CN101113035A - The Method of Treating Oil Refining Sewage Using Multi-stage Inflatable Cyclone Technology - Google Patents

Abstract

The invention provides a method for treating oil refinery sewage by adopting a multi-stage inflatable swirl technology, which can efficiently recover floating oil, dispersed oil and emulsified oil in the oil refinery sewage, and remove most suspended matter at the same time. Its main feature is that through the setting of at least two inflatable hydrocyclones, combined with the use of demulsifiers, coagulants and coagulants, the physical and chemical treatment of relatively high-concentration oily sewage generated by various devices in the refining process, after treatment The effluent meets the water intake index of the biochemical section of general refining and chemical sewage treatment plants. The process of the invention can replace the physical and chemical treatment section (primary treatment) in the existing oil refinery sewage treatment process, and has the characteristics of high efficiency, small occupied area, low investment and the like.

Description

The Method of Treating Oil Refining Sewage Using Multi-stage Inflatable Cyclone Technology

technical field

The invention relates to a method for treating oil refinery sewage by adopting multi-stage inflatable swirl technology, which belongs to the technical category of oil refinery sewage treatment.

Background technique

Oil refinery sewage treatment focuses on solving two problems: first, remove petroleum and suspended solids in sewage through physical and chemical methods (primary treatment); and then consider removing COD, BOD, NH ₃ -N, etc. in water through biochemical methods organic pollutants.

Oil in refinery sewage generally exists in four forms: slick oil, dispersed oil, emulsified oil, and dissolved oil: (1) slick oil, which spreads on the surface of sewage to form an oil film or oil layer, and the particle size of oil droplets is relatively large, generally greater than 100 μm , accounting for more than 70% to 80% of the total oil content; (2) dispersed oil, dispersed in the sewage in the form of oil particles, unstable, often becomes oil slick after standing for a period of time, and the particle size of oil droplets is 100 ~ 25μm (3) Emulsified oil, which is milky in sewage, and the oil droplets are covered with a layer of hydration film and has a certain amount of negative charge, and the water contains a certain amount of surfactant, making it difficult for the oil particles to merge , long-term stability, oil particle size is generally 25 ~ 0.1μm; (4) dissolved oil, oil dissolved in water, particle size below 0.1μm, extremely difficult to separate.

At present, the physical and chemical treatment (primary treatment) of this kind of oily sewage from the refinery is combined with a variety of equipment, and the treatment process is as follows: incoming water - advection grease trap - inclined plate grease trap - air flotation. Oil separation is a kind of gravity separation method. The principle is that under the action of gravity, the petroleum and other suspended impurities contained in the wastewater are separated by themselves according to different relative densities. The sinking, so as to achieve the purpose of separation, the object of treatment is slick oil and coarse dispersed oil. The advection grease trap can remove oil droplets with a particle size greater than or equal to 150 μm, and the inclined plate grease trap can remove oil droplets with a particle size greater than or equal to 60 μm. Since the advection grease trap and inclined plate grease trap are all gravity separation, the driving force for the separation of the two phases through gravity settlement is only one gravitational acceleration, so the treatment process requires a long residence time for sewage, and the equipment is bulky and occupies a large area. High investment cost, difficult management, discontinuous operation, and difficult to deal with finely dispersed oil (particle size less than 50μm oil droplets) and emulsified oil, only when the emulsified oil content in the sewage is less than 30mg/L, and the dissolved oil content is less than 10mg/L It has a good degreasing effect.

Since oil separation is not effective in removing finely dispersed oil and emulsified oil in refinery wastewater, air flotation treatment is required after oil separation. The air flotation method uses highly dispersed micro-bubbles as a carrier to remove oil droplets or suspended solids whose relative density is close to water, so that they can be removed with the bubbles floating to the water surface, and can remove finely dispersed oil and most of them. emulsified oil. At present, pressurized dissolved air flotation, vortex-concave flotation and jet flotation are widely used in refining oily sewage treatment. Vortex-concave flotation machines have problems such as troublesome manufacturing, troublesome maintenance, high energy consumption, and a sharp drop in efficiency when the temperature of the processing medium is high. The jet flotation device is a kind of oily sewage treatment equipment that has appeared in recent years. The jet flotation method can be powered by a water pump, which reduces energy consumption compared with the vortex-concave flotation, but there are problems such as high equipment cost, difficult maintenance, and poor operation stability. question. Pressurized dissolved air flotation is the more commonly used method. During the operation of this dissolved air flotation device, the pressurized dissolved air water obtained by dissolving air enters the flotation tank (also known as the air flotation tank) and is decompressed and released through the release device to generate microbubbles. Contact with the suspended matter in the sewage in the same direction and stick to become particles with a certain speed. The particles are floated to the surface and scraped away by the slag scraping mechanism, thereby completing the removal of the suspended matter in the raw water. The device is generally equipped with complex settings such as a booster pump, an air compressor, an ejector, a high-pressure dissolved air tank, and a release device. The entire device is bulky and has relatively high requirements for operation and maintenance.

Therefore, the conventional physical and chemical treatment process (primary treatment) has the following disadvantages: large floor area, high equipment investment, infrastructure and operation and maintenance costs, and long residence time of sewage.

In response to the shortcomings of the above methods, hydrocyclone separation technology has been gradually developed since the 1960s.出现了一系列关于旋流分离技术的专利，部分专利的专利号分别为US4237006、US4231368、US4544486、US4464264、US4719014、US4721565、US4749490、CN2459311Y、CN1112522A、CN2221996Y、CN1199871C、CN1570033A、CN1817404A、CN1541948A、CN1546196等， The applications of the cyclone separation technology in various oil-water separation processes are disclosed respectively. Cyclone separation technology is considered as a high-efficiency and energy-saving oil-water separation technology, which has the following advantages: simple structure; low cost, light weight, low maintenance cost, low energy consumption; flexible and convenient installation, and the cyclone can be installed at any angle; Continuous and reliable work, convenient operation and maintenance, high efficiency; good adaptability, wide operation and adjustment range, etc.

At the same time, cyclone separation also has disadvantages: due to the shearing effect generated by the flow of fluid in the cyclone, if the parameters are not designed properly, it is easy to break the liquid droplets (oil droplets or water droplets) and cause emulsification to deteriorate the separation process; Processing materials of different properties often requires cyclones of different structural sizes or operating conditions, so the versatility of cyclone separation operation is poor. In short, oil-water mixtures of different crude oils often have different physical properties, so cyclones used for different water qualities are often not interchangeable.

The common hydrocyclone is a columnar hydrocyclone, which has a better treatment effect on floating oil and dispersed oil, but the removal effect on emulsified oil is still relatively poor, and the advantage of the flotation device is that it has a relatively high treatment efficiency on emulsified oil. , the technology is mature and reliable, but the adaptability to the situation of relatively high oil content in the incoming water is relatively poor. It can be seen that the hydrocyclone and the flotation device have their own characteristics and shortcomings. On the other hand, the composition of oily sewage from domestic refineries is complex, and it is hoped that cyclones can be used instead of flotation devices in the treatment of oily sewage within a wider range of adaptability, and specific research results are needed to support it.

Air-Sparged Hydrocyclone (ASH) is a further development of hydrocyclone separation technology based on ordinary columnar hydrocyclones. In 1983, Miller and Hupka used a φ50mm inflatable hydrocyclone to carry out the research of oil-water separation test for the first time, and the test proved that ASH can successfully separate oil-water. In 1993, J.P.Beeby and S.K.Nicol used a φ50×500mm inflatable hydrocyclone to study the concentrated oil-in-water emulsion. The results showed that ASH can successfully separate chemically stable emulsion oil from sewage. Taking turbidity as the index of emulsion concentration, when the oil concentration of the feed is 400mg/L, the removal rate of turbidity in the underflow can reach 96%. In 1996, Yu Renhuan and others used self-made φ55mmASH to conduct research on purifying oily sewage. The oil removal rate reached 74.6% under the condition of influent flow rate of 53.3L/min, oil content of 75mg/L, and gas-liquid volume ratio=1.

As an improvement of the conventional hydrocyclone, the gas-filled hydrocyclone combines dissolved air flotation with the flow characteristics of the hydrocyclone through the side wall of the hydrocyclone, and its application in the field of oil-water separation is more It is still in the research and exploration stage, the treatment effect, operating conditions, and the selection of equipment parameters are still limited by the specific conditions of the water quality to be treated. The composition of various oils in oil refinery sewage is quite different due to the different processing objects of crude oil. It is of great practical significance to establish a treatment system with wider applicability to achieve efficient treatment of oil refinery sewage. The aerated hydrocyclone The industrial application of the device in oil refinery sewage treatment has not been reported yet.

Contents of the invention

The purpose of the present invention is to provide a refinery sewage physical and chemical treatment system and method with simple process, short process, convenient control, simple management, small footprint, high efficiency, low consumption, and investment saving for the pretreatment of oil refinery sewage, so as to replace the existing The oil separation and flotation units in the sewage physical and chemical treatment process make the oil content of the sewage treated by this process below 30mg/L, and the suspended solids drop below 90mg/L, which meets the water inlet requirements of the biochemical section of the oil refinery sewage treatment plant.

The invention provides a method for (pre)treating oil refinery sewage by adopting multi-stage inflatable swirl technology, comprising the following process:

The high-concentration oily sewage produced by various units of the refinery is pressurized to 0.2-0.3MPa and then enters the conveying pipeline, and a demulsifier is added to the conveying pipeline to make it pass through a static mixer or Venturi together with the pressurized oily sewage After being kept in the pipeline for 15-25 seconds, it enters the first-stage inflatable hydrocyclone for oil-water separation. The separated oil components overflow from the upper part into the waste oil tank for recovery, and the oily sewage after preliminary purification overflows from the bottom. Enter the sewage buffer tank; the demulsifier is a polyacrylamide demulsifier, which is basically neutral, with a molecular weight of 6 million to 7 million, and the dosage of the demulsifier is 0 to 20 mg/L of sewage to be treated;

Add coagulant to the oily sewage discharged from the sewage buffer tank, use pumps to fully mix the chemical and sewage and pressurize to 0.2-0.3MPa, so that the sewage mixed with coagulant After maintaining the reaction time for 20-25 seconds, add the coagulant aid, the sewage with the coagulant and coagulant aid passed through the static mixer or Venturi mixer, and then enter the secondary aerated hydrocyclone, and control the flow of the sewage The time from passing through the mixer to entering the secondary aerated hydrocyclone is 15 to 25 seconds. After the sewage is treated by the secondary cyclone, the flocs in the sewage overflow from the upper part of the cyclone to form scum to be removed. The effluent overflows from the bottom and becomes pretreated water for further biochemical treatment.

According to the pretreatment process provided by the present invention, after the high-concentration oily sewage (raw water) produced by each device in the refinery is collected, before entering the first-stage aerated hydrocyclone, an appropriate amount of demulsifier can be added according to the oil content in it, and the oily sewage can be fully mixed with the oily sewage. Mixing and maintaining in the pipeline for a certain period of time (15 to 25 seconds) is beneficial to the demulsification of sewage. The reaction time depends on the content of emulsified oil and suspended solids SS in the sewage, and then enters the first-stage inflatable hydrocyclone for oil-water separation . Aiming at the properties of oil refinery sewage, the present invention can first add an appropriate amount of polyacrylamide as a demulsifier to strengthen the demulsification of the sewage, and recover most of the emulsified oil and dispersed oil in the sewage as much as possible while removing the slick oil. The demulsifier basically Neutral, with a molecular weight of 6 million to 7 million, it can be purchased directly or produced by manufacturers. According to the solution of the present invention, when the emulsified oil content in the oily sewage produced from each refinery device is as low as 150 mg/liter or less, the dosage of the demulsifier in the delivery pipeline is 0-10 mg/liter of sewage to be treated . If the content of the emulsified oil in the oily sewage produced from each device of the refinery is higher than 150 mg/liter, the dosage of the demulsifier in the delivery pipeline is 10-20 mg/liter of sewage to be treated.

According to the method of the present invention, most of the petroleum components in the sewage can be basically recovered through the preliminary oil-water separation treatment of the first-stage inflatable hydrocyclone, so that the final drainage can meet the water intake requirements of the biochemical section of the refinery sewage treatment plant , It is also necessary to add coagulant and coagulant respectively for bridging, netting, etc., so that the suspended solids in the water and the remaining oil (petroleum) form larger flocs, and then enter the secondary aerated hydrocyclone Further purification treatment. At this time, conventional coagulants and coagulants can be used. For example, the coagulant can be aluminum salt-based or iron-based flocculants (aluminum chloride, polyaluminum ferric chloride, basic aluminum chloride, calcium aluminate etc.), the coagulant can be an acrylamide polymer (polyacrylamide agents such as FO4190SH, FO4440SH, FO4800, FO4190PG of the French SNF company), and the specific dosage of the coagulant and coagulant can be operated according to the routine , preferably, the dosages of coagulant aid and coagulant are 1-2 milligrams and 50-150 milligrams per liter of water to be treated, respectively.

According to the process of the present invention, the sewage to be treated enters the pipeline through appropriate pressurization (for example, by a centrifugal pump or other delivery pump), and the incoming water is added with a demulsifier and mixed by a static mixer or a Venturi mixer, and then the length of the pipeline The sewage (under the set flow rate) should be kept in it for 20-25 seconds, and the oil-water separation and the demulsifier should be given sufficient contact reaction time with the sewage, so that the emulsified oil can be demulsified to form larger oil droplets, and then enter the first stage of aeration The cyclone separator completes the recovery of dirty oil (petroleum).

According to the process of the present invention, the timing of adding the coagulant is in the pipeline before the outlet water of the first-stage inflatable hydrocyclone enters the pump, and the pumps used here can realize the stirring and mixing of the incoming water, and make the mixed The incoming water has a certain flow rate. For example, a centrifugal pump can be used. The sewage mixed with the coagulant can make full use of the stirring and mixing effect of the impeller to react. The reaction time between the coagulant and the sewage is sufficient; at the same time, a pipeline mixer is also installed in the pipeline. The mixer can be a static mixer or a Venturi mixer. Before the sewage enters the mixer, a coagulation aid needs to be added. After the sewage is fully mixed, the time for controlling the sewage added with the coagulant to flow through the pipeline mixer and enter the secondary aerated hydrocyclone is 15 to 25 seconds (control the flow rate of the sewage and the length of the pipeline), and give bridges, nets The reaction time of capture makes the petroleum oil and suspended solids in the sewage form larger flocs.

According to the process of the present invention, the water inlet pressure of the inflatable hydrocyclone is 0.2-0.3MPa; the gauge pressure of the inflatable pipeline is 0.3-0.4MPa; from the practical point of view, the inflatable air source can be provided by compressed air or an air compressor in the factory. .

According to the process of the present invention, in the on-site treatment system, the oily sewage generated from each device of the refinery passes through a settling oil removal tank or a sewage buffer tank before being sent to the first-stage aerated hydrocyclone, and the recovered part of the floating water Oil and disperse oil and remove sediment. The effluent of the first-stage aerated hydrocyclone also passes through the sewage buffer tank before entering the second-stage aerated hydrocyclone;

As can be understood from the foregoing description, the key of the present invention is that multi-stage (at least two) aerated hydrocyclones and related supporting equipment are set in the system for implementing pretreatment of high-concentration oily sewage discharged from refineries, According to the characteristics of the sewage to be treated, the first-stage aerated hydrocyclone and/or the second-stage aerated hydrocyclone respectively include a combination of one or more than one set of cyclones, for example, any one-stage cyclone separation Both can be a series connection of two or three sets of cyclones to achieve the desired treatment effect. For oily sewage with special properties, more than two levels of inflatable hydrocyclones can also be installed (the outlet water of the second level cyclone enters the next level or multi-level cyclone) to ensure that the output water reaches the refinery oilfield sewage field Water quality standards for biochemical treatment.

The structure and working principle of the gas-filled hydrocyclone are well known to those of ordinary skill in the art, as shown in Figure 2. The difference between it and the ordinary cyclone separator is that the wall of the flotation section of the device adopts micropores The material becomes a porous tube with pores ranging from 5 to 100 μm, and the size of the pores can be controlled during manufacture according to different uses. During operation, the gas flow (air or nitrogen or other inert gas) is "squeezed" into the flow field from the outer jacket through the pores of the wall under a certain pressure, and the oily sewage is squeezed into the flow field along the tangential inlet of the cyclone feed section under a certain pressure. Entering, the swirl flow is formed due to the restriction of the wall. The airflow entering from the pores is divided into a large number of fine bubbles by the shearing action of the high-speed rotating fluid. The hydrophobic particles in the water (such as oil droplets, suspended solids, etc.) collide with and adsorb each other with the bubbles, and enter the foam column in the center under the action of centrifugal force. , and then flow vertically upward into the overflow pipe to form an overflow; while most of the liquid flow close to the wall flows out from the bottom to form an underflow. The whole process realizes the combination of flotation and cyclone, which improves the removal efficiency.

The inner cavity of the gas-filled hydrocyclone adopted in the process of the present invention is preferably a sintered titanium porous tube, with an average pore diameter of 5 μm, a porosity of 30-50%, a wall thickness of 3 mm, and an air permeability of 2-9. ×10 ^-3 L/min·cm ² ·mmH ₂ O, the residence time of the water body in the cyclone is less than 1 second. Compared with the traditional air flotation method, the process of the present invention is the most outstanding under the condition of equivalent oil removal rate The advantage is that the sewage can stay in the separator for a very short time, which can usually be completed within 1 second, while the traditional air flotation method usually takes 15 to 20 minutes; with the use of chemical agents, the present invention can remove oil slicks, Dispersing oil can also remove emulsified oil. The test results show that the present invention can realize the removal of oil droplets with a particle size as low as 4 μm in the sewage by using the inflatable hydrocyclone.

In a word, the treatment system and process of the present invention replace the conventional oily sewage treatment physicochemical section, and can treat not only oil refinery sewage, but also other high-concentration oily sewage. The oil separation and/or flotation treatment in the traditional process is replaced by an inflatable hydrocyclone, the equipment occupies a small area, and the operating conditions and parameters are adjusted accordingly according to the nature of the sewage to be treated. The process is simpler and more convenient to control, and the versatility is improved. , the whole process achieves the purpose of high efficiency, low consumption and investment saving. The promotion in the industry as a supporting technology for sewage treatment of refining and chemical enterprises will produce very significant social and economic benefits.

Description of drawings

Fig. 1 is a schematic process flow diagram of embodiment 1 of the present invention.

Fig. 2 is a schematic cross-sectional view of an air-filled hydrocyclone used in Example 2.

Detailed ways

The implementation process and beneficial effects of the present invention are described in detail below in conjunction with the accompanying drawings and specific examples, aiming to help readers better understand the spirit of the present invention, but should not be construed as any limitation to the scope of the present invention.

Embodiment 1 The process of using multi-stage inflatable cyclone technology to treat oil refinery sewage

Please refer to Figure 1. The high-concentration oily sewage produced by each device in the refinery is firstly pressurized to 0.2-0.3 MPa by the centrifugal pump 12 connected in series on the pipeline to the first-stage aerated hydrocyclone 2, and then passed through The demulsifier dosing tank 1 is mixed with an appropriate amount of demulsifier, so that the pressurized sewage mixed with demulsifier passes through the static mixer 16 (or Venturi mixer) and then remains in the pipeline for 15-25 seconds (depending on the amount of emulsified oil in the sewage). depends on the SS content) and then enters the first-stage inflatable hydrocyclone 2 for oil-water separation. The air source used for the cyclone separation operation can be provided by compressed air or air compressor in the factory, and the petroleum oil in the sewage overflows from the upper part and flows back to the sewage The recovery of the oil tank (not shown in the figure) is completed; after preliminary purification, the oily sewage overflows from the bottom and enters the buffer tank 13 . In this process, the demulsifier in the medicine tank 1 needs to be dosed into the sewage according to the content of the emulsified oil in the incoming water.

The effluent of the buffer tank 13 and the coagulant are stirred together by the impeller of the centrifugal pump 14 to fully mix the medicament and the sewage and pressurize to 0.2-0.3 MPa. The flow is controlled so that the sewage reacts in the pipeline for 20-25 seconds, and then the coagulant is added. After the mixed water body is treated and discharged by the static mixer or the Venturi mixer 15, it continues to maintain the reaction in the pipeline for a period of time (the time required for sewage to flow through the mixer 15 and the subsequent pipeline into the secondary aerated hydrocyclone 3 is about 15 ~25 seconds) to complete bridging and netting, so that the suspended solids in the sewage and the remaining petroleum oils form larger flocs, and then enter the secondary inflatable hydrocyclone 3, and the flocs overflow from the upper part of the cyclone 3 to form floating flocs. The slag is discharged to the sludge tank for removal, and the effluent overflows from the bottom of the cyclone 3 and a return line is set to a buffer tank (not shown in the figure) to complete the pretreatment. After testing, the effluent after this process can meet the influent requirements of biochemical treatment of sewage field.

In the above process, the water inlet pressure of the primary and secondary aerated hydrocyclones is 0.2-0.3 MPa; the gauge pressure of the aerated pipeline is 0.3-0.4 MPa, and the gas-liquid volume ratio is 2-3.

Same as the current operation, the sewage from each unit of the refinery can first be collected into a settling degreasing tank or sewage buffer tank (not shown in the figure), so as to stabilize the water quality and quantity in the whole treatment process and at the same time treat the sewage in the sewage Oil slick and mud sand are initially removed.

Embodiment 2 Inflatable hydrocyclone

The primary and secondary aerated hydrocyclones 2 and 3 used in the process of Example 1 can be conventional aerated hydrocyclones, or an aerated hydrocyclone (ASH) as described in FIG. 2 .

Referring to Figure 2, the aerated hydrocyclone consists of three parts: the feed section, the flotation section, and the underflow section. The sections are connected by flanges. The shape of the entire cyclone device is cylindrical.

In the middle and upper part of the feeding section is the feeding pipe 21, from which the sewage enters the cyclone in a tangential feeding manner. An overflow pipe 22 and a gland 23 are designed on the top of the feed section. The outer side of the gland 23 is threaded with the top of the feed section, and the inner side is threaded with the overflow pipe 22, so that glands and overflow pipes with different inner diameters can be used according to water quality requirements, while the outer diameter of the gland 23 remains unchanged, and its inner diameter Then keep supporting with overflow pipe 22 external diameters.

The flotation section is composed of two inner and outer chambers. The inner chamber 24 is made of sintered titanium porous tube manufactured by Beijing Institute of Nonferrous Metals. The average pore diameter is 5 μm and the wall thickness is about 3 mm. Equal, outer layer 24 ' is the pipe body that 1Cr18Ni9Ti stainless steel material is made and concentric with inner layer cavity 24, both form interlayer (also claim jacket), and this interlayer one side is provided with the inlet pipe 25 of same material with outer layer. In order to make the air intake uniform, the air intake pipe 25 is divided into two branch pipes at the wall of the device, and the air intake is divided into two shares. There are a plurality of uniform air inlet holes in the radial upward direction of each branch pipe extending into the interlayer part, and air enters the jacket through these air inlet holes.

The bottom flow section is made of ordinary carbon steel, and its bottom is covered with inner wire (internal thread) 29, which cooperates with screw rod 27. The top of the screw rod 27 fastens the foam base 26 through threaded connection. The foam base 26 is in the shape of a truncated cone. Through the rotation of the screw rod 27, the lift in the underflow section can be realized, thereby changing the area of the underflow annular gap between the foam base 26 and the outlet of the inner cavity of the flotation section. In addition, an underflow pipe 28 is designed at the bottom of the device for discharging purified water.

Example 3

According to the process and operation of Example 1 and Example 2, the field pilot test of using multi-stage aerated hydrocyclone technology to treat oil refinery sewage was first carried out in Liaohe Petrochemical Branch Company. The design processing capacity is 5t/h; the expected operation effect is achieved.

Liaohe Petrochemical Company mainly processes heavy oil and super heavy oil from Liaohe Oilfield, and the sewage to be treated has the typical characteristics of heavy oil sewage. The percentages of slick oil, dispersed oil, emulsified oil, and dissolved oil in raw water were 40.4%, 6.1%, 51.7%, and 1.6%, respectively. It can be seen that the oil contained in raw water is mainly slick oil and emulsified oil, and the degree of emulsification is relatively high, so the oily sewage to be treated in this embodiment belongs to the refractory oily sewage with high oil content, high emulsification, and high suspended solids.

The scope of main water quality indicators is as follows:

serial number project unit Index range 1 water temperature ℃ ＜38 2 pH 6-9 3 Oil mg/L 800-1000 4 CODcr mg/L 1000-2500 5 Suspended solids (SS) mg/L 1000-3000

Refer to the description of Example 1 for the specific process operation of Liaohe petrochemical refinery sewage treatment. The high-concentration oily sewage produced by each device is pressurized to 0.3MPa by the centrifugal pump 12, and is simultaneously poured into the water flow line according to the set flow rate. Add a demulsifier to make the two fully mixed through the static mixer 16, and react in the subsequent pipeline for about 25 seconds before entering the first-stage inflatable hydrocyclone 2. The air source can be compressed air or an air compressor in the factory. Provided, petroleum overflows from the upper part and is sent to the waste oil tank to be recovered; the oily sewage after preliminary purification overflows into the buffer tank 13 from the bottom flow pipe 28 .

The outlet water of the buffer tank 13 and the coagulant added to the pipeline are stirred together by the impeller of the centrifugal pump 14 to fully mix the medicament and sewage and pressurized to 0.3MPa, and the coagulant is added after reacting in the pipeline for about 25 seconds , flows through the static mixer or Venturi mixer 15, and enters the secondary aerated hydrocyclone 3 through the water delivery pipeline, and the sewage flows through the mixer 15 and enters the secondary aerated hydrocyclone 3 to control the reaction of 20 seconds to complete bridging and netting; suspended solids in water and remaining petroleum oil form large flocs and enter the secondary aerated hydrocyclone 3, and the flocs overflow from the upper part of the cyclone to form scum to be removed, and the water is discharged Overflowing from the underflow pipe 28 at the bottom, the effluent can meet the requirements of influent water for biochemical treatment of the sewage field.

According to the properties of Liaohe Petrochemical oil refining wastewater, polyacrylamide (FO4190SH from French SNF company, molecular weight 6 million to 7 million) was selected as the demulsifier to demulsify and degrease the sewage, and the dosage was 15 mg/L of sewage to be treated ; The coagulant is aluminum sulfate, the dosage is 150mg/L, and the coagulant aid is FO4800 water treatment agent of French SNF company, and the dosage is 2mg/L;

The inlet water pressure of the first-stage air-filled cyclone separator 2 and the second-stage air-filled hydrocyclone 3 is 0.2-0.3 MPa, the source of the air-inflated air is compressed air in the factory, and the gauge pressure of the air-filled pipeline is 0.3-0.4 MPa;

The walls of gas-filled cyclones 2 and 3 are made of sintered titanium porous tubes, with an average pore size of 5 μm, a porosity of 30-50%, a thickness of 3 mm, and an air permeability of 2-9×10 ^-3 L/min·cm ² ·mmH ₂ O; the residence time of the water body in the cyclone is less than 1 second during the treatment process.

The effect of the above pretreatment process on sewage treatment:

The average petroleum oil content in the influent water from the sewage source is between 800-1000mg/L, the CODcr fluctuates between 1000-2500mg/L, and the suspended solids are 1000-3000mg/L. After the secondary cyclone separation, the effluent water quality is basically stable and contains oil (Petroleum content) is less than 30mg/L, CODcr is 600-800mg/L on average, and suspended matter is less than 90mg/L, which can be directly discharged into the biochemical section for subsequent treatment;

It can be considered that the present invention can solve the problem of treating petroleum, COD and suspended matter in sewage, and replace the conventional physical and chemical treatment process.

Example 4

According to the process and operation of Example 1 and Example 2, a field pilot test of using multi-stage aerated hydrocyclone technology to treat oil refinery sewage was carried out in the Olefin Division of Baling Petrochemical Co., Ltd. The design processing capacity is 5t/h; the expected operation effect is achieved.

The Olefin Division of Baling Petrochemical Co., Ltd. mainly processes paraffin-based light crude oil. The water quality is good. The content of slick oil and dispersed oil in the raw water is high, and the proportion of emulsified oil and dissolved oil is low.

Refer to the description of Example 1 for the specific process operation of the treatment of the refining wastewater of the olefin business unit. In view of the nature of the refining wastewater, no demulsifier was added before the primary aerated hydrocyclone.

The effluent of the first-stage air-filled hydrocyclone is fully mixed with coagulant and coagulant aid, and then pumped into the second-stage air-filled hydrocyclone for purification treatment. At this time, conventional coagulant and coagulant aid (with the implementation of Example 3 is the same), the dosage of coagulant aid and coagulant is respectively 1.0 mg and 100 mg per liter of sewage to be treated.

The effect of this pretreatment process on sewage treatment:

The average petroleum content in the influent water from the sewage source is between 300-800mg/L (the emulsified oil content generally does not exceed 20% of the total petroleum), the average CODcr is 600-1500mg/L, and the suspended solids are 300-1600mg/L. Process effluent The water quality is basically stable, the oil content (petroleum content) is less than 25mg/L, the average CODcr is 200-300mg/L, and the suspended matter is less than 60mg/L, which can be directly discharged into the biochemical section for subsequent treatment.

Example 5

According to the process and operation of Example 1 and Example 2, a small-scale test of treating oily sewage with multi-stage aerated hydrocyclone technology was carried out in the laboratory. The design processing capacity is 2.5t/h; the gas-liquid volume ratio is 3, and the experimental results are good.

In the laboratory, 0# diesel oil, crude oil (taken from Jidong Oilfield) and tap water were used to prepare emulsified oily sewage with an oil content of 400 mg/L under the action of a TM50 colloid mill, and the average particle size of the oil droplets was below 10 μm.

The average particle size of oil droplets was measured using a Coulter automatic particle size analyzer (COULTER MULTISTZERII), with a measuring range of 0.4-1200 μm. The oil content was measured using an OIL420 infrared oil meter.

Refer to the description of Example 1 for the specific process operation of treating the prepared emulsified oily sewage. In view of the properties of the oily sewage, a demulsifier (same as in Example 3) was added before the primary aerated hydrocyclone, and the dosage was 15 mg/L of sewage to be treated.

After the first-stage air-filled cyclone effluent is fully mixed with coagulant and coagulant aid, it is pumped into the second-stage air-filled cyclone separator for purification. At this time, conventional coagulant and coagulant aid (similar to that of Example 3) can be used. Same), the dosage of coagulant aid and coagulant is 1.0 mg and 100 mg per liter of sewage to be treated respectively.

The effect of this pretreatment process on sewage treatment:

The average petroleum content in the influent water from the sewage source is about 400mg/L, and the average particle size of oil droplets is less than 10μm; the quality of the effluent water is basically stable, with an average petroleum content of about 15mg/L-30mg/L, and the average particle size of oil droplets is less than 4μm .

Example 6

According to the process and operation of Example 1 and Example 2, a small-scale test of multi-stage aerated hydrocyclone technology for treating sewage containing dispersed oil was carried out in the laboratory. The design processing capacity is 2.5t/h; the gas-liquid volume ratio is 3, and the experimental results are good.

In the laboratory, 0# diesel oil and tap water were used to prepare oily sewage with an oil content of 1000 mg/L, mainly dispersed oil, under the shearing action of a centrifugal pump, and the average particle size of oil droplets was 27 μm.

The average particle size of oil droplets was measured using a Coulter automatic particle size analyzer (COULTER MULTISTZERII), with a measuring range of 0.4-1200 μm. The oil content was measured using an OIL420 infrared oil meter.

Refer to the description of Example 1 for the specific process operation of treating the prepared oily sewage mainly composed of dispersed oil. In view of the nature of the oily sewage, no demulsifier is added to the primary aerated hydrocyclone.

After the first-stage air-filled cyclone effluent is fully mixed with coagulant and coagulant aid, it is pumped into the second-stage air-filled cyclone separator for purification. At this time, conventional coagulant and coagulant aid (similar to that of Example 3) can be used. Same), the dosage of coagulant aid and coagulant is 1.0 mg and 100 mg per liter of sewage to be treated respectively.

The effect of this pretreatment process on sewage treatment:

The average petroleum content in the influent water from the sewage source is about 1000mg/L, and the average particle size of oil droplets is 27μm; the quality of the effluent water is basically stable, with an average petroleum content of about 15mg/L-30mg/L, and the average particle size of oil droplets is less than 4μm.

Claims (8)

1. A method for treating oil refinery sewage by adopting multistage aeration cyclone technology, comprising the following processes: The oily sewage produced by each unit of the refinery is pressurized to 0.2-0.3MPa and then enters the conveying pipeline, and the demulsifier is added to the conveying pipeline to make it mix with the pressurized oily sewage through a static mixer or Venturi and keep it in the pipeline for 15-25 seconds to enter the first-stage inflatable hydrocyclone to implement oil-water separation. The separated oil components overflow from the upper part to the waste oil tank for recovery, and the oily sewage after preliminary purification overflows from the bottom and enters the sewage The buffer tank, the demulsifier is polyacrylamide, which is basically neutral, with a molecular weight of 6 million to 7 million, and the dosage of the demulsifier is 0 to 20 mg/L of sewage to be treated; Add coagulant to the oily sewage discharged from the sewage buffer tank, use pumps to fully mix the chemical and sewage and pressurize to 0.2-0.3MPa, so that the sewage mixed with coagulant After maintaining the reaction time for 20-25 seconds, add the coagulant aid, the sewage with the coagulant and coagulant aid passed through the static mixer or Venturi mixer, and then enter the secondary aerated hydrocyclone, and control the flow of the sewage The time for entering the secondary aerated hydrocyclone through the mixer is 15 to 25 seconds. After the sewage is treated by the secondary cyclone, the flocs in the sewage are removed by overflowing from the upper part of the cyclone to form scum, and the effluent The overflow from the bottom becomes pretreated water for further biochemical treatment. 2. The method according to claim 1, wherein, when the emulsified oil content is as low as 150mg/liter or below from the oily sewage produced by each device of the refinery, the dosage of the demulsifier in the delivery pipeline is 0 ~10 mg/L of sewage to be treated. 3. The method according to claim 1, wherein, when the emulsified oil content in the oily sewage produced from each device in the refinery is higher than 150 mg/liter, the dosage of the demulsifier in the delivery pipeline is 10 to 20 mg/liter. mg/L sewage to be treated. 4. The method according to claim 1, wherein the dosages of the coagulant aid and the coagulant are respectively 1-2 mg and 50-150 mg per liter of sewage to be treated. 5. The method according to claim 1, wherein the water inlet pressure of the primary and secondary aerated hydrocyclones is 0.2-0.3 MPa; the gauge pressure of the aerated pipeline is 0.3-0.4 MPa, and the gas-liquid volume ratio is 2-0. 3. 6. The method according to claim 5, wherein the gas source for the primary and secondary gas-filled hydrocyclones comes from compressed air or air compressors in the refinery. 7. The method according to claim 1, wherein the wall of the primary and secondary gas-filled hydrocyclones adopts sintered titanium porous tube, its average pore diameter is 5 μm, and the porosity is 30-50%. The thickness is 3mm, the air permeability is 2～9×10 ^-3 L/min·cm ² ·mmH ₂ O; the residence time of sewage in the cyclone is less than 1 second. 8. The method according to claim 1, wherein the primary aerated hydrocyclone and/or the secondary aerated hydrocyclone respectively comprise one set or a combination of more than one set.

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