GB1091582A - Demineralization of liquid solutions - Google Patents

Abstract

1,091,582. Desalination of water or other liquid solutions. A. OSDOR. Feb. 9, 1965 [Feb. 10, 1964], No. 5607/65. Heading BIB. In a process for the desalination of water or other liquid solution, wherein the solution, under critical pressure, is heated to the vicinity of the critical temperature for phase separation by direct contact with a gas and then with a second fluid (e.g. paraffin, the fluids are themselves heated, after being increased in pressure, by direct heat exchange with the separated vapour of the demineralized fraction which has also been increased in pressure, and the excess work generated in lowering the pressure of the hot gas over that expended in raising the pressure of the gas when cold to the high pressure is used to mechanically pump or compress the fluids used in the process. Saline water is drawn from R1, through a hydraulic system S-D, which boosts the pressure to about 225 Kg/cm<SP>2</SP>, to a closed reservoir R 2 , and then to a heat exchanger H1. In heat exchanger H1 the water is heated by up-flowing nitrogen and it leaves through line 8 at a temperature less than the critical temperature. It passes through Cl where its pressure is boosted to 226 Kg/cm<SP>2</SP> and then is introduced into exchanger H2 where it is heated to above the critical temperature (374‹C) but below the saturation temperature (428‹C) by downflowing paraffin or other hydrocarbon. The first step of the phase separation takes place in H2 and the second step in tank S1 where washing and filtering of the vapours takes place and the vapours are heated to above saturation temperature by downflowing paraffin. From line 14 the water vapour passes into hydraulic pressure exchanging device A2-B2 where its pressure is boosted to 245 Kg/cm<SP>2</SP> and its temperature to 446‹C and from there through line 16 to heater Fl, temperature now 460‹C, and on to heat exchanger H3 where it heats the paraffin and leaves as condensed water at 270-370‹C at a pressure of 245 Kg/cm<SP>2</SP>. The condensed and desalinated water passes through pressure exchange device A3-B3, exits at 22 at a pressure of 255 Kg/cm<SP>2</SP>, and is introduced to heat exchanger H4, where it heats up-flowing nitrogen, leaving through line 24 for reservoir R3 at a pressure of 255 Kg/cm<SP>2</SP> and at about 37‹C. The desalinated water from reservoir R3 is drawn through system S-D where the nitrogen dissolved in the desalinated water is recovered and the high pressure is used to boost the raw saline water entering from R1 at atmospheric pressure to 225 Kg/cm<SP>2</SP>. The nitrogen cycle The hot nitrogen heats cold saline water in exchanger Hl and cold nitrogen is heated by hot desalinated water in exchanger H4. The hot nitrogen leaving H4 through line 32 at a pressure of 255 Kg/cm<SP>2</SP> takes four paths; (1) it passes into pressure exchanger A4-B4, where its high pressure is used to boost the low pressure nitrogen entering through line 28 from tank R2, before passing through line 38 to heat exchanger H1 (2) it passes into pressure exchanger A3-B3, where it boosts the pressure of the desalinated water from 245 Kg/cm<SP>2</SP> to 255 Kg/cm<SP>2</SP>, before passing to turbine T1, where it produces a mechanical output, and on into line 38 to exchanger H1 (3) it passes directly to turbine T2 and then on into line 38, (4) it passes directly to turbine T3 and ten on into line 38. The nitrogen recovered in S-D from the desalinated water is fed at a pressure of 225 Kg/cm<SP>2</SP> into line 28 leaving R2. The paraffin cycle Paraffin heats saline water in exchanger H2 and is heated by desalinated hot water in exchanger H3. The paraffin leaves exchanger H2 through two lines 60 and 62 at a temperature of 400-450‹C and at a pressure of 226 Kg/cm<SP>2</SP>, the paraffin in both lines 60 and 62 being boosted in exchangers A5-B5 and A6- B6 by higher pressure paraffin leaving exchanger H3, before entering H3. Some of the paraffin leaves H3 through line 84 and is used in A7-B7 to boost the pressure of the paraffin leaving S1 before itself, now at 226 Kg/cm<SP>2</SP>, passing to Sl. Concentrated brine withdrawal Brine and crystallized salt are withdrawn from H2 and fed into exchanger H5 where they are mixed with steam entering through line 102. The water in the brine vapourizes, passes through compressor C2, part being returned to exchanger H2 and part to exchanger H5. The salts settle out and are removed through line 106 to reservoir R5. For pressure exchange devices see Division F1.