Chapter One - Municipal Solid Waste Incineration Process and Generation of Bottom Ash and Fly Ash

Abstract

Municipal solid waste (also known as refuse, garbage, MSW, domestic waste, etc.) incineration (MSWI) is a complex task carried out by equipment comprising a loading system, an incineration system, an energy utilization system, a flue gas cleaning system and a secondary pollution control system. Bottom ash (also known as slag, BA, MSWI BA, etc.), fly ash (also known as FA, MSWI FA, etc.), and flue gas are the main secondary pollutants. Currently, mechanical grate furnaces predominate around the world, followed by fluidized bed incinerators and a few pyrolysis incinerators. The design parameters for an incinerator should comply with the requirements of the refuse components deployed in the cycle above, and lower heating values. The flue gas contains toxic substances and must be cleaned carefully using lime and active carbon. For incineration of the high moisture refuse, the moisture should be reduced through storage in the storage pit for 5–7, days so that the moisture can be decreased to 40–45%. A waste-to-energy power generator is installed to generate electricity, the amount of which is dependent on the heating value of refuse and environmental constraints. In general, over 300kWh/t electricity can be obtained from refuse with 60% moisture. Conflict between local government and concerned local community members usually occurs around incineration plants, and the real root of this lies in the limited public access to the relevant information and the lack of reasonable channels of communication. The basic operation data and normalization process of a full-scale grate firing incinerator with three lines are elucidated and three scenarios with potentially critical assumptions are considered from an life cycle assessment perspective, including increasing the heating values of waste by sorting, a waste dewatering process, and the reduction of pollutants released from the incinerator. The paradox of MSWI is explained, the environmental impacts of a large-scale incinerator with mixed MSW of high water content, and the impact of moistures and components on the incineration process are provided.