A refining separation apparatus for preparing ultra-high purity polyethylene wax

Abstract

The utility model relates to a kind of refining separation devices for preparing ultra-high purity polyethylene wax, the device includes the metal impurity removal module, stripping light module, evaporative separation module sequentially arranged along material flow, wherein metal impurity removal module includes reaction kettle, the reagent storage tank connected with the feeding port of reaction kettle and the filtration unit connected to the downstream of reaction kettle.Compared with the prior art, the device sequentially passes through the multistage purification route of metal impurity removal module, stripping light module, evaporative separation module, realizes the deep removal of metal residue, solvent, light oil component and oligomer in crude wax, and obtains ultra-high purity high-quality polyethylene wax.

Description

Technical Field

[0001] This utility model belongs to the field of polyethylene by-product wax purification technology, specifically relating to a refining and separation device for preparing ultra-high purity polyethylene wax. Background Technology

[0002] Polyethylene wax, also known as polymer wax (PE wax), is widely used in the manufacture of masterbatches, granulation, plastic steel, PVC pipes, hot melt adhesives, rubber, shoe polish, leather brighteners, cable insulation materials, floor wax, plastic profiles, inks, and injection molding due to its excellent cold resistance, heat resistance, chemical resistance, and abrasion resistance. There are three main production processes in the industry: polyethylene pyrolysis, ethylene synthesis, and polyethylene plant by-product method.

[0003] The byproduct method for polyethylene plants mainly involves slurry-process high-density polyethylene plants. Currently, the byproduct wax produced by these plants contains a large amount of water, as well as significant amounts of light components, residual solvents (such as hexane), and catalysts (metal impurities). During downstream processing, the volatilization of light components and hexane generates large amounts of dense smoke, causing VOC content to exceed standards. In severe cases, this can lead to fire accidents, affecting product quality and operational safety. Generally, it needs to be refined before being sold. In particular, the residual tiny metal ions (particle size mostly 0.1-1 nm) in the polyethylene wax affect its thermal stability (e.g., accelerating oxidation) and the performance of downstream products.

[0004] Patent CN117964800A discloses a process for purifying by-product polyethylene wax. Through flash evaporation, condensation, and purification steps, combined with high-temperature negative pressure conditions, it addresses the high water and light component content in polyethylene by-product wax, thereby improving product purity. However, this method cannot obtain polyethylene wax products with higher purity. The process mainly relies on physical flash evaporation and condensation, which struggles to separate fine metallic impurities (mostly 0.1-1 nm in diameter) chemically bonded or encapsulated within the polyethylene wax molecular chains in atomic or ionic form. This results in ineffective removal of metallic impurities, and the purified product still has shortcomings in thermal stability and color. Developing an efficient method for refining and purifying polyethylene by-product wax requires not only reducing the content of hexane and light components and the amount of wastewater generated in the wax product, but also, crucially, reducing the content of metallic impurities to further improve the purity of the polyethylene wax product and reduce energy consumption. Therefore, further development is still needed. Utility Model Content

[0005] The purpose of this invention is to provide a refining and separation device for preparing ultra-high purity polyethylene wax in order to solve the above-mentioned problems.

[0006] The objective of this utility model is achieved through the following technical solution:

[0007] A refining and separation apparatus for preparing ultra-high purity polyethylene wax, comprising:

[0008] A metal removal module is used to remove metal impurities from raw materials, including a reaction vessel, a reagent storage tank connected to the feed port of the reaction vessel, and a filter unit connected downstream of the reaction vessel.

[0009] The stripping module for removing light oil components is in process fluid communication with the metal impurity removal module and is used to strip light oil components under vacuum.

[0010] The evaporation separation module is connected to the heavy phase outlet process fluid of the stripping and light phase removal module, and is used to deeply remove oligomers and moisture under higher vacuum.

[0011] The working principle of this refining and separation device is as follows: after the polyethylene wax raw material is sent to the reaction vessel, it is heated and melted. Relevant reagents (chelating agents / flocculators) are added to the reaction vessel through the reagent storage tank. The reagents chelate and flocculate with the metals in the polyethylene wax raw material, and after agglomeration, they form large particles. After being filtered by the filtration unit, they are effectively removed. Then, after passing through the subsequent stripping module to remove light components, the device further removes oligomers and moisture through the evaporation separation module, and finally obtains ultra-high purity polyethylene wax with low metal impurity content and low organic residue.

[0012] As a preferred technical solution, the reaction vessel is a mixing tank with temperature control and stirring functions;

[0013] The pharmaceutical storage tanks include chelating agent storage tanks for storing polymeric chelating agents and flocculant storage tanks for storing flocculants.

[0014] Furthermore, the polymeric chelating agent is selected from maleic anhydride grafted polymeric chelating agents, ethylene-acrylic acid copolymer (EAA), and ethylene-methacrylic acid copolymer (EMAA). In the molten state, the polymeric chelating agent chelates with the metal components in polyethylene wax to form macromolecular particles.

[0015] Furthermore, maleic anhydride-grafted polymeric chelating agents include maleic anhydride-grafted polyethylene wax, maleic anhydride-grafted polypropylene, and maleic anhydride-grafted polyethylene. In some specific implementation schemes, various commercially available products can be selected, such as Kraton's MA-g-PP and MA-g-PE series products, and Arkema's... 18302, Dow Chemical's AMPLIFYTY1053H, Aladdin polyethylene grafted maleic anhydride (CAS No. 9006-26-2); ethylene-acrylic acid copolymer (EAA) can be selected from DuPont. wait.

[0016] Furthermore, the amount of the polymeric chelating agent is 0.01%-5% of the mass of the polyethylene wax raw material, preferably 0.05%-1.0%, and more preferably 0.1%-0.5%.

[0017] Furthermore, the flocculant can be a polymeric flocculant suitable for solid-liquid separation, selected from polyacrylamide flocculants, acrylic acid / methacrylic acid grafted polyethylene wax, and styrene-maleic anhydride copolymer grafted polyethylene wax (SMA). Polyacrylamide flocculants are preferably non-ionic polyacrylamide, and their molecular weight is more preferably 5 million to 12 million. Flocculants in this molecular weight range have excellent bridging flocculation effect.

[0018] Further, the amount of flocculant used is 0.01%-2% of the mass of the polyethylene wax raw material, preferably 0.01%-0.1%, and more preferably 0.03%-0.05%.

[0019] As a preferred technical solution, the filtration unit is composed of a filter, including but not limited to one of a plate and frame filter, a chamber filter press, and a bag filter.

[0020] As a preferred technical solution, the filtration unit is configured as a multi-stage filtration system, consisting of a coarse filter and a precision filter. The coarse filter uses a filter screen with a pore size of 150-200 micrometers (80-120 mesh), and the precision filter uses a filter screen with a pore size of 1-100 micrometers (such as a pleated filter element or ceramic membrane), more preferably 10-50 micrometers. After the coarse filter performs preliminary filtration of large particles, the particles are then further purified by the precision filter, which reduces the residual particulate impurities in the raw materials more efficiently.

[0021] As a preferred technical solution, the vapor phase outlet of the evaporation separation module is connected to the middle of the stripping light component removal module, so as to reuse the evaporated light component as stripping gas, provide heat for the stripping process, reduce the external stripping steam consumption, realize the recycling of energy inside the device, reduce heat loss, and reduce overall energy consumption.

[0022] Preferably, the absolute pressure of the stripping tower in the evaporation separation module is 10-50 kPa, more preferably 10-20 kPa, and the absolute pressure of the evaporator in the evaporation separation module is 0.1-10 kPa, more preferably 1-8 kPa.

[0023] As a preferred technical solution, the stripping and light-duty removal module includes a stripping tower, a tower bottom pump, and a heater;

[0024] The inlet of the tower bottom pump is connected to the outlet of the stripping tower, and its outlet is returned to the stripping tower via the heater, and connected to the evaporation separation module via another path.

[0025] As a preferred technical solution, the evaporation separation module includes an evaporator, and the vapor phase outlet of the evaporator is connected to the stripping tower through a jet pump. The evaporator can be a scraped film evaporator, a falling film evaporator, or a short-path distiller.

[0026] The bottom outlet of the evaporator is connected to the inlet of a delivery pump. One outlet of the delivery pump returns to the top of the evaporator, and the other outlet serves as the finished product outlet.

[0027] As a preferred technical solution, the device further includes:

[0028] The light component condensation and recovery module is connected to the vapor phase outlet process fluid of the stripping and light component removal module, and is used to condense and recover light oil and treat non-condensable gas.

[0029] The refined wax product forming module is connected to the heavy phase outlet process fluid of the evaporation separation module and is used to solidify and form the refined wax product.

[0030] As a preferred technical solution, the light component condensation and recovery module includes a condenser, a phase separation tank, an oligomer buffer tank, and a wastewater collection tank;

[0031] The light components of the stripping light module are sent to the condenser for condensation, the condensate is sent to the phase separation tank, and the non-condensable gas is sent to the waste gas incinerator for incineration.

[0032] The oil phase outlet of the phase separation tank is connected to the oligomer buffer tank, and the aqueous phase outlet is connected to the wastewater collection tank via a pipeline.

[0033] As a preferred technical solution, the refined wax product forming module includes a wax product buffer tank, which is connected to a downstream flake machine, granulator, or spray molding device.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] This device employs a multi-stage purification route, including a metal removal module, a stripping module for light component removal, and an evaporation separation module, to achieve deep removal of metal residues, solvents, light oil components, and oligomers from crude wax. Particularly addressing the challenge of effectively removing metal impurities, this device utilizes a reaction vessel and the synergistic action of a polymeric chelating agent and a flocculant to transform fine metals into filterable larger particles, achieving deep removal of metal impurities and ensuring the final wax product has higher purity, lighter color, and better thermal stability. Furthermore, the high-temperature light component steam generated in the evaporation separation module is pressurized by a steam jet pump and then returned to the middle of the stripping module as stripping gas. This provides the necessary heat and carrier for the stripping process, reducing external stripping steam consumption, achieving energy recycling within the device, minimizing heat loss, and lowering overall energy consumption. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the overall process flow of this device;

[0037] In the diagram: 1-Reaction vessel; 2-Chlorinating agent storage tank; 3-Flocculant storage tank; 4-Filter unit; 5-Stripping tower; 6-Evaporator; 7-Heater; 8-Ejector pump; 9-First-stage condenser; 10-Second-stage condenser; 11-Phase separation tank; 12-Oligomer buffer tank; 13-Wastewater collection tank; 14-Wax product buffer tank. Detailed Implementation

[0038] The present invention will now be described in detail. Any aspects not described in detail are technical solutions already disclosed in the field.

[0039] Reference Figure 1 As shown, a refining and separation device for preparing ultra-high purity polyethylene wax includes a metal removal module, a stripping module for removing light oil components, and an evaporation separation module. The metal removal module is mainly used to remove metal impurities from the raw materials. Specifically, it includes a reactor 1, a reagent storage tank connected to the feed port of the reactor 1, and a filtration unit 4 connected downstream of the reactor 1. The reagent storage tank includes a chelating agent storage tank 2 for storing polymeric chelating agents and a flocculant storage tank 3 for storing flocculants, used to add polymeric chelating agents and flocculants to the reactor 1, respectively. The filtration unit 4 consists of filters, including but not limited to plate and frame filters, chamber filter presses, and bag filters. The stripping module for removing light oil components is fluidly connected to the metal removal module and is used to strip light oil components under vacuum. The evaporation separation module is fluidly connected to the heavy phase outlet of the stripping module and is used to deeply remove oligomers and moisture under higher vacuum. After the polyethylene wax raw material is fed into reactor 1 and heated and melted, chelating agent and flocculant are added to reactor 1 respectively. The metal impurities in the polyethylene wax raw material are chelated with the chelating agent and then further flocculated with the flocculant. After agglomeration, they form large particles, which are removed by filtration. Then, the solvent and light components are removed by the stripping module, and the oligomers and water are further removed by the evaporation separation module to obtain ultra-high purity polyethylene wax with low metal impurity content and low organic residue.

[0040] As a preferred embodiment, the reactor is a mixing tank with temperature control and stirring functions. It is the place for chelation and flocculation reactions and can be temperature controlled (for example, by setting up a heat exchange jacket or setting up internal heating components).

[0041] The polymeric chelating agent in chelating agent storage tank 2 is selected from maleic anhydride-grafted polymeric chelating agents, ethylene-acrylic acid copolymer (EAA), and ethylene-methacrylic acid copolymer (EMAA). In the molten state, the polymeric chelating agent chelates with the metal in polyethylene wax to form macromolecular chelated particles. Further, maleic anhydride-grafted polymeric chelating agents include maleic anhydride-grafted polyethylene wax, maleic anhydride-grafted polypropylene, and maleic anhydride-grafted polyethylene. In specific implementations, commercially available Kraton MA-g-PP and MA-g-PE series products, and Arkema products can be selected, for example. 18302, Dow Chemical's AMPLIFYTY1053H, Aladdin polyethylene grafted maleic anhydride (CAS No. 9006-26-2); ethylene-acrylic acid copolymer (EAA) can be selected from DuPont. Furthermore, the amount of polymeric chelating agent used is 0.01%-5% of the mass of the polyethylene wax raw material, preferably 0.05%-1.0%, and more preferably 0.1%-0.5%.

[0042] The flocculant in flocculant storage tank 3 can be a polymeric flocculant suitable for solid-liquid separation, selected from polyacrylamide flocculants, acrylic acid / methacrylic acid grafted polyethylene wax, and styrene-maleic anhydride copolymer grafted polyethylene wax (SMA). Preferably, the polyacrylamide flocculant is a nonionic polyacrylamide, with a molecular weight more preferably 5 million to 12 million. Flocculants in this molecular weight range have excellent bridging flocculation effect. Further, the amount of flocculant used is 0.01%-2% of the mass of the polyethylene wax raw material, preferably 0.01%-0.1%, and more preferably 0.03%-0.05%.

[0043] In a preferred embodiment, the filtration unit 4 can be configured as a multi-stage filtration system, consisting of a coarse filter and a precision filter. The coarse filter uses a filter screen with a pore size of 150-200 micrometers (80-120 mesh), while the precision filter uses a filter screen with a pore size of 1-100 micrometers (such as a pleated filter element or ceramic membrane), more preferably 10-50 micrometers. After the coarse filter performs preliminary filtration of large particles, the precision filter further reduces residual particulate impurities in the raw material more efficiently.

[0044] As a preferred embodiment, the stripping and light removal module includes a stripping tower 5, a tower bottom pump, and a heater 7. The inlet of the tower bottom pump is connected to the tower bottom outlet of the stripping tower 5, and its outlet returns to the stripping tower 5 via the heater 7, and is also connected to the evaporation separation module.

[0045] In a preferred embodiment, the evaporation separation module includes an evaporator 6. The vapor phase outlet of the evaporator 6 is connected to the middle of the stripping tower 5 via a jet pump 8. The evaporator 6 can be a scraped film evaporator, a falling film evaporator, or a short-path distiller. The bottom outlet of the evaporator 6 is connected to the inlet of a transfer pump. One outlet of the transfer pump returns to the top of the evaporator 6, and the other outlet serves as the finished product outlet.

[0046] The vapor phase outlet of the evaporation separation module of this device is connected to the middle of the stripping module for removing light components. The distilled light components are reused as stripping gas to provide heat for the stripping process, reducing external stripping steam consumption, achieving energy recycling within the device, reducing heat loss, and lowering overall energy consumption. Preferably, the absolute pressure of the stripping tower 5 in the evaporation separation module is 10–50 kPa, more preferably 10–20 kPa, and the absolute pressure of the evaporator 6 in the evaporation separation module is 0.1–10 kPa, more preferably 1–8 kPa, and even more preferably 1–2 kPa.

[0047] In a preferred embodiment, the device further includes a light component condensation and recovery module and a refined wax product forming module. The light component condensation and recovery module is connected to the vapor phase outlet process fluid of the stripping and light component removal module, and is used to condense and recover light oil and treat non-condensable gas. The refined wax product forming module is connected to the heavy phase outlet process fluid of the evaporation and separation module, and is used to solidify and form the refined wax product.

[0048] Specifically, the light component condensation and recovery module includes a condenser, a phase separation tank 11, an oligomer buffer tank 12, and a wastewater collection tank 13. In a preferred embodiment, the condenser is configured with two stages, including a primary condenser 9 and a secondary condenser 10. The light components are first sent to the primary condenser 9 for condensation, and the incompletely condensed components are sent to the secondary condenser 10 for further condensation. All the condensate is sent to the phase separation tank 11, and the non-condensable gas is sent to the waste gas incinerator for incineration. The oil phase outlet of the phase separation tank 11 is connected to the oligomer buffer tank 12, and the water phase outlet is connected to the wastewater collection tank 13 through a pipeline. The material in the oligomer buffer tank 12 can be sold as a light oil product.

[0049] Specifically, the refined wax product molding module includes a wax product buffer tank 14, which is used to receive the refined polyethylene wax product from the evaporator 6. The wax product buffer tank 14 is connected to downstream flake machine, granulator or spray molding device, etc., and is sold as ultra-high purity and high quality polyethylene wax product after processing.

[0050] In practice, polyethylene wax, a byproduct of the polyethylene unit, is unloaded from a tank truck into a raw material tank (not shown in the figure). Some of the large solid catalyst and other impurities in the raw material are separated out by sedimentation within the tank. The polyethylene wax raw material is then pumped into the unit. The crude wax raw material is first sent to reactor 1 of the unit and heated to a low-viscosity liquid. A high-molecular-weight chelating agent is added through chelating agent storage tank 2. The process is carried out at a relatively high temperature (higher than the melting temperature of the polyethylene wax and the agent, for example, 120-140℃) and a stirring speed of 150-250 rpm. The reaction proceeds for 30-60 minutes, allowing the metal ions to form chelated particles with the chelating agent. Then, flocculant is added through flocculant storage tank 3, and the reaction is carried out at a relatively high temperature (higher than the melting temperature of polyethylene wax and the agent, such as 120-130℃) and a stirring speed of 50-100 rpm for 20-30 minutes. This causes the chelated particles to agglomerate into large flocs. During this process, the polymeric chelating agent expands the metal ions from 0.1-1 nm to 0.1-5 μm, and after combining with the flocculant, they further agglomerate into 5-50 μm flocs, ensuring efficient and reliable retention by subsequent conventional filtration units. The reacted polyethylene wax liquid is filtered through filtration unit 4 to remove metal impurities before entering the top of stripping tower 5. The pressure at the top of the tower is 10-20 kPaA, and low-pressure stripping steam is introduced at the bottom of the tower to directly strip the light oil components from the crude wax. The bottom pump draws out the liquid from the bottom of the stripping tower. A portion is heated by heater 7 and returned to stripping tower 5 to replenish the heat required for light oil evaporation. The other portion enters evaporator 6 for further removal of oligomers. The top vapor and light oil of stripping tower 5 enter the condenser for condensation. The condensate from the condenser enters the phase separation tank, and the non-condensed liquid is sent to the waste gas incinerator for incineration. In the phase separation tank, light oil and condensate are separated. The aqueous phase enters the wastewater collection tank, and the overflow is discharged into the plant's oily wastewater system. The oil phase from the phase separation tank is sent to the oligomer buffer tank for storage and is periodically sold as by-product light oil. The polyethylene wax, from which light oil has been removed, enters evaporator 6 for further processing. For example, a scraped film evaporator can be used. The wax is distributed through a top distribution plate, and the wax flows downward along the wall of the evaporator. The scraper continuously rotates and refreshes the descending liquid film, causing the trace amounts of water and some low-boiling-point polymers to evaporate deeply. The evaporated gas is extracted by a jet pump, pressurized, and then enters the stripping tower as stripping gas. Evaporator 6 provides a higher vacuum level than stripping tower 5, which is more conducive to the evaporation of oligomers in polyethylene wax. After being processed by evaporator 6, qualified wax liquid is drawn out from the bottom. Part of it is returned to the top of evaporator 6 as reflux, and the other part is sent to the wax product buffer tank for storage as finished wax. Then it is sent to the sheeting machine for sheeting and solidification. After being packaged by the packaging machine, it becomes the final wax product for sale.

[0051] The above description of the embodiments is provided to enable those skilled in the art to understand and use the utility model. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present utility model is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present utility model without departing from its scope should be within the protection scope of the present utility model.

Claims

1. A refining and separation apparatus for preparing ultra-high purity polyethylene wax, characterized in that, include: A metal removal module is used to remove metal impurities from raw materials, including a reaction vessel, a reagent storage tank connected to the feed port of the reaction vessel, and a filter unit connected downstream of the reaction vessel. The stripping module for removing light oil components is in process fluid communication with the metal impurity removal module and is used to strip light oil components under vacuum. The evaporation separation module is connected to the heavy phase outlet process fluid of the stripping and light phase removal module, and is used to deeply remove oligomers and moisture under higher vacuum.

2. The refining and separation apparatus for preparing ultra-high purity polyethylene wax according to claim 1, characterized in that, The reactor is a mixing vessel with temperature control and stirring functions; The pharmaceutical storage tanks include chelating agent storage tanks for storing polymeric chelating agents and flocculant storage tanks for storing flocculants.

3. The refining and separation apparatus for preparing ultra-high purity polyethylene wax according to claim 1, characterized in that, The filtration unit consists of a filter, including but not limited to one of a plate and frame filter, a chamber filter press, and a bag filter.

4. The refining and separation apparatus for preparing ultra-high purity polyethylene wax according to claim 3, characterized in that, The filtration unit is configured for multi-stage filtration, consisting of a coarse filter and a precision filter.

5. The refining and separation apparatus for preparing ultra-high purity polyethylene wax according to claim 1, characterized in that, The vapor phase outlet of the evaporation separation module is connected to the middle of the stripping light component removal module so that the evaporated light component can be reused as stripping gas.

6. The refining and separation apparatus for preparing ultra-high purity polyethylene wax according to claim 1, characterized in that, The stripping and light-duty removal module includes a stripping tower, a tower bottom pump, and a heater; The inlet of the tower bottom pump is connected to the outlet of the stripping tower, and its outlet is returned to the stripping tower via the heater, and connected to the evaporation separation module via another path.

7. A refining and separation apparatus for preparing ultra-high purity polyethylene wax according to claim 6, characterized in that, The evaporation separation module includes an evaporator, and the vapor phase outlet of the evaporator is connected to the stripping tower via a jet pump. The bottom outlet of the evaporator is connected to the inlet of a delivery pump. One outlet of the delivery pump returns to the top of the evaporator, and the other outlet serves as the finished product outlet.

8. The refining and separation apparatus for preparing ultra-high purity polyethylene wax according to claim 1, characterized in that, The device also includes: The light component condensation and recovery module is connected to the vapor phase outlet process fluid of the stripping and light component removal module, and is used to condense and recover light oil and treat non-condensable gas. The refined wax product forming module is connected to the heavy phase outlet process fluid of the evaporation separation module and is used to solidify and shape the refined wax product.

9. A refining and separation apparatus for preparing ultra-high purity polyethylene wax according to claim 8, characterized in that, The light component condensation and recovery module includes a condenser, a phase separation tank, an oligomer buffer tank, and a wastewater collection tank. The light components of the stripping light module are sent to the condenser for condensation, the condensate is sent to the phase separation tank, and the non-condensable gas is sent to the waste gas incinerator for incineration. The oil phase outlet of the phase separation tank is connected to the oligomer buffer tank, and the aqueous phase outlet is connected to the wastewater collection tank via a pipeline.

10. A refining and separation apparatus for preparing ultra-high purity polyethylene wax according to claim 8, characterized in that, The refined wax product forming module includes a wax product buffer tank, which is connected to a downstream flake machine, granulator, or spray molding device.

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