Based on the principle of a heat pump, MVR systems use electricity and a fan or a turbo-compressor to run the evaporation process. With negligible consumption of steam and cooling water, MVR systems are an economic alternative especially for solutions with low concentration and low boiling point elevation.
Evaporation of water to increase the concentration of biobased intermediate or final products constitutes a standard unit operation in a number of bioprocesses.
Depending on the boiling point elevation of the concentrate as well as the type of evaporator solutions with single-stage or multi-stage compression are selected.
Hereafter, a selection of typical solutions of MVR driven evaporators within the biobased industry.
| Application |
Boiling point elevation (concentrate) [K] |
Number of MVR stages |
Specific electricity demand [kWh / t] |
COP [-] |
Reduction of energy costs |
|
Glucose |
2.3 | 1 | 19 | 33 | 75%*) |
| HFS-55 final concentration |
9.5 | 2 | 34 | 20 | 57%*) |
| Corn stillage pre-concentration |
1.5 | 1 | 19 | 33 | 75%*) |
|
Corn stillage evaporator |
2.5 | 1 + 1 (50%) | 28.5 | 23 | 62%*) |
| Vinasses evaporator | 8 |
1 + 1 (50%) + 1 (25%) |
33 | 19.5 | 56%*) |
| Citric acid pre-concentration | 4 | 1 | 24 | 27 | 68%*) |
|
Citric acid |
10 | 2 | 35 | 18 | 46%*) |
|
Citric acid crystallizer |
16 | 3 | 72 | 9 | 81%**) |
*) Compared to a quadruple evaporator with thermal recompression, steam costs 30€/t, electricity costs 0.08€/kWh
**) Compared to life steam heating, steam costs 30€/t, electricity costs 0.08€/kwH
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