TPC_Factual_Update_10-29-2020

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1 Fires and Explosions at TPC Group Port Neches Operations Facility Port Neches, Texas | Incident Date: November 27, 2019 | No. 2020-02-I-TX U.S. Chemical Safety and Hazard Investigation Board Factual Update October 29, 2020 Incident Summary • On November 27, 2019, a major loss of containment event occurred, resulting in multiple fires and explosions at the TPC Group (TPC) Port Neches Operations (PNO) facility in Port Neches, TX. The TPC PNO facility manufactured 1,3-butadiene and raffinate-1 [1]. a The incident occurred in the facility’s South Unit ( Figure 1 ). The initial explosion resulted in injuries to two TPC employees and a security contractor and caused significant damage to the facility. Following the incident, county officials issued a mandatory four-mile radius evacuation order [2] which remained in effect until 10:00 a.m. on November 29, 2019. Figure 1 . TPC PNO facility prior to the incident. (Credit: Google Maps) • Because of the incident, TPC has decided to transition to a “terminal and services” operation while they evaluate and plan to rebuild [3]. As part of this transition, TPC terminated the employment of multiple workers and a Raffinate-1 is a byproduct of 1,3-butadiene and is a chemical building block used in the manufacture of methyl tertiary butyl ether (MTBE) and diisobutylene (DIB) [15].

2 Fires and Explosions at TPC Group Port Neches Operations Facility Port Neches, Texas | Incident Date: November 27, 2019 | No. 2020-02-I-TX U.S. Chemical Safety and Hazard Investigation Board supervisors. Marsh JLT Specialty reported the property damage loss resulting from the incident to be $500 million [4]. Background • The South Unit is used to produce 1,3-butadiene, which is primarily used to manufacture synthetic rubber and resins [5, p. 4]. Because 1,3-butadiene is a flammable liquid with a flashpoint below 100 °F, a and because the TPC PNO facility maintains an onsite quantity of 1,3-butadiene greater than 10,000 pounds, the production of 1,3-butadiene at the TPC PNO facility is regulated by the requirements of the Occupational Safety and Health Administration ’s (OSHA) Process Safety Management (PSM) standard , 29 CFR 1910.119 [6]. Also, 1,3- butadiene is a regulated substance under section 112(r) of the Clean Air Act; as such, the process is subject to the Environmental Protection Agency ’s (EPA) Risk Management Plan (RMP) Rule [7]. • In addition to its flammability, 1,3-butadiene is also highly reactive, with several undesirable reactions. In the presence of oxygen, butadiene readily reacts to form a butadiene peroxide. Butadiene peroxides, which are denser than 1,3-butadiene, will separate out and form a second liquid phase. If enough butadiene peroxides become concentrated, a critical mass is achieved which can initiate a fire or explosion [5, p. 30]. Another potential undesirable reaction that can occur between oxygen and 1,3-butadiene is the formation of popcorn polymer. Popcorn polymer, if left uninhibited, grows exponentially [8, p. 4]. When popcorn polymer growth is left unabated inside process equipment, the accumulated material can generate very high pressure inside the equipment and can ultimately lead to equipment rupture [9, p. 240]. • Figure 2 shows a block flow diagram of the butadiene production process at TPC PNO. Crude butadiene ranging from 35 to 75 percent purity proceeds through multiple production phases. After the final fractionation phase, the 1,3-butadiene is at 99.8 percent purity, where it is sent to storage tanks for shipping. The loss of containment occurred in the final fractionation phase. Figure 2 . Block flow diagram of the butadiene production process at TPC PNO. The highlighted area shows where the loss of containment occurred. (Credit: CSB) a The flashpoint of 1,3-butadiene is – 105 o F [9, p. 239].

3 Fires and Explosions at TPC Group Port Neches Operations Facility Port Neches, Texas | Incident Date: November 27, 2019 | No. 2020-02-I-TX U.S. Chemical Safety and Hazard Investigation Board • A simplified process flow diagram of the TPC PNO butadiene post-fractionation process is shown in Figure 3 . Indicated on the process flow diagram by the red ellipse is the area of interest as the potential origin of the flammable vapor release. a Figure 3 . Simplified process flow diagram of the TPC PNO butadiene post-fractionation process at the time of the incident. (Credit: CSB) Preliminary Incident Timeline • During the night shift that began on Tuesday, November 26, 2019, the unit was reportedly operating normally. • At 12:54 a.m., b a loss of containment event occurred, causing the liquid level in the final fractionator A to drop rapidly from its operating level. The CSB calculated the liquid volume at the time of the initial level drop to be a The likely location of release is based on data from the final fractionator A level controller and eyewitness accounts. As of this update, the CSB has not been able to visually confirm the failure location due to the extensive damage at the site. b Time obtained from correlating external time-stamped video to TPC PNO process data, using the initial loss of multiple alarms as the time of the explosion. Since the TPC PNO timestamp from their process control system was found to be four minutes and thirteen seconds ahead of the time stamp from the video, the CSB subtracted four minutes and thirteen seconds from the TPC PNO timestamp.

4 Fires and Explosions at TPC Group Port Neches Operations Facility Port Neches, Texas | Incident Date: November 27, 2019 | No. 2020-02-I-TX U.S. Chemical Safety and Hazard Investigation Board approximately 6,000 gallons. The liquid, which was primarily butadiene, a emptied from the fractionator in less than a minute ( Figure 4 ). The liquid vaporized upon release b and formed a vapor cloud. Three workers were in the unit at that time. Two of them were facing toward the final fractionator A, and they both told the CSB after the incident that they saw a pipe rupture. Of these two workers, one of them identified the release point (circled in red in Figure 3 ) to be in the suction piping of the final fractionator A to B transfer pump. The third worker, who turned toward the sound of the release after the release occurred, also believed it was the suction piping into the final fractionator A to B transfer pump that failed. The workers’ observations are consistent with the unit’s recorded process data. The CSB has not yet visually confirmed the failure location due to the extensive damage and unstable structural conditions at the site. • Immediately following the loss of containment, the three workers quickly departed the unit. • At 12:56 a.m., the vapor cloud ignited, resulting in an explosion that created a pressure wave that heavily damaged the site and caused damage to buildings, including houses, offsite. Thermal imagery c provided by TPC shows multiple fires following the explosion (Figure 5 ). Figure 4 . Process data trend graph showing the liquid level (in percent) in the final fractionator A dropping from its operating level to zero in less than a minute. The estimated liquid quantity in the fractionator at the time of the release was 6,000 gallons (30,000 pounds). d (Credit: CSB) a The composition of the contents at the bottom of the final fractionator A was not analyzed on-line; however, the design specification of the feed into the final fractionator from the methyl acetylene removal tower was 98.00 wt.% 1,3-butadiene minimum. b The normal boiling point of 1,3-butadiene is 24.1 o F [5, p. 7]. c Thermal imaging devices measure infrared (thermal) radiation and translate the data to images. In this instance, the colors progress from black (least amount of radiation) to white (greatest amount of radiation). d Volume calculated based on the final fractionator A dimensions and liquid level of six feet. The weight in pounds was calculated using an assumed density of 38.75 pounds per cubic feet liquid butadiene.

5 Fires and Explosions at TPC Group Port Neches Operations Facility Port Neches, Texas | Incident Date: November 27, 2019 | No. 2020-02-I-TX U.S. Chemical Safety and Hazard Investigation Board Figure 5 . Thermal drone imagery of the TPC PNO facility South Unit taken the morning after the initial explosion. (Credit: TPC) • At least two additional explosions occurred following the initial blast. At 2:40 a.m., a cell phone recording captured an additional explosion ( Figure 6 ). That afternoon at 1:48 p.m., another explosion propelled one of the facility’s towers into the air ( Figure 7 ). The tower landed within the confines of the TPC PNO facility. In addition to the propelled tower (later identified as an out-of-service debutanizer), four additional towers ( Figure 8 ) fell as a result of the blast and/or fires: the final fractionator A, an extractive distillation absorber, an out-of- service water wash tower, and the depentanizer.

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