Improvements in Preparing Milk of Lime, and in Apparatus to be. Used therefor, and for other such like Purposes.
Year: 1885

page_text: Improvements in Preparing Milk of Lime, and in Apparatus to
be. Used therefor, and for other such like Purposes.
:
We, SAMUEL HENRY JOHNSON and CHRISTOPHER CLARKE HUTCHINSON both
of the Engineering Works Stratford in the County of Essex, Engineers do hereby
declare the nature of our invention for "IMPROVEMENTS IN PREPARING MILK OF
LIME AND IN APPARATUS TO BE USED THEREFOR AND FOR OTHER SUCH
PURPOSES to be as follows:-
"
LIKE
In the treatment of sewage, and for other purposes, freshly hydrated lime held.
in suspension in water of the consistence of creain more or less thick, known as
milk of lime, is required and it has hitherto been usual to prepare it either by
slaking quick lime with a small quantity of water and then adding the hydrate
so formed by degrees to a suitable quantity of water contained in a vessel provided
with a revolving mixer, or a pair of edge runners revolving in a pan with a deep
curb or rim is used, into which water is permitted to flow continuously from a
tap; the quicklime is supplied also continuously in suitable quantity, the pan being
allowed to overflow a constant stream of the milk of time is produced.
In the former case difficulty arises in consequence of the presence of clinkers
unburnt stone et accumulating in the mixing vessel and injuring the mixing gear
and there is a separate operation of slaking the lime with its attendant dust and
inconvenience. In the plan with edge runners the core and unburnt stone is ground
to powder and flows away with the milk of lime, but the edge runners are expensive
and require a considerable amount of power to work them and the principal part
of the work done in grinding the hard core is wasted and the milk of lime
produced is rendered impure. Now this invention has mainly for its object to
avoid the difficulties and imperfections hitherto experienced in the preparation
of milk of lime-and to this end we construct our apparatus and use it in the
following way.
---
We construct a cylindrical vessel having a bottom in the form of an inverted
truncated cone the bottom being further depressed at the truncation in the form
of a cylindrical recess; above this recess and concentric with it is fixed a smaller
cone in normal position covering the recess and resting on the conical bottom
by means of three small feet or projections at the base of the smaller cone,-
these projections leave a narrow annular space intervening between the base of the

page_text: smaller cone and the internal surface of the conical bottom. We provide two
pipes with cocks in communication with the cylindrical recess at the bottom of
the receptacle above described, one in communication with a supply of compressed
air, the other for the purpose of drawing off the milk of lime. The apparatus
is provided with a cover and we use it in the following manner. We put the
requisite quantity of quicklime into the receptacle then the quantity of water
required and turn on a gentle stream of compressed air, in a few minutes the milk
of lime may be drawn off of uniform strength and free from clinker unburnt
limestone or core which remain above the conical cover being unable to pass
through the annular space at its base, which in its turn is kept clear from
obstruction by the flow of the incoming air. The sloping bottom formed by the
two cones and the inflow of air at the lowest part where the cones converge
prevents any deposition of the lime in the receptacle, an inconvenience that
otherwise milk of lime is prone to occasion. We thus get rid of the necessity for
a mechanical mixer which has been found to be difficult to keep in repair and the
whole operation of slaking the lime and mixing it with water to form milk of
lime can be effected at once without the necessity of uselessly grinding up the core
and mixing it with the milk of lime but on the contrary retaining it above the
small cone at the bottom of the apparatus and removing it from time to time.
The pipes for inlet of air and outlet for the milk of lime being in communi-
cation with the recess below the small cone there is no liability to stoppage by
solid obstructions. We have thus described what we consider to be the most
appropriate form of the apparatus the subject of our invention, but we wish it to
be particularly understood that in some respects the exact form is not material to
our invention; thus instead of using a cylindrical vessel a square or oblong vessel
in section will answer the purpose, provided that the bottom of the receptacle is so
constructed as that it shall converge towards a narrow space, holes or slot com-
municating with a chamber below, and is made at such an angle from the horizontal
that the deposited material shall not rest thereon but have a tendency to slide
downwards towards the narrow space, holes or slots referred to, and provided that
compressed air can be injected into the chamber beneath the bottom for the
purpose of agitating the material in the receptacle and at the same time keeping
the narrow space, boles or slots clear from obstructions and free for the passage of
the milk of lime out of the vessel.
The apparatus above described may be used not only for the preparation of milk
of lime but also for analogous purposes such as for dissolving substances in liquids
or bringing them into a state of suspension in liquids being simpler than the
employment of mechanical agitators and when the material to be dissolved or
brought into a state of suspension is in large masses the apparatus described would
be effective where a mechanical agitator would be inapplicable.

page_text: Improvements in Preparing Milk of Lime, and in Apparatus to
be Used therefor, and for other such like Purposes.
We SAMUEL HENRY JOHNSON and CHRISTOPHER CLARKE HUTCHINSON both of
the Engineering Works Stratford in the County of Essex Engineers do hereby
declare the nature of this invention and in what manner the same is to be per-
formed to be particularly described and ascertained in and by 'the following
statement:
.
;
In the treatment of sewage, and for other purposes, freshly hydrated lime held
in suspension in water of the consistence of cream more or less thick, known as,
milk of lime, is required and it has hitherto been usual to prepare it either by
slacking quick lime with a small quantity of water and then adding the hydrate
so formed by degrees to a suitable quantity of water contained in a vessel provided
with a revolving mixer, or a pair of edge runners revolving in a pan with a
deep curb or rim is used, into which water is permitted to flow continuously from
a tap; the quicklime is supplied also continuously in suitable quantity, the pan
being allowed to overflow a constant stream of the milk of lime is produced.
In the former case difficulty arises in consequence of the presence of clinkers
unburnt stone etc, accumulating in the mixing vessel and injuring the mixing gear,
and there is a separate operation of slaking the lime with its attendant dust
and inconvenience. In the plan with edge runners the.core and unburnt stone is
ground to powder and flows away with the milk of lime, but the edge runners are
expensive and require a considerable amount of power. to work them, and the
principal part of the work done in grinding the hard core is wasted and the milk
of lime produced is rendered impure. Now this invention has mainly for its object
to avoid the difficulties and imperfections hitherto experienced in the preparation.
of milk of lime. And to this end we construct our apparatus and use it in the
following manner.―
We construct a cylindrical vessel having a bottom in the form of an inverted
truncated cone, the bottom being further depressed at the truncation in the form
of a cylindrical recess; above this recess and concentric with it is fixed a smaller
cone in normal position covering the recess and resting on the conical bottom
by means of three small feet or projections at the base of the smaller cone, these
projections leave a narrow annular space, intervening between the base of the
smaller cone and the internal surface of the conical bottom. We provide two
pipes with cocks in communication with the cylindrical recess at the bottom of the
receptacle above described, one in communication with a supply of compressed
air, the other for the purpose of drawing off the milk of lime. The apparatus
is provided with a cover and we use it in the following manner :-We put the
requisite quantity of quicklime into the receptacle then the quantity of water
required and turn on a gentle stream of compressed air; in a few minutes the milk
of lime may be drawn off of uniform strength and free from clinker unburnt
limestone or core which remain above the conical cover, being unable to pass.

page_text: through the annular space at its base which in its turn is kept clear from obstruc-
tion by the flow of the incoming air. The sloping bottom formed by the two
cones and the inflow of air at the lowest part where the cones converge prevents
any deposition of the lime in the receptacle an inconvenience that otherwise milk
of lime, is prone to occasion. We thus get rid of the necessity for a mechanical
mixer which has been found to be difficult to keep in repair and the whole operation
of slaking the lime and mixing it with water to form milk of lime can be effected
at once without the necessity of uselessly grinding up the core and mixing it with
the milk of lime but on the contrary retaining it above the small cone at the
bottom of the apparatus and removing it from time to time. The pipes for inlet
of air and outlet. for the milk of lime being in communication with the recess
below the small cone there is no liability to stoppage by solid obstructions. We
have thus described what we consider to be the most appropriate form of the
apparatus the subject of our invention, but we wish it to be particularly under-
stood that in some respects the exact form is not material to our invention, thus
instead of using a cylindrical vessel a square or oblong vessel in section will answer
the purpose, provided that the bottom of the receptacle is so constructed as that it
shall converge towards a narrow space, holes or slots communicating with a
chamber below and is made at such an angle from the horizontal that the deposited
material shall not rest thereon but have a tendency to slide downwards towards
the narrow space, holes or slots referred to and provided that compressed air can
be injected into the chamber beneath the bottom for the purpose of agitating
the material in the receptacle and at the same time keeping the narrow space holes
or slots clear from obstructions and free for the passage of the milk of lime out of
the vessel.
The apparatus above described may be used not only for the preparation of milk
of lime but also for analogous purposes, such as for dissolving substances in
liquids or bringing them into a state of suspension in liquids being simpler than
the employment of mechanical agitators and when the material to be dissolved or
brought into a state of suspension is in large masses the apparatus described would
be effective where a mechanical agitator would be inapplicable.
In order that our said invention may be most fully understood and readily
carried into effect we will proceed to describe the drawings hereunto annexed.
gure is an elevation,
Figure 2 is a plan, and
Figure 3 is a vertical section of apparatus constructed according to our invention
and suitable to be used in the manufacture of milk of lime.
a. a. is a vessel in which we place the quick lime in masses resting upon the
perforated partition b. The vessel is provided with a cover c and an outlet pipe d
by which the air blown in at the bottom escapes. e is a water supply pipe it is
perforated with holes and by its aid the lime is sprinkled and the water for making
the milk of lime is introduced. f is an inverted cone at the bottom of the vessel a,
it stands on the tapering or inclined bottom a¹ of the vessel and is retained in
place by the stem f¹ so that there is a narrow opening beneath the edge of the
cone fand between it and the bottom a¹. Beneath the cone f there is a chamber g
with which two pipes h and i communicate; The first pipe h serves for the intro-
duction of air under pressure sufficient to enable it to force its way upwards through
the liquid in the vessel a and to keep the chamber g free from deposit. The pipe i
serves for drawing off milk of lime from time to time.
The process is conducted as follows-Lime having been put into the vessel a in
lumps and in a quantity sufficient to about one quarter fill the vessel the lime is
sprinkled with water from the pipe e, and then a further quantity of water is run
in until the lime is completely submerged, and the vessel filled nearly to the top.
Air is at the same time blown in by the pipe h so as to keep the contents of

page_text: the vessel agitated and the chamberg and the entrance to this chamber free from
deposit. This is continued for say 5 to 20 minutes until the lime and water are
thoroughly mixed and then the cock on the pipe i is opened and the milk of
lime is drawn off. The air blast is regulated if necessary during the drawing off
so as to keep the entrance to the chamber clear and to allow the liquid to pass
out. The vessel then receives a fresh charge of lime and water and the operation
is repeated.
After working several charges the refuse remaining in the vessel on the perforated
partition b is removed.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is:-
1. The preparation of milk of lime by placing lime together with water in a
vessel with a bottom tapering or converging towards a narrow opening or openings
by which the vessel communicates with a chamber below into which air under
pressure is introduced and from which the milk of lime when prepared is
drawn off.
2. The apparatus substantially as herein described and consisting of a vessel
with a bottom tapering or converging towards a narrow opening or openings and
with a chamber below from which liquid can be drawn off and into which air
under pressure can be introduced, the latter in such manner as to keep the chamber
free from deposit and to agitate the contents of the vessel above.