An Improved Boiling and Precipitating Tower.
Year: 1889

page_text: Date of Application, 24th Dec., 1889-Accepted, 1st Mar., 1890
COMPLETE SPECIFICATION.
An Improved Boiling and Precipitating Tower.
I, GUSTAV EMIL HÄNISOH of Beuthen, Upper Silesia, in the German Empire,
Chemist, 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:
This invention relates to a boiling and precipitating tower which is constructed
in two main parts readily placed in and out. of communication with each other,
and the object of the invention is chiefly to provide facilities of access to the
apparatus for cleansing purposes.
Various chemical processes in which precipitates are obtained from hot solutions
by the introduction of steam, or from cold or hot solutions by the introduction of gas
are generally carried out in fixed cylinders or cases. When it is desired to obtain as
large a result as practicable from the introduced steam or gas the procedure is on the
contrary current principle, several of the cylinders or cases being combined in an
apparatus. Although this kind of working is said to be continuous yet each element
of the apparatus is in turn worked intermittently as to charge and empty it, it
must be disconnected from the system and its operation thereby stopped, therefore,
in the place of such apparatus it is more advantageous and convenient to employ
high boiling towers which allow of a very regular and for a certain time continuous
working. With small attendance requirements, regularity of working and profitable
consumption of steam ascending from below, there are two very important physical
and chemical properties possessed by boiling towers as compared with cylinders and
which for some purposes are of great economic value.
Taking for example the boiling out of phosphoric calcium bi-sulphite in a solution
of phosphate of lime in sulphurous acid such as is obtained in the process of extraction
from bones by means of sulphurous acid; in the process of boiling, expelling the
sulphurous acid as pure gas and precipitation of the phosphoric acid as calcium tri-
phosphate, there is in the use of evaporating vessels the great drawback that the most
important evolution of sulphurous acid taking place between 60° and 90° C. of
temperature causes such a violent soap like frothing that the larger portion of the
charge has to be thrown over into the next vessel of the combined apparatus. The
frothing takes place to a greater extent in the second vessel, greater still in the third
and 50 ou as cach succeeding vessel has an increased charge, therefore in order to
avoid frothing over, either very high vessels are employed or these must be worked
with one third or one quarter charge. This course however presents the very great
disadvantage, that the air entering at every time of charging the vessel weakens the
gas and renders it unsuitable for reabsorption. Further than this the special
precipitation of the phosphate of lime has the disadvantage that a large portion of the
sulphurous acid is retained by it and precipitated with it. Notwithstanding several
hours evaporation of a phosphate solution of 16° Bé. strength, the precipitate shews a
content of 15-16 per cent. of sulphurous acid hydrite and the residue lye 0.5-0.6 per
cent. of sulphurous acid, whilst the boiling out of the same solution in the tower
during a space of at most two minutes yields a precipitate of only 7-8 per cent.
sulphurous acid corresponding to the contents of the earths and alkalies present, and
a residuum of only 0.25 per cent. sulphurons acid. Consequently the performance of
the precipitating process in the tower is besides the continuous working and much
lower steam expenditure, of advantage from a double point of view, as the expelled
gas, sulphurous acid anhydrite, after condensation of the water steam is obtained only
of a pure 100 per cent. composition and the precipitate is almost perfectly free from
sulphurous acid mechanically carried down therewith.

page_text: Analagous to the example cited there are several other chemical processes. In
most cases the employment of towers would be preferred for the boiling or treatment of
lyes with gases, if there were not present an important drawback which has hitherto
been the cause of such towers for boiling out and precipitating purposes appearing
advantageous to a small extent only. This drawback consists in their liability to
frequent stoppage of the fittings or passages by the formation of sludge which renders
necessary their frequent complete discharge and cleansing. Attempts have been made
to get over this difficulty by arranging at the sides of the tower large cleaning
apertures closeable with plates and screws but the cleansing can be only imperfectly
done, especially when the sludge bakes firm as does in many boiling processes.
There is also the evil that the necessarily large number of cleaning apertures are very
difficult to keep tight and consequently cause a loss of gas.
.
In order to allow boiling and precipitating towers of the kind referred to, to be
easily and thoroughly cleared out without much loss of time and without removal of
the fittings I have constructed the tower in two main parts as shewn in Figs. 1 and 8
in vertical section and in Figs. 9 and 10 in horizontal section. Fig. 7 is a vertical
section on line A-B of Fig. 8 through that part of the tower which as a passage
of access to the other part. The tower consists substantially of a boarded shaft of
considerable height and rectangular in cross section. The inside of the tower is lined
with sheet lead and made completely air tight. The one half of the shaft serves
specially for the boiling out of lyes or precipitation and for this purpose may be set
out with inclined planes as shewn in Figs. 3, 4, 5, or as shewn in Fig. 6 with square
wood blocks. The second juxtaposed half is without any fittings and serves simply
as a passage for the workman occupied in clearing out the boiling or precipitating
part of the tower. Both halves or parts of the tower are separated from one another
by a partition of single wood planks or boards placed one above another and lined
with lead on the inside and closing nearly air tight, these planks being pressed against
the shaft frame planking by props. As the edges of the shaft frame planking in the
whole height of the tower and also the bearing surfaces of the separate planks are
covered with india rubber or are furnished with india rubber strips a hermetical
closure is rendered practicable but if there should be any leaky places it would
not matter much as any gas passing into the passage cannot escape from it.
Instead of removable wood planks, these may be mounted on hinges and opened
and closed like doors, also if the tower is intended for the treatment of alkaline
instead of acid solutions, as for instance for the evaporation of weak ammonia water
with addition of lime lye, it may be constructed of plate iron, instead of wood with
a lead covering. In order that when, as may frequently be the case a stoppage
or blocking up of the tower takes place at any part of its beight, it may not be
necessary to remove the whole partition from the top to the bottom, square iron
bearers coated with lead are arranged as bearers or supports, from two to three
metres apart, for from four to six planks. In order also to prevent the necessity
of removing the wood blocks such as shewn in Figs. 5 and 6, for the purpose of
cleaning out the tower, these must not be placed to cross each other but all in
the same direction with their ends towards the passage, to allow of the pre-
cipitate being withdrawn by means of a spatula or other suitable instrument, from
a position in the passage. In order when the cleaning or clearing out operation is in
progress to prevent the precipitate from falling down and accumulating at the bottom
in a way to stop up the apparatus the wood blocks in such a kind of internal
arrangement as shewn in Figs. 5 and 6, are arranged in sets from two to three
metres high one above the other, each set being separated by a distance of
about 250 millimetres. In the clearing out operation a board the shape of the
cross section of the tower is slid underneath a set and receives the falling material.
The lye formed with the precipitate to a thin paste flowing off out of the tower
collects in a settling tank (Fig. 2) placed lower down. The precipitate settles to
the bottom sooner or later according to its specific gravity whilst the clear lye flows
off continuously through the upper overflow pipe. In order when the precipitate

page_text: is being withdrawn, not to disturb the superposed clear lye, the bottom of the settling
tank is formed with hopper shaped recesses or pockets from which the precipitate is
drawn off through large-way cocks or slides apertures on to the filtering floor
underneath.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what
I claim, is:
1. For the purpose of facilitating the discharge and cleansing of boiling and pre-
cipitating towers of the kind referred to, the division of the same into two main
parts or halves, in the manner that the part, provided with suitable internal fittings,
serving specially for the boiling or precipitating process is separated from the other
part serving as a passage of excess by a partition formed of planks, plates or doors
one over another so as to close hermetically or nearly so, substantially as described
and shewn.
2. The division of the partition referred to in the preceding claim into several
sections in the manner that between every four, six or other suitable number of
plates or planks one above another forming the partition, there is interposed a fixed
support so as, when the tower is to be cleared or cleaned at the bottom, to
render unnecessary the removal of the whole of the upper part of the partition,
substantially as described and shewn.
3. To prevent the necessity of removing the wood pieces shewn in Figs. 5 and 6,
the arrangement of these parallel with each other with one of their ends against
or pointing towards the partition for the purpose of allowing of the removal of the
precipitate lengthwise of the wood pieces substantially as described and shewn.
4. To prevent stoppage or blocking up of the not removable wood pieces referred
to in claim 3 the arrangement of the same in sets at determined distances apart to
allow of the interposition of a collecting board for the material falling down from
above, substantially as described and shewn.
Dated this 94th day of December 1889
CAPITAINE & VON HERTLING,
89, Chancery Lane, London, W.C., Agents for the Applicant.
CAPITAINE & VON HERTLING,
89, Chancery Lane, London, W.C., Agents for the Applicant.