CN113024355B - Method for recovering ethylene glycol in PTA (pure terephthalic acid) method - Google Patents
Method for recovering ethylene glycol in PTA (pure terephthalic acid) method Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
- C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
Abstract
The invention relates to the technical field of water-soluble polyester chip production, and discloses a method for recovering ethylene glycol in a PTA method. The invention has the following advantages and effects: the method comprises the steps of fractionating ethylene glycol, cooling distillate, recovering cooling liquid, filtering solid impurities and distilling ethylene glycol, separating ethylene terephthalate and ethylene glycol in esterified liquid on line, and optimizing the steps of fractionating the ethylene glycol and distilling the ethylene glycol, so that the purity of the ethylene glycol is ensured, and side reactions easily caused by redundant ethylene glycol in subsequent filtering and polymerization reactions can be avoided.
Description
Technical Field
The invention relates to the technical field of production of water-soluble polyester chips, in particular to a method for recovering ethylene glycol in a PTA (pure terephthalic acid) method.
Background
Polyester chip generally refers to a polyester raw material produced by polymerization and processed into flake-like particles of about 4 x 5 x 2 mm or so. At present, the water-soluble copolyester is prepared by two process routes, namely a direct esterification method (also called PTA method, PTA refers to fine terephthalic acid) or an ester exchange method (also called DMT method, DMT refers to dimethyl terephthalate), by using terephthalic acid and ethylene glycol as two main components, using isophthalic acid-5-sulfonate or dihydroxy ethyl isophthalate-5-sulfonate as a third component and using polyethylene glycol (PEG) as a fourth component. The reaction process can generate excessive glycol, and the recovered glycol can be directly reused in a polyester workshop, so that the raw material cost is saved, and the glycol has high recycling value.
Chinese patent No. CN105152863B discloses a method for recovering ethylene glycol and acetaldehyde from polyester wastewater. Treating the esterification wastewater in a stripping tower, introducing stripping tail gas condensate led out from the top of the stripping tower into an acetaldehyde rectifying tower, treating the acetaldehyde rectifying tower, recovering acetaldehyde vapor at the tower top, and introducing wastewater at the tower bottom into an ethylene glycol primary distillation tower; after being concentrated by the ethylene glycol primary distillation tower, the primarily concentrated ethylene glycol solution collected at the tower bottom enters the ethylene glycol distillation tower, and the gas at the tower top enters the gas stripping system again for circular treatment or is sent to a heating medium furnace for incineration; after being treated by the ethylene glycol rectifying tower, high-concentration ethylene glycol is obtained at the bottom of the tower, and high-temperature waste gas generated at the top of the tower is directly sent to a reboiler of the ethylene glycol primary tower to be used as a heat source.
The essence of the method is that low-content glycol is extracted from a large amount of waste water, and the whole extraction process needs to remove a large amount of water to obtain high-purity glycol. However, the above prior art solutions have the following drawbacks: in the invention, after the polyester chip reaction is finished, the glycol in the wastewater is collected, however, the glycol mainly participates in the esterification reaction, and the redundant glycol is easy to cause side reaction in the subsequent filtration and polymerization reaction, so that a method for separating the ethylene terephthalate and the glycol on line between the esterification reaction and the filtration step is needed, and the purity of the glycol is ensured, and the phenomenon that the redundant glycol is easy to cause side reaction in the subsequent filtration and polymerization reaction can be avoided.
Disclosure of Invention
The invention aims to provide a method for recovering ethylene glycol in a PTA method, which has the effect of ensuring the purity of the ethylene glycol and avoiding the phenomenon that redundant ethylene glycol is easy to cause side reaction in subsequent filtration and polymerization reactions.
The technical purpose of the invention is realized by the following technical scheme:
a method for recovering ethylene glycol in a PTA method comprises the steps of respectively carrying out treatments of ethylene glycol fractionation, distillate cooling, cooling liquid recovery, solid impurity filtration and ethylene glycol distillation by adopting a fractionating tower, a cooling tower, a recovery tank, a fine filter and a distillation kettle which are sequentially connected along the material conveying direction and are arranged between an esterification kettle and a filter of the PTA method, so as to obtain colorless liquid base ethylene glycol;
the specific implementation mode of fractionating the ethylene glycol is that the esterification liquid containing the ethylene glycol terephthalate is put into a fractionating tower, hot steam containing water and the ethylene glycol is introduced, the normal-pressure fractionation is carried out at 95-105 ℃, when the distilled water reaches 90% +/-5% of the theoretical distillation amount, the temperature in the fractionating tower is further raised to 280-;
the specific implementation mode of distilling the ethylene glycol is that the filtrate obtained by filtering solid impurities is put into a distillation kettle, most of water and low molecular substances with the boiling point of less than 195 ℃ are removed under the conditions of 95-105 ℃ and normal pressure, ethylene glycol steam with the gas phase temperature of 195-205 ℃ is condensed, ethylene glycol condensate containing a small amount of water and small molecular impurities is collected, and the content of the ethylene glycol in the condensate is determined to be more than or equal to 98 percent.
By adopting the technical scheme, the fractionating tower arranged between the esterification kettle and the filter of the PTA method is used for directly separating the glycol terephthalate and the glycol in the esterification liquid, so that water with higher content, glycol with lower content and other impurities are evaporated along with hot steam; wherein, the atmospheric fractionation is carried out in a lower temperature range (95-105 ℃) and then in a higher temperature range (280-290 ℃), which is to evaporate the water with larger content in the esterification liquid in the earlier stage of the fractionation so as to prevent a great amount of substances except the glycol from being separated from the esterification liquid in the later stage of the fractionation, thereby reducing the purification energy consumption of the glycol; then, water, low molecular substances, floccules and the like are taken out through three steps of cooling the distillate, recovering the cooling liquid and filtering solid impurities to obtain filtrate of higher-content water and lower-content glycol; finally distilling the filtrate through a distillation kettle to remove water and residual low molecular substances, and after the filtrate is gradually concentrated, continuously condensing and refluxing ethylene glycol steam with the gas phase temperature of 195-205 ℃ to obtain colorless liquid-based ethylene glycol with higher purity; in the process, the ethylene glycol terephthalate and the ethylene glycol in the esterification liquid are separated on line by arranging the processing steps of fractionating the ethylene glycol, cooling the distillate, recovering the cooling liquid, filtering solid impurities and distilling the ethylene glycol, and the purity of the ethylene glycol is ensured, and meanwhile, the phenomenon that the redundant ethylene glycol easily causes side reactions in subsequent filtering and polymerization reactions can be avoided by optimizing the steps of fractionating the ethylene glycol and distilling the ethylene glycol.
Furthermore, in the step of fractionating the glycol, the esterification liquid is statically heated to 260 ℃ and 270 ℃ at normal pressure in advance
Further, in the step of fractionating the ethylene glycol, 100-250kg of hot steam containing water and the ethylene glycol is introduced per ton of the esterification liquid, the temperature of the hot steam is 165-175 ℃, and the pressure of the hot steam is 250-350 kPa.
Specifically, the specific implementation manner of cooling the distillate and recovering the cooling liquid is that the distillate of the fractionating tower is transferred into a cooling tower, the cooling water is adopted to cool to 50-60 ℃, and then the obtained cooling liquid is stored in a recovery tank.
In particular, the recovery tank is used to purify ethylene glycol in a cooling liquid, wherein the heavy component stream is a bottoms stream from the recovery tank.
Furthermore, the recovery tanks are sequentially arranged along the material conveying direction, the recovery tanks sequentially cool the cooling liquid to 5-25 ℃ through cooling water, and the cooling water sequentially passes through the recovery tanks and the cooling tower along the direction opposite to the material conveying path.
Specifically, the specific implementation manner of filtering the solid impurities is to filter the cooling liquid in the recovery tank by using a fine filter to remove solid impurities such as low molecular substances and floccules in the raw material, so as to obtain a filtrate containing the ethylene glycol.
Further, in the step of distilling ethylene glycol, after ethylene glycol vapor with the vapor phase temperature of 195-205 ℃ is condensed, most of the recovery vapor composed of water and low molecular substances with the boiling point of less than 195 ℃ is condensed to obtain recovery liquid, after the recovery liquid passes through a heat exchanger, hot vapor containing water and ethylene glycol is obtained, and the hot vapor is conveyed to a fractionating tower.
Preferably, the reflux ratio of the distillation still is 16-18.
The invention has the beneficial effects that: the method comprises the steps of fractionating ethylene glycol, cooling distillate, recovering cooling liquid, filtering solid impurities and distilling ethylene glycol, separating ethylene terephthalate and ethylene glycol in esterified liquid on line, and optimizing the steps of fractionating the ethylene glycol and distilling the ethylene glycol, so that the purity of the ethylene glycol is ensured, and side reactions easily caused by redundant ethylene glycol in subsequent filtering and polymerization reactions can be avoided.
Detailed Description
The technical solution of the present invention will be clearly and completely described with reference to the specific embodiments. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without inventive step, shall fall within the scope of protection of the present invention.
Example 1: the invention discloses a method for recovering ethylene glycol in a PTA method, which comprises the step of respectively carrying out treatments of fractionating the ethylene glycol, cooling distillate, recovering cooling liquid, filtering solid impurities and distilling the ethylene glycol by adopting a fractionating tower, a cooling tower, three recovery tanks, a fine filter and a distillation kettle which are sequentially connected along the material conveying direction and are arranged between an esterification kettle and a filter of the PTA method, so as to obtain colorless liquid base ethylene glycol.
Specifically, the specific implementation mode of ethylene glycol fractionation is that esterification liquid containing ethylene terephthalate is statically heated to 260 ℃ under normal pressure in advance, then the esterification liquid is put into a fractionating tower, hot steam containing water and ethylene glycol is introduced, then normal-pressure fractionation is carried out at 100 ℃, when the distilled water content reaches 90% +/-5% of the theoretical distillation amount, the internal temperature of the fractionating tower is further raised to 290 ℃, the top temperature of the fractionating tower is raised to 190 +/-5 ℃, and redundant ethylene glycol is distilled out along with the hot steam to obtain distillate containing ethylene glycol. Wherein 150kg of hot steam containing water and ethylene glycol is introduced when feeding each ton of the esterification solution, and the temperature of the hot steam is 170 ℃ and the pressure is 275 kPa. In addition, the recovery rate of ethylene terephthalate in the fractionation column was measured to be 99.60%. 105
The specific implementation of cooling the distillate and recovering the cooling liquid is to transfer the distillate of the fractionating tower into a cooling tower, cool the distillate to 50 ℃ by using cooling water, and then store the obtained cooling liquid in a recovery tank. Wherein, these recovery tanks pass through the cooling water and in proper order with the cooling liquid cooling to 15 ℃, and the cooling water passes through these recovery tanks and cooling tower in proper order along the opposite direction of material transport route. The recovery tank is used for purifying the ethylene glycol in the cooling liquid, and the heavy component stream is a bottom stream from the recovery tank.
The specific implementation mode of filtering solid impurities is that a fine filter is adopted to filter the cooling liquid in the recovery tank, so as to remove solid impurities such as low molecular substances, floccules and the like in the raw materials, and obtain filtrate containing glycol.
The specific implementation mode of distilling the ethylene glycol is that the filtrate obtained by filtering solid impurities is put into a distillation kettle with the reflux ratio of 16, most of water and low molecular substances with the boiling point of less than 195 ℃ are removed under the conditions of 105 ℃ and normal pressure, ethylene glycol steam with the gas phase temperature of 195 ℃ is condensed, ethylene glycol condensate containing a small amount of water and small molecular impurities is collected, and the content of the ethylene glycol in the condensate is measured to be 99.52%. In order to realize the recycling of the mixture of water and glycol, after the glycol steam with the gas phase temperature of 205 ℃ is condensed, the recovered steam consisting of most of water and low molecular substances with the boiling point of less than 195 ℃ is condensed to obtain recovered liquid, the recovered liquid passes through a heat exchanger to obtain hot steam containing water and glycol, and the hot steam is conveyed to a fractionating tower.
Example 2: the invention discloses a method for recovering ethylene glycol in a PTA method, which comprises the step of respectively carrying out treatments of fractionating the ethylene glycol, cooling distillate, recovering cooling liquid, filtering solid impurities and distilling the ethylene glycol by adopting a fractionating tower, a cooling tower, three recovery tanks, a fine filter and a distillation kettle which are sequentially connected along the material conveying direction and are arranged between an esterification kettle and a filter of the PTA method, so as to obtain colorless liquid base ethylene glycol.
Specifically, the specific implementation mode of fractionating ethylene glycol is that esterification liquid containing ethylene terephthalate is statically heated to 265 ℃ at normal pressure in advance, then the esterification liquid is put into a fractionating tower, hot steam containing water and ethylene glycol is introduced, then normal-pressure fractionation is carried out at 105 ℃, when the distilled water content reaches 90% +/-5% of the theoretical distillation amount, the internal temperature of the fractionating tower is further increased to 285 ℃, the top temperature of the fractionating tower is increased to 190 +/-5 ℃, and redundant ethylene glycol is distilled out along with the hot steam to obtain distillate containing ethylene glycol. Wherein 175kg of hot steam containing water and ethylene glycol is introduced when feeding each ton of the esterification liquid, and the temperature of the hot steam is 165 ℃ and the pressure is 300 kPa. In addition, the recovery of ethylene terephthalate in the fractionation column was determined to be 98.60%.
The specific implementation of cooling the distillate and recovering the cooling liquid is to transfer the distillate from the fractionating tower to a cooling tower, cool the distillate to 55 ℃ with cooling water, and store the resulting cooling liquid in a recovery tank. Wherein, these recovery tanks pass through cooling water and cool down the coolant liquid to 25 ℃ in proper order, and cooling water passes through these recovery tanks and cooling tower in proper order along the opposite direction of material transfer route. The recovery tank is used for purifying the ethylene glycol in the cooling liquid, and the heavy component stream is a bottom stream from the recovery tank.
The specific implementation mode of filtering solid impurities is that a fine filter is adopted to filter the cooling liquid in the recovery tank, so as to remove solid impurities such as low molecular substances, floccules and the like in the raw materials, and obtain filtrate containing glycol.
The specific implementation mode of distilling the glycol is that the filtrate obtained by filtering solid impurities is put into a distillation still with the reflux ratio of 18, under the conditions of 100 ℃ and normal pressure, most of water and low molecular substances with the boiling point of less than 195 ℃ are removed, glycol steam with the gas phase temperature of 200 ℃ is condensed, glycol condensate containing a small amount of water and small molecular impurities is collected, and the content of the glycol in the condensate is measured to be 99.33%. In order to realize the recycling of the mixture of water and glycol, after the glycol steam with the gas phase temperature of 200 ℃ is condensed, the recovered steam consisting of most of water and low molecular substances with the boiling point of less than 195 ℃ is condensed to obtain recovered liquid, the recovered liquid passes through a heat exchanger to obtain hot steam containing water and glycol, and the hot steam is conveyed to a fractionating tower.
Example 3: the invention discloses a method for recovering ethylene glycol in a PTA method, which comprises the steps of respectively carrying out treatments of fractionating ethylene glycol, cooling distillate, recovering cooling liquid, filtering solid impurities and distilling ethylene glycol by adopting a fractionating tower, a cooling tower, three recovery tanks, a fine filter and a distillation kettle which are sequentially connected along the material conveying direction and are arranged between an esterification kettle and a filter of the PTA method, so as to obtain colorless liquid-based ethylene glycol.
Specifically, the specific implementation mode of fractionating ethylene glycol is that esterification liquid containing ethylene glycol terephthalate is statically heated to 256 ℃ at normal pressure in advance, then the esterification liquid is put into a fractionating tower, hot steam containing water and ethylene glycol is introduced, then normal-pressure fractionation is carried out at 95 ℃, when the distilled water content reaches 90% +/-5% of the theoretical distillation amount, the internal temperature of the fractionating tower is further raised to 280 ℃, the top temperature of the fractionating tower is raised to 190 +/-5 ℃, and redundant ethylene glycol is distilled out along with the hot steam to obtain distillate containing ethylene glycol. Wherein, when feeding each ton of esterification liquid, 200kg of hot steam containing water and glycol is introduced, and the temperature of the hot steam is 165 ℃ and the pressure is 350 kPa. In addition, the recovery rate of ethylene terephthalate in the fractionation column was determined to be 98.40%.
The specific implementation of cooling the distillate and recovering the cooling liquid is to transfer the distillate of the fractionating tower into a cooling tower, cool the distillate to 60 ℃ by using cooling water, and then store the obtained cooling liquid in a recovery tank. Wherein, these recovery tanks pass through the cooling water and in proper order with the cooling liquid cooling to 10 ℃, and the cooling water passes through these recovery tanks and cooling tower in proper order along the opposite direction of material transport route. The recovery tank is used for purifying the ethylene glycol in the cooling liquid, and the heavy component stream is a bottom stream from the recovery tank.
The specific implementation mode of filtering solid impurities is that a fine filter is adopted to filter the cooling liquid in the recovery tank, so as to remove solid impurities such as low molecular substances, floccules and the like in the raw materials, and obtain filtrate containing glycol.
The specific implementation mode of distilling the ethylene glycol is that the filtrate obtained by filtering solid impurities is put into a distillation kettle with the reflux ratio of 17, most of water and low molecular substances with the boiling point of less than 195 ℃ are removed under the conditions of 100 ℃ and normal pressure, the ethylene glycol steam with the gas phase temperature of 205 ℃ is condensed, the ethylene glycol condensate containing a small amount of water and small molecular impurities is collected, and the content of the ethylene glycol in the condensate is determined to be 98.93%. In order to realize the recycling of the mixture of water and glycol, after glycol steam with the gas phase temperature of 195 ℃ is condensed, the recovered steam consisting of most of water and low molecular substances with the boiling point of less than 195 ℃ is condensed to obtain recovered liquid, the recovered liquid passes through a heat exchanger to obtain hot steam containing water and glycol, and the hot steam is conveyed to a fractionating tower.
Example 4: the invention discloses a method for recovering ethylene glycol in a PTA method, which comprises the step of respectively carrying out treatments of fractionating the ethylene glycol, cooling distillate, recovering cooling liquid, filtering solid impurities and distilling the ethylene glycol by adopting a fractionating tower, a cooling tower, three recovery tanks, a fine filter and a distillation kettle which are sequentially connected along the material conveying direction and are arranged between an esterification kettle and a filter of the PTA method, so as to obtain colorless liquid base ethylene glycol.
Specifically, the specific implementation mode of ethylene glycol fractionation is that the esterification liquid containing ethylene terephthalate is statically heated to 270 ℃ under normal pressure in advance, then the esterification liquid is put into a fractionating tower, hot steam containing water and ethylene glycol is introduced, then normal-pressure fractionation is carried out at 105 ℃, when the distilled water content reaches 90% +/-5% of the theoretical distillation amount, the internal temperature of the fractionating tower is further raised to 290 ℃, the top temperature of the fractionating tower is raised to 190 +/-5 ℃, and redundant ethylene glycol is distilled out along with the hot steam to obtain distillate containing ethylene glycol. Wherein, when feeding each ton of esterification liquid, 100kg of hot steam containing water and glycol is introduced, and the temperature of the hot steam is 170 ℃ and the pressure is 250 kPa. In addition, the recovery rate of ethylene terephthalate in the fractionation column was determined to be 98.80%.
The specific implementation of cooling the distillate and recovering the cooling liquid is to transfer the distillate of the fractionating tower into a cooling tower, cool the distillate to 60 ℃ by using cooling water, and then store the obtained cooling liquid in a recovery tank. Wherein, these recovery tanks pass through cooling water and cool down the coolant liquid to 20 ℃ in proper order, and cooling water passes through these recovery tanks and cooling tower in proper order along the opposite direction of material transfer route. The recovery tank is used for purifying the ethylene glycol in the cooling liquid, and the heavy component stream is a bottom stream from the recovery tank.
The specific implementation mode of filtering solid impurities is that a fine filter is adopted to filter the cooling liquid in the recovery tank, so as to remove solid impurities such as low molecular substances, floccules and the like in the raw materials, and obtain filtrate containing glycol.
The specific implementation mode of distilling the glycol is that the filtrate obtained by filtering solid impurities is put into a distillation kettle with the reflux ratio of 17, most of water and low molecular substances with the boiling point of less than 195 ℃ are removed under the conditions of 95 ℃ and normal pressure, glycol steam with the gas phase temperature of 200 ℃ is condensed, glycol condensate containing a small amount of water and small molecular impurities is collected, and the content of the glycol in the condensate is measured to be 98.18%. In order to realize the recycling of the mixture of water and glycol, after the glycol steam with the gas phase temperature of 200 ℃ is condensed, the recovered steam consisting of most of water and low molecular substances with the boiling point of less than 195 ℃ is condensed to obtain recovered liquid, the recovered liquid passes through a heat exchanger to obtain hot steam containing water and glycol, and the hot steam is conveyed to a fractionating tower.
Example 5: the invention discloses a method for recovering ethylene glycol in a PTA method, which comprises the steps of respectively carrying out treatments of fractionating ethylene glycol, cooling distillate, recovering cooling liquid, filtering solid impurities and distilling ethylene glycol by adopting a fractionating tower, a cooling tower, three recovery tanks, a fine filter and a distillation kettle which are sequentially connected along the material conveying direction and are arranged between an esterification kettle and a filter of the PTA method, so as to obtain colorless liquid-based ethylene glycol.
Specifically, the specific implementation mode of ethylene glycol fractionation is that the esterification liquid containing ethylene terephthalate is statically heated to 265 ℃ under normal pressure in advance, then the esterification liquid is put into a fractionating tower, hot steam containing water and ethylene glycol is introduced, then normal pressure fractionation is carried out at 105 ℃, when the distilled water content reaches 90% +/-5% of the theoretical distillation amount, the internal temperature of the fractionating tower is further raised to 280 ℃, the top temperature of the fractionating tower is raised to 190 +/-5 ℃, and redundant ethylene glycol is distilled out along with the hot steam, so that distillate containing ethylene glycol is obtained. Wherein 250kg of hot steam containing water and ethylene glycol is fed into each ton of esterification solution, the temperature of the hot steam is 175 ℃, and the pressure of the hot steam is 300 kPa. In addition, the recovery of ethylene terephthalate in the fractionation column was measured to be 99.00%.
The specific implementation of cooling the distillate and recovering the cooling liquid is to transfer the distillate from the fractionating tower to a cooling tower, cool the distillate to 55 ℃ with cooling water, and store the resulting cooling liquid in a recovery tank. Wherein, these recovery tanks pass through the cooling water and in proper order with the cooling liquid cooling to 5 ℃, and the cooling water passes through these recovery tanks and cooling tower in proper order along the opposite direction of material transport route. The recovery tank is used for purifying the ethylene glycol in the cooling liquid, and the heavy component flow is the bottom flow from the recovery tank.
The specific implementation mode of filtering solid impurities is that a fine filter is adopted to filter the cooling liquid in the recovery tank, so as to remove solid impurities such as low molecular substances, floccules and the like in the raw materials, and obtain filtrate containing glycol.
The specific implementation mode of distilling the ethylene glycol is that the filtrate obtained by filtering solid impurities is put into a distillation kettle with the reflux ratio of 16, most of water and low molecular substances with the boiling point of less than 195 ℃ are removed under the conditions of 95 ℃ and normal pressure, ethylene glycol steam with the gas phase temperature of 195 ℃ is condensed, ethylene glycol condensate containing a small amount of water and small molecular impurities is collected, and the content of the ethylene glycol in the condensate is measured to be 99.14%. In order to recycle the mixture of water and glycol, after condensing glycol vapor with the gas phase temperature of 205 ℃, condensing most of the recovered vapor consisting of water and low molecular substances with the boiling point of less than 195 ℃ to obtain recovered liquid, passing the recovered liquid through a heat exchanger to obtain hot vapor containing water and glycol, and conveying the hot vapor to a fractionating tower.
Claims (7)
1. A method for recovering ethylene glycol in a PTA method is characterized in that: the method comprises the steps of respectively carrying out treatments of fractionating glycol, cooling distillate, recovering cooling liquid, filtering solid impurities and distilling glycol by adopting a fractionating tower, a cooling tower, a recovery tank, a fine filter and a distillation kettle which are sequentially connected along the material conveying direction and arranged between an esterification kettle and a filter of a PTA method, so as to obtain colorless liquid base glycol;
wherein the specific realization mode of fractionating the ethylene glycol is that the esterification liquid containing the ethylene glycol terephthalate is put into a fractionating tower, hot steam containing water and the ethylene glycol is introduced, the temperature of the hot steam is 165-;
the specific implementation mode of distilling the ethylene glycol is that the filtrate obtained by filtering solid impurities is put into a distillation kettle, most of water and low molecular substances with the boiling point of less than 195 ℃ are removed under the conditions of 95-105 ℃ and normal pressure, the ethylene glycol steam with the gas phase temperature of 195-205 ℃ is condensed, the ethylene glycol condensate containing a small amount of water and small molecular impurities is collected, and the content of the ethylene glycol in the condensate is determined to be more than or equal to 98 percent;
in the step of fractionating the ethylene glycol, the esterification liquid is statically heated to 260-270 ℃ at normal pressure in advance.
2. The process of claim 1, wherein the process comprises the following steps: in the step of fractionating the ethylene glycol, when each ton of esterification liquid is fed, 100-250kg of hot steam containing water and the ethylene glycol are introduced.
3. The process of claim 1, wherein the process comprises the following steps: the specific implementation mode of cooling the distillate and recovering the cooling liquid is that the distillate of the fractionating tower is transferred into a cooling tower, the cooling water is adopted to cool the distillate to 50-60 ℃, and then the obtained cooling liquid is stored in a recovery tank.
4. The process of claim 1, wherein the process comprises the following steps: the recycling tanks are sequentially provided with a plurality of recycling tanks along the material conveying direction, the recycling tanks sequentially cool the cooling liquid to 5-25 ℃ through cooling water, and the cooling water sequentially passes through the recycling tanks and the cooling tower along the direction opposite to the material conveying path.
5. The process of claim 1 for recovering ethylene glycol from a PTA process, wherein: the specific implementation mode of filtering the solid impurities is that a fine filter is adopted to filter the cooling liquid in the recovery tank, and low molecular substances and floccule solid impurities in the raw materials are removed to obtain filtrate containing glycol.
6. The process of claim 1, wherein the process comprises the following steps: in the step of distilling the ethylene glycol, after the ethylene glycol steam with the gas phase temperature of 195-205 ℃ is condensed, the recovery steam consisting of most of water and low molecular substances with the boiling point of less than 195 ℃ is condensed to obtain the recovery liquid, the recovery liquid passes through a heat exchanger to obtain the hot steam containing the water and the ethylene glycol, and the hot steam is conveyed to a fractionating tower.
7. The process of claim 1, wherein the process comprises the following steps: the reflux ratio of the distillation still is 16-18.
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| US4254246A (en) * | 1979-03-26 | 1981-03-03 | Davy International Ag | Column system process for polyester plants |
| US5466776A (en) * | 1994-06-03 | 1995-11-14 | Zimmer Aktiengesellschaft | Process for the multistage generation of vacuum for polyester production |
| JP2002087999A (en) * | 2000-09-11 | 2002-03-27 | Teijin Ltd | Method for recovering effective component from polyester waste |
| CN1634821A (en) * | 2004-10-12 | 2005-07-06 | 浙江大学 | Process for recovering ethylene glycol from esterified waste water |
| CN102037054A (en) * | 2008-08-18 | 2011-04-27 | 卢吉齐默有限公司 | Method and device for the recovery of ethylene glycol for the production of polyethylene terephthalate |
| CN105152863A (en) * | 2015-08-13 | 2015-12-16 | 上海聚友化工有限公司 | Method for recovering ethylene glycol and acetaldehyde from polyester wastewater |
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