JP2003300100A - Method and system for freeze-drying sludge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a system for freeze-drying sludge in a short time and easily adjusting the moisture content of sludge. <P>SOLUTION: This system comprises: a freezing/crushing apparatus 12 for crushing the sludge to be thrown from a sludge tank 10 into minute powder while freezing the moisture in the sludge by the whirling current 26 generated by introducing cooled air; a vacuum pump 14 for sucking the sludge containing minute ice particles from the apparatus 12 by negative pressure suction; and a sludge separator 13 for separating minute ice particles from the sucked sludge. Separation of the minute ice particles from the sludge is conducted mainly by the phase transition of the minute ice particles to steam by making good use of negative pressure. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a sludge for freezing sewage sludge discharged from a sewage treatment facility, or excess sludge discharged from a factory wastewater treatment facility, and separating and removing water in the sludge. Freeze-drying method and system thereof.

[0002]

2. Description of the Related Art Sludge discharged from sewage treatment facilities is bulky because it has a very high water content, and is said to account for almost half of the amount of industrial waste discharged. Most of the discharged sludge is dehydrated and incinerated and disposed of by landfill, but in recent years active ingredients in sludge have been focused on, and effective use as recycled products such as fuel and bricks has been promoted. There is. In any case, the most essential treatment process for sludge treatment is sludge concentration, dewatering, and drying. The water in the sludge is extracted to reduce the volume, and the sludge is discharged in a form as close to the dry matter as possible. It is desired, and various methods have been developed and put to practical use in such processing.

Generally, as a method for separating water from sludge,
First, sludge with a water content of about 98% is concentrated to a water content of about 95% by sedimentation separation by gravity, floatation under pressure, centrifugal separation, etc., and then mechanical means such as a centrifuge, filter press, belt press, etc. Dehydrated to 70-80%,
Next, a method of drying by heat drying, sun drying, etc. is adopted. However, it has been pointed out that the conventional methods have problems such as low efficiency of concentration / dehydration, environmental pollution / increased cost due to introduction of chemicals, generation of soot and dust by incineration, and alteration of sludge components.

Therefore, in recent years, a freeze-thaw method has been developed and put into practical use as a water separation method in the concentration, dehydration and drying of sludge. This utilizes the property of removing impurities other than water to crystallize when freezing water, by slowly cooling the sludge and growing the water content contained in the sludge as ice crystals. The sludge component can be concentrated and separated from water. A wastewater treatment device for dehydrating sludge using such a method is disclosed in JP-A-2000-2464.
1 publication. In the wastewater treatment device 01 as shown in FIG. 3, after the wastewater consisting of kitchen waste and wastewater stored in the primary storage tank 02 is subjected to coagulation and decomposition treatment in the purification treatment unit 022 of the wastewater treatment tank 04, Settling section 02
At 3, sludge solids are settled. And the settling sludge 0
24 is led to the ice heat storage tank 03, where the sludge is frozen and thawed by the cold heat supplied from the heat cogeneration device 06 via the heat exchanger 030.

The water separated from the solid content in the sludge in the ice heat storage tank 03 is returned to the waste water treatment tank 04, while the solid content separated from the water and concentrated is guided to the drying device 05 and heated and dried. It is collected and collected in the container 07. The cold heat recovered when the sludge is thawed in the ice heat storage tank 03 can be used for the steam recovery in the drying device 05 and the space unit 08 for supplying the cold heat to the outside. As described above, according to the sludge concentration method by freeze-thaw treatment, it is possible to separate solid matter from sludge water, reuse water, and effectively use energy by storing heat.

[0006]

However, the freeze-thaw method typified by the above-mentioned Japanese Patent Laid-Open No. 2000-24641 requires a considerable amount of time to transfer cold heat to the inside of the sludge at the time of freezing, and has a large capacity of sludge. It is difficult to treat water, and impurities are likely to be attached to and mixed with frozen water, resulting in low purity of water and limited reusable range. Further, since the dehydration effect is limited, a drying means must be provided in the latter stage of the freeze-thaw treatment, which inevitably increases the size and cost of the device. Therefore, in view of the problems of the prior art, it is an object of the present invention to provide a sludge freeze-drying treatment method and system capable of performing freeze-drying treatment in a short time and easily adjusting the water content of sludge. And

[0007]

In order to solve the above problems, the present invention provides a method for freeze-drying sludge by freeze-separating water contained in sludge. A step of pulverizing the sludge by swirling flow generated by the cooling air while injecting cooling air into the closed space of No. 1 to freeze water in the sludge thrown into the space; While guiding the sludge from the first closed space to the second closed space held in a negative pressure state,
And sublimating fine-grained ice produced by freezing from the sludge in the second closed space to separate water.

According to the invention, since the swirling flow is generated by the cooling air to freeze the sludge while crushing it into fine particles, rapid freezing can be realized, the sludge treatment can be shortened, and the sludge and the water content can be reduced. Since sludge can be easily separated, sludge can be treated with high efficiency. Further, since the water contained in the sludge and the water in the air are frozen, crushed, and then sublimated, reliable water separation is possible, and energy saving can be expected. Furthermore, since the entire process of freeze-drying sludge is performed in a closed space, it is possible to suppress the generation of offensive odors, and since it is not necessary to add chemicals such as coagulants, the impact on the environment is minimized. be able to.

Further, as described in claim 2, the sludge from which water is separated in the second closed space is returned to the first closed space, and the moisture content is increased while additionally adding sludge as necessary. It is preferable to circulate the sludge until it reaches a predetermined value. In this way, by circulating the sludge until the moisture recovery rate from the sludge reaches the required amount, it is possible to easily set the water content of the sludge to the required value, and to easily reuse the recovered sludge. Like

The invention according to claim 3 comprises the step of cooling the air containing water separated from the sludge in the second closed space and condensing and separating the water in the air, and the water is removed. The cooled cooling air is returned to the first closed space and used for freezing the sludge and generating a swirling flow. According to this invention, it is possible to prevent leakage of a bad odor to the outside by circulating the cooling air in the closed space without discharging it, and contribute to energy saving because the supply of cold heat can be minimized. To do.

Further, in the invention according to claim 4, when the water content of the sludge from which the water has been separated reaches a predetermined value, heated air is introduced into the first closed space to recover the sludge. It is characterized by In this way, by collecting the water separated from the sludge by sublimation, highly pure water can be recovered, and the range of reuse of the recovered water is expanded. Further, it is preferable to use the condenser side of the refrigeration cycle for generation of the cooling air, and to use the evaporator side of the refrigeration cycle for generation of high temperature air during sludge recovery. The same device can be used, and space can be saved. Needless to say, a heater may be provided separately from the cooling means.

The invention according to claims 5 to 7 is an invention relating to a sludge freeze-drying treatment system capable of obtaining substantially the same effects and actions as the above-mentioned invention, and the invention according to claim 5 is the introduction of cooling air. A freezing and pulverizing device for generating a swirling flow and pulverizing the sludge by freezing the water in the input sludge by the swirling flow, and a means for sucking fine-grained sludge from the freeze pulverizing device by negative pressure suction And a sludge separator that separates the fine-grained ice generated by freezing from the sucked sludge, and the fine-grained ice separation from the sludge in the sludge separator is mainly performed by using the negative pressure. It is characterized in that it is carried out by a phase change of grain ice into water vapor.

Further, in the invention according to claim 6, a sludge return passage for returning the sludge discharged from the sludge separator to the freeze pulverizer is provided, and is circulated until the water content of the sludge reaches a predetermined value. It is characterized by According to a seventh aspect of the present invention, water recovery means is provided for condensing and recovering the water vapor separated by the sludge separator by cold heat from the refrigeration cycle, and the cooling air from which water has been removed by the water recovery means is frozen. It is characterized in that a cooling air return passage introduced into the crushing device is provided.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention thereto unless specifically stated otherwise, and are merely illustrative examples. Not too much. FIG. 1 is an overall schematic configuration diagram of a sludge freeze-drying treatment system according to a first embodiment of the present invention, and FIG. 2 is an overall schematic configuration diagram of a sludge freeze-drying treatment system according to a second embodiment of the present invention.

The freeze-drying treatment system in this embodiment is suitable for treating sewage sludge discharged from sewage treatment equipment and the like, but can be applied to any sludge regardless of the water content and type of sludge. In FIG. 1, reference numeral 10 is a sludge tank for temporarily storing sludge that has been first subjected to sedimentation and separation treatment in a settling tank, and includes sludge charging means and sludge charging amount control means (not shown). Reference numeral 11 is a chamber equipped with a cooling air injection port, 12 is a freeze-grinding device for crushing the supplied sludge while freezing, 13 is a sludge separator for separating and collecting solid matter in the sludge, 14 is a vacuum pump, and 15 is a blower. , 16 is a refrigerator equipped with a heat exchanger 18, 17 is a water recovery device for recovering water separated from sludge to generate dry cooling air, 19 is a water tank, 20 is recovered by the sludge separator 13. This is a hopper ejector for supplying the sludge with cooling air into the freeze-grinding device 12.

The freeze-grinding device 12 includes the chamber 1
1 and a cooling air injection port, and is provided with a sludge inlet and a fine-grained sludge-containing air outlet, and an on-off valve forms a closed system closed space.
In the freeze-pulverization device 12, a swirling flow is generated by the cooling air supplied from the cooling air jet port, and the particles present in the closed space are pulverized by colliding with the side wall of the freeze-pulverization device 12 or the particles. Be converted. At this time,
It is preferable that the swirl flow is formed by, for example, cooling air that is jetted at a predetermined wind speed from a cooling air jet port that is obliquely attached to the freeze-grinding device 12.

The sludge separator 13 has a function of separating particles having a diameter of about several μm, and is a device provided with a solid-gas separation means utilizing gravity, centrifugal force, inertial force, electric force, etc. Either may be used, but a centrifugal cyclone type separator is particularly preferable. The refrigerator 16 has a refrigeration cycle, and adjusts the temperature of the air passing through the water recovery device 17 by supplying cold heat or warm heat to a heat exchanger 18 extended to the water recovery device 17. . That is, when the cooling air is generated, the heat exchanger 18 is connected to the evaporator side of the refrigeration cycle, and when the high temperature air is generated, the heat exchanger 18 is connected to the condenser side to appropriately supply necessary heat energy. ing. The refrigerator 16 is preferably a refrigerating cycle or a heat cycle device such as a heat pump capable of generating and utilizing cold heat and warm heat as described above, but may be provided with a separate heat source such as a duct heater.

The flow of the first embodiment will be described. First, the rear valve 35 of the hopper ejector 20, the lower valve 36 of the sludge separator 13 and the blower 1 are described.
5, the rear valve 37 of the vacuum pump 14 is opened, the valve 38 below the vacuum pump 14 is closed, the three-way valve 39 located behind the hopper ejector 20 is in the circulation direction, and the freeze-grinding device 12-sludge separator 13-hopper ejector is used. The circulation path of 20 and the circulation path of the freeze-grinding device 12-sludge separator 13-water recovery device 17-hopper ejector 20 are opened. Then, while the operation of the blower 15 and the refrigerator 16 is started, the sludge inlet of the freeze-pulverization device 12 is opened and a predetermined amount of sludge is introduced from the sludge tank 10.

After the sludge is charged, cooling air is introduced from the chamber 11 into the freeze-grinding device 12 through the cooling air injection port while adjusting the wind speed with an inverter. The cooling air introduced into the freeze pulverizer 12 is swirled 26
And the sludge previously charged by the swirling flow 26 is scattered and frozen. At this time, the cooling air swirl flow 2
Cold heat is evenly transferred to the sludge by 6 and freezing progresses rapidly. Here, freezing of sludge means freezing of water contained in the sludge, and the sludge is present in a state of containing granular ice.

In addition to the freezing, the sludge containing the ice cubes is violently collided by the swirling flow 26 between the inner walls of the freeze-grinding device 12 or sludges and gradually pulverized into fine particles. Then, a part of the finely sludge is removed from the swirling flow and transferred to the sludge separator 13 as fine-grain sludge-containing air 30, where it is separated from the sludge by fine-grain ice in the sludge or crushing. The fine-grained ice present in the air is sublimated by the phase change and separated from the sludge as water vapor, and the water-containing air 32 containing the water vapor is discharged to the refrigerator 16 side. On the other hand, the sludge separated from the water-containing air 32 is discharged from the bottom of the sludge separator 13, mixed with the cooling air 33 dried by the hopper ejector 20 through the water recovery device 17, and then the freeze pulverizer. Returned to 12.

The moisture-containing air 32 introduced into the water recovery device 17 is condensed by the cold heat supplied from the refrigerator 16 via the heat exchanger 18 to undergo a phase change into water, and the water tank 19 is appropriately added. Be recovered to. Then, the cooling air 33, from which water has been separated and removed and which has been cooled by the heat exchanger 18, is again introduced into the freeze-grinding device 12 together with the sludge through the hopper ejector 20. As mentioned above,
The sludge and cooling air are circulated until the water content of the sludge reaches a specified value.

When the water content of sludge reaches a predetermined value, the lower valve 36 of the sludge separator 13 is closed and the refrigeration cycle of the refrigerator 16 is connected to the condenser side to generate high temperature air and blower. The inverter frequency of 15 is increased and the dried sludge is collected from the dried sludge collecting section 40 of the freeze-grinding device 12. When the water content of the sludge does not reach the required value, the rear valve 37 of the blower 15 and the rear valve 35 of the hopper ejector 20 are closed, and the lower valve 38 of the vacuum pump 14 is opened to close the vacuum pump 14.
To start. In this way, by further reducing the pressure, a phase change occurs at a low temperature, and the grain ice can be easily converted to water vapor.

By circulating the cooling air and the sludge in this way, the dryness of the sludge can be increased as necessary, regardless of the initial water content. Furthermore, since the freeze-drying process is performed in a closed space, odor does not leak to the outside, and since it is not necessary to add a chemical agent such as a coagulant, it has little influence on the environment. Moreover, the obtained sludge becomes easy to reuse as a dry solid.

The second embodiment shown in FIG. 2 is the first embodiment described above.
Similar to the embodiment, the freeze-grinding device 12 and the sludge separator 13
A vacuum pump 14, a blower 15, a refrigerator 16,
It is composed of a water recovery device 17 and a hopper ejector 20. In this embodiment, the description of the same components as those in the first embodiment will be omitted. The freeze-grinding device 12 has a sludge inlet, a fine-grained sludge-containing air outlet, and a cooling air jet, and a swirling flow is generated by the cooling air introduced from the cooling air jet. The freezing and pulverizing device 12 has a substantially annular shape and has a closed structure having a cavity inside the ring, and the cooling air introduced into the freezing and pulverizing device 12 circulates in the annulus while swirling along the side wall of the cavity. Is configured to.

Further, temperature detectors 22, 23, 24 are installed at the cooling air injection port side of the freeze-pulverizing device 12, the fine-grain sludge-containing air discharge port side and inside the freeze-pulverizing device 12, respectively, and the temperature is Based on the temperature measured by the detector, the controller 21 controls the cold heat supply amount in the refrigerator 16 and the sludge input amount from the sludge tank 10. Further, the pressure gauge 2 provided in the vacuum pump 14
5, the pressure inside the sludge separator 13 is maintained at a predetermined pressure. As described above, the sludge freezing temperature in the freezing and crushing device 12 and the atmospheric pressure in the sludge separator 13 may be controlled by the controller so that the freezing promotion and water separation of the sludge can be performed most efficiently and reliably. .

[0026]

EXAMPLE In this example, based on the freeze-drying treatment system of the second embodiment shown in FIG. 2, the first settling sludge (MLSS concentration: 10,900) collected from the final settling tank of the sewage treatment equipment.
The measurement result when sludge prepared in advance to have a water content of about 90 to 95% (mg / L) is treated is shown. When freeze-grinding sludge, the inverter frequency (IN
V) is 55 Hz, the cooling air temperature (temperature detected by the temperature detector 22) near the cooling air injection port of the freeze-grinding device 12 is −15 ° C., the sludge input amount is 60 mL / min, and the treatment time is 30 minutes each. Set to.

In the drying (sublimation) process, the temperature of the temperature detector 22 is set to 4 ° C. and the INV is 6 at 55 Hz.
I drove for hours. In addition, a mohno pump with a water content of 90% and a roller pump with a water content of 95 to 99% were used for sludge charging. In addition, the temperature detector 2 installed in such a system
The temperature inside the device and the blower air volume in the freeze-drying treatment of sludge were measured by 3, 24, and a pressure gauge 25, and the recovery rate of the dried sludge and the separated water after the recovery treatment was obtained.

As a result, in the sludge prepared to have a water content of 90 to 95%, separation of water from the sludge due to the sublimation phenomenon was confirmed,
Furthermore, the lower the water content, the shorter the time required for freeze-drying and the more efficient the treatment. Separation water recovery rate is about 1
It is 50% to 270%, and it can be seen that water in the air was also recovered at the same time. From this, it was suggested that this device could not only freeze-dry the sludge but also efficiently remove and recover water from the sludge and reuse the separated water.

[0029]

As described above, according to the present invention, a swirling flow is generated by cooling air to freeze sludge while crushing it into fine particles, so that rapid freezing can be realized and the sludge treatment time can be shortened. As a result, sludge and water can be easily separated, so that sludge can be treated with high efficiency. Further, since the water contained in the sludge and the water in the air are frozen, crushed, and then sublimated, reliable water separation is possible, and energy saving can be expected. Furthermore, since the entire process of freeze-drying sludge is performed in a closed space, it is possible to suppress the generation of offensive odors, and since it is not necessary to add chemicals such as coagulants, the impact on the environment is minimized. be able to.

By circulating the sludge until the water content in the sludge reaches the required value, it is possible to easily set the water content of the sludge to the required value and to easily reuse the recovered sludge. become. Further, by circulating the cooling air in the closed space without discharging it, it is possible to prevent leakage of a bad odor to the outside, and it is possible to minimize the supply of cold heat, which contributes to energy saving. Furthermore, by recovering the water separated from the sludge by sublimation, highly pure water can be recovered, and the range of reuse of the recovered water is widened.

[Brief description of drawings]

FIG. 1 is an overall schematic configuration diagram of a sludge concentrating device according to a first embodiment of the present invention.

FIG. 2 is an overall schematic configuration diagram of a sludge concentrating device according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a conventional sludge concentrating device.

[Explanation of symbols]

10 Sludge tank 11 chambers 12 Freezing and crushing equipment 13 Sludge separator 14 Vacuum pump 15 Blower 16 refrigerator 17 Water recovery device 18 heat exchanger 19 water tank 20 hopper ejector 21 Controller 22, 23, 24 Temperature detector 25 pressure gauge 30 Air containing fine sludge 32 Moisture-containing air 33 Cooling air

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masaru Sanada             2-13-1, Peony, Koto-ku, Tokyo Stock market             Shamaegawa Works (72) Inventor Yoshito Nakajima             2-13-1, Peony, Koto-ku, Tokyo Stock market             Shamaegawa Works F-term (reference) 3L113 AA09 AC21 AC24 AC59 AC60                       AC67 BA37 CA02 DA06 DA10                 4D059 AA03 AA05 BD01 BD34 BD40                       BE39 BE51 BF05 BF15 BJ09                       BJ17 BK11 BK30 CA01 CB30                 4D067 CG04 EE27 EE32 EE35 GA03

Claims (7)

[Claims] 1. A method for freeze-drying sludge, which freezes and separates water contained in sludge, wherein cooling air is jetted into the first closed space to freeze the water contained in the sludge. Meanwhile, a step of pulverizing the sludge by the swirling flow generated by the cooling air to make it fine, and guiding the sludge from the first closed space to the second closed space held in a negative pressure state And a step of sublimating fine-grained ice generated from the sludge by freezing in the second closed space to separate water, and a freeze-drying treatment method of sludge. 2. The sludge from which water has been separated in the second closed space is returned to the first closed space, and the sludge is further added as necessary until the water content reaches a predetermined value. The method for lyophilizing sludge according to claim 1, which is circulated. 3. A step of cooling the air containing water separated from the sludge in the second closed space to condense and separate the water in the air, wherein the cooling air from which the water is removed is cooled. The method for freeze-drying sludge according to claim 1 or 2, wherein the sludge is returned to the first closed space and used for freezing the sludge and generating a swirling flow. 4. The sludge is recovered by introducing heated air into the first closed space when the water content of the sludge separated from the water reaches a predetermined value. 4. The method for freeze-drying sludge according to any one of 3 to 3. 5. A freezing and pulverizing device for producing a swirling flow by introducing cooling air, and crushing the sludge into fine particles while freezing the water in the input sludge by the swirling flow; Means for sucking fine-grained sludge by pressure suction,
The sludge separator for separating the fine-grained ice produced by the freezing from the sucked sludge, the fine-grained ice separation from the sludge in the sludge separator is mainly the fine-grained ice using the negative pressure. A freeze-drying treatment system for sludge, which is characterized in that it is carried out by a phase change of water vapor to steam. 6. The sludge discharged from the sludge separator,
The sludge freeze-drying treatment system according to claim 5, wherein a sludge return passage for returning to the freezing and crushing device is provided and is circulated until the water content of the sludge reaches a predetermined value. 7. A water recovery means is provided for condensing and recovering the water vapor separated by the sludge separator by cold heat from a refrigeration cycle, and the cooling air from which water has been removed by the water recovery means is fed to the freeze pulverizer. The freeze-drying treatment system for sludge according to claim 5 or 6, wherein a cooling air return passage to be introduced is provided.