Modular and Sequential Construction of Complex Process Models - Simulation of an Exothermic Batch Reactor

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. R e a c t a n t s c h a r g e d i n i t i a l l y i t t e r T e m p e r a t u r e t r a n s m P T T T T T j X s T e m p e r a t u r e S t e a m s e n s o r r P s t e a m , W , s s C o o l i n g w a t e r o u t l e t S e t p o i n t s e t T e m p e r a t u r e P X T , V , C , C , c g e n e r a t o r A B c o n t r o l l e r ( ” C a m ” ) A c A O T M C M C o o l i n g w a t e r i n l e t V M T , P F C r X j , j , j o w o w M T r a p C o n d e n s a t e W , T c j P r o d u c t s w i t h d r a w n f i n a l l y Simulation of an Exothermic Batch Reactor

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. CONCLUSIONS • 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/