Raw Material Liquid Flow Dehydration System and Raw Material Liquid Flow Dehydration Method

17:

• The feed solution flow dewatering method according to claim 16, which comprises, before the feed solution flow dewatering step, a forward osmosis membrane water content-lowering step, in which the water content of the forward osmosis membrane is lowered.

18:

• The feed solution flow dewatering method according to claim 17, wherein the forward osmosis membrane water content-lowering step is a step in which the water in the forward osmosis membrane is replaced with the organic solvent in the feed solution flow.

19:

• The feed solution flow dewatering method according to claim 16, wherein the difference SWd−SWr between the saturated water content SWd of the draw solution flow and the saturated water content SWr of the feed solution flow is 1.00 mass % or greater.

20:

• The feed solution flow dewatering method according to claim 19, wherein:
• the saturated water content of the feed solution flow is less than 5.00 mass %, and
• the saturated water content of the draw solution flow is 5.00 mass % or greater.

21:

• The feed solution flow dewatering method according to claim 20, wherein the difference SWd−SWr is 5.00 mass % to 25.0 mass %.

22:

• The feed solution flow dewatering method according to claim 21, wherein the draw solution flow comprises a hydrophilic polymer which is liquid at 25° C.

23:

• The feed solution flow dewatering method according to claim 22, wherein the hydrophilic polymer is one or more selected from the group consisting of polyethylene glycol and polypropylene glycol.

24:

• The feed solution flow dewatering method according to claim 22, wherein the number-average molecular weight of the hydrophilic polymer in terms of polyethylene glycol is 200 to 3,000, as measured by gel permeation chromatography.

25:

• The feed solution flow dewatering method according to claim 22, wherein the draw solution flow comprises the hydrophilic polymer at 50 mass % or greater.

26:

• The feed solution flow dewatering method according to claim 23, wherein the draw solution flow comprises the hydrophilic polymer at 50 mass % or greater.

27:

• The feed solution flow dewatering method according to claim 24, wherein the draw solution flow comprises the hydrophilic polymer at 50 mass % or greater.

28:

• The feed solution flow dewatering method according to claim 16, wherein the organic solvent in the feed solution flow comprises one or more selected from the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether, diisopropyl ether, cyclopentyl methyl ether, t-butyl methyl ether, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, benzene, toluene, o-xylene, m-xylene, p-xylene, acetone, acetonitrile, pentane, hexane, cyclohexane, heptane, methylcyclohexane, isooctane, dichloromethane, chloroform, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide and 1,3-dimethyl-2-imidazolidinone.

29:

• The feed solution flow dewatering method according to claim 22, wherein the organic solvent in the feed solution flow comprises one or more selected from the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether, diisopropyl ether, cyclopentyl methyl ether, t-butyl methyl ether, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, benzene, toluene, o-xylene, m-xylene, p-xylene, acetone, acetonitrile, pentane, hexane, cyclohexane, heptane, methylcyclohexane, isooctane, dichloromethane, chloroform, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide and 1,3-dimethyl-2-imidazolidinone.

30:

• The feed solution flow dewatering method according to claim 16, wherein the feed solution flow comprises a solute.

31:

• The feed solution flow dewatering method according to claim 16, wherein the amount of water in the feed solution flow is 50 mass % or lower with respect to the total mass of the feed solution flow.

32:

• The feed solution flow dewatering method according to claim 16, wherein:
• the forward osmosis membrane is a composite semipermeable membrane comprising a support layer and a separation active layer formed on the support layer, and
• the separation active layer comprises a polyamide.

33:

• The feed solution flow dewatering method according to claim 16, wherein the forward osmosis membrane is in the form of hollow fibers.

34:

• The feed solution flow dewatering method according to claim 16, wherein the pressure at the feed solution flow side of the forward osmosis membrane is higher than the pressure at the draw solution flow side of the forward osmosis membrane, the pressure difference being 5 kPa to 200 kPa.

35:

• The feed solution flow dewatering method according to claim 16, wherein the water content of the forward osmosis membrane is 150 g/m2 or lower.