Chemistry Reference
In-Depth Information
Table 11.3 Comparison of integrated RA and RD processes (at a production rate of
1250 kg/ hour fatty esters). Reprinted from Kiss and Bildea
#
2011, with permission from
Elsevier.
Equipment/parameter/units
RD
HI-RD
RA
HI-RA
Reactive column - reboiler duty (heater), kW
136
136
n/a
n/a
HEX-1 heat duty (fatty acid heater), kW
95
0
108
27
HEX-2 heat duty (methanol heater), kW
8
0
65
0
Reactive column - condenser duty (cooler), kW
72
72
n/a
n/a
HEX-3 water cooler/decanter, kW
6
6
77
0
COOLER heat duty (biodiesel cooler), kW
141
38
78
14
FLASH heat duty (methanol recovery), kW
0
0
0
0
Compressor power (electricity), kW
0.6
0.6
0.6
0.6
Reactive column, number of reactive stages
10
10
10
10
Feed stage number, for acid/alcohol streams
3/10
3/10
1/15
1/15
Reactive column diameter, m
0.4
0.4
0.4
0.4
Reflux ratio (mass ratio R/D), kg/kg
0.10
0.10
n/a
n/a
Boil-up ratio (mass ratio V/B), kg/kg
0.12
0.12
n/a
n/a
Productivity, kg ester/kg catalyst/hour
20.4
20.4
19.2
19.2
Energy requirements per ton biodiesel,
kW/hour/ton FAME
191.2
108.8
138.4
21.6
Steam consumption, kg steam/ton FAME
295
168
214
34
product purity [9,18]. However, the integrated biodiesel processes based on RA have fewer
degrees of freedom as compared to RD. This makes it challenging to correctly set the
reactant feed ratio and consequently avoid impurities in the products. Kiss and Bildea [9]
proposed an efficient plantwide control structure that can ensure the stoichiometric ratio of
reactants and which fulfils the excess-of-methanol operating constraint, sufficient for the
total conversion of the fatty acids.
Figure 11.10 depicts the dynamic simulation results for the flow sheet presented in
Figure 11.8 (right) for the recycle of methanol vapours [9]. Production rate changes are easily
achieved and the product purity is maintained at high values, with the acid concentration
in FAME below the 2000 ppm requirement of the ASTM D6751-08 standard.
Figure 11.10 Dynamic simulation results for the flow sheet with methanol recycling: acid
flow rate disturbance of รพ10% at 1 hour and10% at 5 hours. Reprinted from Kiss and Bildea
#
2011, with permission from Elsevier.
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