FR2461005A1 - PROCESS FOR THE PRODUCTION OF ETHANOL BY CONTINUOUS FERMENTATION - Google Patents

Abstract

THE INVENTION RELATES TO A PROCESS FOR THE PRODUCTION OF ETHANOL BY CONTINUOUS FERMENTATION. THE PROCESS CONSISTS OF FERMENTING A SUBSTRATE CONTAINING CARBON HYDRATES IN A FERMENTER, THE FERMENTATION LIQUOR BEING CONDUCTED DIRECTLY TO A SIMPLE EVAPORATION UNIT 2 IN WHICH THE VACUUM IS MAINTAINED TO PERFORM A SEPARATION IN A FIRST AND RICH FLOW. AT A BOTTOM FLOW, OF WHICH PART IS RECIRCULATED TO THE FERMENTER, WHILE THE REMAINDER IS SEPARATED INTO A CONCENTRATED FLOW WHICH IS CIRCULATED TO THE FERMENTER AND INTO A FLOW CONTAINING NO YEAST WHICH IS CONDUCTED TO A UNIT OF EXTRACTION 4. APPLICATION TO THE TREATMENT OF SUBSTRATES FORMED FROM ENZYMATIC CLeavage of Cellulose or Starch.

Description

1 2461005

  PROCESS FOR THE PRODUCTION OF ETHANOL BY CONTINUOUS FERMENTATION

  The invention relates to a method for producing

  ethanol by fermentation of a substrate, containing carbohydrates in one or more fermentors, a yeast-containing stream being separated into a concentrated stream of yeast and a stream containing no yeast. Such methods are known from Swedish patents Nos. 7,801,133 and 7,901,738, which describe processes in which the total flow of fermentation liquor is conducted in a centrifugal separator to be carried out.

  the separation, the concentrated yeast stream being circumscribed

  culation in the fermenter. The centrifugal separator used must have a capacity to separate the entire flow of fermentation liquor, from which

  ethanol continuously, which can be a disadvantage.

  A process in which there is no need for a centrifugal separator

  but in which the yeast is still protected when

  ethanol is recovered from the fermentation liquor

  fermenting continuously is described in the application

  Swedish patent application No. 7,801,134. In this process, fermentation

  tation is carried out at normal pressure, but ethanol is

  obtained by distillation from a flow of iron liquor

  containing the yeast, under vacuum. Although this method may be appropriate in many cases, it has certain disadvantages. The device is complicated. Considering the yeast present, the extent to which a stream enriched with ethanol

can be evaporated, is limited.

  The object of the invention is to provide a method of

  type above in the preamble, in which the

  quoted from the separation unit used should be relatively low, and. wherein the yeast is circulated without being damaged, and in which there is great freedom as to the choice of the appropriate operating data to obtain

ethanol by distillation.

  According to the invention, such a process is characterized in that the fermentation liquor is led directly to a simple unit of preparation, corresponding to one or just a few distillation steps, in which one

  maintains the vacuum, and in which the aforesaid liquor is separated

  partly, in a first stream of steam, enriched with ethanol which is led to a unit for the production of the

  quality of ethanol desired, and partly in a first flow of

  the yeast-containing base, from which a part is recirculated in the fermenter, while the residual part is separated into at least one concentrated yeast stream, which is circulated back into the fermenter,

  and in a flow containing no yeast, which is conducted

  than to an extraction unit in which it is partly separated in a second stream of vapor, enriched in ethanol, and partly in a second bottom liquid stream containing

no ethanol.

  In a preferred embodiment of the method

  form of the invention, the second vapor stream, enriched with ethanol,

  nol, is led directly to the simple unit of evaporation,

  or indirect heat source Depending on the process, the

  It is not exposed to excessive temperature, but the temperature in the extraction unit may be higher than could be tolerated by the yeast. According to the invention,

  we can dispense with the heating surfaces of the unit

  evaporation. No high separation capacity is required

  and the operating conditions for obtaining

  nol can be chosen at best.

  If the substrate has been made by enzymatic cleavage

  As cellulose or starch as a raw material, it is an advantage that the simple evaporation unit operates at low pressure and thus at low temperature, so that the enzymes are not destroyed but can be recovered. The tendency of deposit formation is also less in a

  simple unit of evaporation if one operates at low temperature.

  It is appropriate to separate the bottom stream containing the yeast by a centrifugal separator into a concentrated stream

  in yeast and in a stream containing no yeast.

  The invention will be described in more detail, the references

  are made in the attached drawing, which shows how

  schematic unit to implement the method.

  In the figure, l represents one or more fermen-

  tor (s), 2 is the corresponding simple evaporation unit

  è one or several distillation steps, 3 is a separation

  centrifuge and 4 a single extraction unit. The desired ethanol quality production unit is indicated by a condenser 5 and a distillation column 6. A pipe 7 connects the fermenter 1 to the evaporation unit 2, from which on the other side, a bottom line 8 splits into two branches

  9 and 10 of which the branch 9 is connected to the central separator

  trifuge 3 and the branch 10 is connected to fermenter 1. The

  centrifugal paratridge 3 is equipped with a discharge of wastewater 13. A line 14 connects the single extraction unit 4 with the simple evaporation unit 2, from which it

  There is a line 15 to condenser 5. A fuel pipe

  Tation 16 is intended to feed the substrate into the fermenter, while a discharge pipe 17 is present to discharge the carbon dioxide that is formed. The simple evaporation unit 2 respectively the simple extraction unit 4

  is equipped with heating coils 18 and 19 respectively

  is lying. The unit operates as follows: the substrate is continuously transported by the feed pipe 16, and a suitable yeast concentration is maintained in the fermentor 1. The fermentation liquor comprising the yeast is continuously removed by the pipe 7 and is evaporated to a relatively low temperature under vacuum in the simple evaporation unit 2. The bottom flow is discharged through the pipe 8 and is divided so that a part is put back

  circulating in the fermenter 1 through the pipe 10 and the

  The centrifugal separator 3 in the centrifugal separator 3 conveys the transported stream into a concentrated yeast stream which is circulated back into the fermenter 1 via the pipe 12 and into a flow containing no yeast, which is transported to the single extraction unit through the pipe 11 and an intermittent wastewater stream which is discharged through the pipe 13. The flow

  of steam, enriched with ethanol from the simple unit of

  evacuation 4 is conducted by pipe 14 to the single unit of

  vaporization 2 and contributes to the heat supply of this unit. The steam is supplied as required by the heating coil 1P as well as by the heating coil 19, which heat the single extraction unit 4. The steam flow

  combined, enriched with ethanol from the single unit of

  poration 2 is discharged by the pipe 15 to the condenser 5 and then led to the distillation column 6 for production

  the desired ethanol quality.

  The following transaction data can be

  appeared as an example of a unit's operations

  to perform the process according to the invention.

EXAMPLE

  Molasses of 400Bx cane sugar are fed

  continuously fed by a feed pipe 16 of the fermentor 1. A yeast concentration of 2.5% by weight is maintained

  by recirculation. In these circumstances, a time of

  6 hours is necessary to obtain a fermentation

  complete. The flow of fermentation liquid containing 0.1-

  0.5% (by weight) unfermented sugar and about 5% (in

  weight) of ethanol is pumped continuously to a uniform

  simple evaporation tee 2, in which a pressure of 50 mm of mercury is maintained. The boiled fermented boiled WC and the steam containing 30 to 35% (by weight) of ethanol

  is removed and condensed in a condenser 5. The ethanol di-

  read and concentrate is subsequently purified in column

distil 6.

  The bottom flow coming from the single unit of evapo-

  ration 2 is divided into two streams, so that 80% is recirculated in the fermenter 1 and 20% are centrifuged in the centrifugal separator 3, which operates at high speed of rotation. The yeast concentrate is pumped into the fermenter 1 through the pipe 12, while the stream containing no yeast is removed in the single extraction unit 4, designed in the form of a short column. The steam, enriched with ethanol, is conducted from the extraction unit 4,

  either directly to the single evaporative unit 2 or indirectly

  heating system, which reduces energy losses. The bottom stream from the single extraction unit 4 contains about 35% (by weight) of dry soluble solids and can be processed further.

2 4 6 1005

  simple way, for example in a combustion furnace.

  As it goes without saying and as it follows from elsewhere

  the following, the invention is not limited to those

  of its embodiments and applications which have been

  considered above; it embraces, on the contrary,

all variants.

6 2461005

Claims (3)

  A process for the production of ethanol by fermentation of a substrate, containing carbohydrates in one or more fermentors, a yeast-containing stream being separated into a concentrated stream of yeast and a stream containing   yeast, characterized in that the iron liquor   mentation is conducted directly to a single unit of assessment   poration, corresponding to one or several distillation stages   lation, in which the vacuum is maintained, and in which a   flow is separated, in part, into a first stream of steam,   rich in ethanol, which is driven to a production unit to obtain ethanol of desired quality, and partly, in   a first bottom stream containing yeast from   a portion is recirculated in the fermenter, while the remaining portion is separated into at least one yeast concentrate stream, which is recirculated into the fermentor and into a stream containing no yeast, which   is taken to an extraction unit, in which it is se-   partially parried into a second vapor stream, enriched in ethanol, and partly into a second bottom liquid stream, not containing no ethanol.   2. Method according to claim 1, characterized in   what the second vapor stream, enriched in ethanol, is   duit to a simple unit of evaporation.   3. Process according to any one of the claims   1 or 2, characterized in that the bottom stream containing the yeast is separated by means of a centrifugal separator into a yeast concentrate stream and a stream containing no yeast.