CA2863015A1

CA2863015A1 - Water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water

Info

Publication number: CA2863015A1
Application number: CA2863015A
Authority: CA
Inventors: Daniel J. PETERSON; Dean K. KANENAGA; Ming Ma; Feng Liu; Dong Li
Original assignee: Jiangsu Sunpower Technology Co Ltd
Current assignee: Jiangsu Sunpower Technology Co Ltd
Priority date: 2012-05-18
Filing date: 2012-06-06
Publication date: 2013-11-21
Anticipated expiration: 2032-06-06
Also published as: CA2863015C; CN102659197B; CN102659197A; WO2013170507A1

Abstract

The present invention discloses a water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water. Inlet water containing produced water as the main component is conveyed to a vertical falling-film evaporator equipped with a brine distribution apparatus, so as to produce distilled water as boiler feed water through evaporation. Scrubbing particles are added to the inlet water containing the produced water as the main component or to circulating strong brine of the vertical falling-film evaporator to form slurry. When the slurry is evaporated by the vertical falling-film evaporator, scaling on the heat exchange surface of the evaporator is prevented or reduced by utilizing solid particles in the slurry. According to the process, most of the produced water is processed into high-quality distilled water used for a boiler to produce steam, so as to increase the heavy oil recovery rate, and the process can be directly used for treating the produced water, with a recycling rate higher than 95%, to produce high-quality boiler feed water used for producing the steam required by heavy oil recovery.
The process can also be used for treating boiler blow-off, so as to reduce the emission of a plant, lower the requirements of physicochemical treatment, and increase the overall water recycling rate of a water treatment plant.

Description

WATER TREATMENT PROCESS FOR RECYCLING PRODUCED
WATER FROM HEAVY OIL RECOVERY TO SERVE AS BOILER
FEED WATER
BACKGROUND
Technical Field The present invention belongs to the field of water treatment, and relates to a water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water.
Related Art Heavy oil recovery includes injecting steam into an oil layer and recycling an oil-water mixture from an oil well. Oil is separated from water, and separated water is produced water. In order to recycle the produced water to produce steam, the produced water is required to be processed, so as to meet the requirements of a steam generator or a boiler produced steam.
Injecting steam into a heavy oil layer is a widely adopted method for increasing the oil recovery rate. Generally, several tons of steam is consumed to produce 1 ton of heavy oil, and the steam/oil ratio is always called as the steam-to-oil ratio (SOR).
Because the SOR
value is generally in the range of 2 to 4, and the water consumption is high, in consideration of environmental protection and economic benefits, it is encouraged to process the produced water into feed water used for a boiler to produce steam to be injected into the oil layer.
The produced water is required to be treated, so as to be used by the boiler.
Currently, the commonly adopted treatment processes include (physical) chemical treatment and evaporation treatment. Depending on the quality of water to be treated, the two methods can be adopted alone or be adopted in combination.
Through chemical treatment, the hardness and silica in the water are removed, so that the processed water can be used by one-through steam generator (OTSG). The chemical methods for treating the produced water for making the produced water to be applicable in the OTSG typically include heat lime treatment, filtration and ion exchange, in which the hardness is removed to a level below the detection limit, and silica is removed to a low level.
The OTSG can use low-quality feed water having a hardness of close to zero, a low content of silica and a total dissolved solids (TDS) content of up to 12,000 ppm to produce high-pressure steam. When the steam is evaporated from the brine, for the OTSG, it is basically required that the solubility of salts in the feed water is maintained and the feed water has low-level hardness and low-content silica when the water is concentrated to about one-fifth.
The OTSG produces a mixture of up to 80% vapor and 20% brine (or boiler blow-off).
In the OTSG, the flow path of water allows the entire heat exchange surface to be wetted by the liquid, so that the problem of scaling is solved during generation of steam. Severe problem of scaling occurs in boilers with more various liquid flow paths.
Whether the OTSG blow-off is separated from the steam depends on the quality of the steam required by the heavy oil layer.
When treating the produced water, compared with a conventional boiler or a drum boiler, the OTSG is considered as a reliable boiler. The major advantages that make the OTSG superior to the conventional boiler or the drum boiler is that high-pressure steam can be produced from high TDS feed water. Another advantage of the OTSG is that the OTSG can be cleaned by adopting a pipeline pigging method. If high-quality water is used, the OTSG does not need to be cleaned in a long period of time generally.
In consideration of producing high-quality distilled water from the produced water to serve as the boiler feed water, the evaporation treatment process is superior to the chemical treatment process. The evaporator distilled water produced from the produced water has been successfully used in a 1,000 psig drum boiler and a 1,500 psig OTSG. When the evaporator supplies feed water to the OTSG, the use of the distilled water is beneficial to the OTSG, so that the OTSG is infrequently cleaned.

. CA 02863015 2014-07-09 In general circumstances, about 95% produced water can be recovered through evaporation to serve as high-quality distilled water. The recovery level changes with the chemical composition and the site demands. Generally speaking, the most energy-efficient evaporator system can concentrate the produced water, with the TDS of 0.2% to 2.0% lowered to 10% to 15%. A TDS content of up to 25% can be achieved in an evaporation system. However, the economic feasibility usually needs to be considered, because the more concentrated the brine to be treated is, the more energy for evaporation needs.
In production, due to low operation costs of a physicochemical system, the physicochemical processes are more widely used than the evaporation process, and have been used to improve the oil recovery for several decades. The evaporator needs to use a large amount of energy to evaporate water from the brine, and the operation costs become the important economic factor in selection of the evaporation process.
Although the evaporator has been used to improve the oil recovery for about ten years, the evaporator is a relatively new technique, compared with the physicochemical processes.
- When labor costs are not high, in consideration of the installation costs, it is preferred to use a physicochemical system. With the increase of the installation costs and the labor costs, the final costs of an evaporator may be lower than that of a large-scale physicochemical system, because an evaporator system can be packaged into modules before arriving at the scene.
The TDS of the produced water is generally not high, but the demand for supplement water may lead to treatment of TDS much higher than that of the produced water during the treatment procedure. Due to loss of water in rock layers, loss of water during oil treatment, treatment of boiler blow-off, steam exhaust and strong brine wastes, a certain level of water is required to be supplemented to the system to maintain water balance and steam production.
It is found in some places such as in northern Alberta, Canada, a large amount of water is required to be supplemented in oil recovery with steam. If fresh water is used, generally, the hardness and the silica content are extremely low, compared with brackish water having ... CA 02863015 2014-07-09 ..
, ..
high content of salts, hardness and silica, the TDS is very low, and the TDS
required to be treated by the water treatment process is very less. However, the use of fresh water in the Alberta oil sands is restricted, and the local government protects the freshwater resources by restricting the use of fresh water and restricting emissions of brine of plants, and thus, the plants are required to use brine with high TDS, which has high contents of scaling ingredients such as calcium, magnesium and silicon.
According to the laws of Alberta, plants using the chemical treatment (such as hot lime softening) are required to consider to add a treatment procedure to treat the supplement water and boiler blow-off, so as to meet the requirements for water supplement and water emissions regulated by the laws. Therefore, evaporation becomes the preferred process for treatment of produced water, or an evaporation process is required to be added in the downstream to reduce the total emissions of the plant, such as OTSG blow-off.
Once environmental regulations appear in the place using steam in heavy oil recovery, = the evaporation process begins to be more attractive economically.
Therefore, reduction of waste and restriction of use of fresh water are the trends, and more evaporation systems will be used in treatment of produced water.
=
Compared with the physicochemical treatment processes, application of an evaporator has the following advantages and disadvantages.
The main advantage of the evaporator lies in the high quality of the recycled water.
The non-volatile matters in the boiler feed water are less than 2 ppm, and such water generates very less blow-off in the boiler. Presently, in an apparatus for treating produced water by using an evaporator, the resulting distilled water is directly sent to the boiler as feed water, and the amount of the boiler blow-off is less than 2%.
The high-quality distilled water produced by an evaporator adopting a conventional boiler or a drum boiler has a working pressure of up to 1000 psig. Presently, there are discussions about directly using the evaporator distilled water in a conventional boiler or a drum boiler of exceeding 1000 psig, and many organizations recommend using boiler water of higher quality. In order to achieve the water quality of a higher pressure, it is required to perform additional water treatment on the distilled water obtained from the produced water.
Compared with hot lime softening, the main disadvantage of the evaporator lies in that energy is used to evaporate the salt-containing produced water. The latent heat of vaporization of water from the liquid state into the gas state is high, and the required energy is high. If there is no inexpensive steam available, use of mechanical vapor compression as the energy source is generally an economical choice. Adjusting the evaporator design can reduce the energy costs, but increases the investment in equipment.
In the last ten years, conventional hot lime softening and ion exchange are replaced by the evaporation process utilizing a falling-film evaporator driven by a steam compressor.
Two competitive evaporation processes are currently applied, in which one evaporation process has been applied in several apparatuses, and the other evaporation process will be commercially applied for the first time in the second half of 2012. The several apparatuses applying the evaporation process all use the same falling-film evaporator design, and the difference merely lies in the chemical methods for preventing formation of scale. Except of the chemical feed system, the chemical composition of the feed, the chemical composition of the brine in the evaporator and the evaporator are the same.
Any evaporation treatment process must overcome the difficulties in concentration of produced water with a high content of dissolved silicon. All the systems for improving oil recovery generally generate produced water with high silicon content, because silicon will be dissolved from rocks when steam is condensed in the rock layers. Some produced water not only contains silica easy to form hard scale, but also contains other chemicals, for example, dissolved or immiscible hardness and organics. Oil deposits in different regions of the world have different chemical properties. The main ingredients in the produced water that cause scaling on the heat exchange surface of the evaporator will finally make the evaporator does not work and be shut down.
Inorganic scaling components such as calcium carbonate, calcium sulfate, magnesium hydroxide and compounds of other heavy metals are required to be removed in the evaporation process, so as to make the system operate more efficient and prolong the .. CA 02863015 2014-07-09 ' . i , working life. In the hot lime softening process, silica and other scaling components in the wastewater are removed, but other components will not be concentrated; in the evaporation process, removal of moisture in the strong brine will lead to formation of suspended solids by scaling component, and once the suspended solids are formed, scale is generated on the heat exchange surface. The two produced water evaporation processes applied in Alberta, Canada adopt different scaling processing methods, so as to achieve the operability of the evaporation system.
Presently, the evaporation process applied in northern Alberta, Canada is relatively new, compared with the hot lime softening process. At least one evaporation process has not yet been commercially operated. The two main produced water evaporation processes are as follows:
(1) High-pH process: The pH value of the wastewater is adjusted to be greater than 12 by adding a base, so as to dissolve silica in water without scaling on the evaporation surface.
= This process needs to consume a large amount of base. When high hardness exists, in high-pH evaporation process, scaling of the high hardness components scaling on the = evaporation surface cannot be avoided. If an additive such as a chelating agent or a dispersant is used to inhibit the scaling of the hardness components, the system needs higher chemical costs. Presently, the several high-pH evaporation units adopted in Alberta, in addition to a large amount of base consumed, the units need to be cleaned frequently or a large amount of chemicals are required to be added, so as to avoid scaling of the hardness components.
(2) Absorption slurry process: The pH value of the produced water is adjusted to be 10 to 11 by adding magnesium oxide and a small amount of base. Magnesium is used to precipitate the silicon components, and also serves as the seed to prevent silicon and other hardness components from scaling. Since the brine has a high alkalinity (high carbonate content), and the distilled water that is produced has a low pH value (bicarbonate in the brine is decomposed with CO2 generated). As for low-quality distilled water, an additional apparatus is required to remove CO2, or a base is added in the steam boiler to increase the pH value of the distilled water (boiler feed water). However, due to the , k addition of the base, the amount of the boiler blow-off is increased. Because the boiler blow-off is finally recycled back to the evaporator, higher operation costs are caused. The several absorption slurry evaporation units under construction in Alberta, Canada will be finished in 2012 or 2013, and have not yet been commercially operated.
In the above two evaporation processes, a waste solution (concentrate) is generated, and the waste solution must be processed subsequently or be discharged in the manner having no harm to the environment. The amount of the concentrate depends on the chemical components of the produced water and the quality and amount of the system supplement water. Compared with the conventional hot lime softening process, the volume of the concentrate generated in the evaporation process is much less, and the water recycling rate is higher, because the boiler blow-off in the evaporation process is less, and the concentration of the concentrate needing to be treatment is higher.
FIG. 1 and FIG. 2 are respectively the layout of main devices of the hot lime softening process and the evaporation process.
..
If the concentrate generated by the evaporation system is sent to a treatment well, the suspended solids must be first removed, so as to avoid blockage of the treatment well.
Since the suspended solids content and the dissolved silicon content are high, when treating the concentrate, the above two evaporation processes has the problem that once the concentrate enters the treatment well containing low-pH natural water, precipitation occurs.
In the high-pH process, high-pH brine contains dissolved silicon of several thousands ppm, which must be removed before the concentrate enters the deep well for treatment. If the high-content silicon is not removed, the concentrate will react with the natural water in the sewage well, and after operation of a short-period of time, precipitated silicon will block the treatment well. In order to remove silicon in the solution, an acid needs to be added, which causes another main item of operation costs. Due to addition of an acid to the concentrate generated in the high-pH evaporation process, very fine silicon suspended particles are generated, which are difficult to be settled or filtered.
In the absorption slurry process, magnesium is added into the evaporator to precipitate . , silicon. When the concentrate is discharged out from the evaporator, the concentrate contains suspended solids (mainly being magnesium hydroxide and silicon compounds) of tens of thousands ppm.
Both the brines of the above two evaporation processes contain fine suspended solids that are difficult to be removed. A long period of residence time is generally required to allow the suspended solids to be settled. A reactor clarifier (slow rising speed and sludge circulation) is used to concentrate the suspended solids to form thick sludge.
Even if the suspended solids are moderately concentrated, treatment of the thick slurry by filtering is still not commercially operated. If the suspended solids are successfully separated, the generated supernatant is sent into the sewage well, and the generated solids are sent to a ground landfill.
In order to solve the problem that it is difficult to separate the suspended solids in the strong brine of the evaporator, many processing companies use slat caves to settle the strong brine. The salt caves provide a large volume to settle the suspended solids. The , brine slurry is injected to the bottom of the salt caves. The brine exhausted from the top = of the salt caves is sent to the deep well for treatment. The salt caves provide space for separating and storing the suspended solids in the strong brine.
Another method for replacing deep well to process the evaporator concentrate is to separate solids that can be processed by using an additional evaporation device. In the water treatment industry, this is called as zero emission. As for high-pH
concentrate, zero emission has been achieved, but it is reported that the requirements for device maintenance are high. The absorption slurry process has not been put into use on large-scale apparatuses, so the application of the zero emission device is not yet known.
In other industries, there are several evaporation processes, calcium sulfate-containing strong brine may be used to recycle produced water, and the recycled water is used as OTSG boiler and conventional boiler (drum boiler) feed water. Regardless of the process, in the produced water evaporation process, the difficulty to be overcome is that silicon components and hardness components are easily to form scale, which influences the operation of the evaporation system. Additionally, due to the existence of volatile components such as organics and carbonates, generation of distilled water through evaporation needs more production costs, because additional water treatment facilities needs to be installed, the chemical composition requirements for the boiler feed water are higher, and the amount of the boiler blow-off is higher.
SUMMARY
In view of the disadvantages of the prior art, an objective of the present invention is to provide a water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water.
Another objective of the present invention is to provide a brine distributor for a vertical falling-film evaporator used in the process of the present invention.
Still another objective of the present invention is to provide a water treatment system for recycling produced water from heavy oil recovery to serve as boiler feed water.
The objectives of the present invention can be achieved by adopting the following technical solutions:
A water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water is provided. Inlet water containing produced water as the main component is conveyed to a vertical falling-film evaporator equipped with a brine distribution apparatus, so as to produce distilled water as boiler feed water through evaporation. Scrubbing particles are added to the inlet water containing the produced water as the main component or to circulating strong brine of the vertical falling-film evaporator to form slurry. When the slurry is evaporated by the vertical falling-film evaporator, scaling on the heat exchange surface of the evaporator is prevented or reduced by utilizing the solid particles in the slurry.
In the present invention, the evaporation treatment process of the produced water is combined with the brine slurry containing the scrubbing particles, and the brine slurry circulates in the falling-film evaporator. This process is called as the ShaVap process, and the inventive feature is that the evaporation system includes the brine slurry having the scrubbing function, the falling-film evaporator, and the brine distribution apparatus.

=
FIG. 5 shows the scrubbing particles and scale particles suspended in the slurry that flows downwards along the pipe wall. According to the ShaVap process, the scrubbing particles are added to the circulating brine to form brine slurry, the particles scrubs the heat exchange surface, silica, the hardness and organics are removed before being deposited on the pipe wall, so that the heat exchange surface is maintained clean, and no scale components are deposited on the pipe wall when the brine undergoes falling-film concentration. In addition to the scrubbing effect of the added particles, substances precipitated from the brine can be adhered to the added particles, but not adhered to the heat exchange surface of the evaporator. The scrubbing particles are solid particles insoluble in the inlet water and having scrubbing effect. The selection of the particle material is depending on the properties of the precipitate of the strong brine, and the particle material is selected from sand, gravel, glass beads or other metal derivative particles having a particle size greater than 0 and less than 100 microns, with the particle density of 0.1 g/cm3 to 10 g/cm3. When being selected as the added particles, sand (that is, silicon oxide) can not only scrub the heat exchange surface, but also can serve as seeds.
The concentration of the scrubbing particles in the brine slurry is preferably 0.5% to 5% (% represents mass percentage).
The ShaVap evaporation process includes adding the scrubbing particles into two sub-systems of the system. One sub-system is a supplementary particle system for continuously adding the supplementary particles into the system and adding a part of the particles when the evaporator operates. The other sub-system is a particle recycling system for recycling the particles back into the evaporator, so as to reduce the amount of the continuously added particles.
The supplementary particle system includes a conventional solid slurry supplementing device, depending on the size of the system. This type of system uses a solid feeder (for example, a screw feeder) to store and move the solid particles to a slurry mixing tank.
The slurry mixing tank mixes the scrubbing particles and clear liquid (cooled distilled water or clear brine), and the formed slurry flow may be directly added to the evaporator through a circulation line or an evaporator tank. There are many types of the device that are , = .
applied in many industrial fields.
The supplementary particle system can produce slurry having a content of the scrubbing particles of up to 50%, depending on the physical properties of the selected particles.
The particle recycling system separates the brine from the suspended scrubbing particles and other suspended components generated through concentration in a conventional method. Separation may be implemented by using a cyclone separator, a cone-bottom tank, a centrifugal machine or a filter. The scrubbing particles are preferentially removed by the circulation system, because the density of the selected scrubbing particles is greater than that of the precipitate generated in the inlet water. The circulating flow contains thicker scrubbing particles, and the discharged brine flow or the brine mixed flow contains more other suspended components generated from the feed through concentration.
_ The brine distribution apparatus according to the present invention includes a brine distribution box located at the tope of the vertical falling-film evaporator and a liquid distributor located at the top of each heat exchange tube.
As a preferred embodiment of the present invention, the liquid distributor mainly includes a division body and a supporting part, where the periphery of the main part of the division body has a concave surface, and the top cover of the division body has a cross-sectional area greater than that of the opening of the heat exchange tube of the vertical falling-film evaporator; and the supporting part movably or fixedly supports the division body at a corresponding position at the upper part inside the heat exchange tube of the vertical falling-film evaporator, so that the bottom surface edge of the top cover of the division body is spaced from the upper surface of the upper tube plate of the vertical falling-film evaporator for a certain gap to form an inlet channel. The liquid enters the heat exchange tube along the inlet channel and the concave surface of the division body and is distributed on the inner surface of the heat exchange tube.
The diameter of the bottom surface of the division body is greater than or equal to 0.3 . CA 02863015 2014-07-09 . , fold the inner diameter of the heat exchange tube, and is less than the inner diameter of the heat exchange tube.
The height of the upper surface of the division body exposed from the upper opening of the heat exchange tube is 0.3 to 3 folds the inner diameter of the heat exchange tube.
The division body is symmetrically distributed around the central axis of the heat exchange tube of the vertical falling-film evaporator.
The top cover has a hemispherical shape, a plate-like shape, or a shape having a flat bottom surface and a bottom surface area greater than that of the opening of the heat exchange tube.
The periphery of the main part of the division body has a concave surface, or the main part of the division body is a whole body having a concave periphery and formed by an inverted cone, a cylinder and an upright cone through seamless connection from top to bottom, the bottom surface of the inverted cone is connected to the cylinder having the _ same diameter of the bottom surface, and the bottom surface of the cylinder is connected to the upright cone, where the diameter of the bottom surface of the cylinder is the same as the diameter of the upper surface of the upright cone. The diameter of the bottom surface of the upright cone is greater than or equal to 0.3 fold the inner diameter of the heat exchange tube, and is less than the inner diameter of the heat exchange tube.
2 to 6 supporting parts exist, and the supporting parts are polygon ribs. One edge of the supporting part is seamlessly connected to the concave surface of the division body, and at least two adjacent edges of the other edges are perpendicular to each other. The supporting part stands on the upper tube plate of the vertical falling-film evaporator by means of the adjacent perpendicular edges, so that the division body is movably or fixedly supported at a corresponding position at the upper part inside the heat exchange tube of the vertical falling-film evaporator, and an inlet channel is formed by the bottom surface edge of the top cover of the division body and the top surface of the upper tube plate of the vertical falling-film evaporator.
Or, the supporting part includes 3 to 6 spiral vanes connected to the bottom surface of the top cover and support pieces integrally downwards connected at the lower end of the rear of the vanes. The diameter of the circle formed by the track of the outer edge of the tip of the vane is slightly greater than the outer diameter of the heat exchange tube, so that the tip of the vane presses against the upper port of the heat exchange tube or the upper tube plate, and the bottom edge of the top cover of the division body is spaced from the top surface of the upper tube plate of the vertical falling-film evaporator for a certain gap, so as to form an inlet channel. The height of the spiral part of the vane (that is, the vertical distance from the tip of the spiral part to the bottom surface of the top cover of the division body) is the height of the inlet channel. The width of the support piece closely matches the distance between the inner wall of the heat exchange tube and the outer wall at a corresponding position of the division body, so that the support piece of the vane abuts against the inner wall of the heat exchange tube and the outer wall at the corresponding position of the division body, thereby movably or fixedly supporting the division body at a corresponding position at the upper part inside the heat exchange tube of the vertical falling-film evaporator.
As another preferred embodiment of the present invention, the liquid distributor mainly includes a division body and a supporting part, where the periphery of the division body has a concave surface; and the supporting part movably or fixedly supports and connects the division body at a corresponding position at the upper part inside the heat exchange tube of the vertical falling-film evaporator, and the upper surface of the division body is exposed from the upper opening of the heat exchange tube. The diameter of the upper surface of the division body is greater than the outer diameter of the heat exchange tube, so that the upper part edge of the concave surface of the division body is spaced from the top surface of the upper tube plate of the vertical falling-film evaporator for a certain gap, so as to form an inlet channel. The liquid enters the heat exchange tube along the inlet channel and the concave surface of the division body and is distributed on the inner surface of the heat exchange tube.
The diameter of the bottom surface of the division body is greater than or equal to 0.3 fold of the inner diameter of the heat exchange tube, and is less than the inner diameter of the heat exchange tube.
The height of the upper surface of the division body exposed from the upper opening of the heat exchange tube is 0.3 to 3 folds the inner diameter of the heat exchange tube.
The division body is symmetrically distributed around the central axis of the heat exchange tube of the vertical falling-film evaporator.
The periphery of the main part of the division body has a concave surface, or the main part of the division body is a whole body having a concave periphery and formed by an inverted cone, a cylinder and an upright cone through seamless connection from top to bottom, the diameter of the upper surface of the inverted cone is greater than the outer diameter of the heat exchange tube, the bottom surface of the inverted cone is connected to the cylinder having the same diameter of the bottom surface, and the bottom surface of the cylinder is connected to the upright cone, where the diameter of the bottom surface of the cylinder is the same as the diameter of the upper surface of the upright cone.
The diameter of the bottom surface of the upright cone is greater than or equal to 0.3 fold the inner diameter of the heat exchange tube, and is less than the inner diameter of the heat = exchange tube.
2 to 6 supporting parts exist, and the supporting parts are polygon ribs. One edge of the supporting part is seamlessly connected to the concave surface of the division body, and at least two adjacent edges of the other edges are perpendicular to each other. The supporting part stands on the upper tube plate of the vertical falling-film evaporator by means of the adjacent perpendicular edges, so that the division body is movably or fixedly supported at a corresponding position at the upper part inside the heat exchange tube of the vertical falling-film evaporator, and an inlet channel is formed by the bottom surface edge of the top cover of the division body and the top surface of the upper tube plate of the vertical falling-film evaporator.
The brine slurry is distributed on the upper tube plate of the vertical falling-film evaporator by the brine distribution box, permeates through the top part of the division body, enters the liquid distributor in an inward radiation-like manner through the inlet channel formed between the bottom surface edge of the top cover and the upper surface of . CA 02863015 2014-07-09 . .
the upper tube plate of the vertical falling-film evaporator or the inlet channel formed between the upper part edge of the concave surface of the division body and the top surface of the upper tube plate of the vertical falling-film evaporator, and flows downwards along the concave periphery of the division body. When reaching the bottom of the division body, the liquid flows towards the inner surface of the heat exchange tube in an outward radiation-like manner. When the brine is evenly distributed in all the heat exchange tubes by the distributor, steam from a compressor or externally supplied steam is condensed outside the heat exchange tube to heat the heat exchange tube, and the slurry in the tube begins to evaporate (FIG. 5). The liquid slurry (FIG. 5) and the steam (FIG.
5) flow downwards together in the tube, and flow out through the lower tube plate and enter the brine tank, and then are pumped into the brine distribution apparatus by using a circulation pump, together with the inlet water introduced into the brine tank. The steam is separated from the falling-off slurry, and enters a demisting system located at an annual space of the evaporator tank.
The demisting system may have several types of demisting manner, including a vane, a screen, a liquid contacting apparatus, a washing system, or a combination thereof. The demisting apparatus in FIG. 4 is a demisting device applicable in an evaporator system. In addition to the demisting apparatus, other arrangement layouts are possible, and have no influence on the implementation of the present invention.
The steam departs from the demisting system and is drawn into the compressor.
If the steam is directly used to heat and evaporate the brine, the steam departs from the demisting system and enters a condenser. In the case that a compressor is used, in order to maintain a temperature difference between the slurry boiling inside the tube and the steam condensed outside the tube, the steam is compressed to a higher temperature. If the steam is directly used, the steam is required to have a sufficiently high pressure at the shell side of the evaporator, so as to achieve the same heat exchange. Generally speaking, the compression system has higher energy efficiency than direct use of the steam, unless several evaporators are used for multi-effect evaporation.
The steam from the compressor or the externally supplied steam is condensed at the = CA 02863015 2014-07-09 =
outer wall of the heat exchange tube inside the shell side. The condensed water is converged at the bottom of the shell side and then flows into the distilled water tank.
Hot distilled water generated through driving by the compressor or hot distilled water generated through heating using the steam is conveyed from the distilled water tank by using a distilled water pump. The hot distilled water is cooled by the coming inlet water at an inlet water preheater, and as described above, the inlet water is heated at the same time.
The cooled distilled water is sent to a boiler system, and is used by the boiler directly or after further treatment. Table 2 and Table 3 respectively show the requirements of feed water for a drum boiler and a one-through boiler (OTSG).
In the ShaVap evaporation process, the produced water is preferably subjected to one or more of chemical treatment, preheating treatment and degassing treatment, and then enters the vertical falling-film evaporator. The chemical treatment may be arranged before the preheating treatment and the degassing treatment, and may also be arranged after the preheating treatment and the degassing treatment and before the evaporation treatment, and chemicals also be directly added into an evaporator brine tank (FIG. 4).
The inlet water preheater (FIG. 4) and a degasser (FIG. 4) may be designed in such a manner that the slurry can be fed, or the evaporator system is designed and adapted in such a manner that these pretreatment devices are omitted, depending on the overall demand of the entire plant shown in FIG. 3.
The added chemicals are determined by the chemical composition of the inlet water.
The chemicals include, but not limited to the following types:
(1) A scale inhibitor, used for preventing generation of substances that may turn into scale and preventing scaling in the inlet water preheater, the degasser and the evaporator.
Commonly used scale inhibitors are sodium nitrate, sodium phosphate and the like.
(2) A dispersant, used for preventing the precipitate from adhering on the surface of the inlet water preheater and the degasser, so as to avoid formation of scale. The dispersant is also used to prevent solid particles from depositing on the heat exchange surface of the falling-film evaporator and other surfaces, so as to avoid formation of scale.
The commonly used dispersants are phosphates, polyethylene glycol and the like.
(3) A defoamer, used for preventing generation of foam in the system including the inlet water preheater, the degasser and the evaporator.
(4) An acid, used for adjusting the pH value to a lower level. In a conventional method, an acid is added to the inlet water tank, basic carbonates and bicarbonates into carbon dioxide, and the generated carbon dioxide can be removed in the degasser. This technique eliminates the possibility of scaling of carbonate compounds on the evaporator surface by removing an element in the compound.
(5) A base, used for adjust the pH value to a higher level. In the prior art, addition of a base is to increase the pH value to dissolve the silica compound.
(6) A soluble magnesium compound, such as water-soluble magnesium chloride, used for providing a magnesium source for precipitation of silica when the falling-film evaporator concentrates the brine. This process is called as an adsorption slurry process.
In order to improve the performance of downstream treatment procedure, other chemicals can be added into the evaporator at a certain ratio to remove all the carbonates (CaCO3). The formed CaCO3 solid particles assist calcium and other hardness components to be adhered on seeds formed by slaked lime added. In addition to controlling scaling by using CaCO3 seeds, converting bicarbonates into solid state carbonate can prevent generation of CO2 that can volatilize into the distilled water, while CO2 will make the distilled water unsuitable for being directly used in the boiler.
A water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water preferably includes the following steps:
(1) using produced water as inlet water, adding chemicals into the inlet water for chemical treatment, and preheating outlet water for degassing treatment;
(2) charging the outlet water after degassing treatment into a brine tank at the bottom of a vertical falling-film evaporator, and at the same time, adding thick slurry containing scrubbing particles of a high concentration into the brine tank by using a supplementary particle system, so as to form slurry having a concentration of insoluble solid particles of 0.5% to 5% in the brine tank; pumping the slurry into a brine distribution apparatus at the top of the vertical falling-film evaporator by using a circulation pump, and distributing the slurry into each heat exchange tube through a liquid distributor of the brine distribution apparatus, where, during the procedure that the slurry is evaporated in the heat exchange tube, the insoluble solid particles scrub the inner wall of the heat exchange tube, so that scale on the inner wall of the heat exchange tube is scrubbed off; the resulting steam and slurry flowing downwards together in the tube, the steam entering a demisting system located at an annual gap of the evaporator brine tank for treatment, and then entering a compressor to provide heat for the vertical falling-film evaporator, or entering a condenser for condensing, to obtain cooled distilled water, and the slurry flowing out at a lower tube plate of the vertical falling-film evaporator and entering a brine tank for recycling, where a particle recycling system is set on the brine circulating path, and is used for circulating insoluble solid particles back to the vertical falling-film evaporator; and the outer wall of the vertical falling-film evaporator heat exchange tube is used for collecting steam for providing heat after exothermic condensation, at the bottom of the vertical falling-film evaporator, and the condensed steam enters the distilled water tank, and is used for preheating the inlet water to obtain cooled distilled water.
A water treatment system for recycling produced water from heavy oil recovery to serve as boiler feed water applicable in the ShaVap process includes an evaporation system, a supplementary particle system and a particle recycling system, where the evaporation system is a vertical falling-film evaporator, includes a brine tank, a brine distribution apparatus, a vertical heat exchange tube, a circulation pump, a circulation pipeline and an energy drive used for evaporation (a compressor or externally supplied steam equipped condenser), the supplementary particle system includes a solid feeder, a slurry mixing tank and a corresponding conveying pipeline, and the particle recycling system mainly includes one of a cyclone separator, a cone-bottom tank, a centrifuge and a filter, and a corresponding conveying pipeline; the produced water conveying pipeline is connected to the brine tank of the vertical falling-film evaporator in the evaporation system, a thick slurry output pipeline of the supplementary particle system is connected to the brine tank or = CA 02863015 2014-07-09 the circulation pipe of the vertical falling-film evaporator, a strong brine input end and a particle output end of the particle recycling system are respectively connected to the circulation pipe of the vertical falling-film evaporator.
The brine distribution apparatus includes a brine distribution box located at the top of the vertical falling-film evaporator and a liquid distributor located at the top of each heat exchange tube.
The water treatment system for recycling produced water from heavy oil recovery to serve as boiler feed water further includes a inlet water pre-treatment system and/or a strong brine further concentration or crystallization system, where the inlet water pre-treatment system includes one or more of a chemical treatment apparatus, an evaporator inlet water pump, a preheating apparatus and a degassing apparatus, the strong brine further concentration or crystallization system includes a concentrator or a crystallizer, and the strong brine is further treated in the concentrator or the crystallizer.
The chemical treatment apparatus includes an inlet water tank, an inlet water tank stirrer and a chemical adding apparatus, but the number of the chemical adding apparatus is not limited to 2, and depends on the chemical composition of the inlet water.
In FIG. 4, the mixed inlet water enters the inlet water tank at a stable flow rate and composition. The inlet water includes the produced water (for the typical composition, see Table 1), the supplement water (two compositions are shown in Table 1), the boiler blow-off, and other possible wastewater from plants. The flow rate is required to be controlled, and the components are mixed by using a conventional method (for example, mixed in a large sedimentation tank equipped with a mixer).
The inlet water tank provides a mixing place equipped with a stirrer. The size of the inlet water tank is generally calculated based on a retention time of about 10 min, but should be specifically determined according to the chemical reactions that occur.
The mixed inlet water is adjusted by added chemicals, and then is conveyed from the inlet water tank to the inlet water preheater by an inlet water pump, and the inlet water is heated in the inlet water preheater by the hot distilled water from the distilled water pump.

The heated inlet water enters the top of a degasser. The degasser removes non-condensable gas in the inlet water flowing downwards by means of the steam flowing upwards. Some volatile components in hot water, such as light component organics, sulfide and ammonia compounds, are removed. The most import is that oxygen that may cause evaporator corrosion in the inlet water is removed.
After chemical treatment and degassing, the inlet water enters the vertical falling-film evaporator brine tank. According to the equipment arrangement, a pump may be selected and set to convey the inlet water to the vertical falling-film evaporator brine tank. In the adsorption slurry method in the prior art, in order to reduce the hardness of water and remove silica, the pump is mounted here, and before entering the evaporator brine tank, the magnesium oxide slurry is mixed with the degassed inlet water. The purpose of adding chemicals here is to prevent occurrence of blockage in the device when the slurry passes through the inlet water preheater and the degasser.
When the ShaVap evaporation system is running, the scrubbing effect of the added particles and the effects of the selected brine distribution apparatus become evident. FIG.
= 5 shows a liquid distributor at the top of a heat exchange tube of a vertical falling-film evaporator in the ShaVap process. The brine distribution box located at the top of the vertical falling-film evaporator and the liquid distributor that is specially designed and inserted on each heat exchange tube together make the brine slurry to be evenly distributed on the upper tube plate and the heat exchange tube of the vertical falling-film evaporator in the form of turbulence. The design that the brine slurry of the liquid distributor enters in 360 degrees provides thin layer turbulence in the distributor. This type of turbulence keeps all the scrubbing particles suspended in the brine.
The present invention provides a key process for treating produced water from heavy oil recovery and for reducing emissions of water treatment plant. The process can be directly used to treat produced water, with the recycling rate up to 95% or more, so as to produce high-quality boiler feed water for producing steam required for heavy oil recovery.
The process may also be used to treat boiler blow-off, so as to reduce emissions of a plant, thereby lowering the requirements for physicochemical treatment and increasing the overall = CA 02863015 2014-07-09 recycling rate of the water treatment plant. This process includes a special falling-film evaporation system, for concentrating the produced water and controlling formation of scale at the same time, and processing most of the produced water into high-quality distilled water to serve as boiler feed water for increasing the heavy oil recovery rate.
Table 1 Chemical Composition of Produced Water Treatment System Produced Supplement Water Supplement Water Water (Fresh water) (Salt water) Calcium (Ca) 20 6 130 Magnesium (Mg) 10 2 112 Sodium (Na) 1004 968 6335 Sulfate Radical (5042) 70 8 140 Chlorine (Cl) 1310 1100 9173 Bicarbonate Radical (HCO3-) Carbonate Radical (C032-) 2 4 10 Silica (Si02) 195 5 8 Total Dissolved Solids (TDS) Suspended Solids (SS) <25 <2 <10 Total organic carbon (TOC) 200 <1 35 Grease 20 <1 <1 pH 7.9 8.0 8.0 Temperature, ri 185 41 41 Table 2 Requirements for Drum Boiler Feed Water Boiler Feed Water Boiler Feed Water (0 1000 psig) (0 1001 psig) Unit Dissolved Oxygen <0.007 <0.007 ppm Iron LI0.02 El 0.02 ppm Copper P0.01 E0.01 ppm Hardness P0.05 Undetectable ppm (CaCO3) pH (250) 8.8-9.6 8.8-9.6 pH value Non-volatile TOC <0.2 <0.2 ppm (C) Oily Substance <0.2 <0.2 ppm Table 3 Requirements for OTSG Boiler Feed Water boiler feed water (E 1800 psig) Unit Dissolved Oxygen Negligible ppm Iron E0.25 ppm TDS P12000 ppm Hardness 00.5 ppm (CaCO3) SiO2 P50 ppm pH (25E) 7.5-9.0 pH value Non-volatile TOC Reasonable " Oily Substance P0.5 ppm Beneficial effects:
The ShaVap evaporation process of the present invention can avoid formation of hard scale by silica, calcium sulfate, calcium carbonate, magnesium hydroxide and inorganic salts of other metals and hardness compounds in the produced water, and can also avoid formation of scale by organics separated or precipitated from the brine during evaporation and concentration. The particles suspended in the liquid polishes the evaporation heat exchange surface and prevents the scale particles from being adhered on the tube wall, so that the scrubbing effects of the particles avoids scaling in the evaporator.
Inexpensive sand, gravel, glass beads or other metal derivative particles may be used in polishing the heat exchange surface. Additionally, the suspended scrubbing particles that are added may also increase the heat transfer efficiency of the produced water having a content of organics.

The ShaVap process reduces the chemical costs and produces high-quality distilled water used for a boiler to produce steam, so as to increase the oil recovery rate. The obtained distilled water can be directly used in a packaged boiler steam generating device at a pressure of up to 1,000 psig, and can also be directly used in a one-through steam generator (OTSG) or circulating tube boiler at a pressure of up to 1,500 psig.
In the present invention, the liquid distributor having a special structure is used to uniformly distribute the brine slurry on the inner wall of the heat exchange tube, since the liquid distributor enables the slurry horizontally flows in a direction of 360 degrees of the liquid distributor, deposition of the suspended solids on the heat exchanger tube plate can be avoided due to the flow characteristics of the device.
On one hand, due to the structure of the liquid distributor division body of the present invention, the area of low velocity zone of the liquid is reduced, so that the deposition of the suspended solids is reduced; on the other hand, a smooth flow is formed on the inner of the heat exchange tube, with very small amount of entrained air bubbles, so that uniform film is easily formed.
Due to the concave surface at the bottom of the liquid distributor division body of the present invention, the amount of liquid falling into the center of the heat exchange tube can be reduced, so that more liquid can be distributed on the inner wall of the heat exchange tube, thereby increasing the evaporation efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
The disclosure will become more fully understood from the detailed description given herein below for illustration only, and thus are not limitative of the disclosure, and wherein:
FIG. 1 shows a current process for treating produced water generated by a steam assisted gravity drainage (SAGD) heavy oil recovery device, which adopts hot lime softening, filtering and weak acid cation exchange, and is the most conventional process for treating produced water and is generally used in combination with OTSG, and OTSG can utilize the low-quality water generated by the physicochemical process to generate steam;
FIG. 2 shows another current process, in which the physicochemical process step in FIG. 1 is replaced by an evaporator system, and the evaporation process may have several different chemicals added, and correspondingly includes a high-pH evaporation process, an absorption slurry evaporation process or a crystal slurry evaporation process using calcium sulfate as a seed to control scaling;
FIG. 3 shows a process flow of the present invention, including a particle adding and recycling system for reducing the addition amount of main chemicals, where a boiler in FIG. 3 may be a drum boiler or an OTSG boiler according to the system requirements, FIG.
3 illustrates how to integrate a ShaVap evaporation process into an overall process for increasing oil recovery, and is similar to the prior art shown in FIG. 2, the ShaVap evaporation system shown in FIG. 3 is characterized by including a particle adding and recycling system, which makes the ShaVap evaporation process different from the prior art;
FIG. 4 describes the ShaVap process in detail, and provides components of an evaporator and specific implement of particle adding and recycling;
where 8 is a heat exchange tube, 7 is an upper tube plate, 11-1 and 11-2 are chemical adding devices, 12 is an inlet water tank mixer, 13 is an inlet water tank, 14 is an inlet water pump, 15 is an inlet water preheater, 16 is a degasser, 17 is a vertical falling-film evaporator, 18 is a brine tank, 19 is a brine distribution box, 20 is a lower tube plate, 21 is a circulation pump, 22 is a circulation pipe, 23 is a compressor, 24 is a condenser, 25 is a supplementary particle system, 26 is a particle recycling system, 27 is a demisting system, 28 is a distilled water tank, and 29 is a distilled water pump;
FIG. 5 describes how scrubbing particles and suspended dirt solids that are precipitated flow through the system together, where a brine distributor is specifically designed for this process, to avoid deposition of heavy scrubbing particles on the upper tube plate of the vertical falling-film evaporator;
where 7 is an upper tube plate of the vertical falling-film evaporator, 8 is a heat exchange tube of the vertical falling-film evaporator, and 10 is a liquid distributor;
FIG. 6 is a schematic structural diagram of a liquid distributor in Embodiment 1;
where 1 is top plate, 2 is an inverted cone, 3 is cylinder, 4 is an upright cone, 5 is a supporting part, 6 is a main part of a division body, 7 is an upper tube plate of a vertical falling-film evaporator, 8 is a heat exchange tube of the vertical falling-film evaporator, 9 is a division body, and 10 is the liquid distributor;
FIG. 7 shows a supporting part in Embodiment 1, where 5 is a supporting part, and 7 is an upper tube plate of a vertical falling-film evaporator;
FIG. 8 shows a supporting part in Embodiment 1, where 5 is a supporting part;
FIG. 9 is a schematic structural diagram of a liquid distributor in Embodiment 2, where 1 is a top cover, 5 is a supporting part, 6 is a main part of a division body, 7 is an upper tube plate of a vertical falling-film evaporator, 8 is a heat exchange tube of the vertical falling-film evaporator, 9 is a division body, and 10 is the liquid distributor; and FIG. 10 is a bottom view of the supporting part in Embodiment 2, where 1 is a top cover, and 5 is a spiral supporting part.
DETAILED DESCRIPTION
In the following, the protection scope of the present invention is illustrated with reference to the accompanying drawings, which are not intended to be interpreted as limitation of the protection scope of the present invention.
Embodiment 1 As shown in FIG. 6, a liquid distributor 10 for a vertical falling-film evaporator mainly includes a division body 9 and a supporting part 5, where the periphery of the main part 6 of the division body 9 has a concave surface, and the area of the bottom of the top cover 1 of the division body 9 is greater than the area of the opening of a heat exchange tube 8 of a vertical falling-film evaporator; and the supporting part 5 movably supports the division body 9 at a corresponding position at the upper part inside the heat exchange tube 8 of the vertical falling-film evaporator, so that the bottom surface edge of the top cover 1 of the division body 9 is spaced from the upper surface of an upper tube plate 7 of the vertical falling-film evaporator for a certain gap to form an inlet channel. The division body 9 is symmetrically distributed around the central axis of the heat exchange tube of the vertical falling-film evaporator, and includes the main part 6 and the top cover 1. The top cover 1 has a cap-like shape, and the bottom of the top cover 1 is seamlessly connected to the upper surface of the main part 6 of the division body, and the bottom area is greater than the area of the opening of the heat exchange tube. The diameter of the bottom surface of the main part 6 of the division body is approximately 0.5 fold of the inner diameter of the heat exchange tube. 3 supporting parts 5 exist, and the supporting parts are polygon ribs (FIG.
7 and FIG. 8). One edge of the supporting part is seamlessly connected to the concave surface of the main part 6 of the division body, one edge is seamlessly connected to the bottom edge of the top cover 1, and at least two adjacent edges of the other edges are perpendicular to each other. The supporting part 5 stands on the upper tube plate 7 of the vertical falling-film evaporator by means of the adjacent perpendicular edges, so that the division body 9 is movably supported at a corresponding position at the upper part inside the heat exchange tube 8 of the vertical falling-film evaporator, and an inlet channel is formed by the bottom surface edge of the top cover 1 of the division body 9 and the top surface of the upper tube plate 7 of the vertical falling-film evaporator.
The liquid enters the liquid distributor 10 in an inward radiation-like manner through the inlet channel formed between the bottom surface edge of the top cover 1 and the upper surface of the upper tube plate 7 of the vertical falling-film evaporator, flows downwards along the concave periphery of the main part 6 of the division body, and when reaching the bottom of the main part 6 of the division body, the liquid flows towards the inner wall of the heat exchange tube in an outward radiation-like manner.
The flow speed of the liquid entering the heat exchange tube 8 depends on the height of the inlet channel. The height of the inlet channel is 0.3 to 3 folds of the inner diameter of the heat exchange tube 8. According to actual situation, the height of the inlet channel is changed by changing the shape of the supporting part 5, so as to adjust the flow rate of each heat exchange tube.
Embodiment 2 As shown in FIG. 9, a liquid distributor 10 for a vertical falling-film evaporator mainly includes a division body 9 and a supporting part 5, where the periphery of the main part 6 of the division body 9 has a concave surface, and the area of the bottom of the top cover 1 of the division body 9 is greater than the area of the opening of a heat exchange tube 8 of a vertical falling-film evaporator; and the supporting part 5 movably supports the division body 9 at a corresponding position at the upper part inside the heat exchange tube 8 of the vertical falling-film evaporator, so that the bottom surface edge of the top cover 1 of the division body 9 is spaced from the top surface of an upper tube plate 7 of the vertical falling-film evaporator for a certain gap to form an inlet channel. The division body 9 is symmetrically distributed around the central axis of the heat exchange tube of the vertical falling-film evaporator, and the diameter of the bottom surface of the division body 9 is 0.6 fold of the inner diameter of the heat exchange tube 8. The supporting part 5 includes 4 spiral vanes connected to the bottom surface of the top cover 1 and support pieces integrally downwards connected at the lower end of the rear of the vanes (FIG.

10). The diameter of the circle formed by the track of the outer edge of the tip of the vane is slightly - Comment IT1j: In the original PCT
greater than the ktuted_diameter of the heat exchang_e tube 8, so that the .tip of the vane_, - application, it is "inner" due to clerical mistake, It is revised as presses against the upper port of the heat exchange tube 8 or the upper tube plate 7, the "outer" during translation.
bottom edge of the top cover 1 of the division body 9 is spaced from the top surface of the upper tube plate 7 of the vertical falling-film evaporator for a certain gap, so as to form an inlet channel. The height of the vane spiral part is the height of the inlet channel; the width of the support piece closely matches the distance between the inner wall of the heat exchange tube 8 and the outer wall at a corresponding position of the division body, so that the support piece of the vane abuts against the inner wall of the heat exchange tube 8 and the outer wall at the corresponding position of the division body, thereby movably or fixedly supporting the division body 9 at a corresponding position at the upper part inside the heat exchange tube 8 of the vertical falling-film evaporator.
The liquid enters the liquid distributor 10 in an inward radiation-like manner through the inlet channel formed between the bottom surface edge of the top cover 1 and the upper surface of the upper tube plate 7 of the vertical falling-film evaporator, and flows into the liquid distributor 10 in a spiral manner along adjacent spiral vanes, so that the liquid can be easily distributed on the inner wall of the heat exchange tube, and after entering the heat exchange tube, the liquid flows downwards along the concave periphery of the main part 6 of the division body, and when reaching the bottom of the main part 6 of the division body, % CA 02863015 2014-07-09 , . , the liquid flows towards the inner wall of the heat exchange tube in an outward radiation-like manner.
The flow speed of the liquid entering the heat exchange tube 8 depends on the height of the inlet channel. According to actual situation, the height of the inlet channel is changed by changing the shape of the supporting part 5, so as to adjust the flow rate of each heat exchange tube.
Embodiment 3 A water treatment system for recycling produced water from heavy oil recovery to serve as boiler feed water includes an inlet water pre-treatment system, an evaporation system, a supplementary particle system and a particle recycling system.
The inlet water pre-treatment system includes an inlet water pre-treatment system, including a chemical treatment apparatus, an inlet water preheater and a degasser. The chemical treatment apparatus includes chemical adding devices 11-1 and 11-2, an inlet _ water tank mixer 12 and an inlet water tank 13. The inlet water tank and the inlet water preheater are connected through an inlet water pump 14. The inlet water containing produced water as the main component enters the inlet water tank, and chemical treatment agent is added to the inlet water tank 13 through the chemical adding devices 11-1 and 11-2, with stirring by the inlet water tank mixer 12 for reaction. After chemical treatment, the inlet water is pumped into the inlet water preheater 15 for preheating by the inlet water pump 14, and then enters the degasser through the top end of the degasser 16 for degassing treatment; after degassing, the inlet water enters the brine tank 18 of the vertical falling-film evaporator 17.
The evaporation system is a vertical falling-film evaporator, including a brine tank 18, a brine distribution apparatus, a vertical heat exchange tube 8, a circulation pump 21, a circulation pipe 22 and a energy drive for evaporation (may be a compressor 23 or a externally supplied steam equipped condenser 24).
The supplementary particle system 25 includes a conventional solid slurry supplementing device, depending on the size of the system. This system uses a solid % CA 02863015 2014-07-09 ' . .
feeder (for example, a screw feeder) to store and transfer the scrubbing particles to a slurry mixing tank, the slurry mixing tank mixes the scrubbing particles and the clear liquid (cooled distilled water or clear brine output from the particle recycling system, and the formed thick slurry containing the scrubbing particles of a high concentration may be directly added into the vertical falling-film evaporator through the circulation pipe or the brine tank of the vertical falling-film evaporator. This device has a variety of options and is applied in many industries. The supplementary particle system can produce slurry having a content of the scrubbing particles of up to 50%, and the specific concentration depends on the physical properties of the selected particles.
The particle recycling system 26 separates the brine from the suspended scrubbing particles and other suspended components generated through concentration in a conventional method. Separation may be implemented by using a cyclone separator, a cone-bottom tank, a centrifugal machine or a filter. The strong brine input end and the particle output end of the particle recycling system are respectively connected to the circulation pipe of the vertical falling-film evaporator. The scrubbing particles obtained through separation is preferentially input into the circulation pipe and is removed, because the density of the selected scrubbing particles is greater than that of the precipitate generated in the inlet water. Therefore, the circulating flow refluxed back to the circulation pipe contains thicker scrubbing particles, and the discharged brine flow or the brine mixed flow contains more other suspended components generated from the feed through concentration.
The degassed inlet water enters the brine tank 18, and is mixed with the thick slurry of the scrubbing particles input from the supplementary particle system 25 to form brine slurry of the scrubbing particles of a concentration of 0.5% to 5%, and is delivered to the brine distribution apparatus at the top of the evaporator by using the circulation pump, together with the brine slurry falling down in the heat exchange tube during the evaporation procedure. The brine distribution apparatus includes a brine distribution box 19 and a liquid distributor 10 inserted at the top of each heat exchange tube (as described in Embodiment 1 or 2), and evenly distribute the slurry in the upper tube plate and the heat exchange tube in the form of turbulence. The slurry enters the brine distribution box 19 of the brine distribution apparatus, and the brine slurry is distributed on the upper tube plate 7 of the evaporation by the vane (FIG. 5). The brine slurry enters the liquid distributor 10 in the form of thin layer turbulence in 360 degrees, and through this turbulence, even suspension of all the scrubbing particles in the brine slurry are maintained.
The slurry flows downwards along the outer surface of the liquid distributor, and at the same time, is distributed on the surface of the inner wall of the heat exchange tube 8, and is heated by the steam through condensing, and evaporation begins in the tube. The brine slurry and the steam flow downwards together in the tube, and flow out through the lower tube plate 20.
The scrubbing particles contact the inner wall of the heat exchange tube 8, and the surface of the tube is maintained to be clean due to the scrubbing effect of the scrubbing particles, and the substance precipitated from the brine can be adhered on the added particles, instead of being adhered on the heat exchange surface of the evaporator, so no dirt components are deposited on the tube wall during falling-film concentration of the brine.
The steam is separated from the falling down brine, and enters the demisting system 27 at an annular space at the brine tank of the vertical falling-film evaporator.
The demisting system may include several demisting forms, including a vane, a screen, a liquid contact apparatus, a washing system or a combination thereof.
The steam departs from the demisting system, and is sucked into the compressor 23.
If the external steam is directly used to heat the brine for evaporation, the steam departs from the demisting system and enters the condenser 24. The distilled water obtained in the condenser can be directly used in a packaged boiler steam generation device at a pressure of up to 1,000 psig or be directly used in a one-through steam generator (OTSG) or a circulating tube boiler at a pressure of up to 1,500 psig.
The steam from the compressor 23 or externally supplied steam is condensed on the outer wall of the heat exchange tube 8. The condensed water is converged at the bottom of the falling-film evaporator 17 and then flows into the distilled water tank 28. The hot distilled water is delivered to the inlet water preheater by using the distilled water pump 29, and preheats the inlet water in the inlet water preheater and is cooled by the inlet water at =
the same time. The cooled distilled water can be directly used in a packaged boiler steam generating device at a pressure of up to 1,000 psig or be directly used in a one-through steam generator (OTSG) or a circulating tube boiler at a pressure of up to 1,500 psig.

Claims

1. A water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water, wherein inlet water containing produced water as the main component is conveyed to a vertical falling-film evaporator equipped with a brine distribution apparatus, so as to produce distilled water as boiler feed water through evaporation, wherein scrubbing particles are added to the inlet water containing the produced water as the main component or to circulating strong brine of the vertical falling-film evaporator to form brine slurry, and when the brine slurry is evaporated by the vertical falling-film evaporator, scaling on the evaporator heat exchange surface is prevented or reduced by utilizing solid particles in the brine slurry

2. The water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water according to claim 1, wherein the scrubbing particles are solid particles that are insoluble in the inlet water and have scrubbing effects, are selected from sands, gravels, glass beads or other particles of metal derivatives having a particle size of greater than 0 and less than 100 microns, and has a particle density of 0.1 to 10 g/cm3.

3. The water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water according to claim 2, wherein the concentration of the scrubbing particles in the brine slurry is 0.5% to 5%.

4. The water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water according to claim 1, wherein the scrubbing particles are added into the vertical falling-film evaporator through a supplementary particle system and a particle recycling system.

5. The water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water according to claim 4, wherein the supplementary particle system comprises a conventional solid slurry supplementing device: a solid feeder is used to store and transfer the scrubbing particles to a slurry mixing tank, and the slurry mixing tank charges the scrubbing particles and the supplement water into a brine tank or a circulation pipe of the vertical falling-film evaporator after mixing.

6. The water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water according to claim 5, wherein the particle recycling system separates, by adopting a conventional method, the brine from the suspend scrubbing particles and other suspended components resulted from concentration, to obtain a scrubbing particles recycling solution of a higher concentration, a brine of a higher concentration, and a brine suspension containing other suspended components resulted from concentration of a higher concentration; the obtained scrubbing particles recycling solution of a higher concentration is added into the circulating strong brine of the vertical falling-film evaporator, and the obtained brine is refluxed to a supplementary particle treatment system; and the separation is completed by using a cyclone separator, a conical bottom tank, a centrifuge, or a filter.

7. The water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water according to claim 1, wherein the brine distribution apparatus comprises a brine distribution box at the top of the vertical falling-film evaporator and a liquid distributor at the top of each heat exchange tube.

8. The water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water according to claim 7, wherein the liquid distributor mainly comprises a division body and a supporting part, wherein the periphery of the main part of the division body has a concave surface, and the area of the bottom of the top cover of the division body is greater than the area of the opening of the heat exchange tube of the vertical falling-film evaporator; and the supporting part movably or fixedly supports the division body at a corresponding position at the upper part inside the heat exchange tube of the vertical falling-film evaporator, so that the bottom surface edge of the top cover of the division body is spaced from the upper surface of the upper tube plate of the vertical falling-film evaporator for a certain gap to form an inlet channel; the brine slurry enters the heat exchange tube along the inlet channel and the concave surface of the division body and is distributed on the inner surface of the heat exchange tube;
or the liquid distributor mainly comprises a division body and a supporting part, wherein the periphery of the division body has a concave surface; and the supporting part movably or fixedly supports and connects the division body at a corresponding position at the upper part inside the heat exchange tube of the vertical falling-film evaporator, and the upper surface of the division body is exposed from the upper opening of the heat exchange tube; the diameter of the upper surface of the division body is greater than the outer diameter of the heat exchange tube, so that the upper part edge of the concave surface of the division body is spaced from the top surface of the upper tube plate of the vertical falling-film evaporator for a certain gap, so as to form an inlet channel; the brine slurry enters the heat exchange tube along the inlet channel and the concave surface of the division body and is disturbed on the inner surface of the heat exchange tube.

9. The water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water according to claim 8, wherein the diameter of the bottom surface of the division body is greater than or equal to 0.3 fold the inner diameter of the heat exchange tube, and is less than the inner diameter of the heat exchange tube.

10. The water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water according to claim 9, wherein 2 to 6 supporting parts exist, and the supporting parts are polygon ribs having one edge seamlessly connected to the concave surface of the division body, and at least two adjacent edges of the other edges perpendicular to each other, the supporting part stands on the upper tube plate of the vertical falling-film evaporator by means of the adjacent perpendicular edges, so that the division body is movably or fixedly supported at a corresponding position at the upper part inside the heat exchange tube of the vertical falling-film evaporator, and an inlet channel is formed by the bottom surface edge of the top cover of the division body and the top surface of the upper tube plate of the vertical falling-film evaporator;
or the supporting part comprises 3 to 6 spiral vanes connected to the bottom surface of the top cover and support pieces integrally downwards connected at the lower end of the rear of the vanes, the diameter of the circle formed by the track of the outer edge of the tip of the vane is slightly greater than the outer diameter of the heat exchange tube, so that the tip of the vane presses against the upper port of the heat exchange tube or the upper tube plate, and the bottom edge of the top cover of the division body is spaced from the top surface of the upper tube plate of the vertical falling-film evaporator for a certain gap, so as to form an inlet channel, the height of the spiral part of the vane is the height of the inlet channel; the width of the support piece closely matches the distance between the inner wall of the heat exchange tube and the outer wall at a corresponding position of the division body, so that the support piece of the vane abuts against the inner wall of the heat exchange tube and the outer wall at the corresponding position of the division body, thereby movably or fixedly supporting the division body at a corresponding position at the upper part inside the heat exchange tube of the vertical falling-film evaporator.

11. The water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water according to claim 1, wherein the produced water is subjected to one or more of chemical treatment, preheating treatment and degassing treatment, and then enters the vertical falling-film evaporator; the chemical treatment is arranged before the preheating treatment and the degassing treatment, or is arranged after the preheating treatment and the degassing treatment and before the evaporation treatment.

12. The water treatment process for recycling produced water from heavy oil recovery to serve as boiler feed water according to any one of claims 1 to 11, comprising:
(1) inlet water pre-treatment: the produced water is used as the inlet water, chemicals are added to the produced water for chemical treatment, and degassing treatment is performed on the outlet water after preheating;
(2) evaporation treatment: the outlet water after degassing treatment enters a brine tank at the bottom of the vertical falling-film evaporator, and at the same time, thick slurry of the scrubbing particles of a high concentration is added into the brine tank through a supplementary particle system, so as to form brine slurry of the scrubbing particles of a concentration of 0.5% to 5% in the brine tank; the brine sluny is pumped into a brine distribution apparatus at the top of the vertical falling-film evaporator by using a circulation pump, and is distributed into each heat exchange tube by using a liquid distributor of the brine distribution apparatus, during procedure that the brine slurry is evaporated in the heat exchange tube, the scrubbing particles have friction with the inner wall of the heat exchange tube, and scrubs off the dirt on the inner wall of the heat exchange tube; the resulting steam and slurry flows downwards in the tube together, and the steam enters a demisting system at an annular space at the evaporator brine tank for treatment, and then enters a compressor and is used to provide heat for the vertical falling-film evaporator, or the steam enters a condenser for condensing to obtain cooled distilled water, and the brine slurry flows out at the lower tube plate of the vertical falling-film evaporator and enters the brine tank for circulation; a particle recycling system is disposed on the brine circulating path, and is used to circulating the scrubbing particles back to the vertical falling-film evaporator; after the steam at the outer wall of the heat exchange tube of the vertical falling-film evaporator releases heat and is condensed, the condensate is converged at the bottom of the vertical falling-film evaporator and enters a distilled water tank, and is used for preheating the inlet water to obtain cooled distilled water.

13. A water treatment system for recycling produced water from heavy oil recovery to serve as boiler feed water, comprising an evaporation system, a supplementary particle system, and a particle recycling system, wherein the evaporation system is a vertical falling-film evaporator, comprising a brine tank, the brine distribution apparatus according to claim 7, a heat exchange tube, a circulation pump, a circulation pipe and an energy drive for evaporation; the supplementary particle system comprises a solid feeder, a slurry mixing tank and a corresponding conveying pipeline; the particle recycling system mainly comprises one selected from a cyclone separator, a cone-bottom tank, a centrifugal machine or a filter and a corresponding conveying pipeline; the produced water conveying pipeline is connected to the brine tank of the vertical falling-film evaporator, a thick slurry output pipeline of the supplementary particle system is connected to the brine tank or the circulation pipe of the vertical falling-film evaporator, a strong brine input end and a particle output end of the particle recycling system are respectively connected to the circulation pipe of the vertical falling-film evaporator.

14. The water treatment system for recycling produced water from heavy oil recovery to serve as boiler feed water according to claim 13, further comprising an inlet water pre-treatment system and/or a further concentration or crystallization system for strong brine, wherein the inlet water pre-treatment system comprises one or more of a chemical treatment apparatus, a preheating apparatus and a degassing apparatus; and the further concentration or crystallization system for strong brine comprises a concentrator or a crystallizer, and the strong brine is further treated in the concentrator or the crystallizer.