Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Preparing oxygen-containing organic compound
Patent
1986-06-19
1990-08-28
Warden, Robert J.
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Preparing oxygen-containing organic compound
203 19, 426 7, 426 11, 426 13, 426 14, 435162, 435165, 435813, C17P 706
Patent
active
049525034
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the production of ethanol by continuous fermentation of a carbon hydrate containing substrate in a fermentor, in which process a stream of fermentation liquor is continuously withdrawn from the fermentor and divided in a centrifugal separation step into a yeast enriched stream, which is recirculated to the fermentor, and into an essentially yeast-free stream, which is divided in a primary distillation step into a top stream enriched in ethanol and a remaining liquid bottom stream, of which a part is recirculated to the fermentor and the remaining part is fed to a secondary distillation step for division into a vapour stream containing the remaining ethanol and an ethanol impoverished stillage stream.
In a known continuous ethanol fermentation process of the kind introductively mentioned, such as disclosed in applicant's international application WO No. 83/01627, coarse solid particles are first separated in a straining step from the fermentation liquor continuously withdrawn from the fermentor, whereafter the stream that passes through the sieves is fed to a centrifugal separation step for separation into a yeast phase, which is recirculated to the fermentor, and a phase freed from yeast, which is fed to a primary distillation step in a distillation plant. Part of the solid, non-fermentable or inert material continuously fed to the process with the raw material is discharged from the process circuit in the form of coarse particules, which as sieve rejects is discharged from the circulation loop, which comprises the fermentor and the primary distillation step. The remaining part of inert solid material that continuously must be removed, is discharged with that part of the bottom stream from the primary distillation step which is fed to a secondary distillation step, also called stripping step, in which the remaining ethanol is stripped off and the liquid stream is concentrated to a final stillage stream. As a consequence thereof, the part of the solid inert material which cannot be screened off with the sieves must, at steady-state condition, reach a certain concentration in the bottom stream from the primary distillation step to be discharged in the correct amount from the process circuit through the stillage stream from the stripper.
In certain cases, such as in fermentation on grain raw material, a considerable concentration of fine particles arises in the streams to and from the primary distillation step, for example in the range of 4-6% by weight. Moreover, it can be foreseen that a still higher concentration of these "fines" must be built up in the fermentor-yeast separator-circuit, since the inert particles further tend to be enriched in the yeast phase, which is recirculated from the periphery of the yeast separators to the fermentor. Since further the proportion in the fermentation liquor from the fermentor normally amounts to no more than 2% by weight DS (dry solids), the sludge capacity of the yeast separators will to a large part be occupied by the inert material. As a consequence, the very large part of the flow fed to the yeast separator, at grain fermentation in the range of 60-70% , must be recirculated as sludge phase to the fermentor. Therefore large separator capacity is acquired, since the amount of sludge in this case is the dimensioning factor.
One way to reduce the need for yeast separator capacity is to change the flow rate between effluent and sludge phase, that is to increase the effluent flow and decrease the sludge, flow. Thereby the required concentration of inert solid material in the stream to and from the primary distillation step could be achieved simultaneously as a lower steady-state concentration of solid inert material in the fermentor-yeast separator circuit would be required, which could make possible a reduction in yeast separator capacity. However, the disadvantage of such a modification is increased yeast losses, which arise due to increased yeast drainage with the effluent to the primary distillation step, in which ali
REFERENCES:
patent: 4361651 (1982-11-01), Keim
patent: 4376163 (1983-03-01), Ehnstrom
patent: 4460687 (1984-07-01), Ehnstrom
patent: 4497896 (1985-02-01), Assarsson et al.
patent: 4522920 (1985-06-01), Thorsson et al.
patent: 4617270 (1986-10-01), Anderson et al.
McMahon Timothy M.
Warden Robert J.
LandOfFree
Process for the production of ethanol does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the production of ethanol, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the production of ethanol will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1589410