CN113511965B - Process method for concentrating dilute formaldehyde aqueous solution by composite solvent extraction - Google Patents
Process method for concentrating dilute formaldehyde aqueous solution by composite solvent extraction Download PDFInfo
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Abstract
The invention relates to a process method for extracting and concentrating dilute formaldehyde aqueous solution by using a composite solvent, which comprises a recovery extraction tower, a concentration extraction tower, a desolventizing rectifying tower and a plurality of heat exchangers, wherein tower equipment in the process is a plate tower with a plurality of sieve plates, the solvent is selected as a continuous phase in operation, and the formaldehyde aqueous solution is selected as a disperse phase. The specific steps of the process method are that formaldehyde in the dilute formaldehyde solution is completely extracted into a composite solvent phase in a recovery extraction tower and flows out from the tower top, and then most of cosolvent is removed by heating evaporation and then enters the bottom of a concentration extraction tower, and the formaldehyde content in the solvent phase is continuously increased by adding concentrated formaldehyde into the tower top until the concentration requirement is met. The composite solvent adopted by the process method can obviously improve the distribution coefficient of formaldehyde at a lower concentration, and the concentrated product is obtained by further concentrating through fractional extraction, so that the efficient purification and phase separation are realized, and an energy-saving and effective production method is provided for concentrating the low-concentration formaldehyde aqueous solution.
Description
Technical Field
The invention relates to the technical field of chemical production, in particular to a process method for extracting and concentrating a dilute formaldehyde aqueous solution by a composite solvent.
Background
The formaldehyde has wide industrial application, can be used as a basic raw material for producing resin such as urea formaldehyde, phenolic aldehyde, melamine and the like, and can also be used for producing chemical products such as vinylon, pentaerythritol, isoprene and the like, but low-concentration formaldehyde waste liquid is often generated during use, and great difficulty is brought to purification treatment and environmental protection.
The recovery of formaldehyde can be concentrated by adopting a rectification method, for example, under the conventional rectification, the concentration of formaldehyde can be increased to about 20 percent, but the energy consumption is high, and the further concentration effect is limited. There are also methods of reactive distillation to convert formaldehyde into methylal and then concentrating, but the process equipment is complicated and side reactions exist. In principle, the solvent extraction method can be used for concentrating formaldehyde, but as formaldehyde and water mainly exist in the form of hemiacetal and have strong binding force, an effective extraction solvent is difficult to find.
Through analyzing the characteristics of the formaldehyde aqueous solution, the method of solvent extraction can be adopted to realize the separation of formaldehyde and water to a certain extent when the concentration of formaldehyde is moderate, but when the concentration of formaldehyde is low, the extraction effect of the solvent is greatly reduced, so that the formaldehyde is difficult to be completely separated by means of the solvent extraction method. In fact, the solvent extraction mainly utilizes the condensation of formaldehyde and a polyol solvent to form an aldol hemiacetal structure, but the weak polarity of the polyol is difficult to compete with water to generate chemical reaction with formaldehyde when the concentration of formaldehyde is low.
Disclosure of Invention
The invention aims to solve the defects of the technology, and provides a process method for concentrating a dilute formaldehyde aqueous solution by using a composite solvent extraction, which can continuously and effectively remove water to concentrate and recycle the dilute formaldehyde and obtain higher yield.
Therefore, the invention provides a process method for concentrating a dilute formaldehyde aqueous solution by composite solvent extraction, which comprises the following steps:
the method comprises the steps of (1) preparing a composite solvent from a main solvent and a cosolvent according to a certain proportion, filling a recovery extraction tower with the composite solvent before production operation, filling a concentration extraction tower with the main solvent, operating the recovery extraction tower under the condition that the composite solvent is an extractant, and operating the concentration extraction tower under the condition that the main solvent is the extractant, wherein the solvent is selected as a continuous phase in operation, and formaldehyde aqueous solution is selected as a disperse phase; adding the dilute formaldehyde solution into a recovery extraction tower from a feed inlet at the top of the recovery extraction tower, dispersing the dilute formaldehyde solution, flowing downwards along the recovery extraction tower, heating the composite solvent through a primary heat exchanger, entering the recovery extraction tower from the feed inlet at the bottom of the recovery extraction tower, and mixing with a continuous phase to flow upwards along the recovery extraction tower; the solvent phase leaving from the top of the recovery extraction tower is gasified by an evaporator and sent to the bottom of the desolventizing rectifying tower, and the solvent phase is condensed by a condenser after coming out from the top of the desolventizing rectifying tower through rectification to obtain the cosolvent; the residual liquid of the evaporator and the liquid at the bottom of the desolventizing rectifying tower are pressurized by a transfer pump, then sequentially enter a first-stage heat exchanger and a second-stage heat exchanger, are cooled and then are sent to an inlet at the bottom of a concentrated extraction tower, are mixed with a continuous phase in the concentrated extraction tower and flow upwards along the tower, fresh concentrated formaldehyde solution is added into the concentrated extraction tower from a feed inlet at the top of the concentrated extraction tower, and after being dispersed, flows downwards along the concentrated extraction tower, and an extraction phase leaving from the top of the concentrated extraction tower enters an extraction phase storage tank to obtain a concentrated formaldehyde solution with low water content;
the disperse phase in the concentration extraction tower flows downwards along the concentration extraction tower, is condensed into a whole in the concentration extraction tower bottom tank, enters the secondary heat exchanger through a delivery pump connected with the tower bottom, is heated and then is sent to a feed inlet at the top of the recovery extraction tower to enter the recovery extraction tower together with the dilute formaldehyde solution, so that the disperse phase flows downwards along the recovery extraction tower until a coacervate is formed at the lower part of the recovery extraction tower bottom tank, and is discharged from a tower bottom outlet of the recovery extraction tower.
Preferably, 5-8 sieve plates of theoretical plates are arranged in the recovery extraction tower and the concentration extraction tower, and the theoretical plates of the desolventizing and rectifying tower are 8-12.
Preferably, the main solvent is a saturated monohydric alcohol having a boiling point of 150-180 ℃ at atmospheric pressure.
Preferably, the main solvent is at least one of n-hexanol, n-heptanol or cyclohexanol, and the cosolvent is methanol.
Preferably, the mass percentage of the main solvent in the composite solvent is 85-92%, and the mass percentage of the cosolvent is 8-15%.
Preferably, the recovery extraction column is operated at a temperature of 50-65deg.C and the concentrate extraction column is operated at a temperature of 25-40deg.C.
Preferably, the mass percentage of formaldehyde in the dilute formaldehyde aqueous solution added from the feed inlet at the top of the recovery extraction tower is 5-12.5%, and the mass percentage of formaldehyde in the concentrated formaldehyde aqueous solution added from the feed inlet at the top of the concentration extraction tower is 44-48%.
Preferably, the feed mass flow ratio of the composite solvent to the dilute aqueous formaldehyde solution in the recovery extraction tower is 1.1-2.4:1.
Preferably, the mass flow ratio of the concentrated formaldehyde feed to the dilute formaldehyde feed is 0.25-0.4:1.
The formaldehyde molecules in the formaldehyde aqueous solution exist in a chain multimerization state in water, and the structural formula is
Has strong binding force with water and is dissolved in alcohol with moderate concentrationThe agent can be converted into +.>
Is a polymer of (a) and (b). The alcohol substance adopts methanol with the strongest polarity, so that the addition of cosolvent methanol is favorable for promoting the separation of formaldehyde molecules and water to form +.>
Dissolved in an organic solvent, the hemiacetal structure formed by methanol and formaldehyde becomes extremely unstable under heating, and methanol is easily released. However, experiments have found that the enhanced extraction with methanol can only occur at low formaldehyde concentrations, and that the amount of methanol added should not be excessive, as the mutual solubility of solvent and water is increased.
Based on the analysis, the whole extraction process is divided into two sections, the extraction effect of formaldehyde is improved by adding cosolvent methanol in the extraction section (recovery extraction tower) with lower formaldehyde concentration, the mutual solubility of oil and water phases is reduced by removing the cosolvent in advance in the extraction section (concentration extraction tower) with higher formaldehyde concentration, the effective phase separation effect is enhanced, and the concentration is increased to a proper degree by adding high-concentration formaldehyde feed.
The invention provides a process method for extracting and concentrating a dilute formaldehyde aqueous solution by a composite solvent, which has the following beneficial effects:
(1) According to the invention, the dilute formaldehyde aqueous solution is concentrated step by arranging the two sections of extraction towers, so that the two towers operate under different solvent concentration environments, the operation is flexible and convenient, and compared with a simple rectification concentration process, the method has the advantage of energy conservation.
(2) According to the invention, the cosolvent is added into the main solvent, so that the extraction capacity of the low-concentration formaldehyde can be enhanced, the formaldehyde can be thoroughly extracted, and the recovery rate of the formaldehyde can be improved.
(3) The invention removes most of cosolvent before concentration process, can reduce the mutual solubility of liquid and liquid phases in the concentration extraction tower, and is beneficial to strengthening phase separation effect.
(4) According to the invention, the feeding of the concentrated formaldehyde solution is added to the top of the concentrated extraction tower, so that the concentration of formaldehyde in the discharged material of the top of the concentrated extraction tower can be increased, and a concentrated product meeting the quality requirement can be obtained.
The invention is a simple decomposition method in the extraction process, can realize the aim of thickening aiming at the concentration adjustment process parameters of formaldehyde aqueous solutions with different concentrations, and has much lower energy consumption than the traditional rectification separation method. And the processing temperature of the process method is not high, so that the quality of the obtained product is stable and reliable, and the technical indexes in all aspects can meet the requirements of industrial production.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required for the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of the process flow structure of the present invention.
The label specification in the drawings:
1. the method comprises the following steps of recycling an extraction tower, a concentrated extraction tower, a desolventizing rectifying tower, a sieve plate, a recycling extraction tower top feed inlet, a primary heat exchanger, a recycling extraction tower bottom feed inlet, an evaporator, a condenser, a transfer pump, a secondary heat exchanger, a concentrated extraction tower bottom inlet, an extraction phase storage tank, a concentrated extraction tower top feed inlet, a concentrated extraction tower bottom tank, a conveying pump, a recycling extraction tower bottom tank and a recycling extraction tower bottom outlet.
The direction indicated by the arrow in the figure is the gas-liquid flow direction.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved by the present application more clear, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.
A process for concentrating a dilute aqueous formaldehyde solution by composite solvent extraction, which comprises the following steps:
the method comprises the steps of forming a composite solvent by a main solvent and a cosolvent according to a certain proportion, filling a recovery extraction tower 1 with the composite solvent before production operation, filling a concentration extraction tower 2 with the main solvent, operating the recovery extraction tower 1 under the condition that the composite solvent is an extractant, operating the concentration extraction tower 2 under the condition that the main solvent is the extractant, wherein the solvent is selected as a continuous phase in operation, and the formaldehyde aqueous solution is selected as a disperse phase. The dilute formaldehyde solution is added into the recovery extraction tower 1 from the feed inlet 5 at the top of the recovery extraction tower, the dilute formaldehyde solution flows downwards along the recovery extraction tower 1 after being dispersed, the composite solvent enters the recovery extraction tower 1 from the feed inlet 7 at the bottom of the recovery extraction tower after being heated by the primary heat exchanger 6, and the composite solvent is mixed with the continuous phase to flow upwards along the recovery extraction tower 1. The solvent phase leaving from the top of the recovery extraction tower 1 is gasified by an evaporator 8 and sent to the bottom of the desolventizing rectifying tower 3, and the solvent phase is condensed by a condenser 9 after coming out from the top of the desolventizing rectifying tower 3 through rectification to obtain the cosolvent; the residual liquid of the evaporator 8 and the liquid at the bottom of the desolventizing rectifying tower 3 are pressurized by a transfer pump 10, then sequentially enter a primary heat exchanger 6 and a secondary heat exchanger 11, are cooled and then are sent to a concentrated extraction tower bottom inlet 12, are mixed with a continuous phase in a concentrated extraction tower 2, flow upwards along the tower, fresh concentrated formaldehyde solution is added into the concentrated extraction tower 2 from a concentrated extraction tower top feed inlet 14, flow downwards along the concentrated extraction tower 2 after being dispersed, and an extraction phase leaving from the top of the concentrated extraction tower 2 enters an extraction phase storage tank 13 to obtain a concentrated formaldehyde solution with low water content.
The dispersed phase in the concentration extraction tower 2 flows downwards along the concentration extraction tower 2, is condensed into a whole in the concentration extraction tower bottom tank 15, enters the secondary heat exchanger 11 through the conveying pump 16 connected with the tower bottom, is heated and then is sent to the recycling extraction tower top feed inlet 5 to enter the recycling extraction tower 1 together with the dilute formaldehyde solution, the dispersed phase is formed to flow downwards along the recycling extraction tower 1 until a condensed layer is formed at the lower part of the recycling extraction tower bottom tank 17, and is discharged from the recycling extraction tower bottom outlet 18.
The recovery extraction tower 1 and the concentration extraction tower 2 are internally provided with sieve plates 4 which are equivalent to 5-8 theoretical plates, and the theoretical plates of the desolventizing rectifying tower 3 are 8-12.
The main solvent is saturated monohydric alcohol with boiling point of 150-180deg.C under normal pressure, preferably at least one of n-hexanol, n-heptanol or cyclohexanol.
The cosolvent is methanol.
The mass percentage of the main solvent in the composite solvent is 85-92%, and the mass percentage of the cosolvent is 8-15%.
The operation temperature of the recovery extraction tower 1 is 50-65 ℃, and the operation temperature of the concentration extraction tower 2 is 25-40 ℃.
The mass percentage of formaldehyde in the dilute formaldehyde aqueous solution added from the feed inlet 5 of the recovery extraction tower top is 5-12.5%, and the mass percentage of formaldehyde in the concentrated formaldehyde aqueous solution added from the feed inlet 14 of the concentration extraction tower top is 44-48%.
The feeding mass flow ratio of the composite solvent to the dilute formaldehyde aqueous solution in the recovery extraction tower 1 is 1.1-2.4:1.
The mass flow ratio of the concentrated formaldehyde feed to the recovery extraction column 1 and the concentrated formaldehyde feed to the concentration extraction column 2 is 0.25-0.4:1.
Example 1
The extraction process of fig. 1 is adopted, wherein the recovery extraction tower 1 and the concentration extraction tower 2 are both sieve plate towers containing 8 theoretical plates, the theoretical plates of the desolventizing rectification tower 3 are 8, and the normal pressure operation is carried out.
Dilute formaldehyde liquid (the mass fractions of formaldehyde and water are 8.0% and 92.0% respectively) with the temperature of 25 ℃ enters the recovery extraction tower 1 from the feed inlet 5 at the top of the recovery extraction tower at the flow rate of 500 kg/h; the composite solvent (the mass fractions of methanol and n-hexanol are 15 percent and 85 percent respectively) with the temperature of 25 ℃ is heated and then enters the recovery extraction tower 1 from the feed inlet 7 at the bottom of the recovery extraction tower at the flow rate of 900 kg/h; concentrated formaldehyde liquid (formaldehyde and water mass fractions of 44.0% and 56.0%, respectively) at a temperature of 25℃was fed into the concentrate extraction column 2 from the concentrate extraction column top feed inlet 14 at a flow rate of 160 kg/h.
After the operation is stable, the temperature of the recovery extraction tower 1 is 50-60 ℃, the temperature of the concentration extraction tower 2 is 25-35 ℃, the bottom evaporation temperature of the desolventizing rectifying tower 3 is 100-110 ℃, the temperature of the tower top condenser 9 is 50 ℃, and the reflux ratio of the desolventizing rectifying tower 3 is 3.
After stable operation, the amount of raffinate phase material obtained from the bottom outlet 18 of the recovery extraction tower is 465kg/h, wherein the mass fractions of formaldehyde, methanol, water and n-hexanol are respectively 0.21%, 10.8%, 87.6% and 1.4%; the flux of the cosolvent obtained at the top of the desolventizing rectifying tower 3 is 72kg/h, and the flux of the cosolvent contains formaldehyde, methanol, water and n-hexanol which are respectively 0.25%, 98.55%, 0.94% and 0.26%; the top of the extraction column 2 was concentrated to give an extract phase flow of 1023kg/h, containing 10.7%, 1.4%, 13.8% and 74.1% formaldehyde, methanol, water and n-hexanol, respectively.
The mass ratio of formaldehyde to water in the extraction phase is 0.78:1, and the concentration multiple reaches 5.5 compared with the dilute formaldehyde feed.
Example 2
The extraction process of FIG. 1 was used, the apparatus was operated at normal pressure as in example 1.
Dilute formaldehyde liquid (the mass fractions of formaldehyde and water are 12.5% and 87.5% respectively) with the temperature of 25 ℃ enters the recovery extraction tower 1 from the feed inlet 5 at the top of the recovery extraction tower at the flow rate of 500 kg/h; the composite solvent (the mass fractions of methanol and n-hexanol are 8 percent and 92 percent respectively) with the temperature of 25 ℃ is heated and then enters the recovery extraction tower 1 from the feed inlet 7 at the bottom of the recovery extraction tower at the flow rate of 1200 kg/h; concentrated formaldehyde liquid (formaldehyde and water mass fractions of 48.0% and 52.0%, respectively) at a temperature of 25℃was fed into the concentrate extraction column 2 from the concentrate extraction column top feed inlet 14 at a flow rate of 160 kg/h.
After the operation is stable, the temperature of the recovery extraction tower 1 is 55-65 ℃, the temperature of the concentration extraction tower 2 is 30-40 ℃, the bottom evaporation temperature of the desolventizing rectifying tower 3 is 105-115 ℃, the temperature of the tower top condenser 9 is 50 ℃, and the reflux ratio of the desolventizing rectifying tower 3 is 4.
After stable operation, the raffinate phase material amount obtained at the bottom outlet 18 of the recovery extraction tower is 395kg/h, wherein the mass fractions of formaldehyde, methanol, water and n-hexanol are respectively 0.16%, 5.6%, 92.9% and 1.3%; the flux of the cosolvent obtained at the top of the desolventizing rectifying tower 3 is 54kg/h, and the flux of the cosolvent contains formaldehyde, methanol, water and n-hexanol which are respectively 0.22%, 98.64%, 0.90% and 0.24%; the top of the extraction column 2 was concentrated to give an extract phase flow of 1411kg/h, containing formaldehyde, methanol, water and n-hexanol of 9.8%, 1.5%, 10.9% and 77.8%, respectively.
The mass ratio of formaldehyde to water in the extraction phase is 0.90:1, and the concentration multiple reaches 3.8 compared with the dilute formaldehyde feed.
Example 3
The extraction process of FIG. 1 was used, the apparatus was operated at normal pressure as in example 1.
The dilute formaldehyde liquid (formaldehyde and water mass fractions are 5.0% and 95.0% respectively) with the temperature of 25 ℃ enters the recovery extraction tower 1 from the feed inlet 5 at the top of the recovery extraction tower at the flow rate of 800 kg/h; the composite solvent (the mass fractions of methanol and n-hexanol are 12 percent and 88 percent respectively) with the temperature of 25 ℃ is heated and then enters the recovery extraction tower 1 from the feed inlet 7 at the bottom of the recovery extraction tower at the flow rate of 900 kg/h; concentrated formaldehyde liquid (formaldehyde and water mass fractions of 48.0% and 52.0%, respectively) at a temperature of 25℃was fed into the concentrate extraction column 2 from the concentrate extraction column top feed inlet 14 at a flow rate of 200 kg/h.
After the operation is stable, the temperature of the recovery extraction tower 1 is 50-60 ℃, the temperature of the concentration extraction tower 2 is 25-35 ℃, the bottom evaporation temperature of the desolventizing rectifying tower 3 is 100-110 ℃, the temperature of the tower top condenser 9 is 50 ℃, and the reflux ratio of the desolventizing rectifying tower 3 is 5.
After stable operation, the raffinate phase material amount obtained at the bottom outlet 18 of the recovery extraction tower is 769kg/h, wherein the mass fractions of formaldehyde, methanol, water and n-hexanol are respectively 0.26%, 7.4%, 91.0% and 1.3%; the flux of the cosolvent obtained at the top of the desolventizing rectifying tower 3 is 41kg/h, and the flux of the cosolvent contains formaldehyde, methanol, water and n-hexanol which are respectively 0.23%, 98.52%, 1.0% and 0.25%; the flow rate of the extraction phase obtained from the top of the concentration extraction tower 2 is 1090kg/h, and the flow rates of formaldehyde, methanol, water and n-hexanol are respectively 12.2%, 1.0%, 15.0% and 71.7%.
The mass ratio of formaldehyde to water in the extraction phase is 0.81:1, and the concentration multiple reaches 9.0 compared with the dilute formaldehyde feed.
Example 4
The extraction process of FIG. 1 was used, the apparatus was operated at normal pressure as in example 1.
Dilute formaldehyde liquid (the mass fractions of formaldehyde and water are 8.0% and 92.0% respectively) with the temperature of 25 ℃ enters the recovery extraction tower 1 from the feed inlet 5 at the top of the recovery extraction tower at the flow rate of 500 kg/h; the composite solvent (the mass fractions of methanol and n-heptanol are 10 percent and 90 percent respectively) with the temperature of 25 ℃ is heated and then enters the recovery extraction tower 1 from the feed inlet 7 at the bottom of the recovery extraction tower at the flow rate of 1000 kg/h; concentrated formaldehyde liquid (formaldehyde and water mass fractions of 48.0% and 52.0%, respectively) at a temperature of 25℃was fed into the concentrate extraction column 2 from the concentrate extraction column top feed inlet 14 at a flow rate of 200 kg/h.
After the operation is stable, the temperature of the recovery extraction tower 1 is 55-65 ℃, the temperature of the concentration extraction tower 2 is 30-40 ℃, the bottom evaporation temperature of the desolventizing rectifying tower 3 is 110-120 ℃, the temperature of the tower top condenser 9 is 50 ℃, and the reflux ratio of the desolventizing rectifying tower 3 is 4.
After stable operation, the raffinate phase material amount obtained at the bottom outlet 18 of the recovery extraction tower is 446kg/h, wherein the mass fractions of formaldehyde, methanol, water and n-heptanol are respectively 0.15%, 6.85%, 92.6% and 0.4%; the flux of the cosolvent obtained at the top of the desolventizing rectifying tower 3 is 53kg/h, and the flux of the cosolvent contains formaldehyde, methanol, water and n-heptanol which are respectively 0.20%, 98.82%, 0.92% and 0.06%; the top of the extraction column 2 was concentrated to obtain an extract phase flow of 1201kg/h, and formaldehyde, methanol, water and n-heptanol contents of 11.3%, 1.4%, 12.5% and 74.8%, respectively.
The mass ratio of formaldehyde to water in the extraction phase is 0.90:1, and the concentration multiple reaches 5.9 compared with the dilute formaldehyde feed.
When the method is used for recovering and concentrating formaldehyde, the residual formaldehyde in the water discharged from the bottom of the recovery extraction tower 1 is less than 0.3% by adjusting the process conditions, so that a higher formaldehyde recovery rate is achieved; the concentration multiple of the extract phase obtained from the top of the concentration extraction tower 2 is 3.8-10 times compared with the dilute formaldehyde feed.
Example 5
The extraction process of fig. 1 is adopted, wherein the recovery extraction tower 1 and the concentration extraction tower 2 are both sieve plate towers containing 5 theoretical plates, the theoretical plates of the desolventizing rectification tower 3 are 12, and the operation is carried out at normal pressure.
Dilute formaldehyde liquid (the mass fractions of formaldehyde and water are 8.0% and 92.0% respectively) with the temperature of 25 ℃ enters the recovery extraction tower 1 from the feed inlet 5 at the top of the recovery extraction tower at the flow rate of 500 kg/h; the composite solvent (the mass fractions of methanol and cyclohexanol are 15 percent and 85 percent respectively) with the temperature of 25 ℃ is heated and then enters the recovery extraction tower 1 from the feed inlet 7 at the bottom of the recovery extraction tower at the flow rate of 900 kg/h; concentrated formaldehyde liquid (formaldehyde and water mass fractions of 44.0% and 56.0%, respectively) at a temperature of 25℃was fed into the concentrate extraction column 2 from the concentrate extraction column top feed inlet 14 at a flow rate of 160 kg/h.
After the operation is stable, the temperature of the recovery extraction tower 1 is 50-60 ℃, the temperature of the concentration extraction tower 2 is 25-35 ℃, the bottom evaporation temperature of the desolventizing rectifying tower 3 is 107-116 ℃, the temperature of the tower top condenser 9 is 50 ℃, and the reflux ratio of the desolventizing rectifying tower 3 is 2.5.
After stable operation, the raffinate phase material amount obtained at the bottom outlet 18 of the recovery extraction tower is 471kg/h, wherein the mass fractions of formaldehyde, methanol, water and cyclohexanol are respectively 0.22%, 11.4%, 86.1% and 2.3%; the flux of the cosolvent obtained at the top of the desolventizing rectifying tower 3 is 69kg/h, and the flux of the cosolvent contains formaldehyde, methanol, water and cyclohexanol which are respectively 0.27%, 98.6%, 0.91% and 0.22%; the top of the extraction column 2 was concentrated to give an extract phase flow of 1020kg/h, and formaldehyde, methanol, water and cyclohexanol were 10.7%, 1.3%, 14.1% and 73.9%, respectively.
The mass ratio of formaldehyde to water in the extraction phase is 0.76:1, and the concentration multiple reaches 5.4 compared with the dilute formaldehyde feed.
The foregoing description of the preferred embodiments of the present application is not intended to be limiting, but is intended to cover any and all modifications, equivalents, and alternatives falling within the spirit and principles of the present application.
Claims (5)
1. A process for concentrating a dilute aqueous formaldehyde solution by composite solvent extraction, which is characterized by comprising the following steps:
the method comprises the steps of (1) preparing a composite solvent from a main solvent and a cosolvent according to a certain proportion, filling a recovery extraction tower with the composite solvent before production operation, filling a concentration extraction tower with the main solvent, operating the recovery extraction tower under the condition that the composite solvent is an extractant, and operating the concentration extraction tower under the condition that the main solvent is the extractant, wherein the solvent is selected as a continuous phase in operation, and formaldehyde aqueous solution is selected as a disperse phase; adding the dilute formaldehyde solution into a recovery extraction tower from a feed inlet at the top of the recovery extraction tower, dispersing the dilute formaldehyde solution, flowing downwards along the recovery extraction tower, heating the composite solvent through a primary heat exchanger, entering the recovery extraction tower from the feed inlet at the bottom of the recovery extraction tower, and mixing with a continuous phase to flow upwards along the recovery extraction tower; the solvent phase leaving from the top of the recovery extraction tower is gasified by an evaporator and sent to the bottom of the desolventizing rectifying tower, and the solvent phase is condensed by a condenser after coming out from the top of the desolventizing rectifying tower through rectification to obtain the cosolvent; the residual liquid of the evaporator and the liquid at the bottom of the desolventizing rectifying tower are pressurized by a transfer pump, then sequentially enter a first-stage heat exchanger and a second-stage heat exchanger, are cooled and then are sent to an inlet at the bottom of a concentrated extraction tower, are mixed with a continuous phase in the concentrated extraction tower and flow upwards along the tower, fresh concentrated formaldehyde solution is added into the concentrated extraction tower from a feed inlet at the top of the concentrated extraction tower, and after being dispersed, flows downwards along the concentrated extraction tower, and an extraction phase leaving from the top of the concentrated extraction tower enters an extraction phase storage tank to obtain a concentrated formaldehyde solution with low water content;
the disperse phase in the concentration extraction tower flows downwards along the concentration extraction tower, is condensed into a whole in a concentration extraction tower bottom tank, enters a secondary heat exchanger through a delivery pump connected with the tower bottom, is heated and then is sent to a feed inlet at the top of the recovery extraction tower to enter the recovery extraction tower together with the dilute formaldehyde solution, so that the disperse phase flows downwards along the recovery extraction tower until a coacervate is formed at the lower part of the recovery extraction tower bottom tank, and is then discharged from a tower bottom outlet of the recovery extraction tower;
the main solvent is at least one of n-hexanol, n-heptanol or cyclohexanol, and the cosolvent is methanol; the mass percentage of the main solvent in the composite solvent is 85-92%, and the mass percentage of the cosolvent is 8-15%; the operation temperature of the recovery extraction tower is 50-65 ℃, and the operation temperature of the concentration extraction tower is 25-40 ℃.
2. The process for extracting and concentrating a dilute formaldehyde aqueous solution by using a composite solvent according to claim 1, wherein 5-8 sieve plates of theoretical plates are arranged in the recovery extraction tower and the concentration extraction tower, and the theoretical plates of the desolventizing and rectifying tower are 8-12.
3. The process for extracting and concentrating a dilute aqueous formaldehyde solution by using a composite solvent according to claim 1, wherein the mass percentage of formaldehyde in the dilute aqueous formaldehyde solution added from a feed inlet at the top of the recovery extraction tower is 5-12.5%, and the mass percentage of formaldehyde in the concentrated aqueous formaldehyde solution added from a feed inlet at the top of the recovery extraction tower is 44-48%.
4. The process for extracting and concentrating a dilute aqueous formaldehyde solution by using a composite solvent according to claim 1, wherein the mass flow ratio of the composite solvent to the dilute aqueous formaldehyde solution in the recovery extraction tower is 1.1-2.4:1.
5. The process for extracting concentrated aqueous dilute formaldehyde solution by using a composite solvent according to claim 1, wherein the mass flow ratio of the concentrated formaldehyde feed to the dilute formaldehyde feed in the recovery extraction column is 0.25-0.4:1.
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| CN202110468385.4A Active CN113511965B (en) | 2021-04-29 | 2021-04-29 | Process method for concentrating dilute formaldehyde aqueous solution by composite solvent extraction |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1556962A (en) * | 1977-11-10 | 1979-12-05 | Sterlitamax Opytpromysh Neftek | Method for recovering formaldehyde from aqueous solutions thereof |
| CN102372610A (en) * | 2010-08-09 | 2012-03-14 | 江苏恒茂机械制造有限公司 | Extraction and rectification technology and preparation apparatus of high-density methylal |
| CN111454135A (en) * | 2020-04-26 | 2020-07-28 | 青岛迈特达新材料有限公司 | Device and process for preparing high-concentration methylal |
| CN112225650A (en) * | 2019-07-15 | 2021-01-15 | 中国石油化工股份有限公司 | Refining method for obtaining high-purity methylal by purifying industrial-grade methylal |
-
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- 2021-04-29 CN CN202110468385.4A patent/CN113511965B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1556962A (en) * | 1977-11-10 | 1979-12-05 | Sterlitamax Opytpromysh Neftek | Method for recovering formaldehyde from aqueous solutions thereof |
| CN102372610A (en) * | 2010-08-09 | 2012-03-14 | 江苏恒茂机械制造有限公司 | Extraction and rectification technology and preparation apparatus of high-density methylal |
| CN112225650A (en) * | 2019-07-15 | 2021-01-15 | 中国石油化工股份有限公司 | Refining method for obtaining high-purity methylal by purifying industrial-grade methylal |
| CN111454135A (en) * | 2020-04-26 | 2020-07-28 | 青岛迈特达新材料有限公司 | Device and process for preparing high-concentration methylal |
Non-Patent Citations (1)
| Title |
|---|
| 低浓度甲醛提浓技术探讨;林晓燕等;《广州化工》;第42卷(第5期);第119-120页 * |
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