Hazard in Process Industries

Hazards in Process Industries by Dr. AA


1. Introduction

There are three main hazards in chemical industries. These are Fire, Explosion and Toxic Release. In many instances, more than one of these hazards occur either simultaneously or in tandem of each other. For example, a fire may lead to explosion which subsequently causes more fire and toxic release.

1.1  Fire

1.1.1  Fire Triangle

In order for a fuel to burn, heat, fuel and oxygen must be present. These three elements form what is called the fire triangle.

Removal of any one of the sides of this Fire Triangle will extinguish the fire.

– If fuel is removed, the fire will starve and be extinguished.

– If air is removed, the fire will suffocate – because of a lack of oxygen – and go out.

– The removal of heat is the most common form of fire suppression.

There are methods of suppression, however, that work on the basis of suffocating the fire. In most cases water is used to essentially soak up the heat generated by the fire. Without energy in the form of heat the fire cannot heat unburnt fuels to ignition temperature and the fire will eventually go out. Chemicals can be added to water to improve the heat removal properties of water, or to improve the ability of the water to stick to unburnt fuel.

1.2  Heat Radiation


2.0 Explosion

2.1 Types of Explosion

2.1.1 Physical Explosion

2.1.2 Chemical Explosion

2.1.3 Boiling Liquid Expanding Vapour Explosion (BLEVE)

2.1.4 Vapour Cloud Explosion

2.1.5 Dust Explosion

Any combustible material (and some materials normally considered noncombustible) can burn rapidly when in a finely divided form. If such a dust is suspended in air in the right concentration, it can become explosive. The force from such an explosion can cause employee deaths, injuries, and destruction of entire buildings. Such incidents have killed scores of employees and injured hundreds over the past few decades.

Materials that may form combustible dust include metals (such as aluminum and magnesium), wood, coal, plastics, biosolids, sugar, paper, soap, dried blood, and certain textiles. In many accidents, employers and employees were unaware that a hazard even existed.

A combustible dust explosion hazard may exist in a variety of industries, including: food (e.g., candy, sugar, spice, starch, flour, feed), grain, tobacco, plastics, wood, paper, pulp, rubber, furniture, textiles, pesticides, pharmaceuticals, dyes, coal, metals (e.g., aluminum, chromium, iron, magnesium, and zinc), and fossil fuel power generation.

3.0 Toxic Release

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