Simular Reaction Calorimeter
Many chemical reactions in the CPI are performed in a semi-batch process under isothermal conditions. The DIERS methodology in sizing the relief system for runaway reactions is based on adiabatic conditions using the batch process. There are instances where a semi-batch process under isothermal condition is advantageous in significantly reducing the vent size or even possibly eliminating runaway reaction and the need for pressure relief. Singh [20] performed studies involving the esterification reaction between methanol (CH3OH) and acetic anhydride (CH3CO)2O at a constant temperature of 40°C in a calorimeter known as the SIMULAR.
The SIMULAR, developed by Hazard Evaluation Laboratory Ltd., is a chemical reactor control and data acquisition system. It can also perform calorimetry measurements and be employed to investigate chemical reaction and unit operations such as mixing, blending, crystallization, and distillation. Figure 12-24 shows a schematic detail of the SIMULAR, and Figure 12-25 illustrates the SIMULAR reaction calorimeter with computer controlled solids addition.
The instrument consists of a reaction vessel with a size range of 0.2-5.0 l and is made of glass, stainless steel, or any other suitable material and surrounded by a heating/cooling jacket. Silicone oil is circulated through the reaction vessel jacket and a heater/chiller unit before being returned to the jacket. The cooling/heating circulation unit is capable of operating from -50 - 300°C, and controlling temperatures to within 0.1°C. A glass condenser can be added for reflux operation at atmospheric pressure (Figure 12-26). Sensor signals such as reactor temperature, oil inlet and outlet temperatures, condenser inlet and outlet temperatures, condenser flow, calibration heater power, and stirrer speed are logged on a computer that monitors and controls the reactor performance.
Experiments were performed in the SIMULAR calorimeter using the "power compensation" method of calorimetry (note that it can also be used in the heat flow mode). In this case, the jacket temperature was held at conditions, which always maintain a temperature difference (~20°C) below the reactor solution. A calibration heater was used to
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