JPH10300388A - Raw-sewage unused heat utilizing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an unused heat utilizing system of a high reliability which can stably recover heat from raw sewage by adopting a ball cleaning device. SOLUTION: At the time of normal operation, a heat-exchanging is performed by a heat-exchanger 4 is raw sewage from which fiber refuge, etc., are removed by an automatic strainer 2, and clean water in a piping 10, and the discharged raw sewage is discharged to the outside as a from a piping 9. When tubes in the heating-exchanger 4 become contaminated, a three-way switching valve 13 is switched by a control device 16, and the raw sewage from the heat- exchanger 4 is fed to a ball cleaning device 7, and a ball for cleaning is separated and circulated again to the heat-exchanger 4, and cleans the inside of the heat-exchanger 4. The raw sewage from which the ball for cleaning has been removed, is discharged to the outside through a valve 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raw sewage unused heat utilization system for utilizing unused heat of raw sewage.

[0002]

2. Description of the Related Art In a heat pump system for utilizing the unused heat of river water, treated water, etc., it is necessary to periodically remove dirt from tubes in the system. A cleaning method is generally used. In the brush washing method, baskets for receiving brushes reciprocating inside are attached to both sides of the heat exchanger tube, and washing is performed by periodically switching a water flow direction. For this brush cleaning method, for example, a pamphlet “Urban
Heat Sewage Heat Utilization System ". Also,
In the ball washing method, balls are put in the middle of the treated water pipe, passed through the heat exchanger, separated and taken out by a ball collector provided downstream, and the dirt is removed. The ball is recirculated for cleaning, and a known example is disclosed in Japanese Patent Application Laid-Open No. 5-126491.

On the other hand, in recent years, plans for utilizing untreated raw sewage heat for district heating and cooling near a city have increased. The reason is that the terminal wastewater treatment plant is far from the city center, and the cost of conduits is a problem in using treated water.However, untreated raw sewage can be taken out from the relay station in the city, This is because the supply to the tank is relatively easy.

[0004]

In an unused heat utilization system for raw sewage, it is essential to remove large and small debris contained in the raw sewage and to maintain a heat exchanger tube cleaning system with good maintainability. However, at present, only a ball washing device with small-scale domestic wastewater and a removal device that collects fibrous debris upstream of the sewage has been developed.
No method has been developed for cleaning the tubes of heat exchangers applied to large-scale unutilized heat utilization systems of raw sewage. In addition, the above-mentioned brush cleaning method for river water or treated water has a problem that fibrous debris is entangled with the brush and the basket and causes malfunction, and the water chamber cover must be opened every time for maintenance. The problem arises that it must be done. Also, in the ball washing method, when the raw sewage is used for the raw sewage according to the method described in the above-mentioned known example (Japanese Patent Laid-Open No. 5-126491), the raw sewage always passes through the ball collector, so that fibrous debris is entangled. It may accumulate, and the effect of separating the ball may be reduced and the ball may not function.

An object of the present invention is to provide an unused heat utilization system for raw sewage, which has a high washing performance of the heat exchanger tube and has a cleaning mechanism with excellent maintainability.

[0006]

In order to achieve the above object, the present invention provides a pump for pumping raw sewage, and primary waste for removing waste from raw sewage pumped by the pump. A raw sewage unused heat utilization system comprising a removing unit and a heat exchange unit for performing heat exchange between raw sewage passing through the unit and fresh water for transferring heat to a heat source device of the heat utilization device. A ball collector for separating the cleaning ball from the raw sewage when the raw sewage including the cleaning ball is input; and a ball collector for collecting the raw sewage discharged from the heat exchange means. A first valve for guiding the waste water, a second valve, and the cleaning ball separated by the ball collector are mixed into the raw sewage that has passed through the primary waste removing means via the second valve. So that the ball for sending out Pump, a third valve installed in a path for discharging raw sewage discharged from the ball collector to the outside, and closing the second and third valves to stop the operation of the ball pump. And an operation in a normal mode in which the first valve is switched to recover unused heat by switching the first valve so that the raw sewage discharged from the heat exchange means is directly guided to the outside; The cleaning ball is opened by opening a valve, driving the ball pump, and switching the first valve so that the raw sewage discharged from the heat exchange means is input to the ball collector. Is input from the ball collector to the heat exchange means via the second valve to the heat exchange means together with raw sewage, and after passing through the inside of the heat exchange means, to the ball collector via the first valve Input, where it can be separated and heat again The raw sewage discharged from the ball collector while being circulated to the exchange means is guided to the outside through the third valve so that the unused heat is recovered and the heat exchange means by the cleaning ball is used. Operation in the ball circulation mode where washing of
And a first control means for switching control of the wastewater.

Further, according to the present invention, a fourth valve for reversing the flow direction of the raw sewage in the heat exchange means, and an operation in the ball circulation mode is started under the control of the first control means. Prior to the operation, a second control means for controlling the fourth valve to reverse the flow direction of the raw sewage in the heat exchange means for a predetermined time. The present invention discloses a raw sewage unused heat utilization system characterized in that:

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of the configuration of an unused heat utilization system for raw sewage according to the present invention. The raw sewage intake pump 1 is capable of sucking garbage having a relatively large particle size together with raw sewage. Auto strainer 2 for removing waste, piping 3 and automatic valve 12 for leading the removed waste to another processing facility, shell and tube heat exchanger for exchanging heat between raw sewage and fresh water 4. a ball washing device 7 including a ball collector 5 for collecting and circulating balls flowing out after washing the heat exchanger 4 and a ball collector 6 for collecting balls during maintenance; , A three-way switching valve 13 for switching the flow of raw sewage to the ball washing device 7 and closing it, and a raw water flowing out of the heat exchanger 4. Sewage Treatment facilities pipe 9 for guiding the heat exchanger 4 a pipe for guiding takes in raw sewage heat captured in Shimizu at 10, it is formed of a heat pump 11 and the like as a heat source device. The control device 16 controls the four-way switching valve 8, the three-way switching valve 13, and the like.

FIG. 2 is a structural view of the ball collector 5, and FIG. 2 (a) shows the structure as viewed in a longitudinal section, and FIG. 2 (b) shows a cross section taken along the line AA. I have. When the heat exchanger 4 is washed, water containing balls flows from the three-way switching valve 13 into the pipe 51, and the balls are separated by the comb-shaped lattice 54 and are discharged from the nozzles 53. Here, the ball is made of, for example, a sponge having a diameter of 20 mm, and the interval between the comb-like lattices 54 is smaller than the diameter of the sponge. The water that has passed through the grid 54 is discharged from the nozzle 52. Board 56
Is driven up and down by an actuator 55 to scrape off fibrous debris attached to the grid 54. The basic configuration of the ball collector 6 is the same as that of the ball collector 5.

FIG. 3 shows the details of the vicinity of the inlet of the heat exchanger 4, in which sensors 41 to 44 for temperature detection and sensors 45 and 46 for pressure detection are provided. Outputs of these sensors are input to the control device 16.

Next, the operation of the above system will be described with reference to the time chart of FIG. First, at the start of the operation, the control device 16 sets the four-way switching valve 8 to form the flow path indicated by the dotted arrows 8A and 8B in FIG. 1, and the three-way switching valve 13 sets the flow indicated by the dotted arrow 13A. It is set to form a road. Further, valves 14, 1
5 are both closed. In this state, when the pumping of the raw sewage from the pump well via the water intake pump 1 is started (time t1 in FIG. 4), the raw sewage is guided to the auto strainer 2. The auto strainer 2 is provided with a screen made of a predetermined mesh, thereby filtering dust. When the filtered dust accumulates on the screen, the differential pressure across the screen increases, and when the differential pressure reaches a predetermined threshold, a differential pressure switch (omitted in FIG. 1) is activated, and the secondary side (outlet) of the screen is activated. Side) to the primary side (entrance side), and refuse adhering to the primary side of the screen is pushed out to the automatic valve 12. At the same time, automatic valve 1
2 is opened and the waste pushed out of the screen is piped 3
Is removed via The operations of the automatic strainer 2 and the automatic valve 12 are not shown in the figure, but are controlled by the control system of the automatic strainer 2 and are controlled by the times ts1, ts2,.
... It repeats as the differential pressure reaches that threshold as shown by tsn.

On the other hand, the raw sewage filtered to a certain particle size by the auto strainer 2 is led to the heat exchanger 4 through the path indicated by the dotted arrow 8A of the four-way switching valve 8, and is conveyed to the fresh water in the pipe 10. Heat exchange takes place. Thereby, the heat given to the fresh water is input to the heat pump 11 as a heat source device as described above. The raw sewage after the heat exchange with the fresh water is discharged from the heat exchanger 4 and guided to the three-way switching valve 13 through the route of the dotted arrow 8B of the four-way switching valve 8,
It is guided to another processing facility via the pipe 9 through the path indicated by the dotted arrow 13A.

When the above operation continues, dirt accumulates on the inner surface of the tube of the heat exchanger 4 due to the passage of raw sewage. For this reason, the heat transfer performance of the tube is reduced, the heat exchange amount is reduced, and the inlet temperature difference on the raw sewage side of the heat exchanger 4 is reduced. In addition, the pressure loss of the heat exchanger increases due to the progress of the contamination in the heat exchanger tube. The increase in the pressure loss affects the flow rate of the raw sewage according to the characteristics of the intake pump 1. Therefore, the control device 16 monitors the detection value of each sensor (FIG. 3) provided around the heat exchanger 4 and detects contamination on the inner surface of the tube. The detection method here is to determine whether or not the pressure difference between the inlet and outlet of the raw sewage of the heat exchanger 4, that is, the difference ΔP between the detection pressures of the pressure detection sensors 45 and 46 exceeds a predetermined pressure range value Pth1. It shall be detected by. And if

When ΔP> Pth1, the control device 16 controls the four-way switching valve 8
The four-way switching valve 8 is set so that the inner flow paths are indicated by solid arrows 8C and 8D in FIG. As a result, the flow direction of the raw sewage flowing into the heat exchanger 4 is switched in the opposite direction, and the raw sewage flows back inside the tube, whereby fibrous debris attached to the tube inlet passes through the three-way switching valve 13. It is discharged from the pipe 9 together with the raw sewage. At the same time, the dust adhering to the inside of the tube is removed to some extent by the backflow, so that the ball can easily enter the tube in the next operation. When this state is continued for a predetermined period of time, the control device 16 drives the scraping actuator 20 of the ball collector 5 and, upon receiving the drive completion signal, again moves the flow path of the four-way switching valve 8 through the dotted arrows 8A and 8B. (Time t3), and the water flow direction of the heat exchanger is returned to the original state. By driving the actuator 20, dust attached to the ball collector 5 is removed, and the effect of separating the balls is maintained. Further, the control device 16 returns the four-way switching valve 8 to the original state and simultaneously switches the three-way switching valve 13 so that the flow path thereof becomes the solid arrow 13B in FIG. 1 and the raw sewage discharged from the heat exchanger 8 is discharged to the ball. Water is passed through the cleaning device 7, and the valves 14 and 15 are both opened.

The raw sewage that has flowed into the ball washing device 7 flows into the ball collector 5 through the pipe 51, and most of the raw sewage is discharged from the nozzle 52 and passes through the valve 14 as described above.
It is discharged from the pipe 9, but a part thereof passes through the comb-like lattice 54, and the pump 1 together with the ball there is passed through the nozzle 53.
Pulled out from 7. The pump 17 can pass the ball. Since the three-way switching valves 18 and 19 provided at the entrance and exit of the ball collection device 6 are normally set so that water flows by bypassing the ball collection device 6, the raw sewage mixed with balls is passed through the valve 15. The water is sent to the four-way switching valve 8 and passes through the tube in the heat exchanger 4 together with the raw sewage taken in from the pump well to wash the inside of the tube. Thereafter, the raw sewage mixed with the balls is sent from the three-way switching valve 13 to the ball collector 5, where the balls are separated and circulated again to the heat exchanger 4.

As described above, when the operation in the ball circulation mode is performed, the tube cleaning in the heat exchanger 4 gradually proceeds, and as shown in FIG. Then, the value falls below a predetermined second threshold value Pth2 (time t4 in FIG. 4). However, this threshold value Pth2 is

## EQU2 ## By setting Pth1> Pth2, the operation in the ball circulation mode is not started immediately after the stop.
The control device 16

When detecting that △ P ≦ Pth2, the pump 17 of the ball cleaning device 7 is stopped, the valves 14 and 15 are closed, and the flow path of the three-way switching valve 13 is returned to the dotted arrow 13A to operate in the ball circulation mode. At the end, return to the first operating state. When replacing the ball for cleaning or cleaning by taking out the ball, the three-way switching valves 18 and 19 are switched to guide the raw sewage containing the ball to the ball collection device 6, where the ball is separated and the ball is taken out from the outlet. Take out.

As described above, according to the system shown in FIG. 1, when the dirt in the heat exchanger tube is detected and the dirt is advanced to some extent, the operation is performed in the ball circulation mode to automatically remove the dirt. And a highly reliable and maintainable unused heat recovery system can be realized.

In the above description, the stain on the inner surface of the tube is detected from the pressure difference between the raw sewage inlet and outlet of the heat exchanger 4. Another example of this stain detection method will be described below. Generally, the heat transfer performance Q of a heat exchanger is represented by the following equation:

Q = K · θm · A0 = Cp · γ · (tg1-tg2) · wg 1 / K = 1 / α0 + D0 · ln (D0 / DI) / (2 · λw)
+ (D0 / DI) · (1 / αI + γI) where the heat transfer coefficients α0 and αI outside and inside the tube,
The outer and inner diameters D0 and DI of the tube, the heat transfer area A0, and the thermal conductivity λw of the tube are constants determined by the apparatus. The specific heat Cp, the specific weight γ, and the raw sewage amount Wg of the raw sewage are also determined in advance. Further, the raw sewage inlet temperature tg1 and the outlet temperature tg2 of the heat exchanger are the temperature detecting sensors 41 and 42 in FIG.
Is the detected value of The average temperature difference θm is

[Equation 5] θm = 0.5F · {(th1 + th2) − (tg1 + tg2)}, where F is a predetermined correction coefficient, and the inlet temperature th1 and the outlet temperature th2 of the fresh water are temperature detecting sensors 43 and 44.
Is the detected value of From the above, the contamination coefficient γI can be calculated from (Equation 4) and (Equation 5) using the detection value of the temperature detection sensor as an input. Therefore, the control device 16 takes in the output of each of the above temperature sensors, calculates the above-mentioned dirt coefficient γI, and stores the value when there is no dirt at the beginning of operation of the facility as an initial value γI0. And the dirt coefficient γI calculated during operation
For a predetermined constant a

## EQU6 ## When γI> a · γI0, a> 1, the operation is switched to the ball circulation mode and the operation is performed.

## EQU7 ## When γI <b · γI0, 1 <b <a, the operation in the ball circulation mode is stopped.

Another simple method for detecting dirt is as follows.
The average temperature difference θm shown in (Equation 6) is obtained from the detection values of the temperature detection sensors 41 to 44, and when this value exceeds a predetermined value, it is considered that dirt has advanced, and a method of switching to the ball circulation mode is also possible. It is. Of course, in this case as well, the conditions for stopping the ball circulation mode operation are determined as in the other cases. Alternatively, as a condition for stopping the ball circulation mode operation, a method of stopping the operation after a predetermined time by a timer or the like may be used in any of the above-described dirt coefficient, average temperature difference and pressure difference. Or, more simply, the ball circulation mode operation may be periodically started by a schedule timer or the like without using the detected values of the temperature and the pressure.

When a strainer capable of removing fibrous dust in the upstream process is provided, the four-way switching valve 8 is not required, and cleaning by backflow can be omitted. Also in this case, the operating conditions of the ball cleaning device 7 are the same as described above.

[0020]

According to the present invention, it is possible to realize a highly reliable and easy-to-maintain unused heat utilization system capable of stably recovering heat from raw sewage.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a raw sewage unused heat utilization system according to the present invention.

FIG. 2 is a diagram showing a structure of a ball collector.

FIG. 3 is a diagram showing each detector around a heat exchanger.

FIG. 4 is a time chart of operation control.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 intake pump 2 auto strainer 4 heat exchanger 5 ball collector 6 ball collector 7 ball washing device 8 four-way switching valve 11 heat pump 12 automatic valve 13 three-way switching valve 41 to 44 temperature detection sensor 45, 46 pressure detection sensor

Claims (6)

[Claims] 1. A pump for pumping raw sewage, a primary refuse removing means for removing refuse from raw sewage pumped by the pump, and a heat source for the raw sewage and heat utilization device passing through the means. A raw sewage unused heat utilization system comprising heat exchange means for performing heat exchange with fresh water for transferring heat to the equipment, wherein the raw sewage including a cleaning ball is inputted when A ball collector for separating a washing ball from raw sewage, a first valve for guiding raw sewage discharged from the heat exchange means to the ball collector, a second valve, A ball pump for sending out the cleaning balls separated by the ball collector through the second valve so as to be mixed with the raw sewage that has passed through the primary refuse removing means; and discharging the ball from the ball collector. Removed raw sewage A third valve installed in a path for discharging water, closing the second and third valves, stopping the operation of the ball pump, and directly discharging raw sewage discharged from the heat exchange means to the outside. An operation in a normal mode in which the first valve is switched to recover unused heat by being guided, and the second and third valves are opened, the ball pump is driven, and the heat is released. By switching the first valve so that the raw sewage discharged from the exchange means is input to the ball collector, the cleaning ball is discharged from the ball collector via the second valve. The raw sewage is input to the heat exchanging means together with the raw sewage. After passing through the heat exchanging means, it is input to the ball collector via the first valve, where it is separated and circulated again to the heat exchanging means. , While discharged from the ball collector Operation in a ball circulation mode in which the collected raw sewage is guided to the outside through the third valve to simultaneously recover unused heat and wash the heat exchange means with the washing balls, And a first control means for switching control of the raw water. 2. A fourth valve for reversing the flow direction of the raw sewage in the heat exchange means, and when the operation in the ball circulation mode is started under the control of the first control means, Prior to the operation, a second control means for controlling the fourth valve to reverse the direction of the flow of the raw sewage in the heat exchange means for a predetermined time; The raw sewage unused heat utilization system according to claim 1, wherein: 3. Temperature detecting means for detecting an inlet temperature and an outlet temperature of raw sewage of the heat exchange means, and an inlet temperature and an outlet temperature of fresh water of the heat exchange means, and a temperature detection detected by the means. A dirt coefficient of the inner surface of the tube in the heat exchange means is calculated by using the value, and when the calculated dirt coefficient exceeds a predetermined value, the start command of the operation in the ball circulation mode is given by the first control. 3. The system according to claim 1, further comprising: third control means for issuing to said means. 4. Temperature detecting means for detecting an inlet temperature and an outlet temperature of raw sewage of the heat exchange means, and an inlet temperature and an outlet temperature of fresh water of the heat exchange means, and a temperature detection detected by the means. Using the values, the raw sewage temperature average value of the raw sewage inlet temperature and the outlet temperature and the fresh water temperature average value of the fresh water inlet temperature and the outlet temperature are calculated, and the calculated raw sewage temperature average value is further calculated. And a fourth control means for issuing a command to start the operation in the ball circulation mode to the first control means when a temperature difference from the average fresh water temperature exceeds a predetermined value. The raw sewage unused heat utilization system according to claim 1 or 2, wherein: 5. A pressure detecting means for detecting an inlet pressure and an outlet pressure of the raw sewage of the heat exchange means, and a pressure difference between the inlet pressure and the outlet pressure detected by the means is calculated. And a fifth control means for issuing a command to start operation in the ball circulation mode to the first control means when the pressure difference exceeds a predetermined value. Item 3. The raw sewage unused heat utilization system according to item 1 or 2. 6. The unused heat of raw sewage according to claim 1, wherein the first control means periodically executes the operation in the ball circulation mode at predetermined time intervals. Utilization system.