CN114426346A

CN114426346A - Method for treating NMP-containing wastewater

Info

Publication number: CN114426346A
Application number: CN202011102346.4A
Authority: CN
Inventors: 柯月亮; 陈林; 周美均; 刘勇; 黄戚辉
Original assignee: Chongqing Chuanwei Technology Co ltd; China Petroleum and Chemical Corp; Sinopec Chongqing Chuanwei Chemical Co Ltd
Current assignee: Chongqing Chuanwei Technology Co ltd; China Petroleum and Chemical Corp; Sinopec Chongqing Chuanwei Chemical Co Ltd
Priority date: 2020-10-15
Filing date: 2020-10-15
Publication date: 2022-05-03

Abstract

The invention belongs to the technical field of wastewater treatment by an adsorption method, and particularly relates to a treatment method of wastewater containing NMP. The method for treating the NMP-containing wastewater comprises the steps of pretreatment, resin adsorption, blowing, resin desorption and desorption liquid separation and purification of a resin outlet in the resin desorption step, wherein the height-diameter ratio of an adsorption resin layer is controlled to be 3: 1-10: 1 in the resin adsorption step, and the flow speed of the wastewater is 0.5-4 BV/h. The method is suitable for treating the wastewater with a wide NMP concentration range, has a high NMP removal rate, does not influence subsequent treatment, does not cause high-temperature polymerization of NMP, and is energy-saving and environment-friendly.

Description

Method for treating NMP-containing wastewater

Technical Field

The invention belongs to the technical field of wastewater treatment by an adsorption method, and particularly relates to a treatment method of wastewater containing NMP.

Background

N-methyl pyrrolidone (NMP) belongs to nitrogen heterocyclic compound with molecular formula of C₅H₉O, which has a high boiling point, a strong polarity, a low viscosity, a strong dissolving power, no corrosion, a low toxicity, a low volatility, and a stable chemical property, and is widely used in the fields of petrochemical industry, plastic industry, pharmaceuticals, pesticides, fuels, and lithium ion battery manufacturing industry ("recent research progress of N-methylpyrrolidone", jia taixuan, etc., liaoning chemical industry, vol.33, No. 11, p.642, l.1, lines 1-7, published 2004, month 11 and 30). In addition, NMP is also used for separation and purification (such as a concentration process for preparing acetylene by partial oxidation of natural gas) and electronic process cleaning of C2-C5 eneyne.

At present, NMP is used as a solvent in the concentration process for preparing acetylene by partial oxidation of domestic natural gas. The acetylene concentration system mainly comprises a pre-absorption tower, a main absorption tower, a stripping desorption tower and a vacuum extraction tower, wherein an NMP solvent firstly pressurizes and absorbs acetylene hydrocarbon and other components in the cracking gas, and then a saturated solvent decompresses and desorbs the acetylene gas, so that the separation and purification of the acetylene are realized. The acetylene concentration system generates wastewater with NMP concentration of 100 mg/L-20000 mg/L during operation, maintenance, start and stop.

However, the N-methyl pyrrolidone has stable chemical property and poor biodegradability, and if the N-methyl pyrrolidone is sent into sewage for treatment, COD (chemical oxygen demand) and total nitrogen of the sewage external drainage exceed standards, so that downstream water bodies are polluted. The NMP mixed solvent generated by electronic process cleaning mostly adopts extractive distillation and rectification recovery, and NMP wastewater mostly adopts oxidation process and biochemical process for treatment, for example, the patent document with the publication number of CN11170531A discloses a wastewater treatment process in the NMP synthesis process, which pumps wastewater into a water inlet distributor, simultaneously adds hydrogen peroxide into the water inlet distributor to be mixed with the wastewater, pumps the mixed wastewater into an electrolytic reactor, and the mixed wastewater is decomposed under the irradiation of UV light in the electrolytic reactor and the action of electrode materials, so that COD wastewater discharged from the electrolytic reactor can be less than 500 mg/L. Patent document CN204550267U discloses a system for treating lithium ion battery wastewater containing methyl pyrrolidone, which mainly adopts fenton oxidation and subsequent separation and filtration, and can make the COD of the treated wastewater be 303mg/L, and the removal rate be 82.7%.

However, when NMP is treated by an oxidation method, NMP is not easy to oxidize, the consumption of the oxidant is large, resource utilization cannot be realized, and a large amount of oxidant is left in the wastewater, so that the subsequent treatment is not facilitated. The proportion of the molar weight of the oxidant to the molar weight of the NMP solvent is relatively larger when the NMP solvent with low concentration is treated by the oxidation method, the concentration of the oxidant after treatment is relatively excessive, the influence on biochemical bacteria of a downstream biochemical system is larger, and the relative cost is also higher. The biochemical treatment process has certain special requirements on the process route, the existing sewage treatment device of an enterprise mostly has no corresponding conditions, and the old process flow is difficult to carry out process transformation and implement.

Other processes are also adopted for treatment, for example, patent document with publication number CN108218756A discloses a system and method for low-temperature recovery of wastewater, which uses multi-stage rectification to realize low-temperature rectification and recovery of high-concentration NMP wastewater. However, the low-concentration NMP wastewater is recovered by a rectification process, the steam consumption is large, the environment-friendly, energy-saving and emission-reducing policies are not met, and the temperature is high during rectification, so that high-temperature polymerization of NMP is easily caused.

Disclosure of Invention

In view of the above, the present invention aims to provide a method for treating NMP-containing wastewater, which is suitable for treating wastewater with a wide NMP concentration range (NMP mass concentration is 100mg/L to 20000mg/L), has a high NMP removal rate, does not affect subsequent treatment, does not cause high temperature polymerization of NMP, and is energy-saving and environment-friendly.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the treatment method of the NMP-containing wastewater comprises the working procedures of pretreatment, resin adsorption, blowing, resin desorption and desorption liquid separation and purification of a resin outlet in the working procedures of resin desorption, wherein the height-diameter ratio of an adsorption resin layer is controlled to be 3: 1-10: 1 in the working procedure of resin adsorption, and the flow speed of the wastewater is 0.5-4 BV/h.

In the present invention, the separation and purification can be performed by flash evaporation or rectification, but is not limited to flash evaporation or rectification.

Further, the pretreatment comprises the steps of pre-filtration, secondary filtration and pH adjustment.

In the present invention, the filtering medium used for the pre-filtering can be quartz sand, pulverized coal particles or activated carbon particles, but is not limited thereto.

Furthermore, the filtering pore diameter of the filtering medium adopted by the secondary filtering is 0.5-5 μm.

In the present invention, the filter medium used in the secondary filtration can be, but is not limited to, a filter bag or a fiber filter layer.

Further, the pH adjustment means that the pH is adjusted to 5-8.

Furthermore, the dosage of the analysis liquid stock solution adopted in the resin analysis process is 2-5 BV, and the flow rate is 0.5-4 BV/h.

In the present invention, the original solution of the desorption solution may be methanol, but is not limited thereto.

Furthermore, the resin adsorption also comprises a biochemical treatment process.

Further, the resin analysis also includes a secondary purge step and a tertiary purge step.

Further, the purging step and the secondary purging step are purged by using compressed gas.

Further, the tertiary purging process adopts 0.1-0.15 MPa steam for purging.

The invention also relates to the use of the protective resin for the treatment of NMP-containing waste waters.

The invention has the beneficial effects that:

the method of the invention is suitable for treating the wastewater with a wide NMP concentration range (NMP mass concentration of 100 mg/L-20000 mg/L).

The method has high removal rate of NMP, and the removal rate can reach more than 99.5 percent.

The method of the invention does not affect subsequent processing.

The method of the invention does not cause high-temperature polymerization of NMP, and is energy-saving and environment-friendly.

Drawings

FIG. 1 is a flow chart of a treatment process in examples 1 to 4, wherein S01 is a prefilter, S02 is a fine filter, D01 is a resin adsorption column, D02 is a desorption liquid rectifying column, R01 is a washing liquid storage tank, R02 is a desorption liquid storage tank, E01 is a condenser, and E02 is a heater.

Detailed Description

The examples are provided for better illustration of the present invention, but the present invention is not limited to the examples. Therefore, those skilled in the art should make insubstantial modifications and adaptations to the embodiments of the present invention in light of the above teachings and remain within the scope of the invention.

The following NMP content detection method is a gas chromatography, and specifically comprises the following steps:

(1) instrument for measuring the position of a moving object

The device comprises a Bruker 456 gas chromatograph, an FID detector, a DB-624 column and a manual sample injection needle;

(2) reagent

NMP (chromatographically pure), distilled water;

(3) operating conditions of the gas chromatograph:

carrier gas: hydrogen is 30 mL/min; combustion-supporting gas: the air in the steel cylinder is 300 mL/min; blowing nitrogen gas at the tail for 30 mL/min; temperature of the column box: keeping the temperature at 150 ℃ for 10min, and increasing the temperature to 240 ℃ at the heating rate of 20 ℃/min and keeping the temperature for 3 min; sample inlet temperature: 250 ℃; the temperature of the FID detector is 300 ℃; the split ratio is as follows: 10: 1; sample introduction amount: 1 μ L

(4) Experimental procedure

Preparation of a standard solution: preparing 5 100mL volumetric flasks, adding 100g of distilled water into the three volumetric flasks, accurately weighing the three volumetric flasks to 0.0001g, respectively adding 0.5g, 1.0g, 2.0g, 2.5g and 3.0g of NMP (chromatographically pure) reagent, accurately weighing the NMP (chromatographically pure) to 0.0001g, and calculating the percentage content of the NMP in the prepared standard solution;

calibration of the analytical method: injecting 1 mu L of the prepared standard solution according to the operating conditions of a chromatograph, separating on a DB-624 chromatographic column, and detecting by an FID detector; and calculating a correction factor according to the NMP concentration and the peak area of each standard solution, and drawing a standard curve by taking the NMP concentration as an abscissa and the peak area as an ordinate.

Sample detection: and (3) introducing 1 mu L of sample to be detected according to the operating conditions of a chromatograph, separating on a DB-624 chromatographic column, detecting the peak area by an FID detector, and determining the abscissa of the peak area corresponding to the standard curve as the NMP concentration of the sample to be detected.

BV in the unit of flow rate of the present invention is an abbreviation of English bed volume and represents the volume of the resin bed loaded in the adsorption column. For example, the flow rate is 2BV/h, which means that the volume of solution passing through per hour is 2 times the volume of the resin bed.

Example 1

The NMP-containing wastewater treatment method comprises the following specific steps:

A. pretreatment of

A1. The NMP wastewater (namely raw material NMP wastewater) is sent to a prefilter S01, suspended matters are removed, and the effluent is sent to a fine filter S02; wherein, the S01 filter medium layer adopts a quartz sand layer and a coal powder particle layer; s02, adopting a fiber filter head with the aperture of 5 μm;

A2. adjusting the pH value of the wastewater obtained in the step 1 to 5;

B. resin adsorption: feeding the wastewater obtained in the step A2 into the top of an adsorption tower D01 filled with 50ml of macroporous adsorption resin for adsorption; the height-diameter ratio of the adsorption resin layer is 3: 1; the flow speed of the resin layer is 4 BV/h; the adsorption tower adopts a single tower;

C. biochemical treatment: sending the wastewater after the resin adsorption treatment into a biochemical treatment device for treatment;

D. purging: blowing the macroporous adsorption resin tower D01 subjected to resin adsorption treatment from the top by using compressed air, and stopping blowing when no obvious liquid drops exist at the bottom;

E. resin analysis: resolving the macroporous adsorption resin layer by using 2BV of methanol resolving liquid stock solution at the flow rate of 4 BV/h;

F. separation and purification: collecting the desorption solution generated at the resin outlet in the resin desorption step, carrying out rectification separation, collecting refined methanol at the tower top, and collecting a high-purity NMP solvent at the tower bottom;

G. secondary purging and tertiary purging: blowing the macroporous adsorption resin tower subjected to resin analysis treatment by using compressed gas from the top, and stopping blowing when no obvious liquid drop exists at the bottom; then, the macroporous absorption resin tower is purged for 10 minutes from the top by using low-pressure steam of 0.1-0.15 Mpa, and the macroporous absorption resin layer enters the next cycle.

Example 2

A. pretreatment of

A2. adjusting the pH value of the wastewater obtained in the step 1 to 8;

Example 3

A. pretreatment of

A2. adjusting the pH value of the wastewater obtained in the step 1 to 8;

B. resin adsorption: feeding the wastewater obtained in the step A2 into the top of an adsorption tower D01 filled with 50ml of macroporous adsorption resin for adsorption; the height-diameter ratio of the adsorption resin layer is 3: 1; the flow speed of the resin layer is 1 BV/h; the adsorption tower adopts a single tower;

E. resin analysis: resolving the macroporous adsorption resin layer with 4BV of methanol resolving liquid stock solution at the flow rate of 2 BV/h;

Example 4

A. pretreatment of

A2. adjusting the pH value of the wastewater obtained in the step 1 to 8;

Performance detection

The NMP content in the raw material NMP wastewater in the examples 1 to 4 is detected;

the NMP content in the resin column effluent in the resin adsorption step of examples 1-4 was determined according to the formula

The removal rate of NMP was calculated, and the resultsAs shown in table 1;

in the formula, n1 is the content of NMP in raw material NMP wastewater in mg/L, and n2 is the content of NMP in resin column effluent in mg/L.

TABLE 1 Performance test results

Source	Raw material NMP content/(mg/L) in waste water	Content of NMP in effluent of resin column/(mg/L)	Removal rate of NMP/%)
				Example 1	10000	43	99.5
Example 2	10000	39	99.6
				Example 3	10000	Not detected (out of detection lower limit 10mg/L)	Greater than 99.99
Example 4	10000	48	99.7

As is clear from Table 1, the removal rate of NMP in the wastewater by the methods of examples 1 to 4 was 99.5% or more. This demonstrates that the method of the present invention is highly efficient in treating NMP.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. The method for treating the NMP-containing wastewater is characterized by comprising the steps of pretreatment, resin adsorption, blowing, resin desorption and separation and purification of desorption liquid at a resin outlet in the resin desorption step, wherein the height-diameter ratio of an adsorption resin layer is controlled to be 3: 1-10: 1 in the resin adsorption step, and the flow rate of the wastewater is 0.5-4 BV/h.

2. The treatment process according to claim 1, characterized in that said pretreatment comprises the steps of pre-filtration, secondary filtration and adjustment of the pH.

3. The treatment method according to claim 2, wherein the filter medium used in the secondary filtration has a filter pore size of 0.5 to 5 μm.

4. The treatment method according to claim 2 or 3, wherein the adjusting of the pH means adjusting the pH to 5 to 8.

5. The treatment method according to any one of claims 1 to 4, wherein the amount of the used raw solution of the resin analysis solution is 2 to 5BV and the flow rate is 0.5 to 4 BV/h.

6. The treatment method according to any one of claims 1 to 5, further comprising a biochemical treatment step after the resin adsorption.

7. The treatment method according to any one of claims 1 to 6, further comprising a secondary purge step and a tertiary purge step after the resin desorption.

8. The treatment method according to claim 7, wherein the purge step and the secondary purge step are purged with a compressed gas.

9. The process according to claim 7 or 8, wherein the tertiary purging step is performed with 0.1Mpa (A) steam.

10. The application of the resin in the treatment of wastewater containing NMP.