# US 9,751,771 B2 · Method for producing dicalcium silicate

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- Number: US 9,751,771 B2
- Document ID: US9751771B2
- Status: Granted
- Kind: B2
- Application number: 14/418,445
- Filed: 2013-07-24
- Published: 2015-06-11
- Granted: 2017-09-05
- Earliest claimed: 2012-08-01
- Assignees: Karlsruher Institut Fuer Technologie
- Applicants: Karlsruher Institut Fuer Technologie
- Inventors: Hans Hunsinger; Guenter Beuchle; Peter Stemmermann; Uwe Schweike; Karolina Giziewicz; Krassimir Garbev
- Web page: https://patentgrep.com/patent/US9751771B2

## CPC

- C01B 33/24: Alkaline-earth metal silicates
- C04B 7/3453: {Belite cements, e.g. self-disintegrating cements based on dicalciumsilicate}
- Y02P 40/10: Production of cement, e.g. improving or optimising the production methods; Cement grinding
- Y02P 40/18: Carbon capture and storage [CCS]
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A process for preparing dicalcium silicate includes providing a starting material comprising calcium carbonate (CaCO3) and silicon dioxide (SiO2), wherein a molar ratio of calcium:silicon (C:S) is from 1.5:1 to 2.5:1. At least one of an inorganic alkali metal salt and an alkaline earth metal salt is added as a mineralizing agent to the starting material in an amount of from 0.5 wt.-% to 20 wt.-%, based on a total weight of the starting material. The starting material is reacted with the mineralizing agent in a gas atmosphere having a CO2 partial pressure of from 0.05 MPa to 0.2 MPa at a temperature of from 900° C. to 1100° C. so as to obtain a dicalcium silicate product. The dicalcium silicate product comprises a content of an unreacted starting material of <5 wt.-% and a total carbon content of <1.5 wt.-%, each based on a weight of the dicalcium silicate product.

## Claims

### Claim 1

A process for preparing dicalcium silicate, the process comprising:
providing a starting material comprising calcium carbonate (CaCO3) and silicon dioxide (SiO2), wherein a molar ratio of calcium:silicon is from 1.5:1 to 2.5:1;
adding at least one of an inorganic alkali metal salt and an alkaline earth metal salt as a mineralizing agent to the starting material in an amount of from 0.5 wt.-% to 20 wt.-%, based on a total weight of the starting material; and
reacting the starting material with the mineralizing agent in a gas atmosphere having a CO2 partial pressure of from 0.05 MPa to 0.2 MPa at a temperature of from 900° C. to 1100 ° C. so as to obtain a dicalcium silicate product.

### Claim 2 (depends on 1)

The process as recited in claim 1, wherein the molar ratio of calcium:silicon of the starting material is from 1.9:1 to 2.1:1.

### Claim 3 (depends on 1)

The process as recited in claim 1, wherein the CO2 partial pressure of the gas atmosphere is from 0.08 MPa to 0.12 MPa.

### Claim 4 (depends on 1)

The process as recited in claim 1, wherein the starting material is reacted at a temperatures of from 950 ° C. to 1050 ° C.

### Claim 5 (depends on 1)

The process as recited in claim 1, wherein the amount of the mineralizing agent added to the starting material is from 1 wt.-% to 10 wt.-%, based on the total weight of the starting material.

### Claim 6 (depends on 1)

The process as recited in claim 1, wherein the at least one of an inorganic alkali metal salt and an alkaline earth metal salt as the mineralizing agent is provided as a carbonate, a hydrogencarbonate, a fluoride, a chloride, or a mixture thereof.

### Claim 7 (depends on 1)

The process as recited in claim 1, wherein the at least one of an inorganic alkali metal salt and an alkaline earth metal salt as the mineralizing agent is selected from at least one of sodium carbonate (Na2CO3), sodium fluoride (NaF), potassium fluoride (KF), calcium fluoride (CaF2), and magnesium chloride (MgCl2).

### Claim 8 (depends on 1)

The process as recited in claim 1, wherein the mineralizing agent is provided as a mixture of from 0.5 wt.-% to 5 wt.-% Na2CO3 and from 0.5 wt.-% to 5 wt.-% CaF2, in each case based on the weight of the starting material.

### Claim 9 (depends on 8)

The process as recited in claim 8, wherein the mixture is from 1 wt.-% to 1.5 wt.-% Na2CO3 and from 1 wt.-% to 1.5 wt.-% CaF2, in each case based on the weight of the starting material.

### Claim 10 (depends on 1)

The process as recited in claim 1, further comprising at least partially recovering the mineralizing agent from the dicalcium silicate product.

### Claim 11 (depends on 10)

The process as recited in claim 10, wherein the recovering of the mineralizing agent from the dicalcium silicate product is performed by:
suspending the dicalcium silicate product comprising an alkali metal compound in water so that the alkali-metal compound decomposes to form an alkali metal hydroxide;
adding CO2 to convert the alkali metal hydroxide into at least one of a carbonate and a hydrogen carbonate; and
separating off the at least one of a carbonate and a hydrogen-carbonate.