Absorbing solution, method for preparing an absorbing solution, use of the absorbing solution and method for activating an absorbing solution

In fossil-fueled power plants to generate electrical energy produced by the combustion of a fossil fuel, a carbon dioxide-containing flue gas. must be separated from the flue gases to avoid or to reduce carbon dioxide emissions (CO2). For the separation of carbon dioxide from a gas mixture are generally known various methods. In particular for separating carbon dioxide from a flue gas by a combustion process, the method of absorption-desorption is also customary. In industrial scale carbon dioxide (CO2) thereby washed out with an absorbing liquid from the flue gas in an absorber (CO2 capture process). The CO2 reacts with the absorption liquid, whereby it is dissolved in the liquid phase, physically. The reaction takes place in the boundary layer, thereby forming a concentration profile in the boundary layer. The rate of absorption is in particular influenced by the rate of reaction.

Major absorption liquids are based on primary, secondary or tertiary amines, or a mixture thereof, and exhibit good selectivity and a high capacity for carbon dioxide. Preferably used are currently ethanolamines, amino acid salts and potash solutions as absorbents, as they have a comparatively lower regeneration energy consumption.

The advantage of secondary amine compounds (secondary ethanolamines or secondary amino acid salts) towards primary amine compounds (primary ethanolamines or primary amino acid salts) is the considerably lower absorption energy and the resultant lower regeneration energy, which manifests itself in a lower efficiency collapse of the power plant. In addition, show secondary amine compounds a higher loading capacity for CO2.

An advantage of the primary amine compounds, however, is the significantly faster absorption kinetics. This can be compared to the secondary amines or secondary amino acid salts, the columns or reactors in which the carbon dioxide is absorbed in the CO2 capture plant, lay smaller, resulting in lower investment costs.

The advantage of amino acid salts compared to hetrocyklischen amines or alkanolamines is that amino acid salts have no appreciable vapor pressure, and thus do not evaporate and can not be discharged through the CO2 capture process in the environment. Hetrocyklische amines and alkanolamines are volatile and are by emitting into the environment with the flue gas discharged, resulting in adverse environmental impacts.

In the chemical industry, the primary amine MEA (monoethanolamine) is currently mainly used. Since the energy efficiency is not in the chemical industry in the spotlight, the energetic disadvantages have wide extent neglected here previously. In power plants for electricity, however, is just the energy consumption of C02 capture process is of great importance, since it has a significant impact on the overall efficiency of the power plant due to its size. This technical implementation is currently the subject of research and development, which is why this issue is currently being optimized to a great extent.

An object of the invention is to provide an environmentally sound absorption liquid for the absorption of CO2, which has a high absorption rate and at the same time low energy consumption in the regeneration. Another object of the invention is to provide a method for the production and for providing an absorbent liquid through which the disadvantages are avoided in the prior art. It is another object of the invention to provide a use of an absorption liquid for the selective absorption of CO2 from the flue gas of an incinerator in which the disadvantages are avoided in the prior art. Moreover, it is an object of the invention to provide a method for activating an environmentally acceptable solvent, so that the absorption speed is increased and power consumption is reduced in regeneration.

The object relating to an absorption liquid object of the invention is achieved by the features of claim 1. The absorption liquid is an aqueous solution of washing-active substance, which is recognized on the basis of ethanolamines, amino acid salts, or potash, and comprises an activating additive, wherein the activating additive is an inorganic catalyst.

The invention starts from the consideration that the addition of an inorganic activator and a hydration catalyst to a slow-reacting solvents, such as solutions of tertiary ethanolamines, tertiary amino salts and potash, the mass transfer of gaseous C02 accelerated in the liquid phase, and characterized results in a significantly faster absorption kinetics. By then the resulting increase in the rate of absorption, the absorption column can made smaller, whereby the investment costs for a CO2 capture plant can be reduced.

The invention is based in particular on the finding that already sufficient small amounts of an inorganic activator to accelerate the absorption of CO2 significantly.

By the use of an inorganic additive which has no vapor pressure, the solvent is neutral to the environment, as it will no discharge of the additive is the atmosphere.

Since the activator is added in very small quantities, is not expected to increase in the regeneration energy. This can be reduced even by the addition of the activating additive further, since a correspondingly higher loading in the absorber is achieved and increases the driving force due to the increased partial pressure in the desorber. Thus, both savings in the design of the absorber due to the increased rate of absorption, as well as savings in the necessary regeneration energy yield.

An advantageous proportion of the inorganic catalyst is found in the absorption liquid of 0.01 to 10 weight percent. The amount of inorganic catalyst is, however, to minimize in order to minimize potential negative effects inorganic catalyst to the absorption liquid. Particularly advantageous, therefore, a proportion of the inorganic catalyst has been found in the absorption liquid of 0.05 to 2 weight percent. Basically important to remember that the inorganic catalysts are not to participate in the CO2 absorption. They catalyze the carbamate-water reaction (hydration), forming bicarbonate. The proportion of catalyst in the absorption liquid is therefore to be selected such that an optimized possible ratio of shares between the catalyst and washing Active substance is obtained in the absorption liquid.

As washing-active substances are solutions of secondary ethanolamines, tertiary ethanolamines, or hindered amino acids. but particularly advantageous are just solutions of secondary amino acid salts, tertiary amino salts, and also hindered amino acid salts such as amino acid salts have no appreciable vapor pressure, and thus are not discharged when CO2 capture process in the atmosphere. Also useful amino acid salts derived from amino acids, for example of sarcosine, N, N-dimethylalanine, taurine, alpha-alanine, betha-alanine, N-methylalanine, proline, homotaurine or glycine.

Suitable inorganic catalysts is particularly suitable metal oxides from the group of transition metals such as vanadium, molybdenum, tungsten, or titanium, or metal oxides from the group of semi-metals, such as arsenic or selenium. As the inorganic catalysts are suitable as well as acids with a compound from the group of semi-metals such as arsenic, selenium, bromine, or from the group of non-metals, such as phosphorus. Successful results were obtained while in laboratory tests in particular with Molybdenum (VI) oxide (MoO3) and boric acid (H3B03).

Which relates to a method is achieved by a method of providing an absorbing liquid for a CO2 capture process by the features of claim 7, wherein an aqueous solution with a detergent-active substance consisting of amines or potash, is scheduled and the aqueous solution an activating additive is introduced, wherein the activating additive is an inorganic catalyst.

Which relates to a method for activating a solvent to provide a liquid absorbing object of the invention is achieved by the features of claim 8. The solvent is initially an aqueous solution of washing-active substance, based on amines and / or potash. To accelerate a selective absorption of CO2 from the flue gas of a combustion plant an activating additive will be added, wherein the activating additive is an inorganic catalyst.

The proportion of the inorganic catalyst in the absorption liquid is adjusted to a level of from 0.01 to 10 weight percent.

As detergent substance is intrinsically secondary or tertiary amino acids, and especially secondary or tertiary amino acid salts, as well as hindered ethanolamines or amino acid salts.

The absorbent liquid according to the invention, the method for providing an absorption liquid, and the procedure for activation of a solvent come here preferably in the absorption of CO2 from the flue gas of a fossil-fired steam power plant, from the flue gas of a gas turbine plant, or from the flue gas of a combined gas and steam turbine for use.

The directed to a use of an absorption liquid object of the invention is solved by the features of claim 12 according to which the use in the selective absorption of CO2 is from the flue gas of an incineration plant, wherein the absorption liquid is an aqueous solution of washing-active substance (18), consisting of amines or potash, and an activating additive, consisting of an inorganic catalyst includes. The flue gas can come from a fossil-fired steam power plant, from a gas turbine plant, or of a combined gas and steam turbine.

Embodiments of the invention are illustrated by the figures. In which:<dl id="dl0001"><dt>1 shows</dt><dd>a diagram showing the comparison of different absorption liquids</dd><dt>FIG 2</dt><dd>a reaction diagram with the reaction of CO2 with a secondary amino acid salt </dd><dt>FIG 3</dt><dd>a reaction diagram with the reaction of CO2 with a secondary amino acid salt with an inorganic catalyst catalyzes</dd><dt>FIG 4</dt><dd>the chemical structure of potash as an example of a washing-active substance</dd><dt>FIG 5</dt><dd>the chemical structure of amino acid salts as an example of a washing-active substance</dd><dt>FIG 6</dt><dd>an example of a metal oxide activator</dd><dt>FIG 7</dt><dd>an example of an acid activator</dd></dl>

This in <figref idrefs="f0001">1 shows</figref> Chart shown displays required for the separation of CO2 from a flue gas specific energy in kJ per kg CO2 separated. The axis is not scaled, because the energy required is substantially even, depending on other process parameters such as pressure, temperature, pumped circulation, the flue gas mass flow, is to be discussed here in greater detail.

The bars represent different absorption liquids 13 and 14. The left bar shows an absorption liquid 13 with a secondary amino acid salt as an active washing substance. The right bar shows an absorption liquid 14 with a secondary amino acid salt and a proportion of an inorganic catalyst as activating additive. The ratio in the absorption liquid 14 between secondary amino acid salt and active washing substance in this example is in percent by weight 95: 5. Shown is the specific, required output which is required for the separation of CO2 from a flue gas. It is assumed here that apart from the absorption liquid used is changed, no further process parameters.

It can be seen that the absorption liquid 14 13 requires considerably less specific energy as compared to the absorption liquid. This means for the same column size is activated with an inorganic catalyst absorption liquid 14, a substantially lower specific energy required.

<figref idrefs="f0001">FIG 2</figref> shows a reaction diagram with the transfer of CO2 from the gas phase 10 in the boundary layer 21 of the liquid phase 11. The transition from the gas phase 10 in the boundary layer 21 is given by the interfacial 24th In the boundary layer 21, the CO2 reacts with a secondary amino acid salt 4 through a quick response 9 to the reaction product carbamate 5 and protonated amino acid salt 12th

but the subsequent reaction, wherein the reaction product further reacts with water to bicarbonate and further reaction products, is a slow reaction 8, since it is carried out already in the liquid core 20 of the absorbent 19, where it is sterically hindered, and is significantly slower than the Karbamatbildung in the boundary layer 21st

Compared to <figref idrefs="f0001">FIG 2</figref> shows <figref idrefs="f0002">FIG 3</figref> a reaction diagram being contained in the absorbent 19, in addition to the secondary amino acid salt 7 as a washing active substance 18, an inorganic catalyst 17th Shown is the gas phase and the liquid phase is 10 11. The liquid phase 11 is divided thereby into the boundary layer 21 adjacent to the gas phase 10 and the liquid core 20 which adjoins the boundary layer 21st

The inorganic catalyst causes the Bikarbonatbildung runs as fast response. 9 The Bikarbonatbildung takes place in the boundary layer 21 of liquid phase 11, and not in the liquid core 20, so the Bikarbonatbildung is accelerated. The faster Bikarbonatbildung also the CO2 from the gas phase 10 passes faster in the liquid phase 11th

In relation to the invention is only a small addition of an activating additive necessary to already achieve a considerable acceleration of the CO2 capture process. Advantageously, a proportion of less than 10 weight-% has proven.

<figref idrefs="f0003">FIG 4</figref> shows an example of a detergent substance 18. Shown is the chemical structural formula of potassium carbonate, commonly known as potash 16th

<figref idrefs="f0003">FIG 5</figref> shows a further example of a washing-active substance 18. Shown is the chemical structural formula of a general form of an amino acid salt of 7, wherein O represents oxygen, N represents nitrogen, M represents alkali metals or alkaline earth metals and R denotes a Restsubstituenten. The Restsubstituenten R1, R2 and R3 can be hydrogen H, an alkyl radical, an aryl radical, an alkylaryl radical, a heteroaryl radical, a halogen, CN or R-COO- here.

7 amino acid salts are particularly useful as detergent substance, because they have no appreciable vapor pressure, and thus in the absorption can not be discharged with the flue gas into the atmosphere during CO2 capture process.

<figref idrefs="f0003">FIG 6</figref> shows a Metealloxid activator 22 as an example of a catalyst 17. In it are O for oxygen and Me for half metals or transition metals.

<figref idrefs="f0003">FIG 7</figref> shows an acid activator 23 as an example of a catalytic converter 17. In this H are hydrogen, A is semi-metals or non-metals, O is oxygen, and m, n, x, y, z for the number of atoms.