Note: Descriptions are shown in the official language in which they were submitted.
'986
The present invention relates to a method for the production of ethanol, from
a raw mateIial flow, conSistirlg of a carbohydrate-containing substIate "nixed
with cellulosc-containing fibres and/or other nonfel~entable, solid material,
said raw material flow being separated into one flow rich in solid sllbstance
and one substrate flow, free from solid substance, which ]ast flow is fermented
in one or several fermenters, a flow of feI~entation liquor bein~ separated
by centrifug~l separation, into at least one yeast concentrate flow and one
yeast-free flow, of which the yeast concentrate flow is recirculated to the
fermenter, while the yeast-free flow is separated into one flow, enriched in
ethznol, and one residual flow, of which at least part is recirculated to
the feL~nenter.
Ethanoi can be manufactured from several types of raw r~lztcrials of vegetable
origin. ~nese ~aw materials all contain, or are brought -to contain some fe~-
mentable carbohydrate, dissolved in water to a more or less high cGncentration.
~epending on the processes, which the raw materia]s hizve been subject to, in
order to reach at least a certain content of fe~qentable carbchydra'es, such as
en%ymatic or acid hydro]ysis of starch or li~line-containing cellulose rzw
materials, the substrate, which shall be fe~mented into e-thc-Lnol, is more or
less miY.ed with nonfeImentable solid r~atter l-ke cellulose fibres, hulls,
lignine etc.
~nen conceiving fermentation processes for the prGduction of e-hanol it is ai~edat mi~ ni~ing the ener~y demænd ~ld the ~ater cons~Jnptio3l, and increasing thesu~r yield zs far ~s possible.
: "locess, ;:hich meets Ihese demand, as far as 'he raw ~~lerial is not too L-Juch
conte~inated by fib~es, hulls, etc. s clescribed in the S:~e~ish pztent applica-
t-on No. 78011~-5, which is con^erned with a T~ethcd for t e plGC'a~CtiOn of a
~olatile c-~a~ic co--ipGund, in p-rt~c-il^- etha!Gl, by COI-~tin'~CUS fe'-..ell~a'tiCn
9~,6
of 2 c~ o!~ o!l v': i 11 i.l ~ ' ll v.i ~. `: ' ;- ; 1. ~ I ~' f lll~.~ll t ? , ~.n~ ;.n ~ c}. ~ cte-
r~ g f~a'~ re is~ t}lat a flow of ïe-~ t ticn ~ 0r is separated, by ccntr~-fllg~ e~iLration~ into at ]east one y.oss~ OO:.o?r1-urate flow a~d one yeast-free
flow, oi which the ye~ t concentrate fl.ow is :recirculated to the fermenter,
while the yea.st-free flow is separated into one f~.ow, enriched in vola-tlle
organic compound, which is dischargred, a~d a res1dllal flow, of ~hich at ieast
part .s recircu1.ated to the fe77nenter.
If the raw material contains fibres, these rnus~t be removed before the raw ma-
terial flow is fed to the felmenter, in such a rprocec6. Othe-~lise it woll]d be.,npossible to perferolD the reci.-rculation of yeast ~ithout a si~ult~neous re-eirculation of said solid IDatter. For this re~ison, the raw rnateIia.l flow fed is
usually separated into one substrate flow, which is fed to the fe~menter, and
one flow, rieh in solid substance, by centrifl~f~l separation, said last flow
bein~ washed with water, which after washing is enriched with substrate,
adheri.ng to the solid substanee, and is fed to the fe~qenter. It is t~ue that
such a mode of operation would make possible the perfoImance of the rnethod
according to the Swedish Patent App].ication No. 7801133-5, but it would mean
an increased, nondesirable cons~qption of l13ter end energy.
It is the object of the present inventior, to create a lqethod of the type
mentioned by way of introduction, in wl1ich the energy demand and the water con--
sumption is minimi~ed, while the sugar yield is as high as possible.
According to the present invention this -,roblem is solved by brlnging the flow,rich in solid substance, into contact wivh at least part of the residual flow,
the mi~ture thus obtained being separc~t.^-d rartly into a flow of solid substance,
from which remaining substrate has sub t.~ltially been rernoved, and p~rtly intoone flow, em~iched in substrate, ~;hi.ch f1Gw is recirculated to the fe~menter.
In one suitable e!nbodiment of the me~hcd according to the invention, s?id mix-
ture is se-parated by at least one ser)2rc~t`on ~le3~s in the foL~ of a sieve meens,
a flow rich in solid rr!attc-r being fec' to said sieve mec^~s togethe~ ith at
lea.st part of said residual flow and se~.arcated pLr~ly into one .solid ;r,nasefr2ction, which is preve-rlted in a Wây 'r-!~r.;lll ?'r se to pacs the sieve -~ec-ns
ithout foI~ing a filtering la~er on s~r~ -nd partly into one liquid frc-ct~on,
er~iched in substrate, ~hich frectic-i is '-ou~ht to pcass sa~id s-e;es ~.ci~s, end
is rc-cireulated to the fcrmcnter.
Said mixture can also be separated by at ]east one
centrifugal separator provided with a rotor, journalled horizon-
tally in bearings and a conveying screw, arranged coaxially within
the rotor for discharge of separated heavy phase into one solid
substance fraction, which forms heavy phase, and into one liquid
fraction, enriched in substrate, which is recirculated to the
fermenter.
Vacuum sieves can also be used for the separation into
solid phase fraction and substrate-enriched liquid fraction.
It is especially advantageous to bring said flow, rich
in solid substance, into contact with at least part of the re-
sidual flow by providing several separation means in series, the
flow, rich in solid substance and at least part of the residual
flow being brought to move countercurrently.
Such countercurrent washing of substrate from the flow,
rich in solid substance, can also be performed in different
types of extractors, for instance in the form of columns, provided
; with so called extraction trays.
In one especially suitable embodiment of the method
according to the invention the yeast-free flow is separated by a
distillative method into one flow enriched in ethanol and one
residual flow, so called slop, which is thus utilized for trans-
ferring the substrate, that is adhering to the solid substance,
to the fermenter.
Considering the efficiency of the transfer of the
substrate, adhering to the solid substance to the fermenter, the
concentration of the fermentable substance in the slop shall be
much lower than that in the raw material flow fed.
The invention shall now be described more in detail,
reference being made to the enclosed three figures, of which
figure 1 shows, schematically, a flow sheet of a plant for the
performance of the method according to the Swedish ~atent
Application No. 7801133-5; figure 2 shows, schematically, a flow
sheet of a plant for the performance of the method according to
the present invention, three bow-sieves, coupled in series, and
a centrifugal separator with horizontal rotor and a coaxial
conveying screw for recovery of substrate from flow, rich i.n solid
substance, being used.
Figure 3 shows a plant for the perfoxmance of the method
according to the present invention, two centrifugal separators
with horizontal rotor and a coaxial conveyor screw being used for
10 recovery of substrate from flow, rich in solid substance being
used.
In all fi.gures 1 refers to one (or a plurality of)
fermenter, 2 to a centrifugal separator for the recirculation of
yeast to same and 3 to a plant for the separation of a yeast-
free flow into a flow enriched in ethanol and one residual flow,
exhausted from ethanol but containing a certain amount of ferment-
: able viz. nonfermentable material. In the examples shown plant
3 is assumed to be a simple distillation plant, and the residual
flow is in the following referred to as "slop".
From the distillation plant 3 there is discharged an
enriched ethanol flow through a pipe 4 and a slop flow through a
pipe 5. A flow of fermentation liquor is taken through a pipe 6
to centrifugal separator 2, while a separated yeast flow is
recirculated via a pipe 7 to the fermenter and a yeast-free flow
containing ethanol is fed via a pipe 8 to distillation plant 3.
In all three plants shown a raw material flow is fed through a
pipe 9.
The plant disclosed in figure 1 comprises a centrifugal
separator 10, by the aid of which the raw material flow fed is rid
30 of any fibres and other solid matter, which are discharged through
a pipe 11, whiie the substrate flow is fed to the fermenter
through a pipe 12. At least part of the slop from distillation
-- 4
J
plant 3 is recirculated to the fermenter throuqh a pipe 13, while
a certain amount of the slop is discharged from the plant through
a pipe 14.
In the embodiment of a plant for the performance of the
method according to the inventlon disclosed in figure 2, part of
the slop is discharged through a pipe 15. The remaining part of
the slop flow is fed, via a pipe 16, to a unit for efficient
separation of the incoming raw material flow into one solid-
substance flow, substantially free from substrate, and one sub-
strate flow. This unit consists of three bow sieves 7, 18 and 19,
three mixing tanks 20, 21 and 22 with pumps 23, 24 and 25 connected
thereto. This is also a centrifugal separator 26 in the unit.
The former is of a type, comprising a rotor, horizontally jour-
nalled in bearinas with a conveyor screw provided coaxially with-
in the rotor for discharge of separated heavy phase.
The centrifugal separator and the bow sieves are
coupled in series, and the raw material flow, fed through pipe 9
streams countercurrently to the slop flow, fed throuah pipe 16.
The solid substance, which is washed out, is brought to a
relatively high dry solids content in centrifugal separator 26
and leaves the plant for further treatment, like drying, through
a pipe 27. The substrate flow, rid of fibres etc, is fed to the
fermenter throuah a pipe 28. The line design is disclosed more
in detail in the fiaure. It must be observed, that many different
flow sheets are possible. The unit shown is considered to be
efficient and economical in operation.
The embodiment of said unit, which is shown in figure 3,
consists, as mentioned above, of two centrifugal separators 29, 30
of the same type as that with reference number 26 i~ figure 2,
and of two tanks 31,32 provided with stirrers, not shown, the
centrifugal separators and the tanks being coupled in series, as
- is obvious from the figure. A raw material flow is fed to tank
i.`
31 via pipe 9. Also a liquid flow coming from centrifugal separator
30 is fed to this tank through a pi.pe 33. A slop flow is fed,
via a pipe 34 to tan]c 32, and relatively dry substance, rid of
substrate, is discharged from the unit through a pipe 35.
