History of Saginaw county, Michigan; together with ... portraits ... and biographies ... History of Michigan ...

HISTORY OF SAGINAW COUNTY.

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on both sides of the middle wall. The outside flues run into the
chimney, which is placed at one side of the front of the block ---
the space under the pan being reduced to one foot.
The advantage of this arrangement of the flues is that as the
brine boils freely over the fire flue the salt, as it makes, is thrown
to the cool side of the pan, and therefore is not so liable to bake to
the bottom before it is raked out. Another advantage is in the
economy of the heating surface, the entire amount being well used
up before it gets to the chimney. This is shown in the amount of
salt made, Ayers & Co. reporting the making of 140 barrels of salt
with 13 cords of hemlock wood in a day of 24 hours.
Tile brine for pan blocks is settled cold in the outside cisterns,
and in most instances is brought to a saturation by the inside steam
settlers. The salt, as it makes in the pan, is drawn out by rakes
upon the draining board, where it remains for a time, when it is
shoveled into barrows and taken to the store bins for further
drainage. It is very desirable that the draining boards should be
so arranged in pan blocks that the workmen should not be compelled to walk over them in the operation of drawing or wheeling
off the salt.
By Steam.-The evaporation of salt brine by the steam process
is now producing the largest portion of salt made in Michigan. We
take for the purpose of better describing the process a steam salt
block which is 150 feet long, 122 feet wide, and has an elevation of
52 feet to the top of the ventilator. Height of ventilator, 16 feet.
Included, therefore, in the above space are the inside settlers, grainers, salt bins, and packing room:
The inside steam settlers are 150 feet long, 11 feet wide, and 6
feet deep, made of four-inch plank, well keyed together and tightly
calked. This block is supplied with seven grainers, 150 feet long,
11 feet wide and 16 inches deep. Over each grainer are the draining boards running the entire length. Passing through each
settler and grainer, and near the bottom, are four-inch galvanized
tubing, four or five in number, depending on the size of the grainer,
through which exhaust or live steam is forced. In the steam as in
the kettle process, the brine is first pumped into the outside
settlers, where it is partially settled. It is then drawn into the
inside steam settlers, where it is heated up by the steam pipes and
brought to saturation-that is, a point just preceding the
formation of salt crystals. It is allowed to remain until all sediment
of iron has fallen to the bottom, by which time it becomes clear as
crystal. The brine is now ready to be drawn into the grainers,
which are filled to about two-thirds their capacity, or nearly full.
As the settled brine comes into the grainers quite warm and fully
saturated it soon commences to make salt, which forms on the
surface of the brine and then falls to the bottom of the grainers,
when a new lot of crystals are formed to fall in the same way. The
brine is also occasionally stirred so as to make the crystals fine.