Process and system for treatment of acid gases

Abstract

This invention relates to a system for the treatment of acid gases comprising: a combustion unit (19) configured to combust a predetermined gaseous mixture comprising hydrogen sulphide, wherein said combustion leads to the formation of a plurality of substances, including steam; an exhaust gas treatment unit (22) connected downstream of the combustion unit (19) to receive from the combustion unit (19) exhaust gases resulting from the combustion of said predetermined gaseous mixture, the exhaust gas treatment (22) comprising desulphurisation means for separating a gypsum-containing substance from said exhaust gases; a turbine (24) connected downstream of the combustion unit (19) for receiving from the combustion unit (19) the steam produced by the combustion of said predetermined gaseous mixture, the turbine (24) being configured to generate mechanical energy when receiving steam from the combustion unit (19); means for using said mechanical energy to facilitate the operation of at least one component of said system for the treatment of acid gases. This system for the treatment of acid gases also comprises a catalytic hydrogenation unit (10a) connected, directly or indirectly, via fluid communication means, upstream of the combustion unit (19) and intended to receive a gaseous mixture comprising sulphur dioxide, wherein said catalytic hydrogenation unit (10a) is configured to convert sulphur dioxide into hydrogen sulphide by catalytic hydrogenation; a sweetening unit (10b) connected, directly or indirectly, via fluid communication means, upstream of the combustion unit (19) and connected, via fluid communication means, to said catalytic hydrogenation unit (10a), wherein said sweetening unit (10b) is configured to separate, through the use of methyl diethanolamine (MDEA), a determined quantity of hydrogen sulphide from a gaseous mixture comprising hydrogen sulphide; and a distillation unit (20') connected, directly or indirectly, via fluid communication means, upstream of the combustion unit (19) and connected, via fluid communication means, to said catalytic hydrogenation unit (10a) and to said sweetening unit (10b), wherein said distillation unit (20') is configured to separate, by distillation, certain quantities of carbon dioxide and hydrogen sulphide into a gaseous mixture comprising carbon dioxide and hydrogen sulphide, in such a way as to facilitate the combustion of said predetermined gaseous mixture in the combustion unit (19). This invention also relates to a process for the treatment of acid gases.

Description

[0001] PROCESS AND SYSTEM FOR THE TREATMENT OF ACID GASES

[0002] DESCRIPTION

[0003] This invention relates to a process for the treatment of acid gases, i.e. gases containing hydrogen sulphide (H2S) in significant amounts.

[0004] The invention proposed herein also relates to a system for the treatment of acid gases.

[0005] Natural gas extracted from oil wells normally contains sulphur-based compounds.

[0006] Generally, sulphur compounds are difficult to remove and for this reason it is customary to firstly subject gas streams from oil wells to a desulphurisation process, the main product of which is hydrogen sulphide (H2S).

[0007] Hydrogen sulphide is a highly toxic substance and for this reason it must necessarily be eliminated.

[0008] Various types of installations are known for eliminating or neutralizing the hydrogen sulphide present in natural gas.

[0009] A first type of installation involves the use of amine units to separate the hydrogen sulphide from the natural gas streams.

[0010] Normally, an amine solution having the ability to absorb, i.e. capture, hydrogen sulphide and carbon dioxide (CO2) is used in the amine units when the same solution is passed through the raw natural gas.

[0011] Following the separation of the hydrogen sulphide, it is burned in an incinerator and the sulphur dioxide (SO2) resulting from this incineration is then dispersed into the atmosphere, diluted with air. All the non-combustible gases, such as nitrogen, argon and carbon dioxide, which, as is known, is a greenhouse gas, are released into the atmosphere in these installations.

[0012] However, the use of this type of installation involves several problems and disadvantages.

[0013] In fact, the amine units require a considerable expenditure of energy to make it possible for the amine solution to circulate through the natural gas stream.

[0014] Furthermore, the incineration of hydrogen sulphide requires the use of a combustible gas, such as methane, and also leads to the need to emit large quantities of carbon dioxide into the atmosphere, in addition to sulphur dioxide, as indicated above.

[0015] Gas flaring systems are commonly provided downstream of these installations, that is to say, systems designed for the combustion of exhaust gases, which inevitably determine the pollution of the surrounding environment.

[0016] A second type of installation involves the use of amine units in combination with a Claus unit.

[0017] In this case, the hydrogen sulphide separated into the amine units is subsequently transferred to the Claus unit where it is treated to obtain its neutralization.

[0018] In this case, a high consumption of electrical energy is required for the operation of the amine units and the Claus unit, which also requires the supply of thermal energy to operate as intended.

[0019] Furthermore, this installation entails the need to manage and dispose of the sulphur resulting from the treatment in the Claus unit.

[0020] There is also a third type of installation which allows the neutralization of hydrogen sulphide contained in natural gas streams through the use of non-regenerative oxidation materials, such as iron oxide and zinc oxide.

[0021] However, this installation can only be used in the case of gaseous flows at low regimes and with reduced concentrations of hydrogen sulphide.

[0022] Furthermore, the use of a non-regenerative material for the neutralization of hydrogen sulphide evidently entails the need to provide for its replacement it when it is no longer usable.

[0023] An example of a known type plant for the treatment of acid gases is illustrated in US patent application US 2021 / 253966 Al.

[0024] In this plant it is envisaged that the raw natural gas will be passed, firstly, through a desulphurization system and then, possibly, also through a Claus system for the extraction of elemental sulphur, before being introduced into a combustion unit designed to carry out, in fact, the combustion of the gases introduced therein.

[0025] This plant has the disadvantage of having to provide large quantities of energy to the combustion unit to make it possible to completely combust the gaseous mixture introduced into this unit, this mixture in this case containing high concentrations of carbon dioxide.

[0026] Another significant disadvantage to be attributed to the same plant is given by the fact that both the combustion unit and the functional units operatively connected upstream of it, as well as the equipment and auxiliary devices, require rather large and bulky dimensions to be able to receive and treat the gaseous mixture.

[0027] The aim of this invention is to solve the problems of the prior art described above.

[0028] A further aim of the invention is to provide a process for the treatment of acid gases which can be implemented by supplying it with small amounts of energy from outside.

[0029] Another aim of the invention is to provide a process for the treatment of acid gases that can be implemented through the use of relatively small equipment and operating units.

[0030] Yet another aim of the invention is to provide a process for the treatment of acid gases that allows the complete utilization of all the tail gases downstream of the amine units.

[0031] A further aim of the invention is to provide a process for the treatment of acid gases which does not involve gas flaring, i.e. combustion of the exhaust gases.

[0032] Another aim of the proposed invention is to provide a process for the treatment of acid gases, in which direct emissions of waste substances into the atmosphere are not envisaged.

[0033] A further aim of invention is to provide a process for the treatment of acid gases that also supplies mechanical energy as an output that can be used to feed the system for the removal of hydrogen sulphide.

[0034] Another aim of the invention is to provide a process for the treatment of acid gases, the implementation of which involves the emission of small quantities of carbon dioxide.

[0035] A further aim of the invention is to provide a process for the treatment of acid gases, which involves a substantial balance between the quantity of gas emitted and that absorbed, for most of the greenhouse gases.

[0036] Another aim of the invention is to provide a process for the treatment of acid gases, which does not lead to the release of hazardous substances into the atmosphere.

[0037] Another aim of the invention proposed herein is to provide a system for the treatment of acid gases, which requires small amounts of energy from the outside for its correct operation.

[0038] Yet another aim of the invention is to provide a system for the treatment of acid gases, which is composed of equipment and operating units of small dimensions.

[0039] A specific aim of the invention is a therefore system for the treatment of acid gases comprising: a combustion unit configured to combust a predetermined gaseous mixture comprising hydrogen sulphide, wherein said combustion leads to the formation of a plurality of substances, including steam; an exhaust gas treatment unit connected downstream of the combustion unit to receive, in use, from the combustion unit exhaust gases resulting from the combustion of said predetermined gaseous mixture, the exhaust gas treatment unit comprising desulphurisation means for separating, from said exhaust gases, a gypsum-containing substance; a turbine connected downstream of the combustion unit for receiving, in use, from the combustion unit steam produced by the combustion of said predetermined gaseous mixture, the turbine being configured to generate mechanical energy when receiving steam from the combustion unit; means for using said mechanical energy to facilitate the operation of at least one component of said system for the treatment of acid gases; a catalytic hydrogenation unit connected, directly or indirectly, by fluid communication means, upstream of the combustion unit and intended to receive, in use, a gaseous mixture comprising sulphur dioxide, wherein said catalytic hydrogenation unit is configured to convert sulphur dioxide to hydrogen sulphide by catalytic hydrogenation; a sweetening unit connected, directly or indirectly, by fluid communication means, upstream of the combustion unit and connected, by fluid communication means, to said catalytic hydrogenation unit, wherein said sweetening unit is configured to separate, in use, by the use of methyl diethanolamine (MDEA), a determined quantity of hydrogen sulphide from a gaseous mixture comprising hydrogen sulphide; and a distillation unit connected, directly or indirectly, by means of fluid communication, upstream of the combustion unit and connected, by means of fluid communication, to said catalytic hydrogenation unit and to said sweetening unit, wherein said distillation unit is configured to separate, in the use, by distillation, of certain determined quantities of carbon dioxide and hydrogen sulphide in a gaseous mixture comprising carbon dioxide and hydrogen sulphide, in such a way as to facilitate the combustion of said predetermined gaseous mixture in the combustion unit.

[0040] The invention also relates to a process for the treatment of acid gases comprising the steps of: providing a first gaseous mixture comprising sulphur dioxide and carbon dioxide; subjecting said first gaseous mixture to catalytic hydrogenation in such a way as to obtain a second gaseous mixture, wherein said catalytic hydrogenation results in the conversion of said sulphur dioxide into hydrogen sulphide; removing a determined quantity of hydrogen sulphide from said second gaseous mixture by using methyl diethanolamine (MDEA) in such a way as to obtain a third gaseous mixture; removing, by distillation, a determined quantity of carbon dioxide and a determined quantity of hydrogen sulphide from said third gaseous mixture so as to obtain a fourth gaseous mixture; subjecting said fourth gaseous mixture to combustion so as to obtain, as a result of said combustion, the formation of a plurality of substances, including steam; separating, by means of desulphurisation, a substance containing gypsum from exhaust gases resulting from said combustion; providing a turbine; supplying steam produced by said combustion to the turbine in such a manner that said turbine generates mechanical energy when it receives said steam; and using said mechanical energy in at least one step of said process to facilitate said at least one step.

[0041] Preferred embodiments and forms of implementation are defined in the dependent claims.

[0042] Features and advantages will become clearer from the following description of a preferred but not exclusive embodiment illustrated, purely by way of non-limiting example, in the attached Figure 1 which shows a block diagram relating to the process according to the invention.

[0043] More in detail, in the block diagram of Figure 1, a catalytic hydrogenation unit is indicated, with reference 10a, intended to receive raw exhaust or tail gases, namely a gaseous mixture containing hydrogen sulphide (H2S), sulphur dioxide (SO2) and non-combustible gases, namely water vapour (H2O), nitrogen (N2), carbon monoxide (CO) and carbon dioxide (CO2) and other gases including hydrogen (H2) and argon (Ar). For example, this gaseous mixture could come, directly or indirectly, from systems or equipment for the extraction and / or treatment of natural gas from oil wells.

[0044] In the catalytic hydrogenation unit 10a, this mixture is subjected to a catalytic hydrogenation to convert the sulphur dioxide (SO2) into hydrogen sulphide (H2S), thus avoiding having to emit sulphur dioxide (SO2) into the atmosphere.

[0045] In the catalytic hydrogenation unit 10a there is a quench tower i.e. a cooling tower in which a sudden cooling of the aforementioned mixture is carried out.

[0046] A filter is also connected to the quench tower to capture the solid particles of elemental sulphur and thus prevent contamination of the units and systems located downstream of it.

[0047] Downstream of the catalytic hydrogenation unit 10a, a sweetening unit 10b is connected, via a first connection line 10’, where the gaseous mixture leaving the catalytic hydrogenation unit 10a itself is made to flow.

[0048] In the sweetening unit 10b, the gaseous mixture is subjected, through the use of methyl diethanolamine (MDEA), to a sweetening operation, in which a large part of the hydrogen sulphide (H2S) is separated from the main gaseous stream.

[0049] The hydrogen sulphide (H2S) separated in the sweetening unit 10b then passes, via a second connection line 20, from this unit to a distillation unit 20’ for the distillation of carbon dioxide (CO2) and hydrogen sulphide (H2S).

[0050] The distillation unit 20’ includes a distillation column, in addition to a plurality of pumps and compressors to allow operation of the same distillation column.

[0051] A combustion unit 19 is connected downstream of said distillation unit 20’ through a third connection line 19’.

[0052] Specifically, the combustion unit 19 is a boiler in which a small quantity of methane is introduced to start and keep active the combustion of the hydrogen sulphide.

[0053] The combustion of hydrogen sulphide in the combustion unit 19 results in the formation of steam and fumes containing, mainly, sulphur dioxide (SO2) and a small amount of carbon dioxide (CO2).

[0054] According to a particularly advantageous aspect of the invention, in practice, only combustible gas in the form of hydrogen sulphide (H2S) passes from the distillation unit 20’ to the combustion unit 19 thanks to the fact that, upstream of the same combustion unit 19, the catalytic hydrogenation unit 10a, the sweetening unit 10b and the distillation unit 20’ described above have been provided, which operate jointly in such a way as to remove all incombustible gases from the gaseous mixture, thus providing for the separation of the incombustible gases from the combustible gases.

[0055] The aspect just highlighted leads to a significant energy saving in terms of smaller quantities of methane for feeding the boiler constituting the combustion unit 19; according to the invention, it is in fact sufficient to supply a minimum quantity of methane to the combustion unit 19 to obtain the complete combustion of the gaseous mixture introduced therein.

[0056] A further important advantage deriving from this aspect of the invention is given by the possibility of making a combustion unit 19 of small dimensions, in consideration of the fact that the latter is intended to receive and treat, as mentioned above, only combustible gas in the form of hydrogen sulphide (H2S), therefore a gas free of incombustible substances.

[0057] The fact of having a combustion unit 19 that is not bulky makes it possible to install it even in restricted spaces, as well as facilitating the assembly and installation on site of the same unit.

[0058] Clearly, for the same reason highlighted above, the operating units and the related auxiliary devices (including also the interconnection pipes and valves) provided directly upstream and downstream of the combustion unit 19 may also be of small dimensions and therefore can also be installed in restricted spaces.

[0059] In particular, the fact of having envisaged, upstream of the combustion unit 19, the catalytic hydrogenation unit 10a, the sweetening unit 10b and the distillation unit 20’, in this specific order (also shown in figure 1), allows in fact to maximize the removal of the incombustible gases from the gaseous mixture entering the catalytic hydrogenation unit 10a before its entry into the combustion unit 19.

[0060] Furthermore, the gases extracted from the gaseous mixture upstream of the combustion unit 19 can be conveniently used for other applications and / or uses, and thus monetized.

[0061] The aforementioned fumes formed in the combustion unit 19 are made to flow, via a fourth connection line 21, to an exhaust gas treatment unit 22 comprising a combustion gas desulphurisation system or means of flue gas desulphurisation.

[0062] Specifically, this flue gas desulphurisation system comprises an absorber, i.e. an absorption system, to which a "limestone" type washing system is operatively connected.

[0063] When these fumes enter the absorber, the sulphur dioxide (SO2) contained in the fumes reacts with the mixture of limestone and water coming from the "limestone" type washing system, giving rise to a gypsum slurry.

[0064] At the same time, water vapor is introduced into the absorber to ensure that the saturated water vapor fumes can be released into the atmosphere through a humid flue or a cooling tower, as they are not harmful to the external environment.

[0065] The steam generated by the combustion in the combustion unit 19 is transferred, by means of a fifth connection line 23, to a steam turbine 24 which, thanks to the expansion of the steam itself, will produce mechanical energy, which is later converted into electrical energy through the use of an alternator.

[0066] The energy produced by the steam turbine 24 can be used to power the entire process according to the invention.

[0067] A part of the mechanical energy produced by the steam turbine 24 can also be used to facilitate the combustion of hydrogen sulphide in the combustion unit 19, providing for example an energy conversion system for converting the aforementioned mechanical energy into thermal energy, or by connecting an alternator to the steam turbine 24 for converting this mechanical energy into electrical energy and at the same time providing an energy conversion system for converting the electrical energy produced by the alternator into thermal energy. For example, in order to facilitate the combustion of the hydrogen sulphide in the combustion unit 19, the latter may be equipped with a heating system or apparatus provided with one or more electrical resistors powered by the electrical energy produced by an alternator connected to the steam turbine 24.

[0068] Thus, in this case, a minimum supply of methane will be necessary for starting and maintaining the combustion in the combustion unit 19, thanks also to the fact that - as mentioned above - the gaseous mixture entering the combustion unit 19 and subjected to combustion therein contains, substantially, only combustible gas in the form of hydrogen sulphide (H2S).

[0069] The system described above does not therefore need to be powered by external electrical or thermal sources.

[0070] The gaseous mixture resulting from the separation of the hydrogen sulphide (H2S) from the main stream is made to flow, through a sixth connection line 10", from the sweetening unit 10b to a first separation unit 11, where the water vapour is separated and removed from the same mixture.

[0071] The first separation unit 11 may comprise, for example, one or more knockout drums, i.e. vertical separators that exploit gravity to drop the drops of liquid (in this case, water) downwards and allow their removal from the bottom of each separator.

[0072] The gaseous mixture containing any mixture of nitrogen (N2), carbon monoxide (CO), carbon dioxide (CO2) and a small quantity of hydrogen sulphide (H2S) is then transferred via a seventh connection line 12 from the first separation unit 11 to a second separation unit 13.

[0073] The second separation unit 13 comprises membranes and pressure swing absorption (PSA) systems which, operating jointly, allow the separation of carbon monoxide (CO), carbon dioxide (CO2) and nitrogen (N2) from the gaseous mixture to be obtained.

[0074] The second separation unit 13 and the aforementioned distillation unit 20’ are both also connected to a thermal oxidizer 25 respectively through an eighth connection line 26 and a ninth connection line 27.

[0075] Specifically, during the operation of the system according to the invention, the following gases may, for example, pass through the eighth connection line 26: hydrogen, argon, carbon monoxide, ammonia, cyanide, methane, ethane, propane and butane.

[0076] During the operation of the same system, carbon dioxide and water may, for example, also pass through the ninth connection line 27.

[0077] Once the aforementioned substances enter the thermal oxidizer 25 through the eighth connection line 26 and the ninth connection line 27, they react with an incineration gas (e.g. methane) and oxygen present in the air at combustion temperatures close to 1000 °C.

[0078] The high temperature combustion reaction that occurs in the thermal oxidizer 25 produces the effect of destroying all the acid gases present in the aforementioned substances entering the thermal oxidizer 25.

[0079] In this way, such high temperature combustion gives rise to the formation of only inert gases and minimal quantities of carbon dioxide, which are then released into the atmosphere from the thermal oxidizer 25.

[0080] The term "inert gas" refers to a gas that does not produce chemical reactions with its surrounding environment under normal conditions of pressure and temperature. On the basis of the above, the thermal oxidizer 25 therefore performs the function of thermally oxidizing the substances entering it and releasing into the atmosphere the low-energy, non-volatile and non-combustible molecules resulting from the high- temperature combustion reaction.

[0081] The gaseous nitrogen (N2), resulting from the separation carried out in the second separation unit 13, is instead transferred via a tenth connection line 15 from the same second separation unit 13 to a first liquefaction unit 14, where thanks to the use of compressors and heat exchangers the transformation of the gaseous nitrogen (N2) into liquid nitrogen (N2) is obtained.

[0082] The liquid nitrogen (N2) thus obtained is then extracted and removed from the first liquefaction unit 14.

[0083] The nitrogen (N2), gaseous and liquid, can be used for industrial uses.

[0084] The carbon dioxide (CO2) resulting from the separation carried out in the second separation unit 13 is instead transferred via an eleventh connection line 16 from the second separation unit 13 to a second liquefaction unit 17, where thanks to the use of compressors and heat exchangers the transformation of the gaseous carbon dioxide (CO2) into liquid carbon dioxide (CO2) is obtained.

[0085] The liquid carbon dioxide (CO2), thus obtained, is then extracted and removed from the second liquefaction unit 17 by means of a special extraction system.

[0086] Other gases (such as argon) present in the gaseous mixture resulting from the process described above can also be liquefied by means of known techniques and processes. The connection lines and branches mentioned above may comprise pipes, ducts, fittings and, in general, components to allow the transfer of gases, gaseous mixtures and fluid mixtures.

[0087] The system described above may also comprise members and devices for moving gases, gaseous mixtures and fluid mixtures.

[0088] As can be seen from the foregoing description, the process and the system according to the invention have many advantages over the prior art.

[0089] In fact, the system according to the invention can be easily installed even in places where there is limited space available for its installation.

[0090] Furthermore, the process proposed here has been designed in such a way that the combustion phase of the gaseous mixture requires, for its implementation, a minimum energy input (i.e. methane), thanks above all to the particular process phases envisaged upstream of the combustion unit.

[0091] This process has also been conceived in such a way that the chemical energy of hydrogen sulphide (H2S) can be used to power the process itself, or to provide electricity to the latter.

[0092] This means that the external energy input, necessary for the implementation of the aforementioned process, is considerably lower than that required by currently known processes for the treatment of the acid tail gases.

[0093] The fact that this process requires a reduced external contribution of thermal and electrical energy also leads to a substantial reduction in the carbon dioxide released into the atmosphere.

[0094] Having foreseen the combustion of hydrogen sulphide (H2S) in the process proposed her means that carbon dioxide (CO2) is not generated by the combustion process.

[0095] The fact that the gases of the process described above are reusable for industrial applications and uses contributes to the reduction of the carbon footprint, with obvious benefit for the environment. Furthermore, the process according to the invention does not require, for its implementation, the release of hazardous gases into the atmosphere.

[0096] A further advantage of this process is that it does not involve gas flaring.

[0097] It is understood that the above has been described by way of non- limiting example, therefore any constructive variants are understood to fall within the protective scope of this technical solution, as described above and claimed below.

Claims

CLAIMS1. A system for the treatment of acid gases, comprising:- a combustion unit (19) configured for the combustion of a predetermined gaseous mixture comprising hydrogen sulphide; wherein said combustion leads to the formation of a plurality of substances, including steam;- an exhaust gas treatment unit (22) connected downstream of the combustion unit (19) for receiving, in use, from the combustion unit (19) exhaust gases resulting from the combustion of said predetermined gaseous mixture; the exhaust gas treatment unit (22) comprising desulphurisation means for separating, from said exhaust gases, a substance containing gypsum;- a turbine (24) connected downstream of the combustion unit (19) for receiving, in use, from the combustion unit (19) the steam produced by the combustion of said predetermined gaseous mixture; the turbine (24) being configured to generate mechanical energy when receiving steam from the combustion unit (19);- means for using said mechanical energy to facilitate the operation of at least one component of said system for the treatment of acid gases;- a catalytic hydrogenation unit (10a) connected, directly or indirectly, by means of fluid communication, upstream of the combustion unit (19) and intended to receive, in use, a gaseous mixture comprising sulphur dioxide; wherein said catalytic hydrogenation unit (10a) is configured to convert sulphur dioxideto hydrogen sulphide by catalytic hydrogenation;- a sweetening unit (10b) connected, directly or indirectly, by means of fluid communication, upstream of the combustion unit (19) and connected, by means of fluid communication, to said catalytic hydrogenation unit (10a); wherein said sweetening unit (10b) is configured to separate, in use, by the use of methyl diethanolamine (MDEA), a determined quantity of hydrogen sulphide from a gaseous mixture comprising hydrogen sulphide; and- a distillation unit (20’) connected, directly or indirectly, by means of fluid communication, upstream of the combustion unit (19) and connected, by means of fluid communication, to said catalytic hydrogenation unit (10a) and to said sweetening unit (10b); wherein said distillation unit (20’) is configured to separate, in use, by distillation, certain quantities of carbon dioxide and hydrogen sulphide into a gaseous mixture comprising carbon dioxide and hydrogen sulphide, in such a way as to facilitate the combustion of said predetermined gaseous mixture in the combustion unit (19).

2. The system for the treatment of acid gases according to claim 1, characterized in that said sweetening unit (10b) and said distillation unit (20’) are connected, directly or indirectly, downstream of said catalytic hydrogenation unit (10a).

3. The system for the treatment of acid gases according to claim 1 or 2, characterized in that said distillation unit (20’) is connecteddownstream of said sweetening unit (10b).

4. The system for the treatment of acid gases according to any of the preceding claims, characterized in that said catalytic hydrogenation unit (10a) comprises a cooling tower, for rapidly cooling said gaseous mixture comprising sulphur dioxide, and a filter connected to said cooling tower and configured to capture solid particles of elemental sulphur in said gaseous mixture comprising sulphur dioxide.

5. The system for the treatment of acid gases according to any of the preceding claims, characterized in that said distillation unit (20’) comprises a distillation column, at least one pump connected to said distillation column, and at least one compressor connected to said distillation column, to enable the operation of said distillation column.

6. The system for the treatment of acid gases according to any of the preceding claims, characterized in that said means for using said mechanical energy comprise:- means for converting, directly or indirectly, the mechanical energy produced by the turbine (24) into thermal energy; and- means for providing said thermal energy to the combustion unit (19) to promote combustion in the combustion unit (19).

7. The system for the treatment of acid gases according to any of the preceding claims, characterized in that it comprises a thermal oxidizer (25) connected, by means of fluid communication, downstream of the distillation unit (20’) and intended to receive, in use, at least one substance from said distillation unit (20’); said thermal oxidizer (25) being configured to subject said at least one substance to a combustionreaction at a temperature higher than 750°C.

8. The system for the treatment of acid gases according to any of the preceding claims, characterized in that the combustion unit (19) comprises a boiler, and in that it comprises means for supplying methane to said boiler.

9. A process for the treatment of acid gases comprising the steps of:- providing a first gaseous mixture comprising sulphur dioxide and carbon dioxide;- subjecting said first gaseous mixture to catalytic hydrogenation in such a way as to obtain a second gaseous mixture; wherein said catalytic hydrogenation results in the conversion of said sulphur dioxide into hydrogen sulphide;- removing a determined quantity of hydrogen sulphide from said second gaseous mixture by the use of methyl diethanolamine (MDEA) so as to obtain a third gaseous mixture;- removing, by distillation, a determined quantity of carbon dioxide and a determined quantity of hydrogen sulphide from said third gaseous mixture so as to obtain a fourth gaseous mixture;- subjecting said fourth gaseous mixture to a combustion in such a way as to obtain, as a consequence of said combustion, the formation of a plurality of substances, including steam;- separating, by desulphurisation means, a substance containing gypsum from exhaust gases resulting from said combustion;- providing a turbine (24);- providing the steam produced by said combustion to the turbine(24) in such a way that said turbine (24) generates mechanical energy when receiving said steam; and- using said mechanical energy in at least one step of said process to facilitate said at least one step.

10. The process according to claim 9, characterized in that said mechanical energy is used in said step of subjecting said fourth gaseous mixture to combustion.

11. The process according to claim 9 or 10, characterized in that it comprises the step of subjecting to combustion, at a temperature above 750°C, a mixture comprising carbon dioxide and water and resulting from the execution of said step of removing, by distillation, a determined quantity of carbon dioxide and a determined quantity of hydrogen sulphide from said third gaseous mixture.

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