Pyrolysis reactor approach temperature

A hydrocarbon pyrolysis process, the process comprising:

• (a) providing an oxidant, a fuel, and a feed comprising hydrocarbon;
• (b) providing an elongated thermal pyrolysis reactor having (i) an internal volume which includes a pre-heated first heat transfer zone, a pre-cooled second heat transfer zone, a preheated reaction zone located between the first and second heat transfer zones, and (ii) opposed first and second openings in fluidic communication with the internal volume;
• (c) during a first time interval having a duration tp carrying out at least:
• (i) introducing the feed through the first opening, and toward the first heat transfer zone,
• (ii) transferring heat from the reactor to the feed in the first heat transfer zone, which cools the first heat transfer zone and heats the feed to achieve a bulk gas temperature TA at a location adjacent to the first heat transfer zone the reaction zone, wherein TA is substantially equal to a minimum pyrolysis temperature (TMIN) during tp, and TMIN is ≥800° C.,
• (iii) pyrolysing at least a portion of the heated feed's hydrocarbon in the reaction zone under pyrolysis conditions including an average reaction zone temperature (Tav), wherein (A) Tav is ≥TMIN+10° C. at the start of tp, (B) the pyrolysis cools the reaction zone, and (C) the pyrolysis produces a pyrolysis product comprising coke, molecular hydrogen, and ethylene,
• (iv) transferring heat from the pyrolysis product to the reactor in the second heat transfer zone which (A) cools the pyrolysis product from a bulk gas temperature TB at a location adjacent to the reaction zone and the second heat transfer zone to a bulk gas temperature of ≤600° C. proximate to the second opening at the start of tp, wherein TB is substantially equal to TMIN during tp, (B) deposits coke in the second heat transfer zone, and (C) produces a process gas comprising at least a portion of the pyrolysis effluent's molecular hydrogen, ethylene, and propylene, and
• (v) conducting the process gas away from the reactor, the process gas having a bulk gas temperature of ≤600° C. proximate to the second opening at the start of tp;
• (d) during a second time interval having a duration tH which occurs after tp, carrying out at least:
• (i) introducing at least a portion of the oxidant through the second opening and into the second heat transfer zone,
• (ii) transferring heat from the reactor to the oxidant in the second heat transfer zone, which heats the oxidant and re-cools the second heat transfer zone,
• (iii) conducting the heated oxidant to the reaction zone and combusting in the reaction zone at least a portion of the heated oxidant with at least a portion of the fuel under combustion conditions, which re-heats the reaction zone and produces a combustion product,
• (iv) transferring heat from the combustion product to the reactor in the first heat transfer zone, which re-heats the first heat transfer zone and cools the combustion product, and
• (v) conducting the cooled combustion product away from the reactor via the first opening, wherein the combustion product has a bulk gas temperature of ≤600° C. proximate to the first opening at the start of tH;
• and then
• (e) repeating step (c) and (d), wherein one or more of tp, the pyrolysis conditions, tH, and the combustion conditions is pre-selected to achieve an approach temperature proximate to the first opening (“ΔTa1”) that is ≤50° C. at the start of tp and a second approach temperature proximate to the second opening (“ΔTa2”) that is ≤125° C. at the start of tH.

A hydrocarbon pyrolysis process, the process comprising:

• (a) providing a feed comprising C2+ hydrocarbon;
• (b) providing an elongated reverse-flow thermal pyrolysis reactor having (i) an internal volume which includes at least a first heat transfer zone, a second heat transfer zone opposed to the first heat transfer zone, and a reaction zone located between the first and second heat transfer zone and (ii) opposed first and second openings in fluidic communication with the internal volume, wherein the first and second openings are separated by a reactor length (LR);
• (c) providing a pre-heated first thermal mass, at least a segment of which is located in the first heat transfer zone, wherein (i) the thermal mass includes first and second apertures and at least one internal channel, (ii) the first and second apertures are in fluidic communication with the channel, and are separated by a flow-path of length L1 through the channel, (iii) L1 is in the range of from 0.1 * LR to 0.9 * LR, and (iv) the first opening is proximate to the first aperture;
• (d) providing a precooled second thermal mass, at least a segment of which is located in the second heat transfer zone, wherein (i) the thermal mass includes first and second apertures and at least one internal channel, (ii) the first and second apertures are in fluidic communication with the channel, and are separated by a flow-path of length L2 through the channel, (iii) L2 is in the range of from 0.1 * LR to 0.9 * LR, and (iv) the second opening is proximate to the second aperture;
• (e) establishing a flow of the feed in the channel toward the second aperture during a time interval tp by introducing the feed through the first opening and through the first aperture;
• (f) transferring heat from the heated thermal mass to the feed in at least the first heat transfer zone, the heat transfer occurring at least in the channel;
• (g) pyrolysing in the reaction zone at least a portion of the heated feed's C2+ hydrocarbon under pyrolysis conditions to produce a pyrolysis product, wherein the pyrolysis product comprises coke, molecular hydrogen, ethylene and propylene, and wherein the pyrolysis conditions include:
• (i) a first bulk gas temperature profile at the start of the pyrolysis which increases substantially monotonically from a first temperature (T1) proximate to the first aperture to a second temperature (T2) proximate to the second aperture, wherein T1 is ≥250° C. and T2 is in the range of from 800° C. to 1400° C.;
• (ii) an approach temperature proximate to the first aperture (ΔTa1) which at the start of the pyrolysis is ≤50° C.;
• and
• (iii) a peak gas temperature (Tp) within the reactor, wherein Tp is located in the reaction zone;
• (h) conducting a flow of the pyrolysis product through the channel of the second thermal mass toward the second aperture of the second thermal mass, and transferring heat from the pyrolysis product to the second thermal mass which
• (i) heats the second thermal mass,
• (ii) deposits at least portion of the coke in the channel of the second thermal mass, and
• (iii) produces a process gas comprising at least a portion of the pyrolysis product's molecular hydrogen, ethylene, and propylene, and
• (i) conducting the process gas out of the second aperture of the second thermal mass, out of the second opening, and away from the flow-through reactor, the process gas having a bulk gas temperature of ≤600° C. proximate to the second aperture of the second thermal mass at the start of the pyrolysis.