JPH0823408B2 - 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 device for a boiler which obtains steam by utilizing exhaust heat of an internal combustion engine, an incinerator, etc., and more particularly to a water supply control device for a once-through type exhaust heat boiler. It is a thing.

[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 problems, the present invention is based on the knowledge that the heat load of the exhaust heat boiler is proportional to the amount of generated steam or the flow rate of feed water, and based on this heat load. By controlling the water level of the heat receiving water pipe to reach the optimum water level, and properly controlling the amount of water supplied per unit time at this appropriate water level, it is possible to prevent damage to the heat receiving water pipe due to overheating. In addition, it is possible to prevent the precipitation of impurities due to the 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 outlet line of exhaust gas is connected, and a water supply line for supplying water to the heat receiving water pipe is connected, and an extraction line for taking out steam generated by heat exchange with the exhaust gas of the heat receiving water pipe is connected, and the actual water level of the heat receiving water pipe is further connected. It detects the feed water flow rate to the once-through type exhaust heat boiler equipped with a water level detection end that detects the level, and also detects the amount of steam from the exhaust heat boiler, and either one of the detected feed water flow rate and steam amount or Calculate the heat load of the exhaust heat boiler by calculating both, determine the appropriate value of the water level for the heat receiving water pipe under the obtained heat load, the determined appropriate value and the actual value of the heat receiving water pipe Of the water level control unit in the once-through type exhaust heat boiler configured to control the water supply level of the heat receiving water pipe based on the comparison result, a water level control cylinder for detecting the water level of the heat receiving water pipe. A detection end for detecting the water level at each of a plurality of points in the water level control cylinder is installed in the water level control cylinder, and the water level rises between the detection ends based on the detection signal from each detection end. with measuring and fall times and, respectively, the next in response to the rise and fall times
A controller for determining the amount of water supply per unit time when the water level in the can rises and when the water level in the can falls and providing the determined water supply amount as a control signal is provided, and the water supply line is output by the output signal from the controller. It is characterized in that the number of rotations of the water supply pump provided in the above is controlled.

[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 close to proportional control.

[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 thereof, heat-exchange with a large number of heat receiving water pipes 3 accommodated therein and 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. Further, a water supply valve 6 for controlling on / off of water supply to the heat receiving water pipe 3 is provided on the water supply line 5 downstream of the water supply pump P. Further, between the water supply pump P and the water supply valve 6 in the water supply line 5, a water supply flow rate detector 7 that detects the integrated flow rate of water supplied into the heat receiving water pipe 3 is provided. This water supply flow rate detector 7
Detects the integrated flow rate of water supplied into the heat receiving water pipe 3, and outputs the detected feed water flow rate to the feed water flow rate measuring device 8 as a detection signal.

The exhaust heat boiler 1 is connected to an extraction line 9 for extracting steam generated by heat exchange between the heat receiving water pipe group 3 and the exhaust gas. The extraction line 9 is provided with a vapor valve 10 for extraction and use. A vapor amount detector 11 for detecting the amount of generated vapor is provided upstream of the valve 10 in the extraction line 9. The vapor amount detector 11 detects the generated vapor amount and outputs the detected vapor amount to the vapor amount measuring device 12 as a detection signal. Although detailed description is omitted, the extraction line 9 is provided with an appropriate steam separator for extracting high-quality steam.

The exhaust heat boiler 1 is provided with a pressure detector 13 for detecting the internal pressure of the can. The pressure detector 13 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
A water level detecting end 14 for detecting an actual water level in the heat receiving water pipe 3 is provided. The water level detection end 14 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. Bowl 15
Output to.

Further, the water supply control device according to the present invention is
The heat load of the exhaust heat boiler 1 which is proportional to the generated steam amount of the exhaust heat boiler 1 or the integrated feed water flow rate is determined, and the water level of the heat receiving water pipe 3 is controlled according to the heat load. Therefore, in the present invention, the arithmetic processor 16 that calculates the feed water flow rate and the steam amount and determines the heat load of the exhaust heat boiler 1 based on the calculation is provided. The arithmetic processing unit 16 first measures the water supply flow rate in the water supply line 5 via the water supply flow rate detector 7 to measure the water supply flow rate.
Is received as a detection signal from the vapor line, and the vapor amount in the take-out line 9 is detected by the vapor amount detector 12 via the vapor amount detector 11.
It is configured to be received as a detection signal from the.
The arithmetic processing unit 16 that has received these both detection signals performs arithmetic processing on the both detection signals to determine the heat load of the exhaust heat boiler 1 at the time of detection, and the water level of the heat receiving water pipe 3 according to the heat load. Determine the appropriate value for. Further, the arithmetic processor 16 is configured to receive a detection signal regarding the actual water level of the heat receiving water pipe 3 from the water level controller 15 via the water level detecting end 14. Therefore, the processor 1
Reference numeral 6 compares an appropriate value of the water level for the heat receiving water pipe 3 with a detection signal from the water level controller 15, and based on the comparison result, an opening / closing control signal for controlling opening / closing of the water supply valve 6 provided in the water supply line 5. Output. 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 which 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 14, a water level control tube 19 is provided, which is connected to and communicates with the heat receiving water pipe 3, the steam part connecting pipe 17 and the water part connecting pipe 18. The water level control cylinder 19 is connected to the heat receiving water pipe 3 via both connecting pipes 17 and 18, 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 19 at two or more points. In this embodiment, the upper, middle and lower water levels in the water level control cylinder 19 are detected. An upper detection end H, a middle detection end M, and a lower detection end L for detecting each are inserted and installed. These detection terminals H, M, L are configured to output the detected water level as a detection signal to the controller 20. The controller 20, which receives the detection signals from the detection ends H, M, and L, detects the rise time of the water level between the detection ends H, M, and 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 from when the water level leaves the middle detection end M to when it leaves the lower detection end L (that is, the steam generation time), respectively, and in order to make the rising time and the falling time as long as possible, It has a self-learning function that determines the amount of water supply per unit. And the controller 2
0 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 tube 19 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 tube 19 is set to the high load control range T ₂ , that is, the water level in the water level control tube 19 is the middle detection end M and the lower detection end L. It is controlled so that it is between and. Further, the controller 20 determines the amount of water supply per unit time calculated according to both control ranges T ₁ and T ₂ based on the self-learning function, and uses this as a control signal to provide in the water supply line 5. Output to the water supply pump P. That is, the measured rise time and fall time
Based on the following, when the water level inside the can rises and falls next time
To determine the amount of water supply per unit time
The amount of water supplied per unit time is based on the water level in the can.
The rise and fall times are determined to be as long as possible.
It

In this configuration, as described above, the water supply valve 6 is turned on / off by the control signal from the water level controller 15, so that the water supply pump P is controlled by the controller 20. 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 20,
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, in this configuration, as a control of the amount of water supplied from the water supply line 5 to the heat receiving water pipe 3 per unit time, the flow rate of the water supply valve 6 that is on / off controlled is sent to the control signal from the controller 20. 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 20, the 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.

[0018]

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 Exhaust heat boiler 2 Inlet line 3 Heat receiving water pipe 4 Outlet line 5 Water supply line 6 Water supply valve 7 Water supply flow rate detector 8 Water supply flow rate meter 9 Extraction line 11 Steam amount detector 12 Steam amount detector 14 Water level detection end 15 Water level controller 16 Arithmetic processing unit 19 Water level control cylinder 20 Controller H Upper detection end M Medium 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,
By connecting the exhaust gas inlet line 2 to one side, connecting the exhaust gas outlet line 4 to the other side, connecting the water supply line 5 for supplying water to the heat receiving water pipe 3, and exchanging heat with the exhaust gas of the heat receiving water pipe 3. The flow rate of water supplied to the once-through type exhaust heat boiler 1 is connected to an extraction line 9 for taking out the generated steam, and a water level detection end 14 for detecting the actual water level of the heat receiving water pipe 3 is detected. The amount of steam from the boiler 1 is detected, and one or both of the detected feed water flow rate and the amount of steam are subjected to arithmetic processing to obtain the heat load of the exhaust heat boiler 1, and the heat reception under the obtained heat load. An appropriate value of the water level for the water pipe 3 is determined, the determined appropriate value is compared with the actual water level of the heat receiving water pipe 3, and the water supply level of the heat receiving water pipe 3 is controlled based on the comparison result. In the water supply control device for the once-through type exhaust heat boiler configured as described above, a water level control cylinder 19 for detecting the water level of the heat receiving water pipe 3 is provided, and the water levels at a plurality of points in the water level control cylinder 19 are respectively set in the water level control cylinder 19. The detection ends H, M, and L for detection are inserted and installed, and the rise time and the fall time of the water level between the detection ends are measured based on the detection signals from the detection ends H, M, and L, respectively. , Next time according to this rise time and fall time
A controller 20 is provided which determines the amount of water supply per unit time when the water level in the can rises and when the water level falls in the can, and outputs the determined amount of water supply as a control signal. The controller 20 outputs the control signal according to the output signal from the controller 20. A water supply control device for a once-through heat recovery boiler, which controls the number of revolutions of a water supply pump P provided in a water supply line 5. 2. The controller 20 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.