Full-process automatic control system for supercritical unit water supply system

Abstract

The invention provides a full-process automatic control system for a supercritical unit water supply system. The control system provided by the invention comprises a main controller, an electric pump outlet regulating valve controller, an electric pump rotary speed controller, a steam feed pump rotary speed controller, a pump combining block and a pump back block. The automatic control system canbe used for greatly reducing human misoperations, improving the security and improving the operating efficiency of the electric pump.

Description

technical field [0001] The invention relates to a distributed control system (DCS) technology of a thermal power unit, in particular to a whole-process automatic control system for a water supply system of a supercritical unit. Background technique [0002] Such as figure 1 As shown, it is a typical water supply system configuration of a supercritical unit, which includes an electric pump C (capacity is 40%), a first steam-driven feed water pump A, and a second steam-driven water feed pump B (The capacity of the steam-driven feed water pump is 50%), deaerator E, boiler drain expander F, high heater J, economizer I, water wall H and steam-water separator G, and there is an adjustment at the outlet of electric pump C valve D. [0003] During the water supply process of the boiler, the feed water pump flows from the deaerator E through the high heater J, the economizer I, and the water wall H into the steam-water separator G. When the boiler is hot and cold flushing, the unq...

AI Technical Summary

Problems solved by technology

[0007] The disadvantage of the above scheme is: manual control of one of the devices needs to rely on the experience of the operator, and if the operation is not done properly, it is easy to have adverse consequences

For example, in the parallel operation of electric pumps and steam pumps, if the outlet valve of the hand-operated electric pump is improperly caused the outlet pressure of the electric pump to drop, causing the electric pump to withdraw suddenly, it will cause a sudden change in the feed water flow, and in severe cases, it will cause the feed water flow boiler cutoff (MFT) action

On the other hand, manual operation makes the working point of the electric pump change with different operations of the operator, which cannot ensure that the electric pump works in the high-efficiency area, which is not conducive to improving the efficiency of the system

[0008] For the second difficulty, since the commissioning or withdrawing of the feedwater pump is carried out under the working condition of the unit with a certain load, the supercritical unit has high requirements for the stability of the feedwater flow, and the parallel pumping / withdrawal of the feedwater pump has a great impact on the feedwater flow. The water volume has a great influence. In the previous control, the automatic realization of parallel / withdrawal of the pump has not been realized, including the rush control of the turbine of the feed water pump, which is often manually operated by the operator.

[0009] The disadvantages of the above scheme are: manual parallel / withdrawal of the pump is inefficient, takes a long time, and has low safety

During the whole operation period, the total feed water flow should be kept stable, so manual operation often takes longer than automatic operation, and the safety is lower when the system is unstable.

[0010] For the third difficulty, due to the different adjustment characteristics of electric pumps and steam pumps, it is necessary to consider the changes in the adjustment parameters of different feed pump combinations when fully automatic switching on. In the past, it was difficult to achieve full automatic operation because manual intervention was required to switch on and off the feed water pumps.

[0011] The disadvantage of the above scheme is: the operation of the supercritical unit requires the ratio of fuel and water to be kept at a constant value, and the safety of manual operation by the operator is low

[0012] For the fourth difficulty, once the auxiliary machine fails and triggers the rapid load shedding (RUNBACK) condition, especially when a steam-driven feedwater pump trips, the unit is prone to steam-water imbalance, which affects the operation of the unit. In the past, the control system often Compensated by operator manipulation

[0013] The disadvantages of the above scheme are: due to the direct flow of supercritical unit operation, the feedwater flow directly affects the main steam flow, temperature and pressure, and the factors such as fuel and feedwater are highly correlated with each other, and it is difficult to maintain the normal operation of the unit by rescuing the operating conditions of the operator

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