EA041769B1 - DEVICE AND METHOD FOR PRODUCING NEUTRALIZED FLUID FLOW - Google Patents

Description

The present invention relates to a process for producing a neutralized fluid stream, in particular for producing neutralized natural gas, with a low methanol content. In addition, the present invention relates to a device for neutralizing the flow of methanol-containing fluid, and its use.

The removal of acid gases from fluid streams is desirable for various reasons.

After extraction, natural gas contains various other components besides methane, such as other hydrocarbons, water, as well as acid gases such as CO2, H2S or mercaptan.

Raw natural gas, so-called sales gas, must be purified before being sold to meet the specifications and requirements of customers and distribution companies.

For example, it is necessary to remove water from natural gas, since if the natural gas is not dried enough, this can lead to the formation of methane hydrates. Solid methane hydrates can cause severe pressure drops in pressure pipes and blockage or even damage to valves and pipelines.

Drying also guarantees a constant calorific value of the gas when fed into the public gas supply network.

In addition, acid gases such as CO ₂ , H ₂ S and mercaptans must be removed as they are corrosive and can cause corrosion damage in pipelines or raw gas processing plants. In addition, acidic gases such as CO ₂ and H ₂ S are harmful to the environment and can cause so-called acid rain.

During the production of liquefied natural gas (English: Liquid Natural Gas=LNG), before liquefaction, it is necessary to clean the raw gas, including the need to separate CO2 to a value of 50 ppm to prevent the formation of solids in the liquefied stream.

Therefore, raw gas typically goes through various purification steps before it is fed into the natural gas grid as sales gas.

Typically, most of the contained water and natural gas condensate are separated first. In this process, the raw gas is usually cooled so that the water and natural gas condensate components such as long chain alkanes and aromatics are recondensed. Recondensed fluids, i.e. condensate of natural gas and water, can be separated from non-liquefied natural gas. The separation of water and natural gas condensate is generally carried out at or near the gas production site.

In colder regions, methanol is typically added to natural gas after separation of water and natural gas condensate and before transport to a natural gas processing plant. Methanol is an inhibitor for the formation of methane hydrates in the raw gas.

Thus, adding methanol to the raw gas allows it to be transported from the conveyor to the natural gas processing plant at low ambient temperatures.

However, the addition of methanol to the raw gas can lead to problems in downstream processing steps in a natural gas processing plant.

In a natural gas processing plant, one or more of the following steps are typically carried out:

(i) neutralization;

(ii) water removal;

(iii) mercury removal;

(iv) nitrogen removal;

(v) removal of natural gas condensates; and/or (vi) liquefaction to produce liquefied natural gas.

In stage (i) neutralization, the raw gas is usually passed through an absorbent that absorbs at least part of the acid gases, thus producing neutralized natural gas and an absorbent loaded with acid gases.

In the neutralization step (i), the methanol present in the raw gas is generally not completely co-absorbed in the absorbent, so the neutralized natural gas still contains some residual methanol prior to being fed to the water removal step (ii). In particular, in cases where the absorbent itself contains a residual amount of methanol. The absorbent may contain a residual amount of methanol if regenerated absorbent from which the methanol has not been completely removed is used for neutralization.

However, residual methanol can lead to problems in the subsequent step (ii) of water removal.

For example, the removal of water can be in the form of pressure swing adsorption (or pressure swing adsorption (PSA)), preferably in the form of temperature swing adsorption (TSA) or glycol drying.

If step (ii) of removing water is carried out, for example, in the form of PSA or TSA, in which a molar sieve is used as a solid drying agent, then in the presence of residual methanol, it is necessary to use a 4A molar sieve instead of a 3A molar sieve so that in addition to water and methanol will also absorb additional components such as H2S and ethane. In addition, methanol uptake competes with the preferred water uptake. The co-absorption of methane and other components when using a molar sieve requires the use of a larger amount of adsorber. In addition, methanol can lead to more rapid coking of the molar sieve during its regeneration by increasing the temperature.

As with adsorption using PSA or TSA, as well as with the use of dehydrating devices based on the so-called glycol dehydration, methanol outflow can occur through different parts of the device, since the separated water also additionally contains methanol during the regeneration of the drying agent.

The presence of methanol generally requires further post-treatment of the separated water in which methanol is separated from it to re-obtain methanol and/or water of a purity such that the substances can be reused as make-up water or inhibitor.

Therefore, RU 2602908 discloses a raw gas neutralization process in which neutralized natural gas with a low MeOH content is obtained.

In this method, the raw gas containing MeOH is first sent to an absorber. In the absorber, the raw gas containing MeOH comes into contact with an aqueous amine solution. Also, in addition to acid gases such as CO2, most of the MeOH is absorbed. In the regenerator at higher temperatures, the loaded amine solution is regenerated, while acid gases and MeOH are removed from it. The resulting stream is fed through the top of the regenerator to a condenser where the majority of the methanol is recondensed together with the injected vapor and separated from the acid gases remaining in the gas phase. RU 2602908 discloses the subsequent processing of the condensate containing MeOH from the regenerator in a distillation column located below. In this case, the condensate from the regenerator is separated into methanol (top product) and water (bottom product). The MeOH can then be reused as an inhibitor in the raw gas. Almost completely free of MeOH water is placed in a buffer tank and mixed there with regenerated absorbent to compensate for water loss and returned back to the absorber.

The disadvantage of the method described in RU 2602908 is that in the case of recirculation of the bottom stream from methanol distillation to the absorber, it is necessary to return a bottom stream practically free of methanol, since residual amounts of methanol in the returned absorbent reduce the absorption of methanol in the absorber. The methanol content in the methanol distillation bottom stream depends, for example, on the energy entering the evaporator, the reflux factor and the number of plates in the column. A substantially methanol-free bottom stream can be obtained either by operating the column at a high evaporator capacity, by setting a high reflux factor, and/or by having a high number of plates in the column. This increases operating costs and/or capital investment.

Similar problems may arise in the production of synthesis gas. Thus, in the production of synthesis gas using steam reforming of methane, methanol can be formed as a by-product. Thus, in addition to hydrogen and acid gases such as CO ₂ and CO, methanol can also be present in the liquid stream. After separation of at least part of the acid gases during their washing neutralized synthesis gas and/or neutralized hydrogen may also contain a residual amount of methanol. In addition to water, which can generally be supplied via an aqueous absorbent, subsequent drying of the synthesis gas and/or hydrogen can also lead to the problems described above.

Therefore, the object of the present invention was to obtain a neutralized fluid stream, in particular neutralized natural gas, which has a low content of MeOH, while the method of obtaining it should have lower operating costs and/or capital investments.

In particular, this invention should provide a high proportion of recovery of methanol used as an inhibitor.

In addition, it should help to reduce the amount of absorbent components, such as water, that must be supplied to compensate for possible losses in the process. For this reason, the method according to the invention should facilitate the return of streams from certain process steps to other process steps.

The object of the present invention is solved by a process for producing a neutralized fluid stream from a fluid stream containing methanol and at least one acid gas, comprising:

a) an absorption step in which the fluid stream is brought into contact with the absorbent in the absorber to produce an absorbent loaded with methanol and acid gases and, at least in part, a neutralized fluid stream;

b) a regeneration step, in which at least one part of the loaded absorbent obtained in step a) is regenerated in a regenerator, and one, at least partially, regenerated

- 2 041769 porous absorbent and one gaseous stream containing methanol, water and at least one acid gas;

c) a recycling step, in which at least a partial flow of regenerated absorbent from step b) is returned to step a) absorption;

d) a condensation step in which a condensate containing methanol and water is recondensed from the gaseous stream from step b);

e) a distillation step in which at least a portion of the condensate from step d) is sent to a distillation column, whereby an overhead stream containing methanol and a bottom stream containing water are obtained;

characterized in that at least a portion of the bottom flow from the stage is returned e) to the regenerator.

The method according to the invention uses a fluid stream containing methanol and at least one acid gas.

The amount of methanol in the fluid stream is preferably in the range of 50-5000 vpm, particularly preferably 100-1000 vpm and very preferably 200-800 vpm.

Preferably methanol is added to the fluid stream before step a). But methanol can also be formed as a by-product in the production of a fluid stream, such as in steam reforming of methane.

Further, the used fluid stream contains at least one acid gas. Preferably, the raw natural gas contains CO2 and/or H2S. In addition to CO2 and/or H2S, other acid gases such as COS and mercaptan may be present in the raw natural gas. In addition, SO ₃ , SO2, CS2 and HCN may also be contained.

The content of acid gases in the fluid stream is generally in the range of 0.01-40% by volume, preferably 0.05-15% by volume and particularly preferably 0.1-5% by volume.

The fluid stream introduced into the process of the invention may additionally contain water.

The water content of the fluid stream typically ranges from >0 vol% to a content corresponding to the saturation concentration of water in the fluid stream under given pressure and temperature conditions.

In a preferred embodiment, the fluid stream used in the process according to the invention contains hydrocarbons. The hydrocarbon content of the fluid stream is generally 60-99.9% by volume, preferably 85-99.5% by volume and particularly preferably 95-99% by volume.

The hydrocarbons present in the fluid stream preferably contain 80-100% by volume methane, particularly preferably 90-99.9% by volume and very preferably 95-99% by volume methane.

In addition to containing methane and acid gases, the fluid stream may contain other components such as other gases (N2 or He), mercury, or natural radioactive substances.

The amount of other components in the fluid stream is generally 0-4% by volume, preferably 0.0001-3% by volume, and very preferably 0.0005-1.5% by volume.

The fluid stream may be any fluid stream that contains at least one acid gas and methanol. Preferably the fluid stream is raw natural gas. But the fluid stream can also be synthesis gas or biogas to which methanol is added or from which methanol is produced as a by-product. Raw natural gas is usually raw natural gas from which natural gas condensate and water have been separated by recondensation. The separation of natural gas condensate and water can be carried out using methods known to those skilled in the art, for example by lowering the temperature of the transported raw gas and separating recondensed components such as water and natural gas condensate from the non-condensed components of the raw natural gas.

Preferably, a fluid flow is used whose total pressure is in the range of 20-120 bar, particularly preferably 40-100 bar and very preferably 50-80 bar.

absorption stage.

The fluid stream is directed according to the invention to an absorption step in which the fluid stream is brought into contact with the absorbent in the absorber to obtain an absorbent loaded with methanol and acid gases and, at least in part, a neutralized fluid stream.

Absorbent.

The absorbent contains at least one amine. Preferred amines are the following:

i) amines of formula I

NR!(R ² )2 (I), where R ¹ is selected from C1-C6-hydroxyalkyl groups, C1-C6-alkoxy-C2-C6-alkyl groups, hydroxyC1-C6-alkoxy-C2-C6-alkyl groups and 1 -piperazinyl-C2-C6-alkyl groups, and R ² is independently selected from H, C1-C ₆ -alkyl groups and C ₂ -C ₆ -hydroxyalkyl groups;

ii) amines of formula II

R ³ R ⁴ NX-NR ⁵ R ⁶ (II),

- 3 041769 where R ³ , R ⁴ , R ⁵ and R ⁶ are independently selected from H, C1-C ₆ -alkyl groups, C2-C6 hydroxyalkyl groups, C ₁ -C ₆ -alkoxy-C ₂ -C ₆ - alkyl and C ₂ -C ₆ -aminoalkyl groups, and X means

C ₂ -C ₆ -alkylene group, -X1-NR ⁷ -X ² - or -X1-O-X ² -, where X ¹ and X ² independently of each other mean

C ₂ -C ₆ alkylene groups and R ⁷ is H, C ₁ -C ₆ alkyl, C ₂ -C ₆ hydroxyalkyl or C ₂ -C ₆ aminoalkyl;

iii) 5-7 membered saturated heterocycles with at least one nitrogen atom in the ring, which may contain one or two additional heteroatoms selected from nitrogen and oxygen, and iv) mixtures thereof.

Particular examples of preferably used amines are:

i) 2-aminoethanol (monoethanolamine), 2-(methylamino)ethanol, 2-(ethylamino)ethanol, 2-(n-butylamino)ethanol, 2-amino-2-methylpropanol, N-(2-aminoethyl)piperazine, methyl -diethanolamine, ethyldiethanolamine, dimethylaminopropanol, tert-butylaminoethoxyethanol (TBAEE), 2-amino-2-methylpropanol, diisoproanolamine (DIPA);

ii) 3-methylaminopropylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, 2,2-dimethyl1,3-diaminopropane, hexamethylenediamine, 1,4-diaminobutane, 3,3-iminobispropylamine, tris(2-aminoethyl)amine, bis(3-dimethylaminopropyl)amine, tetramethylhexamethylenediamine;

iii) piperazine, 2-methylpiperazine, N-methylpiperazine, 1-hydroxyethylpiperazine, 1,4-bishydroxyethylpiperazine, 4-hydroxyethylpiperidine, homopiperazine, piperidine, 2hydroxyethylpiperidine and morpholine; and iv) mixtures thereof.

In a preferred embodiment, the absorbent contains at least one of the amines monoethanolamine (MEA), methylaminopropylamine (MAPA), piperazine (PIP), diethanolamine (DEA), triethanolamine (TEA), diethylethanolamine (DEEA), diisopropanolamine (DIPA), aminoethoxyethanol (AEE). ), tert-butylaminoethoxyethanol (TBAEE dimethylaminopropanol (DIMAP) and methyldiethanolamine (MDEA) or mixtures thereof.

Other amines that can be used in the process according to the invention are t-butylaminopropanediol, t-butylaminoethoxyethylmorpholine, t-butylaminoethylmorpholine, methoxyethoxyethoxyethyl t-butylamine, t-butylaminoethylpyrrolidone.

Preferably the amine is a hindered amine or a tertiary amine. A hindered amine is a secondary amine in which the amine nitrogen is bonded to at least a secondary carbon atom and/or at least a tertiary carbon atom; or a primary amine in which the amine nitrogen is bonded to a tertiary carbon atom. A preferred hindered amine is t-butylaminoethoxyethanol. The preferred tertiary amine is methyldiethanolamine.

If it is desired to completely or almost completely remove the CO2 contained in the fluid stream, the absorbent also preferably contains an activator if the amine contained in the absorbent is a hindered amine or a tertiary amine. In general, the activator is a sterically unhindered primary or secondary amine. In these sterically unhindered amines, the amine nitrogen of at least the amine group is bonded to primary carbon and hydrogen atoms only. If it is desired to remove a portion of the gas contained in the fluid stream, such as selectively removing H2S from a fluid stream containing H2S and CO2, then the absorbent preferably does not contain an activator.

A sterically unhindered primary or secondary amine which can be used as an activator is selected, for example, from alkanolamines such as monoethanolamine (MEA), diethanolamine (DEA), ethylaminoethanol, 1-amino-2-methyl-propan-2-ol , 2-amino-1-butanol, 2-(2-aminoethoxy)ethanol and 2-(2-aminoethoxy)ethanamine, polyamines such as hexamethylenediamine, 1,4diaminobutane, 1,3-diaminopropane, 3-(methylamino)-propylamine (MAPA ), N-(2hydroxyethyl)ethylenediamine, 3-(dimethylamino)-propylamine (DMAPA), 3-(diethylamino)propylamine, N,N-bis(2-hydroxyethyl)ethylenediamine, 5-, 6- or 7-membered saturated heterocycles with at least one NH group in the ring, which may contain one or two other ring heteroatoms selected from nitrogen and oxygen, such as piperazine, 2-methylpiperazine, N-methylpiperazine, Nethylpiperazine, N-(2-hydroxyethyl)-piperazine, N-(2-aminoethyl)piperazine, homopiperazine, piperidine and morpholine.

Particularly preferred are 5-, 6- or 7-membered saturated heterocycles with at least one NH group in the ring, which may contain one or two other heteroatoms selected from nitrogen and oxygen in the ring. Piperazine is highly preferred.

In an embodiment of the invention, the absorbent contains the tertiary amine methyldiethanolamine and the activator piperazine.

The molar ratio of activator to hindered amine or tertiary amine is preferably in the range of 0.05-1.0, particularly preferably in the range of 0.05-0.7.

In general, the absorbent contains 10-60 wt.% amine.

The absorbent may further contain physical solvents. suitable physical

Solvents are, for example, N-methylpyrrolidone, tetramethylenesulfone, oligoethylene glycol dialkyl ether such as oligoethylene glycol methyl isopropyl ether (SEPASOLV MPE), oligoethylene glycol dimethyl ether (SELEXOL). Physical solvents are present in the absorbent in general in an amount of 1-60% by weight, preferably 10-50% by weight, particularly preferably 20-40% by weight.

The absorbent in a preferred form of execution contains less than 10 wt.%, for example, less than 5 wt.%, particularly preferably less than 2 wt.% inorganic alkaline salts, such as potassium carbonate.

The absorbent also contains additives such as corrosion inhibitors, antioxidants, enzymes, antifoam agents, etc. In general, the amount of such additives is in the range of about 0.01-3% by weight of the absorbent.

Fresh absorbent may be added to the absorber, or regenerated absorbent from the recycling step e) may be added to the absorber. The supply of fresh absorbent means that the absorbent components have not yet completed steps b) to e). The supply of regenerated absorbent requires that at least a portion of the absorbent components complete steps b)-e).

The absorbent preferably contains 0.05 vol% or less methanol, particularly preferably 0.03 vol% or less methanol, very preferably 0.01 vol% or less methanol, and more preferably 0.005 vol% or less methanol.

The absorbent is preferably aqueous. This means that various absorbent components such as amine, methanol, physical solvents, additives are mixed in the above quantities with water.

Very preferably, an aqueous solution of methyldiethanolamine is used as the absorbent.

Absorber.

The connection of the fluid stream with the absorbent in step a) is carried out in the absorber.

The absorber is preferably an absorption tower or an absorption column, such as a packed, packed or tray column.

In general, the absorber comprises an absorption zone and optionally a backwash zone.

absorption zone.

The absorption zone is the section of the absorption column in which the fluid stream is combined with the absorbent for mass transfer.

The connection of the fluid flow with the absorbent in step a) is carried out in the absorption zone, preferably in countercurrent.

In order to improve contact with the absorbent and create a larger boundary mass transfer surface, the absorption zone usually contains built-in elements, for example, fillers, nozzles and/or trays, such as a valve tray, cap tray, Thormann tray or mesh tray.

If the absorption zone contains fillers or packings, the height of the fillers/packings in the absorption zone is preferably in the range of 5-20m, particularly preferably in the range of 6-15m and very preferably in the range of 8-14m.

If the absorption zone contains trays, then the number of absorption zone trays is preferably in the range of 8-30, particularly preferably 12-25 and very preferably 15-23 trays.

In a filled or packed column, the absorption zone may be divided into one or more sections, preferably 2-4 sections. Between the individual sections of the absorption zone can be located bearing and supporting and/or distribution plates, which improve the distribution of the absorbent over the entire cross section of the column.

The temperature of the absorbent entering the absorption zone is generally about 0-60°C, preferably 10-50°C and particularly preferably 25-50°C.

The pressure in the absorber is usually in the range of 30-120 bar, particularly preferably 40-100 bar and very preferably 50-80 bar.

The place of supply of the directional fluid flow is preferably located below the absorption zone or in its bottom part. Preferably, the supply is carried out through a gas distributor.

The absorbent may have one or more absorbent input points. Thus, the absorber may have one feeder for fresh absorbent and one feeder for regenerated absorbent. But fresh and regenerated absorbent can also be fed together into the absorber through the same feeder. One or more feed points are preferably located above the absorption zone or in its upper zone. Individual components of the absorbent, such as seal water, can also be fed through the fresh absorbent feeder.

If the absorber has an additional backwash zone, the feed is preferably carried out between the absorber zone and the backwash zone.

When the fluid stream is combined with the absorbent in the absorption zone, an at least partially neutralized fluid stream and an absorbent loaded with MeOH and acid gases are obtained.

In the upper zone of the absorber is, as a rule, the point of removal of the flow of neutralized fluid. A fluid separator may be placed in the diversion zone to separate any remaining absorbent or flushing fluid from the effluent fluid stream.

- 5 041769

In the lower zone of the absorber, preferably in the sump, is, in General, the place of reception for the loaded absorbent.

At least partially, the neutralized fluid stream in the absorption zone can, if necessary, be combined with the washing liquid.

The flushing agent feeder is preferably located in the upper zone or above the absorption zone.

A particularly preferred flushing fluid is an aqueous fluid. The flushing liquid in the process may mean its own fluid, i.e. an aqueous fluid that occurs elsewhere in the process, or an externally supplied aqueous fluid. Preferably, the Wash Fluid comprises condensate formed upon cooling of the downstream neutralized fluid stream (so-called absorber head condensate) and/or fresh water.

By combining, at least in part, the neutralized fluid stream with the wash liquid, transported absorbent components such as amines can be washed out. When combined with an aqueous washing liquid, the water balance of the process can also be equalized if more water is carried through the outflow streams than enters through the incoming streams.

Backwash zone.

Optionally, the absorber may comprise a so-called backwash zone. In the backwash zone, the neutralized fluid stream is fed countercurrently with the flush fluid.

The backwash zone is typically the section of the absorber that is located above the absorbent loading site.

Preferably, the backwash zone contains fillers, nozzles and/or trays to improve the connection of the fluid stream with the flushing liquid. Particularly preferably, the backwash zone comprises trays, more preferably valve trays, cap trays, Thormann trays or mesh trays.

The backwash zone contains preferably 1-7, particularly preferably 2-6, and very preferably 3-5 trays, or the height of the fillers (fillers/nozzles) is preferably 1-6 m, particularly preferably 2-5 and very preferably 2-3 m .

The washing liquid generally passes over the backwash zone or at the top of the backwash zone. As the flushing fluid, the previously mentioned flushing fluids can be used.

It is possible to recycle the flushing liquid through the backwash zone. To do this, the washing liquid is collected under the washing zone, for example, using a suitable collection plate, and pumped to the top of the end of the backwash zone. You can cool the processed washing liquid, preferably to a temperature of 20-70°C, particularly preferably 30-60°C. To do this, it is advisable to pump the flushing liquid through the cooler. In order to avoid the accumulation of washed-out absorbent components in the washing liquid, it is preferable to pass a part of the washing liquid flow from the backwash zone.

Neutralized fluid flow specification.

The neutralized fluid stream, as previously described, is preferably withdrawn through a vent at the top of the absorber.

The selectively neutralized fluid stream may pass through the condenser.

As a condenser, for example, condensers with a cooling coil or pipe with a spiral weld, a plate heat exchanger, a two-pipe cooler, and a heat exchanger with a tube bundle can be used. In general, the capacitor is used at temperatures in the range of 10-60°C, preferably 20-50°C, particularly preferably 20-30°C.

The neutralized fluid stream obtained in step a) preferably contains 0.0110 vpm methanol, particularly preferably 0.05-5 vpm methanol, and very preferably 0.1-3 vpm ./million methanol.

The water content of the neutralized fluid stream is generally 80% to 100% of the saturation concentration of water in the fluid stream under given pressure and temperature conditions.

If the neutralized fluid stream is used as sales gas, the H ₂ S content of the neutralized fluid stream is preferably 5 vol. ppm or less, and the CO 2 content is 2 vol.% or less.

If the neutralized fluid stream is used as liquefied natural gas, the CO2 content of the neutralized fluid stream is preferably 100 vpm or less, and particularly preferably 50 vpm or less. The content of H2S in the neutralized stream at LNG (liquefied natural gas) is preferably 5 vpm or less, and particularly preferably 2 vpm or less.

Subsequent processing.

In addition to obtaining the neutralized fluid stream in step a), the neutralized fluid stream is subjected to one or more of the following processing steps:

- 6 041769 aa) water removal;

bb) mercury removal;

cc) nitrogen removal;

dd) removal of natural gas condensates; and/or her) liquefaction (LNG)

The removal of water aa) is preferably carried out in the form of pressure swing adsorption (or pressure swing adsorption (PSA)) and particularly preferably in the form of temperature change adsorption (TSA) or glycol drying.

PSA or TSA can be obtained using methods known to the person skilled in the art. Common embodiments are described, for example, in Nag, Ashis, Destination and Hydrocarbon Processing Practices, PennWell 2016, ISBN 978-1-59370-343-1 or A. Terrigeol, GPA Europe, Annual Conference, Berlin, Germany, 23-25 May 2012 (https://www.cecachemicals.com/export/sites/ceca/.content/medias/downloads/products/dtm/molecular-sieves-contami-nants-effects-consequences-and-mitigation.pdf).

When PSA or TSA is preferably used zeolite, active carbon or molecular sieve.

Preferably, the PSA or TSA uses a molecular sieve in the form of a solid adsorbent.

Glycol drying preferably uses a liquid absorbent such as monoethylene glycol (MEG), diethylene glycol (DEG), triethylene glycol (TEG) or tetraethylene glycol (TREG). Particular preference is given to using TEG as the liquid absorbent.

Glycol drying can be carried out according to methods known to the person skilled in the art. Examples of glycol drying are also, for example, found in Nag, Ashis Destination and Hydrocarbon Processing Practices, PennWell 2016, ISBN 978-1-59370-343-1.

After drying aa) additional processing steps can be carried out, if necessary, such as bb) removal of mercury, cc) removal of nitrogen, dd) removal of natural gas condensates and ee) liquefaction of natural gas to liquefied natural gas. Details of these process variants are also given in Nag, Ashis Hydrocarbon Processing Practices.

One or more purification steps aa) to dd) usually produce a fluid stream that meets the specifications of the end user and/or distribution companies, or the natural gas can be sold as sales gas or it can be liquefied during the next step of its) liquefaction to get LNG.

loaded absorbent.

Step a) also produces an absorbent loaded with acid gases.

Loaded absorbent can be fed directly to stage b) regeneration.

Stage of pressure reduction (if necessary).

In a particularly preferred embodiment of this method, the loaded absorbent, before being introduced into regeneration step b), first passes through a pressure reduction step.

In the pressure reduction step, the loaded adsorbents are generally directed to the pressure reduction tank.

To do this, as a rule, in the extracted loaded adsorbent substances on the absorber plate, the pressure is reduced using a throttle valve.

Preferably, the pressure in the loaded adsorbents is reduced to 3-15 bar, more preferably to 4-12 and particularly preferably to 5-10 bar.

The decrease in pressure generally leads to the desorption of co-absorbed hydrocarbons, which pass into the gas phase (the so-called flash gas). The flash gas can be returned to the absorption process with a compressor, burned in situ for energy, or flared.

Pressure reducing tank generally means a container that does not contain special built-in components. A preferred pressure reduction tank is the so-called flash drum. Columns with built-in elements such as fillers, packings or trays are also considered as a pressure reduction tank.

During pressure reduction, a gaseous phase (flash gas) is obtained.

In the upper part of the pressure reduction tank, as a rule, there is a gas outlet channel for the gas that turns into the gas phase. A fluid separator can again preferably be located in the gas venting zone. If necessary, the acid gases contained therein can be separated from the flash gas in another absorption column. Typically, for this, a partial stream of regenerated solvent is fed into an additional absorption column.

At the bottom of the depressurization tank, the absorbent, at least partially loaded with acid gases that have not gone into the gas phase, is usually collected and is usually sent to step b).

regeneration stage.

At least partially, the adsorbent substances loaded with acid gases according to the invention are sent to step b) regeneration.

- 7 041769

During the regeneration step, at least one part of the loaded absorbent obtained in step a) is regenerated in the regenerator, and one at least partially regenerated absorbent and one gaseous stream containing methanol, water and at least one acid gas are obtained.

Before being introduced into regeneration step b), the adsorbent material, at least partially loaded with acid gases, preferably passes through a heat exchanger.

In the heat exchanger, at least partially loaded with acid gases, the absorbent is heated preferably to a temperature in the range of 50-150°C, particularly preferably 70-130°C and very preferably 80-110°C.

In a particularly preferred embodiment, the heat exchanger uses regenerated absorbent recovered from the regenerator sump as heating agent. The advantage of this embodiment is that the thermal energy of the regenerated absorbent from step b) can be used to heat the loaded absorbent. Thanks to this, it is possible to reduce the costs of energy production and its recovery from the entire process.

Regenerator.

According to the invention, the regeneration step is carried out in a regenerator. As a rule, the regenerator is made in the form of a stripping column. The regenerator preferably includes a regeneration zone and an evaporator.

The regenerator is preferably operated at a top pressure in the range of 1-5 bar, preferably 1.2-4 and particularly preferred 1.3-2.5 bar.

In the sump of the regenerator, in General, there is a channel for removing the fluid for the regenerated solvent.

In the upper part of the regenerator, as a rule, there is a gas outlet channel for the gaseous stream. Preferably, a fluid separator is installed in the gas outlet zone.

The gaseous stream is directed according to the invention to stage d) condensation, as described previously.

regeneration zone.

In General, the regenerator contains a regeneration zone located above the sump. Preferably, the regeneration zone is considered to be the region of the regenerator in which the loaded absorbent is combined with the vapor generated before the evaporator of the sump.

In order to improve contact and create a larger mass transfer boundary surface, the regeneration zone typically contains built-in elements, for example, fillers, nozzles and/or trays, such as a valve tray, cap tray, Thormann tray or mesh tray.

If the regeneration zone contains packings or fillers, the height of the packings/fillers in the regeneration zone is preferably in the range of 5-15 m, particularly preferably 6-12 m and very preferably 8-12 m.

If the regeneration zone contains trays, then the number of trays of the regeneration zone is preferably in the range of 10-30, particularly preferably 15-25 and very preferably 17-23 trays.

In a filled or packed column, the regeneration zone can be further divided into several sections, preferably 2-4. Carrying and supporting and/or distributing trays can be located between sections of the regeneration zone, which improve the distribution of the fluid over the entire cross section of the regenerator.

As a rule, the loaded absorbent is preferably directed to or above the upper zone into the regenerator. If the regenerator contains an additional backwash zone, as described below, the loaded absorbent is preferably introduced into the regenerator between the regeneration zone and the backwash zone.

In the regeneration zone, the steam generated in the evaporator mainly flows in countercurrent with the absorbent passing downward through the regeneration zone.

The gaseous stream may contact the washing liquid in the regeneration zone.

If the regenerator does not have a cleaning zone, then the flushing agent feeder is preferably located in the upper region or above the regeneration zone.

More preferably, the flushing fluid is an aqueous fluid such as fresh water or an aqueous fluid obtained elsewhere in the process.

The temperature of the washing liquid is usually in the range of 20-60°C, preferably in the range of 30-55°C and more preferably 30-40°C.

In a preferred embodiment, part of the condensate from step d) is used as flushing liquid.

In a particularly preferred embodiment, this is at least part of the bottom stream washing liquid from step e).

More preferably, the washing liquid consists exclusively of the bottom stream from step e).

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Sump.

The regenerator zone below the regeneration zone is generally referred to as a sump.

In this area, the reclaimed absorbent is typically collected and fed to the evaporator through a liquid bleed at the bottom of the regenerator via pipes and/or partially returned to the absorber as reclaimed absorbent.

The settling tank can be divided by a collection bottom located between the settling tank outlet and the steam supply point, which is formed in the evaporator.

Evaporator.

As a rule, at least a part of the regenerated absorbent is sent to the evaporator from the outlet channel of the sump of the regenerator.

Preferably, the sump bleed from the regenerator extends completely into the evaporator. Evaporator usually means a reboiler (steam boiler evaporator), a natural circulation evaporator (thermosyphon) or a forced circulation evaporator.

The regenerator evaporator is preferably located downstream of the regenerator and connected to the settler outlet channel by means of pipes.

The evaporator is generally heated to 100-150°C, particularly preferably 105-140°C and very preferably 110-130°C.

In the evaporator, at least in general, part of the extract is evaporated from the outlet channel of the settler and returned to the regenerator. The injection of the generated steam and non-vaporized fluids preferably takes place below the regeneration zone, preferably in the sump of the regenerator.

If an additional collection plate (collection tray) is located in the sump, then the supply of the resulting steam is preferably carried out under the collection plate.

Backwash zone:

In a particularly preferred form of execution, the regenerator above the regeneration zone, particularly preferably above the place of supply of the loaded absorbent, contains a backwash zone.

The backwash zone, as a rule, is made in the form of a regenerator section located above the regeneration zone.

Preferably, the backwash zone contains built-in elements, especially preferably fillers, nozzles and/or trays, to improve the connection of the fluid stream with the flushing liquid.

In a preferred embodiment, the built-in elements are fillers and/or nozzles. The height of the nozzles (fillers/nozzles) is preferably in the range of 1-10, particularly preferably 2-8 and more preferably 3-6 m.

In a highly preferred embodiment, the backwash zone comprises trays, particularly preferably valve trays or bubble cap trays.

The washing zone contains preferably 1-10, more preferably 2-7 and most preferably 2-6 plates.

The washing liquid is usually injected into the upper region of the backwash zone or above the backwash zone.

As a washing liquid, as a rule, an aqueous or slightly neutralized aqueous solution is used, particularly preferably water.

In a particularly preferred embodiment, this is at least part of the bottom stream flushing liquid from step e). More preferably, the washing liquid consists solely of the bottom stream from step e).

In yet another embodiment, part of the condensate from step d) can be sent to the backwash zone as a flushing liquid.

The temperature of the washing liquid, as a rule, is in the range of 10-60°C, preferably 20-55°C and particularly preferably 40-50°C.

In the backwash zone, the residual amount of carried amines can be flushed out of the absorbent, so that the acidic waste gas leaving the regenerator is essentially free of amines. In addition, in the backwash zone, the water content of the gas stream that is obtained at the top of the regenerator can be reduced, since on contact with a colder flushing agent, part of the water vapor can condense.

This has the advantage that this water does not need to be separated in a subsequent distillation step.

Step c) recycling.

According to the invention, the regenerated absorbent formed in the sump of the regenerator from step b) is returned to step a) of absorption.

In this case, the return of the regenerated absorbent, as described earlier, occurs in one of the supply points of the absorber for the regenerated absorbent.

Step d) condensation.

The gaseous stream from the regenerator according to the invention is sent to condensation step d).

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In the condensation step, the condensate containing methanol and water is recondensed from the gaseous stream from step b).

Preferably, the condensation step is carried out in such a way that the gaseous stream from the step

b) passes through one or more condensers (regenerator dephlegmators).

In a preferred embodiment, the gaseous stream from step b) passes through one dephlegmator of the regenerator.

Dephlegmators usually contain a heat exchanger and a reservoir in which the liquid phase can be separated from the gas phase. However, the heat exchanger and reservoir can also be combined into one element.

The reflux condensers of the regenerator are operated in such a way that the methanol and, if necessary, water present are condensed, while the acid gases remain predominantly in the gas phase.

As dephlegmators of the regenerator, for example, condensers with a cooling coil or pipe with a spiral weld, a two-pipe cooler, and a heat exchanger with a tube bundle can be used.

In general, the regenerator reflux condenser is used at temperatures in the range of 10-60°C, preferably 20-55°C, particularly preferably 30-40°C.

Preferably, the first of the two regenerator reflux condensers is cooled with air or water for cooling, and the second of the two regenerator reflux condensers is cooled with a cooling fluid.

In general, the first dephlegmator of the regenerator is used at temperatures of 20-60°C and preferably 25-45°C.

The second dephlegmator of the regenerator is generally used with cooling fluid at temperatures of 3-20°C, preferably 5-15°C, particularly preferably 5-10°C.

Another advantage of the embodiment with at least two reflux condensers is that the methanol content of the acidic flue gas can be reduced, since more methanol can be recondensed at low temperatures. This makes it possible to increase the proportion of methanol recovery, for example, to more than 80%, relative to the methanol introduced into the process. In addition, the purity of the resulting methanol can be improved.

The non-recondensed gas phase is preferably removed from the process in the form of exhaust gases (exhaust gas).

According to the invention, at least part of the regenerator overhead condensate is fed to distillation step e). Here it is preferable that, when using several capacitors, the condensates are combined before being introduced into step e).

Preferably 50-100 vol%, more preferably 70-100 vol%, particularly preferably 90 out of 100 vol%, of the overhead regenerator condensate, and most preferably 100 vol%, is fed to distillation step e).

The overhead condensate not introduced in step e) can be returned to the regenerator as a wash liquid.

Here, the overhead condensate can be returned to the regenerator, preferably together with the bottom stream from step e) to the regenerator.

Step e) distillation.

In accordance with the present invention, step d) of condensation is followed by step e) of distillation, during which at least part of the condensate from step d) is sent to a distillation column to obtain an overhead stream containing methanol and a bottom stream containing water.

Step e) distillation is usually carried out in a distillation column.

Rectification can be carried out using devices known to those skilled in the art, such as bubble-cap tray columns, sieve tray columns, or fill/packed columns.

The distillation column preferably contains 3-25 trays, more preferably 5-20 trays and most preferably 7-15 trays.

Feeding to the distillation column is preferably carried out in the spatial region located between 25 and 95% of the plates of the distillation column (counting from the bottom), more preferably in the spatial region between 40 and 60% of the plates of the distillation column. For example, the feed to the distillation column may be in the area of the middle of the plates.

The energy required for distillation is usually provided by an evaporator at the bottom of the column. Such an evaporator is typically a heat recovery evaporator, a natural circulation evaporator, or a forced circulation evaporator.

Thus, according to a preferred embodiment, the absolute pressure at the top of the distillation column is preferably in the range of 1-5 bar, more preferably 1-4 bar, particularly preferably 1.1-3 bar.

At appropriate pressures, the temperatures at the top of the distillation column are generally in the range of 50-80°C, preferably 55-75°C, more preferably 60-70°C.

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The gas stream which is withdrawn at the top of the distillation column usually enters through a condenser.

The operating temperature in the condenser is preferably 10-50°C, preferably 2045°C, particularly preferably 30-40°C.

In accordance with the present invention, for example, cooling coil condensers or coil condensers, jacketed tubular condensers, plate type heat exchangers and shell and tube heat exchangers can be used.

The condenser typically produces a condensate containing predominantly methanol.

The condensate produced in the condenser, preferably in excess of 50% by volume, is refluxed to the top of the distillation column, preferably in excess of 65% by volume, most preferably in excess of 80% by volume.

The portion of the condensate that is not recycled can be removed from the process and reused as an inhibitor to prevent the formation of methane hydrate in the raw natural gas.

In the bottom part of the distillation column, as a rule, carry out the removal of the bottom stream containing mainly water.

The methanol content of the bottom stream obtained in step e) is preferably 10 ppmw-5 wt%, more preferably 100 ppmw-3 wt%, most preferably 200 ppmw. ppm wt%.

Recirculation of the bottom stream from distillation step e).

According to the present invention, at least part of the bottom stream obtained in step e) of distillation is returned to the regenerator used in step b).

Preferably, the bottom stream from distillation step e) is recycled to the regenerator, in an amount of 50-100% by volume, more preferably 70-100% by volume, most preferably 90-100% by volume. In a preferred embodiment of the invention, the bottom stream obtained in step e) of distillation is returned to the regenerator in its entirety (100% by volume). This can reduce the supply of fresh water needed to maintain water balance in the overall process.

If the regenerator does not have an additional backwash zone, the bottom stream obtained from distillation step e) is preferably fed back to the top of the regeneration zone or above the regeneration zone via a feeder.

If the regenerator has an additional backwash zone, the bottom stream from distillation step e) is preferably fed back to the top of the backwash zone or above the backwash zone via a feeder.

The supply of the bottom stream obtained in step e) to the regenerator is preferably carried out as described above.

The bottom stream from distillation step e) is preferably fed as wash water back to the top of the regeneration zone or above the regeneration zone, and in the case of a backwash zone, to the backwash zone as described above.

If necessary, together with the bottom stream obtained in step e), additional fresh water can be supplied to the regenerator. This water supply can be carried out through the same supply device. Alternatively, water may be supplied through a separate feeder.

However, the regenerator is fed preferably exclusively with the condensate obtained in step e), without fresh water, as described above.

In a preferred embodiment of the invention, the bottom stream obtained in step e) is used as a heat transfer medium in a heat exchanger before it is recirculated to the regenerator. Preferably, the bottom stream from step e) is used as heat transfer medium in a heat exchanger that heats the overhead regenerator condensate from step d) before it is sent to distillation step e). This embodiment of the invention makes it possible to reduce power consumption.

Device.

The present invention also relates to a device for neutralizing a fluid stream containing methanol and at least one acid gas according to claim 1, including the following components:

a) an absorber comprising an absorption zone, at least one feeder for the absorbent, one feeder for the fluid stream to be neutralized, a liquid outlet channel for the loaded absorbent, a gas outlet channel for the neutralized fluid stream and, if necessary, a backwash zone with a feeder for a flushing agent;

b) a regenerator containing a regeneration zone, an evaporator, a supply device for loaded absorbent, a liquid outlet channel at the bottom of the regenerator and a gas outlet channel at the top of the regenerator;

c) at least one upper condenser connected to the gas outlet of the regenerator, comprising a gas outlet and a condensate outlet; And

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d) a distillation column comprising a condenser, an evaporator, a feeder for removing condensate from the upper condenser, a vapor outlet in the upper region of the column, and a liquid outlet in the bottom of the distillation column, the regenerator comprising a feeder connected to a liquid outlet in the bottom distillation column.

A preferred embodiment of such a device is shown in FIG. 1.

In FIG. 2 shows a preferred embodiment of the invention, in which the regenerator further comprises a backwash zone.

The absorber is preferably in the form of an absorption column or absorption tower.

The absorption column preferably contains an absorption zone. Within the scope of this invention, an absorption zone is a section of an absorption column in which a fluid stream is combined with an absorbent for mass transfer. In order to improve contact and create a larger boundary mass transfer surface, the absorption zone preferably contains built-in elements, for example, fillers, nozzles and/or plates.

When using a column with fillers or packings, the absorption zone is preferably divided into two to four sections located one above the other, which are separated from each other by carrier and support and/or distribution plates.

If the absorption zone contains fillers or packings, the height of the fillers/packings in the absorption zone is preferably in the range of 5-20 m, particularly preferably 6-15 m and very preferably 8-14 m.

If the absorption zone contains trays, then the number of absorption zone trays is preferably in the range of 8-30, particularly preferably 12-25 and very preferably 15-23 trays.

In the lower part of the zone or below it is a supply device for the flow of fluid to be neutralized.

Above the absorption zone, preferably at the top of the absorption column, there is preferably a vent for the fluid stream to be neutralized.

Preferably, a fluid separator is installed in the area of the outlet channel for the neutralized fluid flow.

In accordance with a particularly preferred embodiment of the invention, a feeder for washing agent is located in the upper part of the absorption zone or above the absorption zone.

According to a particular embodiment of the invention, the absorber includes an additional backwash zone above the absorption zone.

The backwash zone, as a rule, is made as an absorber section in the form of a distillation section located above the absorbent feeder. The backwash zone preferably has fillers or nozzles and/or trays to enhance contact between the fluid stream and the cleaning fluid. In particular, the backwash zone comprises trays, more preferably valve trays, bubble cap trays, Tormann trays, or mesh trays.

Preferably, above the backwash zone there is a dispenser for the flushing agent.

The backwash zone contains preferably 1-7 trays, more preferably 2-6, most preferably 3-5 trays, the height of the nozzles (fillers/nozzles) is preferably 1-6 m, more preferably 2-5 m, most preferably 2-3 m .

Below the backwash zone, there may be a cleaning fluid collection tray from which the cleaning fluid will be recirculated. In this case, the recirculation is usually carried out by means of a pump, which pumps the cleaning liquid from the dish for collecting the cleaning liquid to the feeder. In the case of recirculation, the cleaning liquid can be cooled by means of a heat exchanger.

At the bottom of the absorber is preferably located a liquid outlet channel for the loaded absorbent.

In a preferred embodiment of the invention, a heat exchanger is provided between the liquid outlet for the loaded absorbent in the absorber and the feeder for the loaded absorbent in the regenerator. The heat transfer fluid used for this heat exchanger is preferably a recycled absorbent recycle stream from the bottom of the regenerator to the absorber. In such a preferred embodiment, the energy consumption of the entire process can be reduced.

The liquid outlet channel from the absorber is preferably connected via a heat exchanger to the regenerator b) via a pipeline.

The heat exchanger can be made in the form of a plate heat exchanger or a shell and tube heat exchanger. The heat transfer medium used in the heat exchanger is preferably the bottom stream from the regenerator b).

The regenerator contains a regeneration zone, an evaporator, a supply device for the loaded absorbent, a liquid outlet channel in the bottom part of the regenerator and a gas outlet channel in the upper part of the regenerator.

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In the context of the present invention, the regeneration zone is considered as the area of the regenerator, in which the loaded absorbent is in contact with the steam that is generated in the recuperator evaporator.

To improve contact efficiency and provide a large mass transfer margin, the regeneration zone preferably includes internal elements, which are preferably fillers or nozzles and/or trays.

In a column with fillers or packings, the regeneration zone is preferably divided into 2-4 packed sections, which are located one above the other and are separated from each other by carrier and retention trays and/or a distribution tray.

If the regeneration zone includes fillers or packings, the height of the fillers/packings in the regeneration zone is preferably 5-15 m, more preferably 6-12 m and most preferably 8-12 m.

If the regeneration zone includes trays, the number of trays in the regeneration zone is preferably 10-30 trays, more preferably 15-25 trays, most preferably 17-23 trays.

The feeder for loaded absorbent is usually located above the regeneration zone or in the upper part of the regeneration zone.

The regenerator additionally includes an evaporator.

The evaporator is preferably a heat recovery evaporator, a natural circulation evaporator or a forced circulation evaporator.

The evaporator is preferably connected to the liquid outlet channel at the bottom of the regenerator via a pipeline. The term bottom generally refers to the area below the regeneration zone.

The mixture of liquid and vapor that is produced in the evaporator is preferably fed into the bottom of the regenerator through a feeder located above the liquid outlet at the bottom but below the regeneration zone.

According to a preferred embodiment, the bottom of the regenerator is divided by an absorbent collection plate. The absorbent collected in it is fed into the heat exchanger. Steam is supplied under the absorbent collecting tray and liquid is recirculated.

The regenerator further comprises a tapping point for the gaseous flow generated during the regeneration. The point of withdrawal of the gaseous stream formed during the regeneration is preferably located in the upper part of the regenerator. In the area where the tap-off point is located, a fluid separator is preferably installed.

In a particularly preferred embodiment of the invention, the regenerator further comprises a backwash zone. The backwash zone, as a rule, is made as a regenerator section in the form of a distillation section located above the regeneration zone or feeder for the loaded absorbent.

To improve contact efficiency and provide a large mass transfer margin, the backwash zone preferably includes internal elements, which are preferably fillers or packings and/or trays.

Particularly preferably, trays such as valve trays, cap trays, Thormann trays or mesh trays are located in the backwash zone.

The backwash zone preferably contains 1-10 trays, more preferably 2-7 trays, most preferably 2-6 trays.

If the backwash zone includes fillers or nozzles, the height of the internals is preferably 1-10m, more preferably 2-8m, most preferably 3-6m.

Preferably, above the backwash zone or at the top of the backwash zone, there is a liquid feeder.

The point of withdrawal of the gaseous flow generated during the regeneration is connected to the upper condenser. The upper condenser includes a gas outlet channel and a condensate outlet channel.

In accordance with the present invention, for example, cooling coil condensers or coil condensers, jacketed tubular condensers and shell and tube heat exchangers can be used.

In a preferred embodiment, the apparatus of the invention comprises at least two condensers each having one gas outlet and one condensate outlet, the first condenser being preferably air or water cooled and the second condenser preferably being cooled using a refrigerant. An advantage of this embodiment is that the methanol content of the acidic off-gases can be reduced due to more methanol condensing. As a result, the degree of methanol recovery can be increased, for example to more than 80%, of the total amount of methanol fed into the process.

The apparatus of the present invention further comprises a distillation column comprising a condenser, an evaporator, a feeder connected to a condensate outlet from the top condenser, a vapor outlet at the top of the column, and a liquid outlet at the bottom of the distillation column,

The distillation column is preferably in the form of a column with bubble caps or a column with sieve plates, or preferably in the form of a column with fillers/packings. Internal elements can be located in one or more layers. The distillation column preferably contains 3-25 trays, more preferably 5-20 trays and most preferably 7-15 trays.

The feeder connected to the condensate outlet from the top condenser is preferably located in the spatial region between 25% and 95% of the distillation column trays (counting from the bottom), more preferably in the spatial region between 40 and 60% of the fractionator trays. For example, the feeder may be located in the region of the middle of the plates.

At the bottom of the distillation column, there is preferably a liquid outlet channel.

The liquid outlet channel is preferably connected to the evaporator via a pipeline.

The evaporator is preferably a heat recovery evaporator, a natural circulation evaporator or a forced circulation evaporator.

The mixture of liquid and vapor which is produced in the evaporator is preferably fed to the bottom of the distillation column through a vapor feeder.

Steam removal is preferably carried out in the upper part of the distillation column.

The vapors generated during the distillation are sent through a pipeline to the upper condenser. The top condenser typically includes a heat exchanger and a vessel in which the liquid phase can be separated from the gas phase.

In accordance with the present invention, for example, cooling coil condensers or coil condensers, jacketed tubular condensers and shell and tube heat exchangers can be used.

The condenser typically produces a condensate containing predominantly methanol.

The condensate produced in the condenser, preferably more than 50% by volume, is returned via a pipeline to the top of the distillation column, preferably more than 65% by volume, more preferably more than 80% by volume.

That part of the condensate that is not returned can be withdrawn from the process through the pipeline and reused as an inhibitor to prevent hydrate formation at low temperatures.

According to the present invention, the regenerator has a feeder connected to a liquid outlet channel at the bottom of the distillation column.

If the regenerator does not have a backwash zone, the feeder is preferably located above the regeneration zone or at the top of the regeneration zone.

If the regenerator has a backwash zone, the feeder is preferably located above the backwash zone or at the top of the backwash zone.

In accordance with another preferred embodiment, the heat exchanger is located between the liquid outlet channel at the bottom of the distillation column c) and the feeder to the regenerator. In this heat exchanger, the effluent from the bottom of the distillation column c) is used as a heat transfer medium for the condensate coming from the top condenser of the regenerator before the exiting condensate is fed to the distillation column c).

According to a particularly preferred embodiment, the device according to the invention comprises an expansion vessel.

The expansion tank is connected to the absorber a) and the regenerator b).

Preferably, a liquid outlet channel from the bottom of the absorber is connected to the expansion vessel via a valve.

In the expansion tank, at least part of the acid gases in the loaded absorbent is converted into the gas phase and separated from the non-evaporated liquid phase.

The gas phase is generally withdrawn at the top of the expansion vessel as an acid off-gas and then removed from the process.

At the bottom of the expansion vessel, there is preferably a liquid outlet channel of the non-evaporated liquid phase, which is connected to the regenerator via a pipeline. The liquid phase feeder from the expansion vessel is preferably located above the regeneration zone.

More preferably, the heat exchanger is located between the expansion vessel and the regenerator, while in the heat exchanger the effluent from the bottom of the regenerator is used as a heat carrier.

Application of the device.

The present invention also relates to the use of the apparatus of the invention, or one of the preferred embodiments thereof, or combinations of preferred embodiments, for the production of natural gas with reduced acidity and low methanol content. Such a device can in particular be used in countries and regions where the climatic conditions require the suppression of hydrate formation using methanol.

The device can be used in accordance with the above process conditions.

Advantages.

The device of the present invention, the use of the device of the present invention and the method of the present invention, in which the bottom stream obtained in step e) is returned to the regenerator, are advantageous compared to the absorber according to the prior art, when used in the bottom stream obtained in step e), there may be a higher residual methanol content.

In distillation step e), the distillation column can be equipped with fewer trays or run at a lower evaporator capacity than in the prior art. In this way, operating costs and/or capital costs can be reduced.

Furthermore, it is an advantage of the process according to the invention that the methanol fed as an inhibitor can be recycled at a high ratio, preferably more than 80%, relative to the methanol fed. This further reduces the operating costs of the entire process.

In the context of the present invention, it has surprisingly been found that when the bottom stream obtained in step e) is fed into the regenerator according to the invention, only a small amount of absorption in the regenerated absorbent is achieved (or no absorption at all).

The reconstituted absorbent thus has such a low methanol content that the methanol which is introduced in step a) by means of the acidified liquid stream can be almost completely removed. In this way, the recycle streams can be optimally used and the supply of absorbent components can be reduced to compensate for losses.

The advantage of removing methanol from an acidified liquid stream is that the problems associated with the presence of methanol can be reduced in subsequent processing steps.

If the subsequent water removal is carried out, for example, as PSA or TSA, in which a molar sieve is used as a solid drying agent, then a 3A molar sieve must be used instead of a 4A molar sieve, since the adsorption of water does not compete with the adsorption of methanol. This also prevents other components such as H2S and ethane from being adsorbed. This allows less use of the neutralization step. A small content of methanol leads to a decrease in the coking of the molar sieve during its recovery by increasing the temperature.

For example, if glycol drying is the so-called TEG unit (TEG=triethylene glycol), the presence of methanol makes it difficult to regenerate the TEG. These disadvantages can also be reduced by the method or device according to the invention and their application.

In both cases (PSA/TSA and glycol drying) the leakage of methanol through plant parts is reduced. Particularly preferably, the water separated during the regeneration of the drying agent contains less methanol, as a result of which, if necessary, costs for the subsequent processing of water are reduced or completely avoided.

Examples.

The invention is explained in detail with the help of the following examples.

The examples are based on calculations made with a simulation model. The Pitzer model (K. S. Pitzer, Activity Coefficients in Electrolyte Solutions 2nd ed., CRC Press, 1991, Chapter 3, Ion Interaction Approach: Theory) was used to describe phase equilibrium. Simulation of absorption processes is described using the mass transfer coefficient; for details, see Asprion (Asprion, N.: None-quilibrium Rate-Based Simulation of Reactive Systems: Simulation Model, Heat Transfer, and Influence of Film Discretization, Ind. Eng. Chem. Res. (2006) 45(6), 2054 -2069). The design of the distillation column or the separation of water and methanol at the top of the regenerator was carried out using a thermodynamic model based on the use of NRTL to describe the vapor-liquid balance of aqueous methanol.

The pressure given in this document is an absolute pressure.

In this document, nm ³ /h means the volumetric flow indicated in normal cubic meters per hour. The normal cubic meter refers to a temperature of 273.15 K and a pressure of 1.01325 bar. All information in the unit vol.% also applies to these conditions.

For all examples, the following process conditions are used.

Feed gas: 0.2 vol% CO2, 520 vol. ppm methanol, trace hydrocarbons (CH4, C2H6) at 26°C and 63.5 bar.

Absorbent: Amine solution consisting of piperazine and methyl diethanolamine with a total amine content of 40% by weight. For 1000 Nm ³ /h of gas supplied, 0.1 m ³ /h of regenerated absorbent is used. The recovered absorbent has a temperature of 35°C.

The absorption column has as built-in elements a filler with a total filling height of 14 m.

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The regenerator for the regeneration column also uses packings with a filling height of 10 m. The regenerator operates at a pressure of 1.5 bar.

The distillation column is operated at a pressure of 1.25 bar. In the simulation, the column is modeled with 10 theoretical separation stages. The feed is in the 6th step, counted from the bottom.

All examples must perform the same partitioning task, defined in the following.

The methanol content of the acidified liquid stream (natural gas) obtained at the top of the absorber must not exceed 1 ppm v/v.

The CO ₂ content of the acidified liquid stream (natural gas) obtained at the top of the absorber must not exceed 15 ppm v/v.

The methanol recovered at the top from the methanol distillation must have a purity greater than 96% by weight.

In the following, only the difference in relation to the distillation step e) will be discussed, since no significant differences arise with respect to the main operating parameters in the absorption, regeneration, condensation and recirculation steps a) to d).

Example 1

Simulate the method in the plant according to FIG. 1. The method includes an absorption column, an expansion tank (high-pressure flash tank), a regenerator with an evaporator, and an overhead condenser. The liquid stream (methanol+water), which is condensed in the upper condenser, is fed through a heat exchanger to a downstream column. Here, methanol (upper product) and water (lower product) are separated by distillation. The bottom product is fed back to the top of the regenerator.

The reflux ratio v in the distillation column is 7.5. The degree of regeneration of methanol is 90% of the amount of methanol in the fluid stream that is fed to step a).

Example 2

Simulate the method in the plant according to FIG. 2. The form of execution largely corresponds to example 1, except that the regenerator was additionally included in the backwash section with three trays.

All other components, as well as the process conditions, correspond to example 1. When the backwash zone is included in the regenerator with the same evaporator capacity in the regenerator, as well as with methanol distillation, the degree of methanol regeneration is also 90%. The backwash section makes it possible to reduce the amine content in the regenerator condenser and therefore in the distillation section; in addition, the amount of amines dissolved in the gas is reduced and the possible droplet entrainment through the backwash section is reduced.

Comparative example 1.

Based on the patent application RU2602908, the method according to FIG. 3. The raw gas stream to be treated is identical to the two examples detailed above; in addition, a device of the same dimensions and an evaporator of the same capacity (regenerator and distillation stage) were used. The significant difference is that the methanol distillation water is returned directly to the top of the absorption column rather than to the top of the regenerator as previously described. With the same number of trays and evaporator capacity in the methanol in purified natural gas column, it is no longer possible to achieve the required methanol content (<1 ppmv) using the described embodiment. The residual methanol content is 27 vpm In other words, to achieve the same degree of methanol recovery, it is necessary to use a distillation column with more trays and/or a higher evaporator capacity.

Claims (16)

1. A method for producing a neutralized fluid stream from a fluid stream containing methanol and at least one acid gas, comprising: a) an absorption step in which the fluid stream is brought into contact with the absorbent in the absorber to produce an absorbent loaded with methanol and acid gases and at least partially neutralized fluid stream; b) a regeneration step, in which at least one part of the loaded absorbent obtained in step a) is regenerated in the regenerator, and at least partially, the recovered absorbent and a gaseous stream containing methanol and at least one acid gas are obtained; c) a recycling step in which at least a portion of the regenerated absorbent stream obtained in step b) is returned to absorption step a) d) a condensation step, in which a condensate containing methanol and water is obtained from the gaseous stream obtained in step b); e) a distillation step in which at least a portion of the condensate obtained in step d) is - 16 041769 correct in the distillation column, receiving the top stream containing methanol, and the bottom stream containing water; characterized in that at least part of the bottom stream obtained in step e) is returned to the regenerator. 2. The method according to claim 1, characterized in that the fluid stream used in the method contains methanol in the range of 50-5000 ppm. 3. The method according to one of claims 1 and 2, characterized in that the fluid stream used in the method contains hydrocarbons, and the hydrocarbons used in the method contain methane in the range of 90-99.5 vol.%, and / or moreover, the used in the process, the fluid stream contains acid gases in the range of 0.01-40 vol.%. 4. Method according to one of claims 1 to 3, characterized in that an additional pressure reduction step is carried out between the absorption step a) and the regeneration step b). 5. Method according to one of claims 1 to 4, characterized in that 50-100% by volume of the bottom stream from step e) is returned to the regenerator. 6. The method according to one of claims 1 to 5, characterized in that at least part of the bottom stream obtained in step e) is returned to the upper region or above the regeneration zone in step b), or in that the regenerator, used in step b), contains a regeneration zone and a backwash zone, and the loaded absorbent is introduced between the regeneration zone and the backwash zone, and at least part of the bottom stream obtained in step e) is returned to the upper region or above the backwash zone . 7. Method according to one of claims 1 to 6, characterized in that the pressure in the upper zone of the distillation column in step e) is in the range of 1-3 bar. 8. Process according to one of claims 1 to 7, characterized in that the distillation column in step e) contains 3 to 25 trays. 9. Process according to one of claims 1 to 8, characterized in that the distillate obtained in the condenser of the distillation column in step e) is returned to the extent of more than 50% by volume as reflux to the distillation column. 10. Method according to one of claims 1 to 9, characterized in that at least two condensers are used in step d) of condensation, wherein the first condenser is cooled with air or cooling water and the second condenser is cooled with a coolant. 11. The method according to one of claims 6-10, characterized in that the backwash zone of the regenerator contains trays or fillers or nozzles, and the number of trays is in the range of 1-10 trays, or the height of the fillers / nozzles is in the range of 1-10 m. 12. The method according to one of claims 1 to 11, characterized in that the absorbent is a water absorbent. 13. The method according to one of claims 1 to 12, characterized in that the neutralized fluid stream obtained in step a) is subjected to one or more of the following processing steps: aa) water removal; bb) mercury removal; cc) nitrogen removal; dd) removal of natural gas condensates; and/or ee) liquefaction. 14. A device for neutralizing a fluid stream containing methanol and at least one acid gas, by the method of claim 1, comprising: a) an absorber comprising an absorption zone, at least one feeder for absorbent, one feeder for a fluid stream to be neutralized, a liquid outlet channel for the loaded absorbent, a tapping point for the neutralized fluid stream; b) a regenerator containing a regeneration zone, an evaporator, a supply device for loaded absorbent, a liquid outlet channel at the bottom of the regenerator and a gas outlet channel at the top of the regenerator; c) at least one upper condenser connected to the gas outlet of the regenerator, comprising a gas outlet and a condensate outlet; And d) a distillation column comprising a condenser, an evaporator, a feeder for removing condensate from the upper condenser, a vapor outlet in the upper region of the column, and a liquid outlet in the bottom of the distillation column, the regenerator comprising a feeder connected to a liquid outlet in the bottom distillation column. 15. The device according to claim 14, characterized in that the absorber further comprises a backwash zone with a feeder for the flushing agent. 16. Use of the device according to claim 14 or 15 as a device for the production of neutralized natural gas with a low methanol content.