Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/04—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium
  • B01J20/043—Carbonates or bicarbonates, e.g. limestone, dolomite, aragonite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
  • B01D53/48—Sulfur compounds
  • B01D53/50—Sulfur oxides
  • B01D53/508—Sulfur oxides by treating the gases with solids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/81—Solid phase processes
  • B01D53/83—Solid phase processes with moving reactants
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
  • B01J20/0225—Compounds of Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
  • B01J20/0233—Compounds of Cu, Ag, Au
  • B01J20/0237—Compounds of Cu
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
  • B01J20/0274—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04 characterised by the type of anion
  • B01J20/0296—Nitrates of compounds other than those provided for in B01J20/04
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/04—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium
  • B01J20/041—Oxides or hydroxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
  • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J20/28057—Surface area, e.g. B.E.T specific surface area
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
  • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J20/28057—Surface area, e.g. B.E.T specific surface area
  • B01J20/28059—Surface area, e.g. B.E.T specific surface area being less than 100 m2/g
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
  • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J20/28069—Pore volume, e.g. total pore volume, mesopore volume, micropore volume
  • B01J20/28071—Pore volume, e.g. total pore volume, mesopore volume, micropore volume being less than 0.5 ml/g
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
  • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
  • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
  • B03C3/01—Pretreatment of the gases prior to electrostatic precipitation
  • B03C3/013—Conditioning by chemical additives, e.g. with SO3
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/40—Alkaline earth metal or magnesium compounds
  • B01D2251/402—Alkaline earth metal or magnesium compounds of magnesium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/40—Alkaline earth metal or magnesium compounds
  • B01D2251/404—Alkaline earth metal or magnesium compounds of calcium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/60—Inorganic bases or salts
  • B01D2251/604—Hydroxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/60—Inorganic bases or salts
  • B01D2251/606—Carbonates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/102—Carbon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/106—Silica or silicates
  • B01D2253/11—Clays
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/112—Metals or metal compounds not provided for in B01D2253/104 or B01D2253/106
  • B01D2253/1122—Metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2258/00—Sources of waste gases
  • B01D2258/02—Other waste gases
  • B01D2258/0283—Flue gases
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2220/00—Aspects relating to sorbent materials
  • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
  • B01J2220/42—Materials comprising a mixture of inorganic materials

Definitions

• the present invention relates to a calcium-magnesium compound and to a sorbent composition for use in flue gas installation equipped with an electrostatic precipitator, a method for obtaining such sorbent composition and a process of flue gas treatment using an electrostatic precipitator which comprises a step of injecting such a sorbent composition.
• the present invention is related to a flue gas treatment installation using the sorbent composition according to the invention.
• An electrostatic precipitator generally comprises a shell with a flue gas inlet and a flue gas outlet, the shell enclosing a plurality of collection electrodes, and discharge electrodes spaced from each other and a plurality of hoppers positioned under the collecting plates.
• a voltage is applied between the discharge electrodes and the collection electrodes such as to create an electrostatic field charging the particulate material in the flue gas to obtain charged particulate material.
• the charged particulate material is collected by the collecting electrodes.
• the electrostatic precipitator further comprises rappers which provide mechanical shocks or vibrations to the collecting electrodes to remove the collected particles from the collecting electrodes.
• the collected particles fall down into hoppers arranged at the bottom of the shell and which are periodically or continuously emptied.
• the collecting electrodes can be planar or in a form of tubular or honeycomb structure and the discharge electrodes, are generally under the form of a wire or a rod.
• the flue gas treatment installations including electrostatic precipitators are provided with an air preheater, which latter being sometimes included in a boiler and/or otherwise provided as an additional element of the flue gas installation.
• the air preheater comprises a heat exchanger transferring the heat from the flue gas stream produced by the boiler to heat the combustion air to the boiler to increase the thermal efficiency of the boiler.
• the flue gas treatment comprises multiple electrostatic precipitators. Cold-side electrostatic precipitators are located downstream the air preheater, thereby operate at lower temperatures generally less than 200°C (392 °F). Hot side electrostatic precipitators are located upstream the air preheater and operate at higher temperatures, generally more than 250°C (482°F).
• the electrostatic precipitator units already operate at the boundary of their design capability due to more stringent particulate matter emission limits that have been introduced over the years and/or changes to plant operating conditions such as fuel switching.
• ⁇ is the fractional collection efficiency
• a c is the area of the collection electrode
• V pm is the particle migration velocity
• Q. is the volumetric flow rate of gas.
• the properties of the particles that influence collection efficiency are primarily the particle size distribution and their resistivity. The resistivity of the particles influences the particle migration velocity as described previously in the Deutsch-Anderson equation.
• fly ash is generally higher and chemical additives were used such as S0 3 , HCI, NH 3 , Na 2 C0 3 , Na 2 S0 4 and NH(CH 2 CH 2 OH) to lower the resistivity of fly ash.
• chemical additives such as S0 3 , HCI, NH 3 , Na 2 C0 3 , Na 2 S0 4 and NH(CH 2 CH 2 OH) to lower the resistivity of fly ash.
• those additives are susceptible to release undesired compounds.
• polymers for lowering the resistivity of fly ash.
• polymer additives generally degrade at high temperatures and must be injected to the flue gas stream at low temperatures.
• the document WO2015/119880 relates to the drawbacks of trona or hydrated lime as sorbents for flue gas treatment process with electrostatic precipitator units.
• Sodium based sorbents are known to decrease the resistivity of particulate matter, however a main drawback of the use of sodium sorbents is the leaching of heavy metals from the fly ash is enhanced leading to potential environmental contamination.
• Calcium hydroxide based sorbents do not present the problem of heavy metal leaching from fly ash, but they are known to increase resistivity of the particulate matter (fly ash) entrained in the flue gas stream so that the efficiency of the electrostatic precipitator unit may be lowered when calcium based sorbents are used.
• compositions for reducing particulate resistivity in a flue gas and for capturing acid gases wherein the composition comprises an alkali metal/alkali earth particulate having a formula ( ⁇ _ ⁇ - ⁇ Na a K ) w (Mgi_6 Ca 6 ) x (OH) y (C0 3 ) z -nH 2 0, more specifically a formula Na w Ca x (OH) y (C0 3 ) z -nH 2 0 wherein a ratio of W to x is about 1/3 to about 3/1. Therefore the composition still presents a high amount of sodium which would be likely to not only leach itself, but sodium is also know to increase the leaching of heavy metals contained in the fly ash.
• US 6,797,035 discloses a process for reducing the resistivity of fly ash by spraying an aqueous solution of potassium nitrate or potassium nitrite on the stream of flue gas or by injecting powder of potassium nitrate or potassium nitrite into the duct through which the flue gas flows.
• a drawback of using those powders of nitrate or nitrite salts is that they react with other species than fly ash and results in less reactive chemical reaching the collection plates of the electrostatic precipitator. Therefore, it is suggested to inject those nitrate salts as finely divided powders to reduce the exposed reactive surface area and inhibit reactions with nitrous oxides and sulfur oxides.
• US 7,744,678 B2 discloses a method where addition of an alkali metal species, comprising sodium, between 0.2 and 3.5 wt%, to calcium hydroxide sorbents provides an improved reactivity towards S0 2 capture. Addition of the alkaline metal species is carried out in such a way that the BET specific surface area (SSA) by nitrogen adsorption remains high at 30 ⁇ SSA ⁇ 40 (m 2 /g).
• SSA BET specific surface area
• Enhanced hydrated lime of this paper has a surface area greater than 40 m 2 /g, a pore volume greater than 0.2 cm 3 /g and a median particle size d 50 comprised between 6 and 12 micrometers and has been found to present acceptable maximum resistivity of 1E11 (lxlO 11 ) Ohms. cm.
• the object of the present invention is to provide calcium- magnesium compound and sorbent composition comprising said calcium- magnesium compound removing the intrinsic drawback of these sorbents in their application in electrostatic precipitator units.
• the present invention is related to powdery calcium-magnesium compound comprising at least a calcium- magnesium carbonate content greater or equal to 80 weight % or a calcium- magnesium hydroxide content greater or equal to 80 weight %, with respect to the total weight of the powdery calcium-magnesium compound, further presenting a resistivity at 300°C (372°F) R 300 lower than 1E11 (lxlO 11 ) Ohms. cm and higher than 1E7 (lxlO 7 ) Ohms.
• cm advantageously lower than 1E10 (lxlO 10 ) Ohms.cm and higher than 5E7 (5xl0 7 ) Ohms.cm, preferably lower than 5E9 (5xl0 9 ) Ohms.cm, more preferably lower than 1E9 (lxlO 9 ) Ohms.cm, even more preferably lower than 5E8 (5xl0 8 ) Ohms.cm.
• a powdery calcium- magnesium compound can be successfully used in flue gas treatment using electrostatic precipitators when the resistivity at 300°C (372°F) is still lower than 1E11 (lxlO 11 ) Ohms.cm, preferably lower than 1E10 (lxlO 10 ) Ohms.cm, meaning that the powdery calcium-magnesium compound is robust and does not decompose at relatively high temperature. Accordingly, this powdery calcium-magnesium compound is able to positively modify the fly-ash resistivity without impacting negatively the operation of the electrostatic precipitator.
• the powdery calcium-magnesium is a calcium- magnesium compound comprising at least a calcium-magnesium carbonate content greater than or equal to 80 weight %, preferably greater than or equal to 82 weight %, more preferably greater than or equal to 85 weight %, advantageously greater or equal to 88 weight %, with respect to the total weight of the powdery calcium-magnesium compound, it will be preferably injected at a location near to the boiler or even in the boiler as in that location of the flue gas flow inside which the calcium-magnesium compound is to be injected, the temperature is favorable for a proper capture of polluting compounds of the flue gases by the high carbonate content.
• the resistivity at a temperature of 300°C (372°F) is still low enough to modify the resistivity of the mixture of the fly ashes present in the flue gas and the calcium-magnesium compound injected.
• calcium-magnesium compound with a calcium- magnesium carbonate content greater than or equal to 80 weight %, preferably greater than or equal to 82 weight %, more preferably greater than or equal to 85 weight %, advantageously greater or equal to 88 weight %, with respect to the total weight of the powdery calcium-magnesium compound, it is meant within the meaning of the present invention natural calcium and/or magnesium carbonate such a dolomite, limestone, or even precipitated carbonate of calcium and/or magnesium.
• the molar proportion of calcium to magnesium in dolomite can vary from 0.8 to 1.2.
• the proportion of calcium to magnesium can be also higher or lower up to 0.01 to 10 or even 100.
• natural limestone comprises magnesium carbonate at a level which can vary from 1 to 10 weight % with respect to the total weight of the powdery calcium-magnesium compound. If the compound in question is a magnesium carbonate, its content in calcium carbonate can also vary from 1 to 10 weight %.
• the calcium-magnesium compound can also contain impurities.
• the impurities notably comprise all those which are encountered in natural limestones and dolomites, such as clays of the silico-aluminate type, silica, impurities based on iron or manganese.
• the powdery calcium-magnesium compound is a calcium-magnesium compound comprising at least a calcium-magnesium hydroxide content greater than or equal to 80 weight %, preferably greater than or equal to 82 weight %, more preferably greater than or equal to 85 weight %, advantageously greater or equal to 88 weight %, with respect to the total weight of the powdery calcium-magnesium compound, it will be preferably injected at a location near upstream the preheater as in that location of the flue gas flow inside which the calcium-magnesium compound is to be injected, the temperature is favorable for a proper capture of polluting compounds of the flue gases by the high hydroxide content.
• the resistivity at a temperature of 300°C (372°F) is still low enough to modify the resistivity of the mixture of the fly ashes present in the flue gas and the calcium-magnesium compound injected.
• calcium-magnesium compound with a calcium- magnesium hydroxide content greater than or equal to 80 weight %, preferably greater than or equal to 82 weight %, more preferably greater than or equal to 85 weight %, advantageously greater or equal to 88 weight %, with respect to the total weight of the powdery calcium-magnesium compound it is meant within the meaning of the present invention
• Said at least one calcium-magnesium compound according to the present invention is therefore at least formed with (calcitic) slaked lime, slaked dolomitic lime (or dolime), magnesium slaked lime.
• the molar proportion of calcium to magnesium in dolomitic lime can vary from 0.8 to 1.2.
• the proportion of calcium to magnesium can be also higher or lower up to 0.01 to 10 or even 100.
• natural limestone which is baked to form quicklime, which latter being further slaked to provide hydrated lime comprises magnesium carbonate at a level which can vary from 1 to 10 weight % with respect to the total weight of the powdery calcium-magnesium compound.
• the compound in question is a magnesium carbonate which is baked to form magnesium oxide, which latter being further slaked to provide magnesium hydroxide, its content in calcium carbonate can also vary from 1 to 10 weight %. It has to be noted that a part of the magnesium oxide might remain unslaked.
• the calcium-magnesium compound can also contain impurities.
• the impurities notably comprise all those which are encountered in natural limestones and dolomites, such as clays of the silico-aluminate type, silica, impurities based on iron or manganese
• the CaC0 3 , MgC0 3 , Ca(OH) 2 and Mg(OH) 2 contents in calcium- magnesium compounds may easily be determined with conventional methods. For example, they may be determined by X fluorescence analysis, the procedure of which is described in the EN 15309 standard, coupled with a measurement of the loss on ignition and a measurement of the C0 2 volume according to the EN 459-2:2010 E standard.
• the calcium-magnesium compound according to the present invention presents a maximum resitivity R max lower than 5E11 (5x1 ⁇ 11 ) Ohms. cm, preferably lower than 1E11 (lxlO 11 ) Ohms. cm and more preferably lower than 5E10 (5xl0 10 ) Ohms.cm.
• the calcium-magnesium compound is doped with at least one metallic ion M chosen in the group of the metallic ion having an atomic number less than or equal to 74 and belonging to the group consisting of a transition metal ion or a post-transition metal ion at an amount greater than or equal to 0.05 weight % and lower or equal to 5 weight % with respect to the total weight of the powdery calcium-magnesium compound.
• the calcium-magnesium compound according to the present invention is further doped with at least one counter ion X chosen in the group consisting of nitrates, nitrites, and their mixture at an amount greater than or equal to 0.05 weight % and lower or equal to 5 weight % with respect to the total weight of the powdery calcium-magnesium compound.
• the total weight of said metallic ion and said counter ion is greater than or equal to 0.1 weight % and lower than or equal to 5 weight %, preferably between 0.3 and 3 weight %, with respect to the total weight of the powdery calcium-magnesium compound.
• the calcium-magnesium compound of the invention further comprises sodium in an amount up to 3.5 weight % with respect to the total weight of the powdery calcium-magnesium compound, expressed as sodium equivalent.
• sodium is in a minimum amount of 0.2 wt.% with respect to the total weight of the powdery calcium-magnesium compound and expressed as sodium equivalent.
• Sodium under the form of sodium additive in such amounts is known to have a slight effect on decreasing the resistivity of the sorbent, as presented by Foo et al. (2016) document previously mentioned. The applicant found that sodium additive in such amounts in combination with the presence as described hereunder of at least a metallic ion and/or a counter ion further provides an additional effect on the decreasing of the resistivity of the sorbent composition.
• the use of sodium additive in combination with the presence as described hereunder of at least a metallic ion and/or a counter ion decreases the resistivity of sorbent composition more than when presence as described hereunder of at least a metallic ion and/or a counter ion is used alone in the calcium-magnesium compound and more than when sodium is used alone in the calcium-magnesium compound.
• the said metallic ion M is one of the ions among Cu 2+ , Fe 2+ , Fe 3+ , Mn 2+ , Co 2+ , Mo 2+ , Ni 2+ , Zn 2+ .
• the said metallic ion M is one of the ions among
• the said counter ion X is nitrate.
• the powdery calcium-magnesium comprises particles having a d 50 comprised between 5 and 25 ⁇ , preferably between 5 and 20 ⁇ , more preferably between 5 and 16 ⁇ .
• the notation d x represents a diameter expressed in ⁇ , as measured by laser granulometry in methanol optionally after sonication, relatively to which X % by mass of the measured particles are smaller or equal
• the powdery calcium-magnesium compound is a calcium-magnesium compound comprising at least a calcium- magnesium hydroxide content greater than or equal to 80 weight %
• the calcium-magnesium compound according to the invention has a BET specific surface area of at least 20 m 2 /g, preferably of at least 25 m 2 /g, preferably of at least 30 m 2 /g, more preferably of at least 35 m 2 /g-
• the BET surface area is determined by manometry with adsorption of nitrogen after degassing in vacuum at 190°C (374°F) for at least 2 hours and calculated according to the multipoint BET method as described in the ISO 9277/2010E standard.
• the powdery calcium-magnesium compound is a calcium-magnesium compound comprising at least a calcium- magnesium hydroxide content greater than or equal to 80 weight %
• the sorbent composition according to the invention has a BJH pore volume of at least 0.1 cm 3 /g, preferably of at least 0.15 cm 3 /g, preferably of at least 0.17 cm 3 /g, more preferably of at least 0.2 cm 3 /g-
• the BJH pore volume is determined by manometry with desorption of nitrogen after degassing in vacuum at 190°C (374°F) for at least 2 hours and calculated according to the BJH method as described in the ISO 9277/2010E standard.
• the present invention also relates to a sorbent composition for flue gas treatment installation including an electrostatic precipitator comprising said calcium-magnesium compound according to the present invention.
• the sorbent composition according to the invention further comprises activated charcoal, lignite coke, halloysite, sepiolite, clays such as bentonite, kaolin, vermiculite or any other sorbent such as fire clay, aerated cement dust, perlite, expanded clay, lime sandstone dust, trass dust, Yali rock dust, trass lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulphide, organic sulphide, calcium sulfate, open-hearth coke, lignite dust, fly ash, or water glass.
• activated charcoal lignite coke, halloysite, sepiolite
• clays such as bentonite, kaolin, vermiculite or any other sorbent such as fire clay, aerated cement dust, perlite, expanded clay, lime sandstone dust, trass dust, Yali rock dust, trass lime, fuller's earth, cement, calcium aluminate
• the sorbent composition according to the present invention comprises sodium additive comprising sodium in an amount up to 3.5 weight % with respect to the total weight of the powdery calcium-magnesium compound and expressed as sodium equivalent.
• the amount of sodium in the composition would be higher than 0.2 weight % with respect to the total weight of the powdery sorbent composition.
• the sorbent composition according to the present invention comprises said metallic ion M and/or said counter ion X being present at an amount greater than or equal to 0.05 weight % and lower or equal to 5 weight % with respect to the total weight of the powdery calcium-magnesium compound and wherein preferably the total weight of said metallic ion and said counter ion is greater than or equal to 0.1 weight % and lower than or equal to 5 weight %, preferably between 0.3 and 3 weight %, with respect to the total weight of the dry sorbent composition.
• the sorbent composition comprises water in such an amount that the sorbent composition is under the form of a suspension.
• Exemplary amounts can be from 40 to 90 weight % of water wherein the sorbent is comprised in an amount of 10 to 60 weight % with respect to the total weight of the sorbent composition under the form of a suspension.
• the sorbent composition under the form of a suspension can be used for example in a spray dry absorber, which can be followed by an electrostatic precipitator.
• the said calcium- magnesium compound is hydrated lime.
• the sorbent composition is under the form of a suspension, it will be under the form of a milk of lime where the solid content will be from 10 et 50 weight % with respect to the total weight of the milk of lime.
• the present invention is related to a process for manufacturing a sorbent composition for a flue gas treatment installation including an electrostatic precipitator, comprising the step of : a) Providing a calcium-magnesium compound to a reactor
• an additive or a mixture of additives comprising at least one metallic ion M and /or a counter ion X with M being a metallic ion having an atomic number less than or equal to 74 and is a transition metal ion or a post-transition metal ion, and X being one of the counter ion amongst nitrates, nitrites, oxides (0 2 ⁇ ), hydroxides (OH ), and their mixture in an amount calculated to obtain between 0.1 weight % and 5 weight %, preferably between 0.3 weight % to 3 weight % of said metallic ion M and /or counter ion X in weight of dry sorbent composition.
• the present invention is related to a process for manufacturing a sorbent composition for a flue gas treatment installation including an electrostatic precipitator, comprising the step of : a) Providing a calcium-magnesium compound to a reactor
• an additive or a mixture of additives comprising at least one metallic ion M and /or a counter ion X with M being a metallic ion having an atomic number less than or equal to 74 and is a transition metal ion or a post-transition metal ion, and X being one of the counter ion amongst nitrates, nitrites, oxides (0 2 ⁇ ), hydroxides (OH ), and their mixture in an amount calculated to obtain between 0.1 weight % and 5 weight %, preferably between 0.3 weight % to 3 weight % of said metallic ion M and /or counter ion X in weight of calcium-magnesium compound.
• the sorbent composition comprises particles having a d 50 comprised between 5 and 25 ⁇ , preferably between 5 and 20 ⁇ , more preferably between 5 and 16 ⁇ .
• said calcium-magnesium compound comprises at least a calcium-magnesium carbonate content greater or equal to 80 weight % with respect to the total weight of the dry calcium-magnesium compound.
• said calcium-magnesium compound comprises a calcium-magnesium hydroxide content greater or equal to 80 weight %, with respect to the total weight of the dry calcium-magnesium compound.
• the said metallic ion M is one of the ions among Cu 2+ , Fe 2+ , Fe 3+ , Mn 2+ , Co 2+ , Mo 2+ , Ni 2+ , Zn 2+ .More preferably in the process of manufacturing said sorbent composition said metallic ion M is one of the ions among Cu 2+ , Fe 2+ , Fe 3+ .
• said counter ion X is nitrate.
• the process of 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% of sodium equivalent in weight of the dry sorbent composition.
• the step of providing a calcium-magnesium compound to a reactor comprises the step of providing a quicklime to said reactor, slaking said quicklime with a predetermined amount of water to obtain said calcium- magnesium compound comprising at least a calcium hydroxide content greater or equal to 80 weight %, with respect to the total weight of the dry calcium-magnesium compound with an predetermined amount of moisture.
• said step of slaking is performed in conditions such as to obtain hydrated lime with a BET specific surface area by nitrogen adsorption of at least 20m 2 /g, preferably of at least 25 m 2 /g, preferably of at least 30 m 2 /g, more preferably of at least 35 m 2 /g-
• said step of slaking is performed in conditions such as to obtain hydrated lime with a BJH pore volume for pores having a diameter lower or equal to 1000 A by nitrogen desorption of at least 0.1 cm 3 /g, 0.15 cm 3 /g, preferably of at least 0.17 cm 3 /g, more preferably of at least 0.2 cm 3 /g-
• said step of slaking is performed in the same conditions as the ones described in US patent 6,322,769 of the applicant and incorporated by reference.
• the said step of slaking is performed in the same conditions as the ones described in the US patent 7,744,678 of the applicant and incorporated by reference.
• the step of adding an additive or a mixture of additives, comprising at least one metallic ion M and /or a counter ion X is performed before said step of slaking quicklime.
• the said step of adding an additive or a mixture of additives, comprising at least one metallic ion M and /or a counter ion X is performed during said step of slaking quicklime.
• the said step of adding an additive or a mixture of additives, comprising at least one metallic ion M and /or a counter ion X is performed after the said step of slaking quicklime.
• the step of adding an additive or a mixture of additives, comprising at least one metallic ion M and /or a counter ion X is performed during or after the said step of slaking does not substantially change the specific surface area nor the pore volume of the calcium-magnesium compound, for example as sorbent.
• the specific surface area and the pore volume of the sorbent composition according to the present invention is substantially the same as for calcium hydroxide sorbent prepared by the known methods such as the one described in US patents 6,322,769 and 7,744,678 incorporated by reference. Therefore, the properties of the sorbent ensuring the efficiency of S0 2 removal are preserved.
• the said process of manufacturing is characterized in that it further comprises a step of adding activated charcoal, lignite coke, halloysite, sepiolite, clays, bentonite, kaolin, vermiculite, fire clay, aerated cement dust, perlite, expanded clay, lime sandstone dust, trass dust, Yali rock dust, trass lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulphide, organic sulphide, calcium sulfate, open-hearth coke, lignite dust, fly ash, or water glass, preferably performed after the said step of slaking.
• Other embodiments of the process for manufacturing a sorbent composition according to the present invention are mentioned in the appended claims
• the present invention is related to a flue gas treatment process using an installation comprising an injection zone arranged upstream an electrostatic precipitator, characterized in that it comprises a step of injecting in said injection zone a sorbent composition according to the present invention.
• the flue gas treatment process using an installation including an electrostatic precipitator, and an injection zone arranged upstream said electrostatic precipitator and through which flue gas is flowing towards said electrostatic precipitator is characterized in that the said process comprises a step of injection of a sorbent composition in said injection zone, said sorbent composition comprising a calcium-magnesium sorbent, at least one metallic ion M having an atomic number less than or equal to 74 and being a transition metal ion or a post-transition metal ion, and optionally at least a counter ion X chosen amongst nitrates, nitrites, and their mixture, the total amount of said at least one metallic ion M and said optionally at least one counter ion X being comprised between 0.1 % and 5 %, preferably 0.3 to 3.5% in weight of the dry composition.
• the said sorbent composition has a lower resistivity compared to calcium-magnesium sorbents of prior art, especially at a temperature of 300°C (372°F).
• Injection of the sorbent composition according to the invention in an injection zone to mix with flue gas is effective for the removal of S0 2 and other gaseous acids and the lower resistivity of such sorbent composition improves the collection of particulate matter on the collecting electrodes of the electrostatic precipitator.
• the sorbent composition comprises as calcium-magnesium compound at least a calcium-magnesium carbonate, and said sorbent composition is injected in said injection zone, wherein said flue gas has a temperature greater than or equal to 850°C ( 1562 °F).
• the sorbent composition comprises a calcium- magnesium compound at least a calcium-magnesium hydroxide, and said sorbent composition is injected in said injection zone wherein said flue gas has a temperature greater than or equal to 180°C (356°F), preferably greater than 200°C (392°F), more preferably comprised between 300°C (372°F) and 425°C (797°F).
• the said calcium-magnesium compound in the sorbent composition is mixed with an additive or a mixture of additives, comprising at least one metallic ion M and /or a counter ion X before the said step of injection.
• the calcium-magnesium compound and an additive or a mixture of additives, comprising at least one metallic ion M and /or a counter ion X are injected separately and mixed with said flue gas in the said injection zone.
• the said sorbent composition can be used in the flue gas treatment process according to the present invention under a broad range of temperatures, for example between 100°C (212°F) and 425°C (797°F) or even higher when the sorbent composition mainly comprises carbonate sorbent (typically temperature higher than 850°C (1562 °F)
• the said additives of the sorbent composition according to the present invention do not encounter degradation at temperatures higher than 180°C (356°F) so that said sorbent composition can be injected in the said injection zone wherein the temperature is greater than or equal to 180°C (356°F), preferably greater than or equal to 300°C (372°F).
• temperatures at the injection zone can range between 300°C (372°F) to 425°C (797°F), preferably 350°C (662°F) to 380°C (716°F).
• the said injection zone is located upstream an air preheater itself located upstream said electrostatic precipitator.
• the said ion M is one of the ions among Cu 2+ , Fe 2+ , Fe 3+ , Mn 2+ , Co 2+ , Mo 2+ , Ni 2+ , Zn 2+ .
• the said ion M is one of the ions among Cu 2+ , Fe 2+ , Fe 3+ .
• said counter ion X is nitrate.
• the said sorbent composition comprises another additive comprising sodium in an amount up to 3.5% in weight of the dry composition and expressed as sodium equivalent.
• the said sorbent composition has a BET specific surface area of at least 20m 2 /g.
• the said sorbent composition has a BJH pore volume obtained from nitrogen desorption of at least 0.1 cm 3 /g.
• the said sorbent composition has a BJH pore volume obtained from nitrogen desorption of at least 0.15 cm 3 /g, preferably of at least 0.17 cm 3 /g, more preferably of at least 0.2 cm 3 /g.
• the said sorbent composition further comprises activated charcoal, lignite coke, halloysite, sepiolite, clays, bentonite, kaolin, vermiculite, fire clay, aerated cement dust, perlite, expanded clay, lime sandstone dust, trass dust, Yali rock dust, trass lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulphide, organic sulphide, calcium sulfate, open-hearth coke, lignite dust, fly ash, or water glass.
• activated charcoal lignite coke, halloysite, sepiolite, clays, bentonite, kaolin, vermiculite, fire clay, aerated cement dust, perlite, expanded clay, lime sandstone dust, trass dust, Yali rock dust, trass lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulphide, organic sulphide,
• the present invention is related 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 duct, characterized in that it further comprises an injection zone for injecting a sorbent composition according to the present invention arranged upstream of said air preheater.
• the said flue gas treatment device or installation is used for treating flue gas of a plant, in particular a power plant , using coal or fuel containing sulfur species or other acid gas precursors.
• the said flue gas treatment installation further comprises a reservoir comprising said sorbent composition to provide said sorbent composition to the said injection zone through a sorbent inlet.
• the present invention can also be described as a process for reducing the resistivity a powdery sorbent composition for flue gas treatment installation including an electrostatic precipitator under 1E11 Ohms. cm and over 1E07 Ohms. cm at 300°C, wherein said resistivity of said powdery sorbent composition is measured in a resistivity cell in an oven under a stream of air comprising 10% of humidity, said powdery sorbent composition comprising a powdery calcium-magnesium compound comprising at least a calcium-magnesium carbonate content greater than or equal to 80 weight % or a calcium-magnesium hydroxide content greater or equal to 80 weight %, with respect to the total weight of the powdery calcium-magnesium content, the process comprising the steps of : a) providing the said powdery sorbent composition in a reactor and; b) adding to said powdery sorbent composition an additive or a mixture of additives, comprising at least one metallic ion M and /or a counter ion X with M being a metallic
• said metallic ion M is selected from the group consisting of Cu2+, Fe2+, Fe3+, Mn2+, Co2+, Mo2+, Ni2+ and Zn2+.
• said counter ion X is nitrate.
• said powdery calcium-magnesium compound presents a BET specific surface area by nitrogen adsorption of at least 20m2/g, preferably of at least 25 m 2 /g, preferably of at least 30 m 2 /g, more preferably of at least 35 m 2 /g-
• said powdery calcium-magnesium compound presents a BJH pore volume for pores having a diameter lower or equal to 1000 A by nitrogen desorption of at least 0.1 cm3/g, 0.15 cm 3 /g, preferably of at least 0.17 cm 3 /g, more preferably of at least 0.2 cm 3 /g-
• said powdery sorbent composition further comprises activated charcoal, lignite coke, halloysite, sepiolite, clays, bentonite, kaolin, vermiculite, fire clay, aerated cement dust, perlite, expanded clay, lime sandstone dust, trass dust, Yali rock dust, trass lime, fuller's earth, cement, calcium
• the said process for reducing the resistivity of said powdery sorbent composition further comprises a step of adding to the said powdery sorbent composition a sodium additive comprising sodium in an amount up to 3.5 weight % with respect to the total weight of the powdery sorbent composition and expressed as sodium equivalent.
• the said powdery calcium magnesium compound is hydrated lime.
• the invention is also related to the use of a powdery sorbent composition as described herein in a flue gas treatment process using an installation comprising an electrostatic precipitator.
• FIG. 1 presents a schematic embodiment of a flue gas treatment installation carrying out the flue gas treatment process with the sorbent composition according to the present invention.
• the present invention is related to a sorbent composition for flue gas treatment installation including an electrostatic precipitator, said sorbent composition comprising calcium- magnesium compound, characterized in that it further comprises an additive or a mixture of additives in an amount comprised between 0.1% and 5%, preferably 0.3% to 3% in weight of the dry composition, said additive or additives containing at least one metallic ion M having an atomic number less than or equal to 74 and is a transition metal ion or a post-transition metal ion, and at least one counter ion X chosen amongst nitrates, nitrites, and their mixture.
• the calcium-magnesium compound is based on hydrated lime.
• Calcium hydroxide sorbents are manufactured by reacting (or slaking) calcium oxide, CaO or quick lime, with water in a so called hydrator, also called slaking unit.
• calcium magnesium hydroxide sorbents are manufactured by reacting dolomitic lime (also called dolime) or magnesium lime with water in a hydrator.
• dolomitic lime also called dolime
• quick lime and dolomitic lime can be mixed together and slaked with water in a hydrator to provide a mixture of calcium hydroxide and calcium magnesium hydroxide.
• the process of manufacturing of the sorbent composition will refer to quick lime but the process of manufacturing is not limited to quick lime as a starting material and dolomitic lime or a combination of dolomitic lime and/or magnesium lime and quick lime can also be used as starting materials.
• the process of manufacturing of the said sorbent composition according to the invention comprises a step of slaking quicklime with a predetermined amount of water to obtain hydrated lime with an predetermined amount of moisture, and is characterized in that it comprises a step of adding an additive or a mixture of additives in an amount calculated to obtain between 0.1% and 5 %, preferably between 0.3 and 3.5% of said additive or mixture of additives in weight of the dry sorbent composition, said additive or additives containing at least one metallic ion M having an atomic number less than or equal to 74 and is a transition metal ion or a post- transition metal ion, and at least one counter ion X chosen amongst nitrates, nitrites, O 2" , and OH and their mixture.
• the predetermined amount of water in the said step of slaking is in a water to lime ratio 2:1 by weight or higher.
• the amount of water in the slaking step can be adapted to obtain a hydrated lime with a moisture less than or equal to 10 wt.%, preferably less than or equal to 5 wt.%, preferably less than or equal to 2 w%, more preferably less than or equal to 1 w% with respect to the total weight of the sorbent composition at a powdery state.
• the amount of water in the slaking step can be adapted to obtain a hydrated lime with a moisture content comprised between 5 wt.% and 20 wt.%.
• the amount of water in the slaking step can also be higher such as to obtain a hydrated lime with a moisture content above 20 wt.%, all % being expressed with respect to the total weight of the sorbent composition at a powdery state.
• the hydrated lime obtained after the slaking step is dried in a further step.
• the said additive containing at least one metallic ion M and at least one counter ion X is added as an aqueous solution or as a suspension or as a powder before or during the said step of slaking of calcium oxide or calcium magnesium oxide or a combination thereof.
• the said additive or mixture of additives containing at least one metallic ion M and at least one counter ion X is added as aqueous solution or as a suspension or as a powder after the said step of slaking.
• the said additive or mixture of additives containing at least one metallic ion M and at least one counter ion X is preferably added to calcium hydroxide or calcium magnesium hydroxide before injection in an injection zone of the flue gas treatment installation.
• the said additive or mixture of additives containing at least one metallic ion M and at least one counter ion X can be added during injection in an injection zone of the flue gas treatment installation, separately from the calcium hydroxide or calcium magnesium hydroxide and upstream the electrostatic precipitator.
• the said step of slaking quicklime is performed in the conditions such as to obtain hydrated lime with a BET specific surface area from nitrogen adsorption of at least 20m 2 /g and a BJH pore volume obtained from nitrogen desorption of at least 0.1 cm 3 /g-
• a BET specific surface area from nitrogen adsorption of at least 20m 2 /g
• a BJH pore volume obtained from nitrogen desorption of at least 0.1 cm 3 /g-
• particles of quicklime are advantageously used having a particle size distribution of less than 5 mm, in particular quicklime particles of particle size distribution 0-2 mm.
• the said additive or mixture of additives containing at least one metallic ion M and at least one counter ion X can be added before the said step of slaking, during the step of slaking or after the step of slaking without substantially changing the BET specific surface area nor the BJH pore volume for pores having a diameter lower than or equal to 1000 A of the sorbent composition.
• the BET specific surface area and the BJH pore volume of the sorbent composition according to the present invention is substantially the same as for calcium hydroxide sorbent prepared by the known methods such as the one described in US patents 6,322,769 and 7,744,678 incorporated by reference.
• a hydrated lime composition is prepared according to the method described in US patent 7,744,678, such method comprises a step of adding a quantity of an alkali metal, preferably sodium in an quantity to the quicklime or to the slaking water or to the hydrated lime, sufficient to obtain in the hydrated lime an alkali metal content that is equal to or greater than 0.2 % and equal or less than 3.5 % by weight based on the total weight of the dry sorbent composition.
• the said additives or mixture of additives containing at least one metallic ion M and at least one counter ion X is further added to the quicklime or to the slaking water or to the hydrated lime with an amount such as to obtain a content in additive or in a mixture of additives containing at least one metallic ion M and at least one counter ion X between 0.1 % and 5%, preferably 0.3% to 3% in weight of the dry sorbent composition.
• sorbent compositions have been prepared according to the method of the present invention and measurements of the resistivity of dry powders of said sorbent compositions have been carried out in following the procedure outlined by IEEE (Esctcourt, 1984). Basically, a resistivity cell of a determined volume is filled by a dry powder of sorbent composition and the powder is then compacted with a weight such as to obtain a flat surface. An electrode with a guard is placed over the surface of the powder and the resistivity of the powder is measured in an oven under a stream of air comprising 10% of humidity at various temperatures comprised between 150°C (302°F) and 300°C (372°F). The resistivity of comparatives examples have been measured in the same conditions. For each measurement, a maximum resistivity Rmax and a resistivity at 300°C (372°F) has been determined. The resistivity measurements are presented herein after:
• Example 1 is a comparative sample of calcium hydroxide sorbent designed for the removal of acid gas pollutants manufactured according to US 6,322,769 Bl. No sodium nor additive of general formula MX have been added.
• Example 2 is a comparative sample of a calcium hydroxide sorbent designed for the removal of acid gas pollutants manufactured according to US 7,744,678 B2. This sample comprises 1 wt.% of sodium as Na 2 C0 3 . No further sodium or additive of general formula MX has been added.
• Example 3 is a calcium hydroxide sorbent manufactured according to the present invention using iron nitrate as dopant.
• Table 1 shows the measured resistivity parameters R max and
• Table 1 Resistivity parameters of calcium hydroxide sorbents doped with sodium and iron salts.
• Example Composition Na 2 C0 3 Fe(N0 3 ) 3 Cu(N0 3 ) 2 m a x ( ⁇ cm) R 300 ( ⁇ cm) (wt.%) (wt.%) (wt.%) (wt.%)
• Addition of 1 wt.% of sodium in Example 2 reduces the R max and R300 values by more than one order of magnitude. Surprisingly the addition of a small amount of iron nitrate at 0.5 wt% reduces the R max value by nearly one order of magnitude and by nearly two orders of magnitude for R 300 . Surprisingly the addition of iron nitrate is more effective than the addition of sodium.
• a set of sorbents was prepared by taking the sorbents manufactured according to US 7,744,678 B2 and adding iron and copper salts according to the method of present invention to said sorbents.
• Example 4 is a sample of a calcium hydroxide sorbent designed for the removal of acid gas pollutants manufactured according to US 7,744,678 B2 wherein an amount of iron nitrate has been added. According to the manufacturing method presented in US 7,744,678 an amount of sodium has been added.
• Example 5 is a sample of a calcium hydroxide sorbent designed for the removal of acid gas pollutants manufactured according to US 7,744,678 B2 wherein an amount of copper nitrate has been added. According to the manufacturing method presented in US 7,744,678 an amount of sodium has been added.
• Table 2 shows that for these sorbents, the addition of an iron nitrate result in resistivity value R max nearly two orders of magnitude lower than that of the comparative Example 1.
• the addition of copper nitrate results in nearly three orders of magnitude lower resistivity for R max and more than three orders of magnitude resistivity drop of R 300 .
• Example 4 is a sample of a calcium hydroxide sorbent designed for the removal of acid gas pollutants manufactured according to US 7,744,678 B2 wherein an amount of iron nitrate has been added. According to the manufacturing method presented in US 7,744,678 an amount of sodium has been added.
• Example 6 is a comparative sample of a calcium hydroxide sorbent designed for the removal of acid gas pollutants manufactured according to US 7,744,678 B2 wherein an amount of iron sulfate has been added. According to the manufacturing method presented in US 7,744,678 an amount of sodium has been added.
• Example 7 is a comparative sample of a calcium hydroxide sorbent designed for the removal of acid gas pollutants manufactured according to US 7,744,678 B2 wherein an amount of iron acetate has been added. According to the manufacturing method presented in US 7,744,678 an amount of sodium has been added.
• Table 3 shows that the use of iron nitrate results in a resistivity value R max four times lower than that of comparative Example 2 and one order of magnitude lower for R 30 o- Surprisingly the use of iron salts of different composition such as sulfate and acetate result in an increase of the resistivity, both for R max and for R 30 o compared to the comparative Example 2. Note that the use of iron sulfate results in a resistivity that does not show lower values for R 3 oo compared to R max .
• a set of sorbent was prepared by taking the sorbents according to US 7,744,678 and various copper salts have been added to measure the influence of the counter ion on the resistivity of the sorbent.
• sorbent compositions presented herein above are not limitative for the present invention, and other additives in the amounts comprised between 0.1 and 5 % in weight of the dry sorbent composition can be used to decrease the resistivity of sorbent compositions destined to be used in flue gas treatment processes using an electrostatic precipitator. It is to be mentioned that improvements of particulate matter collection on collecting electrodes of an electrostatic precipitators can be observed with the use of the sorbent according to the present invention.
• the present invention is related to a flue gas treatment installation.
• Figure 1 shows a schematic embodiment of a flue gas treatment installation 100 comprising an electrostatic precipitator 101 arranged downstream a first duct portion 102 arranged downstream an air preheater 103, characterized in that an injection zone 104 is arranged upstream said air preheater 103 and comprises a sorbent inlet 105.
• the said flue gas treatment installation 100 further comprises a reservoir 106 comprising said sorbent composition S to provide said sorbent composition to the said injection zone through the said sorbent inlet.
• the hot flue gas FG produced by a boiler 10 is flown through the injection zone wherein the sorbent S according to the invention is injected to react with S0 2 and other acidic gases from the flue gas, then the hot flue gas crosses the air preheater through which cold air CA is flown to absorb the heat of the hot flue gas and to be injected as hot air HA in the boiler. Then the flue gas flows through the electrostatic precipitator 101 wherein charged collecting electrodes collects the particulate matter including the sorbent composition according to the invention that has reacted with undesired acidic gases.
• the flue gas treatment installation described herein is relatively simple and is well adapted for the use of the sorbent composition according to the present invention.
• the said flue gas treatment installation is used for treating flue gas of a power plant using coal or fuel containing sulfur species or other acid gas precursors.
• the installation for flue gas treatment was described with an electrostatic precipitator downstream of an air preheater, said air preheater being connected to said electrostatic precipitator by a duct with an injection zone for injecting a sorbent composition according to the present invention arranged upstream of said air preheater.
• An alternative within the scope of the present may comprises a particulate collection device upstream of said preheater.
• flue gas treatment device comprises in sequence an electrostatic precipitator, a preheater followed by optionally a particulate collection device, before reaching the chimney.
• the particulate collection device can be another electrostatic precipitator or any king of filter, such as a bag house filter.
• the sorbent composition according to the present invention is injected in an injection zone located upstream of said electrostatic precipitator, before or after the preheater, depending on the on-site configuration.

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