JPS5843308A - Boiler - 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 a boiler.

The furnace water-cooled wall of a boiler is usually located at the center of the furnace, as shown in Figures 1a and 2a, which show its cross-sectional view and longitudinal sectional view, and Figures 1b and gZb, which show the heat absorption rate distribution curves of each part, respectively. Part (a) has a large amount of heat absorption, 1 peripheral part (b), (b
ri is small. Due to the difference in heat absorption during startup, etc., the pressure inside the pipe increases as shown in the relationship diagram between the pressure loss Δp in the pipe and the flow rate G in the pipe at each part (a), (b), and (b) in the pipe in Figure 3. This is even more noticeable when the low heat absorption tube in the peripheral area is cooled by combustion air, etc., and in some cases, the flow rate may be extremely reduced or stagnate, and the tube may be damaged due to local overheat. In other words, as shown in Fig. 4, the liquid temperature at startup changes over time, and as a result, the flow rate G in the pipe changes at each part (a) of the furnace. , (b), (br) As shown in Fig. 5, the local distribution is connected. The temperature changes and may exceed the limit of the material used (as in the case of the temperature of the tube metal in the process).

Nowadays, it is an essential condition for 6BOI 2 to be able to operate smoothly and safely up to the required full load even with increasingly frequent starting and stopping operations, and the present invention aims at providing a complete solution to this problem. That is, it is intended to prevent the tendency shown in (b') in FIGS. 5 and 6 and to obtain the characteristics shown in (C). .

FIG. 7 is a system diagram of a conventional boiler.

That is, the feed water sent from the feed water heater is heated by the economizer 1 and enters the mixing method. The fluid exiting the mixing method is pressurized by the boiler circulation pump 3 and enters the water cooling wall 4 of the furnace. 4a
is the group of tubes in the center of the furnace that absorbs a lot of heat.

4b shows a tube group with a small amount of heat absorption in the peripheral portion. The fluid heated in the furnace passes through the boiler throttle valve 5, passes through the superheater 6, and reaches the turbine. - A part of the universal reactor outlet fluid passes through the recirculation line 7 from the upstream side of the boiler throttle valve 5 during low load, passes through the check valve 8, and is mixed with the feed water in the mixing method 2, and is mixed with the feed water in the water cooling wall of the furnace. However, even in this case, if there is a large difference in the amount of heat absorbed, the flow will be obstructed, and in some cases, this may lead to a pipe blowout. That's right.

The present invention can fundamentally solve these problems all at once, and the system of one embodiment thereof is shown in FIG.

・′:111 The paintbrush sent from the feed water heater passes through the coal selector 1, passes through the movable orifice 10, and enters the mixing method 2. The fluid exiting the mixing method 2 passes through the boiler circulation pump 3, and the furnace water-cooled wall is divided into a tube group 4a with a relatively large amount of heat absorption and a tube group 4b with a relatively small amount of heat absorption. It is divided into chambers 12a% and 12b. The fluid exiting the furnace water-cooled wall passes through the boiler throttle valve 5, passes through the superheater 6, and reaches the turbine. Also, a part of the fluid leaving the furnace at low loading is branched from the upstream side of the boiler throttle 9F5, passes through the recirculation line 7, passes through the check valve 8, enters the mixing method 2, and is mixed with the feed water.

Next, a description will be given of how the present invention improves the problems encountered when starting a boiler.

First, when the boiler is started, the movable orifice 10 is throttled at a certain point to provide resistance. Normally, the amount of water supplied when starting a boiler is small, so the frictional resistance inside the pipe is small, but by incorporating this movable orifice, a sufficient differential pressure can be provided. The tube group 4a of the furnace water-cooled wall is supplied with the fluid that passes through this movable orifice 10 and passes through the boiler circulation pump 3. At the same time, stop valve 9 is closed and piping valve 11 is opened, so that pipe 1v+4b has movable orifice 1.
A branched fluid flows from the upstream side of 0. Tube groups 4a and 4
In b, the outlet header is common, and if the movable orifice 10 is given a loss greater than the differential pressure of the boiler circulation pump 3, the differential pressure at the outlet and outlet of the tube group 4b can be made larger than the differential pressure at the outlet and outlet of the tube group 4a. . This flow rate difference can be freely adjusted by adjusting the opening degree of the movable orifice lO. When using the present invention, the flow rate in the pipe at startup is shown in (C) in Figure 5. If the load on the pipe increases and such flow rate adjustment is no longer necessary, close the bypass valve '11 and open the valve 9. The same operation as before is possible.

Of course, at this time, the movable orifice 10 is fully opened to minimize the pressure loss of the thread.

FIG. 9 shows a modification of the present invention in which a movable orifice lO is installed at the entrance of the economizer l. This makes the design easy because the design temperature is low (and the volumetric flow rate is small).On the other hand, if the design temperature is low (and the volumetric flow rate is small), the fluid temperature difference 7
9 (Since there is a concern that excessive thermal stress may occur, the temperature can be raised to an appropriate temperature using the heat exchanger 20. In other words, the temperature detected by the thermometer 22 is The heating side outlet fluid temperature is controlled to a predetermined temperature.

In this method, instead of providing a throttle to the main stream, a pump increases the pressure of the fluid flowing to the low heat absorption tube group to ensure a sufficient flow rate.

30 is a boost pump, 31 is an inlet/outlet valve, and 3:2 is a boost pump bypass pipe check valve.

In addition, some ideas for further enhancing the practicality of the present invention will also be presented. Fig. 11 is a vertical cross-sectional view showing the structure of the movable orifice lO in Fig. 9.9. Even if the valve stem 41 is completely closed, the flow path will not be fully open, so consideration has been given to providing the necessary and sufficient differential pressure at startup. It is. This is a cross-sectional view showing an example of the twelfth valve 42, and three port areas can be selected as needed. Figure 13 shows valve 9 in Figure 8.9.
．． 11 is a vertical cross-sectional view of one switching valve 43 that interlocks the switching valve 11, and is designed to improve safety by preventing the flow rate from becoming zero even if a malfunction occurs.

[Brief explanation of the drawing]

Figures 1a and 2a are a cross-sectional view and a vertical cross-sectional view of the furnace ice wall, respectively. Figures 1b and 2b are distribution diagrams of the heat absorption rate at various parts inside the furnace, and Figure 3 shows the pressure loss at various parts inside the pipe. Figures 4 to 6 are curve diagrams showing the relationship with the flow rate in the pipe, respectively.
Fig. 7 is a system diagram of a conventional boiler, Figs. 8 to 10 are system diagrams of a boiler showing an embodiment of the present invention, and Figs.
2 is a sectional view of different embodiments of the movable orifice, and FIG. 13 is a longitudinal sectional view of the embodiment of the switching valve. 1. Economizer, 2. Mixing method, 3. Boiler circulation pump, 4. Furnace water wall, 5. Boiler throttle valve, 6. Superheater, 7. Recirculation line, 8. Check valve, 9-・stop valve,
10...Movable orifice, 11... 2. Nio, 1
□0. stomach. W□Island 2a, 12b * *Omuro, 2°...
Heat exchanger, 2, - Capacity adjustment valve, 2゜... Thermometer, 30
- Boost pump, 31- Pump inlet/outlet valve, 32... Bypass pipe check valve, 41... Valve stem, 42... Ball valve, 4
3...Switching valve. “; ・,′ :・ 11゜Fig. 14 Fig. δ

Claims (1)

[Claims] In a boiler that has a heating tube group consisting of tube groups with different heat absorption amounts on the water cooling wall of the furnace, a group with a large amount of heat absorption and a group with a small amount of heat absorption are separated by a water chamber, which is a wing of the inlet header of the tube group. A boiler characterized by being equipped with a circuit device that increases and gates the flow rate through a group of tubes with a small amount of heat absorption when the boiler is started.