Flue gas desulfurization method

Abstract

The present application belongs to the field of flue gas desulfurization, and particularly relates to a flue gas desulfurization method. The method comprises reacting a desulfurizer containing calcium hydroxide with flue gas, wherein the particle of the desulfurizer contains all pores with a pore size distribution satisfying that at least 40% of the pores have a pore size of 5-35 nm, and the flue gas has a temperature of 80-400 DEG C. The present application significantly improves the desulfurization efficiency, improves the desulfurization effect, reduces the CPM concentration in the flue gas, thereby reduces the desulfurization cost, and does not affect the cement clinker quality by selecting a specific desulfurizer (especially a desulfurizer having a specific pore size distribution), a specific desulfurizer adding position, and a flue gas temperature at the desulfurizer adding position.

Description

Technical Field

[0001] This invention belongs to the field of flue gas desulfurization, and particularly relates to flue gas desulfurization methods. Background Technology

[0002] For flue gas desulfurization, there are currently several main processes, including dry methods (sodium-based / calcium-based), wet methods (amino-based desulfurization agents (ammonia / urea solution), limestone gypsum), and combined methods (dry + wet). However, each of these processes has certain drawbacks and limitations. For example, existing flue gas desulfurization processes suffer from slow reaction rates, low desulfurization efficiency, high energy consumption, and the inability to reduce (or even significantly increase) the content of condensable particulate matter (CPM) in the flue gas.

[0003] Especially for flue gas desulfurization in the cement production industry, existing processes have at least the following problems.

[0004] Sodium-based dry desulfurization technology utilizes desulfurizing agents such as sodium bicarbonate to react with sulfur dioxide in flue gas at high temperatures. However, the reaction of sodium bicarbonate in this method is incomplete, requiring a far greater amount of sodium bicarbonate than the amount of SO2. This results in a large amount of sodium entering the cement clinker along with the dust collector ash, severely impacting the quality of the cement clinker. Furthermore, the accumulation of alkali metals through circulation can cause preheater scaling problems. Moreover, it fails to reduce CPM emissions (the main components of CPM in the cement industry are sulfates and nitrates), and may even increase the CPM content in the flue gas.

[0005] Existing calcium-based dry desulfurization technologies typically feed hot raw materials from the decomposer furnace or commercially purchased ordinary CaO, Ca(OH)2, or other desulfurizing agents into the preheater via a bucket elevator along with the raw materials entering the kiln. These materials participate in the calcination reaction, directly reacting with SO2 to achieve desulfurization. However, existing calcium-based dry desulfurization methods suffer from slow reaction rates and low efficiency, leading to increased fan resistance, higher power consumption, and impacting the stability of raw material batching. Furthermore, current calcium-based dry methods generally cannot reliably meet emission standards and are only suitable for low background SO2 emissions (e.g., background SO2 ≤ 300 mg / Nm³). 3 The production line of this desulfurization technology also fails to reduce CPM emissions and may even increase the CPM content in the flue gas.

[0006] The ammonia desulfurizing agents used in wet desulfurization technology can cause serious ammonia escape pollution and corrosion of metal equipment. Moreover, existing wet and combined desulfurization technologies significantly increase the CPM content in flue gas during application. Summary of the Invention

[0007] To solve the aforementioned technical problems, through numerous experiments, the inventors discovered that by selecting specific types of desulfurizing agents, their addition locations, and the flue gas temperature at the point of addition, the efficiency of the desulfurization process can be significantly improved, the desulfurization effect enhanced, the desulfurization cost reduced, the CPM content in the flue gas lowered, and the quality of cement clinker unaffected.

[0008] In one aspect, the present invention provides a flue gas desulfurization method, the method comprising reacting a desulfurizing agent containing calcium hydroxide with flue gas, wherein the particles of the desulfurizing agent contain pores, and the pore size distribution of all the pores contained in the particles of the desulfurizing agent satisfies the following: at least 40% of the pores have a pore size of 5-35 nm (e.g., 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35 nm, or a subrange thereof, preferably 15-35 nm), preferably, at least 60% (e.g., 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%). The flue gas temperature is 80-400°C (e.g., 80, 85, 90, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 115, 120, 125, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 300, 350 or 400°C, or a sub-range of values ​​therein, preferably 100-220°C, more preferably 120-220°C, and most preferably 150-200°C).

[0009] In some embodiments, the pore size distribution of all pores contained in the particles of the desulfurizing agent satisfies that at most 40% (e.g., 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1% or 0%, or a subrange thereof) have a pore size of less than 15 nm (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 nm, or a subrange thereof).

[0010] In some embodiments, the pore size distribution of all pores contained in the particles of the desulfurizing agent satisfies the following: and at most 40% (e.g., 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1% or 0%, or a subrange thereof) have a pore size of 35 nm or more (e.g., 35, 36, 37, 38, 39 or 40 nm, or a subrange thereof).

[0011] In some embodiments, the pore size distribution of all pores contained in the desulfurizing agent particles satisfies the following: at least 40% (preferably at least 60%) of the pores have a pore size of 5-35 nm (e.g., 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35 nm, or a subrange thereof, preferably 15-35 nm), and at most 40% (e.g., 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1% or 0%, or a subrange thereof, preferably 15-35 nm). The sub-ranges of values ​​therein have an aperture of no more than 15 nm (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 nm, or the sub-ranges of values ​​therein, preferably no more than 5 nm); and at most 40% (e.g., 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1% or 0%, or the sub-ranges of values ​​therein) have an aperture of more than 35 nm (e.g., 35, 36, 37, 38, 39 or 40 nm, or the sub-ranges of values ​​therein).

[0012] In one embodiment, the desulfurizing agent has a D90 ≤ 20 μm, that is, 90% of the particles in the desulfurizing agent have a particle size of less than 20 μm.

[0013] In one embodiment, the desulfurizing agent has a specific pore volume of at least 0.15 mL / g (e.g., 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24 or 0.25 mL / g, or a subrange of such values).

[0014] In one embodiment, the desulfurizing agent has at least 40m 2 / g (e.g., 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50mg) 2 Specific surface area ( / g, or a subrange consisting of the values ​​therein).

[0015] In a preferred embodiment, the desulfurizing agent has a specific pore volume of at least 0.15 mL / g (e.g., 0.15, 0.16, 0.17, 0.18, 0.19, or 0.20 mL / g, or a subrange thereof) and / or at least 40 m³ / g. 2 / g (e.g., 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50mg) 2 Specific surface area ( / g, or a subrange consisting of the values ​​therein).

[0016] In one embodiment, the desulfurizing agent contains at least 85% by weight (e.g., 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99% by weight, or a subrange of such values, preferably at least 90% by weight).

[0017] In one embodiment, the desulfurizing agent contains less than 2.0% by weight (e.g., 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1% by weight, or a subrange thereof, preferably less than 1.5% by weight, most preferably 0.9-1.0% by weight).

[0018] In one embodiment, the desulfurizing agent contains less than 3.0% by weight (e.g., 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1% by weight, or a subrange of such values).

[0019] In one embodiment, the desulfurizing agent contains less than 10.0% by weight of impurities selected from the following: calcium carbonate, silicon dioxide, aluminum oxide, ferric oxide, magnesium oxide, and magnesium hydroxide. For example, less than 1.5% by weight of silicon dioxide, less than 1.0% by weight of aluminum oxide and ferric oxide, and less than 1.0% by weight of magnesium oxide and magnesium hydroxide, etc. These impurities originate from limestone raw materials and are unavoidable trace components that will not significantly affect the desulfurization process of the desulfurizing agent.

[0020] In a preferred embodiment, the desulfurizing agent contains at least 85% by weight (e.g., 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99% by weight, or a subrange thereof, preferably at least 90% by weight) of calcium hydroxide and less than 2.0% by weight (e.g., 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1% by weight, or a subrange thereof, preferably less than 1.5% by weight, most preferably less than 1.0% by weight) of water.

[0021] In one embodiment, the flue gas is selected from at least one of the following: sulfur dioxide-containing flue gas produced by fossil fuel combustion, mineral roasting, or solid waste incineration.

[0022] In one embodiment, the flue gas is selected from at least one of the following: flue gas from coal-fired power generation, flue gas from iron and steel sintering, flue gas from coke oven combustion, flue gas from cement rotary kiln, flue gas from non-ferrous metal smelting, flue gas from coal chemical industry, or flue gas from waste incineration; preferably at least one of coke oven combustion flue gas and flue gas from cement rotary kiln; more preferably flue gas from cement rotary kiln.

[0023] In a preferred embodiment, the desulfurizing agent is added to any location between the preheater outlet and the dust collector inlet at the tail of the cement rotary kiln (e.g., the flue at the dust collector inlet, the flue between the high-temperature fan outlet and the kiln tail bag filter inlet), for example, by spraying.

[0024] In one embodiment, atomized water is added to the flue gas before adding the desulfurizing agent, for example, by spraying. More specifically, the atomized water is added approximately 1-5 meters before the location where the desulfurizing agent is added. In one embodiment, the amount of atomized water added to the flue gas before adding the desulfurizing agent is at least 1 meter. 3 / h, at least 2m 3 / h, at least 3 m 3 / h, at least 4 m 3 / h, at least 5 m 3 / h.

[0025] In one embodiment, the background SO2 concentration in the flue gas is 300 mg / Nm³. 3The following (e.g., 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290 or 300 mg / Nm) 3 (or a subrange consisting of the values ​​therein). In another embodiment, the background SO2 concentration in the flue gas is 300 mg / Nm³. 3 The above (e.g., 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000 mg / Nm) 3 , or a subrange consisting of its numerical values.

[0026] In one embodiment, the molar ratio of calcium hydroxide in the desulfurizing agent to the removed sulfur dioxide (referred to as the "calcium-sulfur molar ratio") is 15 or less, for example, it can be 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, or a subrange of values ​​therein.

[0027] In one embodiment, the amount of calcium hydroxide in the added desulfurizing agent is 0.5-5 t / h, for example, it can be 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 t / h, or a subrange consisting of such values.

[0028] In one embodiment, after treatment by the method (e.g., for at least 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes, or a sub-range consisting of such values), the SO2 concentration in the flue gas is 35 mg / Nm³. 3 The following (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 mg / Nm) 3 , or a subrange consisting of its numerical values.

[0029] In one embodiment, after treatment by the method (e.g., for at least 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes, or a sub-range consisting of such values), the CPM content in the flue gas is 10 mg / Nm³. 3 The following (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mg / Nm) 3 Or a subrange consisting of its numerical values.

[0030] In another aspect, the present invention provides a preparation method for preparing a highly active desulfurizing agent used in the flue gas desulfurization method described in this application, comprising: a) mixing calcium oxide raw material with water and additives, and adding it to a digester for reaction to obtain a reactant; b) drying the reactant obtained in step a) at low temperature; c) ultra-fine grinding, grading and screening to obtain a highly active desulfurizing agent.

[0031] The desulfurizing agent described herein can be prepared by methods known in the art. An exemplary preparation process may include the following steps: a) Modification treatment: Modifying any existing desulfurizing agent containing calcium hydroxide (containing at least 85% by weight (e.g., 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99% by weight, or a subrange thereof, preferably at least 90% by weight)). An exemplary step includes adding 1-2% by weight of one or more additives selected from: glucose, sodium citrate, triethanolamine, polyethylene glycol (PEG), nano-alumina particles, sodium sulfonate, and stearic acid.

[0032] Further, the exemplary preparation process may also include: b) drying treatment: for example, using a rotary kiln or spray drying tower to control the moisture content to below 2.0% by weight (e.g., 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1% by weight, or sub-ranges thereof, preferably below 1.5% by weight, most preferably 0.9-1.0% by weight). Optionally, impurities and coarse particles are removed prior to the drying treatment (e.g., by a hydrocyclone, filter press, or other equipment).

[0033] Furthermore, the exemplary preparation process may also include: c) pulverization: pulverizing the dried material (e.g., using an ultrafine pulverizer) to a fineness of 300 mesh or more.

[0034] In addition, calcium oxide (e.g., a material obtained by calcining limestone) can be reacted with water (e.g., industrial softened water).

[0035] An exemplary process for calcining limestone includes selecting limestone (e.g., high-grade limestone, such as limestone with a calcium carbonate content of at least 98% by weight) and calcining it in a vertical or rotary kiln at 900-1150°C. Optionally, the calcined raw material may be crushed and sieved. An exemplary process includes crushing lumpy quicklime (CaO) to a specific particle size (e.g., less than 1 mm or 100-200 mesh) and sieving out waste residue.

[0036] In one embodiment, the "calcium hydroxide-containing desulfurizing agent" described herein can be any commercially available desulfurizing agent with calcium hydroxide as its main component, as long as it meets one or more of the pore size distribution conditions and the specific pore volume, specific surface area, calcium hydroxide content, and water content conditions described herein. In another embodiment, the "calcium hydroxide-containing desulfurizing agent" described herein is obtained by processing a commercially available desulfurizing agent with calcium hydroxide as its main component (e.g., through the exemplary preparation process described herein, or other existing processes) to make it meet one or more of the pore size distribution conditions and the specific pore volume, specific surface area, calcium hydroxide content, and water content conditions described herein. In other embodiments, the "calcium hydroxide-containing desulfurizing agent" described herein can be prepared from limestone using any existing process (e.g., the exemplary preparation process described herein), which meets one or more of the pore size distribution conditions and the specific pore volume, specific surface area, calcium hydroxide content, and water content conditions described herein.

[0037] The pore size distribution, specific pore volume, and specific surface area of ​​the desulfurizing agent described in this article can be measured using any existing method. Exemplary methods include the gas adsorption method (BET / BJH method), which measures the amount of inert gas (typically nitrogen) adsorbed by the desulfurizing agent sample at liquid nitrogen temperature (-196°C). The specific surface area is calculated using BET theory by analyzing the adsorption-desorption isotherms, and the pore size distribution and specific pore volume are calculated using methods such as BJH. Furthermore, high-resolution images of the desulfurizing agent particles can be directly captured using scanning electron microscopy (SEM) or transmission electron microscopy (TEM) to visually observe their surface morphology and internal pore structure, thereby corroborating the measured parameter characteristics.

[0038] This invention significantly improves desulfurization efficiency and reduces CPM concentration in flue gas by selecting specific desulfurizing agents (especially those with specific pore size distributions), specific desulfurization locations, and flue gas temperatures at the desulfurization point, without affecting cement clinker quality. Furthermore, adding atomized water at specific locations further enhances the desulfurization and CPM reduction effects of this method. Moreover, the flue gas desulfurization method of this invention can be used when the background SO2 concentration is 300 mg / Nm³.3 The following flue gas (i.e., flue gas with low background SO2 concentration) can also be used for flue gas with a background SO2 concentration of 300 mg / Nm³. 3 The above refers to flue gas (i.e., flue gas with a high background SO2 concentration).

[0039] The background SO2 concentration mentioned in this article refers to the SO2 concentration naturally released into the kiln tail flue gas during the calcination process from sulfur compounds contained in the raw materials and fuels of the cement production line (including but not limited to limestone, clay, corrective raw materials, fuels, and alternative fuels) without any external desulfurization measures. Its value is expressed in milligrams of sulfur dioxide per standard cubic meter of dry flue gas (mg / Nm³). 3 The measurement location is at the outlet of the high-temperature blower at the kiln tail, and the flue gas conditions have been converted to standard conditions (temperature 273.15 K or 293.15 K, pressure 101.325 kPa, dry basis, O2 content corrected according to process reference). The SO2 concentration in the flue gas treated by the method described in this article refers to the SO2 concentration in the flue gas measured at the chimney outlet of the final emission flue gas after treatment for a certain period of time using the method or system described in this article, and the flue gas conditions are also converted to the above standard conditions.

[0040] The CPM content in flue gas mentioned in this article refers to the concentration of gaseous or vaporous substances that can condense into solid or liquid fine particles as the flue gas temperature decreases to ambient conditions, measured within the final emission flue gas duct. The value is expressed as the mass (milligrams) of condensable particulate matter contained in a standard cubic meter of dry flue gas, with units of mg / Nm³. 3 The concentration was determined using sampling and analysis methods that conform to national or industry standards (such as the dry impact condensation method).

[0041] The desulfurization efficiency described in this article is calculated as: (Background SO2 concentration - SO2 concentration in the treated flue gas) / Background SO2 concentration. 100%.

[0042] Unless otherwise specified, percentages, proportions, ratios, contents, or parts mentioned in this application are by weight. Concentrations mentioned in this application are weight concentrations. Attached Figure Description

[0043] Figure 1 This shows an exemplary desulfurizer addition point used in this invention.

[0044] Figure 2 A production line illustrating an exemplary cement preparation process of the present invention. Detailed Implementation

[0045] To better understand the present invention, the following embodiments further illustrate the content of the invention, but the content of the invention is not limited to the following embodiments. Unless otherwise specified, the experimental operations described in the following embodiments are routine operations; the reagents and materials described are commercially available unless otherwise specified.

[0046] Preparation Examples The desulfurizer of this invention is prepared by a semi-dry production process, specifically as follows: 92% calcium oxide ash and approximately equal amounts of water are mixed in a digester to allow a reaction to occur. During the reaction, the temperature is controlled at 80-90°C, and 1.5% by weight of sodium sulfonate and stearic acid are added as additives to regulate the pore structure of the final desulfurizer, including specific surface area, specific pore volume, and pore size distribution. Subsequently, the reactants are fully digested in the digester, resulting in a low free calcium content and a moisture content of approximately 15%. The product is then dried at a low temperature with controlled temperature to stabilize the moisture content below 2%. Finally, the product is processed using conventional techniques such as grading, screening, and ultrafine grinding to obtain the final desulfurizer. The pore structure of the final desulfurizer is measured using a gas adsorption method (BET / BJH method), resulting in a desulfurizer with high specific surface area, high specific pore volume, and / or a specific pore size distribution used in the following embodiments.

[0047] Example 1: The effect of flue gas temperature on desulfurization efficiency Example 1-1: In a 5000t / d new dry-process cement production line in Hunan Province, the actual monitored background concentration of SO2 in the flue gas was 380mg / Nm³. 3 The desulfurizing agent of the present invention, which has a high specific surface area and high specific pore volume (wherein, the calcium hydroxide content is 90%, the moisture content is 1.0%, and the specific surface area is approximately 45 m²), is used. 2 The desulfurizing agent (approximately 0.2 mL / g with a pore volume of about 0.2 mL / g and a pore size of about 60% in the 5-35 nm range) is evenly sprayed into the flue gas duct between the high-temperature fan outlet and the kiln tail bag filter inlet of the cement production line (flue gas temperature approximately 150-200℃) via pneumatic conveying in four separate streams. The dosage of the desulfurizing agent is approximately 0.6 tons per hour. After 3 minutes of treatment, the SO2 concentration in the flue gas can be stabilized at 30 mg / Nm³. 3 The lowest level can be reduced to 20 mg / Nm³. 3 The desulfurization efficiency of the cement kiln flue gas was 94.7%, the sodium ion content in the clinker did not increase, and the average CPM emission concentration of the flue gas from the chimney was only 2.5 mg / Nm³. 3 .

[0048] Examples 1-2: In a 5000t / d new dry-process cement production line in Zhejiang, the actual monitored background concentration of SO2 in the flue gas was 550mg / Nm³. 3The calcium hydroxide desulfurizer of the present invention, which has a high specific surface area and specific pore volume (wherein, the calcium hydroxide content is 90%, the moisture content is 1.0%, and the specific surface area is approximately 45 m²), is used. 2 The desulfurizing agent (approximately 0.2 mL / g with a pore volume of about 0.2 mL / g and a pore size of about 60% in the 5-35 nm range) is evenly sprayed into the flue gas duct between the high-temperature fan outlet and the kiln tail bag filter inlet using pneumatic conveying in four separate channels (flue gas temperature approximately 150-200℃). The dosage is approximately 1 ton per hour, and the SO2 concentration in the flue gas stabilizes at 50 mg / Nm³ after 3 minutes. 3 The lowest level can be reduced to 30 mg / Nm. 3 The desulfurization efficiency of the cement kiln flue gas was 96.4%, the sodium ion content in the clinker did not increase, and the average CPM emission concentration of the flue gas from the chimney was only 3.2 mg / Nm³. 3 .

[0049] Examples 1-3: In a 5000t / d new dry-process cement production line in Zhejiang, the actual monitored background concentration of SO2 in the flue gas was 1020mg / Nm³. 3 The calcium hydroxide desulfurizer of the present invention, which has a high specific surface area and specific pore volume (wherein, the calcium hydroxide content is 90%, the moisture content is 1.0%, and the specific surface area is approximately 45 m²), is used. 2 The desulfurizing agent (approximately 0.2 mL / g with a pore volume of about 0.2 mL / g and a pore size of about 60% in the 5-35 nm range) is evenly sprayed into the flue gas duct between the high-temperature fan outlet and the kiln tail bag filter inlet using pneumatic conveying in four separate channels (flue gas temperature approximately 150-200℃). The dosage is approximately 2 tons per hour, and the SO2 concentration in the flue gas stabilizes at 20 mg / Nm³ after 3 minutes. 3 The lowest level can be reduced to 10 mg / Nm 3 The desulfurization efficiency of the cement kiln flue gas was 98.1%, with no increase in sodium ion content in the clinker, and the average CPM emission concentration of the flue gas from the chimney was only 3.7 mg / Nm³. 3 .

[0050] Comparative Example 1-1: In a 5000t / d new dry-process cement production line in Hunan Province, the actual monitored background concentration of SO2 in the flue gas was 550mg / Nm³. 3 Traditional calcium-based desulfurizers (calcium hydroxide content approximately 90%, moisture content 1.0%, specific surface area approximately 15 m²) 2 The desulfurizing agent (approximately 0.06 mL / g, with a specific pore volume of about 0.06 mL / g) was added to the cement kiln preheater (flue gas temperature approximately 500℃) via a kiln elevator. The desulfurizing agent was added at a rate of approximately 1 ton per hour. After 7 minutes of treatment, the SO2 concentration in the flue gas dropped to a minimum of 420 mg / Nm³. 3 The desulfurization efficiency of the cement kiln flue gas was 76.3%, and the average CPM emission concentration of the flue gas from the chimney was approximately 20 mg / Nm³. 3 .

[0051] Comparative Examples 1-2: In a 5000t / d new dry-process cement production line in Hunan Province, the actual monitored background concentration of SO2 in the flue gas was 550 mg / Nm³. 3 SDS sodium-based desulfurizer (ultra-fine sodium bicarbonate powder, sodium bicarbonate content approximately 99%, moisture content <1.0%, fineness 500 mesh) is pneumatically conveyed to the high-temperature fan outlet flue (flue gas temperature approximately 200℃). The dosage of desulfurizer is approximately 1 ton per hour. After 5 minutes of treatment, the SO2 concentration in the flue gas drops to a minimum of 80 mg / Nm³. 3 The desulfurization efficiency of the cement kiln flue gas was 86.8%, which increased the sodium ion content in the clinker by about 0.4%, affecting the clinker quality. The average CPM emission concentration of the flue gas from the chimney was measured to be approximately 15 mg / Nm³. 3 .

[0052] Comparative Examples 1-3: In a 5000t / d new dry-process cement production line in Zhejiang, the actual monitored background concentration of SO2 in the flue gas was 550mg / Nm³. 3 Traditional calcium-based desulfurizers are used (calcium hydroxide content approximately 90%, moisture content approximately 1.0%, specific surface area approximately 15 m²). 2 (with a specific pore volume of approximately 0.06 mL / g), it is added along with the raw meal powder to the high-temperature blower outlet flue (flue gas temperature approximately 200℃) via a kiln elevator. The desulfurizing agent is added at a rate of approximately 1 ton per hour. After 7 minutes, the SO2 concentration in the flue gas is reduced to a minimum of 520 mg / Nm³. 3 The desulfurization efficiency of cement kiln flue gas is 4%, and the average CPM emission concentration of flue gas from the chimney is approximately 17 mg / Nm³. 3 .

[0053] Comparative Examples 1-4: In a 5000t / d new dry-process cement production line in Zhejiang, the actual monitored background concentration of SO2 in the flue gas was 550mg / Nm³. 3 SDS sodium-based desulfurizer (ultra-fine sodium bicarbonate powder, sodium bicarbonate content approximately 99%, moisture content <1.0%, fineness 500 mesh) is pneumatically conveyed to the cement kiln preheater (flue gas temperature approximately 500℃). The dosage of desulfurizer is approximately 1 ton per hour. After 5 minutes of treatment, the SO2 concentration in the flue gas drops to a minimum of 360 mg / Nm³. 3 The desulfurization efficiency of the cement kiln flue gas was 87.3%, and the sodium ion content in the clinker increased by about 0.7%, which seriously affected the clinker quality. The average CPM emission concentration of the flue gas from the chimney was measured to be about 13 mg / Nm³. 3 .

[0054] Table 1 below records the desulfurization efficiency and CPM concentration in the above-mentioned examples and comparative examples. The results show that when the flue gas temperature is about 150-200°C, the desulfurizing agent with high specific surface area and high specific pore volume described in this invention is added, and its desulfurization efficiency is significantly improved and its CPM concentration can be effectively reduced.

[0055] Table 1: Desulfurization results of Example 1

[0056] Example 2: The effect of specific pore volume of desulfurizing agent on desulfurization efficiency The actual monitored background concentration of SO2 in the flue gas of a 5000t / d new dry-process cement production line in Zhejiang Province was 550mg / Nm³. 3 The present invention utilizes calcium hydroxide desulfurizing agents with different specific pore capacities (wherein, calcium hydroxide content is 90%, moisture content is 1.0%, and specific surface area is approximately 45 m²). 2 The desulfurizing agent (approximately 1 ton / g) is evenly sprayed into the flue between the outlet of the medium-high temperature blower and the inlet of the bag filter at the kiln tail using pneumatic conveying in four separate channels (temperature approximately 150-200℃). The desulfurization agent dosage is approximately 1 ton per hour. The desulfurization efficiency and CPM concentration after treatment with the desulfurizing agent for a period of time are shown in Table 2 below. The results in the table show that using the calcium hydroxide desulfurizing agent of this invention, which has a specific pore volume of at least 0.15 mL / g, can significantly improve the desulfurization efficiency, and the specific pore volume of the desulfurizing agent is positively correlated with the desulfurization efficiency.

[0057] Table 2: Desulfurization efficiency of desulfurizers with different specific pore volumes

[0058] Example 3: The effect of the specific surface area of ​​the desulfurizing agent on the desulfurization efficiency The actual monitored background concentration of SO2 in the flue gas of a 5000t / d new dry-process cement production line in Zhejiang Province was 550mg / Nm³. 3 Using the calcium hydroxide desulfurizing agent of the present invention with different specific surface areas (wherein, the calcium hydroxide content is 90%, the moisture content is 1.0%, and the specific pore volume is about 0.2 mL / g), it was uniformly sprayed in four directions using pneumatic conveying into the flue between the outlet of the medium-high temperature fan and the inlet of the bag filter at the kiln tail (temperature about 150-200℃). The dosage of the desulfurizing agent was about 1 ton per hour. The desulfurization efficiency and CPM concentration after treatment with the desulfurizing agent for a period of time are shown in Table 3 below. As can be seen from the results shown in the table below, using a calcium hydroxide desulfurizing agent with a specific surface area of ​​at least 40m 2 Calcium hydroxide desulfurizing agent with a specific surface area of ​​ / g can significantly improve desulfurization efficiency, and the specific surface area of ​​the desulfurizing agent is positively correlated with the desulfurization efficiency.

[0059] Table 3: Desulfurization efficiency of desulfurizers with different specific surface areas

[0060] Example 4: The effect of pore size distribution of desulfurizing agent on desulfurization efficiency The actual monitored background concentration of SO2 in the flue gas of a 5000t / d new dry-process cement production line in Zhejiang Province was 550mg / Nm³. 3 The present invention uses a calcium hydroxide desulfurizing agent with different pore size distribution (wherein, the calcium hydroxide content is 90%, the moisture content is 1.0%, and the specific surface area is approximately 45 m²). 2 / g (pore volume approximately 0.2 mL / g), the desulfurizing agent was evenly sprayed in four pneumatic conveying channels into the flue between the outlet of the medium-high temperature blower and the inlet of the bag filter at the kiln tail (temperature approximately 150-200℃). The dosage of the desulfurizing agent was approximately 1 ton per hour. The desulfurization efficiency and CPM concentration after treatment with the desulfurizing agent for a period of time are shown in Table 4 below. The results in the table show that the pore size distribution of the calcium hydroxide desulfurizing agent particles affects the desulfurization efficiency. Desulfurizing agents with at least 40% pore size of 5-35 nm achieve higher desulfurization efficiency, and the percentage of pore size of 5-35 nm in the desulfurizing agent is positively correlated with the desulfurization efficiency.

[0061] Table 4: Effect of pore size distribution of desulfurizing agent on desulfurization efficiency

[0062] Example 5: Effects of calcium hydroxide and water content in the desulfurizing agent on desulfurization efficiency The actual monitored background concentration of SO2 in the flue gas of a 5000t / d new dry-process cement production line in Zhejiang Province was 550mg / Nm³. 3 Using the calcium hydroxide desulfurizing agent of the present invention with different calcium hydroxide and water contents, it was uniformly sprayed in four directions via pneumatic conveying into the flue between the outlet of the medium-high temperature fan and the inlet of the bag filter at the kiln tail (temperature approximately 150-200℃). The dosage of the desulfurizing agent was approximately 1 ton per hour. The desulfurization efficiency and CPM concentration after treatment with the desulfurizing agent for a period of time are shown in Table 5 below. The results in the table show that the calcium hydroxide and water contents in the desulfurizing agent affect the desulfurization efficiency. Specifically, the desulfurization efficiency is higher when the calcium hydroxide content is at least 85% and the water content is below 1.5%.

[0063] Table 5: Effects of calcium hydroxide content and water content on desulfurization efficiency

[0064] Example 6: The effect of atomized water spray on desulfurization efficiency The actual monitored background concentration of SO2 in the flue gas of a 5000t / d new dry-process cement production line in Zhejiang Province was 550mg / Nm³. 3The calcium hydroxide desulfurizing agent of the present invention (in which the calcium hydroxide content is 90%, the moisture content is 1.0%, and the specific surface area is about 45 m²) is used. 2 (Porosity approximately 0.2 mL / g, pore size approximately 60% of which is 5-35 nm). Before adding the desulfurizing agent, atomized clean water was added to the flue gas duct, with the spray volume shown in Table 6. Then, the water was evenly sprayed into the flue gas duct between the outlet of the medium-high temperature fan and the inlet of the kiln tail bag filter (temperature approximately 150-200℃) using pneumatic conveying in four separate channels. The desulfurizing agent dosage was approximately 1 ton per hour. The desulfurization efficiency and CPM concentration after a period of treatment with the desulfurizing agent are shown in Table 6. The results in the table show that adding atomized clean water to the flue gas duct before adding the desulfurizing agent significantly improves the desulfurization efficiency, and the spray volume also affects the desulfurization efficiency.

[0065] Table 6: Summary of Desulfurization Effects

[0066] Example 7: Desulfurization efficiency of the desulfurizing agent obtained by the preparation method of this application The actual monitored background concentration of SO2 in the flue gas of a 5000t / d new dry-process cement production line in Zhejiang Province was 550mg / Nm³. 3 The calcium hydroxide desulfurizer obtained using the preparation method of the present invention (wherein, the calcium hydroxide content is 90%, the moisture content is 1.0%, and the specific surface area is approximately 45 m²) 2 / g, specific pore volume approximately 0.2mL / g, 5-35nm pore size accounts for approximately 60%) and commercially available ordinary calcium hydroxide desulfurizer (purchased from Beijing Yuzhi Company, calcium hydroxide content 90%, moisture content 1.0%, specific surface area approximately 15m²). 2 The desulfurizing agent (with a specific pore volume of approximately 0.6 mL / g and a pore size of approximately 5-35 nm accounting for about 50%) is evenly sprayed into the flue between the outlet of the medium-high temperature fan and the inlet of the bag filter at the kiln tail using pneumatic conveying in four separate streams (temperature approximately 150-200℃). The dosage of the desulfurizing agent is approximately 1 ton per hour. The desulfurization efficiency and CPM concentration after treatment with the desulfurizing agent for a period of time are shown in Table 7 below. The results shown in the table indicate that the desulfurization efficiency of the desulfurizing agent obtained by the preparation method of this application is significantly higher than that of commonly used commercially available desulfurizing agents.

[0067] Table 7: Comparison of desulfurization effects between the desulfurizing agent of this invention and commercially available desulfurizing agents

[0068] As can be seen from the above embodiments and comparative examples, firstly, compared with existing calcium-based or sodium-based desulfurizers, the desulfurizer of the present invention, with its high specific surface area, high specific pore volume, and specific pore size distribution, can achieve higher desulfurization efficiency and better reduce the CPM concentration in flue gas. Furthermore, compared to other locations, the desulfurizer addition location selected in this invention exhibits superior desulfurization effect and better reduction of CPM concentration in flue gas. Moreover, the inventors unexpectedly discovered that controlling the flue gas temperature at the desulfurizer addition location within a specific range can further improve desulfurization efficiency and reduce the CPM concentration in flue gas. Additionally, adding atomized water to the flue before adding the desulfurizer can also significantly improve the desulfurization efficiency of the desulfurizer.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A flue gas desulfurization method, the method comprising reacting a desulfurizing agent containing calcium hydroxide with flue gas, wherein the particles of the desulfurizing agent contain pores, and the pore size distribution of all the pores contained in the particles of the desulfurizing agent satisfies the following: at least 40% of the pores have a pore size of 5-35 nm (preferably 15-35 nm), preferably at least 60% of the pores have a pore size of 5-35 nm (preferably 15-35 nm), and the flue gas temperature is 80-400°C (preferably 100-220°C, more preferably 120-220°C, most preferably 150-200°C).

2. The method according to claim 1, wherein the desulfurizing agent has a specific pore volume of at least 0.15 mL / g.

3. The method according to claim 1 or 2, wherein the desulfurizing agent has a concentration of at least 40m 2 Specific surface area per g.

4. The method according to any one of the preceding claims, wherein the desulfurizing agent contains at least 85% by weight (preferably at least 90% by weight) calcium hydroxide.

5. The method according to any one of the preceding claims, wherein the desulfurizing agent contains less than 2.0% by weight (preferably less than 1.5% by weight, most preferably less than 1.0% by weight) of water.

6. The method according to any one of the preceding claims, wherein the flue gas is selected from at least one of the following: sulfur dioxide-containing flue gas produced by fossil fuel combustion, mineral roasting or solid waste incineration.

7. The method according to any one of the preceding claims, wherein the flue gas is selected from at least one of the following: flue gas from coal-fired power generation, flue gas from iron and steel sintering, flue gas from coke oven combustion, flue gas from cement rotary kiln, flue gas from non-ferrous metal smelting, flue gas from coal chemical industry, or flue gas from waste incineration; preferably at least one of coke oven combustion flue gas and flue gas from cement rotary kiln; more preferably flue gas from cement rotary kiln.

8. The method according to any one of the preceding claims, wherein the desulfurizing agent is added at any position between the preheater outlet and the dust collector inlet at the tail of the cement rotary kiln.

9. The method according to any one of the preceding claims, wherein atomized water is added to the flue gas before the desulfurizing agent is added.

10. The method according to any one of the preceding claims, wherein the pore size distribution of all pores contained in the particles of the desulfurizing agent satisfies the following: at most 40% having a pore size of 15 nm or less (preferably 5 nm or less); and / or at most 40% having a pore size of 35 nm or more.

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