6
lems in processing machines (for example, in conveyers and grinders), boilers, and
decreases the digestibility of rice straw when used as fodder. Rice straw is also
characterized by a high volatile matter as compared to wood and coal; and a lower
fixed carbon compared than that in coal. The high ash content in rice straw decreases
its calorific value and causes problems in energy conversion. A high potassium and
alkali content in ash may increase corrosion and fouling problems in grates, since
alkali metals are known triggers for these phenomena. Table 1.3 shows the ash analysis of rice straw.
Fig. 1.3 Van Krevelen diagram for various solid fuels. Source: Adapted from Mando (2013)
Table 1.2 Rice straw ash properties
SiO 2
Al 2 O 3 TiO 2 Fe 2 O 3 CaO
MgO
Na 2 O K 2 O 3
SO 3
P 2 O 5
Sources
% of ash
(d.b)
75.00
1.40
0.02
2.00
1.50
1.90
1.90
10.00
0.90
2.70 Liu, et al.
(2011)
74.67
1.04
0.09
0.85
3.01
1.75
0.96
12.30
1.24
1.41 Jeng, et al.
(2012)
82.60
1.10
0.60
1.00
3.30
1.70
0.30
6.30
0.90
1.70 Guillemot
(2014)
67.78
1.54
2.08
1.11
1.48
11.87
Migo (2019)
Range
67.78
1.04
0.02
0.85
2.08
1.11
0.30
6.30
0.90
1.41
−82.60 −1.54 −0.6 −2.00 −3.01 −1.90 −1.90 −12.30 −1.24 −2.70
N. V. Hung et al.