Heptafluoropropane (HFC-227ea): a Halon Alternative During the past 20 years it has become widely accepted that the release of volatile man-made halocarbons (notably CFCs and bromine containing Halons into the earth’s atmosphere) causes depletion of stratospheric ozone. In response to society’s concern over potential effects of ozone depletion, a variety of national and international regulations have been promulgated, the best known being the Montreal Protocol- 1987 on substances that deplete the Ozone Layer. This landmark international agreement has already been revised from time to time in response to ever-worsening news about stratospheric ozone levels.
The unique combination of properties associated with certain fluorinated methanes and ethanes has led to their widespread use in fire suppression systems. These fire suppression agents are characterized by high fire suppression efficiency, low toxicity, low residue formation after extinguishments, low electrical conductivity and long term storage stability.
The three popular halogenated fire suppression agents are bromotrifluoromethane (CF3Br, BTM, Halon 1301), bromochlorodifluoromethane (CF2BrCl, BCF, Halon 1211) and 1,2–dibromotetrafluoroethane (BrCF2CF2Br, Halon 2402). Currently Halon-1301 (Bromotrifluoromethane, CF3Br) and Halon-1211 (Bromochlorodifluoromethane CF2ClBr) are used as fire extinguishants and have high ozone depletion potential. However, because of their recent implication in the destruction of stratospheric ozone, the production and use of these life-saving agents is being severely restricted. As a result, intensive research efforts are currently underway in both the industrial and academic sectors to find suitable replacements for these agents. It is being realized world over that in the absence of Halons due to Montreal Protocol to phase out Ozone Depletion Potential (ODP) substances, the search for alternatives was begun and identified Heptafluoropropane (HFP) as one of the best and closest chemical substitute for Halons.
Heptafluoropropane (HFP) is a hydrofluorocarbon and has been accepted world over for many applications due to its zero ODP, low GWP & toxicity in comparison to other chemical substitutes like NAFS-III (A blend of HCFs), PFCs (C4F10) etc. Heptafluoropropane (HFP) may find wide applications where Halon-1301, was the choice of user industries in the past.
The consumption of Halon-1211 and Halon-1301 in India was 750 MT in 1991, this has gradually decreased to 210 MT in 1997, presently it is around 25 MT. Based on this, it can be safely assumed that, the balance is met from the newer substitutes like Heptafluoropropane (HFP). Therefore, the present Indian demand will be in the range of 500-750 MT/annum for Heptafluoropropane (HFP).
The critical properties for alternatives to the halons are
- High fire suppression efficiency
- No residue level
- No electrical conductivity
- High stability and
- Low toxicity of original vapors and decomposed products.
In addition, the new chemical substitutes must have:
- Zero or near zero Ozone depletion potential
- Lowest possible global warming potential and
- Low atmospheric life time.