A preparation method and system for activated coke

Abstract

The present invention discloses a preparation method and system of activated coke. The preparation method of the activated coke includes: impregnating raw coal particles in a first solution containing urea and biuret to obtain an impregnated material; carbonizing the impregnated material to obtain a carbonized material; performing primary activation on the carbonized material in steam to obtain a primary activated material; and performing secondary activation on the primary activated material in a mixed gas of ammonia, carbon dioxide and steam to obtain the activated coke. In the preparation method of the activated coke of the present invention, by using the first solution containing urea and biuret as the impregnating solution for the raw coal particles and combining primary activation with steam and secondary activation with ammonia, activated coke with rich nitrogen-containing functional groups for desulfurization and denitrification can be prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation, and particularly relates to a preparation method and system for activated coke. Background Art

[0002] As of the end of 2019, more than 90% of coal-fired units above 300MW in China have completed ultra-low emission transformation, and the emissions of SO2, NOx, and dust reach 35mg / m 3 , 50mg / m 3 , 10mg / m 3 emission requirements, and the pollutant treatment has reached the world-leading level. On the other hand, the SCR+ESP+WFGD pollutant control process route is generally adopted in coal-fired power plants in China. Due to the excessive pursuit of denitrification efficiency in the SCR denitrification process, corrosion occurs in the tail flue and equipment. The existing catalysts generally use V2O5 / WO3-TiO2 catalysts, which produce a large amount of hazardous waste after the service life expires, causing secondary pollution; the wet flue gas desulfurization is mainly based on the limestone-gypsum method, mining 125 million tons of high-quality limestone every year, damaging the ecological environment, and producing 215 million tons of inferior gypsum as by-products, which is difficult to use in large quantities. The wet flue gas desulfurization has a large water consumption, and the zero discharge of desulfurization wastewater further increases the cost. The activated coke flue gas purification technology is the only industrialized dry flue gas purification technology. As an adsorbent and catalyst, activated coke has high pollutant removal efficiency, can remove multiple pollutants simultaneously, has no secondary pollution, and can realize the recycling of resources. It is the most promising pollutant control technology in coal-rich and water-scarce areas of China.

[0003] At present, the vast majority of activated coke used for flue gas purification is columnar activated coke with a size of 5-9mm. Its preparation process needs to go through complex pretreatment processes such as bonding, shaping, and compaction, and then is prepared by carbonization and steam activation. The obtained activated coke generally shows a microporous distribution, with problems such as large internal diffusion resistance, low internal surface utilization rate, low content of active functional groups, and poor pollutant removal and regeneration and desorption performance. The problem of carbon materials is the key bottleneck for the large-scale popularization and application of the activated coke gas purification technology.

[0004] Research shows that the nitrogen-modified activated coke has a significant increase in the nitrogen-containing functional groups on the surface. During the desulfurization process, the nitrogen-containing functional groups have good catalytic activity, which can significantly promote the adsorption, oxidation, and conversion of SO2 in the flue gas, increasing the adsorption rate and desulfurization capacity of the activated coke. During the denitrification process, the nitrogen-containing functional groups improve the catalytic oxidation activity of the activated coke for NO in the flue gas and accelerate the denitrification reaction.

[0005] The common nitrogen modification process is a loading preparation process in which the activated coke with an existing pore structure is impregnated with a nitrogen-containing precursor solution and then calcined. This process has the disadvantages of a large amount of ineffective decomposition of the nitrogen-containing modification components, uneven loading, low content of nitrogen-containing functional groups in the micropores, complex preparation process, and high cost. Summary of the Invention

[0006] In view of this, an object of the present invention is to provide a preparation method of activated coke. By using a first solution containing urea and biuret as the impregnating solution for raw coal particles, and combining primary activation with steam and secondary activation with ammonia, activated coke rich in nitrogen functional groups can be prepared.

[0007] Another object of the present invention is to provide a preparation system for activated coke.

[0008] To this end, an embodiment of the first aspect of the present invention provides a preparation method of activated coke, including

[0009] Impregnating raw coal particles in a first solution containing urea and biuret to obtain an impregnated material;

[0010] Carbonizing the impregnated material to obtain a carbonized material;

[0011] Performing primary activation on the carbonized material in steam to obtain a primary activated material;

[0012] Performing secondary activation on the primary activated material in a mixed gas of ammonia, carbon dioxide, and steam to obtain the activated coke.

[0013] In some embodiments of the present invention, the ash content of the raw coal particles does not exceed 6 wt%, and the sulfur content does not exceed 3 wt%; the particle size of the raw coal particles is between 2 - 15 mm.

[0014] In some embodiments of the present invention, the volume ratio of the raw coal particles to the first solution is 1:1 - 10; the impregnation is carried out under ultrasonic conditions, and the impregnation time is 0.5 - 5 h.

[0015] In some embodiments of the present invention, the content of urea in the first solution is 25 - 35 wt%, and the content of biuret is 3 - 8 wt%.

[0016] In some embodiments of the present invention, the first solution is the wastewater from urea hydrolysis for ammonia production in a power plant; the mixed gas is the pyrolysis gas at the outlet of the urea hydrolyzer in the power plant.

[0017] In some embodiments of the present invention, the carbonization temperature is 400 - 500 °C, and the carbonization time is 2 - 4 h.

[0018] In some embodiments of the present invention, the primary activation temperature is 500 - 800 °C, and the primary activation time is 2 - 4 h.

[0019] In some embodiments of the present invention, the secondary activation temperature is 800 - 900 °C, and the secondary activation time is 1 - 2 h.

[0020] In some embodiments of the present invention, in the mixed gas, the volume ratio of ammonia, carbon dioxide and water vapor is (6-9):(6-9):(8-12).

[0021] The beneficial effects of the method for preparing activated coke according to the embodiments of the present invention are as follows:

[0022] (1) The nitrogen-containing functional groups are evenly distributed, and the micropores are also rich in nitrogen-containing functional groups.

[0023] In the traditional preparation process, the pore structure of activated coke adsorbs the nitrogen-modified precursor solution and then calcines. However, most of the micropores of activated coke are not easily impregnated with the modified solution, so nitrogen-containing functional groups cannot be formed in the micropores during the calcination process, and the catalytic active centers in the desulfurization and denitrification processes are mainly on the micropore surface.

[0024] The technical idea of the method for preparing activated coke according to the embodiments of the present invention is to first impregnate raw coal particles with a first solution containing urea and biuret, then perform carbonization and primary steam activation, and finally perform secondary activation with a nitrogen-containing mixed gas. By impregnating the raw coal particles before carbonization and activation, it is beneficial for the nitrogen-containing components urea and biuret to penetrate into the carbon material skeleton. Finally, the secondary activation with the nitrogen-containing mixed gas after pore formation is to allow ammonia to penetrate into the mesopores and micropores inside the activated coke. While the secondary activation mixed gas etches to form pores, the formation of nitrogen-containing functional groups is achieved, and the nitrogen-containing functional groups are more evenly distributed in the pores.

[0025] (2) The utilization rate of the nitrogen-containing activation component mixed gas is high, and the activated coke has a large load of nitrogen-containing functional groups.

[0026] The method for preparing activated coke according to the embodiments of the present invention adopts a preparation process of preliminary impregnation + primary activation to form pores + secondary activation for nitrogen activation, which enables the urea and biuret components to be deeply combined with the activated coke preparation process. The thermal decomposition process of the active components urea and biuret and the pore structure formation process of the activated coke promote each other. At the same time, the nitrogen-containing activation component mixed gas is more likely to penetrate into the interior of the activated coke for etching reaction, the utilization rate of the nitrogen-containing activation component mixed gas is high, and the activated coke has a large load of nitrogen-containing functional groups.

[0027] (3) The activated coke has a hierarchical pore distribution, good adsorption performance, and high desulfurization and denitrification efficiency.

[0028] The method for preparing activated coke according to the embodiments of the present invention directly uses raw coal particles to prepare activated coke. Since the preparation process does not go through complex processes such as bonding, kneading, and extrusion, it avoids pore collapse and blockage during the forming process. After carbonization and activation, a hierarchical pore structure is formed, with good adsorption performance and high desulfurization and denitrification efficiency.

[0029] (4) The preparation process is simple and the cost is low.

[0030] The method for preparing activated coke according to the embodiment of the present invention uses a nitrogen-containing precursor solution. The first solution can be the wastewater from the hydrolysis of urea to ammonia in a power plant. Both urea and biuret are good nitrogen-containing precursor solutions. The nitrogen-containing activation gas can also be the gas components produced by the urea hydrolyzer in the power plant, with low production cost. The preparation process is coupled with the urea hydrolysis system, and the preparation process is simple and low-cost.

[0031] To achieve the above object, the second aspect of the embodiment of the present invention provides a preparation system for activated coke, including an impregnation tank, a carbonization furnace, a primary activation furnace, and a secondary activation furnace connected in sequence;

[0032] An ultrasonic transducer is installed on the impregnation tank; the impregnation tank is connected to a raw coal particle storage bin and a urea hydrolysis wastewater pipeline;

[0033] The primary activation furnace is connected to a steam pipeline;

[0034] The secondary activation furnace is connected to a urea hydrolysis gas pipeline and an activated coke collection tank.

[0035] The beneficial effects of the preparation system for activated coke according to the embodiment of the present invention are basically the same as those of the preparation method for activated coke according to the embodiment of the present invention, and will not be elaborated here.

[0036] Additional aspects and advantages of the present invention will be partially given in the following description, partially will become obvious from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the following description of the embodiments in conjunction with the drawings, where:

[0038] Figure 1 It is a simple structural schematic diagram of the preparation system for activated coke according to an embodiment of the present invention (i.e., the process flow chart of the preparation method for activated coke).

[0039] Figure 2 It is a comparison chart of the desulfurization performance of the activated coke in Example 1 and the activated coke in Comparative Example 4.

[0040] Figure 3 It is a comparison chart of the denitrification performance of the activated coke in Example 1 and the activated coke in Comparative Example 4.

[0041] Figure 4 It is a comparison chart of the nitrogen functional group distribution of the activated coke in Example 1 and the activated coke in Comparative Example 4. Among them, in the abscissa: N-6 is pyridine nitrogen, N-5 is pyrrole nitrogen, N-Q is graphite nitrogen, and N-O is nitrogen oxide.

[0042] Figure 5 It is the adsorption isotherm of the activated coke in Example 1.

[0043] Figure 6 It is the pore size distribution diagram of the activated coke in Example 1.

[0044] Reference numerals:

[0045] 1 - Impregnation tank; 2 - Carbonization furnace; 3 - Primary activation furnace; 4 - Secondary activation furnace; 5 - Raw coal particle storage bin; 6 - Urea hydrolysis wastewater pipeline; 7 - Steam pipeline; 8 - Urea hydrolysis gas pipeline; 9 - Activated coke collection tank. Detailed implementation manners

[0046] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as a limitation to the present invention.

[0047] The preparation method of activated coke and the preparation system of activated coke according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0048] Figure 1 It is a simple structural schematic diagram of the preparation system of activated coke according to an embodiment of the present invention.

[0049] As Figure 1 shown, the preparation system of activated coke according to the embodiment of the present invention includes an impregnation tank 1, a carbonization furnace 2, a primary activation furnace 3, and a secondary activation furnace 4 that are connected in sequence; an ultrasonic transducer is installed on the impregnation tank 1; the impregnation tank 1 is connected to the raw coal particle storage bin 5 and the urea hydrolysis wastewater pipeline 6; the primary activation furnace 3 is connected to the steam pipeline 7; the secondary activation furnace 4 is connected to the urea hydrolysis gas pipeline 8 and the activated coke collection tank 9.

[0050] It can be understood that the impregnation tank, the raw coal particle storage bin, the activated coke collection tank, etc. are not limited by the names. They are respectively containers with the function of storing impregnating liquid, containers with the function of storing raw coal particles, and containers with the function of storing activated coke.

[0051] Among them, the impregnation tank 1, the carbonization furnace 2, the primary activation furnace 3, the secondary activation furnace 4, the raw coal particle storage bin 5, the activated coke collection tank 9, the ultrasonic transducer, etc. are all existing devices and are not the focus of the present invention.

[0052] Optionally, the impregnation tank 1 is provided with a first inlet, a second inlet, and a first outlet; the first inlet can be connected to the outlet of the raw coal particle storage bin 5 through a pipeline, etc., the second inlet is connected to the urea hydrolysis wastewater pipeline 6, and the first outlet is connected to the inlet of the carbonization furnace 2.

[0053] Preferably, in order to achieve solid-liquid separation after impregnation, the preparation system of activated coke according to the embodiment of the present invention further includes a filtering unit, which may be a vacuum belt filter press, etc. The first outlet is connected to the inlet of the filtering unit through a pipeline, and the solid outlet of the filtering unit is connected to the inlet of the carbonization furnace 2 through a first bucket conveyor, etc.

[0054] Optionally, the primary activation furnace 3 is provided with a third inlet, a fourth inlet and a second outlet, and the secondary activation furnace 4 is provided with a fifth inlet, a sixth inlet and a third outlet; wherein the third inlet is connected to the outlet of the carbonization furnace 2 through a second bucket conveyor, etc., the fourth inlet is connected to the steam pipeline 7, the second outlet is connected to the fifth inlet through a third bucket conveyor, etc., the sixth inlet is connected to the urea hydrolysis gas pipeline 8, and the third outlet is connected to the inlet of the activated coke collection tank 9 through a pipeline or a third bucket conveyor, etc.

[0055] Optionally, in some embodiments, the ultrasonic transducer is fixedly installed on the side wall of the impregnation tank 1 through bolts, etc.; in other embodiments, the ultrasonic transducer is fixedly installed at the bottom of the impregnation tank 1 through bolts, etc.

[0056] During use, the raw coal particles enter the impregnation tank 1. Under the condition of ultrasonic waves, after being impregnated with urea hydrolysis wastewater for a period of time, the impregnated raw coal particles (i.e., impregnated materials) enter the primary activation furnace and are primarily activated under the action of steam to obtain primary activated materials; then the primary activated materials enter the secondary activation furnace and are secondarily activated under the action of urea hydrolysis gas to obtain activated coke; the activated coke is collected by the activated coke collection tank 9 for standby. In the above process, if the impregnated raw coal particles can be obtained by filtering through the filtering unit, they can also be directly fished out from the impregnation tank and drained of water.

[0057] The preparation method of activated coke according to the embodiment of the present invention includes the following steps:

[0058] (1) Impregnating raw coal particles in a first solution containing urea and biuret to obtain impregnated materials;

[0059] (2) Carbonizing the impregnated materials to obtain carbonized materials;

[0060] (3) Primarily activating the carbonized materials in steam to obtain primary activated materials;

[0061] (4) Secondarily activating the primary activated materials in a mixed gas of ammonia, carbon dioxide and steam to obtain activated coke.

[0062] The preparation method of activated coke according to the embodiments of the present invention adopts a process of first impregnating raw coal particles and then performing high-temperature activation with a nitrogen-containing activating component. Functional groups are generated synchronously during the formation process of hierarchical pores, which can improve the problem of uneven loading of nitrogen-containing modification components in the prior art. At the same time, in the high-temperature secondary activation process of the nitrogen-containing activating component, ammonia directly participates in the etching reaction, effectively generating nitrogen-containing structures and avoiding the problem of a large amount of ineffective decomposition of nitrogen-containing modification components. The activated coke prepared by the preparation method of the activated coke according to the embodiments of the present invention has a hierarchical pore structure form with accessible medium and large pores and well-developed micropores, and it is also easy to form desulfurization and denitrification catalytic active centers inside the pores.

[0063] The technical principle of the preparation method of the activated coke according to the embodiments of the present invention is as follows:

[0064] The first solution contains urea and biuret, and both urea and biuret are good nitrogen-containing precursor solutions. Mixing the first solution with raw coal particles for impregnation, the nitrogen-containing precursors urea and biuret are more likely to enter the interior of the raw coal particle material. Through carbonization and primary activation with water vapor, it can promote the nitrogen-containing precursors to participate in the cross-linking, decomposition, and solidification of the organic polymer long-chain structure in the raw coal particles, and initially form nitrogen-containing functional groups. The mixed gas for nitrogen-modified activation (i.e., secondary activation), in which ammonia, carbon dioxide, and water vapor can deeply activate the primary activated material and expand its dendritic large, medium, and small hierarchical pore structure. The reaction formulas are as follows:

[0065] H2O + C → CO + H2

[0066] CO2 + C → CO

[0067] NH3 + C → CH4 + N2

[0068] At the same time, as the micropores develop at high temperature, ammonia continuously reacts with the carbon structure on the surface of the micropores to generate structures such as pyridine and pyran, making the distribution of nitrogen-containing functional groups (pyridine nitrogen, pyrrole nitrogen, graphite nitrogen, nitrogen oxide, etc.) uniform and the content continuously increasing.

[0069] Optionally, in step (1), the ash content of the raw coal particles does not exceed 6 wt%, and the sulfur content does not exceed 3 wt%. The raw coal particles can be obtained by crushing and screening low-ash and low-sulfur coal as raw materials.

[0070] The preparation method of the activated coke according to the embodiments of the present invention requires the raw coal particles to have a low ash content because the preparation method of the activated coke according to the embodiments of the present invention does not prepare activated coke through conventional processes such as grinding, binding, and pressing. If the ash content of the raw coal particles is high, after carbonization and activation of the raw coal particles, the proportion of ash in the prepared activated coke will further increase, resulting in a serious decline in the strength of the prepared activated coke. At the same time, the preparation method of the activated coke according to the embodiments of the present invention requires the raw coal particles to have a low sulfur content because the desulfurization performance of the activated coke prepared from raw coal particles with a sulfur content exceeding 3 wt% is poor.

[0071] Optionally, the particle size of the raw coal particles is between 2 and 15 mm. The smaller the raw coal particles, the better the impregnation effect when the raw coal particles are impregnated in the first solution containing urea and biuret. However, the smaller the particle size of the raw coal particles is not necessarily better: on the one hand, if the particle size is less than 2 mm, although the impregnation effect will be better, the bulk density will be relatively high during the primary activation process, and it is not easy for water vapor to contact the surface of the carbonized raw coal particles (i.e., carbonized material); on the other hand, if the particle size is less than 2 mm, the strength of the prepared activated coke will be relatively weak. When the particle size of the raw coal particles is greater than 15 mm, the overall contact area between the raw coal particles and the first solution decreases, the impregnation effect deteriorates, the amount of urea and biuret adsorbed by the raw coal particles decreases, and thus the loading amount of nitrogen-containing functional groups in the prepared activated coke is reduced. Optionally, in step (1), the volume ratio of the raw coal particles to the first solution is 1:1 - 10; the impregnation is carried out under ultrasonic conditions, and the impregnation time is 0.5 - 5 h. Carrying out the impregnation under ultrasonic conditions can make the impregnation of the raw material particles more sufficient.

[0072] Optionally, in step (1), the content of urea in the first solution is 25 - 35 wt%, and the content of biuret is 3 - 8 wt%; preferably, the content of urea in the first solution is 30 wt%, and the content of biuret is 5 wt%. In the first solution, except for urea and biuret, the rest is water. The contents of urea and biuret are based on the total mass of the entire first solution.

[0073] Optionally, in step (4), in the mixed gas, the volume ratio of ammonia, carbon dioxide, and water vapor is (6 - 9):(6 - 9):(8 - 12); preferably, in the mixed gas, the volume ratio of ammonia, carbon dioxide, and water vapor is 3:3:4.

[0074] Optionally, since the main components of the waste water from the urea hydrolysis to ammonia in the power plant (i.e., the waste liquid discharged from the urea hydrolyzer) are 30% urea (CO(NH2)2), about 5% biuret (C2H5N3O2), and trace amounts of Cr +6, and the rest is water (Chen Xi, Wang Junli, Discussion on the Treatment Method of Waste Liquid in the Urea Hydrolysis to Ammonia Process [J], Environment and Development, 2018, 89 - 90). The composition of the pyrolysis gas at the outlet of the urea hydrolyzer is mainly ammonia, carbon dioxide and water vapor, and the volume ratio of the three of them meets the above requirements of (6 - 9):(6 - 9):(8 - 12). Preferably, the composition of the pyrolysis gas at the outlet of the urea hydrolyzer is 30% (volume fraction) ammonia, 30% (volume fraction) carbon dioxide and 40% (volume fraction) water vapor. In order to simplify the preparation process of activated coke, reduce production costs, and at the same time realize the resource utilization of waste water and waste gas in the urea electrolysis to ammonia process in power plants, the preparation method of the activated coke in the embodiments of the present invention can be coupled with the urea electrolysis to ammonia in power plants. The first solution in step (1) uses the waste water from the urea hydrolysis to ammonia process in power plants; the mixed gas in step (4) uses the pyrolysis gas at the outlet of the urea hydrolyzer in power plants.

[0075] It should be noted that trace amounts of Cr in the waste water from the urea hydrolysis to ammonia process in power plants +6 do not affect the performance of the activated coke prepared by the preparation method of the activated coke in the embodiments of the present invention. Optionally, in step (2), the carbonization temperature is 400 - 500 °C and the carbonization time is 2 - 4 h.

[0076] Optionally, in step (3), the primary activation temperature is 500 - 800 °C and the primary activation time is 2 - 4 h.

[0077] Optionally, in step (4), the secondary activation temperature is 800 - 900 °C and the secondary activation time is 1 - 2 h.

[0078] The preparation method of the activated coke in the embodiments of the present invention can be implemented by means of the preparation system of the activated coke in the embodiments of the present invention, but is not limited to this preparation system.

[0079] Next, with the help of the preparation system of the activated coke in the embodiments of the present invention, the preparation method of the activated coke in the embodiments of the present invention will be described in combination with specific embodiments.

[0080] For the raw material reagents and equipment involved in the embodiments and comparative examples of the present invention, unless otherwise specified, they are all reagents and equipment that can be obtained through commercial channels; for the methods involved in the embodiments and comparative examples of the present invention, unless otherwise specified, they are all conventional methods.

[0081] I. Embodiments and Comparative Examples

[0082] Example 1

[0083] Taixi anthracite with ash content of 6wt% and sulfur content of 3wt% was selected, and raw coal particles with a size of 3-10mm were screened after crushing and added to the impregnation tank. The volume ratio of the raw coal particles to the wastewater from urea hydrolysis to ammonia production in the power plant entering the impregnation tank (the content of urea is 30wt%, the content of biuret is 5wt%) is 1:5. The raw coal particles are immersed in the wastewater of urea hydrolysis to produce ammonia in the power plant for 1 hour under the action of an ultrasonic transducer to obtain an impregnated material; then, the impregnated material is taken out and the water is controlled and added to a carbonization furnace, and carbonized at 400°C for 4 hours to obtain a carbonized material; thereafter, the carbonized material is cooled and added to a primary activation furnace, and activated once at 800°C for 2 hours with water vapor as the primary activation gas to obtain a primary activated material; finally, the primary activated material is added to a secondary activation furnace, and the pyrolysis gas from the outlet of the urea hydrolyzer of the power plant (composed of 30% (volume fraction) ammonia, 30% (volume fraction) carbon dioxide and 40% (volume fraction) water vapor) is used as the secondary activation gas, and nitrogen-modified activation (i.e., secondary activation) is performed at 900°C for 1 hour, and activated coke is obtained after cooling.

[0084] Example 2

[0085] Taixi anthracite with an ash content of 5wt% and a sulfur content of 3wt% was selected, and the raw coal particles with a size of 8-15mm were screened after crushing and added to the impregnation tank. The volume ratio of the raw coal particles to the wastewater from urea hydrolysis to ammonia production in the power plant entering the impregnation tank (the content of urea is 30wt%, the content of biuret is 5wt%) is 1:10. The raw coal particles are immersed in the wastewater of urea hydrolysis to produce ammonia in the power plant for 0.5 hours under the action of an ultrasonic transducer to obtain an impregnated material; then, the impregnated material is taken out and the water is controlled and added to a carbonization furnace, and carbonized at 500°C for 2 hours to obtain a carbonized material; thereafter, the carbonized material is cooled and added to a primary activation furnace, and activated once at 500°C for 4 hours with water vapor as the activation gas to obtain a primary activated material; finally, the primary activated material is added to a secondary activation furnace, and the pyrolysis gas from the outlet of the urea hydrolyzer of the power plant (composed of 30% (volume fraction) ammonia, 30% (volume fraction) carbon dioxide and 40% (volume fraction) water vapor) is used as the secondary activation gas, and nitrogen modified and activated (i.e., secondary activation) is performed at 850°C for 2 hours, and activated coke is obtained after cooling.

[0086] Example 3

[0087] Select Datong coal with an ash content of 5.3 wt% and a sulfur content of 2.5 wt%. After crushing, raw coal particles with a size of 3 - 10 mm are screened and added to the impregnation tank. The volume ratio of the raw coal particles to the wastewater from the urea hydrolysis to ammonia production in the power plant (urea content is 30 wt%, biuret content is 5 wt%) entering the impregnation tank is 1:4. The raw coal particles are impregnated in the wastewater from the urea hydrolysis to ammonia production in the power plant under the action of an ultrasonic transducer for 3 h to obtain an impregnated material; subsequently, the impregnated material is fished out, drained of moisture, and then added to a carbonization furnace, and carbonized at 450 °C for 3 h to obtain a carbonized material; then, after the carbonized material is cooled, it is added to a primary activation furnace, and activated with steam as the activation gas at 600 °C for 3 h to obtain a primary activated material; finally, the primary activated material is added to a secondary activation furnace, and the pyrolysis gas from the outlet of the urea hydrolyzer in the power plant (composition: 30% (volume fraction) ammonia, 30% (volume fraction) carbon dioxide, and 40% (volume fraction) water vapor) is used as the secondary activation gas, and nitrogen-modified activation (i.e., secondary activation) is carried out at 900 °C for 1.5 h, and after cooling, activated coke is obtained.

[0088] Example 4

[0089] Select Yulin bituminous coal with an ash content of 4.5 wt% and a sulfur content of 2.8 wt%. After crushing, raw coal particles with a size of 5 - 10 mm are screened and added to the impregnation tank. The volume ratio of the raw coal particles to the wastewater from the urea hydrolysis to ammonia production in the power plant (urea content is 30 wt%, biuret content is 5 wt%) entering the impregnation tank is 1:6. The raw coal particles are impregnated in the wastewater from the urea hydrolysis to ammonia production in the power plant under the action of an ultrasonic transducer for 4 h to obtain an impregnated material; subsequently, the impregnated material is fished out, drained of moisture, and then added to a carbonization furnace, and carbonized at 500 °C for 4 h to obtain a carbonized material; then, after the carbonized material is cooled, it is added to a primary activation furnace, and activated with steam as the activation gas at 650 °C for 4 h to obtain a primary activated material; finally, the primary activated material is added to a secondary activation furnace, and the pyrolysis gas from the outlet of the urea hydrolyzer in the power plant (composition: 30% (volume fraction) ammonia, 30% (volume fraction) carbon dioxide, and 40% (volume fraction) water vapor) is used as the secondary activation gas, and nitrogen-modified activation (i.e., secondary activation) is carried out at 900 °C for 2 h, and after cooling, activated coke is obtained.

[0090] Example 5

[0091] Select Taixi anthracite with an ash content of 4.7 wt% and a sulfur content of 2.9 wt%. After crushing, raw coal particles with a size of 7 - 15 mm are screened and added to the impregnation tank. The volume ratio of the raw coal particles to the wastewater from the urea hydrolysis to ammonia production in the power plant entering the impregnation tank (urea content is 30 wt%, biuret content is 5 wt%) is 1:8. The raw coal particles are impregnated in the wastewater from the urea hydrolysis to ammonia production in the power plant under the action of an ultrasonic transducer for 1 h to obtain an impregnated material; subsequently, the impregnated material is fished out, drained of water, and then added to a carbonization furnace, and carbonized at 430 °C for 2 h to obtain a carbonized material; then, after the carbonized material is cooled, it is added to a primary activation furnace, and activated with steam as the activation gas at 750 °C for 2 h to obtain a primary activated material; finally, the primary activated material is added to a secondary activation furnace, and the pyrolysis gas from the outlet of the urea hydrolyzer in the power plant (composition: 30% (volume fraction) ammonia, 30% (volume fraction) carbon dioxide, and 40% (volume fraction) water vapor) is used as the secondary activation gas, and nitrogen-modified activation (i.e., secondary activation) is carried out at 850 °C for 1 h, and after cooling, activated coke is obtained.

[0092] Example 6

[0093] Select Xinjiang lignite with an ash content of 3.5 wt% and a sulfur content of 1.8 wt%. After crushing, raw coal particles with a size of 3 - 8 mm are screened and added to the impregnation tank. The volume ratio of the raw coal particles to the wastewater from the urea hydrolysis to ammonia production in the power plant entering the impregnation tank (urea content is 30 wt%, biuret content is 5 wt%) is 1:10. The raw coal particles are impregnated in the wastewater from the urea hydrolysis to ammonia production in the power plant under the action of an ultrasonic transducer for 2 h to obtain an impregnated material; subsequently, the impregnated material is fished out, drained of water, and then added to a carbonization furnace, and carbonized at 400 °C for 3 h to obtain a carbonized material; then, after the carbonized material is cooled, it is added to a primary activation furnace, and activated with steam as the activation gas at 500 °C for 4 h to obtain a primary activated material; finally, the primary activated material is added to a secondary activation furnace, and the pyrolysis gas from the outlet of the urea hydrolyzer in the power plant (composition: 30% (volume fraction) ammonia, 30% (volume fraction) carbon dioxide, and 40% (volume fraction) water vapor) is used as the secondary activation gas, and nitrogen-modified activation (i.e., secondary activation) is carried out at 800 °C for 1.5 h, and after cooling, activated coke is obtained.

[0094] Example 7

[0095] Select Datong coal with an ash content of 4.9 wt% and a sulfur content of 3 wt%. After crushing, raw coal particles with a size of 5-10 mm are screened and added to the impregnation tank. The volume ratio of the raw coal particles to the wastewater from the urea hydrolysis to ammonia production in the power plant (urea content is 30 wt%, biuret content is 5 wt%) entering the impregnation tank is 1:5. The raw coal particles are impregnated in the wastewater from the urea hydrolysis to ammonia production in the power plant under the action of an ultrasonic transducer for 5 h to obtain an impregnated material. Subsequently, the impregnated material is fished out, drained of moisture, and then added to a carbonization furnace and carbonized at 480 °C for 4 h to obtain a carbonized material. After that, the carbonized material is cooled and then added to a primary activation furnace, and activated with steam as the activation gas at 800 °C for 2 h to obtain a primary activated material. Finally, the primary activated material is added to a secondary activation furnace, and the pyrolysis gas from the outlet of the urea hydrolyzer in the power plant (composition: 30% (volume fraction) ammonia, 30% (volume fraction) carbon dioxide, and 40% (volume fraction) water vapor) is used as the secondary activation gas, and nitrogen-modified activation (i.e., secondary activation) is carried out at 800 °C for 2 h, and after cooling, activated coke is obtained.

[0096] Example 8

[0097] Select Yulin bituminous coal with an ash content of 4.2 wt% and a sulfur content of 2.6 wt%. After crushing, raw coal particles with a size of 8-15 mm are screened and added to the impregnation tank. The volume ratio of the raw coal particles to the wastewater from the urea hydrolysis to ammonia production in the power plant (urea content is 30 wt%, biuret content is 5 wt%) entering the impregnation tank is 1:7. The raw coal particles are impregnated in the wastewater from the urea hydrolysis to ammonia production in the power plant under the action of an ultrasonic transducer for 3 h to obtain an impregnated material. Subsequently, the impregnated material is fished out, drained of moisture, and then added to a carbonization furnace and carbonized at 480 °C for 2 h to obtain a carbonized material. After that, the carbonized material is cooled and then added to a primary activation furnace, and activated with steam as the activation gas at 700 °C for 3 h to obtain a primary activated material. Finally, the primary activated material is added to a secondary activation furnace, and the pyrolysis gas from the outlet of the urea hydrolyzer in the power plant (composition: 30% (volume fraction) ammonia, 30% (volume fraction) carbon dioxide, and 40% (volume fraction) water vapor) is used as the secondary activation gas, and nitrogen-modified activation (i.e., secondary activation) is carried out at 900 °C for 1 h, and after cooling, activated coke is obtained.

[0098] Example 9

[0099] This example is basically the same as Example 1, except that: the wastewater from the urea hydrolysis to ammonia production in the power plant is replaced with an aqueous solution containing only urea and biuret, where the urea content is 30 wt% and the biuret content is 5 wt%; the pyrolysis gas from the outlet of the urea hydrolyzer in the power plant is replaced with a mixed gas of ammonia, carbon dioxide, and water vapor, and the volume ratio of ammonia, carbon dioxide, and water vapor in the mixed gas is 3:3:4.

[0100] Example 10

[0101] This example is basically the same as Example 9, except that: the wastewater from the urea hydrolysis to ammonia in the power plant is replaced with an aqueous solution containing only urea and biuret, where the content of urea is 25 wt% and the content of biuret is 3 wt%.

[0102] Example 11

[0103] This example is basically the same as Example 9, except that: the wastewater from the urea hydrolysis to ammonia in the power plant is replaced with an aqueous solution containing only urea and biuret, where the content of urea is 35 wt% and the content of biuret is 8 wt%.

[0104] Example 12

[0105] This example is basically the same as Example 9, except that: the volume ratio of ammonia, carbon dioxide and water vapor in the mixed gas is 1:1:2.

[0106] Example 13

[0107] This example is basically the same as Example 9, except that: the volume ratio of ammonia, carbon dioxide and water vapor in the mixed gas is 9:6:8.

[0108] Example 14

[0109] This example is basically the same as Example 9, except that: the volume ratio of ammonia, carbon dioxide and water vapor in the mixed gas is 2:3:4.

[0110] Comparative Example 1

[0111] This comparative example is basically the same as Example 1, except that: the step of impregnating the raw coal particles is not included, and the raw coal particles are directly carbonized.

[0112] Comparative Example 2

[0113] This comparative example is basically the same as Example 1, except that: the step of adding the primary activated material to the secondary activation furnace for secondary activation is not included, and the primary activated material is directly used as the final activated coke product.

[0114] Comparative Example 3

[0115] This comparative example is basically the same as Example 1, except that: the step of adding the carbonized material to the primary activation furnace for primary activation after cooling is not included, and the carbonized material is directly added to the secondary activation furnace, and the pyrolysis gas (composition: 30% (volume fraction) ammonia, 30% (volume fraction) carbon dioxide and 40% (volume fraction) water vapor) from the outlet of the urea hydrolyzer in the power plant is used as the activation gas, and nitrogen modification activation is carried out at 900 °C for 1 h, and the activated coke is obtained after cooling.

[0116] Comparative Example 4

[0117] This comparative example is basically the same as Example 1, except that: the raw coal particles are directly carbonized and activated once (steam activation) to obtain activated coke; then the activated coke is impregnated in the wastewater from the hydrolysis of urea to ammonia in a power plant (the content of urea is 30 wt%, and the content of biuret is 5 wt%), and finally the impregnated activated coke is calcined at 900 °C for 1 h to obtain the final activated coke product.

[0118] II. Performance testing

[0119] 1. Performance testing method

[0120] (1) Desulfurization and denitrification performance of activated coke

[0121] The prepared activated coke is crushed and screened to obtain 20 - 40 μm particles, which are added to the reactor of the fixed-bed desulfurization and denitrification test bench. The activated coke is respectively subjected to a 2-h simulated flue gas desulfurization and denitrification performance test experiment. The sulfur dioxide content and nitrogen oxide content of the simulated flue gas at different times are measured, and the desulfurization efficiency and denitrification efficiency are calculated.

[0122] The composition of the simulated flue gas during the desulfurization process is: 6% (volume percentage) oxygen, 2600 mg / m 3 SO2, 3% (volume percentage) water vapor content, and the rest is N2; the calculation formula for the desulfurization efficiency after 2 h is:

[0123] Desulfurization efficiency after 2 h = (inlet SO2 concentration - outlet SO2 concentration) / inlet SO2 concentration * 100%.

[0124] The composition of the simulated flue gas during the denitrification process is: 6% (volume percentage) oxygen, 350 mg / m 3 NO, 350 mg / m 3 NH3, and the rest is N2; the calculation formula for the denitrification efficiency after 2 h is:

[0125] Denitrification efficiency after 2 h = (inlet NO concentration - outlet NO concentration) / inlet NO concentration * 100%.

[0126] (2) Nitrogen content on the surface of activated coke

[0127] The nitrogen content on the surface of the activated coke is analyzed by X-ray photoelectron spectroscopy (XPS).

[0128] (3) Pore size distribution of activated coke

[0129] The pore size distribution of the activated coke is obtained by plotting the adsorption isotherm and the pore size distribution diagram.

[0130] (4) Specific surface area analysis of activated coke

[0131] The specific surface area of the activated coke is analyzed by the multi-point BET method.

[0132] 2. Performance test results

[0133] (1) Desulfurization and denitrification performance of activated coke and surface nitrogen content

[0134] The desulfurization and denitrification performance and surface nitrogen content of the activated coke prepared by the activated coke preparation methods of Examples 1-14 and Comparative Examples 1-4 were tested, and the test results are shown in Table 1.

[0135] Table 1 Test results of desulfurization and denitrification performance and surface nitrogen content of activated coke in Examples 1-14 and Comparative Examples 1-4

[0136]

[0137]

[0138] As can be seen from Table 1, the activated coke prepared by the activated coke preparation method of the embodiments of the present invention has improvements in terms of desulfurization efficiency, denitrification efficiency, and surface nitrogen content. In particular, the 2-hour desulfurization efficiency has a more significant increase.

[0139] Figure 2 It is a comparison chart of the desulfurization performance of the activated coke of Example 1 and the activated coke of Comparative Example 4. From Figure 2 it can be seen that the activated coke prepared by the activated coke preparation method of Example 1 of the present invention has significantly better desulfurization performance. The desulfurization efficiency after 2 hours is 60%, while the desulfurization efficiency of the activated coke prepared by the activated coke preparation method of Comparative Example 4 is only 15% after 2 hours.

[0140] Figure 3 It is a comparison chart of the denitrification performance of the activated coke of Example 1 and the activated coke of Comparative Example 4. From Figure 3 it can be seen that the denitrification performance of the activated coke prepared by the activated coke preparation method of Example 1 of the present invention is significantly enhanced. The denitrification efficiency after 2 hours is still 65%, while the denitrification efficiency of the activated coke prepared by the activated coke preparation method of Comparative Example 4 is only 32% after 2 hours.

[0141] Figure 4 It is a comparison chart of the nitrogen functional group distribution of the activated coke of Example 1 and the activated coke of Comparative Example 4. From Figure 4 it can be seen that the content of various nitrogen-containing functional groups in the activated coke of Example 1 of the present invention is higher than that of the activated coke of Comparative Example 1.

[0142] (2) Pore size distribution of activated coke

[0143] The pore size distribution of the activated coke prepared by the activated coke preparation methods of Example 1 and Comparative Example 4 was investigated.

[0144] Figure 5 It is the adsorption isotherm of the activated coke of Example 1,Figure 6 is the pore size distribution diagram of the activated coke in Example 1. From Figure 5 and Figure 6 it can be seen that in addition to well-developed micropores on the surface of the activated coke prepared by the preparation method of the activated coke in Example 1 of the present invention, there are also a large number of medium and large pores, and there is an obvious hierarchical pore structure.

[0145] (3) Specific surface area analysis of activated coke

[0146] The specific surface areas of the activated cokes prepared by the preparation methods of the activated cokes in Example 1 and Comparative Example 4 were analyzed, and the results are shown in Table 2.

[0147] Table 2 Analysis results of the specific surface areas of the activated cokes in Example 1 and Comparative Example 4

[0148]

[0149] From the analysis results of the specific surface areas in Table 2, it can be seen that the specific surface area of the activated coke prepared by the preparation method of the activated coke in Example 1 of the present invention is significantly increased. The proportion of the specific surface area of micropores is 38%, the proportion of the specific surface area of medium and large pores is 62%, the proportion of the pore volume of medium and large pores is 78.4%, and the average pore diameter is 4.352 nm. While the specific surface area of the activated coke prepared by the preparation method of the activated coke in Comparative Example 4 is small, the proportion of the specific surface area of micropores is as high as 85%, the proportion of the specific surface area of medium and large pores is only 15%, the proportion of the pore volume of medium and large pores is 41.3%, and the average pore diameter is 2.836 nm.

[0150] In summary, for the problem that the content of surface active functional groups of conventional activated coke is low and there are generally poor adsorption and catalytic performances during the application in flue gas desulfurization and denitrification, the preparation method of the activated coke in the embodiment of the present invention uses the first solution containing urea and biuret as the impregnating solution for raw coal particles, and combines steam primary activation and ammonia secondary activation to prepare desulfurization and denitrification activated coke rich in nitrogen functional groups.

[0151] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without conflict, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0152] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A preparation method of activated coke, characterized in that, Including Impregnating raw coal particles in a first solution containing urea and biuret to obtain an impregnated material; Carbonizing the impregnated material to obtain a carbonized material; Performing primary activation on the carbonized material in steam to obtain a primary activated material; Performing secondary activation on the primary activated material in a mixed gas of ammonia, carbon dioxide, and steam to obtain the activated coke; in the mixed gas, the volume ratio of ammonia, carbon dioxide, and steam is (6 - 9):(6 - 9):(8 - 12); The activated coke has a hierarchical pore structure of medium and large pores and micropores, and the micropores contain nitrogen-containing functional groups; The volume ratio of the raw coal particles to the first solution is 1:1 - 10; the impregnation is carried out under ultrasonic conditions, and the impregnation time is 0.5 - 5 h; The content of urea in the first solution is 25 - 35 wt%, and the content of biuret is 3 - 8 wt%; The carbonization temperature is 400 - 500 °C, and the carbonization time is 2 - 4 h; The primary activation temperature is 500 - 800 °C, and the primary activation time is 2 - 4 h; The secondary activation temperature is 800 - 900 °C, and the secondary activation time is 1 - 2 h.

2. The preparation method according to claim 1, characterized in that, The ash content of the raw coal particles does not exceed 6 wt%, and the sulfur content does not exceed 3 wt%; the particle size of the raw coal particles is between 2 - 15 mm.

3. The preparation method according to claim 1, wherein The first solution is the wastewater from urea hydrolysis to ammonia in a power plant; the mixed gas is the pyrolysis gas at the outlet of a urea hydrolyzer in a power plant.

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