Process Flowsheeting

Mass Balance
1. The Phase Rule
  1. DOF = n - π + 2
    1. Specify variables
      1. Simulation problem
        feed stream and unit parameters
      2. Design problems
        Other specifications
2. Calculation Procedure
  1. Sequential Modular
    1. uses matrix representation to solve the flowsheet by solving each set of equations for each unit in order of which they appear in the flowsheet.
    2. 1. Guess values for stream 4
      1. 2. Using these values, solve for streams 2, 3, 5 and new set of values for stream 4
        3. Modify the guessed values for stream 4
        4. Redo the flowsheet calculations until calculated values are equal to the guessed values for stream 4
        5. When the two values are essentially the same, the procedure is said to have converged
        What is essentially equal? When comparing the guessed value and calculated value for stream 4, a ‘tolerance’ or ‘ԑ’ value may be set as an acceptable accuracy (10-3 , 10-7 etc.)
        Successive substitution
        ADV: simple, easy to implement DIS: may diverge (unlikely), very slow rate of convergence
        Convergence acceleration techniques
        ADV: faster convergence DIS: possible divergence, more complex implementation
  2. Equation Oriented
    1. uses matrix representation of material and energy balance problems to solve the flowsheet. It solves the equations simultaneously.
    3. occurrence matrix
      1. When the matrix is square, the degree of freedom is zero – this means the number of equations is equal to the number of variables, hence a solution can be sought.
      2. Jacobian matrix (refer to slides on equation solving methods) to find a solution.

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Process Flowsheeting

Beschreibung

Zusammenfassung der Ressource

Medienanhänge

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