Reburning Treatment of the Froths Obtained after the Flotation of Incinerator Fly Ash

Abstract

Flotation has been proven to successfully remove most polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) and carbon constituents from hospital solid waste incinerator (HSWI) fly ash. The resultant froths contain large quantities of carbon constituents that can reburn in the incinerator. In this paper, the reburning behavior of froths at temperatures from 800°C to 1200°C was compared with that of HSWI fly ash. Results showed that the destruction efficiency of PCDD/Fs was higher in the froths than in the fly ash at the same reburning temperature. The destruction efficiencies of PCDD/Fs in the froths exceeded 98% at temperatures higher than 1000°C. The volatilization ratio of Pb, Zn, and Cu was lower in the froths than in the fly ash. Furthermore, reburning of the froths can achieve energy recovery of the carbon constituents. Therefore, flotation followed by reburning treatment in a combustion chamber could be a suitable process for the detoxification and reutilization of HSWI fly ash.

Characteristics and Treatment Methods of Medical Waste Incinerator Fly Ash: A Review

“…Because of the high absorbent efficiency and simple implementation, PAC injection followed by BF application is a standard configuration to reduce POPs, such as dioxins emitted from incinerators [40,41]. With a higher level of dioxin emission and stricter emission standard for dioxins, a larger amount of PAC must be injected upstream of the BF [42]. Usually, 105-115 ng of dioxins can be absorbed per gram of PAC [43].…”

“…Liu found approximately 90% of carbon constituents and dioxins in MWIFA could be enriched and then separated as froths by flotation [12,54,153]. A novel process for the successive removal of dioxins and recovery of heavy metals from MWIFA was also developed by Wei [42]. Thereafter, by the process of acid leaching-sulfidation and precipitation-flotation, 42.0% of Pb, 48.7% of Cu, and 49.9% of Zn could be recovered [1].…”

“…This mechanism is similar to sorptive-flotation phenomenon [54]; (3) the free and naturally hydrophobic dioxin molecules may directly attach to kerosene collectors or adhere to air bubbles, and float to the froth product (Figure 3). destruction efficiencies of dioxins in the froths could exceed 98% at above 1000 °C after reburning treatment of the froths, so it seems that recirculation of froths in the incinerator can serve the dual purpose of destruction of dioxins and energy recovery of carbon constituents [42]. After flotation, dioxin content in the tailings was significantly reduced to approximately 1.55 ng I-TEQ/g, which meets the standard of landfill site of municipal solid waste (3 ng I-TEQ/g).…”

“…If regenerated PAC can be used as a dioxin adsorbent in flue gas, the treated froths might be injected again into APCDs of incinerator, which would significantly reduce the usage amount of parent PAC in the incinerator and decrease the costs. Thus, a combination of flotation and microwave treatment might be a promising method to resolve the MWIFA problem, which would possess many advantages, such as complete decomposition of dioxins, low-cost, and recovery of waste resources [42] (Figure 5).…”

Two-Step Flotation Treatment for Removal of Toxic Matter from Hospital Solid Waste Incinerator Fly Ash

“…Based on the lipophilic and hydrophobic nature of PCDD/Fs and PCDD/Fs' characteristic enrichment of carbon constituents, decarburization flotation has been suggested for removing them from HSWI fly ash (Liu et al, 2013). Most dioxins and carbon constituents in ash sample can be effectively removed by transference to froths, this can not only achieve the detoxification of dioxins but also the reburning of carbon constituents can provide energy for the incinerator (Wei et al, 2017). After the aforementioned treatment for dioxins in tailings, the toxic equivalent (TEQ) would be reduced to meet the landfill standard value of 3 ng TEQ g -1 for municipal solid waste.…”