JPS588901A - Device for recovering waste heat - 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 improvement in a waste heat recovery device that generates steam using waste heat in exhaust gas from a diesel main engine as a heat source.

Exhaust gas economizers or waste heat recovery boilers are well known as devices of this type that recover waste heat from diesel main engines, and are particularly used in ships to save energy by obtaining steam for driving a generator turbine or miscellaneous steam on board from the exhaust gas of a diesel main engine. It is used as a device. First, a conventional exhaust gas economizer will be explained.

1 is a water supply tank called a cascade tank, which contains condensate from the generator turbine, condensate from low-pressure miscellaneous steam,
Drainage etc. is flowing back. Additionally, if the water level in the tank drops due to loss or consumption of steam or water within the system, water is replenished from a separate makeup water tank. These pipes connected to the cascade tank from the outside are omitted in this system diagram. 2 is a pipe for discharging boiler water at saturated temperature from the drain reservoir 4 of the low-pressure steam steam separator 3, which will be described later. 5 is a heat exchange coil for cooling this boiler water. If high-temperature saturated water is discharged into the cascade tank 1 without being cooled, phenomena such as noise can be expected, so it was decided to cool it in advance in order to achieve smooth operation.

6 is a water level control valve for the drain reservoir 4. The water level in the drain reservoir 4 is detected, and the valve opening degree is always automatically adjusted so that the deviation between this and a preset target water level is zero. 7 is a cooled water outlet. 8 is a water supply pump, and 9 is a water supply control valve.

The water supply control valve 9 detects the water level of a high-pressure steam steam separator 10 (described later), and always automatically adjusts the valve opening so that the deviation between this and a preset target water level is zero. It's being adjusted.

11 is an exhaust gas economizer main body into which exhaust gas from a main engine (not shown) is introduced, 12 is an exhaust gas inlet, and 13 is an exhaust gas outlet.

14 is a preheating section inlet header, 15 is a preheating section outlet header, and 16 is a preheating tube.

The water supplied by the water supply pump 8 is supplied to the preheating section population 1.
4 and approximately 90°C. This is done using boiler water from a drain reservoir 4 that has passed through a water supply separator 3 at a temperature of up to 90°C. Note that a feed water heater may be provided between the feed water pump 8 and the feed water control valve 9, and in this case, the feed water temperature at the inlet of the preheating section will be higher than 90°C. The heat transfer area of the preheating tube 16 is determined so that the temperature of the feed water at the outlet 15 of the preheating section is approximately equal to the saturation temperature of the operating pressure of the low pressure evaporation section 17, which will be described later. That is, when the low-pressure evaporator 17 is operated at 4, the temperature is approximately equal to the saturation temperature at 4. Note that the operating pressure of the low-pressure evaporator 17 is determined based on the required pressure of low-pressure steam.

18 and 19 are the inlet and outlet headers of the low pressure evaporation section, respectively. A portion of the feed water at the outlet 15 of the preheating section heated to a temperature approximately equal to the saturation temperature of the operating pressure of the low pressure evaporation section is supplied to the low pressure evaporation section, and the remaining portion is supplied to the steam water separator 10 for high pressure steam. .

Although the high-pressure steam/water separator 10 is sometimes installed separately as a dedicated device, in many cases it is also used as a steam drum of an oil-fired boiler.

When the feed water supplied to the low-pressure evaporator enters the low-pressure evaporator pipe 17 via the inlet header 18 and receives heat from the exhaust gas from the main diesel engine, it immediately starts evaporating because it has been preheated to almost the saturation temperature. The steam and water mixture is collected at the outlet header 19 and enters the low-pressure steam steam-water separator 3, where it is separated into low-pressure steam and saturated water.

Both the steam separator main body 3 and the drain reservoir 4 are cylindrical in shape. The steam/water mixture exiting the outlet header 19 is introduced tangentially into the steam/water separator main body 3, swirls within the separator main body 3, and is devised so that the steam/water is separated by centrifugal force. . The steam rises slowly and is taken out of the vessel through the steam pipe 20.

It is thought that the saturated water forms a water surface at the bottom of the separator 3 that can curve the four parabolas of the middle gate. Such a structure of the steam/water separator is effective in making the separator main body 3 compact, but it also forms a stable water surface by controlling the water level.

21 is a flow control valve. The main purpose of installing this valve is to control the amount of water flowing to the low pressure evaporator 17. Even if this valve opening degree is increased or decreased, the amount of evaporation in the low-pressure evaporator 17 does not change.

This is because the amount of evaporation is controlled only by the amount and temperature of the exhaust gas from the diesel main engine, which is the heating medium. When the opening degree of this valve 210 increases or decreases, the temperature of the water supplied to the cascade tank 1 changes. This is because if the valve 21 is opened wide, the amount of saturated water flowing into the cascade tank 1 will increase, and if the valve opening is narrowed, the amount of saturated water flowing in will be decreased.

For the above purpose, the opening degree of the flow control valve 21 is set so that the temperature of the water supplied to the cascade tank 1 becomes 90°C. However, the opening degree of the control valve 21 is not automatically changed according to the temperature of the water supply, but is set manually. Once the valve opening is set so that the water supply temperature is 90°C during normal output, the valve opening is not adjusted each time even if the load fluctuates or the water supply temperature slightly goes up or down from 90°C. ' The reason why the water supply temperature was set at 90°C is as follows. That is, in order to remove dissolved oxygen in the water supply, i.e., to degas it, it is preferable to bring the temperature of the water supply as close to the saturation temperature as possible, but since the cascade tank 1 is an atmospheric pressure tank, the saturation temperature is 100°C, so it is not too saturated. If the temperature is approached, the water supply temperature will drop to 10% due to slight changes in driving disputes, etc.
This is because there is a risk that the temperature will reach 0°C and boil inside the tank.

The second function of the flow control valve 21 is to reduce the bulging phenomenon. When the low-pressure evaporator pipe 17 is filled with saturated or unsaturated water and is stagnant or flowing, when the main diesel engine starts and exhaust gas flows in, the water in the pipe will eventually begin to boil and turn into steam. It becomes a mixture. When the mixture becomes a steam/water mixture, the volume of the contents increases all at once due to the steam bubbles, and is pushed out of the tube with great force, flowing into the low-pressure steam steam/water separator 3 and raising the water level in the separator. This phenomenon is called the bulging phenomenon. Although this water level fluctuation is a transient phenomenon, if the water level rises excessively and water is mixed into the steam multiple times, it will have various negative effects on the place where the steam is used, so it is necessary to control it so that it does not rise excessively. As mentioned above, the water level control valve 6 is provided, but it is technically difficult to provide a sufficient response to such sudden and wide-ranging disturbances. Therefore, the flow control valve 21 detects the rotational speed of the main diesel engine, the position of the control notch of the fuel valve, etc., and increases the valve opening in conjunction with this to limit the amount of water flowing. This prevents a large amount of saturated water from flowing into the steam/water separator 3 all at once at the start of evaporation, that is, when the diesel main engine speeds up.

Next, the high pressure evaporation section will be explained.

22 is a boiler water circulation pump, 23 and 24 are high-pressure evaporator inlet and outlet headers, respectively, and 25 is a high-pressure evaporator pipe.

Saturated water from the high-pressure steam steam separator 1o is sent by the boiler water circulation pump 22, passes through the high-pressure evaporator inlet header 23, enters the high-pressure evaporator 25, receives heat from the exhaust gas from the diesel main engine, and becomes a steam-water mixture. They were gathered at the exit entrance 24.

The water enters a high-pressure steam separator 10, where it is separated into high-pressure steam and saturated water.

The above-mentioned swelling phenomenon occurs not only in the low-pressure evaporator but also in the high-pressure evaporator, and by increasing the internal volume of the steam-water separator 10, sudden and large water level fluctuations can be prevented. Can be absorbed or alleviated.

The high-pressure steam separated by the steam-water separator 10 is introduced into the superheater tube 27 via the superheater inlet header 26, where it is superheated by heat exchange with the exhaust gas, and then transferred to the superheater outlet header 28. The water is then supplied to, for example, a power generation steam turbine (not shown).

By the way, in the above-mentioned conventional exhaust gas economizer, the pressure-resistant components of the low-pressure evaporator section include the evaporator pipe 17, the inlet header 18, the outlet header 19, the steam separator 3, and the drain reservoir 4.
Since there are a large number of such devices, the system configuration becomes complicated and reliability is degraded.

The present invention aims to provide a waste heat recovery device that can improve system reliability and obtain stable boiler water circulation performance by simplifying the configuration of the low-pressure evaporator and reducing the number of pressure-resistant parts. It has been done.

The present invention will be explained in detail below based on the embodiments shown in FIGS. 2 to 4. In addition, in FIGS. 2 to 4, the same parts as in FIG. 1 are indicated with the same reference numerals, so
The explanation of that part will be omitted.

Figure 2 shows a system diagram of an exhaust gas economizer as an embodiment of the waste heat recovery device according to the present invention.
In the figure, 31 is a steam-water separator for low-pressure steam, 32 is a low-pressure evaporation partial pipe, 33 is one or more downcomers, 3
4 is a water level control valve.

A portion of the feed water exiting the preheating section 16 is supplied to the low pressure evaporation section 17 through the water level control valve 34, and the remaining portion is supplied to the high pressure steam steam separator 10 through the water level control valve 35.

The feed water that has passed through the water level control valve 34 enters the low pressure steam steam separator 31. Boiler water (saturated water) in the steam water separator 31
descends through the downcomer pipe 33 and enters the low-pressure evaporator pipe 17 via the distribution piping 32. The saturated water is then heated by the exhaust gas from the main diesel engine, becomes a steam-water mixture, flows upward through the pipe 17, and returns to the steam-water separator 31. Here, it is separated into low pressure steam and saturated water, and the low pressure steam is led out through the steam pipe 20.

Since the inside of the downcomer pipe 33 is saturated water and the inside of the low pressure evaporation pipe 17 is a temperature mixture of air and water, the water flows downward in the downcomer pipe 33 and upward in the low pressure steam pipe 17 due to the difference in specific gravity. In other words, it is a natural cycle.

A feature of the present invention is that the low-pressure evaporation section is of a natural circulation type. In the conventional case (FIG. 1), if the opening degree of the flow rate control valve 21 is too large, the temperature of the water supply in the cascade tank 1 becomes too high and boils, so there is an upper limit to the amount of water that can be supplied.

This is the reason why it is not possible to increase the boiler water circulation ratio (the value obtained by dividing the total flow rate in the pipes by the amount of evaporation). In the case of the present invention (Fig. 2), it is natural that the water supply flow rate must be equal to the evaporation amount, but the low-pressure evaporation pipe 17
The circulation ratio within the chamber is not determined by the amount of water supplied, but is determined by the number, geometric shape, and dimensions of the downcomer pipes 33 and evaporator pipes 170, or the difference in height between the steam separator 31 and the distribution piping 32. (hydraulic head difference), etc., it is possible to secure a larger circulation ratio than before.

In addition, in FIG. 2, 36 is a feed water heater.

Preheating section 1 by water supply pump 8 from cascade tank 1
This is provided to heat the water supplied to the tank 6. Steam may be used as the heating medium for heating this water supply, or the low-pressure steam steam separator 3
1 or the high-pressure steam steam separator 10 (ゝO As described above, according to the present invention, the pressure-resistant parts in the low-pressure evaporation section include the evaporation pipe 17, the steam-water separator 31, the number of distribution piping ports 32 is reduced compared to the conventional one, and the conventional flow control valve 21 is no longer required, and the circulation type is not a forced circulation type but a natural circulation type, so the system configuration is simplified. A waste heat recovery device is provided that has great effects such as contributing to improved reliability.1.

FIG. 3 shows the main parts of another embodiment of the present invention, in which a low-pressure steam steam separator 31 is connected to an exhaust gas economizer main body 11.
The steam separator 31
is arranged at a high place, and the outlet of the evaporation pipe 17 and the steam/water separator 31 are connected by a riser pipe 37. Note that the other configurations are similar to those shown in FIG.

FIG. 4 shows an embodiment in which the present invention is applied to a single pressure exhaust gas economizer.

In FIG. 4, 1 is a cascade tank, 8 is a feed water pump, and 36 is a feed water heater. 14 and 15 are the inlet and outlet headers of the hand heating section, respectively, and 16 is the water supply preheating pipe, and these functions are the same as in the case of FIG. 2. Further, 34 is a water supply control valve, 31 is a steam/water separator, 32 is a distribution pipe, 17 is an evaporation pipe, and 33 is a downpipe, and these functions are the same as in the case of FIG. 41 is a saturated steam communication pipe, 26 and 2B are superheater inlet and outlet headers, respectively, and 27 is a superheater tube. The steam taken out from the steam-water separator 31 passes through the Japanese steam pipe 411 and the superheater inlet header 26, enters the superheater tube 27, receives heat from the exhaust gas of the main diesel engine, becomes superheated steam, and enters the outlet header. 28 and taken out of the system.

In this embodiment, the preheating section constituted by 14, 15, and 16 can be omitted, and the feed water heater 36 and the feed water regulating valve 34 can be directly connected.

Further, the superheater constituted by 26, 27, and 28 may be omitted, and the steam may be directly taken out from the steam separator 31 to the outside of the system. That is, a small-capacity exhaust gas economizer whose purpose is only to obtain steam for miscellaneous purposes is generally not provided with a preheating section or a superheater.

[Brief explanation of drawings]

Figure 1 is a system diagram showing a conventional exhaust gas economizer, M2
The figure is a system diagram showing an exhaust gas economizer as an embodiment of the waste heat recovery device according to the present invention, FIG. 3 is a diagram showing the main parts of another embodiment of the present invention, and FIG. FIG. 3 is a system diagram showing another embodiment. 1. Cascade tank, 10. High-pressure steam steam separator, 11. Exhaust gas economizer body, 16. Preheating pipe, 17. Low-pressure evaporation pipe, 20. Steam pipe, 25. High-pressure evaporation pipe. 27...Superheater tube. 31... Low pressure steam steam separator, 33... Downpipe 34...
・Water level control valve. Figure 3 t Figure 4 ゛

Claims (1)

[Claims] In a waste heat recovery device that generates steam using waste heat in exhaust gas from a main diesel engine as a heat source, a preheater that preheats feed water from a tank by the heat source, and a part of the preheated feed water or A water separator, all of which is introduced via a water level control valve, a downcomer pipe that extends downward from the water separator and drops the water introduced into the water separator, and a an evaporator whose upper part is connected to the steam-water separator and which snakes along the flow direction of the gas so that the introduced water is heated by the heat source to generate steam; , and a steam pipe for extracting steam from the steam separator.