Device, method and application for recovering triethylamine and methanol from wastewater by combining two-tower rectification and one phase splitter

Abstract

The invention belongs to the technical field of chemical separation, and discloses a device and a method for recovering triethylamine and methanol from wastewater by combining two-tower rectification and a phase splitter, and application of the device and the method. The device comprises an extractive distillation tower, an extraction agent recovery tower, a phase splitter, a first reboiler, a second reboiler, a third condenser, a first condenser, a second condenser, a reflux tank, a mixer and a separator, and the first reboiler and the second reboiler are connected to the bottoms of the extractive distillation tower and the extraction agent recovery tower respectively. The second condenser and the reflux tank are sequentially connected to the top of the extracting agent recovery tower. According to the device and the method, the process of treating ternary azeotropy by combining two-tower rectification and one phase splitter is adopted, so that the process is simple, the limitation of azeotropy is broken through by adopting water generated by the device as an extracting agent, and the energy consumption and the cost of the process are reduced.

Description

Technical Field

[0001] This invention belongs to the field of chemical separation technology, and relates to the field of multi-component azeotropic material separation technology, as well as extractive distillation and phase separation technology. In particular, it relates to an apparatus, method and application for recovering triethylamine and methanol from wastewater by combining a two-tower distillation and a phase separator. Background Technology

[0002] Currently, in the acylation stage of cephalosporin drug production, it is necessary to use catalysts and solvents containing triethylamine, methanol, etc., to react the acylation agent with the amino compound. During this process, due to the incomplete reaction of triethylamine, methanol and other chemicals, a large amount of wastewater containing triethylamine and methanol is generated.

[0003] Triethylamine, also known as N,N-diethylethylamine, or TEA for short, is an amine organic compound. It is a colorless, transparent liquid with a strong ammonia odor and produces a slight fumes in air. It is slightly soluble in water, soluble in ethanol and ether, and its aqueous solution is weakly alkaline. It is flammable, explosive, toxic, and highly irritating, and is classified as a difficult-to-biodegrade wastewater. Industrially, it is mainly used as a solvent, curing agent, catalyst, polymerization inhibitor, preservative, and synthetic raw material.

[0004] Methanol, also known as hydroxymethane, wood alcohol, or wood spirits, is an organic compound and the simplest saturated monohydric alcohol. It is light, highly volatile, colorless, flammable, and has an odor very similar to ethanol (a drinking alcoholic beverage). However, unlike ethanol, methanol is highly toxic and should not be consumed. It is commonly used as a solvent, antifreeze, fuel, or ethanol denaturant, and can also be used to produce biodiesel through transesterification.

[0005] Triethylamine is a volatile liquid that is readily miscible with water at low temperatures. In industrial production, the separation of triethylamine from water typically involves using caustic soda to absorb the water content, or adding a third component (azeotropic agent or extractant) for special distillation. However, this special distillation process introduces impurities and has high energy consumption. Currently, there are no published patent documents on the treatment of ternary mixtures containing triethylamine, methanol, and water. This wastewater exhibits both ternary azeotropes (triethylamine-methanol-water) and binary azeotropes (triethylamine-water), making the treatment of wastewater containing triethylamine and methanol a pressing problem.

[0006] Chinese patent publication CN106977409A discloses a method for separating triethylamine and water. This method targets a binary mixture containing triethylamine and water and employs a three-distillation-column technology without the use of an azeotropic agent. Although it achieves the separation of the triethylamine and water mixture, the entire process cannot recycle the waste liquid multiple times, resulting in a low first-pass yield, high heat loss, and unsatisfactory product separation effect.

[0007] Chinese patent publication CN109369419A discloses a process and apparatus for separating triethylamine from industrial waste liquid. This method targets a binary mixture containing triethylamine and water and employs two distillation columns, two phase separators, and a molecular sieve adsorption column. Although it achieves the separation of the binary mixture of triethylamine and water, the process is complex and greatly increases the process cost and energy consumption.

[0008] Therefore, there is an urgent need for one or more related methods or devices. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide an apparatus, method and application for recovering triethylamine and methanol from wastewater by combining a two-tower distillation and a phase separator.

[0010] The technical solution adopted by this invention to solve its technical problem is: An apparatus for recovering triethylamine and methanol from wastewater by combining a two-tower distillation and a phase separator is disclosed. The apparatus includes an extractive distillation column, an extractant recovery column, a phase separator, a first reboiler, a second reboiler, a third condenser, a first condenser, a second condenser, a reflux tank, a mixer, and a separator. The first and second reboilers are respectively connected to the bottom of the extractive distillation column and the extractant recovery column, and the second condenser and the reflux tank are sequentially connected to the top of the extractant recovery column T2.

[0011] Furthermore, the extractive distillation column includes an extractive distillation column body, which is arranged vertically. A top output end is provided at the top of the extractive distillation column body, a middle input end is provided in the upper middle part of the extractive distillation column body, a bottom output end is provided at the bottom of the extractive distillation column body, an upper input end is provided on the extractive distillation column body near the top of the extractive distillation column body between the top output end and the middle input end, and a lower input end is provided on the extractive distillation column body near the bottom of the extractive distillation column body between the bottom output end and the middle input end. The extractant recovery tower includes an extractant recovery tower body, which is arranged vertically. A top output end is provided at the top of the extractant recovery tower body, a middle input end is provided in the upper middle part of the extractant recovery tower body, a bottom output end is provided at the bottom of the extractant recovery tower body, an upper input end is provided on the extractant recovery tower body near the top of the extractant recovery tower body between the top output end and the middle input end, and a lower input end is provided on the extractant recovery tower body near the bottom of the extractant recovery tower body between the bottom output end and the middle input end.

[0012] Furthermore, the wastewater feedstock, a ternary wastewater mixture exhibiting both triethylamine-methanol-water ternary azeotropic and triethylamine-water binary azeotropic phenomena, is fed into the extractive distillation column body through the middle input end. The top output end of the extractive distillation column is tightly connected to the input end of a first condenser, a pump, and a phase separator in sequence. The pump pressurizes the mixture to ensure it remains in a liquid phase. The output end of the phase separator can directly output triethylamine product. The output end of the phase separator can also sequentially pass through a mixer, a third condenser, and... The pump is tightly connected to the upper inlet of the extractive distillation column to feed the extractant into the column. The bottom outlet of the extractive distillation column is tightly connected to the lower inlet of the column via a first reboiler, which provides a heat source for the cold stream at the bottom of the column. The bottom outlet of the extractive distillation column is tightly connected to the middle inlet of the extractant recovery column via a pump. The bottom outlet of the extractive distillation column is also tightly connected to the lower inlet of the column via a first reboiler. The top output of the extractant recovery tower is connected to the upper input of the extractant recovery tower in sequence via a second condenser, a reflux tank, a pump, and a pressure reducing valve. The second condenser cools the vapor at the top of the extractant recovery tower into liquid. The top output of the extractant recovery tower also directly outputs methanol product in sequence via the second condenser, the reflux tank, and the pump. The bottom output of the extractant recovery tower is connected to the lower input of the extractant recovery tower in sequence via a second reboiler. The second reboiler provides a heat source for the cold stream at the bottom of the extractant recovery tower. The bottom output of the extractant recovery tower is also connected to the mixer in sequence via a pump and a separator. The separator can also directly output product water.

[0013] The method for recovering triethylamine and methanol from wastewater using the apparatus described above includes the following steps: (1) Extractive distillation section: The wastewater raw material, namely the triethylamine-methanol-water ternary liquid azeotrope, enters the extractive distillation column through pumps and pipelines. At the same time, the extractant water in the mixer is condensed by the third condenser and then enters the extractive distillation column through pipelines for mass and heat transfer. The mixture at the top of the column does not need to be condensed and directly enters the first condenser outside the column in the form of gas through pipelines to be condensed into a liquid mixture. The liquid mixture at the bottom of the column enters the extractant recovery column along the pipeline. (2) Phase separation process: The liquid stream from the first condenser enters the phase separator through pumps and pipelines. The upper layer of the phase separator is a liquid stream containing high-purity triethylamine product, and the lower layer of the phase separator is a liquid stream containing high-purity water product. The lower liquid stream of the phase separator enters the mixer through pipelines and then enters the extractive distillation column for recycling. (3) Extractant recovery section: The liquid stream from the bottom of the extractive distillation column enters the extractant recovery column through pipeline. At the top of the extractant recovery column, a liquid stream containing high-purity methanol is obtained, and at the bottom, a liquid stream containing high-purity water is obtained. The liquid stream from the separator enters the separator through pipeline. A portion of the stream from the separator enters the mixer through pipeline and mixes with the liquid stream containing high-purity water obtained in the lower layer of the phase separator. The mixture then enters the extractive distillation column for recycling. The other portion of the stream from the separator is produced as a product.

[0014] Furthermore, the product water obtained from the phase separation treatment section and the extractant recovery section is used as the extractant entering the extractive distillation column, and no liquid phase reflux is required at the top of the extractive distillation column.

[0015] Furthermore, the operating pressure of the extractive distillation column T1 is 1 atm, the operating pressure of the extractant recovery column T2 is 1 atm, and the operating temperature of the phase separator is at least 130°C.

[0016] Furthermore, the extractive distillation column T1 has a theoretical number of 25-40 plates, the feed plates for the triethylamine-methanol-water ternary liquid azeotrope are 19-28 plates, and the feed plate for the circulating extractant water is the first plate; the extractant recovery column T2 has a theoretical number of 25-40 plates, the feed position for the mixture is 15-23 plates, and the reflux ratio is 2.23-3.51.

[0017] Furthermore, the product triethylamine obtained by the method has a purity of ≥99.50% and a recovery rate of ≥99.99%, the product methanol has a purity of ≥99.98% and a recovery rate of ≥99.98%, and the product water has a purity of ≥99.99% and a recovery rate of ≥97.81%.

[0018] The apparatus described above is used in the simultaneous recovery of triethylamine and methanol from wastewater.

[0019] The advantages and positive effects of this invention are as follows: 1. This invention addresses ternary wastewater mixtures exhibiting both ternary azeotropic and binary azeotropic phenomena of triethylamine-methanol-water. It provides an apparatus and method for recovering triethylamine and methanol from wastewater using a combination of two-tower distillation and a phase separator. This invention, targeting triethylamine-methanol-water ternary azeotropes, utilizes self-generated water as the extractant. The process employs an extractive distillation tower, an extractant recovery tower, and a phase separator to separate high-purity triethylamine, methanol, and water. A portion of the high-purity water obtained is used as the extractant, eliminating the need for introducing additional fresh water, and eliminating the need for liquid phase reflux at the top of the first distillation tower. The process is simple, the apparatus is basic, and production costs and energy consumption are significantly reduced. This apparatus and method, combining two-tower distillation with a phase separator to treat ternary azeotropes, not only simplifies the process but also breaks the azeotropic limitation by using self-generated water as the extractant, reducing process energy consumption and costs.

[0020] 2. The method of the present invention selects product water produced by the raw material itself as the extractant. By using extractive distillation and phase separation, high-purity recovery of triethylamine, methanol and water is achieved without introducing other extractants to contaminate the raw material. This saves on the equipment and energy consumption problems caused by the addition of other components.

[0021] 3. The device of the present invention uses two distillation columns and one phase separator. The process is simple, highly operable, and has good economic and social benefits.

[0022] 4. The apparatus and method of this invention use only water as the extractant, achieving not only high-purity recovery of triethylamine and methanol, but also using the generated high-purity water as its own extractant, eliminating the need to introduce fresh water and achieving true self-sufficiency. This apparatus and method employ only two distillation columns and one phase separator, with no need for liquid phase reflux at the top of the first distillation column. The process is simple and easy to operate, yielding high-purity products while significantly reducing production costs and energy consumption.

[0023] 5. Apparatus and Method of the Invention. First, a wastewater mixture containing triethylamine and methanol, along with a circulating extractant, enters an extractive distillation column. The overhead stream, in vapor form, is condensed and pressurized before entering a phase separator. The upper layer yields high-purity triethylamine, and the lower layer yields high-purity circulating extractant water. Subsequently, the bottom stream of the extractive distillation column enters an extractant recovery column. After simple distillation separation, high-purity methanol is obtained at the top of the recovery column. A portion of the high-purity product water obtained at the bottom of the recovery column is collected as product, and the remainder is returned to the extractive distillation column as circulating extractant, eliminating the need for introducing additional fresh water. This method uses product water generated from the wastewater itself as the extractant, recovering high-purity products while avoiding the introduction of other extractants that could contaminate the raw materials. It saves energy and requires only two distillation columns and one phase separator, simplifying the process and reducing equipment costs. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of one structural connection of the device in this invention. Detailed Implementation

[0025] The present invention will be further described below with reference to the embodiments. The embodiments described below are descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0026] The various experimental operations involved in the specific embodiments are all conventional techniques in the field. For parts not specifically annotated in this document, those skilled in the art can refer to various commonly used reference books, scientific and technological documents or related instructions and manuals prior to the filing date of this invention to carry out the operations.

[0027] This invention relates to an apparatus and method for treating triethylamine-methanol-water ternary azeotrope using a combination of two-tower distillation and a phase separator. The process includes an extractive distillation section, a phase separation section, and an extractant recovery section, yielding products triethylamine and water, as well as products methanol and water, respectively.

[0028] like Figure 1 As shown, an apparatus for recovering triethylamine and methanol from wastewater by combining two-tower distillation and a phase separator is disclosed. The apparatus includes an extractive distillation column T1, an extractant recovery column T2, a phase separator D, a first reboiler R1, a second reboiler R2, a third condenser CS, a first condenser C1, a second condenser C2, a reflux tank A, a mixer M, and a separator S. The first reboiler R1 and the second reboiler R2 are respectively connected to the bottom of the extractive distillation column T1 and the extractant recovery column T2, and the second condenser C2 and the reflux tank A are sequentially connected to the top of the extractant recovery column T2. The extractive distillation column includes an extractive distillation column body (not labeled in the figure), which is arranged vertically. A top output end (not labeled in the figure) is located at the top of the extractive distillation column body, a middle input end (not labeled in the figure) is located in the upper middle part of the extractive distillation column body, and a bottom output end (not labeled in the figure) is located at the bottom of the extractive distillation column body. An upper input end (not labeled in the figure) is located on the extractive distillation column body near the top of the extractive distillation column body between the top output end and the middle input end, and a lower input end (not labeled in the figure) is located on the extractive distillation column body near the bottom of the extractive distillation column body between the bottom output end and the middle input end. The extractant recovery tower includes an extractant recovery tower body (not labeled in the figure), which is arranged vertically. A top output end (not labeled in the figure) is located at the top of the extractant recovery tower body, a middle input end (not labeled in the figure) is located in the upper middle part of the extractant recovery tower body, and a bottom output end (not labeled in the figure) is located at the bottom of the extractant recovery tower body. An upper input end (not labeled in the figure) is located on the extractant recovery tower body near the top of the extractant recovery tower body between the top output end and the middle input end, and a lower input end (not labeled in the figure) is located on the extractant recovery tower body near the bottom of the extractant recovery tower body between the bottom output end and the middle input end. The wastewater feedstock, a ternary wastewater mixture exhibiting both triethylamine-methanol-water ternary azeotropic and triethylamine-water binary azeotropic phenomena, is fed into the extractive distillation column through its middle inlet. The top outlet of the extractive distillation column is connected in sequence to the inlet of the phase separator (not labeled in the diagram) via a first condenser, a pump (not labeled in the diagram), and a phase separator (not labeled in the diagram). This pump pressurizes the mixture to ensure it remains in a liquid phase. The phase separator (not labeled in the diagram) directly outputs triethylamine product. The phase separator's outlet is also connected in sequence to the top inlet of the extractive distillation column via a mixer, a third condenser, and another pump (not labeled in the diagram). The extractant is then fed into the extractive distillation column. (The extractant is a substance that selectively interacts with a specific component in the mixture to be separated through strong intermolecular forces (such as hydrogen).) This invention cleverly selects a substance naturally present in the mixture as the extractant (due to its inherent properties and polarity), which significantly reduces the apparent volatility in the liquid phase, thereby altering the relative volatility between the components and achieving mixture separation. This avoids the energy consumption and equipment cost issues associated with adding a third component for separation and reuse. The bottom output of the extractive distillation column is tightly connected to the lower input of the column via a first reboiler, which provides a heat source for the cold stream at the bottom of the column. The bottom output of the extractive distillation column is also tightly connected to the middle input of the extractant recovery column via a pump (not labeled in the figure). Furthermore, the bottom output of the extractive distillation column is also tightly connected to the lower input of the column via the first reboiler, providing a heat source. The top output of the extractant recovery tower is connected to the upper input of the extractant recovery tower in sequence via a second condenser, a reflux tank, a pump (not labeled in the figure), and a pressure reducing valve (not labeled in the figure). The second condenser cools the vapor at the top of the extractant recovery tower into liquid. The top output of the extractant recovery tower also directly outputs methanol product in sequence via the second condenser, the reflux tank, and the pump (not labeled in the figure). The bottom output of the extractant recovery tower is connected to the lower input of the extractant recovery tower in sequence via a second reboiler. The second reboiler provides a heat source for the cold stream at the bottom of the extractant recovery tower. The bottom output of the extractant recovery tower is also connected to the mixer in sequence via a pump (not labeled in the figure), a separator, and a mixer. The separator can also directly output product water.

[0029] The working principle of the above-mentioned device for recovering triethylamine and methanol from wastewater by combining a two-tower distillation unit and a phase separator is as follows: A ternary mixture of triethylamine, methanol, and water, along with circulating extractant water, simultaneously enters the extractive distillation column T1. The extraction effect of water alters the interaction between triethylamine and methanol. In addition, the heat exchange stream obtained from the bottom of the column via the first reboiler R1 continuously transfers mass and heat to the raw materials, extractant, and cold liquids such as water. This process ensures that the methanol in the triethylamine-methanol-water ternary mixture is essentially carried to the bottom of the extractive distillation column T1 to obtain a liquid mixture of methanol and water. At the top of the extractive distillation column T1, a vapor mixture containing triethylamine and water is obtained. The top of extractive distillation column T1 yields a mixture containing triethylamine and water vapor. Based on the physicochemical properties between triethylamine and water, after the triethylamine and water vapor mixture at the top of extractive distillation column T1 is completely cooled into a liquid phase by the first condenser C1, it is immediately pressurized by a pump to ensure that the mixture remains in a liquid phase. It is then sent to the phase separator D through a pipeline. At a given operating temperature, the triethylamine and water liquid phase mixture undergoes mass exchange in the phase separator D, resulting in stratification. High-purity triethylamine is recovered in the upper layer of the phase separator D, while high-purity product water is obtained in the lower layer of the phase separator D and used as the extractant in extractive distillation column T1 for recycling through pipeline. The liquid mixture of methanol and water obtained at the bottom of extractive distillation column T1 enters the extractant recovery column T2 through pipeline. The heat exchange stream obtained at the bottom of the column through the second reboiler R2 continuously transfers mass and heat with the reflux cold liquid at the top of the column. In addition, the methanol and water mixture itself does not exhibit azeotropic behavior and the physical properties of the two are significantly different, making mass and heat transfer easy. High-purity methanol product is obtained at the top of the extractant recovery column T2, and high-purity product water is obtained at the bottom of the column. Part of the product water is collected as product after passing through separator S, and the other part enters the mixer M through pipeline and mixes with the lower product water of phase separator D. After being cooled by the third condenser CS, it is returned to the top of extractive distillation column T1.

[0030] The method for recovering triethylamine and methanol from wastewater using the apparatus described above, which combines a two-tower distillation column with a phase separator, mainly includes the following steps: (1) Extractive distillation section: The wastewater raw material, namely the triethylamine-methanol-water ternary liquid azeotrope, enters the extractive distillation column T1 through pumps and pipelines. At the same time, the extractant water in the mixer M is condensed by the third condenser CS and then enters the extractive distillation column T1 through pipelines for mass and heat transfer. The mixture at the top of the column does not need to be condensed and directly enters the first condenser C1 outside the column in the form of gas phase through pipelines to be condensed into a liquid phase mixture. The liquid phase mixture at the bottom of the column enters the extractant recovery column T2 along the pipeline. (2) Phase separation process: The liquid stream from the first condenser C1 enters the phase separator D through pumps and pipelines. The upper layer of the phase separator D is a liquid stream containing high-purity triethylamine product, and the lower layer of the phase separator D is a liquid stream containing high-purity water product. The lower liquid stream of the phase separator D enters the mixer M through pipelines and then enters the extractive distillation column T1 for recycling. (3) Extractant recovery section: The liquid stream from the bottom of the extractive distillation column T1 enters the extractant recovery column T2 through the pipeline. At the top of the extractant recovery column T2, a liquid stream containing high-purity methanol is obtained, and at the bottom, a liquid stream containing high-purity water is obtained. The liquid stream from the bottom enters the separator S through the pipeline. A part of the stream from the separator S enters the mixer M through the pipeline and mixes with the liquid stream containing high-purity water obtained in the lower layer of the phase separator D. The mixture then enters the extractive distillation column T1 for recycling. The other part of the stream from the separator S is produced as a product.

[0031] The product water obtained from the phase separation treatment section and the extractant recovery section is used as the extractant in the extractive distillation column T1. No liquid phase reflux is required at the top of the extractive distillation column T1, which further reduces the energy consumption of heating the cold stream from the bottom of the column in the reboiler.

[0032] Furthermore, the operating pressure of the extractive distillation column T1 is 1 atm, the operating pressure of the extractant recovery column T2 is 1 atm, and the operating temperature of the phase separator D is at least 130°C.

[0033] Furthermore, the extractive distillation column T1 has a theoretical number of 25-40 plates, the feed plates for the triethylamine-methanol-water ternary liquid azeotrope are 19-28 plates, and the feed plate for the circulating extractant water is the first plate; the extractant recovery column T2 has a theoretical number of 25-40 plates, the feed position for the mixture is 15-23 plates, and the reflux ratio is 2.23-3.51.

[0034] Furthermore, the product triethylamine obtained by the method has a purity of ≥99.50% and a recovery rate of ≥99.99%, the product methanol has a purity of ≥99.98% and a recovery rate of ≥99.98%, and the product water has a purity of ≥99.99% and a recovery rate of ≥97.81%.

[0035] The specific preparation and testing methods are as follows: The devices used in the following related embodiments are all as follows: Figure 1 The apparatus shown is a combination of two-tower distillation and a phase separator for recovering triethylamine and methanol from wastewater. The methods used in the following related embodiments are all "methods for recovering triethylamine and methanol from wastewater using the apparatus described above that combines two-tower distillation and a phase separator".

[0036] The following example uses the demand of an industrial park in northern my country that produces approximately 50,000 tons of wastewater containing triethylamine and methanol annually (assuming 300 days of production per year and 24 hours per day).

[0037] Example 1: The fresh feed temperature is 77℃, and the total wastewater flow rate is 7216 kg / h, containing 0.623% triethylamine, 0.239% methanol, and 0.138% water. The extractive distillation column T1 has a theoretical number of 25 plates, with 20 plates for wastewater feed and the first plate for the circulating extractant water feed. The operating pressure is 1 atm, the column inner diameter is 0.741 m, and the reboiler heat load is 1211.17 kW. The extractant recovery column T2 has a theoretical number of 40 plates, with 21 plates for feed. The operating pressure is 1 atm, the column inner diameter is 0.937 m, the reflux ratio is 2.41, and the reboiler heat load is 1956.17 kW. The phase separator temperature is 130℃. The purity of the obtained products was 99.50% for triethylamine and 99.99% for methanol. The purity of the obtained products was 99.99% for methanol and 99.98% for water. The purity of the obtained products was 99.99% for water and 97.81% for water.

[0038] Comparative Example 1 The specific methods are the same as in Example 1, except that this invention uses an extractive distillation column T1 with its own water as the extractant. Comparative Example 1 uses an extractive distillation column with similar functions but using other extractants. This inevitably introduces impurities of the third component and necessitates the addition of equipment for separating and recovering the third component, thus increasing energy consumption and cost.

[0039] Comparative Example 2 The specific methods are the same as in Example 1, except that the present invention uses an extraction and recovery tower T2 without cold liquid reflux at the top. Comparative Example 2 sets it up as an extractive distillation tower with similar function but with liquid phase reflux at the top. Therefore, the total amount of cold liquid stream that needs to be vaporized in the reboiler at the bottom will increase, which will inevitably increase the energy consumption of the reboiler.

[0040] Meanwhile, by comparing Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that the extractive distillation column T1 and the extractive recovery column T2 in the method of the present invention have a synergistic effect, which can synergistically improve the quality purity and quality recovery rate of the prepared related products, and at the same time reduce energy consumption.

[0041] Example 2: The fresh feed temperature is 77℃, and the total wastewater flow rate is 7216 kg / h, containing 0.623% triethylamine, 0.239% methanol, and 0.138% water. The extractive distillation column T1 has a theoretical number of 25 plates, with 19 plates for wastewater feed and the first plate for the circulating extractant water feed. The operating pressure is 1 atm, the column inner diameter is 0.743 m, and the reboiler heat load is 1219.45 kW. The extractant recovery column T2 has a theoretical number of 25 plates, with 15 plates for feed. The operating pressure is 1 atm, the column inner diameter is 1.083 m, the reflux ratio is 3.51, and the reboiler heat load is 2517.66 kW. The phase separator temperature is 130℃. The purity of the obtained products was 99.50% for triethylamine and 99.99% for methanol. The purity of the obtained products was 99.99% for methanol and 99.94% for water. The purity of the obtained products was 99.99% for water and 97.83% for water.

[0042] Example 3: The fresh feed temperature is 77℃, and the total wastewater flow rate is 7216 kg / h, containing 0.623% triethylamine, 0.239% methanol, and 0.138% water. The extractive distillation column T1 has a theoretical number of 30 plates, with 23 plates for wastewater feed and the first plate for the circulating extractant water feed. The operating pressure is 1 atm, the column inner diameter is 0.738 m, and the reboiler heat load is 1203.18 kW. The extractant recovery column T2 has a theoretical number of 30 plates, with 17 plates for feed. The operating pressure is 1 atm, the column inner diameter is 0.965 m, the reflux ratio is 2.61, and the reboiler heat load is 2035.14 kW. The phase separator temperature is 130℃. The purity of the obtained products was 99.50% for triethylamine and 99.99% for methanol. The purity of the obtained products was 99.99% for methanol and 99.95% for water. The purity of the obtained products was 99.99% for water and 97.82% for water.

[0043] Example 4: The fresh feed temperature is 77℃, and the total wastewater flow rate is 7216 kg / h, containing 0.623% triethylamine, 0.239% methanol, and 0.138% water. The extractive distillation column T1 has a theoretical number of 40 plates, with 28 plates for wastewater feed and the first plate for the circulating extractant water feed. The operating pressure is 1 atm, the column inner diameter is 0.739 m, and the reboiler heat load is 1201.26 kW. The extractant recovery column T2 has a theoretical number of 40 plates, with 23 plates for feed. The operating pressure is 1 atm, the column inner diameter is 0.912 m, the reflux ratio is 2.23, and the reboiler heat load is 1833.38 kW. The phase separator temperature is 130℃. The purity of the obtained products was 99.51% for triethylamine and 99.99% for methanol. The purity of the obtained products was 99.99% for methanol and 99.98% for water. The purity of the obtained products was 99.99% for water and 97.83% for water.

[0044] Example 5: The fresh feed temperature is 77℃, and the total wastewater flow rate is 7216 kg / h, containing 0.623% triethylamine, 0.239% methanol, and 0.138% water. The extractive distillation column T1 has a theoretical number of 40 plates, with 28 plates for wastewater feed and the first plate for the circulating extractant water feed. The operating pressure is 1 atm, the column inner diameter is 0.740 m, and the reboiler heat load is 1201.30 kW. The extractant recovery column T2 has a theoretical number of 30 plates, with 18 plates for feed. The operating pressure is 1 atm, the column inner diameter is 0.957 m, the reflux ratio is 2.57, and the reboiler heat load is 1991.10 kW. The phase separator temperature is 130℃. The purity of the obtained products was 99.51% for triethylamine and 99.99% for methanol. The purity of the obtained products was 99.99% for methanol and 99.95% for water. The purity of the obtained products was 99.99% for water and 97.81% for water.

[0045] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. An apparatus for recovering triethylamine and methanol from wastewater by combining a two-tower distillation unit with a phase separator, characterized in that: The apparatus includes an extractive distillation column, an extractant recovery column, a phase separator, a first reboiler, a second reboiler, a third condenser, a first condenser, a second condenser, a reflux tank, a mixer, and a separator. The first and second reboilers are respectively connected to the bottom of the extractive distillation column and the extractant recovery column, and the second condenser and the reflux tank are sequentially connected to the top of the extractant recovery column T2.

2. The apparatus according to claim 1, characterized in that: The extractive distillation column includes an extractive distillation column body, which is arranged vertically. A top output end is provided at the top of the extractive distillation column body, a middle input end is provided in the upper middle part of the extractive distillation column body, a bottom output end is provided at the bottom of the extractive distillation column body, an upper input end is provided on the extractive distillation column body near the top of the extractive distillation column body between the top output end and the middle input end, and a lower input end is provided on the extractive distillation column body near the bottom of the extractive distillation column body between the bottom output end and the middle input end. The extractant recovery tower includes an extractant recovery tower body, which is arranged vertically. A top output end is provided at the top of the extractant recovery tower body, a middle input end is provided in the upper middle part of the extractant recovery tower body, a bottom output end is provided at the bottom of the extractant recovery tower body, an upper input end is provided on the extractant recovery tower body near the top of the extractant recovery tower body between the top output end and the middle input end, and a lower input end is provided on the extractant recovery tower body near the bottom of the extractant recovery tower body between the bottom output end and the middle input end.

3. The apparatus according to claim 2, characterized in that: The wastewater feedstock, a ternary wastewater mixture exhibiting both triethylamine-methanol-water ternary azeotropic and triethylamine-water binary azeotropic phenomena, is fed into the extractive distillation column through its central inlet. The top outlet of the extractive distillation column is sequentially connected to the inlet of a first condenser, a pump, and a phase separator. This pump pressurizes the mixture to ensure it remains in a liquid phase. The phase separator directly outputs triethylamine product. The phase separator's outlet also sequentially connects to a mixer, a third condenser, and a pump. The upper inlet of the extractive distillation column is tightly connected to the extractant, which is then fed into the column. The lower outlet of the extractive distillation column is tightly connected to the lower inlet via a first reboiler, which provides a heat source for the cold stream at the bottom of the column. The lower outlet of the extractive distillation column is also tightly connected to the middle inlet of the extractant recovery column via a pump. Furthermore, the lower outlet of the extractive distillation column is also tightly connected to the lower inlet via the first reboiler. The top output of the extractant recovery tower is connected to the upper input of the extractant recovery tower in sequence via a second condenser, a reflux tank, a pump, and a pressure reducing valve. The second condenser cools the vapor at the top of the extractant recovery tower into liquid. The top output of the extractant recovery tower also directly outputs methanol product in sequence via the second condenser, the reflux tank, and the pump. The bottom output of the extractant recovery tower is connected to the lower input of the extractant recovery tower in sequence via a second reboiler. The second reboiler provides a heat source for the cold stream at the bottom of the extractant recovery tower. The bottom output of the extractant recovery tower is also connected to the mixer in sequence via a pump and a separator. The separator can also directly output product water.

4. A method for recovering triethylamine and methanol from wastewater using the apparatus according to any one of claims 1 to 3, characterized in that: Includes the following steps: (1) Extractive distillation section: The wastewater raw material, namely the triethylamine-methanol-water ternary liquid azeotrope, enters the extractive distillation column through pumps and pipelines. At the same time, the extractant water in the mixer is condensed by the third condenser and then enters the extractive distillation column through pipelines for mass and heat transfer. The mixture at the top of the column does not need to be condensed and directly enters the first condenser outside the column in the form of gas through pipelines to be condensed into a liquid mixture. The liquid mixture at the bottom of the column enters the extractant recovery column along the pipeline. (2) Phase separation process: The liquid stream from the first condenser enters the phase separator through pumps and pipelines. The upper layer of the phase separator is a liquid stream containing high-purity triethylamine product, and the lower layer of the phase separator is a liquid stream containing high-purity water product. The lower liquid stream of the phase separator enters the mixer through pipelines and then enters the extractive distillation column for recycling. (3) Extractant recovery section: The liquid stream from the bottom of the extractive distillation column enters the extractant recovery column through pipeline. At the top of the extractant recovery column, a liquid stream containing high-purity methanol is obtained, and at the bottom, a liquid stream containing high-purity water is obtained. The liquid stream from the separator enters the separator through pipeline. A portion of the stream from the separator enters the mixer through pipeline and mixes with the liquid stream containing high-purity water obtained in the lower layer of the phase separator. The mixture then enters the extractive distillation column for recycling. The other portion of the stream from the separator is produced as a product.

5. The method according to claim 4, characterized in that: The product water obtained from the phase separation treatment section and the extractant recovery section is used as the extractant entering the extractive distillation column, and no liquid phase reflux is required at the top of the extractive distillation column.

6. The method according to claim 4, characterized in that: The operating pressure of the extractive distillation column T1 is 1 atm, the operating pressure of the extractant recovery column T2 is 1 atm, and the operating temperature of the phase separator is at least 130°C.

7. The method according to claim 4, characterized in that: The extractive distillation column T1 has a theoretical number of 25-40 plates, the feed plates for the triethylamine-methanol-water ternary liquid azeotrope are 19-28 plates, and the feed plate for the circulating extractant water is the first plate; the extractant recovery column T2 has a theoretical number of 25-40 plates, the feed position for the mixture is the 15-23 plates, and the reflux ratio is 2.23-3.

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8. The method according to any one of claims 4 to 7, characterized in that: The product obtained by the method has a triethylamine purity of over 99.50% and a triethylamine recovery rate of over 99.99%, a methanol purity of over 99.98% and a methanol recovery rate of over 99.98%, and a water purity of over 99.99% and a water recovery rate of over 97.81%.

9. The application of the apparatus according to any one of claims 1 to 3 in the simultaneous recovery of triethylamine and methanol from wastewater.

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