WO2001021269A2

WO2001021269A2 - Carbon dioxide absorption unit and regeneration method for said unit

Info

Publication number: WO2001021269A2
Application number: PCT/EP2000/008606
Authority: WO
Inventors: Silvia Casagrande; Valter Richiardone; Renato Ugo; Carlo Dossi; Rinaldo Psaro; Gianmario Martra; Salvatore Coluccia; Leonardo Marchese
Original assignee: Edison Termoelettrici SpA
Current assignee: Edison Termoelettrici SpA
Priority date: 1999-09-23
Filing date: 2000-09-04
Publication date: 2001-03-29
Anticipated expiration: 2002-03-23
Also published as: AU7649500A; WO2001021269A3; ITTO990817A1; IT1307053B1

Abstract

A carbon dioxide adsorption unit (1) comprises a container (4) having an inlet (8) and an outlet (9). A cartridge (5) of adsorption material, which may be an ion exchange resin or an oxide of an element of the lla group, is removably placed inside the container. A method for regenerating the carbon dioxide adsorption unit, where the adsorption material is an ion exchange resin comprises a hydration phase, a regeneration phase and a purging phase. The regeneration phase may comprise treatment with an aqueous alkaline solution or treatment with a heated air stream. An alternative method for regenerating the carbon dioxide adsorption unit, where the adsorption material is an oxide of an element of the lla group comprises heating the oxide at temperatures above 500 °C.

Description

CARBON DIOXIDE ABSORPTION UNIT AND THE REGENERATION

METHOD OF SAID UNIT

DESCRIPTION

The present invention relates to a The present invention refers to a carbon dioxide absorption unit which can be advantageously used both with metal -air batteries and in environments wherein it is necessary to move the carbon dioxide away.

Usually, the known type absorption units are placed along the air feeding duct towards a metal-air

battery in order to reduce the carbon dioxide rate of the air, or, given their characteristics, said absorption units can be used to treat the air in closed environments.

The European Patent Application no. EP 0 677

883 discloses an absorption unit comprising a

container placed through the duct, one or more drawer-like permeable elements arranged in series, in a removable way, inside the container, each of said

drawer-like elements contains a material which absorbs the carbon dioxide .

Each drawer-like element can be periodically removed to regenerate the material therein contained,

and said element is preferably formed by hydroxide or

hydrate beads of a metal of the la group, or by beads of a porous alkaliproof material impregnated with an aqueous solution of a hydroxide of a metal of the la group .

The absorption unit described in the above mentioned patent application has some disadvantages due to the material used to absorb the carbon dioxide, since said material is rather expensive, and to the regeneration methods required by said material. In fact, these methods, besides being rather complex and expensive as well, require not

only the lifting of the drawer-like elements, but also the lifting of said material from the drawer¬

like element.

The purpose of the present invention is to realise a carbon dioxide absorption unit, which can be easily regenerated, has a high absorption power

with respect to the carbon dioxide, and which does not require the lifting of the active material from the absorption bed during the regeneration phase.

According to the present invention, a carbon dioxide absorption unit is realised which comprises a container device having an entry and an exit, both of

which are connected to a feeding duct of a forced air flow, and absorption means placed, in a removable way, inside the container device, said absorption means are made of a material which can absorb the carbon dioxide present in said air flow; the unit is characterised in that said absorption means comprise a cartridge of absorption material made of a ion

exchange base resin which can be regenerated and which has a carbon dioxide absorption power from the gaseous phase.

Further, the present invention refers to a method to regenerate a carbon dioxide absorption unit.

According to the present invention, a method to regenerate a carbon dioxide absorption unit is disclosed, said method is characterised by comprising the hydration phase of an absorption material made of

a renewable ion exchange resin contained inside a cartridge and previously saturated through the absorption of carbon dioxide; a regeneration phase of said material by removing the carbon dioxide and by

restoring the initial basicity; and a phase of

injection of inert gas or of carbon dioxide free air through said cartridge in order to remove liquid residues which might be present in said material .

The invention will now be described with

reference to the attached drawing which shows,

through section views and by removing certain parts for clarity sake, a preferred embodiment disclosed as a non limiting example of an embodiment of an absorption unit of the removal of the carbon dioxide. With reference to the attached figure, numeral 1 indicates a whole carbon dioxide absorption unit.

The unit 1 is placed along a duct 2 which feeds air to a user device 3 formed by a battery or by an

environment for the use of the treated air, and said unit is suitable to eliminate the carbon dioxide from the air fed to said user device 3.

The unit 1 comprises a container 4, an absorption cartridge 5 placed inside a housing 6 of said container 4, and a blower 7 to feed the air to

the user device 3. The container 4 has just one section, and is

provided with an entry 8 and with an exit 9 both of

which are connected to the duct 2. Further, the container 4 comprises a distribution device 10

connected to the entry 8 in order to guarantee a homogeneous distribution of the incoming air flow

over the entire surface of the cartridge 5, a manifold 20 to collect the outgoing flow, and a fixed

perforated upper cover 11 placed close to the distribution device 10. The container 4 further comprises a removable perforated cover 12 suitable to lay on the cartridge 5, and four elastic elements 13 (ηust two of said elastic elements are shown) defined by the respective springs, said elements are compressed between the two

covers 11 and 12 m order to press the cover 12 against the cartridge 5.

According to another embodiment (not shown) , the springs which define the above mentioned elements 13 can be substituted by pressing means preferably, but not necessarily, made of rubber or of other materials having defined elastic characteristics.

Finally, the container 4 comprises a lower cover 14, a screen net 15 placed over said cover 14,

and a series of annular tabs 16 placed inside the housing 6, and suitable to improve the air flow circulation through the cartridge 5 by preventing the formation of preferred paths.

The cartridge 5 is permeable and is realised with a renewable material which can absorb the carbon

dioxide and is formed by a strongly basic ion exchange resin, and, as it will be better explained hereinafter, the regeneration of said cartridge is realised through water steam stripping with a humid

air or inert gas flow, which do not require any

further treatment. Alternatively, the material of the cartridge 5 is made of an oxide of an element of the Ila Group, m particular of magnesium, m order to realise a system suitable to absorb the carbon dioxide and which can be easily regenerated by heating.

The dimensions of the cartridge 5 are selected,

during the design phase, as a function of the concentration of incoming carbon dioxide and of the desired concentration at the exit 9, and as a function of the air flow to be treated and of the desired lifetime of the cartridge 5.

Alternatively, m order to improve the

purification characteristics of the unit 1, or m order to better suit said unit 1 to the specific situations, it is possible to place several cartridges 5 m series, or, further, to place them m

two blocks.

The previously described unit 1 has some advantages, as, for instance, the achievement of a low carbon dioxide concentration m the air which exits from said unit 1, the complete absence of residues to be disposed of inside the cartridge 5,

and a low hydrostatic load loss along said unit 1, with the possibility to have blowers 7 or similar devices with reduced dimensions and costs. During use, the air flow to be sent to the user device 3 is directed through the cartridge 5 thus causing the carbonation of the absorption material.

In the case that the absorption material of the cartridge 5 is made of ion exchange resms, it is possible to see, during use, a decrease of the volume of the absorption material following dehydration of said absorption material .

The presence of the elastic materials 13, during the volume decrease of the resms, causes the movable cover 12 to stay continuously contact with the upper surface of said cartridge 5, thus preventing the change of the mechanical characteristics of said cartridge 5. Once that, at the exit 9 from the unit 1, the

air flow does not meet the characteristics required by the user device 3, i.e. the filtering characteristics of the material of the cartridge 5

have decreased, the cartridge 5 is extracted from the

container 4 and is introduced into a regeneration unit (not shown) wherein the material therein contained is, through subsequent steps, hydrated; regenerated; and subjected to a carbon free flow of air m order to move away the liquid residues still

present the material. The regeneration is alternatively realised

using an aqueous solution of sodium or ammonium hydroxide, followed by washing with water until the achievement of neutral conditions, while the hydration is realised using a flow of carbonate free air or of humid inert gas through the cartridge 5, or, alternatively, by placing said cartridge 5 in

carbonate free water, or, else, by using a flow of inert gas or of carbonate free air at growing values of humidity and temperature through the cartridge 5.

By percolating the cartridge 5 with an aqueous

solution of sodium or ammonium hydroxide, after having hydrated the material inside said cartridge 5, there is the advantage of saving sodium or ammonium hydroxide.

Alternatively to the above, the regeneration of the material of the cartridge 5 can be realised by

using a gaseous flow at a temperature comprised between 50°C and 70°C. The just described gaseous flow is formed by inert gas or by carbonate free air which are both saturated with water steam.

Alternatively, when the material contained in

the absorption cartridge is formed by an oxide of the

Ila group with a pellet shape, the regeneration is simply realised by heating at temperatures higher than 500°C in a flow of carbonate free air or inert

gas .

The heating and the cooling of the absorption material is realised through a gradual ramp up of the

temperatures in order to minimise the inner stresses between the single particles due to the thermal expansion.

The regeneration of the cartridge 5, as it has been above described in the different embodiments, has the advantage of not producing or of reducing to the minimum terms the residues to be disposed of or toxic and harmful substances .

Claims

1. A carbon dioxide absorption unit (1) comprising a container device (4) having an entry (8) and an exit (9) , both of which are connected to a feeding duct (2) of a forced air flow, and absorption means (5) placed, in a removable way, inside the container device (4) , said absorption means are made of a material which can absorb the carbon dioxide present in said air flow; the unit (1) is characterised in that said absorption means (5) comprise a cartridge (5) of absorption material made of a ion exchange base resin which can be regenerated and which has a carbon dioxide absorption power from the gaseous phase .

2. A unit as claimed in claim 1, characterised

in that the material of said cartridge (5) is an oxide of an element belonging to the Ila Group.

3. A unit as claimed in claim 2, characterised in that said element is magnesium.

4. A unit as claimed in claims 1 and 2,

characterised in that said container device (4) comprises a container (4) for said filtering means, a

distribution device (8) to distribute, inside the container (4) , said air flow, and a cover (12) movable with respect to the container (4) and suitable to lay on said cartridge (5) independently from the volume of material contained inside said cartridge (5) .

5. A unit as claimed in claim 4, characterised

in that the container device (4) comprises a fixed cover (11) and a determined number of elastic elements (13) placed between the fixed cover (11) and said movable cover (12) .

6. A unit as claimed in claim 5, characterised

in that each of said elastic elements (13) is defined by a respective spring.

7. A unit as claimed in claim 4, characterised in that said container device (4) comprises a

plurality of baffles (16) placed inside said container (4) in order to deflect said air flow

through said cartridge (5) .

8. A method to regenerate a carbon dioxide absorption unit (1) , said method is characterised by comprising the hydration phase of an absorption

material made of a renewable ion exchange resin contained inside a cartridge (5) ; a regeneration phase of said material; and a phase of injection of inert gas or of carbon dioxide free air through said

cartridge (5) in order to remove liquid residues which might be present in said material.

9. A method as claimed m claim 8, characterised that said regeneration phase of said material is realised by using an aqueous solution of sodium or ammonium hydroxide; and a washing phase of said cartridge (5) using water until the neutral conditions of said material are achieved.

10. A method as claimed m claim 8, characterised in that said regeneration phase of said material is realised by using an air flow at a temperature comprised between 50°C and 70°C.

11. A method as claimed m claim 8, characterised by understanding that said regeneration phase of said material is realised by using a gaseous water saturated flow of carbonate free air or of inert gas at a temperature comprised between 50°C and

70°C.

12. A method as claimed in claim 8, characterised in that said hydration phase is realised by using a humid gaseous flow through said

cartridge (5) .

13. A method as claimed m claim 8, characterised m that said hydration phase is realised by placing said cartridge (5) water.

14. A method as claimed m claim 8,

characterised m that said hydration phase is realised by using a gaseous flow at growing values of humidity and temperature through said cartridge (5) .

15. A method to regenerate an absorption unit, said method is characterised by comprising a heating phase of an absorption material formed by an oxide of an element of the Ila Group contained inside a cartridge (5); a regeneration phase of said material ; and a cooling phase of said material.

16. A method as claimed in claim 15, characterised in that said regeneration phase is realised by heating at a temperature higher than 500°C by holding the absorption cartridge (5) in a flow of carbonate free air or of inert gas .

17. A method as claimed in claim 2, characterised in that the oxide of the element of the

Ila Group can have, without being limited to, a pellet shape.