Improved Process for the Manufacture of Sugar.
Year: 1890

page_text: e of Application, 6th Mar., 1890--Accepted, 10th May, 1890
COMPLETE SPECIFICATION.
Improved Process for the Manufacture of Sugar.
I, CARL STEFFEN, of No. 40 Heugasse, in the City of Vienna, in the Austrian
Empire, Engineer, 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 :-
My invention relates to an improved process for obtaining the entire crystallisable
sugar contained in more or less pure saccharine solutions, juices of plants and the
like by employing the same for washing crystalline sugar mass in special manner prior
to the said saccharine solutions being subjected to a novel method of boiling in order
to produce sugar crystals.
The present customary method of crystallising cleare thick juice of the solution of
sugar of the sugar factories is effected in such manner that the cleare or liquor is
successively so evaporated in the boiling apparatus that the crystallisation and new
formation of crystals from the thickened liquor is produced. As the liquor becomes
poorer in sugar through the formation of crystals it will he evident that a mother
liquor remains in the apparatus which has less crystallisable sugar than the original
liquor, but as fresh liquor is continuously and gradually fed into the evaporating
apparatus the consequence is that the mother liquor cannot give off its maximum of
crystallisable sugar with this process, so that the energy of the crystallisation for a
certain time attains its maximum capacity.
The curve in the accompanying diagram, Figure 1, represents the quotient value
of the liquor during the crystallisation and evaporation in the vacuum apparatus, the
said diagram showing the ordinates of the quotients of purity and the abscissas and
the distribution of time from 10 to 10 minutes. The curve C shows a constant
increase in the value of the mother liquor in the vacuum apparatus through the liquor
taken up by the same, so that the other liquor will not be able to attain its lowest
value, which according to the duration of the process ought to take place through the
crystallisation of the sugar in the same.
The mistake made in the ordinary process can be hereby readily detected and one
notices that through the increasing quality of the mother liquor the same has not been
able to separate its sugar crystals in a given time. Boiling in vacuum apparatus
further premises that the liquor or cleare shall possess such crystallising capacity that
grains of sugar can be produced. This property of the liquor is requisite in order to
render a corresponding rapid boiling in vacuum and the production of properly
formed crystals possible, as such crystals formed at the commencement of the boiling
process act as crystallising axis and increase in size during the boiling process; the
more numerous these crystals are, the better it is for the purpose.
Poor masses cannot be boiled for producing grain as no formation of grain takes
place at the commencement of the boiling, consequently no crystallising axis is
present, and the means for producing the crystallisation of the cleare or liquor are
wanting.
It has been known almost since the existence of sugar manufacture that when
yrups of little value are mixed with a sufficient quantity of crystal generators a very
effective crystallisation in vacuum is produced. Bad boiling juices are, for instance,
nixed with a small quantity of raw sugar washed with water, in raw sugar factories.
In the sugar refineries and especially where fine grained goods are required, powdered
ugar is mixed with the liquor in the vacuum in order to prevent the so called
remature grain. In the first case it is desired to meet the slowness of the crystalli-
ation, in the second, however, a larger quantity of fine crystal producers are employed
or reducing the duration of the boiling process in order to prevent a too prolific
ormation of crystals and for producing fine crystals.

page_text: .
It will be evident from the foregoing that sugar crystals can be produced from
masses with small crystallising capacity by successive evaporation of the mother liquor
when crystal producers are present.
If the curve C, Figure 1, is now consulted it will be found that the boiling process
will be carried out more correctly and energetically when an improvement of the
mother liquor during the boiling process by the addition of liquor does not take place,
and if liquor or cleare were added to the mother liquor which does not considerably
vary from the quality of the liquor in the act of crystallising out there is no doubt that
a mother liquor of much inferior quality will, in a corresponding space of time be
obtained in the vacuum apparatus.
The object amongst others of the process forming the subject matter of this
application is to produce a certain quantity of liquor about sufficient for one operation
in portions of increasing purity, from very inferior quality up to great purity, in the
subsequently described manner from sugar solutions, thick juices, of plants, and in
general from the liquor to be operated on.
If the liquor has been made into portions with increasing purity, the process in the
vacuum apparatus is so commenced that the entire quantity of liquor in successively
decreasing purity is brought to the boiling point, id est, the formation of grains in the
vacuum apparatus is commenced with the pure solution of sugar so as to rapidly
produce a large quantity of crystallising cores or axis, the liquor used having high
crystallising capacity, and then feeding fresh quantities of liquor in succession
according to their decreasing purity under continuous boiling and crystallising, so
that at last only liquor of inferior quality is fed into the vacuum apparatus and is
thus caused to give off its entire crystallisable sugar, which combines with the smaller
crystals already in the mass until the amount of crystallisable sugar in the liquor has
become exhausted, so that the mother liquor when separated from the crystals will be
nothing more than molasses.
Besides the possibility of thoroughly exhausting the crystals from the liquor in the
vacuum apparatus another advantage is attained, that by the continued boiling only
liquor of small crystallising capacity enters the vacuum apparatus, whereby the new
formation of fine crystals is decreased and is, in the latter stage of the boiling
process, prevented, as the crystallisable sugar will be deposited on the existing
crystals thus increasing the production of large crystals and decreasing the production
of small grain.
The curve B shown in the diagram R, S, 0, Figure 2, represents the course of the
value of a liquor of stable purity, (for instance 90°), during the crystallising process
and evaporating period in the vacuum apparatus.
The ordinates R, S, represent the quotients of purity, the abscissas SO the
duration and periods of boiling. The diagram M, K, W, in Figure 2 shows a curve A,
which represents the course of the value of another liquor during the crystallising
and evaporating period in the vacuum apparatus. This liquor is not of stable purity
but was divided into portions forming a series of syrups from inferior syrup upwards
to a sugar solution of high value. This separated liquor was submitted to the
crystallising and evaporating process in the vacuum apparatus in succession according
to its decreasing purity, that is, beginning with the solution of sugar of highest value
and ending with the most inferior syrup. The ordinates in this case also denote the
quotients of purity of the mother liquor in the vacuum apparatus during the various
stages of boiling and the abscissas K, W, the duration of the said stages.
The figures given for the coordinates are the results of experiments, the curves
showing that a liquor applied for the last case, diagram M, K, W, can in the same
time produce considerably inferior mother liquor in comparison with the first
case given.
The explanation is that,
1, in the first grain forming period where the crystallising axis is produced by
the crystallising of a very pure solution of sugar the well formed and numerous
grains are formed in a very short time.
than kauan to

page_text: any great extent but only increases the volume of the same and by being simul-
taneously evaporated in the vacuum apparatus gives off its sugar and produces a
mother liquor of poor quality to which a quantity of liquor of like value is added and
the same effects attained.
This new method of boiling liquor divided into portions according to the quality
of the same is described in the foregoing and I will now proceed to describe the
manufacture of such liquor from beet root and plant juices or solutions of sugar.
The liquor formed by the conspissation of juices of plants and the like are not, as
hitherto customary, boiled direct in the vacuum apparatus for producing crystallisation
but are inspissated to such a consistency that they will not dissolve sugar at the
temperature employed.
The same are then used as lixiviating fluid and for driving off the molasses from
the crystalline mass or masse cuite produced by a preceding boiling operation. This
washing is continued and the last quantity of liquor or washing fluid adhering to the
crystals freed from molasses driven off by steam, water or a pure saturated solution
of sugar. By passing the liquor through the crystalline mass or filling mass one is
able to separate the quantity of molasses which ought to be in the liquor after
boiling out the mass in the continuous process and obtain a lixiviating fluid, which
can be divided into quantities of varying quality and collected, the same showing at the
one end a very valuable solution of sugar, the last washing having been effected by
means of water, steam or a pure solution of sugar. If now this washing fluid is
submitted to the foregoing boiling process the same will give a crystalline or filling
mass with a mother liquor fully bare of crystallisable sugar and is washed with a like
quantity of lixiviating liquor. In this manner the entire crystallisable sugar in such
a quantity of fluid is won in pure form and a mother lye separated off as real
molasses. By means of this combination, viz., (1), the utilization of the liquor or
cleare as lixiviating fluid for sugar filling masses obtained in a preceding boiling
process, and (2), the boiling of the so resulting liquor in the afore described manner
according to the differences in quality in the vacuum apparatus for producing a
crystallised mass, the entire crystallisable sugar from a predetermined liquor can be
won as pure sugar in a single boiling process and the impurities of the same separated
as spent non-crystallisable mollasses.
The practical carrying out of the process can
manner :-
be effected in the following
The juices of plants or solutions of sugar are inspissated to the requisite consistence
in the ordinary evaporating apparatus, so that they appear as saturated solutions of
sugar. If it is not desired to work at warm but at ordinary temperature the material
can be cooled in the well known cooling apparatus. Crystalline mass or filling
mass from a preceding boiling process is, either in warm condition or cooled in
the ordinary refrigerators, filled into suction vessels, subjected to the suction process
and lixiviated by means of the above described liquor.
A pump sucks off the molasses to be drawn from the suction vessels, the latter
being provided with sieve bottoms, and removes the same.
When the requisite
quantity of molasses has been drawn off the lixiviating fluid passes into a number of
reservoirs which separate the same into different qualities. In the meantime
liquor is constantly fed onto the mass of crystals until a fluid proceeds from the suction
vessels similar in quality to the original liquor. A pure saturated solution of sugar
is fed as liquor into the suction vessels until almost perfectly pure sugar solution is
sucked by the pump through the suction vessel and the entire crystal mass appears
saturated with a solution of pure sugar.
This pure crystalline mass can be molten into refined sugar, boiled or dried. The
fine liquor and the entire washing fluid which almost represents a like quantity of
liquor or cleare which was necessary for producing the washed masse cuite of filling
mass, and, as above mentioned, is separated into different qualities in the reservoirs is
boiled in a vacuum apparatus in succession according to the decreasing purity to
crystalline mass which is treated with a newly produced quantity of liquor so as

page_text: to be separated into pure white crystalline sugar and a perfectly crystal free
molasses.
The separating of the molasses, the washing with liquor and the subsequent
lixiviating with water or steam can also be carried out in centrifugal machines, the
outlets for the washing fluid separating out the molasses in the manner described
into portions according to quality in sufficient number for the desired purpose. It
is recommended that not less than 10 portions of varying quality and if possible more
be employed when it is desired to attain a high effect.
If the entire quantity of liquor is not used for the washing process, the surplus is
to be added to that quantity of liquor, which is of like capacity with the original
boiling liquor and the next higher quality of washing liquor, is then used for
boiling.
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 :-
A process for treating more or less pure sugar solutions, juices of plants and the
like so as to obtain the entire crystallisable sugar in pure form and eliminate the
molasses poor in sugar, consisting herein that suitably concentrated juices of plants or
solutions of sugar, (liquor), are used as lixiviating fluid for the crystalline mass or
filling mass and these driven off out of the crystalline mass by water, steam or pure
solution of sugar, so that after the molasses have been eliminated the liquor remains
as a washing fluid, which is separated during the washing process into portions with
distinguishable differences in quality in order that the same may be treated in the
vacuum apparatus in succession, according to the decreasing purity of the liquor, to
produce a crystalline mass which, by means of a fresh quantity of cleare or liquor, is
subjected to the lixiviating process in like manner and for the purpose herinbefore
specified.
Dated this 6th day of March 1890