JPS6059406B2 - Control method and device for power plant using low boiling point medium steam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for controlling a power plant that utilizes low-boiling medium vapor, and particularly relates to a direct heat exchanger for obtaining low-boiling medium vapor and a heating medium such as waste heat gas. The present invention relates to a method and apparatus for controlling a power plant that utilizes low boiling point medium vapor and is suitable for circulating an intermediate heat medium through a heater that heats the intermediate heat medium at a power plant.

Power plants that use low-boiling point medium steam are capable of generating high-energy steam even if the low-boiling point medium, which is the pin working medium, is a low heat source medium such as waste heat gas or geothermal fluid from power plants, steel plants, etc. In recent years, it has attracted attention as it is effective in utilizing resources.

Low boiling point medium vapor is composed of these low heat source medium and low boiling point medium.
This occurs due to heat exchange. Such low-boiling point media generally have low thermal conductivity, so the thermal resistance due to evaporation is large, so it is not possible to increase the heat transfer coefficient of the heat exchange section, and the heat transfer area is also considerably larger than that in conventional plants. Become. Therefore, in order to obtain the desired heat transfer area, when using an indirect heat exchanger, the structure becomes complicated due to heat transfer tube piping, etc., and it is obvious that the size will inevitably increase. It was desired to use a type heat exchanger to make the heat exchanger smaller and simpler in structure. Certain restrictions here include that the low-boiling point medium and the heating medium do not react due to direct contact, and that the heating medium supplied to the direct heat exchanger contains substances that react with the vapor of the low-boiling point medium. It does not contain impurities that affect thermal performance, and it handles sudden changes in the temperature of the low boiling point medium so as not to cause thermal reactions of the low boiling point medium itself as described below. This certain limitation is due to the use of an intermediate heat medium that has no reactivity with the low boiling point medium, and after heating the intermediate heat medium with the low heat source medium, it is supplied to the direct heat exchanger that is supplied with the low boiling point medium. I was filled with that. Furthermore, it was desired that the intermediate heat medium be recycled for efficient resource use. However, if the intermediate heat medium and the low-boiling point medium come into direct contact, some low-boiling point medium will be dissolved in the intermediate heat medium, and this low-boiling point medium is explosive and flammable at a certain temperature or higher. Freon has attracted attention in recent years because it does not exhibit these properties, but it decomposes on its own above a certain temperature and generates corrosive decomposition products.On the other hand, it does not exhibit these properties. However, since the supplied medium (hereinafter referred to as heating medium) is high temperature and fluctuates in temperature, such as waste heat gas or geothermal medium, thermal reactions such as combustion and decomposition of low boiling point medium in the heater may occur. It is necessary to take measures to prevent the occurrence of Conventionally, it has been considered to detect the temperature of the heating medium or intermediate heating medium at the inlet side of the heater to control the flow rate or stop the supply of the heating fluid or intermediate heating medium, but this conventional method has the following drawbacks. Was. First, an expensive and large high-temperature valve is required to control the flow rate or stop the supply of the heating medium. Next, controlling the flow rate or stopping the supply of the intermediate heat medium changes the amount of intermediate heat medium supplied to the direct heat exchanger, so the amount of dissolved low boiling point medium, the amount of generated steam,
Considering the accumulation in the direct heat exchanger, the amount of low boiling point medium supplied to the direct heat exchanger must also be controlled, making the control system complex, and the amount of low boiling point medium supplied to the heater. As described above, it is difficult to prevent the thermal reaction of the low boiling point medium.
An object of the present invention is to control the thermal reaction of a low-boiling medium in a heater installed on a path through which an intermediate heat medium mixed with a low-boiling medium circulates through a direct heat exchanger that generates low-boiling medium vapor. The purpose is to prevent it.

The invention described in claims 1 and 2 provides a direct heat exchanger in which the intermediate heat medium directly contacts the low boiling point medium and the intermediate heat medium to obtain low boiling point medium vapor; In a system in which the medium is circulated through a heater that heats the medium with a heating medium such as waste heat gas, the direct type The temperature on the path leading to the input side of the heat exchanger fluctuates, and by controlling the amount of low boiling point medium supplied to the direct heat exchanger based on this temperature fluctuation, the temperature inside the heater is brought to the set temperature. If the intermediate heat medium mixed with a low boiling point medium is supplied to the heater through direct heat exchange, the thermal reaction of the low boiling point medium in the intermediate heat medium will not occur in the heater. supply to the direct heat exchanger based on a comparison between the temperature detected on the path from the outlet side of the heater to the front of the direct heat exchanger and the set temperature. The amount of heat exchanged in the direct heat exchanger is controlled by adjusting the flow rate of the low boiling point medium, thereby controlling the temperature of the intermediate heat medium supplied to the heater.

The invention as recited in claims 3 and 4 further provides that if the temperature at the exit side of the direct heat exchanger is controlled so as not to fall below a set value, the temperature in the heater described above It has been confirmed that the response to set temperature is faster and a decrease in the efficiency of low boiling point medium vapor in the direct heat exchanger can be prevented. Based on a comparison between the detected temperature (hereinafter referred to as inlet temperature) and the corresponding set temperature, the flow rate of the low boiling point medium supplied to the direct heat exchanger is adjusted (hereinafter referred to as main control); When the temperature detected on the path from the outlet side of the direct heat exchanger to the front side of the heater (hereinafter referred to as outlet temperature) becomes lower than the corresponding set temperature, priority is given to the main control. The flow rate of the low boiling point medium supplied to the direct heat exchanger is adjusted based on the comparison between the outlet temperature and the corresponding set temperature, and the exchange rate in the direct heat exchanger is thereby adjusted. It controls the increase and decrease of the amount of heat and controls the temperature of the intermediate heat medium supplied to the heater.

Hereinafter, embodiments of the invention described in claims 1 and 2 will be described with reference to FIG.

In this embodiment, waste heat gas is used as the heating fluid, and the intermediate heat medium is supplied at a constant speed by a circulation pump 5 to the heater 2 through which the waste heat gas 1 flows. The heater 2 is a shell-and-tube type indirect heat exchanger, and the intermediate heat medium flows through heat transfer tubes in the heater 2. The temperature of the intermediate heat medium heated by passing through the heater 2 is detected by a temperature detector 13 installed at the outlet of the heater 2, and the temperature of the intermediate heat medium is detected by the temperature detector 13 installed at the outlet of the heater 2. A direct heat exchanger 6 is supplied with boiling point medium. The heated heat medium whose temperature has been lowered by heat exchange in the direct heat exchanger 6 is supplied to the heater 2 again via the intermediate heat medium discharge pipe 4 by the circulation pump 5, and the above operation is repeated thereafter. circulates. On the other hand, most of the liquid low boiling point medium supplied to the direct heat exchanger 6 is heated by heat exchange with the intermediate heat medium to become low boiling point medium vapor, and the generated low boiling point medium vapor transport pipe 7 is heated. The turbine 8 is then driven. The low boiling point medium vapor that drove the turbine 8 is recovered, liquefied by passing through the condenser 9, and then passed through the low boiling point medium supply pipe 12 provided with the flow rate control valve 11 by the circulation pump 10, and is again directly converted into heat. It is supplied to the exchanger 6 and thereafter circulated by repeating the above operation. The intermediate heat medium and the low boiling point medium come into direct contact with each other through the direct heat exchanger 6, and most of the low boiling point medium turns into steam and reaches the generated low boiling point medium vapor transport pipe 7, but due to the direct contact, It is unavoidable that a portion of it will be mixed into the intermediate heat medium. Therefore, the intermediate heat medium is
It is supplied to the heater 2 in a state containing a low boiling point medium. The temperature sensor 13 is heated by the heater 2 and is heated by the direct heat exchanger 6.
The temperature of the intermediate heat medium supplied to the intermediate heat medium is detected, and an output detected temperature signal 15 is sent to the flow control valve control device 14. The detected temperature signal 15 sent into the flow rate adjustment control device 14 is subjected to a deviation from the set temperature signal 16 in an adder 17 to generate a deviation signal 18. It is converted into a control signal 20 which is a control signal, that is, the control signal 20 is generated in the flow control valve control device 14 to control the opening degree of the flow control valve 11 installed in the low boiling point medium supply pipe 12. Here, the opening degree is made larger as the temperature of the intermediate heat medium detected by the temperature detector 13 is higher. In this embodiment, as will be described later, the set temperature signal 16 and the circulation speed of the intermediate heat medium mean that the intermediate heat medium, whose temperature has been lowered by heat exchange with a low boiling point medium, flows through the temperature sensor 13. The temperature is set so that it does not exceed a specific temperature. Since the configuration and operation of this embodiment and a power generation plant to which this embodiment is applied are as described above, this embodiment has the following effects. Since the temperature detector 13 is installed at the outlet of the heater 2, the maximum temperature inside the heater 2 is constantly detected, and the flow rate is immediately determined based on this maximum temperature. The control valve 11 is controlled, that is, from the time when the temperature is detected by the temperature sensor 13 until the direct heat-exchanged low-temperature intermediate heat medium generated based on the detected temperature signal 15 is supplied to the heater 2. Since the time becomes extremely fast, the maximum temperature inside heater 2 is at a low boiling point! It is prevented that a certain temperature is reached which would cause a thermal reaction of the medium, and thus the prevention of a thermal reaction of the low-boiling medium in the heater is achieved with an early response. Next, an embodiment of the invention described in claims 3 and 4 will be described with reference to FIG.

This embodiment is also applied to the same power plant as the first embodiment. The differences from the first embodiment are as follows:
The point is that a temperature detector 21 is also provided at the outlet of the direct heat exchanger 6. That is, the temperature of the intermediate heat medium heated by passing through the heater 2 is detected by the temperature detector 13 installed at the outlet of the heater 2, and the intermediate heat medium is directly heated as in the first embodiment. It is supplied to the exchanger 6. The temperature of the heated heat medium that has been lowered by the heat exchange in the direct heat exchanger 6 is detected by the temperature detector 21 installed at the outlet of the direct heat exchanger 6, and the temperature of the heated heat medium is lowered by the heat exchange in the direct heat exchanger 6. The water is sent to the heater 2 in the same manner as above, and is then circulated by repeating the above operation. The circulation route for the low boiling point medium is also the same as in the first embodiment. The temperature detector 13 detects the temperature of the intermediate heat medium heated by the heater 2 and supplied to the direct heat exchanger 6, and outputs a detected temperature signal 15 to the flow rate regulating valve control device 14. The detected temperature signal 15 sent into the flow control valve control device 14 is subjected to a deviation from the set temperature signal 16 in an adder 17 to generate a deviation signal 18, and the deviation signal 18 is sent to a signal priority circuit 28. on the other hand,
The temperature detector 21 detects the temperature of the intermediate heat medium after it has contributed to heat exchange in the steam generator 6, and outputs a detected temperature signal 2.
2 is also sent to the flow control valve control device 14. The detected temperature signal 22 sent to the flow rate regulating valve control device 14 is subjected to a deviation from the set temperature signal 23 in an adder 24 to generate a deviation signal 25, that is, α, and α is a selected deviation signal in the signal selection circuit 26. 27, that is, β, and β is also sent to the signal priority circuit 28. The relationship between α and β is as follows: when α×O, β=K·α (K is a constant), and when α≧0, β=0.

When β is sent into the signal priority circuit 28, β=K・α
(K is a constant), the deviation signal 18 is sent to the proportional/integral controller 19 via the relay 29, and when β=0, the deviation signal 18 is sent to the proportional/integral controller 19 via the relay 30. Both β and the deviation signal 18 are converted into a control signal 20 which is a proportional-integral control signal in the proportional-integral controller 19, that is, the control signal 20 is generated in the flow rate regulating valve control device 14, and the low-boiling point medium supply pipe 12 The opening degree of the flow control valve 11 installed in the flow control valve 11 is controlled. Flow rate control valve 11 (:i)
More specifically, the opening degree control is as follows. stomach
The temperature of the intermediate heat medium flowing through the temperature detector 13 begins to rise beyond the set value.

Immediately, the flow rate of the low boiling point medium supplied to the direct heat exchanger 6 begins to increase by proportional-integral control based on the flow rate regulating valve control device 14.

C. The temperature of the intermediate heat medium flowing through the temperature sensor 21 begins to decrease.

2. The temperature of the intermediate heat medium flowing through the temperature detector 21 exceeds the set value and begins to drop.

E Immediately, the flow rate of the low boiling point medium supplied to the direct heat exchanger 6 begins to decrease by proportional-integral control based on the flow rate adjustment valve control device 14.

Due to E and E, the temperature of the intermediate heat medium flowing through the temperature sensor 21 begins to exceed the set value.

G. The mouth movement starts immediately, and the mouth movement is repeated thereafter.

H. By repeating this process, the temperature of the intermediate heat medium flowing through the temperature detector 21 becomes equal to or higher than a certain value.

The intermediate heat medium that has passed through the outlet side of the direct heat exchanger 6 is sent to the heater 2 and heated; By supplying the temperature, the temperature of the intermediate heat medium flowing through the temperature sensor 13 is returned to the set value. Even if the temperature of the intermediate heat medium flowing through the temperature sensor 13 drops beyond the set value, it can be returned to the set value again by the above-mentioned reverse action, and in this way, the temperature can be detected. The temperature of the intermediate heat medium flowing through the heater 2, that is, the maximum temperature of the intermediate heat medium flowing through the heater 2, is such that the low boiling point medium does not cause a thermal reaction in the heater 2, and the direct heat exchanger 6 The temperature falls within a temperature range that does not reduce the efficiency of generating low boiling point medium vapor within the temperature range. Also in this embodiment, as described later, the set temperature signal 16
and the circulation speed of the intermediate heat medium means that the intermediate heat medium, whose temperature has been lowered by heat exchange with a low boiling point medium,
The temperature is set so that the temperature does not exceed a specific temperature at the time the fluid flows through the fluid. Further, the set temperature of the set temperature signal 23 is set lower than when the temperature at the time when the intermediate heat medium flows through the temperature detector 13 is the set temperature. Since the configuration and operation of this embodiment and the power plant to which this embodiment is applied are as described above, this embodiment has the following effects in addition to the effects of the first embodiment. Since the temperature detector 21 is installed at the outlet of the direct heat exchanger 6, the lowest temperature of the intermediate heat medium in the direct heat exchanger 6 is always and immediately detected. If the temperature drops below a certain level, control based on the set temperature signal 23 is started immediately, so the temperature inside the direct heat exchanger will not drop more than necessary, and the temperature that is supplied to the direct heat exchanger will not be lowered more than necessary. Therefore, in addition to the effects of the first embodiment, highly efficient low boiling point medium vapor generation in the direct heat exchanger 6 is achieved.
This can be achieved with early response. For example, a power generation plant is given the following conditions.

B Temperature of waste heat gas supplied to heater 2; 200 to 5
000C port Intermediate heat medium used; Hindered ester oil C Low boiling point medium used; Freon R-113 2 The temperature of 500°C of waste heat gas 1 passes through the heat exchanger tube wall, causing Freon R in the hindered ester oil. -1
13 decomposes (circulation speed) and time constant) 1900C e Set temperature corresponding to temperature detector 13 (set temperature of set temperature signal 16) to 1500C Set temperature corresponding to temperature detector 21 ( The set temperature of the set temperature signal 23) is 1000 C. Therefore, in the control based on the comparison between the temperature detected by the temperature detector 13 and the set temperature (e), the output side of the direct heat exchanger 6 is 120 ± 40 °C. The temperature of the intermediate heat medium flowing through the temperature detector 13 via the heater 2 reaches 150.
The temperature is within the range of ±30°C, and thermal decomposition of Freon R-113 is prevented.

Claims (1)

[Scope of Claims] 1. A heater that heats an intermediate heat medium with a heating medium such as waste heat gas, and a direct heat exchange for obtaining low boiling point medium vapor by bringing the low boiling point medium into direct contact with the intermediate heat medium. In a method for controlling a power generation plant using low boiling point medium steam having a
A low boiling point medium that detects the temperature on a path from the outlet side of the heater to the front side of the direct heat exchanger, and supplies the low boiling point medium to the direct heat exchanger based on a comparison between the detected temperature and a set temperature. A low boiling point medium, characterized in that the flow rate of the medium is controlled to increase or decrease the amount of heat exchanged in the direct heat exchanger, thereby controlling the temperature of the intermediate heat medium supplied to the heater. A method of controlling a power generation plant that uses steam. 2. A low boiling point device that has a heater that heats an intermediate heat medium with a heating medium such as waste heat gas, and a direct heat exchanger that brings the low boiling point medium and the intermediate heat medium into direct contact to obtain low boiling point medium vapor. In a control device for a power generation plant that uses medium steam,
a temperature detector provided on a path from the outlet side of the heater to before the direct heat exchanger; a flow rate control valve for adjusting the supply flow rate of the low boiling point medium before the direct heat exchanger; A flow rate adjustment valve control device is provided to control the flow rate adjustment valve in order to control an increase or decrease in the amount of heat exchanged in the direct heat exchanger based on a comparison between the detected temperature detected by the detector and the set temperature. A control device for a power generation plant that utilizes low boiling point medium steam, characterized by: 3. A low boiling point device that has a heater that heats an intermediate heat medium with a heating medium such as waste heat gas, and a direct heat exchanger that brings the low boiling point medium and the intermediate heat medium into direct contact to obtain low boiling point medium vapor. In a method of controlling a power generation plant using medium steam,
The temperature at the inlet side of the direct heat exchanger is detected on the path from the outlet side of the heater to the front side of the direct heat exchanger, and the detected temperature at the inlet side of the direct heat exchanger is compared with the temperature at the inlet side of the direct heat exchanger. Based on the comparison with the set temperature on the side, the flow rate of the low boiling point medium supplied to the direct heat exchanger is adjusted and the flow rate of the low boiling point medium supplied to the direct heat exchanger is adjusted. The temperature on the outlet side of the direct heat exchanger is detected, and when the detected temperature on the outlet side of the direct heat exchanger becomes lower than the set temperature on the outlet side of the direct heat exchanger, the temperature on the inlet side of the direct heat exchanger is detected. Priority is given to control based on a comparison between the detected temperature of the direct heat exchanger and the set temperature on the inlet side of the direct heat exchanger. the flow rate of the low boiling point medium supplied to the direct heat exchanger based on the heat exchanger, thereby controlling the temperature of the intermediate heat medium supplied to the heater. A method of controlling a power generation plant that uses medium steam. 4. A low boiling point device that has a heater that heats an intermediate heat medium with a heating medium such as waste heat gas, and a direct heat exchanger that brings the low boiling point medium into direct contact with the intermediate heat medium to obtain low boiling point medium vapor. In a control device for a power generation plant that uses medium steam,
A temperature detector on the inlet side of the direct heat exchanger provided on the path from the outlet side of the heater to the front side of the direct heat exchanger, and a temperature detector on the path from the outlet side of the direct heat exchanger to the front side of the heater. a temperature detector on the outlet side of the direct heat exchanger, a flow rate control valve for adjusting the supply flow rate of the low boiling point medium before the direct heat exchanger, and a temperature detector on the inlet side of the direct heat exchanger. Based on the comparison between the detected temperature detected by the heat exchanger and the set temperature on the inlet side of the direct heat exchanger, the detected temperature detected by the temperature detector on the outlet side of the direct heat exchanger Control based on a comparison between the detected temperature detected by the temperature detector on the direct heat exchanger inlet side and the set temperature on the direct heat exchanger inlet side when the temperature becomes lower than the set temperature on the input side of the direct heat exchanger. Based on the comparison between the detected temperature detected by the temperature detector on the outlet side of the direct heat exchanger and the set temperature on the outlet side of the direct heat exchanger, the amount of heat exchanged in the direct heat exchanger is given priority to 1. A control device for a power generation plant using low boiling point medium vapor, characterized in that a flow rate regulating valve control device is provided for controlling the flow rate regulating valve in order to control an increase or decrease in the amount of water.