KR101615615B1 - Preparing Method of Struvite for Chemicals Reduction - Google Patents

Abstract

The present invention relates to a struvite preparing method and, more specifically, to a struvite preparing method using continuous operation. The struvite preparing method using the continuous operation comprises the steps of: (a) processing digested sludge within a digesting tank with a suspended solid removal device to remove a suspended solid, and then transferring the suspended solid to a dehydrated and filtered liquid storage tank; (b) transferring the dehydrated and filtered liquid stored in the dehydrated and filtered liquid storage tank to an inline mixer, adding a pH adjustment agent and chemicals to the liquid and crystallizing the liquid via a high speed mixing operation; (c) transferring the crystallized reactant to a struvite generating precipitation tank and generating a struvite complex; and (d) transferring the struvite complex to a hydroclone type solid-liquid separator and separating and recovering struvite crystals. In the case of using the struvite preparing method according to the present invention, eutrophication caused by phosphorus can be inhibited and chemical fertilizers causing oxidization of soil can be replaced in terms of an environment effect. In addition, the present invention can save the amount of chemicals needed in generating the struvite and secure phosphorite substitute to reduce import volume of the phosphorite with a high level of import dependence, thereby contributing to national industry and economy in terms of an economic effect.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for preparing a drug-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a struvite, and more particularly, to a method for manufacturing a drug-saving stru bite capable of continuous operation.

Phosphorus from phosphorus, a resource that is becoming depleted, is biologically essential for plant growth along with nitrogen (N) and potassium (K).

Since there are no known alternative resources to date, much research is underway on the recovery of waste from waste, and a lot of efforts are underway to reduce the demand for phosphorus.

In light of the recent international situation in which phosphorus resources are lacking and the domestic circumstances of importing phosphorus, it is essential for Korea to develop and disseminate the technology to recover and recycle the discarded phosphorus.

In general, the method of recovering phosphorus in Korea is to chemically treat the bottom and wastewater and solidify the precipitated ginseng salt. However, since the sludge obtained is not suitable for reuse due to impurities, moisture content, organic substances, etc., have.

Techniques for removing and recovering phosphorus are known to include chemical precipitation, biological removal, crystallization, and ion exchange, but these methods require simple removal of phosphorus It is a technology that is not suitable for recovery and recycling. In order to utilize phosphorus as a fertilizer or the like, there is a method of precipitating a phosphorus compound into a struvite form and a method of producing a fertilizer usable form by applying various processes or additives to a biological processing by-product.

Of these, struvite (MgNH ₄ PO ₄ · 6H ₂ O) is a magnesium-ammonium-phosphate type material that can be recovered in the best form at the wastewater treatment plant. It also contains nitrogen as well as fertilizer (Slow release fertilizer ), And is being actively studied all over the world. Struvite is generally known as guanite or magnesium ammonium phosphate (MAP) and is a crystal in which NH ₄ ⁺ , PO ₄ ^3- and Mg ²⁺ are bonded in an equimolar ratio, Molar ratio and is produced rapidly when the pH is 9.5 or higher.

Normally, the pH regulator for the struvite crystallization and the amount of the Mg source are manually controlled according to the intuition (visual observation and experience) of the field workers, I am putting too much medicine.

Korean Patent No. 1304396 discloses a process for stripping phosphorus and magnesium and a struvite production system for waste activated sludge, Korean Laid-Open Patent Application No. 2015-0065329 discloses a process for treating livestock wastewater using magnesium fuel cells, A method of manufacturing a bite is disclosed.

However, the above-mentioned techniques have been disadvantageous in that the continuous production of struvite is impossible, the fluctuation of the treatment efficiency and the facility scale are large, and the operation ratio is high.

As a result of efforts to solve the above problems, the present inventors have found that (a) removing stagnant substances of digested sludge with a floating material removing device can increase the production efficiency of struvite, and (b) ) It is possible to continuously accelerate the crystallization reaction of struvite while realizing automatic control of chemicals by using measurement sensor and inline mixer in real time while reducing the amount of chemical used, and (c) equipped with a liquid / solid separator When a liquid-solid two-phase fluidized-bed conical reactor is used as a struvite-generating settler, the crystal size of the struvite particles can be increased while minimizing the outflow of the microstruvite particles, and the struvite can be efficiently produced continuously And the present invention was completed.

It is an object of the present invention to provide a highly efficient processing and recovery integrated process for solving resource exhaustion problems.

(A) digested sludge in a digestion tank is treated with a floating material removal device to remove suspended substances, and then transferred to a dehydrated filtrate storage tank; (b) transferring the dehydrated filtrate stored in the dehydrated filtrate storage tank to an inline mixer, adding a pH adjusting agent and a drug, and crystallizing the dehydrated filtrate through a high-speed mixing; (c) transferring the crystallization reagent to a struvite production settler and producing a StruBite complex; And (d) transferring the resulting Strumite complex to a Hydrocyclone type solid-liquid separator, and separating and recovering the Struvite crystal.

In the present invention, a sensor capable of measuring the pH and phosphate of the dehydrated filtrate is provided in the dehydrated filtrate storage tank, and the amount of the pH adjuster and the drug to be administered to the inline mixer is automatically controlled in real time, And the use amount of the medicine is reduced.

In the present invention, the pH adjusting agent is NaOH, and the drug is magnesium chloride (MgCl ₂ ).

In the present invention, the inline mixer is installed in a sludge transfer pipe connected between a dehydration filtrate storage tank and a struvite generation sedimentation tank, thereby promoting the formation of struvite crystals by high-speed mixing of influent and chemicals.

In the present invention, the inline mixer is provided with a hollow for supplying a pH adjusting agent and a medicament to the center of the rotating shaft rotating normally and reversely by drive motor driving, a plurality of stirring blades are attached to the outer surface of the rotating shaft at equal intervals, A pH adjusting agent and a chemical spray opening are formed between the wing and the stirring wing so that the chemical can be injected at a high speed, and the sludge transferring pipe and the rotating shaft are perpendicular to each other in the axial direction.

In the present invention, the struvite generation settling tank is a liquid-solid two-phase fluidized bed conical reactor, and a liquid / solid separator for minimizing the outflow of fine struvite particles is provided on the upper portion, And a crystallization reactant inlet pipe through which the crystallization reactant generated in the mixer flows is located.

In the hydrocyclone type solid-liquid separator according to the present invention, the struvite crystal having a specific gravity of 1.6 or more is separated and recovered.

When the method for producing struvite according to the present invention is used, there is an environmental effect that can suppress the occurrence of eutrophication derived from phosphorus and replace chemical fertilizers that cause soil acidification. In addition, by securing alternate phosphate, it is economically effective to contribute to the national industrial economy by reducing the amount of phosphorus imports that are highly dependent on foreign countries.

1 is a manufacturing process diagram of a drug-reduced struvite according to an embodiment of the present invention.
2 is a block diagram of an inline mixer according to an embodiment of the present invention.
Fig. 3 shows the result of stirring according to the shape of a stirring blade constituting the inline mixer of the present invention.
4 is a configuration diagram of a struvite generation settling tank according to an embodiment of the present invention.
5 is a plan view of a liquid / solid phase separation membrane according to an embodiment of the present invention.
6 is a block diagram of a hydrocyclone type solid-liquid separator according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. The thicknesses of the lines and the sizes of the components shown in the accompanying drawings may be exaggerated for clarity and convenience of explanation.

In addition, the terms described below are defined in consideration of the functions of the present invention, and these may vary depending on the intention of the user, the operator, or the precedent. Therefore, definitions of these terms should be made based on the contents throughout this specification.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a manufacturing process diagram of a drug-reduced struvite according to an embodiment of the present invention.

As shown in FIG. 1, the method of manufacturing struvite by continuous operation according to the present invention comprises the steps of (a) treating digested sludge in a digester 100 with a device 200 for removing suspended solids, To the dehydrated filtrate storage tank (300); (b) transferring the dehydrated filtrate stored in the dehydrated filtrate storage tank 300 to the inline mixer 500, adding a pH adjusting agent and chemicals, and crystallizing the dehydrated filtrate through high-speed mixing; (c) transferring the crystallization reactant to struvite generation settler 600 and producing a StruBite complex; And (d) transferring the generated Strumite complex to a hydrocyclone type solid-liquid separator 700, and separating and recovering Struvite crystals.

Generally, there is a suspended material in the digested sludge in the digester 100, which is known to lower the efficiency of the struvite crystallization reaction. Therefore, in the present invention, suspended substances in the digested sludge are removed by the floating substance removing apparatus 200, and the floating substances are transferred to the dehydrated filtrate storage tank 300.

Although the floating material removal apparatus 200 can be used without any limitation as long as it can remove suspended matters, it can improve the flux and the concentration ratio (recovery rate) by suppressing the deposition of the contaminants due to strong turbulence generated on the surface of the membrane It is preferable to use a vortex-generating high-concentration separator.

The dehydrated filtrate from which the suspended matters have been removed through the suspended solids removal device 200 is transferred to the dehydrated filtrate storage tank 300. The dehydrated filtrate storage tank 300 stores the pH and phosphate of the dehydrated filtrate Sensors 420 and 430 capable of measuring in real time are installed to automatically control the amount of the pH adjusting agent and the chemicals to be supplied to the inline mixer 500 in accordance with the change of the characteristics of the influent water, can do.

That is, the pH adjusting agent and the chemicals (not shown) that are input to the inline mixer 500 from the control unit (not shown) based on the results measured by the pH sensor 420 and the phosphate sensor 430 installed on the dehydrated filtrate storage tank 300 The amount is adjusted to optimize the struvite crystallization reaction. For example, if the pH of dehydrated filtrate in the in-line mixer 500 is 8 to 10.5 and the molar ratio of Mg: N: P is 1: 1.5: 1: 1, 1, the amount of the pH adjusting agent and the amount of the drug can be controlled.

In the present invention, it is possible to use the pH adjusting agent and the pharmaceutical agent, respectively, without particular limitation, as long as the pH can be adjusted and the magnesium concentration can be controlled. Examples of the pH adjuster include NaOH and magnesium chloride (MgCl ₂ ).

FIG. 2 is a configuration diagram of an inline mixer 500 according to an embodiment of the present invention, and FIG. 3 is a result of stirring according to the shape of a stirring blade 530 constituting an inline mixer.

As shown in FIG. 2, the inline mixer 500 is for mixing medicines using a vortex generated in a tube, and a stirring vane 530 having a specific shape is disposed inside a tube to which the dehydrated filtrate is delivered at a predetermined pressure It is a device that continuously injects chemicals into a high speed rotating section while converting a fluid of a certain pressure into a turbulent fluid. In Struvite crystallization, the agitation time is short and the agitation time is long as the agitation intensity is small. The inline mixer 500 has a higher agitation strength than the conventional agitation agitator, thereby improving the struvite crystallization reaction .

The inline mixer 500 includes a driving motor 510, a rotating shaft 520 connected to the driving motor 510, a plurality of stirring vanes 530 attached to the outer surface of the rotating shaft 520, 530) for injecting the medicament.

The inline mixer 500 is installed in the sludge transfer pipe connected between the dehydrated filtrate storage tank 300 and the struvite generation settling tank 600. The inline mixer 500 mixes the pH adjuster and the drug through the drug injection port 540 of the rotating shaft 520 And the rotary shaft rotates at a high speed, so that sufficient mixing energy can be transmitted.

The inline mixer 500 is provided with a hollow for supplying a pH adjusting agent and chemicals to the center of the rotating shaft 520 rotated in normal and reverse directions by driving of the driving motor 510. On the outer surface of the rotating shaft 520, A drug jetting port 540 is formed between the agitating blade 530 and the agitating blade 530 so that the supplied pH adjusting agent and the medicament can be sprayed at a high speed and the sludge (dehydrated filtrate) And the pipe and the rotating shaft 520 are perpendicular to each other in the axial direction.

As shown in FIG. 3, the stirring efficiency of the sludge may be varied depending on the formation of the stirring vane 530.

The driving motor 510 can be variably adjusted by an inverter, and the stirring vane 530 can rotate at a high speed of about 1,000 to 4,000 rpm according to the flow rate or concentration.

A pH control agent storage part 400 in which a pH control agent is stored and a drug storage part 410 in which a drug is stored are connected to a transfer pipe so as to supply pH adjusters and chemicals to the inline mixer 500, The pipe is connected to a connection port opposite to the inline mixer drive motor 510 so that the pH adjuster and the medicine are supplied by the pump pressure in the hollow of the rotation shaft 520. The cross section of the chemical injection port 540 is smaller than the cross sectional area of the chemical supply pipe, Designed to be fully filled inside hollow, high-speed injection to the front of piping is possible. The pH adjusting agent and the drug sprayed at high speed react strongly with the dehydrated filtrate by the agitating blade 530 rotating at a high speed to form struvite crystals.

The crystallization reactant formed in the in-line mixer 500 is transferred to the StruByte production settling tank 600, and then is produced as a StruByte complex.

4 is a configuration diagram of a struvite generation sedimentation tank 600 according to an embodiment of the present invention.

4, the struvite generation settling tank 600 according to the present invention is a liquid-solid two-phase fluidized-bed conical reactor, and has a liquid / solid separator for minimizing the outflow of fine- And a crystallization reactant inlet 640 through which the crystallization reactant generated in the in-line mixer flows is disposed in the lower portion.

When gravity sedimentation is applied by injecting the crystallization reaction material to the upper part of the reactor, the generation of struvite and the efficiency of swirling water are reduced due to a small and light floating material near the water surface. However, when the crystallization reaction material flows into the lower part, Since the truvite particles are moved upward by the fluidized bed and the crystal size of the particles is increased, the particles can be precipitated to the bottom and recovered. Thus, the production and recovery of the struvite complex can be efficiently performed simultaneously in the reactor.

As shown in FIG. 5, the liquid / solid separator 620 is in the shape of a ladder, and is formed of a material such as SUS, polyethylene or the like in order to facilitate the sidestream flow of the fluid. , And the outer portion is composed of a mesh net that allows the fluid to escape while preventing the struvite crystals from flowing out, thereby minimizing the outflow of floating microstruvite particles to the outside of the settler.

The middle portion of the liquid / solid separation membrane and the mesh network are connected to each other through a connection portion 610. The liquid / solid separation membrane 620 can be fixed to the upper part of the struvite generation sedimentation tank by a combination of welding, have.

The struvite produced in the struvite production settling tank 600 precipitates together with various organic matter and particulate matter in the water to form a struvite complex. Therefore, in order to use struvite as a fertilizer or feed product, Recovery process is essential.

Therefore, in the present invention, the Struvite complex generated in the StruByte producing sedimentation tank 600 is transferred to the hydrocyclone type solid-liquid separator 700, and then separated and recovered as struvite crystals.

The hydraulic fluid-solid-liquid separator 700 of the present invention is characterized by separating and recovering struvite crystals having a specific gravity of 1.6 or more.

As shown in FIG. 6, in the present invention, a conventional hydraulic type solid-liquid separator composed of a cylindrical section 720 and a conical section 710 can be used.

The principle of the hydraulic liquid-solid separator is that the fluid including the StruBite complex is tangentially introduced through the inlet 760 located above the cylinder by the pressure, and as the fluid enters the inlet, The centrifugal force that accelerates the movement of the Struvite Complex toward the outer wall is generated and the Struvite Complex moves downward in the form of a spiral through the cylindrical portion and the conical portion.

In the case of a large Struvite complex, the particles collide with the inner wall of the cyclone to lose the inertia force of the particles and flow along the wall of the conical part through the lower outlet 750. Part of the very fine particles move to the center, (730).

Gravity, centrifugal force and drag force are mainly applied to the particles in the flow inside the hydraulic liquid-solid separator 700. Since the influence of gravity is negligibly small, the centrifugal force and the drag force . These centrifugal forces act in the circumferential direction, preventing the particles from flowing inwardly, and the particles moved to the inner wall by the centrifugal force collide with the inner wall and lose the inertia force and can be separated and discharged through the lower outlet. If the centrifugal force acting on the particles is larger than the drag force, the particles move downward in a circle and are discharged to the lower discharge port. On the contrary, when the drag force is larger, the particles move inward and are discharged through the upper discharge port.

Although the struvite crystals separated in the hydraulic type solid-liquid separator 700 can be recovered as they are, they can be further transferred to the StruBite hopper 800 for easier recovery, A further step of drying the struvite may be performed.

As described above, the struvite produced through the continuous operation according to the present invention can be utilized as an environmentally friendly fertilizer source.

StruBite is a slowly decomposing crystal fertilizer that can maintain the growth of crops with only one or two applications per year and thus can save labor, It is advantageous in that it is prevented from being lost in the rainy season. It also prevents acidification of the soil and has great potential to be used in other chemical and feed industries.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is understandable. Accordingly, the true scope of the present invention should be determined by the following claims.

100: digester
200: Floating material removal device
300: dehydrated filtrate storage tank
400: pH adjusting agent storage part
410: drug store
420: pH sensor
430: Phosphorus sensor
500: Inline Mixer
510: drive motor
520:
530: stirring wing
540: Spray nozzle
600: Struvite production sedimentation tank
610:
620: liquid / solid membrane
640: Crystallization reactant inlet
700: Hydrocyclone type solid-liquid separator
710:
720:
730: upper outlet
750: Lower outlet
760: Inlet
800: StruBite hopper

Claims (7)

(a) treating a digested sludge in a digestion tank with a floating substance removal device to remove suspended substances, and then transferring the suspended substance to a dehydrated filtrate storage tank;
(b) transferring the dehydrated filtrate stored in the dehydrated filtrate storage tank to an inline mixer, adding a pH adjusting agent and a drug, and crystallizing the dehydrated filtrate through a high-speed mixing;
(c) transferring the crystallization reagent to a struvite production settler and producing a StruBite complex; And
(d) transferring the generated Strumite complex to a hydraulic liquid-solid separator, and separating and recovering struvite crystals, the method comprising the steps of:
The dehydrated filtrate storage tank is provided with a sensor capable of measuring the pH and phosphate of the dehydrated filtrate, so that the amount of the pH adjuster and the chemical to be administered to the inline mixer is automatically controlled in real time,
The struvite generation settler is a liquid-solid two-phase fluidized-bed conical reactor having a liquid / solid separator for minimizing the outflow of fine struvite particles, The center of which is pointed upwardly and is made of SUS or polyethylene in order to facilitate the sidestream flow of the fluid, and the circumference of the sludge is formed in a manner such that the fluid can escape while preventing the outflow of the struvite crystal And a mesh network.
delete The method according to claim 1, wherein the pH adjusting agent is sodium hydroxide (NaOH), and the agent is magnesium chloride (MgCl ₂ ).
2. The method of claim 1, wherein the inline mixer is installed in a sludge transfer pipe connected between a dehydrating filtrate storage tank and a struvite generation settling tank.
The inline mixer according to claim 1, wherein the inline mixer has a hollow for supplying a pH adjusting agent and a medicament to the center of a rotating shaft rotating normally and reversely by drive motor driving, a plurality of stirring blades are attached to the outer surface of the rotating shaft at equal intervals, Wherein a pH adjusting agent and a chemical spray opening are formed between the stirring blade and the stirring blade so that the chemical can be sprayed at a high speed, and the sludge transferring pipe and the rotating shaft are perpendicular to each other in the axial direction.
delete The method for producing struvite according to claim 1, wherein the struvite crystal having a specific gravity of 1.6 or more is separated and recovered in the hydraulic type solid-liquid separator.

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