Home >> Industry Knowledge >> Nitrogen Generator (Nitrogen System) in the application and operation of
Preface
Sha Steel Group 6.5 million t hot coil project supporting six sets of
21000m / h hydrogen-free argon air separation plants. Of the main equipment consists of Hangzhou Oxygen Health
Production, air compressor with the United States Copper Corporation 3MSG. 25/10 Type 3
Level compression compressor, and the supporting ABB, 9800kW motor, soft
Starter for the HTR. 10000S Tank High Pressure Thermal Resistor. Currently 5
Sets of air separation equipment has been put into production, the sixth set under construction. The first, the first
Air compressor control system uses two sets of original exclusive QUAD2000 Control
System device (MCU). But following the compressor controller and power supply question
Problem resulted in frequent stop, it was decided after the construction of four sets of air separation plants
Air compressor switch to DCS system (Yokogawa Centum CS3000)
Control, self-configuration Shagang design.
An open parking control scheme
The air compressor pressure, temperature, vibration, displacement and current, etc.
Direct access to analog DCS systems, DCS systems to control cabinet of the
The amount of signal switching system through the machine next to the PLC executive control. May actually
Control cabinet on-site parking is open or remote DCS automatic control system,
Open parking feature.
Control requirements of air compressor compressor air separation process requirements of the pressure
Power flow changes within the safe operation of the unit to achieve the start,
Loading, unloading and fault interlock stopping power and a series of automatic control
Able. Core content of the DCS system based on mechanical and electrical outlet pressure and electrical
Flow measurement by multiple control modules regulate entry guide vane valve
(IGV) and anti-surge venting valve (BOV, fast-pneumatic valves) between the two
The opening so that the two valves coordinated action, to ensure a stable outlet pressure, engineering
Conditions away from the surge zone (shown in Figure 1). V3002 venting valve (with
Solenoid valve, pneumatic amplifier) only as a complement BOV and air
Pre-cooling system, low pressure interlock shorting to use, does not participate in the core control.
IGV and the BOV are equipped with automatic (AUTO) and manual (MAN)
Two kinds of operating position in order to facilitate operation of human intervention. Manual operation
Each device by hand parade MIGV and MBOV.
2 air compressor system control theory, motor overload protection control, and anti-surge control.
Air compressor control principle shown in Figure 2, including the constant pressure control
Figure 1 Air Compressor Gas Path Control Chart
IGV an entry guide vane valve, air-open ,4-20mADC (O 1 100%) B0V an anti-surge valve venting, gas and closed

Type, 4 20mADC (O 100%)
IIc3200 a motor overload protection module PIC3009-, ~, mouth pressure control module nc3200 an anti-surge control

Module PIc3Ol1 a pressure control module cap
MB0V an anti-surge valve manual operator MIGV an entry guide vane HC3001-V3001 manual operator manual operator to send valve

PIC3002-V3002 venting valve control module
Figure 2 Schematic diagram of compressor control
KIY3001A-~ Jl upload speeds limited to the module KIY3001B-it ~ upload speeds limits the module KPY30o9 an anti-surge Qu

Line calculation module
KPY3011-~ edge cap calculation module AS1, AS2, As3 a low value selector FOuT a Distributor
2.1 Constant Pressure Control
The technological requirements of an air separation plant air compressor outlet pressure as much as possible
Constant (design value is 0.52MPa), which is the most basic of control to
Demand. Compressor outlet pressure from the constant voltage regulator controller PIC3009
(Set value SV practical requirements for the system pressure value), the control object is
IGV.
2.2 Motor Overload Control
When the air separation unit after the system pressure consistently lower than the compressor exit pressure
Power settings (such as equipment for heating purge gas load time), constant
Pressure controller will control the entry guide vanes continue to open up to full-large at this time
Drag the motor may overload. In order to prevent electrical overload, the introduction of electric
Machine overload controller IIC3200 (set value SV as the motor rated
Current) regulation I. Ye Kai degrees.
When the motor current exceeds rated value, the motor overload protection control
Device with constant pressure controller, for low-election limit the entrance of the guide vane opening,
However, to protect motor set. Of course, you can drive the process by adjusting the
IIC3200 controller's current settings to define the entrance of the opening of guide vane
Degree; to achieve variable load, low load conditions the purpose of the operation.
2.3 The anti-surge control (flow control)
Air compressor during operation there is always pressure and flow matching
Issues (specifically manifested as pressure and motor current), in particular, the emergence of
High pressure, low flow conditions likely to lead to compressor surge occurs
Vibration, severe damage to unit (caused by high pressure, low flow causes
There are improper operation or after the system failure caused by conditions such as gas plummeted
Status). Therefore, anti-surge control is very important aim is to make air compressor
Always work in a limited context, rather than surge into the area to do
Ensure the safe operation of unit. Anti-surge control is targeted at BOV.
When the compressor operating point near the surge zone ahead of schedule to open venting valve, increase
Large flow, so that the operating point away from the surge zone.
Air Compressor surge occurs when the pressure corresponds to a minimum for each current
Value, pressure and a linear relationship between the minimum current value constitute a surge curve
(Shown in Figure 3). Surge line in the field testing process required to get the measured
Out (usually measured by three-point surge, to select the most suitable of the two).
As the surge took place very quickly, so the surge line on the right to set a
Of anti-surge control curve, regulating venting valve to open ahead of schedule, with surge
Line distance of 5% to 8% of the flow of value (did not take current range, or else
Energy-loss large). This offset the smaller the venting valve is opened opportunities for more
Small, less energy loss, but also more easily affected by the valve into the breath
Zhen-line or less; the larger the venting valve is opened the greater the chance,
The greater the energy loss, but the better they can ensure the crew's security. The offset
The value of choice is the key to driving the process of testing need to explore.
Surge line equation: Y = aX + b
Where: Y axis corresponds to the pressure; x axis corresponds to current.
When
0
8

FIC3200 Value / A
Figure 3 anti-surge control curve
The two points will be measured by substituting into the equation surge, find a and b
Will be able to establish the value of the surge line. Anti-surge control curve of equation (C
To take 8%):
: (1 + C) (Y-b) / a
In the air compressor control principle diagram, KPY3009 and FIC3200
After the two controllers in series constitute the anti-surge function, KPY3009 controller
According to surge curve and the anti-surge control curve equation corresponding
Current, FIC3200 controller regulating venting valve opening, its settings
SV curve for the control of current, with the compressor outlet pressure changes in the variable
Of. Units operating point once it has reached the surge line, anti-surge valve will rapidly
Full-pressure relief (MBOV switch to "manual" position), when you want to boost
MBOV playing the "automatic" position.
2.4 Pressure cap control
For the constant pressure control, compressor guide vane adjustment of the entrance alone
Outlet pressure is also sufficient to ensure stability in the design value. When the pressures continue to
Increase and reach a certain value, the pressure cap controller came into play, playing
Open air valve, and the anti-surge controller, low-election, to protect its export pressure is not
Rise again. Pressure cap controller actually played a pre-open air valve
Effect.
2.5 Start interlock logic
Mechanical conditions in the relevant technology and all are met, according to "re -
Bit "key program initialization:
(1) All alarm interlock reset information.
(2) IGV in manual fully closed state, BOV is in manual Full
Open state.
(3) The load limit device is in manual "0" bit, unloading limit
Device is in manual "0" bit.
While before the electric air compressor control, instrument control and normal to ensure that DCS
NR: 1 (no alarm), TRIP: 0 (no chain) and the STOP CP
: 1 (no parking accident, compressor start the logical conditions are met) before
Can be a normal car. Images from the process called STOP CP-bit number, only the
When the STOP CP = 1, it can immediately drive, click "Start" button.
Start interlock program, the original with the vibration of interlocking vibrometer
Multiplier function, but in fact start the process of vibrometer often over-range
Caused by parking interlock. So start a program to design a "vibration joint
Lock "and" vibration reduction "switch to start the pre-vibration interlock switch solution
In addition to. Air compressor to start after the success of 10s, IGV opening is 10%, air
Press the low load operation. At this point click "vibration reduction" button, the vibration
Interlock information to initialize, and then click "Vibration interlocking" key, the vibration
Move, shift interlock program voted by the accident, of course, this process also can be designed to
Into a complete process control.
2.6 Load Control
Air compressor motor starts 50s before they can be loaded, time-time
1 that there is operational information flow chart pop-up prompts. Operator under
Choice of automatic or manual loading of load mode.
Auto-loading process: the operator selection mode automatically loaded
, The first constant pressure controller, PIC3009, and the manual operator MIGV
MBOV are playing the "automatic" position, and then click "Add" button to enter
Loader. Point loading rate qualifier KIY3001A beginning
Role (in the 35s within MIGV slowly opening up to 10% from 100%,
At the same time MBOV opening from 0 to 100%), and PIC3009,
IIC3200 controller, low-entry guide vane adjustment after the election, slowly open, and the
FIC3200, PIC3011 controller, adjustable low-post-election anti-surge valve slowly
Closed (see Figure 2). At this point the operator in the anti-surge curve of flow
Map in real time to monitor the compressor operating point, operating point control
Line up the right side of right.
Manual loading process: Select the operator to manually load the way
After the entry guide vane manual operator (MIGV) and anti-surge valve manual operator
(MBOV) were placed in "manual" position, slowly open the entrance
Slowly close the guide vanes at the same time anti-surge valve, two valves coordinate operations, Paul
Permit a steady increase in outlet pressure unit, away from the surge zone. Load end
Both hands are placed after the parade "automatic" position.
2.7 Uninstall Control
Press the flow chart on the screen to uninstall the "Uninstall" button: ①
MBOV "automatic" turn "manual" position, BOV valve position from the current
Value suddenly dropped to 0, fast fully open; ② unloading rate qualifier
(KIY3001B) came into play at the same time MIGV turn "Manual"
Location, limited to within the IGV valve located in the 10s down to 10% from the current value,
A small air compressor load operation.
For this time loaded, hands-speaking device to turn "automatic" position,
Then click "Add" button, air compressor loaded automatically. For more information stop by
"Stop" button.
2.8 Parking Interlocking Logic
When any unit is an important process parameters (eg vibration
Move, bearing temperature, etc.) high alarm or crew failure, the emergency
Parking, to ensure the crew's security. Parking logic is electric parking,
BOV fast full open, IGV off to 10%.
Parking plan process: the operator press "Stop" button, unit
Uninstall, slow wicket off the entrance to 10%, anti-surge valve fast full
Open, compressor unloading to a small load, and then stopping the main motor, stopping off
Cheng concluded.
Parking is divided into two kinds of interlocking failures: ① As the park interlock
Conditions are met (TRIP = 1) caused by the parking process, stop compression
Machine, anti-surge valve fully open fast, entrance guide vane slowly off to 10%;
② In the control room emergency button is pressed an emergency button sets, electric control directly to stop
Car (not through the electric control PLC), anti-surge valve fully open quickly, import
Slow wicket off to 10%.
Failure to start after stopping treatment, you must manually reset by the beginning of
The beginning of.
2.9 auxiliary pump interlock logic
Motor does not start or hydraulic (PIAS3104) is less than 110kPa
When the auxiliary pump start-up; When the motor starts after 50s, and the hydraulic
(PIAS3104) is greater than 190kPa when the auxiliary pump shutdown.
2.10 fuel tank heater interlock
When the auxiliary pump running and the oil temperature (TIAS3105) Small
At 30 ℃, the fuel tank heater put into operation; oil temperature
(TIAS3105) is greater than 40 ~ C or the air compressor starts, the fuel tank plus
Heat shutdown.
3 Configuration Design
Centum CS3000 distributed control system has powerful data
Acquisition, process control, logic control and sequence control functions, to adopt
With the Windows 2000 operating system, user-friendly, design control
System programs as far as possible in order to facilitate participation of the operator to monitor and operate.
3.1 Design flow chart
Flowchart design 5 screen window, the graph design equipment transport
Turn, outage of the pale (running time-varying red, outage time-varying green),
With information on alarm operator.
(1) air compressor gas path control charts: there are involved in controlling figure
IGV, BOV two PID controller, the main valve, while in office under No.
PID controller's output value is labeled MV, and will "start, Canada
Uploading, unloading, parking, reset, vibration reduction, vibration chain ", etc.
Button placed on the map.
(2) air compressor machinery monitoring plan: This plan mainly vibration, bit
Shift, bearing temperature-bit number, and the hydraulic system.
(3) The air compressor start condition Figure: Figure will be all the air compressor Kai
Terms and conditions set out in tabular form to facilitate the operator at any time to view,
No. mere mention you design features information on alarm conditions are met.
(4) Accident Parking records Figure: Figure will stop all the accidents caused by
Vehicle parameters and the high limit set out in tabular form, there is discoloration Gong
Able. Stop when the accident record first stop chain incident, and red
Color punctuation mark. Reset and then disappeared.
(5) anti-surge control curves: the operator in the graph
See air compressor operating point location, timely adjustment of the controller's
Setting, maintaining a stable condition.
3.2 Configuration design should pay attention to the problem
Historical trends real-time trends in window design points, historical trends in long -
Two forms.
(1), vibration, displacement, pressure and current PID controller
PV, MV value, etc. measuring point using 1 s scan cycle, as a real-time trend
See the startup process is mainly used in the vibration value of the maximum value and change
Trend.
Bearing temperature measurement points using 1min scan cycle, as long
Time to look at the use of.
(2) Each bit numbers by setting the operating level, the operation confirmed that anti -
Only misuse. In which the pressure controller, manual operator and buttons and other settings
The "squad level" read-write; related to cascade functions, all
Digital Output DO-point is set to "engineer grade" only non-readable
写.
(3) program configurations designed using Yokogawa's unique
Sequential control and logic diagram form the method of combining to reduce the preparation of difficulty, with the
To read an intuitive and easy to modify.
4 steps
4.1 to drive the process of
When the air compressor through the original performance test drive, got the pressure
Conditions of the surge force points, calculated anti-surge control curve, and the
Measuring point of each instrument checked to confirm the value of the alarm chain, start, Canada
Upload, unloading and parking procedures such as tests have confirmed the incident, after an accurate on a
Preparation of fully automated driving conditions, air compressor can be put into normal production. When
Ran air compressor to drive car should be guided by the following sequence:
(1) car ready: First-pass cooling water, instrument air source, check
Entry guide vane valve, anti-surge valve venting the accuracy of movements, on-site instrument
Table, instrumentation and electrical control systems to ensure normal, mechanical equipment, normal;
Machine next to the control cabinet on the full range of choice will switch placed in the "automatic"
Position to carry out instrumentation to run automatically, the soft starter connected to the main circuit
On the open exhaust fan. At this time assisted by the pump and fuel tank heaters, etc.
DCS system. Unified automatic control, and timely view the oil pressure, oil temperature for the
Degrees.
(2) open air compressor before the click "Reset" button is initialized, "vibration
Dynamic interlocking "switch placed in" OFF "position.
(3) Click "Start" button, the air compressor is operating normally, the press
"Vibration Reset" button, and then the "vibration Interlocking" placed "ON" .
(4) The motor starts 50s after the load of information prompted, the pressure
Controller PIC3009, manual operator MIGV, MBOV turn "automatically"
Location, click "Load" button.
4.2 Parking process
(1) Normal Parking: Press "Stop" button.
(2) Accident Parking: fully automatic process, DCS control system power
Aircraft parking, unloading step sequence.
(3) Emergency stop: Taiwan press the button in the control room emergency button,
Electrical direct parking, unloading step sequence.
5 Conclusion
Shagang air separation plant air compressor switch to Centum CS3000 systems
Automatic control, the normal operation of such control procedures can be extended to an empty
Booster separation plant in the turbine expander, turbine compressor and turbine nitrogen oxygen
Press the automatic control.