Worked Examples Intentional Chemistry Example

Transcription

1 Worked Examples 5 Several worked examples of identifying chemical reactivity hazards are presented in this chapter. The objective of this chapter is to illustrate the use of the Preliminary Screening Method for Chemical Reactivity Hazards (Chapter 3) by way of a few, relatively simple examples that show different decision paths Intentional Chemistry Example Charbroiled Chemicals has one facility adjacent to an industrial park on the outskirts of the city. The facility manufactures a range of products in 200 to 1000 gal batch reactors by chlorinating various organic feed materials. The reaction products go through several purification stages, with the chlorinated organic products sealed and labeled in 55 gal drums for delivery to customers. Byproducts that cannot be recycled are neutralized and stabilized in the waste treatment facility prior to disposal. The Questions in these worked examples refer to the twelve questions in Chapter 3. Question 1 ( Is intentional chemistry performed at your facility? ) should be answered for this example, since raw materials are processed such that a chemical reaction is intended to take place. Products are of a different chemical composition than the starting materials. Intentional chemistry is also likely being practiced in the waste treatment facility. Question 5 ( Is combustion with air the only chemistry intended at your facility? ) should be answered, since the intentional chemistry involves chlorination reactions. The Note in Section 3.1 pertains to this pro- 119

2 120 Managing Chemical Reactivity Hazards cess. It states that it is not the intention of this Concept Book to cover all the complexities of intentional chemistry. Although the essential practices in Chapter 4 are appropriate considerations for facilities such as this one, additional resources are likely to be required to identify and control the chemical reactivity hazards. Table 5.1 shows what the documentation of the screening might look like for this example, if the user decided to proceed to answer the remaining questions. The Comments column is used to indicate where information was obtained for answering each question. The information in Table 5.1 gives an idea of what chemical reactivity hazards will need to be controlled to operate the facility safely. Figure 5.1 indicates the path taken through the screening flowchart for this example. Figure 5.1. Screening flowchart path for intentional chemistry example Combustor Example Rarified Research operates a ram-fed incinerator for destruction of select wastes at its large, centralized research facility, including liquid flammable solvents in small plastic containers. The incinerator is fired by natural gas and is brick-lined. Temperatures are closely monitored, and stack emissions are routinely sampled. Referring to the questions in Chapter 3, Question 1 ( Is intentional chemistry performed at your facility? ) should be answered for this example.

3 5 Worked Examples 121 TABLE 5.1 Intentional Chemistry Example Documentation (All Questions Answered) FACILITY: Charbroiled Chemicals Do the answers to the following questions indicate chemical reactivity hazard(s) are present? 1 AT THIS FACILITY:,, or BASIS FOR ANSWER; 1. Is intentional chemistry performed? Batch chlorination; waste neutralization 2. Is there any mixing or combining of different substances? 3. Does any other physical processing of substances occur? 4. Are there any hazardous substances stored or handled? 5. Is combustion with air the only chemistry intended? 6. Is any heat generated during the mixing or physical processing of substances? 7. Is any substance identified as spontaneously combustible? 8. Is any substance identified as peroxide forming? 9. Is any substance identified as water reactive? 10. Is any substance identified as an oxidizer? 11. Is any substance identified as selfreactive? 12. Can incompatible materials coming into contact cause undesired consequences? Raw materials combined in reactor Purification steps Organic feed materials; concentrated hydrochloric acid; oxygen Chlorination No indication of exothermic behavior Organics in feed have propensity to form organic peroxides under right conditions Oxygen feed; chlorine gas intermediate No scenarios identified beyond those for intentional chemistry abnormal situations 1 Use Figure 3.1 with answers to Questions 1 12 to determine if answer is or

4 122 Managing Chemical Reactivity Hazards Raw materials (wastes) are processed such that a chemical reaction is intended to take place, with products (combustion gases, ash and slag) being of a different chemical composition than the starting materials. Question 5 ( Is combustion with air the only chemistry intended at your facility? ) can be answered 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. Question 2 should be answered if there is any combining of wastes before being fed to the combustion chamber. Question 6 will likely be answered if similar wastes are combined, such that no significant heat effects (such as heat of solution) are experienced. The answers to Questions 7 through 11 will likely determine whether chemical reactivity hazards are present. For example, a jar of liquid ether that is a peroxide former may be brought to the facility for incineration. If it had been stored a long time and the contents had been exposed to air, unstable peroxides may be present that could explode when handled or fed to the incinerator. The information in Section 3.3 may be helpful in identifying whether any reactive chemicals are present. If the answer to all of Questions 7 through 11 are, then Question 12 ( Can incompatible materials coming into contact cause undesired consequences? ) should be addressed. This involves the three steps described at the end of Section 3.3: decide on undesired consequences of concern, identify mixing scenarios, and document mixing scenario consequences. The bottom rows of Table 5.2 give a couple of mixing scenarios that may be possible for this system. If mixing scenarios with undesired consequences are identified that have a reasonable likelihood of occurring during the lifetime of the facility, then it can be concluded that operation of the incinerator does not involve chemical reactivity hazards. In this case, the information in Chapter 4 will not need to be applied. If the answer to any of the Questions 7 through 12 is, then one or more chemical reactivity hazards are present. The information in Chapter 4 should be used to identify and manage the hazards. Figure 5.2 indicates the path taken through the screening flowchart for the combustor example, as documented in Table 5.2.

5 5 Worked Examples 123 TABLE 5.2 Combustor Example Documentation FACILITY: Rarified Research/Incinerator Do the answers to the following questions indicate chemical reactivity hazard(s) are present? 1 AT THIS FACILITY:,, or BASIS FOR ANSWER; 1. Is intentional chemistry performed? Combustion is a chemical reaction 2. Is there any mixing or combining of different substances? 3. Does any other physical processing of substances occur? 4. Are there any hazardous substances stored or handled? 5. Is combustion with air the only chemistry intended? 6. Is any heat generated during the mixing or physical processing of substances? 7. Is any substance identified as spontaneously combustible? 8. Is any substance identified as peroxide forming? 9. Is any substance identified as water reactive? Wastes are mixed before feeding to incinerator Designed for controlled combustion No indication of exothermic behavior when premixing wastes 10. Is any substance identified as an oxidizer? 11. Is any substance identified as selfreactive? 12. Can incompatible materials coming into contact cause undesired consequences, based on the following analysis? See analysis on the next page

6 124 Managing Chemical Reactivity Hazards TABLE 5.2 (continued) SCERIO CONDITIONS RMAL? 2 R, NR, or? 3 INFORMATION SOURCES; 1. Acetone from leaking bottle contacts paper material in feeder No feeder is enclosed and above ambient temperature NR Acetone not reactive with paper material by common experience; feeder is hot but below autoignition temperatures; seal should prevent flashback 2. Container of dicumyl peroxide powder breaks in feeder and contacts residual combustible solids or liquids No feeder is enclosed and above ambient temperature R May ignite and burn rapidly in feeder; however, analysis indicates feeder design will contain material and flame, and no significant undesired consequences are expected; also, this material would not normally be put into incinerator 1 Use Figure 3.1 with answers to Questions 1 12 to determine if answer is or 2 Does the contact/mixing occur at ambient temperature, atmospheric pressure, 21% oxygen atmosphere, and unconfined? (IF T, DO T ASSUME THAT PUBLISHED DATA FOR AMBIENT CONDITIONS APPLY) 3 R = Reactive (incompatible) under the stated scenario and conditions NR = Nonreactive (compatible) under the stated scenario and conditions? = Unknown; assume incompatible until further information is obtained 5.3. Repackaging Example Eastown Industries conducted a Management of Change review for switching to a new propylene dichloride supplier. The propylene dichloride was purchased in railcar quantities and unloaded into a large storage tank, from which it was metered into 55 gal drums for sale to customers. During the Management of Change review, it was identified that the supplier sometimes used aluminum railcars for other products. The shift supervisor raised the question of what would happen if the propylene dichloride was received in an aluminum railcar and remained on the siding for a few days before unloading its contents into the storage tank. Referring to the questions in Chapter 3, Question 1 ( Is intentional chemistry performed at your facility? ) can be answered for this example, since the unloading, storage and repackaging operation involves no intended chemical reactions. Likewise, Questions 2 and 3 can be answered, since mixing and physical processing are also not intended. Question

7 5 Worked Examples 125 Figure 5.2. Screening flowchart path for combustor example.

8 126 Managing Chemical Reactivity Hazards 4 should be answered, since propylene dichloride (1,2-dichloropropane) is a flammable liquid, having a flash point of 60 F (16 C). A review of material safety data and standard references for propylene dichloride would result in answering to Questions 7 through 11, since this material is not indicated to be spontaneously combustible, peroxide forming, water reactive, an oxidizer, or self-reactive. Addressing the scenario for Question 12 of the consequences of receiving the material in an aluminum railcar, it would be found that propylene dichloride will react with oxidizing materials, alkalis, and alkali and other metals such as aluminum (NFPA 2002). The consequences of such a reaction might range from causing a leak and a fire if ignited, to a more catastrophic railcar incident. Group compatibility data indicates no reaction between propylene dichloride and aluminum oxide (which would form an outside layer on the aluminum metal). However, heat generation, may cause pressurization and forms very unstable explosive metallic compounds are the results of combining propylene dichloride and aluminum powder (AA 2002). A review of previous incidents found a reported incident where an aluminum railcar filled with this material leaked from the railcar within 24 hours. Based on this information, it was decided that positive steps needed to be taken to: Convey and retain this information throughout the lifetime of the facility Ensure propylene dichloride is never received in an aluminum railcar Conduct tests to determine all possible consequences under the full range of ambient conditions which could be experienced Contact the supplier to communicate the hazard and ensure provisions are in place for avoidance. If more severe consequences than a leaking railcar were found, then even greater precautions would likely be warranted. These precautions would need to ensure no material is received in an aluminum container. Also, aluminum must be excluded from the facility as a material of construction in pipes, tanks, valves, pumps, and especially any container in which product would be transferred to a customer. Table 5.3 shows what the documentation of the screening might look like for this example.

9 TABLE 5.3 Repackaging Example Documentation FACILITY: Eastown Industries Do the answers to the following questions indicate chemical reactivity hazard(s) are present? 1 AT THIS FACILITY:,, or BASIS FOR ANSWER; 1. Is intentional chemistry performed? Repackaging only 2. Is there any mixing or combining of different substances? 3. Does any other physical processing of substances occur? 4. Are there any hazardous substances stored or handled? 5. Is combustion with air the only chemistry intended? 6. Is any heat generated during the mixing or physical processing of substances? 7. Is any substance identified as spontaneously combustible? 8. Is any substance identified as peroxide forming? 9. Is any substance identified as water reactive? 10. Is any substance identified as an oxidizer? 11. Is any substance identified as selfreactive? 12. Can incompatible materials coming into contact cause undesired consequences, based on the following analysis? Repackaging only Repackaging only Propylene dichloride is a flammable liquid See analysis below SCERIO CONDITIONS RMAL? 2 R, NR, or? 3 INFORMATION SOURCES; 1. Propylene dichloride received in aluminum railcar No confinement within railcar R Previous incident resulted in leak within 24 hours. AA Chemical Reactivity Worksheet indicates combining propylene dichloride with aluminum powder results in heat generation, may cause pressurization and forms very unstable explosive metallic compounds. 1 Use Figure 3.1 with answers to Questions 1 12 to determine if answer is or 2 Does the contact/mixing occur at ambient temperature, atmospheric pressure, 21% oxygen atmosphere, and unconfined? (IF T, DO T ASSUME THAT PUBLISHED DATA FOR AMBIENT CONDITIONS APPLY) 3 R = Reactive (incompatible) under the stated scenario and conditions NR = Nonreactive (compatible) under the stated scenario and conditions? = Unknown; assume incompatible until further information is obtained

10 128 Managing Chemical Reactivity Hazards 5.4. Physical Processing Example 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. Referring to the questions in Chapter 3, Question 1 can be answered for this example, since the physical processing involves no intended chemical reactions. Question 2 is answered, since mixing or combining of different substances is not intended. Question 3 should be answered, since the operation involves physical processing. The input of mechanical energy to the ammonium dichromate raises its temperature somewhat in the screw conveyor, so Question 6 should be answered. Consequently, the Preliminary Screening Method indicates that a chemical reactivity hazard should be expected. The information in Chapter 4 would be useful in both identifying and managing any chemical reactivity hazards that are present. Questions 7 through 12 of the Preliminary Screening Method could be used to give an indication of what chemical reactivity hazards to expect. Table 5.4 shows what the documentation of the Preliminary Screening might look like for this example Mixing Example This example presents a simplified retrospective of the 1995 explosion and fire at the Napp Technologies facility in Lodi, New Jersey (EPA 1997). The intent is to illustrate the Preliminary Screening Method for the type of process involved in the incident. A contract manufacturer is contracted to prepare one 8100 lb batch of a gold precipitating agent. Ingredients are mixed in a 125 ft 3 (6 m 3 ) cone blender which is insulated and has a steel jacket to allow cooling and heating with a water/glycol mixture. The precipitating agent consists of approximately 66% sodium hydrosulfite, 22% aluminum powder and 11% potassium carbonate by weight. After blending these dry ingredients, a small amount of liquid benzaldehyde is added for odor control. The product blend is packaged into eighteen 55 gal drums for shipment.

11 5 Worked Examples 129 TABLE 5.4 Physical Processing Example Documentation FACILITY: Upstream Feeds Do the answers to the following questions indicate chemical reactivity hazard(s) are present? 1 AT THIS FACILITY:,, or BASIS FOR ANSWER; 1. Is intentional chemistry performed? Physical processing only 2. Is there any mixing or combining of different substances? 3. Does any other physical processing of substances occur? 4. Are there any hazardous substances stored or handled? 5. Is combustion with air the only chemistry intended? 6. Is any heat generated during the mixing or physical processing of substances? 7. Is any substance identified as spontaneously combustible? 8. Is any substance identified as peroxide forming? 9. Is any substance identified as water reactive? Ammonium dichromate only Mechanical screw conveyor Some temperature increase due to mechanical energy of screw conveyor Ammonium dichromate is water soluble 10. Is any substance identified as an oxidizer? Listed in NFPA 430 as Class 3 Oxidizer 11. Is any substance identified as selfreactive? 12. Can incompatible materials coming into contact cause undesired consequences? Decomposes at 170 C, generating gas, swelling dramatically, rupturing closed containers; may also be shock sensitive No scenarios identified 1 Use Figure 3.1 with answers to Questions 1 12 to determine if answer is or

12 130 Managing Chemical Reactivity Hazards Referring to the questions in Chapter 3, Question 1 ( Is intentional chemistry performed at your facility? ) would be answered for this example, since the operation consists only of loading, blending, and packaging, with no intended chemical reactions. Question 2 ( Is there any mixing or combining of different substances? ) would be answered, since the blending operation involves mixing of the ingredients. Assuming no indication of heat generation is reported for the intended operation, Question 6 would be answered. A review of material safety data and standard references for the ingredients may result in answering Questions 7 through 11 as shown in Table 5.5. Two of the ingredients, aluminum powder and sodium hydrosulfite, are known to be reactive chemicals, so a chemical reactivity hazard is obviously present. At this point, the Preliminary Screening Method would point the user to the information in Chapter 4, for identifying and managing chemical reactivity hazards. Two example scenarios for Question 12 are also shown in Table 5.5. A third scenario that could be investigated would be the addition of excess benzaldehyde to the mixture. The group contribution method of the AA Chemical Reactivity Worksheet (AA 2002) predicts the generation of heat and flammable gases if benzaldehyde and sodium hydrosulfite were combined. A fourth scenario might be found by a review. For example, Bretherick s Handbook (Urben 1999) indicates an equimolar mixture of potassium carbonate and magnesium gives an explosive substance. Since aluminum and magnesium have analogous hazards, potassium carbonate and aluminum might likewise pose a reactivity hazard. Other scenarios are also possible. The Preliminary Screening Method is not intended to identify all conditions under which reactive chemicals and incompatibilities may lead to uncontrolled reactions. However, it should give an indication whether chemical reactivity hazards exist, as well as what to investigate more closely by analysis and testing.

13 5 Worked Examples 131 TABLE 5.5 Mixing Example Documentation FACILITY: Napp Technologies, Inc., Lodi, New Jersey Do the answers to the following questions indicate chemical reactivity hazard(s) are present? 1 AT THIS FACILITY:,, or BASIS FOR ANSWER; 1. Is intentional chemistry performed? Loading, blending, and packaging only 2. Is there any mixing or combining of different substances? 3. Does any other physical processing of substances occur? 4. Are there any hazardous substances stored or handled? 5. Is combustion with air the only chemistry intended? 6. Is any heat generated during the mixing or physical processing of substances? 7. Is any substance identified as spontaneously combustible? 8. Is any substance identified as peroxide forming? 9. Is any substance identified as water reactive? 10. Is any substance identified as an oxidizer? 11. Is any substance identified as selfreactive? 12. Can incompatible materials coming into contact cause undesired consequences, based on the following analysis? Blending of ingredients in cone blender No indication of heat generation from previous batch or from nature of blend Sodium hydrosulfite is DOT/UN Hazard Class 4.2, Spontaneously Combustible Material; finely divided aluminum powder is pyrophoric without oxide coating Sodium hydrosulfite is water reactive; uncoated aluminum powder is DOT/UN Hazard Class 4.3, Dangerous When Wet Heating of sodium hydrosulfite can initiate self-sustaining exothermic decomposition See analysis on the next page

14 132 Managing Chemical Reactivity Hazards TABLE 5.5 (continued) SCERIO CONDITIONS RMAL? 2 R, NR, or? 3 INFORMATION SOURCES; 1. Vacuum seal cooling water enters blender, reacts with aluminum powder and sodium hydrosulfite, and initiates exothermic decomposition No N 2 atmosphere, confinement in blender R Both aluminum powder and sodium hydrosulfite are water reactive 2. Glycol/water mixture leaks from jacket into blender, reacts with aluminum powder and sodium hydrosulfite, and initiates exothermic decomposition No N 2 atmosphere, confinement in blender R AA Worksheet indicates combining sodium hydrosulfite with ethylene glycol is explosive due to vigorous reaction or reaction products may produce detonation, may cause fire, and indicates flammable gas generation and heat generation by chemical reaction, may cause pressurization 1 Use Figure 3.1 with answers to Questions 1 12 to determine if answer is or 2 Does the contact/mixing occur at ambient temperature, atmospheric pressure, 21% oxygen atmosphere, and unconfined? (IF T, DO T ASSUME THAT PUBLISHED DATA FOR AMBIENT CONDITIONS APPLY) 3 R = Reactve (incompatible) under the stated scenario and conditions NR = Nonreactive (compatible) under the stated scenario and conditions? = Unknown; assume incompatible until further information is obtained

15 5 Worked Examples Oxygen System Example A University Lab expansion includes installation of a distribution system to provide gaseous oxygen from manifolded cylinders to a biological laboratory. No chemical reactivity hazards have been previously identified for the lab facilities. Referring to the questions in Chapter 3, Questions 1, 2, and 3 can be answered for this example, assuming chemical reactions, mixing, and physical processing are not intended to be part of the laboratory facilities. Question 4 should be answered, since oxygen is considered hazardous as an oxidizing gas. With respect to Questions 7 through 11, a review of material safety data and standard references for oxygen would result in answering only to Question 10. Table 5.6 shows how this example might be documented, including an incompatibility scenario.

16 TABLE 5.6 Oxygen System Example Documentation FACILITY: University Lab Oxygen Distribution System Do the answers to the following questions indicate chemical reactivity hazard(s) are present? 1 AT THIS FACILITY:,, or BASIS FOR ANSWER; 1. Is intentional chemistry performed? Not part of laboratory procedures 2. Is there any mixing or combining of different substances? 3. Does any other physical processing of substances occur? 4. Are there any hazardous substances stored or handled? 5. Is combustion with air the only chemistry intended? 6. Is any heat generated during the mixing or physical processing of substances? 7. Is any substance identified as spontaneously combustible? 8. Is any substance identified as peroxide forming? 9. Is any substance identified as water reactive? 10. Is any substance identified as an oxidizer? 11. Is any substance identified as selfreactive? 12. Can incompatible materials coming into contact cause undesired consequences, based on the following analysis? Not part of laboratory procedures Not part of laboratory procedures Oxygen is an oxidizing compressed gas Noncombustible gas Oxygen is a strong oxidizing agent See analysis below SCERIO CONDITIONS RMAL? 2 R, NR, or? 3 INFORMATION SOURCES; 1. Oxygen gas contacts oil film remaining in oxygen distribution system after installation No pressurized, enclosed R AA Worksheet indicates mixing O 2 with petroleum lubricating oil may cause fire; reaction may cause pressurization 1 Use Figure 3.1 with answers to Questions 1 12 to determine if answer is or 2 Does the contact/mixing occur at ambient temperature, atmospheric pressure, 21% oxygen atmosphere, and unconfined? (IF T, DO T ASSUME THAT PUBLISHED DATA FOR AMBIENT CONDITIONS APPLY) 3 R = Reactive (incompatible) under the stated scenario and conditions NR = Nonreactive (compatible) under the stated scenario and conditions? = Unknown; assume incompatible until further information is obtained 134