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BROCHUREEngineering Servicesfor Dynamic SimulationWhile plants may be designed to operate at steady state, transientoperations drive up the cost, time, and risk. Dynamic phenomenaoften define the limits of safety systems. AVEVA’s experienceddynamic simulation services team can help you solve problemsthroughout the lifecycle of the project, from design to controlsengineering, startup, and ongoing operation.
IntroductionWhy use Dynamic Simulation for ProcessEngineering?AVEVA’s engineering services program, based onDYNSIM Dynamic Simulation, delivers both operatingand design recommendations, as well as a completesimulation model. DYNSIM Dynamic Simulation isa state-of-the-art, field-proven dynamic processsimulation program. DYNSIM Dynamic Simulation’sprocess plant modeling environment covers the entirelifecycle of the plant, from simulation through systemcheckout, operator training and start up.Reduce Equipment Costs. Many plant designparameters are based on transient operatingconditions. Dynamic simulation accuratelysimulates transient events to predict the conditionsthat set equipment mechanical design temperaturesand pressures.Evaluate First of a Kind Plants. These plants oftenhave unforeseen process, control and relief problems.Dynamic simulation can be used as a process designtool to reveal these problems early in the design phaseto avoid costly modifications during or after startup.Our engineering services program offers anunparalleled combination of industry experience,process simulation knowledge and best in classtechnologies, enabling customers in all processindustries to realize significant benefits in thesefour key areas:Design and Validate Control Strategy. Test the controlstrategy as defined on the control narrative and Pipingand Instrumentation Diagrams (P&ID) before the plantgoes online to avoid costly troubleshooting and tuningefforts in the field. Compressor systems and complexfractionation systems are good examples.y Capital Cost Savingsy Decreased Time to Markety Improved SafetyTest Heat Integration. Complex designs with tight heatintegration may need supplemental heat for startup.Dynamic simulation can validate the process design todetermine if adequate startup heat is available.y Improved AvailabilityDynamic Simulation for Process DesignAVEVA’s Lifecycle Modeling concept is based on theuse of dynamic simulation tools throughout the lifecycleof a project, from design, controls engineering, startupand ongoing operation. Engineering services addressprocess engineering and design, verifying equipmentand controls design and evaluating startup andshutdown procedures using dynamic simulation.Analyze Flare and Relief Systems for Hazop.DYNSIM Dynamic Simulation can be used for safetystudies to validate relief system design as a result of aHazop analysis.Lifecycle ning02ImprovePerformanceEngineering Services for Dynamic Simulation
DYNSIM Dynamic Simulation DecisionSupport SimulatorsCompressor Surge AnalysisDynamic simulation can be used to test and validatecompressor surge control systems to keep a largecentrifugal compressor out of surge, especially duringstartup and shutdown. In some instances, dynamicsimulation can be used to model startup and determineproper throttle valve positions and startup horsepowerrequirements, as well as evaluate performance usinghot gas bypass or cold gas bypass designs.The DYNSIM Dynamic Simulation graphical interfacecan easily be set up as a decision support simulator.The graphical interface allows easy execution byindividuals who are not trained in building dynamicsimulation models.Some features for the development of decision supportsimulators include:Benefits: Prevent damage to multi-milliondollar machinery.y The ability to drag-and-drop widgets directly on tothe flowsheet for easy operation of the simulation.These widgets include sliders, buttons, dials,indicators and check boxes.y Multiple flowsheet capability so dynamic modelsmatch plant PFDs or Piping and InstrumentationDiagrams (P&IDs) for easy navigation.y Password protected access modes for Administrator,Engineer, Instructor and Operator, so only theappropriate individuals can make changes to thesimulation.y Preconfigured malfunctions in most equipmentmodels.y Link to Microsoft Excel for data collection andvisualization.y Remote functions for the operation of controls, valvesand motors.Compressor Startup AnalysisCompressors with large constant speed motorsmay have insufficient horsepower to start under alloperating conditions. For example, a hot restart of acompressor may not be possible at settle-out pressure,unless the compressor discharge pressure is reduced.This may delay compressor restart to depressuredownstream equipment, increase flaring, or requiremotor cooldown periods after a failed motor start.Dynamic simulation with detailed motor startup torquecurves can be used to determine the appropriate motorsize while avoiding overdesign.y Trainee performance monitoring to give a numericalscore based on maintaining key process parametersbetween a low and high operational band.DataThermodynamics HistorianCrossReferencingEngineering/Model BuildingOperation ModeBoth Engineering and anceMonitoring (TPM)Model LibraryInitial Conditionsand BacktracksCustom WidgetsMalfunctionsBenefits: Improve plant availability and reduce flareemissions.Trends03Engineering Services for Dynamic Simulation
Column Control Strategy Selectioncomposition. Dynamic simulation is consistent with APIRP-521 methods. Dynamic simulation provides a safeand documented alternative to conventional relief loadcalculations methods resulting in substantially lowercalculated relief loads.Dynamic simulation can be used for difficultdistillation and fractionation control system problems.Sophisticated control systems can be designed andvalidated using dynamic simulation. Also, transientvapor and liquid profiles can be used to confirm traydesigns. Dynamic simulation is particularly usefulwhere product quality constraints are tight, blendingof off-spec products may be difficult, or frequent feedvariations are expected.Benefits: Save relief and flare system capitalexpenditures – up to several million dollars.Flare System StudiesDynamic simulation can evaluate the effect of vesseland flare header packing. Packing is the pressurizationof the flare system, particularly the blowdown andknockout vessels within a unit. Packing may reduce thecalculated backpressures in the flare – particularly fordepressuring or staged relief loads.Benefits: Reduce plant commissioning time and reduceoff spec production.Column Relief Load AnalysisConventional methods for calculating column reliefloads are very conservative and can lead to overlyexpensive flare systems or unnecessary flare orflare header replacements during unit revamp anddebottlenecking projects. Also, refiners may haveinsufficient plot space because they are confined by theflare radiation radius or are restricted by governmentpermits. Dynamic simulation provides an alternativeto conventional calculation methods and providessubstantially lower relief loads.Benefits: Relief and flare system capital expenditures –up to several million dollars.Cryogenic Depressuring for Minimum MetalTemperature SpecificationDynamic simulation can be used to calculate themean metal temperature as a function of timeduring depressurization for gas processing and LNGapplications, where the vessel and outlet piping canreach extreme cold temperatures. In most cases, themean metal temperature is considerably less severethan the fluid temperature and may alleviate expensivemetallurgy and design choices.For fractionation towers with wide boiling ranges: flareload reductions (up to 50%) are possible as dynamicsimulation accounts for the limited inventory of lightcomponents and the sensible heat required to boiloff the heavier components. Dynamic simulation alsoprovides a realistic calculation of the reboiler pinchat elevated pressures using the time-dependent feedBenefits: Avoid use of stainless steel metallurgy forsavings up to 1 million U.S. dollars.04Engineering Services for Dynamic Simulation
Benefits: Reduce feed / effluent exchanger and reactoreffluent air cooler capital costs, avoid additional pipingthermal expansion loops, and eliminate the need forsecured power. Calculated savings up to 4 million U.S.dollars.Integrated Pipeline/Topsides ModelingDynamic simulation can be integrated with a subseapipeline simulator (such as Scandpower’s OLGA2000) to study the interaction of the pipeline withthe topsides. For example, the impact of slugging ontopsides operation can be analyzed.Benefits: Validate impact of slug induced transientsthat might reduce or stop production.Hydroprocessor Depressuring For Feed/Effluent Heat Exchanger DesignHeat exchangers in feed / effluent service for highpressure hydrocrackers and other hydroprocessorsmust be designed for the temperatures associatedwith reactor depressurization. During depressurization,the feed is stopped and cooling is unavailable forthe reactor effluent. One conventional steady-statemethod of calculation predicts that the heat exchangertemperature will rise instantaneouslyto the reactor outlet temperature.Accordingly, the design temperature and pressure forthe entire heat exchange train may be specified thesame as the reactor outlet condition. Alternatively,dynamic simulation can minimize heat exchangerdesign temperatures by accounting for the heatcapacitance of the metal in the piping and tubebundles. The simulation giving the fluid temperaturescorresponding to the actual pressure at every point intime provides a coincident pressure and temperaturetrajectory. Mean metal temperatures can be determinedfrom this temperature profile.Cryogenic Exchanger Stress AnalysisDynamic simulation can be used to model spiral woundand plate fin heat exchangers. DYNSIM DynamicSimulation has a rigorous multi-stream exchangermodel that can be used to calculate metal temperaturedynamics.This analysis can be used to determine the thermalstress on the exchanger to determine if mechanicalfailure can result during startup or other severetransient conditions.Benefits: Verify transient operating conditions toprevent damage to expensive heat exchangers.05Engineering Services for Dynamic Simulation
Benefits: Avoid unnecessary boiler stiffening forconversion of forced draft to balanced draft operation(costing in excess of several million U.S. dollars).Develop MFT control logic which prevents implosiondamage to a boiler.Refinery Steam Systems AnalysisThe process dynamics and controls system designfor refinery steam systems, cogeneration plants,integrated gasification and combined cycle (IGCC)and conventional power plants are often evaluatedwith dynamic simulation. The reliability of the steamsystem is crucial to refiners as the loss of steam canshutdown the entire refinery – costing lost production.Typical systems are combined-cycle facilities wherethe gas turbine exhaust gas is used to generate steamin a heat recovery steam generator (HRSG) which isthen provided to a steam turbine and process steamusers. Dynamic simulation can be used to validatecontrol systems, check control valve sizes and responsetimes, and provide initial controller tuning parameters.Dynamic simulation can also be used to insure thatafter a gas turbine or boiler trip, the backup steamsystems such as HRSG supplemental firing andauxiliary boilers can produce additional steam quicklyenough to maintain steam to the process users.Boiler Draft Studies for FGD RetrofitsA Flue Gas Desulfurization (FGD) retrofit will affect apower plant’s controllability and may expose it to anunplanned shutdown or mechanical damage duringupset conditions. Dynamic simulation is a valuabledesign tool for FGD retrofit process and controldesign. In particular, Dynamic simulation can assessthe possibility of boiler implosion due to continuedoperation of an induced draft fan, seconds after amaster fuel trip. Dynamic simulation can also assesscontrollability issues associated with parallel unitsusing a shared FGD system. Dynamic simulationprovides the required information to make importantdesign decisions that can significantly improve thecontrollability and safety of the boiler and FGD system.Benefits: Design and verify steam system process andcontrols to avoid refinery wide shutdown because ofloss of steam supply, saving several million U.S. dollarsin lost production.Refining Example: Dynamic Simulation for aDelayed Coker Main Fractionator1. Delayed Coker Main Fractionator Control Strategyfor Coke Drum SwitchDynamic simulation can be used to design and validatethe delayed coker main fractionator control system.Delayed coker main fractionators experience dramaticchanges in coke drum vapor rates during a typical cokedrum switch operation. These changes impact columnoperation and product qualities which may lead to offspecification products. DYNSIM Dynamic Simulationcan be used to develop a control strategy whichmaintains product quality during a switch to improveproduct qualities by providing a test bed for controlstrategy changes.06Engineering Services for Dynamic Simulation
As a first step, a dynamic model of the mainfractionator should be developed and validatedagainst actual plant data. This validation includescomparing simulated and actual product flow rates andfractionator tray temperatures as a function of timeduring the coke drum switch. After the dynamic modelis validated, alternative control system designs can beevaluated.the vapor rate will decay exponentially based on theinitial amount of unreacted liquid within the drum.This coke drum decay rate can be determined fromactual plant data for a typical coke drum switch.y There is limited light ends inventory inside thecolumn. Dynamic simulation considers the inventoryof volatile components in the column and theadditional sensible heat that must be added to boiloff heavier components once the lighter material isrelieved. There are other considerations such as thepossibility of continued cooling in the overhead aircooler.One option may be to explore the use of feed forwardcontrol on coke drum vapor rate, measured by thepressure drop from the coke drum to the fractionatorflash zone, to change product draw rates.Highly Integrated Plant ComplexThe result of the study will include a final reportwith graphical results showing model validation,results of the control strategies implemented andrecommendations on control strategy modifications.Engineering studies via dynamic simulation can be usedto verify the adequacy of C2 storage, export pump,vaporizer design, as well as, the control system. Majordisturbances on the ethylene header can be modeledto assure that an upset will not cause shutdown to PEunits. Sample scenarios for reliability and safety include(1) Trip of C2 compressor, (2) Lost of C2 demand(trip of PE unit), and (3) Changes in C2 demandduring grade transition in PE unit. A recommendationfor optimum control performance, in terms of headerpressure measurement location or controller tuning anddesign, can be made.2. Delayed Coker Main Fractionator Relief LoadReductionDelayed cokers have a major contribution to the totalflare system load. Delayed coker main fractionatorsmay also require substantial investment in column reliefsystem, due to their high calculated relief loads andlow operating pressure. Typical calculations methodsassume the full energy content of the coke drum vaporis applied to a fluid composition on a tray near the topof the column, which can lead to an overestimation ofthe actual relief load for the following reasons:y The coke drum vapor rate decays after the feedheater charge pump is tripped. Calculating how thecoke drum vapor rate decays with time after a powerfailure is critical for predicting the relief rate. Thecoke drum will continue to produce vapor even afterfeed to the drum is stopped, due to the continuingreaction of the liquid inventory in the drum. However,07Engineering Services for Dynamic Simulation
Other Application AreasDepressurizing Analysisy Estimate the lowest possible temperature duringdepressurizationHigh Integrity Pressure Protection System (HIPPS)designy Meet safety constraint fast but do not constrainoperating windowy Determine depressurization strategies that meetsafety/design standardsFlare gas recovery furnace operationy Determine the control strategy to operate flare-gasrecovery furnace in emergency situationsFor more information on Dynamic Simulation,please visit: ineering-and-simulation/dynamic-simulationy Determine FG header pressure, Maximize heatingvalueDetermining safety system design for flare/reliefscenarioy Determine safety system setpoints (e.g. cut off steamsupply in tower reboiler when tower pressure risesbeyond certain value)Copyright 2020 AVEVA Group plc and its subsidiaries. All rights reserved.All product names mentioned are the trademarks of their respective holders.aveva.com
use of dynamic simulation tools throughout the lifecycle . of a project, from design, controls engineering, startup and ongoing operation. Engineering services address process engineering and design, verifying equipment and controls design and evaluating startup and shutdown procedures using dynamic simulation. Why use Dynamic Simulation for .
