Reactivity hazards screening

Use reactor calorimetry testing to determine thermodynamics and kinetics of process. See Appendix 2A (Chemical reactivity hazards screening). 

Up to this point, the chemical reactivity hazards of individual substances, either by themselves or in contact with common environmental materials, have been considered. This last question in the chemical reactivity hazards screening will address the potential for an unintended chemical reaction due to incompatible materials contacting each other. Compatibility, in this context, means the ability of materials to exist in contact without specified (usually hazardous) consequences under a defined scenario. A scenario, in this context, is a detailed physical description of the process whereby a potential inadvertent combination of materials may occur (ASTM E 2012-00). 

Reactive System Screening Tool (RSST) The RSST is a calorimeter that quickly and safely determines reactive chemical hazards. It approaches the ease of use of the DSC with the accuracy of the VSP. The apparatus measures sample temperature and pressure within a sample containment vessel. Tne RSST determines the potential for runaway reactions and measures the rate of temperature and pressure rise (for gassy reactions) to allow determinations of the energy and gas release rates. This information can be combined with simplified methods to assess reac tor safety system relief vent reqiiire-ments. It is especially useful when there is a need to screen a large number of different chemicals and processes. 

Experience has shown that reactive chemistry hazards are sometimes undetected during bench scale and pilot plant development of new products and processes. Reactive chemistry hazards must be identified so they can be addressed in the inherent safety review process. Chemists should be encouraged and trained to explore reactive chemistry of "off-normal operations. Simple reactive chemicals screening tools, such as the interactions matrix described in Section 4.2, can be used by R D chemists. 

Careful attention to such detail is necessary as a second line of defence against the effects of reactive hazards. The level of protection considered necessary may range from the essential and absolute minimum of effective eye protection, via the safety screen, fume cupboard or enclosed reactor, up to the ultimate of a remotely controlled and blast-resistant isolation cell (usually for high-pressure operations). In the absence of facilities appropriate to the assessed level of hazard, operations must be deferred until such facilities are available. 

The Reactive System Screening Tool (RSST), marketed by Fauske and Associates, is a relatively new type of apparatus for process hazard calorimetry [192, 196-198]. The equipment is designed to determine the potential for runaway reactions and to determine the (quasi) adiabatic rates of temperature and pressure rise during a runaway as a function of the process, vessel, and other parameters. 

Based on the level of knowledge of chemical reactivity hazards, determine if additional screening of reactivity hazards is necessary. Having reactive functional groups might indicate the need to perform literature searches, access databases, or run differential scanning calorimetry. 

FIG. 23 18 CCPS preliminary screening for chemical reactivity hazards. [From Johnson et al. (2003) copyright AIChE reproduced with permission. ]... 

Chapter 3 provides a screening tool to help determine whether chemical reactivity hazards are present that need to be managed and controlled. 

Chapter 3 is a Preliminary Screening Method designed to help identify whether chemical reactivity hazards are present at a facility. It can be used to determine whether the information in this publication is sufficient, or whether additional resources are going to be required, for managing identified chemical reactivity hazards. 

Table 3.1, Example Form to Document Screening of Chemical Reactivity Hazards, with the accompanying flowchart of Figure 3.1, for use with the preliminary screening method of Chapter 3. 

Table 2.3 gives one way for an existing facility to get started toward successfully managing chemical reactivity hazards. This assumes you already have an idea as to what chemical reactivity hazards must be addressed by the management system, such as by answering the questions in the Preliminary Screening Method of Chapter 3. 

Preliminary Screening Method for Chemical Reactivity Hazards... 

A form such as Table 3.1 can be used to document answers to the screening questions and the conclusions that are drawn. The flowchart in Figure 3.1 is an overview of how these questions are connected to determine whether a chemical reactivity hazard can be expected at your facility. 

This screening method may be used by either a single person or a group of persons. A team approach, involving several persons with different knowledge and functional perspectives, has the possibility of better identifying and assessing the potential for chemical reactivity hazards. 

Figure 3.1. Preliminary screening for chemical reactivity hazards summary flowchart.

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