Method for continuously removing light components in polyether polyol

Abstract

The invention relates to the technical field of polyether polyol refining, and particularly discloses a method for continuously removing light components in polyether polyol, which comprises the following steps: mixing polyether polyol and deoxygenated water; according to the method, polyether polyol is continuously added into a light component removal tower and a dehydration tower, light components and water in the polyether polyol are removed through a process combining reduced-pressure flash evaporation, bubbling temperature increasing, steam stripping and nitrogen stripping, and purified polyether polyol is obtained. The difficulty of polyol quality control in the production stage is reduced, and the content of formaldehyde, acetaldehyde and propionaldehyde in the purified polyether polyol product obtained by the method can be as low as 10 ppm or below and is at the advanced level of the industry.

Description

Technical Field

[0001] The invention belongs to the technical field of polyether polyol refining, and in particular relates to a method for continuously removing light components from polyether polyol. Background Art

[0002] The existing production process of polyether polyols (KOH intermittent process for producing polyether) mainly includes the preparation of initiator, preparation of prepolymer, polyol polymerization reaction, neutralization and dehydration, polyol filtration and other processes. Through the above process, the polyether polyol products are temporarily stored in the polyol quality control tank, which can meet the requirements of low-end products on the market. However, at this time, there are still trace amounts of volatile monomers in the finished polyols. They have odors. Although the content is very small and the odor is very low, it will affect the sales and quality of the terminal products. Therefore, how to obtain low-odor polyol products has become a key task in the industry.

[0003] Chinese patent CN201510963018.6 describes a method for reducing residual ethylene oxide in polyether polyols, in which amine substances are added to a closed reactor to react under a certain pressure and temperature, and then high-quality polyols are obtained through post-treatment. This method is limited to reducing ethylene oxide and has no effect on other volatile components.

[0004] Chinese patent CN201911153406.2 introduces a method for reducing volatile components in polyether polyols, which includes adding a formaldehyde remover into a reactor, adding water and an adsorbent after the reaction, and then stirring, drying, and filtering to obtain a qualified product. The volatile components are effectively removed by chemical methods and nitrogen bubbling.

[0005] Chinese patent CN105037703A introduces a method for extracting formaldehyde and acetaldehyde from polyether polyols, which uses steam and nitrogen directly introduced into a reactor, and then vacuum extraction for a long time to remove formaldehyde and acetaldehyde from the polyols. The method directly uses a reactor and operates intermittently, and each batch of treatment takes 4-10 hours.

[0006] The above patents either only have the effect of removing ethylene oxide, or the treatment process is intermittent production, and the process is relatively complicated and may generate solid waste.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for continuously removing light components in polyether polyols. The method is continuously operated, which makes up for the shortcomings of intermittent operation in traditional processes causing product quality fluctuations, reduces energy consumption, and further reduces the remaining light components in polyether polyols, thereby improving the quality of polyether polyol products.

[0009] The technical solution adopted by the present invention is a method for continuously removing light components in polyether polyols, comprising: mixing polyether polyols and deoxygenated water to obtain a first mixture; continuously adding the first mixture to a light-removing tower to form a countercurrent with the water vapor introduced into the light-removing tower to remove light components in the polyether polyols; and the second mixture discharged from the bottom of the light-removing tower enters a dehydration tower to remove water in the polyether polyols under the stripping action of an inert gas.

[0010] Optionally, the second mixture discharged from the bottom of the light removal tower enters a dehydration tower, and forms a countercurrent with the inert gas introduced into the dehydration tower to remove water from the polyether polyol.

[0011] Compared with common stripping, the present invention adds the process of premixing polyol and deoxygenated water and flash distillation under reduced pressure. Before entering the tower, polyether polyol and deoxygenated water are mixed to add a small amount of water. The water is used as a volatile medium, and the drop of the tower top pressure is fully utilized to form flash distillation, so as to promote the volatilization of light components. The light components are mainly aldehydes such as formaldehyde, acetaldehyde, and acrolein.

[0012] In certain technical solutions, the mass ratio of deoxygenated water to polyether polyol is 0.1%-0.5%, and the mixing temperature is 100°C-130°C.

[0013] Optionally, the first mixture of deoxygenated water and polyether polyol is an emulsion.

[0014] Optionally, the mass ratio of deoxygenated water to polyether polyol is 0.4%.

[0015] The present invention selects to use an oil-water mixer to mix deoxygenated water with polyether polyol. The oil-water mixer can be in various forms. Polyol and water are not miscible, but in the temperature range of 100°C to 130°C, the densities of water and polyol are relatively close. Therefore, the present invention selects to mix deoxygenated water with polyether polyol in the temperature range of 100°C to 130°C, preferably to form an emulsion. The smaller the droplet diameter in the emulsion and the more uniform the distribution in the polyol, the more fully the deoxygenated water and polyether polyol are mixed. The more fully the polyether polyol and the deoxygenated water are mixed, the more convenient it is for the light components in the polyether polyol to volatilize with the water when entering the light component removal tower for flash evaporation, so that the light component removal effect is better. At the same time, the ratio of the amount of water vapor introduced in the subsequent bubbling and heating stage to the amount of deoxygenated water is generally greater than 1.15. In order to reduce steam consumption and ensure the light component removal effect, the mass ratio of deoxygenated water to polyether polyol is maintained at 0.1%-0.5%.

[0016] In certain technical solutions, the operating temperature of the light-removal tower for polyether polyol is 120-145° C., and the tower top pressure is controlled at 3-10 kPaG.

[0017] Optionally, the operating temperature is 135°C and the top pressure is 5 kPaG.

[0018] The first mixture is preheated to 120℃-145℃ and enters the light-removal tower for reduced pressure flash evaporation to separate the water and some light components in the polyether polyol. This is the first removal of light components. If the temperature of the first mixture after preheating is too low, the light components cannot be effectively removed. If it is too high, the polyol will self-decompose. If the mass ratio of deoxygenated water to polyether polyol is too low, the flash evaporation effect will not be obvious. When the first mixture enters the light-removal tower for reduced pressure flash evaporation, the temperature of the polyether polyol will be reduced. Therefore, it is necessary to control the feed mass ratio of deoxygenated water and the pressure at the top of the tower. The temperature reduction range in the light-removal tower is controlled within 5℃-10℃.

[0019] In some technical schemes, a bubbling warming section is set in the light-removal tower, and a first packing section and a second packing section are respectively placed in the area above and below the bubbling warming section. Water vapor is introduced into the bubbling warming section. The mass of the introduced water vapor is 0.5%-0.75% of the mass of the polyether polyol, and the steam pressure is greater than 300KPaG.

[0020] Optionally, the mass of the water vapor introduced is 0.5% of the mass of the polyether polyol, and the steam pressure is 350 kPaG.

[0021] Optionally, a bubbling distributor is provided in the bubbling heating section.

[0022] Optionally, the bubble distributor is in the form of an accumulator.

[0023] The present invention creatively integrates steam bubbling inside the stripping tower, adds a packing section, and solves the effect of the temperature reduction of the polyether polyol after flash evaporation on the stripping effect. In the bubbling and warming section, two main purposes are achieved. The first purpose is to use superheated steam bubbling to increase the chance of gas-liquid contact again, achieve the re-mixing contact of steam in the polyether polyol, and the polyether polyol containing saturated water can be used as the liquid phase of the next stage of stripping to improve the stripping efficiency. The second purpose is that the steam after bubbling enters the first packing section. At this time, through the contact between the packing and the superheated steam, the temperature of the polyether polyol after flash evaporation is restored to the normal operating temperature, and at the same time, the effect of bubbling on the removal of light components is improved. This is the second removal of light components.

[0024] The water vapor introduced into the bubbling heating section is greater than 300KPaG to avoid the temperature being too low and affecting the heating effect. The amount of water vapor used is slightly higher than the amount of deoxygenated water. It is appropriate to control the bubbling residence time to 5-10min. Long-term high temperature will cause the self-decomposition of the polyether polyol, which will increase the amount of light components. The bubbling distributor set in this part can evenly disperse the steam inside the polyether polyol to improve the removal efficiency of the light components.

[0025] In certain technical solutions, the specific surface area of ​​the filler in the first filler section is smaller than the specific surface area of ​​the filler in the second filler section; and the height of the first filler section is smaller than the height of the second filler section.

[0026] Optionally, the height of the second packing section is 2-6 times the height of the first packing section.

[0027] Optionally, the height of the second packing section is four times the height of the first packing section.

[0028] The height of the first packing section above the bubbling warming section does not need to be too high. It does not focus on mass transfer, but only needs to consider the recovery of the polyol temperature to increase the bubbling removal effect and increase the efficiency of the lower stripping section. The second packing section below the bubbling warming section mainly considers the separation efficiency. Its height needs to be determined in combination with the light component content in the polyether polyol. It should not be too high to avoid increasing the pressure drop in the tower and affecting the removal of light components.

[0029] In certain technical solutions, the mass ratio of stripping steam to polyether polyol is 1%-4%, and the steam pressure is greater than 300 KPaG.

[0030] Optionally, the steam pressure is greater than 350 KPaG.

[0031] After the stripping steam from the bottom of the tower enters the tower, it is initially distributed to improve the uniform distribution of the gas phase load in the tower. The tower uses the steam and vacuum system to form a high-temperature / high-vacuum volatile environment. The steam and polyether polyol form a large area of ​​gas-liquid contact on the surface of the filler to achieve complete removal of light components. This is the third removal of light components and is also the final stage of light component removal.

[0032] The tail gas at the top of the light-removal tower is mainly water vapor, and the rest are volatilized light components. There is no need to set up a demister in the tower to prevent the falling droplets from carrying dissolved light components into the polyether polyols. Instead, all gas phases enter the condenser for condensation. Most of the water is condensed and discharged as waste water, and a small amount of gas containing water and light components enters the vacuum system. This operation significantly reduces the load of the subsequent vacuum system. Considering the vacuum degree at the top of the tower, the gas phase temperature after condensation should be controlled at around 15°C, at which time most of the water in the tail gas is condensed into waste water.

[0033] In certain technical solutions, the operating temperature of the polyether polyol dehydration tower is 120°C-145°C, and the top pressure is controlled at 1-5 kPaG.

[0034] Optionally, the operating temperature is 135°C and the top pressure is 1 kPaG.

[0035] In certain technical solutions, the dehydration tower uses nitrogen as the stripping medium, the nitrogen temperature does not exceed 145° C., and the mass ratio of nitrogen to polyol is 0.1%-0.5%.

[0036] Optionally, the nitrogen temperature is 85°C-120°C.

[0037] Optionally, the mass ratio of nitrogen to polyol is 0.2%.

[0038] When the light-removal tower uses steam to strip polyether polyol, the material will contain a small amount of water, which needs to be further removed. The material after the light components are removed flows out from the bottom of the light-removal tower, and the temperature of the polyether polyol entering the dehydration tower is preheated to 120℃-145℃; the dehydration tower uses hot nitrogen as the stripping medium, which flows in the tower in the opposite direction to the polyol to remove the water. The tail gas at the top of the dehydration tower contains nitrogen and water vapor, which is condensed by the condenser and extracted by the vacuum pump. Nitrogen can be heated by the tail gas discharged from the top of the light-removal tower. The temperature of the heated nitrogen does not exceed the temperature at the top of the dehydration tower, and no additional energy consumption is added.

[0039] In certain technical solutions, the internal temperature of the lightness removal tower and the dehydration tower is between 120°C and 145°C.

[0040] Optionally, the de-light tower and dehydration tower can be heated by external jackets.

[0041] Optionally, the heating temperature of the lightness removal tower and the dehydration tower is within ±5°C of the operating temperature of the polyether polyol.

[0042] The temperature changes at the top and bottom of the light-removal tower and the top and bottom of the dehydration tower are small and negligible. The use of external jacket heating in the light-removal tower and the dehydration tower can prevent the poor insulation effect of the tower wall, which causes the wall temperature to be significantly lower than the temperature inside the tower, and improve the fluidity of the polyether polyol near the tower wall.

[0043] The invention provides a device for stripping light components in polyether polyols, comprising: an oil-water mixer (7), connected to a lightness removal tower preheater (3) and a lightness removal tower (1) through a pipeline, the top of the lightness removal tower (1) is connected to a nitrogen preheater (8) and a lightness removal tower condenser (5) through a pipeline, the bottom of the lightness removal tower (1) is connected to a dehydration tower preheater (4) and the top of a dehydration tower (2) through a pipeline, and the top of the dehydration tower (2) is connected to a dehydration tower condenser (6) through a pipeline.

[0044] After adopting the above technical scheme, the present invention has the following beneficial effects compared with the prior art.

[0045] Compared with common steam stripping, the present invention adds the process of premixing polyether polyol and deoxygenated water and vacuum flash evaporation, increases the contact between water and polyether polyol, strengthens the removal effect of light components, and effectively reduces the steam consumption;

[0046] The present invention creatively integrates steam bubbling inside the stripping tower, adds a packing section, and solves the problem of the influence of the temperature reduction of the polyether polyol after flash evaporation on the stripping effect;

[0047] The present invention is operated continuously and is not very sensitive to the light component content in the raw material (tens to 1000 ppm can be removed), which makes up for the disadvantage of product quality fluctuation caused by intermittent operation in the traditional process, and at the same time reduces the difficulty of polyol quality control in the production stage. The steam consumption of the present invention can be reduced to 2.5%-6% of the mass flow rate of the polyether polyol, which is significantly lower than the steam consumption in intermittent processing;

[0048] The content of formaldehyde, acetaldehyde and propionaldehyde in the purified polyether polyol product obtained by the present invention can be as low as below 10 ppm, which is at a relatively advanced level in the industry.

[0049] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings described below are only some embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the accompanying drawings:

[0051] Figure 1 This is a schematic diagram of a process flow for continuously removing light components from polyether polyols according to the present invention;

[0052] Figure numerals: 1-delightness removal tower; 2-dehydration tower; 3-delightness removal tower preheater; 4-dehydration tower preheater; 5-delightness removal tower condenser; 6-dehydration tower condenser; 7-oil-water mixer; 8-nitrogen preheater.

[0053] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. The molecular weight of the polyether polyol in this application is the weight average molecular weight. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0055] Reference Figure 1The present invention provides a process flow diagram for continuously removing light components from a polyether polyol. The oil-water mixer (7), the light components removal tower preheater (3) and the light components removal tower (1) are sequentially connected via pipelines. The top of the light components removal tower (1) is sequentially connected to a nitrogen preheater (8) and a light components removal tower condenser (5). The bottom of the light components removal tower (1) is sequentially connected to a dehydration tower preheater (4) and the top of a dehydration tower (2) via pipelines. The top of the dehydration tower (2) is connected to a dehydration tower condenser (6).

[0056] The interior of the light-removal tower (1) is composed of a flash section, a first packing section, a bubbling and heating section, a second packing section, and a stripping section from top to bottom. The heating water vapor is introduced from the bottom of the bubbling and heating section. The bubbling and heating section is located in the middle of the light-removal tower (1). The stripping steam is introduced from the bottom of the light-removal tower (1), and the steam flow direction is countercurrent to the material. The light-removal tower (1) is provided with an outer jacket, and the heating steam enters from the top of the outer jacket from top to bottom, and the condensed water is discharged from the bottom.

[0057] The dehydration tower (2) uses hot nitrogen as a stripping medium. The nitrogen is heated by the tail gas at the top of the light removal tower through a nitrogen preheater (8) and enters from the bottom of the dehydration tower (2). The nitrogen flow direction is countercurrent to the material. The dehydration tower (2) is provided with an outer jacket, and the heating steam enters from the top of the outer jacket from top to bottom, and the condensed water is discharged from the bottom.

[0058] The polyether polyol and deoxygenated water are fully mixed in an oil-water mixer (7), and the mixed material is preheated in a lightness removal tower preheater (3) and then enters the lightness removal tower (1) from the top, undergoes reduced pressure flash evaporation, bubbling heating, and steam stripping in sequence, and then flows out from the bottom of the tower kettle of the lightness removal tower (1) to obtain a light-removed polyether polyol; the removed light components are discharged from the top of the lightness removal tower (1) along with the steam, and are discharged as condensed waste water through a lightness removal tower condenser (5).

[0059] The polyether polyol after light removal is heated by a dehydration tower preheater (4), enters the dehydration tower (2) from the top, undergoes nitrogen stripping, and flows out from the bottom of the dehydration tower (2) to obtain a purified polyether polyol product; the removed water is discharged from the top of the dehydration tower (2) along with the nitrogen, and is discharged as condensed waste water through a dehydration tower condenser (6).

[0060] Example 1

[0061] Combined with Figure 1 The process flow for continuously removing light components from polyether polyols is shown, and the polyether polyols produced by the PPG device are post-treated to obtain purified polyether polyol products.

[0062] 1) Raw materials:

[0063] The molecular weight of the polyether polyol is about 4800, the temperature is 50°C, and the mass content of light components is 0.11wt% (mainly formaldehyde, acetaldehyde and other aldehydes).

[0064] 2) Main equipment and specifications:

[0065] Lightness removal tower: diameter 1000mm, height 15000mm, outer jacket heating,

[0066] Heating section filler: height 1 meter, specific surface area 250m 2 / m 3

[0067] Stripping section packing: height 4 meters, specific surface area 250m 2 / m 3

[0068] Dehydration tower: diameter 800mm, height 13000mm, outer jacket heating,

[0069] Stripping section packing: height 4 meters, specific surface area 250m 2 / m 3

[0070] Lightness removal tower preheater: heat exchange area 114m 2 , Dehydration tower preheater: heat exchange area 76m 2

[0071] Light removal tower condenser: heat exchange area 120m 2 , Dehydration tower condenser: heat exchange area 70m 2

[0072] Oil-water mixer: diameter 200mm, height 500mm

[0073] Nitrogen preheater: internal coil.

[0074] 3) Main operation steps:

[0075] S1: Deoxygenated water and polyether polyol enter the oil-water mixer at flow rates of 10 kg / h and 10 t / h respectively and are fully mixed at 50° C. to obtain a first mixture;

[0076] S2: The first mixture is preheated by a lightness removal tower preheater;

[0077] S3: The preheated first mixture enters the light removal tower from the top of the tower at a flow rate of 10 t / h and a temperature of 121°C, the bubbling heating steam is introduced into the light removal tower at a flow rate of 15 kg / h, and the stripping steam is introduced into the light removal tower from the bottom of the tower at a flow rate of 235 kg / h for mixed stripping;

[0078] The top temperature of the light removal tower is 119°C, and the top pressure is 3-5.4 kPaA; the bubbling steam pressure is 300 KPaG, and the stripping steam pressure is 250 KPaG;

[0079] S4: The removed light components (mainly formaldehyde, acetaldehyde and other aldehydes) are discharged from the top of the light removal tower along with steam as the top tail gas at a flow rate of 271 kg / h and a temperature of 121°C; the second mixture after light removal is discharged from the bottom of the tower;

[0080] S5: The second mixture is preheated by a dehydration tower preheater;

[0081] S6: the preheated second mixture enters from the top of the dehydration tower at a flow rate of 10 t / h and a temperature of 122°C, and the heated nitrogen enters from the bottom of the dehydration tower at a flow rate of 15 kg / h and a temperature of 90°C, and the second mixture contacts the nitrogen to be stripped;

[0082] The top temperature of the dehydration tower is 120°C and the pressure is 1.5 kPaA;

[0083] S7: The removed water is discharged from the top of the dehydration tower along with nitrogen as tail gas, and the tail gas temperature is 20°C; the purified polyether polyol product obtained after stripping flows out from the bottom of the dehydration tower.

[0084] 4) Removal effect:

[0085] No light components were detected in the purified polyether polyol, and the odor was slight and basically odorless.

[0086] 5) Stripping medium dosage:

[0087] Total steam consumption: 250kg / h, nitrogen consumption: 15kg / h

[0088] Example 2

[0089] Combined with Figure 1 The process flow for continuously removing light components from polyether polyols is shown, and the polyether polyols produced by the PPG device are post-treated to obtain purified polyether polyol products.

[0090] 1) Raw materials:

[0091] The molecular weight of polyether polyol is about 6000, the temperature is 70°C, and it contains light components (mainly formaldehyde, acetaldehyde and other aldehydes).

[0092] 2) Main equipment and specifications:

[0093] Light-removal tower: flash head diameter 700mm, flash head height 1500mm, flash head lower tower body diameter 600mm, total height of light-removal tower 15000mm, outer jacket heating,

[0094] Heating section filler: height 1 meter, specific surface area 100m 2 / m 3

[0095] Stripping section packing: height 4 meters, specific surface area 250m2 / m 3

[0096] Dehydration tower: diameter 600mm, height 13000mm, outer jacket heating,

[0097] Stripping section packing: height 3 meters, specific surface area 350m 2 / m 3

[0098] Lightness removal tower preheater: heat exchange area 50m 2 , Dehydration tower preheater: heat exchange area 20m 2

[0099] Light removal tower condenser: heat exchange area 50m 2 , Dehydration tower condenser: heat exchange area 20m 2

[0100] Oil-water mixer: diameter 200mm, height 500mm

[0101] Nitrogen preheater: internal coil.

[0102] 3) Main operating parameters:

[0103] S1: Deoxygenated water and polyether polyol enter the oil-water mixer at flow rates of 12.5 kg / h and 5 t / h respectively and are fully mixed at 70° C. to obtain a first mixture;

[0104] S2: The first mixture is preheated by a lightness removal tower preheater;

[0105] S3: The preheated first mixture enters the light removal tower from the top of the tower at a flow rate of 5 t / h and a temperature of 130°C, the bubbling heating steam is introduced into the light removal tower at a flow rate of 10 kg / h, and the stripping steam is introduced into the light removal tower from the bottom of the tower at a flow rate of 190 kg / h for mixed stripping;

[0106] The top temperature of the light removal tower is 125℃, and the top pressure is 4-5kPaA; the bubbling steam pressure is 300KPaG, and the stripping steam pressure is 250KPaG;

[0107] S4: The removed light components (mainly formaldehyde, acetaldehyde and other aldehydes) are discharged from the top of the light removal tower along with steam as the top tail gas at a flow rate of 217 kg / h and a temperature of 125°C; the second mixture after light removal is discharged from the bottom of the tower;

[0108] S5: The second mixture is preheated by a dehydration tower preheater;

[0109] S6: The preheated second mixture enters from the top of the dehydration tower at a flow rate of 5 t / h and a temperature of 130°C, and the heated nitrogen enters from the bottom of the dehydration tower at a flow rate of 10 kg / h and a temperature of 85°C, and the second mixture contacts the nitrogen to be stripped;

[0110] The top temperature of the dehydration tower is 130°C and the pressure is 1kPaA;

[0111] S7: The removed water is discharged from the top of the dehydration tower along with nitrogen as tail gas, and the tail gas temperature is 20°C; the purified polyether polyol product obtained after stripping flows out from the bottom of the dehydration tower.

[0112] 4) Removal effect:

[0113] The purified polyether polyol is odorless, and the light component content in the product is compared as shown in Table 1.

[0114] Table 1:

[0115]

[0116] As can be seen from Table 1, the light component content of the purified polyether polyol product obtained by post-treatment in Example 2 meets the requirements.

[0117] 5) Stripping medium dosage:

[0118] Total steam consumption: 200kg / h, nitrogen consumption: 10kg / h

[0119] Comparative Example 1:

[0120] The polyether polyol was treated by an intermittent operation device. 1 t of the same polyether polyol raw material as in Example 1 was prepared and placed in a reactor. Steam at 180° C. was introduced into the reactor for light removal treatment. The steam flow rate was 1 m 3 / min, the duration is 2h, and the material after light removal is dehydrated using nitrogen as the medium to obtain a purified polyether polyol product.

[0121] According to the water vapor density table, the steam density is 0.8036 kg / m 3 The total steam consumption for intermittent operation to process 1 ton of polyether polyol is 120m 3 The steam consumption is calculated to be 96.4 kg. When treating 10 t of the same polyether polyol as in Example 1, the steam consumption is 964 kg, which is much higher than the 250 kg steam used in Example 1.

[0122] Comparative Example 2:

[0123] Combined with Figure 1 The process flow for continuously removing light components from polyether polyols is shown, and the polyether polyols produced by the PPG device are post-treated to obtain purified polyether polyol products.

[0124] When the temperature of the first mixture entering the lightness removal tower is changed to 115°C, the other raw material conditions, main equipment and specifications, and main operating steps are the same as those in Example 1. The formaldehyde and acetaldehyde contents in the obtained purified polyether polyol product are less than 10 ppm, meeting the process requirements. The propionaldehyde content is 156 ppm, which is significantly higher than the technical requirements (general technical requirements for the propionaldehyde content to be less than 20 ppm, preferably less than 10 ppm).

[0125] Comparative Example 3:

[0126] Combined with Figure 1 The process flow for continuously removing light components from polyether polyols is shown, and the polyether polyols produced by the PPG device are post-treated to obtain purified polyether polyol products.

[0127] When the temperature at which the first mixture enters the light-removal tower is changed to 150° C., other raw material conditions, main equipment and specifications, and main operating steps are the same as those in Example 1, and the formaldehyde and acetaldehyde contents in the obtained purified polyether polyol product are 15 ppm and 23 ppm, respectively. Therefore, the temperature at which the first mixture enters the light-removal tower is too high, which increases the self-decomposition of the polyol and reduces the removal effect of the light components.

[0128] Comparative Example 4

[0129] Combined with Figure 1 The process flow for continuously removing light components from polyether polyols is shown, and the polyether polyols produced by the PPG device are post-treated to obtain purified polyether polyol products.

[0130] In step S1, deoxygenated water and polyether polyol enter the oil-water mixer at flow rates of 0 kg / h and 10 t / h respectively and are fully mixed at 50° C. to obtain a first mixture, wherein the mass ratio of deoxygenated water to polyether polyol is less than 0.1%;

[0131] Other raw material conditions, main equipment and specifications, and main operating steps are the same as those in Example 1. The required stripping steam for the obtained polyol product of the same specifications is as high as 450 kg / h, which significantly increases the amount of stripping steam, while the consumption of warming steam is only reduced by 15 kg / h. The total steam consumption is significantly increased compared with Example 1, so the amount of deoxygenated water must not be too low.

[0132] Comparative Example 5

[0133] Combined with Figure 1 The process flow for continuously removing light components from polyether polyols is shown, and the polyether polyols produced by the PPG device are post-treated to obtain purified polyether polyol products.

[0134] In step S1, deoxygenated water and polyether polyol enter the oil-water mixer at flow rates of 100 kg / h and 10 t / h, respectively, and are fully mixed at 50° C. to obtain a first mixture, wherein the mass ratio of deoxygenated water to polyether polyol is 1%;

[0135] Other raw material conditions, main equipment and specifications, and main operating steps are the same as those in Example 1. Purified polyether polyol products of the same specifications are obtained. The required amount of bubbling and heating steam is increased to 120 kg / h, and the amount of stripping steam is the same as in Example 1. The total steam consumption is significantly increased. Therefore, in order to reduce steam consumption and ensure the de-lightening effect, the amount of deoxygenated water should not be too high.

[0136] Conclusion: The amount of steam used when indirectly treating polyether polyols using comparative example 1 is significantly greater than the amount of steam used in Example 1; the removal effect of light components in the purified polyether polyol products obtained in comparative examples 2-3 is lower than that in Example 1, indicating that too low or too high a temperature after preheating of the first mixture will reduce the removal effect of light components; compared with Example 1, purified polyether polyol products of the same specification obtained in comparative examples 4-5 have significantly increased steam consumption, indicating that while ensuring the light component removal effect, reducing steam consumption requires controlling the mass ratio of deoxygenated water to polyether polyol to 0.1%-0.5%; the above embodiments and comparative examples can prove that the method provided by the present invention provides a method for continuously removing light components in polyether polyols, which reduces energy consumption compared to the intermittent operation of the traditional process, further reduces the remaining light components in the polyether polyols, and improves the quality of the polyether polyol products.

[0137] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with the present invention can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A method for continuously removing light components from a polyether polyol, comprising: The polyether polyol and deoxygenated water are mixed to obtain a first mixture; the first mixture is continuously added to a light component removal tower to form a countercurrent with the water vapor introduced into the light component removal tower to remove light components in the polyether polyol; the second mixture discharged from the bottom of the light component removal tower is introduced into a dehydration tower to remove water in the polyether polyol under the stripping action of an inert gas; Preferably, the second mixture discharged from the bottom of the light-removal tower enters a dehydration tower, and forms a countercurrent with the inert gas introduced into the dehydration tower to remove water from the polyether polyol.

2. The method for continuously removing light components from polyether polyols according to claim 1, characterized in that: The mass ratio of deoxygenated water to polyether polyol is 0.1%-0.5%, and the mixing temperature is 100℃-130℃; Preferably, the first mixture of deoxygenated water and polyether polyol is an emulsion; preferably, the mass ratio of deoxygenated water to polyether polyol is 0.4%.

3. A method for continuously removing light components from polyether polyols according to claim 1 or 2, characterized in that: The operating temperature of the polyether polyol removal tower is 120-145°C, and the top pressure is controlled at 3-10kPaG. Preferably, the operating temperature is 135° C. and the tower top pressure is 5 kPaG.

4. A method for continuously removing light components from polyether polyols according to any one of claims 1 to 3, characterized in that: A bubbling temperature-increasing section is arranged in the light-removal tower, and a first packing section and a second packing section are respectively placed in the area above and below the bubbling temperature-increasing section, and water vapor is introduced into the bubbling temperature-increasing section, the mass of the introduced water vapor is 0.5%-0.75% of the mass of the polyether polyol, and the steam pressure is greater than 300KPaG; Preferably, the mass of the water vapor introduced is 0.5% of the mass of the polyether polyol, and the steam pressure is 350 kPaG Preferably, a bubbling distributor is provided in the bubbling temperature increasing section; Preferably, the bubble distributor is in the form of a liquid accumulator.

5. A method for continuously removing light components from polyether polyols according to claim 4, characterized in that: The specific surface area of ​​the filler in the first filler section is smaller than the specific surface area of ​​the filler in the second filler section; the height of the first filler section is smaller than the height of the second filler section; Preferably, the height of the second packing section is 2-6 times the height of the first packing section. More preferably, the height of the second packing section is 4 times the height of the first packing section.

6. A method for stripping light components from polyether polyols according to any one of claims 1 to 4, wherein the mass ratio of stripping steam to polyether polyol is 1% to 4%, the steam pressure is greater than 300 KPaG, Preferably, the steam pressure is greater than 350 KPaG.

7. The method for removing light components from polyether polyols by steam stripping according to claim 1, characterized in that: The operating temperature of the dehydration tower polyether polyol is 120℃-145℃, and the top pressure is controlled at 1-5kPaG. Preferably, the operating temperature is 135° C. and the tower top pressure is 1 kPaG.

8. A method for stripping light components in polyether polyols according to claim 7, characterized in that: The dehydration tower uses nitrogen as the stripping medium. The nitrogen temperature does not exceed 145°C. The mass ratio of nitrogen to polyol is 0.1%-0.5%. Preferably, the nitrogen temperature is 85°C-120°C; More preferably, the mass ratio of nitrogen to polyol is 0.2%.

9. A method for stripping light components from polyether polyols according to any one of claims 1 to 8, characterized in that: The internal temperature of the de-light tower and dehydration tower is 120℃-145℃. Preferably, the lightness removal tower and the dehydration tower are heated by external jackets. More preferably, the heating temperature of the lightness removal tower and the dehydration tower is within ±5°C of the operating temperature of the polyether polyol.

10. A device for use in the method for stripping light components in polyether polyols as claimed in claim 1, comprising: The oil-water mixer (7) is connected to the lightness removal tower preheater (3) and the lightness removal tower (1) through pipelines; the top of the lightness removal tower (1) is connected to the nitrogen preheater (8) and the lightness removal tower condenser (5) through pipelines; the bottom of the lightness removal tower (1) is connected to the dehydration tower preheater (4) and the top of the dehydration tower (2) through pipelines; and the top of the dehydration tower (2) is connected to the dehydration tower condenser (6) through pipelines.

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