Patent Application
20220205734
This application claims the benefit of Chinese Patent Application No. 202011593639.7, filed Dec. 29, 2020, the entire contents of which are incorporated herein by reference.
The present invention relates to the field of high-temperature fluid heat recovery, in particular to the recovery of heat from hot flue gas of a glass melting furnace for the purpose of heating a fuel and/or an oxygen-enriched gas.
Protecting the environment, saving energy, conserving land and reducing costs are issues of concern in modern industrial development. Various technical processes such as metallurgy, glass melting and industrial chemical production need to consume large amounts of energy, at the same time generating products or by-products containing large amounts of thermal energy. For example, flue gas or steam generated during combustion, syngas and steam generated by natural gas reforming, etc. are all high-temperature fluids containing large amounts of thermal energy. If the thermal energy in these high-temperature fluids cannot be recovered, the result will be considerable wastage of energy and production efficiency.
Taking plate glass production as an example, in the prior art, many kilns operate via oxygen-enriched combustion, and this means that combustion no longer takes place between fuel and air (air combustion) but instead takes place between fuel and oxygen-enriched gas with a higher oxygen concentration than air. Using exhaust gas from combustion products, i.e. flue gas, to preheat the fuel and/or oxygen-enriched gas enables the recovery of some of the energy contained in the flue gas, and can also increase the energy efficiency of such combustion. In the case of oxygen-enriched combustion, the energy contained in flue gas accounts for 30% of the energy consumed.
CN100575788C disclosed an indirect heat exchanger. In a heat exchange region, hot flue gas heats an inert gas contained in a hermetic apparatus first, then the hot inert gas further heats a combustion gas located in another of the airtight apparatuses. This design requires the addition of a new heat exchange region outside an existing flue gas pipeline of the factory; because the amount of space occupied is increased, the cost of investment is increased, so this design is not widely applied in practice.
An object of the present invention is to overcome the shortcomings of the prior art, modifying an existing horizontally arranged high-temperature fluid pipeline, e.g. a flue gas pipeline, in a factory so as to integrate a heat exchange apparatus with the pipeline, thus achieving the technical effects of recovering thermal energy to the maximum extent, saving space and reducing cost input.
In one aspect, the present invention provides a high-temperature fluid transporting pipeline, wherein at least a part of a casing thereof is formed by a heat exchange apparatus.
The heat exchange apparatus comprises a heat exchange base plate in contact with the high-temperature fluid and a thermal isolation layer in contact with an external environment, the thermal isolation layer being connected to the heat exchange base plate by two end faces and two weight-bearing plates, wherein the heat exchange base plate, thermal isolation layer, end faces and weight-bearing plates enclose a hermetic heat exchange cavity, a heat-receiving fluid coil being installed in the heat exchange cavity, and the two end faces being parallel.
Optionally, the thermal isolation layer of the heat exchange apparatus comprises an inner layer and an outer layer, and the inner wall of the thermal isolation layer at least partially comprises a heat-reflecting plate. A thermal isolation material is packed between the inner and outer walls of the thermal isolation layer or a vacuum is maintained therebetween, the thermal isolation material comprising rock wool and/or perlite. A heat-receiving fluid inlet and a heat-receiving fluid outlet are provided on an outer wall of the thermal isolation layer, the heat-receiving fluid inlet being sequentially in communication with a heat-receiving fluid inlet distributor located inside the heat exchange accommodating cavity and an inlet of the heat-receiving fluid coil, and the heat-receiving fluid outlet being sequentially in communication with a heat-receiving fluid outlet distributor located inside the heat exchange cavity and an outlet of the heat-receiving fluid coil. Optionally, a temperature sensor is provided on a heat-receiving fluid outlet pipeline and/or the heat-receiving fluid outlet distributor.
The outer wall of the thermal isolation layer is further provided with an auxiliary fluid inlet and an auxiliary fluid outlet, each being in communication with the heat exchange cavity. A gas component analyser is provided at the auxiliary fluid outlet, for the purpose of ensuring that there is no leakage of heat-receiving fluid in the heat exchange cavity.
Optionally, the heat exchange plate is an arch or has multiple undulations. The transporting pipeline is arranged horizontally, the casing of the transporting pipeline comprises a refractory layer at a lower half and the heat exchange apparatus at an upper half, the weight-bearing plates of the heat exchange apparatus are pressed tightly against the refractory layer under the action of gravity, and a sealing refractory material is used for sealing between the weight-bearing plates and the refractory layer. When the heat exchange base plate is undulating, a supporting structure is provided between the heat exchange base plate and the weight-bearing plates. The sealing refractory material comprises one of ceramic fiber, glass fiber and refractory mortar, or a combination of more than one thereof.
Optionally, the materials of the heat exchange base plate, the inner and outer walls of the thermal isolation layer, the heat-reflecting plate, the end faces, the weight-bearing plates and the heat-receiving fluid coil comprise stainless steel and/or aluminium.
Optionally, a number of heat exchange apparatuses are arranged in the axial direction of the transporting pipeline, with the end faces of the heat exchange apparatuses being tightly arranged against each other, and a sealing refractory material being used for sealing between the end faces.
Optionally, in the high-temperature fluid transporting pipeline, the heat-receiving fluid flows in the heat-receiving fluid coil, the auxiliary fluid flows or is stationary in the heat exchange cavity, and the heat-receiving fluid is heated by the high-temperature fluid through heat conduction by the auxiliary fluid and heat radiation by the heat exchange base plate.
Optionally, in the high-temperature fluid transporting pipeline, the high-temperature fluid comprises flue gas generated by combustion and/or thermal cracking, the auxiliary fluid comprises one of air, N2, CO2 and steam or a combination of more than one thereof, and the heat-receiving fluid comprises O2, natural gas or other fuel gases.
In another aspect, the present invention further discloses a heat exchange apparatus suitable for the high-temperature fluid transporting pipeline as described above, characterized in that the heat exchange apparatus comprises a heat exchange base plate in contact with the high-temperature fluid and a thermal isolation layer in contact with an external environment, the thermal isolation layer being connected to the heat exchange base plate by two end faces and two weight-bearing plates, wherein the heat exchange base plate, thermal isolation layer, end faces and weight-bearing plates enclose a hermetic heat exchange cavity, a heat-receiving fluid coil being installed in the heat exchange cavity.
Optionally, the two end faces of the heat exchange apparatus are parallel.
Optionally, the thermal isolation layer of the heat exchange apparatus comprises an inner layer and an outer layer, and the inner wall of the thermal isolation layer at least partially comprises a heat-reflecting plate. A thermal isolation material is packed between the inner and outer walls of the thermal isolation layer or a vacuum is maintained therebetween, the thermal isolation material comprising rock wool and/or perlite.
Optionally, the heat exchange base plate is an arch or has multiple undulations; when the heat exchange base plate has multiple undulations, a supporting structure is provided between the heat exchange base plate and the weight-bearing plates.
Optionally, in the heat exchange apparatus, the materials of the heat exchange base plate, the inner and outer walls of the thermal isolation layer, the heat-reflecting plate, the end faces, the weight-bearing plates and the heat-receiving fluid coil comprise stainless steel and/or aluminium.
In another aspect, the present invention further discloses a heat exchange method, characterized in that at least a part of a casing of the transporting pipeline is formed by a heat exchange apparatus, the heat exchange apparatus comprising a heat exchange base plate in contact with the high-temperature fluid and a thermal isolation layer in contact with an external environment, the thermal isolation layer being connected to the heat exchange base plate by two end faces and two weight-bearing plates, wherein the heat exchange base plate, thermal isolation layer, end faces and weight-bearing plates enclose a hermetic heat exchange cavity, a heat-receiving fluid coil being installed in the heat exchange cavity; a heat-receiving fluid flows in the heat-receiving fluid coil, an auxiliary fluid flows or is stationary in the heat exchange cavity, and the heat-receiving fluid is heated by the high-temperature fluid through heat conduction by the auxiliary fluid and heat radiation by the heat exchange base plate.
Optionally, the high-temperature fluid comprises flue gas generated by combustion and/or thermal cracking. The auxiliary fluid comprises one of air, N2, CO2 and steam or a combination of more than one thereof, and the heat-receiving fluid comprises O2, natural gas or another fuel gas.
Optionally, the temperature range of the flue gas is 500-1200° C., and the temperature range of the heat-receiving fluid is 300-600° C. The range of flow rates of the heat-receiving fluid is 5-100 m/s, preferably 20-60 m/s; and the range of flow rates of the auxiliary fluid is 0-50 m/s, preferably 20-30 m/s.
The use of the technical solution of the present invention will produce several beneficial technical effects.
Firstly, the design of the heat exchange apparatus in the present invention makes the modification of an existing transporting pipeline and the installation of the new apparatus very convenient, and can increase the heat exchange area while reducing costs, thus increasing the heat exchange efficiency.
Secondly, multiple heat exchange apparatuses can be installed in parallel, and the multiple heat exchange apparatuses can heat the same type of heat-receiving fluid, or different heat-receiving fluids.
Thirdly, the heat exchange apparatus employs a method of indirect heating, and the use of the auxiliary fluid, temperature sensor and gas component analyser, etc. increases the safety and controllability of the heat exchange apparatus.
The drawings in the present disclosure merely serve to illustrate the present invention, such that the spirit of the present invention can be understood and explained, but do not limit the present invention in any respect.
The references in the drawings are as follows: 1—heat exchange base plate, 2—weight-bearing plate, 3—thermal isolation layer, 4—end face, 5—heat-receiving fluid inlet, 6—heat-receiving fluid outlet, 7—temperature sensor, 8—heat-receiving fluid inlet distributor, 9—heat-receiving fluid outlet distributor, 10—auxiliary fluid inlet, 11—auxiliary fluid outlet, 12—heat-receiving fluid coil, 13—thermal isolation layer outer wall, 14—thermal isolation layer inner wall, 15—thermal isolation material, 16—heat-reflecting plate, 17—sealing refractory material, 18—refractory bricks, 19—gas component analyser, 20—heat exchange cavity, 21—hoisting lug, 22—transporting pipeline casing, 25—supporting frame, 26—supporting arm, 27—supporting column, 28—crossbeam.
In the present invention, it should be understood that orientational or positional relationships indicated by terms such as “up”, “down”, “front”, “rear”, “perpendicular”, “parallel”, “top”, “bottom”, “inner” and “outer” are based on the orientational or positional relationships shown in the drawings, and use a horizontal plane as a reference.
Unless otherwise stated, qualifiers similar to “a” appearing herein do not indicate a definition of quantity, but describe technical features distinguished from one another. Similarly, modifiers similar to “about” and “approximately” appearing in front of numerals herein generally include the number itself, and the specific meaning thereof should be understood in conjunction with the meaning of the context. Unless modified by a specific quantifying measure word, nouns herein should be regarded as including both singular and plural forms, i.e. the technical solution may include a single one of the technical feature concerned, but may also include a plurality of the technical feature.
In the present invention, unless otherwise clearly specified and defined, terms such as “installed”, “connected together”, “connected” and “in communication” should be understood in a broad sense, e.g. may mean connected in a fixed manner, but may also mean removably connected, or forming a single piece; may mean mechanically connected; may mean directly connected together, but may also mean connected indirectly via an intermediate medium; and may mean internal communication between two elements, or an interactive relationship between two elements. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.
The high-temperature fluid in the present invention may have various forms and compositions, including gases as well as liquids; and may be a single component or a mixture. “High-temperature” means that the temperature thereof is higher than the temperature of the fluid being heated, with a range of variation of 100-1500° C. When the high-temperature fluid is a gas such as flue gas, the pipeline for transporting same is generally formed of refractory bricks; when the high-temperature fluid is a liquid, the casing of the pipeline for transporting same is often formed of metal. The present invention is suitable for the modification of various high-temperature fluid transporting pipelines arranged substantially horizontally. In the process of modification, a portion of the casing located above a horizontal plane through the central axis of the pipeline is replaced by an apparatus having a heat exchange function, i.e. the heat exchange apparatus of the present invention.
As shown in
The thermal isolation layer 3 is a hollow structure comprising an inner wall 14 and an outer wall 13. At least a part of the thermal isolation layer inner wall 14 is formed by a heat-reflecting plate 16 or covered by the heat-reflecting plate 16. A cavity between the inner wall 14 and outer wall 13 of the thermal isolation layer may be evacuated, or may be filled with a thermal isolation material 15 comprising rock wool and/or perlite, etc. Multiple fluid outlets/inlets are provided on the thermal isolation layer outer wall 13, including a heat-receiving fluid inlet 5, which is connected sequentially to a heat-receiving fluid inlet distributor 8 located in the heat exchange cavity and an inlet of the heat-receiving fluid coil 12; and also including a heat-receiving fluid outlet 6, which is connected sequentially to a heat-receiving fluid outlet distributor 9 located in the heat exchange cavity and an outlet of the heat-receiving fluid coil 12. Variables such as temperature and pressure of the heat-receiving fluid are important parameters in industrial production; for this reason, a measuring device such as a temperature sensor 7 and/or pressure sensor is provided on the heat-receiving fluid outlet distributor 9 or a heat-receiving fluid outlet pipeline connected to the heat-receiving fluid outlet 6. Outside the heat exchange apparatus, the heat-receiving fluid inlet 5 and outlet 6 are each connected to a heat-receiving fluid delivery system, optionally by means of a flange; the system comprises a valve capable of adjusting the flow rate of the heat-receiving fluid, a heat-receiving fluid controller, etc. (not shown in the figure). The heat-receiving fluid controller can receive a heat-receiving fluid outlet temperature and/or pressure measured by the measuring device, and on this basis can adjust the flow rate (or flow speed), temperature and pressure, etc. of the heat-receiving fluid.
An auxiliary fluid inlet 10 and an auxiliary fluid outlet 11 are also provided on the thermal isolation layer outer wall 13. Outside the heat exchange apparatus, the auxiliary fluid inlet 10 and outlet 11 are each connected to an auxiliary fluid delivery system, which comprises a valve capable of adjusting the flow rate of an auxiliary fluid, an auxiliary fluid controller, etc. (not shown in the figure). The auxiliary fluid flows within the heat exchange cavity 20, in a space outside the heat-receiving fluid coil 12. The auxiliary fluid controller can also receive a heat-receiving fluid outlet temperature and/or pressure measured by the measuring device, and on this basis can adjust the flow rate (or flow speed), temperature and pressure, etc. of the auxiliary fluid.
The heat exchange apparatus of the present invention adopts a method of indirect heat exchange. High-temperature fluid in the transporting pipeline first heats the heat exchange base plate 1 by conduction, radiation and convection, etc.; the heat exchange base plate 1 then heats the auxiliary fluid in contact therewith by conduction and radiation, etc. The heated auxiliary fluid flows or is stationary around the heat-receiving fluid coil 12, and thus further conducts heat to the heat-receiving fluid in the coil. The use of the heat-reflecting plate 16 of the thermal isolation layer inner wall 14 and the thermal isolation material 15 retains heat inside the heat exchange cavity 20 as much as possible. When the heat-receiving fluid comprises a substance that is reactive, corrosive or otherwise dangerous at high temperatures, e.g. O2, CH4, etc., the use of indirect heat exchange greatly increases the safety of the heat exchange process. This is because inert air, steam, N2 or CO2, etc. can be chosen as the auxiliary fluid, and the heat exchange base plate 1 is not likely to suffer corrosion, aging or other damage when heated in an inert atmosphere, so safety incidents such as leakage will not occur. Stainless steel, aluminium or ceramic fiber can be chosen as the material of the heat exchange base plate, end faces and weight-bearing plates.
The choice of material for each part of the heat exchange apparatus of the present invention (including component composition, thickness, strength and finish, etc.) depends on the nature of the fluid in contact therewith and conditions such as temperature and pressure during use. For example, the heat exchange base plate 1 needs to have excellent thermal conduction properties, and can tolerate rapid variation of temperature within a large range. The weight-bearing plates 2 and end faces 4 need to have sufficient strength and tolerance to temperature variation. A tube wall of the heat-receiving fluid coil 12 not only needs to have good thermal conduction properties, but also must not react with the heat-receiving fluid within the range of temperatures that might be reached during operation. When the heat-receiving fluid is O2 or an oxygen-enriched gas (i.e. a mixed gas with an oxygen content higher than the content of O2 in air, optionally higher than 50%, and further higher than 80%), the material in contact therewith must not burn in a hot oxygen atmosphere, and is resistant to corrosion and oxidation.
The heat exchange efficiency of the heat exchange apparatus and the temperature of the heat-receiving fluid outlet can be regulated in various ways. When the temperature and flow rate of the high-temperature fluid in the pipeline remain substantially the same, if the flow rate and flow speed of the auxiliary fluid are increased, the temperature of the auxiliary fluid after being heated will fall, and correspondingly the temperature of the heat-receiving fluid will also fall; if the auxiliary fluid is a gas, increasing the pressure thereof will cause the density thereof to increase, thereby increasing the heat transfer efficiency. Similarly, as long as other conditions remain unchanged, if the flow speed or flow rate of the heat-receiving fluid is increased, the outlet temperature thereof will also fall.
In order to prevent leakage due to corrosion or aging of the heat-receiving fluid coil 12 under heated conditions, a gas component analyser 19 is provided at the auxiliary fluid outlet 11; if the determined gas components are not the same as the components of the auxiliary fluid and the heat-receiving fluid content is increased, this indicates that the heat-receiving fluid coil has suffered damage or leakage. In this case, it is advisable to immediately stop using the heat exchange apparatus, and carry out maintenance.
In the case of an existing high-temperature fluid pipeline, for example a high-temperature flue gas pipeline formed of refractory bricks 18, when installing the heat exchange apparatus, the refractory bricks can first be removed from the upper half of the pipeline, and the heat exchange apparatus can then be hoisted to the proper position by means of hoisting lugs 21, with the weight-bearing plates 2 of the heat exchange apparatus pressed flat against the remaining part of the pipeline. A sealing refractory material 17, such as ceramic fiber, glass fiber or refractory mortar, etc., is used for sealing between the heat exchange apparatus and each contact face of the transporting pipeline. As required, multiple heat exchange apparatuses are installed on the pipeline with the end faces 4 thereof substantially parallel, and a refractory blanket is used for sealing between contact faces. The auxiliary fluids and heat-receiving fluids in the multiple heat exchange apparatuses can be the same or different.
Various forms can be chosen for the heat exchange base plate 1 of the heat exchange apparatus. As shown in
As an example, a heat exchange apparatus according to
Flue gas generated by combustion is passed into the transporting pipeline, the main components of the flue gas being carbon dioxide, water, carbon monoxide, sulfur dioxide and nitrogen oxides, etc., with a range of temperature variation of 500-1200° C.: the heat-receiving fluid is O2, and it is expected that the temperature capable of being attained by the O2 through heating will have a range of variation of 300-600° C.; and air is chosen as the auxiliary fluid.
The flow rates, flow speeds and pressures, etc. of the heat-receiving fluid and auxiliary fluid are each controlled by controllers in their respective delivery systems. The range of variation of the flow speed of the heat-receiving fluid is 5-100 m/s, preferably 20-60 m/s; the range of variation of the flow speed of the auxiliary fluid is 0-50 m/s, preferably 20-30 m/s.
Using CFD software to perform simulated calculations for the heat exchange apparatus in this example, when the temperature of the heat exchange base plate 1 is 850° C., the flow speed of air is 0.5 m/s and the flow speed of O2 is 14 m/s, the O2 entering the heat exchange apparatus at room temperature reaches a temperature of 500° C. at the outlet.
In various technical processes involving oxygen-enriched combustion, for example in oxygen-enriched combustion in a glass melting furnace, if heated O2 is delivered to the burner together with the fuel, a higher combustion temperature can be achieved while reducing the energy loss in flue gas, thus increasing the combustion efficiency and reducing the production of nitrogen oxides and dust.
The present invention is not limited to the illustrated examples and embodiments described; various equivalent modifications and substitutions made by those skilled in the art on the basis of this text shall be included in the scope defined by the claims of the present application.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202011593639.7 | Dec 2020 | CN | national |
