Can Fire Suppressants Promote Ignition? A Study Of HFC-125 and HFC-227

Global Congress on Process Safety
AIChE Spring Meeting and Global Congress on Process Safety
April 30, 2013 - 4:00pm-4:30pm
C2HF5 (HFC-125,) and C3HF7 (HFC-227ea or FM-200) have gained considerable acceptance in the field of fire protection, especially after the restriction of several ozone-depleting substances under the Montreal Protocol. These two substitutes are currently included in the list of the Significant New Alternatives Policy (SNAP) Program of the U.S Environmental Protection Agency (EPA). Their desired properties such as low Ozone Depleting Potential (ODP), relatively low toxicity, electrical non-conductivity, high dispersion capabilities, and low flammability, make them two of the most-used total flooding fire suppressants at the moment. In terms of Minimum Extinguishing Concentration (MEC), C3HF7 and C2HF5, although less effective than bromo-containing compounds, are more efficient than other clean alternatives in the market. Nevertheless, the combustion properties of these agents are not well understood. In fact, previous numerical studies have shown that these compounds can act as combustion promoters at certain conditions, but there are scarce experimental data of HFCs that can be used to certify such predictions. This lack of data shows the necessity of having accurate measurements that can be used for model validation but also to better understand the role of different fire suppressants on the combustion initiation stage towards an optimal and safer application.  To this end, this paper examines the effect of C2HF5 and C3HF7 on the high-temperature chemistry of methane and propane flames at different conditions. Ignition delay time measurements are obtained using a shock tube with reaction monitoring capability. Theoretical analysis is conducted using a detail chemical kinetics mechanism that includes the hydrocarbon and fire suppressants set of reactions. Results show that C2HF5 and C3HF7 can actually act as ignition promoters at certain conditions. These results suggest that these fire suppressants may not be good alternatives to prevent flames, however they can still be used as fire extinguishers after the flame is well established. Finally, sensitivity analysis is carried out to identify the most significant reactions responsible for such behavior, and the results are compared with CF3Br over a similar range of conditions. 
Professional Development Hours
0.5 PDHs
You will be able to download and print a certificate for these PDH credits once the content has been viewed. If you have already viewed this content, please click here to login.
Presenter(s): 

Would you like to access this content?

No problem. You just have to complete the following steps.

You have completed 0 of 2 steps.

  1. Log in

    You must be logged in to view this content. Log in now.

  2. Purchase Technical Presentation

    You must purchase this technical presentation using one of the options below.
    If you already purchased this content recently, please click here to refresh the system's record of ownerships.

Pricing

Credits 0.5 Use credits
List Price $25.00 Buy now
AIChE Members $15.00 Buy now
AIChE Undergraduate Student Members Free Free access
AIChE Graduate Student Members Free Free access
Related Topics: 
Skill Level: