CN217323388U

CN217323388U - Phosphorus recovery system

Info

Publication number: CN217323388U
Application number: CN202123173461.3U
Authority: CN
Inventors: 玄小立; 籍文法
Original assignee: Suez Water Treatment Co Ltd
Current assignee: Suez Environmental Technology Beijing Co Ltd
Priority date: 2021-12-16
Filing date: 2021-12-16
Publication date: 2022-08-30
Anticipated expiration: 2031-12-16

Abstract

The utility model provides an including phosphorus recovery system, phosphorus recovery system includes: the system comprises an anaerobic reaction tank, a pre-dehydration device, an anaerobic digestion tank, a sludge dehydration device, a first phosphorus recovery device and a second phosphorus recovery device, wherein the first phosphorus recovery device is connected to the pre-dehydration device and recovers phosphorus in a first concentrated solution to generate first phosphorus-rich solid particles, and the second phosphorus recovery device is connected to the sludge dehydration device and recovers phosphorus in a second concentrated solution to generate second phosphorus-rich solid particles. The two phosphorus-rich granules can be stored or bagged for use after being screened, washed and dried. The utility model provides a phosphorus recovery system passes through phosphorus recovery unit, realizes reducing the risk of scale deposit, wearing and tearing and jam that phosphorus-containing liquid leads to resource recovery and utilization of the phosphorus that can not reproduce, reduces pipeline maintenance and administrative cost.

Description

Phosphorus recovery system

Technical Field

The utility model relates to a sludge treatment field, concretely relates to phosphorus recovery system.

Background

Phosphorus is a precious and scarce non-renewable resource, activated sludge discharged by a sewage treatment plant contains a considerable amount of phosphorus elements, phosphorus in the sludge is feasible to be recycled as a phosphate fertilizer, and the phosphorus recycling is also a sustainable development requirement. It is therefore necessary to recover phosphorus from sewage or sludge.

At present, most sewage treatment plants in China adopt a treatment process with biological phosphorus removal as a main part and chemical phosphorus removal as an auxiliary part, so that the biological sludge and the chemical sludge are rich in phosphorus. During sludge treatment, phosphorus causes problems:

(1) if the anaerobic digestion tank is arranged for sludge treatment, phosphorus can be released again after phosphorus-rich excess sludge enters the anaerobic digestion tank, and crystals can be generated under appropriate conditions (such as pH value rise and magnesium ions contained in the sludge), so that the problems of blockage and scaling of subsequent pipelines and equipment are caused.

(2) The concentration of phosphorus in the concentrated solution generated by sludge dehydration is very high, and the return of phosphorus to a biochemical treatment system increases the treatment load and difficulty of a sewage treatment plant, possibly causing unstable effluent quality.

Therefore, there is a need for a mature, reliable technology for recovering phosphorus from sludge suitable for engineering applications with high phosphorus recovery efficiency and low investment and operating costs, while reducing the risk of scaling, wear and blockage caused by phosphorus-containing liquids, and reducing pipeline maintenance and management costs.

SUMMERY OF THE UTILITY MODEL

In view of the above-mentioned problems and needs, the present invention provides a phosphorus recovery system that solves the above-mentioned problems and brings other technical effects by adopting the following technical features.

In an aspect of the present invention, there is provided a phosphorus recovery system for processing a first group of sludge and a second group of sludge from a sludge treatment line, the phosphorus recovery system comprising: the anaerobic reaction tank receives the first group of sludge and releases phosphorus in the first group of sludge in an anaerobic environment; the pre-dehydration device is connected to the anaerobic reaction tank and is used for concentrating and dehydrating the sludge after the phosphorus release is finished to generate concentrated sludge and a first concentrated solution; an anaerobic digester for digesting a second set of sludge to produce biogas and digested sludge products; a sludge dewatering device connected to the anaerobic digester and dewatering and digesting sludge products to produce a sludge cake and a second concentrate; a first phosphorus recovery device connected to the pre-dehydration device and recovering phosphorus in the first concentrated solution to generate first phosphorus-rich solid particles; and a second phosphorus recovery device connected to the sludge dewatering device and recovering phosphorus in the second concentrated solution to produce second phosphorus-rich solid particles.

According to above characteristic, the utility model provides a phosphorus recovery system passes through phosphorus recovery unit, realizes reducing the risk that forms struvite scale deposit, wearing and tearing, jam in the pipeline to the resource recovery and the utilization of the phosphorus that can not give play to, reduces pipeline maintenance and administrative cost. In addition, different processes can be adopted for treating sludge with different properties so as to improve the release and recovery rate of phosphorus to the maximum extent. In addition, this phosphorus recovery system includes two phosphorus recovery units to retrieve phosphorus respectively from different process flow products, improve the phosphorus recovery rate.

In some examples, at least a portion of the second phosphorus recovery unit effluent is directed to the first phosphorus recovery unit as its ammoniacal nitrogen source.

According to the above features, the second phosphorus recovery device has a drain rich in ammonia nitrogen at a higher concentration, and the drain containing high ammonia nitrogen from the second phosphorus recovery reactor is used as an ammonia nitrogen source of the first phosphorus recovery reactor, so that the operation cost can be reduced and the phosphorus recovery rate can be improved.

In some examples, the phosphorus recovery system further comprises: and the screening and washing device is used for receiving the first phosphorus-rich solid particles and the second phosphorus-rich solid particles, screening and washing the first phosphorus-rich solid particles and the second phosphorus-rich solid particles, and separating fine particles and impurities to obtain the wet fertilizer. A drying device for drying the wet fertilizer to obtain dried fertilizer particles; and the storage and bagging device is used for storing and bagging the dried fertilizer particles.

According to the above feature, the granulated fertilizer is discharged from the first phosphorus recovery device and the second phosphorus recovery device, and is finally sold as a fertilizer after being washed, dried and bagged.

In some examples, the first set of sludge includes excess biological sludge and the second set of sludge includes thickened sludge.

According to the characteristics, different processes are adopted for sludge with different properties, such as primary sludge and biological sludge, so that the release and recovery rate of phosphorus are improved to the maximum extent. For example, the first group of sludges includes excess biological sludge rich in phosphorus and the second group of sludges includes thickened sludges.

In some examples, the first set of sludge further comprises at least one of concentrated primary sludge, raw primary sludge, fermented primary sludge, and the second set of sludge further comprises at least one of concentrated primary sludge and concentrated biological sludge.

According to the characteristics, different types of primary sludge are adopted as carbon sources for releasing phosphorus from biological sludge in the anaerobic reaction tank, so that the tank capacity, investment and operating cost of the anaerobic reaction tank can be reduced.

In some examples, the anaerobic reaction tank adds an additional carbon source.

According to the above features, an additional carbon source may be added to increase the release rate of phosphorus in the case of shortage of the carbon source.

In some examples, the first phosphorus recovery apparatus and/or the second phosphorus recovery apparatus is a fluidized bed phosphorus recovery reactor comprising: the reactor main part, the reactor main part has set gradually from bottom to top along vertical direction: a water inlet zone from which phosphorus-containing liquid enters the reactor body; a precipitation and selection zone, said precipitation and selection zone being of inverted conical shape, solid particles formed by crystallization reaction ultimately precipitating in said precipitation and selection zone; a fluidization zone, wherein the mixture of solid particles and the phosphorus-containing liquid forms a fluidized state, and the solid particles settle to the precipitation and selection zone; a settling zone, said settling zone being inverted cone shaped, said solid particles being formed in said settling zone; a water collecting region configured to collect drain water after the reaction and to discharge the drain water out of the reactor main body; and a stripping device disposed within the reactor body and at least partially disposed in the fluidization region and the settling region, the stripping device configured to strip carbon dioxide from the mixed liquor to increase the pH.

According to the characteristics, the first phosphorus recovery device and/or the second phosphorus recovery device adopts a fluidized bed phosphorus recovery reactor, phosphorus is recovered from sludge through a homogeneous crystallization method, and nucleation and crystallization are realized through a homogeneous reaction without adding seed crystals in the reactor. Compared with the method for recovering phosphorus from the fly ash after sludge incineration, the method has the advantages of more mature and reliable technology, more suitability for engineering application, simple operation and maintenance and small occupied area. The crystallization method has high efficiency of recovering phosphorus, so that the phosphorus in water is separated out in the form of crystals, theoretically, no sludge is generated, and no secondary pollution is caused; the crystallization method for recovering phosphorus has simple operation and wide application range, not only can be used for recovering phosphorus from the supernatant liquid of the sludge treatment with higher phosphorus concentration, but also can be used for recovering phosphorus from other liquid phases rich in phosphorus.

In some examples, the water inlet zone is provided with at least a water inlet pipe and a water inlet valve for phosphorus-containing liquid to enter the reactor body; the upper part of the water inlet area is provided with a first adding pipe and a second adding pipe which are respectively used for adding a magnesium salt solution and an alkaline solution when needed; and wherein a discharge pipe for discharging solid particles is provided at a side of the water inlet region. If necessary, the water inlet area can be provided with a water inlet pump (not shown).

According to the characteristics, the fluidized bed phosphorus recovery reactor is an upward-flow fluidized bed reactor, phosphorus-containing liquid enters from the bottom of the reactor main body, is mixed with magnesium salt solution (usually MgCl2), and sodium hydroxide (NaOH) is added to adjust the pH value if necessary, and the reaction mechanism of the applicable magnesium ammonium phosphate precipitation method is as follows: mg (magnesium) ²⁺ +NH ₄ ⁺ +HPO ₄ ^2- +6H ₂ O→MgNH ₄ PO ₄ ·6H ₂ O+H ⁺ . The produced solid granular fertilizer (phosphate fertilizer) is almost the same as natural struvite, and can be directly or indirectly applied to agriculture or forestry and the like.

In some examples, the phosphorus recovery system further comprises a thermal insulation pipe disposed in at least one of a pipe between the sludge dewatering device and the second phosphorus recovery device, the second phosphorus recovery device drain pipe, the second phosphorus recovery device to the first phosphorus recovery device drain pipe, and a pipe to an anammox treatment device.

The higher temperature is beneficial to the crystallization reaction of phosphorus, the temperature of the sludge discharged from the anaerobic digestion tank is higher, and the concentrated solution is still in a temperature state even though the sludge is dehydrated. Therefore, according to the above feature, the second concentrated solution after the heat preservation treatment, the second phosphorus recovery device drainage and the first phosphorus recovery device drainage contribute to the improvement of the crystallization reaction efficiency of phosphorus. In addition, the reaction speed of a subsequent ammonia nitrogen treatment reactor can be improved by adopting heat preservation measures.

In some examples, the fluidized bed phosphorus recovery reactor further comprises: the circulating device comprises a water suction pipe and a return pipe which are oppositely arranged and communicated, the water suction pipe is connected to the sedimentation area, the return pipe is connected to the sedimentation and selection area, the circulating device is configured to return the liquid in the sedimentation area to the sedimentation and selection area, and the circulation ratio of the circulating device ranges from 1 to 21.

According to the above feature, the return pipe of the circulating device is disposed in the precipitation and selection zone, and the returned circulating water is mixed with the phosphorus-containing liquid to which the chemical is added, thereby improving the efficiency of the precipitation reaction. The proper circulation ratio is set to be beneficial to maintaining a fluidized state and controlling the separation of the precipitate, and meanwhile, the concentration of phosphate in the reactor can be controlled by circulating water back flow.

In some examples, the gas stripping apparatus includes a gas stripping tube, an aeration head, and a gas stripping guide cylinder, the aeration head is disposed at a bottom of the gas stripping tube, the gas stripping tube is connected to an air inlet tube communicating with an outside of the reactor main body through the aeration head, the gas stripping guide cylinder is disposed above the gas stripping tube, and a bottom of the gas stripping guide cylinder is located at a top of the fluidization region and below the water suction tube, wherein at least a portion of the top of the gas stripping tube protrudes into the gas stripping guide cylinder, and a length of the gas stripping tube protruding into the gas stripping guide cylinder is 1/3 to 2/3 of a height of the gas stripping guide cylinder.

According to the characteristics, the compressed air enters the aeration head through the air inlet pipe, the compressed air is uniformly distributed in the air stripping pipe to achieve the air stripping effect, and the carbon dioxide in the mixed liquid is blown out to improve the pH value and keep the pH value in the reactor main body stable, so that the optimal crystallization and precipitation state is kept.

In some examples, the reactor body has a reaction height defined as the sum of the body height of the feed water zone, the height of the settling and selection zone, the height of the fluidization zone, and the height of the settling zone, wherein the ratio of the diameters of the reaction height and the fluidization zone is between 2.5 and 3.0.

In accordance with the above characteristics, the reactor is ensured to be in and maintain a fluidized state by selecting a suitable reaction height and ratio of the fluidization zone diameters.

In some examples, the water entry zone has an upward flow velocity in the range of 0.1 to 0.55 meters per second, the fluidization zone has a cross-sectional flow velocity in the range of 15 to 30 meters per hour, and the water collection zone has a cross-sectional flow velocity in the range of 2 to 5 meters per hour.

According to the characteristics, the fertilizer particles with different diameters can be obtained by selecting proper water inlet area ascending flow velocity, fluidizing area cross-section flow velocity and water collection area cross-section flow velocity, and the optimal precipitation effect can be obtained. The technical scheme of the utility model beneficial effect lies in at least: (1) the phosphorus recovery device realizes resource recovery and utilization of non-renewable phosphorus, reduces the risks of scaling, abrasion and blockage caused by phosphorus-containing liquid, and reduces the cost for maintaining and managing pipelines; (2) different processes can be adopted for treating sludge with different properties, so that the release and recovery rate of phosphorus are improved to the maximum extent, the operation cost is reduced, and the actual recovery rate of phosphorus in the sludge can reach more than 35 percent; (3) the phosphorus recovery device adopts a fluidized bed phosphorus recovery reactor, does not need additional seed crystals, realizes nucleation and crystallization through homogeneous reaction, has simple operation and maintenance, small occupied area and high phosphorus recovery efficiency, and cannot cause secondary pollution.

Drawings

FIG. 1 shows a schematic diagram of a phosphorus recovery system in accordance with at least one embodiment of the present invention;

figure 2 illustrates a schematic diagram of a fluidized bed phosphorus recovery reactor in accordance with at least one embodiment of the present invention.

Description of the reference numerals

In fig. 1: a, concentrating primary sludge; b, concentrating the biological sludge; c, digesting a sludge product; d, sludge cake; e, second concentrated solution; f, primary sludge settling; g, fermenting the primary sludge; h, residual biological sludge; i a carbon source; j phosphorus release sludge; k, a first concentrated solution; l, sludge concentration; m mixed solution; draining water from a second phosphorus recovery device; o second phosphorus-rich solid particles; p first phosphorus-rich solid particles; q, wet fertilizer; r drying the fertilizer granules; s, bagging fertilizers; t screening and washing the wastewater; u, draining water from a first phosphorus recovery device; v, draining water from the ammonia nitrogen treatment device; w to a first phosphorus recovery device; s1 anaerobic digester; s2 sludge dewatering device; s3 anaerobic reaction tank; s4 a pre-dewatering device; s5 a first phosphorus recovery unit; s6 second phosphorus recovery unit; s7 screening and washing device; s8 drying device; s9 storing and bagging apparatus.

In fig. 2: 1, water inlet pipe; 2, a water inlet valve; 3 a pressure sensor; 4, a first feeding pipe; 5, a second feeding pipe; 6, a flow meter; 7 discharging pipe; 8 a return pipe; 9 a suction pipe; 10, a circulating water pump; 11 circulating the flowmeter; 12 an organic matter discharge port; 13 air inlet pipe; 14 a gas stripping tube; 15 gas stripping guide shell; 16 an overflow weir; 17 a drain pipe; 18 a water collection sump; 19 a main drainage channel; 20 a pH sensor; 21 a liquid level sensor; 22 a support; 23 an observation window; 24 sampling tube; 25 aeration heads.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure more clear, the embodiments of the present disclosure will be described in detail and completely with reference to the accompanying drawings of specific embodiments of the present disclosure. Like reference symbols in the various drawings indicate like elements. It should be noted that the described embodiments are part of the embodiments of the present disclosure, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the disclosure without any inventive step, are within the scope of protection of the disclosure.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The terms "first," "second," and the like, as used in the description and in the claims of the present disclosure, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not necessarily denote a limitation of quantity. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

Preferred embodiments of a phosphorus recovery system according to the present disclosure are described in detail below with reference to the accompanying drawings. Fig. 1 shows a schematic diagram of a phosphorus recovery system in accordance with at least one embodiment of the present invention. Figure 2 illustrates a schematic diagram of a fluidized bed phosphorus recovery reactor in accordance with at least one embodiment of the present invention.

Possible embodiments within the scope of the disclosure may have fewer components, have other components not shown in the figures, different components, differently arranged components or differently connected components, etc. than the embodiments shown in the figures. Further, two or more of the components in the drawings may be implemented in a single component, or a single component shown in the drawings may be implemented as multiple separate components, without departing from the concepts of the present disclosure.

It is noted that the phosphorus recovery system is used to treat a first group of sludge and a second group of sludge from a sludge treatment line. It is noted that the "first group of sludge" according to the present disclosure may include at least one of concentrated primary sludge, primary sludge and fermented primary sludge, for example, including primary sludge F, concentrated primary sludge a and fermented primary sludge G, in addition to excess biological sludge H. Similarly, the "second group of sludges" described in this disclosure includes the concentrated sludge. Further, at least one of concentrated primary sludge and concentrated biological sludge, for example, concentrated primary sludge a and/or concentrated residual biological sludge (simply referred to as concentrated biological sludge B) from an upstream sludge concentration tank may be included. The disclosure is not limited to this, and the kind and proportion of the sludge can be adjusted according to actual needs and process requirements.

As shown in fig. 1, the phosphorus recovery system according to at least one embodiment of the present invention includes an anaerobic digestion tank S1, a sludge dewatering device S2, an anaerobic reaction tank S3, a pre-dewatering device S4, a first phosphorus recovery device S5, and a second phosphorus recovery device S6. The anaerobic digester S1 is connected to a sludge dewatering device S2, the sludge dewatering device S2 is connected to a second phosphorus recovery device S6, the anaerobic reaction tank S3 is connected to a pre-dewatering device S4, and the pre-dewatering device S4 is connected to a first phosphorus recovery device S5.

In a sewage treatment process with a biological phosphorus removal function, in an anaerobic tank, under the condition that a carbon source (such as organic matters, volatile fatty acid and the like contained in sewage) is sufficient, bacteria release phosphorus (in the form of phosphate) under anaerobic conditions; under aerobic environment, the bacteria can absorb the soluble phosphate in the sewage and store the phosphate in the form of multi-phosphorus in the cells. In the enhanced biological phosphorus removal reactor (EBPR), sludge is circulated through the above anaerobic and aerobic environments to remove soluble phosphate in sewage. These phosphates enter the sludge with the discharge of the excess biological sludge. In general, the phosphorus content of the residual biological sludge of the EBPR can reach about 5% of the dry weight of the sludge. Therefore, there is a need to recover phosphorus from such excess biological sludge.

The anaerobic reaction tank S3 receives a first group of sludge, which may specifically include excess biological sludge H as described above, and releases phosphorus from the first group of sludge in an anaerobic environment. Under anaerobic conditions, phosphate in the sludge is released again. The extent of phosphate release is related to the amount of carbon source. The larger the amount of carbon source in the wastewater, the more complete the release and the shorter the time required. Measures that can be taken to meet the carbon source requirements for phosphorus release include the introduction of primary sludge and the addition of additional carbon sources.

(1) Introducing primary sludge into an anaerobic reaction tank S3, wherein the primary sludge can be original primary sludge F, concentrated primary sludge A and fermented primary sludge G, and the preferred sequence is G, A, F. The order and type of the sludge can be adjusted by those skilled in the art according to the actual requirement, for example, only the fermented primary sludge G or only the fermented primary sludge G and the concentrated primary sludge a are included, and the disclosure is not limited thereto.

(2) And adding an additional carbon source I, wherein the additional carbon source I can be acetic acid (sodium), methanol and the like which are commonly used in sewage treatment. In the case where the carbon source is sufficient, the residence time of the sludge in the anaerobic reaction tank S3 is recommended to be 1 to 3 hours. The release rate of phosphorus in the sludge can reach about 30 percent within about 3 hours. If the carbon source is insufficient, the residence time should be extended to 24 hours, or even 48 hours.

The phosphorus-released sludge J with the released phosphorus enters a pre-dehydration device S4, the pre-dehydration device S4 carries out concentration dehydration on the phosphorus-released sludge J after the phosphorus release is finished, and the phosphorus-released sludge J is separated into dehydrated concentrated sludge L and a first concentrated solution K rich in phosphate (but basically not containing ammonia nitrogen) after the dehydration. Alternatively, the thickened sludge L may be introduced into an anaerobic digester S1 (which may also be referred to as an anaerobic digestion reactor) for digestion reactions. The first concentrated solution K enters a first phosphorus recovery device S5. The first phosphorus recovery apparatus S5 recovers phosphorus in the first concentrated solution K to produce first phosphorus-rich solid particles P.

The second group of sludge enters an anaerobic digester S1, anaerobic digestion reaction of the sludge is carried out in the anaerobic digester S1, and organic matter in the sludge is partially digested to generate biogas (not shown) and digested sludge product C. The digested sludge product C comprises digested sludge and a digestive liquid rich in phosphate and ammonia nitrogen. Phosphorus in organisms in the sludge is converted into soluble phosphorus under an anaerobic environment and released into the digestive juice, and meanwhile, part of nitrogen elements are also released into the digestive juice in the form of ammonia nitrogen. Alternatively, the residence time of the second group of sludge in the anaerobic digester S1 is typically 10 to 40 days, for example, predominantly 20 to 30 days.

The digested sludge product C enters a sludge dewatering device S2, and the sludge dewatering device S2 dewaters the digested sludge product C. The sludge dewatering device S2 can be in the form of a belt, a centrifuge, a plate frame, etc., and after dewatering, the digested sludge product C is separated into a second concentrated solution E and a sludge cake D in the form of liquid. The solid content of the sludge cake D can reach 20 percent or more. The second concentrated solution E is rich in phosphate and ammonia nitrogen.

The second concentrate E then enters a second phosphorus recovery unit S6, where the phosphate in solution is recovered, the recovered phosphate being discharged in the form of water-containing particles, i.e. second phosphorus-rich solid particles O produced by the second recovery unit.

Alternatively, the first phosphorus recovery apparatus S5 may have the same configuration as the second phosphorus recovery apparatus S6. For example, the first phosphorus recovery unit S5 and/or the second phosphorus recovery unit S6 are fluidized bed phosphorus recovery reactors, and are mainly characterized in that additional seed crystals are not required to be added, and CO in the dehydrated water is blown off in a stripping mode ₂ So as to increase the pH value and form a fluidized state by recycling the circulating liquid. Additional magnesium salts (such as magnesium chloride) and/or a pH-adjusting lye (such as sodium hydroxide) are added to the recovery unit. With respect to the specific structure of the first phosphorus recovery apparatus S5 and/or the second phosphorus recovery apparatus S6, it will be described later with reference to fig. 2.

Considering that the incoming water of the first phosphorus recovery device S5 is rich in phosphate but low in ammonia nitrogen content, in order to form struvite, ammonia nitrogen needs to be supplemented in the first phosphorus recovery device S5 in addition to the same chemical agent added in the second phosphorus recovery device S6.

It is known that a relatively high temperature is advantageous for the crystallization reaction, and that the temperature of the sludge discharged from the anaerobic sludge digester S1 is relatively high, and the second concentrated solution E is still in a warm state even after dehydration. Therefore, the phosphorus recovery system may further include a heat-insulating pipe provided at least one of a pipe between the sludge dewatering device S2 and the second phosphorus recovery device S6 (specifically, a pipe discharging the second concentrate E), a second phosphorus recovery device drain pipe, a pipe from the second phosphorus recovery device S6 to the first phosphorus recovery device S5, and a pipe to the ammonia nitrogen treatment device.

And the second phosphorus recovery device effluent N of the second phosphorus recovery device S6 still contains relatively high ammonia nitrogen, and this portion of high ammonia nitrogen wastewater can be directly discharged to a process unit (such as anammox) that can treat high ammonia nitrogen wastewater, or can be partially or completely discharged to the first phosphorus recovery device S5 as an ammonia nitrogen source to supplement ammonia nitrogen required by the device, thereby reducing the operation cost, for example, to the first phosphorus recovery device effluent W. The high ammonia nitrogen wastewater N discharged from the second phosphorus recovery device S6 is preferably subjected to heat preservation measures when being conveyed by a pipeline, so that the reaction speed of a subsequent ammonia nitrogen treatment reactor can be increased. The remaining part of the second phosphorus recovery apparatus effluent N is used as the effluent V to the subsequent ammonia nitrogen treatment reactor (such as anammox), in addition to the first phosphorus recovery apparatus effluent W to the first phosphorus recovery apparatus S5.

The first phosphorus-rich solid particles P discharged from the first phosphorus recovery apparatus S5 and the second phosphorus-rich solid particles O discharged from the second phosphorus recovery apparatus S6 may be mixed, and the wet fertilizer may have a solid content of about 5% to 10% (by volume) and contain a large amount of water to ensure the fluidity of the particles in the pipeline, prevent the particles from settling and blocking the pipeline.

In this embodiment, the phosphorus recovery system may further include a sieving and washing apparatus S7, a drying apparatus S8, and a storing and bagging apparatus S9.

The screening and washing device S7 receives the first phosphorus-rich solid particles P and the second phosphorus-rich solid particles O, and screens and washes them to separate out fine particles and impurities, so as to obtain a wet fertilizer Q.

The drying device S8 dries the wet fertilizer Q to obtain dried fertilizer particles R, and the storage and bagging device S9 stores and bags the dried fertilizer particles R.

In the screening and washing device S7, a vibrating screen is usually used to screen out very fine fertilizer particles, and the first phosphorus-rich solid particles P and part of the water in the second phosphorus-rich solid particles O are separated, and these fine fertilizer and water, i.e. the screening and washing wastewater T, can be mixed with the first phosphorus-recovery device effluent U discharged from the first phosphorus-recovery device S5 to form a mixed solution M, and then discharged to the subsequent wastewater treatment process (optionally, the wastewater treatment process in a wastewater treatment plant).

The wet fertilizer Q discharged from the sieving and washing apparatus S7 has a diameter of 1 to 3mm and contains no water on the surface layer. The wet fertilizer Q enters a drying device S8, wherein the drying device S8 is generally in a drum form, and dried fertilizer particles R are formed under the direct heat conduction action of a heating medium. The temperature of a heating medium of the drying device S8 is not more than 50 ℃, ammonia nitrogen in the crystal particles is prevented from sublimating, and the solid content of the dried fertilizer particles R is generally 95-99%. And the waste gas at the heat medium outlet is provided with a dust removal measure. The dried pellets R are stored in a storage and bagging unit S9 and bagged to form bagged fertilizer S for transport and use.

In conclusion, the phosphorus recovery rate in the sludge can reach more than 35% through the phosphorus recovery system and the process flow. The utility model provides a phosphorus recovery system has following technical advantage at least: 1. different processes are adopted for treating sludge (primary sludge and biological sludge) with different properties, so that the release and recovery rate of phosphorus are improved to the maximum extent; 2. different types of primary sludge are used as carbon sources for releasing phosphorus from biological sludge, so that the tank capacity, investment and operating cost of the contact tank are reduced; 3. the high ammonia nitrogen-containing drainage of the second phosphorus recovery reactor is used as an ammonia nitrogen source of the first phosphorus recovery reactor, so that the operation cost is reduced, and the phosphorus recovery rate is improved. In addition, the resource recovery and utilization of the non-renewable phosphorus are realized through the phosphorus recovery process. By recovering phosphorus, the risk of struvite scaling, abrasion and blockage formed in the pipeline is reduced, and the maintenance and management cost of the pipeline is reduced.

It should be noted that, in the above system and process of the present disclosure, the treatment of the residual biological sludge H is not unique, and the residual biological sludge H may be released phosphorus by using the anaerobic reaction tank S3, or may directly enter the anaerobic digestion tank S1 after being concentrated. Similarly, the primary sludge is not only treated, but the primary sludge is concentrated to become concentrated primary sludge A, which can directly enter the anaerobic digestion tank S1 for digestion reaction, or can enter the anaerobic reaction tank S3 wholly or partially to be mixed with the rest biological sludge to provide carbon sources. In the above different processing methods, the first phosphorus recovery apparatus S5 and the second phosphorus recovery apparatus S6 may be changed and combined.

Figure 2 illustrates a schematic diagram of a fluidized bed phosphorus recovery reactor in accordance with at least one embodiment of the present invention. An embodiment of a fluidized bed phosphorus recovery reactor used in the first phosphorus recovery unit S1 and/or the second phosphorus recovery unit S6 is described below with reference to FIG. 2. As shown in FIG. 2, a fluidized bed phosphorus recovery reactor may include a reactor body supported by a support frame 22 and arranged in a vertical orientation, and a gas stripping apparatus. The reactor main body can be provided with a water inlet area, a sedimentation and selection area, a fluidization area, a sedimentation area and a water collection area from bottom to top in sequence along the vertical direction. The above-described respective sections are mainly divided in their functions and structures, and the functions and structures of the respective sections will be described below, respectively.

It is noted that in the following description, the term "reactor" refers to a fluidized bed phosphorus recovery reactor as set forth in the present invention. "DN 40", "DN 150" and the like refer to pipe diameters specified by the national standard of nominal caliber, which one skilled in the art can directly use as the dimensions of the components.

The phosphorus-containing liquid enters the reactor main body from the water inlet area. Specifically, phosphorus-rich liquid or other phosphorus-rich liquid from a sludge digestion or concentration and dehydration system enters the reactor main body from the water inlet pipe 1, and a pressure sensor 3 can be arranged on the water inlet pipe 1 for monitoring whether the water inlet pipe is blocked due to scaling. The feed water may be pressurized into the reactor body by a feed water pump (not shown) to form an upward flow. The intake pump may be additionally provided with a coating.

The preferable concentration of the dissolved phosphate in the water inlet area is 30-55 mg/L, and the concentration of the phosphate in the reactor main body can be controlled by circulating water backflow.

The diameter setting in the district of intaking is relevant with the upwelling velocity in the inlet pipe, and the upwelling velocity scope in the district of intaking is 0.10 to 0.55 meters per second, through setting up the different upwelling velocities, can obtain the solid fertilizer granule of different diameters, and the technical staff in the field can select suitable upwelling velocity and the diameter in district of intaking according to required solid fertilizer granule diameter, the utility model discloses do not limit this.

The water inlet pipe 1 can be isolated from the reactor body by a water inlet valve 2, and the water inlet valve 2 can be a gate valve generally.

The upper part of the water inlet area is provided with a first adding pipe 4 and a second adding pipe 5 which can be respectively used for adding a magnesium salt solution and an alkaline solution if necessary. The first addition pipe 4 may be added with magnesium chloride (MgCl), for example ₂ ). A flow meter 6 can be arranged on the first feeding pipe 4 to monitor the amount of the magnesium salt solution to be fed. The second addition pipe 5 may add, for example, a sodium hydroxide (NaOH) solution. When the pH value of the reactor, which is displayed by a pH sensor 20 in a water collecting area in the reactor main body, needs to be adjusted, a second adding pipe 5 is adopted to add sodium hydroxide (NaOH).

At the side of the water intake zone, a discharge pipe 7 for discharging solid particles may be provided, and the fertilizer solid particles generated in the reactor are intermittently discharged in batches by the discharge pipe 7. The discharge of the manure can be controlled by the pressure sensor 3 or by a time interval. The discharge pipe 7 may be at an angle of 45 degrees to the horizontal. The diameter of the fertilizer discharge pipe is at least DN40, so as to prevent blockage by fertilizer particles due to the undersize diameter.

The water inlet area and the precipitation and selection area can be connected by flanges, so that when the water inlet flow changes, parts in the water inlet area and the water inlet pipe 1 can be replaced, and the flow rate in the water inlet pipe 1 is prevented from being too small.

The sedimentation and selection area is positioned at the upper part of the water inlet area, the shape of the sedimentation and selection area is in an inverted cone shape (also called a cone hopper shape), and solid particles formed by crystallization reaction are finally precipitated in the sedimentation and selection area.

The angle theta between the lower cone angle of the settling and selecting zone and the horizontal direction of the water inlet zone ₂ Should be greater than 60 degrees to ensure rapid settling of the solid fertilizer particles.

In this embodiment, the fluidized bed phosphorus recovery reactor may further comprise a recycling device configured to return liquid from the settling zone to the settling and selection zone. The circulating device comprises a return pipe 8 and a suction pipe 9 which are oppositely arranged and communicated, the return pipe 8 is connected to the sedimentation and selection area, and the suction pipe 9 is connected to the sedimentation area.

The return pipe 8 is located in the sedimentation and selection zone where the returned circulating water is mixed with the phosphorus-containing liquid to which the agent has been added.

A viewing window 23 and a sampling tube 24 may be provided in the sedimentation and selection zone. The observation window 23 can monitor the properties and sedimentation of the solid particles, and the size of the observation window 23 can be, for example, DN 150. The sampling tube 24 may be configured to sample or monitor pressure.

The fluidization zone is a critical region of the reactor where the mixture of solid particles and phosphorus-containing liquid is brought into a fluidized state. The cross-sectional flow velocity of the fluidizing zone is from 15 to 30 meters per hour. The solid particles formed in this zone settle into the settling and selection zone.

A gas stripping device is disposed within the reactor body and at least partially within the fluidization region and the settling region, the gas stripping device configured to blow off carbon dioxide from the mixed liquor to increase the pH.

In this embodiment, the stripping apparatus may include a stripping tube 14, an aeration head 25, and a stripping cylinder 15. The aeration head 25 is arranged at the bottom of the air stripping pipe 14, the air stripping pipe 14 is connected with the air inlet pipe 13 communicated with the outside of the reactor main body through the aeration head 25, the air stripping guide cylinder 15 is arranged above the air stripping pipe 14, and the bottom of the air stripping guide cylinder 15 is positioned at the top of the fluidization area and below the water suction pipe 9.

Compressed air enters the aeration head 25 through the air inlet pipe 13, and is uniformly distributed in the air stripping pipe 14 in steps to achieve the air stripping effect. The gas flow rate in the stripper tube 14 is 250 to 300Nm ³ /m ² H is used as the reference value. The compressed air is supplied by an air compressor (not shown) and the flow rate of the compressed air is adjusted as the diameter of the reactor changes, typically from 1 to 2Nm ³ /m ² At a pressure of 1 to 2 bar/h. When the scaling tendency of the inlet water is relatively strong, high-pressure compressed air is recommended, and the pressure can be selected to be 10bar, so that the air stripping pipe 14 can bear the pressure of 10 bar.

At least a portion of the top of the stripper tube 14 extends into the stripping guide shell 15, and the length of the stripper tube 14 extending into the stripping guide shell 15 is 1/3 to 2/3 of the height of the stripping guide shell 15. In the present exemplary embodiment, the length of the stripping tube 14 projecting into the stripping guide shell 15 is 1/2 of the height of the stripping guide shell 15. Alternatively, the diameter of the stripping guide shell 15 is 4 times the diameter of the stripping tube 14.

The fluidisation zone may also be provided with an organic discharge 12 for discharging excess organic material from the mixed liquor.

The settling zone is located above the fluidization zone and is also inverted cone-shaped (cone-bucket-shaped), where solid particles are formed. The angle theta between the settling zone and the horizontal direction ₁ Should be greater than 60 degrees.

The stripping guide cylinder 15 at the upper part of the stripping pipe 14 is mainly located in the settling zone, and the length of the stripping guide cylinder 15 is enough, the bottom of the stripping guide cylinder is located at the top of the fluidization zone, and the bottom of the stripping guide cylinder is arranged below the suction inlet of the suction pipe 9. The top of the air stripping guide cylinder 15 is positioned at the upper part 5-20 cm of an overflow weir 16 for draining water in the water collecting area. The diameter of the stripping guide shell 15 ranges from 500 to 900 mm.

The water suction pipe 9 of the circulating device sucks water from the air stripping guide cylinder 15, and the flow speed of a water suction port is 1-1.5 meters per second.

The circulation device may further include a circulation water pump 10. The circulating water is circulated to the return pipe 8 by a circulating water pump 10, and a circulation flow meter 11, such as an electromagnetic flow meter, may be provided on a pipe of the circulation device. The circulating water pump 10 may be provided with a variable frequency. The circulation ratio of the circulation device ranges from 1 to 21.

The water collection zone is disposed above the settling zone and configured to collect the reacted effluent and discharge the effluent out of the reactor body. The flow velocity of the cross section of the water collecting area is more than 2 meters per hour, and the flow velocity of the cross section ranges from 2 meters per hour to 5 meters per hour, so that suspended sludge is discharged from the pool, and excessive fine particles can be prevented from losing. The height of the water collection area is at least 400 mm.

The water collection area is provided with an overflow weir 16 for collecting the drained water and a water collection tank 18 communicating with the overflow weir, and the water collection area further includes a main water discharge tank 19, and the drained water enters the main water discharge tank 19 from the water collection tank 18 and is then discharged through a water discharge pipe 17. The height of the weir 16 should be at least 2 to 3mm higher than the depth of the liquid level in the water collection tank 18 to ensure a sufficient flow velocity in the water collection tank 18 to prevent the deposition of fine suspended particles in the tank.

The water from the sump 18 into the main drainage channel 19 should have sufficient fall and the level of the liquid in the main drainage channel should be at least 5cm below the bottom of the sump 18 to ensure that the sediment is drained quickly.

Optionally, a pH sensor 20 and a level sensor 21 are provided in the water collection area. The pH sensor 20 is configured to monitor the pH value within the reactor to remain within the range of 7.5 to 8.5. The level sensor 21 is configured to monitor the liquid level of the reactor, and one of examples of the level sensor 21 may be a liquid level meter.

Optionally, the fluidized bed phosphorus recovery reactor may further comprise a header region disposed above the sump region, the header region comprising a header enclosing an upper portion of the reactor body.

The fluidized zone of the fluidized bed phosphorus recovery reactor has a diameter in the range of 1900 to 2800mm and an overall height from the bottom of the shelf 22 to the highest point of the top cover in the range of 7300 to 8700 mm. The total volume of the reactor is in the range of 10 to 30m ³ 。

In order to ensure the fluidization regime of the reactor, the reactor body has a reaction height, the ratio of which to the diameter of the fluidization zone is between 2.5 and 3.0. The reaction height of the reactor is defined as the sum of the height of the main body of the water inlet zone (i.e., the height of the main body above the water inlet cone of the water inlet zone), the height of the settling and selecting zone, the height of the fluidizing zone, and the height of the settling zone.

On average in normal operation, with the fluidized bed phosphorus recovery reactor according to the present invention, 65% -90% of the phosphate in solution can be recovered as phosphorus-containing fertilizer, and this recovery rate is related to the concentration of the phosphate of the incoming water. The diameter of the fertilizer solid particles finally formed is between 1.5 and 3 mm. The produced solid granular fertilizer (phosphate fertilizer) is almost the same as natural struvite, and can be directly or indirectly applied to agriculture or forestry and the like.

The utility model provides an above-mentioned fluidized bed phosphorus recovery reactor need not plus the seed crystal, realizes nucleation and crystallization through homogeneous reaction. Simple operation and maintenance, small occupied area, high efficiency of phosphorus recovery and no secondary pollution. The first phosphorus recovery unit S5 and/or the second phosphorus recovery unit S6 have corresponding technical advantages due to the use of the fluidized bed phosphorus recovery reactor described above.

Exemplary embodiments of the present invention have been described in detail herein with reference to the preferred embodiments, however, it will be understood by those skilled in the art that various modifications and changes may be made to the specific embodiments described above without departing from the spirit of the present invention, and various combinations of the various features and structures presented in the present invention may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. A phosphorus recovery system for treating a first set of sludge and a second set of sludge from a sludge treatment line, comprising:

the anaerobic reaction tank receives the first group of sludge and releases phosphorus in the first group of sludge in an anaerobic environment;

the pre-dehydration device is connected to the anaerobic reaction tank and is used for concentrating and dehydrating the sludge subjected to phosphorus release to generate concentrated sludge and a first concentrated solution;

an anaerobic digester for digesting a second set of sludge to produce biogas and digested sludge products;

a sludge dewatering device connected to the anaerobic digester and dewatering the digested sludge product to produce a sludge cake and a second concentrate;

a first phosphorus recovery device connected to the pre-dehydration device and recovering phosphorus in the first concentrated solution to generate first phosphorus-rich solid particles; and

and the second phosphorus recovery device is connected to the sludge dewatering device and recovers phosphorus in the second concentrated solution to generate second phosphorus-rich solid particles.

2. The phosphorus recovery system of claim 1, wherein at least a portion of the effluent of the second phosphorus recovery unit is directed to the first phosphorus recovery unit as its ammoniacal nitrogen source.

3. The phosphorus recovery system of claim 1, further comprising:

the screening and washing device is used for receiving the first phosphorus-rich solid particles and the second phosphorus-rich solid particles, screening and washing the first phosphorus-rich solid particles and the second phosphorus-rich solid particles, and separating fine particles and impurities to obtain a wet fertilizer;

a drying device for drying the wet fertilizer to obtain dried fertilizer particles; and

and the storage and bagging device is used for storing and bagging the dried fertilizer particles.

4. The phosphorus recovery system of claim 1, wherein the anaerobic reaction tank adds an additional carbon source.

5. The phosphorus recovery system of any one of claims 1 to 4, wherein the first phosphorus recovery device and/or the second phosphorus recovery device is a fluidized bed phosphorus recovery reactor comprising:

the reactor main part, the reactor main part has set gradually from bottom to top along vertical direction:

a water inlet zone from which phosphorus-containing liquid enters the reactor body;

a precipitation and selection zone, said precipitation and selection zone being of inverted conical shape, solid particles formed by crystallization reaction ultimately precipitating in said precipitation and selection zone;

a fluidization zone, wherein the mixed liquid of the solid particles and the phosphorus-containing liquid forms a fluidized state, and the solid particles settle to the precipitation and selection zone;

a settling zone, said settling zone being of an inverted cone shape, said solid particles forming in said settling zone; and

a water collection region configured to collect the reacted drain water and discharge the same out of the reactor body; and

a stripping device disposed within the reactor body and at least partially disposed in the fluidization region and the settling region, the stripping device configured to strip carbon dioxide from the mixed liquor to increase the pH.

6. The phosphorus recovery system of claim 5, wherein the water inlet zone is provided with at least a water inlet pipe and a water inlet valve for the phosphorus-containing liquid to enter the reactor body;

wherein, a first feeding pipe and a second feeding pipe are arranged at the upper part of the water inlet area; and is

Wherein a discharge pipe for discharging phosphorus-rich solid particles is arranged at the side part of the water inlet area.

7. The phosphorus recovery system of claim 6, further comprising: and the heat insulation pipeline is arranged in at least one of a pipeline between the sludge dewatering device and the second phosphorus recovery device, a drainage pipeline of the second phosphorus recovery device, a drainage pipeline from the second phosphorus recovery device to the first phosphorus recovery device and a pipeline from the second phosphorus recovery device to the ammonia nitrogen treatment device.

8. The phosphorus recovery system of claim 5, wherein the fluidized bed phosphorus recovery reactor further comprises:

a circulation device, the circulation device comprises a suction pipe and a return pipe which are oppositely arranged and communicated, the suction pipe is connected to the sedimentation area, the return pipe is connected to the sedimentation and selection area, the circulation device is configured to return the liquid in the sedimentation area to the sedimentation and selection area,

wherein the circulation ratio of the circulation device ranges from 1 to 21.

9. The phosphorus recovery system of claim 8, wherein the stripping apparatus comprises a stripping tube, an aeration head, and a stripping guide cylinder, the aeration head is disposed at a bottom of the stripping tube, the stripping tube is connected to an air inlet tube communicating with an exterior of the reactor body through the aeration head, the stripping guide cylinder is disposed above the stripping tube, and a bottom of the stripping guide cylinder is located at a top of the fluidization region and below the water suction tube, wherein at least a portion of the top of the stripping tube protrudes into the stripping guide cylinder, and a length of the stripping tube protruding into the stripping guide cylinder is 1/3 to 2/3 of a height of the stripping guide cylinder.

10. The phosphorus recovery system of claim 5, wherein the reactor body has a reaction height defined as the sum of the height of the body of the water entry zone, the height of the settling and selection zone, the height of the fluidization zone, and the height of the settling zone, wherein the ratio of the diameter of the reaction height to the fluidization zone is between 2.5 and 3.0.