JP4030439B2 - Method and apparatus for concentrating substances having higher boiling point than water in exhaust gas - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a method for concentrating and recovering hydrophilic and volatile chemical substances having a boiling point higher than that of water contained in exhaust gas and not azeotropically with water using the difference in boiling point with water and purifying the exhaust gas. And device .
[0002]
[Prior art]
Conventionally, in order to purify exhaust gas containing a water-soluble solvent having a boiling point higher than that of water, the exhaust gas containing a water-soluble solvent is blown from the lower part of the absorption tower, and a large amount of water is allowed to flow from the upper part of the absorption tower. Was washing. In such a cleaning method, a large amount of water is required for cleaning, and since the concentration of the solvent contained in the waste water is extremely low, the solvent recovery is costly, so that the solvent recovery is practically impossible. Moreover, there is a problem that wastewater treatment is required.
[0003]
As another prior art, while rotating the horizontally arranged drum filled with an adsorbent such as zeolite, the exhaust gas cooled to about room temperature is passed through, and a part of the passing gas is released into the atmosphere as it is. Part of the sample is heated (to expel the component adsorbed on the adsorbent) and then passed again through a horizontally arranged drum filled with adsorbent such as zeolite, and the solvent adsorbed on the adsorbent is desorbed. The process gas containing a high concentration of was cooled again to recover the solvent. This method is also very inefficient in energy efficiency because it requires an operation of cooling the exhaust gas once, heating it after the adsorption treatment, and cooling it again for solvent recovery.
[0004]
For example, a conventional adsorption method has been used to remove N-methyl-2-pyrrolidone (NMP) contained in exhaust gas discharged from the drying process of the lithium electrode. In view of the fact that the adsorption efficiency of -2-pyrrolidone is significantly reduced, a step of cooling the high-temperature exhaust gas discharged from the drying step is necessary, and after adsorbing N-methyl-2-pyrrolidone on the adsorbent In order to purge N-methyl-2-pyrrolidone from the adsorbent, this time, an operation of heating in the opposite direction was necessary. Such prior art processes are shown in Figure 3.
According to the conventional method, the cooling step, the adsorption step, it must be a three steps of the desorption step, and after cooling the exhaust gas with a considerable temperature, the problem of involving a large energy loss for heating again had It was.
[0005]
[Problems to be solved by the invention]
The first object of the present invention is to recover efficiently by substituting water vapor with a hydrophilic or volatile chemical substance that has a boiling point higher than that of water contained in the exhaust gas and does not azeotrope with water , for example, a water-soluble solvent. A further object is to provide a method and apparatus for purifying exhaust gas.
The second object of the present invention is to evaporate the makeup water introduced from the outside by using the calorific value of the high temperature exhaust gas discharged from 100 ° C. to 120 ° C. from the lithium ion battery electrode manufacturing process or the like. The water-soluble volatile chemicals that have a higher boiling point than the water contained in the exhaust gas are condensed, that is, the components in the exhaust gas are replaced with water for efficient recovery, and the absorption effect of the low-temperature makeup water is improved. It is the point which provides the method and apparatus which cleans waste gas by adding.
[0006]
In the first aspect of the present invention, a tray having a structure in which gas cannot escape to the upper part unless passing through water existing on the tray is provided in a multistage manner, or from a lower portion of a packed tower packed with a hydrophilic packing. In addition, an exhaust gas containing a substance having a boiling point higher than that of water is introduced, while water is supplied from the upper part of the tower, and a substance having a higher boiling point than that of water is concentrated in the lower part of the tower due to a gas-liquid equilibrium relationship between the exhaust gas and water, "in a boiling point higher than that of water, forming an azeotropic mixture with water and not hydrophilic, volatile chemicals" in the exhaust gas in the upper portion of the column, characterized in that shifting to more water the substances in the exhaust gas remaining method for concentrating met Thus, the amount of water supplied from the top of the tower is controlled based on the concentration information at the bottom of the tower, and the concentration of hydrophilic and volatile chemical substances having a boiling point higher than that of water recovered from the bottom of the tower and not azeotropic with water is 20 to Exhaust that is controlled to 100% by weight In a boiling point higher than that of water in the scan, forming an azeotropic mixture with water and not hydrophilic, to a method of concentrating the volatile chemicals.
In the second aspect of the present invention, hydrophilic and volatile chemical substances having a boiling point higher than that of water and not azeotropic with water are NMP (N-methylpyrrolidone), DMF (N, N-dimethylformamide), DMAC (N, N-dimethylacetamide), DMSO (dimethyl sulfoxide), EG (ethylene glycol), DEG (diethylene glycol), TEG (triethylene glycol), PGME (propylene glycol monoethyl ether), PG (propylene glycol), 1,4-BD (1,4-butanediol), MEA (monoethanolamine) and DGME at a boiling point higher than that of water in the exhaust gas according to claim 1, wherein the (diethylene glycol monomethyl ether) solvents, selected from the group consisting of water and co The present invention relates to a method for concentrating non-boiling hydrophilic and volatile chemical substances.
The third aspect of the present invention is
(1) A multi-stage tray tower or a packed tower packed with a hydrophilic packing, in which the gas cannot escape upward unless it passes through the water present on the tray,
(2) A water supply means provided in the stage tower above the multi-stage tray or above the packed bed or a water supply means provided in the packed tower above
(3) A processing gas discharge port provided at the top of the plate tower or the top of the packed bed,
(4) Liquid discharge port provided at the lower part of the column tower or the lower part of the packed bed,
(5) A liquid reservoir containing hydrophilic and volatile chemicals that has a higher boiling point than water connected through a pipe from the liquid discharge outlet and does not azeotrope with water.
(6) Hydrophilicity that has a higher boiling point than water provided in the stage column or packed column and does not azeotrope with water.
Measuring means for detecting the concentration of volatile chemicals in the system,
(7) The amount of water supplied from the water supply means is determined by the information from the measurement means as the volatile chemical.
Means for controlling the quality concentration to be 20-100% by weight ;
The present invention relates to a concentrating device for “hydrophilic and volatile chemical substances having a boiling point higher than water and not azeotropic with water” in exhaust gas.
[0007]
In the present invention, the amount of heat of exhaust gas, which usually has a considerably high temperature (for example, 80 to 120 ° C.), is effectively used , and the exhaust gas is passed through the stage column or packed column in one step. Is an extremely efficient method and apparatus for simultaneously recovering substances having a boiling point higher than that of water and treating exhaust gas.
The present invention, in particular, from the lower part of a stage column or a packed column packed with a hydrophilic packing, in which a tray having a structure in which the gas cannot escape to the upper part unless passing through the water present on the tray, High temperature exhaust gas at 100 to 120 ° C. containing N-methylpyrrolidone discharged from the lithium ion battery electrode manufacturing process is introduced, while water is supplied from the upper part of the tower and supplied using the calorific value of the exhaust gas at the lower part of the tower. On the other hand, water having a boiling point higher than that of water contained in the exhaust gas and water-soluble N-methylpyrrolidone is condensed and dropped to the lower part of the tower. Furthermore, it is very suitable as a method and apparatus for purifying exhaust gas from a lithium ion battery electrode manufacturing factory and recovering N-methylpyrrolidone by transferring it to water.
[0008]
The amount of water to be replenished is the amount of water (B) that is contained in the treated gas released from the upper part of the column tower after exhaust gas treatment and the condensate of volatile chemicals having a boiling point higher than that of water. At the same time, it may be an amount (A) that compensates for the amount of water (C) coming out from the bottom of the tower. In other words A ≒ B + C
Therefore, the amount of water used is much less than that of the conventional exhaust gas treatment method by water washing, and even if only this point is seen, it has achieved resource saving and substantially discharged wastewater that requires wastewater treatment. It is also a great merit that it does not occur.
[0009]
The temperature at the top of the column is higher than the outside air temperature. Since the higher the temperature, the higher the saturated moisture content, the moisture in the gas in the column tower is always below the saturation point, so even if make-up water is added, the conditions to satisfy Xac ≦ Xs can be created. Can do. Xac is the calculated moisture content, and Xs is the gas saturated moisture content. The temperature of the make-up water is preferably low in terms of absorption efficiency, but if it is too low, not only the amount of water flowing down in the tower will be insufficient, but also energy for cooling will be required. Since the outside air is not normally saturated and exists at a moisture content that does not reach saturation represented by humidity, the amount of makeup water is larger than that in the saturated state.
[0010]
Examples of the substance having a boiling point higher than that of the water of the present invention include volatile chemical substances.
[0011]
And a high boiling point of the volatile chemical substances from the water, and more particularly to a high water-soluble solvent having a boiling point than water representative.
[0012]
Examples of such solvents include NMP (N-methylpyrrolidone, BP: 197 ° C), DMF (N, N-dimethylformamide, BP: 153 ° C), DMAC (N, N-dimethylacetamide, BP: 165 ° C). , DMSO (dimethyl sulfoxide, BP: 189 ° C.), EG (ethylene glycol, BP: 197 ° C.), DEG (diethylene glycol, BP: 245 ° C.), TEG (triethylene glycol, BP: 278 ° C.), PGME (propylene glycol mono Ethyl ether), PG (propylene glycol, BP: 188 ° C), 1,4-BD (1,4-butanediol, BP: 235 ° C), MEA (monoethanolamine, BP: 170.5 ° C) and DGME ( Diethylene glycol monomethyl ether) and other non-azeotropic properties It is preferred.
[0013]
There is a valve cap tray (bubble bell plate) that has been used since the oldest as a tray with a structure that allows gas to escape to the top if it does not pass through the water present in the tray. And a sieve tray (perforated plate). The valve cap tray is better from the viewpoint of stability, but the sheave tray is better from the viewpoint of cost.
[0014]
The hydrophilic packing in the packed tower packed with the hydrophilic packing may be in the form of regular packing or irregular packing, but considering the pressure loss, Is preferred. These fillers are hydrophilic and have a large surface area, such as porous materials made of a hydrophilic material, specifically porous ceramics and porous carbon.
[0015]
The present invention can be suitably used for treating exhaust gas discharged from a drying process for removing N-methyl-2-pyrrolidone (NMP) solvent, particularly in a lithium ion battery manufacturing plant. As shown in FIG. 1, in order to remove the N-methyl-2-pyrrolidone (NMP) solvent, normal air is taken from outside the factory, filtered, and then heated air is blown to the drying process by a blower. .
Normal intake air from outside the factory is outside temperature t
Flow rate V Nm ³ / min
Moisture content Xa kg / m ³
Water content V · [(273 + t) / 273] · Xa kg / min
It is. The exhaust gas discharged from the drying process for removing the N-methyl-2-pyrrolidone (NMP) solvent in the lithium ion battery manufacturing factory is exhaust gas temperature t ₁ = 100 to 120 ° C.
NMP content Cn = 0.005-0.01 kg / N m ³
(113-2260 ppm, vol./vol.)
NMP flow rate VCn kg / min
Flow rate of exhaust gas V Nm ³ / min
Water content V · [(273 + t) / 273] · Xa kg / min
It is blown from the lower part of the stage tower (water displacement tower) under the conditions of From the uppermost stage such as valve cap trays and sheave trays provided in multiple stages in the water displacement tower, make-up water at normal temperature, for example, t ₃ ° C is supplied at a flow rate of M kg / min. The treated gas (gas temperature t ₂ ) released from the upper part of the water displacement tower is obtained by using R as the recovery rate (weight fraction) of volatile chemical substances such as NMP.
Release amount V Nm ³ / min
Calculated water content V · [(273 + 15) / 273] · Xa +
[M-VCnR (1 / Xn-1)] kg / min
Calculated moisture content Xac = {[(273 + 15) / 273] · Xa +
[M-VCnR (1 / Xn-1)] / V}.
[273 / (273 + t ₂ )] kg / m ³
When the gas temperature _{t 2,} gas saturated water content: Xs
As a control condition, when Xac ≦ Xs, the apparatus can be operated normally.
On the other hand, N-methyl-2-pyrrolidone (liquid temperature t ₄ ) containing water is recovered from the lower part of the water displacement column.
[0016]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto. In the examples, percentages are by weight unless otherwise indicated.
[0017]
Example 1
The intake air in the drying process for removing the N-methyl-2-pyrrolidone (NMP) solvent of the lithium ion battery shown in FIG.
Outside air temperature t = 15 ℃
Flow rate V = 4 Nm ³ / min
Moisture content Xa = 0.0128 kg / m ³ (assuming saturation)
The water content was V · [(273 + 15) / 273] · Xa = 0.054 kg / min. The exhaust gas discharged from the drying process for removing the N-methyl-2-pyrrolidone (NMP) solvent in the lithium ion battery manufacturing plant is exhaust gas temperature t ₁ = 120 ° C.
NMP content Cn = 0.0031 kg / N m ³
(700 ppm, vol./vol.)
NMP flow rate VCn = 0.124 kg / min
Flow rate of exhaust gas V = 4 Nm ³ / min
Moisture amount V · [(273 + 15) / 273] · Xa = 0.054 kg / min. Make-up water with a water temperature t ₃ = 20 ° C. is supplied at a flow rate of M = 0.1786 kg / min from the uppermost stage of the valve cap tray provided in multiple stages in the water displacement tower. The treated gas released from the upper part of the water displacement tower (gas temperature t ₂ = 42 ° C.) is released V = 4 Nm ³ / min
Calculated water content V [(273 + 15) / 273] · Xa +
[M-VCnR (1 / Xn-1)] = 0.2208 kg / min
Calculated moisture content Xac = {[(273 + 15) / 273] · Xa +
[M-VCnR (1 / Xn-1)] / V}.
[273 / (273 + t ₂ )] = 0.0478 kg / m ³
When gas temperature t ₂ = 42 ° C., gas saturated moisture content: Xs = 0.0565 kg / m ³
Therefore,
Xac = 0.0478 kg / m ³ ≦ Xs = 0.0565 kg / m ³
NMP content Cn (1-R) = 0.00015 kg / N m ³
This device can be operated normally.
On the other hand, N-methyl-2-pyrrolidone (liquid temperature t ₄ = 80 ° C.) containing water was recovered from the lower part of the water displacement column under the following conditions.
t ₄ = 80 ° C
Water in the collected liquid VCnR (1 / Xn-1) = 0.118 kg / min
NMP in the collected liquid VCnR = 0.118 kg / min
NMP recovery rate R = 0.95 (weight fraction)
NMP concentration Xn = 0.50 (weight fraction)
The water displacement column material balance was as shown in FIG.
[0018]
【The invention's effect】
(1) According to the present invention, remarkable simplification of the process and energy saving can be achieved.
(2) In the conventional method, a means is adopted in which water is supplied from the top of the solvent component to be recovered, etc., and the solvent is dissolved in the water and poured down. In this case, if the temperature of the system is high, the solvent dissolved in the water volatilizes again, so that the water supplied to the washing tower needs to be cooled to about room temperature in advance. Therefore, energy for cooling is required. On the other hand, in the present invention, the heat of the exhaust gas is used effectively, so that the exhaust gas supplied to the concentrating device can be supplied as it is without heating or cooling, so that the thermal efficiency is extremely high.
(3) According to the present invention, only a small amount of replenishing water is required for recovery, but so-called washing water is used in the prior art, so in the present invention, water is used compared to the conventional method. The amount can be reduced to about a thousandth.
[Brief description of the drawings]
1 is a flow sheet showing the recovery method of the present invention used in Example 1. FIG.
FIG. 2 is a flow sheet showing a heat balance analysis diagram and a material balance of Example 1.
FIG. 3 is a flow sheet showing a recovery method using a conventional adsorbent.

Claims (3)

Substances with a boiling point higher than water from the bottom of a packed column or a packed column filled with a hydrophilic packing, in which multiple trays with a structure in which gas cannot escape through the water present on the tray are not allowed to escape. On the other hand, water is supplied from the upper part of the tower, and substances having a higher boiling point than the water are concentrated in the lower part of the tower due to the vapor-liquid equilibrium relationship between the exhaust gas and water, and in the remaining exhaust gas at the upper part of the tower The above-mentioned substance is further transferred to water, which is a method for concentrating “hydrophilic and volatile chemical substances having a higher boiling point than water and not azeotropic with water” in exhaust gas , which is supplied from the upper part of the tower The amount of water is controlled based on the concentration information at the bottom of the tower so that the concentration of hydrophilic and volatile chemicals that have a higher boiling point than water recovered from the bottom of the tower and does not azeotrope with water is 20 to 100% by weight. Higher than the water in the exhaust gas being controlled In point, the method of concentrating water azeotroped not hydrophilic, volatile chemicals. Hydrophilic and volatile chemical substances having a boiling point higher than that of water and not azeotropic with water are NMP (N-methylpyrrolidone), DMF (N, N-dimethylformamide), DMAC (N, N-dimethylacetamide), DMSO. (Dimethyl sulfoxide), EG (ethylene glycol), DEG (diethylene glycol), TEG (triethylene glycol), PGME (propylene glycol monoethyl ether), PG (propylene glycol), 1,4-BD (1,4-butanediol) ), MEA (monoethanolamine) and DGME (boiling point higher than that of water in the exhaust gas according to claim 1, wherein the solvents, selected from the group consisting of diethylene glycol monomethyl ether), water and azeotroped not hydrophilic, volatile A method of concentrating chemical substances. (1) A multi-stage tray tower or a packed tower packed with a hydrophilic packing, in which the gas cannot escape upward unless it passes through the water present on the tray,
(2) A water supply means provided in the stage tower above the multi-stage tray or above the packed bed or a water supply means provided in the packed tower above
(3) Process gas discharge port provided at the upper part of the column tower or the upper part of the packed bed,
(4) Liquid discharge port provided at the lower part of the column tower or the lower part of the packed bed,
(5) A liquid reservoir containing hydrophilic and volatile chemicals that has a higher boiling point than water connected through a pipe from the liquid discharge outlet and does not azeotrope with water.
(6) Hydrophilicity that has a higher boiling point than water provided in the stage column or packed column and does not azeotrope with water.
Measuring means for detecting the concentration of volatile chemicals in the system,
(7) The amount of water supplied from the water supply means is determined by the information from the measurement means as the volatile chemical.
Means for controlling the quality concentration to be 20-100% by weight ;
A concentrating device for "hydrophilic and volatile chemical substances having a boiling point higher than water and not azeotropic with water" in exhaust gas, characterized by comprising:

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