There is an interesting post over at Energy.BlogNotions.com
about a potential replacement for hydrocarbon fuels, anhydrous ammonia. The
author, Kurt Cobb describes six advantages to the use of ammonia:
• It contains no carbon, therefore no greenhouse gasses produced;
• Well-known processes for making ammonia;
• Worldwide ammonia production industry;
• Distribution technology understood;
• Enviable safety record (more on that later);
• Creates nothing that can be classed as pollution
In general this is a well thought out and well documented
discussion about the pro-ammonia arguments. I do however, take exception to the
glib statement about the anhydrous ammonia safety record and note that there
are some serious security issues that must be taken into account in this
discussion.
Safety Record
Anhydrous ammonia is a toxic inhalation (TIH) hazard
chemical. This means that relatively low concentrations in the air can kill
people. Kurt does make one good point about this particular TIH chemical; it is
detectable and obnoxious at concentrations much lower than the lethal
concentration in the air. This does mean that most people on the periphery of
an ammonia cloud will be self-alerted to the danger so that they can undertake
evacuation efforts.
One of the reasons that there have been fewer deaths from
large scale accidents with anhydrous ammonia as compared to chlorine gas
(another industrial scale TIH chemical) is that anhydrous ammonia is lighter
than air so it generally rises above ground level in a release. Chlorine gas is
about twice as heavy as air so that it hugs the ground.
You have to be careful about that word ‘generally’ there are
all sorts of thing that can happen that will affect the rate of ascent of the
gas cloud including air temperature profiles, amount of humidity in the air and
the wind speed in the area. And, of course, if the gas cloud is inside of a
building, all bets are off. And even if the bulk of the release cloud rises
above ground level, air mixing is sure to keep non-lethal ammonia
concentrations over a wide swath of down-wind ground, making life miserable for
people in the short term.
As the 2009 incident
in Swansea, SC showed even a gas cloud that is generally rising can cause
deaths and this was from a relatively small volume release. If there is a
drastic increase in the amount of anhydrous ammonia used in commerce the number
of accidents can be expected to increase and I suspect that the accident rate
would increase as small spills tend to cause personnel to evacuate the area
rather than take immediate actions to stop the leak.
CFATS
Anhydrous ammonia is a DHS chemical of interest (COI) for
the CFATS program. Any facility that has over 10,000 lbs of anhydrous ammonia
on site (about 1800 gallons, a relatively small pressure tank) is required to
register with DHS and to submit a Top Screen. The current extended CFATS
community includes more than 40,000 facilities that have submitted Top Screens.
That number would significantly increase if we replaced oil/gas fired energy
producing facilities with anhydrous ammonia fueled facilities.
Once a Top Screen is submitted DHS looks at the potential
effects of a release of chemicals like anhydrous ammonia to determine if they
are at high-risk for terrorist attack. While DHS will not share the details of
their assessment regime for security reasons, it is clear that the more people
that would be affected by a release the higher the probability that DHS would
declare the facility to be at high-risk. That declaration brings with it the
requirement to fully implement the security standards set forth in the CFATS
regulations.
Those security measures would seriously add to the cost
(capital and operational) of an anhydrous ammonia fueled power generation
facility. Coal, oil or natural gas power plants are not currently covered
because of fuels (they may be covered for other chemicals) since coal, oil, and
natural gas are not listed COI.
TSA Security
Anhydrous ammonia is specifically listed {§1580.100(b)(2)} in the
TSA freight rail security regulations (49
CFR §1580.100 et seq)
as a rail security-sensitive material. These materials require special handling
by shippers, railroads, and receivers in high-threat urban areas (HTUA).
These special handling
requirements, including train speed limits, will also add costs to the use
of anhydrous ammonia as a power generation fuel. Again, these costs need to be
taken into account in determining the economic viability of this ‘new’ fuel.