Mercury adsorbent, method of preparation and use

Abstract

The application provides a mercury adsorbent, a preparation method and application. The mercury adsorbent is a mesoporous material, and the mercury adsorbent comprises cobalt sulfide and biomass charcoal. The cobalt sulfide is loaded on the biomass charcoal, the cobalt sulfide is CoS2, and the mass percentage of the cobalt sulfide is 10-70%. The mercury adsorbent has the following advantages: the cobalt sulfide is uniformly dispersed, the mesoporous pore size of the mercury adsorbent is larger than the micropore size, the diffusion of mercury Hg is promoted, the mercury Hg is fully contacted with the cobalt sulfide, and the mercury Hg is adsorbed by the cobalt sulfide, so that the mercury adsorption capacity of the mercury adsorbent is improved. The mercury adsorbent has a high mercury adsorption capacity, and can effectively adsorb mercury.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of mercury removal, in particular to a mercury adsorbent, a preparation method and application thereof. BACKGROUND

[0002] In the mercury-containing flue gas, there are three different forms of mercury: particulate mercury Hg(p), oxidized mercury (Hg 2+ ), and elemental mercury (Hg 0 ). Among them, elemental mercury is inert and difficult to capture.

[0003] In order to effectively capture elemental mercury, it is necessary to provide an adsorbent with high mercury adsorption capacity. In some related technologies, a composite adsorbent mercury CoS2 / PC (porous carbon) is used as an adsorbent. The mercury adsorption capacity of this adsorbent is relatively small. The mercury adsorption capacity of the composite adsorbent is determined by the content of the surface adsorption active site. It is considered to increase the CoS2 content on the carbon carrier by increasing the impregnation amount of cobalt nitrate, so as to increase the mercury adsorption capacity. However, the mercury removal efficiency of CoS2 / PC is reduced. SUMMARY

[0004] The main purpose of the present application is to provide a mercury adsorbent, a preparation method and application thereof, so as to solve the technical problem of relatively low mercury adsorption capacity of the adsorbent.

[0005] To achieve the above-mentioned purpose, the present application provides a mercury adsorbent. The mercury adsorbent is a mesoporous material. The mercury adsorbent comprises a cobalt sulfide and a biomass carbon. The cobalt sulfide is loaded on the biomass carbon. The cobalt sulfide is CoS2. The mass percentage of the cobalt sulfide is 10-70%.

[0006] According to the embodiment of the present application, the mass percentage of the cobalt sulfide is 40-60%.

[0007] The present application further provides a preparation method of a mercury adsorbent, comprising the following steps:

[0008] The cobalt-containing gel is frozen and freeze-dried to obtain a freeze-dried material. The cobalt-containing gel comprises water, a cobalt salt and a saccharide substance. The mass ratio of the cobalt salt and the saccharide substance is 1:5-16. The cobalt salt comprises at least one of cobalt nitrate, cobalt acetate and cobalt sulfate. The saccharide substance comprises at least one of starch, sucrose and glucose.

[0009] The freeze-dried material is carbonized under the condition of a protective gas to obtain a carbonized material.

[0010] The carbonized material is oxidized at 300-400℃ for 0.5-2 hours to obtain an oxidized material.

[0011] The oxidized material is mixed with elemental sulfur by grinding, and then is heated at 300-500°C for 1-4 hours under a protective gas to obtain the mercury adsorbent. The mass ratio of the oxidized material to elemental sulfur is 1:0.5-9.

[0012] According to an embodiment of the present application, the step of freezing the cobalt-containing gel and lyophilizing the frozen material comprises:

[0013] The cobalt-containing gel is placed at -20°C for 1-5 hours to obtain a frozen material.

[0014] The frozen material is subjected to lyophilization for 24-72 hours.

[0015] According to an embodiment of the present application, the step of carbonizing the lyophilized material under a protective gas comprises:

[0016] The lyophilized material is carbonized under a protective gas to obtain a carbonized material.

[0017] According to an embodiment of the present application, the step of oxidizing the carbonized material at 300-400°C for 0.5-2 hours comprises:

[0018] The carbonized material is oxidized in air at 350°C for 1 hour.

[0019] According to an embodiment of the present application, the step of mixing the oxidized material with elemental sulfur by grinding and heating at 400°C for 2 hours under a protective gas comprises:

[0020] The oxidized material is mixed with elemental sulfur by grinding, and then is heated at 400°C for 2 hours under N2 atmosphere at a heating rate of 5-20°C / min.

[0021] According to an embodiment of the present application, the method for preparing the cobalt-containing gel comprises:

[0022] The aqueous cobalt salt solution and the saccharide are mixed, and then are stirred at 80-100°C for 20-60 minutes, and are aged for 10-20 hours to obtain the cobalt-containing gel.

[0023] The application of the mercury adsorbent obtained by the above method to the treatment of mercury-containing flue gas.

[0024] According to an embodiment of the present application, the temperature of the mercury-containing flue gas is 25-100°C. And / or;

[0025] The mercury-containing flue gas comprises at least one of N2, O2, SO2, NO, HCl and H2O.

[0026] The mercury adsorbent has uniformly dispersed cobalt sulfide, and the mesopore size of the mercury adsorbent is larger than the micropore size, which can promote the adsorption of mercury element Hg 0The mercury adsorbent is in full contact with the cobalt sulfide, and is adsorbed by the cobalt sulfide, so that the mercury adsorption capacity of the mercury adsorbent is improved. The mercury adsorbent has high mercury adsorption capacity, and can effectively adsorb elemental mercury. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings shown.

[0028] Figure 1 is an XRD diffraction pattern of CoS2-fx prepared at different calcination temperatures according to an embodiment of the present application;

[0029] Figure 2 is an XRD diffraction pattern of CoS2-f 350 prepared by calcination at 350°C according to an embodiment of the present application;

[0030] Figure 3 is a nitrogen adsorption-desorption isotherm curve of CoS2-f 350 according to an embodiment of the present application;

[0031] Figure 4 is a pore size distribution graph of CoS2-f 350 according to an embodiment of the present application;

[0032] Figure 5 is an SEM graph of CoS2-fx prepared at different calcination temperatures according to an embodiment of the present application;

[0033] Figure 6 is an SEM graph of CoS2-f 350 according to an embodiment of the present application;

[0034] Figure 7 is an HR-TEM graph of CoS2-f 350 according to an embodiment of the present application;

[0035] Figure 8 is a mapping graph and an eds graph of CoS2-f 350 according to an embodiment of the present application;

[0036] Figure 9 is a curve graph of the influence of calcination temperature on the Hg0 removal performance of CoS2-fx according to an embodiment of the present application;

[0037] Figure 10 is a curve graph of the Hg0 removal performance of CoS2-f 350 at different temperatures in N2 according to an embodiment of the present application;

[0038] Figure 11is a plot of the desulfurization performance of CoS2-f 350 under different atmospheres according to an embodiment of the present application;

[0039] Figure 12 is a plot of the long time saturated adsorption curve of CoS2-f 350 according to an embodiment of the present application.

[0040] The object, the functional characteristics and the advantages of the present application will be further described in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0042] It should be noted that all the directional indications (such as up, down, and the like) in the embodiments of the present application are only used to explain the relative position relationship, movement condition and the like between components in a certain posture (as shown in the accompanying drawings), and if the certain posture changes, the directional indications also change accordingly.

[0043] In addition, the descriptions such as “first”, “second” and the like in the present application are only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined with “first”, “second” can explicitly or implicitly include at least one of the features.

[0044] In addition, the technical solutions of the various embodiments of the present application can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it, and when the combination of technical solutions appears to be contradictory or unachievable, it should be considered that the combination of technical solutions does not exist and is not within the protection scope required by the present application.

[0045] The applicant found through a large number of studies that the preparation process of CoS2 / PC is to immerse cobalt nitrate in porous carbon PC, and then convert cobalt nitrate into CoS2 through a sulfidation reaction. In this direct loading method, CoS2 is mostly generated in the pores of the porous carbon. When the amount of CoS2 generated increases to a certain extent, it will cause the pores of the porous carbon carrier to be blocked, reducing the exposure of active substances. Therefore, in actual experiments, when the CoS2 content is increased to about 10wt% (based on the total mass of CoS2 / PC), the mercury adsorption capacity of the adsorbent will actually decrease.

[0046] Based on this, the application provides a mercury adsorbent, the mercury adsorbent is a mesoporous material, the mercury adsorbent comprises a cobalt sulfide and a biomass charcoal, the cobalt sulfide is loaded on the biomass charcoal, the cobalt sulfide is CoS2, and the mass percentage of the cobalt sulfide is 10-70%.

[0047] The mesoporous material refers to a kind of porous material with a pore size of 2-50 nm according to the provisions of International Union of Pure and Applied Chemistry (IUPAC). The mercury adsorbent is a porous structure, and the pore size meets the condition of 2-50 nm, which is a mesoporous material.

[0048] In the mercury adsorbent, the biomass charcoal is a substrate, and the cobalt sulfide is uniformly loaded on the substrate. The biomass charcoal is a porous material, which is a mesoporous material.

[0049] The mercury adsorbent is tested by XRD, and the results show that the characteristic peaks are obvious, and each diffraction peak corresponds to each crystal face of the cubic CoS2, indicating that the cobalt sulfide is cubic CoS2.

[0050] The microstructure and structure of the mercury adsorbent are analyzed by SEM and HR-TEM. The mercury adsorbent has an irregular block structure. In the HR-TEM image, clear lattice fringes can be observed, Figure 8 indicating that the crystal grows regularly to form a long-range ordered structure, and the interplanar spacing is 0.273 nm, corresponding to the (200) plane of the CoS2 phase, which is consistent with the XRD analysis result. The element distribution map shows the existence of Co and S elements, and the eds point scanning energy spectrum map shows that the atomic ratio of Co and S is close to 1:2, confirming that the surface material of the mesoporous adsorbent is CoS2.

[0051] The mass percentage of the cobalt sulfide can be tested by microwave digestion and ICP-MS to obtain the content of cobalt element, and then the content of the cobalt sulfide in the composite adsorbent is calculated according to the molar ratio of cobalt to sulfur.

[0052] The above-mentioned mercury adsorbent has uniformly dispersed cobalt sulfide, and the mesoporous pore size of the mercury adsorbent is larger than that of the micropore, which can promote the diffusion of mercury Hg 0 0 and fully contact with the cobalt sulfide, so that the mercury Hg 0 is adsorbed by the cobalt sulfide, thereby improving the mercury adsorption capacity of the mercury adsorbent. The above-mentioned mercury adsorbent has high mercury adsorption capacity and can effectively adsorb mercury.

[0053] According to the embodiments of the application, the mass percentage of the cobalt sulfide is 40-60%.

[0054] The application also provides a preparation method of the mercury adsorbent, comprising the following steps:

[0055] S110: freeze and lyophilize the cobalt-containing gel to obtain a lyophilized material; the cobalt-containing gel comprises water, a cobalt salt and a saccharide substance, the mass ratio of the cobalt salt and the saccharide substance is 1:5-16; the cobalt salt comprises at least one of cobalt nitrate, cobalt acetate and cobalt sulfate; the saccharide substance comprises at least one of starch, sucrose and glucose.

[0056] In this step, the cobalt salt is a substrate for generating cobalt sulfide. Specifically, the cobalt salt is converted into cobalt oxide in the carbonization and oxidation process, and then the cobalt oxide reacts with sulfur to generate CoS2 in the sulfidation process. Cobalt nitrate, cobalt acetate and cobalt sulfate can all be converted into cobalt oxide in the carbonization and oxidation process, and therefore the cobalt salt can be selected from at least one of cobalt nitrate, cobalt acetate and cobalt sulfate.

[0057] The saccharide substance is a substrate for generating biomass charcoal. The organic macromolecules of starch, sucrose and lignin are dissolved or dispersed in water and then cooled to obtain a gel. Both starch and sucrose can be subsequently carbonized. Therefore, the saccharide substance can be selected from at least one of starch, sucrose and glucose.

[0058] In the cobalt-containing gel, the cobalt salt and the saccharide substance are uniformly mixed, which helps to uniformly load the cobalt sulfide in the final product, the mercury adsorbent, on the biomass charcoal. The preparation method of the cobalt-containing gel is not limited.

[0059] The cobalt-containing gel is frozen to convert the water therein into ice. Exemplarily, the cobalt-containing gel is frozen below 0°C, such as in a freezing device. Exemplarily, the cobalt-containing gel is frozen by rapidly drawing a vacuum in a drying chamber.

[0060] Lyophilization, also known as sublimation drying, is a drying method in which ice is converted into vapor to be removed under a relatively high vacuum. In the embodiments of the present application, the ice in the frozen cobalt-containing gel is directly converted into vapor to be removed. During the freezing process of the cobalt-containing gel, the water expands when it freezes, and during the lyophilization process, the water evaporates, so that the channels formed have a larger pore size than micropores, which are mesopores. This can be one of the reasons for the formation of mesopores in the mercury adsorbent.

[0061] S120: carbonize the lyophilized material under the condition of a protective gas to obtain a carbonized material.

[0062] In this step, the protective gas can be nitrogen or an inert gas. Solid or organic matter is heated to decompose under air isolation, or a way of heating solid matter to produce liquid or gaseous (usually solid) products.

[0063] S130: oxidize the carbonized material at 300-400°C for 0.5-2 hours to obtain an oxidized material.

[0064] In this step, the carbonized material is subjected to an oxidation reaction, i.e., the carbonized material is subjected to a reaction in the presence of oxygen (e.g., in air or other oxygen-containing gas atmosphere).

[0065] When the oxidation reaction temperature is low, the characteristic peaks of the product obtained by subsequent vulcanization reaction are weak, which may be due to the fact that the material particles are too small, i.e., belong to the nanometer level. When the oxidation reaction temperature is too high, e.g., 600°C, the XRD result of the product obtained by subsequent vulcanization reaction shows that, in addition to the characteristic peaks of CoS2, there are also characteristic peaks of CoOx, which is presumably due to the fact that high-temperature calcination affects the redox property of the precursor, resulting in incomplete subsequent vulcanization.

[0066] S140: grinding and mixing the oxidized material with elemental sulfur, and obtaining the mercury adsorbent by heat preservation at 300-500°C for 1-4 hours in the presence of a protective gas; the mass ratio of the oxidized material to the elemental sulfur is 1:0.5-9.

[0067] In this step, grinding and mixing not only makes the particles of the oxidized material and the elemental sulfur small, but also makes the two substances in close contact, thereby facilitating the reaction of the oxidized material and the elemental sulfur.

[0068] In the above preparation method of the mercury adsorbent, the cobalt salt and the sugar substance are uniformly mixed in the cobalt-containing gel, and then carbonization is performed to form the carbonized material. Therefore, the cobalt salt is added into the system before the channels of the carbonized material are formed, and is in a highly dispersed state. During the freezing process, the water in the organic molecules will freeze and expand, and the ice will evaporate during the freeze-drying process, thereby leaving a large number of mesoporous structures in the freeze-dried gel. These mesopores are retained during the carbonization process, thereby obtaining an adsorbent with mesoporous structures, which avoids reducing the exposure of active sites. The sulfur vulcanization reaction temperature is higher than the sulfur evaporation temperature, and thus, during the vulcanization process, the sulfur other than the sulfur that reacts with cobalt oxide will evaporate, and thus will not block the channels.

[0069] In some embodiments, the step of freeze-drying the cobalt-containing gel after freezing comprises:

[0070] S111: placing the cobalt-containing gel at -20°C for 1-5 hours to obtain a frozen material.

[0071] Under this condition, the cobalt-containing gel can be completely frozen, and local incomplete freezing can be avoided, which is conducive to the uniform distribution of mesopores in the final product.

[0072] S112: freeze-drying the frozen material for 24-72 hours.

[0073] Under this condition, the ice in the frozen material is completely evaporated, and channels are formed.

[0074] In some embodiments, the step of carbonizing the freeze-dried material under a protective gas comprises:

[0075] The freeze-dried material is carbonized at 400-800°C for 0.5-3 hours under N2 atmosphere. Under this condition, the freeze-dried material is carbonized more completely, and the carbonized material formed has a uniform pore distribution, which is beneficial to the formation of mesoporous adsorbents. Illustratively, the freeze-dried material is carbonized at 600°C for 1 hour under N2 atmosphere.

[0076] In some embodiments, the step of oxidizing the carbonized material at 300-400°C for 0.5-2 hours comprises:

[0077] The carbonized material is oxidized in air at 350°C for 1 hour.

[0078] In this step, the carbonized material is oxidized in air, which reduces the production cost. The calcination temperature in the preparation process has a great influence on the Hg removal activity of mesoporous adsorbents 0 The Hg removal activity of mesoporous adsorbents prepared by oxidizing at 350°C for 1 hour is high, and the mercury adsorption capacity is large. 0 The Hg removal activity of mesoporous adsorbents prepared by oxidizing at 350°C for 1 hour is high, and the mercury adsorption capacity is large.

[0079] In order to improve the rate and effect of the oxidation reaction, in some embodiments, the carbonized material is further broken up, such as grinding, before oxidation.

[0080] In some embodiments, the step of mixing the oxidized material with elemental sulfur by grinding and heating at 400°C for 2 hours under a protective gas comprises:

[0081] The oxidized material and elemental sulfur are mixed by grinding and heated to 400°C at a heating rate of 5-20°C / min under N2 atmosphere for 2 hours.

[0082] This heating rate can reduce the influence of carbonization on the pore structure, and generally industrial furnaces can only withstand this range of heating rates.

[0083] In some embodiments, the method for preparing the cobalt-containing gel comprises:

[0084] The cobalt salt aqueous solution and the saccharide material are mixed and stirred at 80-100°C for 20-60 minutes, and then aged for 10-20 hours to obtain the cobalt-containing gel. Illustratively, a cobalt nitrate aqueous solution and starch are mixed and stirred at 90°C for 30 minutes, and then aged for 20 hours to obtain the cobalt-containing gel. Aging is to allow the hot starch gel to cool and form a gel solid like jelly, and there is no requirement for the type and degree of polymerization of the starch.

[0085] The application also provides application of the mercury adsorbent or the mercury adsorbent prepared by the preparation method in treatment of mercury-containing flue gas.

[0086] In some embodiments, the temperature of the mercury-containing flue gas is 25-100°C. In this embodiment, the mercury adsorbent has better mercury removal performance. Illustratively, the temperature of the mercury-containing flue gas is 50°C, and the mercury adsorbent has better mercury removal performance.

[0087] In some embodiments, the mercury-containing flue gas at least contains one of O2, SO2, NO and HCl. O2, SO2, NO and HCl in the flue gas all promote the removal of Hg 0 have a promoting effect.

[0088] Example 1

[0089] 0.0015 mol (0.4365 g) of cobalt nitrate was weighed and dissolved in 50 ml of deionized water, and ultrasonic treatment was performed for 5 minutes; 5 g of starch was added, and stirring was performed at 90°C for 30 minutes. The mixture was poured into a culture dish and aged for 20 hours to obtain a cobalt-containing gel.

[0090] The cobalt-containing gel was placed in a refrigerator and frozen for 20 hours, and after complete freezing, the gel was placed in a freeze dryer and freeze-dried for 72 hours to obtain a freeze-dried material.

[0091] The freeze-dried material was carbonized at 600°C for 1 hour under N2 atmosphere to obtain a carbonized material.

[0092] The carbonized material was ground and then oxidized in air at 0°C, 200°C, 300°C, 350°C, 400°C and 600°C respectively for 1 hour to obtain corresponding oxidized materials.

[0093] Each of the oxidized materials was further mixed with 0.24 g of sulfur to obtain a product, wherein the mass percentage of cobalt sulfide was 0°C (60%), 200°C (56%), 300°C (53%), 350°C (50%), 400°C (45%) and 600°C (40%). For the convenience of description, the corresponding products were named as CoS2-fx (f represents freeze-drying; x represents the calcination temperature, for example, CoS2-f 350 is the carbonized material calcined at 350°C and then sulfidized to form).

[0094] Test Example 1

[0095] XRD was used to analyze the phase structure of each product, and the results are shown in Table 1. Figure 1The characteristic peaks of the products synthesized at 0, 200, 300, 350, 400°C, respectively, and the products after calcination at 0 and 200°C and sulfuration are weak, which may be due to the small particle size of the material, which is in the nanometer range. As the calcination temperature increases, the characteristic peaks become more obvious, and the peak intensity increases significantly. The diffraction peaks correspond to the crystal faces of the cubic CoS2 phase. CoS2 is successfully loaded on the carbon substrate by freeze-drying. The XRD results of the product calcined at 600°C show that, in addition to the characteristic peaks of CoS2, there are also characteristic peaks of CoOx, which is speculated to be due to the influence of high-temperature calcination on the redox properties of the precursor, resulting in incomplete sulfuration.

[0096] As Figure 2 mentioned, the multiple diffraction peaks at 27.8°, 32.3°, 36.2°, 39.8°, 46.3°, 54.9°, 60.1°, and 62.7° correspond to the (111), (200), (210), (211), (220), (311), (023), and (321) crystal faces of the cubic CoS2 phase, confirming that the synthesized product is a composite material of CoS2 and carbon.

[0097] Test Example 2

[0098] The specific surface area, pore volume, pore size, and other physical properties of CoS2-f 350 were analyzed, as shown in Figure 3 and Figure 4 The nitrogen adsorption-desorption curve of CoS2-f 350 shows capillary condensation at a high P / P0, and the desorption isotherm does not coincide with the adsorption isotherm, resulting in a hysteresis loop, which is a type IV isotherm. The specific surface area is 96.5 m2 / g, the total pore volume is 0.183 cm3 / g, and the average pore size is 8.1427 nm. According to the IUPAC classification of pores, a pore size of 2-50 nm is defined as a mesopore. This indicates that CoS2-f 350 is a typical mesoporous material.

[0099] Test Example 3

[0100] The microstructure and structure of CoS2-fx were analyzed by SEM and HR-TEM, as shown in Figures 5 to 8 CoS2-fx has an irregular block structure. As the calcination temperature increases, large particles appear on the surface of the material, which may be due to the agglomeration of CoS2 nanoparticles. In the HR-TEM image, clear lattice fringes Figure 7 can be observed, indicating that the crystal grows regularly to form a long-range ordered structure, and the crystal face spacing is 0.273 nm, corresponding to the (200) plane of the CoS2 phase, which is consistent with the XRD analysis results. Referring to Figure 8 , the elemental distribution map shows the presence of Co and S elements, and the eds point scanning energy spectrum shows that the atomic ratio of Co and S is close to 1:2, confirming that the surface material of the mesoporous adsorbent is CoS2.

[0101] Example 2

[0102] The corresponding flue gas was configured, and the corresponding to-be-tested substance was placed in the tank body to obtain an absorption tank. The mass of the to-be-tested substance was recorded. Then the absorption tank was placed in the flue gas for absorption, and the mass of the absorption tank before and after the flue gas absorption was weighed. In this way, the mercury removal performance of the to-be-tested substance was calculated. The following examples were tested in this way.

[0103] Referring to Figure 9 , in this example, the flue gas was composed of pure N2 and Hg 0 , wherein the concentration of Hg 0 was 200 μg / m 3 .

[0104] Under the condition that the flue gas temperature was 50°C, the influence of the calcination temperature in the preparation process of the adsorbent on the mercury removal performance was explored.

[0105] Referring to Figure 10 , the Hg 0 removal ability of CoS2-fx prepared without calcination and at 200°C was weak, the highest Hg 0 removal efficiency was only 80%-90%, the mercury removal efficiency decreased rapidly after 2 minutes, and the mercury removal efficiency decreased to 45% at 15 minutes and 30 minutes; the initial Hg 0 removal efficiency of CoS2-fx prepared by calcination at 300-400°C was 100%, but the mercury removal efficiency of CoS2-f 400 began to decrease after 60 minutes, the mercury removal performance was poor, CoS2-f 350 had a very strong Hg 0 removal ability, and the mercury removal efficiency was as high as 100% at 120 minutes, and the Hg 0 removal ability was stable for a long time. The highest mercury removal efficiency of CoS2-f 600 was less than 5%, and the mercury removal performance was very poor. On the one hand, the sulfuration was not complete, and there were CoOx impurities, which was consistent with the previous XRD results. On the other hand, the high-temperature calcination caused the serious agglomeration of the active particles on the material surface, and the active particles and Hg 0 had a small effective contact area, which was also confirmed by the TEM results. The mercury removal performance of CoS2-f 350 was obviously better than that of other CoS2-fx, which indicated that the calcination temperature in the preparation process had a great influence on the Hg 0 removal activity of the mesoporous adsorbent. This may be caused by the different sulfuration reaction activities caused by the influence of the calcination temperature on the redox properties of the precursor, and further research is needed. The optimal product CoS2-f 350 was selected for subsequent testing.

[0106] The mercury removal ability of the original freeze-dried carbon was tested under pure N2. The Hg 0 removal ability of the original freeze-dried carbon was poor, and the highest mercury removal efficiency was only 22%.

[0107] Example 3 Influence of flue gas temperature and flue gas components

[0108] The composition of the flue gas is the same as Example 3. This example tests the mercury removal performance of the adsorbent at other flue gas temperatures, as shown in Table 3. Figure 9 CoS2-f 350 has the best mercury removal performance at a flue gas temperature of 50°C, with Hg 0 The removal efficiency is still more than 90%. At flue gas temperatures of 25°C and 75°C, the mercury removal efficiency remains at 100% within 80 minutes, and decreases to about 90% and 70% respectively after 150 minutes. At 100°C, the mercury removal efficiency remains stable for a short time, and then decreases rapidly after 30 minutes.

[0109] Example 4

[0110] In this example, 6% (volume ratio) O2, 6% (volume ratio) SO2, 400 ppm NO, and 10 ppm HCl are respectively introduced into the flue gas of Example 2 to obtain various flue gases of Example 4.

[0111] Mercury removal tests are carried out for 3.5 hours under the various flue gas conditions of Example 4. It is found that the mercury adsorbent CoS2-f 350 maintains a mercury removal efficiency of 100% during the long-term mercury removal process of 3.5 hours, which is compared with the mercury removal efficiency of 90% under the flue gas of Comparative Example 2 (without other gases, which can be regarded as a pure N2 atmosphere), indicating that O2, SO2, NO, and HCl in the flue gas all promote the removal of Hg 0 by CoS2-f 350. When 8% water vapor is introduced into N2, the mercury removal efficiency is still 90% after 3.5 hours, indicating that H2O has no effect on the mercury removal performance of the adsorbent. This confirms that CoS2-f 350 has excellent resistance to complex high-sulfur flue gas.

[0112] Example 5 Mercury adsorption capacity test

[0113] The composition of the flue gas is the same as Example 4. Long-term adsorption tests are carried out under this flue gas to evaluate the stability and adsorption capacity of CoS2-f 350 for Hg 0 , as shown in Table 5. Figure 12

[0114] The initial Hg 0 removal efficiency of CoS2-f 350 is close to 100%, and decreases to 20% after 16000 minutes. During the test, 10 mg of the product is used, and it is calculated that the Hg 0 breakthrough rate of CoS2-f 350 is 80%, and the adsorption capacity is 74.4 mg / g.

[0115] It can be seen that the Hg​0 The adsorption capacity is obviously superior to typical carbon-based adsorbents and other metal sulfide adsorbents, and the Hg 0 The adsorption capacities are all tested under high-concentration sulfur dioxide atmosphere. The mercury adsorbent with high mercury adsorption capacity is successfully prepared, and the mercury adsorbent has good stability during long-time use and strong resistance to sulfur dioxide poisoning.

[0116] In the above technical solutions of the present application, the above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made under the technical concept of the present application, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A method for producing a mercury adsorbent, characterized by, The method comprises the following steps: freezing and freeze-drying a cobalt-containing gel to obtain a freeze-dried material; the cobalt-containing gel comprises water, a cobalt salt and a saccharide substance, the mass ratio of the cobalt salt and the saccharide substance being 1:5-16; the cobalt salt comprises at least one of cobalt nitrate, cobalt acetate and cobalt sulfate; the saccharide substance comprises at least one of starch, sucrose and glucose; carbonizing the freeze-dried material under the condition of a protective gas to obtain a carbonized material; oxidizing the carbonized material at 300-400 ℃ for 0.5-2 hours to obtain an oxidized material; grinding and mixing the oxidized material with elemental sulfur, and heat-treating the mixture at 300-500 ℃ for 1-4 hours under the condition of a protective gas to obtain the mercury adsorbent; the mass ratio of the oxidized material and the elemental sulfur is 1:0.5-9; The mercury adsorbent is a mesoporous material, the mercury adsorbent comprises cobalt sulfide and biomass carbon, the cobalt sulfide is loaded on the biomass carbon, the cobalt sulfide is CoS2, and the mass percentage of the cobalt sulfide is 10-70%.

2. The method for producing a mercury adsorbent according to claim 1, characterized by, The mass percentage of the cobalt sulfide is 40-60%.

3. The method for producing a mercury adsorbent according to claim 1, characterized by, The step of freezing and freeze-drying the cobalt-containing gel comprises: placing the cobalt-containing gel at -20 ℃ for 1-5 hours to obtain a frozen material; freeze-drying the frozen material for 24-72 hours.

4. The method for producing a mercury adsorbent according to claim 1, characterized by, The step of carbonizing the freeze-dried material under the condition of a protective gas comprises: carbonizing the freeze-dried material at 400-800 ℃ for 0.5-3 hours under N2 atmosphere.

5. The method of producing a mercury adsorbent according to claim 1, characterized by, The step of oxidizing the carbonized material at 300-400 ℃ for 0.5-2 hours comprises: oxidizing the carbonized material in air at 350 ℃ for 1 hour.

6. The method of producing a mercury adsorbent according to claim 1, characterized by, The step of grinding and mixing the oxidized material with elemental sulfur, and heat-treating the mixture at 300-500 ℃ for 1-4 hours under the condition of a protective gas comprises: grinding and mixing the oxidized material with elemental sulfur, and heat-treating the mixture at 400 ℃ for 2 hours under N2 atmosphere at a temperature increasing rate of 5-20 ℃ / min.

7. The method of producing a mercury adsorbent according to any one of claims 1 to 6, characterized by, The preparation method of the cobalt-containing gel comprises: mixing a cobalt salt aqueous solution and a saccharide substance, stirring at 80-100 ℃ for 20-60 minutes, and then aging for 10-20 hours to obtain the cobalt-containing gel.

8. Use of the mercury adsorbent prepared by the preparation method in any one of 1-7 in treating mercury-containing flue gas.

9. Use according to claim 8, characterized in that, The temperature of the mercury-containing flue gas is 25-100 ℃; and / or; The mercury-containing flue gas at least comprises one of N2, O2, SO2, NO, HCl and H2O.

Images