Sintering flue gas purification device and purification method

Abstract

The present invention discloses a sintering flue gas purification device, which relates to the technical field of sintering flue gas purification treatment. The device includes a circulating fluidized bed incinerator, a cooling mechanism and a denitrification mechanism. The circulating fluidized bed incinerator includes a furnace chamber, a cyclone separator and a tail flue. The temperature in the furnace chamber is 900-1100°C, and the residence time of the sintering flue gas is not less than 5 s to achieve the combustion of CO in the sintering flue gas and the decomposition of dioxins. The cooling mechanism cools the combustion flue gas to inhibit the re-generation of dioxins. The denitrification mechanism includes an SNCR denitrification device, an SCR high-temperature catalyst denitrification device and an SCR low-temperature catalyst denitrification device. The present invention also provides a sintering flue gas purification method, which is implemented by using the above-mentioned sintering flue gas purification device. The present invention can basically achieve the complete combustion of CO in the sintering flue gas and the complete decomposition of dioxins, effectively inhibit the re-generation of dioxins, and also enable the NOx emission concentration to reach the ultra-low emission standard.

Description

Technical Field

[0001] The present invention relates to the technical field of sintering flue gas purification treatment, and particularly to a sintering flue gas purification device and a purification method. Background Art

[0002] Currently, conventional denitrification treatment processes such as SCR or COA method are usually used to treat sintering flue gas. However, since the temperature of sintering flue gas is 120 - 180°C and the reaction temperature of conventional SCR denitrification catalyst is about 350°C, blast furnace gas is required to heat the flue gas temperature to 350°C before desulfurization. Another method is to use catalytic oxidation method, i.e., ozone method, at the tail. This denitrification method must set up an oxygen production system, and the process is complex. Both of the above two methods have problems of high process investment cost, high operation cost, and the inability to remove CO, dioxins and other harmful gases.

[0003] Therefore, a sintering flue gas purification device and a purification method are provided to solve the above problems existing in the prior art. Summary of the Invention

[0004] The purpose of the present invention is to provide a sintering flue gas purification device and a purification method to solve the above problems existing in the prior art, which can basically achieve the complete combustion of CO and the complete decomposition of dioxins in sintering flue gas, effectively inhibit the re-generation of dioxins, and enable the NOx emission concentration to reach the ultra-low emission standard, while greatly reducing the investment and operation costs of the original sintering flue gas denitrification process.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] The present invention provides a sintering flue gas purification device, including a circulating fluidized bed incinerator, a cooling mechanism and a denitrification mechanism. The circulating fluidized bed incinerator includes a furnace chamber, a cyclone separator and a tail flue. An air inlet is provided on the furnace chamber for introducing sintering flue gas, and a feed inlet is also provided on the furnace chamber for adding fuel. A flue gas outlet is provided at the top of the furnace chamber, and the flue gas outlet is connected to the cyclone separator. The gas outlet of the cyclone separator is connected to the tail flue. Among them, the temperature in the furnace chamber is 900 - 1100°C, and the residence time of the sintering flue gas in the furnace chamber is not less than 5 s to achieve the combustion of CO and the decomposition of dioxins in the sintering flue gas.

[0007] The cooling mechanism is arranged in the tail flue and is used to cool the combustion flue gas formed by combustion in the furnace chamber to inhibit the re-generation of dioxins.

[0008] The denitration mechanism includes an SNCR denitration device, an SCR high-temperature catalyst denitration device, and an SCR low-temperature catalyst denitration device. The SNCR denitration device is arranged at the inlet of the cyclone separator, or is arranged at the inlet of the cyclone separator and on the tail flue connected to the gas outlet at the same time. The SCR high-temperature catalyst denitration device is arranged on the tail flue between the cooling mechanisms. The SCR low-temperature catalyst denitration device is arranged at the outlet end of the cooling mechanism. The outlet end of the cooling mechanism and the outlet end of the SCR low-temperature catalyst denitration device can also be connected to a desulfurization, purification, and dust removal device.

[0009] Preferably, the side walls, top, and bottom of the furnace are all of membrane water wall structure. When the temperature of the furnace is 900 - 1100 °C, the heat transfer coefficient of the membrane water wall structure is 120 - 140 kcal / m 2 ·h·°C. The flow rate of the sintering flue gas in the furnace is 3 - 4 m / s. The residence time of the sintering flue gas in the furnace is not less than 8 s. The excess air coefficient at the flue gas outlet of the furnace is 1.5 - 1.7. The oxygen content in the flue gas in the furnace is not less than 6%.

[0010] Preferably, the fuel is gasified ash from gasifiers, including gasified ash from entrained flow gasifiers and fluidized bed gasifiers.

[0011] Preferably, the solid outlet of the cyclone separator is connected to the furnace for the circulating ash separated by the cyclone separator to enter the furnace. A dust discharge pipe is also arranged at the bottom of the cyclone separator, and a switching valve is arranged on the dust discharge pipe;

[0012] Among them, the flue gas flow rate at the inlet of the cyclone separator is 27 - 29 m / s, and the flue gas flow rate at the gas outlet of the cyclone separator is 40 - 42 m / s.

[0013] Preferably, the cooling mechanism includes a superheater, a economizer, and an air preheater arranged in sequence in the tail flue, which can reduce the temperature of the combustion flue gas from 400 °C to 200 °C within 3 s; among them, the SCR high-temperature catalyst denitration device is located between the economizer and the air preheater, and the SCR low-temperature catalyst denitration device is located behind the air preheater.

[0014] Preferably, it further includes a dust removal mechanism. The air inlet of the dust removal mechanism is used to communicate with the outlet of the sintering machine. The air outlet of the dust removal mechanism is connected to the main sintering flue gas pipe. The main sintering flue gas pipe is respectively communicated with the primary cold air inlet and the secondary cold air inlet of the air preheater through a first air pipe and a second air pipe. The air inlets of the furnace include a first air inlet and a second air inlet. The first air inlet is arranged at the bottom of the furnace, and the second air inlet is arranged at the lower part of the side of the furnace. The primary air outlet and the secondary air outlet of the air preheater are respectively communicated with the first air inlet and the second air inlet.

[0015] Preferably, the dust removal mechanism is an electrostatic precipitator;

[0016] A primary air fan and a secondary air fan are respectively arranged on the first air pipe and the second air pipe to provide power for the transportation of the sintering flue gas.

[0017] Preferably, the outlet end of the air preheater is connected to a lower pipeline. The diameter of the lower pipeline is larger than that of the tail flue. A flue gas baffle is arranged in the lower pipeline. The SCR low-temperature catalyst denitration device is arranged on one side of the flue gas baffle, and the other side is an empty pipeline. A flue gas damper is also arranged above the SCR low-temperature catalyst denitration device to block the flue gas from entering the SCR low-temperature catalyst denitration device;

[0018] The main sintering flue gas pipe is also communicated with the lower pipeline through a third air pipe. The third air pipe is located behind the second air pipe, and an electric air damper and a blower are arranged on the third air pipe.

[0019] Preferably, it further includes a waste heat recovery and utilization device. The waste heat recovery and utilization device is arranged at the tail end of the lower pipeline to absorb the waste heat in the sintering flue gas.

[0020] The present invention also provides a method for purifying sintering flue gas, which is implemented by using the sintering flue gas purification device as described above, and includes the following steps:

[0021] S1. Raise the temperature of the furnace to 900 - 1100 °C, introduce the sintering flue gas, and make the residence time of the sintering flue gas in the furnace not less than 5 s to realize the combustion of CO and the decomposition of dioxins in the sintering flue gas;

[0022] S2. Transport the combustion flue gas formed by combustion in the furnace to the cyclone separator for cyclone separation to remove the circulating ash, and transport the combustion flue gas after removing the circulating ash to the cooling mechanism. Among them, the combustion flue gas is denitrified once by the SNCR denitration device in front of the cyclone separator or simultaneously in front of and behind the cyclone separator;

[0023] S3. Cool down the combustion flue gas through the cooling mechanism to inhibit the re-generation of dioxins, and perform secondary denitrification on the combustion flue gas through the SCR high-temperature catalyst denitrification device during the cooling process;

[0024] S4. Introduce sintering flue gas into the outlet end of the cooling mechanism to mix the sintering flue gas with the combustion flue gas to form a mixed flue gas. When the flow rate of the introduced sintering flue gas and the nitrogen oxide content of the mixed flue gas both exceed the set values, perform tertiary denitrification on the mixed flue gas through the SCR low-temperature catalyst denitrification device; otherwise, introduce the mixed flue gas into the desulfurization, purification and dust removal device.

[0025] The present invention has achieved the following technical effects compared with the prior art:

[0026] In the present invention, the temperature of the furnace is 900 - 1100 °C, the residence time of the sintering flue gas in the furnace is not less than 8 s, the oxygen content of the combustion flue gas generated after the complete combustion of the sintering flue gas with 16% oxygen in the furnace is greater than 6%, and dioxins can be completely decomposed in the furnace; moreover, CO in the sintering flue gas can be completely burned with oxygen to generate CO2 at this temperature, achieving the purpose of removing CO and avoiding the emission of toxic CO gas; thus, it is possible to achieve the complete combustion of CO and the complete decomposition of dioxins in the sintering flue gas as much as possible.

[0027] Furthermore, in the present invention, a cooling mechanism is also provided in the tail flue, which can cool down the flue gas to effectively inhibit the re-generation of dioxins, achieving the purpose of removing dioxins and avoiding dioxin pollution.

[0028] Moreover, in the present invention, the SNCR + SCR high-temperature catalyst + SCR low-temperature catalyst combined denitrification process is adopted, which can not only make the NOx emission concentration in the sintering flue gas generated under all operating conditions of the sintering machine reach the ultra-low emission standard, but also make the NOx emission concentration in the combustion flue gas generated by the combustion and gasification of ash slag in the incinerator reach the ultra-low emission standard, and at the same time greatly reduce the investment and operating costs of the original sintering flue gas denitrification process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 It is a schematic structural diagram of the sintering flue gas purification device in the embodiment of the present invention;

[0031] Figure 2This is a schematic cross-sectional structure diagram of the SCR low-temperature catalyst denitration device in the tail flue of the embodiment of the present invention;

[0032] Figure 3 This is a working flow chart of the sintering flue gas purification method in the embodiment of the present invention.

[0033] In the figure: 1 - circulating fluidized bed incinerator; 2 - SNCR denitration device; 3 - pneumatic switch valve; 4 - ash discharge pipe; 5 - SCR high-temperature catalyst denitration device; 6 - flue gas baffle; 7 - flue gas partition; 8 - SCR low-temperature catalyst denitration device; 9 - electric control valve; 10 - waste heat recovery and utilization device; 11 - forced draft fan; 12 - electric damper; 13 - secondary air fan; 14 - primary air fan; 15 - electrostatic precipitator; 16 - sintering machine; 101 - furnace chamber; 102 - cyclone separator; 103 - superheater; 104 - economizer; 105 - air preheater. Specific Embodiments

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] The purpose of the present invention is to provide a sintering flue gas purification device and a purification method to solve the problems existing in the above-mentioned prior art, which can basically achieve the complete combustion of CO and the complete decomposition of dioxins in the sintering flue gas, effectively inhibit the re-generation of dioxins, and can also make the NOx emission concentration reach the ultra-low emission standard, while greatly reducing the investment and operation costs of the original sintering flue gas denitration process.

[0036] To make the above-mentioned objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. Embodiment 1

[0037] As Figures 1 - 3As shown in the figure, this embodiment provides a sintering flue gas purification device, which mainly includes a circulating fluidized bed incinerator 1, a cooling mechanism and a denitrification mechanism. The circulating fluidized bed incinerator 1 mainly includes a furnace chamber 101, a cyclone separator 102 and a tail flue. An air inlet is provided on the furnace chamber 101 for introducing sintering flue gas, and a feed inlet is also provided on the furnace chamber 101 for adding fuel. The oxygen content in the sintering flue gas is not less than 16%, and the available sintering flue gas can be used as the primary and secondary air of the circulating fluidized bed incinerator 1 to provide oxygen for fuel combustion. A flue gas outlet is provided at the top of the furnace chamber 101, and the flue gas outlet is connected to the cyclone separator 102. The gas outlet of the cyclone separator 102 is connected to the tail flue. Specifically, the inlet of the cyclone separator 102 is communicated with the flue gas outlet of the furnace chamber 101 through a connecting flue, and this section of the connecting flue is a horizontal flue. The gas outlet of the cyclone separator 102 is communicated with the tail flue, and the connecting section between the tail flue and the gas outlet of the cyclone separator 102 is a first vertical flue extending vertically upward. The top of the first vertical flue is connected to a second vertical flue through a horizontal flue, and the second vertical flue extends downward. The cooling mechanism is arranged in the second vertical flue, and the first vertical flue, the second vertical flue and the horizontal flue therebetween together form the tail flue. Among them, the temperature in the furnace chamber 101 is 900 - 1100 °C, and the residence time of the sintering flue gas in the furnace chamber 101 is not less than 5 s (preferably not less than 8 s).

[0038] In this embodiment, the temperature of the furnace chamber 101 is 900 - 1100 °C, the residence time of the sintering flue gas in the furnace chamber 101 is not less than 8 s, the oxygen content of the flue gas generated after the sintering flue gas with 16% oxygen is completely burned in the furnace chamber 101 is greater than 6%, and the dioxin can be completely decomposed in the furnace chamber 101. Moreover, CO in the sintering flue gas can be completely burned with oxygen to generate CO2 at this temperature, achieving the purpose of removing CO and avoiding the emission of toxic CO gas. Thus, the complete combustion of CO and the complete decomposition of dioxin in the sintering flue gas can be realized as much as possible.

[0039] Furthermore, a steam pipeline can also be provided on the furnace chamber 101 to utilize the heat generated by fuel combustion to by-produce steam with different parameters, generating considerable economic benefits and turning the investment in environmental protection equipment into an investment in electricity or heat that can produce benefits.

[0040] In this embodiment, the cooling mechanism is arranged in the second vertical flue of the tail flue and is used to rapidly cool the combustion flue gas formed by combustion in the furnace chamber 101 to inhibit the re-generation of dioxin.

[0041] In this embodiment, the denitration mechanism includes an SNCR denitration device 2, an SCR high-temperature catalyst denitration device 5, and an SCR low-temperature catalyst denitration device 8. The spray gun of the SNCR denitration device 2 is separately arranged on the horizontal flue connected to the inlet of the cyclone separator 102, or is simultaneously arranged on the horizontal flue connected to the inlet of the cyclone separator 102 and the first vertical flue of the tail flue. The SCR high-temperature catalyst denitration device 5 is arranged on the tail flue (second vertical flue) between the cooling mechanisms, and the SCR low-temperature catalyst denitration device 8 is arranged at the outlet end of the cooling mechanism. In this embodiment, a circulating fluidized bed incinerator 1 is adopted, which can increase the temperature of the sintering flue gas and make the temperature of the sintering flue gas reach the optimal temperature window for SNCR and SCR denitration. The optimal temperature window for SNCR denitration is 800-1100°C, the optimal temperature window for SCR high-temperature catalyst denitration is 350-420°C, and the optimal temperature window for SCR low-temperature catalyst denitration is 200-250°C. In this embodiment, the SNCR+SCR high-temperature catalyst+SCR low-temperature catalyst combined denitration process is adopted, which can not only make the NOx emission concentration in the sintering flue gas generated under all operating conditions of the sintering machine 16 reach the ultra-low emission standard, but also make the NOx emission concentration in the combustion flue gas generated by the incinerator burning and gasifying ash slag reach the ultra-low emission standard, and at the same time greatly reduce the investment and operating costs of the original sintering flue gas denitration process.

[0042] In this embodiment, the outlet end of the cooling mechanism and the outlet end of the SCR low-temperature catalyst denitration device 8 can also be connected to a desulfurization, purification and dust removal device for transporting the flue gas after denitration to the desulfurization, purification and dust removal device for subsequent treatment. It should be noted that the desulfurization, purification and dust removal device is a mature existing technology in the art and can be selected according to specific working needs, so it will not be elaborated in this embodiment.

[0043] In this embodiment, the fuel is preferably gasified ash slag from a gasifier, including gasified ash slag from a entrained flow gasifier and gasified ash slag from a fluidized bed gasifier. Gasified ash slag is a solid waste that is difficult to burn in a conventional circulating fluidized bed boiler. The characteristics of fluidized bed gasified ash slag are fine particle size, high calorific value, and poor reactivity. The characteristics of entrained flow gasified ash slag are fine particle size, very high moisture content, and very low calorific value. The ignition points of both types of gasified ash slag are above 800°C. In view of the characteristics of gasified ash slag, the temperature in the furnace 101 is set at 900-1100°C in this embodiment, which can also achieve efficient combustion of gasified ash slag, and the carbon conversion rate can reach more than 99%.

[0044] In this embodiment, in order to ensure that the temperature of the furnace 101 is controlled within 900 - 1100 °C, the side walls, top and bottom of the furnace 101 all adopt a membrane water wall structure. When the temperature of the furnace 101 is 900 - 1100 °C, the heat transfer coefficient of the membrane water wall structure is 120 - 140 kcal / m 2 ·h·°C; Generally, a wear-resistant castable is arranged on the inner side of the membrane wall of a conventional circulating fluidized bed boiler that is prone to wear. At this time, the heat transfer coefficient is 0.2 times that without the castable. Therefore, the height and area of the bare tubes along the height direction of the furnace 101 are determined through the heat balance calculation of the furnace 101 to ensure that the temperature of the furnace 101 is controlled within 900 - 1100 °C. Secondly, the flow velocity of the sintering flue gas in the furnace 101 is controlled within 3 - 4 m / s, and the residence time of the sintering flue gas in the furnace 101 is not less than 8 s, so as to determine the height and cross-sectional area of the furnace 101. Finally, when using sintering flue gas to replace air to provide oxygen for the combustion of gasified ash slag, the excess air coefficient at the outlet of the furnace 101 is taken as 1.5 - 1.7 to ensure that the oxygen content in the flue gas of the furnace 101 is not less than 6%. The above structural design can not only ensure the complete combustion of the gasified ash slag, but also ensure the complete combustion of CO and the complete decomposition of dioxins in the sintering flue gas.

[0045] In this embodiment, the solid outlet of the cyclone separator 102 is communicated with the furnace 101 for the circulating ash formed by the separation of the cyclone separator 102 to enter the furnace 101. A dust discharge pipe 4 is further arranged at the bottom of the cyclone separator 102, and a switching valve, preferably a pneumatic switching valve 3, is arranged on the dust discharge pipe 4; wherein, the flue gas flow velocity at the inlet of the cyclone separator 102 is 27 - 29 m / s, and the flue gas flow velocity at the gas outlet of the cyclone separator 102 is 40 - 42 m / s, which can ensure that the separation efficiency of the cyclone separator 102 is above 99%, and the carbon content of the fly ash is controlled below 5%. The sizes of the inlet and outlet flue ducts are calculated by selecting the flow velocity.

[0046] In this embodiment, the higher the separation efficiency of the cyclone separator 102, the higher the circulation ratio and the larger the amount of circulating ash. The gasified ash slag added to the furnace 101 can quickly heat up to the ignition temperature, effectively improving the combustion efficiency; at the same time, too large an amount of circulating ash will also carry away more heat from the furnace 101, which is not conducive to maintaining the design temperature of the furnace 101 at 900 - 1100 °C. Therefore, a dust discharge pipe 4 is arranged at the bottom of the cyclone separator 102, and a pneumatic switching valve 3 is arranged on the dust discharge pipe 4. During operation, when the temperature of the furnace 101 is lower than 900 °C, the pneumatic switching valve 3 is opened for ash discharge, and when the temperature of the furnace 101 rises above 900 °C, the pneumatic switching valve 3 is closed again.

[0047] In this embodiment, the cooling mechanism includes a superheater 103, an economizer 104, and an air preheater 105 that are sequentially arranged from top to bottom in the second vertical flue of the tail flue. By using the above different heating surfaces to absorb the heat of the flue gas, the flue gas temperature can be reduced from 400 °C to 200 °C within 3 s, effectively inhibiting the re-generation of dioxins, achieving the purpose of removing dioxins, and avoiding dioxin pollution. The SCR high-temperature catalyst denitration device 5 is located between the economizer 104 and the air preheater 105. The optimal temperature window for SCR high-temperature catalyst denitration is 350-420 °C. The heating surface arrangements of the superheater 103 and the economizer 104 are determined through thermal calculations to ensure that the designed flue gas temperature at the outlet of the economizer 104 is controlled between 350-420 °C; among them, the quantity of the high-temperature catalyst is determined based on enabling the sintering flue gas volume to be treated to be 110% of the designed sintering flue gas volume, so that the flue gas reaches the ultra-low emission standard of ≤50 mg / Nm³ for the final emission concentration.

[0048] In this embodiment, a dust removal mechanism is further included. The air inlet of the dust removal mechanism is used to communicate with the outlet of the sintering machine 16. The air outlet of the dust removal mechanism is connected to a sintering flue gas main pipe. The sintering flue gas main pipe is respectively communicated with the primary cold air inlet and the secondary cold air inlet of the air preheater 105 through a first air duct and a second air duct; the air inlets of the furnace 101 include a first air inlet and a second air inlet. The first air inlet is arranged at the bottom of the furnace, and the second air inlet is arranged at the lower part of the side of the furnace. The primary air outlet and the secondary air outlet of the air preheater 105 are respectively communicated with the first air inlet and the second air inlet through flues. The sintering flue gas entering the furnace 101 can be preheated by the air preheater 105, and heat recovery is realized. Among them, the dust removal mechanism is preferably an electrostatic precipitator 15; a primary fan 14 and a secondary fan 13 are respectively arranged on the first air duct and the second air duct to provide power for the transportation of the sintering flue gas, so as to use the sintering flue gas as the primary and secondary air of the incinerator and provide oxygen for fuel combustion.

[0049] In this embodiment, to solve the problem that when the sintering machine 16 operates unstably and the sintering flue gas volume exceeds the designed value by more than 10%, the NOx final emission reaches the ultra-low emission standard, an SCR low-temperature catalyst denitration device 8 is arranged behind the air preheater 105. At the same time, a third air duct is led from the sintering flue gas main pipe at the outlet of the electrostatic precipitator 15 and sent to the outlet flue of the air preheater 105 through a blower 11. An electric air damper 12 is arranged on the third air duct.

[0050] After the sintering flue gas is incorporated into the outlet of the air preheater 105, the total flue gas flow rate increases. To ensure the SCR low-temperature catalyst denitration efficiency, the flow rate of the flue gas flowing through the catalyst needs to be controlled. Therefore, the cross-sectional area of the lower flue at the sintering flue gas inlet of the outlet flue of the air preheater 105 is increased and connected by a reducing flue, asFigure 2 As shown in the figure. An electric flue gas baffle 6 is arranged at the upper part of the SCR low-temperature catalyst denitration device 8 and the lower part of the reducer flue. A flue gas partition 7 is arranged between the front and rear walls of the lower flue. The SCR low-temperature catalyst denitration device 8 is arranged on one side of the flue gas partition 7, and the other side is an empty flue.

[0051] Among them, the optimal temperature window for SCR low-temperature catalyst denitration is 200 - 250 °C, the designed outlet temperature of the air preheater 105 is 250 - 300 °C, and the flue gas temperature after the sintering flue gas at 120 - 180 °C is mixed and incorporated can be controlled between 200 - 250 °C. The SCR low-temperature catalyst denitration device 8 is arranged on the outlet flue of the air preheater 105. The quantity of the low-temperature catalyst is determined according to the condition that when the incorporated sintering flue gas volume is 50% of the designed sintering flue gas volume, the flue gas can reach the ultra-low emission standard with the final emission concentration ≤ 50 mg / Nm³.

[0052] In this embodiment, the flue gas temperature discharged from the lower pipeline is between 200 - 300 °C, and there is still a large amount of recoverable heat energy. And to enter the subsequent dust removal and desulfurization processes, the flue gas temperature needs to be reduced to 130 - 150 °C. Therefore, a waste heat recovery device 10 is arranged at the tail end of the lower pipeline. Among them, a flue gas passage for high-temperature flue gas to pass through is arranged on the waste heat recovery device 10, and a cooling passage is also arranged. The inlet of the cooling passage is connected with a cold water pipe for introducing cold water. An electric control valve 9 (or a variable-frequency adjustable electric water pump) is arranged on the cold water pipe to adjust the water supply flow rate. By adjusting the water supply flow rate, the change in the exhaust gas temperature caused by the large fluctuation of the sintering flue gas can be satisfied, so that the flue gas at the outlet of the waste heat recovery device 10 can be stably reduced to 130 - 150 °C. It should be noted that the water supply of the waste heat recovery device 10 and the steam system of the circulating fluidized bed incinerator 1 are two independent systems. The high-temperature water at the outlet of the waste heat recovery device 10 can be sent to other sections of the factory area to meet the needs of other processes, and the steam with different parameters by-produced by the circulating fluidized bed incinerator 1 can obtain very considerable economic benefits.

[0053] This embodiment also provides a sintering flue gas purification method, which is implemented by using the above-mentioned sintering flue gas purification device, and mainly includes the following steps:

[0054] S1. Raise the temperature of the furnace chamber 101 to 900 - 1100 °C, introduce the sintering flue gas, and make the residence time of the sintering flue gas in the furnace chamber 101 not less than 8 s to achieve the combustion of CO and the decomposition of dioxins in the sintering flue gas;

[0055] S2. Convey the combustion flue gas formed by combustion in the furnace 101 to the cyclone separator 102 for cyclone separation to remove the circulating ash, and convey the combustion flue gas after removing the circulating ash to the cooling mechanism; wherein, perform primary denitrification on the combustion flue gas through the SNCR denitrification device 2 in front of the cyclone separator 102 or simultaneously in front of and behind the cyclone separator 102.

[0056] S3. Cool the combustion flue gas through the cooling mechanism to inhibit the re-generation of dioxins, and perform secondary denitrification on the combustion flue gas through the SCR high-temperature catalyst denitrification device 5 during the cooling process.

[0057] S4. Introduce sintering flue gas into the outlet end of the cooling mechanism, so that the sintering flue gas is mixed with the combustion flue gas to form a mixed flue gas. When both the flow rate of the introduced sintering flue gas and the nitrogen oxide content of the mixed flue gas exceed the set value, perform tertiary denitrification on the mixed flue gas through the SCR low-temperature catalyst denitrification device 8; otherwise, convey the mixed flue gas to the desulfurization, purification and dust removal device.

[0058] As Figure 3 shown, the sintering flue gas purification method in this embodiment specifically includes the following steps:

[0059] First, obtain the flue gas outlet temperature of the furnace 101. When it is ≥900 °C, close the pneumatic switch valve 3 and convey the combustion flue gas to the SNCR denitrification device 2; otherwise, open the pneumatic switch valve 3 to discharge the circulating ash until the flue gas outlet temperature of the furnace 101 is ≥900 °C.

[0060] Obtain the NOx concentration of the combustion flue gas at the inlet end and the outlet end of the SNCR denitrification device 2. When the NOx concentration decreases by 60%, make the combustion flue gas flow backward; otherwise, stop the furnace for maintenance of the performance of the SNCR denitrification device 2.

[0061] Make the combustion flue gas flow through the superheater 103 and the economizer 104 in sequence. The temperature of the combustion flue gas decreases, and obtain the flue gas temperature at the outlet of the economizer 104. When the flue gas temperature > 420 °C, turn on the soot blower to blow the economizer 104 for 10 minutes to reduce the flue gas temperature at the outlet of the economizer 104; when the flue gas temperature at the outlet of the economizer 104 ≤ 420 °C, make the combustion flue gas flow backward.

[0062] The combustion flue gas flows through the SCR high-temperature catalyst denitrification device 5, and its NOx concentration decreases; when the NOx concentration in the flue gas at the outlet of the SCR high-temperature catalyst denitrification device 5 ≤ 50 mg / Nm³, make the combustion flue gas continue to flow backward; otherwise, stop the furnace for maintenance of the performance of the SCR high-temperature catalyst denitrification device 5.

[0063] The combustion flue gas flows through the air preheater 105, and its temperature decreases. The flow rate of the sintering flue gas at the outlet of the electrostatic precipitator 15 is obtained. When it is > 1.1 times the design value, the electric damper 12 is opened and the forced draft fan 11 is started to mix the sintering flue gas with the flue gas at the outlet of the air preheater 105, and the NOx concentration in the mixed flue gas is obtained. When the NOx concentration ≤ 50 mg / Nm³, the flue gas damper 6 is closed to make the mixed flue gas flow backward; otherwise, the flue gas damper 6 is opened to make the mixed flue gas flow through the SCR low-temperature catalyst denitration device 8, and the NOx concentration in the flue gas at its outlet is obtained. When the NOx concentration ≤ 50 mg / Nm³, the mixed flue gas flows backward; otherwise, the furnace is stopped for maintenance of the performance of the SCR low-temperature catalyst denitration device 8.

[0064] When the flow rate of the sintering flue gas at the outlet of the electrostatic precipitator 15 ≤ 1.1 times the design value, the flue gas damper 6 is closed, and the flue gas temperature at the outlet of the air preheater 105 is obtained. When the flue gas temperature > 300 °C, the soot blower is turned on to purge the air preheater 105 for 10 minutes to remove the accumulated ash and reduce the flue gas temperature; when the flue gas temperature at the outlet of the air preheater 105 ≤ 300 °C, the mixed flue gas flows backward.

[0065] The flue gas flows through the waste heat recovery and utilization device 10, and its temperature decreases. The outlet flue gas temperature is obtained. When the outlet flue gas temperature is greater than 150 °C, the opening degree of the electric control valve 9 on the cold water pipe is increased to reduce the flue gas temperature; when the flue gas temperature ≤ 150 °C, the operation is stopped.

[0066] In the present invention, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A sintering flue gas purification device, characterized in that: It includes a circulating fluidized bed incinerator, a cooling mechanism and a denitrification mechanism. The circulating fluidized bed incinerator includes a furnace, a cyclone separator and a tail flue. An air inlet is provided on the furnace for introducing sintering flue gas, and a feed inlet is also provided on the furnace for adding fuel. A flue gas outlet is provided at the top of the furnace, and the flue gas outlet is connected to the cyclone separator. The gas outlet of the cyclone separator is connected to the tail flue. Among them, the temperature in the furnace is 900-1100°C, and the residence time of the sintering flue gas in the furnace is not less than 5 s to achieve the combustion of CO and the decomposition of dioxins in the sintering flue gas. The fuel is the gasification ash of a gasifier, including the gasification ash of a entrained flow gasifier and the gasification ash of a fluidized bed gasifier. A steam pipeline is also provided on the furnace to by-product steam using the heat generated by the combustion of the fuel. The cooling mechanism is arranged in the tail flue and is used to cool the combustion flue gas formed by combustion in the furnace to inhibit the re-generation of dioxins. The denitrification mechanism includes an SNCR denitrification device, an SCR high-temperature catalyst denitrification device and an SCR low-temperature catalyst denitrification device. The SNCR denitrification device is arranged at the inlet of the cyclone separator, or is simultaneously arranged at the inlet of the cyclone separator and the tail flue connected to the gas outlet. The SCR high-temperature catalyst denitrification device is arranged on the tail flue between the cooling mechanisms. The SCR low-temperature catalyst denitrification device is arranged at the outlet end of the cooling mechanism. The outlet end of the cooling mechanism and the outlet end of the SCR low-temperature catalyst denitrification device can also be connected to a desulfurization, purification and dust removal device. The cooling mechanism includes a superheater, an economizer and an air preheater arranged in sequence in the tail flue. A lower pipeline is connected to the outlet end of the air preheater. The diameter of the lower pipeline is larger than that of the tail flue. A flue gas baffle is arranged in the lower pipeline. An SCR low-temperature catalyst denitrification device is arranged on one side of the flue gas baffle, and the other side is an empty pipeline. A flue gas damper is also arranged above the SCR low-temperature catalyst denitrification device to block flue gas from entering the SCR low-temperature catalyst denitrification device. It also includes a dust removal mechanism. The air inlet of the dust removal mechanism is used to communicate with the outlet of the sintering machine. The air outlet of the dust removal mechanism is connected to a sintering flue gas main pipe. The sintering flue gas main pipe is respectively communicated with the primary cold air inlet and the secondary cold air inlet of the air preheater through a first air pipe and a second air pipe. The sintering flue gas main pipe is also communicated with the lower pipeline through a third air pipe. The third air pipe is behind the second air pipe, and an electric air valve and a blower are arranged on the third air pipe.

2. The sintering flue gas purification device according to claim 1, characterized in that: The side walls, top and bottom of the furnace are all of membrane water wall structure. When the temperature of the furnace is 900 - 1100 °C, the heat transfer coefficient of the membrane water wall structure is 120 - 140 kcal / m 2 ·h·°C. The flow rate of the sintering flue gas in the furnace is 3 - 4 m / s. The residence time of the sintering flue gas in the furnace is not less than 8 s. The excess air coefficient at the flue gas outlet of the furnace is 1.5 - 1.

7. The oxygen content in the flue gas in the furnace is not less than 6%.

3. The sintering flue gas purification device according to claim 1, characterized in that: The solid outlet of the cyclone separator is communicated with the furnace to supply the circulating ash separated by the cyclone separator to enter the furnace. A dust discharge pipe is also arranged at the bottom of the cyclone separator, and a switch valve is arranged on the dust discharge pipe. Among them, the flue gas velocity at the inlet of the cyclone separator is 27-29 m / s, and the flue gas velocity at the gas outlet of the cyclone separator is 40-42 m / s.

4. The sintering flue gas purification device according to claim 1, characterized in that: The cooling mechanism can reduce the temperature of the combustion flue gas from 400°C to 200°C within 3 s; wherein, the SCR high-temperature catalyst denitration device is located between the economizer and the air preheater, and the SCR low-temperature catalyst denitration device is located behind the air preheater.

5. The sintering flue gas purification device according to claim 4, characterized in that: The intake ports of the furnace include a first intake port and a second intake port. The first intake port is arranged at the bottom of the furnace, and the second intake port is arranged at the lower part of the side of the furnace. The primary air outlet and the secondary air outlet of the air preheater are respectively communicated with the first intake port and the second intake port.

6. The sintering flue gas purification device according to claim 5, characterized in that: The dust removal mechanism is an electrostatic precipitator; A primary air fan and a secondary air fan are respectively arranged on the first air duct and the second air duct to provide power for the transportation of the sintering flue gas.

7. The sintering flue gas purification device according to claim 5, wherein: It further includes a waste heat recovery and utilization device, which is arranged at the tail end of the lower pipeline to absorb the waste heat in the flue gas.

8. A sintering flue gas purification method, characterized in that: Implemented by using the sintering flue gas purification device as described in any one of claims 1-7, including the following steps: S1. Raise the temperature of the furnace to 900-1100°C, introduce the sintering flue gas, and make the residence time of the sintering flue gas in the furnace not less than 5 s to achieve the combustion of CO and the decomposition of dioxins in the sintering flue gas; S2. Transport the combustion flue gas formed by combustion in the furnace to the cyclone separator for cyclone separation to remove the circulating ash, and transport the combustion flue gas after removing the circulating ash to the cooling mechanism; wherein, the combustion flue gas is subjected to primary denitration by the SNCR denitration device in front of the cyclone separator or simultaneously in front of and behind the cyclone separator. S3. Cool the combustion flue gas through the cooling mechanism to inhibit the re-generation of dioxins, and perform secondary denitration on the combustion flue gas through the SCR high-temperature catalyst denitration device during the cooling process. S4. When the sintering machine flue gas volume exceeds 10% of the rated working condition flue gas volume, the part exceeding the sintering machine rated working condition sintering flue gas volume is introduced into the outlet end of the cooling mechanism, so that the sintering flue gas is mixed with the combustion flue gas to form a mixed flue gas. When both the flow rate of the introduced sintering flue gas and the nitrogen oxide content of the mixed flue gas exceed the set value, the mixed flue gas is subjected to tertiary denitration by the SCR low-temperature catalyst denitration device, otherwise the mixed flue gas is introduced into the desulfurization, purification and dust removal device.

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