Energy-saving system of self-contained power plant of iron and steel enterprise and operation method

Abstract

The invention discloses an energy-saving system of a self-contained power plant of an iron and steel enterprise and an operation method. The system comprises a boiler, a steam turbine and the like. Blast furnace gas is conveyed to an inlet of the boiler, one path of a steam outlet of the boiler communicates with an inlet of the steam turbine, the other path of the steam outlet of the boiler communicates with an inlet of the fused salt energy storage system, steam generated by the fused salt energy storage system returns to the steam turbine, and the steam turbine is used for driving the generator sets to generate electricity. The self-contained power plant high-voltage bus is connected to a power transmission line; the self-contained power plant high-voltage bus is connected with a power distribution bus through a step-down transformer, and the power distribution bus is connected with a super-capacitor energy storage device and a production load. The method comprises the steps that a base point unit bears a basic load of an iron and steel enterprise, and the generated power is kept constant; the adjusting unit adjusts the power generation power according to the load change condition of the iron and steel enterprise; and the super capacitor monitors the exchange power between an external power transmission line and the iron and steel enterprise. According to the invention, an energy-saving target can be achieved.

Description

Technical Field

[0001] The invention belongs to an electric power system, and in particular relates to an energy-saving system and an operation method of a self-provided power plant of a steel enterprise. Background Art

[0002] Steel companies are typical carbon emitters and energy consumers. Among them, carbon emissions account for about 15% of the country, energy consumption accounts for about 11% of the country, and electricity consumption accounts for 9% of the country's industrial electricity consumption. Based on the 6 trillion kWh of electricity consumption of my country's secondary industry in 2023, the electricity consumption of the entire steel industry will exceed 540 billion kWh. In this context, steel companies have more diversified demands for energy storage. In addition to the explicit factor of reducing electricity costs through peak-valley arbitrage, reducing carbon emissions and maintaining electricity stability are also crucial.

[0003] For steel companies that need to purchase electricity from the power grid, the cost of electricity cannot be ignored, accounting for about 10% of the production cost of steel companies. Reducing the cost of purchasing electricity has become the biggest consideration for steel companies to deploy energy storage. Taking Jiangsu, a major steel-producing province, as an example, according to the existing electricity price policy, Jiangsu has set peak electricity prices for large industries in four months of the year, which allows energy storage to be charged during off-peak or normal times and discharged during two peak periods, thus achieving "two charges and two discharges" per day, ensuring the basic benefits of the project.

[0004] However, for steel companies with their own power plants, they can use the blast furnace gas generated in the steel production process to generate electricity, which can meet the electricity demand of the steel production process, thereby saving the cost of purchasing electricity. In many cases, the electricity generated by a self-owned power plant can not only meet its own production needs, but the excess electricity will also be fed back to the power grid. However, according to the power grid policy, this part of the electricity fed back to the power grid cannot bring corresponding electricity sales income. Therefore, the self-owned power plants of steel companies need to ensure that while meeting the electricity demand of steel production, the amount of electricity fed back to the power grid is as small as possible.

[0005] Most of the production processes of steel enterprises are continuous processes, and the power load has a certain continuity, that is, the power load at each moment has a certain similarity with the power load in the previous period that is close to each other. But at the same time, some equipment has a particularly large power load and a relatively short power cycle, which has a strong impact on the internal power grid and causes power grid fluctuations. For the former case, the self-provided power plant can adjust the output of the generator set by tracking the load conditions over the past period of time through the molten salt energy storage system. For the latter case, the self-provided power plant can quickly respond to rapid changes in power load through supercapacitor energy storage devices. Through the combination of molten salt energy storage and supercapacitor energy storage, the self-provided power plant of the steel enterprise can achieve a power generation capacity that just matches the current power demand of steel production, reducing the purchase of electricity from the power grid or the reverse transmission to the power grid. Summary of the invention

[0006] The purpose of the present invention is to provide an energy-saving system and operation method for a self-provided power plant of a steel enterprise, which can achieve the best match between the power generation of the self-provided power plant and the steel production load, thereby achieving the goal of energy saving.

[0007] The present invention is achieved by adopting the following technical solutions: An energy-saving system for a self-provided power plant of a steel enterprise, comprising a boiler, a steam turbine, a molten salt energy storage system and several generator sets; Blast furnace gas is transported to the boiler inlet. The boiler steam outlet is divided into two routes, one route is connected to the turbine inlet, and the other route is connected to the molten salt energy storage system inlet. The steam generated by the molten salt energy storage system returns to the turbine. The turbine is used to drive the generator set to generate electricity. Several generator sets are connected to the high-voltage bus of the self-provided power plant through a step-up transformer, and the high-voltage bus of the self-provided power plant is connected to the power transmission line. The high-voltage busbar of the captive power plant is also connected to the distribution busbar through a step-down transformer, and the distribution busbar is connected to a supercapacitor energy storage device and production load.

[0008] A further improvement of the present invention is that one of the plurality of generator sets is a regulating set and the other sets are base point sets.

[0009] A further improvement of the present invention is that blast furnace gas can be replaced by coke oven gas or converter gas.

[0010] A further improvement of the present invention is that switches are provided between the high-voltage busbar of the self-provided power plant and each transformer, between the high-voltage busbar of the self-provided power plant and the power transmission line, and between the high-voltage busbar of the self-provided power plant and the distribution busbar, and switches are provided between the distribution busbar and the supercapacitor device and the production load.

[0011] A method for operating an energy-saving system of a self-provided power plant of a steel enterprise, comprising: 1) The base unit bears the basic load of the steel enterprise, and its power generation capacity remains constant; 2) The regulating unit adjusts the power generation according to the load changes of the steel enterprise; 3) The supercapacitor monitors the exchange power between the external power transmission lines and the steel enterprises. When the power transmitted by the steel enterprises to the power grid through the power transmission lines exceeds the set threshold, the supercapacitor starts to charge. When the power absorbed by the steel enterprises from the power grid through the power transmission lines exceeds the set threshold, the supercapacitor starts to discharge. The threshold value is one tenth of the rated power of the supercapacitor.

[0012] A further improvement of the present invention is that in step 1), the basic load of the base unit is predicted according to the production plan of the steel enterprise, the approximate range of the load is determined, and then the power generation power of the base unit is determined to meet 85% of the predicted load.

[0013] A further improvement of the present invention is that in step 2), the generating power of the unit is adjusted and determined based on the moving average of the power load of the steel enterprise in the past four hours minus the power of the base unit.

[0014] A further improvement of the present invention is that in step 2), when the regulating unit needs to reduce the power generation, the amount of steam entering the steam turbine is extracted through the molten salt energy storage system to reduce the power generation of the regulating unit, and the extracted steam is used to heat the molten salt and stored in the molten salt tank; when the regulating unit needs to increase the power generation time, the high-temperature molten salt in the molten salt tank generates steam through heat exchange and is sent to the steam turbine to increase the power generation of the regulating unit.

[0015] A further improvement of the present invention is that in step 3), the control target of the supercapacitor energy storage system is to minimize the sum of the absolute values ​​of the exchange power between the external power transmission line and the steel enterprise.

[0016] A further improvement of the present invention is that in step 3), the rated power of the supercapacitor is determined according to the load fluctuation of the steel enterprise, and the determination method is to calculate the standard deviation of the load of the steel enterprise for 3 days randomly selected from each month in the past 12 months, for a total of 36 days, and the rated power of the supercapacitor is selected to be 2 times of the standard deviation.

[0017] Compared with the prior art, the present invention has at least the following beneficial technical effects: The present invention provides an energy-saving system and operation method for a self-provided power plant of a steel enterprise, which can achieve optimal matching of the power generation power of the self-provided power plant and the steel production load on multiple scales, thereby ensuring that the power generation of the self-provided power plant of the steel enterprise is utilized to the greatest extent, reducing the cost of purchasing electricity from the power grid, and reducing the loss of electricity sent back to the power grid.

[0018] For steel companies with their own power plants, they use blast furnace gas (or coke oven gas, converter gas) generated during the steel production process to generate electricity, which can meet the electricity demand of the steel production process, thereby saving the cost of purchasing electricity. In many cases, the electricity generated by a self-owned power plant can not only meet its own production needs, but the excess electricity will also be fed back to the power grid. However, according to the power grid policy, this part of the electricity fed back to the power grid cannot bring corresponding electricity sales income. Therefore, the self-owned power plants of steel companies need to ensure that while meeting the electricity demand of steel production, the amount of electricity fed back to the power grid is as small as possible.

[0019] Most of the production processes of steel enterprises are continuous processes, and the power load has a certain continuity, that is, the power load at each moment has a certain similarity with the power load in the previous period that is close to each other. But at the same time, some equipment has a particularly large power load and a relatively short power cycle, which has a strong impact on the internal power grid and causes power grid fluctuations. For the former case, the self-provided power plant can adjust the output of the generator set by tracking the load conditions over the past period of time through the molten salt energy storage system. For the latter case, the self-provided power plant can quickly respond to rapid changes in power load through supercapacitor energy storage devices. Through the combination of molten salt energy storage and supercapacitor energy storage, the self-provided power plant of the steel enterprise can achieve a power generation capacity that just matches the current power demand of steel production, reducing the purchase of electricity from the power grid or the reverse transmission to the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a schematic structural diagram of an energy-saving system for a self-provided power plant of a steel enterprise.

[0021] Figure 2 This is a curve diagram of the electricity load of a steel enterprise in an embodiment of the present invention.

[0022] Figure 3 A schematic diagram of the structure of the present invention in which a molten salt energy storage system and a supercapacitor energy storage system are added.

[0023] Figure 4 This is a curve chart of the power load of a steel enterprise after configuring a molten salt energy storage system and a supercapacitor energy storage system in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0025] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0027] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0028] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0029] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0030] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0031] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0032] Example 1 like Figure 1As shown, the present embodiment provides an energy-saving system for a self-provided power plant of a steel enterprise, including a boiler, a steam turbine, a molten salt energy storage system and a plurality of generator sets; blast furnace gas is transported to the boiler inlet, and the steam outlet of the boiler is divided into two paths, one path is connected to the inlet of the steam turbine, and the other path is connected to the inlet of the molten salt energy storage system. The steam generated by the molten salt energy storage system returns to the steam turbine, and the steam turbine is used to drive the generator set to generate electricity. The plurality of generator sets are respectively connected to the high-voltage bus of the self-provided power plant through a step-up transformer, and the high-voltage bus of the self-provided power plant is connected to the power transmission line; the high-voltage bus of the self-provided power plant is also connected to the distribution bus through a step-down transformer, and the distribution bus is connected to a supercapacitor energy storage device and a production load.

[0033] In this embodiment, one of the plurality of generator sets is a regulating set, and the other sets are base point sets.

[0034] In this embodiment, blast furnace gas can be replaced by coke oven gas or converter gas. Blast furnace gas, coke oven gas and converter gas are three common types of gas in steel mills. The output of blast furnace gas is the highest in steel mills, and the gas output per ton of iron can reach 1600-2000 standard cubic meters. Coke oven gas has a higher calorific value and is the highest calorific value among the three types of gas. The calorific value of converter gas is between blast furnace gas and coke oven gas.

[0035] Since the calorific value of coke oven gas is much higher than that of blast furnace gas, mixing the two can increase the calorific value of the mixed gas, thereby improving combustion efficiency. In practical applications, this mixed gas is called "mixed gas" and is widely used in the heating process of steel plants.

[0036] The calorific value of converter gas is also higher than that of blast furnace gas, so mixing it can also increase the calorific value. In addition, the higher CO content in converter gas helps to increase the combustibility of the mixed gas. In some cases, in order to balance the utilization of gas resources and meet production needs, steel mills may choose to mix blast furnace gas with converter gas.

[0037] Blast furnace gas can be mixed with coke oven gas or converter gas to improve the calorific value and combustion efficiency of the mixed gas. This mixed use is common in steel plants and helps optimize the utilization of gas resources and reduce production costs. However, attention should be paid to safety issues and combustion efficiency control during the mixed use process.

[0038] In this embodiment, switches are provided between the high-voltage busbar of the self-provided power plant and each transformer, between the high-voltage busbar of the self-provided power plant and the power transmission line, and between the high-voltage busbar of the self-provided power plant and the distribution busbar, and switches are provided between the distribution busbar and the supercapacitor device and the production load.

[0039] Example 2 This embodiment provides a method for operating an energy-saving system of a self-provided power plant of a steel enterprise, comprising: 1) The base unit bears the basic load of the steel enterprise, and its power generation capacity remains constant; 2) The regulating unit adjusts the power generation according to the load changes of the steel enterprise; 3) The supercapacitor monitors the exchange power between the external power transmission lines and the steel enterprises. When the power transmitted by the steel enterprises to the power grid through the power transmission lines exceeds the set threshold, the supercapacitor starts to charge. When the power absorbed by the steel enterprises from the power grid through the power transmission lines exceeds the set threshold, the supercapacitor starts to discharge. The threshold value is one tenth of the rated power of the supercapacitor.

[0040] In this embodiment, in step 1), the basic load of the base unit is predicted according to the production plan of the steel enterprise, the approximate range of the load is determined, and then the power generation power of the base unit is determined to meet 85% of the predicted load.

[0041] In this embodiment, in step 2), the generating power of the unit is adjusted, which is determined by subtracting the power of the base unit from the moving average of the power load of the steel enterprise in the past four hours.

[0042] When the regulating unit needs to reduce the power generation capacity, the molten salt energy storage system extracts the steam entering the steam turbine to reduce the power generation capacity of the regulating unit. The extracted steam is used to heat the molten salt and stored in the molten salt tank. When the regulating unit needs to increase the power generation capacity, the high-temperature molten salt in the molten salt tank generates steam through heat exchange and is sent to the steam turbine to increase the power generation capacity of the regulating unit.

[0043] In this embodiment, in step 3), the rated power of the supercapacitor is determined according to the load fluctuation of the steel enterprise. The determination method is to calculate the standard deviation of the load of the steel enterprise for 3 days randomly selected each month in the past 12 months, a total of 36 days, and the rated power of the supercapacitor is selected as 2 times the standard deviation. Among them, the supercapacitor is also called an electrochemical capacitor, a double-layer capacitor, a golden capacitor or a farad capacitor. It is a new type of energy storage device between traditional capacitors and rechargeable batteries. The working principle of the supercapacitor is mainly based on the double layer theory. When the electrode contacts the electrolyte, due to the action of Coulomb force, intermolecular force and interatomic force, a stable and opposite double-layer charge appears at the solid-liquid interface to form a double-layer capacitor. The supercapacitor can be regarded as two non-reactive porous electrode plates suspended in the electrolyte. After the plate is powered, the positive plate attracts negative ions in the electrolyte, and the negative plate attracts positive ions, thereby forming a double-layer capacitor on the surface of the two electrodes.

[0044] The heat storage capacity of the molten salt energy storage system is enough to absorb 80% of the blast furnace (coke oven, converter) gas emissions of steel enterprises.

[0045] Example 3 A certain steel enterprise is equipped with three 135MW self-contained generator sets, which increase the voltage to 110kV through a step-up transformer and connect to the 110kV bus of the self-contained power plant. The voltage level of the steel plant's power load is 10kV, and it draws power from the 110kV bus of the self-contained power plant through a 110kV step-down transformer. The steel enterprise's blast furnace (coke oven, converter) gas output is relatively large, which is provided to the self-contained power plant as fuel. The power generated by the self-contained generator sets can meet the normal production needs of the steel enterprise. However, since the power load of some steel production equipment is particularly large and the power consumption cycle is relatively short, the impact on the internal power grid is relatively strong. The self-contained generator sets cannot track the rapidly changing load, resulting in the steel plant needing to exchange power with the external power grid. The power load of a certain steel enterprise is as follows: Figure 2 It is estimated that 30 million kWh of electricity is fed back to the grid each year. According to grid policy, this amount of electricity cannot generate sales revenue. At the same time, due to load fluctuations, an additional 90 million kWh of electricity purchase costs will be incurred.

[0046] According to the method of the present invention, a molten salt energy storage system and a supercapacitor energy storage system are added, such as Figure 3 shown.

[0047] Among them, there are three 135MW self-contained generator sets, and Unit 1 is selected as the regulating unit, and a molten salt energy storage system is configured for it. Units 2 and 3 are used as base units to bear the basic load. At the same time, a supercapacitor energy storage system is configured on the 10kV plant bus. After configuring the molten salt energy storage and supercapacitor energy storage systems according to the method of the present invention, the fluctuation of the steel production load is reduced. Figure 4 As shown in the bold curve, the power exchanged between the steel plant and the external power grid is greatly reduced.

[0048] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0049] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An energy-saving system for a self-provided power plant of a steel enterprise, characterized in that: Includes boilers, steam turbines, molten salt energy storage systems and several generator sets; Blast furnace gas is transported to the boiler inlet. The boiler steam outlet is divided into two routes, one route is connected to the turbine inlet, and the other route is connected to the molten salt energy storage system inlet. The steam generated by the molten salt energy storage system returns to the turbine. The turbine is used to drive the generator set to generate electricity. Several generator sets are connected to the high-voltage bus of the self-provided power plant through a step-up transformer, and the high-voltage bus of the self-provided power plant is connected to the power transmission line. The high-voltage busbar of the captive power plant is also connected to the distribution busbar through a step-down transformer, and the distribution busbar is connected to a supercapacitor energy storage device and production load.

2. The energy-saving system of a self-provided power plant of a steel enterprise according to claim 1, characterized in that: Among several generating units, one unit is a regulating unit and the other units are base units.

3. The energy-saving system of a self-provided power plant of a steel enterprise according to claim 1, characterized in that: Blast furnace gas can be replaced by coke oven gas or converter gas.

4. The energy-saving system of a self-provided power plant of a steel enterprise according to claim 1, characterized in that: Switches are installed between the high-voltage busbar of the self-provided power plant and each transformer, between the high-voltage busbar of the self-provided power plant and the power transmission line, and between the high-voltage busbar of the self-provided power plant and the distribution busbar. Switches are installed between the distribution busbar and the supercapacitor device and the production load.

5. The method for operating the energy-saving system of the self-provided power plant of a steel enterprise according to claim 1, characterized in that: include: 1) The base unit bears the basic load of the steel enterprise, and its power generation capacity remains constant; 2) The regulating unit adjusts the power generation according to the load changes of the steel enterprise; 3) The supercapacitor monitors the exchange power between the external power transmission lines and the steel enterprises. When the power transmitted by the steel enterprises to the power grid through the power transmission lines exceeds the set threshold, the supercapacitor starts to charge. When the power absorbed by the steel enterprises from the power grid through the power transmission lines exceeds the set threshold, the supercapacitor starts to discharge. The threshold value is one tenth of the rated power of the supercapacitor.

6. The method for operating an energy-saving system of a self-provided power plant of a steel enterprise according to claim 5, characterized in that: In step 1), the base load of the base unit is predicted according to the production plan of the steel enterprise, the approximate range of the load is determined, and then the power generation capacity of the base unit is determined to meet 85% of the predicted load.

7. The method for operating an energy-saving system of a self-provided power plant of a steel enterprise according to claim 5, characterized in that: In step 2), the generating power of the unit is adjusted, which is determined by subtracting the power of the base unit from the moving average of the power load of the steel enterprise in the past four hours.

8. The method for operating an energy-saving system of a self-provided power plant of a steel enterprise according to claim 5, characterized in that: In step 2), when the regulating unit needs to reduce the power generation, the amount of steam entering the steam turbine is extracted through the molten salt energy storage system to reduce the power generation of the regulating unit. The extracted steam is used to heat the molten salt and stored in the molten salt tank; when the regulating unit needs to increase the power generation time, the high-temperature molten salt in the molten salt tank generates steam through heat exchange and is sent to the steam turbine to increase the power generation of the regulating unit.

9. The method for operating an energy-saving system of a self-provided power plant of a steel enterprise according to claim 5, characterized in that: In step 3), the control target of the supercapacitor energy storage system is to minimize the sum of the absolute values ​​of the exchange power between the external power transmission line and the steel enterprise.

10. The method for operating an energy-saving system of a self-provided power plant of a steel enterprise according to claim 5, characterized in that: In step 3), the rated power of the supercapacitor is determined according to the load fluctuation of the steel enterprise. The determination method is to calculate the standard deviation of the load of the steel enterprise for 36 days in total, randomly selected from 3 days per month in the past 12 months, and the rated power of the supercapacitor is selected as 2 times the standard deviation.

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