Device for preparing calcium phosphate by recovering waste phosphoric acid in electronic industry

Abstract

The utility model provides a device for preparing calcium phosphate by recycling waste phosphoric acid in electronic industry, which comprises a primary reaction tank, a cooling unit, a secondary reaction tank, a high-pressure filter pressing unit and a drying unit, an outlet of the primary reaction tank is connected with an inlet of the cooling unit, an outlet of the cooling unit is connected with an inlet of the secondary reaction tank, and an outlet of the high-pressure filter pressing unit is connected with an outlet of the drying unit. An outlet of the secondary reaction tank is connected with an inlet of the high-pressure filter-pressing unit, an outlet of the high-pressure filter-pressing unit is connected with an inlet of the drying unit, the drying unit is connected with an external steam source, and the drying unit is provided with a discharge port. The utility model solves the problem of how to efficiently convert waste phosphoric acid into active calcium phosphate in the prior art.

Description

Technical Field

[0001] The utility model relates to the technical field of comprehensive utilization of hazardous wastes, in particular to a device for recovering waste phosphoric acid in the electronics industry to prepare calcium phosphate. Background Art

[0002] The concentration of waste phosphoric acid from the electronics industry is very high, reaching 30%-75%, and is classified as waste acid among hazardous wastes (category HW34). Because the electronics industry has very high requirements for the purity of phosphoric acid, the difficulty and cost of purifying waste phosphoric acid are very high. The previous disposal method was to mix it with other hazardous wastes and send it to the incinerator for high-temperature incineration. However, the calorific value of waste acid is low, it is highly corrosive, and there is a phenomenon of inorganic salt coking when it is not properly mixed, which poses great challenges to the matching of the feed of the incineration line and the operation and maintenance of the equipment.

[0003] When waste phosphoric acid is discharged into sewage without proper treatment, it will lead to eutrophication of water bodies, rapid growth of algae in the water, consumption of oxygen in the water, causing hypoxia of fish, shrimp, lake water and bacteria, and ultimately causing the lake water to stink and the lake to age.

[0004] On the other hand, phosphorus resources play an important role in both industrial and agricultural production. They are non-renewable and irreplaceable elements. With the increasing consumption of phosphorus resources, the recycling and utilization of phosphorus resources is of great significance to alleviate the increasing scarcity of phosphorus resources.

[0005] Therefore, how to efficiently convert waste phosphoric acid into active calcium phosphate becomes a technical problem that needs to be solved. Utility Model Content

[0006] The utility model aims to provide a device for recovering waste phosphoric acid in the electronics industry to prepare calcium phosphate, mainly to solve the problem of how to efficiently convert waste phosphoric acid into active calcium phosphate in the above-mentioned prior art.

[0007] In order to achieve the above-mentioned purpose, the technical solution adopted by the utility model is: a device for recovering waste phosphoric acid in the electronics industry to prepare calcium phosphate, characterized in that: the device includes a primary reaction tank, a cooling unit, a secondary reaction tank, a high-pressure filter press unit and a drying unit, the outlet of the primary reaction tank is connected to the inlet of the cooling unit, the outlet of the cooling unit is connected to the inlet of the secondary reaction tank, the outlet of the secondary reaction tank is connected to the inlet of the high-pressure filter press unit, the outlet of the high-pressure filter press unit is connected to the inlet of the drying unit, the drying unit is connected to an external steam source, and the drying unit is provided with a discharge port.

[0008] Further, the cooling unit includes a plate and frame heat exchanger;

[0009] The outlet of the primary reaction tank is located at the bottom of the primary reaction tank, and the outlet of the primary reaction tank is connected to the inlet of the plate-frame heat exchanger via an intermediate lifting pump, and the outlet of the plate-frame heat exchanger is connected to the inlet of the secondary reaction tank.

[0010] Further, the high pressure filter press unit includes a high pressure diaphragm filter press;

[0011] The outlet of the secondary reaction tank is located at the bottom of the secondary reaction tank, and the outlet of the secondary reaction tank is connected to the inlet of the high-pressure diaphragm filter press via a slurry pump.

[0012] Further, the drying unit includes a vacuum rake dryer;

[0013] The filter cake outlet of the high-pressure diaphragm filter press is connected to the inlet of the vacuum rake dryer via a screw conveyor;

[0014] The high pressure diaphragm filter press is also provided with a filtrate outlet.

[0015] Furthermore, the air outlet of the vacuum rake dryer is connected to a vacuum pump, the vacuum pump is connected to a gas-water separator, and the gas-water separator is connected to a condensate heat exchanger.

[0016] Further, the vacuum rake dryer, vacuum pump, gas-water separator and condensate heat exchanger are located in the first layer space at the bottom;

[0017] The high-pressure diaphragm filter press and screw conveyor are located in the middle second space;

[0018] The primary reaction tank, intermediate lifting pump, plate and frame heat exchanger, secondary reaction tank and slurry pump are located in the third space at the top.

[0019] Furthermore, the filter plate of the high-pressure diaphragm filter press is made of PP material.

[0020] In view of the above technical features, the utility model has the following advantages:

[0021] 1. The utility model adopts a two-stage reaction device for recovering waste phosphoric acid in the electronics industry to produce calcium phosphate. The first-stage reaction tank generates calcium dihydrogen phosphate with a relatively high solubility to avoid scaling in the plate-frame heat exchanger; the second-stage reaction tank generates calcium phosphate with an extremely low solubility, which is filtered and dried to obtain a high-purity active calcium phosphate product. The design of the two-stage reaction tank enables the waste phosphoric acid and lime milk to react more fully and thoroughly, thereby improving the efficiency of converting waste phosphoric acid into active calcium phosphate; the design of adding a plate-frame heat exchanger between the first-stage reaction tank and the second-stage reaction tank reduces the temperature rise caused by the neutralization heat of acid-base materials on the second-stage reaction tank and its subsequent high-pressure diaphragm filter press and delivery pump and other equipment materials, thereby extending the service life of these equipment.

[0022] 2. The device for recovering waste phosphoric acid from the electronics industry of the utility model to prepare calcium phosphate adopts a high-pressure diaphragm filter press with a pressing pressure of up to 1.2-2.0 MPa, which greatly reduces the moisture content of the filter cake and the energy consumption of the dryer; the filter plate is made of PP material, which has strong corrosion resistance and low equipment investment.

[0023] 3. The utility model of the device for recovering waste phosphoric acid in the electronics industry to prepare calcium phosphate adopts a vacuum rake dryer, which greatly reduces the vaporization temperature of water under vacuum state, reduces steam consumption (i.e., low energy consumption), and the discharge temperature of the dryer is only about 60°C, which can be directly packaged; the hollow rotating shaft and rake teeth not only play the role of stirring the material and renewing the surface, but also serve as a heating surface, which transfers heat simultaneously with the container jacket, improves the heat transfer efficiency, and reduces energy consumption.

[0024] 4. The device for recovering waste phosphoric acid in the electronics industry to produce calcium phosphate can efficiently convert waste phosphoric acid into active calcium phosphate, solving the problem of recycling phosphorus resources in waste phosphoric acid, greatly reducing the difficulty of disposing of these hazardous wastes, and at the same time more safely realizing the resource utilization of phosphorus elements, and avoiding the harmful effects of waste phosphoric acid on the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic structural diagram of a device for recovering waste phosphoric acid from the electronics industry to produce calcium phosphate in specific embodiment 1.

[0026] In the figure: 1. primary reaction tank; 2. plate and frame heat exchanger; 3. secondary reaction tank; 4. high-pressure diaphragm filter press; 5. vacuum rake dryer; 6. intermediate lifting pump; 7. slurry pump; 8. screw conveyor; 51. vacuum pump; 52. gas-water separator; 53. condensate heat exchanger. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

[0028] See also Figure 1 , Specific embodiment 1, this embodiment 1 provides a device for recovering waste phosphoric acid in the electronics industry to prepare calcium phosphate, the device includes a primary reaction tank 1, a cooling unit, a secondary reaction tank 3, a high-pressure filter press unit and a drying unit, the outlet of the primary reaction tank 1 is connected to the inlet of the cooling unit, the outlet of the cooling unit is connected to the inlet of the secondary reaction tank 3, the outlet of the secondary reaction tank 3 is connected to the inlet of the high-pressure filter press unit, the outlet of the high-pressure filter press unit is connected to the inlet of the drying unit, the drying unit is connected to an external steam source, and the drying unit is provided with a discharge port.

[0029] The primary reaction tank 1 is used for the preliminary reaction of waste phosphoric acid with lime milk to generate calcium dihydrogen phosphate with greater solubility.

[0030] The cooling unit includes a plate-frame heat exchanger 2. The outlet of the primary reaction tank 1 is located at the bottom of the primary reaction tank 1, and the outlet of the primary reaction tank 1 is connected to the inlet of the plate-frame heat exchanger 2 via the intermediate lifting pump 6, and the outlet of the plate-frame heat exchanger 2 is connected to the inlet of the secondary reaction tank 3. The plate-frame heat exchanger 2 can also be disassembled for cleaning and descaling, which is more convenient to use.

[0031] The function of the plate-frame heat exchanger 2 is to reduce the temperature rise of the acid-base materials flowing out of the primary reaction tank 1 due to the heat of neutralization, which affects the equipment materials such as the secondary reaction tank 3, the high-pressure diaphragm filter press 4 and the delivery pump, thereby extending the service life. In addition, due to the cooling effect of the plate-frame heat exchanger 2, the material requirements of these equipment are also reduced (for example, the filter plate of the high-pressure diaphragm filter press 4 can be made of PP material instead of stainless steel or titanium alloy), thereby reducing the overall manufacturing cost of the device.

[0032] The intermediate lifting pump 6 is used to flow the material in the primary reaction tank 1 into the plate and frame heat exchanger 2 , helping the material to flow from low to high and avoiding the accumulation of the material at the bottom of the primary reaction tank 1 .

[0033] The secondary reaction tank 3 is used for further reaction of waste phosphoric acid with lime milk, so that all waste phosphoric acid is converted into calcium phosphate precipitate with extremely low solubility. The design of the two-stage reaction tank can make the waste phosphoric acid and lime milk react more fully and thoroughly, and improve the efficiency of converting waste phosphoric acid into active calcium phosphate.

[0034] The high-pressure filter press unit includes a high-pressure diaphragm filter press 4, such as the high-pressure diaphragm filter press 4 produced by Henan Dazhang Filtration Equipment Co., Ltd. and Hangzhou Xingyuan Environmental Protection Equipment Co., Ltd. The high-pressure diaphragm filter press 4 is used to physically squeeze the slurry containing a large amount of calcium phosphate precipitation flowing out of the secondary reaction tank 3 to form a filtrate D and a filter cake. The outlet of the secondary reaction tank 3 is located at the bottom of the secondary reaction tank 3, and the outlet of the secondary reaction tank 3 is connected to the inlet of the high-pressure diaphragm filter press 4 via a slurry pump 7. The high-pressure diaphragm filter press 4 is also provided with a filtrate outlet, and the filtrate D of the high-pressure diaphragm filter press 4 flows out from the filtrate outlet, is collected and reused for the preparation of lime milk, and the excess phosphorus-containing filtrate (i.e., filtrate D) is sent to a sewage treatment plant for treatment or incineration.

[0035] The drying unit includes a vacuum rake dryer 5, such as the vacuum rake dryer 5 produced by Jiangsu Fanqun Drying Equipment Factory Co., Ltd. and Jiangsu Jinling Drying Technology Co., Ltd. The vacuum rake dryer 5 is used to heat and dry the filter cake. The filter cake outlet of the high-pressure diaphragm filter press 4 is connected to the inlet of the vacuum rake dryer 5 via a screw conveyor 8, and the filter cake of the high-pressure diaphragm filter press 4 enters the cavity of the vacuum rake dryer 5 via the screw conveyor 8 for drying. The vacuum rake dryer 5 is provided with a discharge port, and the product that meets the quality standard of active calcium phosphate is finally discharged from the discharge port of the vacuum rake dryer 5.

[0036] The air outlet of the vacuum rake dryer 5 is connected to a vacuum pump 51, the vacuum pump 51 is connected to a gas-water separator 52, and the gas-water separator 52 is connected to a condensate heat exchanger 53. The vacuum pump 51 is used to extract the water vapor removed from the cavity of the vacuum rake dryer 5 during the feeding process and maintain the vacuum degree in the cavity of the vacuum rake dryer 5; the extracted water vapor is condensed in the gas-water separator 52 to form a condensate, and the condensate is cooled by the condensate heat exchanger 53 and then recovered for use. Part of the condensate is used to replenish the vacuum pump 51, part of it is used to prepare lime milk, and the excess is sent to a sewage treatment plant for treatment.

[0037] The vacuum rake dryer 5, vacuum pump 51, gas-water separator 52 and condensate heat exchanger 53 are located in the first layer of space at the bottom. The high-pressure diaphragm filter press 4 and screw conveyor 8 are located in the middle second layer of space. The primary reaction tank 1, intermediate lifting pump 6, plate-frame heat exchanger 2, secondary reaction tank 3 and slurry pump 7 are located in the third layer of space at the top, that is, the primary reaction tank 1, plate-frame heat exchanger 2, secondary reaction tank 3, high-pressure diaphragm filter press 4 and vacuum rake dryer 5 are arranged from high to low in a three-layer structure according to the material flow direction, which not only saves space and has a compact layout, but also utilizes the gravity of the material flow itself, so that the material flow can flow through the primary reaction tank 1, plate-frame heat exchanger 2, secondary reaction tank 3, high-pressure diaphragm filter press 4 and vacuum rake dryer 5 in sequence better.

[0038] A device for recovering waste phosphoric acid in the electronics industry to prepare calcium phosphate has the following working principle: waste phosphoric acid A to be recovered and lime milk B are successively injected into a primary reaction tank 1, and the pH value is controlled between 6.0 and 7.0 to generate calcium dihydrogen phosphate with relatively large solubility, thereby avoiding scaling inside a plate-frame heat exchanger 2; the material coming out of the primary reaction tank 1 enters a plate-frame heat exchanger 2, and the material temperature is reduced to ≤40°C, so as to reduce the influence of the temperature rise caused by the neutralization heat on the equipment materials such as the reaction tank (i.e., a secondary reaction tank 3), a filter press (i.e., a high-pressure diaphragm filter press 4) and a delivery pump (i.e., a slurry pump 7), thereby extending the service life; the cooled material enters the secondary reaction tank 3, and lime milk B is continuously injected, and the pH value is controlled between 11.0 and 12.0, so that all the waste phosphoric acid generates calcium phosphate precipitates with extremely low solubility, thereby forming a slurry containing a large amount of calcium phosphate precipitates.

[0039] The slurry containing a large amount of calcium phosphate precipitate is injected into the high-pressure diaphragm filter press 4 through the slurry pump 7. Using the principle of physical pressing, after filtering and pressing at a pressure of 1.2-2.0MPa, the solid content of the filter cake is greater than 50%, which greatly reduces the energy consumption of the dryer (i.e., the vacuum rake dryer 5); the filter plate of the high-pressure diaphragm filter press 4 is made of PP material, which has strong corrosion resistance and low equipment investment; the filtrate D is collected and reused in the preparation of lime milk B, and the excess filtrate D is sent to a sewage treatment plant for treatment or incineration.

[0040] The filter cake is finally conveyed into the inner cavity of the vacuum rake dryer 5 by the screw conveyor 8. The external steam source injects steam E into the vacuum rake dryer 5. The filter cake is quickly heated under the stirring of the rotating shaft and rake teeth in the vacuum rake dryer 5. At this time, the hollow rotating shaft and rake teeth in the vacuum rake dryer 5 not only play the role of stirring the material and renewing the surface, but also serve as a heating surface, which transfers heat with the container jacket at the same time to evaporate the water in the filter cake, and then the water vapor and other gases are extracted from the vacuum rake dryer 5 by the vacuum pump 51; The air pump 51 maintains the vacuum degree of the inner cavity of the vacuum rake dryer 5 between 0.065-0.095MPa, which greatly reduces the vaporization temperature of water under vacuum (see the boiling point temperature in Table 1), thereby greatly reducing the steam consumption; the operating temperature of the inner cavity of the vacuum rake dryer 5 is less than 100°C, and the discharge temperature is only about 60°C, so the product C can be directly packaged; when the moisture content of the material is less than 2.5%, it is discharged from the discharge port of the vacuum rake dryer 5, which is the product C that meets the quality standards of active calcium phosphate.

[0041] Table 1:

[0042] Boiling point of water at various vacuum levels

[0043] Vacuum degreeMpa Boiling point℃ -0.099 7.0 -0.095 32.9 -0.090 45.8 -0.085 54.0 -0.080 60.1 -0.075 65.0 -0.070 69.1 -0.065 72.7 -0.060 75.9 -0.055 78.7 -0.050 81.3 -0.045 83.7

[0044] The gas extracted by the vacuum pump 51 is separated by the gas-water separator 52, and the liquid part is cooled by the condensate heat exchanger 53 to form condensate F, part of which is returned to the vacuum pump 51 for water replenishment, part of which is returned to the preparation of lime milk B, and the excess is sent to the sewage treatment plant for treatment.

[0045] Waste phosphoric acid from the electronics industry generally does not contain heavy metal impurities. Converting it into active calcium phosphate with higher economic value can be used as an additive for glass, ceramics and coatings, etc.

[0046] Compared with the traditional device, the utility model has the advantages of simple process, compact layout, high efficiency, low energy consumption, simple and flexible operation and long service life.

[0047] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0048] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0049] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A device for recovering waste phosphoric acid from the electronics industry to produce calcium phosphate, characterized in that: The device comprises a primary reaction tank (1), a cooling unit, a secondary reaction tank (3), a high-pressure filter press unit and a drying unit; the outlet of the primary reaction tank (1) is connected to the inlet of the cooling unit, the outlet of the cooling unit is connected to the inlet of the secondary reaction tank (3), the outlet of the secondary reaction tank (3) is connected to the inlet of the high-pressure filter press unit, the outlet of the high-pressure filter press unit is connected to the inlet of the drying unit, the drying unit is connected to an external steam source, and the drying unit is provided with a discharge port.

2. The device for recovering waste phosphoric acid from the electronics industry to produce calcium phosphate according to claim 1, characterized in that: The cooling unit comprises a plate-frame heat exchanger (2); The outlet of the primary reaction tank (1) is located at the bottom of the primary reaction tank (1), and the outlet of the primary reaction tank (1) is connected to the inlet of the plate-frame heat exchanger (2) via an intermediate lifting pump (6), and the outlet of the plate-frame heat exchanger (2) is connected to the inlet of the secondary reaction tank (3).

3. A device for recovering waste phosphoric acid from the electronics industry to produce calcium phosphate according to claim 2, characterized in that: The high-pressure filter press unit comprises a high-pressure diaphragm filter press (4); The outlet of the secondary reaction tank (3) is located at the bottom of the secondary reaction tank (3), and the outlet of the secondary reaction tank (3) is connected to the inlet of the high-pressure diaphragm filter press (4) via a slurry pump (7).

4. The device for recovering waste phosphoric acid from the electronics industry to produce calcium phosphate according to claim 3, characterized in that: The drying unit comprises a vacuum rake dryer (5); The filter cake outlet of the high-pressure diaphragm filter press (4) is connected to the inlet of the vacuum rake dryer (5) via a screw conveyor (8); The high-pressure diaphragm filter press (4) is also provided with a filtrate outlet.

5. The device for recovering waste phosphoric acid from the electronics industry to produce calcium phosphate according to claim 4, characterized in that: The air outlet of the vacuum rake dryer (5) is connected to a vacuum pump (51), the vacuum pump (51) is connected to a gas-water separator (52), and the gas-water separator (52) is connected to a condensate heat exchanger (53).

6. The device for recovering waste phosphoric acid from the electronics industry to produce calcium phosphate according to claim 5, characterized in that: The vacuum rake dryer (5), vacuum pump (51), gas-water separator (52) and condensate heat exchanger (53) are located in the first layer space at the bottom; The high-pressure diaphragm filter press (4) and the screw conveyor (8) are located in the middle second space; The primary reaction tank (1), the intermediate lifting pump (6), the plate and frame heat exchanger (2), the secondary reaction tank (3) and the slurry pump (7) are located in the third layer space at the top.

7. The device for recovering waste phosphoric acid from the electronics industry to produce calcium phosphate according to claim 6, characterized in that: The filter plate of the high-pressure diaphragm filter press (4) is made of PP material.

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