Malfunction and Process Deviation Testing

A part of the test plan must include testing for the consequences of equipment malfunction, deviations in process conditions, and human error. Bench-scale equipment, for example, the RC1, is quite suitable for such experiments. By analysis of the process, critical conditions can be defined, which then need to be tested in order to be able to proceed safely from the laboratory to pilot plant studies. In testing abnormal conditions or process deviations, caution is required to assure that no uncontrollable hazard is created in the laboratory. Typical deviations, including impact on the process, are discussed in the following paragraph. 

Agitation failure during a reaction can affect the following system parameters  

The state of mixing generally controls tire mass transfer. In a liquid-liquid system, for example, the reaction rate is based on the mass transfer which depends on the interface area of the two liquid layers. This area is dramatically changed by a change in the mixing rate. If, for example, the agitator is started late, the increase in mass transfer area will lead to a rapid increase in the conversion rate and hence in the heat production rate. 

Insufficient mixing may lead to a poorly dispersed system which can result in an accumulation of reactants. The reaction may not start readily or perhaps will start only after a considerable accumulation of reactants leading to a runaway. 

If agitation fails during a semi-batch operation, the transfer of heat will essentially stop. The resulting increase in temperature depends on the concentration of the reactants at that moment, the global kinetics, and the mass transfer rate. The effect of the temperature increase is easily simulated in a reaction calorimeter both with and without addition of reactants. 

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