Cyclone preheater, cyclone air preheater and operating method of cyclone preheater

Abstract

A cyclone preheater, a cyclone air preheater, and a cyclone preheater operating method. The cyclone preheater includes a heat absorption section, a heat release section, a heating pipe, a temperature control valve, a steam delivery pipe, a condensate delivery pipe, and an air release valve. The heat absorption section is used to absorb heat, and the heat release section is used to release heat. The heating pipe cooperates with the heat release section to absorb the heat energy released by the heat release section. The heat absorption section and the heat release section form a hot water exchange circuit through the steam delivery pipe and the condensate delivery pipe. The air release valve is provided on the hot water exchange circuit and is used to release steam so that the hot water exchange circuit forms a negative pressure circuit. The present invention constructs a complete and interconnected whole by providing a steam delivery pipe and a condensate delivery pipe. The present invention can ensure that the wall temperature is controllable and adjustable. While retaining the efficient heat transfer characteristics of the heat pipe heat exchanger, the discharge of non-condensable gas through the exhaust valve group effectively solves the aging problem that may occur in the phase change heat exchanger, and can greatly extend the service life of the equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat exchanger equipment, and more specifically, relates to a cyclone preheater, a cyclone air preheater and an operating method of a cyclone preheater. Background Art

[0002] At present, the fuel used by the burners equipped in oil refining and chemical plants has a low sulfur content, which can significantly reduce the temperature of the flue gas emitted by the burners.

[0003] Conventional phase-change heat exchangers generally operate under normal pressure or positive pressure conditions, which requires the flue gas temperature to be above 100°C. The flue gas temperature cannot be further reduced, which means that a large amount of low-temperature waste heat cannot be recycled and reused, resulting in a large amount of energy waste. Summary of the Invention

[0004] In summary, how to provide a heat exchanger suitable for safe and normal operation in an operating environment below 100°C for a long period of time has become an urgent problem to be solved by those skilled in the art.

[0005] In order to solve the above problems, the present invention provides a cyclone preheater, which comprises:

[0006] A heat absorbing section capable of absorbing heat from flue gas;

[0007] a heat release section capable of releasing heat;

[0008] A heating pipe that cooperates with the heat release section for heat exchange, and is provided with a temperature control valve that can regulate the delivery flow of the heated medium;

[0009] a steam delivery pipe disposed between the heat absorbing section and the heat releasing section and used for delivering steam generated in the heat absorbing section to the heat releasing section;

[0010] A condensed water delivery pipe is provided between the heat release section and the heat absorption section, and is used to deliver condensed water formed by heat release and condensation in the heat release section to the heat absorption section. The heat absorption section and the heat release section form a heat exchange device through the steam delivery pipe and the condensed water delivery pipe.

[0011] An air release valve is provided on the heat exchange condensate circuit and is used to release steam so that the heat exchange water circuit forms a negative pressure circuit.

[0012] Preferably, in the cyclone preheater provided by the present invention, a water injection pipe for injecting water into the heat absorption section is connected to the heat absorption section.

[0013] Preferably, in the cyclone preheater provided by the present invention, a flow regulating valve is provided on the condensed water delivery pipe to adjust the reflux speed of the condensed water.

[0014] Preferably, in the cyclone preheater provided by the present invention, the water injection pipe is connected to the condensed water delivery pipe, and the connection point between the water injection pipe and the condensed water delivery pipe is located between the flow regulating valve and the heat absorption section.

[0015] Preferably, in the cyclone preheater provided by the present invention, the air release valve is connected to the condensate delivery pipe, and the connection point between the air release valve and the condensate delivery pipe is located between the flow regulating valve and the heat release section.

[0016] Preferably, in the cyclone preheater provided by the present invention, a plurality of branch pipes arranged in parallel are provided on the condensed water delivery pipe, and each of the branch pipes is provided with a flow regulating valve.

[0017] Preferably, in the cyclone preheater provided by the present invention, the steam delivery pipe is a pipeline capable of delivering steam; the heat absorption section and the heat release section are directly connected through the steam delivery pipe; the heat absorption section and the heat release section both have multiple rows of finned tube groups, and along the flow direction of the flue gas, the fins of two adjacent rows of finned tube groups have different rotation directions.

[0018] The present invention also provides a cyclone air preheater. In the aforementioned cyclone preheater, the cyclone preheater includes a heating tube, through which flows a heated medium. The heated medium is a fluid, such as water or air. The cyclone air preheater provided by the present invention, based on the aforementioned cyclone preheater, specifically specifies that the heated medium flowing through the heating tube is air.

[0019] The present invention also provides an operating method based on the above-mentioned cyclone preheater, in which the present invention includes:

[0020] Step 1: The heat absorption section is heated under positive pressure to generate steam;

[0021] Step 2: When steam is discharged from the air release valve, close the air release valve. When the air release valve is closed, no negative pressure is generated at the exhaust port of the air release valve, and the wall temperature is above 110° C. The wall temperature is used to characterize the wall temperature of the heat absorption section.

[0022] Step 3: When the temperature control valve is adjusted to increase the heat released by the heat release section, the wall temperature decreases. When the temperature is lower than 100° C., the cyclone preheater automatically enters a negative pressure operation state.

[0023] Preferably, in the operating method provided by the present invention, in the step 1, water is first injected into the heat absorption section, and the air release valve is kept open while the water is injected.

[0024] Preferably, in the operating method provided by the present invention, in the step 2, when steam is discharged from the air release valve, the opening of the flow regulating valve is manually controlled so that the air release valve is always in a positive pressure exhaust state.

[0025] Compared with the prior art, the technical solution provided by the present invention has the following beneficial technical effects:

[0026] The present invention provides a cyclone preheater comprising a heat-absorbing section, a heat-releasing section, a heating pipe, a temperature-control valve, a steam delivery pipe, a condensate delivery pipe, and a bleed valve. The heat-absorbing section absorbs heat, while the heat-releasing section releases heat. The heating pipe cooperates with the heat-releasing section to absorb the heat energy released by the heat-releasing section. The heat-absorbing and heat-releasing sections form a hot water exchange circuit via a steam delivery pipe and a condensate delivery pipe. The bleed valve is provided in the hot water exchange circuit to release steam, thereby creating a negative pressure circuit. The split flue gas waste heat utilization device provided by the present invention is based on the structure of the original heat pipe heat exchanger. Through optimized design, it is divided into two parts (the heat-absorbing section and the heat-releasing section). The steam delivery pipe and the condensate delivery pipe form a complete and interconnected whole. This device fully utilizes the heat transfer characteristics of "phase change heat transfer" and adjusts the heat exchange rate through other additional components of the "heat exchanger" (the temperature-control valve provided on the heating pipe), ensuring that the wall temperature is controllable and adjustable. While retaining the high-efficiency heat transfer characteristics of the heat pipe heat exchanger, the discharge of non-condensable gas through the exhaust valve group effectively solves the aging problem that may occur in the phase change heat exchanger, which can greatly extend the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic structural diagram of a cyclone preheater in an embodiment of the present invention;

[0028] Figure 2 This is a schematic structural diagram of a multi-row fin tube group in an embodiment of the present invention;

[0029] Figure 3 for Figure 2 Schematic diagram of the cross section along line AA;

[0030] Figure 4 for Figure 2 A schematic cross-sectional view along line BB;

[0031] Figure 5 This is a schematic structural diagram of the swirl preheating of the fin tube group in an embodiment of the present invention.

[0032] In the figures, the corresponding relationship between component names and reference numerals is as follows:

[0033] Heat absorption section 1, heat release section 2, heating tube 3, temperature control valve 4, steam delivery pipe 5, condensate delivery pipe 6, air release valve 7, water injection pipe 8, flow control valve 9, branch pipe 10, base pipe 11, and fin 12. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0035] In addition, in the description of the present invention, the terms "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention. The terms "connected" and "connected" used in the present invention should be understood in a broad sense. For example, they can be fixed connections or detachable connections; they can be directly connected or indirectly connected through intermediate components. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] Please refer to Figures 1 to 5 , Figure 1 This is a schematic structural diagram of a cyclone preheater in an embodiment of the present invention; Figure 2 This is a schematic structural diagram of a multi-row fin tube group in an embodiment of the present invention; Figure 3 for Figure 2 Schematic diagram of the cross section along line AA; Figure 4 for Figure 2 A schematic cross-sectional view along line BB; Figure 5 This is a schematic structural diagram of the swirl preheating of the fin tube group in an embodiment of the present invention.

[0037] The present invention provides a cyclone preheater (or a split adjustable flue gas waste heat utilization heat exchanger), which includes a heat absorption section 1 and a heat release section 2. The heat absorption section 1 and the heat release section 2 can be set separately. A steam conveying pipe 5 and a condensed water conveying pipe 6 are set between the heat absorption section 1 and the heat release section 2. In this way, the heat absorption section 1, the heat release section 2, the steam conveying pipe 5 and the condensed water conveying pipe 6 can form a hot water exchange circuit. The hot water absorbs heat in the heat absorption section 1 and becomes steam, which is conveyed to the heat release section 2 by the steam conveying pipe 5. After releasing heat in the heat release section 2, the steam condenses into condensed water, and then flows back to the heat absorption section 1 through the condensed water conveying pipe 6 to be heated and evaporated again.

[0038] In the prior art, phase change heat exchangers are all operated at normal pressure or positive pressure. During normal pressure operation or positive pressure operation, the evaporation temperature of water is at least 100°C, which requires that the ambient temperature of the heat absorption section 1 (that is, the flue gas temperature in the flue) is at least 100°C. The flue gas is discharged after passing through the heat absorption section 1 at a temperature of not less than 100°C (the discharge temperature of the flue gas needs to be further reduced), which will cause a large amount of waste heat to be lost, resulting in energy waste.

[0039] To further reduce the flue gas emission temperature, while simultaneously allowing the low-temperature flue gas (no more than 100°C) to cause a phase change (from liquid to gas) in the water in the heat exchanger, it is necessary to optimize the heat exchanger structure so that it can operate under negative pressure. Water's boiling point decreases under negative pressure, which lowers the flue gas temperature and allows the heat exchanger to capture more waste heat from the flue gas, achieving energy conservation, emission reduction, and improved waste heat energy utilization. The fuel used by the burners in oil refining and chemical plants has a low sulfur content. Analysis and calculation of the fuel composition indicates that the fuel dew point temperature can be below 100°C, for example, 50°C.

[0040] In order to achieve negative pressure operation of the heat exchanger, in the present invention, the cyclone preheater includes the following structure: a heat absorption section 1 that can absorb flue gas heat; a heat release section 2 that can release heat; a heating pipe 3 that cooperates with the heat release section 2 for heat exchange, and a temperature control regulating valve 4 that can regulate the conveying flow rate of the heated medium is provided on the heating pipe 3; a steam conveying pipe 5 arranged between the heat absorption section 1 and the heat release section 2, for conveying the steam generated in the heat absorption section 1 to the heat release section 2; a condensate conveying pipe 6 arranged between the heat release section 2 and the heat absorption section 1, for conveying the condensate formed by heat release and condensation in the heat release section 2 to the heat absorption section 1, and the heat absorption section 1 and the heat release section 2 form a hot water exchange circuit through the steam conveying pipe 5 and the condensate conveying pipe 6; and an air release valve 7 arranged on the hot water exchange circuit, for releasing steam to form a negative pressure circuit in the hot water exchange circuit.

[0041] The heat absorption section 1 is a device installed in the flue at the rear of the burner. The heat absorption section 1 is made of a metal material with excellent thermal conductivity. The heat absorption section 1 is installed in the flue, and the outer surface of the heat absorption section 1 is in contact with the flue gas in the flue. At the same time, the heat absorption section 1 is also loaded with water (or other phase-changing liquids). The heat energy in the flue gas can be absorbed by the water through the heat absorption section 1. After absorbing heat, the water evaporates and becomes saturated steam. The heat absorption section 1 is installed in the flue at the rear of the burner. Under normal operating conditions of the present invention, the temperature of the water loaded in the heat absorption section 1 will not exceed the temperature of the flue gas in the flue at the rear of the burner. At one atmosphere, the boiling point of water is 100°C, which means that the heat absorption section 1 must operate in a flue environment of not less than 100°C, so that the exhaust temperature is relatively high (not less than 100°C). The present invention enters the operating state by discharging saturated steam before the equipment is operated, and then realizes negative pressure operation of the equipment by controlling the heating tube 3. When the equipment is operated at negative pressure, the boiling point of water will be reduced, for example, to 70°C-90°C, specifically, 70°C, 75°C, 80°C, 85°C, 90°C, so that the emission temperature of the flue gas in the tail flue of the burner will also be reduced accordingly, for example, to 80°C-95°C, specifically, 80°C, and the waste heat energy recovery rate is improved.

[0042] Both the heat absorption section 1 and the heat release section 2 have multiple rows of finned tube groups. Each row of finned tube groups includes multiple finned tubes arranged at intervals. The finned tubes are composed of a base tube 11 and fins 12 arranged on the outside of the base tube 11. The base tube 11 is used for the flow of water (or steam) or air, and the fins 12 are used to increase the contact area with the flue gas and improve the heat exchange efficiency. The fins 12 are spiral-shaped. Figure 3-4 The rotation direction of the fins 12 of adjacent fin tubes in the same row of fin tubes (or the rotation direction of the fin tubes) can be the same, such as right-handed or left-handed. Figure 5 The rotation direction of the fins 12 of adjacent fin tubes in the same row of fin tube groups (or called the rotation direction of the fin tubes) can be different. For example, the rotation direction of the fins 12 of one of the two adjacent fin tubes is right-handed, and the rotation direction of the fins 12 of the other fin tube is left-handed.

[0043] See also Figure 2 Along the flow direction of the flue gas, the fins 12 of two adjacent rows of finned tube groups have different rotation directions. For example, if the rotation direction of the first row of finned tube groups is clockwise, the rotation direction of the second row of finned tube groups is counterclockwise, and the rotation direction of the third row of finned tube groups is clockwise, etc. The rotation direction of the fins 12 of a row of finned tube groups refers to the rotation direction of the first or last finned tube in the row.

[0044] A steam delivery pipe 5 is connected to the heat absorbing section 1. The end of the steam delivery pipe 5 is connected to the top of the heat absorbing section 1. Water in the heat absorbing section 1 absorbs heat, evaporates, and rises, and is then discharged from the heat absorbing section 1 through the steam delivery pipe 5. In one embodiment of the present invention, the steam delivery pipe 5 is a metal pipe, and the section of the steam delivery pipe 5 located outside the flue is provided with an insulation layer to reduce heat loss.

[0045] The heat release section 2 is arranged outside the flue. The heat release section 2 is made of a metal material with excellent thermal conductivity. The heat release section 2 is arranged outside the flue. After the steam is transported to the heat release section 2, a large amount of heat energy can be released. The steam releases heat and condenses into water, and then flows back to the heat absorption section 1 through the condensed water delivery pipe 6.

[0046] The heating tube 3 is made of a metal material with excellent thermal conductivity. The heating tube 3 cooperates with the heat exchange section of the heat release section 2. Specifically, through the structural design of the designer, when the heat release section 2 releases heat energy, if there is a heated medium flowing in the heating tube 3, then the heat energy released by the heat release section 2 will be absorbed by the heated medium in the heating tube 3.

[0047] In the present invention, the heated medium is a fluid medium. Generally, the heated medium can be water or air. Based on the above-mentioned cyclone preheater, the present invention also provides a cyclone air preheater. The cyclone preheater provided by the present invention has a structure that is basically the same as that of the cyclone air preheater. The difference is that the cyclone air preheater provided by the present invention specifically limits the heated medium flowing in the heating tube 3 to air. Accordingly, when the heated medium flowing in the heating tube 3 is water (or other liquid), the cyclone preheater can also be called a cyclone liquid preheater.

[0048] If the heated medium in the heating tube 3 is always in a flowing state, the flow rate of the heated medium in the heating tube 3 has a certain proportional relationship with the heat release efficiency of the heat release section 2. In layman's terms, the more heated medium flows through the heating tube 3 per unit time, the more heat energy is taken away, and the higher the heat release of the heat release section 2 per unit time. Under normal working conditions of the burner, the amount of flue gas generated is close to a certain amount, and the heat energy contained in the flue gas is basically constant. Then the heat absorption rate of the heat absorption section 1 can be close to a certain amount. Under the premise of a constant heat absorption rate, the operating temperature of the heat exchanger can be adjusted by adjusting the heat release rate of the heat release section 2 (that is, adjusting the flow rate of the heated medium), thereby achieving the adjustment of the flue gas emission temperature. When air is transported in the heating tube 3, the swirl preheater can be called a swirl air preheater.

[0049] The present invention provides a split (the heat absorption section 1 and the heat release section 2 are arranged separately), temperature-adjustable (the operating temperature of the heat absorber is adjustable, or the exhaust flue gas temperature is adjustable) flue gas waste heat utilization equipment. In the present invention, a saturated steam riser is provided between the heat absorption section 1 and the heat release section 2, which is used to transport the hot steam generated by the heat absorption section 1 to the heat release section 2. A condensate downcomer is provided between the heat release section 2 and the heat absorption section 1, which is used to return the condensed water formed by condensation of the steam in the heat release section 2 after heat release to the heat absorption section 1. At the same time, the present invention is also provided with a flow regulating valve 9 (for adjusting the reflux speed or flow of the condensed water) and a water injection pipe 8 on the condensate downcomer, and a water inlet valve is provided on the water injection pipe 8. The present invention also provides a heating tube 3 that cooperates with the heat release section 2 in a heat exchange manner. A heated medium flows in the heating tube 3, and the heated medium can absorb the heat released by the heat release section 2. A temperature control regulating valve 4 is provided on the heating tube 3. The temperature control regulating valve 4 is used to adjust the flow rate of the heated medium in the heating tube 3, thereby achieving the purpose of achieving the operating temperature of the entire heat exchanger, and further achieving the purpose of regulating the flue gas emission temperature.

[0050] Before commissioning, the present invention sets a flue gas emission temperature threshold, such as 80°C (or other temperatures, such as 82°C or 85°C). Heat is absorbed by the heat absorption section 1 and released in the heat release section 2. A flue gas temperature sensor is provided to detect the flue gas emission temperature. When the flue gas emission temperature exceeds or falls below the set value, the temperature control valve 4 can be opened or closed, thereby increasing (increased flow rate increases heat absorption and the equipment operating temperature decreases) or decreasing (decreased flow rate decreases heat absorption and the equipment operating temperature increases) the fluid flow in the heating tube 3, thereby achieving the purpose of flue gas emission temperature regulation. Furthermore, by monitoring a preset target wall temperature, the temperature control valve 4 can be opened or closed when the measured wall temperature exceeds or falls below the target wall temperature. The target wall temperature = dew point temperature + A. A can range from 12°C to 22°C, preferably from 15°C to 20°C, such as 15°C, 18°C, or 20°C. The measured wall temperature can be displayed on a wall display.

[0051] The present invention is a cyclone preheater. It releases heat in the heat release section 2, heating the cold air entering the final inlet of the air preheater (the cold air is transported and heated by the heating pipe 3), raising the wall temperature entering the air preheater, thereby protecting the equipment from low-temperature corrosion. The present invention absorbs heat in the heat absorption section 1, controlling the flue gas temperature below 100°C and above the acid dew point. This effectively reduces the exhaust temperature and increases the heat absorption capacity of the heat exchanger. This not only improves the utilization rate of waste heat energy, but also protects subsequent dust collectors and other equipment from high-temperature corrosion, thereby saving fuel and reducing carbon dioxide emissions.

[0052] The key innovation of this invention lies in the fact that the cyclone preheater regulates the flow of the heated medium (the medium within heating tube 3) to achieve automatic closed-loop control of the entire device for varying possible minimum wall temperatures. This ensures that the wall temperature can be simultaneously controlled and adjusted in response to changes in the acid dew point caused by changes in fuel type. While ensuring the safe operation of the equipment, the energy-saving goal of maximizing flue gas waste heat recovery is achieved. Once implemented, this invention can also reduce carbon dioxide emissions, providing significant social, environmental, and economic benefits.

[0053] Specifically, the swirl preheater provided by the present invention is based on the structure of the original heat pipe heat exchanger. Through optimized design, it is divided into two parts (heat absorption section 1 and heat release section 2). By providing a steam conveying pipe 5 and a condensed water conveying pipe 6, it forms a complete and interconnected whole. It fully utilizes the heat transfer characteristics of "phase change heat transfer" and adjusts the heat transfer capacity through other additional components of the "heat exchanger" (temperature control valve 4 provided on the heating pipe 3), ensuring that the wall temperature is controllable and adjustable. While retaining the efficient heat transfer characteristics of the heat pipe heat exchanger, the exhaust valve group discharges non-condensable gas, effectively solving the aging problem that may occur in the phase change heat exchanger, and significantly extending the service life of the equipment.

[0054] The cyclone preheater provided by the present invention comprises a heat absorption section 1 and a heat release section 2 forming a hot water exchange circuit. A heat exchange medium (preferably water in the present invention) circulates within the hot water exchange circuit (during the circulation process, the heat exchange medium undergoes a phase change, such as from liquid to gas, or vice versa). During operation of the heat exchanger, there is heat exchange medium loss (e.g., steam emission). Therefore, the heat exchange circuit needs to be replenished with heat exchange medium (supplemental water) as appropriate during the operation of the cyclone preheater. Therefore, the present invention also provides a water injection pipe 8, which is used to inject water into the heat absorption section 1 to replenish the heat exchange medium.

[0055] As can be seen from the above, the present invention heats the heat exchange medium by absorbing heat in the heat absorption section 1. The cyclone preheater can operate at negative pressure, allowing the heat exchange medium (water) to boil and evaporate at temperatures below 100°C. The water vapor enters the heat release section 2 through the evaporation pipeline. The heat release section 2 is used in conjunction with the heating tube 3, which absorbs the heat released by the heat release section 2. The steam in the heat release section 2 condenses into condensed water, which then flows back to the heating section through the condensate water pipe 6. To control the condensate return flow rate, the present invention provides a flow control valve 9 on the condensate water pipe 6 to adjust the condensate return rate. Based on the above structure, the present invention connects the water injection pipe 8 to the condensate water pipe 6. The connection point between the water injection pipe 8 and the condensate water pipe 6 is located between the flow control valve 9 and the heat absorption section 1. Therefore, the heat exchange medium loaded in the heating section can be replenished through condensation reflux and active replenishment, avoiding the "dry pot" problem.

[0056] The swirl preheater provided by the present invention operates under negative pressure conditions. The premise of negative pressure operation is to exclude cold air at the initial start-up of the heat exchanger, fill the entire hot water circuit with high-temperature steam (110°C), and then absorb heat through the heating pipe 3 in a closed state of the hot water circuit to reduce the temperature of the hot water circuit and realize negative pressure operation of the heat exchanger. Therefore, the present invention must be provided with an air release valve 7, and the air release valve 7 is installed in the hot water circuit to achieve the removal of cold air in the early stage. In addition, after the heat release section 2 releases heat, the steam becomes condensed water, and the condensed water flows back to the heating section through the condensed water delivery pipe 6. This requires that the fluid delivered by the condensed water delivery pipe 6 is liquid (condensed water). In order to ensure stable operation of the system, the mixed delivery of gas and liquid should be avoided as much as possible. Therefore, if there is steam in the heat release section 2 that does not fully release heat and enters the condensed water delivery pipe 6 in gaseous form, it should be excluded. Therefore, the present invention proposes the following structural optimization: the air release valve 7 is connected to the condensate delivery pipe 6, and the connection point between the air release valve 7 and the condensate delivery pipe 6 is located between the flow regulating valve 9 and the heat release section 2. The flow regulating valve 9 limits the flow of condensate, so that the gas (steam) and liquid (condensate) can be intercepted at the upper part of the condensate delivery pipe 6. At the same time, the air release valve 7 is connected to the upper part of the condensate delivery pipe 6, so that the gas can be fully discharged, and only the liquid (condensate) can flow back to the heat absorption section 1 through the flow regulating valve 9. The above structural optimization can ensure the stable operation of the system to the greatest extent.

[0057] The temperature control valve 4 is a component of the fluid flow control valve 9 provided on the heating tube 3. The temperature control valve 4 can control the flow of the heated medium flowing through the heating tube 3. As can be seen from the above, the flow of the heated medium is related to temperature regulation. Therefore, the present invention can be provided with a temperature sensor, a controller, and a temperature control valve 4 to realize automatic operation of the system. That is, the temperature sensor obtains the system wall temperature, and the controller controls the temperature control valve 4 according to the system wall temperature. In the initial stage of operation of the heat exchanger, the temperature inside the heat exchanger needs to rise rapidly. At this time, the temperature control valve 4 should not be automatically adjusted and can be kept in an open state with a small opening. Therefore, the temperature control valve 4 provided by the present invention can realize free switching between manual operation and automatic control.

[0058] Specifically, the steam delivery pipe 5 is a pipeline capable of delivering steam; the heat absorption section 1 and the heat release section 2 are directly connected via the steam delivery pipe 5 .

[0059] The present invention also provides an operating method for a cyclone preheater, and the operating object of the operating method for a cyclone preheater is the above-mentioned cyclone preheater.

[0060] Specifically, the cyclone preheater includes a heat absorption section 1, a heat release section 2, a steam delivery pipe 5, a condensed water delivery pipe 6, a heating pipe 3, a temperature control regulating valve 4, a flow regulating valve 9, an air release valve 7 and a water injection pipe 8. The heat absorption section 1 and the heat release section 2 are connected through the steam delivery pipe 5 and the condensed water delivery pipe 6 to form a water circulation loop. A flow regulating valve 9 is provided on the condensed water delivery pipe 6, and a water injection pipe 8 is connected to the condensed water delivery pipe 6. The heating pipe 3 cooperates with the heat release section 2, and a temperature control regulating valve 4 is provided on the heating pipe 3, and a air release valve 7 is connected to the condensed water delivery pipe 6.

[0061] In a preferred embodiment of the present invention, multiple parallel branch pipes 10 are provided on the condensate delivery pipe 6. Specifically, three (or two or four) branch pipes 10 are provided, each of which is equipped with a flow control valve 9. In this embodiment, the flow control valve 9 is used to regulate the return flow of condensate. Multiple parallel branch pipes 10 and multiple flow control valves 9 are provided on the condensate delivery pipe 6 to facilitate the regulation of the condensate flow rate. Partitions are provided between the branch pipes 10 to isolate the multiple branch pipes 10 from each other.

[0062] The branch pipe 10 can adopt a finned tube structure design, which can release a certain amount of heat energy, so that the fluid passing through the branch pipe 10 releases heat energy. If there is steam in the fluid flowing in the branch pipe 10, the steam can be condensed into liquid, avoiding the "gas-liquid mixing" causing unstable equipment operation.

[0063] Based on the above structure, the operating method of the cyclone preheater provided by the present invention specifically includes the following steps:

[0064] Step 1: The heat absorbing section 1 is heated to generate steam.

[0065] In step 1, it is first necessary to ensure that a sufficient amount of water is loaded into the heat absorption section 1 to ensure the normal operation of the heat exchanger. Since the heat exchanger provided by the present invention is a phase-change heat exchanger with steam transport, the entire heat exchanger can be considered an airtight structure. Therefore, when water is injected through the water injection pipe 8, to prevent the internal pressure of the heat exchanger from increasing and affecting the water injection, the air release valve 7 remains open during water injection. This maintains the internal pressure of the heat exchanger (atmospheric pressure).

[0066] Step 2: When steam is discharged from the air release valve 7, close the air release valve 7. Before closing the air release valve, the temperature control valve is opened by manual control.

[0067] In step 2, when steam is discharged from the air vent valve 7, manually open the opening of the temperature control valve 4, and then adjust the flow control valve 9 so that the air vent valve 7 is always in a positive pressure exhaust state. At this time, the wall temperature is 110°C, for example, 110°C-150°C, preferably, 120°C, 130°C, 140°C. In step 2, if the heat absorption section 1 continues to absorb heat consistently, the operating temperature of the heat exchanger will continue to rise, and the heat exchanger is likely to be damaged when it is operated at a high temperature. Therefore, the present invention requires manual control of the temperature control valve 4 to adjust the wall temperature of the heat exchanger. In step 2, while the air vent valve 7 is discharging steam, it should also ensure that the air vent valve 7 is always discharging steam. This can avoid the problem of negative pressure adsorption of external cold air by the air vent valve 7.

[0068] Step 3: After the heat release section 2 releases a certain amount of heat, the heat exchanger enters a negative pressure operation state.

[0069] From the above structural design, it can be seen that the present invention provides a swirl preheater. Through the structural design of the preheater, it can be operated below 100°C. The heat energy in the exhaust gas of the combustion furnace can be largely recovered and utilized, thereby improving the thermal efficiency of the combustion furnace and reducing fuel consumption and production costs.

[0070] Regarding the exhaust gas temperature being lower than 100°C and the negative pressure operation of the heat exchanger in the present invention, this is achieved by regulating the flow of the heated medium through temperature control. The heat absorption section is heated to generate steam, and the vent valve (vent ball valve) discharges gas, and exhaust begins; during the exhaust process, the flow regulating valve is switched to automatic control mode, and the control target value is set to 110°C, while the purpose is to prevent negative pressure from being generated at the exhaust port (steam is always discharged). After the exhaust is completed, the control of the temperature control valve is switched from manual to automatic, and the regulating valve automatically adjusts the cold source flow. Thereafter, the heat exchanger displays wall temperature values ​​of 70°C. At this time, the exhaust gas temperature is about 80°C, and the equipment enters normal operating conditions.

[0071] The negative pressure operation of the present invention does not require the installation of a pressure sensor. When the exhaust temperature is lower than 100°C, the device is in a negative pressure operation state. If the exhaust temperature is higher than 100°C, the device is in a positive pressure operation state.

[0072] The specific use of the present invention is as follows:

[0073] 1. When the combustion furnace starts to operate, open the water injection valve of the swirl preheater and start injecting water into the heat exchanger cavity of the heat absorption section;

[0074] 2. When the water injection volume reaches the design requirement, close the water injection valve;

[0075] 3. Exhaust: When water is added, open the bleed valve 7. Wait until the heat absorption section 1 is heated to generate steam. When you see gas being discharged from the bleed valve 7 (when gas is discharged, first the air in the heat exchanger is discharged, then mainly high-temperature steam is discharged. The steam is usually white and can be directly observed visually), exhaust begins. When exhaust is completed, close the bleed valve 7. During the exhaust process, it is best if the exhaust port does not generate negative pressure (if negative pressure is generated, air is sucked in, and then the exhaust port will not discharge steam. This can be directly judged by visual observation) and the wall temperature display shows a temperature above 110°C.

[0076] 4. Adjust the heat exchanger wall temperature and exhaust temperature

[0077] After the exhaust is completed, the flow rate of the heated medium is adjusted as needed. With the target temperature of the equipment wall temperature at 70°C, the temperature control valve that automatically adjusts the flow rate of the heated medium is put into operation, and the heat exchanger can operate automatically. At this time, the exhaust gas temperature of the furnace is 80°C, realizing negative pressure operation of the heat exchanger.

[0078] The above-mentioned regulation is a dual regulation, that is, the heat exchange amount can be adjusted (the flow rate is regulated by the temperature control valve 4) to achieve a minimum wall temperature higher than the dew point temperature, and the return flow of the condensed water of the internal medium of the heat exchanger can be adjusted (achieved by the flow control valve 9) to adjust the pressure or temperature of the heat exchanger, so that the pressure or temperature in the cavity of the heat exchanger increases or decreases.

[0079] The beneficial effects of the present invention are: through flow regulation of the heat exchange flow (the delivery flow of the heated medium is regulated by the temperature control valve 4), closed-loop control of the different minimum wall temperatures that may occur in the entire equipment is achieved, the exhaust temperature is reduced to the greatest extent, and the wall temperature is synchronously controllable and adjustable, so that a large amount of low-temperature waste heat can be safely and effectively utilized; and the exhaust temperature of the furnace is achieved below 100°C. The minimum wall temperature refers to the tube wall temperature of the heat exchanger, that is, this temperature is the dew point temperature calculated based on the fuel composition during furnace combustion. As long as the minimum wall temperature is higher than the dew point temperature, it is the set temperature; by implementing the heat exchange flow regulation of the heat exchanger, the minimum wall temperature is ensured to be higher than the dew point temperature, thereby ensuring the long-term safe operation of the heat exchanger.

[0080] Under the premise of ensuring the safe operation of the equipment, the energy-saving goal of recovering waste heat from flue gas is achieved to the greatest extent possible, reducing CO2 emissions and achieving good social, environmental and economic benefits.

[0081] It is understood from common technical knowledge that the present invention may be implemented by other embodiments that do not depart from its spirit or essential features. Therefore, the embodiments disclosed above are, in all respects, merely illustrative and not exclusive. All modifications within the scope of the present invention or equivalent to the scope of the present invention are intended to be encompassed by the present invention.

Claims

1. A cyclone preheater, characterized in that: include: A heat absorbing section capable of absorbing heat from flue gas; A heat releasing section capable of releasing heat, wherein the heat absorbing section and the heat releasing section form a hot water exchange circuit; A heating pipe that cooperates with the heat release section for heat exchange, and is provided with a temperature control valve that can regulate the delivery flow of the heated medium; a steam delivery pipe disposed between the heat absorbing section and the heat releasing section and used for delivering steam generated in the heat absorbing section to the heat releasing section; A condensed water delivery pipe is provided between the heat release section and the heat absorption section, and is used to deliver condensed water formed by heat release and condensation in the heat release section to the heat absorption section. The heat absorption section and the heat release section form a heat exchange device through the steam delivery pipe and the condensed water delivery pipe. an air release valve provided on the hot water exchange circuit and used for releasing steam to form a negative pressure circuit in the hot water exchange circuit; At the initial start-up of the cyclone preheater, cold air is removed to allow high-temperature steam to fill the entire hot water circuit. Then, when the hot water circuit is closed, heat is absorbed through the heating pipe to reduce the temperature of the hot water circuit and achieve negative pressure operation of the cyclone preheater. When steam is discharged from the bleed valve, manually open the temperature control valve, and then adjust the flow control valve to make the bleed valve always in a positive pressure exhaust state. Manually control the temperature control valve to adjust the wall temperature of the cyclone preheater. Ensure that the bleed valve is always discharging steam while discharging steam. A vent valve is connected to the upper part of the condensate delivery pipe to fully discharge the gas, allowing only the liquid to flow back to the heat absorption section through the flow control valve.

2. The cyclone preheater according to claim 1, characterized in that: A water injection pipe is connected to the heat absorbing section and is used to inject water into the heat absorbing section; A flow regulating valve is provided on the condensed water delivery pipe to adjust the reflux speed of the condensed water.

3. The cyclone preheater according to claim 2, characterized in that: The water injection pipe is connected to the condensed water delivery pipe, and the connection point between the water injection pipe and the condensed water delivery pipe is located between the flow regulating valve and the heat absorption section.

4. The cyclone preheater according to claim 2, characterized in that: The air release valve is connected to the condensed water delivery pipe, and the connection point between the air release valve and the condensed water delivery pipe is located between the flow regulating valve and the heat release section.

5. The cyclone preheater according to claim 2, characterized in that: A plurality of branch pipes arranged in parallel are provided on the condensate delivery pipe, and each branch pipe is provided with a flow regulating valve.

6. The cyclone preheater according to claim 1, characterized in that: The steam delivery pipe is a pipeline capable of delivering steam; The heat absorbing section and the heat releasing section are directly connected via the steam delivery pipe; The heat absorption section and the heat release section both have multiple rows of finned tube groups. Along the flow direction of the flue gas, the fins of two adjacent rows of finned tube groups have different rotation directions.

7. A cyclone air preheater, characterized in that: comprising a cyclone preheater as claimed in any one of claims 1 to 6; The cyclone preheater includes a heating tube, and the heated medium flowing through the heating tube is air.

8. An operating method of a cyclone preheater according to any one of claims 1 to 6, characterized in that: include: Step 1: The heat absorption section is heated under positive pressure to generate steam; Step 2: When steam is discharged from the air release valve, close the air release valve. When the air release valve is closed, no negative pressure is generated at the exhaust port of the air release valve, and the wall temperature is above 110° C. The wall temperature is used to represent the pipe wall temperature of the heat absorption section. Step 3: When the temperature control valve is adjusted to increase the heat released by the heat release section, the wall temperature decreases. When the temperature is lower than 100° C., the cyclone preheater automatically enters a negative pressure operation state.

9. The operating method according to claim 8, characterized in that: In the step 1, water is first injected into the heat absorption section, and the air release valve is kept open during the water injection.

10. The operating method according to claim 8 or 9, characterized in that: In the step 2, when steam is discharged from the air release valve, the opening of the flow regulating valve is manually controlled so that the air release valve is always in a positive pressure exhaust state.

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