DE10325358A1 - 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 that contains 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 can be, for example, gas streams (such as natural gas, refinery gas, the oxidation of organic organic materials, such as organic waste coal or petroleum, or reaction gases resulting from the composting of waste materials containing 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 suitable processing measures directly on the Natural gas source can be reduced, because also form the sulfur compounds in that of natural gas often entrained Water acids, that have a corrosive effect. For The transport of natural gas in a pipeline must therefore have predetermined limit values of sulfur-containing impurities are observed. The at the oxidation of organic materials such as organic waste, coal or petroleum, or in the composting of waste materials containing organic substances emerging reaction gases must be removed to reduce the emission of gases that harm nature or can influence the climate to prevent.

There is also extensive patent literature on the scrubbing solutions used in gas scrubbing processes. Basically, there are 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 in molecular form. Typical physical solvents are cyclotetramethylene sulfone (sulfolane) and its derivatives, aliphatic acid amides (acetylmorpholine, N-formylmorpholine), NMP (N-methyl-pyrrolidone), propylene carbonate, N-alkylated pyrrolidones and corresponding piperidones, methanol and mixtures of dialkyl ethers of polyethylene glycols ^® , Union Carbide, Danbury, Conn., USA).

To the others become chemical solvents used, whose mode of action is based on chemical reactions, in which, after absorption, the dissolved acid gases in the form of chemical Connections exist. For example, in industrial scale most often as chemical solvents used aqueous solutions inorganic bases (e.g. potash solution in the Benfield process) or organic bases (e.g. alkanolamines) are formed when dissolving acid gases. The solvent can be done by relaxing to a lower pressure or stripping be regenerated, the ionic species reacting back to acid gases and / or stripped using steam. After the regeneration process can the solvent be reused. Preferred when removing acid gas impurities 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 acid gases becomes the fluid flows in one absorption step with the washing solution brought into contact. It is 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 washing columns. It is also described (loc. cit.) that the steel, unless costly high-alloyed steels are used, due to the proportion of acid gases, by Corrosion is attacked. This will extend the life of the equipment significantly restricted.

It there was therefore the task of a device for absorbing Acid gases from fluid flows comprising providing a washing column in which the washing column across from the fluid flows is largely inert.

Accordingly a process for deacidification found a fluid stream containing acid gases as impurities, wherein one in at least one absorption step at a pressure of 0.5 up to 5 bar inside the fluid flow with an absorbent Brings in contact with the proviso that one 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.

The Fluid flow, mostly a source gas rich in acidic gas components (Raw gas), is in an absorption step in an inert wash column brought into contact with an absorbent, causing 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 source gas is generally a gas stream that is formed in the following way:

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

As organic substances that are subjected to oxidation it usually is about fossil fuels such as coal, natural gas or petroleum or organic Waste containing substances.

As waste materials containing organic substances that are prone to oxidation, that are subjected to composting or storage are mainly household waste, plastic waste or Packaging waste used.

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

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

As Organic substances in bacterial decomposition are common Manure, straw, liquid manure, sewage sludge, Fermentation residues used.

The bacterial decomposition takes place e.g. in common biogas plants.

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

As Absorbents are practically all common 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 with 4 to 12 carbon atoms, alkanolamines with 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, which may contain piperazine or methylethanolamine
• - aqueous NaOH lye or milk of lime.

Especially Preferred chemical solvents are solutions consisting mainly of from monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), Diethylethanolamine (DEEA), Diisopropylamine (DIPA), Aminoethoxyethanol (AEE) and methyldiethanolamine (MDEA) mixtures of the above solutions and aqueous solutions of the above mixtures and solutions, used.

This has proven particularly useful in the US patent US 4,336,233 described absorbent. It is an aqueous solution of methyldiethanolamine (MDEA) and piperazine as an absorption accelerator or activator (aMDEA ^® , BASF AG, Ludwigshafen). The washing liquid described there 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 others preferred chemical solvent reference is made to DE-A-10306254, DE-A-10210729, DE-A-10139453, and EP-A-1,303,345th

As Absorbents have continued to be physical solvents selected from the group consisting of cyclotetramethylene sulfone (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.

The inert wash columns used in the process of this invention consist essentially of plastics, selected from the group consisting of polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, ethylene-chlorotrifluoroethylene copolymer (Halar ^® from. Allied Chemical Comp.), Polyfluoroethylenepropylene, perfluoroalkoxy polymers, copolymers of tetrafluoroethylene and Perfluoro vinyl ether, polytetrafluoroethylene. Also suitable are washing columns made of steel, the interior of which is coated with rubber. These plastics are preferably glass fiber reinforced.

Suitable inert wash columns are, for example, packing, packing and tray columns. Only inert wash columns are preferably used as absorbers, but it is also possible to use them in combination with other known absorbers such as membrane contactors, radial flow washers, jet washers, Venturi washers and rotary spray washers or washing columns made of steel. The treatment of the fluid flow with the absorbent is carried out preferably in an inert wash column in countercurrent. The fluid is generally fed into the lower region and the absorbent into the upper region of the column.

The Temperature of the absorbent is in the absorption step in Generally around 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 in the absorption step is Generally about 0.5 to 5 bar, preferably about 0.7 to 3 bar. It a low in acidic gas components, i.e. one on these ingredients depleted product gas (leg gas) and one with acidic gas components get loaded absorbent.

The inventive method can be one or more, in particular two, successive Absorption steps include. The absorption can be in several successive Partial steps carried out be, 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 is brought into contact with acidic gases be loaded, i.e. it can be, for example, an absorbent, that from a subsequent absorption step into the first absorption step was returned or act as partially regenerated absorbent. Regarding the execution the two-stage absorption is referred to the documents 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 done so that the fluid containing the acid gases is initially in a first absorption step with the absorbent at a temperature of 40 to 100 ° C, preferred 50 to 90 ° C and especially 60 to 90 ° C is treated. The fluid depleted in acid gases then becomes 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 loaded with the acidic gas components can the acidic gas components in the usual Manner (analogous to the publications cited below) in one Regeneration step are released, being a regenerated Absorbent is obtained. In the regeneration step, the Loading of the absorbent is reduced and the regenerated obtained Absorbent is preferably subsequently in the absorption step recycled.

In general, the regeneration step includes at least relieving the pressure of the loaded absorbent from a high pressure, as prevails when the absorption step is carried out, to a lower pressure. The pressure relief can take place, for example, by means of a throttle valve and / or an expansion turbine. Regeneration with a relaxation level is described, for example, in the publications US 4,537,753 and US 4,553,984 ,

The acidic gas constituents can be released in the regeneration step, for example in a relaxation column, for example a vertically or horizontally installed flash container or a countercurrent column with internals. Several relaxation columns can be connected in series, in which regeneration takes place at different pressures. For example, in a pre-expansion column at high pressure, which is typically about 1.5 bar above the partial pressure of the acidic gas components in the absorption step, and in a main expansion column at low pressure, for example 1 to 2 bar absolute, can be regenerated. Regeneration with two or more relaxation levels is described in the documents 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 relaxation stage can also be carried out under vacuum, which is generated, for example, by means of a water vapor jet, 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 optimal coordination of the content of the amine components the absorbent according to the invention a high loadability with acid gases, which also desorbs easily can be. This allows in the method according to the invention energy consumption and solvent circulation can be significantly reduced.

The method according to the invention is described below using the 1 explained.

In 1 a device is schematically shown in which the absorption stage is carried out in one stage and the relaxation stage in two stages. The feed gas is piped 1 in the lower part of the absorber 2 fed. At the absorber 2 it is a column packed with packing to effect mass and heat exchange. The absorbent where it is regenerated absorbent with a low residual acid gas content, is via the line 3 on the head of the absorber 2 abandoned in counterflow to the feed gas. The gas depleted in acidic gases leaves the absorber 2 overhead (line 4 ). The absorbent enriched with acidic gases leaves the absorber 2 on the ground via pipe 5 and is in the upper area of the high pressure flash column 6 initiated, 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 absorption medium is generally carried out with the aid of conventional devices, for example a level control valve, a hydraulic turbine or a pump running in reverse. During the relaxation, most of the dissolved non-acidic gases and a small part of the acidic gases are released. These gases are piped 7 from the high pressure relaxation column 6 discharged overhead.

The absorbent, which is still loaded with the majority of the acid gases, leaves the high-pressure expansion column via line 8th and is in the heat exchanger 9 heated, whereby a small part of the acidic gases can be released. The heated absorbent is in the upper area of a low pressure relaxation column 10 initiated, which is equipped with a packing in order to achieve a large surface area and thus to release the CO ₂ and bring about the equilibrium. In the low pressure relaxation column 10 most of the CO ₂ and H ₂ S are released almost completely by flashing. In this way, the absorbent is regenerated and cooled at the same time. At the top of the low-pressure relaxation column 10 is a reflux condenser 11 with a collecting container 12 provided to cool the released acid gases and to condense some of the vapor. Most of the acid gas leaves the reflux condenser 11 via line 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 at the bottom via line 15 and is pumped 16 via line 3 on the head of the absorber 2 given up. Via line 17 fresh water can be fed in to compensate for the water discharged with the gases.

Claims (18)

Process for deacidifying a fluid stream, the Contains acid gases as impurities, with at least one an absorption step at a pressure of 0.5 to 5 bar the fluid flow brings into intimate contact with an absorbent, provided that one the absorption step and in the case of several absorption steps at least one of the absorption steps in an inert washing column, their inner surface consists essentially of plastic or rubber. The method of claim 1, which is Fluid flow is, which at a) the oxidation of organic substances b) the composting or storage of organic substances containing waste, or c) bacterial decomposition organic substances is formed. A method according to claim 2, wherein the organic Substances that are subject to oxidation, fossil fuels or waste containing organic substances. A method according to claim 2, wherein the organic Waste containing substances that are subject to composting or Be subjected to storage, household waste, plastic waste or packaging waste used. A method according to claim 2, wherein the organic Substances that are subject to bacterial decomposition, Manure, straw, liquid manure, sewage sludge or fermentation residues are used. Method according to one of the preceding claims, wherein inert wash 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 4, wherein one inert steel washing column, the interior of which is coated with rubber is, begins. Method according to 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 with 4 to 12 carbon atoms, alkanolamines with 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 solutions of the above mixtures and solutions, - aqueous solutions containing salts of amino acids - aqueous potash solutions, which may contain piperazine or methylethanolamine - use aqueous NaOH lye or milk of lime. A method according to claim 8, wherein the chemical solvent Solutions, consisting mainly of from 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 of the above mixtures and solutions. Method according to one of the preceding claims, wherein a physical solvent selected as the absorbent the group consisting of cyclotetramethylene sulfone (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 one as a washing solution a mixture of a physical and chemical solvent starts. Method according to one of the preceding claims, wherein one as a washing solution containing an aqueous solution Methyldiethanolamine and piperazine. Method according to one of the preceding claims, wherein one the washing liquid regenerated after going through the absorption step and then in returns an absorption step. 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. Procedure according to a the preceding claims, taking the absorption step in several consecutive Performs partial steps and the acid gas-containing fluid flow in each of the substeps brings a partial flow of the washing solution into contact. Method according to one of the preceding claims, wherein a fluid stream is used which contains less than 50 mg / m ³ sulfur dioxide under normal conditions. Device for performing the method according to a of claims 1 to 16, consisting of one or more washing columns connected in series, which with a washing solution filled are, with at least one wash column being an inert one Washing column deals, the inner surface of plastic or rubber consists.