Investigating the appropriate method for use of date fermentation mother liquor
2013
Khanahmadi, Morteza | Azizi, Aslan | Miranzadeh, Mokhtar | Shaahin, Amrollah
An appropriate process for reuse of ethanol plant waste water was determined. Press-filter, micro-filter, flocculation, and decanter centrifuge were tested in this regard. Advantages and disadvantages of each method were determined. Wet particles of the suspension had a size range of 180-300 µm and a density near to that of water due to their large water absorption capacity. Applying a pressure of 10 bars in the press-filter, the suspension's solids were separated as a cake having 80% moisture. However the filtration rate was about 10 liter per m2 per hour which is insufficient and needs a large filtration area leading to a high investment and operational costs. Recommended dose of flocculating agent could not give a considerable improvement in settling rate of the solids. Hollow fiber microfiltration was not a suitable method since filtration rate was diminished fatly. Moreover, the solids could not be removed from the bulk of fibers. More than 90% of the solids were separated into a cake of less than 80% moisture using the semi industrial decanter-centrifuge. The filtration rate was 400 liter per hour. By use of the governing equations, the industrial scale decanter-centrifuge capacity was predicted to be higher than 7 m3 per hour which is appropriate for the alcohol plant. According to the estimations, 75% of filtrate could be recycled back to the plant without any adverse affects on process performance.
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