CN112399884A - Adsorbent composition for electrostatic precipitator - Google Patents

Adsorbent composition for electrostatic precipitator Download PDF

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CN112399884A
CN112399884A CN201980044391.8A CN201980044391A CN112399884A CN 112399884 A CN112399884 A CN 112399884A CN 201980044391 A CN201980044391 A CN 201980044391A CN 112399884 A CN112399884 A CN 112399884A
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calcium
magnesium compound
sorbent composition
flue gas
weight
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罗德尼·傅
大卫·里昂斯
伊恩·萨拉托夫斯基
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Lhoist Recherche et Developpement SA
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    • 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
    • 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
    • B01D53/02—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
    • B01D53/06—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 with moving adsorbents, e.g. rotating beds
    • 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
    • B01D53/06—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 with moving adsorbents, e.g. rotating beds
    • B01D53/10—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 with moving adsorbents, e.g. rotating beds with dispersed adsorbents
    • 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
    • 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
    • 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
    • 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
    • B01D2253/1124—Metal oxides
    • 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

Abstract

A powdered calcium magnesium compound which is useful as an adsorbent composition in flue gas treatment, compatible with electrostatic precipitators. The calcium magnesium compound is doped with calcium nitrate or nitric acid to reduce the resistivity of the particles, thereby improving the collection efficiency of the particles.

Description

Adsorbent composition for electrostatic precipitator
Technical Field
The present invention relates to a calcium magnesium compound and to a sorbent composition for use in a flue gas stream equipped with an electrostatic precipitator, a method for obtaining such a sorbent composition and a process for flue gas treatment using an electrostatic precipitator, comprising the step of injecting such a sorbent composition. In another aspect, the invention relates to a flue gas treatment plant using the sorbent composition according to the invention.
Background
Combustion of fuel in industrial processes or energy production produces particulate matter (e.g., fly ash) and acid gases, the release of which in the atmosphere must be minimized. Fly ash removal from flue gas streams by electrostatic precipitators (ESP) can be performed. Some examples of electrostatic precipitators are described in US4502872, US8328902 or US 6797035. An electrostatic precipitator typically comprises a housing having a flue gas inlet and a flue gas outlet, the housing enclosing a plurality of collecting electrodes, spaced apart discharge electrodes and a plurality of hoppers below the collecting plates. A voltage is applied between the discharge electrode and the collecting electrode such that an electrostatic field is generated that charges the particulate material in the flue gas to obtain charged particulate material. The charged particulate material is collected by a collecting electrode. The electrostatic precipitator further comprises a rapper which provides mechanical shock or vibration to the collecting electrode to remove the collected particles from the collecting electrode. The collected particles fall into a hopper arranged at the bottom of the housing and are emptied periodically or continuously. The collecting electrodes may be planar or in the form of a tubular or honeycomb structure, and the discharge electrodes are typically in the form of wires or rods.
Typically, flue gas treatment devices comprising electrostatic precipitators are provided with an air preheater which may be included in the boiler and/or otherwise provided as an additional element of the flue gas device. The air preheater includes a heat exchanger that transfers heat of a flue gas stream generated by the boiler to heat combustion air to the boiler to increase thermal efficiency of the boiler. In some embodiments, the flue gas treatment comprises a plurality of electrostatic precipitators. The cold-side electrostatic precipitator is located downstream of the air preheater and thus operates at a lower temperature, typically below 200 c (392F). The hot side electrostatic precipitator is located upstream of the air preheater and operates at a relatively high temperature, typically above 250 ℃ (482 ° F).
Sometimes with existing plants, electrostatic precipitator units have been operated within the design capabilities of the electrostatic precipitator due to the introduction of stricter particulate matter emission limits and/or changes in plant operating conditions (e.g., fuel transfers) over the years.
The equation of doi-Anderson (Deutsch-Anderson) approximately describes the collection efficiency of an electrostatic precipitator:
Figure BDA0002873761240000021
where eta is fractional collection efficiency, AcIs the area of the collecting electrode, VpmIs the particle migration velocity and Q is the volumetric flow rate of the gas. The properties of the particles that affect the collection efficiency are mainly the particle size distribution and the resistivity of the particles. The resistivity of the particles affects the particle migration velocity, as previously described in the doherty-anderson equation.
Various attempts have been made to reduce the resistivity of particles. For example, it is known from US4439351 that for an electrostatic precipitator to work effectively, the resistivity of fly ash must be at 1E7(1 × 10)7) To 2E10 (2X 10)10) Within ohms cm. Another document, the impact of injected slaked lime on electrostatic precipitator performance as published by massopietro, r.a. at the American Society for Testing Materials (ASTM) lime utilization seminar, 2012, indicates on pages 2-10 that the resistivity of fly ash should be within the limits of the resistivity of fly ash1E8(1×108) To 1E11 (1X 10)11) Within ohms cm. However, fly ash resistivity is generally high and chemical additives (e.g., SO) are used3、HCl、NH3、Na2CO3、Na2SO4And NH (CH)2CH2OH)) to reduce the resistivity of the fly ash. However, these additives are prone to release undesirable compounds. The same document discloses the use of polymers for reducing the resistivity of fly ash. However, polymer additives typically degrade at high temperatures and must be injected into the flue gas stream at low temperatures.
Document US6126910 discloses the removal of acid gases from flue gases with an electrostatic precipitator by spraying a solution of sodium bisulfite, calcium bisulfite, magnesium bisulfite, potassium bisulfite or ammonium bisulfite or a combination thereof into the gas stream upstream of the electrostatic precipitator unit. The bisulfite selectively removes acid gases, e.g., HCl, HF, and SO3But does not remove sulfur dioxide. Reagents (e.g., slaked lime) must then be used to remove sulfur dioxide from the flue gas. Document US6803025 discloses a similar process using a reaction compound selected from the group consisting of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonium hydroxide, potassium carbonate and potassium bicarbonate to remove acid gases such as HCl, HF, SO in flue gas3And part of SO2. However, it is still necessary to remove the residual SO by using another reagent (e.g. slaked lime)2. For treating flue gases released from power plants, chlorides (as opposed to SO) released by burning fuel or coal2) The amount of (a) is usually very low and therefore the use of only slaked lime as sorbent can simplify the flue gas treatment process.
The document W02015/119880 relates to the disadvantage of trona or slaked lime as an adsorbent for flue gas treatment processes in electrostatic precipitator units. Sodium-based sorbents are known to reduce the resistivity of particulate matter; however, the main disadvantage of using sodium sorbent is the enhanced leaching of heavy metals from the fly ash, resulting in potential environmental pollution. Calcium hydroxide-based adsorbentThere is a problem of leaching of heavy metals from fly ash, but it is known that the calcium hydroxide-based sorbent increases the resistivity of the particulate matter (fly ash) generated in the flue gas stream, so that the efficiency of the electrostatic precipitator unit may be reduced when the calcium-based sorbent is used. The same document discloses a composition for reducing the resistivity of particles in flue gases and capturing acid gases, wherein the composition comprises alkali/alkaline earth particles having the formula (Li)1-α-βNaαKβ)w(Mg1-δCaδ)x(OH)y(CO3)2·nH2O, more specifically of the formula NawCax(OH)y(CO3)z·nH2O, wherein the ratio of w to x is from about 1/3 to about 3/1. Thus, the composition still presents a large amount of sodium, which not only may leach out of the sodium itself, but it is also known that sodium increases leaching of the heavy metals contained in the fly ash.
US6797035 discloses a method of reducing the resistivity of fly ash by injecting an aqueous solution of potassium nitrate or potassium nitrite onto the flue gas stream or by injecting a powder of potassium nitrate or potassium nitrite into a duct through which the flue gas stream passes. A disadvantage of using these nitrate or nitrite powders is that the nitrate or nitrite reacts with other substances than fly ash and causes less reactive chemicals to reach the collection plates of the electrostatic precipitator. It is therefore suggested to inject these nitrates as fine powders to reduce the exposed reaction surface area and to inhibit reactions with nitrogen oxides and sulfur oxides.
US7744678B2 discloses a process wherein the addition of an alkali metal species (including between 0.2% and 3.5% by weight sodium) to a calcium hydroxide sorbent provides for the sequestration of SO2Increased reactivity of capture. The addition of the alkali metal substance is carried out in such a manner that the BET Specific Surface Area (SSA) by nitrogen adsorption is kept as high as 30 < SSA < 40 (m)2/g)。
Combinations of sodium salts and hydrated lime in concentrations beyond that described in US7744678B2 are undesirable because of two adverse effects: (1) an increase in sodium content will lead to an increased leaching of heavy metals from the fly ash residue, (2) the addition of sodium in the form of water to the slaked lime will reduce the BET specific surface area of the slaked lime and thus the reactivity towards acid gases.
In article 49, published at the workshop on pollution control and carbon management "MEGA" at 2016, 16.8.19.M., Baltimore, Md, Foo et al, Maryland, described the use of enhanced calcined lime sorbents for SO removal in cold-side electrostatic precipitators2Successful industrial application of the method. With CaSO4Laboratory resistivity measurements were made of fly ash with hydrated lime and enhanced hydrated lime mixtures with CaSO added4To simulate typical fly ash residues. The enhanced slaked lime of this paper has a surface area of more than 40m2Per g, pore volume greater than 0.2cm3Per g and median particle size d50Including between 6 microns and 12 microns, and has been found to exhibit an acceptable maximum resistivity, 1E11(1 x 10)11)Ohms·cm。
However, there is still a need to provide calcium magnesium compounds which can be advantageously used in flue gas treatment devices which are highly compatible with electrostatic precipitators.
It is an object of the present invention to provide calcium magnesium compounds and sorbent compositions comprising said calcium magnesium compounds which eliminate the disadvantages inherent in the use of these sorbents in electrostatic precipitator units.
Disclosure of Invention
According to a first aspect, the invention relates to a calcium-magnesium compound in powder form, comprising at least calcium-magnesium hydroxide in a content greater than or equal to 80% by weight relative to the total weight of the calcium-magnesium compound in powder form, the calcium-magnesium compound in powder form further exhibiting a resistivity lower than 1E11 (1X 10F) at 300 ℃ (372 DEG F)11) Ohms cm and higher than 1E7 (1X 10)7) Ohms cm, advantageously less than 1E10 (1X 10)10) Ohms cm and higher than 5E7 (5X 10)7) Ohms · cm, preferably lower than 5E9 (5X 10)9) Ohms cm, more preferably less than 1E9 (1X 10)9) Ohms cm, even more preferably below 5E8 (5X 10)8) Ohms cm and the calcium-magnesium compound is doped with calcium nitrate in an amount greater than or equal to 0.05% and less than or equal to 5% by weight relative to the total weight of the powdered calcium-magnesium compound.
It was surprisingly observed that the resistivity at 300 ℃ (372 ° F) was still lower than 1E11(1 × 10)11) Ohms · cm, preferably lower than 1E10 (1X 10)10) Ohms cm, the powdered calcium magnesium compound can be successfully used in flue gas treatment using an electrostatic precipitator, which means that the powdered calcium magnesium compound is robust and does not decompose at relatively high temperatures. Therefore, the powdery calcium magnesium compound can positively change the resistivity of the air pollution control residue without adversely affecting the operation of the electrostatic precipitator.
If the powdered calcium-magnesium compound is a calcium-magnesium compound comprising at least calcium-magnesium hydroxide in a content of greater than or equal to 80%, preferably greater than or equal to 82%, more preferably greater than or equal to 85%, advantageously greater than or equal to 88% by weight relative to the total weight of the powdered calcium-magnesium compound, the calcium-magnesium compound is preferably injected at a point in the vicinity upstream of the preheater, for example at a point inside the flue gas stream, which temperature is favorable for capturing compounds of pollutants in the flue gas due to the high hydroxide content. In this case, since the product does not decompose at typical temperatures upstream or near upstream of the air preheater, after exposure to such typical temperatures (e.g., 370 ℃ (700 ° F)), the resistivity of the calcium magnesium compounds is still low enough at typical temperatures of the cold side or hot side ESP devices to change the resistivity of the mixture of fly ash and injected calcium magnesium compounds present in the flue gas.
By the term calcium-magnesium compound, it has a content of calcium-magnesium hydroxide of greater than or equal to 80%, preferably greater than or equal to 82%, more preferably greater than or equal to 85%, advantageously greater than or equal to 88% by weight relative to the total weight of the powdered calcium-magnesium compound, and this therefore means in the sense of the present invention that at least one calcium-magnesium compound according to the invention is formed at least from (calcium) slaked lime, dolomitic lime (or dolomitic lime) and magnesium slaked lime.
The molar ratio of calcium to magnesium in dolomitic lime (also known as dolomite) can vary between 0.8 and 1.2. In the calcium-magnesium compound, the ratio of calcium to magnesium may also be higher or lower, from 0.01 to 10 or even 100. In practice, the natural limestone is calcined to form quick lime, which is further slaked to provide slaked lime comprising magnesium carbonate, the content of magnesium carbonate being variable from 1% to 10% in weight with respect to the total weight of the powdery calcium-magnesium compound. If the compound in question is magnesium carbonate, which is calcined to form magnesium oxide, which is then further slaked to provide magnesium hydroxide, the content of which in calcium carbonate also varies from 1 to 10% by weight. It should be noted that a portion of the magnesium oxide may remain uncured.
The calcium magnesium compound may also contain impurities. The impurities include in particular all the impurities encountered in natural limestone and dolomite, for example clays of the aluminosilicate type, silicas, impurities based on common transition metals (for example iron or manganese). CaCO in calcium-magnesium compounds3、MgCO3、Ca(OH)2And Mg (OH)2The content of (b) can be easily determined by a conventional method. For example, the content can be determined by X-ray fluorescence analysis, which is described in EN15309 and according to EN459-2:2010E for the ignition loss and CO2The volume is measured.
Preferably, the maximum resistivity R of the calcium-magnesium compound according to the inventionmaxLess than 5E11 (5X 10)11) Ohms · cm, preferably lower than 1E11 (1X 10)11) Ohms cm and more preferably lower than 5E10 (5X 10)10)Ohms·cm。
In a preferred embodiment of the calcium-magnesium compound according to the invention, the percentage by weight of the total weight of the calcium nitrate with respect to the total weight of the powdered calcium-magnesium compound is greater than or equal to 0.1% and less than or equal to 5%, preferably between 0.3% and 3%.
In a further preferred embodiment, the calcium-magnesium compound of the invention further comprises a sodium-based compound in an amount of up to 3.5% by weight, expressed as sodium equivalents, relative to the total weight of the powdered calcium-magnesium compound. Preferably, the minimum amount of sodium is 0.2% by weight relative to the total weight of the powdered calcium-magnesium compound, expressed as sodium equivalents.
Sodium in the form of such an amount of sodium-based additive is known to have a slight effect on reducing the resistivity of the adsorbent, as described in the aforementioned Foo et al (2016) reference. Applicants have found that the sodium-based additive in such amounts, in combination with calcium nitrate as described below, further provides the additional effect of reducing the resistivity of the sorbent composition. The use of a sodium additive in combination with calcium nitrate present as described below reduces the electrical resistivity of the sorbent composition compared to the use of calcium nitrate present as described below alone in the calcium magnesium compound, and compared to the use of a sodium additive alone in the calcium magnesium compound.
In a preferred embodiment, the powdered calcium magnesium comprises particles having d50Between 5 μm and 25 μm, preferably between 5 μm and 20 μm, more preferably between 5 μm and 16 μm.
Symbol dxRepresents the diameter, expressed in μm, measured by a laser particle size analyzer in methanol, optionally after sonication, the percentage by mass of the particles measured relative to this diameter being smaller or equal.
Preferably, the BET specific surface area of the calcium-magnesium compound according to the invention is at least 20m, in particular if the powdery calcium-magnesium compound is a calcium-magnesium compound comprising at least calcium-magnesium hydroxide in a content of greater than or equal to 80% by weight2A/g, preferably of at least 25m2A/g, preferably at least 30m2G, more preferably at least 35m2(ii) in terms of/g. BET surface area was determined by pressure measurement of nitrogen adsorption after degassing in a vacuum of 190 ℃ (374 ° F) for at least 2 hours and calculated according to the multipoint BET method described in ISO9277/2010E standard.
Preferably, in particular if the powdered calcium-magnesium compound is a calcium-magnesium compound comprising at least calcium-magnesium hydroxide in a content greater than or equal to 80% by weight, the BJH pore volume of the sorbent composition according to the invention is at least 0.1cm3In g, preferably at least 0.15cm3In g, preferably at least 0.17cm3G, more preferably at least 0.2cm3(ii) in terms of/g. BJH pore volume was determined by manometry of nitrogen desorption after degassing in vacuo at 190 ℃ (374 ° F) for at least 2 hours and calculated according to BJH method described in ISO9277/2010E standard.
Further embodiments of the calcium-magnesium compound according to the invention are mentioned in the appended claims.
According to a second aspect, the invention also relates to a sorbent composition for a flue gas treatment device comprising an electrostatic precipitator comprising a calcium-magnesium compound according to the invention.
Preferably, the sorbent composition according to the invention further comprises activated carbon, lignite coke, halloysite, sepiolite, clay (e.g. bentonite, kaolin, vermiculite) or any other sorbent (e.g. fire clay), aerated cement dust, perlite, expanded clay, lime sandstone dust, pozzolan dust, halite dust, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulphide, organic sulphides, calcium sulphate, hearth coke, lignite dust, fly ash or water glass.
In a preferred embodiment, the sorbent composition according to the invention comprises a sodium-based additive in an amount of up to 3.5% by weight, expressed as sodium equivalents, relative to the total weight of the powdered calcium-magnesium compound. In particular, the amount of sodium in the composition is higher than 0.2% by weight relative to the total weight of the powdered sorbent composition.
In a preferred embodiment, the sorbent composition according to the invention comprises said calcium nitrate in an amount greater than or equal to 0.05% and less than or equal to 5% by weight relative to the total weight of the powdered calcium-magnesium compound, and wherein preferably the total weight of said calcium nitrate is greater than or equal to 0.1% and less than or equal to 5% by weight relative to the total weight of the dry sorbent composition, preferably between 0.3% and 3%.
In a preferred embodiment of the sorbent composition according to the invention, the calcium magnesium compound is slaked lime.
Further embodiments of the sorbent composition according to the invention are mentioned in the appended claims.
According to a third aspect, the present invention relates to a method for manufacturing a sorbent composition for a flue gas treatment device comprising an electrostatic precipitator, the method comprising the steps of:
a) providing a calcium magnesium compound to a reactor;
b) calcium nitrate or nitric acid or a combination thereof is added in a calculated amount to obtain calcium nitrate, which is between 0.1% and 5%, preferably between 0.3% and 3.5% by weight of the dry sorbent composition.
In a preferred embodiment, the sorbent composition comprises particles having d50Between 5 μm and 25 μm, preferably between 5 μm and 20 μm, more preferably between 5 μm and 16 μm.
In another preferred embodiment of the process according to the invention, the calcium-magnesium compound comprises calcium-magnesium hydroxide in a content greater than or equal to 80% by weight relative to the total weight of the dry calcium-magnesium compound.
Preferably, the method of making the sorbent composition comprises the steps of: sodium-based additives are added in calculated amounts expressed as sodium equivalents to obtain sodium equivalents up to 3.5% by weight of the dry sorbent composition.
In one embodiment of the production method according to the present invention, the step of supplying a calcium-magnesium compound into the reactor comprises the steps of: providing quicklime into the reactor, slaking the quicklime with a predetermined amount of water to obtain the calcium-magnesium compound, the calcium-magnesium compound comprising at least calcium-magnesium hydroxide, the content of calcium-magnesium hydroxide being greater than or equal to 80% by weight relative to the total weight of the dry calcium-magnesium compound with a predetermined amount of moisture.
More advantageously, said slaking step is carried out under the following conditions to obtain slaked lime: having a BET specific surface area of at least 20m by nitrogen adsorption2A/g, preferably of at least 25m2A/g, preferably at least 30m2G, more preferably at least 35m2/g。
In a further preferred embodiment, said slaking step is carried out under the following conditions to obtain slaked lime: has a diameter less than or equal to by nitrogen desorption
Figure BDA0002873761240000091
The BJH pore volume of the pores is at least 0.1cm3In g, preferably at least 0.15cm3In g, preferably at least 0.17cm3G, more preferably at least 0.2cm3/g。
Preferably, said maturing step is carried out under the same conditions as those described in the applicant's US patent US6322769, which is incorporated by reference.
In an alternative embodiment of the manufacturing process according to the invention, said curing step is carried out under the same conditions as described in the applicant's US patent US7744678, which is incorporated by reference.
In one embodiment of the method for manufacturing the sorbent according to the invention, the step of adding an additive or a mixture of additives comprising at least calcium nitrate or nitric acid or a combination thereof is performed before the step of slaking quicklime.
In another embodiment of the method of manufacturing the sorbent composition, the step of adding an additive or a mixture of additives comprising at least calcium nitrate or nitric acid or a combination thereof is performed during the step of slaking quicklime.
Alternatively, in the method of manufacturing the sorbent composition, after the slaking quicklime step, the step of adding an additive or a mixture of additives comprising at least calcium nitrate or nitric acid or a combination thereof is performed.
The applicant has found that the step of adding an additive or a mixture of additives comprising at least calcium nitrate or nitric acid or a combination thereof in the above-mentioned amounts does not substantially alter the pore volume of the calcium-magnesium compound before, during or after said maturing step. In addition, the specific surface area is in any case kept at more than 20m2(ii) in terms of/g. In particular, the specific surface area of the sorbent composition according to the invention is substantially the same as the specific surface area of calcium hydroxide sorbents prepared by known methods, such as the methods described in US6322769 and US7744678, incorporated by reference, provided that the addition of calcium nitrate or nitric acid or a combination thereof is performed after the slaking step and preferably before the drying step. Thus, ensuring SO is preserved2The nature of the adsorbent to remove efficiency.
Preferably, the manufacturing method is characterized in that the method further comprises the steps of: activated carbon, lignite coke, halloysite, sepiolite, clay, bentonite, kaolin, vermiculite, fireclay, aerated cement dust, perlite, expanded clay, lime sandstone dust, pozzolan dust, halite dust, pozzolan lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulphide, organic sulphides, calcium sulphate, hearth coke, lignite dust, fly ash or water glass is added, this step preferably being performed after the slaking step.
Further embodiments of the method for manufacturing a sorbent composition according to the invention are mentioned in the appended claims.
In a fourth aspect, the present invention relates to a flue gas treatment process using a device comprising an injection zone arranged upstream of an electrostatic precipitator, characterized in that it comprises the step of injecting in said injection zone a sorbent composition as disclosed herein according to the present invention.
More particularly, the flue gas treatment process uses a plant comprising an electrostatic precipitator and an injection zone arranged upstream of said electrostatic precipitator and through which the flue gas flows towards said electrostatic precipitator, characterized in that it comprises a step of injecting in said injection zone a sorbent composition comprising a calcium-magnesium sorbent, calcium nitrate, the total amount of said calcium nitrate being comprised between 0.1% and 5% by weight, preferably between 0.3% and 3.5% by weight of the dry composition.
According to the present invention, the sorbent composition has a lower electrical resistivity than prior art calcium magnesium sorbents, for example, after exposure to a temperature of 300 ℃ (572 ° F), at a temperature of 200 ℃ or less. Injection of sorbent compositions according to the invention in an injection zone for mixing with flue gas for SO removal2And other acid gases, and the lower resistivity of such sorbent compositions improves the collection of particulate matter on the collecting electrode of an electrostatic precipitator.
In another preferred embodiment of the process according to the invention, the sorbent composition comprises calcium magnesium compounds and at least calcium magnesium hydroxide, and said sorbent composition is injected into said injection zone, wherein the temperature of said flue gas in said injection zone is greater than or equal to 180 ℃ (356 ° F), preferably greater than 200 ℃ (392 ° F), more preferably between 300 ℃ (572 ° F) and 425 ℃ (797 ° F).
The sorbent composition can be used in the flue gas treatment process according to the present invention over a wide temperature range, for example, between 100 ℃ (212 ° F) to 425 ℃ (797 ° F).
Advantageously, the additive of the sorbent composition according to the invention does not degrade at temperatures above 180 ℃ (356 ° F), so that the sorbent composition can be injected into the injection zone at a temperature greater than or equal to 180 ℃ (356 ° F), preferably greater than or equal to 300 ℃ (572 ° F). Since the injection zone is located upstream of the air preheater, the temperature range of the injection zone can be between 300 ℃ (372 ° F) to 425 ℃ (797 ° F), preferably between 350 ℃ (662 ° F) to 380 ℃ (716 ° F).
Preferably, in the flue gas treatment process according to the invention, the injection zone is located upstream of an air preheater located upstream of the electrostatic precipitator.
Preferably, in the flue gas treatment process of the present invention, the sorbent composition comprises another sodium-based additive in an amount up to 3.5% by weight of the dry composition, expressed as sodium equivalents.
Preferably, in the flue gas treatment process of the present invention, the adsorbent composition has a BET specific surface area of at least 20m2/g。
Preferably, in the flue gas treatment process of the present invention, the BJH pore volume obtained by nitrogen desorption of the sorbent composition is at least 0.1cm3/g。
Preferably, in the flue gas treatment process of the present invention, the sorbent composition has a BJH pore volume obtained by nitrogen desorption of at least 0.15cm3In g, preferably at least 0.17cm3G, more preferably at least 0.2cm3/g。
Preferably, in the flue gas treatment method of the present invention, the sorbent composition further comprises activated carbon, lignite coke, halloysite, sepiolite, clay, bentonite, kaolin, vermiculite, fireclay, aerated cement dust, perlite, expanded clay, lime sandstone dust, volcanic ash dust, halite dust, volcanic lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organosulfides, calcium sulfate, furnace coke, lignite dust, fly ash, or water glass.
In one embodiment of the flue gas treatment process of the present invention, the sorbent composition is injected into the dry injection system in the form of a dry powder or into the spray dryer absorber in the form of an atomized slurry.
Further embodiments of the flue gas treatment method according to the invention are mentioned in the appended claims.
In a fifth aspect, the present invention relates to a flue gas treatment plant comprising an electrostatic precipitator downstream of an air preheater, said air preheater being connected to said electrostatic precipitator by a duct, characterized in that the flue gas treatment plant further comprises an injection zone for injecting a sorbent composition according to the invention, arranged upstream of said air preheater.
Further embodiments of the flue gas treatment plant according to the invention are mentioned in the appended claims.
Preferably, the flue gas treatment plant or apparatus is used to treat flue gases of a plant (particularly a power plant) using a fuel or coal containing a sulphur species or other acid gas precursor.
Preferably, the flue gas treatment device further comprises a vessel comprising the sorbent composition to provide the sorbent composition to the injection zone through a sorbent inlet.
Drawings
FIG. 1 shows a schematic view of an embodiment of a flue gas treatment plant for performing a flue gas treatment process with a sorbent composition according to the invention.
Detailed Description
According to a first aspect, the present invention relates to a sorbent composition for use in a flue gas treatment plant comprising an electrostatic precipitator, said sorbent composition comprising a calcium-magnesium compound, characterized in that said sorbent composition further comprises an additive or a mixture of additives in an amount comprised between 0.1% and 5%, preferably between 0.3% and 3%, by weight of the dry composition, said additive or mixture of additives comprising at least calcium nitrate.
In a preferred embodiment, the calcium-magnesium compound is based on hydrated lime.
The calcium hydroxide adsorbent is produced by reacting (or slaking) calcium oxide, CaO, or quicklime with water in a so-called hydrator (also referred to as a slaking unit). Alternatively, the calcium magnesium hydroxide sorbent is made by reacting dolomitic lime (also known as dolomitic lime) or magnesium lime with water in a hydrator. Alternatively, quicklime and dolomitic lime may be mixed together and slaked with water in a hydrator to provide a mixture of calcium hydroxide and calcium magnesium hydroxide. Hereinafter, the manufacturing process of the sorbent composition will refer to quicklime as a raw material, but the manufacturing process is not limited to quicklime as a raw material, and dolomitic lime or a combination of dolomitic lime and/or magnesiu lime and quicklime may also be used as a raw material.
The manufacturing process of the adsorbent composition according to the present invention comprises the steps of: slaking quick lime with a predetermined amount of water to obtain slaked lime having a predetermined amount of moisture, and is characterized in that the manufacturing process comprises the steps of: adding an additive or a mixture of additives to dope the sorbent composition, the amount of the additive or mixture of additives being calculated to obtain between 0.1% and 5%, preferably between 0.3% and 3.5% by weight of the dry sorbent composition of said additive or mixture of additives, said additive or mixture of additives comprising at least calcium nitrate or nitric acid or a combination thereof.
In one embodiment of the process for making the sorbent composition, in the slaking step, the predetermined amount of water is a weight ratio of water to lime of 2: 1 or higher.
In one embodiment of the process for manufacturing the sorbent composition, in the slaking step, the amount of water may be adapted to obtain a slaked lime having a moisture content of less than or equal to 10%, preferably less than or equal to 5%, preferably less than or equal to 2%, more preferably less than or equal to 1% by weight relative to the total weight of the sorbent composition in the powdered state.
In another embodiment, the amount of water may be adapted to obtain slaked lime having a moisture content of between 5% and 20% by weight in the slaking step. The amount of water can also be higher in the slaking step to obtain a slaked lime having a moisture content higher than 20% by weight, all% being expressed relative to the total weight of the sorbent composition in the powder state.
In one embodiment, in a further step, the slaked lime obtained after the slaking step is dried.
In one embodiment of the process for manufacturing a sorbent composition according to the invention, said additive comprising calcium nitrate is used for doping the sorbent composition by adding the additive comprising calcium nitrate in the form of an aqueous solution or suspension or powder before or during said slaking step of calcium oxide or calcium magnesium oxide or a combination thereof.
In another embodiment of the process for manufacturing the sorbent composition according to the invention, the calcium nitrate is added after the slaking step in the form of an aqueous solution or suspension or powder. Preferably, the drying step is performed after the aging step and after the calcium nitrate adding step. Preferably, the calcium nitrate is added to the calcium hydroxide or calcium magnesium hydroxide prior to injection into the injection zone of the flue gas treatment device.
In a preferred embodiment of the process for manufacturing the sorbent composition, the step of slaking quicklime is performed under the following conditions to obtain slaked lime: BET specific surface area of at least 20m obtained by nitrogen adsorption2Per g and a BJH pore volume obtained by nitrogen desorption of at least 0.1cm3(ii) in terms of/g. Various processes can be used by the person skilled in the art to obtain slaked lime having this property and are disclosed, for example, in the applicant's documents US6322769 and US7744678, which are incorporated by reference.
In the manufacture of the sorbent composition according to the invention, it is advantageous to use quicklime particles having a particle size distribution of less than 5mm, in particular quicklime particles having a particle size distribution of 0 to 2 mm.
For example, in US patent 549685, other processes for obtaining slaked lime having a high specific surface area and/or a high pore volume can be found, in which, during and/or before the step of slaking quicklime, a certain amount of alcohol (for example methanol or ethanol) is added and removed after drying; in patent DE3620024, wherein in the maturing step, sugars are added for increasing the specific surface area, and wherein glycols or amines are added to increase the fluidity; in US patent US5277837 and US patent US5705141, wherein in the slaking step, additives such as ethylene glycol, diethylene glycol, triethylene glycol, monoethanolamine, diethanolamine, triethanolamine or combinations thereof are added for increasing the surface area of the slaked lime.
In the manufacture of sorbent compositions, in accordance with the invention disclosed herein, an amount of calcium nitrate can be added before, during, or after the slaking step, while being less than or equal to the sorbent composition diameter
Figure BDA0002873761240000141
Does not substantially change the BJH pore volume. Furthermore, the BJH pore volume of the sorbent compositions according to the invention is substantially the same as that of calcium hydroxide sorbents prepared by known methods, for example as described in US patents US6322769 and US7744678, incorporated by reference. In addition, the BET specific surface area of the adsorbent composition is more than 20m2(ii) in terms of/g. Thus, ensuring SO is preserved2The nature of the adsorbent to remove efficiency. Alternatively, nitric acid or calcium nitrate and nitric acid may be added before, during or after the slaking step. Preferably, a higher BET specific surface area is obtained when calcium nitrate or nitric acid or a combination thereof is added after the slaking step and preferably before the drying step.
In said process for manufacturing the sorbent composition according to the invention, if a slaked lime composition is prepared according to the method described in US patent US7744678, this method comprises the following steps: to the quicklime or slaked water or slaked lime is added an amount of alkali metal, preferably sodium, sufficient to obtain an alkali metal in the slaked lime in an amount equal to or greater than 0.2% and equal to or less than 3.5% by weight based on the total weight of the dry sorbent composition. The sodium may be, for example, Na2CO3Is added in the form of (1). According to this embodiment, after the slaking step, and preferably before the drying step, a further amount of calcium nitrate or nitric acid or a combination thereof is added, the amount added being such that a content of calcium nitrate is obtained which is present in a percentage by weight of the dry sorbent compositionThe ratio is between 0.1% and 5%, preferably between 0.3% and 3%.
Various sorbent compositions have been prepared according to the method of the present invention and the measurement of dry powder resistivity of the sorbent compositions is carried out according to the following procedure outlined by IEEE (Estcourt, 1984). Basically, a defined volume of the resistivity cell is filled with a dry powder of the adsorbent composition, and then the powder is compacted with a weight to obtain a flat surface. An electrode with a protective layer was placed on the surface of the powder and the resistivity of the powder was measured in an oven with an air flow at a humidity of 10% at various temperatures between 150 ℃ (302 ° F) to 300 ℃ (372 ° F). The resistivity of the comparative example was measured under the same conditions. For each measurement, the maximum resistivity RmaxAnd 300 deg.C (572 deg.F) were determined. The resistivity measurements are described below:
example group A
Example 1 is a comparative sample of a calcium hydroxide sorbent designed to remove acid gas contaminants manufactured according to US6322769B 1. The sample was obtained from an industrial setting. No sodium, calcium nitrate or nitric acid was added.
Example 2 is a comparative sample of a calcium hydroxide sorbent designed to remove acid gas contaminants manufactured according to US7744678B 2. Ca (OH) of this sample2The content of (B) is more than 90 percent, CaCO3The content of (B) is less than 8% by weight, Na2CO3Is about 0.8% by weight, the balance being impurities. No sodium nitrate or calcium nitrate or nitric acid was added. The sample was obtained from an industrial setting.
Example 3 is another sample of a calcium hydroxide sorbent designed to remove acid gas contaminants manufactured according to US7744678B2, and wherein the lime is from another source. Ca (OH) of this sample2In percentage by weight of>90％、CaCO3In percentage by weight of<7％，Na2CO3The content of (A) is 2.1% by weight, and the balance is impurities. No sodium nitrate or calcium nitrate or nitric acid was added. The sample was obtained from an industrial setting.
Example 4 is a calcium hydroxide sorbent according to the invention, manufactured using the same lime source as example 3 and using 1% calcium nitrate as doping agent with respect to the amount of dry product. The sample was obtained from an industrial setting.
Example 5 is a calcium hydroxide sorbent according to the invention, manufactured using the same lime source as example 3 and using 2% calcium nitrate as doping agent with respect to the amount of dry product. The sample was obtained from an industrial setting.
Example 6 is a calcium hydroxide sorbent according to the invention made by: quicklime is mixed with stoichiometric amounts of water and certain amounts of NaCO in a mixer with paddles on a laboratory scale3Mixing (slaking) was carried out in order to obtain sodium in a content of 2% by weight, based on the total weight of the dry powder composition obtained. Quicklime was obtained by calcining lime from the same lime source as in example 3. After reaction in the mixer, the slaked lime (calcium hydroxide) was discharged, dried and treated with 1% by weight of HNO based on the weight of the dry product3And performing post-processing.
Table 1 shows the resistivity parameter R measured for these examplesmaxAnd R300. All resistivity parameter measurements were made by measuring the resistivity of the sample at elevated temperatures.
Table 1: resistivity parameters of the calcium hydroxide adsorbents of examples 1 to 6.
Examples of the invention Rmax(Ω·cm) R300(Ω·cm)
Example 1 8E12 3E12
Example 2 4E11 1E11
Example 3 9E10 4E09
Example 4 9E09 1E08
Example 5 6E09 4E07
Example 6 4E10 1E08
As is clear from Table 1, R of example 1maxValue and R300The values are all high at and above a preferred range of resistivity values between 10e7ohms.cm and 2e10 ohms.cm.
R relative to the composition of example 1maxAnd R300Value, 0.8% by weight of Na present in the sorbent composition of example 22CO3R is to bemaxAnd R300The value is reduced by more than one order of magnitude. R relative to the composition of example 1maxAnd R300Value, 2.1% by weight of Na present in the sorbent composition of example 32CO3R is to bemaxAnd R300The value is reduced by more than two orders of magnitude. Surprisingly, it is possible to obtainWith respect to R of the composition of example 1maxAnd R300The composition of example 4, in which a small amount of 1% by weight calcium nitrate was present, was treated withmaxThe value is reduced by nearly three orders of magnitude, and R is reduced300The value is reduced by nearly four orders of magnitude. Calcium nitrate was present in the composition of example 5 at 2% by weight relative to the composition of example 1, even R was addedmaxAnd R300The value of (c) is further decreased. Thus, surprisingly, the addition of calcium nitrate or nitric acid is more effective in reducing resistivity than the addition of sodium. Although there were some differences due to the different production process conditions (industrial scale and laboratory scale), in the composition of example 6 by the addition of HNO3Rather than adding calcium nitrate, the presence of calcium nitrate has the same effect as adding Ca (NO)3)2The same tendency to lower the resistivity of the adsorbent.
Example group B
Example 7 is a fly ash sample obtained from a coal fired power plant.
Example 8 is a mixture of 80 weight percent of the fly ash of example 7 and 20 weight percent of the sorbent according to example 3.
Example 9 is a mixture of 80 weight percent of the fly ash of example 7 with 20 weight percent of the sorbent according to example 4.
Example 10 is a mixture of 80 weight percent fly ash of example 7 and 20 weight percent sorbent according to example 5.
Table 2 shows R for these examples 7 to 10maxAnd R300Of the resistivity parameter of (a). One set of R is performed by measuring the resistivity of the sample at elevated temperaturesmaxAnd R300And a set of R is performed by measuring the resistivity of the sample at a reduced temperaturemaxThe measurement of (2).
TABLE 2
Figure BDA0002873761240000181
Knots shown in Table 2The results show that for the same ratio of fly ash and calcium-based sorbent, the mixture of fly ash and calcium-based sorbent without calcium nitrate additive has a higher resistivity parameter R than fly ash without calcium-based sorbentmaxAnd R300However, only 1 weight percent, preferably 2 weight percent, of CaNO is present in the calcium-based sorbent3Resistivity parameter R of additive to mixturemaxAnd R300A positive effect is produced.
It should be mentioned that the examples of sorbent compositions given above are not limiting to the invention, and that other additives in amounts between 0.1% and 5% by weight of the dry sorbent composition may be used to reduce the resistivity of the sorbent composition intended for use in flue gas treatment processes using electrostatic precipitators.
It should be mentioned that by using the adsorbent according to the invention, an improved collection of particulate matter on the collecting electrode of an electrostatic precipitator can be observed.
According to another aspect, the invention relates to a flue gas treatment device. Fig. 1 shows a schematic view of an embodiment of a flue gas treatment device 100, the flue gas treatment device 100 comprising an electrostatic precipitator 101, the electrostatic precipitator 101 being arranged downstream of a first duct section 102, the first duct section 102 being 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. The flue gas treatment plant 100 further comprises a vessel 106, which vessel 106 comprises the sorbent composition S, to provide the sorbent composition to the injection zone through the sorbent inlet. The hot flue gases FG generated by the boiler 10 flow through an injection area, into which the sorbent S according to the invention is injected, to react with the SO in the flue gases2And other acid gases, and then the hot flue gas is passed through an air preheater through which cool air CA flows to absorb the heat of the hot flue gas and is injected into the boiler as hot air HA. The flue gas then flows through an electrostatic precipitator 101, where it is chargedThe collecting electrode(s) collects particulate matter comprising the sorbent composition according to the invention that has reacted with the undesirable acid gas. The flue gas treatment apparatus described herein is relatively simple and well suited for use with the sorbent compositions according to the invention.
Preferably, the flue gas treatment device is used for treating flue gases of a power plant with a fuel or coal containing a sulphur species or other acid gas precursor.
It is to be understood that the invention is not limited to the described embodiments and that modifications may be applied without departing from the scope of the appended claims.
For example, in a preferred embodiment, a device for flue gas treatment is described, having an electrostatic precipitator downstream of an air preheater, said air preheater being connected to said electrostatic precipitator by a duct, and having an injection zone for injecting a sorbent composition according to the invention, arranged upstream of said air preheater. Alternatives within the scope of the invention may include a particulate collection device upstream of the preheater.
Another alternative of the flue gas treatment device according to the invention comprises an electrostatic precipitator, a preheater followed by an optional particle collection device in that order before reaching the stack.
The particle collection apparatus may be another electrostatic precipitator or any kind of filter, such as a bag filter.
In all of these examples, the sorbent composition according to the invention was injected into an injection zone located upstream of the electrostatic precipitator, either before or after the preheater, according to an on-site configuration.

Claims (21)

1. A powdery calcium-magnesium compound comprising at least calcium-magnesium hydroxide in a content greater than or equal to 80% by weight relative to the total weight of the powdery calcium-magnesium compound, characterized in that it exhibits a resistivity at 300 ℃ lower than 1E11 Ohms-cm and higher than 1E7 Ohms-cm and is doped with calcium nitrate 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 calcium-magnesium compound.
2. The powdered calcium magnesium compound according to claim 1, having a maximum resistivity RmaxLess than 1E11Ohms cm.
3. The powdered calcium-magnesium compound according to claim 1 or claim 2, further comprising a sodium-based additive in an amount of up to 3.5% by weight, expressed as sodium equivalents, relative to the total weight of the powdered calcium-magnesium compound.
4. The powdery calcium-magnesium compound according to any one of claims 1 to 3, which exhibits a BET specific surface area of at least 20m by nitrogen adsorption2A/g, preferably of at least 25m2A/g, preferably at least 30m2G, more preferably at least 35m2/g。
5. The powdered calcium-magnesium compound according to any one of claims 1 to 4, which has a diameter less than or equal to that exhibited by nitrogen desorption
Figure FDA0002873761230000011
The BJH pore volume of the pores is at least 0.1cm3/g。
6. A sorbent composition for a flue gas treatment device comprising an electrostatic precipitator comprising a powdered calcium magnesium compound according to any one of claims 1 to 5.
7. The sorbent composition of claim 6, further comprising an additive selected from the group consisting of activated carbon, lignite coke, halloysite, sepiolite, clay, bentonite, kaolin, vermiculite, fireclay, aerated cement dust, perlite, expanded clay, lime sandstone dust, volcanic ash dust, rillite dust, volcanic lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organosulfides, calcium sulfate, furnace coke, lignite dust, fly ash, and water glass.
8. A sorbent composition in accordance with claim 6 or claim 7, comprising a sodium-based additive in an amount up to 3.5% by weight, expressed as sodium equivalents, relative to the total weight of the powdered sorbent composition.
9. The sorbent composition of any of claims 6 to 8, wherein the calcium nitrate is in an amount greater than or equal to 0.05% and less than or equal to 5% by weight relative to the total weight of the dry sorbent composition.
10. The sorbent composition of any of claims 6-9, wherein the calcium-magnesium compound is hydrated lime.
11. A method for manufacturing a sorbent composition comprising between 0.1 and 5 weight percent calcium nitrate for use in a flue gas treatment device comprising an electrostatic precipitator, the method comprising the steps of:
a) providing a calcium magnesium compound to a reactor;
b) adding a compound selected from the group consisting of calcium nitrate and nitric acid and combinations thereof.
12. The process according to claim 11, wherein the calcium-magnesium compound comprises calcium-magnesium hydroxide in a content greater than or equal to 80% by weight relative to the total weight of the dry calcium-magnesium compound.
13. The method according to claim 11 or 12, wherein said step of providing a calcium magnesium compound into a reactor comprises the steps of: providing quicklime into the reactor, slaking the quicklime with a predetermined amount of water to obtain the calcium-magnesium compound, the calcium-magnesium compound comprising at least calcium-magnesium hydroxide, the calcium-magnesium hydroxide being present in an amount greater than or equal to 80% by weight relative to the total weight of the dry calcium-magnesium compound with a predetermined amount of moisture.
14. A method for manufacturing a sorbent composition according to any one of claims 11 to 13, characterized in that the method comprises the steps of: sodium-based additives are added in calculated amounts expressed as sodium equivalents to obtain sodium equivalents up to 3.5% by weight of the dry sorbent composition.
15. The method for manufacturing a sorbent composition according to any one of claims 11 to 14, wherein the slaking step is performed under the following conditions to obtain slaked lime: a BET specific surface area, measured by nitrogen adsorption, of at least 20m2/g。
16. The method for manufacturing a sorbent composition according to any one of claims 11 to 15, wherein the slaking step is performed under the following conditions to obtain slaked lime: has a diameter of less than or equal to as measured by nitrogen desorption
Figure FDA0002873761230000031
The BJH pore volume of the pores is at least 0.1cm3/g。
17. The method for manufacturing a sorbent composition according to any one of claims 11 to 16, further comprising the steps of: adding an additional additive selected from the group consisting of activated carbon, lignite coke, halloysite, sepiolite, clay, bentonite, kaolin, vermiculite, fireclay, aerated cement dust, perlite, expanded clay, lime sandstone dust, volcanic ash dust, rillite dust, volcanic lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organosulfides, calcium sulfate, furnace coke, lignite dust, fly ash, and water glass.
18. A flue gas treatment process using a plant comprising an injection zone arranged upstream of an electrostatic precipitator, characterized in that it comprises the step of injecting a sorbent composition according to any one of claims 6 to 10 in the injection zone.
19. The flue gas treatment process of claim 18, wherein the sorbent composition comprises a calcium magnesium compound, and wherein the sorbent composition is injected into the injection zone, wherein the temperature of the flue gas is greater than or equal to 180 ℃.
20. The flue gas treatment process according to claim 18 or 19, wherein the sorbent composition is injected into the dry sorbent injection system in the form of a dry powder or into the spray dryer absorber system in the form of an atomized slurry.
21. Flue gas treatment plant comprising an electrostatic precipitator downstream of an air preheater connected to the electrostatic precipitator by a duct, characterized in that the flue gas treatment plant further comprises an injection zone arranged upstream of the air preheater for injecting a sorbent composition according to any of claims 6 to 10.
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