A method of exhaust gas scrubbing includes providing recycled concrete fines as a waste material rich in carbonatable Ca and/or Mg phases and with d.sub.90≤1000 μm and a Rosin-Rammler slope n from 0.6 to 1.4 , injecting the waste material into an exhaust gas stream containing CO.sub.2 and/or SO.sub.x for reaction with CO.sub.2 and/or SO.sub.x at a relative humidity of 50 to 100 Vol.-% and a temperature from 40 to 130° C. in an amount of dry waste material ranging from 5 to 30 kg/m.sup.3, withdrawing a partly carbonated and/or sulphurized waste material and purified exhaust gas, and recycling a part of the partly carbonated and sulphurized waste material while the remainder is discharged, as well as use of a waste material slurry for exhaust gas cleaning of CO.sub.2 and/or SO.sub.x.

A method of exhaust gas scrubbing includes providing recycled concrete fines as a waste material rich in carbonatable Ca and/or Mg phases and with d.sub.90≤1000 μm and a Rosin-Rammler slope n from 0.6 to 1.4 , injecting the waste material into an exhaust gas stream containing CO.sub.2 and/or SO.sub.x for reaction with CO.sub.2 and/or SO.sub.x at a relative humidity of 50 to 100 Vol.-% and a temperature from 40 to 130° C. in an amount of dry waste material ranging from 5 to 30 kg/m.sup.3, withdrawing a partly carbonated and/or sulphurized waste material and purified exhaust gas, and recycling a part of the partly carbonated and sulphurized waste material while the remainder is discharged, as well as use of a waste material slurry for exhaust gas cleaning of CO.sub.2 and/or SO.sub.x.

Provided herein are integrated biomass combustion-carbonation gas conditioning systems to directly sequester carbon dioxide from biomass-derived CO.sub.2-containing flue gas. The CO.sub.2 is sequestered by mineral carbonation in concrete materials within a carbonation reactor. The mineral carbonation processes sequester CO.sub.2 in concrete materials, aqueous slurries, or aggregates without any additional carbon enrichment process. Contacting a CO.sub.2-containing gas stream from a biomass combustion apparatus with concrete, aggregate, or alkaline solutions, causes a carbonation reaction in which carbonation products such as calcium carbonate (CaCO.sub.3) and alumina silica gel are formed. The carbonation reactions set forth herein are useful for strengthening concrete and concrete components. Certain processes herein condition the biomass-derived flue gas. The conditioning includes condensing the gas to remove acidic gas, and to remove particulates and water. The conditioning includes adjusting the temperature, relative humidity, and gas flow rate of the biomass-derived flue gas without any carbon capture step before entering the carbonation reactor. The permanent storage of CO.sub.2 in concrete materials reduces carbon emissions from biomass combustion systems. The process does so, in certain embodiments, at low temperatures, ambient pressure, and even under dilute CO.sub.2 concentrations in CO.sub.2-containing flue gas streams. For example, the CO.sub.2 concentration in a CO.sub.2-containing flue gas stream from a biomass combustion system may be lower than 20 volume percent (vol %) and be used to produce low-carbon concrete materials.

Sorbent components containing halogen, calcium, alumina, and silica are used in combination during coal combustion to produce environmental benefits. Sorbents such as calcium bromide are added to the coal ahead of combustion and other components are added into the flame or downstream of the flame, preferably at minimum temperatures to assure complete formation of the refractory structures that result in various advantages of the methods. When used together, the components reduce emissions of elemental and oxidized mercury; increase the level of Hg, As, Pb, and/or Cl in the coal ash; decrease the levels of leachable heavy metals (such as Hg) in the ash, preferably to levels below the detectable limits; and make a highly cementitious ash product.

Sorbent components containing halogen, calcium, alumina, and silica are used in combination during coal combustion to produce environmental benefits. Sorbents such as calcium bromide are added to the coal ahead of combustion and other components are added into the flame or downstream of the flame, preferably at minimum temperatures to assure complete formation of the refractory structures that result in various advantages of the methods. When used together, the components reduce emissions of elemental and oxidized mercury; increase the level of Hg, As, Pb, and/or Cl in the coal ash; decrease the levels of leachable heavy metals (such as Hg) in the ash, preferably to levels below the detectable limits; and make a highly cementitious ash product.

The disclosure herein sets forth processes and compositions for producing carbonated materials comprising calcium carbonates through a mechanochemical process. The present disclosure concerns the production of calcium carbonate by sequestrating CO.sub.2. Certain processes herein include providing alkaline-rich mineral materials that include carbonatable solid wastes such as lime kiln dust, cement kiln dust, and coal combustion residues, and simultaneously fractioning the alkaline-rich mineral materials, while contacting the alkaline-rich mineral materials with a CO.sub.2-containing gas in carbonation reactor at low temperature and ambient pressure. In some embodiments, the alkaline-rich mineral materials are partially carbonated before being used in the processes disclosed herein. After contacting the alkaline-rich mineral materials with a CO.sub.2-containing gas in carbonation reactor at low temperature and ambient pressure, solid calcium carbonate is produced. In aqueous reactors, the solid calcium carbonate is filtered from a solution in which it precipitated, and the remaining solution includes hydroxide as well as alkaline metal ions. The solution filtered from the solid calcium carbonate can be sequentially contacted with a CO.sub.2-containing gas stream to precipitate additional calcium carbonate. The carbonated materials formed from these processes can be used in the form of a slurry, as a moist powder, as a dried powder, as a reactive filler or as a supplementary cementitious material in a mixture that is used to make concrete.

The disclosure herein sets forth processes and compositions for producing carbonated materials comprising calcium carbonates through a mechanochemical process. The present disclosure concerns the production of calcium carbonate by sequestrating CO.sub.2. Certain processes herein include providing alkaline-rich mineral materials that include carbonatable solid wastes such as lime kiln dust, cement kiln dust, and coal combustion residues, and simultaneously fractioning the alkaline-rich mineral materials, while contacting the alkaline-rich mineral materials with a CO.sub.2-containing gas in carbonation reactor at low temperature and ambient pressure. In some embodiments, the alkaline-rich mineral materials are partially carbonated before being used in the processes disclosed herein. After contacting the alkaline-rich mineral materials with a CO.sub.2-containing gas in carbonation reactor at low temperature and ambient pressure, solid calcium carbonate is produced. In aqueous reactors, the solid calcium carbonate is filtered from a solution in which it precipitated, and the remaining solution includes hydroxide as well as alkaline metal ions. The solution filtered from the solid calcium carbonate can be sequentially contacted with a CO.sub.2-containing gas stream to precipitate additional calcium carbonate. The carbonated materials formed from these processes can be used in the form of a slurry, as a moist powder, as a dried powder, as a reactive filler or as a supplementary cementitious material in a mixture that is used to make concrete.

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for processing recycled concrete aggregate (RCA). One of the methods includes obtaining first optical measurements of RCA particles as the RCA particles are conveyed past the first optical sensors; determining, based on the first measurements, an initial characterization of the RCA particles; iteratively performing a carbonation process on the RCA particles, obtaining second optical measurements of the RCA particles, and determining, from the second measurements, a second characterization of the RCA particles, wherein conditions of the carbonation process are initially set based on the initial characterization, and the conditions of the carbonation process are adjusted based on the second characterization; ceasing the iterative performance of the carbonation process in response to the second characterization meeting target carbonation characteristics; iteratively performing a densification process on the RCA particles, obtaining third optical measurements of the RCA particles, and determining, from the third measurements, a third characterization of the RCA particles, wherein conditions of the densification process are initially set based on the initial characterization or the second characterization, and the conditions of the densification process are adjusted based on the third characterization; and ceasing the iterative performance of the densification process in response to the third characterization meeting target densification characteristics.

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for processing recycled concrete aggregate (RCA). One of the methods includes obtaining first optical measurements of RCA particles as the RCA particles are conveyed past the first optical sensors; determining, based on the first measurements, an initial characterization of the RCA particles; iteratively performing a carbonation process on the RCA particles, obtaining second optical measurements of the RCA particles, and determining, from the second measurements, a second characterization of the RCA particles, wherein conditions of the carbonation process are initially set based on the initial characterization, and the conditions of the carbonation process are adjusted based on the second characterization; ceasing the iterative performance of the carbonation process in response to the second characterization meeting target carbonation characteristics; iteratively performing a densification process on the RCA particles, obtaining third optical measurements of the RCA particles, and determining, from the third measurements, a third characterization of the RCA particles, wherein conditions of the densification process are initially set based on the initial characterization or the second characterization, and the conditions of the densification process are adjusted based on the third characterization; and ceasing the iterative performance of the densification process in response to the third characterization meeting target densification characteristics.

A process for producing a crosslinked cellulose ether including the steps of (i) contacting at least one cellulose material with a mixture comprising (ia) at least one crosslinking agent and (ib) at least one alkalization reagent to form an activated cellulose material; and (ii) contacting the activated cellulose material of step (i) with at least one etherification reagent; wherein the at least one etherification reagent reacts with the activated cellulose material to form the crosslinked cellulose ether; and a crosslinked cellulose ether produced by the above process.