DE10334002A1 - Deacidifying fluid stream containing acid gas impurities, e.g. from fuel combustion, involves performing at least one absorption stage in inert scrubber column with plastic or rubber interior surface - Google Patents

Abstract

Deacidifying a fluid stream containing acid gas impurities by contacting the fluid stream with an absorbent at 0.5-20 bar in at least one absorption stage involves performing at least one absorption stage in an inert scrubber column with a plastic or rubber interior surface. An independent claim is also included for an apparatus for carrying out the process, comprising one or more series-connected scrubber columns filled with wash solution, at least one of the columns being an inert scrubber column with a plastic or rubber interior surface.

Description

The The present invention relates to a method for deacidifying a Fluid stream containing acid gases as impurities and a Device for this.

In numerous processes in the chemical industry, fluid flows occur which contain acid gases such as CO ₂ , H ₂ S, SO ₂ , CS ₂ , HCN, COS or mercaptans as impurities. These fluid streams may be, for example, gas streams (such as natural gas, refinery gas, reaction gases resulting from the oxidation of organic organic materials, such as organic wastes, coal or petroleum, or waste materials resulting from the composting of organic substances.

The Removal of the acid gases is due to different reasons special meaning. For example, the content of sulfur compounds of natural gas by appropriate treatment measures directly at the Natural gas source can be reduced, because even the sulfur compounds form in that of natural gas frequently entrained Water acids, which have a corrosive effect. For Therefore, the transport of natural gas in a pipeline must have predetermined limits the sulphurous impurities are maintained. The at the oxidation of organic materials, such as organic waste, coal or petroleum, or in the composting of organic substances containing waste materials must arise reaction gases be removed to prevent the emission of gases that damage nature or can influence the climate to prevent.

The washing solutions used in gas scrubbing processes also have extensive patent literature. Basically, one can distinguish two different types of absorption or solvents for gas scrubbing:
On the one hand, so-called physical solvents are used in which, after absorption, the dissolved acid gases are present in molecular form. Typical physical solvents are cyclotetramethylenesulfone (sulfolane) and its derivatives, aliphatic acid amides (acetylmorpholine, N-formyl morpholine), NMP (N-methylpyrrolidone), propylene carbonate, N-alkylated pyrrolidones and the corresponding piperidones, methanol, and mixtures of dialkylethers of polyethylene glycols (Selexol ^®, Union Carbide, Danbury, Conn., USA).

To the others become chemical solvents whose mode of action is based on chemical reactions, in which, after absorption, the dissolved acid gases in the form of chemical Compounds are present. For example, in the industrial scale most often chemical solvents used aqueous solutions inorganic bases (e.g., potash solution in the Benfield process) or organic bases (e.g., alkanolamines) are formed upon dissolving sour gas ions. The solvent Can relax by relaxing at a lower pressure or stripping be regenerated, the ionic species react back to sour gases and / or stripped by steam. After the regeneration process can the solvent be reused. Preferred, when removing sour gas contaminants from hydrocarbon gas streams Alkanolamines used include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diethylethanolamine (DEEA), diisopropylamine (DIPA), aminoethoxyethanol (AEE) and methyldiethanolamine (MDEA).

to Absorption of the sour gases, the fluid streams in an absorption step with the washing solution brought into contact. It's from "Gas Purification," Arthur Kohl, Richard Nielsen, Gulf Publishing Company, Houston, Texas, 1997, 5th edition, Chapter 3, Subchapter Amine Plant Corrosion, 187-230 known, this absorption step to be carried out in steel wash columns. Likewise is described (loc.cit.) that the steel, if not expensive high alloyed steels are used, due to the proportion of acid gases, by Corrosion is attacked. This will increase the life of the equipment considerably limited.

It Therefore, the object was to provide a device for the absorption of Suction gases from fluid streams comprising a washing column, wherein the washing column across from the fluid streams is largely inert.

Accordingly, became a process for deacidification a Fluidfroms found containing acid gases as impurities, wherein in at least one absorption step at a pressure of 0.5 up to 20 bar the fluid flow with an absorbent in intimate Contact brings, with the proviso that the absorption step and in the case of several absorption steps at least one of the absorption steps in an inert wash column, the inner surface consists essentially of plastic or rubber, performs.

Of the Fluid stream, usually an acidic gas constituents rich source gas (Crude gas), is in an absorption step in an inert wash column brought into contact with an absorbent, reducing the acidic Gas components are at least partially washed out.

• a) der Oxidation organischer Substanzen,
• b) der Kompostierung und Lagerung organischer Substanzen enthaltender Abfallstoffe, oder
• c) der bakteriellen Zersetzung organische Substanzen.

The starting gas is generally natural gas or a gas stream formed in the following manner:

• a) the oxidation of organic substances,
• b) the composting and storage of waste substances containing organic substances, or
• c) the bacterial decomposition organic substances.

When organic substances which are subjected to oxidation is it usually to fossil fuels such as coal, natural gas or oil or organic Substances containing substances.

When organic substances containing waste, oxidation, be subjected to composting or storage, especially household waste, plastic waste or Used packaging waste.

The Oxidation of organic substances usually takes place in the usual way Incinerators with air.

The Composting and storage of organic substances containing waste materials generally takes place in landfills.

When Organic substances in bacterial decomposition usually become Manure, straw, manure, sewage sludge, Fermentation residues used.

The bacterial decomposition occurs e.g. in usual biogas plants.

In general, these gas streams contain less than 50 mg / m ^{3 of} sulfur dioxide under normal conditions.

The Starting gases can either have the pressure which is approximately the pressure of the ambient air corresponds, e.g. Normal pressure or a pressure of normal pressure deviates by up to 0.2 bar. Furthermore, the starting gases can have a higher Pressure than 0.2 bar than normal pressure, a pressure up to 20 bar. Starting gases with a higher Pressure as are gilldet by the output gases with the pressure, the nearby the pressure of the ambient air is compressed by compression or the starting gas at higher Pressure generates e.g. by oxidation of organic substances with Compressed air arise. The resulting volume flow of the gas is reduced thereby and additionally increases the partial pressure of to be separated sour gas, what for the absorption and the resulting regeneration need advantageous is. The disadvantages are on the one hand the compression effort (investment and operating costs) and the possibly additionally incurred higher investment costs due to the use of printing apparatus, so it's here Cost optimum exists.

When Absorbents are practically all conventional absorbents.

• – Lösungen bestehend hauptsächlich aus aliphatischen oder cycloaliphatischen Aminen mit 4 bis 12 Kohlenstoffatomen, Alkanolaminen mit 4 bis 12 Kohlenstoffatomen, cyclischen Amine bei denen 1 oder 2 Stickstoffatome zusammen mit 1 oder 2 Alkandiylgruppen 5-, 6- oder 7-gliedrige Ringe bilden, Mischungen der vorstehenden Lösungen, wässrige Lösungen der vorstehenden Mischungen und Lösungen,
• – wässrige Lösungen enthaltend Salze von Aminosäuren
• – wässrige Pottaschelösungen, die ggf. Piperazin oder Methylethanolamin enthalten
• – wässrige NaOH-Lauge oder Kalkmilch.

Preferred absorbents are, for example, chemical solvents selected from the group consisting of

• Solutions consisting mainly of aliphatic or cycloaliphatic amines having 4 to 12 carbon atoms, alkanolamines having 4 to 12 carbon atoms, cyclic amines in which 1 or 2 nitrogen atoms together with 1 or 2 alkanediyl groups form 5-, 6- or 7-membered rings, mixtures of above solutions, aqueous solutions of the above mixtures and solutions,
• - aqueous solutions containing salts of amino acids
• - Aqueous potash solutions containing possibly piperazine or methylethanolamine
• - aqueous NaOH lye or milk of lime.

Especially solutions are preferred as the chemical solvent consisting mainly monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), Diethylethanolamine (DEEA), diisopropylamine (DIPA), aminoethoxyethanol (AEE) and methyldiethanolamine (MDEA) mixtures of the above solutions and aqueous solutions of above mixtures and solutions, used.

Especially proven in the US patent US 4,336,233 described absorbent. This is an aqueous solution of methyldiethanolamine (MDEA) and piperazine as an absorption accelerator or activator (aMDEA ^®, BASF AG, Ludwigshafen). The scrubbing liquid described therein contains 1.5 to 4.5 mol / l methyldiethanolamine (MDEA) and 0.05 to 0.8 mol / l, preferably up to 0.4 mol / l piperazine.

Regarding further preferred chemical solvent Reference is made to DE-A-10306254, DE-A-10210729, DE-A-10139453, and EP-A-1,303,345th

When Absorbents continue to have physical solvents selected from the group consisting of cyclotetramethylenesulfone (sulfolane) and its derivatives, aliphatic acid amides (acetylmorpholine, N-formylmorpholine), NMP (N-methylpyrrolidone), propylene carbonate, N-alkylated pyrrolidones and corresponding piperidones, methanol and mixtures of dialkyl ethers of polyethylene glycols proven.

The inert washing columns used in the process of the invention consist essentially of plastics selected from the group consisting of polyvinyl chloride, polyethylene, poly propylene, polyvinylidene fluoride, ethylene-chlorotrifluoroethylene copolymer (Halar ^® from. Allied Chemical Comp.), polyfluoroethylenepropylene, perfluoroalkoxy polymers, copolymers of tetrafluoroethylene and perfluoro-ethers, polytetrafluoroethylene. Preferably, these plastics are glass fiber reinforced. Furthermore, wash columns are made of steel whose interior is coated with plastic or rubber.

suitable inert wash columns are, for example, random packings, packing columns and tray columns. Preferred absorbers are exclusively inert wash columns However, it is also possible to use these in combination with other known absorbers such as membrane contactors, radial flow scrubber, jet scrubber, Venturi scrubber and rotary scrubber or To use washing columns made of steel. The treatment of the fluid flow with the absorbent is preferably carried out in an inert Washing column in countercurrent. The fluid is generally in the lower area and the absorbent in the upper area fed to the column.

The Temperature of the absorbent is in the absorption step in Generally about 40 to 100 ° C, when using a column, for example 40 to 70 ° C at the top the column and 50 to 100 ° C. at the bottom of the column. The total pressure is in the absorption step in Generally about 0.5 to 20 bar, preferably about 0.7 to 12 bar, more preferably 0.7 to 6. Quite particularly preferred is lies the pressure at normal pressure or a pressure that is normal pressure deviates by up to 0.2 bar. It becomes an acidic Gasbestanteilen poor, i. a depleted in these components product gas (Beigas) and a loaded with acidic gas components absorbent receive.

in the Generally, absorption columns made of plastic become constructive Conditionally used only up to a pressure of 5 bar. The use Although absorption columns made of plastic is generally possible even at higher pressures, however are in such cases because of the generally lower strength compared to steel the plastic comparatively high wall thicknesses required. By pressing More than 5 bar are therefore absorption columns made of steel whose Interior coated with plastic or rubber is preferred.

The inventive method may be one or more, in particular two, consecutive Include absorption steps. The absorption can be in several consecutive Sub-steps performed be, wherein the raw gas containing the acidic gas components in each of the substeps, each with a partial flow of the absorbent is brought into contact. The absorbent with which the raw gas can already be partially contacted with acidic gases be laden, i. it may be, for example, an absorbent, from a subsequent absorption step in the first absorption step was returned, or act to partially regenerated absorbent. Regarding the execution the two-stage absorption is referred to the pamphlets EP-A 0 159 495, EP-A 0 20 190 434, EP-A 0 359 991 and WO 00100271.

According to one preferred embodiment the inventive method so performed that the fluid containing the acidic gases first in a first absorption step with the absorbent at a temperature of 40 to 100 ° C, preferably 50 to 90 ° C and in particular 60 to 90 ° C is treated. The depleted in acidic gases fluid is then in a second absorption step with the absorbent a temperature of 30 to 90 ° C, preferably 40 to 80 ° C and in particular 50 to 80 ° C, treated. The temperature is 5 to 20 ° C lower than in the first absorption stage.

Out the absorbent laden with the acid gas components can the acid gas components in usual Manner (analogous to the publications cited below) in one Regeneration step to be released, with a regenerated Absorbent is obtained. In the regeneration step, the Reduced loading of the absorbent and the resulting regenerated Absorbent is preferably subsequently in the absorption step recycled.

In general, the regeneration step involves at least depressurizing the loaded absorbent from a high pressure prevailing in the absorption step to a lower pressure. The pressure release can be done for example by means of a throttle valve and / or an expansion turbine. The regeneration with a relaxation stage is described for example in the publications US 4,537,753 and US 4,553,984 ,

The release of the acidic gas constituents in the regeneration step can be carried out, for example, in a flash column, for example a vertically or horizontally installed flash tank or a countercurrent column with internals. Several expansion columns can be connected in series, in which it is regenerated under different pressures. For example, in a pre-relaxation column at high pressure, which is typically about 1.5 bar above the partial pressure of the acid gas components in the absorption step, and in a main expansion column at low pressure, for example 1 to 2 bar absolute, regenerated. The regeneration with two or more flash stages is described in the references US 4,537,753 . US 4,553,984 , EP-A 0 159 495, EP-A 0 202 600, EP-A 0 190 434 and EP-A 0 121 109.

The last expansion stage can also be carried out under vacuum, which is produced, for example, by means of a steam radiator, optionally in combination with a mechanical vacuum generator, as described in EP-A 0 159 495, EP-A 0 202 600, EP-A 0 190 434 and EP-A 0 121 109 ( US 4,551,158 ).

Because of the optimum balance of the content of the amine components points the absorbent according to the invention a high loadability with acidic gases, which also easily desorbed again can be. Thereby can in the inventive method the energy consumption and the solvent circulation be significantly reduced.

The inventive method is described below with reference to 1 and 2 explained.

In 1 schematically a device is shown, in which the absorption stage is carried out in one stage and the relaxation stage in two stages. The starting gas (also referred to as feed gas) is supplied via line 1 in the lower area of the absorber 2 fed. At the absorber 2 it is a column packed with packing to effect mass and heat exchange. The absorbent, which is a regenerated absorbent having a low residual content of acidic gases, is passed over the line 3 on the head of the absorber 2 abandoned in countercurrent to the feed gas. The depleted in acid gases gas leaves the absorber 2 over head (pipe 4 ). The absorbent enriched with acidic gases leaves the absorber 2 on the ground via pipe 5 and enters the top of the high pressure flash column 6 which is generally operated at a pressure which is above the CO ₂ partial pressure of the raw gas supplied to the absorber. The expansion of the absorbent is generally carried out by means of conventional devices, for example a stationary control valve, a hydraulic turbine or a reverse pump. Relaxation releases most of the dissolved non-acidic gases and a small portion of the acidic gases. These gases are via line 7 from the high-pressure expansion column 6 discharged over head.

The absorbent, which is still loaded with most of the acidic gases, leaves the high pressure flash column via line 8th and is in the heat exchanger 9 heated, wherein a small portion of the acidic gases can be released. The heated absorbent is placed in the upper part of a low-pressure expansion column 10 equipped with a packed body in order to achieve a large surface area and thus to effect the release of the CO ₂ and the adjustment of the equilibrium. In the low-pressure expansion column 10 Most of the CO ₂ and H ₂ S are released almost completely by flashing. The absorbent is thus regenerated and cooled simultaneously. At the top of the low pressure relaxation column 10 is a reflux cooler 11 with a collection container 12 provided to cool the liberated acid gases and to condense a portion of the vapor. The bulk of the sour gas leaves the reflux condenser 11 via wire 13 , The condensate is pumped 14 on the head of the low pressure relaxation column 10 pumped back. The regenerated absorbent, which still contains a small part of the CO2, leaves the low-pressure expansion column 10 on the ground via pipe 15 and is done by pump 16 via wire 3 on the head of the absorber 2 given up. Via wire 17 Fresh water can be fed in to balance the water discharged with the gases.

2 schematically shows an apparatus for carrying out the method according to the invention using a two-stage absorber and a two-stage relaxation. The absorber comprises the raw sorbent 1 and the pure absorber 2 , The feed gas is 20 via line 3 in the lower area of the Rohabsorber 1 fed and treated in countercurrent with regenerated absorbent, via line 4 on the head of the Rohabsorber 1 is abandoned and still contains some acidic gases. On the head of the pure absorber 2 will be over line 5 abandoned regenerated absorbent, which contains substantially no acid gases. Both parts of the absorber contain a packing to effect the mass and heat exchange between the raw gas and the absorbent. The treated gas leaves the pure absorber 2 over head (pipe 6 ). The absorbent laden with acid gases is at the bottom of the Rohabsorbers 1 discharged and over line 7 in the upper part of the high-pressure expansion column 8th fed. The column 8th is equipped with a packing and is operated at a pressure between the pressure in the absorber and the subsequent low-pressure expansion column 11 lies. The relaxation of the laden with acidic gases absorbent is carried out using conventional devices, such as a stationary control valve, a rule hydraulic turbine or a reverse pump running. During high-pressure release, most of the dissolved non-acidic gases and a small portion of the acidic gases are released. These gases are via line 9 from the High-pressure expansion column 8th discharged over head.

The absorbent, which is still loaded with most of the acid gases, leaves the high pressure flash column 8th via wire 10 and enters the top of the low pressure flash column 11 fed, where most of the CO2 and H2S are released by flashing. The absorbent is regenerated in this way. The low-pressure expansion column 11 is equipped with a packing to provide a large surface area for heat and mass transfer. At the top of the low pressure relaxation column 11 is a reflux cooler 12 with 20 condensate tanks 13 provided to the over head from the low-pressure expansion column 11 To cool escaping acid gases and to condense a portion of the vapor. The uncondensed gas, which contains the major amount of acidic gases, is sent via pipe 14 discharged. The condensate from the condensate tank 13 is over pump 15 on the head of the low pressure relaxation column 11 given up.

The partially regenerated absorbent, which still contains some of the acidic gases, leaves the low-pressure expansion column 11 on the ground via pipe 16 and is split into two sub-streams. The larger partial flow is via pump 17 and direction 4 on the head of the Rohabsorber 1 abandoned, whereas the smaller part over lead 18 by pump 19 in the heat exchanger 20 is heated. The heated absorbent is then placed in the top of the stripper 21 fed, which is equipped with a pack. In the stripper 21 Most of the absorbed CO ₂ and H ₂ S is stripped out by means of steam, which in the reboiler 22 generated and in the bottom of the stripper 21 is fed. That's the stripper 21 on the ground via pipe 23 leaving absorbent has a low residual content of acidic gases. It gets over the heat exchanger 20 passed, which from the low-pressure expansion column 11 upcoming, partially regenerated absorbent is heated. The cooled, regenerated absorbent is pumped 24 via heat exchangers 25 back to the head of the leg absorber 2 pumped. Via wire 26 can be on the head of the leg absorber 2 Fresh water to be replaced to replace the discharged through the gas streams water. That from the stripper 21 Gas escaping overhead is sent via line 27 in the lower part of the low-pressure expansion column 11 fed.

Claims (18)

A process for deacidifying a fluid stream, the Contains acid gases as impurities, wherein in at least an absorption step at a pressure of 0.5 to 20 bar the Fluid flow into intimate contact with an absorbent, with the proviso that is the absorption step and in the case of several absorption steps at least one of the absorption steps in an inert wash column, their inner surface consists essentially of plastic or rubber, performs. The method of claim 1, which is a Fluid flow is, which at a) the oxidation of organic substances b) the composting or storage of organic substances containing waste materials, or c) bacterial decomposition organic substances is formed. Process according to claim 2, wherein as organic Substances that are subject to oxidation, fossil fuels or organic substances containing wastes used. Process according to claim 2, wherein as organic Substances containing waste, the composting or Be subjected to storage, household waste, plastic waste or packaging waste uses. Process according to claim 2, wherein as organic Substances that undergo bacterial decomposition Stable manure, straw, manure, sewage sludge or fermentation residues used. Method according to one of the preceding claims, wherein inert washing columns essentially consisting of glass fiber reinforced plastics, selected from the group consisting of polyvinyl chloride, polyethylene, polypropylene, Polyvinylidene fluoride, ethylene chlorotrifluoroethylene copolymers, Halar, Polyfluoroethylene propylene, perfluoroalkoxy polymers, copolymers of Tetrafluoroethylene and perfluoro-vinyl ether, polytetrafluoroethylene, starts. Method according to one of claims 1 to 5, wherein a inert steel wash column, the interior of which is coated with rubber is, uses. A process according to any one of the preceding claims, wherein the absorbent is a chemical solvent selected from the group consisting of solutions consisting mainly of aliphatic or cycloaliphatic amines having from 4 to 12 carbon atoms, alkanolamines having from 4 to 12 carbon atoms, cyclic amines in which 1 or 2 nitrogen atoms together with 1 or 2 alkanediyl groups form 5-, 6- or 7-membered rings, mixtures of the above solutions, aqueous Lö solutions of the above mixtures and solutions, - aqueous solutions containing salts of amino acids - aqueous Pottaschelösungen containing possibly piperazine or methylethanolamine - aqueous NaOH solution or lime. A method according to claim 8, wherein as chemical solvent Solutions, consisting mainly monoethanolamine (MEA), methylaminopropylamine (MAPA), piperazine, Diethanolamine (DEA), triethanolamine (TEA), diethylethanolamine (DEEA), Diisopropylamine (DIPA), aminoethoxyethanol (AEE), dimethylaminopropanol (DIMAP) and methyldiethanolamine (MDEA), mixtures of the above solutions and watery solutions the above mixtures and solutions used. Method according to one of the preceding claims, wherein as a sorbent, a physical solvent selected from the group consisting of cyclotetramethylenesulfone (sulfolane) and its derivatives, aliphatic acid amides (acetylmorpholine, N-formylmorpholine), NMP (N-methylpyrrolidone), propylene carbonate, N-alkylated pyrrolidones and corresponding piperidones, methanol and mixtures of dialkyl ethers of polyethylene glycols. Method according to one of the preceding claims, wherein as a washing solution a mixture of a physical and a chemical solvent starts. Method according to one of the preceding claims, wherein as a washing solution an aqueous solution containing Methyldiethanolamin and piperazine. Method according to one of the preceding claims, wherein one the washing liquid regenerated after passing through the absorption step and then into an absorption step leads back. Method according to claim 12, taking the washing liquid regenerated by single or multi-stage relaxation. Method according to claim 12, taking the washing liquid after relaxing by stripping with an inert fluid, in particular Nitrogen or water vapor, regenerated. Method according to one the preceding claims, wherein the absorption step in several successive Sub-steps performs and the acid-containing fluid flow in each of the substeps each brings a partial stream of the washing solution in contact. A process according to any one of the preceding claims, wherein a fluid stream is used which under normal conditions contains less than 50 mg / m ^{3 of} sulfur dioxide. Apparatus for carrying out the method according to one the claims 1 to 16, consisting of one or more consecutive washing columns, which with a washing solution filled are, wherein it is at least one wash column to an inert Washing column is the inner surface of plastic or rubber consists.