Research and Discussion on Process Issues Related to the Major Explosion Incident at Lianyungang Juxin Biotechnology Co., Ltd. on December 9
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The investigation report on the serious explosion that occurred at Lianyungang Juxin Biotechnology Co., Ltd. on December 9th has been available for some time now (there are many versions online; you can check them out). In line with the principle of learning from past experiences, I have analyzed the parts of the report related to the manufacturing processes. However, some aspects may not have been explained clearly, possibly due to my limited knowledge. Therefore, I’m posting this to discuss the matter and draw lessons from it. The cause of the accident was the backflow of nitrogen oxides in the exhaust gases (along with sulfuric acid) into the insulated tank, where they reacted chemically with the materials inside, releasing nitrogen oxide gases. Since air was used to push the materials around, this accelerated the reaction and led to excessive pressure. An emergency pressure release was carried out, but static electricity caused a fire (as the exhaust pipes were made of PP, which tends to generate static electricity?) At this point, the pressure inside the tank rises suddenly, causing the material to be ejected; this material then mixes with the air outside the tank to form an explosive mixture, leading to an explosion. Question 1: For nitrogen oxides to return to the insulated tank, they must pass through a diaphragm valve that is already closed (it wasn’t closed at first but was closed later), an activated carbon adsorption unit, and a vacuum pump in order to make their way back into the insulated tank. How is this achieved? Question 2: I don’t know what the explosive mixture mentioned in the report is Because I checked the substances involved, and none of them have an explosive limit. What exactly exploded? Question 3: Nitrogen oxides return to the insulated tank, where they react with the materials inside, releasing nitrogen oxide gases. What is this process?
It’s hard to say. The owner hid a lot of things; no one knows what exactly was being produced. It’s possible that secrets were kept throughout the entire process, from design and construction to production, which led to the explosion.
Production process of the accident device. M-phenylenedichloride is added to a dehydration tank, where it is heated and dehydrated under vacuum; thereafter it is placed in an insulated tank. Nitrogen is used to push the substance into a high-level tank, and after measurement it enters a chlorination reactor. There, at a certain temperature and under slight negative pressure, m-phenylenedichloride reacts with chlorine to produce crude m-dichlorobenzene, which is then refined through processes such as distillation and washing to yield pure m-dichlorobenzene. The distillation residues generated during the production process are subjected to vacuum distillation, resulting in the formation of Compound 1 (1,3,5-trichlorobenzene and m-dichlorobenzene), Compound 2 (1,2,4-trichlorobenzene), and Compound 3 (m-chloro***, m-dichlorobenzene, m-***, etc.). Compounds 2 and 3 are further mixed with dehydrated m-***benzene and placed together in a heat-retaining tank, where they are pressurized and stored in a high-level tank as raw materials for the production of m-dichlorobenzene. Changes in the pressing medium of the accident device. The medium originally used to push the materials in the insulated tank into the high-level tank was nitrogen; around June 2017, due to damage to the nitrogen generator, the company switched to compressed air without authorization.
The material composition is complex, and it’s difficult for non-professionals to explain clearly