JP2838125B2 - Treatment of amine-containing wastewater - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an advanced treatment technology for amine-containing wastewater discharged from an amine production plant.

[Related Art] An amine-containing wastewater or a wastewater containing an amine and an inorganic salt is generated from an amine production plant by a reaction between an organic halogen compound and a nitrogen-containing compound. Generally, amine-containing wastewater is generally subjected to a coagulation treatment using an anionic polymer coagulant due to its properties. This method requires an expensive polymer flocculant, and not only cannot recover useful amines in wastewater, but also has a problem in terms of new treatment of generated sludge. When high concentrations of inorganic salts coexist in the wastewater, the coagulation-sedimentation method cannot be said to be an appropriate treatment method.

Various adsorbent treatment methods have been attempted for amine-containing wastewater.

As described in The Chemical Society of Japan 1985 (4) 802,
Activated carbon has poor adsorption capacity for nitrogen-containing compounds such as ammonia and amines. Silica-titania and silica-magnesia gels have been proposed as highly active adsorbents to overcome the drawbacks of activated carbon. For example, for 100 ppm amine-containing wastewater, these adsorbents show a maximum removal rate of 58%, which is not sufficiently satisfactory in terms of the removal rate. Further, a composite oxide adsorbent such as silica-titania has an acid property and is easily eluted into a liquid phase by a basic substance such as an amine, and thus has a problem in durability.

Japanese Patent Application Laid-Open No. Sho 62-49990 proposes a silica gel adsorbent for overcoming the drawback of poor adsorption performance of activated carbon and activated clay.

When wastewater containing a high concentration of amine of 20,000 ppm is treated with silica gel, the removal rate is 57%, and the COD load of the wastewater is still large and cannot be said to be a sufficiently satisfactory treatment technology.

[Problems to be Solved by the Invention] As described above, a wastewater treatment technique for highly treating amine-containing wastewater and significantly reducing the amine concentration in the wastewater includes:
It is hard to say that it is still industrially established. In particular, there is a strong demand for the development of an industrial treatment technology that selectively removes and recovers amine from amine-containing wastewater in which high concentrations of inorganic salts coexist and suppresses the COD load in the wastewater to a low level.

The present invention uses activated carbon that can be obtained industrially at low cost,
An object of the present invention is to provide an advanced treatment technology for amine-containing wastewater that satisfies the following points.

1) Achieve a low level of COD load in wastewater by performing adsorption treatment at a high removal rate.

2) Efficient recovery of amine adsorbed on activated carbon.

3) Non-polluting wastewater treatment system by completely closed.

[Means for Solving the Problems] The present inventors have made intensive studies with the aim of significantly reducing the COD load of amine-containing wastewater and developing a wastewater treatment system for a pollution-free amine production plant. As a result, amine-containing wastewater discharged from the amine production process
a step of adjusting the pH to a predetermined range, treating with activated carbon, and then desorbing the amine adsorbed on the activated carbon under specific conditions. Furthermore, by devising a method for collecting the desorbed liquid from the desorption step, the possibility of a wastewater treatment technique that almost eliminates amine discharge to the outside and enables efficient amine recovery has been reached.

That is, the present invention provides a wastewater treatment process for treating an amine-containing wastewater discharged from an amine production plant or an amine-containing wastewater coexisting with an inorganic salt with an activated carbon, by adding an alkali metal hydroxide or an alkaline earth metal hydroxide to the wastewater. An adsorption step in which the hydrogen ion concentration is adjusted to 10.8 or more, followed by contact with activated carbon. A desorbed liquid containing 2 to 20% by weight of a mineral acid is fed to the activated carbon packed bed adsorbed with an amine at a linear velocity of 0.
Amine desorption step supplied at 1 to 15 m / hr A step of sending the desorption liquid to an amine production plant to recover the amine. A method for treating amine-containing wastewater, comprising the steps of:

In addition, the present invention, of the desorption solution generated from the desorption step, adding an inorganic alkaline substance to the desorption solution having an amine concentration of 30 g / l or less, adjusting the pH to 10.8 or more, and then feeding the activated carbon packed bed as a desorption step feed. How to recycle.

Furthermore, of the desorbing liquid generated from the desorbing step, a mineral acid is added to the desorbing liquid having an amine concentration of 50 g / l or less to adjust the free hydrochloric acid concentration to 2 to 20% by weight, and then used as a desorbing liquid in the desorption step. how to.

That is, the present invention is a wastewater treatment method by treating an amine-containing wastewater generated in an amine production plant by a reaction between an organic halogen compound and a nitrogen-containing compound with activated carbon by the above operation.

[Operation] Hereinafter, the present invention will be described in more detail.

The wastewater treatment method of the present invention can be effectively applied to an amine production plant using an organic halogen compound and a nitrogen-containing compound as raw materials.

The organic halogen compound is an aliphatic halogen compound or an aromatic halogen compound having a halogen such as chlorine, bromine, fluorine or iodine as a substituent. Specifically, methyl chloride, methyl bromide, butyl chloride, dichloroethane, dibromoethane, chlorobromoethane, dichlorobutane, benzyl chloride, 2-bromo-1-phenylethane, fluoroalkylcarboxylic acid, iodine methyl, alkylene diiodide Aliphatic compounds having mono- and polyhalogen groups such as dyed. Aromatic compounds having mono- and polyhalogen substituents such as chlorobenzene, dichlorobenzene, dibromobenzene, fluorobenzene, chlorobenzyl chloride, bromotoluene and chloronaphthalene. Further, even if these halogen-containing compounds have functional groups such as an ether group, an ester group, an amide group, a thioether group, a carbonyl group, and a carboxyl group, there is no problem.

The nitrogen-containing compound is a compound having a primary amino group and a secondary amino group in a molecule including ammonia. Specifically, alkylamines such as methylamine, propylamine, diethylamine, octylamine, and dilaurylamine; polyalkylenepolyamines such as ethylenediamine, piperazine, diethylenetriamine, propylenediamine, hexamethylenediamine, tetraethylenepentamine, and polyethyleneimine; And aromatic amines such as aniline, phenylenediamine, aminophenol and aminonaphthalene.

The present invention is an amine production plant using these raw materials, for example, a wastewater treatment method such as an ethyleneamine production plant using dichloroethane and ammonia, a phenylenediamine production plant using dichlorobenzene and ammonia, and a laurylethylenediamine production plant using lauryl bromide and ethylenediamine. Effectively applicable.

The method of the present invention is not limited to the above specific examples, and can be widely applied to an amine production plant using an organic halogen compound and a nitrogen-containing compound.

The amine concentration in the wastewater to which the method of the present invention is applied is not particularly limited, but wastewater containing 10 to 100,000 ppm of amine is usually treated. Even with high concentration amine-containing wastewater of 100,000 ppm or more, it can be treated at a high removal rate by the method of the present invention, but considering the load at the time of recovering adsorbed amine, it is not necessarily economically advantageous wastewater treatment method. Does not. Therefore, the method of the present invention can be applied by lowering the concentration by dilution or the like.

The inorganic salt that coexists in the wastewater of the present invention is preferably an inorganic salt in which the cation portion of the inorganic salt is an alkali metal or alkaline earth metal ion and the anion portion is a halogen ion. The amine-containing wastewater coexisting with these inorganic salts, for the activated carbon contact treatment of the present invention,
It is a wastewater having suitable properties, and the method of the present invention enables effective and selective removal of amine.

The concentration of these inorganic salts coexisting in the wastewater is not particularly limited, and may be acceptable up to a concentration at which the inorganic salts are uniformly dissolved in the system.

As the activated carbon used in the present invention, any of charcoal, coal and coconut shell charcoals which are used as general adsorbents and water treatment agents can be effectively used. Among them, in the treatment method of the present invention, coconut shell charcoal is extremely useful industrially. The form may be granular or powdery.

In the amine adsorption step of the present invention, an alkali metal hydroxide or an alkaline earth metal hydroxide is added to the amine-containing wastewater discharged from the plant to reduce the hydrogen ion concentration to 1
By adjusting to 0.8 or more, preferably 11.0 or more, and then contacting with activated carbon, a high amine removal rate can be achieved. When amine-containing wastewater that does not reach pH 10.8 is subjected to activated carbon adsorption treatment, the leakage of amine is large and it is difficult to achieve advanced wastewater treatment.

As an alkali metal hydroxide, calcium hydroxide and magnesium hydroxide are used from an economic viewpoint as caustic soda, caustic potash or alkaline earth metal hydroxide. Usually, the use of caustic soda or caustic potash is advantageous. However, the present invention is not limited to these alkali metal hydroxides.

The wastewater treatment method using activated carbon can be applied to the present invention in any of a batch method, a continuous fixed bed method, a continuous fluidized bed method, and the like. Among them, a continuous activated carbon treatment method is extremely advantageous industrially.

The temperature of the wastewater between the wastewater and the activated carbon is lower than the boiling point of water, but the low-viscosity wastewater is usually treated at 70 ° C or lower.

The treatment time in the batch method varies depending on the properties of the wastewater and the amount of activated carbon, but the contact equilibrium is reached by contacting for 15 minutes to 24 hours.

The liquid passing rate in the fixed bed fluidization system largely depends on properties such as the amount of amine contained in the wastewater and the molecular weight of the amine. Usually, the liquid is passed at a linear velocity of 0.1 to 20 m / hr.
Although processing can be performed even at a linear velocity of 20 m / hr or more, the concentration of amine leaking into the processing solution is undesirably increased.

The amine adsorbed on the activated carbon by the above operation is desorbed by the operation described below.

A mineral acid aqueous solution having a concentration of 2 to 20% by weight is used as the desorbing liquid. Mineral acids such as sulfuric acid, nitric acid and phosphoric acid can also be used,
Hydrochloric acid is most effective for desorption of an amine compound derived from the organic halogen compound of the present invention. If the concentration is 2% by weight or less, the concentration of amine in the desorbing solution is remarkably reduced, which is not industrially preferable. If the content is more than 20% by weight, the amine concentration in the desorbing solution is undesirably lowered.

In the case of the activated carbon packed bed method, the supply speed of the desorbed liquid is optimally 0.1 to 15 m / h as a linear velocity. If it is 0.1 m / hr or less, it is not preferable from the viewpoint of productivity, and if it is 15 m / hr or more, the amine concentration in the desorbing solution is lowered and the desorption efficiency is lowered.

The amount of the mineral acid used varies depending on the desorption conditions, but is usually 1 to 5 equivalents, preferably 1 to 3 equivalents, to the number of nitrogen equivalents of the adsorbed amine. Below 1 equivalent, the desorption of the amine is incomplete.

The temperature of the feed / desorption liquid can be usually operated at 0 to 100 ° C, but the preferable temperature is 0 to 75 ° C. Feeding at a desorption liquid temperature of 75 ° C. or higher undesirably lowers the desorption efficiency.

The desorption solution containing the amine and the mineral acid is sent to an amine production plant, and the amine is recovered in a separation and purification step of the plant. All of the desorption liquid may be processed in an amine production plant. Further, the desorption solution may be fractionated according to the amine concentration in the desorption solution, and the following treatment may be performed.

That is, the desorption solution having an amine concentration of 30 g / l or less is adjusted to a hydrogen ion concentration of 10.8 or more, preferably 11.0 or more by adding an alkali, and then supplied to the activated carbon layer as a feed solution to the adsorption step to perform the adsorption treatment. I do. By performing this operation, the load of the desorbing liquid treatment in the separation and purification process of the manufacturing plant can be reduced.

In addition, a mineral acid is added to a low-concentration desorbing solution having an amine concentration of 50 g / l or less to adjust the free mineral acid concentration to 2 to 20% by weight, and then used as a desorbing solution in the desorption step. By performing this operation, the amine concentration in the desorbing liquid can be significantly increased, and the load on the amine recovery equipment is greatly reduced. When a liquid obtained by adding a mineral acid to a desorption liquid having an amine concentration of 50 g / l or more is used as a desorption liquid, the efficiency of desorption of amine from activated carbon decreases, which is not preferable in terms of operation.

As described above, the desorbed solution may be fractionated and treated according to its concentration, or may be fractionated into two at an amine concentration of 50 g / l or 30 g / l and subjected to each treatment. .

[Effects of the present invention] From a plant for producing an amine by a reaction between an organic halogen compound and a nitrogen-containing compound, an amine-containing wastewater in which high-concentration inorganic salts coexist is discharged. For wastewater having such properties, application of the adsorption treatment method using activated carbon of the present invention results in a synergistic increase in amine adsorption capacity to activated carbon, resulting in a reduced activated carbon regeneration cycle and easier plant operation management. . In particular, a marked decrease in the amine concentration in the treatment liquid was caused, and as a result, advanced wastewater treatment became possible.

It is generally known that the properties of wastewater change. For example, in an EDC ethyleneamine production plant, the amine concentration in the wastewater discharged from the plant and the composition of the type of amine (ethylenediamine, diethylenetriamine, triethylenetetramine, etc.) change depending on the plant operating conditions. The adsorptive treatment method of the present invention has a feature that it can stably maintain a high degree of wastewater treatment while allowing fluctuations in the wastewater state. By applying the specified conditions of the present invention to the desorption step, the desorption rate of amine from activated carbon can be reduced to almost 10
0%, so that a long life of activated carbon can be achieved. Further, the amine in the desorption solution can be obtained at a high concentration, and the burden on the amine recovery operation can be significantly reduced. The desorbed liquid thus obtained is sent to a separation and purification step of an amine production plant, and useful amine is recovered. Also,
The amine recovery efficiency can be increased by appropriately changing the treatment method according to the amine concentration in the desorption solution.

The features of the wastewater treatment method according to the present invention are that it captures amines in wastewater with almost 100% removal rate, and realizes a completely pollution-free manufacturing plant by applying an efficient complete closed system. It is in the point which was made.

EXAMPLES Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 Caustic soda was added to wastewater containing 300 g / l of sodium chloride and mg / l of ethyleneamine discharged from a dichloroethane method ethyleneamine production plant to adjust the hydrogen ion concentration (pH) to 11.2. 200 liters of this wastewater is applied to a jacketed glass column filled with 4 liters of granular coconut shell activated carbon,
The solution was passed at 3 m / hr at a liquid temperature of 60 ° C. As a result of analyzing the ethyleneamine concentration in the processing solution by TOC meter and Kjeldahl method, 2pp
m and the amine removal rate was 99.8%. Next, 4 l of water was passed through to wash the inside of the column. 4.5 L of a 7.3% hydrochloric acid desorbed solution was passed at a linear velocity of 3 m / hr at a liquid temperature of 40 ° C. 27 liters of water
Was passed through. The desorbed solution was fractionated into three fractions according to the amine concentration, and the amine concentration of each solution was measured. As a result, the amine concentration was 85%
g / l, solution B 7 g / l, solution C 1 g / l.

The amine in the solution A was quantitatively recovered by an operation method usually performed in a separation and purification step of an amine production plant. The amine recovery was 70% with respect to the amine in the wastewater.

Example 2 180 liters of wastewater containing the same concentration of sodium chloride and ethyleneamine as in Example 1 and 25 liters of Solution C of Example 1 (a part of the desorption solution containing an ethyleneamine concentration of 1 g / l and hydrochloric acid) Then, 85 g of caustic soda was added to adjust the hydrogen ion concentration to 11.5. The adjusted wastewater was passed through the same coconut shell activated carbon packed tower as in Example 1 at a linear velocity of 5 m / hr and a liquid temperature of 40 ° C. The amine concentration in the liquid passed through the packed tower was analyzed by a TOC analyzer and the Kjeldahl method. As a result, the removal rate was 89.3 and the removal rate was 99.3%. The column was washed by passing 4 l of water.

Next, a 35% hydrochloric acid aqueous solution was added to the solution B of Example 1 (desorption solution containing 8 g / l of ethyleneamine and hydrochloric acid) to adjust the free hydrochloric acid concentration to 9.2%, and used as a desorption solution. 5.5
l was passed through an activated carbon layer at a liquid temperature of 35 ° C. at a linear velocity of 2 m / hr. Subsequently, 27 l of water was passed to obtain a desorbed liquid. The amine concentration in the desorbed solution obtained by fractionation according to the amine concentration was 95 g / l for solution A and 1 for solution B, respectively.
The amount was 8 g / l and the C solution was 1 g / l. The solution A and the solution B were combined and mixed, and the amine therein was quantitatively recovered by an operation method usually performed in a separation and purification step of an amine production plant. Amine recovery rate is 89% (amine in 205 l of wastewater treated in the adsorption process
(Based on the total amount with amine in liquid B of Example 1).
The liquid C of this example was used as a solution for dissolving solid salt produced as a by-product from an amine manufacturing plant without being discarded, and the resulting aqueous solution of by-produced salt was adjusted to pH 11.4 and then adsorbed with activated carbon and recovered. . By performing this operation, 99.3% of the amine in the wastewater was recovered, and the discharge of the amine to the outside of the plant system was almost suppressed, so that complete closure could be achieved.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-149171 (JP, A) JP-A-2-90985 (JP, A) JP-A-2-126989 (JP, A) JP-A-54-1979 115556 (JP, A) JP-A-58-30384 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C02F 1/28

Claims (6)

(57) [Claims] In an activated carbon treatment process for an amine-containing wastewater or an amine-containing wastewater coexisting with an inorganic salt discharged from a plant for producing an amine by a reaction between an organic halogen compound and a nitrogen-containing compound, the wastewater is treated with an alkali metal hydroxide. Step of adding amine or alkaline earth metal hydroxide to adjust the hydrogen ion concentration (pH) to 10.8 or more, and then contacting with activated carbon.
Amine desorption step of supplying a desorption liquid having a concentration of 0.1% by weight at a linear velocity of 0.1 to 15 m / hr. A step of sending the desorption liquid to an amine production plant and recovering the amine. Wastewater treatment method. 2. An alkali metal hydroxide or an alkaline earth metal hydroxide is added to a desorbing solution having an amine concentration of 30 g / l or less from the desorbing solution generated from the amine desorbing step, and the hydrogen ion concentration The wastewater treatment method according to claim 1, wherein after the (pH) is adjusted to 10.8 or more, the solution is recycled to the activated carbon packed bed as a feed solution in the desorption step. 3. A deacidifying solution having an amine concentration of 50 g / l or less among the desorbing solutions generated from the amine desorbing step, and a mineral acid is added to the solution to adjust the free mineral acid concentration to 2 to 20% by weight.
The wastewater treatment method according to claim 1, wherein the method is used as a desorption solution in a desorption step. 4. An amine-containing wastewater or an amine-containing wastewater coexisting with an inorganic salt, which is an ethyleneamine-containing wastewater discharged from a dichloroethane method ethyleneamine production plant or an ethyleneamine-containing wastewater coexisting with sodium chloride or calcium chloride. The wastewater treatment method according to any one of (1), (2) and (3). 5. A wastewater treatment method according to claim 1, wherein the activated carbon is coconut shell activated carbon. 6. The wastewater treatment method according to any one of claims (1), (2), (3), (4) and (5), wherein the mineral acid is hydrochloric acid.