Assessment of emissions and removal of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) at start-up periods in a hazardous waste incinerator

Abstract

A study was conducted to observe the changes in polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) levels and congener profiles in the flue gas of a hazardous waste incinerator during two start-up periods. Flue gas samplings were performed simultaneously through Air Pollution Control Devices (APCDs) (including boiler outlet, electrostatic precipitator (ESP) outlet, wet scrubbers (WS) outlet, and activated carbon (AC) filter outlet) in different combustion temperatures during a planned cold (long) start-up and an unplanned warm (short) start-up. The results showed that PCDD/F concentrations could be elevated during the start-up periods up to levels 3-4 times higher than those observed in the normal operation. Especially lower combustion temperatures in the short start-ups may cause high PCDD/F concentrations in the raw flue gas. Assessment of combustion temperatures and Furans/Dioxins values indicated that surface-catalyzed de novo synthesis was the dominant pathway in the formation of PCDD/Fs in the combustion units. PCDD/F removal efficiencies of Air Pollution Control Devices suggested that formation by de novo synthesis existed in ESP also when in operation, leading to increase of gaseous phase PCDD/Fs in ESP. Particle-bound PCDD/Fs were removed mainly by ESP and WS, while gaseous phase PCDD/Fs were removed by WS, and more efficiently by AC filter.Implications: This paper evaluates PCDD/F emissions and removal performances of APCDs (ESP, wet scrubbers, and activated carbon) during two start-up periods in an incinerator. The main implications are the following: (1) start-up periods increase PCDD/F emissions up to 2-3 times in the incinerator; (2) low combustion temperatures in start-ups cause high PCDD/F emissions in raw gas; (3) formation of PCDD/Fs by de novo synthesis occurs in ESP; (4) AC is efficient in removing gaseous PCDD/Fs, but may increase particle-bound ones; and (5) scrubbers remove both gaseous and particle-bound PCDD/Fs efficiently.

An Evaluation of PCDD/Fs Mass Flux from a Hazardous Waste Incinerator: The Need for a Reasonable Start-Up Procedure

“…Results showed that PCDD/Fs are removed primarily by wet scrubbers and ESP, while PCDD/F removal rate of the scrubbers is slightly higher than that of ESP. Higher removal efficiency of the Downloaded by [New York University] wet scrubbers (which was confirmed by the flue gas measurements made at the inlet and outlet of the scrubbers during the start-ups in Karademir and Korucu (2013)) could be explained by the removal of some gaseous fraction in the lime scrubber, in addition to the removal of particulate fraction in the scrubbers. On the other hand, PCDD/F analyses in the flue gas through APCE during the start-ups indicated that some PCDD/F formation may occur in ESP (possibly by de novo synthesis), leading to an increase in the gaseous fraction of PCDD/Fs through ESP.…”

“…Since Startup-1 was a long start-up performed in a period of 136 h, residence time of the flue gas in the temperature window of PCDD/F formation by de novo synthesis (i.e., about 400-250 • C) in the cooling zone (including boiler) should be higher in Startup-1, which may lead to higher formation rates of PCDD/F by catalytically heterogeneous synthesis on fly ash surfaces in the boiler and ESP (Eduljee and Cains, 1996;Lu et al, 2007). High furan/dioxin (F/D) ratios observed both in the boiler fly ash (about 2.5) and in the flue gas leaving the boiler (especially in the particle-bound phase, which is about 4.5, given in Karademir and Korucu (2013)) support the heterogeneous de novo synthesis assumption (Chi et al, 2005;Wang et al, 2007).…”

Emissions of polychlorinated diphenyl ethers from a municipal solid waste incinerator during the start-up operation

“…PCDD/Fs are generally formed due to incomplete combustion at the related emission sources [23][24][25][26][27]. Several recent studies have focused on the high PCDD/F emissions during the start-up of MSWIs [28][29][30][31][32][33][34][35][36]. These elevated PCDD/F concentrations remain at high levels even 18 h after the injection of activated carbon (AC) during the start-up process [37].…”

Reduction of Persistent Organic Pollutant Emissions during Incinerator Start-up by Using Crude Waste Cooking Oil as an Alternative Fuel

“…Start-up procedures have been shown to be significant and important periods in terms of PCDD/F emissions during incinerator operations (Tejima et al, 2007;Wang et al, 2007;Karademir and Korucu, 2013;Lin et al, 2014). According to Wang et al (2007) and Karademir and Korucu (2013), the PCDD/F emissions during start-up procedures could be 2-4 times higher than those of the whole year normal operations (Cheruiyot et al, 2016).…”

“…According to Wang et al (2007) and Karademir and Korucu (2013), the PCDD/F emissions during start-up procedures could be 2-4 times higher than those of the whole year normal operations (Cheruiyot et al, 2016). The elevated PCDD/F emissions during start-up procedures of incinerators have been attributed to incomplete combustion of diesel and feeding wastes, state of cleaning of boiler section as well as furnace temperature passing through PCDD/F formation window inevitably (Wang et al, 2007).…”