PI – Dr. Luc Véchot
Co-PI – Dr. Walid Khalfaoui
1. Polyethylene dust Explosion Research
The lack of fundamental understanding and improper hazard assessment of primary and secondary dust explosions are frequently the cause of serious incidents in the chemical process industry. Very few statistics of dust explosions are available in the open literature. However, from those that can be found, the severity and catastrophic consequences of these explosions are clearly reflected.
The explosions that occur in the petrochemical industry can be mainly attributed to four different categories: (1) Pressure vessel explosions, (2) condensed phase explosion, (3) runaway reactions and (4) dust explosions.
Many organic materials encountered in the petrochemical industry have the potential of being explosive when present in dust form. The potential explosibility of the dust handled in the petrochemical industry is reflected in the numerous explosions that occurred every year inside the equipment that process, transport and storage chemical dusts. For example, in different petrochemical industries in China 13 explosions in a powder silo of Low density polyethylene (LDPE) occurred in a 11 year period; 14 explosions of a powder silo of polypropylene (PP) in a 5 year period and 12 explosion of a powder silo of High Density Polyethylene (HDPE) in a 3 year period. The most widely known incident involving Polyethylene combustible dust is the incident that occurred at the West Pharmaceuticals plant, located in North Carolina, United States. This incident occurred on June 23, 2003, when a roughing fire and explosion, completely destroyed the plant. According to the final CSB report, the explosion was caused by the deflagration of fine polyethylene powder, whit less than 63 microns in diameter, which had accumulated above a suspended ceiling in the manufacturing area of the facility. The incident killed 14 and injured 81 people. Polyethylene is the most widely used polymer in daily life, some of its uses include: plastic bottles for not carbonates drinks, automobiles’ fuel tanks, chemicals and household packing, tubing, toys, etc. Therefore, it is of paramount importance to assure the safety in this product during its entire life cycle, i.e., production, storage, transportation and consumption. Polyethylene has very law flammability. However, fine polyethylene dust dispersed in air in a sufficient concentration, and in the presence of an ignition source, may pose a potential dust explosion hazard. This has been demonstrated in the different dust explosion incidents involving this polymer described above.
As a part of its expansive economic strategy set in the National Vision 2030 and the national development strategic 2011-2016, the Qatari petrochemical industry have been rapidly growing in the latest years and this growing trend will continue, particularly in the production of polyethylene.
Although, dust explosion research has been going on for more than a century, incidents continue to occur. Some of the identified research needs are addressed below:
- Effect of Polyethylene particle size disparity;
- Study of polyethylene dust in non-traditional forms (flocculent materials, hybrid mixtures, nano-particles);
- Use of powder aerosols for suppression of dust explosions;
- Study of Secondary Polyethylene Dust Explosions.
Texas A&M and the Mary Kay O’Connor Process Safety Center have been developing research on dust explosions in the last 5 years. The expertise team is composed by industry experts, professors and PhD students with a significant background on experimental and theoretical dust explosion research. The research group at MKOPSC-Qatar has recently invested in a 20 liter explosion test sphere that can be used to determine the different explosive parameters of dust clouds, e.g., the minimum ignition concentration, maximum overpressure and Kst value. The 20 litre sphere can also be used to study the turbulence effects on dust explosion; proper venting designing; and to study nano-materials and hybrid mixtures.
The laboratory at MKOPSC-Qatar is also equipped with a Modified Hartmann Tube designed as qualitative pre-test of the explosion behavior of a dust/air mixture.
In addition Texas A&M is equipped with the suitable supercomputer and software packages to perform CFD modeling.