This article discusses a method for optimizing chemical-technological processes using training complexes. The article also describes the requirements for the mathematical model of the simulator. Using computer training complexes of «real time”, it is possible to solve a number of technological problems.
Keywords: simulator, optimization, chemical-technological processes, mathematical model, dynamic modeling.
Chemical-technological processes are classified as high-risk facilities, the operation errors of which can lead to irreparable consequences. In this case, safety can be maintained with the help of a high level of training and the availability of special education for staff. To acquire special skills such as the ability to quickly and adequately act in emergency situations, professionalism and the necessary experience apply special tools and training methods, among which various simulators are most in demand. In addition, each code in the oil and gas industry is progressing. Equipment and technologies are being updated intensively to ensure increased reliability and cost-effectiveness of power plants. The introduction of new technology while maintaining the old knowledge base should be accompanied by constant retraining and retraining of operational personnel, while the value of computer training complexes is obvious [1, 2, 3].
The most effective approach to operator training and advanced training is the use of computer simulators that fully imitate a real installation. The main task of such simulators is the formation of a comprehensive decision-making skill, which is based on the ability to simulate the dynamic response of an object and a control system to arbitrary operator control actions. Such simulators are the same programs for modeling chemical-technological processes in dynamic mode with the obligatory requirement of real-time mode [4].
This article suggests the use of a simulator to optimize the process. Specialized simulators with high accuracy simulate real technological installations and, as a rule, are made in the environment used in the automated process control system.
The core of the computer simulator is a mathematical model of the process. The main advantages of the model of the training complex include:
models are based on fundamental modeling of processes (kinetics, hydraulics, mass and heat transfer, etc.);
models are «real-time” systems, that is, they respond in a certain way to previously unforeseen disturbances and control actions;
models should be adequate, since inconsistencies in the model are fraught with the most dangerous consequences in the training of operators — the acquisition of a “false” skill, that is, an incorrect reflection of the subject area of activity.
The accuracy of the simulator depends on the boundaries of technological modeling. The inclusion in the model of the entire technological scheme, significantly increases the cost of the simulator and reduces the simulation speed. At the same time, with all the simplifications of the model, it is important to take into account the reproduction volume in the simulator of the emergency protection system, for the correct operation of which it is necessary to provide the imperative amount of modeling of process variables. Among other things, the model must be sufficiently complete so that all technological violations in the operation of equipment and control systems are implemented [5].
Another requirement for the simulator model is its connectivity. The simulator model should provide the calculation of the entire simulated technological scheme, so that changes in any part of it are reflected in the entire scheme in accordance with the actual physical and chemical processes taking place in the installation. Without modeling of especially important parts of the technological process, a deviation from the reality of the technological parameters, can occur thereby the resulting mathematical model will be incoherent.
The last requirement for the model is the adequacy of the static and dynamic behavior of the model to the real technological process. Practice shows as an achievable goal an accuracy of ± 5 % for critical and ± 10 % for non-critical parameters in static modes while providing simulation acceleration in the range of two to five. The adequacy of the simulator in transient dynamic modes is more difficult to verify and, as a rule, is evaluated by experts at the highest level [6, 7].
A necessary condition for adequacy is also the stability of the model, which refers to the belonging of the model parameters (both external and internal) to a predetermined working range, without interruptions and malfunctions in the calculation [8].
The main reason limiting the right to use a computer simulator as a tool for engineering is the adequacy of its output information, that is, the correspondence of the information received from the simulator to its real object, includes a number of requirements:
1) reproduction of static and dynamic modes with the accuracy necessary to solve the task in the right amount;
2) the comprehensiveness of mathematical modeling of technological processes, including emergency situations;
3) the accuracy of ACS TP modeling (reproduction of the facility monitoring and control systems on the simulator in full with the properties of measuring sensors, the features of their installation, transmission, signal processing, etc.).
Dozortsev I.V, Itskovich E. L., Kneller D. V. [5] considere existing methods for assessing the accuracy of dynamic models of simulators and a new approach based on the results of their analysis, which consists in dividing the simulation process into stages, each of which is given an individual quality assessment criterion:
identification — the criterion of maximum similarity;
simulations — a criterion for regression analysis (student and Fisher criteria);
implementation is an information and expert criterion.
The dependencies obtained by the authors allow to: control the quality of the model at all stages from design to the implementation of the training complex; assess accuracy regardless of the physical nature of the simulated technological processes; describe the static and dynamic modes of operation of the object and model, taking into account their stochastic nature.
This approach to the optimization of technological processes is possible only for the simulator developer when designing it, since the computer simulator is used as a finished product. The user has no idea which model is embedded in the simulator, which calculation algorithms are used, what relationships are established between the components of the model, and so on. Given the possibility of changing the properties of raw materials, catalyst and equipment characteristics, the simulator becomes an object of research and an indispensable apparatus in order to improve the real technological process.
References:
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- Dozortsev V. M., Shestakov N. V. Computer simulators for chemical-technological type productions: utility, efficiency, payback // Safety problems in emergency situations. — 1997. — No. 7. — S. 24–39.
- Dozortsev V. M., Kneller D. V., Levit M. Yu. On the problem of the adequacy of simulator models of technological processes // Proceedings of the international conference «System Identification and Control Tasks (SICPRO’2000)”. — 2000. — S. 51–61.
- Beetles. I.V., Khabarov M. D., Kharazov V. G. Computer simulators for testing and developing advanced process control systems // Bulletin of the St. Petersburg State Technological Institute. — 2017. — S. 111–114.
- Dozortsev V. M., Itskovich E. L., Kneller D. V. Advanced Process Control (APC): 10 years in Russia. // Automation in industry. — 2013. — No. 1. — S. 12 –18.
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- Gershberg A. F., Podiapolsky S. V., Sorkin L. R. A computer simulator for training catalytic reforming unit operators inLLC “PO“ Kirishinefteorgsintez ”// Automation in industry. — 2003. -No. 7. — S. 52–53.
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