What are the uses of the products from sludge pyrolysis?

Sludge pyrolysis is typically carried out in a dedicated pyrolysis reactor maintained at atmospheric or high pressure, with controlled temperature and anoxic conditions. The sludge undergoes a series of complex chemical reactions within the reactor, including dehydration, pyrolysis, and reforming, ultimately producing products such as fuel oil, fuel gas, sludge carbon, and reaction water. The properties and yields of these products depend on factors such as the sludge composition, pyrolysis temperature, reaction time, and the catalyst used.

During pyrolysis, the sludge first undergoes a dehydration stage to remove moisture. As the temperature rises, organic matter in the sludge, such as fats, proteins, and carbohydrates, begins to decompose. Fatty compounds evaporate and decompose into small-molecule hydrocarbons at lower temperatures (e.g., 200–450°C); proteins and carbohydrates decompose at higher temperatures (e.g., above 390°C), producing liquid fatty acids and gaseous small-molecule hydrocarbons. These hydrocarbons further polymerize and reform in the reactor to form final products such as fuel oil and fuel gas.

The fuel oil produced by pyrolysis has high energy value, with a calorific value of 29–42.1 MJ/kg, comparable to traditional energy sources such as oil and natural gas. This fuel oil, after further processing, can be used for power generation, heating, and industrial fuel.

In addition to fuel oil, the pyrolysis process also produces large amounts of combustible gas and sludge carbon. The combustible gas, mainly composed of combustible gases such as hydrogen, methane, and carbon monoxide, has a high calorific value and can be used for power generation and as a chemical feedstock. The sludge carbon, rich in carbon and small amounts of metals, can be used as an adsorbent and catalyst carrier in environmental protection and chemical industries.