METHOD AND INSTALLATION FOR THE PRODUCTION OF HYDROCARBONS

Abstract

A process is disclosed for the production of hydrocarbons with removal of coke from a product stream. In a first mode, hydrocarbons and steam are subjected to steam cracking to obtain a cracked gas. The removal of coke from the steam is performed using a coke trap thus obtaining a coke-depleted cracking gas which is subjected to quench heat exchange in the first mode downstream of the coke trap, effecting cooling. Product stream is formed in the first operating mode using the cracked gas cooled in the quench heat exchange. The coke trap is emptied in a second mode using a stream extracted from a cracking furnace, bypassing the quench heat exchange, to obtain a coke stream. The coke stream in the second mode is passed to a coke collector.

Claims

1. A process for the production of hydrocarbons with removal of coke from a product stream containing the hydrocarbons and steam, wherein in a first operating mode a feed fluid containing hydrocarbons and steam is subjected to steam cracking to obtain a cracked gas, wherein the removal of coke downstream of the steam cracking in the first mode of operation is performed using a coke trap and obtaining a coke-depleted cracking gas, wherein the coke-depleted cracked gas is subjected to quench heat exchange in the first operating mode downstream of the coke trap, effecting cooling, and wherein the product stream is formed in the first operating mode using the cracked gas cooled in the quench heat exchange, wherein the cracked gas, downstream from the steam cracking, is sent via a conduit in a first direction, around a bend and is sent in a second direction downstream of the bend, wherein an inlet of the coke trap is arranged downstream of the bend in the first direction and a fluid connection from the conduit to the inlet starts from the bend, wherein the first direction is a direction deviating from the vertical direction, and wherein the coke trap is emptied in a second operating mode using an extraction stream extracted from a cracking furnace used for said steam cracking, bypassing the quench heat exchange, to obtain a coke stream, the coke stream in the second operating mode being passed to a coke collection.

2. The process according to claim 1, wherein the withdrawal stream is passed through the coke trap in the second operating mode, the withdrawal stream thereby being enriched with the coke retained in the coke trap, wherein the coke stream is formed from the withdrawal stream and the coke retained in the coke trap and is passed to the coke collection.

3. The process according to claim 1, wherein a steam cracking plant with the cracking furnace, a quench heat exchanger, the coke trap and a coke collecting device is used, wherein the coke trap has an inlet and an outlet, wherein the inlet is arranged downstream of the cracking furnace and upstream of the quench heat exchanger and is fluidly connected to a conduit carrying the cracked gas and the withdrawal stream, the outlet is fluidly connected to the coke collection device, bypassing the quench heat exchanger, and the coke trap is adapted to retain coke particles from the withdrawal stream in a first operating mode and in a second operating mode, to eject the coke in the direction of the coke collecting device using the withdrawal stream and obtaining a coke stream, and wherein the quench heat exchanger is adapted to cool down the withdrawal stream.

4. The method according to claim 3, wherein the steam cracking plant used comprises downstream of the quench heat exchanger a further coke trap, the outlet of which having a fluid connection to the coke collection device.

5. The method according to claim 4, wherein in the steam cracking plant used the connection of the coke trap to the coke collecting device upstream of the coke collecting device opens at a shallow angle, in particular in the range of 40° to 50° into the connection of the further coke trap to the coke collecting device.

6. The method according to claim 3, wherein in the steam cracking plant used the coke collection device comprises one or more of a cyclone, a fire box and a flow brake.

7. The method according to claim 3, wherein the steam cracking plant used further comprises one or more of the group of a steam generator, a feed mixer, a reaction vessel, a cracked gas cooler and a primary quench heat exchanger, in particular wherein the primary quench heat exchanger is arranged downstream of the cracking furnace and upstream of the coke trap.

8. The method according to claim 3, wherein in the steam cracking plant the conduit carrying the withdrawal stream runs from the cracking furnace in a first direction, has a bend, and runs downstream of the bend in a second direction.

9. The method according to claim 8, wherein in the steam cracking plant used the inlet of the coke trap is located downstream of the bend in the first direction and the fluid connection of the inlet to the line starts from the bend.

10. The method according to claim 8, in which the first direction is a direction deviating from the vertical direction.

11. The method according to claim 3, wherein in the steam cracking plant used in the first and the second direction encloses an angle in the range of 30° to 120°.

12. A steam cracking plant for the production of hydrocarbons comprising a cracking furnace, a quench heat exchanger, a coke trap and a coke collection device, wherein the coke trap has an inlet and an outlet, wherein the inlet is arranged downstream of the cracking furnace and upstream of the quench heat exchanger and is fluid-connected to a conduit carrying a withdrawal stream generated in the cracking furnace from a feed fluid containing hydrocarbons and/or steam, the outlet is fluid-connected to the coke collecting device, bypassing the quench heat exchanger, and the coke trap is adapted to retain coke particles from the extraction stream in a first operating mode, wherein the coke trap is adapted to eject the coke particles in a second operating mode in the direction of the coke collecting device using the withdrawal stream and obtaining a coke stream, wherein a conduit carrying the withdrawal stream runs from the cracking furnace in a first direction, has a bend and runs downstream of the bend in a second direction. wherein the inlet of the coke trap is arranged downstream of the bend in the first direction and the fluid connection of the inlet to the conduit starts from the bend, and wherein the first direction is a direction deviating from the vertical direction.

13. The method according to claim 11, wherein in the steam cracking plant used in the first and the second direction encloses an angle in the range of 80° to 100°.

14. The method according to claim 13, wherein in the steam cracking plant used the first and the second direction encloses an angle of about 90°.

15. The method according to claim 5, wherein in the steam cracking plant used the connection of the coke trap to the coke collecting device upstream of the coke collecting device opens at a shallow angle of about 45° into the connection of the further coke trap to the coke collecting device.

Description

DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 shows an advantageous embodiment of a plant in the form of a schematic block diagram.

[0035] FIG. 2 shows another advantageous embodiment of a plant in a schematic representation.

DETAILED DESCRIPTION

[0036] In the Figures, structurally or functionally corresponding elements are indicated with identical reference signs and are not repeatedly explained, just for the sake of clarity.

[0037] The steam cracking plant 100 as shown in FIG. 1 comprises a cracking furnace 10, a coke trap 20, a quench heat exchanger 30 and a coke collector 40.

[0038] One or more feed fluids 1, of which at least one contains hydrocarbons and at least one contains water molecules, are fed into the cracking furnace 10. In the cracking furnace, the hydrocarbons react at least partially with the water molecules to form a cracked gas 2, which typically contains coke particles in addition to low-molecular hydrocarbon compounds. The cracked gas 2 is discharged from the cracking furnace 10 as the withdrawal stream 2 and passes through the coke trap 20. For example, the conduit carrying the withdrawal stream 2 can have a bend of 30° to 120°, for example essentially 90°, immediately upstream of the coke trap 20, so that the withdrawal stream 2 is guided in the conduit towards the coke trap 20 before the bend, but directly away from the coke trap 20 after the bend. The coke trap 20 has an inlet in the direction of the cracking furnace 10 which is open to fluids in relation to the conduit, i.e. it is in fluid connection with the conduit which carries the withdrawal stream 2 out of the cracking furnace 10. Due to the higher inertia of the coke particles compared to the gaseous molecules, especially the low-molecular hydrocarbon compounds, of the withdrawal stream 2, the coke particles move largely linearly into the inlet of the coke trap, while the gaseous components of the stream, especially the low-molecular hydrocarbon compounds, follow the bend preferentially. As a result, the withdrawal stream is depleted of coke in the bend of the pipeline before it is further directed towards quench heat exchanger 30. Coke is initially retained in the coke trap 20.

[0039] The cracked gas or the withdrawal stream is cooled in the quench heat exchanger 30, for example against the one or more feed fluids 1, and withdrawn from the system 100 as product stream 5 via a product valve 35.

[0040] At certain times the coke trap 20 is emptied. For this purpose, a control valve 25, which closes an outlet of the coke trap 20 at an end facing away from the cracking furnace 10, is opened. At the same time, the product valve 35, for example, can be closed completely or partially and/or a pressure of the withdrawal stream can be increased to increase a flow through the coke trap 20. The outlet of the coke trap 20 is in fluid communication with the coke collecting device 40, as described above. As a result, the withdrawal stream 2 flows through the coke trap 20 and, especially due to turbulence, strongly enriches itself with the coke retained therein. In this way, a coke-rich stream 4 is formed from the withdrawal stream 2 and the coke retained in the coke trap 20, which is led to the coke collecting device 40. At the end of an emptying period, the control valve 25 is closed again and, if necessary, the product valve 35 is opened again and/or the pressure of the withdrawal stream is reduced again.

[0041] In particular, it may be provided that the cracking furnace 10 is basically operated at a pressure level which corresponds to the natural atmospheric pressure and that the withdrawal stream 2 is compressed to a pressure level in the range between 1.2 and 2.5 times the natural atmospheric pressure when the pressure is increased. For this purpose, for example, the pressure in the cracking furnace 10 itself can be increased or the withdrawal stream 2 leaving the cracking furnace 10 can be subjected to compression downstream of the cracking furnace 10.

[0042] The points in time at which the coke trap is emptied in the described manner can, for example, be selected at regular, especially predetermined, intervals. In certain configurations of the disclosed embodiments, it may also be provided that the points of time are selected depending on a degree of filling of the coke trap 20 or a quality parameter of the withdrawal stream 3 depleted of coke, for example in a regulated or controlled manner. For this purpose, sensors in or at the coke trap can be provided, for example, which monitor the degree of filling. For example, these can be light barriers that monitor a visual path through the coke trap 20 and define an upper threshold value of the filling level as exceeded if the visual path is blocked. Another possibility to determine the filling degree of the coke trap 20 can be a scale in the area of the geodetic bottom of the coke trap 20, which defines the upper threshold value of the filling degree as exceeded when the mass of the trap is predetermined. To monitor the quality parameter of the coke-poor withdrawal stream or cracked gas 3, for example, sensors are conceivable which measure a turbidity of the gas of which the withdrawal stream 3 is composed. If a predetermined threshold turbidity is exceeded, this indicates that not enough coke particles are retained in the coke trap 20, so that it is necessary to empty the coke trap 20 in order to increase its capacity and effectiveness again. This should be seen as a purely exemplary list of possible monitoring techniques, although other suitable parameters can also be monitored to determine a reasonable time for emptying coke trap 20. This means that the emptying of coke trap 20 is only carried out when it is actually necessary, which is economically advantageous.

[0043] Especially in case of direct monitoring of the filling level of coke trap 20, the emptying time can also be adjusted, especially in a controlled or regulated manner. For this purpose e.g. a lower threshold value can be defined as being undercut if for example a predetermined mass is undercut or a second light barrier, which is positioned closer to the geodetic bottom of the coke trap 20 than the one described above, recognizes a visual path through the volume of the coke trap 20 as free. Thus, the emptying of the coke trap is carried out in a time as short as possible and as long as necessary, which has a positive effect on the overall efficiency and the yield of the plant 100.

[0044] The described periodic emptying of the coke trap 20 will advantageously reduce the total amount of coke contained in plant 100 compared to the prior of the art. This reduces the probability of the retained coke igniting or, in case of ignition, the fire load, which increases the plant safety.

[0045] The plant 200 shown in FIG. 2, in comparison to plant 100, has an additional coke trap 33, located downstream of the quench heat exchanger, with an associated additional control valve or decoking gas valve 37. The operating principle of this further coke trap 33 is identical to that of the coke trap 20. The separation of coke particles is again based on the higher inertia of the coke particles compared to the gaseous components of the withdrawal stream 3. The emptying of the further coke trap 33 is done in a similar way by opening the further control valve 37 and advantageously by closing the other valves 25, 35 of the plant 200 and preferably by increasing the pressure of the withdrawal stream or cracked gas 2, 3 at the same time. By separating further coke particles in the further coke trap 33, the purity of the product stream 5 can be further increased.

[0046] Advantageously, the coke streams 4 from the coke trap 20 and 6 from the further coke trap 33 are passed together into the coke collecting device 40. This allows an existing plant to be retrofitted with the coke trap 20 very easily without having to intervene significantly in the piping of the other plant components 30, 33, 40.

[0047] As shown in FIG. 2, it is particularly preferable to design the inlet of the coke stream 4 into the conduit of the coke stream 6 at a flat angle, especially an angle of about 45°. This reduces abrasion of the conduit wall, especially in relation to the point of introduction, so that this wall can be designed with less material. This in turn is particularly advantageous for retrofitting, since existing pipelines may not have been designed for such lateral feed and would otherwise have to be rebuilt. According to the embodiment described here, this is advantageously not necessary, so that existing pipelines can continue to be used or, in the case of a new construction of such a plant 200, conventionally dimensioned pipelines can be used. In addition, this non-vertical feed prevents the formation of a dynamic pressure, so that no or significantly fewer particles are deposited at the discharge point.

[0048] In alternative configurations of the plant according to the disclosed embodiments, it may also be provided that each coke trap 20, 33 has its own conduit from its respective outlet to the coke collecting device 40. Thus, when laying the respective conduits, it is not necessary to take into account the course of the other conduit, which facilitates the overall design of the plant. It can also be provided that for certain coke traps 20, 33 a common coke collecting device is provided, while other coke traps 20, 33 are assigned a dedicated coke collecting device 40. For example, it is conceivable that several plants 200 are operated in parallel and all coke traps 20 are emptied into a first coke collecting device 40, while all other coke traps 33 are emptied into a second coke collecting device 40. In this way, for example, a separation of the coke particles into different size fractions can be realized, since the flow velocities in front of the coke trap 20 and in front of the further coke trap 33 can differ and thus particles of different sizes can be retained in the respective coke traps 20, 33.

[0049] Regardless of the assignment to specific coke traps 20, 33, the coke collector 40 can be designed using a cyclone, a fire box and/or a flow brake. The functional principles of these components are only briefly outlined below for better understanding: the respective coke stream 4, 6 can be introduced into a cyclone, especially tangentially. The inert coke is thus separated from the less inert components of the coke stream in a radially outer area of the cyclone, in particular at a cylinder wall, or is slowed down there by friction and sinks to a bottom of the cyclone which is geodetically located at the bottom. From this bottom, the coke can be removed from the cyclone. In a fire box, coke particles of the coke stream 4, 6 are at least partially burned and/or sintered. This is particularly advantageous if the coke is not to be used as a by-product. The combustion heat can be taken from the fire box and used to operate the plant 100, 200, for example to preheat the feed fluid 1. A flow brake reduces the flow velocity of the coke flow 4, 6 and thus enables the usually denser coke particles to be separated from the other components of the coke flow 4, 6.

[0050] Especially in cases where the constituents of the coke stream 4, 6, especially gaseous components of the cracked gas in the withdrawal stream 2 used to form the coke stream 4, 6, are not chemically modified in the coke collector 40, it may be advantageous to return the gaseous constituents to the one or more feed fluids 1, the withdrawal stream 2, the low-coke withdrawal stream 3 or the product stream 5. This increases the overall yield and increases the efficiency of the plant 100, 200.

[0051] As explained at the beginning, it can also be advantageous, especially during emptying times, to provide a withdrawal stream that is low in cracked gas or free of it. Thus, measures for the separation and recirculation of the gaseous components of the coke stream can be omitted, which has a positive effect on the necessary investment costs.

[0052] In the design of plant 100 as shown in FIG. 1, the control valve 37 or a corresponding coke flow 6 may also be necessary or advantageous, although not explicitly illustrated, to maintain a regular decoking path, so that only the discharge system 40 can be installed separately or twice. This makes it possible to produce coke as a product (e.g. via dry coke extraction).