JP3643845B2 - Organic sludge liquefaction reactor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reaction apparatus for liquefying solid organic sludge such as surplus sludge generated from a biological treatment apparatus of organic wastewater represented by sewage.
[0002]
[Prior art]
It is known that solid organic sludge (hereinafter also simply referred to as sludge) is placed in a hermetic container and liquefied by treatment at high temperature and high pressure. In such organic sludge liquefaction technology, in order to efficiently liquefy the sludge at low cost, it is necessary to develop a reactor having excellent operability and high device efficiency.
According to Japanese Examined Patent Publication No. 7-75718, the whole consists of a bowl-shaped hermetic cylindrical container, which has a screw mechanism for stirring at its lower part, and peels and removes solid matter adhering to the inner wall surface at its upper part. A reactor having a navel-type scraper has been proposed. In this apparatus, the dewatered sludge is supplied from the lower part of the apparatus, rises inside the container, and is liquefied during that time, and the liquefied material obtained is extracted from the upper part of the apparatus. In this case, the apparatus is heated by an external heating method, and the amount of heat necessary for the sludge liquefaction reaction is introduced into the inside through the container wall.
Such a device is a distribution-type device, and is capable of continuously treating sludge, so it is originally efficient, but its heating method is an external heating method, so it can be scaled up to When the cylinder diameter is increased, heat transfer from the outer wall of the cylinder to the axial center of the cylindrical container is deteriorated, and the uniform liquefaction reaction of sludge cannot be sufficiently achieved. For this reason, if it is going to raise the amount of heat transfer, the wall surface temperature of an apparatus will become high too much, inconveniences, such as local overheating, will arise, and as a result, the viscous material from sludge will produce | generate and adhere to a wall surface. And it is difficult to scrape and remove the sticky material adhering to the wall surface from the wall surface by the scraper, and it remains adhering to the wall surface and finally becomes a solidified product, which significantly deteriorates the heat transfer coefficient of the wall surface. . Moreover, since this viscous material has strong adhesiveness and tends to be agglomerated, clogging occurs in the storage tank, pump, and piping of the equipment. Furthermore, when solid sludge with a low moisture content and high viscosity is used, the sludge resistance is greater than the force of the leaf spring that presses the blade of the brazing scraper against the inner wall surface, and the blade contacts the inner wall surface. Since it becomes impossible to contact, the sludge of an inner wall surface cannot be peeled off, but the problem also arises that the heat transfer surface is reduced and the sludge is insufficiently heated.
[0003]
[Problems to be solved by the invention]
The present invention is an organic sludge liquefaction reaction apparatus having a screw-type cylindrical container as a whole, having a screw mechanism at the front stage and a scraper mechanism at the rear stage, and is easily solidified with high viscosity. It is an object of the present invention to provide an apparatus capable of stable operation even with sludge.
[0004]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, according to the present invention, in an external heating system reactor that continuously liquefies organic sludge in a solid state under high-temperature and high-pressure conditions, (i) the whole consists of a bowl-shaped cylindrical container; (Ii) having a screw mechanism at the front stage of the cylindrical container; (iii) having a scraper mechanism at the rear stage of the cylindrical container; and (iv) having the cylindrical shape at the middle stage of the cylindrical container. the inner diameter of the container when the R ^1, 0. 5 R ¹ ~0. 8 R ¹ having an outer diameter R ^{2 of} which both ends are sealed and a rotating cylindrical body is inserted, and (v) a lift-up type scraper mechanism is attached to the outer peripheral surface of the cylindrical body. A characteristic organic sludge liquefaction reactor is provided.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an explanatory structural diagram of an example of the apparatus of the present invention, and FIG. 2 shows an explanatory sectional view along the central axis of the container.
In these figures, 1 is a vertical cylindrical container, 2 is a rotating shaft, 3 is a screw mechanism, 4 is a cylindrical body, 5 and 6 are scraper mechanisms, 7 is a sludge inlet, 8 is a sludge liquefied material outlet, Reference numerals 9 and 10 denote lids, reference numerals 11 and 12 denote rotating shaft connecting portions, and reference numerals 21 and 22 denote heating jackets. A, B, and C respectively show the front stage part, the middle stage part, and the rear stage part in the container 1.
[0006]
A screw mechanism 3 is disposed in the front part A of the container 1. The screw mechanism 3 is for rotating through the rotating shaft 2 and pushing up the sludge supplied to the lower part of the container while stirring, and a conventional one can be used.
[0007]
In the middle part B of the container 1, a cylindrical body 4 having a lifting scraper mechanism attached to the outer peripheral surface is inserted.
The cylindrical body 4 is fixed to the rotary shaft 2 at both ends thereof, and is rotated via the rotary shaft 2. Further, both ends of the cylindrical body 4 are sealed so that sludge does not enter the inside.
[0008]
FIG. 3 shows a sectional view of the cylindrical body 4 (a sectional view taken along the line CC in FIG. 2).
In FIG. 3, d is a blade of the scraper mechanism, and e is a stopper of the scraper mechanism.
The blade d is made of a band-shaped metal plate, and its tip is formed on the blade edge. As shown in FIG. 3, these are arranged in a plurality of rows at intervals in the circumferential direction. Each of these blades is fixed to the outer peripheral surface of the cylindrical body by a stopper e such as a threaded bolt to form a lift-up type scraper.
[0009]
In the cylinder 4, the outer diameter ^{R 2} is suitably determined corresponding to the inner diameter of the cylindrical vessel ^{R 1,} in general, to decide such that ^0.5 R ^{1 ~0.8R} 1 Good. Since the lifting scraper is attached to the outer peripheral surface of the cylindrical body 4, the sludge scraping action by the scraper effectively prevents the sludge from adhering to the inner wall surface of the container. As described above, in the middle stage B of the container 1, sludge is prevented from adhering to the inner wall surface of the container, so that heat transfer from the outside to the inside of the container is smoothly performed. In addition, by inserting the cylindrical body 4 into the container 1, the sludge flows through an annular gap between the outer peripheral surface of the cylindrical body 4 and the inner peripheral surface of the container 1, so that uniform heat supply to the sludge is also achieved. It is done smoothly. As a result, in the middle stage B, a smooth thermochemical reaction of sludge is achieved. In addition, even when high-viscosity solid sludge is provided, the blade of the middle section B is pressed against the inner wall surface, and the sludge can be lifted to reliably prevent adhesion to the inner wall surface.
[0010]
The rear stage C of the container 1 has scraper mechanisms 5 and 6 inside thereof. The scraper mechanisms 5 and 6 are fixed to the rotary shaft 2 and rotate via the rotary shaft 2.
4 shows a sectional view of the scraper mechanism 6 (AA sectional view in FIG. 2), and FIG. 5 shows a sectional view of the scraper mechanism 5 (BB sectional view in FIG. 2). The scraper mechanism 5 and the scraper mechanism 6 have the same structure, but have a positional relationship in which the arrangement position with respect to the rotating shaft 2 is shifted by 90 degrees.
[0011]
Although the scraper mechanisms 5 and 6 can be various conventionally known scraper mechanisms, generally, as shown in FIGS. 4 to 5, a stroking-type scraper mechanism is used. This stroking-type scraper mechanism has a structure in which the tip (blade edge) of the blade is in contact with the inner peripheral wall of the container 1 and the rear end of the blade is supported and fixed to the rotary shaft 2 when the blade is rotated. Further, the tip of the blade comes into contact with the inner peripheral wall surface of the container 1 by stroking.
The blades g shown in FIGS. 4 to 5 have an effect of promoting uniform heating by promoting the flow of sludge to the center of the container.
[0012]
The sludge that has passed through the middle stage B of the container 1 enters the rear stage C having the scraper mechanism and rises in the container 1, but the rising linear velocity is determined by the horizontal cross-sectional area of the sludge passage in the rear stage being the middle stage. Since it is larger than the horizontal cross-sectional area of the sludge passage of B, it is significantly slower than the rising linear velocity at the middle stage B. For this reason, in the rear stage C, the sludge rises at a slow speed and is heated during that time to receive the final stage thermochemical reaction and secure a reaction time for liquefaction. The sludge introduced into the rear part C has already been liquefied to a considerable extent in the middle part B and has decreased in viscosity, so that it is difficult to adhere to the inner peripheral wall surface of the container 1. Even so, it is easy to scrape. Therefore, the scraper mechanism in the rear stage portion C does not need to have a large scraping force, and it is sufficient to use a stick-type scraper mechanism having a simple structure as described above.
[0013]
Solid organic sludge used as a raw material to be treated in the present invention includes sludge obtained by dewatering sewage sludge discharged from a normal sewage treatment plant or surplus sludge discharged from various organic wastewater biological treatment equipment. Is included.
The organic sludge is usually dehydrated by mechanical dehydration (vacuum dehydration, pressure dehydration, belt press dehydration, and centrifugal dehydration), but is not particularly limited. However, it is desirable to add sludge refining chemicals to the organic sludge before dehydration, and it is particularly advantageous to add a polymer flocculant. Therefore, regarding the dehydration method, belt press dehydration or centrifugal dehydration suitable for addition of the polymer flocculant is desirable. The organic sludge should be dehydrated so that the water content of the obtained dehydrated sludge is 60 to 90% by weight, preferably 70 to 80% by weight.
Moreover, in order to accelerate | stimulate the liquefaction, this sludge can be performed in presence of the alkaline substance as a liquefaction promoter as needed. This alkaline substance is added in a proportion of 0 to 20% by weight, preferably 0 to 5% by weight, based on the solid content in the dewatered sludge. Examples of the alkaline substance include alkali metal compounds such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium formate, potassium formate, calcium oxide, calcium hydroxide, and hydroxide. Examples thereof include alkaline earth metal compounds such as magnesium.
[0014]
In order to liquefy the organic sludge using the reaction apparatus of the present invention shown in FIG. 1, the sludge is supplied to the front part A of the container 1 through the line 23. A screw mechanism 3 that rotates via a rotating shaft 2 is attached to the front stage A, and sludge is transferred upward by the rotation of the screw mechanism.
The rotating shaft 2 is rotated by a motor M.
This front part A does not need to be heated in particular, but can be heated to 50 to 150 ° C. by an external heating method as necessary.
[0015]
The sludge transported upward by the screw mechanism 3 from the front stage A is further pushed up into the middle stage B, and rises in the gap between the outer peripheral surface of the cylindrical body 4 and the inner peripheral surface of the container 1, In the meantime it is heated. This heating is performed by a heat medium introduced into the heating jacket 22, but it can also be heated by an electric heating method.
The sludge heating temperature in the middle stage B is 150 to 300 ° C, preferably 200 to 250 ° C.
[0016]
By the screw mechanism 3 in the front stage A, the sludge is further pushed up to the rear stage C through the middle stage B, rises in the container 1, is extracted to the outside through the line 24, and is heated while the rear stage C is raised. Is done. This heating is performed by a heat medium introduced into the heating jacket 21, but it can also be heated by an electric heating method. The heating temperature of the sludge in the latter stage part C is 200-300 degreeC, Preferably it is 250-300 degreeC. The pressure in the reaction apparatus may be maintained at a saturated water vapor pressure or higher at the maximum temperature in the reaction apparatus. For example, when the temperature is 200 ° C., it is 16 kg / cm ² Abs, and when it is 300 ° C., it is 88 kg / cm ² Abs. Although this pressurization can utilize the self-generated pressure by the water vapor | steam from sludge, it can pressurize using nitrogen gas, a carbon dioxide gas, argon gas etc. as needed. The sludge residence time in the rear part C is 1 to 120 minutes, preferably 0 to 60 minutes.
By the heating in the rear stage C, the sludge undergoes a thermochemical reaction, and the liquefaction of the sludge is completed.
[0017]
The organic sludge liquefied material obtained as described above is further treated according to a conventionally known method. Such processing includes incineration processing, oil recovery processing, and the like.
The organic sludge liquefied material is excellent in transportability and can be transported by pipe pumping, vacuum car, or tank truck. Moreover, since it is excellent in spray combustibility, incineration processing by spray combustion through a burner is easy.
[0018]
【Example】
Next, the present invention will be described in more detail with reference to examples.
[0019]
Example 1
Sewage sludge was selected as the organic sludge, and the mixed raw sludge dewatered cake discharged from the standard activated sludge treatment plant was used for the test. This sludge is dehydrated with a belt press after adding a polymer flocculant. Its typical properties are a moisture content of 78% by weight, an organic matter ratio of 78% by weight and a lower heating value of 3940 kcal / kg.
[0020]
The dewatered sludge was liquefied using the continuous sludge liquefaction apparatus (processing capacity: 250 kg / hr) shown in FIG.
In the apparatus shown in FIG. 1, the height of the container 1 is 7.3 m, and the lengths A, B, and C of the front stage A, the middle stage B, and the rear stage C are respectively A = 2.4 m, B = 2.1 m and C = 2.8 m. The inner diameter R ^{1 of the} container 1 was 43 cm, and the outer diameter R ² of the cylindrical body 4 was 30 cm.
The temperature of the sludge was 30 ° C. at the front stage A, 250 ° C. at the outlet temperature of the middle stage B, and 260 ° C. at the outlet temperature of the rear stage C. The pressure in the container 1 was 85 kg / cm ² Abs.
[0021]
Organic sludge was liquefied continuously under the above conditions. This treated product was sufficiently liquid at the outlet of the reactor, and liquid sludge in a high temperature and high pressure state was discharged to a flash tank at atmospheric pressure through a pressure reducing valve. In the flash tank, the water in the sludge evaporated, and the temperature of the sludge was cooled to 100 ° C. Low boiling components such as organic acids and oily substances were discharged from the upper part of the flash tank together with water vapor, cooled to room temperature with a condenser, and stored in a dilute liquid tank. On the other hand, the concentrate remaining in the lower part of the flash tank was automatically discharged by valve operation and stored in the concentrate tank.
By the above operation, a concentrated liquid having a solid content concentration of 25% by weight and a dilute liquid having a solid content concentration of 2% by weight were obtained from dehydrated sludge having a water content of 78% by weight (solid content concentration of 22% by weight). The thick juice liquid was liquid and had sufficient fluidity.
[0022]
【The invention's effect】
By liquefying the organic sludge using the reactor of the present invention, it is possible to prevent the sludge from being converted to a viscous material due to local overheating on the reactor wall surface of the reactor, and Adhesion can be effectively prevented, and organic sludge can be liquefied continuously for a long time. In addition, according to the present invention, it is possible to provide an apparatus that can be easily scaled up and can be applied to high-viscosity solid sludge.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of the overall structure of an apparatus according to the present invention.
FIG. 2 is an explanatory cross-sectional view along the axial direction of a cylindrical container used in the present invention.
FIG. 3 is a cross-sectional view taken along the line CC in FIG.
4 is a cross-sectional view taken along line AA in FIG.
5 is a cross-sectional view taken along the line BB in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylindrical container 2 Rotating shaft 3 Screw mechanism 4 Cylindrical bodies 5 and 6 Stroke type scraper mechanism 21 and 22 Heating jacket A The front part B of the container 1 The middle part C of the container 1 The rear part d of the container 1 The lifting scraper Mechanism blade e Blade stopper f Cushion material g Blade

Claims (2)

In an external heating type reactor that continuously liquefies organic sludge in a solid state under high-temperature and high-pressure conditions, (i) the whole consists of a bowl-shaped cylindrical container, (ii) the cylindrical container (Iii) having a scraper mechanism in the rear stage of the cylindrical container, and (iv) having the cylinder in the middle stage between the front stage and the rear stage of the cylindrical container. the inner diameter of the Jo container when the R ^1, 0. 5 R ¹ ~0. 8 R ¹ having an outer diameter R ^{2 of} which both ends are sealed and a rotating cylindrical body is inserted, and (v) a lift-up type scraper mechanism is attached to the outer peripheral surface of the cylindrical body. A characteristic organic sludge liquefaction reactor.  2. The apparatus according to claim 1, wherein the scraper mechanism at the rear stage is a stroking type scraper mechanism.

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