1. A process for the gas-phase polymerization of at least one alpha-olefin in the presence of a polymerization catalyst, the process comprising:
polymerizing in at least a polymerization step wherein the polymer particles flow downward in densified form under the action of gravity so as to form a densified polymer bed,
metering an anti-fouling agent in said polymerization step by means of at least N feeding lines placed at different heights of said densified polymer bed, N being the integer number satisfying the equation N\u2267(1+0.08\xb7H), where H is the height (expressed in meters) of the polymer bed.
2. The process according to claim 1, wherein said integer number N satisfies the equation N\u2267(1+0.1\xb7H).
3. The process according to claim 1, wherein said antifouling agent is metered in an amount ranging from 5 to 250 ppm weight based on the weight of polyolefin being produced.
4. The process according to claim 1, wherein the gas-phase polymerization of at least one alpha-olefin is performed in a gas-phase reactor having two interconnected polymerization zones, the first polymerization zone, denominated the riser, comprising polymer particles flowing upward under fast fluidization or transport conditions, the second polymerization zone, denominated the downcomer, comprising polymer particles flowing downward in densified form under the action of gravity so as to form said densified polymer bed.
5. The process according to claim 4, wherein said anti-fouling agent is metered in said gas-phase reactor having two interconnected polymerization zones by means of three separate feeds comprising
a first feed F1 distributed along the height of said downcomer by means of at least N feeding lines, N being an integer number satisfying said equation N\u2267(1+0.08\xb7H);
a second feed line F2 arranged on the line feeding the prepolymer to said riser; and
a third feed line F3 arranged along the gas recycle line.
6. The process according to claim 5, wherein said antifouling agent is added to said polymerization reactor in a total amount ranging from 20 to 500 ppm weight, based on the weight of polyolefin being produced.
7. The process according to claim 5, wherein said first feed F1 comprises from 30 to 60% by weight of the total amount of said anti-fouling agent, the second feed F2 comprises from 5 to 20% by weight of the total amount of said anti-fouling agent, and the third feed F3 comprises from 30 to 60% by weight of the total amount of said anti-fouling agent.
8. The process according to claim 1, wherein said anti-fouling agent is selected from:
(1) alkyldiethanolammines of formula R\u2014N(CH2CH2OH)2 wherein R is an alkyl radical comprised between 10 and 20 carbon atoms, preferably between 12 and 18 carbon atoms;
(2) Polyepoxidate oils, such as epoxidate linseed oil and epoxidate soya oil;
(3) Polyalcohols having from 4 to 8 carbon atoms;
(4) Hydroxyesters with at least two free hydroxyl groups, obtained from carboxylic acids with from 8 to 22 carbon atoms and from polyalcohols;
(5) Amides of formula R\u2014CONR\u2032R\u2033, wherein R, R\u2032, and R\u2033 may be the same or different and is a saturated or unsaturated hydrocarbon radical having 1 to 22 carbon atoms;
(6) Fatty acid soaps represented by the general formula R\u2014COOM, wherein R is a saturated or unsaturated hydrocarbon radical having 12 to 22 carbon atoms, and M is an alkali or alkaline earth metal;
(7) Salts of sulfuric acid esters of higher alcohols represented by the general formula ROS03M, wherein R is a saturated or unsaturated hydrocarbon radical having 12 to 22 carbon atoms, and M is an alkali or alkaline earth metal;
(8) Salts of sulfuric acid esters of higher secondary alcohols represented by the
wherein R and R\u2032 may be the same or different and are selected from saturated or unsaturated hydrocarbon radical having 12 to 22 carbon atoms, M is an alkali or alkaline earth metal;
(9) Compounds represented by the general formula
wherein R, M and n are the same as above defined;
(10) Salts of (higher alkyl) sulfonic acids represented by the general formula RS03M,
wherein R, M and n are the same as above defined;
(11) Salts of alkylarylsulfonic acids;
(12) Alkali or alkaline earth metal salts of dialkylsulfosuccinic acids;
(13) Alkali or alkaline earth metal salts of partial esters of higher alcohols with phosphoric acid;
(14) Salts of primary amines represented by the general formula
R\u2014NH3+A\u2212
wherein R is a saturated or unsaturated hydrocarbon radical; A is chlorine, bromine;
(15) Compounds of the alkylaminesulfonic acid type represented by the general formula
(16) Compounds represented by the general formula
wherein R is a saturated or unsaturated hydrocarbon radical having 4 to 22 carbon atoms; n and m, which may be the same or different, are numbers of from 1 to 10; or
(17) mixtures thereof.
9. The process according to claim 8, wherein said anti-fouling agent is selected from the group consisting of classes (1), (2), (3), (4) and (5).
10. The process according to claim 9, wherein said anti-fouling agent is selected from alkyldiethanolammines of formula R\u2014N(CH2CH2OH)2, where R is an alkyl radical C12-C18; epoxidate linseed oils; epoxidate soya oils; or glyceryl monosterate.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An optical line of sight toggle apparatus comprising:
a first optical element; and
a second optical element positioned to shift a line of sight upon a lateral displacement of said first optical element relative to said second optical element.
2. The optical line of sight toggle apparatus of claim 1 wherein at least one optical surface on said first optical element and said second optical element is diffractive.
3. The optical line of sight toggle apparatus of claim 1 wherein at least one optical surface on said first optical element and said second optical element is diffractive and at least one optical surface on said first optical element and said second optical element is aspherical or spherical.
4. The optical line of sight toggle apparatus of claim 1 wherein said first optical element and said second optical element are both made of silicon.
5. The optical line of sight toggle apparatus of claim 1 wherein said first optical element and said second optical element are both made of germanium.
6. The optical line of sight toggle apparatus of claim 1 wherein said first optical element is made of silicon and said second optical element is made of germanium.
7. The optical line of sight toggle apparatus of claim 1 wherein image quality is corrected by a combination of aspheric or spheric shapes and diffractive surfaces on said optical surfaces of said first and second optical elements.
8. The optical line of sight toggle apparatus of claim 1 wherein said first and second optical elements are rotationally symmetrical.
9. The optical line of sight toggle apparatus of claim 1 wherein said optical surfaces of said first and second elements are shaped to work in combination with said lateral displacements of said first and second optical elements such that the line of sight angle is shifted.
10. An optical line of sight toggle apparatus comprising:
a first optical element comprised of a material selected from the group consisting of silicon and germanium; and
a second optical element comprised of a material selected from the group consisting of silicon and germanium positioned to shift a line of sight upon a lateral displacement of said first optical element relative to said second optical element, wherein at least one optical surface on said first optical element and said second optical element is diffractive, and at least one optical surface on said first optical element and said second optical element is diffractive and at least one optical surface on said first optical element and said second optical element is aspherical or spherical.
11. The optical line of sight toggle apparatus of claim 10 wherein image quality is corrected by a combination of aspheric or spheric shapes and diffractive surfaces on said optical surfaces of said first and second optical elements.
12. The optical line of sight toggle apparatus of claim 10 wherein said first and second optical elements are rotationally symmetrical.
13. The optical line of sight toggle apparatus of claim 10 wherein said optical surfaces of said first and second elements are shaped to work in combination with said lateral displacements of said first and second optical elements such that the line of sight angle is shifted.
14. A method of scanning a wide field of view optical sensor through multiple fields of regard comprising:
positioning a first optical element and a second optical element wherein at least one optical surface on said first optical element and said second optical element is diffractive and at least one optical surface on said first optical element and said second optical element is aspherical or spherical; and
shifting a line of sight upon a lateral displacement of said first optical element relative to said second optical element.
15. The method of claim 14 further comprising correcting image quality by a combination of aspheric or spheric shapes and diffractive surfaces on said optical surfaces of said first and second optical elements.
16. The method of claim 14 wherein said first and second optical elements are rotationally symmetrical.
17. The method of claim 14 wherein said optical surfaces of said first and second elements are shaped to work in combination with said lateral displacements of said first and second optical elements such that the line of sight angle is shifted.
18. The method of claim 14 wherein the first optical element is comprised of a material selected from the group consisting of silicon and germanium.
19. The method of claim 14 wherein the first optical element is comprised of a group consisting of silicon and germanium.