Thermal screening of samples (crude reaction mixtures, distillation residues, single components, etc.) is used to reveal exothermic chemical reaction hazards and to identify the temperature range over which they occur. But the real chemical reaction hazards associated with an exotherm are the potential for pressure generation, not the temperature. The pressure may be the result of non-condensable gas generation or it may simply be due to the increasing vapour pressure associated with the sample. Any thermal screening that fails to measure pressure is seriously flawed. For this reason we abandoned DSC testing many years ago and now use the Thermal Screening Unit (TSu) for all our tests. The TSu can be used for ramped temperature tests, for isothermal tests or tests that combine sequences of temperature ramps and isothermal holds.
Studying the desired process
The SIMULAR reaction calorimeter is almost infinitely flexible in terms of both hardware and software: we can configure and operate it to simulate almost any sequence of batch or semi-batch operations. The reactor is usually glass (up to 10 bara) or stainless steel (up to 60 bara). The system can be operated with controlled liquid feeds and a gas feed such as to maintain either a constant rate or a constant pressure. All usual process variables can be controlled and logged and the system can operate under reflux conditions. Use of SIMULAR facilitates scale up that is both rapid and safe. We measure reaction enthalpy, predict the required plant cooling capacity and calculate the enthalpy 'accumulation' (and hence the potential for thermal runaway) during normal operations.
Revealing what could happen if things go wrong
Chemical processes should be designed so that they are 'robust', i.e. error tolerant. But if the chemical recipe that is used contains errors, the reagents are added in the wrong order, agitation fails, the temperature is out of range or the cooling is lost, then what is the worst that can happen- The Phi-TEC II adiabatic calorimeter is used to study these types of maloperation and to generate scaleable data. Without this type of information it is impossible to move towards inherently safer designs or to ensure that foreseeable maloperations will not lead to a major incident. The Phi-TEC II is used to measure the 'onset' temperature, the adiabatic temperature rise and the pressure generated during a runaway reaction. With low phi factor test cells the data can be used for reactor relief line sizing using the DIERS methodology.