| abstract |
BACKGROUND OF THE INVENTION The present invention relates to a process for the complex utilization of a large scale production of bioethanol, wherein the end products of the process are biogas, low salt sludge sludge, anaerobic granular sludge, solid ammonium phosphate based fertilizer, elemental sulfur, aerobic sludge and waste heat from process water. In the process, the crude stillage is freed from the insoluble fraction by centrifugation and the liquid fraction in the secondary separation stage is freed from residual dispersed substances by compressed air flotation, centrifugation, vacuum filtration or a combination of these processes, whereby the thick dense portions of these two low salt contents are subjected to further processing the feed, the liquid fractions of the two stages, after mixing, are subjected to acidified acidification under a pH of 4.8 to 9.2, and discharged to anaerobic degradation from below into a granular biomass reactor consisting of acidifying and methanogenic bacteria; a temperature of 25 to 40 degC, a residence time of 2 to 50 hectares under a granular biomass load of 5-105 kg CODm.sup.-3.n..den.sup.-n., multiplied granular sludge is collected and dried biogas is discharged from the head of the anaerobic reactor and subjected to a biological desulphurisation process to produce the biogas. As the byproduct of elemental sulfur and the biogas is removed for energy recovery, the nitrogenous components are removed by the addition of magnesium chloride and phosphoric acid to precipitate insoluble magnesium ammonium phosphate, which is separated off as a valuable fertilizer and the liquid is further fed to aerobic treatment, from where the sludge is separated after the sludge |