CARBONATED BIOMASS ASH AS A SUBSTITUTE CEMENTITIOUS MATERIAL

Abstract

A method of producing a cementitious material substitute includes preparing a carbonated biomass ash.

Claims

1. A method of producing a cementitious material substitute comprising: preparing a carbonated biomass ash.

2. The method according to claim 1, wherein the carbonated biomass ash contain at least 4.5% of inorganic carbon.

3. The method according to claim 2, wherein the carbonated biomass ash contain at least 5% of inorganic carbon.

4. The method according to claim 3, wherein the carbonated biomass ash contain at least 5.5% of inorganic carbon.

5. The method according to, claim 1, wherein the carbonated biomass ash contain less than 10% of lime.

6. The method according to claim 1, wherein the carbonated biomass ash contain more than 2% of carbonates.

7. The method according to claim 1, wherein the carbonated biomass ash contain less than 60% of SiO.sub.2.

8. The method according to claim 1, wherein the carbonated biomass ash contain less than 40% of Al.sub.2O.sub.3.

9. The method according to claim 1, wherein the carbonated biomass ash contain calcite, kalcinite, carbo-hydroxyapatite and/or hydrocalumine.

10. The method according to claim 1, wherein the carbonated biomass ash have a loss on ignition of at least 5%.

Description

[0025] In the context of the present invention: [0026] the term biomass ash means any mainly basic residue from the combustion of various plant, natural and non-fossil organic materials such as wood, so-called annual plants, agricultural residues, paper and wastewater treatment plant sludge (or STEP sludge) containing less than 11% total carbon, less than 4% inorganic carbon, and at least 1% Na.sub.2O equivalent. Preferably, the biomass ash further contain at least one of the following phases: whitlockite, hydroxyapatite, tremolite and/or tricalcium phosphate; [0027] the term carbonated biomass ash means any biomass ash which, after being brought into contact with a CO.sub.2-enriched gas flow, retains part of it and contains more than 4% inorganic carbon;

[0028] the term aluminous cement means any cement, amorphous or not, obtained by cooking a mixture of limestone and bauxite and containing at least 5% monocalcium aluminate CA; 20 [0029] the term quick natural cement means any hydraulic binder with rapid setting and hardening according to standard NF P 15-314:1993 in force on the date of the present invention. Preferably, quick natural cement designates a cement prepared from a clinker comprising: [0030] from 0% to 20% of C.sub.3S; [0031] from 40% to 60% of C.sub.2S; [0032] from 7% to 12% of C.sub.4AF; [0033] from 2% to 10% of C.sub.3A; [0034] from 10% to 15% of CaCO.sub.3 (calcite); [0035] from 10% to 15% of Cas (SiO.sub.4).sub.2CO.sub.3 (spurrite); [0036] from 3% to 10% of sulfate phases: yeelimite C.sub.4A.sub.3$, langbeinite (K.sub.2Mg.sub.2(SO.sub.4).sub.3, anhydrite (CaSO.sub.4); and [0037] from 10% to 20% lime, periclase, quartz and/or one or more amorphous phases; [0038] the term Portland cement means any Portland clinker-based cement classified as CEM (I, II, III, IV or V) according to standard NF EN 197-1; [0039] the term sulfo-aluminous cement means any cement prepared from a sulfo-aluminous clinker containing 5% to 90% of yeelimite phase C.sub.4A.sub.3$, a source of sulfate, and, optionally, a limestone addition; [0040] the term cement composition means any composition based on cement or an alkali-activated binder and free of aggregates, preferably any composition comprising an aluminous cement, a quick natural cement, a Portland cement and/or a sulpho-aluminous cement and free of aggregates, capable of being used for the preparation of a construction material; [0041] the term cementitious material substitute means any composition capable of partly replacing a cementitious composition in the preparation of a construction material while contributing to the increase in performance of the cementitious binder resulting from this combination; [0042] the term Na.sub.2O equivalent or Na.sub.2O eq. means the alkali content of a cement calculated according to the following formula: % Na.sub.2O eq.=(% Na.sub.2O+0.658% K.sub.2O) soluble in acid; [0043] the term loss on ignition means the cumulative content of bound water, organic matter, CO.sub.2 of carbonates (limestone fillers and carbonated part of the material) and possible oxidizable elements. The loss on ignition is determined by calcination in air at a temperature of (950+/25 C.) according to the method described in standard NF EN 196-2 (classification index P 15-472)-Cement testing methods-Part 2: Chemical analysis of cements; and [0044] the term construction material means mortar or concrete.

[0045] In the context of the present invention, the following notations are adopted to designate the mineralogical components of cement: [0046] C represents CaO; [0047] A represents Al.sub.2O.sub.3; [0048] F represents Fe.sub.2O.sub.3; [0049] S represents SiO.sub.2; and [0050] $ represents SO.sub.3.

[0051] In the context of the present invention, the inorganic carbon rate or CIT corresponds to the amount (% w/w) of inorganic carbon contained in an entity (e.g. carbonated biomass ash) relative to the total weight of said entity (e.g. said carbonated biomass ash).

[0052] To determine the level of inorganic carbon, different methods can be used, such as for example a previously calibrated Carbon Hydrogen Sulfur (CHS) elemental analyzer. To do this, approximately 250 mg of the product to be analyzed is placed in a nickel boat. This boat is then introduced into a tubular quartz furnace allowing a gradual rise in temperature and stages in temperature in order to separate the different carbon species in a sample. It can thus be determined: [0053] the COT, namely the amount (% w/w) of total organic carbon of the entity determined by analysis of the signal obtained between 100 C. and 400 C. with a temperature hold at 400 C.; [0054] the C, namely the amount (% w/w) of elemental carbon of the entity determined by analysis of the signal obtained between 400 C. and 600 C. with a temperature hold at 600 C.; and [0055] the CIT, namely the amount (% w/w) of total inorganic carbon of the entity determined by analysis of the signal obtained between 600 C. and 1000 C. with a temperature hold at 1000 C.

[0056] The total carbon CT corresponds to the sum of these three values: CT=COT+C+CIT

[0057] Finally, in the context of the present invention, the proportions expressed in % correspond to weight percentages relative to the total weight of the considered entity (e.g. ash).

[0058] The subject of the present invention is therefore the use of carbonated biomass ash as a cementitious material substitute. Preferably, the carbonated biomass ash possess the following characteristics, selected alone or in combination: [0059] carbonated biomass ash contain at least 4.5% of inorganic carbon; preferably the carbonated biomass ash contain at least 5% of inorganic carbon; very preferably, the carbonated biomass ash contain at least 5.5% of inorganic carbon; [0060] carbonated biomass ash contain less than 10% of lime; preferably the carbonated biomass ash contain less than 5% of lime; very preferably, the carbonated biomass ash contain less than of 3% lime; [0061] carbonated biomass ash contain more than 2% of carbonates; preferably the carbonated biomass ash contain more than 15% of carbonates; very preferably, the carbonated biomass ash contain more than 25% of carbonates; [0062] carbonated biomass ash contain less than 60% of SiO.sub.2; preferably the carbonated biomass ash contain less than 40% of SiO.sub.2; very preferably, the carbonated biomass ash contain less than 30% of SiO.sub.2; [0063] carbonated biomass ash contain less than 40% of Al.sub.2O.sub.3; preferably carbonated biomass ash contain less than 30% of Al.sub.2O.sub.3; very preferably, the carbonated biomass ash contain less than 20% of Al.sub.2O.sub.3; [0064] carbonated biomass ash contain calcite, kalcinite, carbo-hydroxyapatite and/or hydrocalumine; and/or [0065] carbonated biomass ash have a loss on ignition of at least 5%; preferably the carbonated biomass ash have a loss on ignition of at least 15%; very preferably, the carbonated biomass ash have a loss on ignition of at least 20%;

[0066] The carbonated biomass ash according to the present invention make it possible to achieve substitution rates of up to 45% of the cementitious composition, preferably up to 40% of the cementitious composition, most preferably up to 35% of the cementitious composition, while maintaining mechanical properties, and in particular medium and long-term compressive strengths of the construction material finally prepared, compatible with the intended uses.

[0067] The carbonated biomass ash used in the context of the present invention can be obtained by any method known to those skilled in the art. By way of example, it can in particular be cited a method for preparing carbonated biomass ash comprising the following steps: [0068] introducing biomass ash into a rotary drum, mixer, container or fluidized bed type reactor; [0069] bringing the ash into contact with a source of CO.sub.2 such as exhaust gas from a cement plant or a thermal power plant; and [0070] recovering the obtained carbonated biomass ash.

[0071] The present invention can be illustrated in a non-limiting manner by the following examples.

Example 1Carbonated Biomass Ash

[0072] Different carbonated biomass ash are obtained by placing a mixture of approximately 250 g of ash obtained by combustion of different biomasses and 15% by mass of water ash in a hermetically sealed bowl which is itself fixed on the base of a heated mixing robot.

[0073] The compositions and features of the used biomass ash (Ash 1 to 4) before carbonation are reported in Table 1 below, in comparison with the composition and features of fly ash (non-carbonated) usually used in the cement industry.

TABLE-US-00001 TABLE 1 Composition and features of biomass ash before carbonation Composition (% (w/w)) Wood Wood Paper Paper Type C ash ash Ash ash coal fly Features (Ash 1) (Ash 2) (Ash 3) (Ash 4) ash (Ref.) CaO 31 21 54 63 18.3 SiO.sub.2 4 2 20 10 43.5 Al.sub.2O.sub.3 1 2 9 67 20.4 Fe.sub.2O.sub.3 1 1 1 5.4 SO.sub.3 12 14 2 1 1.8 P.sub.2O.sub.5 4 3 1 Na.sub.2O 1 1 1 1 1.5 K.sub.2O 25 26 1 1 MgO 5 3 2 2 4.3 TiO.sub.2 1 Loss on ignition 15 20 8 14 0.9 CIT 3.4 3.1 1.9 3.9

[0074] The reactor is equipped with a cup containing water to regulate the relative humidity in the reactor.

[0075] The temperature of the bowl is maintained at 55 C. The bowl cover is equipped with 2 orifices which allow the injection of a gas and its evacuation.

[0076] The gas is injected for a mixing time of 1 hour and is made up of 100% CO.sub.2.

[0077] The biomass ash thus carbonated have the following features (Table 2), in comparison with non-carbonated biomass ash.

TABLE-US-00002 TABLE 2 Ash/carbonate ash CIT (%) Ash 1 Before carbonation 3.4 Carbonated 4.8 Ash 2 Before carbonation 3.1 Carbonated 8.6 Ash 3 Before carbonation 1.9 Carbonated 4.8 Ash 4 Before carbonation 3.9 Carbonated 7.8

Example 2Cementitious Compositions According to the Invention

[0078] A reference Portland cement of class CEM I 52.5 R is mixed with different quantities of non-carbonated or carbonated ash from Example 1.

[0079] The compositions of cementitious compositions 2 to 5 (compositions according to the invention) and 6 to 9 (cementitious compositions prepared from non-carbonated ash) thus obtained are reported in the following Tables 3.1, 3.2 and 3.3.

TABLE-US-00003 TABLE 3.1 Cementitious compositions 1 to 9 Cementitious composition 1 (% w/w) (Ref.) 2 3 4 5 6 7 8 9 CEM I 52, 5 100 75 75 75 75 75 75 75 75 Carbonated 0 25 0 0 0 0 0 0 0 ash 1 Carbonated 0 0 25 0 0 0 0 0 0 ash 2 Carbonated 0 0 0 25 0 0 0 0 0 ash 3 Carbonated 0 0 0 0 25 0 0 0 0 ash 4 Non-carbonated 0 0 0 0 0 25 0 0 0 ash 1 Non-carbonated 0 0 0 0 0 0 25 0 0 ash 2 Non-carbonated 0 0 0 0 0 0 0 25 0 ash 3 Non-carbonated 0 0 0 0 0 0 0 0 25 ash 4

TABLE-US-00004 TABLE 3.2 Cementitious compositions 1 to 9 (phasic composition) Cementitious composition (% w/w) 1 2 3 4 5 6 7 8 9 C.sub.3S 61.2 48.6 47.3 46.5 46.8 48.6 48.1 46.7 46.8 C.sub.2S AlphaH 2.8 2.8 2.3 5.3 2.8 2.6 2.2 6.3 5.9 C.sub.2S beta 7.0 7 6.2 7.8 7.5 6.4 6.9 8.5 7.6 C.sub.3A 3.3 3.3 3.1 2.9 2.9 3.1 2.5 2.9 2.9 C.sub.4AF 12.2 9 8.3 9.3 9 9.2 9.8 9.1 9 C.sub.12A.sub.7 0.5 0.5 0.5 0.7 0.6 1.1 0.8 0.7 1.6 Calcite 5.2 6.1 12.5 19.6 2.6 4.9 3.9 8.5 Kalicinite 3.3 0 Sylvite 0.5 Lime 0.1 0.1 0.2 0.7 0.3 0.9 5.6 6.5 Periclase 0.9 0.5 1.4 0.6 0.4 1.4 0.6 0.8 0.5 Hydroxyapatite 2.1 1.7 Carbo-hydroxyapatite 2 2.7 0.2 Hydrocalumite 0.7 0.5 Quartz 0.6 0.2 0.1 1.6 0.4 0.3 0.3 1.7 0.9 Anhydrite 0.9 1 1.1 1.3 1 1.2 1.1 1.4 1.1 Bassanite 1.8 1.6 1.3 1.5 1.5 1.8 2 1.5 1.5 Gypsum 2.3 2 1.9 1.2 1.2 2.2 1.9 1.2 1.2 Syngenite 1.7 1.3 1.5 1.5 1.4 Aphtithalite 1.2 0.3 0.3 0.2 0.2 0.5 0.4 0.2 0.2 Arcanite 1.0 8.9 10.8 0.3 0.3 6.9 8.9 0.3 0.3 Ca-Langbeinite 0.3 0.1 0.2 0.3 Portlandite 0.2 2.1 1.8 1.9 1.6 5 4.6 1.8 1.6 Amorphous 7 6.7 5.7 5.3 6.5 6.3 5.1 3.6

TABLE-US-00005 TABLE 3.3 Cementitious compositions 1 to 9 (elemental analysis) Cementitious composition (% w/w) 1 2 3 4 5 6 7 8 9 SiO.sub.2 20.3 15.9 15.6 19.8 17.6 16.1 15.8 20.1 17.8 Al.sub.2O.sub.3 4.6 3.7 3.9 5.5 4.9 3.8 4 5.8 5.3 Fe.sub.2O.sub.3 3.3 2.5 2.7 2.7 2.6 2.6 2.7 2.7 2.6 CaO 61.6 52.4 51 57.3 57.8 53.1 51.3 59.8 61.9 MgO 1.9 2.4 2.2 1.9 1.7 2.6 2.2 1.9 1.8 SO.sub.3 3.6 5.2 6.4 3.2 3 5.4 6.5 3.3 3 K.sub.2O 1.0 7 7.7 0.9 1 7.1 8.1 0.9 0.8 Na.sub.2O 0.2 0.4 0.5 0.3 0.4 0.4 0.5 0.3 0.4 SrO 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 TiO.sub.2 0.3 0.2 0.2 0.4 0.3 0.2 0.2 0.5 0.3 P.sub.2O.sub.5 0.2 0.9 1 0.4 0.2 1 1 0.4 0.1 MnO 0.07 0.3 0.4 0.1 0.1 0.3 0.43 0.1 0.1 Na.sub.2O eq. 5 5.5 0.9 1 5.5 5.8 0.9 1 Loss on 1.86 8.6 7.6 5.3 8.4 6.1 6.7 1.9 3.6 ignition (950 C.)

[0080] The gain in CO.sub.2 emissions for the cement compositions 2 to 5 compared to the reference cement composition 1 is reported in the following Table 4.

TABLE-US-00006 TABLE 4 CO.sub.2 gain for cementitious compositions 2 to 5 Cementitious composition 2 3 4 5 CO.sub.2 gain compared to the 213 201 219 226 reference (KgCO.sub.2 eq/t)

Example 3Workability (Spreading)

[0081] A spreading measurement was carried out in accordance with standard EN 1015-3 on 3 mortars manufactured according to standard 196-1 by mixing 450 g of binder 1, 4 or 8, 1350 g of sand and 225 g of water.

[0082] The results are reported in the following Table 5.

TABLE-US-00007 TABLE 5 Spreading measurement for the cementitious compositions 1, 3 and 8 Mortar prepared Mortar prepared Mortar prepared from cementitious from cementitious from cementitious composition 1 composition 3 composition 8 Spread (in mm) 185 142 133

[0083] As these results show, the use of a mixture of cement and non-carbonated ash leads to a loss of almost 30% in workability. Carbonating the ash before mixing with the cement makes it possible to limit the loss of rheology and maintain it at an acceptable level for a good implementation.

Example 4Mechanical Performances

[0084] The compressive strength of the cementitious compositions obtained in Example 2 was measured on prismatic specimens of standardized mortar (4416 cm3), at different time periods (1, 2, 7 and 28 days) according to standard EN 196-1.

[0085] The obtained results are reported in the following Table 6.

TABLE-US-00008 TABLE 6 Compressive strength of cementitious compositions 1 and 4 to 9 Cementitious composition 1 4 5 6 7 8 9 R.sub.c (in MPa) 29.3 17.4 18.8 3 at 1 day R.sub.c (in MPa) 41.7 30.7 35.1 26.1 7 at 2 days R.sub.c (in MPa) 52.9 43.7 48.1 3.2 17.8 41.4 15 at 7 days R.sub.c (in MPa) 62 52.5 51 3.5 25.5 43.4 21 at 28 days

[0086] The cementitious compositions according to the invention (i.e. compositions 4 and 5) present acceptable performances with regard to those observed for the reference CEM I at all deadlines. It is thus noted that mechanical performance is maintained in the short, medium and long term at an acceptable level.

[0087] On the other hand, there is a sharp reduction in the mechanical performance of cementitious compositions containing non-carbonated biomass ash.

Example 5Comparative Examples

5.1Coal-Type Fly Ash-Based Cementitious Composition

[0088] The coal-type fly ash whose composition is reported in Table 1 are carbonated according to the protocol of Example 1.

[0089] The cementitious composition 10 is obtained by mixing a reference Portland cement of class CEM I 52.5 R with the carbonated ash thus obtained in a proportion (% w/w) 75/25.

5.2Carbonated Cementitious Composition after Addition of Non-Carbonated Ash

[0090] The cementitious composition 11 is obtained by carbonation according to the protocol of Example 1 of a 75/25 mixture (% w/w) of a reference Portland cement of class CEM I 52.5 R with paper ash No. 4 of Example 1 (non-carbonated ash).

5.3Comparative Results

5.3.1Workability (Spreading)

[0091] The workability of the cementitious composition 11 is evaluated according to the protocol of Example 3.

[0092] The mortar prepared from the cementitious composition 11 is too dry and therefore does not spread, making its implementation impossible.

5.3.2Compressive Strength

[0093] The compressive strength of cementitious compositions 10 and 11 is evaluated according to the protocol of Example 4.

[0094] The obtained results are reported in the following Table 7.

TABLE-US-00009 TABLE 7 Compressive strength of cementitious compositions 10 and 11 Cementitious composition 10 11 R.sub.c (in MPa) at 2 days 29.5 14 R.sub.c (in MPa) at 7 days 40.6 28.8 R.sub.c (in MPa) at 28 days 48.5 30.8

[0095] The compressive strengths of the cement compositions prepared from fly ash from coal combustion are significantly lower than the compressive strengths of the cementitious compositions prepared from carbonated biomass ash at 2, 7 and 28 days. The obtained results for cementitious composition 11 are extremely low (loss of more than 50% of performance compared to the 100% Portland reference) and render it unusable.