Multiple-effect evaporators Mixed feed

Figure 17. Patterns ofliquid flow in multiple-effect evaporators Forward feed, Backward feed, fcj Mixed Feed.

Patterns of liquor flow in multiple..effect evaporators (rz) forward feed b) backward feed (c) mixed feed d) parallel feed, (omn) Liquor streams. (-) Steam and vapor condensate streams. 

In the grain fermentation process, 8 to 10 percent corn mashes were fermented (corn contains 70-72% starch on a dry basis). Fermentation yields were on the order of 29 to 32 grams mixed solvent per 100 grams starch used, with a solvent ratio of approximately 60-30-10 (butanol-acetone-ethanol, respectively). The organisms possessed good diastatic activity, so malting was not required. The cooked sterile cornmeal suspension was aseptically transferred to sterile fermentors, inoculated, and incubated for about 65 hours at 37°C, after which the solvents were recovered by distillation. The aqueous residue (slop or stillage) was concentrated in multiple-effect evaporators and drum-dried for use in animal and poultry feeds. 

A flash evaporator system having no heating surfaces has been developed for separating salts with normal solubility from salts having inverse solubility. Steam is injected directly into the feed slurry to dissolve the normal-solubility salt by increasing the temperature and dilution of the slurry. The other salt remains in suspension and is separated. The hot dilute solution is then flashed to a lower temperature where the normal-solubility salt crystallizes and is separated. The brine stream is then mixed with more mixed salts and recycled through the system. This system can be operated as a multiple effect by flashing down to... 

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