Development of Control and Monitoring System of UCG by Promotic
Karol KOSTÚR, Ján KAČUR Institute of Control and Informatization of Production Processes, Faculty BERG, Technical University of Košice, Košice, Slovak Republic e-mail:
[email protected]
Abstract—Monitoring and late control system for Underground Coal Gasification (UCG) in laboratory condition were developed. Architecture server & client were used. Hardware configuration consists from PC an PLC. Software package was created on base Automation Studio and Promotic. Data processing of measured variables including visualization (monitoring system) is realized in Promotic and DDC by a help PLC. The connection between Control and Monitoring system is realized with interfaces OPC and PVI. This solution appears as stable and one providing quick exchange of data between PLC and PC Keywords-monitoring system; control system; UCG; OPC; PVI.
I.
INTRODUCTION
Underground coal gasification is a potential coal utilisation technology, receiving renewed interest around the world. Coal supplies are 909 billions t in world. 85 % coal is impossible to exploit by classical mining techniques. But today in Europe a coal have to be extracted from a bigger depth. It increases costs to coal extraction. The transformation of coal in underground into synthetic gas appears as one technology which has smaller specific energy consumption in comparing with traditional mining methods. The mainly advantage is fact that UCG can use otherwise inaccessible coals, can produce syngas for power and for fuels (i.e., liquid fuels, synthetical natural gas, or hydrogen), various chemical products and has attractive economics. Based on published and new cost estimates, engineering analyses and new commercial pilots it appears that UCG can produce syngas for ½ to ¼ of the cost compared to surfaces gasifiers [1]. In the process of underground coal gasification (UCG), the gas movement not only influences the concentration distribution and movement of fluid in the burning zone directly, but also restricts the diffusion of the gasification agent in the whole gasifier [2]. Therefore, it eventually determines the rate of chemical reaction between gas and solid, and the process of burning and gasification. Evidently, the study of moving patterns of fluid in the gasifier should precede the study of the process of chemical reaction, the moving patterns of agents, and the distribution regularity of temperature fields near the flame working face. Due to the complexity of the process of
underground coal gasification, the establishment and solution of its mathematical models are relatively difficult. Nevertheless, at one time, a number of experiments and theoretical studies concerning the features of fluid movement in the process of underground coal gasification are conducted in many countries such as the Former Soviet Union and USA. Therefore UCG was studied by experimental way on Technical University Kosice. The gasifier in the experiment is an oblong steel box (5180 x 2160 x 550 mm), as shown in Fig. 1. The net weight of coal injected in the gasifier is approximately 1184 kg, with the length of the coal layer of 4000 mm, the wide of coal layer of 500 mm, and thickness of 350 mm. The ratio of the length of hypotenuse to vertical height is 10:1. Therefore, the coal layer belongs to a slight slope. A number of blasts are buried in the coal layer. Temperature-controlled blasting loosens the coal layer, which is conducive to burning [3]. Along the direction of the slope, a checkered steel pipeline is buried beneath two sides of the coal layer, respectively, for air injection and gas production. The direction of air supply and exhaust is regulated by the reversing valve. The gasifier contents sounds system for sampling gas along length and one enables change input variables. The whole gasifier consists of heat insulation fireproof layer, heat preservation layer, and insulator [5].
Figure 1. Cut of experimental gasifier.
The research of UCG requires the creating convenience process control because there are more measured variables and the duration one experiment is very long (six days on average). II.
ARCHITECTURE OF PROCESS CONTROL SYSTEM
UCG process is studied very intensively from standpoint of geological conditions, chemical reactions oxidation agent with coal but there has not been information about UCG
control system. Described the proposal of UCG process control has been based on its required functions: • real time data processing, • secure saving measured data, • stabilization (feedback control) of process variables, • optimization of process, • visualization of relevant data, • transparent operation of UCG process. From this function’s analyses followed that process control system should to be decentralized control system which provided optimal control [4]. Therefore control on stabilization level was separate from optimal control. Then, the structure of process control consists of two levels. Optimization level sends required optimal values w to stabilization of process variables. Stabilization level is based on feed forward, feedback and extremely control. Optimization level is based on using suitable method for optimal control. The principle of process control is shown on Fig. 2.
III.
CONTROL SYSTEM ON STABILIZED LEVEL
PLC B & R with processor 400MHz Intel Celeron is the hardware core of control system. PLC contents modules for connection pressure sensors (absolute and differential pressures), frequency changer module for ventilator, input digital modules for operation solenoid valves, control unit for compressor, and thermocouples modules. Type K of thermocouples was used for measured temperatures in gasifier. Communication between PLC and PC is provided by standard interface RS232. The project structure of the UCG control system is shown on Fig. 3. I/O modules of PLC are shown on left side and cycle’s modules on right side as names of cycle’s tasks. Configuration is possible for each module. By help of this structure is possible to link a module port with process variable from control procedures (program). Control procedures are localized in cyclical tasks where is defined the repeating time interval. After compilation of built project is binary code from AS sent to PLC. Then cyclic task is carried out in PLC. Variables used in PC and PLC also must be defined as global variables. Configuration same variables is necessary for PC by help OPC configuration.
Figure 2. Structure of optimal control
Control system on stabilized level is realized by PLC and optimizations level including further functions is provided by PC. Software realized on PC is named as monitoring system. Used hardware and software platform is shown on Tab. 1. TABLE I.
REVIEW OF HARDWARE, SOFTWARE FOR DEVELOPMENT OF UCG PROCESS CONTROL
Level
Hardware platform
Stabilization
PLC
Optimalization
PC
Software platform
Application software
Automation software (IDE), Automation Runtime Promotic, Windows XP
Control system
Figure 3. The project structure of the UCG control system in AS.
Algorithms of DDC based on algorithm of bang- bang control (1) and PS type (proportional summing) controller (2).
u i = u max u i = u min
if x i < x r if x i ≥ x r
u i + 1 = u i + K P (ei − ei −1 ) + K I ei δτ Monitoring system
(1a) (1b) (2)
where: u – control variable, e – regulation deviation , KP– proportional constant, KIi – integration constant, xi - controlled variable, xr –, required value, i – index of control period, δτ – control period. Control algorithms were programmed in environment B&R Automation studio (AS) by help of language the Automation basic. Parameters of PS algorithm were proposed by standard MATLAB procedures. Control system provided some continuous cycles of tasks which carry out following operations: • Input / output compressors with the aim to control pressure in pressure vessel between two positions (max., min.), • feedback control of volume oxidizing agents by help servo valves, • feedback control of temperature in oxidizing coal zone, • feedback control of the content CO in syngas, • feedback control of the content O2 in syngas • extremely regulation for temperatures or CO or calorific value or ratio CO/(CO+CO2) in production syngas [6] IV. MONITORING SYSTEM This application provides following functions: • optimal control, • processing of data, • storing and saving of data • visualization of measured, controlled and control variables, • communication and operation between user and process control system • event processing (scripts). Monitoring system (MS) was created in Promotic. Promotic is a complex SCADA object software tool for creating applications that monitor, control and display technological processes in various industrial areas. It is designed for Windows 7/Vista/XP/2000/XPe/2003-8 Server operation systems and higher. Promotic allows effective creation of distributed and open applications in various industrial branches. Also offers user friendly environment for application design. There are all necessary components for creating both simple and extensive visualization and control systems built-in the Promotic system: • Application editor with a hierarchical object tree. • Wide offer of Promotic objects. • Microsoft Basic (VBScript) language for writing the algorithms. • Panel editor. • Wide palette of technological images created in vector SVG graphics. • Graphic objects - both elementary and complex items configurable on a very general level. • Automatic panel conversion to HTML and XML format. • The trend system (i.e. storing values with the time stamp).
• Alarm and operator event systems. • Support of web Internet/Intranet technologies. • SQL and ODBC interfaces for databases. • Built-in interfaces: XML, OPC, ActiveX, DDE. • Communication drivers for access to PLC's. • User management, permissions and login system. • Security of running applications. • Promotic language versions. • INFO - information and diagnostic system. • Electronic and printed documentation [7]. User creates the conception of MS by using tools as are Editor of pictures, and configuration elements. Then visualizations elements are necessary to link with required variables (PLC, PC, applications) and to provide event processing by scripts. Monitoring system consists of procedures/programs which support described functions. Monitoring systems is divided to 20 windows which care out the visualization, configuration operation of control algorithms saving of measured data by one sec. period.. Measured variables are saved in database of type csv (comma separated values). Main windows with name Generator is shown on Fig. 4.
Figure 4. Basic panel of the monitoring system
This window shows actually values of technological variables as there are volume flow, pressures of air, syngas and oxygen, concentrations of individual syngas components, and calorific value, etc. Some control algorithms are switched on / switched off from this main window. For example, constant value controls of air volume flow, constant value control of
concentration oxygen or CO in syngas. Of course, there are any possibilities for manual control (revolutions of an exhausted ventilator). Parameters of control algorithms, including controlled period are defined in other windows. Similarly, was created special windows for setting parameters of extremely control and UCG optimal control. V.
THE CONNECTION OF THE MONITORING SYSTEM WITH CONTROL SYSTEM ON STABILIZATION LEVEL. In this chapter is described a principle of communication between control system which is realized by PLC and monitoring system that is implemented on PC. A. Hardware connection Used model PLC had possibilities of connection with PC by a help RS 232 with 9 pins connectors and external USB port. Therefore was used RS 232 but PC was spread about special card because PC had not original input 9 pin connector .The connection between PLC and PC is shown on Fig. 5.
Figure 6. Software interconnection on PC.
This way requires OPC Server on PC. It is resident driver which is possible to find in Automation studio B&R. The activity is following. After start of monitoring system in Promotic environment runs application PVI Manager. This application gets data from RS 232 or TCP/IP protocol and PVI Manager send data to resident OPC Server. The configuration of OPC Server is done by parameters which are written to file C:\BRAutomation\PVI\Cfg\PviOPC.mdb. In this file are written setting data for transported variables from PLC to PC. The edition of configuration file (see details in Fig. 7) is done by program with name PVI OPC Configurator.
Figure 5. Schceme of the hardware interconnection
B. Software connection During development of control and monitoring system was proposed three ways for mutual communication. At first was tested a principle DDE (Dynamic Data Exchange). This way was slowest and it caused sometime switching off monitoring system. Second way utilized interface serves B&R PVI (Process Visualization Interface). Monitoring system used a serves of library PVICom.dll. This way had some shortages of communication stability and communication was often interrupted. On this place is necessary to emphases that monitoring system was developed in environment Pascal Delphi in that time. Later, monitoring system was evolved in Promotic. Third way of communication used SCADA system Promotic. There were used interfaces B&R PVI and OPC (OLE for Process Control). Three possibilities of communication solution are shown on Fig. 6.
Figure 7. Example of variable setting in OPC Configurator.
In this place is necessary to emphases, at first is needed to create the name OPC Server for communication between Promotic and application (Monitoring system). OPC client is monitoring system and data are sent from OPC server to client. The configuration window in Promotic is shown on Fig. 8. Connection between OPC client and OPC server is defined by parameters in this window. Next step is the configuration of transported variables (name, path, item ID, type). This configuration in Promotic is done by object OpcClient. This procedure is shown on Fig. 8. For illustration, the variable CO (name) in monitoring system
(PC) is linked with variable Pvar161 (double type) in control system (PLC) by path PVI … PVItest-see Fig. 9.
Figure 10. Dataflow and temporary saving of measured data.
Figure 8. Connection of the Promotic with OPC Server.
VI.
CONCLUSION
Process control system of UCG has been evolved for research project “Underground coal gasification by thermal dissociation” .This system enables to attain better results in basic UCG research and one is model for development of Control of UCG in situ. There has been described the architecture, functions of Monitoring and Control system. Hardware and software connection between both systems are described also. The connection between Control and Monitoring system is realized with interfaces OPC and PVI. This solution appears as stable and one providing quick exchange of data between PLC and PC. Control system was evolved by using Automation studio and Monitoring system in PROMOTIC. Figure 9. Connection of the Promotic variable with PLC variable.
C. Data protection Basic shortage of this architecture based on operation system WINDOWS is its unreliability. Of course, Windows was evolved as software for offices/administration. Correctly, the process control system should to be evolved by using other OS. Operation systems, for example type of Real Time and from family UNIX are suitable for these aims. But breakdown of Windows does not influence basic control functions because they are provided by PLC. Breakdown of Windows is reason of a loss measured data which are necessary namely for optimal control and their visualization. This problem was solved following. Sampling data by PLC are stored at moment of Windows breakdown to temporary file in RWM of PLC. After restart Windows are these data read from temporary file and sent to OPC client-see Fig. 10.
ACKNOWLEDGMENT This work was supported by the Slovak Research and Development Agency under the contract no. APVV-058206 and grant VEGA No. 1/0567/10. REFERENCES: [1]
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