KR20210031934A - Adsorbent composition for electrostatic dust collector - Google Patents

Abstract

Powdered calcium-magnesium compounds used as adsorbent compositions in flue gas treatment compatible with electrostatic precipitators. This calcium magnesium compound is doped with calcium nitrate or nitric acid to reduce the electrical resistivity of the particles and increase their collection efficiency.

Description

Adsorbent composition for electrostatic dust collector

The present invention relates to a flue gas treatment process using an electrostatic precipitator comprising a calcium-magnesium compound, an adsorbent composition for use in a flue gas stream equipped with an electrostatic precipitator, a method of obtaining such an adsorbent composition, and injecting such an adsorbent composition. It is about. In another aspect, the invention relates to a flue gas treatment plant using the adsorbent composition according to the invention.

Fuel combustion in industrial processes or energy production produces particulate matter (eg fly ashes) and acidic gases, whose emissions to the atmosphere have to be minimized. The removal of fly ash from the flue gas stream can be carried out by means of an electrostatic precipitator (ESP). Some examples of electrostatic precipitators are described in U.S. Patent 4,502,872, U.S. Patent 8,328,902 or U.S. Patent 6,797,035. The electrostatic precipitator generally includes a shell having a flue gas inlet and a flue gas outlet, which shell surrounds a plurality of collecting electrodes and a plurality of hoppers located below the discharge electrodes and collecting plates spaced apart from each other. A voltage is applied between the discharge electrode and the collection electrode to create an electrostatic field that charges the particulate matter in the flue gas to obtain the charged particulate matter. The charged particulate matter is collected by the collection electrode. This electrostatic precipitator further includes a wrapper that provides mechanical shock or vibration to the collection electrode to remove the collected particles from the collection electrode. The collected particles fall into a hopper placed at the bottom of the shell, and the hopper is emptied periodically or continuously. The collecting electrode may be in the form of a flat or tubular or honeycomb structure, and the discharge electrode is generally in the form of a wire or rod.

In general, flue gas treatment plants comprising electrostatic precipitators are provided with an air preheater, which may be included in the boiler and/or provided as an additional element of the flue gas installation. The air preheater includes a heat exchanger that transfers heat from the combustion gas stream generated by the boiler to heat the combustion air to the boiler, thereby increasing the thermal efficiency of the boiler. In some embodiments, the flue gas treatment includes multiple electrostatic precipitators. The cold-side electrostatic precipitator is placed downstream of the air preheater, through which it operates at a lower temperature, typically less than 200°C (392°F). The hot side electrostatic precipitator is placed upstream of the air preheater, through which it operates at higher temperatures, typically in excess of 250°C (482°F).

Sometimes in the case of existing plants, electrostatic precipitator units are already operating at the boundaries of their design capabilities due to changes in plant operating conditions such as fuel conversion and/or stricter particulate matter emission limits introduced over the years.

The Deutsch-Anderson equation approximates the collection efficiency of an electrostatic precipitator as follows:

Where η is the fractional collection efficiency, A _c is the area of the collection electrode, V _pm is the particle movement speed, and Q is the volume flow rate of the gas. The properties of particles that affect collection efficiency are mainly particle size distribution and resistivity. The resistivity of the particles affects the particle movement speed as described in the Deutsche-Andersson equation.

Various attempts have been made to reduce the resistivity of particles. For example, it is known from U.S. Patent 4,439,351 that the electrical resistivity of the fly ash must be in the range of ^{1E7 (1x10 7} ) to 2E10 (2x10 ^{10) Ohm·cm in order for the electrostatic precipitator to operate efficiently.} In another document (Mastropietro, RA Impact of Hydrated Lime Injection on Electrostatic Percipitator Performance in ASTM Symposium on Lime Utilization; 2012; pp 2-10), the resistivity of fly ash is 1E8 (1x10 ⁸ ) to 1E11 (1x10 ¹¹ ) ohm cm It is stated to be within range. However, the electrical resistivity of fly ash is generally high, and to lower the electrical resistivity of this fly ash, chemicals such as _{SO 3} , HCl, NH ₃ , Na ₂ CO ₃ , Na ₂ SO ₄ and NH(CH ₂ CH _{2 OH)} Additives were used. However, these additives are prone to release undesirable compounds. The same document discloses the use of polymers to lower the resistivity of fly ash. However, polymer additives generally degrade at high temperatures and must be injected into the flue gas stream at low temperatures.

Document U.S. Patent 6,126,910 discloses an electrostatic precipitator by spraying a solution of sodium bisulfite, calcium bisulfite, magnesium bisulfite, potassium bisulfite or ammonium bisulfite or a combination thereof into a gas stream upstream of the electrostatic precipitator unit. Discloses the removal of acidic gases from flue gases. These bisulfite salts selectively remove acidic gases such as HCl, HF and SO _{3 but not sulfur dioxide.} Sulfur dioxide in the flue gas has to be removed later with a reagent such as hydrated lime. Document U.S. Patent 6,803,025 discloses sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonium hydroxide, potassium hydroxide, potassium hydroxide, potassium carbonate and potassium bicarbonate to remove acidic gases such as _{HCl, HF, SO 3} and partly SO _{2 from the flue gas.} Similar processes using reactive compounds selected from the group consisting of are disclosed. However, residual SO ₂ still has to be removed using a separate reagent such as hydrated lime. In the case of the treatment of flue gas discharged from power plants, the amount of chloride released by burning fuel or coal is _{generally very low with respect to SO 2} , so the flue gas treatment process can be simplified by using only hydrated lime as adsorbent. .

Document WO2015/119880 relates to a drawback of trona or hydrated lime as an adsorbent for a flue gas treatment process using an electrostatic precipitator unit. Sodium-based adsorbents are known to reduce the resistivity of particulate matter, but the main drawback of the use of sodium adsorbents is that the leaching of heavy metals from fly ash is enhanced, leading to potential environmental pollution. Calcium hydroxide-based adsorbent does not cause the problem of heavy metal leaching from fly ash, but this is known to increase the resistivity of particulate matter (fly ash) entrained in the combustion gas stream, so the efficiency of the electrostatic precipitator unit when calcium-based adsorbent is used. This can be degraded. The same document discloses a composition for reducing particulate resistivity in flue gas and for trapping acidic gas, which composition has the formula (Li _1-α-β Na _α K _β ) _w (Mg _1-δ Ca _δ ) _x ( OH) _y (CO ₃ ) _z ·nH ₂ O, more specifically the formula Na _w Ca _x (OH) _y (CO ₃ ) _z ·nH ₂ O (here, the ratio of W to x is about 1/3 to about 3/1) and alkali metal/alkali earth fine particles. Thus, not only does this composition still provide a large amount of sodium, which itself is likely to leach, but sodium is also known to increase the leaching of heavy metals contained in fly ash.

US 6,797,035 discloses a process for reducing the resistivity of fly ash by spraying an aqueous solution of potassium nitrate or potassium nitrite into the flue gas stream or by injecting a powder of potassium nitrate or potassium nitrite into the duct through which the flue gas passes. The drawback of using a powder of nitrate or nitrite is that it reacts with species other than fly ash, resulting in fewer reactive chemicals reaching the collecting plate of the electrostatic precipitator. Therefore, it is proposed to inject nitrate as finely divided powder to reduce the exposed reactive surface area and to suppress the reaction with nitrous oxide and sulfur oxide.

US 7,744,678 B2 discloses a method for improving the reactivity to _{SO 2} entrapment by adding an alkali metal species comprising 0.2 to 3.5% by weight of sodium to a calcium hydroxide adsorbent. The addition of the alkali metal species is carried out so that the BET specific surface area (SSA) by nitrogen adsorption is maintained as high as ^{30 <SSA <40 (m 2 /g).}

Combinations of sodium salt and hydrated lime in excess of the concentrations mentioned in US 7,744,678 B2 are undesirable due to two side effects: (1) increasing sodium content leads to increased leaching of heavy metals from fly ash residues, and (2) ) Addition of aqueous form of sodium to hydrated lime reduces the BET specific surface area of hydrated lime, reducing its reactivity to acid gases.

In paper #49 presented at the "MEGA" Symposium on Pollutant Control and Carbon Management at Power Plants in Baltimo, Maryland from August 16-19, 2016, Foo et al. introduced reinforced hydrated lime adsorbents used in cold-side electrostatic precipitators. The successful industrial application of SO _{2 removal using has been presented.} Hydrated lime and a higher hydrated lime and laboratory measurements of resistivity fly ash mixture has been carried out using the CaSO _4, CaSO _4, where was added to simulate typical fly ash residue. The reinforced hydrated lime in this paper has a surface area exceeding 40 m²/g, a pore volume exceeding 0.2 cm³/g, and a median particle size (d ₅₀ ) of 6 to 12 micrometers, 1E11 (1x10 ¹¹ ) ohm.cm It was found to show the maximum allowable resistivity of.

However, there is still a need to provide a calcium-magnesium compound that can be advantageously used in flue gas treatment plants that are very suitable for electrostatic precipitators.

It is an object of the present invention to provide a calcium-magnesium compound and an adsorbent composition comprising the calcium-magnesium compound, wherein the adsorbent composition eliminates the inherent drawbacks of the adsorbent when applied to an electrostatic precipitator unit.

According to a first aspect, the present invention comprises at least a calcium hydroxide-magnesium content of 80% by weight or more with respect to the total weight of the powdered calcium-magnesium compound, and also 1E7 (1x10 ⁷ ) Ohm _{at 300°C (372°F) R 300} From more than cm to less than 1E11 (1x10 ¹¹ ) ohms cm, advantageously from more than 5E7 (5x10 ⁷ ) ohms cm to ^{less than 1E10 (1x10 10} ) ohms cm, preferably 5E9 (5x10 ⁹ ) It relates to a powdered calcium-magnesium compound exhibiting a resistivity of less than ohm·cm, more preferably less than 1E9 (1x10 ⁹ ) ohm·cm, more preferably less than 5E8 (5x10 ^{8) ohm·cm, and the calcium-magnesium} The compound is doped with calcium nitrate in an amount of 0.05% by weight or more and 5% by weight or less based on the total weight of the powdered calcium-magnesium compound.

Surprisingly, when the resistivity at 300°C (372°F) is much lower than ^{1E11 (1x10 11 ) ohm.cm, preferably less than 1E10 (1x10 10} ) cm, the powdered calcium-magnesium compound is a flue gas using an electrostatic precipitator. It has been observed that it can be used successfully in the treatment, which means that the powdered calcium-magnesium compound is strong and does not decompose at relatively high temperatures. Thus, this powdered calcium-magnesium compound can positively change the resistivity of the air pollution control residue without negatively affecting the operation of the electrostatic precipitator.

The powdered calcium-magnesium compound is at least 80% by weight, preferably at least 82% by weight, more preferably at least 85% by weight, advantageously at least 88% by weight of calcium hydroxide based on the total weight of the powdered calcium-magnesium compound. -In the case of a calcium-magnesium compound containing a magnesium content, this is preferably injected at a position close to the upstream of the preheater, which is the corresponding position of the flue gas stream to be injected, and the temperature is increased due to the high hydroxide content. It is advantageous for the capture of contaminating compounds of the. In this case, the product does not decompose at typical temperatures upstream or upstream of the air preheater, so the resistivity of the calcium-magnesium compound after exposure to this typical temperature, e. At the typical temperature of the side ESP plant, it is low enough to change the resistivity of the mixture of injected calcium-magnesium compounds with fly ash present in the flue gas.

Calcium-containing calcium hydroxide-magnesium content of at least 80% by weight, preferably at least 82% by weight, more preferably at least 85% by weight, advantageously at least 88% by weight, based on the total weight of the powdered calcium-magnesium compound. The term magnesium compound is, within the scope of the meaning of the present invention, wherein at least one calcium-magnesium compound according to the present invention is formed as slaked lime (containing calcined stone), slaked dolomite (or dolime), or slaked magnesium. Means.

The molar ratio of calcium to magnesium in dolomite lime (also called dolime) can vary from 0.8 to 1.2. The ratio of calcium to magnesium in the calcium-magnesium compound may be higher or lower, from 0.01 to 10 or even 100. In fact, natural limestone is calcined to form quicklime, which is further slaked to provide hydrated lime, a concentration that can vary from 1 to 10% by weight relative to the total weight of the powdered calcium-magnesium compound. Contains magnesium carbonate. If the compound in question is magnesium carbonate (this magnesium carbonate forms magnesium oxide by calcination, and this magnesium oxide is further slaked to provide magnesium hydroxide), its content in calcium carbonate will also vary from 1 to 10% by weight. I can. It should be noted that some of the magnesium oxide may remain unslaved.

Calcium-magnesium compounds may also contain impurities. These impurities include, in particular, all impurities encountered in natural limestone and dolomite, such as silica-aluminate type clay, impurities based on common transition metals such as silica, iron or manganese. _{The content of CaCO 3} , MgCO ₃ , Ca(OH) ₂ and Mg(OH) ₂ in the calcium-magnesium compound can be easily determined by a conventional method. For example, this can be determined by X-ray fluorescence analysis in combination with measurement of _{loss on ignition and measurement of CO 2} volume according to EN 459-2:2010 E standard, the procedure of which is according to EN 15309 standard. It is described.

Preferably, the calcium-magnesium compound according to the present invention is ^{less than 5E11 (5x10 11} ) ohm·cm, preferably less than 1E11 (1x10 ¹¹ ) ohm·cm, more preferably 5E10 (5x10 ¹⁰ ) It represents the maximum resistivity (R _max ) of less than ohm·cm.

In a preferred embodiment of the calcium-magnesium compound according to the present invention, the total weight of the calcium nitrate is 0.1% by weight or more to 5% by weight or less, preferably 0.3 to 3% by weight based on the total weight of the powdered calcium-magnesium compound. to be.

In another 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 based on the total weight of the powdered calcium-magnesium compound expressed as sodium equivalent. Preferably, sodium is a minimum amount of 0.2% by weight based on the total weight of the powdered calcium-magnesium compound, and is expressed in sodium equivalents.

This amount of sodium in the form of a sodium-based additive is known to have a slight effect on reducing the resistivity of the adsorbent, as suggested by the aforementioned Foo et al. (2016). The Applicant has found that such an amount of sodium-based additive has an additional effect on the reduction of the resistivity of the adsorbent composition in combination with the presence of calcium nitrate, as described below. As described below, when the sodium additive is used in combination with the presence of calcium nitrate, as described below, the presence of calcium nitrate is more than when used alone in the calcium-magnesium compound, and the sodium additive is calcium- Among the magnesium compounds, the resistivity of the adsorbent composition is further reduced than when used alone.

In a preferred embodiment, the powdered calcium-magnesium comprises particles with an _{ad 50} of 5 to 25 μm, preferably 5 to 20 μm, more preferably 5 to 16 μm.

The mark d _X indicates the diameter measured by laser particle size measurement in methanol optionally after sonication in μm, and the X mass% of the measured particles is less than or equal to that.

Preferably, particularly when the powdered calcium-magnesium compound is a calcium-magnesium compound comprising a calcium hydroxide-magnesium content of at least 80% by weight or more, the calcium-magnesium compound according to the invention is 20 m ² /g or more, preferably Has a BET specific surface area of 25 m 2 /g or more, preferably 30 m 2 /g or more, more preferably 35 m 2 /g or more. The BET surface area is determined by a pressure method by nitrogen adsorption after degassing in vacuum at 190° C. (374° F.) for at least 2 hours and calculated according to the multipoint BET method as described in the ISO 9277/2010E standard.

Preferably, particularly when the powdered calcium-magnesium compound is a calcium-magnesium compound comprising a calcium hydroxide-magnesium content of at least 80% by weight or more, the adsorbent composition according to the invention is 0.1 cm ³ /g or more, preferably 0.15 It has a BJH pore volume of not less than cm 3 /g, preferably not less than 0.17 cm 3 /g, more preferably not less than 0.2 cm 3 /g. The BJH pore volume is determined by a pressure method with nitrogen desorption after degassing in vacuum at 190° C. (374° F.) for at least 2 hours and calculated according to the BJH method as described in the ISO 9277/2010E standard.

Other embodiments of the calcium-magnesium compound according to the invention are mentioned in the appended claims.

According to a second aspect, the present invention also relates to an adsorbent composition for a flue gas treatment facility comprising an electrostatic precipitator containing the calcium-magnesium compound according to the present invention.

Preferably, the adsorbent composition according to the invention is activated carbon, lignite coke, haloysite, sepiolite, clay (e.g., bentonite), kaolin, vermiculite or any other adsorbent, e.g. refractory clay, aerated cement. Dust, Perlite, Expanded Clay, Lime Sandstone Dust, Tras Dust, Yaly Rock Dust, Tras Lime, Fuller Soil, Cement, Calcium Aluminate, Sodium Aluminate, Calcium Sulfide, Organic Sulfide, Calcium Sulfate, Open-hearth ) Coke, lignite dust, fly ash, or water glass.

In a preferred embodiment, the adsorbent composition according to the present invention comprises a sodium-based additive in an amount of at most 3.5% by weight based on the total weight of the powdered calcium-magnesium compound expressed in sodium equivalents. In particular, the amount of sodium in this composition exceeds 0.2% by weight based on the total weight of the powdered adsorbent composition.

In a preferred embodiment, the adsorbent composition according to the present invention comprises the calcium nitrate in an amount of 0.05% by weight or more and 5% by weight or less based on the total weight of the powdered calcium-magnesium compound, and preferably the calcium nitrate The total weight is 0.1% by weight or more and 5% by weight or less, preferably 0.3 to 3% by weight, based on the total weight of the dry adsorbent composition.

In a preferred embodiment of the adsorbent composition according to the invention, the calcium-magnesium compound is hydrated lime.

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

According to a third aspect, the present invention relates to a process for producing an adsorbent composition for a flue gas treatment facility comprising an electrostatic precipitator, the process comprising the following steps:

Providing a calcium-magnesium compound to the reactor,

Adding calcium nitrate or nitric acid or a combination thereof in an amount calculated to obtain 0.1% to 5% by weight, preferably 0.3% to 3% by weight of calcium nitrate by weight of the dry adsorbent composition.

In a preferred embodiment, the adsorbent composition comprises particles having _{an ad 50} of 5 to 25 μm, preferably 5 to 20 μm, more preferably 5 to 16 μm.

In another preferred embodiment of the process according to the invention, the calcium-magnesium compound contains a calcium-magnesium hydroxide content of 80% by weight relative to the total weight of the dry calcium-magnesium compound.

Preferably the process of preparing the adsorbent composition comprises adding a sodium-based additive expressed in sodium equivalents in an amount calculated to obtain a sodium equivalent weight of at most 3.5% by weight of the dry adsorbent composition.

In an embodiment of the manufacturing process according to the invention, the step of providing the calcium-magnesium compound to the reactor comprises providing quicklime to the reactor, and based on the total weight of the dry calcium-magnesium compound containing a predetermined amount of moisture. Slaking the quicklime with a predetermined amount of water to obtain the calcium-magnesium compound containing a calcium hydroxide content of at least 80% by weight or more.

More advantageously, the slaking step is a ^{BET specific surface area by nitrogen adsorption of 20 m 2} /g or more, preferably 25 m²/g or more, preferably 30 m²/g or more, more preferably 35 m²/g or more. It is carried out under the same conditions as obtaining hydrated lime having

In a more preferred embodiment, the slaking step is 0.1 cm ³ /g or more, 0.15 cm 3 /g or more, preferably 0.17 cm 3 /g or more, more preferably 0.2 cm 3 /g or more by nitrogen desorption of 1000 Å or less. It is carried out under the same conditions as obtaining hydrated lime with BJH pore volume for pores with diameter.

Preferably, the slaking step is performed under the same conditions as described in Applicant's US Pat. No. 6,322,769, which is incorporated by Won Yong.

In an alternative embodiment of the manufacturing process according to the present invention, the slaking step is performed under the same conditions as described in Applicant's US Pat. No. 7,744,678, which is incorporated by reference.

In one embodiment of the process for producing the adsorbent according to the present invention, the step of adding an additive or mixture of additives comprising at least calcium nitrate or nitric acid or a combination thereof is carried out prior to the step of slaking the quicklime.

In another embodiment of the process for preparing the adsorbent 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 step of slaking the quicklime.

Alternatively, in the process for preparing the adsorbent composition, the step of adding the additive or mixture of additives comprising at least calcium nitrate or nitric acid or a combination thereof is performed after the step of slaking the quicklime.

Applicants, in the amount described above, adding an additive or mixture of additives comprising at least calcium nitrate or nitric acid or a combination thereof carried out before the slaking step, during the slaking step, or after the slaking step. It has been found that the step does not substantially change the pore volume of the calcium-magnesium compound. In addition, in any case, the specific surface area is maintained in excess of 20 m²/g. In particular, the specific surface area of the adsorbent composition according to the present invention is, if the addition of calcium nitrate or nitric acid or a combination thereof is carried out after the slaking step, preferably before the drying step, U.S. Patents 6,322,769 and 7,744,678, which are incorporated by reference. It is substantially the same as in the case of a calcium hydroxide adsorbent prepared by a known method as described in. Thus, the properties of the adsorbent ensuring the _{SO 2 removal efficiency are preserved.}

Preferably, the manufacturing process is activated carbon, lignite coke, haloysite, sepiolite, clay, bentonite, kaolin, vermiculite, refractory clay, aerated cement dust, pearlite, expanded clay, preferably performed after the slaking step. , Lime Sandstone Dust, Tras Dust, Yaly Rock Dust, Tras Lime, Fuller Earth, Cement, Calcium Aluminate, Sodium Aluminate, Calcium Sulfide, Organic Sulfide, Calcium Sulfate, Pyeongro Coke, Lignite Dust, Fly Ash, or Water It characterized in that it further comprises the step of adding glass.

Other embodiments of the process for preparing the adsorbent composition according to the invention are mentioned in the appended claims.

In a fifth aspect, the present invention relates to a flue gas treatment process using an installation comprising an injection zone disposed upstream of an electrostatic precipitator, wherein an adsorbent composition as disclosed herein according to the invention is prepared in the injection zone. It characterized in that it comprises the step of injecting.

More specifically, a flue gas treatment process using an electrostatic precipitator, and an injection zone disposed upstream of the electrostatic precipitator, through which the flue gas flows toward the electrostatic precipitator, is used to inject the adsorbent composition in the injection zone. It characterized in that it comprises a step, wherein the adsorbent composition comprises a calcium-magnesium adsorbent and calcium nitrate, and the total amount of calcium nitrate is 0.1% to 5% by weight, preferably 0.3% by weight, based on the weight of the dry composition. It consists of 3.5% by weight.

According to the present invention, the adsorbent composition exhibits a lower resistivity, for example, at 200° C. or lower, after exposure to a temperature of, for example, 300° C. (572° F.), compared to a calcium-magnesium adsorbent of the prior art. Have. The injection of the adsorbent composition according to the invention in the injection zone for mixing with the flue gas _{is effective in the removal of SO 2} and other gaseous acids, and the low resistivity of this adsorbent composition prevents the collection of particulate matter on the collecting electrode of the electrostatic precipitator. Improve.

In another preferred embodiment of the process according to the invention, the adsorbent composition comprises at least calcium hydroxide-magnesium hydroxide as a calcium-magnesium compound, wherein the adsorbent composition has the flue gas at least 180°C (356°F), preferably 200°C. (392° F.) or higher, more preferably 300° C. (572° F.) to 425° C. (797° F.).

The adsorbent composition may be used in the flue gas treatment process according to the present invention under a wide temperature range, for example, from 100° C. (212° F.) to 425° C. (797° F.).

Advantageously, since the additive of the adsorbent composition according to the present invention does not deteriorate at a temperature exceeding 180°C (356°F), the adsorbent composition has a temperature of at least 180°C (356°F), preferably 300°C (572°F). ) Can be injected in the injection zone. Since the spraying zone is located upstream of the air preheater, the temperature of the spraying zone can range from 300°C (372°F) to 425°C (797°F), preferably 350°C (662°F) to 380°C (716°F). have.

Preferably, in the flue gas treatment process according to the present 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 adsorbent composition comprises other sodium-based additives in an amount of up to 3.5% by weight expressed as sodium equivalents and by weight of the dry composition.

Preferably, in the flue gas treatment process of the present invention, the adsorbent composition has a ^{BET specific surface area of 20 m 2} /g or more.

Preferably, in the flue gas treatment process of the present invention, the adsorbent composition has a BJH pore volume obtained from nitrogen desorption ^{of 0.1 cm 3 /g or more.}

Preferably, in the flue gas treatment process of the present invention, the adsorbent composition has a BJH pore volume obtained from nitrogen desorption ^{of 0.15 cm 3 /g or more, preferably 0.17 cm 3 /g or more, more preferably 0.2 cm 3 /g or more.} Has.

Preferably, in the flue gas treatment process of the present invention, the adsorbent composition is activated carbon, lignite coke, haloysite, sepiolite, clay, bentonite, kaolin, vermiculite, refractory clay, aerated cement dust, perlite, expanded clay, lime. Sandstone Dust, Tras Dust, Yaly Rock Dust, Tras Lime, Fuller Soil, Cement, Calcium Aluminate, Sodium Aluminate, Calcium Sulfide, Organic Sulfide, Calcium Sulfate, Pyeongro Coke, Lignite Dust, Fly Ash, or Water Glass. Include more.

In one embodiment of the flue gas treatment process of the present invention, the adsorbent composition is injected as a dry powder in a dry injection system or as an atomized slurry in a spray dryer absorber.

Another embodiment of the flue gas treatment process according to the invention is mentioned in the appended claims.

In a fifth aspect, the present invention relates to a flue gas processing apparatus comprising an electrostatic dust collector downstream of an air preheater, wherein the air preheater is connected to the electrostatic dust collector by a duct, and the flue gas processing apparatus is of the air preheater. It is characterized in that it further comprises a spraying zone for spraying the adsorbent composition according to the invention disposed upstream.

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

Preferably, the flue gas treatment device or equipment is used to treat the flue gas of a plant, particularly a power plant, using fuel or coal containing sulfur species or other acidic gas precursors.

Advantageously, the flue gas treatment facility further comprises a reservoir containing the adsorbent composition to provide the adsorbent composition to the injection zone through an adsorbent inlet.

1 shows a schematic embodiment of a flue gas treatment facility for performing a flue gas treatment process with an adsorbent composition according to the present invention.

According to a first aspect, the present invention relates to an adsorbent composition for flue gas treatment equipment comprising an electrostatic dust collector, wherein the adsorbent composition comprises a calcium-magnesium compound, and the adsorbent composition comprises 0.1% to 5% by weight of the dry composition. %, preferably an additive or mixture of additives in an amount of 0.3% to 3% by weight, wherein the additives or additives contain at least calcium nitrate.

In a preferred embodiment, the calcium-magnesium compound is based on hydrated lime.

Calcium hydroxide adsorbent is prepared by reacting (or slaking) calcium oxide, CaO or quicklime with water in a so-called hydrator, also called a slaking unit. Alternatively, the calcium magnesium hydroxide adsorbent is prepared by reacting dolomite lime (also called dolime) or magnesium lime with water in a hydrator. Alternatively, quicklime and dolomite lime can be mixed together and slaked with water in a hydrator to provide a mixture of calcium hydroxide and calcium magnesium hydroxide. In the following, the manufacturing process of the adsorbent composition will refer to quicklime, but this manufacturing process is not limited to quicklime as a starting material, and a combination of dolomite lime or dolomite lime and/or magnesium lime and quicklime can also be used as a starting material.

The manufacturing process of the adsorbent composition according to the present invention comprises the step of slaking quicklime with a predetermined amount of water to obtain hydrated lime containing a predetermined amount of moisture, the manufacturing process being 0.3 weight by weight of the dry adsorbent composition And adding an additive or mixture of additives to dope the adsorbent composition in an amount calculated to obtain an additive or mixture of additives from% to 3.5% by weight, wherein the additive or additives are at least calcium nitrate or Nitric acid or combinations thereof.

In one embodiment of the process for preparing the adsorbent composition, the predetermined amount of water in the slaking step has a water to lime ratio of at least 2:1 by weight.

In one embodiment of the process for preparing the adsorbent composition, the amount of water in the slaking step is 10% by weight or less, preferably 5% by weight or less, preferably 2% by weight or less, based on the total weight of the adsorbent composition in a powder state, More preferably, it can be adjusted to obtain a hydrated lime containing up to 1% by weight of moisture.

In another embodiment, the amount of water in the slaking step can be adjusted to obtain a hydrated lime containing a moisture content of 5% to 20% by weight. The amount of water in the slaking step may be higher to obtain hydrated lime containing a moisture content in excess of 20% by weight, all percentages expressed in powder form relative to the total weight of the adsorbent composition.

In one embodiment, the hydrated lime obtained after the slaking step is dried in a further step.

In one embodiment of the process for preparing the adsorbent composition according to the present invention, the additive containing calcium nitrate before or during the slaking step of calcium oxide or calcium magnesium oxide or a combination thereof contains calcium nitrate as an aqueous solution or suspension or powder. It is used to dope the adsorbent composition by adding an additive to it.

In another embodiment of the process for preparing the adsorbent composition according to the present invention, calcium nitrate is added as an aqueous solution or suspension or powder after the slaking step. Preferably, the drying step is carried out after the slaking step and after the calcium nitrate addition step. Calcium nitrate is preferably added to the calcium hydroxide or calcium magnesium hydroxide prior to injection in the injection zone of the flue gas treatment plant.

In a preferred embodiment of the process for preparing the adsorbent composition, the step of slaking the quicklime comprises, for example, a BJH having a BET specific surface area of at least ^{20 m 2 /g from nitrogen adsorption and at least 0.1 cm 3} /g obtained from nitrogen desorption. It is carried out under conditions to obtain hydrated lime having a pore volume. To obtain hydrated lime with these properties, one of skill in the art can use the various processes disclosed in, for example, Applicants' US Pat. Nos. 6,322,769 and 7,744,678, which are incorporated by reference.

In the process for preparing the adsorbent composition according to the invention, the particles of quicklime are advantageously used having a particle size distribution of less than 5 mm, in particular 0-2 mm.

There are other processes for obtaining hydrated lime with high specific surface area and/or high pore volume, for example, in U.S. Patent 5,492,685, a certain amount of alcohol, such as methanol or ethanol, is used in and/or prior to the slaking step of quicklime. It is added and removed after drying, and in German patent DE3620024 sugar is added to increase the specific surface area in the slaking step, glycol or amine is added to increase its fluidity, and in U.S. Patent 5,277,837 and U.S. Patent 5,705,141, hydrated lime Additives such as ethylene glycol, diethylene glycol, triethylene glycol, monoethanolamine, diethanolamine, triethanolamine or a combination thereof are added in the slaking step to increase the surface area of the.

In the manufacturing process of the adsorbent composition, before the slaking step, during the slaking step, or after the slaking step, the present invention does not involve a substantial change in the BJH pore volume for the pores of the adsorbent composition having a diameter of 1000 Å or less. Calcium nitrate may be added in a specific amount according to the present invention as disclosed in the specification. In addition, the BJH pore volume of the adsorbent composition according to the present invention is substantially the same as in the case of the calcium hydroxide adsorbent prepared by a known method as described in U.S. Patents 6,322,769 and 7,744,678, which are incorporated by Wonyong. In addition, the BET specific surface area of the adsorbent composition exceeds 20 m²/g. Thus, the properties of the adsorbent ensuring the _{SO 2 removal efficiency are preserved.} Alternatively, nitric acid or calcium nitrate and nitric acid may be added before, during or after the slaking step. Preferably, when calcium nitrate or nitric acid or a combination thereof is added after the slaking step and preferably before the drying step, a higher BET specific surface area is obtained.

In the process for preparing the adsorbent composition according to the present invention, when the hydrated lime composition is prepared according to the method described in US Pat. No. 7,744,678, this method is 0.2% to 3.5% by weight based on the total weight of the dry adsorbent composition in the hydrated lime. Adding an amount of an alkali metal, preferably sodium, to the quicklime, slaking water, or hydrated lime in an amount sufficient to obtain an alkali metal content of weight percent. Sodium is added as, for example, Na ₂ CO _3. According to this embodiment, for example, in an amount to obtain a content of calcium nitrate of 0.1% to 5% by weight, preferably 0.3% to 3% by weight of the dry adsorbent composition, calcium nitrate or nitric acid or Combinations of these are further added after the slaking step and preferably before the drying step.

Various adsorbent compositions were prepared according to the method of the present invention, and the measurement of the resistivity of the dry powder of the adsorbent composition was carried out according to the procedure outlined by IEEE (Estcourt, 1984). Basically, a dry powder of the adsorbent composition is filled in a resistivity cell of a determined volume, and then this powder is compressed using a weight to obtain a flat surface. An electrode having a guard is installed on the surface of the powder, and the resistivity of the powder is measured in an oven under an air flow containing 10% humidity at various temperatures from 150°C (302°F) to 300°C (372°F). Measure. The resistivity of the comparative example was measured under the same conditions. For each measurement, the maximum resistivity (R _max ) and a resistivity of 300° C. (572° F.) were determined. The resistivity measurement is presented below.

Example set A

Example 1 is a comparative sample of calcium hydroxide adsorbent designed for removal of acidic gaseous contaminants prepared according to US 6,322,769 B1. This sample was obtained from an industrial facility. Sodium, calcium nitrate, and nitric acid were not added.

Example 2 is a comparative sample of a calcium hydroxide adsorbent designed for removal of acidic gaseous contaminants prepared according to US 7,744,678 B2. The content of this sample is Ca(OH) ₂ >90% by weight, CaCO ₃ <8% by weight, and about 0.8% by weight of Na ₂ CO ₃ , and the balance impurities. No additional sodium or calcium nitrate or nitric acid was added. This sample was obtained from an industrial facility.

Example 3 is another sample of calcium hydroxide adsorbent designed for removal of acidic gaseous contaminants prepared according to US 7,744,678 B2, wherein lime is from a different source. The content of this sample is Ca(OH) ₂ >90% by weight, CaCO ₃ <7% by weight, and 2.1% by weight of Na ₂ CO ₃ and the remainder of impurities. No additional sodium or calcium nitrate or nitric acid was added. This sample was obtained from an industrial facility.

Example 4 is a calcium hydroxide adsorbent prepared according to the present invention using the same lime source as in Example 3 and using calcium nitrate as a dopant in an amount of 1% relative to the dry product. This sample was obtained from an industrial facility.

Example 5 is a calcium hydroxide adsorbent prepared according to the present invention using the same lime source as in Example 3 and using calcium nitrate as a dopant in an amount of 2% relative to the dry product. This sample was obtained from an industrial facility.

Example 6 is in accordance with the present invention, for example, to obtain a sodium content of 2% by weight, based on the total weight of the dry powder composition obtained, on a laboratory scale, in a mixer equipped with a paddle, chemical quicklime It is a calcium hydroxide adsorbent prepared by mixing (slaking) a stoichiometric amount of water and a certain amount of NaCO _3. This quicklime was obtained by calcination of lime from the same source of lime as in Example 3. After the reaction in the mixer, hydrated lime (calcium hydroxide) was discharged, dried, and post-treated using _{1% by weight of HNO 3 by weight of the dried product.}

Table 1 shows the measured resistivity parameters R _max and R ₃₀₀ for these examples. Measurement of the resistivity parameter was performed by measuring the resistivity of the sample while increasing the temperature.

Resistivity parameters of calcium hydroxide adsorbents of Examples 1 to 6 Example R _max (Ω·cm) R ₃₀₀ (Ω·cm) Example 1 8 E12 3 E12 Example 2 4 E11 1 E11 Example 3 9 E 10 4 E09 Example 4 9 E09 1 E08 Example 5 6 E 09 4 E07 Example 6 4 E10 1 E08

From Table 1, _{it is clear that both of the R max} value and the R ₃₀₀ value of Example 1 are high in the preferred range of resistivity values included in 10E7 ohm·cm to 2E10 ohm·cm and in a higher range. Exemplary case the presence of the adsorbent of the Na ₂ CO ₃ 0.8% by weight in the composition 2 is reduced by greater than 1-fold compared to R _max and R ₃₀₀ value of the composition of R _max and R ₃₀₀ value carried in one case. Three exemplary cases the presence of the adsorbent of the Na ₂ CO ₃ 2.1% by weight of the composition, thereby reducing as much as in excess of twice the value of R _max and R ₃₀₀ and R ₃₀₀ to R _max value of the exemplary cases 1. Surprisingly, the presence of a small amount of calcium nitrate of 1% by weight in the composition of Example 4 _{reduces the R max} value by almost 3 times and the R ₃₀₀ value by almost 4 times based on _{the R max} and R _{300 values of Example 1.} The presence of 2% by weight of calcium nitrate in the composition of Example 5 further reduces the values _{of R max} and R _{300 based on the composition of Example 1.} Therefore, surprisingly, the addition of calcium nitrate or nitric acid is more effective in lowering the resistivity compared to the addition of sodium. Despite some differences due to different process conditions (industrial scale and laboratory scale), _{the presence of calcium nitrate in the composition by adding HNO 3} instead of adding calcium nitrate tends to lower the adsorbent resistivity Ca(NO ₃ ). _{It is the} same as the addition of 2.

Example set B

Example 7 is a sample of fly ash obtained from a coal power plant.

Example 8 is a blend of 80% by weight fly ash from Example 7 and 20% by weight adsorbent according to Example 3.

Example 9 is a blend of 80% by weight fly ash from Example 7 and 20% by weight adsorbent according to Example 4.

Example 10 is a blend of 80% by weight fly ash from Example 7 and 20% by weight adsorbent according to Example 5.

Table 2 shows the measured values of _{resistivity parameters R max} and R ₃₀₀ for Examples 7 to 10. One set of measurements of R _max and R ₃₀₀ was performed by measuring the resistivity of the sample while increasing the temperature, and one set of measurements of _{R max was performed by measuring the resistivity of the sample while decreasing the temperature.}

_{R max} under temperature rise (Ω·cm) _{R 300} under temperature rise (Ω·cm) _{R max} under temperature drop (Ω·cm) Example 7 3E10 5E09 3E10 Example 8 2E12 3E10 1E12 Example 9 1E11 1E09 2E10 Example 10 4E10 7E07 2E09

The results presented in Table 2 show that for the same ratio of fly ash and calcium-based adsorbent, the blend of calcium-based adsorbent and fly ash containing no calcium nitrate additive has a higher resistivity parameter R _{max than that of fly ash without calcium-based adsorbent.} And R ₃₀₀ , whereas the presence of only 1% by weight, preferably 2% by weight of CaNO ₃ additive in the calcium-based adsorbent has a positive effect on the resistivity parameters R _max and R _{300 of this blend.}

The examples of the adsorbent composition presented above do not limit the present invention, and that other additives in an amount consisting of 0.1 to 5% by weight can be used to reduce the resistivity of the adsorbent composition to be used in the flue gas treatment process using an electrostatic precipitator. It should be mentioned.

It should be mentioned that with the use of the adsorbent according to the invention an improvement in the collection of particulate matter on the collecting electrode of the electrostatic precipitator can be observed.

According to another aspect, the present invention relates to a flue gas treatment plant. 1 shows a schematic embodiment of a flue gas treatment facility 100 comprising an electrostatic precipitator 101 disposed downstream of a first duct portion 102 disposed downstream of an air preheater 103, and The zone 104 is arranged upstream of the air preheater 103 and is characterized in that it comprises an adsorbent inlet 105. The flue gas treatment facility 100 further comprises a reservoir 106 containing the adsorbent composition S for providing the adsorbent composition to the injection zone through the adsorbent inlet. The hot flue gas (FG) produced by the boiler 10 flows through the injection zone, where the adsorbent (S) according to the present invention is injected to _{react with SO 2} and other acid gases from the flue gas, followed by a low temperature The hot flue gas passes through an air preheater so that the air CA absorbs the heat of the hot flue gas and is injected into the boiler as hot air HA. The flue gas then passes through the electrostatic precipitator 101, where the charged collecting electrode collects particulate matter comprising the adsorbent composition according to the present invention reacted with an undesired acidic gas. The flue gas treatment equipment described herein is relatively simple and suitable for the use of the adsorbent composition according to the present invention.

Preferably, the flue gas treatment facility is used to treat the flue gas of a power plant using fuel or coal containing sulfur species or other acidic gas precursors.

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

For example, in a preferred embodiment, a flue gas treatment facility having an electrostatic precipitator downstream of an air preheater has been described, wherein the air preheater is for injecting the adsorbent composition according to the present invention disposed upstream of the air preheater. It is connected to the electrostatic precipitator by a duct with an injection zone. An alternative within the scope of the present invention may include a particulate collection device upstream of the preheater.

Another alternative to the flue gas treatment apparatus according to the invention comprises an electrostatic precipitator, a preheater, and optionally a particulate collection apparatus in sequence before reaching the chimney.

This particulate collection device may be an electrostatic precipitator or any kind of filter, for example a bag house filter.

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

Claims (21)

As a powdered calcium-magnesium compound comprising at least 80% by weight or more of calcium hydroxide-magnesium based on the total weight of the powdered calcium-magnesium compound,
The powdered calcium-magnesium compound exhibits a resistivity of greater than 1E7 ohm·cm to less than 1E11 ohm·cm at 300°C, and the powdered calcium-magnesium compound is 0.05% by weight based on the total weight of the powdered calcium-magnesium compound. Powdered calcium-magnesium compound, doped with calcium nitrate in an amount of not less than 5% by weight. The method of claim 1,
The powdered calcium-magnesium compound _{exhibits a maximum resistivity R max} of less than 1E11 ohm·cm, a powdered calcium-magnesium compound. The method according to claim 1 or 2,
The powdered calcium-magnesium compound further comprises a sodium-based additive in an amount of up to 3.5% by weight expressed as a sodium equivalent based on the total weight of the powdered calcium-magnesium compound. The method according to any one of claims 1 to 3,
The powdered calcium-magnesium compound is 20 m ² /g or more, preferably 25 m ² /g or more, preferably 30 m ² /g or more, more preferably 35 m ² /g or more BET by nitrogen adsorption A powdered calcium-magnesium compound that exhibits a specific surface area. The method according to any one of claims 1 to 4,
^{The powdered calcium-magnesium compound exhibits a BJH pore volume of 0.1 cm 3} /g or more for pores having a diameter of 1000 Å or less by nitrogen desorption, a powdered calcium-magnesium compound. An adsorbent composition for flue gas treatment facilities comprising an electrostatic precipitator comprising the powdered calcium-magnesium compound according to any one of claims 1 to 5. The method of claim 6,
The adsorbent composition is activated carbon, lignite coke, haloysite, sepiolite, clay, bentonite, kaolin, vermiculite, refractory clay, aerated cement dust, perlite, expanded clay, lime sandstone dust, tras dust, yalyroc dust, tras Lime, fuller soil, cement, calcium aluminate, sodium aluminate, calcium sulfide, organic sulfide, calcium sulfate, open-hearth coke, lignite dust, fly ash, and water glass. To, the adsorbent composition for flue gas treatment equipment. The method of claim 6 or 7,
The adsorbent composition comprises a sodium-based additive in an amount of up to 3.5% by weight expressed in terms of sodium equivalents based on the total weight of the powdered adsorbent composition and the adsorbent composition for a flue gas treatment facility. The method according to any one of claims 6 to 8,
The calcium nitrate is present in an amount of 0.05% by weight or more and 5% by weight or less based on the total weight of the dry adsorbent composition. The method according to any one of claims 6 to 9,
The calcium-magnesium compound is hydrated lime, an adsorbent composition for flue gas treatment equipment. As a method for producing an adsorbent composition containing 0.1% to 5% by weight of calcium nitrate for a flue gas treatment facility including an electrostatic dust collector,
The manufacturing method is:
a) providing a calcium-magnesium compound to the reactor;
b) adding a compound selected from the group consisting of calcium nitrate, nitric acid, and combinations thereof. The method of claim 11,
The calcium-magnesium compound comprises a calcium hydroxide-magnesium content of 80% by weight or more with respect to the total weight of the dry calcium-magnesium compound. The method of claim 11 or 12,
Providing the calcium-magnesium compound to the reactor includes providing quicklime to the reactor, and the dry calcium-magnesium compound containing a predetermined amount of moisture by slaking the quicklime with a predetermined amount of water. A method for producing an adsorbent composition comprising the step of obtaining the calcium-magnesium compound comprising at least a calcium hydroxide content of 80% by weight or more based on the total weight of. The method according to any one of claims 11 to 13,
The method for preparing the adsorbent composition comprises adding a sodium-based additive expressed as a sodium equivalent in an amount calculated to obtain a sodium equivalent weight of at most 3.5% by weight of the dry adsorbent composition. The method according to any one of claims 11 to 14,
The slaking step is performed under conditions for obtaining hydrated lime having a BET specific surface area measured by nitrogen adsorption of ^{20 m 2 /g or more.} The method according to any one of claims 11 to 15,
The slaking step is performed under conditions for obtaining hydrated lime having a BJH pore volume of ^{0.1 cm 3} /g or more for pores having a diameter of 1,000 Å or less measured by nitrogen desorption. The method according to any one of claims 11 to 16,
The preparation method of the adsorbent composition is activated carbon, lignite coke, haloysite, sepiolite, clay, bentonite, kaolin, vermiculite, refractory clay, aerated cement dust, perlite, expanded clay, lime sandstone dust, tras dust, yalyloc dust. , Trass lime, fuller soil, cement, calcium aluminate, sodium aluminate, calcium sulfide, organic sulfide, calcium sulfate, plain coke, lignite dust, fly ash, and water glass. The method of manufacturing an adsorbent composition further comprising the step of. As a flue gas treatment method using a facility including an injection zone disposed upstream of an electrostatic precipitator,
The flue gas treatment method comprises the step of injecting the adsorbent composition according to any one of claims 6 to 10 in the injection zone. The method of claim 18,
The adsorbent composition comprises a calcium-magnesium compound, and the adsorbent composition is injected into the injection zone where the temperature of the flue gas is 180° C. or higher. The method of claim 18 or 19,
The method of treating flue gas, wherein the adsorbent composition is injected as a dry powder in a dry adsorbent injection system or as an atomized slurry in a spray dryer absorber system. A flue gas treatment apparatus including an electrostatic precipitator downstream of an air preheater,
The air preheater is connected to the electrostatic dust collector by a duct, and the flue gas treatment device comprises an injection zone for injecting the adsorbent composition according to any one of claims 6 to 10 disposed upstream of the air preheater. Further comprising, flue gas treatment apparatus.

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