Investigation Report on the Explosion of the Slag Cooler in the “4•22” Unit of the Xinjiang Qinghua Coal-to-Natural Gas Project

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Investigation Report on the “4•22” Cold Slag Machine Explosion Incident at the Xinjiang Qinghua Coal-to-Natural Gas Project Author/Source: Date: 2017-06-29 Clicks: 30 At around 16:20 on April 22, 2017, local time, an explosion occurred in a cold slag machine in the thermal power plant of Xinjiang Qinghua Energy Group Co., Ltd., resulting in the death of one worker. After the accident, the party committees at the state and county levels attached **great importance to it. On that day, in accordance with the relevant provisions of the Work Safety Law of the People’s Republic of China, the Regulations on the Reporting, Investigation and Handling of Production Safety Accidents, and the Implementation Measures for the Reporting, Investigation and Handling of Production Safety Accidents in the Xinjiang Uygur Autonomous Region, the county people’s government authorized the establishment of an accident investigation team composed of departments such as the County Work Safety Supervision Bureau, Public Security Bureau, Human Resources and Social Security Bureau, General Trade Union, and the Management Committee of Yidong Industrial Park, as well as externally hired experts, to conduct investigations and gather evidence regarding this accident. An accident analysis meeting was held on June 15, 2017, during which consensus was reached regarding the course of the accident, its causes, nature, allocation of responsibilities, and actions to be taken against those responsible. The details are reported as follows: 1. Time of the accident: Around 16:20 on April 22, 2017, according to Beijing time. 2. Location of the accident: The thermal power plant of Xinjiang Qinghua Energy Group Co., Ltd. 3. Entity involved in the accident: Xinjiang Qinghua Energy Group Co., Ltd. 4. Type of accident: Container explosion (not related to special equipment). 5. Basic information of the deceased: Shawukaiti Rejapov, male, Uyghur, born on August 15, 1976, aged 41; his residential address is Group 6, Wurilek Village, Quluhaixiang, Yining County, Xinjiang; his ID number is 654121197608152330. He is an employee of Xinjiang Qinghua Energy Group Co., Ltd. VI. Nature of the accident: Liability accident. VII. Direct economic losses: 1.01 million yuan. VIII. Overview of Xinjiang Qinghua Energy Group Co., Ltd.: Xinjiang Qinghua Energy Group Co., Ltd. is located in the Yidong Industrial Park in Yining County, Ili Kazakh Autonomous Prefecture, Xinjiang. It serves as the base for Xinjiang Qinghua’s coal-to-natural gas demonstration project; the core of this project is the production of 5.5 billion cubic meters of coal-to-natural gas per year. Additional facilities include a 600,000-ton coal tar hydrogenation plant, an ammonia synthesis plant, a thermal power plant for comprehensive utilization, and a plant that produces 2 million tons of cement from fly ash per year. The total investment in the construction of this coal-to-gas project is 27.8 billion yuan. Once the entire coal-to-natural gas project is operational, it will generate annual sales revenue of 16 billion yuan and profits and taxes of 2.5 billion yuan, while creating more than 10,000 direct or indirect jobs. Xinjiang Qinghua’s coal-to-natural gas project, with an annual production capacity of 5.5 billion cubic meters, is the first modern coal chemical project in Xinjiang to receive **-level approval. It is also the largest **-level demonstration project among private enterprises in China in terms of scale. IX. Accident course and rescue efforts: The thermal power plant of Xinjiang Qinghua Energy Group Co., Ltd. is equipped with 5 high-pressure (10 MPa, 540°C) fluidized bed boilers with a capacity of 280 t/h each, which generate steam for power generation as well as for other mechanical devices. The operation mode is 4 units in use and 1 unit on standby. The boilers were manufactured by Jiangsu Wuxi Huaguang Boiler Factory; each boiler is equipped with 2 drum-type slag coolers, which were produced by Jiangsu Dongan Special Steel Machinery Equipment Co., Ltd. Boiler No. 1 was put into low-load trial operation in November 2012 and has been operating stably for 4 years to date. It was shut down for maintenance on March 21, 2017, and restarted on April 11. The boiler itself and its auxiliary equipment (including the slag cooler) are functioning properly, and no abnormalities have been detected by the company. On April 18, workers from Shift 4 of the thermoelectric workshop discovered that the safety valve of the slag cooler on the south side of Boiler No. 1 was leaking. The workers on duty closed the inlet and outlet valves of the slag cooler, resulting in its shutdown. At around 15:00 on April 22, 2017, local time in Jingzhou, Xiao Wukaiti Rejafu and Shih* Sheng Maheshati Serihazhi, workers from Shift 3 of the thermal power plant at Xinjiang Qinghua Energy Group Co., Ltd., were assigned by their shift leader Zhao Guohui to go to the zero-meter level of the boiler house to carry out slag removal operations on Boiler No. 1 and Boiler No. 2. Upon arriving at the work site, Shawukaiti Rejgafu carried out slag removal operations at the cold slag extractor on the south side of Boiler No. 1, while Maheshati Seryahaz was responsible for slag removal at Boiler No. 5. At around 16:20 local time, the cold slag extractor on the south side of Boiler No. 1 suddenly exploded. The cylinder of the cold slag extractor was pushed 14 meters to the west due to the reaction force; the inlet and outlet pipes on the east side of the device were broken, and the slag discharge pipe was damaged. The end cover on the exit side of the water chamber of the cold slag extractor came loose and fell off, with pieces of the machinery flying out and hitting Shawukaiti Rejapov, causing him to be injured and fall to the ground. At that time, Li Bo, the shift supervisor in the control room of the boiler house, noticed that the primary fan of Boiler No. 1 had tripped, and he reported the situation to Liu Jianjun, the director of the thermal power workshop. When Liu Jianjun arrived at the south gate of the boiler room, he saw steam escaping from beneath Boiler No. 1, along with slag coming out as well. Subsequently, Liu Jianjun took charge of the search and rescue operations and found Shawukaiti Rejagap lying injured on the ground. He immediately reported the accident to the company’s management and the Safety and Environment department, and also directed the control room to isolate and shut down Boiler No. 1. After the on-site ambulance and fire truck arrived, they rescued the injured Shawukaiti Rejgap and transported him to Yining County People’s Hospital for treatment. Upon arrival at the hospital, doctors diagnosed that Shawukaiti Rejgap had died. X. Causes and nature of the accident: (I) Direct cause of the accident: Shawukaiti Rejgap made a mistake while carrying out slag removal operations, which led to the vaporization of the cooling water in the cooling chamber of the slag cooler. This resulted in the generation of a large amount of steam rapidly, causing a sharp increase in pressure. The pressure exceeded what the cooling chamber could withstand, and a large amount of energy was released suddenly, transforming into mechanical energy. This led to a rupture at a weak point, which was the direct cause of the accident. (II) Indirect causes of the accident: 1. Xinjiang Qinghua Energy Group Co., Ltd. failed to conduct adequate risk identification and to address potential accident hazards; it ignored the significant safety risks associated with the slag cooling machine, and failed to detect and effectively rectify the existing accident hazards in a timely manner ； 2. Xinjiang Qinghua Energy Group Co., Ltd. failed to install clear status identification markers and other safety warning signs on the equipment that had been shut down due to significant risk factors ； 3. Xinjiang Qinghua Energy Group Co., Ltd. provides inadequate safety production training and education; its workers have a weak sense of safety and lack knowledge of safe operating procedures ； 4. The water supply system for the slag cooler is poorly designed and inadequately configured ； 5. The control and protection mechanisms are inadequate. The water cut-off protection did not activate; there is no pressure gauge behind the cooling water inlet valve of the cold slag machine, and no thermometer in front of the outlet valve. There is no monitoring or protection in case of overheating or overpressure during equipment operation ； 6. The instrument protection system for the slag coolers at Xinjiang Qinghua Energy Group Co., Ltd. is not regularly calibrated to ensure it remains in proper working condition ； 7. The boiler operation procedures of Xinjiang Qinghua Energy Group Co., Ltd. do not match the actual conditions, and they have not been improved in a timely manner. XI. Division of responsibilities and handling recommendations: (I) Entities and individuals recommended for administrative penalties: 1. Xinjiang Qinghua Energy Group Co., Ltd.: Inadequate identification of safety risks and investigation and resolution of potential accident hazards ； No obvious status identification markers or other safety warning signs have been installed on the decommissioned equipment that presents significant risks ； Inadequate safety production training and education ； There is no practice of regularly calibrating the instrument protection for the cold slag machine to ensure it remains in good working condition. It violated the relevant provisions of Article 25, Paragraph 1, Article 32, Article 33, Paragraph 2, and Article 38, Paragraph 1 of the Work Safety Law of the People’s Republic of China, and is liable for the management aspects related to the occurrence of the accident. It is recommended that the Work Safety Supervision and Administration Bureau of Yining County impose administrative penalties on Xinjiang Qinghua Energy Group Co., Ltd., the entity at fault in the accident, in accordance with Article 109, Paragraph 1 of the Work Safety Law of the People’s Republic of China. 2. Liu Fusheng, General Manager of Xinjiang Qinghua Energy Group Co., Ltd.: As the primary person responsible for safety in the enterprise, he failed to establish adequate safety management systems and operating procedures for the slag cooling machines; he also did not adequately supervise and inspect the safety measures in place at his company, failing to eliminate potential hazards related to production accidents in a timely manner. It violated the relevant provisions of Article 18, Items 2 and 5, of the Work Safety Law of the People’s Republic of China, and bears leadership responsibility for the occurrence of the accident. It is recommended that the Work Safety Supervision and Administration Bureau of Yining County impose administrative penalties on Liu Fusheng, who bears leadership responsibility, in accordance with the relevant provisions of Article 92, Item 1 of the Work Safety Law of the People’s Republic of China. (II) Other handling suggestions: 1. It is recommended that Xinjiang Qinghua Energy Group Co., Ltd. take appropriate action against the relevant responsible persons in accordance with its internal rules and regulations, and report the results of such actions to the Yining County Work Safety Supervision Bureau. 2. It is recommended that the Human Resources and Social Security Bureau of Yining County handle the matters related to the funeral arrangements and compensation for the deceased, Shawukaiti Rejaf, in accordance with the provisions of the Work-related Injury Insurance Regulations, and report the progress of these actions to the county’s Work Safety Supervision Bureau for record-keeping. XII. Preventive Measures and Recommendations 1. Xinjiang Qinghua Energy Group Co., Ltd. should hold a company-wide staff meeting to inform them of the details of the accident, draw lessons from it, carry out accident-awareness education, and use this incident as a typical case to provide safety training for the company’s employees ； 2. Immediately conduct a comprehensive safety inspection throughout the company, and promptly eliminate and rectify any existing safety hazards ； In strict accordance with the requirements of the \"Guidelines for the Identification and Rectification of Hazardous Incident Risks in Chemical Hazardous Enterprises\", we will further improve our company’s system for identifying and addressing such risks, and enforce it strictly ； 3. The company’s top management must ensure that the safety production responsibility system is strictly implemented among all employees, with responsibilities assigned to specific departments, workshops, positions, and individual persons. 4. Establish a specific management system for marking the status of equipment, and enforce it strictly; strengthen the management of the usage status of equipment and facilities to prevent errors in their use. 5. Reform the water supply system for the slag cooler to ensure stable flow in the water chamber; install safety valves, flow meters, pressure gauges, and thermometers to provide protection against water supply interruptions, and feed the measurement signals back to the boiler control room. This enables strict monitoring of various parameters related to slag discharge, thereby preventing the equipment from experiencing overpressure. All testing instruments for the five furnaces must be regularly calibrated to ensure their accuracy and effectiveness ； 6. Immediately organize the revision and improvement of the operating procedures for the cold slag machine, to clarify the key points for safe operation. At the same time, organize boiler operators, relevant management and technical personnel to study the accident reports and the revised operating procedures ； Exams are conducted, with strict evaluation; those who fail must leave their posts to continue learning and are not allowed to take up their duties ； 7. Strengthen safety management by learning from the management practices of advanced enterprises; it is recommended that cold slag machines be included in the category of pressure vessels for management within the enterprise ； 8. Provide feedback to the cold slag machine manufacturers, listen to their analyses, discuss possible improvement measures, and implement them in new orders. Attachment: List of members of the investigation team for the “4•22” cold slag machine explosion incident. Investigation team for the “4•22” cold slag machine explosion incident, June 15, 2017