JPS6015215B2 - Boiler water injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water injection device suitable for boilers, particularly small capacity, high pressure boilers.

Since the contact heat transfer area of the superheater in the Z natural circulation boiler is constant, at low loads the amount of combustion gas decreases and the amount of contact heat transfer decreases rapidly, and at high loads the amount of combustion gas increases and the amount of contact heat transfer decreases. This is something that is rapidly increasing. In other words, the superheated steam temperature changes with the load. Therefore, in order to obtain a predetermined steam temperature under low load, the heat transfer surface of the superheater is made large, and in order to obtain a constant steam temperature under high load, water is injected. On the other hand, in the Benson boiler, the evaporation completion point moves depending on the ratio of the amount of water supplied to the amount of fuel, and therefore the heat area of the superheater changes, so the superheated steam temperature can be kept constant regardless of the load.

However, this is the case in a static state, and in a dynamic state such as during load fluctuations, there is a time difference in the influence of feed water and fuel on the superheated steam temperature. The temperature is not constant. For this reason, water is injected near the boiler outlet, usually in the middle of the superheater, to keep the superheated steam temperature constant even in dynamic conditions. By the way, since the amount of water injected is about 5 to 10% of the normal amount of water supply, the amount is extremely small in the case of a small capacity boiler.

Furthermore, water injection control is normally performed by a control valve installed in a water injection pipe extending from the water supply pump to the middle of the superheater, and the pressure required to control the water injection is considerably large. Therefore, in a small capacity, high pressure boiler, the control valve is a valve with a high differential pressure and an extremely small flow rate, making it difficult to obtain a flow rate proportional to the degree of opening. That is, when the valve starts to open, even a small degree of opening results in a considerable flow rate, and thereafter the flow rate changes depending on the degree of valve opening. When the superheated steam temperature becomes high, the water injection control valve is opened and a large amount of water is injected at once, and as a result, the superheated steam temperature rapidly drops and the water injection control valve is closed. Thus, in practice, the water injection control valve has the same function as an on-off valve and is repeatedly opened and closed, making it extremely difficult to control the superheated steam temperature at a constant level. The present invention has been made to solve this problem, and a separate water injection pipe is provided between the inlet or the outlet of the main water supply pump of the boiler and the intermediate part of the superheater or the boiler outlet, and the water injection pipe is installed in the middle of the water injection pipe. It is an object of the present invention to provide a water injection device for a pourer, characterized in that a positive displacement pump is provided and the temperature of superheated steam is controlled to a constant temperature by adjusting the amount of water injected by the positive displacement pump.

Below, an embodiment of the boiler water injection device according to the present invention will be described with reference to the drawings. In FIG. 1, 1 is a boiler water supply system;
2 is a main water supply pump, 3 is a energy saver/evaporator, and 4 and 5 are superheaters.

A separate water injection pipe 6 is provided between the vicinity of the inlet of the main water supply pump 2 of the boiler water supply system 1 and the middle of the superheaters 4 and 5 (or the boiler outlet), and a positive displacement pump 7 is provided in the middle of the water injection pipe 6. As shown in FIG. 2, this positive displacement pump 7 has an inlet valve 9 and an outlet valve 10 at both ends of a casing 8 connected to a water injection pipe 6.
A cylinder 1 is integrally provided at right angles to the intermediate outer periphery of a casing 8, a plunger 12 is inserted into the cylinder 11, and a crank-type drive mechanism 13 is connected to the plunger 12. The drive mechanism 13 has a rotation speed changing mechanism (not shown), and is adapted to change the rotation speed in response to a signal from, for example, a superheated steam temperature regulator at the boiler outlet. Next, we will explain the operation of the boiler water injection system configured as described above, but before that, we will explain the water supply to the boiler.The boiler water is supplied to the boiler through the energy saver/evaporator 3 by the operation of the main water supply pump 2, and then to the superheater. 4 and 5, where it is heated by a combustion device (not shown), evaporated and heated, and exits from the boiler as superheated steam.

On the other hand, the boiler water injection device according to the present invention has a positive displacement pump 7.
The water sucked into the water injection pipe 6 from near the inlet of the main water supply pump 2 of the water supply system 1 by the operation is injected into the middle of the superheaters 4 and 5 (or the boiler outlet) via the positive displacement pump 7. .

That is, when the drive mechanism 13 of the positive displacement pump 7 rotates,
The plunger 12 reciprocates and the water sucked into the water injection pipe 6 is sucked into the casing 8 from the inlet valve 9, and the water is drawn into the casing 8 through the inlet valve 9.
The water is discharged from the boiler and injected into the middle of the superheaters 4 and 5 (or the boiler outlet). At this time, the amount of water injected varies as the amount of water discharged from the outlet valve 10 changes due to the reciprocation of the plunger 12 by the drive mechanism 13 whose rotation speed changes in response to a signal from a superheated steam temperature regulator (not shown) at the boiler outlet. It is. That is, when the superheated steam temperature at the boiler outlet is high, the amount of water injection is increased, and when it is low, the amount of water injection is decreased. In addition, the pressure difference between the front and rear of the positive displacement pump 7 is created by the movement of the plunger 12, so that water may be injected in excess of the required amount due to the small size of the inlet valve 9 and outlet valve 10, for example. Never. The amount of water injected can be adjusted using the drive mechanism 13.
In addition to changing the rotational speed of the plunger 12, this may be done by changing the effective stroke of the plunger 12.

It should also be noted that the plunger type positive displacement pump 70 usually has three or more pumps in order to prevent pulsation of water injection. FIG. 3 shows another embodiment of the boiler water injection device according to the present invention, including a positive displacement pump? A water injection pipe 6 is installed between the vicinity of the outlet of the main water supply pump 2 and the middle of the superheaters 4 and 5 (or the boiler outlet), and is a positive displacement pump? The ten outlet valves are provided with a spring 14 as shown in FIG. 4, and the spring 14 always holds the outlet valve 10 in the closing direction.

The other configurations are exactly the same as those shown in FIGS. 1 and 2. Thus the outlet valve 10', the main water pump 2 and the superheater 4,
It does not move due to the differential pressure generated between the water injection point in the middle of the pump 5 (or the pourer outlet), but moves in relation to the movement of the plunger 12.

The embodiment shown in Figs. 3 and 4 operates in substantially the same way as the embodiment shown in Figs. Main water pump 2
This pressure difference is between the outlet of the main water pump 2 and the water injection point between the superheaters 4 and 5 (or the boiler outlet).
Compared to the pressure difference between the inlet of the boiler and the water injection point between the superheaters 4 and 5 (or the boiler outlet), the higher the pressure is, the smaller the pressure difference is. Therefore, the amount of suction from the inlet valve 9 and the amount of discharge from the outlet valve 10 due to the reciprocating motion of the plunger 12 are balanced, the required amount of water is injected, and the superheated steam temperature is finely adjusted. As can be seen from the above description, the boiler water injection device according to the present invention has a separate water injection pipe installed between the inlet or the outlet of the main water pump of the boiler and the middle of the superheater or the boiler outlet, and a positive displacement type Since a pump is provided and the drive of the positive displacement pump is controlled, for example, by the superheated steam temperature at the boiler outlet, the amount of water injected by the positive displacement pump into the intermediate part of the superheater or the boiler outlet is appropriate. This has an excellent effect in that the superheated steam temperature can be finely adjusted accurately and reliably, and the superheated steam temperature can be controlled to a constant temperature.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of the water injection layer of a boiler according to the present invention, FIG. 2 is a schematic sectional view of a positive displacement pump in the water injection device, and FIG. 3 is a water injection device for a boiler according to the present invention. FIG. 4 is a schematic sectional view of a positive displacement pump in the water injection device. 1... Boiler water supply system, 2... Main water supply pump, 3... Energy saver/evaporator, 4, 5...
...Superheater, 6...Water injection pipe, 7...Positive displacement pump~8...Casing 9...Inlet valve, 1
0... Outlet valve, 1... Schilling, 12... Plunger, 13... Drive mechanism, 14... Spring. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A separate water injection pipe is installed from near the inlet or outlet of the boiler's main feed water pump to the middle of the superheater or the boiler outlet, and a positive displacement pump is installed in the middle of the water injection pipe to adjust the amount of water injected by the positive displacement pump. A water injection device for a boiler, characterized in that the temperature of superheated steam is controlled to a constant temperature.