1. Modular and Sequential Construction of Complex Process Models – Applications to Process Hazard Assessment Mordechai Shacham Dept. of Chem. Engng, Ben Gurion University of the Negev, Beer-Sheva Neima Brauner School of Engineering, Tel-Aviv University, Tel-Aviv Michael B. Cutlip Dept. of Chemical Engineering, University of Connecticut, Storrs

2.  Preparation and debugging of complex process models is a difficult and time-consuming task.  Combining the use of several software packages reduces considerably the time and effort required for constructing and debugging the simulation model  A complex model is broken down into smaller modules representing one unit operation or one stage of operation.  The modules are modeled and tested using a software package that requires minimal technical coding efforts.  The debugged modules are compiled to the format required by a more powerful and flexible programming language.  Finally the modules are combined to properly represent the complete and complex process model.

3. Simulation of an Exothermic Batch Reactor Reactants charged initially TT Temperature transm itter P TT Temperature controller Set point generator (”Cam”) Steam P steam, W s,  s T, V, C A, C B, X w X s T jo, P j, C j, F wo Cooling water inlet X set P c Products withdrawn finally Trap     V    A c Cooling water outlet Tj Condensate W c, T j A O Temperature sensor

4.  An exothermic liquid-phase reaction A → B → C is carried out in a batch reactor.  After the reactant is charged into the vessel, steam is fed into the jacket to heat the reaction mass up to the desired temperature.  Thereafter, cooling water is fed into the jacket to remove the exothermic heat of reaction  The objective of the simulation is to study the effects of operation in abnormal conditions:  reactant overcharging, failure to control duration of the steam heating, cooling water pipe blockage and cooling water failure of various durations in various phases of the reaction.

5. Model Equations – Heating Stage – POLYMATH Input

6. Constants – Heating Stage – POLYMATH Input

7. Heating Stage – POLYMATH Results

8. Model Equations - Cooling Stage – POLYMATH Input

9. Cooling Stage – POLYMATH Results

10. Model Equations - Cooling Stage – MATLAB Function

11. Combined Program – MATLAB’s Main Program Heating Period, Stiff Integrator Cooling Period, RK45 Integrator

12. Simulation Program – Changeable Parameters

13. Simulation Program – Operation Instructions

14. Batch Reactor Temperatures – Normal Operating Conditions >> batch_reactor K>> return

15. Batch Reactor Temperatures – Reactant Overcharging >> batch_reactor K>> CA0=1.0; K>> return

16. Reactant Overcharging – Heating Period Shortening K>> CA0=1.0; K>> Theatmax=125; K>> return

17.  The effort involved in construction of simulation programs for complex processes can be reduced using the "modular and sequential" approach.  This is achieved by using the most effective software tools for the various tasks.  The modules are modeled and tested using a software package that requires minimal technical coding efforts.  The executive program, written in a programming language, takes care of the interaction with the user, sequencing and integration of the results and preparing the report  Programs available at: ftp://ftp.bgu.ac.il/shacham/batchsim/ CONCLUSIONS