JPH01208602A - Method and apparatus for controlling an exhaust gas economizer - Google Patents

Abstract

PURPOSE:To prevent adhesion of soot onto surfaces of heat transfer tubes even upon operation below rated load, by allowing the inner pressure of the low pressure steam separation drum to exceed the setting pressure at the time of rated load, and also by restraining the feed of circulating water to elevate the temperature of the circulating water fed to the low pressure vaporization zone. CONSTITUTION:A three way valve 13 is provided in the vicinity of an outlet of a heater 12 for heating a low pressure circulating water and is connected to a temperature controller 14 to which a signal from a microprocessor 18 is inputted to control an amount of water being bypassed and therefore to adjust a temperature of the low pressure circulating water. The signal from the microprocessor 18 is also inputted into a pressure controller 16 to adjust a preset pressure. In order to elevate a temperature of the low pressure circulating water, an inner pressure of a low-pressure steam system is increased, though the amount of steam is thereby decreased. Moreover, a flow amount of water bypassed through the heater 12 is decreased to elevate an inlet temperature of the low-pressure circulating water introduced into a low-pressure preheating section 6. As a result, it is prevented to adhere soot on the heat-transfer conduits.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method and device for controlling an exhaust gas economizer that generates steam using the thermal energy of exhaust gas from an engine, and is particularly applicable to ships and the like. 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 engine operation.

(Conventional technology) Since the rise in oil prices, energy saving measures have been promoted to save fuel, and various measures have been taken to use exhaust gas energy from engines, etc., and measures are being taken to use more energy. I came here. The high/low pressure dual pressure system in exhaust gas economizers is one such example.

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 cause the amount of steam to exceed a certain limit. Even if the heat transfer 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 six system.

To explain the conventional high/low pressure double pressure six type exhaust gas economizer using Fig. 3, the high pressure circulating water system that supplies high pressure steam and the low pressure circulating water system that supplies low pressure steam are as follows.
Each has an independent steam/water separation drum 1.2.

That is, 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, and heated saturated water is returned to the high-pressure steam/water separation drum 1 in an independent circulating water system. Has a lineage. Separately, the circulating water in the low-pressure steam/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 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 a population valve 21 and a valve 21 are provided at the entrance and exit to the feedwater heater 12, respectively. An outlet valve 22 is provided, and both are normally fully open, but the valve 23 of one bypassed pipeline is normally fully closed. Makeup water is sucked from the water supply tank 20 by the water supply pump 11 and supplied to the water supply heater 12, and is supplied to the water supply control valves 9. Water is supplied to the high-pressure steam-water separation drum 1 and the low-pressure steam-water separation drum 2 while being controlled by the IO. 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. There is. Both are communicated via a steam replenishment valve 5 for low-pressure steam pressure control, and insufficient steam is automatically sent through the high-pressure steam pipe 31 so that the steam pressure reaches the preset steam pressure with the 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 six type exhaust gas economizer, the utilization rate of exhaust gas energy is high, so the temperature of the exhaust gas 25 near the outlet of the exhaust gas flow path 3 is low. 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 a result, large amounts of soot adhere to the heat exchanger tubes of the exhaust gas flow path 3, especially the low-pressure preheating section 6, which deteriorates heat exchange efficiency and reduces the amount of evaporation. At the same time, the main engine exhaust gas back pressure increases and This may result in an inoperable condition.

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 control method for an exhaust gas economizer, to achieve the above-mentioned object is an exhaust gas economizer that generates steam using thermal energy of engine exhaust gas. - The circulating water system is divided into two systems: a high-pressure system equipped with a high-pressure evaporator and a high-pressure air-water separation drum, and a low-pressure system equipped with a low-pressure evaporator and a low-pressure air-water separation drum, and , Exhaust gas eco-tsuma and isers equipped with a bypass pipe that detours circulating water as a heat dissipation fluid to the make-up water heater, when the engine load becomes lower than the rated load, the pressure in the low-pressure air-water separation drum is specified. The temperature of the circulating water to the low-pressure evaporator section is increased by raising the pressure higher than the set pressure at rated load and by limiting the supply of circulating water from the low-pressure steam/water separation drum to the make-up water heater. .

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 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 the exhaust gas economizer, the low-pressure steam/water separation drum is connected via a pressure regulating valve and is provided with a bypass line upstream of the low-pressure evaporator for bypassing the circulating water as a heat radiation fluid to the make-up water heater. A flow rate adjustment valve for adjusting the amount of circulating water supplied from the supply water to the make-up water heater is provided near the outlet or inlet of the bypass pipe, and a pressure control means for setting a pressure and controlling the pressure regulating valve so that the pressure in the drum reaches the set pressure; and a pressure control means for controlling the temperature of circulating water to the low pressure evaporator based on the pressure in the low pressure air/water separation drum. and temperature control means for controlling the bypass flow rate regulating valve so that the circulating water reaches the set temperature.

(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 comparing and controlling the pressure regulating valve,
The pressure inside the low-pressure steam/water separation drum is set to the above-mentioned set pressure. Then, the temperature control means sets the temperature of the circulating raw 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 specified temperature, the engine load is low and the surface of the heat transfer tube in the low-pressure preheating section is maintained. If soot tends to adhere to the
Since the pressure of the circulating water in the low-pressure system is increased and the temperature is controlled to be high, soot is prevented from adhering to the surface of the heat exchanger tube in 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 of the low-pressure circulating water, and a signal from the microprocessor 18 is input to the temperature controller 14 to adjust the amount of bypass and thereby control the temperature of the low-pressure circulating water. Temperature control means are provided. Feedwater heater inlet valve 21. Outlet valve 22. The bypass valves 23 are both fully opened. Furthermore, in the prior art, the set pressure of the steam replenishment valve 15 for controlling the pressure 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 which allows the set pressure to be adjusted manually by signals from the microprocessor 18.

The microprocessor 18 receives a load signal (such as an engine)
For example, the scavenging pressure of the engine or the engine speed in a ship, etc.) is input, and the steam pressure of the steam supply valve 15 is set according to a preset program based on the signal, and then the three-way control valve 13 is set according to the steam pressure. The set temperature of the temperature controller 14 can be changed.

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 normally used (rated) in engines, etc.
It is designed to generate the required amount of steam at the time of output.

Therefore, during low-load operation, the amount of steam generated naturally decreases, and the exhaust gas economizer alone cannot cover the entire amount of steam required. In such cases, reducing evaporation loss is not 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 I2 is reduced to increase the population 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 rotational speed) is received. microprocessor-18
Accordingly, the pressure controller 16 of the steam replenishment valve 15 is set to the design pressure PA (for example, 2 atg). Then, since the check valve 19 is provided 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 PA.

At this time, the temperature controller 14 of the three-way control valve 13 is set to the design temperature TA (for example, 120° C.) by the microprocessor 18. Therefore, the low-pressure preheating section 6 of the exhaust gas economizer 3 is operated at TA, 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 steam replenishing valve 15 is operated by the microprocessor 18 that receives the load signal.
The pressure controller 16 of Pmax (for example, 3atg
) is set. At that time, the temperature controller 14 of the three-way control valve 13 is set to T by the calculation of the microprocessor 18.
max (for example, 130°C). Pressure controller 1 when engine load is between 85% and 50%
6 is set to Px by a predetermined program of the microprocessor 18, and accordingly, the temperature controller 14 and the like are set to Tx by a predetermined program of the microprocessor 18. When the engine load is below 50%, Pmax and T
The microprocessor I8 is designed to have a constant value of max.

Thus, when the engine load is 85% or less, the temperature of the low-pressure circulating water in the low-pressure preheating section 6 rises above the Fujiki bond design point, and the evaporation m decreases, but the temperature of the low-pressure preheating section 6 increases. This is because the soot removal rate is reduced to a large degree [1], thereby preventing the heat exchange efficiency from decreasing even during continuous deceleration operation of the engine.

(Effect of the invention) As explained above, the exhaust gas economizer of this invention
According to the control method and its device, the temperature of the circulating water supplied to the low-pressure steam section increases compared to a conventional exhaust gas economizer, especially when the engine is operating at low speed, so the amount of exhaust gas is reduced because the engine is under low load. Even though the exhaust gas temperature decreases, the adhesion of soot to the surface of the heat exchanger tube in the low-pressure evaporator section is significantly reduced, and problems such as soot removal work and a decrease in heat exchange efficiency can be solved all at once. .

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an exhaust gas economizer according to an embodiment of the present invention, Fig. 2 is a diagram of the calculation principle of a microprocessor used in the control method according to the present invention, and Fig. 3 is a diagram of a conventional exhaust gas economizer. It is a system diagram. 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 control valve, IO...Low pressure water supply control valve, DESCRIPTION OF SYMBOLS 11... Water supply pump, 12... Feed water heater, 13... Three-way control valve, 14... Temperature controller, [5... Steam supply valve, 16... Pressure controller, 17... Pressure sensor, 18...Microprocessor-119...
・Check valve, 20... Water supply tank, 21... Population valve,
22... Outlet valve, 23... Bypass valve, 24... Engine load signal, 25... Exhaust gas.

Claims (2)

[Claims] (1) The circulating water system of the exhaust gas economizer, which 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. In an exhaust gas economizer, the exhaust gas economizer is divided into two low-pressure systems, and a bypass pipe is provided upstream of the low-pressure evaporator section to bypass the circulating water as a heat radiation fluid to the make-up water heater. If the pressure in the low-pressure air-water separation drum becomes lower than the set pressure at the rated load, the pressure in the low-pressure air-water separation drum is increased, and the supply of circulating water from the low-pressure air-water separation drum to the make-up water heater is restricted. . A method for controlling an exhaust gas economizer, comprising increasing the temperature of circulating water to the low-pressure evaporator. (2) The circulating water system of the exhaust gas economizer, which 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 a make-up water heater is connected to the upstream side of the low-pressure evaporator. In an exhaust gas economizer provided with a bypass pipe for detouring circulating water as a heat dissipation fluid, 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 connected to the bypass pipe. The pressure regulating valve is provided near the outlet or near the inlet of the pipe, 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. pressure control means; 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; An exhaust gas economizer characterized by being equipped with.