Use of an additivie for improving the flowability of fines and their reintroduction into a continuous gas-phase (co-) polymerisation of olefins reactor
View Patent ↗The present invention relates to the use of an additive for improving the flowability of fines and their reintroduction into a process for the continuous gas-phase (co-) polymerisation of olefins in a fluidized bed or sub-fluidized bed reactor.
1. Process for the gas-phase (co-) polymerisation of olefins in the presence of a catalyst in a fluidized bed or sub-fluidised bed reactor system comprising the reactor, a recycle line connecting the top of the reactor to its bottom and a cyclone, the cyclone inlet being connected to the top of the reactor and the cyclone outlet being connected back to the reactor at a lower elevation, the process comprising:
keeping polymer particles that are being formed in a fluidised or sub-fluidised state by means of a gaseous reaction mixture traveling as an ascending stream in the reactor,
recycling the gas mixture leaving via the top of the reactor to the base of the reactor by means of the recycle line,
passing at least part of said gas mixture leaving the top of the reactor through at least one cyclone in order to separate the gas from the fine particles,
recovering the fine particles from the bottom of the cyclone, recycling the fine particles back to the reactor, and
adding a flowability improver additive at a location comprised between the top of the reactor and the cyclone entry.
2. Process according to claim 1 wherein the additive comprises at least one of the components selected from:
(1) a polysulphone copolymer,
(2) a polymeric polyamine, and
(3) an oil-soluble sulphonic acid.
3. Process according to claim 1 wherein the catalyst is a chromium oxide catalyst.
4. Process according to claim 2 wherein the additive comprises at least two components selected from components (1), (2) and (3).
5. Process according to claim 4 wherein the additive comprises a mixture of (1), (2) and (3).
6. Process according to claim 5 wherein the additive comprises about 5-70 weight percent polysulphone copolymer, 5-70 weight percent polymeric polyamine, and 5-70 weight percent oil-soluble sulphonic acid.
7. Process according to claim 1 wherein the additive represents from about 0.00001 to about 35 parts by weight per million parts by weight of the olefin introduced.
8. Process according to claim 1 wherein the sole or main olefin is either ethylene or propylene, and an optional comonomer is selected from the group consisting of but-1-ene, pent-1-ene, hex-1-ene, 4-methylpent-1-ene and oct-1-ene.
9. Process according to claim 8 wherein the main olefin is ethylene and the optional comonomer is selected from the group consisting of but-1-ene, hex-1-ene and 4-methylpent-1-ene.
10. Process according to claim 7 wherein the additive represents from about 0.001 to about 10 parts by weight per million parts by weight of the olefin introduced.
11. Process according to claim 7 wherein the additive represents from about 0.1 to about 7.5 parts by weight per million parts by weight of the olefin introduced.
12. Process according to claim 1 , wherein all of said gas mixture leaving the top of the reactor is passed through at least one cyclone in order to separate the gas from the fine particles.