At approximately 7:00pm on February 7, 2008, a massive dust explosion shook the Imperial Sugar refinery in Port Wentworth, Georgia. The explosion killed 14, injured 42, and destroyed 12 percent of the 872,000 square foot facility. OSHA investigations of the event found that the explosion had been “entirely preventable.” The disaster led to the development of new technology designed to prevent future combustible dust explosions in similar situations.
Background: The Dixie Crystals Refinery
The sugar processing plant, known as the Dixie Crystals Refinery, was built in 1916, opened a year later, and had been in operation almost continuously since then. Constructed on a 160 acre site, the facility was the second largest sugar refinery in the United States. Sugar Land, Texas-based Imperial Sugar bought the factory from the previous, local owner. In 2007, the facility refined roughly nine percent of all the sugar used in the US that year, making it one of the highest-producing sugar refineries in the world.
Many areas of the factory had never been fully updated or renovated, and still contained the now-outdated construction methods and materials used in the plant’s initial construction. The facility’s ceilings were made of wood; creosote tar was still plentiful, despite being a well-known fire risk.
In 2005, after three similar and fatal explosions two years prior, the US Chemical Safety and Hazard Investigation Board (CSB) had released the findings of a study that investigated the risks of combustible dust explosions. The report stated that dust explosions posed a severe risk, with evidence showing that 281 combustible dust explosions had occurred in the US between 1980 and 2005. The CSB subsequently made numerous recommendations to the Occupational Safety and Health Administration (OSHA), only some of which had been implemented by 2008.
The explosion occurred at roughly 7pm, erupting from the center of the Dixie Crystals Refinery, in a building where processed sugar was fed to storage and bagging equipment via a series of conveyor belts and elevators. One-hundred-twelve employees were onsite at the at the time, including Imperial Sugar CEO John Sheptor.
Sheptor, who survived the blast only because he was protected by a firewall, stated that the accumulated dust from countless tons of processed sugar had acted like gunpowder. Sugar dust, a highly combustible substance, would be officially identified as the fuel for the explosion within 24 hours of the explosion. Evidence suggests that a spark, caused by equipment that was overheating due to the significant accumulated buildup of sugar dust along the conveyor line, served as the source of ignition.
The building at the event’s epicenter was destroyed in the explosion and ensuing fire, as were several others nearby. Two 100-foot tall, reinforced concrete storage silos adjacent to the building caught fire, as well, and the sugar inside the silos continued to burn and smolder for seven days before finally being extinguished. Over 3 million pounds of fire-hardened sugar were eventually recovered from the silos.
Ambulances from 12 counties and fire fighters from three responded, as the US Coast Guard, which closed off a portion of the Savannah River alongside the refinery.
OSHA & CSB Investigate
OSHA arrived on the scene within two hours. An OSHA investigation was launched immediately, as well as an independent CSB investigation. Interviews with employees of the refinery revealed a lack of training and preparedness—40 of those interviewed had never received training on exiting the building in an emergency, and only five recalled any instance of a fire drill having been conducted.
Less than a month later, OSHA sent a letter to 30,000 employees across the US, altering them to the danger of dust explosions in the workplace. A Congressional bill was soon proposed by OSHA as well; the Combustible Dust Explosion and Fire Prevention Act of 2008 was passed by the House of Representatives, but stalled out in the Senate. Numerous new OSHA regulations were enacted in the wake of the Dixie Crystals Refinery dust explosion.
The CSB completed their investigation the next year, and released their report in September 2009. In it, the explosion was called “entirely preventable.” CSB investigators noted that companies in all areas of the sugar industry had been well aware of the potential for combustible dust explosions since 1926, citing memos from the late 1960s that voiced concerns about these risks. The CSB also revealed that Imperial Sugar’s own construction changes on the site had exacerbated the accumulation of sugar dust, and that the company had never practiced evacuation procedures.
From Disaster Springs Innovation
Following the Dixie Crystals Refinery dust explosion, equipment manufacturers for the sugar processing and the broader chemical processing industry set out to develop new ways to reduce or eliminate the risk of combustible dust explosions. As the Georgia plant’s conveyor system was identified as the source of ignition, a good deal of these efforts were focused on improving material conveyors.
The first step was safer, more efficient conveyors that utilized fewer moving parts, thus reducing friction and heat generation. From there, industry engineers went on to develop pneumatic conveyor systems that can transport materials with almost no friction and that significantly reduce the creation of material dust.
Currently, the most advanced solution yet for preventing combustible dust explosion is being developed by Nol-Tec Systems in partnership with Air Products and Chemicals. This new system will incorporate a state-of-the-art pneumatic conveyor, and, for further improved safety, will replace the combustible system’s oxygen flow with an inert gas. This inert gas will not operate in a vacuum, but rather will be pumped through the system in high enough quantities to displace oxygen down to a non-combustible level—less than 15 percent of the volume of the conveying flow.
The two companies co-authored a related research paper, “Prevent Combustible Dust Explosions with Nitrogen Inerting”, in the March 2015 issue of Chemical Engineering.