A systematic overview
A Pharmaceutical Co., Ltd. oxycodone hydrochloride production process system consists of three reactors and two dryers, namely oxidation reactor (abbreviated as R1); hydrogenation reactor (abbreviated as R2); neutralization and crystallization kettle (referred to as R3). Double cone dryer (abbreviated as H1) and finished dryer (abbreviated as H2) are composed of five parts. The temperature-controlled agitation control pressure control for these five parts is the core of this program.
In the temperature control, according to the composition features and working conditions of this production process system, we adopt a two-stage PLC cascade control method to accurately control the system temperature. One of the primary PLCs (Siemens S7-315) is responsible for controlling the operation status of all five major equipments in the process system, the transmission, display and control of all data, and the output and printing of the report graphics. The two-stage PLC II (Siemens S7) -200) The controller of the heating and cooling equipment manufactured by a third-party manufacturer, which is responsible for the temperature control of the equipment, and cascades with the first-level PLC to control the internal temperature of the two dryers. , In order to achieve accurate temperature control, temperature control accuracy of ± 1 °C.
In the safety protection, the industrial control computer used in the field shall be subjected to positive pressure explosion-proof treatment to ensure that the safety protection level reaches zone FM1 zone 1, temperature group T4 (<=135 degrees), and an emergency stop button is set on each console. When the production is in a non-safety situation and cannot be resolved in a short time, pressing any one of the emergency stop buttons will stop the system and maximize the safety of people and equipment.
Second system control plan
2.1 Control of Production Process Flows for R1, R2, and R3
2.1.1 Control of stirring speed of R1, R2 and R3 The mixing system is composed of: PLC-inverter-stirring motor-speed sensor-PLC control loop, control range: 20-200 rpm, control deviation is 5 rpm /Minute.
The process requires R1, R2, and R3 to have different stirring speeds at different production times. Therefore, in order to ensure the consistency of production conditions and to reduce the arbitrariness of human operations, five are set in the speed control system under different working conditions. The speed control formula, and each formula can be modified according to specific conditions, set up and stored in the system in order, in the production of the operator only need to call the formula number can be completed in each production, stirring, Stop and intermediate speed change, so play a role in the assurance of product quality. The system's monitoring of the speed is through the speed sensor to upload the real stirring speed to the PLC, after the calculation of the theoretical speed and the actual speed comparison chart, to achieve the production process of the mixing speed of the precise control and complete records.
Comparison between theoretical control speed and actual control speed
2.1.2 Temperature Control of R1, R2 and R3 The precise control of temperature of R1, R2 and R3 is an important condition for ensuring product quality. The temperature control range in the boiler is -10°C--+80°C, and the deviation is controlled at ±1. °C, heating and cooling rate is 2 °C/min. The production process requires that the temperature control of R1, R2, R3 can be started after the start of stirring, otherwise it cannot be started. When the stirring stops, the temperature control also stops working.
The temperature control scheme of R1 and R2 is as follows. Taking R1 as an example: Because the temperature in the kettle is different at different time intervals, in order to make the temperature in the R1 tank to be accurately controlled, the cascade control method of S7315 and S7200 is used to implement. When R1 needs to be warmed up, the system program gives a gradient heating instruction to S7315 and S7200:
1 S7315 Closes the cooling water inlet solenoid valve of the plate heat exchanger.
2 S7315 passes the internal temperature sensor of TIC-101, TV101 three-way control valve, and combined with the current SV value and heating rate to form an external loop control method to control the heating water flow as a unit.
3 Use infinitely close SV PID control mode to control the hot water temperature in the heating unit to form an inner loop control unit to ensure that the hot water temperature is not over-regulated. (Because the water temperature entering the R1 heating water jacket will not overshoot, the contents of the R1 kettle will not overshoot)
When SV-PV is negative, R1 enters the cooling period, and the system program issues gradient cooling commands to S7315 and S7200:
1 The S7315 sends a gradient cooling command to the S7200 via DP communication and gives the current SV value (the cooling at this time is achieved by reducing the heating of the heating unit's incoming water). The S7200 collects the temperature data of the water temperature through the TIC-102 pipeline temperature sensor. When the temperature of the water temperature collected by the TIC-102 differs from the temperature of the incoming water by 5°C (this value can be adjusted according to operating conditions during actual operation), heating is completely stopped.
2 When the system program detects that the temperature of the water temperature collected by the TIC-102 is different from the incoming water temperature by 5°C, the S7315 opens the cooling inlet electromagnetic valve of the plate heat exchanger and starts the TV101 three-way control valve.
3 The S7315 passes the internal temperature sensor of the TIC-101, and the TV101 three-way control valve, combined with the current SV value and the cooling rate, forms an external-loop control method that controls the cooling water flow rate as the unit to achieve the cooling operation of the R1.
4 In the cooling control process, the S7315 uses infinitely-approached PID control to control the water flow of the TV101 three-way control regulator to achieve no overshoot control.
R2 is controlled in the same way as R1
R3 control process: TIC-301 is the kettle temperature sensor, TIC-302 is the jacket temperature sensor, FC is the heating and cooling equipment with flow controller. Its role is to make a logic condition, when the FC has flow, it can start the heating and cooling equipment. , If there is no flow, the device cannot start running. In the program design, E=SV-PV is set as such. When the E value is positive, the heating is performed. When the E value is negative, the cooling is performed. At the same time, the heating and cooling are interlocked and only one of them can be activated. At the same time, the following settings are made for TIC-302. When the heating conditions are fixed, the upper and lower limits are set to ±0.5 degrees. The inside temperature control loop TIC-101 is a main regulator temperature control unit consisting of S7-315. The kettle jacket circulating water temperature control loop TIC-302 is an auxiliary regulator temperature control unit composed of the S7-200 built-in heating and cooling equipment. In the heating process, R3 has the same control mode and control output as R1 and R2, except that the temperature control PID output is slightly different. How to use the cascade control loop to achieve precise control?
2.1.2.1 Principle of Cascade Control The following is a standard diagram. Cascade control system is one of the effective methods to improve the control quality. It has been widely used in process control and mainly consists of the following parts:
Main regulator - A regulator that operates in accordance with the deviation of the measured value of the main controlled parameter from the setpoint, the output of which acts as a reference for the secondary regulator.
Sub-regulator - A regulator that operates on the deviation of the measured value of the secondary controlled parameter from the output of the primary regulator, and the output controls the operation of the regulating valve.
2.1.2.2 Specific Scheme of Cascade Control The cascade control loop diagram of this scheme is as follows:
As can be seen from the above figure, the main regulator in this solution is composed of Siemens S7-315, while the sub-regulator is composed of Siemens S7-200.
The main regulator performs PID operation according to the temperature value in the reactor (ie, the set value) required in the process, and the measured actual temperature value (ie, process value) in the tank, and the output is used as the auxiliary regulator's given value, and the auxiliary adjustment. Based on the deviation between the output value of the primary regulator (ie, the secondary regulator given value) and the secondary regulator output circulating water temperature value (process value), the operation result controls the temperature of the circulating water and then injects the circulating water. The reactor was sandwiched to control the temperature in the reactor.
The main features of cascade control:
1 Improved the dynamic characteristics of the controlled process and improved the system control quality;
2 Increased system operating frequency;
3 Has strong anti-disturbance ability;
4 has a certain degree of self-adaptation.
Cascade control applications:
1 to overcome the large capacity lag of the controlled process;
2 Used to overcome the pure lag of the controlled process;
3 used to suppress severe and large amplitude disturbances;
4 Used to overcome the non-linearity of the controlled process.
2.1.2.2 Temperature control monitoring and data output The main PLC of the system, in addition to the cascade control of the system temperature, reads the control parameters and temperature parameters of the auxiliary heating and cooling equipment and calculates them during the heating and cooling process. Heating rate, cooling rate, and the actual temperature control curve are plotted together with the theoretical temperature control curve to realize the monitoring, control and complete recording of the reactor temperature in the production process.
The theoretical temperature control curve and the actual temperature control curve comparison diagram:
2.1.3 Control of the pressure of R1, R2, R3 Maintaining the reasonable pressure inside the tank is an important part of safety production. The pressure value collected by the high precision pressure transmitter (accuracy 0.25 ‰) is sent to the system. Two-stage safety alarm system is used in the program to ensure the safe production of the reactor (the value of the alarm value is customized according to the specific conditions of the field conditions).
1 When the reactor pressure exceeds the first level, the buzzer starts, reminding the operator that the reaction system has exceeded the pressure. Please pay attention to the operation. The yellow overpressure dialog box will appear on the man-machine interface until human intervention will solve the overpressure and the system will recover. normal.
2 When the reactor pressure exceeds the secondary pressure, the buzzer starts and a red overpressure dialog box appears on the man-machine interface. At the same time, the system automatically closes the feed valve and opens the reactor vent valve, stopping other operating steps until artificial The intervention will resolve the overpressure and the system will return to normal.
The pressure protection for R2 is the focus of system pressure protection.
2.2 Control of H1, H2 When the operator starts H1, H2 on the display unit:
1 S7315 controls the dryer speed by controlling the smart motor controller.
2 The control of temperature rise of H1 and H2 is the same as that of R1. The main system only records the temperature and pressure data in the system and prints them in the form of a table or graph to achieve accurate control and complete recording of temperature and pressure in the production process.
2.3 Control of vacuum system In the main system interface, two sets of vacuum pump start button and stop button are set, and parameters such as vacuum degree are not controlled.
The composition and characteristics of three control systems
3.1 Selection of Operation Console Because the production site of this case is a hazardous area in the presence of hydrogen in zone 1, the operation console must be an explosion-proof product, and the explosion-proof rating must be Ex(ia)IIC T4 and above. Through the understanding of the market, get the following kinds of information:
1: Proface touch screen has an explosion-proof function and passed the explosion-proof certification of Europe, but it does not seem to pass the certification in the country, and it is expensive.
2: The explosion-proof screen of P+F EXTEC in Germany can be used in Zone 1 and pass the domestic explosion-proof certification, but the price of nearly 200,000 seems to be much higher for this case.
3: The explosion-proof explosion-proof box will be specially treated after the touch screen package to achieve the purpose of explosion-proof, the price is moderate.
4: The positive pressure type explosion-proof operation console will be used for the industrial control computer; the monitor will be sealed with an explosion-proof keyboard and explosion-proof mouse to achieve the purpose of explosion protection and the price is moderate.
For the above four programs, combined with the actual situation of the case: the first and second programs are imported explosion-proof touch screen, the performance is not easy to use, and the price is very high. The cost of using this case seems to be too high. The explosion protection method of the third scheme works well, but due to the limited function of the touch screen, the screen is relatively small, and the complicated process interface cannot be effectively expressed, and the touch screen in the explosion-proof area is more expensive and the time to be used is short. Wearing gloves can not operate the touch screen. The touch screen will not be used for a long time, and it will become dirty and faulty. In addition, many nestings will be added during the program setting, which will affect the response speed of the touch screen. The fourth scheme uses a positive-pressure explosion-proof control console. The industrial computer is first safely packaged, and then the proprietary screen explosion-proof technology is used to encapsulate the IPC monitor with an explosion-proof keyboard and an explosion-proof mouse. The operating console has positive pressure gas from the protection system. When the pressure of the console is not safe, the console cannot be powered on. The product has a national explosion-proof certification and the explosion-proof grade reaches Ex(ia)IIC T4 or higher, achieving safety protection. . It is simple and intuitive in operation, improves the operating speed, and is more than capable of handling multiple interfaces. Compared with the third scheme, it is more cost-effective to use and more user-friendly in terms of design concept. Therefore, the program is preferred.
3.2 WINCC Configuration Software
WinCC stands for Windows Control Center (Windows Control Center) is the leader in industrial control software technology. At present, the operator monitoring system based on PC is developing rapidly. In the SIMATIC HMI products used for monitoring and control, WinCC has the powerful function of controlling the automation process. It is based on a personal computer and has a very high cost-effective SCADA level operation. monitoring system. The distinguishing feature of WinCC is that it is fully open. It is easy to set up man-machine interfaces in conjunction with standard and user programs to precisely meet actual production requirements. Therefore, as part of the Siemens TIA concept, WinCC works in harmony with automation systems belonging to the SIMATIC product family.
3.3 Features of the control system in this case
3.3.1 Good security Based on years of experience in industrial control for petrochemical companies, our system development is based primarily on safety. Security is a key to the success or failure of a system. In this system design, we made a full demonstration of the security of software and hardware. According to the requirements of users, the system is based on explosion protection. First of all, in the program set up a number of different measures to deal with security to maximize the use of program security to ensure the safety of production. Secondly, the two operation consoles are protected by positive pressure explosion protection, which achieves isolation from the on-site environment and reaches explosion-proof grades in the primary area. Thirdly, we installed an explosion-proof emergency stop button on each console. Once a non-safety situation occurs during operation, the entire system can be stopped by pressing the button to ensure maximum personal and equipment safety. Finally, in the control cabinet, different conventional electrical protection units such as fuses, overload protectors, and short-circuit protectors are respectively installed according to different electrical appliances.
3.3.2 Strong practicality In the design of the system, it emphasizes the human-oriented design concept, reduces the difficulty of use and operation, and enables the operator to use the simplest and most effective method in the human-machine interface and control mode. The method is not simple to control. For example, in the man-machine interface, the controlled equipment is represented in an animated form. The operating status of the heating and cooling equipment is represented by different colors. When the reactor is heated, the circulating water circuit is indicated in red; the circulating water is cooled. The loop is represented in blue, and there are many places in the system that use this design to make the operator at a glance.
3.3.3 High reliability Relies on years of system integration experience and methods, we will make S7315 play a strong communication capabilities, high control accuracy, and between software and software; between software and hardware; between hardware and hardware The connection, communication, and data exchange have reliable guarantees, making the system safe, fast, stable, and accurate. The remote monitoring is easy to understand at a glance, and it is easier for the supervisor to understand and monitor the production status. The powerful report function will record every detail in the production, so that you can find the problem in the traceability of product quality.
IV. Summary This is a communication between Ethernet and two host computers. A 315-2DP and multiple S7200s exchange data through PROFIBUS. The PID algorithm is mainly used to control the temperature through the heater and the regulating valve. The control accuracy is plus or minus 0.8 degrees. The control accuracy far exceeds the user's plus or minus two degrees of error.