Agriculture Reference
In-Depth Information
Results of SEM analysis are given in Table 21. SEM scan is shown in Figure 13. Flue gas
analyses of the natural gas-raffinate co-combustion are given in Table 22. The table shows
that the introduction of raffinate decreased O
2
level showing that raffinate was burning.
However change in O
2
concentration was very low indicating that combustible matter in
raffinate introduced was very low as compared to total fuel flow. Also emissions of CO show
that raffinate results in incomplete combustion. Presence of hydrogen in the combustion
products after raffinate introduction indicates the possibility of occurring water gas shift
reaction.
Table 21. SEM results of Raffinate-Natural gas Combustion test
Site of i
n
terest 1
Site of i
n
terest 2
Weight (%)
Atomic (%)
Weight (%)
Atomic (%)
O
51.44
65.84
50.22
64.2
F
-0.08
-0.09
-
-
Na
4.48
3.99
3.7
3.29
Mg
-
-
0.19
0.16
Al
1.23
0.94
0.85
0.64
Si
35.32
25.75
39.57
28.81
P
-
-
0.23
0.15
K
4.6
2.41
4.86
2.54
Ca
0.42
0.21
0.38
0.19
Fe
2.59
0.95
-
-
NO
x
emissions after the introduction of raffinate rose considerably, unlike in the case of
coal-raffinate test where they were almost same before and after raffinate introduction. This is
possibly due to lower nitrogen content of natural gas which resulted in lower NO
x
emissions
before raffinate introduction. The NO
x
emissions increased after raffinate introduction due to
the fuel bound nitrogen as raffinate contains about 1.6% nitrogen in it. Presence of NO
2
is
also evidenced in the flue gas after the introduction of raffinate. The balance between NO and
NO
2
depends upon the nature of the nitrogen compounds present in the fuel and operating
conditions. Increase in CO and NO
x
emissions could be due to lack of temperature
homogeneity caused by poor mixing and improper combustion which led to de-fluidization.
5.3. Co-Firing of Vinasse with Coal
Vinasse has relatively lower Na and K content as compared to raffinate. After achieving a
bed temperature of 600 °C, coal feed was started and subsequently after few minutes the gas
burner was turned off. Finally, after the bed temperature stabilised, vinasse feed was started.
The experimental conditions are given in Table 23.
It was observed that vinasse behaved similar to raffinate, despite its low alkali content.
Bed slumped within 37 minutes of the start of vinasse feeding. Temperature and pressure
variations as a function of time are plotted in Figure 14. Sudden changes in bed and freeboard
temperatures and bed pressure were observed and this was thought to be the onset of
agglomeration process. At this stage both coal and vinasse feeds were stopped. However,
there were some abnormal parameters observed.
