Evaluating Potentially Reactive Materials

Determining the potential for dangerous interactions is not always easy. Take concentrated sulfuric acid as an example. By itself, it is very stable unless heated to high temperatures. It is nonflammable, and has a fairly low vapor pressure. However, mix it with water, or worse, a caustic solution, and it can rupture a tank in seconds. The key to evaluating the reactive hazard in this example is to first identify that both concentrated sulfuric acid and caustic are present. Then, safeguards can be put in place to ensure the two materials do not come into uncontrolled contact. 

Raw materials, process streams, products and waste of any new process that has reached the pilot or production plant stage shall be reviewed and evaluated to determine if any potential reactive chemical hazards are involved. The GPM process fGlobal Project Methodology) requires an evaluation of the need to complete a project version review of the RC/PHA (Reactive Chemicals Process Hazard Assessment) review. This evaluation and recommendation is to be done by a member of the Process Safety Technology Center organization and should follow the RC/PHA protocol. 

As can be seen from the Global Reactive Chemicals Standard, all existing chemical processes will have a Reactive Chemicals/Process Hazard Analysis review on a predefined periodic basis. In addition, every new plant Production Leader should review their process with the Reactive Chemicals Committee within 90 days of assuming responsibility for a pilot or production plant. Prior to the review, the Leader should acquire training on the chemistry and processes that they are working with. This should include an evaluation of raw materials, processes, products and waste to understand any potential reactive chemical hazards. They should review and be prepared to answer questions from the completed and updated RC/PHA protocol questionnaire as well as other relevant materials in their plant Process Safety Folder, such as F EI, CEI, etc. The review should cover all auxiliary operations to the process such as raw material and product storage drum, tank car and truck loading. 

ASTM Saul Patai s book "The Chemistry of Peroxides" (41) was reviewed with some hope of finding either a systematic evaluation of reactivity as it relates to the potential hazard of peroxides or some basic concepts that would allow formulation of a unifying theory that would permit an algorithmic solution to the classification problem. Unfortunately, when Saul got to the chapter on safety he acknowledges that he gave up. Bretherick s "Handbook of Reactive Chemical Hazards" (42) presents some useful information and incident histories, but provides little in the way of coordinated insight based on molecular composition and structure to allow for systematic extrapolation to new materials. 

The index was originally developed for plants where flammable or reactive materials are stored, handled or processed. Yet it may also be used in analyzing the loss potential of sewage treating facilities, distribution systems, pipelines, rectifiers, transformers, boilers, thermal oxidizers and certain elements of power plants. The procedure can also be used for risk evaluations of small processes with modest inventories of potentially hazardous materials. Its application to pilot plants is strongly recommended. The procedure can be applied if a minimum of approximately 454 kg (1,000 lb) of a flammable or reactive material is handled. 

Fig 2 shows the annual global wanning potential impacts caused by using different systems. A lifetime of 15 years is assumed for evaluation. SOLARSTORE system creates more environmental impacts during its manufacturing processes. It is caused by the use of the thermo-chemical unit and the reactive materials. More material and energy is required for this phase. 

If chemical-specific information is not available, the consequences may be able to be predicted by methods using compatibility groups, or chemicals with similar chemical structures that are expected to have similar chemical reactivity characteristics. One computerized tool that uses this approach is the Chemical Reactivity Worksheet made available by the U.S. National Oceanic and Atmospheric Administration (NOAA 2002). This program has over 6000 chemicals, mixtures, and solutions included in its database. It also predicts chemical reaction consequences of combining two materials at a time (e.g., "Heat generation by chemical reaction, may cause pressurization"). Examples from the Chemical Reactivity Worksheet are shown in Section 4.2. It is critical that all chemicals be positively identified to have a complete evaluation of all potential incompatibilities. 

Bacteria indigenous to Cr(VI)-polluted areas are Cr(VI) tolerant and/or resistant and have been considered as potential candidates for bioremediation of Cr(VI)-contaminated sites.16 However, the ability of bacteria to reduce Cr(VI) to the less-toxic Cr(III) compounds may produce reactive intermediates (such as Cr(V), Cr(IV), radicals), which are known to be active genotoxins and are likely to be carcinogenic.17 Therefore, the formation and lifetimes of Cr(V) intermediates, produced via bacterial reduction of Cr(VI), need to be evaluated carefully if microorganisms are to be employed as a means for remediation of chromium-polluted subsurface environments. Similarly, Cr(V) accumulation should first be monitored when considering plants and algae as biosorption materials for the bioremediation in the event of chromium pollution.18... 

---