DE102010025819A1 - Process and apparatus for regenerating amine-containing detergent solutions derived from gas washes - Google Patents

Abstract

The invention relates to a method and device for the regeneration of loaded amine-containing detergent solutions from gas scrubbing processes for gases such as biogases, exhaust gases from chemical processes or associated petroleum and petroleum gases, in which CO2 and / or H2S are chemically bound, which are used before further use or safe discharge the atmosphere must be separated by being subjected to a chemical and physical gas scrubbing, which is preferably carried out using an amine-containing detergent solution, from which CO2 and / or sulfur compounds are released by means of a circulated flush gas in accordance with the following process steps, in that the loaded detergent solution (rich ) using a heat source, heated to a temperature below the pressure-dependent boiling point of the detergent solution, of at least 20 ° C, preferably 60-96 ° C and brought into contact with a flushing gas, the chemical in the detergent solution d physically fixed CO2 and / or chemically bound sulfur compounds is stripped into the offgas with a residence time of 3 to 180 minutes, preferably 30-80 minutes. The flush gas component is then separated from the resulting off-gas mixture in a two-stage separation in a gas liquefier and a selective element, preferably a membrane or membrane cascade, and is subsequently passed through an evaporator zone. From here, the gaseous flush gas is transferred to the stripping zone and the flush gas portion remaining in the liquid state, including the remaining non-evaporated liquid portions, into the heating zone charged with the detergent solution to be desorbed, where it is expanded and evaporated and the process cycle of the flush gas is closed again. The heat energy available from technical low-temperature sources, in particular CHP cooling water waste heat and / or CHP exhaust gas heat and / or solar heat, geothermal energy, industrial waste heat and / or process heat, which is brought to the level of the desorption temperature by heat pumps, is used as heat energy for the desorption process.

Description

The invention relates to a process for the regeneration of laden amine-containing detergent solutions from gas scrubbing processes, in which CO ₂ and / or H ₂ S are chemically bound, and to a device for implementing the process.

Various gases such as biogas, waste gases from chemical processes or natural gas and associated gases contain CO ₂ and / or H ₂ S, which must be separated from further use or safe discharge into the atmosphere. Among others, chemical and physical gas scrubbing methods are suitable, whereby a chemical scrub preferably takes place by means of an amine-containing detergent solution in which CO ₂ and sulfur compounds are chemically bound.

Out DE 203 00 663 U1 is a biogas upgrading plant known that binds by physical solution under pressure, inter alia, CO ₂ in the detergent. The regeneration takes place by carrying out a first expansion step, a heating of the detergent with subsequent second expansion and a final stripping with ambient air.

Stripping with air is known for systems for physical adsorption of CO ₂ and / or H ₂ S known method, it is suitable for oxidation-stable detergent. Amine-containing detergent solutions, however, are characterized by a low oxidation stability.

The classical desorption of amine-containing detergent solutions by stripping with water vapor is in "Gas Processing", 5th Ed., By Kohl and Nielsen described in detail. Disadvantage is the high energy consumption for generating the steam flow, also already moderate temperatures of 115-130 ° C contribute to shortening the service life of the detergent solutions.

Out US Pat. No. 3,471,370 For example, a configuration for removing water from glycol amine solutions for gas drying purposes and desulfurizing the gas is known, which describes stripping with naphtha to remove small amounts of water from the solution, from about 6 to 2.5 vol%. For this purpose, a Napthastrom is led to the stripping of the glycol-amine solution by evaporation and subsequent condensation in a circle. The separation of the condensed water content is carried out by phase separation in the liquid phase naphtha-water. The water to be removed is withdrawn liquid from the system. Noncondensing portions of the stripping gas are discharged from the system in gaseous form. The recovered by condensation Naphtaanteil is evaporated again. A portion of the separated water is added to adjust a reflux to the top of the stripping column.

Furthermore, from the treatment of H ₂ and CO _2- containing synthesis gases, Fischer-Tropsch reaction products u. ä. the stripping of physical, physio-chemical and chemical detergents and solvents with gases other than air known.

EP 1 543 874 A2 describes a combined absorption and high pressure stripping in which the pressure of the stripping is above the absorption pressure. The stripping gas can be heated. A specified application case is z. B. the discharge of a Rich detergent, wherein the expelled Flushgasstrom for pressing in oil reservoirs (enhanced oil recovery) is intended or should find use in other synthesis reactions. The stripping gases are natural gas, nitrogen, hydrocarbons with C2 and longer chains.

Stripping with water vapor and with product gas, especially for gas purification and especially for the removal of one or all acidic gas components such as hydrogen sulfide and carbon dioxide from gas streams such as natural gas and industrial gases by chemisorption in a two-pass process includes DE 698 09 393 T2 ( US 6,139,605 ).

The proposed method for achieving a particularly high degree of desorption of the loaded detergent for CO ₂ with a depletion target of well below 100 ppm in the product gas is carried out by sharing the desorption, wherein the loaded Rich detergent stream is first regenerated in a classical countercurrent contact with water vapor. Part of the semi-lean detergent is returned to coarse absorption, while a partial stream of the semi-lean detergent is additionally stripped with the product gas to increase the desorption level. The additional stripped lean detergent is used in a coarse absorption downstream fine cleaning. The existing after stripping offgas, consisting of desorbed CO ₂ and the product gas used for stripping, is completely attributed to the Rohgasfeed the absorption. For economic reasons, the stripping gas flow must remain limited to 0.01-5% of the product gas flow.

The process improves the desorption level of the detergent used in the fine cleaning and shifts the CO ₂ desorption performance internally to the classical water vapor desorption of the semi-lean branch. The method can thus achieve a higher degree of desorption of the detergent, but retains the already outlined disadvantages of classical steam desorption.

From PCT WO 03/031028 An apparatus is known which serves to strip an amine-containing washing solution with air. For this purpose, the washing solution is heated in the range of 90-130 ° C and stripped in a packed column with slightly compressed ambient air. The apparatus comprises the following functional groups: a bed column, a heated liquid reservoir with circulation pump and a mechanical coalescence separator for the retention of foams and entrained droplets. Purpose is the removal of CO ₂ in concentrations of less than 1 vol.%, For conditioning the combustion air of fuel cells.

However, the proposed arrangement has the mentioned significant disadvantage that the stripping is done with air and the washing liquid is subject to an oxidative stress, which leads to a shortening of their life and durability.

The dissertation JS Wallace "Development of a Carbon Dioxide Continuous Scrubber (CDOCS) System for Alkaline Fuel Cells", Univ. Canterbury, New Zealand (2005) points out that with a comparable apparatus for a representative aqueous MEA glycol solution, extensive oxidative destruction of the detergent occurs within 4 weeks of operation. For larger systems outside the laboratory scale and for high mass flows of CO ₂ and / or H ₂ S such a short detergent life is economically unsatisfactory, as associated with high costs for replacement and disposal of the oxidized detergent.

A second disadvantage is the fact that a high Strippgasbedarf accrues. As soon as a stripping is carried out with a gas other than air, the expense of providing this stripping gas must be considered. The article of Owen J. Curnow, Susan P. Krumdiek, Elizabeth M. Jenkins, "Regeneration of Carbon Dioxide Saturated Monoethanolamines - Glycol Aqueous Solutions at Atmospheric Pressure in a Packed Rubble Reactor", Ind. Eng. Chem. Res. 2005, 44, 1085-1089 , describes the stripping of CO ₂ from an aqueous MEA glycol solution with nitrogen. The stated excess of nitrogen is 5-20 times greater than the volume of desorbed CO ₂ . The desorbed CO ₂ is released together with the stripping gas to the environment. It is also possible to use helium and argon. A disadvantage for applications outside of small laboratory applications is the high expenditure required for providing the stripping gas.

With EP 1 967 249 A1 a method based on a two-phase distillation for the use of low-temperature heat for the regeneration of CO ₂ solvents in the CO ₂ separation from exhaust gases by CO ₂ scrubbing is proposed. It describes a primary power plant stripping option for aqueous amine solutions involving a combination of absorption and combined desorption.

The latter realizes in a desorber column the combination of a stripping-assisted detergent desorption with a classical steam desorption. A circulating Strippgasstrom is ensured by condensation and in some embodiments, also by a downstream separator for the stripping gas from the separated CO ₂ stream.

This reduces the possibility of protecting the detergent from thermal stress since the detergent in the lean reboiler is then subjected to a full desorption temperature of 110-130 ° C.

Since the application was designed primarily with a view to CO ₂ landfill, the aspect of a practically complete. Retention of the stripping gas not developed. In particular, the retention of the stripping gas from the CO ₂ stream is not specified and described in detail.

As in the non-power sector, a CO ₂ discharge to the environment is to be regarded as a frequent use case, and a discharge of organic stripping to the environment for environmental reasons practically prohibits a further development of the prior art is urgently required to exclude environmental pollution and at the same time to be able to use the energetic advantages.

In addition, the document contains no approach to optimize the Strippgaseinsatzes. Especially for smaller used heat sources of z. B. some MW thermal performance is finer thermal management to maximize the CO ₂ deposition with minimal heat input makes sense.

O. g. Writing also combines absorption and desorption very closely and, in particular, provides for the realization of the Semilean and Lean provision in one unit. In particular, the outlined task of the rich medium on a heat exchanger is a limitation because too low heat flow of the rich medium in the column task can lead to undesirable condensation phenomena of the stripping gas in the upper column segment.

For the treatment of hydrocarbon-containing gas mixtures and for the deposition of CO ₂ , other methods are known, which are deepened in the following. A common treatment process of hydrocarbons is based on the separation of higher hydrocarbons by deep-freeze condensation and upstream adsorptive drying by means of glycol. The deep-freeze condensation process is a process and energy consuming, which causes a compression of the gas streams after the relaxation. In some cases, an additional pre-cooling of the gas streams is required. By applying a suitable membrane process for the fine depletion of hydrocarbons, the energy requirement and thus the costs can be reduced since the gases do not have to undergo the above-mentioned preconditioning. The membrane process thus represents a more environmentally friendly process.

With regard to the present separation problem, the use of polymer membranes for the enrichment of carbon dioxide from gas streams is known. However, this separation method is technically unfavorable in the present case due to the mass flows to be handled, since preferably small amounts of material can be handled by membranes and the achievable Trennscharfen for a safe direct discharge of the off-gas into the environment are not sufficient

In general, for the separation or enrichment of hydrocarbons from carbon dioxide, especially methane is of general interest. For example, in DE 10 2007 058 548 B4 describes the use of a membrane that converts raw biogas into a methane-enriched and a methane-depleted product stream.

In addition to the necessary and difficult to handle high gas flows through membranes, especially the poor separation performance is disadvantageous for difficult to condense components. In contrast, compounds that can condense in a membrane and separated by an adsorption-diffusion mechanism have proven to be more technologically easier to handle. Furthermore, a fine depletion is favored in terms of manageable low gas flows.

Much work has been done in the field of hydrocarbon conditioning, with preferably a readily condensable component, such as a higher hydrocarbon (HKW), being separated from a hardly condensable one. For the fine depletion of flushing gases of CO ₂ , therefore, a clear difference in the condensation behavior must be present.

In the article "Gas conditioning by means of permeable membranes" by G. HINNERS in ERDÖL ERDGAS KOHLE 120th ed. 2004, Issue 2 the trial of polymer-based membranes for the separation of HKW from natural gases under elevated pressure conditions is described. These show the disadvantage of swelling due to the moisture and HKW contained in the gas stream, whereby the selectivity decreases. The prerequisite for the use of such membranes would therefore be complete predrying of the gas streams.

In contrast, membranes made of inorganic-non-metallic materials do not have this swelling capacity and are therefore more versatile. In addition, their high chemical resistance, pressure and pressure swing resistance and thermal stability.

A prerequisite for a selective separation is a uniform pore size of the inorganic membrane material in the molecular size of the components to be separated. Therefore, zeolite membranes are suitable because they have an inherent, defined pore system. The hydrophobic silicalite or low-aluminum ZSM-5 from the group of MFI zeolites is particularly suitable for the separation of nonpolar components.

So describes WO 94/01209 the synthesis of dense ZSM-5 layers and their use in the selective adsorption of hydrocarbons up to an applied feed pressure of 100 kPa.

In DE 695 33 513 T2 is reported by the principle separation of various so-called feedstocks, which may also consist of hydrocarbons, such as those found in natural gas. However, the separation principle of molecular diffusion (p _feed = p _permeate ) is assumed.

DE 10 2004 001 974 A1 the possibility of olefin separation under elevated pressure conditions is described. It describes the separation of close-boiling mixtures by molecular radii. Here, feed side pressures of 1 to 100 bar and a permeate side pressure of 0.01 to 10 bar are reported. In the in DE 10 2004 001 974 A1 described invention preferably flow the molecules with smaller diameters through the membrane, for. B. 1-butene is enriched in the permeate while 2-butenes are retained.

In DE 693 26 254 T2 It is described that it is possible to separate butanes from methane by means of supported MFI membranes, whereby adsorption increases the higher hydrocarbon in the permeate. Porous metal carriers were used as well as ZSM-5 zeolites as selective layer, which in contrast to silicalite are more aluminous and therefore more hydrophilic. The permeation tests were carried out using a sweep gas on the permeate side.

Further separations of hydrocarbons and comparable components on inorganic porous membranes have been described. For example, was through Santamaria et al. [M. Arruebo et al., Separation and Purification Technology 25 (2001) 275-286] on MFI membranes the separation of natural gas components at 1-4 bar and pressure differences up to 3 bar described. Here and as in all previously described separations of natural gas and Erdölbegleitgas components according to the adsorption method, the separation is preferably carried out by the so-called surface diffusion, which has so far deteriorated after increasing the feed pressure and the differential pressures between feed and permeate.

Zeolite membranes on porous supports can be prepared in various ways. Common is in situ crystallization directly on the support, or seed-based synthesis for more oriented, uniform growth.

Seed crystals are usually prepared and separated separately, see Fonts DE 10 2004 0001 974 A1 respectively. DE 100 27 685 B4 , Or a seed layer is produced directly on the support during a separate synthesis step, as in patent DE 103 04 322 A1 described. Subsequently, the formation of a continuous synthesis layer out of a dilute solution, which is mainly to support crystal growth. Both methods are very process-intensive.

In the published patent application DE 101 07 539 A1 describes the production of a composite membrane on a ceramic, porous support material, on which a mesoporous zeolite layer is deposited, wherein subsequently the closed zeolite layer is formed on or within the surface thereof by hydrothermal synthesis. No details are given on this mesoporous intermediate layer and the hydrothermal synthesis.

Based on the above-mentioned prior art, it is appropriate for economic reasons to regenerate the loaded amine-containing detergent solution in order to recycle it in recycle use. Furthermore, it may be necessary by the process to remove chemically bound H ₂ S and / or CO ₂ fractions largely or completely from the amine-containing detergent solution.

The invention is therefore an object of the invention to provide a process for the at least partial regeneration of an obtained in the purification of gases amine-containing detergent solution in which CO ₂ and / or sulfur compounds are chemically bonded, which at low flush gas consumption desorption laden detergent solution at a temperature preferably below the boiling point of the detergent solution, namely pressure-dependent allowed below + 100 ° C, so reduces the oxidative stress of the detergent solution, increases their life and thus significantly retards aging. Overall, such an economical operation is to allow and at the same time a minimum content of the flushing gas in the CO ₂ -Off gas is to be ensured.

The method should be particularly suitable to use those technically usable heat potentials that are below the boiling point of the detergent solution.

For carrying out the method, a suitable device with an efficient technique for the retention of unwanted, with the off-gas entrained shares to create according to the parameters mentioned.

According to the invention the object is achieved by the features specified in claim 1. The advantageous embodiment of the method are set forth in claims 2 to 10.

A suitable for carrying out the process plant is the subject of claim 11. Further advantageous embodiments are given in claims 12 and 14.

• /1/ die beladene Rich-Waschmittellösung unter Nutzung einer Wärmequelle, beispielsweise der Abwärme von Blockheizkraftwerken (BHKW), die typischerweise mit Temperaturen von bis zu +98°C verfügbar ist oder auch das von Wärmepumpen und/oder Solaranlagen bereitgestellte Wärmepotentiale für die Regeneration von aminhaltiger Waschmittellösungen genutzt wird, in dem in einer Heizzone die betreffende wässrige Waschmittellösung auf eine Temperatur unterhalb ihres druckabhängigen Siedepunktes, wenigstens auf 20°C bis vorzugsweise auf 96°C erwärmt wird (Verfahrensschritt A);
• /2/ ein weiterer, der Waschmittellösung zugeführter chemisch inerter bzw. den Betriebsablauf durch chemische Nebenreaktionen nicht störender Stoff, sich bei der angelegten Temperatur oberhalb seines Siedepunktes und somit im gasförmigen Aggregatzustand befindet bzw. in diesen übergeht und als Flushgas fungiert und die Strippung des chemisch fixierten CO₂ und chemisch gebundener Schwefelverbindungen aus der Waschmittellösung in das Offgas bewirkt;
• /3/ die erwärmte Waschmittellösung in einer Strippzone mit dem gasförmigen Flushgas intensiv für eine mittlere Verweilzeit von 3 Minuten bis 180 Minuten, vorzugsweise von 30–80 Min. in Kontakt gebracht wird, wobei die aminhaltige Waschmittellösung vom Flushgas gestrippt und gelöstes CO₂ bzw. gelöste Schwefelverbindungen ausgetrieben werden (Verfahrensschritt B); dies kann mittels Blasen-, Füllkörper-, Packungskolonnen, Membrankontaktoren oder Gegenstrom-Sprühkolonnen oder eine Kolonne, die statische Mischelemente enthält, in dem ein Teil der beladenen Waschmittellösung im Gegenstrom zum Flushgas geführt wird, erfolgen;
• /4/ mitgerissene Flüssigkeitspartikel, Schäume u. ä. werden in einer anschließenden Koaleszenz- und Schaumabscheidezone abgefangen und wieder in den Flüssigkeitskreislauf der vorgelagerten Heiz- und/oder Strippzone zurückgeführt und damit einen unerwünschten Flüssigkeitstransport in den abfürenden Gasweg des Offgas-Flushgasgemischs unterbinden;
• /5/ die Flushgaskomponente aus dem Gemisch mit dem desorbierten CO₂ und/oder Schwefelverbindungs-Anteil über eine mindestens zweistufig geführte Abtrennung zurückgewonnen wird, wobei in einer ersten Stufe, einem Gasverflüssiger, durch Abkühlung oder durch eine Kombination von Abkühlung und Druckerhöhung eine Kondensation des Flushgases erfolgt, so dass ein Flushgasanteil aus dem Offgasstrom nach Kondensation als abtrennbare Flüssigkeit vorliegt und am Ausgang Flüssigkeit des Gasverflüssigers zusammen mit weiteren mitauskondensierenden Gaskomponenten wie z. B. Wasser abgezogen wird (Verfahrensschritt C);
• /6/ der verbliebene, nicht kondensierte Flushgasanteil innerhalb des CO₂ und/oder H₂S haltigen Offgasgemischs in einem zweiten Verfahrensschritt (Verfahrensschritt D) in eine Flushgasabtrennung abgeleitet und so:
• a) durch eine einzelne Membran oder eine Membrankaskade, oder
• b) durch physikalische Adsorption oder bevorzugte Porenkondensation an geeigneten Zeolithen oder Aktivkohlen, mit und ohne deren Regeneration, oder
• c) durch eine Wasche, oder
• d) durch eine beliebige Kombination von Membran, Adsorptions- und Waschverfahren weiter abgetrennt wird; wobei der in der Flushgasabtrennung, d. h. der der Kondensation folgenden Separationsstufe, zurückgewonnene Flushgasanteil durch Kondensation verflüssigt oder aber gasförmig belassen wird.

According to the invention, it is provided that:

• / 1 / the loaded rich detergent solution using a heat source, such as the waste heat of cogeneration units (CHP), which is typically available with temperatures up to + 98 ° C or also provided by heat pumps and / or solar thermal energy potentials for the regeneration of amine-containing detergent solutions is used in which in a heating zone, the aqueous detergent solution in question is heated to a temperature below its pressure-dependent boiling point, at least to 20 ° C to preferably at 96 ° C (process step A);
• / 2 / another, the detergent solution supplied chemically inert or the operation by chemical side reactions non-interfering substance is located at the applied temperature above its boiling point and thus in the gaseous state and passes into this and acts as a flushing gas and the stripping of the chemical fixed CO ₂ and chemically bound sulfur compounds from the detergent solution into the offgas causes;
• / / The heated detergent solution in a stripping zone is contacted intensively with the gaseous flushing gas for a mean residence time of from 3 minutes to 180 minutes, preferably from 30-80 minutes, the amine-containing detergent solution being stripped of the flushing gas and dissolved CO ₂ or dissolved sulfur compounds be driven off (step B); this can be done by means of bubble, packing, packing columns, membrane contactors or countercurrent spray columns or a column containing static mixing elements in which a portion of the loaded detergent solution is passed in countercurrent to the flushing gas;
• / 4 / entrained liquid particles, foams and the like Ä. Are intercepted in a subsequent coalescing and Schaumabscheidezone and returned to the liquid circulation of the upstream heating and / or stripping and thus prevent unwanted liquid transport in the abfürenden gas path of the offgas Flushgasgemischs;
• / 5 / the flush gas component is recovered from the mixture with the desorbed CO ₂ and / or sulfur compound content via a separation carried out at least two stages, wherein in a first stage, a gas liquefier, by cooling or by a combination of cooling and pressure increase a condensation of the Flushing takes place, so that a Flushgasanteil from the offgas stream after condensation is present as a separable liquid and at the output liquid of the gas liquefier together with other mitauskondensierenden gas components such. B. water is withdrawn (step C);
• / 6 / the remaining, non-condensed Flushgasanteil within the CO ₂ and / or H ₂ S-containing offgas mixture in a second process step (step D) derived in a Flushgasabtrennung and so:
• a) by a single membrane or a membrane cascade, or
• b) by physical adsorption or preferred pore condensation on suitable zeolites or activated carbons, with and without their regeneration, or
• c) by a wash, or
• d) is further separated by any combination of membrane, adsorption and washing processes; wherein the recirculated in the Flushgasabtrennung, ie the condensation of the subsequent separation stage, liquefied flue gas fraction is liquefied or left in gaseous form.

The separation membrane material for separating the CO ₂ -flush gas mixture in a) is characterized by its meso and macroscopic tightness. Membrane material can therefore be: ceramic, dense microporous layers (zeolite membranes) or dense polymer membranes zeolite membranes operate on the principle of adsorption diffusion or preferred pore condensation. Polymer membranes preferably work on the principle of solution diffusion.

For Flushgasabtrennung and adsorptive methods for the selective binding of gas components can be provided, such as binding to a Zeolithschüttung. When fully charged, this is regenerated and again available flushing gas is returned to the circulation or discharged from the system.

• /7/ das flüssig oder gasförmig vorliegende Flushgas erneut in der Strippzone verwendet und im Kreislauf geführt wird (Verfahrensschritt E), indem das kondensierte flüssige Flushgas in einer beheizten Verdampfungszone verdampft und über einen ersten Eintragungsweg gasförmig in die Strippzone eingetragen und mit der beladenen Waschmittellösung in einen intensiven Kontakt gebracht wird und das nach Passieren der Verdampfungszone flüssig verbleibene Flushgasanteile flüssig in die mit der zu desorbierenden Waschmittellösung gefüllte Heiz- und/oder Kontaktzone verbracht werden bzw. dass über einen zweiten Eintragungsweg das Flushgas im flüssigem Aggregatzustand direkt in die mit der zu desorbierenden Waschmittellösung gefüllten Heizzone und/oder Strippzone verbracht wird, und hier in der Waschmittellösung verdampft, wobei nicht verdampfende Kondensatanteile, insbesondere Wasser, von der aminhaltig Waschmittellösung aufgenommen werden.
• /8/ die Abtrennung des Flushgases vom Offgastrom auch dessen Wasseranteil umfassen kann, der z. B. zur Trocknung des Offgases oder zur Regulierung des Wassergehalts der aminhaltigen Waschmittellösung auch gesondert abgezogen werden kann;
• /9/ als Flushgas Verwendung findet:
• – chemisch inerte organische Stoffe geeignet zur bevorzugten Abtrennung an keramischen Membranen (Trennprinzip Adsorptionsdiffusion bzw. bevorzugte Porenkondensation) bzw. Polymermembranen (Trennprinzip Lösungs-Diffusion) oder
• – chemisch inerte organische Stoffe geeignet zur physikalischen Adsorbtion z. B. an Zeolithen oder
• – chemisch inerte organische Stoffe geeignet zur Ad- und Absorbtion in Waschlösungen, wie z. B. polaren Lösemitteln oder
• – chemisch inerte organische Stoffe mit einem Siedepunkt oberhalb des Frostpunkts der wässriger Aminlösung bis unterhalb des Siedepunktes der wässrigen Aminlösung oder
• – organische Stoffe, bevorzugt Kohlenwasserstoffe oder Alkohole jedoch mit 2 bis 7 Kohlenstoffatomen je Molekül oder mehr.

Also useful are washing process for binding the gaseous Flüssigsgasgasz z. Using a selective solubility of the flushing gas in a solvent to minimize the discharge of flushing gas from the system.

• / 7 / the liquid or gaseous flue gas used again in the stripping zone and recirculated (step E) by the condensed liquid flushed gas evaporated in a heated evaporation zone and introduced via a first entry path gaseous in the stripping zone and with the loaded detergent solution in an intense contact is made and the liquid remaining after passing the evaporation zone Flushgasanteile liquid spent in the filled with the desorbed detergent solution heating and / or contact zone or that a second entry way the flushing gas in the liquid state directly into the desorbing with the Detergent solution filled heating zone and / or stripping zone is spent, and evaporated here in the detergent solution, wherein non-evaporating condensate, in particular water, are absorbed by the amine-containing detergent solution.
• / 8 / the separation of the flush gas from Offgastrom may also include its water content, the z. B. for drying the off-gas or for regulating the water content of the amine-containing detergent solution can also be deducted separately;
• / 9 / is used as a flush gas:
• - Chemically inert organic substances suitable for the preferred separation of ceramic membranes (separation principle adsorption or preferred pore condensation) or polymer membranes (separation principle solution-diffusion) or
• - chemically inert organic substances suitable for physical adsorption z. B. to zeolites or
• - Chemically inert organic substances suitable for adsorption and absorption in washing solutions, such. As polar solvents or
• - Chemically inert organic substances having a boiling point above the freezing point of the aqueous amine solution to below the boiling point of the aqueous amine solution or
• - Organic substances, preferably hydrocarbons or alcohols but having 2 to 7 carbon atoms per molecule or more.

The achievable degree of desorption is - depending on the effective stripping time and stripping intensity, the type of aqueous amine washing solution and its temperature for temperatures around 100 ° C at over 50% of the CO ₂ chemical absorption capacity of a loaded amine-containing detergent solution.

At a temperature and load-dependent desorption time of 30 to 80 minutes, the detergent solution undergoes a CO ₂ discharge of 50 to 60% of its inlet-side initial charge. The discharge achieved can be determined directly on the basis of parameters for the degree of loading of the washing liquid such as pH, density, conductivity and as a criterion for achieving the required average residence time of the detergent solution in the stripping. In addition, the direct spectrometric determination of the detergent loading level is possible. Another method is the direct determination of the amount of CO ₂ discharged in the offgas stream using the CO ₂ concentration and the offgas volume flow.

In some cases, for example to comply with the highest emission requirements, such. As regards the permitted amount of released organic carbon, the downstream of an afterburner can be done, which can also oxidize other mittransportierte hydrocarbon shares at the same time.

• a) eine Desorptionskolonne mit einer Heizzone, einer Strippzone und eine Koaleszenz- und Schaumabtrennzone in Kaskadenanordnung,
• b) ein CO₂-Sensor zur Messung der CO₂-Konzentration des aus der Koaleszenz- und Schaumabtrennzone abgeführten Flushmedium-Offgas-Gemischs und zur Einstellung des Flushgasvolumenstromes,
• c) eine Kühlzone für das Flushmedium-Offgas-Gemisch unter Einbezug des Waschmittelstroms oder eines separaten Kühlmittelstrom, beispielsweise durch einen Kaltwassersatz bereitgestellt,
• d) eine nachfolgende primäre Abscheidezone, bestehend aus einem Gasverflüssiger,
• e) eine zweite nachgeordnete Flushgasabtrenneinrichtung als sekundäre Abscheidezone zur Abscheidung der im Gasverflüssiger nicht kondensierten Teile des Gasstroms, bestehend einerseits aus CO₂, H₂S, Methan, Aminwaschmittel, Wasserdampf und dem im Dampfdruck gasförmig verbliebenen Anteilen des Flushmediums,
• f) ein Verdichter zwischen der primären und sekundären Abscheidezone;
• g) ein selektives Element für das Flushgas
• h) einer Fördereinrichtung für das Flushgas aus den Abscheidezonen,
• i) eine Verdampfungszone, vorzugsweise als Verdampfer für das flüssig anfallende Flushgas, einschließlich Fremdwärmeversorgung (BHKW-Abwärme, Wärme von Wärmepumpen und/oder Solaranlagen),
• j) eine Flushgasleitung von der Verdampfungszone zur Strippzone,
• k) eine Verbindungsleitung von der Verdampferzone zur Heizzone,
• l) einer Kreislaufleitung mit Förderpumpe zwischen Heizzone (Sumpf) und Strippzone für eine mehrfachen Umlauf der aminhaltigen Waschmittellösung,
• m) eine Wärmezuführung für die Heizzone, wobei die Betriebstemperatur unter der druckabhängigen Siedetemperatur der Waschmittellösung eingestellt ist,
• n) ein Injektor zum Anschluss der Kondensatleitung an der Heizzone.

The device for carrying out the method comprises the following functional elements that are present in the interaction group, such that there are:

• a) a desorption column with a heating zone, a stripping zone and a coalescing and foam separation zone in cascade arrangement,
• b) a CO ₂ sensor for measuring the CO ₂ concentration of the flushmedium offgas mixture discharged from the coalescing and foam separation zone and for adjusting the volume of the flushing gas,
• c) a cooling zone for the flushmedium offgas mixture with the inclusion of the detergent stream or a separate coolant stream, for example provided by a chiller,
• d) a subsequent primary separation zone consisting of a gas liquefier,
• e) a second downstream Flushgasabtrenneinrichtung as a secondary separation zone for the separation of non-condensed in the gas liquefier parts of the gas stream, consisting on the one hand of CO ₂ , H ₂ S, methane, amine detergent, water vapor and the gaseous in vapor pressure fractions of the flushmium,
• f) a compressor between the primary and secondary separation zones;
• g) a selective element for the flush gas
• h) a conveying device for the flushing gas from the separation zones,
• i) an evaporation zone, preferably as an evaporator for the liquid arising flushing gas, including external heat supply (cogeneration waste heat, heat from heat pumps and / or solar systems),
• j) a flush gas line from the evaporation zone to the stripping zone,
• k) a connecting line from the evaporator zone to the heating zone,
• l) a circulation line with feed pump between heating zone (sump) and stripping zone for a multiple circulation of the amine-containing detergent solution,
• m) a heat supply for the heating zone, wherein the operating temperature is set below the pressure-dependent boiling temperature of the detergent solution,
• n) an injector for connecting the condensate line to the heating zone.

The liquid-gas separation in the coalescing and Schaumabscheidezone is preferably carried out by mechanically acting separation elements such as perforated plates, sieves, Koaleszenzabscheider, filter elements, foam domes u. It is also possible to use spray elements for spraying detergent solution or water or energy-carrying devices, such as ultrasonic actuators, evaporation sections, infrared radiant heat sources or electromagnetic heating in the RF or microwave range, which effectively act on foams or on foam surfaces and so on Allow liquid-gas separation. The addition of surface-active chemical foam inhibitor is possible to prevent unwanted liquid transport in the laxative gas path of the offgas Flushgasgemischs.

The Flushgasabtrennung within the Flushgasabtrenneinrichtung mentioned under g) is a membrane separation unit, which is executed within the Flushgasabtrenneinrichtung as a single membrane or membrane cascade. The membrane is characterized by meso and macroscopic tightness and preferably consists of ceramic, dense microporous layers (zeolite membranes) or dense polymer membranes, which operate on the principle of adsorption diffusion or preferred pore condensation.

• a) durch physikalische Adsorption oder bevorzugte Porenkondensation an geeigneten Zeolithen oder Aktivkohlen, mit und ohne deren Regeneration, oder
• b) durch eine Wäsche, oder
• c) durch eine beliebige Kombination von Membran, Adsorptions- und Waschverfahren.

The remaining, non-condensed Flushgasanteil within the CO ₂ and / or H ₂ S-containing offgas mixture is safely derived, the Flushgasabtrenneinrichtung next to the arrangement of single membrane or membrane cascade subsequent arrangements or their combinations are possible, so:

• a) by physical adsorption or preferred pore condensation on suitable zeolites or activated carbons, with and without their regeneration, or
• b) through a wash, or
• c) by any combination of membrane, adsorption and washing processes.

A fundamental positive effect of the method is that the risk of premature oxidation and aging of the detergent solution can be significantly reduced by the low process temperatures and in a special way enables effective use of heat sources with relatively low heat potential and thus energy optimization is achieved. The lower process temperatures can also reduce the technical requirements of the plant and thus increase its durability and availability. Also, the expenses for the operation and maintenance of the plant are lower, resulting in an overall more economical advantage.

In the following, the invention will be clarified again on an exemplary embodiment on the basis of a functional scheme of a plant for the regeneration of laden scrubbing solution, in which CO ₂ and / or H ₂ S are bound.

The plant is z. B. part of a biogas upgrading plant, the CO ₂ and / or H ₂ S removed by amine scrubbing. In order to keep the detergent solution usable, it is necessary to reduce the CO ₂ or H ₂ S loading of the detergent solution in order to be able to use a sufficiently high loading difference in the recirculation of the detergent solution.

The loaded rich detergent solution with an amine concentration of 50%, a temperature of 60 ° C and a loading of 0.35 red CO ₂ per mole of amine, is passed through the line rich detergent 1 on the stripping zone 3 guided. The stripping zone 3 can be equipped with surface-enlarging elements such as structured packings, random packings, contactors, spray nozzles. The rich detergent solution flows through these elements into the heating zone 4 executed section. The volume of the heating zone 4 and the stripping zone 3 including a connection line 6 between heating zone 4 and the stripping zone 3 is dimensioned so that an average residence time of the detergent solution of 3 to 180 minutes, preferably from 30 to 80 minutes is achieved. About the inlet 5 becomes the heat transfer medium of the heating zone 4 supplied from a technical low temperature source of up to + 96 ° C, so that the detergent solution in the heating zone 4 is kept at a temperature of> 80 ° C.

The flush gas passes through the stripping zone 3 and possibly from the heating zone 4 in the stripping zone 3 in countercurrent to the detergent solution and thus causes the stripping effect and thus the desorption of the detergent solution. Some of the dissolved in the detergent solution CO ₂ and / or H ₂ S is stripped by the Flushgasstrom in an advantageous and surprising manner already at temperatures below the boiling point of the amine-containing detergent solution, typically from 60 ° C desorbed. The flush gas stream circulates over surface enlarging internals in the stripping zone 3 , Thus, the flushing gas is intensively swirled in countercurrent with the detergent solution. Within a mean residence time of 30-80 min. Thus, the stripping effect is maximally enhanced and causes effective depletion of the fixed CO ₂ and / or sulfur compounds in the amine-containing detergent solution. The depleted detergent solution is passed through the Lean detergent line 2 withdrawn from the facility for reuse.

At the upper exit of the stripping zone 3 is a gas mixture of the flushing gas, CO ₂ and / or H ₂ S and water vapor. This flush gas mixture is used for liquid-gas separation through the coalescing and foam separation zone 8th led, where liquid droplets are retained with the means mentioned and foaming is prevented. The retained liquid enters the stripping and heating zone 3 . 4 derived.

A CO ₂ sensor 9 measures the CO ₂ concentration of the coalescence and foam separation zone 8th discharged, gaseous Flushgas-offgas mixture. As the desorption of the detergent solution over heating zone 4 and stripping zone 3 kinetiklimiert, it is expedient to limit the volume flow used flushing gas to a point at which a maximum CO ₂ discharge coincides with a minimum Flushgasvolumenstrom, since the enthalpy of vaporization of the flushing gas phase transition is applied in addition to the chemical desorption of the detergent solution. For this purpose, the signal of the CO ₂ sensor 9 used to regulate an optimum value in the ratio of CO ₂ desorption to generated Flushgasvolumenstrom. This is done via the heat input into the evaporation zone 17 or by regulating the circulation of the liquid flushing gas when it is evaporated directly in the detergent solution.

The volume ratio of expelled CO ₂ and / or H ₂ S to the circulating Flushgastrom is 1: 1 to 1:20.

To maintain an intensive countercurrent contact of the detergent solution with the Flush gas flow, ensuring a consistent process temperature and for optimum desorption is the detergent solution from a feed pump 7 from the heating zone 4 via connection line 6 on the head of the stripping zone 3 circulated.

From the outlet of the coalescence and foam separation zone 8th is the CO ₂ and / or H ₂ S enriched gas stream via connecting line 10 in a gas liquefier 11 performed, in which a thermal condensation of the flushing gas takes place; at least a part of the flush gas is thereby transferred into the liquid state of matter. The cooling takes place via a cooling medium, which is tempered below the boiling point of the flushm medium. This may be the detergent stream itself or a separate coolant flow z. B. that of a chiller. An alternative known to a person skilled in the art is liquefaction by a pressure increase or a combination of cooling and pressure change.

The condensate, which also contains condensing non-flush gas components, is removed from the gas liquefier 11 withdrawn liquid and via connecting line 13 the evaporation zone 17 fed. Here, with the supply of heat of vaporization, the phase transition from the liquid to the gaseous flushing gas takes place. Via the first entry path, the recovered flush gas is then passed through the flush gas line 18 directly into the stripping zone 3 traced back to the process.

Via the second entry route, the unevaporated liquid fractions of the flushmium, including the condensed water from the evaporation zone 17 over the connecting line 19 and the injector 20 in the heating zone 4 derived. In the detergent solution then evaporates the remaining Flushgasanteil. Thus, the main circuit of the Flushgasstroms is closed.

Regardless, the liquid present Flushmedium with the co-condensed water without upstream vaporization phase directly through the connecting line 19 and injector 20 in the heating zone 4 be initiated. Here, the flushing gas is evaporated in the detergent solution heated above the flushing gas boiling point.

The one in the gas liquefier 11 uncondensed part of the gas stream consists of CO ₂ , sulfur compounds, traces of methane, traces of amine, water vapor and the gaseous in vapor pressure remaining proportions of the flushmium.

Since a loss of flush gas with the desorbed CO ₂ and / or sulfur compound gas stream should be avoided for economic and emission-side reasons as far as possible, closes the gas liquefier 11 over a connecting line 12 a second process stage in the form of a Flushgasabtrennung 15 at.

Within the Flushgasabtrennung 15 the separation of gaseous components of the flushing gas from the offgas stream, by means of a selective element 14 , Preferably by a ceramic separation membrane with meso and macroscopic tightness, which allows a direct recovery of the flushing gas, so that the CO ₂ and / or H ₂ S off-gas contains only very small proportions of the flushing gas and are derived for further use can.

If required, the forces acting on the membrane driving forces can be enhanced by compressors or vacuum pumps (not shown here).

The separated from the offgas flushing gas mixture and retained gaseous portion of the flushing gas is via connecting line 16 , in the evaporation zone 17 and, as stated in section [0066], [0067] or also [0068], returned to the process cycle. Thus, the desorption of the detergent solution (Rich) is a rationally regenerated flushing gas for re-efficient use available.

LIST OF REFERENCE NUMBERS

1

Direction Rich detergent

2

Head Lean detergent

3

stripping

4

heating zone

5

Inlet (heating zone)

6

connecting line

7

feed pump

8th

Coalescence and foam separation zone

9

CO ₂ sensor

10

connecting line

11

Gas liquefier

12

connecting line

13

connecting line

14

selective element

15

Flush gas separation

16

connecting line

17

Evaporation zone

18

Flush gas line (gas phase)

19

Connecting line (aqueous phase)

20

injector

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 20300663 U1 [0003]
• US 3471370 [0006]
• EP 1543874 A2 [0008]
• DE 69809393 T2 [0009]
• US 6139605 [0009]
• WO 03/031028 [0012]
• EP 1967249 A1 [0016]
• DE 102007058548 B4 [0025]
• WO 94/01209 [0031]
• DE 69533513 T2 [0032]
• DE 102004001974 A1 [0033, 0033]
• DE 69326254 T2 [0034]
• DE 1020040001974 A1 [0037]
• DE 10027685 B4 [0037]
• DE 10304322 A1 [0037]
• DE 10107539 A1 [0038]

Cited non-patent literature

• "Gas Processing", 5th Ed., By Kohl and Nielsen [0005]
• JS Wallace "Development of a Carbon Dioxide Continuous Scrubber (CDOCS) System for Alkaline Fuel Cells", Univ. Canterbury, New Zealand (2005) [0014]
• Owen J. Curnow, Susan P. Krumdiek, Elizabeth M. Jenkins, "Regeneration of Carbon Dioxide Saturated Monoethanolamines - Glycol Aqueous Solutions at Atmospheric Pressure in a Packed Rubble Reactor", Ind. Eng. Chem. Res. 2005, 44, 1085-1089 [0015]
• "Gas conditioning by means of permeable membranes" by G. HINNERS in ERDÖL ERDGAS KOHLE 120. Jg. 2004, No. 2 [0028]
• Santamaria et al. [M. Arruebo et al., Separation and Purification Technology 25 (2001) 275-286] [0035]

Claims (15)

A process for the regeneration of laden amine-containing detergent solutions from gas scrubbing processes of gases such as biogas, waste gases from chemical processes or associated gas and associated gases, in which CO ₂ and / or H ₂ S are chemically bound, which are separated before further use or safe discharge into the atmosphere must be subjected to a chemical and physical gas scrubbing, preferably by means of an amine-containing detergent solution, from which CO ₂ and / or sulfur compounds are released by a recirculating flush gas according to the following process steps: a) the loaded detergent solution (Rich ) is heated using a heat source to a temperature below the pressure-dependent boiling point of the detergent solution, at least 20 ° C, preferably 60-96 ° C and held during the process of desorption; b) another, the detergent solution supplied chemically inert material is at the applied temperature above its boiling point and thus in the gaseous state or passes into this and acts as a flushing gas of the loaded detergent solution (Rich-) and the stripping of the detergent in the detergent solution and physically fixed CO ₂ and / or chemically bonded sulfur compounds in the offgas causes; c) the heated detergent solution (Rich) in a stripping zone ( 3 ) is contacted with the gaseous flush gas for a mean residence time of 3 minutes to 180 minutes, preferably 30-80 minutes in countercurrent with the flushing gas and the amine-containing detergent solution is stripped and dissolved CO ₂ and / or dissolved sulfur compounds is expelled; d) entrained liquid detergent solution particles in the form of particles and foams in a subsequent coalescence and foam separation zone ( 8th ) separated from the gas stream and into the stripping and / or heating zone ( 3 u. 4 ) to be led back; e) the flue gas component from the mixture with the desorbed CO ₂ and / or sulfur compound fraction is passed over an at least two-stage separation and recovered by separating in a first primary stage the separation in a gas liquefier ( 11 ), wherein cooling and / or pressure increase a condensation of the flushing gas and excess water and other liquid fractions takes place, and that thereafter this liquid mixture is separated, wherein the cooling medium is heated below the boiling point of the flusher medium; f) the non-condensed flue gas fraction from gas liquefier remaining within the CO ₂ and / or H ₂ S-containing offgas mixture ( 11 ) in a second secondary stage of a Flushgasabtrenneinheit ( 15 ) with selective element (s) ( 14 ) and here a) further separated by a single membrane or a membrane cascade, or b) further separated by a physical adsorption process, or c) further separated by a washing process, or d) by a combination of membrane, adsorption and / or washing process is further separated, and that recovered from the offgas mixture Flushgasanteile are liquefied by condensation or left in gaseous form and that the released CO ₂ and / or H ₂ S-containing offgas is discharged separately; g) the recovered flush gas in a heated evaporation zone ( 17 ) evaporated and gaseous in the stripping zone ( 3 ) and brought here in contact with the recirculated amine-loaded detergent solution and in contact; h) the liquid gas remaining in the liquid state, including the remaining unevaporated liquid components, directly into the heating zone charged with the detergent solution to be desorbed ( 4 ) and evaporated in the detergent solution. A method according to claim 1, characterized in that the heat energy for the Desorbtionsverfahren of technical low temperature sources, in particular CHP cooling water waste heat and / or cogeneration heat and / or solar heat, geothermal heat, industrial waste heat and / or process heat by heat pumps to the level of desorption brought is used. A method according to claim 1, characterized in that the detergent solution within the stripping zone ( 3 ) via bubble columns, packed columns, packed columns, membrane contactors, static mixers or countercurrent spray columns. A method according to claim 1, characterized in that the volume flow of flushing gas is controlled by the CO ₂ concentration in the flush gas offgas mixture. A method according to claim 1, characterized in that the degree of loading of the detergent for determining the actual desorption of the detergent solution based on the pH, the conductivity, the density, the speed of sound, the spectroscopic properties of the detergent solution or in their combination measured and as a demolition criterion of desorption is being used. A method according to claim 1, characterized in that the amine-loaded Detergent solution Foam-inhibiting substances with an anti-foam dosage can be added. A method according to claim 1, characterized in that as a flush gas - chemically inert organic substances suitable for the preferred separation of ceramic membranes based on zeolite (separation principle adsorption diffusion or preferred pore condensation) or polymer membranes or - chemically inert organic substances with a boiling point of 0 ° C to below the boiling point of the washing solution or - organic substances with a chain length of C2 ... C7 or more are used. A method according to claim 1, characterized in that the total recovered flushing gas in the liquid state of aggregation directly into the heating and / or stripping zone ( 4 . 3 ) and or evaporated in the heated detergent solution. A method according to claim 1, characterized in that the operating temperature is set to a value between the boiling point of the Flushmediums but below the boiling point of the aqueous amine-laden detergent solution. A method according to claim 1, characterized in that the gaseous portion of the flushing gas remaining in the offgas is oxidized together with the gaseous hydrocarbons from the aqueous amine-laden detergent solution in a post-treatment unit. Device for carrying out the method according to claim 1, comprising the following functional elements in the composite action, that there are a) a desorption column with a heating zone ( 4 ), a stripping zone ( 3 ) and a coalescence and foam separation zone ( 8th ) in cascade arrangement, b) a CO ₂ sensor ( 9 ) for measuring the CO ₂ concentration of the from the coalescing and Schaumabtrennzone ( 8th ) discharged flushmedium offgas mixture, c) a primary separation zone with a gas liquefier ( 11 ), which is supplied with the detergent stream or a separate coolant stream, preferably that of a chiller, as a cooling medium, d) a secondary deposition zone with a Flushgasabtrenneinheit ( 15 ) for the separation in the gas liquefier ( 11 ) non-condensed parts of the flushing gas from the gas stream consisting of CO ₂ , H ₂ S, gaseous amine detergent, methane, water vapor and the remaining gaseous in vapor pressure fractions of the fluffing medium, e) a compressor for increasing the pressure between the primary and secondary separation zone according to c) and d), f) a membrane separation unit as a selective element ( 14 ) within the Flushgasabtrenneinheit ( 15 g) a pump for the flushing gas from the separation zones according to c) and d) h) an evaporator ( 17 ) for the condensed and in the liquid state of matter accumulating flushing gas, i) a circulation line ( 6 ) with pump ( 7 ) between heating zone ( 4 ) and stripping zone ( 3 ) for the circulation of the detergent solution, j) a feed ( 5 ) for the heat energy in the heating zone ( 4 ), k) a flush gas line ( 18 ) from the evaporator zone ( 17 ) to the stripping zone ( 3 ), l) a connecting line ( 19 ) from the evaporator zone ( 17 ) to the heating zone ( 4 ) as well as m) an injector ( 20 ) for connecting the connecting line ( 19 ) to the heating zone ( 4 ). Device according to claim 11, characterized in that in the coalescence and foam separation zone ( 8th ) Separating elements, such as perforated plates, sieves, Koaleszenzabscheider, filter elements, foam domes or spray elements for spraying detergent solution or water or energy-carrying devices such as ultrasonic actuators, evaporation lines, infrared radiation heat sources or electromagnetic heating means in RF or microwave range are arranged or the mechanical means are provided for the addition of surface-active chemical foam inhibitors. Device according to claim 11, characterized in that the selective element ( 14 ) is formed as a membrane separation unit and is characterized by meso and macroscopic tightness and consists of ceramic, dense microporous layers (zeolite membranes) or dense polymer membranes, which operate on the principle of adsorption diffusion or preferred pore condensation. Device according to claim 11, characterized in that the flush gas separation unit ( 15 ) is formed as a zeolite absorber are physically adsorbed on the gaseous Flushgasanteile. Device according to claim 10, characterized in that a post-combustion unit is provided as a post-treatment unit.

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