Yeast
Yeast

Yeast

Added value instead of waste When brewing beer, a side product occurs, named yeast. This product is usually treated as disposal. Beer yeast, however, contains valuable ingredients, such as amino acids, proteins and minerals. These ingredients can be re-used in several (animal) food products. For this purpose ANDRITZ Gouda developed an efficient drying process. First, the (beer) yeast is concentrated by means of an ANDRITZ Decanter centrifuge to the highest achievable dry solid content and subsequently it is dried on an ANDRITZ Gouda drum dryer, thus resulting in a favorable energy consumption. This process can also be used for yeast that remains from large scale alcohol production facilities.

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Flyer yeast

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Features

 

  • Compact, safe and simple
  • Perfect solution to dry brewers' yeast and yeast from alcohol plants
  • No additional autolysis necessary
  • High energy efficieny due to pre-evaporation

 

The Process

The wet yeast is collected and processed over a multi-stage evaporator. The alcohol that is evaporated with water vapour, can be recovered by means of distillation.
In the multi-stage evaporator the yeast is evaporated until 35% of dry solid content. Subsequently the yeast is fed to a holding tank. From there on the product is fed to the drum dryer by means of a pump. Because of the drum dryer's heat treatment process further treatment to breakdown the yeast cells is no longer necessary. After drying the yeast to a dry solid content of 95%, it is transported by means of a pneumatic conveyor, passes a mill-sifter and finally arrives in a storage silo. From there the dried yeast is prepared for packaging.

Efficiency

Compared to direct drying processes, the indirect drying on a drum dryer, requires less hot air in order to achieve evaporation. The heat is generated by, for instance, steam. The (metal) drum wall transfers the heat to the product. The drum wall enables that all the heat is used to dry the product and does not leave the machine or chimney unused. This makes indirect drying a much more efficient process. An added advantage is that large dust recovery systems (such as filters) are no longer necessary due to the absence of big amounts of drying gas.

To obtain low emission values, it is recommended to clean the exhaust vapours in a small biofilter before releasing them to the atmosphere.

The heart of the process

The heart of the installation is the ANDRITZ Gouda Double drum dryer. It mainly consist of two cast iron cylinders that are heated inside with saturated steam. The thickened yeast concentrate is fed between the turning drying cylinders so that the product can build a so called hot "sump". From this sump the yeast is distributed across the rollers in a thin layer. Inside the drum dryers, the cylinders are heated up with saturated steam which then condenses on the wall. The condensate is continuously removed from the drum, so that the largest possible surface area remains available on the inside of the drum for condensation of the steam. The steam system is a closed system, which means that the product cannot come into contact with the steam or condensate. As a result of the contact with the hot cylinder surface, the water in the thin yeast layer evaporates. After 2/3 rotation of the cylinders, the dry, solid matter is scraped off with a knife from the cylinders.

Knife holder

The smart construction of the knife holder guarantees an even pressure of the knife over the total length of the drum. The use of specific materials prevents vibrations that result from scraping and guarantees uniform product removal. The pressure of the knife can be controlled easily outside the process area.

Two discharge screws and a pneumatic conveying system transport the dried yeast to the down-stream process steps. This drum dryer is available in a variety of sizes, from 1.5 m2 up to 38 m2. A large number of ANDRITZ Gouda drum dryers for this application are operating around the world.

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Yeast drying
Yeast drying
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