Patent Application
20160214875
The present invention relates to a water treatment system for separating a solid from a raw water containing a water-soluble polymer.
When oil/gas are mined, a water discharged in association therewith is called produced water. Produced water contains therein inorganic solid components such as sand, oil components, and in accordance with a district where oil/gas are mined, the water contains salt, organic substances, heavy metals and others in a large proportion. About the produced water, therefrom, the solid components and the oil components are mainly removed; and subsequently the water is injected into the underground under pressure, or discharged into a river or the sea to be disposed of. The produced water may be reused as water for irrigation, or water for boilers by removing, besides the removal of these components, the salt, the organic substances, the heavy metals, and the others. As a technique for separating oil components from produced water, JP 2003-144805 A (Patent Document 1) is known. Patent Document 1 discloses a technique of emulsifying oil components in associated water and coagulating the oil components to be separated and removed.
In recent years, in order to recover and increase the production amount of oil/gas wells (production wells) in which the production amount has been decreased, enhanced oil recovery (EOR) has been performed. EOR is a technique of injecting various fluids from an injecting well located around a production well into the production well to promote the shift of oil/gas into the production well, thereby increasing the production amount of the oil/gas from the production well. Examples of a method for enhanced oil recovery include water flood of injecting water into a well to increase the pressure in its oil/gas phase, thermal recovery of injecting a heat source, such as steam, thereinto to lower the oil in viscosity to be heightened in fluidity, and chemical flood of injecting, for example, a surfactant thereinto to change the oil in interfacial tension to be heightened in fluidity.
In order to cause injected water to extend over a wide sphere in the underground to heighten the effect of forcing out oil/gas, in recent years, as a method of enhanced oil recovery, polymer flooding has been widely performed, in which a viscous water the viscosity of which is increased by an aqueous polymer is injected. Non-patent Document 1 (see below) discloses that a comparison is made between the production-amount-increase when water is used as injected water, and that when a viscous water composed of water and a polymer (aqueous polymer solution) is used as the same, and the production amount is increased when the viscous water is used. The polymer used therein is a polymer typical examples of which include saccharide and polyacrylamide.
However, in each of Patent Document 1 and Non-patent Document 1, no consideration is made about a point of adjusting the viscosity of a water-soluble polymer contained in a produced water collected, so as to separate a solid contained in the produced water effectively.
When an aqueous polymer solution is caused to flow into a separating apparatus for separating a solid from the solution in the state that the solution is high in viscosity, a bad effect is produced onto the separation or the like, which is based on specific gravity difference. In other words, in the high viscosity state, the solid is lowered in shift speed, so that the solid does not easily undergo an appropriate sedimentation separation.
Water-soluble polymer is used not only as the injected water but also as various articles, such as an agent for fiber-processing, a dispersant, an emulsifier, an agent for paper-making, and a water treatment coagulant. The above-mentioned problem may be caused in general industrial wastewater treatments.
An object of the present invention is to provide a water treatment system capable of separating a solid and others effectively from an aqueous polymer solution.
In order to solve the above-mentioned problem, the present invention is a water treatment system to be configured to include: a water intake section for taking in a raw water containing a water-soluble polymer; a stirring unit for stirring the raw water flowing into this unit from the water intake section; a separating unit for separating a solid from the raw water after the raw water is stirred; and a viscosity measuring section for measuring the viscosity of at least one of the raw water flowing in the stirring unit, and the raw water after the stirring; wherein on the basis of a result measured through the viscosity measuring section, a decision is made about at least one of the amount of an additive to be charged into the stirring unit, and the stirring intensity of the stirring unit.
According to the present invention, a water treatment system can be provided in which the viscosity of an aqueous polymer solution is adjustable before a solid and others are separated from the solution, so as to attain the separation effectively.
Any object, structure and advantageous effect of the present invention other than those described above will be made clear through the description of embodiments thereof that will be demonstrated below.
Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.
In the present specification, the wording “chemical viscosity decrease” is defined as a matter that a polymeric chain of a polymer is shrunken or decomposed by a chemical reaction of the polymer with an additive to decrease the viscosity of the polymer; and the wording “physical viscosity decrease”, as a matter that a polymeric chain of a polymer is cut by shear stress or some other to decrease the viscosity thereof.
In the specification, the following are called a line mixer and a static mixer, respectively: a mixer having a rotary member therein, this rotary member being driven from the outside of the mixer to apply shear force to a raw water flowing in the mixer; and a mixer having no rotary member therein to apply shear force to a raw water flowing in the mixer.
The following will describe, as an example, a case where a water treatment system is used to treat produced water. The water treatment system of the present invention is applied not only any treatment of produced water but also other various treatments, such as seawater desalting treatment, domestic wastewater treatment, and industrial wastewater treatment.
A highly-viscous produced water is generated in shale-gas/oil mining spots, and oil/gas mining spots where enhanced oil recovery is performed by a polymer flooding method. In these spots, a water having a viscosity increased by a water-soluble polymer is injected into the underground. This polymer may be a polymeric typical examples of which include polysaccharide and polyacrylamide. Polysaccharide is a polymeric compound in which a large number of monosaccharide molecules are bonded to each other. Specific examples thereof include pectin, guar gum, xanthan gum, tamarind gum, carrageenan, propylene glycol, and carboxymethylcellulose, which are widely used also as food additives. Polyacrylamide is a polymer compound in which a large number of acrylamide molecules are bonded to each other, and is used also as a coagulant for wastewater treatment. The polymer is not limited to these species, and may be an appropriate species selected from all polymeric compounds and used in accordance with the state of an oil phase/gas phase into which the polymer is to be injected, and the usage thereof.
Next, a description will be made about chemical viscosity decrease based on the additive(s) from the additive charge section 3. An oxidizer is added to the aqueous polymer solution as the raw water, and then a mixed solution of the raw water and the oxidizer is stirred by means of the stirring unit 1. Inside a water tank of the stirring unit 1, the oxidizer and the raw water are mixed with each other and caused to react chemically with each other to decrease the viscosity of the aqueous polymer solution as the raw water (chemical viscosity decrease). The material of the water tank, which constitutes the stirring unit 1, is rendered a material having corrosion resistance and acid resistance. The shape thereof may be a rectangular or circular shape. In the case of the circular water tank, the mixing effect in the water tank is heightened by locating a baffle plate inside the water tank. The baffle plate is a plate arranged at a predetermined position of an inner wall of the circular water tank, and having a form projected toward the center of the water tank. A flow of the aqueous polymer solution that is generated by stirring-blades of the stirring unit 1 collides with this baffle plate to generate a turbulent flow. Thus, the effect of the mixing of the raw water with the oxidizer can be heightened. The stirring unit 1 used should be a unit having a capability of stirring the whole of the inside of the tank. The volume of the water tank, in which oxidization treatment is conducted by the addition of the oxidizer, is preferably a volume permitting the average retention period of the raw water to become at least one minute. When the raw water is a produced water, it is desired to render the water tank a sealed-up water tank which is not in contact with air, or make the water tank into an anaerobic state by purging the inside of the tank with an inert gas such as nitrogen in order to prevent a rise in the concentration of oxygen dissolved in the raw water. The reason therefor will be described as follows:
The oxidizer may be any one of ozone, hypochlorites, and hydrogen peroxide. In order to improve the oxidizing effect, a metal salt and/or a pH adjuster in addition with the oxidizer may be simultaneously, as the additive(s), to the raw water. However, hydrogen peroxide causes an increase in oxygen dissolved in the raw water. When the raw water is a produced water and a treated water thereof is reused as an injecting water, oxygen dissolved therein causes the propagation of bacteria which decompose oil/gas in the underground: thus, the treated water is required not to contain dissolved oxygen. Thus, when the raw water is a produced water and is reused as an injected water, it is desired to use an oxidizer other than hydrogen peroxide. In the case of using, as the oxidizer, sodium hypochlorite (NaClO), it is advisable to fit, to the additive charge section 3, a unit in which sodium hypochlorite is produced from salt water containing sodium chloride by the principle of electrolysis. When the raw water is a produced water, the water contains a large proportion of salts in many cases. Thus, sodium hypochlorite can be produced, using a treated water from which a solid has been separated from the raw water through the separating unit 2. When the water treatment system is established near the sea, seawater can be pumped up to be used. When the water treatment system of the present embodiment is arranged adjacently to seawater desalting equipment, a discharged water is usable, the water being discharged from its RO membrane vessel, which is a reverse osmosis membrane, and being high in salt concentration.
A description is described herein about a viscosity decreasing effect produced when sodium hypochlorite as the oxidizer is added to an aqueous solution of a polyacrylamide based polymer, and the resultant solution is stirred.
The adding rate of the oxidizer is largely varied in accordance with the viscosity of the raw water, a target viscosity of the resultant treated water, and the kind of the water-soluble polymer. Thus, it is desired to make a laboratory test beforehand to decide an oxidizer species producing a maximum viscosity decreasing effect onto the water-soluble polymer which is a target to be treated, and the adding rate thereof. Under the experimental conditions shown in
In
Fe2++H2O2>Fe3++OH.+OH−, and
Fe3++H2O2>Fe2++OOH.+H+
Next, a description will be made about physical viscosity decrease based on the stirring unit 1. The stirring blades of the stirring unit 1 are rotated at an outermost peripheral velocity of 0.5 to 20 m/s both inclusive, thereby giving a high shear force to a flow field inside the water tank of the stirring unit 1 (physical viscosity decrease). The form of the stirring blades may be a general-purpose form, such as the form of propeller blades, paddle blades, or turbine blades. The form is preferably a rotary body form having, on the outermost periphery thereof, projections each having an acute angle tip since the form induces a high shear force to the flow field. The G value of the stirring unit 1, which is an index of energy given to a fluid, is from several thousands (Ws) or more to several millions (1/s) or more. The G value is represented by the following equation:
In the equation (1), ν is the kinetic viscosity (m2/s) of the fluid; V, the volume (m3) of the fluid; CD, the resistance coefficient (dimensionless) of the stirring blades; Ai, the area (m3) of each of the blades; and v, the peripheral velocity of the blades (m/s). The peripheral velocity of the blades is represented by the following equation (2):
In the equation, r is the turning radius (m) of the blades, and N is the rotation number (rpm) of the blades. According to the equations (1) and (2), the G value increases in proportion to (the rotation number N)3/2.
The stirring intensity is specified in accordance with the volume of the water tank of the stirring unit 1, the velocity of the stirring blades, and the stirring period. Since the volume of the water tank is fixed, the stirring intensity can be controlled in accordance with the velocity of the stirring blades, or the stirring period. In the present embodiment, the description has been made about the case where the stirring period is controlled. However, the velocity of the stirring blades may be controlled. In this case, the viscosity of the aqueous polymer solution can be decreased by increasing the rotation number of a motor for driving the stirring blades.
It is allowable to use, in addition to the physical viscosity decrease based on the stirring unit 1, an effect based on the addition of the above-mentioned additives) (one or more oxidizers, metal salts and/or pH adjusters). In this case, a higher viscosity decreasing effect can be gained by a synergetic effect of chemical viscosity decrease based on the additive(s) and the physical viscosity decrease based on the stirring unit 1.
Next, a description will be made about the first measuring section 5 for measuring the viscosity of the raw water at the upstream side of the stirring unit 1, and the second measuring section 6 for measuring the viscosity of the raw water at the downstream side of the stirring unit 1, that is, the viscosity of the raw water after the raw water is stirred.
It is sufficient for the first measuring section 5 and the second measuring section 6 to be each a commercially available in-line type viscosity viscometer. In the present embodiment, the first measuring section 5 is fitted to the raw water inflow part (water intake pipe 8) of the stirring unit 1; and the second measuring section 6, to the outflow part (connecting pope 9) of the stirring unit 1. Examples of the principle for measuring viscosity include capillary tube mode, vibrating mode, and rotating mode principles. A viscometer based on any one of these principles is favorably usable. When the period of a change in the viscosity is long, for example, the viscosity is changed in the unit of day, it is allowable to: collect the raw water from each of the measuring sections, for example, one time per day without using any in-line type viscometer; measure the viscosity thereof in a place such as a laboratory; and then adjust, on the basis of the result, the adding rate of the additive(s), or the stirring intensity of the stirring unit. When the viscosity is measured in such a place in this way, the above-mentioned cone plate type viscometer is favorably usable. In a case where the raw water is collected from each of the measuring sections and the viscosity thereof is measured in the place, the first and second measuring sections 5 and 6 correspond to spots where the raw water is collected, respectively. By measuring the viscosity of each of the collected raw waters without fitting any actual measuring section to the water treatment system, this case also produces the same effect and advantages produced when the measuring sections are fitted thereto. As the viscosity of the raw water flowing into the stirring unit 1 becomes higher, the torque of the stirring blades of the stirring unit 1 becomes larger, so that electric current flowing into the motor for driving the stirring blades becomes larger. It is therefore allowable to measure, in advance, a correlation between the viscosity of the raw water, and the torque of the motor or the electric current, and then measure the viscosity indirectly from the measured value of the torque or the electric current. Moreover, when the viscosity of the raw water becomes high, a pressure loss in the pipe in which the raw water flows is changed. It is therefore allowable to measure, in advance, a correlation between the viscosity of the raw water, and the pressure loss, and then measure the viscosity indirectly from a pressure value measured through a pressure gauge fitted to the above-mentioned pipe.
The following will describe the operation of the control unit 4. The control unit 4 has a CPU, and memories such as ROMs and RAMs, which are each not illustrated, and reads out programs memorized in the memories to attain various processing. In the memories is memorized the relationship shown in
A description is made herein about the reason why the target viscosity value is set into the range of 2.0 to 3.0 mPa·s both inclusive. The viscosity of a produced water depends mainly on the water temperature thereof, and the salt concentration therein. The water temperature of the produced water and the salt concentration therein are largely varied in accordance with a district where oil/gas are mined. The water temperature is from 5 to 80° C. both inclusive, and the salt concentration is from 3.0 to 30% both inclusive in many cases. The viscosity shows a highest value when the water temperature is 5° C. and the salt concentration is 30%. At this time, the viscosity is 3 mPa·s. By contrast, the viscosity shows a lowest value when the water temperature is 80° C. and the salt concentration is 0% (fresh water). The viscosity is 0.3 mPa·s.
Accordingly, the viscosity of a produced water containing no water-soluble polymer is from 0.3 to 3.0 mPa·s both inclusive. Thus, in many cases, existing associated water treatment devices have been designed on the supposition that the produced water viscosity is 3.0 mPa·s or less. In the present embodiment, the target viscosity is set to a relative high value in this range, i.e., a value of 2.0 to 3.0 mPa·both inclusive. This is because the use amount of the additive(s) necessary for decreasing the viscosity can be saved by setting the target viscosity to the relative high value. Moreover, by setting the target viscosity to the relative high value, the use amount of the water-soluble polymer necessary for increasing the viscosity again can also be saved when the water that has been treated is reused for a polymer flooding method.
In the next step, with reference to the relationship between the respective adding rates of the additives and the aqueous polymer solution viscosity, the relationship between the velocity of the stirring blades of the stirring unit and the aqueous polymer solution viscosity, and the relationship between the stirring period and the aqueous polymer solution viscosity, which are each stored in the memories, at least one of the following is carried out in accordance with a difference between the target viscosity and the measured viscosity (step S43): the adjustment of the adding rates of the additives; and the adjustment of the stirring intensity of the stirring unit. About the adjustment of the adding rates of the additives, the adding rates corresponding to the difference are calculated from the above-mentioned reference result, and the calculated adding rates are outputted, as command values, to the additive charge section 3. About the adjustment of the stirring intensity of the stirring unit, the stirring blade velocity corresponding to the difference is calculated from the reference result, and the calculated stirring blade velocity is outputted, as a command value, to the stirring unit 1. The stirring period is decided in accordance with the period when the raw-water remains in the stirring unit 1. Thus, the stirring period is usually made constant. However, the inflow rate of the raw water into the stirring unit 1 may be controlled through the raw water valve 17 to control the stirring period.
Next, from the second measuring section 6, the control unit 4 takes in the measured viscosity, that is, the measured viscosity of the raw water after the raw water is stirred (step S44). The control unit 4 compares the taken-in measured viscosity with the target viscosity memorized beforehand in the memories to determine whether or not the measured viscosity is over the target viscosity (step S45). As a result of the determination, when the measured viscosity is the target viscosity or less, the processing is ended. When the measured viscosity is over the target viscosity, the present processing is advanced to a next step.
In the next step, it is determined whether or not the measured viscosity is over 110% of the target viscosity (step S46). As a result of the determination, when the measured viscosity is 110% of the target viscosity, or less, at least one of the following is carried out in accordance with a difference between the measured viscosity and the target viscosity (step S43): the adjustment of the respective adding rates of the additives; and the adjustment of the stirring intensity of the stirring unit 1. When the measured viscosity is over 110% of the target viscosity, the processing is advanced to a next step. In the next step, the raw water valve 17 is narrowed down to decrease the amount of the raw water flowing into the stirring unit 1 temporarily, or stop the raw water temporarily until the measured viscosity through the second measuring section 6 reaches down to the target viscosity or less (step S47). As a result, the measured viscosity reaches to 110% of the target viscosity or less (step S46), at least one of the following is carried out in accordance with a difference between the measured viscosity and the target viscosity (step S43): the adjustment of the respective adding rates of the additives; and the adjustment of the stirring intensity of the stirring unit 1.
In the above-mentioned example, a criterion for the determination in the step S46 is set to 110% of the target viscosity. However, this numerical value may be set to 120% for the following reason: in general, when the viscosity of a raw water is over 4.0 mPa·s, in the afterward-located separating unit 2 the processing capability is remarkably lowered or fluctuated; however, the viscosity can be controlled not to be over 4.0 mPa·s through the step S47 not only when the determination criterion in the step S46 is set to 3.3 mPa·s, which is 110% of the target viscosity upper limit value, 3.0 mPa·s, but also when the determination criterion is set to 3.6 mPa·s, which is 120% of the target viscosity upper limit value, 3.0 mPa·s. The control unit 4 carries out steps from the step S41 to the step S47 in a predetermined period.
Although the target viscosity is set into the range of 2.0 to 3.0 mPa·s both inclusive, the target value of the viscosity may be set in accordance with the processing capability of the afterward-located separating unit 2. About a wastewater (raw water) having a viscosity of several tens of millipascal seconds to several hundreds of millipascal seconds, such a control makes it possible that the afterward-located separating unit 2 constantly exhibits an original processing capability thereof even when the viscosity fluctuates. Thus, a treated water good in water quality can be constantly obtained.
The present embodiment is configured to measure both of the viscosity of the raw water flowing into the stirring unit 1 and that of the raw water flowing out from the stirring unit 1. However, the water treatment system of the present invention may be configured to measure the viscosity of either one of the two.
Next, a description will be described about the separating unit 2. The separating unit 2 is preferably a separating unit using a difference in specific gravity between solid components and oil, and water to separate the former from the latter. Examples of the unit include a hydrocyclone using oil and water, which are different from each other in specific gravity to separate the two from each other; a corrugated plate interceptor (CPI) separator using an inclined plate having a corrugated cross section to separate solid components and oil simultaneously and effectively from water; a dissolved air floatation (DAF) separator in which fine air bubbles are caused to adhere onto solid components and oil to make the specific gravity thereof light, thereby floating these substances to be separated; and a coagulating sedimentation separator in which a coagulant is injected onto a raw water containing solid components and oil to coagulate particles of these substances to each other, thereby forming lumps called flocs, and then sedimenting the flocs by gravitation to be separated from the water. The separating unit 2 is not limited to these units, and may be a unit in any other form as far as the unit is a unit using a specific gravity difference to separate solid components and oil from water. In the present embodiment, the viscosity of the raw water (aqueous polymer solution) flowing into the separating unit 2 is controlled into the range of 2.0 to 3.0 mPa·s both inclusive by action of the stirring unit 1 or the additive charge section 3. Thus, even when the viscosity of the raw water fluctuates, solid components and oil can be separated therefrom stably at any time through the separating unit 2.
According to the present embodiment, the viscosity of a raw water flowing into the separating unit 2 can be decreased; thus, also from a raw water having a viscosity of several tens of millipascal seconds to several hundreds of millipascal seconds, solid components and oil therein can be certainly removed without increasing a treatable volume of existing equipment. Through the second measuring section 6, a treated water (raw water that has been stirred) discharged from the stirring unit 1 is measured about the viscosity thereof, and on the basis of the measurement result, the stirring unit 1 or the additive charge section 3 can be controlled. Thus, even the viscosity of the raw water fluctuates, solid components and oil therein can be stably removed. Accordingly, when the raw water is a produced water, a treated water therefrom, in which solid components and oil have been removed, can be favorably reused as an injecting water by configuring a pipe through which the treated water is discharged from the separating unit 2 to be connected to an injecting well for a gas field. However, when the treated water is reused for a polymer flooding method, it is necessary to incorporate a water-soluble polymer into the treated water to increase the viscosity thereof. As the viscosity of the treated water is higher, the necessary amount of the water-soluble polymer at this time is permissible to be smaller. Thus, when the treated water is reused for a polymer flooding method, the target viscosity in
When the treated water is not reused as an injecting water, it is sufficient for the target viscosity to be set into an appropriate value from a relationship between the treating performance of the separating unit 2, and the use amount of the additive(s) and the stirring intensity. When the inflow rate of the raw water has, for example, no margin for the capacity of the separating unit 2, the target viscosity is made as low as a value of 0.3 to 1.0 mPa·s both inclusive, whereby a load onto the separating unit 2 can be made small. When the target viscosity is set on the basis of the viscosity result measured through the first measuring section 5, an appropriate control can be made about the treating performance of the separating unit 2, the use amount of the additive(s), and the stirring intensity. When the viscosity result measured through the first measuring section 5 is, for example, over 4.0 mPa·s, which generally lowers the treating capability of the afterward-located separating unit 2, the target viscosity is made as high as a value of 2.0 to 3.0 mPa·s both inclusive, whereby the use amount of the additive(s) can be saved, or the target viscosity can be attained only by stirring. Moreover, by making the target viscosity as low as a value of 0.3 to 1.0 mPa·s both inclusive, the treating capability of the separating unit 2 can be caused to have a margin. Furthermore, even when the viscosity result measured through the first measuring section 5 is 3.0 mPa·s or less, the target viscosity can be set to an appropriate value in the range of 0.3 to 3.0 mPa·s both inclusive, thereby making it possible to save the use amount of the additive(s), and gain a required separating performance through the adjustment of the stirring intensity.
The water treatment system has a water intake pipe 8 through which an aqueous polymer solution, which is a raw water, is taken in; a first measuring section 5 connected to the water intake pipe 8 to measure the viscosity of the raw water flowing into this section; the line mixer 10 connected to the water intake pipe 8 to apply shear stress to the raw water flowing into this mixer; a connecting pipe 9 through which the raw water discharged from the line mixer 10 is caused to flow into a separating unit 2; and a second measuring section 6 fitted to the connecting pipe 9 to measure the viscosity of the raw water discharged from the line mixer 10. This system also has an additive charge section 3 in which one or more additives are charged into the raw water flowing in the water intake pipe 8; and a control unit 4 for controlling the additive charge section 3 on the basis of the viscosity of the raw water flowing into the line mixer 10, which is measured through the first measuring section 5, and the viscosity of the raw water discharged from the line mixer 10, which is measured through the second measuring section 6. A rotary member inside the line mixer 10 is driven to be rotated through an outside motor.
In the same manner as in Example 1, the additive(s) charged through the additive charge section 3 is/are (each) any one of oxidizers, metal salts and pH adjusters, or a combination of two or more thereof. Thus, a description thereof is omitted herein.
The shear force applied to the raw water flowing in the line mixer 10 is decided in accordance with the driving power of the rotary member. In the present embodiment, the raw water viscosity is adjusted by controlling the driving power of the rotary member, i.e., the rotation number of the motor, and the adding rate of the additive(s). In the present embodiment, the control unit 4 is operated by adjusting at least one of the rotation number of the motor, and the adding rate of the additive(s) in the step S43 described with reference to the
According to the present embodiment, the viscosity of the raw water flowing into the separating unit 2 can be decreased. Accordingly, from a discharged water having a viscosity of several tens of millipascal seconds to several hundreds of millipascal seconds, solid components and oil therein can be certainly removed without increasing a treatable volume of existing equipment. Moreover, through the second measuring section 6, the viscosity of the treated water (raw water that has been stirred) discharged from the line mixer 10 is measured, and on the basis of the measurement result, the driving power of the line mixer 10, and the additive charge section 3 can be controlled, so that solid components and oil therein can be stably removed even when the viscosity of the raw water fluctuates. Accordingly, when the raw water is a produced water, a treated water thereof, in which solid components and oil have been removed, can be favorably reused as an injecting water by configuring a pipe through which the treated water is discharged from the separating unit 2 to be connected to an injecting well for a gas field.
A description is made herein about the configuration of the static mixer 20.
In
The raw water viscosity in the static mixer 20 is adjusted by adjusting the flow rate of the circulated water supplied into the static mixer 20. As the flow rate is larger, the shear stress applied to the raw water is larger. Thus, when the viscosity decreasing effect is desired to be made large, it is advisable to make a control for increasing the flow rate of the circulated water. In the present embodiment, physical viscosity decrease is performed by the static mixer 20. It is therefore sufficient for the decrease that a minimum stirring is continued without adjusting the stirring intensity of the stirring unit 1. In other words, the static mixer 20 and the stirring unit 1 take partial charge of the physical viscosity decrease. The partial charge ratio between the two can be appropriately set.
According to the present embodiment, the viscosity of the raw water flowing into the separating unit 2 can be decreased. Accordingly, from a discharged water having a viscosity of several tens of millipascal seconds to several hundreds of millipascal seconds, solid components and oil therein can be certainly removed without increasing a treatable volume of existing equipment. Moreover, through the second measuring section 6, the viscosity of the treated water (raw water that has been stirred) discharged from the stirring unit 1 is measured, and on the basis of the measurement result, the flow rate of the static mixer 20, the stirring unit 1, and the additive charge section 3 can be controlled, so that solid components and oil therein can be stably removed even when the viscosity of the raw water fluctuates. Accordingly, when the raw water is a produced water, a treated water thereof, in which solid components and oil have been removed, can be favorably reused as an injecting water by configuring a pipe through which the treated water is discharged from the separating unit 2 to be connected to an injecting well for a gas field.
The static mixer 20 may be any one of the mixers illustrated in
According to the present embodiment, the viscosity of the raw water flowing into the separating unit 2 can be decreased. Accordingly, from a discharged water having a viscosity of several tens of millipascal seconds to several hundreds of millipascal seconds, solid components and oil therein can be certainly removed without increasing a treatable volume of existing equipment. Moreover, through the second measuring section 6, the viscosity of the treated water (raw water that has been stirred) discharged from the static mixer 20 is measured, and on the basis of the measurement result, the flow rate of the static mixer 20, and the additive charge section 3 can be controlled, so that solid components and oil therein can be stably removed even when the viscosity of the raw water fluctuates. Accordingly, when the raw water is a produced water, a treated water thereof, in which solid components and oil have been removed, can be favorably reused as an injecting water by configuring a pipe through which the treated water is discharged from the separating unit 2 to be connected to an injecting well for a gas field.
The water treatment system has a bypass channel 7 having two ends, one thereof being connected to a water intake pipe 8 through which the raw water is taken into the stirring unit 1, and the other being connected to a connecting pipe 9 through which the stirring unit 1 and a separating unit 2 are connected. This system also has a switching valve 11 for making a switch between an operation of causing the raw water branched from the water intake pipe 8 to flow into the measuring section 50, and an operation of causing the raw water branched from the connecting pipe 9 to flow into the measuring section 50. The raw water that has flowed in the measuring section 50 and then has been measured about the viscosity thereof is discharged through a water-discharging pipe.
By effect of the switching valve 11, the raw water which is to flow into the stirring unit 1 through the water intake pipe 8 is partially taken into the measuring section 50, and the measured viscosity of the raw water is taken into the control unit 4 (corresponding to the step S41 in
In the present embodiment, the number of viscosity measuring sections to be used can be made smaller than in Embodiment 1 to make the number of parts to be used smaller.
According to the present embodiment, the viscosity of the raw water flowing into the separating unit 2 can be decreased. Accordingly, from a discharged water having a viscosity of several tens of millipascal seconds to several hundreds of millipascal seconds, solid components and oil therein can be certainly removed without increasing a treatable volume of existing equipment. Moreover, through the second measuring section 50, the viscosity of the treated water (raw water that has been stirred) discharged from the stirring unit 1 is measured, and on the basis of the measurement result, the stirring unit 1 or the additive charge section 3 can be controlled, so that solid components and oil therein can be stably removed even when the viscosity of the raw water fluctuates. Accordingly, when the raw water is a produced water, a treated water thereof, in which solid components and oil have been removed, cars be favorably reused as an injecting water by configuring a pipe through which the treated water is discharged from the separating unit 2 to be connected to an injecting well for a gas field.
In each of Embodiments 1 to 5, a case where polyacrylamide is used as the water-soluble polymer has been described. However, polymer referred to also as polysaccharide also produces the same advantageous effects as produced by polyacrylamide by selecting an appropriate oxidizer or metal salt. For example, polysaccharide is widely used as a food additive, such as a thickener, a stabilizer, a gelatinizer or a sticker, as indicated as a thickening polyose in a food product. In order to adjust the food feeling and others of the product, a viscosity adjuster is used therein. In the water treatment system of the present invention, the use of such a viscosity adjuster makes it possible to treat stably a raw water containing polysaccharide as a water-soluble polymer.
The present invention is not limited to the above-mentioned embodiments, and includes various modified embodiments thereof. For example, the above-mentioned embodiments are each a system described in detail for describing the present invention to be easily understandable. Thus, the invention is not necessarily limited to any embodiment having all the constituents described in each of the embodiments. The constituents of some one of the embodiments of the invention may be partially substituted with one or more of the constituents of one or more of the other embodiments. To the constituents of some one of the embodiments of the invention may be added one or more of the constituents of one or more of the other embodiments. One or more parts of the constituents of anyone of the embodiments of the invention may be deleted. Moreover, to the part(s) may be added one or more of the constituents of one or more of the other embodiments, or the part(s) may be substituted with the constituent(s) under the same condition.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-211662 | Oct 2013 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/075026 | 9/22/2014 | WO | 00 |
