Safety in Chemical and Process Industries: A Comprehensive Assessment

Accidental events in chemical and process industries may have catastrophic consequences. The present chapter aims at discussing the hazards and risks in chemical and process industries, where chemical species are used and/or transformed. After defining the concept of chemical risk, the possible accidental events in the process industry are presented based on their probability of occurrence. Some examples of relevant chemical accidents that occurred in the past are thoroughly discussed further. Safety measures (i.e., preventive and protective procedures) in safety and process industries and primary and secondary reactions are also described. Finally, a screening method capable of providing a hazard evaluation by calculating the power released during the thermal decomposition of a substance (i.e., the CHETAH method) is presented. 

The theory on thermal explosions according to Semenov’s approach is thoroughly described in this chapter. The main calorimetric tests to be carried out for a safe thermal analysis are also reported. The thermal inertia is defined and its effects on the characterization of reactive chemical systems is evaluated. 

Calorimetric techniques allow us to evaluate the kinetics and heat developed during a reaction. In this chapter, adiabatic and scanning calorimeters are presented. An application of adiabatic calorimetry to evaluate Self Accelerating Decomposition Temperature (SADT) is also presented. 

Gas and vapour explosions can be classified as homogeneous and heterogeneous. Homogeneous explosions are characterized by an autoignition temperature and a delay time to ignition.

Heterogeneous explosions are very common accidental typologies in chemical and process industries. The lower and upper flammability limits are presented in the present chapter. These threshold values differ depending on the mixture composition, as reported in detail. 

Flammability limits depend on different parameters, such as pressure and flame propagation direction. In the present Chapter, Le Chatelier’s equations and the Flash Point and Upper temperature are presented. The Minimum Oxygen Content is also defined. 

Triangular flammability diagrams are herein presented as useful tools to evaluate the flammability of air-combustible mixtures. The nose-type diagrams and the Minimum Ignition Energy are also described in the following chapter.

Heterogeneous explosions may occur in confined systems, thus leading to confined explosions. In the present chapter, mechanical and chemical explosions in confined and unconfined systems are considered, focusing the attention on their consequences by adopting the TNT-Equivalency method. Additional incidental typologies, such as Pool fire and BLEVE, are also described.

 In this chapter, the main routes of exposure to toxic chemicals and methods of eliminating them by the human body are presented. In particular, both defense and biotransformation mechanisms are described. The threshold limit values (TLV) and Material Safety Data Sheets are also introduced. 

Preventive measures are used to prevent explosive phenomena. In particular, inertization and ventilation procedures are discussed. Despite the adoption of these measures, explosive phenomena may still occur. Therefore, protective measures are necessary to reduce damages. Fire classes are also presented in this chapter.

Emissions of dangerous substances from ordinary industrial activities or industrial accidents may compromise the quality of soil and water. Indeed, industrial sites can be contaminated by a wide range of compounds, which represent a risk to the health of workers. To individuate whether the presence of contaminants represent a risk and how it is possible to remediate contaminated sites, it is necessary to apply the Risk Assessment technique. Risk assessment allows evaluation of the risk associated with the presence of contaminants, as well as remediation goals. The present chapter provides fundamentals on the risk assessment procedure applied to industrial contaminated sites. The main object is to provide a methodology to individuate contaminated sites and evaluate the remediation goals. To this aim, the main contents of the chapter are: basic concepts on contaminated sites, a description of the risk assessment method, an overview of the possible remediation techniques. Moreover, a practical exercise as well as a list of the most used software are provided.

Sustainability and sustainable development play a central role in addressing strategies and policies at the national and international level. Both these concepts have been largely discussed and different approaches have been proposed over time to promote their practical implementation, including the preventive one. In this context, Environmental Impact Assessment (EIA) has been built and developed to prevent or mitigate the negative impacts of a variety of anthropogenic activities on several environmental factors, including human health. Among the activities undergoing EIA, the building and operation of various chemical industrial plants may represent relevant scenarios to assess their wider health implications from a preventive perspective. The evaluation of these impacts on human health has been recently approached following a formally identified procedure, namely the Health Impact Assessment (HIA). This chapter aims at providing an overview on HIA, with particular reference to its integration within the EIA procedures: the legislative framework is thus figured out and the main features of HIA are discussed to point out its strengths and weaknesses as a decision supporting tool during the assessment of the environmental impacts of projects.