阅读说明：本技术 亲油/亲水微孔膜协同耦合强化的油水分离工艺 (Oleophylic/hydrophilic microporous membrane synergistic coupling enhanced oil-water separation process ) 是由 阮雪华 马杨 贺高红 王佳铭 姜晓滨 代岩 郑文姬 焉晓明 于 2020-12-31 设计创作，主要内容包括：本发明提供了一种亲油/亲水微孔膜协同耦合强化的油水分离工艺,属于石油化工领域。油品蒸汽冷凝液化过程产生的油水混合物,含有大量微米级水滴,在短时间内难以充分聚并,受此限制,传统的重力沉降方法很难实现油相和水相的充分分离。本发明以微孔膜法油水分离技术为基础,提出将亲油型微孔膜和亲水型微孔膜集成装配成双膜分离器,同步从油水混合物中渗透分离油相和水相,壁面被截留组分在微孔膜表面逐渐富集而造成的渗透通量下降现象。本发明提供的协同耦合工艺,分离程度高、速度快,可以产出水含量不超过0.2wt％的无水油相,不含有直径超过2μm的水滴；与对应的单膜分离器相比,双膜分离器中亲油型微孔膜的油通量可高出85％。(The invention provides an oleophylic/hydrophilic microporous membrane synergistic coupling enhanced oil-water separation process, and belongs to the field of petrochemical industry. The oil-water mixture generated in the process of condensing and liquefying oil steam contains a large amount of micron-sized water drops, and is difficult to be fully merged in a short time, so that the traditional gravity settling method is difficult to realize the full separation of an oil phase and a water phase. The invention provides a method for separating oil from water by a microporous membrane method, which is based on the oil-water separation technology of the microporous membrane method, integrates an oleophilic microporous membrane and a hydrophilic microporous membrane to form a double-membrane separator, and synchronously permeates and separates an oil phase and a water phase from an oil-water mixture, wherein the phenomenon of permeation flux reduction caused by gradual enrichment of intercepted components on the surface of the microporous membrane on the wall surface is provided. The synergistic coupling process provided by the invention has high separation degree and high speed, can produce an anhydrous oil phase with the water content not more than 0.2 wt%, and does not contain water drops with the diameter more than 2 mu m; compared with a corresponding single-membrane separator, the oil flux of the oleophilic microporous membrane in the double-membrane separator can be 85% higher.)

1. An oil-water separation process reinforced by the synergistic coupling of an oleophylic/hydrophilic microporous membrane is characterized by comprising the following steps: the oil-water mixture (S-1) firstly enters a first oil-water separation tank (1), water phase droplets with the diameter of more than 40 mu m are separated from an oil phase main body through gravity settling, a formed lean oil water phase (S-2) is extracted from the bottom of the first oil-water separation tank (1), and a formed lean oil phase (S-3) is extracted from the side of the first oil-water separation tank (1); the lean water-oil phase (S-3) is pressurized by a delivery pump (2) and then sent to a double-membrane separator (3) to further realize oil-water separation, the anhydrous oil phase (S-4) is obtained at the permeation side of an oleophilic microporous membrane (4), meanwhile, a rich water-oil phase (S-5) is obtained at the permeation side of a hydrophilic microporous membrane (5), the rest lean water-oil phase is extracted from a retentate material outlet of the double-membrane separator (3), and is converted into a circulating lean water-oil phase (S-6) after passing through a pressure control valve (7), and the circulating lean water-oil phase (S-6) returns to the first oil-water separation tank (1); and the water-rich oil phase (S-5) enters a second oil-water separation tank (6), water drops with larger diameters are removed primarily through gravity settling, the formed oil-water mixture is extracted from the side part of the second oil-water separation tank (6), the oil-water mixture and the oil-water mixture (S-1) are combined and enter a first oil-water separation tank (1), and the formed lean oil water phase is extracted from the bottom of the second oil-water separation tank (6) and combined with the lean oil water phase (S-2) extracted from the bottom of the first oil-water separation tank (1).

2. The oleophilic/hydrophilic microporous membrane cooperative coupling enhanced oil-water separation process as claimed in claim 1, wherein a double-membrane separator (3) equipped with oleophilic microporous membrane (4) and hydrophilic microporous membrane (5) is employed to further dehydrate the lean oil phase (S-3) after gravity settling separation to obtain anhydrous oil phase (S-4), water-rich oil phase (S-5) and circulating lean oil phase (S-6); in the double-membrane separator, the oleophilic surface of the oleophilic microporous membrane (4) and the hydrophilic surface of the hydrophilic microporous membrane (5) are close to each other in an oil-water mixture, and the distance between the oleophilic surface and the hydrophilic surface is less than 5 mm.

3. The oleophilic/hydrophilic microporous membrane cooperative coupling enhanced oil-water separation process as claimed in claim 1 or 2, wherein if a flat-plate membrane assembly is adopted, the whole periphery of the double-membrane separator is a frame (8) of a plate-and-frame membrane separator, the inside of the double-membrane separator is divided into a plurality of stages of separation units, and each stage of separation unit is divided into an oil-rich permeation cavity (13), a flow cavity (11) and a water-rich permeation cavity (14) from top to bottom through the oleophilic microporous membrane (4) and the hydrophilic microporous membrane (5); the ends of the oleophilic microporous membrane (4) and the hydrophilic microporous membrane (5) are provided with sealing elements (9); the feeding cavity (10), the flowing cavity (11) and the discharging cavity (12) are sequentially communicated, the water-rich permeation cavities (14) of all levels of separation units are gathered to the water outlet main pipe through the water outlet branch pipes, and the oil-rich permeation cavities (13) of all levels of separation units are gathered to the oil outlet main pipe through the oil outlet branch pipes.

4. The oleophilic/hydrophilic microporous membrane cooperative coupling enhanced oil-water separation process as claimed in claim 1 or 2, wherein if a hollow fiber membrane is adopted for assembly, the oleophilic microporous membrane (4), the hydrophilic microporous membrane (5), the membrane shell (15) and the epoxy end sockets (16) arranged at two ends of the oleophilic microporous membrane (4) and the hydrophilic microporous membrane (5) divide the interior of the double-membrane separator into a flow chamber (11), an oil-rich permeation chamber (13) and a water-rich permeation chamber (14).

Technical Field

The invention relates to an oil-water separation process reinforced by the synergistic coupling of an oleophylic microporous membrane and a hydrophilic microporous membrane, belonging to the field of petrochemical industry. Aiming at a mixed system in which water formed in the oil processing process is dispersed in a continuous oil phase in a micron-sized droplet state, the process provides a double-membrane component in which a lipophilic microporous membrane and a hydrophilic microporous membrane are cooperatively coupled, water in the mixed system is synchronously removed through selective permeation of the hydrophilic microporous membrane, the influence on the separation capacity and the separation effect of the lipophilic microporous membrane after the raw material side water droplets are enriched and coalesced is weakened, and the rapid and efficient separation of an oil-water mixture is realized.

Background

In the process of condensing and liquefying steam, after the gaseous substances are rapidly cooled, micron-sized liquid drops are usually formed first and then are combined to form a liquid phase main body. In the process of condensing and liquefying oil steam, micron-sized water drops formed by condensing a small amount of water steam in a system are difficult to be fully combined in a short time due to the separation effect of an oil phase main body, so that the limitation is met, the traditional gravity settling method is difficult to realize the full separation of the oil phase and the water phase, and the micron-sized water drops remaining in the oil product have great adverse effects on downstream processing and the quality of the oil product. Taking the processing and refining of crude oil as an example, the water content of crude oil after electric desalting treatment is about 1.8 wt%, water is enriched at the top of a distillation tower in the atmospheric distillation process, and an oil-water mixture (the water content is usually 5-10 wt%) is formed with naphtha after condensation. The gravity settling separation time of micron-sized water droplets in naphtha is shown in table 1.

TABLE 1 gravitational settling velocity of micron-sized water droplets in naphtha

As can be seen from the data presented in table 1, micron-sized water droplets are difficult to separate by conventional gravity settling methods. Even if the micro water drops with the diameter of 40 mu m, the time for separating can be 3-4 hours. In order to reduce the free water content of naphtha as much as possible, the atmospheric and vacuum distillation apparatus is generally provided with a large liquid-liquid phase separation tank. Taking a 500 ten thousand tons atmospheric and vacuum distillation device as an example, the liquid-liquid phase separation tank for naphtha water separation has the volume of over 100 cubic meters, not only occupies large area, but also has serious potential safety hazard. Even if such a huge water separation device is provided, a large amount of free water remains in the naphtha, and the water content exceeds 1.2 wt% in most cases. The hydrous naphtha has a plurality of unstable factors in the deep processing process, for example, the bumping phenomenon is easy to occur in the rectification refining process, and the catalyst pulverization and equipment chlorine corrosion are accelerated in the catalytic reforming process.

In order to solve the problem that naphtha contains free water, a novel oil-water separation technology capable of overcoming the limitation of particle settling drag becomes a research hotspot in recent years. The oil-water separation technology by a microporous membrane method is based on material surface affinity, and oil and water are separated by selective permeation of oil or water under the action of pressure difference. The technology does not depend on the gravity settling effect, has the advantages of simple operation, high separation efficiency, low operation cost and the like, and is a novel oil-water separation technology with great potential. Depending on the permeation target, the microporous membrane separation process may use oleophilic (hydrophobic and oil-permeable membrane material) or hydrophilic (hydrophilic and oleophobic and water-permeable membrane material) microporous membranes. Microporous membranes, whether oleophilic or hydrophilic, exhibit very good selectivity and permeability during short-term experiments. However, when a microporous membrane is used for a long-period oil-water separation process, the selectivity and permeability of the membrane are remarkably reduced. Generally, the selectivity is attenuated by 10-20%, and the permeability is attenuated by 20-40%. When the oil-water mixture contains more intercepted components and a higher separation cutting ratio (the permeation flow accounts for the proportion of the feeding flow), the permeability of the microporous membrane can be attenuated by 50-80%. Due to the above problems, the oil-water separation technique by the microporous membrane method is rarely used in an actual industrial process even though it has been studied for more than ten years and shows great advantages. After deeply analyzing the mass transfer behavior and the oil-water distribution on the surface of the microporous membrane, the trapped components are gradually enriched on the surface of the microporous membrane and then coalesce to form large liquid drops to occupy the surface of the microporous membrane, so that the contact of the permeated components with the surface of the membrane is prevented, and the root cause of the remarkable reduction of the separation performance of the microporous membrane is found. In summary, if the enrichment of the trapped component on the surface of the microporous membrane can be slowed down, it is hoped to ensure that the microporous membrane maintains higher selectivity and permeability for a long time in the oil-water separation process, thereby promoting the industrial application of the novel oil-water separation process.

Disclosure of Invention

The invention aims to provide a microporous membrane separation process capable of synchronously permeating and separating an oil phase and a water phase from an oil-water mixture.

The technical scheme of the invention is as follows:

an oil-water mixture S-1 firstly enters a first oil-water separation tank 1, water phase liquid drops with the diameter exceeding 40 mu m are separated from an oil phase main body through gravity settling, a formed lean oil water phase S-2 is extracted from the bottom of the first oil-water separation tank 1, and a formed lean oil phase S-3 is extracted from the side part of the first oil-water separation tank 1; the lean water oil phase S-3 is pressurized by a delivery pump 2 and then is sent to a double-membrane separator 3 for further oil-water separation, anhydrous (anhydrous in the invention means that water drops with the diameter larger than 2 mu m are not contained) oil phase S-4 is obtained at the permeation side of an oleophilic microporous membrane 4, meanwhile, rich water oil phase S-5 is obtained at the permeation side of a hydrophilic microporous membrane 5, the rest lean water oil phase is extracted from a retentate material outlet of the double-membrane separator 3, and is converted into a circulating lean water oil phase S-6 after passing through a pressure control valve 7, and the circulating lean water oil phase S-6 returns to a first oil-water separation tank 1; and the water-rich oil phase S-5 enters the second oil-water separation tank 6, water drops with larger diameters are removed primarily through gravity settling, the formed oil-water mixture is extracted from the side part of the second oil-water separation tank 6 and enters the first oil-water separation tank 1 together with the oil-water mixture S-1, and the formed lean oil water phase is extracted from the bottom of the second oil-water separation tank 6 and is combined with the lean oil water phase S-2 extracted from the bottom of the first oil-water separation tank 1.

The core unit of the process is a double-membrane separator which is simultaneously provided with an oleophilic microporous membrane and a hydrophilic microporous membrane. In the double-membrane separator, the oleophilic surface of the oleophilic microporous membrane and the hydrophilic surface of the hydrophilic microporous membrane are close to each other in an oil-water mixture, and the distance between the oleophilic surface and the hydrophilic surface is less than 5 mm.

If a flat membrane assembly is adopted, the schematic structure of the double-membrane separator is shown in the attached figure 2, the whole periphery of the double-membrane separator is a frame 8 of a plate-frame type membrane separator, the interior of the double-membrane separator is divided into a plurality of stages of separation units, and each stage of separation unit is divided into an oil-rich permeation cavity 13, a flow cavity 11 and a water-rich permeation cavity 14 from top to bottom through an oleophilic microporous membrane 4 and a hydrophilic microporous membrane 5; the ends of the oleophilic microporous membrane 4 and the hydrophilic microporous membrane 5 are provided with sealing elements 9; the feeding cavity 10, the flowing cavity 11 and the discharging cavity 12 are sequentially communicated, the water-rich permeation cavities 14 of all levels of separation units are gathered to the water outlet main pipe through the water outlet branch pipes, and the oil-rich permeation cavities 13 of all levels of separation units are gathered to the oil outlet main pipe through the oil outlet branch pipes.

If a hollow fiber membrane is adopted for assembly, the schematic structure of the double-membrane separator is shown in the attached figure 3, and the oleophilic microporous membrane 4, the hydrophilic microporous membrane 5, the membrane shell 15 and the epoxy end sockets 16 arranged at two ends of the oleophilic microporous membrane 4 and the hydrophilic microporous membrane 5 divide the interior of the double-membrane separator into a flow cavity 11, an oil-rich permeation cavity 13 and a water-rich permeation cavity 14.

The invention has the beneficial effects that: through the coupling integration of gravity settling separation and microporous membrane separation, the rapid and efficient separation of an oil-water mixture can be realized, and an anhydrous oil phase and a lean oil water phase are obtained. The water content of the anhydrous oil phase is not more than 0.2 wt%, water drops with the diameter of more than 2 mu m are not contained, the bumping phenomenon in the rectification refining process can be avoided for naphtha processing, the catalyst pulverization and the equipment chlorine corrosion in the catalytic reforming process are reduced, the freezing temperature of free water can be obviously reduced for finished oil processing, and the phenomenon that pipelines are frozen and blocked in the oil using process in winter is reduced. In addition, through the coupling integration of the hydrophilic porous membrane and the oleophilic porous membrane, the enrichment of the water phase on the raw material side of the membrane separator can be obviously reduced, so that the problems of the aggregation of the water phase on the surface of the oleophilic porous membrane and the blockage of an oil permeation channel by the water phase are reduced, and the oil flux and the oil-water selectivity of the oleophilic porous membrane are always maintained at a higher level. In conclusion, compared with the traditional gravity settling method, the oleophylic/hydrophilic microporous membrane synergistic coupling enhanced oil-water mixture separation process provided by the invention has the advantages of higher separation degree and higher separation speed.

Drawings

FIG. 1 is a schematic diagram of a lipophilic/hydrophilic microporous membrane synergistic coupling enhanced oil-water separation process.

FIG. 2 is a schematic diagram of the structure of a flat membrane-assembled double membrane separator.

FIG. 3 is a schematic diagram of a hollow fiber membrane-assembled dual membrane separator.

Fig. 4 is a graph comparing the synergistic coupling enhancement effect of oleophilic/hydrophilic microporous membranes.

In the figure: 1 a first oil-water separation tank; 2 a delivery pump; 3, a double-membrane separator; 4, oleophilic microporous membrane; 5 hydrophilic microporous membrane; 6, a second oil-water separation tank; 7 a pressure control valve; 8 plate and frame membrane separator frames; 9 plate and frame membrane separator sealing elements; 10 a feeding cavity; 11 a flow chamber; 12 discharging cavity; 13 a rich oil permeate chamber; 14 a water-rich permeate chamber; 15 hollow fiber type membrane separator membrane shell; 16 epoxy seal heads of the hollow fiber type membrane separator; s-1, mixing oil and water; s-2 a lean aqueous phase; s-3 lean aqueous oil phase; s-4 anhydrous (anhydrous in the invention means that water drops with the diameter larger than 2 mu m are not contained) oil phase; s-5, preparing a water-rich oil phase; s-6 circulating the lean aqueous phase.

Detailed Description

The following further describes a specific embodiment of the present invention with reference to the drawings and technical solutions.

Example 1

Example 1 the separation effect of aqueous naphtha was compared by continuous pilot permeation experiments with a single membrane separator and a double membrane separator, the main objective of which was to demonstrate the synergistic coupling enhancement effect of oleophilic microporous membranes and hydrophilic microporous membranes. The single-membrane separator is internally provided with a hollow fiber type oleophilic microporous membrane, and the double-membrane separator is internally provided with the hollow fiber type oleophilic microporous membrane and the hollow fiber type hydrophilic microporous membrane at the same time. The oleophilic microporous membrane is made of polyvinylidene fluoride and has an average pore diameter of 0.1 μm. The hydrophilic microporous membrane is made of polyether sulfone and has an average pore diameter of 0.1 micron. In the double membrane separator, the oleophilic microporous membrane occupied 90% of the total packed area and the hydrophilic microporous membrane occupied 10% of the total packed area. The water content of the crude gasoline is about 2.0 wt%, the crude gasoline enters a membrane separator after being pressurized by a delivery pump, the temperature is 25 ℃, and the transmembrane pressure difference of the membrane separator during operation is 8 kPa.

The synergistic coupling strengthening effect of the oleophylic microporous membrane and the hydrophilic microporous membrane is shown in figure 4. By comparing the oil flux of the oleophilic microporous membrane in the four separation processes (anhydrous gasoline treatment by the single membrane separator, anhydrous gasoline treatment by the double membrane separator, aqueous gasoline treatment by the single membrane separator, aqueous gasoline treatment by the double membrane separator), it can be found that: because the oil phase and the water phase can be synchronously removed by the synergistic coupling of the oleophilic microporous membrane and the hydrophilic microporous membrane, the enrichment of the water phase on the raw material side of the membrane separator is obviously reduced, thereby reducing the problems of the accumulation of the water phase on the surface of the oleophilic microporous membrane and the blockage of an oil permeation channel by the water phase, and keeping the oil flux of the oleophilic microporous membrane at a higher level all the time. As can be seen from the figure, for the crude gasoline system with the water content of 2.0 wt% and the transmembrane pressure difference of 8kPa, the oil flux of the oleophilic microporous membrane in the single-membrane separator is attenuated to 1280L/m after a test of 100 minutes²About/bar/h (compared with the flux of the anhydrous gasoline, the attenuation amplitude reaches 56.6 percent), and the oil flux of the oleophilic microporous membrane in the double-membrane separator is attenuated to 2370L/m after 100 minutes of test²Around/bar/h (the decay amplitude compared to the flux of anhydrous gasoline is about 19.7%).

Example 2

Example 2 for naphtha extracted from the top of an atmospheric distillation tower in an atmospheric and vacuum distillation apparatus of an enterprise, the total flow rate in a water-containing state is predicted to be 20 ten thousand tons/year, and anhydrous naphtha (not containing water droplets with the diameter of more than 2 μm) is obtained by processing through the oil-water separation process enhanced by the synergistic coupling of the oleophilic/hydrophilic microporous membrane.

As shown in the attached figure 1, hydrous naphtha (flow rate 25t/h, pressure 0.0MPaG, temperature 40 ℃, water content about 7.5 wt%) produced by an atmospheric and vacuum distillation device, namely an oil-water mixture S-1, firstly enters a first oil-water separation tank 1, aqueous phase droplets with the diameter of more than 40 mu m are separated from an oil phase main body by gravity settling, a formed lean oil-water phase S-2 is extracted from the bottom of the first oil-water separation tank 1, and a formed lean oil phase S-3 is extracted from the side part of the first oil-water separation tank 1; the lean water-oil phase S-3 is pressurized to 0.01MPaG by a delivery pump 2 and then is sent to a double-membrane separator 3 for further oil-water separation, anhydrous (water drops with the diameter larger than 2 mu m are not contained) oil phase S-4 is obtained at the permeation side of an oleophilic microporous membrane 4, namely anhydrous naphtha, the total water content is not more than 0.2 wt%, meanwhile, a water-rich oil phase S-5 is obtained at the permeation side of a hydrophilic microporous membrane 5, the residual lean water-oil phase is extracted from a retentate material outlet of the double-membrane separator 3 and is changed into a circulating lean water-oil phase S-6 through a pressure control valve 7, and the circulating lean water-oil phase S-6 returns to the first oil-water separation tank 1; and the water-rich oil phase S-5 enters the second oil-water separation tank 6, water drops with larger diameters are removed primarily through gravity settling, the formed oil-water mixture is extracted from the side part of the second oil-water separation tank 6 and enters the first oil-water separation tank 1 together with the oil-water mixture S-1, and the formed lean oil water phase is extracted from the bottom of the second oil-water separation tank 6 and is combined with the lean oil water phase S-2 extracted from the bottom of the first oil-water separation tank 1.

Table 2 composition and mass flow of key streams in example 2

Compared with the traditional gravity settling separation process, the oleophylic/hydrophilic microporous membrane synergistic coupling enhanced oil-water separation process provided by the invention has the advantages of higher separation degree and higher separation speed. The water content of naphtha after gravity settling separation is over 1.2 wt%, and the water-oil separation process can ensure that the water content is not over 0.2 wt%. In addition, the retention time of naphtha in the first oil-water separation tank in the process is shortened by 45.7 percent compared with the traditional gravity settling separation process. In conclusion, the oil-water separation process disclosed by the invention breaks through the limitation of the traditional gravity sedimentation through the synergistic coupling reinforcement of the oleophylic/hydrophilic microporous membrane.