ELECTRICAL TRANSFORMER FOR TREATING COMBUSTION GASES PRODUCED DURING THE REACTIVATION OF THE ADSORBENT MATERIAL – ASSOCIATED PROCESS

Abstract

The present invention relates to an electrical transformer of the type comprising: a cooling circuit containing an insulating oil; a unit for regenerating said oil comprising a regeneration column (51; 52) filled with a solid adsorbent material capable of adsorbing oxygenated and / or sulfur-containing organic compounds contained in said oil. According to the invention, said regeneration unit further comprises: - a catalytic reactor (12) containing at least one first catalyst capable of oxidizing carbon monoxide and volatile organic compounds and at least one second catalyst capable of reducing sulfur and / or nitrogen oxides, the inlet of said catalytic reactor (12) being connected to said outlet of said regeneration column (51; 52); and - a particle filter (14) connected to the outlet of said catalytic reactor (12) and the outlet is connected to the atmosphere.

Description

Title of the invention: ELECTRICAL TRANSFORMER FOR PROCESSING COMBUSTION GASES PRODUCTS DURING REACTIVATION OF THE ADSORBENT MATERIAL - ASSOCIATED PROCESS Technical field

[0001] The present invention relates to an electrical transformer for treating the combustion gases produced by the thermal reactivation of the adsorbent material which serves for the regeneration of the insulating oil circulating in the transformer. The present invention also relates to an associated method. Previous Art

[0002] Currently, the conventional regeneration of insulating oils in power transformers consists of two treatments: vacuum degassing, which allows the elimination of dissolved gases along with the water present in the water, and the filtration of acid compounds with so-called oil regeneration columns. These regeneration columns are filled with a solid adsorbent material generally referred to as "fuller's earth." This material preferentially adsorbs oxygenated compounds, thus eliminating the majority of acid and sulfur compounds responsible for the degradation of the insulating oil.

[0003] When the adsorbent material is saturated, it is then reactivated by a thermal reactivation process which allows it to be reused several hundred times. This reactivation is carried out by calcining the adsorbed organic compounds at a temperature of 250 to 700°C. This reactivation method produces toxic fumes which must be treated before being released into the atmosphere. The regeneration column therefore includes heating means (resistors) for heating the volume of adsorbent material it contains in order to burn the adsorbed organic compounds; the oil regeneration column therefore also serves to reactivate the adsorbent material.

[0004] Currently, most transformers include an oil regeneration unit which is equipped with activated carbon filters that filter the gases produced during the reactivation of the adsorbent material. These filters are not selective, saturating quickly in the presence of significant quantities of gases produced. They prove insufficiently effective and do not allow compliance with regulations in terms of solid particles emitted as well as concentrations of carbon monoxide, nitrogen oxides and / or sulfur.

[0005] An aim of the present invention is to propose a method for regenerating the oil of an electrical transformer which allows the treatment of gases and possible particles produced during the thermal reactivation of the solid adsorbent material used for the regeneration of the oil.

[0006] Another aim is to propose a method as mentioned above which complies with the legislation in force with regard to the contents of particles, carbon monoxide, sulphur oxides, possibly nitrogen oxides and VOCs (VOCt, VOCnm and VOCm) in the discharged gases.

[0007] Another aim of the invention is to propose an electrical transformer which complies with the regulations in force regarding work safety and air pollution.

[0008] The present invention relates to an electrical transformer of the type comprising: - a cooling circuit in which an insulating oil circulates; - a unit for regenerating said oil which comprises at least one column regeneration column filled with a solid adsorbent material capable of adsorbing oxygenated and / or sulfurous organic compounds contained in said oil, said regeneration column having an inlet and an outlet and comprising means for heating said adsorbent material;

[0009] characterized in that said regeneration unit further comprises:

[0010] - a catalytic reactor containing at least one first catalyst capable of oxidizing the carbon monoxide and volatile organic compounds and at least one second catalyst capable of reducing sulfur and / or nitrogen oxides, the inlet of said catalytic reactor being connected to said outlet of said regeneration column; and

[0011] - a particle filter whose inlet is connected to the outlet of said catalytic reactor and the outlet is connected to the atmosphere.

[0012] The above-mentioned catalysts may be catalysts used for the treatment of exhaust gases from motor vehicles. The inventors have the merit of having found that the gases emitted did not comply with the regulations. Furthermore, in the case of a motor vehicle, there are not three gas production regimes which vary in flow rate and chemical nature, as is the case during the reactivation of an adsorbent material of the Fuller's earth type, for example. It was therefore not obvious to use catalysts contained in motor vehicle catalytic converters to treat the above-mentioned gases. Furthermore, the inventors also found that the catalytic reactions could take place at the temperatures existing at the outlet of the regeneration column when the latter is used for the reactivation of the adsorbent material which it contains.

[0013] Advantageously, said oil regeneration unit further comprises a first gas / liquid separator mounted at the outlet of said regeneration column and possibly a gravity separator mounted on the condensate outlet of said first gas / liquid separator, the gas outlet of said first gas / liquid separator being connected at the inlet of said catalytic reactor. It is the inventors' merit to have noted that during the thermal reactivation of the adsorbent material contained in the regeneration column, the gases at the outlet of the regeneration column contain water in the form of droplets, formed by the combustion of the adsorbed compounds and still a small proportion of oil in liquid form also. Water and oil form an azeotrope. Condensing the water and oil helps to preserve the catalysts and to obtain a better yield for the catalytic reactions. The oil can then be separated from the water in the liquid phase by phase separation, the oil supernatant on the water. The supernatant oil is stored in a buffer tank which is connected to the transformer oil tank.

[0014] Advantageously, said oil regeneration unit also comprises a second gas / liquid separator of the coalescence filter type, mounted upstream of said catalytic reactor.

[0015] Advantageously, whatever the embodiment, the regeneration unit further comprises a heater mounted upstream of said catalytic reactor and downstream of the gas outlet of said first or said second gas / liquid separator, when the regeneration unit comprises two gas / liquid separators. This heater makes it possible to obtain the optimum temperature for the catalysis of the compounds produced by the reactivation of the adsorbent material.

[0016] Whatever the embodiment, the oil regeneration unit may further comprise suction means (one or more vacuum pumps), mounted upstream of said catalytic reactor and connected to the outlet of said regeneration column. These suction means make it possible to create a partial vacuum which sucks the gases out of the regeneration column and allows the formation of a homogeneous mixture when air or oxygen is mixed with the combustion gases. The pressure in the catalytic reactor and in the particulate filter is not the same as that created in the columns; it is for example greater than or equal to 700 mbar absolute and less than or equal to 850 mbar absolute in the columns, this pressure increases in the catalytic reactor and the particulate filter it is for example greater than or equal to 1013 mbar and less than or equal to 1213 mbar in the latter.

[0017] The vacuum pump draws in the oil- and moisture-laden gases leaving the regeneration columns. This azeotropic mixture passes through the liquid / gas separator to condense the water present in the gases and then through the coalescence filter to remove the remaining traces of oil and water, before passing into the vacuum pump, which discharges the dry gases into the catalytic reactor.

[0018] The adsorbent material is not limited according to the invention. It can be chosen from clays, bauxite, bentonite, attapulgite, kaolin, and calcium montmorillonate and mixtures thereof. Preferably, the adsorbent material contains by mass at least 70% aluminum oxide (A12O3) and preferably at least 78% aluminum oxide. Preferably it contains 95% or less aluminum oxide. Preferably, the adsorbent material may have the following composition, in mass percentages: SiO2: 2.75%, TiO2: 0.33%, Fe2O3: 3.99%, A12O3: 92.5% MgO: 0.05%, Na2O: 0.03%. The adsorbent material may also contain calcium oxide. The adsorbent material is heat resistant and in particular resistant to the combustion temperature of the adsorbed compounds. For example, it may lose % by mass or 6.32% by mass when heated to 1000°C for 60 min.

[0019] The regeneration unit may contain two second catalysts. The number of catalysts depends on the type of catalyst (volume, nature, porosity, etc.) and the volume of combustion gas to be treated. The person skilled in the art is able to size the catalytic reactor according to the catalysts used.

[0020] The type of catalyst is not limited according to the invention. It may be, for example, for both catalysts, a catalyst which comprises a solid and porous support forming a block on which is deposited a catalytic material containing a platinum group metal, in particular, platinum, palladium or a palladium and platinum mixture.

[0021] The support may contain at least one metal oxide selected from the group consisting of optionally stabilized alumina, optionally stabilized titanium of acidic character (which reduces the formation of sulfates, the SO2 storage capacity and promotes the reactivation of the catalyst), a mixed oxide of cerium-titanium oxide and / or an optionally stabilized mixed oxide of cerium-zirconium (reducing character, increases the O2 storage capacity) and mixtures of any two or more of these, and a composition comprising silica and / or silicon oxide (thermal stability).

[0022] The particle filter is not limited according to the invention. It can be made of ceramic. In all cases, it must allow the filtration of particulate matter (PMI, PM2.5, PM5, PM 10) generated by combustion.

[0023] Advantageously, said particle filter comprises at least one metal from the platinum group, in particular platinum or palladium or a palladium and platinum mixture. The presence of this metal makes it possible to increase the temperature in the particle filter and to regenerate it more easily thereafter. Indeed, the aforementioned metal can cause the combustion of the filtered particles; the filter is thus capable of self-reactivating / self-regenerating.

[0024] Advantageously, the regeneration unit may comprise means for admitting an adjustable flow of air or oxygen mounted upstream of said catalytic reactor and downstream of said regeneration column and / or mounted at the inlet of said regeneration column. When they are mounted upstream of said catalytic reactor, they are mounted upstream of the suction means, upstream of said second gas / liquid separator, upstream of the heater and downstream of said first gas / liquid separator. The dilution of the combustion gases facilitates the catalytic reaction and makes it possible to adjust the flow rate when the combustion gas flow rate varies according to the speed and progress of the combustion reaction.

[0025] The regeneration column may contain, below the layer of adsorbent material, an alumina layer and a graphite filter. The alumina layer, which is highly heat-resistant, protects the adsorbent material by absorbing excessive heat; the filtering graphite layer allows the fines from the adsorbent material to be retained in the regeneration column.

[0026] Advantageously, the regeneration unit may comprise means for adjusting the distance separating the outlet of said thermal reactivation column and the inlet of said catalytic reactor and / or means for adjusting the distance separating the outlet of said catalytic reactor and the inlet of said particle filter. These adjustment means may be, for example, more or less long branch circulation pipes equipped with valves so as to be able to be closed. When the gases pass through these longer pipes, the wall of which is in contact with the atmospheric air, the gases cool and reach the temperature most suitable for the catalytic reaction or filtration.

[0027] The electrical transformer may also include a heat exchanger capable of recovering heat from the gases leaving said particle filter to heat the gases entering said catalytic reactor. Part of the heat exchanger may act as a heater.

[0028] The catalytic reactor may also comprise other catalytic blocks, for example, a catalytic block allowing the Fischer-Tropsch reaction or a catalytic block allowing the Sabatier reaction; in this case, a hydrogen source may also be connected to the catalytic reactor.

[0029] The oil is not used according to the invention. It may be a mineral oil which mainly contains a mixture of paraffins, naphthenes, aromatics and alkenes.

[0030] The present invention also relates to a method for regenerating the insulating oil contained in an electrical transformer on at least one column containing an adsorbent material according to which said adsorbent material is thermally reactivated by causing the combustion of the oxygenated and possibly sulfurous organic compounds adsorbed on said adsorbent material. Typically, according to the invention, a liquid / gas separation of the gases produced during the reactivation of said adsorbent material is carried out and then said gases are passed over at least one catalyst so as to transform the organic compounds into carbon dioxide, oxidize carbon monoxide into carbon dioxide and reduce the nitrogen and / or sulfur oxides formed and then filter the solid particles contained in said gases.

[0031] Advantageously, said gases are heated before passing over said catalyst and in particular in that said gases are heated at least partially with the heat of the filtered gases.

[0032] Advantageously, said gases produced are diluted with air or oxygen before the gas / liquid separation and / or during the catalytic reaction.

[0033] Advantageously, said catalyst comprises a metal from the platinum group, in particular platinum, palladium or a mixture of platinum and palladium.

[0034] Advantageously, said gases are filtered on a filter containing a catalyst containing a metal from the platinum group and in particular platinum.

[0035] According to a preferred embodiment, the hourly volumetric velocity of the gases entering said catalyst is greater than 20 and less than 100 kh1, said incoming gases being diluted by 20 to 50% by volume with air and heated to a temperature greater than or equal to 300°C, said at least one catalyst containing a concentration of platinum or platinum and palladium greater than or equal to 0.5 and less than or equal to 4 g / l of catalyst.

[0036] Advantageously, said gases are sucked in by creating a pressure greater than or equal to 700mb absolute and less than atmospheric pressure before passing them over said at least one catalyst. If the vacuum is higher, the catalytic reaction does not take place. This vacuum also allows the gases to be mixed and circulated out of the regeneration column.

[0037] All information relating to catalysts, adsorbent material and filter applies to the installation and the process indifferently.

[0038] The process of the invention makes it possible to treat fumes / gases containing at least 100 ppm of carbon monoxide (CO), 30 ppm of volatile organic compounds (NMVOC), 100 ppm of nitrogen oxides (NOx), 50 ppm of sulfur oxides (SOx) generated by the reactivation of bauxite (adsorbent material used for the reactivation of transformer oils) saturated by the adsorbed compounds originating from the treated oil.

[0039] As already mentioned, the treated (regenerated) oils can be mineral, synthetic or vegetable oils.

[0040] The method according to the invention allows in parallel the treatment of fine particulate matter of the PMI type; PM2.5; PM5; PM10.

[0041] The catalysis step is advantageously carried out in a temperature range from 250°C to 350°C, preferably from 300°C to 350°C.

[0042] The filtration is advantageously carried out at a temperature of 350°C.

[0043] As a catalyst, a single type of monolithic substrate or different types of monolithic substrate comprising at least one platinum group metal (PGM) and one platinum-containing metal may be used, the catalysts being placed in series.

[0044] The distance between the catalytic monolithic substrate and the filter should be between 0.3 m and 1 m, preferably 0.3 m to 0.5 m.

[0045] The dilution of the gas and / or combustion gases by air is carried out between 35% and 100%.

[0046] The sizing is carried out with the parameter of the hourly volumetric velocity (WH) which is expressed in (h1) and which is defined by the ratio between the gas flow rate Q in (m3 / h) and the volume of the catalyst V in (m3). The value of the WH must be between 20 k h-1 and 100 k h1.

[0047] Proper sizing of the catalyst allows for better treatment efficiency.

[0048] The method has been industrially validated for a single gas and / or mixed gases initially containing CO, NMVOCs / VMOCs, SOX, NOx and particulate matter.

[0049] The variation of the operating parameters makes it possible to optimize the process of the invention. The parameters are in particular the distance between the catalyst and the regeneration columns, the distance between the catalyst and the particle filter, the heating time upstream and downstream of the catalyst, the filtration of oil and / or water upstream of the process and the dry or wet state of the catalyst. Definitions

[0050] The acronym COVT stands for total volatile organic compounds.

[0051] The acronym COVnm stands for non-methane volatile organic compounds.

[0052] The acronym COVm designates methane volatile organic compounds, i.e. methane and its derivatives.

[0053] The term "bauxite" designates a solid mixture in a divided state containing in variable proportions alumina hydrates, kaolinite, silica and iron III oxides.

[0054] The terms “hourly volumetric velocity” expressed in h 1 designate the ratio of the gas flow rate (m3 / h) to the catalyst volume (m3). Figures

[0055] The present invention, its characteristics and the various advantages that it provides will appear better on reading the description of the examples which follow and the appended figures, presented as illustrative and non-limiting examples.

[0056] [Fig. 1] schematically represents a particular embodiment of the installation according to the present invention;

[0057] [Fig.2] represents a particular embodiment of the catalytic reactor of the installation of [Fig.l].

[0058] With reference to [Fig.l], the transformer of the invention comprises an electricity production unit 1, in which circulates oil which serves as a heat transfer fluid. The oil comes from a tank 2. The transformer comprises an oil regeneration unit. This comprises a degasser 3 which separates the oil from the water and air it contains and two regeneration columns 51 and 52. Each column 51 and 52 contains an adsorbent material and is equipped with resistors for heating the volume of adsorbent material. The oil regeneration columns 51 and 52 are connected in parallel. The oil regeneration unit also comprises a gas / liquid separator 7. The liquid outlet of the separator 7 is connected to a buffer tank 9, a part 91 of which serves as a phase separator. The gas outlet of the separator 7 is connected to a vacuum pump 10.The outlet of the vacuum pump 10 is connected to a coalescence filter 71 which allows the condensing of water and oil in the form of gas still present in the gas flow. A preheater 5 is mounted downstream of the coalescence filter 71. The outlet of the preheater 5 is connected to the inlet of the catalytic reactor 12. The outlet of the catalytic reactor 12 is connected to a particle filter 14. A heat exchanger 20 is thermally connected to the particle filter 14 and to the preheater 5 so as to recover the calories transported by the gases leaving the transformer of the invention to bring them to the heater 5. An adjustable flow valve 61 allows air to be introduced into the reactivation columns 51 and 52, during the incineration of the compounds adsorbed on the adsorbent material which they contain. In [Fig.l], an adjustable flow valve 61 is also arranged upstream of the vacuum pump and downstream of the first gas / liquid separator 7.This second valve is optional. It can replace the valve 61 mounted at the inlet of the regeneration columns 51 and 52, be added to the latter or not be present. The vacuum pump 10 makes it possible to create a pressure greater than or equal to 700 mbar absolute downstream of the regeneration columns 51, 52; another vacuum pump (not shown) makes it possible to maintain a partial vacuum in the catalytic reactor 12 and in the filter 14. The vacuum in the catalytic reactor 12 and the particle filter 14 is less advanced than that in the regeneration columns 51 and 52.

[0059] With reference to [Fig. 2], according to a particular embodiment, the catalytic reactor 12 contains three catalytic blocks C1, C2 and C3 each of which can be crossed by the combustion gases. The first block C1 is a catalyst capable of reducing sulfur oxides; the second and third catalytic blocks C2 and C3 are capable of reducing nitrogen oxides and oxidizing CO VT. The first block C1 is located upstream of the other two blocks, it has a smaller volume than that of the other two; it serves, by the reaction that it catalyzes, to also protect the two blocks catalytic blocks which are located downstream. The three blocks are arranged one behind the other in the direction of gas flow. The reactor can also contain other catalytic blocks allowing the Sabatier reaction or the Fischer-Tropsch reaction.

[0060] The three porous catalytic blocks comprise, for example, a support containing at least one metal oxide chosen from the group consisting of optionally stabilized alumina, optionally stabilized titanium (reduces the formation of sulfates and promotes their regeneration), a mixed oxide of cerium-titanium oxide and / or an optionally stabilized mixed cerium-zirconium oxide (reducing character, increases the O2 storage capacity) and mixtures of any two or more of these; and a composition comprising silica and / or silicon oxide (thermal stability). The particle filter 14 may be made of ceramic which allows the reduction of particulate matter (PMI, PM2.5, PM5, PM 10) generated by the combustion of the oils adsorbed on the adsorbent material.

[0061] In a transformer, the oil treatment unit is composed of 1 to 15 columns or more with a maximum of 30 columns (example of unit layout 15 columns: 3 rows of 5 columns) containing the adsorbent material (bauxite or clay in general). The oil is distributed over these columns by a system of conduits equipped with solenoid valves, each thermal reactivation column contains a total quantity of 110 kg of adsorbent material to be regenerated.

[0062] The regeneration columns 51 and 52 also have temperature sensors to measure the progress during the reactivation of the adsorbent material.

[0063] The used oil is filtered by the adsorbent material in one or more passes. When the saturation degree of the material is reached, the thermal reactivation process must be started. The air supply valve 61 ensures homogeneous combustion in each regeneration column 51, 52.

[0064] An example of a method according to the invention will now be described with reference to Figures 1 and 2. Columns 51 and 52 are saturated with oxygenated and sulfurous organic compounds from the transformer oil. The adsorbent material contained in columns 51 and 52 is heated so as to initiate the combustion of the adsorbed compounds. Once released from the active site of the adsorbent, the combustion gases which contain water and oil (in the form of droplets) are driven by the vacuum pump 10 towards the catalytic reactor. The gases first pass through the gas / liquid separator 7. In the latter, the water and oil droplets separate from the gas phase. The oil / liquid water mixture is sent to the buffer tank 9. The mixture first accumulates in the part 91 of the latter, which acts as a phase separator.The lighter oil will gradually flow into buffer tank 9 to then be recycled to electricity production unit 1. The gases. sucked by the vacuum pump 9 first pass through a coalescence filter 71 which allows the condensation of residual water and oil. The combustion gases are then reheated by the heater 5 and then enter the catalytic reactor 12. In the catalytic reactor 12, the carbon monoxide from the incomplete combustion of the adsorbed compounds is oxidized to carbon dioxide. The TVOCs are oxidized to carbon dioxide and water and the sulfur and nitrogen oxides are reduced to sulfur and nitrogen. These chemical reactions take place on the different catalytic blocks C1, C2 and C3 contained in the catalytic reactor 12. The gases from the catalytic reactor 7 then pass over the particulate filter 14; when passing through the particulate filter 9, the gases give off heat to the heat exchanger 2, which will supply the calories thus recovered to the heater 5. EXPERIMENTAL EXAMPLES

[0065] Example 1: Effect of catalytic treatment on the gas mixture to be treated containing carbon monoxide (CO) and propylene (C3H6)

[0066] The combustion gas mixtures containing by volume 13% O2, 4% CO2, 0 or 6% H2O, 0.1% C3H6 (represents the NMVOCs in this example) and N2 as a complement, were treated with a catalyst comprising a platinum-coated alumina support. In this example the WH (hourly volumetric flow rate) is 70 kh 1 and the final temperature is between 320 °C and 350 °C.

[0067] The catalytic conversion efficiency % CE (Eq.l) of a pollutant is defined, with Cin and Cout the concentrations of the pollutant respectively at the inlet and outlet of the catalyst, such that:

[0068] % CE = ((Cin - Cout) / Cin) * 100 [formula 1]

[0069] Efficiency can also be defined with the initiation temperature (T50), which is by definition the temperature of the gases to be treated for which a 50% conversion of the pollutants is obtained during an experiment in which the temperature is variable. The T50 is easily exceeded in the catalyst since the catalytic reactions are exothermic. The T50 also constitutes a criterion characterizing the activity of the catalyst; the T50 increases when the catalyst ages and its characteristics (specific surface area, porosity, dispersion of the active sites, etc.) deteriorate.

[0070] The determination of the ignition temperature was carried out on the BGS (Synthetic Gas Bench) but also on an industrial scale on a mineral oil reactivation machine.

[0071] The aim of the tests implemented is to determine the limiting conditions for the proper functioning of the device of the invention as a function of the temperature of the treated gases, the flow rates of treated gases and the composition of the gases to be purified.

[0072] The flow rate of the gas mixture is fixed, in a manner similar to the priming tests. For have a WH between 20 and 100 kh1, namely a maximum WH which must not be reached under the process conditions on the 12 bauxite column system.

[0073] The purpose of the accelerated catalyst aging protocol implemented is to represent the state of the catalyst at the end of the life of the bauxite columns, i.e. after 300 cycles of reactivation of the earth columns, at a rate of 6 to 8 hours of burning by regeneration. This therefore represents an operation of the installation of 1800 hours to 2400 hours at temperatures evaluated around 500°C-550°C. At such temperatures and in the presence of humidity, the catalyst is deactivated by various thermally activated processes (sintering of the support, sintering of the metals, encapsulation of the metals, diffusion of the metals, phase change of the support thus involving a reduction in specific surface area, porosity.

[0074] Accelerated hydrothermal aging, HTA (hydrothermal aging), of at least one catalyst was therefore carried out by subjecting the catalyst to temperatures higher than its ordinary use and under an oxidizing and humid atmosphere.

[0075] The following HTA treatment was applied to a catalyst comprising platinum deposited on an alumina base: 850°C under humid air at 10% v / v in H2O for 5 hours. For this, the catalyst is placed under flux in a tubular furnace. This protocol can be considered as hard aging. Indeed, the temperature of 850°C corresponds to the pivotal temperature for the change of the phase of alumina γ to alumina δ. On the other hand, the presence of water vapor particularly favors the sintering of alumina.

[0076] The ignition temperatures of the aforementioned new catalyst obtained for CO and C3H6 individually or in a mixture together are gathered in Table 1. Three tests were carried out for each pollutant considered alone and in the mixture of pollutants.

[0077] [Tables 1] New catalytic system Aged catalytic system T50 - dry gases (°C) T50 - wet gases (°C) T50 - dry gases (°C) T50 - wet gases (°C) CO c3h6 CO c3h6 CO c3h6 CO c3h6 Mixture tu tu gg (D / (D / (D — ri rr 214.0 213.0 210.5 209.0 210.0 208.0 213.0 215.0 215.0 210.0 214.5 212.5 265.0 269.0 267.0 265.0 265.0 265.0 265.0 264.0 264.5 258.0 258.0 258.0 average 212.5 209.0 214.5 212.3 267.0 265.0 264.5 258.5 Pollutant only 1st ^th ^th | 193.0 194.0 193.0 182.0 182.0 182.0 191.5 191.5 191.5 180.0 178.0 182.0 222.0 220.0 221.0 226.0 226.0 226.0 219.0 219.0 219.0 240.0 241.51 43.0 average 193.3 182.0 191.5 180.0 221.0 226.0 219.0 241.5

[0078] The T50s obtained for the 2 pollutants in mixture are similar, being around 210-215°C, and are not significantly influenced by the humidity of the gases as illustrated in Table 1. Furthermore, very good repeatability of the measurements is obtained for a given catalyst (deviations < 6°C).

[0079] Concerning the tests carried out with a single pollutant, they show lower initiation temperatures of approximately 20-25°C for CO (~190-195°C) and 30-35°C for C3H6 (180-183°C). No significant difference is observed between the T50 obtained for dry and wet gases. This decrease in T50 when a single pollutant is present in the gases is well known and corresponds to a decrease in adsorption competition and inhibition of the active sites. Indeed, the active sites adsorb CO, C3H6 and O2, higher concentrations of pollutants lead to inhibition of sites and slowing down the catalytic reaction. It should be noted that the humidity level of the treated gases (0%v / v and 6%v / v) does not play a significant role in the initiation temperature and that the measurements carried out are very repeatable from one test to another.

[0080] In the case of the aged catalyst, when the pollutants are mixed, their T50s are around 265°C. No clear difference is observed between dry and wet gases for CO. On the other hand, propylene has a slightly lower T50 of 6-7°C with humidity. Compared to a new catalyst, the HTA treatment has a major impact on the catalytic activity leading to a very significant increase of almost 50-55°C as illustrated in Table 1.

[0081] Regarding the T50 obtained with the injection of a single pollutant, they are significantly lower. For CO, the T50 is around 220°C both in dry gases than wet, which represents a decrease of ~45°C to ~55°C compared to the T50 in mixture. For propylene, higher T50s than those for CO are obtained indicating that the initiation of hydrocarbon catalysis is more difficult. Indeed, the T50s decrease by about 30°C (226°C to 246°C). Compared to a new catalyst (Table 1). The HTA treatment leads to an increase in the T50s of the pollutants injected individually by about 28°C for CO and 50°C for propylene, showing again that HTA aging has a greater impact on the conversion of NMVOCs.

[0082] Finally, the impact of accelerated hydrothermal aging highlighted is characterized by a degradation of more than 50°C of the T50 of the catalyst for the CO-propylene mixture, i.e. values ​​of 265°C-275°C.

[0083] It can be deduced that the gas / liquid separation which is carried out before the catalytic phase makes it possible to reduce the water content of the gases treated on the catalyst. This drying of the gases makes it possible to reduce the ignition temperatures which leads to better energy performance of the installation of the invention.

[0084] Example 2: Effect of catalytic treatment on a gas mixture to be treated containing carbon monoxide (CO), methane volatile organic compounds (MVOCs) and non-methane volatile organic compounds (NMVOCs) under real conditions

[0085] The mixtures treated in this example were generated by the thermal reactivation (combustion) of bauxite saturated with adsorbed compounds from a mineral oil used as a heat transfer fluid in electrical transformers. The gas mixture produced contains from 6 to 21% O2, 3 to 8% CO2, 0 or 6% H2O, ~ > 20,000 ppm CO, ~ > 10,000 ppmC VOC (NM / M) and N2 as a complement. The gas mixture was treated according to the process of the invention on an installation according to the invention as described with reference to [Fig.l]. In this example the WH is between 40 and 70 kh 1 and the inlet temperature in the catalytic reactor is between 320 °C and 350 °C.

[0086] The analyses were carried out during a bauxite reactivation process in a column which involves the combustion of the compounds adsorbed on the adsorbent material following the filtration of 2 m3 of oil having an acidity equivalent to 0.3 mg KOH / kg. The acidity of the oil reflects its degree of saturation in compounds to be eliminated and which are adsorbed on the adsorbent material.

[0087] The oil filtration step lasted ~4h and the reactivation of the adsorbent material columns about 9h. The first catalyst comprises a 50mm monolithic aluminum substrate on which platinum was deposited. The catalytic reactor also comprises two 90mm monolithic aluminum / ceramic catalytic substrates coated with platinum. Preheating of the catalysts housed in the catalytic reactor was implemented by the early start-up of the heater.

[0088] The reactivation of the adsorbent material contained in the columns is carried out by calcination and takes place in 3 distinct regimes, characterized by the regulation of the air supply (regulation of the O2 concentration) and the temperature in the fumes.

[0089] 1) A 1st regime characterized by a start of combustion (0-45min), by a consumption and therefore a decrease in the O2 rate and an increase in temperature. Combustion stabilizes between 45 and 180 min with an O2 rate and flue gas composition also stabilized. A plateau at 13% O2 ​​is observed at the outlet of the catalytic reactor and the flue gas temperature settles around 360-380°C,

[0090] 2) A 2nd stable regime of more intense combustion (~180-300min), with a rate lower O2 (-10% plateau at catalyst outlet), a temperature stabilized around 460-480°C and more concentrated pollutant emissions.

[0091] 3) A 3rd regime corresponding to the progressive stopping of combustion (~ 300-400min), correlated with the rise in the rate up to 21% and decrease in temperature.

[0092] The measurements and samples were taken during the three regimes upstream and downstream of the catalytic reactor. The reactivation of the adsorbent material is controlled by temperature probes.

[0093] The three aforementioned regimes are defined in Table 2.

[0094] [Tables2] Regime Time (min) Air supply (%) O2 (%) 1 45 - 180 35 11-15 2 180-300 45 8-11 3 300-400 100 19-21

[0095] Table 3 and Table 4 (below) present the average concentrations of VOCs, CH4 and CO as well as the minima and maxima recorded during the test.

[0096] [Tables3] Regime 1 Regime 2 Regime 3 Upstream Downstream Upstream Downstream Upstream Downstream [CH4] (PPm) min. 235 3.0 80.0 1.0 60.0 1.0 Max. 707 9.0 1049 13.0 849 11.0 Average 445 6.0 677 9.0 566 7.0 [VOCnm] (ppm) min. 1401 4.0 3343 7.0 3343 3.0 Max. 7420 5.0 11133 10.0 11133 9.0 Average 4163 2.0 8519 3.0 8519 2.0 [TVOC] (ppm) min. 1950 1.0 3494 1.0 3494 1.0 Max. 8120 6.0 11741 9.0 8102 8.0 Average 4612 2.0 10000 8.0 5265 3.0 TVOC Reduction Efficiency EC (%) Average 99.0 98.5 99.2

[0097] The limit value to be respected for COVnm and COVT is 30 ppm.

[0098] The process according to the invention is effective for mVOCs, nmVOCs and TVOCs during regime 1 with a reduction of approximately 98% of methane and 97% of nmVOCs resulting in a reduction of 99% of TVOCs. During regimes 2 and 3, the reduction of methane and nmVOCs remains fairly stable. This results in a reduction of 98.5% and 99.2% of TVOCs with very low concentrations at the outlet of the catalytic reactor. The VOC concentrations are lower during regime 3 than the three regimes studied.

[0099] [Tables4] Regime 1 Regime 2 Regime 3 Upstream Downstream Upstream Downstream Upstream Downstream

[02] (%) min. 15.9 12.4 13.3 8.7 15.6 10.0 Max. 16.7 13.9 15.5 9.8 19.9 12.9 Average 16.3 13.0 15.4 8.3 18.7 13.0 [CO2] (%) min. 4.3 4.5 3.5 4.2 3.0 4.1 Max. 5.1 6.1 7.7 8.3 4.5 5.4 Average 4.7 4.0 5.6 5.7 4.1 5.3 [CO] (ppm) min. 5805 0.0 7797 0.0 5649 0.0 Max. 10828 2.0 24000 4.0 9113 2.0 Average 10690 1.0 20000 4.0 11610 2.0 CO Conversion Efficiency (%) Average 99.9 99.8 99.9

[0100] The limit value to be respected for CO is 100 ppm.

[0101] It is noted that at the three regimes, the efficiency of the process of the invention with regard to the rate of conversion of CO into carbon dioxide is greater than 99%.

[0102] The O2 and CO2 concentrations are relatively stable during the first three regimes; they appear to be influenced by the air supply introduced for each regime into the regeneration column. During regime 1, the O2 concentration at the outlet is 13% on average. This concentration decreases in regimes 2 and 3 due to the increase in the overall flow rate by supplying air via the adjustable flow valve 61.

[0103] The CO2 concentration increases at the outlet during the three regimes.

[0104] This increase confirms the conversion of CO into CO2 in the presence of O2 under the conditions described. The installation is efficient and gives stable results with a CO reduction of 99.8%.

[0105] The concentrations of CO ([Fig.l] and table 4) and VOC (table 3) remain relatively minimal or zero at the outlet of the installation with high temperatures of approximately 550°C due to the exothermic oxidation reactions of the pollutants.

[0106] The concentrations of CO and VOCs comply with current environmental legislation.

[0107] Example 3: Effect of catalytic treatment on a gas mixture to be treated containing sulfur oxides (SOx) and nitrogen oxides (NOx)

[0108] The gas mixtures treated are the same as those used in Example 2. They contain 8 to 13% O2, 4% CO2, 0 or 6% H2O, 10,000 to 20,000 ppm CO, 10,000 ppm TVOC (mg / m3 eq. toluene), 50 to 600 ppm SOX (mg eq.SO2 / Nm3), 100 ppm NOx (mg eq.NO2 / Nm3) and N2 as a complement. They were treated according to the process of the invention in the installation described in [Fig.l]. In this example, the WH is 70 kh 1 and the final temperature is between 320 °C and 350 °C. The NOX and SOX analysis was carried out with the TESTO 350 flue gas analyzer using specific electrochemical cells. Sampling was carried out at a flow rate of 11 / min with a steel probe capable of withstanding high temperatures (up to 1000°C) and was therefore carried out directly upstream and downstream of the catalyst using specially designed orifices. The sampled flow passed through a water condenser and particulate filters to protect the cells.The gas temperature at the sampling point is also recorded by a K-type thermocouple (NiCr).

[0109] This type of measurement no longer allows the reactivation of the electrochemical cells. The detection threshold is 1 ppm. The analyzer is zeroed before measurements on ambient air. The detection threshold is 1 ppm. The analyzer is zeroed before measurements on ambient air.

[0110] The measured concentrations of NOx and SOX are summarized in Table 5 during the three combustion regimes. The analyses / measurements were carried out upstream and downstream of the process of the invention. During combustion regime 1, it is noted that the emission of NOx and SOx represents almost half of the two regimes which follow.

[0111] Stabilized combustion regimes 2 and 3 lead to the most intense and stable emissions (regime 3 more intense). Nitrogen oxides (NOX) in the form of NO and NO2 were not detected in significant quantities during the three regimes.

[0112] Regarding SO2, very high emissions are measured upstream of the catalyst system while downstream they are not measurable or only a few mg / Nm3.

[0113] [T ableaux5 ] Regime 1 Regime 2 Regime 3 Upstream Downstream Upstream Downstream Upstream Downstream [SOX] (mg eq.SO2 / Nm3) min. 11.0 3.0 165.0 4.2 102.0 4.2 Max. 880.0 7.0 1500.0 8.3 1450.0 6.3 Average 714.0 <2.9 1428.0 <2.9 1330.0 <2.9 [NOX] (mg eq.NO2 / Nm3) min. 2.0 0.0 5.0 0.0 12.0 0.0 Max. 22.0 1.0 116.0 1.0 31.0 1.0 Average 21.0 1.0 40.0 1.0 25.0 1.0 Treatment efficiency (%) Average SOX / NOX 99.9 / 99.0 99.8 / 99.0 99.9 / 99.0

[0114] The limit values ​​not to be exceeded are 50 mg eq.SO2 / Nm3 and 100 mg eq.NO2 / Nm3.

[0115] The concentrations of NOX and SOX after treatment by the process of the invention comply with the European standards set by the decree of 17 / 12 / 19, relating to the best available techniques (BAT) applicable to certain waste treatment installations falling under the authorization regime and the IED directive. These include in particular those indicated in Annex 3.4 - chapter IX and the decree of 20 September 2002, relating to incineration and co-incineration installations for non-hazardous waste and to installations incinerating infectious risk healthcare waste.

[0116] During the three regimes, the NOX and SOX treatment performances are stabilized with reduction rates reaching 98% and 99%.

[0117] Example 4: Effect of catalytic treatment on a gas mixture to be treated containing suspended particles PM 1, PM2.5 and PM10

[0118] The gas or gas mixtures loaded with suspended particles (PM) treated in this example are generated by combustion / reactivation of 12 to 15 columns, under a WH of 70 kh1, a pressure of 800 mbar and a temperature regulated between 320°C and 350°C at the inlet of the process.

[0119] The combustion gas or mixtures of combustion gases and suspended particulate matter (PM) were treated with the method of the invention in the installation described above.

[0120] The objective of this example is to determine and prove the filtration efficiency / yield of fine particles (PM) of the process according to the invention already described.

[0121] An analysis of the total particle concentration is carried out upstream and downstream of the post-treatment during the three combustion regimes studied. The analysis of the particle size distribution (PM10, PM2.5, PMI) in mass was carried out in order to estimate the number distribution of the particles.

[0122] The sampling is carried out with the help of a cascade impactor type sampler (DEKATI Model - PM10 Impactor). The impactor consists of three impaction stages for particles with a diameter between 10 and 1 pm and a quartz fiber filter (Back-up) retaining particles with a diameter of less than 1 pm (up to 0.3 pm). Aluminum supports are also placed on the upper stages to facilitate the impaction and recovery of the particles. The particle sampling is carried out upstream and downstream of the treatment process of the invention.

[0123] [Tableauxô] PM (mg / Nm3) Regime 1 Regime 2 Regime 3 Upstream Downstream Upstream Downstream Upstream PM10 3.344 0.944 1.849 0.024 82.841 2.184 PM2.5 3.325 0.629 1.715 0.021 81.392 1.426 PMI 2.972 0.291 1.704 0.021 79.478 0.862 PM<1 2.942 <0.06 1.485 0.019 75.186 < 0.090 Total 3.340 0.94 1.85 0.024 82.840 2.180 Treatment efficiency (%) 95.5 97.75 99.0

[0124] The limit value to be respected in order to comply with current legislation is mg / Nm3.

[0125] It is noted that the reduction obtained by implementing the method of the invention appears stable and little influenced during the different regimes. Regimes 1 and 2 are characterized by reductions greater than 95.9% and effective treatment of PM<1. Filtration efficiency appears to increase during regime 2, going from -96% to -98%. The particle size profiles obtained upstream and downstream of the process during regime 3 appear to be little modified.

[0126] The emissions measured at the outlet of the treatment process during the three regimes present concentrations significantly lower than the threshold of 50 mg / Nm3 at 3% O2 ​​referred to by the Order of 20 / 09 / 02 relating to installations for the incineration and co-incineration of non-hazardous waste and to installations incinerating infectious risk healthcare waste.

[0127] Example 5: Effect of catalyst sizing on the gas treatment process

[0128] The combustion gas mixtures treated by the invention in the plant described above were generated by combustion of the compounds adsorbed / absorbed on bauxite and originating from a mineral oil. The gas mixture contains from 6 to 21% O2, 3 to 8% CO2, 0 or 6% H2O, ~20,000 ppm CO, ~10,000 ppmC VOC(NM / M) and N2 as a complement.

[0129] In this example the catalyst volume was changed twice in order to analyze the behavior of the hourly volume velocity (WH, expressed in h '). This last parameter defined as the ratio of the gas flow rate (m3 / h) to the catalyst volume (m3) and constitutes a parameter linked to the residence time of the gases in the catalyst. The WH also makes it possible to evaluate the quantity of gas to be treated and therefore the sizing of the catalyst. The gas inlet temperature is between 320°C and 350°C with a gas dilution of 20 to 50% by volume.

[0130] Since there are several regimes in the combustion reaction which takes place in the regeneration column, the flow rate of gas leaving the column is therefore variable. The variation in the flow rate is proportional to the concentration of the compounds adsorbed by the bauxite and to the air dilution during the three regimes described above.

[0131] The variation in flow rate indicates that the WH changes regularly and that the catalyst must be well sized for the three combustion regimes. The inventors have determined that to obtain good efficiency, it is essential that the WH is between 20 and 100 kh-1 under a reheating of the diluted gases of 20 to 50% at a temperature > 300°C, with a load of 0.5 to 4 g / l of Pt or Pt / Pd catalyst. This makes it possible to remain in oxidizing conditions.

Claims

Claims

1. Electrical transformer of the type comprising: - a cooling circuit in which an insulating oil circulates; - a unit for regenerating said oil which comprises at least one regeneration column (51; 52) filled with a solid adsorbent material capable of adsorbing oxygenated and / or sulfur-containing organic compounds contained in said oil, said regeneration column (51; 52) having an inlet and an outlet and comprising means for heating said adsorbent material; characterized in that said regeneration unit further comprises: - a catalytic reactor (12) containing at least one first catalyst (C1) capable of oxidizing carbon monoxide and volatile organic compounds and at least one second catalyst (C2) capable of reducing sulfur and / or nitrogen oxides, the inlet of said catalytic reactor (12) being connected to said outlet of said regeneration column (51; 52);and - a particulate filter (14) whose inlet is connected to the outlet of said catalytic reactor (12) and whose outlet is connected to the atmosphere.;

2. Transformer according to claim 1, characterized in that it further comprises a first gas / liquid separator (7) mounted at the outlet of said regeneration column (51; 52) and possibly a gravity separator (9) mounted on the condensate outlet of said first gas / liquid separator, the gas outlet of said gas / liquid separator (7) being connected to the inlet of said catalytic reactor (12).

3. Transformer according to any one of the preceding claims, characterized in that said oil regeneration unit comprises a second gas / liquid separator, in particular of the coalescence filter type (71), mounted upstream of said catalytic reactor (12).

4. Transformer according to any one of the preceding claims, characterized in that said regeneration unit further comprises a heater (5) mounted upstream of said catalytic reactor (12).

5. Transformer according to any one of the preceding claims, characterized in that said regeneration unit further comprises suction means (10), mounted upstream of said catalytic reactor. (12) and connected to the outlet of said regeneration column (51; 52).

6. Transformer according to any one of the preceding claims, characterized in that said at least first catalyst (C1) and / or second catalyst (C2) comprises a solid and porous support forming a block on which is deposited a catalytic material containing a metal from the platinum group, in particular platinum, palladium or a mixture of palladium and platinum and / or in that said particle filter comprises at least one metal from the platinum group, in particular platinum or palladium or a mixture of palladium and platinum.

7. Transformer according to any one of the preceding claims, characterized in that said regeneration unit comprises admission means (61) for an adjustable flow of air or oxygen mounted upstream of said catalytic reactor (12) and downstream of said regeneration column (51; 52) and / or mounted at the inlet of said regeneration column (51; 52).

8. Transformer according to any one of the preceding claims, characterized in that said adsorbent material is capable of being thermally reactivated and is chosen in particular from clays, bauxite, bentonite, attapulgite, kaolin, calcium montmorillonate and mixtures thereof.

9. Method for regenerating the insulating oil contained in an electrical transformer on at least one column containing an adsorbent material according to which said adsorbent material is thermally reactivated by causing the combustion of the oxygenated and possibly sulfurous organic compounds adsorbed on said adsorbent material, characterized in that a liquid / gas separation of the gases produced during the reactivation of said adsorbent material is carried out and in that said gases are then passed over at least one catalyst so as to transform the organic compounds into carbon dioxide, oxidize the carbon monoxide into carbon dioxide and reduce the nitrogen and / or sulfur oxides formed and the solid particles contained in said gases are then filtered.

10. Method according to claim 9, characterized in that said gases are sucked in by creating a pressure greater than or equal to 700mb and less than atmospheric pressure before passing them over said at least one catalyst.

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