VACUUM SWING CALCINATION PROCESS TO PRODUCE HIGH PURITY CO2 FROM CaCO3

Patent metadata

Field	Value
Publication number	US-2024278176-A1
Application number	US-202218566897-A
Country	US
Kind code	A1
Filing date	May 31, 2022
Priority date	Jun 3, 2021
Publication date	Aug 22, 2024
Grant date	—

Abstract

This invention discloses a calcination process to produce high purity CO 2 from solids containing CaCO 3 which operates cyclically and continuously on the solids, arranged in a packed or a moving bed, and wherein each cycle comprises a first step where the combustion at atmospheric pressure of a fuel in the bed of solids containing CaCO 3 heats them up to 800-900° C. and a second step wherein a vacuum pressure between 0.05 and 0.5 atm is applied to extract pure CO 2 from the solids containing CaCO 3 while cooling them by 30-200° C. Said combustion can be carried out directly with air, oxygen enriched air or O 2 /CO 2 mixtures when the process is applied to the calcination of a continuous flow of limestone in a moving bed shaft kiln. The process is also applied to calcine CaCO 3 formed in reversible calcium looping processes comprising a carbonation reaction step to form CaCO 3 from CaO.

First claim

1 . Process to recover in high purity form the CO 2 released from the calcination of solids containing CaCO 3 , with said solids being preheated to a temperature between 650-800° C. and arranged in a thermally insulated vessel ( 1 ) able to withstand vacuum swings, wherein the process is characterized by the continuous repetition, at least twice, of a sequence of at least the following consecutive steps:
i) a heating up step lasting between 5-20 minutes, combusting a fuel ( 8 ) within the bed of solids to heat up the bed of solids containing CaCO 3 to 800-900° C.
ii) a vacuum step lasting between 5-20 minutes, applying an under-atmospheric pressure of 0.05-0.5 atm to the bed of solids.

2 . The process of claim 1 where the combustion of the fuel ( 8 ) is carried out with air, oxygen-enriched air or O 2 —CO 2 comburent mixtures ( 9 ).

3 . The process of any one of the preceding claims wherein the fuel ( 8 ) is a hydrocarbon gas or hydrogen.

4 . The process of any one of the preceding claims further comprising a step of introducing a batch of particles of solids containing CaCO 3 ( 4 ) in the thermally insulated vessel ( 1 ) so that the solids are displaced downwards in each combustion step while extracting a batch of particles containing CaO ( 5 ).

5 . The process of any one of the preceding claims wherein the combustion taking place in the thermally insulated vessel ( 1 ) during the step i) is a chemical looping combustion of the gaseous fuel ( 8 ) with air ( 9 ) by dividing the step i) in two sub-steps:
j) a first sub-step involving the oxidation with air ( 9 ) at a pressure of 1-5 atmospheres of a second solid ( 12 ) containing a metal such as Ni or Cu, the second solid being mixed in the bed of CaCO 3 containing solids and releasing a flue gas ( 10 ) composed of a major fraction of nitrogen and a minor fraction of CO 2 from the partial decomposition of CaCO 3 ; and
jj) a second sub-step at atmospheric pressure, involving the reduction of the of the oxidised form of the metal fuel formed in sub-step j) by feeding a fuel gas ( 8 ) to regenerate the metal fuel in the second solid ( 12 ) while releasing concentrated CO 2 ( 11 ).

6 . The process of any one of the preceding claims further comprising an additional carbonation step iii) of the CaO ( 5 ) generated in step ii) by feeding a combustion flue gas or any other gas containing CO 2 to the packed bed of solids to increase the molar conversion of CaO to CaCO 3 between 0.03 and 0.1 and restore the CaCO 3 ( 4 ) in the bed of solids ( 1 ) that is at the beginning of step i).

7 . The process of any one of claims 1 to 5 further comprising an additional carbonation step iii) of the CaO ( 5 ) generated in step ii) by feeding a fuel gas ( 13 ) and steam ( 14 ) to the packed bed of solids containing CaO and Ni to catalyse the steam reforming of the fuel gas ( 13 ) to hydrogen ( 15 ) while increasing the molar conversion of CaO to CaCO 3 between 0.03 and 0.1 and restore the CaCO 3 ( 4 ) that is in the bed of solids ( 1 ) at the beginning of step i).

8 . The process of claim 7 further comprising an additional step after the sorption enhanced process by carbonation iii) and before the beginning of a new cycle N+1 with step i), consisting in the feeding a fuel gas ( 13 ) and steam ( 14 ) to the packed bed of carbonated solids to produce a syngas that is used as fuel gas ( 8 ) in sub-step jj) of the next step i) in the cycle N+1.

9 . The process of any one of claims 1 to 5 further comprising an additional carbonation step iii) of the CaO ( 5 ) generated in step ii) by feeding a gas containing CO ( 13 ) and steam ( 14 ) to the packed bed of solids containing CaO and Cu to catalyse the water gas shift reaction of the CO contained in ( 13 ) to hydrogen ( 15 ) an CO 2 while increasing the molar conversion of CaO to CaCO 3 between 0.03 and 0.1 and restoring the CaCO 3 ( 4 ) that is in the bed of solids ( 1 ) at the beginning of step i).

10 . The process of claim 5 wherein the fuel ( 8 ) is a solid metal such as Fe, Ni or Cu, that exothermically oxidizes with air ( 9 ) and that is fed alone or contained in the second solid ( 12 ) that is mixed with the solids containing CaCO 3 ( 4 ).

11 . The process of any one of claims 1 to 10 further comprising an additional gas rejection step by which a gas volume of 1-3 times of the void volume of gas in the packed bed of solids ( 1 ) is discharged at the beginning of the vacuum period in step ii).

12 . The process of any one of the preceding claims , wherein the thermal power of the combustion during step i) is the result of the multiplication of the average power input in the equivalent kiln without CO 2 capture and the ratio between the sum of the duration step i) and ii) divided by the duration of step i).

13 . Shaft kiln to carry out the process of claim 4 to calcine CaCO 3 ( 4 ) in the form of limestone and produce concentrated CO 2 ( 7 ) and CaO ( 5 ), the shaft kiln comprising:
a first vertical shaft;
means to stage the burning a fuel ( 8 ) with preheated air or other comburent mix ( 9 ) in its calcination zone, wherein the kiln being characterized by comprising:
inlet and outlet gas and solid pipes comprising switching valves with at least one of the pipes having a vacuum switching valve ( 20 ) connected to a vacuum pump ( 6 ) configured to allow the continuous repetition of a sequence of at least a first operating mode and a second operating mode:
means for feeding a batch of limestone through a solid valve and extracting lime ( 5 ) with another solid valve during the first operating period lasting between 5-20 min where fuel ( 8 ) is burned within the calcination zone in a staged mode, with the air or other comburent mix being preheated by the CaO ( 5 ) and the limestone ( 4 ) being preheated with the combustion flue gases flowing from the calcination zone, and
means for sealing the gas entries/outlets and valves for solids except one gas outlet during the second operating period lasting between 5-20 minutes, where a vacuum pressure is applied using the vacuum pump ( 6 ) to extract pure CO 2 ( 7 ).

14 . The shaft kiln of claim 13 further comprising a second vertical shaft connected to the first vertical shaft, the second vertical shaft comprising an additional flow of air to enter the second vertical shaft, in order to transport heat from the lime cooling region and the hot flue gases to the limestone preheating region.

15 . The shaft kiln of any one of claim 13 or 14 , wherein the thermally insulated vessel ( 1 ) is the calcination section of a shaft kiln further comprising a limestone preheating zone at the top of the kiln ( 30 ) and a CaO cooling section ( 31 ) that preheats combustion air or other comburent mix ( 9 ).

Assignees

• Consejo Superior Investigacion

Inventors

• Abanades García Juan Carlos
• Arias Rozada Borja
• Fernández García José Ramón

Classifications

• F27M2003/03

  Calcining · CPC title

• F27B1/04

  Combinations or arrangements of shafts · CPC title

• F27B1/005

  wherein no smelting of the charge occurs, e.g. calcining or sintering furnaces · CPC title

• C04B2/12

  in shaft or vertical furnaces (shaft or vertical furnaces in general F27B1/00) · CPC title

• C04B2/108

  Treatment or selection of the fuel therefor · CPC title