Smelting flue gas waste heat power generation system based on modular heat storage and control method thereof

Abstract

The invention belongs to the technical field of waste heat recovery, and relates to a smelting flue gas waste heat power generation system based on modular heat storage and a control method thereof.The system comprises a smelting kiln and a flue gas system thereof, and the smelting kiln and the flue gas system comprise the smelting kiln, a cooling flue, a flue, a high-temperature dust remover, a high-temperature induced draft fan, a chimney, a quench cooler and a waste heat boiler; the modular heat storage system comprises modular heat storage units, and each modular heat storage unit comprises a first-stage modular heat storage unit group and a second-stage modular heat storage unit group which are connected in series; the steam power generation system comprises a steam-water pipeline, a steam pocket, a steam heat accumulator, a steam turbine, a condenser, a deaerator and a circulating pump. The modular heat storage unit is used for recycling and storing part of flue gas waste heat in a stepped mode, most of the remaining flue gas still enters a conventional waste heat boiler to release heat, smoothness of steam generation fluctuation of the steam heat accumulator and overheating of all saturated steam are achieved, and the technical bottleneck of stable overheating steam power generation of smelting flue gas waste heat is broken through.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste heat recovery, and relates to a smelting flue gas waste heat power generation system based on modular heat storage and its control method. Background Art

[0002] The waste heat recovery of high-temperature flue gas / gas / exhaust gas in the metallurgical production process is a key link to reduce energy consumption. At present, metallurgical enterprises mainly use a variety of technical means to utilize waste heat to generate steam, mainly including dry coke quenching waste heat power generation, sintering ring cooler waste heat power generation, gas power generation, converter / electric furnace flue gas waste heat recovery, and heating furnace flue gas vaporization cooling and other technical means. Among them, except for the gas power generation technical means, the waste heat steam generated by the remaining technical means generally has the problem of low heat source grade. And affected by the periodicity of the production process, some steam also shows significant intermittent and periodic fluctuation characteristics, resulting in poor steam parameter stability, directly restricting the improvement of the thermoelectric conversion efficiency of steam.

[0003] Taking the waste heat recovery system of an electric steelmaking furnace as an example, the typical production process cycle is about 40 minutes, of which 35 minutes is the feeding and high-temperature melting stage (including the oxygen blowing and carbon powder addition processes), and the remaining 5 minutes is the discharging and heating pause stage. The high-temperature flue gas reaches the peak temperature during the oxygen blowing process, and the temperature at the outlet of the high-temperature dust collector is about 850°C, while the flue gas temperature is the lowest during the discharging stage, dropping sharply to 200°C. This drastic temperature fluctuation makes the existing steam heat storage power generation system face technical bottlenecks: on the one hand, for the waste heat recovery with large flue gas temperature fluctuations, the saturated steam power generation method based on a steam accumulator is usually adopted, which can only generate saturated steam, and the power generation efficiency has been at a low level for a long time; on the other hand, it is difficult for the accumulator to suppress large-span heat source fluctuations, resulting in insufficient steam production stability and threatening the safe operation of the steam turbine unit.

[0004] In view of the above problems, the prior art has proposed improvement schemes. For example, a heat storage coupled electric furnace flue gas waste heat recovery power generation system and method disclosed in the invention patent with the application number 202310274069.2 uses a double-tank molten salt heat storage system to store the energy in the full temperature range of the waste heat flue gas, although it solves the problem of flue gas volatility. However, there are significant defects in practical applications: 1. During the operation stage, the pipeline electric tracing system needs to be maintained throughout the process to prevent the molten salt from solidifying during transportation, resulting in additional energy consumption; 2. Continuous electric heating is still required during the shutdown period of the storage tank to maintain the molten salt in a liquid state, and the operation and maintenance cost is high; 3. The double-tank heat storage system has a large volume, and the investment in the heat storage system may reach nearly 50% of the total investment; 4. The system reliability is subject to the construction quality of large storage tanks, and a single-point failure can cause the entire system to shut down. In addition, the high-temperature corrosion characteristics of the molten salt medium pose strict requirements on the pipeline materials, further increasing the difficulty of technology implementation.

[0005] In summary, the technical problems of the existing technology can be summarized into two aspects: in terms of heat source adaptability, the power generation efficiency of traditional steam heat storage systems is low and the stability is average; in terms of system economy, although the conventional double-tank molten salt heat storage solution has heat source adaptability, its high initial investment and operation and maintenance costs seriously restrict industrialization promotion. This contradictory situation has led to the current general dilemma faced by metallurgical enterprises that it is difficult to balance waste heat recovery efficiency and economic benefits, and there is an urgent need to develop a new type of smelting flue gas waste heat power generation system to break through the technical bottleneck. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a smelting flue gas waste heat power generation system based on modular heat storage and its control method, to solve the problem that it is difficult to generate electricity with low cost, high efficiency and stability for the waste heat of smelting flue gas in the existing technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A smelting flue gas waste heat power generation system based on modular heat storage, comprising a smelting furnace and its flue gas system, a modular heat storage system and a steam power generation system;

[0009] The smelting furnace and its flue gas system include a smelting furnace, a cooling flue, a flue, a high-temperature dust collector, a high-temperature induced draft fan, a chimney, a quench cooler and a waste heat boiler;

[0010] The modular heat storage system includes modular heat storage units, and the modular heat storage units include a series-connected first-level modular heat storage unit group and a second-level modular heat storage unit group;

[0011] The steam power generation system includes a steam-water pipeline, a steam drum, a steam accumulator, a steam turbine, a condenser, a deaerator and a circulating pump;

[0012] Among them, the flue gas outlet of the smelting furnace is sequentially connected to the cooling flue and the high-temperature dust collector, and then is divided into three branches through the flue to enter the quench cooler, the waste heat boiler and the modular heat storage unit respectively. The flue gas at the outlet of the modular heat storage unit enters the waste heat boiler through the high-temperature induced draft fan. The flue gas at the outlet of the quench cooler and the flue gas at the outlet of the waste heat boiler are merged and then enter the chimney to be discharged to the external environment;

[0013] The steam-water outlet of the circulating pump is connected to the deaerator through the steam-water pipeline. The steam-water outlet of the deaerator is divided into two branches to enter the cooling flue and the waste heat boiler respectively. The steam-water pipeline branch entering the cooling flue penetrates through the cooling flue and is communicated with the steam drum;

[0014] The steam-water outlet of the waste heat boiler is divided into two branches to enter the second-level modular heat storage unit group of the modular heat storage unit and the steam drum respectively, and the steam-water outlet of the second-level modular heat storage unit group is communicated with the steam drum;

[0015] The steam-water outlet of the steam drum is sequentially connected to a steam accumulator, a first-stage modular heat storage unit group, and a steam turbine through steam-water pipelines;

[0016] The steam-water outlet of the steam turbine is sequentially connected to a condenser and the steam-water inlet of a circulating pump through steam-water pipelines.

[0017] Further, it also includes a dust collector and an induced draft fan arranged between the quench cooler and the chimney.

[0018] Further, the modular heat storage unit further includes a third-stage modular heat storage unit group or a multi-stage modular heat storage unit group connected in series after the second-stage modular heat storage unit group;

[0019] Each of the first-stage modular heat storage unit groups includes at least 2 parallel-connected first-stage modular heat storage units, and each of the second-stage modular heat storage unit groups includes at least 2 parallel-connected second-stage modular heat storage units.

[0020] Further, the first-stage modular heat storage unit and the second-stage modular heat storage unit have the same structure, and both have built-in flue gas heat exchange pipelines and steam-water heat exchange pipelines to be respectively connected to the flue and the steam-water pipelines, so as to realize the storage of flue gas energy and the heating of steam-water working medium.

[0021] Further, the heat storage medium of the first-stage modular heat storage unit and the second-stage modular heat storage unit is one of water, heat-conducting oil, binary molten salt, ternary molten salt, multi-component molten salt, molten sulfur, and solid-liquid hybrid heat storage, or other media that can have the same function.

[0022] Further, electric heaters and heat storage medium pumps are also configured in the first-stage modular heat storage unit group and the second-stage modular heat storage unit group to heat and drive the heat storage medium; specifically, each first-stage modular heat storage unit group or second-stage modular heat storage unit group can be configured with 1 - n electric heaters and 1 - n heat storage medium pumps, where n is the number of first-stage modular heat storage units or second-stage modular heat storage units in the first-stage modular heat storage unit group or the second-stage modular heat storage unit group.

[0023] Further, the smelting furnace is one of an electric furnace, a converter, a rotary hearth furnace, an AOD furnace, an LF furnace, a VD furnace, a VOD furnace, or a pusher / step / ring heating furnace; it should be noted that in fact, the smelting furnace can be any other industrial smelting device that generates flue gas / gas / waste gas with temperature or flow fluctuations.

[0024] The present invention also provides a control method for a smelting flue gas waste heat power generation system based on modular heat storage, which is applicable to the smelting flue gas waste heat power generation system, and specifically includes the following steps:

[0025] Under normal operating conditions, the control logics of the smelting furnace, its flue gas system, and the flue gas side of the modular heat storage system are divided into the smelting period and the non-smelting period;

[0026] Smelting period: The flue duct branch connecting the high-temperature dust collector to the quench cooler is closed, and the two flue duct branches connecting to the waste heat boiler and the modular heat storage unit are opened. The flue gas enters the waste heat boiler and the modular heat storage unit respectively. The flue gas at the outlet of the modular heat storage unit converges with the flue gas in the waste heat boiler through the high-temperature induced draft fan, and the regulation of the flue gas volume entering the modular heat storage unit is achieved by controlling the opening degree of the flue duct branch connecting to the modular heat storage unit and the power of the high-temperature induced draft fan, so as to ensure the energy required for superheating and evaporation of the steam-water working medium;

[0027] Non-smelting period: The two flue duct branches connecting the high-temperature dust collector to the quench cooler and the modular heat storage unit are closed, and the flue duct branch connecting to the waste heat boiler is opened. The flue gas only enters the waste heat boiler.

[0028] Under normal operating conditions, the control logics of the steam power generation system and the steam-water side of the modular heat storage system are divided into the smelting period and the non-smelting period;

[0029] Smelting period: The circulating pump is turned on. The steam-water pipeline branch connecting the waste heat boiler to the secondary modular heat storage unit group is closed, and the steam-water pipeline branch connecting the waste heat boiler to the steam drum is opened. The steam-water working medium discharged from the deaerator enters the steam drum, the steam accumulator, and the superheat stage group of the modular heat storage unit in sequence through the cooling flue and the steam generated by the waste heat boiler, and then enters the steam turbine to do work;

[0030] Non-smelting period: The circulating pump is turned on. The steam-water pipeline branch connecting the waste heat boiler to the secondary modular heat storage unit group is opened, and the steam-water pipeline branch connecting the waste heat boiler to the steam drum is closed. The steam-water working medium discharged from the waste heat boiler enters the steam generated by the secondary modular heat storage unit group and enters the steam drum to supplement the insufficient steam production of the steam accumulator. The steam at the outlet of the steam accumulator enters the steam turbine to do work after passing through the primary modular heat storage unit group;

[0031] Furthermore, both the primary modular heat storage unit group and the secondary modular heat storage unit group are at least 1 group, and each primary modular heat storage unit group includes at least 2 parallel primary modular heat storage units, and each secondary modular heat storage unit group includes at least 2 parallel secondary modular heat storage units;

[0032] When a single primary modular heat storage unit or a single secondary modular heat storage unit fails, the corresponding flue duct branch and steam-water pipeline branch connecting to the primary modular heat storage unit or the secondary modular heat storage unit are closed, and the power of the high-temperature induced draft fan is adjusted;

[0033] Under the condition of a complete shutdown due to a failure of the smelting furnace, its flue gas system, the modular heat storage system, or the steam power generation system:

[0034] Turn off the high-temperature induced draft fan, turn off the circulating pump, close the two flue gas branches connecting the high-temperature dust collector to the waste heat boiler and the modular heat storage unit, open the flue gas branch connecting to the quench cooler, and all the flue gas is cooled by the quench cooler and then discharged to the external environment through the chimney.

[0035] Furthermore, during the smelting period, the volume of flue gas introduced into the modular heat storage unit accounts for the range of 0%-50% of the total volume of flue gas, and the absolute value of the temperature difference between the flue gas temperature at the outlet of the modular heat storage unit and the flue gas temperature at the place where it converges into the waste heat boiler should be ≤100°C.

[0036] The beneficial effects of the present invention are as follows:

[0037] 1. The present invention provides a smelting flue gas waste heat power generation system based on modular heat storage, which uses the modular heat storage unit to recover and store part of the flue gas waste heat in a cascade manner. Most of the remaining flue gas still enters the conventional waste heat boiler to release heat, greatly reducing the heat storage cost, realizing the smoothing of the steam production fluctuation of the steam accumulator and the superheating of all saturated steam, and breaking through the technical bottleneck of stable superheated steam power generation from smelting flue gas waste heat.

[0038] 2. The present invention uses the modular heat storage unit to replace the conventional double-tank heat storage. The modular heat storage unit integrates the storage tank and the heat exchanger without a pipeline electric tracing device. Multiple modules can be conveniently connected in series and parallel to form a heat storage and heat exchange system. The heat storage medium in the module can solidify when not in use, and a single module can be isolated and repaired without shutting down the machine, enabling factory standardized production and modular installation, with high safety and low investment, operation and maintenance costs, and solving the defects of double-tank heat storage.

[0039] 3. The present invention provides a control method for the smelting flue gas waste heat power generation system based on modular heat storage. During the smelting period, part of the flue gas energy is stored and all saturated steam is superheated. During the non-smelting period, partial evaporation generates water vapor and all saturated steam is superheated. Through the control cooperation during the smelting period and the non-smelting period, the ultimate recovery of flue gas energy and efficient power generation are achieved. In addition, the control logic under single-module failure and severe failure conditions is provided, further improving the stability of the original smelting process and power generation system.

[0040] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0042] Figure 1 It is a flowchart of a smelting flue gas waste heat power generation system based on modular heat storage in the embodiment;

[0043] Figure 2 It is a schematic principle diagram of the modular heat storage unit in the embodiment.

[0044] Reference numerals: 1 - smelting furnace; 2 - cooling flue; 3 - flue; 4 - high-temperature dust collector; 5-1 - first flue gas valve; 5-2 - second flue gas valve; 5-3 - third flue gas valve; 5-4 - fourth flue gas valve; 5-5 - fifth flue gas valve; 5-6 - sixth flue gas valve; 5-7 - seventh flue gas valve; 5-8 - eighth flue gas valve; 5-9 - ninth flue gas valve; 5-10 - tenth flue gas valve; 6 - steam-water pipeline; 7 - modular heat storage unit; 7-1 - first-level modular heat storage unit group; 7-2 - second-level modular heat storage unit group; 8-1 - first steam-water valve; 8-2 - second steam-water valve; 8-3 - third steam-water valve; 8-4 - fourth steam-water valve; 8-5 - fifth steam-water valve; 8-6 - sixth steam-water valve; 8-7 - seventh steam-water valve; 8-8 - eighth steam-water valve; 9 - steam drum; 10 - steam accumulator; 11 - steam turbine; 12 - generator; 13 - cooling tower; 14 - condenser; 15 - high-temperature induced draft fan; 16 - deaerator; 17 - chimney; 18 - induced draft fan; 19 - dust collector; 20 - quench cooler; 21 - waste heat boiler; 22 - circulation pump. Specific embodiments

[0045] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0046] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and cannot be construed as limitations on the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, and do not represent the dimensions of actual products; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0047] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the accompanying drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the accompanying drawings are only for illustrative purposes and cannot be construed as a limitation of the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0048] Embodiment 1: A smelting flue gas waste heat power generation system based on modular heat storage

[0049] This embodiment provides a smelting flue gas waste heat power generation system based on modular heat storage, as Figure 1 shown. The system includes the following three major subsystems:

[0050] 1. The smelting furnace and its flue gas system:

[0051] The smelting furnace 1, the cooling flue 2, the flue 3, the high-temperature dust collector 4, the high-temperature induced draft fan 15, the chimney 17, the quench cooler 20, the waste heat boiler 21, the dust collector 19, and the induced draft fan 18.

[0052] 2. The modular heat storage system:

[0053] The modular heat storage unit 7, including a series-connected first-stage modular heat storage unit group 7-1 and a second-stage modular heat storage unit group 7-2.

[0054] In this embodiment, the first-stage modular heat storage unit group 7-1 includes three parallel first-stage modular heat storage units, and the second-stage modular heat storage unit group 7-2 includes three parallel second-stage modular heat storage units.

[0055] Specifically, in this embodiment, the first-stage modular heat storage unit group 7-1 is a superheat-stage modular heat storage unit group, the first-stage modular heat storage unit is a superheat-stage modular heat storage unit, the second-stage modular heat storage unit group 7-2 is an evaporation-stage modular heat storage unit group, and the second-stage modular heat storage unit is an evaporation-stage modular heat storage unit.

[0056] 3. The steam power generation system:

[0057] The steam-water pipeline 6, the steam drum 9, the steam accumulator 10, the steam turbine 11, the generator 12, the cooling tower 13, the condenser 14, the deaerator 16, and the circulating pump 22.

[0058] The system connection and working principle are as follows, where Figure 1In it, the flue gas flow path is represented by solid lines and the steam-water working medium flow path is represented by dashed lines.

[0059] Flue gas flow path:

[0060] The high-temperature flue gas containing waste heat generated by the smelting furnace 1 first enters the cooling flue 2 for preliminary cooling, and then enters the high-temperature dust collector 4 through the flue 3 to remove particulate matter in the flue gas.

[0061] The high-temperature flue gas after dust removal is divided into three branches through the flue 3:

[0062] The first branch enters the quench cooler 20 for rapid cooling, and a first flue gas valve 5-1 is provided on this branch;

[0063] The second branch enters the waste heat boiler 21 for heat recovery, and a second flue gas valve 5-2 is provided on this branch;

[0064] The third branch enters the modular heat storage unit 7 to store heat, and a third flue gas valve 5-3 is provided on this branch;

[0065] The flue gas at the outlet of the modular heat storage unit 7 enters the waste heat boiler 21 under the suction of the high-temperature induced draft fan 15 and merges with the flue gas in the waste heat boiler.

[0066] After the flue gas at the outlets of the quench cooler 20 and the waste heat boiler 21 merges, it passes through the dust collector 19 for further dust removal and is driven by the induced draft fan 18, and finally is discharged to the external environment through the chimney 17.

[0067] Steam-water working medium flow path:

[0068] The circulating pump 22 transports the water working medium through the steam-water pipeline 6 to the deaerator 16 for deaeration treatment.

[0069] The deaerated water working medium is divided into two branches:

[0070] The first branch enters the cooling flue 2, absorbs the heat of the flue gas and is directly connected to the steam drum 9;

[0071] The second branch enters the waste heat boiler 21, absorbs heat and is divided into two small branches:

[0072] One small branch enters the secondary modular heat storage unit group 7-2, is further heated and then connected to the steam drum 9, and a seventh steam-water valve 8-7 is provided on this small branch;

[0073] The other small branch directly enters the steam drum 9, and an eighth steam-water valve 8-8 is provided on this small branch.

[0074] The water vapor in the steam drum 9 flows through the steam accumulator 10 and the primary modular heat storage unit group 7-1 in sequence through the steam-water pipeline 6, is heated and superheated, and then enters the steam turbine 11 to drive it to cooperate with the generator 12 to generate electricity.

[0075] The low-pressure steam discharged from the steam turbine 11 is cooled and condensed into water by the condenser 14 in cooperation with the cooling tower 13, and then returns to the circulating pump 22 to form a closed cycle.

[0076] Specifically, the steam turbine 11 is drivingly connected to a generator 12 for power generation, and the condenser 14 is connected to a cooling tower 13 to condense steam.

[0077] Technical features

[0078] 1. Smelting furnace:

[0079] In this embodiment, the smelting furnace 1 selects an electric furnace, which is suitable for high-temperature smelting processes.

[0080] 2. Modular heat storage unit:

[0081] The first-level modular heat storage unit group 7-1 is composed of 3 parallel superheat-stage modular heat storage units, and the second-level modular heat storage unit group 7-2 is composed of 3 parallel evaporation-stage modular heat storage units. The structures of the second-level modular heat storage unit and the first-level modular heat storage unit are as Figure 2 shown.

[0082] Each modular heat storage unit is internally provided with a flue gas heat exchange pipeline and a steam-water heat exchange pipeline, which are respectively connected to the flue 3 and the steam-water pipeline 6 for heat transfer.

[0083] Fourth flue gas valves 5-4, fifth flue gas valves 5-5, and sixth flue gas valves 5-6 are respectively provided on the flue at the inlets of the flue gas heat exchange pipelines connecting 3 parallel first-level modular heat storage units. Seventh flue gas valves 5-7, eighth flue gas valves 5-8, and ninth flue gas valves 5-9 are respectively provided on the flue at the outlets of the flue gas heat exchange pipelines connecting 3 parallel second-level modular heat storage units. A tenth flue gas valve 5-10 is provided between the modular heat storage unit 7 and the high-temperature induced draft fan 15.

[0084] First steam-water valves 8-1, second steam-water valves 8-2, and third steam-water valves 8-3 are respectively provided on the steam-water pipeline at the inlets of the steam-water heat exchange pipelines connecting 3 parallel first-level modular heat storage units. Fourth steam-water valves 8-4, fifth steam-water valves 8-5, and sixth steam-water valves 8-6 are respectively provided on the steam-water pipeline at the inlets of the steam-water heat exchange pipelines connecting 3 parallel second-level modular heat storage units;

[0085] The heat storage medium of the superheat-stage modular heat storage unit adopts a binary molten salt (a mixture of sodium nitrate and potassium nitrate), and the evaporation-stage modular heat storage unit adopts a ternary salt (a mixture of potassium nitrate + sodium nitrite + sodium nitrate) for heat storage, which has a high heat capacity and stability.

[0086] Each modular heat storage unit group is equipped with one external electric heater and one heat storage medium pump, which are used to heat and circulate the heat storage medium during the non-smelting period or when the heat is insufficient.

[0087] In another embodiment, each modular heat storage unit can also be configured with one external electric heater and one heat storage medium pump.

[0088] 3. Flue gas distribution:

[0089] The flue gas volume entering the modular heat storage unit 7 accounts for 30% of the total flue gas volume, and its outlet flue gas temperature is controlled at 200 °C, which is the same as the outlet flue gas temperature of the waste heat boiler 21, 200 °C. The absolute value of the temperature difference is less than 100 °C, meeting the requirements of efficient heat utilization.

[0090] In this embodiment, the modular heat storage unit is used to achieve the cascade recovery and storage of the waste heat of the smelting flue gas, and the steam accumulator is used to smooth the steam flow fluctuation, thereby improving the steam quality and power generation efficiency, which is applicable to the intermittent smelting process.

[0091] In another embodiment, the smelting furnace is one of an electric furnace, a converter, a rotary hearth furnace, an AOD furnace, an LF furnace, a VD furnace, a VOD furnace, a pusher / step / ring heating furnace; it should be noted that in fact, the smelting furnace can be any other industrial smelting device that generates flue gas / gas / waste gas with temperature or flow fluctuations;

[0092] The heat storage medium of the primary modular heat storage unit and the secondary modular heat storage unit is one of water, heat-conducting oil, binary molten salt, ternary molten salt, multi-component molten salt, molten sulfur, and solid-liquid mixed heat storage, or other media that can have the same function.

[0093] In another embodiment, the modular heat storage unit 7 includes a series-connected primary modular heat storage unit group and a secondary modular heat storage unit group, but both the primary modular heat storage unit group and the secondary modular heat storage unit group are superheat-stage modular heat storage unit groups.

[0094] In another embodiment, the modular heat storage unit 7 includes a series-connected primary modular heat storage unit group, a secondary modular heat storage unit group, and a tertiary modular heat storage unit group, where the primary modular heat storage unit group and the secondary modular heat storage unit group are both set as superheat-stage modular heat storage unit groups, and the tertiary modular heat storage unit group is set as an evaporation-stage modular heat storage unit group;

[0095] The second branch enters the waste heat boiler 21, and after absorbing heat, it is divided into three small branches:

[0096] Two small branch circuits respectively enter the secondary modular heat storage unit group 7-2 and the tertiary modular heat storage unit group, are further heated and then communicated with the steam drum 9, and a seventh steam-water valve 8-7 is arranged on each of the two small branch circuits;

[0097] Another small branch circuit directly enters the steam drum 9, and an eighth steam-water valve 8-8 is arranged on this small branch circuit.

[0098] Embodiment 2: Control method for a smelting flue gas waste heat power generation system based on modular heat storage

[0099] Method overview

[0100] This embodiment provides a control method applicable to the system described in Embodiment 1, and designs detailed control logics for normal working conditions and fault conditions to ensure the efficient and safe operation of the system.

[0101] Normal working condition control logic:

[0102] Flue gas side control:

[0103] 1. Smelting period:

[0104] Close the first flue gas valve 5-1 of the flue branch connecting the high-temperature dust collector 4 and the quench cooler 20.

[0105] Open the two flue branches connecting the waste heat boiler 21 and the modular heat storage unit 7, and open the second flue gas valve 5-2 and the third flue gas valve 5-3.

[0106] Start the high-temperature induced draft fan 15 to make the flue gas enter the waste heat boiler 21 and the modular heat storage unit 7 respectively.

[0107] By adjusting the opening degree of the flue gas branch valve connecting the modular heat storage unit 7 and the power of the high-temperature induced draft fan 15, control the flue gas volume entering the modular heat storage unit 7 to 30% of the total flue gas volume to meet the heat required for the evaporation and superheat of the steam-water working medium.

[0108] 2. Non-smelting period:

[0109] Close the two flue branches connecting the high-temperature dust collector 4 to the quench cooler 20 and the modular heat storage unit 7, that is, close the first flue gas valve 5-1 and the third flue gas valve 5-3.

[0110] Keep the flue branch connecting the waste heat boiler 21 open, close the high-temperature induced draft fan 15, and the flue gas only enters the waste heat boiler 21 for waste heat recovery.

[0111] Steam-water side control

[0112] 1. Smelting period:

[0113] Start the circulating pump 22, close the seventh steam-water valve 8-7 of the steam-water pipeline branch connecting the waste heat boiler 21 to the secondary modular heat storage unit group 7-2, and open the eighth steam-water valve 8-8 of the steam-water pipeline branch connecting the waste heat boiler 21 to the steam drum 9.

[0114] The steam-water working medium output by the deaerator 16 absorbs heat through the cooling flue 2 and the waste heat boiler 21 to generate steam, and successively enters the steam drum 9, the steam accumulator 10, and the primary modular heat storage unit group 7-1, and drives the steam turbine 11 to do work after heating up.

[0115] 2. Non-smelting period:

[0116] Start the circulating pump 22, open the seventh steam-water valve 8-7 of the steam-water pipeline branch connecting the waste heat boiler 21 to the secondary modular heat storage unit group 7-2, and close the eighth steam-water valve 8-8 of the steam-water pipeline branch connecting the waste heat boiler 21 to the steam drum 9.

[0117] The steam-water working medium enters the secondary modular heat storage unit group 7-2 to generate steam by using the stored heat, and makes up for the steam shortage of the steam drum 9 and the steam accumulator 10.

[0118] The steam output by the steam accumulator 10 is further superheated by the primary modular heat storage unit group 7-1 and then enters the steam turbine 11 to do work.

[0119] In another embodiment, when the modular heat storage unit 7 includes a series-connected primary modular heat storage unit group, a secondary modular heat storage unit group, and a tertiary modular heat storage unit group, wherein the primary modular heat storage unit group and the secondary modular heat storage unit group are both set as superheating-stage modular heat storage unit groups, and the tertiary modular heat storage unit group is set as an evaporation-stage modular heat storage unit group.

[0120] During its non-smelting period:

[0121] Start the circulating pump 22, open the seventh steam-water valve 8-7 of the steam-water pipeline branch connecting the waste heat boiler 21 to the secondary modular heat storage unit group 7-2 and the tertiary modular heat storage unit group, and close the eighth steam-water valve 8-8 of the steam-water pipeline branch connecting the waste heat boiler 21 to the steam drum 9.

[0122] The steam-water working medium enters the secondary modular heat storage unit group 7-2 and the tertiary modular heat storage unit group to generate steam by using the stored heat, and makes up for the steam shortage of the steam drum 9 and the steam accumulator 10.

[0123] Fault condition control logic

[0124] 1. Single-module fault:

[0125] If a single module in the first-level or second-level modular heat storage unit group fails, close the flue branch and steam-water pipeline branch valves of this module (for example, if the first first-level modular heat storage unit in the first-level modular heat storage unit group fails, close the fourth flue gas valve 5-4 and the first steam-water valve 8-1).

[0126] Adjust the power of the high-temperature induced draft fan 15 to increase the flue gas flow of the remaining modules, and the system can be maintained without shutting down.

[0127] 2. System shutdown for serious faults:

[0128] Close the high-temperature induced draft fan 15 and the circulation pump 22.

[0129] Close the two flue branches of the high-temperature dust collector 4 connecting the waste heat boiler 21 and the modular heat storage unit 7, close the second flue gas valve 5-2 and the third flue gas valve 5-3, and open the flue branch connecting the quench cooler 20, open the first flue gas valve 5-1.

[0130] After all the flue gas is cooled by passing through the quench cooler 20, it is discharged through the dust collector 19, the induced draft fan 18 and the chimney 17 to ensure that the smelting furnace 1 can still operate normally when the system shuts down.

[0131] In this embodiment, through the fine distribution of flue gas and steam-water working medium during the smelting period and the non-smelting period, the heat storage capacity of the modular heat storage unit is fully utilized to ensure the stability and high-efficiency power generation of the system under different working conditions. At the same time, the control logic under fault conditions improves the safety and maintainability of the system.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A smelting flue gas waste heat power generation system based on modular heat storage, characterized in that: Including smelting furnace and its flue gas system, modular heat storage system and steam power generation system; The smelting furnace and its flue gas system include a smelting furnace (1), a cooling flue (2), a flue (3), a high-temperature dust collector (4), a high-temperature induced draft fan (15), a chimney (17), a quencher (20) and a waste heat boiler (21); The modular heat storage system comprises a modular heat storage unit (7), wherein the modular heat storage unit (7) comprises a primary modular heat storage unit group (7-1) and a secondary modular heat storage unit group (7-2) connected in series; The steam power generation system comprises a steam-water pipeline (6), a steam drum (9), a steam accumulator (10), a steam turbine (11), a condenser (14), a deaerator (16) and a circulating pump (22); The flue gas outlet of the smelting furnace (1) is connected to the cooling flue (2) and the high-temperature dust collector (4) in sequence, and then is divided into three branches through the flue (3) to enter the quench cooler (20), the waste heat boiler (21) and the modular heat storage unit (7) respectively. The flue gas at the outlet of the modular heat storage unit (7) enters the waste heat boiler (21) through the high-temperature induced draft fan (15). The flue gas at the outlet of the quench cooler (20) merges with the flue gas at the outlet of the waste heat boiler (21) and enters the chimney (17) to be discharged to the external environment. The steam-water outlet of the circulation pump (22) is connected to the deaerator (16) through a steam-water pipeline (6); the steam-water outlet of the deaerator (16) is divided into two branches, which respectively enter the cooling flue (2) and the waste heat boiler (21); the steam-water pipeline branch entering the cooling flue (2) passes through the cooling flue (2) and is connected to the steam drum (9); The steam-water outlet of the waste heat boiler (21) is divided into two branches, which respectively enter the secondary modular heat storage unit group (7-2) and the steam drum (9) of the modular heat storage unit, and the steam-water outlet of the secondary modular heat storage unit group (7-2) is connected to the steam drum (9); The steam-water outlet of the steam drum (9) is connected in sequence to the steam accumulator (10), the first-stage modular heat storage unit group (7-1) and the steam turbine (11) through a steam-water pipeline (6); The steam-water outlet of the steam turbine (11) is connected in sequence to the steam-water inlet of the condenser (14) and the circulating pump (22) through a steam-water pipeline (6).

2. The smelting flue gas waste heat power generation system according to claim 1 is characterized in that: It also includes a dust collector (19) and an induced draft fan (18) arranged between the quench cooler (20) and the chimney (17).

3. The smelting flue gas waste heat power generation system according to claim 1 is characterized in that: The modular heat storage unit (7) further comprises a third-stage modular heat storage unit group or a multi-stage modular heat storage unit group connected in series after the second-stage modular heat storage unit group (7-2); The first-level modular heat storage unit group (7-1) includes at least two first-level modular heat storage units connected in parallel, and the second-level modular heat storage unit group (7-2) includes at least two second-level modular heat storage units connected in parallel.

4. The smelting flue gas waste heat power generation system according to claim 3 is characterized in that: The primary modular heat storage unit and the secondary modular heat storage unit both have built-in flue gas heat exchange pipelines and steam-water heat exchange pipelines, which are respectively connected to the flue (3) and the steam-water pipeline (6), thereby realizing the storage of flue gas energy and the heating of steam-water working fluids.

5. The smelting flue gas waste heat power generation system according to claim 4 is characterized in that: The heat storage medium of the primary modular heat storage unit and the secondary modular heat storage unit is one of water, heat transfer oil, binary molten salt, ternary molten salt, polybasic molten salt, molten sulfur and solid-liquid mixed heat storage.

6. The smelting flue gas waste heat power generation system according to claim 5 is characterized in that: The first-level modular heat storage unit group (7-1) and the second-level modular heat storage unit group (7-2) are also provided with an electric heater and a heat storage medium pump to heat and drive the heat storage medium.

7. The smelting flue gas waste heat power generation system according to claim 1 is characterized by: The smelting furnace (1) is one of an electric furnace, a converter, a rotary hearth furnace, an AOD furnace, a LF furnace, a VD furnace, a VOD furnace or a pusher / walking / ring heating furnace.

8. A control method for a smelting flue gas waste heat power generation system based on modular heat storage, applicable to the smelting flue gas waste heat power generation system according to any one of claims 1 to 7, characterized in that: Under normal operating conditions, the control logic of the smelting furnace and its flue gas system and the flue gas side of the modular heat storage system is divided into smelting period and non-smelting period; Smelting period: the flue branch connecting the high-temperature dust collector (4) to the quench cooler (20) is closed, and the two flue branches connecting the waste heat boiler (21) and the modular heat storage unit (7) are opened, and the flue gas enters the waste heat boiler (21) and the modular heat storage unit (7) respectively. The flue gas at the outlet of the modular heat storage unit merges with the flue gas in the waste heat boiler through the high-temperature induced draft fan (15), and the amount of flue gas entering the modular heat storage unit (7) is adjusted by controlling the opening of the flue gas branch connecting the modular heat storage unit and the power of the high-temperature induced draft fan (15) to ensure the energy required for superheating and evaporation of the steam-water working medium; Non-smelting period: the two flue branches connecting the high-temperature dust collector (4) to the quench cooler (20) and the modular heat storage unit are closed, and the flue branch connecting to the waste heat boiler (21) is opened, and the flue gas only enters the waste heat boiler (20). Under normal operating conditions, the control logic of the steam power generation system and the steam-water side of the modular heat storage system is divided into smelting period and non-smelting period; Smelting period: the circulation pump (22) is turned on, the steam-water pipeline branch connecting the waste heat boiler (21) to the secondary modular heat storage unit group (7-2) is closed, and the steam-water pipeline branch connecting the waste heat boiler (21) to the steam drum (9) is opened. The steam-water working medium discharged from the waste heat boiler (21) passes through the cooling flue (2) and the water vapor generated by the waste heat boiler (21) and enters the steam drum (9), the steam accumulator (10) and the modular heat storage unit superheating stage group (7-1) in sequence, and then enters the steam turbine (11) to perform work; During the non-smelting period, the circulating pump (22) is turned on, the steam-water pipeline branch connecting the waste heat boiler (21) to the secondary modular heat storage unit group (7-2) is opened, and the steam-water pipeline branch connecting the waste heat boiler (21) to the steam drum (9) is closed. The steam-water working medium discharged from the deaerator (16) enters the secondary modular heat storage unit group (7-2), and the water vapor generated enters the steam drum (9) to supplement the insufficient steam production of the steam accumulator (10). The water vapor at the outlet of the steam accumulator (10) passes through the primary modular heat storage unit group (7-1) and enters the steam turbine (11) to perform work.

9. The control method according to claim 8, characterized in that: Each primary modular heat storage unit group (7-1) includes at least two primary modular heat storage units connected in parallel, and each secondary modular heat storage unit group (7-2) includes at least two secondary modular heat storage units connected in parallel; When a single primary modular heat storage unit or a single secondary modular heat storage unit fails, the flue branch and the steam-water pipeline branch connected to the primary modular heat storage unit or the secondary modular heat storage unit are closed accordingly, and the power of the high-temperature induced draft fan is adjusted; When the smelting furnace and its flue gas system, modular heat storage system or steam power generation system fails and needs to be completely shut down: The high-temperature induced draft fan (15) is turned off, the circulation pump (22) is turned off, the two flue branches connecting the high-temperature dust collector (4) to the waste heat boiler (21) and the modular heat storage unit are turned off, and the flue branch connected to the quench cooler (20) is turned on. All flue gases are cooled by the quench cooler (20) and then discharged to the outside environment through the chimney (17).

10. The control method according to claim 8, characterized in that: During the smelting period, the amount of flue gas introduced into the modular heat storage unit (7) accounts for 0%-50% of the total volume of the flue gas, and the temperature of the flue gas at the outlet of the modular heat storage unit (7) is controlled so that the absolute value of the temperature difference between the temperature of the flue gas at the place where it flows into the waste heat boiler (21) is ≤100°C.

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