Continuous fermentation tower fermenters

Laboratory studies on continuous fermentation of wort by brewers yeast demonstrated that satisfactory beers could be produced only when a number of stirred fermenters were used in series (cascade system) or in tubular (tower) fermenters (Chapter 19). In both cases satisfactory throughputs were only obtained by ensuring a high concentration of yeast remained in the system. To achieve this, in a cascade system, yeast was recycled from the outflow back into the fermenter. Under such conditions in a single vessel homogeneously mixed system at steady state we have ... 

Recent studies on continuous fermenters [62] and in particular the tower fermenters have identified the main requirements (Table 19.7). High concentrations of yeast promote rapid fermentation but if these concentrations... 

The vessels of continuous fermenters are nearly always full, fermentation times may be lower than 6 hr and there is an even demand on services such as cooling. The highly efficient use of the vessel means that the cost of the fermenter is lower per unit of beer produced than it would be for conventional plant [67]. Ancillary equipment is, however, expensive. A great saving in space arises from the rapid throughput and, in the case of tower fermenters,... 

Commercial-scale operations are conducted in batch, fed-batch, or continuous culture systems. Fermentation vessels include the conventional baffled aerated tank, with or without impeller agitation, and the ak-lift tower fermentors in which ak is sparged into an annular space between the... 

The term fermentation is used to describe the biological transformation of chemicals. In its most generic application, a fermentor may be batch, continuous-stirred tank (chemostat), or continuous plug flow (immobilized cell). Most industrial fermentors are batch. Several configurations exist for these batch reactors to facilitate aeration. These include sparged tanks, horizontal fermentors, and biological towers. 

Q., Giudid, R., Continuous ethanol fermentation in a tower reactor,... 

STY is high for a fermentative procedure and ranges from 140 g L-1 d 1 for a continuous tank reactor to 1.2 kg IT1 d 1 in a continuous tower reactor with cell recycle. Depending on the ethanol tolerance of the production species, ethanol is produced to a concentration of 12-20%. The ethanol is traditionally recovered from the fermentation broth via an energy-intensive distillation step, but it is sought to replace the latter by pervaporation or reversed osmosis [25]. 

Continuous ethanol fermentation using a tower fermentor with high floccu-... 

Continuous ethanol fermentation using a tower fermentor with high floccu-lent yeast strains has been studied in depth (see [13] for pertinent references). Overall, the system has the following characteristics ... 

Fig, 19.21 Continuous tower fermenter, (a) Wort-collecting vessels (b) Impellor-type pump (c) Flowmeter (d) Control valve (e) Flash pasteurizer (f) Tower (g) Yeast separator (h) Beer receiver (j) CO2-Collecting vessel. 

Floe formation increases microbial holdup, facilitates the separation of the biomass from the fermentation broth, makes it possible to use particular fermenter configurations (e.g. tower reactors) for continuous culture or to feed back a fraction of the microorganisms to the reactor. 

Continuous fermentors (Figure 12.15) comprise a 400 to 4000 hi stainless steel tower. A 4000 hi system can handle 130 metric tons of harvest per day and it can produce approximately 23 000 hi of wine in 3 weeks. An annual wine production of 40 000 hi is necessary to justify the costs of such a system. These fermentors permit the daily reception of fresh grapes and the evacuation of an equivalent amount of partially fermented wine and skins. In the upper part, a rotating rake removes the... 

For example, different fermentation schemes have been developed for the production of ethanol. Conventional batch, continuous, cell recycle and immobilized cell processes, as well as membrane, extraction and vacuum processes, which selectively remove ethanol from the fermentation medium as it is formed, were compared on identical bases using a consistent model for yeast metabolism (Maiorella et al., 1984). The continuous flow stirred tank reactor (CSTR) with cell recycle, tower and plug flow reactors all showed similar cost savings of about 10% compared to batch fermentation. Cell recycle increases cell density inside the fermentor, which is important in reducing fermentation cost. 

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