Analysis of the Effects of Starch Silos Explosion in Iron Processing Units

One of the causes of accidents in silos is due to dust explosions, generated by airborne dust accumulation in a confined atmosphere, together with the ignition source and oxygen concentrations capable of propagating a flame. The dust explosions can cause property damage and loss of life.

The Objective of this study is to raise the physical effects of a possible dust explosion in starch storage silos, used in iron beneficiation process, and thus propose preventive and mitigating measures to be implemented in the current system and the expansion project of silos area.

This study was conducted because the need for modernization of iron processing facilities, which were installed in the 70's and do not follow the current explosion prevention and mitigation technologies.

This article is a case study in a Brazilian mining company, privately held, where its main product are iron ore pellets produced from the processing of low-grade minerals in a noble product, high value aggregate, and marketed to the global steel industry. The nominal capacity of the production unit studied is 22.250 million tons per year.

The studied plant is responsible for the processing of mining. In this process, use is made of raw materials such as corn and cassava starches, which are stored in silos.

An analysis of qualitative and quantitative dangers of possible accidental hypotheses was carried out by following these steps: characterization surrounding the installation, description of the installation; characterization of related substances; Event Tree Analysis and Estimation of Physical Effects.

Accidental cases were observed where the explosion effects are kept to a minimum, yet it can be seen that there will be repairable damage to structures (walls, doors, roofs), and danger to life. It was also found that near the silos, higher overpressures occur that would provoke serious damage to the structures (buildings and equipment) and therefore represent major health hazard.

The cases where the effects of the explosion are the greatest, the overpressure can reach distances of up to 90m.

The analysis performed in this study showed that there is a possibility of a combination of events, which results in a dust explosion in storage silos.

It was also found that the higher the pressure buildup inside the silo, the greater the damage from the explosion, however, a pressure relief system would be important to reduce this damage.

This study contributed to the design and dimensioning of new silos with relief and explosion suppression systems.