DEVICE FOR INJECTING AND MIXING A REACTIVE FLUID IN HIGH PRESSURE LDPE PROCESSES

Abstract

The invention relates to a device (100) for injecting and mixing a reactive fluid in a flow of a process fluid for the preparation of polyolefins, comprising: an annular part (101) having an outer wall and an inner wall (102), wherein the annular part (101) is arranged for having a flow of the process fluid in a transport direction (F); a support structure (103) connected to the inner wall (102) of the annular part (101); an injector part (104) mounted on the support structure (103), wherein the injector part (104) is cylindrically shaped and wherein the cylindrical axis A-A of the injector part is parallel with a central axis of the annular part and is in the central part of the annular part (101); wherein the injector part (104) comprises a nozzle (105) for injecting the reactive fluid, disposed at a downstream side of the injector part relative to the transport direction (F); a supply channel (106) extending from the outer wall of the annular part (101) through the support structure (103) to the nozzle (105) of the injector part (104), and wherein the annular part (101), the support structure (103) and the injector part (104) are made from a single piece of metal.

Claims

1. A device (100) for injecting and mixing a reactive fluid in a flow of a process fluid, comprising an annular part (101) having an outer wall and an inner wall (102), wherein the annular part (101) is arranged for having a flow of the process fluid in a transport direction (F); a support structure (103) connected to the inner wall (102) of the annular part (101); an injector part (104) mounted on the support structure (103), wherein the injector part (104) is cylindrically shaped and wherein the cylindrical axis A-A of the injector part is parallel with a central axis of the annular part and is in the central part of the annular part (101); wherein the injector part (104) comprises a nozzle (105) for injecting the reactive fluid, disposed at a downstream side of the injector part relative to the transport direction (F); a supply channel (106) extending from the outer wall of the annular part (101) through the support structure (103) to the nozzle (105) of the injector part (104).

2. The device (100) according to claim 1, wherein the annular part (101), the support structure (103) and the injector part (104) are made from a single piece of metal.

3. The device (100) according to claim 1, wherein the cylindrical axis A-A of the injector part (104) is located at a distance of 0 to D from the central axis of the annular part (101), where D is the inner diameter of the annular part (101).

4. The device (100) according to claim 3, wherein the cylindrical axis A-A of the injector part coincides with the central axis of the annular part (101).

5. The device (100) according to claim 1, wherein the support structure (103) has a fin shape.

6. The device (100) according to claim 5, wherein the fin shaped support structure (103) and the injector part (104) have a common wedge shaped upstream front (301).

7. The device (100) according to claim 5, wherein the fin shaped support structure (103) has a wedge shaped downstream front (107).

8. The device (100) according to claim 5, wherein the fin shaped support structure (103) has a rounded base (302) where the fin shaped support structure (103) is connected to the annular part (101).

9. The device (100) according to claim 1, wherein the nozzle (105) is formed as a tapered extension (108) of the injector part (104), having the nozzle opening in the center of the tapered extension (108).

10. The device (100) according to claim 9, wherein the tapered extension has a taper angle in a range of 15-60.

11. A lens ring gasket or a cone ring gasket comprising the device (100) according to claim 1.

12. A reactor system comprising the device according to claim 1, wherein a reactive fluid is to be injected and mixed with a flow of a process fluid in the device.

13. A process for the preparation of a homopolymer or a copolymer of ethylene and a comonomer copolymerizable therewith in the reactor system according to claim 12, wherein the process fluid comprises ethylene and the reactive fluid is selected from the group consisting of the comonomer, an initiator, an inhibitor, a scavenger and a chain regulator.

14. The device (100) according to claim 1, wherein the annular part (101), the support structure (103) and the injector part (104) are made from a single piece of metal; wherein the cylindrical axis A-A of the injector part (104) is located at a distance of 0 to D from the central axis of the annular part (101), where D is the inner diameter of the annular part (101); wherein the support structure (103) has a fin shape, wherein the fin shaped support structure (103) and the injector part (104) have a common wedge shaped upstream front (301), wherein the fin shaped support structure (103) has a wedge shaped downstream front (107), wherein the fin shaped support structure (103) has a rounded base (302) where the fin shaped support structure (103) is connected to the annular part (101); wherein the nozzle (105) is formed as a tapered extension (108) of the injector part (104), having the nozzle opening in the center of the tapered extension (108); and wherein the tapered extension has a taper angle in a range of 15-60

15. The device (100) according to claim 1, wherein the support structure (103) has a fin shape, wherein the fin shaped support structure (103) and the injector part (104) have a common wedge shaped upstream front (301), wherein the fin shaped support structure (103) has a wedge shaped downstream front (107), wherein the fin shaped support structure (103) has a rounded base (302) where the fin shaped support structure (103) is connected to the annular part (101).

16. The device (100) according to claim 3, wherein the cylindrical axis A-A of the injector part coincides with the central axis of the annular part (101).

17. The device (100) according to claim 9, wherein the tapered extension has a taper angle in a range of 25-35.

Description

[0041] The invention is now elucidated by way of the following embodiments and examples, without however being limited thereto.

[0042] FIGS. 1-2 illustrates an embodiment of the device according to the invention;

[0043] FIG. 3 shows the cross section of the embodiment of FIGS. 1-2.

[0044] In FIG. 1 an embodiment of a device 100 for injecting and mixing a reactive fluid in a flow of a process fluid is shown. The device 100 has an annular part 101. Within the annular part 101 an injector part 104 is provided connected to a support structure 103. The support structure 103 is preferably fin shaped and has wedge shaped front 107 in the downstream as well as in upstream direction relative to the flow direction F of the process fluid in the device 100. This wedge shape can prevent back mixing as well as streamline the flow. The injector part 104 has a cylindrical body which is shown aligned with a central axis A-A of the device 100. This central axis A-A may coincide with a central axis of the tubular polymerization reactor. Alternative alignments may be considered. The central axis A-A may also be located in a central region at a distance of 0 to of the diameter from the central axis of the annular part 104.

[0045] The support structure 103 and injector 104 have a supply channel (301, see FIG. 3) which is arranged to supply the reactive fluid to the nozzle 105. The nozzle 105 has a tapered end 108 extending from the injector body.

[0046] In FIG. 2 the device 100 is shown with a wedge shaped front 201 facing upstream. The upstream front of the injector part 104 and support structure 103 have a common front. As shown in FIG. 2, the support structure 103 is preferably connected to the inner wall 102 of the annular part 101 with a rounded base 202.

[0047] The device 100 is preferably manufactured as a single metal part by machining.

[0048] In FIG. 3 a cross section is shown of the device 100 having the injector part 104 aligned with the central axis A-A of the device. A supply channel 301 is shown as a passage through the annular part 101 and the support structure 103, leading to the nozzle 105 of the injector part 104.

[0049] In FIG. 3 a taper angle a is shown for tapered end 108 of the injector part 104, between the surface of the tapered end 108 and the central axis A-A. Various taper angles a may be considered.

[0050] Computer simulation was performed in order to determine the effect of the shape and the position of the injector on mixing and distribution of a reactive fluid in a turbulent flow of a process fluid. In the simulations, a process flow is flowing through a pipe having an inner diameter of 59 mm and a liquid is injected into the pipe. The flow rate ratio between the process flow and the liquid is more than 100. The process flow is a highly turbulent flow before and after the injection of the liquid.

[0051] The flow pattern of the liquid in the flow was visualized, which provided insights on the degree of back mixing. Further, the level of mixing was estimated by the calculation of coefficient of variation (CoV), which is a statistical measure of radial homogeneity. The location at which CoV=0.05 (a common industrial benchmark for good mixing, corresponding to 95% homogeneity) was calculated.

COMPARATIVE EXAMPLE 1

[0052] The reactive fluid is injected from a small-diameter nozzle protruding from the inner wall towards the center of the pipe. The outlet of the nozzle has a circular cross section and was located at 10 mm from the inner wall.

[0053] CoV=0.05 was achieved at 7.1 m, which represents a relatively poor mixing performance. Back mixing was observed.

COMPARATIVE EXAMPLE 2

[0054] The reactive fluid is injected from a small-diameter nozzle protruding from the inner wall towards the center of the pipe. The outlet of the nozzle has a circular cross section and was located at the center of the pipe.

[0055] CoV=0.05 was achieved at 4.0 m, which represents a better mixing performance. Back mixing was reduced but still observed.

COMPARATIVE EXAMPLE 3

[0056] The reactive fluid is injected from a small-diameter nozzle protruding from the inner wall towards the center of the pipe. The outlet of the nozzle has a 45 cut facing downstream and was located at the center of the pipe.

[0057] The results were similar to Comparative Example 2, showing that the 45 cut has little influence under these conditions.

EXAMPLE 4

[0058] The reactive fluid is injected by the device as illustrated in FIGS. 1-3.

[0059] CoV=0.05 was achieved at 2.6 m, which represents a very good mixing performance. No back mixing was observed.