4 people injured in a fire at a desulfurization tower in Xi’an – how to prevent such incidents?

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Recently, a fire broke out at the Zhuque Heat Power Company on Guangda South Road in Xi’an. The fire lasted for nearly 3 hours; thick smoke filled the sky, and ashes kept falling within a radius of one kilometer. The fire injured one construction worker, and three firefighters suffered burns of varying severity. Plastic foam caught fire during the cutting of a desulfurization tower. At 3:32 p.m., Shaanxi Fire Department’s official Weibo account announced that at 11:20 a.m. that same day, the Xi’an Fire Brigade received a report from citizens stating that there was a fire at the Zhuque Thermal Power Company on Zhuque Road in Yanta District. Upon receiving the call, the command center immediately dispatched 14 vehicles and 80 personnel from the Yanta West Road Squad, Xihuamen Squad, Fenglin Road Squad, Special Operations Squad 1, and Taiyi Road Satellite Fire Station in the jurisdiction to the scene for handling the situation; the full-staff command post of the brigade was also sent out. At 11:35, the Yanta West Road squad arrived. According to the investigation report, at the scene, Zhuque Thermal Power Company was cutting a desulfurization tower, and sparks caused plastic foam on the second-floor roof to catch fire; the area affected by the fire was approximately 150 square meters. No people were trapped, and the fire brigade promptly launched a firefighting operation. At 13:46, the fire at the scene was under control with no further spread. At 14:10, the open flames at the scene were successfully extinguished. Relevant information: How to prevent fires in desulfurization towers? 1. The root cause of fires in desulfurization towers is always the anti-corrosion materials used. In recent years, as environmental awareness has increased and environmental regulations have become more stringent, companies have started to adopt desulfurization processes on a larger scale, resulting in an increase in the number of projects related to desulfurization towers. Accidents caused by improper handling during the anti-corrosion process of these towers have been reported from time to time. When searching for information on “fires in desulfurization towers” online, one finds numerous news articles and images that are quite alarming. If one takes the time to examine the causes of these accidents, it becomes clear that in the vast majority of cases, the problem lies in the ignition of the anti-corrosion materials. The glass flake putty commonly used today is primarily composed of about 60% 901 vinyl resin, curing agents of similar type, around 20% glass flakes, fillers such as 15% talcum powder, and 2% styrene as a diluent. During application, approximately 10% styrene is added as a diluent to give the coating fluidity. Due to its relatively high molecular weight and low volatility, styrene has difficulty evaporating, especially under the effective waterproofing and shielding effect of the fish-scale-like structure of the glass flakes. As a result, large amounts of styrene remain in the coating for a long time after the application of the glass flake putty, thereby increasing safety risks ； The density of styrene vapor is greater than that of air; therefore, when styrene evaporates, it settles at the bottom of the construction area. Over time, the concentration of styrene at the bottom increases, and it can even reach its explosive limit. The temperature tolerance limit of glass flake mortar is around 180°C; when exposed to high temperatures such as those generated by welding, the coating is damaged, and substances like styrene and organic resins contained within the coating come into contact with air, creating the conditions necessary for combustion. If the temperature tolerance of glass flake mortar could be increased significantly so that it remains intact under short-term high temperatures, then the coating would prevent oxygen from reaching these substances, thereby preventing or delaying combustion. Unfortunately, the resins used in the production of glass flake mortar cannot achieve a substantial increase in temperature tolerance due to structural limitations, and moreover, this coating material itself is a flammable organic substance. 2. Analysis of human factors contributing to the fire accident in the absorption tower: 1. Engineering management personnel did not pay sufficient attention and failed to provide adequate management. Before applying the anti-corrosion rubber lining in the absorption tower, the project company, the supervision department, and the management personnel of the construction unit failed to recognize the importance of fire prevention measures related to this lining; they did not pay enough attention to it and were careless. No special safety meetings were held, their respective safety responsibilities were not defined, and no safety measures to prevent fires were established. 2. Low awareness of personal safety. The project company, as well as the safety inspectors and technical personnel from the construction unit, failed to provide the construction workers with necessary safety instructions and fire safety training. The workers had a weak awareness of fire safety, did not possess the relevant fire safety skills, and did not understand why fire prevention was necessary during rubber lining operations or how to carry out such prevention measures. 3. The rubber lining installation area was not enclosed completely for isolation. A strict fully enclosed isolation has not been implemented within a 5-m radius around the absorption tower. There were welding operations in the vicinity, and no effective isolation measures were taken, which led to the open flame coming into contact with the volatile gases from the butyl glue and causing a fire. 4. Workers or other construction personnel smoking. Smoking in areas where smoking is prohibited due to rubber lining, and discarding cigarette butts carelessly. The open flame from lighting a cigarette, along with sparks caused by discarded cigarette butts that ignite nearby flammable materials, come into contact with the volatile gases of butyl glue, resulting in a fire. 5. The absorption tower does not use explosion-proof lighting fixtures and electrical switches. 6. Poor ventilation inside the absorption tower. A large accumulation of volatile molecules from butyl glue can lead to an explosive ignition as soon as it comes into contact with even a tiny spark. 7. Lay bamboo stepping boards on the scaffolding inside the absorption tower and flue. Bamboo rungs contain oil and are strip-shaped; they are flammable materials that can easily contribute to the spread of fire in its early stages. 8. Stack the materials to be used inside and outside the flue of the absorption tower. If flammable particles such as welding slag fall into the piled material, they can remain hidden and difficult to detect, posing a fire hazard. 9. Working with fire in violation of regulations during equipment maintenance. After the entire desulfurization system was started up for trial operation (or put into service), equipment installers (or power plant maintenance staff) carried out repairs on the equipment without obtaining a fire work permit and without taking any fire prevention measures; they performed welding or gas cutting tasks in violation of regulations, and the welding slag or open flames ignited the rubber sheets (scale), resulting in a fire. It is particularly noteworthy that most absorption tower fire incidents occur some time after the maintenance personnel who were fixing the issues have left the site, and not at the moment of the incident. This is because the slag falls into the gaps between the rubber sheets (the areas where the rubber has separated) or onto the bottom plate of the absorption tower, where it burns slowly and causes a large fire. 10. After completing the repairs on the equipment, the power supply to the welding machine was not turned off. The welder responsible for carrying out the repair work lacked a strong sense of safety and responsibility; after completing the repairs, he failed to disconnect the power supply of the welding machine. This led to the welding machine overheating or to accidental short circuits due to exposed connections, which in turn caused flammable materials surrounding the absorption tower to catch fire, resulting in the burning of the rubber sheets inside the absorption tower. 3. Fire prevention measures for the absorption tower 1. Strengthen safety management and raise fire prevention awareness. (1) Before the team responsible for applying anti-corrosion linings to the absorption tower enters the construction site, they should sign a safety agreement with the project company’s safety supervision department to clarify their respective safety responsibilities. (2) The project company shall hold a special meeting on fire safety for the anti-corrosion lining of the absorption tower, to approve the fire prevention plan and safety measures for such lining, and to assign fire prevention responsibilities to specific units, departments, and individuals. (3) The safety supervisors in the project company’s Safety Supervision Department, the supervision engineers in the Supervision Department, and the specialized engineers in the Engineering Department shall provide construction workers with technical instructions on fire safety as well as safety education and training, in order to enhance their safety awareness and improve their fire prevention skills. (4) The project department of the construction unit must hold a safety meeting once a week, as well as pre-shift and post-shift meetings on a daily basis, to summarize achievements in terms of safety, commend those who abide by rules and regulations, and criticize behaviors that violate such rules. Truly ensure that safety is discussed constantly and the alarm bells remain ringing. 2. The construction area shall be completely enclosed and isolated. (1) Strictly enclosed isolation measures must be implemented in the area where anti-corrosion lining work is carried out; there should be one entrance and exit, and prominent warning signs reading “Lining work in progress – no smoking or open flames allowed!” shall be hung around the isolation barrier. (2) Strictly enforce the access system for the rubber lining construction area. (3) Establish a security system for the construction area, with dedicated personnel on duty; access is permitted only upon presentation of proper permits, and unauthorized persons are strictly prohibited from entering. Anyone entering the area where gasketing work is being carried out is strictly prohibited from bringing any kind of ignition sources, and smoking is also strictly forbidden. 3. Fire trucks and fire-fighting equipment should be available. One fire truck should be stationed near the absorption tower, and sufficient fire-fighting equipment must be installed in the absorption tower and flue systems as a precaution. 4. Proper clothing for workers: Workers who enter the absorption towers and flues to apply rubber lining or scale must wear appropriate protective equipment. It is strictly prohibited to enter these towers wearing shoes with nails or synthetic fiber clothing; there must be dedicated personnel on standby outside the towers to supervise. 5. Use explosion-proof electrical equipment. Lighting in the absorption tower and flue must be provided by 24V explosion-proof lamps; the power cables must be new flexible rubber cables, and the power control switches must be of the explosion-proof type and placed outside the absorption tower or flue. 6. Improve ventilation in the absorption tower and flue. Sufficiently powerful exhaust fans should be installed in the absorption tower and flue to ensure good ventilation there, thereby minimizing the accumulation of volatile molecules from butyl glue. 7. Open flames are strictly prohibited in the area around the absorption tower. (1) When working on the absorption tower, the clean flue, and the rubber lining, open flames are strictly prohibited within a radius of 15 meters around these areas ； Hot work is strictly prohibited in the area near the GGH of the clean flue. When hot work is absolutely necessary, strict and reliable safety isolation measures must be taken. (2) When carrying out installation work outside the wall of the absorption tower, the installation unit must seal off the access holes, pipe openings, and flue gas inlets and outlets on the absorption tower, to prevent welding sparks and other sources of fire from falling into the tower, which has been lined with rubber, through these openings and connections. (3) When the installation unit requires hot work within 5 meters of the absorber tower, it must strictly adhere to the hot work permit system, prepare fire extinguishers and fire hoses in advance, and set up fire barriers if necessary. 8. At the end of welding work, the construction site must be cleaned. Before leaving the site, welders and other workers must thoroughly clean the area, checking every corner for any hot slag. If necessary, water can be applied to areas where slag has accumulated in order to eliminate heat sources, and it is also important to ensure that the power supply to the welding machine has been disconnected. 9. Reduce combustibles in the absorption tower and flue: Steel treads should be used for scaffolding in the absorption tower and flue; bamboo treads should not be used ； Material stacking is also prohibited; the adhesive sheets and glue used for work must be available immediately and disposed of once they are no longer needed. All combustible materials should be removed to prevent fires.