Discussion on application of anti-surge control system for air compressor unit

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(Shanxi Tianji Group Gaoping Chemical Co., Ltd., Shanxi Gaoping 048400 Ding Guojian) Application of Anti-surge Control System for Air Compressor Units Henan Coal Chemical Industry Group Zhongyuan Dahua Company adopted the ICSTriplex control system for comprehensive control of air compressor units.

The control system includes ESD unit interlock, SOE event sequence recording, PID unit control and general indication recording function, and fault diagnosis function.

The difference between the anti-surge control of the air compressor and the anti-surge control of other centrifuges is as follows: (1) The inlet is atmospheric, so the anti-surge control valve does not control the return flow, but controls the amount of venting (atmosphere).

(2) The function of the anti-surge line is to prevent the unit from surging and to prevent damage to the compressor due to excessive pressure. Therefore, the air compressor surge line and anti-surge line consider the results of the comprehensive test. The margin between the air compressor surge line and the anti-surge line is generally set by the unit manufacturer or design institute as the air compressor surge line data. The most reliable method is the unit manufacturer based on the field test results and the unit. The ability to withstand pressure gives comprehensive data on the air compressor surge line.

1 When the basic function of anti-surge is suddenly overrun or below zero, it is defined as a fault signal in the fallback operation. In this case, fallback replaces this fault signal with its pre-set safety value until the fault is removed.

In the PID regulation loop, the P and D parameters are automatically adjusted as needed: when the operating point moves to the surge zone, the PI adapts the gain to open the anti-surge valve; when the operating point is far from the anti-surge line (SCL) When the controller adjusts the gain to slow the anti-surge valve according to the PI, the anti-surge valve is quickly opened and closed.

(3) Anti-surge puncture detection and prevention. When either the operating point is lower than the anti-surge line or the flow rate is too fast, the surge control line will automatically shift to the right.

(4) Henan Coal Chemical Industry Group Zhongyuan Dahua Company's anti-surge control of air compressor unit adopts ICSTriplex's TRUSTEDT6300 system to realize dynamic anti-surge control, and adopts multi-section folding line connection to form anti-surge control line and anti-surge Control basic functions include surge line (SLL), anti-surge line (SCL), surge margin (10%), anti-surge line down line (5% each time, up to 5 times), automatic / manual / Semi-automatic switching, PID adjustment, etc.

2 Anti-surge control scheme and algorithm 2.1 Anti-surge line According to the comprehensive surge line data given by the unit manufacturer, the surge line (two points variable connected to the line segment) and the anti-surge line are made. The surge line is formed by a plurality of sections of broken lines, and one of the broken line sections is shown.

b - intercept; X - X coordinates, usually using the inlet flow Q; Y - Y coordinates, usually the ratio of the outlet pressure to the inlet pressure.

2.2 Anti-surge line and anti-surge control implementation module to complete the anti-surge control of the unit.

There is a surge graph on the HMI screen, including the surge line and the anti-surge line. When the surge occurs, the anti-surge line increases by 2% each time to generate a surge down line, becoming a new anti-surge line. When the working condition is stable and away from the surge zone, press the reset button to cancel the surge down line and restore the original anti-surge line.

The operating point that moves with the operating condition, indicating the distance between the current operating point and the anti-surge line.

There are three types of anti-surge control methods: automatic, semi-automatic and manual.

Automatic mode: The automatic control output is the value of the PID output and the proportional output high selection value as the surge control output. Manual mode: The operator's 'manual output' is given on the HMI screen to give the surge control output. Semi-automatic mode: The high value of the manual control output value and the surge control output value is used as the surge control output.

(1) Surge occurrence: Surge control consists of the surge line and the anti-surge chemical line and the surge down line. When the actual flow at the working point (aASRHP) is less than the surge of the anti-surge line flow (rPART) At the point (rSULIN), the surge occurs, the signal of the surge flag (铨SUR =1) turns red, and the surge accumulation number (rSURNOlA) is automatically incremented by 1 and displayed on the HMI screen, and the anti-surge valve opens quickly.

=2 (rTTLSMRG=rSAFMRG+rRECBIAS), every time there is a surge, move down kMNGINC by 2% (right shift) to create a new anti-surge line, ie the surge down line KMXA ~ KMXF; when the unit returns to normal In the working condition, you can set the defect by Gsrgrst(3) on the HMI screen: When the working point is on the right side of the control line (safe area), the surge controller set point jumps according to the set slope to reach the current *H "within a fixed percentage of the value; when the operating point moves to the surge region faster than the 移动 point moving speed and exceeds the 徘徊 point, the anti-surge valve opens the recirculation, and the set point is rapidly reduced at the same rate. A new working point is established until the return valve is closed.

High election. 2.3 The control output is implemented using PID adaptive control. According to the requirements of the negative feedback control, the controller is reactive, and the given value SP is given by the HOVER control point setting. The set point 徘徊 function is cancelled due to the requirements of the production process shop, so the hovering margin kHOVER is set to 55. The given value SP is generally TOTALSAFETY, and the PV value is rMARGIN. The number AdptvTn1 is automatically given, and the parameters can be changed to change the ratio and differential. value.

The controller sets a separate proportional term for forcibly opening the anti-surge valve, independent of the conventional PI regulator output. When the operating point is operating on the left side of the surge control line rSUCLN, this proportional term begins to open the anti-surge valve in a certain setting area of ​​rMAR to the left of the surge control line. This system is set to .

7. Set the distance between the surge line and the anti-surge line to be 0%~100%. When the working point is 70% from the surge line, the anti-surge valve starts to open. When the working point reaches the surge line, the proportional output is 100%, to achieve fast opening and slowing down.

3 Conclusion Henan Coal Chemical Industry Group Zhongyuan Dahua Company's air compressor unit anti-surge adopts ICSTriplex control system, and realizes anti-surge control by means of multi-section folding line connection to form anti-surge line. Since the system was put into operation in 2008, the control function has achieved the expected goal and can meet the process and production needs.

(Henan Coal Chemical Industry Group Zhongyuan Dahua Company, Fuyang, Henan 457004, China)

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