PVC resin drying device and operation method thereof

Abstract

The invention discloses a PVC resin drying device and an operation method thereof, and relates to the technical field of material drying. The device comprises a second heat pump system, a drying bed and a first heat pump system which are sequentially communicated, the first heat pump system comprises a first evaporator, a first compressor, a first condenser and a throttle valve which are communicated in sequence; the second heat pump system comprises a second condenser set, a throttling valve, a second evaporator and a second compressor. The first evaporator is communicated with the drying bed; the first condenser is communicated with the second condenser group, and the second condenser group is communicated with the drying bed; the drying bed communicates with the second evaporator; and the first evaporator is communicated with the first condenser through a waste gas recovery pipeline. The first heat pump system is used for recovering heat of waste gas of the drying bed, the second heat pump system is used for recovering heat of steam condensate discharged by the radiator of the drying bed, heat which is not utilized by the drying bed is reasonably recycled for the drying bed, and external source steam consumption and energy loss in equipment operation are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of material drying, and in particular to a PVC resin drying device and an operating method thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] In the polyvinyl chloride production process, PVC resin drying is an important part of the polyvinyl chloride production process. The solid content of the PVC resin slurry produced by polymerization is about 30%. After being mechanically dried by a centrifuge to remove most of the water in the material, it enters the drying bed. The drying bed is the main equipment for drying PVC resin, and a boiling fluidized bed is usually used. During the drying process of PVC resin, the wet PVC material is added to the fluidized bed dryer by the feeder, and the filtered clean air is preheated by the air preheater and sent to the air heat exchanger by the drying blower. It exchanges heat with the steam in the radiator to become hot air. The hot air enters the bottom of the drying bed from the wind chamber at the bottom of the drying bed. The wet material entering the drying bed contacts the hot air above the air distribution plate, and the material particles are suspended in the air flow, forming a fluidized state to achieve gas-solid heat and mass exchange. In order to prevent the material from short-circuiting, a baffle is installed inside the drying bed, dividing the drying bed into two parts, the first bed and the second bed. The material staying in the first bed increases continuously. When the set amount is reached, the material overflows over the baffle to the second bed for further drying. When the set amount is reached, the material overflows to the discharge port for discharge. Among them, the design of the baffle overflow ensures the length of time the material stays in the drying bed. In addition, steam enters the built-in radiator of the drying bed. Under the dual effects of the hot air and the built-in radiator in the drying bed, the moisture of the PVC resin is removed to become a qualified PVC resin.

[0004] In the above process, the wet air containing water in the drying bed is drawn out by the induced draft fan, and the entrained resin is separated by the cyclone separator. The separated material returns to the drying bed, and the wet air enters the exhaust gas washing tower.

[0005] In the prior art, the wet air at the outlet of the drying bed needs to be treated before it can be discharged in compliance with the standards, and some of the energy contained in this wet air cannot be recycled. The water content of the clean air entering the drying bed changes from time to time due to the influence of the temperature and humidity of the environment, which has a certain degree of impact on the subsequent drying. In addition, the condensate temperature of the steam discharged from the built-in radiator of the drying bed is relatively high, and this part of the energy cannot be recycled. Summary of the invention

[0006] In view of the deficiencies in the prior art, the object of the present invention is to provide a PVC resin drying device and an operating method thereof, wherein a first heat pump system is arranged at the air outlet of a drying bed to recover the heat of exhaust gas from the drying bed, and a second heat pump system is arranged at the hot air inlet of the drying bed to recover the heat of steam condensate discharged from a built-in radiator of the drying bed and to transport hot air into the drying bed. By connecting the first heat pump system and the second heat pump system, the drying air can be circulated and used, thereby making the operating state of the drying bed more stable.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] A first aspect of the present invention provides a PVC resin drying device, comprising: a second heat pump system, a drying bed and a first heat pump system connected in sequence;

[0009] The first heat pump system comprises a first evaporator, a first compressor, a first condenser and a throttle valve which are connected in sequence;

[0010] The second heat pump system comprises a second condenser group, a throttle valve, a second evaporator and a second compressor which are connected in sequence;

[0011] The first evaporator is connected to the drying bed; the first condenser is connected to the second condenser group, and the second condenser group is connected to the drying bed;

[0012] The drying bed is connected to the second evaporator;

[0013] The first evaporator and the first condenser are also connected via an exhaust gas recovery pipeline.

[0014] Optionally, a cyclone separator is provided on the connecting pipeline between the drying bed and the first evaporator.

[0015] Optionally, the second condenser group includes a second condenser A and a second condenser B, and the second condenser A and the second condenser B are respectively connected to the first condenser.

[0016] Optionally, the drying bed includes a first bed and a second bed connected in sequence, the second condenser A is connected to the first bed, and the second condenser B is connected to the second bed.

[0017] Optionally, the second condenser A and the second condenser B are connected to the second evaporator through a second compressor respectively.

[0018] Optionally, an air inlet is provided between the first evaporator and the first condenser, and a blower is provided between the air inlet and the first condenser.

[0019] Optionally, a temporary exhaust gas outlet is provided between the first evaporator and the drying bed.

[0020] Optionally, a throttle valve is provided on the first working fluid pipeline between the first evaporator and the first condenser.

[0021] Optionally, a throttle valve is provided on the second working fluid pipeline between the condenser in the second condenser group and the second evaporator.

[0022] In the second aspect, the operation method of the above-mentioned PVC resin drying device includes the following process:

[0023] The high-temperature dry air input to the drying bed by the second condenser group transfers mass and heat with the wet PVC material and becomes waste gas to be discharged. The waste gas enters the first evaporator for cooling and dehumidification to become dry cold air. The dry cold air enters the first condenser to absorb heat to become medium-temperature air, and then enters the second condenser group to further absorb heat to become high-temperature dry air input to the drying bed; the steam enters the built-in radiator of the drying bed and becomes steam condensate after releasing heat. The steam condensate enters the second evaporator and is discharged from the boundary area after recovering heat;

[0024] The first condenser inputs the low-temperature and low-pressure first working fluid in the first evaporator to absorb the heat of the exhaust gas, and then passes through the first compressor to become the high-temperature and high-pressure first working fluid. The high-temperature and high-pressure first working fluid enters the first condenser to release heat and becomes the low-temperature and low-pressure first working fluid to continue to circulate;

[0025] The low-temperature and low-pressure second working fluid input into the second evaporator of the second condenser group absorbs the heat of steam condensation, and then passes through the second compressor to become the high-temperature and high-pressure second working fluid. The high-temperature and high-pressure second working fluid enters the second condenser group to release heat and becomes the low-temperature and low-pressure second working fluid to continue circulation.

[0026] Optionally, the waste gas enters the first evaporator for cooling and dehumidification and is separated into dry cold air and waste water, and the waste water is mixed with the mother liquor water produced by the PVC slurry centrifuge and enters the centrifugal mother liquor water pool.

[0027] Optionally, the exhaust gas is cooled to 10-30° C. after passing through the first evaporator.

[0028] Optionally, the dry cold air is heated to 40-60° C. after passing through the first condenser.

[0029] Optionally, the medium-temperature air is heated to 60-90° C. after passing through the second condenser.

[0030] The beneficial effects of the present invention are as follows:

[0031] 1. The present invention sets a first heat pump system to recover the heat of the exhaust gas from the drying bed, uses a second heat pump system to recover the heat of the steam condensate discharged from the drying bed, and uses the two grades of heat to heat the dry air in the drying bed, so as to reasonably return the heat that cannot be used by the drying bed to the drying bed itself, thereby reducing the external steam consumption and energy loss during the operation of the equipment.

[0032] 2. The dry air in the drying bed of the present invention is circulated in the entire device, during which waste gas is no longer discharged but condensed waste water is discharged, thereby eliminating the waste gas treatment device, reducing the operating cost of the waste gas treatment device, and reducing material losses; the discharged condensed waste water is mixed with the mother liquor water produced by the PVC slurry centrifuge and enters the centrifugal mother liquor water pool.

[0033] 3. The dry air in the present invention is circulated and used inside the system without using the air in the environment, so that the drying process is less affected by the temperature and humidity of the environment, the operation of the PVC production device is stable and easy to control, and impurities in the air are prevented from entering the product, thereby improving the product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0035] In order to show the positions of various parts, the distances or sizes between them are exaggerated in the figure, and the schematic diagram is for illustration only.

[0036] Figure 1 Schematic diagram of the PVC resin drying device in Example 1.

[0037] Figure 2 It is a schematic diagram of an existing PVC resin drying device in a specific implementation manner.

[0038] Among them, 1. the first heat pump system; 11. the first evaporator; 12. the first condenser; 13. the first compressor; 14. the blower; 15. the temporary exhaust gas outlet; 16. the air filter; 17. the induced draft fan; 2. the second heat pump system; 211. the second condenser A; 212. the second condenser B; 22. the second evaporator; 23. the second compressor; 3. the drying bed; 31. the first bed; 32. the second bed; 33. the radiator; 4. the cyclone separator; 6. the throttle valve; 7. the air heat exchanger; 8. the drying blower; 9. the tail gas washing tower. DETAILED DESCRIPTION

[0039] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0040] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0041] Existing PVC resin drying devices such as Figure 2 As shown, the process flow is as follows:

[0042] The wet PVC material is added into the fluidized bed dryer by the feeder, and the clean air filtered by the air filter 16 is preheated by the air preheater and sent to the air heat exchanger 7 by the drying blower 8. The air heat exchanger 7 uses the external steam as the heat source to heat the clean air into hot air, and the hot air enters the drying bed 3 from the wind chamber at the bottom of the drying bed 3; the wet PVC material entering the drying bed 3 from the top of the drying bed 3 contacts the hot air above the air distribution plate, and the material particles are suspended in the air flow, forming a fluidized state to achieve gas-solid heat and mass exchange; in order to prevent the material from short-circuiting, a baffle is provided inside to divide the drying bed 3 into two parts, the first bed 31 and the second bed 32, and the material staying in the first bed 31 does not It keeps increasing. When it reaches the set amount, it overflows over the baffle to the second bed 32 for further drying. When it reaches the set amount, it overflows to the discharge port for discharge. The baffle overflow design ensures the residence time of the material in the drying bed 3 and allows it to be fully dried. In addition, external steam enters the built-in radiator 33 of the drying bed 3. Under the dual effects of the hot air and the built-in radiator 33 in the drying bed 3, the moisture of the PVC resin is removed to become a qualified PVC resin. The wet air containing moisture in the drying bed 3 is led out by the induced draft fan 17 to the cyclone separator 4, where the entrained resin is separated by the cyclone, and the material returns to the drying bed 3. The waste gas with high humidity enters the tail gas washing tower 9 for treatment. In the tail gas washing tower 9, the waste gas is washed with fresh water supplemented from the external source and discharged after being qualified. The sewage formed in the tail gas washing tower 9 is centrally treated.

[0043] Example 1

[0044] A PVC resin drying device, such as Figure 1 As shown, it includes: a second heat pump system 2, a drying bed 3 and a first heat pump system 1 which are connected in sequence;

[0045] The first heat pump system 1 includes a first evaporator 11, a first compressor 13, a first condenser 12 and a throttle valve 6 which are sequentially connected through a first working medium circuit;

[0046] The second heat pump system 2 includes a second condenser group, a throttle valve 6, a second evaporator 22 and a second compressor 23 which are sequentially connected through a second working medium circuit;

[0047] The air inlet of the first evaporator 11 is connected to the exhaust gas outlet of the drying bed 3; the gas outlet of the first condenser 12 is connected to the second condenser group (including the second condenser A211 and the second condenser B212), and the second condenser group is connected to the hot air inlet of the drying bed 3;

[0048] The outlet of the radiator 33 of the drying bed 3 is connected to the second evaporator 22;

[0049] The first evaporator 11 and the first condenser 12 are also connected via an exhaust gas recovery pipeline.

[0050] Through the above arrangement, the first heat pump system 1 is used to recover the heat of the exhaust gas from the drying bed 3, and the second heat pump system 2 is used to recover the heat of the steam condensate from the radiator 33 of the drying bed 3. The two grades of heat are used to heat the dry air in the drying bed 3, and the heat discharged from the drying bed 3 is reasonably recycled to the drying bed 3 itself, thereby reducing the exogenous steam consumption and energy loss during the operation of the equipment.

[0051] A cyclone separator 4 is provided on the connecting pipeline between the drying bed 3 and the first evaporator 11 for cyclone separation of the resin entrained in the exhaust gas. The material falls into the drying bed 3 and the exhaust gas is discharged to the first evaporator 11 .

[0052] The second condenser A211 and the second condenser B212 are respectively connected to the first condenser 12 through an exhaust gas recovery pipeline, and the gas output from the first condenser 12 can be regulated separately by using two branches.

[0053] The second condenser A211 and the second condenser B212 are connected to the second evaporator 22 through the second compressor 23 respectively.

[0054] The interior of the drying bed 3 includes a first bed 31 and a second bed 32 which are connected in sequence. The second condenser A211 is connected to the first bed 31, and the second condenser B212 is connected to the second bed 32. Since the device specifications and heat flux densities of the radiators 33 in the first bed 31 and the second bed 32 are different, the dry air entering the drying bed 3 can be adjusted to different temperatures and flow rates through two branches.

[0055] An air inlet is arranged between the first evaporator 11 and the first condenser 12 , and a blower 14 is arranged between the air inlet and the first condenser 12 for adding air when the device is started or supplementing air during operation. The air supplemented by the air inlet is filtered by a supplementary air filter 16 .

[0056] A temporary exhaust gas outlet 15 is provided between the first evaporator 11 and the drying bed 3 for exhausting air when the device is shut down or in a fault state. An induced draft fan 17 is provided on the exhaust gas pipeline between the temporary exhaust gas outlet 15 and the cyclone separator 4 to supplement power for the transportation of gas in the pipeline.

[0057] A throttle valve 6 is provided on the first working medium pipeline between the first evaporator 11 and the first condenser 12 for controlling the pressure of the first working medium.

[0058] A throttle valve 6 is provided on the second working medium pipeline between the second condenser A211 / the second condenser B212 and the second evaporator 22 for controlling the pressure of the second working medium.

[0059] The operating method of the PVC resin drying device of this embodiment includes the following process:

[0060] The gas loop is represented by a thin solid line. The high-temperature dry air input to the drying bed 3 by the second condenser group (including the second condenser A211 and the second condenser B212) transfers mass and heat with the wet PVC material and becomes waste gas to be discharged. The waste gas enters the first evaporator 11 to be cooled and dehumidified to become dry cold air. The dry cold air enters the first condenser 12 to absorb heat to become medium-temperature air, and then enters the second condenser group (including the second condenser A211 and the second condenser B212) to further absorb heat to become high-temperature dry air to be input to the drying bed 3. The built-in radiator 33 of the drying bed 3 transports steam condensate to the second evaporator 22. The steam condensate recovers heat through the second evaporator 22 and is discharged from the boundary area.

[0061] The first working medium loop is indicated by a thin dot-dash line. The first working medium of low temperature and low pressure inputted into the first evaporator 11 by the first condenser 12 absorbs the heat of the exhaust gas, and then passes through the first compressor 13 to become the first working medium of high temperature and high pressure. The first working medium of high temperature and high pressure enters the first condenser 12 to release heat, and becomes the first working medium of low temperature and low pressure to continue to circulate.

[0062] The second working fluid loop is represented by a thin dotted line. The low-temperature and low-pressure second working fluid input into the second evaporator 22 of the second condenser group absorbs the heat of steam condensation, and then passes through the second compressor 23 to become a high-temperature and high-pressure second working fluid. The high-temperature and high-pressure second working fluid enters the second condenser group to release heat and becomes a low-temperature and low-pressure second working fluid to continue circulating.

[0063] The waste gas enters the first evaporator 11 and is cooled and dehumidified before being separated into dry cold air and waste water. The waste water is mixed with the mother liquor water produced by the PVC slurry centrifuge and then enters the centrifugal mother liquor water pool for the next step of treatment.

[0064] The wet PVC material is added into the fluidized bed dryer by the feeder, and the heated air (hot air) enters the drying bed 3 from the wind chamber at the bottom of the drying bed 3. The wet PVC material entering the drying bed 3 contacts the hot air above the air distribution plate, and the material particles are suspended in the air flow, forming a fluidized state to achieve gas-solid heat and mass exchange; in order to prevent the material from short-circuiting, a baffle is provided inside to divide the drying bed 3 into two parts, the first bed 31 and the second bed 32. The material staying in the first bed 31 increases continuously. When the set amount is reached, it overflows over the baffle to the second bed 32 for further drying. When the set amount is reached, it overflows to the discharge port for discharge. The baffle overflow design ensures that the material stays in the drying bed 3 for a sufficiently long time; there is also external steam entering the built-in radiator 33 of the drying bed 3. Under the dual action of the hot air and the built-in radiator 33 in the drying bed 3, the moisture of the PVC resin is removed to become a qualified PVC resin product.

[0065] like Figure 1 As shown, the exhaust gas is cooled to 10-30°C after passing through the first evaporator 11; the dry cold air is heated to 40-60°C after passing through the first condenser 12; and the medium-temperature air is heated to 60-90°C after passing through the second condenser group.

[0066] Compared with the prior art, the present invention recycles the waste gas (the wet air at the outlet of the drying bed 3 is first cooled and dried, and then heated for drying), avoids waste gas emission, eliminates the tail gas washing tower 9, and further saves water resources. During the cooling and drying process of the waste gas from the first evaporator 11, the moisture in the waste gas condenses into waste water, and the waste water is mixed with the mother liquid water produced by the PVC slurry centrifuge and enters the centrifugal mother liquid water pool.

[0067] In the present invention, the dry air is preliminarily heated by the first condenser 12 of the first heat pump system 1 to a temperature of 40-60°C, and the heated dry air enters the second condenser group in the second heat pump system 2 for reheating, and enters the drying bed 3 after the temperature is heated to 60-90°C; the dry air is successively heated by the first heat pump system 1 and the second heat pump system 2, and the energy of the wet air and steam condensate discharged from the drying bed 3 is recovered respectively, so that energy can be recovered in stages. And because the air in the environment is not used, it is less affected by the temperature and humidity of the environment, and the device runs smoothly and is easy to control; thereby preventing impurities in the air from entering the product.

[0068] On the other hand, the present invention has the same production process as the PVC resin in the prior art, and can directly use existing process parameters for production, thereby ensuring stable product quality.

[0069] By adopting the technical solution of the present invention, according to the calculation of a drying device of 200,000 tons / year of PVC, it is estimated that about 1.5 tons of external steam will be saved per hour, and sewage discharge will be reduced by 20-25m per hour. 3 .

[0070] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A PVC resin drying device, characterized in that: include: A second heat pump system, a drying bed and a first heat pump system connected in sequence; The first heat pump system comprises a first evaporator, a first compressor, a first condenser and a throttle valve which are connected in sequence; The second heat pump system includes a second condenser group, a throttle valve, a second evaporator and a second compressor; The first evaporator is connected to the drying bed; the first condenser is connected to the second condenser group, and the second condenser group is connected to the drying bed; The drying bed is connected to the second evaporator; The first evaporator and the first condenser are also connected via an exhaust gas recovery pipeline.

2. The PVC resin drying device according to claim 1, characterized in that: A cyclone separator is provided on the connecting pipeline between the drying bed and the first evaporator.

3. The PVC resin drying device according to claim 1, characterized in that: The drying bed includes a first bed and a second bed which are connected in sequence.

4. The PVC resin drying device according to claim 3, characterized in that: The second condenser group includes a second condenser A and a second condenser B, and the second condenser A and the second condenser B are respectively connected to the first condenser; the second condenser A is connected to the first bed, and the second condenser B is connected to the second bed.

5. The PVC resin drying device according to claim 4, characterized in that: The second condenser A and the second condenser B are connected to the second evaporator through the second compressor respectively.

6. The PVC resin drying device according to claim 1, characterized in that: An air inlet is arranged between the first evaporator and the first condenser, and a blower is arranged between the air inlet and the first condenser.

7. The PVC resin drying device according to claim 1, characterized in that: A temporary exhaust gas outlet is provided between the first evaporator and the drying bed.

8. The PVC resin drying device according to claim 1, characterized in that: A throttle valve is provided on the first working medium pipeline between the first evaporator and the first condenser; Optionally, a throttle valve is provided on the second working fluid pipeline between the condenser in the second condenser group and the second evaporator.

9. An operating method of a PVC resin drying device as claimed in any one of claims 1 to 8, characterized in that: The process includes: The high-temperature dry air input to the drying bed by the second condenser group transfers mass and heat with the wet PVC material and becomes waste gas to be discharged. The waste gas enters the first evaporator for cooling and dehumidification to become dry cold air. The dry cold air enters the first condenser to absorb heat to become medium-temperature air, and then enters the second condenser group to further absorb heat to become high-temperature dry air input to the drying bed; the steam enters the built-in radiator of the drying bed and becomes steam condensate after releasing heat. The steam condensate enters the second evaporator and is discharged from the boundary area after recovering heat; The first condenser inputs the low-temperature and low-pressure first working fluid in the first evaporator to absorb the heat of the exhaust gas, and then passes through the first compressor to become the high-temperature and high-pressure first working fluid. The high-temperature and high-pressure first working fluid enters the first condenser to release heat and becomes the low-temperature and low-pressure first working fluid to continue to circulate; The low-temperature and low-pressure second working fluid input into the second evaporator of the second condenser group absorbs the heat of steam condensation, and then passes through the second compressor to become the high-temperature and high-pressure second working fluid. The high-temperature and high-pressure second working fluid enters the second condenser group to release heat and becomes the low-temperature and low-pressure second working fluid to continue circulation.

10. The operating method of the PVC resin drying device according to claim 9, characterized in that: The waste gas enters the first evaporator for cooling and dehumidification and is separated into dry cold air and waste water. The waste water is mixed with the mother liquid water produced by the PVC slurry centrifuge and enters the centrifugal mother liquid water pool.

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