Chemical oxidation-nucleation granulation method for removing and recovering boron in water

Abstract

A chemical oxidation-nucleation granulation integrated device for removing and recycling boron in water is divided into an inner cylinder and an outer cylinder, the outer cylinder is a pre-oxidation reaction tank, and the inner cylinder is a nucleation granulation reactor. The water to be treated enters from the top of the outer cylinder, and an oxidizing agent and an alkaline substance are added for pre-oxidation. The water outlet at the bottom of the outer cylinder enters the inner barrel nucleation granulation reactor under the action of water pressure. By adding a precipitant, the coagulation of boron on the surface of the crystal seed is improved, the boron is induced to crystallize and nucleate rapidly and densify, and the content of boron in the water is reduced. The present application can realize efficient removal of boron in water. Compared with the traditional coagulation and sedimentation method, the present application not only reduces the dosage of reagents, but also reduces the sludge production, improves the treatment efficiency, precipitates boron in the form of crystals, facilitates subsequent recycling of boron, improves the water quality of the effluent, avoids waste of boron resources, and realizes maximum utilization of resources.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment technology, specifically relating to an integrated device and method for removing and recovering boron from water by chemical oxidation and nucleation granulation. Background Technology

[0002] Boron is a non-metallic element with wide applications in various industries. For example, borax or organoboron compounds are commonly used crosslinking agents in the preparation of fracturing fluids for oil and gas fields; nuclear power plants typically use boron to control the rate of uranium fission, thereby effectively controlling power generation; during bright nickel plating, boric acid is used as a buffer solution to maintain a certain acidity, which can effectively improve the quality of the electroplated layer; in addition, boron is also found in wastewater from chemical processes, borosilicated glass, and waste treatment, and excessive boron has significant harmful effects on human health and the growth and development of plants and animals.

[0003] Taking fracturing flowback fluid as an example, given its complex composition, purification and reuse are crucial for reducing water pollution. However, the presence of residual boron in fracturing flowback fluid severely restricts its reuse. Currently, compounded fracturing flowback fluids generally require a residual boron content below 5 mg / L, while direct discharge requires a residual boron content below 0.5 mg / L. However, the actual boron content in fracturing flowback fluid is far higher than these requirements.

[0004] In recent years, to control the boron content in wastewater, foreign wastewater discharge standards have successively added boron-related indicators. Although my country's "Integrated Wastewater Discharge Standard" (GB 8978-1996) has not yet set requirements for boron discharge values, local standards in Beijing, Shanghai, and other cities have limits on boron discharge. For example, Beijing's "Integrated Discharge Standard for Water Pollutants" (DB 11 / 307-2013) sets the limit at only 0.5 mg / L. Therefore, it is evident that domestic requirements for boron discharge will gradually increase in the future, making the development of advanced and efficient technologies an urgent necessity to provide a technological foundation for boron removal from industrial wastewater.

[0005] Currently, common boron removal methods mainly include chemical precipitation, membrane separation, extraction, and resin methods. Traditional chemical precipitation typically requires large amounts of precipitant, produces significant sludge, and has low boron removal efficiency. Membrane separation is costly, suffers from membrane fouling, and is difficult to apply on-site. Extraction is prone to secondary pollution, is easily damaged, and is costly. Resin methods are only suitable for treating wastewater with low boron content, have limited saturation capacity, and are costly. Summary of the Invention

[0006] Considering the practical needs of field applications such as oil fields, the treatment of boron-containing wastewater should generally be completed on-site. Therefore, developing an efficient, convenient, and low-cost boron removal device has significant application value. To overcome the shortcomings of existing technologies and address the problems of low efficiency and large footprint associated with traditional sedimentation methods for removing boron from water, the present invention aims to provide an integrated device and method for chemical oxidation and nucleation granulation coupling for removing and recovering boron from water. This reduces reagent dosage and sludge production, efficiently removes and recovers boron from water, reduces water pollution, and maximizes the utilization of boron resources.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides an integrated chemical oxidation-nuclear crystal granulation device for removing and recovering boron from water, comprising a vertical outer cylinder and an inner cylinder. The inner cylinder is located within the outer cylinder, which is a pre-oxidation reaction tank with a first water inlet and a first chemical inlet at its top. The first chemical inlet is connected to an oxidant tank. The inner cylinder is a nucleation crystal granulation reactor, which is connected to the outer cylinder through a second water inlet at its bottom. The inner cylinder is filled with characteristic seed crystals and is connected to a precipitant tank through the second chemical inlet. There are spaces between the top and sides of the pre-oxidation reaction tank and the nucleation crystal granulation reactor. The oxidized effluent enters the nucleation crystal granulation reactor from the second water inlet under water pressure and is discharged from the water outlet at the top of the inner cylinder.

[0009] In one embodiment, the outer cylinder and the inner cylinder are fixedly connected by connecting brackets to ensure the stability of the inner cylinder during operation. The number of connecting brackets is determined according to the amount of water to be treated.

[0010] In one embodiment, the first inlet is also connected to an alkaline substance tank, and the pre-oxidation tank is also equipped with a stirring device to improve oxidation efficiency.

[0011] In one embodiment, the side of the nucleogranulation reactor is provided with a seed inlet at an angle of 60° to the horizontal direction, which is connected to the side of the inner cylinder from the side of the outer cylinder. The second water inlet is provided with a pressure sensor, which sets a threshold based on the water quality and the seed filling height to measure the seed state. When the seed is saturated, it is discharged from the seed outlet at the bottom of the side of the inner cylinder.

[0012] In one embodiment, the drain outlet is located at the top of the side wall of the nuclear crystal granulation reactor and is connected to the second inlet via a detachable return pipe. The connection method of the drain outlet is selected based on the water quality and treatment requirements: when the water quality meets the requirements, the return pipe is disassembled and the water is discharged directly from the drain outlet; when the water quality does not meet the requirements, the treated effluent is returned to the bottom of the reactor for further purification.

[0013] A second aspect of the present invention provides a chemical oxidation-nucleation granulation method for removing and recovering boron from water, based on the integrated chemical oxidation-nucleation granulation device for removing and recovering boron from water described in the first aspect of the present invention. The boron-containing wastewater to be treated is fed into a pre-oxidation reaction tank through a first inlet, while an oxidant is added to the tank through a first inlet to generate perborate ions. The boron-containing wastewater to be treated is continuously added, so that the oxidized wastewater containing perborate ions enters a nucleation granulation reactor through a second inlet. Simultaneously, a precipitant is added to the reactor through the second inlet to react with the perborate ions to produce calcium perborate precipitate, which crystallizes on a characteristic seed crystal, thereby precipitating boron from the boron-containing wastewater in the form of crystals and reducing the boron content in the water.

[0014] In one embodiment, while adding the oxidant through the first inlet, an alkaline substance is also added to the pre-oxidation reaction tank to adjust the pH of the wastewater to between 10 and 11.

[0015] In one embodiment, the oxidant is a hydrogen peroxide solution, and the amount added is 5%-10% of the volume of the boron-containing wastewater to be treated, depending on the specific water quality; the alkaline substance for adjusting the pH of the wastewater is a sodium hydroxide solution; and the precipitant is a calcium chloride solution, and the amount added is 500-2500 mg / L, depending on the specific water quality.

[0016] In one embodiment, the precipitant is added after the seed crystals in the reactor have reached a fully fluidized state.

[0017] In one embodiment, the effluent from the nucleation granulation reactor is fed into a regulating tank to adjust the pH range to 10-11, and then fed back into the nucleation granulation reactor from the second inlet for reaction.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. Pre-oxidation reaction before nucleus crystal granulation can improve the precipitation effect of boron by subsequent alkaline earth metal reagents and increase removal efficiency.

[0020] 2. When it is necessary to remove boron from water, the water to be treated is directly introduced through the inlet of the outer cylinder, and an oxidant and an alkaline substance are added. The water will then enter the inner cylinder containing characteristic seed crystals of a certain height under water pressure. Adding a precipitant to the inner cylinder will cause the boron in the water to crystallize on the characteristic seed crystals, thereby precipitating the boron in the form of crystals and reducing the boron content in the water.

[0021] 3. A detachable return pipe is connected between the inner cylinder drain outlet 6 and the bottom inlet 10. The connection method of the drain outlet can be selected according to the water quality and treatment requirements of the water to be treated: when the water quality is good or the treatment requirements are not high, the return pipe at the drain outlet can be removed and the water can be discharged directly from the drain outlet; when the water quality is poor or the treatment requirements are high, the treated effluent can be returned to the reactor through the return pipe for further purification treatment, and the removal effect can be significantly improved by increasing the number of return stages.

[0022] 4. When water is introduced from the bottom of the nucleation granulation reactor, the characteristic seed crystals are disturbed to promote their complete fluidization, thereby improving the uniformity of mixing among the characteristic seed crystals, boron, and reagents, increasing the efficiency of boron crystallization on the surface of the characteristic seed crystals, and improving the boron removal efficiency. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0024] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0025] like Figure 1 As shown, this invention discloses an integrated chemical oxidation-nuclear crystal granulation device for removing and recovering boron from water, comprising a vertical outer cylinder 1 and an inner cylinder 2. The inner cylinder 2 is located within the outer cylinder 1, and is preferably coaxially arranged to ensure uniform reaction. The outer cylinder 1 serves as a pre-oxidation reaction tank, with a first water inlet 3 and a first chemical inlet 4 at its top. The first water inlet 3 is the device inlet for the boron-containing wastewater to be treated, and the first chemical inlet 4 is connected to an oxidant tank, serving as the oxidant inlet for the pre-oxidation reaction tank. The inner cylinder 2 is a nucleation crystal granulation reactor, connected to the outer cylinder 1 only through a second water inlet 10 at its bottom. The inner cylinder 2 is filled with characteristic seed crystals and is connected to a precipitant tank through a second chemical inlet 9. There is a certain space between the top of the pre-oxidation reaction tank and the top of the nucleation granulation reactor, and there is also a certain space between the side of the pre-oxidation reaction tank and the side of the nucleation granulation reactor. The arrangement of the second inlet 10 allows the effluent after oxidation in the pre-oxidation reaction tank to enter the nucleation granulation reactor under water pressure and be discharged from the outlet 6 at the top of the inner cylinder 2, thus eliminating the need for pumps.

[0026] According to the above-described apparatus, the process for removing and recovering boron from water according to the present invention is as follows:

[0027] The boron-containing wastewater to be treated is fed into the pre-oxidation reaction tank through the first inlet 3, while an oxidant is added through the first chemical inlet 4 for pre-oxidation. During this process, the boron-containing wastewater to be treated is continuously added, allowing the oxidized wastewater to enter the nucleation granulation reactor under water pressure through the second inlet 10 for continuous treatment. Simultaneously, a precipitant is added to the nucleation granulation reactor through the second chemical inlet 9 to produce precipitate, which crystallizes onto characteristic seed crystals. This precipitates boron from the boron-containing wastewater in the form of crystals, reducing the boron content in the water. The treated water is then discharged from the outlet 6 at the top of the inner cylinder 2.

[0028] The principle of this invention is:

[0029] By adding an oxidant to the pre-oxidation reactor, boron in the wastewater can be oxidized to generate perborate ions. The wastewater containing perborate ions then enters a nucleation granulation reactor filled with characteristic seed crystals of a certain height. A precipitant is added through the second inlet 9 for nucleation granulation. Under the action of the precipitant, the cohesion of boron on the seed crystal surface is improved, inducing rapid boron crystallization. The dense calcium borate precipitate produced by the reaction of boron with the reagent crystallizes on the characteristic seed crystals, thereby precipitating boron from the water in the form of crystals and reducing the boron content in the water. Furthermore, when water enters through the second inlet 10 at the bottom of the nucleation granulation reactor, the characteristic seed crystals are disturbed to promote complete fluidization, thereby improving the uniformity of mixing among the characteristic seed crystals, boron, and reagents, increasing the efficiency of boron crystallization on the seed crystal surface, and improving boron removal efficiency. Therefore, this invention, by combining pre-oxidation and nucleation granulation technologies, can efficiently remove and recover boron from water, reducing reagent dosage and sludge production, and achieving rational resource utilization.

[0030] Furthermore, in an embodiment of the present invention, while adding the oxidant to the pre-oxidation reaction tank through the first inlet 4, an alkaline substance is also added to adjust the pH of the wastewater to between 10 and 11. The purpose of adding the alkaline substance to adjust the pH here is to promote the precipitation of boron by subsequent reagents. That is, in the nucleation granulation reactor, the coagulation of boron on the seed crystal surface can be further improved through the action of pH and reagents. At this time, the first inlet 4 can be connected to an alkaline substance tank, or a separate alkaline substance inlet can be added. Simultaneously, to improve oxidation efficiency, a stirring device 5 can be installed in the pre-oxidation tank. The stirring device 5 can be started synchronously with the incoming water. It can be installed only between the top of the inner cylinder 2 and the top of the outer cylinder 1, or it can also be installed between the side of the inner cylinder 2 and the side of the outer cylinder 1.

[0031] For example, the oxidant used in this invention is hydrogen peroxide solution, preferably with a purity of 30%, and the amount added is 5%-10% of the volume of the boron-containing wastewater to be treated, depending on the specific water quality. In practice, oxidants such as sodium hypochlorite or peracetic acid with a purity of 20%-30% can also be used instead of hydrogen peroxide. The alkaline substance used to adjust the pH of the wastewater is sodium hydroxide solution, and the precipitant is calcium chloride solution, with an addition amount of 500-2500 mg / L depending on the specific water quality.

[0032] Furthermore, in embodiments of the present invention, depending on the different water quality conditions and treatment requirements of the water to be treated, pretreatment processes such as filtration and activated carbon adsorption can be added at the front end of the boron removal device of the present invention to remove some impurities in the water and ensure the subsequent removal effect.

[0033] Furthermore, in an embodiment of the present invention, when water is introduced from the bottom of the nucleation granulation reactor, the characteristic seed crystals are disturbed to promote their complete fluidization. Therefore, it is preferable to add the precipitant after the seed crystals in the reactor are in a completely fluidized state, thereby improving the uniformity of mixing among the characteristic seed crystals, boron-containing wastewater and precipitant, improving the efficiency of boron crystallization on the surface of the characteristic seed crystals, and improving the boron removal efficiency.

[0034] Furthermore, in embodiments of the present invention, when the quality of the boron-containing wastewater to be treated is poor or the treatment requirements are high, reflux treatment can be performed. For example, an adjusting tank can be set up before the effluent is refluxed to the bottom of the reactor, and sodium hydroxide can be added to strictly control the pH of the influent at 10-11. Then, the effluent is fed back into the nucleation granulation reactor through the second inlet 10 for reaction, ensuring a better removal effect. That is, the alkaline substance used to adjust the pH of the present invention can be added to the pre-oxidation reaction tank or to the nucleation granulation reactor.

[0035] In terms of mechanical structure, the outer cylinder 1 and inner cylinder 2 of this invention are fixedly connected by connecting brackets 7 to ensure the stability of the inner cylinder during operation. The number of connecting brackets is determined according to the volume of water to be treated. When the water volume is small, fewer brackets 7 may be needed to meet the stability requirements; while when the water volume is large, more brackets are needed to provide additional support. The connecting brackets 7 can be made of high-strength materials and have multiple fixing points to ensure the stability and alignment of the inner cylinder 2 in all directions. The connecting brackets 7 can be connected to the outer cylinder 1 and inner cylinder 2 by bolts, welding, or bonding to ensure the firmness of the connection. During operation, the inner cylinder 2 can maintain its position and posture stability due to the presence of the connecting brackets 7, avoiding performance degradation caused by vibration or eccentric load.

[0036] To facilitate seed crystal replenishment, this invention includes a seed crystal addition port 8 on the side of the nucleogranulation reactor, positioned at a 60° angle to the horizontal. The seed crystals enter the inner cylinder 2 from the side of the outer cylinder 1, promoting uniform distribution and effective addition while minimizing interference with the internal flow pattern of the reactor. For seed crystal monitoring, a pressure sensor is installed at the second inlet 10. A threshold is set based on water quality and seed crystal filling height to measure the seed crystal state. When the seed crystals are saturated, indicating they have reached their maximum adsorption or reaction capacity, they are discharged from the seed crystal outlet 11 at the bottom of the inner cylinder side, allowing for timely seed replacement and ensuring optimal treatment results. The outlet 11 can be equipped with a valve or an automatic control system. The overall system design ensures a coordinated process for seed crystal addition, monitoring, saturation detection, and discharge.

[0037] To achieve water recirculation, drain outlet 6 is located at the top of the side wall of the nucleogranulation reactor and connected to the second inlet 10 via a detachable recirculation pipe. The connection method of the drain outlet can be selected based on the water quality and treatment requirements: when the water quality is good or the treatment requirements are not high, the recirculation pipe can be disassembled, the connection between the recirculation pipe and the second inlet 10 can be closed, and the effluent can be discharged directly from the drain outlet; when the water quality is poor or the treatment requirements are high, the connection between the recirculation pipe and the second inlet 10 can be opened, and the treated effluent can be recirculated back to the bottom of the reactor for further purification, increasing the residence time of the water in the reactor and thus improving the removal rate of pollutants. Increasing the number of recirculation stages can significantly improve the removal effect. For this purpose, the system can be equipped with water quality monitoring equipment to monitor the water quality parameters of the water to be treated in real time, mainly the boron content. The detachable design of the recirculation pipe simplifies maintenance and cleaning, helping to maintain the long-term stable operation of the system.

[0038] Therefore, compared with traditional chemical precipitation methods, this invention does not require other auxiliary coagulation and sedimentation processes. The overall process is simple, requires less land area, and has lower equipment costs. It reduces the amount of reagents added and the amount of sludge produced. At the same time, it precipitates boron in the form of crystals, which can achieve efficient removal of boron from water and facilitate subsequent recovery and reuse of boron. This improves the quality of effluent while avoiding waste of boron resources and maximizing resource utilization.

Claims

1. An integrated device for chemical oxidation and nucleation granulation coupling for removing and recovering boron from water, characterized in that, It consists of two parts: a vertical outer cylinder (1) and an inner cylinder (2). The inner cylinder (2) is located inside the outer cylinder (1). The outer cylinder (1) is the pre-oxidation reaction tank, which has a first water inlet (3) and a first chemical inlet (4) at its top. The first chemical inlet (4) is connected to the oxidant tank. The inner cylinder (2) is the nucleation granulation reactor, which is connected to the outer cylinder (1) through a second water inlet (10) at the bottom. The inner cylinder (2) is filled with characteristic crystal seeds and is connected to the precipitant tank through a second chemical inlet (9). The pre-oxidation reaction tank and the nucleation granulation reactor are connected to the outer cylinder (1). There are spaces between the top and sides of the reactor. The oxidized effluent enters the nucleation granulation reactor from the second inlet (10) under water pressure and is discharged from the outlet (6) at the top of the inner cylinder (2). The pre-oxidation reaction tank is also equipped with a stirring device (5) to improve the oxidation efficiency. The stirring device (5) is only set between the top of the inner cylinder (2) and the top of the outer cylinder (1); or it is set simultaneously between the top of the inner cylinder (2) and the top of the outer cylinder (1) and between the side of the inner cylinder (2) and the side of the outer cylinder (1).

2. The integrated chemical oxidation-nucleation granulation device for removing and recovering boron from water according to claim 1, characterized in that, The outer cylinder (1) and the inner cylinder (2) are fixedly connected by connecting brackets (7) to ensure the stability of the inner cylinder during operation. The number of connecting brackets is determined according to the amount of water to be treated.

3. The integrated chemical oxidation-nucleation granulation device for removing and recovering boron from water according to claim 1, characterized in that, The first inlet (4) is also connected to an alkaline substance medicine box.

4. The integrated chemical oxidation-nucleation granulation device for removing and recovering boron from water according to claim 1, characterized in that, The side of the nuclear crystal granulation reactor is provided with a seed inlet (8) at an angle of 60° to the horizontal direction. The seed is introduced into the side of the inner cylinder (2) from the side of the outer cylinder (1). The second water inlet (10) is provided with a pressure sensor. The threshold is set according to the water quality and the seed filling height to measure the seed status. When the seed is saturated, it is discharged from the seed outlet (11) at the bottom of the side of the inner cylinder.

5. The integrated chemical oxidation-nucleation granulation device for removing and recovering boron from water according to claim 1, characterized in that, The outlet (6) is located at the top of the side wall of the nuclear crystal granulation reactor and is connected to the second inlet (10) through a detachable return pipe. The connection method of the outlet is selected according to the water quality and treatment requirements of the water to be treated: when the water quality meets the requirements, the return pipe is disassembled and the water is discharged directly from the outlet (6); when the water quality does not meet the requirements, the treated water is returned to the bottom of the reactor for further purification.

6. A chemical oxidation-nucleation granulation method for removing and recovering boron from water, implemented based on the integrated chemical oxidation-nucleation granulation device for removing and recovering boron from water as described in any one of claims 1 to 5, characterized in that, Includes the following steps: The boron-containing wastewater to be treated is fed into the pre-oxidation reaction tank through the first inlet (3), and an oxidant is added to it through the first inlet (4) to generate perborate ions. The boron-containing wastewater to be treated is continuously added, so that the oxidized wastewater containing perborate ions enters the nucleation granulation reactor through the second inlet (10), and a precipitant is added to it through the second inlet (9) to react with the perborate ions to generate calcium perborate precipitate, which crystallizes on the characteristic seed crystal, thereby precipitating the boron in the boron-containing wastewater to be treated in the form of crystals and reducing the boron content in the water.

7. The chemical oxidation-nucleation granulation method for removing and recovering boron from water according to claim 6, characterized in that, While adding oxidant through the first inlet (4), alkaline substances are also added to the pre-oxidation reaction tank to adjust the pH range of the wastewater to between 10 and 11.

8. A chemical oxidation-nucleation granulation method for removing and recovering boron from water according to claim 6 or 7, characterized in that, Add the precipitant only after the seed crystals in the reactor have reached a completely fluidized state.

9. A chemical oxidation-nucleation granulation method for removing and recovering boron from water according to claim 6 or 7, characterized in that, The effluent from the nucleogranulation reactor is fed into a regulating tank to adjust the pH range to 10-11, and then fed back into the nucleogranulation reactor from the second inlet (10) for reaction.

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