Direct Thermochemical Conversion of Sewage Sludge to Fuel Oil

摘要

A disposal method for primary sewage sludge and industrial sludges which generates boiler fuel as a product and is energy self sufficient or energy-generating is described. The method involves direct liquefaction in a mild aqueous alkali above 250 degs. C and was demonstrated for about 100 hours in a reactor having a 50 pound per hour capacity. The boiler fuels recovered from the process were in the form of a water insoluble oil, char and gas and contained up to 73% of the energy from the input sludge. Analytical results show that most of the heavy metals from the sludge are concentrated in the char and remain in the ash residual when the char is burned. Burning the oil and char as fuel will generate gaseous pollutants from sulfur and nitrogen in the sludge which could be a problem in commercial versions of the process.