Energy-saving control method for ethylene production device

Abstract

The application discloses an energy-saving control method for an ethylene production device, and belongs to the technical field of chemical production. The energy-saving control method comprises a first ethylene unit, a second ethylene unit and a low-temperature ethylene storage tank. The first ethylene unit comprises an ethylene rectifying column reflux tank and a refrigerant heat exchanger. The ethylene rectifying column reflux tank is connected with the refrigerant heat exchanger through a pipeline. The saturated liquid-phase ethylene is cooled to a supercooled state through the refrigerant heat exchanger. A breather valve is opened. The low-temperature ethylene is discharged to a flare system. When downstream ethylene users reduce loads or stop running, the method that the first ethylene unit and the second ethylene unit simultaneously send out low-temperature ethylene is adopted. The opening degrees of various valves on the pipeline are adjusted through a flow display controller, a temperature display controller, a pressure display controller and a pressure display. The temperature, the pressure, the flow and other parameters of the sent-out low-temperature ethylene are strictly controlled, so that full-load stable production of the ethylene production device is ensured, and two-phase flow working conditions are prevented.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical production, in particular to an energy-saving control method for an ethylene production device. BACKGROUND

[0002] In the ethylene production and processing process, an ethylene intermediate product spherical tank and a normal pressure low-temperature ethylene storage tank are often matched to balance the ethylene inventory. In normal production, the ethylene product obtained by the ethylene production device is sent to the ethylene intermediate product tank, and after being vaporized and pressurized, it is sent to the downstream ethylene user. When the downstream device is shut down or produces at a reduced load, the excess ethylene product needs to be sent to the low-temperature ethylene storage tank to prevent the ethylene production device from producing at a reduced load.

[0003] Since the low-temperature ethylene storage tank is in a normal pressure or slightly positive pressure state, in order to ensure that the ethylene is stored in a liquid state in the tank, the ethylene sent to the tank needs to be strictly controlled to be supercooled or saturated, that is, the maximum temperature of the ethylene in the tank is the saturation temperature corresponding to the normal pressure, which is -103.9℃. The operating temperature of the ethylene rectification column reflux tank in the ethylene production device is -40℃, and it needs to be cooled to -103.9℃ or below by a heat exchanger to meet the storage conditions of ethylene.

[0004] When multiple sets of ethylene production devices are simultaneously sent to the low-temperature ethylene, since the operating pressures of the ethylene rectification columns of each set of ethylene production devices are different, when the high-pressure side is sent to the low-temperature ethylene, it will inevitably lead to poor sending of the low-pressure side to the low-temperature ethylene. Due to the inconsistent pressure of the low-temperature ethylene sent, the low-temperature ethylene storage tank of the post-system is a normal pressure tank, and two-phase flow is prone to occur on the low-temperature ethylene sending line. In a chemical production device, two-phase flow must be strictly controlled. When two-phase flow occurs, it will cause violent impact of the medium at the elbow and flange, causing pipeline vibration, and in severe cases, it will cause medium leakage, and further cause safety production accidents. SUMMARY

[0005] In order to solve the technical problems mentioned in the background art, the present application provides an energy-saving control method for an ethylene production device, which adopts the following technical solutions:

[0006] The application comprises 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, the first ethylene unit and the second ethylene unit are connected with the low-temperature ethylene storage tank through pipelines, the first ethylene unit comprises an ethylene rectification column reflux tank and a refrigerant heat exchanger, the ethylene rectification column reflux tank is connected with the refrigerant heat exchanger through a pipeline, saturated liquid-phase ethylene is cooled to a supercooled state through the refrigerant heat exchanger and is 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 DEG C, a breather valve is arranged at the top of the low-temperature ethylene storage tank, when the pressure in the low-temperature ethylene storage tank reaches the upper breather valve discharge pressure, the breather valve is opened, and the low-temperature ethylene is discharged to a flare system.

[0007] Preferably, when the temperature of the low-temperature ethylene entering the low-temperature ethylene storage tank is high or the flow is large, the breather valve needs to be opened for discharge, i.e. ethylene material loss occurs, therefore, to avoid ethylene loss, the flow or temperature of the low-temperature ethylene sent out is controlled by controlling the opening of the valve through the flow display controller and the temperature display controller.

[0008] Preferably, by arranging the low-temperature ethylene storage tank, when the downstream device appears to have a reduced load, to avoid the ethylene production device having a reduced load, the ethylene produced by the ethylene device is sent to the low-temperature ethylene storage tank through a pipeline, thereby playing a role in temporarily balancing the ethylene consumption.

[0009] Preferably, the refrigerant heat exchanger is a brazed aluminum plate-fin heat exchanger, the refrigerant heat exchanger has the characteristics of small floor area and high heat transfer coefficient, to prevent the internal tube bundle of the refrigerant heat exchanger from being blocked, a filter with high filtering precision is usually arranged 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, after being discharged from the refrigerant heat exchanger, the refrigerant is cooled by a self-throttling valve and then re-enters the refrigerant heat exchanger, thereby realizing the cooling process, when it is necessary to increase the flow of the low-temperature ethylene sent out, the self-throttling valve is opened to realize stable control of the temperature of the low-temperature ethylene sent out.

[0011] Preferably, an adjusting valve is arranged on the low-temperature ethylene sending pipeline, the adjusting valve adopts single-loop flow control, i.e. the change of the flow of the low-temperature ethylene sent out is realized by changing the set value of the flow control loop.

[0012] The application has the following advantages:

[0013] The application adopts the method of simultaneously sending low-temperature ethylene by the first ethylene unit and the second ethylene unit when the downstream ethylene user reduces load or stops, and adjusts the opening of each valve on the pipeline through the flow display controller, the temperature display controller, the pressure display controller and the pressure display, strictly controls the temperature, pressure, flow and other parameters of the sent low-temperature ethylene, so as to ensure the full-load stable production of the ethylene production device and prevent the occurrence of two-phase flow conditions. When the ethylene sending flow of a single ethylene unit is large, too much refrigerant is consumed and the power consumption of the refrigeration compressor is increased, and the method of jointly sending by multiple ethylene units can effectively reduce the refrigerant consumption of a single ethylene device. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The flow chart of the application.

[0015] The drawings: 1 low-temperature ethylene storage tank, 2 ethylene rectification column 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 technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0017] The application provides an energy-saving control method for an ethylene production device, which comprises a first ethylene unit, a second ethylene unit and a low-temperature ethylene storage tank 1, the first ethylene unit is the same as the second ethylene unit, the first ethylene unit and the second ethylene unit are connected with the low-temperature ethylene storage tank 1 through pipelines, the first ethylene unit comprises an ethylene rectification column reflux tank 2 and a refrigerant heat exchanger 3, ethylene produced by the ethylene production device enters the ethylene rectification column reflux tank 2 through a pipeline, the ethylene rectification column reflux tank 2 is connected with the refrigerant heat exchanger 3 through a pipeline, ethylene in the ethylene rectification column reflux tank 2 enters the refrigerant heat exchanger 3 through a pipeline to be cooled, the saturated liquid-phase ethylene is cooled to a supercooled state by the refrigerant heat exchanger 3 and is sent to the low-temperature ethylene storage tank 1 through a pipeline, a valve, a flow display controller 4, a temperature display controller 5, a pressure display controller 6 and a pressure display 7 are arranged on the pipeline between the refrigerant heat exchanger 3 and the low-temperature ethylene storage tank 1, the low-temperature ethylene storage tank 1 is a normal-pressure storage tank, the boiling point of ethylene under normal pressure is -103.9 DEG C, a breather valve is arranged at the top of the low-temperature ethylene storage tank 1, when the pressure in the low-temperature ethylene storage tank 1 reaches the upper breather valve discharge pressure, the breather valve is opened, the low-temperature ethylene is discharged to a flare system, when the downstream ethylene user reduces load or stops, the method that the first ethylene unit and the second ethylene unit simultaneously send out low-temperature ethylene is adopted, and the opening degrees of the valves on the pipeline are adjusted through the flow display controller 4, the temperature display controller 5, the pressure display controller 6 and the pressure display 7, the parameters such as the temperature, the pressure and the flow of the sent-out low-temperature ethylene are strictly controlled, so that full-load smooth production of the ethylene production device is ensured and two-phase flow conditions are prevented.

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

[0019] When the temperature or the flow of the low-temperature ethylene entering the low-temperature ethylene storage tank 1 is high, the breather valve needs to be opened for discharge, that is, ethylene material loss occurs, therefore, to avoid ethylene loss, the flow or the temperature of the sent-out low-temperature ethylene is controlled by adjusting the opening degrees of the valves through the flow display controller 4 and the temperature display controller 5.

[0020] The normal operating pressure of the low-temperature ethylene storage tank 1 is normal pressure or slightly positive pressure, and a breather valve is arranged at the top of the tank, when the temperature or the flow of the low-temperature ethylene entering the tank is high, the breather valve needs to be opened for discharge, that is, ethylene material loss occurs, therefore, to avoid ethylene loss, the flow or the temperature of the sent-out low-temperature ethylene needs to be strictly controlled.

[0021] By arranging the low-temperature ethylene storage tank 1, when the downstream device reduces load, to avoid the ethylene production device reducing load, the ethylene produced by the ethylene device is sent to the low-temperature ethylene storage tank 1 through a pipeline, so as to temporarily balance the ethylene consumption.

[0022] The low-temperature ethylene delivery process is used when the downstream ethylene user reduces load or stops production, and the purpose is to ensure full-load production of the ethylene production device and temporarily balance the liquid-phase ethylene.

[0023] The refrigerant heat exchanger 3 is a brazed aluminum plate-fin heat exchanger, which has the characteristics of small floor area and high heat transfer coefficient, and a filter with high filtering precision is usually arranged at the inlet of the plate-fin heat exchanger to remove solid impurities carried by the medium.

[0024] The cooling of the liquid-phase ethylene is realized by throttling of the refrigerant, and the temperature of the refrigerant will drop to about -100 DEG C after throttling, and the part of the stream is returned to the refrigerant heat exchanger 3 for cooling of the liquid-phase ethylene.

[0025] The high-pressure refrigerant enters the refrigerant heat exchanger 3, and after exiting the refrigerant heat exchanger 3, the refrigerant is cooled by a self-throttling valve and then enters the refrigerant heat exchanger 3 again to realize the cooling process, and when it is necessary to increase the flow of the delivered low-temperature ethylene, the self-throttling valve is opened to realize stable control of the delivery temperature.

[0026] When the downstream ethylene user reduces load or stops production, only the first ethylene unit or the second ethylene unit delivering low-temperature ethylene may increase the power consumption of the refrigeration compressor, and in severe cases, the outlet temperature or pressure of the compressor may be high, and there is a risk of compressor shutdown, and the method of simultaneously delivering liquid-phase ethylene by the first ethylene unit and the second ethylene unit can effectively reduce the consumption of single ethylene refrigerant and increase the flexibility of device operation.

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

[0028] An adjusting valve is arranged on the low-temperature ethylene delivery pipeline, and the adjusting valve adopts single-loop control of flow, that is, the change of the flow of the delivered low-temperature ethylene is realized by changing the set value of the flow control loop.

[0029] The present application is simple to operate, convenient to use, and suitable for comprehensive promotion and application. Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application 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. The saturated liquid ethylene is cooled to a supercooled state through the refrigerant heat exchanger and sent to the low-temperature ethylene storage tank through the pipeline. The pipeline between the refrigerant heat exchanger and the low-temperature ethylene storage tank is provided with a valve, a flow display controller, a temperature display controller, a pressure display controller and a pressure display. 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 provided 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, which means that ethylene material loss occurs. Therefore, in order to avoid ethylene loss, the flow rate or temperature of the low-temperature ethylene sent out is controlled by controlling the opening of the valve through the flow display controller and the temperature display controller.

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 from experiencing load reduction, the ethylene produced by the ethylene unit is sent to the low-temperature ethylene storage tank through a pipeline, which plays a role in 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 with 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 high-precision filter 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 to be sent out, the throttle valve is opened to achieve stable control of the sending temperature.

6. The energy-saving control method for an ethylene production device according to claim 1, characterized in that: A regulating valve is set 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.

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