Abstract
Sludge is one of the main pollutants from sewage treatment and contains a high content of water and organic matter. The co-combustion of sludge and coal can bring about the energy conversion of sludge. However, the high moisture content in sludge and the inorganic pollutants generated by co-combustion have adverse effects on combustion and the environment. In this work, through experimentation, it was demonstrated that co-combustion does not release obvious toxic elements or create an environmental hazard. On the basis of the TG/DTG curves, the ignition points of sludge and coal and the temperature of each group were obtained, which provided boundary conditions for a numerical simulation. Co-combustion with various mixing ratios and moisture contents was studied via the numerical simulation of a 330 MW boiler. The numerical results show that a high mixing ratio reduced the boiler temperature and created more moisture and fuel NOx. When the mixing ratio reached 40%, the boiler temperature became less than the combustion temperature. Sludge drying improved the internal temperature of the boiler, but it created thermal NOx. When the moisture content decreased to 40%, the temperature in the boiler rose, which improved combustion.
Highlights
Sludge treatment has become an important topic in current environmental protection research and is of great significance for environmental protection and ecological security.Currently, the most common methods to treat sludge are through landfills, agriculture, or incineration [1], among others
The results show the co-combustion of sludge significantly flue gas theofboiler
When the mixing ratio increased from 0% to 20%, the flue-gas temperature at the the boiler outlet only decreased by °C
Summary
Sludge treatment has become an important topic in current environmental protection research and is of great significance for environmental protection and ecological security. Nadziakiewicz [9] studied the co-combustion of sludge and coal by thermogravimetric (TG) analysis and concluded that the substances contained in sludge strongly affect mixing and combustion. Chen et al [20] studied the thermochemical and kinetic behavior of coal, municipal sludge (MS), and their mixed combustion in different proportions by thermogravimetric analysis and demonstrated that the co-combustion of coal and sludge can effectively reduce the volatilization rate of toxic elements. Li et al [21] studied the combustion behavior of municipal and residual petrochemical sludge and their co-combustion characteristics using a differential thermal gravimetric (DTG) analysis and determined the optimal heating rate of a mixed sample combustion. It is vital to better understand the co-combustion characteristics of coal–sludge mixtures and the resulting pollutants
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