BE1025977B1 - SORBENT COMPOSITION FOR AN ELECTROSTATIC PRECIPITATOR - Google Patents

Abstract

Powdered mineral compound, mineral-based sorbent composition for use in treating flue gas, compatible with electrostatic precipitators, and method for reducing the resistivity of a powder sorbent composition for the treatment plant of flue gas comprising an electrostatic precipitator.

Description

BE2018 / 5533 1

SORBENT COMPOSITION FOR AN ELECTROSTATIC PRECIPITATOR

Technical area

The present invention relates to an inorganic compound and a sorbent composition for use in a smoke gas installation equipped with an electrostatic precipitator, a method for obtaining such a sorbent composition and a process for treating smoke gas using an electrostatic precipitator which comprises a step of injecting such a sorbent composition. In another aspect, the present invention relates to a smoke gas treatment installation using the sorbent composition according to the invention.

State of the art

Burning fuel in industrial processes or producing energy generates fly ash and acid gases which must be minimized to the atmosphere. The removal of fly ash from the flue gas stream can be achieved by an electrostatic precipitator (ESP). Some examples of electrostatic precipitators are described in US Patent 4,502,872, US Patent 8,328,902 or US Patent 6,797,035. An electrostatic precipitator generally includes a shell with a flue gas inlet and a flue gas outlet , the shell containing a plurality of collection electrodes, and discharge electrodes spaced from each other and a plurality of hoppers positioned under the collection plates. A voltage is applied between the discharge electrodes and the collection electrodes so as to create an electrostatic field charging the particulate matter in the flue gases to obtain a charged particulate matter. The charged particulate matter is collected by the collection electrodes. The electrostatic precipitator further includes knockers which provide mechanical shock or vibration to the collection electrodes to remove the particles collected from the collection electrodes. The collected particles fall in

BE2018 / 5533 hoppers arranged at the bottom of the hull and which are emptied periodically or continuously. The collection electrodes can be flat or in the form of a tubular or honeycomb structure and the discharge electrodes are generally in the form of a wire or a rod.

Generally, smoke gas treatment installations including electrostatic precipitators are provided with an air preheater, which is sometimes included in a boiler and / or otherwise supplied as an additional element of the combustion gas installation. smoke. The air preheater includes a heat exchanger that transfers heat from the flue gas stream produced by the boiler to heat combustion air to the boiler to increase the thermal efficiency of the boiler. In some embodiments, the treatment of flue gases includes multiple electrostatic precipitators. Electrostatic precipitators on the cold side are located downstream of the air preheater, thus operating at lower temperatures generally below 200 ° C (392 ° F). Electrostatic precipitators on the hot side are located upstream of the air preheater and operate at higher temperatures, usually above 250 ° C (482 ° F).

Sometimes for existing factories, the electrostatic precipitator units are already operating at the limit of their design capacity due to the more drastic limits on particulate matter emissions that have been introduced over the years and / or changes in conditions. factory operations such as fuel change.

The Deutsch-Anderson equation describes with some approximations the collection efficiency of an electrostatic precipitator by:

where η is the fractional collection efficiency, A _c is the area of the collection electrode, V _pm is the particle migration speed and Q is the volumetric flow of gas. The particle properties that influence the collection yield are essentially the particle size distribution

BE2018 / 5533 and their resistivity. The particle resistivity influences the particle migration speed as described previously in the DeutschAnderson equation.

Various attempts have been made to reduce the resistivity of particles. It is known for example from US Pat. No. 4,439,351 that for an electrostatic precipitator to function effectively, the electrical resistivity of the fly ash must be between 1E7 (1x10 ⁷ ) and 2E10 (2x10) ohms.cm. Another document, Mastropietro, RA Impact of Hydrated Lime Injection on Electrostatic Percipitator Performance in ASTM Symposium on Lime Utilization; 2012; pages 2 to 10, states that the resistivity of fly ash should be between 1E8 (1x10 ⁸ ) and 1E11 (1x10 ¹¹ ) ohms.cm. However, the electrical resistivity of fly ash is generally higher and chemical additives have been used such as SO ₃ , HCl, NH ₃ , Na ₂ CO ₃ , Na ₂ SO ₄ and NH (CH ₂ CH ₂ OH) to lower the resistivity of fly ash. However, these additives are capable of releasing undesirable compounds. The same document discloses the use of polymers to lower the resistivity of fly ash. However, polymer additives generally degrade at high temperatures and must be injected into the flue gas stream at low temperatures.

Document US Pat. No. 6,126,910 discloses the removal of acid gases from a smoke gas with an electrostatic precipitator by spraying with a solution of sodium bisulfite, calcium bisulfite, magnesium bisulfite, potassium bisulfite or potassium bisulfite. ammonium or one of their combinations in a gas flow upstream of the electrostatic precipitator unit. Such bisulfite salts selectively remove acid gases such as HCl, HF and SO ₃ but they do not remove sulfur dioxide. The sulfur dioxide in the flue gases must be removed later with a reagent such as hydrated lime. Patent document US 6,803,025 discloses a similar process using a reaction compound selected from the group consisting of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonium hydroxide, potassium hydroxide , hydroxide

BE2018 / 5533 potassium, potassium carbonate and potassium bicarbonate to remove acid gases such as HCl, HF, SO3 and partially SO2 from smoke gases. However, the remaining SO2 should always be removed by the use of another reagent such as hydrated lime. For the treatment of smoke gases released by power stations, the quantities of chloride released by a fuel or coal in combustion are generally very small compared to SO2, consequently the process of treatment of smoke gases can be simplified by n ' using only hydrated lime as a sorbent.

Document WO2015 / 119880 relates to the drawbacks of trona or hydrated lime as sorbents for a process for treating flue gas with electrostatic precipitator units. Sorbents based on sodium are known to decrease the resistivity of particulate matter, however a main drawback of using sodium sorbents is that the leaching of heavy metals from fly ash is increased, leading to potential environmental contamination. . Calcium hydroxide sorbents do not have the problem of leaching heavy metals from fly ash, but they are known to increase the resistivity of particulate matter (fly ash) entrained in the flue gas stream if although the efficiency of the electrostatic precipitator unit can be lowered when using calcium-based sorbents. The same document discloses a composition for reducing particulate resistivity in flue gases and capturing acid gases, wherein the composition comprising a particulate alkali / alkaline earth metal having the formula (Lii. _A .ß Na _a Kß) _w (Mgi . ₅ CaO) _x (OH) _y (CO _{3) z} -nH ₂ O, more specifically formula Na _w Ca _x (OH) _y (CO _{3) z} · nH ₂ O, in which a W x is of about 1/3 to about 3/1. Consequently, the composition still has a large amount of sodium which would not only be capable of leaching, but sodium is also known to increase the leaching of heavy metals contained in the fly ash.

Document US 6,797,035 discloses a method for reducing the resistivity of fly ash by spraying with an aqueous solution of

BE2018 / 5533 potassium nitrate or potassium nitrite on the flue gas stream or by injecting potassium nitrate or potassium nitrite powder into the flue through which the flue gases pass. A disadvantage of using these nitrate or nitrite salt powders is that they react with other species than fly ash and result in a less reactive chemical reaching the collector plates of the electrostatic precipitator. Therefore, it is suggested to inject these nitrate salts as finely divided powders to reduce the reactive area exposed and inhibit reactions with nitrous oxides and sulfur oxides.

However, there is still a need to provide an inorganic compound which can be advantageously used in smoke gas treatment plants highly compatible with electrostatic precipitators.

The object of the present invention is to provide an inorganic compound and a sorbent composition comprising said inorganic compound eliminating the intrinsic drawback of these sorbents during their application to electrostatic precipitator units.

Summary of the invention

According to a first aspect, the present invention relates to a powdery mineral compound having a resistivity at 300 ° C (372 ° F) R ₃₀₀ lower than 1E11 (1x10 ¹¹ ) Ohms.cm and higher than 1E7 (1x10 ⁷ ) Ohms .cm, preferably lower than 1E10 (1x10 ¹⁰ ) Ohms.cm and higher than 5E7 (5x10 ⁷ ) Ohms.cm, preferably lower than 5E9 (5x10 ⁹ ) Ohms.cm, more preferably lower than 1E9 (1x10 ⁹ ) Ohms.cm, even more preferably lower than 5E8 (5x10 ⁸ ) Ohms.cm.

Indeed, it has surprisingly been observed that a powdery mineral compound can be successfully used in the treatment of flue gases using electrostatic precipitators when the resistivity at 300 ° C (372 ° F) is even lower than 1E11 (1x10 ¹¹ ) Ohms.cm, preferably lower than 1E10 (1x10 ¹ °) Ohms.cm, meaning that the compound

BE2018 / 5533 mineral powder is robust and does not decompose at a relatively high temperature. Consequently, this powdery mineral compound is able to positively modify the resistivity of fly ash without negatively impacting the operation of the electrostatic precipitator.

Depending on the type of mineral compound, it will preferably be injected

- at a location near the boiler or even in the boiler because at this location of the smoke gas flow inside which the mineral compound must be injected, the temperature would be favorable for an adequate capture of pollutants of smoke gas . In this case, as the product does not decompose, the resistivity at a temperature of 300 ° C (372 ° F) is still low enough to modify the resistivity of the mixture of fly ash present in the flue gases and the injected mineral compound , or

- It will preferably be injected at a location close to the upstream of the preheater since at this location of the flue gas flow inside which the mineral compound must be injected, the temperature would be favorable for an adequate capture of polluting compounds of flue gases. In this case, too, as the product does not decompose, the resistivity at a temperature of 300 ° C (372 ° F) is still low enough to modify the resistivity of the mixture of fly ash present in the smoke gases and the compound mineral injected.

Preferably, the mineral compound according to the present invention has a maximum resistivity R _max lower than 5E11 (5x10 ¹¹ ) Ohms.cm, preferably lower than 1E11 (1x10 ¹¹ ) Ohms.cm and more preferably lower than 5E10 ( 5x10 ¹⁰ ) Ohms.cm.

Advantageously, the mineral compound is doped with at least one metal ion Μ chosen from the group of the metal ion having an atomic number less than or equal to 74 and belonging to the group consisting of a transition metal ion or a metal ion of post-transition in an amount greater than or equal to 0.05% by weight and less than or equal to 5% by weight relative to the total weight of the powdery mineral compound.

BE2018 / 5533

In a particular embodiment, the mineral compound according to the present invention is further doped with at least one counterion X chosen from the group consisting of nitrates, nitrites, and their mixture in an amount greater than or equal to 0, 05% by weight and less than or equal to 5% by weight relative to the total weight of the powdery mineral compound.

In a preferred embodiment of the mineral compound according to the present invention, the total weight of said metal ion and of said counterion is greater than or equal to 0.1% by weight and less than or equal to 5% by weight, preferably between 0.3 and 3% by weight, relative to the total weight of the powdery mineral compound.

In yet another preferred embodiment, the mineral compound of the invention further comprises sodium in an amount of up to 3.5% by weight relative to the total weight of the powdery mineral compound, expressed in sodium equivalent. Preferably, the sodium is in a minimum amount of 0.2% by weight relative to the total weight of the powdery mineral compound and expressed in sodium equivalent.

Sodium as a sodium additive in such amounts is known to have a slight effect on decreasing the resistivity of the sorbent. The applicant has found that the sodium additive in such amounts in combination with the presence as described below of at least one metal ion and / or a counterion additionally confers an additional effect on the reduction of the resistivity of the sorbent composition. The use of sodium additive in combination with the presence as described below of at least one metal ion and / or a counterion decreases the resistivity of the sorbent composition more than when the presence as described below below at least one metal ion and / or a counterion is used alone in the mineral compound and more than when sodium is used alone in the mineral compound.

In an advantageous embodiment of the mineral compound, said metal ion Μ is one of the ions from Cu ²⁺ , Fe ²⁺ , Fe ³⁺ , Mn ²⁺ , Co ²⁺ , Mo ²⁺ , Ni ²⁺ , Zn ²⁺ .

BE2018 / 5533

Preferably, said metal ion Μ is one of the ions from Cu ²⁺ , Fe ²⁺ , Fe ³⁺ .

Preferably, said counterion X is nitrate.

It has been found that the presence of a metal ion as disclosed above and / or of a counterion as previously described in the mineral compound, decreases the resistivity of the mineral compound.

In a preferred embodiment, the powdery mineral comprises particles having an d ₅₀ of between 5 and 25 μm, preferably between 5 and 20 μm, more preferably between 5 and 16 μm.

The notation d _x represents a diameter expressed in μm, as measured by laser granulometry in methanol optionally after sonication, with respect to which X% by mass of the particles measured are less than or equal.

Preferably, in particular, the pulverulent mineral compound is chosen from the group of the Phyllosilicates family which comprises the four key groups of the groups of Serpentine, Clay mineral, Mica and Chlorite.

In particular, the powdery mineral compound is chosen from the group of halloysite and phyllosilicates according to the Dana classification, preferably from the group consisting of allophane, bentonite, chlorite, dickite, halloysite, l 'illite, kaolinite, montmorillonite, nacrite, nontronite, palygorksite, saponite, sepiolite, serpentine, talc and mixtures thereof, more preferably in the group consisting of bentonite, halloysite, l 'illite, kaolinite, montmorillonite, sepiolite, smectite, talc, vermiculite and their mixtures, and most preferably in the group consisting of bentonite, halloysite, kaolinite, montmorillonite, sepiolite and their mixtures.

Other embodiments of the mineral compound according to the present invention are mentioned in the appended claims.

According to a second aspect, the present invention also relates to a sorbent composition for an installation for treating

BE2018 / 5533 smoke gas including an electrostatic precipitator comprising said mineral compound according to the present invention.

Preferably, the sorbent composition according to the invention further comprises activated carbon, lignite coke, refractory clay, air-entrained cement dust, perlite, expanded clay, lime sandstone dust, trass dust, Yali rock dust, trass lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organic sulfide, calcium sulfate, open hearth coke, lignite dust, fly ash, or water glass or a calcium-magnesium compound such as lime or carbonate.

In a preferred embodiment, the sorbent composition according to the present invention comprises a sodium additive comprising sodium in an amount of up to 3.5% by weight relative to the total weight of the powdery mineral compound and expressed in sodium equivalent . In particular, the amount of sodium in the composition would be greater than 0.2% by weight relative to the total weight of the powdery sorbent composition.

In a preferred embodiment, the sorbent composition according to the present invention comprises said metal ion Μ and / or said counterion X which are present in an amount greater than or equal to 0.05% by weight and less than or equal to 5% weight relative to the total weight of the dry sorbent composition and in which preferably the total weight of said metal ion and of said counterion is greater than or equal to 0.1% by weight and less than or equal to 5% by weight, preferably between 0.3 and 3% by weight, relative to the total weight of the dry sorbent composition.

In a particular embodiment according to the present invention, the sorbent composition comprises water in an amount such that the sorbent composition is in the form of a suspension. Examples of amounts can be 40 to 90% by weight of water, where the sorbent is included in an amount of 10 to 60% by weight relative to the total weight of the sorbent composition in the form of a suspension.

BE2018 / 5533

The sorbent composition in the form of a suspension can be used for example in a dry spray absorber, which can be followed by an electrostatic precipitator.

Other embodiments of the sorbent composition according to the present invention are mentioned in the appended claims.

According to a third aspect, the present invention relates to a method of manufacturing a sorbent composition for a smoke gas treatment installation including an electrostatic precipitator, comprising the steps of:

a) supply of a mineral compound to a reactor

b) addition of an additive or a mixture of additives, comprising at least one metal ion Μ and / or a counterion X, Μ being a metal ion having an atomic number less than or equal to 74 and is an ion of transition metal or a post-transition metal ion, and X being one of the counterions among nitrates, nitrites, oxides (O ² '), hydroxides (OH'), and their mixture in an amount calculated to obtain between 0.1% by weight and 5% by weight, preferably between 0.3% by weight and 3% by weight of said metal ion Μ and / or of said counterion X by weight of the composition of dry sorbent.

As a variant, the present invention relates to a method of manufacturing a sorbent composition for a smoke gas treatment installation including an electrostatic precipitator, comprising the steps of:

a) supply of a mineral compound to a reactor

b) addition of an additive or a mixture of additives, comprising at least one metal ion Μ and / or a counterion X, Μ being a metal ion having an atomic number less than or equal to 74 and being an ion of transition metal or a post-transition metal ion, and X being one of the counterions among nitrates, nitrites, oxides (O ² '), hydroxides (OH'), and their mixture in an amount calculated to obtain between 0.1% by weight and 5% by weight, preferably between 0.3% by weight and 3% by weight of said metal ion Μ and / or of said counterion X by weight of the mineral compound.

BE2018 / 5533

In a preferred embodiment, the sorbent composition comprises particles having an d ₅₀ of between 5 and 25 μm, preferably between 5 and 20 μm, more preferably between 5 and 16 μm.

Preferably, in the process for manufacturing said sorbent composition, said metal ion Μ is one of the ions from Cu ²⁺ , Fe ²⁺ , Fe ³⁺ , Mn ²⁺ , Co ²⁺ , Mo ²⁺ , Ni ²⁺ , Zn ²⁺ . More preferably, in the process for manufacturing said sorbent composition, said metal ion Μ is one of the ions from Cu ²⁺ , Fe ²⁺ , Fe ³⁺ .

In the process for manufacturing said sorbent composition, said counterion X is preferably nitrate.

Preferably, the method for manufacturing said sorbent composition comprises a step of adding another additive comprising sodium expressed as sodium equivalent in an amount calculated to obtain up to 3.5% sodium equivalent by weight of the composition of dry sorbent.

Preferably, said manufacturing process is characterized in that it further comprises a step of adding activated carbon, lignite coke, refractory clay, air-entrained cement dust, perlite, expanded clay, lime sandstone dust , trass dust, Yali rock dust, trass lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organic sulfide, calcium sulfate, open coke, lignite dust, ash flying, composed of calcium-magnesium or soluble glass.

In one embodiment of the method for manufacturing said sorbent according to the invention, the step of adding an additive or a mixture of additives, comprising at least one metal ion Μ and / or a counterion X is carried out before said step of adding activated carbon, lignite coke, refractory clay, air-entrained cement dust, perlite, expanded clay, lime sandstone dust, trass dust, Yali rock dust, trass lime , fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organic sulfide, calcium sulfate, open hearth coke, lignite dust, fly ash, calcium magnesium compound or soluble glass.

BE2018 / 5533

In another embodiment of the method for manufacturing said sorbent composition, said step of adding an additive or a mixture of additives, comprising at least one metal ion Μ and / or a counterion X is carried out during said step of adding activated carbon, lignite coke, refractory clay, air-entrained cement dust, perlite, expanded clay, lime sandstone dust, trass dust, Yali rock dust, trass lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organic sulfide, calcium sulfate, open coke , lignite dust, fly ash, calcium-magnesium compound or water glass.

As a variant, in the method for manufacturing said sorbent composition, said step of adding an additive or a mixture of additives, comprising at least one metal ion Μ and / or a counterion X is carried out after said step of adding activated carbon, lignite coke, refractory clay, air-entrained cement dust, perlite, expanded clay, lime sandstone dust, trass dust, Yali rock, trass lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organic sulfide, calcium sulfate, open hearth, lignite dust, fly ash, calcium-magnesium compound or water glass.

Other embodiments of the process for manufacturing a sorbent composition according to the present invention are mentioned in the appended claims

In a fourth aspect, the present invention relates to a method for treating smoke gases using an installation comprising an injection zone arranged upstream of an electrostatic precipitator, characterized in that it comprises an injection step in said zone for injecting a sorbent composition according to the present invention.

More particularly, the smoke gas treatment method using an installation including an electrostatic precipitator, and an injection zone arranged upstream of said electrostatic precipitator and crossed by

BE2018 / 5533 flue gases to said electrostatic precipitator is characterized in that said method comprises a step of injecting a sorbent composition into said injection zone, said sorbent composition comprising a mineral sorbent, at least one ion metallic Μ having an atomic number less than or equal to 74 and which is a transition metal ion or a post-transition metal ion, and optionally at least one counterion X chosen from nitrates, nitrites, and their mixture , the total amount of said at least one metal ion Μ and of said optionally at least one counterion X being between 0.1% and 5%, preferably 0.3 and 3.5% by weight of the dry composition.

According to the present invention, said sorbent composition has a lower resistivity compared to prior art mineral sorbents, especially at a temperature of 300 ° C (372 ° F). An injection of the sorbent composition according to the invention into an injection zone for mixing with smoke gases is effective for the removal of SO2 and other pollutants and the lower resistivity of such a sorbent composition improves the collection of particulate matter on the electrodes for collecting the electrostatic precipitator.

In a preferred embodiment of the process according to the present invention, said sorbent composition is injected into said injection zone, in which said smoke gases have a temperature between 180 ° C (356 ° F) and 1000 ° C ( 1832 ° F), preferably greater than or equal to 200 ° C (392 ° F), more preferably greater than 300 ° C (372 ° F), preferably less than 900 ° C (1652 ° F), so more preferred below 500 ° C (932 ° F).

Preferably, in the smoke gas treatment method according to the invention, said mineral compound in the sorbent composition is mixed with an additive or a mixture of additives, comprising at least one metal ion Μ and / or a counter ion X before said injection step.

Alternatively, in the smoke gas treatment process according to the invention, the mineral compound and an additive or a mixture of additives, comprising at least one metal ion Μ and / or a counterion X are injected

BE2018 / 5533 separately and mixed with said smoke gases in said injection zone.

Preferably, in the smoke gas treatment process according to the invention, said injection zone is located upstream of an air preheater itself located upstream of said electrostatic precipitator.

Preferably, in the smoke gas treatment method according to the invention, said ion ion is one of the ions from Cu ²⁺ , Fe ²⁺ , Fe ³⁺ , Mn ²⁺ , Co ²⁺ , Mo ²⁺ , Ni ²⁺ , Zn ²⁺ .

More preferably, in the flue gas treatment method of the invention, said Μ ion is one of the ions from Cu ²⁺ , Fe ²⁺ , Fe ³⁺ .

Preferably, in the smoke gas treatment process of the invention, said counterion X is nitrate.

Preferably, in the smoke gas treatment process of the invention, said sorbent composition comprises another additive comprising sodium in an amount up to 3.5% by weight of the dry composition and expressed in sodium equivalent .

Preferably, in the smoke gas treatment process of the invention, said sorbent composition further comprises activated carbon, lignite coke, refractory clay, air-entrained cement dust, perlite, expanded clay, lime sandstone dust, trass dust, Yali rock dust, trass lime, fuller's earth, cement, aluminate calcium, sodium aluminate, calcium sulfide, organic sulfide, calcium sulfate, open hearth coke, lignite dust, fly ash, calcium magnesium sorbent or water glass.

Other embodiments of the flue gas treatment method according to the present invention are mentioned in the appended claims.

In a fifth aspect, the present invention relates to a flue gas treatment device comprising an electrostatic precipitator downstream of an air preheater, said air preheater being connected to said electrostatic precipitator by a conduit, characterized in that he

BE2018 / 5533 further comprises an injection zone intended for injecting a sorbent composition according to the present invention arranged upstream of said air preheater.

Other embodiments of the flue gas treatment device according to the present invention are mentioned in the appended claims.

Preferably, said smoke gas treatment device or installation is used to treat smoke gases from a factory, in particular from a power plant, using coal or a fuel containing sulfur species or other precursors. of acid gases.

Preferably, said smoke gas treatment installation further comprises a reservoir comprising said sorbent composition for supplying said sorbent composition to said injection zone through a sorbent inlet.

The present invention can also be summarized as a method of reducing the resistivity of a powdery sorbent composition for a smoke gas treatment installation comprising an electrostatic precipitator below 1E11 Ohms.cm and above 1E07 Ohm.cm at 300 ° C, wherein said resistivity of said powdery sorbent composition is measured in a resistivity cell in an oven under an air flow comprising 10% humidity, said powdery sorbent composition comprising a powdery mineral compound of halloysite type according to Dana's classification, the process comprising the steps of:

a) supplying said powdery sorbent composition to a reactor and;

b) adding to said pulverulent sorbent composition an additive or a mixture of additives, comprising at least one metal ion Μ and / or a counterion X, Μ being a metal ion having an atomic number less than or equal to 74 and being a transition metal ion or a posttransition metal ion, or Mg ²⁺ or Na ⁺ or Li ⁺ and X being one of the counterions chosen from the group consisting of nitrates, nitrites, oxides O ² ', and hydroxide OH' and their mixtures in an amount calculated to obtain between 0.1% by weight and 5% by weight, preferably between 0.3% by weight

BE2018 / 5533 and 3% by weight of said metal ion Μ and / or of said counterion X by weight relative to the total weight of the dry sorbent composition.

Preferably, said metal ion Μ is chosen from the group consisting of Cu ²⁺ , Fe ²⁺ , Fe ³⁺ , Mn ²⁺ , Co ²⁺ , Mo ²⁺ , Ni ²⁺ and Zn ²⁺ .

Preferably, said counterion X is nitrate.

Preferably, said pulverulent sorbent composition further comprises activated carbon, lignite coke, halloysite, sepiolite, clays, bentonite, kaolin, vermiculite, refractory clay, air entrained cement dust, perlite, expanded clay, lime sandstone dust, trass dust, Yali rock dust, trass lime, earth to fuller, cement, calcium aluminate, sodium aluminate, calcium sulfide, organic sulfide, calcium sulfate, open hearth coke, lignite dust, fly ash, or water glass.

Preferably, the method of reducing the resistivity further comprises a step of adding to said powdery sorbent composition a sodium additive comprising sodium in an amount of up to 3.5% by weight relative to the weight total of the powdery sorbent composition and expressed in sodium equivalent.

Preferably, the powdery mineral compound comprises particles having an d ₅₀ of between 5 and 25 μm, preferably between 5 and 20 μm, more preferably between 5 and 16 μm.

According to the invention, the powdery sorbent composition for a smoke gas treatment installation including an electrostatic precipitator, comprises a powdery mineral compound of halloysite type according to the Dana classification, characterized in that said powdery sorbent composition has a resistivity reduced below 1E11 Ohms.cm and above 1E07 Ohms.cm at 300 ° C, wherein said resistivity of said powdery sorbent composition is measured in a resistivity cell in an oven under an air flow comprising 10 % humidity, said reduced resistivity being provided by an additive or a mixture of additives, comprising at least one metal ion Μ and / or a counterion X, Μ being a metal ion

BE2018 / 5533 having an atomic number less than or equal to 74 and is a transition metal ion or a post-transition metal ion, or Mg ²⁺ or Na ⁺ or Li ⁺ and X being one of the counterions chosen from the group consisting of nitrates, nitrites, oxides O ² ', and hydroxide OH' and their mixtures in an amount calculated to obtain between 0.1% by weight and 5% by weight, preferably between 0.3% by weight and 3% by weight of said metal ion Μ and / or counterion X by weight relative to the total weight of the dry sorbent composition.

The present invention also relates to the use of a pulverulent sorbent composition as described here in a method for treating smoke gases using an installation comprising an electrostatic precipitator.

Brief description of the drawings

Figure 1 shows a schematic embodiment of a smoke gas treatment installation carrying out the smoke gas treatment process with the sorbent composition according to the present invention.

Detailed description of the invention

According to a first aspect, the present invention relates to a sorbent composition for a smoke gas treatment installation including an electrostatic precipitator, said sorbent composition comprising a mineral compound, characterized in that it further comprises an additive or a mixture additives in an amount of between 0.1% and 5%, preferably between 0.3% and 3% by weight of the dry composition, said additive or said additives containing at least one metal ion Μ having a lower atomic number or equal to 74 and being a transition metal ion or a post-transition metal ion, and at least one counterion X chosen from nitrates, nitrites, and mixtures thereof.

In a preferred embodiment, the powdery mineral compound is chosen from the group consisting of allophane, bentonite, chlorite, dickite, halloysite, illite, kaolinite, montmorillonite, nacrite,

BE2018 / 5533 nontronite, palygorksite, saponite, sepiolite, serpentine, talc and mixtures thereof, more preferably from the group consisting of bentonite, halloysite, illite, kaolinite, montmorillonite, sepiolite, smectite, talc, vermiculite and their mixtures, and most preferably in the group consisting of bentonite, halloysite, kaolinite, montmorillonite, sepiolite and their mixtures.

The method of manufacturing said sorbent composition according to the invention comprises a step of supplying a mineral sorbent and is characterized in that it comprises a step of adding an additive or a mixture of additives to an amount calculated to obtain between 0.1% and 5%, preferably between 0.3 and 3.5% of said additive or mixture of additives by weight of the dry sorbent composition or by weight of the mineral sorbent, said additive or said additives containing at least one metal ion Μ having an atomic number less than or equal to 74 and being a transition metal ion or a post-transition metal ion, and at least one counterion X chosen from nitrates, nitrites, O ² ', and OH' and their mixtures.

In one embodiment of the process for manufacturing the sorbent composition according to the invention, said additive containing at least one metal ion Μ and at least one counterion X is added in the form of an aqueous solution or of suspension or powder.

Said additive or mixture of additives containing at least one metal ion Μ and at least one counterion X is preferably added to a mineral sorbent before injection into an injection zone of the smoke gas treatment installation.

As a variant, said additive or mixture of additives containing at least one metal ion Μ and at least one counterion X can be added during the injection into an injection zone of the smoke gas treatment installation, separately mineral sorbent and upstream of the electrostatic precipitator.

Various sorbent compositions were prepared according to the method of the present invention and measurements of the resistivity of the dry powders of said sorbent compositions were carried out by following the

BE2018 / 5533 procedure underlined by ΙΊΕΕΕ (Esctcourt, 1984). Basically, a resistivity cell of a determined volume is filled with a dry powder of sorbent composition and the powder is then compacted with a weight so as to obtain a flat surface. An electrode with protection was placed on the surface of the powder and the resistivity of the powder was measured in an oven under an air flow comprising 10% humidity at various temperatures between 150 ° C (302 ° F ) and 300 ° C (372 ° F). For each measurement, a maximum resistivity Rmax and a resistivity at 300 ° C (372 ° F) were determined.

It should be mentioned that improvements in particulate matter collection on electrodes for collecting an electrostatic precipitator can be observed with the use of the sorbent according to the present invention.

According to another aspect, the present invention relates to a smoke gas treatment installation. FIG. 1 shows a schematic embodiment of a smoke gas treatment installation 100 comprising an electrostatic precipitator 101 arranged downstream of a first portion of duct 102 arranged downstream of an air preheater 103, characterized in that an injection zone 104 is arranged upstream of said air preheater 103 and comprises a sorbent inlet 105. Said smoke gas treatment installation 100 further comprises a tank 106 comprising said sorbent composition for supplying said sorbent composition at said injection area through said sorbent inlet. The hot smoke gases FG produced by a boiler 10 pass through the injection zone into which the sorbent S according to the invention is injected to react with SO ₂ and other acid gases from the smoke gases, then the combustion gases hot smoke pass through the air preheater through which cold air CA circulates to absorb the heat from the hot smoke gases and to be injected as hot air HA into the boiler. Then, the smoke gases pass through the electrostatic precipitator 101 in which charged collection electrodes collect the particulate matter, including the sorbent composition according to the invention which has reacted with undesirable acid gases. The smoke gas treatment installation described here is

BE2018 / 5533 relatively simple and well suited to the use of the sorbent composition according to the present invention.

Preferably, said smoke gas treatment installation is used to treat smoke gases from a power plant using coal or a fuel containing sulfur species or other acid gas precursors.

It should be understood that the present invention is not limited to the embodiments described and that variations can be applied without departing from the scope of the appended claims.

For example, in the preferred embodiment, the installation intended for the treatment of smoke gases has been described with an electrostatic precipitator downstream of an air preheater, said air preheater being connected to said electrostatic precipitator by a conduit. with an injection zone intended for injection of a sorbent composition according to the present invention arranged upstream of said air preheater. An alternative within the scope of the present invention may include a particulate collection device upstream of said preheater.

Another alternative of the smoke gas treatment device according to the present invention comprises in sequence an electrostatic precipitator, a preheater optionally followed by a particulate collection device, before reaching the chimney.

The particulate collection device can be another electrostatic precipitator or any type of filter, such as a bag filter.

In all these embodiments, the sorbent composition according to the present invention is injected into an injection zone located upstream of said electrostatic precipitator, before or after the preheater, according to the configuration on site.

Claims (8)

1. Method for reducing the resistivity of a powdery sorbent composition for a smoke gas treatment installation comprising an electrostatic precipitator below 1E11 Ohms.cm and above 1E07 Ohms.cm at 300 ° C, in wherein said resistivity of said powdery sorbent composition is measured in a resistivity cell in an oven under an air flow comprising 10% humidity, said powdery sorbent composition comprising a powdery mineral compound of halloysite type according to the Dana classification , the method comprising the steps of: a) supplying said powdery sorbent composition to a reactor and; b) adding to said pulverulent sorbent composition an additive or a mixture of additives, comprising at least one metal ion Μ and / or a counterion X, Μ being a metal ion having an atomic number less than or equal to 74 and being a transition metal ion or a posttransition metal ion, or Mg ²⁺ or Na ⁺ or Li ⁺ and X being one of the counterions chosen from the group consisting of nitrates, nitrites, oxides O ² ', and hydroxide OH' and their mixtures in an amount calculated to obtain between 0.1% by weight and 5% by weight, of said metal ion Μ and / or of said counterion X by weight relative to the total weight of the dry sorbent composition. 2. The method of claim 1, wherein said metal ion Μ is selected from the group consisting of Cu ²⁺ , Fe ²⁺ , Fe ³⁺ , Mn ²⁺ , Co ²⁺ , Mo ²⁺ , Ni ²⁺ and Zn ²⁺ . 3. The method of claim 1 or 2, wherein said counterion X is nitrate. 4. Method according to any one of the preceding claims, in which said pulverulent sorbent composition further comprises activated carbon, lignite coke, halloysite, sepiolite, clays, bentonite, kaolin, vermiculite, refractory clay, air-entrained cement dust, perlite, expanded clay, BE2018 / 5533 22 lime sandstone dust, trass dust, Yali rock dust, trass lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organic sulfide, calcium sulfate, open hearth coke, lignite dust, fly ash, or water glass. 5. Method according to any one of the preceding claims, further comprising a step of adding to said pulverulent sorbent composition a sodium additive comprising sodium in an amount of up to 3.5% by weight relative to the weight total of the powdery sorbent composition and expressed in sodium equivalent. 6. Method according to any one of the preceding claims, in which said pulverulent mineral compound comprises particles having an d ₅₀ of between 5 and 25 μm. 7. powder sorbent composition for a smoke gas treatment installation including an electrostatic precipitator, said powder sorbent composition comprising a mineral powder compound of halloysite type according to the Dana classification, characterized in that said powder sorbent composition has a reduced resistivity below 1E11 Ohms.cm and above 1E07 Ohms.cm at 300 ° C, wherein said resistivity of said powdery sorbent composition is measured in a resistivity cell in an oven under an air flow comprising 10 % humidity, said reduced resistivity being provided by an additive or a mixture of additives, comprising at least one metal ion Μ and / or a counterion X, Μ being a metal ion having an atomic number less than or equal to 74 and being a transition metal ion or a posttransition metal ion, or Mg ²⁺ or Na ⁺ or Li ⁺ and X being one of the counter-i ons selected from the group consisting of nitrates, nitrites, oxides O ² ', and hydroxide OH' and their mixtures in an amount calculated to obtain between 0.1% by weight and 5% by weight, of said ion metallic Μ and / or of said counterion X by weight relative to the total weight of the dry sorbent composition. BE2018 / 5533 8. Use of a pulverulent sorbent composition according to claim 7 in a process for treating smoke gases using an installation comprising an electrostatic precipitator.