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Table 1 Membrane characteristics taken from the producers’ factsheets, testing conditions of the membrane according to the fact sheets (n.s.) for not specified and the calculated Reynolds numbers according to the flow-through velocity for each membrane

From: Investigation of spiral-wound membrane modules for the cross-flow nanofiltration of fermentation broth obtained from a pilot plant fermentation reactor for the continuous production of lactic acid

Membrane DK73 DL73 NP30 NF45 NF90 TW30 SW30
NMWCO (g/mol) 150–300 ns 200 ns ns ns
Minimum pH (–) ns ns 0 3 2 2 2
Maximum pH (–) ns ns 14 10 11 11 11
Maximum temperature (°C) 50 50 95 45 40 45 45
Maximum pressure (bar) 41.4 41.5 40 41 41 41 69
Active area (m2) 1.6 1.7 1.8 2.6 2.6 2.6 2.8
Feed spacer thickness (mm) 1.27 1.27 1.1 ns ns 0.7 ns
Permeate flow rate (m3/d) 1.3 1.7 1.728 3.5 2.3 3.2 2.6
Salt rejection (%) 98 96 80–95 98 90 99.5 99.4
Substance (–) MgSO4 MgSO4 Na2SO4 MgSO4 MgSO4 NaCl NaCl
Concentration (ppm) 2.000 2.000 ns 2.000 2.000 2.000 32.000
Temperature (°C) 25 25 20 25 25 25 25
Duration (h) 24 24 ns ns ns ns ns
Variation (± X %) 25 25 ns ns ns ns ns
Recovery (%) 15 15 ns 15 15 15 8
Pressure (bar) 7.6 7.6 40 8.9 5 15.5 55
Permeate flux (m3/d) 1.3 1.7 1.728 3.5 2.3 3.2 2.6
Membrane width (m) 1.57 1.67 1.77 2.56 2.56 2.56 2.76
Feed spacer thickness (mm) 1.27 1.27 1.1 0.9 0.9 0.7 0.9
(m) 0.001 0.001 0.001 0.001 0.001 0.001 0.001
Feed spacer area (m2) 0.002 0.002 0.002 0.002 0.002 0.002 0.002
Circular area diameter (m) 0.050 0.052 0.050 0.054 0.054 0.048 0.056
Flow velocity (m/s) 0.042 0.039 0.043 0.036 0.036 0.047 0.034
Reynolds number (–) 2624 2546 2659 2445 2445 2773 2357
Friction losses (–) 0.046 0.047 0.046 0.047 0.047 0.045 0.048
B (–) 0.939 0.920 0.9472 0.896 0.896 0.974 0.874