On the afternoon of May 3, Wang Moumou, deputy director of the hydrogenation workshop, arranged the operation of the No. 1 hydrogenation reactor. At 13:41 the manhole of No. 1 hydrogenator was opened. Wang then gradually opened the vacuum valve on the kettle three times, causing a large amount of air to be sucked into the No. 1 hydrogenation reactor to form an explosive mixed gas with the ethanol vapor in the kettle. Then Wang Mou went to the mouth of the kettle, and rinsed the paddles of the No. 1 hydrogenator and the residual catalyst on the wall. During the rinsing process, the No. 1 hydrogenation kettle flashed, and Wang Moumou was "bumped" by the explosion shock wave.
Wang Moumou violated the regulations. In the state where the manhole of No. 1 hydrogenator was opened, it was not filled with nitrogen gas protection, but the vacuum pump was turned on, causing a large amount of air to be sucked into the reaction vessel to form an explosive mixed gas with ethanol vapor, and the catalyst Raney nickel was exposed to air. Spontaneous combustion, causing flash explosion, is the direct cause of the accident.