JPH0949606A - Variable pressure once-through boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit conducting the reduction of deterioration in water quality at the inlet port of an economizer as well as the reduction in consumption of life of the pipe base of a feed water pipe upon the inflow of stagnated water, kept in the condition of dead water for a long period of time whereby the water quality is deteriorated and the temperature thereof is reduced, by a method wherein a purge water tube, connecting the outlet port of a boiler recirculating flow rate regulating value and a feed water tube at the outlet port of the economizer, is installed. SOLUTION: The outlet port of a boiler recirculating flow rate regulating valve 12 is connected to the outlet port of an economizer 2 through a purge water tube 19 whereby dead water in the outlet port of the boiler recirculating flow rate regulating valve 12 is purged to the outlet port of the economizer 2 utilizing a pressure difference between the outlet port and the inlet port of the economizer 2. This operation can not be covered by the warming tube 16 of a boiler circulation pump. According to this method, boiler feed water, treated by chemical treatment, is taken into the outlet port tube of the boiler recirculating flow rate regulating valve 12 at all times whereby dead water is prevented, local deterioration of water quality as well as the cooling of a pipeline is prevented, the deterioration of quality of boiler feed water upon starting the recirculatlng operation and the thermal shock of a tube base are prevented. Especially, when composite water treatment is applied on the feed water treatment of the boiler, it is effective as the countermeasure of corrosion of parts whereat dead water is stagnated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer once-through boiler,
In particular, the present invention relates to a transformer once-through boiler suitable for reducing deterioration of water quality of boiler feed water in a water recirculation device in a boiler recirculation pipe when the transformer once-through boiler is activated and has a low load.

[0002]

2. Description of the Related Art As shown in FIG. 3, a conventional boiler apparatus includes a boiler circulation pump 11, a boiler recirculation pipe 13 at the inlet and outlet of the boiler circulation pump, a brackish water separator water storage tank drain level control valve 15 and a brackish water separator water storage. Tank drain pipe 1
No. 4 is a dead water part because boiler water is not recirculated during normal operation.

As a measure to prevent a temperature drop in the stagnant portion of the boiler recirculation pipe 13 until the boiler recirculation operation at the time of dead water and load drop of these systems, a part of the boiler feed water at the outlet of the economizer is used as a boiler circulation pump. Warming piping 16, brackish water separator water storage tank drain level control valve warming piping 17
The water is taken out at the outlet of the boiler circulation pump 11 and injected into the brackish water separator drain tank level control valve 15 to remove dead water and warm the boiler circulation pump 11 and the brackish water separator storage tank drain level control valve 15. It was

However, measures against dead water and warming in the boiler recirculation pipe 13 at the outlet of the boiler recirculation flow rate control valve 12 have not been considered.

In FIG. 3, 1 is a water supply pipe, 2 is a economizer, 3 is a furnace, 4 is an evaporator, 5 is a superheater, 6 is an overheat reducer, 7 is an overheat reducer spray pipe, and 9 is Brackish water separator, 1
0 is a brackish water separator water storage tank, 18 is a boiler circulation pump warming relief pipe, and 20 is a main steam pipe.

[0006]

In the above-mentioned prior art, the dead water during normal operation is not removed and warming is not taken into consideration, and the boiler circulation flow rate control valve outlet retention during boiler recirculation operation during load drop It is considered that there is a problem that the quality of the water supply at the inlet of the economizer is deteriorated due to the flow of water into the water supply, and the lifespan consumption is increased due to the thermal shock of the water supply pipe abutment due to the inflow of accumulated cold water.

An object of the present invention is to reduce the deterioration of the water quality at the inlet of the economizer and the consumption of the life of the water supply nozzle when the accumulated water, which has been dead water for a long period of time and whose water quality has deteriorated and whose temperature has decreased, flows into the water supply pipe. The purpose is to provide a transformer once-through boiler.

[0008]

The above object can be achieved by installing a purge water pipe connecting the outlet of the boiler recirculation flow rate control valve and the economizer outlet water supply pipe.

[0009]

[Operation] A differential pressure between the inlet and outlet of the economizer acts on the purge water pipe. As a result, the water at the boiler recirculation flow rate control valve outlet flows to the economizer outlet communication pipe side, and the new water flows from the water supply pipe to the boiler recirculation flow rate control valve side by that amount, and the water supply is always replaced, so dead water is generated. The quality of accumulated water is not deteriorated, and it is not cooled by heat radiation.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a water supply system diagram of a variable pressure once-through boiler according to a first embodiment of the present invention.

At the time of starting the boiler, about 5% of the rated flow rate of the feed water is sent from the feed water pipe 1 to the economizer 2, the furnace 3, and the evaporator 4, and further passes through the brackish water separator 9 and the brackish water separation water storage tank 10 to the boiler. Water is supplied to the recirculation pipe 13 by the boiler circulation pump 11
And is adjusted by the boiler recirculation flow rate control valve 12,
About 23% of the rated flow rate of boiler feed water flows, and the minimum feed amount of boiler is secured.

At this time, the feed water is subjected to brackish water separation by the brackish water separator 9, and the entire amount of the feed water as a drain flows into the brackish water separator storage tank 10, of which the brackish water separator storage tank drain level control valve 15 has about 5 The level of the brackish water separator water storage tank 10 is controlled while letting% water supply to a condenser not shown.

When the boiler is ignited in this state, steam is generated at the outlet of the evaporator 4, the temperature of the boiler is raised and the pressure is increased to 85 kg / cm ² , and the generated steam is superheated. 5, it is supplied to a turbine (not shown) via the main steam pipe 20.

Further, when the amount of fuel increases as the load increases, the steam ratio in the evaporator 4 increases, and at the load of about 28%, all steam becomes steam at the outlet of the evaporator 4, the boiler shifts to the once-through mode, and the feed water is further supplied. The amount of fuel and the amount of fuel are increased, and the boiler pressure and turbine output are increased. When the load is 28% or more, the drainage generated in the brackish water separator 9 disappears, so the boiler recirculation flow rate control valve 12 is fully closed, and the boiler circulation pump 1
The operation of 1 is stopped.

In this state, the boiler circulation pump 11, the boiler recirculation pipe 13, and the brackish water separator water storage tank drain level control valve 15 become dead water. When the boiler is stopped or the load is reduced, the reverse operation described above shifts from the once-through mode to the circulation mode. Therefore, in the steam separator 9, water (about 300 ° C., 8
5 kg / cm ² saturated water) is generated. Then, the boiler water is supplied to the boiler circulation pump 11, the boiler recirculation pipe 13,
In order to flow to the drain water tank level control valve 15 of the brackish water separator, and to prevent deterioration of boiler water quality and thermal shock of the nozzle of the economizer 2, it is necessary to purge and warm dead water in the once-through mode in advance. is there.

The method is carried out by injecting the boiler water at the outlet of the economizer 2 into the outlet of the boiler circulation pump 11 and the steam tank separator drain tank level control valve 15 and purging it into the steam separator water storage tank 10. Since the purged water is recovered in the brackish water separator water storage tank 10 in the system, the boiler circulation pump warming relief pipe 18 is used to remove the overheat reducer 6.
Is released to the superheat reducer spray pipe 7 at the inlet of the.

The present invention utilizes the differential pressure between the outlet and inlet of the economizer 2 by connecting the outlet of the boiler recirculation flow rate control valve 12 and the outlet of the economizer 2 with the purge water pipe 19. The dead water at the outlet of the boiler recirculation flow rate control valve 12 that cannot be covered by the boiler circulation pump warming pipe 16 is purged to the outlet of the economizer 2.

As a result, the boiler feed water, which has been always treated with chemicals, is taken into the outlet pipe of the boiler recirculation flow rate control valve 12 to prevent dead water, to prevent local deterioration of water quality and cooling of the pipe, and to start the boiler recirculation operation. Prevents water quality deterioration and thermal shock of the nozzle. FIG. 2 is a water supply system diagram of a once-through type boiler according to a second embodiment of the present invention.

In this embodiment, the purge water take-out position is the inlet of the boiler recirculation flow rate control valve 12, and the boiler recirculation flow rate control valve 12 is opened.

The effect of this embodiment is that the purge range can be extended to the upstream pipe of the boiler recirculation flow rate control valve 12, and the large startup valve itself can be warmed.

[0022]

As described above, according to the present invention,
Since a purge water pipe that connects the outlet of the boiler recirculation flow rate control valve and the water supply pipe of the economizer is installed, it is possible to reduce the dead water portion when stopping and reducing the load after long-term high load operation of the boiler. There is an effect that water quality deterioration at the beginning of the circulation mode and thermal shock of the nozzle can be reduced. Especially when applying complex water treatment to boiler feedwater treatment,
It is effective as a measure against corrosion (pitting corrosion) in the dead water area.

[Brief description of drawings]

FIG. 1 is a water supply system diagram of a variable pressure once-through boiler according to a first embodiment of the present invention.

FIG. 2 is a water supply system diagram of a variable pressure once-through boiler according to a second embodiment of the present invention.

FIG. 3 is a water supply system diagram of a conventional once-through transformer.

[Explanation of symbols]

 1 Water supply pipe 2 Coal saver 3 Furnace 4 Evaporator 5 Superheater 6 Superheat reducer 7 Superheat reducer Spray pipe 9 Brackish water separator 10 Brackish water separator Water storage tank 11 Boiler circulation pump 12 Boiler recirculation flow control valve 13 Boiler recirculation Piping 19 Purge water pipe

Claims (1)

[Claims] 1. A transformer once-through boiler having a boiler start-up recirculation system consisting of a boiler circulation pump, a boiler recirculation flow rate control valve, and a boiler recirculation pipe, wherein the boiler recirculation pipe and the outlet of the economizer are connected to each other. A transformer once-through boiler, wherein a purge pipe for purging dead water during normal operation is provided from the boiler recirculation pipe to the outlet of the economizer.