Elemental phosphorus oxidation recovery method for phosphorus-containing wastewater

Abstract

The invention discloses a simple substance phosphorus oxidation recovery method for phosphorus-containing wastewater, belongs to the field of pollutant treatment, and aims to solve the problems that simple substance phosphorus is high in density and not easy to oxidize in the simple substance phosphorus wastewater treatment process. The method provided by the invention breaks through the limitation that the traditional elemental phosphorus wastewater only focuses on pollution treatment, successfully realizes the dual goals of deep pollution treatment and closed-loop recovery of phosphorus resources, and has both environmental benefits and economic benefits. According to the application, the stage treatment logic of'temporary storage oxidation pond (simple substance phosphorus oxidation)-(primary phosphorus removal)-(fine phosphorus removal)-(deep phosphorus removal) 'is adopted, and the tail end purification of the sand filter is matched, so that the efficient oxidation of simple substance phosphorus is ensured (the problem that the simple substance phosphorus is difficult to contact with air due to deposition is solved), and the phosphate in the effluent is controlled at an extremely low level; and finally, the effluent of the recycling water tank can be directly recycled. The utilization rate of water resources is increased, the consumption cost of fresh water is reduced, and the treatment efficiency and the recycling value are both considered.

Description

Technical Field

[0001] This application relates to the field of pollutant treatment, specifically a method for the oxidation and recovery of elemental phosphorus in phosphorus-containing wastewater. More specifically, this application provides a method for treating elemental phosphorus wastewater, which can effectively achieve deep pollution treatment and closed-loop recovery of phosphorus resources, thus achieving both environmental and economic benefits. Background Technology

[0002] Elemental phosphorus wastewater (primarily composed of yellow phosphorus P4) is a characteristic pollutant from phosphorus chemical production (such as yellow phosphorus smelting and phosphide synthesis). It is highly toxic, flammable, and difficult to degrade, posing a serious threat to the ecological environment and human health. After entering water bodies, elemental phosphorus will settle at the bottom (the density of elemental phosphorus is approximately 1.6 g / cm³). 3 Phosphorus (greater than water) releases its toxicity slowly over a long period, affecting aquatic life and accumulating through the food chain, ultimately harming human health. Furthermore, elemental phosphorus is spontaneously combustible (ignition point 30℃), potentially causing combustion accidents during wastewater treatment, posing a safety hazard. Direct discharge without effective treatment can also lead to eutrophication, triggering cyanobacterial blooms and severely impacting water resource utilization.

[0003] Currently, treatment methods for elemental phosphorus wastewater mainly revolve around the core objective of "removing elemental phosphorus." Commonly used methods include physical separation, single chemical oxidation, oxidation-precipitation combination, and membrane separation enhancement. However, existing treatment methods have certain drawbacks. For example, for elemental phosphorus wastewater, physical separation methods mainly use sedimentation and flotation to deposit phosphorus, but this can only remove 60%-80% of large phosphorus particles (>10μm), while the removal rate of fine particles is <30%, and the sludge needs to be disposed of as hazardous waste. Single chemical oxidation methods mainly use sodium hypochlorite for oxidation, but due to insufficient contact, the oxidation rate is only 50%-70%, and the amount of sodium hypochlorite added is about 20 times the mass of phosphorus, resulting in high costs. The oxidation-precipitation combination method mainly uses a combination of air aeration and calcium salt precipitation, but air bubbles are difficult to reach the bottom of the water, the oxidation reaction takes 24-48 hours, the utilization rate of calcium phosphate sludge is 0%, and the treatment cost is high. Membrane separation enhancement methods use high-pressure interception filtration after oxidation, but the system recovery rate is only 50%-70%, and 30%-50% of concentrated water is generated that needs to be retreated, and the membrane replacement cost accounts for about 40% of the operating cost, resulting in high costs.

[0004] Existing methods for treating elemental phosphorus wastewater generally suffer from insufficient contact with the oxidant, resulting in low oxidation efficiency, high reagent consumption, and non-resource utilization of oxidation products. This creates a vicious cycle of treating elemental phosphorus wastewater, generating waste, and then treating it again.

[0005] Therefore, there is an urgent need for a new method and / or apparatus to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to address the problem of high phosphorus density and difficulty in oxidation of elemental phosphorus in the treatment of elemental phosphorus wastewater, and to provide a method for the oxidation and recovery of elemental phosphorus from phosphorus-containing wastewater. This invention overcomes the limitations of traditional methods that only focus on pollution control in the treatment of elemental phosphorus wastewater, successfully achieving the dual goals of "deep pollution treatment" and "closed-loop recovery of phosphorus resources," thus combining environmental and economic benefits.

[0007] To achieve the above objectives, this application adopts the following technical solution: A method for recovering elemental phosphorus from phosphorus-containing wastewater by oxidation includes the following steps: (1) The wastewater containing elemental phosphorus is sent into a temporary oxidation tank, and then air is introduced for aeration. An oxidant is added to the temporary oxidation tank to rapidly oxidize the elemental phosphorus in the wastewater to obtain the first treated wastewater. (2) The first treated wastewater is sent into the coarse phosphorus removal sedimentation tank and the pH value of the first treated wastewater is adjusted to 9-10. Then, calcium chloride is added to the coarse phosphorus removal sedimentation tank to generate phosphate precipitate, and the effluent from the coarse phosphorus removal sedimentation tank is recorded as the second treated wastewater. (3) The second wastewater is sent into the fine phosphorus removal sedimentation tank, and phosphorus removal agent and flocculant are added to the fine phosphorus removal sedimentation tank respectively for phosphorus removal and flocculation sedimentation treatment, and the third sludge and the third treated water are obtained respectively; the third sludge is sent into the sludge tank for temporary storage. (4) The third treated water is sent to a sand filter for filtration and the fourth treated water is obtained. The fourth treated water is then reused. (5) The third sludge in the sludge tank is sent to the sludge dewatering machine for dewatering treatment. During the dewatering treatment, a dewatering agent is added to the third sludge to obtain the fifth dry sludge. (6) After mixing the fifth dry mud with the drum ash, the mixture is spherical to obtain the sixth spherical material; (7) The sixth spherical material is used to replace part of the phosphate rock, and the sixth spherical material, phosphate rock, coke and silica are fed into the electric furnace in a set ratio to produce yellow phosphorus.

[0008] In step (1), wastewater containing elemental phosphorus is fed into a temporary oxidation tank, and a micro / nano aeration disc is installed at the bottom of the tank. Oxygen is introduced into the micro / nano aeration disc to aerate the wastewater containing elemental phosphorus. The micro / nano aeration disc in this application is prior art, such as the floating micro / nano aeration device disclosed in CN110204034B.

[0009] In step (1), the oxygen content of the wastewater in the temporary oxidation tank is measured by an online dissolved oxygen meter.

[0010] In step (1), the oxidant added to the temporary oxidation tank is sodium hypochlorite.

[0011] In step (2), calcium phosphate precipitate is generated, and the generated calcium phosphate is reused.

[0012] In step (3), the phosphorus removal effect is enhanced by phosphorus removal agent, and suspended impurities are removed by flocculant, and third sludge and third treated water are obtained respectively, with the phosphate concentration in the third treated water ≤0.2 mg / L.

[0013] In step (4), a sand filter medium is installed inside the sand filter; the third treated water is sent into the sand filter for filtration treatment, and the fourth treated water is obtained.

[0014] In step (4), the fourth treated water is used for cooling or rinsing to achieve the recycling of water resources.

[0015] In step (6), the drum ash is the ash produced after the mud phosphorus is recovered by rotating drum phosphorus distillation. In a specific example, the operating procedure for rotating drum phosphorus distillation is as follows: mud phosphorus is scooped into a wheelbarrow or pumped into a tractor and transported to the production site. Mud phosphorus is added into the drum using a pump or shovel. Then, the exhaust gas is ignited to heat the drum. The elemental phosphorus in the mud phosphorus generates phosphorus vapor when exposed to high temperature. The phosphorus vapor enters the gas scrubbing tower through the phosphorus receiving tank. After cooling, it forms liquid phosphorus and flows into the phosphorus receiving tank. The liquid phosphorus containing impurities is siphoned into the ground pot using a rubber tube. Then, it is pumped into the refining pot for further refining and rinsing to remove impurities. After being kept warm and allowed to stand, the finished yellow phosphorus is obtained.

[0016] In step (6), the weight ratio of the fifth dry mud to the drum ash is (1-6):1. Preferably, in step (6), the weight ratio of the fifth dry mud to the drum ash is 4:1.

[0017] In step (6), the fifth dry mud, drum ash, and clay are mixed and then pelletized to obtain the sixth spherical material. Normally, when the fifth dry mud and drum ash can meet the pelletizing requirements, clay does not need to be added; when the fifth dry mud and drum ash cannot be formed, clay is added to make pellets, where the clay acts as a binder, and the amount of clay added is sufficient to meet the pelletizing requirements (excessive addition of clay will lead to increased costs).

[0018] In step (7), phosphate rock, coke, and silica are used as raw materials and fed into an electric furnace to produce yellow phosphorus. During the production of yellow phosphorus, the sixth spherical material is used to replace part of the phosphate rock to achieve the reuse of the sixth spherical material.

[0019] To address the aforementioned problems, this application provides a method for the oxidation and recovery of elemental phosphorus from phosphorus-containing wastewater. Based on the coordinated oxidation of oxygen and sodium hypochlorite, along with chemical precipitation and briquetting in an electric furnace, this application effectively achieves deep treatment of phosphorus-containing wastewater and closed-loop recovery of phosphorus resources. In this application, oxygen or air is introduced into the wastewater, supplemented by a chemical oxidant (such as sodium hypochlorite), and under enhanced mixing conditions, elemental phosphorus is rapidly oxidized to phosphoric acid, which then undergoes a precipitation reaction to generate usable products such as calcium phosphate. Next, the generated calcium phosphate (the main component of the fifth dry sludge is calcium phosphate) is briquetting with rotary drum ash and clay. Finally, the resulting briquettes are recycled as raw materials into the electric furnace production system, forming a complete resource recycling chain. This application overcomes the limitations of traditional methods that only focus on pollution control for elemental phosphorus wastewater treatment, successfully achieving the dual goals of "deep pollution control" and "closed-loop recovery of phosphorus resources," thus combining environmental and economic benefits. Attached Figure Description

[0020] The present invention will be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 This is a process flow diagram of the elemental phosphorus oxidation and recovery method for phosphorus-containing wastewater in Example 1. Detailed Implementation

[0021] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0022] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is merely one example of a series of equivalent or similar features.

[0023] Those skilled in the art will understand that the terms "first," "second," etc., in this specification are only used to distinguish different devices, modules, or parameters, and do not represent any specific technical meaning, nor do they indicate a necessary logical order between them.

[0024] As indicated in this specification and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0025] This specification covers any alternatives, modifications, equivalent methods, and solutions made within the spirit and scope of this specification as defined in the claims. Furthermore, to provide a better understanding of this specification, certain specific details are described in detail below. However, this specification will be fully understood by those skilled in the art even without these detailed descriptions. Example

[0026] This embodiment provides a method for the oxidation and recovery of elemental phosphorus from phosphorus-containing wastewater, which includes the following steps, and its process flow diagram is shown below. Figure 1 As shown.

[0027] (1) Wastewater containing elemental phosphorus is sent into a temporary oxidation tank, then aerated with air, and sodium hypochlorite is added to the temporary oxidation tank to rapidly oxidize the elemental phosphorus in the wastewater (i.e., oxidize elemental phosphorus to phosphate), thus obtaining the first treated wastewater. In a specific example, wastewater containing elemental phosphorus is sent into a temporary oxidation tank, and micro-nano aeration discs are set at the bottom of the temporary oxidation tank. Oxygen is introduced into the micro-nano aeration discs to aerate the wastewater containing elemental phosphorus; at the same time, the oxygen content of the wastewater in the temporary oxidation tank is measured by an online dissolved oxygen meter.

[0028] (2) The first-treated wastewater is sent to the coarse phosphorus removal sedimentation tank, and alkali is added to adjust the pH value of the first-treated wastewater to 9-10. Then, calcium chloride is added to the coarse phosphorus removal sedimentation tank to generate phosphate precipitate, and the effluent from the coarse phosphorus removal sedimentation tank is recorded as the second-treated wastewater. In a specific example, calcium oxide is added to adjust the pH value of the first-treated wastewater to 9-10; after adding calcium chloride, the phosphorus element in the wastewater is initially removed by chemical precipitation reaction, and phosphate precipitate is generated; the generated calcium phosphate can be directly reused to realize resource utilization.

[0029] (3) The second treated wastewater is sent to a fine phosphorus removal sedimentation tank, and phosphorus removal agent and flocculant are added to the fine phosphorus removal sedimentation tank for phosphorus removal and flocculation sedimentation treatment, and the third sludge and third treated water are obtained respectively; the third sludge is sent to a sludge tank for temporary storage. In this embodiment, the phosphorus removal agent and flocculant are commercially available products; by adding phosphorus removal agent, the phosphorus removal effect is further enhanced; by adding flocculant, suspended impurities are removed by flocculation; at the same time, the phosphate concentration in the third treated water is ensured to be ≤0.2 mg / L. The sludge generated in this step is discharged into the sludge tank for temporary storage, while the third treated water flows into the intermediate water tank.

[0030] (4) The third-treated water is sent to a sand filter for filtration to obtain the fourth-treated water, which is then reused. The fourth-treated water can be temporarily stored in a reuse water tank before reuse. The sand filter is equipped with sand filter media, which intercepts residual suspended solids, colloids and other impurities to achieve deep filtration. The fourth-treated water can be used in production processes such as cooling or rinsing to achieve the recycling of water resources.

[0031] (5) The third sludge in the sludge tank is sent to the sludge dewatering machine for dewatering treatment. During the dewatering treatment, a dewatering agent is added to the third sludge to obtain the fifth dry sludge. By using this process and adding a dewatering agent, it is beneficial to reduce the water content of the sludge and obtain the fifth dry sludge. The dewatering agent is a commercially available product, and a polymer flocculant can be selected.

[0032] (6) The fifth dry mud and the drum ash are mixed and then pelletized to obtain the sixth spherical material. In a specific example, the mass ratio of the fifth dry mud to the drum ash is close to 4:1.

[0033] (7) Using phosphate rock, coke, and silica as raw materials, the raw materials are fed into an electric furnace to produce yellow phosphorus. During the production of yellow phosphorus, the sixth spherical material is used to replace part of the phosphate rock, thereby realizing the reuse of the sixth spherical material. In the electric furnace, phosphate rock, coke, and silica are converted into yellow phosphorus through the action of electric current. Since the drum ash contains phosphorus, it can replace part of the phosphate rock. The sixth spherical material prepared by the fifth dry sludge and the drum ash not only solves the problem of sludge hazardous waste treatment, but also realizes the recycling of solid waste, which is conducive to further reducing production costs.

[0034] In traditional processes, phosphorus-containing sludge is mostly disposed of as hazardous waste. However, this application mixes the dewatered sludge with rotary drum ash to "pelletize" it, which is then fed into an electric furnace for reuse. This application not only solves the problem of secondary pollution from phosphorus-containing sludge but also converts the phosphorus resources in the sludge back into production raw materials, realizing a closed-loop cycle of phosphorus from "wastewater pollutant" to "production raw material," which is in line with the concept of a circular economy.

[0035] In actual production, the concentration of elemental phosphorus in the wastewater containing elemental phosphorus in step (1) is 0.3~0.5 mg / L; after treatment in a temporary oxidation tank (i.e., co-oxidation treatment with air and sodium hypochlorite), the removal rate of elemental phosphorus is ≥99.5%, and the residual elemental phosphorus after oxidation is ≤0.0025 mg / L.

[0036] In step (2), the phosphate concentration of the first treated wastewater is 300~1000mg / L; in steps (2) and (3), after passing through the phosphorus removal sedimentation tank (calcium salt precipitation) and the fine phosphorus removal sedimentation tank (deep treatment with phosphorus removal agent), the phosphate removal rate is ≥99.9%, and the effluent phosphate concentration is stable below 0.2mg / L, which is far lower than the first-class standard of the "Integrated Wastewater Discharge Standard" (GB 8978-1996) (phosphate ≤0.5mg / L).

[0037] In step (4), after purification by the terminal sand filter, the suspended solids in the effluent from the recycled water tank are ≤5mg / L, the pH value is 6.8~7.5, and the COD is ≤50mg / L, with a water resource reuse rate of over 85%. Using this application, deep removal of pollutants can be achieved, and the effluent can stably meet the standards.

[0038] Furthermore, this embodiment employs a staged treatment logic of "temporary oxidation tank (elemental phosphorus oxidation) → phosphorus removal sedimentation tank (preliminary phosphorus removal) → fine phosphorus removal sedimentation tank (deep phosphorus removal)," combined with end-of-pipe purification using a sand filter. This ensures efficient oxidation of elemental phosphorus (solving the problem of its sedimentation and difficulty in contacting air) while controlling effluent phosphate levels to extremely low levels. Finally, the effluent from the reuse tank can be directly reused. This application improves water resource utilization while reducing the cost of fresh water consumption, balancing treatment efficiency and reuse value.

[0039] Furthermore, traditional phosphorus-containing sludge is difficult and costly to dispose of due to the presence of toxic elemental phosphorus. This invention, based on a rotary drum ash and electric furnace system in the production process, directly reuses the dried sludge after pelletizing, achieving synergistic adaptation between sludge disposal and production processes. The rotary drum ash and clay neutralize acidic substances in the sludge, and the pelletized material is suitable for the high-temperature production environment of the electric furnace. This avoids the hazardous waste properties of the sludge and eliminates the need for a separate sludge disposal step, significantly reducing environmental costs.

[0040] This application enables 100% closed-loop recovery of phosphorus resources and zero hazardous waste discharge from sludge. In this application, after dewatering, the phosphorus-containing sludge has a phosphorus content of approximately 8% to 10%; the dry sludge is mixed with rotary drum ash and clay to form pellets, which are then fed into an electric furnace, achieving a 100% phosphorus resource recovery rate in the sludge.

[0041] Furthermore, by adopting this application, the cost of sludge disposal can be reduced to zero. In traditional processes, phosphorus-containing sludge needs to be disposed of as hazardous waste, while this process converts dry sludge into production raw materials. In step (1), the temporary oxidation tank adopts a combination of air aeration and sodium hypochlorite oxidation, which avoids the risk of spontaneous combustion of elemental phosphorus deposits, effectively eliminates safety risks, and upgrades compliance. At the same time, this application does not have the problem of hazardous waste discharge, which is conducive to helping enterprises pass the "green factory" certification.

[0042] In summary, unlike existing technologies, this application constructs an integrated process of "pretreatment homogenization → synergistic oxidation with oxygen and sodium hypochlorite → calcium phosphate precipitation → pelletizing and electric furnace reuse." Through triple innovation of "enhanced mixing, directional oxidation, and resource closed-loop," it effectively solves the pain points of existing technologies. This application achieves quantifiable high efficiency in pollutant removal, resource reuse, and cost control through its staged treatment and resource closed-loop design. In this application, phosphorus removal and reuse of wastewater are achieved through chemical precipitation and filtration; simultaneously, sludge dewatering and pelletizing for furnace reuse complete the resource utilization of solid waste. This invention realizes both wastewater treatment and phosphorus resource utilization, taking into account both environmental protection and economic benefits.

[0043] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A method for the oxidation and recovery of elemental phosphorus from phosphorus-containing wastewater, characterized in that, Includes the following steps: (1) The wastewater containing elemental phosphorus is sent into a temporary oxidation tank, and then air is introduced for aeration. An oxidant is added to the temporary oxidation tank to rapidly oxidize the elemental phosphorus in the wastewater to obtain the first treated wastewater. (2) The first treated wastewater is sent into the coarse phosphorus removal sedimentation tank and the pH value of the first treated wastewater is adjusted to 9-10. Then, calcium chloride is added to the coarse phosphorus removal sedimentation tank to generate phosphate precipitate, and the effluent from the coarse phosphorus removal sedimentation tank is recorded as the second treated wastewater. (3) The second wastewater is sent into the fine phosphorus removal sedimentation tank, and phosphorus removal agent and flocculant are added to the fine phosphorus removal sedimentation tank respectively for phosphorus removal and flocculation sedimentation treatment, and the third sludge and the third treated water are obtained respectively; the third sludge is sent into the sludge tank for temporary storage. (4) The third treated water is sent to a sand filter for filtration and the fourth treated water is obtained. The fourth treated water is then reused. (5) The third sludge in the sludge tank is sent to the sludge dewatering machine for dewatering treatment. During the dewatering treatment, a dewatering agent is added to the third sludge to obtain the fifth dry sludge. (6) After mixing the fifth dry mud with the drum ash, the mixture is spherical to obtain the sixth spherical material; (7) The sixth spherical material is used to replace part of the phosphate rock, and the sixth spherical material, phosphate rock, coke and silica are fed into the electric furnace in a set ratio to produce yellow phosphorus.

2. The method according to claim 1, characterized in that, In step (1), wastewater containing elemental phosphorus is sent into a temporary oxidation tank, and a micro-nano aeration disc is set at the bottom of the temporary oxidation tank. Oxygen is introduced into the micro-nano aeration disc to aerate the wastewater containing elemental phosphorus.

3. The method according to claim 2, characterized in that, In step (1), the oxygen content of the wastewater in the temporary oxidation tank is measured by an online dissolved oxygen meter.

4. The method according to any one of claims 1 to 3, characterized in that, In step (1), the oxidant added to the temporary oxidation tank is sodium hypochlorite.

5. The method according to claim 1, characterized in that, In step (2), calcium phosphate precipitate is generated, and the generated calcium phosphate is reused.

6. The method according to claim 1, characterized in that, In step (4), a sand filter medium is installed inside the sand filter; the third treated water is sent into the sand filter for filtration treatment, and the fourth treated water is obtained.

7. The method according to any one of claims 1 to 6, characterized in that, In step (4), the fourth treated water is used for cooling or rinsing to achieve the recycling of water resources.

8. The method according to claim 1, characterized in that, In step (6), the drum ash is the ash produced after the phosphorus mud is recovered by rotating drum stenosis.

9. The method according to any one of claims 1 to 8, characterized in that, In step (7), phosphate rock, coke, and silica are used as raw materials and fed into an electric furnace to produce yellow phosphorus. During the production of yellow phosphorus, the sixth spherical material is used to replace part of the phosphate rock to achieve the reuse of the sixth spherical material.

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