IMPROVEMENTS IN GENERATING AND APPLYING HEAT IN EVAPORATING SALINE AND OTHER LIQUIDS, IN THE MANUFACTURE OF CHLORIDE OF SODIUM AND OTHER CRYSTALINE SUBSTANCES, AND FOR OTHER HEATING PURPOSES, AND IN APPARATUS CONNECTED THEREWITH
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by William Bull at the Office of
the Commissioners of Patents, with his Petition, on the 4th June
1875.
I, WILLIAM BULL, of Lower Norwood, in the County of Surrey,
Civil Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN GENERATING AND APPLYING HEAT IN EVAPORATING SALINE
AND OTHER LIQUIDS, IN THE MANUFACTURE OF CHLORIDE OF SODIUM AND OTHER
CRYSTALINE SUBSTANCES, AND FOR OTHER HEATING PURPOSES, AND IN APPARATUS
CONNECTED THEREWITH," to be as follows, that is to say :-
-
To illustrate the nature and object of the improvements which
constitute the first part of this Invention I take an ordinary evaporating
pan, such as is commonly used in the separation of salt from brine in
salt works, or crystals from other liquids in chemical works.
In the ordinary way the mother liquor is placed in such pans
unheated, and except they are worked by steam the evaporating heat
is generated under each pan separately and applied thereto separately,
ordinary open furnaces being used for that purpose in which, from
several causes, perfect combustion of the fuel is a practical impossibility,

page_text: and consequently the evils which result are a great waste of fuel, constant
variation in the temperature of the furnaces and pans, a large quantity
of the heat evolved is rendered non-effective by the crude products
of combustion accompanying it; the deposit of a non-conducting car-
bonaceous matter or crustation upon the heating surface of the pans
in the flues or heating chambers, rapid deterioration of the pan plates
over the furnaces, unequal heating of the "fore" and "aft" portions of
the pans, imperfect crystallization or the formation of crystals of different
sizes and texture in different parts of the pans, and varying also in like
manner at different stages of the process in the "fore as well as in the
"aft" part of the pans.
"
To obviate these evils and improve the character, texture, and granular
uniformity of the salt and other crystaline substances, I generate and
apply the heat in the manner hereinafter described; and instead of
working the pans separately and with separate furnaces to each I work
them in sets placed side by side level with each other, and connected
with each other by pipes or troughs at their apposite ends, and cause
the brine or other liquid to circulate through the same from pan to pan,
such circulation being effected by simple induction and without the aid
of any mechanical contrivance (or in some cases aided or partially
produced thereby).
Instead of supplying the brine, saline, or other liquor in the ordinary
manner and unheated, I supply it to the pans from a heated or other
receptacle in or by and from which the flow can be regulated so as to
keep pace with the evaporation. I effect this by a self-acting apparatus
similar to that herein-after described for feeding the furnace boiler. I
also cover such pans and cause dry or heated air to circulate through the
spaces under such covers to raise and carry off aqueous vapours from the
evaporating surface or surfaces, and I use any available waste heat for
this purpose. I make these covers removeable or to open and close when
required.
To form a "set" of pans I place and couple three such pans in the
manner before described, or use a large pan divided into three compart-
ments. Under the centre pan or compartment I form a heating chamber
or flues, and make or line the floors and sides of such chambers or flues.
of or with any suitable heat non-conducting concrete or other material
to prevent or diminish the loss of heat from radiation. Under one of

page_text: the side pans or compartments I also form a heating chamber protected
in a similar manner; these chambers and flues are made as nearly
air-tight at the bottoms and sides as possible. Under the other side pan
I form a chamber also similarly protected, and made as nearly steam
and water-tight as possible, or form this pan or compartment with a
double bottom.
The centre and first-mentioned side pan I heat by means of a furnace,
and the last-mentioned side pan I heat by means of steam from a multi-
tubular or other boiler placed in such furnace. The boiler which is of
a rectangular form is placed under the fore part of the centre pan
transversely, and at a distance of ten or fifteen feet from the front wall of
the heating chamber, dividing this chamber into “ "fore" and "aft"
compartments, the former constituting the furnace. The heat is
generated in this furnace in combustion chambers, formed with an open
grate or fire-bars at the bottom, and with side walls and roof of good
fire-resisting heat radiating material. In these combustion chambers
hot air and hot carbonaceous matter are brought together, and an intense
heat is obtained and maintained. Small openings are formed in the
sides and roofs of these chambers for the passage of a certain quantity
of heat into the open space above them, and under the front portion of
the bottom of the centre evaporating pan.
The combustion chambers extend about three-fourths (more or less) of
the length of the "fore" heating chamber or furnace, a space being left
between their ends and the face of the transverse boiler. The heat
generated in these chambers acts in part directly and in part by radiation,
the main body of the heat flashes from the open (or partially closed) ends
of the combustion chambers into the open space last-mentioned, and
through the multitubular openings in the boiler, and thence through the
"aft" heating chamber to the back end of the centre pan, traverses a
suitably formed and lined passage (in which air or brine heating tubes
may be placed) opening into the heating chamber under the second pan
or a compartment, and through and under which and
space pan the heat
now passes from the back to the front, and thence through an air heating
battery into the shaft of a suitable chimney. The third pan or compart-
ment is heated by the steam generated as above described in the
multitubular transverse boiler; the steam from this boiler is conducted
by a steam pipe opening into the steam-tight space or chamber under
this pan before mentioned. The floor of this chamber is formed with

page_text: t
inclines to a center channel, and this channel with an incline to the
mouth of the steam pipe (or to a back flow pipe), so that the hot water
from the condensed steam may flow back into the boiler as fast as
condensation takes place; the boiler being thus constantly re-fed with its
own hot water at a temperature only a few degrees below the boiling
point.
For making good any waste in this boiler it is fitted with a self-acting
feed pipe supplied from an elevated reservoir. This feed pipe passes
through a tank or feed regulater placed at such a level with regard to
the boiler that the surfaces of the water in the former and in the latter
'may be level with each other. The boiler and tank are connected by
a second pipe. A valve actuated by a float and lever is placed upon
this feed pipe in the regulating tank. This valve is so constructed that
it remains closed when the lever is in an horizontal position, but instantly
opens if the lever rises or falls, so that it acts as a feed regulater and
steam pressure regulater at the same time. It acts as a steam pressure
regulater in the following manner, that is to say:-Suppose the boiler
should generate an excess of steam and an undue pressure should result
in the boiler (and under the third evaporating pan), so as to drive the
water through the connecting pipe into the tank & cause the latter to
prime, the valve would be immediately opened, and cold water would
immediately rush into the boiler and replace the boiling water dis-
placed by the steam, lower the temperature, and reduce the volume and
pressure of the steam.
The valve is also so constructed that it closes when the lever rises
beyond a certain point, and thus prevents the boiler from priming
under the conditions last-mentioned. Instead of the steam being allowed
to enter the steam chamber under this pan in a free state, it may be
confined in pipes laid with an incline towards the boiler, and in the
latter case the steam may be worked at a pressure, and the steam
chamber may be converted into a boiler for working the pan above it.
The furnaces before mentioned are fired as follows, that is to say, they
are closed in front and fitted with fuel holders from which small coal
or other fuel can be supplied to the combustion chambers by hand or
machine power. Under the fuel holders and above the fire bars there is
an opening which is closed by a rising and falling door through which
air can be admitted and clinkers withdrawn when necessary; under the

page_text: combustion chambers ash-pits are provided; these ash-pits are divided
into upper and lower compartments by a perforated or other plate or
plates, or a grate by which air from the lower compartment can be
admitted or shut off as required. The upper compartment forms a hot-
air chamber; the air previously heated as much as possible by passing
through the battery before mentioned is further heated in its passage
through this hot-air chamber before it comes into contact with the
carbonaceous matter in the combustion chamber. The fuel (small coal)
is first deposited from the fuel holders upon a plate or shelf in the front
part of the furnace where it is heated by the radiated heat from the
interior of the combustion chamber nearly to ignition temperature, the
carbonaceous gases or crude products of combustion which are given
off during this first heating of the fuel pass through the combustion
chamber, where they are ignited and become incandescent by the intense
heat which is therein maintained by regular charges of such heated fuel
and hot air, or hot air and superheated steam, should the latter be
preferred. As the fuel is consumed the ashes and cinders fall upon the
plate or grate at the bottom of the hot-air chamber, which is made to
open or tip, so that they can be discharged into the lower compartment
of the ash-pit and be thence withdrawn without admitting cold air into
the hot-air chamber.
The cinders are separated from the ashes by the grate and transferred
to the fuel holders. The combustion chamber forms a kind of furnace
within a furnace, so that a most intense heat is generated in the former
and diffused through the latter, perfect combustion of the fuel and gases
is insured, a white heat may be obtained therein without injury to the
bottom of the pan, while a clear heat is made to circulate through the
heating chambers and flues instead of the opaque heavily charged vapours
(from imperfect combustion in the ordinary furnaces) which carry and
deposit unconsumed carbonaceous matter upon the under surface of the
pans where it becomes a non-conductor and prevents the heat from
acting upon the brine or other liquids contained therein.
I give a quick or slow draught through the combustion chambers and
through the heating chambers under the pans by placing a screw or fan
(or in some cases a coke furnace) at the bottom of the chimney shaft
where such screw or fan is made to operate by induction instead of
by blast (inthe ordinary way) so that the heat is drawn forward in
greater or less volum, as the temperature of the brine, saline, or other
"

page_text: liquors in the pans may require. By this mode of generating and apply-
ing the heat three ordinary pans are worked by one set instead of three
sets of furnaces, and both fuel and labour are saved, and the pans thus
formed or placed, fitted, and heated, may be worked separately at different
temperatures, or collectively at any required temperature for producing
rapid or slow evaporation.
By the improved mode of heating the pans the mother liquor is raised
to and maintained at an uniform temperature in all parts of the pan, and
the required temperature may be thus raised and maintained uniformly
in the three pans when the connecting pipes or troughs before mentioned
are opened; in the latter case the heat thus applied causes a circulation
of the fluid or liquid through the pans and a mean temperature results.
In the manufacture of chlorides of sodium (white salt) it is of great
consequence that there should be uniformity in the size and texture of
the crystaline substances or granular particles resulting from the evapor-
ation, and consequently that the heat should be as equal as possible in
all parts of the pan and uniformly maintained throughout the process.
In order to insure this uniformity I introduce and fix a bell thermo-
meter in each pan, in which columns of mercury make and break contact
with two platinum wires, the ends of which are placed about 4 or 5
degrees one above and one below the required thermal heat (as indicated
by the thermometer scale); these wires are separately connected to the
opposite poles of a galvanic battery, and upon the positive wire a
sharp" bell is placed, while upon the negative wire a "flat" is
fitted, so that the former bell rings if the heat of the pan exceeds the
required temperature, and the flat bell rings if the heat of the pan falls
below the required temperature, and the fireman is thus enabled to
regulate the damper and feed mechanism accordingly.
The ends of the platinum wires in the thermometer can be adjusted to
and fixed so as to indicate any required heat and range of temperature_in
the pans.
The combustion chamber, furnace, and mode of generating incandescent
heat may be applied for other evaporating and heating purposes, and the
heat be regulated as herein described, and for indicating and regulating
the heat of such furnaces I introduce and fix a bell pyrometer therein,
and cause two finger pieces on a reciprocating pyrometer rod to make

page_text: contact with the opposite poles of a similar battery, the connecting wires
of which are similarly fitted with " sharp " and "flat" bells, and by
suitable mechanism cause this rod to open and close a valve for
admitting cold air to the furnace as required.