A main steam temperature control device and method

Abstract

This invention relates to a main steam temperature control device and method, belonging to the field of biomass thermal power. The device includes a superheating system and a PID control module. The superheating system includes a four-stage superheater, a three-stage desuperheater, three desuperheater regulating valves, a first temperature sensor, a second temperature sensor, a third temperature sensor, and a fourth temperature sensor. These sensors are used to measure the real-time inlet steam temperature, the inlet flue gas temperature, the outlet flue gas temperature, and the real-time outlet steam temperature of the four-stage superheater, respectively. The PID control module detects and determines whether the main steam temperature has reached the setpoint, and adjusts the opening of the three desuperheater regulating valves based on the inlet and outlet flue gas temperatures to ensure the inlet steam temperature reaches the desired value, thereby achieving the setpoint. This invention significantly improves the control accuracy and stability of the main steam temperature.

Description

Technical Field

[0001] This invention relates to the field of biomass thermal power, and in particular to a main steam temperature control device and method. Background Technology

[0002] Biomass cogeneration projects, using agricultural and forestry waste as primary fuel, have seen rapid development in China over the past decade due to their economic viability, demonstrative value in new rural construction, and clean and environmentally friendly characteristics. However, compared to traditional coal-fired power plants, distributed biomass cogeneration projects are still in their early stages. Ensuring continuous and stable production is the primary task for every biomass cogeneration project. However, in the past decade or so, biomass cogeneration projects have primarily relied on manual operation by personnel, resulting in extremely low rates of automatic control implementation. In most cases, automatic control is either not activated or its effectiveness is extremely poor. Consequently, problems exist such as unstable automatic control of main steam temperature, large deviations between target and setpoint values, and the inability to operate long-term.

[0003] With the continuous development of control technology, emerging control strategies are gradually being put into practice. How to put biomass cogeneration projects into automatic operation, reduce labor intensity, improve work efficiency, and achieve quality improvement, cost reduction, and efficiency enhancement has once again become a challenge for biomass cogeneration projects. Summary of the Invention

[0004] The purpose of this invention is to provide a main steam temperature control device and method to solve the problems of unstable and large deviation in the main steam temperature control of the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A main steam temperature control device includes: a superheating system and a PID control module; the superheating system and the PID control module are connected; the PID control module is used to adjust the inlet steam temperature of the superheating system, thereby adjusting the main steam temperature of the superheating system.

[0007] The superheating system includes a four-stage superheater, a three-stage desuperheater, three desuperheating valves, a first temperature sensor, a second temperature sensor, a third temperature sensor, and a fourth temperature sensor.

[0008] The third-stage desuperheater is connected to the fourth-stage superheater; the third-stage desuperheater is used to cool the superheated steam output from the third-stage superheater, and the cooled superheated steam is input into the fourth-stage superheater; the third-stage desuperheater is also connected to one end of the third-stage desuperheater regulating valve; the third-stage desuperheater regulating valve is used to control the water flow into the third-stage desuperheater; the other end of the third-stage desuperheater regulating valve is connected to the high-pressure water supply main pipe; the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor are all connected to the fourth-stage superheater; the first temperature sensor is used to measure the real-time inlet steam temperature of the fourth-stage superheater; the second temperature sensor is used to measure the inlet flue gas temperature of the fourth-stage superheater; the third temperature sensor is used to measure the outlet flue gas temperature of the fourth-stage superheater; the fourth temperature sensor is used to measure the real-time outlet steam temperature (i.e., main steam temperature) of the fourth-stage superheater.

[0009] The PID control module is connected to the three-stage reducing valve, the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor, respectively. The PID control module is used to determine whether the real-time outlet steam temperature of the fourth-stage superheater reaches the main steam temperature setpoint. If the real-time outlet steam temperature of the fourth-stage superheater does not reach the main steam temperature setpoint, the opening of the three-stage reducing valve is adjusted according to the inlet flue gas temperature and the outlet flue gas temperature to make the real-time inlet steam temperature of the fourth-stage superheater reach the desired inlet temperature value, thereby making the real-time outlet steam temperature of the fourth-stage superheater reach the main steam temperature setpoint.

[0010] Optionally, the superheating system further includes a primary superheater, a secondary superheater, a tertiary superheater, a primary desuperheater, a secondary desuperheater, a primary desuperheater, and a secondary desuperheater;

[0011] The primary superheater is connected to the secondary superheater via the primary desuperheater; the primary desuperheater is used to cool the steam output from the primary superheater, thereby controlling the outlet temperature of the secondary superheater.

[0012] The secondary superheater is connected to the tertiary superheater through the secondary desuperheater; the secondary desuperheater is used to cool the steam output from the secondary superheater, thereby controlling the outlet temperature of the tertiary superheater.

[0013] The third-stage superheater is connected to the fourth-stage superheater via the third-stage desuperheater;

[0014] The first-stage desuperheater is also connected to one end of the first desuperheater regulating valve; the first desuperheater regulating valve is used to control the amount of water entering the first-stage desuperheater; the second-stage desuperheater is also connected to one end of the second desuperheater regulating valve; the second desuperheater regulating valve is used to control the amount of water entering the second-stage desuperheater.

[0015] The other end of the first reducing valve and the other end of the second reducing valve are both connected to the high-pressure water supply main pipe.

[0016] A main steam temperature control method, the method being applied to the aforementioned main steam temperature control device, the method comprising:

[0017] The real-time outlet steam temperature of the fourth-stage superheater is detected, and it is determined whether the real-time outlet steam temperature of the fourth-stage superheater reaches the main steam temperature set value.

[0018] If the real-time outlet steam temperature of the fourth-stage superheater does not reach the main steam temperature set value, obtain the inlet flue gas temperature and outlet flue gas temperature of the fourth-stage superheater.

[0019] Calculate the intensity of the influence of the flue gas temperature changes at the inlet and outlet of the fourth-stage superheater on the main steam inside the fourth-stage superheater based on the inlet flue gas temperature and the outlet flue gas temperature.

[0020] Based on the intensity of the influence, adjust the opening of the three-stage reducing valve to ensure that the real-time inlet steam temperature of the fourth-stage superheater reaches the desired inlet temperature value.

[0021] Optionally, the step of calculating the influence of the flue gas temperature changes at the inlet and outlet of the fourth-stage superheater on the main steam within the fourth-stage superheater based on the inlet and outlet flue gas temperatures specifically includes:

[0022] Using formula Calculate the intensity of the influence of flue gas temperature changes at the inlet and outlet of the fourth-stage superheater on the main steam within the fourth-stage superheater; where K is the adjustment coefficient; T′ 0A (t) represents the real-time average temperature of the flue gas at the outlet of the fourth-stage superheater; T′0(t)-T′ 0A (t) represents the change in the outlet flue gas temperature of the fourth-stage superheater from its real-time average; D represents the influence factor of the outlet flue gas temperature of the fourth-stage superheater on the main steam; T′ 1A (t) represents the real-time average temperature of the flue gas at the inlet of the fourth-stage superheater; T′1(t)-T′ 1A (t) represents the change in the inlet flue gas temperature of the fourth-stage superheater from the real-time average; E represents the influence factor of the inlet flue gas temperature of the fourth-stage superheater on the main steam.

[0023] Optionally, the expected inlet temperature includes a first expected temperature and a second expected temperature;

[0024] When the real-time main steam temperature is at point P x2, when \(x = \{1, 3, 5, 7, \ldots, 2n + 1\}\), according to the influence intensity, adjust the opening degree of the three - reducing regulating valve so that the real - time inlet steam temperature of the four - stage superheater reaches the first temperature expectation value; the first temperature expectation value \(T\) 1SP = \(T\) 1A + \(k(v)*(\Delta T)+\alpha\) T'(t) ; where, \(T\) 1A is the average value of the real - time inlet steam temperature of the four - stage superheater; \(\Delta T\) is the deviation between the main steam temperature \(T\) 0PV and the main steam set temperature \(T\) 0SP ; \(k(v)\) is a time - varying function of \(v\), and \(v\) is the change rate of the main steam temperature at point \(P\) x or point \(P\) y ;

[0025] When the real - time main steam temperature is at point \(P\) y2 , \(y=\{2, 4, 6, 8, \ldots, 2n\}\), and when the deviation \(\Delta T\lt z\), according to the influence intensity, adjust the opening degree of the three - reducing regulating valve so that the real - time inlet steam temperature of the four - stage superheater reaches the second temperature expectation value; the second temperature expectation value \(T\) 1SP = \(T\) 1A +\(\alpha\) T'(t) ; where, \(z\) is the expected control deviation.

[0026] Optionally, the main steam temperature is the real - time outlet steam temperature of the four - stage superheater.

[0027] Optionally, point \(P\) x2 , point \(P\) x , point \(P\) y and point \(P\) y2 are points on the main steam temperature - time curve; where, point \(P\) x2 and point \(P\) x are adjacent; point \(P\) y and point \(P\) y2 are adjacent.

[0028] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0029] This invention measures the real-time inlet and outlet steam temperatures of a four-stage superheater to determine the desired inlet temperature. A PID control module adjusts the opening of the three-stage reducing valve based on this desired inlet temperature, ensuring the inlet steam temperature reaches the desired value. This, in turn, brings the outlet steam temperature of the four-stage superheater to the main steam temperature setpoint. The main steam temperature is controlled within a certain range, with minimal deviation between the setpoint and actual value. This significantly improves the control accuracy and stability of the main steam temperature, demonstrating a strong demonstration effect in improving efficiency, increasing profitability, and ensuring safe equipment operation, and thus possesses significant value for widespread application. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A structural block diagram of a main steam temperature control device provided by the present invention;

[0032] Figure 2 This is a schematic diagram of the overheating system provided by the present invention;

[0033] Figure 3 This is a schematic diagram of the structure of the PID control module provided by the present invention;

[0034] Figure 4 This is a schematic diagram showing the arrangement of the superheater in a boiler according to the present invention.

[0035] Figure 5 This is a schematic diagram illustrating the effect of traditional cascaded PID control provided by the present invention;

[0036] Figure 6 A flowchart of a main steam temperature control method provided by the present invention;

[0037] Figure 7 A graph showing the real-time main steam temperature and the main steam temperature setpoint provided by the present invention;

[0038] Figure 8 A schematic diagram illustrating how changes in flue gas temperature before and after the four-stage superheater cause changes in the outlet steam temperature of the four-stage superheater, as provided by this invention.

[0039] Figure 9 A schematic diagram illustrating the operational effect of a biomimetic discrimination-based main steam temperature control method provided by this invention.

[0040] Symbol explanation: 1. First-stage superheater; 2. First-stage desuperheater; 3. First desuperheater regulating valve; 4. Second-stage superheater; 5. Second-stage desuperheater; 6. Second desuperheater regulating valve; 7. Third-stage superheater; 8. Third-stage desuperheater; 9. Third desuperheater regulating valve; 10. Fourth-stage superheater. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The purpose of this invention is to provide a main steam temperature control device and method to solve the problem of unstable main steam temperature control in the prior art.

[0043] This invention takes the automatic control and regulation optimization of main steam temperature at Shanxi Jianghe Biomass Power Generation Co., Ltd. as an example. It innovatively applies a main steam temperature control strategy and implementation based on artificial intelligence discrimination and traditional PID control (main steam temperature control device and method), aiming to promote the application of intelligent control and unit-level automatic control in biomass cogeneration projects.

[0044] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] Figure 1 A structural block diagram of a main steam temperature control device based on biomimetic discrimination provided by the present invention; Figure 2 This is a schematic diagram of the overheating system provided by the present invention; Figure 3 This is a schematic diagram of the PID control module provided by the present invention. Figure 1 As shown, a main steam temperature control device based on biomimetic discrimination includes: a superheating system and a PID control module; the superheating system and the PID control module are connected; the PID control module is used to adjust the main steam temperature of the superheating system, thereby adjusting the main steam temperature of the superheating system.

[0046] like Figure 2 As shown, the superheating system includes a four-stage superheater 10, a three-stage desuperheater 8, a three-stage desuperheater valve 9, a first temperature sensor, a second temperature sensor, a third temperature sensor, and a fourth temperature sensor. The first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor are not shown in the figure.

[0047] The three-stage desuperheater 8 is connected to the four-stage superheater 10; the three-stage desuperheater 8 is used to cool the superheated steam output from the three-stage superheater 7, and the cooled superheated steam is input into the four-stage superheater 10; the three-stage desuperheater 8 is also connected to one end of the three-stage desuperheater regulating valve 9; the three-stage desuperheater regulating valve 9 is used to control the water flow into the three-stage desuperheater 8; the other end of the three-stage desuperheater regulating valve 9 is connected to the high-pressure water supply header; the first temperature sensor, the second temperature sensor, and the third temperature sensor are all connected to the four-stage superheater 10; the first temperature sensor is used to measure the real-time inlet steam temperature of the four-stage superheater 10; the second temperature sensor is used to measure the inlet flue gas temperature of the four-stage superheater 10; the third temperature sensor is used to measure the outlet flue gas temperature of the four-stage superheater 10; the fourth temperature sensor is used to measure the real-time outlet steam temperature of the four-stage superheater 10, i.e., the main steam temperature.

[0048] Furthermore, the superheating system also includes a primary superheater 1, a secondary superheater 4, a tertiary superheater 7, a primary desuperheater 2, a secondary desuperheater 5, a primary desuperheater valve 3, and a secondary desuperheater valve 6.

[0049] The primary superheater 1 is connected to the secondary superheater 4 through the primary desuperheater 2; the primary desuperheater 2 is used to cool the steam output from the primary superheater 1, thereby achieving the purpose of controlling the outlet temperature of the secondary superheater.

[0050] The secondary superheater 4 is connected to the tertiary superheater 7 via the secondary desuperheater 5; the secondary desuperheater 5 is used to cool the steam output from the secondary superheater 4, thereby controlling the outlet temperature of the tertiary superheater.

[0051] The third-stage superheater 7 is connected to the fourth-stage superheater 10 via the third-stage desuperheater 8.

[0052] The first-stage desuperheater 2 is also connected to one end of the first desuperheater regulating valve 3; the first desuperheater regulating valve 3 is used to control the amount of water entering the first-stage desuperheater 2; the second-stage desuperheater 5 is also connected to one end of the second desuperheater regulating valve 6; the second desuperheater regulating valve 6 is used to control the amount of water entering the second-stage desuperheater 5.

[0053] The other end of the first reducing valve 3 and the other end of the second reducing valve 6 are both connected to the high-pressure water supply main pipe.

[0054] PID control module such as Figure 3As shown, the PID control module is connected to the three-stage reducing valve 9, the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor, respectively. The PID control module determines whether the real-time outlet steam temperature of the fourth-stage superheater reaches the main steam temperature setpoint. If the real-time outlet steam temperature of the fourth-stage superheater does not reach the main steam temperature setpoint, the opening of the three-stage reducing valve 9 is adjusted according to the inlet and outlet flue gas temperatures to bring the real-time inlet steam temperature of the fourth-stage superheater to the desired inlet temperature, thereby bringing the real-time outlet steam temperature of the fourth-stage superheater to the main steam temperature setpoint. The outlet temperature of the fourth-stage superheater is also affected by changes in the inlet and outlet flue gas temperatures. When the inlet and outlet flue gas temperatures of the fourth-stage superheater change significantly, the outlet temperature of the fourth-stage superheater also changes significantly. Figure 3 In the middle, T 1VP T represents the real-time inlet steam temperature of the fourth-stage superheater 10. 1SP The inlet steam temperature is the setpoint for the fourth-stage superheater 10. AO is the opening command for the third-stage regulating valve 9. The inlet and outlet flue gas temperatures are not shown in the figure.

[0055] In practical applications, Shanxi Jianghe Biomass Power Generation Co., Ltd. uses a 130t / h biomass circulating fluidized bed boiler manufactured by Taiyuan Boiler Factory. The boiler produces saturated steam by heating the water inside the boiler with the heat released from the combustion of fuel. The saturated steam passes through a superheater located inside the furnace and is then heated again by the flue gas to become superheated steam (main steam). With the help of a desuperheater, the superheated steam reaches the design temperature.

[0056] Based on the requirements of the turbine body and boiler materials, the main steam temperature fluctuation range generally needs to be controlled within -10 to +5℃. The superheater is arranged within the boiler as follows: Figure 4 As shown.

[0057] The superheating system adopts a control method of four-stage superheater heating and three-stage desuperheater spraying water to control the main steam temperature to fluctuate around the main steam temperature setpoint.

[0058] The control principle of the overheating system is as follows: Figure 2 As shown, the outlet temperature of the first-stage superheater, the inlet temperature of the second-stage superheater, the outlet temperature of the second-stage superheater, the inlet temperature of the third-stage superheater, the outlet temperature of the third-stage superheater, the inlet temperature of the fourth-stage superheater, and the outlet temperature of the fourth-stage superheater (i.e., the main steam temperature) are all directly measured by temperature elements (such as temperature sensors) and displayed in real time on the DCS system; the first-stage desuperheating valve 3, the second-stage desuperheating valve 6, and the third-stage desuperheating valve 9 control the amount of desuperheating water injected into the first-stage desuperheater 2, the second-stage desuperheater 5, and the third-stage desuperheater 8 respectively, according to their different opening degrees, in order to regulate the main steam temperature.

[0059] Saturated steam is heated four times through superheater 1, superheater 4, superheater 7, and superheater 10 to become main steam. Superheater 2, superheater 5, and superheater 8 are the places where superheated steam and desuperheating water are mixed. The purpose is to control the temperature of superheated steam. The amount of desuperheating water is controlled by desuperheating valve 3, desuperheating valve 6, and desuperheating valve 9, respectively. The temperature of superheated steam cannot be too high or too low when passing through each superheater. There is a temperature range.

[0060] The working process of the superheating system is briefly described as follows:

[0061] Saturated steam from the steam drum is heated by the first-stage superheater 1 and then enters the first-stage desuperheater 2. The amount of desuperheating water (from the high-pressure feedwater header) entering the first-stage desuperheater 2 is controlled by manually or automatically adjusting the opening of the first-stage desuperheater valve 3, thereby regulating the inlet temperature of the second-stage superheater 4 and achieving the purpose of controlling the outlet temperature of the second-stage superheater.

[0062] Steam is heated by the secondary superheater 4 and then enters the secondary desuperheater 5. The amount of desuperheating water entering the secondary desuperheater 5 is controlled by manually or automatically adjusting the opening of the secondary desuperheater regulating valve 6, thereby regulating the inlet temperature of the tertiary superheater 7 and thus achieving the purpose of controlling the outlet temperature of the tertiary superheater.

[0063] The steam is then heated by the third-stage superheater 7 and enters the third-stage desuperheater 8. The opening of the third-stage desuperheater regulating valve 9 is manually or automatically adjusted to control the amount of desuperheating water entering the third-stage desuperheater 8, thereby regulating the inlet temperature of the fourth-stage superheater 10, and thus controlling the outlet temperature of the fourth-stage superheater. Finally, superheated steam that meets the needs of the steam turbine, i.e., main steam, is generated.

[0064] Based on the traditional three-stage desuperheating cascade regulation method of thermal power units, the first desuperheating valve 3, the second desuperheating valve 6, and the third desuperheating valve 9 are respectively implemented with cascade PID control. At the same time, in order to meet the requirements of main steam superheat, the desuperheating water flow rate of the first-stage desuperheater 2, the second-stage desuperheater 5, and the third-stage desuperheater 8 decreases in a progressively decreasing manner.

[0065] Due to the uncertainty and unevenness of ash content, moisture, calorific value, and feed rate of biomass fuel, which is mainly composed of agricultural and forestry waste, biomass boilers cannot achieve the stable combustion of coal-fired boilers. Variations in biomass fuel quality lead to fluctuating fluctuating fluctuating fluctuating fluctuating fluctuating fluctuating fluctuating fluctuating fluctuating fluctuates. Under normal operating conditions, the main steam temperature varies within a range of ±6℃. Traditional cascade PID control is ineffective in this situation. Figure 5 As shown.

[0066] The inlet steam temperature of the fourth-stage superheater 10 and the outlet steam temperature of the third-stage superheater 7 also vary significantly, with frequent and large fluctuations, which is not conducive to the stable and economical operation of the unit.

[0067] from Figure 5 It can be seen that the main steam temperature fluctuates irregularly and with a large range under the influence of changes in fuel quality. Traditional PID control is a feedback controller, and its control effect is not particularly ideal in systems with large inertia and large time delay.

[0068] The accuracy of main steam temperature control mainly depends on the opening control of the third reducing valve 9. The first reducing valve 3 and the second reducing valve 6 assist the third reducing valve 9 in overall control. Therefore, the control of the third reducing valve 9 is the focus here. The control of the first reducing valve 3 and the second reducing valve 6 refers to "Joint Control Strategy and Method of Desuperheating Water in Agricultural and Forestry Biomass Water-Cooled Vibrating Grate Boiler".

[0069] Experiments showed that the three-stage reducing valve 9 responded promptly to the inlet steam temperature of the fourth-stage superheater 10, demonstrating good control performance. Through in-depth communication with on-site operators to understand their operating habits and concepts under manual control, and analyzing the temperature change trends at the superheater inlet and outlet, a biomimetic discrimination-based main steam temperature control method was proposed, taking into account the development of artificial intelligence control technology. Figure 6 As shown, it can more effectively overcome the influence of changes in combustion state on the outlet steam temperature of the fourth-stage superheater 10.

[0070] The method is applied to the aforementioned biomimetic discrimination-based main steam temperature control device, and the method includes:

[0071] Step 601: Detect the real-time outlet steam temperature of the fourth-stage superheater and determine whether the real-time outlet steam temperature of the fourth-stage superheater has reached the main steam temperature set value.

[0072] Step 602: If the real-time outlet steam temperature of the fourth-stage superheater does not reach the main steam temperature setpoint, obtain the inlet flue gas temperature and outlet flue gas temperature of the fourth-stage superheater.

[0073] Step 603: Calculate the intensity of the influence of the flue gas temperature changes at the inlet and outlet of the fourth-stage superheater on the main steam inside the fourth-stage superheater based on the inlet flue gas temperature and the outlet flue gas temperature.

[0074] Further, step 603 specifically includes:

[0075] Using formula Calculate the intensity of the influence of flue gas temperature changes at the inlet and outlet of the fourth-stage superheater on the main steam within the fourth-stage superheater; where K is the adjustment coefficient; T′ 0A (t) represents the real-time average temperature of the flue gas at the outlet of the fourth-stage superheater; T′0(t)-T′ 0A (t) represents the change in the outlet flue gas temperature of the fourth-stage superheater from its real-time average; D represents the influence factor of the outlet flue gas temperature of the fourth-stage superheater on the main steam; T′1A (t) is the real-time average value of the flue gas temperature at the inlet of the four-stage superheater; T′1(t) - T′ 1A (t) is the change amount of the flue gas temperature at the inlet of the four-stage superheater from the real-time average value; E is the influence factor of the flue gas temperature at the inlet of the four-stage superheater on the main steam.

[0076] Step 604: According to the influence intensity, adjust the opening degree of the third-stage desuperheating valve to make the real-time temperature of the steam at the inlet of the four-stage superheater reach the expected inlet temperature.

[0077] Specifically, the expected inlet temperature includes a first expected temperature and a second expected temperature.

[0078] When the real-time main steam temperature is at point P x2 , x = {1, 3, 5, 7,... 2n + 1}, according to the influence intensity, adjust the opening degree of the third-stage desuperheating valve to make the real-time temperature of the steam at the inlet of the four-stage superheater reach the first expected temperature; the first expected temperature T 1SP = T 1A + k(v)*(△T) + α T'(t) ; where, T 1A is the average value of the real-time temperature of the steam at the inlet of the four-stage superheater; △T is the deviation between the main steam temperature T 0PV and the set main steam temperature T 0SP ; k(v) is a time-varying function of v, and v is the change rate of the main steam temperature at point P x .

[0079] When the real-time main steam temperature is at point P y2 , y = {2, 4, 6, 8,... 2n}, and when the deviation △T < z, according to the influence intensity, adjust the opening degree of the third-stage desuperheating valve to make the real-time temperature of the steam at the inlet of the four-stage superheater reach the second expected temperature; the second expected temperature T 1SP = T 1A + α T'(t) ; where, z is the expected control deviation. The point P x2 , the point P x , point P y and the point P y2 are points on the main steam temperature - time curve; where, the point P x2 and the point P x are adjacent; the point P y and the point P y2 are adjacent.

[0080] In practical applications, the main steam temperature is the real-time outlet steam temperature of the four-stage superheater. In this invention, adjusting the real-time inlet steam temperature of the four-stage superheater to the desired inlet temperature value enables the real-time outlet steam temperature of the four-stage superheater to reach the set value (main steam temperature set value). The temperature rise of each stage of the superheater can be considered a constant value in the short term, but after long-term operation, the temperature rise will change significantly due to factors such as ash accumulation and scaling. The method of this invention effectively avoids the impact of superheater temperature rise changes on the control effect.

[0081] In practical applications, during actual boiler operation, the real-time main steam temperature fluctuates around the set value, and its trend can be referenced. Figure 7 The analysis is as follows:

[0082] Figure 7 In this context, SP represents the main steam temperature setpoint (i.e., the desired main steam temperature), PV represents the real-time main steam temperature, and the PV curve represents the curve of main steam temperature changing over time (main steam temperature-time curve), which is an irregular, time-varying continuous curve.

[0083] Points P1, P2, P3...P8 on the PV curve are representative points that characterize temperature changes, and the temperature at each point is expressed in terms of T. P1 T P2 T P3 ...T P8 express.

[0084] P on the PV curve 12 Point P is a point immediately adjacent to P1, P 22 Point P is a neighboring point of P2, P 32 Points are the immediate neighbors of P3, ..., P. 82 Point P8 is a point immediately adjacent to it, and the temperature at each point is expressed in terms of T. P12 T P22 T P32 ...T P82 This indicates that its physical meaning characterizes the main steam temperature as determined by T. Px To T Px2 change.

[0085] The actual physical meaning of each temperature point on the PV curve is described as follows:

[0086] 1) Rate of change of PV at point P1: For P which is adjacent to it 12 Point, rate of change of PV: v 12 >0 and T P12 >SP indicates that the real-time main steam temperature is greater than the set value and is still rising, with a growth rate of v. 12, its physical meaning is expressed as: the temperature starts to increase rapidly, the current desuperheating water volume is insufficient, and the desuperheating water volume needs to be increased.

[0087] 2) For point P2, the change rate of PV: For the P 22 point adjacent to it, the change rate of PV: v 22 <0 and T P22 > SP, indicating that the real-time main steam temperature is greater than the set value but has started to decrease. Its physical meaning is expressed as: the current desuperheating water volume has been increased too much, the temperature has started to drop, and at this time, the desuperheating water volume needs to be reduced in advance.

[0088] 3) For point P3, the change rate of PV: For the P 32 point adjacent to it, the change rate of PV: v 32 <0 and T P32 < SP, indicating that the real-time main steam temperature is less than the set value and is still decreasing, and its decreasing rate is v 32 . Its physical meaning is expressed as: the temperature starts to decrease rapidly, the current desuperheating water volume is excessive, and the current desuperheating water volume needs to be reduced.

[0089] 4) For point P4, the change rate of PV: For the point P42 adjacent to it, the change rate of PV: v 42 > 0 and T P42 < SP, indicating that the real-time main steam temperature is less than the set value but has started to increase. Its physical meaning is expressed as: the current desuperheating water volume has been reduced too much, the temperature has started to rise, and at this time, the desuperheating water volume needs to be increased appropriately in advance.

[0090] 5) P5 is the same as P1, and P6 is the same as P2, so no further elaboration is given.

[0091] 6) For point P7, the change rate of PV: For the P 72 point adjacent to it, the change rate of PV: v 72 <0 and T P72 > SP, indicating that the real-time main steam temperature starts to rise again before dropping to the set value during the process of decreasing. Its physical meaning is expressed as: the current desuperheating water volume has been reduced too much and the temperature has not dropped but started to rise again, and more desuperheating water is needed.

[0092] 7) Control key points:

[0093] ① For the P 22 point, in the case where the desuperheating water volume has been increased too much, to what extent or what amount should the desuperheating water volume be controlled so that it is neither too much nor too little to cause the main steam temperature to rise again.

[0094] ② For the P 42If the amount of desuperheating water is already too low, how much desuperheating water should be controlled to ensure that it is not too low or does not cause the main steam temperature to drop again?

[0095] 8) Assuming the temperature rise δT of the fourth-stage superheater is constant, the setpoint for the fourth-stage superheater outlet steam temperature is: T 0SP =535℃, then the inlet temperature: T 1PV =535-δT℃, which is also a fixed value. Based on this, the real-time average value of the inlet steam temperature of the fourth-stage superheater is calculated: T 1A The average duration is 1 hour. Looking at the 1-hour real-time average, the inlet steam temperature of the fourth-stage superheater is almost a straight line. Similarly, the hourly real-time average of the outlet steam temperature of the fourth-stage superheater (i.e., the main steam temperature) is taken: T 0A It can be observed that the steam temperature at the outlet of the fourth-stage superheater is also almost a straight line.

[0096] Based on this assumption, if the inlet steam temperature of the fourth-stage superheater is ideal, then the outlet steam temperature of the fourth-stage superheater should also be ideal.

[0097] 9) When the boiler combustion conditions change, the flue gas temperature before and after the fourth-stage superheater changes, which in turn causes a change in the outlet steam temperature of the fourth-stage superheater, such as... Figure 8 As shown. Therefore, by adjusting the opening of the three-stage desuperheating valve in a timely manner according to the change in flue gas temperature, the amount of desuperheating water injected into the three-stage desuperheater can be controlled, thereby adjusting the inlet temperature T1 of the fourth stage, which can achieve the purpose of regulating the main steam temperature T0;

[0098] 10) Based on the analysis in 9), the intensity of the influence of flue gas temperature changes before and after the fourth-stage superheater on the superheated steam inside the fourth-stage superheater:

[0099] α T'(t) As a feedforward, it controls the opening of the three-stage reducing valve to counteract the effect of flue gas temperature changes in the fourth-stage superheater on the superheated steam temperature, thus achieving the purpose of advance adjustment.

[0100] Based on the above analysis, the three-reduction control valve uses single PID regulation, as follows: Figure 3 As shown, the PID output AO is the opening command of the three-stage reducing valve, and the inlet temperature regulation accuracy of the four-stage superheater is usually ±1℃.

[0101] The control rules for the three-stage reduction regulating valve are as follows:

[0102] 1) Initially, the setpoint for the inlet steam temperature of the fourth-stage superheater is: T 1SP =T 1A , among which, T 1A The average inlet temperature of the fourth-stage superheater is taken in real time, with the average duration tentatively set at 1 hour.

[0103] Process variable of PID: T 1PV It is the real-time value of the inlet steam temperature.

[0104] The output AO of PID is the opening command of the three-way regulating valve. The regulation accuracy of the inlet steam temperature of the four-stage superheater is usually within ±1°C.

[0105] 2) When the real-time main steam temperature is at point P x2 , x = {1, 3, 5, 7,... 2n + 1}, the deviation between the real-time main steam temperature T 0PV and the set value of the main steam temperature T 0SP is: ΔT = T 0PV - T 0SP .

[0106] At this time, the set value of the inlet steam temperature of the four-stage superheater is:

[0107] T 1SP = T 1A + k(v) * (ΔT) + α T'(t) , aiming to dynamically adjust the deviation coefficient according to the deviation between the real-time main steam temperature and the set value, and accelerate the PID regulation speed and intensity.

[0108] 3) At point P y2 , y = {2, 4, 6, 8,... 2n}, when the deviation ΔT < z (expected control deviation),

[0109] At this time, the set value of the inlet steam temperature of the four-stage superheater is:

[0110] T 1SP = T 1A + α T'(t) , aiming to control the inlet steam temperature to quickly return to the hourly average value.

[0111] Based on the above analysis, the operation effect of the main steam temperature control method based on bionic discrimination is as Figure 9 shown. The main steam temperature is controlled to fluctuate within the range of ±2°C of the set value, greatly improving the control accuracy and control stability of the main steam temperature.

[0112] The present invention effectively utilizes the stability and high efficiency of traditional PID in single-PID regulation, and at the same time absorbs the experience and concept of manual control, enabling industrial control to have a human-like thinking mode.

[0113] The application of the成果 of the present invention has greatly improved the control accuracy and control stability of the main steam temperature, has a great demonstration effect on improving efficiency, increasing benefits, and ensuring the safe operation of equipment, and has strong promotion and application value.

[0114] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0115] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A main steam temperature control device, characterized in that, include: A superheating system and a PID control module are connected; the PID control module is used to adjust the main steam temperature of the superheating system, thereby adjusting the main steam temperature of the superheating system. The superheating system includes a four-stage superheater, a three-stage desuperheater, three desuperheating valves, a first temperature sensor, a second temperature sensor, a third temperature sensor, and a fourth temperature sensor. The third-stage desuperheater is connected to the fourth-stage superheater; the third-stage desuperheater is used to cool the superheated steam output from the third-stage superheater, and the cooled superheated steam is input into the fourth-stage superheater; the third-stage desuperheater is also connected to one end of the third-stage regulating valve; the third-stage regulating valve is used to control the water flow into the third-stage desuperheater; the other end of the third-stage regulating valve is connected to the high-pressure water supply header; the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor are all connected to the fourth-stage superheater; the first temperature sensor is used to measure the real-time inlet steam temperature of the fourth-stage superheater; the second temperature sensor is used to measure the inlet flue gas temperature of the fourth-stage superheater; the third temperature sensor is used to measure the outlet flue gas temperature of the fourth-stage superheater; the fourth temperature sensor is used to measure the real-time outlet steam temperature of the fourth-stage superheater. The PID control module is connected to the three-stage reducing valve, the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor, respectively. The PID control module is used to determine whether the real-time outlet steam temperature of the fourth-stage superheater reaches the main steam temperature setpoint. If the real-time outlet steam temperature of the fourth-stage superheater does not reach the main steam temperature setpoint, the opening of the three-stage reducing valve is adjusted according to the inlet flue gas temperature and the outlet flue gas temperature to make the real-time inlet steam temperature of the fourth-stage superheater reach the desired inlet temperature value, thereby making the real-time outlet steam temperature of the fourth-stage superheater reach the main steam temperature setpoint.

2. The main steam temperature control device according to claim 1, characterized in that, The superheating system also includes a primary superheater, a secondary superheater, a tertiary superheater, a primary desuperheater, a secondary desuperheater, a primary desuperheater, and a secondary desuperheater; The primary superheater is connected to the secondary superheater via the primary desuperheater; the primary desuperheater is used to cool the steam output from the primary superheater, thereby controlling the outlet temperature of the secondary superheater. The secondary superheater is connected to the tertiary superheater through the secondary desuperheater; the secondary desuperheater is used to cool the steam output from the secondary superheater, thereby controlling the outlet temperature of the tertiary superheater. The third-stage superheater is connected to the fourth-stage superheater via the third-stage desuperheater; The first-stage desuperheater is also connected to one end of the first desuperheater regulating valve; the first desuperheater regulating valve is used to control the amount of water entering the first-stage desuperheater; the second-stage desuperheater is also connected to one end of the second desuperheater regulating valve; the second desuperheater regulating valve is used to control the amount of water entering the second-stage desuperheater. The other end of the first reducing valve and the other end of the second reducing valve are both connected to the high-pressure water supply main pipe.

3. A method for controlling the temperature of main steam, characterized in that, The method is applied to the main steam temperature control device according to any one of claims 1-2, and the method includes: The real-time outlet steam temperature of the fourth-stage superheater is detected, and it is determined whether the real-time outlet steam temperature of the fourth-stage superheater reaches the main steam temperature set value. If the real-time outlet steam temperature of the fourth-stage superheater does not reach the main steam temperature set value, obtain the inlet flue gas temperature and outlet flue gas temperature of the fourth-stage superheater. Calculate the intensity of the influence of the flue gas temperature changes at the inlet and outlet of the fourth-stage superheater on the main steam inside the fourth-stage superheater based on the inlet flue gas temperature and the outlet flue gas temperature. Based on the intensity of the influence, adjust the opening of the three-stage reducing valve to ensure that the real-time inlet steam temperature of the fourth-stage superheater reaches the desired inlet temperature value.

4. The main steam temperature control method according to claim 3, characterized in that, The calculation of the influence of the flue gas temperature changes at the inlet and outlet of the fourth-stage superheater on the main steam within the fourth-stage superheater, based on the inlet and outlet flue gas temperatures, specifically includes: Using formula Calculate the intensity of the influence of flue gas temperature changes at the inlet and outlet of the fourth-stage superheater on the main steam within the fourth-stage superheater; where K represents the adjustment coefficient; T0' A (t) represents the real-time average temperature of the flue gas at the outlet of the fourth-stage superheater; T0'(t)-T0' A (t) represents the change in the outlet flue gas temperature of the fourth-stage superheater from its real-time average; D represents the influence factor of the outlet flue gas temperature of the fourth-stage superheater on the main steam; T1' A (t) represents the real-time average temperature of the flue gas at the inlet of the fourth-stage superheater; T1'(t)-T1' A (t) represents the change in the inlet flue gas temperature of the fourth-stage superheater from the real-time average; E represents the influence factor of the inlet flue gas temperature of the fourth-stage superheater on the main steam.

5. The main steam temperature control method according to claim 4, characterized in that, The expected inlet temperature includes a first expected temperature and a second expected temperature. When the real-time main steam temperature is at point P x2 , x={1, 3, 5, 7,...2n+1}, according to the influence intensity, the opening of the three-reduction regulating valve is adjusted to make the real-time steam temperature at the inlet of the fourth-stage superheater reach the first temperature expected value; the first temperature expected value T 1SP =T 1A +k(v)*(△T)+α T'(t) ; wherein, T 1A is the average value of the real-time steam temperature at the inlet of the fourth-stage superheater; △T is the deviation of the main steam temperature T 0PV and the main steam set temperature T 0SP ; k(v) is the time-varying function of v, and v is the change rate of the main steam temperature at point P x or point P y . When the real-time main steam temperature is at point P y2 , y = {2, 4, 6, 8,... 2n}, and when the deviation △T < z, according to the influence intensity, adjust the opening degree of the third desuperheater control valve so that the real-time inlet steam temperature of the fourth superheater reaches the second temperature expectation value; the second temperature expectation value T 1SP = T 1A + α T'(t) ; where z is the expected control deviation.

6. The main steam temperature control method according to claim 5, characterized in that, The real-time main steam temperature is the real-time outlet steam temperature of the fourth-stage superheater.

7. The main steam temperature control method according to claim 5, characterized in that, Point P x2 Point P x Point P y and the point P y2 Point P is a point on the main steam temperature-time curve. x2 and the point P x Adjacent; the point P y and the point P y2 Adjacent.

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