Production of bioethanol in addition with heat, power and valuable byproducts
The Energiepark Bruck/Leitha was founded in 1995 with the objective of realising all possible forms of renewable energy, along with making them accessible and understandable for the population of the region. Today the municipality Bruck/Leitha has already achieved the goal of reducing 50% of carbon dioxide emissions by using renewable energy sources within the areas of heat and power.
In the production of bioethanol the optimisation of the total energy balance is substantial. Even if the used technology for bioethanol is already highly developed, the total energy balance can be further enhanced by fitting the production facility into the existing local energy system. Furthermore regional material employment can be optimised for power production.
This work endeavours an insight into the special requirements for a sustainable production of bioethanol at the location Bruck/Leitha. Several process scenarios are analysed by means of process simulation.
The analysis focused on the heat and power production facilities, as well as process variations resulting from different types of feedstock, and the integration of by-products from the DDGS drying process, the biogas production and conversion. With the heat integration of the individual components of bio ethanol production (with or without DDGS production) considerable amounts of heat can be saved.
Generally speaking, energy efficiencies increase with plant size. As a consequence larger plants are to be favoured at least regarding the specific energy requirement.
As the drying of the distiller's wash from the ethanol distillation is a very energy intensive process step, this by-product was alternatively used for the production of biogas, including its conversion to heat and electricity.
The investigation on the integration of the biogas process and the CHP-plant into the bioethanol plant shows that electric energy can be produced, but the obtained heat does not cover the required thermal energy demand. Therefore it seems to be reasonable to use the entire biogas for the production of heat. The demand of electric energy can be covered with the existing wind powered devices.
The usage of the biogas in conventional gas-fired boilers enables a heat coverage for plant sizes of 60.000 t/a ethanol or higher. The highest investigated design case (200.000 t/a ethanol) provides sufficient steam from the biogas process to cover the heat demand of the ethanol process and produce electricity in a back-pressure steam turbine.
For sustainability reasons and due to regional criteria (raw material and disposal) small plants are to be preferred. The self-supply of the region Auland Carnuntum with petrol can be obtained with a bioethanol plant with a capacity of only 15.000 t/a. For this plant size regional supply with raw material is ensured to some extent, and the integration into the existing facilities for providing biomass based energy (district heating, biogas facility) is feasible.
However, economy and energy efficiency as well as self supply of thermal energy argue for large plants. The comparison of energetic, economic and ecologic aspects leads to plant variants with capacities that exceed the demand of the region by far. Therefore a realisation with integration of the bioethanol plant into the existing facilities at the location Bruck/Leitha is not recommended.
Starting points for further work are the coverage of the heat requirement by the use of production residues for instance in form of combustion of resulting corn and/or wheat straw.
Ao. Univ.-Prof. Dipl.-Ing. Dr. Anton Friedl
TU-Wien, Institut für Verfahrenstechnik
Tel: +43 (0)1/58801-15925
Fax: +43 (0)1/58801-15999
TU-Wien, Institut für Verfahrenstechnik
Energiepark Bruck/Leitha (Werkvertragspartner)
Biogas Bruck/Leitha GmbH & Co KG (Projektpartner)
Fernwärmeversorgung Bruck/Leitha GmbH & Co KEG (Projektpartner)
Windpark Bruck/Leitha GmBH & Co KG (Projektpartner)
Technisches Büro Dr. Georg Beckmann (Projektpartner)