Steam generation system based on solid heat accumulation and molten salt heating and control method thereof

Abstract

The embodiment of the present application provides a steam generation system based on solid heat storage and molten salt heating and a control method thereof, and belongs to the technical field of oil exploitation equipment. The system comprises: a preheating device connected with the water supply device, used for preheating softened water; a steam generation device connected at the outlet end of the preheating device, used for performing multi-stage evaporation on the preheated softened water to obtain wet saturated steam for steam injection; wherein the steam generation device is correspondingly arranged with a molten salt heat storage device, and the steam generation device exchanges heat with high-temperature molten salt in the molten salt heat storage device to obtain wet saturated steam for steam injection; and a control device is used for generating a linkage control scheme of the water supply device, the preheating device and the steam generation device based on real-time steam injection demand. The present application overcomes the problems of slow start response and poor linkage in the prior art, and significantly improves the operation efficiency and energy efficiency of the steam generation system.

Description

Technical Field

[0001] This invention relates to the field of oil extraction equipment technology, specifically to a steam generation system based on solid heat storage and molten salt heating, and a control method for the steam generation system based on solid heat storage and molten salt heating. Background Technology

[0002] Heavy oil thermal recovery technology is a crucial method for oilfield development, with wet saturated steam injection systems serving as key equipment that requires efficient steam generation and low-carbon operation. However, traditional steam generation systems typically rely on gas-fired boilers, resulting in high energy consumption, large carbon emissions, and slow equipment start-up response, making it difficult to meet current requirements for energy conservation, emission reduction, and efficient operation. Under the dual-carbon goals, steam generation systems based on electrothermal energy are gaining increasing attention. While existing molten salt thermal storage-based steam generation systems offer the advantage of efficient thermal storage using electricity, they suffer from the following shortcomings under complex steam injection requirements:

[0003] 1) Slow start-up response and poor operational flexibility: Existing systems typically use molten salt as the sole heat source for steam generation. During the molten salt heating process, effective heat exchange can only occur after the salt reaches a high temperature, resulting in a long system start-up response time. Furthermore, the system usually preheats softened water through steam recirculation, increasing the complexity of steam pipelines and heat loss, while also placing higher demands on the scale of pumps and piping equipment, leading to increased energy consumption.

[0004] 2) Lack of dynamic linkage control, unable to meet real-time demands: Traditional systems typically operate according to a fixed process flow and lack the ability to adjust in conjunction with real-time steam injection demands. When steam injection demands change, the lack of effective linkage control between water supply, preheating, and steam generation units makes it difficult to quickly adjust heating load and steam output parameters, resulting in energy waste and reduced operating efficiency.

[0005] To address the above problems, a new steam generation system is needed. Summary of the Invention

[0006] The purpose of this invention is to provide a steam generation system based on solid heat storage and molten salt heating, so as to at least solve the problems of slow response speed and poor control performance of existing steam generation systems.

[0007] To achieve the above objectives, a first aspect of the present invention provides a steam generation system based on solid heat storage and molten salt heating. The system includes: a water supply device for supplying softened water; a preheating device connected to the water supply device for preheating the softened water; wherein the preheating device is correspondingly configured with a solid heat storage device, and the preheating device preheats the softened water by exchanging heat with the solid heat storage device; a steam generation device connected to the outlet end of the preheating device for performing multi-stage evaporation on the preheated softened water to obtain wet saturated steam for injection; wherein the steam generation device is correspondingly configured with a molten salt heat storage device, and the steam generation device obtains wet saturated steam for injection by exchanging heat with the high-temperature molten salt in the molten salt heat storage device; and a control device for generating a coordinated control scheme for the water supply device, preheating device, and steam generation device based on real-time steam injection demand.

[0008] Optionally, the water supply device includes: a softened water tank for storing softened water; and a plunger pump connected by a pipeline to the outlet side of the softened water tank for pressurizing the softened water when supplying it to the preheating device, so as to supply water under high pressure.

[0009] Optionally, the solid heat storage device is equipped with one or multiple solid heat storage devices arranged in stages; a temperature sensor is installed at the outlet of the preheating device to collect the real-time temperature of the output softened water; the control module is also used to determine whether the real-time temperature of the output softened water of the preheating device meets the required temperature of the steam generating device.

[0010] Optionally, the solid heat storage device includes a circulation pipeline; if the real-time temperature of the softened water output by the preheating device does not meet the required temperature of the steam generating device, the softened water output by the preheating device flows back to the inlet of the preheating device through the circulation pipeline to perform secondary preheating until the real-time temperature of the softened water output by the preheating device meets the required temperature of the steam generating device, at which point the circulation pipeline is closed.

[0011] Optionally, the control device is configured to: collect in real time the current storage capacity of the steam injection well, system operating status parameters, and historical steam injection data as prediction basis data; perform steam injection demand prediction for a predetermined future time based on the long short-term memory network and the prediction basis data; determine the operating parameters of the water supply device, preheating device, and steam generation device based on the predicted steam injection demand value; and generate a corresponding joint control scheme based on the determined operating parameters of the water supply device, preheating device, and steam generation device.

[0012] Optionally, the rule for predicting steam injection demand at a predetermined future time based on the Long Short-Term Memory network and the aforementioned prediction base data is as follows:

[0013]

[0014] in, For prediction models of long short-term memory networks; Historical steam injection data; The time span of historical steam injection data; The method further includes determining the rate of change of demand based on the steam injection demand at a predetermined future time and the current storage capacity of the steam injection well.

[0015] Optionally, the operating parameters of the water supply device are determined according to the following rules: based on the steam injection demand at a predetermined future time and the current operating efficiency of the system, the target water supply volume to meet the corresponding steam injection demand is determined, and the determination rule is as follows:

[0016]

[0017] in, The target water supply volume; To determine the current system's operating efficiency, based on the determined target water supply volume and the time interval between the future scheduled time and the current time, the minimum operating power of the water supply device is determined as the operating parameter of the water supply device.

[0018] Optionally, the operating parameters of the preheating device are determined according to the following rules: the target water supply temperature is determined based on the saturation temperature of the steam required for the steam injection demand at a predetermined future time and the heat exchange efficiency of the steam generator; the target preheating heat is determined based on the target water supply temperature and the current water supply temperature, and the determination rules are as follows:

[0019]

[0020] in, Preheat the target with heat; The target water supply volume; The specific heat capacity of softened water; and The target temperature and the current water supply temperature are respectively used; based on the determined target preheating heat and the time interval between the future predetermined time and the current time, the minimum operating power of the preheating device is determined as the operating parameter of the preheating device.

[0021] Optionally, the operating parameters of the steam generating unit are determined by the following rule: based on the steam injection demand at a predetermined future time and the latent heat of vaporization of the steam in the steam generating unit, the target steam generation heat is determined by the following rule:

[0022]

[0023] in, To generate heat for the target steam; The latent heat of vaporization of steam in the steam generating unit is determined; the molten salt circulation flow rate is determined based on the target steam generation heat; and the minimum operating power of the steam generating unit is determined based on the target steam generation heat and the molten salt circulation flow rate, as well as the time interval between a future predetermined time and the current time, serving as the operating parameters of the preheating unit.

[0024] Optionally, the rule for determining the molten salt circulation flow rate based on the target steam generation heat is as follows:

[0025]

[0026] in, This refers to the molten salt circulation flow rate; The specific heat capacity of molten salt; and These are the temperatures of hot salt and cold salt, respectively.

[0027] Optionally, a corresponding joint control scheme is generated based on the determined operating parameters of the water supply device, preheating device, and steam generation device. This includes: performing state initialization based on the minimum operating power of the water supply device, the minimum operating power of the preheating device, and the minimum operating power of the steam generation device; randomly adjusting the operating power of one operating device and updating the operating power of the other two operating devices based on the adjusted operating power, and calculating the function value of the pre-constructed objective function after adjustment; updating the operating power of each operating device based on the function value until the function value of the objective function meets the iteration termination condition or reaches the preset number of iterations, and outputting the operating power of each operating device in the optimal state; and generating a corresponding joint control scheme based on the operating power of each operating device in the optimal state and the current operating power of each operating device.

[0028] Optionally, the pre-constructed objective function is:

[0029]

[0030] in, Total power; The time interval between a future scheduled time and the current time; , and These represent the operating power of the water supply device, preheating device, and steam generation device after this round of iteration.

[0031] Optionally, the step of generating a corresponding joint control scheme based on the operating power of each operating device under optimal conditions and the current operating power of each operating device includes: determining the power to be adjusted based on the operating power of each operating device under optimal conditions and the current operating power of each operating device; performing decoupling on the power to be adjusted to obtain the adjustment amount of each execution component, so as to determine the adjustment scheme of each component; and combining the adjustment schemes of all components to obtain the joint control scheme.

[0032] Optionally, the system further includes: a pressure relief device for releasing the gas pressure in the outlet pipe of the preheating device when the steam supply is stopped; the pressure relief device is connected to the water supply pipe between the preheating device and the steam generating device via a three-way valve; the pressure relief device includes a discharge expansion container for storing the high-pressure softened water that flows in during the pressure relief process.

[0033] Optionally, the control device is also configured to control the valve on the discharge expansion container side of the three-way valve to open in response to a pressure relief request command.

[0034] A second aspect of the present invention provides a control method for a steam generation system based on solid thermal storage and molten salt heating. The method is applied to the aforementioned steam generation system based on solid thermal storage and molten salt heating. The method includes: real-time acquisition of the current steam injection well's storage capacity, system operating status parameters, and historical steam injection data as prediction basis data; performing steam injection demand prediction for a predetermined future time based on a long short-term memory network and the prediction basis data; determining the operating parameters of the water supply device, preheating device, and steam generation device based on the predicted steam injection demand values; and generating a corresponding joint control scheme based on the determined operating parameters of the water supply device, preheating device, and steam generation device.

[0035] Optionally, the rule for predicting steam injection demand at a predetermined future time based on the Long Short-Term Memory network and the aforementioned prediction base data is as follows:

[0036]

[0037] in, For prediction models of long short-term memory networks; Historical steam injection data; The time span of historical steam injection data; The method further includes determining the rate of change of demand based on the steam injection demand at a predetermined future time and the current storage capacity of the steam injection well.

[0038] Optionally, a corresponding joint control scheme is generated based on the determined operating parameters of the water supply device, preheating device, and steam generation device. This includes: performing state initialization based on the minimum operating power of the water supply device, the minimum operating power of the preheating device, and the minimum operating power of the steam generation device; randomly adjusting the operating power of one operating device and updating the operating power of the other two operating devices based on the adjusted operating power, and calculating the function value of the pre-constructed objective function after adjustment; updating the operating power of each operating device based on the function value until the function value of the objective function meets the iteration termination condition or reaches the preset number of iterations, and outputting the operating power of each operating device in the optimal state; and generating a corresponding joint control scheme based on the operating power of each operating device in the optimal state and the current operating power of each operating device.

[0039] Optionally, the pre-constructed objective function is:

[0040]

[0041] in, Total power; The time interval between a future scheduled time and the current time; , and These represent the operating power of the water supply device, preheating device, and steam generation device after this round of iteration.

[0042] On the other hand, the present invention provides a computer-readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the above-described control method for a steam generation system based on solid heat storage and molten salt heating.

[0043] Through the above technical solution, this invention combines a solid heat storage device with a preheating device, utilizing the stable heat provided by the solid heat storage device to efficiently preheat softened water, shortening system start-up time and reducing energy waste during preheating. Simultaneously, the steam generation device is linked with the molten salt heat storage device, using high-temperature molten salt to perform multi-stage evaporation of the preheated softened water, achieving efficient generation of wet saturated steam and improving thermal energy utilization. By setting up a control device, the system can monitor steam injection demand in real time and dynamically generate a linkage control scheme for the water supply device, preheating device, and steam generation device, thereby quickly responding to changes in steam injection demand, avoiding energy waste, and improving the flexibility and stability of system operation. This invention overcomes the problems of slow start-up response and poor linkage in existing technologies, significantly improving the operating efficiency and energy efficiency of the steam generation system.

[0044] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0045] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0046] Figure 1 This is a system structure diagram of a steam generation system based on solid heat storage and molten salt heating provided in one embodiment of the present invention;

[0047] Figure 2 This is a structural diagram of a steam generation system based on solid heat storage and molten salt heating provided in one embodiment of the present invention;

[0048] Figure 3 This is a flowchart of the steps of a steam generation system control method based on solid heat storage and molten salt heating provided by one embodiment of the present invention.

[0049] Explanation of reference numerals in the attached figures

[0050] 1. Softened water tank; 2. Water supply booster pump; 3. Water supply flow meter; 4. Plunger pump; 5. High-pressure water supply pipeline; 6. Solid heat storage preheater; 7. Direct-flow molten salt heater; 8. Direct-flow molten salt evaporator; 9. Steam pipeline; 10. High-temperature and high-pressure water supply pipeline; 11. Start-up and discharge pipeline; 12. Three-way regulating valve; 13. Discharge expansion tank; 14. High-temperature molten salt pump; 15. Control device. Detailed Implementation

[0051] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0052] Figure 1 This is a system structure diagram of a steam generation system based on solid thermal storage and molten salt heating according to one embodiment of the present invention. Figure 1As shown, this invention provides a steam generation system based on solid heat storage and molten salt heating. The system includes: a water supply device for supplying softened water; a preheating device connected to the water supply device for preheating the softened water; wherein the preheating device is correspondingly arranged with the solid heat storage device, and the preheating device preheats the softened water by performing heat exchange with the solid heat storage device; a steam generation device connected to the outlet end of the preheating device for performing multi-stage evaporation on the preheated softened water to obtain wet saturated steam for injection; wherein the steam generation device is correspondingly arranged with the molten salt heat storage device, and the steam generation device obtains wet saturated steam for injection by performing heat exchange with the high-temperature molten salt in the molten salt heat storage device; and a control device for generating a linkage control scheme for the water supply device, the preheating device, and the steam generation device based on real-time steam injection demand.

[0053] In this embodiment of the invention, the solution combines a solid-state thermal storage device with a preheating device. The stable heat provided by the solid-state thermal storage device efficiently preheats the softened water, shortening the system start-up time and reducing energy waste during preheating. Simultaneously, the steam generation device is linked with the molten salt thermal storage device, using high-temperature molten salt to perform multi-stage evaporation of the preheated softened water, achieving efficient generation of wet saturated steam and improving thermal energy utilization. By incorporating a control device, the system can monitor steam injection demand in real time and dynamically generate a coordinated control scheme for the water supply device, preheating device, and steam generation device. This allows for rapid response to changes in steam injection demand, avoiding energy waste and improving the flexibility and stability of system operation. This invention overcomes the problems of slow start-up response and poor linkage in existing technologies, significantly improving the operating efficiency and energy efficiency of the steam generation system.

[0054] Preferably, the water supply device includes: a softened water tank for storing softened water; and a plunger pump connected by a pipeline to the outlet side of the softened water tank for pressurizing the softened water when supplying it to the preheating device, so as to supply water under high pressure.

[0055] In this embodiment of the invention, the softened water tank, through the storage of softened water, can adapt to the dynamic water supply needs of the steam injection system, ensuring a sufficient supply of softened water in a short period of time. Meanwhile, the plunger pump, through its precise pressure regulation function, provides a constant high-pressure input of softened water to the preheating device and the steam generation device. This design is particularly suitable for the dynamic demand for wet saturated steam in heavy oil field steam injection systems.

[0056] In existing technologies, due to dynamic fluctuations in steam injection demand, insufficient water supply pressure and flow directly affect the efficiency of subsequent preheating and steam generation. This is especially true during system startup or load fluctuations, when the softened water supply is prone to instability, leading to reduced preheating device efficiency and increased energy consumption. This invention uses a plunger pump to pressurize the softened water, delivering it to the preheating device under high pressure. This not only increases the water supply pressure but also optimizes the heat exchange efficiency of the preheating device, thereby reducing energy loss during system load adjustments.

[0057] Based on the present invention, and combining solid-state thermal storage with molten salt thermal storage design, the high-pressure water supply method of the water supply device of the present invention significantly improves the problem of unstable water supply in existing systems, providing constant and stable input conditions for the preheating device and the steam generation device. The combined design of the softened water tank and the plunger pump can quickly respond to the water supply parameter adjustment scheme generated by the control device, ensuring the continuous and stable operation of the water supply system even when the dynamic steam injection demand changes. At the same time, through the efficient pressurization of the plunger pump, the softened water can quickly heat up and enter the multi-stage evaporation stage, shortening the system start-up time and reducing energy waste during the system start-up process. In addition, the precise control function of the plunger pump can reduce the operating energy consumption of the water supply device, which is consistent with the goal of improving the overall operating efficiency of the system and optimizing energy consumption proposed in the original document, providing strong support for energy conservation and emission reduction of the steam injection system.

[0058] Preferably, the solid heat storage device is equipped with one or multiple solid heat storage devices arranged in stages; a temperature sensor is installed at the outlet of the preheating device to collect the real-time temperature of the output softened water; the control module is also used to determine whether the real-time temperature of the output softened water of the preheating device meets the required temperature of the steam generating device.

[0059] Furthermore, the solid heat storage device includes a circulation pipe; when the real-time temperature of the softened water output by the preheating device does not meet the required temperature of the steam generating device, the softened water output by the preheating device flows back to the inlet of the preheating device through the circulation pipe to perform secondary preheating until the real-time temperature of the softened water output by the preheating device meets the required temperature of the steam generating device, at which point the circulation pipe is closed.

[0060] In this embodiment of the invention, the solid-state heat storage device includes one or more tiered solid-state heat storage units. Different heat storage units can provide heat exchange at different temperature levels according to the preheating requirements of the softened water, thereby achieving efficient heat distribution and utilization. To further improve the accuracy of the preheating process, a temperature sensor is installed at the outlet of the preheating device to monitor the output temperature of the softened water in real time. The temperature sensor can feed back the real-time collected softened water temperature data to the control module. The control module then compares the real-time temperature of the softened water output from the preheating device with the target temperature required by the steam generation device to determine whether the temperature requirement for subsequent steam generation is met.

[0061] In actual operation, when the real-time temperature of the softened water output from the preheating unit does not reach the required temperature of the steam generator, the control module can use the circulation pipeline designed for the solid heat storage device to return the softened water from the preheating unit outlet to the preheating unit inlet for secondary preheating. This circulating preheating design not only ensures that the softened water temperature reaches the target requirement of the steam generator, but also avoids the problems of reduced heat exchange efficiency and system performance degradation caused by the water directly entering the steam generator due to insufficient temperature. The secondary preheating process continues until the real-time temperature of the softened water reaches the target required temperature, at which point the control module closes the circulation pipeline and restores the normal water supply process.

[0062] Through the above design, the solid heat storage device can not only provide heat in stages to meet different preheating needs, but also establish a high-precision softened water temperature regulation mechanism by combining temperature sensors and circulation loops.

[0063] Preferably, the control device is configured to: collect in real time the current storage capacity of the steam injection well, system operating status parameters, and historical steam injection data as prediction basis data; perform steam injection demand prediction for a predetermined future time based on the long short-term memory network and the prediction basis data; determine the operating parameters of the water supply device, preheating device, and steam generation device based on the predicted steam injection demand value; and generate a corresponding joint control scheme based on the determined operating parameters of the water supply device, preheating device, and steam generation device.

[0064] In this embodiment of the invention, the control device establishes a comprehensive predictive dataset by real-time acquisition of the current storage capacity of the steam injection well, system operating status parameters (such as softened water flow rate, preheating temperature, steam output pressure, etc.), and historical steam injection data. Based on time series prediction algorithms such as Long Short-Term Memory (LSTM) networks, the control device can capture the temporal characteristics of historical data and accurately predict the steam injection demand at a predetermined future time. The use of the LSTM model enables the system to handle complex trends in steam injection demand, making it particularly suitable for nonlinear and variable operating conditions in oilfield steam injection processes.

[0065] After obtaining the predicted steam injection demand, the control unit further dynamically determines the operating parameters of the water supply unit, preheating unit, and steam generation unit based on the prediction results. For example, the predicted steam injection demand determines key operating parameters such as the target softened water supply, the heat output of the preheating unit, and the molten salt circulation flow rate of the steam generation unit, ensuring that all modules of the system work efficiently and collaboratively while meeting the steam injection demand. Finally, the control unit generates a linkage control scheme based on the calculated operating parameters, realizing the full-process linkage control of the water supply unit, preheating unit, and steam generation unit, and quickly responding to dynamically changing steam injection demands.

[0066] Specifically, the rules for predicting steam injection demand at a predetermined future time based on the Long Short-Term Memory network and the aforementioned prediction base data are as follows:

[0067]

[0068] in, For prediction models of long short-term memory networks; Historical steam injection data; The time span of historical steam injection data; The method further includes determining the rate of change of demand based on the steam injection demand at a predetermined future time and the current storage capacity of the steam injection well.

[0069] In this embodiment of the invention, the present invention uses a Long Short-Term Memory (LSTM) network combined with predictive baseline data to predict steam injection demand at a predetermined future time. The predictive baseline data includes historical steam injection data, the current operating status of the steam injection wells, and relevant external parameters such as steam injection pressure, temperature, and steam flow rate. Historical steam injection data records the changing trends of steam injection demand over different time periods. By modeling and analyzing this data using the LSTM network, the time-series characteristics and potential nonlinear relationships of steam injection demand can be effectively captured. Compared to traditional linear prediction models, LSTM can remember data features over a longer time span and is more sensitive to short-term changes, thereby improving prediction accuracy.

[0070] Based on this, the system analyzes the storage capacity of the injection well (such as the maximum acceptable steam volume and current storage status) and further combines this with the real-time demand change rate to revise the steam injection demand for future predetermined times. This process can dynamically adjust the prediction results to better reflect actual operating conditions. For example, when the current storage capacity of the injection well is low, the system can appropriately lower the predicted value of future steam injection demand to avoid excessive steam generation and resource waste; when the storage capacity is sufficient, it can maintain an efficient steam injection plan.

[0071] Based on the present invention, by introducing a Long Short-Term Memory (LSTM) network, the long-term trends and short-term variation patterns of historical steam injection data can be captured simultaneously, improving the accuracy of future steam injection demand forecasting. By combining the storage capacity of the injection wells and real-time operating conditions to correct the forecast results, the system can dynamically respond to changes in actual demand, avoiding deviations caused by traditional static forecasting methods. By optimizing the matching of forecast results with the current operating status, the system can effectively avoid steam surplus or shortage due to forecast errors. High-precision steam injection demand forecasting provides a reliable basis for the coordinated control of subsequent water supply, preheating, and steam generation units, thereby improving the overall system operating efficiency.

[0072] Furthermore, the rules for determining the operating parameters of the water supply device are as follows: based on the steam injection demand at a predetermined future time and the current operating efficiency of the system, the target water supply volume to meet the corresponding steam injection demand is determined, and the determination rules are as follows:

[0073]

[0074] in, The target water supply volume; To determine the current system's operating efficiency, based on the determined target water supply volume and the time interval between the future scheduled time and the current time, the minimum operating power of the water supply device is determined as the operating parameter of the water supply device.

[0075] In this embodiment of the invention, the operating parameter determination rule for the water supply device, based on the future steam injection demand at a predetermined time and the current system operating efficiency, aims to meet the needs of dynamic adjustment of the steam injection system. Specifically, the determination of the target water supply volume requires comprehensive consideration of the future steam injection demand and the current actual operating efficiency of the system. By converting the steam injection demand into a water supply demand, the operating parameters of the water supply device are coordinated with the overall system target. The future steam injection demand is obtained through real-time data acquisition and prediction algorithms, combined with the key parameter of the current system operating efficiency, to adjust the target water supply volume to ensure that the output flow of the water supply device meets the needs of the preheating and steam generation devices. After the target water supply volume is determined, the minimum operating power of the water supply device needs to be further calculated based on the current operating capacity of the water supply device and the time interval between the future predetermined time and the current time. This power parameter ensures both the timeliness and stability of the water supply and minimizes the energy consumption of the water supply device, thereby achieving the dual goals of efficiency and energy saving. The operating parameters of the water supply device, including flow rate and power, are dynamically adjusted and, under the coordinated control of the control device, are consistent with the preheating device and the steam generation device.

[0076] Furthermore, the rules for determining the operating parameters of the preheating device are as follows: The target water supply temperature is determined based on the saturation temperature of the steam required for future steam injection demand and the heat exchange efficiency of the steam generator; the target preheating heat is determined based on the target water supply temperature and the current water supply temperature, and the determination rules are as follows:

[0077]

[0078] in, Preheat the target with heat; The target water supply volume; The specific heat capacity of softened water; and The target temperature and the current water supply temperature are respectively used; based on the determined target preheating heat and the time interval between the future predetermined time and the current time, the minimum operating power of the preheating device is determined as the operating parameter of the preheating device.

[0079] In this embodiment of the invention, the operating parameter determination rule for the preheating device aims to meet the steam injection demand at a predetermined future time. Combining the saturation temperature required for steam generation and the heat exchange efficiency of the steam generator, the target temperature of the water supply is first determined. Determining the target temperature is core to meeting the needs of the steam generator, ensuring that the softened water entering the steam generator has a high initial temperature, thereby reducing energy consumption during the evaporation process. The calculation of the target preheating heat is based on the difference between the target water supply temperature and the current water supply temperature, combined with the water supply flow rate and the specific heat capacity of the softened water, which can accurately describe the amount of heat required by the preheating device. By calculating the target preheating heat, the preheating device can dynamically determine the minimum required operating power based on the time interval between the predetermined future time and the current time, thus serving as the operating parameter input for the preheating device. This calculation rule not only meets the stringent temperature requirements of dynamic steam injection demand changes but also avoids unnecessary energy waste through accurate calculation of the minimum power, achieving system energy efficiency optimization.

[0080] Furthermore, the operating parameters of the steam generation unit are determined according to the following rules: based on the steam injection demand at a predetermined future time and the latent heat of vaporization of steam in the steam generation unit, the target steam generation heat is determined according to the following rules:

[0081]

[0082] in, To generate heat for the target steam; The latent heat of vaporization of steam in the steam generating unit is determined; the molten salt circulation flow rate is determined based on the target steam generation heat; and the minimum operating power of the steam generating unit is determined based on the target steam generation heat and the molten salt circulation flow rate, as well as the time interval between a future predetermined time and the current time, serving as the operating parameters of the preheating unit.

[0083] In this embodiment of the invention, the operating parameter determination rule for the steam generation device is based on the steam injection demand at a predetermined future time. Combining the operating characteristics of the steam generation device and the latent heat of vaporization of steam, the target steam generation heat is first calculated. The target steam generation heat is a key parameter for meeting future steam injection demand and directly affects the operating power of the steam generation device. By converting future steam injection demand into the heat required for steam generation, the total energy that the steam generation device needs to transfer to the water supply is determined to ensure that the steam injection demand is met.

[0084] Based on the target steam generation heat, the molten salt circulation flow rate is further calculated. As the primary heat source for the steam generator, the circulation flow rate of the molten salt determines the heat exchange efficiency and heat supply capacity of the steam generator. According to the target steam generation heat, the specific heat capacity of the molten salt, and the temperature difference between the inlet and outlet of the molten salt, the required circulation flow rate of the molten salt can be accurately determined, ensuring efficient heat exchange while avoiding energy waste caused by excessive circulation. Furthermore, by combining the time interval between a future predetermined time and the current time, the minimum operating power of the steam generator is calculated as an input condition for operating parameters. The calculation of the minimum operating power ensures that the steam generator meets the steam injection requirements while minimizing operating energy consumption, thereby optimizing the overall energy utilization efficiency of the system.

[0085] Furthermore, the rule for determining the molten salt circulation flow rate based on the target steam generation heat is as follows:

[0086]

[0087] in, This refers to the molten salt circulation flow rate; The specific heat capacity of molten salt; and These are the temperatures of hot salt and cold salt, respectively.

[0088] In this embodiment of the invention, the determination rule for the molten salt circulation flow rate is based on the target steam generation heat. By analyzing the specific heat capacity, inlet temperature, and outlet temperature of the molten salt, the molten salt circulation flow rate is accurately calculated to ensure that the heat demand of the steam generation device is met. As a highly efficient heat storage medium, the heat transfer capacity of molten salt is closely related to the circulation flow rate and temperature difference. By reasonably controlling the molten salt circulation flow rate, not only can the required heat be stably delivered to the steam generation device, but also insufficient heat transfer due to insufficient molten salt circulation or energy waste due to excessive circulation can be avoided.

[0089] In this rule, the specific heat capacity of the molten salt is a key parameter, reflecting the amount of heat that a unit mass of molten salt can transfer when the temperature changes. The inlet and outlet temperatures determine the effective temperature difference that the molten salt can actually provide during circulation. Based on the target steam generation heat and combined with the heat transfer characteristics of the molten salt, the required flow rate of the molten salt can be precisely determined to ensure that the heat supply of the steam generator always meets the steam injection demand. This rule not only enables dynamic adjustment of the molten salt circulation flow rate but also allows for flexible optimization of the molten salt circulation energy efficiency ratio according to different steam injection demands and changes in steam generation heat, thereby improving the overall operating efficiency of the system.

[0090] Furthermore, based on the determined operating parameters of the water supply device, preheating device, and steam generation device, a corresponding joint control scheme is generated, including: performing state initialization based on the minimum operating power of the water supply device, the minimum operating power of the preheating device, and the minimum operating power of the steam generation device; randomly adjusting the operating power of one operating device, and updating the operating power of the other two operating devices based on the adjusted operating power, and calculating the function value of the pre-constructed objective function after adjustment; updating the operating power of each operating device based on the function value until the function value of the objective function meets the iteration termination condition or reaches the preset number of iterations, and outputting the operating power of each operating device in the optimal state; generating a corresponding joint control scheme based on the operating power of each operating device in the optimal state and the current operating power of each operating device.

[0091] Specifically, the pre-constructed objective function is:

[0092]

[0093] in, Total power; The time interval between a future scheduled time and the current time; , and These represent the operating power of the water supply device, preheating device, and steam generation device after this round of iteration.

[0094] In this embodiment of the invention, to achieve efficient coordinated operation of the water supply device, preheating device, and steam generation device, a joint control optimization scheme based on minimum operating power is designed. Specifically, this joint control scheme initializes the entire system based on the minimum operating power of the water supply device, preheating device, and steam generation device. By initializing the operating power, the initial operating state of each device is determined, and in subsequent steps, the operating power of one device is gradually adjusted. The objective function value is dynamically calculated based on the adjusted operating power, and the operating power of the other two devices is updated accordingly to optimize the overall energy consumption of the system.

[0095] After each adjustment, the system calculates the objective function value of the current system to assess whether the current operating state meets the optimization conditions. If the objective function value does not reach the set optimization termination condition, the system will continue to iteratively adjust the operating power of each device until the objective function value converges or reaches the preset optimization accuracy. Finally, the system outputs the optimal operating power of each device under the current conditions and generates a corresponding joint control scheme based on the optimal state. The joint control scheme includes the real-time operating power of each device and the detailed logic of how they work together during the steam injection process.

[0096] The core objective of this optimization scheme is to minimize the system's total energy consumption by dynamically adjusting the operating power of the water supply unit, preheating unit, and steam generation unit. The total system energy consumption depends not only on the power of individual units but also on the degree of operational coordination between them. Therefore, this scheme significantly improves the system's energy efficiency while ensuring overall system operational stability.

[0097] Furthermore, the step of generating a corresponding joint control scheme based on the operating power of each operating device under optimal conditions and the current operating power of each operating device includes: determining the power to be adjusted based on the operating power of each operating device under optimal conditions and the current operating power of each operating device; performing decoupling on the power to be adjusted to obtain the adjustment amount of each execution component, so as to determine the adjustment scheme of each component; and combining the adjustment schemes of all components to obtain the joint control scheme.

[0098] In this embodiment of the invention, based on the optimal operating power of each operating device, a corresponding joint control scheme is generated to achieve coordinated and optimized operation of the water supply device, preheating device, and steam generation device. Specifically, the scheme first determines the optimal operating power of each operating device under the current operating conditions. These optimal operating powers are obtained through optimization calculations, which can meet the steam injection requirements of the system while minimizing the total energy consumption of the system. Based on this, the power difference that needs to be adjusted is further calculated by combining the current actual operating power of each operating device, and this difference is used as the power input to be adjusted for each device.

[0099] Subsequently, by decomposing and analyzing the power to be adjusted for each operating device, the adjustment parameters for each actuator (such as plunger pumps or centrifugal pumps, flow control valves, pressure sensors, solid heat accumulators, heating tubes or electric heaters, return pipeline valves, molten salt circulation pumps, etc.) are obtained. Through precise calculation of the specific adjustment parameters for each device, an independent control scheme for each device is generated. All control schemes are then integrated to form a joint control scheme covering the three stages of water supply, preheating, and steam generation. This joint control scheme not only clarifies the specific adjustment actions of each device under current operating conditions but also ensures that the power adjustments of each device work collaboratively within the overall system framework, avoiding adverse effects on other stages caused by adjustments to a single device.

[0100] Preferably, the system further includes: a pressure relief device for releasing the gas pressure in the outlet pipe of the preheating device when the steam supply is stopped; the pressure relief device is connected to the water supply pipe between the preheating device and the steam generating device via a three-way valve; the pressure relief device includes a discharge expansion container for storing the high-pressure softened water that flows in during the pressure relief process.

[0101] Furthermore, the control device is also used to control the valve on the discharge expansion container side of the three-way valve to open in response to a pressure relief request command.

[0102] In an embodiment of the present invention,

[0103] Example:

[0104] like Figure 2 A steam generation system based on solid thermal storage and molten salt heating is provided, the specific execution process of which is as follows:

[0105] The device mainly comprises a softened water tank 1; a water supply pressurization pump 2; a water supply flow meter 3; a plunger pump 4; a high-pressure water supply pipeline 5; a solid thermal storage preheater 6; a direct-flow molten salt heater 7; a direct-flow molten salt evaporator 8; a steam pipeline 9; a high-temperature and high-pressure water supply pipeline 10; a start-up discharge pipeline 11; a three-way regulating valve 12; a discharge expansion tank 13; a high-temperature molten salt pump 14; and a control device 15. Among these, the softened water tank 1, water supply pressurization pump 2, water supply flow meter 3, plunger pump 4, and high-pressure water supply pipeline 5 together constitute the water supply device. The direct-flow molten salt heater 7, direct-flow molten salt evaporator 8, steam pipeline 9, high-temperature and high-pressure water supply pipeline 10, and start-up discharge pipeline 11 together constitute the preheating device.

[0106] The working principles and processes of each part of the system are explained in detail below, using examples.

[0107] 1) The oilfield steam injection softening water is connected to softening water tank 1; the average flow rate is 18t / h and the water temperature is 40-90℃.

[0108] 2) The softened water in the softened water tank 1 is pressurized by the water supply pressurization pump 2 and then metered 3. After being pressurized by the plunger pump 4, it is sent to the solid heat storage preheater 6 for preheating to above the molten salt freezing point temperature. The pressurized softened water pressure is 18MPa and the flow rate is 18t / h.

[0109] 3) The solid thermal storage preheater 6 uses green electricity or off-peak electricity for heating. Multiple units can be connected in series or parallel depending on the scale. It can be started in real time and plays a role in absorbing abandoned electricity and regulating the power grid.

[0110] 4) The softened water temperature at the outlet of the solid thermal storage preheater 6 is interlocked with the frequency converter of the preheater fan. The softened water temperature at the outlet of the solid thermal storage preheater 6 is automatically controlled at the set value by controlling the air volume. The set value of the softened water temperature at the outlet of the solid thermal storage preheater 6 is 250℃.

[0111] 5) Before the softened water temperature at the outlet of the solid thermal storage preheater 6 reaches the set value, the softened water flows through the start-up discharge pipe 18 to the discharge expansion tank 19.

[0112] 6) After the softened water temperature at the outlet of the solid thermal storage preheater 6 reaches the set value, the softened water goes to the direct-flow molten salt heater 7 and the direct-flow molten salt evaporator 8.

[0113] 7) Softened water preheated to a certain temperature is supplied to the direct-flow molten salt heater 7 and the direct-flow molten salt evaporator 8 for heat exchange with high-temperature molten salt. The direct-flow molten salt heater 7 and the direct-flow molten salt evaporator 8 are direct-flow immersion heat exchange structures, with serpentine coils. The coils contain wet saturated steam, and the shell side contains molten salt. After heat exchange between the softened water and the high-temperature molten salt, wet saturated steam with a certain dryness requirement is generated and supplied to the steam injection well for steam injection. The wet saturated steam parameters are: 14.1 MPa, dryness 80%.

[0114] 8) The three-way regulating valve 12 on the start-up discharge pipe 11 of the solid thermal storage preheater outlet is interlocked with the stop signal of the plunger pump 4. When the plunger pump 4 stops, the interlock opens the three-way regulating valve 12 at the outlet of the solid thermal storage preheater. The high-pressure softened water in the system is transported to the discharge expansion container 13 through the bypass pipe 11 at the outlet of the solid thermal storage preheater, thereby realizing the depressurization of the system.

[0115] Figure 3 This is a flowchart of a method for controlling a steam generation system based on solid thermal storage and molten salt heating, according to one embodiment of the present invention. Figure 3 As shown, this invention provides a control method for a steam generation system based on solid thermal storage and molten salt heating, the method comprising:

[0116] Step S10: Collect the current storage capacity of the steam injection well, system operating status parameters, and historical steam injection data in real time as the basis for prediction.

[0117] Step S20: Perform steam injection demand prediction for future predetermined times based on the long short-term memory network and the prediction basis data.

[0118] Step S30: Based on the predicted steam injection demand, determine the operating parameters of the water supply unit, preheating unit, and steam generation unit respectively.

[0119] Step S40: Generate the corresponding joint control scheme based on the determined operating parameters of the water supply device, preheating device, and steam generation device.

[0120] Preferably, the rule for predicting steam injection demand at a predetermined future time based on the Long Short-Term Memory network and the aforementioned prediction base data is as follows:

[0121]

[0122] in, For prediction models of long short-term memory networks; Historical steam injection data; The time span of historical steam injection data; The method further includes determining the rate of change of demand based on the steam injection demand at a predetermined future time and the current storage capacity of the steam injection well.

[0123] Preferably, a corresponding joint control scheme is generated based on the determined operating parameters of the water supply device, preheating device, and steam generation device, including: performing state initialization based on the minimum operating power of the water supply device, the minimum operating power of the preheating device, and the minimum operating power of the steam generation device; randomly adjusting the operating power of one operating device, and updating the operating power of the other two operating devices based on the adjusted operating power, and calculating the function value of the pre-constructed objective function after adjustment; updating the operating power of each operating device based on the function value until the function value of the objective function meets the iteration termination condition or reaches the preset number of iterations, and outputting the operating power of each operating device in the optimal state; generating a corresponding joint control scheme based on the operating power of each operating device in the optimal state and the current operating power of each operating device.

[0124] Preferably, the pre-constructed objective function is:

[0125]

[0126] in, Total power; The time interval between a future scheduled time and the current time; , and These represent the operating power of the water supply device, preheating device, and steam generation device after this round of iteration.

[0127] The present invention also provides a computer-readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the above-described control method for a steam generation system based on solid heat storage and molten salt heating.

[0128] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a microcontroller, chip, or processor to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0129] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details described above. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not further describe the various possible combinations.

[0130] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the embodiments of the present invention, they should also be regarded as the content disclosed by the embodiments of the present invention.

Claims

1. A steam generation system based on solid heat storage and molten salt heating, characterized by, The system comprises: a water supply device for performing softened water supply; a preheating device connected with the water supply device for performing preheating on the softened water; wherein, the preheating device is correspondingly arranged with a solid heat storage device, and the preheating device performs heat exchange with the solid heat storage device to perform preheating on the softened water; a steam generation device connected at an outlet end of the preheating device for performing multi-stage evaporation on the preheated softened water to obtain wet saturated steam for steam injection use; wherein, the steam generation device is correspondingly arranged with a molten salt heat storage device, and the steam generation device performs heat exchange with high-temperature molten salt in the molten salt heat storage device to obtain wet saturated steam for steam injection use; a control device for generating a linkage control scheme of the water supply device, the preheating device and the steam generation device based on real-time steam injection demand; wherein, the control device is configured to: collect, in real time, current injection well storage capacity of the injection well, system operation state parameters and historical steam injection data as prediction basis data; perform steam injection demand prediction at a future scheduled time based on a long short-term memory network and the prediction basis data; perform operation parameter determination of the water supply device, the preheating device and the steam generation device respectively based on the steam injection demand prediction value; and generate a corresponding linkage control scheme based on the determined operation parameters of the water supply device, the preheating device and the steam generation device.

2. The system of claim 1, wherein, The water supply device comprises: a softened water tank for storing softened water; a plunger pump connected at an outlet side of the softened water tank based on a pipeline for performing pressure increase on the softened water when supplying the softened water to the preheating device to perform water supply in a high-pressure state.

3. The system of claim 1, wherein, The solid heat storage device is provided with one or a plurality of solid heat accumulators arranged in stages; a temperature sensor is arranged at an outlet end of the preheating device for collecting real-time temperature of the output softened water; the control device is further configured to judge whether the real-time temperature of the output softened water of the preheating device meets the demand temperature of the steam generation device.

4. The system of claim 3, wherein, The solid heat storage device comprises a circulating pipeline; when the real-time temperature of the output softened water of the preheating device does not meet the demand temperature of the steam generation device, the output softened water of the preheating device is returned to an inlet of the preheating device based on the circulating pipeline to perform secondary preheating until the real-time temperature of the output softened water of the preheating device meets the demand temperature of the steam generation device, and the circulating pipeline is closed.

5. The system of claim 1, wherein, The rule for performing steam injection demand prediction at a future scheduled time based on a long short-term memory network and the prediction basis data is: wherein, is a long short-term memory network prediction model; Historical gas injection data; The time span of historical steam injection data; steam injection demand for a future scheduled time; The method further comprises: determining a demand change rate based on the steam injection demand at the future scheduled time and the current injection well storage capacity of the injection well.

6. The system of claim 5, wherein, The determination rule of the operation parameter of the water supply device is: based on the steam injection demand at the future scheduled time and the current system operation efficiency, performing target water supply amount determination meeting the corresponding steam injection demand, the determination rule being: wherein, Qtargetis the target water supply; the current system's operational efficiency; based on the determined target water supply amount and the time interval between the future scheduled time and the current time, determining the minimum operation power of the water supply device as the operation parameter of the water supply device.

7. The system of claim 5, wherein, The determination rule of the operation parameter of the preheating device is: based on the saturated temperature of the steam required by the steam injection demand at the future scheduled time and the heat exchange efficiency of the steam generation device, performing water supply target temperature determination; The target preheating heat determination is performed based on the target water supply temperature and the current water supply temperature, and the determination rule is: wherein, Qtarget is the target preheat heat quantity; Qtarget is the target water supply; Specific heat capacity of water softened; and Ttarget and Tcurrent are the target temperature and the current water supply temperature, respectively. Based on the determined target preheating heat and the time interval between the future scheduled time and the current time, the minimum operating power of the preheating device is determined as the operating parameter of the operating parameter of the preheating device.

8. The system of claim 5, wherein, The determination rule of the operating parameter of the steam generating device is: Based on the steam injection demand at the future scheduled time and the steam latent heat of the steam generating device, the target steam generation heat is determined, and the determination rule is: wherein, to generate heat for the target vapor; vaporization latent heat of steam for the steam generating device; Based on the target steam generation heat, the molten salt circulation flow rate is determined; Based on the target steam generation heat and the molten salt circulation flow rate, and the time interval between the future scheduled time and the current time, the minimum operating power of the steam generating device is determined as the operating parameter of the operating parameter of the steam generating device.

9. The system of claim 8, wherein, The rule for determining the molten salt circulation flow rate based on the target steam generation heat is: wherein, is the molten salt circulation flow rate; Cp is the specific heat capacity of the molten salt; and Tcand Tmare the temperatures of the hot and cold salt, respectively.

10. The system of claim 1, wherein, Based on the determined operating parameters of the water supply device, the preheating device and the steam generating device, a corresponding joint control scheme is generated, including: Based on the minimum operating power of the water supply device, the minimum operating power of the preheating device and the minimum operating power of the steam generating device, state initialization is performed; Randomly adjust the operating power of one operating device, and update the operating power of the other two operating devices based on the adjusted operating power, and calculate the function value of the pre-constructed target function after adjustment; Based on the function value, update the operating power of each operating device until the function value of the target function meets the iteration termination condition or reaches the preset iteration number, and output the operating power of each operating device under the optimal state; Based on the operating power of each operating device under the optimal state and the current operating power of each operating device, a corresponding joint control scheme is generated.

11. The system of claim 10, wherein, The pre-constructed target function is: wherein Ptotai is the total power; a time interval to a future scheduled time and a current time; , and are the operating powers of the water supply device, the preheating device and the steam generating device, respectively, after the present iteration.

12. The system of claim 10, wherein, Based on the operating power of each operating device under the optimal state and the current operating power of each operating device, a corresponding joint control scheme is generated, including: Based on the operating power of each operating device under the optimal state and the current operating power of each operating device, the power to be adjusted is determined; Perform decoupling on the power to be adjusted to obtain the adjustment amount of each execution component to determine the adjustment scheme of each component; Combine the adjustment schemes of all components to obtain the joint control scheme.

13. The system of claim 1, wherein, The system further comprises: A pressure relief device for releasing the air pressure in the preheating device outlet side pipeline when stopping steam supply; The pressure relief device is connected to the water supply pipeline between the preheating device and the steam generating device through a three-way valve; The pressure relief device comprises a discharge expander for storing high-pressure softened water collected during pressure relief.

14. The system of claim 13, wherein the control device is further configured to control the valve on the discharge expander side of the three-way valve to open in response to a pressure relief request instruction.

15. A control method of a steam generation system based on solid heat accumulation and molten salt heating, characterized by, The method is applied to the solid heat storage and molten salt heating based steam generating system of any one of claims 1-14, and the method comprises: Real-time acquisition of the current injection well storage capacity of the injection well, system operating state parameters and historical injection data as prediction basis data; Perform injection demand prediction at the future scheduled time based on the long short-term memory network and the prediction basis data; Based on the steam injection demand prediction value, the operation parameter determination of the water supply device, the preheating device and the steam generation device is respectively performed; Based on the determined operation parameters of the water supply device, the preheating device and the steam generation device, the corresponding joint control scheme is generated.

16. The method of claim 15, wherein, The rule for performing the steam injection demand prediction at the future scheduled time based on the long short-term memory network and the prediction basis data is: wherein, is a long short-term memory network prediction model; Historical gas injection data; The time span of historical steam injection data; steam injection demand for a future scheduled time; The method further comprises: Based on the steam injection demand at the future scheduled time and the storage capacity of the current steam injection well, the demand change rate is determined.

17. The method of claim 15, wherein, Based on the determined operation parameters of the water supply device, the preheating device and the steam generation device, the corresponding joint control scheme is generated, comprising: Performing state initialization based on the minimum operation power of the water supply device, the minimum operation power of the preheating device and the minimum operation power of the steam generation device; Randomly adjusting the operation power of one operation device, and updating the operation power of the other two operation devices based on the adjusted operation power, and calculating the function value of the pre-constructed target function after adjustment; Based on the function value, the operation power of each operation device is updated until the function value of the target function meets the iteration termination condition or reaches the preset iteration number, and the operation power of each operation device under the optimal state is output; Based on the operation power of each operation device under the optimal state and the current operation power of each operation device, the corresponding joint control scheme is generated.

18. The method of claim 17, wherein, The pre-constructed target function is: wherein, Ptotai is the total power; a time interval to a future scheduled time and a current time; , and are the operating powers of the water supply device, the preheating device and the steam generating device, respectively, after the present iteration.

19. A computer-readable storage medium, characterized in that, The computer readable storage medium stores instructions, which when executed on a computer, cause the computer to perform the control method of the steam generation system based on solid heat accumulation and molten salt heating according to any one of claims 1-14.

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