Carbon Dioxide Sequestration Involving Two-Salt-Based Thermolytic Processes
The present invention relates to an energy efficient carbon dioxide sequestration processes whereby calcium silicate minerals and CO 2 are converted into limestone and sand using a two-salt thermolytic process that allows for the cycling of heat and chemicals from one step to another.
1 . A method of sequestering carbon dioxide produced by a source, comprising:
(a) reacting MgCl 2 or a hydrate thereof with water in a first admixture under conditions suitable to form a first product mixture comprising a first step (a) product comprising Mg(OH)Cl and a second step (a) product comprising HCl;
(b) reacting some or all of the Mg(OH)Cl from step (a) with a quantity of water and a quantity of MgCl 2 in a second admixture under conditions suitable to form a second product mixture comprising a first step (b) product comprising Mg(OH) 2 and a second step (b) product comprising MgCl 2 , wherein the quantity of water is sufficient to provide a molar ratio of water to MgCl 2 of greater than or equal to 6 to 1 in the second product mixture;
(c) admixing some or all of the Mg(OH) 2 from the first step (b) product with CaCl 2 or a hydrate thereof and carbon dioxide produced by the source in a third admixture under conditions suitable to form a third product mixture comprising a first step (c) product comprising MgCl 2 or a hydrate thereof, a second step (c) product comprising CaCO 3 , and a third step (c) product comprising water; and
(d) separating some or all of the CaCO 3 from the third product mixture,
whereby some or all of the carbon dioxide is sequestered as CaCO 3 .
2 . The method of claim 1 , wherein some or all of the water in step (a) is present in the form of a hydrate of the MgCl 2 .
3 . The method according to claim 1 , wherein the molar ratio of water to MgCl 2 in the second product mixture is between 6 and 10.
4 . The method of claim 3 , wherein the molar ratio of water to MgCl 2 in the second product mixture is between about 6 and about 7.
5 . The method according to claim 1 , further comprising monitoring the concentration of Mg in the second admixture.
6 . The method of claim 5 , wherein the amount of Mg(OH)Cl or the quantity of water in a second admixture is adjusted based on said monitoring.
7 . The method according to claim 1 , wherein the MgCl 2 of step (a) is a MgCl 2 hydrate.
8 . The method of claim 7 , wherein the MgCl 2 hydrate of step (a) is MgCl 2 .6H 2 O.
9 . The method according to claim 1 , wherein the MgCl 2 of step (a) is greater than 90% by weight MgCl 2 .6(H 2 O).
10 . The method according to claim 1 , wherein the first step (a) product comprises greater than 90% by weight Mg(OH)Cl.
11 . The method according to claim 1 , further comprising separating the step (b) products.
12 . The method of claim 11 , wherein the Mg(OH) 2 product of step (b) is a solid and wherein separating the step (b) products comprises separating some or all of the solid Mg(OH) 2 from the water and the MgCl 2 .
13 . The method according to claim 1 , wherein the MgCl 2 product of step (b) is aqueous MgCl 2 .
14 . The method according to claim 1 , wherein some or all of the MgCl 2 formed in step (b) or step (c) is the MgCl 2 used in step (a).
15 . The method according to claim 1 , where some or all of the water in step (a) is present in the form of steam or supercritical water.
16 . The method according to claim 1 , where some or all of the water of step (a) is obtained from the water of step (c).
17 . The method of claim 1 , further comprising:
(e) admixing a calcium silicate mineral with HCl under conditions suitable to form a third product mixture comprising CaCl 2 , water, and silicon dioxide.
18 . The method of claim 17 , where some or all of the HCl in step (e) is obtained from step (a).
19 . The method of claim 17 , wherein step (e) further comprises agitating the calcium silicate mineral with HCl.
20 . The method according to claim 17 , wherein some or all of the heat generated in step (e) is recovered.
21 . The method according to claim 17 , where some or all of the CaCl 2 of step (c) is the CaCl 2 of step (e).
22 . The method according to claim 17 , further comprising a separation step, wherein the silicon dioxide is removed from the CaCl 2 formed in step (e).
23 . The method according to claim 17 , where some or all of the water of step (a) is obtained from the water of step (e).
24 . The method according to claim 17 , wherein the calcium silicate mineral of step (e) comprises a calcium inosilicate.
25 . The method according to claim 17 , wherein the calcium silicate mineral of step (e) comprises CaSiO 3 .
26 . The method according to claim 17 , wherein the calcium silicate mineral of step (e) comprises diopside (CaMg[Si 2 O 6 ]) or tremolite Ca 2 Mg 5 {[OH]Si 4 O} 2 .
27 . The method according to claim 17 , wherein the calcium silicate further comprises iron and or manganese silicates.
28 . The method of claim 27 , wherein the iron silicate is fayalite (Fe 2 [SiO 4 ]).
29 . The method according to claim 1 , wherein the carbon dioxide is in the form of flue gas, wherein the flue gas further comprises N 2 and H 2 O.
30 . The method according to claim 1 , wherein suitable reacting conditions of step (a) comprise a temperature from about 200° C. to about 500° C.
31 . The method of claim 30 , wherein the temperature is from about 230° C. to about 260° C.
32 . The method of claim 30 , wherein the temperature is about 250° C.
33 . The method of claim 30 , wherein the temperature is from about 200° C. to about 250° C.
34 . The method of claim 30 , wherein the temperature is about 240° C.
35 . The method according to claim 1 , wherein the suitable reacting conditions of step (b) comprise a temperature from about 140° C. to about 240° C.
36 . The method according to claim 17 , wherein suitable reacting conditions of step (c) comprise a temperature from about 20° C. to about 100° C.
37 . The method of claim 36 , wherein the temperature is from about 25° C. to about 95° C.
38 . The method according to claim 17 , wherein suitable reacting conditions of step (e) comprise a temperature from about 50° C. to about 200° C.
39 . The method of claim 38 , wherein the temperature is from about 90° C. to about 150° C.
40 . The method according to claim 1 , wherein some or all of the hydrogen chloride of step (a) is admixed with water to form hydrochloric acid.
41 . The method of claim 1 , wherein step (a) occurs in one, two or three reactors.
42 . The method of claim 1 , wherein step (a) occurs in one reactor.