CN110845642A - Production device and method for low-VOC (volatile organic compound) polyethylene product by slurry process - Google Patents
Production device and method for low-VOC (volatile organic compound) polyethylene product by slurry process Download PDFInfo
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Abstract
The invention relates to a production device and a production method of a slurry-process low-VOC polyethylene product, and mainly solves the problem that the content of residual hexane solvent VOC is high in the prior art. According to the production device and method for the low-VOC polyethylene product by the slurry method, a set of powder degassing bin is added behind a roller dryer in the existing flow of polyethylene by the slurry method, and the combination of the roller dryer and the powder degassing bin is carried out, so that the VOC content of the polyethylene product can be well reduced, the VOC content of a hexane solvent in product powder is reduced to be below 100ppm in the invention from 200ppm in the prior art, the problems are well solved, and the production device and method can be applied to production of the low-VOC polyethylene product by the slurry method.
Description
Technical Field
The invention relates to the technical field of polyethylene production, in particular to a production device and a production method for a slurry-process low-VOC polyethylene product, and specifically relates to a device and a method for reducing residual VOC in polyethylene powder by using a combination of a roller dryer and a powder degassing bin in a slurry-process polyethylene powder drying process, and the device and the method can be applied to slurry-process production of low-VOC food-grade polyethylene products.
Background
The slurry process polyethylene adopts parallel or serial polymerization process, high purity ethylene as main material, hexane as solvent, high efficiency catalyst and butene-1 or propylene as comonomer or functional assistant are added to obtain high density polyethylene product in dozens of grades. However, in the high-temperature processing process and daily use process of the high-density polyethylene product, harmful Volatile Organic Compounds (VOC) can be released to different degrees by the additives, and particularly in the high-density polyethylene product, about 2000-5000 ppm of hexane solvent remains, so that the quality of the food-grade polyethylene product is seriously influenced.
The invention patent application No. 201210209208.5 in the prior art discloses a method for removing odor of a high-density polyethylene food-grade special material, which utilizes the working principle of steaming and drying, and adopts a technology of closed circulation steaming and drying of nitrogen by taking a steamer and a dryer as key equipment combination to remove hexane solvent in the high-density polyethylene food-grade special material, so that the hexane solvent in the high-density polyethylene product is about 200ppm, the value and the quality of the high-density polyethylene product are increased, the three-waste discharge is not increased, and the problem of residual solvent in the high-density polyethylene food-grade special material is solved. The invention patent application number 201710600963.9 discloses a low-odor low-VOC polyethylene composite material and a preparation device and a method thereof, and discloses a method for removing harmful volatile organic compounds in the composite material by stages by combining 55-97 parts of linear high-density polyethylene resin with other additives, an extracting agent and an adsorbing agent, adding the extracting agent and the adsorbing agent by stages in the preparation process, and improving the position of a vacuum port in the preparation device. The invention discloses a modified thermoplastic elastomer material with low odor and low VOC (volatile organic compounds) and a preparation method thereof, and discloses a modified thermoplastic elastomer material consisting of 5-35 parts of polyethylene resin and other additives; because a small amount of auxiliary agents, antioxidants, lubricants, acid absorbing agents and anti-aging agents are used and carry out chemical reaction with small molecules generated in the preparation process, the odor and VOC in the material are thoroughly reduced, the odor of the material is still less than or equal to 3.0 grade after the material is used for a year, and the VOC content still meets the GB/T27630-plus 2011 index requirement. The invention has patent application number 201910071136.4, a predispersion color sheet and a preparation method thereof, namely a pencil and a manufacturing method thereof, and discloses that the predispersion color sheet consists of polyethylene resin and other additives, uses non-toxic organic materials and does not contain any solvent, thereby reducing VOC (volatile organic compounds) emission, causing no pollution to the environment and meeting the national standard; the pencil coated with the pre-dispersion color piece to prepare the coating is more suitable for children, and the pencil manufacturing process is clean and environment-friendly, short in surface drying time, high in production efficiency, low in production cost and strong in applicability.
At present, in the process flow of producing polyethylene products by a slurry method, powder is only dried by a roller dryer, and finally, the extruded polyethylene products mainly contain VOC (volatile organic compounds) of hexane solvent, and the content of the VOC is as high as 2000-5000 ppm. Although the invention patent application No. 201210209208.5 in the prior art adopts a nitrogen closed circulation steaming and drying technology which takes a steamer and a dryer as key equipment combination to remove the hexane solvent in the high-density polyethylene food-grade special material, two additional equipment are needed, and the water vapor is directly injected into a polyethylene powder system, so that the hexane solvent in the final high-density polyethylene product still reaches about 200 ppm. The invention patent application numbers 201710600963.9 and 201711237536.5 and 201910071136.4 in the prior art all adopt a method for reducing the content of VOC by mixing polyethylene resin with other auxiliary agents, and the target products of polyethylene are different, so that the technical method, the production technical process and the manufacturing technical means are also different, but the VOC content can be reduced only in a qualitative way, and no data for reducing the VOC content in a quantitative way is available.
Therefore, the method for reducing VOC by using the polyethylene powder in the prior art has the problems that the number of equipment is large, the water vapor condensate and the polyethylene powder need to be separated again, the residual hexane solvent is not thoroughly removed, and the content of Volatile Organic Compounds (VOC) is high. With the continuous improvement of the environmental protection requirement and the HSE requirement of the polyethylene product, a new high-efficiency removal technical means is urgently needed to reduce the content of VOC in the polyethylene product.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention adopts a production device and a production method of a slurry-process low-VOC polyethylene product to remove residual hexane solvent VOC in polyethylene powder so as to solve the problem of high VOC content in the slurry-process polyethylene product. The invention relates to a production device and a production method of a slurry-process low-VOC polyethylene product, which are characterized in that a powder degassing bin is added behind a roller dryer in the existing process flow of slurry-process polyethylene by taking the reference of the degassing process of gas-phase-process polyethylene powder, and the VOC content in the polyethylene product can be well reduced through the combination of the roller dryer and the powder degassing bin. The VOC-containing polyethylene powder discharged from the roller dryer is conveyed into the newly-added degassing bin through an air conveying system, and is subjected to gas-solid countercurrent contact with dry nitrogen to remove VOC impurities and then conveyed to a downstream working section, so that the VOC content of the obtained polyethylene product can be reduced to be below 100 ppm.
In order to achieve the purpose, the technical measures adopted by the invention comprise:
a first aspect of the present invention provides an apparatus for producing a slurry process low VOC polyethylene product, comprising:
the inlet of the roller dryer is communicated with the spiral feeder, the outlet of the roller dryer is communicated with the powder collector, the polyethylene wet cake containing the hexane solvent VOC from the upstream section is in countercurrent contact with first dry nitrogen in the roller dryer, so that the hexane solvent VOC is volatilized and removed, and the first VOC-containing nitrogen leaves the roller dryer;
the powder degassing bin is used for conveying nitrogen gas to enter the top of the powder degassing bin together with the dry powder leaving the roller dryer after being pressurized, the nitrogen gas and the second dry nitrogen gas blown from the lower part of the powder degassing bin flow in a reverse direction to volatilize and remove the hexane solvent VOC in the powder, and the product powder flows out of the bottom of the powder degassing bin and is conveyed to a downstream working section; the second VOC-containing nitrogen leaves the powder filter, is treated and then is returned for reuse as powder conveying circulating gas.
The second aspect of the invention provides a method for producing a low VOC polyethylene product by a slurry process, which adopts the production device and comprises the following steps:
step a) the polyethylene wet cake containing the hexane solvent VOC from the upstream section enters the roller dryer through the spiral feeder, the first drying nitrogen also enters the roller dryer and is in countercurrent contact with the polyethylene wet cake for a period of time, the hexane solvent VOC volatilizes and is removed, and the first VOC-containing nitrogen leaves the roller dryer;
step b) the low-pressure steam enters the roller dryer, the polyethylene wet cake and the first dry nitrogen are indirectly heated, the hexane solvent VOC is volatilized, and the low-pressure condensate liquid leaves the roller dryer;
step c) pressurizing the conveying nitrogen by the powder conveying fan, allowing the conveying nitrogen and the dry powder which leaves the roller dryer and passes through the powder rotary valve to enter the top of the powder degassing bin and flow out from top to bottom, and blowing in the second dry nitrogen from the lower part of the powder degassing bin and blowing out from bottom to top; the gas and the powder flow in reverse directions, the hexane solvent VOC in the powder is volatilized and removed, the content of VOC adsorbed in the powder is reduced, and the product powder flows out from the bottom of the powder degassing bin and is conveyed to a downstream working section;
and d) the second VOC-containing nitrogen gas leaves the powder filter, is treated and then is used as powder conveying circulating gas to return for reuse.
Further, in the above method, the polyethylene wet cake containing the hexane solvent VOC from the upstream section enters the drum dryer through the screw feeder, the first dry nitrogen gas enters the drum dryer through the powder collector, low-pressure steam enters the drum dryer, the polyethylene wet cake and the first dry nitrogen gas are indirectly heated, and low-pressure condensate exits the drum dryer.
Further, in the above method, the conveying nitrogen is pressurized by a powder conveying fan, and the dry powder is mixed with the pressurized nitrogen at the outlet of the powder conveying fan through a powder rotary valve arranged at the outlet at the bottom of the powder collector; the mixed conveying nitrogen and the dry powder enter the top of the powder degassing bin together and flow out from top to bottom, and the second dry nitrogen is blown in from the lower part of the powder degassing bin and blown out from bottom to top; and volatilizing the hexane solvent VOC in the powder, and delivering the product powder to a downstream working section from the bottom of the powder degassing bin.
Further, in the method, the production scale of the production device is 1-60 ten thousand tons per year of a slurry polyethylene device.
Further, in the method, the content of VOC (volatile organic compounds) of the hexane solvent in the polyethylene wet cake from the upstream section is 5-50%; the residual content of VOC (volatile organic Compounds) in the hexane solvent in the dried powder which leaves the roller dryer and passes through a rotary powder valve is 2000-5000 ppm; the VOC content of the hexane solvent in the product powder flowing out of the powder degassing bin and sent to a downstream section is reduced to be below 100 ppm.
Further, in the method, the operation pressure of the roller dryer is 2-6 KPaG, the operation temperature is 50-150 ℃, and the material retention time is 0.1-5.0 hours.
Further, in the method, the operation pressure of the powder degassing bin is 5-50 KPaG, the operation temperature is 20-80 ℃, and the material stays for 0.1-5.0 hours.
Further, in the method, the operation pressure of the nitrogen conveying is 1-5 KPaG, and the operation temperature is 0-40 ℃.
Further, in the method, the operation pressure of the second dry nitrogen is 10-55 KPaG, and the operation temperature is 30-90 ℃.
Compared with the prior art, the invention adopts the technical scheme that the invention has the following effects:
for a polyethylene device with the production scale of 1-60 ten thousand tons/year, the production device and the production method of the slurry-process low-VOC polyethylene product have the advantages that a set of powder degassing bin is added behind a roller dryer in the existing process flow of the slurry-process polyethylene, the VOC content in the polyethylene product can be well reduced through the combination of the roller dryer and the powder degassing bin, and the problems in the prior art are well solved. The VOC content of the hexane solvent in the product powder is reduced from about 200ppm in the prior art to less than 100ppm in the invention, and a good technical effect is achieved.
Drawings
FIG. 1 is a process flow diagram for the production of a slurry process low VOC polyethylene product of the invention;
FIG. 2 is a flow diagram of a prior art process for producing a low VOC polyethylene product using a slurry process;
wherein the reference numerals in the figures are:
a screw feeder 1; a drum dryer 2; a powder collector 3; a powder rotary valve 4; a powder conveying fan 5; a powder filter 6; a powder degassing bin 7; polyethylene wet cake 11; a first VOC-containing nitrogen gas 12; first dry nitrogen 13; low-pressure steam 14; low-pressure condensate 15; conveying nitrogen 16; drying the powder 17; a second VOC containing nitrogen gas 18; second dry nitrogen gas 19; a product powder 20; a buffer bin 27; and blowing back the nitrogen 29.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.
Example 1
The embodiment is a production process of a low-VOC polyethylene product by a slurry method with a combination of a roller dryer and a powder degassing bin, and as shown in figure 1, the process flow is as follows:
after the polyethylene wet cake 11 containing the hexane solvent VOC from the upstream section enters the drum dryer 2 through the screw feeder 1 and the first dry nitrogen 13 also enters the drum dryer 2 and is in countercurrent contact with the polyethylene wet cake 11 for a period of time, the hexane solvent VOC is volatilized and the first VOC-containing nitrogen 12 leaves the drum dryer 2. Low pressure steam 14 enters the drum dryer 2, indirectly heats the polyethylene wet cake 11 and the first dry nitrogen 13, volatilizes the hexane solvent VOC, and low pressure condensate 15 leaves the drum dryer 2. The conveying nitrogen 16 is pressurized by the powder conveying fan 5, enters the top of the powder degassing bin 7 together with the dry powder 17 leaving the drum dryer 2 and passing through the powder rotary valve 4, and flows out from the top, and the second dry nitrogen 19 is blown in from the lower part of the powder degassing bin 7 and blown out from the bottom and the top. The gas and the powder reversely flow to volatilize and remove the hexane solvent VOC in the powder, the content of the VOC absorbed in the powder is reduced, and the product powder 20 flows out from the bottom of the powder degassing bin 7 and is sent to a downstream working section. The second VOC-containing nitrogen gas 18 leaves the fines filter 6 and is treated and returned for reuse as a recycle gas for the transport of fines.
In the embodiment, the process flow is suitable for a slurry method polyethylene device with the production scale of 1-60 ten thousand tons/year. Wherein the content of VOC (volatile organic compounds) in the hexane solvent in the polyethylene wet cake 11 from the upstream working section is 5-50%; the operation pressure of the roller dryer 2 is 2-6 KPaG, the operation temperature is 50-150 ℃, and the material stays for 0.1-5.0 hours; the residual VOC of the dried powder 17 hexane solvent which leaves the roller dryer 2 and passes through the powder rotary valve 4 is 2000-5000 ppm; the operation pressure of conveying nitrogen 16 is 1-5 KPaG, and the operation temperature is 0-40 ℃; the operation pressure of the second drying nitrogen 19 is 10-55 KPaG, and the operation temperature is 30-90 ℃; the operation pressure of the powder degassing bin 7 is 5-50 KPaG, the operation temperature is 20-80 ℃, and the material stays for 0.1-5.0 hours; the VOC content of the hexane solvent in the product powder 20 which flows out from the powder degassing bin 7 and is sent to the downstream working section is reduced to be below 100 ppm.
Comparative example 1
The comparative example is a production process of a low-VOC polyethylene product by a slurry method only adopting a roller dryer in the prior art, and as shown in figure 2, the process flow is as follows:
after the polyethylene wet cake 11 containing the hexane solvent VOC from the upstream section enters the drum dryer 2 through the screw feeder 1 and the first dry nitrogen 13 also enters the drum dryer 2 and is in countercurrent contact with the polyethylene wet cake 11 for a period of time, the hexane solvent VOC is volatilized and the first VOC-containing nitrogen 12 leaves the drum dryer 2. Low pressure steam 14 enters the drum dryer 2, indirectly heats the polyethylene wet cake 11 and the first dry nitrogen 13, volatilizes the hexane solvent VOC, and low pressure condensate 15 leaves the drum dryer 2. The conveying nitrogen 16 is pressurized by a powder conveying fan 5, enters a powder filter 6 together with the dry powder 17 which leaves the roller dryer 2 and passes through a powder rotary valve 4, the back-blowing nitrogen 29 also enters the powder filter 6, and the second VOC-containing nitrogen 18 leaves the powder filter 6 and is treated to be returned as powder conveying circulating gas for reuse. The polyethylene powder in the powder filter 6 falls into the buffer powder bin 27 to be stored, and the product powder 20 flows out from the bottom of the buffer powder bin 27 to be sent to a downstream working section.
By the prior art process described in comparative example 1, the product powder had a VOC content of about 200 ppm.
Application example 1
Taking a 12-ten-thousand-ton/year polyethylene production device as an example, the production device and the method for producing the low-VOC polyethylene product by the slurry method in the embodiment 1 are adopted, and the process flow is as follows: after the polyethylene wet cake 11 containing the hexane solvent VOC from the upstream section enters the drum dryer 2 through the screw feeder 1 and the first dry nitrogen 13 also enters the drum dryer 2 and is in countercurrent contact with the polyethylene wet cake 11 for a period of time, the hexane solvent VOC is volatilized and the first VOC-containing nitrogen 12 leaves the drum dryer 2. Low pressure steam 14 enters the drum dryer 2, indirectly heats the polyethylene wet cake 11 and the first dry nitrogen 13, volatilizes the hexane solvent VOC, and low pressure condensate 15 leaves the drum dryer 2. The conveying nitrogen 16 is pressurized by the powder conveying fan 5, enters the top of the powder degassing bin 7 together with the dry powder 17 leaving the drum dryer 2 and passing through the powder rotary valve 4, and flows out from the top, and the second dry nitrogen 19 is blown in from the lower part of the powder degassing bin 7 and blown out from the bottom and the top. The gas and the powder reversely flow to volatilize and remove the hexane solvent VOC in the powder, the content of the VOC absorbed in the powder is reduced, and the product powder 20 flows out from the bottom of the powder degassing bin 7 and is sent to a downstream working section. The second VOC-containing nitrogen gas 18 leaves the fines filter 6 and is treated and returned for reuse as a recycle gas for the transport of fines.
The technological parameters are as follows: the content of the VOC (volatile organic Compounds) in the hexane solvent in the polyethylene wet cake 11 is 22%; the operation pressure of the roller dryer 2 is 3KPaG, the operation temperature is 90 ℃, and the material stays for 2.3 hours; dried powder 17 hexane solvent VOC residual 3160ppm leaving the drum dryer 2 and passing through the powder rotary valve 4; the operation pressure of conveying nitrogen 16 is 2KPaG, and the operation temperature is 20 ℃; the operating pressure of the second dry nitrogen gas 19 was 19KPaG and the operating temperature was 48 ℃; the operation pressure of the powder degassing bin 7 is 14KPaG, the operation temperature is 38 ℃, and the material stays for 2.3 hours.
By adopting the production device and the production method of the low-VOC polyethylene product by the slurry method, the VOC content of the polyethylene product is well reduced, the VOC content of the hexane solvent in the product powder is reduced from about 200ppm in the prior art to 98ppm in the embodiment, and a better technical effect is achieved.
Application example 2
The production process flow of the slurry method low-VOC polyethylene product adopted in the embodiment is the same as that of the application example 1, the production scale is only enlarged to a 30-ten-thousand-ton/year polyethylene device, and the process parameters are modified as follows: the content of the VOC (volatile organic Compounds) in the hexane solvent in the polyethylene wet cake 11 is 41 percent; the operation pressure of the roller dryer 2 is 5KPaG, the operation temperature is 120 ℃, and the material stays for 3.5 hours; dried powder 17 hexane solvent VOC residual 3980ppm leaving the drum dryer 2 and passing through the powder rotary valve 4; the operation pressure of conveying nitrogen 16 is 4KPaG, and the operation temperature is 25 ℃; the operating pressure of the second dry nitrogen gas 19 was 38KPaG and the operating temperature was 75 ℃; the operation pressure of the powder degassing bin 7 is 35KPaG, the operation temperature is 65 ℃, and the material stays for 3.5 hours.
By adopting the production device and the production method of the low-VOC polyethylene product by the slurry method, the VOC content of the polyethylene product is well reduced, the VOC content of the hexane solvent in the product powder is reduced from about 200ppm in the prior art to 96ppm in the embodiment, and a better technical effect is achieved.
Application example 3
The production process flow of the slurry method low-VOC polyethylene product adopted in the embodiment is the same as that of the application example 1, only the production scale is modified into a 1 ten thousand ton/year polyethylene pilot plant, and the process parameters are modified as follows: the content of the VOC (volatile organic Compounds) in the hexane solvent in the polyethylene wet cake 11 is 5%; the operation pressure of the roller dryer 2 is 2KPaG, the operation temperature is 50 ℃, and the material stays for 0.1 hour; dried powder 17, leaving the drum dryer 2 and passing through the powder rotary valve 4, had a residual of 2000ppm of hexane solvent VOC; the operation pressure of conveying nitrogen 16 is 1KPaG, and the operation temperature is 0 ℃; the operating pressure of the second dry nitrogen gas 19 was 10KPaG, and the operating temperature was 30 ℃; the operation pressure of the powder degassing bin 7 is 5KPaG, the operation temperature is 20 ℃, and the material stays for 0.1 hour.
By adopting the production device and the production method of the low-VOC polyethylene product by the slurry method, the VOC content of the polyethylene product is well reduced, the VOC content of the hexane solvent in the product powder is reduced from about 200ppm in the prior art to 100ppm in the embodiment, and a better technical effect is achieved.
Application example 4
The production process flow of the slurry method low-VOC polyethylene product adopted in the embodiment is the same as that of the application example 1, the production scale is only enlarged to 60 ten thousand tons/year polyethylene device, two production lines are adopted, and the process parameters are modified as follows: the content of the VOC (volatile organic Compounds) in the hexane solvent in the polyethylene wet cake 11 is 50%; the operation pressure of the roller dryer 2 is 6KPaG, the operation temperature is 150 ℃, and the material stays for 5.0 hours; dried powder 17 leaving drum dryer 2 and passing through powder rotary valve 4 had 5000ppm of hexane solvent VOC remaining; the operation pressure of conveying nitrogen 16 is 5KPaG, and the operation temperature is 40 ℃; the operating pressure of the second dry nitrogen gas 19 was 55KPaG, and the operating temperature was 90 ℃; the operation pressure of the powder degassing bin 7 is 50KPaG, the operation temperature is 80 ℃, and the material stays for 5.0 hours.
By adopting the production device and the production method of the low-VOC polyethylene product by the slurry method, the VOC content of the polyethylene product is well reduced, the VOC content of the hexane solvent in the product powder is reduced from about 200ppm in the prior art to 95ppm in the embodiment, and a better technical effect is achieved.
According to the embodiment and the application embodiment, the production device and the production method of the low-VOC polyethylene product by the slurry method can greatly reduce the VOC content in the polyethylene product through the combination of the roller dryer and the powder degassing bin, and well solve the problems in the prior art. The VOC content of the hexane solvent in the product powder is reduced from about 200ppm in the prior art to less than 100ppm in the invention, and a good technical effect is achieved.
The embodiments of the present invention have been described in detail, but the embodiments are merely examples, and the present invention is not limited to the embodiments described above. It will be appreciated by those skilled in the art that any equivalent modifications and substitutions are within the scope of the present invention. Accordingly, equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered by the present invention.
Claims (10)
1. A production device for low VOC polyethylene products by a slurry method is characterized by comprising the following steps:
a roller dryer (2), wherein the inlet of the roller dryer (2) is communicated with a spiral feeder (1), the outlet of the roller dryer is communicated with a powder collector (3), a polyethylene wet cake (11) containing the hexane solvent VOC from an upstream section is in countercurrent contact with first dry nitrogen (13) in the roller dryer (2) to volatilize and remove the hexane solvent VOC, and the first VOC-containing nitrogen (12) leaves the roller dryer (2);
the powder degassing bin (7) is used for conveying nitrogen (16) into the top of the powder degassing bin (7) after being pressurized, enabling the nitrogen and dry powder (17) leaving the roller dryer (2) to flow in a reverse direction to a second dry nitrogen (19) blown from the lower part of the powder degassing bin (7) so as to volatilize and remove a hexane solvent VOC in the powder, and enabling product powder (20) to flow out from the bottom of the powder degassing bin (7) and be conveyed to a downstream working section; the second VOC-containing nitrogen (18) leaves the dust filter (6) and is treated and returned for reuse as dust conveying recycle gas.
2. A method for producing a slurry process low VOC polyethylene product using the production apparatus as claimed in claim 1, characterized in that it comprises the steps of:
step a) the polyethylene wet cake (11) containing the hexane solvent VOC from the upstream section enters the drum dryer (2) through the screw feeder (1), the first drying nitrogen (13) also enters the drum dryer (2) and is in countercurrent contact with the polyethylene wet cake (11) for a period of time, the hexane solvent VOC volatilizes, and the first VOC-containing nitrogen (12) leaves the drum dryer (2);
step b) the low-pressure steam (14) enters the drum dryer (2), indirectly heats the polyethylene wet cake (11) and the first dry nitrogen (13) to volatilize the hexane solvent VOC, and the low-pressure condensate (15) leaves the drum dryer (2);
step c) pressurizing the conveying nitrogen (16) through the powder conveying fan (5), allowing the conveying nitrogen to enter the top of the powder degassing bin (7) together with the dry powder (17) which leaves the roller dryer (2) and passes through the powder rotary valve (4) and flow out from top to bottom, and blowing in the second dry nitrogen (19) from the lower part of the powder degassing bin (7) and blowing out from bottom to top; the gas and the powder flow in the reverse direction, the hexane solvent VOC in the powder is volatilized and removed, the content of VOC adsorbed in the powder is reduced, and the product powder (20) flows out from the bottom of the powder degassing bin (7) and is sent to a downstream working section;
step d) the second VOC-containing nitrogen (18) leaves the dust filter (6) and is treated and returned for reuse as dust transport recycle gas.
3. A slurry process low VOC polyethylene product production method according to claim 2, characterized in that the polyethylene wet cake (11) containing hexane solvent VOC from upstream section enters the drum dryer (2) through the screw feeder (1), the first dry nitrogen (13) enters the drum dryer (2) through the powder collector (3), low pressure steam (14) enters the drum dryer (2), indirectly heats the polyethylene wet cake (11) and the first dry nitrogen (13), and low pressure condensate (15) leaves the drum dryer (2).
4. The method for producing a slurry process low VOC polyethylene product according to claim 2, wherein the conveying nitrogen (16) is pressurized by a powder conveying fan (5), and the dry powder (17) is mixed with the pressurized nitrogen at the outlet of the powder conveying fan (5) through a powder rotary valve (4) arranged at the outlet of the bottom of the powder collector (3); the mixed conveying nitrogen (16) and the dry powder (17) enter the top of the powder degassing bin (7) and flow out from top to bottom, and second dry nitrogen (19) is blown in from the lower part of the powder degassing bin (7) and blown out from bottom to top; and volatilizing and removing the hexane solvent VOC in the powder, and flowing out the product powder (20) from the bottom of the powder degassing bin (7) to be sent to a downstream working section.
5. The method for producing a slurry process low VOC polyethylene product of claim 2, wherein the production scale of said method is 1-60 million tons per year of slurry process polyethylene plant.
6. The slurry process low VOC polyethylene product production process according to claim 2 wherein the hexane solvent VOC mass fraction content in the polyethylene wet cake (11) from upstream section is between 5 and 50%; the hexane solvent VOC residue in the dry powder (17) leaving the drum dryer (2) and passing through the rotary powder valve (4) is between 2000 and 5000 ppm; the VOC content of the hexane solvent in the product powder (20) flowing out of the powder degassing bin (7) and sent to a downstream section is reduced to be below 100 ppm.
7. The method for producing a slurry process low VOC polyethylene product as claimed in claim 2, wherein the operating pressure of the drum dryer (2) is 2-6 KPaG, the operating temperature is 50-150 ℃, and the material residence time is 0.1-5.0 hours.
8. The method for producing low VOC polyethylene products by slurry process according to claim 2, wherein the operation pressure of the powder degassing bin (7) is 5-50 KPaG, the operation temperature is 20-80 ℃, and the material residence time is 0.1-5.0 hours.
9. The method for producing a slurry process low VOC polyethylene product as claimed in claim 2, wherein said nitrogen gas (16) is delivered at an operating pressure of 1-5 KPaG and an operating temperature of 0-40 ℃.
10. The method for producing a slurry process low VOC polyethylene product as claimed in claim 2, wherein the operating pressure of the second dry nitrogen (19) is 10-55 KPaG and the operating temperature is 30-90 ℃.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910996147.3A CN110845642A (en) | 2019-10-18 | 2019-10-18 | Production device and method for low-VOC (volatile organic compound) polyethylene product by slurry process |
Applications Claiming Priority (1)
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