CN104496080A - Advanced treatment method for low-rank coal upgrading wastewater - Google Patents

Abstract

The invention discloses a method for advanced treatment of low-rank coal upgrading wastewater, which relates to a treatment method for refractory industrial wastewater. It solves the problems of unsatisfactory removal of organic matter, high chromaticity of effluent, and difficulty in discharge of wastewater in the biochemical treatment process. The process method is as follows: select the waste water to be treated; pass it into the pre-acidification tank, the hydraulic retention time is 2.5-7.5min; the acidified wastewater enters the redox tank, the hydraulic retention time is 0.5-1h; install the pipeline to mix Add ferrous sulfate by wet method; add H ₂ O ₂ to the redox pool, and control the dosage of H ₂ O ₂ and ferrous sulfate to the following mass ratio: COD: _{H 2} O ₂ :FeSO ₄ =1:2 ~3:40~70; the treated wastewater enters the post-neutralization flocculation tank, and the hydraulic retention time is 0.25~0.5h. After the reaction, the waste water is separated from solid and liquid in the sedimentation tank, and the supernatant enters the sand filter tank. The invention is suitable for advanced treatment of low-rank coal quality-upgrading wastewater, can effectively remove refractory organic matter and chroma, and makes the low-rank coal quality-upgrading wastewater meet discharge standards.

Description

A method for advanced treatment of low-rank coal upgrading wastewater

technical field

The invention relates to a process method for treating wastewater in the field of low-rank coal upgrading, in particular to an advanced treatment method for low-rank coal upgrading wastewater, belonging to the field of advanced wastewater treatment and reuse.

Background technique

my country's low-rank coal reserves and production account for a relatively high proportion. This type of coal is in the low-metamorphism stage and has the characteristics of low ash, low sulfur, high volatile matter, and strong activity. The main coal types include lignite and low-metamorphism bituminous coal. Because low-rank coal has high total water and internal water content and hydroxide content, is prone to spontaneous combustion, and has low calorific value, it must be processed and upgraded for development and application. With the increasing global energy shortage, low-rank coal will become an important available coal resource. The upgrading of low-rank coal is an important part of clean coal technology. The upgraded coal has high calorific value and improved combustion characteristics, which can provide clean and low-cost energy for production and life, protect the environment and make full use of my country's coal resources .

The process of upgrading low-rank coal will consume a large amount of clean water and produce a large amount of wastewater containing organic pollutants. If the wastewater is not treated, it will have a toxic effect on the human body and the surrounding ecological environment. In addition, my country's low-rank coal reserves are abundant in Inner Mongolia and other regions where water resources are relatively scarce, which seriously restricts the development of low-rank coal upgrading industrial technology. Therefore, the research and development of low-rank coal upgrading wastewater treatment technology can not only make full use of water resources, but also bring broad prospects for the application of upgrading technology.

Low-rank coal upgrading wastewater has complex organic substances, high chroma, and is difficult to treat. After traditional physical and chemical treatment, the residual COD is high, and the chroma does not meet the standard. Therefore, an advanced treatment process must be added.

At present, the commonly used advanced treatment processes mainly include: (1) Activated carbon adsorption process. The activated carbon adsorption process can achieve better results when applied to the advanced treatment of wastewater, but the operating cost of the device is high, and the reusability of activated carbon is poor, so the treatment cost is high. The economy is poor. (2) Coagulation-sedimentation process. Coagulation-sedimentation method is a commonly used advanced treatment method, but when it treats coal upgrading wastewater, the residual organic matter content is high and the chroma is relatively large. (3) Fenton oxidation process, Fenton oxidation process is an advanced oxidation technology, the oxidation system (Fenton reagent) composed of H ₂ O ₂ and catalyst Fe ²⁺ can generate extremely strong oxidation ability under low pH conditions Hydroxyl radicals (·OH), these hydroxyl radicals can oxidize organic substances that are difficult to remove by biological methods or general chemical methods, and finally decompose them into CO ₂ and H ₂ O, destroying complex chromogenic groups and reducing chromaticity. At the same time, the generated iron hydroxide flocs have the function of flocculation, which can strengthen the treatment effect of Fenton method.

Contents of the invention

The invention provides an advanced treatment method for low-rank coal upgrading wastewater, which relates to a treatment method for refractory industrial wastewater, which solves the problems of unsatisfactory removal of organic matter, high chromaticity of effluent, and difficulty in discharging wastewater in a biochemical treatment process. . It is suitable for the advanced treatment of low-rank coal upgrading wastewater, and can effectively remove the refractory organic matter and chromaticity remaining after the low-rank coal upgrading wastewater has passed through the biological treatment process, so that it can meet the discharge standards and realize reuse. The dosage of chemicals can be adjusted according to the requirements of effluent water quality, and the control is flexible. The required materials are cheap and easy to obtain, the reaction is rapid, and there is no secondary pollution.

The technical scheme mainly adopted in the present invention is: ①The low-rank coal upgrading wastewater treated by the combined process of anaerobic digestion-aerobic biological contact oxidation enters the pre-acidification tank through gravity flow, and acid solution is added to the pool to reduce the waste water in the pre-acidification tank. The pH value is adjusted to 3~4, and the hydraulic retention time of the sewage in the pool is 2.5~7.5min; ②The acidified wastewater enters the redox pool through gravity flow, and the hydraulic retention time of the sewage in the redox pool is 0.5~1h;③ Install a pipe mixer near the redox pool on the connecting pipeline between the pre-acidification pool and the redox pool, and use wet method to add ferrous sulfate; ④ Add H ₂ O ₂ , H ₂ O ₂ to the redox pool and ferrous sulfate dosing control is as follows mass ratio: COD: H ₂ O ₂ : FeSO ₄ =1: 2~3: 40~70; Add lye to the tank, adjust the pH value to 8.0-9.0, and the hydraulic retention time of the post-neutralization flocculation tank is 0.25-0.5h; ⑥The waste water after acid-base neutralization and flocculation reaction enters the sedimentation tank Separation, the supernatant enters the sand filter by gravity, and is discharged or reused after filtration. The filtration rate of the sand filter is 8~10m/h.

Description of drawings

Figure 1 is a schematic diagram of the advanced treatment process of low-rank coal upgrading wastewater.

Detailed ways

Specific implementation mode 1: This implementation mode is a method for advanced treatment of low-rank coal upgrading wastewater, which is specifically completed according to the following steps:

① The low-rank coal upgrading wastewater treated by the combined process of anaerobic digestion and aerobic biological contact oxidation enters the pre-acidification tank through gravity flow, and acid solution is added to the tank to adjust the pH value of the pre-acidification tank to 3~4. The hydraulic retention time in the pool is 2.5~7.5min; ②The acidified wastewater enters the redox pool through gravity flow, and the hydraulic retention time of the sewage in the redox pool is 0.5~1h; ③Between the pre-acidification pool and the redox pool Install a pipeline mixer near the redox tank, and use the wet method to add ferrous sulfate; ④ Add H ₂ O ₂ to the redox tank, and the control of H ₂ O ₂ and ferrous sulfate is as follows Mass ratio: COD: H ₂ O ₂ : FeSO ₄ =1: 2~3: 40~70; ⑤ The low-rank coal upgrading wastewater after redox treatment enters the post-neutralization flocculation tank, and lye is added to it, Adjust the pH value to 8.0-9.0, and the hydraulic retention time of the post-neutralization flocculation tank is 0.25-0.5h; ⑥The wastewater after acid-base neutralization and flocculation reaction enters the sedimentation tank for solid-liquid separation, and the supernatant enters the sand by gravity The filter is discharged or reused after filtration. The filtration rate of the sand filter is 8~10m/h.

Specific implementation mode 2: The difference between this implementation mode and specific implementation mode 1 is that in step ①, the hydraulic retention time of sewage in the pre-acidification tank is 5 minutes.

Embodiment 3: The difference between this embodiment and Embodiment 1 or 2 is that in step ③, a pipeline mixer is installed near the position of the pre-acidification tank in the connecting pipeline between the pre-acidification tank and the redox tank.

Embodiment 4: The difference between this embodiment and Embodiments 1 to 3 is that in step ④, the dosage of H ₂ O ₂ and FeSO ₄ is controlled to the following mass ratio: COD:H ₂ O ₂ :FeSO ₄ =1 :2.5:60.

Embodiment 5: The difference between this embodiment and Embodiments 1 to 4 is that in step ⑤, the hydraulic retention time of the post-neutralization flocculation tank is 0.3h.

Example 1-2

Taking the effluent of a low-rank coal upgrading wastewater biochemical pool as an example, its original pH value is 7.46, COD is 320mg/L, and the chroma is 800 times. Take 1000mL test wastewater, adjust the pH value to 3, add a certain amount of FeSO ₄ 7H ₂ O, mix evenly, add the H ₂ O ₂ solution with a mass fraction of 30%, stir and react for 1 hour, adjust the pH value to 8.0 with NaOH solution, Let it stand for 30 minutes, take the supernatant to measure and calculate the removal rate of COD and chroma, the results are shown in Table 1.

It can be seen from the examples that the treatment process responds quickly, and the removal effect on COD and chroma is better. When the dosage is small, the water outlet effect is already good, and the dosage can be increased according to the water quality requirements to achieve Better processing effect.

Table 1

the adjust pH H ₂ O ₂ and COD mass ratio Reaction time COD removal rate (%) Chroma removal rate (%) Example 1 3 1.99 1h 81.6 95.0 Example 2 3 2.65 1h 95.3 98.9

Claims (5)

1. the invention discloses a kind of low-rank coal upgrading advanced waste treatment method, it is characterized in that: described technological method is: the low-rank coal upgrading waste water through anaerobic digestion-aerobic bio-contact oxidation method process integration process enters in pre-acidified pond, add acid solution wherein and the pH value in pre-acidified pond is regulated to 3 ~ 4, the hydraulic detention time of sewage in pre-acidified pond is 2.5 ~ 7.5min; Waste water after acidifying enters redox pond through flow by gravity, and the hydraulic detention time of sewage in redox pond is 0.5 ~ 1h; Connecting tube between pre-acidified pond and redox pond, near the position pipe laying mixing tank in redox pond, adopts wet method, adds ferrous sulfate; H is added in redox pond ₂o ₂, H ₂o ₂add with ferrous sulfate and control as following mass ratio: COD:H ₂o ₂: FeSO ₄=1:2 ~ 3:40 ~ 70; In after low-rank coal upgrading waste water after redox process enters and flocculation basin, add alkali lye wherein, pH value is regulated to 8.0 ~ 9.0, in rear and flocculation basin hydraulic detention time be 0.25 ~ 0.5h, waste water after acid-base neutralisation, flocculation reaction enters in settling tank and carries out solid-liquid separation, supernatant liquor relies on flow by gravity to enter sand filter, and discharge or reuse after filtering, the filtering velocity of sand filter is 8 ~ 10m/h.

2. low-rank coal upgrading advanced waste treatment method according to claim 1, is characterized in that: the hydraulic detention time of sewage in pre-acidified pond is 5min.

3. low-rank coal upgrading advanced waste treatment method according to claim 1, is characterized in that: the connecting tube between pre-acidified pond and redox pond is near position, pre-acidified pond pipe laying mixing tank.

4. low-rank coal upgrading advanced waste treatment method according to claim 1, is characterized in that: H ₂o ₂and FeSO ₄dosage control as following mass ratio: COD:H ₂o ₂: FeSO ₄=1:2.5:60.

5. low-rank coal upgrading advanced waste treatment method according to claim 1, is characterized in that: in rear and the hydraulic detention time of flocculation basin be 0.3h.