Around 15:35 on September 7, 2023

Ordos City, Inner Mongolia

Hangjinqi Yiding Ecological Agriculture Development Co., Ltd

High pressure gas leakage accident occurred in the gasification workshop

Causing 10 deaths and 3 injuries

As of April 2024

The accident caused a direct economic loss of 33.9414 million yuan. Recently, the website of the Emergency Management Department of Inner Mongolia Autonomous Region released the investigation report of the accident. After investigation, it was determined that the "9 · 7" major high-pressure gas leakage accident of Erdos Hangjin Banner Yiding Ecological Agriculture Development Co., Ltd. was caused by an illegal change in the position of a pressure transmitter for remote transmission in a pressure pipeline. The connection between the main pipeline and the vent flare pipeline, as well as the pressure measuring device's short section pipe, were severely blocked. The equipment maintenance was inadequate, and the operators commanded and operated in violation of regulations. A large number of on-site personnel gathered and dismantled the valve cover under high medium pressure in the main pipeline, resulting in a major production safety liability accident caused by the instantaneous leakage and spraying of high-pressure crude synthetic gas in the pipeline.

Basic information of the accident:

1. Accident unit: Erdos Yiding Ecological Agriculture Development Co., Ltd., jointly established by Yili Clean Energy Co., Ltd. and Shandong Energy Group Northwest Mining Co., Ltd., with a main product scale of 300000 tons/year of synthetic ammonia and 520000 tons/year of urea. 2. Superior company: Yili Jieneng Co., Ltd. Yili Jieneng Co., Ltd. has established the Kubuqi Industrial Division internally to unify the scheduling and management of safety, production, and operation of four enterprises including Yiding Company. The personnel of the division are composed of some management personnel from the four enterprises. Yili Clean Energy Co., Ltd. is a subsidiary of Yili Resources Group Co., Ltd.
2. Maintenance unit: Inner Mongolia Kubuqi New Energy Equipment Manufacturing Engineering Co., Ltd.
3. Special equipment testing unit: China Special Equipment Testing and Research Institute.

Accident process:

On August 17, 2023, Yiding Ecological Agriculture Development Co., Ltd. prepared an overall parking plan and a single plan for equipment maintenance, and reported it to the Hangjin Banner Emergency Management Bureau. The planned major maintenance period is from August 20 to September 16, and comprehensive maintenance will be carried out on air separation, thermal power, gasification, purification, synthetic urea, etc. On August 24th, the system was shut down for annual maintenance as planned. Prior to the shutdown, no abnormalities were found in the accident pipeline pressure gauge and pressure transmitter. On September 5th, Yiding Company began trial production. At 0:36 on September 7th, gasification furnace B was ignited and started. At 4:23 am, coal was added to gasification furnace B, and the furnace began to heat up and increase pressure. At around 9:22, the outlet pressure of the gasifier washing tower showed 3.06MPa and the temperature showed 154.72 ℃. Yang Liang, the deputy director of the fertilizer plant, arranged for personnel to organize the transformation of gasification and gas supply.

At around 11 o'clock, the section chief Qi Rentang found that the remote pressure transmitter (1210PI0001) displayed 0MPa and did not raise the pressure normally. Yang Liang arranged for the opening and closing of the vent valve to confirm the smooth flow of crude synthesis gas transportation. Qirentang's commanding personnel closed the vent valve, and the pressure displayed on the remote pressure transmitter was 3.11MPa. Opening the vent valve would quickly decrease the pressure. This process was repeated three times, with the third valve opening at 12:12:02 and the pressure displayed as 0.03MPa. At 12:37:55, the pressure displayed as 0MPa. Until the time of the accident, the vent valve remained open and the pressure displayed as 0MPa. During this period, on-site personnel Li Long repeatedly touched the vent pipe with his hand to confirm that the temperature was at room temperature. Yang Liang arranged multiple people to repeatedly operate and confirm the status of the regulating valve (17PV2004) and the accident valve (17MV2017), in order to locate the fault point. Around 12 o'clock

Yang Liang mistakenly judged that the accident valve had malfunctioned, resulting in a blockage that prevented the crude synthesis gas from being sent to the transformation process. After reporting the situation to Liu Gang, the director of the fertilizer plant, and Zhou Yu, the deputy general manager of the business unit, Zhou Yu decided to arrange for a shutdown for maintenance. At 12:33:24, Yang Liang returned to the central control room and pressed the stop button, causing the gasification system to stop. At 13:31, the outlet pressure of the gasifier washing tower (17PT2013) dropped to 0.25MPa, and nitrogen was blown three times. At 14:10, the pressure value showed 0MPa. 14:30

Li Peng, the general manager of the equipment manufacturing company, organized maintenance workers Ren Wei and others to inspect the accident valve. Ren Wei then organized workers Wu Nengqi and Men Guijun to begin dismantling the accident valve cover. Halfway through the bolt dismantling, five temporary external workers, including Wang Kanghui, Jing Hongwen, Liu Xiaogang, Liu Wangjie, and Gao Yafeng, arrived at the site to install the gantry frame and hanging the chain block, and continued to dismantle the remaining bolts. In violation of the requirements of the "Equipment Pipeline Opening Operation Guide", after disassembling all the bolts, the accident valve cover still cannot be removed. During this process, Liu Gang arrived at the scene, and there were a total of 10 people on the platform. At 14:45, Yang Liang arrived at the scene and judged that there was no gas pressure in the system based solely on the DCS indication of the outlet pressure of the gasification washing tower (17PT2013), the reading of the local pressure gauge (17PG2002), and the DCS indication of 0MPa from the remote pressure transmitter (1210PI0001). After observing the situation on site, let Ren Wei go and fetch a pry bar to pry open the accident valve cover. Ren Wei retrieved the pry bar, and Yang Liang began to pry the valve cover. During this process, the synthesis process engineer Feng Peiyun arrived at the site on his own, and there were a total of 12 people on the platform. From 15:10 to 15:33, safety officer Chai Fu, dispatch chief Wang Jiaqi, engineer Zhang Fei, deputy manager of the mobile department Wei Jian, deputy general manager Zhou Yu, and legal representative Kang Jie arrived at the scene one after another. At this time, there were a total of 18 people on the platform.

At 15:34, Hu Weiwei, the leader of the fourth shift of the gasification workshop working in other areas, and Bai Yongfei, the on-site inspector, heard on the intercom that Yang Liang needed a portable gas detector. They then arrived at the scene and handed the detector to Yang Liang. At this time, there were a total of 20 people on the platform. At 15:35, Yang Liang held onto the accident valve cover and commanded the on-site personnel to operate the hydraulic expander 4-5 times. High pressure gas was sprayed out, and the personnel working on the valve were impacted by the gas. After colliding with the north guardrail, they fell and died. The shock wave also caused injuries to personnel on the side of the accident valve. The accident caused the valve cover, valve stem, and valve plate (weighing a total of 556kg) of the accident valve to be thrown northward at high speed. The horizontal distance of the first landing point was 89.4m, and the horizontal distance of the second landing point was 112.4m. The upright pole of the fence was broken, and the length and height of the damaged fence were 7.6m and 1.1m, respectively. The electric actuator, handwheel transmission mechanism, and gantry of the accident valve are scattered on the ground in the north direction of the platform. The insulation layer at the lower bend of the pipeline on the north side of the valve was peeled off by the impact of the airflow, exposing the surface of the bent pipeline. The back side (south side) of the accident valve was not damaged by the accident. The direct cause of the accident was the unauthorized change of the position of the remote pressure transmitter in the accident pipeline. The connection between the main pipeline and the vent flare pipeline, as well as the pressure gauge and remote pressure transmitter short section pipe, were severely blocked. The display of the local pressure gauge and remote pressure transmitter was distorted, and the operators misjudged and dismantled the valve cover under the high medium pressure in the main pipeline, resulting in the instantaneous leakage and spraying of high-pressure crude synthesis gas in the pipeline. A large number of on-site operators gathered, leading to the expansion of casualties and causing significant casualties.

Suggestions for handling responsible personnel:

（1） Personnel exempted from accountability due to death (6 people): 1. Ren Wei, Deputy Director of the Maintenance Branch of the Equipment Manufacturing Company, and Head of the Major Maintenance Project of the Fertilizer Branch of Yiding Company. 2. Li Peng, General Manager of the Equipment Manufacturing Company and the first person responsible for the company's safety production. 3. Chai Fu, the safety officer of Yiding Company, is responsible for the safety management of gasification and purification equipment. 4. Yang Liang, Deputy Director of the Fertilizer Plant of Yiding Company, responsible for gasification and purification safety management. 5. Kang Jie, the legal representative and general manager of Yiding Company, is the deputy general manager of safety for the business unit of Yili Jieneng Company, and also fulfills the responsibilities of safety director of Yiding Company. He is the first person responsible for the company's safety production. 6. Zhou Yu, Deputy General Manager of the Business Unit of Yili Jieneng Company and Deputy General Manager of Yiding Company, in charge of the Fertilizer Plant.

（2） The judicial authorities have taken compulsory measures against 7 individuals. 1. Wang Gangjun, a safety engineer in the safety management department of an equipment manufacturing company, is responsible for the company's safety production management work. 2. Zhang Hailong, Deputy Manager of the Production Department (Maintenance) and Director of the Maintenance Branch of the Equipment Manufacturing Company, is responsible for coordinating the maintenance and repair of Yiding Company. 3. Hao Laijiang, Safety Director of Equipment Manufacturing Company. 4. Liu Gang, Director of the Fertilizer Plant and Special Equipment Safety Director of Yiding Company. 5. Wang Bo, Deputy Manager of the Business Unit of Yili Jieneng Company and the Safety Management Department of Yiding Company. 6. Jia Rangping, Deputy General Manager of the Business Unit of Yili Jieneng Company, and Acting Safety Director of Yiding Company (actually fulfilled by Kangjie). 7. Gao Zhijun, General Manager of the Business Unit of Yili Jieneng Company, responsible for the overall work of the Business Unit. In addition, 15 people including the safety officer of the equipment manufacturing company, the process engineer and safety engineer of Yiding Company, the person in charge and project leader of the Ordos area of China Special Inspection Institute, and the safety director, general manager, and chairman of Yili Jieneng Company were recommended to be given administrative penalties.

The start-up, shutdown, and maintenance operations of chemical plants are highly dangerous and risky. Once mishandled or abnormal, accidents can easily occur, especially due to the gathering of maintenance workers or other unrelated personnel at the scene of the incident, resulting in increased casualties or mass deaths and injuries. According to the "Guidelines for the Investigation and Management of Safety Risks in Hazardous Chemical Enterprises", enterprises should investigate densely populated areas and potential major risks in the factory area: (1) During the trial production and feeding period, there should be no construction operations in the area;

(2) Production workshops (areas) involving key regulated chemical processes such as nitrification, hydrogenation, fluorination, chlorination, and other reaction processes with a hazard level of 2 or above, with no more than 3 on-site operators at the same time;

(3) During systematic maintenance, no more than 9 people are allowed on the same work platform or in the same confined space;

(4) When there is an abnormal situation such as leakage in the device, strictly control the number of personnel on site. In addition, the "Guidelines for the Investigation and Management of Safety Risks and Hidden Hazards in Hazardous Chemical Enterprises" require that during the trial production process, enterprises should strictly control the number of people on site and strictly prohibit unrelated personnel from entering the site.

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