Energy-saving control method for ethylene production device

Abstract

The invention discloses an energy-saving control method for an ethylene production device, and belongs to the technical field of chemical production, the ethylene production device comprises a first ethylene unit, a second ethylene unit and a low-temperature ethylene storage tank, the first ethylene unit comprises an ethylene rectifying tower return tank and a refrigerant heat exchanger, and the ethylene rectifying tower return tank is connected with the refrigerant heat exchanger through a pipeline; when a downstream ethylene user is subjected to load reduction or parking, the first ethylene unit and the second ethylene unit are used for simultaneously delivering the low-temperature ethylene to the outside, so that the low-temperature ethylene can be discharged to the flare system, and the low-temperature ethylene can be discharged to the flare system. The opening degree of each valve on the pipeline is adjusted through the flow display controller, the temperature display controller, the pressure display controller and the pressure display, and parameters such as the temperature, the pressure and the flow of the delivered low-temperature ethylene are strictly controlled, so that the full-load stable production of the ethylene production device is ensured, and the two-phase flow working condition is prevented.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production, and in particular to an energy-saving control method for an ethylene production device. Background Art

[0002] In the process of ethylene production and processing, ethylene intermediate product spherical tanks and atmospheric low-temperature ethylene storage tanks are often used to balance ethylene inventory. In normal production, the ethylene products obtained by the ethylene production unit are sent to the ethylene intermediate product tank, which is then vaporized and pressurized and sent to downstream ethylene users. When the downstream unit is shut down or produces at a reduced load, the excess ethylene products need to be sent to the low-temperature ethylene storage tank to prevent the ethylene production unit from producing at a reduced load.

[0003] Since the low-temperature ethylene storage tank is at normal pressure or slightly positive pressure, in order to ensure that the ethylene is stored in liquid form in the tank, the ethylene sent to the tank must be strictly controlled to be supercooled or saturated, that is, the highest temperature of the ethylene in the tank is the saturation temperature corresponding to normal pressure, which is -103.9°C. The operating temperature of the ethylene distillation tower reflux tank in the ethylene production unit is -40°C, and it needs to be cooled to -103.9°C or below through a heat exchanger to meet the storage conditions of ethylene.

[0004] When multiple ethylene production units simultaneously deliver low-temperature ethylene, the operating pressures of the ethylene distillation towers of each ethylene production unit are inconsistent. When the high-pressure side delivers low-temperature ethylene, it is bound to cause the low-pressure side to deliver low-temperature ethylene unsmoothly. Since the pressures of the delivered low-temperature ethylene are inconsistent, the low-temperature ethylene storage tanks of the subsequent system are atmospheric pressure tanks, which easily lead to two-phase flow on the low-temperature ethylene delivery line. In chemical production units, two-phase flow must be strictly controlled. When two-phase flow occurs, it will cause the medium to violently collide at the elbows and flanges, causing pipeline vibration. In severe cases, it will cause medium leakage, which will lead to production safety accidents. Summary of the invention

[0005] In order to solve the technical problems mentioned in the above background technology, the present invention provides an energy-saving control method for an ethylene production device, and the technical solution adopted is as follows:

[0006] It includes a first ethylene unit, a second ethylene unit and a low-temperature ethylene storage tank. The first ethylene unit is the same as the second ethylene unit. Both the first ethylene unit and the second ethylene unit are connected to the low-temperature ethylene storage tank through a pipeline. The first ethylene unit includes an ethylene distillation tower reflux tank and a refrigerant heat exchanger. The ethylene distillation tower reflux tank is connected to the refrigerant heat exchanger through a pipeline. Saturated liquid ethylene is cooled to a supercooled state through the refrigerant heat exchanger and sent to the low-temperature ethylene storage tank through a pipeline. A valve, a flow display controller, a temperature display controller, a pressure display controller and a pressure display are arranged on the pipeline between the refrigerant heat exchanger and the low-temperature ethylene storage tank. The low-temperature ethylene storage tank is a normal pressure storage tank. The boiling point of ethylene under normal pressure is -103.9°C. A breathing valve is arranged on the top of the low-temperature ethylene storage tank. When the pressure in the low-temperature ethylene storage tank reaches the discharge pressure of the upper breathing valve, the breathing valve is opened and the low-temperature ethylene is discharged to the flare system.

[0007] Preferably, when the temperature of the low-temperature ethylene entering the low-temperature ethylene storage tank is high or the flow rate is large, the breathing valve needs to be opened for discharge, that is, ethylene material loss occurs. Therefore, in order to avoid ethylene loss, the flow display controller and the temperature display controller are used to control the opening of the valve to control the flow or temperature of the sent low-temperature ethylene.

[0008] Preferably, by setting up a low-temperature ethylene storage tank, when the downstream device produces at a reduced load, in order to avoid the ethylene production device from experiencing a reduced load, the ethylene produced by the ethylene device is sent to the low-temperature ethylene storage tank through a pipeline, thereby temporarily balancing the ethylene consumption.

[0009] Preferably, the refrigerant heat exchanger is a brazed aluminum plate-fin heat exchanger, which has the characteristics of small footprint and high heat transfer coefficient. In order to prevent blockage of the internal tube bundle of the refrigerant heat exchanger, a filter with high filtration accuracy is usually set at the inlet of the plate-fin heat exchanger to remove solid impurities carried by the medium.

[0010] Preferably, high-pressure refrigerant enters the refrigerant heat exchanger, is cooled by the throttle valve after leaving the refrigerant heat exchanger, and then enters the refrigerant heat exchanger again to realize the cooling process. When it is necessary to increase the flow rate of low-temperature ethylene for external delivery, the throttle valve is opened to realize stable control of the external delivery temperature.

[0011] Preferably, a regulating valve is provided on the low-temperature ethylene export pipeline, and the regulating valve adopts single-loop flow control, that is, the flow rate of the exported low-temperature ethylene is changed by changing the set value of the flow control loop.

[0012] The present invention has the following advantages:

[0013] When the downstream ethylene users reduce the load or stop the operation, the present invention adopts the method that the first ethylene unit and the second ethylene unit simultaneously deliver low-temperature ethylene, and adjusts the opening of each valve on the pipeline through a flow display controller, a temperature display controller, a pressure display controller and a pressure display to strictly control the temperature, pressure, flow and other parameters of the delivered low-temperature ethylene, so as to ensure the full-load and stable production of the ethylene production device and prevent the occurrence of a two-phase flow condition. When the flow rate of the low-temperature ethylene delivered by a single ethylene unit is large, too much refrigerant will be consumed, increasing the power consumption of the refrigeration compressor. The method of jointly delivering multiple ethylene units can effectively reduce the amount of refrigerant used in a single ethylene device. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a flow chart of the present invention.

[0015] Figures: 1 low-temperature ethylene storage tank, 2 ethylene distillation tower reflux tank, 3 refrigerant heat exchanger, 4 flow display controller, 5 temperature display controller, 6 pressure display controller, 7 pressure display. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The present invention provides an energy-saving control method for an ethylene production device, comprising a first ethylene unit, a second ethylene unit and a low-temperature ethylene storage tank 1, wherein the first ethylene unit is the same as the second ethylene unit, and the first ethylene unit and the second ethylene unit are both connected to the low-temperature ethylene storage tank 1 through a pipeline, and the first ethylene unit comprises an ethylene rectification tower reflux tank 2 and a refrigerant heat exchanger 3, and the ethylene produced by the ethylene production device enters the ethylene rectification tower reflux tank 2 through a pipeline, and the ethylene rectification tower reflux tank 2 is connected to the refrigerant heat exchanger 3 through a pipeline, and the ethylene in the ethylene rectification tower reflux tank 2 enters the refrigerant heat exchanger 3 through a pipeline for cooling, and the saturated liquid phase ethylene is cooled to a supercooled state through the refrigerant heat exchanger 3 and sent to the low-temperature ethylene storage tank 1 through the pipeline, and a valve and a flow display are arranged on the pipeline between the refrigerant heat exchanger 3 and the low-temperature ethylene storage tank 1 Controller 4, temperature display controller 5, pressure display controller 6 and pressure display 7. Low-temperature ethylene storage tank 1 is a normal pressure storage tank. The boiling point of ethylene under normal pressure is -103.9°C. A breathing valve is set on the top of the low-temperature ethylene storage tank 1. When the pressure in the low-temperature ethylene storage tank 1 reaches the discharge pressure of the upper breathing valve, the breathing valve is opened and the low-temperature ethylene is discharged to the flare system. When the downstream ethylene users reduce the load or stop, the first ethylene unit and the second ethylene unit are used to simultaneously deliver the low-temperature ethylene. The flow display controller 4, temperature display controller 5, pressure display controller 6 and pressure display 7 are used to adjust the opening of each valve on the pipeline, and strictly control the temperature, pressure, flow and other parameters of the delivered low-temperature ethylene to ensure the full-load and stable production of the ethylene production unit to prevent the occurrence of two-phase flow conditions.

[0018] The liquid ethylene produced in the ethylene production device is in a saturated state. The saturated liquid ethylene needs to be cooled to a supercooled state by the refrigerant heat exchanger 3 before it can be sent to the low-temperature ethylene storage tank 1.

[0019] When the temperature of the low-temperature ethylene entering the low-temperature ethylene storage tank 1 is high or the flow rate is large, it is necessary to open the breathing valve for discharge, that is, ethylene material loss occurs. Therefore, in order to avoid ethylene loss, the flow display controller 4 and the temperature display controller 5 control the valve opening to control the flow rate or temperature of the low-temperature ethylene sent out.

[0020] The normal operating pressure of the low-temperature ethylene storage tank 1 is atmospheric pressure or slightly positive pressure. A breathing valve is provided on the top of the tank. When the temperature of the low-temperature ethylene entering the storage tank is high or the flow rate is large, the breathing valve needs to be opened for discharge, that is, ethylene material loss occurs. Therefore, in order to avoid ethylene loss, the flow rate or temperature of the sent low-temperature ethylene needs to be strictly controlled.

[0021] By setting up a low-temperature ethylene storage tank 1, when the downstream device experiences load reduction, in order to avoid load reduction in the ethylene production device, the ethylene produced by the ethylene device is sent to the low-temperature ethylene storage tank 1 through a pipeline, which plays a role in temporarily balancing the ethylene consumption.

[0022] The low-temperature ethylene export process is used when downstream ethylene users experience load reduction or shutdown. Its purpose is to ensure full-load production of the ethylene production unit and to temporarily balance the liquid ethylene.

[0023] The refrigerant heat exchanger 3 is a brazed aluminum plate-fin heat exchanger, which has the characteristics of small footprint and high heat transfer coefficient. In order to prevent the internal tube bundle of the refrigerant heat exchanger 3 from being blocked, a filter with high filtration accuracy is usually set at the inlet of the plate-fin heat exchanger to remove solid impurities carried by the medium.

[0024] The cooling of the liquid ethylene is achieved by throttling the refrigerant. After throttling, the temperature of the refrigerant will drop sharply to about -100°C, and this part of the flow will return to the refrigerant heat exchanger 3 to cool the liquid ethylene.

[0025] The high-pressure refrigerant enters the refrigerant heat exchanger 3, and after leaving the refrigerant heat exchanger 3, it is cooled by the throttle valve and enters the refrigerant heat exchanger 3 again to realize the cooling process. When it is necessary to increase the flow rate of low-temperature ethylene to be sent out, the throttle valve is opened to realize stable control of the external temperature.

[0026] When downstream ethylene users reduce load or stop production, relying solely on the first ethylene unit or the second ethylene unit to deliver low-temperature ethylene may increase the power consumption of the refrigeration compressor. In severe cases, it may cause high compressor outlet temperature or pressure, and there is a risk of compressor tripping. The method of using the first ethylene unit and the second ethylene unit to simultaneously deliver liquid ethylene can effectively reduce the usage of a single ethylene refrigerant and increase the flexibility of the device operation.

[0027] When the method of simultaneously delivering low-temperature ethylene from the first ethylene unit and the second ethylene unit is adopted, since the pressure of the low-temperature ethylene delivered from each ethylene production unit is inconsistent, in order to prevent two-phase flow in the low-temperature ethylene pipeline, the temperature, pressure and flow rate of the low-temperature ethylene delivery must be strictly controlled to ensure the stable production of the device;

[0028] A regulating valve is arranged on the low-temperature ethylene export pipeline, and the regulating valve adopts a single-loop flow control, that is, the flow rate of the exported low-temperature ethylene is changed by changing the set value of the flow control loop.

[0029] The present invention is simple to operate, convenient to use, and suitable for comprehensive promotion and application. Although the embodiments of the present invention have been shown and described, it is understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An energy-saving control method for an ethylene production device, characterized in that: It includes a first ethylene unit, a second ethylene unit and a low-temperature ethylene storage tank. The first ethylene unit is the same as the second ethylene unit. Both the first ethylene unit and the second ethylene unit are connected to the low-temperature ethylene storage tank through a pipeline. The first ethylene unit includes an ethylene distillation tower reflux tank and a refrigerant heat exchanger. The ethylene distillation tower reflux tank is connected to the refrigerant heat exchanger through a pipeline. Saturated liquid ethylene is cooled to a supercooled state through the refrigerant heat exchanger and sent to the low-temperature ethylene storage tank through a pipeline. A valve, a flow display controller, a temperature display controller, a pressure display controller and a pressure display are arranged on the pipeline between the refrigerant heat exchanger and the low-temperature ethylene storage tank. The low-temperature ethylene storage tank is a normal pressure storage tank. The boiling point of ethylene under normal pressure is -103.9°C. A breathing valve is arranged on the top of the low-temperature ethylene storage tank. When the pressure in the low-temperature ethylene storage tank reaches the discharge pressure of the upper breathing valve, the breathing valve is opened and the low-temperature ethylene is discharged to the flare system.

2. The energy-saving control method for an ethylene production device according to claim 1, characterized in that: When the temperature of the low-temperature ethylene entering the low-temperature ethylene storage tank is high or the flow rate is large, the breathing valve needs to be opened for discharge, that is, ethylene material loss occurs. Therefore, in order to avoid ethylene loss, the flow display controller and the temperature display controller are used to control the opening of the control valve to control the flow or temperature of the sent low-temperature ethylene.

3. The energy-saving control method for an ethylene production device according to claim 1, characterized in that: By setting up a low-temperature ethylene storage tank, when the downstream unit experiences load reduction, in order to avoid the ethylene production unit experiencing load reduction, the ethylene produced by the ethylene unit is sent to the low-temperature ethylene storage tank through a pipeline, thereby temporarily balancing the ethylene consumption.

4. The energy-saving control method for an ethylene production device according to claim 1, characterized in that: The refrigerant heat exchanger is a brazed aluminum plate-fin heat exchanger, which has the characteristics of small footprint and high heat transfer coefficient. In order to prevent the internal tube bundle of the refrigerant heat exchanger from being blocked, a filter with high filtration accuracy is usually installed at the inlet of the plate-fin heat exchanger to remove solid impurities carried by the medium.

5. The energy-saving control method for an ethylene production device according to claim 1, characterized in that: The high-pressure refrigerant enters the refrigerant heat exchanger, and after leaving the refrigerant heat exchanger, it is cooled by the throttle valve and enters the refrigerant heat exchanger again to realize the cooling process. When it is necessary to increase the flow rate of low-temperature ethylene for external delivery, the throttle valve is opened to achieve stable control of the external delivery temperature.

6. The energy-saving control method for an ethylene production device according to claim 1, characterized in that: A regulating valve is arranged on the low-temperature ethylene export pipeline, and the regulating valve adopts a single-loop flow control, that is, the flow rate of the exported low-temperature ethylene is changed by changing the set value of the flow control loop.

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