| 摘要 |
Treatment of sewage sludge (ca. 2% solids) from a biological clarification plant is carried out (a) opt. increasing the solids content of the sludge in a concentrator, (b) generating gas from the sludge in an anaerobic digester, (c) opt. dewatering the sludge to 25% solids, (d) mixing with equal vols. of recycled compost (45% solids) and a carbonaceous carrier (60% solids, e.g. wood shavings or tree bark), and (e) composting the mixt. in a composting unit (pref. a tunnel reactor) operating with a residence time of 10-14 days and an air supply of 170 Nm3/m3/day, thereby generating heat at a rate of 419 J/Nm3 of air. The improvement comprises (i) recovering heat from the composting unit (170 x 419 J/Nm3/day) by passing the effluent air (at 65 deg.C and 95% RH) via a blower to a heat exchanger, where heat is transferred to a liq. heat carrier, (ii) using the heat carrier to supply heat to the digester and concentrator (if present), thereby increasing the solids content of the sludge raising its temp. to 35 deg.C and increasing the amt. of gas generated, and (iii) using the extra gas to produce additional electricity in a generator. |
