Energy from waste: Plant design and control options for high efficiency and emissions' compliance under waste variability

摘要

Variations in composition and charging rates of waste constituents in energy-from-waste (EfW) plants disturb throughput and power output from nominal design (ND) levels. Off gas flowrates and composition are affected, impinging on operating expenses, profitability and emissions. State-of-the-art facilities. claim improved efficiency and emissions' compliance, by controlling the combustor via fluegas recirculation, fluegas heat recovery, excess air and oxygen enrichment. The work investigates the mutual influence of plant ND and of the above controls. Given a ND, it assesses the concurrent effect on performance and pollution abatement efficacy, under variability in key waste constituents. Based on the combined mass and enthalpy balance and on necessary and sufficient conditions for emissions' compliance, it determines appropriate manipulations (directions, gains and ranges) for high efficiency and reduced emissions under large waste variability (e.g., biodegradable fraction varying by 50%). It quantifies how heat integration and oxygen enrichment enable higher throughput of poor constituents (by boosting combustion), whereas higher fluegas recirculation and excess air suppress it, enabling higher throughput and power production from rich waste constituents. Concurrent action of the control variables enhances performance. ND affects the directions (increase or decrease) and manipulation ranges and provides safety margins ensuring compliance over the entire waste uncertainty range. (C) 2019 Published by Elsevier Ltd.