US20140197102A1

US20140197102A1 - Evaporative recirculation cooling water system, method of operating an evaporative recirculation cooling water system and a method of operating a water deionizing system

Info

Publication number: US20140197102A1
Application number: US14/152,840
Authority: US
Inventors: Albert van der Wal; Aurora Maaike Anne SPRAGG; Bart van Limpt; Hank Robert Reinhoudt
Original assignee: Voltea BV
Current assignee: Voltea BV
Priority date: 2013-01-15
Filing date: 2014-01-10
Publication date: 2014-07-17
Also published as: EP2754644A1

Abstract

An evaporative recirculation cooling water system, the system having a recirculation loop to recirculate water through the system, a construction with a space to cool the water in the recirculation loop by evaporation, and a water entry point to allow water into the recirculation loop. The system has a charge barrier flow through capacitor constructed and arranged to remove ions from the water and a dosing system whereby a scale inhibitor is continuously dosed into the inlet flow into the flow through capacitor.

Description

FIELD

This disclosure relates to an evaporative recirculation cooling water system and to an evaporative recirculation cooling system comprising an ion removal apparatus.

BACKGROUND

In recent years one has become increasingly aware of the impact of human activities on the environment and the negative consequences this may have. Ways to reduce, reuse and recycle resources are becoming more important. In particular, clean water is becoming a scarce commodity.
An evaporative recirculation cooling water system may receive water from a water make-up stream. The water may be used in a recirculation loop and it may receive a heat load from, for example, a heat exchanger. The water may be cooled in an open space e.g. a cooling tower where the water comes in contact with air. The cooling may be enhanced by a partial evaporation of the water in the recirculation loop and this may cause the water to be lost in the recirculation system which requires an intake of water from the make-up stream. The evaporation and the addition of water from the make-up stream may cause an accumulation of dissolved species in the water of the recirculation loop. This accumulation of dissolved species may result in scaling in the recirculation system.

SUMMARY

U.S. Pat. No. 4,532,045 discloses a chemical ion removal apparatus for removing ions from the make-up water to minimize the accumulation of dissolved species. For this purpose the apparatus is provided with an ion exchange system which includes weak acid cation exchange resin. A disadvantage of the use of the weak acid cation exchange resin may be the need for regeneration or replacement of the cation exchange resin.
Japanese patent application publication no. JP2002-310595 discloses a cooling tower with a reverse osmosis membrane module which can separate cooling water into processed water from which ions are removed and concentrated water with ions. A disadvantage of the use of a membrane may be that it also removes silica ions which are a good corrosion inhibitor and another disadvantage may be that the membrane is sensitive to silica fouling and therefore anti-foulants may be required.
PCT patent application publication no. WO 2011-144704 discloses a cooling tower with a flow through capacitor which removes hardness ions from the water while leaving silica ions in the water. The hardness ions are fed to a waste water stream. The flow through capacitor may not function optimally because of a scaling tendency of the waste water stream of the flow through capacitor.
It is, for example, an objective to improve the evaporative recirculation cooling water system.
Accordingly, in an embodiment, there is provided an evaporative recirculation cooling water system comprising:
a recirculation loop to recirculate water through the system;
a construction with a space to cool the water in the recirculation loop by evaporation;
a water entry point to allow water into the recirculation loop;
a charge barrier flow through capacitor constructed and arranged to remove ions from the water between the water entry point and the recirculation loop; and
a scale inhibitor dosing system downstream of the water entry point and upstream of the charge barrier flow through capacitor to dose a scale inhibitor into the water flow from the water entry point to the charge barrier flow through capacitor.
A scaling tendency of the waste water stream of the flow through capacitor may be reduced by applying the scale inhibitor. By using the scale inhibitor the concentration of ions in the waste water may be increased. The ratio of purified water with respect to waste water may thereby be improved.
The flow through capacitor may be equipped with a charge barrier that is chosen such that it allows limited to no transport of weakly dissociated molecules and/or charged molecules with a weight greater than 200.
The scale inhibitor may comprise weakly dissociated molecules. The molecules may have a weight between 200 and 20,000, between 200 and 10,000 or between 200 and 2,000.
The dosed scale inhibitor may comprise a charged scale inhibitor. A charged scale inhibitor may be removed from the water by the flow through capacitor. However if the weight of the inhibitor is between 200 and 20,000, between 200 and 10,000 or between 200 and 2,000 and the charge barrier is constructed to substantially allow no transport of weakly dissociated molecules and/or charged molecules with a molecular weight greater than 200, these weakly dissociated molecules and/or the charged scale inhibitor may pass the flow through capacitor without being removed.
The flow through capacitor may comprise the water entry point and the recirculation loop so as to remove hardness ions from the water of the entry point before providing the water to the recirculation loop. The scale inhibitor is left in the water.
The charge barrier present in the flow through capacitor may cause the dosed scale inhibitor to pass through unhindered. The same feed stream is used for the purification process as well as for the waste process, therefore the concentration of scale inhibitor in the purified stream and in the waste stream is substantially equal to the concentration of scale inhibitor in the feed stream.
The scale inhibitor present in the waste stream will result in a lower scaling tendency for the flow through capacitor. The scale inhibitor present in the purified stream will enter the recirculation loop, where it will result in a lower scaling tendency for the recirculation loop, eliminating the need for additional scale inhibitor dosing.
The system may comprise a sensor to measure a chemical and/or physical property of the water in a waste water output and/or a purified water output and/or the recirculation loop, for example measure one or more selected from: pH, alkalinity, hardness, conductance of the water, flow rate of the water and/or concentration of scale inhibitor.
The system may comprise a flow adjuster, e.g. a pump, configured to adjust the velocity of the water flowing through the flow through capacitor.
The system may comprise a logic circuit configured to calculate a scaling potential of waste water and/or the water in the recirculation loop in response to a function of the chemical and/or physical property of the water in a waste water output as measured with a sensor, as well as the water velocity in the charge barrier flow through capacitor.
The system may comprise a controller configured to control dosing of the scale inhibitor based on the scaling potential of the waste water as determined by the logic circuit.
The system may comprise a controller configured to control the scaling potential in the waste stream by adjusting the flow adjuster.
The scale inhibitor dosing system may be constructed to continuously dose a scale inhibitor in the water from the water entry point.
In an embodiment, there is provided a method of operating an evaporative recirculation cooling water system, the method comprising:
recirculating water through a recirculation loop of the evaporative recirculation cooling water system;
cooling the water by evaporation;
adding water from a water entry point to the recirculation loop;
removing ions from the water from the water entry point with a charge barrier flow through capacitor; and
dosing a scale inhibitor into the water flow from the water entry point to the charge barrier flow through capacitor.
The charge barrier flow through capacitor may comprise a charge barrier substantially not allowing transport of weakly dissociated molecules and/or charged molecules with a molecular weight greater than 200.
The method may comprise dosing a scale inhibitor comprising weakly dissociated molecules.
The method may comprise dosing a scale inhibitor having a molecular weight between 200 and 20,000, between 200 and 10,000 or between 200 and 2,000.
The method may comprise dosing a charged scale inhibitor.
The method may comprise continuously dosing a scale inhibitor into the water flow.
According to an embodiment, there is provided a method of operating a water deionizing system, the method comprising:
dosing an amount of scale inhibitor into water upstream of a charge barrier flow through capacitor; and
removing ions from the water by allowing the water with the dosed amount of scale inhibitor to flow through the charge barrier flow through capacitor while charging the charge barrier flow through capacitor and directing the water from the charge barrier flow through capacitor to an outlet after the hardness ions have been removed.
A scaling tendency of the waste water stream of the flow through capacitor may be reduced by applying the scale inhibitor and thereby the desired water savings may be reached.
The rate of addition of the scale inhibitor may be dependent on the scaling potential of the charge barrier flow through capacitor waste water.
The rate of addition of the scale inhibitor may be dependent on the scale inhibitor concentration in the charge barrier flow through capacitor waste water.
The scale inhibitor concentration may be between 0.5 and 20 ppm, between 0.5 and 10 ppm, or between 1 and 4 ppm.
The dosed scale inhibitor may comprise a charged scale inhibitor.
The dosed scale inhibitor may contain weakly dissociated groups, and/or may have a molecular weight between 200 and 20,000, between 200 and 10,000 or between 200 and 2.000.
The scaling potential expressed as LSI may be between 1.5 and 4, between 1.7 and 3.5, or between 2 and 3.
The charge barrier flow through capacitor may be between a water entry point and a recirculation loop and the hardness ions may be removed from the water of the entry point before the water is provided to the recirculation loop, while leaving the scale inhibitor in the water.
The method may comprise measuring with a sensor a chemical and/or physical property of the water, the chemical and/or physical property may be one or more selected from: pH, alkalinity, hardness, conductance of the water, flow rate of the water and/or concentration of scale inhibitor.
The method may comprise:
controlling charging and/or discharging of a first and second electrode of the charge barrier flow through capacitor with a controller; and
controlling a regulator to direct water to a purified water output during charging of the charge barrier flow through capacitor and to a waste water output during discharging of the charge barrier flow through capacitor with the controller, wherein the controller controls a flow adjuster so as to adjust the water velocity in the charge barrier flow through capacitor in response to a function of a chemical and/or physical property of the water in the waste water output and/or the purified water output as measured with the sensor.
The method may comprise: calculating the scaling potential of the waste water in response to a function of the chemical and/or physical property of the water in the waste water output as measured with a sensor, as well as the water velocity in the charge barrier flow through capacitor.
The method may comprise controlling the dosing of the scale inhibitor based on the calculated scaling potential of the waste water.
These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from reading the following detailed description and the appended claims. For the avoidance of doubt, any feature of one aspect of the present invention may be utilized in any other aspect of the invention. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se. Similarly, all percentages are weight/weight percentages unless otherwise indicated. Numerical ranges expressed in the format “from x to y” are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format “from x to y”, it is understood that all ranges combining the different endpoints are also contemplated.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the invention will be described, by way of example only, with reference to the accompanying schematic drawings in which:

FIG. 1 schematically shows an evaporative recirculation cooling water system according to an embodiment;

FIG. 2 shows the concentration in the waste stream and in the purified stream as measured during a testing period of a scale inhibitor continuously dosed according to an embodiment of the invention; and

FIG. 3 shows the measured differential pressure normalized for the flow through capacitor in three periods, one period according to an embodiment.

DETAILED DESCRIPTION

FIG. 1 schematically shows an evaporative recirculation cooling water system ES according to an embodiment. The system comprises a water entry point WS to provide water to the recirculation loop RS from, for example, tap water via a flow through capacitor FTC. The recirculation loop RS may comprise a heat exchanger HE which warms the water and a construction e.g. cooling tower CT provided with a space to cool the water. An ion removal apparatus configured to remove ions e.g. a flow through capacitor FTC may be connected with the recirculation loop RS via a water outlet 9 provided with a regulator e.g. valve 12 to direct the flow of water from the water outlet 9 to the recirculation circuit RS via purified water outlet 10 or to direct the flow of water to a waste water output 16.
A chemical addition system AD2 may be present to provide one or more chemical additives to the water entry point WS.
The flow through capacitor may have a housing comprising a first housing part 1 and a second housing part 3 made of a relatively hard material e.g. a hard plastic. By pressing the first and second housing parts on each other, for example with a bolt and nut (not shown) the housing is made water tight.
The housing may have a water inlet 7 and a water outlet 9. During ion removal of the water, the water will flow from the inlet 7 to the outlet 9 through the spacers 11 which separate a first charge barrier M1 and a first electrode 13 and a second charge barrier M2 and a second electrode 15 of the flow through capacitor from each other. The current collectors 14 a and 14 b are clamped within the housing and connected to the power converter PC. By creating an electrical potential difference between the first and second electrode by a power converter PC, for example by applying a positive voltage to the first electrode (the anode) 13 and a negative voltage to the second electrode (cathode) 15 the anions of the water flowing through the spacer 11 are attracted to the first electrode and the cations are attracted to the second electrode. In this way ions (anions and cations) may be removed from the water flowing through the spacer 11. The purified water with reduced level of hardness ions may be discharged to the purified water outlet 10 by the valve 12.
Once the electrodes are saturated with ions the electrodes may be regenerated, whereby the ions will be released in the water in the spacer 11 in between the electrodes. The water in the spacer compartment with the increased ion content will be flushed away by closing the purified water outlet 10 with valve 12 under control of the controller CN and opening the waste water outlet 16. Once most ions are released from the electrodes and the water with increased ion content is flushed away via the waste water outlet 16 the electrodes are regenerated and can be used again for attracting ions.
A power converter PC under control of the controller CN is used to convert the power from the power entry point PS to the right electrical potential. The electrical potential differences between the anode and the cathode are rather low, for example lower than 12 volts, lower than 6 volts, lower than 2 volts or less than 1.5 volts. The electrical resistance of the electrical circuit should be low. For this purpose, current collectors 14 a which are in direct contact with the first electrodes are connected to each other with the first connector 17 and the current collectors 14 b which are in direct contact with the second electrodes are connected to each other with the second connector 19. The current collectors 14 a and 14 b may be made substantially metal free to keep them corrosion free in the wet interior of the housing and at the same time cheap enough for mass production.
The charge barriers M1 and M2 comprise a membrane, selective for anions or cations or certain specific anions or cations, and may be placed between the electrode and the spacer. The charge barrier may be applied to the high surface area electrode layer as a coating layer or as a laminate layer.
Suitable membrane materials may be homogeneous or heterogeneous. Suitable membrane materials comprise anion exchange and/or cation exchange membrane materials, desirably ion exchange materials comprising strongly dissociating anionic groups and/or strongly dissociating cationic groups. Examples of such membrane materials are Neosepta™ range materials (from Tokuyama), the range of PC-SA™ and PC-SK™ from PCA GmbH, ion exchange membrane materials from Fumatech, ion exchange membrane materials Ralex™ (from Mega) or the Excellion™ range of heterogeneous membrane material (from Snowpure).
The charge barriers M1 and M2 are chosen such that they allow limited to no transport of weakly dissociated molecules and/or charged molecules with a weight greater than 200. The same feed stream is used for the purification process as well as for the waste process, therefore the concentration of scale inhibitor in the purified stream and in the waste stream is substantially equal to the concentration of scale inhibitor in the feed stream.
The electrodes 13, 15 may be produced from a substantially metal free electrically conductive high surface area material, such as activated carbon, carbon black, carbon aerogel, carbon nanofibers, carbon nanotubes, graphene or a mixture thereof, which are placed on both sides of the current collector. The high surface area layer is a layer with a high surface area in square meters per weight of material, for example more than 500 square meters per gram of material. This set-up may help ensure that the capacitor works as an electrical double layer capacitor with sufficient ion storage capacity. The overall surface area of even a thin layer of such a material is many times larger than a traditional material like aluminum or stainless steel, allowing many more charged species such as ions to be stored in the electrode material. The ion removal capacity of the ion removal apparatus is thereby increased.
A sensor SN1 configured to measure a chemical and/or physical property of the water in the purified water outlet 10 may be included in the system. The sensor SN1 measures one or more selected from: alkalinity, hardness, flow rate of the water, conductance of the water, and/or concentration of scale inhibitor in the purified water outlet 10.
A sensor SN2 configured to measure a chemical and/or physical property of the water in the waste water outlet 16 may be included in the system. The sensor SN2 measures one or more selected from: alkalinity, hardness, flow rate of the water, conductance of the water, and/or concentration of scale inhibitor in the waste water outlet 16.
A sensor SN3 configured to measure a chemical and/or physical property of the water in the recirculation loop RS may be included in the system. The sensor SN3 measures one or more selected from: alkalinity, hardness, flow rate of the water, conductance of the water, and/or concentration of scale inhibitor in the recirculation loop RS.
A sensor P configured to measure a pressure differential between the water inlet 7 and water outlet 9 of the flow through capacitor may be included in the system.
The ion removal apparatus may comprise a flow adjuster FA, for example, a pump, configured to adjust the velocity of the water flowing through the flow through capacitor FTC.
The evaporative recirculation cooling water system may comprise a first addition device AD1 configured to provide one or more chemical additives to the recirculation loop RS. The first addition device AD1 may be connected to tanks CI and BIO to provide a corrosion inhibitor and a biocide respectively to the water. As depicted the addition device AD1 adds one or more chemicals to the water in the recirculation loop RS, however the one or more chemicals may also be provided in the water make-up stream after the FTC. By locating the flow through capacitor FTC between the water entry point WS and the addition device AD, the addition device AD may add the corrosion inhibitor CI and the biocide BIO after the water has passed the FTC. The one or more chemical additives will therefore not influence or harm the working of the FTC.
The evaporative recirculation cooling water system may comprise a second addition device AD2 configured to provide a chemical additive to the water entry point WS. The second addition device AD2 may be connected to tank SI to provide a scale inhibitor to the water. By providing a scale inhibitor that is weakly dissociated and/or has a high molecular weight before the flow through capacitor FTC, the scale inhibitor is present in both the water in the purified water outlet 10 and the water in the waste water outlet 16. As the purified water outlet feeds the cooling tower recirculation loop RS, the scale inhibitor will also be present in the water in the cooling tower recirculation loop RS. The scale inhibitor will therefore reduce the scaling potential for both the FTC as well as for the cooling tower.
A logic circuit LC may be connected to sensor SN1 and/or SN2 and/or P so as to calculate a scaling potential of the water in the waste water outlet 16 and/or the recirculation loop RS in response to a function of the chemical and/or physical property of the water and/or the scale inhibitor concentration in the waste water outlet 16 and/or the purified water outlet 16, as well as calculate the water velocity in the FTC and/or the pressure drop over the FTC. The sensor inputs may also be obtained from preset values.
A logic circuit LC may be connected to sensor SN3 so as to calculate a scaling potential of the water in the recirculation loop RS in response to a function of the chemical and/or physical property of the water and/or the scale inhibitor concentration in the recirculation loop RS.
The scaling potential of the water may be expressed as the Langelier Scaling Index, and the scaling potential of the water may be corrected for the scale inhibitor concentration in the water in the waste water outlet 16 and/or in the recirculation loop RS.
The controller CN may be connected to the addition device AD2 so as to adjust the scale inhibitor dosing rate in the water entry point in response to the calculated scaling potential in the water in the waste water outlet 16 and/or in the recirculation loop RS by logic circuit LC. For example if the calculated scaling potential by logic circuit LC is higher than a threshold value the addition device AD2 may increase the dosing rate of the scale inhibitor SI.
The controller CN may be connected to the flow adjuster FA so as to adjust the water velocity in the flow through capacitor FTC in response to the calculated scaling potential by logic circuit LC. For example if the calculated scaling potential by logic circuit LC is higher than a threshold value the flow adjuster FA may increase the waste water flow 16 to reduce the scaling potential.
The controller CN may be connected to a power converter PC which is operably connected to the first electrodes 13 via the first connector 17 and the current collectors 14 a and with the second electrodes 15 via current collectors 14 b and second connector 19. The controller CN may control the power converter PC to apply less or more power to the FTC in response to the calculated scaling potential by logic circuit LC. For example if the calculated scaling potential within the FTC by logic circuit LC is higher than a threshold value the power converter PC may reduce the FTC power to reduce the amount of ions taken up by the flow through capacitor and therefore reduce the scaling potential within the FTC.
Once the electrodes of the flow through capacitor become saturated with ions the capacitor may be regenerated by going in the regeneration mode by reducing the applied voltage or even reversing the polarity of the electrodes or by shunting the electrical circuit. The energy that is released during the regeneration mode can be recovered and returned to the power entry point PS. This may help to reduce the overall energy consumption of the ion removal apparatus. During regeneration the ions released from the electrodes will be release in the water in the flow through capacitor and flushed away to the waste water output 16 by the valve 12. An advantage of the use of the evaporative recirculation cooling water system according to an embodiment of the invention is that less water is needed via the make-up water system because the concentration of dissolved species in the water of the recirculation loop may be lower with the flow through capacitor.
In the evaporative recirculation cooling water system, one or more certain chemicals may be added in order to avoid or minimize common problems such as corrosion (rust), deposit formation (in the -warm- heat exchanger and cooling tower packings), and slime formation (due to excessive microbial growth). These one or more chemicals are called corrosion inhibitors, scale inhibitors and microbiocides respectively. By using the flow through capacitor less water will be used from the make-up water system and flushed to the waste water output 16 so that less chemicals may need to be added.
Corrosion inhibitors are substances which, when added in small amounts to a corrosive environment such as recirculating cooling water, reduce the rate of corrosion of the metal piping and one or more heat exchangers present in the cooling system. Corrosion inhibitors may be classified as anodic, cathodic, or both, depending on which portion of the electrochemical corrosion cell they disrupt. Combining cathodic with anodic corrosion inhibitors, provides a synergy in corrosion inhibition.
Corrosion inhibitors that may be used in the evaporative recirculation cooling water system include phosphate (orthophosphate, polyphosphate or combinations thereof), nitrite, zinc, lignosulphonate, molybdate, triazole (mercaptotriazole, benzotriazole, tollyltriazole), phosphonate (such as aminomethylenephosphonate, hydroxyethylenediphosphonate, phosphonobutane tricarboxylic acid, phosphonosuccinic acid), tannin, silicate (ionic silica and/or colloidal or polymerized silica) and/or sarcosinate.
Microbiocides are substances which, when added in small amounts to recirculating cooling water, may reduce the rate of microbial growth in the cooling system, and avoid formation of biofouling (which causes a secondary problem such as microbially induced corrosion (MIC) and which negatively affects heat exchange efficiency both in cooling towers and heat exchangers). Microbiocides may be classified either as oxidizing or as non-oxidizing biocides. Typically, small amounts of more expensive non-oxidizing biocides may be combined with larger amounts of less expensive oxidizing biocides. G proteins microbiocides inhibit microorganisms in a variety of ways. Some of these mechanisms are: altering permeability of the cell wall and/or cell membrane thereby interfering with vital processes of the microbe, destroying or denaturating essential proteins such as proteins involved in energy production of microbes, inhibition of enzyme-substrate reactions, oxidation of protein groups, etc.
Biocides that may be used in the evaporative recirculation cooling water system include microbiocides such as: isothiazolin, bronopol, glutaraldehyde, diethyl-m-toluamide, hydrogen peroxide, chlorine dioxide, bromochlorodimethylhydantoin, bromide activated by bleach (either sodium bromide or ammonium bromide), quaternary ammonium salts, THPS (tetrakis(hydroxymethyl)phosphonium sulfate), sodium hypochlorite, peracetic acid, DBNPA (dibromonitrilopropionamide).
Scale inhibitors are chemical compounds which, when added in small amounts to flow through capacitors and/or evaporative recirculation cooling water systems, reduce the scaling potential of the water. Some of the mechanisms of scale inhibition are: chelation, where soluble salts are formed from cations and scale inhibitors; dispersion, where increased anionic charge repels crystals, and thus prevents crystallization; crystal modification, where there is buildup of irregular shaped, less adherent crystals; and threshold inhibition, where active crystal growth sites are blocked, preventing further growth.
Scale inhibitors that may be used in the evaporative cooling water system should not pass through the charge barrier in the flow through capacitor. Since the same feed stream is used for the purification process as well as for the waste process, the concentration of scale inhibitor in the purified water outlet 10 and in the waste water outlet 16 is substantially equal to the concentration of scale inhibitor in the feed stream in water inlet 7. The dosed scale inhibitor may contain weakly dissociated groups, and/or have a molecular weight between 200 and 20,000, between 200 and 10,000 or between 200 and 2,000.
The scale inhibitors that may be used in the evaporative cooling water system include scale inhibitors that are weakly dissociated and/or have a high molecular weight. The scale inhibitors may be 2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTC) commercially available as Bayhibit® AM from Lanxess AG, Germany or a polymaleic acid commercially available as Belclene® 200 from BioLab Water Additives, United Kingdom.
There are a range of scale inhibitors that may be used for this application, such as: (poly)aspartic acid; acetate; NTA; TDA; (poly)carboxylic acid; STP; citrate; polycarboxylate; polyacrylate mixed with phosphonic acid (1-hydrorxyethlyidine) bis (HEPD) & proponoic acid (GE GenGuard™); other phosphonic acid derivatives (GE Hypersperse™); carbonate; dipicolinic acid; alkyl- and alkenyl succinate; other succinates; THS; TDS; BHMDS; CMOS; ODS; IDS; HIDS; EDTA in combination with acrylic polymer and/or other organic salt (Ashlands Advantage® Plus, Amersperse™ and Ameroyal™ lines); tetrasodium (1-hydroxyethylidene)bisphosphonate, 2-phosphono-1,2,4 butanetricarboxylic acid, disodium phosphate and amino-tris-methylene phosphonic acid (GE ScaleTrol™); alkaline compound with amine-like functionality (Nalco's PermaTreat®); mix of sodium nitrate and sodium molybdate (Nalco 2833); and/or modified polyacrylic acid (BASF Sokalan® CP).
If the concentration of hardness ions in the water in the recirculation loop increases because of evaporation then the water may be drained via a blow down port BO. The sensor SN may together with the logic circuit LC be used to determine the scaling potential in the water of the recirculation loop and via controller CN the valve 21 to control the draining of the water may be opened if the scaling potential in the water is too high. The controller CN may control the flow adjuster FA to refresh the water in the recirculation loop with water with a low concentration of hardness ions because the majority of the hardness ions is removed by the FTC.

Example 1

A scale inhibitor e.g. 2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTC, Bayhibit® AM) was continuously dosed into a feedstream, to achieve a 5 ppm concentration of active product in the feed stream of an evaporative recirculation cooling water system similar to FIG. 1. This feed stream was deionized by a charge barrier flow through capacitor where the charge barriers were ion exchange membrane materials (Fumasep FKS and Fumasep FAS, from Fumatech). The flow through capacitor was set to remove 75% of the ions in the feed stream. The concentration factor of the flow through capacitor was set to 4.4, meaning that the concentration of salts in the waste stream was set to 4.4 times higher than the concentration of salts in the feed stream. The purified stream was directed into a recirculation loop, containing a space to cool the water in the recirculation loop by evaporation. The concentration factor in this recirculation loop was set to 5, meaning that the concentration of dissolved solids in the recirculation loop is 5 times higher than the concentration of dissolved solids in the purified stream coming from the flow through capacitor. The concentration of hardness and alkalinity in the feed stream and in the purified stream coming from the flow through capacitor was determined with titration, the concentration of Bayhibit® AM in the feed stream and in the purified stream coming from the flow through capacitor was determined with chromatographic detection of orthophosphate after hydrolysis. The scale inhibitor is substantially not removed from the water in the feed stream.
FIG. 2 shows the concentration in mg/liter in the waste stream WS and in the purified stream PS as measured during a testing period (t) of a scale inhibitor B, e.g., 2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTC, Bayhibit® AM) continuously dosed. It shows the measured concentration of Bayhibit® AM for the waste stream WS as well as the purified stream PS. The figure shows that the concentration Bayhibit® AM is substantially equal in the waste stream WS as in the purified stream PS. The scale inhibitor B is substantially not removed from the water in the feed stream leading to substantially equal concentrations in the waste stream WS as in the purified stream PS.

TABLE 1

Chemical composition of the waste water and purified water
stream as measured by sensors SN1 and SN2 in FIG. 1

	Alkalinity	Hardness		Conductivity	Temperature	Bayhibit ® AM
Sensor	(ppm CaCO3)	(ppm CaCO3)	pH	(uS/cm)	(deg. C.)	(ppm)

Waste water	2136	907	8.27	2300	25	5.3
Purified water	74.5	29.89	7.625	130.75	25	5.2

The data in Table 1 can be transformed into a scaling tendency by using the Langelier Scaling Index, resulting in a LSI of 2.5 for the waste water. The logic circuit linked the LSI to the current dosing rate of Bayhibit® AM, where the concentration was adjusted accordingly by increasing or decreasing the addition of Bayhibit® AM by addition device AD2.
The purified water stream was fed into the cooling tower, which at a cycle of concentration of 10 resulted in a Bayhibit® AM concentration of 53 ppm and a conductivity in the cooling tower of 1300 uS/cm. This is monitored by sensor SN3, and controller CN controlled the valve 21 to control the draining of the water if the scaling potential in the water was too high.

Example 2

In the evaporative recirculation cooling water system according to Example 1, the differential pressure over the flow through capacitor was measured between the inlet and the outlet of the flow through capacitor. FIG. 3 shows the measured differential pressure normalized for the flow through capacitor in three periods, the first period being where a scale inhibitor was continuously dosed into the feedstream, according to Example 1, the second period being where no scale inhibitor was continuously dosed into the feedstream, and the third period being where, after acid cleaning of the module, the concentration factor in the flow through capacitor was reduced to allow for no scale inhibitor dosing.
As can be seen from FIG. 3, in period 1 the normalized pressure is not increasing, indicating that no scaling occurs in the flow through capacitor due to the dosing of scale inhibitor, which results in low scaling tendency in the flow through capacitor. In period 2 the normalized pressure increases rapidly, indicating that scaling occurs in the flow through capacitor due to the lack of scale inhibitor, resulting in a higher scaling tendency in the flow through capacitor. In period 3, after acid cleaning of the module, the normalized pressure is not significantly increasing, indicating that no scaling occurs in the flow through capacitor due to the decreased concentration factor in the flow through capacitor, which results in lower scaling tendency in the flow through capacitor.

Example 3

A scale inhibitor e.g. polymaleic acid (Belclene® 200) was continuously dosed into a feed stream being deionized by a charge barrier flow through capacitor of an evaporative recirculation cooling water system similar to FIG. 1. The dosing rate is 3 ppm of active product. The FTC removed 90% of the ions in the feed stream. The concentration factor of the FTC was 8. The concentration factor of the cooling tower was 5. The sensor SN3 was used to determine the calcium, alkalinity and pH of the waste stream. Using the logic circuit, the LSI of the waste stream was determined to be 3. At a LSI of 3, the concentration of Belclene® 200t was deemed insufficient to prevent scaling, therefore the controller CN increased the dosing rate of the active product to 5 ppm.

Example 4

A proprietary scale inhibitor was continuously dosed into a feedstream being deionized by a charge barrier flow through capacitor in an evaporative recirculation cooling water system similar to FIG. 1. The dosing rate was 10 ppm of active product. The FTC removed 90% of the ions in the feed stream. The concentration factor of the FTC was 4. The concentration factor of the cooling tower was 5. The sensor SN2 was used to determine the flow rate in the waste stream. The logic circuit predicted the waste stream composition using the predefined ingoing water composition, the FTC removal and the FTC concentration factor, from which it calculated the LSI to be 2. At a LSI of 2 the waste flow rate was deemed too low given the scale inhibitor dosing rate, therefore the controller CN decreased the flow rate of the waste stream to achieve a concentration factor in the FTC of 6.
The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

1. An evaporative recirculation cooling water system comprising:

a recirculation loop to recirculate water through the system;

a construction with a space to cool the water in the recirculation loop by evaporation;

a water entry point to allow water into the recirculation loop;

a charge barrier flow through capacitor constructed and arranged to remove ions from the water between the water entry point and the recirculation loop; and

a scale inhibitor dosing system downstream of the water entry point and upstream of the charge barrier flow through capacitor to dose a scale inhibitor into the water flow from the water entry point to the charge barrier flow through capacitor.

2. The system according to claim 1, wherein the charge barrier flow through capacitor comprises a charge barrier constructed to substantially allow no transport of weakly dissociated molecules and/or charged molecules with a molecular weight greater than 200.

3. The system according to claim 1, wherein the scale inhibitor dosing system is constructed to dose a scale inhibitor comprising weakly dissociated groups.

4. The system according to claim 1, wherein the scale inhibitor dosing system is constructed to dose a scale inhibitor having a molecular weight between 200 and 20,000.

5. The system according to claim 1, wherein the scale inhibitor dosing system is constructed to dose a charged scale inhibitor.

6. The system according to claim 1, further comprising a sensor to measure a chemical and/or physical property of the water in a waste water output and/or a purified water output and/or the recirculation loop.

7. The system according to claim 1, further comprising a controller configured to control charging and/or discharging of a first and second electrode of the charge barrier flow through capacitor; and control a regulator to direct water to a purified water output during charging of the charge barrier flow through capacitor and to a waste water output during discharging of the charge barrier flow through capacitor, wherein the controller is configured to control a flow adjuster so as to adjust the water velocity in the charge barrier flow through capacitor in response to a function of a chemical and/or physical property of the water in the waste water output and/or the purified water output as measured with a sensor.

8. The system according to claim 1, further comprising a logic circuit configured to calculate a scaling potential of waste water in response to a function of a chemical and/or physical property of the water in a waste water output as measured with a sensor, as well as the water velocity in the charge barrier flow through capacitor.

9. The system according to claim 8, comprising a controller configured to control dosing of the scale inhibitor based on the scaling potential of the waste water as determined by the logic circuit.

10. The system according to claim 1, wherein the scale inhibitor dosing system is constructed to continuously dose a scale inhibitor.

11. A method of operating an evaporative recirculation cooling water system, the method comprising:

recirculating water through a recirculation loop of the evaporative recirculation cooling water system;

cooling the water by evaporation;

adding water from a water entry point to the recirculation loop;

removing ions from the water from the water entry point with a charge barrier flow through capacitor; and

dosing a scale inhibitor into the water flow from the water entry point to the charge barrier flow through capacitor.

12. The method according to claim 11, wherein the charge barrier flow through capacitor comprises a charge barrier substantially not allowing transport of weakly dissociated molecules and/or charged molecules with a molecular weight greater than 200.

13. The system according to claim 11, wherein the dosing comprises dosing a scale inhibitor comprising weakly dissociated molecules.

14. The method according to claim 11, wherein the dosing comprises dosing a scale inhibitor having a molecular weight between 200 and 20,000.

15. The method according to claim 11, wherein the dosing comprises dosing a charged scale inhibitor.

16. The method according to claim 11, comprising continuously dosing a scale inhibitor into the water flow.

17. A method of operating a water deionizing system, the method comprising:

dosing an amount of scale inhibitor into water upstream of a charge barrier flow through capacitor; and

removing ions from the water with the dosed amount of scale inhibitor by allowing the water to flow through the charge barrier flow through capacitor while charging the charge barrier flow through capacitor and directing the water from the charge barrier flow through capacitor to an outlet after the hardness ions have been removed.

18. The method according to claim 17, wherein the rate of addition of the scale inhibitor is dependent on a scaling potential of a charge barrier flow through capacitor waste water.

19. The method according to claim 17, wherein the rate of addition of the scale inhibitor is dependent on a scale inhibitor concentration in a charge barrier flow through capacitor waste water.

20. The method according to claim 17, wherein the scale inhibitor concentration is between 0.5 and 20 ppm.

21. The method according to claim 17, wherein the dosed scale inhibitor comprise a charged scale inhibitor.

22. The method according to claim 17, wherein the dosed scale inhibitor comprises weakly dissociated groups, and/or has a molecular weight between 200 and 20,000.

23. The method according to claim 17, wherein the scaling potential expressed as LSI is between 1.5 and 4.

24. The method according to claim 17, wherein the charge barrier flow through capacitor is provided between a water entry point and a recirculation loop and the hardness ions are removed from the water of the entry point before the water is provided to the recirculation loop, while leaving the scale inhibitor in the water.

25. The method according to claim 17, further comprising measuring with a sensor a chemical and/or physical property of the water.

26. The method according to claim 25, further comprising:

controlling charging and/or discharging of a first and second electrode of the charge barrier flow through capacitor with a controller; and

controlling a regulator to direct water to a purified water output during charging of the charge barrier flow through capacitor and to a waste water output during discharging of the charge barrier flow through capacitor with the controller, wherein the controller controls a flow adjuster so as to adjust the water velocity in the charge barrier flow through capacitor in response to a function of the chemical and/or physical property of the water in the waste water output and/or the purified water output as measured with the sensor.

27. The method according to claim 17, further comprising calculating a scaling potential of the waste water in response to a function of a chemical and/or physical property of the water in the waste water output as measured with a sensor, as well as the water velocity in the charge barrier flow through capacitor

28. The method according to claim 27, further comprising controlling the dosing of the scale inhibitor based on the calculated scaling potential.