A spherical silica denitrification process and apparatus

Abstract

This invention relates to a spherical silica denitrification process and apparatus, including the preparation of ammonia as a denitrification reducing agent, the spraying of a catalyst in a denitrification ceramic filter cartridge, the preparation and transport of spherical silica micropowder, the denitrification process of the spherical silica micropowder, and the collection of silica micropowder and exhaust gas emission. Combined with a specially designed denitrification device, it can achieve nitrogen oxide concentrations of ≤50mg / Nm³ and particulate matter concentrations of ≤5mg / Nm³, with a denitrification rate exceeding 98%, which is of great significance for addressing the flue gas problem generated after silica production.

Description

Technical Field

[0001] This invention relates to a denitrification process, specifically to a spherical silica denitrification process and apparatus. Background Technology

[0002] Silica possesses excellent dielectric properties and a low coefficient of thermal expansion, making it widely used in epoxy molding compounds and copper-clad laminates. High silica filler content can reduce costs, improve thermal conductivity, lower the coefficient of thermal expansion, and increase strength. Therefore, there is a significant demand for spherical silica production. However, the high nitrogen oxide content in the flue gas generated during the production of spherical silica is a serious issue that requires attention. Wastewater and wastewater must be treated to meet national standards before being discharged to minimize environmental pollution.

[0003] Nitrogen oxides, commonly known as nitrous oxide, are a general term for nitrogen and oxygen compounds. They are among the most common irritating gases and mainly include nitrous oxide (N₂O, commonly known as laughing gas), nitric oxide (NO), nitrogen dioxide (NO₂), dinitrogen trioxide (N₂O₃), dinitrogen tetroxide (N₂O₄, also known as nitrite anhydride), and dinitrogen pentoxide (N₂O₅, also known as nitric anhydride). Except for dinitrogen pentoxide, which is a solid, the rest are gases. Except for NO₂, the others are extremely unstable and will eventually turn into NO₂ upon exposure to light, moisture, or heat. NO is a five-colored gas with a boiling point of -151.8℃ and a melting point of -163.6℃. NO₂ is a highly toxic, irritating reddish-brown gas with a boiling point of 21.2℃ and a melting point of -9.3℃. NO₂ reacts with water to produce nitric acid (HNO₃) and other nitrogen oxides. Neither NO nor NO₂ is flammable, but both can promote the combustion of other substances; they are strong oxidizing agents and can react with combustible and reducing substances.

[0004] NO x NO emissions cause significant harm to human production, daily life, and the natural environment. Regarding human health, NO readily binds to hemoglobin, causing oxygen deficiency; NO2 primarily irritates the lungs and respiratory tract, causing corrosive damage to organs, and in severe cases, death; furthermore, NO can lead to bronchitis, asthma, and chronic bronchitis. In terms of the ecological environment, NO... x It will trigger acid rain, acid fog, and photochemical smog, promoting global warming. Furthermore, increased nitrogen deposition will lead to eutrophication of surface water and acidification and toxicity of land, wetlands, and groundwater systems, further damaging terrestrial and aquatic ecosystems. Given NO... x The harm that NO poses to humans and the ecological environment, and the control of NO x The generation and emission of [something] are very important issues. Summary of the Invention

[0005] The technical objective of this invention is to solve the problems in the background art and provide a spherical silica denitrification process and apparatus.

[0006] A spherical silica denitration process includes the following steps:

[0007] Step S1: Preparation of ammonia as a denitrification reducing agent: Urea is dissolved in pure water to prepare a urea solution, which is stored in a storage tank. The urea solution is hydrolyzed to generate ammonia gas, which then enters the ceramic filter cartridge for reaction.

[0008] Step S2: Catalyst spraying in the denitrification ceramic filter cartridge: Alum pentoxide is used as the catalyst in the denitrification reaction, and the treated alum pentoxide is evenly sprayed on the inner wall of the ceramic filter cartridge, penetrating to the point where there is still 1-2 mm left from the outer wall of the ceramic filter cartridge.

[0009] Step S3: Preparation and transport of spherical silica micro powder: Silica is fed into a spheroidizing furnace and spheroidized to generate spherical silica powder. The generated silica powder and flue gas enter the denitrification device.

[0010] Step S4: Denitrification process of spherical silica micropowder: The silica micropowder generated in step S3 and the flue gas with high nitrogen and oxygen content first enter the mixing chamber for mixing and then enter the denitrification chamber for denitrification reaction. The spherical silica micropowder is retained in the outer layer of the ceramic filter cartridge, while the mixed flue gas enters the inner layer of the ceramic filter cartridge to react with ammonia for denitrification.

[0011] Step S5: Silica powder collection and exhaust gas emission: The spherical silica particles after denitrification in step S4 are collected and discharged through the outlet. The treated clean exhaust gas is stored and then directly emitted.

[0012] The working principle of this invention is as follows: The upstream process is a micro-negative pressure system containing fine powder flue gas. After flowing through the cyclone collection chamber, the flue gas velocity at the outlet is approximately 16 m / s before entering the integrated denitrification device system for fine powder collection and denitrification. At the start-up of the spheroidizing furnace, considering that the system uses natural gas with oxygen enrichment and contains a large amount of moisture, the condensate generated in the low-temperature pipeline easily caking the filter cake layer, causing increased resistance. Therefore, a bypass pipeline is provided outside the integrated denitrification device. During low-temperature startup, the bypass pipeline is opened, and the inlet valve of the integrated denitrification device is closed. When the inlet flue gas temperature is ≥330℃, the inlet valve is opened, and the bypass inlet valve is closed.

[0013] At the inlet of the mixing chamber, there is a urea solution atomizing spray gun. The urea solution is pumped to the atomizing gun by a metering pump. The liquid is atomized by compressed gas and vaporized, decomposed, and converted into ammonia, water, and carbon dioxide at the temperature. The flue gas and the ammonia produced by the hydrolysis of urea are fully mixed in the mixing chamber.

[0014] To achieve high denitrification efficiency, the flue gas entering the mixing chamber must be ≥330℃. After the atomized urea solution is injected and vaporized for cooling, the flue gas must be kept within the temperature range (280-300℃) required for high-efficiency SCR denitrification.

[0015] To ensure sufficient mixing and hydrolysis time, a diversion guide plate is installed in the mixing chamber to ensure that the urea solution is hydrolyzed and fully mixed with nitrogen oxides in the flue gas, and to allow the micro powder to depressurize and separate into gas and solid, settling into the unloading chamber.

[0016] The mixed flue gas passes through a filter element with an attached catalyst. Fine powder is trapped on the outer surface of the filter element and falls into the ash discharge bin via pulse backwashing. Clean gas enters the clean gas chamber and is discharged. While flowing through the filter element, ammonia and nitrogen oxides undergo a reduction reaction under the action of the catalyst. The following are the hydrolysis and neutralization reaction equations for nitrogen oxides:

[0017] CO(NH2)2 + 2H2O → 2NH3 + CO2 Hydrolysis process

[0018] 4NO + 6NH3 → 5N2 + 6H2O (Neutralization of nitrogen oxides)

[0019] 4NH3 + 4NO2 + O2 → 4N2 + 6H2O (Neutralization of nitrogen oxides)

[0020] High-temperature flue gas containing fine powder enters the dust-laden zone. Under differential pressure, it passes through the filter element from the outside in. The surface of the filter element traps solid particles, which are then retained on the outer surface. As the thickness of the powder cake increases, the pressure difference between the inside and outside of the filter element increases. A pulse soot blowing system controls the pressure difference balance. The mixed flue gas passes through a filter element with a catalyst for catalytic denitrification, becoming clean gas that is then discharged through subsequent pipelines. Pulse soot blowing is controlled by a controller, with compressed air rapidly injected to expand the internal air pressure of the filter element, balancing the pressure difference between the inside and outside of the filter element. This effectively breaks down and loosens the powder cake, which falls into the unloading hopper. The discharge from the bottom of the unloading hopper is conveyed to a conveying device. The collected fine powder is then transported to a centralized point for storage, weighing, and packaging.

[0021] Preferably, the denitrification reaction in the ceramic filter cartridge during step S4 mainly produces NO. x The flue gas reacts with ammonia under the catalysis of vanadium pentoxide to produce nitrogen and water. The temperature is controlled at 280-300℃ during the reaction. The filter pores of the ceramic filter cartridge have a diameter of 0.1-0.8 micrometers and a flow rate of 0.5-0.7 m / min inside the filter cartridge. After one filtration cycle, the device automatically pulses backflushes to clean the dust and then enters a new filtration cycle.

[0022] The advantages of this invention are that, unlike existing denitrification technologies that use bag filters, denitrification devices installed outside the bags, or denitrification devices with honeycomb-shaped ceramic blocks, this invention uses a ceramic filter cartridge with vanadium pentoxide catalyst sprayed on the inner surface and ammonia passed through for denitrification. The ceramic filter cartridge replaces the bag filter, which has the advantage of low flow rate. When dust-laden gas (containing silica products, water vapor, dust, nitrogen oxides, etc.) passes through the ceramic filter cartridge, the ammonia (added to treat nitrogen oxides) reacts fully with the nitrogen oxides under the catalysis of vanadium pentoxide (at a temperature of about 280-300 degrees Celsius), thereby effectively reducing nitrogen oxides. Furthermore, the inner ring of the ceramic filter cartridge is a catalyst filter element, while the outer ring, with a thickness of 1-2 mm, is a normal filter cartridge, which can prevent the silicon electronic-grade products that need to be collected from production from coming into contact with vanadium pentoxide, as shown in Figure 3.

[0023] Preferably, in step S1, the urea solution concentration is 20-35%, the urea solution is pumped to the atomizing gun by a metering pump, the liquid is atomized by compressed gas, and vaporized and decomposed at the temperature, converting into ammonia, water and carbon dioxide. The flue gas and the ammonia after urea hydrolysis are fully mixed in the mixing chamber, and the temperature of the flue gas entering the mixing chamber is ≥330℃.

[0024] As a further preferred option, the urea solution concentration is 32%.

[0025] The advantage of this invention lies in the fact that the denitrification reducing agent (32% urea solution) is atomized and sprayed into the flue gas mixing chamber at the front end of the integrated collection and denitrification unit. The ammonia gas generated by hydrolysis is mixed and then enters the integrated denitrification device. The flue gas flows through the fiber layers with a large specific surface area and the attached catalyst, ensuring close contact with the catalyst. x It reacts with ammonia to produce nitrogen and water, achieving a denitrification rate of over 98%. The treated clean gas meets the emission requirements for dust and nitrogen oxides in the national comprehensive air pollutant emission standards.

[0026] Preferably, in step S2, alum pentoxide is first sprayed onto the inner surface of the ceramic filter cartridge using starch as a carrier in a rotary motion, and cannot penetrate to the outer surface. After the spraying is completed, the starch is burned off, and carbon dioxide is generated and emitted after the starch is burned off. The inside of the ceramic filter cartridge then becomes a catalyst ceramic filter element.

[0027] Preferably, in step S3, spherical silicon dioxide is generated by flame method, and the production adopts oxygen-enriched combustion of natural gas; the silicon powder generated by spheroidization is divided into coarse powder and fine powder. The coarse powder is discharged from the bottom of the cyclone separator, and the fine powder is collected by the dust collector at the top of the cyclone separator and sent to the denitrification device for denitrification.

[0028] As a preferred option, the downstream emission outlet is equipped with online NO monitoring. x The detector enables automatic tracking, adjustment, and control.

[0029] As a preferred option, after the initial production, the reaction water generated during the heating process (oxygen + natural gas, heated to 1000 degrees Celsius) (which will become condensate in the first 3 hours due to the low temperature) should not pass through the ceramic filter cartridge. Otherwise, the condensate will be adsorbed on the ceramic filter cartridge and will clog the filter cartridge when combined with the powder. Therefore, a bypass should be set up in the reactor during the heating stage of production to discharge the reaction water.

[0030] As a preferred method, ammonia is added (pure water is added to urea). The optimal conditions for ammonia vaporization are around 280-300 degrees Celsius. Therefore, in order to make denitrification more complete and to ensure that the flow velocity of dust-laden gas passing through the ceramic filter cartridge is 0.5-0.7 m / min.

[0031] A specially designed silica denitrification device includes a urea solution stirring tank, a urea solution storage tank, a conveying and valve device, an induced draft fan, an integrated denitrification device, a cyclone collection chamber, and a spheroidizing silicon furnace.

[0032] The urea solution stirring tank and the urea solution storage tank are connected front and rear. The conveying and valve device runs through the switches and pipelines of the entire device. The induced draft fan is connected to the integrated denitrification device and the flue gas bypass pipe through pipelines and expansion joints. The induced draft fan is equipped with an exhaust duct. The inlet of the cyclone collection chamber is connected to the outlet of the spheroidizing silicon furnace through a pipeline. The integrated denitrification device is the main reaction part of the device, which includes a denitrification chamber with multi-layer ceramic filter cartridges as the main body.

[0033] Preferably, the urea solution mixing tank includes a bucket elevator, a urea conveying bin, and a three-bladed agitator inside the tank. The bucket elevator is installed in front of the urea solution mixing tank, the urea conveying bin is installed on the bucket elevator to convey urea into the tank, and the three-bladed agitator is fixed inside the urea solution mixing tank. The urea solution storage tank is equipped with high and low level gauges, and the outlet of the urea solution storage tank is connected to the delivery pump pipeline for valve control. The delivery and valve device includes a delivery pump, a pipe valve, a flue gas bypass pipe, an expansion joint, a urea solution pipe, and a denitrification exhaust pipe. The pipe valve is located on the outlet pipe of the cyclone collection bin and the flue gas bypass pipe. The reducing section is located on the outlet pipe of the spheroidizing silicon furnace and the outlet pipe of the cyclone collection chamber. The urea solution pipe is located after the urea solution storage tank and is also equipped with several valves. The denitrification exhaust pipe is installed on the integrated denitrification device and connected to the induced draft fan. The integrated denitrification device also includes a mixing chamber, a clean gas chamber, a static pressure box, and a discharge chamber. Several diversion guide plates are installed in the mixing chamber, and an exhaust channel is provided outside the clean gas chamber. A crossbar is installed in the static pressure box, and several spray nozzles are installed on the crossbar. The discharge chamber includes a baffle, a discharge auger, and a discharge port. The discharge port is installed below the discharge auger, and the baffle surrounds the discharge chamber.

[0034] Preferably, the cyclone collection chamber is provided with a coarse silicon discharge port, the spheroidizing silicon furnace is divided into a angular silicon powder zone and a spherical silicon powder zone, and an auger feed port is installed on the top of the spheroidizing silicon furnace.

[0035] The advantage of using this invention is that by combining the denitrification process with a specially customized denitrification device, the process concept can be better applied to actual production, thereby improving the degradation rate of nitrogen oxide flue gas generated from the production of spherical silica.

[0036] In summary, the present invention has the following beneficial effects:

[0037] 1. By replacing the filter bag with a ceramic filter cartridge, the filter bag's drawbacks—high flow rate and poor temperature resistance—mean that it can only react with the incoming flue gas at a maximum temperature below 260°C, and the flue gas flow rate is too high, resulting in insufficient reaction. In this invention, the flue gas has a low flow rate after entering the filter cartridge. Alum pentoxide is sprayed inside the ceramic filter cartridge as a catalyst. When dust-laden gas (containing silica products, water vapor, dust, nitrogen oxides, etc.) passes through the ceramic filter cartridge, ammonia (added to treat nitrogen oxides) reacts fully with the nitrogen oxides under the catalysis of alum pentoxide (at a temperature of around 280-300°C), greatly improving the denitrification rate to over 98%.

[0038] 2. Due to the replacement of ceramic filter cartridges and their temperature resistance (above 330℃), the optimal conditions for ammonia water vaporization are around 280-300 degrees Celsius. Therefore, in order to make denitrification more complete;

[0039] 3. Use in conjunction with a specially designed denitrification device to make denitrification more thorough and exhaust gas cleaner;

[0040] 4. The process is efficient and simple, the equipment is relatively simple and easy to operate, which can also reduce the difficulty of actual operation of the denitrification process. Attached Figure Description

[0041] Figure 1 This is an overall diagram of the denitrification device of the present invention;

[0042] Figure 2 This is an enlarged view of section A of the denitrification device of the present invention;

[0043] Figure 3 is a structural diagram of the ceramic filter cartridge for the denitrification chamber of the present invention;

[0044] Figure 4 is a schematic diagram of the diversion guide plate of the present invention;

[0045] In the diagram: 1. Urea solution mixing tank; 11. Bucket elevator; 12. Urea conveying bin; 13. Three-bladed agitator; 2. Urea solution storage tank; 21. High and low level gauges; 3. Conveying and valve device; 31. Conveying pump; 32. Pipe valve; 33. Flue gas bypass pipe; 34. Expansion joint; 35. Urea solution pipe; 36. Denitrification exhaust pipe; 4. Exhaust fan; 41. Exhaust stack; 5. Integrated denitrification unit; 51. Mixing bin; 52. Denitrification bin; 521. Ceramic Filter cartridge; 522, catalyst filter element; 523, filter holes; 53, clean air chamber; 54, static pressure box; 55, unloading chamber; 541, crossbar; 542, spray nozzle; 551, baffle; 552, discharge auger; 6, cyclone collection chamber; 61, crude silicon discharge port; 7, spheroidizing silicon furnace; 71, angular silicon powder zone; 72, spherical silicon powder zone; 73, auger feed port; 8, diversion guide plate; 81, mounting rod; 82, guide plate; 83, adjusting component; 84, strip hole. Detailed Implementation

[0046] The following specific embodiments are merely illustrative of the present invention and are not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of the present invention.

[0047] Example 1

[0048] Step S1: Preparation of ammonia as a denitrification reducing agent: Urea is dissolved in pure water to prepare a urea solution, which is stored in a storage tank. The concentration of the urea solution is 32%. The 32% urea solution is pumped to the atomizing gun through a metering pump. The liquid is atomized by compressed gas, and then vaporized and decomposed at the temperature, converting into ammonia, water, and carbon dioxide. In the mixing chamber, the flue gas and the ammonia produced by urea hydrolysis are fully mixed. The temperature of the flue gas entering the mixing chamber is ≥330℃. The ammonia generated by the hydrolysis of the urea solution then enters the ceramic filter cartridge for reaction.

[0049] Step S2: Catalyst spraying in the denitrification ceramic filter cartridge: Sufficient alum pentoxide is sprayed onto the inner surface of the ceramic filter cartridge using starch as a carrier in a rotary motion. It cannot penetrate to the outer surface. After spraying, the starch is burned off, and carbon dioxide is generated and emitted. The inside of the ceramic filter cartridge then becomes a catalyst ceramic filter element, which serves as a catalyst in the denitrification reaction. It penetrates to within 2 mm of the outer wall of the ceramic filter cartridge.

[0050] Step S3: Preparation and transport of spherical silica micro powder: Spherical silica is generated by flame method, and the production adopts oxygen-enriched combustion of natural gas; the silica powder generated by spheroidization is divided into coarse powder and fine powder. The coarse powder is discharged from the bottom of the cyclone separator, and the fine powder is collected by the dust collector at the top of the cyclone separator and sent to the denitrification device for denitrification.

[0051] Step S4: Denitrification process of spherical silica micropowder: The silica micropowder generated in step S3 is mixed with flue gas with high nitrogen and oxygen content first and then enters the denitrification chamber for denitrification reaction. The spherical silica micropowder is retained on the outer layer of the ceramic filter cartridge, while the mixed flue gas enters the inner layer of the ceramic filter cartridge to react with ammonia for denitrification.

[0052] Step S5: Silica powder collection and exhaust gas emission: The spherical silica particles after denitrification in step S4 are collected and discharged through the outlet, and the treated clean exhaust gas is directly emitted.

[0053] As shown in Figures 1-2, a specially designed denitrification device is used, including a urea solution stirring tank 1, a urea solution storage tank 2, a conveying and valve device 3, an induced draft fan 4, an integrated denitrification device 5, a cyclone collection chamber 6, and a spheroidizing silicon furnace 7.

[0054] The urea solution stirring tank 1 and the urea solution storage tank 2 are connected front and rear. The conveying and valve device 3 runs through the switches and pipelines of the entire device. The induced draft fan 4 is connected to the integrated denitrification device 5 and the flue gas bypass pipe 33 through the pipeline and expansion joint 34. The induced draft fan 4 is equipped with an exhaust duct 41. The inlet of the cyclone collection chamber 6 is connected to the outlet of the spheroidizing silicon furnace 7 through the pipeline. The integrated denitrification device 5 is the main reaction part of the device, which includes a denitrification chamber 52 with multi-layer ceramic filter cartridges as the main body.

[0055] The urea solution mixing tank 1 includes a bucket elevator 11, a urea conveying bin 12, and a three-bladed agitator 13 inside the tank. The bucket elevator 11 is installed in front of the urea solution mixing tank 1, and the urea conveying bin 12 is installed on the bucket elevator 11 to convey urea into the tank. The three-bladed agitator 13 is fixed inside the urea solution mixing tank 1. The urea solution storage tank 2 is equipped with a high and low level gauge 21, and the outlet of the urea solution storage tank 2 is connected to the conveying pump 31 by a valve for control. The conveying and valve device 3 includes a conveying pump 31, a pipe valve 32, a flue gas bypass pipe 33, an expansion joint 34, a urea solution pipe 35, and a denitrification exhaust pipe 36. The pipe valve 32 is located on the outlet pipe of the cyclone collection bin 6 and the flue gas bypass pipe 33, and the expansion joint 34 is located on the spheroidizing silicon furnace. On the outlet pipe of 7 and the outlet pipe of cyclone collection chamber 6, urea solution pipe 35 is located after urea solution storage tank 2 and is also equipped with several valves; denitrification exhaust pipe is installed on integrated denitrification device 5 and connected to induced draft fan 4; integrated denitrification device 5 also includes mixing chamber 51, clean gas chamber 53, static pressure box 54 and unloading chamber 55, several diversion guide plates 8 are installed in mixing chamber 51, and exhaust channel 531 is provided outside clean gas chamber 53; a crossbar 541 is installed in static pressure box 54, and several spray nozzles 542 are installed on crossbar 541; unloading chamber 55 includes baffle 551, discharge auger 552 and discharge port 553, discharge port 553 is installed under discharge auger 552, and baffle 551 surrounds unloading chamber 55;

[0056] The cyclone collection chamber 6 is equipped with a coarse silicon discharge port 61. The spheroidizing silicon furnace 7 is divided into a angular silicon powder zone 71 and a spherical silicon powder zone 72. The top of the spheroidizing silicon furnace 7 is equipped with an auger feed port 73.

[0057] The working principle of the device in this embodiment is as follows: After the raw silicon is introduced into the auger feed inlet 73, it first enters the angular silicon powder zone 71 for 2500℃ natural gas oxygen-enriched combustion to convert it into spherical silicon powder, which then enters the spherical silicon powder zone 72. The material composition of the flue gas entering the cyclone collection chamber 6 from the silicon furnace is silicon powder, H2O, CO2, and nitrogen oxides. The coarse silicon outlet 61 under the cyclone collection chamber 6 first outputs the primary coarse silicon, and the fine silicon and flue gas enter the integrated denitrification device 5 together. On the other side, a 32% urea solution is dissolved and, after the temperature reaches 330℃, it enters the mixing chamber 51 through the urea solution pipe 35 to fully mix with the flue gas. It should be noted here that... Production must be completed before collection and denitrification; denitrification and production should not be carried out simultaneously. During the denitrification process, flue gas and silicon powder first enter the mixing chamber 51 and are mixed evenly through the diversion guide plate 8. Then, ammonia is sprayed onto the static pressure box 54 and then enters the denitrification chamber 52. The ceramic filter cartridge undergoes a catalyst denitrification reaction. After the reaction is completed, the treated clean gas is stored in the clean gas chamber 53 and then directly discharged. The fine silicon powder enters the unloading chamber 55, passes through the unloading plate, and enters the unloading auger 552 and discharge port 553 for collection. Water vapor and carbon dioxide clean gas in the process can be introduced into the exhaust stack of the induced draft fan through the flue gas bypass pipe 33 and the denitrification exhaust pipe 36 connected to the denitrification device before being discharged.

[0058] Example 2

[0059] Step S1: Preparation of ammonia as a denitrification reducing agent: Urea is dissolved in pure water to prepare a urea solution, which is stored in a storage tank. The concentration of the urea solution is 20%. The 20% urea solution is pumped to the atomizing gun through a metering pump. The liquid is atomized by compressed gas, and then vaporized and decomposed at the temperature, converting into ammonia, water, and carbon dioxide. In the mixing chamber, the flue gas and the ammonia produced by urea hydrolysis are fully mixed. The temperature of the flue gas entering the mixing chamber is ≥330℃. The ammonia generated by the hydrolysis of the urea solution then enters the ceramic filter cartridge for reaction.

[0060] Step S2: Catalyst spraying in the denitrification ceramic filter cartridge: Sufficient alum pentoxide is sprayed onto the inner surface of the ceramic filter cartridge using starch as a carrier in a rotary motion. It cannot penetrate to the outer surface. After spraying, the starch is burned off, and carbon dioxide is generated and emitted. The inside of the ceramic filter cartridge then becomes a catalyst ceramic filter element, which serves as a catalyst in the denitrification reaction. It penetrates to within 2 mm of the outer wall of the ceramic filter cartridge.

[0061] Step S3: Preparation and transport of spherical silica micro powder: Spherical silica is generated by flame method, and the production adopts oxygen-enriched combustion of natural gas; the silica powder generated by spheroidization is divided into coarse powder and fine powder. The coarse powder is discharged from the bottom of the cyclone separator, and the fine powder is collected by the dust collector at the top of the cyclone separator and sent to the denitrification device for denitrification.

[0062] Step S4: Denitrification process of spherical silica micropowder: The silica micropowder generated in step S3 is mixed with flue gas with high nitrogen and oxygen content first and then enters the denitrification chamber for denitrification reaction. The spherical silica micropowder is retained on the outer layer of the ceramic filter cartridge, while the mixed flue gas enters the inner layer of the ceramic filter cartridge to react with ammonia for denitrification.

[0063] Step S5: Silica powder collection and exhaust gas emission: The spherical silica particles after denitrification in step S4 are collected and discharged through the outlet, and the treated clean exhaust gas is directly emitted.

[0064] Example 3

[0065] Step S1: Preparation of ammonia as a denitrification reducing agent: Urea is dissolved in pure water to prepare a urea solution, which is stored in a storage tank. The concentration of the urea solution is 35%. The 35% urea solution is pumped to the atomizing gun through a metering pump. The liquid is atomized by compressed gas, and then vaporized and decomposed at the temperature, converting into ammonia, water, and carbon dioxide. In the mixing chamber, the flue gas and the ammonia produced by urea hydrolysis are fully mixed. The temperature of the flue gas entering the mixing chamber is ≥330℃. The ammonia generated by the hydrolysis of the urea solution then enters the ceramic filter cartridge for reaction.

[0066] Step S2: Catalyst spraying in the denitrification ceramic filter cartridge: Sufficient alum pentoxide is sprayed onto the inner surface of the ceramic filter cartridge using starch as a carrier in a rotary motion. It cannot penetrate to the outer surface. After spraying, the starch is burned off, and carbon dioxide is generated and emitted. The inside of the ceramic filter cartridge then becomes a catalyst ceramic filter element, which serves as a catalyst in the denitrification reaction. It penetrates to within 2 mm of the outer wall of the ceramic filter cartridge.

[0067] Step S3: Preparation and transport of spherical silica micro powder: Spherical silica is generated by flame method, and the production adopts oxygen-enriched combustion of natural gas; the silica powder generated by spheroidization is divided into coarse powder and fine powder. The coarse powder is discharged from the bottom of the cyclone separator, and the fine powder is collected by the dust collector at the top of the cyclone separator and sent to the denitrification device for denitrification.

[0068] Step S4: Denitrification process of spherical silica micropowder: The silica micropowder generated in step S3 is mixed with flue gas with high nitrogen and oxygen content first and then enters the denitrification chamber for denitrification reaction. The spherical silica micropowder is retained on the outer layer of the ceramic filter cartridge, while the mixed flue gas enters the inner layer of the ceramic filter cartridge to react with ammonia for denitrification.

[0069] Step S5: Silica powder collection and exhaust gas emission: The spherical silica particles after denitrification in step S4 are collected and discharged through the outlet, and the treated clean exhaust gas is directly emitted.

[0070] Example 4

[0071] Step S1: Preparation of ammonia as a denitrification reducing agent: Urea is dissolved in pure water to prepare a urea solution, which is stored in a storage tank. The concentration of the urea solution is 25%. The 25% urea solution is pumped to the atomizing gun through a metering pump. The liquid is atomized by compressed gas, and then vaporized and decomposed at the temperature, converting into ammonia, water, and carbon dioxide. In the mixing chamber, the flue gas and the ammonia produced by urea hydrolysis are fully mixed. The temperature of the flue gas entering the mixing chamber is ≥330℃. The ammonia generated by the hydrolysis of the urea solution then enters the ceramic filter cartridge for reaction.

[0072] Step S2: Catalyst spraying in the denitrification ceramic filter cartridge: Alum pentoxide is sprayed onto the inner surface of the ceramic filter cartridge using starch as a carrier in a rotary motion. It cannot penetrate to the outer surface. After the spraying is completed, the starch is burned off, and carbon dioxide is emitted after the starch is burned off. The inside of the ceramic filter cartridge then becomes a catalyst ceramic filter element, which serves as a catalyst in the denitrification reaction. It penetrates to within 2 mm of the outer wall of the ceramic filter cartridge.

[0073] Step S3: Preparation and transport of spherical silica micro powder: Spherical silica is generated by flame method, and the production adopts oxygen-enriched combustion of natural gas; the silica powder generated by spheroidization is divided into coarse powder and fine powder. The coarse powder is discharged from the bottom of the cyclone separator, and the fine powder is collected by the dust collector at the top of the cyclone separator and sent to the denitrification device for denitrification.

[0074] Step S4: Denitrification process of spherical silica micropowder: The silica micropowder generated in step S3 is mixed with flue gas with high nitrogen and oxygen content first and then enters the denitrification chamber for denitrification reaction. The spherical silica micropowder is retained on the outer layer of the ceramic filter cartridge, while the mixed flue gas enters the inner layer of the ceramic filter cartridge to react with ammonia for denitrification.

[0075] Step S5: Silica powder collection and exhaust gas emission: The spherical silica particles after denitrification in step S4 are collected and discharged through the outlet, and the treated clean exhaust gas is directly emitted.

[0076] Example 5

[0077] Step S1: Preparation of ammonia as a denitrification reducing agent: Urea is dissolved in pure water to prepare a urea solution, which is stored in a storage tank. The concentration of the urea solution is 30%. The 30% urea solution is pumped to the atomizing gun through a metering pump. The liquid is atomized by compressed gas, and then vaporized and decomposed at the temperature, converting into ammonia, water, and carbon dioxide. In the mixing chamber, the flue gas and the ammonia produced by urea hydrolysis are fully mixed. The temperature of the flue gas entering the mixing chamber is ≥330℃. The ammonia generated by the hydrolysis of the urea solution then enters the ceramic filter cartridge for reaction.

[0078] Step S2: Catalyst spraying in the denitrification ceramic filter cartridge: Alum pentoxide is sprayed onto the inner surface of the ceramic filter cartridge using starch as a carrier in a rotary motion. It cannot penetrate to the outer surface. After the spraying is completed, the starch is burned off, and carbon dioxide is emitted after the starch is burned off. The inside of the ceramic filter cartridge then becomes a catalyst ceramic filter element, which serves as a catalyst in the denitrification reaction. It penetrates to within 2 mm of the outer wall of the ceramic filter cartridge.

[0079] Step S3: Preparation and transport of spherical silica micro powder: Spherical silica is generated by flame method, and the production adopts oxygen-enriched combustion of natural gas; the silica powder generated by spheroidization is divided into coarse powder and fine powder. The coarse powder is discharged from the bottom of the cyclone separator, and the fine powder is collected by the dust collector at the top of the cyclone separator and sent to the denitrification device for denitrification.

[0080] Step S4: Denitrification process of spherical silica micropowder: The silica micropowder generated in step S3 is mixed with flue gas with high nitrogen and oxygen content first and then enters the denitrification chamber for denitrification reaction. The spherical silica micropowder is retained on the outer layer of the ceramic filter cartridge, while the mixed flue gas enters the inner layer of the ceramic filter cartridge to react with ammonia for denitrification.

[0081] Step S5: Silica powder collection and exhaust gas emission: The spherical silica particles after denitrification in step S4 are collected and discharged through the outlet, and the treated clean exhaust gas is directly emitted.

[0082] Comparative Example 1

[0083] Unlike Example 1, no special denitrification device was used; the ceramic filter cartridge was replaced with a cloth bag, and the denitrification ceramic blocks were collected.

[0084] The detection standards for the embodiments and comparative examples of this invention are as follows:

[0085] Flue gas emission requirements: Meet the "DB11 / 501-2017 Integrated Emission Standard for Air Pollutants"; nitrogen oxides (≤50mg / Nm³); particulate matter concentration ≤5mg / Nm³.

[0086]

[0087] The test results show that in Example 1, the hydrolysis ammonia production denitrification with a 32% urea concentration, combined with a specially designed denitrification device, achieved the highest denitrification rate, reaching 98.5%. However, the denitrification process with a 35% urea concentration did not significantly improve the effect, and the effect decreased below 32%. Furthermore, the ammonia slip in the examples was all within 5 mg. Compared with the comparative example, it can be concluded that the denitrification effect of the process and device of the present invention is significant.

Claims

1. A spherical silica denitrification device, characterized in that, It includes a urea solution mixing tank (1), a urea solution storage tank (2), a conveying and valve device (3), an induced draft fan (4), an integrated denitrification device (5), a cyclone collection chamber (6), and a spheroidizing silicon furnace (7). The urea solution stirring tank (1) is connected to the urea solution storage tank (2) at the front and rear. The conveying and valve device (3) runs through the switches and pipes of the entire device. The induced draft fan (4) is connected to the integrated denitrification device (5) through pipes and expansion joints (34) and to the flue gas bypass pipe (33). The induced draft fan (4) is equipped with an exhaust duct (41). The inlet of the cyclone collection chamber (6) is connected to the outlet of the spheroidizing silicon furnace (7) through a pipe. The integrated denitrification device (5) is the main reaction part of the device, which includes a denitrification chamber (52) with multi-layer ceramic filter cartridges as the main body. The urea solution mixing tank (1) includes a bucket elevator (11), a urea conveying bin (12), and a three-bladed agitator (13) inside the tank. The bucket elevator (11) is installed in front of the urea solution mixing tank (1), and the urea conveying bin (12) is installed on the bucket elevator (11) to convey urea into the tank. The three-bladed agitator (13) is fixed inside the urea solution mixing tank (1). The urea solution storage tank (2) is equipped with a high / low level gauge (21), and the urea solution storage... The outlet of the spare tank (2) is connected to the pipeline of the conveying pump (31) and controlled by a valve; the conveying and valve device (3) includes the conveying pump (31), a pipe valve (32), a flue gas bypass pipe (33), an expansion joint (34), a urea solution pipe (35), and a denitrification exhaust pipe (36). The pipe valve (32) is located on the outlet pipe of the cyclone collection chamber (6) and the flue gas bypass pipe (33), and the expansion joint (34) is located on the outlet pipe of the spheroidizing silicon furnace (7) and the outlet pipe of the cyclone collection chamber (6). The urea solution pipe (35) is located after the urea solution storage tank (2) and is also equipped with several valves; the denitrification exhaust pipe is installed on the integrated denitrification device (5) and connected to the induced draft fan (4); the integrated denitrification device (5) also includes a mixing chamber (51), a clean gas chamber (53), a static pressure box (54), and a discharge chamber (55). The static pressure box (54) is located between the mixing chamber (51) and the denitrification chamber (52), and the discharge chamber (55) is located at the bottom of the clean gas chamber (53). The mixing chamber (51) is equipped with several diversion guide plates (8), and the clean air chamber (53) is provided with an exhaust channel; a crossbar (541) is installed in the static pressure box (54), and several spray nozzles (542) are installed on the crossbar (541); the unloading chamber (55) includes a baffle (551), a discharge auger (552) and a discharge port (553), the discharge port (553) is installed under the discharge auger (552), and the baffle (551) surrounds the unloading chamber (55); Flue gas and silicon powder first enter the mixing chamber (51) and are mixed evenly by the diversion guide plate (8). Then ammonia is sprayed into the static pressure box (54) and then enters the denitrification chamber (52) and the ceramic filter cartridge is used for catalyst denitrification reaction. After the reaction is completed, the treated clean gas is stored in the clean gas chamber (53) and then directly discharged. The fine silicon powder enters the unloading chamber (55) and enters the unloading auger (552) through the unloading plate and is discharged and collected at the outlet (553).

2. The spherical silica denitrification device according to claim 1, characterized in that, The cyclone collection chamber (6) is provided with a crude silicon discharge port (61).

3. The spherical silica denitrification device according to claim 1, characterized in that, The spheroidizing silicon furnace (7) is divided into a angular silicon powder zone (71) and a spherical silicon powder zone (72). The top of the spheroidizing silicon furnace (7) is equipped with an auger feed inlet (73).

4. The denitrification process of the spherical silica denitrification device according to claim 1, characterized in that, The process includes the following steps: Step S1: Preparation of ammonia as a denitrification reducing agent: Urea is dissolved in pure water to prepare a urea solution, which is stored in a storage tank. The urea solution is hydrolyzed to generate ammonia gas, which then enters the ceramic filter cartridge for reaction. Step S2: Catalyst spraying in the denitrification ceramic filter cartridge: Alum pentoxide is used as the catalyst in the denitrification reaction, and the treated alum pentoxide is evenly sprayed on the inner wall of the ceramic filter cartridge, penetrating to the point where there is still 1-2 mm left from the outer wall of the ceramic filter cartridge. Step S3: Preparation and transport of spherical silica micro powder: Silica is fed into a spheroidizing furnace and spheroidized to generate spherical silica powder. The generated silica powder and flue gas enter the denitrification device. Step S4: Denitrification process of spherical silica micropowder: The silica micropowder generated in step S3 and the flue gas with high nitrogen and oxygen content first enter the mixing chamber for mixing and then enter the denitrification chamber for denitrification reaction. The spherical silica micropowder is retained in the outer layer of the ceramic filter cartridge, while the mixed flue gas enters the inner layer of the ceramic filter cartridge to react with ammonia for denitrification. Step S5: Silica powder collection and exhaust gas emission: The spherical silica particles after denitrification in step S4 are discharged and collected through the outlet. The treated clean exhaust gas can be stored and then directly emitted.

5. The denitrification process of the spherical silica denitrification device according to claim 4, characterized in that, The denitrification reaction inside the ceramic filter cartridge in step S4 mainly produces NO. x The flue gas reacts with ammonia under the catalysis of vanadium pentoxide to produce nitrogen and water. The temperature is controlled at 280-300℃ during the reaction. The pore size of the ceramic filter cartridge is 0.1-0.8 micrometers, and the flow rate inside the filter cartridge is 0.5-0.7 m / min. After one filtration cycle, the device automatically pulses backflushing to clean the dust, and then enters a new filtration cycle.

6. The denitrification process of the spherical silica denitrification device according to claim 4, characterized in that, In step S1, the urea solution concentration is 20-35%. The urea solution is pumped to the atomizing gun through a metering pump. The liquid is atomized by compressed gas, vaporized and decomposed at the temperature, and converted into ammonia, water and carbon dioxide. The flue gas and the ammonia after urea hydrolysis are fully mixed in the mixing chamber. The temperature of the flue gas entering the mixing chamber is ≥330℃.

7. The denitrification process of the spherical silica denitrification device according to claim 4, characterized in that, In step S2, vanadium pentoxide is first sprayed onto the inner surface of the ceramic filter cartridge using starch as a carrier in a rotary motion. It cannot penetrate to the outer surface. After the spraying is completed, the starch is burned off, and carbon dioxide is generated and emitted. The inside of the ceramic filter cartridge then becomes a catalyst ceramic filter element.

8. The denitrification process of the spherical silica denitrification device according to claim 4, characterized in that, In step S3, spherical silicon dioxide is generated by flame method, and the production adopts oxygen-enriched combustion of natural gas. The silicon powder generated by spheroidization is divided into coarse powder and fine powder. The coarse powder is discharged from the bottom of the cyclone separator, and the fine powder is collected by the dust collector at the top of the cyclone separator and sent to the denitrification device for denitrification.

9. The denitrification process of the spherical silica denitrification device according to claim 4, characterized in that, In the clean exhaust gas treated in step S5, the dust concentration is ≤5mg / Nm³ and the nitrogen oxide concentration is ≤50mg / Nm³, which meets the national emission standards.

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