Polymerization plant having parallel cooling channels in a recycle connection

Abstract

The present disclosure relates to a plant for performing polymerization, such as the polymerization of ethylene, having a recycle connection with two or more cooling channels arranged in parallel, a process for polymerization and downstream processes, and a plant for polymerization, comprising the following plant components in fluid communication: a) A reactor with an inlet side and an outlet side; b) A recycle connection positioned in fluid communication between the outlet side of the reactor and the inlet side of the reactor; wherein the recycle connection comprises two or more cooling channels arranged in parallel.

Claims

1. A plant for performing polymerization, comprising the following plant components in fluid communication: a) a reactor with an inlet side and an outlet side; and b) a recycle connection positioned in fluid communication between the outlet side of the reactor and the inlet side of the reactor; wherein the recycle connection comprises two or more cooling channels arranged in parallel wherein the reactor is a tubular reactor or an autoclave reactor.

2. The plant of claim 1, wherein the recycle connection comprises a bundle cooler comprising two or more cooling channels.

3. The plant of claim 1, wherein the recycle connection comprises two or more bundle coolers arranged in parallel, each comprising two or more cooling channels.

4. The plant of claim 1, wherein at least one of the cooling channels is arranged vertically.

5. A process for the preparation of a polymer by polymerizing ethylene at a pressure from about 100 MPa to about 400 MPa in a plant according to claim 1.

6. The process of claim 5, wherein the process is a continuous process.

7. The process of claim 5, wherein there is a pressure drop across the recycle connection, and wherein the pressure drop across the recycle connection is less than about 20 MPa.

8. The process of claim 5, wherein a fluid to be cooled is flowing one or more of the cooling channels, and wherein the speed of fluid to be cooled flowing in one or more of the cooling channels is less than about 10 m/s.

9. The process of claim 5, wherein the ethylene is comprised in a fluid, comprising the following step: a) a first portion of the fluid flows through a subset A, consisting of one or more of the cooling channels, with a mass flow rate , and a second portion of the fluid flows through a subset B, consisting of one or more of the cooling channels not belonging to subset A, with a mass flow rate , wherein is at least twice ; wherein the mass flow rates and are in terms of the mass flowing through respective cooling channels per second, expressed in kg.Math.s.sup.1.

10. The process of claim 9, wherein, in step a), the mass flow rate of coolant supplied to the subset A is higher than the mass flow rate of coolant supplied to the subset B by at least about 10%, based on the mass flow rate of coolant supplied to the subset B, wherein mass flow rate is in terms of the mass of coolant flowing per second, expressed in kg.Math.s.sup.1.

11. The process of claim 9, wherein, in step a), the temperature of the coolant supplied to the subset B is higher than the temperature of coolant supplied to subset A by at least about 5 K.

12. The process of claim 9, further comprising the following step: b) a first portion of the fluid flows through the subset A of the cooling channels with a mass flow rate , and a second portion of the fluid flows through the subset B of the cooling channels with a mass flow rate , wherein is at least twice ; wherein mass flow rates and are in terms of the mass flowing through the respective cooling channels per second, expressed in kg.Math.s.sup.1.

13. A process for the preparation of a downstream product comprising the following preparation steps: a) the preparation of a polymer by the process of claim 5; b) further treatment of the polymer to obtain the downstream product.

14. The process of claim 13, wherein the polymer or downstream product is converted into a shaped body.

15. A process for the preparation of a polymer by polymerizing ethylene at a pressure from about 100 MPa to about 400 MPa in a plant comprising the following plant components in fluid communication: a) a reactor with an inlet side and an outlet side; and b) a recycle connection positioned in fluid communication between the outlet side of the reactor and the inlet side of the reactor; wherein the recycle connection comprises two or more cooling channels arranged in parallel; wherein the recycle connection comprises two or more bundle coolers arranged in parallel, each comprising two or more cooling channels wherein the reactor is a tubular reactor or an autoclave reactor.

16. The process of claim 15, wherein at least one of the cooling channels is arranged vertically.

17. The process of claim 15, wherein the ethylene is comprised in a fluid and a first portion of the fluid flows through a subset A, consisting of one or more of the cooling channels, with a mass flow rate , and a second portion of the fluid flows through a subset B, consisting of one or more of the cooling channels not belonging to subset A, with a mass flow rate , wherein is at least twice ; wherein the mass flow rates and are in terms of the mass flowing through respective cooling channels per second, expressed in kg.Math.s.sup.1.

18. The process of claim 17, wherein the mass flow rate of coolant supplied to the subset A is higher than the mass flow rate of coolant supplied to the subset B by at least about 10%, based on the mass flow rate of coolant supplied to the subset B, wherein mass flow rate is in terms of the mass of coolant flowing per second, expressed in kg.Math.s.sup.1.

19. The process of claim 17, wherein the temperature of the coolant supplied to the subset B is higher than the temperature of coolant supplied to subset A by at least about 5 K.

Description

DESCRIPTION OF THE FIGURES

(1) The disclosure is now explained by means of figures which are intended for illustration only and are not to be considered as limiting the scope of the disclosure. In brief, the figures show the following:

(2) FIG. 1 shows embodiments of a plant according to the present disclosure.

(3) FIG. 2 shows schematically the layout of an embodiment of a plant according to the present disclosure.

(4) FIG. 3 shows schematically the layout of a group of coolers.

(5) FIG. 4 shows schematically an embodiment for a bundle cooler.

(6) FIG. 1 shows schematically the general function of a plant 101 according to the present disclosure. Ethylene and optionally other reactants, such as copolymers and/or modifiers, enter the plant. Optionally, other species such as initiators enter the plant. A product, such as a polymer, exits the plant, for example in the form of solid pellets.

(7) FIG. 2 shows schematically the layout of a plant 200 according to the present disclosure. Polymerization is carried out in a reactor 4, such as a tubular reactor. Ethylene and optionally other comonomers and/or modifiers are introduced via a primary compressor 1, passing subsequently into a secondary compressor 2, through a heater 3 and into the inlet 21 of the reactor 4. Subsequent to the reactor 4, fluid passes from the outlet 22 of the reactor 4 through a high pressure let down 6, through a cooler 7 and into a high pressure separator 8. Higher density products from the high pressure separator 8 pass through a pressure let down 23 to a low pressure separator 9. Higher density products from the low pressure separator 9 pass to a pelletizer 10 which outputs solid pellets of product. A high pressure recycle 11 provides a fluid connection between the outlet side 22 of the reactor and the inlet side 21 of the reactor 4. The inlet of the high pressure recycle 11 is in fluid connection with one outlet of the high pressure separator 8 and the outlet of the high pressure recycle is in fluid connection with the inlet side of the secondary compressor 2. The high pressure recycle comprises one or more cooling channels 12 & 12, and one or more separators 13. Two components 12 and 12 have been shown on the diagram in order to make explicit the fact that there are two or more cooling channels. According to the present disclosure, the high pressure recycle comprises two or more cooling channels arranged in parallel. These cooling channels may be grouped into one or more coolers, such as one or more bundle coolers, or two or more bundle coolers. A low pressure recycle 14 also provides a fluid connection between the outlet side of the reactor and the inlet side of the reactor 4. The low pressure recycle comprises one or more coolers 17, 15, and one or more separators 18, 16. Arrows indicate directions of fluid flow for which the plant is designed.

(8) FIG. 3 shows schematically the layout of a group of coolers 300, for example in a recycle connection, or in a high pressure recycle connection. The group of coolers are arranged as follows, ordered in the direction of intended fluid flow: First, a single cooler 301a. Then two parallel paths, one comprising cooler 301b and cooler 301c arranged in series, the other comprising 301d and 301e arranged in series. Each of the coolers 301a-301e comprises one or more cooling channels, such as two or more cooling channels, for example arranged as a bundle cooler. This schematic representation does not express the orientation of the constituent parts relative to vertical. The flow through the coolers of the fluid to be cooled may be downward. The present disclosure is not restricted to such an arrangement. This figure merely shows one embodiment of the configuration.

(9) FIG. 4 shows schematically the layout of a bundle cooler 400. The bundle cooler comprises an entry chamber 403 into which fluid to be cooled enters prior to the parallel cooling channels 404. The cooling channels 404 are each connected to the entry chamber 403. In this embodiment, all of the cooling channels 404 are cooled by a common coolant 401. The contiguous nature of the volume of common coolant 401 is not apparent from the two-dimensional figure. The cooling channels 404 could alternatively be cooled by two or more coolants. The cooling channels 404 are all connected to a common exit chamber 402 from which the cooled fluid exits. A exit for waxy residue is provided at the bottom of the cooler and a further exit is provided for the cooled gas stream. This two-dimensional cross section does not demonstrate an arrangement of the cooling channels 404 which has one or more layers of cooling channels 404 parallel to the displayed layer of channels 404.

Test Methods

(10) Density

(11) Density is the polymer density in accordance with standard DIN EN ISO 1183-1:2004, method A (immersion).

(12) Melt Flow Rate (MFR)

(13) The melt flow rate (MFR) was determined according to DIN EN ISO 1133:2005, procedure B, condition D at a temperature of 190 C. under a load of 2.16 kg.

EXAMPLES

Example 1

(14) A polymerization reaction was carried out in a plant according to FIGS. 2. 12 and 12 each are two bundle coolers having 168 cylindrical steel tubes, with each tube having an internal diameter of 12 mm, a length of 11 m for the first cooler second cooler, and cooled with water at a temperature of 37 C. 4 is a tubular reactor comprising a cylindrical steel tube 1.0 km long, folded into 10 m sections, having an internal diameter of 40 mm, and cooled by water at a temperature of 170 C. The average output of polymer (MFR=0.26 g/10 min, density=0.927 g/cm.sup.3) and the electrical energy consumption per ton of polymer was measured for a period of 8 hours during normal operation and is given in Table 1. During that time, the suction and discharge conditions of the compressors remained constant.

(15) Over an extended period of operation, wax build up in the bundle coolers was removed by alternating the bundle coolers 12 and 12 in anti-phase between a normal/cooling mode and a cleaning/dewaxing mode. In normal/cooling mode, fluid flowed through the cooling channels of the bundle cooler with a speed of 1.5 to 2 m/s, and the cooling channels were supplied with coolant at a temperature of 37 C. In cleaning/dewaxing mode, fluid flowed through the cooling channels of the bundle cooler with a speed of 0.1 m/s, and the cooling jacket of the bundle cooler was supplied with coolant at a temperature of 140 C.

(16) For one year, no plant shut down for dewaxing was required.

Comparative Example

(17) A polymerization reaction was carried out in a plant according to FIG. 2, except that in place of the coolers 12 and 12, a single cooling channel of steel, with steel thickness of 16 mm, a tube length of 915 m, and cooled by water at a temperature of 20 C., was employed. Fluid passed through the cooling channel with a speed of 4.5 m/s. The average output of polymer (MFR=0.29 g/10 min, density 0.927 g/cm.sup.3) and the electrical energy consumption per ton of polymer was measured for a period of 8 hours during normal operation and is given in Table 1. During that time, the suction and discharge conditions of the compressors remained constant.

(18) Over an extended period of time, wax build ups were periodically removed by shutting down the plant and cleaning the cooling channel. 6 days of plant shut down in a year were required for dewaxing of the cooling channel.

(19) TABLE-US-00001 TABLE 1 suction suction discharge Electric pressure temperature pressure Energy Shutdown Polymer of secondary of secondary secondary consumption requirement output compressor compressor compressor [kWh/t for Example [kg/hour] [bar] [ C.] [bar] LDPE] dewaxing Example 1 7160 280 45 2980 1049 0 days per annum Comparative 7130 257 45 2950 1064 6 days per example annum

REFERENCE LIST

(20) 1. Compressor (primary) 2. Compressor (secondary) 3. Heat exchanger 4. Reactor 5. Initiator injection nozzles I. Initiator 6. Pressure let down (primary) 7. Cooler 8. Separator 9. Separator 10. Pelletizer 11. Recycle connection (high pressure) 12. Cooling channel 12. Cooling channel 13. Separator 14. Recycle connection (low pressure) 15. Cooler 16. Separator 17. Cooler 18. Separator 21. Reactor inlet 22. Reactor outlet 23. Pressure letdown (secondary) 100. Polymerization process 101. Plant 200. Plant 300. Group of coolers 301. Cooler 400. Bundle cooler 401. Coolant 402. Exit chamber 403. Entry chamber 404. Cooling channels 405. Gas outlet

(21) While multiple embodiments are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description. As will be apparent, certain embodiments, as disclosed herein, are capable of modifications in various obvious aspects, all without departing from the spirit and scope of the claims as presented herein. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.