A method for treating distillation residue

Abstract

The invention discloses a method for treating distillation residues, comprising the following steps: mixing a carbonamide aqueous solution with an alkali aqueous solution to obtain a treatment liquid; adding the treatment liquid to the distillation residue, stirring evenly, adjusting the pH value of the system to 7-9 and maintaining it, adding a loosening agent and stirring evenly; after standing, performing solid-liquid separation, purifying the liquid phase to recover dimethylformamide in the distillation residue, and incinerating the solid phase. The method for treating distillation residues of the invention comprises mixing the distillation residues with a solution containing carbonamide and an alkaline substance, adding a loosening agent, standing and layering, separating the solid and liquid phases, and further purifying and refining the liquid phase through a recovery device to obtain DMF, which can realize resource recycling and reduce secondary pollution.

Description

Technical Field

[0001] The invention belongs to the technical field of waste treatment, and in particular relates to a distillation residue treatment method. Background Art

[0002] With the rapid development of the textile industry, the pollution caused by the three wastes (waste gas, waste water and waste residue) generated in the process of industrial development has become increasingly serious, and has also attracted great attention from the society. In recent years, great progress has been made in the treatment of industrial waste gas and waste water. The waste gas generated in the textile printing and dyeing finishing industry can be disposed of by recyclable waste gas, which not only solves the environmental pollution problem, but also obtains good economic benefits from the recycling and disposal process.

[0003] However, the disposal of the distillation residue after recycling has not been well solved. For example, in the coating finishing industry, DMF (dimethylformamide) solvent is widely used as a raw material diluent. The waste gas generated after production and drying is treated by a circulating spraying process to obtain an organic solvent waste liquid, which is purified by distillation. In the distillation process, secondary hazardous waste of distillation residue is formed, which has special characteristics. First, after the distillation residue is evaporated at high temperature, a viscous oily waste residue is formed. The main components of the distillation residue are formic acid, polyurethane, color paste, surfactant, chemical additives and wood powder, calcium bicarbonate, cloth wool and residual dimethylformamide, etc. These are all heavy pollution sources, which are extremely harmful to the environment, ecology and the personal safety of operators; second, the oily waste residue contains about 10% dimethylformamide, which will cause waste of resources if it is directly disposed of.

[0004] For the above-mentioned distillation residue, the traditional operations in the industry are as follows: 1. Use the combustion disposal method, pour the residue into the coal, and put it into the boiler for direct combustion; it has the following disadvantages: incomplete combustion, easy to block the chain, resulting in the inability of blast, airtightness, mixed with coal, uneven stirring, forming lumps, so that the coal cannot be completely burned, which is not environmentally friendly and wastes energy. 2. Use water dilution and gas spraying method for combustion; it has the following disadvantages: during the spray combustion process, a large amount of thick smoke and harmful gas substances will be generated, seriously polluting the air and the surrounding environment; and during combustion, a tar-like substance will be released and deposited around the boiler furnace and the inner wall of the boiler air duct, which is seriously corrosive and has a high risk factor.

[0005] Based on the above reasons, there is an urgent need for a method that can carry out physical and chemical disposal of distillation residues in a relatively environmentally friendly manner to achieve resource recycling. Summary of the invention

[0006] In view of this, in order to overcome the defects of the prior art, the object of the present invention is to provide a distillation residue treatment method, which can realize the recovery of dimethylformamide in the distillation residue.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for treating distillation residues comprises the following steps: mixing a carbonamide aqueous solution with an alkali aqueous solution to obtain a treatment liquid; adding the treatment liquid to the distillation residues, stirring evenly, adjusting the pH value of the system to 7-9 and maintaining it, adding a loosening agent and stirring evenly; after standing, performing solid-liquid separation, purifying the liquid phase to recover dimethylformamide in the distillation residues, and incinerating the solid phase.

[0009] According to some preferred implementation aspects of the present invention, the concentration of the carbonamide aqueous solution is 8% to 12%, preferably 10%. The preferred carbonamide aqueous solution is 10% concentration, mainly because this concentration range and the sodium hydroxide as a whole synergistically create a weakly alkaline reaction environment, making the effect of the loosening agent optimal.

[0010] According to some preferred embodiments of the present invention, the base is sodium hydroxide.

[0011] According to some preferred implementation aspects of the present invention, the concentration of the aqueous solution of alkali is 8% to 12%, preferably 10%. When the aqueous solution of sodium hydroxide is preferably about 10%, the distillation residue is clearly layered, which is convenient for separation. When the concentration is above 10%, the mixed liquid appears in a relatively obvious mixed state, and there is no relatively clear upper liquid. In addition, if the concentration of the alkali solution is too high, the supernatant returns to the distillation purification system, which is not convenient for controlling the process. When the concentration is about 10%, the supernatant returns to the recovery and purification system, which is convenient for maintaining the neutral state of the waste liquid, which promotes the control of the purification quality.

[0012] According to some preferred implementation aspects of the present invention, the mass ratio of carbonamide to alkali in the treatment liquid is 1:0.8-1.2, and preferably the mass ratio of urea to alkali is 1:1. The acidity and alkalinity of the mixed liquid are used as a reference for adjustment, and the mixed liquid is controlled to be weakly alkaline (pH value is about 8) as a whole, and the above mass mixing ratio is used according to the deployment to achieve the best effect.

[0013] According to some preferred implementation aspects of the present invention, the distillation residue and the treatment liquid are mixed in a mass ratio of 1:1.5 to 3, preferably a mass ratio of 1:2. Since the distillation residue has different viscosities, some are thin and some are thick, the final mixed liquid should be kept in a uniform state, and the loosening agent and the mixed liquid should be more fully reacted and contacted.

[0014] According to some preferred embodiments of the present invention, the mass ratio of the distillation residue to carbonamide and the alkali is 1:0.08-0.12:0.08-0.12. That is, the mass ratio of the distillation residue to urea is 1:0.08-0.12, preferably 1:0.1; the mass ratio of the distillation residue to the alkali is 1:0.08-0.12, preferably 1:0.1; and preferably the mass ratio between urea and the alkali is 1:1.

[0015] According to some preferred implementation aspects of the present invention, the loosening agent is polyacrylamide. The loosening agent is added in an amount of 2.5-3.5% by mass, preferably 3% of the mixed treatment liquid, and its main function is to mix and flocculate the oily substances in the mixed liquid and separate the solid and liquid.

[0016] According to some preferred embodiments of the present invention, the content of formic acid in the distillation residue is 3%-5%.

[0017] According to some preferred embodiments of the present invention, the concentration of dimethylformamide in the liquid phase is 4% to 8%.

[0018] The present invention controls the acidity and alkalinity of the treatment liquid to be weakly alkaline by controlling the mass ratio of urea and sodium hydroxide in the treatment liquid, and then prepares the treatment liquid according to the mass ratio according to the focus of the distillation residue to be disposed, and uses a containing container to load the distillation residue, and then adds the calculated treatment liquid to the distillation residue, and simultaneously uses a stirring device to mix it evenly, and then tests the pH of the mixed liquid. When it is within the set value range, according to the dilution degree of the mixed liquid, it is supplemented with appropriate materials, and after the material is in a relatively uniform state, according to the mass ratio requirements, loosening agents are gradually added and stirred, and the mixed liquid is allowed to stand after being mixed and stirred evenly, and finally according to the solid waste separation operation, the supernatant liquid is pumped into the storage system for reuse, and the solid waste is uniformly sealed and stored for further treatment.

[0019] Compared with the prior art, the advantages of the present invention are as follows: the distillation residue treatment method of the present invention mixes the distillation residue with a solution containing carbon amide and an alkaline substance, adds a loosening agent, and separates the layers after standing to separate the solid and liquid phases, and further purifies and refines the liquid phase through a recovery device to obtain DMF, thereby realizing resource recycling and reducing secondary pollution. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0021] The distillation residue treatment method of the present invention mainly comprises the following steps:

[0022] 1) dissolving carbamide (urea) in water to prepare a carbamide aqueous solution (with a concentration of 10%) for standby use; dissolving sodium hydroxide in water to obtain a sodium hydroxide aqueous solution (with a concentration of 10%) for standby use; mixing the carbamide aqueous solution and the sodium hydroxide aqueous solution to form a treatment solution, and cooling to room temperature. The carbamide aqueous solution and the alkali solution are separately configured to facilitate control of their respective concentrations and added mass ratios, and in the process of synchronous diversion and mixing, it is more sufficient, and it is also convenient to prepare in advance and classify and store.

[0023] 2) Place the distillation residue into the reaction tank (about 5m 3 ), due to the high viscosity of the distillation residue, the treatment liquid is added in a mass ratio of 1:2 to the residue and the treatment liquid and stirred evenly, the pH value of the system is adjusted to about 8, and a loosening agent is added. After stirring, it becomes a suspension, and the solid and liquid are separated after standing. The liquid phase is purified to recover dimethylformamide, and the solid phase is incinerated. In actual operation, the solid phase separated initially is allowed to stand and drain, and then incinerated. The liquid obtained by draining is purified and recovered together with the previously separated liquid phase.

[0024] Among them, the main components of the solid phase flocculated precipitate are solid matter in the residue, wood powder, cloth wool, CaCO3 and some small molecular PU, additives and their carbides and polymers, with a content of about 30%; the DMF in the distillation residue is dissolved in water by utilizing the hygroscopicity of DMF; because the formic acid content in the distillation residue is relatively high (about 3%-5%), and because too high pH will cause urea to decompose and overflow with ammonia smell, the pH value of the system is strictly controlled at around 8, so that urea can play a greater effect. The amount of urea is generally controlled at about 0.8Kg of urea for 1T of distillation residue.

[0025] The composition of the distillation residue is complex. In addition to DMF and high-boiling-point additives, the formic acid content is very high, and it must be diluted and neutralized before it can be recycled. Urea is added as a catalyst and stirred to promote the reaction of urea, sodium hydroxide, and the solid content in the residue. The flocs formed settle slowly (about 3 hours).

[0026] Experiments have shown that the treatment effect of urea as a catalyst for the distillation residue after purification of organic wastewater such as printing and dyeing is more significant, the removal rate of suspended matter and chromaticity is high, and a large amount of organic solvent (DMF) in the distillation residue can be precipitated, and the color of the flocculent precipitate changes from black to yellow, and it is non-sticky and dispersed, which reduces and avoids the adhesion and blockage problems of the feeding mechanism that finally enters the incinerator for treatment, and ensures the safety of the incinerator. And the separation ratio can reach: about 60% solid phase and about 40% liquid phase. The treated wastewater is clear, and the concentration of DMF in the liquid phase is about 4%-8%, which can be recycled and purified again, and the economic profit is considerable. At the same time, the odor of the distillation residue is reduced, reducing secondary pollution. The point treatment method of the present invention has the characteristics of small urea dosage, strong flocculation ability, small volume of precipitate, high separation efficiency, etc., does not require temperature adjustment, mild reaction conditions, excellent sedimentation performance, and low comprehensive treatment cost.

[0027] Example 1

[0028] The distillation residue treatment method in this embodiment comprises the following steps:

[0029] 1) Prepare a 10% carbonamide aqueous solution.

[0030] 2) Prepare a 20% sodium hydroxide aqueous solution.

[0031] 3) The carbonamide aqueous solution and the sodium hydroxide aqueous solution are mixed in a mass ratio of 1:1 to form a treatment solution.

[0032] 4) adding the treatment liquid to the distillation residue and stirring, wherein the mass ratio of the distillation residue to the treatment liquid is 1:2; and controlling the pH value of the system to be 8.

[0033] After stirring for 20 minutes, add loosening agent to the system and continue stirring for 5 minutes.

[0034] After the loosening agent is mixed evenly, the system is sealed and allowed to stand for 5 hours, and after the upper and lower layers are separated, the supernatant is poured out.

[0035] 5) The supernatant is purified to recover the dimethylformamide therein, and the precipitate is sent to an incinerator for incineration.

[0036] Embodiments 2 to 4

[0037] The steps of Examples 2 to 4 are basically the same as those of Example 1, except that the concentrations and addition amounts of the urea aqueous solution and the alkaline solution are different. For details, please refer to the parameters in Table 1.

[0038] Comparative Example 1

[0039] The steps of this comparative example are basically the same as those of Example 1, except that in this comparative example, the pH of the system is controlled to be 6 by adjusting the concentration and addition amount of the urea aqueous solution and the alkaline solution.

[0040] Comparative Example 2

[0041] The steps of this comparative example are basically the same as those of Example 1, except that in this comparative example, the pH of the system is controlled to be 10 by adjusting the concentration and addition amount of the urea aqueous solution and the alkaline solution.

[0042] Comparative Example 3

[0043] The steps of this comparative example are basically the same as those of Example 1, except that the mass ratio of the residue to urea and alkali in this comparative example is 1:0.08:0.2, that is, the alkali is added in excess.

[0044] Comparative Example 4

[0045] The steps of this comparative example are basically the same as those of Example 1, except that the mass ratio of the residue to urea and alkali in this comparative example is 1:0.16:0.12, that is, the addition of urea is excessive.

[0046] Comparative Example 5

[0047] The steps of this comparative example are basically the same as those of Example 2, except that the amount of loosening agent added in this comparative example is 1.5% of the mass of the treatment liquid.

[0048] Test and Results Discussion

[0049] During the treatment process of the above-mentioned embodiments and comparative examples, the supernatant was sampled to test its DMF concentration and recorded; the precipitate was sampled to test its weight, and the weight percentage was converted to calculate the suspended matter removal rate; the precipitate was compared with the colorimeter to confirm the chromaticity removal efficiency.

[0050] Table 1 Process parameters and test results

[0051]

[0052]

[0053] The results in the above table show that: according to the different treatment liquid mass ratios tested and the mixed mass ratio of the distillation residue and the treatment liquid adjusted, different reaction system pH values ​​were set, the same mixing method was used, and finally the conditions of Example 2 were used to confirm that the final treatment effect was optimal, a large amount of DMF solution in the distillation residue could be recycled and reused, and the solid-liquid separation could be more efficient.

[0054] Compared with the traditional residue treatment method, the treatment method of the present invention is more reasonable. The treatment method of the present invention reduces the harmful polluting components of the distillation residue, reducing it from hazardous solid waste to ordinary solid waste, and at the same time is beneficial to the recycling of resources.

[0055] The present invention reprocesses the distillation residue produced by the distillation and purification of DMF (dimethylformamide) waste liquid, adds urea aqueous solution and alkaline water to the distillation residue, and easily stirs to form a precipitate, and then stands for a certain period of time to finally achieve solid-liquid two-phase stratification, and the stratified solution is transferred to the waste liquid storage tank, and the stratified aqueous solution contains dimethylformamide, and its concentration can reach 4-8%. This part of the solution is re-rectified to reduce the waste of dimethylformamide. The color of the solid phase residue after stratification changes from black to yellow, is non-sticky, and has a loose appearance. It can be uniformly collected and reasonably stored, and entrusted to a qualified unit for disposal. This process can realize the recycling of dimethylformamide, reduce resource waste, and reduce the viscosity of the distillation residue, which is convenient for the pretreatment of the later hazardous waste incineration treatment. The present invention has low processing cost, simple operation, and is conducive to resource recycling. The process route of the residue treatment of the present invention can realize resource recycling, reduce secondary pollution, have both obvious social benefits and good economic benefits, and can realize resource recycling.

[0056] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for treating distillation residue, characterized in that: The method comprises the following steps: mixing a carbonamide aqueous solution with an alkali aqueous solution to obtain a treatment liquid; adding the treatment liquid to the distillation residue, stirring evenly, adjusting the pH value of the system to 7-9 and maintaining it, adding a loosening agent and stirring evenly; after standing, performing solid-liquid separation, purifying the liquid phase to recover dimethylformamide in the distillation residue, and incinerating the solid phase; The mass ratio of the distillation residue to carbonic acid amide and alkali is 1:0.08-0.12:0.08-0.

12.

2. The processing method according to claim 1, characterized in that: The concentration of the carbonamide aqueous solution is 8% to 12%.

3. The processing method according to claim 1, characterized in that: The base is sodium hydroxide.

4. The processing method according to claim 2, characterized in that: The concentration of the aqueous solution of alkali is 8% to 12%.

5. The processing method according to claim 1, characterized in that: The distillation residue and the treatment liquid are mixed in a mass ratio of 1:1.5-3.

6. The processing method according to claim 1, characterized in that: The loosening agent is polyacrylamide.

7. The processing method according to claim 1, characterized in that: The mass proportion of formic acid in the distillation residue is 3%-5%.

8. The processing method according to any one of claims 1 to 7, characterized in that: The concentration of dimethylformamide in the liquid phase is 4% to 8%.

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