WO2012001125A2

WO2012001125A2 - Method and device for the desorption of loaded amine-containing detergent solutions from gas scrubbing processes

Info

Publication number: WO2012001125A2
Application number: PCT/EP2011/061054
Authority: WO
Inventors: Ralf Boback; Sebastian Wohlrab; Felix FRÖHLICH
Original assignee: Leibniz-Institut Für Katalyse E.V. An Der Universität Rostock
Priority date: 2010-07-01
Filing date: 2011-06-30
Publication date: 2012-01-05
Also published as: WO2012001125A3; DE102010025819A1; EP2588216A2

Abstract

The invention relates to a method and device for regenerating loaded amine-containing detergent solutions from gas scrubbing processes of gases such as biogases, waste gases from chemical processes or associated petroleum gases in which CO₂ and/or sulfur compounds are present in chemically bound form. The detergent solution is heated to 20 - 96ºC, brought in contact with a flush gas and stripped over 3 to 180 minutes and after separation of the flush gas component said detergent solution is fed as a condensate to a membrane or similar separating unit, where the non-condensed flush gas component is separated. The condensed flush gas is evaporated again and circulated back into the circuit. The desorption is very effective and nearly complete, and because of the low heating temperature, technical low-temperature sources can be used such as co-generation plant cooling water waste heat, solar heat, geothermal heat, industrial waste heat and/or process heat.

Description

Process and apparatus for desorption of loaded amine-containing detergent solutions from gas scrubbing processes

The invention relates to a process for the desorption and regeneration of laden amine-containing detergent solutions from gas scrubbing processes in which C0 ₂ and / or sulfur compounds such as H ₂ S are chemically bound and to an apparatus for carrying out the process.

Various gases such as biogas, waste gases from chemical processes or natural gas and earth gases contain C0 ₂ and / or sulfur compounds which must be separated from further use or safe discharge into the atmosphere. Chemical and physical gas scrubbing methods are suitable for this purpose, in which case a chemical scrubbing preferably takes place by means of an amine-containing detergent solution in which CO ₂ and sulfur compounds are chemically bound.

From DE 203 00 663 U1 a biogas upgrading plant is known, which binds by physical solution under pressure inter alia C0 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. Air stripping is a process known for physical adsorption installations for CO ₂ and / or sulfur compounds, and is suitable for oxidation-stable detergents. However, detergent solutions containing amine are characterized by a low oxidation stability.

The classic desorption of amine-containing detergent solutions by stripping with steam is described in detail in "Gas Processing", 5th Ed., By Kohl and Nielsen Disadvantage is the high energy expenditure for the generation of the steam flow, furthermore already moderate temperatures of 115 - 130 ° C to shorten the service life of detergent solutions. US Pat. No. 3,471,370 discloses a configuration for removing water from glycol amine solutions for gas drying purposes and desulfurizing the gas, 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 Giykol 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 C0 ₂ -containing synthesis gases, Fischer-Tropsch reaction products u. the stripping of physical, physio-chemical and chemical detergents and solvents with gases other than air.

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 and in which the stripping gas is exposed to two different pressure stages. As stripping gases natural gas, nitrogen and C2 to C5 hydrocarbons are given.

The 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-circuit process includes the DE 698 09 393 T2 (US 6,139,605). The process improves the desorption level of the detergent used in the fine cleaning and internally shifts the CO ₂ desorption performance to the classical water vapor desorption of the semi-lean branch. The method can thus achieve a higher desorption of the detergent, but retains the already outlined disadvantages of classical steam desorption.

From WO 03/031028 an apparatus is known, which serves the stripping of an amine-containing washing solution with air. For this, the washing solution is in the range of Heated to 90 - 130 ° C and stripped in a packed column with slightly compressed ambient air. Purpose is the removal of C0 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 service life and life.

Curnow et al. in Ind. Eng. Chem. Res. 2005, 44, 1085-1089 describe the stripping of C0 ₂ from an aqueous MEA glycol solution with nitrogen. The indicated excess of nitrogen is by a factor of 5 to 20 above the volume of the desorbed C0 ₂ . The desorbed C0 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 the provision of the stripping gas.

For the treatment of hydrocarbon-containing gas mixtures and for the

Deposition of C0 ₂ , other methods are known, which are deepened below. A common treatment process of hydrocarbons based on the separation of higher hydrocarbons by deep-freeze condensation and upstream adsorptive drying by means of glycol. The deep-freeze condensation is a process and energy consuming process that 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 because the gases do not have to be subjected to 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 to deplete 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 matter are handled by membranes and the erzieibaren separating sharpness for a safe direct discharge of the off-gas into the environment are not sufficient. For example, DE 10 2007 058 548 B4 describes the use of a membrane which converts raw biogas into a methane-enriched and a methane-depleted product stream. Disadvantages, however, are difficult to handle high gas flows through the membranes and a poor separation efficiency.

In ERDÖL ERDGAS KOHLE 120.Jg. 2004, No. 2, Hinners describes the testing of polymer-based membranes for the separation of HKW from natural gases under elevated pressure conditions. 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.

For example, WO 94/01209 describes the synthesis of dense ZSM-5 layers and their use in selective adsorption and the like. a. from hydrocarbons to an applied feed pressure of 100 kPa.

In DE 693 26 254 T2 it is described that it is possible to separate butane from methane mitteis carrier-supported MFI membranes, which is enriched by adsorption of 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. In this and in other known methods, the separation is carried out by the so-called surface diffusion. Zeolite membranes on porous supports can be prepared in a variety of ways. Common is in situ crystallization directly on the support, or seed-based synthesis for more oriented, uniform growth.

The invention has for its object to provide a process for the desorption of an obtained in the purification of gases amine-containing detergent solution in which C0 ₂ and / or sulfur compounds are chemically bonded to provide low exhaust gas consumption, a substantial desorption of the loaded detergent solution and thereby the significantly reduce the oxidative load on the detergent solution, thereby increasing its service life and thus significantly delaying aging. Another object is to ensure a minimum content of the flushing gas in the C0 ₂ -Off gas.

Another object of the method is to use those technically usable existing heat potentials, which are below the boiling point of Waschmitteliösung. According to the invention, the method consists in that

IM the loaded amine-containing detergent solution, also referred to as rich detergent solution, using a heat source in a column with a heating zone to a temperature below the pressure-dependent boiling point of Waschmitteliösung, heated to at least 20 ° C to 96 ° C (method step A), wherein the temperature is maintained during the process;

121 the heated detergent solution in a stripping zone with a chemically inert flushing gas is contacted intensively for a mean residence time of 3 minutes to 180 minutes, preferably from 30 to 80 minutes, wherein the amine-containing detergent solution stripped from the flushing gas and dissolved C0 ₂ or dissolved sulfur compounds be driven off (process step B), wherein the intensive contact mitteis bubble, packing, packing columns, membrane contactors or spray columns or a column containing static mixing elements, in which a portion of the laden detergent solution is passed in countercurrent to the flushing gas can take place;

/ 3 / entrained liquid particles, foams and the like Ä. in a subsequent

Coalescence and Schaumabscheidezone caught and returned to the liquid circulation of the upstream heating and / or stripping and thus prevent unwanted liquid transport in the laxative gas path of the offgas flushing gas mixture;

141, the flushing gas is recovered as a gas component from the mixture with the desorbed C0 ₂ or the sulfur compound or the two parts through a two-stage separation at least, wherein carried out in a stage by cooling or by a combination of cooling and pressure increase condensation of the flushing gas , So that a first Flushgasanteil from the offgas stream after condensation is present as a separable liquid and at the exit as a liquid of this condensation zone together with other mitauskondensierenden gas components such. B. water is withdrawn, z. B. after a gas liquefier (process step C);

/ 5 / the remaining, uncondensed second Flushgasanteil within the C0 ₂ or sulfur compounds such as H ₂ S or both containing Offgasgemisches in a second process step (step D) is transferred to a Flushgasfeinabtrennung and there:

a) by a single membrane or a membrane cascade, or

b) by physical adsorption or preferential pore condensation on suitable Zeoiithen or activated carbons, with and without their regeneration, or

c) by a wash, or

d) by any combination of membrane, adsorption and washing methods

is further separated, wherein the recovered in the Flushgasfeinabtrennung Flushgasanteil liquefied by condensation or left in gaseous form;

IQI the liquid or gaseous flue gas is used again in the stripping and recirculated (step E) by the condensed liquid flushed gas evaporated in a heated evaporation zone and introduced via a first entry path together with already gaseous Flushgasanteilen also in gaseous form in the stripping zone and the laden detergent solution is brought into intensive contact, or the remaining after passing through the evaporation zone liquid Flushgasanteile liquid in the filled with the desorbed Waschmitteliösung heating and / or Are brought to the contact zone or that the flushing gas is spent together with the washing solution in a pressurized Heäzzone and brought via a nozzle by flash evaporation for proportional evaporation or that a second entry path, the flushing gas in the liquid state directly into the filled with the desorbed detergent solution heating zone and / or spent in the stripping zone, and here in the washing medium solution is evaporated, wherein non-evaporating condensate, in particular water, are taken up by the amine-containing detergent solution.

The separation of the flushing gas from the offgas stream may also comprise its water content, e.g. for drying the off-gas or for regulating the water content of the amine-containing detergent solution can also be deducted separately.

The coalescing and foam separation zone may be omitted if

Defoamer be used.

As a flush gas find use:

- 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, e.g. on zeolites or activated carbons or

not or poorly water-soluble chemically inert organic substances suitable for adsorption and absorption in washing solutions, e.g. in nonpolar solvents or

water-soluble chemically inert organic substances suitable for adsorption and absorption in washing solutions, e.g. in 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 separation membrane material for separating the CO ₂ -flush gas mixture in a) is characterized by its tightness in the form of leakage. Membrane materials can therefore be: ceramic, dense microporous layers (zeolite membranes) or dense polymer membranes. Zeolite membranes work on the principle of adsorption, preferably via pore condensation. Polymer membranes preferably work on the principle of solution diffusion. Preference is given to inorganic zeolite membranes. In this method, the remaining Flushgasanteile that pass through the membrane and accumulate within the membrane or condense in the otherworldly Permeatraum, separated from the remaining components of the off-gas containing CO ₂ , H ₂ S and eg still methane, Arninwaschmittel and water vapor. H ₂ S is understood here to mean in general sulfur compounds which can usually be present, such as thiols, H ₂ S, COS or mercaptans.

Particularly preferred materials for porous layer inorganic membranes are densely grown zeolite-based crystallites, most preferably MF1, FAU, LTA, MOR, FER, MEL, BEA; ITR and KFi, preferably MFI and FAU, and here particularly preferably the MFI structure with Silikalithmembranen without AI share or MFi membranes with an aluminum content. Particularly preferably, the known ZSM-5 with Na _n ALNs! G ₆ -nOi9 ₂ ^"16H ₂ O (0 <n <27). Particularly preferred in MFI membranes with aluminum contents are Si / Al units of greater than 75. Further preferred zeolites are CIT-1, DAF-1, Stilbite, Beta, Boggsite, EMC-2 and STA-1.

Generally, the pore sizes are in the range of Moieküldurchmesser the hydrocarbons to be separated at 0.3 - 2 nm, preferably 0.5 - 0.8 nm.

Also, amorphous inorganic membranes are preferred. Particularly preferred herein are silica membranes and carbon membranes having pore sizes in the range of 0.5-2 nm.

The membranes should be dense and thus leak-free and thus allow only adsorptive processes on the inner surface, whereby the mass transfer thus proceeds only through the intra-crystalline pore system. Advantageous for the separation process are membranes that allow high permeate flows due to their small layer thickness. The thickness of the separating layer is therefore preferably less than 50 μm, for example 2 to 40 μm, more preferably less than 30 μm, for example 2 to 20 μm. Membranes of asymmetric construction are preferred, as explained below. The preparation of such a membrane can be advantageously carried out such that on a macroporous support, such as corundum, a mesoporous layer is produced by applying a slurry of ground commercial zeolite materials (<1 μιη, advantageously <500 nm) and subsequent temperature treatment at 500 - 700 ° C. Thereafter, to produce the microporous layer on the mesoporous layer, the latter with a synthesis solution at 140 to 200 ° C, treated hydrothermally for 12 to 72 hours and z. B. coated with silicalite.

The composition of a silicalite synthesis solution can vary depending on the synthesis method, the reagents used, the physical synthesis parameters as well as the desired membrane properties with respect to selectivity and flux. Possible synthesis compositions in the range 100 mo! Si0 ₂ : 0 - 35 mol SDA: 0 - 50 mol NaOH: 0 - 17 mol ΑΙ _Ξ 0 ₃ and 1,000 - 100,000 moi H ₂ 0, wherein SDA stands for the structure-directing agents, also called template. SDA may be, for example, tripropylammonium hydroxide or tripropylammonium bromide or a mixture of both.

Generally, macroporous refers to pores of> 1,000 nm, mesoporous pores of 2 to 50 nm and microporous pores of 0.1 to 2 nm.

For Flushgasfeinabtrennung also adsorptive method for the selective binding of gas components can be provided, such as the 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.

Also useful are washing processes for binding the gaseous liquid gas component, e.g. utilizing a selective solubility of the flushing gas in a solvent to minimize the discharge of flushing gas from the system.

The term "flush gas" is understood to mean a substance which is chemically inert for the substances involved in the process and which is at least partially gaseous at the temperature of the amine-containing detergent solution or which changes into the gaseous state when introduced into the detergent solution, and which stripping the chemically and physically fixed in the detergent solution C0 ₂ or chemically bonded sulfur compounds or both in the discharged offgas. Furthermore, the term "flush gas" is understood to mean a condensable gas which boils in the defined temperature range, a low heat of vaporization and is compatible with the product gas. The condensation of the flushing gas must be in the range of 5 to 98 ° C at a pressure in the range of 0.1 to 6 bar (a). Low heat of vaporization is understood to mean a range of 10 to 60 kJ / mol. An advantageous temperature range is 60-95 ° C, preferably 80-92 ° C. Another preferred range is 90-95 ° C. If the Waschmitteilösung is under pressure, the temperature can be up to 120 ° C. A preferred temperature range is then 90-1 10 ° C.

Suitable as a flush gas in the context of the present process are, for example, saturated linear and cyclic alkanes such as n-pentane, cyclopentane, n-hexane. Cyclohexane, n-heptane, cycloheptane, 2,2-dimethylbutane, 2-methylpentane, 3-methylpentane, mixtures thereof; Ethers such as tert-butyl ether, tert-butyl ethyl ether, isopropanol, di-n-propyl ether and mixtures thereof; primary, secondary and tertiary alcohols such as ethanol, i-propanol, n-propanol, secondary and tertiary butyl alcohol and mixtures thereof. Particular preference is given to saturated hydrocarbons or mixtures thereof, in particular pentanes or hexanes, especially n-pentane or n-hexane, and tert-butyl ether and tert-butyl ethyl ether.

Also preferred for the selection of the flushing gas is a small temperature difference between the boiling temperature of the flushing gas and the operating temperature, i. the temperature range in which the stripping of Waschmitteilösung takes place.

"Chemically inert" for the flush gas means that the flush gas does not undergo any chemical reaction with any of the components of the wash solution to interfere with the functionality of the reversible bond detergent with respect to CO ₂ and sulfur compounds.

Heat sources preferred for the invention for heating the amine-containing Waschmitteilösung in the heating zone to the operating temperature are heat transfer such as cooling liquids or gases with waste heat from combined heat and power plants (CHP), which are typically available with temperatures up to +98 ° C, or those of heat pumps from Geothermal or solar plants or waste heat or process heat of other industrial processes. These heat sources in the form of water or thermal oil can be brought to the level of desorption temperature by heat pumps. Particularly suitable amine-containing wash-solution solutions for the present process are those which are used in the scrubbing of C0 ₂ from gas mixtures such as biological sewage, ground and mine gas and which are liquid at normal temperature. Preferably, these are aqueous solutions. Such detergent solutions react chemically with C0 ₂ , but also chemically bind sulfur compounds as well as H ₂ S, thiols, mercaptans or mixtures thereof. Furthermore, C0 ₂ and gaseous sulfur compounds can also be physically dissolved to a lesser extent. With the aid of the flushing gas, both the chemically bound sulfur compounds and the C0 _{2 are} stripped off.

Other suitable detergent solutions are those obtained in the amine scrubbing in other chemical processes, or resulting from the scrubbing of natural gas or associated gas.

The degree of loading of the detergent to determine the actual desorption of WaschmitteNösung is measured by the pH, the conductivity, the density, the speed of sound, the spectroscopic properties of the detergent solution or in their combination and used as a demolition criterion of desorption.

The achievable degree of desorption is dependent on the effective stripping time and stripping intensity, the type of aqueous amine washing solution and its temperature for temperatures around 90-95 ° C at about 50% of the chemical C0 ₂ absorption capacity of a loaded amine-containing detergent solution.

It is particularly advantageous that the stripping can be carried out at low temperatures just above the Gieichgewichtspunkt "absorption of C0 ₂ to desorption of C0 ₂ ", since the stripping shifts the equilibrium in the desorption reaction in favor of the released gas C0 ₂ . Thus, the lowest possible desorption temperature can be used.

Another important advantage of the invention is that the flushing gas used for stripping can be recovered almost completely with relatively little technical and energy expenditure and reused in the circuit. At a temperature- and load-dependent desorption time of 30 to 80 minutes, the detergent solution undergoes a C0 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, refractive index, conductivity and as a criterion for achieving the required average residence time of the detergent solution in the stripping. In addition, the direct spectrometric or titrimethsche determination of the detergent loading level is possible. Another method is the direct determination of the discharged C0 ₂ amount in the offgas stream using the CO ₂ concentration and the off-gas volume flow.

In some cases, such as meeting highest emission requirements, e.g. With regard to the permissible amount of organic carbon released, it is possible to connect an afterburner plant, which at the same time can also oxidise other hydrocarbons that are transported along with it.

The device for carrying out the method according to the invention comprises the following functional elements which are in the interaction of action:

a) a desorption column with a Hetzzone, a stripping zone and a coalescing and Schaumabtrennzone in cascade arrangement;

b) a sensor for measuring the CO ₂ - or Flushgas concentration of discharged from the coalescing and Schaumabtrennzone gas mixture and

Adjustment of the flush gas volume flow;

c) a subsequent primary deposition zone consisting of a gas liquefier or a region in which flash evaporation can take place;

d) a second downstream Flushgasabtrenneinrichtung as secondary

Separation zone for separating the non-condensed parts of the gas stream, consisting on the one hand of CO ₂ , H ₂ S, methane, amine detergent, water vapor and on the other hand, the gaseous in vapor pressure remaining fractions of the flushing gas; and means for recirculating the flushing gas into the circuit.

The device is supplemented by:

e) a conveying device for the flushing gas from the separation zones, f) an evaporation zone as an evaporator for direct or flash evaporation for the liquid flushing gas, including external heat supply by cogeneration waste heat, heat from heat pumps and / or solar systems, wherein in the case of expansion evaporation evaporation zone and stripping zone coincide spatially,

g) a flush gas line from the evaporation zone to the stripping zone, h) a connecting line from the evaporator zone to the heating zone, i) a circulation line with feed pump between heating zone (sump) and stripping zone for a multiple circulation of the amine-containing detergent solution,

j) a heat supply for the heating zone, wherein the operating temperature is set below the pressure-dependent boiling temperature of the detergent solution, k) an injector for connecting the condensate line (connecting line aqueous phase) to the heating zone.

The sensor mentioned under b) can measure the ratio of CO ₂ to flush gas, both as direct CO ₂ measurement or Flushgaskonzentrationsmessung or both, by determining mixture characteristics such as speed of sound, density, heat of condensation of the offgas stream. He can also evaluate the ratio of effective Flushgasvolumenstrom to change the loading of the detergent in the course of desorption.

The liquid-gas separation in the coalescing and Schaumabscheidezone preferably takes place by mechanically acting separation elements such as perforated bends, screens, Koaleszenzabscheider, filter elements, foam domes u. ä .. It is also possible to use spray elements for spraying WaschmitteHÖsung or water or energy-carrying facilities, such as ultrasonic actuators, evaporation lines, infrared radiant heat sources or electromagnetic heating in the RF or microwave range, which act effectively on foams or foam surfaces and allow such a liquid-gas separation. The addition of surface-active chemical foam inhibitor is possible to prevent unwanted transport of liquid in the laxative gas path of the offgas Flushgasgemischs.

Said Flushgasabtrennung within the Flushgasabtrenneinrichtung is a fine separation by means of a membrane separation unit, which within the Flushgasabtrenneinrichtung is designed as a single membrane, membrane bundle or membrane cascade. The membrane is characterized by impermeability (leak-free) and preferably consists of ceramic, dense microporous layers (zeolite membranes) or dense polymer membranes, which operate on the principle of adsorption diffusion or, preferably, pore condensation. Preference is given to zeolite membranes.

The remaining, non-condensed Flushgasanteil within the C0 ₂ - and / or H ₂ S-containing offgas mixture is safely separated by the membrane (s), the Flushgasabtrenneinrichtung next to the arrangement of single membrane or membrane cascade subsequent arrangements or combinations thereof are possible or the alternatively can be used:

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 substantially reduced by the low process temperatures and that heat sources with relatively low heat level can be used effectively and thus energy optimization is achieved. Due to the lower process temperatures, the aniagentechnischen requirements can be lowered and thus their durability and availability can be increased. 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 once again on an exemplary embodiment on the basis of a functional scheme of a system for the desorption of aadequate washing solution, in which CO ₂ and / or H ₂ S are bound.

The plant is part of a biogas upgrading plant that removes CO ₂ and / or sulfur compounds by amine scrubbing. In order to keep the detergent solution containing diglycolamine (DGA®) usable, it is necessary to reduce the CO ₂ or H ₂ S loading of the detergent solution in order to obtain a be able to use sufficiently high loading difference in the recirculation of the detergent solution.

The loaded Rich detergent solution having an amine concentration of about 50%, a temperature of 60 ° C and a loading of 0.35 mol C0 ₂ per mole of amine is fed through the Rich-detergent line 1 to the stripping zone 3. 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 in the running as a heating zone 4 section. The volume of the heating zone 4 and the stripping zone 3 including a connecting line 6 between the heating zone 4 and the stripping zone 3 is dimensioned so that the average residence time of the detergent solution is 30 minutes. Through the inlet 5, the heat transfer medium of the heating zone 4 is supplied from a technical low-temperature source of 94 ° C, so that the detergent solu ung in the heating zone 4 is maintained at a temperature in the range of 86 - 92 ° C.

The flushing gas n-hexane with a boiling point at atmospheric pressure of 69 ° C is passed through the stripping zone 3 and possibly from the heating zone 4 in the stripping zone 3 in countercurrent to the detergent solution and causes the stripping effect in gaseous form and thus the desorption of the detergent solution. Part of the dissolved in the detergent solution CO2 and / or H ₂ S is stripped by the Flushgasstrom in an advantageous and surprising manner already at temperatures below about 105 ° C, the previous minimum temperature for effective DGA® desorption desorbed, ie the Detergent solution does not need to be boiled. The Flushgastrom 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 minutes, the stripping effect is maximally enhanced and effective depletion of the fixed CO2 and the sulfur compounds in the amine-containing detergent solution is effected. The depleted detergent solution is withdrawn from the device via the Lean Detergent 2 line for reuse.

In a further embodiment of the invention, the evaporation in

Form of a flash evaporation take place.

Advantageously, the liquid flushing gas can be heated with the detergent to achieve a superheated liquid state under pressure and by Relaxing of the detergent flushing gas mixture by a nozzle arrangement in the stripping zone evaporation of the flushing gas can be brought about. The mixture of both mixture components can also be done directly in front of the nozzle. The method is particularly advantageous when the difference between the boiling temperature of the flushing gas and the temperature of the available heat source is small, ie less than 10K.

At the upper outlet of the stripping zone 3 is a gas mixture of the flushing gas, C0 ₂ , H ₂ S and water vapor. This Flushgasgemisch is performed for liquid-gas separation through the coalescing and Schaumabscheidezone 8, where liquid keitströpfchen be retained and foaming is prevented. The retained liquid is discharged into the stripping and heating zone 3, 4.

A CO2 sensor 9 measures the C0 ₂ concentration of the gaseous fuel gas offgas mixture discharged from the coalescing and foam separation zone 8. Since the desorption of the detergent solution via the heating zone 4 and stripping zone 3 is kinetikümiert, it is expedient to limit the volume flow of flushing gas used to a point at which a maximum CO ₂ discharge coincides with a minimum Flushgasvolumenstrom, since the enthalpy of enthalpy of Flushgas- phase transition in addition to the chemical desorption enthaiphie the detergent solution and to heat both substances / substance mixtures is applied. For this purpose, the signal of the CO ₂ sensor 9 is used to regulate an optimum value in the ratio of CO ₂ desorption to generated Flushgasvolumenstrom. This is done in an operative manner via the heat input into the evaporation zone 17 or by regulation of 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 sulfur compounds to the circulating Flushgasstrom is 1: 1 to 1:20.

The Kinetiklimitierung results from the first reaction at about + 82 to 85 ° C reverse reaction of the carbamate to DGA® under CO ₂ release at a reduced reaction rate. Therefore, the possible release of C0 ₂ is limited by the stripping with the flushing gas. For others, z. B. non-carbamate-forming amine detergent this applies in a comparable manner.

To maintain an intensive countercurrent contact of the detergent solution with the flushing gas stream, ensuring a consistent Process temperature and to achieve optimum desorption, the detergent solution is circulated from a feed pump 7 from the heating zone 4 via connecting line 6 to the top of the stripping zone 3.

From the outlet of the coalescing and Schaumabscheidezone 8 enriched with C0 ₂ and H ₂ S gas stream is passed via connecting line 10 in a gas liquefier 11, 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 else a separate coolant stream, for example that of a cold water salt. An alternative known to a person skilled in the art is liquefaction by a pressure increase or a combination of cooling and pressure change.

In another embodiment of the invention, the gas liquefier 11 alone constitutes a liquified gas separation zone when the stripping zone 3 serves as a flash evaporation zone.

The condensate, which also contains non-flushing gas fractions, e.g. Contains water is withdrawn liquid from the gas liquefier 11 and fed via the connecting line 13 of the evaporation zone 17. Here, under the supply of heat of vaporization of the phases, the transition from liquid to gaseous flushing gas takes place. Then the recirculated flushing gas is returned via the flushing gas line 18 directly into the stripping zone 3 into the process via the first entry path.

Via the second entry path, the unevaporated liquid portions of the flushmium, including the co-condensed Wasseranteiie be derived from the evaporation zone 17 via the connecting line 19 and the injector 20 in the heating zone 4. In the detergent solution then evaporates the remaining Flushgasanteil. Thus, the main circuit of the Flushgasstroms is closed.

Regardless, the liquid present Flushmedium can be introduced with the co-condensed water without upstream evaporation phase directly via the connecting line 19 and injector 20 in the heating zone 4. Here, the flushing gas is evaporated in the detergent solution heated above the flushing gas boiling point. The uncondensed in the gas liquefier 1 1 part of the gas stream consists of C0 ₂ , sulfur compounds, traces of methane, traces of amine, water vapor, dissolved permanent gases and the gaseous vapor pressure in the remaining parts of the flushmium. Since a loss of flushing gas with the desorbed CO2 and / or sulfur compound gas stream should be avoided as far as possible for economic and emission-related reasons, the gas liquefier 11 is connected via a connecting line 12 to a second process stage in the form of a fine-gas recirculation 15. within the Flushgasfeinabtrennung 15, the separation is gaseous

Components of the flushing gas from the offgas stream, by means of a selective element 14, here a ceramic separation membrane with leak-free, which allows a direct recovery of the flushing gas, so that the CO ₂ and H ₂ S-containing offgas contains only very small proportions of the flushing gas and so further utilization at 23 can be derived. The membrane unit used is an MFI membrane bundle consisting of individual MFI-coated corundum monoco channels with an asymmetrical structure. These are characterized by an (I) MFI separation layer hydrothermally obtained on the inside of the monochannels, 30 pm thick, pore diameter 0.5-0.7 nm, according to the synthesis composition of 100 mol SiO ₂ : 0, 169 mol Al ₂ O ₃ : 3.3 moles of TPABr: 3.3 moles of TPAOH: 3.3 moles of Na ₂ O: 2000 moles of H ₂ O, and templated outgassing (II) under an ozone atmosphere, an MF MFI mesoporous layer below, 30 μm thick (III ), including a corundum MF layer with 200 nm pores and 40 pm thick on the underlying (IV) corundum support.

If required, the forces acting on the membrane driving forces through

Compressor or vacuum pumps are reinforced (not shown here).

The separated and retained from the offgas-Flushgasgemisch gaseous fraction of the flushing gas is recycled via the connecting line 16 in the evaporation zone 17 and as in the section above, returned to the process cycle. LIST OF REFERENCE NUMBERS

1 line of rich detergent

2 line Lea n-washing medium

3 stripping zone

4 heating zone

5 heat transfer inlet (heating zone)

6 connection line

7 feed pump

8 coalescing and foam separation zone

9 sensor

10 connection line

11 gas liquefier

12 connection line

13 Connecting pipe for condensate

14 selective element Flushgasfeinabtrennung

15 Flush gas fine separation

16 connection line

17 evaporation zone

18 flush gas line (gas phase)

19 connecting line (aqueous phase)

20 injector

21 Cooling medium supply

22 heat of vaporization

23 Offgas discharge

Claims

claims

Anspruch [en] A process for desorbing charged amine detergent solutions from gas scrubbing processes of gases in which CO ₂ and / or H ₂ S are chemically bound by means of a flush gas, characterized in that

a) the loaded aqueous aminhaltige Waschmitteilösung using a heat source, heated to a temperature below the pressure-dependent boiling point of the detergent solution in the range of 20 ° C to 96 ^D C and held during the process of desorption;

b) a chemically inert substance for the substances involved as Ffushgas in the heated detergent solution in a stripping zone for a median refueling time of 3 minutes to 180 minutes in countercurrent contacted with the flushing gas and the amine-containing detergent solution stripped and dissolved C0 ₂ or dissolved sulfur compounds or both are expelled;

c) entrained liquid Waschmitteilösungsteile in the form of particles and

Foams in a subsequent coalescence and foam separation zone are separated from the gas stream obtained at b) and returned to the stripping zone or heating zone;

d) the flue gas from the mixture with the desorbed C0 ₂ or sulfur compound fraction or both obtained in c) is passed through an at least two-stage separation and recovered by separation in a first primary stage by cooling or pressure increase or both measures Condensation of the flushing gas and excess water and other Flüssigkeitsanteiie takes place, and that after this liquid mixture is separated;

e) the remaining within the C0 ₂ or H ₂ S or both offgas mixture remaining, in step d) uncondensed Flushgasanteil in a second secondary stage of a Flushgasfeinabtrenneinheit with selective elements is supplied, wherein the selective elements

represent a single membrane or a membrane cascade or

a unit for physical adsorption on solid surfaces or a washing unit or

a combination of membrane, adsorption unit and washing unit and with these elements the non-condensed Flushgasanteil is separated, and the C0 ₂ or H ₂ S or both containing offgas is derived separately; f) the recovered condensed flush gas in a heated

Evaporated evaporation zone and transported in gaseous form in the stripping zone and brought here in contact with the circulated, laden amine detergent solution in contact;

g) the liquid gas remaining in the liquid state, including the remaining unevaporated liquid components, is transferred directly into the heating zone charged with the detergent solution to be desorbed and evaporated in the detergent solution.

2. The method of claim 1, wherein the heat source is a technical low temperature source selected from CHP cooling water, CHP exhaust gas, solar heat, geothermal, industrial waste heat, process heat technical and mixtures thereof.

3. The method of claim 1 or 2, wherein the detergent solution is guided within the stripping zone on bubble columns, packed columns, packing columns, membrane contactors, static mixers or countercurrent spray columns and vortexed intensively with the flushing gas.

4. The method according to any one of claims 1 to 3, wherein the volume flow of the flushing gas is controlled by the CO ₂ concentration in the flush gas offgas mixture.

5. The method according to any one of claims 1 to 4, wherein the temperature of the Waschmitteliösung is in the range of 60 to 92 ° C.

6. The method of claim 5, wherein the temperature is in the range of 90 to

120 ° C, when the detergent solution is under pressure.

7. The method according to any one of claims 1 to 6, wherein are used as a flushing gas chemically inert organic substances suitable for separation by zeolite-based ceramic membranes by adsorption diffusion or pore condensation or by polymer membranes; or

chemically inert organic substances with a boiling point of 0 ° C below the boiling point of the washing solution or

organic saturated C ₂ to C ₇ hydrocarbons or mixtures thereof.

8. The method according to any one of claims 1 to 7, wherein the total recovered flushing gas in the liquid state is introduced directly into the heating zone or in the stripping zone or both or evaporated in the heated detergent solution.

9. The method according to any one of claims 1 to 8, wherein as a flushing gas, a substance selected from the group consisting of n-hexane or n-heptane, cyclopentane, cyclohexane, 2,2-dimethylbutane, 2-methylpentane, 2-methylpentane and Mixtures thereof.

10. The method according to any one of claims 1 to 8, wherein the separation of the flushing gas in the first primary stage takes place in a gas liquefier.

11. The method according to any one of claims 1 to 10, wherein the remaining in the off-gas gaseous portion of the flushing gas is oxidized together with those from the aqueous amine detergent solution with stripped gaseous hydrocarbons in an aftertreatment unit.

12. The method according to any one of claims 1 to 11, wherein the membrane is an inorganic membrane having a microporous layer with zeolithic structure selected from ZSM-5, MFI, FAU, silicalite, CIT-1, DAF-1, stilbite, beta, Boggsite, E C-2 and STA-1.

13. Apparatus for carrying out the method according to claim 1 to 12, characterized by

a) a desorption column with a heating zone (4), a stripping zone (3) and a coalescing and Schaumabtrennzone (8) in cascade arrangement;

b) a sensor (9) for measuring the C0 ₂ concentration of a Coalescence and Schaumabtrennzone (8) discharged gas mixture;

c) a primary separation zone with a gas liquefier (11);

d) a secondary separation zone with a Flushgasabtrenneinheit (15) for separating the non-condensed in the gas liquefier (11) parts of the flushing gas from the gas stream, which consists of C0 ₂ , sulfur compounds, gaseous amine detergent, methane, water vapor and gaseous fractions of the flushmium ;

e) a compressor for increasing the pressure between the primary and secondary deposition zone according to c) and d); and means for recirculating the flushing gas into the circuit.

14. The apparatus of claim 13, wherein the means for recycling the flushing gas comprise

f) a pump for the flushing gas from the separation zones according to c) and d),

g) an evaporator (17) for the condensed and in the liquid

State of matter accumulating flushing gas,

h) a Kreisiaufleitung (6) with feed pump (7) between the heating zone (4) and stripping zone (3) for the circulation of the detergent solution,

i) a feed (5) for the thermal energy into the heating zone (4),

j) a flush gas line (8) from the evaporator zone (17) to the stripping zone

(3)

k) a connecting line (19) from the evaporator zone (17) to the heating zone (4) and

I) an injector (20) for connecting the connecting line (19) to the heating zone (4).

15. Device according to claim 13 or 14, wherein in the coalescence and foam separation zone (8) separation elements, such as perforated plates, sieves, Koaieszenz- separator, filter elements, foam domes or spray elements for spraying detergent solution or water or energy-carrying devices, such as ultrasonic actuators, evaporation sections, Infrared radiant heat sources or Electromagnetic means are arranged for heating in the RF or microwave range.

16. Device according to one of claims 13 to 15, wherein a selective element (14) in the Flushgasfeinabtrenneinheit (15) is formed as inorganic membranes with dense microporous layers or a dense polymer membrane, wherein the inorganic membranes according to the principle of adsorption or pore condensation work.

17. Device according to one of claims 13 to 16, wherein the stripping zone (3) at the same time constitutes a region for a flash evaporation.

18. Device according to one of claims 13 to 17, wherein the

Gas liquefier (1) alone represents a deposition zone for liquefied gas, when the stripping zone (3) serves as a region for a flash evaporation.