As shown, in this embodiment, the housing 612 is cylindrical, and both the first partition 613 and the second partition 614 are circular plates. Multiple through holes 6131 are provided on the first partition 613 and the second partition 614. A filter element support is provided at the unopened portion of the first partition 613, and a sealing structure can be provided inside the support for a sealed connection with the bottom end of the filter element 611. The through holes 6131 of the second partition 614 are adapted to the top of the filter element 611, and a sealing sleeve can be provided at the through holes 6131 of the second partition 614 for a sealed connection with the top of the filter element 611. Liquid enters the housing 612 from the inlet 615 and passes through the filter element. After filtration at 611, the liquid enters the interior of filter element 611, rises along the axial direction of filter element 611, and finally flows out from outlet 616. This configuration, with through holes in the first partition 613, allows the liquid entering the housing 612 to fall into the space between the first partition 613 and the bottom of the housing 612, with the liquid level gradually rising from low to high. This ensures that the solution is evenly distributed in the outer space of the housing 612 before entering filter element 611, preventing larger impurities or particles from directly impacting filter element 611. This serves as a preliminary screening, reducing the impact force on filter element 611, thereby avoiding excessive local filtration load and extending the service life of filter element 611.

[0067] In some embodiments, the waste acid settling tank 4 includes a tank body 41, a water distributor 42, and multiple inclined plate layers 43. The multiple inclined plate layers 43 are spaced apart at the top of the tank body 41. The water distributor 42 is located inside the tank body 41 and below the multiple inclined plate layers 43. An outlet 616 is provided at the top of the tank body 41. Each inclined plate layer 43 includes multiple parallel inclined plates or inclined pipes. Figure 2 As shown, the bottom of the tank 41 has a conical structure, which is conducive to the collection of sediment at the bottom. The water distributor 42 includes an inlet pipe and multiple 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 receive water flow. By setting multiple inclined plate layers 43, when the waste acid mixture passes through the inclined plates or inclined pipes from bottom to top, the inclined plates or inclined pipes block 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 and flow velocity difference of the inclined plates, impurities and suspended matter will continue to accumulate, gradually forming an increasingly thick suspension layer. This suspension layer can continuously enhance the interception and adsorption of small flocs. The floc particles collide, agglomerate and settle continuously in the suspension layer, thereby improving the sedimentation efficiency and effectively removing suspended matter and impurities in the solution.

[0068] In this embodiment, the low-temperature vacuum evaporation device 2 includes a distillation kettle, a vacuum pump, an evaporator, a vortex separator, a condenser, a compressor, and a drain pump. The inlet of the distillation kettle is connected to the outlet of the second temporary storage tank via a pipeline, and the outlet of the distillation kettle is connected to the inlet of the evaporator, for conveying the ferrous chloride solution to the evaporator for heating and evaporation of water. The vacuum pump is connected to the evaporator to reduce the pressure inside the evaporator, thereby lowering the boiling point of the ferrous chloride solution. The inlet of the vortex separator is connected to the outlet of the evaporator to separate the vapor generated by the evaporator from the concentrated solution. The drain pump is connected to the outlet of the vortex separator via a pipeline to pump the concentrated ferrous chloride solution from the vortex separator into the freeze crystallization device 3.

[0069] The condenser inlet is connected to the outlet of the vortex separator to cool and liquefy the vapor separated by the vortex separator; the compressor inlet is connected to the condenser outlet to compress the liquid vapor discharged from the condenser to increase its pressure and temperature; the compressor outlet is connected to the distillation vessel to send the compressed liquid vapor into the distillation vessel.

[0070] In this embodiment, the pickling equipment includes at least 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 sequentially along a first direction, and the steel strip passes through each of the above pickling tanks sequentially along the first direction. The third pickling tank 11 is connected to the inlet of the waste acid settling 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.

[0071] In a further embodiment, a grinding mill is also included, which is used to grind the iron oxide. After grinding, the iron oxide can be used as an inorganic pigment in industrial production, as well as as a colorant for rubber, artificial marble, terrazzo flooring, plastics, asbestos, artificial leather, etc.

[0072] This invention achieves the recovery and utilization of over 95% of free acid through the treatment of pickling waste liquid. FeCl2 crystals are purified by combining low-temperature vacuum evaporation with freeze crystallization technology, and the FeCl2 crystals are directly incinerated 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 waste liquid discharge standards.

[0073] This utility model provides a schematic flowchart of a method for recovering waste acid from cold rolling, which is applied to the above-mentioned waste acid recovery system from cold rolling and includes the following steps;

[0074] Step 1: Pickling treatment is performed on the surface of the steel strip.

[0075] Step 2: The waste acid mixture containing ferrous ions after pickling is subjected to adsorption treatment to recover free acid ions from the waste acid mixture.

[0076] Step 3: The adsorbed acid ions are rinsed out with deionized water to form a recovered acid solution, which is then used to continue the pickling process on the steel strip.

[0077] Step 4: The ferrous chloride solution after adsorbing free acid ions is subjected to low-temperature vacuum evaporation to remove the water and obtain a saturated ferrous chloride solution.

[0078] Step 5: The saturated ferrous chloride solution is subjected to freeze crystallization to precipitate ferrous chloride crystals, and the solution after the ferrous chloride crystals have precipitated is subjected to low-temperature vacuum evaporation again.

[0079] Furthermore, step 5 is followed by step 6: burning the precipitated ferrous chloride crystals into iron oxides and recycling the iron oxides.

[0080] This invention combines waste acid treatment with resource recycling. By recovering free acid ions and ferrous chloride from waste acid, it achieves resource recycling, reduces environmental pollution and production costs. At the same time, the iron oxides obtained by burning ferrous chloride crystals can also be reused as resources, improving economic efficiency.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A cold rolling spent acid recovery system characterized by, The application relates to a pickling device for treating oxidized rust on the surface of a strip plate, a free acid adsorption mechanism (1) connected with the pickling device for adsorbing free acid ions in waste acid mixed solution containing ferrous ions discharged by the pickling device and for washing the adsorbed acid ions out by deionized water to form recovered acid liquid which is sent back into the pickling device, a low-temperature vacuum evaporation device (2) connected with the free acid adsorption mechanism (1) for removing water in ferrous chloride solution discharged by the free acid adsorption mechanism (1) after the free acid ions are adsorbed and obtaining saturated ferrous chloride solution, and a freezing crystallization device (3) connected with the low-temperature vacuum evaporation device (2) for precipitating ferrous chloride crystals by freezing crystallization treatment of the saturated ferrous chloride solution and for returning the solution after the ferrous chloride crystals are precipitated back to the low-temperature vacuum evaporation device (2) for treatment. The application further comprises a burning furnace connected with the freezing crystallization device (3) for burning the precipitated ferrous chloride crystals into iron oxides. The free acid adsorption mechanism (1) comprises a waste acid settling tank (4) with an inlet connected with the pickling device through a pipeline for settling solid impurities in the waste acid mixed solution containing ferrous ions discharged by the pickling device to the bottom by gravity to form acid sludge, a first temporary storage tank (5) with an inlet connected with an outlet of the waste acid settling tank (4) through a pipeline for storing filtered waste acid mixed solution, a filtering device (6) with an inlet connected with an outlet of the waste acid settling tank (4) through a pipeline for filtering the waste acid mixed solution containing ferrous ions and for returning backwash liquid to the inlet of the waste acid settling tank (4), an adsorption resin bed (7) with one end connected with an outlet of the filtering device (6) through a pipeline for introducing the filtered waste acid mixed solution and adsorbing free acid in the waste acid mixed solution, and the other end of the adsorption resin bed (7) for introducing deionized water to wash the adsorbed free acid out of the adsorption resin bed (7) to form recovered acid liquid, and a second temporary storage tank with an inlet connected with a liquid outlet of the adsorption resin bed (7) through a pipeline for storing ferrous chloride solution after the free acid is removed, and an outlet connected with the low-temperature vacuum evaporation device (2) through a pipeline. The application further comprises a third temporary storage tank (8) with an inlet connected with an acid outlet of the adsorption resin bed (7) through a pipeline for storing recovered acid liquid, and an outlet connected with the pickling device through a pipeline for sending the recovered acid liquid into the pickling device for reuse. The filtering device (6) comprises a first filter and a second filter (61) connected in series, the inlet of the first filter is connected with the outlet of the waste acid settling tank (4) through a pipeline, and the outlet of the second filter (61) is connected with the adsorption resin bed (7) through a pipeline.

2. The cold rolling spent acid recovery system of claim 1, wherein, ​ 3. The cold rolling spent acid recovery system of claim 1, wherein, ​ ​ ​ ​ ​ ​ 4. The cold rolling spent acid recovery system of claim 3, wherein, ​ 5. The cold rolling spent acid recovery system of claim 3, wherein, ​ 6. The cold rolling spent acid recovery system of claim 3, wherein, The waste acid settling tank (4) comprises a tank body (41), a water distributor (42) and a plurality of inclined plate layers (43), the plurality of inclined plate layers (43) are arranged at the top of the tank body (41) in a spaced manner, the water distributor (42) is arranged in the tank body (41) and below the plurality of inclined plate layers (43), and the top end of the tank body (41) is provided with a water outlet (616).

7. The cold rolling spent acid recovery system of claim 3, wherein, The low-temperature vacuum evaporation device (2) comprises: a distillation kettle, an inlet of the distillation kettle being connected with an outlet of the second temporary storage tank through a pipeline; an evaporator, an inlet of the evaporator being connected with an outlet of the distillation kettle through a pipeline, for conveying the ferrous chloride solution to the evaporator to be heated and evaporate water in the ferrous chloride solution; a vacuum pump, the vacuum pump being connected with the evaporator, for reducing the pressure inside the evaporator to reduce the boiling point of the ferrous chloride solution; a vortex separator, an inlet of the vortex separator being connected with an outlet of the evaporator through a pipeline, for separating the steam generated by the evaporator and the concentrated ferrous chloride solution; a liquid discharge pump, the liquid discharge pump being connected with a liquid outlet of the vortex separator through a pipeline, for pumping the concentrated ferrous chloride solution in the vortex separator into the refrigeration crystallization device (3); a condenser, an inlet of the condenser being connected with an air outlet of the vortex separator, for cooling and liquefying the steam separated by the vortex separator; a compressor, an inlet of the compressor being connected with an outlet of the condenser, for compressing the liquid steam discharged by the condenser to increase the pressure and temperature thereof, and an outlet of the compressor being connected with the distillation kettle, for sending the compressed liquid steam into the distillation kettle.

8. The cold rolling spent acid recovery system of claim 2, wherein, The incinerator comprises a furnace body, an air blower, an air pipe and a feeding mechanism, the feeding mechanism is arranged outside the furnace body and is used for feeding the ferrous chloride crystals into the inlet of the furnace body, one end of the air pipe is connected with the air outlet of the air blower, and the other end of the air pipe is arranged at the top inlet of the furnace body and can blow the ferrous chloride crystals sent to the inlet of the furnace body into the furnace body.

9. The cold rolling spent acid recovery system of claim 5, wherein, The first filter is a fiber filter, and the second filter (61) comprises a filter core (611), a shell (612), a first partition plate (613), a second partition plate (614), a water inlet (615) and a water outlet (616). The first partition plate (613) and the second partition plate (614) are arranged in the shell (612) in a horizontal and spaced manner, the first partition plate (613) and the second partition plate (614) are respectively provided with mounting holes, the filter core (611) is arranged in a vertical manner, the top end of the filter core (611) is sealingly connected with the mounting hole of the first partition plate (613), the bottom end of the filter core (611) is sealingly connected with the mounting hole of the second partition plate (614), the water inlet (615) is arranged on one side of the shell (612) and communicates with the space between the first partition plate (613) and the second partition plate (614), and the water outlet (616) is arranged at the top end of the shell (612).

10. The cold rolling spent acid recovery system of claim 9, wherein, The first partition plate (613) and the second partition plate (614) are provided with a plurality of through holes (6131).

Images