Automatic steam dryness control method for electric heating molten salt energy storage steam injection system
By adopting a combination of feedforward control and PID control in the electric-thermal molten salt energy storage steam injection system, stable and precise control of steam dryness is achieved, solving the problem of difficult dryness in the steam injection in heavy oil heat recovery steam, and improving the safety and economics of the system.
Patent Information
- Application Number
- CN202311668799.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-07
- Publication Date
- 2025-06-10
AI Technical Summary
During the steam injection process of heavy oil heat, stable control of steam dryness is difficult to achieve, resulting in excessive pipeline temperature or oil stratum water accumulation, affecting the safety and economics of the electric and hot molten salt heat storage steam injection system.
The outlet flow of the high-temperature molten salt pump is roughly adjusted by feedforward control and cascade control, and the flow of the bypass regulating valve in the heat exchanger is finely adjusted through PID control to ensure that the steam dryness is fast and precisely stable at the optimal value.
It realizes stable and precise control of steam dryness, improves the safety and economy of the electric molten salt energy storage steam injection system, is suitable for electric molten salt energy storage steam injection system, and provides safety technical guarantees for oilfield steam injection.
Smart Images
Figure CN120120537A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical fields of petrochemical industry and new energy, and particularly relates to an automatic control method for steam dryness of an electrothermal molten salt energy storage steam injection system. Background Art
[0002] Under the requirements of the dual-carbon goal, explore the electrothermal molten salt heat storage technology to replace gas consumption and achieve "replacing gas with valley electricity / green electricity". After the implementation of this technology, it can not only reduce carbon dioxide emissions, but also make full use of valley electricity / green electricity to reduce the power grid pressure.
[0003] During the steam injection process of heavy oil thermal recovery, high-pressure and high-temperature wet steam is injected into the heavy oil layer. During the production operation, the steam dryness value in the steam generation system needs to be maintained at a stable value. Too high will cause the pipeline temperature to be too high and damage, and too low will cause more oil layer water accumulation. Therefore, the dryness value is the key index for heavy oil thermal recovery work and also the key parameter affecting the stable and safe operation of electrothermal molten salt heat storage steam injection. At present, the control of dryness is mostly based on traditional gas-fired steam boilers. Therefore, there is an urgent need to develop an automatic control method for steam dryness suitable for electrothermal molten salt energy storage steam injection systems. Summary of the Invention
[0004] The purpose of the present invention is to propose an automatic control method for steam dryness of an electrothermal molten salt energy storage steam injection system, which can quickly and accurately stabilize the injection steam dryness at the optimal value and improve the safety and economy of the molten salt energy storage steam injection system.
[0005] To achieve the above purpose, an automatic control method for steam dryness of an electrothermal molten salt energy storage steam injection system proposed in the present application includes:
[0006] Establish an electrothermal molten salt heat storage and heat exchange loop system;
[0007] Coarsely adjust the outlet flow of the high-temperature molten salt pump of the electrothermal molten salt heat storage and heat exchange loop system through feedforward control + cascade control;
[0008] Finely adjust the flow of the bypass regulating valve in the heat exchanger of the electrothermal molten salt heat storage and heat exchange loop system through PID control.
[0009] Furthermore, the electrothermal molten salt heat storage and heat exchange loop system includes a loop formed by sequentially connecting an electric heater, a hot tank, a high-temperature molten salt pump, a feed water flow sensor, a heat exchanger, a cold tank, and an electric heater. A dryness sensor is provided at the outlet of the heat exchanger.
[0010] Furthermore, the specific implementation method of the coarse adjustment is:
[0011] Taking the steam dryness as the main variable, the high-temperature molten salt flow rate as the secondary variable, and the feed water flow rate as the disturbance quantity, the feed water flow rate signal is introduced as a feed-forward signal into the coarse adjustment control loop, and a flow rate ratio operation is formed with the high-temperature molten salt flow rate; meanwhile, a dead zone module is set after the comparator of the steam dryness set value and the steam dryness measured value.
[0012] Further, the coarse adjustment control loop includes a comparator, a PI controller, a deviation calculator, a P controller, a high-temperature molten salt pump, a dryness sensor, and a loop formed by connecting the comparators in sequence. The deviation calculator is also connected to a feed water flow rate sensor. If the feed water flow rate changes, the high-temperature molten salt flow rate is adjusted to ensure an energy balance between the high-temperature molten salt flow rate and the feed water flow rate.
[0013] Further, the steam dryness deviation obtained by the comparator is input to the PI controller. The deviation calculator is used to obtain the deviation signal between the output signal of the PI controller and k times the feed water flow rate. This deviation signal is amplified by a factor of k and acts on the high-temperature molten salt pump through the P controller to control the flow rate of the high-temperature molten salt pump to adjust the steam dryness.
[0014] Even further, the implementation method inside the dead zone module is as follows: when the input signal is less than -0.01 or greater than 0.01, the signal is output with a certain value, and this value increases as the input signal increases and also decreases as the input signal decreases. When the input signal is greater than -0.01 and less than 0.01, the output signal is 0.
[0015] Even further, the specific implementation method of the fine adjustment is as follows: a bypass regulating valve on the water side of the heat exchanger is used to finely adjust the steam dryness, and a similar integral saturation module is set after the comparator of the steam dryness set value and the steam dryness measured value; when the steam dryness after coarse adjustment does not reach the set value, it will enter the fine adjustment control loop to finely adjust the steam dryness to the set value through the bypass regulating valve.
[0016] Even further, the fine adjustment control loop includes a comparator, a PI controller, a bypass regulating valve, a dryness sensor, and a loop formed by connecting the comparators in sequence.
[0017] Even further, the implementation method inside the similar integral saturation module is as follows: when the input signal is less than -0.01 or greater than 0.01, the output signal is 0. When the input signal is greater than -0.01 and less than 0.01, the signal is output with a certain value, and this value increases as the input signal increases and also decreases as the input signal decreases.
[0018] Even further, the water vapor coming out of the heat exchanger enters the steam injection well, and the electric heater is connected to the power controller.
[0019] The advantages of the above technical solutions adopted by the present invention compared with the prior art are:
[0020] 1) The steam dryness control method of the present invention can achieve stable and precise control of dryness under the interference of initial steam dryness and feed water flow rate.
[0021] 2) The simulation accuracy of dryness control reaches ±0.01.
[0022] 3) The above-mentioned automatic steam dryness control method is applicable to the electrothermal molten salt energy storage steam injection system, and provides safety technical guarantee for the future development of molten salt heat storage application in oilfield steam injection. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0024] Figure 1 It is a system architecture diagram of electrothermal molten salt heat storage and heat exchange loop;
[0025] Figure 2 It is a schematic diagram of the coarse adjustment control loop;
[0026] Figure 3 It is a broken line diagram of the implementation method of the dead zone module;
[0027] Figure 4 It is a schematic diagram of the fine adjustment control loop;
[0028] Figure 5 It is a broken line diagram of the implementation method of a similar integral saturation module;
[0029] Figure 6 It is a system diagram built for the simulation of the automatic steam dryness control method;
[0030] Figure 7 It is a curve diagram of the change of dryness and the flow rate of the high-temperature molten salt pump;
[0031] Figure 8 It is a curve diagram of the change of dryness and the flow rate of the bypass regulating valve.
[0032] SPECIFIC IMPLEMENTATION METHODS
[0033] The principles of the present disclosure will be described below with reference to several exemplary embodiments shown in the drawings. Although the preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the description of these embodiments is only for enabling those skilled in the art to better understand and then implement the present disclosure, rather than limiting the scope of the present disclosure in any way.
[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the specification of the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. Components of the embodiments of this application described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.
[0035] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of this application that is claimed, but merely represents selected embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts fall within the scope of protection of this application.
[0036] It should be noted that in this text, the term "including", "comprising", or any other variant thereof is intended to cover non-exclusive inclusion, so that an article or device including a series of elements not only includes those elements but also includes other elements not explicitly listed, or further includes elements inherent to such a process, method, article, or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article, or device including the element.
[0037] In the description of this application, it should also be noted that unless otherwise clearly specified and limited, the terms "installed", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0038] This embodiment provides an automatic steam dryness control method for an electrothermal molten salt energy storage steam injection system. By establishing an electrothermal molten salt heat storage and heat exchange loop system as Figure 1 shown, the heat storage and heat exchange processes are simulated and analyzed; at the same time, considering the actual on-site conditions, fluctuations in dryness within a certain range are caused by the accuracy of high-temperature molten salt pumps or other situations. Therefore, the high-temperature molten salt pump outlet flow in the electrothermal molten salt heat storage and heat exchange loop system is roughly adjusted through a dead zone module; then, the bypass regulating valve flow in the heat exchanger of the electrothermal molten salt heat storage and heat exchange loop system is finely adjusted through a module similar to an integral saturation module, and simulation analysis of multi-scenario applications is carried out for different water supply conditions. The heat exchanger includes a preheater, a heater, and an evaporator connected in sequence.
[0039] As Figure 2As shown in the figure, the specific implementation method of the coarse adjustment is as follows: taking the steam dryness as the main variable, the high-temperature molten salt flow rate as the secondary variable, and the feed water flow rate as the disturbance quantity, introducing the feed water flow rate signal as a feed-forward signal into the coarse adjustment control loop, and forming a certain flow ratio operation with the high-temperature molten salt flow rate. Once the feed water flow rate changes and a disturbance occurs, the high-temperature molten salt flow rate is quickly adjusted to ensure the energy balance between the high-temperature molten salt flow rate and the feed water flow rate. At the same time, a dead zone module is set after the comparator of the steam dryness set value and the steam dryness measured value to simulate the situation where the accuracy of the high-temperature molten salt pump on site is insufficient and the steam dryness cannot be accurately adjusted.
[0040] Exemplarily, the steam dryness set value is 0.8, and the deviation obtained by comparing it with the steam dryness measured value is input into the PI controller. The output signal of the PI controller and the k-fold value of the feed water flow rate monitoring are used to calculate the deviation signal, and the deviation signal is amplified by the k-fold coefficient and acts on the high-temperature molten salt pump to control the flow rate of the high-temperature molten salt pump to adjust the steam dryness.
[0041] As Figure 3 shown in the figure, the implementation method inside the dead zone module is as follows: when the input signal is less than -0.01 or greater than 0.01, the signal is output with a certain value, and this value increases (decreases) as the input signal increases (decreases). When the input signal is greater than -0.01 and less than 0.01, the output signal is 0.
[0042] As Figure 4 shown in the figure, the specific implementation method of the fine adjustment is as follows: using the bypass regulating valve on the water side of the heater to finely adjust the steam dryness, and setting a similar integral saturation module after the comparator of the steam dryness set value and the steam dryness measured value. Its purpose is that when the high-temperature molten salt pump fails to adjust the steam dryness to the set value, it will enter the bypass regulating valve to adjust the steam dryness to the set value. For example, the steam dryness set value is 0.8. When the steam dryness measured value is less than 0.79 or greater than 0.81, the high-temperature molten salt pump acts to adjust the steam dryness; when the steam dryness measured value is within the range of 0.79 or 0.81 and enters the dead zone, the input signal of the PI controller is 0, and at this time the high-temperature molten salt pump does not act and enters the bypass valve adjustment.
[0043] As Figure 5 shown in the figure, the implementation method inside the similar integral saturation module is as follows: when the input signal is less than -0.01 or greater than 0.01, the output signal is 0. When the input signal is greater than -0.01 and less than 0.01, the signal is output with a certain value, and this value increases (decreases) as the input signal increases (decreases).
[0044] In as Figure 6Simulation and analysis of steam dryness control in the system shown. Set the feed water flow rate to a fixed flow rate (normal flow rate) of 7 t / h. Under the interference of the initial steam dryness being 0.97, the initial opening of the bypass regulating valve is set to 0.4. The corresponding parameter settings of the controller are shown in the following table.
[0045] Controller type Parameter setting Main controller of high-temperature molten salt pump PI k = 0.1, Ti = 0.1s Proportional control of high-temperature molten salt pump P k＝17 Proportional control of water supply P k＝0.1 Bypass valve controller PI k = -10, Ti = 0.1s
[0046] Figure 7 To adjust the steam dryness with a fixed feed water flow rate, corresponding to the changes in dryness and the flow rate of the high-temperature molten salt pump. According to the simulation results, when the feed water flow rate is fixed at (normal flow rate) 1.94 kg / s (7 t / h), since the initial steam dryness at the evaporator outlet is 0.97, this monitoring signal and the set target signal of 0.8 enter the comparator. The error output by the comparator enters the dead zone module, and the dead zone module will output a corresponding numerical signal to roughly adjust the steam dryness of the high-temperature molten salt pump. Before 2.5 s, the dryness drops from 0.97 to 0.81, and the high-temperature molten salt pump keeps working. The molten salt flow rate drops from 7.4 kg / s to 6.245 kg / s (22.48 t / h). At 2.5 s, the dryness is adjusted to 0.81, and at this time the pump regulation stops, and the pump flow rate runs at 22.48 t / h.
[0047] Figure 8 To adjust the steam dryness with a fixed feed water flow rate, corresponding to the changes in dryness and the flow rate of the bypass regulating valve. According to the simulation results, when the feed water flow rate is fixed at (normal flow rate) 1.94 kg / s (7 t / h), since the initial steam dryness at the evaporator outlet is 0.97, this monitoring signal and the set target signal of 0.8 enter the comparator. The error output by the comparator enters a module similar to the integral saturation module, and the module similar to the integral saturation module will output a corresponding numerical signal to finely adjust the steam dryness of the bypass regulating valve. Before 2.5 s, the dryness drops from 0.97 to 0.81, and it is always the high-temperature molten salt pump that works. The input signal of the PI controller before the bypass regulating valve is always 0, and the bypass regulating valve does not act and remains at the initial opening of 0.4. At 2.5 s, the dryness is adjusted to 0.81. At this time, the high-temperature molten salt pump stops regulating, and the flow rate of the bypass regulating valve increases until the flow rate reaches 0.7 kg / s (2.52 t / h) and the dryness reaches 0.8, and then the bypass valve stops regulating.
[0048] The above description is only an optional embodiment of the present disclosure and is not used to limit the present disclosure. For those skilled in the art, various changes and modifications can be made to the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included within the protection scope of the present disclosure.
[0049] Although the claims in this application have been formulated for specific combinations of features, it should be understood that the scope of the present disclosure also includes any novel feature or any novel combination of features that are explicitly or implicitly disclosed herein or any generalization thereof, whether or not it relates to the same solution as in any of the currently claimed claims.
Claims
1. An automatic control method for steam dryness in an electrothermal molten salt energy storage steam injection system, characterized in that, it includes: Establish an electrothermal molten salt heat storage and heat exchange loop system; Coarsely adjust the outlet flow rate of the high-temperature molten salt pump in the electrothermal molten salt heat storage and heat exchange loop system through feedforward control + cascade control; Finely adjust the flow rate of the bypass regulating valve in the heat exchanger of the electrothermal molten salt heat storage and heat exchange loop system through PID control.
2. The automatic control method for steam dryness in an electrothermal molten salt energy storage steam injection system according to claim 1, characterized in that, The electrothermal molten salt heat storage and heat exchange loop system includes a loop formed by sequentially connecting an electric heater, a hot tank, a high-temperature molten salt pump, a feed water flow sensor, a heat exchanger, a cold tank, and an electric heater in sequence, and a dryness sensor is provided at the outlet of the heat exchanger.
3. The automatic control method for steam dryness in an electrothermal molten salt energy storage steam injection system according to claim 2, characterized in that, The specific implementation method of the coarse adjustment is: Take the steam dryness as the main variable, the high-temperature molten salt flow rate as the secondary variable, and the feed water flow rate as the interference quantity. Introduce the feed water flow rate signal as a feedforward signal into the coarse adjustment control loop and form a flow ratio operation with the high-temperature molten salt flow rate; at the same time, set a dead zone module after the comparator of the steam dryness set value and the steam dryness measured value.
4. The automatic control method for steam dryness in an electrothermal molten salt energy storage steam injection system according to claim 3, characterized in that, The coarse adjustment control loop includes a loop formed by sequentially connecting a comparator, a PI controller, a deviation calculator, a P controller, a high-temperature molten salt pump, a dryness sensor, and a comparator. The deviation calculator is also connected to the feed water flow sensor. If the feed water flow rate changes, the high-temperature molten salt flow rate is adjusted to ensure an energy balance between the high-temperature molten salt flow rate and the feed water flow rate.
5. The automatic control method for steam dryness in an electrothermal molten salt energy storage steam injection system according to claim 4, characterized in that, The steam dryness deviation obtained by the comparator is input to the PI controller. Use the deviation calculator to obtain the deviation signal of k times the output signal of the PI controller and the feed water flow rate. This deviation signal is amplified by a k-fold coefficient and acts on the high-temperature molten salt pump through the P controller to control the flow rate of the high-temperature molten salt pump to adjust the steam dryness.
6. The automatic control method for steam dryness in an electrothermal molten salt energy storage steam injection system according to claim 3, characterized in that, The implementation method in the dead zone module is: when the input signal is less than -0.01 or greater than 0.01, output a signal with a certain value, and this value increases as the input signal increases and also decreases as the input signal decreases. When the input signal is greater than -0.01 and less than 0.01, the output signal is 0.
7. The automatic control method for steam dryness in an electrothermal molten salt energy storage steam injection system according to claim 2, characterized in that, The specific implementation method of the fine adjustment is as follows: a bypass regulating valve on the water side of the heat exchanger is used to finely adjust the steam dryness, and a similar integral saturation module is set after the comparator of the steam dryness set value and the steam dryness measured value; when the steam dryness after the rough adjustment does not reach the set value, it will enter the fine adjustment control loop to finely adjust the steam dryness to the set value through the bypass regulating valve.
8. The automatic steam dryness control method for an electrothermal molten salt energy storage steam injection system according to claim 7, characterized in that the fine adjustment control loop includes a comparator, a PI controller, a bypass regulating valve, a dryness sensor, and a loop formed by connecting the comparators in sequence.
9. The automatic steam dryness control method for an electrothermal molten salt energy storage steam injection system according to claim 7, characterized in that the implementation method in the similar integral saturation module is as follows: when the input signal is less than -0.01 or greater than 0.01, the output signal is 0; when the input signal is greater than -0.01 and less than 0.01, the output signal is output with a certain value, and this value increases as the input signal increases and also decreases as the input signal decreases.
10. The automatic steam dryness control method for an electrothermal molten salt energy storage steam injection system according to claim 2, characterized in that the water vapor coming out of the heat exchanger enters the steam injection well, and the electric heater is connected to the power controller.