An Analysis of Extinction Coefficients of Particles and Water Moisture in the Stack after Flue Gas Desulfurization at a Coal-Fired Power Plant

Figures & data

Figure 1. Schematic diagram of the coal-fired power plant used in experiments.

Table 1. Basic information on the power plant

Parameter	Basic Information
Analysis of coal
Coal type	Subbituminous
Total moisture (as received)	8.89%
Inherent moisture (air-dried basis)	2.01%
Sulfur content (air-dried basis)	0.88%
Volatile matter (air-dried basis)	31.3%
Ash (air-dried basis)	15.2%
Heating value (air-dried basis)	1570 kJ/kg
Boiler conditions
Boiler type	Four radiative burner units
Coal flow	∼1.45–1.72 kg/sec
Main steam pressure	∼119–120 kg/cm^2
Main steam flow	∼11.8–13.4 kg/sec
Air pollution control equipment	Low-NOx burner (LNB)
	ESP
	FGD
Stack parameters
Stack height	70 m
Stack diameter	2.4 m

Table 2. Summary of flue gas and particle characteristics

Stack Flue Gas Conditions	Test Data Range
SOx	∼20–36 ppm
NOx	∼150–186 ppm
NO2	∼4.7–5.7 ppm
O2 (at sampling hole of stack)	∼9.3–12.1%
(leaving the G/A heater)	∼3.5–3.8%
Flow rate	∼20.3–23.8Nm^3/sec
Exhaust temperature	48.1∼51.1°C
Water content	∼9.25–12.13%
Particle density	2.66 ± 0.09 g/cm^3
Mass mean diameter	4.00 ± 1.03 μm
Unburned carbon	6.68% ± 1.10%
Ash analysis of oxides
SiO2	46.89% ± 0.53%
Al2O3	42.71% ± 0.26%
Iron(III) oxide (Fe2O3)	3.27% ± 0.34%
Calcium oxide (CaO)	3.33% ± 0.26%
Titanium dioxide (TiO2)	1.59% ± 0.02%
SO3	0.50% ± 0.03%
Potassium oxide (K2O)	0.35% ± 0.00%
Sodium oxide (Na2O)	0.14% ± 0.01%
MgO	0.32% ± 0.03%
Other	0.91% ± 1.23%

Figure 2. Mass and cumulative distributions of emitted particles at various boiler loads.

Figure 3. SEM micrograph of particles collected by filter.

Table 3a. Data obtained by regulating ESP currents for various particle concentrations

Range	∼100–200 mA (current)
Load	− → +
Particle concentration W p (mg/Nm^3)	110 ± 6	90.8 ± 5.5	79.1 ± 9.0	70.3 ± 8.5	59.2 ± 5.5
Water content W w (g/N m^3)	90.2 ± 0.5	92.8 ± 1.1	91.7 ± 1.0	91.1 ± 0.7	90.0 ± 1.8
NO2 emission (ppm)	5.6 ± 0.1	5.1 ± 0.2	5.4 ± 0.2	5.3 ± 0.3	4.7 ± 0.1
Flue gas temperature (°C)	50.5 ± 0.4	51.1 ± 0.3	50.3 ± 0.6	49.9 ± 0.4	50.9 ± 0.6
Water content X w (%)	11.2 ± 0.1	11.6 ± 0.1	11.4 ± 0.1	11.3 ± 0.1	11.2 ± 0.2
Saturated vapor content X tw (%)	12.7 ± 0.1	13.1 ± 0.3	13.0 ± 0.2	12.3 ± 0.3	13.3 ± 0.2
RH (%)	88.4 ± 0.4	88.1 ± 2.9	88.1 ± 0.5	92.4 ± 2.5	84.3 ± 2.6
Measured opacity (%)	25.7 ± 0.6	24.7 ± 0.4	23.7 ± 0.3	22.7 ± 0.5	20.9 ± 0.6
Theoretical opacity (%)	26.0	24.8	23.7	22.8	21.7
Extinction by particles (%)	40.2	35.1	32.2	29.8	26.7
Extinction by water moisture (%)	56.9	62.1	64.7	66.9	70.2
Extinction by NO2 emission (%)	2.9	2.8	3.1	3.3	3.1

Table 3b. Data obtained by adjusting the FGD unit's precooling and circulating water rate

Range	∼0.27–0.40 m^3/sec (circulating water)
Load	− → +
Particle concentration W p (mg/N m^3)	83.4 ± 8.1	74.2 ± 9.0	70.1 ± 8.9	59.2 ± 5.5	37.8 ± 1.9
Water content W w (g/N m^3)	74.4 ± 1.8	80.3 ± 1.6	81.5 ± 1.7	90.0 ± 1.8	97.5 ± 0.3
NO2 emission (ppm)	4.8 ± 0.1	4.6 ± 0.2	5.3 ± 0.1	4.7 ± 0.1	5.1 ± 0.2
Flue gas temperature (°C)	50.3 ± 0.5	50.1 ± 0.4	49.1 ± 0.5	50.9 ± 0.6	50.4 ± 0.4
Water content X w (%)	9.3 ± 0.2	10.0 ± 0.2	10.2 ± 0.2	11.2 ± 0.2	12.1 ± 0.1
Saturated vapor content X tw (%)	13.4 ± 0.2	12.6 ± 0.4	11.9 ± 0.4	13.3 ± 0.2	13.2 ± 0.5
RH (%)	69.0 ± 2.5	79.6 ± 4.0	85.0 ± 0.7	84.3 ± 2.6	92.3 ± 3.7
Measured opacity (%)	21.5 ± 0.1	21.0 ± 0.4	21.0 ± 0.3	20.9 ± 0.6	21.7 ± 0.7
Theoretical opacity (%)	21.3	21.5	21.4	21.7	21.0
Extinction by particles (%)	38.1	33.8	32.0	26.7	17.7
Extinction by water moisture (%)	58.8	63.2	64.5	70.2	78.9
Extinction by NO2 emission (%)	3.1	3.0	3.5	3.1	3.4

Table 3c. Data obtained by varying the operation condition of the boiler load

Range	∼11.78–13.44 kg/sec (main steam flow)
Load	− → +
Particle concentration W p (mg/Nm^3)	45.5 ± 1.9	59.2 ± 5.5	66.1 ± 1.9	78.7 ± 2.8	96.6 ± 1.7
Water content W w (g/Nm^3)	87.7 ± 0.6	90.0 ± 1.8	94.8 ± 2.6	91.6 ± 1.5	89.6 ± 0.3
NO2 emission (ppm)	5.0 ± 0.4	4.7 ± 0.1	5.0 ± 0.4	5.3 ± 0.2	5.7 ± 0.1
Flue gas temperature (°C)	48.1 ± 0.4	50.9 ± 0.6	49.3 ± 0.2	50.3 ± 0.6	49.3 ± 0.4
Water content X w (%)	10.9 ± 0.1	11.2 ± 0.2	11.8 ± 0.3	11.4 ± 0.2	11.2 ± 0.1
Saturated vapor content X tw (%)	11.1 ± 0.1	13.3 ± 0.2	12.0 ± 0.1	11.9 ± 0.5	11.6 ± 0.2
RH (%)	98.7 ± 1.2	84.3 ± 2.6	98.2 ± 2.6	95.6 ± 4.0	96.1 ± 0.9
Measured opacity (%)	19.8 ± 0.3	20.9 ± 0.6	22.7 ± 0.3	24.6 ± 0.7	25.6 ± 0.3
Theoretical opacity (%)	20.2	21.7	23.0	23.6	24.9
Extinction by particles (%)	22.3	26.7	27.9	32.1	37.2
Extinction by water moisture (%)	74.2	70.2	69.1	64.8	59.7
Extinction by NO2 emission (%)	3.5	3.1	3.0	3.1	3.1

Table 4. Results of K _p , K _w , k _p, and k _w, estimated from measurements

Parameter	ESP Operation	FGD Operation	Boiler Operation
K p (cm^3/m^2)	1.522	1.890	1.191
Mean K p (cm^3/m^2)		1.642
k p (m^2/g)	0.247	0.199	0.316
Mean k p (m^2/g)		0.229
K w (cm^3/m^2)	2596.1	2346.7	2896.0
Mean K w (cm^3/m^2)		2520.2
k w (m^2/g)	0.000385	0.000426	0.000345
Mean k w (m^2/g)		0.000397
Notes: ρp= 2.66 g/cm^3, ρw = 1.00 g/cm^3.

Table 5. Calculated values of the theoretical particle parameter K _p for the measured particle size distribution at various absorption indices

Set	Particle Diameter Size Interval (μm)	Mean Particle Radius (μm)	Mass Fraction Interval (%)	Accumulated Weight Fraction (%)	K pi at m = 1.5, n = 0.0043 (cm^3/m^2)	K pi at m = 1.5, n = 0.01 (cm^3/m^2)	K pi at m = 1.5, n = 0.025 (cm^3/m^2)
	>9.3	10.00	5.11	100.0	6.536	6.413	6.401
	6.0–9.3	3.825	4.69	94.89	2.322	2.344	2.358
	4.1–6.0	2.525	10.82	90.20	1.496	1.477	1.506
	2.8–4.1	1.725	15.31	79.38	1.162	1.095	1.053
	1.8–2.8	1.150	33.06	64.07	0.737	0.708	0.685
1	1.0–1.8	0.700	16.73	31.01	0.527	0.493	0.461
	0.49–1.0	0.373	9.18	14.28	0.115	0.118	0.123
	0.36–0.49	0.213	3.47	5.10	0.119	0.118	0.117
	0.056–0.36	0.104	1.63	1.63	0.410	0.333	0.298
	K p (cm^3/m^2)				1.284	1.252	1.233
	k p (m^2/g)				0.293	0.300	0.305
	>11.0	10.00	10.97	100.0	6.441	6.413	6.401
	7.1–11.0	4.525	3.95	89.03	2.901	2.868	2.829
	4.8–7.1	2.975	8.55	85.08	1.862	1.848	1.827
	3.3–4.8	2.025	14.69	76.53	1.102	1.126	1.165
	2.2–3.3	1.375	29.61	61.84	0.808	0.800	0.794
2	1.1–2.2	0.825	17.54	32.23	0.456	0.454	0.450
	0.59–1.1	0.423	11.18	14.69	0.149	0.150	0.155
	0.44–0.59	0.258	2.19	3.51	0.102	0.103	0.105
	0.056–0.44	0.124	1.32	1.32	0.252	0.243	0.224
	K p (cm^3/m^2)				1.624	1.623	1.629
	k p (m^2/g)				0.231	0.232	0.231
	>9.9	10.00	3.29	99.99	6.447	6.413	6.401
	6.4–9.9	4.075	6.85	96.71	2.568	2.554	2.533
	4.3–6.4	2.675	10.68	89.85	1.559	1.571	1.598
	3.0–4.3	1.825	30.68	79.17	1.172	1.152	1.118
	1.9–3.0	1.225	14.52	48.49	0.810	0.795	0.762
3	1.0–1.9	0.725	14.52	33.97	0.486	0.474	0.452
	0.53–1.0	0.383	12.33	19.45	0.119	0.121	0.127
	0.39–0.53	0.230	3.56	7.12	0.107	0.107	0.108
	0.056–0.39	0.112	3.56	3.56	0.304	0.293	0.265
	K p (cm^3/m^2)				1.095	1.089	1.081
	k p (m^2/g)				0.343	0.345	0.348
Mean	K p (cm^3/m^2)				1.334	1.321	1.314
Mean	k p (1/(ρp K p), m^2/g)				0.282	0.285	0.286

Figure 4. Theoretical parameter K _p as a function of particle size for fly ash at various values of absorption index and a light wavelength of 550 nm.

Table 6. Comparison of measured K _p values with previously reported values from experiments on coal-fired boilers

Source	Apparatus	Light Path (m)	Parameter k p (m^2/g)	Density ρp (g/cm^3)	Parameter K p (cm^3/m^2)	Reference
Coal power plant (fly ash)	Transmissometer	4.80	0.228	2.66	1.642	This study
Coal power plant (fly ash)	Transmissometer	6.15	∼1.11–1.56	1.00	∼0.683–0.905	9
Coal power plant (fly ash)	Bolometer	1.14	0.78	2.00	0.64	8
Kraft mill recovery furnace	Bolometer	1.52	1.70	1.00	0.60	5
Kraft mill recovery furnace	Smoke meter	0.92	∼0.33–0.50	2.50	∼0.80–1.20	6

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