Abstract
PurposeIncineration has become increasingly important in many large cities around the world because of fast urbanization and population growth. The benefits of energy production and large reduction in the waste volume to landfills also contribute to its growing adaptation for solid waste management for these cities. At the same time, the environmental impact of the pollutant gases emitted from the incineration process is a common concern for various stakeholders which must be properly addressed. To minimize the pollutant gas emission levels, as well as maximize the energy efficiency, it is critically important to optimize the combustion performance of an incinerator freeboard which would require the development of reliable approaches based on computational fluid dynamics (CFD) modeling. A critical task in the CFD modeling of an incinerator furnace requires the specification of waste characteristics along the moving grate as boundary conditions, which is not available in standard CFD packages at present. This study aims to address this gap by developing a numerical incinerator waste bed model.Design/methodology/approachA one-dimensional Lagrangian model for the incineration waste bed has been developed, which can be coupled to the furnace CFD model. The changes in bed mass due to drying, pyrolysis, devolatilization and char oxidation are all included in the model. The mass and concentration of gases produced in these processes through reactions are also predicted. The one-dimensional unsteady energy equations of solid and gas phases, which account for the furnace radiation, conduction, convection and heat of reactions, are solved by the control volume method.FindingsThe Lagrangian model is validated by comparing its prediction with the experimental data in the literature. The predicted waste bed height reduction, temperature profile and gas concentration are in reasonable agreement with the observations.Originality/valueThe simplicity and efficiency of the model makes it ideally suitable to be used for coupling with the computational furnace model to be developed in future (so as to optimize incinerator designs).
Highlights
Proper management of municipal solid wastes (MSW) has become increasingly important in many large cities throughout the world because of fast urbanization and population growth
An efficient alternative of MSW management is through the adaptation of modern incineration, which has the advantages of high volume reduction, low space occupation, relatively stable residues, and potential energy recovery
With the recent advances in computational power and developments in thermo-fluid dynamics theory, the design of incinerators can be greatly assisted by using computational fluid dynamics (CFD)
Summary
Proper management of municipal solid wastes (MSW) has become increasingly important in many large cities throughout the world because of fast urbanization and population growth. Gaseous products released from the grate rise and enter the freeboard above These gases react with each other inside the incinerator under high temperature combustion, and the resultant gas mixes are emitted out of the freeboard; with the final solid products being the bottom ashes which are treated and disposed. Optimizing the combustion performance of an incinerator freeboard (Figure 1) can generally minimize the pollutant gas emission levels. This was solely relied on the experience of designs over the past decades, based on intuitions developed from a few established thermo-fluid dynamics principles (Niessen, 2002). Optimization of the incinerator design can be sought through computation before finalizing with pilot and field testing
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