JP2011122736A - Drain recovery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drain recovery system in a closed method, which enables injection of a medical agent, in particular permitting injection of a medical agent, while preventing the possibility of a corrosion of an economizer when the economizer is installed. <P>SOLUTION: In the drain recovery system in the closed method, drain discharged from a load apparatus 6 using generated steam by boilers 1a-1c is recovered to inside of a closed type drain tank 9, and the drain recovered to the inside of the drain tank 9 is supplied to the boiler 1a-1c on the downstream side of the drain tank 9. The medical agent is injected by chemical dosing equipment 23 to the downstream side of the drain tank 9 and upstream side of a water supply pump 12. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a drain recovery system that recovers drain discharged from a load device that uses steam from a boiler as a heat source and recirculates the drain to the boiler. More specifically, the drain discharged from the load device is a sealed drain. The present invention relates to a closed drain recovery system that recovers to a tank and returns to a boiler.

  Conventionally, in order to save boiler fuel costs and water, a drain recovery system has been proposed in which drain discharged from load equipment is returned to a tank and reused. As a drain recovery method in the drain recovery system according to this proposal, in general, the drain discharged from the load device is recovered in an open tank opened to the atmosphere, and the drain that is less than 100 ° C. is supplied to the boiler. A closed system is known in which drained drainage is collected in a sealed tank that does not open to the atmosphere, and the high-temperature and high-pressure drain that is collected in the sealed tank is supplied to a boiler (for example, , See Patent Document 1).

Japanese Patent Laid-Open No. 06-341605

  The drain recovery system usually includes a boiler and a water supply channel connected to the boiler. When the boiler is operated, the boiler is affected by dissolved oxygen, chloride ions, sulfate ions, etc. contained in the feed water. In order to prevent the inside from corroding or to prevent the scale from adhering due to hardness components contained in the water supply, various chemicals are injected into the water supply channel.

  However, in the conventional closed-type drain recovery system such as the above-mentioned Patent Document 1, with regard to what form of the medicine is injected, in particular, a plurality of boilers are provided and the number of operating boilers is adjusted according to the load amount. In the case of the system, no consideration is given as to what form the drug is injected into.

  For example, a configuration as shown in FIG. 3 is conceivable with respect to the injection of the drug in the closed drain recovery system including a plurality of boilers.

  In the drain recovery system shown in FIG. 3, steam generated in a plurality of, for example, three boilers 50 a to 50 c is supplied to the load device 51 and used, and the drain discharged from the load device 51 is used as a steam trap. After being collected in the drain header 53 via 52, the drain feed pump 54 supplies the boilers 50a to 50c via the motor valves 55a to 55c to the high-temperature and high-pressure drain water supply system 56 and the low-temperature and low-pressure from the makeup water tank 57. Supply water system 59 for supplying the makeup water to the boilers 50a to 50c by the makeup water pumps 58a to 58c, and water supply paths 59a to 59c corresponding to the boilers 50a to 50c of the low-pressure makeup water system 59. Corresponding to each of the chemical injection devices 60a to 60b, medicines are injected from these chemical injection devices 60a to 60b. It has become adult.

  According to the above-described system, since the medicine is injected into the low-pressure makeup water system 59, the low-pressure medicine is less expensive than the structure in which the medicine is injected into the high-pressure drain water supply system 56. The injection devices 60a to 60c can be used, and the cost of the system can be reduced accordingly.

  And in this system, the water supply signal which shows whether the setting of the timing which inject | pours a chemical | medical agent to each of the water supply path 59a-59c from the inexpensive low-pressure chemical injection apparatus 60a-60c is supplied to each boiler 50a-50c It is possible to inject a medicine according to the amount of water supplied to each of the boilers 50a to 50c.

  However, the boilers 50a to 50c are mainly supplied with high-temperature and high-pressure drains from the drain water supply system 56, and when the recovered water alone is not enough to supply the boilers 50a to 50c in time, The low temperature makeup water from the makeup water system 59 is supplied to cover the shortage.

  Therefore, in a situation where the water supply of the boilers 50a to 50c is in time for the recovered drain, for example, the high temperature and high pressure drain from the drain water supply system 56 is turned on by turning on the water supply signals of the three boilers 50a to 50c. While supplying to each boiler 50a-50c via the drain feed water pump 54 and the motor valves 55a-55c, the supplementary water pumps 58a-58c of the supplementary water system 59 are stopped to prevent supply of supplementary water. Therefore, when the water supply signal is ON, make-up water stays in the water supply paths 59a to 59c of the make-up water system 59, and the water supply paths 59a to 59c in the state where the make-up water stays stays in the medicine. The chemical | medical agent according to the water supply of the boilers 50a-50c will be inject | poured from the injection apparatus 60a-60c.

  When the recovered drain alone is insufficient to supply water to the boilers 50a to 50c, the supply water pumps 58a to 58c of the supply water system 59 are driven and the boilers 50a to 59c are driven from the water supply paths 59a to 59c. 50c is supplied with makeup water containing a high concentration of medicine.

  In the boilers 50a to 50c, the makeup water containing the high-concentration medicine is mixed with the drain into which no medicine is injected from the drain water supply system 56, so that the concentration of the medicine is made uniform.

  However, in the above configuration, in order to increase the thermal efficiency of the boiler, assuming that an economizer that preheats water supply with exhaust gas is installed upstream of each of the boilers 50a to 50c, there are the following problems.

  As described above, when the water supplied to the boiler is in time for the recovered drain, high-temperature and high-pressure drain into which no chemical is injected from the drain water supply system 56 is supplied to the boiler, and thus the economizer. . In addition, when the recovered drain alone is insufficient to supply water to the boiler in time, the high amount of the drug is retained from the water supply paths 59a to 59c of the makeup water system 59 as described above. The makeup water injected to the concentration will be supplied to the boiler and thus the economizer.

  In this way, the economizer is supplied with drain that is not injected with chemicals at all according to the state of water supply to the boiler, or supplementary water containing a high concentration of chemicals, but the economizer has a large volume. Unlike a boiler, since the concentration of the drug cannot be made uniform, the economizer has a state of preheating water supply containing no drug at all, and the economizer may corrode.

  The present invention has been made in view of the problems as described above, and aims to provide a closed-type drain recovery system capable of injecting a drug, particularly when an economizer is installed. It is an object of the present invention to provide a closed drain recovery system capable of injecting the chemical so that the economizer is not corroded.

 (1) In order to achieve the above object, a drain recovery system according to the present invention recovers drain discharged from a load device using steam generated in a boiler into a closed drain tank and also into the drain tank. A closed-type drain recovery system for supplying the recovered drain to the boiler on the downstream side of the drain tank, wherein a medicine is injected into the downstream side of the drain tank by a chemical injection device. .

  The number of the boilers is not particularly limited, and may be one or more.

  The downstream side of the drain tank refers to a path between the drain tank and a boiler on the downstream side thereof.

  According to the drain recovery system of the present invention, in the closed-type drain recovery system, the chemical can be injected into the water supply to the boiler, the chemical is injected downstream of the drain tank, and the boiler is supplied with water. As a result, in the present invention, a replenishment water system for supplying low-temperature replenishment water, which is different from the drain water supply system for supplying drain to the boiler, can be obtained. As in the case of the structure in which the medicine is injected, drain that is not injected with any medicine is not supplied to the boiler, or supply water in which the medicine is injected at a high concentration is not supplied to the boiler. When an economizer for preheating is installed, it is possible to effectively prevent the economizer from corroding.

 (2) In a preferred embodiment of the drain recovery system of the present invention, a water supply pump for supplying the recovered drain to the boiler is provided on the downstream side of the drain tank, and the drain tank and the water supply pump are provided by the chemical injection device. Drugs are injected into the path between the two.

  According to this embodiment, since the medicine is injected into the path between the drain tank and the water supply pump, that is, the upstream side of the water supply pump, compared with the case of injecting the medicine downstream of the water supply pump that becomes high pressure due to the discharge pressure. In addition, since a low-pressure chemical injection device can be used, the cost can be reduced.

 (3) In another preferred embodiment of the drain recovery system of the present invention, a flow rate sensor that detects the amount of water supplied to the boiler is provided on the downstream side of the drain tank, and the chemical injection device includes the flow rate The injection of the medicine is controlled based on the detection output of the sensor.

  According to this embodiment, since the flow rate sensor is provided on the downstream side of the drain tank and the injection of the drug is controlled based on the detection output of the flow rate sensor, the injection amount of the drug is appropriately set according to the amount of water supplied to the boiler. Can be controlled.

 (4) In the embodiment of the above (3), the drain side of the drain tank is branched to provide a drain circulation path for circulating the drain, and an automatic valve is installed in the drain circulation path. The opening and closing of the automatic valve may be controlled based on the detection output of the flow sensor.

  According to this embodiment, there is no need for water supply to the boiler, and when the drain from the drain tank becomes excessive, the automatic valve can be opened to return the excess drain to the drain tank. There is no need to drive or stop depending on whether or not to supply water to the boiler. Further, when water is supplied to the boiler, by closing the automatic valve of the circulation path, the water into which the medicine has been injected does not return to the drain tank via the circulation path and the concentration of the medicine does not decrease. The boiler can be supplied with an appropriate chemical concentration.

 (5) In another preferred embodiment of the drain recovery system of the present invention, a plurality of the boilers are provided, and the drain recovered in the drain tank is supplied to each boiler.

  According to this embodiment, the number of boilers to be operated can be adjusted according to the required steam amount (load amount).

 (6) In a preferred embodiment of the drain recovery system of the present invention, a pressure reducing valve for reducing the pressure of the drain discharged from the load device upstream of the drain tank is provided on the upstream side of the drain tank. Yes.

  According to this embodiment, since the pressure is reduced by the pressure reducing valve provided on the upstream side of the drain tank, there is no need to use an expensive drain tank for high pressure as the drain tank. In addition, an inexpensive chemical injection device for normal pressure can also be used as a chemical injection device for injecting a medicine downstream of the drain tank.

  ADVANTAGE OF THE INVENTION According to this invention, a chemical | medical agent can be inject | poured into the feed water to a boiler in a closed-type drain collection system. In addition, since the chemical is injected downstream of the drain tank and supplied to the boiler, the drain that has not been injected with any chemical is injected into the boiler as in the configuration in which the chemical is injected into a makeup water system different from the drain water supply system. The economizer is corroded when an economizer that preheats the water supplied to the boiler is installed without the supply or supply of high-concentration replenishment water to the boiler. Can be effectively prevented.

FIG. 1 is a diagram showing a configuration of a drain recovery system according to an embodiment of the present invention. FIG. 2 is a diagram showing a configuration of a drain recovery system according to another embodiment of the present invention. FIG. 3 is a diagram illustrating an example of a configuration in the case of performing chemical injection in a closed drain recovery system.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram showing a configuration of a drain recovery system according to an embodiment of the present invention. The drain recovery system according to this embodiment is provided with a plurality of boilers, in the embodiment, three boilers 1a to 1c, and adjusts the number of operating boilers according to the load amount to increase boiler efficiency. After the steam generated in 1a to 1c is accumulated in the steam header 5 via the steam pipes 4a to 4c in which the first ball valve 2, the first check valve 3 and the second ball valve 4 are respectively installed, The steam header 5 is supplied to a load device 6 such as a heat exchanger using steam via a third ball valve 11.

  Since the load device 6 uses the heat of the steam, the steam is deprived of heat and condensed to be drained and discharged from the load device 6. The drain discharged from the load device 6 is recovered, for example, to 0.98 MPa or less by a first pressure reducing valve 8 installed in the drain recovery pipe 7 and recovered in a drain tank 9 which is a sealed pressurizing tank. The A first steam trap 27 and a second steam trap 28 are connected to the drain recovery pipe 7 and the steam header 5, respectively.

  The drain tank 9 and the boilers 1a to 1c are respectively connected by a common common water supply pipe 10 and three branch water supply pipes 10a to 10c individually corresponding to the boilers 1a to 1c. Are provided with a water supply pump 12 and a flow rate sensor 26 described later, and motor valves 13a to 13c are installed in the respective branch water supply pipes 10a to 10c.

  The water supply pump 12 is a closed type water supply pump, and is always driven regardless of the presence or absence of water supply to the boilers 1a to 1c. By opening the motor valves 13a to 13c, the water supply pump 12 is provided in the drain tank 9. The collected drain is supplied to the corresponding boilers 1a to 1c. That is, water supply to each boiler 1a-1c is controlled by opening / closing of each motor valve 13a-13c, and these motor valves 13a-13c are individually controlled by each boiler 1a-1c.

  The downstream side of the water supply pump 12 is connected to the drain tank 9 by a circulation pipe 17 branched from the common water supply pipe 10, and the circulation pipe 17 includes a second check valve 14 and an automatic valve for circulation. A motor valve 15 and a flow rate adjustment valve 16 are installed.

  When water is not supplied to any of the three boilers 1 a to 1 c, the control unit 30 opens the circulation motor valve 15 to return the excess drain from the water supply pump 12 to the drain tank 9.

  The drain tank 9 is connected to a make-up water tank 20 by a make-up water pipe 19 provided with a water pump 18, and the amount of drain used is large, and the water level in the drain tank 9 is lower than the lower limit water level. When detected by a detector (not shown), the control unit 30 drives the water pump 18 to supply makeup water from the makeup water tank 20 to the drain tank 9.

  The drain tank 9 is also connected to the make-up water tank 20 by a surplus drain recovery pipe 22 provided with a second pressure reducing valve 21, and the second pressure reducing valve 21 is opened and closed according to the pressure in the drain tank 9. When the amount of drain used is small and the water level in the drain tank 9 becomes high, the second pressure reducing valve 21 is opened and the excess drain in the drain tank 9 is collected in the makeup water tank 20. A motor valve may be provided in place of the second pressure reducing valve 21, and the water level in the drain tank 9 may be detected to control the opening and closing of the motor valve.

  When the water level in the drain tank 9 is within a predetermined range, neither supply of the above-described makeup water nor recovery of surplus drain is performed, and the recovered drain is supplied to the boilers 1a to 1c as they are.

  Since the make-up water tank 20 stores low-temperature make-up water, it can be an open tank.

  In this embodiment, when an economizer that preheats water supplied to the boilers 1a to 1c with exhaust gas is installed on the water supply line upstream of the boilers 1a to 1c, for example, downstream of the motor valves 13a to 13c. In order to prevent corrosion, the following structure is provided.

  That is, in this embodiment, the medicine is injected by the chemical injection device 23 downstream of the drain tank 9 and upstream of the water supply pump 12. The medicine is injected through a medicine injection pipe 25 in which a third check valve 24 is installed.

  The chemical injection device 23 controls the injection of the medicine according to the detection output of the flow rate sensor 26 installed in the middle of the common water supply pipe 10 on the downstream side of the water supply pump 12, that is, the amount of water supplied to the boilers 1a to 1c. I am doing so.

  The above-described control unit 30 supplies water to at least one of the three boilers 1a to 1c so that the poured water is not returned to the drain tank 9 through the circulation pipe 17, that is, When supply of water to any one of the boilers 1a to 1c is detected by the flow sensor 26 and the medicine injection device 23 is injecting medicine, the circulation motor valve 15 installed in the circulation pipe 17 is controlled to be closed.

  In this way, since the chemical is injected into the common water supply pipe 10 on the downstream side of the drain tank 9, the high-temperature and high-pressure drain water supply system 56 and the low-temperature and low-pressure makeup water system 59 are used as shown in FIG. As in the case of injecting medicine into the replenishing water systems 59a to 59c, the medicine is not injected into the water supply to the boiler or the concentration of the medicine does not become high. Water can be supplied to the boilers 1a to 1c at a concentration. Thereby, when the economizer which preheats the water supply to the boilers 1a-1c is installed, it can prevent that an economizer corrodes.

  In addition, in the configuration shown in FIG. 3, the medicine injection devices 60 a to 60 c are installed for each of the boilers 50 a to 50 c, but in this embodiment, it is necessary to install the medicine injection device for each of the boilers 1 a to 1 c. In addition, a single medicine injection device 23 is sufficient, and the cost can be reduced.

  Furthermore, in this embodiment, since the high-pressure drain is decompressed by the first pressure reducing valve 8 and is poured into the upstream side of the feed water pump 12, the chemical injection device 23 uses an inexpensive chemical injection device for normal pressure. be able to.

  In this embodiment, the medicine injection device 23 injects the medicine based on the detection output of the flow sensor 26. However, as another embodiment of the present invention, the flow sensor 26 is omitted and water is supplied to the boiler. You may make it inject | pour a chemical | medical agent based on the water supply signal etc. which show whether or not.

  In this embodiment, the first pressure reducing valve 8 is provided to depressurize the high pressure drain. However, as another embodiment of the present invention, the first pressure reducing valve 8 is omitted and the drain is collected in the high pressure drain tank. It may be.

  In this embodiment, the medicine is injected upstream of the feed water pump 12, but as another embodiment of the present invention, the medicine may be injected downstream of the feed water pump.

(Embodiment 2)
FIG. 2 is a diagram showing a configuration of a drain recovery system according to another embodiment of the present invention, and parts corresponding to those in FIG. 1 described above are denoted by the same reference numerals and detailed description thereof is omitted. .

  In the above-described embodiment, water supply to the boilers 1a to 1c is only one system from the drain tank 9, but in this embodiment, the water supply path 31 from the makeup water tank 20 to each of the boilers 1a to 1c is provided. At the same time, it is configured so that medicine can be injected from the drug injection devices 32a to 32c into the branch water supply paths 31a to 31c to the boilers 1a to 1c of the water supply path 31.

  According to this embodiment, for example, when the water supply pump 12 on the downstream side of the drain tank 9 is broken, the boiler feed pumps 33a to 33c of the boilers 1a to 1c are used to supply the boilers 1a to 1 from the makeup water tank 20. While supplying water to 1c, a chemical | drug | medicine apparatus 32a-32c can inject | pour a chemical | medical agent into the branch water supply path 31a-31c to each boiler 1a-1c.

  Other configurations are the same as those of the above-described embodiment.

  The present invention is not limited to the above-described embodiments, and includes various changes or modifications within the scope described in the claims.

The present invention is useful as a closed type drain recovery system.

DESCRIPTION OF SYMBOLS 1a-1c Boiler 6 Load apparatus 8 1st pressure-reduction valve 9 Drain tank 12 Water supply pump 13a-13c Motor valve 15 Circulation motor valve 17 Circulation piping 20 Supplementary water tank 23, 32a-32c Chemical injection device 26 Flow sensor

Claims (6)

A closed-type drain that collects drain discharged from a load device that uses steam generated in a boiler in a closed drain tank and supplies the drain collected in the drain tank to the boiler on the downstream side of the drain tank. A drain collection system,
A drain recovery system, wherein a medicine is injected into the downstream side of the drain tank by a chemical injection device. A water supply pump for supplying the recovered drain to the boiler is provided on the downstream side of the drain tank,
Injecting a medicine into a path between the drain tank and the water supply pump by the chemical injection device,
The drain recovery system according to claim 1. Provided on the downstream side of the drain tank is a flow sensor for detecting the amount of water supplied to the boiler,
The medicine injection device controls the injection of medicine based on the detection output of the flow sensor.
The drain recovery system according to claim 1 or 2. A drain circulation path for branching the drain tank to circulate the drain is provided, and an automatic valve is provided in the drain circulation path. The automatic valve is installed on the basis of the detection output of the flow sensor. Control the opening and closing of the valve,
The drain recovery system according to claim 3. A plurality of the boilers are provided, and the drains collected in the drain tank are supplied to the respective boilers.
The drain recovery system according to any one of claims 1 to 4. A pressure reducing valve for reducing the pressure of the drain discharged from the load device upstream of the drain tank is provided on the upstream side of the drain tank.
The drain recovery system according to any one of claims 1 to 5.

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