Method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by using extraction method

Abstract

The invention discloses a method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by using an extraction method, which comprises the following steps: evaporating the ammonium nitrate-containing wastewater to obtain a solid-containing concentrated solution, filtering and collecting the solid; adding a poor solvent into the filtrate, filtering, and collecting a solid; combining the two solids to obtain an ammonium nitrate crude product; carrying out extraction treatment on the ammonium nitrate crude product by adopting an extracting agent to obtain an extract and an extracting solution; drying the extract to obtain a relatively pure ammonium nitrate product; and adding a poor solvent into the obtained extract, and recovering to obtain ammonium nitrate. The method for treating the ammonium nitrate-containing wastewater and recovering the ammonium nitrate by utilizing the extraction method is simple to operate, environment-friendly and economical, the purity of the recovered ammonium nitrate is at least 95%, and the method has a very high industrial application value.

Description

Technical Field

[0001] The invention belongs to the technical field of cutting fluid wastewater treatment in mechanical processing industry, and relates to a method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by utilizing an extraction method. Background Art

[0002] In industry, the production of HMX mostly adopts the nitration method of hexamethylenetetramine, also known as the acetic anhydride method or Beckmann method. The typical material ratio of the acetic anhydride method is the mass ratio of hexamethylenetetramine, HNO3, NH4NO3, Ac2O and HAc = 1:(5-5.5):(3.7-4.5):(11-12):(16-23). ​​For every ton of HMX produced, about 1 ton of wastewater is generated, and ammonium nitrate accounts for as high as 80% to 95% of the wastewater.

[0003] The production of ammonium nitrate will produce a large amount of industrial wastewater, causing serious pollution to the environment. In particular, when using the old process to produce ammonium nitrate, a large amount of dilute nitric acid will be used, which will inevitably introduce a large amount of water. As the temperature rises, the water carries a large amount of ammonium nitrate and ammonia gas and escapes in the form of water vapor, which is then cooled by the outside world to form condensed waste liquid, which is also the main source of wastewater from ammonium nitrate production. Nitrates are highly toxic to both humans and aquatic plants. If the condensate is directly discharged into surface water, high concentrations of ammonium nitrate and ammonia can easily cause eutrophication of surface water, causing damage to the local ecological water circulation system.

[0004] At present, the research on HMX wastewater treatment methods mainly includes direct oxidation method, advanced oxidation method, photo-fenton method and electrochemical method. These methods tend to directly degrade ammonium nitrate and residual HMX, RDX (cyclotrimethylene trinitramine) and other substances into harmless substances, which makes a large amount of ammonium nitrate unable to be recycled and increases production costs.

[0005] The mainstream methods for recycling ammonium nitrate production wastewater include electrodialysis, ion exchange, integrated membrane, etc. The front-end membrane of the electrodialyzer used in the electrodialysis method is frequently replaced, which may cause water leakage from the electrodialyzer and water cross-linking between the membranes. The desalination rate of the electrodialyzer is only about 70%, and it is difficult for the treated fresh water to meet the national standard of ammonia nitrogen ≤ 10 mg / L. The regeneration operation of the ion exchange method is frequent, and the regenerated water needs to be treated. If the mass concentration of ammonium nitrate in the wastewater is higher than 2g / L or the wastewater is acidic, the resin life cycle will be greatly shortened. The price of the membrane in the integrated membrane method is relatively high, which will increase the product cost; and the membrane assembly can only be used once. If the membrane assembly is damaged somewhere inside, it is difficult to repair and the entire assembly needs to be replaced. In addition, most membranes are polymer membranes, which will be dissolved by organic solvents. Therefore, the integrated membrane method is generally not used in occasions containing organic solvents.

[0006] If the ammonium nitrate in HMX wastewater and ammonium nitrate production wastewater can be purified, it will undoubtedly strengthen the treatment and utilization of wastewater and play a certain role in improving the environment. Summary of the invention

[0007] The purpose of the present invention is to provide a method for treating ammonium nitrate-containing wastewater such as octogen production wastewater and ammonium nitrate production wastewater by extraction method and recovering ammonium nitrate in view of the problems existing in the prior art.

[0008] The technical solution adopted by the present invention is:

[0009] A method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by extraction method comprises the following steps:

[0010] Step (1), evaporating the ammonium nitrate-containing wastewater to obtain a concentrated solution containing solids, filtering, and collecting solids; adding a poor solvent to the filtrate, filtering, and collecting solids; combining the two solids to obtain a crude ammonium nitrate;

[0011] Step (2), extracting the crude ammonium nitrate product with an extractant to obtain an extract and an extract solution; the extract is dried to obtain a relatively pure ammonium nitrate product;

[0012] Step (3), adding a poor solvent to the extract obtained in step (2) to recover ammonium nitrate.

[0013] In step (1), the ammonium nitrate-containing wastewater is Octogen production wastewater or ammonium nitrate production wastewater.

[0014] The octoquin production wastewater mainly contains ammonium nitrate and acetic acid, with the content of ammonium nitrate being 55-65wt%, the content of acetic acid being 2-10wt%, and the water content being 20-30wt%. The octoquin production wastewater also contains a small amount of HMX, RDX, and other undetectable components, with the content of HMX being 0.1-0.5wt%, and the content of RDX being 0.1-0.5wt%.

[0015] The content of ammonium nitrate in the ammonium nitrate wastewater is 5-8g / L.

[0016] The temperature of the evaporation treatment is 80°C±10°C.

[0017] The volume of the concentrated solution is 3% to 7% of the volume of the waste water containing ammonium nitrate.

[0018] The poor solvent is petroleum ether or n-hexane.

[0019] The volume ratio of the poor solvent to the concentrated liquid is 1:1 to 1:4.

[0020] In step (2), the extractant is anhydrous ethanol or acetone.

[0021] The dosage ratio of the crude ammonium nitrate to the extractant is 1:1 to 1:2 kg / L or g / mL, preferably 1:1.45 to 1:1.55 kg / L or g / mL.

[0022] The extraction treatment is as follows: adding an extractant to the crude ammonium nitrate, stirring at room temperature, filtering, and obtaining an extract (i.e., filter cake) and an extract. The extraction treatment can be carried out in a suitable device.

[0023] The drying temperature is 80°C±10°C.

[0024] In step (3), the poor solvent is petroleum ether or n-hexane; specifically, the poor solvent can be the poor solvent obtained after filtering in step (1), so as to achieve the recycling of the poor solvent.

[0025] Calculated on the basis of the extractant, the volume ratio of the extract to the poor solvent is 1:1 to 1:1.5.

[0026] Specifically, a poor solvent is added to the extract obtained in step (2), solids are precipitated at room temperature, the solids are collected, dried, and ammonium nitrate is recovered; the filtrate is distilled, and according to the difference in boiling points between the poor solvent and the extractant, the poor solvent and the extractant are recovered by distillation.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The method of the present invention uses an extraction method to treat ammonium nitrate-containing wastewater such as Octogen production wastewater and recover ammonium nitrate. The operation is simple, environmentally friendly and economical. The purity of the recovered ammonium nitrate is at least 95%, and it has a high application value. Specifically, it is as follows:

[0029] (1) The present invention evaporates acetic acid and water in wastewater according to the difference in boiling points through evaporation operation, thereby reducing the difficulty of subsequent treatment. At the same time, a poor solvent is added to the filtrate from which the crude ammonium nitrate is filtered out to further precipitate the ammonium nitrate, thereby reducing the loss of ammonium nitrate.

[0030] (2) The present invention utilizes the difference in solubility to extract the crude ammonium nitrate obtained by evaporation, thereby washing away the residual acetic acid and almost all of the HMX and RDX in the crude ammonium nitrate to obtain ammonium nitrate with a purity of ≥95%. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below through specific implementation methods.

[0032] Example 1

[0033] The treatment object is HMX production wastewater taken from a certain factory. The HMX production wastewater contains 60.87wt% ammonium nitrate, 10wt% acetic acid, 26wt% water, a total of 0.5wt% HMX and RDX, and other components that cannot be detected.

[0034] A method for treating Octogen production wastewater and recovering ammonium nitrate by extraction, the steps are as follows:

[0035] Step (1), taking 20L (24kg) of HMX production wastewater and placing it in a distillation tower, evaporating it at a temperature of 90°C to obtain 0.6L of concentrated solution containing solids, filtering it, and collecting solids; at room temperature, adding 0.6L of n-hexane to the filtrate, filtering it, collecting solids, and obtaining 0.5L of n-hexane; combining the solids collected twice (a total of 12.65kg) to obtain crude ammonium nitrate;

[0036] Step (2), adding 19L of anhydrous ethanol to the crude ammonium nitrate obtained in step (1), stirring at room temperature for about 1-2 minutes, filtering to obtain an extract and a filter cake, and directly drying the filter cake at 80° C. to obtain 8.12kg of ammonium nitrate product. The ammonium nitrate product was analyzed by comprehensive ion chromatography and high performance liquid chromatography, and the purity was 97%;

[0037] Step (3), adding 19L of n-hexane to the extract obtained in step (2), precipitating solid at room temperature, collecting the solid, and drying to obtain 0.5kg of ammonium nitrate with a purity of 95%. According to the different boiling points of n-hexane and ethanol, n-hexane and ethanol are recovered by distillation.

[0038] The total recovery rate of ammonium nitrate is as high as 57.2%.

[0039] Example 2

[0040] Anhydrous ethanol, acetone, acetonitrile, tetrahydrofuran, n-hexane and petroleum ether were selected as extractants, and the purification effects of different extractants on ammonium nitrate were investigated.

[0041] Take 150mL of HMX production wastewater (same as Example 1), evaporate at a temperature of 85°C until no solid is precipitated, filter the concentrated solution to obtain 80.6g of crude ammonium nitrate, take 6 portions of crude ammonium nitrate, each portion of 8.5g, add 13mL of extractant to the crude product, stir and wash at room temperature, filter, and obtain pure ammonium nitrate.

[0042] The results are shown in Table 1, which show that the purity of ammonium nitrate after washing with acetone and anhydrous ethanol is the highest, and the recovery rate of ammonium nitrate is relatively higher, so these two solvents are selected as extraction agents.

[0043] Table 1. Purification results of different extractants

[0044]

Claims

1. A method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by extraction, characterized in that: The following steps are involved: Step (1), evaporating the ammonium nitrate-containing wastewater to obtain a concentrated solution containing solids, filtering, and collecting solids; adding a poor solvent to the filtrate, filtering, and collecting solids; combining the two solids to obtain a crude ammonium nitrate; Step (2), extracting the crude ammonium nitrate product with an extractant to obtain an extract and an extract solution; and drying the extract to obtain an ammonium nitrate product; Step (3), adding a poor solvent to the extract to recover the ammonium nitrate.

2. The method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by extraction method according to claim 1, characterized in that: In step (1), the ammonium nitrate-containing wastewater is Octogen production wastewater or ammonium nitrate production wastewater; The content of ammonium nitrate in the Octogen production wastewater is 55-65wt%, the content of acetic acid is 2-10wt%, and the water content is 20-30wt%; The content of ammonium nitrate in the ammonium nitrate wastewater is 5-8g / L.

3. The method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by extraction method according to claim 1, characterized in that: In step (1), the temperature of the evaporation treatment is 80°C±10°C.

4. The method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by extraction method according to claim 1, characterized in that: In step (1), the volume of the concentrated solution is 3% to 7% of the volume of the ammonium nitrate-containing wastewater; and the volume ratio of the poor solvent to the concentrated solution is 1:1 to 1:

4.

5. The method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by extraction method according to claim 1, characterized in that: In step (1), the poor solvent is petroleum ether or n-hexane.

6. The method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by extraction method according to claim 1, characterized in that: In step (2), the extractant is anhydrous ethanol or acetone.

7. The method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by extraction method according to claim 1, characterized in that: In step (2), the usage ratio of the crude ammonium nitrate to the extractant is 1:1 to 1:2 kg / L or g / mL.

8. The method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by extraction method according to claim 1 or 7, characterized in that: In step (2), the usage ratio of the crude ammonium nitrate to the extractant is 1:1.45 to 1:1.55 kg / L or g / mL.

9. The method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by extraction method according to claim 1, characterized in that: In step (3), the poor solvent is petroleum ether or n-hexane.

10. The method for treating ammonium nitrate-containing wastewater and recovering ammonium nitrate by extraction method according to claim 1, characterized in that: In step (3), the volume ratio of the extract to the poor solvent is 1:1 to 1:1.5 based on the extractant.

Images