Intentional chemistry

Intentional Chemistry (e.g., batch or continuous reaction processes). 

Many millions of tons of useful products and substances are safely made by chemical reactions each year. Nevertheless, intended reactions can lead to major loss events if inadequately controlled. The following is an example of a chemical reactivity incident in a process with intentional chemistry (EPA 1999a). 

Intentional Chemistry Incident Columbus, Ohio, September 10,1997 ... 

Documentation of example chemical reactivity hazard management programs from CCPS sponsor companies that practice intentional chemistry. 

Bibliography of articles and publications related to chemical reactivity and intentional chemistry processes. 

The first question to be addressed is whether intentional chemistry is performed at your facility. Intentional chemistry means processing of substances, such that a chemical reaction is intended to take place. If so, then products are of a different chemical composition than the starting materials. 

A chemist or other expert should be consulted if you need assistance in determining whether intentional chemistry is being performed at your facility. The following information may also be helpful. 

The following are some indications that intentional chemistry is being performed ... 

Various processes such as mixing, dissolving, distilling, or extracting may involve intentional chemistry or may be purely physical processes. A... 

One borderline circumstance, which should be considered as intentional chemistry for purposes of managing chemical reactivity hazards, is hydration. For example, anhydrous copper sulfate is a white solid with the formula CuS04. When it is crystallized from water, a blue crystalline solid with the formula CuS04-5H20 results, and the water molecules are an integral part of the crystal (Parker 1997). 

Exothermic reactions are those chemical reactions that liberate heat as products are formed. The occurrence of an exothermic reaction in normal operations is usually an indicator that some intentional chemistry is taking place. 

Many different loss event scenarios are possible with intentional chemistry. All of them relate to losing containment or control of the intended reaction, starting another reaction, side reaction or series of reactions that are not intended or expected. A process hazard analysis, using a hazard and operability (HAZOP) study or other appropriate method, should be used to systematically identify and evaluate a full set of loss event scenarios. General causes of uncontrolled reactions include, but are not confined to, the following list ... 

Some of the key factors to consider when designing, operating and maintaining intentional chemistry processes are listed below. These factors can have a major effect on either the likelihood of a chemical reactivity incident or the severity of the incident consequences. 

If intentional chemistry is performed, chemical reactivity hazards can be expected to exist at your facility. An exception is intentional, essentially complete combustion with air, such as the burning of propane in a gas-fired heater. The burning of ordinary flammable and combustible materials has been excluded from our definition of chemical reactivity hazards and is adequately treated elsewhere. If the answer to Question 5 is YES, then the rest of this section on intentional chemistry need not be considered further, and you should proceed to Question 2 at the beginning of this chapter. 

If intentional chemistry is practiced at your facility and the answer to Question 5 is NO, then chemical reactivity hazards can be expected. As was noted earlier, it is not the intention of this Concept Book to cover all the complexities of the intentional chemical reactions being practiced in indus-... 

Deviations are abnormal situations, outside the bounds of intended design and operation. (The example shown in Table 4.10 does not indicate the possible causes for each deviation.) Examples of other deviations that are typically encountered in reactive systems involving intentional chemistry include ... 

Hendershot (2002) gives additional inherently safer process considerations when dealing with intentional chemistry. 

Question 5 ("Is combustion with air the only chemistry intended at your facility ") should be answered NO, since the intentional chemistry involves chlorination reactions. The Note in Section 3.1 pertains to this pro-... 

Figure 5.1. Screening flowchart path for intentional chemistry example.

Referring to the questions in Chapter 3, Question 1 ("Is intentional chemistry performed at your facility ") should be answered YES for this example. 

Intentional Chemistry Example Documentation (All Questions Answered)... 

Is intentional chemistry performed YES Batch chlorination waste neutralization... 

Can incompatible materials coming into contact cause undesired consequences NO No scenarios identified beyond those for intentional chemistry abnormal situations... 

Question 5 ("Is combustion with air the only chemistry intended at your facility ") can be answered YES in this case, assuming the "facility" being addressed is limited to the incinerator system. Due to the great number of combustion systems in operation, many other resources are available for ensuring safe design and operation of the combustion part of the incinerator facility. However, it should be noted that many combustors now have effluent treatment systems, such as selective catalytic reduction (SCR) systems, that involve intentional chemistry beyond the combustion reaction. 

Referring to the questions in Chapter 3, Question 1 ("Is intentional chemistry performed at your facility ") can be answered NO for this example, since the unloading, storage and repackaging operation involves no intended chemical reactions. Likewise, Questions 2 and 3 can be answered NO, since mixing and physical processing are also not intended. Question... 

In a Downstream Decomposing facility not the subject of this example, intentional chemistry is performed as ammonium dichromate is heated to decomposition to make chromium dioxide, which is used in the production of magnetic tape products. In the Upstream Feeds facility under study, physical processing is performed as ammonium dichromate is fed through a screw conveyor. The Preliminary Screening Method is to be used as a first-cut determination whether chemical reactivity hazards will need to be managed in the physical processing facility. 

Is intentional chemistry performed NO Physical processing only... 

---