Proceedings

Introduction

▪ Variation in sludge composition

▪ The impact of the pre-treatment before pyrolysis (Raw sludge vs THP vs THP-AD) Sludge characterisation The five sludges are: → Different material will decompose at different rate → The decomposition kinetics for the overall and individual reactions can be obtained → The technic is called thermogravimetry analysis (TGA) Reduction in activation energy of pyrolysis for sludge after THP AD (Using air-dried sewage sludge powder) The composition of the pyrolysis gas ↓ ↓ Char characterisation Morphological analysis 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 Combustion behaviour in TGA (the graphs show the mass loss rate during combustion in air) 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 In comparison with the origin sludge feedstock, the pyrolysis chars shows similar level of C, H, N, while the O content is greatly reduced For the fibrerich sludges, the fibrous structure remains after pyrolysis. The higher the temperature of pyrolysis, the more thermally stable the char is – except secondary sludge, and the raw sludge which contains secondary sludge. Organic phase (heavy phase) Aqueous phase (light phase) Organic phase (heavy phase) How much light phase is there in the pyrolysis liquid? With gravity alone the phases settle and separate – and the separation is enhanced by centrifuging. The phases are immiscible. When shaken an emulsion is formed – except the liquid from primary sludge pyrolysed at 500˚C, because its heavy phase is too dense and viscus to mix with the aqueous phase. Sewage sludge is currently recycled to agricultural lands as a fertiliser, and water companies are seeking alternatives to diversify sludge management options. Pyrolysis is a potential alternative. It decomposes the material under heat in the absence of oxygen. The pyrolysis outputs offer opportunities in energy and resource recovery.