Energy-saving depropanizing tower system applying waste steam heat energy

Abstract

The utility model relates to the technical field of depropanization equipment, in particular to an energy-saving depropanization tower system applying dead steam heat energy, which comprises a depropanization tower, a liquid collecting box is arranged in the depropanization tower and is close to the middle lower part of the depropanization tower, a heat exchanger is arranged on one side outside the depropanization tower, and the liquid collecting box is connected with the heat exchanger through a pipeline. The heat exchanger is connected with the depropanizing tower through a pipeline and connected to the lower portion of the liquid collecting box, the heat exchanger is connected with the jet type mixer through a pipeline, the jet type mixer is connected with the hot water pipeline and the dead steam pipeline respectively, and the hot water pipeline is connected with the hot water circulating pump which is connected with the low-temperature hot water tank through a pipeline. The low-temperature hot water tank is connected with the heat exchanger. According to the utility model, the problem of on-site discharge of the dead steam can be solved, low-temperature heat of the dead steam can be fully utilized, heat energy and water resources are recovered, the steam consumption of the reboiler of the depropanizing tower is reduced, and the purposes of saving energy, reducing consumption and reducing operation cost are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of depropanizing equipment, in particular to an energy-saving depropanizing tower system using exhaust steam thermal energy. Background Art

[0002] The depropanizer is a common distillation tower in chemical plants and is widely present in various chemical and petrochemical systems. The depropanizer has high energy consumption, the bottom temperature is about 100°C, and steam above 0.3MPaG is often used as the reboiler heat source. At the same time, a large amount of exhaust steam is often generated in various chemical and petrochemical plants, such as exhaust steam generated by flash evaporation of steam condensate, exhaust steam from steam turbines, exhaust steam from thermal deaerators, etc. This exhaust steam has the characteristics of low pressure (about 0.01-0.05MPaG), low temperature (about 104-115°C), large latent heat, and difficult to use. This exhaust steam is usually discharged directly into the atmosphere, which will cause a great waste of exhaust steam heat energy and water resources, generate noise pollution when venting, and the water droplets after the exhaust steam is condensed will cause corrosion of equipment and pipelines.

[0003] How to solve the on-site emission of exhaust steam, how to realize exhaust steam recovery and save water resources, how to utilize the low-temperature heat of exhaust steam to save energy and reduce consumption, and reduce operating costs are the technical problems to be solved by the utility model. Utility Model Content

[0004] In order to solve the above technical problems, the utility model provides an energy-saving depropanizer system using exhaust steam thermal energy.

[0005] The utility model provides the following technical solutions:

[0006] An energy-saving depropanizer system using exhaust steam heat energy comprises a depropanizer, a liquid collecting tank is arranged inside the depropanizer, the liquid collecting tank is arranged near the middle and lower part of the depropanizer, a heat exchanger is arranged on one side outside the depropanizer, the liquid collecting tank is connected to the heat exchanger through a pipeline, the heat exchanger is connected to the depropanizer through a pipeline and connected to the lower part of the liquid collecting tank, the heat exchanger is connected to a jet mixer through a pipeline, the jet mixer is respectively connected to a hot water pipeline and an exhaust steam pipeline, the hot water pipeline is connected to a hot water circulation pump, the hot water circulation pump is connected to a low-temperature hot water tank through a pipeline, and the low-temperature hot water tank is connected to the heat exchanger through a pipeline.

[0007] The top of the low-temperature hot water tank is fixedly connected with a tube-sheet heat exchanger, the tube-sheet heat exchanger and the low-temperature hot water tank are connected by a flange, and cooling water is introduced into the shell side of the tube-sheet heat exchanger.

[0008] The top of the low-temperature hot water tank is connected to a nitrogen pipeline, and a nitrogen replenishing valve is arranged on the nitrogen pipeline.

[0009] The top of the warm water tank is connected to a drain pipeline, and a drain valve is arranged on the drain pipeline.

[0010] The bottom of the depropanizer is connected to a reboiler.

[0011] The top of the depropanizer is connected to a depropanizer condenser through a pipeline, and the depropanizer condenser is connected to a depropanizer reflux tank.

[0012] The height of the heat exchanger is lower than that of the liquid collecting tank.

[0013] The beneficial effects achieved by the utility model are:

[0014] The utility model can not only solve the problem of exhaust steam on-site emission, but also make full use of the low-temperature heat of the exhaust steam, recover heat energy and water resources, reduce the steam consumption of the depropanizer reboiler, and achieve the purpose of energy saving and consumption reduction and lowering operating costs.

[0015] The utility model has the following key innovative features in structure:

[0016] First, the utility model sets a liquid collecting box at a suitable position in the middle and lower part of the depropanizer, and sets a one-way energy-saving heat exchanger. The depropanizer flow flows in and out of the heat exchanger purely by gravity, and no pump pressurization is required, which saves energy and investment;

[0017] Second, the utility model uses low-temperature hot water to inject exhaust steam through a jet mixer to form high-temperature hot water as a heat source for the energy-saving heat exchanger;

[0018] Third, the utility model has a closed circulation of hot water, and the low-temperature hot water tank is a composite structure. A vertical fixed tube-sheet heat exchanger is arranged on the top of the low-temperature hot water tank. The tube-sheet heat exchanger is connected to the low-temperature hot water tank by a flange, and cooling water is introduced into the shell side. The flash steam that may be flashed out of the low-temperature hot water tank condenses and flows back to the low-temperature hot water tank along the inner wall of the tube-sheet heat exchanger by gravity. The low-temperature hot water tank is closed, and the top is nitrogen-sealed to realize pressure range control and maintain a slight positive pressure, which neither flashes steam nor helps to meet the cavitation margin of the hot water circulation pump below, thereby ensuring that the hot water circulation pump does not cavitation, and preventing the problem of equipment corrosion caused by hot water contacting the air.

[0019] Fourth, the low-temperature hot water tank is arranged at a lower height than the heat exchanger, which can ensure that the low-temperature hot water flows smoothly into the low-temperature hot water tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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:

[0021] Figure 1 It is a system structure diagram of the utility model.

[0022] In the figure: 1. Depropanizer; 2. Liquid collecting tank; 3. Heat exchanger; 4. Jet mixer; 5. Hot water circulation pump; 6. Low-temperature hot water tank; 7. Drain valve; 8. Nitrogen replenishment valve; 9. Reboiler; 10. Depropanizer condenser; 11. Depropanizer reflux tank; 12. Tube-sheet heat exchanger. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0024] Example:

[0025] like Figure 1 As shown, an energy-saving depropanizer system using exhaust steam heat energy includes a depropanizer 1, a liquid collecting tank 2 is arranged inside the depropanizer 1, and the liquid collecting tank 2 is arranged near the middle and lower part of the depropanizer 1. A heat exchanger 3 is arranged on one side of the outside of the depropanizer 1. The reason why the liquid collecting tank 2 and the heat exchanger 3 are arranged here is that the temperature here is much lower than the tower kettle, which is conducive to improving the temperature difference on both sides of the heat exchanger 3, improving the heat exchange effect, improving the utilization rate of hot water on the hot side, and reducing the heat exchange area. The liquid collecting tank 2 is connected to the heat exchanger 3 through a side line pipeline, and the heat exchanger 3 is connected to the depropanizer 1 through a pipeline and connected to the lower part of the liquid collecting tank 2. The height of the heat exchanger 3 is lower than the height of the liquid collecting tank 2, so that the logistics enters and exits the heat exchanger 3 purely by gravity.

[0026] In the above structure, the liquid material flowing out of the liquid collecting tank 2 enters the heat exchanger 3, and the material after heat exchange with the high-temperature hot water is in vapor-liquid two-phase, and is self-pressurized back to the lower part of the liquid collecting tank 2, and realizes gravity flow by utilizing the high head difference.

[0027] The heat exchanger 3 is connected to the jet mixer 4 through a pipeline, the jet mixer 4 is respectively connected to the hot water pipeline and the exhaust steam pipeline, the hot water pipeline is connected to the hot water circulation pump 5, the hot water circulation pump 5 is connected to the low-temperature hot water tank 6 through a pipeline, and the low-temperature hot water tank 6 is connected to the heat exchanger 3 through a pipeline.

[0028] The above structure is a set of hot water circulation system. The high-pressure and low-temperature hot water at the outlet of the hot water circulation pump 5 enters the jet mixer 4. When the hot water passes through the nozzle, negative pressure is formed at the nozzle, and the low-pressure exhaust steam from other devices is sucked in. The exhaust steam and the low-temperature hot water are mixed in the mixing tube, and the exhaust steam is condensed. The temperature of the low-temperature hot water is increased to form high-temperature hot water. The high-temperature hot water flows out from the outlet end of the jet mixer 4, enters the heat exchanger 3, and exchanges heat with the low-temperature material drawn from the side line. After the heat exchange, the high-temperature hot water becomes low-temperature hot water and flows to the low-temperature hot water tank 6 at the bottom. The jet mixer 4 is a commonly used structure in the prior art, which can mix two or more liquids or gases.

[0029] The top of the low-temperature hot water tank 6 is fixedly connected with a tube-sheet heat exchanger 12 , which is connected to the low-temperature hot water tank 6 via a flange, and cooling water is introduced into the shell side of the tube-sheet heat exchanger 12 .

[0030] In order to prevent possible flash exhaust from the low-temperature hot water tank 6, the low-temperature hot water tank 6 is of a composite structure, that is, a vertical fixed tube sheet heat exchanger 12 is arranged on the top of the horizontal tank of the low-temperature hot water tank 6. The tube sheet heat exchanger 12 is flange-connected to the low-temperature hot water tank 6, and cooling water is introduced into the shell side. The flash steam that may be flashed out of the hot water tank is condensed and flows back to the low-temperature hot water tank 6 along the inner wall of the heat exchange tube.

[0031] The top of the low-temperature hot water tank 6 is connected to a nitrogen pipeline, and a nitrogen replenishing valve 8 is provided on the nitrogen pipeline.

[0032] The top of the low-temperature hot water tank 6 is nitrogen sealed to achieve pressure range control, which is beneficial for the low-temperature hot water tank 6 to maintain a certain micro-positive pressure and prevent steam flashing, and is beneficial for satisfying the cavitation margin of the hot water circulation pump 5 below, ensuring that the hot water circulation pump 5 does not cavitate, and can also prevent the problem of equipment corrosion caused by hot water contacting the air. The low-temperature hot water is pressurized by the hot water circulation pump 5, a part of it is sent out of the device, and most of it is circulated back to the jet mixer 4, and this cycle is repeated.

[0033] The top of the warm water tank is connected to an emptying pipeline, on which an emptying valve 7 is provided for use during emptying.

[0034] The bottom of the depropanizer 1 is connected to a reboiler 9 to provide heat for the depropanizer 1. The top of the depropanizer 1 is connected to a depropanizer condenser 10 through a pipeline, and the depropanizer condenser 10 is connected to a depropanizer reflux tank 11, and propane is removed through the above structure.

[0035] The specific application cases of this utility model are as follows:

[0036] Case 1: The feed rate of the depropanizer 1 of a petrochemical company is 80t / h, and the feed composition is: propane 55%wt, C4 44%wt, C5 1%wt. The operating pressure of the depropanizer 1 is 1.6MPaG, the top temperature is 50℃, the bottom temperature is 100℃, and there are 75 trays. The normal consumption of 1.0MPaG steam is about 19t / h. Now a liquid collecting box 2 is set between the 62nd and 63rd trays, and the liquid in the tower is extracted from the side line and enters the heat exchanger 3. The material extraction temperature is 79℃, and the temperature after heat exchange is 81℃, and the vaporization fraction is increased to 33%. The steam turbine of the catalytic cracking unit produces 7t / h of exhaust steam, with an exhaust steam pressure of 0.015 MPaG and a temperature of 110℃. The low-temperature water at the inlet of the jet mixer 4 is 90℃, and the low-temperature water circulation volume is 270t / h. After absorbing the exhaust steam, the temperature rises to 104℃, 277t / h. After heat exchange in the heat exchanger 3, the temperature drops to 90℃, enters the low-temperature hot water tank 6, and is pressurized to 0.5 MPaG by the hot water circulation pump 5, and enters the jet mixer 4, and the cycle repeats. After adopting this energy-saving system, the 1.0MPaG steam consumption of the depropanizer 1 is reduced to 11t / h, saving 8t / h of 1.0MPaG steam, saving 42.1% of steam, and recovering 7t / h of water resources, which greatly reduces the energy consumption of the device, and has significant effects in energy saving, consumption reduction, and operating cost reduction.

[0037] Case 2: The feed rate of the propane dehydrogenation unit of a chemical company is 40t / h, and the feed composition is: 60%wt of propane, 39.5%wt of C4, and 0.5%wt of C5. The operating pressure of the depropanizer 1 is 1.62MPaG, the top temperature is 51℃, the bottom temperature is 102℃, and there are 73 layers of trays. The normal consumption of 0.6MPaG steam is about 10t / h. Now a liquid collecting box 2 is set between the 60th and 61st layers of trays, and the liquid in the tower is pumped out from the side line and enters the heat exchanger 3. The steam boiler deaerator produces 3t / h of exhaust steam, with an exhaust steam pressure of 0.01MPaG and a temperature of 105℃. After adopting this energy-saving system, the 0.6 MPaG steam consumption of the depropanizer 1 is reduced to 6.5t / h, saving 3.5t / h of 0.6MPaG steam, saving 35% of steam, and recovering 3t / h of water resources, greatly reducing the energy consumption of the device, and achieving significant effects in energy saving, consumption reduction and operating cost reduction.

Claims

1. An energy-saving depropanizer system using exhaust steam thermal energy, characterized in that: The invention comprises a depropanizer (1), wherein a liquid collecting tank (2) is arranged inside the depropanizer (1), the liquid collecting tank (2) is arranged near the middle and lower part of the depropanizer (1), a heat exchanger (3) is arranged on one side outside the depropanizer (1), the liquid collecting tank (2) is connected to the heat exchanger (3) through a pipeline, the heat exchanger (3) is connected to the depropanizer (1) through a pipeline and is connected to the lower part of the liquid collecting tank (2), the heat exchanger (3) is connected to a jet mixer (4) through a pipeline, the jet mixer (4) is respectively connected to a hot water pipeline and an exhaust steam pipeline, the hot water pipeline is connected to a hot water circulation pump (5), the hot water circulation pump (5) is connected to a low-temperature hot water tank (6) through a pipeline, and the low-temperature hot water tank (6) is connected to the heat exchanger (3) through a pipeline.

2. The energy-saving depropanizer system using exhaust steam heat energy according to claim 1, characterized in that: A tube-sheet heat exchanger (12) is fixedly connected to the top of the low-temperature hot water tank (6); the tube-sheet heat exchanger (12) and the low-temperature hot water tank (6) are connected by a flange, and cooling water is introduced into the shell side of the tube-sheet heat exchanger (12).

3. The energy-saving depropanizer system using exhaust steam heat energy according to claim 2, characterized in that: The top of the low-temperature hot water tank (6) is connected to a nitrogen pipeline, and a nitrogen replenishment valve (8) is provided on the nitrogen pipeline.

4. The energy-saving depropanizer system using exhaust steam heat energy according to claim 3, characterized in that: The top of the hot water tank is connected to a drain pipeline, and a drain valve (7) is provided on the drain pipeline.

5. The energy-saving depropanizer system using exhaust steam heat energy according to claim 1, characterized in that: The bottom of the depropanizer (1) is connected to a reboiler (9).

6. The energy-saving depropanizer system using exhaust steam heat energy according to claim 1, characterized in that: The top of the depropanizer (1) is connected to a depropanizer condenser (10) via a pipeline, and the depropanizer condenser (10) is connected to a depropanizer reflux tank (11).

7. The energy-saving depropanizer system using exhaust steam heat energy according to claim 1, characterized in that: The height of the heat exchanger (3) is lower than the height of the liquid collecting tank (2).

Images