CN1180986C - A method and special device for treating oilfield wastewater by electric-heterogeneous catalytic reaction - Google Patents

Abstract

The present invention provides a method for treating industrial wastewater, that is, a method for treating oilfield wastewater by using electric-heterogeneous catalytic reaction. Under the condition of an external electric field, the organic pollutants in the oilfield wastewater are catalyzed and oxidized on the surface of the catalyst, wherein the The catalyst is composed of an active component and a carrier, with one or more oxides of Fe, Co, Ni, Mn, Cu, Ti, W or Pb as the active component supported on SiO ₂ , Al ₂ O ₃ , zeolite molecular sieve Or activated carbon carrier, wherein the weight percentage of the metal component is 1-10%, the DC voltage between the electrodes in the electric field is 12-14V, and the current density is 125mA-600mA/square decimeter; wherein the catalyst can be added One or several oxides of rare earth metals are used as additives. The catalyst is made by impregnation, drying and roasting; it can effectively treat oily wastewater and dinitrophenol wastewater generated in the process of oilfield exploitation, wastewater from chemical fertilizer plants, cutting Liquid wastewater, etc.; the pilot test results show that this technology can directly discharge the oilfield wastewater up to the standard, and the operation cost is low.

Description

A method and special device for treating oilfield wastewater by electro-heterogeneous catalytic reaction

technical field

The invention relates to industrial waste water treatment, in particular to a method and a special device for treating oil field waste water by electric-heterogeneous catalytic reaction.

Background technique

Oil extraction wastewater (oily wastewater generated during oilfield exploitation) mainly comes from different sections such as drilling, oil extraction, well washing, and downhole operations. The wastewater discharged from these sections contains petroleum, COD _Cr , volatile phenol, sulfide, SS, etc. things. These oilfield wastewaters are refractory organic wastewaters, which are difficult to be treated by common methods such as biochemistry; biodegradation is the most commonly used process for treating wastewater, but industrial wastewater such as dinitrophenol wastewater, fertilizer factory wastewater, and cutting fluid wastewater is difficult to use. Biodegradable methods must be used to deal with new technologies and new processes.

Electrocatalytic oxidation mainly utilizes a large number of OH free radicals generated in the electrolytic treatment process to degrade organic pollutants (Song Weifeng et al., Water Treatment Technology, 27 (2001.2) 90-92). However, electro-heterogeneous catalytic oxidation (Xie Maosong et al., Journal of Dalian Railway Institute, 19 (1998.2) 35-37) is different from electrocatalytic oxidation. The effect of wastewater has no obvious influence; Xie Maosong and others have proposed an electric-heterogeneous catalytic reaction process (ZL.92106153.6) in the early stage. The combined effect of electroactivation and electroactivation activates the reaction molecules, and can carry out reactions that cannot occur with catalysts alone under milder reaction conditions. This technology can be used to treat brewery wastewater (ZL.92106153.6), chemical fertilizer factory wastewater (ZL.00122912), etc., and has built an industrialized device for treating fertilizer wastewater with a processing capacity of 200 tons per hour. It has passed the provincial and municipal levels Acceptance by the environmental protection department. It has been in operation for more than two years so far, and the treated wastewater can be reused, saving a lot of industrial water; the electro-heterogeneous catalytic oxidation is at normal temperature and pressure, under the synergistic effect of an electric field and a catalyst, to convert macromolecular organic matter For small molecules or CO ₂ and water, reduce the content of harmful substances, so as to meet the discharge standards of wastewater.

Compared with other water treatment technologies, electro-heterogeneous catalytic oxidation has many advantages: such as mild reaction conditions, carried out under normal temperature and pressure; no special requirements for water quality; low operating costs; simple equipment required, occupying an area of Small, easy to operate; no secondary pollution; especially suitable for treating some medium-concentrated wastewater that is difficult to degrade, and can also receive good results for some wastewater that is not high in concentration but highly toxic and not suitable for biochemical treatment.

In the process of using electro-heterogeneous catalytic reaction to treat industrial wastewater containing organic matter, the degradation of organic matter is actually the decomposition of organic matter by catalytic oxidation; the reaction process is that, on the one hand, under the activation of an external electric field, the following OH-based free radicals, because the generated OH free radicals have strong oxidation and non-selectivity to organic reactions, make it possible to catalyze the oxidation of biodegradable organics at normal temperature and pressure; on the other hand, The organic matter to be treated can be selectively catalyzed and oxidized on the surface of the catalyst; therefore, electro-heterogeneous catalytic technology needs to realize the degradation of organic matter under the synergistic effect of electric field and catalyst. Efficiently carry out the reaction of catalytic oxidation and decomposition of organic matter.

Contents of the invention

The object of the present invention is to provide a method and a special device for treating oilfield wastewater by electro-heterogeneous catalytic reaction with suitable active component catalyst and electric field conditions.

In order to achieve the above object, the technical solution of the present invention is: under the condition of the presence of an external electric field, the organic pollutants in the oilfield wastewater are catalyzed and oxidized on the surface of the catalyst, wherein the catalyst is composed of an active component and a carrier, and is composed of Fe, Co, Ni One or several oxides of Mn, Cu, Ti, W or Pb are active components loaded on SiO ₂ , Al ₂ O ₃ , zeolite molecular sieves or activated carbon supports, and the weight percentage of metal components is 1-10%, the rest is the carrier, the DC voltage between the electrodes in the electric field is 12-14V, and the current density is 125mA-600mA per square decimeter;

Wherein: one or more oxides of rare earth metals can be added as additives in the catalyst, and the weight percentage is 1/6 to 1/5 of the total weight of the metal component; the metal component in the catalyst The weight percentage is preferably 1 to 5%;

The catalyst can be prepared by an impregnation method. The carrier is impregnated with a soluble chloride or nitrate aqueous solution containing metal ions, left to stand, dried, and then roasted at 300-450°C for 2-4 hours to obtain the finished product ;

The concentration of the soluble chloride or nitrate aqueous solution in the preparation of the catalyst is 0.12-2.0mol/l, and the volume ratio of the solution to the carrier is 0.8-1.5:1; 10-24 hours, the drying is carried out in the temperature range of 110-130 ° C; when the catalyst is supported by activated carbon, the roasting is carried out under the protection of nitrogen;

The special device for the catalyst preparation method is a trough structure reactor, which is mainly composed of a tank body, a top cover, an electrode, and a catalyst. The reactor is made of PVC, and a water inlet pipe is provided on the side wall of its lower part. There is an outlet pipe on the side wall, an aeration pipe at the bottom, and a distribution plate above the aeration pipe. One or more pairs of parallel titanium electrodes with diamond mesh are placed on the distribution plate. The area depends on the reaction. Depending on the volume of the reactor, the volume contained in the electrode is 32-56% of the volume of the reactor, and the catalyst is filled around the electrode.

The present invention has the following advantages:

1. The inventive method can effectively process industrial waste water such as oily waste water, dinitrophenol waste water, chemical fertilizer plant waste water and cutting fluid waste water in the process of oil field exploitation; It is to make the oily wastewater which is difficult to biochemically meet the national first-class discharge standard. Compared with the method in the prior art which can only reduce COD _Cr to 200 mg/L, the COD _Cr of the present invention can be reduced to 92 mg/L.

2. The method of the present invention is easy to operate, has mild reaction conditions, and is carried out under normal temperature and pressure. It is especially suitable for treating some medium-concentration refractory wastewater, with low operating costs, simple equipment, and no secondary pollution.

3. the inventive method adopts PVC to be the trough structure reactor of material, places one or more pairs of parallel titanium electrodes with diamond-shaped mesh in the reactor, and the contained volume of the electrodes is 32～56% of the reactor volume, and the treatment effect up to max.

Description of drawings

Figure 1 is a map of the influence of different electrode widths on wastewater treatment results; where B: L _{electrode width} /L _{reactor width} : below 32%, C: L _{electrode width} /L _{reactor width} : between 32% and 56%, D: L _{electrode width} /L _{reactor width} : more than 56%. (Electrode width refers to the width of the pole plate, the distance between electrodes and the height of the electrodes remain unchanged)

Figure 2 is a schematic diagram of the electro-heterogeneous catalytic reactor.

Detailed ways

Example 1

Preparation of M/ _SiO2 catalyst:

Take 100ml of 0.18mol/L Fe(NO ₃ ) ₃ solution, pour 100 grams of 40-60 mesh SiO ₂ particles into the impregnating solution and stir, let stand for 10 hours, dry at 110°C for 2 hours, and then dry at 400°C Calcined for 3 hours, naturally cooled to room temperature to make catalyst A. The weight of metal components in catalyst A is: Fe: 1%, the rest is carrier SiO ₂ .

Example 2

Preparation _of M/ _Al2O3 and M/zeolite catalysts:

Replace the _SiO particles in Example 1 with Al ₂ O ₃ or molecular sieve zeolite, and the others are the same as in Example 1 to prepare M/Al ₂ O ₃ catalyst B containing Fe: 1% or M/Al containing Fe: 1%. Zeolite catalyst C.

Example 3

Preparation of M/activated carbon catalyst:

① Replace the _SiO2 powder in Example 1 with mesoporous activated carbon, and roast it under a nitrogen atmosphere. The rest are the same as Example 1, and prepare M/activated carbon catalyst D1 containing Fe: 1%.

2. replace the _SiO powder in Example 1 with mesoporous activated carbon, and add 10ml of lanthanum nitrate solution of 0.18mol/L in the impregnation solution in Example 1, and roast under _N atmosphere, and all the other conditions and steps are implemented with the same example 1. The M/activated carbon type catalyst D2 prepared as La0.2%-Fel%.

Example 4

Static experiment of electro-heterogeneous catalysis for oil field wastewater:

The raw water COD _Cr : 503mg/l, BOD ₅ : 18mg/l, BOD ₅ /COD _Cr : 0.036, PH: 7, light yellow.

The electro-heterogeneous catalytic tank structure reactor made of PVC is composed of a tank body (2), a top cover (3), an electrode (4), and a catalyst (5), and a water inlet pipe is provided on its lower side wall (1), an outlet pipe (6) is provided on its upper side wall, an aeration pipe (8) is provided at its bottom, and a distribution plate (7) is installed above the aeration pipe (8). (7) vertically place 3 pairs of parallel titanium electrodes (4) with diamond-shaped meshes, its area is that the contained volume of the electrodes is 56% of the reactor volume, and the catalyst (5) is filled around the electrodes (4); 400ml of raw water Added to the reactor equipped with electrodes, static reaction. After different processing times, samples were taken and analyzed, and the results are shown in Table 1. (COD _Cr is analyzed by the dichromate method (GB 11914-89) for the determination of chemical oxygen demand in water quality)

Table 1. Static treatment results of oilfield wastewater by electro-heterogeneous catalysis Processing time (h) Voltage and current COD _Cr after reaction (mg/l) 1 12V-400mA 253 2 195 3 149 4 120

From the experimental results in Table 1, it can be seen that the treatment of oilfield wastewater by electro-heterogeneous catalysis has a good effect, and the treated wastewater can meet the national secondary discharge standard.

Example 5

Continuous experiment of electro-heterogeneous catalysis for oilfield wastewater (I):

In an electric-heterogeneous catalytic reactor made of PVC, two titanium electrodes with diamond-shaped meshes are placed in parallel, and 100ml of catalyst A prepared in Example 1 is filled, and a peristaltic pump is used for continuous sample injection. Next, different airspeeds are used for processing. Each water sample takes the value after complete equilibrium.

The reaction temperature is 25°C, normal pressure, raw water COD _Cr : 506mg/, PH: 6-7, light beige, and the effluent is almost colorless. The reaction results are listed in Table 2.

Table 2. Catalyst A treatment results for oilfield wastewater Space velocity (V _water : V _catalyst ) 2.2 2.5 2.9 3.3 4.0 COD _Cr after reaction (mg/l) 65 78 97 115 137

Example 6

Continuous experiment of electro-heterogeneous catalysis for oilfield wastewater (II):

Raw water COD _Cr : 504mg/l. Adopt the catalyst B prepared by embodiment 2, all the other conditions are the same as embodiment 5, and the reaction results are listed in table 3.

Table 3. Results of Catalyst B Treating Oilfield Wastewater Space velocity (V _water : V _catalyst ) 2.2 2.5 2.9 3.3 4.0 COD _Cr after reaction (mg/l) 50 65 84 102 117

Example 7

Continuous experiment of electro-heterogeneous catalysis for oilfield wastewater (III):

Raw water COD _Cr : 503mg/l. Catalyst C prepared in Example 3 was adopted, and all the other conditions were the same as in Example 5. The reaction results are listed in Table 4.

Table 4. Results of Catalyst C Treating Oilfield Wastewater Space velocity (V _water : V _catalyst ) 2.2 2.5 2.9 3.3 4.0 COD _Cr after reaction (mg/l) 48 60 70 77 93

Example 8

For the electric-multiphase continuous experiment of oilfield wastewater (IV):

Raw water COD _Cr : 506mg/L, adopts the catalyst D2 prepared in embodiment 3②, all the other conditions are the same as embodiment 5, and the treatment results are listed in table 5.

Table 5. Results of Catalyst D2 Treating Oilfield Wastewater Space velocity (V _water : V _catalyst ) 2.2 2.5 2.9 3.3 4.0 COD _Cr after reaction (mg/l) 32 40 56 69 80

Example 9

Influence of electrode width on treatment effect:

In the same electro-heterogeneous catalytic reactor, the same amount of catalyst was used, the electrode width was changed, and the other conditions were the same as in Example 7. The reaction results are listed in Table 6.

Table 6. Effect of different electrode widths on wastewater treatment efficiency

L _{electrode width} /L _{reactor width} : below 32% Space velocity (V _water : V _catalyst ) 2.9 3.3 3.7 4.0 COD _Cr after reaction (mg/l) 72 83 104 120

L _{electrode width} /L _{reactor width} : between 32% and 56% Space velocity (V _water : V _catalyst ) 2.9 3.3 3.7 4.0 COD _Cr after reaction (mg/l) 62 75 82 93

L _{electrode width} /L _{reactor width} : more than 56% Space velocity (V _water : V _catalyst ) 2.9 3.3 3.7 4.0 COD _Cr after reaction (mg/l) 80 89 99 112

The influence spectrum of different electrode widths on the wastewater treatment results is shown in Figure 1. It can be seen from Figure 1 that when the electrode width is 32-56% of the reactor width, the treatment efficiency is the highest.

Example 10

For the electro-heterogeneous catalysis pilot test of oilfield wastewater:

Based on the good reaction results in the laboratory, a pilot test was carried out in the oil field. The pilot test adopts a tank reactor, uses catalyst C, and uses titanium electrodes with rhombic mesh as the electrodes. There are multiple sets of electrodes with an electrode spacing of 20 cm, and 400 liters of catalyst are added to the reaction tank. Use a submersible pump to pump out the water in the pool, and enter the reaction tank after being measured by the rotameter. The COD _Cr of oily waste water is 200mg/L, and the inflow is 800 liters/hour. After the reaction, the pH of the effluent is 6-7, the color is very light, and it runs stably for 12 days. The results of the pilot test are shown in Table 7.

Table 7. Pilot test results of electro-heterogeneous catalytic treatment of oilfield wastewater Space velocity (V _water : V _catalyst ) COD _Cr after reaction (mg/l) Operating cost ^* (yuan/ton) 2.1 92 1.0

^* Operating cost includes electricity consumption only

Table 8. The stability results of the pilot test for the treatment of oilfield wastewater by electro-heterogeneous catalysis days of operation 1 2 3 4 5 6 7 8 9 10 11 12 After treatment COD _Cr (mg/L) 50 90 92 98 85 87 90 90 92 89 92 88

^* V _{water water} : V _{water:: catalyst} = 2.1, voltage: 14V, current density: 125mA/square decimeter

From the experimental results in Tables 7 and 8, it can be seen that the electro-heterogeneous catalytic oxidation technology is used to treat oily wastewater with low COD _Cr , which can meet the national first-level discharge standards and has broad application prospects in oil fields.

Claims (7)

1. an electricity consumption-heterogeneous catalytic reaction is handled the method for oil field waste, it is characterized in that: under the condition that extra electric field exists, make in the oil field waste organic pollutant at the catalyst surface catalyzed oxidation, wherein said catalyzer is made up of active ingredient and carrier, is that active ingredient is supported on SiO with one or more oxide compound among Fe, Co, Ni, Mn, Cu, Ti, W or the Pb ₂, Al ₂O ₃, on zeolite molecular sieve or the absorbent charcoal carrier, wherein the weight percentage of metal component is 1～10%, in its electric field between electrode volts DS be 12～14V, current density is every square decimeter of 125mA～600mA; Electrode width is 32～56% of a reactor width.

2. method according to claim 1 is characterized in that: the oxide compound that can add in the rare earth metal one or more in the wherein said catalyzer is as auxiliary agent, and weight percentage is 1/6～1/5 of a metal component gross weight.

3. method according to claim 1 and 2 is characterized in that: the weight percentage of metal component is 1～5% in the described catalyzer.

4. method according to claim 1 and 2, it is characterized in that: wherein said catalyzer can adopt immersion process for preparing, with soluble chloride that contains metal ion or nitrate aqueous solution, behind the impregnated carrier, leave standstill, roasting 2～4 hours is carried out in oven dry again under 300～450 ℃, can obtain finished catalyst.

5. method according to claim 4 is characterized in that: soluble chloride or nitrate aqueous solution concentration are 0.12～2.0mol/l in the wherein said catalyzer, and solution is 0.8～1.5: 1 with the carrier bulk ratio.

6. method according to claim 4 is characterized in that: wherein said catalyzer leaves standstill and is meant under 25～30 ℃ of conditions and put 10～24 hours, and oven dry is to carry out in 110～130 ℃ of temperature ranges.

7. method according to claim 4 is characterized in that: wherein said catalyzer is when being carrier with the gac, and roasting is to carry out under nitrogen protection.

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