Improvements in or relating to the Treatment of Salt and in the Means Employed therefor.
Year: 1888

page_text: Date of Application, 6th Dec., 1888
Complete Specification Left, 6th Sept., 1889-Accepted, 19th Oct., 1889
PROVISIONAL SPECIFICATION.
Improvements in or relating to the Treatment of Salt and in the
Means Employed therefor.
1, JAMES WILLIAM HEWSON, of Stockton-on-Tees, in the County of Durham,
Drysalter, do hereby declare the nature of this invention to be as follows :-
My Invention relates to improvements in the process of treating salt in the free
state so as to consolidate it into blocks or moulds of any size or shape and of the
requisite degree of hardness and toughness to enable the said blocks or moulds to
retain their form and condition when packed, stored, or otherwise handled in trans-
mission from producer to consumer.
In the process in general use for moulding and drying salt from the free or dis-
integrated and wet state in which it. leaves the evaporating pans, the salt is moulded
or pressed in wooden moulds and is then exposed for a considerable time to a
uniform temperature after remaining in wood moulds until it sets, when it is taken
out and placed on the flues; this process also requires that the stoves for drying and
consolidating the salt be connected with the same plant employed for evaporating the
brine, the evaporation of the brine and the drying the salt in blocks forming practically
one continuous process.
By my invention I render the process of drying and moulding the salt independent
of the previous process of immediate treatment whilst in the hot state, and by exposing
the salt at any time afterwards in its cold state to a high and increasing temperature.
I accelerate the process of drying and moulding the salt and obtain moulds of the
requisite hardness for commercial purposes, thus enabling salt to be shipped in bulk
and moulded into blocks at any time afterwards at the other end of its journey.
In carrying my invention into effect I employ a drying or annealing oven
specially constructed in which the moulds of salt are subjected first to a moderate
temperature, then to an increased temperature, and finally to a very high temperature.
A stove to effect this purpose may be varied both in general design and arrange-
ment of details, the following construction being found suitable :-an iron plate forms
the cover of a long rectangular chamber and an adjoining fluo divided therefrom
by a partition. The stove is provided with a furnace at one end and an outlet to
a chinney controlled by a damper at the other end, one part of this iron plate is
exposed on its upper side to the outside air, the other part being occupied by a
rectangular chamber extending its full length above the flue so that the same iron
plate which forms the cover or roof of the chamber below and the adjoining fluo
serves as the floor to the chamber above, the furnace communicates with the lower
chamber and the adjoining flue so that the products of combustion pass through
this lower chamber to the chimney. In the place of the wooden moulds or boxes
at present in use I provide moulds made of tin, earthenware, or such other material
as will bear the high temperature to which the salt is exposed. The moulds or
blocks of salt are first placed in the chamber below the iron plate, afterwards on
the exposed part of the upper side of the iron plate, and finally in the chamber
above that part of the iron plate which covers the flue, and are thus subjected to
three grades of temperature of which owing to the position of the iron plate and
the direction of the currents of the hot gases the first is the lowest, the second
an intermediate, and the third the highest temperature.
Dated this 5th day of December 1888.
G. J. CLARKSON,
Agent for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in or relating to the Treatment of Salt and in the
Means Employed therefor.
I JAMES WILLIAM HEWSON of Stockton on Tees in the county of Durham Dry-
salter do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :-
My Invention relates to the process of treating salt and in the means employed
therefor by which salt in the free state is consolidated into blocks of the dimensions or
shapes in ordinary use for commercial purposes and of the requisite degree of hardness
and toughness to enable the said blocks of salt to retain their form and condition when
packed or otherwise handled in transmission from producer to consumer.
In the process in ordinary use for consolidating salt into blocks it is requisite that
the salt be moulded or pressed in a hot and soaked condition such as that in which it
leaves the evaporating pan, which blocks are stored for several days on the flues of
the stove which are a continuation of the flues from the evaporating pan.
In this existing process the adhesiveness of the salt to the hot and soaked state in
which it is moulded or pressed is relied upon to effect the consolidation of the salt into
blocks in combination with the heat of the stove room this process consequently
requires that the drying and consolidating the salt be carried out in stoves connected
with or in easy reach of the plant employed for evaporating the brine so that the
evaporation of the brine and the storing of the salt practically become consecutive
stages of one continuous process; otherwise if the salt is allowed to part with this
heat and moisture until it has reached what is termed the cold free or non-adhesive
state it must be restored to the hot and soaked condition in which it again becomes
adhesive before being moulded and stoved.
By my invention I enable the process of moulding and consolidating salt into blocks
of the requisite fineness, hardness, and toughness, for commercial purposes to be
applied to salt in the free cold state, that is without regard to when and where the
process of evaporating the brine has been carried out or what is practically the same
thing to the amount of heat and moisture contained in the salt at the commencement
of my improved process except that the proportion of moisture should not be below
that which salt in the free state naturally retains salt which has become abnormally
dry should be remoistened to this extent by the addition of water. My invention thus
enables salt to be conveyed from one place to another or shipped in bulk, and after-
wards moulded or consolidated into blocks from the cold free state in which it is
delivered. A further important result of my invention is the facility afforded for
reducing coarse grained salt to fine table salt by substiting a grinding process for
the less certain and more expensive boiling process at present in use for that purpose,
in which the fineness of the salt depends on the intensity and rapidity of the operation
of boiling. By my improved process rough grained salt, such as common salt, broad
salt, fishery salt, or butter salt, on being first reduced by grinding to any required
degree of fineness can be consolidated with certainty and economy into blocks com-
posed of salt of a corresponding degree of fineness.
In carrying my invention into effect I employ a suitably constructed drying or
annealing oven or stove in which the blocks of salt are exposed to a greater heat than
is employed in the ordinary process, but are first consolidated in a lower temperature
to which they are exposed for a short time to enable the blocks of salt to bear handling
out of the moulds, as well as to bear the higher temperature requisite to complete the
process without being burnt or singed. A stove to effect this purpose may be varied
both in general design and arrangement of details so long as it serves the intended
purpose. And in order that my invention may be fully understood, I will now
refer to the accompanying drawing, in which is illustrated by way of example, a
stove suitably constructed for treating salt according to my improved process.
Figure 1 is a longitudinal section of the stove and Figure 2 is a corresponding
end view, a, a a are the blocks of salt standing in the stov. The salt is first put

page_text: g
into moulds of tin or iron lined out with asbestos to prevent rust and is placed in
the lower compartment b adjoining the furnace, and afterwards turned out of the
moulds and placed in the chamber c formed above the plate d by the hoods or
covers e. The hot gases or products of combustion from the furnace pass through
the chamber b to the chimney and are controlled in their passage by any suitable
damper provided between the end of the chamber b and the chimney and by the
oscillating valve g provided between the chamber 6 and the furnace which valve
turns on a spindle for the purpose of diverting at will the currents of hot gases
from the furnace to the upper or lower passages formed in chamber 6 by partition
plates ². The valve g and plates h¹² to which are united the vertical plate h³
Screen the blocks of salt in chamber from contact with the said hot gases or
products of combustion by which the chamber b is heated. The chambers c. c
formed upon the top of chamber by the removable hoods or covers e derive
their heat from the currents of hot gases or products of combustion which in passing
through chamber impinge upon the top plate d, which also forms the bottom
plate of the chambers c, and therefor transmits its heat thereto. The blocks of
salt are first placed in chamber enclosed in the moulds in which they have been
pressed where they remain until sufficently consolidated to bear being removed from
the moulds and the greater temperature of chambers c. The partial consolidation
which takes place in chamber occupies about half an hour with the temperature
of this chamber at about 170° Fah., whilst the completion of this process in
chambers c occupies from one to two days with the temperature at about 220° Fah.
In addition to the temperatures to which the blocks of salt are exposed in the
chamber and afterwards in the chambers c they may if desired be subjected to
an intermediato temperature by leaving them when placed on the plate d exposed for
any desired length of time to the atmosphere. In any case this exposure to an
intermediate temperature will occur whilst the covers are lifted to arrange the set of
blocks on plate d'and for a certain time after the hoods are let down to keep the heat
in. Although I prefer to subject the blocks of salt first to the heat in chainber b so
as to partly consolidate them, they may at a risk of burning or singeing the salt be
placed direct in the chambers the increasing temperature of which serves as the
equivlent for the gradation of temperature from chamber b to chambers c.
To carry
out the process of consolidation of the blocks in one chamber only requires more care
and time than when two chambers of different temperatures are employed as herein-
before described. .
It must be understood that the particular construction or design of the stove herein-
before described and illustrated in the accompanying drawing by way of example is not
absolutely essential to my invention and that stoves to consolidate salt in blocks may
be constructed to any design which will enable the salt to be subjected to the
requisite temperatures to effect this purpose in the manner hereinbefore described.
Having now particularly ascertained the nature of my invention and in what
manner the same may be carried into effect I declare that what I claim is :-
:-
Firstly. The consolidation of cold free salt into blocks for commercial purposes, sub-
stantially as, and for the purpose herein before described.
Secondly. The production of blocks of fine salt from rough grained salt by first
grinding the rough grained salt to the required degree of fineness and subsequently
consolidating it in the cold free state into blocks substantially as and for the purpose
as hereinbefore described.
Thirdly. The stove or annealing oven constructed and arranged to subject the blocks
of salt to the requisite variation of temperatures to consolidate them from salt in the
cold free state substantially as herein before described and illustrated by way of example
in the accompanying drawing.
°
Ditted this on day of September 2009
G. J. CLARKSON,
Stockton-on-Tees, Agent for the Applicant.