NL2007927C2

NL2007927C2 - A method for producing reduced carbon footprint lime sandstone products and building materials, and building materials obstainable by said method.

Info

Publication number: NL2007927C2
Application number: NL2007927A
Authority: NL
Inventors: Eric Govers
Original assignee: Harlinger Kalkzandsteenfabriek Holding B V
Priority date: 2011-12-06
Filing date: 2011-12-06
Publication date: 2013-06-10

Description

-1- A method for producing reduced carbon footprint lime sandstone products and building materials, and building materials obtainable by said method.

Background of the invention 5 [0001] The present Invention relates to a method for the manufacture of a lime sandstone product having a reduced carbon footprint. The method also relates to the lime sandstone products, in particular building materials, obtainable by said method, and to the use thereof to reduce the carbon footprint of buildings or construction works. The invention relates in particular to a process for producing lime sandstone bricks (also named calcium silicate or lime-sand bricks) 10 and to the lime sandstone bricks obtainable by said process.

[0002] Global climate change is believed to be caused for a large part by increased carbon dioxide levels In the atmosphere. The rate of emissions of carbon dioxide (C02) is highly correlated to both economic and industrial activity and growth. C02 is typically generated by combustion of hydrocarbons, for example from fossil fuels, waste incineration and/or by various 15 industrial processes that generate carbon dioxide byproduct. There generally Is a strong desire to reduce carbon dioxide emissions. Governments are creating incentives and legislation for industry to stimulate reduction of carbon dioxide emissions by development of processes and engines making more efficient use of the caloric value of the hydrocarbons, by more efficient and cleaner production processes and thus achieving products that have a low carbon footprint.

20 [0003] A reduced carbon footprint may be a low, zero or even negative carbon footprint. A low carbon footprint product means that the production and the distribution of the product as a whole results on balance in a relatively low net amount of emitted carbon dioxide. A zero carbon footprint product is a product of which the production and distribution does not contribute to any carbon dioxide emission to the environment. A negative carbon footprint product is a product in which 25 more C02 has been sequestrated or Incorporated than the C02 emitted by the process for producing the product.

Description of the Related Art

[0004] An approach to reducing the carbon dioxide emissions is to remove C02 from gas 30 streams for example by chemical absorption/adsorption with particular solvent systems (amine scrubbing), membrane separation, cryogenic fractionation, and/or adsorption using molecular sieves. The carbon dioxide can be pumped to absorbing layers deep beneath the Earth's surface to be absorbed and stored there. However, this creates great anxiety and concern with the people living on the Earth's surface in view of the subterranean stability and other safety issues. The 35 carbon dioxide can also be absorbed on an active absorption material and disposed. However, this Is less desirable due to the added expense and maintenance associated with the disposal of larger amounts of spent active material. Regenerative absorbing systems have been designed to regenerate the active material after carbon dioxide absorption, making it suitable for subsequent productive passes through the reactor. Such regenerative absorbing systems for example are 40 molecular sieves, such as zeolites and activated carbon. Such systems have the disadvantage of -2- requiring high capital investment and operating costs as well as relatively small throughput capacity and low removal efficiency in some cases.

[0005] W02007106372 describes a process for reducing C02 emissions from exhaust gasses from an industrial effluent fluid stream containing carbon dioxide by contacting the stream with a 5 scrubbing material comprising a first component and a second component wherein the first component comprises a source of calcium oxide and a source of alkali metal ions, and the second component comprises a slag having one or more reactive silicate compounds. It is further described to reduce carbon dioxide emissions from a manufacturing facility such as a cement manufacturing facility which method comprises reacting a cement manufacturing raw material to 10 produce clinker and an effluent stream comprising carbon dioxide; contacting at least a portion of the effluent stream with a carbon dioxide scrubbing material comprising a first component, a second component distinct from the first component, and water, wherein the first component comprises a source of calcium oxide and a source of alkali metal ions, the second component comprises a slag having one or more reactive silicate compounds, and generating a product 15 comprising calcium carbonate and a spent scrubbing composition.

[0006] WO 2010/039903 generally describes a method for producing a formed building material comprising: a) producing a C02 sequestering component from divalent cations and a gaseous waste stream comprising C02; and b) forming a building material comprising the C02 sequestering component, wherein the formed building material comprises 5% to 90% (w/w) C02-sequestering 20 component. The formed building material has a carbon footprint that is neutral or negative. The formed building material are for example a brick, a block, a tile, a cement board, a conduit, a beam, a basin, a column, drywall, fiber-cement siding, a slab, an acoustic barrier, or insulation.

[0007] Although the prior art describes in general terms the desire to reduce carbon dioxide emissions, the sequestration of carbon dioxide, and the use of the CSP in building materials to 25 reduce the carbon footprint thereof, there still remains a general desire for methods for further improving the environment by reducing carbon dioxide emissions. There also remains a concrete desire for a process for production of building materials that is realistic, technically feasible and economically viable and which results In building materials products that are commercially attractive and competitive with existing products with a positive carbon footprint.

30 [0008] One object of the invention is to provide a method for the manufacture of a lime sandstone product, in particular a lime sandstone building material, having a reduced carbon footprint. A further object of the invention is to provide reduced carbon footprint lime sandstone building materials, in particular lime sandstone bricks (sand lime bricks), that are obtainable from said method. A still further object of the invention is to provide a reduced carbon footprint lime 35 sandstone product or building material prepared with sand, lime, and an amount of CSP such that the carbon footprint of the product or building material is substantially zero or negative. A still further object of the invention is the use of the lime sandstone building materials of the invention for reducing the carbon footprint of buildings or construction works by incorporating the building materials into the buildings or works. By the incorporation of the CSP into the lime sandstone -3- products and building materials, the carbon footprint thereof will preferably be reduced to substantially zero, or even more preferably will be negative.

[0009] In the context of this invention, "products" include all types of materials including building materials, "building materials" include materials suitable for building and construction 5 works, and "buildings" include buildings that are newly built as well as repaired or reconstructed, as well as construction works. In the context if this invention, a reduced carbon footprint may be a low, zero or even negative carbon footprint as explained herein above. The use of the reduced carbon footprint building materials in a building or construction work, especially when they have a negative carbon footprint, opens the possibility of using building materials in said building or 10 construction work that in themselves have a higher, undesired carbon footprint, because the net value of carbon footprint would still be within the legal limits.

Description of the invention

[0010] According to the invention there is provided a method for the manufacture of a lime 15 sandstone product having a reduced carbon footprint comprising the steps of i. preparing a mixture comprising sand, lime and water, ii. allowing the mixture to react, III. shaping the mixture in a form, iv. hardening of the shaped form in an autoclave at high temperature and high pressure, 20 characterized in that in process step i) the mixture further comprises a carbon dioxide sequestrated product (CSP), which is a (hydro-)siiicate and carbonate containing product of a reaction between a reactive silicate absorbent and carbon dioxide. By the incorporation of a CSP in the mixture of sand, lime and water used for the production of the lime sandstone product, or in particular the lime sandstone building material, a reduced carbon footprint product or building 25 material is obtained. Surprisingly, even a zero or negative carbon footprint product or building material can be obtained by the process of the invention. A negative footprint building material enables the use of higher footprint materials in the building, whilst at the same time still reaching the goals of reducing the total carbon footprint of the building.

[0011] In a preferred embodiment the invention relates to the production of lime sandstone 30 building materials with a reduced carbon footprint that are shaped in the form of bricks. Apart from achieving the reduced carbon footprint of the lime sandstone building material, it was surprisingly found that lime sandstone bricks according to the invention using the CSP can have an even higher compressive strength than the same lime sandstone bricks without the CSP. Without wishing to be bound by theory it is assumed that this CSP improves the cohesive gluing of sand 35 particles in the building material.

[0012] In the method according to the invention the carbon footprint of the product or building material is reduced or preferably equal to or even less than zero by incorporating into the mixture of step i) an amount X of CSP (expressed in fraction of weight relative to the total weight of the product or building material) according to the formula: CFb + X(CFs - CS), wherein CFb is the 40 carbon footprint of said process for the manufacture of the product, CFs is the carbon footprint of -4- the carbon dioxide sequestering process and CS is the footprint reduction of the CSP due to sequestrated carbon dioxide The formula (CFs - Cs) equals CFcsp, which is the carbon footprint of the CSP. Therefore the above formula can also be expressed as CFb + X(CFcsp). The carbon footprint of a material (CFb, CFs) is expressed as the weight of carbon dioxide generated per 5 weight of the material; CS is the weight of sequestrated C02 per weight of CSP. The value of CFb + X(CFs - CS) is preferably less than or equal to zero.

[0013] The carbon footprint of the production process (CFb, CFs, CFcsp) can be calculated in a variety of ways which may be different from country to country and which may develop over time. It is currently preferred that the carbon footprint is calculated according to MRPI methodoiogy/NEN 10 8006. The carbon footprint of the product or building material can be expressed as the weight of carbon dioxide generated per ton of product/buiiding material produced and distributed. For example, it is estimated that current production routes for lime sandstone bricks generate about 57 kg additional C02 per ton iime sandstone bricks (equal to 5.7wt% C02). A brick comprising 5.7wt% additional carbon dioxide sequestrated would have a zero carbon footprint. The term 15 "additional" means in addition to the "naturally" occurring C02 in the same product. The terms "sequestrated", "absorbed" and "bonded" are used interchangeably, but all mean that the additional C02 is not able to exit the product under typical conditions of use, application, transport, storage, etc, including mechanical damage due to e.g. dropping; e.g. the C02 is preferably chemically bound in the material.

20 [0014] It is contemplated herein that the CFb value (the carbon footprint of the production process of the building material) does not change substantially by adding CSP to the mixture of sand, lime and water, or by replacing any amount of sand and/or lime with the CSP as used in the Invention. For convenience, the CFb is calculated as the CFb for the manufacture of the product of the Invention. It Is further contemplated that the CFs value (the carbon footprint of the process for 25 producing the CSP Itself) is substantially zero. This can be accomplished by sequestering in the production process of the CSP preferably all emitted C02 by said process into the CSP itself, or by producing the CSP together with the building material.

[0015] For reducing the carbon footprint of a building material It does not matter in principle from which source the carbon dioxide is obtained. Different carbon dioxide sources may provide 30 different advantages. Purity and concentration may be a consideration in choosing a particular carbon dioxide source for a particular application or particular carbon dioxide sequestration process. However, in a preferred embodiment the CSP is prepared at least in part from the carbon dioxide emitted by the process of production of the iime sandstone building material. In particular in circumstances where the amount of carbon dioxide that can be used and stored in the building 35 material exceeds the amount of carbon dioxide that can be captured in a commercially attractive way from the building material production process, it is preferred to use an additional external source of carbon dioxide. Therefore, the carbon dioxide used in the CSP for the building material can be at least in part from an external source.

[0016] The external source of C02 for example can be a waste incineration plant or an energy 40 production plant (power generation plant) using fossil fuel. These plants, in particular a waste -5- incineration plant, can provide not only the carbon dioxide, but also fly ash and bottom ash which can be used as a primary or secondary source of reactive silicate absorbent (i.e. carbon dioxide absorbent). Furthermore, the waste incineration plant or power generation plant can provide thermal energy that can be used in the production process. Therefore, in an alternative and 5 preferred embodiment, the method according to the invention relates to an integrated combination of a building material production process and a waste incineration or power generation process, wherein the carbon dioxide produced in the incineration or power generation process is converted to a CSP and used as a component of the building material. Between both production plants, preferably one or more pipelines extend for the supply of C02 and/or ash, preferably each in a 10 separate pipeline. It is feasible that the ash, that can be used as a source of the reactive silicate absorbent, is supplied as an aqueous mixture/solution/emulsion/dispersion.

[0017] The invention also provides shaped building materials having a negative carbon footprint (i.e. positive for the environment). These have a clear economic advantage and can be substantially higher priced. Nowadays strict building regulations are imposed requiring that 15 complete building and construction works must have a specified low carbon footprint. Therefore, the building materials according to the invention having a negative carbon footprint can be used to compensate for the positive carbon footprint of other building materials in the building or construction to reduce the total cost.

[0018] In the method according to the invention, the process for the production of the building 20 material preferably involves a high pressure and/or high temperature treatment step of the building material in high pressure and/or high temperature equipment. In one preferred embodiment the CSP is prepared in the same equipment. This significantly reduces the capital investment of the carbon dioxide sequestration process. It was found that the reaction conditions of the building material production, in particular the lime sandstone production, are similar enough 25 to reaction conditions of the CSP production process to allow the use of the same equipment. In a more preferred embodiment the CSP is prepared concurrent with the high pressure and/or high temperature treatment of the building material. In this way the value of CFs is significantly reduced, preferably such that it is substantially zero.

[0019] In principle the amount of CSP can vary between wide ranges as it can replace sand in 30 the product. In a sand limestone product the amount of sand typically is between 90 and 97wt% and the amount of CSP in the product can be between 0,5 and 50 wt%. Preferred amounts of CSP are between 5 and 35wt% or between 10 and 30wt%. The CSP mostly replaces the sand but can also replace some of the lime, for example between 0,1 and 3wt%. In a preferred embodiment the invention relates to a method for the manufacture of a lime sandstone building material wherein in 35 step i) the mixture comprises between 50 and 97 wt% sand, between 0.5 and 50 wt% CSP and between 3 and 10 wt% lime (wt% to total solids) and between 0.5 and 5 wt% of water (relative to total solids). In a further preferred embodiment, in process step ii) the mixture is reacted for a reaction time between 0.5 and 2 hours. In still another preferred embodiment, in step III) the mixture is shaped in the form of a brick. In still another preferred embodiment, the hardening of 40 the shaped form in step iv) is performed in an autoclave at high-temperature and high-pressure, -6- preferably in a steam filed autoclave and preferably at temperatures between 150 and 300 °C and a pressure between 10 and 30 bar, and preferably in the presence of carbon dioxide gas. The amount of CSP calculated in accordance with the method of the invention is preferably mixed in the mixture in process step i).

5 [0020] The CSP preferably is a reaction product of carbon dioxide and a reactive silicate absorbent that acts as a carbon dioxide absorbent (sequestering the carbon dioxide). The reactive silicate absorbent is preferably one or more components chosen from the group consisting of fly ash, bottom ash, mineral silicates, in particular Wollastonite (calcium silicate), Oiivine (Magnesium silicate) or Serpentine (Magnesium Iron Silicate), Phosphor slag and Steel slag. Particularly high 10 carbon dioxide absorption levels were obtained with Woiiastonite as the reactive silicate absorbent. Absorption levels of at least 10, more preferably 20 even more preferably at least 30 and most preferably at least 35 weight percent (Kg C02/kg absorbent) can be achieved. The absorption levels depend on process economy considerations and on the type of silicate absorbent used. Typically, the CSP comprises at most 95 wt%, preferably at most 90 wt% of the stoichiometric 15 maximum amount of absorbed carbon dioxide. This may have the advantage of providing additional glueing power for improving the strength properties of the brick. The CSP can be prepared in a variety of ways. For example, the carbon dioxide can be bubbled through a sludge of a reactive silicate absorbent and water, or the carbon dioxide can be added as a gas flow of carbon dioxide and water vapour through the reactive silicate absorbent. However, best results were 20 obtained in a process wherein a continuous feed of carbon dioxide is added to a rotating autoclave vessel containing a sludge of a reactive silicate absorbent and water.

[0021] The invention in particular relates to a reduced carbon footprint lime sandstone building material, that is preferably shaped in the form of a brick, and is obtainable by the method according to the invention as described above in its various embodiments. The lime sandstone 25 building material according to the invention comprises a carbon dioxide sequestrated product (CSP) being a (hydro-) silicate reaction product of carbon dioxide and a reactive silicate absorbent. The invention further in particular relates to a reduced carbon footprint lime sandstone building material prepared with sand, lime and an amount of CSP such that the carbon footprint of the building material is substantially zero or negative.

30 [0022] The building material of the invention is a substantially lime sandstone based building material. In the process of the invention, an amount X of CSP is incorporated into the mixture of step i), wherein X is typically an amount between 5 and 50 wt%, more preferably between 10 and 40 wt% (relative to the total weight of the lime sandstone building material). The chosen amount of CSP depends on the one hand on the required reduction of the carbon footprint and on the other 35 hand on the envisaged properties of the building material.

[0023] The CSP is preferably prepared in an autoclave at temperatures between 150 and 300 °C, preferably between 175 and 250 °C for a time between 0.5 and 25 hours, preferably between 1 and 8 hours. The pressure can vary between wide ranges, but it is advantageous to chose a high pressure, typically between 10 and 100, preferably between 15 and 50 bar. As described above, it 40 is preferred to prepare the CSP in the autoclave used in the brick manufacturing process.

-7- preferably concurrent with the brick hardening process step iv). Concurrent means that in the same autoclave space at the same time both the hardening of the sand lime stone brick and the carbon dioxide sequestration reaction takes place. In case the same autoclave is used for the production of the CSP and of the product, the pressure typically Is between 10 and 30 bar. For 5 example, the autoclave tube can be partitioned along its length In an upper and a lower part wherein the hardening of the lime sandstone brick takes place In the upper part of the autoclave tube and the carbon dioxide sequestration reaction takes place the lower part of the autoclave tube.

[0024] The shaped lime sandstone building material, in particular the lime sandstone brick, 10 comprises sand, lime and CSP being a (hydro-)silicate and carbonate containing reaction product of carbon dioxide and a reactive silicate absorbent, preferably in an amount between 5 and 50 wt% CSP relative to the total weight of the material. The CSP preferably comprises at least 10%, preferably at least 20% more preferably at least 30% of the stoichiometric maximum amount of absorbed carbon dioxide. The lime sandstone shaped building material or brick as a whole 15 preferably comprises at least 6 wt% of sequestrated carbon dioxide. At this level the carbon footprint is approximately zero for most production processes. Preferably the amount of sequestrated carbon dioxide In the building material is at least 3, more preferably at least 6, even more preferably at least 10, and more preferably at least 15 wt%. The building material of the invention can be used for reducing the carbon footprint of a building or construction work, by 20 Incorporating the building material into the building or work, thus enabling the use of higher carbon footprint materials into other parts of the building/work whilst still reaching the goals of reducing the total carbon footprint of the building/work.

[0025] It was surprisingly found that the lime sandstone shaped building material has good retention of mechanical properties which makes it suitable to replace normal lime sandstone 25 bricks. It was found that lime sandstone bricks according to the invention have a binding strength retention of at least 80%, preferably at least 90% and more preferably at least 95% and a compressive strength retention of at least 90%, preferably at least 100% (compared to the same material without CSP). The mechanical properties were retained also at CSP levels that would make the building material have a zero or negative carbon footprint. It is the inventor's 30 achievement to provide a process for production of a building material with zero or negative carbon footprint and with adequate mechanical properties.

[0026] The lime sandstone building materials are typically bricks for e.g. walls of buildings such as houses, particularly sand lime brick which brick type is generally used for load (e.g. ceiling or higher level floor) bearing walls. In heat insulated outer wall constructions, such bricks are 35 typically used to construct the inward facing part, at the outer face of which the insulating material and further outside the weather protecting gable material (e.g. plaster or mortar bound fired clay bricks) is located. The inventive bricks can have several dimensions, e.g. from as small as "waalformaat" (typical Dutch brick standardised dimension) to as large as a length and height of between 1 by 1 and 2 by 2 m at a thickness between 5 and 40 cm, more typically between 10 and -8- 20 cm. The bricks can have weight saving cavities preferably channels, preferably internally located and preferably extending in length or height.

[0027] The invention is to (preferably inertly) bind C02 (carbon dioxide) in sand lime brick by adding additional C02 during the production process. Preferably, mineralised C02 (preferably In 5 the form of a hydro-silicate compound) is added, preferably as a substitute for sand. The additive is preferably a partial or complete substitute for a typically used ingredient, such as sand In case of sand lime to produce e.g. brick.

[0028] It is possible to add additional C02 to the sand lime product, at a level of least 50% and even at least 100% of the C02 generated by the total energy needed for the production and 10 distribution of that product. Additional C02 is preferably added in mineralized form in such an amount that this mineral substitutes at least 10% or 25% or 50% and preferably not more than 75% of the used sand.

[0029] Additionally or alternatively the C02 is preferably an accelerant/catalyst in a gaseous form during the CSP production and is preferably also added In the autoclave phase production of 15 sand lime building material. This can shorten the required autoclave period, e.g. by more then 25% or more then 50% (e.g. between 4 and 6 or between 3 and 4 hours in stead of typically between 6 and 8 hours).

[0030] Preferably the additional C02 is added In an amount such that the brick or sand lime product coming from the process contains more than 10 or 20 or 30 kilograms additional C02 per 20 1,000 kilograms product or alternatively substantially the total amount of C02 generated per capita product. It is expected that the Inventive end product can contain even more than 50 or 60 kilograms additional C02 per 1,000 kilograms end product without losing product quality, conforming to all applicable NEN-norms with an ample safety margin.

[0031] During the hardening process reactions take place between the sand and calcium 25 hydroxide formed from the lime (Calcium oxide) and water sand to form cementitious products such as tobermorite gel and, if impurities are present, phases such as poorly cementitious hydrogarnet crystals. The purity and fineness of the sand is optimized to achieve good mechanical properties. The space between the grains of sand within the shaped blocks are believed to be filled by a hydro-silicate compound that acts as a glue between the sand grains within the pressed 30 block. Blocks that are stacked In the autoclave will not stick together.

[0032] Thus, the invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art. Further modifications in addition to those described above may be made to the structures and techniques described herein without departing 35 from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.

-9-

Examples

Production of carbon dioxide sequestrated products (CSP1

[0033] A carbon dioxide sequestrated product was produced by continuous feed of C02 to a slurry of wollastonite as the absorbent mineral in water in a rotating autoclave vessel. An 8 liter 5 autoclave was used having baffles along the inner wall (as a screw conveyor) and which can roll around its length-axis to achieve mixing of solid-water-C02 phases.

[0034] For this the autoclave was half-filled with the absorbent mineral and heated to above 200 °C. When it has reached this temperature the C02 was added to achieve a pressure of 30 bar. While the autoclave is rotating, with 47-50 rot/min, the C02 is added through a swivel joint to 10 maintain the pressure. During rotation, the vessel cannot be heated and therefore cools down to less than 170 °C. After cooling down, the vessel rotation is stopped and the vessel is again heated to above 200 °C. After approximately 4.5 hours at high temperature the carbonated mineral is harvested. During the test, C02 uptake, pressure and temperature are measured. The results of the experiments are presented in Table 1.

15

Table 1. CQ2 sequestration of wollastonite

Mineral Water Sequestrated Sequestrated

Mineral name amount amount C02 amount C02 [kg C02/ [kg] [kg] [kg] kg mineral]

Wollastonite 3.9 4.41 1.10 0.280

It is clear from the above table that the Wollastonite-CSP material has a relatively high amount of 20 C02 sequestrated, with a CFcsp of 0.280 kg C02 per kg mineral, equal to 280 kg C02 per ton mineral. The percentage of C02 sequestrated in this product is thus 28.0wt%. This Wollastonite-CSP is used in the following experiment.

Production of lime sand bricks

[0035] Lime sand bricks were produced using as a component the Wollastonite-CSP produced 25 above. Sand (gradation between zero and 2.8 mm with moisture content 13.1wt.%) was mixed with lime and different amounts of the above Woiiastonite-CSP. The mixture was left to stand and react for two hours after which the slurry was placed in a mould and a brick was pressed of dimensions 40x40x160 mm using a pressure of 4000kg. The moulded product was removed from the mould and after about 20 min placed in a horizontal 50 cm cylindrical autoclave having a 30 diameter of 18 cm. 1 L of water was added and the pressure and temperature were raised to 16 bar and 180°C. After 20 hours the pressure was released and the produced bricks were removed.

[0036] The bending strength and compressive strength of the bricks were measured (NEN-EN 771-2:2003/AI:2005) and compared with a reference brick that did not contain the CSP. The results are presented in table 2: 35 -10- CSP Bending Compressive

Sample number___strength strength_ (Wt.%) (MPa)__(MPa)_

Comparative Ex. 0.00 2.73__14.90_ 1__12.9 2.89__19.65_ _5__17.6 2.61__19.02_ 6__18.7 1.98__12.73_ _8_21.1 2.63__19.88_ 9 22.2 ZQ4~~ 113.59

The weight percentage of Wollastonite-CSP is calculated relative to the final total weight of the building material (brick).

The examples demonstrate that a lime sand brick can be produced according to the process of the 5 invention having a reduced carbon footprint. Moreover, in sample 8 a lime sand brick has been produced which has approximately 6 weight percent of sequestrated carbon dioxide (21.1wt% of Wollastonite-CSP comprising 28.0wt% of sequestrated carbon dioxide). This amount equals or slightly exceeds the estimated amount carbon dioxide to produce a brick in current production circumstances (estimated to be around 5.7wt% C02, or 57 kg of C02 per ton brick). The brick has 10 approximately the same bending strength but has significantly increased compressive strength.

Claims

A method of manufacturing a sand-lime brick product with a reduced carbon dioxide footprint, which method comprises the steps of: i) preparing a mixture comprising sand, lime and water, II) reacting the mixture, iii) forming the mixture in a mold, iv) curing the molded mold in a high temperature and high pressure pressure vessel, characterized in that In process step i) the mixture further comprises a carbon dioxide sequestered product (CSP) which is a (hydro) silicate and carbonate containing product of a reaction between a reactive silicate absorbent and carbon dioxide.

A method according to claim 1, wherein the carbon dioxide footprint is reduced, or preferably equal to or less than zero, by an amount of X 15 of CSP (expressed in parts by weight calculated on the total weight) in the mixture of step i) of the product) according to the formula: CFb + X (CFs - CS), wherein CFb is the carbon dioxide footprint of said product manufacturing process, CFs is the carbon dioxide footprint of the carbon dioxide sequestering method, and CS is the footprint reduction is from the CSP due to sequestered carbon dioxide.

The method of claim 2, wherein CFb + X (CFs - CS) is less than or equal to zero.

Method according to claims 1-3, wherein in step i) the mixture between 50 and 97% by weight of sand, between 0.5 and 50% by weight of CSP, and between 3 and 10% by weight of lime (% by weight calculated on the total of solids) and between 0.5 and 5% by weight of water (relative to the total of solids).

The method according to any of claims 1-4, wherein in step ii) the reaction time is between 0.5 and 2 hours.

The method of any one of claims 1-5, wherein in step iii) the mixture is formed into the shape of a brick.

7. Method as claimed in any of the claims 1-6, wherein In step iv) the curing of the molded form is carried out in a steam-filled pressure vessel, preferably at temperatures between 150 and 300 ° C and a pressure between 10 and 30 bar.

The method of claim 7, wherein the curing is carried out in the presence of carbon dioxide gas.

9. A method according to any one of the preceding claims, wherein the carbon dioxide footprint 35 is calculated according to MRPI methodology / NEN 8006.

A method according to any one of the preceding claims, wherein the ultra-hardening step Iv) comprises a high-pressure and / or high-temperature treatment step In a high-pressure and / or high-temperature device and wherein the CSP is prepared in the same device.

The method of claim 10, wherein the CSP is prepared simultaneously with and in the same device as the curing step of the sand-lime brick product. -12-

The method of any one of the preceding claims, wherein the CSP is prepared at least in part from the carbon dioxide emitted by the process for producing the sand-lime brick product.

13. A method according to any one of the preceding claims, wherein the CSP is prepared with carbon dioxide obtained at least partially from an external source.

The method of claim 13, wherein the external source is an energy production plant or a waste incineration plant.

15. A method according to any one of the preceding claims, wherein the method for the production of the sand-lime brick product is integrated with a waste incineration or energy production process, and wherein carbon dioxide produced in said process is converted into a CSP which is converted into the sand-lime brick product used.

The method of claim 15, wherein bottom ash and / or fly ash from the waste incineration or energy production process is used as a source of the reactive silicate absorbent in the process for producing the sand-lime brick product.

A sand-lime brick product, preferably a sand-lime brick building material, with a reduced carbon dioxide footprint, obtainable by the method according to any one of claims 1-16.

The sand-lime brick building material according to claim 17, which comprises a carbon dioxide sequestered product (CSP) that is a (hydro) silicate reaction product of carbon dioxide and a reactive silicate absorbent.

The sand-lime brick building material according to any of claims 17-18, which comprises between 5 and 50% by weight of CSP, calculated on the total weight of the material.

The sand-lime brick building material according to any of claims 17-19, wherein the CSP comprises at least 10%, preferably at least 20% and more preferably at least 30% of the stoichiometric maximum amount of carbon dioxide absorbed.

The sand-lime brick building material according to any of claims 17-20, wherein the CSP comprises at most 95%, preferably at most 90% of the stoichiometric maximum amount of carbon dioxide absorbed.

22. Sand-lime brick building material according to any of claims 17-21, which comprises at least 3, preferably at least 6 and more preferably at least 8% by weight of sequestered carbon dioxide.

The sand-lime brick building material according to any of claims 17-22, which is formed in the form of a brick.

A shaped sand-lime brick building material according to claim 23, with a bond strength retention of at least 80%, preferably at least 90% and more preferably at least 95%, and a compressive strength retention of at least 90%, preferably at least 100% (in comparison with the same material without CSP).

Use of the building material according to any of claims 17-24 for reducing the carbon dioxide footprint of buildings or structures.