Preparation method and application of black soil type lean iron ore flue gas demercuration material

Abstract

The invention discloses a preparation method and application of a black soil type lean iron ore flue gas demercuration material, and the preparation method comprises the following steps: S100, crushing black soil type lean iron ore to obtain manganese iron ore powder; s200, the manganese iron ore powder in the step S100 is subjected to low-intensity magnetic separation, and low-intensity magnetic separation iron ore concentrate powder and iron rough concentrate are obtained; s300, the iron rough concentrate obtained in the step S200 is subjected to high-intensity magnetic separation, and high-intensity magnetic separation iron concentrate powder is obtained; and S400, the obtained low-intensity magnetic separation iron ore concentrate powder and the high-intensity magnetic separation iron ore concentrate powder are modified through an acid solvent, and therefore the flue gas demercuration material is obtained. The method can effectively improve the mercury removal rate.

Description

Technical Field

[0001] The present invention belongs to the field of environmental mineral materials, and particularly relates to a preparation method and application of a mercury removal material for black soil type lean iron ore in flue gas. Background Technique

[0002] Mercury is a heavy metal with high toxicity and easy to accumulate in the environment. Its emission not only causes serious pollution to the environment, but also may pose a threat to human health through the food chain. As one of the main global mercury emission sources, coal-fired power plants emit mercury mainly from incomplete combustion during coal combustion and the inherent mercury content in coal. In addition, non-ferrous metal smelting, waste incineration, cement production, and the production and use of other mercury-containing products are also important sources of mercury emissions.

[0003] In coal-fired flue gas, the occurrence states of mercury mainly include elemental mercury (Hg 0 ), oxidized mercury (Hg 2+ ), and particulate mercury (Hgp). Among them, Hg 2+ is soluble in water and can be easily removed by wet flue gas desulfurization devices, while Hgp can be removed by dust collectors. Hg 0 is difficult to remove due to its high volatility and insolubility in water. Therefore, the key to mercury removal in coal-fired flue gas lies in the removal of Hg 0 .

[0004] Post-combustion mercury removal technology is the most widely used existing technology, mainly including traditional physical adsorption methods, chemical adsorption methods, biological technology applications, and emerging technology methods. Activated carbon has become the mainstream commercial mercury removal agent due to its developed pore structure, large specific surface area, and strong adsorption ability. However, activated carbon requires a large carbon-mercury mass ratio (3000:1–18000:1) to remove mercury, resulting in high operating costs, and activated carbon is not suitable for flue gas environments with high temperature, high acid, high humidity, and high SO2 concentration. Metal sulfides are considered a powerful alternative to activated carbon-based adsorbents because of their high surface sulfur coverage and the ability to react spontaneously with mercury at low temperatures. However, the complex precursor preparation and precisely controlled synthesis process significantly increase the production cost and hinder the large-scale production and application of metal sulfide adsorbents. Currently, various mercury adsorbents that are widely studied also include metals and metal oxides, graphene and graphene oxide, fly ash and biomass-based ones. However, many of them require complex chemical synthesis and high additional loading, and the chemical emissions during the preparation process also pose a potential threat to the environment. Therefore, more economical, safe, and efficient mercury removal materials should be actively explored and developed.

[0005] Chinese Patent CN116059955B discloses an EVS-10-based manganese-loaded catalytic adsorbent for mercury and denitration removal from flue gas, its preparation method and application. However, the EVS-10 molecular sieve used as the carrier needs to be prepared by the hydrothermal method first and then impregnated with active components, and the preparation process is complex. Chinese Patent CN115155611B discloses a single-phase spinel-type magnetic high-entropy oxide catalyst, its preparation method and application. However, during the preparation process, various metal oxides need to be ball-milled for a long time and calcined at medium and high temperatures. These two operations will consume a large amount of electric energy or heat energy, increasing production costs. The calcination process will also generate a large amount of waste gas emissions, causing environmental pollution. Summary of the Invention

[0006] To solve the above problems, the present invention discloses a preparation method and application of a mercury removal material for black soil-type lean iron ore flue gas.

[0007] A preparation method of a mercury removal material for black soil-type lean iron ore flue gas includes the following steps: S100: Crushing the black soil-type lean iron ore to obtain manganese iron ore powder; S200: Performing weak magnetic separation on the manganese iron ore powder in step S100 to obtain weakly magnetic iron concentrate powder and iron rough concentrate; S300: Performing strong magnetic separation on the iron rough concentrate in step S200 to obtain strongly magnetic iron concentrate powder; S400: Modifying the obtained weakly magnetic iron concentrate powder and strongly magnetic iron concentrate powder with an acidic solvent to obtain the mercury removal material for flue gas.

[0008] Optionally, the manganese iron ore powder in step S100 is a mixture of iron oxide minerals, manganese oxide minerals and a small amount of clay minerals, and 60-80% of the particle size is less than 0.074 mm; the weak magnetic separation in step S200 is carried out under the condition of a magnetic field intensity of 600-1500 Oe; the strong magnetic separation in step S300 is carried out under the condition of a magnetic field intensity of 5000-13000 Oe; step S400 includes: mixing the acidic solvent with red-brown iron ore and manganese minerals in proportion, continuing to stir at room temperature, standing, separating the precipitate from the solution by a centrifuge, washing and filtering with deionized water, and drying in an oven to obtain the mercury removal material; the acidic solvent is HCl or H2SO4; the acidic solvent is H2SO4; the pH value of the acidic solvent is less than or equal to 3.

[0009] A method for mercury removal from flue gas, characterized in that the mercury removal material for black soil-type lean iron ore flue gas prepared by the preparation method is used for flue gas desulfurization, and the content of SO2 in the flue gas is controlled below 200 ppm. O2 is added to the flue gas.

[0010] The black soil type lean iron ore widely produced in South China has a resource reserve of over 100 million tons. Due to the fact that this kind of ore is both "lean" and "difficult to beneficiate", it has not been industrially utilized for many years. The black soil type lean iron ore is a special type of iron ore, and its main characteristics are low iron content and usually accompanied by a large amount of impurities. The black soil type lean iron ore is an iron ore with an iron content usually below 30%, belonging to lean iron ore. Its appearance is black or dark brown, with a soft texture, and is often mixed with impurities such as clay and quartz. This kind of ore is mostly formed by iron-containing minerals through long-term geological processes such as weathering and leaching. The iron minerals gradually accumulate in the surface soil to form a black or dark brown iron ore layer. The ore is mainly composed of nanohematite, goethite, various types of manganese oxide minerals and clay minerals, etc. And nano iron oxides, nano manganese oxides and clay are compounded at the nano scale, which is a natural nano composite material. Its specific surface area is 37.32m 2 / g, and the pore volume is 0.046cm 3 / g. And this black soil type lean iron-manganese ore has a unique "core-shell" structure, with hematite and limonite as the core and manganese-based oxide minerals such as manganite as the "shell", growing attached to the hematite and limonite. This lean iron ore is loose and porous, with a large specific surface area, and has active components such as iron and manganese oxides, which can adsorb and catalytically oxidize Hg0. It has obvious technical advantages such as rich reserves, low price, non-toxic and harmless compared with the existing mercury removal materials. It not only realizes the high-value utilization of the difficult-to-concentrate and smelt black soil type lean iron ore, but also reduces the production cost of the flue gas mercury removal (Hg 0 ) agent. Description of the Drawings

[0011] Figure 1 shows the main mineral composition of the black soil type lean iron ore and the "core-shell" structure of iron and manganese minerals; in the figure, (a-c) are reflected light microscopic images; (d-i) are BSE images of the black soil type lean iron ore, Pyr - pyrolusite; Hem - hematite; Goe - goethite; Lim - limonite; Cha - chalcophanite; Cry - cryptomelane; Kao - kaolinite;

[0012] Figure 2 shows the SEM, TEM, HRTEM images of the black soil type lean iron ore; in the figure, (a~e) are SEM images of hematite crystals and their aggregates, showing flaky and scaly structures; (f,g) are TEM images of hematite aggregates; (h) is a TEM image of hematite and goethite aggregates; (i) is the SAED pattern at the position shown in item (h); (j) is the HRTEM crystal lattice image of hematite; (k,l) are TEM images of Mn-Fe oxides; (m) is the SAED pattern corresponding to the position shown in (k); (n) is the lattice fringe pattern corresponding to the position shown in (k) in HRAEM. Detailed Embodiments

[0013] The technical solutions of the present invention will be specifically described below through specific embodiments in conjunction with the accompanying drawings. Components or devices in the following experimental examples are all general standard components or components known to those skilled in the art unless otherwise specified, and their structures and principles can all be known by those skilled in the art through technical manuals or obtained through conventional experimental methods.

[0014] The main minerals of the black soil type lean iron ore are hematite and goethite, and it is generally limonitized. The manganese minerals are mainly composed of the manganobaumhauerite group minerals (including manganobaumhauerite, cryptomelane, and manganoplumbite), and are accompanied by a small amount of pyrolusite and hollandite. Among them, it is composed of hematite (limonite) (about 70%), manganobaumhauerite (about 8%), aluminum limonite (about 6%), and kaolinite (about 5%). The iron minerals such as hematite are formed prior to the manganese oxide minerals, making it exhibit a "core-shell structure" characterized by the precipitation and growth of manganese minerals on the surface of iron minerals ( Figure 1 ). The core and shell in this core-shell structure respectively provide more active sites, thus improving the activity and reaction efficiency of the mercury removal material.

[0015] These minerals are in a micro-nano structure, with complex symbiosis and compositional variations. The SEM image of the nano-hematite aggregate shows a layered and platy structure ( Figure 2 ). The hematite crystals are scaly and lath-shaped, with an average width of 10 nm, and can interpenetrate to form a nearly triangular lattice or a radial structure. Due to the similar chemical properties of iron and manganese elements, isomorphic substitution is common in iron and manganese minerals, forming iron-bearing manganese minerals or manganese-bearing iron minerals. Figure 2 The electron diffraction pattern in the circled area shows that this mineral is a manganese-bearing iron mineral, which can be used as a natural manganese-iron composite oxide mercury removal material. The iron and associated manganese in the ore are both good active components for low-temperature mercury removal materials, while elements such as Si and Al in the ore are good catalyst carriers. Therefore, there is no need for complex impurity removal and purification processes to prepare mercury removal materials using black soil type lean iron ore.

[0016] Based on the above findings, the present invention proposes a preparation method for a black soil type lean iron ore flue gas mercury removal material, which is specifically as follows:

[0017] S100: Crush the black soil type lean iron ore to obtain manganese iron ore powder.

[0018] After crushing the black soil type lean iron ore through a jaw crusher and a double-roll crusher, manganese iron ore powder is obtained, which is a mixture of iron oxide minerals, manganese oxide minerals, and a small amount of clay minerals, wherein the Fe2O3 content is 40 - 65%, the MnO content is 5 - 12%, the SiO2 content is 3 - 6%, and the Al2O3 content is 4 - 7%. The particle size of this powder is very fine, and 60 - 80% is less than 0.074 mm;

[0019] S200: Perform weak magnetic separation on the manganese iron ore powder in step S100 to obtain weakly magnetic iron concentrate powder and iron rough concentrate.

[0020] Use a Ф400mm drum-type electromagnetic weak magnetic separator to perform weak magnetic separation on the material powder obtained in step S100 under the condition of a magnetic field intensity of 600 - 1500 Oe to obtain weakly magnetic iron concentrate and weakly magnetic tailings; through this step, iron rough concentrate containing magnetite and maghemite can be recovered; the Fe2O3 content of the weakly magnetic iron concentrate is 70 - 97%, and the Fe recovery rate can reach 45 - 60%;

[0021] S300: Perform strong magnetic separation on the iron rough concentrate in step S200 to obtain strongly magnetic iron concentrate powder.

[0022] Use an SHPФ700 industrial strong magnetic separator to perform strong magnetic separation on the weakly magnetic tailings obtained in step (2) with a magnetic field intensity of 5000 - 13000 Oe. Strong magnetic separation can be used to separate and recover hematite and manganese minerals in the weakly magnetic tailings. The Fe2O3 content of the obtained strongly magnetic iron concentrate is 25 - 45%, and the Fe recovery rate can reach 9 - 35%;

[0023] S400: Modify the obtained weakly magnetic iron concentrate powder and strongly magnetic iron concentrate powder with an acidic solvent.

[0024] Use an acidic solvent (HCl or H2SO4) to modify the material obtained in step (3). First, dilute concentrated hydrochloric acid or sulfuric acid to the required pH (pH = 1, 2, 3), and continue to stir at room temperature for 6 h in a ratio of 100 mL of acid solution: 5 g of the material obtained in step (3). After standing for 2 h, separate the precipitate from the solution by a centrifuge at 10000 rpm, and wash and filter several times with deionized water. Finally, dry in an 80°C oven for 12 h to obtain a mercury-removing material.

[0025] A flue gas desulfurization method uses the above mercury-removing material for flue gas desulfurization. Specifically, a fixed-bed adsorption system is used to evaluate the Hg 0 adsorption performance of the material obtained in step (4). Place 35 mg of the material in a quartz tube with an inner diameter of 6 mm (supported by quartz wool), and control the reaction temperature at 150°C through a temperature controller. Use a U-shaped glass tube equipped with a mercury permeation tube as the Hg 0 vapor generation device, and control the Hg0 concentration (250 μg / m 3 ) through the carrier gas (N2) flow rate and water bath temperature; introduce O2 (4%) and SO2 (100 ppm - 1%), and keep the total gas flow rate at 500 mL / min. Use a Lumex RA 915M mercury analyzer to record the on-line data of the Hg 0 signal, and use a Terkan mercury analyzer for data correction. The material's adsorption of Hg0 The adsorption performance is represented by a breakthrough curve, where the ordinate C / C0 is the concentration of Hg at the outlet monitored in real time divided by the concentration of Hg at the inlet 0 (the mercury removal rate = 1 - C / C0). 0 concentration (mercury removal rate = 1 - C / C0).

[0026] Example 1:

[0027] (1) After crushing the black soil-type lean iron ore through a jaw crusher and a double-roll crusher, manganese iron ore powder is obtained, which is a mixture of iron oxide minerals, manganese oxide minerals and a small amount of clay minerals, with a Fe2O3 content of 59%, a MnO content of 10%, a SiO2 content of 5%, and an Al2O3 content of 7%;

[0028] (2) The material powder obtained in step (1) is subjected to weak magnetic separation under the condition of a magnetic field intensity of 1200 Oe to obtain weak magnetic separation iron concentrate and weak magnetic separation tailings; through this step, iron rough concentrate containing magnetite and maghemite can be recovered; the Fe2O3 content of the weak magnetic separation iron concentrate is 95%, and the Fe recovery rate can reach 56%;

[0029] (3) The weak magnetic separation tailings obtained in step (2) are subjected to strong magnetic separation with a magnetic field intensity of 15000 Oe, and the hematite and manganese minerals in the weak magnetic separation tailings can be separated and recovered by strong magnetic separation. The Fe2O3 content of the obtained strong magnetic separation iron concentrate is 32%, and the Fe recovery rate can reach 31%.

[0030] (4) A fixed-bed adsorption system is used to evaluate the Hg adsorption performance of the material obtained in step (3). 35 mg of the material is placed in a quartz tube with an inner diameter of 6 mm (supported by quartz wool), and the reaction temperature is controlled at 150 °C through a temperature controller. The concentration of Hg in the inlet gas is 250 μg / m, O2 is 4%, SO2 is 200 ppm, and N2 is used as the balance gas, and the total gas flow rate is kept at 500 mL / min. The adsorption performance of the material for Hg is represented by a breakthrough curve, where the ordinate C / C0 is the concentration of Hg at the outlet monitored in real time divided by the concentration of Hg at the inlet 0 concentration (the mercury removal rate = 1 - C / C0). 33% of Hg can be removed at 150 min. After adding 4% O2, its removal rate for Hg reaches 60%. 0 concentration is 250 μg / m 3 , O2 is 4%, SO2 is 200 ppm, N2 is used as the balance gas, and the total gas flow rate is kept at 500 mL / min. The adsorption performance of the material for Hg 0 is represented by a breakthrough curve, where the ordinate C / C0 is the concentration of Hg at the outlet monitored in real time divided by the concentration of Hg at the inlet 0 concentration (the mercury removal rate = 1 - C / C0). 33% of Hg can be removed at 150 min. After adding 4% O2, its removal rate for Hg 0 reaches 60%. 0 , and after adding 4% O2, its removal rate for Hg 0 reaches 60%.

[0031] (5) Different concentrations of SO2 are introduced to test the sulfur resistance performance of the material. 35 mg of the material is placed in a quartz tube with an inner diameter of 6 mm (supported by quartz wool), and the reaction temperature is controlled at 150 °C through a temperature controller. The concentration of Hg in the inlet gas 0Concentration: 250 μg / m 3 , SO2 is 100~500ppm, N2 is used as the balance gas, and the total gas flow rate is maintained at 500mL / min. 0 The adsorption performance is expressed by a breakthrough curve, and its ordinate C / C0 is the real-time monitoring of the Hg 0 Concentration divided by inlet Hg 0 Concentration (mercury removal rate = 1-C / C0). Under the conditions of 100, 200 and 500 ppm SO2, the mercury removal rate of Hg 0 The removal rates were 43%, 37% and 17% respectively.

[0032] Embodiment 2:

[0033] (1) The black soil type poor iron ore is crushed by a jaw crusher and a double roll crusher to obtain manganese iron ore powder, which is a mixture of iron oxide minerals, manganese oxide minerals and a small amount of clay minerals, wherein the Fe2O3 content is 59%, the MnO content is 10%, the SiO2 content is 5%, and the Al2O3 content is 7%;

[0034] (2) subjecting the material powder obtained in step (1) to weak magnetic separation under the condition of a magnetic field strength of 1200 Oe to obtain weak magnetic separation iron concentrate and weak magnetic separation tailings; through this step, the iron rough concentrate containing magnetite and hematite can be recovered; the Fe2O3 content of the weak magnetic separation iron concentrate is 95%, and the Fe recovery rate can reach 56%;

[0035] (3) The weak magnetic separation tailings obtained in step (2) are subjected to strong magnetic separation, and the magnetic field strength is 15000Oe. The strong magnetic separation can separate and recover the hematite and manganese minerals in the weak magnetic separation tailings. The Fe2O3 content of the obtained strong magnetic separation iron concentrate is 32%, and the Fe recovery rate can reach 31%;

[0036] (4) The material obtained in step (3) was modified using HCl. First, concentrated hydrochloric acid was diluted to the desired pH (pH = 1), and the mixture was stirred at room temperature for 6 h at a ratio of 100 mL of acid solution to 5 g of the material obtained in step (3). After standing for 2 h, the precipitate was separated from the solution by centrifuge at 10,000 rpm, and washed with deionized water and filtered several times. Finally, it was dried in an oven at 80°C for 12 h.

[0037] (5) Using a fixed bed adsorption system to remove Hg from the material obtained in step (4) 0 Adsorption performance evaluation: 35 mg of the material was placed in a quartz tube (quartz wool support) with an inner diameter of 6 mm, and the reaction temperature was controlled at 150 °C by a temperature controller. 0 Concentration: 250 μg / m 3, with O2 being 4%, SO2 being 200 ppm, and N2 as the balance gas, the total gas flow rate was maintained at 500 mL / min. The adsorption performance of the material for Hg 0 was represented by a breakthrough curve, and its ordinate C / C0 was the concentration of Hg 0 at the outlet monitored in real time divided by the inlet Hg 0 concentration (mercury removal rate = 1 - C / C0). 67% of Hg 0 could be removed at 150 min, and the effect was improved by 34% compared with that before modification; after adding 4% O2, its removal rate for Hg 0 reached over 80%.

[0038] (6) Different concentrations of SO2 were introduced to test the sulfur resistance performance of the material. 35 mg of the material was placed in a quartz tube with an inner diameter of 6 mm (supported by quartz wool), and the reaction temperature was controlled at 150 °C through a temperature controller. The concentration of Hg 0 in the introduced gas was 250 μg / m 3 , SO2 was 100 - 500 ppm, and N2 was the balance gas. The total gas flow rate was maintained at 500 mL / min. The adsorption performance of the material for Hg 0 was represented by a breakthrough curve, and its ordinate C / C0 was the concentration of Hg 0 at the outlet monitored in real time divided by the inlet Hg 0 concentration (mercury removal rate = 1 - C / C0). Under the conditions of 100 and 200 ppm SO2, the removal rates of Hg 0 were 70% and 67% respectively at 150 min, and 67% of Hg 0 could be removed at 150 min, and the effect was improved by 34% compared with that before modification (Example 1, 37%); the removal rate under the condition of 500 ppm SO2 could also reach 34%.

[0039] Example Three:

[0040] (1) After the black soil type lean iron ore was crushed by a jaw crusher and a double-roll crusher, manganese iron ore powder was obtained, which was a mixture of iron oxide minerals, manganese oxide minerals and a small amount of clay minerals, with the Fe2O3 content being 59%, the MnO content being 10%, the SiO2 content being 5%, and the Al2O3 content being 7%;

[0041] (2) The material powder obtained in step (1) was subjected to weak magnetic separation under the condition of a magnetic field intensity of 1200 Oe to obtain weakly magnetic iron concentrate and weakly magnetic tailings; through this step, iron rough concentrate containing magnetite and maghemite could be recovered; the Fe2O3 content of the weakly magnetic iron concentrate was 95%, and the Fe recovery rate could reach 56%;

[0042] (3) The weak magnetic separation tailings obtained in step (2) are subjected to high-intensity magnetic separation at a magnetic field intensity of 15,000 Oe. High-intensity magnetic separation can be used to separate and recover hematite and manganese minerals in the weak magnetic separation tailings. The Fe2O3 content of the obtained high-intensity magnetic separation iron concentrate is 32%, and the Fe recovery rate can reach 31%;

[0043] (4) The material obtained in step (3) is modified using HCl. First, concentrated hydrochloric acid is diluted to the required pH (pH = 3), and at a ratio of 100 mL of acid solution: 5 g of the material obtained in step (3), stirring is continued at room temperature for 6 h. After standing for 2 h, the precipitate is separated from the solution by a centrifuge at 10,000 rpm, and washed and filtered several times with deionized water. Finally, it is dried in an oven at 80 °C for 12 h.

[0044] (5) A fixed-bed adsorption system is used to evaluate the Hg 0 adsorption performance of the material obtained in step (4). 35 mg of the material is placed in a quartz tube with an inner diameter of 6 mm (supported by quartz wool), and the reaction temperature is controlled at 150 °C by a temperature controller. The Hg 0 concentration in the inlet gas is 250 μg / m 3 , and N2 is used as the balance gas, and the total gas flow rate is maintained at 500 mL / min. The adsorption performance of the material for Hg 0 is represented by a breakthrough curve, and its ordinate C / C0 is the concentration of Hg 0 at the outlet monitored in real time divided by the inlet Hg 0 concentration (mercury removal rate = 1 - C / C0). 49% of Hg 0 can be removed at 150 min.

[0045] Example 4:

[0046] (1) After the black soil type lean iron ore is crushed by a jaw crusher and a double-roll crusher, manganese iron ore powder is obtained, which is a mixture of iron oxide minerals, manganese oxide minerals and a small amount of clay minerals, wherein the Fe2O3 content is 59%, the MnO content is 10%, the SiO2 content is 5%, and the Al2O3 content is 7%;

[0047] (2) The material powder obtained in step (1) is subjected to weak magnetic separation at a magnetic field intensity of 1,200 Oe to obtain weak magnetic separation iron concentrate and weak magnetic separation tailings; through this step, iron rough concentrate containing magnetite and maghemite can be recovered; the Fe2O3 content of the weak magnetic separation iron concentrate is 95%, and the Fe recovery rate can reach 56%;

[0048] (3) The weak magnetic separation tailings obtained in step (2) are subjected to high-intensity magnetic separation at a magnetic field intensity of 15,000 Oe. High-intensity magnetic separation can be used to separate and recover hematite and manganese minerals in the weak magnetic separation tailings. The Fe2O3 content of the obtained high-intensity magnetic separation iron concentrate is 32%, and the Fe recovery rate can reach 31%;

[0049] (4) The material obtained in step (3) was modified using H2SO4. First, concentrated hydrochloric acid was diluted to the desired pH (pH = 1), and the mixture was stirred at room temperature for 6 h at a ratio of 100 mL of acid solution to 5 g of the material obtained in step (3). After standing for 2 h, the precipitate was separated from the solution by centrifuge at 10,000 rpm, washed with deionized water, and filtered several times. Finally, it was dried in an oven at 80°C for 12 h.

[0050] (5) Using a fixed bed adsorption system to remove Hg from the material obtained in step (4) 0 Adsorption performance evaluation: 35 mg of the material was placed in a quartz tube (quartz wool support) with an inner diameter of 6 mm, and the reaction temperature was controlled at 150 °C by a temperature controller. 0 The concentration is 250μg / m3, N2 is used as the balance gas, and the total gas flow rate is maintained at 500mL / min. 0 The adsorption performance is expressed by a breakthrough curve, and its ordinate C / C0 is the real-time monitoring of the Hg 0 Concentration divided by inlet Hg 0 Concentration (mercury removal rate = 1-C / C0). 55% of Hg can be removed in 150 minutes 0 .

[0051] The above examples 1 to 4 are summarized in the following table:

[0052]

[0053]

[0054] From the table above we can see that:

[0055] 1. By comparing 2.1 with 1.1, it can be seen that under the same conditions, the modification will greatly increase Hg 0 Removal rate (60% to 80%);

[0056] 2. It can be seen from Examples 1 and 2 that the content of SO2 will seriously affect the Hg 0 The removal rate of Hg 0 The removal rate of Hg in flue gas is gradually reduced. Unmodified manganese oxides or iron oxides mainly rely on catalytic oxidation to remove mercury from flue gas. 0 Oxidized to Hg 2+ , and then combines with surface active oxygen to form Hg O However, the presence of flue gas SO2 will occupy Hg 0On the other hand, the adsorbed active sites are such that SO2 is easily converted into surface sulfates under the action of catalytic oxidation, breaking the catalytic oxidation cycle and poisoning the adsorbent material. Therefore, in order to ensure the removal rate of Hg 0 , the content of SO2 needs to be controlled below 200 ppm;

[0057] 3. By comparing 1.1 with 1.3, and 2.1 with 2.3, it can be seen that appropriately increasing the O 2 content will significantly improve the removal rate of Hg 0 . Therefore, when removing Hg 0 , an appropriate amount of O 2 can be added to the system. However, the addition of too much O 2 will not only increase the cost but also accelerate the oxidation of SO2, forming surface sulfates that poison the adsorbent material. Therefore, the added O2 content should be less than or equal to 4%;

[0058] 4. By comparing Example 3 with Example 1, it can be seen that the pH value during modification also affects the removal rate of Hg 0 . The removal rate of Hg 0 in 3.1 is only 49%. Therefore, the system pH value needs to be controlled below or equal to 3

[0059] 5. By comparing Example 4 with Example 2, it can be seen that different modification reagents also affect the removal rate of Hg 0 . Through surface acidification treatment, it is easy to increase the content of surface H + . The introduction of a large number of surface acidic sites can weaken the surface adsorption of SO 2 , thereby slowing down the poisoning effect; among different acid modifications, the modification with HCl shows the best effect. On the one hand, the introduction of H + directly increases the content of Cl - . Cl on the material surface is prone to form HgCl2, which can increase the capture rate of mercury in the flue gas, thereby improving the mercury removal efficiency. Although the modification with surface sulfates alleviates the poisoning of flue gas SO2 to a certain extent, the steric hindrance of sulfates is large, and the formation conditions of HgSO4 are relatively harsh. Through comparison, it can be seen that the modification with HCl shows the best effect because the addition of Cl- can accelerate the capture rate of mercury in the flue gas and quickly form stable and easily removable Hg 2+ compounds.

[0060] Compared with the prior art, the advantages and positive effects of the present invention are:

[0061] (1) Excellent mercury removal performance: Its mercury removal adsorption capacity is larger, about 5 - 10 times the mercury adsorption capacity, and it can basically be compared with chemically synthesized manganese oxide mercury removal agents. During actual use, it can be preferably used in the low-temperature section and combined with the dust removal unit as a mercury removal adsorption material.

[0062] (2) Abundant raw materials and low cost: The black soil-type lean iron ore widely produced in South China of our country has a resource reserve of more than 100 million tons. Due to the fact that this kind of ore is both "lean" and "difficult to beneficiate", it has been unable to be industrially utilized for many years. Therefore, the development of new natural environmental protection materials using this nano / micro-structured manganese and iron minerals has the characteristics of simple process and low cost. Compared with the existing commercial bromine-loaded activated carbon with a mercury removal cost of about 500,000 yuan per kilogram, it is conducive to large-scale application.

[0063] (3) Good physical and chemical stability: Through various characterization means such as XRF, XRD, XPS and other analysis methods, the black soil-type lean iron ore has good physical and chemical stability, including the stability of its structure and the stability of its surface properties.

[0064] (4) Environmentally friendly and simple production: The production method of the mercury removal material from the black soil-type lean iron ore is simple and has little impact on the environment, meeting the requirements of green chemistry and green processes. The production end uses natural minerals as raw materials, the material itself is safe and stable, and the mercury removal product is mainly HgO (figure) analyzed by Hg-TPD, with higher thermal stability and easy to remove.

[0065] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Any equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

[0066] Many specific details have been set forth in the above description to facilitate a full understanding of the present invention. However, the above description is only a preferred experimental example of the present invention, and the present invention can be implemented in many other ways different from those described herein. Therefore, the present invention is not limited by the specific implementations disclosed above. At the same time, any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical content disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent experimental example of equivalent changes. Any simple modification, equivalent change and modification made to the above experimental examples based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a black soil type lean iron ore flue gas mercury removal material, characterized in that: The steps include: S100: crushing the black soil type poor iron ore to obtain manganese iron ore powder; S200: performing weak magnetic separation on the manganese iron ore powder in step S100 to obtain weak magnetic separation iron ore concentrate powder and iron coarse concentrate; S300: performing strong magnetic separation on the rough iron concentrate in step S200 to obtain strong magnetic separation iron concentrate powder; S400: using an acidic solvent to modify the obtained weak magnetic separation iron ore concentrate powder and the strong magnetic separation iron ore concentrate powder, so as to obtain the flue gas mercury removal material.

2. The preparation method according to claim 1, characterized in that: In the step S100, the manganese iron ore powder is a mixture of iron oxide minerals, manganese oxide minerals and a small amount of clay minerals, and 60-80% of the particle size is less than 0.074 mm.

3. The preparation method according to claim 1, characterized in that: In the step S200, weak magnetic separation is performed under the condition that the magnetic field strength is 600 to 1500 Oe.

4. The preparation method according to claim 1, characterized in that: In the step S300, strong magnetic separation is performed under the condition of a magnetic field strength of 5000 to 13000 Oe.

5. The preparation method according to claim 1, characterized in that: The step S400 includes: mixing an acidic solvent with hematite and manganese ore in proportion, continuing to stir at room temperature, standing, separating a precipitate from the solution by a centrifuge, washing with deionized water, filtering, and drying in an oven, thereby obtaining the mercury-removing material.

6. The preparation method according to claim 1, characterized in that: The acidic solvent is HCl or H2SO4.

7. The preparation method according to claim 6, characterized in that: The acidic solvent is H2SO4.

8. The preparation method according to claim 6, characterized in that: The pH value of the acidic solvent is less than or equal to 3.

9. A flue gas mercury removal method, characterized in that: The black soil type lean iron ore flue gas mercury removal material prepared by the preparation method according to any one of claims 1 to 9 is used for flue gas desulfurization, and the SO2 content in the flue gas is controlled below 200 ppm.

10. The flue gas demercuration method according to claim 9, characterized in that: O2 is added to the flue gas.

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