Re: wet coal and the water car myth...

... this discussed coal-water fire danger may be one of the many
urban enviro legends,
along with other scare-stories that oil soaked rags do self-ignite,
that open linseed-oil based paint cans do self combust,
that iron filings and flour dust do cause spontaneous explosions,
that leaded paint will cause little kids to chew on house walls
and turn'em insane, etc., etc., etc.
True, there may have been a few isolated incidents where the above
accusations were levied, but do they routinely occur?.... ahahaha...
Watering the coal may simply be a sensible way to prevent the
inhalation of the nasty coal dust that has indeed caused "black lung"
for folks who do work in such environments. Threatening someone
with fire and explosions is more effective than warning them that they
might get sick... in the future, maybe, perhaps, eventually... ahaha...
hanson

------------ PS: ***** enviros! -------------
http://groups.google.com/group/sci.environment/msg/70ed6372eccc32ba

"Ernieman" <ernieman7REMOVECAPS@verizon.net> wrote

"Gordon" <gordonlr@DELETEswbell.net> wrote

schultr@mail.biu.ack.il (Richard Schultz) wrote:

Salmon Egg salmonegg@sbcglobal.net> wrote:
: "Richard Schultz" <schultr@mail.biu.ack.il> wrote:
:> For many grades of coal, wetting the coal is exothermic :> (i.e.
produces heat), which makes it easier to light the
:> rest. There have been cases where coal in storage has :> caught fire
because it got wet, and the wetting released :>enough heat to set the
coal on fire spontaneously.
:
: So what is the reaction?

It's been 25 years since I worked in the coal industry, but as I recall,
it's not a chemical reaction, but simple adsorption of the water on the
interior surfaces of the coal. Coal naturally has a certain amount of
moisture in it. To drive off that moisture, one must heat the coal, so
exposing dry coal to moisture will cause uptake of the moisture and
giving off of heat. The heat given off can be enough to ignite the coal,
especially if the wet coal is in contact with dry coal. IIRC, coal high
in iron pyrite has an especially high heat of wetting, but I'm not sure
exactly why that is.

-----
Richard Schultz

Way back when I was a kid, the local railroad company would buy
carloads of coal, fresh from the mines, then offload it into
piles on an open lot. They sold this to customers (household and
commercial building managers) for heat and cooking fuel. Those
huge piles of fresh coal were exposed to heavy rainfall from time
to time, yet none of these piles of coal ever went ballistic from
the addition of rain to the coal. I don't recall ever seeing
steam or other signs that the coal was getting hot down deep
inside the pile, when they dug into these piles to load up a
customer's truck.

The original poster gunananda <gunananda@yahoo.de> said
"my grandpa told me that they had to wet the coal before they fired
them in the locomotion, because this would increase the efficency."

I wonder if the wetting was to prevent fire in the coal storage
compartment. I read in a book about 40 years ago that in the days of the
wood steam ships, the coal was wetted down once a day to keep the coal
from catching fire. If all of the coal is kept wet, no areas of dry and
wet coal, no heat is released from rehydration, and fire is prevented.

Ernie