CN112399884B - Sorbent compositions for electrostatic precipitators - Google Patents

Sorbent compositions for electrostatic precipitators Download PDF

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CN112399884B
CN112399884B CN201980044391.8A CN201980044391A CN112399884B CN 112399884 B CN112399884 B CN 112399884B CN 201980044391 A CN201980044391 A CN 201980044391A CN 112399884 B CN112399884 B CN 112399884B
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calcium
magnesium compound
sorbent composition
flue gas
calcium magnesium
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CN112399884A (en
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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

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Inorganic Chemistry (AREA)
  • Dispersion Chemistry (AREA)
  • Treating Waste Gases (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)

Abstract

A powdered calcium magnesium compound that is compatible with an electrostatic precipitator and that can be used as an adsorbent composition in flue gas treatment. 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

Sorbent compositions for electrostatic precipitators
Technical Field
The present invention relates to a calcium magnesium compound and to an adsorbent composition for use in a flue gas stream containing an electrostatic precipitator, a method for obtaining such an adsorbent composition and a process for flue gas treatment using an electrostatic precipitator, the process comprising the step of injecting such an adsorbent composition. In another aspect, the invention relates to a flue gas treatment device using the sorbent composition according to the invention.
Background
Combustion of fuels in industrial processes or energy production produces particulate matter (e.g., fly ash) and acid gases, which must be minimized in atmospheric emissions. Removal of fly ash from the flue gas stream by an electrostatic precipitator (electrostatic precipitator, ESP) may be performed. Some examples of electrostatic precipitators are described in U.S. patent No. 4502872, U.S. patent No. 8328902, or U.S. patent No. 6797035. An electrostatic precipitator generally includes a housing having a flue gas inlet and a flue gas outlet, which encloses a plurality of collecting electrodes, spaced apart discharge electrodes, and a plurality of hoppers located below the collecting plates. A voltage is applied between the discharge electrode and the collection electrode such that an electrostatic field is generated that charges the particulate material in the flue gas to obtain a charged particulate material. The charged particulate material is collected by a collection electrode. The electrostatic precipitator further comprises a rapper that provides mechanical impact 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 electrode may be planar or in the form of a tubular or honeycomb structure, and the discharge electrode is typically in the form of a wire or rod.
Typically, a flue gas treatment device comprising an electrostatic precipitator is 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 the combustion air to the boiler to increase the 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 ℃ (392°f). The hot side electrostatic precipitator is located upstream of the air preheater and operates at a higher temperature, typically above 250 ℃ (482°f).
Sometimes with existing plants, electrostatic precipitator units have been operated within the capacity of the electrostatic precipitator design due to the introduction of stricter particulate matter emission limits and/or changes in plant operating conditions (e.g. fuel conversion) over the years.
The equation for the multiple-Endochson (Deutsch-Anderson) approximately describes the collection efficiency of an electrostatic precipitator:
where η is the fractional collection efficiency, A c Is the area of the collecting electrode, V pm Is 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 particle size distribution and resistivity of the particles. The resistivity of the particles affects the particle migration velocity as previously described in the multi-curie-anderson equation.
Various attempts have been made to reduce the resistivity of the particles. For example, it is known from US patent 4439351 that for an electrostatic precipitator to operate effectively, the resistivity of the fly ash must be in the range of 1E7 (1 x 10 7 ) To 2E10 (2X 10) 10 ) Within ohms cm. Another document, published in 2012 at the american society of test materials (American Society for Testing Material, ASTM) lime utilization seminar, masstopietro, r.a., notes that the impact of slaked lime injection on electrostatic precipitator performance, on pages 2-10, states that the resistivity of fly ash should be 1E8 (1 x 10 8 ) To 1E11 (1X 10) 11 ) Within ohms cm. However, the resistivity of fly ash is generally high and chemical additives (e.g., SO 3 、HCl、NH 3 、Na 2 CO 3 、Na 2 SO 4 And NH (CH) 2 CH 2 OH)) to reduce the resistivity of the fly ash. However, these additives tend to release undesirable compounds. The same document discloses the use of polymers for reducing the resistivity of fly ash. However, the polymer additives typically degrade at high temperatures and must be injected into the flue gas stream at low temperatures.
U.S. patent documentS6126910 discloses the removal of acid gases from flue gas 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. Such bisulfites selectively remove acid gases, e.g. HCl, HF and SO 3 But does not remove sulfur dioxide. Reagents (e.g., slaked lime) must then be used to remove sulfur dioxide from the flue gas. U.S. patent No. 6803025 discloses a similar process for removing acid gases, such as HCl, HF, SO, from flue gas using a reactive compound selected from the group consisting of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonium hydroxide, potassium carbonate, and potassium bicarbonate 3 And part of SO 2 . However, residual SO must still be removed by using another reagent (e.g., slaked lime) 2 . For treatment of flue gases released from power plants, the released chlorides (relative to SO) are produced by burning fuel or coal 2 ) The amount of (c) is typically very low and therefore the use of slaked lime alone as a sorbent can simplify the flue gas treatment process.
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 adsorbents are known to reduce the resistivity of particulate matter; however, the main disadvantage of using sodium adsorbents is to enhance leaching of heavy metals in the fly ash, leading to potential environmental pollution. Calcium hydroxide-based sorbents do not present the problem of leaching of heavy metals in fly ash, but are known to increase the resistivity of particulate matter (fly ash) produced in flue gas streams, such that the efficiency of an electrostatic precipitator unit may be reduced when using a calcium-based sorbent. The same document discloses a composition for reducing the resistivity of particles in flue gas and capturing acid gases, wherein the composition comprises alkali/alkaline earth particles having the formula (Li 1-α-β Na α K β ) w (Mg 1-δ Ca δ ) x (OH) y (CO 3 ) 2 ·nH 2 O，More specifically of formula Na w Ca x (OH) y (CO 3 ) z ·nH 2 O, wherein the ratio of w to x is from about 1/3 to about 3/1. Thus, the composition still has a significant amount of sodium present, which not only may leach out of the sodium itself, but it is also known that sodium increases the leaching out of the heavy metals contained in the fly ash.
US6797035 discloses a method of reducing the resistivity of fly ash by spraying an aqueous solution of potassium nitrate or nitrite onto the flue gas stream or by injecting a powder of potassium nitrate or nitrite into a conduit through which the flue gas stream passes. The 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 collector plate of the electrostatic precipitator. It is therefore recommended to inject these nitrates in fine powder form to reduce the exposed reaction surface area and inhibit the reaction with nitrogen oxides and sulfur oxides.
US7744678B2 discloses a process wherein the addition of an alkali metal species (comprising between 0.2 and 3.5% by weight sodium) to a calcium hydroxide adsorbent provides for the conversion of SO 2 The increased reactivity of the capture. The addition of the alkali metal substances is carried out in such a way that the BET specific surface area (specific surface area, SSA) by nitrogen adsorption remains as high as 30 < SSA < 40 (m 2 /g)。
The combination of sodium salts and slaked lime beyond the concentrations described in US7744678B2 is undesirable because of two adverse effects: (1) An increase in sodium content will result in an increase in leaching of heavy metals in the fly ash residue, (2) adding sodium in the form of water to slaked lime will reduce the BET specific surface area of the slaked lime, thus reducing the reactivity towards acid gases.
The use of enhanced slaked lime sorbent to remove SO in cold side electrostatic precipitators is described by 8, 16 to 19 in paper 49, published by the institute of pollution control and carbon management, "MEGA", of Power plant, and by MD, foo et al 2 Is a successful industrial application. By CaSO 4 Laboratory electricity on fly ash and slaked lime and enhanced slaked lime mixturesResistivity is measured, wherein CaSO is added 4 To simulate typical fly ash residue. The surface area of the enhanced slaked lime of this paper is greater than 40m 2 /g, pore volume greater than 0.2cm 3 G and median particle size d 50 Including between 6 and 12 microns, and has been found to exhibit an acceptable maximum resistivity of 1E11 (1 x 10) 11 )Ohms·cm。
However, there remains a need to provide calcium magnesium compounds that can be advantageously used in flue gas treatment devices that 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 inherent drawbacks of the use of these sorbents in electrostatic precipitator units.
Disclosure of Invention
According to a first aspect, the present invention relates to a powdered calcium magnesium compound comprising at least calcium hydroxide magnesium in an amount of greater than or equal to 80% by weight relative to the total weight of the powdered calcium magnesium compound, the powdered calcium magnesium compound further exhibiting a resistivity at 300 ℃ (372°f) of less than 1E11 (1×10) 11 ) Ohms cm and higher than 1E7 (1X 10) 7 ) Ohms cm, advantageously below 1E10 (1X 10) 10 ) Ohms cm and above 5E7 (5X 10) 7 ) Ohms cm, preferably below 5E9 (5X 10) 9 ) Ohms cm, more preferably below 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 of 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.
Surprisingly, it was observed that the resistivity was still lower than 1E11 (1X 10) when at 300 ℃ (372 DEG F) 11 ) Ohms cm, preferably below 1E10 (1X 10) 10 ) At Ohms cm, powdered calcium magnesium compounds can be successfully used in flue gas treatment using an electrostatic precipitator, which means that the powdered calcium magnesium compounds are strong and do not decompose at relatively high temperatures. Thus, the powdered calcium magnesiumThe compounds are capable of positively altering the resistivity of the air pollution control residue without negatively affecting the operation of the electrostatic precipitator.
If the powdered calcium-magnesium compound is a calcium-magnesium compound comprising at least calcium hydroxide-magnesium in an amount of more than or equal to 80%, preferably more than or equal to 82%, more preferably more than or equal to 85%, advantageously more than or equal to 88% by weight relative to the total weight of the powdered calcium-magnesium compound, it is preferred to inject the calcium-magnesium compound into a location near the upstream of the preheater, for example into the interior of the flue gas stream, which temperature is advantageous 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, the resistivity of the calcium magnesium compound after exposure at such typical temperatures (e.g., 370 ℃ (700°f)) is still low enough at typical temperatures of either the cold side ESP device or the hot side ESP device to alter the resistivity of the mixture of fly ash and injected calcium magnesium compound present in the flue gas.
By the term calcium magnesium compound, it is meant that the calcium magnesium compound has a content of calcium hydroxide magnesium 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 therefore in the sense of the present invention it is meant that at least one calcium magnesium compound according to the invention is formed at least of (calcium) slaked lime, dolomitic lime (or calcined dolomite) 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 compounds, the ratio of calcium to magnesium may also be higher or lower, from 0.01 to 10 or even 100. In practice, natural limestone is calcined to form quicklime, which is further slaked to provide slaked lime, which includes magnesium carbonate, the content of which may vary from 1% to 10% by weight relative to the total weight of the powdered calcium magnesium compound. If the compound in question is magnesium carbonate, the magnesium carbonate is calcined to form magnesium oxide, which is then further cured to provide magnesium hydroxide, the weight percent of the magnesium hydroxide in the calcium carbonate also varies from 1% to 10%. 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, such as clays of aluminosilicate type, silica, impurities based on common transition metals (for example iron or manganese). CaCO in calcium-magnesium compound 3 、MgCO 3 、Ca(OH) 2 And Mg (OH) 2 The content of (c) can be easily determined by conventional methods. For example, the content can be determined by X-ray fluorescence analysis, a procedure described in EN15309, and ignition loss and CO according to EN459-2:2010E 2 The volume was measured.
Preferably, the maximum resistivity R of the calcium-magnesium compound according to the invention max Below 5E11 (5X 10) 11 ) Ohms cm, preferably below 1E11 (1X 10) 11 ) Ohms cm and more preferably below 5E10 (5X 10) 10 )Ohms·cm。
In a preferred embodiment of the calcium magnesium compound according to the invention, the weight percentage 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 comprised between 0.3% and 3%.
In a further preferred embodiment, the calcium magnesium compound of the present invention further comprises a sodium-based compound in an amount of up to 3.5% by weight relative to the total weight of the powdered calcium magnesium compound and expressed as sodium equivalent. Preferably, the minimum amount of sodium is 0.2% by weight relative to the total weight of the powdered calcium magnesium compound and expressed as sodium equivalent.
As described in the previously mentioned Foo et al (2016), 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. Applicants have found that this amount of sodium-based additive in combination with calcium nitrate as described below further provides the added 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 resistivity of the sorbent composition compared to the use of calcium nitrate present as described below in the calcium magnesium compound alone, and compared to the use of a sodium additive in the calcium magnesium compound alone.
In a preferred embodiment, the powdered calcium magnesium comprises particles having d 50 Between 5 μm and 25 μm, preferably between 5 μm and 20 μm, more preferably between 5 μm and 16 μm.
Symbol d x Represents the diameter, expressed in μm, which is measured by a laser particle size analyzer, optionally after sonication, in methanol, relative to which the mass percentage X% of the particles measured is smaller or equal.
Preferably, in particular, if the powdered calcium-magnesium compound is a calcium-magnesium compound comprising at least calcium hydroxide magnesium, the content of calcium hydroxide magnesium being greater than or equal to 80% by weight, the BET specific surface area of the calcium-magnesium compound according to the invention is at least 20m 2 /g, preferably at least 25m 2 /g, preferably at least 30m 2 Preferably at least 35m 2 And/g. The BET surface area is determined by pressure measurement by nitrogen adsorption after degassing in a vacuum at 190℃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 hydroxide magnesium in an amount of 80% by weight or more, the BJH pore volume of the adsorbent composition according to the invention is at least 0.1cm 3 /g, preferably at least 0.15cm 3 /g, preferably at least 0.17cm 3 Preferably at least 0.2cm 3 And/g. The BJH pore volume was determined by pressure measurement by nitrogen desorption after degassing in a vacuum at 190 ℃ (374°f) for at least 2 hours and calculated according to the BJH method described in the 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. refractory clay), aerated cement dust, perlite, expanded clay, lime sandstone dust, pozzolan dust, triester dust, pozzolan lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organosulfides, calcium sulfate, hearth coke, brown coal dust, fly ash or water glass.
In a preferred embodiment, the sorbent composition in accordance with the invention comprises a sodium-based additive in an amount up to 3.5% by weight relative to the total weight of the powdered calcium magnesium compound and expressed as sodium equivalent. In particular, the amount of sodium in the composition is higher than 0.2% by weight relative to the total weight of the powdered adsorbent composition.
In a preferred embodiment, the sorbent composition according to the invention comprises said calcium nitrate in an amount of 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 weight percentage of the total weight of the calcium nitrate relative to the total weight of the dry sorbent composition is greater than or equal to 0.1% and less than or equal to 5%, 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 an adsorbent 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) The calculated amount of calcium nitrate or nitric acid or a combination thereof is added to obtain calcium nitrate in a weight percentage of 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 d 50 Between 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 method according to the invention, the calcium magnesium compound comprises calcium hydroxide magnesium, the content of calcium hydroxide magnesium being 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: calculated amounts of sodium-based additive expressed as sodium equivalents were added to obtain sodium equivalents up to 3.5% by weight of the dry sorbent composition.
In one embodiment of the manufacturing method according to the invention, the step of providing the 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 including at least calcium hydroxide magnesium, the content of calcium hydroxide magnesium being greater than or equal to 80% by weight relative to the total weight of the dry calcium magnesium compound having a predetermined amount of moisture.
More advantageously, said slaking step is carried out under the following conditions to obtain slaked lime: has a BET specific surface area of at least 20m by nitrogen adsorption 2 /g, preferably at least 25m 2 /g, preferably at least 30m 2 Preferably at least 35m 2 /g。
In a further preferred embodiment, the slaking step is performed under the following conditions to obtain slaked lime: by passing throughNitrogen desorption has a diameter less than or equal toThe BJH pore volume of the pores of (a) is at least 0.1cm 3 /g, preferably at least 0.15cm 3 /g, preferably at least 0.17cm 3 Preferably at least 0.2cm 3 /g。
Preferably, the curing step is performed under the same conditions as described in applicant's US patent US6322769 and incorporated by reference.
In an alternative embodiment of the manufacturing method according to the invention, the curing step is performed under the same conditions as described in applicant's US patent US7744678, which is incorporated by reference.
In one embodiment of the method according to the invention for manufacturing said sorbent, the step of adding an additive or mixture of additives comprising at least calcium nitrate or nitric acid or a combination thereof is performed before said step of slaking quicklime.
In another embodiment of the method of manufacturing the sorbent composition, the step of adding an additive or mixture of additives comprising at least calcium nitrate or nitric acid or a combination thereof is performed during the slaking quicklime step.
Alternatively, in the method of manufacturing the sorbent composition, the step of adding an additive or mixture of additives comprising at least calcium nitrate or nitric acid or a combination thereof is performed after the step of slaking quicklime.
The applicant has found that the step of adding an additive or mixture of additives comprising at least calcium nitrate or nitric acid or a combination thereof in the amounts described above before, during or after said curing step does not substantially change the pore volume of the calcium magnesium compound. In addition, the specific surface area is kept at more than 20m in any case 2 And/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 a calcium hydroxide sorbent prepared by known methods, such as U.S. Pat. No. 6322, which is incorporated by reference769 and US7744678, provided that the addition of calcium nitrate or nitric acid or a combination thereof is performed after the curing step and preferably before the drying step. Thus, ensure SO 2 The 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, refractory clay, aerated cement dust, perlite, expanded clay, lime sandstone dust, pozzolan dust, asiatic dust, pozzolan lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organosulfides, calcium sulfate, hearth coke, brown coal dust, fly ash or water glass are added, which is preferably performed after the curing step.
Further embodiments of the method of 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 an apparatus comprising an injection zone arranged upstream of an electrostatic precipitator, characterized in that the flue gas treatment process comprises the step of injecting into said injection zone an adsorbent composition according to the present invention as disclosed herein.
More particularly, the flue gas treatment method uses an apparatus comprising an electrostatic precipitator and an injection zone arranged upstream of said electrostatic precipitator, and through which the flue gas flows to said electrostatic precipitator, characterized in that it comprises a step of injecting in said injection zone an adsorbent composition comprising a calcium magnesium adsorbent, calcium nitrate, the total amount of 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, at temperatures of 200 ℃ or less after exposure to temperatures of 300 ℃ (572°f). Implanting roots in implant regions Sorbent compositions according to the invention for SO removal by mixing with flue gas 2 And other acid gases, and the lower resistivity of such sorbent compositions improves collection of particulate matter on the collection electrode of an electrostatic precipitator.
In another preferred embodiment of the method according to the invention, the sorbent composition comprises a calcium magnesium compound and at least calcium hydroxide magnesium, and the sorbent composition is injected into the injection zone where the temperature of the flue gas 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) and 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 of the injection zone may range between 300 ℃ (372°f) and 425 ℃ (797°f), preferably between 350 ℃ (662°f) and 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 a further sodium-based additive in an amount up to 3.5% by weight of the dry composition expressed as sodium equivalent.
Preferably, in the flue gas treatment process of the present invention, the adsorbent composition has a BET specific surface area of at least 20m 2 /g。
Preferably, at the flue gas of the present inventionIn the method, the BJH pore volume of the adsorbent composition obtained by nitrogen desorption is at least 0.1cm 3 /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 0.15cm 3 /g, preferably at least 0.17cm 3 Preferably at least 0.2cm 3 /g。
Preferably, in the flue gas treatment process of the present invention, the sorbent composition further comprises activated carbon, lignite coke, halloysite, sepiolite, clay, bentonite, kaolin, vermiculite, refractory clay, aerated cement dust, perlite, expanded clay, lime sandstone dust, pozzolan dust, triester dust, pozzolan lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organosulfides, calcium sulfate, furnace coke, brown coal 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-dried 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 invention relates to a flue gas treatment plant comprising an electrostatic precipitator downstream of an air preheater connected to said electrostatic precipitator by a duct, characterized in that the flue gas treatment plant further comprises an injection zone for injecting the sorbent composition according to the invention arranged upstream of said air preheater.
Further embodiments of the flue gas treatment device according to the invention are mentioned in the appended claims.
Preferably, the flue gas treatment apparatus or device is for treating flue gas of a plant, in particular a power plant, using fuel or coal containing sulfur species or other acid gas precursors.
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 device for carrying out a flue gas treatment process with an adsorbent composition according to the invention.
Detailed Description
According to a first aspect, the present invention relates to a sorbent composition for a flue gas treatment device comprising an electrostatic precipitator, said sorbent composition comprising a calcium magnesium compound, characterized in that said sorbent composition further comprises an additive or 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 slaked lime.
Calcium hydroxide sorbents are manufactured by reacting (or slaking) calcium oxide, caO or quicklime with water in a so-called hydrator (also known as slaking unit). Alternatively, calcium hydroxide magnesium sorbent is produced by reacting dolomite lime (also known as calcined dolomite) 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 hydroxide magnesium. Hereinafter, the manufacturing process of the sorbent composition will be referred to as taking quicklime as a raw material, but the manufacturing process is not limited to taking quicklime as a raw material, and dolomitic lime or a combination of dolomitic lime and/or magnesium lime and quicklime may be used as a raw material.
The manufacturing process of the adsorbent composition according to the invention comprises the following steps: slaking quicklime with a predetermined amount of water to obtain slaked lime having a predetermined amount of water, and characterized in that the manufacturing process comprises the steps of: the additive or mixture of additives is added to dope the adsorbent composition, the amount of the additive or mixture of additives being calculated to obtain a weight percentage of the additive or mixture of additives comprised at least of calcium nitrate or nitric acid or a combination thereof comprised between 0.1% and 5%, preferably between 0.3% and 3.5% by weight of the dry adsorbent composition.
In one embodiment of the process of 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 of manufacturing the sorbent composition, the amount of water may be adapted to obtain, in the slaking step, slaked lime having a weight percentage of moisture with respect to the total weight of the sorbent composition in powder state 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%.
In another embodiment, the amount of water may be adapted to obtain slaked lime with a moisture content of between 5% and 20% by weight during the slaking step. The amount of water may also be higher during the slaking step, in order to obtain slaked lime with a moisture content higher than 20% by weight, all percentages being expressed with respect to the total weight of the adsorbent composition in the powdered 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 the 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 curing step of calcium oxide or calcium magnesium oxide or a combination thereof.
In another embodiment of the process of manufacturing the sorbent composition in accordance with the invention, the calcium nitrate is added after the curing step in the form of an aqueous solution or suspension or powder. Preferably, the drying step is performed after the curing step and after the calcium nitrate addition 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 by nitrogen adsorption 2 /g and obtaining BJH pore volume of at least 0.1cm by nitrogen desorption 3 And/g. Various processes can be employed by those skilled in the art to obtain slaked lime having this property and are disclosed, for example, in applicant's documents U.S. patent No. 6322769 and U.S. patent No. 7744678, which are incorporated by reference.
In the production 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, wherein during and/or before the step of slaking the quicklime, a certain amount of alcohol (e.g. methanol or ethanol) is added and removed after drying; in patent DE3620024, wherein in the ripening step sugar is added for increasing the specific surface area, and wherein glycols or amines are added to increase the flowability; in US patent 5277837 and US patent 5705141, additives such as ethylene glycol, diethylene glycol, triethylene glycol, monoethanolamine, diethanolamine, triethanolamine or combinations thereof are added during the slaking step for increasing the surface area of the slaked lime.
In the course of making the sorbent composition, in accordance with the invention disclosed herein, an amount of calcium nitrate may be added prior to, during, or after the curing step, for a diameter less than or equal to the sorbent compositionThe BJH pore volume is not substantially changed for the pores of (a). Furthermore, the adsorbent combination according to the inventionThe BJH pore volume of the material is substantially the same as that of a calcium hydroxide adsorbent prepared by known methods, such as the methods described in U.S. patent nos. 6322769 and 7744678, which are incorporated by reference. In addition, the BET specific surface area of the adsorbent composition is greater than 20m 2 And/g. Thus, ensure SO 2 The nature of the adsorbent to remove efficiency. Alternatively, nitric acid or calcium nitrate and nitric acid may be added before, during or after the curing step. Preferably, a higher BET specific surface area is obtained when calcium nitrate or nitric acid or a combination thereof is added after the maturation step and preferably before the drying step.
In the process of manufacturing the sorbent composition according to the invention, if the slaked lime composition is prepared according to the method described in U.S. patent No. 7744678, the method comprises the steps of: an amount of alkali metal, preferably sodium, is added to the quicklime or slaked water or slaked lime 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. Sodium can be, for example, as Na 2 CO 3 Is added in the form of (c). According to this embodiment, after the curing step, and preferably before the drying step, an amount of calcium nitrate or nitric acid or a combination thereof is further added, the amount being such that a content of calcium nitrate of between 0.1% and 5%, preferably between 0.3% and 3% by weight of the dry sorbent composition is obtained.
Various sorbent compositions have been prepared according to the method of the present invention and the dry powder resistivity measurements of the sorbent compositions have been performed according to the 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. The electrode with protective layer was placed on the surface of the powder and at various temperatures between 150 ℃ (302°f) and 300 ℃ (372°f) in an oven with 10% humidity air flowThe resistivity of the powder is measured. The resistivity of the comparative example was measured under the same conditions. For each measurement, the maximum resistivity R max And 300 ℃ (572°f) have been determined. Resistivity measurements are described below:
Example group A
Example 1 is a comparative sample of a calcium hydroxide adsorbent designed to remove acid gas contaminants manufactured according to US6322769B 1. The samples were obtained from industrial plants. No sodium, calcium nitrate or nitric acid was added.
Example 2 is a comparative sample of a calcium hydroxide adsorbent designed to remove acid gas contaminants manufactured according to US7744678B 2. Ca (OH) of the sample 2 More than 90 percent of CaCO by weight 3 The content of (2) is less than 8% by weight, na 2 CO 3 The content of (2) is about 0.8% by weight, the balance being impurities. Sodium nitrate or calcium nitrate or nitric acid is no longer added. The samples were obtained from industrial plants.
Example 3 is another sample of a calcium hydroxide sorbent designed for removal of acid gas contaminants manufactured according to US7744678B2, and wherein the lime is from another source. Ca (OH) of the sample 2 Is contained in the weight percentage of the content of (2)>90％、CaCO 3 Is contained in the weight percentage of the content of (2)<7％，Na 2 CO 3 The weight percentage of the content of (2.1 percent) is the rest is impurities. Sodium nitrate or calcium nitrate or nitric acid is no longer added. The samples were obtained from industrial plants.
Example 4 is a calcium hydroxide sorbent made according to the present invention using the same lime source as example 3 and using 1% calcium nitrate as a dopant relative to the amount of dry product. The samples were obtained from industrial plants.
Example 5 is a calcium hydroxide sorbent made according to the present invention using the same lime source as example 3 and using 2% calcium nitrate as a dopant relative to the amount of dry product. The samples were obtained from industrial plants.
Example 6 is a calcium hydroxide adsorbent made according to the invention byThe method comprises the following steps: quicklime is combined with stoichiometric amounts of water and a quantity of NaCO in a mixer with paddles on a laboratory scale 3 Mixing (curing) to obtain sodium in an amount of 2% by weight based on the total weight of the obtained dry powder composition. Quicklime is obtained by calcining lime from the same lime source as in example 3. After reaction in the mixer, slaked lime (calcium hydroxide) was discharged, dried and treated with 1% HNO by weight of the dried product 3 And (5) performing post-treatment.
Table 1 shows the resistivity parameter R measured for these examples max And R is 300 . All resistivity parameters were measured by measuring the resistivity of the samples at elevated temperatures.
Table 1: resistivity parameters of the calcium hydroxide sorbents of examples 1-6.
Example R max (Ω·cm) R 300 (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 1 max Value sum R 300 The values are both high at and above the preferred range of resistivity values between 10e7ohms.cm and 2e10 ohms.cm.
R relative to the composition of example 1 max And R is 300 The adsorbent composition of example 2 had 0.8 wt% Na 2 CO 3 R is taken as max And R is 300 The value is reduced by more than an order of magnitude. R relative to the composition of example 1 max And R is 300 The value, example 3, of Na present in the sorbent composition at a weight percent of 2.1% 2 CO 3 R is taken as max And R is 300 The value is reduced by more than two orders of magnitude. Surprisingly, R relative to the composition of example 1 max And R is 300 The value, R, was found to be small in the composition of example 4 with 1 weight percent calcium nitrate max The value is reduced by nearly three orders of magnitude and R is reduced 300 The value is reduced by nearly four orders of magnitude. The presence of 2% by weight of calcium nitrate in the composition of example 5 relative to the composition of example 1, even resulted in R max And R is 300 Further decreasing the value of (c). Thus, surprisingly, the addition of calcium nitrate or nitric acid is more effective in reducing resistivity than the addition of sodium. Although there are some due to the difference in the production process conditions (industrial scale and laboratory scale) The difference, however, was obtained by adding HNO to the composition of example 6 3 Instead of calcium nitrate, the presence of calcium nitrate has the same effect as the addition of Ca (NO 3 ) 2 The same trend of decreasing 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% by weight of the fly ash of example 7 with 20% by weight of the adsorbent according to example 3.
Example 9 is a mixture of 80% by weight of the fly ash of example 7 with 20% by weight of the adsorbent according to example 4.
Example 10 is a mixture of 80% by weight of the fly ash of example 7 with 20% by weight of the adsorbent according to example 5.
Table 2 shows R for these examples 7 to 10 max And R is 300 Is provided for the measurement of the resistivity parameter of (a). A set of R's is performed by measuring the resistivity of a sample at an elevated temperature max And R is 300 And performing a set of R's by measuring the resistivity of the sample at a reduced temperature max Is a measurement of (a).
TABLE 2
The results shown in Table 2 demonstrate 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 the fly ash without calcium-based sorbent max And R is 300 However, only 1% by weight, preferably 2% by weight of Cano is present in the calcium-based adsorbent 3 Resistivity parameter R of additive to mixture max And R is 300 Positive effects are 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 electrical 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 collection 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, which flue gas treatment device 100 comprises an electrostatic precipitator 101, which electrostatic precipitator 101 is arranged downstream of a first duct section 102, which first duct section 102 is arranged downstream of an air preheater 103, characterized in that an injection zone 104 is arranged upstream of said air preheater 103 and comprises an adsorbent inlet 105. The flue gas treatment device 100 further comprises a vessel 106, which vessel 106 comprises the sorbent composition S for providing the sorbent composition to the injection zone through the sorbent inlet. The hot flue gas FG produced by the boiler 10 flows through an injection zone into which the sorbent S according to the invention is injected to react with the SO in the flue gas 2 Reacts with other acid gases and then the hot flue gas passes through an air preheater through which cold 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, wherein the charged collecting electrode collects particulate matter comprising the sorbent composition according to the present invention that has reacted with undesired acid gases. The flue gas treatment device described herein is relatively simple and well suited for use with the sorbent composition according to the invention.
Preferably, the flue gas treatment device is for treating the flue gas of a power plant with fuel or coal containing sulfur species or other acid gas precursors.
It is to be understood that the invention is not limited to the described embodiments and that modifications may be applied without exceeding the scope of the appended claims.
For example, in a preferred embodiment, an apparatus for flue gas treatment is described, having an electrostatic precipitator downstream of an air preheater connected to said electrostatic precipitator by a duct, and having an injection zone for injecting the sorbent composition according to the present invention arranged upstream of said air preheater. Alternatives within the scope of the invention may include a particle collection device upstream of the preheater.
Another alternative of the flue gas treatment device according to the invention comprises the sequential inclusion of an electrostatic precipitator, a preheater and then an optional particle collection device before reaching the stack.
The particle collection device may be another electrostatic precipitator or any kind of filter, such as a bag filter.
In all of these embodiments, the sorbent composition according to the invention is injected into an injection zone upstream of the electrostatic precipitator, either before or after the preheater, depending on the in situ configuration.

Claims (24)

1. A powdered calcium magnesium compound comprising at least calcium hydroxide magnesium, the content of which is greater than or equal to 80% by weight relative to the total weight of the powdered calcium magnesium compound, characterized in that the powdered calcium magnesium compound exhibits a resistivity at 300 ℃ of less than 1E11 ohms-cm and greater than 1E7 ohms-cm, and is doped with calcium nitrate in an amount of 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.
2. The powdered calcium-magnesium compound according to claim 1, having a maximum resistivity R max Below 1E11ohms cm.
3. The powdered calcium magnesium compound according to claim 1 or claim 2, further comprising a sodium-based additive in an amount up to 3.5% by weight relative to the total weight of the powdered calcium magnesium compound, expressed as sodium equivalent.
4. The powdered calcium-magnesium compound according to claim 1 or 2, which exhibits a BET specific surface area of at least 20m by nitrogen adsorption 2 /g。
5. The powdered calcium-magnesium compound according to claim 1 or 2, which exhibits a diameter of less than or equal to that exhibited by nitrogen desorptionThe BJH pore volume of the pores of (a) is at least 0.1cm 3 /g。
6. The powdered calcium magnesium compound according to claim 4, which exhibits a BET specific surface area of at least 25m by nitrogen adsorption 2 /g。
7. The powdered calcium magnesium compound according to claim 4, which exhibits a BET specific surface area of at least 30m by nitrogen adsorption 2 /g。
8. The powdered calcium magnesium compound according to claim 4, which exhibits a BET specific surface area of at least 35m by nitrogen adsorption 2 /g。
9. A sorbent composition for a flue gas treatment device comprising an electrostatic precipitator, the sorbent composition comprising the powdered calcium magnesium compound according to any one of claims 1 to 8.
10. The sorbent composition of claim 9, further comprising an additive selected from the group consisting of activated carbon, lignite coke, halloysite, sepiolite, clay, bentonite, kaolin, vermiculite, refractory clay, aerated cement dust, perlite, expanded clay, lime sandstone dust, pozzolan dust, sentry dust, pozzolan lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organosulfides, calcium sulfate, hearth coke, brown coal dust, fly ash, or water glass.
11. The sorbent composition of claim 9 or claim 10, comprising a sodium-based additive in an amount up to 3.5% by weight relative to the total weight of the powdered sorbent composition and expressed as sodium equivalent.
12. The sorbent composition of claim 9 or 10, wherein the amount of calcium nitrate is 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.
13. The sorbent composition of claim 9 or 10, wherein the calcium magnesium compound is slaked lime.
14. A method for manufacturing a sorbent composition comprising between 0.1% and 5% by weight of calcium nitrate 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) Adding a compound selected from the group consisting of calcium nitrate or nitric acid or a combination thereof.
15. The method of claim 14, wherein the calcium magnesium compound comprises calcium hydroxide magnesium in an amount of greater than or equal to 80 weight percent relative to the total weight of dry calcium magnesium compound.
16. A method according to claim 14 or 15, wherein the step of providing 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 including at least calcium hydroxide magnesium having a content of 80% by weight or more with respect to the total weight of the dried calcium magnesium compound having a predetermined amount of moisture.
17. The method for manufacturing a sorbent composition of claim 14 or 15, comprising the steps of: calculated amounts of sodium-based additive expressed as sodium equivalents were added to obtain sodium equivalents up to 3.5% by weight of the dry sorbent composition.
18. The method for manufacturing a sorbent composition of claim 14 or 15, wherein the slaking step is performed under the following conditions to obtain slaked lime: BET specific surface area of at least 20m as measured by nitrogen adsorption 2 /g。
19. The method for manufacturing a sorbent composition of claim 14 or 15, wherein the slaking step is performed under the following conditions to obtain slaked lime: having a diameter less than or equal to that measured by nitrogen desorptionThe BJH pore volume of the pores of (a) is at least 0.1cm 3 /g。
20. The method for manufacturing a sorbent composition of claim 14 or 15, further comprising the steps of: adding a further additive selected from the group consisting of activated carbon, lignite coke, halloysite, sepiolite, clay, bentonite, kaolin, vermiculite, refractory clay, aerated cement dust, perlite, expanded clay, lime sandstone dust, pozzolan dust, sentry dust, pozzolan lime, fuller's earth, cement, calcium aluminate, sodium aluminate, calcium sulfide, organosulfides, calcium sulfate, hearth coke, brown coal dust, fly ash, or water glass.
21. A flue gas treatment process using a device comprising an injection zone arranged upstream of an electrostatic precipitator, characterized in that the flue gas treatment process comprises the step of injecting into the injection zone the sorbent composition according to any one of claims 9 to 13.
22. The flue gas treatment method of claim 21, 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 ℃.
23. A flue gas treatment process according to claim 21 or 22, wherein the sorbent composition is injected into the dry sorbent injection system in the form of a dry powder or into the spray-dried absorber system in the form of an atomized slurry.
24. A 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 for injecting the sorbent composition according to any of claims 9-13 arranged upstream of the air preheater.
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