US2025257267A1PendingUtilityA1
Processes and Systems for Steam Cracking Hydrocarbon Feeds
Assignee: EXXONMOBIL CHEMICAL PATENTS INCPriority: Dec 6, 2021Filed: Nov 18, 2022Published: Aug 14, 2025
Est. expiryDec 6, 2041(~15.3 yrs left)· nominal 20-yr term from priority
C10G 2400/20C10G 2300/807C10G 2300/708C10G 2300/1081C10G 9/203C10G 9/16C10G 2300/4031C10G 75/00C10G 9/36
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Claims
Abstract
Processes for steam cracking hydrocarbons. The process can include introducing a hydrocarbon that can include ethane, propane, or a mixture thereof into radiant coils under steam cracking conditions that produce a steam cracker effluent and deposit coke on an inner surface thereof. An ethane conversion can be ≤75% or a. propane conversion can be ≤93%. Introduction of the hydrocarbon into at least one of the radiant coils can be periodically stopped. A decoking feed can be introduced into the at least one of the radiant coils under decoking process conditions that can include: (i) a decoking effluent that can have a coil outlet temperature of >900° C. (ii) introducing the decoking feed at a. mass flux rate at the quench exchanger inlet of >39 kg m −2 second −1 , and/or (iii) introducing the decoking feed while maintaining introduction of the first hydrocarbon feed into one or more of the radiant coils in the plurality of radiant coils.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1 . A process for steam cracking hydrocarbons, comprising:
(A) providing an olefins production plant comprising a steam cracking furnace and an olefins product recovery section; (B) operating the olefins production plant by: (B1) introducing a first hydrocarbon feed comprising at least one of ethane and propane into a plurality of radiant coils disposed within the steam cracking furnace under first steam cracking conditions that produce a first steam cracker effluent and deposit coke on an inner surface of the radiant coils, wherein a conversion of ethane, if present at a molar concentration in the first hydrocarbon feed equal to or greater than that of propane, to one or more other compounds is ≥75%, or a conversion of propane, if present at a molar concentration in the first hydrocarbon feed higher than that of ethane, to one or more other compounds is ≥93%; (B2) periodically stopping introduction of the first hydrocarbon feed into at least one of the radiant coils in the plurality of radiant coils; and (B3) introducing a decoking feed comprising steam and optionally air into the at least one of the radiant coils under decoking process conditions, wherein the decoking process conditions comprise at least one of: (i) introducing the decoking feed into the at least one of the radiant coils to produce a decoking effluent having a coil outlet temperature of >900° C.; (ii) introducing the decoking feed into the at least one of the radiant coils or into one or more quench exchanger inlets in fluid communication with the at least one of the radiant coils at a mass flux rate at the quench exchanger inlet of >39 kg·m −2 ·second −1 ; and (iii) introducing the decoking feed into the at least one of the radiant coils while maintaining introduction of the hydrocarbon feed into one or more of the radiant coils in the plurality of radiant coils.
2 . The process of claim 1 , wherein the decoking process comprises step (B3)(i), wherein the decoking feed comprises a mixture of steam and air.
3 . The process of claim 1 , wherein the decoking process comprises step (B3)(ii), wherein the decoking feed comprises a mixture of steam and air.
4 . The process of claim 1 , wherein the decoking process comprises step (B3)(iii), wherein the decoking feed is steam.
5 . The process of claim 1 , wherein the steam cracking conditions comprise a residence time of the hydrocarbon feed within the radiant coils of 0.01 second to 5 seconds, heating the hydrocarbon feed within the radiant coils sufficiently to produce a steam cracker effluent having a coil outlet temperature of from 815° C. to 925° C., or a combination thereof.
6 . The process of claim 1 , wherein the hydrocarbon feed comprises ethane and propane at a total concentration of no less than 75 wt %, based on the total volume of the hydrocarbon feed.
7 . The process of claim 1 , wherein the hydrocarbon feed comprises ethane at a concentration of no less than 75 wt %, based on the total volume of the hydrocarbon feed.
8 . The process of claim 1 , further comprising, before step (B):
(C) operating the olefins production plant by: (C1) introducing a reference hydrocarbon feed into the plurality of radiant coils under reference steam cracking conditions that produce a reference steam cracker effluent, wherein a conversion of at least one of ethane, if present at an equal or higher molar concentration than propane in the reference hydrocarbon feed, to one or more other compounds is <75%, and propane, if present at a higher molar concentration than ethane in the reference hydrocarbon feed, to one or more other compounds is <93%; and (D) adjusting step (C) to carry out step (B).
9 . The process of claim 8 , wherein:
in step (C1), the first hydrocarbon feed is introduced into the plurality of radiant coils at a first quantity, in step (B1), the reference hydrocarbon feed is introduced into the plurality of radiant coils at a second quantity, the first hydrocarbon feed and the reference hydrocarbon feed have the same composition, and the second quantity is higher than the first quantity.
10 . The process of claim 8 , wherein:
the quantity of ethane in the first hydrocarbon feed introduced into the plurality of radiant coils in step (B1) is higher than the quantity of ethane in the reference hydrocarbon feed introduced into the plurality of radiant coils in step (C1); and/or the quantity of propane in the first hydrocarbon feed introduced into the plurality of radiant coils in step (B1) is higher than the quantity of propane in the reference hydrocarbon feed introduced into the plurality of radiant coils in step (C1).
11 . The process of claim 8 , wherein:
the reference hydrocarbon feed consists essentially of C5+ hydrocarbons.
12 . The process of claim 8 , wherein:
step (B) further comprises: (B4) separating a process gas stream comprising C1-C4 hydrocarbons from the first steam cracker effluent; (B5) providing a second C1-C4-hydrocarbon-containing stream separate from the process gas stream; and (B6) supplying the process gas stream and the second C1-C4-hydrocarbon-containing stream into the olefins product recovery section.
13 . A process for steam cracking hydrocarbons, comprising:
introducing a first hydrocarbon feed comprising ethane, propane, or a mixture thereof into a plurality of radiant coils disposed within a steam cracking furnace under steam cracking conditions that produce a steam cracker effluent and deposit coke on an inner surface of the radiant coils, wherein a conversion of at least one of ethane, if present at a molar concentration in the first hydrocarbon feed equal to or greater than that of propane, to one or more other compounds is ≥75%, or a conversion of propane, if present at a molar concentration in the first hydrocarbon feed higher than that of ethane, to one or more other compounds is ≥93%; and wherein an inner surface of the radiant coils in the plurality of radiant coils comprises a material that is non-catalytic to coke generation.
14 . The process of claim 13 , wherein the radiant coils are alumina former tubes made of an alloy comprising ≥1.5 wt % of aluminum that have an aluminum oxide layer disposed on the inner surfaces thereof.
15 . The process of claim 13 , wherein the radiant coils comprise a layer comprising silicon carbide, spinel, or a combination thereof disposed on the inner surfaces thereof.
16 . The process of claim 13 , wherein the radiant coils comprise a layer comprising a spinel-type oxide layer disposed on the inner surfaces thereof.
17 . The process of claim 16 , wherein the spinel-type oxide layer comprises 40 wt % to 60 wt % of compounds having the chemical formula: Mn x Cr 3-x O 4 , wherein x is from 0.5 to 2, and from 60 wt % to 40 wt % of oxides of Mn and Si selected from the group consisting of MnO, MnSiO 3 , Mn 2 SiO 4 and mixtures thereof provided that the surface contains less than 5 wt % of Cr 2 O 3 .
18 . The process of claim 13 , further comprising:
periodically stopping introduction of the first hydrocarbon feed into at least one of the radiant coils in the plurality of radiant coils; and introducing a decoking feed comprising a steam and optionally air into the at least one of the radiant coils to remove at least a portion of any coke deposited on an inner surface of the at least one of the radiant coils.
19 . The process of claim 13 , wherein the first hydrocarbon feed comprises ethylene and/or propylene.
20 . The process of claim 12 , wherein the steam cracking conditions comprise a residence time of the first hydrocarbon feed within the radiant coils of 0.01 second to 5 seconds, heating the first hydrocarbon feed within the radiant coils sufficiently to produce a steam cracker effluent having a coil outlet temperature of 815° C. to 925° C., or a combination thereof.
21 . A process for steam cracking hydrocarbons, comprising:
(1) providing an olefins production plant comprising a steam cracking furnace and an olefins product recovery section; (2) operating the olefins production plant by: (2a) in a cracking interval, introducing a first hydrocarbon feed comprising at least one of ethane and propane into a plurality of radiant coils disposed within the steam cracking furnace under first steam cracking conditions that produce a first steam cracker effluent and deposit coke on an inner surface of the radiant coils, wherein a conversion of ethane, if present at a molar concentration in the first hydrocarbon feed equal to or greater than that of propane, to one or more other compounds is >75%, or a conversion of propane, if present at a molar concentration in the first hydrocarbon feed higher than that of ethane, to one or more other compounds is ≥93%; (2b) optionally conducting online decoking in an online decoking interval of at least one of the radiant coils by introducing a decoking steam there into; (2c) periodically stopping introduction of the first hydrocarbon feed into at least one of the radiant coils in the plurality of radiant coils; and (3) providing a reference process comprising: (3a) in a reference cracking interval, introducing a reference hydrocarbon feed into the plurality of radiant coils under reference steam cracking conditions that produce a reference steam cracker effluent and deposit coke on the inner surface of the radiant coils, having a reference conversion of ethane, if present, to one or more other compounds of ≤75%, and a reference conversion of propane, if present, to one or more other compounds of ≤93%; (3b) periodically stopping introduction of the reference hydrocarbon feed into at least one of the radiant coils in the plurality of radiant coils; and (3c) in a reference offline decoking interval, introducing the decoking feed into the at least one of the radiant coils under reference decoking conditions; (4) introducing a decoking feed comprising steam and optionally air into the at least one of the radiant coils under decoking process conditions such that −2 mm≤AA≤2 mm, where
AA
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delta (R1)=R1−R1 (ref), where R1 is average coke deposition rate in the radiant coils in the process during the cracking interval, in mm·day −1 , and R1(ref) is average coke deposition rate in the radiant coils in the reference process during the reference cracking interval, in mm·day −1 ;
D1(ref) is the duration of the reference cracking interval, in days;
delta(D1)=D1−D1(ref), where D1 is duration of the cracking interval, in days;
P1 is coke removed during the online decoking interval, if any, in mm;
P2 is coke removed during the offline decoking interval, in mm; and
P2(ref) is coke removed during the reference offline decoking interval, in mm.
22 . The process of claim 21 , wherein −0.5 mm≤AA≤0.5 mm.
23 . The process of claim 21 , further comprising:
(5) during a plurality of quench exchanger decoking intervals, feeding a quench exchanger decoking feed into a quench exchanger inlet tube operated under quench exchanger decoking conditions; wherein: the reference process further comprises: during a plurality of reference quench exchanger decoking intervals, feeding the quench exchanger decoking feed into the quench exchanger inlet tube operated under reference quench exchanger decoking conditions; the process further comprises selecting the quench exchanger decoking conditions such that: −2 mm≤BB≤2 mm, where:
BB
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delta(R2)=R2−R2(ref), where R2 is average coke deposition rate in the quench exchanger inlet tube between two adjacent quench exchanger decoking intervals, in mm·day −1 ; and R2(ref) is average coke deposition rate in the quench exchanger inlet tube in the reference process between two adjacent reference quench exchanger decoking intervals, in mm·day −1 ;
D2(ref) is the duration between two adjacent quench exchanger decoking intervals, in days;
deltaD2=D2−D2(ref), where D2 is the duration between two adjacent quench exchanger decoking intervals, in days;
P3 is average coke removed during the plurality of quench exchanger decoking intervals in mm; and
P3(ref) is average coke removed during the plurality of reference quench exchanger decoking intervals in mm.
24 . The process of claim 23 , wherein −0.5 mm≤BB≤0.5 mm.
25 . The process of claim 22 , wherein the decoking process conditions comprise at least one of:
(i) introducing the decoking feed into the at least one of the radiant coils to produce a decoking effluent having a coil outlet temperature of >900° C.; (ii) introducing the decoking feed into the at least one of the radiant coils or into one or more quench exchanger inlets in fluid communication with the at least one of the radiant coils at a mass flux rate at the quench exchanger inlet of >39 kg·m −2 ·second −1 ; and (iii) introducing the decoking feed into the at least one of the radiant coils while maintaining introduction of the first hydrocarbon feed into one or more of the radiant coils in the plurality of radiant coils.Join the waitlist — get patent alerts
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