RE: Coal Burning Power Plant.

["Weiner, Ruth" <rfweine@sandia.gov>]

In case you wonder about my information: In 1985-86, I wrote the chapter on
radioactive emissions from power boilers for the EPA BID for radioactive
substances.

Coal in the U. S. ranges from about 10% by weight ash to almost 25% by
weight ash.  The ash is the residue after burning and given the burning
conditions would probably contain little or no combustible substances.  U.
S. coal is between 0.25% and about 2% sulfur, and much of the higher-sulfur
coal is desulfurized before burning (oil can have fairly high sulfur content
as well.  Coal contains nitrogen, and burning coal also fixes atmospheric
nitrogen, so that the NO/NO2 emissions are partly from what is in the coal
and  partly what is in the air.

Emission standards for SO2, nitrogen oxides and particulate matter have been
in place since 1970.  Virtually all plants control fly ash and SO2, the
former usually to at least 95% (this does not count startup, shutdown, or
breakdown).  To my knowledge, no plant tries to control its CO2 emissions,
nor is this required by any air pollution control regulation.

Clearly only my own opinion.

Ruth F. Weiner, Ph. D.
Sandia National Laboratories 
MS 0718, POB 5800
Albuquerque, NM 87185-0718
505-844-4791; fax 505-844-0244
rfweine@sandia.gov


-----Original Message-----
From: denison.8@osu.edu [mailto:denison.8@osu.edu]
Sent: Monday, October 11, 1999 11:19 PM
To: Multiple recipients of list
Subject: Re: Coal Burning Power Plant.


Stewart,

the numbers quoted in the prior message may be correct, but we can't know
for sure without knowing the elemental/chemical composition of the coal
being burned.  Your calculation seems to assume that both the unburned coal
and the remaining ash are pure carbon.  However, a measurable fraction of
the total coal mass will consist of impurities such as sulfur (responsible
for the sulfur dioxide and sulfuric acid consitiuents of the stack gas) and
daughter products from the uranium and thorium decay series.  In addition,
the fact that the ash mass is 20% of the fuel mass indicated that we've got
either a hell of a lot of impurities or incomplete oxidation of the
available carbon.  I'm guessing that the ash consists of a mish-mash of
partially-oxidized carbon species and the solid combustion products from
the impurities.  Since we don't have pure carbon going in as fuel or coming
out as ash, we can't calculate the CO2 yield simply from the mass
difference.

If someone has the data on the elemental/chemical composition of the fuel
used in the British plants, I'd be interested in seeing it.  We'd also need
some sort of data on the efficiency of the combustion process to calculate
the fractions of the carbon and impurities that go up the stack and stay in
the ash.

> A 2000 MW power station burns approximately 5,000,000 tons of coal each
> year.  This produces
>
> CO2                10,000,000 tons
> Ash                  1,000,000 tons >>
>
>The above numbers for C to CO2 seem incorrect. Given the 5,000,000 tons of
>coal to fire a 2,000 MW(e) plant which is right for reasonable capacity
[80%
>of so], with 1,000,000 tons ash, this leaves about 4,000,000 tons of
carbon.
>C combusted to CO2 changes mass from 12 to 44 or the ratio of CO2 to C is
>44/12=3.66. Thus the total CO2 produced should be about 4,000,0000 x 3.66
or
>about 14,666,000 tons not 10,000,000.
>
>What's wrong with the above math which shows the Nuclear Electric plc
>estimates for CO2 production to be low by about 32%?
>


J. Eric Denison
Nuclear Engineering Program
The Ohio State University
2030 Robinson Laboratory
206 West 18th Avenue
Columbus OH 43210
(614) 292-3681 or -1074
denison.8@osu.edu


************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html

************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html