Chemistry Reference
In-Depth Information
nominal design should include a bypass of the hot stream (dashed line in Figure 11.8,
right), which can be used for control objectives.
Process simulations that include experimental results were performed using Aspen
Plus [47]. The RA column was simulated using the rigorous RADFRAC unit with the
RateSep (rate-based) model, and considering three phase balances. The physical
properties required for the simulation and the binary interaction parameters for the
methanol-water and acid-ester pairs were available in the Aspen Plus database of pure
components [47]. The fatty components were conveniently lumped into one fatty acid
and its fatty ester, according to the reaction: R-COOH
R-COO-CH
3
þ
H
2
O. Dodecanoic (lauric) acid/ester was selected as the lumped component due to the
availability of experimental results, kinetics and vapor-liquid-liquid equilibrium
(VLLE) parameters for this system [4,5,7,9,18].
Table 11.1 shows the complete mass balance of the process, while Table 11.2 lists the
main design parameters, such as column size, catalyst loading and feed condition [9]. The
composition, temperature and rate profiles are plotted in Figure 11.9 [9].
High conversion of the reactants is achieved, with the productivity of the RA unit exceeding
19 kg fatty ester/kg catalyst/hour. The purity specification is higher than 99.9%wt for the final
biodiesel product (FAME stream). Note that the total of the optional recycle streams (REC-
BTM) is not significant, representing less than 0.9% of the total biodiesel production rate.
þ
CH
3
OH
$
Table 11.1 Mass balance of a 10 ktpy FAME process based on integrated RA. Reprinted from
Kiss and Bildea
#
2011, with permission from Elsevier.
F-ACID F-ALCO BTM
REC-BTM REC-TOP
TOP
WATER
FAME
Temperature (
C)
160
65.4
136.2
146.2
51.8
162.1
51.8
30
Pressure (bar)
1.05
1.05
1.03
1.216
1
1
1
0.203
Vapour fraction
0
1
0
1
0
1
0
0
Mole flow
(kmol/hour)
5.824
5.876
6.125
0.252
0.059
5.886
5.828
5.873
Mass flow
(kg/hour)
1166.7
188.3
1261.3
11.3
9.369
114.4
105.06
1250
Mass flow
(kg/ hour)
Methanol
0
188.3
9.125
7.544
0.002
0.103
0.101
1.581
Acid
116.74
0
Trace
Trace
9.218
9.233
0.016
Trace
Water
0
0
Trace
Trace
0.24
105.2
104.93
Trace
Fame
0
0
1252.2
3.764
0.846
0.846
Trace
1248.4
Mass fraction
Methanol
0
1
0.007
0.667
172 ppm 894 ppm 965 ppm 0.001
Acid
1
0
Trace
Trace
0.894
0.08
148 ppm Trace
Water
0
0
Trace
10 ppb
0.023
0.912
0.999
Trace
Fame
0
0
0.993
0.333
0.082
0.007
513 ppb
0.999
Mole fraction
Methanol
0
1
0.046
0.931
873 ppm 546 ppm 0.001
0.008
Acid
1
0
Trace
Trace
0.726
0.008
13 ppm
Trace
Water
0
0
Trace
26 ppb
0.211
0.992
0.999
Trace
Fame
0
0
0.954
0.069
0.062
670 ppm 43 ppb
0.992
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