Patent Application
20240407368
The invention relates to a chemical composition, a method for manufacturing hypochlorous acid for obtaining said chemical composition and an installation to perform said method.
Chemical compositions comprising active chlorine can be used as biocides, for example, in the treatment of water. This is a very dynamic field, as microorganisms are constantly evolving, hence, biocides are also constantly being improved.
It is known that active chlorine can be formed in aqueous solution by the electrolysis of sodium chloride. As the sodium chloride used has impurities or contaminants such as metals, the solution obtained will not be very pure. This will affect the quality of the biocide.
An object of the present invention is a method for the manufacturing of hypochlorous acid, starting from sodium hypochlorite or potassic hypochlorite of synthesis. These hypochlorites usually include some amounts of chlorites and chlorates, and the method according to the invention includes some reactions that allow the transformation of these chlorites and chlorates, obtaining, as a beneficial by-product, a certain amount of chlorine dioxide. Therefore, the chemical composition obtained from the method according to the invention also includes a certain amount of chlorine dioxide (always less than hypochlorous acid). Other impurities, such as carbonates (particularly Na2CO3) are also broken down, and in addition, as the starting materials include less sodium chloride, fewer impurities or contaminants such as metals commonly present in sodium chloride are also avoided and the total chloride content in the composition is low. Therefore, the composition obtained with the present invention is much more pure.
So, it is another object of the invention to provide a chemical composition that enhances biocide properties. This purpose is achieved by a chemical composition of the type indicated at the beginning, characterized in that it is an aqueous solution comprising a concentration of hypochlorous acid of from 0.00005 to 0.6% w/w, a concentration of chlorine dioxide of from 0.00001 to 0.5% w/w and a pH comprised between 4.5 and 7.5, where a ratio of ClO2 with respect to HClO is comprised between 0.05:1 and 0.5:1 in w/w. The main advantage of this biocidal product is that it contains 2 disinfectant biocides: HClO (as the main component) and ClO2 within the same chemical solution. Therefore, the product has better disinfectant properties due to the action of the two biocides simultaneously and to the correct proportions in which they are manufactured. In addition, impurities such as chlorites, chlorates and carbonates (present in the reagents for manufacture of the composition) are very low or non existent.
In the present description and claims, the expression “total chlorine” refers to the total free chlorine found as HClO and ClO−.
The invention further includes a number of preferred features that are object of the dependent claims and the utility of which will be highlighted hereinafter in the detailed description of an embodiment of the invention.
Preferably, said pH is comprised between 5 and 7.5, more preferably said pH is comprised between 5.2 and 6.7, and even more preferably it is comprised between 5.3 and 6.2. Within this pH ranges, an optimal concentration of HClO, CIO and ClO2 is obtained. Moreover, these pH ranges ensure that the chemical composition is stable.
Preferably, said concentration of hypochlorous acid is in the range of from 0.002 to 0.4% w/w, and said concentration of chlorine dioxide is in the range of from 0.0002 to 0.3% w/w. More preferably, said concentration of hypochlorous acid is in the range of from 0.01 to 0.2% w/w, and said concentration of chlorine dioxide is in the range of from 0.001 to 0.03% w/w.
Preferably said chemical composition further comprises a concentration of sodium chloride (NaCl) of less than 1.5% w/w and, more preferably less than 1% w/w. As NaCl is not more added to the chemical composition, the chemical composition presents less impurities and metals. This allows to differentiate this chemical composition from the ones placed in the market, as the ones placed in the market are formed using NaCl and, therefore, have a higher content of NaCl, impurities and metals. In particular, if decalcified and osmotized water (preferably having a conductivity of less than 60 μS/cm) is used in the manufacturing of the composition, then the resulting composition can have a concentration of sodium chloride of less than 1% w/w. Alternatively, preferably said chemical composition presents a ratio of NaCl with respect of HClO that is below 4:1 in w/w, more preferably below 3:1 in w/w.
Preferably, said chemical composition presents a ratio of carbonate ion with respect of HClO that is below 0.06:1 in w/w, more preferably below 0.01:1 in w/w and, most preferably below 0.006:1 in w/w. The reduction of the content of carbonate ion improves the stability of the composition.
Preferably, said chemical composition presents a ratio of chlorite ion with respect of HClO that is below 0.01:1 in w/w, more preferably below 0.006:1 in w/w and, most preferably below 0.002:1 in w/w.
Preferably, said chemical composition presents a ratio of chlorate ion with respect of HClO that is below 0.02:1 in w/w, more preferably below 0.015:1 in w/w and, most preferably below 0.01:1 in w/w.
Preferably, said chemical composition presents a ratio of ClO2 with respect to HClO comprised between 0.1:1 and 0.2:1 in w/w. More preferably, said ratio is comprised between 0.11:1 and 0.16:1 in w/w. These are the ranges that have been found to be optimal for the chemical composition to act as a double biocide.
Preferably, said chemical composition presents a conductivity, k, expressed in μS/cm, according to the following formula k=(4.75×C)±100%, wherein C is the concentration of HClO and ClO−, expressed in ppm, expressed in ppm. More preferably, said conductivity, k, is k=(4.75×C)±50%. The conductivity of the chemical composition can be used as a parameter to compare and differentiate this chemical composition from other chemical compositions placed in the market. This is possible because the conductivity is closely related to the concentration of the chemical compounds found in the chemical composition.
It is another object of the invention to provide a manufacturing method to manufacture hypochlorous acid for obtaining said chemical composition. This purpose is achieved by a manufacturing method of the type indicated at the beginning, in an installation that comprises a first reactor (RNK), a basic reactor (RBK) and an acid reactor (RAK), characterized in that it comprises the following steps:
This manufacturing method ensures that the manufacturing process is carried out under a controlled environment.
Reactions that take place:
Transformation of hypochlorite to hypochlorous acid:
2NaClO2+NaOCl+2HCl=2ClO2+3NaCl+H2O (pH 2-5)
4ClO2−+2H+→Cl−+2ClO2+ClO3+H2O (PH<2)
Transformation of Chlorates into Chlorine Dioxide:
As can be seen, the objective of the method is to manufacture hypochlorous acid and the starting reactants are hypochlorite (sodium or potassic hypochlorite) and a strong acid (hydrochloric acid or H2SO4). The chlorites and chlorates are not added on purpose, but they are inevitable impurities in industrial grade hypochlorites produced by the degradation of hypochlorite itself (for example, according to Spanish norm UNE-EN 901). An advantage of the present method is that these impurities are eliminated, and another advantage is that chlorine dioxide is obtained as a beneficious by-product.
The total chlorine control unit allows to fix a total chlorine set point that is well below a limit in which gaseous Cl2 could be generated (at about 5000 ppm). It is possible to work with basic compositions whose exact composition is not known (relative content of hypochlorite/chlorite/chlorate) as chlorites and chlorates are transformed into chlorine dioxide.
Preferably, the basic composition of step iv comprises a least 1% w/w of hypochlorite ion, preferably at least 5% w/w of hypochlorite ion and, more preferably at least 10% w/w of hypochlorite ion.
Preferably, in the basic composition of step iv the combined concentration of sodium or potassium chlorate and/or sodium or potassium chlorite is less than 18% w/w, preferably less than 10% and, more preferably less than 5% w/w.
Preferably, in the basic composition of step iv the concentration of sodium carbonate is less than 2% w/w.
Preferably, said installation further comprises a refrigeration unit, where said aqueous solution of said first reactor is refrigerated and sent back to the first reactor. This way, it is possible to control the temperature at which the manufacturing process is performed.
More preferably, said refrigerated aqueous solution is sent back to said first reactor at least partially through said basic reactor. Therefore, the aqueous solution entering the basic reactor is at a desired temperature, allowing the reaction to happen in a controlled environment.
Even more preferably, said refrigerated aqueous solution is sent back to said first reactor at least partially through said acid reactor. Therefore, the aqueous solution entering the acid reactor is at a desired temperature, allowing the reaction to happen in a controlled environment.
In a further preferred solution, the measuring of the total chlorine of step ix is done in the refrigerated aqueous solution.
Preferably, said salt of said basic composition is sodium hypochlorite.
Preferably, said acid compound of said acid composition is hydrochloric acid, as hydrochloric acid is easier to manipulate.
Preferably, said water is pre-treated water with less than 60 μS/cm. This allows to reduce the consumption of acid.
Preferably, the method comprises adjusting a second pH control unit to a desired second pH set point, measuring the pH level of the mixed solution of step vi, and controlling an addition of the acid composition of step v based on the measuring of the pH level of the mixed solution and on the second pH set point.
Preferably, said method is performed at a temperature comprised between 5 and 35° C. More preferably, said method is performed at a temperature comprised between 15 and 23° C. This temperature range has been found to be the optimal one to perform the manufacturing method, as the chemical composition will degrade slower and will be more stable.
It is another object of the invention to provide an installation to perform the manufacturing method for manufacturing said chemical compound. This purpose is achieved by an installation of the type indicated at the beginning, characterized in that it comprises:
The installation described allows the chemical composition to be manufactured in a controlled environment.
Preferably, said installation further comprises a refrigeration unit with one refrigeration unit inlet in fluid communication with said first reactor and one refrigeration unit outlet in fluid communication with said acid reactor aqueous solution inlet and with said basic reactor aqueous solution inlet. Therefore, this creates a closed loop system to refrigerate the aqueous solution.
Preferably, said installation further comprises a temperature sensor. More preferably, said temperature sensor is connected to said refrigeration unit. When the temperature sensor detects a temperature above or below a threshold value, the refrigeration unit acts accordingly to adjust the temperature of the aqueous solution to the desired value.
Preferably, said installation further comprises a water treatment unit to treat the water with which the manufacturing process will be carried out. Ideally, as previously said, the water will be treated to have less than 60 μS/cm.
Preferably, said acid reactor and said basic reactor are at least partially placed within said first reactor. Therefore, said acid reactor and basic reactor are surrounded by the same temperature.
Preferably, said installation further comprises an oxidation-reduction potential sensor to detect whether the chemical reactions take place under the desired oxidation level.
Preferably, said installation further comprises a chlorine gas sensor to detect if chlorine gas is being released.
Preferably, said installation further comprises a fan unit in fluid communication with said chlorine gas sensor and with an active carbon filter. Therefore, it can air the first reactor towards the chlorine gas sensor.
More preferably, said installation further comprises a water shower in connection with said chlorine gas sensor. So, when a chlorine gas value above a set threshold is detected, the water shower is activated.
Preferably, said installation further comprises a stirring element arranged within said first reactor. This ensure the aqueous solution to be mixed.
Preferably, said installation further comprises a flow meter and conductivity sensor to control the amount of water being administered to the first tank and that said water has the desired quality.
Preferably, said installation further comprises a first level probe to detect whether the aqueous solution within said first reactor exceeds a threshold value and a second level probe to detect the minimum amount of water needed to start performing the chemical reaction.
Likewise, the invention also includes other features of detail illustrated in the detailed description of an embodiment of the invention and in the accompanying figures.
Further advantages and features of the invention will become apparent from the following description, in which, without any limiting character, preferred embodiments of the invention are disclosed, with reference to the accompanying drawings in which:
An installation according to a first embodiment of the invention can be seen in
In one hand, the acid reactor RAK comprises:
In the other hand, the basic reactor RBK comprises:
In order to control the parameters of the chemical reaction and make sure that the chemical reaction takes place under optimal and safe conditions, the installation also comprises:
As explained in this first embodiment, the acid compound of the acid composition is hydrochloric acid. However, the acid compound could also be H2SO4. And the basic composition is an aqueous solution that comprises a salt, which is sodium hypochlorite, and a sodium chlorate. Nevertheless, the salt could also be potassium hypochlorite, and the sodium chlorate could be replaced by any of the following: potassium chlorate, potassium chlorite or sodium chlorite.
In this first embodiment, the manufacturing process starts treating water in the water treatment unit 34. When the conductivity sensor detects that the water has less than 60 μS/cm, the water is delivered to the first reactor RNK. The amount of water delivered can be adjusted according to the flow meter parameters. The first reactor RNK is filled up to a minimum level. When the second level probe detects that this minimum level has been reach, the chemical reaction can start.
Water contained in the first reactor RNK is then sent to the refrigeration unit 26, so its temperature can be adjusted to around 23° C. After that, the water is sent to both the acid reactor RAK and the basic reactor RBK, forming therefore a closed loop refrigeration system. As it will be explained hereinafter, it is only at the very first step of the manufacturing process that the first reactor only contains treated water, since when chemical reactions take place, this treated water is mixed with chemical compounds and will, therefore, turn out to be an aqueous solution with chemical compounds. Indeed, the final chemical composition will be contained in the first reactor RNK.
Two chemical reactions take place at the same time: one in the acid reactor RAK and another in the basic reactor RBK.
In one hand the refrigerated water enters the acid reactor RAK through the acid reactor aqueous solution inlet 14. In parallel, the acid pump BA pumps hydrochloric acid from the acid compound deposit 8 to the acid inlet 12 of the acid reactor RAK. This hydrochloric acid is then mixed in the acid reactor RAK with the refrigerated water, so as to form a first acid solution.
In the other hand, the refrigerated water also enters the basic reactor RBK through the basic reactor aqueous solution inlet 20. In parallel, the basic pump BB pumps a basic composition, which is an aqueous solution that comprises sodium hypochlorite and sodium chlorate, from the basic compound deposit 6 to the basic inlet 18 of the basic reactor RBK. This basic composition is then mixed in the basic reactor RBK with the refrigerated water, so as to form a first basic solution. Once the first basic solution has been formed, it is sent to the acid reactor RAK, downstream of the acid reactor inlets 12, 14 so it can be mixed with the first acid solution. Therefore, a mixed solution is obtained. Then, this mixed solution is discharged to the first reactor RNK and is mixed with the treated water that was initially delivered to the first reactor RNK. When the treated water and the mixed solution are mixed, an aqueous solution is obtained. This aqueous solution will then be delivered again to the refrigeration unit 26. In fact, it is a continuous process, so the chemical composition of this aqueous solution is constantly changing until the desired chemical composition is achieved.
As previously explained, the pH control unit 4 regulates the pH of the aqueous solution contained in the first reactor RNK by governing the acid pump BA. This is, the pH of the aqueous solution will be adjusted by adding more or less hydrochloric acid.
Similarly, the total chlorine control unit 2 regulates the total chlorine of the aqueous solution contained in the first reactor RNK by governing the basic pump BB. This is, the total chlorine found in the aqueous solution is adjusted by adding more or less basic composition.
It is worth mentioning that by performing the manufacturing process just described, a chemical composition comprising HClO and ClO2 is obtained. This is important because nowadays, HClO and ClO2 are manufactured following different manufacturing processes and using different compounds.
The following table shows the chemical composition of a chemical composition obtained by the manufacturing process previously explained:
As previously mentioned, total chlorine, in this case refers to chlorine free found in the form of HClO and ClO−.
The following table shows the conductivity of different chemical compositions, with different HClO contents, obtained through the manufacturing method previously explained, for a pH of 5,5:
A water treatment installation for drinking water of a small city, used sodium hypochlorite as a source of active Cl. The incoming water was quite acidic (pH 5.8) and the use of sodium hypochlorite had the additional advantage of moving the pH to 6. But, as it is usually the case, the sodium hypochlorite did contain certain amounts of chlorate, and the treated water had an excess of chlorates: when adding 2 ppm of sodium hypochlorite in the incoming water (in order to have less than 1 ppm of active CI in the treated water) the treated water had also over 0.25 ppm of chlorates (limit value fixed by the European Directive (UE) 2020/2184 of the European Parliament and of the Council of 16 Dec. 2020 on the quality of water intended for human consumption).
Using the new method and an installation according to the invention, the hypochlorite is transformed into high quality hypochlorous acid, with a small amount of chloride dioxide and without chlorites and chlorates.
The method is done in an installation according to the invention. The first reactor RNK has a capacity of 500 L and has an acid reactor RAK and a basic reactor RBK in its interior. The basic reactor outlet 22 is in fluid communication with the acid reactor RAK, downstream of the inlets 12, 14 of the acid reactor RAK. And the acid reactor outlet 16 is in fluid communication with the first reactor RNK. The whole installation is controlled by a control means that receives the signals of the sensors (total chlorine, pHs, oxidation-reduction potential, flows, etc.) and adjusts the pumps according to these signals. In fact, this control means incudes the control tasks of the total chlorine control unit 2, the pH control unit 4 and other control units that may be present in the installation. A total chlorine set point of, for example, 500 ppm, and a pH set point of 7.5 are introduced. The control means control the addition of the basic composition (i.e., the sodium hypochlorite) so that the amount of hypochlorous acid reaches the established set point. Additionally, the control means controls the addition of a second basic composition (which, in general, preferably is diluted NaOH) until the pH set point is reached. In the present example the incoming water is quite acidic and, therefore, it is necessary to add a certain amount of the second basic composition. In other cases, it may be necessary to add more acid (instead of the second basic composition) in order to reach the pH set point. In this latter scenario, the control means will allow that a greater quantity of the acid composition is added.
The first step is to fill the first reactor with 400 L of decalcified, osmotized water that, in the present case, is slightly acidic (pH 5.8). The basic composition is concentrated sodium hypochlorite (11% w/w, pH>12) and in the basic reactor RBK the basic composition is diluted with the recirculating water from the first reactor and the basic reaction takes place. The acid composition is hydrochloric acid (33% w/w, pH<1) and in the acid reactor RAK the acid composition is diluted with the recirculating water from the first reactor. The first basic solution and the first acid solution are mixed in the acid reactor RAK forming the so-called mixed solution. In this point it is convenient that the pH is very acidic (preferably <1). Therefore, in general, a preferred embodiment of the invention includes a second pH control unit that controls the pH of the mixed solution. In these acidic conditions the chlorates (and chlorites) are eliminated almost entirely. The gaseous Cl2 is hydrolysed obtaining hypochlorous acid.
The installation comprises a refrigeration unit and the refrigerated aqueous solution had a temperature of 15° C.
With the method and installation of the present invention, in order to get 402 L of composition with 500 ppm of hypochlorous acid at a pH of 5.5 it is necessary 1.48 L of hypochlorite (11% w/w) and about 0.5 L of hydrochloric acid (33% w/w). The quantity of chlorine dioxide present in the composition will depend on the quantity of chlorates (and chlorites) present in the basic composition. In the present example, the composition had 98 ppm pf chlorine dioxide, the chlorites were totally eliminated and the chlorates were mainly eliminated. Additionally, 60 ppm of sodium carbonate present in the basic composition were also eliminated.
The manufacturing ratio was 1 ppm HClO: 0.2 ppm ClO2, without chlorites or chlorates, ideal to be dosed without having problems with the formation of trihalomethanes or other unwanted compounds and to have a high disinfecting power for all the following organisms: Yeasts, fungi, viruses, bacteriophages, spores, algae, bacteria, encapsulated bacteria that are difficult to eliminate (type legionella) and biofilm elimination.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21382841.1 | Sep 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/075802 | 9/16/2022 | WO |
