Dryer heat recovery system and method

Abstract

The invention relates to a heat recovery system and method for a dryer, which are used for recycling steam discharged out of the dryer and energy taken away by the steam. The system comprises an A-zone preheating section, a B-zone heating section, a C-zone evaporation section, a D-zone cooling section and the like, each section is provided with a plurality of sections of drying box bodies, and the drying box of each section is connected with a respective circulating fan and a heat exchanger. The method comprises the following steps: heating the system, circulating airflow in the system, introducing a product, and continuously keeping the temperature and humidity of each section of drying box; all air in the drying boxes flows into the steam backflow box, hot air is supplemented in the steam backflow box, then the air is conveyed to the heat exchange box for heat exchange, and the air meeting the temperature requirements of the corresponding drying boxes is output and enters the drying boxes to heat and dry products in the drying boxes. The circulating water system carries secondary steam energy of the high-temperature evaporation area to the heating area to heat products. Closed energy circulation is formed, evaporated water is fully recycled, and water resources are saved.

Description

Technical Field

[0001] The invention relates to a heat recovery system and method for a dryer, and belongs to the technical field of steam recovery and energy saving. Background Art

[0002] The open energy circulation system of the dryer causes more than 70% of the energy to be wasted in the air, and 100% of the evaporated water is discharged in an unorganized manner and cannot be recycled.

[0003] The energy waste phenomenon of open energy cycle dryer is as follows: Every open dryer has one or more exhaust pipes emitting "white smoke".

[0004] The main component of "white smoke" is water vapor, which liquefies into small water droplets suspended in the air when it is cooled.

[0005] The high-temperature exhaust gas takes away 100% of the secondary steam energy, which is equivalent to more than 70% of the input energy for drying.

[0006] The white mist also takes away 100% of the evaporated water, which is not recycled again, resulting in a waste of water resources.

[0007] It is necessary to develop a system that can recover the heat from the dryer to reduce heat waste. Summary of the invention

[0008] In order to solve the above problems, the present invention discloses a heat recovery system and method for a dryer, and its specific technical solution is as follows: A steam dryer heat recovery system, the dryer includes a preheating section in zone A, a heating section in zone B, an evaporation section in zone C and a cooling section in zone D, each section has a plurality of drying boxes, the produced products are sequentially dried and cooled through the drying boxes in the preheating section in zone A, the heating section in zone B, the evaporation section in zone C and the cooling section in zone D of the dryer, the preheating section in zone A, the heating section in zone B, the evaporation section in zone C and the cooling section in zone D are respectively provided with one or more circulating fans and heat exchangers, The drying box of each section is connected to its own circulating fan and heat exchanger. The circulating fan sends hot air into the drying box. The hot air after passing through the product enters the steam return box together with the steam. The gas and steam in the steam return box are all transported to the heat exchange box. The heat exchange box is provided with a heat exchanger and a condensate collector. The condensate formed by the condensation of the gas and steam from the steam return box in the heat exchange box is collected by the condensate collector. The air enters the heat exchanger for heat exchange. After being processed by the heat exchanger to the temperature required by the drying box, the air is transported to the drying box again through the circulating fan to dry the products in the drying box. The heat exchanger is connected to a constant pressure tank and a circulation pump to maintain the pressure and water circulation of the heat exchanger system.

[0009] Furthermore, the dryer is provided with a water circulation system. After absorbing the energy of the secondary steam generated in the evaporation section of area C, the water circulation system transports it to the preheating section of area A and / or the heating section of area B for release, achieving the purpose of heating the preheating section of area A and / or the heating section of area B.

[0010] Furthermore, the heat exchangers in the preheating section of area A and the heating section of area B are selected as hot water heat exchangers, and the heat exchangers in the evaporation section of area C are selected as steam heat exchangers + hot water heat exchangers.

[0011] Furthermore, the preheating section of area A is connected to several series / parallel hot water heat exchangers. The gas inlet end of the heat exchanger upstream of the gas is connected to a dehydration separation heat exchanger. The air inlet end of the dehydration separation heat exchanger is connected to a steam return box, the air outlet end is connected to the air inlet end of the heat exchanger, and the air outlet end of the heat exchanger is connected to a circulation fan. After the hot air and secondary steam from the steam return box pass through the dehydration separation heat exchanger, they enter the hot water heat exchanger.

[0012] Furthermore, several groups of heat exchangers are respectively connected in parallel or in series in the heating section of area B and the high-speed evaporation section of area C, and each group of heat exchangers is connected in series / parallel with several stages of heat exchangers.

[0013] Furthermore, each group of hot water heat exchangers in the heating section of area B is respectively connected to a dehydration separation heat exchanger. The air inlet end of the dehydration separation heat exchanger is connected to a steam return box, and the air outlet end is connected to the gas inlet end of the heat exchanger at the most upstream of the gas in each group of heat exchangers. The gas outlet end of the heat exchanger at the most downstream of the gas in each group of heat exchangers is connected to a circulation fan. After the hot air and secondary steam from the steam return box pass through the dehydration separation heat exchanger, they enter the hot water heat exchanger.

[0014] Furthermore, each group of hot water heat exchangers in the rapid evaporation section of area C is respectively connected to a waste heat heat exchanger and a water separator. The inlet end of the water separator is connected to a steam return box, the outlet end is connected to the inlet end of the waste heat heat exchanger, the outlet end of the waste heat heat exchanger is connected to the gas inlet end of the heat exchanger at the most upstream of the gas in each group of heat exchangers, and the gas outlet end of the heat exchanger at the most downstream of the gas in each group of heat exchangers is connected to a circulation fan.

[0015] Furthermore, each group of parallel or series-connected multi-stage heat exchangers in the heating section of area B and the high-speed evaporation section of area C includes three stages, which are the first-stage heat exchanger, the second-stage heat exchanger, and the third-stage heat exchanger in sequence from the upstream to the downstream of the gas flow direction. The gas temperature increases step by step. The first-stage heat exchanger is connected to a water supply pipe, and the third-stage heat exchanger is connected to a water outlet pipe.

[0016] A dryer heat recovery method based on the above dryer heat recovery system includes the following steps: Step 1: Pass hot air into each drying oven section. Connect external process steam to the steam heat exchanger in the evaporation section of Zone C. Heat the circulating air through the steam, heat the circulating water through the hot air, and the circulating water transfers the heat energy to the preheating section of Zone A and the heating section of Zone B to achieve the purpose of preheating and heating the preheating section of Zone A and the heating section of Zone B; make each drying oven section reach the temperature range required by the process in the corresponding section; Step 2: Start the circulating fan to make the gas in each drying oven section flow with its respective heat exchanger. After the gas circulates, the temperature of each drying oven section is maintained within the temperature range of the corresponding section; Step 3: Feed in the product and continuously maintain the temperature of each drying oven section; Step 4: All the gas in the drying oven flows into the steam return box, hot air is supplemented in the steam return box, and then the gas is transported to the heat exchange box for heat exchange, and the gas meeting the temperature requirements of the corresponding drying oven is output and enters the drying oven to heat and dry the product in each drying oven.

[0017] Further, in Step 3, a dehydration heat exchanger is used to condense and discharge the water vapor evaporated from the product.

[0018] The beneficial effects of the present invention are: The goal of the present invention is to make full use of the energy of the steam in the evaporation section of Zone C again, form an energy-closed cycle, fully recover the evaporated water, and save water resources. Brief Description of the Drawings

[0019] Figure 1 is the system state schematic diagram of the present invention, Figure 2 is the process structure design diagram of the heating section of the present invention, Figure 3 is the process structure design diagram of the evaporation section of the present invention, Figure 4 is the internal state diagram of the hot water heat exchanger in the evaporation section of the present invention. Detailed Embodiments

[0020] The following further clarifies the present invention in conjunction with the drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0021] Figure 1 is the system state schematic diagram of the present invention. As Figure 1 can be seen, the overall system framework of the present invention is: in the order from upstream to downstream according to the path passed by the product (such as fiber) during production, there are a preheating section of Zone A, a heating section of Zone B, an evaporation section of Zone C, and a cooling section of Zone D. Each section has several drying oven sections, and the drying oven sections in each section are connected to their respective heat exchangers. All the heat exchangers are connected to a constant pressure tank and a circulating pump to maintain the internal pressure and water circulation of the heat exchangers.

[0022] Combined with the attached Figure 2 and 3 it can be clearly seen the internal connection relationship of the heating section in Area B and the evaporation section in Area C. The drying boxes in each section are all connected to their respective circulation fans and heat exchangers. The circulation fans send hot air into the drying boxes. The hot air after passing through the products enters the steam reflux box together with the steam. The gas and steam in the steam reflux box are all transported to the heat exchange box. A heat exchanger and a condensate collector are arranged in the heat exchange box. The condensate formed by the condensation of the gas and steam from the steam reflux box in the heat exchange box is collected by the condensate collector. The air enters the heat exchanger for heat exchange. After the air is processed by the heat exchanger to the temperature required by the drying box, it is transported to the drying box again by the circulation fan to dry the products in the drying box.

[0023] The dryer is provided with a water circulation system. After absorbing the energy of the secondary steam generated in the evaporation section of Area C, the water circulation system transports it to the preheating section of Area A and / or the heating section of Area B for release, achieving the purpose of heating the preheating section of Area A and / or the heating section of Area B.

[0024] As an example of an embodiment, the drying boxes in the heating section of Area A, the heating section of Area B, and the high-speed evaporation section of Area C are all 6 sections, and the drying boxes in the cooling section of Area D are all 12 sections.

[0025] The inlet temperature of the heating section in Area A is 70 °C, the outlet temperature is 100 °C, the inlet temperature of the heating section in Area B is 100 °C, the outlet temperature is 120 °C, the inlet temperature of the high-speed evaporation section in Area C is 120 °C, the outlet temperature is 120 °C, the inlet temperature of the cooling section in Area D is 100 °C, and the outlet temperature is 60 °C.

[0026] As a specific implementation: the heat exchangers in the preheating section of Area A and the heating section of Area B are selected as hot water heat exchangers, and the heat exchanger in the evaporation section of Area C is selected as a steam heat exchanger. Several groups of heat exchangers are connected in parallel or in series in the heating section of Area B and the high-speed evaporation section of Area C, and several stages of heat exchangers are connected in series in each group of heat exchangers. Each group of parallel or series multi-stage heat exchangers in the heating section of Area B and the high-speed evaporation section of Area C includes three stages, which are the first-stage heat exchanger, the second-stage heat exchanger, and the third-stage heat exchanger in sequence from the upstream to the downstream of the gas flow direction. The gas temperature increases gradually. The first-stage heat exchanger is connected to a water supply pipe, and the third-stage heat exchanger is connected to a water outlet pipe.

[0027] The connection relationship is further specifically introduced as follows: the preheating section of Area A is connected to several series-connected hot water heat exchangers. The gas inlet end of the heat exchanger at the upstream of the gas is connected to a dehydration separation heat exchanger. The air inlet end of the dehydration separation heat exchanger is connected to the steam reflux box, the air outlet end is connected to the air inlet end of the heat exchanger, and the air outlet end of the heat exchanger is connected to the circulation fan. The hot air and secondary steam from the steam reflux box enter the hot water heat exchanger after passing through the dehydration separation heat exchanger.

[0028] The connection relationship is further specifically described as follows: Each hot water heat exchanger in the heating section of area B is respectively connected to a dehydration and separation heat exchanger. The inlet end of the dehydration and separation heat exchanger is connected to the steam return box, and the outlet end is connected to the gas inlet end of the heat exchanger at the most upstream of the gas in each group of heat exchangers. The gas outlet end of the heat exchanger at the most downstream of the gas in each group of heat exchangers is connected to the circulation fan. After the hot air and secondary steam in the steam return box pass through the dehydration and separation heat exchanger, they enter the hot water heat exchanger.

[0029] The connection relationship is further specifically described as follows: Each hot water heat exchanger in the rapid steaming section of area C is respectively connected to a waste heat heat exchanger and a water separator. The inlet end of the water separator is connected to the steam return box, and the outlet end is connected to the inlet end of the waste heat heat exchanger. The outlet end of the waste heat heat exchanger is connected to the gas inlet end of the heat exchanger at the most upstream of the gas in each group of heat exchangers. The gas outlet end of the heat exchanger at the most downstream of the gas in each group of heat exchangers is connected to the circulation fan.

[0030] Based on the above dryer heat recovery method of the dryer heat recovery system, it includes the following steps: Step 1: Introduce hot air into each drying box, connect external process steam into the steam heat exchanger in the evaporation section of area C, heat the circulating air through the steam, heat the circulating water through the hot air, and the circulating water brings the heat energy to the preheating section of area A and the heating section of area B to achieve the purpose of preheating and heating the preheating section of area A and the heating section of area B; make each drying box reach the process requirement temperature range of the corresponding section; Step 2: Start the circulation fan to make the gas in each drying box flow with its respective heat exchanger. After the gas circulates, the temperature of each drying box is maintained within the temperature range of the corresponding section; Step 3: Feed the product and continuously maintain the temperature of each drying box; to maintain the air humidity in each drying box, use the dehydration heat exchanger to condense and discharge the water vapor evaporated from the product; Step 4: All the gas in the drying box flows into the steam return box, supplement hot air in the steam return box, and then transport the gas to the heat exchange box for heat exchange, output the gas meeting the temperature requirements of the corresponding drying box, enter the drying box, and heat and dry products such as fibers in each drying box.

[0031] Those skilled in the art of this technology can understand that unless otherwise defined, all terms (including technical terms and scientific terms) used here have the same meaning as the general understanding of those of ordinary skill in the field to which this application belongs. It should also be understood that terms defined in common dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as here.

[0032] The meaning of "and / or" described in this application refers to the situation where each exists alone or both exist simultaneously.

[0033] As used in this application, the meaning of "connection" can be a direct connection between components or an indirect connection between components through other components.

[0034] Inspired by the ideal embodiments of the present invention described above, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A steam dryer heat recovery system, characterized in that, The dryer includes a preheating section in Area A, a heating section in Area B, an evaporation section in Area C, and a cooling section in Area D. Each section has several drying chambers. The products to be produced are dried and cooled successively through the drying chambers in the preheating section in Area A, the heating section in Area B, the evaporation section in Area C, and the cooling section in Area D of the dryer. One or more circulating fans and heat exchangers are respectively provided in the preheating section in Area A, the heating section in Area B, the evaporation section in Area C, and the cooling section in Area D. The drying chambers in each section are respectively connected to their own circulating fans and heat exchangers. The circulating fans send hot air into the drying chambers. The hot air after passing through the products enters the steam reflux box together with the steam. All the gas and steam in the steam reflux box are transported to the heat exchange box. A heat exchanger and a condensate collector are provided in the heat exchange box. The condensate formed by the condensation of the gas and steam from the steam reflux box in the heat exchange box is collected by the condensate collector. The air enters the heat exchanger for heat exchange. After the air is processed by the heat exchanger to the temperature required by the drying chamber, it is transported to the drying chamber again by the circulating fan to dry the products in the drying chamber. The heat exchanger is connected to a constant pressure tank and a circulating pump to maintain the internal air pressure and water pressure of the heat exchanger.

2. The dryer heat recovery system according to claim 1, characterized in that, The dryer is provided with a water circulation system. After absorbing the energy of the secondary steam generated in the evaporation section in Area C, the water circulation system transports it to the preheating section in Area A and / or the heating section in Area B for release, so as to achieve the purpose of heating the preheating section in Area A and / or the heating section in Area B.

3. The dryer heat recovery system according to claim 1, wherein, The heat exchangers in the preheating section in Area A and the heating section in Area B are selected as hot water heat exchangers, and the heat exchanger in the evaporation section in Area C is selected as a steam heat exchanger + a hot water heat exchanger.

4. The dryer heat recovery system according to claim 3, wherein The preheating section in Area A is connected to several series / parallel hot water heat exchangers. The gas inlet end of the heat exchanger upstream of the gas is connected to a dehydration separation heat exchanger. The air inlet end of the dehydration separation heat exchanger is connected to the steam reflux box, and the air outlet end is connected to the air inlet end of the heat exchanger. The air outlet end of the heat exchanger is connected to the circulating fan. The hot air and secondary steam from the steam reflux box enter the hot water heat exchanger after passing through the dehydration separation heat exchanger.

5. The dryer heat recovery system according to claim 3, characterized in that, The heating section in Area B and the high-speed evaporation section in Area C are respectively connected in parallel or in series with several groups of heat exchangers, and each group of heat exchangers is connected in series with several stages of heat exchangers.

6. The dryer heat recovery system according to claim 3, wherein Each group of hot water heat exchangers in the heating section in Area B is respectively connected to a dehydration separation heat exchanger. The air inlet end of the dehydration separation heat exchanger is connected to the steam reflux box, and the air outlet end is connected to the gas inlet end of the heat exchanger upstream of the gas in each group. The gas outlet end of the heat exchanger downstream of the gas in each group is connected to the circulating fan. The hot air and secondary steam from the steam reflux box enter the hot water heat exchanger after passing through the dehydration separation heat exchanger.

7. The dryer heat recovery system according to claim 3, characterized in that, Each group of hot water heat exchangers in the rapid evaporation section in Area C is respectively connected to a waste heat exchanger and a water separator. The inlet end of the water separator is connected to the steam reflux box, and the outlet end is connected to the inlet end of the waste heat exchanger. The outlet end of the waste heat exchanger is connected to the gas inlet end of the heat exchanger upstream of the gas in each group. The gas outlet end of the heat exchanger downstream of the gas in each group is connected to the circulating fan.

8. The dryer heat recovery system according to claim 5, wherein, Each group of the multi-stage heat exchangers connected in parallel or in series in the B-zone heating section and the C-zone high-speed evaporation section includes three stages. From the upstream to the downstream in the gas flow direction, they are the first-stage heat exchanger, the second-stage heat exchanger, and the third-stage heat exchanger, and the gas temperature increases step by step. The first-stage heat exchanger is connected to a water pipe, and the third-stage heat exchanger is connected to a water outlet pipe.

9. A drying machine heat recovery method for the drying machine heat recovery system according to any one of claims 1-8, characterized in that, It includes the following steps: Step 1: Introduce hot air into each drying oven. Connect external process steam into the steam heat exchanger in the evaporation section of the C zone. Heat the circulating air through the steam, heat the circulating water through the hot air, and the circulating water brings the heat energy to the A-zone preheating section and the B-zone heating section to achieve the purpose of preheating and heating the A-zone preheating section and the B-zone heating section; make each drying oven reach the process requirement temperature range of the corresponding section; Step 2: Start the circulating fan to make the gas in each drying oven flow with its respective heat exchanger. After the gas circulates, the temperature of each drying oven is maintained within the temperature range of the corresponding section; Step 3: Introduce the product and continuously maintain the temperature of each drying oven; Step 4: All the gas in the drying oven flows into the steam return box. Supplementary hot air is added in the steam return box, and then the gas is transported to the heat exchange box for heat exchange, and the gas meeting the temperature requirements of the corresponding drying oven is output and enters the drying oven to heat and dry the product in each drying oven.

10. The dryer heat recovery method according to claim 9, wherein In step 3, a dehydration heat exchanger is used to condense and discharge the water vapor evaporated from the product.

Images