Visual Modeler. Dynamic process simulation already existed in the. Since the steady-state simulator is more commonly.

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1 Dynamic simulator 1. INTRODUCTION Dynamic simulation already existed in the 1960s, and a substantial number of general-purpose dynamic simulators were developed during the period; some of them were sold for business purposes. It was not, however, until recently that the dynamic simulator made significant improvements in its usage and functions. Today s operation training simulators are very different from conventional ones in that they are upgraded to a level where highly skilled operators can effectively utilize them, and their ability to construct first-principle-based rigorous models enables safe and efficient operations with a smaller number of people; the conventional ones, however, are merely used as a supplementary means to educate non-skilled operators due to lack of fidelity in the models. While the dynamic simulator is generally used to advance operating and control systems for analytical purposes, today s simulator is required to be more accurate to create optimal operation characteristics through online simulation. From a user s standpoint, plant operations have become much harder since the necessity of maintaining safe operations and reducing the number of shutdowns and startups of the plant is becoming greater as plants become more complex. From a provider s stand point, on the other hand, it has become much easier to develop better-quality simulators because of the advancement of graphic user interfaces and computer calculation methods., a dynamic simulator, proudly presented by OSC, was developed to meet those users needs with the goal of not only providing operation training, and developing and inspecting advanced operating control systems, but also offering a next-generation plant simulator as a commonly used tool to achieve optimal operations in online systems. 2. FUNCTIONS REQUIRED FOR DYNAMIC SIMULATORS Since the steady-state simulator is more commonly used, its functions are standardized, whereas the functions of the dynamic simulator are very diverse; therefore, no standardized reference is available. The following describes the features of functions in providing similar and different characteristics between the dynamic simulator and the steady-state simulator. (1) Model Fidelity The unit models constructed in dynamic simulators (e.g. distillation tower, heat exchanger, etc.) require the same or higher level of accuracy than those in steady-state simulators. For example, the vapor-liquid equilibrium, and heat balance calculations are performed at each tray in the distillation column, and the internal pressure caused by changes in the vapor hold-ups is calculated. Both functions are done in the same manner in the dynamic and steady-state simulators. For the heat exchanger, while it is only necessary to show the heat and material balances of the inlet and outlet in the steady-state simulator, the dynamic simulator must have the ability to describe the inner conditions in detail because of its dynamic characteristics. The - 1 -

2 Table 1. Functions ITEM FUNCTION Physical Property Calculation 1) Physical Property Database Built-in library with 200 components (DIPPR database) Built-in parameters between 2 components (140 for each SRK, PR) 2) Physical Property Calculation Methods Table 2 3) User Data Registering to the physical property library (components and parameters between 2 components) and searching Modeling and Calculation Methods 1) Model Input Method Inputting Graphics 2) Number of Built-in Models 122 types (Table 3) 3) Custom Model Creating Functions Unit models - EQUATRAN, C Physical properties - C Unit diagrams (exclusive editors are incorporated.) 4) External Time-Series Data Reading from a real-time database Reading and writing from/into a time-series file 5) Calculation Method for Pressure and Flow Rate Simultaneously solving pressure flow balance equations 6) Calculation of Normal Conditions Accelerated simulation Simulation operability 1) Constant data input From the PFD screen 2) Scenarios Auto Functions 3) Snapshot Snapshot, stepback, auto snapshot functions Modeling of Distillation Tower 1)Vapor hold-ups Calculated for an entire tower 2)Liquid hold-ups Calculated for each tray 3)Heat Loss Under consideration 4)Startup Empty (dry) tower Reactor models 1)Type Complete mixing tank, and general-purpose fixed floor 2)Reaction equations EQUATRAN, parameter input 3)Vapor-Liquid hold-ups Both vapor and liquid are taken into account. Control system models 104 types of (Table 4) 1)Controller type Position type PID, velocity type PID, etc. (Table 4) 2)Control valves A variety of characteristics are available. (Table 3) valves, which are often overlooked or only recognized as units that generate pressure differences in the steady-state simulator, must be modeled as units in the dynamic simulator with which flow rates, velocities (how fast valves are opened and closed) and other variables can be described. The physical property calculation methods in the dynamic simulator are basically the same as those in the steady-state simulator. However, when it is necessary to execute at high speeds, the dynamic simulator can use simple calculation methods, such as quadratic equations with given temperature variables (Table 2). can offer high accuracy and calculation efficiency because of its capability of using any combination of the calculation methods simultaneously in one model. (2) Scale of Simulation To examine the training and operations in dynamic circumstances such as shutdown and startup, dynamic simulators require modeling of control equipment, pipe lines, hand valves, and safety and auxiliary equipment. Thus, for the same type of plant, they require 10 to 100 times more units than - 2 -

3 Table 2. Physical Property Calculation Methods Physical property Vapor-liquid equilibrium coefficient Liquid-liquid equilibrium coefficient Enthalpy Vapor density Liquid density Viscosity Calculation method (1) Ideal solution (Antoine equation + Raoult's law) (2) Ideal gas (Antoine equation) + Liquid activity coefficient (Wilson equation) (3) Ideal gas (Antoine equation) + Liquid activity coefficient (NRTL equation) (4) Ideal gas (Antoine equation) + Liquid activity coefficient (UNIQUAC equation) (5) SRK equation (6) PR equation (7) Steam table approximation equation (pure water system) (8) User-defined function (1) NRTL equation (2) UNIQUAC equation (3) User-defined function (1) Quadratic equation of temperatures (vapor, liquid) (2) SRK equation (3) PR equation (4) Steam table approximation equation (pure water system) (5) User-defined function (1) Ideal gas (2) SRK equation (3) PR equation (4) Steam table approximation equation (pure water system) (5) User-defined function (1) Polynomial (2) Exponential approximation equation (3) SRK equation (4) PR equation (5) Polynomial (pure water system) (6) User-defined function (1) Polynomial (2) Exponential approximation equation (3) Polynomial (pure water system) (4) User-defined function steady-state simulators. Some large-scale plant simulators consist of several thousand units (including measurement and control units). Visual Modeler can handle models with 10,000-20,000 units. (3) Standard Unit Models Units required in the dynamic simulator but not in the steady-state simulator include tanks, safety valves, check valves, time lag pipes, measuring instruments and control equipment. While the same results can be obtained from one unit model in the steady-state simulator, the dynamic simulator often requires each unit model to function identically to the actual one because of its dynamic characteristics and different handling procedures in operations (e.g., pumps, compressors, valves of every kind, filters in the pipes and other small equipment). For this reason, many different types of unit models must be prepared as standards in the dynamic simulator. Tables 3 and 4 show a list of standard unit models registered in the library

4 Table 3. Process Unit Models Valve Pump Piping system unit Mixing/splitting/header Feed/production from/to the outside of the plant Tank Hand valve - Regulation valve - Shutoff valve Pneumatic control valve - Regulation valve - Regulation valve (with HW) - Damper Pneumatic shutoff valve Motor-driven valve General automatic valve Cross valve - Splitting control valve - Mixing control valve - Splitting shutoff valve - Mixing shutoff valve Check valve Relief valve - Vent - Inline - Valve block (vent) - Valve block (inline) Sequence valve Control valve block Pressure regulation valve Centrifugal pump - Pump with check valve - Pump without check valve - Rotation speed control Reciprocating pump Rotary pump General piping Dead time piping Piping with leak U tub Restriction orifice Strainer - Simple type - Strainer with front and rear valves - Strainer with switching function - Gas filter Trap - Inline trap - Drain trap - Trap with heat loss Piping with volume Stabilizing piping Mixing point(2-10 points) Splitting point(2-10 points) Header(2-8 points) Pressure equalizer header Constant pressure - Feed from outside the plant - Product to outside the plant Air - Intake - Vent Constant pressure with contraflow - Feed from outside the plant - Product to outside the plant Constant flow rate - Feed from outside the plant - Product to outside the plant Constant flow rate with contraflow - Feed from outside the plant - Product to outside the plant Air with contraflow - Intake - Vent Connection to another - Feed from another - Outflow to another Stack Liquid tank (open) Liquid tank (sealed) Gas tank - Floating roof - Pressure tank Pot Liquid tank (with stirrer) Phase equilibrium separator Heat exchanger Tower model Compressor/blower Turbine Furnace Reactor Others Flash drum - Water system flash - Flash drum - Conventional vapor-liquid separator Decanter - Decanter - Decanter with pressure equalizing line Total condenser/condenser Vaporizer/reboiler - Thermosyphon reboiler (stream heat) - Thermosyphon reboiler (sensible heat) - Vaporizer (stream heat) - Vaporizer (sensible heat) Partial-condenser - Partial-condenser - Partial-condenser with pressure equalizer line - Partial-condenser with vapor phase holdup Vaporizer condenser Sensible heat type General-purpose heat exchanger Single-flow type Tray tower (blow type) - 1No feed - 1-feed - 1-feed/1-cut - 2-feed - 2-feed/1-cut - 2-feed/2-cut - 3-feed - 3-feed/2-cut Tray tower (reboiler type) - No feed - 1-feed - 1-feed/1-cut - 2-feed - 2-feed/1-cut - 2-feed/2-cut - 3-feed - 3-feed/2-cut Packed tower (blow type) - No feed - 1-feed - 1-feed/1-cut - 2-feed - 2-feed/1-cut - 2-feed/2-cut - 3-feed - 3-feed/2-cut Packed tower (reboiler type) - No feed - 1-feed - 1-feed/1-cut - 2-feed - 2-feed/1-cut - 2-feed/2-cut - 3-feed - 3-feed/2cut Centrifugal compressor Reciprocating compressor Blower Vacuum pump Ejector Gas turbine Steam turbine Heating furnace Vapor-phase fixed bed reactor Tank type liquid phase reactor Cooling tower - 4 -

5 Table 4. Measurement and Control Unit Models General Instrument DCS controller DCS operator unit Flow meter - Variable-head flow meter - Variable-area flow meter - Volumetric flow meter - True-value flow meter Thermometer - For units Liquid-level meter - Differential pressure type - General-purpose Pressure gauge - For units - For dip-type Differential pressure gauge - For units Concentration meter - For units Viscosity meter Density meter -For units Ammeter (power-conversion) Wattmeter Tachometer Limit switch Flame eye Instrument screen Position-type PID controller Velocity-type PID controller Batch PID controller ON/OFF controller Ratio controller Manual controller Batch setup unit Switch (2-position) Switch (3-position) Adder (2/3/4-input) Multiplier Divider Square-root unit High-selector (2/3-input) Low-selector (2/3-input) Signal selector Signal splitting unit(2/3-output) 1st order lag Lead/lag Dead time Dead time + 1st order lag Dead time compensator Transfer function of m/n-th the order Function generator - Sine/Triangular/Rectangular wave - Polyline approximation (non-linear) - M-series signal - Constant setup One-loop controller One-loop operator unit Wiring Unit Logical circuit -AND circuit (2/3-input) - OR circuit (2/3-input) - NOT circuit - EXOR circuit (2/3-input) - IF circuit - Memory circuit - 1Timer circuit - 2of 3 circuit - Bypass circuit - AUTO-BYPASS circuit Range converter Differentiator/integrator - Differentiator - Integrator - Ramp unit Flow rate control (PI/PID) Temperature control (PI/PID) Liquid level controller (PI/PID) Pressure controller (PI/PID) Adder High-selector Low-selector 1st order lag Function generator - Function generator (periodic) - Function generator (non-periodic) Logical circuit - AND circuit - OR circuit - NOT circuit Range converter Wire Terminal board Array converter (scalar /vector/matrix) (4) User Unit Models Although the dynamic simulator carries various types of standard unit models to meet different conditions, the cases where these models are insufficient occur more frequently in the dynamic simulator. The reasons are: 1) the size and shape of equipment and/or the heat capacity are required to be specified to show dynamic movements; thus the structural features are easily reflected as discrepancies in models; and 2) more variety of models are required to be designed for emergency situations and abnormal operations. It is, therefore, of utmost importance that there be functions which users can easily use to add unit models to the library - 5 -

6 at their discretion. features effective functions to achieve this purpose, and as a vital tool for model descriptions, OSC offers software called EQUATRAN, an equation solver language. (5) Execution Functions Simulation enables execution in real time and interactive responses per second. These are extremely important especially when training simulators are used as real-time systems. They also become very effective in situations where engineers use them for analytical purposes and want to feel a sense of realism. The interactive response means that users are able to verify responses every second on the screen after valves are manually opened and closed; longer intervals will not duplicate the sense of realism. uses a high-performance computer to calculate large-scale simulators with rigorous models on a per-second basis. And, it features unique functions to accelerate the calculations of each unit model, physical properties, and the pressure flow network balance of the entire plant. (6) Engineering Environment When dealing with a large-scale plant, the development job becomes much easier if it is divided into groups. In, one plant is divided into several models, and the engineers assigned in each division perform development tests independently. After all the tests are completed, they are combined into an integrated plant model. While the flow diagrams (PFDs) are generally used to build models in the steady-state simulator, the dynamic simulator requires a more Figure 1. PFD Screen in the Editing Phase efficient operating environment with GUI due to the use of a substantial number of unit models. Models are created by 1) selecting necessary unit models from the Library menu, 2) placing them on the PFD, 3) connecting them with streams and signal cables, characteristic data) for each unit model. Figure 1 shows an example of the model-editing panel in. Building one model sometimes requires numerous pages of PFD. Figure 2 shows an example of the execution panel. The entire handling of execution, including running and freezing operations, and changing parameters for each unit model, are performed on this panel. (7) Calculations of Initial Conditions The initial condition is a starting condition of a simulation plant. The condition of a plant model of which the construction is just completed is very close to that of the actual plant, but it is not normally used as the initial condition. Some initial conditions refer to the normal conditions of a 50% or 100% load, and some conditions refer to the conditions at the time of completion of rising pressure during startup. As such, - 6 -

7 3. ACTUAL EXAMPLES Figure 2. PFD Screen in the Model Execution Phase various scenarios must be prepared according to simulation purposes. In recent applications, the initial conditions are created according to the present condition of actual plant operations, and the operational strategies are optimized after simulation is implemented. In, initial conditions are obtained by actually creating certain operational scenarios. For large-scale plants, which require a substantial amount of time to reach their normal conditions due to the use of recycling systems, enables accelerated simulation as a necessary function. can function independently, but it can also be used as a substitute for a plant by incorporating it into other systems. Demand for this type of usage is increasing, and it is expected to increase even more. Table 5 shows examples of typical simulation models developed in Visual Modeler. For oil refineries, detailed simulation models are already developed in each involved with atmospheric crude distillation unit, FCC, VGO hydrocracking and indirect hydrodesulfurization. In addition, they are used for operator training purposes. Plantutor listed in the connection system of the Table is a training simulator on UNIX system using an actual DCS. VMVIEW is a graphical user interface of on UNIX system. 4. CONCLUSION This paper mainly discussed the functions of a state-of-the-art version of. Those functions are expected to be enhanced, and more unit models are scheduled to be added

8 Table 5. Actual Examples Application Area Plant Type Objective Connection system Engineering Petroleum refining Atmospheric crude distillation unit Plantutor (CENTUM-CS) Yokogawa RFCC Plantutor (CENTUM-CS) Yokogawa VGO hydrocracking Plantutor (CENTUM-CS) Yokogawa VGO indirect hydrodesulfurization Plantutor (CENTUM-CS) Yokogawa VGO indirect hydrodesulfurization Plantutor (CENTUM-XL) Yokogawa VGO hydrocracking Plantutor (CENTUM-XL) Yokogawa Atmospheric crude distillation unit Plantutor (CENTUM-XL) OSC RFCC Plantutor (CENTUM-XL) OSC Petrochemicals/ Ethylene production system Plantutor (CENTUM-XL) Yokogawa Chemicals Cyclohexanol production and refining Plantutor (CENTUM-XL) User Propylene rectification (heat pump) Plantutor (CENTUM-CS) User Styrene monomer plant, operations improvement VMVIEW User Alcohol-water refining Plantutor (CENTUM-XL) User Solvent polyolefin production Plantutor (CENTUM-XL) User Unsaturated polyester resin production Plantutor (CENTUM-XL) User Polypropylene plant Operations improvement VMVIEW User Polypropylene plant Plantutor (CENTUM-XL) User VCM plant refining system Control improvement VM alone User VCM Plantutor (CENTUM-CS) OSC Phenol plant refining system Control improvement VM alone User Methanol recovery Education VMVIEW User Polyethylene Plantutor (CENTUM-CS) User Polymer Control improvement VMVIEW User Polyethylene reaction system Control improvement OmegaLand User Polyester resin Plantutor (CENTUM-CS) User Ammonia Plantutor (CENTUM-XL) User Polystyrene Plantutor (CENTUM-XL) User Fiber Plantutor (CENTUM-XL) User Others Utility boiler, facility inspection Plantutor (CENTUM-XL) User Natural Gas Piping System Control improvement VM alone User Solid wastes incineration heat recovery Inspections of facilities and operations VM alone User Piping system of liquefied natural gas evaporation plant Control inspection VM alone OSC Coal-fired boiler Plantutor (CENTUM-XL) User Boiler water supply system Control inspection VM alone OSC Air heating plant Plantutor (CENTUM-CS) User Gas turbine power plant Plantutor (CENTUM-CS) User Extremely critical boiler Education VM alone User Complex boiler, turbine and power Education OmegaLand OSC plant Education simulator for the basis of Education OmegaLand OSC chemical engineering Inspections of facilities and Waste disposal plant OmegaLand User operations Blast furnace plant (hot blast stove and Plantutor (CENTUM-CS) User gas cleaner) Very low temperature physical plant Analysis OmegaLand User Universities Research OmegaLand User - 8 -