Process simulation is a model-based representation of a process plant such as a Sulfur Recovery Unit, in software. Basic prerequisites are a thorough knowledge of chemical and physical properties of pure components and mixtures, of reactions, and of mathematical models which, in combination, allow the calculation of a process in computers.
In general, process simulation uses models which introduce approximations and assumptions but allow the description of a property over a wide range of temperatures and pressures which might not be covered by real data, however; VMGSim™ has implemented onsite testing data of various plant configurations collected by SRE from more than 15 years of on-site process stream sample collection and analysis, which also allow interpolation and extrapolation – within certain limits – and enables the search for conditions outside the range of known properties.
Initially process simulation was used to simulate steady state processes. Steady-state models perform a mass and energy balance of a stationary process (a process in an equilibrium state) however do not depend on time. In a steady state Process simulation software, such as VMGSim™, describes processes in flow diagrams where unit operations, such as Reaction Furnace(RF), Catalytic Convertors and Condensers, are positioned and connected by material and/or energy streams. The software has to solve the mass and energy balance to find a stable operating point. The goal of a process simulation is to find optimal conditions for an examined process. This is essentially an optimization problem which has to be solved in an iterative process.
Dynamic simulation is an extension of steady-state process simulation whereby time-dependence is built into the models via derivative terms (i.e. accumulation of mass and energy). The advent of dynamic simulation means that the time-dependent description, prediction and control of real processes in real time has become possible. This includes the description of starting up and shutting down a plant, changes of conditions during a reaction, holdups, thermal changes and more. Dynamic simulations require increased calculation time and are mathematically more complex than steady state simulations. It can be seen as a steady state simulation repeated multiple times (based on a fixed time step) with constantly changing parameters.
Dynamic simulation can be used in both an online and offline fashion. The online case being model predictive control, where the real-time simulation results are used to predict the changes that would occur for a control input change, and the control parameters are optimized based on the results. Offline process simulation can be used in the design, troubleshooting and optimization of Sulfur plants as well as the conduction of case studies to assess the impacts of process modifications. Dynamic simulation is also used for operator training.
VMGSim™ Dynamics Benefits
VMGSim™ is a powerful tool which can be used for both steady state and dynamic simulations.
The following studies and troubleshooting can be performed using a high fidelity Dynamic VMG™ model.
1. Can implement or study as an off-line virtual SRU
2. Evaluate extreme upset conditions without affecting the Integrity of the process
3. Study bottlenecks like under-sized or oversized equipment and the overall effects on the SRU and sulfur recovery rates for any given scenario.
4. Turndown study under various scenarios.
5. Can perform Co firing study.
6. Blower performance and pressure drop analysis for various scenarios.
7. Duty analysis of Waste Heat boilers and Condensers.
8. Plant upset study.
9. Tuning parameters and set point study.
10. Alternative process modification such as Acid Gas vs Fuel Gas firing at Aux burners and Direct Fired heaters vs Indirect fired heater.
11. Most Effective and Efficient Controller for the Application can be determined
12. Evaluate different control strategies
13. Perform regulatory control system studies
14. Introduce a wide variety of upset conditions
15. OPC Server and Client Compatible
16. On-line Process Monitoring
17. Evaluate various operating process inputs
18. Pressure Profiling and tuning
19. Determine Pinch Points in a System
20. Max out duties of exchangers
21. Valve saturations
22. Evaluate relief loads from causes such as blower, pump, and/or power failures