# US 5,700,435 A · Method and apparatus for separating a substance from a liquid mixture by fractional crystallization > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,700,435 A - Document ID: US5700435A - Status: Granted - Kind: A - Application number: 08/566,792 - Filed: 1995-12-04 - Granted: 1997-12-23 - Earliest claimed: 1994-12-08 - Assignees: Sulzer Chemtech AG - Inventors: Rudolf Bischof - Web page: https://patentgrep.com/patent/US5700435A ## CPC - B01D 9/0013: {by indirect heat exchange} - B01D 9/004: {Fractional crystallisation; Fractionating or rectifying columns} - B01D 9/0059: {General arrangements of crystallisation plant, e.g. flow sheets} - B01D 9/0063: {Control or regulation (control per se G05)} - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) ## Abstract The crystalliser (70) has an inlet (77) for the crystal medium to be fractionated and an outlet (84) from which the mother liquor followed by the molten crystals can be withdrawn at the end of the crystallisation process. During the crystallisation process, a number of tubes (75) closed at the top can be supplied from above with a trickling film of liquid mixture. The tubes are internally supplied with a trickling film of a liquid heat exchange medium used for cooling. The liquid heat exchange medium is supplied via a riser (87), and a medium distributor (92) guides the flow of medium heat exchange under the distribution tray (81). The pressure of the evaporating coolant in the medium chamber (80), to which the inner space of the tubes also belongs, is controlled, thus controlling the temperature of the wall of the tubes where crystallisation takes place. In order to melt the crystals, gaseous heat exchange medium is introduced through a spigot (96) into the crystalliser under controlled pressure. The crystalliser can serve selectively as an evaporator or as a condenser in a refrigeration machine, in order to use both cooling energy and waste heat from the machine. ## Claims ### Claim 1 A method of separating substances from a liquid mixture by fractional crystallisation comprising depositing a crystal medium layer on one side (76) of a wall (75) of a crystalliser (S1, S2, S3, 70); cooling the other side (78) of said wall (75) to obtain a crystal layer; and subsequently melting the crystal layer, wherein, for the purpose of crystallisation, said method comprises the steps of evaporating a heat exchange medium on the said other side (78) of the wall (75); and controlling the pressure of the heat exchange medium in gaseous phase in the crystalliser (S1, S2, S3) in accordance with the temperature required for crystallisation. ### Claim 2 (depends on 1) A method according to claim 1, characterised in that the flow of crystal medium is controlled to trickle in a film down said one side of the wall (75, 78). ### Claim 3 (depends on 1) A method according to claim 1, characterised by supplying the heat exchange medium for melting the crystal layer or for sweating in the gaseous state and condensing said heat exchange medium on said other side of the wall (75), and controlling the pressure of the heat exchange medium in gaseous phase in accordance with the temperature required at the wall (75). ### Claim 4 (depends on 3) A method according to claim 3, characterised in that at least one crystalliser is used for crystallisation and at least one other crystalliser is used for melting the crystals, wherein said heat exchange medium is supplied under compression, and said step of controlling the pressure of the heat exchange medium in gaseous phase comprises controlling the pressure of the heat exchange medium in said one crystalliser during crystallisation by controlling the compression; and further including the step of controlling the pressure of said heat exchange medium in the at least one other crystalliser to determine a condensation temperature for melting the crystals in the other crystalliser. ### Claim 5 (depends on 4) A method according to claim 4, characterised by supplying external heat energy to said at least one other crystalliser by evaporating said heat exchange medium, in liquid form in an auxiliary evaporator. ### Claim 6 (depends on 8) A method according to claim 8, characterised by discharging the excess heat energy by means of an auxiliary condenser (55). ### Claim 7 (depends on 1) A method according to claim 1, characterised in that at least one crystalliser is used for crystallisation and at least one other crystalliser is used for melting the crystals, wherein said heat exchange medium is supplied under compression, and said step of controlling the pressure of the heat exchange medium in gaseous phase comprises controlling the pressure of the heat exchange medium in said one crystalliser during crystallisation by controlling the compression; and further including the step of controlling the pressure of said heat exchange medium in the at least one other crystalliser to determine a condensation temperature for melting the crystals in the other crystalliser. ### Claim 8 (depends on 7) A method according to claim 7, characterised by, during the melting process, supplying said at least one other crystalliser with additional external heat energy, and subsequently discharging the excess heat energy. ### Claim 9 (depends on 1) An apparatus for carrying out the method according to claim 1, comprising at least one crystalliser (70) having a casing (71); at least one wall (75) located in said casing, defining, on one side (76) of said wall, a separate crystallisation space (74) on which crystals can be deposited, and on the other side (78) of said wall (75), a heat exchange medium space (80); inlet means (95) for supplying a vaporizable heat exchange medium into said heat exchange medium space (80), whereby, in operation, at least a portion of said heat exchange medium in said medium space will assume gaseous phase; outlet means (94) for draining at least a portion of said vaporizable heat exchange medium in liquid phase from said heat exchange medium space (80); at least one connection (96) communicating with said heat exchange medium space (80) for communication with the heat exchange medium in gaseous phase; and pressure-control means (33; 18, 28; 19, 29; 20, 30) coupled to said heat exchange medium space (80) for controlling the pressure of the heat exchange medium, in gaseous phase, in the crystalliser. ### Claim 10 (depends on 9) Apparatus according to claim 9, characterised by an auxiliary evaporator (53) coupled to said at least one connection (96). ### Claim 11 (depends on 10) Apparatus according to claim 10, characterised by an auxiliary condenser (55) coupled to said at least one connection (96). ### Claim 12 (depends on 9) Apparatus according to claim 9, characterised in that the wall (75) is formed by at least one tube (75), optionally disposed vertically and closed at one end (69), and in that means (87) are provided for conveying liquid crystal medium to the region of the closed end (69) of the at least one tube (75), from where it can trickle in a film down the wall. ### Claim 13 (depends on 12) Apparatus according to claim 12, characterised in that the menas for supplying liquid heat exchange medium is a riser (87) within the at least one tube (75). ### Claim 14 (depends on 13) Apparatus according to claim 13, characterised by spacers (91) between the inside wall of the tube (75) to hold the riser at a distance from the wall (75) of the at least one tube. ### Claim 15 (depends on 12) Apparatus according to claim 12, comprising a number of tubes which are firmly connected to a base (85); a distributor tray (81) at the top of the crystalliser having openings (82), through which the tubes project with a gap (83) through which a liquid mixture of crystal medium for fractionation can flow downward along the outer wall (76) of the tubes (75). ### Claim 16 (depends on 13) Apparatus according to claim 13, characterised in that the riser (87) extends only into a region below the distribution tray (81). ### Claim 17 (depends on 12) Apparatus according to claim 12, characterised in that a deflecting device (88), optionally a deflecting tube, is provided in the lower region of the outside wall (75) for the trickling film of crystallisation medium, and a cavity (88') is left between the wall (75) and the deflecting device (88). ### Claim 18 (depends on 15) Apparatus according to claim 15, characterised in that a cover (73) for a casing (71) of the crystalliser is provided, disposed above the distribution tray (81). ### Claim 19 A method of separating substances from a liquid mixture by fractional crystallisation comprising depositing a crystal medium layer on one side (76) of a wall (75) of a crystalliser (S1, S2, S3, 70); cooling the other side (78) of said wall (75) to obtain a crystal layer; and subsequently melting the crystal layer, wherein, for the purpose of crystallisation, said method comprises the steps of supplying a heat exchange medium on the other side (78) of the wall (75), whereby, by heat exchange with the crystal medium on said one side (76) of said wall (75), at least a portion of said heat exchange medium will assume gaseous phase; and controlling the pressure of the heat exchange medium in gaseous phase at the other side (78) of said wall in the crystalliser (S1, S2, S3) in accordance with the temperature required by crystallisation. ### Claim 20 (depends on 19) The method of claim 19, characterised in that at least one crystalliser is used for crystallisation and at least one other crystalliser is used for melting the crystals, wherein said heat exchange medium is supplied under compression, and said step of controlling the pressure of the heat exchange medium in gaseous phase comprises controlling the pressure of the heat exchange medium in said one crystalliser during crystallisation by controlling the compression; and further including the step of, in the at least one other crystalliser, controlling the pressure of said heat exchange medium to determine a condensation temperature for melting the crystals in the other crystalliser.