Influence of Sorbent Characteristics on Fouling and Deposition in Circulating Fluid Bed Boilers Firing High Sulfur Indian Lignite

Table 1

Proximate, ultimate, chemical composition of ash, ash fusion temperatures, and ash deposition indices of high sulfur lignite.

Sample ID	Sample 1; Lignite Giral	Sample 2; Lignite Giral	Sample 3; Lignite Giral	Sample 4; Lignite Giral	Sample 5; Lignite Giral	Sample 6; Standpipe blockage Giral
Proximate analysis (wt % on air dried basis)
Moisture	11.8	10.0	29.6	29.1	15.0	9.6
Volatile matter	37.5	29.5	27.8	28.4	33.7	37.8
Ash	18.6	34.5	15.6	13.9	18.7	26.8
Fixed carbon	32.1	26.0	27.0	28.6	32.6	25.8
Gross calorific value Cal/g	4865	3445	3645	4059	4720	4030
Ultimate (wt % on air dried basis)
Carbon	51.6	38.5	35.3	39.5	49.1	41.0
Hydrogen	3.8	2.5	2.6	2.6	3.3	4.0
Nitrogen	0.6	0.6	0.9	0.8	0.7	0.6
Sulfur	6.94	5.5	4.1	4.7	6.70	4.0
Chemical composition of ash (wt %)
SiO2	25.9	39.2	41.0	36.2	25.1	34.1
Al2O3	12.6	27.5	22.0	17.7	14.2	14.8
Fe2O3	28.8	16.5	21.4	25.7	26.4	11.9
TiO2	1.3	2.1	2.3	2.4	1.5	1.6
CaO	8.3	4.2	3.7	5.1	6.6	3.3
MgO	3.3	2.1	2.2	2.2	3.1	1.3
Na2O	7.2	1.4	1.7	2.8	8.3	4.1
K2O	0.3	0.6	0.4	0.4	0.3	0.2
SO3	11.0	6.2	5.7	7.2	13.7	28.7
Ash fusion temperatures °C (oxidizing atmosphere)
Temperatures	1	2	3	4	5	6
Deformation T1	>1152	1267	1275	1311	>1152	1244
Softening T2	>1214	1290	1300	1321	>1214	1260
Hemisphere T3	>1230	1307	1333	1364	>1230	>1300
Fusion T4	>1250	1377	1360	1385	>1250	>1300
Ash deposition indices
Si ratio	39.06	63.22	60.02	52.31	41.01	67.4
Base/acid	1.20	0.36	0.45	0.64	1.78	0.41
Iron index	34.56	5.93	9.63	16.45	47.0	4.9
Fe/Ca	3.47	3.93	5.78	5.04	4.0	3.6
Fe + Ca	37.1	20.7	25.1	30.8	33.0	15.2