JPH0823406B2 - Water supply control device for once-through type exhaust heat boiler - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water supply control of a boiler which obtains steam or hot water by utilizing exhaust heat of an internal combustion engine or an incinerator, and particularly to a water supply control device in a once-through type exhaust heat boiler. It is about.

[0002]

2. Description of the Related Art Generally, a once-through type boiler is designed so that its water level up to the middle of a heat receiving water pipe satisfies a circulating water flow rate ratio of 1/2 or less, and a thermosiphon is constructed with a rated heat load. It is supposed to be done. However, when the heat load decreases, the thermosyphon is not configured, and as a result, overheating occurs in the upper part of the heat receiving water pipe, causing damage to the heat receiving water pipe, and concentrating can water in the heat receiving water pipe. As a result, impurities are deposited, which also causes damage to the heat receiving water pipe.

Conventionally, in order to prevent damage due to overheating of the heat receiving water pipe in this type of boiler, proper control of water supply into the heat receiving water pipe has been performed.

However, the conventional water supply control is on / off control or proportional control for the required water level, and the above problems have not been solved yet. Also,
Some have adopted a means to raise the water level by controlling by two continuous water levels, but this control can detect the water level of only part of the heat receiving water pipes, so it is possible to cover the entire heat receiving water pipes. Therefore, it is difficult to prevent the heat receiving water pipe from overheating. Then, in the water level control by the double water level, it was also difficult to detect the representative value of the entire heat receiving water pipe by the position of the detection sensor. In addition, in the conventional proportional water supply control,
As a sensor for water supply proportional control that optimizes the amount of water supply per unit time, a displacer type, a differential pressure transmitting type, etc. are used, but these are all expensive, and this type of boiler is used. There was a limit to its application.

[0005]

In view of the above-mentioned problems, the present invention improves the on / off control system and properly controls the amount of water supply per unit time at an appropriate water level so that the heat receiving water pipe It is possible to surely prevent damage due to overheating and to prevent precipitation of impurities due to concentration of can water that causes damage to the heat receiving water pipe. Further, the water supply control is made possible by a pseudo proportional control system which can be provided at a low cost with a simple structure.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, in which a large number of heat receiving water pipes are housed and arranged, and an exhaust gas inlet line is connected to one side and the other side is connected to the other side. An exhaust gas outlet line is connected, and the internal pressure of the can in the once-through type exhaust heat boiler connected to a water supply line for supplying water to the heat receiving water pipe is detected, and the temperature of the exhaust gas at the outlet of the exhaust heat boiler is detected and detected. Calculated the internal pressure of the can and the exhaust gas temperature to obtain the heat load of the exhaust heat boiler, determine an appropriate value of the water level for the heat receiving water pipe under the obtained heat load, and the determined appropriate value. In the water supply control device in the once-through heat recovery boiler, which compares the actual water level of the heat receiving water pipe and controls the water supply level of the heat receiving water pipe based on the comparison result, the heat receiving water pipe The water level control cylinder for detecting the water level is provided,
The detection ends for detecting water levels at a plurality of points in the water level control cylinder are respectively inserted and installed in the water level control cylinder,
The rise time and fall time of the water level between the respective detection ends are measured based on the detection signals from the respective detection ends, and the next in-can according to the rise time and the fall time .
A controller is provided that determines the amount of water supply per unit time when the water level rises and when the water level in the can falls, and outputs the determined amount of water supply as a control signal, which is provided in the water supply line by the output signal from the controller. It is characterized by controlling the rotation speed of the water supply pump.

[0007]

According to the water supply control device of the present invention, each detection end inserted and installed in the water level control cylinder outputs each detection signal to the controller. The controller receiving each detection signal measures the rising time and the falling time of the water level between the respective detection ends, and in order to make each of the measured times as long as possible, the water supply amount per unit time To decide.
The amount of water supply is determined as the amount of water supply at an appropriate water level determined based on the heat load of the exhaust heat boiler, and this is output as a control signal to the water supply pump provided in the water supply line. The water supply pump that has received this control signal continuously changes the number of revolutions and supplies the amount of water supply per unit time instructed by the controller into the heat receiving water pipe. As a result, the amount of water supply when the water supply valve is on is adjusted, and the on / off operation interval of the water supply valve is lengthened,
The control is similar to that of proportional water supply.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described in detail below with reference to the drawings. The embodiment shown in the drawings illustrates, as an example, an exhaust heat boiler in which steam is obtained by utilizing exhaust heat from an internal combustion engine, an incinerator, or the like.
FIG. 3 is an explanatory view schematically showing an embodiment of a water supply control device.

First, an outline of an exhaust heat boiler 1 equipped with a water supply control device will be described with reference to FIG. 1. The exhaust heat boiler 1 supplies exhaust gas from an exhaust gas source (not shown) such as an internal combustion engine or an incinerator. It is configured to be introduced from the inlet line 2 on the one side, heat-exchange with a large number of heat receiving water pipes 3 arranged inside thereof to generate steam, and exhaust gas from the outlet line 4 on the other side.

The waste heat boiler 1 has a heat receiving water pipe 3 therein.
A water supply line 5 for supplying water to the inside is connected and connected. The water supply line 5 is provided with a water supply device (not shown) including a check valve, a filter, a chemical injection device, etc., and by operating the water supply pump P, water of an appropriate water source is filtered,
It becomes the chemical can water injected with the chemical liquid and is supplied into the heat receiving water pipe 3 of the exhaust heat boiler 1. A water supply valve 6 is provided downstream of the water supply pump P in the water supply line 5 to control ON / OFF of the water supply into the heat receiving water pipe 3.

The exhaust heat boiler 1 is connected to a take-out line 7 for taking out steam generated by heat exchange between the heat-receiving water pipe group 3 and the exhaust gas. The take-out line 7 is provided with a vapor valve 8 for taking out and using the vapor. Although detailed description is omitted, the extraction line 7 includes
In order to take out good quality steam, an appropriate steam separator (separator) is provided.

The exhaust heat boiler 1 is provided with a pressure detector 9 for detecting the internal pressure of the can. This pressure detector 9 detects the pressure inside the can of the exhaust heat boiler 1 which changes according to the fluctuation of the heat load during the operation of the exhaust heat boiler 1. When the pressure exceeds a set pressure value, an alarm is appropriately generated.

The heat receiving water pipe 3 of the exhaust heat boiler 1 is provided with a water level detecting end 10 for detecting the actual water level in the heat receiving water pipe 3. The water level detection end 10 detects the actual water level in the heat receiving water pipe 3 that changes according to the fluctuation of the heat load during the operation of the exhaust heat boiler 1. The water level control uses the detected water level as a detection signal. Output to the container 11.

The outlet line 4 of the exhaust heat boiler 1 is provided with a temperature detector 12 for detecting the temperature of the exhaust gas discharged from the exhaust heat boiler 1. The temperature detector 12 detects the temperature of the exhaust gas in the outlet line 4, and the detected temperature is used as a detection signal in the temperature measuring device 13.
Output to.

Further, the water supply control device according to the present invention is
While detecting the pressure in the can in the exhaust heat boiler 1, the temperature of the exhaust gas in the outlet line 4 of the exhaust heat boiler 1 is detected,
The heat load of the exhaust heat boiler 1 is judged from the pressure in the can and the detected temperature, and the water level of the heat receiving water pipe 3 is controlled according to the heat load. An arithmetic processor 14 for arithmetically processing the temperature of the exhaust gas and the internal pressure of the can inside the exhaust heat boiler 1 is provided. The arithmetic processing unit 14 receives the exhaust gas temperature in the outlet line 4 as a detection signal from the temperature measuring device 13 via the temperature detector 12, and also determines the can internal pressure in the exhaust heat boiler 1 from the pressure detector 9. It is configured to be received as a detection signal. The arithmetic processing unit 14 that has received both detection signals is based on an arithmetic expression that has been set in advance.
There was arithmetic processing, from the can internal pressure and the exhaust gas temperature, determine the thermal load of the exhaust heat boiler 1 during the detection, to determine the appropriate value of the water level of the heat receiving water pipe 3 in accordance with the thermal load. Then, the determined appropriate value of the water level is output to the water level controller 11 as a control signal.

The water level controller 11, which receives the control signal of the proper water level for the heat receiving water pipe 3 from the arithmetic processing unit 14, determines the control signal and the actual water level from the water level detecting end 10 of the heat receiving water pipe 3. Compared with the detection signal of
An opening / closing control signal for controlling opening / closing of the water supply valve 6 provided in the water supply line 5 is output based on the comparison result. Thereby, the water supply to the heat receiving water pipe 3 is controlled, and the water level of the heat receiving water pipe 3 is appropriately maintained.

Next, regarding the water supply control device according to the present invention that is organically connected to the water supply control device, that is, the structure for appropriately controlling the water supply amount per unit time,
This will be described with reference to FIGS. 2 and 3. In FIG. 2, as a specific example of the water level detecting end 10, a water level control tube 17 is provided which is connected to and communicates with the heat receiving water tube 3, the steam section connecting tube 15 and the water section connecting tube 16. The water level control cylinder 17 is connected to the heat receiving water pipe 3 through both connecting pipes 15 and 16, and therefore displays the same water level as the water level of the heat receiving water pipe 3. Is provided with a detection end for detecting the water level in the water level control cylinder 17 at two or more points. In this embodiment, the upper, middle and lower water levels in the water level control cylinder 17 are respectively detected. The upper detection end H, the middle detection end M, and the lower detection end L for detection are inserted and installed, respectively. These detection ends H, M, L are configured to output the detected water level as a detection signal to the controller 18. The controller 18, which has received the detection signals from the respective detection ends H, M, L, detects the water level rise time between the respective detection ends H, M, L, that is, the middle detection after the lower detection end L detects the water level. Time until the end M detects the water level and the middle detection end M
Time from when the water level is detected to when the upper detection end H detects the water level (that is, water supply time) and the fall time, that is, the time from when the water level leaves the upper detection end H to when it leaves the middle detection end M And the time (that is, the steam generation time) from the time when the water level leaves the middle level detection end M to the time when the water level leaves the lower level detection end L, and a unit time is set in order to maximize the rising time and the falling time. It has a self-learning function that determines the amount of water supply per unit. And the controller 1
8 indicates that when the heat load of the exhaust heat boiler 1 is low, the low load control range T ₁ is set, that is, the water level in the water level control cylinder 17 is between the upper detection end H and the middle detection end M. When the heat load of the exhaust heat boiler 1 is high, the water level in the water level control cylinder 17 is set to the high load control range T ₂ , that is, the water level in the water level control cylinder 17 is the middle detection end M and the lower detection end L It is controlled so that it is between and. Further, the controller 18 determines the amount of water supply per unit time calculated according to the two control ranges T ₁ and T ₂ based on the self-learning function, and uses this as a control signal to provide the water supply line 5. Output to the water supply pump P. That is, based on the measured rise time and fall time.
Next, when the water level inside the can rises and falls next time
Be sure to determine the amount of water supply per unit time in
This is the amount of water supplied per unit time when the water level in the can rises.
The interval and fall time are determined to be as long as possible.

In this configuration, as described above, the water supply valve 6 is turned on / off by the control signal from the water level controller 11, so that the water supply pump P is controlled by the controller 18. The number of revolutions, that is, the discharge amount to the heat receiving water pipe 3 is continuously changed by changing the inverter frequency based on the above. Therefore, by the control signal from the controller 18,
The discharge amount of the water supply pump P continuously changes, and the flow rate passing through the water supply valve 6 continuously changes. That is, the flow rate of the water supply valve 6 in one ON operation continuously changes, and the amount of water supply per unit time becomes appropriate. As a result, as shown in FIG. The interval of on / off operation becomes longer over time, and the number of on / off operations decreases. As a result, the on / off control by the water supply valve 6 becomes close to the proportional control. In other words, this configuration uses the flow rate of the water supply valve 6 that is on / off controlled as a control signal from the controller 18 as the control of the amount of water supplied from the water supply line 5 to the heat receiving water pipe 3 per unit time. On the basis of,
The water supply pump P is used for adjustment.

Here, another preferred embodiment will be described as the control of the amount of water supplied to the heat receiving water pipe 3 per unit time. Not only the on / off control of the water supply valve 6 but also the control at the time of on-operation. If the opening degree, that is, the passing flow rate is continuously changed by the control signal from the container 18, control can be performed only by the water supply valve 6. According to this, the passing flow rate continuously changes by one ON operation, and the amount of water supply per unit time becomes appropriate, and as a result, as shown in FIG. The interval of the off operation becomes longer with the lapse of time, the number of times of the on / off operation is reduced, and it becomes close to the proportional control. That is, depending on the implementation, control by the water supply valve 6 alone is also suitable.

[0020]

As described above, according to the present invention, the rising time of the water level in the can measured so that the proper water level determined based on the heat load of the exhaust heat boiler is maintained, and
Depending on the descent time, the next time the water level in the can rises and the water in the can
Since the amount of water supply per unit time during the descending position is controlled, the on / off control method is very close to the proportional control method, without using an expensive sensor for water supply proportional control. Water supply control can be implemented. In addition, along with this, it is possible to reliably prevent damage due to overheating of the heat receiving water pipe,
It is also possible to prevent impurities from precipitating due to the concentration of can water, which causes damage to the heat receiving water pipe. Furthermore, since it can be implemented with a simple structure and can be provided at a low cost, it is very effective for this type of water supply control.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing an embodiment of an exhaust heat boiler equipped with a water supply control device.

FIG. 2 is an explanatory view schematically showing an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a relationship of water supply control in the embodiment of FIG.

[Explanation of symbols]

 1 Waste heat boiler 2 Inlet line 3 Heat receiving water pipe 4 Outlet line 5 Water supply line 6 Water supply valve 9 Pressure detector 10 Water level detection end 11 Water level controller 12 Temperature sensor 13 Temperature measuring instrument 14 Calculation processor 17 Water level control cylinder 18 Controller H Upper detection end M Middle detection end L Lower detection end P Water pump

Claims (2)

[Claims] 1. A number of heat receiving water pipes 3 are housed and arranged inside,
An exhaust gas inlet line 2 is connected to one side and an exhaust gas outlet line 4 is connected to the other side, and the heat receiving water pipe 3 is further connected.
The internal pressure of the can in the once-through type exhaust heat boiler 1 connected to the water supply line 5 for supplying water to the exhaust gas is detected, and the temperature of the exhaust gas at the outlet of the exhaust heat boiler 1 is detected to detect the detected internal pressure of the can and exhaust gas temperature. To calculate the heat load of the exhaust heat boiler 1, determine an appropriate value of the water level for the heat receiving water pipe 3 under the obtained heat load, and determine the determined appropriate value and the actual value of the heat receiving water pipe 3. A water level control tube for detecting the water level of the heat receiving water pipe 3 in a water supply control device in a once-through type exhaust heat boiler configured to compare with the water level level and control the water supply level of the heat receiving water pipe 3 based on the comparison result. 17 is provided, and the water level control cylinder 17 is provided in the water level control cylinder 17.
The detection ends H, M, and L for detecting water levels at a plurality of points inside are inserted and installed, and the detection ends H, M, and
The rise time and fall time of the water level between the respective detection ends are measured based on the detection signal from L, and the next in-can water level is raised according to the rise time and the fall time.
A controller 18 is provided which determines the amount of water supply per unit time when the water level is rising and when the water level in the can is lowered , and which outputs the determined amount of water supply as a control signal. The output signal from the controller 18 provides the water supply line 5 A water supply control device in a once-through type exhaust heat boiler, characterized in that the number of revolutions of a water supply pump P provided in the above is controlled. 2. The controller 18 continuously changes the opening degree of a water supply valve 6 provided in the water supply line 5 to control the amount of water supply per unit time.
The water supply control device for the once-through heat recovery boiler.