A harmless treatment process for high-COD waste emulsion containing glue

Abstract

The present invention discloses a harmless treatment process for high-COD waste emulsion containing glue. The waste emulsion is demulsified by adding acid, allowed to stand and settle, and density separation is carried out. The aqueous phase is transported to the esterification glue removal pool, heated to precipitate the glue, and the demulsified emulsion after glue removal is transported to the first air flotation pool, where the pH is adjusted, the oil sludge is scraped off, and then defoamed. Evaporation treatment is carried out under acidic conditions. The distilled water produced by evaporation enters the biochemical system after the pH is adjusted by the second air flotation pool to produce qualified effluent; the concentrated liquid formed by evaporation enters the concentrated liquid density separation pool for solid-liquid separation. The separated oil sludge enters the incineration system for harmless treatment, and the separated liquid returns to the pretreatment density separation pool; density interlocks of the density meters and solenoid valves at the sludge outlet and liquid outlet of the pretreatment density separation pool and the concentrated liquid density separation pool can improve the operation accuracy and work efficiency, reduce the manual operation cost, and increase the output; the production process of the whole process is stable, providing guarantee for safe production.

Description

Technical Field

[0001] The present invention belongs to the technical field of harmless treatment of waste emulsion, and particularly relates to a harmless treatment process for high-COD waste emulsion containing glue. Background Art

[0002] Waste emulsion mainly comes from industries such as metal processing and mechanical turning. It is characterized by high concentrations of organic pollutants such as oils, high COD content, usually ranging from tens of thousands to hundreds of thousands. Some waste emulsions contain specific soluble organic substances, which are prone to esterification reaction and form glue blocks when heated under acidic conditions. The above waste emulsions are generally in a mixed state when stored in the tank area of the treatment unit, with complex components, high oil-water mixing degree, poor biodegradability, and great treatment difficulty.

[0003] At present, the treatment methods for waste emulsion include physical and chemical treatment methods and biochemical treatment methods: The physical and chemical treatment method is a method that applies physical and chemical principles to convert the pollutant components in the waste emulsion into harmless substances to purify the waste emulsion. The biochemical treatment method is a method that uses microorganisms to degrade the pollutants in the waste emulsion as its own nutrition and energy, and at the same time purifies the waste emulsion. However, only using physical and chemical treatment methods and biochemical treatment methods to treat high-concentration waste emulsion not only has great treatment difficulty, low efficiency and high cost, but also is difficult to achieve an ideal treatment effect. Using the combined biochemical treatment method has a significant effect on waste emulsion with a COD content lower than 50000mg / L, but has an insignificant treatment effect on high-COD waste emulsion with a COD content as high as hundreds of thousands, and is prone to have an adverse impact on the biological treatment system. In addition, when using the evaporation method to treat waste emulsion, acid evaporation can effectively reduce the occurrence of foaming during the evaporation process, but the waste emulsion containing glue will precipitate large colloids when heated under acidic conditions, blocking the evaporation system. Therefore, this process is not suitable for treating the complex-component waste emulsion containing glue. Summary of the Invention

[0004] In view of the above problems existing in the prior art, the present invention provides a harmless treatment process for high-COD waste emulsion containing glue, which greatly reduces the COD content in the effluent, makes it meet the influent standard of the biochemical treatment system, maintains the stability of the system, and achieves the process purpose of stably treating a large quantity of high-COD waste emulsion containing glue.

[0005] The purpose of the present invention is achieved in the following way:

[0006] A harmless treatment process for high-COD waste emulsion containing glue includes the following steps:

[0007] (1) Transport the waste emulsion to a pretreatment density separation tank, add acid to demulsify, stand still for sedimentation separation, and produce scum and demulsified emulsion;

[0008] (2) After demulsification, the emulsion is transported to the esterification degumming tank, where esterification reaction occurs upon heating to precipitate gum, which is then scraped off by a scraper.

[0009] (3) The emulsion after degumming is transported to the first air flotation tank, where the pH is adjusted to 3 - 4 for the first oil scraping treatment to remove oil sludge.

[0010] (4) The emulsion after removing oil sludge is transported to the feed tank, where an antifoaming agent is added, and then it is transported to the MVR evaporator for evaporation treatment. The distilled water produced by evaporation is transported to the second air flotation tank, where the pH is adjusted and then enters the biochemical system to produce qualified effluent.

[0011] The concentrated liquid formed by evaporation is transported to the concentrated liquid density separation tank for solid - liquid separation. The separated oil sludge enters the incineration system for harmless treatment, and the separated liquid returns to the pretreatment density separation tank.

[0012] Both the pretreatment density separation tank and the concentrated liquid density separation tank are equipped with sludge outlets and liquid outlets. Density meters and solenoid valves are installed at both the sludge outlets and the liquid outlets. The density meters at the sludge outlets and the liquid outlets are interlocked with the solenoid valves. The interlock density of the sludge outlet is 0.7 - 1.0 kg / m³, and the interlock density of the liquid outlet is 1.0 - 1.3 kg / m³.

[0013] In step (2), the heating temperature is 40 - 50 °C.

[0014] The bottom surface of the pretreatment density separation tank is inclined, with an inclination angle of 10°, and the sludge outlet is set at the lowest point of the tank bottom.

[0015] The bottom surface of the concentrated liquid density separation tank is inclined, with an inclination angle of 15°, and the sludge outlet is set at the lowest point of the tank bottom.

[0016] Compared with the prior art, the present invention pre-treats the acidification and demulsification of the density separation tank, separates the emulsified liquid after rough demulsification through density separation, effectively removes impurities in the emulsified liquid, and then removes the colloid in the waste emulsified liquid containing colloid through pre-heating esterification, effectively avoiding the blockage of the MVR evaporation system caused by heating out of the colloid. Then, it is evaporated under acidic conditions, greatly reducing the COD content in the effluent, making it meet the influent standard of the biochemical treatment system. The generated wastewater enters the biochemical system for further treatment to degrade COD, and the effluent pH is 6-9, COD is less than 350 mg / L, ammonia nitrogen is less than 25 mg / L, total phosphorus is less than 4 mg / L, total nitrogen is less than 50 mg / L, and suspended solids are less than 260 mg / L, maintaining the system stability, achieving the process objective of mass-stable treatment of high-COD waste emulsified liquid containing colloid. The generated sludge, colloid, and scum are disposed of through the incineration system, effectively realizing the separation of high-COD and difficult-to-dispose waste emulsified liquid containing colloid and harmless treatment. The density interlock can improve the operation accuracy, reduce the manual operation cost, improve the work efficiency, accurately control the process indicators, improve the production efficiency of the enterprise, and increase the production output; the production process of the entire process is stable, providing guarantee for safe production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the process flow chart of the present invention.

[0018] Figure 2 is the structural schematic diagram of the pre-treatment density separation tank / concentrated liquid density separation tank. DETAILED DESCRIPTION OF THE INVENTION

[0019] As Figure 1 shown, a harmless treatment process for high-COD waste emulsified liquid containing colloid includes the following steps:

[0020] (1) The waste emulsified liquid is transported to the pre-treatment density separation tank, acid is added for demulsification, and after standing and sedimentation separation, scum and demulsified emulsified liquid are generated; a sludge outlet 1 and a liquid outlet 2 are arranged at the bottom of the pre-treatment density separation tank, and density meters 5 and solenoid valves are arranged at both the sludge outlet 1 and the liquid outlet 2. The density meters at the sludge outlet 1 and the liquid outlet 2 are interlocked with the solenoid valves. The interlocked density of the sludge outlet is 0.7-1.0 kg / m³, and the interlocked density of the liquid outlet is 1.0-1.3 kg / m³; the density meter monitors the density of the emulsified liquid or scum, and then gives a signal to the corresponding solenoid valve through the controller. When the density meter monitors that the density of the emulsified liquid is 1.0-1.3 kg / m³, the solenoid valve at the liquid outlet is opened, and the demulsified emulsified liquid is transported to the next scraping colloid tank; when the density meter monitors that the density of the emulsified liquid is less than 1.0 kg / m³, the solenoid valve at the liquid outlet is closed, and the solenoid valve at the sludge outlet is opened to start discharging the scum.

[0021] (2)After demulsification, the emulsion is transported to the esterification degumming tank. Due to acidification demulsification, the demulsified emulsion transported to the scraping tank is acidic. After heating to 40 - 50 °C, an esterification reaction occurs to precipitate gum, and the gum is scraped off by a scraper.

[0022] (3)The emulsion after degumming is transported to the first air flotation tank, and the pH is adjusted to 3 - 4 for the first oil scraping treatment to remove oil sludge. In the air flotation tank, a large amount of air bubbles are injected into the water, causing the particulate suspended solids in the water to float to the surface of the air flotation tank, thus forming a sludge floating layer that is very easy to remove.

[0023] (4)The emulsion after scraping off the oil sludge is transported to the feed tank, and an antifoaming agent is added, and then it is transported to the MVR evaporator. Evaporation treatment under acidic conditions will greatly reduce the foaming rate of the evaporation system. By MVR evaporation treatment, most non-volatile organic and inorganic substances can be separated, which can reduce the COD content, toxicity, and salt content in the waste emulsion entering the subsequent process. The COD content of the distilled water produced by evaporation is < 2000 mg / L. The distilled water is transported to the second air flotation tank, the pH value is adjusted to 6 - 9, and then it is transported into the biochemical system to produce qualified effluent. The qualified effluent has a COD less than 350 mg / L, ammonia nitrogen less than 25 mg / L, total phosphorus less than 4 mg / L, total nitrogen less than 50 mg / L, and suspended solids less than 260 mg / L; for the concentrated liquid formed by evaporation, depending on the nature of the raw material, the concentration rate of the concentrated liquid can reach up to 90%. Compared with the concentration rate of 80% in ordinary evaporation concentration, the concentration rate of the concentrated liquid of the present invention can be increased by about 10%. The concentrated liquid is transported to the concentrated liquid density separation tank for cooling and solid-liquid separation. The separated oil sludge enters the incineration system for harmless treatment, and the separated liquid returns to the pretreatment density separation tank to repeat the processes of demulsification, degumming, air flotation, acidic evaporation, and biochemical treatment.

[0024] The concentrated liquid density separation tank is provided with a sludge outlet 1 and a liquid outlet 2. Density meters and solenoid valves are installed at both the sludge outlet and the liquid outlet. The density meters and solenoid valves at the sludge outlet and the liquid outlet achieve density interlock. The interlock density of the sludge outlet is 0.7 - 1.0 kg / m³, and the interlock density of the liquid outlet is 1.0 - 1.3 kg / m³. The density meter monitors the density of the concentrated liquid or sludge, and then gives a signal to the corresponding solenoid valve through the controller. When the density meter monitors that the density of the concentrated liquid is between 1.0 - 1.3 kg / m³, the solenoid valve at the liquid outlet opens to transport the concentrated liquid to the pretreatment density separation tank; when the density meter monitors that the density of the concentrated liquid is less than 1.0 kg / m³, the solenoid valve at the liquid outlet closes, and the solenoid valve at the sludge outlet opens to start discharging the oil sludge.

[0025] Density interlock can improve the operation accuracy, reduce the manual operation cost; improve the work efficiency, control the process indicators precisely, improve the production efficiency of the enterprise, and increase the production output; the production process of the whole process is stable, providing guarantee for safe production.

[0026] According to the size of the tank body and the flow rate of the liquid or sludge, the pre-treatment density separation tank and the concentrated liquid density separation tank can appropriately increase the liquid outlet, sludge outlet and density meter.

[0027] Manholes 3 for maintenance and vents 4 are also provided at the top of the pre-treatment density separation tank and the concentrated liquid density separation tank. The manholes 3 for maintenance facilitate the maintenance and cleaning of the pre-treatment density separation tank and the concentrated liquid density separation tank, and the vents 4 can discharge the foul smell generated during the emulsified liquid treatment process.

[0028] As Figure 2 shown, the bottom surfaces of the pre-treatment density separation tank and the concentrated liquid density separation tank are both inclined. The inclination angle of the bottom of the pre-treatment density separation tank is 10°, and the inclination angle of the bottom of the concentrated liquid density separation tank is 15°. The sludge outlet 1 is arranged at the lowest point of the bottom surface of the tank. When the floating slag or oily sludge is discharged, it flows along the inclined bottom of the tank to the sludge outlet 1, reducing the sedimentation of bottom sludge, reducing the frequency of bottom cleaning, and extending the service life of the equipment.

[0029] The inclination angles of the pre-treatment density separation tank and the concentrated liquid density separation tank are slightly different, which is a reasonable choice based on the fluidity of the slag or oily sludge in the tank. The fluidity of the oily sludge in the concentrated liquid density separation tank is a bit worse than that of the floating slag in the pre-treatment density separation tank. Therefore, the inclination angle of the bottom of the pre-treatment density separation tank is smaller than that of the bottom of the concentrated liquid density separation tank.

[0030] The traditional treatment mode of acid precipitation and demulsification + biochemical treatment can only reach a maximum treatment volume of 100 tons per day. The treatment process disclosed in the present invention can achieve the effect of large-scale treatment. According to the size of the MVR equipment, it can reach 250 - 300 tons per day. Adopting the acid evaporation mode with pH 3 - 4 will greatly reduce the foaming rate of the evaporation system. Adding an esterification degumming tank can remove the colloid in the emulsified liquid in advance, avoid blocking the evaporation system, and ensure the stable operation of the whole system. The density interlock can improve the operation accuracy, reduce the manual operation cost, improve the work efficiency, accurately control the process indicators, improve the production efficiency of the enterprise, and increase the production output; the production process of the whole process is stable, providing guarantee for safe production.

[0031] The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the overall concept of the present invention, several changes and improvements can still be made, and these should also be regarded as the protection scope of the present invention.

Claims

1. A harmless treatment process for high-COD glue-containing waste emulsion, characterized in that: It includes the following steps: (1) The waste emulsion is transported to the pretreatment density separation tank, acid is added to demulsify it, and it is allowed to stand for sedimentation separation to produce scum and the demulsified emulsion; (2) The demulsified emulsion is transported to the esterification degumming tank, and esterification reaction occurs upon heating to precipitate gum, which is scraped off by a scraper; (3) The emulsion after degumming is transported to the first flotation tank, the pH is adjusted to 3 - 4, and the first oil scraping treatment is carried out to scrape off the sludge; (4) The emulsion after scraping off the sludge is transported to the feed tank, an antifoaming agent is added, and then it is transported to the MVR evaporator for evaporation treatment. The distilled water produced by evaporation is transported to the second flotation tank, and after the pH is adjusted, it enters the biochemical system to produce qualified effluent; The concentrated liquid formed by evaporation is transported to the concentrated liquid density separation tank for solid - liquid separation. The separated sludge enters the incineration system for harmless treatment, and the separated liquid returns to the pretreatment density separation tank; Both the pretreatment density separation tank and the concentrated liquid density separation tank are provided with a sludge outlet and a liquid outlet. Density meters and solenoid valves are installed at both the sludge outlet and the liquid outlet. The density meters at the sludge outlet and the liquid outlet are interlocked with the solenoid valves. The interlock density of the sludge outlet is 0.7 - 1.0 kg / m³, and the interlock density of the liquid outlet is 1.0 - 1.3 kg / m³.

2. The harmless treatment process for high-COD glue-containing waste emulsion according to claim 1 is characterized in that: In step (2), the heating temperature is 40 - 50 °C.

3. The harmless treatment process for high-COD glue-containing waste emulsion according to claim 1, characterized in that: The bottom surface of the pretreatment density separation tank is inclined, with an inclination angle of 10°, and the sludge outlet is arranged at the lowest point of the tank bottom surface.

4. The harmless treatment process for high-COD glue-containing waste emulsion according to claim 1, wherein: The bottom surface of the concentrated liquid density separation tank is inclined, with an inclination angle of 15°, and the sludge outlet is arranged at the lowest point of the tank bottom surface.

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