Sludge pyrolysis takes use of thermal instability of organic matter in the sludge. Heat the sludge under anaerobic conditions, and the make the organic pyrolysis. The organic is cracked according to the proportion of hydrocarbons, and forms gas (pyrolysis gas) with high use value), solid (solid residue). These products are easy to be stored, transported and used, which provides an effective way to reduce, stabilize, harmless and recycle the sludge.
The pyrolysis of sludge can be divided into low temperature pyrolysis, medium temperature pyrolysis and high temperature pyrolysis according to the temperature in the pyrolysis process. Low temperature: within 500 ℃; medium temperature: 500 ℃-800℃; high temperature: 800 ℃ or higher.
The factors that affect pyrolysis process, the yield and composition of end products include pyrolysis temperature, pressure, heating rate, residence time of gas and solid, size of materials and so on, in which the pyrolysis temperature is the most important one.
|100℃-120℃||Drying, separating after absorbing water. There is no observable material decomposition.|
|Within 250℃||Oxygen desulfurization occurs, and observable material decomposition. Structural water and CO2 separate.|
|Above 250℃||Polymer cracks, and hydrogen sulfide begins to split.|
|340℃||The aliphatic compound begins to divide; methane and other hydrocarbons are separated.|
|400℃||Compound containing carbon nitrogen starts to decompose.|
|400℃-420℃||The asphalt materials are converted into pyrolysis oil and tar.|
|With in 600℃||Pyrolysis of the asphalt materials into heat-resistant substances (gas phase, short chain carbohydrates, graphite).|
|Above 600℃||Olefin aromatic formation.|