Jerry Russell estimated that the amount of energy required to crush concrete to 60 micron powder is about 1.5 KWH/ton. (See
http://www.911-strike.com/powder.htm.)
1) Russell’s estimate of 1.5 kWh/t is based off of
http://www.b-i-m.de/public/ibac/mueller.htm This is an erroneous estimate as the 1.5 kWh/t energy cost is of the impact crusher the paper is using for comparative purposes to a different method. Specifically, “mechanical crushing methods (impact crusher: roughly 1.5 kWh/t concrete)”
2) Russell’s use of 60 microns is in response to Eric Hufschmid’s “concrete physics problem” challenge. Hufschmid has been contacted and asked to provide a source for his use of 60 microns. He has opted not to do so.
That paper incorrectly assumes there were 600,000 tons of concrete in each tower, but Russell later provided a more accurate estimate of 90,000 tons of concrete per tower, based on FEMA's description of the towers' construction.
1) Neither Russell, nor Hoffman, provide a source for either estimate of the amount of concrete in each tower.
That estimate implies the energy sink of concrete pulverization was on the order of 135,000 KWH per tower, which is already larger than the energy source of gravitational energy.
1) Given that the selection of 1.5 kWh/t is based off of the energy cost/efficiency of the impact crusher, and not the amount of energy needed to crush the concrete as calculated from a purely energy/work standpoint the 135,000 kWh estimated energy sink of the towers is wrong and is without doubt higher than the actual value.
However, the size of this sink is critically dependent on the fineness of the concrete powder, and on mechanical characteristics of the lightweight concrete thought to have been used in the towers. Available statistics about particle sizes of the dust, such as the study by Paul J. Lioy, et al., characterize particle sizes of aggregate dust samples, not of its constituents, such as concrete, fiberglass, hydrocarbon soot, etc. Based on diverse evidence, 60 microns would appear to be a high estimate for average concrete particle size,
1) The Paul J. Lioy, et al abstract (which is the cited source) states, “The largest mass concentrations were > 53 µm in diameter.”
2) The full paper,
http://www.ehponline.org/members/2002/110p703-714lioy/lioy-full.html , states that the estimated mass of material involved is “> 10 106 tons”
3) The sampling done for the Lioy paper dealt directly with the dust component of the debris, “These two samples were collected from 10-15 cm-thick deposits that were on the top of two automobiles about 0.7 km from the WTC site” and therefore their particle size is dealing specifically with the dust particles and is not a representation of the average particle size of all debris.
4) Lioy used two methods for separating the particles, “a) a gravimetric sieving analysis that separated the mass of lint and nonfibrous material into fractions > 300 µm, 75-300 µm, and < 75 µm in diameter; and b) an aerodynamic separation for the particle size fractions of < 2.5 µm, 2.5-10 µm, and 10-53 µm in diameter, with a gravimetric sieving that separated the particles > 53 µm in diameter before the aerodynamic sizing of the samples. The separations were based on the design or availability of specific size separation techniques in the laboratories.”
5) Lioy’s table here
http://www.ehponline.org/members/2002/110p703-714lioy/tab1.jpg shows that the “> 53 µm in diameter” statement in the abstract dealt specifically with the aerodynamically separated sample and accounted for 61.5%, 52.21% and 63.6% of the mass of the aerodynamically separated sample. However, when looking at the first step of the separation process (sieved sample) we see that particles < 75 µm in diameter account for 38%, 30%, and 37% of the sample masses. Particles between 75 µm and 300 µm in diameter account for 46%, 49%, and 42% of the samples and particles > 300 µm in diameter account for 16%, 23%, and 21% of the samples. The use of 60 µm in diameter for the calculations is erroneous at best, and dishonest at worst. To highlight what this table implies;
in the three samples 62%, 72%, and 63% of the mass of the samples was > 75 µm in diameter.
suggesting 135,000 KWH is a conservative estimate for the magnitude of the sink.
1) At this point I am confident in saying that the estimate of 135,000 kWh is just plain wrong and entirely too high.
2) Couple the poor choice of particle size with this
http://www.epa.gov/wtc/panel/pdfs/meeker-20041115.pdf#search="EPA particle WTC analysis"
3) First, I highly suggest reading the short paper, as it describes the EPA's methodology in a very detailed manner.
4)
5)
6)
Code:
Table 1. Range in area percent of major and minor components for all samples.
7) Particle Type Comment Percent Range, Outdoor Percent Range, Indoor
8) Gypsum Includes all Ca sulfate particles 26.3 – 53.3 63.3 – 63.7
9) Concrete All phases compatible with hydrated cement 19.3 – 30.8 14.0 – 21.0
10) MMVF* Total 20.3 – 40.6 9.5 – 19.2
11) <snip>
12)
13) Wait. You read that too fast. Let me reiterate
14)
Particle Type
15) Gypsum
16)
Percent Range, Outdoor
17) 26.3 – 53.3
18)
Percent Range, Indoor
19) 63.3 – 63.7
20)
21)
Particle Type
22) Concrete
23)
Percent Range, Outdoor
24) 19.3 – 30.8
25)
Percent Range, Indoor
26) 14.0 – 21.0
27)
28) Let me put it another way. In the EPA's sample, drywall dust accounted for more than ~15% more of the outdoor sample than concrete; and account for more than ~46% more of the indoor sample.
29)
30) The bulk of the cloud seen from the collapse of the towers is
drywall dust not concrete dust.
means Hoffman’s entire paper is based upon a
faulty premise
I’m not going to analyze the paper further, because it would be a pointless exercise. His premise if flawed. His initial data is wrong. His paper is crap.
