improvements in Futers Applicable for Caustic Soda Solution.
Year: 1885

page_text: improvements in Futers Applicable for Caustic Soda Solution.
I, WILLIAM PHILLIPS THOMPSON, Fel. Inst. P.A. of the Agency for Foreign
Patent Solicitors, 6 Lord Street, Liverpool, in the County of Lancaster, and
323 High Holborn, in the County of Middlesex, Civil Engineer, do hereby declare
the nature of the said invention for "IMPROVEMENTS IN FILTERS APPLICABLE FOR
CAUSTIC SODA SOLUTION" (a communication from abroad by Messieurs Solvay
et Cie of Brussels, in the Kingdom of Belgium) to be as follows :-
The filtration of lime residues produced in the manufacture of caustic soda is a
difficult operation, and one that has been performed through beds of limestone
or flints broken into continually decreasing fragments or through analagous
materials
Filtration through tissues would be much easier for reasons easily to be under-
stood, but hitherto this system has found no commercial application from the want
of a material capable of resisting the action of caustic soda, while presenting a
sufficiently close web.
This invention chiefly consists in the employment of asbestos or other mineral
fibre, unaffected by water, caustic soda or the liquid employed, woven or strongly
felted into sheets or webs, and used with or without other filtering media. After
numerous experiments Messrs Solvay & Co have found a filter of the following
description to work very well on an experimental commercial scale.
A rectangular box of cast or wrought iron of dimensions suited to the quantity
of liquid to be treated is formed with a bottom slightly curved or sloping down-
ward to the centre or other point of exit. At this point a half round collecting
conduit with notched edges resting on the bottom collects the liquor which has
passed through the filtering media described later on. The lower part of the filter,
that which contains the filtering material is protected by a lining of brick. Beds
of broken inert mineral matter preferably limestone decreasing in size toward the
top in the manner formerly almost universally employed for filtering caustic fill
the lower part or filter bed of the filter.

page_text: The asbestos cloth is disposed in bands resting flat upon the upper part of the
finely powdered limestone, consecutive bands overlapping each other by about two
inches. The joints rest on perfectly level beds of refractory bricks. The bands of
asbestos cloth elsewhere at their edges are fastened solidly to angle irons fixed to
the sides of the filter by means of a movable iron frame which goes all round the
filter. This frame does not rest directly upon the asbestos but rests upon perforated
sheets of iron one eighth to one quarter inch in thickness which cover the whole
area of asbestos with the object of protecting the asbestos and allowing the
sediments to be cleared away without damaging the tissue.
There are in the experimental apparatus two lengths of perforated sheet iron in
the width of the filter. They as well as the asbestos are kept in their places by the
pressure of the frame spoken of above. As to the middle joint it is kept in its
place by a course of thick rails which are bolted on to the iron plates.

page_text: Improvements in Filters Applicable for Caustic Soda Solution.
I, WILLIAM PHILLIPS THOMPSON Fel. Inst. P.A. of the Agency for Foreign
Patent Solicitors 6, Lord Street Liverpool in the County of Lancaster and
323 High Holborn in the County of Middlesex, Civil Engineer, do hereby declare
the nature of this invention (a communication from abroad by Messieurs Solvay
et Cio of Brussels in the Kingdom of Belgium) and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement :-
The filtration of lime residues produced in the manufacture of caustic soda is a
difficult operation, and one that has been performed through beds of limestone
or flints broken into continually decreasing fragments, or through analagous
materials.
Filtration through tissues would be much easier for reasons easily to be under-
stood, but hitherto this system has found no commercial application from the want
of a material capable of resisting the action of caustic soda, while presenting a
sufficiently close web.
This invention chiefly consists in the employment of asbestos or other mineral
fibre unaffected by water, caustic soda or the liquid employed, woven or strongly
felted into sheets or webs and used with or without other filtering media. After
numerous experiments Messrs Solvay & Co have found a filter of which the
following is a description to work very well on an experimental commercial scale.
Referring to the accompanying drawings:-
Figure 1 is a longitudinal section of tank empty.
Figure 2 transverse section of tank filled with filtering material and ready for
action.
Figure 3 plan of same with a small part shown broken away to show interior.
In these T is a rectangular box of cast or wrought iron of dimensions suited to
the quantity of liquid to be treated. It is formed with a bottom D slightly curved
or sloping downward to the centre or other point of exit E. At this point a half
round collecting conduit F with notched edges as shown in Figure 1 resting on the
bottom collects the liquor which has passed through the filtering media described
later on.
The lower part of the filter, that which contains the filtering material is
protected by a lining of brick, G beds of broken inert mineral matter, H preferably
limestone decreasing in size toward the top in the manner formerly almost universally
employed for filtering caustic, fill the lower part or filter bed of the filter.
The asbestos cloth B is disposed in bands resting flat upon the upper part of the
finely powdered limestone, consecutive bands overlapping each other by about two
inches. The joints either rest on perfectly level beds of refractory bricks, or as set
forth in the drawing on the filtering material itself. The bands of asbestos cloth
elsewhere at their edges are fastened solidly to angle irons I fixed to the sides of
the filter by means of a movable iron frame which goes all round the filter, or
themselves form this frame. This frame does not rest directly upon the asbestos,
but rests upon perforated sheets of iron A, one eighth to one quarter inch in
thickness, which cover the whole area of asbestos with the object of protecting the

page_text: asbestos and allowing the sediments to be cleared away without damaging the
tissue.
In the experimental apparatus shown in the drawings there are two lengths of
perforated sheet iron in the width of the filter. These as well as the asbestos are
kept in their places by the pressure of the frame spoken of above. As to the
middle joint of the perforated sheets, it is kept in its place by a thick rail J which
is suspended from brackets K K, one at each end by screws L L in such manner
that it can be adjusted to press with all its weight upon the borders of the plates,
or even with some screw pressure if desired as well, and which yet can be raised up
and suspended by the screws, so as to take all the weight from the perforated
plates and enable the latter to be easily shifted or taken out as required.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, as communicated to
me by my foreign correspondents, I declare that what I claim is :-
--
1st. The application of asbestos cloth as the filtering material of industrial filters
applicable for filtering caustic soda solution whether in combination with other
filtering material or otherwise.
2nd. The manufacture and use of filters, substantially as and for the purposes
described in which the filtering material is asbestos protected by perforated plates,
and supported on brickwork or the like, and upon other filtering material, such as
broken limestone or sand.
3rd. The filter applicable for filtering caustic soda solution constructed and
arranged as a whole, substantially as shown and described.
WP. THOMPSON & Co.,
Agents for the Applicant..