Table 6. Results of Optimal and Suggested Conditions from Models, Real Tests, and Retention Time for Double-Step Esterificationa.
| condition |
||
|---|---|---|
| optimized | recommended | |
| first step (continuous esterification) | ||
| condition | ||
| methanol (vol %) | 70.2 | 46.4 |
| sulfuric acid (vol %) | 5.5 | 6.6 |
| length of US reactor (mm) | 700 | 400 |
| residence time in US reactor (s) | ≈27 | ≈16 |
| purity of methyl ester purity | ||
| predictive model (wt %) | 89.79 | 60.00 |
| actual experiment (wt %) | 88.89 | 60.24 |
| second step (continuous esterification) | ||
| condition | ||
| methanol (vol %) | 80.0 | 61.6 |
| sulfuric acid (vol %) | 5.2 | 5.6 |
| length of US reactor (mm) | 300 | 400 |
| residence time in US reactor (s) | ≈12 | ≈16 |
| purity of methyl ester purity | ||
| predictive model (wt %) | 93.88 | 93.00 |
| actual experiment (wt %) | 90.91 | 93.32 |
| total | ||
| methanol consumption (vol %) | 150.2 | 108 |
| sulfuric acid consumption (vol %) | 10.7 | 12.2 |
| total length of US reactor (mm) | 1000 | 800 |
| total retention time in US reactor (s) | ≈39 | ≈32 |
| chemical cost | ||
| methanol costb (USD/h) | 12.84 | 9.24 |
| sulfuric acid costc (USD/h) | 0.58 | 0.66 |
| total chemical cost | 14.76 | 10.88 |
| ultrasonic powerd | 6400 (16 × 400W) | 4800 (12 × 400W) |
a
Exchange rate from 1 RMB = 0.15 USD at 10 February 202240
b
The methanol cost referred 1 kg = 0.432 USD41
c
The sulfuric acid cost referred 1 kg = 0.118 USD42
d
The electricity consuming was calculated based on the total units ultrasound clamps under optimal and recommended conditions for whole process.