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Environmental study of the lignocellulose ethanol production at the Sekab pilot plant (ETEC)
2007 (English)Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

In order to design a future large-scale lignocellulose ethanol plant it is of crucial importance to monitor and minimize the discharge from the factory to the environment. The Ethanol Pilot Plant in Örnsköldsvik, which is being operated near industrial conditions, is an excellent tool to study these effects. In the present study, the liquid and gas process streams have been analysed in order to close the mass balances of the studied chemical compounds. Of special interest was to close the mass balance on sulphur from H2SO4 or SO2 used for hydrolysis catalysts. Sulphur containing compounds have unpleasant smells and are often highly toxic to animals and human. High sulphur concentration in effluent wastewater leads to formation of high concentration of sulphide that upset the anaerobic biological organisms of wastewater. The existing gas treatment unit, wet scrubbers were also studied for their removal efficiency of TOC. The removal of TOC is very important because in air organic compounds along with oxides increase the level of ozone in the atmosphere. Wastewater samples obtained during continuous operation were investigated for COD, TOC, pH, total sulphur and TS as well as SS. The waste waters were sampled individually from the membrane filter press, the scrubbers, the condensate from the evaporation unit and the stillage. Mass balance estimation of sulphur indicates a lost of sulphur in the reactors, evaporators as well as the fermentation unit. The estimations further indicate that most sulphur emissions end up in the stillage. In the gas stream after the H2O scrubber, the largest sulphur emission release (43 mg/m3) into atmosphere was registered when SO2 was used as a catalyst in the hydrolysis. The use of H2SO4 as a catalyst however release small amount of sulphur (4 mg/m3) into air, which is advantageous for environment. The TOC discharged into air on all occasions were in the range (9-17mg/m3). The removal efficiency of TOC is found to be a function of TOC loading, the gas flow rate and the liquid hold up. Results indicate that high liquid hold up as well as high inlet TOC concentration results in higher TOC absorption efficiency whereas a higher inlet gas flow rate decrease the absorption efficiency. The removal efficiency of the SO2 scrubber shows that almost 85-97% removal efficiency could be achieved. H2O scrubber shows 2-97% removal efficiency. Wastewater parameters investigated indicate high strength wastewater effluent asit contains high residual COD and TOC. The TOC and COD levels in the wastewater were however not dependent on the acid catalyst used in the hydrolysis process. The total effluent wastewater has a pH level that is acidic (pH 3-6) and sulphur concentration in the range (180-240 mg/l) that will be problematic for biological wastewater treatment and methane production in an anaerobic treatment plant. The stillage stream contributes to the largest COD, TOC, TS as well as sulphur emission in wastewater.

Place, publisher, year, edition, pages
Keyword [en]
Physics Chemistry Maths, ethanol, bio-fuels, environment, TOC, BOD, COD, mass balance, lignocellulose, catalyst, sulphur, scrubber, wastewater, stillage
Keyword [sv]
Fysik, Kemi, Matematik
URN: urn:nbn:se:ltu:diva-58957ISRN: LTU-PB-EX--07/031--SELocal ID: f825a9d9-fb4e-429e-b091-02e7d4d010eaOAI: diva2:1032345
Subject / course
Student thesis, at least 15 credits
Educational program
Chemical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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