JPS58214702A - Method and device for operating waste-heat recovery device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to an operating method and device for an exhaust heat recovery device.
The present invention relates to a method and apparatus for operating an exhaust heat recovery apparatus suitable for adjusting heat recovery t according to fluctuations in the amount and temperature of exhaust gas.

If low-temperature corrosion due to SOI in the exhaust gas is a problem in an exhaust heat recovery boiler, the circulating water inlet temperature of the boiler (economizer) should be maintained above a certain value as shown in Figure 1.
In addition, the boiler is operated so that the terminal temperature between the water supply inlet temperature and the exhaust gas outlet temperature is the minimum allowable value, thereby preventing low-temperature corrosion and recovering as much waste heat as possible.

In the case of such an operating method, as shown in FIG. 2, the amount of steam in the low-pressure steam generator varies between an excess low-pressure steam region and a low-pressure steam shortage region depending on the temperature of the exhaust gas and the current flow. As a result, in an exhaust heat recovery device in which the steam generated by the low-pressure steam generator is introduced only into the heating deaerator, if the amount of exhaust gas is large and the exhaust gas temperature is high enough, the amount of steam generated by the low-pressure steam generator is , less than the amount required for heating and deaeration of the feed water.

This loss is usually compensated for by steam generated in a high pressure boiler. On the other hand, when the amount of exhaust gas is small and the exhaust gas inlet temperature is low, the amount of steam generated by the low-pressure steam generator becomes excessive than the amount of steam required by the heating deaerator. There is no problem in the case of an exhaust heat recovery device in which the steam generated by the low-pressure steam generator can be used for heating means other than the heating deaerator. However, with exhaust heat recovery equipment that introduces low-pressure steam only into the heating deaerator, processing of excess low-pressure steam is a problem. Conventionally, such excessive low-pressure steam is either released into the atmosphere or stored in a separate condenser. It had been turned into condensate. In the case of atmospheric release, circulating water is lost. In addition, when condensing water using a condenser, problems arise such as the need for condenser installation and cooling water.

The purpose of the present invention is to solve the problems of the prior art described above,
An object of the present invention is to provide an operating method and device for an exhaust heat recovery device that can adjust heat recovery t in response to fluctuations in the amount and temperature of exhaust gas, which are often accompanied by loss of circulating water and increase in cooling water. .

The present invention provides an exhaust heat recovery device in which steam generated from a low pressure steam generator installed in an exhaust heat recovery boiler is introduced only to a heating deaerator, in which the amount of steam generated by the low pressure steam generator is The heat input to the low pressure steam generator is limited by operating it like a heating deaerator.

Hereinafter, the present invention will be described in detail based on the accompanying drawings.

In Figure 4, water is supplied from water tank 1 to water pump 2.
The water is supplied to a heating deaerator 3, where dissolved oxygen and the like in the feed water are removed, and then introduced to a low pressure steam generator 5 in an exhaust heat recovery boiler via a low pressure circulation pump 4. Steam generated by the low pressure steam generator 5 is supplied to the heating deaerator 3.

In addition, the water supplied from the heating deaerator 3 is supplied via the boiler feed water pump 6 to the economizer 7 in the exhaust heat recovery boiler, where it is preheated and then supplied to the steam drum 8, and the drum water is circulated under high pressure. The water is supplied to a high-pressure boiler 10 via a water pump 9, where it is heated and then introduced into a steam drum 8.

In such an exhaust heat recovery device, the amount of steam generated in the low pressure steam generator 5 is adjusted by changing the temperature and amount of exhaust gas introduced into the exhaust heat recovery boiler, depending on the operating pressure of the low pressure steam generator. This is achieved by controlling the

Here, the pressure controller 11 controls the opening degree of the control valve 13 spanning the control valve 12 according to the input deviation between the pressure setting value of the heating deaerator 3 and the detected pressure value. That is, during constant load operation, if the amount of steam in the low-pressure steam generator 5 is less than the required amount of steam in the heating deaerator 3, the pressure in the heating deaerator 3 drops below the set pressure. At this time, the pressure inside the heating deaerator 3 is detected by the pressure detector 14, this detection signal is input to the pressure controller 11, and the pressure controller The opening degree of the control valve 12 is increased based on the output signal from the steam drum 11, and steam is replenished from the steam drum 8 to the heating deaerator 3. In addition, during constant load operation, if the amount of steam in the low-pressure steam generator 5 is greater than the required amount of steam in the heating deaerator 3, the The opening degree of the control valve 13 is increased based on the output signal from the pressure controller 11.

Surplus steam from the heating deaerator 3 is released into the feed water tank I and used for preheating the feed water. Ru. Here, both the control valve 12 and the control valve 13 are operated in the split range by the output signal of the pressure controller 11.

Next, if the boiler load is sufficiently high and the required steam amount of the heating deaerator 3 is insufficient in the long term compared to low pressure steam generation, the pressure setting value input to the pressure controller 11 is changed from the lower limit setting device 15. The pressure is switched to the output lower limit set value, and constant pressure control is performed based on this lower limit set value.

On the other hand, when the boiler load decreases and the amount of steam generated in the low-pressure steam generator 5 becomes excessive than the required amount of steam in the heating deaerator 3, the pressure in the heating deaerator 3 increases, so the pressure The opening degree of the control valve 13 is controlled based on the output signal from the controller 11, and surplus steam steadily flows into the water supply tank 1. In this case, the temperature of the water at the outlet of the water tank 1 increases. If the feed water temperature rises too much, cavitation of the boiler feed water pump, movement of the boiler drum level, etc. will occur, so the temperature detector 16 detects the feed water temperature, and the temperature controller 17 compares this detected value with the feed water temperature. The deviation from the set value is determined, and when the detected value is high, a voltage transformation control signal is output based on the deviation value. When this pressure transformation control signal is output, the set pressure of the pressure controller 11 is switched to this pressure transformation control signal, and the pressure of the heating deaerator 3 is transformed and controlled based on this pressure transformation control signal.

Therefore, when the boiler load decreases and the amount of steam generated in the low-pressure steam generator 5 exceeds the required amount of steam in the heating deaerator 3, the operating pressure of the low-pressure steam generator 5 is increased. By increasing the saturation temperature, the temperature difference with the gas temperature can be reduced, the amount of heat absorbed by the low pressure steam generator 5 can be reduced, and generation of surplus steam can be prevented. In this case, the heat capacity of the feed water tank 1 is sufficiently large, so even if there is a sudden change in the exhaust gas conditions, the feed water temperature will fluctuate slowly. Therefore, the operating pressure of the low pressure steam generator will also fluctuate gradually, and the boiler water feed water will change slowly. Pump cavitation and boiler drum level fluctuations do not occur.

In addition, in the control process, the voltage transformation control signal output from the temperature controller 7 may exceed the maximum allowable value of the set pressure of the pressure controller 11, so if this set pressure becomes excessive, An upper limit setter 18 is provided on the output signal line of the temperature controller 17 to ensure that the voltage transformation control signal is at this upper limit value (the operating pressure of the suppressing heat heating deaerator 3 (therefore, the operating pressure of the low pressure steam generator This prevents the operating pressure (operating pressure 5) from rising too high.

As described above, according to the present invention, the operating pressure of the low-pressure steam generator is varied according to the temperature and amount of exhaust gas, and the amount of recovered heat is adjusted by changing the saturation temperature, and the amount of heat recovered is adjusted by the release of excess steam. It is possible to prevent loss of circulating water.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the exhaust heat boiler temperature balance, Fig. 2 is a diagram showing the low pressure steam amount balance region, Fig. 3 is a diagram showing an example of the low pressure steam generator operating pressure, and Fig. 4 is a diagram showing an example of the configuration of the present invention. It is a diagram. 1... Water supply tank, 3... Heating deaerator. 5...Low pressure steam generator, 7...Coal economizer. 8...Steam drum, 1o...High pressure boiler. 11...Pressure controller, 12,13°...Control valve. 14...Pressure detector, 15...Lower limit setter. 16... Temperature detector, 17... Temperature controller, 18.
... Upper limit setting value. Agent: Tatsuyuki Unuma (and 2 others) Figure 1: Heat transfer surface axis Figure 2: Heat exchanger entrance heating area

Claims (2)

[Claims] (1) An operating method for an exhaust heat recovery equipment in which the steam generated from the low pressure steam generator installed in the exhaust heat recovery boiler is introduced only to the heating deaerator; When the amount of steam exceeds the amount of steam required in the heating deaerator, the operating pressure of the low pressure steam generator is increased to raise its saturation temperature. How to operate the recovery equipment. (2) In an exhaust heat recovery device in which steam generated from a low-pressure steam generator installed in an exhaust heat recovery boiler is introduced only to the heating deaerator, a detector that detects the pressure inside the heating deaerator. Based on the deviation between the pressure detection value from this detector and the pressure setting value of the heating deaerator, the opening degree of a control valve provided in a system for introducing all steam from the high-pressure steam system to the heating deaerator is determined. Alternatively, an exhaust heat recovery device comprising: a pressure controller for controlling the opening degree of a control valve provided in a system for introducing steam from the heating deaerator to the water supply tank.