Thermodynamic system capable of rapidly adjusting unit load

Abstract

The invention belongs to the technical field of thermal power generation, and relates to a thermodynamic system capable of quickly adjusting unit load, which comprises a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder and a regenerative system, the high-pressure cylinder and the intermediate-pressure cylinder are respectively connected with main steam and reheat steam of the boiler, and the intermediate-pressure cylinder is connected with the low-pressure cylinder in a steam exhaust manner; the regenerative system comprises a mixed heater, a plurality of high-pressure heaters, a plurality of low-pressure heaters, an oxygen removal water supply assembly and a condenser assembly, and the mixed heater is connected with a first-stage steam extraction opening of a high-pressure cylinder; the condenser assembly is used for condensing dead steam of the low-pressure cylinder into water, then the water is heated by the low-pressure heater, the deoxygenization water supply assembly, the high-pressure heater and the mixed heater in sequence, and then the water enters the boiler again. When the unit needs to rapidly increase and decrease the load, the aim of increasing the load adjusting speed of the unit is achieved through the inherent heat storage function in a back heat squeezing or strengthening mode.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal power generation, and in particular relates to a thermal system for rapidly adjusting unit load. Background Art

[0002] With the rapid increase of wind power and photovoltaic installed capacity in my country, new requirements have been put forward for the operation and design characteristics of new thermal power in the future, requiring thermal power units to have the ability of rapid load change and deep peak regulation. For thermal power units, in principle, the output change of the unit is mainly controlled by adjusting the amount of fuel and water entering the boiler. Due to the complex process and long control closed loop time, other auxiliary means are needed to achieve the rapid load change rate required by the power grid.

[0003] At present, the typical thermal system of a thermal power plant is mainly composed of a high-pressure heater, a deaerator, and a low-pressure heater. Large-capacity units of 300MW and above generally have 3-5 levels of high-pressure heaters, 4-5 levels of low-pressure heaters, and one level of deaerator, with a total of 8-11 heat recovery stages. Due to the low heat storage grade of the deaerator, it only has the function of short-term frequency regulation and does not have the function of assisting the unit to quickly change load. At the same time, the best level that the thermal power unit can achieve is when the unit load rate is above 50%, the load change rate is 2.5%Pe / min, which is far from the 4%-5%Pe / min target required for thermal power units to adapt to new power systems in the future. Summary of the invention

[0004] The purpose of the present invention is to solve the defects and shortcomings in the prior art and to design a thermal system for quickly adjusting the unit load.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a thermal system for rapidly adjusting the load of a unit, comprising a boiler, a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder and a heat recovery system;

[0006] The high-pressure cylinder and the medium-pressure cylinder are connected to the main steam and reheated steam of the boiler respectively, and the exhaust steam of the medium-pressure cylinder is connected to the low-pressure cylinder;

[0007] The heat recovery system includes a hybrid heater, multiple high-pressure heaters, multiple low-pressure heaters, a deaerator water supply assembly and a condenser assembly. The hybrid heater is connected to the first-stage steam extraction port of the high-pressure cylinder. The condenser assembly is used to condense the exhaust steam from the low-pressure cylinder into water, which is then heated in sequence by the low-pressure heater, the deaerator water supply assembly, the high-pressure heater and the hybrid heater before re-entering the boiler.

[0008] Preferably, the hybrid heater and the deoxygenation water supply assembly are connected to a high-pressure water supply pump and a low-pressure water supply pump respectively, and a pre-pump is provided between the hybrid heater and the high-pressure water supply pump, and between the deoxygenation water supply assembly and the low-pressure water supply pump.

[0009] Preferably, the high-pressure water supply pump and the low-pressure water supply pump are both driven electrically or pneumatically.

[0010] Preferably, the multiple high-pressure heaters are respectively connected to the high-pressure cylinder and the medium-pressure cylinder, the multiple low-pressure heaters are respectively connected to the low-pressure cylinder, the deoxygenation water supply assembly is connected to the medium-pressure cylinder, and the deoxygenation water supply assembly is located between the multiple high-pressure heaters and the multiple low-pressure heaters.

[0011] Preferably, two low-pressure cylinders are provided, and the condenser assembly includes two condensers respectively connected to the two low-pressure cylinders, and a condensate pump connected to the two condensers.

[0012] Preferably, a desalting device and a steam seal steam cooler are provided between the condenser assembly and the low-pressure heater.

[0013] Preferably, a high-pressure feedwater pump turbine and a low-pressure feedwater pump turbine are respectively arranged between the deoxygenation feedwater assembly and the two condensers.

[0014] Preferably, regulating valve groups are provided between the main steam and the high-pressure cylinder, and between the reheated steam and the medium-pressure cylinder.

[0015] Preferably, a high-pressure bypass valve is provided between the main steam and the boiler reheat steam inlet, and a low-pressure bypass valve is provided between the reheat steam and the condenser assembly.

[0016] After adopting the above technical solution, the thermal system for quickly adjusting the unit load provided by the present invention has the following beneficial effects:

[0017] 1) The thermal system of the present invention, through the design of a large-capacity hybrid heater connected to the first-stage extraction steam of the high-pressure cylinder and the configuration of a corresponding pre-pump and a high-pressure feed water pump, can improve the rate of load regulation of the unit by displacing or enhancing heat recovery when the unit needs to quickly increase or decrease the load.

[0018] 2) The thermal system of the present invention, through the design of the hybrid heater, can effectively reduce the heat exchange end difference of this section of the heat exchanger, reduce the water feed amount of the subsequent high-pressure heaters, thereby reducing the steam extraction amount of the subsequent high-pressure heaters, and increase the power generation, thereby effectively reducing the heat consumption of the unit, saving coal consumption, and reducing carbon emissions.

[0019] 3) The thermal system of the present invention can reduce the operating pressure of the original high-pressure heater system from about 32MPa to about 10MPa, which can significantly reduce the investment in the corresponding high-pressure heater system equipment, pipelines, and valves. Since the leakage of the rupture in the accident condition is smaller, the capacity of the emergency drain system of the high-pressure heater can also be reduced.

[0020] 4) The thermal system of the present invention, under low load conditions, can increase the peak-shaving depth within a certain period of time by utilizing the heat storage capacity of the hybrid heater of the system. When in the energy storage state, the actual operating load is higher and the heat consumption of the unit is lower, which can save coal consumption and reduce carbon emissions.

[0021] 5) In the thermal system of the present invention, since the pressure of the high-pressure heater system drops from about 32MPa to about 10MPa, the risk of water ingress into the steam turbine is reduced, and the action time requirement of the corresponding control valve is reduced, thereby reducing investment and system risks.

[0022] 6) The design of the thermal system of the present invention is completely linear in the process of switching the load adjustment mode. Under the maximum output condition, the steam turbine still has about 20% flow rate for extraction. There is no temperature step or load step in any part of the system, and the control is easier to achieve. Compared with other energy storage technologies, under the premise of achieving the same load adjustment performance, the thermal system of the present invention has lower cost and less system impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of a thermal system for rapidly adjusting unit load according to the present invention.

[0024] Among them: boiler 1, high-pressure cylinder 2, medium-pressure cylinder 3, low-pressure cylinder 4, hybrid heater 5, high-pressure heater 6, low-pressure heater 7, deaeration feed water assembly 8, high-pressure feed water pump 9, low-pressure feed water pump 10, pre-pump 11, condenser 12, condensate pump 13, desalination device 14, steam seal steam cooler 15, high-pressure feed water pump turbine 16, low-pressure feed water pump turbine 17, regulating valve group 18, high-pressure bypass valve 19, low-pressure bypass valve 20. DETAILED DESCRIPTION

[0025] The present invention is further described clearly and completely below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0027] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0028] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0029] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0030] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0031] The invention discloses a thermal system for rapidly adjusting the load of a unit, which is suitable for newly built units or renovation projects with single or double reheating, such as Figure 1 As shown, it includes a boiler 1, a high-pressure cylinder 2, a medium-pressure cylinder 3, a low-pressure cylinder 4 and a heat recovery system;

[0032] The high-pressure cylinder 2 and the medium-pressure cylinder 3 are connected to the main steam and reheated steam of the boiler 1 respectively, and the exhaust steam of the medium-pressure cylinder 3 is connected to the low-pressure cylinder 4, that is, the main steam generated by the boiler 1 enters the high-pressure cylinder 2 to do work, the exhaust steam of the high-pressure cylinder 2 enters the boiler reheater for reheating and then enters the medium-pressure cylinder 3, and the exhaust steam of the medium-pressure cylinder 3 enters the low-pressure cylinder 4;

[0033] The heat recovery system includes a hybrid heater 5, multiple high-pressure heaters 6, multiple low-pressure heaters 7, a deaerator water supply component 8 and a condenser component. The hybrid heater 5 is connected to the first-stage steam extraction port of the high-pressure cylinder 2. The condenser component is used to condense the exhaust steam of the low-pressure cylinder 4 into water, and then heat it in turn through the low-pressure heater 7, the deaerator water supply component 8, the high-pressure heater 6 and the hybrid heater 5 before re-entering the boiler 1. Specifically, the multiple high-pressure heaters 6 are respectively connected to the high-pressure cylinder 2 and the medium-pressure cylinder 3, the multiple low-pressure heaters are respectively connected to the low-pressure cylinder 4, the deaerator water supply component 8 is connected to the medium-pressure cylinder 3, and the deaerator water supply component 8 is located between the multiple high-pressure heaters 6 and the multiple low-pressure heaters 7. Furthermore, the deaerator water supply component 8 includes a deaerator and a water tank. The hybrid heater 5 selects a large-capacity hybrid heater and has a large-capacity heat storage function. As a heat storage device, the heat storage medium is the heat that passes through during operation. Hot water, due to the high saturation pressure, the working fluid in the first-stage hybrid heater 5 has a large energy density, and only about 200-300 cubic meters of additional water storage is needed to meet the rapid load change of the 1000MW unit from 50% to 100% capacity, so that the coal-fired power unit can better improve the power grid's absorption ratio of new energy, which has a good carbon reduction significance; the large amount of water storage in the large-capacity first-stage hybrid heater 5 can ensure that the water inlet demand of the boiler 1 is met during the entire load increase process when the water volume of the high- and low-pressure heaters changes. In this system, the water flow through the high and low-pressure heaters is synchronized, and at the same time, the steam turbine work is squeezed out by reducing the flow rate of the heaters to quickly increase the load adjustment rate of the unit. The main water medium flow is from the condenser to the condensate pump, low-pressure heater, deaerator, low-pressure feed water pump, high-pressure heater, hybrid heater, high-pressure feed water pump, and finally enters the boiler, and each stage of the heater corresponds to the first-stage steam turbine extraction.

[0034] It should be noted that the number of large-capacity first-stage hybrid heaters 5 can be 1 to 4, and its operating pressure is determined by the first-stage steam extraction. In order to prevent water from entering the steam turbine, two quick-closing doors and two check valves are arranged on the pipeline. When the load is increased, the make-up water temperature is still high-temperature water during the water discharge process of the heater. Although the steam extraction of the steam turbine is discharged, the flow is always maintained. During the whole process, cold water will not be mixed into the hybrid heater 5.

[0035] In addition, in the secondary reheat unit, the first-stage steam extraction port is at the exhaust position of the ultra-high pressure cylinder. Those skilled in the art can make adaptive adjustments as needed, which will not be elaborated again.

[0036] The hybrid heater 5 and the deaeration water supply assembly 8 are connected to the high-pressure water supply pump 9 and the low-pressure water supply pump 10 respectively. A pre-pump 11 is provided between the hybrid heater 5 and the high-pressure water supply pump 9, and between the deaeration water supply assembly 8 and the low-pressure water supply pump 10. The high-pressure water supply pump 9 and the low-pressure water supply pump 10 are both driven electrically or pneumatically. With such a design, the original one-stage water supply pump is disassembled into two stages, which can reduce the operating pressure of the original high-pressure heater system from about 32MPa to about 10MPa, and can significantly reduce the investment in corresponding high-pressure heater system equipment, pipelines, and valves. Since the leakage of the rupture in the accident condition is small, the capacity of the high-pressure heater emergency drain system can also be reduced, that is, the manufacturing cost and maintenance difficulty of the equipment are reduced to a certain extent, the risk of equipment leakage is reduced, and the safety of the system is improved.

[0037] The low-pressure cylinder 4 is provided with two, and the condenser assembly includes two condensers 12 respectively connected to the two low-pressure cylinders 4, and a condensate pump 13 connected to the two condensers 12. A desalination device 14 and a steam seal steam cooler 15 are arranged between the condenser assembly and the low-pressure heater 7. Furthermore, a high-pressure feed water pump turbine 16 and a low-pressure feed water pump turbine 17 are respectively arranged between the deoxygenation feed water assembly 8 and the two condensers 12.

[0038] A regulating valve group 18 is provided between the main steam and the high-pressure cylinder 2, and between the reheated steam and the medium-pressure cylinder 3, a high-pressure bypass valve 19 is provided between the main steam and the reheated steam inlet of the boiler 1, and a low-pressure bypass valve 20 is provided between the reheated steam and the condenser assembly.

[0039] When a thermal system for quickly adjusting the load of a unit of the present invention is working, when the unit needs to quickly increase or decrease the load, the rate of adjusting the load of the unit can be effectively improved by adjusting the water volume of each stage of the heater to exclude or enhance the heat recovery; excluding heat recovery is a flexible means of adjustment, which reduces the amount of heat recovery steam extraction and uses more steam for work, thereby quickly increasing the output power of the unit; in the case of a rapid increase in load, this method can quickly mobilize more steam energy, so that the unit can quickly respond to the needs of the power system, and enhancing heat recovery plays a role when the load needs to be reduced quickly, and by increasing the amount of heat recovery steam extraction, the output power of the unit can be quickly reduced; this adjustment method can be flexibly adjusted according to the needs of load changes, so that the unit can respond quickly when facing various operating conditions, thereby improving the response speed and adjustment ability of the unit, although the amount of water passing through each stage of the heater changes, because the large-capacity first-stage hybrid heater 5 stores enough high-temperature water, it can meet the boiler water inlet needs of the entire load increase process.

[0040] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A thermal system for rapidly adjusting unit load, characterized in that: It comprises a boiler (1), a high-pressure cylinder (2), a medium-pressure cylinder (3), a low-pressure cylinder (4) and a heat recovery system; The high-pressure cylinder (2) and the medium-pressure cylinder (3) are respectively connected to the main steam and reheated steam of the boiler (1), and the exhaust steam of the medium-pressure cylinder (3) is connected to the low-pressure cylinder (4); The heat recovery system comprises a hybrid heater (5), a plurality of high-pressure heaters (6), a plurality of low-pressure heaters (7), a deaeration water supply assembly (8) and a condenser assembly. The hybrid heater (5) is connected to a first-stage steam extraction port of a high-pressure cylinder (2). The condenser assembly is used to condense the exhaust steam of the low-pressure cylinder (4) into water, which is then heated in sequence by the low-pressure heater (7), the deaeration water supply assembly (8), the high-pressure heater (6) and the hybrid heater (5) before re-entering the boiler (1).

2. A thermal system for rapidly adjusting unit load according to claim 1, characterized in that: The hybrid heater (5) and the deoxygenated water supply assembly (8) are respectively connected to a high-pressure water supply pump (9) and a low-pressure water supply pump (10); a pre-pump (11) is provided between the hybrid heater (5) and the high-pressure water supply pump (9), and between the deoxygenated water supply assembly (8) and the low-pressure water supply pump (10).

3. A thermal system for rapidly adjusting unit load according to claim 2, characterized in that: The high-pressure water supply pump (9) and the low-pressure water supply pump (10) are both driven electrically or pneumatically.

4. A thermal system for rapidly adjusting unit load according to claim 1, characterized in that: The multiple high-pressure heaters (6) are respectively connected to the high-pressure cylinder (2) and the medium-pressure cylinder (3), the multiple low-pressure heaters are respectively connected to the low-pressure cylinder (4), the deoxygenation water supply assembly (8) is connected to the medium-pressure cylinder (3), and the deoxygenation water supply assembly (8) is located between the multiple high-pressure heaters (6) and the multiple low-pressure heaters (7).

5. A thermal system for rapidly adjusting unit load according to claim 1, characterized in that: The low-pressure cylinders (4) are provided with two, and the condenser assembly comprises two condensers (12) respectively connected to the two low-pressure cylinders (4), and a condensate pump (13) connected to the two condensers (12).

6. A thermal system for rapidly adjusting unit load according to claim 1, characterized in that: A desalting device (14) and a steam seal steam cooler (15) are arranged between the condenser assembly and the low-pressure heater (7).

7. A thermal system for rapidly adjusting unit load according to claim 5, characterized in that: A high-pressure feedwater pump steam turbine (16) and a low-pressure feedwater pump steam turbine (17) are respectively arranged between the deoxygenated feedwater assembly (8) and the two condensers (12).

8. A thermal system for rapidly adjusting unit load according to claim 1, characterized in that: A regulating valve group (18) is provided between the main steam and the high-pressure cylinder (2), and between the reheated steam and the medium-pressure cylinder (3).

9. A thermal system for rapidly adjusting unit load according to claim 1, characterized in that: A high-pressure bypass valve (19) is arranged between the main steam and the reheat steam inlet of the boiler (1), and a low-pressure bypass valve (20) is arranged between the reheat steam and the condenser assembly.

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