JPS5929970A - Method and device for drying muddy material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to sewage sludge, raw sludge, general wastewater treatment, sludge, and other muddy materials that have been reduced in water content to, for example, 60 to 90% by concentrating or dehydrating them. The present invention relates to a drying method and apparatus for drying objects with high efficiency and obtaining granular dried products.

Conventionally, sludge discharged from sewage treatment facilities and the like has been previously digested or concentrated and dehydrated, and then treated by methods such as landfilling, returning to farmland, incineration, and composting.

However, in recent years it has become increasingly difficult to secure disposal sites.
In order to minimize the amount of waste to be disposed of, we have had no choice but to rely on drying and incineration.

Generally, these muds have a high water content, and in addition, their stickiness and fluidity pose great obstacles to the heat transfer operation described above. In particular, when the moisture content is high, it is no exaggeration to say that the overall incineration process is dominated by the method of reducing the moisture content before combustion begins, that is, the drying operation.

Conventional sludge incinerators are devices that have functional parts that are merely terminologically distinguished, such as a drying zone and a combustion zone, in the same machine, but due to the strong demand for energy-saving and self-combustion incinerators, for example In multi-stage furnaces, hot air is circulated in the upper drying zone to stabilize and increase the efficiency of the drying process, and fluidized bed furnaces have also been devised that are equipped with a multi-stage furnace type drying mechanism at the top of the furnace.

As described above, in the drying and incineration treatment of sludge, it is expected that further improvements will be made in dryers and drying methods in the future.

An effective method for disposing of sludge other than the above-mentioned incineration treatment is to return it to farmland, and in this case, in addition to composting, returning dried matter to farmland is also widely practiced. From the viewpoint of using this method, it is preferable to use a granular dried product that does not have problems such as scattering of fine powder.

The adoption of fluidized fluidized furnaces is expected to increase further in the future.
Due to the high movement intensity of the materials inside the furnace, very fine incineration ash is emitted. This ash problem should be alleviated considerably if granular dry matter with a strength higher than that in the furnace is introduced.
The present inventor has confirmed that when a dry product that is hard and firm in the form of granules is incinerated using a rotary kill machine, it becomes granular ash, and that by adjusting the incineration temperature, a granular fired product can be obtained.

As mentioned above, it is understood that the role of the dryer is important in realizing a good incineration process, but the performance of the dryers currently in general use is still insufficient. The reality is that this cannot be said.

Among conventionally used dryers, the most effective and proven one for treating muddy materials is a horizontal cylindrical rotary dryer with internal rotating blades. In this device, the sludge that is thrown into the container will stick to the vessel wall and form agglomerates, so it is scraped up with a scraping plate on the inside of the cylinder, and the fallen material is crushed by a rotating blade. The drying efficiency is improved by this method.

While other conventional models have good drying efficiency,
There are problems such as a large amount of fine powder mixed into the product and a large amount of dust contained in the exhaust gas.

Another type of conventional dryer that has a proven track record is the indirect heating type horizontal stirring dryer. This mainly consists of one or two hollow shafts, and a plurality of hollow wedge-shaped or annular pipes attached to these shafts.
It is dried by flowing steam or a heat medium inside. Since this dryer is an indirect heating type, the amount of exhaust gas is extremely small, which is advantageous in terms of deodorization and the like.

However, on the other hand, there is no means to mechanically recover the reduction in drying efficiency due to the adhesion of muddy substances, and therefore a method is taken in which a portion of the dried product is returned to its original state and mixed. In addition, the structure is complicated and there is a limit to increasing the size, and there is also the problem that a large amount of fine powder is mixed into the product.

It is an object of the present invention to provide a method and apparatus for eliminating the above-mentioned problems of conventional dryers and efficiently producing high value-added dry* products.

That is, in the present invention, the slurry is forced into the bottom of the drying chamber or from below the side wall of the drying chamber, hot air is introduced, and the slurry is forcibly rolled by the rotating action of a rotatable stirring blade. This method of drying a slurry is characterized by granulating and drying the slurry, and continuously or intermittently overflowing and discharging the dried product from an outlet of the drying chamber.

Further, the present invention provides a granulation mechanism consisting of stirring blades rotating horizontally in a vertical cylindrical drying chamber, and a slurry supply port and hot air introduction at the bottom of the drying chamber or the lower side wall of the drying chamber. This sludge drying apparatus is characterized in that an overflow weir is provided above the drying chamber and connected to a dry material discharge port.

Next, an embodiment of the present invention will be described based on the drawings.A stirring blade 2 is attached to a vertical rotating shaft in a vertical cylindrical drying chamber 1.
is provided. On the bottom plate of the drying chamber 1, two slurry supply pipes 6 connected to a pressure feeding device 5 such as a piston pump or a snake pump are branched symmetrically with respect to the center point of the bottom plate (three or more pipes may be provided). Although the supply pipe 6 is connected in the vertical direction, it may be connected to the lower part of the side wall of the drying chamber 1. A hot air introduction pipe 8 connected to the blower 7 is connected to the lower part of the side wall of the drying chamber 1 in a tangential and horizontal direction to the side wall, but it may also be connected to the bottom plate of the drying chamber 1. Further, a dry matter discharge pipe 14 is connected to the upper side wall so as to be inclined downward. The stirring blade 2 is rotated by a driving machine B via a υ gear box 4.

In the figure, 9 is an airtight discharge device such as a rotary damper, and 10
11 is a dry exhaust gas exhaust pipe, 12 is a hot air oven (or heat exchanger), and 13 is an overflow weir for leading the dried product to a dry product discharge pipe 14.

As shown in the figure, a plurality of supply pipes 6 are provided on the bottom plate of the drying chamber 1 symmetrically with respect to the center thereof, and hot air introduction pipes 8 are provided symmetrically with respect to the center of the bottom plate at the lower part of the side wall of the drying chamber 1. It is particularly desirable to provide a plurality of them in a tangential direction to the side wall.

It is preferable that the stirring blade 2 has an inclination angle of the blade plate 2' of 5 to 30 degrees with respect to the horizontal direction as shown in the diagram.
A two-blade type in which two blade plates 2' are assembled on opposite sides of the rotation axis is most suitable. Feather plate 2
In the illustrated example, the shape of ' is a flat plate, but it may be a curved plate. The stirring blades 2 are designed and operated in such a way that the stirring blades 2 are arranged vertically in multiple stages at intervals of 40 or more, and the circumferential speed of the tip in the longitudinal direction of the blade plate 2' is 0.5 to s2, 1/sec. It is preferable.

Thus, the sludge is supplied to the drying chamber 1 through the pressure feeding device 5 through the supply pipe 6, and the hot air is supplied to the blower 7 through the hot air introduction pipe 8.
It is then introduced into the drying chamber 1.

The slurry that has entered the drying chamber 1 is dried and subjected to a kind of forced transfer granulation effect by the action of the stirring blades 2, so that it becomes roundish granules. The slurry having a high moisture content that has entered the drying chamber 1 adheres thinly and evenly to the surface of the dried material, which has already become granular, due to the action of the stirring blades 2. Therefore, the water evaporation rate is always kept at its highest. Particles that have become large in size due to dry matter adhering to and growing on the surface are divided into two or three at a certain point, and the particle size range of the dry matter is determined by the properties of the slurry and the circumferential speed of the stirring blade 2. Equilibrium is reached at this value.

The above-mentioned particle group moves circularly along the side wall of the drying chamber by the stirring blade 2, and since the circumferential speed is fastest on the outer circumferential side, the particle group performs a convection movement of rising on the side wall side and descending on the central part. However, the mixability within the drying chamber 1 is good and there is very little unevenness in the moisture content. - Therefore, the amount of dry granules commensurate with the amount of slurry supplied exceeds the overflow weir 16 and the dry material discharge pipe 1
4, and is discharged continuously or intermittently by a rotary damper 9. In this way, by supplying the slurry to the lower part of the drying chamber 1 and overflowing and discharging it from the upper part, it is possible to increase the packing density of the slurry and dry matter in the drying chamber 1. The drying device can be downsized.

As mentioned above, it is desirable to introduce the hot air through a duct installed in the tangential direction at the bottom of the side wall. This is because by creating a swirling flow of hot air in the same direction as the blades 2, it is possible to prevent the hot air introduction part from being blocked by mud and to prevent the hot air from sagging.

In addition, as mentioned above, it is preferable to supply the slurry through several branch pipes from the bottom of the drying chamber 1.
This is done by supplying the dry matter discharge pipe 1 from the bottom.
．． The sludge coming out of the supply pipe 6 is cut into small pieces by the shearing force of the stirring blades at the lowest stage, and the supply pipe 6 is branched into many pipes. This is because, in the same way, it is possible to quickly and uniformly disperse the slurry within the drying chamber 1. This operation is facilitated by transporting the slurry through pipes.

The major difference between the drying device of the present invention and conventional drying devices is the way the material to be dried flows. That is, in a conventional drying device, the material moves inside the horizontal device almost like an extrusion flow, so the material to be dried has a large moisture content distribution in the direction of movement from the inlet to the outlet.

As a characteristic of muddy substances, high water content causes strong stickiness and adhesion, while low water content makes it easy to powder due to actions such as stirring, so conventional equipment has a major problem in that a considerable amount of dust is entrained in the exhaust gas. .

In addition, when installing an incinerator in the latter stage, the dried material does not necessarily have to have a low moisture content, and it may be sufficient to discharge it at about 30 to 60 cm. However, with conventional drying equipment, In other words, there are unstable factors such as high moisture content mud in the mud supply section adhering to the inner wall of the device, so it is impossible to operate the system to constantly discharge semi-dry material with a medium moisture content. be. Therefore, as a method to solve the above-mentioned adhesion problem, a portion of the dried product is returned via another conveyance means.

However, even in this case, the moisture content of the dry product at the outlet is required to be low for the purpose of obtaining returned products.

In the drying apparatus of the present invention, particles rotate in the drying chamber and convection movement occurs between the entrance and exit, so the moisture content distribution in the drying chamber is very small, which causes problems such as adhesion at the entrance and exit. It becomes possible to solve the problem of powdering at the outlet at the same time. In addition, by knowing the hot air conditions, exhaust gas measurement, slurry supply conditions, etc., it is possible to easily operate to obtain semi-dry products with a moisture content of 30 to 60%, and products with a low moisture content. Of course, it is also possible to obtain

Another major difference when comparing the drying device of the present invention and the conventional drying device is the difference in the drying mechanism itself.

That is, in the conventional drying apparatus, the slurry supplied as a lump of a certain size comes into contact with hot air to evaporate the moisture on the surface, and at the same time, the particle size is gradually reduced by the stirring mechanism. However, since water is lost from the surface of the agglomerates, the moisture content distribution of the agglomerates is high inside and low at the surface. Therefore, the water inside the grains faces great resistance to reaching the surface and volatilizing.

On the other hand, in the drying apparatus of the present invention, since the high water content sludge is spread thinly on the surface of the dried particles, the resistance due to internal diffusion of water becomes almost zero. What can be said theoretically is that in the conventional device, the particle temperature becomes high and the particles may burn, producing a strong odor, whereas in the device of the present invention, the particle temperature is low, the odor is weaker, and the temperature of the exhaust gas is lowered. It has the advantage that it can be lowered and the humidity can be raised much higher.

This alone shows that the thermal efficiency is high.

Furthermore, since the device of the present invention can increase the relative humidity of the dry exhaust gas, it is also practical to carry out an energy-saving process of cooling and dehumidifying it by some method, such as water spraying, and then reheating it and reusing it as a heat source for drying. Become something. This energy-saving effect appears in the form of a significant reduction in the cost of processing foul-smelling gas. In the present invention, it is preferable to set the drying conditions so that the temperature of the dry exhaust gas is 90° or less and the relative humidity is 30% or more.

Next, examples of the drying apparatus of the present invention will be described.

■ Drying device specifications (units not indicated are throat)・O body...500φxsoohi (effective volume 0, 1
i) O stirring blade...length 490. Width 40. Inclination angle 15° with respect to horizontal plane, spacing between two blades O blades...1001 Number of stages 30 Power for stirring...3. TSKW, rotation speed 100 rp
mO heat source; hot air stove with heavy oil burner, 350°OX 5.5
NW? A1i inO test sludge: ■ Sewage mixed dehydrated cake, moisture content 78% ■ Human waste activated sludge, moisture content 84. In addition, both ■ and ■ were dehydrated with a belt press with the addition of an organic polymer flocculant. It is.

■ Experimental results As is clear from the experimental results above, the evaporation capacity is 400~4.
50 seconds - HtO/h, blur conventional dryer 200 seconds -
)120/h,,? That's about twice as much. This is the result of using a vertical device to perform highly efficient drying on the particle surface.

When the dried product obtained in the above manner was incinerated in a rotary kiln, it ignited in a short time after being put into the kiln and burned without pulverizing.When it was kept in the firing temperature range, the unconfined compressive strength was 2 hours, and 7 particles of granules were formed. A baked product was obtained. This is because a dried product with high strength was obtained by forced rolling granulation while drying.

By the way, solids that have fuel value generally have a moisture content of 40%.
It is said to have an ignition point nearby, because the volatilization of water is limited by internal resistance and the temperature of the product rises. Therefore, it is more rational to put the waste into the incinerator without drying it to a moisture content of 40% or less.

The current method of burning incineration ash is ashing.

Pre-treatments such as crushing, mixing, granulation, and drying are required, which increases equipment costs, running costs, etc., but according to the present invention, the above unit operations can be performed without It is possible to dry and incinerate materials with high efficiency and save energy, and the final disposal product has high added value.The device structure is simple and can be manufactured at low cost, and operation and maintenance are simple. There are many practical benefits that can be obtained by doing this.

[Brief explanation of the drawing]

The drawing is a partially sectional front view of an embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Drying chamber, 2... Stirring blade, 2'... Vane plate, 6... Drive machine, 4... Gear box, 5... Pressure feeding device, 6... Supply pipe, 7... Blower, 8... Hot air introduction pipe, 9... Rotary damper, 10... Discharge port, 11... Exhaust pipe, 12... Hot blast furnace (or heat exchanger), 16... ... Overflow weir, 14... Dry matter discharge pipe. 361

Claims (1)

[Scope of Claims] 1. Supplying sludge and hot air to the lower part of the drying chamber, granulating and drying the sludge while forcibly rolling the sludge by the rotating action of stirring blades, and granulating and drying the sludge into the dryer. A sludge drying method characterized by overflowing and discharging from an outlet in a chamber. 2. The slurry is press-fitted from a plurality of locations symmetrically with respect to the center in the cross-sectional direction of the drying chamber, and the hot air is injected symmetrically with respect to the center and in a plurality of locations tangentially to the side wall of the drying chamber. Claim 1 provided from the point
The method described in section. 5. The method according to claim 1 or 2, wherein the slurry is dried to a water content of 30 to 60 and then discharged. 4. The dry exhaust gas discharged from the drying chamber is heated to a temperature of 90°C.
The method according to claim 1, 2 or 3, wherein the air is evacuated at a relative humidity of 30 - or more. 5. A granulation mechanism consisting of horizontally rotating stirring blades is provided in a vertical cylindrical drying chamber, and a slurry supply port and a hot air inlet are provided below the drying chamber. A sludge drying device characterized by having an overflow weir connected to a dry material discharge port above the chamber. 6. A plurality of the slurry supply ports are arranged at symmetrical positions with respect to the center in the cross-sectional direction of the drying chamber, and the hot air introduction ports are arranged at symmetrical positions with respect to the center of the drying chamber and on the side wall of the drying chamber. 6. The device according to claim 5, wherein a plurality of devices are arranged in a tangential direction. Z. The apparatus according to claim 6, wherein the slurry supply port is provided at the bottom of the drying chamber, and the hot air introduction port is provided at the lower side wall of the drying chamber. a The granulation mechanism including the stirring blades is configured by arranging stirring blades having two blades inclined at an angle of 5 to 30 degrees with respect to the horizontal direction in multiple stages. The device according to paragraph 5, paragraph 6 or paragraph 7.