JPS60164179A - Control system of solar heat absorber - Google Patents

Abstract

PURPOSE:To enable to stably supply the steam produced at solar heat absorbers by a method wherein the difference between the pressure in a steam separator drum and the pressure in a heat accumulator is kept constant by means of a control valve and a circulating pump for a downcomer is driven when the percentage of void in an absorber and the temperature in a boiler section exceed the predetermined values. CONSTITUTION:When heat absorbing boiler surfaces 4 absorb heat by receiving the solar heat (a) concentrated by a concentrating type solar heat collector, the natural circulation (b) of water generates, resulting in causing to rise the pressure in an absorber. At the time, when the difference between the pressure in a steam separator drum 1 and the pressure in a heat accumulator 12 reaches the predetermined value, which enables to transport steam, a control valve 7 is brought into actuation in order to supply the steam (c) through the heat accumulator 12 to load. If the detected percentage of void in an evaporating tube 6 or the detected temperature at the upper part of the boiler surface shows the excess over the predetermined value, a controlling circulating pump 8 is driven, resulting in preventing the boiler section including the heat absorbing boiler surfaces 4 and the evaporating tube 6 from overheating.

Description

[Detailed description of the invention] related to instrument control systems.

Development and research into the use of solar energy as a means of effectively utilizing energy is becoming more active.

Solar water heaters and air conditioning/heating hot water systems that use solar heat are being put into practical use, but industrial thermal energy (steam, conventional saturated steam, which uses solar heat to generate steam when hot water is used) is becoming more and more practical. The solar heat absorber for generation is the first
It has a structure as shown in the figure.

In Figure 1, l is a steam drum for steam and water separation, 2 is a downcomer pipe, 3 is a downcomer header, 4 is a heat absorption boiler, 5 is an evaporator header, and 6 is an evaporator pipe, which generates heat. The absorber is connected to allow circulation of hot water. Numeral 7 is a steam take-off valve which is controlled to keep the pressure of the steam and water drum 1 constant.

Above heat + $. The collector receives solar heat (al) concentrated by a known concentrating type collector, absorbs the heat with a heat absorption boiler 4,
While generating boiling steam due to solar heat, it goes up the steam pipe 6 through the steam pipe header 5 and flows into the steam-water drum 1 in the upper part. Steam and hot water are separated in a steam and water drum, and the steam (C) passes through a steam extraction valve 7. The extracted steam (C1 is generally
The water is led to a pressure water tank (heat storage) (not shown), where the heat is stored as high-pressure hot water, and when necessary, such as for power generation, it is taken out as steam by a depressurization operation.

On the other hand, the hot water tb+ from which steam has been separated in the air-water drum 1 flows into the downcomer pipe 2 and circulates through the downcomer header 3 to the heat absorption boiler 4 again. Note that the circulating water (BL) may be forcibly circulated by a pump.

FIG. 2 shows changes in the pressure or temperature inside the heat absorber, the flow rate of generated steam, and the pressure or temperature inside the heat storage device during one day when the heat absorber and pressure water tank (heat storage device) are used on a sunny day.

As shown in Figure 2(a), with the start of early morning light gathering,
When the pressure and temperature inside the heat absorber begin to rise and steam is generated and reaches the rated pressure, the steam extraction valve 7 opens and steam is extracted. Thereafter, steam is extracted while the pressure inside the chamber is controlled to be constant until the end of the light collection. The take-out valve 7 closes when the light collection ends, and thereafter, heat continues to be released at the start of light collection 1 the next morning, so that both the pressure and temperature inside the vessel decrease.

The corresponding changes in the pressure and temperature inside the heat storage device are determined by the second (
b) As shown in the figure, heat storage starts as steam is generated in the heat absorber, and the pressure and temperature inside the heat storage device rise. Then, when power generation starts and steam begins to be taken out from the heat storage device, the pressure inside the device rises slowly, and when the amount of concentrated light decreases in the evening, the pressure inside the device begins to fall.

Thereafter, the inflow of steam stops due to the completion of condensation, and heat storage also ends. Then, when the pressure inside the heat storage device reaches a predetermined value, steam is extracted and power generation continues. After power generation is completed, the pressure and temperature inside the heat storage device decrease somewhat due to the heat released to the atmosphere. When only heat is stored without extracting steam, the behavior is as shown by the dotted line. In addition, since heat storage units are generally heat-insulated,
Heat radiation to the atmosphere is not as large as a heat absorber.

In addition, the second (
C) As shown in the figure.

In other words, the heat absorber reaches its rated pressure, the extraction valve opens and steam is taken out, and at the same time a constant flow rate is reached.After that, the flow rate gradually increases, but after that, the steam flow rate decreases until it reaches the condensing paper, and when the condensation ends, the flow rate decreases. becomes zero.

However, in the heat absorber constant pressure control system as described above,
During the temperature rise before the rated pressure is reached (if the light collection is interrupted due to clouding, the heat collected up to that point must be discarded as heat radiation to the atmosphere. Also, after the light collection is completed, the heat absorber must be retained) The same goes for heat.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and it minimizes the heat collection loss in the heat absorber,
The purpose of this project is to develop a solar heat absorber control system that can stably supply the steam generated by the heat absorber.

The heat absorber control system of the present invention is a concentrating solar heating system that connects a heat absorption boiler and an air/water drum so that hot water circulates, and prevents the steam separated in the air/water drum from being taken out. In the absorber, a steam outlet valve and a heat storage device are provided so as to communicate with the steam drum, and a forced circulation pump is provided between the steam drum and the heat absorption boiler, and the steam outlet control valve is connected to the steam outlet valve. It is characterized in that the differential pressure between the drum and the heat storage device is controlled to be constant, and the forced circulation pump is driven when the internal void ratio and the boiler temperature are within a predetermined temperature range.

Hereinafter, the present invention will be explained in detail with reference to FIGS. 3 and 4 showing one embodiment thereof.

FIG. 3 shows the configuration of a heat absorber implementing the control system according to the invention.

In the same figure, numbers l to 6 and a to 01 correspond to those shown in Fig. 1, respectively, where l is an air/water tram, 2 is a downcomer pipe, 3 is a downcomer header, and 4 is a heat absorption boiler. , 5 is an evaporator header, 6 is an evaporation tube, a indicates solar heat, I) indicates circulating hot water, and C indicates steam. a/ is a steam outlet control valve, 8 is a pump for forced circulation of hot water, and 9 is a steam/water drum 1.
A device that detects the differential pressure (DP) between and the heat storage device 12 and gives a control signal to the control valve 7,
A device 11 that detects BI and provides a drive signal to the pump 8 is a device that detects the temperature T of the upper part of the heat absorption boiler 4 and provides a drive signal to the pump 8, and 12 is a pressure water tank (heat storage).
It is.

At this point, the operation of the heat absorber of the above embodiment will be explained.

When the heat absorption boiler surface 4 absorbs the solar heat (al) concentrated by the concentrating type heat collector, the natural water circulation (1
)) occurs, and internal pressure increases. Furthermore, while generating boiling steam due to solar heat, it passes through the steam pipe header 5 to the steam pipe 6.
The air rises and flows into the air-water drum l. Steam and hot water are separated in the air-water drum 1.

Then, when the differential pressure (DP) between the steam drum 1 and the heat storage device 12 reaches a predetermined value and steam can be transported from the steam drum 1 to the heat storage device 12, the control device 9 activates the control valve 7'. is operated, and steam FC+ is supplied to the load via the heat storage device 12. Thereafter, the control valve 71 is controlled so that the differential pressure between the air-water drum 1 and the heat storage device 12 is constant.

In the above control system, steam FC+ may be extracted even when the internal pressure of the heat absorber is low, but if the solar heat is strong at this time, the void ratio (Bl) in the heat absorption boiler 4 and the evaporation tube 6 increases. On the other hand, the hot water (b) after steam separation in the air-water drum 1 flows into the downcomer pipe 2.
・It circulates through the ladder 3 to the heat absorption boiler 4, but as mentioned above, when the void ratio iBl becomes high, the natural circulation of hot water is inhibited, and the boiler section including the heat absorption boiler 4 and the evaporation tube 6 becomes overheated. There is a danger that it will be destroyed.

In order to prevent this, the control device JO111
The void ratio fBl within the boiler and/or the temperature (T) of the upper part of the boiler surface is detected, and when the temperature (T) at the top of the boiler surface exceeds a predetermined value, the forced circulation pump 8 is driven. In addition, the void ratio in the steam pipe 6 (B
1 and/or when the temperature (T) of the upper part of the boiler surface is steady, the pump 8 is stopped in order to save a certain amount of power, and natural circulation of hot water is performed.

As described above, the expected behavior of the heat absorber and heat storage device by employing the solar heat absorber control system of the present invention is shown in FIG. 4 in comparison with the case using the conventional constant pressure control system. In this figure, the actual lines indicate the characteristics obtained by the control system according to the present invention, and the dotted lines indicate the characteristics obtained by the conventional control system shown in FIG.

As is clear from FIG. 4(a), the steam generation time of the heat absorber is early, and the steam can be taken out by self-evaporation even after the light collection is completed, so the steam stop time is also delayed. Therefore, the fourth
(C) As shown in the figure, the flow rate of generated steam increases. Further, since the temperature of the heat absorber does not become higher than necessary, the heat collection efficiency is improved, which contributes to increasing the flow rate of generated steam. As a result, as shown in Figure 4 (tl)), the power generation time is extended, resulting in an increase in the amount of power generation.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a conventional solar heat absorber, Fig. 2 is a characteristic diagram showing the temporal behavior of the pressure or temperature of the heat absorber and heat storage device and the flow rate of generated steam in the conventional solar heat absorber, and Fig. 3 is a schematic diagram showing a solar heat absorber control system according to an embodiment of the present invention, and FIG. 4 is a schematic diagram showing a solar heat absorber control system according to an embodiment of the present invention.
FIG. 2 is a characteristic diagram similar to FIG. 2 for the stem. ]... Air/water drum, 2... Downcomer pipe, 3... Downcomer pipe header, 4... Heat absorption boiler, 5... Evaporation pipe, ~... -shi version 7
Resist /, -Kyo 1a Tanaka "] Shishu 1111 it t8...
Forced circulation pump, 9. ], '0.11...Control device, 12...Pressure water tank (heat storage). Figure 3 Figure 4 (α) Figure 4 (b)

Claims (1)

[Claims] In a concentrating solar heat absorber that connects a heat absorption boiler and a steam/water drum so that hot water circulates therebetween, and extracts steam separated by the steam/water drum, the heat absorption boiler is connected to the steam/water drum. A steam outlet control valve and a heat storage device are provided to communicate with each other, and a forced circulation pump is provided between the steam drum and the heat absorption boiler, and the steam ratio 1 control valve is connected to the steam drum and the heat storage device. A solar heat absorber control system, characterized in that the pressure difference in the boiler is controlled to be constant, and the forced circulation pump is driven when the void ratio inside the boiler and the temperature of the boiler section are above a predetermined temperature. .