What Is a Blowpipe?

Pipe blowing is one of the important trial operation steps before the power station boiler is put into operation. The quality control of the blowpipe and the correct implementation of the blowpipe process have a self-connecting effect on the safe operation of the boiler and the steam turbine. There are two main types of boiler tube blowing technology at home and abroad, namely the reduced pressure steam blowing method and the constant pressure steam blowing method. Both the reduced-pressure torch and the pressure-stabilized torch technology have been applied in the blowing process of the self-flow boilers of super (super) critical units ^[1] .

With the development of China's power industry, there are more and more super (super) critical units with a capacity of 600MW and above.

In order to ensure the effectiveness of the steam blow pipe,

The steam blowing method can be generally divided into a constant pressure steam blowing method and a reduced pressure steam blowing method. The pressure-stabilized steam torch is to maintain a relatively constant system pressure during the blowing process. It is a relatively steady state process in which the boiler maintains the energy balance between the input and output and the quality between the water supply and evaporation. balance.

Depressurized steam blow pipe refers to the boiler pressure rise to maintain a high blow pipe pressure, and then quickly open the temporary blow pipe door fully, so that the boiler pressure drops rapidly, and the amount of evaporation suddenly increases, so that the boiler is heated and purged.

The reduced pressure torch method has a simple system arrangement and requires less input systems, and it can ensure that the blowing coefficient of the superheater is greater than 1 during the effective time of the torch.

The pressure-stabilized blowing tube requires the boiler to be operated in ten states. The requirements for the boiler and the turbine sub-systems are relatively high. When the pressure-stabilizing blowing tube is used, the boiler has basically reached the start-up requirements. The steam feed water system, vacuum system, lubricant system, The shaft seal system must be commissioned. In addition, the pressure-stabilizing torch consumes more coal and demineralized water than the pressure-lowering torch; compared with the pressure-lowering torch process, the progress of the ignition torch may be delayed, but from the entire infrastructure process From the point of view, after the completion of the boiler pressure-stabilizing blowing pipe, the overall trial operation of the unit is relatively close to the start-up conditions, so it will not delay the overall trial operation period of the unit. The pressure-stabilized pipe blowing method can maintain a long time for each blowing, reducing the number of times required to complete the boiler blowing; the blowing coefficient of the boiler steam system is greater than 1 during the blowing; and the boiler pressure basically changes during the blowing process, and the steam temperature change rate And small change range, less thermal stress on thick-walled pressure-bearing parts of the boiler ^[3]

The scope of the blowing pipe mainly includes: boiler superheater system, reheater system, main steam pipe, cold and hot section reheat steam pipe, furnace body soot blower pipe cleaning is arranged after the main system blowing pipe is qualified. When the pressure reducing blowpipe of the power plant is used, the steam side backwashing is performed on the boiler side primary and secondary superheater and reheater desuperheating water pipelines. The power plant boiler side primary and secondary superheater and reheater desuperheating water pipelines are in the pressure-stabilizing blowpipe. Blow clean with auxiliary steam before.

The specific process of the blowing pipe in the power plant is the same: start the separator, superheater system, main steam pipe, high-pressure main steam valve, temporary pipe, temporary flush door, temporary pipe, pelletizer, cold section reheat steam pipe, reheater system, Hot section reheat steam pipe, medium pressure main steam valve, temporary pipe, temporary mother pipe, target board, temporary mother pipe, muffler, exhaust air ^[2]

The pressure-stabilized steam blow pipe of the power plant maintains the separator pressure at 5.5MPa. During this process, the main steam temperature is strictly controlled by the desuperheater to be less than 440 ° C. The reheated steam temperature is controlled by the reheater flue gas baffle and the accident water spray desuperheater. Within 490 ; when the pressure of the steam blower of Xinchang Power Plant is reduced, the temporary control door of the blower is opened when the separator pressure is 6.5MPa, and the temporary control door is closed when the separator pressure drops to 4MPa ^[1]

Through the practice of the torch process, several key issues that need attention in the torch process are summarized.

1. In the trial operation planning of the infrastructure construction headquarters, comprehensive consideration must be given to the system burden on the water supply, ash and slag, and powder production caused by the use of the Xiaotong process.

The small capacity requirements of the load capacity, the advancement of the site installation progress and production materials preparation.

2. When the pressure-lowering blower is selected for the operation mode with the starting circulating pump, when the blower switch is close to the flushing door, the phenomenon of the separator's low water level protection tripping and starting the circulating pump is prone to occur, which causes the low flow of the economizer to cause the boiler MFT protection action. . Open the temporary blow pipe electric door and increase the feed water flow rate at the same time. The full water level displayed by the separator water level in the early stage of the blow pipe is a false water level. At this time, the feed water flow rate can be reduced. The water level of the separator will suddenly drop when the door is close to the door. When the water level is visible, the feedwater flow rate is reduced.

3. When selecting the blowing method and designing the blowing parameters, the boiler water supply capacity should be fully considered. For the units equipped with "two steam pumps and one electric pump", it is necessary to calculate whether the electric pump meets the water supply requirements of the reduced pressure blow pipe and whether the steam pump water is required. In order to arrange the trial operation plan of the relevant system in advance.

4. In order to increase the effective time of the blowing pipe when the pressure is blown, the water storage and make-up capacity of the condenser needs to be increased. The water supply system of the condenser of the Guixi Power Plant has 2 small pumps and 1 large pump. Water replenishment, with 3 pumps fully open, the maximum water replenishment capacity can reach 800t / h. In addition, the separator overflow valve is recovered to the condenser. When the maximum feed water flow of the starting feed pump is 890t / h, the longest effective blowing time is 4h.

5. In the operation of the stabilized pressure torch, try to shorten the low-load stay time between the two blows as much as possible, save the amount of desalinated water in low-load operation, extend the effective time of the blower, and 5 hours from the ignition of the boiler to the completion of a stabilized blower. The effective blowing time is 4h.

6. If conditions permit, the on-line target installation and target taking device should be installed as far as possible to avoid load reduction and target plate installation and consume the demineralized water from the boiler tube. Guixi Power Plant's power construction unit does not have online target installation and target taking The device uses a step-down method to hit the target when the blowpipe is stabilized.

7. After the blowing pipe is finished, the residual impurities in the dead end of the inlet of the screen superheater and the small inlet of the inlet should be cleaned up to avoid the accident of overheating of the screen superheater and ensure the smooth operation of the unit ^[2] .