Method and system for steamcracking

1 . A method of steam cracking, comprising:

providing a steam cracking arrangement including:

an electric cracking furnace without a convection zone; and

a quench cooling train;

forming a feed stream from feed hydrocarbons and process steam;

supplying at least a part of the feed stream to the electric cracking furnace;

withdrawing a cracked gas stream from the electric cracking furnace; and

passing at least a part of the cracked gas stream through the quench cooling train;

wherein the quench cooling train is operated in at least two distinct cooling steps arranged in either order, wherein:

in a first one of the cooling steps at least a part of the cracked gas stream is cooled against vaporizing boiler feed water at an absolute pressure level between 30 and 175 bar; and

in a second one of the cooling steps at least a part of the cracked gas stream is cooled against at least a part of the feed stream which is thereby heated to a temperature level between 35° and 750° C.; and

wherein the method further comprises producing saturated steam in at least one of the first one of the cooling steps and the second one of the cooling steps of the quench cooling train, and indirectly heating at least one of the feed stream or a part thereof, the feed hydrocarbons or a part thereof, boiler feed water or a part thereof, and dilution steam or a part thereof using at least a part of the saturated steam, thereby condensing said saturated steam.

2 . The method according to claim 1 , wherein, a heat amount of not more than 1000 kW is transferred in the electric cracking furnace as sensible heat to streams other than the feed stream or the cracked gas stream.

3 . The method according to claim 2 , wherein the quench cooling train includes a primary quench exchanger and a secondary quench exchanger, wherein the primary quench exchanger performs at least a part of the first one of the cooling steps and the secondary quench exchanger performs at least a part of the second one of the cooling steps or vice versa.

4 . The method according to claim 3 , further comprising:

providing a steam generation arrangement operated in thermal association with the steam cracking arrangement; and

using the steam generation arrangement to produce at least superheated high pressure steam at a first pressure level of 30 and 175 bar absolute pressure and at a first temperature level;

wherein:

no steam at a higher temperature level than the first temperature level is generated;

the superheated high pressure steam at the first pressure level is at least in part adiabatically and is enthalpically expanded to a second pressure level below the first pressure level such that its temperature level is lowered to a second temperature level; and

the first temperature level is selected such that the second temperature level is between 5 and 120 K above a dew point of steam at the second pressure level.

5 . The method according to claim 4 , wherein the steam generation arrangement comprises:

a multi-flow heat exchanger in which heat is transferred from the cracked gas stream or a part thereof to boiler feed water and/or to a steam stream used in forming the superheated high pressure steam; and/or

an electric steam superheater.

6 . The method according to claim 3 , wherein at least a part of the feed hydrocarbons used in forming the feed stream are preheated using at least a part of the cracked gas stream in a multi-flow heat exchanger.

7 . The method according to claim 5 , wherein the quench cooling train comprises a further secondary quench exchanger and/or a tertiary quench exchanger, the further secondary quench exchanger and/or the tertiary quench exchanger being provided as the multi-flow heat exchanger.

8 . The method according to claim 4 , wherein the superheated high pressure steam at the first pressure level and at the first temperature level does not include steam generated from process water and/or only includes steam generated from boiler feed water, such that the superheated high pressure steam at the first pressure level and at the first temperature level is provided as high-purity superheated high pressure steam.

9 . The method according to claim 1 , wherein the steam cracking arrangement is operated in different operating modes, using differing electric power consumption rates, while maintaining a constant total cracking product yield.

10 . The method according to claim 1 , wherein at one of the feed stream or a part thereof, the feed hydrocarbons or a part thereof, dilution steam or a part thereof, and boiler feed water or a part thereof is preheated using a saturated or subcooled condensate water stream.

11 . The method according to claim 1 , wherein the quench cooling train includes a primary quench exchanger and a secondary quench exchanger, wherein the primary quench exchanger performs at least a part of the first one of the cooling steps and the secondary quench exchanger performs at least a part of the second one of the cooling steps or vice versa.

12 . The method according to claim 11 , further comprising:

providing a steam generation arrangement operated in thermal association with the steam cracking arrangement; and

using the steam generation arrangement to produce at least superheated high pressure steam at a first pressure level of 30 and 175 bar absolute pressure and at a first temperature level;

wherein:

no steam at a higher temperature level than the first temperature level is generated;

the superheated high pressure steam at the first pressure level is at least in part adiabatically and is enthalpically expanded to a second pressure level below the first pressure level such that its temperature level is lowered to a second temperature level; and

the first temperature level is selected such that the second temperature level is between 5 and 120 K above a dew point of steam at the second pressure level.

13 . The method according to claim 11 , wherein the steam generation arrangement comprises:

a multi-flow heat exchanger in which heat is transferred from the cracked gas stream to boiler feed water and/or to a steam stream used in forming the superheated high pressure steam; and/or

an electric steam superheater.

14 . The method according to claim 11 , wherein at least a part of the feed hydrocarbons used in forming the feed stream are preheated using at least a part of the cracked gas stream in a multi-flow heat exchanger.

15 . The method according to claim 13 , wherein the quench cooling train comprises a further secondary quench exchanger and/or a tertiary quench exchanger, the further secondary quench exchanger and/or the tertiary quench exchanger being provided as the multi-flow heat exchanger.

16 . The method according to claim 14 , wherein the quench cooling train comprises a further secondary quench exchanger and/or a tertiary quench exchanger, the further secondary quench exchanger and/or the tertiary quench exchanger being provided as the multi-flow heat exchanger.

17 . The method according to claim 12 , wherein the superheated high pressure steam at the first pressure level and at the first temperature level does not include steam generated from process water and/or only includes steam generated from boiler feed water, such that the superheated high pressure steam at the first pressure level and at the first temperature level is provided as high-purity superheated high pressure steam.

18 . The method according to claim 1 , wherein the steam cracking arrangement comprises a plurality of steam cracking arrangements, at least one steam cracking arrangement of the plurality of steam cracking arrangements being-operated, in different operating modes, using differing electric power consumption rates, while maintaining a constant total cracking product yield.

19 . A system for performing a method of steam cracking, comprising:

a steam cracking arrangement, including:

an electric cracking furnace without a convection zone; and

a quench cooling train;

wherein:

the system is configured to;

supply at least a part of the feed stream to the electric cracking furnace;

withdraw a cracked gas stream from the electric cracking furnace; and

pass at least a part of the cracked gas stream through the quench cooling train;

the quench cooling train comprises means to perform at least two distinct cooling steps, wherein:

a first one of the cooling steps is adapted to cool at least a part of the cracked gas stream against vaporizing boiler feed water at an absolute pressure level between 30 and 175 bar; and

a second one of the cooling steps is adapted to cool at least a part of the cracked gas stream withdrawn from the electric cracking furnace against at least a part of the feed stream which is thereby heated to a temperature level between 35° and 750° C.; and

the system is further configured to produce saturated steam in at least one of the first one of the cooling steps and the second one of the cooling steps of the quench cooling train, and indirectly heating at least one of the feed stream or a part thereof, the feed hydrocarbons or a part thereof, dilution steam or a part thereof, and boiler feed water or a part thereof using at least a part of the saturated steam, thereby condensing said saturated steam.