An Improved Process and Apparatus for the Production of Acetic Acid of High Percentage and on a Large Scale by means of Fractional Distillation.
Year: 1899

page_text: PROVISIONAL SPECIFICATION..
An Improved Process and Apparatus for the Production of Acetic
Acid of High Percentage and on a Large Scale by means of
Fractional Distillation.
A communication to me from the "KRAUSCHWITZER THONWAARENFABRIK FÜR
CHEMISCHE INDUSTRIE, (vormals LUDWIG ROHRMANN,) COMPANY," of Krau-
schwitz, near Muskau, Silesia, in the Empire of Germany.
I, EDMUND EDWARDS, of the Firm of Edwards and Co., Chartered Patent Agents
& Engineers, of 65 & 66, Chancery Lane, in the County of Middlesex, do hereby
declare the nature of this invention to be as follows:-
By the treatment of acetate of lime or soda with sulphuric acid or hydro-
chloric acid, crude acetic acid is obtained, which is then treated by well-known
processes of fractional distillation, in metal vessels, generally lined with non-
oxidizable metal, and towers and cooling worms or coils of acid-proof material.
In the process hereinafter described the crude acetic acid coming from the
apparatus ordinarily used is passed into large stone chambers 2 metres in
height, width, and length, having a capacity of over 15 cubic metres, and after
treatment with suitable oxidizing agents, by means of a series of successive
fractional distillations is converted to acetic acid of different degrees of concen-
tration, that is to say, 56% as commercial acid, 62% as redistilled acid,"
80%, 90%, and 100%, as chemically pure acid.
In the accompanying drawings, which are in illustration of the invention:-
Figure 1 shows the entire arrangement of plant or apparatus, with the
generating vessel in section
Figures 2 to 4 show different views of the stone chambers used.
The method of arrangement is as follows:-The acetic acid vapour coming
from the generating vessel a is condensed in the refrigerating or cooling
chamber b, from which the acetic acid is run into storing tanks c, from either
of which as desired it can be admitted into the chamber d, of stone free from
lime flaws, as shown in separate views in Figures 2 to 4.
The chamber d is made of flat stone covered outside with lead plates e, and
held together by iron plates or angle irons. Between the bottom stone and the
lead outer plate an iron plate is inserted. In the stone chamber a spiral steam
pipe fis arranged close to the bottom, for the evaporation of the crude acetic
acid. A pressure guage g, and an outlet for condensed steam from the pipe f
are provided, so as to permit the operation to be observed and regulated. A
discharge valve i, operated from the outside, allows the chamber to be emptied
for cleaning.
The acetic acid vapour formed in the chamber d is condensed in the
refrigerator k, and passes to a second chamber m for a fresh evaporation. After
Leing again condensed, the acetic acid vapour formed in the chamber m finally

page_text: passes to the last chamber o, the vapour generated in which is condensed to
concentrated acetic acid in the refrigerator p.
The process is carried on in the above described arrangement of apparatus, in
the following way:
As already explained, crude acetic acid is obtained from gray 82% to 84%
acetate of lime by the addition of sulphuric acid of 60° Bé as free as possible
from arsenic, in the usual way; the acetate of lime (in sufficient quantity) being
placed in the cast iron decomposing vessel «, which is provided with agitators
and a tight cover, together with sulphuric acid of 60° Bé, and is decomposed by
heating with superheated or high pressure steam, the acetic acid vapour pro-
duced passing through stoneware pipes in a long refrigerating chamber b, where
it is condensed by cold water.
Instead of a long refrigerating chamber, a stoneware condensing coil or worm
may be used, such as those used at k, n, and
The double heating generator a is coated inside and outside, before it is used,
with an acid-resisting cement. reduced with hot water to such a consistence that
it can be readily laid on. This treatment prevents the rapid wearing out of
the vessel by the action of the concentrated acid. The removal of the waste
sulphate of lime is effected by opening a discharge door communicating, if
possible, with the open air.
Each operation of the heating vessel takes, including the filling and emptying,
not more than 4 hours, so that each such vessel, working day and night, can
decompose 6 charges of 150 kilos. of acetate of lime.
The crude acetic acid coming from the refrigerator b, which is passed direct
to one of the large storage tanks c, contains an average of 70% pure acetic acid,
with 1 to 1% of sulphurous acid.
As soon as one of these tanks is filled with acetic acid, and has been allowed
to rest for 24 hours, the acid is conveyed directly through a glass or stone-ware
pipe to the first (d) of the stone distilling chambers, the pipe being connected
with the tanks by adjustable cocks, so that the chamber can be filled from
either of the tanks to two-thirds of its capacity (that is, 10,000 kilos.), when the
first fractional distillation is commenced."
The steam is as carefully as possible admitted and regulated, and during the
first two hours must have a pressure of not more than to of an atmosphere,
which can be exactly regulated by the pressure guage g.
The distilling apparatus & for the first distillation of the acetic acid, has in
its stone cover an escape pipe q, for the sulphurous acid separated at first. This
escape pipe permanently fixed above the stone top has a stone-ware cock, above
which is a lantern by means of which the attendant can regulate the closing
exactly to the time when all the sulphurous acid, in the form of a milk-white
vapour, has been driven out, and acetic acid vapour begins to condense in drops
on the glass.
At this moment the cock, which before the commencement of the distillation
was open, is closed, and the distillation is now effected by the heating worm or
coil through which steam of suitable moderate pressure passes.
The first product of condensation (the average strength of the crude acetic
acid having been 70%) which is completely cooled, contains traces of sulphurous
acid and is milky, and its percentage about 45%. This first milky acid is col-
lected separately, and the distillation is then forced by degrees by increasing the
steam pressure, and in such manner that the condensed product of acetic acid
passes from the lower earthenware refrigerating coil quite cold.
In the regular course of the distillation, the strength of the acetic acid rises
as follows: The acid begins to flow with 40% and the distillation of the first
third of the entire charge has an average of 56%,-that of the second third
of 70% and that of the third third of 85%.
Whilst the 56% acid is sold as "commercial acid," the 70% and 80% acid,
after it has passed to the chamber r is admitted either by its own weight or is

page_text: forced by the pressure of air, into the second stone chamber m. In the chamber
the acetic acid received, for the purpose of oxidation, an addition of 2% of
chromate of soda. The chamber m is then filled with the acetic acid of 70%
and after this has been sufficiently reduced, the 85% acid is added.
«
The result of the second distillation is acetic acid of 62%, 77%, and 90%.
Whilst the 62% and 77% acetic acid is marketable as redistilled acetic acid,"
the 90% is oxidised in the chamber s with 2% of permanganate of potash, and
after remaining at rest there for a sufficient time, is conducted to the third stone
chamber o, from which, each time, acetic acid one third of 80%, one third
of 90%, and one third of 100%,, is obtained.
The acetic acid of 90% so produced can be again passed through the chamber o
at the next fractional distillation, and there again results a third glacial or
99% chemically pure acetic acid.
It is obvious that, with the fractional distillation on a large scale, or in
stone chambers of large size, a great economy of capital in plant will be attained
as through the entire distillation no copper apparatus is used, the refrigerating
apparatus p, n, k, being also used of earthenware.
Distillation of the kind in vessels or chambers of lime-free sandstone of the
size described is new, and it would lead to absolute failure if it were attempted
to use copper vessels of the same size instead of stone ones, as in a month they
would be completely destroyed by the acid, and a continual renewal of the
apparatus would be required. Moreover, the acetic acid would be contaminated
with poisonous metallic salts which would render it unsuitable for many
purposes.
Taal 1 201
1000
An Improved Process and Apparatus for the Production of Acetic
Acid of High Percentage and on a Large Scale by means of
Fractional Distillation.
A communication to me from the "KRAUSCHWITZER THONWAARENFABRIK FÜR
CHEMISCHE INDUSTRIE (vormals LUDWIG ROHRMANN,) COMPANY,", of Krau-
schwitz, near Muskau, Silesia, in the Empire of Germany.
I, EDMUND EDWARDS, of the Firm of Edwards & Co., Chartered Patent Agents
& Engineers, of 65 & 66, Chancery Lane, in the County of Middlesex, do hereby
declare the nature of my said invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement, and accompanying drawing, that is to say :—
By the treatment of acetate of lime or soda with sulphuric acid or hydro-
chloric acid crude acetic acid is obtained, which is then treated by well-known
processes of fractional distillation, in metal vessels, generally lined with non-
oxidizable metal, and towers and cooling worms or coils of acid proof material.
In the process hereinafter described the crude acetic acid coming from the
apparatus ordinarily used is passed into large stone chambers 2 metres in
height, width and length, having a capacity of over 15 cubic metres, and after

page_text: Treatment with suitable oxidizing agents by means of a series of successive
fractional distillations is converted to acetic acid of different degrees of concen-
tration, that is to say, 50% as commercial acid, 62% as "redistilled acid,"
80%, 90% and 100% as chemically pure acid.
In the drawings accompanying my Provisional Specification which are in
illustration of the invention:-
Figure 1 shows the entire arrangement of plant or apparatus, with the
generating vessel in section.
Figures 2 to 4 show different views of the stone chambers used.
The method of arrangement is as follows:-The acetic acid vapour coming
from the generating vessel a is condensed in the refrigerating or cooling
chamber from which the acetic acid is run into storing tanks c, from either
of which as desired it can be admitted into the chamber d, of stone free from
lime flaws, as shewn in separate views in Figures 2 to 4.
The chamber d is made of flat stone covered outside with lead plates e, and
held together by iron plates or angle irons. Between the bottom stone and the
lead outer plate an iron plate is inserted. In the stone chamber a spiral steam
pipe is arranged close to the bottom, for the evaporation of the crude acetic
acid. A pressure guage g, and an outlet for condensed steam from the pipe f
are provided, so as to permit the operation to be observed and regulated.
discharge valve i, operated from the outside, allows the chamber to be emptied
for cleaning.
The acetic acid vapour formed in the chamber dis condensed in the
refrigerator and passes to a second chamber m for a fresh evaporation. After
being again condensed, the acetic acid vapour formed in the chamber m finally
passes to the last chamber o, the vapour generated in which is condensed to
concentrated acetic acid in the refrigerator p.
The process is carried on in the above described arrangement of apparatus in
the following way:
As already explained, crude acetic acid is obtained from gray 82%, to 84%
acetate of lime by the addition of sulphuric acid of 60° Bé as free as possible
from arsenic, in the usual way, the acetate, of lime (in sufficient quantity) being
placed in the cast iron decomposing vessel a, which is provided with agitators
and a tight cover, together with sulphuric acid of 60° Bé, and is decomposed by
heating with superheated or high pressure steam, the acetic acid vapour pro-
duced passing through stoneware pipes in a long refrigerating chamber b, where
it is condensed by cold water.
Instead of a long refrigerating chamber, a stoneware condensing coil or worm
may be used, such as those shewn at k, n, and p.
The double heating generator a is coated inside and outside, before it is used,
with an acid resisting cement reduced with hot water to such a consistence that
it can be readily laid on. This treatment prevents the rapid wearing out of
the vessel by the action of the concentrated acid. The removal of the waste
sulphate of lime is effected by opening a discharge door communicating, if
possible, with the open air.
Each operation of the heating vessel takes, including the filling and emptying,
not more than hours, so that each such vessel, working day and night, can
decompose 6 charges of 150 kilo. of acetate of lime.
The crude acetic acid coming from the refrigerator b, which is passed direct
to one of the large storage tanks c contains an average of 70% pure acetic acid
with 1 to 1% of sulphurous acid.
As soon as one of these tanks is filled with acetic acid, and has been allowed
to rest for 24 hours the acid is conveyed directly through a glass or stone-ware
pipe to the first (d) of the stone distilling chambers, the pipe being connected
with the tanks by adjustable cocks, so that the chamber d can be filled from
either of the tanks to two-thirds of its capacity (that is, 10,000 kilo.) when
the first fractional distillation is commenced.
°

page_text: The steam is as carefully as possible admitted and regulated, and during the
first two hours must have a pressure of not more than to 4 of an atmosphere,
which can be exactly regulated by the pressure guage g.
The distilling apparatus d for the first distillation of the acetic acid, has in
its stone cover an escape pipe q, for the sulphurous acid separated at first. This
escape pipe permanently fixed above the stone top has a stone-ware cock, above
which is a lantern by means of which the attendant can regulate the closing
exactly to the time when all the sulphurous acid, in the form of a milk-white
vapour has been driven out, and acetic acid vapour begins to condense in drops
on the glass.
At this moment the cock, which before the commencement of the distillation
was open, is closed, and the distillation is now effected by the heating worm or
coil through which steam of suitable moderate pressure passes.
The first product of condensation (the average strength of the crude acetic
acid having been 70%) which is completely cooled, contains traces of sulphurous
acid and is milky, and its percentage above 45%. This first milky acid is col-
lected separately, and the distillation is then forced by degrees by increasing the
steam pressure, and in such manner that the condensed product of acetic acid
passes from the lower earthenware refrigerating coil quite cold.
In the regular course of the distillation, the strength of the acetic acid rises
as follows:-The acid begins to flow with 40% and the distillation of the first
third of the entire charge has an average of 50%, that of the second third
of 70%, and that of the third of 85% commercial acid" the 70% and 80% acid.
Whilst the 56%, acid is sold as
after it has passed to the chamber is admitted either by its own weight or is
forced by the pressure of air, into the second stone chamber m shewn of smaller
size. In the chamber r the acetic acid received, for the purpose of oxidation,
an addition of 2% of chromate of soda. The chamber m is then filled with the
acetic acid of 70% and after this has been sufficiently reduced, the 85% acid
is added.
"
The result of the second distillation is acetic acid of 62%, 77%, and 90%.
"redistilled acetic acid
Whilst the 62% and 77% acetic acid is marketable as
the 90% is oxidized in the chamber s with 2% of permanganate of potash, and
after remaining at rest there for a sufficient time, is conducted to the third stone
chamber o, from which, each time, acetic acid one third of 80%, one third
of 90%, and one third of 100% obtained.
The acetic acid of 90% so produced can be again passed through the chamber o
at the next fractional distillation, and there again results a third glacial or
99% chemically pure acetic acid.
It is obvious that, with the fractional distillation on a large scale, or in
stone chambers of large size, a great economy of capital in plant will be attained
as through the entire distillation no copper apparatus is used, the refrigerating
apparatus p, n, k, being also used of earthenware.
Distillation of the kind in vessels or chambers of lime-free sandstone of the
size described is new, and it would lead to absolute failure if it were attempted
to use copper vessels of the same size instead of stone ones, as in a month they
would be completely destroyed by the acid, and a continued renewal of the
apparatus would be required. Moreover, the acetic acid would be contaminated
with poisonous metallic salts which would render it unsuitable for many
purposes.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. The process for manufacturing acetic acid by distillation in different degrees
of strength, as intermediate products and finally as glacial acetic acid.
in out the process described and claimed in Claim 1,

page_text: consisting of a series of stone chambers of large capacity arranged and operating
in such manner that acid of different degrees of strength is distilled from the
crude acid, whilst simultaneously glacial acetic acid is finally obtained, substan-
tially as described and illustrated."
Depremo 100
EDWARDS AND CO.
Chartered Patent Agents, 65 and 66, Chancery Lane, London,
Agents for the Applicants.