JPH06265211A - Method for sensing non-condensed gas in pressure reduced boiler type gasification device and method for controlling pressure reduced boiler type gasification device - Google Patents

Abstract

PURPOSE:To prevent occurrence of icing or deterioration of a heat efficiency by a method wherein a temperature sensor is mounted at a heat transfer pipe for low temperature fluid and a staying of non-condensed gas is detected by a reduction of a surface temperature by more than a specified value. CONSTITUTION:A boiler 1 for heating boiler water within it and steam by heating thermal medium and a gasification part 3 having a heat transfer pipe 2 in which low temperature fluid flows are connected by a steam going pipe 4 and a condensed liquid returning pipe 5. There is provided a vacuum pump 6 for reducing pressure within the boiler 1 and within the gasification device 3. A heat transfer pipe 7 acting as a boiler water heating means is installed at the boiler 1. A plurality of temperature sensors S are mounted from the upstream side to the downstream side of the heat transfer pipe 2. A signal from the temperature sensor S is inputted to a changing-over control means 17, a surface temperature of the heat transfer pipe 2 sensed by each of the temperature sensors S is processed by the changing-over control means 17 so as to monitor the surface temperature and the surface temperature difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a non-condensable gas in a pressure reducing boiler type vaporizer for vaporizing a low temperature fluid such as LNG, and a pressure reducing boiler type vaporizer with the detection of the non-condensable gas. It relates to a control method.

[0002]

2. Description of the Related Art As one of vaporizers for vaporizing a low temperature fluid such as LNG, there is a decompression boiler type vaporizer, for example, the one shown in FIG. This vaporizer includes a can body 1 that heats internal can water with a heating heat medium such as burner combustion gas or high-temperature steam to generate steam, and a vaporization section 3 provided with a heat transfer tube 2 through which a low-temperature fluid flows. The vapor transfer pipe 4 and the condensate return pipe 5 are connected to each other.
That is, the inside of the can is evacuated by the vacuum pump 6 to operate. (For example, see Japanese Utility Model Laid-Open No. 2-9755) In such a decompression boiler type vaporizer, there is also one in which the can body 1 and the vaporization section 3 are integrated. (For example, the actual Kaihei 2-975
(See Japanese Patent Publication No. 4) In the above structure, the reduced pressure steam generated by being heated by the heating medium for heating (hereinafter simply referred to as steam).
Flows into the vaporization section 3 through the vapor outflow tube 4 and heat-exchanges with the low temperature fluid flowing through the heat transfer tube 2 to vaporize the low temperature fluid, while condensing itself and passing through the condensate return tube 5 to the can body. It returns to 1.

In the above vaporizer, the feed amount of the heating heat medium is feedback controlled so that the can water is kept at a constant set temperature, and the feed forward amount is derived corresponding to the flow rate of the low temperature fluid. Based on this, feedforward control is performed.

In the figure, reference numerals 8a and 8b are flow rate adjusting means for adjusting the flow rates of the heating medium for heating and the low temperature fluid, respectively.
a and 9b are flow rate control valves, 10a and 10b are flow rate sensors,
Reference numerals 11a and 11b are controllers. Further, reference numeral 13 is a setting means for deriving and setting a target value of the flow rate of the controller 11a on the heating heat medium side based on the can water temperature detected by the temperature sensor 12 and the set temperature thereof. As described above, the controller 11a performs feedback control of the temperature of the can water through the setting means 13, and the controller 11b on the low temperature fluid side.
Feedforward control is performed based on the feedforward amount given by.

[0005]

In the conventional method for directly detecting and controlling the temperature of the can water, the can water has a large heat capacity and the temperature sensor itself used for temperature detection has a detection delay. Due to these two factors, the dead time and the time constant are both large, so that there is a problem that it takes time for the control to return to stability after the disturbance caused by the change in the flow rate of the low temperature fluid enters. Therefore, an object of the present invention is to solve such a problem by performing control by the pressure inside the can, which has a one-to-one correspondence with the temperature of the can water, instead of the control by the temperature of the can water.

By the way, the one-to-one correspondence relationship between the temperature of the can water and the pressure in the can is established only when the non-condensable gas such as air does not stay in the can in the saturated state. When performing control, it is necessary to monitor the retention of non-condensable gas and take appropriate measures when this is detected. It is an object of the present invention to provide a method for detecting such non-condensable gas retention and a control method associated therewith.

[0007]

In order to solve the above-mentioned problems, the present invention first installs a temperature sensor on a heat transfer tube for a low temperature fluid in a decompression boiler type vaporizer to monitor the surface temperature, and Provided is a method for detecting the retention of non-condensable gas by lowering a surface temperature by a predetermined amount or more. Further, the present invention, as another method for solving the above-mentioned problems, in a heat transfer tube for a low temperature fluid in a decompression boiler type vaporizer, a plurality of temperature sensors are installed from its upstream side to its downstream side. Provided is a method of monitoring a surface temperature difference between points and detecting a non-condensable gas retention based on a surface temperature difference of a predetermined value or more. Further, the present invention, as still another method for solving the above-mentioned problems, in a heat transfer tube for a low temperature fluid in a decompression boiler type vaporizer,
A plurality of temperature sensors are installed from the upstream side to the downstream side to monitor the surface temperature of those points and the surface temperature difference between those points, and reduce the surface temperature at any point more than a predetermined value or a predetermined value. Provided is a method for detecting the retention of non-condensable gas based on the above surface temperature difference.

Further, the present invention is a method of controlling a decompression boiler type vaporizer with the detection of the above-mentioned non-condensable gas, in which the feed amount of the heating medium for heating is feedback-controlled so that the temperature of the can water becomes a predetermined temperature. A canister temperature sensor and a canister pressure sensor are provided in a decompression boiler type vaporizer that regulates the amount of depressurized steam generated, and the flow rate control means of the heating heat medium is determined from the detected value and set value of each of these sensors. The flow rate setting means for deriving the target value of the controller, the switching means for the flow rate setting means, and the switching control means for controlling the switching means are constituted, and the switching control means is non-condensable by the above-described detection method. Provided is a control method for detecting a gas retention and controlling a switching means to switch from control based on can internal pressure to control based on can water temperature.

[0009]

When non-condensable gas such as air stays in the can and adheres to the heat transfer tube of the low temperature fluid, it becomes difficult for steam to contact the surface of the heat transfer tube, and the surface temperature of the heat transfer tube decreases. And the temperature of the discharged gas also decreases. Therefore, if the surface temperature is monitored, it is possible to detect the retention of the non-condensable gas due to the decrease. However, the decrease in the surface temperature of the heat transfer tube also occurs due to the increase in the load of the low temperature fluid, that is, the increase in the flow rate.Therefore, the reference value of the surface temperature detected as the retention of the noncondensable gas should be changed according to the flow rate. The non-condensable gas is detected as a stagnation of the non-condensable gas when it is set or a value lower than the minimum temperature lowering due to the increase of the flow rate, that is, when the surface temperature lowers more than a predetermined value.

By the way, since the noncondensable gas does not necessarily adhere to the heat transfer tube uniformly, the temperature distribution on the surface of the heat transfer tube becomes non-uniform due to the adhesion of the noncondensable gas, and a temperature difference occurs between the surfaces. Therefore, if a plurality of temperature sensors are installed from the upstream side to the downstream side of the heat transfer tube and the surface temperature difference at those points is monitored, the case where the surface temperature difference exceeds a predetermined value is detected by the non-condensable gas. It can be detected as retention.

In the decompression boiler type vaporizer, in a saturated state and when non-condensable gas such as air does not stay in the can, there is a certain correspondence between the can water temperature and the can pressure. Since there is a relationship, if the can internal pressure is detected, the can water temperature can be indirectly detected by this correspondence. Therefore, the can water temperature can be indirectly adjusted to a predetermined temperature by controlling the detected can internal pressure to a predetermined pressure instead of the control by detecting the can water temperature. In such control, since the dead time and the time constant in detecting the change in the pressure inside the can are both small, control with good response characteristics can be performed, and the system can be guided more quickly and stably against external disturbances. be able to. Therefore, when non-condensable gas retention is detected, the one-to-one correspondence between can water temperature and can pressure is broken by switching control from can pressure to can water temperature as before. In the case of failure, appropriate control is performed.

[0012]

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 is a system diagram showing the configuration of a decompression boiler type carburetor to which the control method of the present invention is applied together with control elements. The same components as those of the conventional configuration shown in FIG. There is.

The vaporizer shown in FIG. 1 has a structure in which a can body 1 for generating steam and a vaporizing section 3 for vaporizing a low temperature fluid are separated from each other, that is, the can water inside is heated by a heating medium for heating to vaporize the steam. The vaporizing section 3 provided with the generated can body 1 and the heat transfer tube 2 through which the low-temperature fluid flows is connected by the vapor outgoing pipe 4 and the condensed liquid return pipe 5,
Vacuum pump 6 for decompressing the inside of the can body 1 and the inside of the vaporization section 3
Is provided. The can body 1 is provided with a heat transfer tube 7 as a heating means for the can water, and the can water is heated by a heating heat medium such as high-temperature steam flowing through the heat transfer tube 7. As described above, the vaporizer to which the present invention is applied may have an appropriate configuration such as a configuration in which the can body 1 and the vaporization section 3 are integrated, in addition to the above-described configuration, and a heating medium for heating and heating means for supplying the heating medium to the can body 1. The configuration of is also appropriate.

Flow rate adjusting means 8a and 8b are provided in the heat transfer tubes 7 and 2 for the heating heat medium and the low temperature fluid, respectively, and these flow rate adjusting means 8a and 8b are flow rate adjusting valves 9a and 9b, respectively. And flow rate sensors 10a, 10b and controller 1
It is composed of 1a and 11b. Reference numeral 12 is a temperature sensor that detects the temperature of the can water, and 13 is a first value that derives and sets the target value of the controller 11a on the heating medium side for heating based on the can water temperature detected by the temperature sensor 12 and its set temperature. Is a setting means. Reference numeral 14 is provided with a pressure sensor for detecting the pressure inside the can via the pressure guiding pipe 15, and the controller 1 on the heating medium side for heating is based on the detected pressure inside the can and the set pressure thereof.
It is a second setting means for deriving and setting the target value of 1a. Reference numeral 16 is a switching means for switching the control of the controller 11a to one of the first and second setting means 13 and 14, and this switching means 16 is configured to be switched by the switching control means 17. Reference numeral 18 is a third setting means for deriving and setting the feedforward amount of the controller 11b on the heating heat medium side, and the third setting means 18 is
A feedforward amount from a constant flow rate ratio obtained from the static balance of heat in the heat exchange between the steam and the low temperature fluid at the condition of the can water temperature and the flow rate of the low temperature fluid obtained from the low temperature fluid side controller 11b. Derive. Reference numeral S is a temperature sensor that measures the surface temperature of the heat transfer tube 7. A plurality of temperature sensors S are installed from the upstream side to the downstream side of the heat transfer tube 2. FIG. 1 shows five temperature sensors S, and FIG. 3 shows nine temperature sensors S. The signals of these temperature sensors S are input to the switching control means 17, and the switching control means 17 processes the surface temperature of the heat transfer tube 2 by each temperature sensor S to monitor the surface temperature and the difference in surface temperature. It is configured to do.

In the above structure, when the non-condensable gas such as air does not stay in the can and the switching control means 17 is not in the detection state, the switching control means 17 causes the switching means 16 to operate. The controller 11a on the heating heat medium side is controlled by switching to the second setting means 14 side. Since such control is performed by detecting the pressure inside the can, which has a small dead time and a small time constant compared to the detection of the temperature of the can water, it is possible to perform control with a fast response speed and to guide the system more quickly and stably. it can.

FIG. 5 shows the control by the pressure in the can as described above.
FIG. 6 shows an example of an implementation result applied to the vaporization of NG, and FIG. 6 shows a result of performing control by detecting the temperature of the can water as in the conventional case. In both cases, when the LNG flow rate is changed. The behaviors of the can internal pressure, the can internal temperature, the amount of high temperature steam as a heating heat medium, and the opening degree of the flow rate control valve 9a are shown. As shown in these figures, in the control by measuring the pressure in the can, compared with the control by detecting the temperature of the can water, the fluctuation amount of each of the above variables is small, the controllability is good, and the system becomes stable more quickly. You can see that you will be guided.

In the above control, when air enters and stays in the can and adheres to the heat transfer tube 2 of the low temperature fluid, it becomes difficult for steam to contact the surface of the heat transfer tube 2 and the surface temperature thereof decreases. For example, FIG. 4 shows the temperature sensor S as shown in FIG.
(S1, S2, S3, S4, S5, S6, S7, S8,
In the heat transfer tube 2 in which S9) is installed, the case where air adheres to a portion corresponding to the temperature sensor S5 is shown. The surface temperature of this portion gradually decreases with the passage of time, while the other temperature sensors The surface temperature of the portions corresponding to S1 and S3 does not decrease. If this state is left, the temperature sensor S
The surface temperature of the corresponding portion of 5 finally becomes 0 ° C. or lower and icing occurs. In such an air adhering state, the difference between the detected value of the temperature sensor S5 and the detected value of any other temperature sensor, in this case, the temperature sensor S1, is a predetermined width Δ.
By controlling whether the temperature is equal to or higher than T, or by monitoring whether any one of the temperature sensors, in this case the temperature sensor S5, is higher or lower than the reference temperature T, the above-mentioned air adhesion state switching control means 17 is controlled. Can be detected at. Further, if both of these are monitored and detected as the logical sum of them, it is possible to detect the adhering state of air in which a phenomenon exceeding a predetermined level appears in only one of them.

By the way, in the vaporizer described above, the relationship between the can water temperature (θs), the low temperature fluid flow rate (G), the low temperature fluid inlet temperature (θi) and the outlet gas temperature (θ) is in the can. By solving a differential equation obtained from the heat balance of minute elements and obtaining a steady solution, it can be expressed as the following equation. θ = (1−f (G)) θs + f (G) θi (1) where f (G) is a monotonically increasing function having the heat transfer area as a parameter. In the above equation, since θs> θi,
If the can water temperature (θs) is constant, the outlet gas temperature (θ) decreases monotonically with an increase in the low temperature fluid flow rate (G). Further, the temperature of the heat transfer tube 2 also decreases as the temperature of the discharged gas decreases. Therefore, the reference value of the surface temperature detected as the retention of the non-condensable gas may be set differently in accordance with the flow rate, or may be set as a value lower than the minimum temperature which is decreased by the increase of the flow rate. In the former case, the switching control means 17 performs the above detection by referring to the flow rate signal from the controller 11b on the low temperature fluid side.

As described above, when the switching control means 17 detects the retention of air, the switching control means 17 operates the switching means 16 to operate the controller 11 by the first setting means 13.
A predetermined backup operation can be performed by switching to the control of a. In such backup operation,
Even if the one-to-one correspondence between the can water temperature and the can internal pressure is broken, the can water temperature can be directly controlled to the set temperature.

The method for detecting a non-condensable gas according to the present invention is
Of course, it can also be applied to the control method of the conventional decompression boiler type carburetor that performs only the control by detecting the temperature of the can water,
In this case, the non-condensable gas is detected to stay and the vacuum pump 6
Can be operated to eliminate the inconvenience caused by staying.

[0021]

INDUSTRIAL APPLICABILITY As described above, the present invention can detect the retention of non-condensable gas such as air which causes a decrease in the surface temperature of the heat transfer tube and a decrease in the temperature of the discharged gas in the decompression boiler type vaporizer. By performing a predetermined process based on this detection, it is possible to prevent the occurrence of icing and the like and the deterioration of thermal efficiency.

Further, by applying such a method of detecting non-condensable gas retention to a control method of a pressure reducing boiler type carburetor configured to be switchable between control by can pressure and can water temperature, When there is no such retention, the former control can be switched over to control both the dead time and the time constant to be small, and therefore control with good response characteristics can be performed, and the system can be treated faster against disturbance. In addition to the stable control, if the retention occurs, by switching to the latter control, the appropriate control is maintained even if the one-to-one correspondence between the can water temperature and the can pressure is broken. Therefore, there is an effect that the former control can be performed safely and stably.

[Brief description of drawings]

FIG. 1 is a system diagram showing the configuration of a decompression boiler type vaporizer to which the method of the present invention is applied together with control elements.

FIG. 2 is a system diagram showing the configuration of a conventional decompression boiler type carburetor together with control elements.

FIG. 3 is an explanatory diagram showing an installation example of a temperature sensor in the method of the present invention.

4 is an explanatory diagram showing an example of detecting the surface temperature of a heat transfer tube by the temperature sensor of FIG.

FIG. 5 is an explanatory diagram showing a control characteristic in the case where control is performed by the pressure inside the can in the control method of the present invention.

FIG. 6 is an explanatory diagram showing control characteristics in the control method of the present invention in the case where control is performed according to the can water temperature as in the conventional case.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Can body 2 Heat transfer pipe 3 Vaporization part 4 Steam forward pipe 5 Condensate return pipe 6 Vacuum pump 7 Heat transfer pipe 8a Flow rate adjusting means 8b Flow rate adjusting means 9a Flow rate adjusting valve 9b Flow rate adjusting valve 10a Flow rate sensor 10b Flow rate sensor 11a Regulator 11b Controller 12 Temperature sensor 13 First setting means (setting means) 14 Second setting means 15 Pressure guide tube 16 Switching means 17 Switching control means 18 Third setting means S Temperature sensor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kanji Kujii 5-5-43- 211 Higashiterao, Tsurumi-ku, Yokohama-shi, Kanagawa (72) Inventor Masahiro Arakawa 4-8-3, old works, Funabashi, Chiba

Claims (4)

[Claims] 1. A temperature sensor is installed in a heat transfer pipe for a low temperature fluid in a decompression boiler type vaporizer to monitor the surface temperature, and the retention of the non-condensable gas is detected by lowering the surface temperature more than a predetermined value. Method for Detecting Noncondensable Gas in Decompression Boiler Vaporizer 2. A heat transfer pipe for a low temperature fluid in a decompression boiler type carburetor is provided with a plurality of temperature sensors from the upstream side to the downstream side thereof to monitor the surface temperature difference between those points, and to detect the temperature difference above a predetermined level. Method for detecting noncondensable gas in a decompression boiler type vaporizer characterized by detecting retention of noncondensable gas by surface temperature difference 3. A heat transfer pipe for a low temperature fluid in a decompression boiler type vaporizer is provided with a plurality of temperature sensors from the upstream side to the downstream side thereof, and the surface temperature of those points and the surface temperature between those points. Non-condensation in a decompression boiler type vaporizer characterized by monitoring the difference and detecting a decrease in the surface temperature at any point above a predetermined level, or detecting the retention of non-condensable gas due to a difference in surface temperature above a predetermined level. Method for detecting volatile gas 4. A can water temperature sensor and a can pressure sensor in a decompression boiler type carburetor that controls the amount of heating medium supplied by feedback so that the temperature of the can water becomes a predetermined temperature and adjusts the amount of depressurized steam generated. With the provision of a flow rate setting means for deriving the target value of the controller of the flow rate adjusting means of the heating heat medium from the detected value and the set value of each of these sensors, and a switching means of these flow rate setting means, And a switching control means for controlling the switching means, the switching control means comprising:
Accompanied by detection of the non-condensable gas, which is characterized by detecting the retention of the non-condensable gas by the detection method 2 or 3 and controlling the switching means to switch from control by the pressure inside the can to control by the temperature of the can water. Control method of decompression boiler type vaporizer