Waste heat recovery system for polyethylene production

Abstract

The utility model relates to the technical field of heat recycling, in particular to a waste heat recovery system for polyethylene production, which comprises a polymerization reactor, a primary shell-and-tube heat exchanger, a slurry pump, a double-pipe heat exchanger, a diode shell-and-tube heat exchanger and a wax treatment tank. According to the utility model, the polymerization reactor and the wax treatment tank are thermally combined, polymerization reaction heat is fully utilized, the consumption of cooling water is reduced, the power consumption is saved, the use amount of steam is reduced, and the energy consumption is saved.

Description

Technical Field

[0001] The utility model relates to the technical field of heat recovery and utilization, in particular to a waste heat recovery system for polyethylene production. Background Art

[0002] In the current slurry process for producing polyethylene, a large amount of polyethylene wax with relatively low molecular weight is inevitably produced. The polyethylene wax is extracted into the wax treatment tank through hexane, resulting in a large amount of hexane that needs to be recovered. The recovery process consumes a lot of heat. The common recovery design is to heat the wax treatment tank with low-pressure steam to recover hexane, but this solution will consume a lot of low-pressure steam.

[0003] At the same time, the polymerization reaction of polyethylene produced by the slurry process is a highly exothermic reaction, that is, the polymerization is accompanied by the release of a large amount of heat, but the polymerization reaction is required to be controlled at 85-88°C, which requires an external medium to take away a large amount of reaction heat. The usual way to remove heat is to rely on the cooling effect of the reactor wall and the jacket water of the external cooler, among which the cooling effect of the reactor wall is smaller than that of the external cooler. After the polymerization reaction heat is transferred to the jacket water, the jacket water is sent to the jacket water system, cooled by cooling water, and then recycled. In the jacket water system, the large heat transfer temperature difference leads to large exergy loss, so this process not only causes a lot of heat waste, but also the jacket water device consumes a lot of electricity, which will also cause high power loss.

[0004] Therefore, a waste heat recovery system for polyethylene production is proposed. Utility Model Content

[0005] The purpose of the utility model is to provide a waste heat recovery system for polyethylene production to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the utility model provides the following technical solutions: a waste heat recovery system for polyethylene production, the system comprising:

[0007] Polymerization reactor, primary shell and tube heat exchanger, slurry pump, shell and tube heat exchanger, diode shell heat exchanger, wax treatment tank, including

[0008] The polymerization reactor is provided with a reactor jacket water inlet pipe and a reactor jacket water outlet pipe, and the reactor jacket water outlet pipe is connected to the shell side feed pipe of the primary shell and tube heat exchanger;

[0009] The tube-side feed pipe of the first-stage shell and tube heat exchanger is used to inject desalted water, and the tube-side discharge pipe of the first-stage shell and tube heat exchanger is connected to the tube-side feed pipe of the diode shell heat exchanger;

[0010] The slurry pump is connected to the polymerization reactor through a slurry pump feed pipe;

[0011] The shell-side feed pipe of the shell-and-tube heat exchanger is used to inject desalted water, the tube-side feed pipe of the shell-and-tube heat exchanger is connected to the slurry pump, and the tube-side discharge pipe of the shell-and-tube heat exchanger is connected to the polymerization reactor;

[0012] The shell-side feed pipe of the diode shell heat exchanger is connected to the shell-side discharge pipe of the shell-and-tube heat exchanger;

[0013] The wax treatment tank is provided with a wax treatment tank jacket water inlet pipe and a wax treatment tank jacket water outlet pipe, and the wax treatment tank jacket water inlet pipe is connected with the tube side discharge pipe of the diode shell heat exchanger.

[0014] According to the above technical solution, the shell side discharge pipe of the primary shell and tube heat exchanger, the shell side discharge pipe of the diode shell heat exchanger, and the jacket water outlet pipe of the wax treatment tank are all connected to the jacket water cooling system.

[0015] Compared with the prior art, the beneficial effects achieved by the utility model are: the utility model thermally combines the polymerization reactor and the wax treatment tank, fully utilizes the polymerization reaction heat, reduces the consumption of cooling water, saves electricity consumption, reduces the use of steam, and saves energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0017] Figure 1 It is a structural schematic diagram of the utility model;

[0018] In the figure: 1. polymerization reactor; 2. primary shell and tube heat exchanger; 3. slurry pump; 4. sleeve heat exchanger; 5. diode shell heat exchanger; 6. wax treatment tank; 7. reactor jacket water inlet pipe; 8. reactor jacket water outlet pipe; 9. slurry pump feed pipe; 10. wax treatment tank jacket water inlet pipe; 11. wax treatment tank jacket water outlet pipe. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0020] See also Figure 1The utility model provides a technical solution: a waste heat recovery system for polyethylene production, the system comprising:

[0021] Polymerization reactor 1, primary shell and tube heat exchanger 2, slurry pump 3, shell and tube heat exchanger 4, diode shell heat exchanger 5, wax treatment tank 6, wherein

[0022] The polymerization reactor 1 is provided with a reactor jacket water inlet pipe 7 and a reactor jacket water outlet pipe 8, and the reactor jacket water outlet pipe 8 is connected to the shell side feed pipe of the primary shell and tube heat exchanger 2;

[0023] The tube-side feed pipe of the first-stage shell and tube heat exchanger 2 is used to inject desalted water, and the tube-side discharge pipe of the first-stage shell and tube heat exchanger 2 is connected to the tube-side feed pipe of the diode shell heat exchanger 5;

[0024] The slurry pump 3 is connected to the polymerization reactor 1 through a slurry pump feed pipe 9;

[0025] The shell-side feed pipe of the shell-and-tube heat exchanger 4 is used to inject desalted water, the tube-side feed pipe of the shell-and-tube heat exchanger 4 is connected to the slurry pump 3, and the tube-side discharge pipe of the shell-and-tube heat exchanger 4 is connected to the polymerization reactor 1;

[0026] The shell-side feed pipe of the diode shell heat exchanger 5 is connected to the shell-side discharge pipe of the shell-and-tube heat exchanger 4;

[0027] The wax treatment tank 6 is provided with a wax treatment tank jacket water inlet pipe 10 and a wax treatment tank jacket water outlet pipe 11, and the wax treatment tank jacket water inlet pipe 10 is connected to the tube side outlet pipe of the diode shell heat exchanger 5;

[0028] The shell-side discharge pipe of the primary shell and tube heat exchanger 2, the shell-side discharge pipe of the diode shell heat exchanger 5, and the jacket water outlet pipe 11 of the wax treatment tank are all connected to the jacket water cooling system.

[0029] Under the stirring action of the polymerization reactor stirrer, ethylene polymerization reaction occurs in the polymerization reactor 1, and a large amount of reaction heat is released. Reactor jacket water is injected from the reactor jacket water inlet pipe 7 to remove heat from the polymerization reactor 1, and then enters the shell side feed pipe of the primary shell and tube heat exchanger 2 through the reactor jacket water outlet pipe 8, and desalted water is injected from the tube side feed pipe of the primary shell and tube heat exchanger 2. The desalted water and the reactor jacket water exchange heat in the primary shell and tube heat exchanger 2. After cooling, the reactor jacket water enters the jacket water system through the shell side discharge pipe of the primary shell and tube heat exchanger 2 for cooling. The heated desalted water is injected from the tube side discharge pipe of the primary shell and tube heat exchanger 2 into the tube side feed pipe of the diode shell heat exchanger 5.

[0030] The slurry pump 3 pumps the reaction slurry in the polymerization reactor 1 out through the slurry pump feed pipe 9, and then pumps the reaction slurry into the shell-and-tube heat exchanger 4 through the tube-side feed pipe of the shell-and-tube heat exchanger 4, and injects desalted water through the shell-side feed pipe of the shell-and-tube heat exchanger 4 to fully remove heat from the reaction slurry. The reaction slurry reduced to a specific temperature is returned to the polymerization reactor 1 through the tube-side discharge pipe of the shell-and-tube heat exchanger 4, and the desalted water after heat exchange is injected into the shell-side feed pipe of the diode shell heat exchanger 5 through the shell-side discharge pipe of the shell-and-tube heat exchanger 4.

[0031] The desalted water heated in the primary shell and tube heat exchanger 2 is reheated by the diode shell heat exchanger 5, and the heat source of the diode shell heat exchanger 5 comes from the desalted water after heat exchange in the shell and tube heat exchanger 4. Finally, the reheated desalted water enters the wax treatment tank jacket water inlet pipe 10 through the tube discharge pipe of the diode shell heat exchanger 5 to heat the wax treatment tank 6, and the desalted water after heat exchange and temperature reduction enters the jacket water system through the wax treatment tank jacket water outlet pipe 11 to be cooled.

[0032] Finally, it should be noted that the above description is only a preferred embodiment of the utility model and is not intended to limit the utility model. Although the utility model is described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions recorded in the above embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A waste heat recovery system for polyethylene production, characterized in that: The system comprises: Polymerization reactor, primary shell and tube heat exchanger, slurry pump, shell and tube heat exchanger, diode shell heat exchanger, wax treatment tank, including The polymerization reactor is provided with a reactor jacket water inlet pipe and a reactor jacket water outlet pipe, and the reactor jacket water outlet pipe is connected to the shell side feed pipe of the primary shell and tube heat exchanger; The tube-side feed pipe of the first-stage shell and tube heat exchanger is used to inject desalted water, and the tube-side discharge pipe of the first-stage shell and tube heat exchanger is connected to the tube-side feed pipe of the diode shell heat exchanger; The slurry pump is connected to the polymerization reactor through a slurry pump feed pipe; The shell-side feed pipe of the shell-and-tube heat exchanger is used to inject desalted water, the tube-side feed pipe of the shell-and-tube heat exchanger is connected to the slurry pump, and the tube-side discharge pipe of the shell-and-tube heat exchanger is connected to the polymerization reactor; The shell-side feed pipe of the diode shell heat exchanger is connected to the shell-side discharge pipe of the shell-and-tube heat exchanger; The wax treatment tank is provided with a wax treatment tank jacket water inlet pipe and a wax treatment tank jacket water outlet pipe, and the wax treatment tank jacket water inlet pipe is connected with the tube side discharge pipe of the diode shell heat exchanger.

2. The waste heat recovery system for polyethylene production according to claim 1, characterized in that: The shell side discharge pipe of the primary shell and tube heat exchanger, the shell side discharge pipe of the diode shell heat exchanger, and the jacket water outlet pipe of the wax treatment tank are all connected to the jacket water cooling system.

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