Use of Calorimetry for Management of Change
Legacy chemical processes, which are often decades old, are still being run in the chemical industry today. The products produced remain useful and the long operating experience generally results in dependable operations.
However, often through M&A changes or just the sheer length of time, aspects of the technical history of chemical processes can be lost. The people who developed these processes are often no longer available and full documentation of their work may no longer be accessible. Further, the process safety philosophy at the time of development may be very different than it is today. That may mean the questions we ask today concerning process operations and possible upset conditions may not have been asked during development.
This state of operations may work well so long as no changes are made or need to be made to these legacy processes. Problems, some serious, can arise when changes occur, either planned or unplanned. These problems can, in part, be traced to lost or missing appropriate information and expertise on chemical reactivity.
Example 1: In one process a solid residue slowly collected in a storage tank for one of the reactants and the tank needed to be cleaned. Like the reactant itself, the solid residue was acidic and water reactive. There was no process for disposal. Based on what seemed to be sound chemistry, the plan was to neutralize and then dispose the residue with caustic. When implemented, this resulted in the unexpected release of a large volume of gas. Fortunately there were no injuries, but this still considered a serious incident. Subsequent detailed process calorimetric studies were conducted to design a safe disposal process.
Example 2: The chemical process, itself, was to be moved to another facility, which actually represented a significant change, as the reactor volume, mixing, and cooling capacity were all different than the current reactor. Subsequent process calorimeter studies quantified the basic theromochemistry of this legacy process, allowing an efficient and safe transition to the new facility.
Example 3: Sometimes, legacy processes are also run in legacy equipment, which eventually needs to be repaired or replaced. One such operation ran flawlessly for decades, until a piece of equipment had to be replaced. The new system required the process to be run at higher temperatures, with no information available to determine if this temperature change could pose a problem. The temperature increase unfortunately resulted in a thermally initiated runaway reaction with loss of containment of the material. Fortunately, there were no injuries but this was still considered a serious incident. The initial thinking was that the process material in the incident was unusual in some way and not representive of typical material. Subsequent calorimetry testing quickly showed the onset temperature of a significant exothermic decomposition corresponded to the higher operating temperature at the time of the incident. For decades, this process had been operated at temperatures sufficiently below this onset region that no incidents occurred.
In conclusion, changes in chemical processes should be considered carefully. Questions asked about effects on chemical reactivity should be asked and answers provided by readily available calorimetry techniques. This is especially true for legacy processes, where important chemical reactivity data was either never determined or was determined but lost to time.