FR3026652A1 - PROCESS FOR REMOVING ACIDIC COMPOUNDS FROM A GASEOUS EFFLUENT WITH AN ABSORBENT SOLUTION BASED ON DIAMINES BELONGING TO THE 1,3-DIAMINO-2-PROPANOL FAMILY - Google Patents

Abstract

The invention relates to a method for removing acidic compounds contained in a gaseous effluent by contacting in an absorption column (101) a gaseous effluent (1) with an aqueous absorbent solution (2) comprising one or more diamines belonging to the 1,3-diamino-2-propanol family and corresponding to the following formula (A): The process comprises a regeneration step of the acid-enriched absorbent solution obtained after contacting in the column ( 101), as well as a step of washing with water in a specific section (100) of the absorption column (101) to limit the amount of diamine entrained in the treated gas. The process according to the invention makes it possible to limit the amount of absorbing solution used.

Description

Field of the Invention The present invention relates to the field of deacidification processes of a gaseous effluent. The invention is advantageously applicable to the treatment of industrial gas and natural gas.

General Context Absorption processes employing an aqueous amine solution are commonly used to remove acidic compounds present in a gas, in particular carbon dioxide (002), hydrogen sulfide (H2S), oxysulfide carbon (COS), carbon disulfide (CS2), sulfur dioxide (SO2) and mercaptans (RSH) such as methyl mercaptan (CH3SH), ethyl mercaptan (CH3CH2SH) and propyl mercaptan (CH3CH2CH2SH). The gas is deacidified by contact with the absorbent solution, and the absorbent solution is thermally regenerated. For example, US 6,852,144 discloses a method for removing acidic compounds from hydrocarbons using a water-N-methyldiethanolamine or watertriethanolamine absorbent solution containing a high proportion of a compound belonging to the following group: piperazine and / or methylpiperazine and / or or morpholine.

A limitation of the absorbent solutions commonly used in deacidification applications is an insufficient selectivity of absorption of H25 compared to 002. Indeed, in certain cases of deacidification of natural gas, selective removal of H25 is sought. limiting this absorption to the maximum. This constraint is particularly important for gases to be treated which already contain a content of 002 less than or equal to the desired specification. A maximum absorption capacity of H25 with a maximum selectivity of absorption of H25 with respect to 002 is then sought. This selectivity makes it possible to maximize the quantity of gas treated and to recover an acid gas at the regenerator outlet having a highest possible concentration in H25 which limits the size of the sulfur chain units downstream of the treatment and guarantees a better operation. In some cases, an H25 enrichment unit is needed to concentrate the acid gas in H25. In this case, the most selective amine is also sought. Tertiary amines, such as N-methyldiethanolamine, or congested secondary ones exhibiting slow reaction kinetics with CO2 are commonly used, but have limited selectivities at high H2S loading rates.

Another limitation of the absorbent solutions commonly used in total deacidification applications is the kinetics of CO 2 capture or SOC too slow. In the case where the desired specifications on the CO2 or in COS are very advanced, one seeks a kinetics of reaction as fast as possible so as to reduce the height of the absorption column. This pressure equipment represents a significant part of the investment costs of the process. Whether CO2 uptake kinetics and maximum COS are sought in a total deacidification application, or a minimum CO2 capture kinetics in a selective application, it is always desired to use an absorbent solution having the greatest possible cyclic capacity. This cyclic capacity, denoted by Aa, corresponds to the difference in charge ratio (a designating the number of moles of acidic compounds absorbed n acid gas per kilogram of absorbent solution) between the absorbing solution supplying the absorption column and the absorbing solution withdrawn in bottom of said column. Indeed, the more the absorbent solution has a high cyclic capacity, the more the flow of absorbent solution that must be used to deacidify the gas to be treated is limited. In gas treatment processes, the reduction of the absorbent solution flow rate also has a strong impact on the reduction of investments, especially in the dimensioning of the absorption column. Another essential aspect of industrial gas treatment or flue gas treatment operations is the regeneration of the separating agent.

Depending on the type of absorption (physical and / or chemical), regeneration by expansion, and / or distillation and / or entrainment by a vaporized gas called "stripping gas" is generally envisaged. The energy consumption necessary for the regeneration of the solvent can be very important, which is particularly true in the case where the partial pressure of acid gases is low, and represent a considerable operating cost for the process. This energy consumption can be broken down into three different positions: the energy required to heat the solvent between the head and the bottom of the regenerator, the energy required to lower the partial pressure of acid gas in the regenerator by vaporization of a gas. stripping, and finally the enthalpy necessary to break the chemical bond between the amine and the acid gas. The first two stations are proportional to the flow rates of absorbent solution that must be circulated in the unit to achieve a given specification. To reduce the energy consumption associated with the regeneration of the solvent, it is therefore preferable once again to maximize the cyclic capacity of the solvent. One way envisaged to increase the cyclic capacity of the solvent and to reduce the flow rate circulating in the unit is to increase the concentration of amine.

This concentration is, however, often limited to 50% in order to limit the dynamic viscosity of the absorbent solution, beyond which the increase in viscosity slows the transfer of material and the absorption kinetics, which requires an increase in the absorption height to achieve the desired acid gas specifications in the treated gas.

Depending on the absorbent solution used and the type of gas to be treated, the volatility of the amine can cause a significant entrainment of the amine in the treated gas at the outlet of the absorption column. The amount of amine entrained must be reduced to below an acceptable maximum, in particular for the drying and degassing units downstream of the deacidification for a natural gas for example. While respecting this specification, the rate of loss of amine by vapor pressure must be reduced to limit the operating costs related to amine additions. It is known, to limit these losses of amines, to implement a washing section downstream of the absorption zone of acidic compounds by the amine solution.

There is thus a need to provide compounds which are good candidates for the deacidification of gases, in particular for the selective removal of H25 with respect to CO2, and which make it possible to operate at lower operating costs, including those related to regeneration energy and amine losses by entrainment, and investments, among which the costs associated with the absorption column and the washing section. It is therefore an object of the present invention to overcome one or more of the above-mentioned disadvantages of the prior art by providing a method for removing acidic compounds, such as 002, H2S the COS, the CS2 and the mercaptans, by the use of a family of specific amines whose properties make it possible to limit the quantity of absorbing solution used.

SUMMARY OF THE INVENTION The present invention relates to a process for removing acidic compounds contained in a gaseous effluent, such as natural gas and fumes, comprising: a) a step of absorption of the acidic compounds by contacting the effluent with an aqueous solution comprising at least one diamine belonging to the family of general formula (A) defined below, so as to obtain a gaseous effluent depleted of acidic compounds and comprising diamine, and an absorbent solution loaded with compounds acids; b) a washing step in a washing section of the gaseous effluent depleted in acidic compounds obtained in step a) by contacting with a stream of liquid water, to obtain a dehydrated deacidified gaseous effluent and a flow of water enriched in diamine; c) at least one regeneration step of the absorbent solution loaded with 25 acid compounds from step a). The general formula (A) is the following: R 1 -R 3 1 1 R 2 OH R 4 (A) in which: the radicals R 1 and R 3 are identical or different from each other, and are hydrocarbon chains, branched or unbranched, comprising from 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms; the radicals R2 and R4 are chosen independently from a hydrogen atom and a hydrocarbon chain, branched or unbranched, containing from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms; the two radicals R1 and R2 and / or the two radicals R3 and R4 are connected to each other or not by a covalent bond to form a ring consisting of 5, 6 or 7 atoms. According to the invention, the nitrogen compound corresponding to the general formula (A) may be chosen from the following compounds: 1,3-Bis (dimethylamino) -2-propanol represented by the following formula: - (1-Dimethylamino-3-tert-butylamino) -2-propanol represented by the following formula: 1,3-Bis (tert-butylamino) -2- [1] propanol represented by the following formula: ## STR2 ## The diamine corresponding to the general formula (A) may also be chosen from the following compounds: 1,3-bis (diethylamino) -2-propanol, 1, 3- bis (methylamino) -2-propanol, 1,3-bis (ethylmethylamino) -2-propanol, 1,3 bis (n-propylamino) -2-propanol, 1,3-bis (isopropylamino) - 2-propanol, 1,3 bis (n-butylamino) -2-propanol, 1,3-bis (isobutylamino) -2-propanol, 1,3-bis (piperidino) -2-propanol, and 1 , 3-bis (pyrrolidino) -2-propanol.

The absorbent solution may comprise from 5% to 95% by weight of the diamine, preferably from 10% to 90% by weight of the diamine, and from 5% to 95% by weight. 0 weight of water, and preferably between 10 (3/0 and 90% by weight of water.) According to a particular implementation of the process, the absorbent solution comprises between 70% and 95% by weight of the diamine, preferably Between 85% and 95% by weight of the diamine, and between 5% and 30% by weight of water, preferably between 5% and 15% by weight of the absorbent solution. 3/0 and 95 (3/0 weight of at least one additional amine being either a tertiary amine, a secondary amine comprising two secondary carbon atoms alpha to the nitrogen atom, or a secondary amine comprising at least at least one tertiary carbon atom alpha to the nitrogen atom, said additional amine may be a tertiary amine selected from the group consisting of: N-methyldiethanolamine, triethanol amine, diethylmonoethanolamine; dimethylmonoethanolamine; ethyldiethanolamine. The absorbent solution may further comprise a non-zero amount and less than 30 weight percent of at least one primary amine or secondary amine.This primary or secondary amine is selected from the group consisting of: monoethanolamine Diethanolamine, N-butylethanolamine, aminoethylethanolamine, diglycolamine, piperazine, 1-methylpiperazine, 2-methylpiperazine, homopiperazine, N- (2-hydroxyethyl) piperazine and N- (2-hydroxyethyl) piperazine; 2-aminoethyl) piperazine, morpholine, 3- (methylamino) propylamine, 1,6-hexanediamine, N, N-dimethyl-1,6-hexanediamine, N, N'-dimethyl-1,6-hexanediamine; N-methyl-1,6-hexanediamine, N, N ', N'-trimethyl-1,6-hexanediamine The absorbent solution may further comprise a physical solvent selected from the group consisting of methanol, ethanol, 2-ethoxyethanol, triethyleneglycoldimethylether, tetraethyleneglycoldimethylether, pentaethylene glycoldimethylether, hexaethyleneglycoldimethylether, heptaethyleneglycoldimethylether, octaethylenegolcoldimethylether, diethylene glycol butoxyacetate, glycerol triacetate, sulfolane, N-methylpyrrolidone, N-methylmorpholin-3-one, N, N-dimethylformamide, N- Formyl morpholine, N, N-dimethyl-imidazolidin-2-one, N-methylimidazole, ethylene glycol, diethylene glycol, triethylene glycol, thiodiglycol, and tributyl phosphate. Advantageously, a portion of the stream of water is recycled a diamine-enriched product obtained at the bottom of the washing section in step b) at the top of the washing section. According to a particular implementation of the process, the flow rate of the flow of liquid water introduced into the washing section during step b) is increased to reduce the amount of diamine in the gaseous effluent that has been deacidified, and is separated by distillation. the diamine of said diamine-enriched water stream withdrawn from the washing section to compensate for excess liquid water supplied. The absorption step of the acidic compounds can be carried out at a pressure of between 1 bar and 200 bar, and at a temperature of between 20 ° C. and 100 ° C., and the regeneration step of the absorbent saline loaded with compounds. acid can be carried out at a pressure between 1 bar and 10 bar and at a temperature between 100 ° C and 180 ° C. The process according to the invention may comprise a step of relaxation of the absorbent solution produced before the regeneration step of the aqueous solution. The regeneration step of the process according to the invention can be carried out by thermal regeneration, optionally supplemented by one or more expansion steps. The gaseous effluent may be chosen from natural gas, synthesis gases, combustion fumes, blast furnace fumes, refinery gases such as synthesis gas, cracked gases, combustible gases. , acid gases from an amine unit, gases from a reduction unit at the bottom of the Claus process, biomass fermentation gases, cement gases, incinerator fumes. The process can be carried out for the selective removal of H2S with respect to CO2 from a gaseous effluent comprising H2S and 002. Other features and advantages of the invention will be better understood and will be apparent. clearly on reading the description given below, with reference to the appended figure and given by way of example. BRIEF DESCRIPTION OF THE FIGURE FIG. 1 represents a schematic diagram of the implementation of an acid gas treatment process. In the diagrams of the present description illustrating the preparation of the nitrogen compounds according to the invention, the arrows represent reaction steps. These are reaction schemes. DETAILED DESCRIPTION OF THE INVENTION In the present invention, a gas comprising acidic compounds is deacidified by contacting with an aqueous solution comprising at least one compound selected from particular diamines belonging to the family of 1,3-diamino- 2-propanol, making it possible to achieve very high loading rates of acid compounds, that is to say up to two moles of acidic compounds per mole of absorbent compounds. Composition of the Absorbent Solution The absorbent solution used in the process according to the invention comprises: - water; at least one diamine chosen from diamines of the 1,3-diamino-2-propanol family corresponding to the following general formula (A): ## STR3 ## in which: R 1 and R 3 are chains hydrocarbonaceous, branched or unbranched, having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms. R-1 and R3 are the same or different from each other. R2 and R4 are either a hydrogen atom or a hydrocarbon chain, branched or unbranched, having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms. When R 2 and R 4 are not hydrogen, R 1 and R 2, as well as R 3 and R 4, may be joined together to form a ring, preferably 5 to 6 or 7 atoms. The ring thus formed by linking R-1 and R2, and / or by linking R3 and R4, comprises the nitrogen atom of the amine function concerned. Preferably, the absorbent solution used according to the invention comprises at least the compound covered by the following formula (A): 1,3-Bis (dimethylamino) -2-propanol represented by the following formula According to another embodiment, the absorbent solution used according to the invention comprises at least the compound covered by the formula (A) cited below: (1-dimethylamino-3-yl) tert-butylamino) -2-propanol of the following formula: According to another embodiment, the absorbent solution used according to the invention comprises at least the compound covered by the formula (A) cited below: 1,3-Bis (tert-butylamino) -2-propanol of the following formula: According to another embodiment, the absorbent solution used according to the invention comprises at least the compound covered by the formula (A) chosen from one of the following molecules: 1,3-Bis (diethylamino) -2-propanol, 1,3-bis (methylamino) -2-propanol, e 1,3-bis (ethylmethylamino) -2-propanol, 1,3-bis (n-propylamino) -2-propanol, 1,3-bis (isopropylamino) -2-propanol, 1,3-bis (n-butylamino) -2-propanol, 1,3-bis (isobutylamino) -2-propanol, 1,3-bis (piperidino) -2-propanol, and 1,3-bis (pyrrolidino) -2 propanol. The absorbent solution may comprise a mixture of diamines according to the general formula (A). The compounds according to the general formula (A) have a capacity to absorb a quantity of acidic compounds which is much greater than the amines conventionally used. With a solution comprising a conventional amine, such as methyldiethanolamine (MDEA) well known to those skilled in the art, the amount of absorbed acidic compounds is limited to always less than 1 mole of acidic compounds per mole of absorbent compounds under the classic conditions of industrial implementation. In general, the deacidification processes are conventionally operated so that 1 mole of absorbing molecules absorbs between 0.2 and 0.7 moles of acidic compounds. The compounds of general formula (A), such as 1,3-bis (dimethylamino) -2-propanol, can surprisingly absorb up to 2 moles of acidic compounds per mole of absorbent compounds. According to the invention, the absorption step is carried out so that the mole of absorbent compounds absorbs at least 0.4 or even 0.5 and preferably at least 0.7 moles of acidic compounds. The rate of acidic compounds absorbed according to the invention results, for a given gas and for a target specification, a significant reduction, up to 50% (3/0) of the required flow of absorbent solution. the size of the absorbers, the size of the regenerator and a significant reduction of the energy supplied by the reboiler during the regeneration step of the absorbent solution The charge rate of the absorbing solution is the number of moles of compounds Acids which have reacted with one mole of absorbent compounds In order to achieve a charge rate greater than 0.4, or even 0.5, and preferably greater than 0.7, the flow rate of absorbing solution is regulated and adjusted. and / or the composition of the absorbent solution, depending on the flow rate of the gas to be treated and the partial pressure of acidic compounds The inventors have also demonstrated that the compounds according to the general formula (A) allow ent to improve the absorption selectivity of hydrogen sulfide with respect to CO2 and therefore are of interest for the process used in the case of a selective deacidification. The compounds according to general formula (A) have a very good solubility in aqueous solution, in particular thanks to the presence of the hydroxyl group. The diamines according to the general formula (A) may be in variable concentration in the absorbent solution, and the absorbent solution may thus comprise between 5% and 95% (3/0) of at least one diamine according to the formula ( A), preferably between 10 (3/0 and 90%) and between 5% and 95% by weight of water, and preferably between 10% and 90% by weight of water, inclusive. According to one embodiment, the absorbent solution may comprise between 20% and 60% by weight of at least one diamine according to formula (A), preferably between 25% and 50%, and between 40% and 80% by weight. Preferably, the inventors have demonstrated that the diamines according to the general formula (A) can be used in aqueous solution at very large, much higher concentrations, preferably between 50% and 75%. than for the reference amines, while remaining efficient in terms of absorption kinetics. The use of these high concentrations makes it possible to maintain the absorption kinetics of the acidic compounds, whereas the reference amines, such as MDEA, can reach significantly higher viscosities in the same concentration ranges. Thus, the absorbent solution may comprise between 70% and 95% by weight of at least one diamine of general formula (A), or even comprise between 85% and 95% by weight of at least one of these diamines, and between 5% and 30% water, preferably between 5% and 15% water, inclusive. It is thus possible to use the diamines of general formula (A) in a process according to the invention by attaining even greater reductions in solvent flow rate because of the concentration of amine used as a percentage by weight. Furthermore, the molecules of general formula (A) are simple to implement because they form in aqueous solution a liquid which is low viscosity, even at high concentration. The inventors have also demonstrated that, surprisingly, the formulation of the compounds corresponding to the general formula (A) according to the invention with a primary or secondary amine makes it possible to bring significant gains in terms of absorption kinetics. COS and 002, compared to a conventional solvent such as MDEA mixed with the same primary or secondary amine at an identical primary or secondary amine concentration. This improvement contributes to significantly reducing the size of the absorption columns and therefore the investment costs of the process. Thus, according to one embodiment, the diamines according to the general formula (A) are formulated with one or more compounds containing at least one primary or secondary amine function. For example, the absorbent solution comprises up to a concentration of 30% by weight, preferably less than 15% by weight, preferably less than 10% by weight of said compound containing at least one primary amine function. or preferably, the absorbent solution comprises at least 0.5% by weight of said compound containing at least one primary or secondary amine function, a non-exhaustive list of compounds containing at least one primary or secondary amine function which may enter in the formulation is given below: monoethanolamine, diethanolamine, N-butylethanolamine, aminoethylethanolamine, diglycolamine, piperazine, 1-methyl-piperazine, 2-methyl-piperazine, homopiperazine, N - (2-hydroxyethyl) piperazine, N- (2-aminoethyl) piperazine, morpholine, 3- (methylamino) propylamine, 1,6-hexanediamine and all its variously N-alkylated derivatives such as for example N, N -diméthy1-1 6-hexanediamine, N, N'-dimethyl-1,6-hexanediamine, N-methyl-1,6-hexanediamine or N, N ', N'-trimethyl-1,6-hexanediamine; According to one embodiment, the absorbent solution may further contain at least one additional amine which is a tertiary amine such as methyldiethanolamine, triethanolamine, diethylmonoethanolamine, dimethylmonoethanolamine, or ethyldiethanolamine, or which is a secondary amine having a severe steric hindrance, this space being defined either by the presence of two secondary carbon atoms in alpha of nitrogen, or by at least one tertiary carbon atom in alpha of nitrogen. The concentration of tertiary or secondary secondary amine which is severely congested in the absorbent solution may be between 5% and 95% by weight, preferably between 5% and 50% by weight. very preferred between 5% and 30% by weight.

The absorbent solution according to the invention may comprise a mixture of additional amines as defined above. According to one embodiment, the absorbent solution contains organic compounds that are non-reactive with respect to the acidic compounds, commonly called "physical solvents", which make it possible to increase the solubility of at least one or more acidic compounds of the gaseous effluent . For example, the absorbent solution may comprise between 5% and 50% by weight of physical solvent such as alcohols, ethers, ether-alcohols, glycol ethers and polyethylene glycol ethers, glycol thioethers, glycol esters and alkoxy esters. and polyethylene glycol, glycerol esters, lactones, lactams, N-alkylated pyrrolidones, morpholine derivatives, morpholin-3-one, imidazoles and imidazolidinones, N-alkylated piperidones, cyclotetramethylenesulfones, N-alkylformamides, N-alkylacetamides, ether-ketones, alkyl carbonates or alkyl phosphates and their derivatives. By way of example and without limitation, it may be a solvent or a mixture of several solvents selected from methanol, ethanol, 2-ethoxyethanol, triethyleneglycoldimethylether, tetraethyleneglycoldimethylether, pentaethyleneglycol. lycoldimethylether, hexaethyleneglycoldimethylether, heptaethyleneglycoldimethylether, octaethyleneglycoldimethylether, diethylene glycol butoxyacetate, glycerol triacetate, sulfolane, N-methylpyrrolidone, N-methylmorpholin-3-one, N, N-dimethylformamide, N-formyl morpholine, N, N-dimethylimidazolidin-2-one, N-methylimidazole, ethylene glycol, diethylene glycol, triethylene glycol, thiodiglycol, and tributyl phosphate. Synthesis of a diamine according to the general formula (A) The diamines corresponding to the general formula (A) can be synthesized according to any route permitted by organic chemistry.

For example, one or more primary and / or secondary amines chosen and defined by the general formulas R 1 R 2 NH and R 3 R 4 NH may be reacted with 1,3-dichloro-2-propanol or, more generally, a 1,3-dihalo-propanol. , or with epichlorohydrin, or more generally an epihalohydrin. One or more of these amines can also be reacted with glycerol. These amines may be chosen from primary or secondary alkylamines. The reaction of a primary amine with the precursor 1,3-dichloro-2-propanol or more generally a 1,3-dihalo-2-propanol, or with epichlorohydrin or more generally an epihalohydrin or with glycerol, may to give a diamine according to the general formula (A) whose two amine functions are secondary, or a tertiary amine. The reaction of a secondary amine with the precursor 1,3-dichloro-2-propanol, or more generally a 1,3-dihalo-2-propanol, or with epichlorohydrin or more generally an epihalohydrin, or with glycerol , leads to a diamine according to the general formula (A), the two amine functions are tertiary. When several of these amines are used, they can be reacted either simultaneously with the precursor molecule glycerol, epihalohydrin or 1,3-dihalo-2-propanol, or sequentially and a diamine of general formula (A) or a mixture of several molecules according to the general formula (A).

The amines may be chosen, for example, and without being exhaustive, from primary or secondary alkylamines such as dimethylamine, diethylamine, methylethylamine, isopropylamine, isobutylamine and terbutylamine. The amines may be heterocyclic and belong to the family of pyrrolidines, piperidines, homopiperidines.

As an indication, some of these synthesis routes can be schematically represented in the general scheme 1, in which RRNH is a general generic formula which represents all the amines or mixtures of primary and secondary amines leading to the molecules of the general formula (A). ). In this general representation, the formula RRNH represents both a molecule or molecules defined by the general formula R1R2NH and a molecule or molecules defined by the general formula R3R4NH. In RRNH, R corresponds to the definitions of R1, R2, R3 or R4, knowing that not all RRNH molecules are identical to each other and that all R radicals are not necessarily identical. In the case where these amines are primary amines, a single radical R will automatically be a hydrogen atom. Glyceryl Epichlorohydrin 1,3-Dichloro-2-propanol RRNH I e2 OH R OH RRNH and H20 RRNH I RRN eHCl R, Cl HCl R, N <I 0 R OH RRNH RRNH o HCI RR R OH R - Scheme 1 - 15 One of the synthetic routes may consist in the reaction of one mole of 1,3-dichloro-2-propanol with at least 2 moles of an amine or a mixture of amines corresponding to the definition of RRNH. This is a sequence of two reactions of condensation of an amine on an alkyl halide, the conditions of which are well known to those skilled in the art. Another synthetic route is to react on a mole of epichlorohydrin at least 2 moles of an amine or a mixture of amines corresponding to the definition of RRNH. In this case, it is a question of 2 reactions: i) the addition of an amine on an oxirane ring which leads to a chlorohydrin and ii) the condensation of an amine on the alkyl halide that constitutes this chlorohydrin or the intramolecular cyclization of the chlorohydrin which leads to an oxirane ring, which will react with an amine. These reactions can be carried out in simultaneous or successive ways, which can in this case favor the obtaining of an asymmetric product in which the R1 R2N- motif is different from the R3R4N- motif. 1,3-Dichloro-2-propanol may be a precursor of epichlorohydrin. A third synthetic route is the reaction of one mole of glycerol with at least 2 moles of an amine or a mixture of amines corresponding to the definition of RRNH. This is a sequence of two reactions of condensation of an amine on a primary alcohol whose conditions are well known to those skilled in the art. The condensation of an amine molecule on the secondary alcohol function, if it is not excluded, is less favorable.

In these reactions, the amines of formula RRNH may be used in excess relative to the precursor glycerol, epihalohydrin or 1,3-dihalo-2-propanol. When one of these amines is primary and used in excess, one mainly obtains a secondary amine.

Nature of the gaseous effluents The process according to the invention can be used to deacidify the following gaseous effluents: natural gas, synthesis gases, combustion fumes, blast furnace fumes, refinery gases such as synthesis gas, gas produced by cracking, fuel gases commonly referred to as "fuel gas", acid gases from an amine unit, gases from a Claus tail reduction unit, fermentation gases biomass, cement gases, incinerator fumes. These gaseous effluents contain one or more of the following acidic compounds: 002, H2S, mercaptans, COS, CS2, SO2. The combustion fumes are produced in particular by the combustion of hydrocarbons, biogas, coal, in a boiler or for a combustion gas turbine, for example in order to produce electricity. By way of illustration, the process according to the invention can be used to absorb at least 70%, preferably at least 80% (3/0 or even at least 90%) of the CO2 contained in the combustion fumes. These fumes generally have a temperature of between 20 ° C. and 60 ° C., a preson of between 1 and 5 bar and may comprise between 50 and 80% of nitrogen, between 5% and 40%. 0 of carbon dioxide, between 1% (3/0 and 20%) of oxygen, and some impurities such as SOx and NOx, if they have not been removed upstream of the deacidification process. the process according to the invention is particularly well adapted to absorb the CO2 contained in combustion fumes comprising a low partial pressure of 002, for example a partial pressure of CO2 of less than 200 mbar. for the deacidification of a synthesis gas The synthesis gas contains carbon monoxide CO, Hydrogen H2 (usually in a ratio H2 / 00 equal to 2), water vapor (usually at saturation at the temperature where the washing is done) and carbon dioxide CO2 (in the order of tens of percent). The pressure is generally between 20 and 30 bar, but can reach up to 70 bar. It may contain, in addition, sulfur impurities (H2S, COS, etc.), nitrogen (NH3, HCN) and halogenated impurities. The process according to the invention can be used to deacidify a natural gas. Natural gas consists mainly of gaseous hydrocarbons, but may contain several of the following acidic compounds: 002, H2S, mercaptans, COS, CS2. The content of these acidic compounds is very variable and can be up to 70% by volume for CO2 and 40% by volume for H 2 S. The temperature of the natural gas can be between 20 ° C and 100 ° C. C. The pressure of the natural gas to be treated can be between 10 and 200 bar The invention can be implemented to achieve specifications generally imposed on the deacidified gas, which are less than 2 (3/0 of 002, or even less than 50 ppm of CO2 to subsequently liquefy natural gas and less than 4 ppm H2S, and less than 50 ppm or less than 10 ppm total sulfur volume Process for removing acidic compounds in an effluent The process for removing the acidic compounds contained in a gaseous effluent according to the invention comprises at least: a) a step of absorption of the acidic compounds by contacting the effluent with an aqueous solution comprising at least one diamine of general formula (A): a gauze effluent Depleted acidic compounds are obtained which comprise a certain amount of diamine entrained by the gaseous effluent depleted of acidic compounds, as well as an absorbent solution loaded with acidic compounds; b) a step of washing in a washing section of the gaseous effluent depleted in acidic compounds at the end of the absorption step, by contacting with a stream of liquid water, to obtain a gaseous effluent deacidified depleted of diamine and a stream of water enriched in diamine; c) at least one regeneration step of the absorbent solution loaded with acid compounds from the absorption step. The absorption step involves contacting the gaseous effluent with the absorbent solution. The gas / liquid contact between the gas to be deacidified and the absorbing solution can be carried out at the gas availability pressure of between 1 and 200 bar and at a temperature of between 20 ° C. and 100 ° C., preferably between 40 ° C. and 60 ° C. For example, in the case of treating a natural gas, the absorption step of the acidic compounds can be carried out at a pressure of between 20 and 200 bar absolute, generally between 30 and 80 bar absolute. In the case of combustion smoke to decarbonate, the absorption step is preferably carried out at a pressure of between 1 and 5 bar absolute. During the absorption step, the acidic compounds are transferred into the absorbent solution in which they react with at least one diamine of general formula (A), alone or in admixture with other amines, according to well-known reactions of those skilled in the art, and already described in the case of alkanolamines conventionally used for the deacidification of a gaseous effluent.

The absorption step of the acidic compounds may be followed by one or more steps of relaxation of the absorbent solution, loaded with acid compounds, in order to release the co-absorbed elements. For example, in the application of the invention to the treatment of natural gas, it is possible to carry out the expansion at an intermediate pressure between that of the raw gas to be treated and the pressure of the regeneration thermal step, typically it relaxes until a pressure of between 5 and 15 bar. In the case of the treatment of a natural gas, is thus separated from the absorbent solution rich in H2S and CO2 a gas containing most of the dissolved hydrocarbons, which can be used as a fuel gas, commonly called "fuel gas". This step is not implemented in a flue gas treatment process. The absorbent solution resulting from the absorption step and containing the products of the reactions between the acidic compounds and the absorbent compounds of general formula (A), is regenerated by thermal regeneration, and optionally by expansion. The thermal regeneration step is carried out at pressures of between 1 and 10 bar absolute, and generally between 1 and 3 bar absolute. The temperature at the bottom of the column is correlated with the regeneration pressure and the amine content of the absorbent solution to be regenerated. This temperature can be between 100 ° C and 18000 and is generally between 110 ° C and 150 ° C. The acid-depleted gas from the absorption step causes a certain amount of chemical compounds from the absorbent solution, by vaporization or by mechanical entrainment, for example amines, their degradation products, or other organic compounds. or inorganic. The washing step with water following the absorption step limits the amount of absorbing solution entrained in the treated gas. The compounds according to formula (A), in particular because of their volatility, and because they can also be in high concentration in the absorbing solution, can indeed be found in a significant amount in the treated gas, causing problems already mentioned of toxicity, of expensive losses in absorbing components, of non-respect of specifications for the various uses of the treated gas. Thus, according to the invention, the volatility of the compounds according to the general formula (A) and the entrainment problems in the treated gas can be advantageously overcome by the installation of a washing section, the excess cost of which is much lower than the gains provided by the increase in capacity to absorb acid gases by said compounds.

The process according to the invention is preferably carried out for the deacidification of a natural gas, although other gases can be treated, as already described above. An example of implementation of the deacidification process according to the invention is illustrated schematically in Figure 1. The gas to be treated is admitted by a line 1 in the bottom of an absorber 101, which is an absorption column provided with means contacting between gas and liquid, for example loose packing, structured packing or trays. At the head of the absorber 101 is recovered through line 3 the gas from which are extracted H2S and CO2 absorbed by the absorbent solution, which is injected at the head of the absorber 101 by the line 2. The absorber 101 operates in generally at temperatures close to or slightly above room temperature, typically between 20 and 100 ° C, and preferably between 30 ° C and 90 ° C, and at pressures typically between 1 and 200 bar, preferably between 20 and 100 bar. According to the expected limit specifications, the treated gas obtained by line 3 can undergo a cooling step followed by a separation of the condensates. The cooling can be achieved by any suitable means such as for example a water exchanger or more commonly an air cooler. Such an optional step is not shown in FIG.

In order to limit the losses of amines in the treated gas at the top of the absorber 101, a washing section 100 is provided at the top of the absorber 101. A stream of water is injected after a possible cooling 110 by the line 16 at the top of the washing section 100 at the absorber head 101. This flow is contacted countercurrently with the treated gas from the absorption section in order to extract the absorbed absorbed solution. The washing section 100 comprises gas-liquid contacting elements, for example trays, loose packing or structured packing. The deacidified gaseous effluent depleted in amines is discharged through line 3. The amine-laden water is recovered at the bottom of the washing section 100. This surplus of washing water is then recycled via lines 17, 18 and 16. and the pump 111 at the top of the washing section 100 at the top of the absorber 101. A purge can be carried out downstream of the pump 111. According to the operating conditions, the addition of water of the process at the level of the Washing section is sufficient to limit amine losses by entrainment. Under certain conditions, it may be envisaged to increase the flow rate of the wash water to reduce the entrainment of amines in the treated gas. The recovered amines are then separated by distillation of the purge flow withdrawn from the washing section 100 to compensate for the excess water supplied. The purge flow corresponds to a portion of the stream of amine-enriched water withdrawn from the washing section. The absorbent solution rich in CO2 and H25 obtained at the bottom of the absorber 101, is sent in the line 4 and is expanded by an expansion means 102, then admitted into a flash tank 103. This expansion step is optional for the setting implementation of the method according to the invention. In the case of a natural gas, it makes it possible to obtain, via line 5, a gas containing the major part of the aliphatic hydrocarbons co-absorbed by the absorbing solution. This gas may optionally be washed with a fraction of the regenerated absorbent solution and the gas thus obtained may be used as a fuel gas. Such washing, optional, however, is not shown here. The expansion flask 103 operates at a pressure lower than that of the absorber 101 and greater than that of the regenerator 106. This pressure is generally set by the conditions of use of the fuel gas, and is typically of the order of 5 to 15 bars. This flask 103 operates at a temperature substantially identical to that of the absorbent solution obtained at the bottom of the absorber 101. For applications where the pressure of the absorber is close to atmospheric pressure, for example decarbonation of the fumes, such relaxation stage is not implemented.

The absorbent solution rich in CO2 and H2S obtained after expansion is sent via line 6 to a preheating means. There is shown in Figure 1 a heat exchanger 104 which heats the absorbent solution by heat exchange with the regenerated absorbent solution obtained at the bottom of the regeneration column 106. Any other suitable means of preheating can be used. After preheating, the absorbent solution rich in CO2 and H2S is sent via line 7, after optional passage through a circulation pump (not shown in the diagram), and after optional expansion by expansion means 105, at the top of the regenerator 106 The regenerator 106 is a column equipped with gas-liquid contacting internals, for example trays, loose or structured packings. In this regenerator the acidic compounds absorbed by the absorbent solution, in particular CO2 and H2S, are vaporized by an effect commonly called "stripping" with steam generated by the reboiler 107 at the bottom of the regenerator. These vaporized acid compounds are recovered via the line 8 at the top of the regenerator 106, cooled in the exchanger 108 and then sent via line 9 to a reflux tank 109. The water and the absorbent solution contained in the top gas of the regenerator 106 are mainly condensed, separated in the reflux tank 109 and recycled as reflux at the top of the regenerator 106 via lines 11 and 12 via the reflux pump 110. The cooling of the acidic gas can be carried out for example by a water exchanger , an air cooler or any other suitable cooling means. The acidic compounds released in gaseous form are discharged through line 10. The temperature and operating pressure conditions of the regenerator 106 depend on the type of absorbent compounds used. Regenerator 106 can operate under a pressure generally between atmospheric pressure and 10 bar, and preferably between 1.5 and 3 bar. The temperature at the bottom of the regenerator is generally between 100 and 180 ° C, and preferably between 110 and 150 ° C to prevent thermal degradation of the absorbent solution. At the bottom of regenerator 106, line 13 produces a flow of regenerated absorbent solution at high temperature, which must be cooled. Figure 1 shows a heat exchange with the absorbent solution rich in CO2 and H2S in the exchanger 104, but any other suitable cooling means can be implemented. The absorbent solution thus cooled is recycled via the lines 14 and 15 via a pump 108, then after a possible additional cooling 109 by the line 2 at the head of the absorber 101. This additional cooling can be achieved for example in a dry cooler or any other means of adequate cooling. Examples The examples below illustrate, in a nonlimiting manner, the synthesis of the compounds used in the process according to the invention, as well as some of the performances of these compounds used in aqueous solution in the process according to the invention. Example 1 Synthesis of the Molecules According to the Invention The following example illustrates the synthesis of the preferred molecules of the invention, it being understood that all the possibilities of synthesis of these molecules both at the level of the synthetic routes and the possible procedures are not here described. Synthesis of 1,3-bis (dimethylamino) -2-propanol 1,3-bis (dimethylamino) -2-propanol may be prepared by any means permitted by organic chemistry, in particular by reaction of 2 molecules of dimethylamine with a molecule of either 1,3-dichloro-2-propanol, or epichlorohydrin, or glycerol. Its synthesis has been described in particular in FR 2,844,793 or in "Symmetrical 1,3-bis-dialkylamino-2-propanols, Th. D. Perrine, J. Org. Chem (1953), 9, p1137-1141. ". Synthesis of (1-dimethylamino-3-tert-butylamino) -2-propanol To 100.0 g (1.08 mol) of epichlorohydrin in 400 ml of ethanol, 125.0 g (1.08 mol) of dimethylamine at 2 ° C to 6 ° C, then the medium is allowed to reach room temperature. 476.0 g (6.52 moles) of terbutylamine are then introduced slowly while maintaining the temperature below 25 ° C. After the end of the addition, the medium is stirred for 2 hours and then 45.6 g of sodium hydroxide in pellet and stirring is continued for 30 minutes. After evaporation of the volatiles followed by filtration and distillation under reduced pressure, 92.0 g of a product whose 13C-NMR-CDCl3 spectrum is in line with that of (1-dimethylamino-3-ter) are isolated. butylamino) -2-propanol. 45.6 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -NH-C (CH 3) 3 63.8 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -NH-C (CH 3) 3 66.8 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -NH-C (CH 3) 3 46.2 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -NH-C (CH 3) 3 49.3 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -NH-C (CH 3) 3 28.4 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -NH-C (CH 3) 3 Synthesis of a mixture of 1,3-bis (dimethylamino) -2-propanol and (1-dimethylamino-3-tert-butylamino) -2-propanol A 75.0 g (0.81 mole) epichlorohydrin in 300 ml 93.7 g of a 40% aqueous dimethylamine solution are introduced over 2 hours at 0 ° C. to 5 ° C. and the medium is then allowed to reach room temperature. Then 257.0 g (4.89 mol) of terbutylamine are slowly introduced while keeping the temperature below 25 ° C. After the end of the addition, the rilieu is stirred for 2 hours, then 34.2 g of pelletized sodium hydroxide are introduced and stirring is continued for 30 minutes. After evaporation of the volatiles followed by filtration and distillation under reduced pressure, 38.0 g of a product whose 13C-NMR-CDCl3 spectrum is in line with that of a mixture of 86% of ( 1-diméthylamino3-ter-butylamino) -2-propanol. and 14% 1,3-bis (dimethylamino) -2-propanol. 45.6 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -NH-C (CH 3) 3 63.8 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -NH-C (CH 3) 3 66.8 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -NH-C (CH 3) 3 46.2 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -NH-C (CH 3) 3 49.3 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -NH-C (CH 3) 3 28.4 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -NH-C (CH 3) 3 and 45.3 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -N (CH 3) 2 63.6 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -N (CH 3) 2 64.7 ppm (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -N (CH 3) 2 63.6 ppm: (CH 3) 2 N -CH 2 -CH (OH) -CH 2 -N (CH 3) 2 45.3 ppm: (CH 3) 2N-CH 2 -CH (OH) -CH 2 -N (CH 3) 2 Synthesis of 1,3-bis (tert-butylamino) -2-propanol In an autoclave reactor, 75.0 g (0.58 mol) of , 3-dichloro-2-propanol, 254.0 g (3.49 moles) of terbutylamine and 50 ml of water. The medium is stirred at 160 ° C. for 5 hours, then, after returning to ambient temperature, a solution of 88.8 g of sodium hydroxide in 10 ml of water is added and stirring is maintained for 30 minutes. After filtration, the excess of terbutylamine is removed by distillation. The biphasic medium is then separated. The aqueous phase is extracted with toluene, and then the organic phases are combined and distilled under reduced pressure to isolate 99.4 g of a product whose 130-NMR-OD013 spectrum is in line with that of 1,3-bis (ter -butylamino) -2-propanol. 28.7 ppm: (CH 3) 30-NH-OH 2 -CH (OH) -OH-NH-C (OH) 3 49.7 ppm: (OH) 3 C -NH-OH-CH (OH) -OH 2 -NH- C (OH 3) 3 46.5 ppm: (OH) 30-NH-CH 2 -CH (OH) -OH-NH-C (OH) 3 69.4 ppm: (OH) 30-NH-OH-CH (OH) - 0H2-NH-C (OH3) 3 46.5ppm: (OH) 30-NH-OH-CH (OH) -CH2-NH-C (OH)) 49.7ppm: (OH) 30-NH-OH-CH (OH) -OH-NH-C (OH) 3 28.7ppm: (OH) 30-NH-OH-CH (OH) -OH-NH-C (CH3) 3 Example 2: Absorbability H2S of an amine formulation. The H 2 S absorption capacity performance at 40 ° C of an aqueous solution of 1,3-bis (dimethylamino) -2-propanol, containing 45% (3/0 by weight of 1,3-bis ( dimethylamino) -2-propanol, are compared with those of an aqueous solution of N-methyldiethamolamine (MDEA) containing 50 (3/0 by weight of MDEA, which constitutes the reference solvent for selective removal in gas treatment. An absorption test is carried out at 40 ° C. on aqueous amine salifions in a thermostatically controlled equilibrium cell This test consists of injecting into the equilibrium cell, previously filled with degassed aqueous amine solution. , a known quantity of acid gas (in this case hydrogen sulphide) and then wait for the establishment of the equilibrium state The quantities of acid gas absorbed in the solvent are then deduced from the temperature and pressure measurements by means of material and volume balances The solubilities are represented in a classical way in the form of H2S partial pressures (in bar) as a function of the H2S loading rate (in moles of H2S / kg of solvent and in moles of H2S / mole of amine). In the case of selective deacidification in natural gas treatment, the partial H 2 S pressures encountered in the acid gases are typically between 0.10 and 1 bar, at a temperature of 40 ° C. By way of example, in this industrial range, the rates of H2S feedstock obtained at 40 ° C. for various partial H 2 S pressures are compared in table 1 between the absorbent solution of MDEA at 50% by weight and the absorbent solution of 1,3-bis (dimethylamino) -2-propanol at 45% w / w.

Aqueous solution of 1,3- aqueous solution of MDEA at 50% by weight at 40 ° C bis (dimethylamino) -2-propanol at 45% by weight at 40 ° C Pressure Rate of Rate of Partial Charge Rate under Load in H25 charge in H2S load in H25 (mol / kg) H25 (bar) (mol / mol (mol / kg) H2S of amine) (mol / mol of amine) 0.10 0.45 1.40 0.21 0.88 0.25 0.81 2.50 0.35 1.47 0.50 1.04 3.20 0.50 2.12 1.00 1.25 3.85 0.70 2.91 - Table At 40 ° C., regardless of the partial pressure at 1-125, the absorption capacity of the aqueous solution of 1,3-bis (dimethylamino) -2-propanol is greater than that of the MDEA solution. In fact, at a partial pressure of 0.1 bar, the loading rate in H25 is 1.40 mol / kg in the absorbent solution of 1,3-bis (dimethylamino) -2-propanol and 0.88 mol / kg in the reference MDEA absorbent solution, an increase in the absorption capacity of 59%. This increase in the absorption capacity of a 1,3-bis (dimethylamino) -2-propanol solution relative to the reference MDEA solution is 70% for a partial pressure of 0.25 bar, 51% for a partial pressure of 0.5 bar, 35% for a partial pressure of 1 bar. It is therefore found that the 45% strength aqueous solution of 1,3-bis (dimethylamino) -2-propanol has a higher H2S absorption capacity than the 50 reference aqueous solution of MDEA ( 3/0 weight in MDEA at 40 ° C, in the range of H2S partial pressures between 0.10 and 0.5 bar corresponding to a range of partial pressure representative of the usual industrial conditions In this range of partial pressure, a mole of 1,3-bis (dimethylamino) -2-propanol absorbs at least 0.40 moles of H 2 S, namely 0.45 moles of H 2 S at a partial pressure of 0.1 bar, 0.81 moles of H 2 S for a partial pressure of 0.25 bar, 1.04 mole of H2S for a partial pressure of 0.5 bar and 1.25 mole of H2S for a partial pressure of 1 bar.

EXAMPLE 3 Capacity and selectivity of removal of HS from a gaseous effluent containing H 2 S and O 2 by a solution of 1,3-bis (dimethylamino) -2-propanol: An absorption test is carried out at 40 ° C. on Aqueous amine solders in a perfectly stirred reactor on the gas side. For each solution, the absorption is carried out in a liquid volume of 50 cm 3 by bubbling a gaseous stream consisting of a nitrogen: carbon dioxide: hydrogen sulphide mixture of 89: 10: 1 in volume proportions, of a flow rate of 3ONL / h for 90 minutes. The resulting H2S loading rate (a = nb of mole of H2S / kg of solvent) is measured at the end of the test as well as the absorption selectivity with respect to 002. This selectivity S is defined by the following way: S = aH2S x (Concentration of gas mixture in CO2) a (Concentration of gas mixture in H2S) co2 aH2S Under the conditions of the test described here S = 10x to co2 By way of example, it is possible to compare the charge rates and the selectivity between an absorbent solution of 1,3-bis (dimethylamino) -2-propanol at 48% by weight and an absorbent solution of MDEA at 47% by weight, reference compound for the selective removal of H2S in treatment of gas, in Table 2. Compound Concentration T (° C) Charge in Selectivity H25 (mole / kg) MDEA 47% 40 0.16 6.3 1,3-bis (dimethylamino) -2-propanol 50% 0.27 8.1 - Table 2 - This example illustrates the gains in charge ratio and selectivity that can be achieved with an absorbent solution according to the invention. taking 48% by weight of 1,3-bis (dimethylamino) -2-propanol compared to the reference absorbent solution (MDEA 47%). Example 4: CO2 Absorption Capacity The CO2 capture capacity performance of an absorbent solution according to the invention containing 39% 1,3-bis (dimethylamino) -2-propanol and 6.7% piperazine is compared in particular to that of a 30% aqueous solution of monoethanolamine (MEA) (30%), which constitutes the reference solvent for a CO 2 capture application contained in post-combustion fumes, as well as a aqueous solution containing 39% of MDEA and 6.7% / opool of piperazine, which constitutes a reference solvent for the treatment of natural gas. An absorption test is carried out on aqueous amine solutions in a reactor. closed, perfectly stirred and whose temperature is controlled by a control system For each solution, the absorption is carried out in a liquid volume of 50 cm3 by pure CO2 injections from a reserve.The solution is previously drawn under empty before any injectio The pressure of the gas phase in the reactor is measured and an overall material balance on the gas phase makes it possible to measure the degree of charge of the solvent a = number of mole acid gas / number of mole amine. By way of example, Table 3 compares the charge rates (a = number of mole acid gas / mole number) obtained at 40 ° C. for different partial pressures of CO 2 between the absorbing solution comprising 1.3 bis (dimethylamino) -2-propanol, and the absorbent solution of MEA, for post-combustion CO 2 capture application. To change from a quantity of the charge rate obtained in the laboratory to a characteristic quantity of the process, some calculations are necessary, and are explained below for the intended application: In the case of a CO2 capture application in after-combustion, the partial pressures of CO2 in the effluent to be treated are typically 0.1 bar with a temperature of 40 ° C., and it is desired to reduce 90% of the acid gas. AaPC expressed in moles of CO 2 per kg of solvent, considering that the solvent reaches a loading level at the bottom of the absorption column corresponding to an equilibrium partial pressure at 40 ° C. equal to 50% of the partial pressure in the the effluent to be treated, ie aPPCO2 = 0.05 bar, and must at least be regenerated at a loading rate corresponding to an equilibrium partial pressure at 40 ° C equal to 50 (3/0 of the pressure under the conditions of the column head, ie aPPCO2 = 0.005 bar for real Ser 90 (3/0 abatement of 002. Aapc = (aPPCO2 = 0.05bar - a PPCO2 = 0.005bar). [A] - 10 / M where [A] is the total concentration of amine expressed in (3/0 weight, M is the molar mass of the amine, or in the case of a mixture of amines, the mass molar average of the mixture of amines in g / mol: M = [A] / ([B] / MB + [Pz] / Mpz) where [B] and [Pz] are respectively the concentrations of 1,3-bis ( dimethylamino) -2-propanol and piperazine, expressed as% by weight, MB, MPZ are the corresponding molar masses expressed in g / mol aPPCO2 = 0.05 bar and aPPCO2 = 0.005 bar are the loading ratios (mole 002 / mole of amine) of the solvent in equilibrium respectively with a partial pressure of 0.05 bar and 0.005 bar of 002. The reaction enthalpy (AH) can be obtained by calculation from several isothermal absorption of CO2 in applying the law of Van't Hoff.

Charge rate = ncoe / namine Formulation T (° C) PP002 = PPCO2 = 0.005 bar AaPC (moloo2 / kg Solvent) AH (kJ / mol 0.05 bar 002) MEA 30% + H20 40 0.50 0.41 0 , 47 92 1,3-bis (dimethylamino) -2-propanol 39% + Pz 6.7% + H20 40 0.51 0.26 0.87 - Table 3 - For post-combustion fume extraction application where the partial pressure of CO2 in the effluent to be treated is 0.1 bar, this example illustrates the greater cyclic capacity obtained thanks to an absorbent solution according to the invention, to reach a slaughter rate of 90 (3 / In this application where the energy associated with the regeneration of the solution is critical, it may be noted that the formulation according to the invention makes it possible to obtain much better performances than with the MEA, in cyclic capacity and reaction enthalpy.

By way of example, the feed ratios expressed in mole / kg (a = number of mole acid gas / mole number amine) obtained at 40 ° C. for different partial pressures of CO 2 between the absorbent solution are compared in Table 4. containing 39% of 1,3-bis (dimethylamino) -2-propanol and 6.7% of piperazine, and the absorbing solution of MDEA at 39% by weight containing 6.7% by weight of piperazine for a total decarbonation treatment application natural gas. In the case of a total decarbonation application in natural gas treatment, the partial pressures of CO2 in the effluent to be treated are typically from several hundred millibars to several bars with a temperature of 40 ° C., and it is desired to eliminate almost all CO2 for liquefaction of natural gas. In order to compare the various solvents, the An (-LNG) cyclic capacity, expressed in moles of CO 2 per kg of solvent, corresponding to different partial equilibrium pressures at the bottom of the absorption column, is calculated and considering that the solvent is completely regenerated. under the column head conditions AaLNG, PPCO2 PPCO2) x- [A1-10 / M where [A] and M are defined as previously aPPCO2 being the loading ratio (mole CO2 / mole of amine) of the solvent in equilibrium with the CO2 partial pressure considered. Cyclic absorption capacity of CO2 Aa LNG, PP CO2 (molCO2 / kg solvent) Formulation T (° C) PPCO2 = PPCO2 = 1 bar PPCO2 = 3 bar 0.5 bar MDEA 39% + Pz 6.7% 40 2, 54 2.96 3.57 1,3-bis (dimethylamino) -2-propanol 39% - Pz 40 3.13 4.13 4.44 6.7% - Table 4 - For a total decarbonation application in natural gas treatment this example illustrates the greater cyclic capacity obtained thanks to the absorbent solution according to the invention compared to the reference formulation containing 39% by weight of MDEA and 6.7% by weight of piperazine, whatever the partial pressure of CO 2 considered equilibrium, corresponding to different compositions of CO2 natural gas to be treated.

EXAMPLE 5 Kinetics of COS Absorption This example corresponds to a comparative test of COS absorption by an aqueous solution of a tertiary monoamine, MDEA, at 40% by weight, activated by piperazine at 3.3 ( 3/0 by weight and by an aqueous solution of amines containing 1,3-bis (dimethylamino) -2-propanol at 35% by weight and activated by piperazine at 3.3 (3/0 For each test, the COS absorption flux is measured by the aqueous solution of amines in a closed Lewis-cell reactor 200 g of solution are introduced into the closed reactor, regulated at a temperature of 40 ° C. C. Four successive injections of carbon fluoride of 100 to 200 mbar are carried out in the vapor phase of the reactor having a volume of 200 cc The gas phase and the liquid phase are agitated at 100 revolutions / minute and fully characterized from the point of contact. For each injection, the absorption rate of the carbon oxysulfide is measured for each injection. r pressure variation in the gas phase. An overall transfer coefficient Kg is thus determined by an average of the results obtained on the four injections. The results obtained are shown in Table 5 as the relative speed of absorption of the reference formulation of MDEA at 40% w / w activated by 3.3% piperazine (3% by weight). relative absorption being defined by the ratio of the overall transfer coefficient of the solvent to the overall transfer coefficient of the reference formulation Composition of the aqueous absorbing liquid Amine Activator Nature Concentrate Nature Concentration (mol / kg) Velocity (% absorption by relative weight of COS MDEA 40 piperazine 0.38 1.00 1,3-bis (dimethylamino) -2-propanol piperazine 0.38 1.48 - Table 5 - Examination of the results shows, under these test conditions, a speed COS absorption by 1,3-bis (dimethylamino) -2-propanol / piperazine increased by 48% relative to the MDEA / piperazine reference formulation Example 6: Absorption rate of the CO of an activated formulation Two CO2 absorption tests by absorbent solutions comprising in aqueous solution a tertiary monoamine, the MDEA, for the first test, 1,3-bis (dimethylamino) -2-propanol for the second test. These tertiary amines are formulated at 39% opoids with the same mass concentration of piperazine, ie 6.7% by weight. In each test, a CO2-containing gas is brought into contact with the absorbent liquid by operating in a vertical falling-film reactor provided in its upper part with a gas outlet and an inlet for the liquid and in its lower part. an inlet for the gas and an outlet for the liquid. Through the gas inlet, a gas containing 10% of CO2 and 90% of nitrogen is injected at a flow rate of between 30 and 50 N / h and the inlet for the liquid is introduced, the absorbent liquid is introduced with a flow rate of 0.5 11h. By the gas outlet, a CO2-depleted gas is evacuated and the liquid outlet is discharged and the enriched liquid is evacuated at 002. The absolute pressure and the liquid outlet temperature are equal to 1 bar and 40 ° C. respectively. For each test, the flow of CO2 absorbed between the gas inlet and the gas outlet is measured as a function of the flow of gas entering. For each gas flow setpoint (30; 35; 40; 45; 50 N / h), the incoming and outgoing gases are analyzed by infrared ray absorption techniques in the gas phase to determine their 002 content. From all these measurements, by carrying out two ups and downs of the range of flow rates, the overall transfer coefficient Kg, which characterizes the rate of absorption of the absorbing liquid, is deduced therefrom.

The operating conditions specific to each test and the results obtained are shown in Table 6. Composition of the aqueous absorbent solution Tertiary amine Activator Nature Concentration (% by weight) Nature Concentration (% by weight) Relative absorption rate of CO2 MDEA 39 Piperazine 6,7 1 1,3-bis (dimethylamino) -2-propanol 39 Piperazine 6,7 1,19 - Table 6 - Examination of the results in Table 6 shows the improved rate of CO2 uptake presented by solution comprising the 1,3-bis (dimethylamino) -2-propanol-piperazine combination relative to that present in the control absorbing solution containing an MDEA-piperazine mixture known to those skilled in the art.

Example 7: Viscosity of a solution of concentrated 1,3-bis (dimethylamino) -2-propanol The kinematic viscosity of various aqueous solutions of amines at 40 ° C. is measured using a capillary viscometer of Ubbelohde. The viscosity is deduced from the measurement of the flow time between two marks of the liquid interface. The flow time obtained by the average of two measurements is multiplied by the tube constant to obtain the kinematic viscosity. The dynamic viscosity is deduced by multiplying this result by the density measured on an Anton Paar densimeter DMA4100. These measurements, carried out at 40 ° C., compare in tab. 7 the dynamic viscosity of aqueous solutions of 1,3-bis (dimethylamino) -2-propanol at different concentrations, with aqueous solutions of MDEA, the reference amine for treatment applications. gas, at the same concentrations, obtained by Tjoon et al. (Journal of Chemical Engineering Data, 1994, 39, 290293) on an experimental device equivalent to ours. Compound ° A. weight Viscosity viscosity 40 ° C (mPas) relative MDEA (reference) 60 9.0 ref. 1,3-bis (dimethylamino) -2-propanol 60 9.0 = ref. MDEA (reference) 70 15.0 ref. 1,3-bis (dimethylamino) -2-propanol 70 9.5 -40% MDEA (reference) 85 29.0 ref. 1,3-bis (dimethylamino) -2-propanol 85 6.7 -77% MDEA (reference) 100 34.0 ref. 1,3-bis (dimethylamino) -2-propanol 100 2.1 -94% - Table 7 - This example illustrates that for concentrations greater than or equal to 60% by weight, the viscosity of an aqueous solution of 1,3-bis ( dimethylamino) -2-propanol is equal to or less than that of an aqueous solution of reference MDEA at the same concentration, this gain exceeding 40% for concentrations greater than or equal to 70% by weight, and exceeding 75% for higher concentrations or equal to 85% weight. Aqueous solutions containing at least 60% by weight of 1,3-bis (dimethylamino) -2-propanol, preferably at least 70%, more preferably at least 85%, therefore have a significant advantage over reference solutions. of MDEA, by their viscosity less than or equal to the reference solution and compatible with their implementation in a gas treatment process.

Very high concentration solutions of 1,3-bis (dimethylamino) -2-propanol, that is to say more than 70% by weight of 1,3-bis (dimethylamino), have been very surprisingly demonstrated. 2-propanol, and preferably more than 85% by weight, could advantageously be used for the deacidification of gas, whereas such concentrations of amines are generally problematic because of the increase in The results of Table 7 show indeed an unexpected behavior of 1,3-bis (dimethylamino) -2-propanol solutions tested vis-à-vis their viscosity, which decreases when the concentration of 1,3-bis (dimethylamino) -2-propanol increases, beyond a concentration of 70% (3/0 by weight of 1,3-bis (dimethylamino) -2-propanol. superior acid gas absorption capacity for aqueous solutions of 1,3-bis (dimethylamino) -2-propanol for mass entries close to or equivalent to those of the aqueous solutions of MDEA, as described in Examples 1, 2 and 3, the possibility of using aqueous solutions of 1,3-bis (dimethylamino) -2-propanol to high concentrations makes it possible to further increase the advantage of these absorbent solutions in terms of flow rate reductions achievable in the process. Example 8: Operating costs of a process according to the invention with washing section. This example, the result of a simulation, makes it possible to compare the investment and exploitation costs (CAP EX / OPEX) of a deacidification process of a natural gas according to the invention with a conventional method implementing an aqueous solution of MDEA. 300 MMSCFD of gas to be treated are admitted in the unit at a temperature of 40 ° C under 72 bar. This gas contains 10% of CO2, 1% of H2S and the desired absorption rate is 80% for CO2 and more than 99% for H2S in order to bring the gas to a "transport" specification that is 2 % CO2 and 4 ppm H2S in the purified gas. The two solvents compared are a solution of MDEA 45% by weight and a solution of 1,3-bis (dimethylamino) -2-propanol at 50% by weight.

The scheme of the method adopted is that shown in Figure 1, with implementation of a washing section to limit losses of amine. The washing is carried out only by the extra water required for the process. There is therefore no additional addition of water, and therefore no purge is performed.

The stages of cooling of the treated gas, at the top of the absorber, the acid gas at the top of the regenerator, and the complementary cooling of the solvent are carried out by drycoolers. The operating costs have been estimated for an operation of 8760 h / year and take into account three positions: The reboiler steam consumption for the regeneration of the solvent. This consumption was taken equally for the two solvents at 120 kg of steam per m3 of solvent to be regenerated. This item represents the majority of operating costs. Power consumption (pumps, air cooler, etc.).

The solvent additions due to amine losses in the various gases (treated gas, flash gas and acid gas), during filtration and degradation. The costs retained are 1.8E / kg for MDEA and 4E / kg for 1,3-bis (dimethylamino) -2-propanol.

Table 8 summarizes the results of this study. The use of a solvent at 50% by weight of BDMAP allows a notable gain of 32% on the flow in circulation. This gain leads to a significant reduction in the overall CAPEX of the unit (-21%). Despite higher losses of amine with 1,325 bis (dimethylamino) -2-propanol, its implementation allows a significant gain on OPEX (-32%) mainly due to the reduction of the flow of solvent in circulation resulting in a significant decrease from the steam consumption to the reboiler. Finally, even if the losses of 1,3-bis (dimethylamino) -2-propanol are 10 times greater than those in MDEA, the implementation of the washing section makes it possible to obtain losses remaining at a very high level. less than the maximum acceptable for the deacidification of gas, that is to say less than 4 lb / MMSCF. 8760 h of operation / year MDEA 1'3-bis (dimethylamino) - 45% weight 2-propanol 50% by weight Process data - Raw gas temperature (° C) 40 40 - Content Yc02 raw gas (% mol) 10 10 - Absorption rate 80% 80% - Raw gas flow rate (MMSCFD) 300 300 - Gross gas pressure (bar (a)) 72 72 - Solvent flow (m3 / h) 497 338 - Reboiler steam consumption (MW) 45 31 Loss Solvent (Ib / MMSCF) 0.048 0.433 CAPEX (ME) 52.7 41.7 -21% OPEX (ME / yr) 15.5 10.6 -32% - Solvent (keen) losses 4.30 86.96 - Electricity (kean) 773.00 526.00 - Steam (kean) 14 681 9 984 - Table 8 -.

Claims (15)

REVENDICATIONS1. Process for removing acidic compounds contained in a gaseous effluent, comprising: a) a step of absorption of the acidic compounds by contacting the gaseous effluent with an aqueous solution comprising at least one diamine belonging to the family of general formula (A), so as to obtain a gaseous effluent depleted of acidic compounds and comprising diamine, and an absorbent solution loaded with acidic compounds, the general formula (A) being the following: R 1 R 3 N R 2 R 2 R 4 (A) in which: the radicals R-1 and R3 are identical or different from each other, and are hydrocarbon chains, branched or unbranched, comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms; - The radicals R2 and R4 are independently selected from a hydrogen atom and a hydrocarbon chain, branched or unbranched, having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms; the two radicals R-1 and R2 and / or the two radicals R3 and R4 are connected to each other or not by a covalent bond to form a ring consisting of 5, 6 or 7 atoms; b) a washing step in a washing section of said gaseous effluent 25 depleted of acidic compounds obtained in step a) by contacting with a stream of liquid water, to obtain a de-acidified gaseous effluent depleted in diamine and a flow enriched water diamine; c) at least one regeneration step of the absorbent solution loaded with acid compounds from step a). 30 2. Process according to claim 1, in which the absorbing solution comprises at least 1,3-bis (dimethylamino) -2-propanol diamine of the following formula: ## STR2 ## 3. Method according to claim 1, wherein the absorbent solution comprises at least diamine (1-dimethylamino-3-tert-butylamino) -2-propanol of the following formula: 1 OH H 4. Process according to claim 1, in which the absorbing solution comprises at least 1,3-bis (tert-butylamino) -2-propanol diamine of the following formula: 5. The method of claim 1, wherein the absorbent solution comprises at least one diamine corresponding to the general formula (A) selected from the following compounds: 1,3-bis (diethylamino) -2-propanol; 1,3-bis (methylamino) -2-propanol; 1,3-bis (ethylmethylamino) -2-propanol; 1,3-bis (n-propylamino) -2-propanol; 1,3-bis (isopropylamino) -2-propanol; 1,3-bis (n-butylamino) -2-propanol; 1,3-bis (isobutylamino) -2-propanol; 1,3-bis (piperidino) -2-propanol; and 1,3-bis (pyrrolidino) -2-propanol. 10 6. Process according to one of the preceding claims, in which the absorbent solution comprises between 5% and 95% (3/0) of said diamine, preferably between 10% and 3% (3/0) by weight. said diamine, and between 5% and 95% (3/0 weight of water, and preferably between 10% and 90% by weight of water. 7. Method according to one of the preceding claims, wherein the absorbent solution comprises between 70% and 95% by weight of said diamine, preferably between 85% and 95% by weight of said diamine, and between 5% and 30% by weight. water, preferably between 5% and 15% by weight of water. 8. The process as claimed in one of the preceding claims, in which the absorbing solution further comprises between 5% and 95% by weight of at least one additional amine, said additional amine being either a tertiary amine or a secondary amine comprising two secondary carbon atoms alpha to the nitrogen atom or at least one tertiary carbon atom alpha to the nitrogen atom, and said amine preferably being selected from the group consisting of: N-methyldiethanolamine, triethanolamine, diethylmonoethanolamine, dimethylmonoethanolamine, and ethyldiethanolamine. 9. The process as claimed in one of the preceding claims, in which the absorbing solution further comprises a non-zero amount and less than 30% by weight of at least one primary amine or a secondary amine preferably chosen. in the group consisting of: - monoethanolamine - diethanolamine - N-butylethanolamine - aminoethylethanolamine - diglycolamine - piperazine - 1-methyl-piperazine, 2-methyl-piperazine; homopiperazine, N- (2-hydroxyethyl) piperazine, N- (2-aminoethyl) piperazine, morpholine, 3- (methylamino) propylamine, 1,6-hexanediamine, N, N-dimethyl-1, 6-hexanediamine, N, N'-dimethyl-1,6-hexanediamine, N-methyl-1,6-hexanediamine, and N, N ', N'-trimethyl-1,6-hexanediamine. The process according to one of the preceding claims, wherein the absorbent solution further comprises a physical solvent selected from the group consisting of methanol, ethanol, 2-ethoxyethanol, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, hexaethyleneglycoldimethylether, heptaethyleneglycoldimethylether, octaethyleneglycoldimethylether, diethyleneglycol butoxyacetate, glycerol triacetate, sulfolane, N-methylpyrrolidone, N-methylmorpholin-3-one, N, N-dimethylformamide, N-methylformamide, morpholine, N, N-dimethylimidazolidin-2-one, N-methylimidazole, ethyleneglycol, diethyleneglycol, triethyleneglycol, thiodiglycol, and tributylphosphate. 25 11. Method according to one of the preceding claims, wherein is recycled a portion of the diamine-enriched water stream obtained at the bottom of the washing section in step b) at the head of the washing section. 12. Method according to one of the preceding claims, wherein the flow rate of the flow of liquid water introduced into the washing section during step b) is increased to reduce the amount of said diamine in the gaseous effluent deacidified. and said diamine is distilled off from a portion of said diamine-enriched water stream withdrawn from the wash section to compensate for excess liquid water supplied. 13. Process according to one of the preceding claims, in which the step of absorption of the acidic compounds is carried out at a pressure of between 1 bar and 200 bar, and at a temperature of between 20 ° C. and 100 ° C., and wherein said at least one step of regenerating said absorbent solution loaded with acidic compounds is carried out at a pressure of between 1 bar and 10 bar and at a temperature of between 100 ° C and 180 ° C. 14. Method according to one of the preceding claims, wherein the gaseous effluent is selected from natural gas, synthesis gas, combustion fumes, smokes from blast furnaces, refinery gases such as gas from synthesis, gases produced by cracking, combustible gases, acid gases from an amine unit, gases from a Claus tail reduction unit, biomass fermentation gases, cement gases, incinerator fumes. 15. Method according to one of the preceding claims, implemented for the selective removal of H2S with respect to CO2 from a gaseous effluent comprising H 2 S and O 2.