On 11 September 2014 an exothermic chemical reaction at an organic chemical company got out of control, leading to the loss of the container contents and considerable damage to the plant. The exact circumstances and causes of the incident are still being investigated. The details of what triggered the incident are still not known. The temperature in the reactor increased. A member of staff attempted to stop the temperature increase by exchanging the cooling water for brine. On observing rapid gas development, he partially closed the steam shut-off valve, which had been completely open, in order to prevent a pressure surge in the connected glass apparatus. On the controls immediately adjacent to the reactor, reactor pressure was at 6 bar (and climbing) and a temperature of 123 °C was displayed.

Subsequently, a pressure surge must have occurred that was so strong that the seal between the dome cover and the base of the reaction vessel was forced out and partially destroyed. This sprayed the largely gaseous reaction mixture into the production room on the floor above, despite the safety devices having activated (the blowdown container caught around 40 kg of the mixture). The glass safety valve in the water vapour pipe (0.3 bar) most likely also activated, but a glass bend in the supply pipe nonetheless burst, releasing more of the product into the work area. A week previously, the same reaction had been carried out without incident. The heat development was familiar and the gas development was as expected (recognised by very slight foaming close to the stirrer vortex). This was the same as in the laboratory tests carried out. The safety valve and the rupture disc to protect the container (6 bar) activated, leading to around 40 kg of product being released into the blowdown container.

At the time of the incident, 670 kg of formic acid had been mixed with 144 kg of hydrogen peroxide 35 % and tempered for half an hour at 30 °C. It was then heated to 40 °C and 12 kg out of 120 kg of 1-octene was added while stirring continuously. The addition process was stopped because the internal temperature had reached 50 °C. (Controlled amounts are added to keep the product temperature at 45-50 °C.)

Immediate evacuation of the site, activation of ‘fire alarm’, assembly at assembly point. Following clearance from the fire service, the area was inspected. At that point, the lighting and stirrer in the reactor were still operating. In conjunction, preliminary cleaning of the production area was carried out in order to avoid further corrosion damage. The cleaning water was collected. Further cleaning took place after a risk assessment and corrective action. After checks on the electrical installation, equipment was turned off in order to guarantee safety. They could only be put into operation again after parts had been repaired or replaced and tested.
– Initial cleaning of the affected area with water by the fire service;
– The waste water was pumped by operating staff from the collection area into an emergency tank;
– Cleaning and testing of equipment in the affected area;
– Cordoning off of the site;
– Setting up a decontamination bath;
– Measurements in the surroundings;
Evacuation of the site using announcements and the fire alarm, which had activated. Roll-call against presence list. The fire service decontaminated the area around the boiler and significant puddles with a light jet. The rest of the clean-up was carried out internally. The flushing fluids were collected and disposed of by the company. Repairs to the damaged reactor and the floor, including replacing anti-corrosion treatments. Replacement of the boiler control display and other damaged electronic components.

From the reconstruction of the incident and the situation analysis, the reactor’s thermal runaway as a result of the degradation of performic acid was identified as the probable cause of the explosion. In addition, the investigations into the cause showed that a number of circumstances had contributed to the incident. Among other things, the following deficiencies were identified:
– missing chemical kinetic data for the planned reaction;
– lack of knowledge of the heating and cooling capacity of the reactors;
– no systematic risk analysis or considerations regarding scaling-up;
– insufficient cooling capacity owing to a partial malfunction of the cooling system;
– selection of an unsuitable reactor to carry out the reaction in question;
– considerable deficiencies in SMS and operational organisation.
The multiple changes of operator and the transition from being part of a large group with central safety operations to being a contract manufacturer no doubt contributed to the insufficient capacity of the SMS. Unexpected temperature and pressure development.

As a result of the investigation, additional protective measures are regarded as reasonable and recommended in order to prevent the occurrence of similar incidents in the future.
1. Ceasing production of 1,2-Octanediol using the existing production directions.
2. General assessment of the safety data and a risk analysis prior to production. Compliance with data sheet R 005 from the German Social Accident Insurance Institution for the Raw Materials and Chemical Industry (BG RCI): ‘Transfer of chemical syntheses from the laboratory to industry’, 4/2012.

3. Compliance with TRAS 410 ‘Recognising and controlling exothermic chemical reactions’, version 10/2012 for production involving exothermic reactions.
4. The cold water system and the cooling water supply are essential components with regard to safety and must be better managed, monitored and protected. This includes an updated plan of cooling capacity needs, maintaining a sufficient cooling reserve, safety alarms and switching operations, and an effective emergency cooling system for the reactor.
5. Organisational structures must ensure that departures from the setpoints generate an alert and that the cause is investigated.
6. All measurements should be displayed and recorded both locally and centrally. The data storage should enable subsequent evaluation.