Continuous efficient heat storage and exchange converter and method based on convection-radiation conversion

Abstract

The invention discloses a continuous efficient heat storage and exchange converter and method based on convection-radiation conversion, and belongs to the technical field of industrial energy conservation. The converter is of a three-dimensional spiral body structure, and the spiral body is formed by stacking 300-500 layers of shaftless equal-diameter spiral wires; the key structure sizes of the spiral wire comprise a wire diameter d, a spiral diameter D and a screw pitch B; wherein the thread diameter d of the spiral thread is 0.5-1 mm, and the spiral thread diameter D and the thread pitch B are respectively 1-2 mm; the specific surface area of the spiral body is 1800-3000m < 2 > / m < 3 >, so that the high convection heat exchange area is ensured; the thickness of the spiral body is 300-500mm, so that the radiation emissivity is close to 1; the porosity of the spiral body is gradually changed from 0.5 to 0.9 from the center to the heat exchange surface, so that radiation shielding in the three-dimensional spiral body is reduced. The device has the advantages that the device is suitable for efficient recycling of flue gas waste heat of various industrial furnaces, and the waste heat recycling efficiency can be effectively improved to 75% or above; particularly, a heat accumulating type heating furnace capable of reversing periodically can be replaced, the problems of furnace temperature and pressure fluctuation, flue gas waste heat loss and the like caused by frequent reversing in the traditional heat accumulating type heating process are solved, and continuous and efficient production of an industrial furnace is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial energy conservation, and in particular provides a continuous and efficient heat storage and exchange converter based on convection-radiation conversion and a method thereof. Background Art

[0002] Industrial sectors such as metallurgy, building materials, chemicals, and electricity account for approximately 70% of China's total annual energy consumption. However, their average energy efficiency is less than 50%, and a significant amount of energy is released into the environment as waste heat from flue gases. Statistics show that industrial flue gas emissions exceed 3 billion cubic meters annually, carrying waste heat equivalent to 340 million tons of standard coal per year. However, the average waste heat recovery rate from industrial flue gas is only 29%, 15% to 20% lower than the international average, representing significant potential for energy conservation and carbon reduction.

[0003] At present, the main technologies for recovering waste heat from industrial flue gas include continuous tubular heat exchangers and periodic reversing heat storage heat exchangers. Among them, tubular heat exchangers have a simple structure, can operate continuously and stably, and have a low failure rate, but have a low specific surface area - the specific surface area of ​​a bare tube is ~15m 2 / m 3 Even with the expansion of the surface such as fins / plug-ins, it is only about 30 to 50 meters 2 / m 3 , making its heat transfer efficiency low, and the flue gas waste heat recovery rate is usually only about 30%. The thermal storage heat exchanger can effectively increase the heat transfer specific surface area to 800-1000m by using ceramic honeycomb / ceramic balls as heat storage body. 2 / m 3 , the flue gas waste heat recovery rate can reach about 50%; however, the above-mentioned conventional heat storage bodies can only store heat or release heat separately, and the ceramic material cannot be welded, which turns the continuous heat exchange into a periodic reversing heat exchange process. Frequent reversing (about once every 60 seconds) inevitably causes flue gas waste heat loss, and even gas leakage for double-regenerative furnaces. The actual heat recovery rate and energy efficiency improvement are limited, and there are safety hazards.

[0004] Therefore, in order to reduce energy consumption in industrial production processes and improve production efficiency and quality, it is urgent to develop an efficient and continuous flue gas waste heat recovery method and device to promote high-quality industrial development. Summary of the Invention

[0005] The present invention aims to provide a continuous, highly efficient heat storage and exchange converter and method based on convection-radiation conversion, addressing the serious problems of flue gas waste heat emissions and the low efficiency of traditional flue gas waste heat recovery methods in industrial production processes. By designing a three-dimensional, spirally extended surface convection-radiation converter with an ultra-high specific surface area and high vertical emissivity, the heat transfer process in traditional heat exchangers, which is primarily based on "heat convection between flue gas and heat exchange tubes," is converted into a convection-radiation coupled enhanced heat transfer process consisting of "heat convection between flue gas and convection-radiation converter" and "heat radiation between convection-radiation converter and heat exchange tubes."

[0006] The converter of the present invention is a three-dimensional spiral structure, which is composed of 300 to 500 layers of axisless equal-diameter spiral wires stacked together. The key structural dimensions of the spiral wire include wire diameter d, spiral diameter D, and pitch B. Among them, the spiral wire diameter d is 0.5 to 1 mm, the spiral diameter D and pitch B are 1 to 2 mm respectively; the specific surface area of ​​the spiral is 1800 to 3000 m 2 / m 3 , to ensure a high convective heat transfer area; the thickness of the spiral is 300-500 mm to ensure that the radiation emissivity is close to 1; the porosity of the spiral gradually changes from 0.5 to 0.9 from the center to the heat transfer surface to reduce the radiation shielding inside the three-dimensional spiral.

[0007] When in use, the convection-radiation converter (1) is placed on the high-temperature flue gas side, and continuous heat storage and exchange of the flue gas to the heat exchange surface (2) is achieved through convection heat transfer (heat storage) along the flue gas flow direction and radiation heat transfer (heat exchange) perpendicular to the flow direction.

[0008] The single spiral filaments of the helix are placed side by side in the horizontal direction to form a spiral single-layer honeycomb structure, and the spiral single layers are stacked in the vertical direction to form a three-dimensional spiral honeycomb (300 to 500 layers).

[0009] The continuous and efficient heat storage and exchange method based on convection-radiation conversion of the present invention is as follows:

[0010] The convection-radiation converter (1) is placed on the high-temperature flue gas side, and continuous heat storage and exchange of flue gas to the heat exchange surface (2) is achieved through convection heat transfer (heat storage) along the flue gas flow direction and radiation heat transfer (heat exchange) perpendicular to the flow direction. The convection-radiation converter with a high specific surface area composed of a three-dimensional spiral can greatly increase the heat transfer specific surface area on the gas side to 1800-3000m 2 / m 3 At the same time, the random spiral filaments in the honeycomb can induce turbulent flue gas flow disturbances, and by continuously destroying the flow and heat transfer boundary layer, effectively increase the flue gas convection heat transfer coefficient by more than 2 times, thereby quickly storing the flue gas waste heat in the three-dimensional spiral.

[0011] In terms of enhancing the radiation heat transfer between the convection-radiation converter and the heat exchange wall, increasing the thickness of the convection-radiation converter (≥300mm) can effectively break through the limitation of the radiation emission force of the material itself; further optimizing the density structure of the metal spiral wire in the direction perpendicular to the heat exchange tube in the convection-radiation converter, so that the porosity of the spiral gradually increases from the center to the heat exchange surface, reducing the radiation shielding inside the three-dimensional spiral, and achieving a radiation emission force close to 1, thereby efficiently transferring the heat in the three-dimensional spiral to the heat exchange surface.

[0012] The convection-radiation converter involved in this method is placed on the high-temperature flue gas side, and continuous heat storage and exchange of flue gas to the heat exchange surface is achieved through convection heat transfer (heat storage) along the flue gas flow direction and radiation heat transfer (heat exchange) perpendicular to the flow direction.

[0013] The innovation of this invention lies in the design of a three-dimensional spirally extended surface convection-radiation converter with an ultra-high specific surface area and high vertical emissivity. This converts the heat transfer process in a traditional heat exchanger, which is primarily based on "heat convection between flue gas and heat exchange tubes," into a convection-radiation coupled enhanced heat transfer process of "heat convection between flue gas and convection-radiation converter" plus "heat radiation between convection-radiation converter and heat exchange tubes." Specifically, in terms of enhancing the convection heat transfer between flue gas and convection-radiation converter, the high specific surface area convection-radiation converter can greatly increase the heat transfer specific surface area on the gas side. At the same time, the random spiral filaments within the honeycomb can induce turbulent flue gas flow, effectively increasing the flue gas convection heat transfer coefficient by continuously disrupting the flow and heat transfer boundary layer, thereby rapidly storing the flue gas waste heat in the three-dimensional spiral. In terms of enhancing the radiation heat transfer between the convection-radiation converter and the heat exchange wall, increasing the thickness of the convection-radiation converter can effectively overcome the limitation of the radiation emission force of the material itself; the dense structure of the metal spiral wire in the convection-radiation converter in the direction perpendicular to the heat exchange tube makes the porosity of the spiral gradually increase from the center to the heat exchange surface, reducing the radiation shielding inside the three-dimensional spiral and achieving a radiation emission force close to 1, thereby efficiently transferring the heat in the three-dimensional spiral to the heat exchange surface.

[0014] The advantages of the present invention are that it has strong engineering operability and is suitable for the efficient recovery and utilization of waste heat from flue gas of various industrial furnaces, and can effectively improve the waste heat recovery efficiency to more than 75%; in particular, it can be used to replace the periodically reversing heat storage heating furnace, solving the problems of furnace temperature and pressure fluctuations and flue gas waste heat loss caused by the frequent reversing of the traditional heat storage heating process, thereby realizing continuous and efficient production of industrial furnaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of a continuous and efficient flue gas heat storage and exchange device based on convection-radiation conversion according to the present invention.

[0016] Among them: a three-dimensional spiral convection-radiation converter 1 and a heat exchange surface 2.

[0017] Figure 2 Schematic diagram of the helical filament unit.

[0018] Figure 3 Schematic diagram of the spiral formation process. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0020] In response to the problems of serious flue gas waste heat emission in industrial production processes and low efficiency of traditional flue gas waste heat recovery methods, the present invention provides a continuous and efficient heat storage and exchange converter and method based on convection-radiation conversion.

[0021] like Figure 1 As shown, the converter of the present invention includes a three-dimensional spiral convection-radiation converter 1 and a heat exchange surface 2. The convection-radiation converter (1) is placed on the high-temperature flue gas side, and realizes continuous heat storage and exchange of the flue gas to the heat exchange surface (2) through convection heat transfer (heat storage) along the flue gas flow direction and radiation heat transfer (heat exchange) perpendicular to the flow direction. Specifically, the high-temperature flue gas first flows through the convection-radiation converter, and the waste heat it carries is quickly stored in the three-dimensional spiral (1) through convection heat transfer; after the spiral is heated, it is efficiently transferred to the heat exchange surface (2) in the form of radiation heat transfer perpendicular to the flue gas flow direction.

[0022] In practical applications, in order to enhance the convection heat transfer between the flue gas and the convection-radiation converter, the convection-radiation converter (1) is composed of a plurality of three-dimensional spiral bodies with ultra-high specific surface areas. The wire diameter of the three-dimensional spiral monomer is ≤1mm, and the heat transfer specific surface area of ​​the convection-radiation converter is ≥1800m 2 / m 3 At the same time, the three-dimensional spiral can induce flue gas turbulence disturbance, and by continuously destroying the flow and heat transfer boundary layer, it effectively increases the flue gas convection heat transfer coefficient by more than 2 times, thereby quickly storing the flue gas waste heat in the three-dimensional spiral.

[0023] In practical applications, in order to enhance the radiation heat transfer between the convection-radiation converter and the heat exchange surface, the three-dimensional spiral convection-radiation converter (1) has a high vertical emissivity, and the porosity of the spiral gradually changes from 0.5 to 0.9 from the center to the heat exchange surface to reduce the radiation shielding inside the three-dimensional spiral; at the same time, by increasing the thickness of the convection-radiation converter to ≥30 mm, the limitation of the radiation emission force of the material itself can be effectively broken through, and the overall radiation emission force can be close to 1, thereby efficiently transferring the heat in the three-dimensional spiral to the heat exchange surface.

[0024] like Figure 2The figure shows a schematic diagram of a spiral wire unit, which is an axisless spiral structure. The key structural parameters include wire diameter d, spiral diameter D, and pitch B. Among them, the spiral wire diameter d is 0.5~1mm, and the spiral diameter D and pitch B are 1~2mm respectively.

[0025] like Figure 3 The figure shows the process of forming a three-dimensional honeycomb helix. Single spiral filaments are placed side by side in the horizontal direction to form a spiral single-layer honeycomb structure, and the spiral single layers are stacked in the vertical direction to form a three-dimensional spiral honeycomb (300 to 500 layers).

[0026] Using this converter, the heat transfer process in the traditional heat exchanger, which is mainly based on "heat convection between flue gas and heat exchange tubes", is converted into a convection-radiation coupled enhanced heat transfer process of "heat convection between flue gas and convection-radiation converter" + "heat radiation between convection-radiation converter and heat exchange tubes". It can be used for the efficient recovery and utilization of waste heat from flue gas of various industrial furnaces, effectively improving the waste heat recovery efficiency to more than 75%.

[0027] The three-dimensional spiral convection-radiation converter realizes continuous heat storage and exchange from flue gas to the heat exchange surface. It can replace the periodically reversing thermal storage heating furnace, solves the problems of furnace temperature and pressure fluctuations and flue gas waste heat loss caused by frequent reversing in the traditional thermal storage heating process, and realizes continuous and efficient production of industrial furnaces.

[0028] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A continuous high-efficiency heat storage and exchange converter based on convection-radiation conversion, characterized by: The converter is a three-dimensional spiral structure, which is composed of 300 to 500 layers of axisless equal-diameter spiral wires. The key structural dimensions of the spiral wire include wire diameter d, spiral diameter D, and pitch B. Among them, the spiral wire diameter d is 0.5 to 1 mm, the spiral diameter D and pitch B are 1 to 2 mm respectively; the specific surface area of ​​the spiral is 1800 to 3000 m 2 / m 3 , to ensure a high convective heat transfer area; the spiral thickness is 300-500mm to ensure that the radiation emissivity is close to 1; the porosity of the spiral gradually changes from 0.5 to 0.9 from the center to the heat transfer surface to reduce the radiation shielding inside the three-dimensional spiral. When in use, the convection-radiation converter (1) is placed on the high-temperature flue gas side, and continuous heat storage and exchange of the flue gas to the heat exchange surface (2) is achieved through convection heat transfer or heat storage along the flue gas flow direction and radiation heat transfer or heat exchange perpendicular to the flow direction.

2. The continuous high-efficiency heat storage and exchange converter based on convection-radiation conversion according to claim 1, characterized in that: Single spiral filaments are placed side by side in the horizontal direction to form a spiral single-layer honeycomb structure, and the spiral single layers are stacked in the vertical direction to form a three-dimensional spiral honeycomb.

3. A continuous and efficient heat storage and exchange method for the converter according to claim 1, characterized in that: The convection-radiation converter (1) is placed on the high-temperature flue gas side, and continuous heat storage and exchange of flue gas to the heat exchange surface (2) is achieved through convection heat transfer or heat storage along the flue gas flow direction and radiation heat transfer or heat exchange perpendicular to the flow direction. The convection-radiation converter with a high specific surface area composed of three-dimensional spirals greatly increases the heat transfer specific surface area of ​​the gas side to 1800-3000m 2 / m 3 At the same time, the random spiral filaments in the honeycomb induce turbulent flue gas flow disturbances, which effectively increase the flue gas convection heat transfer coefficient by more than 2 times by continuously destroying the flow and heat transfer boundary layer, thereby quickly storing the flue gas waste heat in the three-dimensional spiral. The convection-radiation converter is placed on the high-temperature flue gas side, and realizes continuous heat storage and exchange of flue gas to the heat exchange surface through convection heat transfer or heat storage along the flue gas flow direction and radiation heat transfer or heat exchange perpendicular to the flow direction.

4. The continuous and efficient heat storage and exchange method for a converter according to claim 1, characterized in that: In terms of enhancing the radiation heat transfer between the convection-radiation converter and the heat exchange wall, the limitation of the radiation emission force of the material itself is effectively overcome by increasing the thickness of the convection-radiation converter; the density structure of the metal spiral wire in the convection-radiation converter in the direction perpendicular to the heat exchange tube is further optimized, so that the porosity of the spiral gradually increases from the center to the heat exchange surface, reducing the radiation shielding inside the three-dimensional spiral, and achieving a radiation emission force close to 1, thereby efficiently transferring the heat in the three-dimensional spiral to the heat exchange surface.

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