【Case Analysis】Explosion Incident During the Commissioning of a Ammonia-Alcohol Production Line Upgrade Project at a Chemical Plant in Dezhou, Shandong

Thread Content

At 23:50 on July 11, 2007, an explosion occurred during the commissioning phase of the expansion project for ammonia alcohol production at a capacity of 160,000 tons per year and urea production at a capacity of 250,000 tons per year, at a branch plant of a certain chemical group company in Pingyuan County, Dezhou City, Shandong Province. The accident resulted in 9 deaths and 1 injury. 1. Accident overview and consequences 1. Overview of the accident-affected company: The company was established in 2004 as a private joint-stock enterprise resulting from the restructuring of the former locally-owned Pingyuan County Fertilizer Factory. The annual production capacity of the main products is: 750,000 tons of synthetic ammonia, 1 million tons of urea, 300,000 tons of methanol, 240,000 tons of ammonium bicarbonate, and 30,000 tons of melamine. The accident occurred during the commissioning of the 160,000 tons per year ammonia-alcohol expansion and renovation production line at the first branch plant. This production line consists of process units such as gas generation, desulfurization, decarburization, purification, compression, and synthesis; the explosion took place in the outlet pipeline of stage 7 of compressor No. 2 in the compression section. 2. Accident details: The 160,000 tons per year ammonia-alcohol and 250,000 tons per year urea production lines at the company’s First Plant began single-unit testing in June 2007; the single-unit testing was completed on July 5, after which the project was inspected by the company itself. On July 10, the single-unit testing of Compressor No. 2 was completed, along with air pressure testing (up to 18 MPa) and carbon dioxide displacement. At 15:30 on July 11, the formal feeding and commissioning process began. Unit 2 compressor was started first, and process gas (a mixture of N2 and H2) was introduced, with gas being fed stage by stage to the seventh stage of Compressor 2 (operating pressure of 24 MPa) for testing purposes. At 23:50, the outlet pipeline of stage 7 of compressor No. 2 suddenly exploded; the gas leak triggered a fire that resulted in 8 deaths on the spot. Another person died at 00:10 on the 14th due to severe burns despite efforts to save them, while 1 person suffered minor injuries. The accident also caused part of the factory roof to collapse and the instrument panels to burn out. Two explosions occurred one after another at the time of the accident. Following an investigation and analysis of the accident site, one explosion point was located in the pipeline 1 meter ahead of the first angle valve, after the oil-water separator at the outlet of section 7 of compressor No. 2; the other explosion point was in the pipeline between the two angle valves at the outlet of section 7 of compressor No. 2 (with the first angle valve closed and the second angle valve open). II. Analysis of the accident causes 1. Immediate cause of the accident According to analysis, this explosion was a physical explosion. The direct cause of the accident was issues such as insufficient strength in the seventh-stage outlet pipeline of Compressor No. 2, poor welding quality, and the failure to conduct pressure testing on the pipeline before use. 2. Major management issues: (1) The construction project was carried out without undergoing a safety review. The company split the 160,000 tons per year ammonia alcohol and 250,000 tons per year urea expansion project (with a total investment of 97.24 million yuan) into two separate projects: the \"Technical renovation project for gas generation and compression processes at Fertilizer Plant No. 1\" (with an investment of 48.68 million yuan) and the \"Technical renovation project for ammonia synthesis and urea production at Fertilizer Plant No. 1\" (with an investment of 48.56 million yuan). Work on these projects began after they were registered with the Dezhou Economic Commission in Shandong Province on April 26 and May 30, 2006, without any application being submitted to the local safety authorities for a safety review of the construction projects. (2) The project management for construction projects is chaotic. This project does not have a unified design; construction is carried out based solely on the feasibility study report. For some units, design, manufacturing, and installation are procured through a single tender, while for other units, the company handles the design itself, sources materials from the market, and hires contractors for construction; in yet other cases, construction is carried out directly using existing drawings. Compressor No. 2, which is related to the accident, was manufactured by Shenyang Jinbo Gas Compressor Manufacturing Co., Ltd., and this company was also responsible for the design of the auxiliary pipelines ahead of the compressor’s outlet valve. The project failed to select qualified construction and installation units for the work in accordance with the relevant provisions of the Regulations on Quality Management of Construction Projects. A thorough testing plan was not developed before the trial run, and the high-pressure pipelines were not subjected to hydrostatic testing before being put into use. (3) Refusing to comply with the regulatory orders from safety supervision authorities to suspend construction and testing. In January 2007, the safety regulatory authorities in Dezhou City and Pingyuan County discovered that the company did not possess a permit for the safe construction of the project, and ordered it to halt construction. Only then did the company begin to obtain the necessary permits for the safe construction of hazardous chemical projects; however, it continued with the construction work during this process. On July 7, when the Dezhou Safety Supervision Bureau organized an expert team to conduct a review of the safety permits for this project, it was clearly stated that the layout of the project and the distances between certain installations did not meet the required standards. The company was ordered to make necessary corrections promptly; however, it proceeded with trial operations without making those adjustments, and an explosion occurred during those trials.