During catalytic production, reactor over-temperature and thermal runaway are the most frequent and high-risk abnormal conditions for exothermic reaction units. Over-temperature means the bed temperature of the reactor exceeds the allowable process range with a relatively mild temperature rise, which can generally be controlled through operational adjustments. Thermal runaway refers to severe thermal out-of-control, characterized by rapid temperature surge within a short period. Conventional adjustment methods can hardly stabilize the temperature timely, which may easily lead to equipment damage and safety accidents.
Root causes of over-temperature and thermal runaway fall into three categories: process operation, equipment operation and catalyst condition. Sudden rise of feed flow rate or concentration, or drastic fluctuation of material proportion will sharply boost reaction intensity inside the reactor, generating excessive heat beyond the heat dissipation capacity of the system and directly triggering temperature excess. Uneven material distribution and irregular catalyst bed loading inside the reactor tend to cause local material accumulation and hot spots. Continuous heat accumulation will further develop into overall over-temperature and even thermal runaway.
Equipment failures also serve as critical inducing factors. Scaling of heat exchange equipment or insufficient flow of cooling water/cold quench medium will weaken the overall heat dissipation performance. Malfunction or signal lag of temperature measuring and control instruments prevents operators from detecting temperature abnormalities in time, missing the optimal adjustment window. Besides, over-high activity of fresh catalysts and carbon deposition on catalyst beds will aggravate side reactions and worsen temperature rise.
Over-temperature and thermal runaway bring severe hazards to production. High temperature directly causes catalyst sintering and deactivation, greatly shortening catalyst service life and impairing product quality and yield. Severe thermal runaway will result in reactor overpressure, damage lining and sealing components, and even trigger material leakage, fire and other hazards. The unit will be forced into emergency shutdown, causing heavy economic losses.
On-site handling must be rapid and decisive.Minor over-temperature can be stabilized by reducing feed load, increasing cold quench medium dosage and improving heat exchange efficiency. Once thermal runaway occurs, cut off the feed immediately to stop exothermic reactions and curb continuous temperature and pressure escalation. In daily operation, stabilize feed parameters, maintain heat exchange and temperature measurement equipment regularly, standardize catalyst loading and operation management to prevent thermal out-of-control in advance and ensure stable and continuous unit operation.