PROCESS AND APPARATUS FOR OBTAINING PARAFFINS OR PARAFFIN FRACTIONS

摘要

1. A process for obtaining paraffins or paraffin fractions from a paraffin-containing melt, more particularly from crude paraffin or a mixture containing various paraffin fractions, wherein the melt is cooled in a container equipped with heat exchangers to a temperature below the melting-temperature of the paraffin fractions to be obtained and liquid low-melting fractions and oils are separated from the higher-melting paraffin fractions solidified by cooling, and are discharged, characterized in that during cooling of the initially still-liquid melt, the temperature of the heat exchanger surfaces (39) is chosen at a higher value than the melting temperature of a substantial part of the low-melting fractions and oils for discharge, and after a solid deposit (43, 53) of higher-melting fractions forms on the heat exchanger surfaces (39) the remaining liquid low-melting fractions and oils are discharged from the container (13). 2. A process according to Claim 1, characterized in that the solidifying fractions are deposited from the melt in layers (43) on to substantially vertical or inclined heat-exchanger surfaces (39). 3. A process according to Claim 2, characterized in that the layers (43) are deposited on to substantially planar heat exchanger surfaces (39). 4. A process according to any one of Claims 1 to 3, wherein low-melting fractions and oils are stripped from the solid deposit by heating the fractions solidified by cooling, characterized in that the remaining solid deposit (43, 53) when heated is driven towards a heat exchanger surface (39) by its own weight. 5. A method according to any one of Claims 1 to 4 wherein low-melting fractions and oils are stripped out of the solid deposit by heating the fractions solidified by cooling, characterized in that during heating the remaining solid deposit (43, 53) is divided into separate strips (53). 6. A method according to Claim 4 or 5, characterized in that the remaining solid deposit (43, 53) is at least partly detached from the heat exchanger surfaces (39) on to guide elements (30) inclined to the heat exchanger surfaces (39). 7. A method according to Claim 6, characterized in that the layers (13) are loosened from the heat exchanger surfaces (39) by heating of the latter and are divided by the guide elements (30) into separate strips (53). 8. A method according to Claim 6 or 7, characterized in that the components (55) stripped by heating the solid deposit (43, 53) are partly discharged downwards through special passages (33, 35) in the guide element (30). 9. A method according to any one of Claims 4 to 8, characterized in that the layers (43) are divided by the guide elements (30) into strips (53). 10. A method according to any one of Claims 1 to 3, wherein low-melting fractions and oils are stripped out of the solid deposit by heating the fractions solidified by cooling, characterized in that the layers (43) are deposited in such thickness that their adhesion to the heat exchanger surfaces (39) is sufficient to hold them during heating. 11. A process according to one or more of the preceding Claims, characterized in that a melt is first de-oiled by a process according to any one of Claims 1 to 9 and the resulting fractions are then further purified or fractionated in a process according to Claim 10. 12. A process according to any one of Claims 1 to 10, characterized in that discharged low-melting fractions (55) and/or oils are returned to a process according to any of Claims 1 to 10. 13. A process according to any one of Claims 1 to 12, characterized in that the solid deposit (43, 53) is fractionally melted. 14. A method according to any one of Claims 1 to 13, characterized in that the melt is poured into an empty container (13). 15. Apparatus for obtaining paraffins or paraffin fractions from a paraffin-containing melt, comprising a container equipped with heat exchangers, wherein the heat exchangers have substantially vertically aligned heat exchanger surfaces, for separating higher-melting paraffin fractions, formed as a solid deposit by cooling the melt on the heat exchanger surfaces, from low-melting fractions and oils which can be stripped from the solid deposit by heating, characterized in that a structure (29) permeable to liquid constituents (55) is disposed between the heat exchanger surfaces (39) and prevents the solid deposit (43, 53) from slipping down when heated. 16. Apparatus according to Claim 15, characterized in that the heat exchanger surfaces (39) are substantially planar. 17. Apparatus according to Claim 15 or 16, characterized in that the permeable structure (29) comprises guide elements (39) inclined to the heat exchanger surfaces (39). 18. Apparatus according to Claim 17, characterized in that the inclination of the guide elements (30) is chosen so that during heating the solid deposit (43, 53) is automatically transferred to a heat exchanger surface (39) by the weight of the solid deposit (43, 53). 19. Apparatus according to any one of Claims 15 to 18, characterized in that the guide elements (30) are inclined surfaces (30), which divide the space between the heat exchanger surfaces (39) approximately horizontally. 20. Apparatus according to Claim 19, characterized in that superposed inclined surfaces (30) slope in opposite directions. 21. Apparatus according to any one of Claims 15 to 20, characterized in that the heat exchangers (15) divide the container (13) into spatial zones (18) which are so dimensioned that melt in the container (15) is always at a short distance from the nearest heat exchanger surface (39).