Ultrafine particle emission from incinerators: The role of the fabric filter

Figures & data

Table 1. Main characteristics of the combustion and flue-gas treatment sections of the analyzed plants

Plant	Furnace and waste characteristics	Flue-gas treatment section description
Plant 1	Grate type: moving grateType of waste fed: refuse-derived fuel (RDF)	Semidry process made up of a SNCR, a spray absorber system (lime milk and powder activated carbons), and a fabric filter
Plant 2	Grate type: moving grateType of waste fed: refuse-derived fuel (RDF)	Dry process made up of a SNCR, a spray absorber system (sodium bicarbonate and powder activated carbons), and a fabric filter
Plant 3	Grate type: roller-type grateType of waste fed: municipal solid waste (MSW)	Wet process (wet scrubber) made up of a fabric filter and a SCR
Plant 4	Grate type: moving grateType of waste fed: municipal solid waste (MSW)	Double-filtration approach: injection of lime milk before the first fabric filter and addition of sodium bicarbonate and activated carbon before the second fabric filter; NOx reduction performed through SCR process
Plant 5	Grate type: fluidized bed reactorType of waste fed: biomass	Wet process (wet scrubber) made up of a wet electrostatic precipitator.

Table 2. Main technical data of the analyzed plants

Plant	Waste Capacity (kg hr^−1)	Average Low Heat Value (MJ kg^−1)	Plant Annual Availability (hr)	Gross Electric Power (MW)	Bottom (Fly) Ashes (kg yr^−1)	Reagent Consumption in Flue-Gas Treatment	ExhaustSpeedat theStack(m s^−1)	AnnualMean NOx Conc. atthe stack(mg m^−3)	AnnualMean SO2 Conc. atthe Stack(mg m^−3)	AnnualMeanDustConc. atthe Stack(mg m^−3)
1	10–12 × 10^3	>15 MJ kg^−1	8000	11.7	14 × 10^6 (5 × 10^6)	Calcium oxide CaO: 1.6 × 10^6 kg yr^−1Powder activated carbons: 80 × 10^3 kg yr^−1Urea: 160 m^3 yr^−1	12	123	7.9	0.3
2	15 × 10^3	18.2 MJ kg^−1	8000	11.5	12 × 10^6 (3.4 × 10^6)	Urea: 270 × 10^3 kg yr^−1Powder activated carbons: 80 × 10^3 kg yr^−1Sodium bicarbonate NaHCO3: 1.6 × 10^6 kg yr^−1	20	170	6	0.9
3	9−10 × 10^3	>12 MJ kg^−1	7800	6.0	17.5 × 10^6 (1.2 × 10^6)	Calcium hydroxide Ca(OH)2: 250 × 10^3 kg yr^−1Sodium hydroxide solution (30%): 160 × 10^3 kg yr^−1Ammonia solution (26%): 100 m^3 yr^−1	14	n.a.	n.a.	n.a.
4	12.5 × 10^3	>12.5 MJ kg^−1	8000	12	25 × 10^6 (7 × 10^6)	Sodium bicarbonate NaHCO3: 330 × 10^3 kg yr^−1Calcium hydroxide Ca(OH)2: 2.2 × 10^6 kg yr^−1Powder activated carbons: 130 × 10^3 kg yr^−1NH3 solution (22%): 220 m^3 yr^−1	12	n.a.	n.a.	n.a.
5	11.6 × 10^3	>10 MJ kg^−1	7500	19.5	3.8 × 10^6 (3.3 × 10^6)	n.a.	12	120	0.5	2.0
Note: n.a. = not available.

Table 3. Details of the experimental analyses of the considered plants

Plant	Measurement Periods	Measurement Points
Plant 1	October 2009	At the stack and before the fabric filter	Total particle number:
		Particle size distribution:
			Thermodilution:
Plant 2	September 2010	At the stack and before the fabric filter	Total particle number:
			Particle size distribution:
			Thermodilution:
Plant 3	February 2010	At the stack	Total particle number:
			Particle size distribution:
			Thermodilution:
Plant 4	September 2010	At the stack	Total particle number:
			Particle size distribution:
			Thermodilution:
Plant 5	May 2009	At the stack	Total particle number:
			Particle size distribution:
			Thermodilution:

Table 4. Operative mean condition and corresponding standard deviation for the main parameters of the analyzed plants

	Plant 1		Plant 2		Plant 3		Plant 4		Plant 5
Parameter	Mean Value	Deviation (%)	Mean Value	Deviation (%)	Mean Value	Deviation (%)	Mean Value	Deviation (%)	Mean Value	Deviation (%)
Normalized flow rate (m^3 h^−1)	98.3 × 10^3	1.7%	75.8 × 10^3	1.2%	120.0 × 10^3	2.6%	100.0 × 10^3	1.6%	150.0 × 10^3	2.1%
Stack temperature (°C)	135	3.0%	154	1.1%	150	3.0%	135	2.4%	40	5.2%
Combustion chamber temperature (°C)	991	1.0%	1209	0.9%	1000	1.0%	980	1.1%	950	3.8%
Relative humidity (%)	15.3	6.5%	14.9	6.7%	15	7.3%	13	8.5%	65%	12.5%
O2 in dry flue gas (%)	10.7	2.8%	8.7	1.1%	13	1.5%	10.5	2.9%	12.2	1.8%
SO2 (mg m^−3)	8.2	14.6%	5.1	15.7%	5	15.6%	0.5	12.0%	0.5	12.0%
NO× (mg m^−3)	115.0	7.5%	174.8	10.6%	50	11.2%	60.3	11.3%	120	10.7%
CO (mg m^−3)	5.2	32.7%	5.5	98.2%	10	27.6%	30.1	29.9%	14	21.3%
Total dust (mg m^−3)	0.68	16.2%	1	0.0%	2	34.5%	0.9	27.8%	2.0	26.3%
HCl (mg m^−3)	4.3	7.0%	6.6	16.7%	<1	—	1.1	27.3%	0.6	15.4%

Figure 1. Statistics of total particle concentrations measured through particle counters at the stack of the analyzed incineration plants: minimum, maximum, median, 1st quartile, 3rd quartile values.

Figure 2. Example of a 10-min total particle number concentration measurement through CPC 3775 at the stack of Plant 2.

Figure 3. Particle number distributions measured through mobility particle sizers in the analyzed incineration plants. The data represent the particle number distributions corresponding to the highest emission periods of the plants.

Figure 4. Particle number distributions measured through SMPS 3936 at the stack and before the fabric filter (labeled “pre-filter”) of Plants 1 and 2.