GB2515995A - Method and system of sequestrating carbon dioxide - Google Patents

Abstract

A method of sequestrating Carbon Dioxide (CO2) comprises reacting a magnesium or calcium silicate-based material with sodium hydroxide or potassium hydroxide to form a mixture comprising a hydroxide of the alkaline earth and a silicate of the alkali metal wherein the reaction is carried out at a pressure of less than 10 Bar, and at a temperature of less than 140-220 °C, the thus produced alkaline earth hydroxide is then reacted with carbon dioxide. The Silicate-based material preferably comprises a naturally occurring Olivine, Serpentine and/or Wollastonite mineral.

Description

METHOD AND SYSTEM OF SEQUESIRATING CARBON DIOXIDE

Field of the invention

The present disclosure relates to methods of sequestrating Carbon Dioxide, S for example from flue-gas, for example by utilizing a process involving digestion of metal mineral Silicates. Moreover, the present disclosure also relates to systems for executing aforesaid methods.

Background of the invention

Increasing concentrations of Carbon Dioxide (Ca2) in the Earth's atmosphere have recently caused concerns, namely the concentrations are presently substantially 400 p.p.m. and increasing at a rate of substantially 4 p.p.m. per annum. A major factor contributing to such increase is anthropogenic oxidation of fossil Carbonaceous fuels, for example coal, oil and gas. The World presently consumes circa 100 million barrels of oil per day, for example.

There have been recent initiatives to employ more renewable energy systems, for example wind turbines and tidal power generating systems, as well as sequestration Carbon Dioxide (C02) from flue-gases, for example as emitted from coal-burning electrical generating facilities. Thus, primary initiatives involve utilizing energy efficiency technologies, increased reliance on renewable sources, and developing technologies for long term storage of Carbon Dioxide (C02) emissions. The latter technology field is known as Carbon Dioxide (Ca2) sequestration.

There have been significant developments in Carbon Dioxide (C02) sequestration in recent years, and Carbon Dioxide sequestration technologies have aroused considerable interest among governments, industries and scientific communities. Earlier methods of Carbon Dioxide (C02) sequestration suffered from various drawbacks such as risk of water contamination, and availability of suitable storage spaces for receiving sequestrated Carbon Dioxide (C02), these drawbacks being familiar to the person skilled in the art.

To address aforementioned problems associated with known Carbon Dioxide (CD2) sequestration, there has been considerable interest in mineral Carbonation technologies. A Masters thesis by Mabell Delgado TorrOntegui at ETH in Switzerland, "Assessing the Mineral carbonation science and technoIog' (2010), provides an overview of contemporary research in this field of Carbon Dioxide (GO2) sequestration technology. A key principle of mineral Carbonation is also known as "mineral sequestration technology", wherein sequestration of Carbon Dioxide (C02) is achieved by capturing Carbon Dioxide (GO2) in a form of stable mineral Carbonates. Such sequestration employs a process which is an exothermic reaction of a metal Oxide and Carbon Dioxide (C02) to form stable Carbonate materials as provided in a reaction formula (1): MO + CO2 => MCO3 + Heat (1) wherein M is a metal, preferably an alkaline earth metal such as Calcium or Magnesium; and wherein Most suitable and naturally abundant sources of these metal Oxides are Magnesium or Calcium Silicate minerals such as olivine, wollastonite, and serpentine. The Carbonation reactions of these minerals are as follows: Olivine: Mg2SiO4 + 2C02 => 2MgCO3 + 502 + 89 kJ mol-1CO2 (2) Serpentine: Mg3Si2O5(OH)4 + 3CO2 => 3MgCO3 + 2SiO2 + 2H2O + 64 kJ mol-1 CO2 (3) Wollastonite: CaSiO3 + CO2 => CaCO3 + Si02 + 90 kJ mol-1 CO2 (4) Although the above reactions (2) to (4) are thermodynamically favourable, the reactions have, however, relatively slow reaction rates in a geologic time scale, namely unsuitable for an industrial process. Efforts have been made to try to accelerate these reactions. However, the efforts suffer from various limitations, such as energy wastage and a high cost for mining and transporting large amount of rock, as well as industrial and environmental inefficiencies. Moreover, the mineral Silicates are not easily obtainable in suitable quantities and formats for allowing satisfactory mineral Carbonation to be achieved.

In a published US patent no. U57604787B2 (MAROTO-VALER), "Process for sequestering Carbon Dioxide and Sulphur Dioxide", there is described a method of reacting a Silicate-based material with an acid to form a suspension, which is then combined with Carbon Dioxide to produce a metal salt, silica and regenerating acid in solution. This method has drawbacks of being environmentally harsh and inefficient. Moreover, similar problems with the approach are described in US patent application US2004126293A1 (SHELL INTERNATIONALE RESEARCH), "Process for Removal and Capture of Carbon Dioxide from Flu Gases".

Although, the prior art disclosures have been able to address some of the problems of mineral Carbonation through their indirect sequestration processes, there are several remaining problems which have not yet been resolved, such remaining problems pertaining to industrial scalability, environmental efficiency, and cost.

Lately, research effort has been focused on Carbon Dioxide (002) sequestration by direct' Carbonation of olivine or serpentine. In these recent methods, Carbon Dioxide (Ca2) is sequestered without acid pre-treatment of Silicate feedstock. An olivine reaction is: Mg2SiO4 + 2002 2MgCO3 + 502 (5) And, for serpentine, a corresponding reaction is: Mg3Si2O5(OH)4 + 3002 -. 3MgCO3 + 2SiO2 + 2H20 (6) Experiments to determine the kinetics of these reactions (5) and (6) have shown that such reactions also suffer from poor energy efficiency and a high cost when to scale to industrial plant. In order to accelerate the reactions (5) and (6), high temperatures in a range of 600 °C to 650 °C are required. In a S fuel-fired industrial power plant, attainment of such high temperatures would translate to a requirement of approximately 200 kW-h of electricity per ton of serpentine feedstock. Moreover, with a fossil fuel containing 1 tonne of Carbon, nearly 3.7 tonnes of Carbon Dioxide (C02) is produced. Each tonne of Carbon Dioxide (C02) consumes nearly 2 tonnes of serpentine during Carbonation. The power required for serpentine dehydroxylation is around 20- 30% of total power output from such fuel-fired industrial power plant. All these considerations lead to a huge energy penalty threatening the economic feasibility of this sequestration process.

In a published US patent no. U58114374B2 (BLENCOF), Carbonation of metal Silicates for long-term CO2 sequestration", there is described a method of reacting a Silicate with an alkali metal hydroxide in an aqueous solution.

The reaction with Carbon Dioxide (Ca2) is then used to Carbonate the metal formerly contained in the metal Silicate. This method has drawbacks of inefficiencies and poor overall Carbon capture properties.

Therefore there is an urgent need to develop a process which is energy efficient, which has a high throughput, and is more cost effective than the prior art so that it can be used industrially.

From the foregoing, it will be appreciated that known methods of processing and systems for mineral Carbonation and sequestering Carbon Dioxide (C02) are not optimal in their manner of operation, and their adaptability in broad applications in a cost effective manner.

Summary of the invention:

The present invention seeks to provide an improved method of sequestrating Carbon Dioxide (C02).

The present invention also seeks to provide a system for sequestrating Carbon Dioxide (C02).

In one aspect, embodiments of the present invention provide a method of sequestrating Carbon Dioxide (C02) which comprises: (a) reacting an alkaline earth silicate-based material with an alkali metal compound to form a mixture comprising a hydroxide of the alkaline earth, wherein the alkali metal is selected from sodium and/or potassium, and wherein the alkaline earth is selected from magnesium and/or calcium; (b) reacting the mixture at a temperature in the range of 140-220°C and at a pressure of less than 10 bar; (c) separating the hydroxide of the alkaline earth from the mixture; and (d) combining the hydroxide of the alkaline earth with a source of Carbon Dioxide (C02) producing a Carbonate or Bicarbonate or the alkaline earth.

Optionally, the method includes reacting the mixture in (b) at a pressure of less than the vapour pressure of water at the temperature of reaction. This allows for a capacity for large scale industrial use and continuous carbonation without advanced pressure chambers or equipment.

Optionally, the mixture is in a stoichiometric molar ratio between Si in the Silicate-based material and the alkali metal in the alkaline compound in a rangeofl:ltol:2.

Optionally, the mixture is in a form of an aqueous solution with the molality of >30 molar of alkaline compound per litre water (H20).

Optionally, that the method includes using flue gases with less than 5Ovol% Carbon Dioxide (C02) as part of a gas mixture for carbonation.

In accordance with an embodiment of the present invention, the reaction of the mixture is executed at an ambient pressure and at a reaction temperature of ca 180°C. This has significant benefit over disclosed prior art. The Carbonation of Silicates is an exothermic reaction, but kinetically slow, which requires highly energetically consuming conditions to be accelerated, thus influencing costs and environmental impacts of the reaction. By operating at S an elevated temperature, the reaction of the mixture occurs much more efficient, more economically and thus more favorable for practical industrial applications.

In accordance with an embodiment of the present invention, an alkaline compound Sodium Hydroxide is optionally used when executing the method, thereby providing significant improvement over prior art, and using the alkaline compound in a much more economical and efficient manner.

In yet another aspect, embodiments of the present invention provide a system for sequestrating Carbon Dioxide (C02), wherein a first reaction chamber is arranged to receive a Silicate-based material and an alkaline compound, wherein a blending arrangement is provided for the first reaction chamber to produce a mixture of the Silicate-based material and the alkaline compound therein.

Embodiments of the present invention substantially eliminate the

aforementioned problems in the prior art, wherein:

(i) higher pH values favour the Carbonation reaction in an unpressurized vessel; (ii) a very small amount, namely molar ratio of H20:Mg2SiO4 = 0:2, of water and minimization, namely molar ratio of NaOH:Mg2SiO4 = 1:4, and a very small amount of the Sodium Hydroxide (NaOH) is required to avoid a need to recover excess Sodium Hydroxide (NaOH), thereby avoiding excess consumption of reactants; and (H) an excess consumption of acid to precipitate Silica is avoided, thereby enabling an efficient and cost-effective method and system of sequestrating Carbon Dioxide (Ca2) to be achieved, by way of digestion of metal mineral Silicates.

Additional aspects, advantages, features and objects of the present invention would be made apparent from the drawings and the detailed description of the illustrative embodiments construed in conjunction with the appended claims that follow. It will be appreciated that features of the present invention are susceptible to being combined in various combinations without departing from the scope of the present invention as defined by the appended claims.

Description of Drawings:

The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present invention, exemplary constructions of the disclosure are shown in the drawings.

However, the present invention is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.

FIG. 1 is an illustration of a flow chart of a digestion Step 1 involving alkaline digestion of Serpentine or Olivine to convert them to Brucite and Silica; FIG. 2 is an illustration of a flaw chart of a Carbonation step 2 involving direct Carbonation of Brucite, namely Magnesium Hydroxide, with flue-gas to form Magnesium Carbonate; FIG. 3a and 3b are illustrations of XRD patterns of selected samples, wherein solid products from dissolution of Dunite (a form of Olivine) using Sodium Hydroxide (NaOH) solution of concentration in a range of 15 to 40 mol/kg (left), and using Sodium Hydroxide (NaOH) solution of concentration 50 mol/kg (right) solutions. In the illustrations, following abbreviations are employed: Fo = Forsterite, Bre = Brucite, dc = Clinochlore, En = Enstatite, Srp = Serpentine, TIc = Talc, SpI = Spinel; FIG. 4a and 4bare illustration of TG (4a) and DTG (4b) curves of selected samples: solid products from dissolution of Dunite at a temperature of 1800 C for 6 hours with different concentrations of Sodium Hydroxide (NaOH) solution; FIG.5 is an illustration of a graph wherein there are shown M9(OH)2 concentration in solid products based on IG results: Dunite dissolved at a temperature of 180 °C with different concentrations of Sodium Hydroxide (NaOH) solution; FIG. 6 is an illustration of XRD patterns of solid products from dissolution of Dunite at 180 °C with Sodium Hydroxide (NaOH) solution having a molar concentration of 40 mol/kg solution, for different temporal durations; FIG. 7a and 7b are illustrations of TG (7a) and DTG (7b) curves of solid products from dissolution of Dunite at a temperature of 1800 C with Sodium Hydroxide (NaOH) solution having a molar concentration of 40 mol/kg for different temporal durations; FIG. 8 is an illustration of a graph in which there is shown Magnesium Hydroxide Mg(OH)2 concentration in solid products based on TG results: Dunite dissolved at a temperature of 180° C with a molar concentration of Sodium Hydroxide (NaOH) solution being 40 mol/kg for different durations; FIG. 9 is an illustration showing Rietveld Refinement OPA of raw Dunite, wherein: data points profile = experimental pattern; continue profile = calculated model (above); difference plot (below); FIG. 10 is an illustration showing Rietveld Refinement QPA of dissolved Dunite spiked with 10 wt% Silicon, wherein: data points profile = experimental pattern; continue profile = calculated model; and FIG. ha and hib are illustrations showing Brucite quantification with Rietveld Refinement and IGA (FIG. ha), wherein Forsterite and Brucite concentrations were obtained via Rietveld Refinement QPA of selected samples (FIG. hib).

In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item.

When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.

Detailed description of embodiments of the invention The following detailed description illustrates embodiments of the present invention and ways in which they can be implemented.

In FIG. 1, there is shown an embodiment of digestion system and process 100 of the invention, wherein there occurs alkaline digestion of a Silicate-based material, preferably alkaline earth silicate and more specifically a naturally occurring feedstock containing magnesium or calcium silicate, such as Serpentine, Olivine, Dunite, and/or Wollastonite 101. The process 100 results in reaction products being generated, namely a conversion to Brucite and Silica in a case of Olivine 101 being a feed mineral employed. In the reaction, Olivine 101 is fed into a stirred reactor 102 together with an alkali 103 and heat is provided from a heat source 104. The alkali is beneficially selected from a mineral Hydroxide. Among the many metal Hydroxides that can find utility in this reaction, a preferable alkali used is Sodium Hydroxide (NaOH).

According to one of the embodiments, the reaction mixture of the digestion process 100 comprises a stoichiometric ratio between the soluable silicate based material and solid hydroxide of the alkaline earth compound of about 1:2. This stoichiometric ratio aims to minimises the input of the alkaline compound, such as Sodium Hydroxide (NAOH), into the initial reaction mixture of the process. This limits the regeneration of Sodium Hydroxide (NaQH) from carbonates at the end of the reaction, which is costly and time consuming. The reaction mixture is preferably in an aqueous solution during reaction, but can also be in a non-aqueous mixture.

In the example of magnesium carbonates being produced according to the described method a wide range of compounds including soluble magnesium bicarbonate Mg(HCO3)2 is produced in solution, but generates no separate water in the carbonation reaction: 2002 + Mg(OH)2 = Mg.(HCO3)2 (7) The preferred alkali 103 for this digestion process is beneficially Sodium Hydroxide or Potassium Hydroxide, together with water (H20). It is also possible to use Sodium Carbonate, Sodium Bicarbonate, Potassium Carbonate and Potassium Bicarbonate as the alkali for the digestion process.

The heat source 104 is employed to raise a temperature of the digestion process, whilst stirring of the mixture is implemented, to a temperature of less than 250 °C, and for a temporal period of less than 6 hours. A preferred range of temperature is from 140 °C to 220 00. The reaction can be best performed with the temperature being less than 200 °C, and most preferentially at around 00, throughout the process, as shown in the results Fig. 4-8. The digestion vessels used are most suitably Teflon (PTEE) to withstand hot-conc-NaOH with the maxium operating temperature usually specified at 220°C.

Experiments with Magnesium silicate mineral feedstocks have been showing excellent results for this process. Other alkaline earth silicates such as calcium silicate and wollastonite are also suited for the preferred process.

This digestion process is preferably carried out at a pressure of less than 20 Bar, wherein 1 Bar corresponds to nominal atmospheric pressure at sea-level.

The reaction can be more preferably carried out at a pressure less than 10 Bar. The reaction can be further more preferably be carried out at pressure conditions lower than the vapour pressure of pure water at the temperature of reaction. The benefit of not having to use high pressure vessels to carry out hydrothermal reactions saves cost and also improves the applications of the technology in industrial applications at very high volumes and large scale installations.

The process, after digestion of Olivine, is shown in equation 112. Here, the Brucite (MgOH2) 107, solid phase, is separated from a Silicate solution 108, namely a liquid phase, prepared by adding water 106 to the reaction mixture.

S Thereafter, the Silica precipitation process is carried out as depicted in the equations 113 and 112. The process, namely acid precipitation, can be carried out by adding either Carbon Dioxide (C02) or acid 110. The excess alkali 111 is recovered and fed back to a chamber of the reactor 102.

Performing the digestion process at ambient atmospheric pressure conditions prevents the use of equipment to increase pressure, e.g. an autoclave, and allows large scale, continuous sequestration of industrial Carbon Dioxide (C02) emissions.

In FIG.2, there is provided an illustration of the details of a Carbonation process 200 as also depicted in equations 206 and 207. The Brucite (MgOH2) powder 205 is fed into a continuous reactor 201, together with a flue-gas 204.

The de-carbonised flue gas 202 and Magnesium Carbonate (MgCO3) powder 203 are the reaction products of this Carbonation process 200.

In a preferred embodiment, olivine 101 is mixed with NaOH 103 and water 106 in a mole ratio in the range of 1:(1-6):(O-5). The mixture is reacted at 180°C-220°C in a stirred PTFE vessel at a pressure <lObar to produce a solid mixture 102. Cooling and removal of resulting solid reaction mixture from reaction vessel is followed by separation of brucite powder from the reaction mixture by dissolving the soluble fraction of the reaction mixture in water and filtering the resulting suspension 108. The brucite powder 205 is dispersed in water and a flue-gas 204 containing CO2 sparged into the brucite dispersion to form a dispersion of magnesium carbonate 203 and to remove CO2 from the flue-gas 202.

In an alternative embodiment, it is preferred to capture Carbon Dioxide (C02) directly from low-Carbon Dioxide (C02) flue-gases at a less than ca 5Ovol% Carbon Dioxide (CO2). This flue-gas mixture is used for the carbonation step and more typically 3-25vo1% Carbon Dioxide (CO2) has also been used during -12-carbonation. This is much more cost effective than using previously captured and separated pure Carbon Dioxide (C02) which often also is pressurised.

Experiments have shown that approx. 75% of energy costs in conventional Carbon Capture and Storage (CCS) processes are attributed to the Carbon S Dioxide (C02) capture and/or separation. The use of the propose mineral carbonation process offer the possibility of direct reaction with the dilute, low-pressure Carbon Dioxide (C02) in unseparated flue-gases, at atmospheric pressure and thereby saving energy.

The efficiency of this entire process as illustrated in FIG. 1 and FIG.2 has been analysed through various scalability experiments, wherein it has been found that, for the Magnesium-mineral Silicates, the alkaline treatment is attractive as the associated Carbonation reaction is chemically favorable at a higher pH resulting in a higher reaction rate: Mg2SiO4 + 2NaOH +H20 => 2Mg(OH)2 (J) +Na25i03 (aqueous) (8) Mg(OH)2 + CO2 => MgCO3 (fl + HO (9) In one of the embodiments, it is feasible to convert Dunite, an ultramafic rock rich in Magnesium-bearing minerals, into Magnesium Hydroxide (Mg(OH)2) by using highly concentrated Sodium Hydroxide (NaOH) aqueous solutions. The effect of the reaction time and the Sodium Hydroxide (NaOH) solution concentration on the process were studied to determine optimal conditions for achieving higher rate of conversion of Magnesium-mineral Silicates into Magnesium Hydroxide (Mg(OH)2). The product phases were identified by XRD and TG analysis. Careful quantification of Forsterite and Brucite both in raw materials and products were performed using Rietveld Refinement OPA and TG. The experimental results have been illustrated in the FIG. 3a and 3b, FIG. 4a and 4b, FIG.5, FIG. 6, Fig. 7a and 7b, FIG. 8, FIG. 9, FIG. 10, FIG. ha and hib; these results are indicated by 300, 301, 400, 401, 500, 600, 700, 701, 800, 900, 1000, 1100, 1101 respectively. The experimental results of these drawings have been briefly elucidated in the foregoing.

The tests conducted have shown that Magnesium-mineral Silicates constituting Dunite can be almost completely substituted with Brucite in highly concentrated solutions of Sodium Hydroxide (NaOH) and heated to a temperature of substantially 1800 C. According to the experimental results, increasing the Sodium Hydroxide (NaOH) concentration and the time of reaction are both factors that positively affect the conversion of Magnesium-Silicates into Magnesium Hydroxide. A greatest amount of Magnesium Hydroxide (Mg(OH)2) was produced by either using a solution of Sodium Hydroxide (NaOH) having a molar concentration of 50 rnol/kg for a temporal duration of 6 hours (73 wt%), or by using a solution of Sodium Hydroxide (NaOH) having a molar concentration of 40 mol/kg for a temporal duration of 18 and 24 hours (79 -80 wt%). The TGA analyses results were found to be in accordance with the qualitative XRD results and with the Rietveld Refinement Quantitative Phase Analysis.

During our exploration of optimal experimental conditions for different embodiments of the olivine-NaOH reaction, we have discovered that it is possible to achieve substantial conversion of olivine to brucite in open vessels at ambient atmospheric pressure while heating to temperatures in the range 130-2200. At these elevated temperatures the vapour pressure of water significantly exceeds the reaction pressure. This discovery provides a significant advantage over the processes described by prior art systems in that the reaction can be conducted at much lower pressures (and even at ambient atmospheric pressure) using standard low-cost industrial reactors that typically are designed to withstand operating pressures up to 1 Obar.

In accordance with another embodiment of the present invention, the Olivine and/or Serpentine is a Magnesium mineral which are suitable feedstock materials due to their high content of Magnesium (Mg) and wide abundance and large concentration in mineralogical sites.

From the above description and claimed process, it will be appreciated that there is provided a process that has advancements in the alkali digestion -14-process of minerals required for mineral Carbonation. The process can find utility in sequestration of Carbon Dioxide (Ca2), extraction of valuable minerals, and other processes, known to the person skilled in the art, requiring the digestion of minerals for their Carbonation.

Modifications to embodiments of the invention described in the foregoing are possible without departing from the scope of the invention as defined by the accompanying claims. For example the compound in the reaction may be selected from any one or combination of Hydroxide, Carbonate, and/or Bicarbonate as would be suitable to the person skilled in the art. Expressions such as "including", "comprising", "incorporating", "consisting of', "have", "is" used to describe and claim the present invention are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. Numerals included within parentheses in the accompanying claims are intended to assist understanding of the claims and should not be construed in any way to limit subject matter claimed by these claims.

Claims (9)

1. CLAIMS1. A method of sequestrating Carbon Dioxide (CD2), comprising: (a) reacting an alkaline earth silicate-based material with an alkali metal S compound to form a mixture comprising a hydroxide of the alkaline earth, wherein the alkali metal is selected from sodium and/or potassium, and wherein the alkaline earth is selected from magnesium and/or calcium; (b) reacting the mixture at a temperature in the range 140-220°C and at a pressure of less than 10 Bar; (c) separating the hydroxide of the alkaline earth from the mixture; and (d) combining the hydroxide of the alkaline earth with a source of Carbon Dioxide (CD2) producing a Carbonate or Bicarbonate or the alkaline earth.
2. 2. A method of sequestrating Carbon Dioxide (CD2) as claimed in claim 1, characterized in that the method includes reacting the mixture in (b) at a pressure of less than the vapour pressure of pure water at the temperature of reaction
3. 3. A method of sequestrating Carbon Dioxide (C02) as claimed in claim 1 or 2, characterized in that the method includes using the mixture with a stoichiometric ratio between the Si in the alkaline earth silicate-based material and the alkali metal in the alkaline compound in a range of 1:1 to 1:2.
4. 4. A method of sequestrating Carbon Dioxide (C02) as claimed in any one of claims 1, 2 or 3, characterized in that the method includes using the mixture in a form of an aqueous solution with the molality of >30 molar of alkaline compound per litre water (H2D).
5. 5. A method of sequestrating Carbon Dioxide (C02) as claimed in any one of the preceding claims, characterized in that the method includes reacting the mixture at ambient atmospheric pressure.
6. 6. A method of sequestrating Carbon Dioxide (CD2) as claimed in any one of the preceding claims, characterised in that the method includes executing the reaction at a temperature of ca 180 °C.
7. 7. A method of sequestration Carbon Dioxide (C02) as claimed in any one of the preceding claims, characterized in that the method includes using flue gases with less than 5Ovol% Carbon Dioxide (C02) as part of a gas mixture for carbonation.
8. 8. A system for sequestrating Carbon Dioxide (C02), wherein the system includes a first reaction chamber which is operable to receive a Silicate-based material and an alkaline compound, and a blending apparatus for blending contents of the first reaction chamber to produce a mixture therein.
9. 9. The system for sequestrating Carbon Dioxide (C02) as claimed in claim 8, wherein the system is operable to execute the method as claimed in any one of claims ito 7.