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US 12,065,518 B2Granted
Methods of controlling shutdown of reactor systems
AssigneeExxonMobil Chemical Patents Inc.
InventorsPaul J. Clymans, Jefferson P. Galliano, Philippe A. P. D'Hooghe, Cindy Dewitte, Henri A. Lammens
Life of this patent
Estimating the term…
Abstract
Controlling the shutdown of a polyethylene reactor system that includes a secondary compressor, a reactor, a high pressure let down valve (HPLDV), a high-pressure separator, and a high-pressure recycle gas system is provided. After a partial or complete shutdown of secondary compressor, HPLDV opens to a pre-set open position until the reactor pressure reduces to either a pre-set reduced pressure limit or a until the slope of the reactor gas density to reactor pressure exceeds 0.15. The HPLDV controls the pressure to a pressure set point.
Claims15
A method of controlling shutdown of a polyethylene reactor system comprising:
- providing a polyethylene reactor system comprising a suction heater and drum 150, a primary compressor 152, a secondary compressor 154, a reactor 156, a high pressure let down valve (HPLDV) 130, a high-pressure separator 158, and a high-pressure recycle gas system 160;
- wherein the reactor 156 operates at a pressure of about 3000 bar-g;
- experiencing a partial or complete shutdown of secondary compressor 154;
- opening the HPLDV 130 to a pre-set open position until a reactor 156 pressure reduces to either a pre-set reduced pressure limit or until a slope of the reactor gas density to reactor pressure exceeds 0.15;
- after reactor 156 pressure reduces to either the pre-set reduced pressure limit or after the slope of the reactor gas density to reactor pressure exceeds 0.15:
- controlling the HPLDV 130 to control the pressure in line 114 that connects the high-pressure separator 158 outlet to an inlet of the high-pressure recycle gas system 160 to a pressure set point that is approximately 10 bar-g less than the pressure that would cause the high-pressure recycle gas system 160 to vent to avoid overpressure;
- controlling a flow in first compressor recycled ethylene line 132 that recycles ethylene from a primary compressor outset to an ethylene feed line 100 to the suction heater and drum 150 using valve 134;
- allowing a flow of ethylene leaving the high-pressure recycle gas system 160 to travel through first compressor recycled ethylene line 132 that recycles ethylene from the primary compressor outset to the ethylene feed line 100 to the suction heater and drum 150;
- removing ethylene from purge recycled ethylene line 122 to a liquid storage facility and optionally also removing ethylene from makeup ethylene line 102 to an ethylene header.
6 more elements
A method of controlling shutdown of a polyethylene reactor system comprising:
- (a) providing a polyethylene reactor system comprising a suction heater and drum 150, a primary compressor 152, a secondary compressor 154, a reactor 156, a high pressure let down valve 130, a high-pressure separator 158, and a high-pressure recycle gas system 160;
- wherein:
- the reactor 156 operates at a pressure of about 3000 bar-g;
- the suction heater and drum 150 receives ethylene from an ethylene feed line 100 which receives ethylene from a makeup ethylene line 102, a purge recycled ethylene line 122, and a first compressor recycled ethylene line 132,
- ethylene leaves the suction heater and drum 150 and is transported to the primary compressor 152 through a line 104, the primary compressor compresses ethylene and sends it on to the secondary compressor 154 through a line 106, and a portion of ethylene exiting the secondary compressor 154 is recycled back to the ethylene feed line 100 through first compressor recycled ethylene line 132;
- the line 106 receives a high-pressure recycle gas through line 128 and enters secondary compressor 154, the secondary compressor 154 compresses ethylene and sends it on the reactor 156 where a portion of the ethylene reacts in a presence of an initiator to form polyethylene;
- a material exiting reactor 156 passes through a high pressure let down valve (HPLDV) 130 before entering a high-pressure separator 158;
- and
- the high-pressure separator 158 separates a portion of unreacted ethylene from the material exiting reactor 156, and sends the unreacted ethylene to high-pressure recycle gas system 160 through line 114;
- (b) experiencing a partial or complete shutdown of secondary compressor 154;
- (c) opening the HPLDV 130 to a pre-set open position until a reactor 156 pressure reduces to either a pre-set reduced pressure limit or a until a slope of the reactor gas density to reactor pressure exceeds 0.15;
- (d) after reactor 156 pressure reduces to either the pre-set reduced pressure limit or after the slope of the reactor gas density to reactor pressure exceeds 0.15:
- controlling the HPLDV 130 to control a pressure in line 114 to a pressure set point that is approximately 10 bar-g less than a pressure that would cause the high-pressure recycle gas system 160 to vent to avoid overpressure;
- controlling a flow in first compressor recycled ethylene line 132 using valve 134;
- allowing a flow of ethylene leaving the high-pressure recycle gas system 160 to travel through line 128, into line 106, and through first compressor recycled ethylene line 132 back to ethylene feed line 100 and into either purge recycled ethylene line 122 or makeup ethylene line 102;
- and
- removing ethylene from purge recycled ethylene line 122 to a liquid storage facility and optionally also removing ethylene from makeup ethylene line 102 to an ethylene header.
14 more elements
Dependencies are inferred from the claim text.