Niro's spray drying technology plays major role in treating by-product in new crop friendly bio ethanol production.
Producing energy by transforming crops into bio ethanol at a time when famine and food shortages affects large areas of the world's population is clearly not a sustainable option. But new technology which enables bio waste to be turned into bio ethanol means that much needed energy can now be harvested without damaging the food chain.
Ethanol, a popular type of bio fuel is traditionally produced by fermenting sugars present in plants such as corn and sugarcane with yeast. The process requires the use of the most edible parts of the plants which are rich in starch and certain types of sugars called hexoses, resulting in the loss of a valuable source of nutrition.
Following a project at Delft University of Technology researchers have succeeded in genetically modifying a strain of yeast that can convert bio waste materials like straw, woodchips and cornhusks into ethanol and a technical process using the yeast has been developed at the Danish Technical University. The technique opens up a previously untapped source of plant-based energy without compromising world food supplies.
Niro's expertise in spray drying proteins plays a major role in the process by drying ethanol's by product, yeast cream, decanted from the resulting slurry, into protein powder which can be used for animal feed.
The drying process is achieved in three steps:
• The yeast cream is concentrated to a point where the slurry at 60˚C has a viscosity of approximately 150 centipoise. This concentration is achieved energy efficiently using a Falling Film Evaporator to a level of approximately 20% Total Solids.
• The concentration is then dried in a Spray Drying plant equipped with either rotary or nozzle atomization depending on the required properties of the final powder.
• The resulting powder is transported to silos for immediate use or packed into bags for storage or distribution.
Falling Film Evaporation
In any industrial process operational cost must be kept under control and removing water from a substance can be a costly affair. For example, heating 1 kg of water
1 ̊ C requires 4.18 kJ and when heated to 100 ̊ C it requires further 2,400 kJ to evaporate, therefore the specific water evaporation rate is the energy used to remove a specific amount of water in the evaporation plant.
A Niro Falling Film Evaporation plant operating at low pressure and using thermal or mechanical recompression of vapour has a low specific energy consumption.
Where there are no particular property demands for the dried yeast cream powders Niro recommends spray drying using rotary atomization. The powder produced using this method will have a bulk density of approximately 500 kg/m³ and an average powder size of 100 microns, making it suitable for mixing with animal feedstock.
For more complex powder properties Niro recommends using a spray dryer with nozzle atomization for drying the concentrated slurry.
To keep the initial investment as low as possible in acquiring a spray dryer Niro recommends using the highest possible drying air temperature. This can be achieved using a direct gas heater to increase the temperature of the main air.
Niro's Test Centres offer customers the opportunity to conduct feasibility studies, pilot tests and laboratory analyses. The Centres are equipped with the latest technology and the company is always happy to discuss new partnership opportunities and alliances even when a project requires expertise outside Niro's traditional services.