A system for recovering and utilizing heat energy of dried tail gas

Abstract

The application discloses a dry tail gas heat energy recycling system, and relates to the technical field of energy recycling. The system comprises a first indirect drying machine, a heat exchange system and a second direct drying machine. The heat exchange system has a heat absorption end and a heat release end. The inlet of the heat absorption end is in heat exchange connection with the tail gas outlet of the first indirect drying machine. The heat source inlet of the second direct drying machine is connected with the outlet of the heat release end, and the tail gas outlet of the second direct drying machine is connected with the inlet of the heat release end. The heat exchange system can absorb the heat in the tail gas of the first indirect drying machine and transfer the recycled heat to the heat source inlet of the second direct drying machine through the heat release end, so that the cascade utilization of the waste heat of the tail gas of the first indirect drying machine is realized. The tail gas outlet of the second direct drying machine is connected with the inlet of the heat release end, so that the tail gas generated by the second direct drying machine can be cyclically heated, and the multi-stage recycling and efficient utilization of the waste heat generated in the drying process are realized.

Description

Technical Field

[0001] This invention relates to the field of energy recovery and utilization technology, and in particular to a system for recovering and utilizing the heat energy of dried exhaust gas. Background Technology

[0002] In existing sludge drying processes, saturated steam is commonly used as a heat source, transferring heat to the sludge through indirect contact to achieve drying. However, this method suffers from significant energy waste. Specifically, during the drying process, the sludge evaporates upon heating, generating a large amount of exhaust gas, the main component of which is water vapor with high latent heat of vaporization (i.e., waste heat steam). In actual production, this waste heat steam, typically at 80-100°C, is usually treated as "waste heat" and directly discharged or simply treated, resulting in a large amount of heat energy being lost without being recovered, causing significant energy waste and increased operating costs.

[0003] Therefore, there is an urgent need for a drying tail gas heat energy recovery and utilization system that can effectively recover and utilize the waste heat generated during sludge drying. Summary of the Invention

[0004] The purpose of this invention is to provide a heat recovery and utilization system for drying exhaust gas to solve the problem of heat waste in existing drying exhaust gas. Through a heat circulation system, the heat in the exhaust gas generated by the first indirect dryer can be recovered and transported to the second direct dryer, realizing the recovery and reuse of waste heat.

[0005] To achieve the above objectives, the present invention provides the following solution: This invention provides a system for recovering and utilizing heat energy from drying exhaust gas, comprising: a first indirect dryer, a heat exchange system, and a second direct dryer; wherein, the heat source inlet of the first indirect dryer is connected to an external heat source, and the feed inlet of the first indirect dryer is connected to a wet material silo; the heat exchange system has a heat-absorbing end and a heat-releasing end, the heat-absorbing end and the heat-releasing end are heat-exchange connected, and the inlet of the heat-absorbing end is heat-exchange connected to the exhaust gas outlet of the first indirect dryer; the feed inlet of the second direct dryer is connected to the wet material silo, the heat source inlet of the second direct dryer is connected to the outlet of the heat-releasing end, and the exhaust gas outlet of the second direct dryer is connected to the inlet of the heat-releasing end.

[0006] Preferably, a first dust collector is provided between the first indirect drying machine and the heat absorption end.

[0007] Preferably, the heat exchange system includes a heat exchanger, a heater, and a heat exchange channel; the heat exchanger includes a first heat source pipeline and a first cold source pipeline, which are heat-exchange connected, and the first heat source pipeline is connected to the exhaust gas outlet of the first indirect dryer; the heater includes a second heat source pipeline and a second cold source pipeline, which are heat-exchange connected; the second heat source pipeline and the first cold source pipeline are connected through the heat exchange channel; the outlet end of the second cold source pipeline is connected to the heat source inlet of the second direct dryer, and the inlet of the second cold source pipeline is connected to the exhaust gas outlet of the second direct dryer; the heat exchange channel is filled with a fluid medium.

[0008] Preferably, the fluid medium is circulating water.

[0009] Preferably, it also includes a second dust collector, which is installed between the exhaust outlet of the second direct dryer and the inlet of the second cold source pipeline.

[0010] Preferably, it also includes a condenser, which is installed between the second dust collector and the inlet of the second cold source pipeline.

[0011] Preferably, it also includes an absorption heat pump, which includes a drive pump, a first circuit, and a second circuit. The first circuit and the second circuit are respectively connected to the drive pump. The first circuit is connected to the condenser. The second circuit is heat exchanged with the first circuit. The second circuit is connected to the return side of the heat exchange channel.

[0012] Preferably, it also includes a heating device, which is installed between the outlet of the second cold source pipeline and the second direct dryer.

[0013] Preferably, it also includes a dry material bin, which is located after the first indirect dryer and the second direct dryer, and is connected to the discharge port of the first indirect dryer and the discharge port of the second direct dryer, respectively.

[0014] Preferably, it also includes a deodorization system, which is connected to the outlet of the heat absorption end.

[0015] The present invention achieves the following technical effects compared to the prior art: In the drying exhaust heat recovery and utilization system disclosed in this invention, materials to be dried are fed to a first indirect dryer and a second direct dryer through a wet material silo. An external heat source provides saturated steam to the first indirect dryer to dry the materials inside. The heat exchange system absorbs heat from the exhaust gas of the first indirect dryer and transfers the recovered heat to the heat source inlet of the second direct dryer through the heat release end, realizing the cascade utilization of the waste heat from the exhaust gas of the first indirect dryer. At the same time, the exhaust gas outlet of the second direct dryer is connected to the inlet of the heat release end, so that the exhaust gas generated by the second direct dryer can be circulated and heated, reducing the system's dependence on external heat sources and realizing multi-stage recovery and efficient utilization of waste heat generated during the drying process. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a system for recovering and utilizing the heat energy of dried exhaust gas in one embodiment of the present invention; Figure 2 This is a schematic diagram of a system for recovering and utilizing the heat energy of dried exhaust gas in another embodiment of the present invention.

[0018] Among them, 1. First indirect dryer; 2. Wet silo; 3. Second direct dryer; 4. First dust collector; 5. Heat exchanger; 6. Heater; 7. Heat exchange channel; 8. Second dust collector; 9. Condenser; 10. Absorption heat pump; 11. First loop; 12. Second loop; 13. Dry silo. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The purpose of this invention is to provide a system for recovering and utilizing the heat energy of drying exhaust gas to solve the problems existing in the prior art. Through a heat circulation system, the heat in the exhaust gas generated by the first indirect dryer can be recovered and transported to the second direct dryer, thereby realizing the recovery and reuse of waste heat.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Please refer to Figures 1-2 This embodiment provides a system for recovering and utilizing the heat energy of drying exhaust gas, including: a first indirect dryer 1, a heat exchange system, and a second direct dryer 3; wherein, the heat source inlet of the first indirect dryer 1 is connected to an external heat source, and the feed inlet of the first indirect dryer 1 is connected to a wet material silo 2; the heat exchange system has a heat absorption end and a heat release end, the heat absorption end and the heat release end are connected for heat exchange, and the inlet of the heat absorption end is connected for heat exchange with the exhaust gas outlet of the first indirect dryer 1; the feed inlet of the second direct dryer 3 is connected to the wet material silo 2, the heat source inlet of the second direct dryer 3 is connected to the outlet of the heat release end, and the exhaust gas outlet of the second direct dryer 3 is connected to the inlet of the heat release end. Its working principle is as follows: Materials to be dried are conveyed to the first indirect dryer 1 and the second direct dryer 3 through the wet material silo 2. An external heat source provides saturated steam to the first indirect dryer 1 to dry the materials inside. The high-temperature exhaust gas generated by the first indirect dryer 1 reaches the heat absorption end of the heat exchange system and transfers heat to the system. The heat exchange system then transfers the recovered heat to the heat source inlet of the second direct dryer 3 through the heat release end, thus providing the necessary heat energy for drying and achieving the cascade utilization of the waste heat from the exhaust gas of the first indirect dryer 1. Furthermore, the exhaust gas outlet of the second direct dryer 3 is connected to the inlet of the heat release end, allowing the exhaust gas generated by the second direct dryer 3 to be circulated and heated to maintain the internal thermal balance of the second direct dryer 3 and reduce dependence on external heat sources. This achieves multi-stage recovery and efficient utilization of waste heat generated during the drying process, significantly reducing the overall energy consumption of the system.

[0023] In one embodiment, a first dust collector 4 is provided between the first indirect dryer 1 and the heat absorption end; the inlet of the first dust collector 4 is connected to the exhaust gas outlet of the first indirect dryer 1, and the outlet of the first dust collector 4 is connected to the inlet of the heat absorption end. By providing the first dust collector 4, dust particles entrained in the exhaust gas of the first indirect dryer 1 can be effectively removed, preventing dust from entering the heat exchange system and causing blockage or wear, thereby extending the service life of the heat exchange system and maintaining its heat exchange efficiency.

[0024] In one embodiment, the first dust collector 4 is a water film dust collector. The water film dust collector uses circulating water to adsorb dust in the exhaust gas. The temperature of the circulating water is the same as the temperature of the exhaust gas discharged from the first dust collector 4, so it will not cause the exhaust gas to cool down or reduce the amount of waste steam. This ensures that the exhaust gas entering the heat exchange system still has a high enthalpy value and avoids heat loss caused by the dust removal process.

[0025] In one embodiment, the heat exchange system includes a heat exchanger 5, a heater 6, and a heat exchange channel 7; the heat exchanger 5 includes a first heat source pipeline and a first cold source pipeline, which are heat-exchange connected, and the first heat source pipeline is connected to the exhaust gas outlet of the first indirect dryer 1; the heater 6 includes a second heat source pipeline and a second cold source pipeline, which are heat-exchange connected; the second heat source pipeline and the first cold source pipeline are connected through the heat exchange channel 7; the outlet of the second cold source pipeline is connected to the heat source inlet of the second direct dryer 3, and the inlet of the second cold source pipeline is connected to the exhaust gas outlet of the second direct dryer 3; the heat exchange channel 7 is filled with a fluid medium. The fluid medium filled in the heat exchange channel 7 serves as an intermediate heat transfer medium, forming a closed-loop circulation loop between the first cold source pipeline and the second heat source pipeline. The first heat source pipeline serves as the heat absorption end of the heat exchange system, used to receive the high-temperature exhaust gas after the first dust collector 4, and can absorb the heat in the high-temperature exhaust gas. The fluid medium flowing into the first cold source pipeline absorbs heat and its temperature rises. The heated fluid medium is transported to the second heat source pipeline through the heat exchange channel 7 and transfers the heat to the working fluid in the second cold source pipeline. The second cold source pipeline serves as the heat release end of the heat exchange system. The exhaust gas discharged from the second direct dryer 3 enters the second cold source pipeline and serves as the working fluid in the second cold source pipeline, thereby absorbing the recovered heat and sending this part of the heat into the interior of the second direct dryer 3, thus completing the final heat transfer.

[0026] In one embodiment, the heat exchange system further includes a circulation pump for driving the circulation of the fluid medium, the circulation pump being disposed on the heat exchange channel 7. Power provided by the circulation pump ensures stable flow of the fluid medium in a closed loop, achieving efficient heat transfer from the exhaust gas of the first indirect dryer 1 to the second direct dryer 3.

[0027] In one embodiment, the fluid medium is circulating water. Circulating water has the advantages of high specific heat capacity, low cost, and stable chemical properties, making it suitable as a carrier for long-distance heat transfer, thus meeting the operational requirements where the first indirect dryer 1 and the second direct dryer 3 may be located far apart. Of course, heat transfer oil or organic working fluids can also be used as the fluid medium.

[0028] In one embodiment, the drying exhaust gas heat recovery and utilization system further includes a second dust collector 8, which is installed between the exhaust gas outlet of the second direct dryer 3 and the inlet of the second cold source pipeline. The second dust collector 8 can remove dust from the exhaust gas discharged from the second direct dryer 3, preventing dust from entering the second cold source pipeline and avoiding dust deposition on the inner wall of the pipeline, which could cause blockage or affect heat exchange efficiency.

[0029] In one embodiment, the second dust collector 8 is a water film dust collector.

[0030] In one embodiment, the drying exhaust gas heat recovery and utilization system further includes a condenser 9, which is installed between the second dust collector 8 and the inlet of the second cold source pipeline. The condenser 9 is used to dehumidify the exhaust gas after dust removal treatment, reduce the water vapor content in the exhaust gas, achieve the purpose of removing water from the sludge, improve the ability of hot air to carry water vapor in the second direct dryer 3, improve the drying efficiency of the second direct dryer 3, and at the same time prevent moisture from condensing into a liquid film in the second cold source pipeline to hinder heat exchange, and prevent liquid water from carrying dust to form sludge, further ensuring the unobstructed flow of heat exchange channel 7 and heat exchange efficiency.

[0031] In one embodiment, the drying exhaust gas heat energy recovery and utilization system further includes an absorption heat pump 10, which includes a drive pump, a first loop 11 and a second loop 12. The first loop 11 and the second loop 12 are respectively connected to the drive pump. The first loop 11 is connected to the condenser 9. The second loop 12 is heat exchanged with the first loop 11 and is connected to the return side of the heat exchange channel 7. Both the first loop 11 and the second loop 12 are filled with heat exchange medium. Under the action of the drive pump, the heat exchange medium in the first loop 11 flows to the condenser 9. During the condensation process, the condenser 9 absorbs the waste heat from the exhaust gas and transfers the heat to the heat exchange medium in the first loop 11. Subsequently, the heat is transferred to the heat exchange medium in the second loop 12 through a heat exchange connection. After absorbing heat, the heat exchange medium in the second loop 12 flows to the return side of the heat exchange channel 7. The fluid medium temperature on the return side of the heat exchange channel 7 is lower, which can absorb the heat released by the heat exchange medium in the second loop 12, thereby injecting the recovered waste heat back into the heat exchange channel 7, further improving the overall energy utilization rate of the system. After the heat exchange medium in the first loop 11 completes the heat exchange with the heat exchange medium in the second loop 12, its temperature decreases and it returns to the condenser 9 to continue condensing the exhaust gas discharged from the second direct dryer 3 and absorbing the waste heat of the exhaust gas, forming a closed loop.

[0032] In one embodiment, the first loop 11 is connected to the condenser 9, specifically via a pipeline to the shell side or tube side of the condenser 9, which can be flexibly selected according to the actual heat exchange requirements and the structural form of the condenser 9. For example, when the working fluid in the first loop 11 flows through the tube side of the condenser 9, the exhaust gas flows in the shell side and generates condensate, and the released latent heat is absorbed by the heat exchange working fluid in the tube side; when the working fluid in the first loop 11 flows through the shell side of the condenser 9, the exhaust gas flows in the tube side and generates condensate, and the heat exchange working fluid absorbs heat and rises in temperature in the shell side.

[0033] In one embodiment, the absorption heat pump 10 is a steam-type absorption heat pump, which is an energy-saving device that uses high-temperature steam as the driving energy source and utilizes the absorption cycle principle to raise the low-grade heat in a low-temperature heat source (such as industrial wastewater, geothermal energy, air, etc.) to a medium-to-high grade for utilization. It belongs to the first type of absorption heat pump (heating type), and its total output heat is greater than the heat of the steam consumed.

[0034] In one embodiment, the drying exhaust gas heat recovery and utilization system further includes a heating device installed between the outlet of the second cold source pipeline and the second direct dryer 3. The heating device can raise the temperature of the exhaust gas after heat exchange through the second cold source pipeline, thereby increasing the temperature of the gas entering the second direct dryer 3 from the heat source inlet of the second direct dryer 3.

[0035] In one embodiment, the drying exhaust gas heat recovery and utilization system further includes a dry material silo 13, which is located after the first indirect dryer 1 and the second direct dryer 3. The dry material silo 13 is connected to the outlet of the first indirect dryer 1 and the outlet of the second direct dryer 3, respectively. The dry material silo 13 is used to temporarily store the dried material processed by the first indirect dryer 1 and the second direct dryer 3, thereby achieving material buffering and continuous conveying.

[0036] In one embodiment, the drying exhaust gas heat recovery and utilization system further includes a deodorization system connected to the outlet of the heat absorption end. The deodorization system can remove odors from the low-temperature exhaust gas discharged from the heat absorption end, ensuring that the emitted gas meets environmental protection standards.

[0037] In one embodiment, the first indirect dryer 1 is a disc dryer / thin-layer dryer / paddle dryer, and the heating medium can be steam or heat transfer oil.

[0038] In one embodiment, the second direct dryer 3 is a low-temperature belt dryer / fluidized bed dryer, and the heating medium is air or supersaturated steam.

[0039] In one embodiment, the material to be dried is sludge.

[0040] In one embodiment, the working process of the drying tail gas heat energy recovery and utilization system is as follows: sludge from wet silo 2 is sent to disc dryer and low temperature belt dryer respectively through the conveying system. The external heat source of the disc dryer is saturated steam. The sludge dried by the disc dryer is sent to dry silo 13 for temporary storage and then transported for disposal. The drying exhaust gas generated during the drying process passes through a water film dust collector to remove dust before being sent to the heat exchange system. In the heat exchange system, the exhaust gas heats the circulating water in heat exchange channel 7 to approximately 90°C. The circulating water then heats the gas destined for the second direct dryer 3 to approximately 80°C via heater 6. This portion of the gas heated by heater 6 then enters a low-temperature belt dryer as a heat source, becoming high-temperature, high-humidity gas at approximately 50°C. After dust removal, dehumidification, and water removal, this high-temperature, high-humidity gas becomes dry, cold air at approximately 40°C. This dry, cold air re-enters heater 6 of the heat exchange system, is heated to approximately 80°C, and is then reintroduced into the low-temperature belt dryer as a heat source, thus forming a cycle. The circulating water in heat exchange channel 7 releases heat at heater 6, causing its temperature to decrease. It continues to flow in the closed-loop circuit formed by heat exchanger 5, heater 6, and heat exchange channel 7, re-entering heat exchanger 5 to absorb the residual heat from the drying exhaust gas.

[0041] In one embodiment, the maximum sludge distribution ratio in the disc dryer and the low-temperature belt dryer is 62.5%:37.5%.

[0042] In one embodiment, the saturated steam may be sourced from external purchases, steam boilers, steam generators, heat pumps, etc.

[0043] In one embodiment, the condenser 9 is connected to a cooling tower.

[0044] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A system for recovering and utilizing heat energy from dried exhaust gas, characterized in that, include: The first indirect drying machine (1) has its heat source inlet connected to an external heat source and its feed inlet connected to a wet silo (2). A heat exchange system having a heat-absorbing end and a heat-releasing end, wherein the heat-absorbing end is heat-exchange connected to the heat-releasing end, and the inlet of the heat-absorbing end is heat-exchange connected to the exhaust gas outlet of the first indirect dryer (1). The second direct dryer (3) has its inlet connected to the wet silo (2), its heat source inlet connected to the outlet of the heat release end, and its exhaust outlet connected to the inlet of the heat release end.

2. The system for recovering and utilizing the heat energy of the dried exhaust gas according to claim 1, characterized in that, A first dust collector (4) is provided between the first indirect drying machine (1) and the heat absorption end.

3. The system for recovering and utilizing the heat energy of the dried exhaust gas according to claim 1, characterized in that, The heat exchange system includes a heat exchanger (5), a heater (6), and a heat exchange channel (7); the heat exchanger (5) includes a first heat source pipeline and a first cold source pipeline, which are heat exchanged and connected, and the first heat source pipeline is connected to the exhaust gas outlet of the first indirect dryer (1); the heater (6) includes a second heat source pipeline and a second cold source pipeline, which are heat exchanged and connected; the second heat source pipeline and the first cold source pipeline are connected through the heat exchange channel (7); the outlet end of the second cold source pipeline is connected to the heat source inlet of the second direct dryer (3), and the inlet of the second cold source pipeline is connected to the exhaust gas outlet of the second direct dryer (3); the heat exchange channel (7) is filled with a fluid medium.

4. The system for recovering and utilizing the heat energy of the dried exhaust gas according to claim 3, characterized in that, The fluid medium is circulating water.

5. The system for recovering and utilizing the heat energy of the dried exhaust gas according to claim 3, characterized in that, It also includes a second dust collector (8), which is installed between the exhaust outlet of the second direct dryer (3) and the inlet of the second cold source pipeline.

6. The system for recovering and utilizing the heat energy of the dried exhaust gas according to claim 5, characterized in that, It also includes a condenser (9), which is installed between the second dust collector (8) and the inlet of the second cold source pipeline.

7. The system for recovering and utilizing the heat energy of the dried exhaust gas according to claim 6, characterized in that, It also includes an absorption heat pump (10), which includes a drive pump, a first loop (11) and a second loop (12). The first loop (11) and the second loop (12) are respectively connected to the drive pump. The first loop (11) is connected to the condenser (9). The second loop (12) is heat exchanged with the first loop (11). The second loop (12) is connected to the return side of the heat exchange channel (7).

8. The system for recovering and utilizing the heat energy of the dried exhaust gas according to claim 3, characterized in that, It also includes a heating device, which is installed between the outlet of the second cold source pipeline and the second direct dryer (3).

9. The system for recovering and utilizing heat energy from dried exhaust gas according to claim 1, characterized in that, It also includes a dry material bin (13), which is located after the first indirect dryer (1) and the second direct dryer (3). The dry material bin (13) is connected to the discharge port of the first indirect dryer (1) and the discharge port of the second direct dryer (3), respectively.

10. The system for recovering and utilizing the heat energy of the dried exhaust gas according to claim 1, characterized in that, It also includes a deodorization system, which is connected to the outlet of the heat absorption end.

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