JP3594211B2 - Raw sewage unused heat utilization system - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a raw sewage unused heat utilization system for utilizing unused heat of raw sewage.
[0002]
[Prior art]
In a heat pump system that utilizes the unused heat of river water, treated water, etc., it is necessary to periodically remove dirt from the tubes in the system. For this reason, a brush cleaning method or a ball cleaning method is generally used. Have been. 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. This brush cleaning method is introduced, for example, in a pamphlet “Urban Heat Sewage Heat Utilization System” issued by the Tokyo Metropolitan Government. 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, for example, Japanese Patent Application Laid-Open No. 5-1261491.
[0003]
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 the treated water.However, untreated raw sewage can be removed from the relay station in the city, This is because it is relatively easy to supply them.
[0004]
[Problems to be solved by the invention]
In the system for utilizing the unused heat of raw sewage, it is essential to remove the large and small debris contained in the raw sewage and to maintain the heat exchanger tubes 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. The method of cleaning tubes for heat exchangers applied to the system has not been developed. In addition, the above-mentioned brush cleaning method for river water or treated water has a problem that fibrous debris is entangled in the brush and the basket and causes malfunction, and the water chamber cover must be opened every time for maintenance. The problem arises. Also, in the ball washing method, if 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.
[0005]
An object of the present invention is to provide an unused heat utilization system of raw sewage, which has a high cleaning performance of the heat exchanger tube and has a cleaning mechanism with excellent maintainability.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides:
A pump for pumping raw sewage, primary garbage removing means for removing refuse from raw sewage pumped by the pump, and heat transferred to the raw sewage passing through the means and the heat source equipment of the heat utilization device A raw sewage unused heat utilization system comprising heat exchange means for performing heat exchange with fresh water for
A ball collector for separating the cleaning ball from the raw sewage when the raw sewage including the cleaning ball is input,
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 so as to be mixed into the raw sewage that has passed through the primary refuse removing means via the second valve;
A third valve installed in a path for discharging raw sewage discharged from the ball collector to the outside, closing the second and third valves, stopping the operation of the ball pump, and An operation in a normal mode in which the first valve is switched so as 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, and the second and third valves are opened. By driving the ball pump, and by switching the first valve so that the raw sewage discharged from the heat exchange means is input to the ball collector, the cleaning ball is the ball Raw water is input from the collector to the heat exchange means via the second valve together with the raw sewage, and is input to the ball collector via the first valve after passing through the inside of the heat exchange means, Here it can be separated and returned to the heat exchange means The raw sewage circulated and discharged from the ball collector is guided to the outside through the third valve to recover unused heat and wash the heat exchange means with the washing balls. Driving in the ball circulation mode, which is performed simultaneously,
First control means for switching control of
A raw sewage unused heat utilization system characterized by comprising:
[0007]
The present invention also provides a fourth valve for reversing the direction of the flow of the raw sewage in the heat exchange means,
When the operation in the ball circulation mode is started under the control of the first control means, the direction of the flow of the raw sewage in the heat exchange means is controlled by controlling the fourth valve prior to the operation. Second control means for performing control so as to be inverted for a predetermined time;
Disclosed is a raw sewage unused heat utilization system characterized by the provision of:
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described 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 relatively large particle size garbage together with raw sewage. Auto strainer 2 for removing waste, piping 3 and automatic valve 12 for leading the removed waste to another treatment 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 four-way switching valve 8 for switching the direction of water flow to the heat exchanger 4 to switch the flow direction, a three-way switching valve 13 for switching the flow of raw sewage to the ball washing device 7 and closing, 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.
[0009]
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 AA plane. When the heat exchanger 4 is washed, water containing balls flows into the pipe 51 from the three-way switching valve 13, and the balls are separated by the comb-shaped lattice 54 and are discharged from the nozzle 53. Here, the ball is made of, for example, a sponge having a diameter of 20 mm, and the interval between the comb-shaped 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. The plate 56 is driven up and down by an actuator 55 to scrape 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.
[0010]
FIG. 3 shows details of the vicinity of the inlet of the heat exchanger 4, and is provided with sensors 41 to 44 for temperature detection and sensors 45 and 46 for pressure detection. Outputs of these sensors are input to the control device 16.
[0011]
Next, the operation of the above system will be described with reference to the time chart of FIG. First, at the start of 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 path indicated by the dotted arrow 13A. It is set to form a road. Further, both valves 14 and 15 are closed. In this state, when the pumping of the raw sewage from the pump well via the 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. Backwash from the side (primary side) to the primary side (entrance side), and dust adhering to the primary side of the screen is pushed out toward the automatic valve 12. At the same time, the automatic valve 12 is opened, and the dust pushed out of the screen is removed through the pipe 3. Although the operation of the automatic strainer 2 and the automatic valve 12 here is not shown, it is controlled by the control system of the automatic strainer 2, and the differential pressure is controlled as shown by time ts1, ts2,. It is repeated to reach the threshold.
[0012]
On the other hand, the raw sewage filtered to a certain degree of particle size by the auto strainer 2 is guided to the heat exchanger 4 through the path of the dotted arrow 8A of the four-way switching valve 8, and heat exchange with the fresh water in the pipe 10 is performed. Done. 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, guided to the three-way switching valve 13 through the path of the dotted arrow 8B of the four-way switching valve 8, and separated through the path of the dotted arrow 13A. Through a pipe 9.
[0013]
When the above operation continues, dirt accumulates on the inner surface of the tube of the heat exchanger 4 due to the passage of the 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. Further, the pressure loss of the heat exchanger also 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. In this case, as a detection method, it is determined 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 [Equation 1]
ΔP> Pth1
When, the control device 16 sets the four-way switching valve 8 so that the flow path in the four-way switching valve 8 becomes the 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, so that 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 time, the control device 16 drives the scraping actuator 20 of the ball collector 5 and, upon receiving the drive completion signal, again switches 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 restores the four-way switching valve 8 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.
[0014]
The raw sewage that has flowed into the ball washing device 7 flows into the ball collector 5 from the pipe 51, and as described above, most of the raw sewage is discharged from the nozzle 52, passes through the valve 14, and is discharged from the pipe 9. , A part of which passes through the comb-like lattice 54 and is drawn out of the nozzle 53 by the pump 17 together with the balls there. This pump 17 can pass a 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, 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.
[0015]
In this way, when the operation in the ball circulation mode is being performed, the tube cleaning in the heat exchanger 4 gradually proceeds, and the differential pressure ΔP of the raw sewage starts to decrease as shown in FIG. Eventually, the value falls below a predetermined second threshold value Pth2 (time t4 in FIG. 4). However, this threshold value Pth2 is given by
Pth1> Pth2
By setting it to be such that the operation in the ball circulation mode is not started immediately after stopping. The control device 16
(Equation 3)
ΔP ≦ Pth2
Is detected, the pump 17 of the ball cleaning device 7 is stopped, the valves 14 and 15 are closed, the flow path of the three-way switching valve 13 is returned to the dotted arrow 13A, and the operation in the ball circulation mode is completed to return to the initial operation 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.
[0016]
As described above, according to the system of FIG. 1, when the dirt in the heat exchanger tube is detected and the dirt is advanced to some extent, the operation in the ball circulation mode is performed to automatically remove the dirt. It is possible to realize an unused heat recovery system that is highly reliable and easy to maintain.
[0017]
In the above description, dirt 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 dirt detection method will be described below. Generally, the heat transfer performance Q of a heat exchanger is represented by the following equation:
(Equation 4)
Q = K · θm · A0 = Cp · γ · (tg1-tg2) · wg
1 / K = 1 / α0 + D0 · ln (D0 / DI) / (2 · λw) + (D0 / DI) · (1 / αI + γI)
Here, the heat transfer coefficients α0 and αI outside and inside the tube, the outside and inside diameters D0 and DI of the tube, the heat transfer area A0, and the heat 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 detection values of the temperature detecting sensors 41 and 42 in FIG. 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 outlet temperature th2 of the fresh water are the detection values of the temperature detecting sensors 43 and 44. 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 outputs of the respective temperature sensors, calculates the dirt coefficient γI, and stores a value when there is no dirt at the beginning of operation of the facility as an initial value γI0. Then, the dirt coefficient γI calculated during the operation is expressed by the following equation with respect to a predetermined constant a.
γI> a · γI0, a> 1
When it becomes, the operation is switched to the ball circulation mode described above and the operation is further performed.
γI <b · γI0, 1 <b <a
When it becomes, the operation of the ball circulation mode is stopped.
[0018]
As another simple dirt detection method, 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, the dirt proceeds. It is also possible to switch the mode to the ball circulation mode. Of course, also in this case, the conditions for stopping the ball circulation mode operation are determined in the same manner as in the other cases. Alternatively, as a condition for stopping the ball circulation mode operation, a method of stopping after a predetermined time using a timer or the like may be used in any of the above-described dirt coefficient, average temperature difference, and pressure difference. Alternatively, more simply, the ball circulation mode operation may be periodically started by a schedule timer or the like without using the detected values of temperature and pressure.
[0019]
In addition, 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]
【The invention's effect】
Advantageous Effects of Invention According to the present invention, it is possible to realize a highly reliable and easy-to-maintain unused heat utilization system that can stably recover 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)

A pump for pumping raw sewage, primary garbage removing means for removing refuse from raw sewage pumped by the pump, and heat transferred to the raw sewage passing through the means and the heat source equipment of the heat utilization device A raw sewage unused heat utilization system comprising heat exchange means for performing heat exchange with fresh water for
A ball collector for separating the cleaning ball from the raw sewage when the raw sewage including the cleaning ball is input,
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 so as to be mixed into the raw sewage that has passed through the primary refuse removing means via the second valve;
A third valve installed in a path for discharging raw sewage discharged from the ball collector to the outside,
The second valve and the third valve are closed, the operation of the ball pump is stopped, and the first valve is switched and unused so that the raw sewage discharged from the heat exchange means is directly guided to the outside. Operation in the normal mode where heat recovery is performed,
The second and third valves are opened, the ball pump is driven, and the first valve is switched so that the raw sewage discharged from the heat exchange means is input to the ball collector. Thereby, the cleaning ball is input from the ball collector through the second valve to the heat exchange means together with the raw sewage, passes through the heat exchange means, and then passes through the first valve. And the raw sewage discharged from the ball collector is guided to the outside via the third valve while being separated and circulated again to the heat exchange means. An operation in a ball circulation mode in which the recovery of unused heat and the cleaning of the heat exchange means with the cleaning balls are performed simultaneously,
First control means for switching control of
A raw heat utilization system that does not use raw sewage. A fourth valve for reversing the direction of the flow of the raw sewage in the heat exchange means;
When the operation in the ball circulation mode is started under the control of the first control means, the direction of the flow of the raw sewage in the heat exchange means is controlled by controlling the fourth valve prior to the operation. Second control means for performing control so as to be inverted for a predetermined time;
The raw sewage unused heat utilization system according to claim 1, further comprising: Inlet temperature and outlet temperature of the raw sewage of the heat exchange means, and temperature detection means for detecting the inlet temperature and the outlet temperature of fresh water of the heat exchange means,
A dirt coefficient of the inner surface of the tube in the heat exchange means is calculated using the temperature detection value detected by the means, and when the calculated dirt coefficient exceeds a predetermined value, the operation in the ball circulation mode is performed. Third control means for issuing a start command to the first control means;
The raw sewage unused heat utilization system according to claim 1 or 2, further comprising: Inlet temperature and outlet temperature of the raw sewage of the heat exchange means, and temperature detection means for detecting the inlet temperature and the outlet temperature of fresh water of the heat exchange means,
Using the temperature detection values detected by the means, calculate the raw sewage temperature average value of the inlet temperature and the outlet temperature of the raw sewage, and calculate the fresh water temperature average value of the inlet temperature and the outlet temperature of the fresh water, and further perform the calculation. A fourth command for issuing a command to start operation in the ball circulation mode to the first control means when a temperature difference between the obtained raw sewage temperature average value and the fresh water temperature average value exceeds a predetermined value. Control means;
The raw sewage unused heat utilization system according to claim 1 or 2, further comprising: Pressure detecting means for detecting the inlet pressure and the outlet pressure of the raw sewage of the heat exchange means,
A pressure difference between the inlet pressure and the outlet pressure detected by the means is calculated, and when the calculated pressure difference exceeds a predetermined value, a command to start operation in the ball circulation mode is issued to the first control. Fifth control means for issuing to the means;
The raw sewage unused heat utilization system according to claim 1 or 2, further comprising: The system according to claim 1 or 2, wherein the first control means periodically executes the operation in the ball circulation mode at predetermined time intervals.

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