A control system and control method for on-line blending gasoline with C4 components

Abstract

The present invention discloses a control system and control method for online blending of C4 component gasoline. The control system includes several conventional gasoline component control loops, an online proportional control module, and a C4 component blending loop. The C4 component blending loop includes a C4 component control unit, and an instrument, a C4 component regulating valve, and a C4 component shut-off valve that are sequentially and separately coupled to the C4 component control unit. The C4 component control unit is used to control the C4 component regulating valve and the C4 component shut-off valve based on a C4 component setpoint and control signal output by the online proportional control module, as well as based on detected instrument parameters, thereby controlling pipeline medium back pressure, flow sequence control, and flow shut-off control under abnormal conditions. The control system and control method for online blending of C4 component gasoline proposed by the present invention solve the problem of online blending of gaseous hydrocarbon C4 components, ensure operational safety, and effectively avoid operational risks.

Description

Technical Field

[0001] The present invention relates to the technical field of automatic control in the petrochemical industry, and in particular to a control system and a control method for online blending of C4 components into gasoline. Background Art

[0002] Traditional gasoline is a mixture of C4 to C12 hydrocarbons, with a C4 content of approximately 3% to 5% by volume. With the advancement of deep processing and refined processing capabilities in the refining industry, the C4 components previously retained in the gasoline blend are removed during the distillation stage and separated and purified from other C4 components to serve as feedstock for subsequent units (such as MTBE or alkylation). Butenes and some isobutane react to form new products. The remaining approximately one-third of the reaction is primarily alkanes, such as post-ether C4 components, which are typically mixed with commercial liquefied petroleum gas for export.

[0003] C4, represented by butane, is a very good gasoline blending component. The following are the main gasoline blending indicators of butane / isobutane:

[0004]

[0005] The above indicators demonstrate that C4 gasoline exhibits high octane number, high vapor pressure, and low density, and contains no aromatics or olefins (or contains small amounts of olefins). By effectively controlling the product's Reye's vapor pressure (RVP), the yield of high-grade gasoline can be increased, while also alleviating the conflict between high gasoline density, high olefin and aromatic content, and low RVP. This reduced product density further enhances the competitiveness of volume-based retail outlets, particularly when producing winter-grade gasoline.

[0006] The price advantage of C4 makes its blending into gasoline a significant economic benefit. For example, the price difference between etherified C4 and gasoline after tax is over 1,500 yuan / ton. Theoretically, every ton of C4 blended can produce an equivalent amount of 95-grade gasoline. The main limiting factor for C4 blending is RVP. Experimental results show that every 1% volume fraction of C4 added increases the RVP of the gasoline product by approximately 5 kPa. Because most of the C4 has been removed from the refinery's gasoline blending components, the gasoline product RVP has a significant excess quality, which is particularly pronounced when producing winter-grade gasoline (45 kPa-85 kPa). This excess is typically 15-20 kPa, leaving room for C4 addition. Generally, even with a 3-4% C4 addition, the product RVP still maintains a certain quality margin. For a medium-sized refinery producing 500,000 tons of winter-grade gasoline annually, the corresponding amount of C4 that can be added is 15,000-25,000 tons, generating economic benefits of at least 20 million yuan.

[0007] At present, the gasoline blending method of refining enterprises is mainly based on the online blending process. The so-called online blending process is that the gasoline components involved in the blending enter the static mixer at the same time according to a specific ratio, and are fully mechanically mixed at the outlet to form a product that is then piped into the product tank for storage. Figure 1 shown.

[0008] Relying on online blending processes, some companies deploy online analytical equipment to perform real-time quality analysis of gasoline products and components. The blending system then adjusts the blending ratio of each component based on the analysis results, achieving online optimized blending to ensure product quality. Other companies use laboratory analysis of component oils combined with empirical experience to calculate blending ratios offline and hand them over to the online blending system for execution.

[0009] Because C4 is a gaseous hydrocarbon with a relatively high saturated vapor pressure and is gaseous at atmospheric pressure, applying the same blending process and control methods as other liquid components can lead to uncontrolled pressure and flow in the blending system, potentially even causing gaseous C4 to enter atmospheric pressure product storage tanks, posing a series of safety risks to tank operations. Therefore, companies cannot directly use C4 as a gasoline component in online blending. Therefore, a specific blending process and control method tailored to the characteristics of C4 components is required, addressing both online blending challenges and fundamentally preventing these risks. Summary of the Invention

[0010] To overcome the shortcomings of the above technologies, the present invention provides a control system and method for online blending of C4 components into gasoline. This system, based on the existing online gasoline blending process, adds a process and control method specifically for online blending of C4 components, solving the problem of online blending of gaseous hydrocarbon C4 components. While ensuring production safety, it generates considerable economic and social benefits.

[0011] The technical solution adopted by the present invention to overcome its technical problems is as follows: In the first aspect of the present invention, a control system for online blending of C4 component gasoline is proposed, which includes a plurality of conventional gasoline component control loops and an online proportional control module, wherein each conventional gasoline component corresponds to a conventional gasoline component control loop, and the conventional gasoline component control loop includes at least a conventional gasoline component flow meter and a conventional gasoline component regulating valve. The control system for online blending of C4 component gasoline also includes a C4 component blending loop, and the C4 component blending loop includes at least a C4 component control unit, and a C4 component thermometer, a C4 component flow meter, a C4 component pressure meter, and a C4 component regulating valve, which are sequentially coupled to and respectively coupled to the C4 component control unit. and a C4 component shut-off valve. The online proportional control module is used to monitor the blending ratio of various conventional gasoline components and the C4 component, calculate the blending flow of the conventional gasoline component and the C4 component, and output a given value to each conventional gasoline component control loop and the C4 component flow blending loop, thereby controlling the blending ratio of the conventional gasoline component and the C4 component. The C4 component control unit is used to control the C4 component regulating valve and the C4 component shut-off valve based on the C4 component given value and control signal output by the online proportional control module, as well as the parameters of the detected C4 component thermometer, C4 component flowmeter, and C4 component pressure instrument, thereby performing pipeline medium back pressure control, flow sequence control, and flow shut-off control under abnormal conditions.

[0012] According to the characteristics of the C4 component, a C4 component blending circuit is added, and a C4 component thermometer, C4 component flowmeter, and C4 component pressure instrument are configured to realize parameter detection of the C4 component blending circuit, thereby safely controlling the opening of the regulating valve and ensuring the safe operation of the C4 component through the cut-off valve.

[0013] Furthermore, the C4 component control unit includes a sequential control subunit, a blending flow control subunit, and a pipeline backpressure control subunit. The output ends of the blending flow control subunit and the pipeline backpressure control subunit are both coupled to the C4 component regulating valve through a low selector; the input end of the sequential control subunit is coupled to the online proportional control module, and the output end is coupled to the blending flow control subunit, which is used to start or withdraw the blending flow control based on the state of the online proportional control module, the C4 component flow set value and the command. The pipeline backpressure control subunit is used to control the pipeline backpressure based on the detected parameters of the C4 component pressure instrument; the blending flow control subunit is used to control the opening and closing degree of the C4 component regulating valve through a low selector based on the received start or withdrawal command and the C4 component flow set value, and the pipeline backpressure control subunit based on the pipeline backpressure, so as to complete flow control and pipeline backpressure control, wherein the priority of pipeline backpressure control is higher than that of blending flow control.

[0014] Furthermore, the C4 component control unit also includes an emergency cut-off control subunit coupled to the output end of the sequence control subunit, and the output end of the emergency cut-off control subunit is coupled to the C4 component cut-off valve. The sequence control subunit controls the emergency cut-off control subunit to shut off the C4 component cut-off valve in response to an abnormal situation of the control system of the C4 component online blending gasoline.

[0015] A second aspect of the present invention provides a control method for online blending of C4 component gasoline. The method is applied to the aforementioned control system for online blending of C4 component gasoline. In response to a start command, an online proportional control module controls the opening of a conventional gasoline component regulating valve and determines whether the blending amount of the conventional gasoline component has reached a preset value based on detected instrument parameters of the conventional gasoline component. If the blending amount of the conventional gasoline component has not reached the preset flow rate, the C4 component blending circuit is not started. If the blending amount of the conventional gasoline component has reached the preset value, the C4 component blending circuit is started and the C4 component shut-off valve is opened. The C4 component control unit controls the opening of the C4 component regulating valve via a low selector, thereby completing C4 component blending flow control.

[0016] The upgrade of the original gasoline online blending system, including the control method, solves the online blending problem of gaseous hydrocarbon C4 components, with a short construction period and small investment.

[0017] Furthermore, in response to the end command, the online proportional control module closes the C4 component blending circuit, and the C4 component control unit controls the opening of the C4 component regulating valve through the low selector until the C4 component flow rate drops to 0, and then closes the C4 component shut-off valve. Based on the valve position closing feedback signal from the C4 component shut-off valve, the C4 component control unit feeds back to the online proportional control module that the C4 component blending circuit has been closed; if the online proportional control module receives that the C4 component blending circuit has been closed, it controls the opening of the conventional gasoline component regulating valve based on the preset delay time until the conventional gasoline component blending amount drops to 0.

[0018] Furthermore, the C4 component control unit controls the opening of the C4 component regulating valve through a low selector, thereby completing the C4 component blending flow control, specifically including: the C4 component control unit is based on the C4 component flow given by the online proportional control module, the low selector receives the output of the pipeline back pressure control and the blending flow control, and completes the control of the C4 blending flow based on the pipeline back pressure being greater than the component saturated vapor pressure safety value.

[0019] The pipeline back pressure is preferentially satisfied through the low selector. On the premise of preferentially ensuring that the pipeline back pressure is greater than the safety value of the component saturated vapor pressure, the opening of the C4 component regulating valve is controlled to achieve the flow control of the C4 component.

[0020] Furthermore, the safety value of the saturated vapor pressure of the C4 component SP=0.13332×P+S, wherein S is the safety margin, 0.15≤S≤0.25MPa, P is the saturated vapor pressure in mmHg, lgP=AB / (T+C), A, B, and C are coefficients of 6.748, 882.8, and 240.0, respectively, and T is the temperature of the C4 component.

[0021] The pipeline back pressure safety value is set according to the saturated vapor pressure of isobutane at the current temperature to prevent the formation of vapor-liquid mixed phase under low medium pressure conditions.

[0022] Furthermore, in response to an abnormal state, the online proportional control module controls the C4 component control unit to close the C4 component shut-off valve.

[0023] Set up an abnormal handling process to prevent excessive C4 from entering the downstream pipeline and normal pressure product storage tank under abnormal conditions, causing a series of tank operation risks

[0024] The beneficial effects of the present invention are:

[0025] 1. By adding a C4 component blending circuit based on the characteristics of the C4 component on the basis of the traditional gasoline online blending system and upgrading the control method in the original control system, the online blending problem of the gaseous hydrocarbon C4 component is solved, with a short construction period and low investment.

[0026] 2. The C4 component blending circuit is equipped with temperature and pressure transmitters, flow meters, regulating valves and shut-off valves, thereby realizing parameter detection of the C4 component blending circuit and ensuring the operational safety of the C4 component through the shut-off valve.

[0027] 3. Set up an abnormal handling process to prevent excessive C4 from entering the downstream pipeline and normal pressure product storage tank under abnormal conditions, causing a series of tank operation risks.

[0028] 4. After starting the C4 component blending circuit, refer to the blending volume and pipeline back pressure of other blending parts, then open the shut-off valve and start the regulating valve to ensure operational safety and reduce risks. When completing or pausing preparation, close the C4 component blending circuit first, and then close the other conventional component circuits.

[0029] 5. Set the pipeline back pressure safety value according to the saturated vapor pressure of isobutane at the current temperature to prevent the formation of vapor-liquid mixed phase under low pressure conditions of the medium, causing flow meter distortion and thus causing flow loss of control. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of a control system for online blending and controlling gasoline of C4 components according to an embodiment of the present invention;

[0031] Figure 2This is a principle block diagram of a C4 component control unit according to an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of the control process of the C4 component in an embodiment of the present invention;

[0033] Figure 4 This is a schematic diagram of the application of the control system for online blending of C4 components with gasoline according to the present invention. DETAILED DESCRIPTION

[0034] In order to facilitate those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. The following is only exemplary and does not limit the scope of protection of the present invention.

[0035] Explanation of terms:

[0036] C4, or carbon four, generally refers to C4 hydrocarbons produced as byproducts in petrochemical production processes, including butane, butene, butadiene, and other products or mixtures. Normally, they are gaseous, but become liquid under pressure.

[0037] Component: refers to the individual ingredients in the mixture that make up the product.

[0038] Online blending: The process of simultaneously feeding multiple components into a mixing device in a specific proportion to produce a product that meets certain quality requirements online.

[0039] like Figure 1 As shown in FIG. 1 , a schematic diagram of a control system for online blending of C4 components of gasoline according to this embodiment is shown. A conventional online gasoline blending control system includes several conventional gasoline component control loops and an online ratio control module, such as Figure 1 As shown, the conventional gasoline component control loops are gasoline components 1-4. Each conventional gasoline component control loop includes a conventional gasoline component flowmeter and a conventional gasoline component regulating valve. Multiple conventional gasoline components are fed into a manifold through a blending pump, flowmeter, and regulating valve. After being mixed in a static mixer, they pass through a backpressure regulating loop and enter the product tank. Flow control of each component is achieved by controlling the regulating valve via an online proportional control module. The flow control setpoint for each component is a pre-set value.

[0040] The online proportional control module is also used to detect parameters of a conventional gasoline component instrument of a conventional gasoline component control loop, and to control the opening of a conventional gasoline component regulating valve.

[0041] It should be noted that conventional gasoline components are C5 and above.

[0042] In order to realize the online blending of C4 components into gasoline, a C4 component blending circuit is added to the traditional gasoline online blending control system, such as Figure 1The C4 component blending circuit shown includes a C4 component meter, a C4 component regulating valve, and a C4 component shut-off valve, all coupled in sequence, and a C4 component control unit coupled to each of the C4 component meter, the C4 component regulating valve, and the C4 component shut-off valve. The C4 component control unit controls the blending flow rate and process safety of the C4 component.

[0043] like Figure 2 Figure 1 shows a block diagram of the C4 component control unit, which includes a sequence control subunit, a blending flow control subunit, a pipeline backpressure control subunit, and an emergency shutoff control subunit. The input of the sequence control subunit is coupled to an online proportional control module, while the outputs of the blending flow control subunit and the pipeline backpressure control subunit are both coupled to a regulating valve via a low-pressure selector.

[0044] The output end of the sequence control subunit is coupled to the blending flow control subunit, which starts or ends the blending flow control subunit based on the status of the online proportional control module, the C4 component flow set value and the command.

[0045] In one embodiment of the present invention, the flow setting value of the C4 component is a manually set value, the status of the online proportional control module refers to the working status of other conventional components, and the command refers to the system start command or end command, thereby correspondingly starting or ending the blending flow control subunit.

[0046] The pipeline back pressure control subunit is used to detect whether the pipeline back pressure is less than the safety value of the saturated vapor pressure of the C4 component, and send the back pressure judgment result to the two control subunits for blending.

[0047] Pipeline backpressure control ensures that the backpressure before the regulating valve is greater than the saturated vapor pressure of C4, with a safety margin. This is to prevent the formation of a vapor-liquid mixture under low medium pressure, which could cause flowmeter distortion and loss of flow control. The safety value for the saturated vapor pressure of the C4 component is the saturated vapor pressure of isobutane at the current temperature + the safety margin.

[0048] The blending flow control subunit is used to adjust the opening degree of the regulating valve or shut down the regulating valve based on the start-up or withdrawal command received by the receiving sequence control subunit and the back pressure determination result of the C4 component flow set value and the pipeline back pressure control subunit.

[0049] The control outputs of the blending flow control subunit and the pipeline backpressure control subunit share a regulating valve. Therefore, a low-select control strategy is adopted to complete the online blending flow control of the C4 component while prioritizing ensuring that the pipeline backpressure meets the requirements.

[0050] The emergency shutoff control subunit activates the emergency shutoff control program if any of the following abnormal conditions occur during the C4 component blending process. These conditions include: 1. Blending is completed or paused; 2. The total blending pipe flow rate falls below the lower limit; 3. The actual C4 blend ratio exceeds the upper limit; 4. Manual intervention is required. In these cases, the emergency shutoff control subunit is activated to directly control the shutoff valve, fundamentally preventing excessive C4 from entering downstream pipelines and atmospheric product storage tanks under abnormal conditions, which could lead to a series of tank operation risks.

[0051] Another embodiment of the present invention also provides a control method for online blending of C4 components of gasoline. The flow diagram of starting online blending of C4 components of gasoline is shown in FIG. Figure 3 As shown, the control system applied to the above-mentioned C4 component online blending gasoline specifically includes:

[0052] S1, in response to a start command, the online proportional control module controls the opening of the conventional gasoline component regulating valve and determines whether the blending amount of the conventional gasoline component reaches a preset flow rate based on the detected instrument parameters of the conventional gasoline component.

[0053] The control system for the online C4 component gasoline blending is manually activated. The online proportional control module controls the opening of the conventional gasoline component regulating valve according to the initial settings, allowing multiple conventional gasoline components to enter the static mixer through the blending pump, flowmeter, and regulating valve. The online proportional control module determines whether the conventional gasoline component blending volume has reached the preset value based on the flowmeter of the conventional gasoline component instrument. If the conventional gasoline component blending volume does not reach the preset flow rate, the C4 component blending circuit will not be activated. If the conventional gasoline component blending volume reaches the preset value, the C4 component shut-off valve will be opened after a delay of several seconds (typically 30-120 seconds) before the C4 component blending circuit is reopened.

[0054] S2, the C4 component control unit controls the opening of the C4 component regulating valve through the low selector, thereby completing the C4 component blending flow control.

[0055] The C4 component blending flow rate and pipeline back pressure control share a C4 component regulating valve. Therefore, an override control strategy is adopted to complete the online blending flow rate control of the C4 component, while prioritizing ensuring that the pipeline back pressure meets the safety value requirement of the C4 component saturated vapor pressure.

[0056] Start the C4 component blending circuit and judge the pipeline back pressure of the C4 component blending circuit through the low selector. If the pipeline back pressure of the C4 component blending circuit meets the safety requirement of the saturated vapor pressure safety value of the C4 component, the C4 component control unit controls the opening of the C4 component regulating valve, so that the flow rate of the C4 component increases its flow ramp to the set flow rate.

[0057] The safety value for the saturated vapor pressure of the C4 component, SP, is 0.13332 × P + S, where S is the safety margin, 0.15 ≤ S ≤ 0.25 MPa, P is the saturated vapor pressure, and lg P = AB / (T + C). A, B, and C are coefficients of 6.748, 882.8, and 240.0, respectively, and T is the temperature of the C4 component. Isobutane has the lowest boiling point among the C4 components, so the saturated vapor pressure of C4 is based on isobutane. 0.13332 is the conversion factor between MPa and mmHg.

[0058] S3, manually ending the control system for online blending of C4 component gasoline, and the status of the online proportion control module is 'end preparation' or 'pause preparation'.

[0059] The online proportional control module then sends a shutdown control signal to the C4 blending circuit. The C4 control unit controls the C4 regulating valve opening until the C4 flow rate drops to zero, then closes the C4 shut-off valve. Based on the C4 shut-off valve's valve position closure signal, the C4 control unit notifies the online proportional control module that the C4 blending circuit has been closed. The online proportional control module then issues an "end" or "pause" command, delaying 60 to 120 seconds. This control then controls the opening of the conventional gasoline regulating valve until the conventional gasoline blending volume drops to zero.

[0060] It should be noted that in the end process, the override control strategy is also adopted to complete the online blending flow control of the C4 component under the premise of giving priority to ensuring that the pipeline back pressure meets the safety value requirement of the saturated vapor pressure of the C4 component.

[0061] In some embodiments, the C4 component control unit opens the C4 component shut-off valve and controls the opening of the C4 component regulating valve based on the C4 component flow given by the online proportional control module, and ensures that the blending flow control is set with a preset blending flow maximum limit, thereby ensuring that the blending ratio of the C4 component reaches the set target.

[0062] In some embodiments, if an abnormal situation occurs in the online blending system of the C4 component, such as the completion or suspension of blending, the total blending pipe flow rate being lower than the lower limit, the inter-blending ratio of the C4 components exceeding the upper limit, or manual active intervention, the online proportion control module controls the C4 component control unit to close the C4 component shut-off valve.

[0063] like Figure 4 The figure shows an actual application example of the present invention at a refinery. This C4 component online gasoline blending control system includes five blending components stored in vertical tanks: Merox naphtha, hydrotreated naphtha, hydrocatalytic light gasoline, hydrocatalytic heavy gasoline, and alkylate. The spherical tank at the bottom of the figure contains the butane component.

[0064] The blending flow rate is 250m 3 / h. The maximum butane blending ratio is 5.0% (volume ratio), with an actual blending ratio range of 3.0±0.5%. The backpressure safety margin S is 0.20 MPa. The measured Reigniter vapor pressure (RVP) of the gasoline product is between 75 kPa and 80 kPa%, meeting quality requirements.

[0065] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. The system and system embodiments described above are merely illustrative, and some or all of the modules therein can be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying any creative work.

[0066] Professionals will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

Claims

1. A control system for online blending of C4 components into gasoline, comprising at least several conventional gasoline component control loops and an online proportion control module, wherein each conventional gasoline component corresponds to a conventional gasoline component control loop. The conventional gasoline component control circuit comprises at least a conventional gasoline component flow meter and a conventional gasoline component regulating valve, and is characterized in that: The control system for online C4 component gasoline blending also includes a C4 component blending circuit. The C4 component blending circuit at least includes a C4 component control unit, and a C4 component thermometer, a C4 component flow meter, a C4 component pressure meter, a C4 component regulating valve, and a C4 component shut-off valve, which are sequentially coupled to and respectively coupled to the C4 component control unit. The online proportion control module is used to monitor the blending ratio of various conventional gasoline components and C4 components, calculate the blending flow of conventional gasoline components and C4 components, and output a given value to each conventional gasoline component control loop and C4 component flow blending loop, thereby controlling the blending ratio of conventional gasoline components and C4 components. The C4 component control unit is used to control the C4 component regulating valve and the C4 component shut-off valve based on the C4 component set value and control signal output by the online proportional control module, as well as the parameters of the detected C4 component thermometer, C4 component flowmeter, and C4 component pressure instrument, thereby performing pipeline medium back pressure control, flow sequence control, and flow shut-off control under abnormal conditions.

2. The control system for online blending of C4 component gasoline according to claim 1, characterized in that: The C4 component control unit includes a sequence control subunit, a blending flow control subunit, and a pipeline back pressure control subunit. The output ends of the blending flow control subunit and the pipeline back pressure control subunit are coupled to the C4 component regulating valve through a low selector. The input end of the sequence control subunit is coupled to the online proportional control module, and the output end is coupled to the blending flow control subunit, which is used to start or stop the blending flow control based on the status of the online proportional control module, the C4 component flow set value and the command. The pipeline back pressure control subunit is used to control the pipeline back pressure based on the parameters of the detected C4 component pressure instrument; The blending flow control subunit is used to control the opening and closing degree of the C4 component regulating valve through the low selector based on the received start-up or withdrawal command and the C4 component flow set value, and the pipeline backpressure control subunit is used to control the pipeline backpressure, so as to complete the control of the flow and pipeline backpressure, wherein the pipeline backpressure control has a higher priority than the blending flow control.

3. The control system for online blending of C4 component gasoline according to claim 1, characterized in that: The C4 component control unit further includes an emergency cut-off control subunit coupled to the output end of the sequence control subunit, wherein the output end of the emergency cut-off control subunit is coupled to the C4 component cut-off valve. The sequence control subunit controls the emergency shutoff control subunit to shut off the C4 component shutoff valve in response to an abnormality of the control system for the C4 component online blending gasoline.

4. A control method for online blending of C4 component gasoline, applied to the control system for online blending of C4 component gasoline according to any one of claims 1 to 3, characterized in that: include: In response to the start command, the online proportional control module controls the opening of the conventional gasoline component regulating valve and determines whether the blending amount of the conventional gasoline component reaches the preset value based on the detected instrument parameters of the conventional gasoline component. If the blending amount of conventional gasoline components does not reach the preset flow rate, the C4 component blending circuit will not start; If the blending amount of conventional gasoline components reaches the preset value, the C4 component blending circuit is started and the C4 component shut-off valve is opened. The C4 component control unit controls the opening of the C4 component regulating valve through the low selector, thereby completing the C4 component blending flow control.

5. The control method for online blending of C4 component gasoline according to claim 4, characterized in that: Also includes, In response to the end command, the online proportional control module closes the C4 component blending loop. Then the C4 component control unit controls the opening of the C4 component regulating valve through the low selector until the C4 component flow rate drops to 0, and then closes the C4 component cut-off valve. Based on the valve position closing feedback signal of the C4 component cut-off valve, the C4 component control unit feeds back to the online proportional control module that the C4 component blending circuit has been closed. If the online proportional control module receives that the C4 component blending circuit is closed, it controls the opening of the conventional gasoline component regulating valve based on the preset delay time until the conventional gasoline component blending amount drops to 0.

6. The control method for online blending of C4 component gasoline according to claim 4, characterized in that: The C4 component control unit controls the opening of the C4 component regulating valve through a low selector, thereby completing the C4 component blending flow control, specifically including: the C4 component control unit is based on the C4 component flow given by the online proportional control module, the low selector receives the outputs of the pipeline back pressure control and the blending flow control, and completes the C4 blending flow control based on the pipeline back pressure being greater than the component saturated vapor pressure safety value.

7. The control method for online blending of C4 component gasoline according to claim 6, characterized in that: The safety value of the saturated vapor pressure of the C4 component SP=0.13332×P+S, where S is the safety margin, 0.15≤S≤0.25 MPa, P is the saturated vapor pressure in mmHg, lgP=AB / (T+C), A, B, and C are coefficients of 6.748, 882.8, and 240.0, respectively, and T is the temperature of the C4 component.

8. The control method for online blending of C4 component gasoline according to claim 4, characterized in that: The method also includes responding to an abnormal state, in which the online proportional control module controls the C4 component control unit to close the C4 component shut-off valve.

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