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Wednesday, June 11, 2008

Cellulose based ethanol in Umeå

Abstract. When Umeå Energi was planning the investment in Dåva 2, they also discussed the effects of integrating Dåva 1 with an ethanol plant. This thesis is supposed to identify these effects and find the parameters that are important for the economics of such integration.

Helge: I was talking wit Bionergitidningen in Sweden today.

Two types of cellulose based ethanol plants were evaluated. One plant is based on dilute acid hydrolysis and the other plant on enzymatic hydrolysis. The dilute acid ethanol plant produces 40 700 m3 ethanol annually. The enzymatic ethanol plant has a greater capacity and produces 70 000 m3/year. The result from the simulations indicates that both ethanol plants are profitable.

Helge: We will write about this in Biotouch as well.

The ethanol process results in a few co-products, lignin, combustible solid from the evaporation and barque. These products can be used as fuel in Dåva 2. Waste heat from the ethanol plant is in the range of 25-29 MW. To get a better profit from the ethanol production, this waste heat should be used for district heating.

Helge: Ok.

The evaporation step and the distillation have the greatest steam demands. It is possible to replace the evaporation step in the enzymatic plant by anaerobic fermentation. The anaerobic fermentation will produce 800 kg methane gas/hour. The steam demand will decrease and this will result in a greater effect in both the steam turbine and the condenser.

Helge: Steam.

The high pressure steam to the dilute acid plant should be replaced with steam from an additional boiler. In such case the capacity of the ethanol plant can be increased from 40 700 to 66 000 m3 ethanol/year. The power output from the steam turbine will also increase. Steam from the additional boiler can cost up to 570 SEK/MWh and it will yet be profitable. The most important parameters for the economics of the ethanol plant is in order of precedence, price of ethanol, price of woodchips and the cost of the investment. The uncertainty of the ethanol price is high. The reason is due to a proposal to replace the reduction of taxes with a bio fuel certificate in year 2009.

Helge: Steam turbine.

The income from the dilute acid ethanol plant is 19 MSEK/year, compared to a case without an ethanol plant. For the enzymatic ethanol plant the income is 114 MSEK/year. The greater income from the enzymatic ethanol plant is due to the fact that it has a greater production capacity. The capacity is bigger thanks to a more efficient ethanol process.

Helge: Prices.
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