Zero Liquid Discharge Amine Regeneration Method for Carbon Capture and Other Acid Gas Recovery

Abstract

The proposed technique relates to the step of removing heat-stable amine salts (HSAS) from a contaminated aqueous amine absorption solution containing amine in salt form generated during an amine-based acid gas recovery operation while reducing or avoiding the discharge of any liquid waste. At least a portion of the HSAS is removed from the contaminated aqueous amine absorption solution in an amine regeneration unit to produce a waste liquid stream containing dissolved salts and / or acids and a regenerated amine absorption solution containing reduced heat-stable amine salts. The waste liquid stream is further treated by oxidizing the waste liquid stream to an oxidation product stream containing CO2, water, and nitrogen. Optionally, the concentration of dissolved salts and / or acids in the waste liquid stream can be increased prior to oxidation. The oxidation can advantageously be carried out in a combustion unit that produces flue gas targeted for acid gas recovery as part of an integrated process.

Description

Detailed Description of the Invention

[0001] [Technical Field]

[0001] This technique relates to the removal of thermally stable amine salts from liquid streams, and more particularly to the recovery of waste liquid streams for oxidation and recycling of waste liquid streams to produce net zero liquid discharge.

[0002] [Background]

[0002] A variety of absorption processes have been proposed for removing acid gases, such as carbon dioxide, hydrogen sulfide, and sulfur dioxide, from process gas streams using absorbents containing amines.

[0003]

[0003] Such absorption processes typically require passing a process gas stream containing one or more of the acid gases through an absorption zone where it is contacted with a lean solvent containing an amine absorbent. The product gas stream has a reduced acid gas compared to the process gas stream and is withdrawn from the absorption zone as a product. A rich solvent stream containing the amine absorbent and the absorbed acid gas is also withdrawn from the absorption zone and passed through a regeneration zone, such as a stripping column, where the absorbed acid gas is desorbed from the solvent, providing a tail gas stream containing the acid gas and a stream of the lean solvent described previously herein.

[0004]

[0004] A common problem with such acid gas absorption processes is that thermally stable salts of amines are often formed either during the absorption step and / or during the regeneration step as by-products. For example, strong acids such as hydrochloric acid or sulfuric acid are present in the process gas, thermally stable salts of amines can be formed.

[0005]

[0005] When SO2 is removed from process gas by an amine-based recovery process and sulfite anions are oxidized to sulfate anions, amine thermally stable salts can also be formed. Thermally stable salts, i.e., typical anions that form thermally stable anions, in addition to sulfite anions, which are amines suitable for scrubbing H2S and CO2, include, for example, sulfate anions, thiosulfate anions, polythionate anions, thiocyanate anions, acetate anions, formate anions, nitrate anions, hydrochloride anions, and oxalate ions. Thermally stable salts generally do not have an absorption capacity for acidic gases and are not regenerable under the conditions of the process. Therefore, the level of thermally stable salts needs to be controlled to maintain an appropriate level of absorption capacity for acidic gases. The removal of thermally stable amine salts can be referred to as the regeneration of the amine-containing stream.

[0006]

[0006] Electrodialysis has been proposed as a method for removing thermally stable amine salts from an amine-containing stream. In a typical electrodialysis process, such as that described in U.S. Patent No. 5,910,611, for example, a neutralizing cation, such as sodium hydroxide, is added to a stream containing an amine thermally stable salt to dissociate the thermally stable anion (e.g., sulfate anion) from the thermally stable salt, giving a free-base form (proton-depleted) amine and a simple thermally stable salt, such as sodium sulfate. The simple thermally stable salt is then separated by conventional electrodialysis in which charged ions permeate anion- and cation-selective membranes. The free-base form of the amine is nonionic, does not permeate the membrane, and is discharged from the electrodialysis zone as a product. Often, the conventional electrodialysis process can be operated in batch mode in which the process stream is recycled until the desired amount of thermally stable salt is removed.

[0007]

[0007] Various methods including electrodialysis, such as distillation, ion exchange, and simple bleed & feed, can be utilized to remove salts. In all cases, a waste liquid stream that must subsequently be disposed of is generated. For ion exchange and electrodialysis, the waste liquid stream is typically aqueous. Electrodialysis has the advantage of producing a smaller amount of aqueous waste liquid stream. The stream contains various acids removed by the regeneration process, and depending on the electrodialysis method and / or configuration used, the waste liquid stream may consist of water, dissolved salts, and / or acids that cause the formation of heat-stable salts, possibly cations (e.g., sodium or potassium) used to neutralize said acids, certain amines, and possibly some other contaminants such as solids and trace hydrocarbons.

[0008]

[0008] There is still a need for a technique that overcomes at least some of the drawbacks of those known in the art, such as the aforementioned drawbacks that may result from the disposal / discharge of the aqueous waste liquid stream.

[0009] [Summary]

[0009] In one aspect, a method for removing heat-stable amine salts (HSAS) from a contaminated aqueous amine absorption solution containing amine in salt form generated during an amine-based acid gas recovery operation is provided. The method comprises removing at least a portion of the HSAS from the contaminated aqueous amine absorption solution in an amine regeneration unit, thereby producing a waste liquid stream containing dissolved salts and / or acids, and a regenerated amine absorption solution containing a reduced amount of heat-stable amine salts; and, treating the waste liquid stream by oxidizing it to produce an oxidation product stream containing CO2, water, and nitrogen.

[0010]

[0010] In some embodiments, the treatment of the waste liquid stream further includes adjusting the salt and / or acid concentration in the waste liquid stream before their oxidation. For example, the salt and / or acid concentration may be at least 2 wt%, at least 5 wt%, at least 10 wt%, at least 20 wt%, at least 30 wt%, at least 40 wt%, or at least 50 wt%. For example, the adjustment of the salt and / or acid concentration in the waste liquid stream may include concentrating the waste liquid stream by removing at least a portion of the water from the waste liquid stream to produce a concentrated stream. Optionally, the concentration of the waste liquid stream includes evaporation, distillation, reverse osmosis, electrodialysis, or any combination thereof.

[0011]

[0011] In some embodiments, the method includes returning at least a portion of the water removed by concentration to an amine regeneration unit, or to other units of an amine-based acid gas recovery operation and an acid gas generation operation.

[0012]

[0012] In some embodiments, the adjustment of the salt and / or acid concentration in the waste liquid stream includes controlling the operation of the amine regeneration unit for a given salt and / or acid concentration of the produced waste liquid stream.

[0013]

[0013] In some embodiments, the oxidation of the waste liquid stream includes subjecting the waste liquid stream to combustion to produce an oxidation product stream. For example, the combustion may be carried out with a burner. Optionally, the treatment of the waste liquid stream may further include recycling at least a portion of the oxidation product stream to an amine-based acid gas recovery operation. In another embodiment, the combustion may be carried out in a combustion unit of an acid gas generation operation to produce a feed gas for an amine-based acid gas recovery operation.

[0014]

[0014] In some embodiments, the method includes recovering an acid gas containing CO2 from the oxidation product stream by feeding the oxidation product stream to an absorption unit of an amine-based acid gas recovery operation, where the oxidation product stream is further contacted with an aqueous amine absorption solution for absorption of the acid gas.

[0015]

[0015] In some embodiments, when the oxidation product stream further comprises SO2 and / or SO3, the method comprises subjecting the oxidation product stream to gas conditioning in a scrubbing unit or a quenching unit to remove SO2 and / or SO3 and produce a reduced oxidation product stream; and feeding the reduced oxidation product stream to at least one absorption unit of an amine-based acid gas recovery operation, where the reduced oxidation product stream contacts an aqueous amine absorption solution to recover at least CO2, further comprising recovering acid gas from the oxidation product stream.

[0016]

[0016] For example, the method may comprise withdrawing a bleed stream from the gas conditioning step and involving feeding at least a portion of the bleed stream to an amine regeneration unit to produce a waste liquid stream. Optionally, the method may comprise combining another portion of the bleed stream with the waste liquid stream prior to oxidation of the waste liquid stream.

[0017]

[0017] In some embodiments, oxidation of the waste liquid stream may comprise feeding the waste liquid stream to a wastewater treatment unit that oxidizes salts and / or acids by contact with an oxidizing agent to produce an oxidation product stream.

[0018]

[0018] In some embodiments, the method may comprise discharging the oxidation product stream to the atmosphere.

[0019]

[0019] In some embodiments, the contaminated aqueous amine absorption solution fed to the amine regeneration unit is a slip stream of the regenerated absorption solution produced during the amine-based acid gas recovery operation. The slip stream can be fed to the amine regeneration unit continuously, semi-continuously or batchwise.

[0020]

[0020] In another aspect, recycling the recovered dissolved salt and / or acid to an initial combustion step, and burning the salt to regenerate an acid gas product, and converting the acid gas recovery to a net-zero waste liquid process, an integrated amine regeneration process for recovering a thermally stable amine salt is provided herein. In combustion, the waste liquid thermally stable amine salt is converted to water, CO2 and possibly nitrogen. Thus, for example, the resulting CO2 is mostly captured and becomes a product of the overall process, resulting in an overall net-zero emission facility or process.

[0021]

[0021] In some embodiments, the method may further include at least one feature defined herein.

[0022]

[0022] In yet another aspect, an integrated process is provided, including: Burning a fuel to produce a combustion gas stream comprising at least one of CO2, H2S, SO2 and SO3; Optionally, when SO2 and / or SO3 are present in the combustion gas stream, conditioning the combustion gas stream by feeding the combustion gas stream into a quenching unit or a scrubbing unit to remove at least a portion of at least one of SO2 and SO3 from the combustion gas stream and producing a conditioned feed gas stream; Absorbing at least one of CO2, SO2 and H2S from the conditioned feed gas stream by contacting the conditioned feed gas stream with an amine-based absorption solution to produce an enriched absorption solution and a reduced product gas stream; Desorbing at least one of CO2, SO2 and H2S from the enriched absorption solution to produce an acid gas stream and a reduced absorption solution containing a thermally stable amine salt; Feeding a slip stream (at least a portion) of the reduced absorption solution to an amine regeneration unit to remove at least a portion of the thermally stable amine salt from the slip stream, thereby producing a waste liquid stream containing dissolved salt and / or acid, and a regenerated amine absorption solution containing a reduced amount of thermally stable amine salt; For example, concentrating the waste liquid stream by removing at least a portion of the water from the waste liquid stream to produce a concentrated stream and increasing their dissolved salt and / or acid concentration; and being involved in burning the concentrated stream together with fuel to produce a combustion gas stream.

[0023]

[0023] In some embodiments, the bleed stream can further be withdrawn from a quenching unit or a scrubbing unit during conditioning, and the method further includes transferring at least a portion of the bleed stream to an amine regeneration unit for removal of heat stable salts. Optionally, another portion of the bleed stream can be involved in being transferred to a concentration step for water removal together with the waste liquid stream, thereby producing a concentrated stream.

[0024]

[0024] In some embodiments, the bleed stream can further be withdrawn from a quenching unit or a scrubbing unit during conditioning, and the method further includes transferring at least a portion of the bleed stream to a concentration step for water removal together with the waste liquid stream, thereby being involved in producing a concentrated stream.

[0025]

[0025] In some embodiments, the method may include recovering excess water from the amine regeneration unit or the concentration step and transferring the excess water to a conditioning step within the quenching unit or the scrubbing unit.

[0026]

[0026] In some embodiments, the method may further include at least one feature defined herein.

[0027]

[0027] In another aspect, a system is provided for removing heat stable amine salts from a contaminated aqueous amine absorption solution produced during the amine-based recovery of acid gas representing at least a portion of the flue gas produced by the combustion of fuel and an oxidant.

[0028] The system is An amine regeneration unit configured to receive a slip stream containing a thermally stable amine salt from a regeneration unit for amine-based acid gas recovery, and to produce a regeneration stream with reduced thermally stable salt for supply to an absorption unit for amine-based acid gas recovery, and a waste liquid stream containing dissolved salts and / or acids; A concentration unit configured to receive the waste liquid stream and produce a concentrated waste liquid stream with increased concentration of dissolved salts and / or acids in the waste liquid stream; and An oxidation unit having an inlet in fluid communication with the concentration unit and configured to supply the concentrated waste liquid stream to an oxidation unit for oxidizing the waste liquid stream to produce an oxidation product stream.

[0029]

[0028] In some embodiments, the system further includes, upstream of the amine regeneration unit, an absorption unit for contacting combustion gas with an absorption solution for absorbing at least one acid gas, and a desorption unit for producing a regeneration stream with reduced thermally stable salt, included in an acid gas recovery assembly. For example, the absorption solution is an amine-based absorption solution.

[0030]

[0029] For example, the system further includes at least one additional absorption unit, scrubbing unit, quenching unit, or a combination thereof, located upstream of the absorption unit, capable of removing at least a portion of the acid gas other than CO2 from the flue gas. Optionally, when the acid gas recovery assembly includes at least one additional absorption unit, the system further includes an additional regeneration unit, an additional amine regeneration unit, and an additional concentration unit for each additional absorption unit, operating in parallel with the respective regeneration unit, amine regeneration unit, and concentration unit.

[0031]

[0030] In some embodiments, the oxidation unit may be a combustion unit having an inlet in fluid communication with the concentration unit for receiving the concentrated waste liquid stream. For example, the combustion unit may be a burner. Optionally, the combustion unit may further have an outlet in fluid communication with at least one unit for amine-based acid gas recovery for treating the oxidation product stream together with the flue gas. In another embodiment, the combustion unit further has a fuel inlet configured to receive fuel and an oxidant inlet configured to receive an oxidant, and the oxidation product stream is a flue gas targeted for amine-based acid gas recovery.

[0032]

[0031] In some embodiments, the system further includes a control unit connected to act on at least one of the amine regeneration unit and the concentration unit to control the moisture content of the waste liquid stream and / or the concentration of dissolved salts / acids in the waste liquid stream.

[0033]

[0032] Although the present invention has been described in connection with exemplary embodiments and examples, it will be understood that it is not intended to limit the scope of the present invention to such embodiments or examples. On the contrary, it is intended to cover all alternatives, modifications and equivalents that may be included by the definition of the present description. The objects, advantages and other features of the present invention will become more apparent and better understood by reading the following non-limiting description of the present invention given with respect to the accompanying drawings.

Brief Description of the Drawings

[0034]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0035] [Mode for Carrying Out the Invention]

[0038] The present technique relates to an amine regeneration process that facilitates the disposal of heat-stable amine salts generated in upstream amine-based acidic gas absorption and desorption stages. The regeneration process includes recovery of the heat-stable amine salts and transfer of the recovered heat-stable amine salts to an oxidation step that destroys the heat-stable amine salts. For example, the oxidation step may be a combustion step, and such a combustion step can advantageously be integrated into a process that produces combustion gases that are further processed in the amine-based acidic gas absorption and desorption stages, thereby converting the overall process to a net-zero liquid discharge process.

[0036]

[0039] Heat-stable amine salts (HSAS) can form during the absorption of acidic gases from a feed gas by an amine-based absorption solution and during the desorption of acidic gases from the enriched absorption solution. For example, the feed gas may include hydrogen sulfide, carbon dioxide, sulfur oxides, or any combination thereof. For example, the feed gas can be produced by the combustion step represented in Figure 2.

[0037]

[0040] Referring to FIG. 1, the feed gas 2 may include carbon dioxide and the remainder containing water vapor and nitrogen. The remainder may include other combustion products such as methane and ethane. The feed gas is introduced into the absorption zone 1 via line 2, and the feed gas is contacted with a lean amine-based absorption solution via line 5. The lean amine-based absorption solution contains an amine or a mixture of amines, and the remainder is mostly water. The lean amine-based absorption solution may include, for example, diethanolamine or methyldiethanolamine, a mixture or blend of an amine and perhaps a physical solvent. The absorption zone 1 is maintained at an absorption temperature between 20° C. and 60° C. and an absorption pressure between 1 atm and 150 atm. The absorption zone 1 may be part of a packed tower, spray scrubber or other type of absorption equipment readily available in the art. During the absorption of carbon dioxide (and other acidic gases) from the feed gas in the absorption zone 1, HSAS can be formed. HSAS is derived from the reaction of an amine with an acid stronger than carbonic acid. These acids may include, for example, hydrochloric acid, organic acids, oxalic acid, cyanic acid, thiocyanic acid, thiosulfuric acid, any of their analogs, or any combination thereof.

[0038]

[0041] In some embodiments, the amine may be, for example, an aliphatic amine or amide, an aromatic amine and amide, a heterocyclic amine or amide, or any combination thereof. For example, the aliphatic amine may include an alkanolamine, an alkyleneamine or any combination thereof. For example, the alkanolamine may include monoethanolamine, diethanolamine, triethanolamine and methyldiethanolamine. For example, the alkyleneamine may include ethylenediamine and its alkyl derivatives. For example, the aromatic amine may include aniline and xylidine. For example, the heterocyclic amine may include piperazine and its derivatives. For example, the amide may include piperazinone and its derivatives.

[0039]

[0042] Referring to FIG. 1, a product gas stream with at least partially reduced carbon dioxide compared to the feed gas stream is discharged from the absorption zone 1 via line 3. The enriched absorption solution containing the absorbed carbon dioxide, the amine, and any formed HSAS is discharged from the absorption zone 1 via line 4 and passed to the desorption zone 6 (which can also be referred to as the regeneration zone). During regeneration, carbon dioxide is released from the enriched absorption solution in the regenerated overhead stream further containing water and discharged from the regeneration zone 6 via line 7. Desorption further causes the formation of an acid gas-reduced absorption solution, which can be further cooled and used as the regenerated amine-based absorption solution via line 5. For example, the desorption zone 6 may be a distillation column operated at a desorption temperature between 75°C and 150°C and a desorption pressure between 1 atm and 5 atm under steam stripping conditions.

[0040]

[0043] Acid gases such as CO2 can be released by desorption, but HSAS is not thermally regenerable and cannot be regenerated as an acid under typical regeneration conditions. Also, it is common for HSAS to form further in the regeneration zone as well (in addition to the absorption zone). HSAS thus accumulates in the reduced absorption solution. The recovered CO2 can be compressed and then either used in a conversion process, sequestered, or piped for use elsewhere.

[0041]

[0044] The specific methods and equipment used to perform the regeneration of the absorption solution via acid gas absorption and acid gas desorption are not important to the present invention and it should be noted that they are described herein by examples illustrating the formation of HSAS. For example, the absorber can include one or more stages and can include a packed column, a bubble column, a tray column, or another direct contact gas-liquid vessel, and the desorption stripper may include one or more separation drums or columns.

[0042]

[0045] In addition, the acid gas exemplified in this specification in relation to the figures is referred to as CO2, but the feed gas may contain other acid gases and may be a gas mixture. As a result, it should be noted that the acid gas may further contain, for example, SO2, H2S, or a combination thereof. More specifically, typical feed gases that can be processed in the regenerable amine-based absorption process exemplified above and in Figure 1 include acid gases such as CO2, H2S, SO2, or any mixture thereof.

[0043]

[0046] Depending on the nature of the acid gas present in the feed gas, the proposed amine-based acid gas recovery process may include at least one sequence of three sequential steps: an acid gas recovery stage via a dedicated amine, an amine regeneration stage, and a waste liquid concentration stage. The concentrated waste liquid stream is thereby generated and can be subjected to oxidation to reduce or even eliminate the liquid content of the resulting exhaust stream. In some embodiments, the proposed amine-based acid gas recovery process can be further individually adjusted to completely recycle the oxidized waste liquid stream so that the process can be a zero-waste liquid process.

[0044]

[0047] More details are provided herein for each step / stage.

[0045] Combustion step

[0048] This regeneration technique can be implemented in the context of a post-combustion acid gas recovery process 200 where the feed gas contains flue / gas combustion gases obtained from an upstream combustion stage.

[0046]

[0049] For example, referring to FIG. 2, the supply gas 2 may be combustion gas derived from an upstream combustion stage 11. When carbon dioxide is present in the combustion gas, its concentration is usually in the range of about 2 to 30 volume percent, but high carbon dioxide levels of about 90 volume percent or more are not uncommon. When sulfur oxides, i.e., sulfur dioxide and / or sulfur trioxide, are present in the combustion gas, their overall concentration is usually in the range of about 500 ppm volume to 50 volume %, but high levels of 70 volume % or more are also possible. The combustion gas used as the supply gas may also contain other components such as, for example, nitrogen, water, oxygen, light hydrocarbons, sulfur derivatives of light hydrocarbons, such as mercaptans, etc.

[0047]

[0050] More specifically, referring to FIG. 2, the combustion stage is carried out in a combustion zone 11 which is, for example, a gas turbine, a boiler, a furnace, or any readily available combustion unit or system, to generate combustion gas 18 which may result from the combustion of a fuel 16 such as natural gas, LPG, coke, coal or other materials which will be burned to form CO2.

[0048]

[0051] Depending on the nature of the acid gas present in the combustion gas, the amine-based acid gas recovery process 200 may include at least one sequence of three sequential stages, namely an acid gas recovery stage 210 via a dedicated amine, an amine regeneration stage 220 and a waste liquid concentration stage 230, as described in more detail herein.

[0049] Conditioning of the supply gas before carbon capture

[0052] In some embodiments, the post-combustion acid gas recovery process 200 may include removing acid gases stronger than CO2 before proceeding to CO2 absorption in the CO2 recovery stage using a dedicated amine.

[0050]

[0053] Depending on the composition of the combustion gas, various pretreatment steps can be performed before proceeding with CO2 recovery. For example, the combustion gas can be quenched and / or pretreated in a pre-scrubber, which is generally an aqueous scrubbing to remove solid impurities (including acids). Other pretreatment units or systems configured to pretreat the combustion gas before absorption may include, by way of example and without limitation, filters, venturi tubes, cyclones, or any combination thereof.

[0051]

[0054] For example, as can be seen in FIG. 2, the combustion gas 18 can first be pre-scrubbed to produce a feed gas 2 that is supplied to the acid gas recovery stage 210 dedicated to carbon capture. This pretreatment can be particularly suitable when stronger acids such as SO2 and a lesser amount of SO3 are present in the combustion gas 18 and are derived from the combustion of sulfur species. If SO2 and / or SO3 are present, these latter two species can be mostly captured in the aqueous pre-scrubber 12, which is located upstream of the absorption zone of the acid gas recovery stage 210.

[0052]

[0055] In another embodiment, referring to FIG. 3, the pre-scrubber 12 can be supplemented with an additional acid gas recovery stage 210a configured to capture any remaining amount of acid gas (stronger than CO2), such as SO2, using a first amine. This first strong acid gas recovery stage 210a is performed prior to the CO2 recovery stage 210b, which involves the use of another second amine. For each of the acid gas recovery stages 210a and 210b, corresponding subsequent amine regeneration stages 220a and 220b, as well as waste liquid concentration stages 230a and 230b, are operated in parallel. The process illustrated in FIG. 3 can be particularly suitable when the SO2 concentration of the scrubbed gas is above about 50 ppm to 1,000 ppm and thus requires an additional and dedicated amine-based SO2 recovery stage.

[0053]

[0056] In other embodiments, the post-combustion acid gas recovery process 200 may include directly supplying the combustion gas to the first acid gas recovery stage 210 without any other pretreatment used as the feed gas 2 to the absorber 1 of the acid gas recovery stage 210, as can be seen in FIG. 1.

[0054] Recovery of Acid Gas

[0057] As illustrated in FIG. 3, it is noted that the post-combustion acid gas recovery process 200 may include a plurality of acid gas recovery stages in series that capture various acid gases in the combustion gas stream based on different amines selected according to the strength of the acid gas.

[0055]

[0058] HSAS is an amine in the form of a salt having a thermally stable anion linked thereto and is formed during acid gas recovery. It is known that HSAS formed during CO2 recovery 210 in an amine-based system can be derived from organic acids formed from the reaction of CO2, CO, nitrogen and oxygen, and may include, for example, acetic acid, formic acid, nitric acid or nitrous acid. When sulfur is present during the supply to the combustion step 11, other acids such as sulfurous acid, sulfuric acid and thiocyanuric acid can be formed.

[0056]

[0059] More specifically, during amine-based carbon dioxide recovery 210, typically between 0.01% and 1% (on a molar basis) of the absorbed acid gas (or an equivalent amount thereof) can react with oxygen, deteriorate, or otherwise react with the amine (through a neutralization reaction) to convert to a thermally stable amine salt (i.e., a stronger acid). For example, CO2 can react with water to form acetic acid that gives a thermally stable acetate anion. In another embodiment, CO can react with water under suitable conditions to form formic acid and give a thermally stable formate anion. Other sources of HSAS may be impurities found in the feed gas stream, impurities found in the make-up water stream or in the HSAS derived from the decomposition of the amine, and most often due to reaction with oxygen.

[0057]

[0060] The lean absorption solution thus becomes contaminated with HSAS and accumulates in the solution when recycled to the amine absorption unit. The lean absorption solution exiting the desorption unit can be referred to as a contaminated amine absorption solution. If it is too highly concentrated, it can result in corrosion problems, filtration problems and also loss of capacity. The absorption or loading capacity of an amine-based absorption solution is substantially inversely proportional to the concentration of the heat stable amine salts. For example, it is possible to completely neutralize the amine for the heat stable amine salts, thereby reducing its absorption capacity to zero.

[0058]

[0061] When contaminated, the overall concentration of HSAS in the lean absorption solution is typically from about 0.1 wt% to about 25 wt% based on the total weight of the solution. For example, the concentration of heat stable amine salts in the lean absorption solution resulting from an acid gas absorption process for hydrogen sulfide and carbon dioxide may be from about 1 wt% to about 5 wt%. In another embodiment, the concentration of heat stable amine salts in the lean absorption solution resulting from a sulfur dioxide acid gas absorption process may be from about 1 wt% to about 15 wt%. The concentration of the amine in free base form in the lean absorption solution may be from about 5 wt% to about 60 wt%, optionally from about 20 wt% to 50 wt%. The concentration of water typically corresponds substantially to the remainder of the lean absorption solution and may optionally be from about 30 wt% to about 95 wt% based on the total weight of the solution, further optionally from about 40 wt% to about 70 wt%. In some embodiments, the lean absorption solution may contain small amounts, e.g., less than about 2 wt%, of other components such as neutralizing agents, anti-foaming agents and / or antioxidants.

[0059] Regeneration of the Amine

[0062] A portion of the lean absorption solution or a portion of the enriched absorption solution generated during at least one acid recovery stage 210 can be fed to a corresponding amine regeneration stage 220 that includes an amine regeneration unit for removing the HSAS that accumulates thereby and for maintaining the HSAS concentration in the lean amine absorption solution at a desired or optimal concentration, for example, between 0 wt% and 3 wt% based on the total weight of the solution. The operation of the amine regeneration unit can be carried out continuously or when the monitored concentration of HSAS in the lean absorption solution or the enriched absorption solution reaches a given threshold value.

[0060]

[0063] More specifically, referring to FIG. 1, to avoid the accumulation of the formed HSAS and maintain the absorption capacity of the lean absorption solution, a slip stream is taken from the lean absorption solution flowing through line 5 via line 8, and the slip stream is introduced into an amine regeneration unit 9 to produce a regenerated amine stream and a waste liquid stream. It is noted that the supply of the slip stream to the amine regeneration unit 9 may be carried out in a continuous, semi - continuous or batch mode.

[0061]

[0064] In a particular embodiment shown in FIG. 3, when a plurality of acid gas recovery stages (e.g., 210a for residual SO2 and 210b for CO2) are carried out in series, the corresponding amine regeneration stages (220a, 220b) can be operated in parallel and are each supplied with a slip stream (8a, 8b) from the corresponding acid gas recovery stage (210a, 210b) for removing the accumulating HSAS.

[0062]

[0065] Referring to FIG. 2, the pre - scrubber 12 can generally absorb much of the same species (mostly acid) that the amine regeneration unit 9 removes from the slip stream 8 of the lean absorption solution resulting from acid gas recovery (limited by chemical equilibrium). Thereby, in some embodiments, when the pre - scrubber is present upstream of the acid gas recovery facility, at least a portion 20 of the bleed stream from the pre - scrubber 12 can also be fed to the amine regeneration unit 9.

[0063]

[0066] Referring to FIGS. 1 and 2, the regenerated amine stream has at least partially reduced HSAS and is returned via line 10 to the amine-based acid gas recovery stage 210 process to form a lean amine absorption solution. Referring to FIG. 2, a waste stream 13 is further generated and contains acids and other contaminants recovered from the lean absorption solution in the amine regeneration unit 9, and any neutralizing agent if utilized.

[0064]

[0067] The amine regeneration unit 9 may be an electrodialysis unit and can be operated to remove the acids responsible for the formation of heat stable salts according to the process examples described in U.S. Patent No. 6,517,700, the content of which is incorporated herein by reference, or International Application PCT / CA2022 / 050772, the content of which is incorporated herein by reference. The amine regeneration unit can be operated continuously in situ or may be brought in from time to time as needed.

[0065]

[0068] For example, referring to FIG. 4, the electrodialysis unit may be an electrodialysis zone 9 including a cathode compartment, an anode compartment, and at least one repeating unit, where each repeating unit includes an anion source compartment (A), an amine solution compartment (S), and a waste solution compartment (W). Also in the electrodialysis zone 9, an anion source compartment (A”) and a waste solution compartment (W”) adjacent to the repeating unit are shown. The anion source compartment (A) and the amine solution compartment (S) are separated by an anion selective membrane. The amine solution compartment (S) and the waste solution compartment (W) are separated by an anion selective membrane. The waste solution compartment (W”) and the anion source compartment (A) of adjacent repeating units are separated by a cation selective membrane. A direct current potential is applied across each compartment of the electrodialysis zone. The slip stream of the contaminated lean absorption solution (containing heat stable amine salts) is supplied as a feed stream to each amine solvent compartment via line 110, returned to the acid gas absorption process via line 120, and supplied to line 10 directly or via an intermediate storage tank (not shown). Alternatively, the passage of the feed stream can be operated continuously, in batch mode (periodically), or once only. A source of base or a regenerable anion (referred to as an anion source or anion source solution) circulates through the electrodialysis zone via lines 130 and 140. The anion source can supply an anion that passes through an anionic selective membrane to the product supply compartment (S) in the anion source section, thereby providing a cation in the adjacent waste solution compartment (W”) via a cationic selective membrane to generate waste solution. When an acid, which is a source of regenerable anion, is supplied to the anion source compartment, the acid waste solution is generated in the waste solution compartment instead of a salt solution. Thereby, the waste solution of salt or acid circulates in the electrodialysis zone 9 via lines 150 and 160. Both the anion source solution and the waste solution can be circulated once only, continuously recycled, or recycled in batch mode (periodically). The waste liquid stream containing salts of heat stable anions such as sodium chloride is discharged from the waste solution compartment (W) via line 160.It should be noted that when the waste liquid stream (optionally the bleed stream of the pre-scrubber) is neutralized using cations such as sodium, the neutralizing agent ends up as ash that is generated during the combustion of the waste liquid stream during the oxidation stage.

[0066]

[0069] In another embodiment, referring to FIG. 5, the electrodialysis unit may be an electrodialysis zone 9 including a cathode compartment, an anode compartment, and at least one repeating unit, where each repeating unit includes an amine solution compartment (S) and a waste solution compartment (W). Also shown in the electrodialysis zone 9 are an adjacent amine solution compartment (AS) and an adjacent waste solution compartment (W”) from an adjacent repeating unit. The electrodialysis zone 9 further includes bipolar membranes (BP) and anionic selective membranes (A). A direct current potential is applied across each compartment in the electrodialysis zone 9. A slip stream of the contaminated amine solution (depleted absorption solution or enriched absorption solution) is fed via line 110 to the amine solution compartment (S) to form a product stream that is returned via line 120 to the acid gas absorption stage. Both the feed and product streams can be recycled through the tank using makeup and bleed, which are lines 8 and 10 respectively in FIG. 1. Alternatively, the process can be operated in batch mode or once-through. In the amine solution compartment (S), amine cations dissociate from thermally stable anions such as chloride. Thermally stable anions such as chloride permeate through the anionic selective membrane into the waste solution compartment (W). Hydroxide anions are generated in the bipolar membrane and permeate into the amine solution compartment (S). In the amine solution compartment (S), the hydroxide anions react with the protonated amine cations to form free base amine and water. Protons are also generated in the bipolar membrane and permeate into the waste solution compartment (W). An aqueous stream is introduced into the waste solution compartment (W). A regenerated amine stream containing at least a reduced concentration of some free base form of amine, possibly some thermally stable amine salts, or both thermally stable and thermally regenerable anions is withdrawn from the amine solution compartment via line 120. A waste solution product stream containing an acid of a thermally stable anion such as hydrochloric acid is withdrawn from the waste solution compartment (W) via line 160. Thereby, a waste stream can be produced without any neutralizing agent / chemicals, which may be particularly suitable for recycling in the combustion of ash-free fuels (such as natural gas).

[0067]

[0070] Apart from the separately reduced concentration of the heat-stable salt, a regenerated amine stream having substantially the same composition as the slip stream is discharged from the amine solution compartment. The regenerated amine stream contains the amine in free base form or in the form of non-heat-stable salts (when the regenerable anion is fed to the anion supply loop), which may include amines (plural) containing heat-stable and non-heat-stable salts. Such a regenerated amine stream can be combined with the lean absorption solution 5 or the rich absorption solution 4 via line 10, as can be seen in Figure 1.

[0068]

[0071] Accordingly, the waste stream contains salts or acids of the heat-stable anions of the HSAS. Typical salts of heat-stable anions may include, for example, alkali metal sulfates, alkali metal halides, alkali metal acetates, alkali metal thiocyanates, alkali metal thiosulfates, alkali metal nitrates and nitrites, alkaline earth metal sulfates, alkaline earth metal halides, alkaline earth metal acetates, alkaline earth metal thiocyanates, alkaline earth metal thiosulfates, alkaline earth metal nitrates and nitrites, and mixtures thereof. Preferred salts of heat-stable anions include sodium sulfate, sodium chloride, sodium acetate, sodium thiocyanate and sodium thiosulfate. A carrier stream, such as an aqueous carrier, can be introduced into the waste stream compartment to control at least one of the flow rate, the concentration of the salt or acid, or the moisture content in the waste stream.

[0069]

[0072] Typically, the amount of HSAS that can be removed from the amine-based acid gas recovery facility 210 is less than 1%, for example less than 0.1%, of the total amount of acid gas recovered. Accordingly, the waste stream combined with the downstream amine regeneration stage 220 can be considered relatively small when compared to the overall acid gas 3 recovered via the acid gas recovery stage 210. The proposed regeneration process can eliminate the need for supplementary wastewater treatment systems or harmful waste liquid disposal as encountered in conventional solutions, since the proposed regeneration process produces no liquid discharges or any further waste liquids, whether aqueous or not.

[0070]

[0073] The process for amine regeneration illustrated in FIG. 2 may include removing at least a portion of the HSAS from the lean amine absorption solution recovered as a slip stream from the acid gas recovery process in the amine regeneration unit 9. For example, the process may include removing sufficient HSAS from the slip stream to maintain an HSAS concentration in the lean amine absorption solution between 0 wt% and 3 wt% relative to the total weight of the solution. This acceptable range of HSAS concentration can vary depending on parameters including amine type and amine concentration. For example, a concentration of HSAS in the lean amine absorption solution exceeding 3 wt% may be desirable in certain situations.

[0071] Waste liquid treatment

[0074] The amine regeneration process further includes recycling and oxidizing (e.g., incinerating) the waste liquid stream to return its components and produce additional products (e.g., CO2), effectively reducing the waste liquid from the recycling process to net zero.

[0072]

[0075] According to the present technique, the waste liquid stream / material produced by the amine regeneration stage 210 can be fed to a waste liquid treatment operation including a waste liquid concentration stage 230 and an oxidation stage 240. The oxidation stage 240 can operate within the existing combustion unit 11 as can be seen in FIG. 2, or can operate as an additional downstream step 240 as can be seen in FIG. 3. In both cases, the products of oxidation can be fed to the post-combustion acid gas recovery process 200 either alone or as part of the feed gas (e.g., to the pre-scrubber 12 and / or to the acid gas absorber of the acid gas recovery facility 210).

[0073]

[0076] This post-combustion acid gas recovery process 200 may include recycling and oxidizing the resulting waste liquid stream into components that can be processed by the amine absorption process, contrary to conventional solutions.

[0074]

[0077] For example, in the embodiment shown in FIG. 2, the process can include incinerating the resulting waste liquid stream in an existing upstream combustion step 11 of the acid gas generation stage, where the waste liquid stream is combusted with air and fuel to produce a supply gas 2 that is supplied to the pre-scrubber 12. In the case of a site without a wastewater treatment unit, the waste liquid stream must be transported off-site from a suitable waste liquid treatment site. The ability to recycle, combust, and thereby produce net-zero waste liquid represents significant operating and cost advantages.

[0075]

[0078] In some other embodiments, the amine regeneration process can alternatively include supplying the waste liquid stream to a wastewater treatment system, where all dissolved carbon and nitrogen-based acids are gradually oxidized by contact with an oxidizing agent, resulting in no net waste liquid other than excess water, which can be recycled and reused after appropriate treatment. For example, the oxidizing agent can be air, peroxide, or bleach.

[0076]

[0079] In still other embodiments, as can be seen in FIG. 3, the waste liquid stream can be sent via line 15 to a dedicated burner to operate an oxidation stage 240, where acid gas is generated and can be recycled back via line 22 to the pre-scrubber 12 and / or at least one acid gas recovery stage 210.

[0077]

[0080] Prior to oxidation, the waste liquid treatment operation can optionally include removing at least a portion of the water from the waste liquid stream to produce a further reduced and concentrated waste liquid stream for the waste liquid stream, which is sent to an oxidation via integrated combustion or another oxidation process.

[0078]

[0081] When using ion exchange or electrodialysis as an amine regeneration technique to remove HSAS from a contaminated amine solution under specific regeneration conditions, the resulting waste liquid stream may be too dilute and the amount of the waste liquid stream may be impractical for oxidation. Usually, the concentration of the dissolved salts and / or acids of the thermally stable anions in the waste liquid stream from the amine regeneration unit may be 2% or less. Further, when relying on ion exchange, a large amount of wash water (equal to or exceeding the amount of the waste liquid) containing little or residual concentration of HSAS, neutralizing agent substances (e.g., NaOH), and some amines may be generated.

[0079]

[0082] Therefore, when the waste liquid stream is too dilute, the present regeneration process may include concentrating the waste liquid stream in at least one concentration unit operated according to methods readily available in the art, such as softening, evaporation, distillation, reverse osmosis, electrodialysis, or combinations thereof. It is noted that the concentration step and the concentration unit involve the operation of any method / equipment configured to effect a reduction in the amount of water or an increase in the concentration of the acid and / or salt by another method. For example, referring to FIG. 2, the waste liquid stream 13 is first sent to the concentration step 14, where at least a portion of any excess water is removed to increase the acid and / or salt concentration. For example, referring to FIG. 3, the waste liquid treatment may include performing waste liquid concentration in dedicated steps 230a and 230b that receive the waste liquid stream from the amine regeneration stages 220a and 220b via lines 13a and 13b, respectively. The resulting concentrated waste liquid stream can be collected via lines 15, 15a, and 15b and directed to the oxidation step 240. It is noted that, unlike the apparatus shown in FIG. 3, the waste liquid streams from lines 13a and 13b can be fed to a common waste liquid concentration step to produce the entire concentrated waste liquid stream fed to the oxidation step 240.

[0080]

[0083] Furthermore, it is noted that the water removal / concentration step is optional and may depend on the nature of the water in the waste stream and the amount of excess water. Excess water should be understood as an unnecessary or inappropriate amount of water according to the capabilities of the subsequent oxidation step. The water removal step can be performed to produce a concentrated waste stream having a dissolved salt and / or acid concentration of at least 2 wt%, at least 5 wt%, at least 10 wt%, at least 15 wt%, at least 20 wt%, at least 30 wt%, at least 40 wt% or at least 50 wt% of the total weight of the waste stream.

[0081]

[0084] It should be noted that the level of concentration achieved during the waste stream concentration step can be adapted to a given total volume of water or a given total volume of the concentrated waste stream that can be processed / accepted by the oxidation step (e.g., combustion). Further, it should be noted that the waste stream concentration step can be performed to reach a dissolved salt and / or acid concentration that allows staying within the solubility limit of each of the salt and / or acid.

[0082]

[0085] Referring to the exemplary embodiment of FIG. 2 where a pre-scrubber is present, another portion 19 of the bleed stream from the pre-scrubber 12 can be sent directly to the waste stream concentration step 14, where the portion 19 of the bleed stream is concentrated and then via stream 15 can be returned and fed to the combustion unit 11, where the waste stream is destroyed providing an overall net zero waste stream process. The water recovered from the waste stream concentration step 14 can then be recycled via stream 21 to the pre-scrubber 12 (or to other systems in the plant that require water). By recycling the recovered water 21 back to the feed gas conditioning step, for example, in the pre-scrubber 12, not only is net zero water production achieved, but water consumption is significantly reduced and nearly net zero water consumption is achieved.

[0083]

[0086] It is noted that the recovered water can be recycled to a unit that consumes water for an operation or another operation. For example, the water can be used as boiler feed water to produce steam.

[0084]

[0087] In some embodiments, in addition to or instead of performing the removal of at least a portion of the water from the waste liquid stream, the technique of the operation of regenerating the lean absorption solution into a regenerated amine solution can be selected to minimize the amount of the waste liquid volume and / or to minimize the amount of water contained in the waste liquid. For example, electrodialysis presents the advantages of producing a more concentrated waste liquid stream and the ability to produce a waste liquid stream containing unconnected cations. Electrodialysis can be operated to maximize the concentration of impurities and minimize the water content.

[0085]

[0088] For example, referring to FIGS. 4 and 5, the amount of the aqueous carrier introduced into the waste liquid compartment (W) can be controlled to minimize the water content of the waste liquid stream, preferably less than 90%, ideally less than 80% or less. Thus, the regeneration step can be operated to eliminate the need for the waste liquid concentration step (14) and to rely only on the controlled operation of the amine regeneration unit (9) to produce a waste liquid stream of a sufficiently high concentration in many cases.

[0086]

[0089] The concentration values are provided as examples, and it should be noted that the intended concentrations can deviate from these exemplified values. The salt and / or acid concentration in the waste liquid stream is to be understood as being limited only by further economic considerations regarding the solubility limits of the contained species and the net impact of introducing water into the combustion step (versus the cost of further concentrating the waste liquid stream). The net water consumption can be kept low enough to enable and make practical the combustion of the waste liquid stream. Thus, by using electrodialysis for the amine regeneration step, the waste liquid stream can be produced to contain no non-combustible cations and to contain sufficiently low moisture such that 1) it enables oxidation (e.g., via combustion) and 2) it results in a net zero waste liquid. The ability of the electrodialysis process to independently control and set the moisture and salt / acid concentration of the waste liquid stream is a significant advantage when operated according to the examples described herein, and thus enables the waste liquid stream to be destroyed / consumed via oxidation.

[0087]

[0090] The control of the moisture in the waste liquid stream and / or the concentrated waste liquid stream can thus be accomplished in various ways so as not to send an excessive amount of water to an oxidation step such as combustion.

[0088]

[0091] Referring still to FIG. 2, the concentrated waste liquid stream 15 is then returned to the combustion zone 11 for their combustion to produce combustion gas 18. In combustion, the salts and acids dissolved in the waste liquid contained in the concentrated waste liquid stream are converted to CO2, nitrogen, or nitrogen oxides. If sulfur is present in the fuel being burned, then in that case, some SO2 including some linked SO3 may also be recycled. If cations for neutralization are present in the waste liquid stream, the stronger acids form salts that precipitate after combustion and are recovered in the combustion ash. By relying on the electrodialysis process for amine regeneration, a waste liquid stream free of cations can be produced leading to a true net zero waste liquid process.

[0089]

[0092] As already described, non-organic acids such as sulfur can be captured within the pre-scrubber section or within a separate scrubber (which can be regenerated) that captures SO2. For these gas streams containing sulfur, the sulfur compounds recycled to the combustion step are converted back to sulfur oxides and then recovered in the pre-scrubber or in a water quenching step placed between the combustion process and the acid gas absorber. For any gas stream that does not contain any sulfur, there are thus no sulfur-based acids that form heat-stable salts, and the organic acids are destroyed during the combustion process, resulting in net zero waste liquid production from the regeneration process.

[0090]

[0093] In some embodiments, as can be seen in FIG. 3, when SO2 is present in the combustion gas, since SO2 is a much stronger acid than CO2 or H2S, acid gas recovery includes the recovery of SO2 in a separate first recovery stage 210a installed in series upstream of the acid gas recovery stage 210b for CO2 recovery, whereby a supply gas with reduced SO2 can be produced. Next, the SO2-reduced supply gas is fed to the amine absorption column of the second acid gas recovery stage 210b, where it is contacted with the recycled amine to recover CO2. In a method in which the combustion of fuel 16 is carried out under partially reducing conditions, or in a process that generates other non-combustion acid gases such as natural gas treatment, refining, or ammonia production, H2S may also be present in the resulting acid gas stream. Any waste liquid related to the conditioning of the acid gas stream in the pre-scrubber and amine regeneration can be sent to the oxidation stage, as already described, with minimal moisture and as carried out within the combustion unit.

[0091]

[0094] In some embodiments, for example, when the dilute amine loading rate (usually for CO2) of the reduced absorption solution exceeds a given threshold (e.g., greater than 1,000 ppm), the regeneration process may further include pretreating the reduced absorption solution to remove the excess dilute loading rate upstream of the amine regeneration unit 9, as described in U.S. Patent No. 9,908,085, the content of which is incorporated herein by reference.

[0092] Exemplary embodiments

[0095] For example, a 1,000 tons per day amine-based carbon capture facility from a coal-fired or natural gas-fired power plant, and capturing 95% of the resulting CO2 typically results in approximately 23 kgmoles of heat-stable salts per day, i.e., acetic acid or an acid such as acetic acid present as another acid (at 0.1%). Removing 23 kgmoles or approximately 1,350 kg of acetic acid (or other acid) per day in a 10 wt% solution results in 13,500 kg of waste liquid being incinerated daily, or just over 9 kg per minute. At 30% strength, this is 4,500 kg per day. 23 kgmoles of acetate will result after incineration of 23 kgmoles of CO2, or 1 ton per day of additional captured CO2. No other waste liquid is produced, and at 10% strength, the process consumes 12,500 kg of water per day, with less being consumed the higher the concentration. Thus, the acid or salt of the acid is not sent to the waste liquid, and the only product is CO2. The moisture is evaporated, which can consume some energy and result in a slight overall reduction in the overall energy efficiency. When the gas is cooled, or when the temperature is lower than the feed gas, water condenses in the amine absorption tower, and most of this water can be recovered. The recycled waste liquid stream from the amine regeneration unit can be concentrated, if necessary or advantageous, up to the solubility limit of the impurities it contains.

[0093]

[0096] It should be noted that the same reference numerals refer to similar elements. Further, for simplicity and clarity, i.e., without unduly burdening the figures with too many reference numerals, not all figures include references to all components and features, and references and features to some components may be found only in one figure of the present disclosure and also in components and features described in other figures and can be readily inferred therefrom. The embodiments, geometric figures, materials, and / or dimensions shown in the figures are optional and provided for illustrative purposes only. Thus, the descriptions, examples, methods, and materials presented in the claims and the specification should be construed as illustrative only and not limiting.

[0094]

[0097] In the following description, the term "about" means within an acceptable error range with respect to a particular value required by one of ordinary skill in the art, which depends in part on how the value is measured or determined, i.e., on the limitations of the measurement system. A measurement accuracy of 10% is generally acceptable and includes the term "about".

[0095]

[0098] In the above description, the embodiments or examples are examples of the present invention. Various occurrences of "an embodiment", "embodiments", "some embodiments" or "some examples" do not all necessarily refer to the same embodiment. Although various features of the present invention may be described in the context of a single embodiment or example, the features / aspects may also be provided separately or in any suitable combination. Conversely, although the present invention may be described herein in the context of separate embodiments / examples for clarity, the present invention may also be implemented in a single embodiment / example.

Claims

1. A method for removing thermally stable amine salts (HSAS) from a contaminated aqueous amine absorption solution containing amines in salt form generated during an amine-based acid gas recovery operation, The steps of: removing at least a portion of the HSAS from the contaminated aqueous amine absorption solution in an amine regeneration unit, thereby producing a wastewater stream containing dissolved salts and / or acids, and a regenerated amine absorption solution containing a reduced amount of the thermally stable amine salt; and The aforementioned wastewater flow is oxidized to CO ２ , a step of treating the wastewater stream, including converting it into a stream of oxidation products containing water and nitrogen, A method that includes this.

2. The method according to claim 1, wherein the step of treating the wastewater stream further comprises adjusting the salt and / or acid concentrations in the wastewater stream before oxidation thereof.

3. The method according to claim 2, wherein the concentration of the salt and / or acid is at least 2% by weight.

4. The method according to claim 2, wherein adjusting the concentration of the salt and / or acid in the wastewater stream includes concentrating the wastewater stream to generate a concentrated stream by removing at least a portion of the water from the wastewater stream.

5. The method according to claim 1, wherein oxidizing the wastewater stream includes subjecting the wastewater stream to combustion to produce the oxidation product stream.

6. The method according to claim 5, wherein the step of treating the wastewater stream further comprises recycling at least a portion of the oxidation product stream for the amine-based acid gas recovery operation.

7. By supplying the oxidation product stream to the absorption unit of the amine-based acidic gas recovery operation, CO2 is removed from the oxidation product stream. ２ The method according to any one of claims 1 to 6, comprising the step of recovering an acidic gas containing, wherein the oxidation product stream is brought into contact with an aqueous amine absorption solution for absorbing the acidic gas.

8. The aforementioned oxidation product stream is SO ２ and / or SO ３ If it further includes, The aforementioned oxidation product stream is subjected to gas conditioning in a scrubbing unit or quenching unit to produce SO2. ２ and / or SO ３ To remove and reduce oxidation product flow; and, The reduced oxidation product stream is supplied to at least one absorption unit of the amine-based acid gas recovery operation, and the reduced oxidation product stream is brought into contact with the aqueous amine absorption solution to bring at least CO2 into contact. ２ To recover, The method according to any one of claims 1 to 6, comprising the step of recovering an acidic gas from the oxidation product stream.

9. The method according to claim 8, comprising the steps of withdrawing a bleed flow from the gas conditioning step and supplying at least a portion of the bleed flow to the amine regeneration unit to generate the wastewater flow.

10. The method according to claim 1, wherein oxidizing the wastewater flow includes supplying the wastewater flow to a wastewater treatment unit that oxidizes the salt and / or acid by contact with an oxidizing agent to generate the oxidation product flow.

11. The method according to any one of claims 1 to 6, wherein the contaminated aqueous amine absorption solution supplied to the amine regeneration unit is a slip stream of the regenerated absorption solution generated during the acid gas recovery operation of the amine system.

12. A system for removing thermally stable amine salts from a contaminated aqueous amine absorption solution generated during the recovery of amine systems of acidic gases representing at least a portion of flue gas produced by the combustion of fuel and oxidizer, An amine regeneration unit configured to receive a slip flow containing the thermally stable amine salt from the amine-based acidic gas recovery regeneration unit, and to generate a regenerated flow with reduced thermally stable salt for supply to the amine-based acidic gas recovery absorption unit, and a wastewater flow containing dissolved salt and / or acid; A concentration unit configured to receive the wastewater flow and generate a concentrated wastewater flow in which the concentration of dissolved salts and / or acids in the wastewater flow has increased; and A system comprising an oxidation unit having an inlet for fluid communication with the concentration unit, wherein the oxidation unit is configured to supply the concentrated waste liquid flow to the oxidation unit for oxidation to generate an oxidation product flow.

13. The system according to claim 12, further comprising an acid gas recovery assembly including an absorption unit for bringing the combustion gas into contact with an absorption solution for absorbing at least one acid gas, and a desorption unit for generating the regenerated flow with reduced thermal stability salts.

14. The system further includes at least one additional absorption unit, scrubbing unit, quenching unit, or combination thereof, located upstream of the absorption unit, which absorbs CO from the flue gas. ２ The system according to claim 12 or 13, which removes at least a portion of the acidic gas other than the aforementioned acidic gas.

15. The system according to claim 12 or 13, wherein the oxidation unit is a combustion unit having an inlet that is in fluid communication with the concentration unit for receiving the concentrated wastewater flow.

16. The system according to claim 15, wherein the combustion unit further has a fuel inlet configured to receive the fuel and an oxidizer inlet configured to receive the oxidizer, and the oxidation product stream is a flue gas targeted for the recovery of the amine-based acidic gas.

17. The system according to claim 12 or 13, further comprising a control unit connected to act on at least one of the amine regeneration unit and the concentration unit, for controlling the water content of the wastewater stream and / or the concentration of dissolved salts / acids in the wastewater stream.

18. A method for removing a heat-stable amine salt (HSAS) from a contaminated aqueous amine absorption solution containing an amine in salt form generated during an amine-based acid gas recovery operation, A step of removing at least a portion of the HSAS from the contaminated aqueous amine absorption solution in an amine regeneration unit, thereby producing a wastewater stream containing dissolved salts and / or acids, and a regenerated amine absorption solution containing a reduced amount of the thermally stable amine salt; A step of controlling the operation of the amine regeneration unit to generate the wastewater stream having a salt and / or acid concentration of at least 2% by weight; and, The step of oxidizing the wastewater stream to produce an oxidation product stream containing CO2, water, and nitrogen. A method that includes this.

19. A system for removing a thermally stable amine salt from a contaminated aqueous amine absorption solution generated during the recovery of an amine system of acidic gas representing at least a portion of flue gas produced by the combustion of a fuel and an oxidizer, An amine regeneration unit configured to receive a slip flow containing the thermally stable amine salt from the amine-based acidic gas recovery regeneration unit, and to generate a regenerated flow with reduced thermally stable salt for supply to the amine-based acidic gas recovery absorption unit, and a waste liquid flow containing dissolved salt and / or acid; and A control unit connected to act on the amine regeneration unit to control the water content and / or the concentration of dissolved salts / acids in the wastewater stream; and A system comprising an oxidation unit having an inlet for fluid communication with the amine regeneration unit, wherein the oxidation unit is configured to supply the waste liquid flow to the oxidation unit for oxidation to generate an oxidation product flow.

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