JP7064338B2 - Indirect heating type sludge drying device - Google Patents

Description

The present invention relates to an indirect heating type sludge drying device provided with a plurality of stages of dryers that heat and dry sludge as waste while transporting it.

This type of dryer is a device for drying moisture and solvent in raw materials, and is used in various plants such as food production, sewage sludge and waste incineration plants. The drying method includes a direct heating method in which hot air is directly applied to the material to dry the material, and an indirect heating method in which the metal is heated by a heat medium such as steam and the material is dried by the heat transfer thereof. In addition to drying, these dryers are also used in processing processes such as heating, cooling, baking, roasting, and reaction.

As a direct drying method, an air flow dryer, a fluidized layer dryer, a rotary dryer and the like are known, and as an indirect heating method, a rotary dryer with a steam pipe (for example, FIG. 5 of Patent Document 1, Patent Document 2 and the like). And a groove type stirring dryer (for example, FIG. 4 of Patent Document 1) and the like are known. The indirect heating method has an advantage that the amount of exhaust gas is smaller than that of the direct heating method.

In the rotary dryer with a steam tube, for example, as shown in FIG. 5 of Patent Document 1, a large number of heating tubes extending over the entire length are concentrically arranged inside the rotary cylindrical body. The heat of the heat medium passed through the inside of the heating tube is indirectly transferred to the dehydrated sludge as the object to be treated through the heat transfer body formed by the heating tube to be dried.

As shown in FIG. 1, the conventional groove-type stirring / drying machine 100 is a groove-type (truff-type), low-speed stirring-type conduction heat transfer dryer, and is inside a groove-type trough 3 having a heat transfer jacket 2. , A heat transfer body in which heat transfer blades 5 (also referred to as paddle blades) are arranged at appropriate intervals on a single or a plurality of rotation shafts 4 is rotatably supported. The trough 3 is provided with a receiving port 6 on one end side for receiving dehydrated sludge, which is sludge to be treated, and a discharge port 7 on the other end side for discharging dry sludge. Further, the heat transfer jacket 2 is provided with a heat medium supply port 8 for supplying a heat medium and a heat medium discharge port 9 for discharging the heat medium. The rotary shaft 4 and the heat transfer blade 5 are hollow so as to communicate with each other inside, and the heat medium introduced from the heat medium supply port 8 becomes a drain through the hollow and is discharged from the heat medium discharge port 9. To. The rotary shaft 4 is driven and connected to the electric motor 11 via a transmission chain 10 or the like on the outside of the trough 3 and is rotationally driven. Further, the trough 3 is provided with an exhaust fan (not shown) in order to discharge the water vapor generated by drying, and the carrier gas (external air) is troughed from the carrier gas inlet 12 provided in the trough 3. It is sucked into the trough 3 and the water vapor is exhausted together with the carrier gas from the exhaust port 13 provided in the trough 3. The heat transfer jacket 2 is also provided with a heat medium supply port 14 for a jacket and a heat medium discharge port 15 for a jacket. The trough 3 can also be installed with a downward slope that lowers the side of the discharge port 7.

In the indirect heating type sludge dryer, steam, heat medium oil, or high-temperature water is used as the heat medium, and the heat medium (steam in the example of FIG. 1) supplied from the heat medium supply port 8 is the rotating shaft 4 and heat transfer. While being discharged from the heat medium discharge port 9 through the internal space of the wing 5, the sludge is transported to the discharge port 7 while being dried by contact with the sludge supplied from the receiving port 6, and is generated by drying. The water vapor is exhausted from the exhaust port 13 together with the carrier gas, and the sludge to be dried, which is the input raw material (dehydrated sludge), is dried to the target water content at the discharge port 7.

Japanese Patent No. 3784022 International Publication No. 2016/08843 Pamphlet Japanese Patent No. 5372187 Japanese Patent No. 6139949

The above-mentioned conventional indirect heating type sludge dryer is widely used as an energy-saving type dryer because it can dry a wet raw material having a property that makes it difficult to form a fluidized bed or a wet raw material having a strong adhesiveness with high thermal efficiency, and is a groove type. The stirring dryer is also used in processing processes such as drying, heating / cooling, baking / roasting, and reaction.

In a groove-type agitator / dryer equipped with heat transfer blades, it was thought that the higher the rotation speed of the heat transfer blades constituting the heat transfer body, the higher the evaporation rate per heat transfer area, and the more compact the device could be. Attempts have been made to increase the number of rotations of the thermal blades as much as possible to make them compact, but there is a problem that the higher the number of rotations, the higher the power consumption.

Therefore, it is a main object of the present invention to provide an indirect heating type sludge drying apparatus capable of reducing power consumption and making it compact without lowering the evaporation rate.

In order to achieve the above object, the indirect heating type dry sludge drying apparatus according to the present invention receives the sludge to be dried at the receiving port as the first means, and is provided at intervals in the axial direction of the rotating shaft. It is equipped with a plurality of dryers that are heated and dried while being stirred and conveyed by the heat transfer blades of the above, and are discharged from the discharge port so that the sludge to be dried discharged by the upstream dryer is sequentially received by the downstream dryer. It is characterized in that it is arranged so that the rotation axis of the most upstream dryer is rotated at a lower speed than the rotation axis of the dryer immediately downstream.

The indirect heating type sludge drying device according to the present invention further includes, as a second means, a temperature detector for detecting the in-machine temperature of each of the plurality of dryers in the first means, and the temperature detection. The rotation speed of each rotation axis of the plurality of dryers is set based on the detection value of the device.

In the indirect heating type sludge drying apparatus according to the present invention, as a third means, in the first or second means, the sludge to be dried is preheated to 60 ° C. or higher and lower than 100 ° C. in the most upstream dryer. The rotation speed of the rotation shaft of the most upstream dryer is controlled so as to be discharged from the discharge port of the most upstream dryer.

In the indirect heating type sludge drying apparatus according to the present invention, as a fourth means, in any of the first to third means, from the intermediate portion between the inlet and the outlet of the dryer upstream, the following A bypass line for bypassing sludge to be dried and an opening / closing means for opening / closing the bypass line are further provided in the intermediate portion between the inlet / outlet and the discharge port of the dryer downstream.

In the indirect heating type sludge drying apparatus according to the present invention, as a fifth means, in any of the first to fourth means, each of the plurality of dryers discharges sludge to be dried from the discharge port. It is further provided with a height-adjustable weir for adjusting the amount of discharge.

According to the present invention, since the rotation axis of the most upstream dryer is configured to rotate at a lower speed than the rotation axis of the dryer immediately downstream, it is not affected by the high load of the high viscosity preheating zone. The number of revolutions in the evaporation zone and the crushing zone can be increased, and the maximum amount of evaporation can be obtained according to the sludge shape in each machine while suppressing the power consumption.

It is a partial notch front view which shows the conventional indirect heating type sludge dryer. It is a central vertical sectional view of FIG. It is a graph which shows the drying test result which measured the sludge moisture content and evaporation rate of each area in the machine using the conventional indirect heating type sludge dryer. It is a schematic diagram which shows the state of sludge in the machine of the conventional indirect heating type sludge dryer. It is a schematic block diagram which shows 1st Embodiment of the indirect heating type sludge drying apparatus which concerns on this invention. It is a schematic block diagram which shows the 2nd Embodiment of the indirect heating type sludge drying apparatus which concerns on this invention. It is a schematic block diagram which shows the 3rd Embodiment of the indirect heating type sludge drying apparatus which concerns on this invention.

In order to understand the present invention, first, a drying test using a conventional groove-type stirring dryer (hereinafter referred to as "conventional machine") in which one dryer is used will be described.

A graph showing the results of a drying test in which the sludge moisture content and evaporation rate of each area in the machine are measured by rotating the rotation axis at different predetermined rotation speeds (low speed and high speed) using the conventional machine having the structure shown in FIG. Is shown in FIG.

The specifications of the conventional machine used in the test were that the heat transfer area was about 10 m ² , the machine length was about 4 m, the paddle diameter was φ300 mm, and saturated steam of about 0.5 MPa was used as the heat medium. As a raw material, sewage sludge having a water content of about 80% was used by dehydration treatment. The water content was measured by the method specified in the sewage sludge test method. The evaporation rate is a value obtained by dividing the amount of evaporated water per hour calculated from the sludge water content and sludge supply amount of each of the inlet 6 and the discharge port 7 of the dryer by the heat transfer area of the dryer. .. The rotation speed (low speed, high speed) of the rotating shaft is set so that the power consumption is about 10% lower at low speed than at high speed.

The evaporation rate shown in FIG. 3 is a numerical value calculated by collecting sludge at a plurality of sampling points in the dryer and dividing by the heat transfer area calculated in proportion to the length between the sampling points on the graph. (Plotted points are not shown), and each plotted value is shown by connecting them with a straight line.

As can be seen from the graph of FIG. 3, in the conventional machine, the high water content zone on the inlet 6 side of the dryer (the range where the number of heat transfer blades is up to the 10th) is the one in which the heat transfer blade 5 is rotated at a low speed. However, the evaporation rate is fast and the heat transfer area is effectively used. However, the power consumption is smaller when the rotating shaft 4 rotates at a low speed.

On the other hand, as shown in the graph of FIG. 3, in the conventional machine, the evaporation rate is faster when the heat transfer blades are rotated at high speed after the 10th heat transfer blade number. However, power consumption increases at high speed rotation.

As can be seen from the transition of the water content of the dehydrated sludge shown in the graph of FIG. 3, in the conventional machine, up to the 10th heat transfer blade is a preheating zone of the dehydrated sludge, and these phenomena are present. Since the temperature is low and the viscosity is high, it is recognized that rotating the heat transfer blade at a low speed is advantageous from the viewpoint of evaporation rate and low power consumption. On the other hand, in the graph of FIG. 3, after the 10th number of heat transfer blades, the temperature of the sludge rises and the viscosity decreases. Therefore, it is better to rotate the heat transfer blades at high speed so that the heat transfer blades come into contact with the sludge. It is considered that the evaporation rate is faster because the heat transfer effect is increased.

Further, in the conventional machine, the load applied at the time of rotation of the heat transfer blade is expected to be dominated by the load at the place where the water content is high and the viscosity is high in the preheating zone on the receiving port side. Therefore, in areas other than the preheating zone, it is considered that the load applied to the motor that actually rotationally drives the heat transfer blades is small even if the heat transfer blades are rotated at high speed.

FIG. 4 shows a schematic diagram of the sludge state in the conventional machine. In the conventional machine, referring to FIG. 1, the temperature detector (thermocouple) is placed in the trough 3 at the front stage position F (immediately below the inlet), the middle stage position M (central part in the longitudinal direction of the machine), and the rear stage position R (exhaust port). As a result of measuring the temperature when the sludge was dried, the temperature was measured at 60 ° C or higher and lower than 100 ° C at the front position F, almost 100 ° C at the middle position M , and 90 ° C at the rear position R due to the difference in the moisture content of the dry sludge. It was ~ 120 ° C.

In the conventional machine, the inside of the machine is roughly divided into four zones, from the inlet side to the preheating zone (less than 100 ° C), the evaporation zone (about 100 ° C), and the crushing zone (the zone where clay-like to granular decomposition is performed. , Below 100 ° C.) and a finishing zone (a zone where evaporation is performed again after granulation, below 100 ° C.). However, if the residence time in the finishing zone is long, the sludge dries, and if the sludge water content is less than 20%, the sludge temperature becomes 100 ° C. or higher.

An embodiment of the present invention will be described below with reference to FIGS. 5 to 7 based on the experimental results of the conventional machine. The same or similar components are designated by the same reference numerals throughout the drawings including the prior art.

FIG. 5 is a schematic configuration diagram showing a first embodiment of the indirect heating type sludge drying apparatus according to the present invention. The indirect heating type sludge dryer 1A of the first embodiment includes two dryers 100a and 100b. Each of the dryers 100a and 100b receives the sludge to be dried at the receiving inlets 6a and 6b, and is stirred by a plurality of heat transfer blades 5a and 5b provided at intervals in the axial direction of the rotating shafts 4a and 4b. , Heat and dry while transporting, and discharge from the discharge ports 7 and 7.

The receiving port 6b of the downstream dryer 100b is connected to the discharge port 7a of the upstream dryer 100a, and the sludge to be dried discharged from the upstream dryer 100a is arranged so as to be received by the downstream dryer 100b. There is. In the illustrated example, one rotary shaft 4a and 4b are shown for each of the dryers 100a and 100b, but a plurality of rotary shafts are arranged in parallel in each of the dryers 100a and 100b, and the respective rotary shafts are arranged in parallel. It is also possible to provide a heat transfer wing.

Although the details are not shown in FIG. 5, in the dryers 100a and 100b, the heat medium is circulated in the hollow inside of the rotating shafts 4a and 4b and the heat transfer blades 5a and 5b, as in the conventional example shown in FIG. As a result, the sludge to be dried can be indirectly heated by heat transfer, and an electric motor for rotationally driving the rotating shaft, a heat medium supply port, a heat medium discharge port, an exhaust fan, a heat transfer jacket, and the like can be provided.

In the first embodiment of the present invention, the upstream dryer 100a corresponds to the high viscosity zone corresponding to the preheating zone. The rotation speed of the rotating shaft 4a of the dryer 100a is controlled so that the sludge to be dried is preheated to 60 ° C. or higher and lower than 100 ° C. in the upstream dryer 100a and discharged from the discharge port 7a.

In the preheating zone, as already explained in the conventional machine, in general, the sludge filling rate as a processed product is high, the viscosity is high, and the temperature is low, so that the load (torque) applied by the rotation of the heat transfer blade is large. Therefore, it is possible to minimize the power consumption by operating the rotating shaft 4a at a low rotation speed. On the other hand, since it is a zone where heat is transferred from the heat transfer blade to the sludge to preheat it, it is not necessary to increase the rotation speed more than necessary to quickly update the sludge on the surface of the heat transfer blade. The evaporation rate may be higher.

In the first embodiment of the present invention, the downstream dryer 100b corresponds to an evaporation zone, a crushing zone, and a finishing zone. As can be seen from FIG. 4, in the conventional machine, the sludge filling rate decreases due to drying from the middle stage to the rear stage, and in order to increase the number of contacts with the heat transfer blade, increasing the rotation speed increases the evaporation rate. However, since the rotation speed in the preheating zone of the previous stage also increases at the same time, the evaporation rate in the preheating zone of the previous stage decreases and the power consumption increases.

Therefore, in the first embodiment of the present invention, the rotary shaft 4a of the upstream dryer 100a rotates at a lower speed than the rotary shaft 4b of the dryer 100b immediately downstream, in other words, the rotary shaft of the downstream dryer 100b. 4b is configured to rotate at a speed faster than the rotation shaft 4a of the upstream dryer 100a.

With such a configuration, the upstream dryer 100a is allocated to the preheating zone, and the downstream dryer 100b is not affected by the high load of the high viscosity preheating zone, and the number of rotations in the evaporation zone and the crushing zone is increased. It is possible to obtain the maximum amount of evaporation according to the sludge shape in each machine while suppressing the power consumption. The rotation speed of the rotation shafts 4a and 4b can be adjusted by controlling the rotation speed of an electric motor (control motor) (not shown) that rotationally drives the rotation shafts 4a and 4b.

Each of the dryers 100a and 100b can be provided with a temperature detector T for detecting the temperature inside the machine. The temperature detector T can be arranged, for example, in the vicinity of the inlets 6a and 6b, in the vicinity of the outlets 7a and 7b, and at an intermediate position between the inlet and the outlet. Is not limited. The temperature detector T may be, for example, a thermocouple and may be installed on the inner surface of the trough 3 at a position where sludge to be dried can come into contact.

As described above, in the conventional machine, the sludge to be dried is kept at about 100 ° C. in the evaporation zone where drying is progressing, so that the preheating zone upstream of the evaporation zone is in a high viscosity state at less than 100 ° C. Drying gradually progresses from the preheating zone to the evaporation zone, and when the temperature fluctuates again due to crushing, the drying progresses to some extent and the viscosity becomes low. However, if the water content is less than 20% in the preheating zone, the temperature becomes 100 ° C. or higher.

Therefore, in the first embodiment of the present invention, the rotation speed of the rotating shafts 4a and 4b can be controlled based on the detection result by the temperature detector T provided near the discharge port 7b, for example. In this case, if the purpose is to discharge the sludge to be dried from the discharge port 7b with a water content of less than 20% (a state close to absolute drying), the set temperature is set to 100 ° C. or higher, and conversely, the sludge to be dried is 20% or more. For the purpose of discharging from the discharge port 7 in the form of particles containing some water at about 40%, the set temperature should be less than 100 ° C., and the temperature detector T provided near the discharge port 7b should be set to the set temperature. The rotation speed of the rotation shafts 4a and 4b is controlled.

Next, a second embodiment of the indirect heating sludge dryer according to the present invention will be described with reference to FIG.

In the indirect heating type sludge dryer 1B of the second embodiment, three dryers 100a, 100b, and 100c are arranged in three upper and lower stages, and the dryers 100a, 100b, and 100c are directly connected to the discharge port 7 of the uppermost stream (top stage) dryer 100a. The inlet / outlet 6b of the second-stage dryer 100b downstream (directly below) is connected, and the inlet / outlet of the third-stage dryer 100c downstream (lowermost stage) is connected to the discharge port 7b of the second-stage dryer 100b. 6c is connected.

In the second embodiment of the illustrated example, the transport directions in the machine are opposite in the upper and lower stages, but the transport direction is not limited to this, for example, from the discharge port 7a (7b, 7c) to the inlet 6a (6b) with the transport direction in the same direction. , 6c) can also be provided with an inclined chute (not shown).

In the second embodiment, the rotation shaft 4a of the most upstream (top) dryer 100a is configured to rotate at a lower speed than the rotation shaft 4b of the immediately downstream (second stage) dryer 100b. Further, the rotation shaft 4a of the second-stage dryer 100b is configured to rotate at a lower speed than the rotation shaft 4c of the dryer 100c immediately downstream (third stage) thereof.

Each of the dryers 100a, 100b, 100c is provided with a height-adjustable weir portion 20 for adjusting the discharge amount of sludge to be dried discharged from the discharge ports 7a, 7b, 7c.

As in the second embodiment, the dryer is multi-staged and the dam portion 20 is provided, so that the sludge filling rate of the second stage and the lowest stage (third stage) can be adjusted, which is compared with the conventional machine. As a result, the frequency of contact between the heat transfer blade 5 and sludge becomes higher, and the evaporation rate becomes higher than that of the conventional machine. As a result, the average evaporation rate of the entire dryer (entire multi-stage dryer) as compared with the conventional machine is faster in the indirect heating type sludge dryer of the present invention, so that the required heat transfer area can be determined. Since it can be made smaller than the conventional machine, it can be made compact as a device and the cost can be reduced.

Next, a third embodiment of the indirect heating type sludge dryer according to the present invention will be described with reference to FIG. 7.

The indirect heating type sludge dryer 1C of the third embodiment is a modification of the second embodiment, and is next downstream from the intermediate portion between the inlet 6a and the discharge port 7a of the uppermost stream (top) dryer 100a. A bypass line 21 for bypassing sludge to be dried and an opening / closing means 22 for opening / closing the bypass line 21 are provided in the middle portion between the inlet 6b and the discharge port 7b of the dryer 100b (second stage). Further, from the intermediate portion between the inlet 6b and the discharge port 7b of the second-stage dryer 100b to the intermediate portion between the inlet 6c and the discharge port 7c of the next downstream (third stage) dryer 100c, the object is dried. A bypass line 23 for bypassing sludge and an opening / closing means 24 for opening / closing the bypass line 23 are provided. As the opening / closing means 22 and 24, for example, a slide gate or a rotary valve can be adopted.

By providing such bypass lines 21 and 23, a part or most of the dryers 100a, 100b and 100c can be discharged to the downstream (post-stage) dryer. As a result, the heat transfer area can be adjusted when the amount of sludge to be charged is small or the water content of dehydrated sludge to be charged is low, so that the water content of the discharged dry sludge can be adjusted or kept constant. ..

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention. In the above embodiment, two or three dryers are shown, but four or more dryers may be provided.

1A Indirect heating type sludge dryer 1B Indirect heating type sludge dryer 1C Indirect heating type sludge dryer 2 Heat transfer jacket 3 Traf 4, 4a, 4b, 4c Rotating shaft 5, 5a, 5b, 5c Heat transfer blades 6, 6a, 6b, 6c Inlet 7, 7a, 7b, 7c Outlet 8 Heat transfer port 9 Heat transfer port 10 Transmission belt 11 Electric motor 12 Carrier gas inlet 13 Exhaust port 14 Heat medium supply port for jacket 15 Heat transfer port for jacket 20 Weir 21 Bypass line 22 Opening and closing means 23 Bypass line 24 Opening and closing means 100 Groove type stirring dryer 100a Dryer 100b Dryer 100c Dryer T Temperature detector

Claims (4)

Multiple dryers that receive sludge to be dried at the receiving port, heat-dry it while stirring and transporting it with multiple heat transfer blades provided at intervals in the axial direction of the rotating shaft, and discharge it from the discharge port. Prepare,
The sludge to be dried discharged by the upstream dryer is arranged so as to be sequentially received by the downstream dryer, and the rotation axis of the upstream dryer is slower than the rotation axis of the dryer immediately downstream. It is controlled to rotate and
A bypass line that bypasses sludge to be dried from the intermediate portion between the inlet and the discharge port of the dryer upstream to the intermediate portion between the inlet and the discharge port of the dryer next downstream.
An opening / closing means for opening / closing the bypass line is provided.
An indirect heating type sludge drying device. Further equipped with a temperature detector for detecting the in-machine temperature of each of the plurality of dryers,
The indirect heating type sludge drying apparatus according to claim 1, wherein the rotation speed of each rotation axis of the plurality of dryers is set based on the detection value of the temperature detector. The rotation speed of the rotation shaft of the most upstream dryer so that the sludge to be dried is preheated to 60 ° C. or higher and lower than 100 ° C. in the most upstream dryer and discharged from the outlet of the most upstream dryer. The indirect heating type sludge drying apparatus according to claim 1 or 2, wherein the sludge is controlled. According to any one of claims 1 to 3 , each of the plurality of dryers further includes a height-adjustable weir portion for adjusting the discharge amount of sludge to be discharged from the discharge port. The indirect heating type sludge drying device described.

Images