JP6506011B2 - Drying system - Google Patents

Description

  The present invention relates to a drying system for drying the material to be dried by transferring the heat of the drying vapor passing through the inside of the heat transfer member by contacting the material to be dried with the heat transfer member in the drying chamber.

  In the process of recycling and disposing of waste water treatment sludge, animal and plant residue, food residue, and muddy waste, a drying system is provided to dry the material to be dried such as sludge. As such a drying system, for example, a dryer provided with a multi-tubular heating tube in the drying chamber (for example, see Patent Document 1 etc.) or a dryer provided with a pair of rollers in the drying chamber (See, for example, Patent Document 2 or Patent Document 3) and the like are known.

  The multi-tubular 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 a predetermined distance from each other, and a lifter or the like for scraping a material to be dried is provided. In the drying system described in Patent Document 1, the multi-tube heating tube is rotated while flowing by passing drying steam such as saturated steam into the multi-tube heating tube. As a result, the material to be dried introduced into the drying chamber is scraped up by the lifter or the like of the rotating multi-tubular heating tube and contacts each heating tube of the multi-tubular heating tube while falling, thereby drying the drying steam Heat is transferred to the material to be dried, and the material to be dried can be dried. That is, the multi-tube heating tube corresponds to a heat transfer member for transferring the heat of the drying vapor to the material to be dried. Here, when the vapor evaporated from the material to be dried remains in the drying chamber, the evaporation of water from the material to be dried is inhibited. For this reason, although it is comprised so that the vapor | steam in a drying chamber may be attracted | sucked using an exhaust fan etc., in order to heighten the effect, carrier air is supplied in a drying chamber, and the vapor evaporated from a material to be dried An operation of discharging the air outside the drying room or discharging the steam by the carrier air is performed. When the temperature of the carrier air is low, heat exchange occurs between the carrier air and the multi-tubular heating tube, and the heat of the drying steam for heating the multi-tubular heating tube is lost. In addition, when the vapor evaporated from the material to be dried comes in contact with the carrier air having a low temperature, it condenses and wets the material to be dried and the drying chamber. Therefore, outside air or the like heated to a predetermined temperature by a heater or the like is generally used as the carrier air.

  Further, in the drying system described in Patent Document 2, a pair of rollers, which are provided in contact with each other and consist of a drive roller and a driven roller, is disposed in the drying chamber. Each of the rollers is in the form of a hollow cylinder, 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 drive roller while heating the roller by flowing steam in each of the pair of rollers. When the material to be dried is introduced from above between the pair of rotating rollers, the material to be dried is pressed into the groove of the roller. The heat of the drying steam passing through the roller is transferred to the material to be dried which is pressed into the groove, whereby the material 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 vapor to the object to be dried. The dried material is removed from the groove of the roller by a scraper. In addition, also in the drying system described in Patent Document 2, in order to actively discharge the vapor evaporated from the material to be dried out of the drying chamber, the outside air heated by the heater is supplied as carrier air into the drying chamber, and the material to be dried The vapor evaporated from the air is discharged out of the drying chamber by the exhaust fan together with the carrier air. Further, the roller in the drying system described in Patent Document 3 has a groove not formed in the outer peripheral portion, and by adhering the material to be dried to the curved outer peripheral portion of the roller, the drying vapor passing through the roller Transfer heat to dry the material to be dried.

  In the drying systems described in these Patent Documents 1 to 3, the drying vapor supplied to the heat transfer member such as a multi-tube heating pipe or roller is to be dried while passing through the multi-tube heating pipe or the like. Heat is transferred to the object, which condenses and produces a drain.

JP 2008-284463 A Unexamined-Japanese-Patent No. 2006-90640 Japanese Patent Application Laid-Open No. 2007-10107

  However, in the drying systems described in these Patent Documents 1 to 3, the generated drain is often discharged as it is despite the fact that it is relatively high temperature hot water, and the drain is used. There is room for improvement.

  An object of this invention is to provide the drying system which can utilize efficiently the drain which arose for the steam for drying passing heat to a to-be-dried thing in view of the said situation.

A drying system according to the present invention, which solves the above object, comprises a drying chamber to which carrier air is supplied, and a heat transfer member disposed in the drying chamber and through which the drying vapor passes. The heat of the drying vapor passing through the inside of the heat transfer member is transferred to the material to be dried by bringing the heat transfer member into contact with the heat transfer member to dry the material to be dried, and the vapor generated from the material to be dried is In a drying system which discharges the outside of the drying chamber by the carrier air,
A flash tank for re-evaporating drain collected from the heat transfer member to obtain flush steam having a lower pressure than the drying steam;
A heat exchanger that heats the air by exchanging heat between the flash steam and the air ;
A steam pipe to which overheated steam is supplied from the upstream side toward the heat transfer member;
A steam adjusting unit which lowers the temperature of the superheated steam flowing through the steam pipe upstream of the heat transfer member by utilizing heat exchange between the flash steam and the air and heat condensation between the flash steam and the condensed liquid; Equipped with
The drying chamber is characterized in that the air heated by the heat exchanger is supplied into the chamber as the carrier air.

  Patent Document 1 also describes a drying system in which drying is performed by supplying drying steam to the inside of a large 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. Moreover, although not shown as patent documents, the same drying is performed also in the drying system which uses not the said hollow disk but the hollow paddle-like heat-transfer member. The drying system of the present invention may use such a hollow paddle-like heat transfer member.

  The drain referred to here is a drain drained from the drying chamber by condensing the drying vapor passing through the inside of the heat transfer member. The drying steam may be saturated steam or superheated steam. Furthermore, the drying steam may be supplied into the drying chamber in a superheated steam state, and may change into a saturated steam in the drying chamber.

  According to the drying system of the present invention, the heat exchanger exchanges heat between the flash vapor obtained by re-evaporating the drain collected from the heat transfer member in the flash tank and the air by the heat exchanger and is heated. Air may be supplied into the drying chamber as the carrier air. Thereby, the heat of the drain which arose when the steam for drying transfers heat to a thing to be dried can be collected, and drain can be used efficiently. Furthermore, in the drying system of the present invention, heat exchange between the air and the flash vapor, ie, heat exchange between the gas and the condensable vapor in the heat exchanger, reduces the required heat transfer area in the heat exchanger. Become. Thereby, the heat exchanger can be made compact.

Further, the heat transfer member dries the material to be dried while rotating.
The steam conditioning unit may send the condensed liquid to the steam pipe.
Furthermore, the heat transfer member is preferably configured such that the steam whose temperature has been reduced by the steam adjusting unit pass through the inside as the drying steam.

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

  In addition to recovering the heat of the drain collected from the heat transfer member, the condensed liquid obtained by condensing the flashed vapor is used to lower the temperature of the superheated vapor by the vapor adjustment unit, and the drainage itself is re-used. It can also be used. Incidentally, as a means for lowering the temperature of the superheated steam, pure water has been introduced from the outside of the drying system. The reason for this is that if water containing an impurity is used, the impurity causes scaling inside the heat transfer member to lower the heat transfer efficiency. If the embodiment using the condensed liquid is adopted, drains not containing impurities that cause scaling can be used, and the pure water required so far becomes unnecessary.

Furthermore, in the drying system of the present invention, the steam conditioning unit exchanges the temperature of the superheated steam flowing through the steam pipe with the condensed liquid and a cooling fluid that is cooler than the condensed liquid to obtain the temperature of the condensed liquid. After being lowered, the condensed liquid may be pressurized by a pressurizing means to send the condensed liquid to the steam pipe .

  Here, if 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 used as the steam pipe unless the condensed liquid is pressurized. Can not supply. Therefore, by lowering the temperature of the condensed liquid, for example, a general-purpose pump or the like which is not a heat resistant specification can be adopted as a means for pressurizing the condensed liquid, and equipment cost can be suppressed. Furthermore, the drain can be efficiently used also by exchanging heat between the condensed liquid and the cooling fluid and using the heat of the cooling fluid.

  In the drying system of the present invention, the steam conditioning unit may reduce the temperature of the superheated steam flowing through the steam pipe only to a temperature higher than the temperature at which the superheated steam becomes saturated steam. Hereinafter, the temperature at which the superheated steam becomes saturated may be referred to as the saturation temperature.

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

  Furthermore, in the drying system of the present invention, the steam conditioning unit mixes the condensed liquid with the superheated vapor flowing in the steam pipe, and the pressure of the gas in a state where the condensed liquid is mixed with the superheated vapor The temperature of the gas may be measured, and the flow rate of the condensed liquid mixed with the superheated vapor may be adjusted.

  By so doing, it becomes easy to adjust the flow rate of the condensed liquid in order to lower the temperature of the superheated steam flowing through the steam pipe to the 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 which arose for the steam for drying transferred heat to a to-be-dried thing can be provided.

FIG. 1 is a block diagram illustrating an example of a drying system corresponding to an 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 encircled 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.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drying system according to an embodiment of the present invention is used for recycling and disposing of waste water treatment sludge, animal and plant residues, food residue or mud waste, etc., or in producing chemical products such as processed food and resin products. These are those to be dried.

  FIG. 1 is a block diagram showing an example of a drying system according 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 adjusting unit 5 described later.

  First, the dryer 2 will be described with reference to FIG. FIG. 2 is a view 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-tubular heating tube 22 disposed in the drying chamber 21. The drying chamber 21 is hollow having a substantially circular or elliptical cross section, and is supported in a horizontally extending state by a machine frame (not shown) or the like. 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 inlet 211, an outlet 212, a carrier air port 213 and an outlet 214. The inlet 211 is a port into which an object to be dried such as sludge is introduced, 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 outlet 212 is dried by being subjected to the later-described drying process while the material to be dried which is input from the inlet 211 is staying in the drying chamber 21, and is discharged as a dried material. It is an opening. The discharge port 212 is provided on the right side in the drying chamber 21 shown in FIG. 2 and at a position higher by a predetermined dimension than the bottom of the drying chamber 21. The discharge port 212 is provided with a wedge member 215 which can be adjusted in height, 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 which is fed from the inlet 211 moves from the left to the right in the drying chamber 21 shown in FIG. 2 and is eventually discharged from the outlet 212.

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

  The multi-tubular heating tube 22 is disposed rotatably in the drying chamber 21 about a rotation axis along the extending direction, and a shaft member 221 is provided in the rotation shaft portion. A rotary joint 23 is provided at each end of the shaft member 221 in the extending direction. The multi-tube type heating tube 22 rotates around the rotation axis by rotating the shaft member 221 by a motor or the like (not shown). Further, the multi-tube type heating tube 22 is provided with a heating tube bundle 222. The heating tube bundle 222 is a bundle of a plurality of heating tubes 222 a disposed around the shaft member 221 along the shaft member 221. The plurality of heating pipes 222a have, for example, a circular locus connecting the heating pipes 222a arranged on the outermost side, and the heating pipes 222a are mutually connected also on the inside of the heating pipes 222a arranged outermost. A large number is arranged at predetermined intervals. A disc-shaped end plate 223 is provided at each end of the heating tube bundle 222 in the extending direction. In FIG. 2, the end plate provided on the outlet side is hidden by the drying chamber 21. A plurality of angles 224 are bridged between the pair of end plates 223 at predetermined intervals in the rotational direction of the end plate 223. A plurality of lifters 225 and feed vanes 226 are provided on the angles 224 at predetermined intervals in the extending direction. The lifter 225 scrapes up the material to be dried remaining in the drying chamber 21 when the multi-tube heating tube 22 rotates. The feed vanes 226 feed the material to be dried remaining in the drying chamber 21 to the outlet 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 steam generated in the boiler is heated by the superheater to generate superheated steam, and the superheated steam is the steam pipe 61. Supplied to The saturated steam may be supplied to the dryer 2 from the boiler, for example, when the boiler and the dryer 2 are close to each other. The superheated steam supplied to the steam pipe 61 flows toward the rotary joint 23. In the present embodiment, for example, a boiler generates saturated steam at about 0.5 MPaG and about 158 ° C. by a boiler, and the saturated steam is heated to about 180 ° C. by the superheater to generate superheated steam and generate about 0.5 MPaG and 180 ° C. Superheated steam of a degree (about 22 degrees of superheat degree) 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. According to 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 supplied from the second drain pipe 55 to the superheated steam flowing through the steam pipe 61 It mixes and the temperature of superheated steam falls. 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 supplied to the steam pipe 61 may be referred to as mixed steam in which the drain is mixed from the second drain pipe 55 and the temperature is lowered, and this mixed steam is dried in the multi-tube heating pipe 22. It will be supplied as 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 vapor 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 the respective heating tubes 222 a to heat the respective heating tubes 222 a. In the present embodiment, a mode in which saturated steam is supplied to each heating tube 222a as drying steam is adopted, so each heating tube 222a is kept heated to a substantially constant temperature in the extending direction Be In the present embodiment, the saturated vapor passing through the multi-tube heating pipe 22 corresponds to an example of the drying steam, and the multi-tube heating pipe 22 corresponds to an example of the heat transfer member. Drains generated by condensation of the drying steam supplied to the heating pipes 222a are accumulated in the end plate 223 on the outlet side, and the drains are discharged from the multi-tube heating pipe 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 pipeline for supplying the outside air by a blower (not shown). The outside air supplied to the first heat exchanger 4 by the blower (not shown) is heated to about 100 ° C. by heat exchange with the flash vapor supplied from the flash tank 3 described later, and the carrier air port 213 as carrier air. Are introduced into the drying chamber 21.

  The rotary joint 23 on the outlet side is connected to the flash tank 3 by a pipe having a pressure reducing valve. The flash tank 3 receives a high pressure (e.g., 0.5 MPaG) drain and maintains part of the drain at a lower pressure (e.g. 0.2 MPaG) than the pressure of the received drain to re-evaporate part of the drain and flush It generates steam. This flush vapor is at a pressure (eg, 0.2 MPaG) lower than the pressure (eg, 0.5 MPaG) of the drying vapor passing through the multi-tube heating pipe 22. In the flush tank 3, a liquid level gauge LC for measuring the liquid level of the drain received out of the received drain without re-evaporation, a solenoid valve S for discharging the drain, and a second pressure Total PI2 is provided. Further, the flash tank 3 is connected to the first heat exchanger 4 by a pipe having a flow control valve. The flash vapor supplied from the flash tank 3 to the first heat exchanger 4 is condensed again by heat exchange with the outside air supplied to the first heat exchanger 4 as described above, and a drain is generated. This drain corresponds to a condensed liquid and is hereinafter referred to as recondensing drain. In the first heat exchanger 4, the heat exchange between the ambient air and the flash steam, that is, the heat exchange between the gas and the condensable steam, reduces the heat transfer area required in the first heat exchanger 4, The heat exchanger 4 can be made compact. Furthermore, in the first heat exchanger 4, condensation heat transfer occurs by condensation of the flash steam, and heat can be efficiently exchanged with the outside air.

  The first heat exchanger 4 is connected to the second heat exchanger 52 by a first drain pipe 53, and the second heat exchanger 52 is connected to the drain tank 51 by a pipe line. The first drain pipe 53 is provided with a steam trap 531. A drain replenishment pipe 31 is connected to the first drain pipe 53 for mixing the drain oil stored in the flash tank 3 with the recondensing drain flowing through the first drain pipe 53. 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, for example, 20 ° C. to 32 ° C. cold water from a cooling tower. This cold water is cooler than the recondensing drain and corresponds to the cooling fluid. In addition, the cooling fluid may be supplied with the 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 and flows through the first drain pipe 53 to be supplied to the second heat exchanger 52. In the second heat exchanger 52, the recondensing drain and the cold water supplied from the cold water supply pipe 521 are subjected to heat exchange, and the temperature-reduced recondensing drain is supplied to the drain tank 51. Further, the warm water whose temperature has risen in the cold water flows through the warm water drain pipe 522, and is sent to, for example, a facility or the like that can use waste warm 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 adjustment valve V2, and a check valve. Further, the second drain pipe 55 is provided with a relief valve RV, and from the relief valve RV to the drain tank 51 in order to maintain the pressure of the recondensing drain flowing in the second drain pipe 55 at a predetermined pressure. A drain circulation path 54 is provided. In the drain tank 51, an overflow outlet or the like is appropriately provided when the amount of liquid storage becomes excessive. In the present embodiment, the recondensing drain is pressurized by the pump P to a pressure equivalent to the pressure (for example, 0.5 MPaG) of the superheated steam flowing through the steam pipe 61, from the second drain pipe 55 to the steam pipe 61 mixed with the superheated steam flowing.

  FIG. 3 is an enlarged view of a circled part A 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 from which the recondensed drain is discharged is formed at the downstream end thereof. The downstream end portion of the second drain pipe 55 is inserted into the steam pipe 61 from the side surface portion of the steam pipe 61, and the discharge port 55 a is bent in a direction toward the rotary joint 23. Thus, 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 disposed downstream of the discharge port 55a of the second drain pipe 55 in the steam pipe 61. Thereby, the temperature and the pressure of the mixed vapor in a state where the recondensing drain is mixed with the superheated vapor flowing in the steam pipe 61 are measured by the thermometer TI and the first pressure gauge PI1. 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 may be, for example, a steam according to an appropriate control method or operation method. The pipe 61 may be disposed upstream of the discharge port 55 a of the second drain pipe 55. Further, 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 recondensing drain is mixed may be additionally provided. Furthermore, the position at which the recondensing drain is mixed with the superheated steam is not limited to that shown in FIG. 3. For example, the discharge port 55a of the second drain pipe 55 can be inserted into the end plate 223 of the multitubular heating pipe 22. The recondensing drain may be mixed with the superheated steam in the end plate 223 in place. 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 steam pipe 61, and the superheated steam and the recondensed drain for a long time so that the recondensing drain and the superheated steam can be mixed more uniformly. A mixing chamber with a depth that allows contact is provided, the steam pipe 61 and the second drain pipe 55 are connected to this mixing chamber, and a thermometer TI and a first pressure gauge PI1 are provided near the mixed steam outlet of the mixing chamber. And so on.

  Here, the steam adjusting unit 5 of the present embodiment is to reduce the temperature of the superheated steam flowing through the steam pipe 61 using the recondensing drain, and more specifically, the drain tank 51, the second heat exchange 52, cold water supply pipe 521, hot water drainage pipe 522, first drain pipe 53, drain circulation path 54, second drain pipe 55, first flow control valve V1, second flow control valve V2, thermometer TI, first It has a pressure gauge PI1, a third pressure gauge PI3, a pump P and the like.

  FIG. 4 is a block diagram showing an example of a circuit configuration for controlling the state of steam supplied to the multi-tube heating pipe in the drying system shown in FIG. In addition, in FIG. 4, the circuit structure other than the circuit for controlling the state of the vapor | steam supplied to the multi-tube type heating pipe 22 is abbreviate | omitted.

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

  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 recondensing drain flowing through the second drain pipe 55 of the drain tank 51. The first flow control valve control circuit 91 is a circuit that controls the operation of the actuator of the first flow control valve V1 in accordance with the output signal from the PLC 90. The pump control circuit 92 is a circuit that controls the number of revolutions of the motor of the pump P in accordance with the output signal from the PLC 90. The second flow control valve control circuit 93 is a circuit that controls the operation of the actuator of the second flow control valve V2 in accordance with the output signal from the PLC 90.

  The PLC 90 is provided with temperature setting values of the mixed steam corresponding to the pressure of the mixed steam. In the embodiment where the mixed steam is in the state of saturated steam, the 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 is the saturation temperature Of 158 ° C. is selected. In the case where the mixed steam is brought into the state of superheated steam immediately before changing to saturated steam, ie, superheated steam at a temperature several degrees higher than the saturation temperature, the temperature setting value of the mixed steam is saturated A value a few degrees higher than the temperature is selected.

  The PLC 90 controls the flow rate of the recondensing drain mixed with the superheated steam so that the temperature of the mixed steam becomes the temperature setting value, and specifically, it is based on the operation described below. In addition, the pressure of mixed steam is adjusted with the boiler not shown so that the temperature required for drying of the to-be-dried material in the dryer 2 can be ensured.

  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. Then, the PLC 90 issues a command to the second flow control valve control circuit 93 to drive the actuator of the second flow control valve V2 to increase the flow rate of the recondensing drain mixed with the superheated steam. This causes the temperature of the mixed vapor to decrease. The command to the second flow control 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 control valve V2 is stopped. . Thereby, the opening degree of the second flow rate adjustment valve V2 is maintained, and the flow rate of the recondensing drain mixed with the superheated steam becomes constant. As a result, the temperature of the mixed vapor is maintained at the temperature set value. If the temperature of the mixed steam falls below the temperature set value, the second flow control valve control circuit 93 is commanded to drive the actuator of the second flow control valve V2, and the recondensed drain mixed with the superheated steam Decrease the flow rate of On the other hand, when the temperature of the mixed steam exceeds the temperature set value, the second flow control valve control circuit 93 is commanded to drive the actuator of the second flow control valve V2 to be mixed with the superheated steam. Increase the flow rate of the condensation drain.

  Further, instead of adjusting the flow rate of the recondensing drain, the temperature of the mixed vapor may be controlled to the temperature set value by adjusting the temperature of the recondensing drain. If the temperature of the mixed steam falls below the temperature set value, the first flow control valve control circuit 91 is instructed to drive the actuator of the first flow control valve V1, and the cold water supplied to the second heat exchanger 52 Decrease the flow rate of As a result, the amount of heat removed from the recondensing drain in the second heat exchanger 52 decreases, and the temperature of the recondensing 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 control valve control circuit 91 to drive the actuator of the first flow control valve V1 and supply it to the second heat exchanger 52. Increase the cold water flow rate. As a result, the amount of heat removed from the recondensing drain in the second heat exchanger 52 increases, and the temperature of the recondensing drain mixed with the superheated steam decreases. Thereby, the temperature of mixed steam can be reduced. The adjustment of the flow rate of the recondensing drain and the adjustment of the temperature may be used in combination.

  When the pressure of the recondensing drain flowing through the second drain pipe 55 is lower than the pressure of the overheated steam flowing through the steam pipe 61, the recondensing drain is sent from the second drain pipe 55 into the steam pipe 61. Will be difficult. For this reason, the PLC 90 is a pump so that the pressure of the recondensing 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 number of rotations of the motor of the pump P. As a result, the recondensed drain can be smoothly fed from the second drain pipe 55 into the steam pipe 61.

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

  First, the multi-tube type heating pipe 22 is rotated to supply superheated steam of about 0.5 MPaG and 180 ° C. to the steam pipe 61, and the drying system 1 is preheated in a state where the object to be treated is not introduced. Specifically, preheating is performed until each heating tube 222a to be described later is sufficiently heated to be in a state where an object to be treated can be introduced. In this preheating stage, for example, flash steam may not be generated sufficiently from the flash tank 3, and the recondensed water drain in the drain tank 51 may be at a low temperature. Therefore, in the preheating stage, the flash tank 3 can be supplied with steam from a separate steam pipe (not shown) and the drain tank 51 can be supplied with hot water in advance. As this preheating progresses, the drain tank is accumulated in the flash tank 3, and the drain tank is sent to the first heat exchanger 4 as the flash steam from the flash tank 3, although it also overlaps with the event to be described later in detail. After becoming a condensation drain, it is mixed with the superheated steam flowing through the steam pipe 61 through the second heat exchanger 52 and the drain tank 51. The flow rate etc. of this recondensed drain is controlled by the control method described above, whereby the mixed vapor becomes a state of saturated vapor of about 0.5 MPaG and about 158 ° C., and it is dried from the rotary joint 23 on the inlet side. The steam is supplied to the multi-tube heating pipe 22 as steam. Here, in the aspect in which 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 brought into the state of the superheated steam just before becoming saturated steam, It becomes more reliable that condensation occurs after reaching the heating pipe 222a, and condensation heat transfer can be performed more efficiently on the material to be dried.

  The drying vapor supplied to the multi-tube heating pipe 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 pipe 222a. Each heating tube 222a is heated by this. After each heating pipe 222a is sufficiently heated, a drying object such as sludge is introduced into the drying chamber 21 through the inlet 211, and the carrier air heated to about 100 ° C. by the first heat exchanger 4 is It is introduced into the drying chamber 21 from the carrier air port 213. The carrier air may be supplied from the above-described preheating stage. The input material to be dried is scraped up by the lifter 225 and comes into contact with the heating tube 222a while falling. In the heating pipe 222a, saturated steam is supplied as drying steam, condensation heat is transferred from the drying steam to the material to be dried, and the drying steam is condensed to form a drain. Moreover, the material to be dried is stirred by the rotation of the multi-tube heating tube 22. While the material to be dried is staying in the drying chamber 21, the moisture content gradually decreases and is dried by repeating the heat transfer from the heating tube 222 a and the stirring, and the dried material is eventually dried from the discharge port 212. Will be discharged. Further, the vapor evaporated from the material to be dried is exhausted from the exhaust port 214 together with the carrier air. A bag filter or the like is provided at the exhaust port 214, and after the fine powder is removed from the steam and the carrier air, it is released to the atmosphere through a deodorizing device or the like.

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

  In the first heat exchanger 4, heat exchange is performed between the outside air of about 20 ° C. supplied by a fan (not shown) and the flash vapor of about 0.2 MPaG and about 133 ° C. Thereby, as described above, the outside air is heated to about 100 ° C., and is supplied to the drying chamber 21 as carrier air. In addition, condensation of the flash vapor generates a recondensing drain of about 0.2 MPaG and about 130 ° C. This recondensing drain flows through the first drain pipe 53 and is supplied to the second heat exchanger 52. When the amount of recondensing drain is insufficient, the drain stored in the flash tank 3 is replenished from the drain replenishing pipe 31 to the first drain pipe 53.

  In the second heat exchanger 52, heat exchange is performed between the recondensing 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 recondensing drain becomes about 40 ° C. The recondensed drain, which has dropped to about 40 ° C., is supplied to the drain tank 51. The recondensed drain supplied from the drain tank 51 to the pump P is at 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 level by the second flow rate adjustment valve V2 and supplied to the steam pipe 61. By adjusting the flow rate of the recondensing drain, the state of the steam flowing through the steam pipe 61 can be appropriately adjusted, such as saturated steam or superheated steam immediately before becoming saturated steam. Moreover, the recondensing drain reduces the temperature to about 130 ° C. to about 40 ° C. before being supplied to the steam pipe 61. As a result, a general-purpose pump or the like can be used as means for pressurizing the recondensing drain in order to feed the recondensing drain into the steam pipe 61, and equipment cost can also be suppressed.

  According to the drying system 1 described above, it is possible to efficiently use the drain generated by the drying steam transferring heat to the material to be dried.

  The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. For example, in the above-mentioned embodiment, although the aspect which mixes a recondensation drain with the superheated steam which flows through steam pipe 61 was mentioned as an example and explained, recondensing drain is an installation etc. which collect waste heat in a factory, for example. You may employ | adopt the aspect to supply. Further, the steam supplied to the steam pipe may be saturated steam, and further, instead of mixing the recondensing drain with the superheated steam, heat exchange between the superheated steam flowing through the steam pipe 61 and the recondensing drain is performed. Heat may be exchanged by the heat exchanger. Moreover, although the boiler was mentioned as an example and demonstrated as a means to generate the steam supplied to the steam pipe 61, steam may be generated by steam generators other than a boiler, and the aspect using the steam generated 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, and the heat transfer is performed in the drying chamber as in the drying system described in Patent Document 2 and Patent Document 3 described above It is also possible to use a dryer in which a pair of rollers is disposed as a member, or a dryer in which a hollow disk or the like is disposed as a heat transfer member. In addition, a thermometer or pressure gauge for measuring the temperature or pressure of the superheated steam flowing through the steam pipe 61 before the recondensing drain is mixed is provided, and the temperature or the like measured with these instruments is used to The flow rate of the recondensing drain to be mixed may be controlled.

DESCRIPTION OF SYMBOLS 1 drying system 2 dryer 21 drying room 211 inlet 22 multi-tube type heating pipe 222a heating pipe 23 rotary joint 3 flash tank 4 first heat exchanger 5 steam adjustment unit 51 drain tank 52 second heat exchanger 61 steam pipe 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 disposed in the drying chamber and having the drying vapor passing therethrough are provided, and the object to be dried is brought into contact with the heat transfer member in the drying chamber. A drying system which transfers the heat of the drying vapor passing through the inside of the heat member to the material to be dried to dry the material to be dried and discharges the vapor generated from the material to the outside by the carrier air. In
A flash tank for re-evaporating drain collected from the heat transfer member to obtain flush steam having a lower pressure than the drying steam;
A heat exchanger that heats the air by exchanging heat between the flash steam and the air ;
A steam pipe to which overheated steam is supplied from the upstream side toward the heat transfer member;
A steam adjusting unit which lowers the temperature of the superheated steam flowing through the steam pipe upstream of the heat transfer member by utilizing heat exchange between the flash steam and the air and heat condensation between the flash steam and the condensed liquid; Equipped with
The drying system is characterized in that the air heated by the heat exchanger is supplied into the room as the carrier air in the drying chamber. The heat transfer member dries the object to be dried while rotating.
The drying system according to claim 1 , wherein the steam conditioning unit sends the condensed liquid to the steam pipe . The steam conditioning unit heats the temperature of the superheated steam flowing through the steam pipe between the condensed liquid and a cooling fluid having a temperature lower than that of the condensed liquid to reduce the temperature of the condensed liquid, and The drying system according to claim 1 or 2 , wherein the condensed liquid is pressurized to send the condensed liquid to the steam pipe . The steam control unit according to any one of claims 1 to 3, wherein the steam conditioning 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. The drying system according to claim 1 or 2 . The steam conditioning unit mixes the condensed liquid with the superheated steam flowing through the steam pipe, and measures the pressure of the gas and the 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 1 to 4, wherein the flow rate of the condensed liquid to be mixed with the superheated steam is adjusted.

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