JPH07103405A - Circulating water supplying device in discharged gas economizer - Google Patents

Abstract

PURPOSE:To enable occurrence of cavitation in a pump to be prevented by a method wherein a main bypassing pipe and an auxiliary bypassing pipe for bypassing a main circulating water pump and an auxiliary circulating water pump arranged in series are arranged and a check valve is installed in each of the bypassing pipes. CONSTITUTION:A main circulating water pump 12 and an auxiliary circulating water pump 13 are arranged in series in the midway part of a circulating water pipe 11. There are provided a man bypassing pipe 14 and an auxiliary bypassing pipe 15 bypassing each of the circulating water pumps 12, 13. Check valves 16, 17 are arranged in the midway part of each of the bypassing pipes 14, 15. Accordingly, in the case that an amount of evaporation at a discharged gas economizer 1 is more than a rated value, both check valves 16, 17 are closed and two circulating water pumps 12, 13 are operated while being connected in series, thereby even in the case that resistance in a circulating water system is increased, an amount of circulating water can be increased without reducing a discharging pressure and then a stable evaporation can be carried out within a heat transfer pipe 3. With such an arrangement as above, it is possible to prevent occurrence of cavitation at the pumps 12, 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circulating water supply device for an exhaust gas economizer.

[0002]

2. Description of the Related Art Usually, a ship or the like is provided with a diesel engine, and an exhaust gas economizer for producing steam by utilizing waste heat of exhaust gas discharged from the diesel engine (or boiler).

As shown in FIG. 3, this exhaust gas economizer has a heat transfer pipe 52 arranged in a passage for exhaust gas, for example, a chimney 51, a circulating water supply device 53 for supplying circulating water to the heat transfer pipe 52, and a circulating water supply device 53. It is composed of a steam-water separator 54 for guiding the circulating water which is supplied to the heat transfer pipe 52 by the circulating water supply device 53 and is heated to a high temperature to separate steam.

The circulating water supply device 53 is
Circulating water pipe 61 provided over the upper inlet part and the lower outlet part of the heat transfer pipe 52 and in which the steam separator 54 is arranged, and a circulating water pipe 61 on the outlet side of the steam separator 54 Main circulating water pump 62, a bypass pipe 63 bypassing the main circulating water pump 62, and a preliminary circulating water pump 64 provided in the middle of the bypass pipe 63.
It consists of and. In addition, each circulating water pump 62, 6
Check valves 65 and 66 are provided on the outlet side of the nozzle 4, respectively.

In this structure, during normal operation, the main circulating water pump 62 circulates the circulating water to the heat transfer pipe 52 in the chimney 51 to generate steam, thereby recovering the thermal energy of the exhaust gas. ing.

When the main circulating water pump 62 fails, the auxiliary circulating water pump 64 provided on the side of the bypass pipe 63 is driven to operate. In addition, when the inlet gas temperature of the exhaust gas economizer rises abnormally, or when soot abnormally adheres to the outer surface of the heat transfer pipe 52 of the exhaust gas economizer and burns, the evaporation amount of the exhaust gas economizer exceeds the rating and the circulating water amount is insufficient. To do. In such a situation, the pressure loss increases due to an increase in the amount of evaporation in the exhaust gas economizer, and therefore the amount of circulating water decreases and stable evaporation cannot be performed due to the characteristics of the circulating water pump.

[0007] In some cases, when the circulating water is entirely vaporized, the refiner agent in the circulating water is concentrated and corrosion occurs in the heat transfer tube, so that the pressure resistance of the heat transfer tube decreases as the temperature of the heat transfer tube rises. As a result, the heat transfer tube may burst or melt due to the heat of combustion.

Therefore, in such a case, the preliminary circulating water pump 64 is also operated and both pumps 62, 64 are operated in parallel so that the circulating water amount is not insufficient.

[0009]

As described above, two pumps are operated in parallel in order to prevent instability of evaporation, rupture or dissolution of heat transfer tubes. In this case, however, the following problems occur. Occurs.

That is, conventionally, as a circulating water pump,
A constant rotation-vortex pump is used, and the performance curve of this circulating water pump has a characteristic that the total head H decreases as the flow rate Q increases, as shown by the curve a in FIG. 4 (a). I have. Therefore, when two units are operated in parallel,
As shown by the curve b, the flow rate Q increases, but the total head H
Does not increase that much.

Therefore, when the amount of evaporation in the exhaust gas economizer increases abnormally, the resistance of the circulating water system, that is, the system resistance d becomes larger than the system resistance c during normal evaporation, as shown in FIG. 4 (a). For this reason,
Even when two units were operated in parallel, there was a problem that the amount of circulating water became Q ₁ → Q ₂ and became insufficient.

Further, if the amount of evaporation of the exhaust gas economizer becomes Q ₂ or more due to the combustion of soot, all of it will become steam in the exhaust gas economizer, and it will become overheated steam, and the yield strength of the heat transfer tube will decrease, causing the problem of puncture. there were.

Further, in the exhaust gas economizer, 2
When the circulating water pumps are operated in parallel and the evaporation amount of the exhaust gas economizer becomes zero, the system resistance decreases as shown by the curve e in FIG.
As shown in the curve f of No. 2, the required N in parallel operation of two units
PSH (required net positive suction head) (h _p) is greater than the head (height of the water level in the steam-water separator 54) (h) at the inlet portion of the circulating water pump 62, 64. That is, there is a problem that the pushing pressure to the pump is insufficient, cavitation occurs in the pump, and the impeller and the like are damaged.

Therefore, an object of the present invention is to provide a circulating water supply device for an exhaust gas economizer which can solve the above problems.

[0015]

In order to solve the above-mentioned problems, a circulating water supply apparatus for an exhaust gas economizer according to the present invention includes a heat transfer pipe arranged in a passage of exhaust gas, and a circulating water supply device for supplying circulating water to the heat transfer pipe. A circulating water supply device in an exhaust gas economizer having a water supply device and a steam separator for separating steam by guiding circulating water heated to a high temperature by being supplied to a heat transfer tube by the circulating water supply device, A main circulating water pump and a preliminary circulating water pump are arranged in series in the middle of the circulating water pipe in which the steam separator is disposed along the inlet and outlet of the heat transfer tube and each of these is arranged. A main bypass pipe and a backup bypass pipe that bypass the circulating water pump are provided, and a valve element having a check function is provided in the middle of each bypass pipe.

[0016]

With the above construction, the main circulating water pump and the auxiliary circulating water pump are provided in series in the middle of the circulating water supply pipe for supplying the circulating water to the heat transfer pipe arranged in the exhaust gas passage.
For example, when the amount of evaporation in the exhaust gas economizer exceeds the rated value, the two circulating water pumps are operated in series to increase the circulating water amount without decreasing the discharge pressure even when the circulating water system resistance increases. Can be made. Furthermore, when the amount of evaporation in the exhaust gas economizer becomes zero and the resistance of the circulating water system decreases, the discharge flow rate of the circulating water pump is almost the same as when there is only one unit, so the required NPSH in the pump is also in parallel operation. Therefore, it is possible to prevent cavitation from occurring in the pump.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, 1 is an exhaust gas passage 2 for discharging exhaust gas from a diesel engine of a ship, for example.
It is an exhaust gas economizer installed inside.

The exhaust gas economizer 1 includes a heat transfer pipe 3 arranged in an exhaust gas passage 2, a circulating water supply device 4 for supplying circulating water to the heat transfer pipe 3, and a circulating water supply device 4 for supplying heat to the heat transfer pipe 3. It is composed of a steam separator 5 for guiding the circulating water supplied and heated to a high temperature to separate steam.

The circulating water supply device 4 is provided over the upper inlet portion and the lower outlet portion of the heat transfer tube 3, and the circulating water pipe 1 in which the steam separator 5 is disposed on the way.
1, a circulating water pipe 11 on the outlet side of the steam separator 5, and a main circulating water pump 12 and a standby circulating water pump 13 provided in series in the middle, and a main bypass for bypassing these circulating water pumps 12, 13. Pipe 14 and spare bypass pipe 15
And check valves (valve bodies) 16 and 17 provided on the way of the bypass pipes 14 and 15, respectively.

In the exhaust gas economizer 1 having the above structure, during normal operation, the main circulating water pump 12 is driven to recover thermal energy from the exhaust gas passing through the exhaust gas passage 2. Of course, at this time, the check valve 16 of the main bypass pipe 14 is closed and the backup bypass pipe 15 is closed.
The check valve 17 is opened. When the main circulating water pump 12 fails and stops, if the auxiliary circulating pump 13 is operated, the check valve 16 of the main bypass pipe 14 is opened and the check valve 17 of the auxiliary bypass pipe 15 is opened. Is closed and the circulating water is supplied to the exhaust gas economizer 1.

If, for example, the amount of evaporation in the exhaust gas economizer 1 exceeds the rated value, the two check valves 16 and 17 will be closed if the two circulation pumps 12 and 13 are operated in series. .

Then, for example, when the amount of evaporation in the exhaust gas economizer 1 exceeds the rated value, the two-way check valves 16, 1
7 is closed and the two circulating water pumps 12 and 13 are operated in series.

When two units are operated in series, the pump shown in FIG.
As shown in performance curve B, the system
Even if the system resistance increases from C to D, the amount of circulating water is Q₁ 
→ Q ₂ Increase, and therefore the circulating water volume does not decrease
Therefore, stable evaporation can be performed. Note that FIG.
Curve A in (a) shows the characteristics when one circulating water pump is driven.
Shows Noh.

Further, when the amount of evaporation in the exhaust gas economizer 1 becomes zero and the system resistance E becomes small as shown in FIG. 2 (a), as shown in FIG. 2 (b),
Therefore the discharge flow rate is the same as for one, required NPSH (h _P) of the pump at this time does not increase much, it can be made smaller than the head (h) by steam separator 5. Therefore, since cavitation does not occur in the pump, it is possible to prevent the impeller and the like from being damaged.

In the above embodiment, the bypass pipes 14 and 15 for bypassing the circulating water pumps 12 and 13 are used.
However, the downstream side portion 14a of the main bypass pipe 14 and the upstream side portion 15a of the auxiliary bypass pipe 15 may be combined together as shown by the phantom line in FIG.

Further, in the above-described embodiment, electric or pneumatic automatic on-off valves may be provided in place of the check valves 16 and 17 provided in the bypass pipes 14 and 15, respectively.

Further, in the above-mentioned embodiment, the case of recovering the thermal energy of the exhaust gas discharged from the diesel engine of the ship has been described. May be.

[0028]

As described above, according to the structure of the present invention, the main circulating water pump and the auxiliary circulating water pump are provided in the middle of the circulating water supply pipe for supplying the circulating water to the heat transfer pipe arranged in the exhaust gas passage. Since they are installed in series, for example, when the amount of evaporation in the exhaust gas economizer exceeds the rated value, both valve bodies are closed and the two circulating water pumps are operated in series to increase the resistance of the circulating water system. Even in such a case, the amount of circulating water can be increased without reducing the discharge pressure, and therefore stable evaporation in the heat transfer tube can be performed.

Further, when the amount of evaporation in the exhaust gas economizer becomes zero and the resistance of the circulating water system becomes small, the discharge flow rate of the circulating water pump is almost the same as in the case of one unit, so the required NPSH in the pump is also in parallel. Since it is smaller than in the case of operation, and thus cavitation does not occur in the pump, damage to the pump impeller and the like can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a circulating water supply apparatus in an embodiment of the present invention.

FIG. 2 is a graph showing a performance curve of the circulating water pump in the example.

FIG. 3 is a diagram showing a schematic configuration of a conventional circulating water supply device.

FIG. 4 is a graph showing a performance curve of a circulating water pump in a conventional example.

[Explanation of symbols]

 1 Exhaust gas economizer 2 Exhaust gas passage 3 Heat transfer pipe 4 Circulating water supply device 5 Steam separator 11 Circulating water pipe 12 Main circulating water pump 13 Spare circulating water pump 14 Main bypass pipe 15 Spare bypass pipe 16, 17 Check valve

Claims (1)

[Claims] 1. A heat transfer tube disposed in an exhaust gas passage, a circulating water supply device for supplying circulating water to the heat transfer tube, and a circulation which is supplied to the heat transfer tube by the circulating water supply device and is heated to a high temperature. The circulating water supply device in an exhaust gas economizer having a steam separator for guiding water to separate steam, wherein the steam separator is provided along the inlet and outlet of the heat transfer tube and along the way. A main circulating water pump and a spare circulating water pump are arranged in series in the arranged circulating water pipes, and a main bypass pipe and a spare bypass pipe bypassing each of these circulating water pumps are provided. A circulating water supply device for an exhaust gas economizer, characterized in that a valve body having a check function is provided in the.