Process for monomer recovery from a polymerization process
The present relates to a process for optimizing the recovery of unreacted monomers from a polymerization process, wherein said process comprises the steps of recovering a fluid stream generated by the separation of the polyolefin product from the polymerization fluid comprising unreacted monomers and optionally comonomers; contacting said fluid stream in an absorption zone with a scrub liquid comprising at least one C 4-10 hydrocarbons, thereby absorbing at least a portion of the unreacted monomers in said scrub liquid; and withdrawing from said absorption zone (i) a vapor overhead comprising light gas and (ii) an absorber bottoms scrub liquid comprising said C 4-10 hydrocarbons and said unreacted monomer; thereby recovering said unreacted monomer in said absorber bottoms scrub liquid comprising said C 4-10 hydrocarbons. The present invention also concerns a process for the recovery of unreacted monomers from a gas phase or slurry polymerization process, and also concerns a process for the production of polyolefins.
1. A process for the recovery of unreacted monomers from a slurry polymerization process comprising:
(a) recovering a fluid stream from a polymer slurry comprising essentially liquid diluent, unreacted monomer, comonomers and solid polyolefin particles, by separating at least a majority of the diluent and unreacted monomer and comonomers from said polyolefin solid particles;
(b) distilling said fluid stream, and withdrawing from said distillation a bottom stream comprising C 4-10 hydrocarbons, and an overhead stream comprising unreacted monomer and diluent;
(c) distilling said overhead stream and withdrawing (i) a bottom stream comprising substantially olefin-free hydrocarbon diluent, optionally a side stream comprising hydrocarbon diluent, and (ii) an overhead vapor stream comprising unreacted monomer and light gas;
(d) contacting said removed overhead vapor stream in a gas-liquid absorption zone with a scrub liquid comprising at least one C 4-10 hydrocarbons, thereby absorbing at least a portion of the unreacted monomers in said scrub liquid; and
(e) withdrawing from said absorption zone (i) a vapor overhead and (ii) an absorber bottoms scrub liquid comprising said C 4-10 hydrocarbons and said unreacted monomer, wherein the bottom stream of step (b) comprising C 4-10 hydrocarbons, is combined with makeup scrub liquid and cooled to provide said scrub liquid feed to said gas-liquid absorption zone.
2. The process of claim 1 , wherein said absorber bottoms scrub liquid is recycled to the polymerization reaction.
3. The process of claim 1 , wherein said overhead vapor stream of step (c) comprising unreacted monomer and light gas is compressed and cooled prior to treatment in said gas-liquid absorption zone.
4. The process of claim 1 , wherein said unreacted monomer is recovered from said absorber bottoms scrub liquid by first flashing to a reduced pressure said absorber bottoms scrub liquid, and separating the resulting flashed stream into a vapor containing the unreacted monomer and a liquid comprising said C 4-10 hydrocarbons.
5. The process of claim 4 , wherein said vapor containing the unreacted monomer is compressed and recycled to said polymerization process.
6. The process of claim 4 , wherein said liquid comprising said C 4-10 hydrocarbons is cooled and pumped back to said absorption zone as the scrub liquid.