Abstract: This paper introduces two days steel 28000m3 / h Air Separation Plant Automation Control System network structure and work processes, introduction of the
Circulating water systems such as automatic control, highlighting the compressor and expander system control program and obtain specific results.
Key words: large-scale air separation equipment; automatic control; DCS; compressor; Expander
Tianjin Iron & Steel Co., Ltd. Two 28000m3 / h air separation equipment,
Air separation plant by the Chinese general contracting company, Hangzhou oxygen production. This project has been
Put into operation in September 2005, all performance indicators to normal.
Two 28000m3 / h air separation plant automatic control using
Wang Hexi Instrument Corporation CS3000 system. Automation Design and Control
A wide range, including the circulating water system, instrument air compressor system, the original
Material air filtration system, air compressor systems, air pre-cooling systems, cold
Frozen unit, molecular sieve purification system, pressure machine system, expander system
Unification, distillation systems, nitrogen compressor systems, storage tanks and pressure vaporization of the Department of
Unification, regulator station system and the pressurized liquid vaporization Filling system. Whole
Air separation plant entirely by a DCS control system, fully realized in the
Centralized control of the central control room, especially in the several imported compressor
Of control, achieved good results. All the high-voltage motor
(10000 VAC) have achieved a central control room to start. CS3000
System can fully meet the design requirements for control system, DCS system, transportation
Line stable and reliable.
1 DCS system configuration and network architecture
DCS system architecture shown in Figure 1.
111 DCS system configuration
Engineering Station (CS30002EWS) 1 units; Operator Station
(CS30002HIS) 9 units, the operator keyboard (AIP82722) 9; the
Control Bus Interface Card (VF701) 10; the Dual Process Control
Station (AFS40D2H4223 / 72D82 / CH) 2 sets of double process of
Controller (AFF50D2H41201) 1 units; switch 2 sets; the
Kinds of I / O card and the terminal pieces of plate; package.
112 DCS Systems Network Architecture
CS3000 system has three hierarchical network structure, respectively, so that
Different networks effectively improve the efficiency of communication and reduce
Traffic load. Can provide a standard GSM network system clock system,
Ensure that the various stations on the network bus clock synchronization. CS3000 System-in -
Into the main operating station HIS, engineer station and control station EWS
FCS.
(1) The operating station HIS: used to run operations monitoring and a history of several
According to records, to report up-bit computer display and to provide data
Services. Operator Station using Windows XP as the operating system
Universal PC.
(2) The engineer station EWS: used in the design configuration and simulation of transfer
Test. Engineering Station using Windows Server 2003 operating system as a
Integration of the universal PC.
(3) controllers FCS: for process I / O signal processing, finished
Into the analog acquisition, to achieve continuous control, sequence control and batch control
System, real-time control functions.
System network, including Ethernet, V-NET, and RIO bus.
Ethernet is the operating station, engineers, computer stations and between the upper
Information data transmission channel, in line with IEEE 80213 standard, is
System, open network, communication rate of 10Mb / s. V-NET by
In surveillance and information exchange to operate a dual real-time control network
Network, means of communication using Token-Passing the token bus, Fu
All IEEE 80214 standard, communication speed 10Mb / s, the largest communications
Distance 20km. RIO bus is a CPU with a remote controller I / O section
Point data transfer between the double real-time communication bus, communication
Rate of 2Mb / s, the length of the bus through adapters and fiber optic
Be extended.
Figure 1 DCS system diagram
2 circulating water system control
Two 28000m3 / h Air Separation Plant to share a set of recycling water
Integration. This system is composed by three water pumps, water pumps from the 10kV high-voltage
Machine-driven. The normal mode of operation for the dual-use a prepared, that is, under normal circumstances,
(Two sets of air separation plant will be operational) two pumps running, as the two sets of
An air separation plant to provide cooling water; when the circulating water mains pressure less than
013MPa, by the DCS system to automatically start the standby pump in order to maintain
Permit circulating water supply system is stable. Sets of air separation plant in a single run through
Came from a ring of water consumption can also be prepared with a one, that is normal, a transport
OK, another two in a standby.
After listening to the user's specific requirements, and understand their operation
Habits after the completion of the pump room configuration control procedures, and through real -
Inter-test, to achieve the desired backup control requirements.
(1) The circulating water system to start, any one pump can be in the
The control room to manually start the (local knob in the "automatic" position).
(2) manually start a water pump, the pressure, if normal, then the
Can not manually start the second pump (by the logic control), to prevent
Only the overpressure. Only start a water pump, if the pressure is still low,
In order to manually start the second pump.
(3) spare pump to automatically start (in-place knob in the "self -
Action "position, DCS system control mode in the" focus on self -
Action "). Electric heat must be prepared in order to spare pump to keep Kai
Action. Operators should pay attention to monitor the standby pump "electrical permit Kai
Moving "state.
(4) In the standby mode the choice of more flexible, you can use a
Preparation of equipment or a dual-purpose one, the interface simple and friendly, easier to use.
In addition, the user's request to increase the pump motor current
Instructions for the operators to directly control the load on the pump.
3 compressors and expander system control
Automatic control of compressor control design in the whole instrument has a
An extremely important position, because all of the units have been removed in situ
PLC controller, which requires the control functions of the PLC transplanted into
DCS system control. PLC controller unit is the result of the program
Machine manufacturers the results of repeated testing and modification, suppliers will not process
Preface to the author as a reference, but to present its control requirements, requiring
DCS system configuration to be achieved; and each control unit to
Order to vary, some units almost demanding control requirements. Control Part
Cheng process requires detailed thinking, would not allow the slightest deviation.
Compressor units from the DCS system implementation of all control functions,
On the one hand, saving the user a lot of PLC acquisition costs; another
Regard, the compressor control is no longer a "black box" that allows users
A clear understanding of the machine control theory, and can be in the control room side
Will be to monitor and control units.
MAN-TURBO company in Switzerland, the debugging process air compressor
, The foreign staff in the commissioning crew finished the surge test, refused to
Driving again. The reason is DCS system, anti-surge regulator Scan
Speed and pressure transmitter reacts too slowly, can not meet the minimum time of
100ms requirements. However, this writer With the compressor with the DCS system control
Experience, that control will not be a problem. With foreign personnel into the
OK-depth technical exchanges, and finally adjusting the corresponding PID parameters
Numbers, the automatic air compressor to achieve a smooth launch and safety of anti-asthma
Vibration control, achieved a unit of security control and energy-efficient win-win.
Booster ATLAS, Germany's two-stage compressor,
In the control requirements were very stringent. In the full study of its control to be
Seeking and taking into account the specific needs of an air separation process after the DCS configuration
Its control requirements will be fully achieved. And the air compressor, like all the rest have
The automatic control. Operators in operation is the right number of buttons
Operation, greatly reduces the intensity of the operation, thereby reducing the error occurred
Operation possible. In particular, the paragraphs in the entry guide vanes and the self-return valve
Dynamic control of inputs, after careful consideration and repeated virtual testing
Test, the program designed to achieve good results, achieved a level Booster
Automatic startup stability and safety of anti-surge control.
Ingersoll-Rand Nitrogen press of Italy's five compressors,
Because the previous nitrogen compressor controls are local PLC control, instead
DCS control system, its control requirements are not clear, DCS configuration work
Be met with great difficulties. The on-site staff with the final commissioning,
Has also achieved good control effect.
Through the compressor control system design and debugging, to be
Some experience: ① in the anti-surge control, to use the fast transmission
Device, rather than the general transmitter; ② compressor as far as possible with self -
Has been a surge detector, and if not, must be configured DCS
Must take into account the rapid surge system scan.
311 automatic air compressor
Air compressor can be in situ control cabinet or the control room to start. If
In the control room started to file in-place start converting rotary knob to the "self -
Action "in the receipt of electronically controlled to allow instrument control signal to start air compressor,
By the operator to start the air compressor flow chart using "Start air compressor"
Button to start the air compressor. When the motor allowed to load the signal arrives,
Air compressor guide vane from the entrance of Kai Tak vehicle location "0" jump to the minimum
Opening "10%." If the 20s, the entrance guide Ye Kai-degree feedback
Is also less than 8%, indicating the entrance did not open the guide vane opening to the light-load, air
Press the interlock parking. In the guide vane transition to 10%, and from the Climbing
Ye Kai-degree slope device will continue to open big lead, while shorting solenoid valve was
Electricity, will be left empty by downhill device valve from 100% to begin closing. When the exhaust
The pressure reaches the set value, the constant pressure controller automatically adjust input, into the
I guide vanes in a first automatic control state; when the entrance of differential value is less than
Anti-surge control line, anti-surge controller, auto-input cascade, release
Air valve in the automatic control state, air compressor automatically loaded. When
Unit load operation in a small period of time, preheat the process is completed, gymnastics
Members can be modified to set the value of compressor discharge pressure, so that transport air compressor
Bank rated pressure. At this point, air compressor to start is completed, the operator can be
To open a valve V1100 sent aspirated into the air precooling system. Note
Is sending relief valve must be opened, closed off to be slow. When the Air
Machine control inputs automatically, the operator will be prohibited entry guide vane Constant
Pressure controller and anti-surge controller into manual adjustment.
In addition, set up anti-overpressure control, adjustment of output and
Anti-surge controller's output to do overlay operations, acting on the venting valve,
To achieve security controls. Also set the motor over-current protection, adjustment of the input
Out and constant pressure controller's output to do subtraction, in the constant voltage control
Based on the degree of reduction of lead Ye Kai and reduce compressor load. If the unit
Protection during the operation flow of traffic is less than the value of venting valve in the anti-surge
Regulator under the action of fast open, increase traffic, so that compressor from
Surge condition.
Encounter one of the following situations, the air compressor will immediately light-load
① high exhaust pressure; ② air compressor flow rate is less than the surge flow, machine
Group-surge; ③ operator forced air compressor through an emergency button, light load;
④ air precooling system failure.
Compressor light-load actions: the entrance guide vane limit to 10%, put
Air valve fully open.
After eliminating the malfunction, the operator through the compressor gas path diagram
"Restore Load" button to automatically restore load the compressor, the process
And start the same time.
In the auxiliary control, should pay special attention to auxiliary pump starts automatically
Control, in the days of steel test the process, there have been, after stopping air compressor
Auxiliary pump will not start a dangerous situation. It was determined: on-site control cabinet
On the switch in the "place" position. Must be noted: In the normal
Drive, this switch must be in the "automatic" position. In a
After design, should the location information for this switch back to the
DCS system in order to harmonize monitoring.
In addition, tank heaters logic, only when the oil system
In a cycle of state, in order to start the electric heater, or oil
Due to local overheating and deterioration. Therefore, control logic, by adding
Explorer of the lubricating oil pressure control signals. If there is no oil Explorer
Pressure, then not allowed to start the heater, regardless of the heater control is
In the "place" or "automatic" position.
Booster 312 Automatic Control
Booster start the same manner and air compressor. Motor to allow the addition
Containing the signal comes, Booster will be the entry guide vane position of Kai cart
"0" open to the smallest opening "25%" (in the 25s in).
Booster section of the load to be step-wise, we must first load the Ⅰ
Paragraph of Section Ⅰ exhaust pressure to meet the design value, in order to load Ⅱ
Segment. When the operator through the operation of the button load instruction issuing section Ⅰ,
By the downhill device will return valve from 100% to begin closing. When the exhaust pressure
Reaches the set value, Ⅰ segment return valve pressure controller input auto -
Section, return valve will be in automatic control state. Then the operator can
Open the delivery valve V401, slowly aspirated to the expander needs to pay attention
Is that, V401 to be slow to open, close when you need to ease off.
Section Ⅱ to load when the load instruction issued by the operator, the next
Slope segment Ⅱ return valve device will be from 100% to begin closing. When the exhaust pressure
Up to set the value of 518MPa, the controller inputs automatically adjust,
Automatic return valve will be in the state. Then the operator be able to board
Slowly aspirated fin heat exchangers need to be aware that the delivery valve to be
Slow opening and closing must ease off.
After the compressor load, with the air separation Gas Consumption increases
Canada, two return valve in the pressure controller automatically under the effect of gradually
. When Ⅰ Duan return valve opening is less than 1%, Ⅰ segment return valve
Controller settings automatically increase the value of 011MPa, as a super-pressure control
Uses. When Ⅱ segment return valve opening is less than 1%, Ⅱ segment reflux
Valve controller settings automatically increase 0108MPa, as a super-Voltage Controlled
The system uses. At the same time, the program will automatically import the constant pressure guide vane
Controller PIC1636 (set value 211MPa), PIC1637 (set
Value of 519MPa) into auto-regulation, by continuing to adjust the paragraphs into the
I guide vanes to increase the compressor load. In automatic mode, two
Entry guide vanes of the minimum constant voltage regulator output 25 percent, prevent fat
Health surge.
If the craft Gas Consumption decrease is a direct response to the pressure rise
High, then the entrance guide vane will automatically close down small to stabilize the pressure. If workers
To changing market conditions and pressure continue to rise, more than return valve over-pressure regulator
Set value, the return valve will also be fully closed automatically.
Valve opening is greater than 5%, imported guide vane will automatically be placed in "Manual" position
Set to prevent the entrance of guide vanes and returned due to valve adjustment and built at the same time
Into the regulation of instability; same time, the return valve regulator settings will be restored
Section Ⅰ complex to 211MPa, Ⅱ section 519MPa, to control exhaust pressure
Under normal working conditions. Then the operator can manually close down small guide vanes, to section
Energy efficient.
Booster's two anti-surge control is scheduled to flow control, namely:
No matter how many opening wicket, if the flow rate is less than set value (through the
Surge test) if, it will act on the return valve adder, increase
Return valve opening, increasing the flow, to prevent the surge occurred.
In addition, Section Ⅰ set inlet pressure compensation controller
PIC1631, if the suction pressure below the set value 0145MPa, the control
System devices will act on the return valve adder section Ⅰ, Ⅰ Duan return valve will be
Increase the open. Section Ⅱ set inlet pressure compensation controller
PIC1657, if the suction pressure of less than the segment Ⅱ set value 210MPa,
The controller will be acting on the return valve adder section Ⅱ, Ⅱ segment reflux
Valve opening will be increased. Set the motor over-current protection, if the motor
A, B, C phase current value is higher than the high-selected settings, motor over-current
Protector will be acting on the entrance segment Ⅰ vane subtracter, Ⅰ segment entry
Guide vanes will close down small, to reduce the compressor load.
Encounter one of the following situations, Booster Ⅱ paragraphs light load:
Section Ⅰ ① Booster surge; ② Booster Ⅰ segment ultra-high exhaust pressure;
③ Booster Section Ⅱ surge; ④ Booster Section Ⅱ exhaust pressure high;
⑤ operator through the flowchart on the compulsory light-load segment Ⅱ buttons light load.
Booster Section Ⅱ light-load actions: the entrance guide vane limit to 25%,
Return valve fully open.
Encounter one of the following situations, Booster Ⅰ paragraphs light load:
Section Ⅰ ① Booster surge; ② Booster Ⅰ segment ultra-high exhaust pressure;
③ operator through push-button panel on the HS1603 button light load.
Booster Section Ⅰ light-load actions: the entrance guide vane limit to 25%,
Return valve fully open, namely: Ⅰ segment light load, Ⅱ the same time as light load; Ⅱ Duan
Light-load, Ⅰ segment without light load.
After eliminating the malfunction, the operator can Booster air route map
"Restore Load" button in order to automatically restore load booster machines
Segment of Ⅰ and Ⅱ section, process and start the same.
313 on the surge in situ detection of PLC
In order to better protect the machine, using a supercharged unit comes with
Surge in situ detection of PLC, a total of two PLC, respectively, and Section Ⅰ
Section Ⅱ detection surge protection. PLC includes the following cards Parts: Power Mode
Blocks, CPU processor module, the configuration communication interface cards, analog input
Into the cards, digital input cards and digital output cards. 2 PLC
Were installed in the Booster of the two local cable boxes.
When the compressor to allow loaded, by the DCS system, issued a directive,
PLC 2 activation to work. If a certain period of time (can be
Configuration) detected N times (configurable) exceeds a set value (can be group
State) pressure fluctuations, that is, to determine the "unit surge", PLC's
Digital output card corresponding channel alarm output from the DCS to achieve joint
Lock, emergency open the return valve, while the entrance guide vane limit to achieve machine
Group protection. Surge protection, if you want to reload, you need to
"Booster to start" on the flow chart of the reset button with the PLC to carry out
Fault reset.
If a certain period of time (configurable), PLC to detect M
Times (configurable) surge, surge protection that is judged as failure, PLC
The digital output card corresponding channel output interlock, emergency power outages machine.
According to ATLAS surge detection provided by the schematic diagram, in the DCS
Achieved its surge in detection capability, and the testing process has been
Validation of the compressor control technology is a big step forward.
In its control principle, because the need to preserve the current scan cycle
Previous three cycles of pressure data in order to achieve dynamic slope of the pressure surge
Calculation, which need to use the stack data structure. However, DCS Chang
Regulatory control block did not provide a stack data structure, the final adoption of the
BDSET21L type of point assignment cycle of implementation, simple and convenient.
314 Expansion Control
In the car during debugging, for expansion of the machine next to the junction box machine has done a
Larger changes. Re-adjusted positive light box, retaining
Two lights: "Allow Launch" and "running." When the DCS
Determine expander ready, "allow to start" light bright,
At this time in the DCS or a place to start expander cabinets. When the expander
Emergency shut-off valve is open, "Running" indicator light.
Expander booster also realized end of the automatic loading feature, when the swelling
Inflation machine starts to load, when completed, the operator clicks on the flow chart
"Auto Load" button, downhill device will start from 100% return valve
Closed, when the discharge pressure reaches the set value, the constant pressure controller by the way
Sequence into automatic adjustment.
If the expander speed, automatically adjusted by the SICAS430
Section, with the anti-surge regulator's output to do FIC408 addition operation, the
Open the return valve to control the speed.
Pressurized side of the anti-surge regulator FIC408 set value is pass
Surge test had come. Regulator of the PV value is through the operation were
Out of values, rather than the differential pressure value or values. It is calculated as follows:
FIC4081 PV = pressurized-side exhaust pressure - inlet pressure booster side
Pressure booster side entrance pix
If the PV <SP (through the surge test point of surge parameters derived from
Number), said pressurized side near the surge, the role of regulator in the return valve
Adder, open big return valve, played the role of anti-surge. If workers
Conditions of rapid change, PV is less than surge protection points, will be full-back
Valve, to protect the machine.
In the lubricating oil pressure normal, sealed air pressure normal conditions
, Through the "expander defrost" button, you can open the expander
Emergency shut-off valve to begin defrosting. If the defrosting process, there
The following failure, will automatically interlock protection, shut down for emergency shut-off valve: Run
Lower than normal oil pressure; seal gas pressure is low; speed of more than
500rPmin; shut-off valve after the valve was no electricity 2s action.
If you want to stop defrosting process, the need to "defrost stop" by
Button placed in the "stop" position. Note: In the defrosting process,
Place emergency stop buttons and stop button in the control room to bear does not work, it is
Are only used in the normal course of operation of the emergency stop.
315 N Press Automation
Nitrogen compressor and air compressor start the same way. Motor to allow the addition
Containing the signal arrives, the entrance of nitrogen compressor valve position by Kai cart
"8%" jump to the smallest opening "15%." Climbing devices will be imported butterflies
Open the valve opening to continue the same time, the venting valve device from the downhill from the
100% to begin closing. When the exhaust pressure reaches the set value, the entrance
Put constant pressure controller automatically adjust valve, butterfly valve will be in from the entrance
Dynamic control state; when the exhaust pressure is less than anti-surge control line, put
Air valve control inputs automatically adjust venting valve will be in the automatic control
. Then the operator can change the pressure settings, so that nitrogen compressor
Running at rated pressure. At this point, nitrogen press to start is completed, the operator
Valve can be opened to send to the nitrogen pipe network aspirated. To note that, to send
Relief valve must be opened, closed off to be slow. When the nitrogen compressor control
Input automatically, the operator will be prohibited entry guide vanes of the constant pressure controller
And the venting valve controller into manual adjustment.
In addition, set the current anti-surge controller, if the nitrogen pressure
Machines A, B, C phase current value is less than the high-selected settings, regulator
Output will act on the venting valve adder, venting valve will open. Also set
Purchase of motor over-current protection, if the motor current is higher than the set value, adjusting
Section acting on the subtracter output, import butterfly valve will close down small, lower pressure
Shrinking machine load. If the nitrogen compressor flow rate greater than the set value 20000m3 / h,
The role of regulator in the subtracter output will be a small entrance off valve to prevent the
Affect the distillation column operating conditions.
Encounter one of the following situations, nitrogen press to light-load: ① row
High gas pressure; ② nitrogen compressor surge; ③ operator through the
HS1503 forced nitrogen compressor light load.
Nitrogen compressor light-load actions: the entrance butterfly limit to 15%; release
Air valve fully open.
After eliminating the malfunction, the operator presses nitrogen gas through the road map on
"Restore Load" button to automatically restore load the nitrogen compressor, the process
And start the same time.
Days of steel nitrogen compressor control problems and possible solutions:
(1) steel-making process with the fluctuations in the amount of nitrogen gas: the amount of nitrogen in the
1min period from 0 to 20000m3 / h or from 20000m3 / h change
Delivery to 0. As the nitrogen gas spherical tank is too small, and only 400m3, has caused
The nitrogen compressor large swings in working condition, imported butterfly valve and venting valve frequent
Action, nitrogen easily offset press. Finally by repeatedly adjust PID parameters
It will be a few conditions to stabilize the control of nitrogen compressor adapted to the Gas Consumption
Fluctuations.
(2) The entrance of butterfly valve control: butterfly valve opening degree of change on the nitrogen pressure
Great impact on the operation of machines, so do butterfly valve opening limits
Maximum opening to 55%, the smallest closed to 30%.
(3) Engineering design defect: flow plate is not installed
Nitrogen export in the press, but installed in the aspirated pipe, can not be
Anti-surge for the unit to use, so with the current anti-surge.
(4) The current lack of anti-surge: Because electric current is from the electrical
Control of the conversion from CT, there is a large error and lag right to be
Demand-sensitive compressor anti-surge control is not suitable.
Four other systems, automatic control
(1) Air pre-cooling system: air-cooling tower at the bottom of the valve V1166
Solenoid valve controlled by the switch valve, according to Hang oxygen requirements, its role is to
High level when the air cooling tower, by the control logic for emergency open, to prevent
Zeolite water. Hangyang designed canceled due to the manual trap,
In the testing process, the operator requested that this not only by the logic control valves,
Can also manually control the switches to be used for parking after the air-cooling tower
Hydrophobic. After the modified control logic to meet the technology needs.
(2) The design of the instrument air compressor starts automatically. Grouped under the sky
Reserved parking, meter gas mains pressure below the set value, DCS automatically
Start Instrument air compressor, tank and regulator to ensure that the instrument station system
Table gas supply.
(3) modification of circulating liquid argon after the return pump for liquid level control valve control
System to replace the pressure control.
(4), taking into account security issues, the liquid tank system, Filling
Pump, pump the Central control room filled tankers into place to start to start.