Waste gas treatment multi-stage heavy metal removal synergistic denitration system and waste gas treatment multi-stage heavy metal removal synergistic denitration method

Abstract

The invention discloses a multistage heavy metal removal synergistic denitration system and method for waste gas treatment, and belongs to the technical field of waste gas denitration, the multistage heavy metal removal synergistic denitration system comprises a first thallium and lead removal synergistic denitration layer, a second thallium and lead removal synergistic denitration layer and a third denitration layer; the first thallium and lead removal synergistic denitration layer is arranged at an outlet of the preheater, the end, away from the preheater, of the first thallium and lead removal synergistic denitration layer is connected with the SCR denitration reactor through a flue, the second thallium and lead removal synergistic denitration layer is arranged at an inlet of the SCR denitration reactor, and the third denitration layer is arranged in the SCR denitration reactor. The invention further discloses a waste gas treatment multi-stage heavy metal removal synergistic denitration method. The industrial problem of thallium / lead poisoning in cement kiln SCR denitration is solved through three-stage cooperation of filtration, adsorption and catalytic reduction, dynamic regeneration and anti-poisoning modification technologies, and the method has the four advantages of efficient denitration, heavy metal prevention and control, resource recovery and low-cost operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste gas denitrification, and particularly relates to a system and method for multi-stage heavy metal removal and collaborative denitrification of waste gas treatment. Background Technique

[0002] Nitrogen oxides are one of the most important air pollutants. The SCR denitrification technology is recognized as one of the most effective denitrification technologies. SCR is the full name of Selective Catalytic Reduction. With the requirements of ultra-low emissions in the cement industry, many cement kilns have started to add SCR denitrification systems in recent years. In the cement production process, raw materials, fuels, alternative raw materials, alternative fuels, co-disposed waste, etc. all contain thallium elements. Due to the characteristics of the cement kiln process, thallium will be recycled and enriched in the system. During the operation of the SCR denitrification system, over time, the thallium content in the catalyst will become higher and higher, resulting in catalyst poisoning and inactivation.

[0003] The thallium content in the raw materials is extremely low, all within 1 ppm. The co-disposed materials and coal have concentrations higher than 1 ppm, but relatively low. As the materials enter the production system and pass through high temperatures, up to over 1500 °C, thallium-containing and lead-containing substances will decompose and then become gaseous. As the flue gas exchanges heat with the materials, the gas temperature continuously drops. When it drops to a certain temperature, the gas becomes liquid and solid again and adheres to the soot. The test results show that during the process of cooling from 320 °C to 100 °C, a large amount of thallium and a certain amount of Pb are enriched in the SCR ash, waste heat boiler ash, and bag filter ash. The enrichment factor can reach thousands of times at most, and the thallium enrichment in the catalyst is even more serious, up to 10% at most.

[0004] In order to avoid catalyst poisoning and failure caused by the poisoning effect of Tl and Pb in the catalyst, therefore, it is urgent to design a system and method for multi-stage heavy metal removal and collaborative denitrification of waste gas treatment to solve the above-mentioned problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a system and method for multi-stage heavy metal removal and collaborative denitrification of waste gas treatment, which has the advantages of removing thallium and lead from the process link, ensuring good denitrification efficiency, prolonging the service life of the catalyst, and reducing the operation cost of enterprises, and solves the problems mentioned in the background technique.

[0006] To achieve the above purpose, the specific technical solutions of a system and method for multi-stage heavy metal removal and collaborative denitrification of waste gas treatment of the present invention are as follows: A system for multi-stage heavy metal removal and collaborative denitrification of waste gas treatment includes a first thallium and lead removal and collaborative denitrification layer, a second thallium and lead removal layer, and a third denitrification layer; The first co-denitrification layer for removing thallium and lead is arranged at the outlet of the preheater. One end of the first co-denitrification layer for removing thallium and lead, which is far from the preheater, is connected to the SCR denitrification reactor through a flue. Through the first co-denitrification layer for removing thallium and lead, the dust in the flue gas discharged from the preheater is filtered and primary denitrification is carried out. The second thallium and lead removal layer is arranged at the inlet of the SCR denitrification reactor. Through the second thallium and lead removal layer, the physically and / or chemically adsorbed flue gas after filtration and primary denitrification is treated to remove thallium and lead in the flue gas. The third denitrification layer is arranged inside the SCR denitrification reactor. Through the third denitrification layer, the performance of resisting thallium and lead poisoning is improved, and the service life is extended.

[0007] Furthermore, the first co-denitrification layer for removing thallium and lead includes a filtering component. The dust in the flue gas discharged from the preheater is filtered through the filtering component, and a denitrification layer is arranged on the inner wall of the filtering component. The NOx in the flue gas is initially removed through the denitrification layer.

[0008] Furthermore, a double-outlet cyclone separator is arranged between the preheater and the filtering component. The flue gas discharged from the preheater is first pre-filtered through the double-outlet cyclone separator, and then secondarily filtered by the filtering component.

[0009] Furthermore, a filtering station and a cleaning station are also included. When the filtering component is at the filtering station, the filtering component is connected to the preheater and the SCR denitrification reactor. When the filtering component is at the cleaning station, the filtering component is connected to the pipeline of the storage tank. A cleaning component is arranged at the cleaning station. The cleaning component removes the dust on the filtering component at the cleaning station, and the removed dust is collected by the storage tank and then discharged after the recovery is completed. The specific number of the filtering components is two. When any one of the filtering components is at the filtering station, the other filtering component is at the cleaning station.

[0010] Furthermore, a connecting plate is also included. The connecting plate is connected to the two filtering components. A rotating shaft is connected to the connecting plate. The rotating shaft is driven by a driving member, and the filtering component rotates around the rotating shaft, so that the filtering component can be switched between the filtering station and the cleaning station. When the filtering component is at the filtering station, the filtering component is connected to the connecting plate. When the filtering component is at the cleaning station, the filtering component is separated from the connecting plate.

[0011] Furthermore, a conical sleeve is fixedly connected to the filtering component. The connecting plate is connected to the filtering component through the conical sleeve. An auxiliary plate is also included. The bottom end of the filtering component is attached to the auxiliary plate. The auxiliary plate includes a first plane, an inclined plane and a second plane. Both ends of the first plane are connected to the inclined plane, and the end of the inclined plane far from the first plane is connected to the second plane. The second plane is higher than the first plane. When the filtering component is at the first plane, the filtering component is connected to the connecting plate. When the filtering component is at the second plane, the filtering component is separated from the connecting plate.

[0012] Further, the second thallium and lead removal layer is composed of activated carbon and a binder. Depending on physical and / or chemical adsorption, at an operating temperature of 180 - 350°C, thallium and lead in the flue gas are further removed. Both ends of the second thallium and lead removal layer are respectively connected to two storage rollers, and both storage rollers can rotate around their own centers. There are two desorption stations and one adsorption station in the SCR denitration reactor. The adsorption station is located between the two desorption stations. The second thallium and lead removal layer at the adsorption station physically adsorbs the flue gas. The desorption station is equipped with a desorption component. The second thallium and lead removal layer at the desorption station heats the activated carbon saturated with adsorption in a high-temperature inert gas environment through the desorption component, so that the adsorbed thallium and lead are desorbed.

[0013] Further, when the second thallium and lead removal layer moves in the first direction, the second thallium and lead removal layer saturated with adsorption at the adsorption station moves to the desorption station at the first direction end. The desorption component at the first direction end is activated, and high-temperature inert gas is sprayed on the second thallium and lead removal layer saturated with adsorption at the desorption station at the first direction end, so that the adsorbed thallium and lead are desorbed. The second thallium and lead removal layer that has completed desorption at the desorption station at the second direction end moves to the adsorption station to adsorb thallium and lead; When the second thallium and lead removal layer moves in the second direction, the second thallium and lead removal layer saturated with adsorption at the adsorption station moves to the desorption station at the second direction end. The desorption component at the second direction end is activated, and high-temperature inert gas is sprayed on the second thallium and lead removal layer saturated with adsorption at the desorption station at the second direction end, so that the adsorbed thallium and lead are desorbed. The second thallium and lead removal layer that has completed desorption at the desorption station at the first direction end moves to the adsorption station to adsorb thallium and lead.

[0014] Further, the third denitration layer is composed of 2 - 4 layers of catalysts, and honeycomb denitration catalysts are used to improve the performance of the catalyst against thallium and lead poisoning and extend its service life.

[0015] A method for multi-stage heavy metal removal and synergistic denitration of waste gas treatment includes the above-mentioned system for multi-stage heavy metal removal and synergistic denitration of waste gas treatment, and also includes the following steps: S1. The flue gas at the outlet of the preheater first enters the double-outlet cyclone separator for pre-filtration; S2. The pre-filtered flue gas enters the first thallium and lead removal and denitration layer to perform secondary filtration on the dust in the pre-filtered flue gas and primary denitration; S3. The flue gas after secondary filtration enters the second thallium and lead removal layer to physically and / or chemically adsorb the flue gas that has undergone secondary filtration and primary denitration, and remove thallium and lead in the flue gas; S4. The flue gas subjected to physical and / or chemical adsorption enters the SCR denitration reactor and passes through the third denitration layer to improve the performance against thallium and lead poisoning.

[0016] The present invention has the following advantages: By means of the three-level collaborative, dynamic regeneration and anti-poisoning modification technologies of "filtration - adsorption - catalytic reduction", the industry problem of thallium / lead poisoning in SCR denitrification of cement kilns is overcome, and it has four major advantages of high-efficiency denitrification, heavy metal prevention and control, resource recovery and low-cost operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the positions of the first thallium and lead removal and denitrification layer, the second thallium and lead removal layer and the third denitrification layer of the present invention; Figure 2 It is a schematic diagram of the structure of the first thallium and lead removal and denitrification layer and the auxiliary plate of the present invention; Figure 3 It is a schematic diagram of the structures of the filtration station, the cleaning station and the cleaning assembly of the present invention; Figure 4 It is a schematic diagram of the structures of the auxiliary plate and the conical sleeve of the present invention; Figure 5 It is a schematic diagram of the structures of the adsorption station and the desorption station of the present invention; Figure 6 It is a schematic diagram of the structures of the belt pulley and the belt of the present invention; Figure 7 It is a schematic diagram of the process structure for heating inert gas of the present invention; Explanation of the marks in the figure: 1, flue; 11, filtration station; 12, cleaning station; 13, adsorption station; 14, desorption station; 2, first thallium and lead removal and denitrification layer; 21, conical sleeve; 22, limit plate; 23, first motor; 24, rotating shaft; 25, connecting plate; 26, filtration assembly; 3, auxiliary plate; 31, first plane; 32, inclined plane; 33, second plane; 4, cleaning assembly; 41, pulse jet nozzle; 42, vibrating plate; 5, SCR denitrification reactor; 6, second thallium and lead removal layer; 61, storage roller; 62, rotating rod; 63, belt pulley; 64, belt; 65, second motor; 7, desorption assembly; 8, cyclone separator; 9, third denitrification layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0019] Those skilled in the art can understand that although some embodiments herein include certain features included in other embodiments rather than other features, the combination of features of different embodiments is meant to be within the scope of the present invention and forms different embodiments. For example, in the claims, any one of the claimed embodiments can be used in any combination.

[0020] The following refers to the Figure 1 to the Figure 7 system and method for multi-stage heavy metal removal and collaborative denitrification of waste gas treatment of the present invention are described.

[0021] Nitrogen oxides are one of the most important air pollutants. And the SCR denitrification technology is recognized as one of the most effective denitrification technologies. SCR is the full name of Selective Catalytic Reducation. With the requirements of ultra-low emissions in the cement industry, many cement kilns have started to add SCR denitrification systems in recent years. In the cement production process, raw materials, fuels, alternative raw materials, alternative fuels, co-disposed waste, etc. all contain thallium elements. Due to the characteristics of the cement kiln process, thallium will be cyclically enriched in the system. During the operation of the SCR denitrification system, over time, the thallium content in the catalyst will become higher and higher, resulting in catalyst poisoning and inactivation.

[0022]

[0023] The above are the measured data. The thallium content in the raw materials is extremely low, all within 1 ppm. The co-disposed materials and coal have concentrations higher than 1 ppm, but they are relatively low. As the materials enter the production system and pass through high temperatures, up to above 1500 °C, thallium-containing and lead-containing substances will decompose and then turn into gases. As the flue gas exchanges heat with the materials, the gas temperature continuously drops. When it drops to a certain temperature, the gas changes back to liquid and solid states and adheres to the soot. The test results show that during the process of dropping from 320 °C to 100 °C, a large amount of thallium, as well as a small amount of Pb, are enriched in the SCR ash, waste heat boiler ash, and bag filter ash. The enrichment multiple can reach up to thousands of times, and the thallium enrichment in the catalyst is even more serious, up to 10%.

[0024] In order to avoid catalyst poisoning and failure caused by the poisoning effect of Tl and Pb in the catalyst, the system for multi-stage removal of heavy metals such as thallium, lead, and arsenic and collaborative denitrification of waste gas includes a first thallium and lead removal and collaborative denitrification layer 2, a second thallium and lead removal layer 6, and a third denitrification layer 9; The first thallium and lead co-denitrification layer 2 is arranged at the outlet of the preheater. One end of the first thallium and lead co-denitrification layer 2 away from the preheater is connected to the SCR denitrification reactor 5 through the flue 1. Through the first thallium and lead co-denitrification layer 2, the dust in the flue gas discharged from the preheater is filtered and preliminarily denitrified. Specifically, the first thallium and lead co-denitrification layer 2 includes a filtering component 26. The dust in the flue gas discharged from the preheater is filtered through the filtering component 26, and a denitrification layer is arranged on the inner wall of the filtering component 26. The NOx in the flue gas is initially removed through the denitrification layer.

[0025] Furthermore, the filtering component 26 can be a special ceramic filtering component 26 or a metal filtering component 26. The composition of the denitrification layer is specifically V-Ti or V-W-Ti, V-Mo-Ti. The temperature at the outlet of the preheater is between 280 - 360 °C and contains a high concentration of dust, usually 80 - 120 g / Nm 3 , and the main components of the dust are CaCO3, SiO2, etc. The filtering component 26 can be used to filter the dust, and the dust concentration can be filtered to 1 g / Nm 3 or less. In addition, there is a denitrification component on the inner wall, which can initially remove NO X in the flue gas, and the denitrification efficiency is about 10 - 30%.

[0026] Preparation method for adding a denitrification layer to the inner wall of the filtering component 26: Mix the required materials such as V-Ti or V-W-Ti, V-Mo-Ti to prepare a slurry, place it on the inner wall of the filtering component 26 by impregnation method, and then air-dry it naturally without calcination. However, when it is first installed and used, it is calcined with gradually heated flue gas until the temperature reaches 450 °C, calcined for 4 h, and then cooled to the normal temperature.

[0027] Since the first thallium and lead co-denitrification layer 2 uses a special ceramic or metal filtering component 26, the dust concentration at the outlet of the preheater is high (8(0 - 120 g / Nm³)) and the composition is complex (mainly CaCO3, SiO2, Al2O3, etc.). Long-term operation is likely to cause the filtering component 26 to be blocked, affecting the filtering and denitrification effects. It is difficult to clean the filtering component 26, and frequent replacement will increase the cost.

[0028] Therefore, a double - outlet cyclone separator 8 is provided between the pre - heater and the filter component 26. The flue gas discharged from the pre - heater first passes through the double - outlet cyclone separator 8 for pre - filtration to remove most of the large - particle dust, reduce the dust load entering the filter component 26, and decrease the clogging frequency. Subsequently, the filter component 26 conducts secondary filtration. Specifically, the pre - heater is generally composed of 4 - 6 cyclone cylinders. The double - outlet cyclone separator 8 is installed on the cyclone cylinders of the pre - heater. For example, if the original pre - heater consists of five cyclone cylinders and a new level is added, it becomes six levels. Thus, after the flue gas tangentially enters the double - outlet cyclone separator, the material and air are separated, and the gas is discharged from the upper and lower outlets respectively. The system has low resistance and high separation efficiency, reducing the dust concentration to 50mg / m 3 Below.

[0029] This system also includes a filtration station 11 and a cleaning station 12. When the filter component 26 is at the filtration station 11, the filter component 26 is connected to the pre - heater and the SCR denitration reactor 5. The cleaning station is equipped with a storage tank. When the filter component 26 is at the cleaning station 12, the filter component 26 is connected to the storage tank through a pipeline. The cleaning station 12 is provided with a cleaning component 4. The cleaning component 4 removes the dust on the filter component 26 at the cleaning station 12, and the removed dust is collected by the storage tank and then discharged after the recovery is completed. Specifically, the cleaned dust is transported to a closed storage tank through a pipeline to prevent dispersion and pollution. Subsequently, selective acid leaching extraction is carried out. Dilute nitric acid (HNO3, concentration 5 - 10%) or hydrochloric acid (HCl, concentration 3 - 5%) is used for leaching at room temperature, controlling the pH at 1 - 2 to dissolve thallium (Tl + / Tl 3+ )and lead (Pb 2+ ). An oxidant (such as H2O2) is added to oxidize Tl + to Tl 3+ to improve the leaching efficiency. The leaching solution is separated by a filter press, and the filter residue (mainly composed of CaCO3, SiO2, etc.) enters the solidification process; the filtrate enters the heavy - metal recovery section.

[0030] After that, the step - by - step precipitation method is used to recover heavy metals. First, lead is preferentially precipitated. NaOH is slowly added to the filtrate to adjust the pH to 9 - 10 to form a Pb(OH)2 precipitate. After centrifugal separation, it is calcined to PbO or electrolyzed to recover metallic lead. Subsequently, thallium is deeply separated. The pH of the remaining solution is adjusted to 3 - 4, and Na2S is added to form a Tl2S3 precipitate, or Tl 3+ is selectively adsorbed by an ion - exchange resin. The saturated resin is desorbed with dilute sulfuric acid, and metallic thallium is electrolytically recovered or Tl2SO4 industrial raw materials are prepared.

[0031] For the silicon - calcium - based residue after acid leaching, phosphates (such as Na3PO4) or sulfides (such as Na2S) are added to convert the residual heavy metals into compounds with low solubility products, reducing the leaching toxicity.

[0032] An on-line heavy metal analyzer is set at the inlet of the storage tank at the cleaning station 12 to detect the concentrations of thallium (Tl) and lead (Pb) in the dust in real time. The on-line heavy metal analyzer is set with a first concentration threshold. When the concentration detected by the on-line heavy metal analyzer is higher than the first concentration, the cleaned dust is transported to an independent sealed storage tank, and the dust is selectively acid-leached and extracted, and then the heavy metals are recovered by the fractional precipitation method. When the concentration detected by the on-line heavy metal analyzer is lower than the first concentration, the cleaned dust is transported to the raw material silo and recycled as raw materials to reduce the disposal cost. Specifically, a three-way valve is provided at the inlet of the storage tank. The three-way valve has an inlet, a first outlet and a second outlet. The inlet of the three-way valve is connected to the flue of the cleaning station, the first outlet of the three-way valve is connected to the storage tank, and the first outlet of the three-way valve is connected to the raw material silo through the flue. The inlet of the three-way valve can only be connected to one outlet. The three-way valve is electrically connected to the on-line heavy metal analyzer. When the concentration detected by the on-line heavy metal analyzer is higher than the first concentration, the inlet of the three-way valve is connected to the first outlet. When the concentration detected by the on-line heavy metal analyzer is lower than the first concentration, the inlet of the three-way valve is connected to the second outlet.

[0033] Preferably, the first concentration threshold is thallium (Tl): 250 mg / kg, lead (Pb): 50 mg / kg. In other embodiments of the present invention, the first concentration threshold can also be adjusted according to the characteristics of the raw materials and environmental protection standards. In addition, preferably according to the concentration of thallium (Tl), it is selected to be transported to an independent sealed storage tank or the raw material silo.

[0034] Preferably, the specific number of the filter assemblies 26 is two. When any one of the filter assemblies 26 is at the filtering station 11, the other filter assembly 26 is at the cleaning station 12. In other embodiments of the present invention, the specific number of the filter assemblies 26 can also be not less than two. When any one of the filter assemblies 26 is at the filtering station 11, the remaining filter assemblies 26 are at the cleaning station 12.

[0035] Each filter assembly 26 is composed of multiple filter cartridges, preferably hundreds of filter cartridges.

[0036] The system also includes a connecting plate 25, which is connected to two filtering components 26. A rotating shaft 24 is connected to the connecting plate 25 and is driven by a driving member. The filtering components 26 rotate around the rotating shaft 24, enabling the filtering components 26 to switch between the filtering station 11 and the cleaning station 12. Specifically, devices such as a dust concentration monitor or a differential pressure sensor are installed in the filtering component 26 to monitor the working state of the filtering component 26 in real time. When the dust concentration is too high or the differential pressure reaches a set threshold, the driving member and the dust cleaning program are automatically started. The connecting plate 25 drives the filtering component 26 to rotate, switching the filtering component 26 with too high dust concentration or a differential pressure reaching the set threshold from the filtering station 11 to the cleaning station 12 for cleaning, and switching the filtering component 26 that has been cleaned at the cleaning station 12 to the filtering station 11 for filtering work. By alternately operating the two filtering components 26, the filtering efficiency and service life of the filtering component 26 are ensured.

[0037] The driving member is a first motor 23, and the output end of the first motor 23 is connected to the rotating shaft 24 to drive the rotating shaft 24 to rotate.

[0038] The cleaning component 4 includes a pulse back-blow nozzle 41 and a vibrating plate 42. The pulse back-blow nozzle 41 instantaneously blows high-pressure gas reversely into the filtering component 26 to make the dust on the surface of the filtering component 26 fall off. Moreover, affected by the high-pressure gas, the vibrating plate 42 swings around the pin shaft and collides with the filtering component 26 to make the filtering component 26 vibrate, assisting the dust to separate. Through the dust cleaning technology combining pulse back-blow and mechanical vibration, the dust on the surface of the filtering component 26 is removed more efficiently, and the service life of the filtering component 26 is extended.

[0039] Preferably, the dust is blown into the storage tank along the pipeline through the pulse back-blow nozzle 41. In other embodiments of the present invention, a negative pressure suction device may also be provided to adsorb the dust to the storage tank through the negative pressure suction device.

[0040] When the filtering component 26 is at the filtering station 11, the filtering component 26 is connected to the connecting plate 25. When the filtering component 26 is at the cleaning station 12, the filtering component 26 is separated from the connecting plate 25. Specifically, a conical sleeve 21 is fixedly connected to the filtering component 26, and the connecting plate 25 is connected to the filtering component 26 through the conical sleeve 21. An auxiliary plate 3 is also included. The bottom end of the filtering component 26 is in contact with the auxiliary plate 3. The auxiliary plate 3 includes a first plane 31, an inclined plane 32, and a second plane 33. Both ends of the first plane 31 are connected to the inclined plane 32. The end of the inclined plane 32 far from the first plane 31 is connected to the second plane 33. The second plane 33 is higher than the first plane 31. When the filtering component 26 is at the first plane 31, the filtering component 26 is connected to the connecting plate 25, thereby ensuring that when the filtering component 26 is at the filtering station 11, the connecting plate 25 limits the position at the filtering station 11 and the filtering component 26 does not shake. When the filtering component 26 is at the second plane 33, the filtering component 26 is separated from the connecting plate 25, so that when the filtering component 26 is at the cleaning station 12, there is a gap between the filtering component 26 and the connecting plate 25. When the cleaning component 4 dusts the filtering component 26 at the cleaning station 12, the filtering component 26 at the cleaning station 12 reduces the transfer of vibration to the filtering component 26 at the filtering station 11.

[0041] The auxiliary plate 3 is semi-circular, and the center of the auxiliary plate 3 is the same as the rotation center of the connecting plate 25.

[0042] Preferably, limiting plates 22 are fixedly connected to both ends of the conical sleeve 21. The connecting plate 25 is located between the two limiting plates 22, and the position of the connecting plate 25 is limited by the limiting plates 22.

[0043] The second thallium and lead removal layer 6 is arranged at the inlet of the SCR denitration reactor 5. Through the second thallium and lead removal layer 6, the physically and / or chemically adsorbed flue gas after filtration and primary denitration is used to remove thallium and lead in the flue gas. Specifically, the second thallium and lead removal layer 6 is composed of an oxidant, a porous substrate, and a binder. The oxidant is one or more of manganese oxide, cerium oxide, copper oxide, and vanadium pentoxide. The porous substrate is one or more of activated carbon, molecular sieve, alumina, carbon nanotube, and titanium dioxide. The binder is one or more of polyethylene oxide, cellulose, and resin. The oxidant is 1 - 10 parts, the porous substrate is 80 - 90 parts, and the binder is 5 - 15 parts. The second thallium and lead removal layer 6 serves as a sacrificial layer, with a length of about 200 - 600 mm, in a honeycomb form or a plate form, and further removes thallium and lead in the flue gas at a working temperature of 180 - 350 °C by relying on physical and / or chemical adsorption.

[0044] The second thallium and lead removal layer 6 relies on the physical and / or chemical adsorption of activated carbon to remove thallium, lead and arsenic. The adsorption capacity is limited. When the thallium, lead and arsenic content in the exhaust gas is high or the processing volume is large, the activated carbon material of this layer needs to be replaced frequently, which increases the operating cost and maintenance workload. Moreover, if it is not replaced in time after adsorption saturation, thallium, lead and arsenic will be released back into the flue gas, affecting the treatment effect.

[0045] Therefore, the two ends of the second thallium and lead removal layer 6 are respectively connected to the two receiving rollers 61, and the two receiving rollers 61 can rotate with themselves as the center of the circle. The SCR denitrification reactor 5 is provided with two desorption stations 14 and an adsorption station 13. The adsorption station 13 is located between the two desorption stations 14. The second thallium and lead removal layer 6 located at the adsorption station 13 physically and / or chemically adsorbs the flue gas. The desorption station 14 is provided with a desorption component 7. The second thallium and lead removal layer 6 located at the desorption station 14 is desorbed by the desorption component 7 at high temperature. The adsorption-saturated activated carbon is heated in an inert gas environment to desorb the adsorbed thallium and lead. Specifically, each of the storage rollers 61 is connected to a rotating rod 62, and any one of the rotating rods 62 is connected to the output end of the second motor 65. Both of the rotating rods 62 are fixedly connected to a pulley 63, and the two pulleys 63 are connected by a belt 64. By setting the pulley 63 and the belt 64, the two storage rollers 61 rotate in the same direction, thereby ensuring that one storage roller 61 is storing and the other storage roller 61 is releasing.

[0046] The starting states of the two desorption components 7 are determined according to the forward and reverse rotation conditions of the second motor 65 .

[0047] When the second motor 65 rotates forward and the second thallium and lead removal layer 6 moves toward the first direction, the second thallium and lead removal layer 6 adsorbed saturated by adsorption at the adsorption station 13 moves to the desorption station 14 at the first direction end, and the desorption assembly 7 at the first direction end is started to spray high-temperature inert gas to the second thallium and lead removal layer 6 adsorbed saturated by adsorption at the desorption station 14 at the first direction end, so as to desorb the adsorbed thallium and lead. The second thallium and lead removal layer 6 desorbed by the desorption station 14 at the second direction end moves to the adsorption station 13 to adsorb thallium and lead. When the second motor 65 reverses and the second thallium and lead removal layer 6 moves in the second direction, the second thallium and lead removal layer 6 that is saturated with adsorption at the adsorption station 13 moves to the desorption station 14 at the second direction end, and the desorption component 7 at the second direction end is started to spray high-temperature inert gas to the second thallium and lead removal layer 6 that is saturated with adsorption at the desorption station 14 at the second direction end, so as to desorb the adsorbed thallium and lead, thereby realizing the regeneration and recycling of the activated carbon. The second thallium and lead removal layer 6 that has been desorbed at the desorption station 14 at the first direction end moves to the adsorption station 13 to adsorb thallium and lead.

[0048] The high-temperature flue gas released from the bypass is used to heat the inert gas through a heat exchanger, so that the gas ejected from the desorption component 7 is a high-temperature inert gas.

[0049] The desorption component 7 includes a high-temperature nozzle, through which high-temperature inert gas is sprayed onto the second thallium and lead removal layer 6 to desorb the adsorbed thallium and lead.

[0050] For the desorbed thallium and lead, recovery treatment is carried out. The high-temperature inert gas (such as N2) carries gaseous thallium (possibly volatilized in the form of Tl2O, TlCl) and lead (possibly volatilized in the form of PbO, PbCl2) into the condensation system. Through staged cooling, lead is preferentially condensed into solid particles. Thallium, due to its higher volatility, needs further low-temperature condensation or adsorption and capture. The residual gas is adsorbed by activated carbon or washed to ensure no heavy metal residue.

[0051] The third denitrification layer 9 is arranged below the catalytic layer of the SCR denitrification reactor 5. Through the third denitrification layer 9, the performance of resisting thallium and lead poisoning is improved, and the service life is extended. Preferably, the third denitrification layer 9 is arranged below the first catalytic layer of the SCR denitrification reactor 5.

[0052] Specifically, the third denitrification layer 9 is composed of 2 - 4 layers of catalysts, and honeycomb or plate-type denitrification catalysts are used to improve the performance of the catalyst in resisting thallium and lead poisoning and extend its service life. The catalyst is composed of an active component, a co-active component, a modification additive, and a substrate. The active component is V2O5, MnO, the co-active component is WO3, Mo2O3, the modification additive is one or more of Ce2O3, lanthanum oxide, CuO, and the substrate is one or more of titanium dioxide (TiO2), carbon nanotubes, and diatomite. The active component is 2 - 8 parts, the co-active component is 3 - 20 parts, the modification additive is 1 - 6 parts, and the substrate is 85 - 100 parts.

[0053] When the number of the third denitrification layers 9 is one, the third denitrification layer 9 is arranged below the first catalytic layer of the SCR denitrification reactor 5. When the number of the third denitrification layers 9 is multiple, each third denitrification layer 9 is respectively located below the catalytic layer.

[0054] A method for multi-stage removal of heavy metals such as thallium, lead, and arsenic and synergistic denitrification in waste gas treatment, including a system for multi-stage removal of heavy metals such as thallium, lead, and arsenic and synergistic denitrification in waste gas treatment, further includes the following steps: S1. The flue gas at the outlet of the preheater first enters the double-outlet cyclone separator 8 for pre-filtration; S2. The pre-filtered flue gas enters the first thallium and lead removal and synergistic denitrification layer 2 to perform secondary filtration on the dust in the pre-filtered flue gas and primary denitrification; S3. The secondary-filtered flue gas enters the second thallium and lead removal layer 6 to physically and / or chemically adsorb the secondary-filtered and primary-denitrified flue gas to remove thallium and lead in the flue gas; S4. The physically and / or chemically adsorbed flue gas enters the SCR denitration reactor 5 and passes through the third denitration layer 9 to improve the performance of resisting thallium and lead poisoning.

[0055] Implementation Case 1 Project background: A 5000t / d cement production line, flue gas parameters at the preheater outlet: flue gas volume: 300,000 Nm³ / h, temperature: 320 °C, dust concentration: 110 g / Nm³ (including 65% CaCO3, 20% SiO2, 8% Al2O3), pollutants: NO X 325 mg / Nm³, thallium (Tl) 350 mg / kg, lead (Pb) 46 mg / kg.

[0056] By rotating the dust cleaning of the filter component 26, the differential pressure is stabilized below 1200 Pa, the life of the filter cartridge is extended to 3 years (originally 1 year), the heavy metal online analyzer detects thallium (Tl) 350 mg / kg and lead (Pb) 46 mg / kg, which is higher than the first concentration. The selected cleaned dust is transported to an independent sealed storage tank, and the dust is selectively acid-leached and extracted, and then the heavy metals are recovered by the fractional precipitation method.

[0057] The oxidant of the second thallium and lead removal layer is 5 parts, the porous substrate is 80 parts, and the binder is 8 parts. The oxidant is manganese oxide and cerium oxide, with a mass ratio of 1:1. The porous substrate is alumina, molecular sieve, and carbon nanotube, with a mass ratio of 1:2:2. The binder is polyethylene oxide and cellulose, with a mass ratio of 2:1. By high-temperature desorption of the second thallium and lead removal layer 6, the replacement cycle of the activated carbon is extended from 1 month to 6 months, and the annual material cost is saved by 1.2 million yuan.

[0058] Through the third denitration layer, the catalyst activity of V2O5 is 3 parts, the co-active component WO3 is 3 parts, Mo2O3 is 2 parts, the modified additive Ce2O3 is 2.5 parts, the substrate carbon nanotube is 20 parts, and TiO2 is 90 parts. The activity attenuation within 1 year is <10%, and it is expected to extend the service life of the catalyst by 1 year.

[0059] And through this denitration system and method, the final emissions are:

[0060] Thus, this system and method achieve the integrated treatment of dust, NO X , heavy metals, and the comprehensive operation cost is reduced by 34%.

[0061] Implementation Case 2 Project background: A 3200t / d cement production line, flue gas parameters at the preheater outlet: flue gas volume: 190,000 Nm³ / h, temperature: 350 °C, dust concentration: 95 g / Nm³ (including 62% CaCO3, , Al2O3 8%), Pollutants: NO X 310 mg / Nm³, thallium (Tl) 350 mg / kg, lead (Pb) 46 mg / kg.

[0062] By rotating and cleaning the filter component 26, the differential pressure is stabilized below 1200 Pa, and the filter cartridge life is extended to 3 years (original 1 year). The on-line heavy metal analyzer detects thallium (Tl) 160 mg / kg and lead (Pb) 35 mg / kg, which is lower than the first concentration, and the cleaned dust is selected to be transported to the raw material warehouse for reuse.

[0063] The second thallium and lead removal layer has 4 parts of oxidant, 85 parts of porous substrate, and 10 parts of binder. The oxidant is manganese oxide and cerium oxide, with a mass ratio of 2:1. The porous substrate is alumina, molecular sieve, and carbon nanotube, with a mass ratio of 1:1:1. The binder is polyethylene oxide and cellulose, with a mass ratio of 3:1. By high-temperature desorption of the second thallium and lead removal layer 6, the activated carbon replacement cycle is extended from 1 month to 5 months, saving 1 million yuan in material costs per year.

[0064] Through the third denitrification layer, the catalyst activity of V2O5 is 2.5%, the co-active component WO3 is 4%, Mo2O3 is 3%, the modified additive Ce2O3 is 4%, the substrate carbon nanotube is 15%, and the rest is TiO2. The activity attenuation within 1 year is <10%, and the catalyst service life is expected to be extended by 1 year.

[0065] And through this denitrification system and method, the final emissions are:

[0066] Thus, this system and method achieve the integrated treatment of dust, NO X , heavy metals, and the comprehensive operation cost is reduced by 36%.

[0067] Obviously, the above embodiments of the present invention are merely examples for clearly explaining the present invention, and are not intended to limit the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A system for multi-stage heavy metal removal and synergistic denitrification of waste gas treatment, characterized in that, It includes a first thallium and lead co-denitrification layer (2), a second thallium and lead removal layer (6), and a third denitrification layer (9). The first thallium and lead co-denitrification layer (2) is arranged at the outlet of the preheater. One end of the first thallium and lead co-denitrification layer (2) away from the preheater is connected to the SCR denitrification reactor (5) through a flue (1). Through the first thallium and lead co-denitrification layer (2), the dust in the flue gas discharged from the preheater is filtered and preliminarily denitrified. The second thallium and lead removal layer (6) is arranged at the inlet of the SCR denitrification reactor (5). Through the second thallium and lead removal layer (6), the physically and / or chemically adsorbed flue gas after filtration and preliminary denitrification is processed to remove thallium and lead in the flue gas. The third denitrification layer (9) is arranged inside the SCR denitrification reactor (5). Through the third denitrification layer (9), the performance of resisting thallium and lead poisoning is improved, and the service life is extended.

2. The system for multi-stage heavy metal removal and collaborative denitrification of waste gas treatment according to claim 1, wherein The first thallium and lead co-denitrification layer (2) includes a filtering component (26). Dust in the flue gas discharged from the preheater is filtered by the filtering component (26). A denitrification layer is provided on the inner wall of the filtering component (26), and NO in the flue gas is x initially removed.

3. The system for multi-stage heavy metal removal and synergistic denitrification of waste gas treatment according to claim 2, characterized in that, A double-outlet high-efficiency cyclone separator (8) is provided between the preheater and the filter assembly (26). The flue gas discharged from the preheater is first pre-filtered by the double-outlet cyclone separator (8), and then secondary filtered by the filter assembly (26). By online detecting the ash obtained from separation and filtration, it is selected to be returned to the raw material warehouse for reuse or transported to an independent sealed storage tank for purification treatment according to the contents of thallium, lead, and arsenic in the ash.

4. The system for multi-stage heavy metal removal and collaborative denitrification of waste gas treatment according to claim 2, wherein It also includes a filtering station (11) and a cleaning station (12). When the filter assembly (26) is at the filtering station (11), the filter assembly (26) is communicated with the preheater and the SCR denitrification reactor (5). The cleaning station (12) is provided with a storage tank. When the filter assembly (26) is at the cleaning station (12), the filter assembly (26) is connected to the storage tank through a pipeline. The cleaning station (12) is provided with a cleaning component (4). The cleaning component (4) removes the dust on the filter assembly (26) at the cleaning station (12), and the removed dust is collected by the storage tank and then discharged after the recovery is completed. The specific number of the filter assemblies (26) is two. When any one of the filter assemblies (26) is at the filtering station (11), the other filter assembly (26) is at the cleaning station (12).

5. The system for multi-stage heavy metal removal and synergistic denitrification of waste gas treatment according to claim 4, wherein It also includes a connecting plate (25). The connecting plate (25) is connected to the two filter assemblies (26). A rotating shaft (24) is connected to the connecting plate (25). The rotating shaft (24) is driven by a driving member. The filter assembly (26) rotates around the rotating shaft (24), so that the filter assembly (26) can be switched between the filtering station (11) and the cleaning station (12). When the filter assembly (26) is at the filtering station (11), the filter assembly (26) is connected to the connecting plate (25). When the filter assembly (26) is at the cleaning station (12), the filter assembly (26) is separated from the connecting plate (25).

6. The system for multi-stage heavy metal removal and synergistic denitrification of waste gas treatment according to claim 5, characterized in that, A conical sleeve (21) is fixedly connected to the filtering component (26). The connecting plate (25) is connected to the filtering component (26) through the conical sleeve (21). An auxiliary plate (3) is further included. The bottom end of the filtering component (26) is in contact with the auxiliary plate (3). The auxiliary plate (3) includes a first plane (31), an inclined plane (32), and a second plane (33). Both ends of the first plane (31) are connected to the inclined plane (32). One end of the inclined plane (32) away from the first plane (31) is connected to the second plane (33). The second plane (33) is higher than the first plane (31). When the filtering component (26) is located on the first plane (31), the filtering component (26) is connected to the connecting plate (25). When the filtering component (26) is located on the second plane (33), the filtering component (26) is separated from the connecting plate (25).

7. The system for multi-stage heavy metal removal and synergistic denitrification of waste gas treatment according to claim 1, wherein The second thallium and lead removal layer (6) is composed of an oxidant, a porous substrate, and a binder. The oxidant is one or more of manganese oxide, cerium oxide, copper oxide, and vanadium pentoxide. The porous substrate is one or more of activated carbon, alumina, molecular sieve, carbon nanotube, and titanium dioxide. The binder is one or more of polyethylene oxide, cellulose, and resin. The oxidant is 1 - 10 parts, the porous substrate is 80 - 90 parts, and the binder is 5 - 15 parts. The second thallium and lead removal layer (6) further removes thallium and lead in the flue gas by physical and / or chemical adsorption at a working temperature of 180 - 350°C. Both ends of the second thallium and lead removal layer (6) are respectively connected to two storage rollers (61). Both of the two storage rollers (61) can rotate around their own centers. Two desorption stations (14) and an adsorption station (13) are provided in the SCR denitration reactor (5). The adsorption station (13) is located between the two desorption stations (14). The second thallium and lead removal layer (6) located at the adsorption station (13) physically and / or chemically adsorbs the flue gas. The desorption station (14) is provided with a desorption component (7). The second thallium and lead removal layer (6) located at the desorption station (14) heats the saturated activated carbon by the desorption component (7) in a high-temperature inert gas environment to desorb the adsorbed thallium and lead.

8. The system for multi-stage heavy metal removal and collaborative denitrification of waste gas treatment according to claim 7, wherein When the second thallium and lead removal layer (6) moves in the first direction, the second thallium and lead removal layer (6) saturated with adsorption at the adsorption station (13) moves to the desorption station (14) at the first direction end. The desorption component (7) at the first direction end is started to spray high-temperature inert gas onto the second thallium and lead removal layer (6) saturated with adsorption at the desorption station (14) at the first direction end to desorb the adsorbed thallium and lead. The second thallium and lead removal layer (6) desorbed at the desorption station (14) at the second direction end moves to the adsorption station (13) to adsorb thallium and lead. When the second thallium and lead removal layer (6) moves in the second direction, the second thallium and lead removal layer (6) with saturated adsorption at the adsorption station (13) moves to the desorption station (14) at the second direction end. The desorption assembly (7) at the second direction end starts to eject high-temperature inert gas to the second thallium and lead removal layer (6) with saturated adsorption at the desorption station (14) at the second direction end, so that the adsorbed thallium and lead are desorbed. The second thallium and lead removal layer (6) that has completed desorption at the desorption station (14) at the first direction end moves to the adsorption station (13) to adsorb thallium and lead.

9. The system for multi-stage heavy metal removal and synergistic denitrification of waste gas treatment according to claim 1, wherein, The third denitrification layer (9) is composed of 2 - 4 layers of catalysts. The catalyst is composed of an active component, a co-active component, a modification additive, and a substrate. The active component is V2O5 and MnO. The co-active component is WO3 and Mo2O3. The modification additive is one or more of Ce2O3, lanthanum oxide, and CuO. The substrate is one or more of titanium dioxide, carbon nanotubes, and diatomite. The active component is 2 - 8 parts, the co-active component is 3 - 20 parts, the modification additive is 1 - 6 parts, and the substrate is 85 - 100 parts. The catalyst has high denitrification activity and resistance to thallium and lead poisoning, and has a long service life.

10. A method for multi-stage heavy metal removal and collaborative denitrification of waste gas treatment, characterized in that, It includes the system for multi-stage heavy metal removal and synergistic denitrification of waste gas treatment according to any one of the above claims 1 - 9, and further includes the following steps: S1. The flue gas at the outlet of the preheater first enters the double-outlet cyclone separator (8) for pre-filtration; S2. The pre-filtered flue gas enters the first thallium and lead removal and denitrification layer (2) to perform secondary filtration on the dust in the pre-filtered flue gas and primary denitrification; S3. The flue gas after secondary filtration enters the second thallium and lead removal layer (6) to physically and / or chemically adsorb the flue gas after secondary filtration and primary denitrification to remove thallium and lead in the flue gas; S4. The physically and / or chemically adsorbed flue gas enters the SCR denitrification reactor (5) and passes through the third denitrification layer (9) to improve the performance of resistance to thallium and lead poisoning.

Images