WO2011089290A1

WO2011089290A1 - Elimination of carbon dioxide and other atmospheric gases by means of calcium rich industrial waste

Info

Publication number: WO2011089290A1
Application number: PCT/ES2011/000010
Authority: WO
Inventors: Luis Esquivias Fedriani; Alberto SANTOS SÁNCHEZ; Victor MORALES FLÓREZ
Original assignee: Universidad De Sevilla; Universidad De Cádiz; Consejo Superior Investigaciones Cientificas
Priority date: 2010-01-19
Filing date: 2011-01-19
Publication date: 2011-07-28
Also published as: ES2364420A1; ES2364420B1

Abstract

The present invention relates to the use of an aqueous suspension comprising calcium in a proportion exceeding 15% by weight, the solid phase of such aqueous suspension being preferably portlandite proceeding from chemical industry waste, for the elimination of CO₂ and other greenhouse effect gases. The present invention moreover relates to a procedure of elimination of said gases under conditions of ambient pressure and temperatures, through both induced and environmental carbonatation.

Description

ELIMINATION OF CARBON DIOXIDE AND OTHER ATMOSPHERIC GASES THROUGH INDUSTRIAL WASTE RICH IN

CALCIUM

The present invention relates to a use of an aqueous suspension comprising calcium in a proportion greater than 15% by weight, the solid phase of the aqueous suspension being preferably portlandite from residues of the chemical industry, for the removal of C0 ₂ and other greenhouse gases. The present invention also relates to a method of eliminating said gases under conditions of pressure and ambient temperatures.

STATE OF THE PREVIOUS TECHNIQUE

One of the most promising in the capture and storage of carbon (C0 ₂₎ technologies dioxide is related to the fixation of said gas in the form of insoluble inorganic carbonates. This fixation is achieved through a chemical reaction, known as mineral carbonation. In carbonation reactions, CO ₂ reacts with materials that have metal oxides (typically alkaline earth metals) in their composition, thus forming the corresponding carbonate as a byproduct. However, these reactions are very slow when they occur in natural environments, so that the studies that currently implement these reactions require the addition of an intensive energy (activation), to make the minerals more reactive.

Within the mineral carbonation technology, certain jobs are intended as studies for removal of C0 ₂ a massive scale. Among them stands out "CY Tai, WR Chen and SH Shih. AlChE J., 52: 292 (2005)". Subsequently, comparative studies have been carried out analyzing different types of samples and experimental conditions obtaining, in the face of their application of mass elimination, more hopeful results. The study presented is part of the set of techniques _CO2 removal using calcium - rich minerals or industrial waste from municipal solid waste (G. Hernandez-Montes, R. Lopez-Perez, F. Renard, JM Nieto, L. Charlet, Journal of Hazardous Materials 161, 1347-1354, 2009).

For more than a decade, the possibility of reducing the level of C0 ₂ in the atmosphere has been considered through the reaction of CO ₂ dispersed in the atmosphere with various minerals, as a complementary and alternative measure to the sequestration of CO ₂ . This line of work was developed by Lackner et al. (Klaus S. Lackner, Patrick Grimes and Hans-J. Ziock. 2nd US-China Symposium on C02 Emissions Control Science & Technology May 28th-30th, 2008) at a theoretical level, who compared renewable energy technologies (wind turbines or plates photovoltaic) with a joint technology of fossil fuel-based power generation plants along with atmospheric C0 ₂ mineral sinks. Economic and energy calculations showed that it was more interesting from the standpoint of reducing CO ₂ environment this second option. That is, carbon dioxide can be emitted into the air, where the wind disperses it immediately above cities and borders, and C0 ₂ sinks can be arranged, where this gas reacts with an absorbent, fixing it chemically. To this end, Lackner proposed various absorbents such as calcium, sodium or magnesium hydroxides.

In more practical terms, Dr. Stolaroff (Joshua K. Stolaroff, David W. Keith and Gregory V. Lowry. Environ. Sci. Technol., 42, 2728-2735, 2008) developed a prototype "C0 sequestration column ₂ "by means of a spray system of a solution of sodium hydroxide. This work involves a first start-up of the technologies for the elimination of environmental CO ₂ as a way to reduce the carbon dioxide content of the atmosphere. Your prototype sprays a concentrated solution of NaOH on top of a column. The sodium contained in the drops reacts with the CÜ ₂ of the air contained in the column 5 m high, so that the air that leaves the column contains less CO ₂ than the one that enters. Thus, a system of columns arises to attack excess C0 ₂ atmosphere. Lately, technologies for the reaction of calcium minerals with carbon dioxide have been developed. Thus, for example, Eighmy et al. (in patent application WO2005 / 086843) they propose an experimental device for carbonating calcium-rich minerals in a carbonation column on which it pumps air. Likewise, Mueller et al. (in patent application WO2008055326) propose to circulate contaminated air of CO ₂ with the help of a radial compressor through two tanks in series, where the reaction with calcium oxide (CaO) is forced.

Finally, the use of industrial waste rich in calcium for removing C0 ₂ by chemisorption has been raised by Montes- Hernandez et al. They have carried out several research papers in the most recent of "G. Montes-Hernández, R. Pérez-López, F. Renard, JM Nieto, L. Charlet. Journal of Hazardous Materials 161, 1347-1354 (2009)", waste from the paper industry or coal combustion has been involved. In the case of the paper industry, the waste is composed of 55% portlandite. The development proposed in this work is to attack CO ₂ dry residue dispersed in distilled water, in a reactor with controlled temperature (set at 30 ° C and 60 ° C), in which CO ₂ is injected at various pressures, from 10 bar to 60 bar. On the other hand, the technique directed to the waste of the thermal power plants tries to take advantage of the calcium contained in the residue known as fly ash. This residue is formed by micrometric spherical particles, with a CaO content of 4%. Again, experimental conditions similar to those of the previous work are raised, that is, of controlled temperature and pressure. The low CaO content of the ashes makes the waste of the paper industry much more attractive. These results were reflected in patent application WO2009077358. The claimed experimental configuration involves the use of distilled water as a dispersant of solid waste, temperature control (between 30 ° C and 60 ° C) as well as increasing the pressure of CO ₂ in the reactor between 10 bar and 40 bar . At present, although mineral fixation is the most stable way to remove C0 ₂ from the atmosphere permanently, the technology of carbon dioxide sequestration through mineral uptake has been quite discussed by the difficulties presented by the process , such as very slow reaction times (around years), or the low efficiency of the technique. To remedy these problems, experimental conditions that entail high energy consumption in the process of eliminating C0 ₂ had been raised so far.

DESCRIPTION OF THE INVENTION

The present invention solves the problems posed in the state of the art by simplifying the entire process to a single stage and also involves reusing aqueous industrial waste.

Also, the present invention provides the use of an aqueous suspension comprising a high calcium residue in the form of a portlandite, such as that generated in the acetylene industry, for the elimination of a gas comprising carbon dioxide, and its process of elimination of said gas under ambient temperature and pressure conditions.

In a first aspect, the present invention relates to a use of an aqueous suspension with a weight percentage of calcium greater than 15%, for removal of a gas comprising carbon dioxide.

The percentage by weight of the calcium present in the solid phase of the aqueous suspension is greater than 50%, as the percentage of solid phase in the liquid is greater than 33%, it indicates that the calcium content in the whole of the aqueous suspension is preferably greater than 17%.

In a preferred embodiment the aqueous suspension is a byproduct of acetylene production. In a more preferred embodiment said by-product comprises portlandite as a component with high calcium content.

The present invention seeks to take advantage of the reaction capacity of these wastes with the main purpose of reducing the environmental impact of carbon dioxide emissions, both that It is produced in the production of acetylene as the C0 ₂ already emitted and which is part of the atmosphere. It can also be applied to any chemical industry whose waste or by-products have a high calcium content.

In the present invention two non-exclusive alternatives are described:

a) Carbonation induced: fixing C0 ₂ and other greenhouse gases with the calcium present in the aqueous suspension. It is to deposit the waste in a reactor through which would be circulated gases emitted until the total elimination of C0 _2.

b) environmental Carbonation: The objective is to cause the reaction of C0 ₂ atmosphere rich in calcium slurry of industrial products. Said aqueous suspension is deposited in shallow reservoirs, in a predetermined liquid / solid ratio to guarantee maximum carbonation of Ca. Reservoirs are opened with a high surface / volume ratio suitable for process optimization and to achieve total carbonation of the residue.

By "greenhouse gases" in the present invention refers to the gases responsible for the greenhouse effect (mentioned by the international panel for climate change, IPCC). In this invention, it basically refers to carbon dioxide, but also, for example but not limited to them alone, to methane (CH ₄ ), carbon monoxide (CO), nitrous oxides (NO _x ) and sulphurous (SO _x ).

The carbonation of calcium produces calcite. Which can be dispensed without any harmful impact to the environment or marketed.

By "calcite" in the present invention refers to one of the polymorphs of calcium carbonate CaC03.

Therefore, a second aspect of the present invention relates to a gas stream removal process comprising carbon dioxide by induced carbonation, with a suspension aqueous comprising calcium in a percentage by weight greater than 15%, this calcium may be derived from a by-product rich in calcium, greater than 50% by weight of the solid phase.

Induced carbonation is preferably carried out by forced contact of the aqueous suspension with the gas stream comprising the carbon dioxide gas.

A third aspect of the present invention relates to a method of eliminating a gas comprising carbon dioxide by environmental carbonation, with an aqueous suspension comprising a calcium-rich by-product, the calcium percentage of the aqueous suspension being greater than 15 % in weigh. As in induced carbonation, calcium comes from a by-product (solid phase) with a calcium percentage of over 50% by weight.

Environmental carbonation occurs preferably by contacting the aqueous suspension in a reservoir with the gas contained in the atmosphere. More preferably said reservoir may be open, even more preferably the reservoir is in continuous agitation.

In a preferred embodiment, the aqueous suspension employed in both induced carbonation and environmental carbonation is a byproduct of the acetylene industry.

The surface / volume ratio of the shallow reservoir must be greater than 0.1 cm ^"1 .

By "surface / volume ratio" in the present invention refers to the ratio between the exposed surface of the material contained in a given raft and the volume occupied by said material.

By "solid / liquid ratio" in the present invention refers to the ratio between the amount of solid mass present in a given wet residue, and the mass of liquid, typically water (but not exclusively), in which this solid mass is found . The high calcium by-product used in both procedures is preferably portlandite. And said byproduct is more preferably a byproduct of acetylene production.

The ratio between the volume of the aqueous suspension and the gas flow is preferably between 0.01 s and 1 s.

The procedures described above are carried out at ambient pressure and temperature so that in no case does it entail additional energy expenditure, then the temperature range is preferably between 15 and 50 ° C and more preferably between 15 ° C and 35 ° C . The pressure is preferably in the range between 0.5 and 2 bar, this pressure range being more preferably between 0.9 bar and 1.6 bar.

The C0 ₂ capture process proposed in the present invention through the use of the high-calcium aqueous suspension, such as by-products produced in the acetylene industry, is an innovation in the field of reducing gas emissions of greenhouse effect of the chemical industry. A C0 ₂ mineral sequestration method has not been developed to date under conditions of environmental pressure and temperature of an industrial by-product. The main advantage of using the procedure described in the present invention is a considerable simplification of the process, as it does not use any costly procedure from an energy or technical point of view, but simply uses the waste as it is generated. That is to say, in this procedure, thermal treatments and significant mechanical treatments would not be necessary, so the technical simplicity is considerable and the economic and energy cost of the process would be very small.

Currently there is no procedure designed for this purpose, so today these wastes are not used for the elimination of greenhouse gases. The acetylene production industry generates gases (among which C0 ₂ is found), and an aqueous solution with high calcium content (calcium hydroxide or portlandite, mainly). These wastes are currently dispensed as waste. The procedure defined as "environmental carbonation" is intended to cause the reaction of environmental CO ₂ with the Ca present in industrial waste. It is known that mere contact with the air of saturated or supersaturated calcium solutions causes this carbonation reaction with environmental CO ₂ but this exposure to air usually creates an outer film of calcite in the portlandite grains, finally obtaining only a small part of carbonated calcium. In the examples described in the present invention, the carbonation of the residues is carried out during the drying of the residues in contact with the atmosphere, so that the drying conditions as well as the geometric configuration of the residue causes the total carbonation of the calcium present . The object of this invention is to control the process parameters so that the kinetics of the reactions that occur in the system are the most favorable for the carbonation of the portlandite of the residue.

In summary, in both cases it is a question of using gaseous, liquid and solid waste as reagents to produce calcite (calcium carbonate), which is an added value to the carbonation product.

The two procedures arising in the present invention involve the reaction of these industrial wastes C0 ₂ present in the environment (environmental carbonation) and the CO2 generated in certain industrial sectors (induced carbonation). In both ways proposed in this invention (environmental carbonation and induced carbonation) the use of the industrial waste of the acetylene industry is proposed as it is produced and in environmental conditions (in comparison with the use of distilled water and the pressure conditions and temperature controlled, known in the state of the art). This is a qualitative leap in terms of the technical simplicity of the procedure, which means having many more guarantees of being able to be developed on an industrial scale.

Throughout the description and the claims the word "comprises" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and features of the invention will be derived partly from the description and partly from the practice of the invention. The The following examples and drawings are provided by way of illustration, and are not intended to be limiting of the present invention.

DESCRIPTION OF THE FIGURES

Figure 1.- X-ray diagram of the original sample. The pattern corresponds to the portlandite.

Figure 2.- X-ray diagram of the sample after the induced carbonation experiment of Example 1. The pattern corresponds to calcite.

Figure 3.- Thermogravimetry analysis of the sample after the induced carbonation experiment of Example 1. There is no weight loss due to dehydroxylation of the portlandite, and only the degradation of the calcite appears around 700 ° C.

Figure 4.- Analysis of thermogravimetry of a sample after five days of environmental carbonation.

Figure 5.- X-ray diagram of the sample after one week of environmental carbonation. The pattern corresponds to calcite.

Figure 6.- Thermogravimetry analysis of a sample after one week of environmental carbonation.

EXAMPLES

The invention will be illustrated by tests performed by the inventors which reveals the specificity and effectiveness of calcium rich waste for removing C0 ₂ and other greenhouse gases.

From the residue of the acetylene industry.

In the acetylene industry, calcium-rich residues are generated, which are basically composed of a suspension of portlandite (Ca (OH) ₂ , density = 2.23g / cm ³ ) (Figure 1) in water that contains a small amount of silica (<2.3% by weight) and some impurities such as Al (<1%), S (<0.7%), Fe, Mn, or Sr (<0.1%). On the other hand, the water in equilibrium with the solid residue contains an amount of calcium [Ca] = 1,393 g / l. This liquid has a pH = 12.1. The fraction of the solid in the wet residue is 33% by weight, which implies that the residue has a net density of 1.22 g / cm ³ .

A practically complete carbonation of the residue was obtained. X-ray diffraction analyzes, as well as thermogravimetry experiments demonstrated the total disappearance of the portlandite and the appearance of calcite.

Example 1

Induced carbonation

The object of the carbonation is induced reduction or possible elimination of C0 ₂ and other greenhouse gases that are emitted by the chemical industry in general and in particular acetylene industry. For this, a flow of 150 cm ³ / s C0 ₂ has been used for 5 minutes in a reactor where 25 ml of the calcium-rich aqueous residue was dispersed. There, the bubbling of the gases causes the reaction of the C0 ₂ dissolved in the water with the calcium, giving rise to calcite. Finally, the sample is allowed to dry in atmospheric conditions.

In this materialization we worked with 10.17 g net of portlandite in the aqueous solution (neglecting impurities). The X-ray analysis (Figure 2) and thermogravimetry (Figure 3) confirm that during this attack process, practically 100% of the portlandite has been carbonated, thus capturing 6.05 g of C0 ₂ .

In an extrapolation on an industrial scale, if 100 m ³ of waste is considered, in which two thirds of the volume corresponds to the water in equilibrium with the portlandite, the amount of portlandite present would be about 40 tons. Therefore, 24 tons of C0 ₂ would be fixed in this process.

Example 2

Environmental carbonation Starting from a residue of the acetylene industry of the same composition to that mentioned above, environmental carbonation is carried out with a sample of 10 cm ³ residue with a solid / liquid ratio of 33%, and scattered throughout a container of base 10 cm ² leaving the sample dispersed with 1 cm height, which determines a surface / volume ratio of 1 cm ^"1. In this materialization, the total amount of sample was 12.2 g, and the portlandite present in The sample (disregarding impurities) was 4.07 g, the remainder being supernatant.

In this first embodiment of the invention, the drying process and its consequent environmental carbonation lasted about 5 days. At this time the mass of captured CO2 was slightly higher than 28.1% of the total carbonated sample, as can be seen in the result of the thermogravimetric analysis of the dried sample (Figure 4). If we compare it with the theoretical maximum, which corresponds to a mass of captured CO2 of 44%, it is verified that a carbonation degree of 64% has been reached. This means that in the 12.2 g of the original sample, 1.57 g of C0 ₂ have been captured in five days.

In an extrapolation of this materialization to an industrial volume of 100 m ³ , dispersed in a similar geometry of surface / volume ratio of 1 cm ^"1 , that is, over a hectare (10,000 m ² ), the amount of carbon dioxide that could be sequestered would be about 16 tons in less than a week.

Example 3

Environmental carbonation

In another embodiment of the present invention, the reservoirs were rewetted every day, pouring a small amount of water onto the residue. This prevented the formation of a carbonate inhibitor film, thereby facilitating the access of C0 ₂ to the entire portlandite assembly of the residue. Laboratory experiments demonstrate a practically complete carbonation of the residue after an environmental carbonation procedure by means of this second materialization. Specifically, 12.2 g of sample are found partially dry after 24h. Adding a few milliliters of water every 24h, after seven days the sample was completely carbonated.

X-ray diffraction analyzes (Figure 5), as well as thermogravimetry experiments (Figure 6) demonstrated the total disappearance of the portlandite and the exclusive existence of calcite. In this case, the loss in weight corresponding to the release of C0 ₂ by thermal decomposition of calcite was 37% instead of the theoretical maximum if portlandite was pure and dry. Considering the impurities present in the sample, it would correspond to a practically complete carbonation. In this materialization 2.42 g of C0 ₂ have been captured in one week. An extrapolation to industrial quantities analogous to that of the previous example, the amount of carbon dioxide that could be sequestered would be about 24 tons of carbon dioxide in one week.

The occasional use of mechanical agitation devices, driven at all times by renewable energy, can accelerate these carbonation times and reduce them to 48 hours.

Claims

1. Use of an aqueous suspension with a weight percentage of calcium greater than 15%, for the removal of a gas comprising carbon dioxide.

2. Use of the aqueous suspension according to claim 1, wherein said aqueous suspension is a byproduct of acetylene production.

3. Use of an aqueous suspension according to any of claims 1 or 2, wherein the by-product comprises portlandite.

4. Use of the aqueous suspension according to any of claims 1 to 3, wherein the carbon dioxide comes from the acetylene production itself.

5. The process for removing C0 ₂ from a gas stream comprising carbon dioxide induced by carbonation with an aqueous slurry comprising calcium in a percentage higher than 15% by weight.

6. The method according to claim 5, wherein induced carbonation occurs by forced contact of the aqueous suspension and the gas stream under ambient pressure and temperature conditions.

7. Procedure for eliminating a gas comprising carbon dioxide by environmental carbonation, with an aqueous suspension comprising calcium in a weight percentage greater than 15%.

8. Method according to claim 7, wherein the environmental carbonation occurs by contacting the aqueous suspension in a reservoir with the gas contained in the atmosphere.

9. Method according to claim 8, wherein the reservoir is opened.

10. Method according to any of claims 7 to 9, wherein the reservoir is under agitation.

11. Method according to any of claims 7 to 10, wherein the surface / volume ratio of the aqueous suspension is greater than 0.1 cm ^" .

12. Method according to any of claims 5 to 11, wherein the calcium-rich by-product is portlandite.

13. Process according to any of claims 5 to 12, wherein the aqueous suspension is a byproduct of acetylene production.

14. Method according to any of claims 5 to 13, wherein the ratio between the volume of aqueous suspension and the gas flow is between 0.01 s and 1s.

15. Method according to any of claims 5 to 14, wherein the carbonation is carried out at temperatures between 5 and 50 ° C.

16. The method according to claim 15, wherein the temperature range is between 15 and 35 ° C.

17. Method according to any of claims 5 to 16, wherein the carbonation is carried out at pressures between 0.5 and 2 bar.

18. Method according to claim 17, wherein the pressure range is between 0.9 bar and 1.6 bar.