METHOD FOR CARBONATING WASTE MATERIALS

Abstract

A method for simultaneously drying and carbonating a mineral waste material that includes carbonatable calcium and/or magnesium compounds and/or silicate, aluminate or silicate-aluminate phases in a spray dryer, wherein a starting material slurry is provided including the mineral waste material in the form of particles with a D90500 m and at least 30 wt.-% water, a hot gas is provided including at least 4 Vol.-% CO.sub.2 and fed into the spray dryer, the starting material slurry is sprayed into the hot gas in the spray dryer wherein a temperature of 100 C. and a relative humidity of <50% are adjusted in the spray dryer, the starting material slurry is transformed into evaporated water and a dry, carbonated product comprising calcium carbonate and/or one of silica gel or alumina gel or silica-alumina gel, and the dry, carbonated product is separated from the gas and evaporated water.

Claims

1. A method for simultaneously drying and carbonating a mineral waste material, the mineral waste material comprising carbonatable calcium compounds and/or carbonatable magnesium compounds and/or silicate, aluminate or silicate-aluminate phases able to be converted into silica gel, alumina gel or silica-alumina gel respectively by carbonation, in a spray dryer, wherein a starting material slurry is provided comprising the mineral waste material in the form of particles with a D.sub.90500 m and at least 30 wt.-% water, a hot gas is provided comprising at least 4 Vol.-% CO.sub.2 and fed into the spray dryer the starting material slurry is sprayed into the hot gas in the spray dryer wherein a temperature of 100 C. and a relative humidity of <50% at the outlet are adjusted in the spray dryer the starting material slurry is transformed into evaporated water and a dry, carbonated product comprising calcium and/or magnesium carbonate and/or at least one of silica gel or alumina gel or silica-alumina gel, and the dry, carbonated product is separated from the gas and evaporated water.

2. The method according to claim 1, wherein the mineral waste material is waste concrete, especially recycled concrete paste; waste sand-lime-bricks; waste aerated concrete; by-products from cement production; by-products and wastes from gas treatment installations; residues from combustion processes; slags; mine tailings from mining natural pozzolans, rocks, ores; burned or hydrated lime containing waste; and mixtures of two or more thereof including mixtures of two or more waste concretes; by-products from cement production; by-products and wastes from gas treatment installations; residues from combustion processes; slags; mine tailings from mining natural pozzolans, rocks, ores; and burned or hydrated lime containing wastes.

3. The method according to claim 2, wherein the mineral waste material is selected from the group consisting of recycled concrete paste, waste sand-lime-bricks, waste aerated concrete, fly ash, bottom ash, mine tailings from mining silicate rocks, steel slags, carbide lime, and mixtures of two or more thereof.

4. The method according to claim 1, wherein the particles in the starting material slurry have a D.sub.90250 m, and/or the D.sub.50 ranges from 0.1 to 250 m.

5. The method according to claim 1, wherein the starting material slurry has a solid:liquid mass ratio from 2:1 to 1:20, and/or a water content35 wt.-% and/or a water content95 wt.-%.

6. The method according to claim 1, wherein the temperature in the spray dryer ranges from 100 C. to 800 C.

7. The method according to claim 1, wherein the relative humidity in the spray dryer is 30%.

8. The method according to claim 1, wherein the hot gas contains at least 7 Vol.-% CO.sub.2.

9. The method according to claim 1, wherein the hot gas is an exhaust gas from a cement plant, a lime plant, a coal or gas fired power plant, and/or a waste incinerator or biomass incinerator.

10. The method according to claim 1, wherein the pressure in the spry dryer is ambient pressure or from 10 to 300 mbar overpressure or underpressure.

11. The method according to claim 1, wherein at least one additional material is added to the starting material slurry, wherein the at least one additional material accelerates the carbonation process and/or improves the final properties of the dry, carbonated product or the composite cement or binder or building material made with it.

12. The method according to claim 1, wherein the mineral waste material is hydrothermally treated in an autoclave before the simultaneous carbonation and drying.

13. The method according to claim 12, wherein during hydrothermal treatment a water-solid weight ratio is equal to or larger than 0.1 and/or a temperature ranges from 25 to 400 C. and/or the pressure is endogenous.

14. The method according to claim 3, wherein the starting material slurry has a solid:liquid mass ratio from 1:1 to 1:10, and/or a water content50 wt.-% and/or a water content85 wt.-%.

15. The method according to claim 3, wherein the temperature in the spray dryer ranges from 130 C. to 600 C.

16. The method according to claim 14, wherein the temperature in the spray dryer ranges from 150 C. to 400 C. and the relative humidity in the spray dryer is 30%.

17. The method according to claim 3, wherein the hot gas contains from 12 to 99 Vol. % CO.sub.2.

18. The method according to claim 17, wherein the hot gas is an exhaust gas from a cement plant, a lime plant, a coal or gas fired power plant, and/or a waste incinerator or biomass incinerator.

19. The method according to claim 14, wherein the hot gas contains from 12 to 99 Vol. % CO.sub.2 and is an exhaust gas from a cement plant, a lime plant, a coal or gas fired power plant, and/or a waste incinerator or biomass incinerator.

20. The method according to claim 6, wherein the starting material slurry has a solid:liquid mass ratio from 2:1 to 1:20, and/or a water content35 wt.-% and/or a water content95 wt.-%.

Description

EXAMPLE 1

[0063] Recycled concrete paste obtained according to US 2016/0046532 A1 as a slurry from the carbonation grinding of recycled concrete and filtering off the cleaned aggregate is used as the starting material slurry. The slurry contains 60 wt.-% water and the solids comprise about 40 wt.-% fine aggregate and about 60 wt.-% hardened cement paste. Thus, approximately 30 wt.-% calcium calculated as CaO is contained in carbonatable compounds, namely the CSH gel, calcium hydroxide, AFt and AFm phases, other hydrates and unreacted clinker minerals. Tertiary air from a cement kiln is used as the hot gas. The hot gas contains about 16 Vol.-% CO.sub.2 as well as 12 Vol.-% H.sub.2O (about 2% relative humidity at 175 C.). Both slurry and gas enter the spray dryer at the inlet. Due to the temperature of the hot gas of about 175 C. the drying chamber of the spray dryer has a temperature from 165 C. at the inlet to 130 C. at the outlet. Within the average residence time of 7 seconds the particles are travelling from the inlet nozzle to the outlet end they are dried and 50 wt.-% of the contained carbonatable calcium compounds are carbonated. The relative humidity in the drying chamber is approximately 2% at the gas inlet and 11% at the gas outlet.

EXAMPLE 2

[0064] Calcareous fly ash is used as the starting material in the slurry. The slurry contains 30 wt.-% water. Approximately 23 wt.-% calcium calculated as CaO is contained in carbonatable compounds in the slurry. Tertiary air from a cement kiln is used as the hot gas. The hot gas contains about 22 Vol.-% CO.sub.2 as well as 14 Vol.-% H.sub.2O (about 4% relative humidity at 156.9 C.). Both slurry and gas enter the spray dryer at the inlet. Due to the temperature of the hot gas of about 157 C. the drying chamber of the spray dryer has a temperature from 145 C. at the inlet to 120 C. at the outlet. Within the average residence time of 7 seconds the particles are travelling from the inlet nozzle to the outlet end they are dried and 70 wt.-% of the contained carbonatable CaO is carbonated. The relative humidity in the drying chamber is approximately 4% at the gas inlet and 16% at the gas outlet.

EXAMPLE 3

[0065] Dredged sediments as a slurry are used as starting material slurry. The slurry contains 35 wt.-% of water. Approximately 20 wt.-% calcium calculated as CaO is contained in carbonatable compounds in the slurry, a part of which has been added as burned lime to stabilize and sanitize the slurry. Tertiary air from a cement kiln is used as the hot gas. The hot gas contains about 19 Vol.-% CO.sub.2 as well as 11 Vol.-% H.sub.2O (about 2% relative humidity at 171 C.). Both slurry and gas enter the spray dryer at the inlet. Due to the temperature of the hot gas of about 171 C. the drying chamber of the spray dryer has a temperature from 160 C. at the inlet to 125 C. at the outlet. Within the average residence time of 7 seconds the particles are travelling from the inlet nozzle to the outlet end they are dried and 60 wt.-% of the contained carbonatable CaO is carbonated. The relative humidity in the drying chamber is approximately 3-% at the gas inlet and 14% at the gas outlet.