Chemical Process Simulation

1 Chemical Process SimulationThe objective of this course is to provide the background needed by the Chemical engineers to carry out computer-aided analyses of large-scale Chemical processes. Major concern will fall on steady-state processes with hands on experiences on ChemCadsimulator (CC-5).CAD and the Structure of Design ProcessANALYSISM aterial &EnergybalancesEquip. SizingandCostingEconomicEvaluationFinal flowsheetSocietal needsInitialFlowsheetParameteroptimizati onStructureOptimizationFlowsheetSynthesi sFlowsheet Synthesis1) Rxn path selection2) Material balancing and species allocation3) Separation task selection and sequencing4) Auxiliary task assignment and Process integration5)Evolutionary improvement of initial flowsheetChemical Process SynthesisCADCADD esignVariablesInitialValuesChE Process AnalysisWhat is Process Simulation for?

2 Interpret Process flowsheets, locate malfunctions, predict the performance of Process Simulators Aspen Engineering Suite of Aspen tech., Inc. CHEMCAD of Chemstations Process Engineering Suite of Simulation Sciences, Inc. SUPERPRO DESIGNER of Intelligen, Inc. use of computer aids to perform steady-state heat and mass balances, sizing, costing calculation for a Chemical perform Process Simulation using a Process simulator Convert from a Process flowsheetto a Simulation flowsheet, , replace the Process units with appropriate Simulation unit. Model and solve the Process unit equations a subroutine is written for each Process are Process flowsheets? Process flowsheetsare the language of Chemical processes. They describe an existing Process or a hypothetical Process in sufficient detail to convey the essential features. A Process flowsheetis a collection of icons to represent Process and arcs to represent the flow of material to and from the units.

3 It emphasizes the flow of material and energy in a Chemical Typical Process Flow SheetA Hypothetical Process Flow sheetWhat is a Simulation flowsheet?A Simulation flowsheetis a collection of Simulation units to represent computer program (subroutines or models) that simulate the Process units and arcs to represent the flow information among the Simulation typical Simulation flow sheetA typical Process simulator subroutinesProcess Modeling and SimulationChemical ProcessSimulation(I) Chemical ProcessSimulation(II)Typical Process EquipmentsModeling and Simulation procedure Translating the description of a physical system into an appropriate mathematical form. Selecting a suitable computational technique. Implementing the computational technique in the form of a computer model is the simplification of realityused to predict system = maPhysicalModelPhysicalModelMathematical ModelMathematicalModelModeling and SimulationPhysicalsystemMathematical modelResultsandInterpretationLaws of +Rate+OthersEquation SolverMatlabMathCadCC-5 Aspen PlusHysisothersDefine processDevelop Math modelIdentify constraintDevelop computerprogramRun Simulation programAll parameterscovered?

4 Do model and optimumconditionsYesYesNoNoFlow chart of stepsin simulationGeneral Process Unit system Simulation degrees of design appropriate math AnalysisAnexampleFlash Drum in Vessel (1)A Flash Vessel (2)A Flash Vessel (3)A Flash Vessel (4)Defining Process VariablesMath. ModelInformation FlowinFlash CalculationsInformation Flow (1)Information Flow (2)Information Flow (3)Information Flow (4)Information Flow (5)Information Flow (6)Information Flow (7)Information Flow (8)A typical flash exampleChemical Process Simulation Process Flowsheet Simulation Flow sheetProcess FlowsheetSimulation FlowsheetNature of the Simulation nature of the Process nature of the material being nature of each type of Process specific Process feed stream propertyNature of the Process of the Material Being set values of the pure component properties of each Chemical component in the of the stream variables for the particular stream of interest to determine the temperature, pressure, and composition of the stream model for the thermodynamic and transport behavior of the typical set of pure-component properties for the cal nof thermo propertiesNature of the Process conservation laws: the principles of conservation of mass, energy, and rate laws.

5 relations between rate of flow, heat transfer, mass transfer, Chemical rxn, etc. and driving forces of temperature, pressure, conc., property relations : relations between the thermodynamic and transport properties and the intensive variables of temperature, pressure, and of thermodynamic equilibrium: limitations on the performance of physico- Chemical systems imposed by the 2ndlaw of control theory: relations governing the transfer of information through the topologyof the Process the description of which streams are connected to which inlet and outlet ports of which specificationsof all design and operating parameters that are under the control of the stream could be treated as a Process unit with an outlet and no stream could be treated as a Process unit with an inlet and no Simulation Modular Oriented Modular ApproachMethods of Analysis of System Structure the decomposition of large and precedence ordering units that must be solved together are identified in the flowsheet.

6 The sequence of computations of the partitioned subsystem are : resolving a cyclic partitioned unit to a acyclic variable selection : the best choice of design variables is to render the equations most of a Simulation ProgramExecutiveProgramUnitModule LibraryNumericalRoutinesPhysicalProperty Data BankThermodynamicPackageInputOutputSolut ionOptimizationEconomicAnalysisSequentia l Modular Process w/o recycles-Processes are solved sequentially one module at a Process with recycles-need to cut streams to enable the Process -Mix several inlet streams adiabatically to form one product Split a single inlet stream into two or more product streams with the same composition and Raise the pressure ofa gas by a specific -Raise the pressure ofa liquid by a specific Convert a liquid stream at one pressure to liquid and vapor streams in equilibrium at low Simulate a Chemical , EXTRACT, CRYSTAL, ABSORB Simulate the separation processes of distillation, extraction.

7 Crystallization, and absorption, Subroutine Library(I)Aspen Subroutine Library(II) Simulation of an Acyclic ProcessThe flowsheetshown here depicts a hypothetical multi-unit separation liquid streams are mixed adiabatically; The product streamis pumpedThrough a heater to a distillation column, and the overhead product from the column is partially condensed to yield liquid and vapor products. Using blocksMIX, PUMP, HEAT, DISTILL, and CNDS, construct a block diagram for theSimulation of this for separation of ammonia and water (I) Process for separation of ammonia and water (II)Acyclic Process Calculation sequenceEthylchlorideproduction Process flow sheet(I) Ethylchlorideproduction Process flow sheet(II)Recycle Process calculation sequenceEquation Oriented Approach All the equations of the whole Process are collected and solved as a large system of nonlinear algebraic equations.

8 Mathematically, the problem is formulated as an optimization problem, , Minimize h(x,u) Subject to f(x,u) = 0 ; Process model (x,u) = 0 ; Process xis the vector of state (dep.) variables, anduis the vector of decision (indep.) of Equation-Oriented approachSimulation of an equilibrium reaction/separation processDegrees of Freedom AnalysisSimulation EquationsNumerical SolutionSimultaneous Modular ApproachExecute Rigorous ModelsGenerate SimpleModelParametersSolved ReducedOptimizationProblemInsideLoopOuts ideLoopSteps of simultaneous modular the first iteration, make initial estimates of recycle stream the problem using the sequential modular obtained the first estimate of input and output values for each unit, construct a linear relationship between them, , linearizethe model the interconnection equations are already linear, solve the whole system of model and interconnection equations simultaneously using matrix method to obtain a new set of inlet two successive iterates of assumed stream values converge within a preset tolerance.

9 The Simulation is complete. Otherwise, go back to step (2).The scope of a Process Process design the effects of changes on plant operating energy bottlenecks and increase throughputRunning a up a a engineering the and printing resultsAspen-plus demoProcess Simulation withChemCadTypical ChemCadModule LibraryScope of ChemCadChemCadSimulation flowsheet, components, thermodynamic model, feed streams, equipment parameters, the program, , plot and output the reports and Process Flow SheetBe aware , Synthesis, and Design of Chemical Processes by Richard Turton, et al. Process Simulation by Applications in ChE by H. Th. and Simulation in ChE by R. G. E. Modeling, Simulation and control for Chemical Engineers by W. L. Process Computations by Principles of Chemical Processes, Chapter 10, by Richard M. Felder and Ronald W.

10 Rousseau, (CC-5) user guide.