A pretreatment device for wastewater containing high concentration of formaldehyde

Abstract

The utility model belongs to the technical field of wastewater treatment, and specifically relates to a pretreatment device for wastewater containing high-concentration formaldehyde, the pretreatment device comprising a steam stripping tower, a condenser and a flash tank, a mixed steam discharge pipeline is arranged at the top of the steam stripping tower, the mixed steam discharge pipeline is connected with one end of the condenser, a condensate discharge pipeline is arranged at the other end of the condenser, the condensate discharge pipeline is connected with the flash tank, a wastewater input pipeline is arranged at the upper side wall of the steam stripping tower, a superheated steam input pipeline is arranged at the lower side wall of the steam stripping tower, and a first formaldehyde steam discharge pipeline is arranged at the top of the condenser. The pretreatment device can greatly reduce the formaldehyde content in the wastewater and effectively recycle the formaldehyde.

Description

Technical Field

[0001] The utility model belongs to the technical field of wastewater treatment, and in particular relates to a pretreatment device for wastewater containing high-concentration formaldehyde. Background Art

[0002] Formaldehyde is generated during the acrylic acid production process. Therefore, the acid wastewater discharged from the acrylic acid unit contains a large amount of formaldehyde (20,000 mg / L). Enterprises generally collect wastewater, add a certain amount of sodium hydroxide to neutralize it, and then send it to the sewage station for biological treatment. It is discharged after the formaldehyde content reaches the standard. However, biological treatment has strict requirements on formaldehyde content (≤2000 mg / L). Too high a content can easily lead to the death of bacteria. Therefore, pretreatment is required before biological treatment to make the formaldehyde content reach the standard.

[0003] Formaldehyde is biologically toxic and has an inhibitory effect on anaerobic degradation microorganisms when the concentration is greater than 100 mg / L. When the formaldehyde concentration is greater than 175 mg / L, it has an inhibitory effect on aerobic degradation microorganisms.

[0004] From the current research progress, biological treatment has the advantages of mature technology, low operating cost, good effluent effect, etc., and is still the mainstream method for treating low-concentration formaldehyde-containing wastewater. However, the activity of organisms is greatly affected by the initial concentration of formaldehyde, so high-concentration formaldehyde-containing wastewater needs to be pre-treated by methods such as stripping, oxidation, lime condensation, and precipitation to reduce the formaldehyde concentration in the wastewater to a range that can be tolerated by organisms or to convert formaldehyde into a substance that is non-toxic and biodegradable to organisms.

[0005] At present, most companies use a combination of "pretreatment + biological treatment" to treat formaldehyde-containing wastewater with high concentration (about 20,000 mg / L) and strong toxicity to microorganisms. However, due to the lack of effective pretreatment, it not only increases energy consumption, but the accumulation of formaldehyde in the wastewater will inhibit the activity of sludge in the biochemical pool; once the formaldehyde content accumulates too high, it will inhibit the activity of bacteria and even cause the bacteria to become inactive, making the COD removal rate of the biochemical pool far lower than the design value, causing the effluent COD to exceed the standard, the biochemical system's treatment capacity is significantly reduced, and the wastewater discharged from the sewage pretreatment device does not meet the standard. Utility Model Content

[0006] The purpose of the utility model is to solve the problem of limited effect of pretreatment of formaldehyde wastewater described in the above background technology, and propose a new pretreatment device for wastewater containing high concentration of formaldehyde, which can greatly reduce the formaldehyde content in the wastewater.

[0007] The technical solution adopted to achieve the above-mentioned purpose is a treatment device for wastewater containing high-concentration formaldehyde, the treatment device comprising a steam stripping tower, a condenser and a flash tank, a mixed steam exhaust pipeline is provided at the top of the steam stripping tower, the mixed steam exhaust pipeline is connected to one end of the condenser, a condensate exhaust pipeline is provided at the other end of the condenser, the condensate exhaust pipeline is connected to the flash tank, a wastewater input pipeline is provided on the upper side wall of the steam stripping tower, a superheated steam input pipeline is provided on the lower side wall of the steam stripping tower, and a first formaldehyde steam exhaust pipeline is provided on the top of the condenser.

[0008] In the above technical scheme, the wastewater is vaporized through a steam stripping tower and input into a condenser. The condenser condenses the vaporized wastewater to separate part of the formaldehyde and water vapor, so that the formaldehyde gas is discharged. The condensate enters a flash tank to further separate the formaldehyde and water in the condensate, so that the formaldehyde gas is concentrated for subsequent treatment to reduce the formaldehyde content in the wastewater.

[0009] Furthermore, the treatment device also includes a bottom reflux pump, the water inlet of the bottom reflux pump is connected to the bottom of the steam stripping tower through a pipeline, and the water outlet of the bottom reflux pump is connected to the upper side wall of the steam stripping tower through a pipeline.

[0010] Furthermore, a control valve is provided on the pipeline connecting the bottom of the steam stripping tower and the water inlet of the bottom reflux pump.

[0011] In the above technical solution, the wastewater from which part of the formaldehyde has been removed is recycled to further reduce the formaldehyde content. When the formaldehyde content reaches a predetermined value, it can be introduced into a biochemical pool for biological treatment.

[0012] Furthermore, the processing device also includes a circulating water pump, the water inlet of the circulating water pump is connected to the bottom of the flash tank through a pipeline, and the water outlet of the circulating water pump is connected to the condenser through a pipeline.

[0013] Furthermore, a pressure reducing valve is provided on the condensate discharge pipeline.

[0014] In the above technical solution, the liquid water in the flash tank is returned to the condenser for recycling, thereby reducing energy consumption.

[0015] Furthermore, a second formaldehyde vapor exhaust pipeline is provided on the top of the flash tank, and the second formaldehyde vapor exhaust pipeline is connected to the first formaldehyde vapor exhaust pipeline.

[0016] In the above technical solution, the formaldehyde gas evaporated in the flash tank and the formaldehyde gas in the condenser are combined and discharged, and then enter the next formaldehyde gas treatment step.

[0017] Furthermore, the treatment device also includes a regulating tank, which is connected to the wastewater input pipeline.

[0018] Furthermore, a water quality detection device and a liquid level detection device are provided in the regulating tank.

[0019] In the above technical solution, the regulating tank is used to regulate the water quality and water quantity of wastewater.

[0020] Furthermore, the treatment device also includes an RTO reactor, and the RTO reactor is connected to the first formaldehyde vapor exhaust pipeline.

[0021] In the above technical solution, the RTO reactor is used for incineration and subsequent recovery of formaldehyde gas.

[0022] The advantages of the utility model are:

[0023] 1. The utility model can pre-treat wastewater containing high-concentration formaldehyde, reduce the formaldehyde content in the wastewater, and transport the formaldehyde in the form of gas to the RTO reactor for incineration and subsequent recovery treatment, which greatly reduces the formaldehyde content in the wastewater and reduces the degradation burden of the subsequent biochemical pool.

[0024] 2. The utility model has a simple structure, effectively reduces the formaldehyde content in wastewater, recycles water resources, and reduces energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0026] Figure 1 It is a structural schematic diagram of the utility model.

[0027] Illustrations: 1. Steam stripping tower, 2. Condenser, 3. Flash tank, 4. Mixed steam discharge pipeline, 5. Condensate discharge pipeline, 6. Wastewater input pipeline, 7. Superheated steam input pipeline, 8. Bottom reflux pump, 9. Control valve, 10. Circulating water pump, 11. Pressure reducing valve, 12. First formaldehyde steam discharge pipeline, 13. Second formaldehyde steam discharge pipeline. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only embodiments of a part of the present invention rather than 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 belong to the protection scope of the present invention.

[0029] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0030] like Figure 1 As shown, a pretreatment device for wastewater containing high concentration of formaldehyde comprises a steam stripping tower 1, a condenser 2 and a flash tank 3, wherein a mixed steam exhaust pipeline 4 is provided at the top of the steam stripping tower, and the mixed steam exhaust pipeline is connected to the inlet end of the condenser, a condensate exhaust pipeline 5 is provided at the outlet end of the condenser, and the condensate exhaust pipeline is connected to the flash tank, a wastewater input pipeline 6 is provided on the upper side wall of the steam stripping tower, a superheated steam input pipeline 7 is provided on the lower side wall of the steam stripping tower, and a first formaldehyde steam exhaust pipeline 12 is provided on the top of the condenser.

[0031] In this embodiment, a tower bottom reflux pump 8 is further provided, the water inlet of the tower bottom reflux pump is connected to the bottom of the steam stripping tower through a pipeline, and the water outlet of the tower bottom reflux pump is connected to the feed port of the upper side wall of the steam stripping tower through a pipeline, so as to form a circulation loop, and the wastewater from which part of the formaldehyde is removed is re-input into the steam stripping tower until the formaldehyde content in the wastewater meets the standard of the next biochemical treatment;

[0032] In this embodiment, a control valve 9 is provided on the pipeline connecting the bottom of the steam stripping tower and the water inlet of the tower bottom reflux pump to control the wastewater circulation.

[0033] In this embodiment, a circulating water pump 10 is also provided, the water inlet of the circulating water pump is connected to the bottom of the flash tank through a pipeline, the water outlet of the circulating water pump is connected to the condenser through a pipeline, and a pressure reducing valve 11 is provided on the condensate discharge pipeline to form a circulation loop, and the liquid water with formaldehyde removed is input into the cooler for reuse.

[0034] In this embodiment, a second formaldehyde vapor exhaust pipeline 13 is provided on the top of the flash tank, and the second formaldehyde vapor exhaust pipeline is connected to the first formaldehyde vapor exhaust pipeline to output the formaldehyde vapor in a centralized manner.

[0035] The other end of the wastewater input pipeline is connected to a regulating tank, in which a water quality detection device and a liquid level detection device are arranged to monitor the water quality and water quantity of the wastewater.

[0036] The first formaldehyde vapor exhaust pipeline is connected to the RTO reactor to incinerate and subsequently treat the concentrated formaldehyde gas.

[0037] The working principle of the utility model is as follows: waste water containing high concentration of formaldehyde is extracted from the regulating tank and sent to the steam stripping tower, the pressure in the steam stripping tower is controlled to be 0.4Mpa and the temperature is 90°C, and the formaldehyde in the waste water is evaporated by superheated steam. At this time, the formaldehyde and water parts in the waste water are converted into gas and enter the cooler. In the cooler, most of the formaldehyde gas is discharged from the first formaldehyde steam discharge pipeline and passed into the RTO reactor, and a small part of the formaldehyde gas is dissolved in water and enters the flash tank along with the liquid condensed water. In the flash tank, the water and the formaldehyde are separated, and the formaldehyde is converted into gas and enters the first formaldehyde steam discharge pipeline along with the second formaldehyde steam discharge pipeline and is discharged into the RTO reactor. Water is discharged from the bottom of the flash tank and sent to the cooler to cool the formaldehyde water vapor, and the excess water is discharged from the pipeline at the top of the cooler for recovery.

[0038] Finally, it should be noted that this embodiment is only used to illustrate the present invention and does not limit the scope of the present invention. In addition, it should be understood that after reading the content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A pretreatment device for wastewater containing high concentration of formaldehyde, characterized in that: The pretreatment device comprises a steam stripping tower (1), a condenser (2) and a flash tank (3); a mixed steam discharge pipeline (4) is provided at the top of the steam stripping tower, the mixed steam discharge pipeline is connected to one end of the condenser, a condensate discharge pipeline (5) is provided at the other end of the condenser, the condensate discharge pipeline is connected to the flash tank, a wastewater input pipeline (6) is provided on the upper side wall of the steam stripping tower, a superheated steam input pipeline (7) is provided on the lower side wall of the steam stripping tower, and a first formaldehyde steam discharge pipeline (12) is provided on the top of the condenser.

2. The pretreatment device according to claim 1, characterized in that: The pretreatment device also includes a tower bottom reflux pump (8), the water inlet of the tower bottom reflux pump is connected to the bottom of the steam stripping tower through a pipeline, and the water outlet of the tower bottom reflux pump is connected to the upper side wall of the steam stripping tower through a pipeline.

3. The pretreatment device according to claim 2, characterized in that: A control valve (9) is provided on the pipeline connecting the bottom of the steam stripping tower and the water inlet of the tower bottom reflux pump.

4. The pretreatment device according to claim 1, characterized in that: The pretreatment device also includes a circulating water pump (10), the water inlet of the circulating water pump is connected to the bottom of the flash tank through a pipeline, and the water outlet of the circulating water pump is connected to the condenser through a pipeline.

5. The pretreatment device according to claim 1, characterized in that: A pressure reducing valve (11) is provided on the condensate discharge pipeline.

6. The pretreatment device according to claim 1, characterized in that: A second formaldehyde vapor exhaust pipeline (13) is provided on the top of the flash tank, and the second formaldehyde vapor exhaust pipeline is connected to the first formaldehyde vapor exhaust pipeline.

7. The pretreatment device according to claim 1, characterized in that: The pretreatment device also includes a regulating tank, which is connected to the wastewater input pipeline.

8. The pretreatment device according to claim 7, characterized in that: A water quality detection device and a liquid level detection device are arranged in the regulating tank.

9. The pretreatment device according to claim 1, characterized in that: The pretreatment device further comprises an RTO reactor, and the RTO reactor is in communication with a first formaldehyde vapor exhaust pipeline.

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