The main operating costs of wastewater treatment plants are related to the energy consumption and the disposal of by-products. Energy recovery from sewage sludge may be a solution to face both these challenges, improving the sustainability of wastewater treatment plants and making them an example of a circular economy. In this work, the energy analysis of an integrated combined heat and power system with sewage sludge gasification is proposed. The whole process is simulated by using the commercial software Aspen Plus®. A restricted equilibrium model is used to simulate the gasification of sewage sludge in an atmospheric fluidized bed reactor using air as a gasification agent. In line with the pertinent literature on integrated biomass gasification-internal combustion engine systems, the engine is modeled as a gas turbine. Electric and thermal energy produced by the system is used to supply a fraction of the demand for wastewater and sludge treatment. The energy analysis is carried out for a real wastewater treatment plant that serves 1.2 million of population equivalent, located in Southern Italy. Considering the case study analyzed, the CHP allows covering the 86.4% of the WWTP electricity demand. Due to the high revenue related to the electricity production, the system appears to be feasible from an economic point of view, with a simple payback of about 5 years. The highest investment cost is related to the gasifier, which accounts for 62.3% of total initial costs.
A Cogeneration System Based on Sewage Sludge Gasification
Paola Brachi;
2020
Abstract
The main operating costs of wastewater treatment plants are related to the energy consumption and the disposal of by-products. Energy recovery from sewage sludge may be a solution to face both these challenges, improving the sustainability of wastewater treatment plants and making them an example of a circular economy. In this work, the energy analysis of an integrated combined heat and power system with sewage sludge gasification is proposed. The whole process is simulated by using the commercial software Aspen Plus®. A restricted equilibrium model is used to simulate the gasification of sewage sludge in an atmospheric fluidized bed reactor using air as a gasification agent. In line with the pertinent literature on integrated biomass gasification-internal combustion engine systems, the engine is modeled as a gas turbine. Electric and thermal energy produced by the system is used to supply a fraction of the demand for wastewater and sludge treatment. The energy analysis is carried out for a real wastewater treatment plant that serves 1.2 million of population equivalent, located in Southern Italy. Considering the case study analyzed, the CHP allows covering the 86.4% of the WWTP electricity demand. Due to the high revenue related to the electricity production, the system appears to be feasible from an economic point of view, with a simple payback of about 5 years. The highest investment cost is related to the gasifier, which accounts for 62.3% of total initial costs.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
