External fire is one of the most dangerous situations that can occur at an ethylene oxide (EO) plant due to the possibility of decomposition of EO. Even with good water spray systems and well-insulated equipment, a flame falling from an external fire can lead to an increase in pipeline temperature and vessel wall temperature to the decomposition temperature of the EO in a short period of time. In this case, an internal explosion may occur.
Pump leakage
The leakage of the ethylene oxide pump seal is always a significant incident due to personnel exposure problems. However, if a pump seal leaks, the results can be catastrophic.
At the European ethylene oxide plant, there was a leakage of the EO pump seal, which was ignited on contact with parts of the hot pump. The flame from the pump seal fire fell on an uninsulated minimum flow return line, causing the EO in this line to evaporate. A further supply of heat from the ignition of the flame is allowed when decomposed in the minimum flow line. The decomposition reaction spreads into the reflux drum of the EO purification column where the explosion occurred. The reflux drum and the associated distillation column were destroyed. This incident concerned four dead. The plant was badly damaged and went down for four months.
Fire around the distillation column
A manufacturer of ethylene oxide in the United States had an EO compressor cylinder rupture. This led to a large fire that swallowed the EO distillation column. The resulting increase in temperature on the surface of the column and in the containing EO is taken into account in case of an internal explosion and significant damage.
Flange fire when the plant was lowered
The European producer of ethylene oxide experienced a flange leak in the EO distillation section. The plant was closed, but still contained an EO inventory. Leakage of the flange was eliminated in the event of a fire, and the flame fell on the process line containing the EA. Heat caused the reaction of decomposition of EO to the line. Decomposition spread through the line and into a distillation column. The head of the column was torn off and thrown 100 feet. Large and small parts of the jacket columns were scattered in a radius of 2000 feet. It took only 7 minutes between the start of the fire device and the explosion of the column.
Important notes regarding pumps and compressors in EO maintenance
- potential high temperatures if mechanical energy is not dissipated and
- possibility of fire due to leakage of seals.
A good example of avoiding mechanical energy is pump clogging. The two incidents described here are good examples of ethylene oxide pump performance. Pump leakage leakage is a good example of the potential leakage effects of a leakage seal.
The decomposition in the reflux pump extends to the Reflux drum and tower
The European producer of ethylene oxide had problems with excessive acceleration of the EO column cleaner pump. There were problems with the device with the level control on the drum for phlegm, and the incident was caused by the closing of the reflux control valve. The reflux pump worked dead, heading for the level control valve, causing the temperature in the pump to rise, evaporating the EO and causing a decomposition reaction. The decomposition spread through the suction line of the pump into the vessel with reflux where the explosion occurred. Shortly after the EO cleanup column exploded. This explosion resulted in four deaths. The plant was severely damaged and failed for four months
Decomposition of ethylene oxide in a blocked pump
The American manufacturer of ethylene oxide used high-speed centrifugal pumps to supply EO to two ethylene glycol units. The plant had a common spare feed pump for two glycol blocks. A spare pump was usually left free of EO, 200 psi under nitrogen pressure, and left with suction and double discharge valves closed.
A small amount of EO leaked through two blocked exhaust valves into the pump. A malfunction of the electrical system led to the launch of a high-speed centrifugal pump electric motor. The pump operated for about 10 minutes until the seal area of the pump reached the decomposition temperature of the EO, and the pump exploded.
The decomposition of 0.6 pounds of EO produced more than 450,000 pounds of force and caused a failure of twelve, 3/4 "nuts and stainless steel bolts. The pump and engine landed on the exhaust pipe of another EO feed pump that worked 750 psi, 80 gallons per minute EO. Unfortunately, the pipeline did not fail.
This article has been published in the journal Process Engineer Net.
