Burning Lime
from Right Use Of Lime In Soil Improvement
Methods of Burning. Limestone contains the calcium and magnesium that
must be the chief source of supply of American soils, though marls,
ashes, etc., have their place. The burning of the stone has been the
leading means of bringing it to a condition of availability to the soil,
excepting, of course, the vast work of disintegration carried on through
all the ages by nature. Pulverization of the rock by machinery for use
on land is recent.
The devices for burning are various, a modern lime plant containing
immense kilns, cylindrical in form, the stone being fed into them at the
top continuously, and the lime removed at the bottom. A large part of
the lime that is sold for use on land is made in plants of this kind.
Some is burned in kilns of cheap construction, but a traveler through a
limestone country finds few such kilns now in use.
The Farm Lime Heap. A common method of producing lime for farm use
has been, and continues to be, a simple and inexpensive one, involving
the use only of wood, coal and limestone, with earth as a covering. Dr.
Wm. Frear, chemist of the Pennsylvania station, in Bulletin 261 of the
Pennsylvania department of agriculture, describes a method of burning
lime on the farm as follows: "A convenient oblong piece of ground is
cleared, and leveled if need be, to secure a fit platform. Upon this
level is placed a layer or two of good cord wood, better well seasoned,
arranged in such manner as to afford horizontal draught passages into
the interior of the heap. Between the chinks in the cord wood, shavings,
straw or other light kindling is placed. The stone having been reduced
to the size of a double fist, sometimes not so small, is laid upon the
cord wood, care being taken to leave chinks between the stones just as
between the bricks in a brick kiln. It is preferred that this layer of
stone should not exceed six to ten inches in thickness.
"In some cases, temporary wooden flues, filled with straw, are erected,
either one at the center or, if the heap is elliptical, one near each
end, and the stone and coal are built up around them; thus, when they
are burned out, a chimney or two is secured, which may be damped by
pieces of stone or sod. Upon this first layer of stone is spread a layer
of coal, and upon that a thicker layer of stone (12 inches), and so on,
coal and stone alternating until the heap is topped with smaller stone.
The largest stones should be placed near the top of the heap, but not
near the outside, so that they may be exposed to the highest heat. The
proportion of coal is diminished in the upper layers, the effort being
to distribute one-half of the total coal employed in the two lower
layers, so as to secure the highest economy possible in the use of the
fuel.
"Fire is then kindled in the straw or shavings; when the flames have
communicated themselves to the cord wood and lowermost layer of coal,
and tongues of flame shoot out from the crevices in the sides of the
heap, earth, previously loosened by a few turns of the plow about the
heap, is rapidly spread over the entire heap, thus damping the drafts
and retarding the combustion. Steam and smoke slowly escape during the
first hours, but later the entire heap, including the outer covering of
earth, is heated to a dull red glow. The burning goes on slowly for
several days, the interior often being hot for several weeks. When the
lower portion of the heap has reached an advanced stage of calcination,
a portion of the outer layer of lime sometimes slips down; if so, a
fresh covering of earth must promptly be applied at the exposed point;
otherwise it will serve as a vent for the heat, and the top and other
sides will fail of proper calcination."
Next: Lime Hydrate
Previous: Fresh Burned Lime
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