Verfahren zur Entfernung kondensierbarer Bestandteile aus einem AEthylenruecklaufstrom bei einem Hochdruck-Polymerisationsverfahren

摘要

Ethylene containing entrained condensible polymer is purified for recycle to the polymerisation by passing through (a) a cooling zone previously used for condensation at a temperature sufficient to melt and remove solidified condensed materials, (b) a zone where condensible materials are deposited and (c) a cooling zone wherein further condensible materials are condensed and deposited as solids and periodically reversing the flow. The feed may be a recycle stream 13 in an ethylene high-pressure polymerization process from which most of the polymer products has been removed in zone 11. Gas at above 1000 p.s.i.g. and at 450-550 DEG F. is introduced by line 19 into zone A comprising a fan-cooled condenser 20 and a heat-exchanger 22 which have previously been used for condensation and contain solid polyethylene. No cooling is applied and the polymer is melted and passes with the gas through lines 27 and 29 into separator 30 where by changing the direction and velocity of the gas the polymer is separated. Gas then passes through the cooled condensers 38 and 40 where it is cooled to 40-100 DEG F. and polymer condenses and then through a separator 45 before recycling to the polymerization. When the system begins to plug with polymer the gas flow is reversed, passing first through condensers 38 and 40 and separator 30, then through condensers 20 and 22 now free from polymer. Comonomers may also be present in the ethylene stream, e.g. propylene, butene-1, isobutylene, hexene-1 or vinyl acetate or modifiers, chain transfer agents or diluents, e.g. propane, butane, hexane, cyclohexane, alcohols, ketones, aldehydes, water or aromatics.ALSO:Ethylene containing entrained condensible materials is purified by passing through (a) a cooling zone previously used for condensation at a temperature sufficient to melt and remove solidified condensed materials, (b) a zone where condensible materials are deposited and (c) a cooling zone wherein further condensible materials are condensed and deposited as solids and periodically reversing the flow. The feed may be a recycle stream 13 in an ethylene high-pressure polymerization process from which most of the polymer product has been removed in zone 11. Gas at above 1000 p.s.i.g. and at 450-550 DEG F. is introduced by line 19 into zone A comprising a fan-cooled condenser 20 and a heat-exchanger 22 which have previously been used for condensation and contain solid polyethylene. No cooling is applied and the polymer is melted and passes with the gas through lines 27 and 29 into separator 30 where by changing the direction and velocity of the gas the polymer is separated. Gas then passes through the cooled condensers 38 and 40 where it is cooled to 40-100 DEG F. and polymer condenses and then through a separator 45 before recycling to the polymerization. When the system begins to plug with polymer the gas flow is reversed, passing first through condensers 38 and 40 and separator 30 then through condensers 20 and 22 now free from polymer. Comonomers may also be present in the ethylene stream, e.g. propylene, butene-1, isobutylene, hexene-1 or vinyl acetate or modifiers, chain transfer agents or diluents, e.g. propane, butane, hexane, cyclohexane, alcohols, ketones, aldehydes, water or aromatics.