CN110734558A

CN110734558A - Post-treatment method for polypropylene and polyethylene powder

Info

Publication number: CN110734558A
Application number: CN201810801188.8A
Authority: CN
Inventors: 高煦
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-07-18
Filing date: 2018-07-18
Publication date: 2020-01-31

Abstract

The invention discloses a method for preparing a novel water-soluble film: a post-treatment method for polypropylene and polyethylene powder belongs to the field of petrochemical industry. The invention consists of 2 vacuum dealkylators which are operated alternately in batches, and removes and recovers the hydrocarbons carried by polypropylene and polyethylene powder through a plurality of batches of operations of steam pressurization and vacuum pumping, so that the atmospheric pollutants of the device reach the emission limit of the atmospheric pollutants of GB31572-2015 synthetic resin industry pollutants emission Standard. The invention is connected behind a steaming dryer of Chinese patent (ZL 201010515141.9), changes the post-dehumidification treatment into 2 vacuum dealers alternately operated in batch, and thoroughly removes the hydrocarbon in the polypropylene powder by a method of repeatedly introducing water vapor and vacuumizing, so that the discharged hydrocarbon and the discharge amount of the device reach the special discharge limit value regulation of atmospheric pollutants in the table 5 of the discharge standard of synthetic resin industrial pollutants in China GB 31572-2015: the emission of non-methane total hydrocarbons of a unit product is 0.3kg/t product, and the emission limit of the non-methane total hydrocarbons is 60mg/m 3. The invention replaces a degassing bin of polypropylene and polyethylene process, and can lead the atmospheric pollutants of the device to reach the specification of 0.5kg/t product of total non-methane alkane discharge amount of unit products of GB31572-2015 synthetic resin industrial pollutant discharge standard in China.

Description

Post-treatment method for polypropylene and polyethylene powder

Technical Field

The invention belongs to the field of petrochemical industry.

Background

The invention relates to a method for deactivating and completely removing catalyst remained in polypropylene and polyethylene powder after leaving a polymerization reactor and economically recovering hydrocarbons carried in the powder in a process for producing polypropylene and polyethylene, so that the hydrocarbon concentration and the emission amount of exhaust gas discharged by a device reach the emission limit value of atmospheric pollutants of China GB31572-2-15 discharge Standard of Industrial pollutants for synthetic resins, and the volatile matters of the powder are reduced.

It is known that polypropylene and polyethylene powders leaving the polymerization system after synthesis carry quantities of hydrocarbons, part of which is dissolved in the polymer and part of which is free, and that the post-treatment of the polypropylene and polyethylene powders is aimed at removing these entrained hydrocarbons and at deactivating the catalyst (including catalyst and alkylaluminium) remaining in the powder, the above-mentioned process for removing hydrocarbons is generally called degassing or devolatilization (or drying), and the process for decomposing and deactivating the remaining catalyst is generally called steaming (or deactivating), the following are reported:

(1) the tubular polymerization process described in Japanese patent laid-open No. Sho 58-216735 adopts this post-treatment method, after the initial gas/solid separation of the polymer powder leaving the polymerization reactor, the polypropylene powder still carrying 2% of hydrocarbons first enters the upper part of steamers and contacts with the countercurrent of water vapor from bottom to top, the hydrocarbons carried in the polymer are displaced by the water vapor and leave from the upper part of the steamers and are recovered, the polymer contacts with the water vapor in the steamers, at the same time, the residual catalyst is decomposed and deactivated, the polymer with part of the free water leaves from the bottom of the steamers and enters fluidized bed dryers to remove the water.

The atmospheric pollutants can not reach the emission limit value of GB31572-2-15 discharge Standard of Industrial pollutants for synthetic resins in China.

(2) The post-treatment method is adopted in the polymerization process described in Japanese patent laid-open No. Sho 58-157807, Sho 56-139520 (three-well oiling). after the polymer powder leaving the polymerization reactor is subjected to preliminary gas/solid separation, the polypropylene powder still carrying 2% of hydrocarbons first enters horizontal paddle dryers, the interiors of the jacket, stirring shaft and stirring blades of the dryers are heated by introducing steam, the polypropylene powder is heated to 100 ℃, most of the hydrocarbons carried in the polymer are replaced under the multiple actions of heating, stirring and introducing nitrogen replacement, the polymer powder enters steamers and contacts with nitrogen containing steam, trace hydrocarbons carried in the polymer are replaced by , the residual catalyst is decomposed by steam, and the gas removed by the dryers is a mixture of hydrocarbons and nitrogen, so that the hydrocarbons and the nitrogen are difficult to be completely separated and recovered by an economical method.

(3) The polymerization process described in Japanese patent No. 59-230010(Amoco/Chisso) adopts the post-treatment method, after the polymer powder leaving the polymerization system is undergone the process of preliminary gas/solid separation, the polypropylene powder still carrying-2% of hydrocarbons and-70 deg.C is fed into stand-type degassing bin, the degassing bin is not stirred, and the moving bed operation is implemented, and nitrogen gas and trace water vapour are fed into the degassing bin, the hydrocarbons in the polymer are displaced, and the residual catalyst is decomposed and deactivated by water vapour.

The post-treatment of the polyethylene powder material disclosed in United states Union Carbide Corp patent 4003712 also adopts a degassing bin method, and atmospheric pollutants can not reach the emission limit value of GB31572-2-15 synthetic resin Industrial pollutants emission Standard in China.

In northern Europe chemical industry, patent CN1173187, the polyethylene powder is post-treated by degassing (also known as cleaning) chamber, after leaving gas phase reactor, gas/solid is primarily separated, the polymer is fed into degassing (also known as cleaning) chamber, the powder is treated by hot nitrogen and steam to reduce hydrocarbon content and deactivate catalyst residue, the cleaning chamber is usually operated under slight overpressure at about 80 deg.C, and the retention time is usually 2 hr. The atmospheric pollutants can not reach the emission limit value of GB31572-2-15 discharge Standard of Industrial pollutants for synthetic resins in China.

(4) Batch post-processing method

A process for treating the powdered polypropylene generated by intermittent polymerization of polypropylene includes such steps as polymerizing propylene in small polymerizing reactor, dropping the polypropylene to displacing reactor, vacuumizing to recover propylene, introducing steam to deactivate catalyst, introducing nitrogen gas, vacuumizing , removing hydrocarbon from the powdered polypropylene and deactivating the catalyst, and vacuumizing the displacing reactor to obtain condensed water ( deg.C), which has high volatile content and odor.

Chinese patent (87100218.3) is used for continuous transformation of small bodies in 2009, at present, 6 sets of devices are put into operation, propylene is firstly polymerized in a slurry polymerization kettle in a prepolymerization kettle and a liquid phase kettle (transformed by using a small body polymerization kettle), then the polymerization is carried out in a horizontal kettle, polypropylene powder generated in the horizontal kettle enters 1-2 material receiving tanks (transformed by using the small body polymerization kettle, the rotating speed is reduced, and the stirring is simplified) by virtue of the pressure of the polypropylene powder, the initial separation of the polypropylene powder and gas phase propylene is carried out, the post-treatment of the powder still adopts a small body batch post-treatment method, the replacement kettle (each 1 material receiving tank corresponds to 2 replacement kettles) is alternately vacuumized to recover the propylene, water vapor is introduced to deactivate a catalyst, nitrogen is introduced, the hydrocarbon is removed by vacuumizing, the dehydration is carried out, the series of batch treatment is still adopted, the temperature of the propylene powder in the replacement kettles is usually not more than 70 ℃, the water vapor filling pressure is higher than 572 ℃, the condensed water vapor filling pressure is times, condensed water is transferred into the replacement kettle, the nitrogen filling pressure-vacuumizing operation of removing the hydrocarbon and the hydrocarbon recovery operation can not reach the emission limit value, the emission of the industrial product of the non-hydrocarbon emission standard GB, the emission of methane emission of the atmospheric hydrocarbon can not reach the emission.

(5) Degassing and then steaming for deactivation. Chinese patent (200410053651.3) post-treatment method of polypropylene powder. The method is characterized in that after the polymer powder leaving the polymerization system is subjected to primary gas/solid separation, polypropylene powder still carrying 2 percent of hydrocarbons is subjected to the steps of removing most of the hydrocarbons in the polymer powder under the condition of not contacting with nitrogen, and then steaming and deactivating. The method has the advantages that most of the hydrocarbons in the polypropylene powder are removed and recovered by heating, stirring (mechanical stirring or fluidized bed and gas flow conveying) and powder residence time prolonging.

The substantial improvement of the post-treatment method of "drying and then steaming" of the Chinese patent (200410053651.3) over Japanese patent laid-open No. Sho 58-157807 and No. Sho 56-139520 (Mitsui oil) is that the nitrogen is not introduced into the dryer, and the polypropylene powder is heated to-100 ℃. The hydrocarbons in 100% form are discharged by heating and stirring in a dryer and recovered. Since the dryer is not filled with nitrogen, the polypropylene powder is carried with more hydrocarbons when it is introduced from the dryer into the steamer than when it is introduced from the dryer into the steamer in Japanese patent laid-open publication No. Sho 58-157807, No. Sho 56-139520 (three-well oiling). The atmospheric pollutants can not reach the emission limit value regulated by GB31572-2-15 discharge Standard of Industrial pollutants for synthetic resins in China.

(6) Steaming, drying and dehumidifying. Chinese patent (ZL 201010515141.9) polypropylene powder post-treatment method. The method is characterized in that for the existing polypropylene post-treatment process, polypropylene powder which leaves a polymerization system and is subjected to preliminary gas/solid separation enters a dryer, hydrocarbons in the powder are removed by indirect heating through steam and introducing nitrogen, and then the powder enters a steamer to introduce nitrogen and water vapor so as to inactivate a catalyst; or entering a degassing bin, and introducing nitrogen containing water vapor into the degassing bin for improvement:

the dryer is not introduced with nitrogen gas, but is introduced with steam, the dryer is modified into a steaming dryer which recovers hydrocarbons and deactivates the catalyst, the polymer after removing hydrocarbons enters a steamer (or a degassing bin, the same below), nitrogen gas without water vapor is added into the steamer, and the steamer is modified into a dehumidifier which removes the steam in powder.

The Chinese patent can recover hydrocarbons leaving a polymerization system by economic methods, and reduces unit consumption and energy consumption, but atmospheric pollutants can not reach the emission limit value specified in GB31572-2-15 synthetic resin industry pollutant emission Standard of China.

Disclosure of Invention

The emission limit of air pollutants of GB31572-2015 synthetic resin industrial pollutant emission Standard in China is 100mg/m3 of emission limit of non-methane total hydrocarbon, and 0.5kg/t of total emission limit of non-methane alkane of unit product is very strict requirements, and the emission limit of air pollutants of GB31572-2015 synthetic resin industrial pollutant emission Standard in China is 60mg/m3 of emission limit of non-methane total hydrocarbon and 0.3kg/t of total emission limit of non-methane alkane of unit product, the requirements are more strict, no polyolefin process can reach at present, and only the air pollutants can be incinerated.

Taking the polymer powder leaving the polymerization reactor to undergo preliminary gas/solid separation, the polypropylene powder carries 2% of hydrocarbons, 20kg/t of products and 20Nm3/t of nitrogen in atmospheric pollutants as an example, in order to achieve the special emission limit of non-methane total hydrocarbons of GB31572-2015 synthetic resin industry pollutant emission Standard of China, which is 60mg/m3 and is equivalent to 1200mg/t of products (1.2g/t of products, namely 0.0012kg/t of products), the hydrocarbon removal rate of the powder post-treatment equipment must be higher than (20-0.0012)/20 to 99.994%, and equipment which is operated continuously cannot remove the hydrocarbons in the powder to such a high degree.

The pollutants discharged to the atmosphere by the polypropylene device are a mixture of hydrocarbon and nitrogen, even if the unit product total non-methane emission of the polypropylene device meets the requirement of a special emission limit of less than 0.3kg/t product, 0.3kg/t product/60 mg/m3 is 5000m3/t product, and the hydrocarbon of 0.3kg/t product is mixed with nitrogen of 5000m3/t product to ensure that the hydrocarbon in the pollutants discharged to the atmosphere is less than the limit of 60mg/m3, which cannot be realized. The current practice is to send the atmospheric pollutants to incineration disposal, since the hydrocarbon concentration is too low, the total emission of non-methane hydrocarbons per unit product reaches a special emission limit less than 0.3kg/t product, and the concentration of hydrocarbons in the atmospheric pollutants is less than 0.015kg/m3 calculated by the product of 20Nm3/t nitrogen in the atmospheric pollutants, and the atmospheric pollutants can be burnt by adding fuel and air. Increases investment, increases cost, increases valuable occupied area, increases the emission of carbon dioxide and causes new pollution.

The invention aims to provide novel polypropylene and polyethylene powder batch post-treatment methods, which are composed of 2 vacuum dealkylators operated alternately in batches, and remove and recover hydrocarbons carried by polypropylene and polyethylene powder by repeated batch operation of ' steam pressurization-vacuum pumping ', thereby reducing the emission of non-methane total hydrocarbons of unit products, and enabling the atmospheric pollutants of the device to reach the emission limit value or the special emission limit value of the non-methane total hydrocarbons of GB31572-2015 synthetic resin industry pollutants emission Standard ' of China.

Step is illustrated as follows:

the idea of the batch post-treatment method of the polypropylene powder is to completely recover the hydrocarbon in the polypropylene powder by a batch post-treatment method of pressurizing and vacuumizing water vapor for multiple times, so that the atmospheric pollutants finally reach the emission limit and the special emission limit of GB31572-2015 discharge Standard for Industrial pollutants for synthetic resins in China.

Setting the hydrocarbon that 3/4 can be recovered each time the steam is pressurized and evacuated, 1/4 of the remaining hydrocarbons, after 4 passes, will be (1/4) × (1/4) × (1/4) × (1/4) ═ 1/256.

If the hydrocarbon in the powder material is 0.3kg/t product before th steam pressurization, the residual hydrocarbon after the batch treatment is 0.3/256-0.001171 kg/t product, and the nitrogen of the air pollutant is 20Nm3/t product, the concentration of the discharged hydrocarbon is 0.001171/20-0.0000585 kg/m3 and 58.5mg/m3, and the emission limit of non-methane total hydrocarbon of 100mg/m3 and the special limit of 60mg/m3 in GB31572-2015 synthetic resin industrial pollutant emission standard is reached.

In order to recover 3/4 hydrocarbons per time of steam pressurization and vacuum pumping, residual 1/4 hydrocarbons are assumed, the temperature of the polypropylene powder is maintained to be above 95 ℃, the dew point of the steam at the pressure of-0.02 MPAG is 94 ℃, the temperature of the powder is maintained to be above 95 ℃, and when the pressure of the steam is up to-0.02 MPAG, no condensate water is generated, so that the polypropylene powder is firstly vacuumized to-0.08 MPAG, then the steam is pressurized to-0.02 MPAG, then the vacuum is pumped to-0.08 MPAG, the residual hydrocarbon is only 1/4 x 572, after 4 times of operations, 1/256 hydrocarbons are remained in the polypropylene powder and mixed with the nitrogen of 20 3/t external discharge products in the Nm of atmospheric pollutants, and the hydrocarbon concentration reaches the requirements of the synthetic resin industrial pollutant discharge standard of 31GB-387 in China.

If the temperature of the polypropylene powder is 70 ℃ below zero, the dew point of the steam with the steam charging pressure of-0.075 MPAG and-0.075 MPAG is 66 ℃, the temperature of the powder is kept at 70 ℃, no condensate water is generated when the steam charging pressure reaches-0.075 MPAG, vacuumizing is carried out again until-0.085 MPA6 and hydrocarbons can be recovered 2/5, 1/16 hydrocarbons are left in the polypropylene powder after 4 times of treatment, the requirements of 100mg/m3 for the atmospheric pollutant emission limit of China GB31572-2015 synthetic resin Industrial pollutant 2015 can be met after 15 times of batch operation, the polypropylene process described in the background technologies (1), (3) and (4) can effectively recover the hydrocarbons in the polypropylene powder when the powder is subjected to post-treatment, and for example, the atmospheric pollutant emission limit of China GB 59-230010 (Amoco/sso) is replaced by the invention, so that the loss of the propylene can be reduced to 0.5 t and the atmospheric pollutant emission limit of the synthetic resin products is difficult to meet the requirements of GB31572-2015 industrial pollutant emission standard.

If the polypropylene powder batch post-treatment method of the invention is connected after a steaming dryer of Chinese patent (ZL 201010515141.9), the temperature of the polypropylene powder leaving the steaming dryer is 100-105 ℃, the hydrocarbon in the powder is less than 1kg/t product, the temperature of the polypropylene powder after batch post-treatment can be kept at 95-100 ℃, after entering a vacuum de-hydrocarbonizer of the invention, the polypropylene powder is firstly vacuumized to-008 MPAG, the hydrocarbon carried in the powder is counted by 0.3kg/t powder, then the water vapor is pressurized to-0.02 MPAG each time, and then the polypropylene powder is vacuumized to-0.08 MPAG, and the & "&/lTtTtTtTtTt" & ". gTtTtTtTtTtTt transition" & ". gTtTtTtTtTtTtTtTtTtTtTt" & ". G32 hydrocarbon can be recovered after 4 times, the operation, the atmospheric pollutant can reach the emission limit of China GB 310.09, the emission limit of the emission of the synthetic resin industry, the emission standard" &.

The requirement of vacuumizing to-0.08 MPAG is easy to achieve, 4 times of batch operation is easy to realize in actual production.

If the invention is connected after the dryer of the Chinese patent (200410053651.3) in the background technology (5) and the temperature of the powder after the dryer of the Chinese patent (200410053651.3) can reach 100 ℃, the method of the invention can also be used, after the invention enters the vacuum dealkylator of the invention, the vacuum is firstly pumped to-008 MPAG, then the steam is pressurized to-0.02 MPAG each time and then pumped to-0.08 MPAG, and the & (lTtT transfer =) is used for one & (gTt-one &/Tt devolatilization & (gTt) times to recover 3/4 hydrocarbons, because the dryer of the Chinese patent (200410053651.3) is not filled with the steam to replace the hydrocarbons in the powder, the hydrocarbons carried by the dryer into the vacuum dealkylator of the invention are 10kg/t products, the operation times of the pressurization-vacuum pumping of the steam are increased to reach the emission limit requirements of pollutants emission standard of pollutants for the China 31572-synthetic resin industry, the invention is not as good as compared with the emission limit of pollutants when the dryer enters the vacuum dealkylator of the dryer of the China patent, the dryer of the dryer, the invention, the dryer is connected with the dryer of the China patent (201010515141.9), the dryer is better than the dryer.

The dryer of the polymerization process described in Japanese patent laid-open No. Sho 58-157807, Sho 56-139520 (three-well oiling) is the dryer of the Chinese patent No. 200410053651.3 in which nitrogen gas is not introduced. Therefore, the present invention can also be applied to the modification of the powder post-treatment of the polymerization process described in Japanese patent laid-open publication No. Sho 58-157807, Sho 56-139520 (Mitsui oiling).

The main content of the invention is as follows:

(1) the invention relates to a method for post-treating polypropylene powder in batches, which consists of 2 vacuum dealkylators which are alternately operated in batches, and removes hydrocarbon and volatile matters carried in the polypropylene powder through multiple operations of water vapor pressurization and vacuum pumping;

(2) the invention is connected behind the steaming dryer of Chinese patent (ZL 201010515141.9) to replace the dehumidifier of Chinese patent (ZL 201010515141.9), and the invention adopts 2 vacuum dealkylation devices which are operated alternately in batch, thus being capable of thoroughly recovering residual hydrocarbons in powder and reducing the volatile matters of products. The atmospheric pollutants reach the discharge standard of synthetic resin industrial pollutants of China GB31572-2015, and the discharge limit of the atmospheric pollutants is particularly as follows: the total emission of non-methane hydrocarbon of unit product is 0.3kg/t product, the emission special limit value of non-methane hydrocarbon is 60mg/m3, and the atmospheric pollutant can be directly discharged to the atmosphere. The invention reduces the hydrocarbon content in the atmospheric pollutants and simultaneously reduces the volatile content (including moisture) of the product to 100 ppm.

(3) The operation of the invention following the chinese patent (ZL 201010515141.9) steaming dryer is as follows:

1. vacuum dealkylator receives polypropylene powder from Chinese patent (ZL 201010515141.9) steaming dryer under vacuum state, hydrocarbon carried by the polypropylene powder leaving the Chinese patent (ZL 201010515141.9) steaming dryer is less than 1kg/t of product, the vacuum dealkylator receives material and vacuumizes during receiving process, and water and hydrocarbon carried in the polypropylene powder are recovered by vacuum operation.

2. After the material-receiving vacuum hydrocarbon-removing device reaches the set material level, the material-receiving is stopped, the blanking of the steaming dryer is switched to another moisture-removing and hydrocarbon-removing devices, and the following batch operation is continued by the material-receiving vacuum hydrocarbon-removing device.

3. Continuously pumping vacuum by a propylene vacuum pump, keeping the vacuum degree above-0.08 MPAG, and continuously recovering the water and the hydrocarbon in the polypropylene powder. The residual hydrocarbon in the vacuum dealkylator is reduced to 0.3kg/t product from below 1kg/t product.

4. Introducing steam for pressurizing, increasing the pressure of the dealkylator to the vacuum degree of-0.02 MPAG, stopping the steam pressurizing, wherein the steam pressurizing cannot generate condensed water when being introduced for pressurizing, can enable the condensed water to be vaporized only after generating the condensed water after a long time, the vacuum degree after the steam pressurizing is dependent on the temperature of the powder, when the temperature of the powder is 100 ℃, the steam pressurizing cannot generate the condensed water when being introduced to-0.01 MPAG, and when the temperature of the powder is 95 ℃, the steam pressurizing cannot generate the condensed water when being introduced to-0.02 MPAG.

5. Continuing to vacuumize to-0.08 MPAG, and recovering hydrocarbon and water vapor. After the steam is pressurized to-0.02 MPAG (absolute pressure of 0.08), the vacuum is pumped to-0.08 MPAG (absolute pressure of 0.02), and the residual hydrocarbon in the vacuum dealkylator is 0.02/008-1/4.

The temperature of the powder is above 95 ℃, the conditions of pressurizing the water vapor to-0.02 MPAG and vacuumizing to-0.08 MPAG are easy to realize in engineering.

6. The operations of 4 and 5 are alternated, and the operation is repeated for 4 times, the residual hydrocarbon in the vacuum dealkylator is 1/4 multiplied by 1/4 multiplied by 1/4 multiplied by 1/4 which is 1/256, the hydrocarbon in the vacuum dealkylator is 0.3kg/t product before th steam charging, and the hydrocarbon in the vacuum dealkylator is 0.3/256 which is 0.0011718kg/t product after 4 steam charging-vacuumizing operations.

7. If the powder is directly unpacked, the powder can be cooled by adding purified water and then vacuumized for dehydration.

8. Closing a valve of a propylene removal vacuum pump, introducing nitrogen to a micro positive pressure, opening a nitrogen removal vacuum pump valve to vacuumize, removing residual water and other volatile matters in the polypropylene powder, exhausting tail gas of the nitrogen removal vacuum pump into the atmosphere, repeating the step 7 of adding purified water for cooling, wherein the step needs to be repeated for 2-3 times, and otherwise, the water in the product is higher.

After 0.0011718kg/t of residual hydrocarbon in the vacuum dealkylator is mixed with the replacement nitrogen of 20Nm3/t of product, the concentration of the hydrocarbon in the atmospheric pollutants is 58mg/m3, which is less than the requirement of the special emission limit value of 60mg/m3 of non-methane total hydrocarbon specified by the Chinese synthetic resin industrial pollutant emission standard GB 31572-2-15.

9. Introducing nitrogen, increasing the pressure of the vacuum dealkylator to 0.01MPaG, discharging the polypropylene powder of the vacuum dealkylator to a powder pneumatic conveying system, and if a nitrogen pressure conveying mode is adopted, increasing the pressure of the vacuum dealkylator to about 0.3 MPaG.

10. After the polypropylene powder of the dealkylator is discharged, the nitrogen in the vacuum dealkylator is pumped away by a nitrogen vacuum pump, and water vapor can be introduced during the vacuum pumping so as to reduce the nitrogen in the dealkylator as much as possible and prepare for receiving materials again.

11. The operations 1, 10 are repeated again.

(4) The invention is connected after the drier of Chinese patent (200410053651.3), the steamer continuously operated after the drier is changed into the vacuum dealkylator alternately operated in batch mode of the invention 2, or the invention is used for the modification of the powder post-treatment of the polymerization process described in Japanese patent laid-open No. Sho 58-157807, No. Sho 56-139520 (three-well oiling), nitrogen is not introduced into the drier, and the steamer is replaced by the invention after the drier.

The operation method is substantially the same as the above-mentioned "(3) operation of the present invention following the steaming dryer of chinese patent (ZL 201010515141.9)", except that the number of operations of operation step 6, "alternate 4, 5, repeat 4 times" is increased to 6 or more than 6. The atmospheric pollutants can also reach the emission limit and emission special limit of the atmospheric pollutants in GB31572-2015 synthetic resin industry pollutants emission Standard. Because the dryer is not introduced with replacement steam, the effects of removing hydrocarbon and reducing the volatile content of the product are reduced.

(5) The invention can replace a degassing bin of a polymerization process described in Japanese patent No. 59-230010(Amoco/Chisso) of background technology (3), reduce the total emission of non-methane hydrocarbons of a unit product to 0.5kg/t product, and the atmospheric pollutants are difficult to reach the emission limit value of the non-methane hydrocarbons of 100mg/m3 specified in GB31572-2015 synthetic resin industry pollutants emission Standard of China.

(6) The invention can be used for post-treatment of polyethylene powder carrying-2% hydrocarbons after leaving the polymerizer for gas/solid separation.

For polyethylene powder with the powder temperature of 70 ℃, hydrocarbon and volatile matter in the powder are removed by adopting the ' steam pressurizing-vacuumizing ' batch post-treatment method, and the atmospheric pollutants in the device reach the atmospheric pollutant emission limit value in the table 4 of the GB31572-2015 synthetic resin industrial pollutant emission standard ': the non-methane total hydrocarbon emission per unit product is specified to be 0.5kg/t product.

For polyethylene powder with the temperature higher than 95 ℃, hydrocarbon and volatile matters in the powder are removed by adopting a batch post-treatment method of steam pressurization and vacuum pumping, and the atmospheric pollutants in the device reach the special emission limit of the atmospheric pollutants in the table 5 of GB31572-2015 synthetic resin industrial pollutant emission standard of China: the emission of non-methane total hydrocarbon of the unit product is 0.3kg/t product, and the emission limit of the non-methane total hydrocarbon is 60mg/m 3.

The invention is mainly characterized in that:

1. the invention relates to a method for post-treating polypropylene powder in batches, which consists of 2 vacuum dealkylators which are alternately operated in batches, and removes hydrocarbon and volatile matters carried in polymer powder through multiple operations of water vapor pressurization and vacuum pumping;

2. the invention is connected behind the steaming dryer of Chinese patent (ZL 201010515141.9), changes the dehumidifier which is continuously operated behind the steaming dryer into the vacuum dealkylator which is alternately operated in batch, and thoroughly removes the hydrocarbon in the polypropylene powder by the method of repeatedly introducing water vapor and vacuumizing batch operation, so that the atmospheric pollutants in the device conform to the regulation of the atmospheric pollutant emission limit value of GB31572-2-15 synthetic resin industrial pollutant emission standard of China, and can be discharged to the atmosphere without burning treatment. The volatile content of the product is also reduced to below 100ppm (water vapour is also included).

3. The invention is connected behind the dryer of Chinese patent (200410053651.3), the steamer which is continuously operated behind the dryer is changed into the vacuum dealkylator which is alternately operated in batch, the hydrocarbon in the polypropylene powder is thoroughly removed by the method of repeatedly introducing water vapor and vacuumizing batch operation, so that the atmospheric pollutants of the device conform to the regulation of the atmospheric pollutant emission limit value of GB31572-2-15 synthetic resin industrial pollutant emission standard, and can be discharged to the atmosphere without burning treatment.

The modification of the invention after the drier of Chinese patent (200410053651.3) and the powder after-treatment of the invention for the polymerization process described in Japanese patent laid-open No. Sho 58-157807, No. Sho 56-139520 (three-well oiling) is -like, in Japanese patent laid-open No. Sho 58-157807, No. Sho 56-139520 (three-well oiling) polymerization process, the nitrogen is not introduced into the drier, after the drier, the invention is used for replacing the steamer, the air pollutant of the device reaches the air pollutant emission limit of the Chinese synthetic resin industry pollutant emission standard GB31572-2-15, and the burning treatment is not needed.

Because the replacement steam is not introduced into the dryer, the effects of hydrocarbon removal and devolatilization are reduced, and the reduction of the volatile matters of the product is not favorable.

4. The invention can be used for post-treatment of polypropylene powder after leaving a polymerization kettle and primarily separating hydrocarbon, can replace a degassing bin of a polymerization process described in Japanese patent Sho 59-230010(Amoco/Chisso) in the background technology (3), and reduce the total discharge amount of non-methane hydrocarbon of a unit product to 0.5kg/t product, thereby reaching the specification of the unit product of the non-methane alkane of GB31572-2015 synthetic resin industry pollutant discharge standard in China (0.5 kg/t product).

5. The invention can be used for post-treatment of polyethylene powder after the polyethylene powder leaves a polymerization kettle and is subjected to primary hydrocarbon separation, and can replace a degassing bin of United states Carbide company (Union Carbide Corp) patent 4003712 in the background technology, a degassing bin for post-treatment of polyethylene process powder produced in northern Europe chemical industry, patent CN1173187, and reach the specification of 0.5kg/t product of total non-methane alkane discharge of unit product of GB31572-2015 synthetic resin industry pollutant discharge standard in China.

Drawings

FIG. 1 is a schematic diagram of the work-up of polypropylene powder leaving a polymerizer according to the invention. The steaming dryer of chinese patent (ZL 201010515141.9) is 11. 12 is a stirring shaft, and 13 is a stirring blade. Heating steam enters the jacket of 11 from 104 and steam condensate exits the jacket of 11 from 105. Heating steam is also introduced into the interior of 12 and 13 to discharge steam condensate (not shown). Polypropylene powder carrying-2.0 wt.% hydrocarbons was fed from 100 to the steaming dryer 11 and steam was fed from 101 to the steaming dryer 11. The hydrocarbons in the polypropylene powder are removed under the combined action of heating, stirring and water vapor displacement, and the removed hydrocarbons and water vapor leave the steaming dryer 11 from 102 and are sent to hydrocarbon recovery. The polypropylene powder after most of the hydrocarbons have been removed in the steaming dryer 11 leaves at 103 and alternately enters the vacuum de-hydrocarboner 21A/B of the present invention, or enters the vacuum de-hydrocarboner 21A of the present invention through 103A, or enters the vacuum de-hydrocarboner 21B of the present invention through 103B. 21A/B is 2 devices operating in alternating batches. The water vapor enters 21A/B from 201A/B, the hydrocarbon carrying the polypropylene powder exits 21A/B from 202A/B and enters a propylene vacuum pump 22, and the outlet 207 of the propylene vacuum pump is sent to hydrocarbon recovery. Nitrogen enters 21A/B from 203A/B, water vapor in the carried polypropylene powder leaves 21A/B from 204A/B and enters a nitrogen vacuum pump 23, and the nitrogen vacuum pump is discharged to the atmosphere through a pump outlet 208. If the temperature of the powder needs to be reduced, purified water can be introduced into the powder from 206A/B to 21A/B.

The following is illustrated by taking 21A as an example:

1) the polypropylene powder carrying hydrocarbon and water vapor enters 21A from 103A, the water vapor carried by the polypropylene powder entering 21A and hydrocarbon gases such as propylene, propane and the like are sent to a propylene vacuum pump 22 through 202A, and a propylene vacuum pump outlet 207 for hydrocarbon recovery, after the polypropylene powder entering 21A is fed to a set material level, 103A is closed, and the polypropylene powder from 11 enters 21 B.21A from 103B and enters to remove hydrocarbon.

The hydrocarbon carried in the polypropylene powder leaving the steaming dryer 103 is less than 1kg/t polypropylene. After the 21A finishes receiving the materials, the vacuum pumping is carried out until the pressure is between-0.08 and-0.09 MPAG, and the hydrocarbon carried in the polypropylene powder is between 0.3kg/t polypropylene.

The operation of for removing hydrocarbon from polypropylene powder is as follows:

2) , pressurizing the water vapor, namely closing a valve on a pipeline 202A of the de-propylene vacuum pump 22, opening the 201A to enter the water vapor, increasing the pressure of 21A from-0.08 to-0.09 MPAG to-0.01 to-0.02 MPAG, and stopping the water vapor from the 201A;

3) vacuumizing again, namely opening a valve on a pipeline 202A of the depropenizing vacuum pump 22, and vacuumizing to-0.08 to-0.09 MPAG;

4) repeating the steps of 1) and 2) water vapor pressurizing and vacuumizing for 3-4 times,

the steam is pressurized to-0.02 MPAG and the vacuum is pumped to-0.08 MPAG, the residual hydrocarbon is 1/4 each time, the operation is repeated for 4 times, and the residual hydrocarbon in the polypropylene powder is less than 0.0012 kg/ton of polypropylene;

the steam is pressurized to-0.01 MPAG and the vacuum is pumped to-0.09 MPAG, the residual hydrocarbon is 1/9 each time, the operation is repeated for 3 times, and the residual hydrocarbon in the polypropylene powder is less than 0.0012 kg/ton of polypropylene;

5) and (3) nitrogen replacement, namely closing a valve on a pipeline 202A of the depropylene vacuum pump 22, opening a pipeline of the depropylene vacuum pump 23, opening 203A to replace water vapor in the powder, wherein the amount of the replaced nitrogen is 20Nm3 per ton of polypropylene, the hydrocarbon content in tail gas at the outlet of the nitrogen vacuum pump 23 is 0.0012 kg/20-0.00006 kg/m 3-60 mg/m3, the requirement of GB31572-2015 emission standard of industrial pollutants for synthetic resins is met, and the tail gas replaced by the nitrogen can be directly discharged to the atmosphere.

The nitrogen replacement may be performed 1 to 3 times in such a manner that "the nitrogen is charged to about 0.005MPAG and then the vacuum is pumped by the nitrogen vacuum pump 23 to-0.05 to-0.09 MPAG". The water vapor in the polypropylene powder is exhausted through nitrogen replacement and vacuum pumping. The total amount of displaced nitrogen was not less than 20Nm 3/ton of polypropylene.

6) Powder conveying:

increasing the pressure of the 21A to positive pressure by using nitrogen, discharging the polypropylene powder in the 21A to an air conveying system, or increasing the pressure of the 21A to about 0.3MPAG by using nitrogen, and conveying the polypropylene powder in the 21A to a subsequent system under pressure;

7) the 21A is vacuumized to-0.08 to-0.09 MPAG by a nitrogen vacuum pump, and the higher the vacuum degree is, the better the vacuum degree is;

8) returning to 1), a new round of operation begins.

9) If the temperature of the powder needs to be reduced, operations of introducing purified water can be added between 4) and 5), purified water is added through 206A, 10kg of water is added into each ton of product, the temperature of the powder of the product can be reduced by 10 ℃ through evaporation of the water, and vaporized water vapor is pumped away through a propylene vacuum pump after the purified water is added.

10)21B was operated as in 21A. 21A and 21B operate alternately.

FIG. 2 is a schematic diagram of the post-treatment method of polypropylene powder in Chinese patent ZL 201010515141.9,

FIG. 3 is a schematic diagram of the present invention used to recover hydrocarbons from polypropylene powder after the dryer of the Chinese patent (200410053651.3).

FIG. 4 is a schematic representation of the recovery of hydrocarbons from polypropylene powder using the present invention from powder from the polymerizer of the polymerization process described in Chinese patent (87100218.3).

FIG. 4 is also a schematic drawing of the recovery of hydrocarbons from polypropylene powder using the invention from powder from the polymerizers of the polymerization process described in Japanese patent No. Sho 59-230010 (Amoco/Chisso).

FIG. 4 is a schematic view of a polyethylene powder obtained from a gas phase reactor in a process for producing polyethylene according to northern European patent CN1173187, after preliminary gas/solid separation, for recovering hydrocarbons from the polypropylene powder by applying the present invention.

Detailed Description

Example 1 as shown in figure 1, the steaming dryer 11 is powder heaters (paddle dryer) into which direct steam is introduced, the operating pressure is 0.01Mpag, the heating area is 70 m square, 12 is stirring shaft, 13 is stirring blade, the polymer leaving the polymerizer is subjected to gas/solid separation, the polypropylene powder 100 entering the steaming dryer 11 is 4000kg/hr, entrained hydrocarbons are about 80kg/hr, the direct steam 101 entering the steaming dryer 11 is 16kg/hr, the heating steam enters the jacket of the steaming dryer 11 from 104, the steam condensate leaves the jacket of the steaming dryer 11 from 105, the heating steam and steam condensate (not shown in the figure) can be introduced into the jackets 12 and 13, the polypropylene powder is heated to 105 ℃ in the steaming dryer 11, the hydrocarbon pump (volatile) escapes from the powder under the combined action of heating, stirring and water vapor displacement, the hydrocarbon pump (volatile) is recovered from 102, the hydrocarbon powder recovered from 102 to 76kg/hr, the polypropylene powder enters the steaming dryer 11 from 103, the steaming dryer 11, the boiling dryer is subjected to heating, the water vapor displacement, the boiling dryer, the polypropylene powder enters the boiling dryer 11, the boiling dryer, the boiling drum 21A/B, the boiling water outlet 21A/23B, the boiling water outlet of the boiling water pump, the boiling water outlet 21A/vapor outlet 21A, the boiling water outlet 21B, the boiling water outlet of the boiling water outlet 21A/vapor is 21B, the boiling water outlet of the boiling water pump, the boiling water outlet of the boiling water drum is 21A, the boiling water outlet of the boiling water drum is 21B, the boiling water outlet of.

The batch operation is described below using 21A as an example:

1) receiving materials: the operating temperature of the dealkylator 21A is close to 100 ℃, the hydrocarbon carried by the polypropylene powder is less than 1kg/t of polypropylene, the polypropylene powder is vacuumized to-0.08 to-0.09 MPAG after the 21A finishes receiving, and the hydrocarbon carried by the polypropylene powder remained in the 21A is less than 0.3kg/t of polypropylene.

2) th steam pressurization and evacuation, wherein steam is introduced through 201A to pressurize 21A to-0.02 MPAG, the steam of 201A is turned off, and then 21A is evacuated to-0.08 MPAG by the vacuum pump 22 to reduce the residual hydrocarbon in 21A to original 1/4.

3) Pressurizing with steam for the second time to-0.02 MPAG, vacuumizing to-0.08 MPAG, reducing the residual hydrocarbon in 21A to 1/4, pressurizing with steam for 4 times to-0.02 MPAG, vacuumizing to-0.08 MPAG, reducing the residual hydrocarbon in 21A to 1/4 × 1/4 × 1/4 × 1/4, i.e. 1/256, and reducing the residual propylene in 21A to 0.3kg/t polypropylene × 1/256 to 0.0011718kg/t polypropylene;

4) replacement nitrogen 20Nm3/t polypropylene was passed through 203A to 21A and the tail gas was vented via 204A by nitrogen vacuum pump 23. The concentration of the discharged tail gas is 0.0011718 multiplied by 1000000/20 which is 58.59mg/m 3. Meets the requirement that the special emission limit of air pollutants, namely the emission limit of total methane hydrocarbon, is not 60mg/m3 in GB31572-2015 synthetic resin industrial pollutant emission Standard in China.

5) Closing a valve on a pipeline 204A of a 21A nitrogen removal vacuum pump 23, introducing nitrogen from 203A, increasing the pressure of 21A to 0.01MPAG, discharging the polypropylene powder in 21A to a powder pneumatic conveying system from 205A, or increasing the pressure of 21A to about 0.3MPAG to directly convey the powder to a rear system;

6) opening the valve on the line 204A of the 21A denitrogen vacuum pump 23 to pump 21A to-0.08 to-0.09 MPAG, the lower the pressure the more beneficial the nitrogen in 21A is to be purged, adding steam to 21A via 201A under vacuum during the vacuum pumping to purge the nitrogen in 21A as much as possible;

7) return to 1) start a new round of operation.

8) Through the operations 1) to 6), the requirements of the national people's republic of China GB31572-2015 synthetic resin industry pollutant emission standard on the emission limit of non-methane total hydrocarbon emission of 0.3kg/t product of unit product of special atmospheric pollutant emission limit and the emission limit of non-methane total hydrocarbon emission limit of 60mg/m3 can be met.

Comparative example 1: as shown in the attached figure 2 of the drawings,

as shown in FIG. 2, the steaming dryer 11 is powder heaters (paddle type dryers) for introducing direct steam, the operating pressure is 0.01Mpag, the heating area is 70 square meters, 12 is a stirring shaft, 13 is a stirring blade, the polymer leaving the polymerization kettle is subjected to gas/solid separation, the polypropylene powder 100 entering the steaming dryer 11 is 4000kg/hr, the carried hydrocarbons are about 80kg/hr, the direct steam 101 introduced into the steaming dryer 11 is 16kg/hr, the heating steam enters the jacket of the steaming dryer 11 from 104, the steam condensate exits the jacket of the steaming dryer 11 from 105, the heating steam can be introduced into the jackets of the steaming

dryer

12 and 13, and the steam condensate (not shown in the figure) can be discharged, the polypropylene powder is heated to 105 ℃ in the steaming dryer 11, and under the combined action of heating, stirring and steam displacement, the hydrocarbons (volatile matters) escape from the powder, and are recovered from 102, and the hydrocarbons (volatile matters) recovered from 102 are 76 kg/hr.

The polypropylene powder material leaves the steaming dryer 11 from 103 and enters the dehumidifier 14, the operating temperature of the dehumidifier 14 is 100 ℃, and the operating pressure is 0.004 Mpag. 15 is a stirring shaft, 16 is a stirring blade, 109 is water vapor introduced into the jacket, and 110 is condensed water leaving the jacket. Nitrogen was passed through the dehumidifier at 106 at about 100Nm 3/hr. The hydrocarbons carried in the polypropylene powder entering the dehumidifier 14 from 103 are less than 1kg/t polypropylene. Under the action of heating, stirring and nitrogen displacement, the water vapor and residual hydrocarbon carried in the polypropylene powder are removed. The polypropylene powder exits the dehumidifier 14 at 108. The nitrogen, entrained hydrocarbons and water vapor passed to the dehumidifier 14 exit the dehumidifier 14 at 107 to an incinerator or flare.

The gas 107 leaving the dehumidifier contained 100m3/hr of nitrogen and 4kg/hr of hydrocarbons and 2m3/hr of hydrocarbons, and the gas leaving the dehumidifier 107 was 102m 3/hr. The discharge amount of each ton of polypropylene is 1 kg/t. The hydrocarbon concentration of the gas 107 leaving the dehumidifier was 4kg/hr/102m 3/hr-0.0392 kg/m3, corresponding to 39215mg/m 3.

Comparative example 1 can reach the atmospheric pollutant emission limit in table 4 of the discharge standard of industrial pollutants for synthetic resins of China GB 31572-2015: the emission of non-methane total hydrocarbons per unit product is regulated to be 0.5kg/t product, but the emission limit of non-methane total hydrocarbons, 100mg/m3, cannot be met, and is close to 400 times of the emission limit.

Example 2 As shown in FIG. 3, the dryer 11 is a dryer of Chinese patent (200410053651.3), or a dryer of Japanese patent laid-open No. Sho 58-157807 and No. Sho 56-139520 (three-well oiled), but not introducing replacement nitrogen, the operation pressure is 0.01Mpag, the heating area is 70 square meters, 12 is a stirring shaft, 13 is a stirring blade, the polymer leaving the polymerizer is subjected to gas/solid separation, the polypropylene powder 100 entering the dryer 11 is 4000kg/hr, carried hydrocarbons (volatile matter) are released from the powder 104 into the jacket of 11, the vapor condensate can be introduced into the jackets of 105 and 11, and the vapor condensate (not shown) can be discharged, the polypropylene powder is heated to 105 ℃ in the dryer 11, under the action of a heating vacuum pump and stirring pump, the hydrocarbon (volatile matter) escapes from the powder, the hydrocarbon (volatile matter) is recovered from the powder 102, the hydrocarbon powder 103 recovered from 102 is introduced into the dryer 11, the dryer is heated to 105 ℃, the polypropylene powder enters the bulk dryer 11, the bulk dryer, the water vapor outlet 21A/2, the water outlet 21A/B, the vacuum pump is 21A/201A, the vacuum pump is a vacuum pump, the water outlet is 21A/B, the vacuum pump is 21A/201B, the vacuum pump is a vacuum pump, the vacuum pump is the vacuum pump, the vacuum pump outlet is the vacuum pump, the vacuum pump is the vacuum pump, the vacuum pump outlet is the vacuum pump outlet, the vacuum pump outlet is the vacuum pump outlet, the vacuum pump outlet is the vacuum pump.

The batch operation is described below using 21A as an example:

1) receiving materials: the operating temperature of the dealkylator 21A is close to 100 ℃, the hydrocarbon carried by the polypropylene powder is 10kg/t of polypropylene, the hydrocarbon is pumped out and recovered by the propylene vacuum pump 22 through the 202A after entering the 21A, the vacuum pumping is continued to be between-0.08 and-0.09 MPAG after the 21A finishes receiving, and the hydrocarbon carried by the polypropylene powder remained in the 21A is 4kg/t of polypropylene.

2) th steam charging and vacuum pumping, wherein steam is introduced through 201A, 21A is charged to-0.02 MPAG, 201A steam is closed, propylene is pumped to-0.08 MPAG by a propylene vacuum pump 22, and the residual hydrocarbon in 21A is reduced to original 1/4.

3) The steam is pressurized to-0.02 MPAG for the second time, the vacuum is pumped to-0.08 MPAG, the residual hydrocarbon in 21A is reduced to 1/4, the residual hydrocarbon in 21A is reduced to 1/4 × 1/4 × 1/4 × 1/4 × 1/4 × 1/4, namely 1/4096, after 6 times of steam pressurization to-0.02 MPAG and vacuum pumping to-0.08 MPAG, the residual hydrocarbon in 21A is reduced to 4kg/t polypropylene × 1/4096 ═ 0.000976kg/t polypropylene;

4) if the polypropylene powder in 21A is to be directly packed, condensed water can be added to 21A via 206A to lower the temperature of the polypropylene powder in 21A, and then the water vapor is pumped away by evacuation. The addition of 10kg of water per ton of polypropylene reduces the temperature of the polypropylene powder by about 10 ℃.

5) Replacement nitrogen 20Nm3/t polypropylene was passed through 203A to 21A and the tail gas was vented via 204A by nitrogen vacuum pump 23. The concentration of the discharged tail gas is 0.000976 multiplied by 1000000/20 which is 48.8mg/m 3. The tail gas emission meets the requirement of GB31572-2015 emission Standard for pollutants for synthetic resin industry, that the emission limit of the special air pollutants is not 60mg/m3, which is the emission limit of total methane hydrocarbons.

6) Closing a valve on a pipeline 204A of a 21A nitrogen removal vacuum pump 23, introducing nitrogen from 203A, increasing the pressure of 21A to 0.01MPAG, discharging the polypropylene powder in 21A to a powder pneumatic conveying system from 205A, or increasing the pressure of 21A to about 0.3MPAG to directly convey the powder to a rear system;

7) opening the valve on the line 204A of the 21A denitrogen vacuum pump 23 to pump 21A to-0.08 to-0.09 MPAG, the lower the pressure the more beneficial the nitrogen in 21A is to be purged, adding steam to 21A via 201A under vacuum during the vacuum pumping to purge the nitrogen in 21A as much as possible;

8) back to 1), the operations 1) to 7) are continued.

9) While the receiving operation 1) is performed at 21A, the receiving operation 21B has completed performing the operations 1) to 7).

10) Through the operations 1) to 8), the requirements of GB31572-2015 synthetic resin industrial pollutant emission standard on the emission limit value of the atmospheric pollutants of 0.3kg/t product of non-methane total hydrocarbon emission unit product and the emission limit value of the atmospheric pollutants of 60mg/m3 can be met.

Example 3 As shown in figure 4, from Japanese patent No. 59-230010(Amoco/Chisso) or from Chinese patent No. 87100218.3 polymerization kettle powder 4000kg/hr carry hydrocarbon 800kg/hr from 100 into powder and hydrocarbon separation gas/

solid separator

11, 11 polypropylene powder temperature ~ 70 ℃, pressure ~ 0.1MPAG 11 in the separation of hydrocarbon ~ 720kg/hr from 102 in the hydrocarbon recovery system, polypropylene powder 4000kg/hr carry hydrocarbon 80kg/hr from 103 out gas/solid separator 11 alternately into 2 batch operation of the dealkylator 21A, 21 B.1A, 21B are respectively, the volume is 12 m3.103A/B for polypropylene powder inlet, 201A/B for steam inlet, 203A/B for nitrogen inlet, 202A/B for hydrocarbon, water vapor outlet, 204A/B for nitrogen, water vapor outlet, 205A/B for polypropylene powder outlet, 206A/B for water vapor outlet, 206A/B for propylene pump outlet, 21A/B for vacuum pump 21, 207 for

vacuum pump

21A, 23 vacuum pump for propylene pump outlet, 21A/B for vacuum pump 23.

The batch operation is described below using 21A as an example:

1) receiving materials: the operating temperature of the dealkylator 21A is 70 ℃ below zero, 20kg/t of polypropylene carried by the polypropylene powder enters 21A, is pumped out and recycled by the propylene vacuum pump 22 through 202A, the polypropylene powder is continuously pumped to-0.08 to-0.09 MPAG after the 21A finishes receiving, and 4kg/t of polypropylene carried by the polypropylene powder remained in 21A.

2) th steam pressurization and vacuum evacuation, the steam is introduced through 201A to pressurize to-0.075 MPAG, the 201A steam is turned off, 21A is evacuated to-0.085 MPAG by the vacuum pump 22, and the residual hydrocarbon in 21A is reduced to original 3/5.

3) The second steam pressurization to-0.075 MPAG, the vacuum evacuation to-0.085 MPAG, the remaining hydrocarbons in 21A reduced to 3/5, the operation of 4 steam pressurization to-0.075 MPAG, the vacuum evacuation to-0.085 MPAG, the remaining hydrocarbons in 21A reduced to 3/5 × 3/5 × 3/5 × 3/5, i.e. 81/625, the remaining hydrocarbons in 21A reduced to 4kg/t polypropylene × 81/625 to 0.518kg/t polypropylene, 0.50kg/t polypropylene;

after 7 times of steam pressurization to-0.075 MPAG and vacuum pumping to-0.085 MPAG, the residual hydrocarbon in 21A can be reduced to 0.002kg/t polypropylene, and the residual hydrocarbon is mixed with 20Nm3/t product replacement nitrogen, and the emission standard of non-methane alkane in the discharged tail gas is 100mg/m 3.

In actual operation, after 4-5 times of steam pressurization and vacuum pumping, the discharged hydrocarbon is reduced to 0.5kg/t of polypropylene.

4) Replacement nitrogen 20Nm3/t polypropylene was passed through 203A to 21A and the tail gas was vented via 204A to an incinerator by a nitrogen vacuum pump 23. The concentration of the discharged tail gas is 0.455 multiplied by 1000000/(20+0.24) ═ 22480mg/m 3.

5) Closing a valve on a pipeline 204A of the 21A nitrogen removal vacuum pump 23, introducing nitrogen from 203A, increasing the pressure of 21A to about 0.3MPAG, and directly pumping the powder to a rear system;

7) returning to 1), a new round of operation is started, 21A receives 1), the completed received 21B proceeds with operations 2) through 6).

8) Through the operations 1) to 6), the emission limit of the special atmospheric pollutants of the synthetic resin industrial pollutants of China GB31572-2015 discharge Standard of the synthetic resin Industrial pollutants of the non-methane total hydrocarbon unit product is 0.5kg/t of the product, but the emission limit of the special atmospheric pollutants of the non-methane total hydrocarbon is difficult to meet the regulation of 100mg/m 3.

Example 4: as shown in FIG. 4, the powder post-treatment was the same as in example 3. The powder comes from polyethylene powder obtained after preliminary gas/solid separation in a gas phase reactor of a polyethylene production process in northern European patent CN 1173187.

Claims

The post-treatment method of 1, polypropylene and polyethylene powders is characterized in that the invention is composed of 2 vacuum dealkylators which are operated alternately in batches, and the hydrocarbons carried by the polypropylene and polyethylene powders are removed and recovered through the batch operation of ' water vapor pressurization-vacuum pumping ' for a plurality of times, so that the atmospheric pollutants of the device reach the regulation of the atmospheric pollutant emission limit value of GB31572-2015 synthetic resin industry pollutants emission Standard '.
2. According to the claim 1, the invention is connected behind a steaming dryer of Chinese patent (ZL 201010515141.9) to replace a dehumidifier in Chinese patent (ZL 201010515141.9), 2 vacuum dealkylators which are alternately operated in batch are adopted to thoroughly remove hydrocarbon in polypropylene powder by a method of ' water vapor pressurizing-vacuumizing ' for a plurality of times, so that the atmospheric pollutants in the device reach the special emission limit value of the atmospheric pollutants in the table 5 of GB31572-2015 synthetic resin industrial pollutants emission standard ': the emission of non-methane total hydrocarbon of the unit product is 0.3kg/t product, and the emission limit of the non-methane total hydrocarbon is 60mg/m 3.
3. According to claim 1, the invention is connected to the back of the dryer of the polymerization process described in Japanese patent laid-open No. Sho 58-157807, No. Sho 56-139520 (three-well oiling), the dryer does not feed nitrogen, 2 vacuum dealers which are alternately operated in batch are used to replace the dehumidifier, the hydrocarbon in the polypropylene powder is thoroughly removed by a method of ' steam pressurizing-vacuumizing ' for a plurality of times, and the air pollutant of the device reaches the special emission limit value of the air pollutant in the table 5 of GB31572-2015 synthetic resin industrial pollutant emission standard ': the emission of non-methane total hydrocarbon of the unit product is 0.3kg/t product, and the emission limit of the non-methane total hydrocarbon is 60mg/m 3.
4. According to the claim 1, the invention is connected after the drier of Chinese patent (200410053651.3) and replaces the dehumidifier thereof, the air pollutant of the device reaches the special emission limit of the air pollutant in Table 5 of GB31572-2015 synthetic resin industry pollutant emission Standard: the emission of non-methane total hydrocarbon of the unit product is 0.3kg/t product, and the emission limit of the non-methane total hydrocarbon is 60mg/m 3.
5. According to the claim 1, the invention replaces the degassing bin of the Japanese patent Sho 59-230010(Amoco/Chisso) process, and the air pollutant of the device reaches the regulation of 0.5kg/t product of the total non-methane alkane discharge amount of the unit product of GB31572-2015 synthetic resin industry pollutant discharge standard in China.
6. According to the claim 1, the invention replaces the degassing bin of the post-treatment of the polyethylene powder of United states Carbide company (Union Carbide Corp) patent 4003712, and the air pollutant of the device reaches the specification of 0.5kg/t of the total non-methane alkane discharge of the unit product of GB31572-2015 synthetic resin industry pollutant discharge standard in China.
7. According to the claim 1, the invention replaces the degassing bin for post-treatment of polyethylene in polyethylene process powder produced by northern Europe chemical industry patent CN1173187, and the atmospheric pollutants in the device reach the specification of 0.5kg/t product of non-methane alkane total emission of unit product of GB31572-2015 synthetic resin industry pollutants emission Standard.