JPH052881B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a control method and apparatus for an exhaust gas economizer that generates steam by using the thermal energy of engine exhaust gas, and in particular,
The present invention relates to a control method and device for preventing soot from adhering to the heat transfer tube surface of the low-pressure evaporator of an exhaust gas economizer during low-speed operation of an engine of a ship or the like.

(Conventional technology) Since the rise in oil prices, energy conservation measures have been promoted to save fuel, and various measures have been taken to use exhaust gas energy from engines and other devices, and to use more energy. It's here. One such example is the high/low pressure dual pressure system in exhaust gas economizers.

If you try to obtain steam by matching the pressure to the steam service that requires the highest pressure, the temperature difference between the saturation temperature of the water corresponding to that pressure and the temperature of the exhaust gas will reduce the amount of steam that will be transmitted beyond a certain limit. Even if the thermal area is increased, the amount of evaporation will hardly increase. Therefore, if steam services that do not require very high pressure are combined to form a low-pressure steam system and a low-pressure steam generation section is installed, the temperature of the circulating water will be lower, and the temperature difference between it and the exhaust gas will be larger, and more exhaust gas will be generated. Energy can be used to generate more steam. This is the principle of the high/low pressure dual pressure system.

To explain a conventional high/low pressure dual pressure type exhaust gas economizer using Figure 3, the high pressure circulating water system that supplies high pressure steam and the low pressure circulating water system that supplies low pressure steam each have separate steam and water systems. It has separation drums 1 and 2. That is, the circulating water in the high-pressure steam-water separation drum 1 is supplied to the high-pressure evaporator 4 of the exhaust gas flow path 3 by the high-pressure circulating water pump 7,
It has an independent circulating water system in which heated saturated water returns to the high pressure steam/water separation drum 1. Separately, the circulating water in the low-pressure air-water separation drum 2 is supplied to the feed water heater 12 by the low-pressure circulating water pump 8, and then passes through the low-pressure preheating section 6 and the low-pressure evaporating section 5 of the exhaust gas flow path 3. A low pressure circulating water system is provided which returns to the steam/water separation drum 2. The feedwater heater 12 heats make-up water using low-pressure circulating water, and a bypass pipe to the feedwater heater 12 is provided on the low-pressure circulating water side, and an inlet valve is provided at each entrance and exit to the feedwater heater 12. 21 and an outlet valve 22, both of which are normally fully open, but the valve 2 of one bypassed pipeline
3 is normally fully closed. Makeup water is sucked from the water supply tank 20 by the water supply pump 11 and supplied to the feed water heater 12, and is controlled by water supply control valves 9 and 10 independently provided on the high and low pressure air/water separation drums 1 and 2, respectively. The water is then branched into the high-pressure steam-water separation drum 1 and the low-pressure steam-water separation drum 2 while being supplied with water. A high pressure steam supply line 31 is connected to the steam outlet of the high pressure steam/water separation drum 1, and a low pressure steam supply line 32 is connected to the steam outlet of the low pressure steam/water separation drum 2 via a check valve 19. . Both are communicated via a steam replenishment valve 15 for low-pressure steam pressure control, and insufficient steam is automatically supplied from a high-pressure steam pipe 31 so that the steam pressure reaches a preset steam pressure with a pressure setting device 16. The steam pressure in the low pressure steam line 32 is controlled to be constant.

(Problems to be Solved by the Invention) In the above-mentioned high/low pressure double pressure system exhaust gas economizer, the utilization rate of exhaust gas energy is high, so the temperature of the exhaust gas 25 near the exit of the exhaust gas flow path 3 decreases. Furthermore, since the temperature of the circulating water in the low-pressure preheating section 6 of the exhaust gas flow path 3 is set low, soot is likely to adhere to the surface of the heat exchanger tube in this section. In order to save energy, especially on ships such as tankers, the main engine is often operated continuously at a load lower than its rated output. However, if low load operation continues for a long time, the amount of exhaust gas decreases and the temperature of the exhaust gas due to this decreases. As the temperature decreases, a large amount of soot adheres to the heat exchanger tubes of the exhaust gas flow path 3, especially the low-pressure preheating section 6, and
In addition to deteriorating the heat exchange efficiency and causing a decrease in the amount of evaporation, the main engine exhaust gas back pressure may increase, resulting in a state in which the main engine cannot operate.

The present invention provides a method and apparatus for controlling an exhaust gas economizer that prevents soot from adhering to the surface of heat transfer tubes even during continuous low-load operation of an engine or the like.

(Means for Solving the Problems) The gist of the first invention, a method for controlling an exhaust gas economizer, for achieving the above-mentioned object is as follows:
The circulating water system of the exhaust gas economizer, which generates steam using the thermal energy of engine exhaust gas,
It is divided into two systems: a high-pressure system equipped with a high-pressure evaporator and a high-pressure steam-water separation drum, and a low-pressure system equipped with a low-pressure evaporator and a low-pressure steam-water separation drum. In an exhaust gas economizer equipped with a bypass pipe that detours circulating water as a heat dissipation fluid, when the engine load becomes lower than the rated load, the pressure in the low-pressure air-water separation drum is lowered than the set pressure at the rated load. At the same time, the supply of circulating water from the low-pressure steam/water separation drum to the make-up water heater is restricted to raise the temperature of the circulating water to the low-pressure evaporator. In addition, the exhaust gas economizer as the device, which is the second invention, has a circulating water system of the exhaust gas economizer that generates steam using thermal energy of engine exhaust gas, and is equipped with a high-pressure evaporator and a high-pressure steam/water separation drum. The system is divided into two systems: a high-pressure system equipped with a low-pressure evaporator and a low-pressure system equipped with a low-pressure steam-water separation drum, and the high-pressure steam-water separation drum and the low-pressure steam-water separation drum are connected via a pressure regulating valve. In the exhaust gas economizer, in which a bypass pipe line is provided upstream of the low-pressure evaporation section to bypass the circulating water to the make-up water heater as a heat dissipation fluid, circulating water flows from the low-pressure air-water separation drum to the make-up water heater. A flow rate regulating valve for adjusting the supply amount is provided near the outlet or near the inlet of the bypass pipe, and the pressure of the low-pressure air/water separation drum is set based on engine load fluctuations, and the pressure inside the drum is a pressure control means for controlling the pressure regulating valve so that the set pressure is reached; and a pressure control means for setting the temperature of the circulating water to the low pressure evaporator based on the pressure in the low pressure steam/water separation drum, and the circulating water reaches the set temperature. and a temperature control means for controlling the bypass flow rate regulating valve.

(Function) According to the exhaust gas economizer control method and device of the present invention, the pressure control means sets the pressure in the low-pressure air/water separation drum based on the engine load, and compares this set pressure with the pressure in the drum. After the comparison, the pressure regulating valve is controlled to bring the pressure in the low-pressure steam/water separation drum to the set pressure. Then, the temperature control means sets the temperature of the circulating water supplied to the low-pressure evaporator based on the pressure in the low-pressure steam/water separation drum, compares this set temperature with the temperature of the circulating water, and then adjusts the bypass flow rate. By controlling the valve to adjust the supply amount of make-up water from the drum to the heater and bringing the circulating water temperature to the low-pressure evaporator to the set temperature, the engine load is low and the surface of the heat exchanger tube in the low-pressure preheating section is maintained. If soot tends to adhere to the heat exchanger tube surface of the low-pressure evaporator, the pressure of the circulating water in the low-pressure system is increased and the temperature is controlled to be high, thereby preventing soot from adhering to the surface of the heat exchanger tube of the low-pressure evaporator.

(Example) An example will be explained with reference to FIG. A three-way control valve 13 is provided near the outlet of the feed water heater 12 for low-pressure circulating water, and the temperature of the low-pressure circulating water can be controlled by inputting a signal from a microprocessor 18 to the temperature controller 14 and adjusting the amount of bypass. Temperature control means are provided. The inlet valve 21, outlet valve 22, and bypass valve 23 of the feed water heater are all fully open. In addition, in the conventional technology, the set pressure of the steam replenishment valve 15 for pressure control of the low-pressure steam system was set to a constant value in advance, whereas in the present invention, the pressure controller 16 receives a signal from the microprocessor 18. A pressure control means is provided in which the set pressure can be adjusted by inputting a signal from the microprocessor 18. The microprocessor 18 receives a load signal from the engine (e.g. engine scavenging pressure or engine speed for ships, etc.), and uses that signal to operate the steam replenishment valve 1 according to a preset program.
5 is set, and the set temperature of the temperature controller 14 of the three-way control valve 13 can be changed in accordance with the steam pressure. In addition, since the steam is in contact with circulating water in the steam-water separation drum 2, the steam pressure is approximately equal to the circulating water pressure.

According to this control system, it is possible to operate the engine by changing the pressure and temperature of the low-pressure circulating water depending on the load of the engine or the like.

Exhaust gas economizers are usually designed to generate the amount of steam required during normal (rated) output from an engine, etc. Therefore, during low load operation,
Naturally, the amount of steam generated will decrease, and the exhaust gas economizer alone will not be able to cover the entire amount of steam required. In such cases, the reduction in evaporation does not pose a problem. Therefore, although the amount of evaporation decreases, the pressure of the low-pressure steam system is increased to raise the temperature of the low-pressure circulating water, and the bypass flow rate to the feed water heater 12 is reduced to increase the inlet temperature of the low-pressure circulating water to the low-pressure preheating section 6. , to prevent soot from adhering.

Next, the control method of the present invention will be explained with reference to FIG. 2. In this case, 85% of the engine load is the design point, and when the engine load is 85% or more, the engine load signal (for example, scavenging pressure or rotation speed, etc.) The steam replenishment valve 15 is controlled by the microprocessor 18 that receives the
The pressure controller 16 is set to the design pressure P _A (for example, 2 atg). Then, since there is a check valve 19 at the steam outlet of the low-pressure steam-water separation drum 2, the pressure inside the low-pressure steam-water separation drum 2 also becomes equal to or higher than P _A. At this time, the temperature controller 14 of the three-way control valve 13 is controlled by the microprocessor 18 to set the design temperature T _A
(for example, 120℃). Therefore, the low-pressure preheating section 6 of the exhaust gas economizer 3 is operated at T _A , which is the design temperature condition, and the exhaust gas economizer generates an amount of steam exceeding the rated value. In this case, the entire rated circulating water is designed to pass through the feed water heater 12.

When the engine load reaches 50%, the pressure controller 16 of the steam replenishment valve 15 is set to Pmax by the calculation of the microprocessor 18 that receives the load signal.
(for example, 3atg). At that time, the temperature controller 14 of the three-way control valve 13 is set to Tmax (for example, 130° C.) by the calculation of the microprocessor 18. When the engine load is between 85% and 50%, the pressure controller 16 is set to Px by a predetermined microprocessor 18 program, and the temperature controller 14 is also set to Px by a predetermined microprocessor 18 program accordingly. Set to Tx by the program.
respectively when the engine load is below 50%.
The microprocessor 18 is constructed so that Pmax and Tmax are constant values.

Thus, when the engine load is 85% or less, the temperature of the low-pressure circulating water at the inlet of the low-pressure preheating section 6 rises above the steam amount design point, and the amount of evaporation decreases.
The temperature of the low-pressure preheating section 6 rises, and the adhesion of soot is greatly reduced, so that it is possible to prevent a decrease in heat exchange efficiency even during continuous deceleration operation of the engine.

(Effects of the Invention) As explained above, according to the exhaust gas economizer control method and device of the present invention, the temperature of the circulating water supplied to the low-pressure evaporator is lower than that of the conventional exhaust gas economizer, especially during low-speed operation of the engine. Since the engine rises compared to the miser, even though the engine is under low load, the amount of exhaust gas decreases and the exhaust gas temperature decreases, soot adhesion to the heat transfer tube surface of the low-pressure evaporator section is significantly reduced, making it easier to remove soot. It is possible to solve problems such as heat exchange efficiency and decrease in heat exchange efficiency all at once.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an exhaust gas economizer according to an embodiment of the present invention, Fig. 2 is a diagram showing the calculation principle of a microprocessor used in the control method according to the present invention, and Fig. 3 is a diagram showing a conventional exhaust gas economizer. This is a system diagram of DESCRIPTION OF SYMBOLS 1... High-pressure air-water separation drum, 2... Low-pressure air-water separation drum, 3... Exhaust gas flow path, 4... High-pressure evaporation section, 5... Low-pressure evaporation section, 6... Low-pressure preheating section, 7...
...High pressure circulating water pump, 8...Low pressure circulating water pump,
9... High pressure water supply adjustment valve, 10... Low pressure water supply adjustment valve, 11... Water supply pump, 12... Water supply heater,
13... Three-way control valve, 14... Temperature controller, 15... Steam supply valve, 16... Pressure controller, 17... Pressure sensor, 18... Microprocessor, 19... Check valve, 20... Water supply tank, 21... Inlet valve, 22... Outlet valve, 23
...Bypass valve, 24...Engine load signal, 2
5...Exhaust gas.

Claims (1)

[Claims] 1. The circulating water system of an exhaust gas economizer that generates steam using the thermal energy of engine exhaust gas is a high-pressure system equipped with a high-pressure evaporator and a high-pressure air/water separation drum, and a low-pressure evaporator and a low-pressure air system. In an exhaust gas economizer that is divided into two systems, a low-pressure system equipped with a water separation drum, and provided with a bypass line upstream of the low-pressure evaporator that bypasses circulating water as a heat radiation fluid to a make-up water heater, the engine load becomes lower than the rated load, the pressure in the low-pressure steam/water separation drum is increased above the set pressure at the rated load, and circulating water is supplied from the low-pressure steam/water separation drum to the make-up water heater. A method for controlling an exhaust gas economizer, characterized in that the temperature of circulating water to the low-pressure evaporator is increased by limiting the temperature of the circulating water. 2 The circulating water system of the exhaust gas economizer that generates steam using the thermal energy of engine exhaust gas is equipped with a high-pressure system equipped with a high-pressure evaporator and a high-pressure air-water separation drum, and a low-pressure evaporator and a low-pressure air-water separation drum. The high-pressure steam-water separation drum and the low-pressure steam-water separation drum are connected via a pressure regulating valve, and circulating water is connected to the make-up water heater upstream of the low-pressure evaporator. In the exhaust gas economizer, a flow rate adjustment valve for adjusting the amount of circulating water supplied from the low-pressure air-water separation drum to the make-up water heater is installed in the bypass pipe. A pressure control valve is provided near the outlet or near the inlet of the drum, and sets the pressure of the low-pressure steam/water separation drum based on engine load fluctuations, and controls the pressure regulating valve so that the pressure in the drum reaches the set pressure. and temperature control means for setting the temperature of circulating water to the low-pressure evaporator based on the pressure in the low-pressure steam/water separation drum and controlling the bypass flow rate adjustment valve so that the circulating water reaches the set temperature. This is an exhaust gas economizer that is characterized by: