Preparation method and application of modified calcium hydroxide adsorbent with desulfurization and demercuration synergistic effect

Abstract

The invention discloses a preparation method and application of a modified calcium hydroxide adsorbent with a desulfurization and demercuration synergistic effect, and belongs to the technical field of dry desulfurization and heavy metal mercury removal synergistic effect. Comprising the following steps: mixing a surfactant with calcium chloride, sodium hydroxide and a manganous nitrate solution, carrying out primary digestion, drying, grinding and calcining after the reaction is finished to obtain a precursor, adding the precursor into calcium lignosulphonate, carrying out secondary digestion and hydrothermal reaction, and carrying out centrifugal washing to obtain the manganese lignosulphonate modified calcium lignosulphonate. The modified calcium hydroxide adsorbent with the desulfurization and demercuration synergistic effect is obtained; wherein the surface active agent is a polyoxyethylene polyoxypropylene ether triblock copolymer. The modified calcium hydroxide adsorbent with the desulfurization and demercuration effects can be used for efficiently removing low-concentration SO2, can achieve the synergistic removal of heavy metal mercury, achieves the synergistic desulfurization and demercuration effects, is generally suitable for dry-process removal of medium-low-concentration SO2, and can achieve efficient and economical removal of low-concentration SO2 compared with other flue gas purification modes. In addition, equipment and instruments used in the method have simple requirements, the material source is wide, and the price is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of dry desulfurization for synergistic removal of heavy metal mercury, and particularly relates to a preparation method and application of a modified calcium hydroxide adsorbent with desulfurization and mercury removal functions. Background Art

[0002] Biomass fuel is an environment-friendly new renewable energy source, mainly composed of carbon, hydrogen and oxygen as the main elements, and has a relatively low sulfur content compared with fossil fuels. It is considered that the SO2 generated by biomass combustion in boilers mainly comes from the oxidation of organic sulfides during the devolatilization process and the thermal decomposition of inorganic sulfides during coke combustion. Therefore, it is difficult to reduce SO2 emissions by changing the combustion technology. Chemisorption is commonly used in industry to desulfurize flue gas. The dry desulfurization technology process has advantages such as low investment cost, small floor area, simple equipment structure, etc., and does not produce waste acid and waste water, and has less corrosion to equipment, and has good application prospects.

[0003] The desulfurization agents used in dry desulfurization technology mainly include calcium-based desulfurization agents, metals and supported metal oxides, etc. Among them, the Ca(OH)2 calcium-based desulfurization agent has a relatively low cost and good reactivity, and is the most widely studied and applied. However, traditional calcium-based desulfurization agents have problems such as poor strength, easy pulverization, easy sintering, low specific surface area, small diffusion rate of sulfide products, and low sulfur fixation efficiency. Researchers hope to improve the desulfurization efficiency by modifying the desulfurization agent, mainly by controlling the particle size, specific surface area, and pore structure of the calcium-based granular desulfurization agent. In addition, in addition to traditional flue gas pollutants such as SO2, the flue gas of biomass boilers also contains heavy metal pollutants such as Hg, As, Pb, Cd, Cr, etc. Among them, mercury and its compounds have characteristics such as high toxicity, bioaccumulation, and long-distance transportation, and have serious hazards to human health and the ecological environment. Mercury pollution has attracted global attention. The gaseous mercury in flue gas mainly exists in three forms: elemental mercury (Hg 0 ), oxidized mercury (Hg 2+ ), and particulate-bound mercury (Hg p ), among which Hg 0 has characteristics such as insoluble in water, easy to volatilize, and high chemical inertness. Hg 0 needs to be converted into Hg 2+ through a gas-solid two-phase catalytic oxidation reaction, and then the latter's solubility or easy adhesion is used to achieve removal. It has been found that manganese oxides (MnOx) have good catalytic oxidation and adsorption properties, especially amorphous Mn 4+ plays an important role in the removal of Hg 0 . Chemisorption dominates the entire Hg 0 capture reaction, and has a greater impact on the early adsorption stage and external diffusion process. Mn 4+ and chemisorbed oxygen are responsible for Hg0 It is oxidized to HgO. In addition, it is found that compared with alkali metal materials such as MgO, KCl, and NaCl, calcium-based materials exhibit relatively high HOMO energy levels and low Mulliken electronegativity, which is conducive to promoting their effective capture of HgCl2. Summary of the Invention

[0004] Aiming at the low-concentration SO2 and Hg 0 emission characteristics in biomass boilers, the present invention proposes a preparation method and application of a modified calcium hydroxide adsorbent with desulfurization and mercury co-removal effects. A novel Mn-doped Ca(OH)2 desulfurizer is prepared, and the dispersion characteristics of the calcium-based desulfurizer are improved through the synergistic modification of surfactants such as calcium lignosulfonate and polyether F-127, realizing the efficient co-removal of SO2 and Hg 0

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the objects of the present invention is to provide a preparation method of a modified calcium hydroxide adsorbent with desulfurization and mercury co-removal effects, including the following steps: adding a surfactant, calcium chloride, sodium hydroxide, and manganese nitrate solution to water and mixing them for primary digestion. After the reaction ends, it is dried, ground, and calcined to obtain a precursor. Adding the precursor to calcium lignosulfonate for secondary digestion and hydrothermal reaction, and centrifugally washing to obtain the modified calcium hydroxide adsorbent with desulfurization and mercury co-removal effects; wherein, the surfactant is polyoxyethylene polyoxypropylene ether triblock copolymer (F-127).

[0007] The present invention is produced by mixing an aqueous solution of calcium chloride and an aqueous solution of sodium hydroxide to produce Ca 2+ and OH - , doping F-127 and manganese nitrate to form a supersaturated solution of calcium hydroxide, and further calcining to generate Ca(OH)2 hydrated from CaO. Using F127 as a surfactant, the calcium-based adsorbent is modified by adding an appropriate amount of manganese, significantly improving the desulfurization and mercury removal effects of the adsorbent. The reason is that the transition metal oxide MnO2 has catalytic oxidation properties, which can oxidize SO2 into more active SO3, thereby reducing the reaction energy barrier. SO3 is converted into sulfate, thus realizing the desulfurization performance of the modified calcium hydroxide adsorbent; F127 as a surfactant is conducive to improving the dispersion of Mn in the adsorbent, making it evenly dispersed on the surface of calcium hydroxide to provide more reaction sites, thereby further improving the desulfurization and mercury removal efficiency of adsorption; the addition of the surface modifier is also conducive to making the adsorbent form a uniform flaky structure aggregate, thereby changing the growth morphology of Ca(OH)2 crystal particles and increasing the reaction rate of SO2.

[0008] ​Further, the mass concentration of the manganese nitrate solution is 50 wt% g.

[0009] In the modified calcium hydroxide adsorbent obtained in the present invention, the manganese is further optimized by regulating the mass and concentration of the manganese nitrate solution. When the addition amount of Mn is too high, the greater the doping amount of Mn, the higher the surface coverage rate of MnO2 on the calcium-based surface. Although the oxidation sites increase, the SO2 absorption sites will decrease, resulting in a reduction in the comprehensive desulfurization performance. Therefore, the mass concentration of the manganese nitrate solution is 50 wt%.

[0010] Optionally, the molar ratio of calcium chloride to sodium hydroxide is 1:1; and / or

[0011] the mass ratio of the surfactant to calcium chloride is 1:44.4; and / or

[0012] the mass ratio of calcium lignosulfonate to calcium chloride is 1:296.

[0013] Adding an appropriate amount of surfactant F127 can improve the dispersion of manganese, making it evenly dispersed on the surface of calcium hydroxide to provide more reaction sites.

[0014] Further, the conditions for the first digestion are: reacting at room temperature for 30 - 100 min.

[0015] Appropriate digestion temperature and digestion time are more conducive to the modification reaction. The appropriate digestion temperature enables the modified adsorbent to maintain a high desulfurization activity, thereby reducing the agglomeration effect. When the digestion time is insufficient, the reaction is likely to be incomplete; when it exceeds the critical digestion time, the desulfurizer will lose some of its activity. Therefore, the appropriate digestion temperature and digestion time are considered comprehensively from the aspects of economy and reaction rate.

[0016] Further, the conditions for the calcination are: heating at a heating rate of 10 °C / min to 400 - 600 °C and calcining for 3 - 6 h.

[0017] Treating the product after the first digestion under appropriate calcination conditions can remove the unreacted F127 by high-temperature calcination, completely decompose the manganese nitrate into manganese oxides, and incorporate them into the calcium oxide lattice structure, providing more active reaction sites for the active components and SO2.

[0018] Further, the conditions for the second digestion are: reacting at room temperature for 30 - 100 min.

[0019] Similar to the first digestion reaction, appropriate second digestion temperature and time ensure the highest desulfurization efficiency of calcium hydroxide and contribute to the progress of the desulfurization reaction.

[0020] Further, the conditions of the hydrothermal reaction are as follows: reacting at 100 - 150 °C for 100 - 200 min.

[0021] Appropriate hydrothermal time and hydrothermal temperature can achieve the regulation of the grain size of calcium hydroxide loaded with manganese oxide, while improving the dispersion degree and pore structure of the adsorbent. If the hydrothermal time is short, the reaction is insufficient and the desulfurization efficiency of the calcium-based desulfurizer is not high; however, blindly prolonging the hydrothermal time will cause waste of energy. Appropriate hydrothermal time can not only ensure sufficient reaction but also have good time economy.

[0022] The second object of the present invention is to provide a modified calcium hydroxide adsorbent prepared by using the above preparation method.

[0023] The third object of the present invention is to provide an application of the modified calcium hydroxide adsorbent in the field of desulfurization and co-removal of mercury.

[0024] In the modified calcium hydroxide adsorbent obtained in the present invention, MnO₂ has relatively high catalytic activity and high mercury adsorption capacity due to its relatively high Mn valence state. Its main action mechanism is to first use the catalytic oxidation performance of manganese-based oxides to oxidize Hg adsorbed on the surface 0 to Hg 2+ , and then use its own surface adsorbed oxygen to combine with Hg 2+ to fix mercury on the material surface; on the other hand, transition metal oxide MnO₂ has catalytic oxidation characteristics, can oxidize SO₂ into more active SO₃, thereby reducing the reaction energy barrier, and SO₃ is converted into sulfate, so as to realize the desulfurization performance of the modified calcium hydroxide adsorbent; the modified calcium hydroxide adsorbent prepared in the present invention can promote the dry desulfurization and co-removal of mercury reaction.

[0025] Compared with the prior art, the present invention has the following advantages and technical effects:

[0026] Based on the digestion method, the present invention fully mixes a manganese-containing solution and F127 into an aqueous solution synthesized from calcium hydroxide and calcium chloride, improving the dispersion of metallic manganese in the calcium hydroxide lattice and providing more reaction sites for SO₂. The method of secondary digestion is adopted to further improve the desulfurization efficiency. The modified calcium hydroxide adsorbent prepared in the present invention has reduced agglomeration, an optimized microstructure, a more abundant three-dimensional structure, and good dispersion, can achieve the removal of low-concentration SO₂, and can simultaneously remove mercury in a coordinated manner, which has important guiding significance for the efficient and economical removal of low-concentration SO₂.

[0027] The modified calcium hydroxide adsorbent with the function of synergistic desulfurization and mercury removal provided by the present invention can be used to efficiently remove low-concentration SO2, and can achieve the synergistic removal of heavy metal mercury, achieving the effect of synergistic desulfurization and mercury removal. It is generally applicable to the dry removal of medium and low-concentration SO2. Compared with other flue gas purification methods, it can achieve the efficient and economic removal of low-concentration SO2. Moreover, the equipment and instruments used in the present invention require simple requirements, wide material sources, and low prices. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0029] Figure 1 It is the X-ray diffraction (XRD) pattern of the calcium-based adsorbents prepared in Examples 1-4 of the present invention; wherein, (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4;

[0030] Figure 2 It is the scanning electron microscope (SEM) image of the calcium-based adsorbents prepared in Examples 1-4 of the present invention; wherein, (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4;

[0031] Figure 3 It is the EDS chemical element distribution image of the calcium-based adsorbent prepared in Example 4 of the present invention;

[0032] Figure 4 It is the change diagram of the SO2 concentration with the reaction time during the desulfurization process of the calcium-based adsorbents prepared in Examples 1-4 of the present invention;

[0033] Figure 5 It is the mercury removal efficiency diagram of the calcium-based adsorbents prepared in Examples 1-4 of the present invention during the mercury removal process;

[0034] Figure 6 It is the mercury removal efficiency diagram of the calcium-based desulfurizer prepared in Example 4 of the present invention under different concentrations of SO2 during the mercury removal process. DETAILED DESCRIPTION OF THE INVENTION

[0035] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation manners of the present invention.

[0036] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0037] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0038] Without departing from the scope or spirit of the present invention, various improvements and variations can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0039] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0040] An embodiment of the present invention provides a preparation method of a modified calcium hydroxide adsorbent with the function of desulfurization and mercury removal synergistically, comprising the following steps:

[0041] S1. Mix and stir F127, sodium hydroxide, calcium chloride and manganese acetate solution at room temperature (this process is the first digestion process), and after centrifuging the obtained solution, place it in an oven for drying to obtain the first precursor solid;

[0042] S2. Grind the first precursor solid into powder and calcine it in a muffle furnace to obtain the second precursor solid;

[0043] S3. Add the second precursor solid and calcium lignosulfonate into an aqueous solution for digestion again (this process is the second digestion), wash it alternately by centrifugation with ethanol and water, and place it in an oven for drying to obtain the modified calcium hydroxide adsorbent.

[0044] In some preferred embodiments, during the first digestion process, the mass of F127 added corresponding to every 8.88 g of calcium chloride is 0 - 0.5 g; in more preferred embodiments, the mass of the F127 is 0.2 g.

[0045] In some preferred embodiments, during the primary digestion process, the mass concentration of the manganese nitrate solution is 50 wt%.

[0046] In some preferred embodiments, the mass of the manganese nitrate solution is 0.393% of the mass of calcium chloride.

[0047] In some preferred embodiments, the temperature of the primary digestion is room temperature and the time is 30 - 100 min. Exemplarily, in the following embodiments of the present invention, the time of the primary digestion can be selected as 30 min.

[0048] In some preferred embodiments, the calcination is carried out by heating to 400 - 600 °C at a heating rate of 10 °C / min for 3 - 6 h. Exemplarily, in the following embodiments of the present invention, the calcination can be selected to heat to 500 °C at a heating rate of 10 °C / min for 4 h.

[0049] In some preferred embodiments, the temperature of the secondary digestion is room temperature and the time is 30 - 100 min. Exemplarily, in the following embodiments of the present invention, the time of the secondary digestion can be selected as 30 min.

[0050] In some preferred embodiments, the hydrothermal temperature is 100 - 150 °C and the time is 100 - 200 min. Exemplarily, in the following embodiments of the present invention, the hydrothermal temperature can be selected as 120 °C and the hydrothermal time can be selected as 180 min.

[0051] Since manganese modification is beneficial to regulating the crystal structure of calcium hydroxide, the introduction of F127 during the digestion process is beneficial to controlling the growth of calcium hydroxide and improving the dispersion of Mn on the surface of calcium hydroxide, thereby changing the morphology of calcium hydroxide, and can further improve the reaction rate and sulfur capacity of the desulfurizer. Therefore, the modified calcium hydroxide adsorbent prepared in the embodiments of the present invention can be used as a desulfurization and co - mercury removal absorbent.

[0052] Unless otherwise specified, the room temperature or normal temperature in the embodiments of the present invention both refer to 25 ± 3 °C.

[0053] Unless otherwise specified, the raw materials in the embodiments of the present invention are all obtained through commercial channels.

[0054] The technical solutions of the present invention are further described below through examples.

[0055] Example 1

[0056] A preparation method of a calcium hydroxide adsorbent includes the following steps:

[0057] (1) 8.88 g of calcium chloride and 3.2 g of sodium hydroxide were added to 70 mL of water, stirred at room temperature for 30 min, centrifuged, and then placed in an oven at 60 °C to obtain the first precursor solid;

[0058] (2) The first precursor solid was ground into powder, placed in a muffle furnace, heated to 500 °C at a heating rate of 10 °C / min and calcined for 4 h, and then naturally cooled to obtain the second precursor solid;

[0059] (3) The second precursor and 0.03 g of calcium lignosulfonate were added to 70 mL of water, stirred at room temperature for 30 min, then placed in a reaction kettle for hydrothermal treatment at 120 °C for 180 min. The obtained product was washed alternately with ethanol and water three times, and then placed in an oven at 60 °C and dried for 12 h to obtain calcium-based adsorbent-1.

[0060] Example 2

[0061] A preparation method of a modified calcium hydroxide adsorbent, comprising the following steps:

[0062] (1) 8.88 g of calcium chloride, 0.2 g of F127 and 3.2 g of sodium hydroxide were added to 70 mL of water, stirred at room temperature for 30 min, centrifuged, and then placed in an oven at 60 °C to obtain the first precursor solid;

[0063] (2) The first precursor solid was ground into powder, placed in a muffle furnace, heated to 500 °C at a heating rate of 10 °C / min and calcined for 4 h, and then naturally cooled to obtain the second precursor solid;

[0064] (3) The second precursor and 0.03 g of calcium lignosulfonate were added to 70 mL of water, stirred at room temperature for 30 min, then placed in a reaction kettle for hydrothermal treatment at 120 °C for 180 min. The obtained product was washed alternately with ethanol and water three times, and then placed in an oven at 60 °C and dried for 12 h to obtain calcium-based adsorbent-2.

[0065] Example 3

[0066] A preparation method of a modified calcium hydroxide adsorbent, comprising the following steps:

[0067] (1) 8.88 g of calcium chloride, 45 μl of manganese nitrate solution (mass concentration of 50 wt%) and 3.2 g of sodium hydroxide were added to 70 mL of water, stirred at room temperature for 30 min, centrifuged, and then placed in an oven at 60 °C to obtain the first precursor solid;

[0068] (2) The first precursor solid was ground into powder, placed in a muffle furnace, heated to 500 °C at a heating rate of 10 °C / min and calcined for 4 h, and then naturally cooled to obtain the second precursor solid;

[0069] (3) Add the second precursor and 0.03 g of calcium lignosulfonate to 70 mL of water, stir at room temperature for 30 min, then place it in a reaction kettle for hydrothermal treatment at 120 °C for 180 min. Wash the obtained product alternately with ethanol and water three times, and place it in an oven at 60 °C to dry for 12 h to obtain calcium-based adsorbent-3.

[0070] Example 4

[0071] A preparation method of a modified calcium hydroxide adsorbent, comprising the following steps:

[0072] (1) Add 8.88 g of calcium chloride, 45 μL of manganese nitrate solution (mass concentration of 50 wt%), 0.2 g of F127, and 3.2 g of sodium hydroxide to 70 mL of water, stir at room temperature for 30 min, centrifuge, and then place it in an oven at 60 °C to obtain the first precursor solid.

[0073] (2) Grind the first precursor solid into powder, place it in a muffle furnace, heat it at a heating rate of 10 °C / min to 500 °C, calcine for 4 h, and naturally cool to obtain the second precursor solid.

[0074] (3) Add the second precursor and calcium lignosulfonate to 70 mL of water, stir at room temperature for 30 min, then place it in a reaction kettle for hydrothermal treatment at 120 °C for 180 min. Wash the obtained product alternately with ethanol and water three times, and place it in an oven at 60 °C to dry for 12 h to obtain calcium-based adsorbent-4.

[0075] Comparative Example 1

[0076] Same as Example 4, the difference is that F127 is replaced with polyoxyethylene fatty acid ester in equal mass.

[0077] Performance test

[0078] 1. Perform X-ray diffraction (XRD) characterization on the calcium-based adsorbent materials prepared in Examples 1-4. The characterization results are as Figure 1 shown. Figure 1 In which (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4. Comparing Figure 1 (a), (b), (c), and (d) in it, it can be seen that the introduction of F127 and Mn does not significantly change the crystal structure of Ca(OH)2, but significantly inhibits the rapid growth of Ca(OH)2 grains, reduces the grain size of the calcium-based desulfurizer, and thus is beneficial to enhancing the desulfurization reaction activity.

[0079] 2. Perform scanning electron microscopy (HRTEM) characterization on the calcium-based adsorbents prepared in Examples 1-4. The characterization results are as Figure 2 shown. Figure 2In (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4. As can be seen from the figure, there are a large number of aggregates in Ca(OH)2. The introduction of F127 reduces the particle size; the addition of Mn optimizes the microstructure and forms a partially dispersed structure; the co-introduction of F127 and Mn makes the structure looser and has better dispersibility.

[0080] 3. The EDS chemical element distribution images of the calcium-based adsorbent prepared in Example 4 were taken, and the characterization results are as Figure 3 shown. As can be seen from the figure, the uniform distribution of Ca, O, and Mn elements in the calcium-based desulfurizer indicates that Mn was successfully added to the calcium-based desulfurizer.

[0081] 4. The specific surface area (BET) and pore volume of the calcium-based adsorbents prepared in Examples 1-4 were characterized, and the characterization results are shown in Table 1.

[0082] Table 1

[0083]

[0084] As can be seen from Table 1, the specific surface area of Ca(OH)2 doped with Mn and F127 is lower than that of Ca(OH)2 doped only with Mn, but the desulfurization ability of Ca(OH)2 doped with Mn and F127 is higher than that of Ca(OH)2 doped with Mn, indicating that the specific surface area is not the only factor affecting the desulfurization effect. After Ca(OH)2 is doped with F127, the pore volume increases, and after further doping with Mn, the pore volume decreases, improving the pore structure and increasing the number of active sites.

[0085] 5. The dry desulfurization performance of the calcium-based adsorbents obtained in Examples 1-4 and Comparative Example 1 was tested, and the test results are as Figure 4 shown. Specifically, the reaction conditions during the test were: the SO2 concentration was 400 ppm, the O2 volume concentration was 4 vol.%, N2 was used as the balance gas, the simulated flue gas flow rate was 1 L / min, the desulfurizer loading was 0.3 g, and the reaction temperature was 350 °C. The SO2 concentration after dry desulfurization was detected by a flue gas analyzer to calculate the desulfurization efficiency, and the desulfurization performance of the calcium-based desulfurizer was evaluated by the SO2 breakthrough time. From Figure 4 it can be seen that the introduction of F127 reduces the particle size, but the promotion effect on SO2 is not obvious and the absorption sites are similar to those of Ca(OH)2, so it does not promote SO2 absorption; the SO2 breakthrough time of Ca(OH)2 after adding Mn was successfully extended; the increase in the desulfurization efficiency of Ca(OH)2 co-doped with Mn and F127 indicates that F127 has a dispersing effect on the distribution of Mn in Ca(OH)2; the desulfurization efficiency of the calcium-based desulfurizer doped with polyoxyethylene fatty acid ester and Mn is lower than that of the calcium-based desulfurizer doped with F127 and Mn, indicating that only F127 has a dispersing effect on Mn to improve the desulfurization efficiency.

[0086] 6. The mercury removal performance of the calcium-based sorbents prepared in Examples 1-4 and Comparative Example 1 was tested, and the test results are as Figure 5 shown. Specifically, during the test, the reaction conditions were a Hg concentration of 70 μg / m 3 , an O2 concentration of 4 vol.%, N2 as the balance gas, a simulated flue gas flow rate of 1000 mL / min, a desulfurizer loading of 0.3 g, and a reaction temperature of 350 °C. The concentration of Hg before and after mercury removal was detected by a mercury analyzer, and the mercury removal efficiency was calculated to evaluate the mercury removal performance of the Ca-Mn desulfurizer. 0

[0087] Mercury removal efficiency = (inlet mercury concentration - outlet mercury concentration) / inlet mercury concentration × 100%;

[0088] From Figure 5 it can be seen that the calcium hydroxide desulfurizer has a synergistic mercury removal performance; the addition of the surfactant F127 helps to improve the micro-morphology and pore structure of the calcium-based desulfurizer, thereby providing more Hg adsorption-oxidation sites. The Mn element usually has good oxidation performance, which promotes the synergistic mercury removal performance of the calcium-based desulfurizer; the mercury removal performance of the calcium-based sorbent doped with polyoxyethylene fatty acid ester and Mn is lower than that of the calcium-based sulfur sorbent with F127 and Mn, indicating that only F127 has a dispersing effect on Mn, thereby improving the mercury removal efficiency.

[0089] 7. The mercury removal performance of the calcium-based desulfurizer prepared in Example 4 was tested at different SO2 concentrations. Specifically, during the test, the reaction conditions were a Hg concentration of 70 μg / m 3 , an O2 concentration of 4 vol.%, N2 as the balance gas, a simulated flue gas flow rate of 1000 mL / min, a calcium-based desulfurizer loading of 0.3 g, a reaction temperature of 350 °C, and SO2 concentrations of 300, 400, and 500 ppm, respectively. The concentration of Hg before and after mercury removal was detected by a mercury analyzer, and the mercury removal efficiency was calculated to evaluate the mercury removal performance of the manganese-modified calcium-based desulfurizer. The test results are as 0 shown. From Figure 6 it can be seen that as the SO2 concentration in the simulated flue gas increases, the synergistic mercury removal efficiency of the calcium-based desulfurizer prepared in Example 4 gradually decreases. SO2 has an inhibitory effect on the synergistic mercury removal of the calcium-based desulfurizer. The reason may be that SO2 causes the rapid sulfidation of the calcium-based desulfurizer, thereby reducing the adsorption-reaction sites of Hg Figure 6 . However, when the SO2 concentration increases from 300 ppm to 500 ppm, the synergistic mercury removal efficiency of the calcium-based desulfurizer only decreases by 3.7%, indicating that the prepared desulfurizer still has good synergistic desulfurization and mercury removal performance. 0

[0090] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A preparation method of a modified calcium hydroxide adsorbent with the function of desulfurization and synergistic mercury removal, characterized in that, It includes the following steps: Add a surfactant, calcium chloride, sodium hydroxide, and a manganese nitrate solution to water, mix them, and conduct a primary digestion. After the reaction ends, dry, grind, and calcine to obtain a precursor. Add the precursor to calcium lignosulfonate for a secondary digestion and a hydrothermal reaction, and after centrifugal washing, obtain the modified calcium hydroxide adsorbent with the function of synergistic desulfurization and mercury removal; wherein, the surfactant is a polyoxyethylene polyoxypropylene ether triblock copolymer.

2. The preparation method of the modified calcium hydroxide adsorbent with the function of desulfurization and mercury co-removal according to claim 1, characterized in that, The mass concentration of the manganese nitrate solution is 50 wt%; the mass of the manganese nitrate solution is 0.393% of the mass of calcium chloride.

3. The preparation method of the modified calcium hydroxide adsorbent with the function of synergistic desulfurization and mercury removal according to claim 1, characterized in that The molar ratio of calcium chloride to sodium hydroxide is 1:1; and / or The mass ratio of the surfactant to calcium chloride is 1:44.4; and / or The mass ratio of calcium lignosulfonate to calcium chloride is 1:

296.

4. The preparation method of the modified calcium hydroxide adsorbent with the function of synergistic desulfurization and mercury removal according to claim 1, characterized in that, The conditions for the primary digestion are: react at room temperature for 30 - 100 min.

5. The preparation method of the modified calcium hydroxide adsorbent with the function of desulfurization and synergistic mercury removal according to claim 1, characterized in that, The conditions for the calcination are: heat up to 400 - 600 °C at a heating rate of 10 °C / min and calcine for 3 - 6 h.

6. The preparation method of the modified calcium hydroxide adsorbent with the function of desulfurization and mercury co-removal according to claim 1, characterized in that, The conditions for the secondary digestion are: react at room temperature for 30 - 100 min.

7. The preparation method of the modified calcium hydroxide adsorbent with the function of desulfurization and synergistic mercury removal according to claim 1, characterized in that, The conditions for the hydrothermal reaction are: react at 100 - 150 °C for 100 - 200 min.

8. A modified calcium hydroxide adsorbent prepared by using the preparation method according to any one of claims 1 - 7.

9. An application of the modified calcium hydroxide adsorbent according to claim 8 in the field of synergistic desulfurization and mercury removal.

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