runaway reaction in a propylene hydrogenation reactor

During the start-up of a propylene hydrogenation reactor, very high temperatures were generated in the catalyst bed. At the time, propylene and hydrogen were being fed to the reactor which contained a granular catalyst. The temperature rose rapidly, and the hydrogen supply valve tripped at 176 degrees C. Despite the removal of the reactant supply, the temperature continued to rise to more than 600 degrees C. Temperature stabilised only after that the reactor had been isolated and depressurised (no injury or damage to the reactor).

The INITIATING CAUSE of this incident was over-hydrogenation, which in turn generated sufficiently high temperatures to begin polymerisation of propylene. The cause of the incident was identified in a wrong setting of the propylene/ hydrogen ratio as a result of faulty calibration of the flow instruments. The excess of hydrogen caused the temperature to rise to the point where spontaneous exothermic polymerization of propylene occurred. Investigation of the incident was hampered by the loss of the relevant instrument record charts. The wrong calibration and the lack of recording of the process parameters reveals severe shortcoming in the control of the plant operations

hydrogenation reactor

The broader context of this popylene hydrogenation reactor is not known. It could be related to alternative patways to produce LPG from CO2 through an indirect pathway via methanol/dimethyl ether and propylene/butene. In this process, the final step of this pathway is the hydrogenation reaction of olefins to produce paraffins.
[https://www.tandfonline.com/doi/full/10.1080/00986445.2024.2391845]

The hydrogenation of propylene converts propylene gas (C₃H₆) into propane (C₃H₈) through the addition of hydrogen over a transition metal catalyst:
C₃H₆ + H₂ → C₃H₈ (Exothermic reaction)
The process is usually done at mild temperatures above ambient temperature, but in this case, the run-away reaction triggered by the exothermic reaction caused temperature up to 600C. Pressure condition are unknown, it is probable that near ambient pressure at the start. 

No injury to personnel occurred as a result of this incident and there was no damage to the reactor shell

The following recommendations were made: 1. Stops should be fitted to key controllers/valves to limit flows in the event of a malfunction. 2. Situations where hydrogenation reactors are isolated or have only low flows through them during commissioning, maintenance or other operations should be identified and avoided. 3. The integrity of the trip system should be improved. 4. Good maintenance procedures are required to avoid the possibility of incorrectly calibrated transmitters being returned to process. 5. All records should be retained for a period, and should and incident occur, all relevant records should be impounded immediately (this last recommendation comes from the fact that the Investigation of the incident was hampered by the loss of the relevant instrument record charts).