JPS58122308A - Method and equipment for heat storage operation of waste heat recovery rankine cycle system - Google Patents

Abstract

PURPOSE:To improve the rate of operation of a waste heat recovery Rankine cycle system, by providing an exhaust gas quantity control valve which stops the supply of exhaust gas to a steam generator and by providing a supplied liquid quantity control valve which regulates the suplied liquid quantity of a heat medium. CONSTITUTION:A waste heat recovery Rankine cycle system comprises a steam generator 4, an expander 10, a condenser 12 and a pump 14. When the temperature of exhaust gas at the inlet port of the steam generator 4 has fallen, a gas quantity control valve 2 is entirely closed and a speed governing valve 9 and a supplied liquid quantity control valve 16 are reduced of their degree of opening to effectuate primary heat storage operation. When the temperature has fallen further, an emergency shutoff valve 8 is entirely closed and the supplied liquid quantity control valve 16, a liquid level control valve 7 and the exhaust gas quantity control valve 2 are also entirely closed to effectuate secondary heat storage operation. The heat storage operation in thus enabled to effectively use heat energy to enhance the rate of operation of the heat recovery Rankine cycle system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat storage operation method for an exhaust heat recovery Rankine cycle apparatus and its apparatus, which can improve the operating efficiency of a medium-low temperature exhaust heat recovery apparatus using a Rankine cycle.

Due to the operating mode of the exhaust heat source equipment, periodic maintenance, etc., the exhaust gas temperature may temporarily drop to 111 h%.
In many cases, the temperature decreases to i or exhaust gas generation stops for a short period of time.

In such a case, the Rankine cycle exhaust heat recovery device, which uses the thermal energy of the exhaust gas as a heat source, cannot operate normally and has to be stopped.

Another problem is that once the exhaust heat recovery device is stopped, it takes time to restart the exhaust heat recovery device even if the thermal energy of the exhaust gas is recovered.

As a result, the operating rate of the exhaust heat recovery device decreases, resulting in deterioration of profitability.

However, in order to continue operating the waste heat recovery equipment and avoid a drop in the operating rate, it is necessary to install thermal energy supply equipment separate from the waste heat source equipment originally targeted for recovery, or to install thermal energy supply equipment between the steam generator and the expander. It is necessary to install a large-capacity steam reservoir in the steam line of the exhaust heat, which increases the cost of the exhaust heat recovery equipment and deteriorates the efficiency of extraction.

As described above, a decrease in the operating rate of exhaust heat recovery equipment due to the availability of exhaust heat source equipment or a rise in equipment costs have been major obstacles to the promotion of energy conservation in the past.

On the other hand, waste heat recovery equipment requires particularly high efficiency and high operation rate due to its profitability, and unlike general industrial prime movers, it depends on the amount of thermal energy of the waste heat supplied. The output is not fixed from the driven machine side1. Therefore, the present invention is a Rankine cycle medium-low temperature exhaust heat recovery device that temporarily lowers the exhaust gas temperature due to the exhaust heat source equipment. Even if the exhaust gas decreases significantly or the exhaust gas generation stops for a short time, the exhaust gas thermal energy, i.e.
The purpose of the present invention is to provide an exhaust heat recovery Rankine cycle device that has a high operating rate by performing heat storage operation that effectively utilizes the thermal energy that the exhaust heat recovery device has already absorbed before the exhaust gas temperature and exhaust gas amount decrease. This is what I did.

Here, heat storage operation is an operation method that focuses on the fact that the heat transfer tubes of the steam generator have a large amount of heat. Because the temperature difference between the exhaust gas, which is the heat source, and the Lankino cycle heat medium is very small, the weight of the steam generator heat transfer tubes per unit of heat exchanged is 5 to 10 times heavier than that of a normal fuel-fired boiler, and the heat transfer tubes are large. It holds a certain amount of heat.

Therefore, when the exhaust gas thermal energy supplied to the exhaust heat recovery device decreases due to some reason in the exhaust heat source equipment, conventionally the exhaust heat recovery device was stopped, but in the present invention, the primary heat storage operation is started. , the heat source is switched from the exhaust gas to the heat exchanger tube of the steam generator, and the exhaust heat recovery device continues to operate continuously. When the exhaust heat source equipment is restored and the exhaust gas thermal energy increases, the heat source is returned to the exhaust gas and the operation returns to normal. If the primary heat storage operation cannot be maintained, the secondary heat storage operation will be started, and the heat medium liquid and steam that were heated before the start will be confined in the steam generator and steam line in a high temperature state. The feature of the present invention is to maintain the heat storage state so that it can be restarted immediately by slight heating after the exhaust heat source equipment is restored, and to rapidly increase the heat energy of the exhaust gas supplied to the steam generator. In the past, the heat storage capacity was not maintained sufficiently, so the rate of increase in the heat energy of the supplied exhaust gas during restart was slow, and it took a long time to generate steam.

That is, in the Rankine cycle device to which the heat storage operation method of the waste heat recovery Rankine cycle device of the present invention is applied, the heat medium that is heated and turned into steam by the steam generator that introduces the exhaust gas generated in the waste heat source equipment is transferred to the expander. The temperature of the exhaust gas supplied to the steam generator in an exhaust heat recovery device that expands and converts it into power, condenses the heat medium that has finished its work in the expander, and supplies it to the steam generator again. In addition to providing an exhaust gas amount control valve that can stop the supply of exhaust gas to the steam generator when the amount of water becomes abnormally low, a regulating valve that can reduce the steam consumption of the expander at the same time is provided. A supply liquid amount control valve is provided that can operate by adjusting the liquid amount to the amount using the heat transfer tube of the steam generator as a heat source, and when the above operation cannot be maintained, the supply of heat medium steam to the expander is It is constructed by providing an emergency shutoff valve that can be shut off.

The exhaust heat recovery Rankine cycle device according to an embodiment of the present invention will be described below with reference to the drawings.The exhaust heat recovery Rankine cycle device according to the present embodiment mainly includes a steam generator 4,
It is composed of an expander 10, a condenser 12, and a pump 14. During normal operation, exhaust gas generated in the exhaust heat source equipment 20 is sucked in by the induced draft fan 3 and guided to the steam generator 4 through the exhaust gas duct 1.

The exhaust gas, which has been heated to a heat medium by the steam generator 4 and has become low temperature, is discharged to the outside through the exhaust gas amount control valve 2 and the induced draft fan 3.

On the other hand, the heat medium absorbs heat in the steam generator 4 and becomes steam, which is supplied to the expander 10 through the gas-liquid separator 6, the emergency shutoff valve 8, and the regulating valve 9, and the absorbed thermal energy is The power is converted into power and transmitted to the driven machine 11.

The heat medium vapor that has completed its work in the expander 10 is condensed in the condenser 12 to become a liquid, is pumped by the pump 14, and is supplied to the steam generator 4 through the supply liquid amount control valve 15. However, the above heat medium is circulated by repeating the above steps.

Normally, the exhaust gas amount control valve 2 adjusts its opening degree so as to supply the maximum amount of exhaust gas to the steam generator at a rotation that does not adversely affect the exhaust heat source equipment 20.

In addition, the liquid supply amount control valve 16 adjusts its opening degree to adjust the amount of heat medium supplied to the steam generator 4 according to the amount of exhaust gas thermal energy, so that the heat medium steam reaches an appropriate temperature. ing.

Next, the liquid level control valve 7 opens when the level of the heat medium liquid in the gas-liquid separator 6 rises, and discharges the heat medium liquid to the condenser 12 so as not to exceed a certain level.

In addition, in the figure, F indicates a flow meter, T indicates a thermometer, and P indicates a pressure gauge.

Further, during normal operation, the liquid level control valve 7 is fully closed because only steam flows out from the steam generator 4.

Therefore, when the exhaust gas at the entrance of the steam generator 4 drops to a certain temperature due to some reason in the exhaust heat source equipment 20, the next operation is performed at the same time.

First, the speed regulating valve 9 is throttled down to operate the expander 10 at a low load to reduce steam consumption, and at the same time, the exhaust gas amount control valve 2 is fully closed to stop the exhaust gas supply to the steam generator 4, and the exhaust gas temperature is The heat exchanger tube 5 and the heat medium inside the heat exchanger tube 5, which were heated before the temperature decreased, are prevented from being adversely cooled by the exhaust gas whose temperature has decreased.

In addition, the supply liquid amount control valve 16 is throttled to reduce the amount of heat medium supplied, and the expansion machine uses the heat retained mainly in the heat transfer tubes 5, which is heated before the exhaust gas temperature drops and has reached a high temperature, as a heat source. 10 to generate steam at an appropriate temperature.

In this way, the primary heat storage operation is performed, and by the time the waste gas has fallen to a certain temperature, the heat medium itself and the heat transfer tubes 5 have already been heated by the waste gas, and the steam generated using the amount of heat held in t1 as a heat source. continues to be supplied to the expander 10, and even if the exhaust gas temperature drops to a certain level, the expander 10 continues to operate and waits until the 11F heat source equipment 20 is restored and the exhaust gas temperature rises. It has become.

Next, when the exhaust gas rises to a certain temperature, the next operation is performed at the same time.

That is, the exhaust gas amount control valve 2 is rapidly opened to start supplying plowing gas to the gas generator 4, and the liquid supply amount control valve 16 is opened to adjust the heat medium supply amount to an amount corresponding to the thermal energy of the exhaust gas. Then, gradually open the regulating valve 9, and expander 1
o load restriction is lifted, and in this way the primary heat storage operation shifts to normal operation.

On the other hand, since the exhaust gas temperature does not rise for a long time, the heat exchanger tube 5
When the temperature of the expander 1o decreases and steam at a temperature suitable for the expander 1o cannot be generated, the following operation is performed at the same time from the silk-secondary heat storage operation state.

That is, the emergency shutoff valve 8 and the speed control valve 9 are fully closed and the expander 10 is closed.
At the same time, the supply liquid level control valve 16 is fully opened to stop the heat medium supply to the steam generator 4, and the liquid level control valve 7 is kept fully closed from the first heat storage operation. I'll keep it.

In addition, the exhaust gas amount control valve 2 is also switched off from the first heat storage operation. It continues to be fully opened.

In this way, the secondary heat storage operation is performed, and the heat medium liquid and steam are confined to the steam generator 4 and the steam line, thereby preventing steam from leaking from the steam generation system to the power generation section. , the exhaust heat source equipment 2 is maintained at a constant temperature so as not to further lower the heat medium and steam generator heat transfer tube temperatures.
Wait for the temperature to return to 0 and the exhaust gas temperature to rise.

Furthermore, when the exhaust gas rises to a certain temperature, the following operation will be performed.

That is, by rapidly opening the exhaust gas amount control valve 2, the steam generator 4
At the same time, the liquid supply amount control valve 16 is opened to increase the heat medium supply amount to an amount corresponding to the thermal energy of the exhaust gas, and then the appropriate amount of steam to operate the expander 10 is generated. When this occurs, the emergency shutoff valve 8 is fully opened, the speed regulating valve 9 is gradually opened, the generated steam is supplied to the expander 10, and the expander 10 is restarted.

In this way, you can quickly restart from the secondary heat storage operation,
Shift to normal operation.

Here, the state of steam generation during the primary heat storage operation is shown in Figure 2.
As shown in FIG. 3, when the expander 10 of the exhaust heat recovery device is operated at a constant pressure, the exhaust gas temperature (8)A immediately before the primary heat storage operation and the primary heat storage From heat exchanger tube temperature B immediately before operation to heat exchanger tube temperature C immediately before secondary heat storage operation
By using the amount of heat in the heat transfer tubes 4, which decreases to 100, as a heat source, it is possible to generate steam at a heat medium temperature that is the same as that immediately before the primary heat storage operation.

When the exhaust heat recovery device is operated at variable pressure according to the exhaust gas thermal energy of the heat source, as shown in Fig. 3, the heat exchanger tube temperature B immediately before the first heat storage operation is changed to the heat exchanger tube temperature C immediately before the second heat storage operation. By using the heat quantity of the heat exchanger tubes 5, which decreases to 5, as a heat source, it is possible to generate steam at the heat medium temperature E immediately before the secondary heat storage operation.

Since the usable heat amount of the heat transfer tubes 5 is larger in variable pressure operation than in constant pressure operation, variable pressure operation can further enhance the effect of heat storage operation.

The state of the heat medium during the secondary heat storage operation is almost maintained at the heat medium temperature shown in Figure 2 and the heat medium temperature E immediately before the secondary heat storage operation shown in Figure 3, although there is a slight temperature drop due to atmospheric heat radiation. and heat is stored.

As a result of carrying out all the operations according to the present invention automatically and putting it into practical use, the operating rate of the exhaust heat recovery equipment has been greatly improved. For example, when the exhaust gas temperature drops extremely for one hour a day, Experimental results have also demonstrated that the ratio can be improved by about 3.5 inches.

Therefore, by applying the present invention, in the exhaust heat recovery device, even if the exhaust gas temperature drops abnormally or the exhaust gas generation stops for a short time due to the exhaust heat source equipment, the special thermal energy supply equipment can be used. The present invention provides an exhaust heat recovery method and equipment that enables heat storage operation by effectively utilizing the thermal energy already absorbed by the equipment before the exhaust gas thermal energy decreases without providing a large-capacity steam reservoir, and that has a high operating rate. 1".

[Brief explanation of the drawing]

Fig. 1 is a main system diagram of the heat recovery Rankine cycle device in the first embodiment of the present invention, and Fig. 2 shows the heat of the steam generator during the primary heat storage operation during constant pressure operation of the device in Fig. 1. 3 is a heat exchange diagram of the steam generator during the primary heat storage operation during the variable pressure operation of the apparatus shown in FIG. 1. 2...Exhaust gas amount control valve, 4...Steam generator, 8...
・Emergency shutoff valve, 9... Speed control valve, 10... Expander, 1
6... Liquid supply amount control valve, 20... Exhaust heat source equipment. Agent: Patent Attorney Makoto Ogawa − Patent Attorney: Ken Noguchi Patent Attorney: Kazuhiko Saishita

Claims (1)

[Scope of Claims] 1. A steam generator that introduces exhaust gas generated from exhaust heat source equipment, which heats the heat medium that becomes steam, expands it in an expander, converts it into power, and uses the expander to generate work. In an exhaust heat recovery Rankine cycle device that condenses the heat medium that has finished heating into a liquid and supplies it again to the steam generator, when the temperature of the exhaust gas supplied to the steam generator drops abnormally, the temperature of the exhaust gas supplied to the steam generator drops abnormally. In addition to stopping the supply of exhaust gas, the system uses the heat in the steam generation system, which was already heated by the exhaust gas before the exhaust gas temperature drops abnormally, as a heat source to prevent this heat from flowing outside the power generator. A heat storage operation method for an exhaust heat recovery Rankine cycle device, characterized in that: 2. Introducing the exhaust gas generated by the exhaust heat source equipment.The heat medium that has been heated to steam by the steam generator is expanded in an expander and converted into power, and the heat medium that has completed its work in the expander is converted into liquid. The amount of exhaust gas that can stop the exhaust gas supply to the steam generator when the temperature of the exhaust gas supplied to the steam generator drops abnormally in the exhaust heat recovery equipment that condenses the waste gas and supplies it to the steam generator again. In addition to providing a regulating valve, a regulating valve is also provided that can reduce the amount of steam consumed by the expander, and furthermore, the amount of heat medium supplied can be adjusted to the amount using the heat transfer tubes of steam generation as the heat source. An exhaust heat recovery Rankine cycle device characterized by being provided with a liquid supply amount control valve and an emergency shutoff valve that can stop the supply of heat medium vapor to the expander when the above operation cannot be maintained.