The emissions from co-firing of biomass and torrefied biomass with coal in a chain-grate steam boiler

Figures & data

Table 1. Sizes of various carbonaceous materials used in this study.

	BC	RS	WD	RST	WDT
Pellet diameter (mm)	1-30	8	12	7.5 ± 0.5	11 ± 0.5
Thickness^a or length^b (cm)	1-3^a	1.5–2.5^b	1.5–3.0^b	1-2^b	1.5–3.0^b

Notes. BC, RS, WD, RS_T, WD_T: Bituminous coal, rice straw, wood, torrefied RS, torrefied WD;

^{a, b}Thickness, length.

Table 2. The amount of fuels used for co-firing in full-scale tests.

Test	Coal (BC): Percent to heat load (kcal %)	Biomass: Percent to heat load (kcal %)	Total heat demand (kcal/hr)	Coal weight (kg)	Biomass weight (kg)
100%BC	100	0	8,250,000	4288	0
2%RS	98	2	8,250,000	4202	125
5%RS	95	5	8,250,000	4074	313
10%RS	90	10	8,250,000	3859	626
2%WD	98	2	8,250,000	4202	107
5%WD	95	5	8,250,000	4074	266
10%WD	90	10	8,250,000	3859	533
15%WD	85	15	8,250,000	3645	799
2%RST	98	2	8,250,000	4202	93
5%RST	95	5	8,250,000	4074	233
10%RST	90	10	8,250,000	3859	466
2%WDT	98	2	8,250,000	4202	90
5%WDT	95	5	8,250,000	4074	224
10%WDT	90	10	8,250,000	3859	448
15%WDT	85	15	8,250,000	3645	672
20%WDT	80	20	8,250,000	3430	896
50%WDT	50	50	8,250,000	2144	2241

Figure 1. Schematic diagram of chain-grate steam boiler system for co-firing process.

Table 3. Measurements of flue gas and instruments.

Item	Measure method	Instrument
Particle size distribution	USEPA M201A	Apex cascade impactor CI-700-K
CO	NIEA A704.04C	HORIBA PG250
CO2	NIEA A415.72A	HORIBA PG250
O2	NIEA A432.73C	HORIBA PG250
SO2	NIEA A413.74A	HORIBA PG250
NOx	NIEA A411.74A	HORIBA PG250
HCl	NIEA A412.73A	Spectrophotometer

Table 4. Proximate analyses of fuels.

Fuel	Moisture^a (%)	Volatile matter^a (%)	Fixed carbon^a (%)	Ash^a (%)	Ash^b (%)
Coal (BC)	30.84 ± 0.07	31.42 ± 0.23	30.5 ± 0.13	7.24 ± 0.17	10.47
RS	10.87 ± 0.03	58.26	18.71	12.16	13.64
WD	6.72 ± 0	77.96 ± 0.41	14.08 ± 0.52	1.24 ± 0.11	1.33
RST	11.84 ± 0.08	50.61 ± 0.02	20.37 ± 0.53	17.18 ± 0.44	19.49
WDT	5.28 ± 0.14	61.41 ± 0.03	16.14 ± 0.3	17.17 ± 0.18	18.13

Notes. ^awt.% on wet basis; b: wt.% on dry basis.

Table 5. Ultimate analyses of fuels.

Fuel	C (%)	H (%)	O (%)	N (%)	S (%)
Coal (BC)	58.769 ± 2.063	4.361 ± 0.198	21.634 ± 0.376	0.812 ± 0.047	0.708 ± 0.066
RS	40.68 ± 0.949	5.95 ± 0.275	38.204 ± 0.453	0.781 ± 0.059	0.685 ± 0.099
WD	48.167 ± 0.095	6.809 ± 0.004	43.246 ± 0.019	0.246 ± 0.037	0.469 ± 0.023
RST	51.196 ± 0.033	4.501 ± 0.187	22.332 ± 0.788	1.017 ± 0.051	0.356 ± 0.238
WDT	51.709 ± 0.123	6.411 ± 0.018	39.257 ± 0.257	0.273 ± 0.002	0.434 ± 0.049

Notes. wt.% on dry basis.

Figure 2. Heating values in dry basis of fuels.

Table 6. Chemical compositions of fuels.

Composition	Coal (BC)	RS	WD	RST	WDT
K (%)	0.0242	1.69	0.23	1.83	0.167
Na (%)	0.00907	0.0397	0.0254	0.0502	0.0375
Ca (%)	0.151	0.552	0.338	0.73	0.333
Mg (%)	0.0776	0.256	0.136	0.312	0.125
Al (%)	0.226	0.0498	0.0118	0.0989	0.00444
Fe (%)	0.632	0.126	0.0223	0.246	0.0117
Ti (%)	0.00928	<0.00025	0.000357	0.000464	<0.00025
Si (%)	0.0204	0.0211	0.00573	0.0104	0.00268
Hg (%)	<0.0000015
Ni (%)	<0.0005
Cl (%)	<0.002	0.359	0.113	0.313	0.195

Notes. wt.% on dry basis.

Table 7. Components of flue gas in full-scale co-firing tests.

Test	NOx (ppmv)	SO2 (ppmv)	CO (ppmv)	CO2 (vol.%)	O2 (vol.%)	HCl (kg/hr)	HCl (ppmv)
Coal (BC)	52.0 ± 1.4	42.1 ± 3.6	228.2 ± 108.3	5.47 ± 0.24	13.67 ± 0.28	0.12	ND<2.85
2%RS	62.3 ± 5.8	37.9 ± 3.2	281.9 ± 132.9	5.48 ± 0.29	14.30 ± 0.36	0.12	3.00
5%RS	41.7 ± 7.3	22.9 ± 4.0	394.4 ± 97.2	3.21 ± 0.56	17.00 ± 0.65	0.25	6.48
10%RS	31.9 ± 15.1	21.7 ± 4.6	652.7 ± 189.7	1.79 ± 0.60	18.55 ± 0.74	0.25	6.35
2%WD	41.9 ± 7.3	27.7 ± 5.2	246.6 ± 142.2	5.11 ± 0.96	15.29 ± 1.00	0.12	ND<2.66
5%WD	48.3 ± 1.4	48.5 ± 5.8	521.6 ± 88.5	6.56 ± 0.25	13.68 ± 0.29	0.12	ND<2.66
15%WD	40.3 ± 2.2	32.7 ± 12.4	676.1 ± 493.6	6.60 ± 0.74	13.72 ± 0.84	0.10	ND<2.61
2%RST	47.3 ± 8.5	6.4 ± 2.1	141.9 ± 61.6	5.36 ± 1.08	15.14 ± 1.26	0.11	ND<2.69
5%RST	42.9 ± 1.5	7.6 ± 1.4	80.6 ± 14.1	4.90 ± 0.34	15.69 ± 0.37	0.11	ND<2.69
10%RST	44.4 ± 3.1	10.7 ± 2.5	163.1 ± 115.7	5.56 ± 0.35	14.91 ± 0.36	0.22	ND<5.36
2%WDT	46.4 ± 2.0	33.9 ± 4.0	429.4 ± 297.3	6.42 ± 0.47	13.91 ± 0.51	0.11	ND<2.69
5%WDT	39.2 ± 2.4	34.1 ± 4.5	532.8 ± 222.5	6.03 ± 0.29	15.02 ± 0.31	0.19	4.84
10%WDT	43.4 ± 1.9	35.8 ± 1.6	231.3 ± 77.4	6.19 ± 0.17	14.87 ± 0.18	0.12	2.94
15%WDT	39.4 ± 2.1	27.1 ± 2.4	238.6 ± 121.2	6.02 ± 0.35	15.04 ± 0.37	0.12	ND<2.72
20%WDT	35.7 ± 3.0	21.4 ± 2.9	227.8 ± 87.9	5.50 ± 0.44	15.62 ± 0.48	0.12	ND<2.72
50%WDT	99.0	97	461	15.00	15.24	0.10	ND<2.59
Emission standard^a	150^b 250^c 350^d	100^b 300^c,d	2000

Notes. ^aEmission standards of stationary sources in Taiwan (TEPA, 2013a);

^bGas fuels

^cLiquid fuels

^dSolid fuels

The volume concentrations of emitted gaseous pollutants were adjusted to the conditions at 273 K and 1 atm with 6% O₂.

Figure 3. Carbon contents in fly and bottom ashes and CO emission of coal and SBF.

Figure 4. Effect of calcium content in fly ash on SO₂ emissions.

Table 8. Particulate matters (PM) concentration (mg/Nm³) and percentiles of PM₁, PM_2.5, and PM₁₀ (wt.%).

Test	PM concentration (mg/Nm^3)	PM1/PM100	PM2.5/PM100	PM10/PM100	PM2.5/PM10	PM1/PM10	PM1/PM2.5
100%BC	0.6105	21.92	34.87	99.10	35.19	22.12	62.87
2%RS	0.6441	53.91	73.89	99.97	73.91	53.93	72.96
5%RS	0.7893	44.36	61.99	99.99	62.00	44.36	71.55
10%RS	0.5707	45.47	65.70	99.92	65.75	45.51	69.21
2%WD	0.6210	57.27	75.36	99.98	75.38	57.28	75.98
5%WD	0.6503	56.43	73.20	99.98	73.22	56.44	77.09
10%WD	0.6091	53.23	73.87	100.00	73.87	53.23	72.05
15%WD	0.6294	53.35	71.68	99.94	71.73	53.38	74.42
2%RST	0.9461	56.94	76.17	100.00	76.17	56.94	74.75
5%RST	0.6253	58.34	76.80	100.00	76.80	58.34	75.96
10%RST	0.6211	56.52	76.31	99.98	76.32	56.53	74.06
2%WDT	0.7803	55.53	74.69	99.99	74.70	55.54	74.35
5%WDT	0.6293	54.12	73.67	100.00	73.70	54.13	73.47
10%WDT	0.6262	55.03	75.12	99.99	75.12	55.04	73.27
15%WDT	0.6117	57.22	75.90	100.00	75.90	57.22	75.39
20%WDT	0.6348	56.25	74.48	99.99	74.48	56.25	75.52
50%WDT	0.4717	59.75	78.35	99.96	78.37	59.78	76.27

Figure 5. Particle size distribution of PM in flue gas in full-scale co-firing tests.

Table 9. Comparison of air pollution standards of gas emissions.

Item	Unit	Taiwan 1 (ST1)^a	Taiwan 2 (ST2)^b	Germany 1 (SG1)^c (Solid coals, 50–100 MW)	Germany 2 (SG2)^c (Solid biomasses, 50–100 MW)
PM	mg/m^3	20-50	50	10	10
CO	ppmv	-	2000	150	150
NOX	ppmv	70-175	350	300	250
SO2	ppmv	60-150	300	400	200
HCl	ppmv	-	80	-	-

Notes. ^aEmission standards of steam and electricity symbiosis equipment boilers in Taiwan (TEPA, 2013b);

^bEmission standards of stationary sources in Taiwan (TEPA 2013a);

^c“13. Bundes-Immissionsschutzgesetz (13. Blmschv)-Die Verordnung über Großfeuerungs- und Gasturbinenanlagen” (Bundesministerium der Justiz und fürVerbraucherschutz, 2018a).

TEPA (Taiwan Environmental Protection Administration). 2013a. Air pollutant emission standards of stationary sources. Accessed June 4, 2019. https://law.moj.gov.tw/LawClass/LawAll.aspx?pcode=O0020006.

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