An investigation into the accident concluded that detonation of fertilizer-grade ammonium nitrate caused the blast, and that, according to the federal Chemical Safety Board, “the construction of the bins and other building materials as well as the lack of an automatic sprinkler system plausibly contributed to the detonation.”
Largely due to this accident — the worst the CSB has ever had to investigate — the U.S. Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA) last year issued guidelines on chemical plant safety. The wide-ranging guidelines cover aspects of chemical facility safety from design to plant startup to ongoing operations. While a number of the recommendations fall outside the roles played by analytical chemists, a number of them can be addressed by analytics:
- Determining toxicity, flammability, vapor pressure, and reactivity of all chemicals on site.
- Monitoring chemical properties in case of process mishaps such as power failures, tank overfills, or temperature spikes.
- Replacing hazardous chemicals with those that are less hazardous or pose no hazard, minimizing quantities of hazardous substances, or changing process conditions to reduce the possibility of incidents.
While most analytical chemistry functions focus on quality control of manufactured chemicals, safety and integrity of final products, and reducing emissions of hazardous gases or liquids during manufacturing, those same functions play a role in improving facility safety.
Any new manufacturing process that requires novel synthetic routes, new raw materials, or intermediate production procedures generates a variety of technical problems and health and safety requirements, and requires new analytical methods and techniques.
Much of the role played by analytical chemists in improving facility safety involves process analytical technology. This includes on-line analysis, which can take measurements and readings immediately during manufacturing without the need for sampling, and at-line analysis, which takes place near the plant and usually requires sampling methods. Analytical chemistry is useful for determining parameters of raw material purity, product quality, worker safety, environmental effects, reactor control, and processing control.
Assuming that starting materials are within certain specifications, it’s then necessary to control temperature, pressure, and flow of materials to produce desired chemical reactions and create a product of acceptable quality. While traditional measurements work well, multivariate chemical sensors can provide additional real-time information to improve the safety and efficiency of the process or consistency of the product. Some analytical techniques used in improving plant safety are:
- (Process)-Raman spectroscopy, using inelastic scattering of monochromatic light to identify molecules based on their specific vibration frequencies.
- Process gas analysis, determining the nature of gases from a number of sources in manufacturing, from flue exhaust to production of simple to complex gases. Gas chromatography is frequently used here.
- X-ray fluorescence spectroscopy (XRF), a non-destructive technique that determines the elemental composition of materials, and determines the chemistry of a sample by measuring fluorescent (or secondary) X-rays emitted from a sample excited by an X-ray source.
- Quantitative Process NMR (nuclear magnetic resonance) spectroscopy is used to quantify content or purity of organic substances. The method is based on a direct comparison of NMR signal intensities.
- Process-Ultraviolet/VIS and near-infrared spectroscopy, using absorption spectra from other fringes of the visible light spectrum to characterize a wide range of chemicals.
These techniques may go beyond making sure that manufacturing processes are moving smoothly. They also can provide real-time, instant alerts of a problem of cleanliness, contamination, or hazardous event. Finally, they also can help point to the cause of a potential (or actual) hazard.
The new government guidelines come with some teeth. After the EPA and OSHA issued their guidelines last year, Congress passed a law allowing OSHA to boost its civil fines from $7,000 to $12,600 for “serious violations,” and from $70,000 to $126,000 for “willful violations.” OSHA also will team up with the U.S. Justice Department to conduct criminal investigations involving plant accidents.
While implementing analytical technology to assess potential hazards (and hopefully, prevent accidents) is important, any technological changes occur in the context of an overall safety culture. “An inadequate safety culture normally ranks among the top causes of incidents and accidents in the industry,” warned Luis Duran, a safety business development manager for ABB Inc., a Houston-based automation and power engineering firm. Just using technology that’s been certified according to national or international standards isn’t enough.
For deeper conversation about how to deploy techniques like these at your own facility, reach out.