JP2016090091A - Drying system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drying system which can utilize drain caused because steam for drying conducts heat to dried matter efficiently.SOLUTION: A drying chamber 21 supplied carrier air and a multitubular heating tube 22 which is arranged in the drying chamber 21 and steam for drying passes inside are comprised by a drying system 1. A dried matter is dried because heat of the steam for drying passing inside of the multitubular heating tube 22 is conducted to the dried matter by making the dried matter contact with the multitubular heating tube 22, and steam caused from the dried matter is discharged outside of the drying chamber 21 by the carrier air. A flash tank 3 re-vaporizing the drain collected from the multitubular heating tube 22 and gaining flash steam with lower voltage than the steam for drying and a first heat exchanger 4 heating open air by performing a heat exchange of the flash steam and the open air are comprised. In the drying chamber 21, the open air heated by the first heat exchanger 4 is supplied as carrier air.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a drying system in which the object to be dried is brought into contact with a heat transfer member in a drying chamber to transmit heat of drying steam passing through the inside of the heat transfer member to dry the object to be dried.

  In the process of recycling and disposing of wastewater treatment sludge, animal and vegetable residues, food residues, or sludge waste, etc., a drying system is provided for drying and treating dried matter such as sludge. As such a drying system, for example, a dryer provided with a dryer having a multi-tube heating tube arranged in a drying chamber (see, for example, Patent Document 1), or a dryer having a pair of rollers arranged in a drying chamber. (For example, refer to Patent Document 2 or Patent Document 3) and the like are known.

  The multi-tube heating tube in the drying system described in Patent Document 1 has a heating tube bundle in which a plurality of heating tubes are arranged at predetermined intervals, and is provided with a lifter or the like that scrapes up an object to be dried. In the drying system described in Patent Document 1, a multi-tube heating tube is rotated while being heated by flowing drying steam such as saturated steam through the multi-tube heating tube. As a result, the material to be dried put into the drying chamber is scraped up by a lifter of a rotating multitubular heating tube, etc., and comes into contact with each heating tube of the multitubular heating tube while falling, thereby generating drying steam. Heat is transmitted to the object to be dried, and the object to be dried can be dried. That is, the multi-tube heating tube corresponds to a heat transfer member that transfers the heat of the drying steam to the object to be dried. Here, in a state where the vapor evaporated from the object to be dried remains in the drying chamber, the evaporation of moisture from the object to be dried is inhibited. For this reason, it is configured to suck the steam in the drying chamber using an exhaust fan or the like, but in order to enhance the effect, carrier air is supplied into the drying chamber, and the vapor evaporated from the object to be dried is accompanied with the carrier air. Then, an operation of exhausting out of the drying chamber or discharging the vapor out of the drying chamber by extruding steam with carrier air is performed. If the temperature of the carrier air is low, heat exchange occurs between the carrier air and the multitubular heating tube, and the amount of heat of the drying steam for heating the multitubular heating tube is lost. Further, when the vapor evaporated from the object to be dried comes into contact with carrier air having a low temperature, it condenses and wets the object to be dried and the drying chamber. For this reason, as the carrier air, outside air heated to a predetermined temperature by a heater or the like is generally used.

  Further, in the drying system described in Patent Document 2, a pair of rollers including a driving roller and a driven roller disposed in contact with each other are disposed in the drying chamber. Each roller has a hollow cylindrical body shape, and a plurality of grooves along the circumferential direction are formed in the outer peripheral portion. In the drying system described in Patent Document 2, the pair of rollers is rotated by driving the driving roller while heating the roller by flowing steam through the pair of rollers. When an object to be dried is introduced between the pair of rotating rollers from above, the object to be dried is press-fitted into the groove of the roller. The object to be dried press-fitted into the groove is transferred with the heat of the drying steam that passes through the roller, whereby the object to be dried can be dried. That is, the pair of rollers corresponds to a heat transfer member that transfers the heat of the drying steam to the object to be dried. The dried material to be dried is taken out from the groove of the roller by a scraper. In the drying system described in Patent Document 2, in order to positively discharge the vapor evaporated from the object to be dried to the outside of the drying chamber, the outside air heated by the heater is supplied into the drying chamber as carrier air, and the object to be dried The vapor evaporated from the air is discharged out of the drying chamber together with the carrier air by the exhaust fan. Further, the roller in the drying system described in Patent Document 3 has no groove formed on the outer peripheral portion, and the drying steam that passes through the roller by adhering an object to be dried to the curved outer peripheral portion of the roller. The heat is transferred to dry the material to be dried.

  In the drying systems described in these Patent Documents 1 to 3, drying steam supplied to a heat transfer member such as a multi-tube heating tube or a roller is dried while passing through the multi-tube heating tube or the like. Heat is transferred to the object, condensing and draining.

JP 2008-284463 A JP 2006-90640 A JP 2007-101071 A

  However, in the drying systems described in Patent Documents 1 to 3, the generated drain is often discharged as it is in spite of being relatively hot hot water, and the drain is used. There is room for improvement.

  In view of the above circumstances, an object of the present invention is to provide a drying system that can efficiently use drain generated by drying steam transferring heat to an object to be dried.

The drying system of the present invention that solves the above object comprises a drying chamber to which carrier air is supplied, and a heat transfer member that is disposed in the drying chamber and through which drying steam passes, and to be dried in the drying chamber. Is brought into contact with the heat transfer member to transmit the heat of the drying steam passing through the heat transfer member to the object to be dried to dry the object to be dried, and the steam generated from the object to be dried is removed. In the drying system for discharging outside the drying chamber by the carrier air,
A flash tank that re-evaporates the drain recovered from the heat transfer member to obtain flash steam having a pressure lower than that of the drying steam;
A heat exchanger that heats the air by heat-exchanging the flash steam and air,
The drying chamber is characterized in that air heated by the heat exchanger is supplied into the chamber as the carrier air.

  Patent Document 1 also describes a drying system that performs drying by flowing a drying steam through a number of rotating hollow disks, and drying using carrier air is performed in the same manner as described above. The heat transfer member in the drying system of the present invention may be such a large number of hollow disks. Although not shown in the patent literature, similar drying is performed in a drying system that uses a hollow paddle-shaped heat transfer member instead of the hollow disk. The drying system of the present invention may use such a hollow paddle-shaped heat transfer member.

  The drain referred to here is a drain that is condensed from the drying steam passing through the heat transfer member and discharged from the drying chamber. Further, the drying steam may be saturated steam or superheated steam. Furthermore, the drying steam may be supplied into the drying chamber in the form of superheated steam, and change its state to saturated steam in the drying chamber.

  According to the drying system of the present invention, the flash steam obtained by re-evaporating the drain recovered from the heat transfer member in the flash tank and the air are heat-exchanged by the heat exchanger and heated. Air can be supplied into the drying chamber as the carrier air. Thereby, the heat | fever of the drain produced | generated when the said vapor | steam for drying transfers heat to a to-be-dried object can be collect | recovered, and a drain can be utilized efficiently. Furthermore, in the drying system of the present invention, heat exchange between the air and the flash steam in the heat exchanger, that is, heat exchange between the gas and the condensable steam, the required heat transfer area in the heat exchanger is small. Become. Thereby, the said heat exchanger can be made compact.

In the drying system of the present invention, a steam pipe to which superheated steam is supplied from the upstream side toward the heat transfer member,
A steam adjustment unit that lowers the temperature of superheated steam flowing through the steam pipe by using a condensed liquid in which the flash steam is condensed by heat exchange between the flash steam and the air upstream of the heat transfer member; With
In the heat transfer member, it is preferable that the steam whose temperature has been lowered by the steam adjusting unit passes through the inside as the drying steam.

  Here, the steam whose temperature has been lowered by the steam adjusting unit may be saturated steam or superheated steam in a state immediately before becoming saturated steam.

  In addition to recovering the heat of the drain recovered from the heat transfer member, the steam control unit uses the condensed liquid in which the flash steam is condensed to lower the temperature of the superheated steam. It can also be used. Until now, as means for lowering the temperature of superheated steam, pure water was introduced from outside the drying system. The reason for this is that when water containing impurities is used, the impurities cause scaling inside the heat transfer member, thereby reducing the heat transfer efficiency. If the aspect using the said condensed liquid is employ | adopted, the drain which does not contain the impurity which becomes a cause of scaling can be utilized, and the pure water required until now becomes unnecessary.

  Furthermore, in the drying system of the present invention, the steam adjustment unit exchanges the temperature of the superheated steam flowing through the steam pipe with the condensed liquid and a cooling fluid having a temperature lower than the condensed liquid, thereby adjusting the temperature of the condensed liquid. It may be lowered by the condensed liquid after being lowered.

  Here, when the superheated steam flowing through the steam pipe is at a high pressure and the pressure of the condensed liquid is lower than the pressure of the superheated steam, the condensed liquid is not pressurized in the steam pipe unless the condensed liquid is pressurized. Can not be supplied to. For this reason, by lowering the temperature of the condensed liquid, for example, a general-purpose pump that is not heat-resistant can be adopted as means for pressurizing the condensed liquid, and the equipment cost can be suppressed. Furthermore, the drain can be efficiently used by exchanging heat between the condensed liquid and the cooling fluid and using the heat of the cooling fluid.

  Moreover, the drying system of this invention WHEREIN: The said steam adjustment unit may reduce only the temperature of the superheated steam which flows through the said steam pipe to the temperature higher than the temperature from which this superheated steam becomes saturated steam. Hereinafter, the temperature at which superheated steam becomes saturated steam may be referred to as saturation temperature.

  For example, by reducing the temperature of the superheated steam flowing through the steam pipe to a temperature slightly higher than the saturation temperature, the state of the superheated steam flowing through the steam pipe changes to saturated steam when entering the heat transfer member. Condensation heat transfer in which latent heat is released from the heat transfer member to the object to be dried can be promoted.

  Further, in the drying system of the present invention, the steam adjustment unit mixes the condensed liquid with the superheated steam flowing through the steam pipe, and the pressure of the gas in a state where the condensed liquid is mixed with the superheated steam and You may measure the temperature of this gas and adjust the flow volume of this condensed liquid mixed with this superheated steam.

  By doing so, it becomes easy to adjust the flow rate of the condensed liquid for reducing the temperature of the superheated steam flowing through the steam pipe to a saturation temperature or a temperature slightly higher than the saturation temperature.

  ADVANTAGE OF THE INVENTION According to this invention, the drying system which can utilize efficiently the drain produced when the vapor | steam for drying transmits heat to to-be-dried material can be provided.

It is a block diagram showing an example of a drying system equivalent to one embodiment of the present invention. It is a figure which shows typically the dryer shown in FIG. It is a figure which expands and shows the A section enclosed with the circle | round | yen in FIG. In the drying system shown in FIG. 1, it is a block diagram showing an example of the circuit structure for controlling the state of the vapor | steam supplied to a multitubular heating pipe.

  Embodiments of the present invention will be described below with reference to the drawings. The drying system according to an embodiment of the present invention is used for recycling and disposal of wastewater treatment sludge, animal and vegetable residues, food residues or sludge waste, or the manufacture of chemical products such as processed foods and resin products. These dried products are dried.

  FIG. 1 is a block diagram showing an example of a drying system corresponding to an embodiment of the present invention.

  As shown in FIG. 1, the drying system 1 includes a dryer 2, a flash tank 3, a first heat exchanger 4, a drain tank 51, and a second heat exchanger 52. The drain tank 51 and the second heat exchanger 52 constitute a part of the steam adjustment unit 5 described later.

  First, the dryer 2 will be described with reference to FIG. FIG. 2 is a diagram schematically showing the dryer shown in FIG. In FIG. 2, the dryer 2 is broken and a part of the inside of the dryer 2 is shown.

  As shown in FIG. 2, the dryer 2 has a drying chamber 21 and a multi-tube heating tube 22 disposed in the drying chamber 21. The drying chamber 21 has a hollow shape having a substantially circular or substantially elliptical cross section, and is supported in a horizontally extending state by a machine frame (not shown). Hereinafter, the direction in which the drying chamber 21 extends may be referred to as the extending direction. The drying chamber 21 is provided with an input port 211, a discharge port 212, a carrier air port 213 and an exhaust port 214. The charging port 211 is a port for charging a material to be dried such as sludge, and is provided on the left side of the drying chamber 21 shown in FIG. 2, for example, at the upper end portion of the drying chamber 21. The discharge port 212 is dried by being subjected to a drying process to be described later while the material to be dried input from the input port 211 stays in the drying chamber 21, and is discharged as a dry product. It is an opening. This discharge port 212 is provided on the right side in the drying chamber 21 shown in FIG. 2 and at a position higher than the bottom of the drying chamber 21 by a predetermined dimension. The discharge port 212 is provided with a dam member 215 whose height can be adjusted, and a chute 216 is disposed in a portion of the drying chamber 21 where the discharge port 212 is provided. The material to be dried input from the input port 211 moves from the left side to the right side in the drying chamber 21 shown in FIG. 2 and is discharged from the discharge port 212 before long.

  The carrier air port 213 is a port through which the carrier air heated to, for example, about 100 ° C. by heat exchange in the first heat exchanger 4 shown in FIG. 1 is introduced into the drying chamber 21. The exhaust port 214 is a port through which the vapor evaporated from the object to be dried by an unillustrated exhaust fan or the like is discharged out of the drying chamber 21 together with the carrier air introduced from the carrier air port 213. The vapor and carrier air discharged from the exhaust port 214 are sent to a dust collector (not shown) and the like, and after being subjected to predetermined processing such as removal of fine powder, are exhausted.

  The multi-tube heating tube 22 is rotatably arranged in the drying chamber 21 around a rotation axis along the extending direction, and a shaft member 221 is provided on the rotation shaft portion. A rotary joint 23 is provided at each of both end portions in the extending direction of the shaft member 221. The multi-tube heating tube 22 rotates about a rotation shaft when the shaft member 221 is rotated by a motor (not shown) or the like. The multi-tube heating tube 22 includes a heating tube bundle 222. The heating tube bundle 222 is a bundle of a plurality of heating tubes 222 a arranged along the shaft member 221 around the shaft member 221. The plurality of heating tubes 222a have, for example, a circular trajectory connecting the outermost heating tubes 222a, and the heating tubes 222a are connected to each other inside the outermost heating tubes 222a. Many are arranged at predetermined intervals. Disc-shaped end plates 223 are provided at both ends of the heating tube bundle 222 in the extending direction. In FIG. 2, the end plate provided on the discharge port side is hidden in the drying chamber 21. A plurality of angles 224 are spanned between the pair of end plates 223 at a predetermined interval in the rotation direction of the end plate 223. Each of these angles 224 is provided with a plurality of lifters 225 and feed blades 226 at predetermined intervals in the extending direction. The lifter 225 scrapes up an object to be dried that stays in the drying chamber 21 when the multi-tube heating tube 22 rotates. The feed blade 226 feeds an object to be dried that remains in the drying chamber 21 to the discharge port side when the multi-tube heating tube 22 rotates.

  As shown in FIG. 1, a steam pipe 61 is connected to the rotary joint 23 on the inlet side. A boiler and a superheater (not shown) are connected to the upstream side of the steam pipe 61, and the superheated steam is generated by heating the steam generated by the boiler with the superheater. To be supplied. In some cases, for example, when the boiler and the dryer 2 are close to each other, saturated steam is supplied from the boiler to the dryer 2. The superheated steam supplied to the steam pipe 61 flows toward the rotary joint 23. In this embodiment, for example, a saturated steam of about 0.5 MPaG and 158 ° C. is generated by a boiler, and the saturated steam is heated to about 180 ° C. by a superheater to generate superheated steam, and 0.5 MPaG and 180 ° C. Superheated steam having a degree of superheat (about 22 degrees superheat) is supplied to the steam pipe 61.

  The steam pipe 61 is provided with a thermometer TI and a first pressure gauge PI1, and a second drain pipe 55 is connected thereto. Depending on the temperature of the steam measured by the thermometer TI and the pressure of the steam measured by the first pressure gauge PI1, a predetermined amount of drain is generated from the second drain pipe 55 to the superheated steam flowing through the steam pipe 61. As a result, the temperature of the superheated steam decreases. Thereby, the superheated steam supplied to the steam pipe 61 is sent to the rotary joint 23 in a state of being changed to a saturated steam of about 0.5 MPaG and about 158 ° C., and is supplied to the multi-tube heating pipe 22 as drying steam. . Hereinafter, the steam in which the temperature is lowered by mixing the drain supplied from the second drain pipe 55 to the steam supplied to the steam pipe 61 may be referred to as mixed steam, and this mixed steam is dried to the multi-tube heating pipe 22. It will be supplied as industrial steam. A detailed description of the operation of mixing the drain with the superheated steam flowing through the steam pipe 61 will be described later.

  The mixed steam sent to the rotary joint 23 flows from the shaft member 221 into the end plate 223 and is supplied from the end plate 223 to each heating tube 222a, whereby each heating tube 222a is heated. In this embodiment, since the saturated steam is supplied to each heating pipe 222a as drying steam, each heating pipe 222a is kept heated to a substantially constant temperature in the extending direction. It is. In the present embodiment, the saturated steam passing through the multi-tube heating tube 22 corresponds to an example of drying steam, and the multi-tube heating tube 22 corresponds to an example of a heat transfer member. Drain generated by condensation of the drying steam supplied to each heating tube 222a is accumulated in the end plate 223 on the discharge port side, and this drain is discharged from the multi-tube heating tube 22 by a siphon-type drainage device or the like. .

  A carrier air pipe 62 is connected to the carrier air port 213. The first heat exchanger 4 is connected to the upstream side of the carrier air pipe 62, and the first heat exchanger 4 is connected to a conduit for supplying outside air by a blower (not shown). The outside air supplied to the first heat exchanger 4 by a blower (not shown) is heated to about 100 ° C. by exchanging heat with flash steam supplied from a flash tank 3 to be described later, and is used as carrier air. Are introduced into the drying chamber 21.

  The rotary joint 23 on the discharge port side is connected to the flash tank 3 by a pipe line having a pressure reducing valve. The flash tank 3 receives a high-pressure (for example, 0.5 MPaG) drain, and re-evaporates a part of the drain by maintaining the inside of the tank at a pressure (for example, 0.2 MPaG) lower than the received drain pressure. It generates steam. The flash steam has a pressure (for example, 0.2 MPaG) lower than the pressure (for example, 0.5 MPaG) of the drying steam that passes through the multi-tube heating pipe 22. Further, the flush tank 3 includes a liquid level gauge LC for measuring the liquid level of the drain stored in the tank without re-evaporating, the electromagnetic valve S for discharging the drain, and the second pressure. A total PI2 is provided. The flash tank 3 is connected to the first heat exchanger 4 by a pipe line having a flow rate adjusting valve. The flash steam supplied from the flash tank 3 to the first heat exchanger 4 is condensed again by exchanging heat with the outside air supplied to the first heat exchanger 4 as described above, and drainage is generated. This drain corresponds to a condensed liquid and is hereinafter referred to as recondensed drain. In the first heat exchanger 4, the heat exchange between the outside air and the flash steam, that is, the heat exchange between the gas and the condensable steam, the heat transfer area required in the first heat exchanger 4 is reduced. 1 The heat exchanger 4 can be made compact. Furthermore, in the 1st heat exchanger 4, condensation heat transfer arises because flash vapor condenses, and it can exchange heat efficiently with external air.

  The 1st heat exchanger 4 is connected to the 2nd heat exchanger 52 by the 1st drain pipe 53, and the 2nd heat exchanger 52 is connected to the drain tank 51 by the pipe line. The first drain pipe 53 is provided with a steam trap 531. The first drain pipe 53 is connected to a drain replenishment pipe 31 that mixes the drain stored in the flash tank 3 with the recondensed drain flowing through the first drain pipe 53. In addition, a cold water supply pipe 521 and a hot water drain pipe 522 are connected to the second heat exchanger 52, and the cold water supply pipe 521 is provided with a first flow rate adjustment valve V1. The second heat exchanger 52 is supplied with a fluid having a temperature lower than that of the recondensing drain, and is supplied with cold water of 20 ° C. to 32 ° C. from a cooling tower, for example. This cold water has a lower temperature than the recondensation drain and corresponds to a cooling fluid. Further, the cooling fluid may supply outside air only for the purpose of cooling the condensed liquid. The recondensed drain generated in the first heat exchanger 4 passes through the steam trap 531, flows through the first drain pipe 53, and is supplied to the second heat exchanger 52. In the second heat exchanger 52, heat is exchanged between the recondensed drain and the cold water supplied from the cold water supply pipe 521, and the recondensed drain whose temperature has decreased is supplied to the drain tank 51. Further, the hot water whose temperature has been increased flows through the hot water drain pipe 522 and is sent to, for example, equipment that can use the discharged hot water.

  The drain tank 51 includes a second drain pipe 55 that connects the stored recondensed drain to the steam pipe 61. The second drain pipe 55 is provided with a pump P, a third pressure gauge PI3, a second flow rate adjusting valve V2, and a check valve. The second drain pipe 55 is provided with a relief valve RV. In order to maintain the pressure of the recondensed drain flowing in the second drain pipe 55 at a predetermined pressure, the relief valve RV is connected to the drain tank 51. A return drain circuit 54 is provided. The drain tank 51 is appropriately provided with an overflow outlet or the like when the amount of stored liquid is excessive. In the present embodiment, the recondensation drain is supplied from the second drain pipe 55 to the steam pipe while being pressurized by the pump P to a pressure equivalent to the pressure of superheated steam flowing through the steam pipe 61 (for example, 0.5 MPaG). 61 is mixed with superheated steam flowing through 61.

  FIG. 3 is an enlarged view showing a portion A surrounded by a circle in FIG.

  As shown in FIG. 3, the second drain pipe 55 is a pipe thinner than the steam pipe 61, and a discharge port 55a through which recondensed drain is discharged is formed at the downstream end thereof. The second drain pipe 55 has a downstream end portion inserted into the steam pipe 61 from a side surface portion of the steam pipe 61, and the discharge port 55 a is bent in a direction toward the rotary joint 23. As a result, the recondensed drain is discharged from the discharge port 55 a of the second drain pipe 55 to the front side region of the rotary joint 23 in the steam pipe 61. That is, the recondensed drain is mixed with the superheated steam flowing through the steam pipe 61 from the upstream side before the rotary joint 23. The thermometer TI and the first pressure gauge PI1 are arranged in the steam pipe 61 on the downstream side of the discharge port 55a of the second drain pipe 55. Thereby, in the thermometer TI and the first pressure gauge PI1, the temperature and pressure of the mixed steam in a state where the recondensed drain is mixed with the superheated steam flowing through the steam pipe 61 are measured. Note that the position where the thermometer TI and the first pressure gauge PI1 are provided is not limited to the position shown in FIG. 3, and the first pressure gauge PI1 is, for example, a steam according to an appropriate control method or operation method. You may arrange | position in the pipe | tube 61 upstream from the discharge outlet 55a of the 2nd drain pipe | tube 55. FIG. In addition to the thermometer TI and the first pressure gauge PI1, a thermometer and a pressure gauge for measuring the temperature and pressure of the superheated steam before the recondensation drain is mixed may be provided. Furthermore, the position where the recondensed drain is mixed with the superheated steam is not limited to that shown in FIG. 3. For example, the discharge port 55 a of the second drain pipe 55 is placed in the end plate 223 of the multi-tube heating pipe 22. And the recondensed drain may be mixed with superheated steam in the end plate 223. In the case of this aspect, the thermometer TI and the first pressure gauge PI1 may be disposed in the end plate 223. Alternatively, on the upstream side of the rotary joint 23, the cross-sectional area wider than the cross-sectional area of the pipe of the steam pipe 61 and the superheated steam and the recondensed drain are long time so that the recondensed drain and the superheated steam can be mixed more uniformly. A mixing chamber having a depth allowing contact is provided, a steam pipe 61 and a second drain pipe 55 are connected to the mixing chamber, and a thermometer TI and a first pressure gauge PI1 are provided near the mixed steam outlet of the mixing chamber. Etc.

  Here, the steam adjustment unit 5 of the present embodiment lowers the temperature of the superheated steam flowing through the steam pipe 61 by using the recondensed drain, and specifically, the drain tank 51, the second heat exchange. 52, cold water supply pipe 521, hot water drain pipe 522, first drain pipe 53, drain circulation path 54, second drain pipe 55, first flow rate adjustment valve V1, second flow rate adjustment valve V2, thermometer TI, first A pressure gauge PI1, a third pressure gauge PI3, a pump P, and the like are included.

  FIG. 4 is a block diagram illustrating an example of a circuit configuration for controlling the state of steam supplied to the multitubular heating tube in the drying system illustrated in FIG. 1. In FIG. 4, circuit configurations other than the circuit for controlling the state of steam supplied to the multi-tube heating tube 22 are omitted.

  In this embodiment, a programmable logic controller (hereinafter abbreviated as PLC) 90 is used as the control means. Note that the PLC 90 includes a CPU, a memory, and the like. The PLC 90 is connected with a thermometer TI, a first pressure gauge PI1, a third pressure gauge PI3, a first flow rate adjustment valve control circuit 91, a pump control circuit 92, and a second flow rate adjustment valve control circuit 93.

  The thermometer TI measures the temperature of the mixed steam, and the first pressure gauge PI1 measures the pressure of the mixed steam. The third pressure gauge PI3 measures the pressure of the recondensed drain flowing through the second drain pipe 55 of the drain tank 51. The first flow rate adjusting valve control circuit 91 is a circuit that controls the operation of the actuator of the first flow rate adjusting valve V1 in accordance with an output signal from the PLC 90. The pump control circuit 92 is a circuit that controls the rotational speed of the motor of the pump P in accordance with an output signal from the PLC 90. The second flow rate adjustment valve control circuit 93 is a circuit that controls the operation of the actuator of the second flow rate adjustment valve V <b> 2 according to the output signal from the PLC 90.

  The PLC 90 is provided with a mixed steam temperature setting value corresponding to the mixed steam pressure. In an embodiment in which the mixed steam is in a saturated steam state, a saturation temperature is selected as the temperature setting value of the mixed steam. For example, when the pressure of the mixed steam is 0.5 MPaG, the temperature setting value of the mixed steam includes the saturation temperature. 158 ° C is selected. In addition, when adopting a mode in which the mixed steam is in a state of superheated steam immediately before the state change to saturated steam, that is, superheated steam having a temperature several degrees higher than the saturation temperature, the temperature setting value of the mixed steam is saturated. A value several degrees higher than the temperature is selected.

  The PLC 90 controls the flow rate of the recondensed drain mixed with the superheated steam so that the temperature of the mixed steam becomes a temperature set value, and specifically, according to the operation described below. Note that the pressure of the mixed steam is adjusted by a boiler (not shown) so that a temperature necessary for drying the material to be dried in the dryer 2 can be secured.

  First, the PLC 90 selects the temperature setting value of the mixed steam based on the pressure of the mixed steam measured by the first pressure gauge PI1, and monitors the temperature of the mixed steam measured by the thermometer TI. Next, the PLC 90 issues a command to the second flow rate adjustment valve control circuit 93, drives the actuator of the second flow rate adjustment valve V2, and increases the flow rate of the recondensation drain mixed with the superheated steam. Thereby, the temperature of mixed steam falls. The command to the second flow rate adjusting valve control circuit 93 is continued until the temperature of the mixed steam reaches the temperature set value, and when the temperature of the mixed steam reaches the temperature set value, the driving of the actuator of the second flow rate adjusting valve V2 is stopped. . Thereby, the opening degree of the 2nd flow regulating valve V2 is maintained, and the flow volume of the recondensation drain mixed with superheated steam becomes constant. As a result, the temperature of the mixed steam is maintained at the temperature set value. When the temperature of the mixed steam falls below the temperature set value, a command is sent to the second flow rate adjusting valve control circuit 93 to drive the actuator of the second flow rate adjusting valve V2, and the recondensed drain mixed with the superheated steam. Reduce the flow rate. On the other hand, when the temperature of the mixed steam exceeds the temperature set value, a command is issued to the second flow rate adjusting valve control circuit 93 to drive the actuator of the second flow rate adjusting valve V2, and the remixed steam is mixed with the superheated steam. Increase the flow rate of the condensed drain.

  Further, instead of adjusting the flow rate of the recondensed drain, the temperature of the mixed steam may be controlled to a temperature set value by adjusting the temperature of the recondensed drain. When the temperature of the mixed steam falls below the temperature set value, a command is sent to the first flow rate adjustment valve control circuit 91 to drive the actuator of the first flow rate adjustment valve V1 and to supply the second heat exchanger 52 with the cold water Reduce the flow rate. As a result, the amount of heat taken from the recondensation drain in the second heat exchanger 52 decreases, and the temperature of the recondensation drain mixed with the superheated steam rises. Thereby, the temperature of mixed steam can be raised. On the other hand, when the temperature of the mixed steam exceeds the temperature set value, a command is issued to the first flow rate adjustment valve control circuit 91 to drive the actuator of the first flow rate adjustment valve V1 and supply it to the second heat exchanger 52. Increase the flow rate of cold water. As a result, the amount of heat taken from the recondensation drain in the second heat exchanger 52 increases, and the temperature of the recondensation drain mixed with the superheated steam decreases. Thereby, the temperature of mixed steam can be reduced. Note that the adjustment of the flow rate of the recondensation drain and the adjustment of the temperature may be used in combination.

  In addition, when the pressure of the recondensed drain flowing through the second drain pipe 55 is lower than the pressure of the superheated steam flowing through the steam pipe 61, the recondensed drain is sent from the second drain pipe 55 into the steam pipe 61. Becomes difficult. For this reason, the PLC 90 is pumped so that the pressure of the recondensed drain flowing through the second drain pipe 55 measured by the third pressure gauge PI3 approaches the pressure of the mixed steam measured by the first pressure gauge PI1. A command is issued to the control circuit 92 to control the rotational speed of the motor of the pump P. Thereby, the recondensed drain can be smoothly fed into the steam pipe 61 from the second drain pipe 55.

  Next, an example of a drying process using the drying system 1 of the present embodiment will be described. In the following description, the temperature and pressure of steam and the like are exemplified, but the drying system of the present invention is not limited to the exemplified temperature and pressure as in the above description.

  First, the multi-tube heating pipe 22 is rotated, superheated steam of about 0.5 MPaG and 180 ° C. is supplied to the steam pipe 61, and the drying system 1 is preheated without putting an object to be processed. Specifically, the preheating is performed until each heating tube 222a, which will be described later, is sufficiently heated so that an object to be processed can be charged. In this preheating stage, for example, flash steam is not sufficiently generated from the flash tank 3, and the recondensed water drain in the drain tank 51 may be at a low temperature. Therefore, at the preheating stage, it is possible to take measures such as supplying the flash tank 3 with steam from a separate steam pipe (not shown) and supplying hot water to the drain tank 51 in advance. As this preheating progresses, the details will overlap with the events described later. However, drainage accumulates in the flash tank 3, and this drain is sent to the first heat exchanger 4 as flash vapor from the flash tank 3, and is recycled. After becoming condensed drain, it is mixed with superheated steam flowing through the steam pipe 61 through the second heat exchanger 52 and the drain tank 51. The flow rate and the like of this recondensed drain are controlled by the above-described control method, whereby the mixed steam becomes a saturated steam state of about 0.5 MPaG and about 158 ° C., and is dried from the rotary joint 23 on the inlet side. The steam is supplied to the multi-tube heating tube 22 as steam. Here, the temperature setting value of the mixed steam is set to a value several degrees higher than the saturation temperature, and the mixed steam is supplied to the multi-tube heating pipe 22 in a state of superheated steam just before becoming saturated steam. It is more reliable that the vapor that has reached the heating tube 222a condenses, and condensation heat transfer can be performed more efficiently on the object to be dried.

  The drying steam supplied to the multi-tube heating tube 22 passes through the shaft member 221 and flows into the end plate 223, and is also supplied from the end plate 223 to each heating tube 222a. Thereby, each heating tube 222a is heated. After each heating tube 222a has been sufficiently heated, an object to be dried such as sludge is introduced into the drying chamber 21 from the inlet 211, and the carrier air heated to about 100 ° C. by the first heat exchanger 4, The air is introduced into the drying chamber 21 from the carrier air port 213. The carrier air may be supplied from the above preheating stage. The to-be-dried material is scraped up by the lifter 225 and contacts the heating tube 222a while falling. Saturated steam is supplied as drying steam into the heating pipe 222a, and heat is condensed from the drying steam to an object to be dried, and the drying steam is condensed to generate drain. Further, the material to be dried is agitated by the rotation of the multi-tube heating tube 22. While the material to be dried stays in the drying chamber 21, the heat content from the heating tube 222 a and the stirring are repeated, so that the moisture content is gradually reduced and dried. And discharged. Moreover, the vapor | steam which evaporated from the to-be-dried material is discharged | emitted from the exhaust port 214 with carrier air. Note that a bag filter or the like is provided at the exhaust port 214, and after fine particles are removed from the vapor and carrier air, it is released into the atmosphere through a deodorizing device or the like.

  The drain generated by the condensation of the drying steam in the multi-tube heating tube 22 has the same pressure and temperature as the saturated steam and is about 0.5 MPaG and 158 ° C., and this drain is supplied to the flash tank 3. . In the flash tank 3, the accepted drain is held at about 0.2 MPaG, so that part of the drain is re-evaporated, and flash vapor of about 0.2 MPaG and 133 ° C. is generated. This flash steam is supplied to the first heat exchanger 4. When the level gauge LC detects that the drain stored in the flash tank 3 has exceeded a predetermined amount, the solenoid solenoid valve S is driven to discharge a certain amount of drain. Since the drain stored in the flash tank 3 is hot water of about 130 ° C., a device for recovering the heat of this drain may be provided.

  In the first heat exchanger 4, heat exchange is performed between outside air of about 20 ° C. supplied by a fan (not shown) and flash steam of about 0.2 MPaG and 133 ° C. Thereby, as above-mentioned, external air is heated to about 100 degreeC and is supplied to the drying chamber 21 as carrier air. Further, the flash vapor condenses to generate a recondensation drain of about 0.2 MPaG and about 130 ° C., and this recondensed drain flows through the first drain pipe 53 and is supplied to the second heat exchanger 52. If the amount of recondensed drain is insufficient, the drain stored in the flash tank 3 is replenished from the drain replenishment pipe 31 to the first drain pipe 53.

  In the second heat exchanger 52, heat exchange is performed between the recondensation drain at about 130 ° C. and the cold water at about 20 ° C. to 32 ° C. supplied from the cold water supply pipe 521. Here, the flow rate of the cold water is adjusted so that the recondensation drain is about 40 ° C. The recondensed drain lowered to about 40 ° C. is supplied to the drain tank 51. The recondensed drain supplied from the drain tank 51 to the pump P has a pressure of about 0.2 MPaG, but is pressurized by the pump P to a pressure of about 0.5 MPaG, equivalent to the superheated steam flowing through the steam pipe 61. In this state, the flow rate is adjusted to a predetermined value by the second flow rate adjustment valve V <b> 2 and supplied to the steam pipe 61. By adjusting the flow rate of this recondensed drain, the state of the steam flowing through the steam pipe 61 can be adjusted as appropriate, such as saturated steam or superheated steam immediately before becoming saturated steam. Further, the recondensed drain lowers the temperature from about 130 ° C. to about 40 ° C. before being supplied to the steam pipe 61. Accordingly, a general-purpose pump or the like can be used as means for pressurizing the recondensed drain in order to send the recondensed drain into the steam pipe 61, and the equipment cost can be suppressed.

  According to the drying system 1 described above, the drain generated by the drying steam transferring heat to the object to be dried can be efficiently used.

  The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope described in the claims. For example, in the above-described embodiment, an example in which the recondensed drain is mixed with the superheated steam flowing through the steam pipe 61 has been described as an example. You may employ | adopt the aspect supplied. Further, the steam supplied to the steam pipe may be saturated steam, and, instead of the mode in which the recondensed drain is mixed with the superheated steam, heat exchange between the superheated steam flowing in the steam pipe 61 and the recondensed drain is performed. It is good also as an aspect made to heat-exchange with a container. Moreover, although the boiler was mentioned and demonstrated as an example as a means to generate | occur | produce the vapor | steam supplied to the steam pipe 61, you may generate | occur | produce a vapor | steam by vapor | steam generators other than a boiler, and the aspect using the vapor | steam produced in a factory etc. Can also be adopted. Furthermore, the heat transfer is not limited to the dryer 2 in which the multi-tubular heating tube 22 is disposed in the drying chamber 21, but in the drying chamber as in the drying systems described in Patent Document 2 and Patent Document 3 described above. A dryer in which a pair of rollers is arranged as a member, or a dryer in which a hollow disk or the like is arranged as a heat transfer member can also be used. In addition, a thermometer and a pressure gauge for measuring the temperature and pressure of the superheated steam flowing through the steam pipe 61 before the recondensation drain is mixed are provided, and the temperature measured by these instruments is used for the superheated steam. It is good also as a structure which controls the flow volume etc. of the recondensation drain to mix.

DESCRIPTION OF SYMBOLS 1 Drying system 2 Dryer 21 Drying chamber 211 Input port 22 Multi-tube heating tube 222a Heating tube 23 Rotary joint 3 Flash tank 4 First heat exchanger 5 Steam adjustment unit 51 Drain tank 52 Second heat exchanger 61 Steam tube 90 PLC
PI1, PI2, PI3 Pressure gauge TI Thermometer V1, V2 Solenoid valve

Claims (5)

A drying chamber to which carrier air is supplied; and a heat transfer member that is disposed in the drying chamber and through which the drying steam passes, and the object to be dried is brought into contact with the heat transfer member in the drying chamber. A drying system for transferring the heat of the drying steam passing through the inside of the heat member to the object to be dried, drying the object to be dried, and discharging the vapor generated from the object to be dried out of the drying chamber by the carrier air. In
A flash tank that re-evaporates the drain recovered from the heat transfer member to obtain flash steam having a pressure lower than that of the drying steam;
A heat exchanger that heats the air by heat-exchanging the flash steam and air,
The drying system is characterized in that the air heated by the heat exchanger is supplied into the room as the carrier air. A steam pipe to which superheated steam is supplied from the upstream side toward the heat transfer member;
A steam adjustment unit that lowers the temperature of superheated steam flowing through the steam pipe by using a condensed liquid in which the flash steam is condensed by heat exchange between the flash steam and the air upstream of the heat transfer member; With
2. The drying system according to claim 1, wherein the heat transfer member is configured such that the steam whose temperature has been lowered by the steam adjusting unit passes through the inside as the drying steam.   The steam adjustment unit lowers the temperature of superheated steam flowing through the steam pipe by the heat exchange between the condensed liquid and a cooling fluid having a temperature lower than that of the condensed liquid to lower the temperature of the condensed liquid. The drying system according to claim 2, wherein   The drying according to claim 2 or 3, wherein the steam adjusting unit reduces the temperature of the superheated steam flowing through the steam pipe only to a temperature higher than a temperature at which the superheated steam becomes saturated steam. system.   The steam adjustment unit mixes the condensed liquid with superheated steam flowing through the steam pipe, and measures the pressure and temperature of the gas in a state where the condensed liquid is mixed with the superheated steam, The drying system according to any one of claims 2 to 4, wherein the flow rate of the condensed liquid mixed into the superheated steam is adjusted.

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