Why can’t liquid chlorine cylinders come into direct contact with the reactor?

The buffer mainly serves an isolating function. To prevent the material from being sucked back into the chlorine cylinder when the reactor pressure exceeds the pressure inside the cylinder.

To prevent the material from flowing back into the liquid chlorine cylinder; in the past, some manufacturers have experienced serious accidents as a result of this, and the buffer cylinder acts as a one-way valve

Explosion of a liquid chlorine cylinder. Date of occurrence: September 7, 1979. Incident location: a factory in Zhejiang. Course of the accident: A 0.5-t capacity electrolytic 30-grade steel cylinder in the liquid chlorine section suddenly exploded. Following the loud explosion, the entire plant was filled with smoke, and large amounts of vaporized liquid chlorine along with chemical reaction products rapidly formed a huge mushroom-shaped plume that rose into the sky. At the center of the explosion, a 1-ton steel cylinder containing liquid chlorine, with a total weight of 1735 kg, was lifted vertically by the shock wave; it flew over high-voltage power lines at a height of 12 meters, broke through the roof of the salt storage facility, and fell inside the salt warehouse located 303 meters away from the explosion site. Another one-ton liquid chlorine cylinder, with a total weight of 1754 kg, was also blown 20 meters away by the shock wave and fell into the lotus pond located to the west of the liquid chlorine packaging facility. The blast generated a wide range of fragment waves; one fragment weighing 0.8 kg was thrown 830 meters away, while a steel cylinder lid weighing 72.5 kg flew over the factory area to a distance of 85 meters from the explosion site, breaking tree trunks, passing through the brick walls of residential houses, and killing an elderly person. The explosion site left a crater with a diameter of 6 meters and a depth of 1.82 meters. The factories and equipment have been severely damaged. The fragments of the steel cylinders after the explosion caused 4 of the 59 cylinders present at the site to explode as well. In addition, 5 were punctured, and 13 were injured or severely deformed. The explosion also caused the 414 m2 mixed-structure packaging plant in the liquid chlorine section to collapse completely; part of the adjacent brick-and-wood structure freezer plant was damaged as well. A 5-ton electric crane crashed, its wires were broken, and multiple I-beams were damaged. Two 3-ton weighing scales were destroyed, the 5-ton measuring tank leaked, and a valve on the 10-ton liquid chlorine tank was broken; all the pipelines in the liquid chlorine section were damaged as well. The 8 operators on duty died on the spot. The 10.2-ton wave of chlorine gas that spread following the explosion covered an area of 7.35 km2, resulting in 59 deaths and 779 cases of poisoning. The electrically charged cylinder No. 30 that exploded was manufactured by Beijing Metal Structure Factory, made of 16MNR material, with a filling capacity of 0.5 tons. The bottle was purchased in August 1978 and put into use in December; it has been used a total of 16 times. On August 29, 1979, it was filled and sent to the city’s pharmaceutical chemical plant; the empty bottle was returned on September 3, and after being filled with chlorine on September 7, an explosion occurred at 13:55 on that same day. The Ruihua Model 45 cylinder and the Ruihua Model 9 cylinder were manufactured by Hangzhou Chemical Machinery Factory No. 2; they are made of 16MNR material, have a filling capacity of 1 ton, and a weight of 567 kg. They exploded as a result of being struck by the explosion debris from the Ruihua Model 30 cylinder. Two more 1t and 0.5t cylinders also exploded as a result of being struck by the explosion debris from the No. 30 cylinder. Cause analysis: (1) The production process in the chlorinated paraffin section of this factory does not comply with the relevant regulations set by the Ministry of Chemical Industry; no buffer is installed between the liquid chlorine cylinders and the chlorination reactor, and chlorine gas enters the reactor directly through copper pipes from the needle valves on the cylinders. The operators in the chlorinated paraffins production section of this plant violated the relevant provisions of the **Regulations on Safety Supervision of Gas Cylinders**; when the pressure of chlorine in cylinder No. 30 made of electrochemical steel was similar to the pressure in the chlorination reactor, they still illegally started the vacuum pump to draw all the air out of the cylinder. According to the factory’s production records, 813.3 kg of semi-finished products were supposed to be produced, but in reality only 700 kg were produced. The missing semi-finished product, paraffin, flowed into the No. 30 electrochemical steel tank, creating a potential hazard. (2) The liquid chlorine filling personnel on duty at the plant where the accident occurred violated the **Regulations on Safety Supervision of Gas Cylinders** and relevant regulations issued by the Ministry of Chemical Industry; they failed to check whether there was any residual pressure inside the electrochemical 30-type cylinder before filling it with liquid chlorine. It was not checked what kind of foreign substances were present inside the cylinder, nor was the weight measured; instead, the filling volume was calculated based on the tare weight indicated on the cylinder’s stamp, after which liquid chlorine was added. This caused the liquid chlorine to react with the paraffin in the cylinder, and under the catalysis of ferric trichloride remaining in the cylinder, a large amount of heat was generated. Once a certain critical threshold was reached, a violent and uncontrolled reaction occurred, resulting in the cylinder exploding violently. Lesson: (1) Strictly follow the requirements of gas cylinder safety supervision regulations when filling, using, transporting, and storing hazardous gases. (2) Provide general education to the employees of chlorine production and utilization units as well as the residents living near these enterprises regarding the properties of chlorine, its harmful effects, clinical symptoms, and prevention methods. (3) Medical staff in factories, mines, enterprises, hospitals, and health clinics that produce and use chlorine should learn* and master the rescue methods for chlorine poisoning. (4) Units that produce and use chlorine gas should be equipped with a sufficient number of filter-type, isolation-type, and other types of gas masks.

It mainly prevents reaction materials from entering the steel cylinder and causing accidents.