Apparatus for accelerated mineralization of carbon dioxide with by-products of industrial processing and related process

Abstract

The present invention concerns an apparatus (10) for the mineralization of carbon dioxide in the forms of solid carbonates of a precursor material comprising at least one material capable of reacting with carbon dioxide in molecular or dissociated form, the apparatus comprising at least one containment tank (11) configured to operate at internal pressures up to at least 6 bar and comprising a head portion (12) placed above and a bottom portion (17) placed below, the containment tank (11) comprising at least one loading mouth (18,19) for loading a precursor material or a water suspension (50) of the precursor material; and at least one inlet (16a,16b) for gas injection; a mechanical stirring device (13) arranged and configured to act inside the containment tank (11) near the bottom portion (17) thereof; and a homogenization device (14) arranged at the bottom portion (17) of the containment tank (11).

Description

[0001] APPARATUS FOR ACCELERATED MINERALIZATION OF CARBON DIOXIDE WITH BY-PRODUCTS OF INDUSTRIAL PROCESSING AND RELATED PROCESS

[0002] TECHNICAL FIELD

[0003] The present invention relates to an apparatus for the accelerated mineralization of carbon dioxide with by-products (slag) of industrial processes and a related process to achieve it.

[0004] In particular, the apparatus of the invention allows to create a new industrial process for obtaining the mineralization of carbon dioxide, hereinafter also CO2, in the forms of solid carbonates of a precursor material comprising at least one material capable of reacting with carbon dioxide in molecular or dissociated form, such as for example at least one of alkali metals, alkaline earth metals and transition metals and, possibly, carbonated synthetic carbonate materials, using a methodology which effectively accelerates the mineralization reaction thereof, avoiding the phenomenon of passivation inside the reactor.

[0005] The aforesaid process relates to the activation of said by-products (slag) of industrial processing (henceforth referred to as “precursors” for convenience) and the mineralization of carbon dioxide by means of the reaction with the aforementioned precursors.

[0006] The materials obtainable from the process which is the subject matter of the invention are essentially mineral powders of carbonates of alkaline elements, alkaline earth and / or transition metals and, possibly, carbonated synthetic carbonate materials, derived from the substantially superficial carbonation of said industrial processing slag (precursors), and the aforesaid treated precursors having pozzolanic characteristics.

[0007] What are known as the treated precursors can be not carbonated, because they have not reacted with the CO2, or they can be only partially carbonated due to the residual CO2 still present in the wastewater, for recovery, which could react further with the precursor.

[0008] STATE OF THE ART

[0009] Carbonation technologies allow the achievement of two important objectives: the reduction of CO2, SO2 and NO2 greenhouse gases, and the practical utilization of the large amounts of special industrial waste with alkaline chemistry present throughout the world (steel mill slag, water treatment sludge, alumina red sludge, incineration slag, alkaline fly ash, and so on).

[0010] Carbonation is the crystallization process of carbonates by means of injected CO2. The technology behind carbonation has been studied more and more intensively because of the need to meet the demands to remove as much CO2 from the planet's atmosphere as possible, through what is known as Carbon Capture Storage (CCS). Among the CCS techniques, CO2 mineralization is undoubtedly the most adequate and least invasive. This is essentially for two reasons: because it produces materials which can be used immediately, the proceeds of which make these technologies more cost-effective, and because the CO2 stored remains permanently fixed.

[0011] From a quantitative point of view, we can make a prediction of the effects of carbonation on emissions. For example, take the case of a gas-fired power plant of the most modern type (e.g., Armaroli and Po, 2003). A 780 MW gas-fired power plant produces 2 Mt of CO2, 2700 t of NO2, 1500 t SO2, 1350 t of CO, 3200 t of hydrocarbons and benzene and 620 t of particulate matter annually. To break down such contents, at least 4 million tonnes of reagent are needed, which could consist of steel slag (in Italy about 6 Mt of slag from steel and cast iron production and 2 Mt of red alumina sludge per year).

[0012] Of these materials, about 3 million tonnes become carbonates, to be used as raw material in the preparation of lime and dolomite for the steel and cement industry, and 1 million tonnes of aluminium silicates and iron oxides. The latter part of spent reagents can easily be reintroduced into pozzolanic cement production cycles, with great advantages for the environment.

[0013] The carbonation is usually carried out using a source of CO2 (rarely air, more often compressed CO2), blown into aqueous solutions where alkaline ions or solids exchanging alkaline ions are present. There are diverse methods for obtaining carbonation and we can arbitrarily divide them into two categories:

[0014] Carbonation in solution, known as “ex situ"

[0015] Carbonation in solution, known as “zn situ"

[0016] The first group of processes (“ex situ" is among those most frequently used. They involve the use of aqueous solutions where CO2 is injected pressurized and where the substances to be carbonated are present, either in solid or dissolved form. The ex situ technologies involve carbonation on minerals taken from their deposit, brought to a special plant, enriched and activated there (mechanically or thermally) and subjected to a carbonation reaction in reactors under pressure at controlled temperatures. For example, in the work of O'Connor et al. (2000) presented at the 2000 International Conference on Coal Utilization in Albany (OR, USA), described a technology that adopts serpentinite and olivine residues as precursors for carbon dioxide absorption. The idea was to use such materials to absorb the 10,000 tonnes of CO2 emitted per day by a 500 MW coal-fired power plant. The process which requires crushing and granulating the ore with relative size sorting (only granules smaller than 5 mm in average diameter) has a yield of about 83%.

[0017] From the above, it is clear that handling and processing thousands of tonnes of ore per day is only possible in sites where there is already a large amount of disused material, e.g., a mining dump. In such a condition, the CO2 cannot be pumped and maintained under supercritical conditions, which is a condition which can only be achieved in a closed, pressurized vessel, or at the moment of contact between the solution and the gas in input. This is why mention is made of the second group of processes (“zw situ").

[0018] The idea is, therefore, to create a dense network of air ducts within the mining dump, introduce a solution of water and sodium chloride and pump high-pressure CO2 into the ducts, so as to promote the mobility of the solution in the interstices between the ore granules. From this point of view, the technique is simple and economical: there is no preliminary grinding or conditioning, nor any handling of the ore. This involves bringing CCh from large users (e.g., steel mills, thermal power plants and cement kilns), at the outlet pressure of the flue gases (spent gases), directly to the landfill through a suitable pipeline, then pumping such fluid in a controlled manner into the basin and then activating the carbonation. The problem in this case is the reaction time, which can be considerably long.

[0019] In US 2010 / 141013 Al, a process and apparatus for sequestering CO2 in a waste gas within freshly crushed oligocene serpentine rock particles is described, using a specific apparatus to crush the rock up to obtaining small fragments in a pressurized gas atmosphere. The process selects the small fragments of crushed rock and, after absorbing the CO2, covers them with a cement coating for use as building material components. The apparatus comprises some parts which are only formally similar to those in the present patent application, however, its operation is completely different, its running costs are considerably high and it does not suggest how to effectively answer the technical problem described below.

[0020] EP 4 005 995 Al describes a process for transforming fly ash derived from combustion into starting materials for obtaining industrial products. The process comprises, inter alia, the injection of CO2 under pressure from 3 to 15 bar.

[0021] In DE 10 2008 039171 Al, a process and apparatus for separating CO2 from flue and exhaust gases is described. The process uses different types of reactions to capture the CO2 and thus, even if some of the reactor's constituent parts seem similar to those in the present patent application, their purpose and operation is overall completely different, thus not describing the characteristics thereof.

[0022] For all these reasons, there is a particular need to have an optimal reactor for the carbonation process and a related process which can provide high mineralization yields, recycling of produced wastewater and ease of use, as well as significant savings in the overall operating costs.

[0023] The main problems inherent in mineralization processes comprise, for example: the problem of precursor passivation; the insufficiently high rate of mineralization; the management of the concretionary masses formed in the reactors.

[0024] The first problem arises from the fact that the precursor granules, placed inside a liquid batch, tend to react from the surface of the granule inwards. Once a certain depth is reached, the exchange of the ions forming the carbonate compounds ceases with the outside, whereby the mineralization process stops. To attempt to overcome these drawbacks, attempts are made to reduce the size of the granules as much as possible through preliminary grinding processes, but this significantly increases the cost of the process.

[0025] The second problem depends on the solubility of CO2 at ambient pressure in water. The phenomenon of CO2 mineralization essentially occurs upon the contact between the CO2 molecules and the surface of the precursor mineral; thereby, water plays a fundamental role, both in removing the reactive cations from the mineral and in allowing the carbonate formation reaction to occur. On the other hand, a low solubility of cations (e.g., Ca2+and Mg2+) and a low solubility of CO2 in water do not allow a high reaction rate. To give an example, consider a solubility of calcium hydroxide of 1.7 g / 1 (20 mM / 1) and CO2 equal to 1.48 g / 1 (38 mM / 1). Thus, forming one mole of CaCOs (PM = 100.09 g / M) requires 44 1 of mineralized water with Ca(OH)2 and 26 1 of water with dissolved CO2, respectively. In essence, one cubic metre of water would produce 14.3 kg of CaCCh, forming the dissolutions of 74 kg of calcium hydroxide and 44 kg of carbon dioxide. The yield in terms of water and time is thus extremely low.

[0026] The third problem concerns the inevitable formation of static concretionary masses inside the reactors, which create, in the long run, enormous problems for plant management, blocking valves and pipes.

[0027] OBJECTS AND SUMMARY OF THE INVENTION

[0028] It is the object of the present invention to overcome the drawbacks of the prior art. In particular, an object of the present invention is to make a new apparatus for the mineralization of carbon dioxide preferably in the forms of solid carbonates of alkali metals, alkaline earth and transition metals, and possibly of carbonated synthetic carbonate materials.

[0029] A further object of the present invention is to make available a process for the mineralization of carbon dioxide in the forms of solid carbonates of alkali metals, alkaline earth and transition metals, and possibly of carbonated synthetic carbonate materials.

[0030] A further object of the present invention is to provide a process for the mineralization of carbon dioxide in the forms of solid carbonates of alkali metals, alkaline earth and transition metals, and possibly of carbonated synthetic carbonate materials, with the recycling of the reaction water.

[0031] A further object of the present invention is to provide a process by which carbonates can also be obtained from the treatment of hazardous waste, such as “fly ash” from municipal waste incineration, from which useful industrial products such as pozzolan can also be extracted.

[0032] A further object of the present invention is to have a process which allows to obtain processed precursors which can be used as raw materials in production cycles such as, but not limited to, the production of cements, concretes, building materials or road substrates.

[0033] Not least object of the present invention is to provide a process for the permanent storage of carbon dioxide that allows to reduce or remove - depending on the origin of the carbon dioxide - the climate-altering gases, permanently fixing the carbon dioxide in the carbonates that are formed during the process for mineralization. In fact, consider that the typical thermal decomposition of magnesium carbonates takes place from 350 °C and that of calcium carbonates takes place from 600 °C.

[0034] These and other objects of the present invention are achieved by a system incorporating the features of the annexed claims, which form an integral part of the present description.

[0035] To meet the purposes of the present invention, the precursor material of the process of the invention comprises, in general terms, at least one material capable of reacting with carbon dioxide in molecular or dissociated form, such as, for example, at least one of alkali metals, alkaline earth metals and transition metals and, possibly, carbonated synthetic carbonate materials, and preferably has the following characteristics: be a composition enriched in alkali with high reactivity in water at basic pH; have a controlled particle size, possibly less than 1 mm; be available in large amounts.

[0036] Furthermore, the precursor can, by way of example, be waste / slag such as steel mill slag, basic industrial sludge from civil and industrial wastewater, from paper mills, from alumina, zinc and titanium dioxide treatment processes (red sludge), and fly ash from incineration. Preferably, the precursor can additionally comprise an additive to make the reaction process with CO2 more efficient. By way of example, in the case of fly ash, the precursor is preferably additivated with sodium hydroxide (NaOH) to efficiently capture the CO2 in the reaction with calcium sulphate. By way of further example, the precursor is preferably additivated with sodium carbonate (NfeCCh) and / or sodium bicarbonate (NaHCCh) to efficiently capture CO2 in the reaction with calcium sulfate.

[0037] Such materials have very large volumetries, particle sizes often below 10 microns, and an extremely high alkali content. Of course, these materials also include mining waste, e.g., serpentine waste, iron and manganese mine waste, phosphoritic waste deposits, and the like.

[0038] In general terms, within the scope of the present description and in the claims appended with “material capable of reacting with carbon dioxide” it is intended to indicate at least one calcium- or magnesium-based compound, such as at least one of a calcium oxide, a calcium hydroxide, a calcium hydroxyl chloride, a calcium silicate, a calcium aluminate, a calcium silicoaluminate, a magnesium oxide, a magnesium hydroxide, a magnesium hydroxyl chloride, a magnesium silicate, a magnesium aluminate and a magnesium silicoaluminate.

[0039] In the context of the present description and in the appended claims, “carbon dioxide in molecular or dissociated form” is intended to mean carbon dioxide in gaseous form or in the form of salt dissolved in water.

[0040] According to a first aspect thereof, the present invention relates to an apparatus for the mineralization of carbon dioxide in the forms of solid carbonates of a precursor material comprising at least one material capable of reacting with carbon dioxide in molecular or dissociated form, the apparatus comprising at least: a containment tank comprising a head portion placed above and a bottom portion placed below, the containment tank comprising

[0041] - at least one loading mouth for loading a precursor material or a water suspension of the precursor material; and

[0042] - at least one inlet for gas injection; a mechanical stirring device arranged and configured to act inside the containment tank near the bottom portion thereof, wherein the mechanical stirring device is controlled through a control rod; and a homogenization device arranged at the bottom portion of the containment tank, wherein the homogenization device is controlled through a control shaft, wherein the control rod is operable independently of the control shaft.

[0043] Advantageously, the provision in the apparatus for the mineralization of carbon dioxide according to the invention of a mechanical stirring device and a homogenization device that are operable independently of each other, allows a multiplicity of operating regimes to be implemented according to the specific process needs. For example, it is possible to carry out cavitation cycles that are added discontinuously to the stirring activity, such as, among other things, at the time when the carbon dioxide is flushed. In this way, the material is prevented from being excessively stressed by the action of the homogenization device, concentrating it only at the moment when a reaction with carbon dioxide can actually take place.

[0044] Alternatively, the independent activation of the homogenization device with respect to the mechanical stirring device allows to achieve a homogenization action driven also through devices other than a sonotrode.

[0045] The integration of the homogenization device into the containment tank in turn entails considerable savings in terms of process times and in energy terms, eliminating the need to provide for dedicated infrastructure and apparatuses for the recirculation of the process liquid through an external cavitation and / or homogenization device.

[0046] A second aspect of the present invention is directed to a process for the mineralization of carbon dioxide in the forms of solid carbonates of a precursor material comprising at least one material capable of reacting with carbon dioxide in molecular or dissociated form, such as, for example, comprising the steps consisting of: a) loading a process liquid comprising a water suspension of the precursor material into a containment tank through at least one loading mouth; b) injecting into the containment tank a gaseous stream containing, or consisting of, CO2 until a process pressure is reached; c) stirring the process liquid using a mechanical stirring device at least partially immersed in it; and d) transferring energy to the process liquid through a homogenization device arranged at a bottom portion of the containment tank and operable independently of the mechanical stirring device until a desired pH value is obtained in the process liquid.

[0047] Within the scope of the present description and in the appended claims, the term “desired pH value” is intended to indicate an input value selected according to the specific process needs. By way of example, the desired pH value may be comprised between 10 and 6, or preferably, between 9 and 7.

[0048] Suitably, the process for the mineralization of carbon dioxide achieves the same advantages discussed above with reference to the apparatus for the mineralization of carbon dioxide according to the invention.

[0049] A third aspect of the present invention is directed to a process for the permanent storage of carbon dioxide comprising the steps of:

[0050] - making available a precursor material comprising at least one material capable of reacting with carbon dioxide in molecular or dissociated form;

[0051] - mixing the precursor material with water to generate a solution of water and precursor material;

[0052] - injecting the solution of water and precursor material into an apparatus for the mineralization of carbon dioxide in the forms of solid carbonates; and

[0053] - performing a process for the mineralization of carbon dioxide in the forms of solid carbonates as described above.

[0054] The proposed invention is therefore also configured as an effective process for the permanent storage of CO2. The amount of CO2 that is permanently fixed depends on the chemical characteristics of the precursor, with values ranging from 5% to over 20% by weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Further features, objects and advantages of the present invention will become clearer from the detailed description which follows made with reference to the attached figures. It is in any case to be noted that there is no intention to limit the invention to the specific embodiment illustrated in said figures, rather on the contrary, the invention intends covering all the modifications, alternative and equivalent constructions and variants which fall within the scope of the invention as defined in the attached claims.

[0056] Figure 1 schematically depicts a first preferred embodiment of an apparatus for the accelerated mineralization of carbon dioxide according to the present invention; and

[0057] Figure 2 is a flowchart illustrating the process for the accelerated carbon dioxide mineralization according to the present invention.

[0058] DETAILED DESCRIPTION OF THE INVENTION

[0059] Unless otherwise defined, all the terms of the art, notations and other scientific terms used herein are intended to have the meanings commonly understood by those skilled in the art to which this description belongs. In some cases, terms with commonly understood meanings are defined herein for clarity’s sake and / or ready reference; the insertion of such definitions in the present description must therefore not be interpreted as representative of a substantial difference with respect to what is generally understood in the art.

[0060] The terms “comprising”, “having”, “including” and “containing” are to be understood as open terms (i.e. the meaning “comprising, but not limited to”) and are to be considered as a support also for terms such as “essentially consist of’, “essentially consisting of’, “to consist of’ or “consisting of’.

[0061] The use of “for example”, “etc.”, “or” indicates non-exclusive alternatives without limitation, unless otherwise indicated. The use of “comprises” and “includes” means “comprises or includes, but not limited to”, unless otherwise indicated.

[0062] With regard to the detailed description of the invention with particular reference to the appended figures, they schematically depict the preferred equipment and process scheme(s) of the present invention, albeit in a non-limiting manner for the person skilled in the art, respectively, as described below.

[0063] With particular reference to Figure 1, an apparatus for the accelerated mineralization of carbon dioxide according to the present invention is shown, overall indicated with 10, hereinafter also only “apparatus for the mineralization”.

[0064] The apparatus for the mineralization 10 comprises a containment tank 11 comprising a head portion 12 placed above and a bottom portion 17 placed below with respect to an operating configuration of the apparatus 10. The containment tank 11 may have a flat, conical, elliptical, semi-circular or inclined bottom portion.

[0065] The containment tank 11 is provided with a first loading mouth 18 for loading a precursor material or a precursor-water suspension 50 therein and, preferably, with a second loading mouth 19 for the possible addition of water. In the illustrated embodiment, the first loading mouth 18 comprises an opening and closing door. In alternative embodiments (not illustrated), the first loading mouth 18 is configured to be connected to a piping system for feeding the precursor material or a precursor-water suspension 50.

[0066] Both the first 18 and the second 19 loading mouth are preferably placed near the head portion 12 of the containment tank 11, preferably at the head portion 12.

[0067] The apparatus for the mineralization 10 also comprises a mechanical stirring device 13 acting inside the containment tank 11. In the illustrated embodiment, the mechanical stirring device 13 is constrained to the head portion 12 of the containment tank 11 and acts by immersion in the precursor- water suspension. For example, the mechanical stirring device 13 is a rod mixer. In particular, the mechanical stirring device 13 is connected to the head portion 12 of the containment tank 11 through a rod 13a rotatably controlled by a first rotary actuator 13b.

[0068] Within the scope of the present description and in the appended claims with “mechanical stirring device” it is intended to indicate a device comprising a rotating termination configured to set in motion the fluid in which it is immersed, in the substantial absence of shear stresses sufficient to reduce the size of the solid suspensions or of the gas bubbles comprised in the fluid.

[0069] In the illustrated embodiment, the head portion 12 of the containment tank 11 comprises a cover that can be constrained to a corresponding upper opening of the containment tank 11 in such a way as to seal it in a watertight manner. By way of example, the cover 12 is of the flanged type. In this embodiment the mechanical stirring device 13 is constrained to the cover.

[0070] The apparatus for the mineralization 10 still comprises a homogenization device 14 placed at the bottom 17 of the containment tank 11. The homogenization device 14 is for example a vertical stirrer, a mixer, a turbo-mixer, a rotor-stator homogenizer, an emulsifier, a cavitator, an ultrasonic sonicator or other equivalent homogenization devices.

[0071] Within the scope of the present description and in the appended claims with “homogenization device” it is intended to indicate a device comprising a rotating termination configured to generate shear stresses sufficient to reduce the size of the solid suspensions or gas bubbles comprised in a fluid so as to obtain a substantially homogeneous mixture from a chemical point of view, i.e. having substantially the same composition in space.

[0072] The homogenization device 14 is connected to the bottom 17 of the containment tank 11 through a shaft 14a, preferably rotatably controlled through a second rotary actuator 14b. Preferably, the control rod 13a of the mechanical stirring device 13 and the control shaft 14a of the homogenization device 14 are distinct and / or independent elements, so as to be able to transfer to the mechanical stirring device 13 a rotation speed which is distinct from the rotation speed transferred to the homogenization device 14. Similarly, the first and second rotary actuators 13b, 14b are independent actuators, so as to impart to the control rod 13a of the mechanical stirring device 13 a rotation speed distinct from the rotation speed imparted to the control shaft 14a of the homogenization device 14.

[0073] The containment tank 11 internally has a plurality of fins 15 which extend along the internal wall of the tank 11 between the head portion 12 and the bottom portion 17 according to a substantially vertical development. The fins 15 have an extension suitable for acting as breakwaters, preventing the fluid moved by the mechanical stirring device 13 from being induced to rise along the internal walls of the containment tank 11.

[0074] The containment tank 11 comprises at least one inlet 16a, 16b for gas injection, preferably at least two inlets 16a, 16b for gas injection.

[0075] At least one first inlet 16a for gas injection is placed near or at the head portion 12 of the containment tank 11, such as at a distance hi from the head portion 12 which is less than or equal to one third of a vertical extension H of the containment tank 11 which develops between the bottom portion 17 and the head portion 12 (hi < 1 / 3H), preferably at a distance hi from the head portion 12 which is less than or equal to a quarter of a vertical extent H of the containment tank

[0076] 11 which develops between the bottom portion 17 and the head portion 12 (hi < 1 / 4H), more preferably at a distance hi from the head portion 12 which is less than or equal to a fifth of a vertical extent H of the containment tank 11 which develops between the 17 and the head portion

[0077] 12 (hi < 1 / 5H).

[0078] For example, the first inlet 16a for gas injection is placed substantially at the height of the first loading mouth 18 and / or of the second loading mouth 19. Alternatively, the first inlet 16a for gas injection is placed on the cover of the head portion 12.

[0079] In this way, with reference to the normal operating conditions of the apparatus for the mineralization 10, it is ensured that the first inlet 16a is always above the level of the content of the containment tank 11, allowing gas to be injected into the free part of the containment tank 11.

[0080] At least one second inlet 16b for gas injection is placed near the bottom portion 17 of the containment tank 11, such as at a distance I12 from the bottom portion 17 which is less than or equal to one third of a vertical extension H of the containment tank 11 which develops between the bottom portion 17 and the head portion 12 (I12 < 1 / 3H), preferably at a distance hi from the bottom portion 17 which is less than or equal to a quarter of a vertical extension H of the containment tank 11 which develops between the bottom portion 17 and the head portion 12 (I12 < 1 / 4H), more preferably at a distance I12 from the bottom portion 17 which is less than or equal to a fifth of a vertical extension H of the containment tank 11 which develops between the bottom portion 17 and the head portion 12 (h2 < 1 / 5H).

[0081] In this way, with reference to the normal operating conditions of the apparatus for the mineralization 10, it is ensured that the second inlet 16b is below the level of the content of the containment tank 11, allowing gas to be injected directly into the fluid present inside the containment tank 11.

[0082] According to a variant of the invention, the containment tank 11 is configured to operate at pressures up to at least 6 bar, preferably up to at least 8 bar, more preferably up to at least 10 bar. By way of example, the containment tank 11 has a wall thickness of at least 3 mm and is made of an austenitic (amagnetic) stainless steel alloy composed of a low carbon content (~ 0.05%) and a higher content of chromium (16-18%), nickel (11-14%) and molybdenum (2-3%), such as for example the alloy AISI 316 or Inox 18-8-3 or X5CrNiMol7-12-2 or DIN 1.4401. Alternatively, or in addition, the containment tank 11 has a wall thickness of at least 3 mm and is made of an amagnetic austenitic stainless steel, composed of a low carbon content (about 0.05%), a content of chromium between 18% and 20% and of nickel between 8% and 11%, such as for example AISI 304 or Inox 18-10 or X5CrNil8-10 or DIN 1.4301 alloy. Or still, the containment tank 11 has a wall thickness of at least 3 mm and is made of super duplex steel and / or equivalent materials.

[0083] Advantageously, having provided in the apparatus for the mineralization of carbon dioxide to work in a pressurizable containment tank allows to store greater amounts of CO2 and, consequently, to maximize the dissolution of the same and its reaction in the process liquid. This makes it possible to operate efficiently even with a homogenization device integrated inside the tank, despite the fact that the geometry of the tank is not optimised for cavitation and / or homogenization.

[0084] A gas discharge valve 20 is also provided to rebalance the internal pressure, preferably placed on the head portion 12 of the containment tank 11. The first loading mouth 18 is also configured to counteract pressures up to at least 6 bar, preferably up to at least 8 bar, more preferably up to at least 10 bar.

[0085] The containment tank further comprises at least one measuring device 21 necessary for operating the process control, such as a pH measuring device, a gas pressure measuring device, a temperature measuring device and / or an inlet water flow measuring device. The at least one measuring device is connected to a control unit (not illustrated) in turn connected to at least one regulating device, such as flow regulating devices for regulating the gas flow and / or the liquid flow in input to and / or in output from the containment tank 11.

[0086] There is also provided a device for regulating the inlet water flow (not illustrated) which drives a valve (not illustrated) present upstream of the second loading mouth 19. Finally, the containment tank 11 comprises a discharge opening 22 placed at the bottom portion 17 and configured to discharge the reaction materials. Preferably, the discharge opening 22 is controlled by a valve (not illustrated).

[0087] The discharge opening 22 may be connected to a separator device (not illustrated) configured to separate the solid portion of the flow of reaction materials from its aqueous portion. The latter is sent to storage, disposal or recycling by re-injecting it in the containment tank 11. The separator device may be, for example, but not limited to, selected from a hydro-cyclone separator and / or a settler and / or a flotation chamber and / or a bag and / or a tank and / or a drainage belt and / or a centrifuge and / or a filter press and / or a tubular press.

[0088] The process 100 implemented by the apparatus 10 for the mineralization of carbon dioxide according to the present invention is as follows.

[0089] The containment tank 11 is previously filled (step 110) with process liquid usually comprising a solution of water and precursor material through the first loading mouth 18. If necessary, more water is additivated to reach the desired liquid / solid ratio through the second loading mouth 19. The concentration of the precursor material in the water is on average comprised from 0.5% to 50% w:w (i.e., by weightweight), more preferably from 1% to 25% w:w.

[0090] Through the first 16a or the second 16b inlet, a gaseous stream containing, or consisting of, CO2 is injected (step 120) into the containment tank 11 until a process pressure is reached, usually comprised between 0 and 10 bar, preferably comprised between 0 and 8 bar, more preferably comprised between 0 and 6 bar.

[0091] The gas injected into the containment tank 11 can consist of an artificial mixture of air and carbon dioxide (in which the concentration of carbon dioxide can vary from 1% to 100%), or (exhaust) fumes, containing carbon dioxide in a concentration of at least 1%, deriving, for example, from industrial processes. For example, the gas injected into the containment tank 11 can be compressed air, pure CO2 or a mixture of the two components in any mutual ratio. It may also be a mixture of CO2 and other gas species, such as, for example, methane or the like. Preferably, the gas injected into the containment vessel 11 is a gas mixture comprising at least 60% CO2, preferably at least 70% CO2, even more preferably at least 80% CO2, up to a gas substantially consisting of pure CO2 .

[0092] The process liquid is then placed under stirring (step 130), activating the mechanical stirring device 13. The mechanical stirring device 13 has the function of keeping the suspension stirred and, at the same time, directing the precursor material towards the homogenization device 14.

[0093] The homogenization device 14 is then activated (step 140), possibly simultaneously with the stirring device 13. In particular, the stirring device 13 is activated by rotating the control rod 13a, specifically of the illustrated embodiment, through the first rotary actuator 13b. Similarly, the homogenization device 14 is activated by rotating the control shaft 14a, specifically of the illustrated embodiment, through the second rotary actuator 14b. In particular, the control rod 13a is rotated at a first rotational speed which is greater than a second rotational speed at which the control shaft 14a is rotated. By way of example, the second rotational speed is at least one order of magnitude greater than the first rotational speed, such as, for example, the first rotational speed is comprised between 50-100 rpm, while the second rotational speed is comprised between 1000 - 5000 rpm.

[0094] The homogenization device 14 has the function of transferring energy to the solution with the aim of maximizing the solubilization of the CO2 and, at the same time, reducing the size of the suspended precursor material particles. This phenomenon increases the reactivity of the precursor material, as the breaking of the particles exposes new reactive surface. In addition, finer particles typically prove more reactive.

[0095] In particular, the energy transfer takes place through the cavitation phenomenon: the homogenization device 14 generates cavitation bubbles that by imploding transfer thermal energy locally to the solution, causing a local increase in pressure and temperature.

[0096] During the process activity, the pressure inside the containment tank 11 tends to decrease by virtue of the mineralization of CO2 in the precursor material. Therefore, if the process pressure is greater than atmospheric pressure, when the gas pressure measuring device detects (step 150) a reduction in the process pressure, it sends (step 160) a corresponding signal to the control unit, which in turn activates (step 170) the injection of another gas comprising CO2 in order to bring the pressure back to the desired process pressure value and maintain a substantially constant process pressure value over time.

[0097] The process for the accelerated mineralization of carbon dioxide also provides for cyclic sub-steps of measuring a plurality of control parameters on the basis of which to determine whether the conclusion of the process has been achieved, including for example the pH value of the solution, the reaction time and the pressure inside the chamber.

[0098] For example, the process for the accelerated mineralization of carbon dioxide is continued until obtaining, in the solution contained in the containment tank 11 , a preset pH value, for example comprised between 10 and 6, more preferably, between 9 and 7, after which it is proceeded with separating the residual solid part from the liquid one.

[0099] In any case, the process for the mineralization of carbon dioxide is terminated once a pre- established reaction time has been reached or if the pressure inside the chamber exceeds a preset threshold value.

[0100] At the end of the process for the mineralization of carbon dioxide, the pressure inside the containment tank 11 is rebalanced by acting on the gas discharge valve 20 to bring it back to the value of the process pressure.

[0101] Such a process for the mineralization of carbon dioxide may for example be part of a larger carbon dioxide permanent storage process which involves the preventive steps of making available a precursor material comprising at least one material capable of reacting with carbon dioxide in molecular or dissociated form, and mixing the precursor material with water to generate a solution of water and precursor material.

[0102] The solution is therefore injected into the apparatus 10 for the mineralization of carbon dioxide in the forms of solid carbonates, in particular into its containment tank 11 and subsequently the process 100 for the mineralization of carbon dioxide in the forms of solid carbonates described above is performed.

[0103] [1] An apparatus (10) for the mineralization of carbon dioxide in the forms of solid carbonates of a precursor material comprising at least one material capable of reacting with carbon dioxide in molecular or dissociated form, the apparatus comprising at least: a containment tank (11) comprising a head portion (12) placed above and a bottom portion (17) placed below, the containment tank (11) comprising

[0104] - at least one loading mouth (18,19) for loading a precursor material or a water suspension (50) of the precursor material; and

[0105] - at least one inlet (16a, 16b) for gas injection; a mechanical stirring device (13) arranged and configured to act inside the containment tank (11) near the bottom portion (17) thereof; and a homogenization device (14) arranged at the bottom portion (17) of the containment tank (11).

[0106] [2] An apparatus (10) according to what is described in the previous point [1], wherein the at least one inlet (16a, 16b) for gas injection comprises a first inlet (16a) for gas injection placed near the head portion (12) of the containment tank (11) and / or a second inlet (16b) for gas injection placed near the bottom portion (17) of the containment tank (11).

[0107] [3] An apparatus (10) according to what is described in the previous points from [1] and [2], wherein the at least one inlet (16a, 16b) for gas injection comprises a first inlet (16a) for gas injection placed at a distance (hi) from the head portion (12) which is less than or equal to one third of a vertical extension (H) of the containment tank (11) which develops between the bottom portion (17) and the head portion (12), preferably at a distance (hi) from the head portion (12) which is less than or equal to a quarter of a vertical extension (H) of the containment tank (11) which develops between the bottom portion (17) and the head portion (12), more preferably at a distance (hi) from the head portion (12) which is less than or equal to a fifth of a vertical extension (H) of the containment tank (11) which develops between the bottom portion (17) and the head portion (12).

[0108] [4] An apparatus (10) according to what is described in the previous points from [1] to [3], wherein the at least one inlet (16a, 16b) for gas injection comprises a second inlet (16b) for gas injection placed at a distance (I12) from the bottom portion (17) which is less than or equal to one third of a vertical extension (H) of the containment tank (11) which develops between the bottom portion (17) and the head portion (12), preferably at a distance (hi) from the bottom portion (17) which is less than or equal to a quarter of a vertical extension (H) of the containment tank (11) which develops between the bottom portion (17) and the head portion (12), more preferably at a distance (I12) from the bottom portion (17) which is less than or equal to a fifth of a vertical extension (H) of the containment tank (11) which develops between the bottom portion (17) and the head portion (12).

[0109] [5] An apparatus (10) according to what is described in the previous points, wherein the mechanical stirring device (13) is constrained to the head portion (12) of the containment tank (11) in such a way as to act by immersion in the water suspension (50) of the precursor material comprised in the containment tank (11).

[0110] [6] An apparatus (10) according to what is described in the previous points, wherein the homogenization device (14) is selected from the group consisting of:

[0111] - a vertical stirrer,

[0112] - a mixer,

[0113] - a turbo-mixer,

[0114] - a rotor-stator homogeniser,

[0115] - an emulsifier,

[0116] - a cavitator, and

[0117] - an ultrasonic sonicator.

[0118] [7] An apparatus (10) according to what is described in the previous points, wherein the containment tank (11) internally has a plurality of fins (15) which extend along the internal wall of the tank (11) between the head portion (12) and the bottom portion (17), preferably according to a substantially vertical development.

[0119] [8] An apparatus (10) according to what is described in the previous point [7], wherein the fins (15) have a sufficient extension to substantially prevent the fluid moved by the mechanical stirring device (13) from rising along the internal walls of the containment tank (11).

[0120] [9] An apparatus (10) according to what is described in the previous points, wherein the at least one loading mouth (18,19) is placed near the head portion (12) of the containment tank (11), preferably at the head portion (12).

[0121]

[0010] An apparatus (10) according to what is described in the previous point [9], wherein the at least one inlet (16a, 16b) for gas injection comprises a first inlet (16a) for gas injection placed substantially at the height of the at least one loading mouth (18,19) and / or placed at a cover of the head portion (12) which can be constrained to a corresponding upper opening of the containment tank (11).

[0122]

[0011] An apparatus (10) according to what is described in the previous points, wherein the containment tank (11) comprises at least one measuring device (21) selected from the group consisting of:

[0123] - a pH measuring device,

[0124] - an internal pressure measuring device,

[0125] - a temperature measuring device, and

[0126] - an inlet water flow measuring device.

[0127]

[0012] An apparatus (10) according to what is described in the previous points, wherein the containment tank (11) is configured to operate at pressures up to at least 6 bar, preferably up to at least 8 bar, more preferably up to at least 10 bar.

[0128]

[0013] An apparatus (10) according to what is described in the previous points, wherein the containment tank (11) is made of at least one material selected from the group consisting of:

[0129] - an austenitic (amagnetic) stainless steel alloy composed of a low carbon content (~ 0.05%) and a higher content of chromium (16-18%), nickel (11-14%) and molybdenum (2-3%);

[0130] - an amagnetic austenitic stainless steel, composed of a low carbon content (about 0.05%), a chromium content between 18% and 20% and a nickel content between 8% and 11%; and / or

[0131] - a super duplex steel.

[0132]

[0014] A process (100) for the mineralization of carbon dioxide in forms of solid carbonates of a precursor material comprising at least one material capable of reacting with carbon dioxide in molecular or dissociated form, comprising the steps of: a) loading (110) a process liquid comprising a water suspension (50) of the precursor material in a containment tank (11) through at least one loading mouth (18,19); b) injecting (120) into the containment tank (11) a gaseous stream containing, or consisting of, CO2 until a process pressure is reached; c) stirring (130) the process liquid using a mechanical stirring device (13) at least partially immersed in it; and d) transferring energy to the process liquid through a homogenization device (14) arranged at a bottom portion (17) of the containment tank (11) until a desired pH value is obtained in the process liquid.

[0133]

[0015] A process (100) according to what is described in the previous point

[0014] , wherein the process pressure is comprised between 0 and 10 bar preferably between 0 and 8 bar, more preferably comprised between 0 and 6 bar.

[0134]

[0016] A process (100) according to what is described in the previous point

[0014] or

[0015] , wherein the step of injecting (120) a gaseous stream containing, or consisting of, CO2, comprises injecting the gaseous stream below a free surface of the process liquid loaded in the containment tank (11).

[0135]

[0017] A process (100) according to what is described in the previous points from

[0014] to

[0016] , wherein the step of injecting (120) a gaseous stream containing, or consisting of, CO2, comprises injecting the gaseous stream above a free surface of the process liquid loaded in the containment tank (11).

[0136]

[0018] A process (100) according to what is described in the previous points from

[0014] to

[0017] , comprising the additional step consisting of:

[0137] - measuring a pressure inside the containment tank (11);

[0138] - transmitting an activation signal in case the detected internal pressure is below the process pressure of a threshold value; and

[0139] - activating gas injection comprising CO2 until the pressure inside the containment tank (11) is brought back to a value substantially equal to the value of the process pressure.

[0140]

[0019] A process (100) according to what is described in the previous points from

[0014] to

[0018] , wherein the desired pH value is comprised between 10 and 6, more preferably, between 9 and 7.

[0141]

[0020] A process (100) according to what is described in the previous points from

[0014] to

[0019] , wherein said precursor is selected from waste / slag such as steelworks slag and / or basic industrial sludge from civil and industrial wastewater and / or from paper mills and / or from alumina and / or zinc and / or titanium dioxide treatment processes (red sludge) and / or from fly ash from incineration.

[0142]

[0021] A process (100) according to what is described in the previous points from

[0014] to

[0020] , wherein the precursor material additionally comprises an additive suitable for streamlining the reaction with the gaseous stream containing, or consisting of, CO2, wherein the additive is preferably sodium hydroxide (NaOH) or is preferably sodium carbonate (TSfeCCh) or is preferably sodium bicarbonate (NaHCCh).

[0143] In all preferred embodiments of the process of the present invention, advantageously the homogenization device: maximizes the solubility of carbon dioxide in solution; maximizes mass transfer from the precursor to the solution; intensifies the reactivity of the species involved; renews the reactive surface of the precursor and, therefore, maximizes the overall release of the reactive material towards carbon dioxide. With respect to the direct CO2 pumping technologies of the known art (mentioned above), advantageously, the apparatuses and related processes of the invention tend to remove carbonate substances, avoiding fouling in the system. In particular, the homogenization effect has proved to be crucial in achieving this type of result.

[0144] Furthermore, advantageously, in the preferred embodiments of the present invention, a particle size control element is not required. In fact, particle size control depends on the physics of homogenization itself: the bubbles formed close to the surfaces of the precursor materials have a very short life (from a few ms to a few tens of ms), after which they implode, causing an increase in pressure inside the bubble which leads to the formation of a real plasma; their implosion fragments the surfaces of the granules, reducing them to mini-fragments of the order of a few tens of nm, preferably between 10 and 100 nm. The nanoscopic fragments thus obtained then crystallize rapidly in the form of carbonates.

[0145] The benefits of the innovative technology provided by the present invention are many, such as:

[0146] 1) The precursor is maximally consumed and the conditions for the passivation of the material are not created;

[0147] 2) Carbon dioxide is maximally solubilized by the effects of the cavitator action;

[0148] 3) No fouling conditions are created; in fact, the system remains clean;

[0149] 4) The system can also (preferably) be used in continuous production.

[0150] In conclusion, all the details are substitutable by other technically equivalent elements; the materials used, as well as the contingent shapes and dimensions, which may be any according to the specific implementation requirements without departing from the scope of protection of the following claims.

Claims

CLAIMS1. Apparatus (10) for the mineralization of carbon dioxide in the forms of solid carbonates of a precursor material comprising at least one material capable of reacting with carbon dioxide in molecular or dissociated form, the apparatus comprising at least: a containment tank (11) comprising a head portion (12) placed above and a bottom portion (17) placed below, the containment tank (11) comprising- at least one loading mouth (18,19) for loading a precursor material or a water suspension (50) of the precursor material; and- at least one inlet (16a, 16b) for gas injection; a mechanical stirring device (13) arranged and configured to act inside the containment tank (11) near the bottom portion (17) thereof, wherein the mechanical stirring device (13) is controlled through a control rod (13a); and a homogenization device (14) arranged at the bottom portion (17) of the containment tank (11), wherein the homogenization device (14) is controlled through a control shaft (14a), wherein the control rod (13a) is operable independently of the control shaft (14a).

2. Apparatus (10) according to claim 1, wherein the at least one inlet (16a, 16b) for gas injection comprises a first inlet (16a) for gas injection placed near the head portion (12) of the containment tank (11) and / or a second inlet (16b) for gas injection placed near the bottom portion (17) of the containment tank (11).

3. Apparatus (10) according to claim 1 or 2, wherein the at least one inlet (16a, 16b) for gas injection comprises a first inlet (16a) for gas injection placed at a distance (hi) from the head portion (12) which is less than or equal to one third of a vertical extension (H) of the containment tank (11) which develops between the bottom portion (17) and the head portion (12), preferably at a distance (hi) from the head portion (12) which is less than or equal to one quarter of a vertical extension (H) of the containment tank (11) which develops between the bottom portion (17) and the head portion (12), more preferably at a distance (hi) from the head portion (12) which is less than or equal to one fifth of a vertical extension (H) of the containment tank (11) which develops between the bottom portion (17) and the head portion (12).

4. Apparatus (10) according to any one of claims 1 to 3, wherein the at least one inlet (16a, 16b) for gas injection comprises a second inlet (16b) for gas injection placed at a distance (I12) from the bottom portion (17) which is less than or equal to one third of a vertical extension (H) of the containment tank (11) which develops between the bottom portion (17) and the head portion (12), preferably at a distance (hi) from the bottom portion (17) which is less than or equal to a quarter of a vertical extension (H) of the containment tank (11) which develops between the bottom portion (17) and the head portion (12), more preferably at a distance (I12) from the bottomportion (17) which is less than or equal to a fifth of a vertical extension (H) of the containment tank (11) which develops between the bottom portion (17) and the head (12).

5. Apparatus (10) according to any one of the previous claims, wherein the mechanical stirring device (13) is constrained to the head portion (12) of the containment tank (11) through the control rod (13a) in such a way as to act by immersion in the water suspension (50) of the precursor material comprised in the containment tank (11); and / or wherein the homogenization device (14) is connected to the bottom (17) of the containment tank (11) through the control shaft (14a).

6. Apparatus (10) according to any one of the previous claims, wherein the containment tank (11) internally has a plurality of fins (15) which extend along the internal wall of the tank (11) between the head portion (12) and the bottom portion (17), preferably according to a substantially vertical development, wherein optionally the fins (15) have a sufficient extension to substantially prevent the fluid moved by the mechanical stirring device (13) from rising along the internal walls of the containment tank (11).

7. Apparatus (10) according to any one of the previous claims, wherein the at least one loading mouth (18,19) is placed near or at the head portion (12) of the containment tank (11), wherein preferably the at least one inlet (16a, 16b) for gas injection comprises a first inlet (16a) for gas injection placed substantially at the height of the at least one filling mouth (18,19) and / or placed at a cover of the head portion (12) which can be constrained to a corresponding upper opening of the containment tank (11).

8. Apparatus (10) according to any one of the previous claims, wherein the containment tank (11) is configured to operate at pressures up to at least 6 bar, preferably up to at least 8 bar, more preferably up to at least 10 bar.

9. Process (100) for the mineralization of carbon dioxide in the forms of solid carbonates of a precursor material comprising at least one material capable of reacting with carbon dioxide in molecular or dissociated form, comprising the steps consisting of a) loading (110) a process liquid comprising a water suspension (50) of the precursor material in a containment tank (11) through at least one loading mouth (18,19); b) injecting (120) into the containment tank (11) a gaseous stream containing, or consisting of, CO2 until a process pressure is reached; c) stirring (130) the process liquid using a mechanical stirring device (13) at least partially immersed in it; and d) transferring energy (140) to the process liquid through a homogenization device (14) arranged at a bottom portion (17) of the containment tank (11) and operable independently of the mechanical stirring device (13) until a desired pH value is obtained in the process liquid.

10. Process (100) according to claim 9, wherein the step of injecting (120) a gaseous stream containing, or consisting of, CO2, comprises injecting the gaseous stream below a free surface of the process liquid loaded in the containment tank (11).

11. Process (100) according to claim 9 or 10, wherein the desired pH value is comprised between 10 and 6, preferably between 9 and 7.

12. Process (100) according to any one of claims 9 to 11, wherein the precursor material additionally comprises an additive suitable for streamlining the reaction process with the gaseous stream containing, or consisting of, CO2, wherein the additive is preferably at least one of sodium hydroxide (NaOH), sodium carbonate (Na2COs) and sodium bicarbonate (NaHCOs).

13. Process (100) according to any one of claims 9 to 12, wherein the process pressure is less than or equal to 10 bar, preferably less than or equal to 8 bar, more preferably less than or equal to 6 bar.

14. Process (100) according to claim 13, comprising the additional step consisting of:- measuring (150) a pressure inside the containment tank (11);- transmitting (160) an activation signal in case the detected internal pressure is below the process pressure of a threshold value; and- activating (170) the injection of gas comprising CO2 until the pressure inside the containment tank (11) returns to a value substantially equal to the value of the process pressure.

15. Process for the permanent storage of carbon dioxide comprising the steps of:- making available a precursor material comprising at least one material capable of reacting with carbon dioxide in molecular or dissociated form;- mixing the precursor material with water to generate a solution of water and precursor material;- injecting the solution of water and precursor material into an apparatus (10) for the mineralization of carbon dioxide in the forms of solid carbonates; and- performing a process (100) for the mineralization of carbon dioxide in the forms of solid carbonates according to any one of claims 9 to 14.

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