JP7468578B2 - Method and device for drying liquid-containing material - Google Patents

Description

The present invention relates to a method and device for drying liquid-containing materials (water-containing materials when the liquid is water), and more specifically to a method and device for drying liquid-containing materials in a slurry, paste, or other state. One aspect of the present invention relates to a method and device suitable for drying water-containing materials such as various sludges discharged from water treatment processes, i.e., precipitates, filtrates, coagulation treatment sludge, and biological treatment sludge, or for drying liquid-containing waste containing liquid and solid matter in various manufacturing processes, or for drying liquid-containing materials such as organic fermentation residues.

As a method for drying sludge, Patent Document 1 describes a method in which the sludge is sifted, then dehydrated, and then dried with hot air.

Patent document 2 describes how fragmented sludge is dried while being moved around in a drying chamber.

Patent document 3 describes how sludge treated in a dehydration device having a gravity filtration section and a dehydration section is cut into pieces and dried.

JP 2000-263098 A JP 2009-101276 A JP 2016-209814 A

It is well known that a large amount of energy is required to evaporate water. In addition, water-containing materials such as biological treatment sludge are more difficult to evaporate than simply water molecules due to the hydration of water with solids, the presence of proteins and carbohydrates that have the property of holding water, or the fact that the coagulant holds water. Therefore, water-containing materials are very difficult to dry, and even with the methods of Patent Documents 1 to 3, it was not easy to sufficiently evaporate the water and dry the material.

In addition to temperature (heat) and humidity (saturated water vapor pressure), important factors in drying include the expected flow (wind force, wind speed) for quickly moving the water vapor saturated layer at the interface where water and gas meet. The present invention provides a method and device for efficiently drying liquid-containing materials by skillfully combining and controlling these factors related to the evaporation of moisture.

[1] A method for drying a slurry or paste-like liquid-containing material containing a liquid and particles, comprising the steps of:
A method for drying a liquid-containing material, comprising: an adhesion step of adhering the liquid-containing material to a planar portion of a body having a planar portion; and a drying step of drying the liquid-containing material thereafter.

[2] A method for drying a liquid-containing material according to [1], in which the planar portion has slit-shaped gaps.

[3] A method for drying a liquid-containing material according to [1], wherein the planar portion is mesh-like.

[4] A method for drying a liquid-containing material according to [1], in which the planar portion has irregularities.

[5] The method for drying a liquid-containing material according to [1], further comprising a liquid-draining step of draining the liquid-containing material adhered to the planar portion after the adhesion step.

[6] The method for drying a liquid-containing material according to [5], wherein the liquid-draining step is carried out by placing the body having a liquid-containing material adhering surface portion in an upright position.
[7] The method for drying a liquid-containing material according to [6], wherein in the liquid-draining step, heat is applied so that the liquid-containing material adhering to the planar portion can be maintained at a desired temperature.

[8] A method for drying a liquid-containing material according to [1], in which, in the drying step, room temperature or heated gas is caused to flow along the surface of the liquid-containing material adhering to the planar portion to perform drying.

[9] A method for drying a liquid-containing material according to [8], in which the flow rate and/or direction of the gas is changed during the drying process.

[10] A method for drying a liquid-containing material according to [9], in which the body having a liquid-containing material adhering surface portion is placed in an upright position and the drying step is carried out.

[11] A method for drying a liquid-containing material according to [10], in which the rising angle of the body having a liquid-containing material adhering surface portion is changed in the drying process.

[12] A method for drying a liquid-containing material according to [9], in which the top-bottom direction of the body having a liquid-containing material adhering surface portion is reversed in the drying step.

[13] A drying device for a liquid-containing material in the form of a slurry or paste that contains liquid and particles, the drying device being characterized by having an attachment means for attaching the liquid-containing material to a planar portion of a body having a planar portion, and a drying means for drying the liquid-containing material thereafter.

[14] A drying device for a liquid-containing material according to [13], wherein the planar portion has a slit-shaped gap.

[15] A drying device for liquid-containing materials according to [13], wherein the planar portion is mesh-shaped.

[16] A drying device for liquid-containing material according to [13], in which the planar portion has irregularities.

[17] A drying device for liquid-containing material according to [13], further comprising a liquid-draining means for draining the liquid-containing material adhering to the planar portion.

[18] A drying device for liquid-containing material according to [17], which has a standing means for setting the body having a liquid-containing material adhering surface portion in an upright state.

[19] A drying device for liquid-containing material according to [18], which has a means for applying heat so that the liquid-containing material adhering to the planar portion can be maintained at a desired temperature.

[20] The drying device for liquid-containing material according to [13], wherein the drying means is a means for drying the liquid-containing material by flowing room temperature or heated gas along the surface of the liquid-containing material attached to the planar portion.

[21] A drying device for a liquid-containing material according to [20], having a means for changing the flow rate and/or direction of the gas.

[22] A drying device for liquid-containing material according to [21], which has a standing means for setting the body having a liquid-containing material adhering surface portion in an upright state.

[23] A drying device for liquid-containing material according to [22], which has a means for changing the standing angle of the body having a liquid-containing material adhering surface portion.

[24] A drying device for liquid-containing material according to [22], which has a means for reversing the top-bottom direction of the body having a liquid-containing material adhering surface portion.

According to the present invention, even liquid-containing materials that are difficult to dry, such as slurries and pastes, can be attached to the planar portion of a planar portion-equipped body and dried efficiently.

FIG. 2 is a diagram showing the configuration of a planar portion-equipped body. FIG. 2 is a diagram showing the configuration of a planar portion-equipped body. FIG. 2 is a diagram showing the configuration of a planar portion-equipped body. FIG. 2 is a diagram showing the configuration of a planar portion-equipped body. FIG. 2 is a diagram showing the configuration of a planar portion-equipped body. FIG. 2 is a diagram showing the configuration of a planar portion-equipped body. FIG. 2 is a diagram showing the configuration of a planar portion-equipped body. FIG. 2 is a diagram showing the configuration of a planar portion-equipped body. FIG. 4 is an explanatory diagram of a method for forming an adhesion layer. FIG. 4 is an explanatory diagram of a method for forming an adhesion layer. FIG. 4 is an explanatory diagram of a method for forming an adhesion layer. FIG. 4 is a configuration diagram of a frame-shaped holder and a plane-shaped portion-equipped body. FIG. 4 is a configuration diagram of a frame-shaped holder and a plane-shaped portion-equipped body. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. 13 is an explanatory diagram of an experimental example of draining. 13 is a graph showing the results of a drainage experiment. 13 is a graph showing the results of a drainage experiment. 13 is a graph showing the results of a drainage experiment.

The present invention will be described in more detail below.

[Liquid-containing matter]
In the present invention, the liquid-containing material to be dried is in the form of a slurry or a paste. The term "slurry" as used herein refers to a liquid-containing material in which solid matter is suspended in a liquid. The term "paste" refers to a liquid-containing material that has fluidity but is more viscous than a slurry. Specific examples of liquid-containing materials include, but are not limited to, biological treatment sludge from wastewater, particularly wastewater containing organic matter, sludge generated in a wastewater treatment process, floating scum, and other water-containing materials, such as residues generated in methane fermentation, alcohol fermentation, lactic acid fermentation, hydrogen fermentation, oxidative fermentation, and acetone-butanol fermentation, or residues discharged during the production of soy sauce or soy milk. The liquid-containing material may be a non-aqueous liquid-containing material that contains a non-aqueous liquid other than water, such as oil or an organic solvent, and a solid substance, and is in the form of a slurry or a paste, or may be a liquid-containing material that contains water and a non-aqueous liquid and is in the form of a slurry or a paste.

[Planar portion-equipped body]
In the present invention, the liquid-containing material is adhered to the planar portion of a planar portion-equipped body and dried. The planar portion may be any shape that extends two-dimensionally, such as a plate, a sheet, a net, a cloth (particularly a woven cloth), or a lattice. The planar portion may be flat or curved, such as a corrugated plate.

Suitable surface parts include a lattice-like part, net, woven fabric, nonwoven fabric, water-permeable film, etc. A suitable lattice-like surface part is a lattice-like part in which thin rod-like bodies are arranged in parallel and connected with a binding material such as string. The rod-like bodies may be round or square rod-like, but a round rod-like body with a circular cross section is preferred.

Synthetic resins are suitable for the materials of the surface parts of the rods and binding materials, taking into consideration the problems of water absorption, corrosion, and salt precipitation. It is preferable to select synthetic resins that have excellent properties such as water resistance, heat resistance, and weather resistance.

When the planar portion is plate-shaped or sheet-shaped, a number of holes may be provided penetrating the planar portion in the thickness direction. The more holes there are, the better the water permeability, but there is a risk of solid matter leaking out. It is desirable to have at least one hole per 1 cm square. There is no limit to the shape of the hole, and it may be polygonal, circular, or complex. On the other hand, the diameter of the hole needs to be adjusted according to the state of the material to be dried. If the hole is too large, there is a risk of solid matter leaking out, and if it is close to the size of the solid matter, the hole may be clogged with solid matter and become blocked. If the hole is too small, it takes time for the liquid to pass through and the permeability is poor. In consideration of the permeability of the liquid, the hole diameter or width is preferably 0.1 mm to 10 mm, especially 0.5 to 5 mm, and it is good to design the appropriate center hole diameter and hole diameter range according to the state of the material to be dried.

The planar portion-equipped body may consist of only a planar portion, or may have a frame portion provided around the entire periphery of the planar portion or around a pair of parallel sides.

The object having a planar portion may be in the form of a container, with the bottom surface of the container being the planar portion.

An example of a body having a planar portion is shown in Figures 1 to 8.

Figure 1 shows a planar part-equipped body 1 consisting of a simple flat tray (18 cm x 30 cm) with no holes in the bottom plate. (b) is a cross-sectional view taken along line B-B in (a).

Figure 2 shows a planar body 2 consisting of a tray with a punched plate having a number of holes 2a on the bottom plate. (b) is a view taken along line B-B in (a).

Figure 3 shows a planar body 3 made of a plate with a slit 3a in the bottom plate that is wide enough for liquid to pass through. (b) is a view taken along line B-B in (a).

Figure 4 shows a mesh-like surface-equipped body 4 made by connecting bamboo strips like a raft. (b) is a view taken along line B-B in (a).

Figure 5 shows a lattice-like surface-equipped body 5 made using a net (for a screen door, e.g., 18 mesh) 5a. (b) is a cross-sectional view taken along line B-B in (a). Although not shown, a lattice made of a filter cloth for a dehydrator (made of polypropylene, plain weave) or a water-permeable nonwoven fabric sheet may be used instead of the net 5a.

The planar body may be a planar body 5' made by stretching a water-permeable film 5f over a wire mesh 5m instead of a net 5a, as shown in FIG. 5(c).

6 shows a planar portion-equipped body 6 made of a plate having unevenness (comb-shaped) on its surface, with (b) being a cross-sectional view taken along line BB in (a).
By forming the recesses, spaces are created for the liquid to seep out, and in the subsequent liquid draining step, particularly when the planar portion-equipped body is held upright to drain the liquid, the liquid can be more efficiently removed.

7 shows a planar portion-equipped body 7 made of a plate having irregularities (triangular protrusions) on its surface, with (b) being a view taken along line BB in (a).
The expected effect is similar to that of unevenness (triangular protrusions), but since the flow of gas on the slope during drying will be smoother, it is expected to have the effect of further increasing the removal efficiency of the vapor-saturated layer.

Figure 8 shows a planar body 8 made of a plate with unevenness (wave-like) on its surface. (b) is a view taken along line B-B in (a).

[Method of attaching liquid-containing material to a surface-shaped portion-equipped body]
The liquid-containing material may be applied to the planar body by coating or spraying. When the liquid-containing material has high fluidity, such as a liquid state, the liquid-containing material may be filtered through the planar body or may be poured into the planar body and filtered.

After the liquid-containing material is applied to the planar body, the top surface of the material may be smoothed flat.

The preferred thickness of the deposit when spread evenly varies depending on the properties of the liquid-containing material, but in the case of biological treatment sludge or fermentation residues, if the deposit is too thick, the drying time will be longer, and if it is too thin, the packing efficiency will be low and the volumetric efficiency will be poor, so the thickness at the time of drying is preferably 0.1 to 20 mm, and especially 1 to 5 mm.

The liquid-containing material may be applied to the entire surface of the planar portion, or may be applied only to the surface of the planar portion excluding the peripheral portion. In the latter case, the distance between the liquid-containing material application area and the peripheral portion of the planar portion is preferably 30 cm or less, more preferably 10 cm or less.

Specific examples of how liquid-containing materials can be attached to a surface-equipped body are shown in Figures 9 to 11.

Figure 9 shows a method of attaching the liquid-containing material by straining a slurry-like liquid-containing material onto a planar body. As shown in the figure, a form 11 is placed on the planar body 10, and the liquid-containing material 13 in the tank 12 is poured into the form 11 to form an attached layer of the liquid-containing material 13. The material to be dried (sludge slurry, etc.) and a flocculant may be mixed in the tank 12 to form a flocculant. In this case, although not shown, the tank 12 is equipped with a stirring blade. In addition, when the material to be dried and the flocculant are poured into the tank 12, they may be mixed by using the pouring force or flow rate. For example, both may be dropped in at the same time, and the mixture may be created by the rupture and diffusion force caused by the impact, or they may be sprayed toward the inner wall to create a swirling flow and mix.

The formwork 11 moves downward only when the liquid-containing material is poured in, preventing side leakage of the liquid-containing material and forming a layer of deposits (cake layer) with little variation. After the liquid-containing material is placed on the planar portion-equipped body 10, it moves upward in preparation for the next straining. At this time, a mechanism or process may be provided that can scrape off or wash away any material remaining on the walls inside the formwork.

When the slurry is a water-containing liquid, the entrained water after straining includes water that passes directly through the sheet-like portion-equipped body 10, water that seeps out from the sides of the deposit layer, and water that accumulates and floats on the top surface of the deposit layer. In order to remove the water from the sides and top surface, draining is performed in a later process. If water remains on the sides or top surface, a large amount of water will evaporate at once, forming a water vapor saturated layer at the interface between the water surface and the gas, slowing down the evaporation rate, or a temperature drop due to the latent heat of evaporation, reducing the efficiency of water evaporation and lengthening the drying time.

Figure 10 shows a method for forming an adhesion layer of the liquid-containing material 14 by supplying a paste-like liquid-containing material onto a non-hole surface-equipped body 16 using a spray nozzle 15 and then smoothing it using a press 17.

Figure 11 shows a method in which a paste-like liquid-containing material 19 in a measuring tank 21 on a load cell type measuring device 20 is poured onto a non-perforated surface-equipped body 22, and the upper surface is smoothed by a wiper 23 to form a layer of the deposit.

Although not shown, in FIG. 10, the liquid-containing material 14 may be leveled using a wiper 23. In FIG. 11, the liquid-containing material may be leveled using a press 17.

In the present invention, the planar body may be used individually and independently, or two or more may be held in a frame-shaped holder. Figure 12 shows an example of this, in which multiple planar body 30 are held in a frame-shaped holder 31, as shown in (a) and (b). Note that (b) is a view taken along line B-B in (a).

After the liquid-containing material is attached to the planar portion-equipped body 30, the frame-shaped holder 31 is arranged upright and parallel as shown in (c) and (d). In this case, the layers of the attached material do not face each other. Note that (c) is a view taken along the arrows C-C in (d).

In the present invention, as shown in FIG. 13, multiple frame-shaped holders 31 may be connected with connectors (hinges) 32 to form an integrated frame-shaped holder unit. This frame-shaped holder unit can be folded so that the attachment layers alternate between back-to-back and face-to-face. Note that FIG. (b) is a view taken along line B-B in FIG. (a).

[Draining (water draining)]
The planar member to which the liquid-containing substance is attached may be immediately dried, but the planar member may be placed in an upright position (standing state) to drain the liquid.

When the liquid-containing material is sludge or the like, when the liquid-containing material is attached to a planar body, the liquid floats to the surface of the layer of attached material, so it is preferable to hold the planar body upright to allow the floating liquid to fall by gravity and drain off (or drain off water in the case of a water-containing material).

When the planar body is in an upright position, the planar portion of the planar body may be vertical, or may be inclined within a range of ±45° from the vertical.

When the planar body is in an upright position (standing state) and has slit-like portions extending in one direction like a slat-like body, the slit-like portions may be oriented in the vertical direction, the horizontal direction, or a direction between the two. If the slit-like portions are oriented approximately vertically, the liquid-draining properties are improved, but the liquid-containing material is more likely to slide off. If the slit-like portions are oriented approximately horizontally, the liquid-containing material is prevented from sliding off, but the liquid-draining properties are inferior to when they are oriented in the vertical direction.

<Another embodiment of draining>
The draining may be performed by gravity filtration, centrifugal force, or squeezing. In addition, two or more of the above methods of draining using gravity, centrifugal force, and squeezing may be combined.

An example of a draining method is shown in Figures 14 to 23.

Figure 14 shows an example of draining using the gravity filtration method, in which the planar body 40 is held approximately horizontally and the slurry-like deposits 39 on the planar body 40 are drained off.

In this method, the planar portion-equipped body 40 may be at an angle, as shown in FIG. 15. When it is at an angle, drops (water droplets, etc.) are more likely to fall than when it is horizontal.

In FIG. 15, the deposit 39 is on the upper side of the planar body 40, but it may be on the lower side as shown in FIG. 16. In FIG. 16, there is less liquid in the deposit near the planar body 40 compared to FIG. 15, so it dries more easily.

Figures 17 to 20 show a method for removing paste-like deposits using a centrifugal method. Reference numeral 44 indicates a rotating shaft. In Figures 19 and 20, reference numeral 45 indicates a rotating arm, and 46 indicates a rotating bucket.

In Figures 17 to 19, rotation in either direction is acceptable. Rotation in both directions is more preferable. In Figures 17 to 19, the rotation speed is set to a value at which the deposit 39 does not peel off. With the method of Figure 20, the rotation speed can be increased compared to Figures 17 to 19, but there is a drawback in that liquid collects near the planar portion-equipped body in the deposit 39.

Figure 21 shows a form in which the adhering matter 39 is pressed by a press machine 50 to remove the liquid. While the planar body 40 is left stationary, the press machine 50 moves up and down to apply a squeezing force, causing the liquid to seep out of the adhering matter 39. In Figure 22, the adhering matter is squeezed by a roller 51. Figure 22(a) shows a form in which the position of the roller 51 is fixed and the planar body 40 moves to perform squeezing. Figure 22(b) shows a form in which the planar body 40 is left stationary and the roller 51 moves to perform squeezing. The effect of removing the liquid is the same, so either form may be used.

In FIG. 23, the planar body 40 and the deposit 39 thereon are sandwiched from above and below by presser plates 55 and 56 made of perforated plates or the like, and compressed. 57 denotes a roller.

If the material is squeezed too hard, it may get caught in the gaps of the net of the planar body, causing poor drying or making it difficult to peel off after drying. Unlike a dehydrator, the purpose is not to squeeze out the interstitial water between the particles or the water adhering to the particles, but rather to remove the liquid that seeps out (such as free water), so it is desirable to control the applied pressure appropriately.

The above-mentioned process of attaching the liquid-containing material to the planar portion of the planar portion-equipped body and the subsequent liquid-draining process may be carried out in the same space as the subsequent drying process, for example, in a drying chamber, but it is better to configure it so that it can be carried out in a separate space from the drying chamber so as not to unnecessarily increase the humidity in the drying chamber and lower the drying efficiency.

Furthermore, in the liquid-draining process, it is advisable to provide a mechanism that can apply heat to the liquid-containing material attached to the planar portion so that it can be maintained at any desired temperature. For example, the viscosity of water increases rapidly at temperatures lower than about 15°C, causing the movement speed to decrease. Even if the water is allowed to drip vertically, the droplets will stretch out and cause problems with draining. Furthermore, if the temperature of the liquid-containing material drops, not only will energy be consumed to raise the temperature in the subsequent drying chamber, but the drying time will also be longer due to the time it takes to raise the temperature.

Therefore, when erecting the body with a liquid-containing surface portion before entering the drying chamber, it is preferable to have a structure that allows heat to be applied. By providing a cover such as a hood and placing a heat source (such as an electric heater) inside to heat the inside of the hood, the dripping of water can be promoted.

The heat source can be placed anywhere, but if it is placed on the top of the hood, detailed consideration is required, as water vapor may become trapped on the surface of the heat source depending on the design and structure of the hood. If placed on the bottom, water droplets that fall may land on the top of the heat source, generating water vapor and creating a high humidity environment inside the hood, so detailed consideration of the gas flow inside the hood is required. If the heat source is placed on the side, the liquid-containing material and the body equipped with a planar portion can be heated relatively efficiently.

Steam or hot air can also be sent into the hood to raise the temperature. In this case, by directing part of the hot air introduced into the drying chamber into the hood, or directing part of the hot air taken in from inside the drying chamber into the hood, or directing part or all of the exhaust air from the drying chamber outlet into the hood, the atmosphere inside the hood can be heated and the temperature of the body equipped with a liquid-containing material adhering surface portion can be adjusted or maintained so that the temperature does not drop. Of course, it may be equipped with both a power source and hot air introduction.

The longer the residence time in this covered space, the better, but it is best to ensure at least 5 minutes, and more preferably 10 minutes. The temperature should be designed to be 15°C or higher, and preferably 25°C or higher. Humidity is not an issue.

[Drying of liquid-containing materials]
If necessary, after the liquid has been removed, the planar portion-equipped body with the liquid-containing substance attached thereto is subjected to a drying step to dry the liquid-containing substance.

This drying is preferably carried out by flowing a gas such as air along the liquid-containing material adhering to the planar body.

When performing the drying process, it is preferable to have the body with a liquid-containing material adhering surface portion in an upright position. In this case, too, the body with a liquid-containing material adhering surface portion may be vertical, or may be inclined within a range of ±45° from the vertical.

This angle may be constant throughout the drying process, or it may be changed. For example, it may be initially tilted, and then become approximately vertical when the drying of the liquid-containing material progresses and it becomes difficult for the liquid-containing material to fall off the planar portion. Also, by tilting it from a vertical position to an angle during drying, creating a depression angle with respect to the gas flow, the gas flow can be made to directly hit a position away from the periphery of the liquid-containing material adhesion surface, such as the center, thereby reducing uneven drying.

It is believed that the faster the flow rate of the drying gas along the surface of the liquid-containing object, the higher the evaporation rate; however, the gas flow may separate from the liquid surface-gas interface, making it difficult to remove the water vapor saturated layer. Also, if the flow rate is too fast, the attached liquid-containing object may fall off. Therefore, the flow rate of the drying gas flowing along the surface of the liquid-containing object is preferably 0.5 m/sec or more, for example, about 0.5 to 10 m/sec. The gas flow rate may be constant or may be varied. By varying the air speed, the way and position at which the air hits the liquid-containing object changes, which is expected to have the effect of reducing uneven drying.

The gas may be made to flow in a roughly horizontal direction along the surface of the liquid-containing object, or from below upwards, or from above downwards. The direction of this flow may also be constant or variable. Changing the direction of the airflow is expected to have the effect of reducing uneven drying.

The evaporation rate of a liquid is determined by the saturated vapor pressure near the boundary between the liquid surface and the gas, and is not governed solely by temperature conditions. However, the higher the temperature, the higher the vapor pressure, and when taking into account the latent heat of evaporation, a higher temperature is more advantageous.
In this drying method, drying is performed by blowing air, so it is advisable to adjust the temperature of the gas beforehand so that there is no temperature drop (cooling) due to the blowing air. For example, when the liquid to be evaporated is water, the gas temperature is preferably 37°C or higher, particularly about 40 to 70°C. Also, it is advisable to adjust the humidity to 50% or lower. When the material to be treated is organic, if the temperature exceeds 70°C, the proteins and the like may undergo material denaturation, and may entrap the liquid (water) or emit an unpleasant odor.
The boiling point of water at one atmospheric pressure is 100°C, but if the liquid to be evaporated is an organic solvent, the boiling point is generally lower than that of water, for example, 34.6°C for ether, 56°C for acetone, and 78.4°C for ethyl alcohol. As with water, if the temperature conditions are adjusted to the above, the liquid will be sufficiently suitable as a gas for evaporation.

The drying step is preferably carried out in a space for drying, such as a drying chamber. In this case, the planar body with the liquid-containing material attached thereto may be moved within the drying chamber.

In one aspect of the present invention, a large number of bodies having planar portions for adhering to liquid-containing materials are arranged in an upright state on a transfer member at a predetermined interval, and are continuously moved within a drying chamber. In this case, the topmost first running zone within the drying chamber may be moved from one end side to the other end side of the chamber, and then the bodies having planar portions may be moved in the first running zone to a second running zone directly below the bodies having planar portions, and in the second running zone, the bodies having planar portions may be moved from the other end side to the one end side. Furthermore, the bodies may be moved from the one end side of the second running zone to a third running zone directly below, and in the third running zone, the bodies having planar portions may be moved from the one end side to the other end side, or further, from the third running zone to a fourth running zone directly below, and in the fourth running zone, the bodies having planar portions may be moved from the one end side to the other end side.

The top-bottom direction of the body with a liquid-containing material adhering surface portion may be inverted when moving from the first traveling zone to the second traveling zone, the top-bottom direction of the body with a liquid-containing material adhering surface portion may be inverted again when moving from the second traveling zone to the third traveling zone, and the top-bottom direction of the body with a liquid-containing material adhering surface portion may be inverted a third time when moving from the third traveling zone to the fourth traveling zone. Reversing the top-bottom direction during drying changes the direction in which the wind hits the liquid-containing material, i.e., the direction in which the wind flows (upwind/downwind), and is expected to have the effect of reducing uneven drying compared to when the wind hits the material from one direction.

When transferring from the upper traveling zone to the lower traveling zone, the surface of the treated object is no longer exposed to wind, so it is preferable to provide a heating means to prevent the temperature of the liquid-containing material on the planar portion from dropping. The heating means can be a method that directly applies heat, such as an electric heater, or a method that indirectly applies heat, such as an oil heater equipped with a heat transfer tube, a hot water heater, or a hot air heater. In addition, the space can be lined with insulating material or a panel that emits far infrared rays.

It is preferable to remove the dried deposits from the surface-equipped body using a scraper or the like.

An example of the drying process is shown in Figures 24 to 27. Figures 24 to 27 show a state in which a planar portion-equipped body 30 having an attachment thereon is placed in a drying chamber 60, and hot air is blown into the drying chamber 60 from an air chamber 61.

In Figures 24 to 27, multiple planar body members 30 are held in a frame-shaped holder 31 and arranged in one tier (Figures 24 and 25) or in multiple tiers (two tiers in Figures 26 and 27). The planar body members 30 have their surfaces on which material adheres facing up and down. In Figures 24 and 26, hot air is blown from the bottom up. In Figures 25 and 27, hot air is blown from the right side to the left side of the figure.

The hot air is preferably generated by a fan and a heating means (such as a heat exchanger or heater), but the exhaust gas from gas combustion may be introduced as is, or after mixing with other gases such as outside air, or after being cooled or otherwise adjusted in temperature. The blower fan may be located upstream or downstream of the heating means. In the latter case, the blower fan may be located inside the air chamber 61 as shown in Figures 24 and 25.

However, the ventilation direction and ventilation mechanism may be other than those described above.

Figures 28 and 29 show an example of the process from attaching the liquid-containing material to the planar body to introducing it into the drying chamber and removing it from the drying chamber.

In FIG. 28, a liquid-containing material 68 is supplied onto a planar body 67 from a supply device 69, and a press device 71 smooths the top surface of the liquid-containing material and removes the liquid. Next, the planar body 67 is made to stand up and moved in an upright state within the drying chamber 60 by a transport means (not shown), and the attached matter is dried by hot air from the air chamber 61. When the planar body 67 with the attached matter dried to become a dried matter 68D leaves the drying chamber 60, the dried matter 68D is scraped off by a scraper 74, and the dried matter is stored in a storage box 76. The scraper 74 may move vertically or horizontally.

The planar body 67 is collected in a collection box 77. Reference numeral 78 denotes a gas heating means, and 79 denotes a blower fan.

In FIG. 29, a liquid-containing material 68 is supplied onto a planar body 67 from a supply device 69, and a press device 72 smooths the top surface of the liquid-containing material and dehydrates it. Next, the planar body 67 is made to stand up and moved in the standing state within the drying chamber 60 by a transport means (not shown), and the attached matter is dried by hot air from the air chamber 61. In FIG. 29, the planar body 67 moves through the upper section of the drying chamber 60, then moves to the lower section and moves through the lower section in the opposite direction.

When the planar body 67, in which the attached matter has dried and become a dried matter 68D, leaves the drying chamber 60, the dried matter 68D is scraped off by a scraper 75, and the dried matter is stored in a storage box 76. The planar body 67 is transported by a circulating transport means (not shown) and sent to the liquid-containing matter attachment process. Other reference numerals in Figure 29 indicate the same parts as in Figure 28.

As described above, the drying method and drying apparatus according to the present invention are new inventions that differ from those disclosed in Patent Documents 1 to 3 in the following respects.

Patent Document 1 (JP Patent Publication 2000-263098A) describes a sludge treatment system and treatment device that efficiently treats sludge produced by biological treatment, such as sludge that settles naturally or sludge that settles using a flocculant, using (1) a simple, small container to concentrate sludge from all fields and (2) an air-permeable, water-permeable sheet, and dries the sludge by passing hot air through the air-permeable, water-permeable sheet in the thickness direction of the sludge. This differs from the present invention in that the device is configured to dry the sludge.

Patent Document 2 (JP Patent Publication 2009-101276A) is a sludge drying method and apparatus for efficiently drying sludge in the sun, which is provided with a drying chamber configured to transmit sunlight, (1) a sludge placement section where sludge is placed and dried, and a sludge supplying means, (2) an air blowing means for blowing air within the drying chamber, and (3) a sludge drying method and apparatus configured to blow air in a direction parallel to the sludge placement surface. In other words, it is configured to utilize a drying chamber that transmits sunlight, and it is configured to supply and place sludge within the drying chamber, which differs from the embodiment of the present invention.

Patent Document 3 (JP Patent Publication 2016-209814A) is a sludge dehydration and drying system that includes a concentrating device that concentrates sludge to which chemicals have been added by gravity filtration while transporting it with a filter body, a dehydrating device that pressurizes and dehydrates the sludge concentrated in the concentrating device while transporting it between a pair of belts, a cutting device that cuts the sludge dehydrated in the dehydrating device, and a drying device that dries the sludge cut by the cutting device while transporting it on a conveyor with a ventilation structure. This system is significantly different from the embodiment of the present invention in that it is configured to blow air in the direction of travel of the belt conveyor that travels around and carries the sludge fragmented by the cutting device.

[Example 1]
＜Objective of the experiment＞
The effect of promoting drainage by setting up lattices with sludge attached will be confirmed.

<Experimental Method>
A screen door net with 18 mesh openings was stretched over a resin frame to create a screen rack with inner dimensions of 25 cm x 35 cm.

Sewage digestion sludge that had been previously flocculated was placed on this screen and its drainage characteristics were investigated.

The sewage digested sludge used in the evaluation was collected from the second digestion tank of the anaerobic sludge digester at Treatment Plant A. The TS concentration immediately after collection was 1.8%.

The flocculant used was PC696, a product sold by Kurita Water Industries Ltd., which was adjusted to a dissolution concentration of 0.2% using tap water.

100 ml of polymer solution was added to 1000 ml of sludge slurry and stirred in a beaker at a rotation speed of 100 rpm for 30 seconds. This flocculated slurry was poured onto the above-mentioned lattice frame with a 20 cm x 30 cm formwork placed on it, as shown in Figure 30.

After one minute, the formwork was removed, and a permeate collection funnel and a measuring cylinder were placed under the rack. In Case-1, the formwork was removed and the water was drained while it was held horizontally, while in Case-2, the formwork was removed and the water was drained while it was held vertically. Draining was continued for a total of 60 minutes.

The amount of drained water was measured using the graduated cylinder. The results are shown in Figure 31.

As shown in Figure 31, Case 2, which used a rack, recovered about 15% more entrained water, which reduced the amount of moisture brought into the drying chamber. If a large amount of moisture is brought in, the humidity in the drying chamber will increase, reducing the drying efficiency, and the temperature of the moisture and sludge layer will drop due to the latent heat of evaporation, leading to a decrease in evaporation efficiency.

[Example 2]
＜Objective of the experiment＞
The drying effect of setting up a rack with sludge attached to it will be confirmed.

<Experimental Method>
The sludge prepared under the conditions shown in Example 1 was placed on a lattice to drain off the water, and then lined up vertically in a commercially available horticultural greenhouse made with a vinyl cover. Warm air was blown in from the sides to investigate the drying characteristics.

A small fan was used to blow air at a speed of 3 m/sec (both the flow direction and wind speed were fixed), and drying was performed by blowing air that had been adjusted in advance to a temperature of 65°C and a humidity of 40%.

100 ml of polymer solution was added to 1000 ml of sludge slurry and stirred in a beaker at a rotation speed of 100 rpm for 30 seconds. This flocculated slurry was poured onto the above-mentioned lattice with a 20 cm x 30 cm formwork placed on it, as in Figure 30. In Case-1, after removing the formwork, nine sheets were prepared by leaving them horizontally for 59 minutes to drain the water, and these nine sheets were kept horizontally at 3 cm intervals during drying, and hot air was blown from the side parallel to the lattice to dry. In Case-2, after removing the formwork, nine sheets were prepared by standing vertically for 59 minutes to drain the water, and these nine sheets were kept vertically at 3 cm intervals during drying, and hot air was blown from the side parallel to the lattice to dry. For Case 3, after removing the formwork, nine pieces were prepared by standing them vertically for 59 minutes to drain the water, and when drying, these nine pieces were returned to a horizontal position at 3 cm intervals so that they could be held in place, and hot air was blown in from the side parallel to the lattice to dry them.

Every hour, a sample was taken from the center of the middle lattice of the nine lattices, and the moisture content of each was analyzed. The results are shown in Figure 32.

As shown in Figure 32, Case-2, where the lattice was upright, had significantly better drying characteristics than Case-1, where the lattice was horizontal, and the drying time to reach 30% moisture content was about 50% shorter. In addition, Case-3, where the lattice was left upright when draining, but then returned to a horizontal position for subsequent drying, had a drying time that was inferior to Case-2 but far shorter than Case-1. These results show that draining the lattice in an upright position contributes greatly to shortening the drying time, and that drying in an upright position can also shorten the drying time. Furthermore, a shorter drying time also means less energy is consumed for drying, which can reduce drying costs and also allows the drying equipment to be made more compact.

[Example 3]
＜Objective of the experiment＞
Using paste-like sludge, which does not require draining when adhering to a sieve, the drying characteristics are compared when the sludge is placed horizontally and when it is placed vertically during drying to confirm which is better in terms of drying effect.

<Experimental Method>
The sludge used in the evaluation was the same as that used in Examples 1 and 2, and was collected from the second digestion tank of the anaerobic sludge digestion tank at the A treatment plant. This was concentrated in a centrifuge without using a flocculant. The centrifuge used was the H-103n type manufactured by Kokusan Co., Ltd., and the centrifuge tube and bucket were selected so that 2500G could be applied, and the rotation speed was adjusted. Centrifugation was performed for 5 minutes (as the steady-state holding time excluding acceleration and deceleration time), the supernatant separated water was discarded, and the precipitate was scraped out with a spatula. This operation was repeated to prepare the required amount of concentrated sludge to be used in the experiment. The volume ratio of water to solids was 2:1 by centrifugation, and the concentration of the concentrated sludge was calculated to be approximately 5.4%, and the analytical value by the drying method was 5.5%. 50 g of the concentrated sludge prepared here was weighed out and dropped onto a 20 cm x 30 cm polypropylene flat plate (thickness: approximately 2 mm), hereinafter referred to as the "plate", and spread evenly with a spatula.

In Case 1, nine plates carrying concentrated sludge were prepared, and the nine plates were held horizontally at 3 cm intervals during drying, and hot air was blown from the side parallel to the plates to dry. In Case 2, nine plates carrying concentrated sludge were prepared, and the nine plates were held vertically at 3 cm intervals during drying, and hot air was blown from the side parallel to the plates to dry. In Case 3, nine plates carrying concentrated sludge were also prepared, and the nine plates were held vertically at 3 cm intervals during drying, but unlike Case 2, hot air was blown vertically from the bottom to the top, parallel to the plates to dry.

A small fan was used to blow air at a speed of 3 m/sec (both the flow direction and wind speed were fixed), and drying was performed by blowing air that had been adjusted in advance to a temperature of 65°C and a humidity of 40%.

Every hour, a sample was taken from the center of the middle lattice of the nine lattices, and the moisture content of each was analyzed. The results are shown in Figure 33.

As shown in Figure 33, Case-2, in which the lattice was erected, had significantly better drying characteristics than Case-1, and the drying time required to reach a moisture content of 30% was approximately 40% shorter. Additionally, Case-3, in which air was blown from below to above, was able to reduce the drying time by approximately 15% compared to Case-2, in which air was blown from the side. These results show that drying in an upright position can reduce the drying time. Furthermore, even when the lattice was erected during drying, the effect of changing the air blow direction was demonstrated, and the effect of blowing air vertically was demonstrated.

1 to 8, 10, 16, 22, 30, 40, 67 Planar portion-equipped body 15 Spray nozzle 23 Wiper 39 Deposit 44 Rotating shaft 51 Roller 57 Roller 60 Drying chamber 74 Scraper 75 Scraper

Claims (18)

A method for drying a slurry or paste-like liquid-containing material containing a liquid and particles, the method comprising the steps of: adhering the liquid-containing material to a planar portion of a planar portion-equipped body; and thereafter, drying the liquid-containing material adhered to the planar portion ,
The method for drying a liquid-containing material comprises attaching the liquid-containing material to the planar portion, standing the planar portion-equipped body vertically or at an angle within a range of ±45° to the vertical, and then carrying out the drying step . The method for drying a liquid-containing material according to claim 1, wherein the planar portion has a slit-shaped gap. The method for drying a liquid-containing material according to claim 1, wherein the planar portion is mesh-like. The method for drying a liquid-containing material according to claim 1, wherein the planar portion has irregularities. 2. The method for drying a liquid-containing material according to claim 1 , wherein in the liquid-draining step, heat is applied so that the liquid-containing material adhering to the planar portion can be maintained at a desired temperature. The method for drying a liquid-containing material according to claim 1, wherein in the drying step, drying is performed by flowing room temperature or heated gas along the surface of the liquid-containing material attached to the planar portion. 7. The method for drying a liquid-containing material according to claim 6 , wherein a flow velocity and/or a flow direction of the gas is changed in the drying step. 2. The method for drying a liquid-containing material according to claim 1 , wherein the rising angle of the body having a liquid-containing material adhering surface portion is changed in the drying step. 2. The method for drying a liquid-containing material according to claim 1 , wherein the body having a liquid-containing material adhering surface portion is turned upside down in the drying step. An apparatus for drying a slurry or paste-like liquid-containing material containing liquid and particles,
An attachment means for attaching the liquid-containing material to the planar portion of the planar portion-equipped body;
a raising means for raising the planar portion-equipped body having the liquid-containing substance adhered to the planar portion so as to raise the planar portion-equipped body vertically or at an angle within a range of ±45° to the vertical;
and a drying means for drying the liquid-containing material adhered to the planar portion . The drying device for a liquid-containing material according to claim 10 , wherein the planar portion has a slit-shaped gap. The device for drying a liquid-containing material according to claim 10 , wherein the planar portion is in a mesh shape. The device for drying a liquid-containing material according to claim 10 , wherein the planar portion has projections and recesses. 11. The drying device for a liquid-containing material according to claim 10 , further comprising a means for applying heat so as to maintain the liquid-containing material adhering to said planar portion at a desired temperature. 11. The apparatus for drying a liquid-containing material according to claim 10 , wherein the drying means is a means for drying the liquid-containing material by flowing a room temperature or heated gas along the surface of the liquid-containing material adhering to the planar portion. 16. The apparatus for drying a liquid-containing material according to claim 15 , further comprising a means for changing the flow rate and/or direction of the gas. 11. The drying device for a liquid-containing material according to claim 10 , further comprising a means for changing an upright angle of said body having a liquid-containing material adhering surface portion. 11. The drying device for a liquid-containing material according to claim 10 , further comprising a means for reversing the upside-down direction of the body having a liquid-containing material adhering surface portion.

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