Method and system for producing calcium bicarbonate starting from calcium carbonate of geological, chemical or biological origin and carbonic acid

Abstract

Method for producing calcium bicarbonate, comprising: mixing, by means of a mixer (101), water and calcium carbonate, thereby obtaining a first solution; providing a multiple scrubber (100) comprising: a cold steam scrubber (200), a shower scrubber (201), a plate scrubber (202) and a dehumidifier / fan (203); feeding, to the multiple scrubber (100), the first solution and a fluid comprising carbon dioxide; activating said multiple scrubber (100) to obtain a second solution comprising water, calcium bicarbonate and residues of calcium carbonate; obtaining, from said second solution, an aqueous solution of calcium bicarbonate. A system for producing calcium bicarbonate is also described.

Description

[0001] “METHOD AND SYSTEM FOR PRODUCI NG CALCI UM BI CARBONATE STARTI NG FROM CALCI UM CARBONATE OF GEOLOGI CAL, CHEMI CAL OR Bl OLOGI CAL ORI Gl N AND CARBONI C ACI □”

[0002] DESCRI PTI ON

[0003] Technical field

[0004] The present invention relates to a method for producing calcium bicarbonate starting from calcium carbonate and carbonic acid.

[0005] The present invention further relates to a system for producing calcium bicarbonate starting from calcium carbonate and carbonic acid.

[0006] Preferably, calcium carbonate is of geological, chemical or biological origin.

[0007] Preferably, carbonic acid is obtained from carbon dioxide that is present in air or in industrial emissions processed in a system equipped with one or more wet scrubbers.

[0008] Background of the invention

[0009] Usually, calcium for calcium bicarbonate production is obtained by using a soluble calcium salt such as, for example, calcium chloride or calcium nitrate, which is made to react with sodium bicarbonate or carbon dioxide. Calcium bicarbonate is normally a by-product of water desalination or industrial calcium carbide reclaiming.

[0010] Document CN 110 183 126 describes a method for preparing carbonate cementing material with limestone as raw material.

[0011] Document CN 109 516 487 describes a method for preparing calcium bicarbonate powder by using a solvent method.

[0012] Document WO 2022 / 229326 describes an apparatus and a method for producing purified calcium carbonate.

[0013] Summary of the invention

[0014] It is one object of the present invention to surpass the techniques currently available for producing calcium bicarbonate by proposing an alternative solution for the production of calcium bicarbonate which may suit many applications, e.g. in the food industry, and which proves particularly effective when used for sea water deacidification purposes.

[0015] It is a further object of the invention to provide a method and a system which can ensure an effective transformation of carbon dioxide, in compliance with emission reduction policies.

[0016] According to a first aspect, the invention concerns a method for producing calcium bicarbonate starting from calcium carbonate and carbonic acid.

[0017] Preferably, the method comprises mixing, by means of a mixer, water and calcium carbonate, thereby obtaining a first solution.

[0018] Preferably, the method comprises providing a multiple scrubber.

[0019] Preferably, the multiple scrubber comprises a cold steam scrubber.

[0020] Preferably, the multiple scrubber comprises a shower scrubber.

[0021] Preferably, the multiple scrubber comprises a plate scrubber.

[0022] Preferably, the multiple scrubber comprises a dehumidifier / fan.

[0023] Preferably, the method comprises feeding, to the multiple scrubber, the first solution and a fluid comprising carbon dioxide.

[0024] Preferably, the method comprises activating said multiple scrubber to obtain a second solution comprising water, calcium bicarbonate and residues of calcium carbonate.

[0025] Preferably, the method comprises obtaining, from said second solution, an aqueous solution of calcium bicarbonate.

[0026] According to a second aspect, the invention concerns a system for producing calcium bicarbonate starting from calcium carbonate and carbonic acid.

[0027] Preferably, the system comprises a mixer configured for mixing water and calcium carbonate, thereby obtaining a first solution.

[0028] Preferably, the system comprises a multiple scrubber.

[0029] Preferably, the multiple scrubber comprises a cold steam scrubber.

[0030] Preferably, the multiple scrubber comprises a shower scrubber. Preferably, the multiple scrubber comprises a plate scrubber.

[0031] Preferably, the multiple scrubber comprises a dehumidifier / fan.

[0032] Preferably, said multiple scrubber is configured for receiving said first solution from said mixer and a fluid containing carbon dioxide.

[0033] Preferably, said multiple scrubber is configured for outputting a second solution comprising water, calcium bicarbonate and residues of calcium carbonate.

[0034] Preferably, the system comprises a distribution tank configured for receiving said second solution.

[0035] Preferably, the system comprises a settler configured for obtaining, from said second solution, an aqueous solution of calcium bicarbonate.

[0036] In one or more of the above aspects, the invention may comprise one or more of the following preferred features.

[0037] Preferably, activating said multiple scrubber comprises activating said cold steam scrubber to obtain, from said fluid and said first solution, a liquid component, containing calcium bicarbonate, and a first fluid component.

[0038] Preferably, activating said multiple scrubber comprises activating said shower scrubber to obtain, from said first fluid component and said first solution, a liquid component, containing calcium bicarbonate, and a second fluid component.

[0039] Preferably, activating said multiple scrubber comprises activating said plate scrubber to obtain, from said second fluid component and said first solution, a liquid component, containing calcium bicarbonate, and a third fluid component.

[0040] Preferably, activating said multiple scrubber comprises activating said dehumidifier / fan to obtain, from said third fluid component and said first solution, a liquid component, containing calcium bicarbonate, and a fourth fluid component.

[0041] Preferably, the liquid component produced by said cold steam scrubber, shower scrubber, plate scrubber and dehumidifier / fan is collected and recirculated into the same cold steam scrubber, shower scrubber, plate scrubber and dehumidifier / fan.

[0042] Preferably, the liquid component is recirculated into said cold steam scrubber, shower scrubber, plate scrubber and dehumidifier / fan in addition or as an alternative to said first solution, in order to obtain a liquid component with a higher concentration of calcium bicarbonate.

[0043] Preferably, based on the concentration of calcium bicarbonate in the liquid component produced by said cold steam scrubber, shower scrubber, plate scrubber and dehumidifier / fan, it is envisaged to either continue to recirculate said liquid component into the multiple scrubber or output, from the multiple scrubber, said liquid component, which in this case constitutes said second solution.

[0044] Preferably, obtaining from said second solution an aqueous solution of calcium bicarbonate comprises feeding the second solution to the mixer, said mixer being inactive and containing water and calcium carbonate.

[0045] Preferably, obtaining from said second solution an aqueous solution of calcium bicarbonate comprises combining the second solution with the water and calcium carbonate that are present in the inactive mixer.

[0046] Preferably, obtaining from said second solution an aqueous solution of calcium bicarbonate comprises withdrawing the liquid part of said combination, said liquid part comprising water, calcium bicarbonate and residues of calcium carbonate.

[0047] Preferably, obtaining from said second solution an aqueous solution of calcium bicarbonate comprises feeding said liquid part to a settler.

[0048] Preferably, obtaining from said second solution an aqueous solution of calcium bicarbonate comprises leaving the residues of calcium carbonate to settle in said settler.

[0049] Preferably, obtaining from said second solution an aqueous solution of calcium bicarbonate comprises extracting from said settler the aqueous solution of water and calcium bicarbonate. Preferably, said cold steam scrubber is configured for obtaining, from said fluid and said first solution, a liquid component, containing calcium bicarbonate, and a first fluid component.

[0050] Preferably, said shower scrubber is configured for obtaining, from said first fluid component and said first solution, a liquid component, containing calcium bicarbonate, and a second fluid component.

[0051] Preferably, said plate scrubber is configured for obtaining, from said second fluid component and said first solution, a liquid component, containing calcium bicarbonate, and a third fluid component.

[0052] Preferably, said dehumidifier / fan is configured for obtaining, from said third fluid component and said first solution, a liquid component, containing calcium bicarbonate, and a fourth fluid component.

[0053] Preferably, said multiple scrubber comprises a collector / distributor configured for collecting the liquid component produced by said cold steam scrubber, shower scrubber, plate scrubber and dehumidifier / fan.

[0054] Preferably, said collector / distributor is configured for recirculating the liquid component produced by said cold steam scrubber, shower scrubber, plate scrubber and dehumidifier / fan into the same cold steam scrubber, shower scrubber, plate scrubber and dehumidifier / fan in addition or as an alternative to said first solution, in order to obtain a liquid component with a higher concentration of calcium bicarbonate.

[0055] Preferably, the system comprises a control unit configured to control said collector / distributor for: based on the concentration of calcium bicarbonate in the liquid component produced by said cold steam scrubber, shower scrubber, plate scrubber and dehumidifier / fan, either continuing to recirculate said liquid component into the multiple scrubber or outputting, from the multiple scrubber, said liquid component, which in this case constitutes said second solution.

[0056] Further features and advantages will become more apparent in the light of the following detailed description of a preferred, but non-limiting, embodiment of the invention. Such description is provided herein with reference to the annexed drawings, which are also supplied by way of nonlimiting example, wherein:

[0057] Figure 1 shows a block diagram of a system in accordance with the present invention;

[0058] Figure 2 shows a block diagram of a stage of the system of Figure 1.

[0059] In general, the invention is based on the use of calcium carbonate, which, in an aqueous solution with carbonic acid, is transformed into calcium bicarbonate, as shown in the following equations:

[0060] Preferably, the pH of the solution is controlled. In particular, the pH is maintained higher than or equal to 8 (pH>8); more particularly, it is maintained higher than or equal to 8 and lower than or equal to 10 (8< pH <10).

[0061] Calcium carbonate may be of geological origin (marble quarries, travertine quarries, etc.). In addition or as an alternative, chemically formed calcium carbonate may be used. A further option is calcium carbonate of biological origin (eggs, shells, etc.).

[0062] Preferably, the calcium carbonate size is less than 1mm. In particular, the smaller the granularity of calcium carbonate, the better it will mix with water, resulting in improved kinetics of reaction with carbonic acid.

[0063] In the case of calcium carbonate of biological origin, it is subjected to granularity reduction and treated to eliminate any microbiological species. This treatment can be carried out either thermally or by sterilization using an electromagnetic field with wavelengths in the microwave range, e.g. between 6mm and 300mm (6mm<A<300mm) and in the ultraviolet range, e.g. between lOnm and 500nm (10nm<A<500nm). Wavelengths are selected according to the origin / type of biological calcium carbonate.

[0064] Carbonic acid is produced by reaction of carbon dioxide and water. Carbon dioxide is obtained from air or from industrial emissions.

[0065] Figure 1 shows a block diagram of a system in accordance with the present invention, through which the above-described technique can be implemented.

[0066] The system 1 comprises a multiple scrubber 100, a mixer 101, a settler 102, and a distribution tank 103. There are also a number of oneway hydraulic pumps and a number of hydraulic valves for transferring the substances among the various components.

[0067] In the mixer 101, calcium carbonate is mixed with water. The mixture thus obtained is then fed to the multiple scrubber 100 through a hydraulic circuit, which preferably comprises a hydraulic pump 104a and a valve 105a.

[0068] The number of multiple scrubbers included in the system may be one or more, depending on the rate at which carbonic acid needs to be produced in order to obtain the desired quantities of calcium bicarbonate.

[0069] Another line of the hydraulic circuit, preferably comprising a hydraulic pump 104b and a valve 105b, connects the mixer 101 to the settler 102.

[0070] At the outlet of the settler 102 there is a hydraulic circuit, preferably comprising a pump 104c and a valve 105c, through which calcium bicarbonate in aqueous solution is collected. In the settler 102, the calcium bicarbonate in solution is separated from the precipitating substances (e.g. calcium carbonate).

[0071] In the multiple scrubber 100, processes occur wherein calcium carbonate is transformed into calcium bicarbonate. In order to circulate the aqueous solution, the multiple scrubber 100 is connected to the distribution tank 103. The connection between the multiple scrubber 100 and the distribution tank 103 is provided by a hydraulic circuit consisting of a first branch, comprising a pump 104d and a valve 105d, and a second branch, comprising a pump 104e and a valve 105e.

[0072] It should be noted that the connection between the multiple scrubber 100 (in particular, as will become apparent below, the collector / distributor 204 of the multiple scrubber 100) and the distribution tank 103 is a two- way connection: from the multiple scrubber 100 to the distribution tank 103 (pump 104d, valve 105d, this flow being indicated by arrow Fl in Figure 2) for discharging the aqueous solution rich in calcium bicarbonate, and from the distribution tank 103 to the multiple scrubber 100 (pump 104e, valve 105e, this flow being indicated by arrow F2 in Figure 2) for making any compensation in terms of pressure / quantity of solution to be processed.

[0073] The distribution tank 103 is connected to the mixer 101 by means of a hydraulic circuit, preferably comprising a pump 104f and a valve 105f, in order to feed the mixer 101 with the aqueous solution containing calcium bicarbonate supplied by the multiple scrubber.

[0074] The multiple scrubber 100 (so called because it performs "scrubbing", i.e. component separation, operations) is schematically represented in Figure 2.

[0075] The multiple scrubber 100 preferably comprises: a cold steam scrubber 200, a shower scrubber 201, a plate scrubber 202, a dehumidifier / fan 203, and a liquid solution collector / distributor 204.

[0076] The cold steam scrubber 200 transforms the incoming air into a fluid saturated with moisture; in practical terms, the cold steam scrubber 200 is a wet scrubber fitted with nebulizing nozzles producing substantially spherical droplets of liquid. The water droplets have a size in the range of [50nm - 5,000nm], e.g. approx. lOOnm. This operation starts the production of carbonic acid.

[0077] In more detail, the air taken into the system undergoes a first washing phase. Through the cold steam scrubber 200 (which may be considered as a Venturi scrubber, particularly a weak Venturi scrubber), the air is hit by a water jet and tends to mix with it, thereby generating a fluid. This operation results in a first pollutant reduction, since part of the pollutants are trapped in the liquid phase.

[0078] The number of cold steam scrubbers may be equal to or greater than 1, depending on the amount of carbonic acid required to maintain the desired calcium bicarbonate production rate.

[0079] The fluid exiting the cold steam scrubber 200 is then fed to the shower scrubber 201, where the ratio between fluid mass and solution mass is maintained. This maximizes the interaction between the fluid and the aqueous solution, and hence the transformation of calcium carbonate into calcium bicarbonate.

[0080] The Applicant observes that a shower scrubber is a tower scrubber in which the nozzles are arranged on one level only; such nozzles are so positioned as to spray the aqueous solution in aeraulic counterflow.

[0081] In more detail, the fluid exiting the cold steam scrubber flows into a large volume where it is hit by a water spray in countercurrent generated by said nebulizing nozzles, which are suitably distributed on a manifold. During this operation, water and fluid flow in countercurrent, i.e. the sprayers produce millimetric ellipsoidal droplets and micrometric spherical droplets directed downwards, while the aspirated fluid is drawn upwards.

[0082] As the pollutants in the fluid meet the droplets, the latter capture and carry the pollutants into a collection tank.

[0083] The fluid exiting the shower scrubber 201 is fed to the plate scrubber 202.

[0084] In the plate scrubber 202, smaller pollutants that, under the action of the shower scrubber 201, have not precipitated into the collection tank, undergo a further abatement process. The plate scrubber 202 comprises perforated plates so arranged, relative to the flow, as to generate variable crossing velocities therein. Here, as aforesaid, pollutants undergo an additional abatement process. In particular, the water used for capturing pollutants is circulated also on the surface of the perforated plates, thus generating a thin liquid film that promotes the capture of residual pollutants, while at the same time removing any residues from the surface. The configuration of this scrubber (number of plates, distance between the plates, etc.) can be changed as necessary to optimize its efficiency.

[0085] Preferably, the plates of the scrubber 202 are parallel to one another; such plates may be either equally or diversely spaced apart.

[0086] The plates are substantially perpendicular to the fluid flow.

[0087] The through holes of the plates may have different geometries (rectangular, square, circular, etc.) and different sizes.

[0088] By way of example, the plates may have an area of 0.1m2to 10m2, e.g. 0.2m2to 6m2.

[0089] By way of example, the holes may have an area of 3cm2to 500cm2.

[0090] In the plate scrubber 202, the fluid flow is not laminar, but turbulent. Advantageously, the plates of the plate scrubber 202 are coated with titanium oxide.

[0091] Due to the presence of suitably designed LEDs (emission wavelength ranging between 180nm and 600nm), a photocatalysis operation is carried out in order to improve the efficiency of the production process, wherein carbon dioxide is extracted from molecules containing carbon atoms, such as, for example, methane or hydrocarbons in general, which are species that can be found concentrated in the air, especially in industrial plants.

[0092] The fluid exiting the plate scrubber 202 is fed to the dehumidifier / fan 203 (the so-called "demister"), where the aqueous part of the fluid is extracted and the air is discharged into the environment surrounding the fan. The collector / distributor 204 receives the solution of water and calcium carbonate from the mixer 101 (arrow F3 in Figure 2), distributes it to the various stages of the multiple scrubber 100, and then delivers the solution again to the distribution tank 103 as a function of the concentration of the calcium bicarbonate solution. The arrows 206 represent the flow from the stages 200, 201, 202, 203 of the multiple scrubber 100 to the collector / distributor 204, whereas the arrows 207 represent the flow from the collector distributor 204 to the stages 200, 201, 202, 203 of the multiple scrubber 100.

[0093] In the block diagram of Figure 2, reference 205 denotes a fluid consisting substantially of air (input of the cold steam scrubber 200 and output of the dehumidifier / fan 203), whereas reference 208 denotes a fluid consisting of air and a substantial moisture component.

[0094] The process temperature of the liquid solution is comprised between the triple point temperature of water and the boiling temperatures of the solution; preferably, It is at ambient temperature.

[0095] The process temperature of the incoming air may range from ~50°C up to a temperature of 750°C.

[0096] The process pressure of the liquid solution is less than 15bar. For example, it may be approximately Ibar.

[0097] If the system 1 comprises more than one multiple scrubber, the collector / distributor 204 of each multiple scrubber will be connected to the distribution tank 103, which in this case will work as a "system tank" and will return to the mixer 101 the aqueous calcium bicarbonate solutions produced by each multiple scrubber.

[0098] The following will describe the process carried out by the system 1.

[0099] The process starts by feeding water and calcium carbonate to the mixer 101. By mechanical stirring, a solution of calcium carbonate in water is obtained.

[0100] The solution is then fed to the collector / distributor 204. The collector / distributor 204 feeds the solution to each component of the multiple scrubber (cold steam scrubber 200, shower scrubber 201, plate scrubber 202 and dehumidifier / fan 204). Each component executes its subprocess operations and returns to the collector / distributor 204 a solution containing also calcium bicarbonate.

[0101] When the calcium bicarbonate concentration reaches a predetermined threshold (an / or when the multiple scrubber 100 can no longer provide a significant increase in calcium bicarbonate concentration), the solution in the collector / distributor 204 is discharged into the distribution tank 103. From the latter, the solution is fed to the mixer 101. Note that, in the meantime (i.e. after the solution of water and calcium carbonate has been fed to the multiple scrubber 100 from the mixer 101), the mechanical stirring in the mixer has been interrupted; therefore, in the mixer there is now residual water and precipitated residual calcium carbonate. As aforesaid, the solution of water, calcium carbonate and calcium bicarbonate coming from the distribution tank 103 is supplied to the mixer 101 and there it combines with said residual water and calcium carbonate. The liquid component of the content of the mixer 101 is then fed to the settler 102.

[0102] It should be noted that the liquid component coming from the mixer 101 mostly contains, in addition to water, calcium bicarbonate. There are also some calcium carbonate residues, which are made to precipitate in the settler 102; it is thus possible, in the end, to remove the liquid part through the hydraulic circuit portion comprising the pump 104c and the valve 105c.

[0103] All the elements of the system 1 are controlled by a PLC and by software that manages the algorithm to ensure a correct production procedure. All the elements of the multiple scrubber 100 are controlled by a local PLC. The system PLC is connected to all of the multiple scrubbers included in the system. More generally, the system 1 is equipped with a control unit (which may be implemented by means of one or more PLCs), configured to control the operation of the various stages of the system 1 and of the various components of the multiple scrubber 100.

[0104] Within the multiple scrubber 100, the fluid dynamics is always turbulent.

[0105] In one embodiment, predetermined quantities of salts may be dissolved, if necessary, in the water used by the system. Such salts can perform a dual function: i) preventing system failures due to broken parts, under circumstances wherein ambient temperature may drop below 0 °C (or remain such for a long time); ii) improving the abatement of pollutants, facilitating their transformation into stable compounds which are not harmful for humans and for the environment.

[0106] The Applicant observes that all pollutants also affect the climate. The compounds belonging to the large family of VOCs (volatile organic compounds) have high steam pressure and low solubility in water. Many VOCs are chemical substances produced by humans, which are generated and used for the production of paints, pharmaceutical products and coolants. VOCs are typically industrial solvents, e.g. trichloroethylene; fuel oxygenates, e.g. methyl tert-butyl ether (MTBE); or by-products of chlorination for water purification, e.g. chloroform. VOCs are often components of oil-based fuels, hydraulic fluids, paint diluents and dry cleaning agents. VOCs are common contaminants of subterranean waters. By using the technology of the present invention, most VOCs in the air are transformed into CO2.

[0107] The stoichiometric oxidation of the hydrocarbon is described by the following equation: Considering the lightest hydrocarbon, i.e. methane (CH4), the reaction develops as follows:

[0108] As mentioned above, through the use of titanium dioxide photocatalysts and a UV-A electromagnetic field, hydrocarbons In crude oil can be transformed into H2O and CO2. Larger amounts of oxygen and UV radiation may further improve this degradation.

[0109] In addition to the above, the Applicant observes that the efficiency of the process improves as the electromagnetic field increases. For better efficiency, for example, materials may be used which are characterized by high electromagnetic field reflectance.

[0110] The CO2 in the air and the CO2 produced by the transformation of pollutants occurring during the above-described process are transformed into bicarbonate as a result of the process. By having carbonates react with carbonic acid produced from CO2 reacting with water, a stable transformation into environmentally-friendly compounds is attained.

[0111] For illustrative purposes, below we list again the characteristic equations of the process dynamics:

[0112] The following will describe some examples of implementation of the invention.

[0113] Example 1 Calcium carbonate can be obtained from marble slurry, which, instead of being sent to collection and disposal centres, can be transformed into calcium bicarbonate in accordance with the principles of the present invention.

[0114] Example 2

[0115] Calcium carbonate can be obtained from scraps of the frozen food industry, from mollusc shells, mussel shells, oyster shells and, in general, from any shellfish and Crustacea scraps, which, instead of being sent to collection and disposal centres, can be processed in accordance with the principles of the present invention to obtain calcium bicarbonate.

[0116] Example 3

[0117] Calcium carbonate can be obtained from scraps of the food industry, e.g. egg shells, which, instead of being sent to collection and disposal centres, can be processed in accordance with the principles of the present invention to obtain calcium bicarbonate.

[0118] Example 4

[0119] Calcium carbonate transformed into calcium bicarbonate can be used in a liquid reaction with sodium chloride, in order to produce a dietary supplement formed of sodium bicarbonate and calcium chloride, by exploiting the following reaction:

[0120] Experimental example

[0121] The Applicant has created a system with aeraulic capacity of l,000m3 / h, which has been placed in an industrial environment with CO2 concentrations of [400ppm-430ppm] and PM10 particulate matter concentrations of [140pg-150pg]. The system has been adjusted to give a CO2 transformation yield of 5,4% and a PM10 particulate matter absorption yield of 90%.

[0122] The system uses 120 litres of water, in which calcium carbonate is mixed, and where CO2 is transformed into carbonic acid, which then reacts with calcium carbonate with the above-defined efficiency, thereby forming calcium bicarbonate.

[0123] 2.5kg of calcium carbonate are used every 24 hours, transforming 1kg of CO2 and obtaining 4kg of calcium bicarbonate. These components are given in 120 litres of aqueous solution.

[0124] The Applicant observes that the above data have been measured and validated by the National Research Council - Institute of Bioeconomy (CNR- IBE, Consiglio Nazionale delle Ricerche - Istituto per la BioEconomia), using monitoring systems owned by CNR.

[0125] Transformation efficiency can be further increased by modifying the system's working point, e.g. by changing the pH of the aqueous solution, the calcium carbonate concentration, and the system's aeraulic capacity.

[0126] As to the pH value, it is necessary to work within the interval [pH7- pHll], with pH values preferably equal to approximately 11.

[0127] As to calcium carbonate concentration, it is advisable to work within the interval [0.01g / l - 100g / l], with a concentration preferably equal to approximately 20g / l.

[0128] Calcium carbonate granulometry is preferably less than 100pm, in particular less than or equal to 20pm.

[0129] The system's aeraulic capacity is in the range of [500m3 / h - 150,000m3 / h], preferably approximately 50,000m3 / h.

[0130] Calcium bicarbonate exists in aqueous solution only, but its solubility in water is 105 times higher than that of calcium carbonate.

[0131] The solution that is left to settle will have a solid deposit of calcium carbonate, and the liquid part will only contain calcium bicarbonate with carbonate contamination of the order of lOppm.

[0132] In the above-described example, approximately 4kg of calcium bicarbonate are produced per day; assuming that air-borne particle materials (carbon, iron and silicon particles) will not deposit together with calcium carbonate, but remain all in solution, the produced calcium bicarbonate will have a purity of at least 99.92%. If necessary for food use, this bicarbonate can be further purified by using the same magnetic method employed for purifying the calcium carbonate raw material, which was contaminated by metals during production process. The aqueous solution is made to circulate on the surface of electromagnets.

[0133] Further observations about the state of the art

[0134] The Applicant believes it to be appropriate to highlight that the invention described herein shows some significant differences from the current state of the art, and particularly from the above-mentioned document CN 110 183 126.

[0135] Document CN 110 183 126 describes a method that uses a pressurized reactor where, for a reaction time of 30 minutes to 3 hours, an aqueous solution is reacted with limestone (calcium carbonate, magnesium carbonate, calcium sulphate, silica, alumina, etc.) and carbon dioxide under high pressure, ranging between Ibar and 15bar, to give calcium bicarbonate as an intermediate product; the latter is then mixed with other components for cement production. Document CN 110 183 126 mentions calcium oxide (CaO) as being massively present in amounts of at least 48% of the limestone; therefore, the most dense element in the process is calcium oxide. The latter is produced by means of a calcium carbonate calcination process: heating calcium carbonate to high temperature gives calcium oxide and carbon dioxide. De facto, the process described in CN 110 183 126 does not absorb carbon dioxide; as a whole, in fact, it generates carbon dioxide.

[0136] On the contrary, the technology described and claimed herein operates continuously over time at atmospheric pressure, and the CO2 which is transformed with calcium carbonate is present in the ambient air that is fed into the system. Therefore, the method and the system claimed herein are carbon negative in that they need CO2 to produce calcium bicarbonate.

Claims

CLAH yS1. Method for producing calcium bicarbonate, comprising: mixing, by means of a mixer (101), water and calcium carbonate, thereby obtaining a first solution; providing a multiple scrubber (100), comprising: a cold steam scrubber (200), a shower scrubber (201), a plate scrubber (202) and a dehumidifler / fan (203); feeding, to the multiple scrubber (100), the first solution and a fluid comprising carbon dioxide; activating said multiple scrubber (100) to obtain a second solution comprising water, calcium bicarbonate and residues of calcium carbonate; obtaining, from said second solution, an aqueous solution of calcium bicarbonate.

2. Method according to claim 1, wherein activating said multiple scrubber (100) comprises: activating said cold steam scrubber (200) to obtain, from said fluid and said first solution, a liquid component, containing calcium bicarbonate, and a first fluid component; activating said shower scrubber (201) to obtain, from said first fluid component and said first solution, a liquid component, containing calcium bicarbonate, and a second fluid component; activating said plate scrubber (202) to obtain, from said second fluid component and said first solution, a liquid component, containing calcium bicarbonate, and a third fluid component; activating said dehumidifier / fan (203) to obtain, from said third fluid component and said first solution, a liquid component, containing calcium bicarbonate, and a fourth fluid component.

3. Method according to claim 2, comprising collecting the liquid component produced by said cold steam scrubber (200), shower scrubber (201), plate scrubber (202) and dehumidifier / fan (203), and recirculating it into the same cold steam scrubber (200), shower scrubber (201), plate scrubber (202) and dehumidifier / fan (203) in addition or as an alternative to said first solution, in order to obtain a liquid component with a higher concentration of calcium bicarbonate.

4. Method according to claim 3, comprising: based on the concentration of calcium bicarbonate in the liquid component produced by said cold steam scrubber (200), shower scrubber (201), plate scrubber (202) and dehumidifier / fan (203), either continuing to recirculate said liquid component into the multiple scrubber (100) or outputting, from the multiple scrubber (100), said liquid component, which in this case constitutes said second solution.

5. Method according to any one of the preceding claims, wherein obtaining from said second solution an aqueous solution of calcium bicarbonate comprises: feeding the second solution to the mixer (101), said mixer being inactive and containing water and calcium carbonate; combining the second solution with the water and the calcium carbonate that are present in the inactive mixer (101); withdrawing the liquid part of said combination, said liquid part comprising water, calcium bicarbonate and residues of calcium carbonate; feeding said liquid part to a settler (102); leaving the residues of calcium carbonate to settle in said settler (102); extracting from said settler the aqueous solution of water and calcium bicarbonate.

6. System for producing calcium bicarbonate, comprising: a mixer (101), configured for mixing water and calcium carbonate, thereby obtaining a first solution; a multiple scrubber (100), comprising a cold steam scrubber (200), a shower scrubber (201), a plate scrubber (202) and a dehumidifier / fan (203); said multiple scrubber (100) being configured for receiving said first solution from said mixer (101) and a fluid containing carbon dioxide, and for outputting a second solution comprising water, calcium bicarbonate and residues of calcium carbonate; a distribution tank (103), configured for receiving said second solution; a settler (102), configured for obtaining, from said second solution, an aqueous solution of calcium bicarbonate,7. System according to claim 6, wherein: said cold steam scrubber (200) is configured for obtaining, from said fluid and said first solution, a liquid component, containing calcium bicarbonate, and a first fluid component; said shower scrubber (201) is configured for obtaining, from said first fluid component and said first solution, a liquid component, containing calcium bicarbonate, and a second fluid component; said plate scrubber (202) is configured for obtaining, from said second fluid component and said first solution, a liquid component, containing calcium bicarbonate, and a third fluid component; said dehumidifier / fan (203) is configured for obtaining, from said third fluid component and said first solution, a liquid component, containing calcium bicarbonate, and a fourth fluid component.

8. System according to claim 7, wherein said multiple scrubber (100) further comprises a collector / distributor (204) configured for collecting the liquid component produced by said cold steam scrubber(200), shower scrubber (201), plate scrubber (202) and dehumidifier / fan (203), and for recirculating it into the same cold steam scrubber (200), shower scrubber (201), plate scrubber (202) and dehumidifier / fan (203) in addition or as an alternative to said first solution, in order to obtain a liquid component with a higher concentration of calcium bicarbonate.

9. System according to claim 8, comprising a control unit configured to control said collector / distributor (204) for: based on the concentration of calcium bicarbonate in the liquid component produced by said cold steam scrubber (200), shower scrubber(201), plate scrubber (202) and dehumidifier / fan (203), either continuing to recirculate said liquid component into the multiple scrubber (100) or outputting, from the multiple scrubber (100), said liquid component, which in this case constitutes said second solution.

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