Method and device for treating oil field sewage
Technical Field
The invention relates to the technical field of sewage treatment, in particular to a method and a device for treating oil field sewage.
Background
Steam or fracturing fluid is required to be injected in the process of oil exploitation, the water content of the exploited oil is high, and oil-water settling separation or electric desalting and dehydration are required. A large amount of high-temperature oil field sewage is generated in the process of oil field exploitation, the sewage is various and complex in composition, contains a large amount of petroleum, suspended matters, auxiliaries and organic matters, is difficult to degrade generally, and can not be directly discharged or utilized, and the oil field sewage can be reused or discharged after reaching the standard after being effectively treated. In recent years, the rapid and efficient realization of high-temperature oil field sewage treatment becomes a key problem to be solved urgently in the oil field exploitation process.
At present, the traditional treatment process of high-temperature oil field sewage comprises three steps of oil-water separation, medicament flocculation and sedimentation, biochemical degradation and the like, the treatment period of the whole process flow is long, and the temperature of the extracted high-temperature oil field sewage needs to be reduced to normal temperature for subsequent treatment, so that the treatment cost is increased, and the heat of oil field water waste cannot be effectively utilized, thereby causing part of heat loss. In addition, the traditional treatment process needs to add a large amount of chemical agents to obtain better treatment effect. Although the use of drugs has achieved certain effects, it still suffers from a series of problems such as unstable treatment quality, limited use, complicated process, high cost, and secondary pollution. The final aim of the oil field sewage is to realize complete reuse or reinjection, and besides the requirement of water quality, the oil field sewage also means that the sewage treated by the traditional treatment process can be reused or reinjected after being heated; this additionally increases the cost of sewage reuse.
With the increasing environmental protection requirements and the development of sewage treatment technologies, the attention of people is also paid to the release of Volatile Organic Compounds (VOCs) and other toxic waste gases into the atmosphere during sewage treatment. The open type sewage treatment mode inevitably has the problem of direct discharge of VOCs and other toxic waste gases, so the open type sewage treatment mode is about to be limited, and the closed type sewage treatment mode can well avoid the direct discharge of VOCs and other toxic waste gases, so the closed type sewage treatment mode is about to be fully opened, and the transition from the open type sewage treatment mode to the closed type sewage treatment mode in the treatment process of the oilfield sewage is a necessary trend for future development.
Therefore, the rapid and efficient treatment of high-temperature oil field sewage, the heat loss problem of high-temperature sewage and the discharge problem of VOCs generated in sewage treatment limit the development of oil field exploitation industry, and the research and development of efficient and rapid effective treatment method and device which can reduce heat loss and realize closed type are urgent.
Disclosure of Invention
The invention aims to provide a treatment method of oil field sewage, which can realize the rapid and efficient treatment of the oil field sewage, reduce the heat loss in the sewage treatment process and greatly reduce the discharge amount of VOCs in the sewage treatment; the invention also aims to provide a device for treating the oilfield sewage.
Specifically, the invention provides the following technical scheme:
the invention provides a treatment method of oilfield sewage, which comprises the following steps:
(1) performing multi-stage three-phase separation treatment on oil field sewage to be treated to obtain oil, mud and sewage;
(2) and sequentially carrying out electric flocculation treatment and electrochemical oxidation treatment on the sewage.
The invention discovers that the separation of oil, mud and sewage can be realized by carrying out multi-stage three-phase separation treatment on the oilfield sewage, then the removal of suspended matters, small-particle oil, colloids and macromolecular organic matters can be realized by carrying out electrocoagulation treatment on the sewage, and finally the electrochemical oxidation treatment is carried out on the sewage after the electrocoagulation treatment, so that the soluble oils and organic matters in the sewage are degraded, and the recycling of the sewage is realized.
Preferably, the temperature of the oil field sewage is 40-200 ℃;
further, the temperature of the oilfield sewage is 60-160 ℃.
The treatment method is particularly suitable for the oilfield sewage with the temperature of 40-200 ℃ (especially 60-160 ℃).
Further, the oilfield sewage is mainly one or a combination of more of oilfield produced water, tank field precipitation water and electric desalting separated water.
Preferably, the electrocoagulation treated cationThe polar plate is a soluble metal polar plate, the negative plate is a stainless steel polar plate or a graphite polar plate, the distance between the plates is 0.2-2.0 cm, and the current density is 5-20 mA/cm2;
Further, the soluble metal electrode plate is an aluminum plate or an iron plate;
furthermore, the distance between the plates is 0.5-1.0 cm, and the current density is 10-15 mA/cm2。
As one of the better technical proposal, the anode plate of the electric flocculation treatment is a soluble iron plate, the cathode plate is a stainless steel electrode plate, the distance between the plates is 0.5cm, and the current density is 15mA/cm2。
As a second preferred technical scheme, the anode plate of the electrocoagulation treatment is a soluble aluminum plate, the cathode plate is a stainless steel electrode plate, the plate interval is 1.0cm, and the current density is 15mA/cm2。
As a third preferred technical scheme, the anode plate of the electrocoagulation treatment is a soluble iron plate, the cathode plate is a stainless steel electrode plate, the plate interval is 1.0cm, and the current density is 10mA/cm2。
Fourth, the anode plate of the electrocoagulation treatment is a soluble aluminum plate, the cathode plate is a stainless steel electrode plate, the distance between the plates is 0.5cm, and the current density is 15mA/cm2。
The cathode plate and the anode plate, the plate spacing and the current density are arranged according to the four better technical schemes, so that the electric flocculation effect is better.
Preferably, the time of the electric flocculation treatment is 5-30 min; preferably 10-20 min.
Preferably, the anode plate subjected to electrochemical oxidation treatment is a DSA electrode or a BDD electrode, the cathode plate is a stainless steel electrode, the plate spacing is 1.0-10.0 cm, and the current density is 20-100 mA/cm2。
Further, the anode plate subjected to electrochemical oxidation treatment is a titanium plate or a titanium mesh plated with a metal oxide film with electrocatalytic activity, and the metal oxide is one or a combination of more of ruthenium, iridium, tantalum, tin and antimony oxide.
Furthermore, the distance between the plates is 3.0-5.0 cm, and the electricity is suppliedThe current density is 30-60 mA/cm2。
As one of the better technical proposal, the anode plate treated by the electrochemical oxidation is a titanium plate or a titanium mesh plated with tin and antimony, the cathode plate is a stainless steel electrode, the distance between the plates is 3.0cm, and the current density is 30mA/cm2。
As a second preferred technical scheme, the anode plate subjected to electrochemical oxidation treatment is a titanium plate or titanium mesh plated with iridium tantalum, the cathode plate is a stainless steel electrode, the distance between the plates is 5.0cm, and the current density is 40mA/cm2。
The cathode plate and the anode plate, the plate spacing and the current density are arranged according to the two better technical schemes, so that the electrochemical oxidation effect is better.
Preferably, the time of the electrochemical oxidation treatment is 20-120 min, preferably 30-60 min.
The treatment method of the invention adopts a closed form, and both the electric flocculation and the electrochemical oxidation are carried out in the closed tubular reactor, so that the method can be applied to pipeline sewage conveying engineering, the heat loss of sewage is reduced to the maximum extent, and the secondary pollution caused by the discharge of VOCs is avoided.
The invention also provides a device for treating the oil field sewage; the processing method can be realized by the processing device.
Specifically, the processing device includes: a multi-stage three-phase separator, an electric flocculation reactor and an electrochemical oxidation reactor;
the water outlet of the multistage three-phase separator is connected with the water inlet of the electric flocculation reactor through a pipeline, and the water outlet of the electric flocculation reactor is connected with the water inlet of the electrochemical oxidation reactor through a pipeline.
Preferably, the multistage three-phase separator, the electric flocculation reactor and the electrochemical oxidation reactor are connected with an oil field sewage conveying pipeline in a prying block mode through flanges; and forming a closed system by the devices and the oilfield sewage conveying pipeline according to the mode.
In the invention, the multistage three-phase separator, the electric flocculation reactor and the electrochemical oxidation reactor can be connected with an actual oil field sewage conveying pipeline in a prying block mode through flanges, the prying block size can be customized according to the pipeline size, and meanwhile, free combination can be carried out according to the oil field sewage quality condition.
Preferably, the multistage three-phase separator is a centrifugal separator and/or a hydrocyclone separator; preferably a hydrocyclone.
In the invention, the multistage three-phase separator is a container with certain pressure resistance; furthermore, the multistage three-phase separator can bear the pressure of 1-5 MPa.
Preferably, the electric flocculation reactor comprises an electrode prying block module I, wherein an anode plate of the electrode prying block module I is a soluble metal electrode plate, a cathode plate of the electrode prying block module I is a stainless steel electrode plate or a graphite electrode plate, the distance between the plates is 0.2-2.0 cm, and the current density is 5-20 mA/cm2;
Further, the soluble metal electrode plate is an aluminum plate or an iron plate;
furthermore, the distance between the plates is 0.5-1.0 cm, and the current density is 10-15 mA/cm2。
Preferably, the electrochemical oxidation reactor comprises an electrode prying block module II, wherein an anode plate of the electrode prying block module II is a DSA electrode or a BDD electrode, a cathode plate of the electrode prying block module II is a stainless steel electrode, the distance between the plates is 1.0-10.0 cm, and the current density is 20-100 mA/cm2;
Furthermore, the anode plate of the electrode pry block module II is a titanium plate or a titanium mesh plated with a metal oxide film with electrocatalytic activity, and the metal oxide is one or a combination of more of ruthenium, iridium, tantalum, tin and antimony oxide;
furthermore, the distance between the plates is 3.0-5.0 cm, and the current density is 30-60 mA/cm2。
In a specific embodiment, the electrocoagulation reactor is characterized in that an electrode prying block module I fixed by a polytetrafluoroethylene frame is embedded in an oil field sewage conveying pipeline; the electrochemical oxidation reactor is characterized in that an electrode prying block module II fixed by a polytetrafluoroethylene frame is embedded in an oil field sewage conveying pipeline.
Preferably, a filter is arranged on a connecting passage of the electric flocculation reactor and the electrochemical oxidation reactor;
the filter is connected with an oil field sewage conveying pipeline through a flange in a prying block mode;
further, a filtering membrane of the filter is a high-temperature-resistant inorganic membrane;
further, the filter membrane of the filter is a ceramic membrane and/or a metal membrane.
Preferably, the filter is made of ceramic or stainless steel; the filter made of the material has good high temperature resistance and pressure resistance.
Preferably, an insulating layer is arranged outside the treatment device (including all devices and pipelines) so as to reduce the heat loss of the sewage in the treatment process and ensure the maximum recycling of the heat of the sewage.
The electrocoagulation reactor and the electrochemical oxidation reactor are both closed tubular reactors, and no extra processing of a reactor shell is needed, only a polytetrafluoroethylene polar plate frame and a prying block (namely an electrode prying block module I or an electrode prying block module II) are embedded in the existing pipeline (namely an oilfield sewage conveying pipeline), a polytetrafluoroethylene gasket is arranged at the joint of the pipeline, and a prying block fixed on the polytetrafluoroethylene gasket is connected with an external power supply; the electrodes of the electric flocculation reactor and the electrochemical oxidation reactor are connected with a direct current power supply or a direct current pulse power supply.
Compared with the prior art, the invention has the beneficial effects that:
(1) the treatment method provided by the invention realizes the high-efficiency and rapid treatment of the high-temperature oil field sewage, and greatly shortens the treatment time; the removal rate of COD of the oil field sewage treated by the method reaches more than 90 percent, the removal rate of petroleum reaches more than 95 percent, and the removal rate of ammonia nitrogen reaches more than 90 percent; the invention simultaneously adopts a closed treatment mode to reduce the heat loss of the recycled sewage and realize the recycling of most heat of the high-temperature sewage; the prior biological advanced treatment technology cannot realize high-efficiency and rapid treatment, has limited biological high-temperature resistance, mostly needs to be carried out at normal temperature, and after the heat of the sewage is completely wasted, the sewage can enter a recycling system again after being heated, thereby causing heat loss and energy consumption.
(2) The treatment device provided by the invention adopts the closed tube type reactor, can perform sewage treatment at high temperature, does not directly discharge VOCs and other toxic waste gases in the whole process, and meets the requirement of environmental protection; and the traditional biological method has obvious VOCs emission and needs to invest equipment again for treatment.
(3) The treatment device provided by the invention, especially the electric flocculation reactor and the electrochemical oxidation reactor have strong practicability, can directly utilize the existing pipeline, embed the frame and the electrode plate and realize the minimization of investment and space; meanwhile, the device can be designed into a skid-mounted mode, and is directly butted with a field pipeline, so that short-time emergency treatment is realized, and the treated water quality is guaranteed to reach the standard.
Drawings
FIG. 1 is a schematic view of an apparatus for treating oilfield wastewater according to the present invention;
in the figure: 1. a first-stage three-phase separator; 2. a secondary three-phase separator; 3. an electrocoagulation reactor; 4. a filter; 5. an electrochemical reactor.
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
The examples do not show the specific techniques or conditions, according to the technical or conditions described in the literature in the field, or according to the product specifications. The reagents or instruments used are conventional products available from regular distributors, not indicated by the manufacturer.
Example 1
The present embodiment provides an oil field sewage treatment device, as shown in fig. 1, including: a first-stage three-phase separator 1, a second-stage three-phase separator 2, an electric flocculation reactor 3 and an electrochemical oxidation reactor 5;
the first-stage three-phase separator 1 and the second-stage three-phase separator 2 are connected, and the combination of the first-stage three-phase separator and the second-stage three-phase separator is a multi-stage three-phase separator; the water outlet of the secondary three-phase separator 2 is connected with the water inlet of the electric flocculation reactor 3 through a pipeline, and the water outlet of the electric flocculation reactor 3 is connected with the water inlet of the electrochemical oxidation reactor 5 through a pipeline.
The primary three-phase separator 1, the secondary three-phase separator 2, the electric flocculation reactor 3 and the electrochemical oxidation reactor 5 are all connected with an oil field sewage conveying pipeline through flanges in a prying block mode.
The electric flocculation reactor 3 comprises an electrode prying block module I, wherein an anode plate of the electrode prying block module I is a soluble aluminum plate or a soluble iron plate, a cathode plate is a stainless steel electrode plate, the distance between the plates is 0.5-1.0 cm, and the current density is 10-15 mA/cm2。
The electrochemical oxidation reactor 5 comprises an electrode prying block module II, wherein an anode plate of the electrode prying block module II is a tin-antimony plated titanium plate/titanium mesh or an iridium-tantalum plated titanium plate/titanium mesh, a cathode plate is a stainless steel electrode, the distance between the plates is 3.0-5.0 cm, and the current density is 30-60 mA/cm2。
A filter 4 is arranged on a connecting passage of the electric flocculation reactor 3 and the electrochemical oxidation reactor 5; the filter 4 is connected with an oilfield sewage delivery pipeline through a flange in a prying block mode.
And an insulating layer is arranged outside the treatment device (comprising all devices and pipelines).
Example 2
The embodiment provides a treatment method of oilfield sewage, which is realized by the treatment device of the embodiment 1 and specifically comprises the following steps:
sending oilfield sewage (150 ℃) of a certain oilfield into a multistage three-phase separator with an external heat insulation layer, and carrying out primary physical separation on the oilfield sewage to realize primary separation of oil, mud and sewage; then the sewage after primary treatment is sent into the electric flocculation reactor through a pipeline with an external heat-insulating layer.
The electric flocculation reactor is formed by connecting an electrode prying block module I (an anode plate is a soluble iron plate, and a cathode plate is a stainless steel electrode plate) and an actual oil field sewage conveying pipeline through flanges, a polytetrafluoroethylene gasket is arranged at the position of a pipeline joint, the electrode prying block module I is embedded into a polytetrafluoroethylene frame, the plate interval between a cathode plate and an anode plate is controlled to be 0.5cm, and the polytetrafluoroethylene frame and the gasket are provided with connecting wires for fixing electrodes and an external power supply. Electric currentThe sewage treated by the flocculation reactor needs to be filtered before entering the electrochemical reactor, so a filter prying block is arranged in the water outlet direction of the electrochemical flocculation reactor (namely before entering the electrochemical oxidation reactor), the filter prying block consists of a high-temperature-resistant inorganic membrane (such as a ceramic membrane and a metal membrane), and the filter prying block is also connected with a pipeline through a flange. The electric flocculation reactor is assembled according to the description, a direct current power supply is connected, the primarily treated sewage enters the electric flocculation reactor, the residence time of the primarily treated sewage in the electric flocculation reactor is controlled by controlling the length of a pipeline, the residence time of the sewage in the electric flocculation reactor is controlled to be 20min (a plurality of groups of electric flocculation reactors can be connected in series to control the residence time according to the water quality condition), and the current density of each group of electric flocculation reactors is controlled to be 15mA/cm2. After filtering, the mixture is sent into an electrochemical oxidation reactor.
The structure of the electrochemical oxidation reactor is similar to that of the electric flocculation reactor, and the electrochemical oxidation reactor is mainly distinguished by an electrode prying block module (namely an electrode prying block module II). An electrode prying block module II in the electrochemical oxidation reactor takes a tin antimony plated titanium plate or titanium mesh as an anode and a stainless steel plate as a cathode, and is embedded into a polytetrafluoroethylene frame, and the plate spacing between the cathode plate and the anode plate is controlled to be 3 cm. The polytetrafluoroethylene frame and the gasket are provided with fixed electrodes and external power supply connecting wires. The electrochemical oxidation reactor is assembled according to the above description, and is connected with a direct current power supply, sewage treated by the electrocoagulation reactor enters the electrochemical oxidation reactor, the retention time of the sewage in the electrochemical oxidation reactor is controlled to be 60min (a plurality of groups of electrochemical oxidation reactors can be connected in series according to the water quality condition to control the retention time), and the current density of each group of electrochemical oxidation reactors is controlled to be 30mA/cm2. After detection, the temperature of the sewage after the treatment reaches the standard is 128 ℃, and the sewage can be reinjected or recycled after heat exchange or heating, so that the heat loss is reduced to the maximum extent, and the sewage recycling is realized.
In this example, the influent water quality and the effluent water quality of the wastewater are shown in table 1.
TABLE 1 Water quality of inlet and outlet water
Item
|
COD/mg·L-1 |
petroleum/mg/L
|
NH4-N/mg·L-1 |
Quality of inlet water
|
540
|
30
|
25
|
Quality of effluent water
|
50
|
1.5
|
2.5 |
Example 3
The embodiment provides a treatment method of oilfield sewage, which is realized by the treatment device of the embodiment 1 and specifically comprises the following steps:
sending oilfield sewage (130 ℃) of a certain oilfield into a multistage three-phase separator with an external heat insulation layer, and carrying out primary physical separation on the oilfield sewage to realize primary separation of oil, mud and sewage; then the sewage after primary treatment is sent into the electric flocculation reactor through a pipeline with an external heat-insulating layer.
The electric flocculation reactor is formed by connecting an electrode prying block module I (an anode plate is a soluble aluminum plate, a cathode plate is a stainless steel electrode plate) and an actual oil field sewage conveying pipeline through flanges, a polytetrafluoroethylene gasket is arranged at the position of a pipeline joint, the electrode prying block module I is embedded into a polytetrafluoroethylene frame, the distance between the cathode plate and the anode plate is controlled to be 1cm, and the polytetrafluoroethylene frame is used for supporting the anode plate and the cathode plateThe frame and the gasket are provided with connecting wires for fixing the electrodes and an external power supply. The sewage treated by the electrocoagulation reactor needs to be filtered before entering the electrochemical reactor, so that a filter prying block is arranged in the water outlet direction of the electrocoagulation reactor (namely before entering the electrochemical oxidation reactor), the filter prying block consists of high-temperature-resistant inorganic membranes (such as ceramic membranes and metal membranes), and the filter prying block is also connected with a pipeline through a flange. The electric flocculation reactor is assembled according to the description, a direct current power supply is connected, the primarily treated sewage enters the electric flocculation reactor, the residence time of the primarily treated sewage in the electric flocculation reactor is controlled by controlling the length of a pipeline, the residence time of the sewage in the electric flocculation reactor is controlled to be 20min (a plurality of groups of electric flocculation reactors can be connected in series to control the residence time according to the water quality condition), and the current density of each group of electric flocculation reactors is controlled to be 15mA/cm2. After filtering, the mixture is sent into an electrochemical oxidation reactor.
The structure of the electrochemical oxidation reactor is similar to that of the electric flocculation reactor, and the electrochemical oxidation reactor is mainly distinguished by an electrode prying block module (namely an electrode prying block module II). An electrode prying block module II in the electrochemical oxidation reactor takes a tin antimony plated titanium plate or titanium mesh as an anode and a stainless steel plate as a cathode, and is embedded into a polytetrafluoroethylene frame, and the plate spacing between the cathode plate and the anode plate is controlled to be 3 cm. The polytetrafluoroethylene frame and the gasket are provided with fixed electrodes and external power supply connecting wires. The electrochemical oxidation reactor is assembled according to the above description, and is connected with a direct current power supply, sewage treated by the electrocoagulation reactor enters the electrochemical oxidation reactor, the retention time of the sewage in the electrochemical oxidation reactor is controlled to be 60min (a plurality of groups of electrochemical oxidation reactors can be connected in series according to the water quality condition to control the retention time), and the current density of each group of electrochemical oxidation reactors is controlled to be 30mA/cm2. After detection, the temperature of the sewage after the treatment reaches the standard is 105 ℃, and the sewage can be reinjected after heat exchange or heating, so that the heat loss is reduced, and the sewage can be recycled.
In this example, the influent water quality and the effluent water quality of the wastewater are shown in table 2.
TABLE 2 Water quality of inlet and outlet water
Item
|
COD/mg·L-1 |
petroleum/mg/L
|
NH4-N/mg·L-1 |
Quality of inlet water
|
540
|
30
|
25
|
Quality of effluent water
|
45
|
2
|
2 |
Example 4
The embodiment provides a treatment method of oilfield sewage, which is realized by the treatment device of the embodiment 1 and specifically comprises the following steps:
the oil field sewage (160 ℃) of a certain oil field is sent into a multistage three-phase separator with an external heat insulation layer, and primary physical separation of the oil field sewage is carried out, so that primary separation of oil, mud and sewage is realized. Then the sewage after primary treatment is sent into the electric flocculation reactor through a pipeline with an external heat-insulating layer.
The electric flocculation reactor is formed by connecting an electrode prying block module I (an anode plate is a soluble iron plate, and a cathode plate is a stainless steel electrode plate) and an actual oil field sewage conveying pipeline through flanges, a polytetrafluoroethylene gasket is arranged at the joint of the pipelines, the electrode prying block module I is embedded into a polytetrafluoroethylene frame, and the negative and positive plates are controlledThe distance between the plates is 1cm, and the polytetrafluoroethylene frame and the gasket are provided with connecting wires for fixing the electrodes and an external power supply. The sewage treated by the electrocoagulation reactor needs to be filtered before entering the electrochemical reactor. Therefore, a filter prying block is arranged in the water outlet direction of the electrocoagulation reactor (namely before entering the electrochemical oxidation reactor), the filter prying block consists of a high-temperature-resistant inorganic membrane (such as a ceramic membrane and a metal membrane), and the filter prying block is also connected with a pipeline through a flange. The electric flocculation reactor is assembled according to the description, a direct current power supply is connected, the primarily treated sewage enters the electric flocculation reactor, the residence time of the primarily treated sewage in the electric flocculation reactor is controlled by controlling the length of a pipeline, the residence time of the sewage in the electric flocculation reactor is controlled to be 20min (a plurality of groups of electric flocculation reactors can be connected in series to control the residence time according to the water quality condition), and the current density of each group of electric flocculation reactors is controlled to be 10mA/cm2. After filtering, the mixture is sent into an electrochemical oxidation reactor.
The structure of the electrochemical oxidation reactor is similar to that of the electric flocculation reactor, and the electrochemical oxidation reactor is mainly distinguished by an electrode prying block module (namely an electrode prying block module II). An electrode prying block module II in the electrochemical oxidation reactor takes an iridium-tantalum-plated titanium plate or titanium mesh as an anode and a stainless steel plate as a cathode, and the titanium plate or the titanium mesh is embedded into a polytetrafluoroethylene frame, and the plate spacing between the cathode plate and the anode plate is controlled to be 5 cm. The polytetrafluoroethylene frame and the gasket are provided with fixed electrodes and external power supply connecting wires. The electrochemical oxidation reactor is assembled according to the above description, the direct current power supply is connected, the sewage treated by the electrocoagulation reactor enters the electrochemical oxidation reactor, the retention time of the sewage in the electrochemical oxidation reactor is controlled to be 60min (a plurality of groups of electrochemical oxidation reactors can be connected in series according to the water quality condition to control the retention time), and the current density of each group of electrochemical oxidation reactors is controlled to be 40mA/cm2. After detection, the temperature of the sewage after the treatment reaches the standard is 136 ℃, and the sewage can be recycled after proper heat exchange or heating, so that the heat loss is reduced to the maximum extent, and the sewage recycling is realized.
In this example, the influent water quality and the effluent water quality of the wastewater are shown in table 3.
TABLE 3 Water quality of inlet and outlet water
Example 5
The embodiment provides a treatment method of oilfield sewage, which is realized by the treatment device of the embodiment 1 and specifically comprises the following steps:
the oil field sewage (90 ℃) of a certain oil field is sent into a multistage three-phase separator with an external heat insulation layer, and primary physical separation of the oil field sewage is carried out, so that primary separation of oil, mud and sewage is realized. Then the sewage after primary treatment is sent into the electric flocculation reactor through a pipeline with an external heat-insulating layer.
The electric flocculation reactor is formed by connecting an electrode prying block module I (an anode plate is a soluble aluminum plate, and a cathode plate is a stainless steel electrode plate) and an actual oil field sewage conveying pipeline through flanges, a polytetrafluoroethylene gasket is arranged at the position of a pipeline joint, the electrode prying block module I is embedded into the polytetrafluoroethylene frame, the plate interval between the cathode plate and the anode plate is controlled to be 0.5cm, and the polytetrafluoroethylene frame and the gasket are provided with connecting wires for fixing electrodes and an external power supply. The sewage treated by the electrocoagulation reactor needs to be filtered before entering the electrochemical reactor. Therefore, a filter prying block is arranged in the water outlet direction of the electrocoagulation reactor (namely before entering the electrochemical oxidation reactor), the filter prying block consists of a high-temperature-resistant inorganic membrane (such as a ceramic membrane and a metal membrane), and the filter prying block is also connected with a pipeline through a flange. The electric flocculation reactor is assembled according to the description, a direct current power supply is connected, the primarily treated sewage enters the electric flocculation reactor, the residence time of the primarily treated sewage in the electric flocculation reactor is controlled by controlling the length of a pipeline, the residence time of the sewage in the electric flocculation reactor is controlled to be 20min (a plurality of groups of electric flocculation reactors can be connected in series to control the residence time according to the water quality condition), and the current density of each group of electric flocculation reactors is controlled to be 15mA/cm2. After filtering, feeding electrochemical oxygenA chemical reactor.
The structure of the electrochemical oxidation reactor is similar to that of the electric flocculation reactor, and the electrochemical oxidation reactor is mainly distinguished by an electrode prying block module (namely an electrode prying block module II). An electrode prying block module II in the electrochemical oxidation reactor takes an iridium-tantalum-plated titanium plate or titanium mesh as an anode and a stainless steel plate as a cathode, and the titanium plate or the titanium mesh is embedded into a polytetrafluoroethylene frame, and the plate spacing between the cathode plate and the anode plate is controlled to be 5 cm. The polytetrafluoroethylene frame and the gasket are provided with fixed electrodes and external power supply connecting wires. The electrochemical oxidation reactor is assembled according to the above description, the direct current power supply is connected, the sewage treated by the electrocoagulation reactor enters the electrochemical oxidation reactor, the retention time of the sewage in the electrochemical oxidation reactor is controlled to be 60min (a plurality of groups of electrochemical oxidation reactors can be connected in series according to the water quality condition to control the retention time), and the current density of each group of electrochemical oxidation reactors is controlled to be 40mA/cm2. After detection, the temperature of the sewage after the treatment reaches the standard is 67 ℃, and the sewage can be reinjected or discharged.
In this example, the influent water quality and the effluent water quality of the wastewater are shown in table 4.
TABLE 4 Water quality of inlet and outlet water
Item
|
COD/mg·L-1 |
petroleum/mg/L
|
NH4-N/mg·L-1 |
Quality of inlet water
|
1320
|
56
|
37
|
Quality of effluent water
|
100
|
2
|
2.5 |
Although the invention has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that many modifications and improvements can be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.