WO2008151485A1

WO2008151485A1 - A controlling method of a generator set provided with a bypass system

Info

Publication number: WO2008151485A1
Application number: PCT/CN2007/003432
Authority: WO
Inventors: Weizhong Feng
Original assignee: Shanghai Waigaoqiao No.3 Power Generation Co. Ltd
Priority date: 2007-06-11
Filing date: 2007-12-03
Publication date: 2008-12-18
Also published as: CN100439659C; EP2175105A4; CN101096917A; EP2175105A1; EP2175105B1

Abstract

A controlling method of a generator set provided with a bypass system, includes the following steps that: during the starting of the generator set provided with bypass system, a boiler (1) firstly is started, wherein the bypass system includes the first side bypass valve group (6,7) and the second side bypass valve group (8,9); the second side bypass valve group (8,9) is closed, at the same time the first side bypass valve group (6,7) is made to open a bigger degree, so that the steam from the outlet header (5) only passes through the first side bypass valve group (6,7) to discharge; the first side bypass valve group (6,7) is kept to open a desired time, then the first side bypass valve group (6,7) is closed, at the same time the second side bypass valve group (8,9) is opened, so that the steam from the header (5) only passes through the second side bypass valve group (8,9) to discharge; the second side bypass valves group (8,9) is kept to open a desired time, the normal work of the bypass system is resumed and the rotating of the steam turbine (10) is prepared. By controlling the bypass system, solid particle erosion is decreased and the safety of the generator set is enhanced.

Description

Generator set bypass control method

The invention relates to the field of electric heat engineering automation, and in particular to an alternating opening control method for a steam turbine bypass valve. Background technique

With the continuous improvement of the parameters of steam turbine generator sets, the steam oxidation of metal and the retention of the falling scale in the furnace tube are increasingly threatening the safe operation of the unit. In the boiler header, the retention and accumulation of scale is prone to occur. As shown in Fig. 1, the main reason for the scale accumulation is that after the steam tube 3 inlet port distributed in the entire header merges the steam 3 into the header 2, the concentrated steam 3 is again connected from the steam connected to both sides of the header 2 Pipe eight, B. sent out. The steam flow rate in the header is different when passing steam, and the flow velocity on both sides of the A/B is the largest, while the velocity of the steam at the 0 point in the header is approximately zero, forming the lowest flow rate, and the steam flow rate is the lowest, the impulse The smallest, foreign matter such as scale is easy to accumulate.

Similarly, in other embodiments, if the O point of the header is the outlet of the steam pipe, the flow velocity of the steam at point A or B of the corresponding header is substantially close to zero, forming the lowest flow rate zone (not shown) Show).

Foreign matter such as scales from the serpentine tube will remain in the low flow rate zone after entering the header. Foreign matter entering the junction will gradually increase in areas where the steam impulse is small. Only in special working conditions, such as the one-side closing of the main valve, etc., this part of the foreign object can be blown out of the header. A large amount of particulate foreign matter such as oxide skin accumulated in the low flow rate zone may endanger the piping connected to the area and the entire unit.

Therefore, it is necessary to develop a technology to eliminate foreign matter such as scale in the header, reduce the erosion rate of the solid particles of the turbine, and improve the safety of the unit. Summary of the invention

In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a low-cost, high-efficiency to achieve the removal of foreign matter such as oxide scale in the header, and to reduce the erosion rate of the solid particles of the steam turbine. The purpose of the high unit safety control method.

In order to achieve the above object, the present invention provides a bypass control method comprising the following steps: Step 1: A unit provided with a bypass system is started by the bypass system in a conventional manner during startup. The steam parameter has substantially reached the turbine cranking condition; the bypass system includes a first side bypass valve group respectively disposed on the main and reheat steam pipes connected to the boiler superheater or the reheater outlet header And a second side bypass valve group;

Step 2: closing the second side bypass valve group while opening the first side bypass valve group, so that the steam in the passing header is only in the first side of the open state The valve group is discharged on one side;

Step 3: After the first side bypass valve group is kept in an open state for a required period of time, the first side bypass valve group is closed, and the second side bypass valve group is opened, so that the passage is performed. The steam in the header is discharged from the other side only through the second side bypass valve group in an open state;

Step 4: After the second side bypass valve group is in the open state for a required period of time, the normal control state of the bypass system is restored and the turbine is ready to be rushed.

Preferably, in the first step, the boiler needs to complete startup and prepare to flush the steam turbine. Preferably, after the step three, the second step and the third step are repeated until it is ensured that the foreign matter in the header is cleared and the quality of the steam reaches a qualified value.

Preferably, the first side bypass valve group and/or the second side bypass valve group are alternately opened and closed by a program control mode.

Preferably, after the step four, the bypass system can resume the conventional control mode and prepare to flush the steam turbine.

Preferably, the bypass system is a high pressure bypass or a low pressure bypass. The control strategy of this method is also applicable to low pressure bypass to reduce the accumulation of foreign matter such as scale in the reheater outlet header.

Preferably, the first side bypass valve group and the second side bypass valve group respectively comprise at least one bypass valve.

Preferably, the greater the capacity of the bypass valve group, the better the purging effect for the header.

The bypass control method of the invention realizes the alternating change of the steam flow direction in the header box by using the alternate opening control of the bypass valves without adding any hardware facilities and additional economical expenditure. Due to the alternating flow of steam in the header, the lowest flow rate zone in the header is alternately shifted with the alternating flow direction of the steam, so that there is no fixed minimum flow velocity in the header, ie there is no flow velocity dead point, in the header All areas were thoroughly purged to remove foreign matter such as oxide scale in the header, reduce the erosion rate of solid particles of the turbine, and improve the safety of the unit.

The concept, the specific structure, and the technical effects produced by the present invention will be further described in conjunction with the accompanying drawings in order to fully understand the objects, features and effects of the invention. DRAWINGS

1 is a schematic view of steam flow in a unit header using a conventional conventional bypass control method; FIG. 2 is a schematic view showing a setting with a bypass unit;

Figure 3 is a schematic illustration of the steam flow rate in the header of the unit in the alternate opening phase using the bypass control method of the present invention;

4 is a flow chart of a control method of the present invention. detailed description

Figure 2 is a schematic diagram of the setup of a primary reheat unit with a bypass. In the thermal power unit, at least two main engines are included: Turbine 10 and Boiler 1, and the bypass system is the main component of the two mainframes. During the operation of the unit, the steam from the boiler 1 enters the superheater outlet header 5 through the superheater 2, and then enters the high pressure of the turbine 10 through the main steam line 11 through the main steam inlet valve and the regulating valve (not shown). The cylinder works, and the exhaust gas enters the reheater 3 in the boiler through the reheater cold section 4. The high pressure bypass is located between the boiler outlet header 5 and the reheater cold section 4, and the low pressure bypass is located between the reheater outlet header and the condenser (not shown). The same applies to low voltage bypass. The bypass system employing the method of the present invention includes a first side bypass valve group and a second side bypass valve group respectively disposed on the main and reheat steam lines connected to both sides of the superheater or reheater outlet header or Low pressure bypass (not shown); in this embodiment, the first side bypass valve group includes bypass valves 6, 7 and second side bypass valve group bypass valves 8, 9.

In normal operating conditions, steam enters the high pressure cylinder of the turbine 10 through the main steam line 11 to perform work. In a non-normal working condition such as a startup phase, a specific example of the bypass control method of the present invention includes the following steps (low voltage The bypass control method is the same as this:

Step one, the unit with the bypass system is in the startup phase, and the superheater 2 of the boiler 1 passes through the outlet header 5 through the bypass system through the cold and then enters the boiler reheater; the bypass system includes the connection boiler 1 respectively. The first side bypass valve group bypass valve 6, 7 and the second side bypass valve group bypass valve 8, 9 on the main and reheat steam pipes on both sides of the superheater 2 or reheater 3 outlet header;

Step 2: In the start-up phase, when the steam parameters have basically reached the turbine cranking condition; (At this time, both sets of bypass valves should be in the open state) First close the outlet header 5 - the bypass valve installed on the side outlet pipe 8 9, at the same time open the bypass valve 6, 7, so that the steam passing through the outlet header 5 is only discharged through the bypass valves 6, 7 in the open state; as shown in Figure 3, because the bypass valves 6, 7 open While the bypass valves 8, 9 remain closed, the steam in the outlet header 5 flows out from the pipe located on the same side as the bypass valves 6, 7 through point A, at which point B is zero flow point, stacked in Foreign matter such as scales outside the vicinity of point B is flushed out of the outlet header 5 with steam, and the momentum of the steam flushing momentum from point B is greater as the momentum increases.

Step 3: Keep the bypass valves 6, 7 in the open state, and the steam pressure in the pipeline tends to stabilize and maintain for a required period of time, close the bypass width 6, 7 and simultaneously open the bypass valve 8, 9, The steam passing through the outlet header 5 is discharged through the other side bypass valves 8, 9,; since the bypass valves 8, 9 are opened, the steam passing through the outlet header 5 is located on the same side as the bypass valves 8, 9. The pipe flows out at point B. At this point, point A is zero flow point. The foreign matter such as oxide scale deposited outside the area near point A is flushed out of the outlet header 5 with steam. The distance of the momentum from the point A is farther. Big

Step 4: Keep the bypass valves 8, 9 in the open state. After the steam pressure in the pipeline tends to stabilize and maintain for a required period of time, the normal control state of the bypass system is restored and the turbine is ready to be rushed.

The above described steps are as shown in Figure 4.

The bypass control method of the present invention does not add any hardware facilities and additional economical expenses, and alternately opens and controls the sides of the bypass valve to realize the alternating change of the steam flow direction in the header. As the flow direction of the steam in the header is alternately changed, the lowest flow velocity zone in the header is alternately transferred with the alternating flow direction of the steam, so that there is no fixed minimum flow velocity zone in the header, and all zones in the header are completely purged. It can eliminate the foreign matter such as scale in the header, reduce the erosion rate of the solid particles of the turbine, and improve the safety of the unit.

The method of the present invention is not limited to the above embodiments.

Preferably, in other embodiments of the present invention, a full program control mode may be employed, the present invention The control system is fully implemented in the unit start-up program control, and automatically switches between opening and closing the first side bypass valve group and/or the second side bypass valve group without human intervention or intervention. At the same time, this control method can be designed into the startup mode of the bypass itself, without affecting the start-up time of the unit and the operational safety of the unit.

Further, the control method of the present invention is not limited to the one-time opening and closing operation of the above embodiment. According to actual needs, after the above step three, the process of step two and step three may be repeated one or more times, that is, including multiple single-sided alternate opening and closing operations until the foreign matter in the header is cleared. And the quality of the steam reaches a qualified value.

After step four, when the unit completes the start-up process, the normal control state of the bypass system is restored and the turbine is ready for cranking.

The first side bypass valve group and the second side bypass valve group described in the present invention are not limited by the number of valves. In the above embodiment, the first side bypass valve group and the second side bypass valve group They are in two groups. In other embodiments of the present invention, each group may be a bypass valve, or each group may be a plurality of bypass valves, and the number of selections is mainly determined by the size of the steam flow and the size of the bypass capacity.

The method of the present invention can also be used in conjunction with other control methods for bypass systems.

In summary, the description in this specification is only a few preferred embodiments of the present invention. Any technical solution that can be obtained by a person skilled in the art according to the prior art by logic analysis, reasoning or limited experimentation based on the prior art is within the scope of the claims of the present invention.

Claims

1. A generator set bypass control method comprising the following steps:

Step 1: The unit provided with the bypass system is started by the bypass system in a normal manner during startup; the bypass system includes a superheater and/or a reheater respectively connected to the boiler a first side bypass valve group and a second side bypass valve group on the main steam and/or reheat steam pipe on both sides of the outlet header;

Step 2: closing the second side bypass valve group while opening the first side bypass valve group, so that the steam in the passing header is only in the first side of the open state The valve group is discharged;

Step 3: After the first side bypass valve group is kept in an open state for a required period of time, the first side bypass valve group is closed, and the second side bypass valve group is opened, so that The steam passing through the header is discharged only through the second side bypass valve group in an open state;

Step 4: After the second side bypass valve group is in an open state for a required period of time, the normal control state of the bypass system is restored and the turbine is ready to be rushed.

2. The bypass control method according to claim 1, wherein in said step 1, it is performed before said steam turbine is reversed.

3. The bypass control method according to claim 1, wherein: after the step three, the step two and the third step are repeated until the foreign matter in the header is cleared and the steam The quality reached the qualified value.

4. The bypass control method according to claim 1, wherein: said first side bypass valve group and/or said second IJ bypass valve group are alternately opened and closed by a program control mode.

5. The bypass control method according to claim 1, wherein: after said step four, said bypass system is capable of returning to a normal control mode and preparing to flush the steam turbine.

6. The bypass control method according to claim 1, wherein: said bypass system is a high pressure bypass or a low pressure bypass.

7. The bypass control method according to claim 1, wherein: said first side bypass valve group and said second side bypass valve group respectively comprise at least one bypass valve.