EP1152985A1 - Traitement au dioxyde de carbone des eaux de refroidissement atmospherique - Google Patents
Traitement au dioxyde de carbone des eaux de refroidissement atmospheriqueInfo
- Publication number
- EP1152985A1 EP1152985A1 EP00981459A EP00981459A EP1152985A1 EP 1152985 A1 EP1152985 A1 EP 1152985A1 EP 00981459 A EP00981459 A EP 00981459A EP 00981459 A EP00981459 A EP 00981459A EP 1152985 A1 EP1152985 A1 EP 1152985A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- water
- carbon dioxide
- cooling
- atmospheric
- circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
- C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
- C02F5/10—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances
- C02F5/12—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances containing nitrogen
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
- C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/02—Non-contaminated water, e.g. for industrial water supply
- C02F2103/023—Water in cooling circuits
Definitions
- the present invention relates to a new process for treating atmospheric cooling water. It is common in the industry to use a water circulation to cool an installation. The nature of the devices to be cooled is extremely varied. They can be condensers, heat exchangers, chemical reactors.
- Atmospheric cooling water is meant that said water is at a given time in contact with air which causes entrainment and / or partial evaporation of this cooling water.
- Cooling water circuits can be classified into three categories:
- the atmospheric cooling circuits or semi-open circuits are therefore cooling water circuits in which part of the water to be cooled is evaporated at at least one point by evaporation and / or entrainment by means of natural convection or forced atmospheric air.
- An example of such circuits consists of cooling water circuits in which the water used to cool an installation (hot water) arrives at the top of a cooling tower provided with a lining and convection means. of air and passes through this cooling tower from top to bottom, the cold water arriving in the lower part of the cooling tower being then returned to the installation to be cooled.
- Another example of a semi-open circuit is that of the water recirculation circuits in which the heat exchanger which it is sought to cool acts as an atmospheric refrigerant.
- Dirt is made up of materials that can settle or form in a circuit. They can have several sources: make-up water, atmospheric air or manufacturing within the installation.
- Scaling is linked to the precipitation on the surfaces of pipes of poorly soluble calcium salts and possibly silica.
- the main parameters controlling the precipitation of tartar are the temperature, the rise of which generally decreases the solubility of the salts concerned, the concentration of ions and agitation.
- Carbonate is the most common cause of scale formation which can be redissolved in service by chemical means.
- Calcium sulfate with a maximum solubility at 40 ° C can precipitate cold as gypsum or hot as anhydrous or hemihydrate.
- microbial corrosion is a direct consequence of poor control of microbiology in a water circuit. This results directly from biofilms which degenerate, resulting in a size such that the area in contact with the material is deprived of oxygen or meets an acid pH. Corrosion being one of the major risks for industry, it is generally preferred to work at a higher pH, often of the order of 7.9 to 8.4, and to counter the risks of scale formation of the carbonate, phosphate or calcium sulphate using sequestering and / or dispersing agents.
- This gel or slime Bacterial then serves as protection for the colony of bacteria which it will nourish by capturing the particles present in the waters necessary for microbial growth.
- This phenomenon also increases the size of deposits.
- This growing deposit also causes not only progressive losses in thermal efficiency of the installations but also an oxygen and pH gradient within the same biofilm. This gradient will induce in contact with the material an anaerobic zone representing conditions conducive to the development of sulfato-reducing bacteria producing hydrogen and responsible for the meteoric microbial corrosions well known in the industrial environment.
- the control of deposits remains a problem if scale and corrosion phenomena are present in the cooling circuit.
- Chemical scale additives are also used which inhibit scaling. These are specific reagents, for example synthetic organic polymers in the form of polyacrylates or polyphosphonates. These chemical additives have drawbacks. Thus, when these chemical additives are of the polyphosphonate type, they increase the hardness of the water, therefore the concentration of the salts. In addition, these chemical additives are expensive. Agents used to delay precipitation are also used. Such agents are generally acids. However, when an acid is added, the hardness of the water is reduced, which increases the risk of corrosion.
- Another solution is to try to limit the calcium and magnesium concentration and to use a prior softening process for the make-up water.
- investments and maintenance of this type of device are important.
- the patent FR 2 697 827 proposes a method of descaling and protection against scaling of structures in contact with scaling water circulating in an open circuit.
- Application WO 85-03697 uses carbon dioxide for the recovery of oils in flotation cells.
- European patent EP 0 380 299 describes a method for reducing corrosion in a water supply system which consists in using carbon dioxide. However, this document in no way concerns the particular problem of cooling water circuits, and even less of semi-open cooling water circuits.
- the patent FR 2 570 393 relates to a process intended to eliminate encrustations in a closed water circuit, by introduction of carbon dioxide under pressure.
- These chemical additives can be polymers or copolymers of maleic acid, polyphosphonates, derivatives of phosphonic acid, derivatives of aminophosphonic acid, derivatives of polyacrylic acid and polymethacrylic acid, polyesters or polyphosphates.
- the disadvantage of this implementation is that these chemical additives are expensive and are gradually eliminated in the cooling tower. It is therefore necessary to add them regularly which increases the cost of their use.
- the aim of the present invention is to propose a simplified process for treating atmospheric cooling water circulating in a recirculation loop in a semi-open circuit and implementing the injection of C0 2 without the latter desorbing in the atmosphere and without adding chemical additives
- the dispersants and the mineral acids conventionally used generate mineral sludge by the salinity which they induce. Such an effect is in no way observed with carbon dioxide, which only releases soluble bicarbonate ions.
- the present invention therefore provides a method which makes it possible to reduce or even eliminate the various drawbacks of the methods of the prior art.
- the inventors have in fact shown that, by virtue of the addition of C0 2 at a point in a semi-open type water cooling circuit, it is possible to reduce the amounts of salts generated by the addition of inhibitor of tartar and mineral acids, which reduces the amount of make-up water while maintaining the same salt concentration rate.
- C0 2 lowers the pH by adding carbonic acid and the soluble bicarbonates capture the calcium and magnesium ions, which no longer precipitate and no longer serve as a nutrient for bacteria.
- C0 2 captures Ca 2+ ions from the tartar dissolved by the acid and prevents it from precipitating or being absorbed by the bacterial films.
- the invention relates to a process for treating atmospheric cooling water circulating in a recirculation loop in a semi-open circuit, comprising an atmospheric cooling device provided with means of natural or forced convection of atmospheric air, a purge device and a make-up water supply, into which carbon dioxide is introduced at at least one point of the recirculation loop or of the make-up water supply or of a derivative circuit provided on the loop or supply for the purpose of the introduction and in which no chemical additive to control tartar is introduced into the water.
- the C0 2 can be injected either on the cooling water recirculation loop or on the supply of make-up water or on a branched water circuit specially fitted to facilitate this introduction.
- carbon dioxide is introduced at the outlet of a water circulation pump, such as the pump of the recirculation loop or of the make-up water supply or of the derivative circuit. Good results have been obtained if carbon dioxide is introduced at a point in the process where the water has a pressure of at least 1 bar.
- Carbon dioxide can be introduced in liquid form or in gaseous form. It is also possible to use mixtures of carbon dioxide and an inert gas, for example nitrogen. Combustion fumes from a boiler are an example of such a mixture.
- carbon dioxide is advantageously used in substitution for the mineral acids conventionally used in the treatment of such a semi-open circuit, in particular in total substitution for H 2 S0 4 or HCl.
- a substitution makes it possible to decrease the pH of the water by releasing calcium ions, originating from the dissolution of the tartar.
- the addition of CO2 can thus be regulated by measuring the calcium hardness of the treated water.
- CO 2 can also be used in partial substitution or doping of a mineral acid, in particular in doping H 2 S0 4 or HCl.
- the C0 2 is advantageously injected in doses such that we get as close as possible to the conditions of carbon-carbon balance of water, that is to say say conditions such as to avoid precipitation of carbonates.
- a person skilled in the art may either subject the quantities of C0 2 injected to a water metering operation establishing a carbon-carbon balance of the water, or to a measurement of the pH of the water in regulating this pH to a set value close to the calco-carbonic equilibrium value, ie to a measurement of dissolved calcium ions.
- the method of the invention makes it possible to completely eliminate the use of the chemical scale-inhibiting additives conventionally used.
- the treatment of the invention applies to all cooling circuits of the semi-open type. As appears from the detailed description which follows, the treatment of the invention applies to all types of semi-open circuits containing an atmospheric refrigeration system. It also applies to circuits in which the cooling of the water within the cooling loop is ensured by an air heater exchanger.
- Figure 1 schematically shows a semi-open circuit for cooling water of a heat exchanger.
- FIG. 2 schematically represents a semi-open circuit for cooling water of a heat exchanger acting as atmospheric refrigerant.
- FIG. 3 given with reference to the example shows the evolution of the pH measured at the inlet and at the bottom of the cooling tower in a process according to the invention, in comparison with a control process not using the use of C0 2 .
- FIGS 1 and 2 schematically represent two types of semi-open cooling water circuit to which the invention applies in particular.
- FIG. 1 thus illustrates an example of a semi-open circuit for cooling water of a heat exchanger 1, in which a hot fluid enters
- the part not evaporated or entrained during circulation in the cooling tower is recovered at the lower outlet of the tower in a recovery tank 4.
- This tank is provided with a purging device represented by the arrow D and is connected to a make-up water supply represented by the arrow E.
- a pump 5 ensures the recirculation of the water collected in the tank 4 (cold water) to the heat exchanger.
- the cold water can also undergo an intermediate washing step in a derivative circuit shown in dotted lines (-) comprising a washing device 6 intended to remove the impurities due to the air, the water returning to the exchanger thermal by means of a pump 7.
- a derivative circuit shown in dotted lines (-) comprising a washing device 6 intended to remove the impurities due to the air, the water returning to the exchanger thermal by means of a pump 7.
- the C0 2 can be injected either on the loop at any point of the water loop or on the supply of make-up water. It is also possible to inject the C0 2 at a point in a derivative circuit specifically provided for this purpose.
- An example of such a circuit is represented by a broken line consisting of a succession of dashes and dots.
- the bypass is provided in this case at the recovery tank 4 located at the base of the cooling tower 2.
- Circulation in this bypass circuit is ensured by the pump 8.
- Examples of possible injection position are shown in the figure by the indication "C0 2 -".
- the C0 2 is preferably injected at the outlet of at least one of the pumps (5, 6 and / or 8) and in particular at the outlet of the water recovery pump from the tank to the heat exchanger.
- FIG. 2 represents a variant of the invention in which the heat exchanger to be cooled acts as an atmospheric refrigerant.
- the thermal gradient is reversed at the water level with respect to the system shown in Figure 1.
- the heat exchanger 1 provided with its hot fluid inlet A and its cold fluid outlet B is located inside the cooling tower 1.
- the cold water arrives according to arrow C at the upper part of the cooling tower 2 and ensures the cooling of the heat exchanger down to the base of said tower to be collected in the cover 4.
- the water during its circulation inside tower 2 in which air circulates by natural or forced convection is partially evaporated or entrained by the upper part of the cooling tower.
- the part not eliminated by evaporation and / or entrainment is recovered in the tank 4 provided, as in FIG. 1, with water make-up means E and purge means D.
- a pump 5 then ensures the recirculation of the water recovered in tarpaulin 4 towards the cooling tower.
- the process according to the invention therefore makes it possible, without increasing the salinity of the water circulating in the circuit, to decrease the importance of the purge and, consequently, to increase the concentration rate, which allows considerable savings to be made. and increased productivity.
- the invention applies to all types of semi-open type cooling water circuit.
- the evaporative condenser consists of a tower 2 inside which is installed the heat exchanger to be cooled which acts as atmospheric refrigerant in said tower.
- the exchanger has a power of 1,556,000 kcal, i.e.
- the make-up is 4.6 m3 / d.
- the water purge is 11.3 m3 / h.
- a comparative test in every point equivalent but not including an injection of C0 2 made it possible to show that the injection of C0 2 under the conditions of this test made it possible to triple the rate of maximum concentration of salts and to eliminate the scaling at the exchanger.
- the water purge goes to 5 m 3 / h.
- the water make-up is reduced by 50%. No redeposition of tartar is observed.
- the tartar present before the injection is dissolved and disappears (by purging).
- FIG. 3 gives the pH of the water at the bottom and at the top of the cooling tower, respectively in the case of the test according to the invention in the presence of C0 2 injected after the delivery pump and in the case of a control test.
- the pH at the top is maintained at the equilibrium value, while the pH at the bottom approaches the initial pH of the make-up water.
- a gradient is established during the exchange but the limitation of the desorption of C0 2 surprisingly avoids scaling even at the bottom of the column where the pH is the highest.
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Physical Water Treatments (AREA)
- Preventing Corrosion Or Incrustation Of Metals (AREA)
- Food Preservation Except Freezing, Refrigeration, And Drying (AREA)
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9914732A FR2801300B1 (fr) | 1999-11-23 | 1999-11-23 | Traitement au dioxyde de carbone des eaux de refroidissement atmospherique |
FR9914732 | 1999-11-23 | ||
PCT/FR2000/003252 WO2001038237A1 (fr) | 1999-11-23 | 2000-11-22 | Traitement au dioxyde de carbone des eaux de refroidissement atmospherique |
Publications (1)
Publication Number | Publication Date |
---|---|
EP1152985A1 true EP1152985A1 (fr) | 2001-11-14 |
Family
ID=9552444
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP00981459A Withdrawn EP1152985A1 (fr) | 1999-11-23 | 2000-11-22 | Traitement au dioxyde de carbone des eaux de refroidissement atmospherique |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP1152985A1 (fr) |
CA (1) | CA2360517C (fr) |
FR (1) | FR2801300B1 (fr) |
WO (1) | WO2001038237A1 (fr) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8153010B2 (en) * | 2009-01-12 | 2012-04-10 | American Air Liquide, Inc. | Method to inhibit scale formation in cooling circuits using carbon dioxide |
DE102013006504A1 (de) | 2013-04-16 | 2014-10-16 | Messer Group Gmbh | Verfahren zum Vermeiden von Ablagerungen in Kühlwasserkreisläufen |
NL2010885C2 (en) * | 2013-05-29 | 2014-12-02 | Stichting Dienst Landbouwkundi | Cooling water. |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3925523A (en) * | 1973-11-12 | 1975-12-09 | Marley Co | Opposed air path wet-dry cooling tower and method |
DE2638983A1 (de) * | 1976-08-30 | 1978-03-02 | Kurt Dipl Chem Dr Dannhaeuser | Verfahren und anordnung zur kuehlleistungsgesteuerten regelung der abflutwassermenge in wasser-rueckkuehlern |
US4444675A (en) * | 1981-07-16 | 1984-04-24 | Mechanical Equipment Company, Inc. | Alkaline scale abatement |
DE3135783A1 (de) * | 1981-09-10 | 1983-05-19 | Ekkehard Dipl.-Ing. 7302 Ostfildern Bretting | Kombinierter trocken- und nasskuehlturm |
US4547294A (en) * | 1982-02-18 | 1985-10-15 | Mechanical Equipment Company, Inc. | Alkaline scale abatement in cooling towers |
HUT39482A (en) * | 1984-09-19 | 1986-09-29 | Budapesti Mueszaki Egyetem | Process and equipment for acid-free elimination of scale |
JPH1128461A (ja) * | 1997-07-10 | 1999-02-02 | Kurita Water Ind Ltd | 水系の金属の腐食抑制方法 |
-
1999
- 1999-11-23 FR FR9914732A patent/FR2801300B1/fr not_active Expired - Lifetime
-
2000
- 2000-11-22 EP EP00981459A patent/EP1152985A1/fr not_active Withdrawn
- 2000-11-22 WO PCT/FR2000/003252 patent/WO2001038237A1/fr active Application Filing
- 2000-11-22 CA CA002360517A patent/CA2360517C/fr not_active Expired - Lifetime
Non-Patent Citations (1)
Title |
---|
See references of WO0138237A1 * |
Also Published As
Publication number | Publication date |
---|---|
WO2001038237A1 (fr) | 2001-05-31 |
CA2360517C (fr) | 2007-05-08 |
FR2801300B1 (fr) | 2001-12-28 |
CA2360517A1 (fr) | 2001-05-31 |
FR2801300A1 (fr) | 2001-05-25 |
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