Dry-process calcium-based fixed bed for flue gas desulfurization and denitration of blast furnace hot blast stove and method for realizing ultra-low emission of dry-process calcium-based fixed bed

Abstract

According to the dry-process calcium-based fixed bed for flue gas desulfurization and denitration of the blast furnace hot blast stove and the method for achieving ultralow emission, part or all of the flue gas of the blast furnace hot blast stove is introduced into a desulfurization and denitration tower through valve feedback control, and desulfurization and denitration materials have chemical reaction and adsorption effects on pollutants such as SO2 and NOx in the flue gas, so that the flue gas of the blast furnace hot blast stove is completely desulfurized and denitrated. And removing part of or all pollutants. The waste gas with small temperature drop is sent to a coal pulverizing system to utilize waste heat or is discharged from a chimney; and after saturation, the desulfurization and denitration agent is unloaded through a tower bottom unloading device, is delivered to a raw material field through automobile transportation, and is crushed and uniformly mixed into the sintering uniform mineral aggregate for sintering.

Description

TECHNICAL FIELD

[0001] The present application relates to the environmental protection technical field of steel industry flue gas pollutant treatment, in particular, the present application relates to integrated treatment of blast furnace hot blast stove flue gas to achieve ultra-low emission technology, more particularly, the present application relates to a dry method calcium-based fixed bed for desulfurization and denitrification of blast furnace hot blast stove flue gas and a method for achieving ultra-low emission. BACKGROUND

[0002] On April 28, 2019, the State Department of Ecological Environment officially issued the "Opinions on Promoting the Implementation of Ultra-Low Emission in the Steel Industry", which determined the national ultra-low emission standard. The emission requirements for blast furnace hot blast stove flue gas are: the hourly average concentration of particulate matter, sulfur dioxide and nitrogen oxides is not higher than 10, 50 and 200 mg / m respectively; the emission standard area and time requirements are: new (including relocation) steel projects should achieve ultra-low emission level in principle; by the end of 2020, about 60% of the production capacity of steel enterprises in key areas (Beijing-Tianjin-Hebei and surrounding areas, Yangtze River Delta region, Fenwei Plain) will strive to complete the ultra-low emission transformation; by the end of 2025, steel enterprises in key areas will basically complete the ultra-low emission transformation, and more than 80% of the production capacity in the country will complete the transformation.

[0003] Currently, there is no emission requirement for blast furnace hot blast stove flue gas internationally, and no related flue gas treatment process and technology has been disclosed. However, from the domestic steel plants, most of the blast furnace hot blast stove flue gas can achieve standard emission of particulate matter and NOx, but SO2 is difficult to achieve ultra-low emission, with a concentration of 50-150 mg / m X . Currently, the process technology for treating blast furnace hot blast stove flue gas in China is basically focused on the following two aspects: 3 One is source treatment: that is, desulfurization treatment of blast furnace gas used for hot blast stove combustion, and at the same time, a package solution to solve all the flue gas emission problems of blast furnace gas users. According to the analysis, the sulfur in blast furnace gas is mainly carbonyl sulfur, and the methods for removing carbonyl sulfur are mainly divided into wet and dry methods. Wet method for removing carbonyl sulfur is mainly divided into absorption method and hydrolysis conversion method; dry desulfurization is mainly divided into adsorption method, membrane separation method and hydrogenation conversion method.

[0004] Two is end treatment: that is, only treating hot blast stove exhaust gas to achieve standard emission. Although wet, semi-dry and dry desulfurization process technologies for sintering, coking and other processes can be applied, the key is to see which process technology has better adaptability to blast furnace process production conditions, lower cost, easier waste treatment and less secondary pollution.

[0005] However, the current source treatment and end treatment of blast furnace hot blast stove flue gas have the following problems:

[0006]

[0007] ​The mature process technology currently in operation for source treatment is the hydrothermal catalytic alkali washing method. The main problem of this process is that it requires a hydrolysis process to convert organic sulfur, which requires a certain temperature of flue gas, and the hydrolysis agent is sensitive to chlorine ions in the flue gas, so it needs to be removed first, and the system is complex. At the same time, inorganic sulfur uses a wet process, which has the problem of subsequent wastewater treatment. The entire system has a short running time, and the system encounters technical problems during the initial running period, resulting in long-term shutdown for rectification. The stability and reliability of the system need to be verified.

[0008] The problem of end treatment is that the temperature of the hot blast furnace flue gas is high and needs to be cooled down first. The initial flue gas temperature of the hot blast furnace is limited to 250℃, which is much higher than the limit temperature of 180℃ that the dust removal link can withstand, and the ultra-high temperature will seriously affect the desulfurization effect. However, if the temperature is lower than 80℃, the bag will appear dew condensation and hardening, which will seriously restrict production. If water spraying is used for cooling, the effect is limited, not only the energy consumption is increased, but also secondary pollution is caused. According to the design value of 10mg / Nm3 of sulfur dioxide emission concentration, the water consumption is 336 tons per day. If high-temperature cloth bags are used for dust removal, it only treats the symptoms and does not treat the root cause, and it will greatly increase the project investment and operating costs.

[0009] In summary, source treatment of flue gas treatment is concentrated investment, management, and unified process planning, which occupies less land and can avoid repeated investment. It is more scientific and reasonable than end treatment, but it is not suitable for steel plants that need to meet the emission standard in the short term due to its high technical difficulty, long construction period, and more one-time investment. End treatment has the disadvantages of multiple steel plant flue gas treatment points, repeated investment, and large land occupation, but it has the advantages of more reliable multiple process technologies for selection, small technical difficulty, short reconstruction period, step-by-step and regional implementation, and less one-time investment, which is more suitable for steel plants that need to meet the emission standard in the short term.

[0010] The utility model with publication number CN213668631U and the invention name "A dry desulfurization device special for blast furnace hot blast furnace" discloses a hot blast furnace gas desulfurization device, but does not involve a desulfurization and denitrification device and method for hot blast furnace flue gas as in the present invention.

[0011] The invention application with publication number "CN107899414A" and the invention name "A hot blast furnace waste gas desulfurization and denitrification collaborative treatment method" discloses a hot blast furnace waste gas desulfurization and denitrification collaborative treatment method using an ozone oxidation denitrification device and a wet desulfurization device, but does not involve a multiple dry desulfurization and denitrification fixed bed type reaction tower as in the present invention.

[0012] The utility model with publication number "CN214666094U", invention name "a system for reducing sulfur and nitrogen in blast furnace hot blast furnace flue gas", discloses that the desulfurizer injection port is arranged on the flue gas pipeline, and the SDS desulfurizer injection desulfurization is carried out before entering the bag type dust removal process, but does not involve the multiple dry desulfurization and denitrification fixed bed type reaction tower like the present application.

[0013] The utility model with publication number "CN211936312U", invention name "a blast furnace hot blast furnace waste gas desulfurization and denitrification system", discloses that dry desulfurization and denitrification reaction tower and low-temperature SCR denitrification catalyst are used to catalyze and remove NOx in hot blast furnace flue gas desulfurization and denitrification dust removal scheme, but the process requirement is relatively complex compared with multiple dry desulfurization and denitrification fixed bed type reaction tower, and the system equipment maintenance workload is large.

[0014] The invention application with publication number "CN112403215A", invention name "a high-sulfur coke oven flue gas dry method super-clean integrated treatment device and process thereof", discloses a high-sulfur coke oven flue gas dry method super-clean integrated treatment device and process thereof, which adopts medium-low temperature SCR denitrification and digestion dry lime desulfurization technology, which is different from the present application.

[0015] In summary, there is no very stable and mature hot blast furnace flue gas treatment technology that is generally recognized by the industry. The main reason is that the operating conditions of blast furnace hot blast furnace flue gas are very different from those of sintering and coking, and the original sintering and coking desulfurization and denitrification process technology route may not be the most suitable for blast furnace hot blast furnace operating conditions. Therefore, it is necessary to explore a stable and mature hot blast furnace flue gas treatment technology. SUMMARY

[0016] To overcome the above problems, the present application provides a dry method calcium-based fixed bed device for blast furnace hot blast furnace flue gas desulfurization and denitrification and a method for achieving ultra-low emission, which combines the operating characteristics of blast furnace hot blast furnace flue gas and can safely, continuously and stably remove SO2 or NOx in blast furnace hot blast furnace flue gas alone or simultaneously remove SO2 and NOx in blast furnace hot blast furnace flue gas, reaching the national ultra-low emission standard.

[0017] The technical scheme of the dry method calcium-based fixed bed for blast furnace hot blast furnace flue gas desulfurization and denitrification of the present application is as follows:

[0018] A dry method calcium-based fixed bed for blast furnace hot blast furnace flue gas desulfurization and denitrification, characterized in that,

[0019] The dry method calcium-based fixed bed comprises:

[0020] A flue gas induced draft system is provided with an induced draft fan and a pressure gauge, which is used to introduce blast furnace hot blast furnace flue gas into the desulfurization and denitrification system and control the flue gas flow at the same time;

[0021] The desulfurization and denitration body system comprises:

[0022] The desulfurization and denitration reaction tower is mainly used for chemical reaction or adsorption of the desulfurization and denitration agent and SO2 and NOx in the flue gas, so as to ensure that the content of SO2 and NOx in the flue gas reaches the ultra-low emission requirement.

[0023] The tower top feeding system;

[0024] The tower bottom discharging system is used for discharging the desulfurization and denitration agent reaching saturation and losing efficacy, and

[0025] The flue gas pollutant on-line detection system is used for detecting the composition, temperature, pressure and flow of the original flue gas and the treated flue gas.

[0026] The control system is used for data acquisition, monitoring and operation control of each link of the process flow, and comprises interlocking control with the blast furnace hot blast stove and the pulverizing system.

[0027] The method for realizing ultra-low emission by using the dry-process calcium-based fixed bed for flue gas desulfurization and denitration of the blast furnace hot blast stove according to the application is characterized in that:

[0028] Step 1) controlling the content of flue gas pollutant discharged by the hot blast stove to be stable, so as to control the emission concentration of the flue gas pollutant not to exceed the standard:

[0029] According to the content of the inlet and outlet flue gas pollutants, the inlet flue gas amount is feedback controlled and adjusted;

[0030] According to the detected composition data of the inlet CEMS and the outlet chimney CEMS, the inlet and outlet flue gas amounts are compared and adjusted;

[0031] Step 2) combining the saturation state of the desulfurization and denitration agent, cross using the silos and replacing the discharged adsorbed saturated materials, so as to control the emission concentration of the flue gas pollutant not to exceed the standard:

[0032] That is, the replacement order of the desulfurization and denitration reaction tower is designed in advance, the inlet flue gas amounts of different desulfurization and denitration reaction towers are set, and the saturation time of the desulfurization and denitration agent of different desulfurization and denitration reaction towers is controlled;

[0033] According to the saturation degree of different silos, the materials are sequentially fed and discharged, so as to ensure that the discharged flue gas is stably controlled below the ultra-low emission target.

[0034] The method for realizing ultra-low emission by using the dry-process calcium-based fixed bed for flue gas desulfurization and denitration of the blast furnace hot blast stove according to the application is characterized in that:

[0035] Step 1) adjusting the valve opening degree of the inlet damper valve K01-04 of the induced draft fan, the valve opening degree of the original flue gas to the pulverizing damper valve K01-03, and the valve opening degree of the clean flue gas to the pulverizing damper valve K01-06, so as to ensure that the SO2 concentration emission data reaches the standard ≦50 mg / m3 average per hour,

[0036] Preferably, the valve opening degree of the induced draft fan inlet baffle valve K01-04 is adjusted by the lifting operation of the induced draft fan frequency, and the induced draft fan frequency ranges from 20 HZ to 50 HZ.

[0037] According to the method for realizing ultra-low emission by using the dry method calcium-based fixed bed for flue gas desulfurization and denitrification of the blast furnace hot blast stove,

[0038] After the system runs stably, gradually open the valve (K01-06) of the purified flue gas to the pulverizing system flow from 0 to 100%, and then gradually close the valve (K01-03) of the original flue gas to the pulverizing system flow from 100% to 0;

[0039] Then gradually close the valve (K01-02) of the original flue gas directly into the chimney flow, and control the valve opening degree at 20-60% to ensure that the SO2 concentration emission data meets the standard ≦50mg / m 3 average per hour.

[0040] According to the method for realizing ultra-low emission by using the dry method calcium-based fixed bed for flue gas desulfurization and denitrification of the blast furnace hot blast stove,

[0041] When the SO2 at the outlet of the desulfurization and denitrification reaction tower is ≧40mg / Nm 3 , or when the running time exceeds 3 months, any condition is met, the system is unloaded and loaded according to the outlet flue gas pollutant emission concentration value and the replacement time and material level of the desulfurizer in each bin.

[0042] The valve K01-02 is digitally controlled, and can be adjusted between 0% and 100%. However, as a safety pressure balance valve of the purification system, if the valve is fully closed, once the induced draft fan jumps and the hot blast stove is not stopped, the flue gas will continue to enter the system, causing the system to be blocked; on the contrary, if the hot blast stove is stopped but the induced draft fan continues to run, the purification system will change from a slight negative pressure to a higher negative pressure, and air will be sucked into the system or equipment will be damaged due to excessive negative pressure.

[0043] According to the method for realizing ultra-low emission by using the dry method calcium-based fixed bed for flue gas desulfurization and denitrification of the blast furnace hot blast stove,

[0044] The dry method calcium-based fixed bed is connected in series with the pulverizing system, and a safety interlock is arranged between the hot blast stove system, the desulfurized flue gas system and the pulverizing system as follows:

[0045] When the flue gas purification fails, the hot blast stove is stopped by interlocking control to prevent the flue gas from backflowing into the gas pipe network;

[0046] When the hot blast stove is shut down, the "emergency stop" safety interlock control is set with the pulverizing system to prevent the coal powder explosion accident caused by the increase of oxygen concentration due to the stop of the air extraction from the chimney by the induced draft fan after the hot blast stove is shut down.

[0047] The application discloses a method for realizing ultra-low emission by using a dry-process calcium-based fixed bed for flue gas desulfurization and denitrification of a hot blast stove of a blast furnace.

[0048] Interlocking is realized between the induced draft fan and the pressure gauge,

[0049] When the main flue pipe pressure is between -500 Pa and 100 Pa, the induced draft fan is normally operated, and the motor frequency is unchanged;

[0050] When the main flue pipe pressure is less than -200 Pa, the motor frequency of the induced draft fan is reduced, and the opening degree of the induced draft fan inlet regulating valve (k01-04) is reduced simultaneously;

[0051] When the main flue pipe pressure is greater than 0 Pa, the motor frequency of the induced draft fan is increased, and the opening degree of the induced draft fan inlet regulating valve (k01-04) is increased simultaneously;

[0052] When the main flue pipe pressure continues to increase and reaches greater than 100 Pa, the original chimney inlet electric regulating valve (k01-02) and the original coal grinding flue electric regulating valve (k01-03) are immediately opened to ensure that the pressure difference between the two is within a safe range.

[0053] The application discloses a method for realizing ultra-low emission by using a dry-process calcium-based fixed bed for flue gas desulfurization and denitrification of a hot blast stove of a blast furnace.

[0054] When the oxygen content in the chimney waste gas is controlled to be 1% to 5%, if the oxygen content is greater than 5%, the motor frequency of the induced draft fan is reduced, and the opening degree of the induced draft fan inlet regulating valve (k01-04) is reduced simultaneously;

[0055] When the oxygen content continues to increase and reaches a certain high value, the original chimney inlet electric regulating valve (k01-02) and the original coal grinding flue electric regulating valve (k01-03) are immediately opened, and whether the oxygen content control range of the hot blast stove waste gas exceeds the standard is confirmed; and / or

[0056] If the oxygen content exceeds the standard, the air-fuel ratio is appropriately reduced to ensure that the oxygen content of the system does not exceed the safety value, and the oxygen content control range is in the interval of 5% to 8%.

[0057] The application discloses a method for realizing ultra-low emission by using a dry-process calcium-based fixed bed for flue gas desulfurization and denitrification of a hot blast stove of a blast furnace.

[0058] In the timing of the hot blast stove operation, the hot blast stove feeds back a signal in advance before entering the timing of changing the stove, when the feedback signal of changing the stove, i.e. the combustion signal disappears, the frequency of the motor of the induced draft fan starts to be reduced accordingly, so as to control the negative pressure to be stable between-500Pa and 100Pa.

[0059] Preferably, in the timing of the hot blast stove operation, the hot blast stove feeds back a signal in advance 15 minutes before entering the timing of changing the stove; the combustion signal of the hot blast stove of the blast furnace, the opening instruction of the blast furnace gas cut-off valve and the closing instruction signal of the blast furnace gas cut-off valve, and the opening and closing signal of the coke oven gas cut-off valve are received.

[0060] The method for realizing ultra-low emission by using the dry method calcium-based fixed bed for desulfurization and denitrification of the blast furnace hot blast stove flue gas according to the application is characterized in that:

[0061] After the hot blast stove operates normally, when the flue gas is cut into the desulfurization device to operate, the original chimney inlet electric regulating valve (k01-02) should keep a certain opening degree, preferably, the opening degree ranges from 20% to 60%; so that the original chimney inlet electric regulating valve (k01-02) can be remotely opened in any state, including the emergency state of the PLC stopping working.

[0062] The method for realizing ultra-low emission by using the dry method calcium-based fixed bed for desulfurization and denitrification of the blast furnace hot blast stove flue gas according to the application is characterized in that:

[0063] In the timing of the hot blast stove operation, the hot blast stove feeds back a signal in advance before entering the timing of changing the stove, when the feedback signal of changing the stove, i.e. the combustion signal disappears, the frequency of the motor of the induced draft fan starts to be reduced accordingly, so as to control the negative pressure to be stable between-500Pa and 100Pa.

[0064] The method for realizing ultra-low emission by using the dry method calcium-based fixed bed for desulfurization and denitrification of the blast furnace hot blast stove flue gas according to the application is characterized in that:

[0065] After the hot blast stove operates normally, when the flue gas is cut into the desulfurization device to operate, the original chimney inlet electric regulating valve (k01-02) should keep a certain opening degree, preferably, the opening degree ranges from 20% to 60%; so that the original chimney inlet electric regulating valve (k01-02) can be remotely opened in any state, including the emergency state of the PLC stopping working.

[0066] Because the flow among the hot blast stove system, the desulfurization flue gas system and the powder making system is that the hot blast stove combustion produces high-temperature flue gas, which enters the flue gas purification system for desulfurization after being cooled by waste heat recovery, and the low-oxygen containing hot waste gas is supplied to the powder making system for heating and dehumidifying the raw coal and the coal powder, therefore, the interlocking design is that when the flue gas purification fails, the hot blast stove is interlocked to stop burning, so as to prevent the flue positive pressure from pouring into the gas pipe network;

[0067] When the hot blast stove is shut down, the "emergency stop" safety interlock control is set with the pulverizing system to prevent the waste gas entering the pulverizing system from stopping after the hot blast stove is shut down, the induced draft fan of the pulverizing system draws air from the chimney, and the oxygen concentration increases to cause coal dust explosion.

[0068] The application discloses a method for realizing ultra-low emission by using a dry calcium-based fixed bed for flue gas desulfurization and denitrification of a blast furnace hot blast stove.

[0069] In the timing of the hot blast stove, when a combustion signal disappears and a cut-off valve closing instruction indicates that the hot blast stove stops combustion, when a cut-off valve opening instruction is received, it indicates that the hot blast stove is ready to combust, and about 18s after a combustion signal is received, it indicates that the hot blast stove enters combustion, when a stove changing feedback signal (the combustion signal disappears) is received, the frequency of the induced draft fan motor starts to be reduced correspondingly (the frequency converter is used to adjust the frequency in the form of how many seconds and how many HZ, and if the whole system is shut down, the inlet damper valve signal can be superimposed to determine the frequency; the negative pressure is controlled to be stable at a level of -500-100Pa).

[0070] When a combustion signal disappears and a cut-off valve closing instruction indicates that the hot blast stove stops combustion, when a cut-off valve opening instruction is received, it indicates that the hot blast stove is ready to combust, and about 18s after a combustion signal is received, it indicates that the hot blast stove enters combustion.

[0071] The application discloses a method for realizing ultra-low emission by using a dry calcium-based fixed bed for flue gas desulfurization and denitrification of a blast furnace hot blast stove.

[0072] When the hot blast stove operates normally and flue gas is cut into the desulfurization device to operate, the original chimney inlet electric regulating valve (k01-02) should keep a certain opening degree; so that the original chimney inlet electric regulating valve (k01-02) can be remotely opened in any state, including an emergency state in which a PLC (programmable logic controller) stops working.

[0073] Since the flue gas system is an independent PLC system, when the PLC fails or is powered off to stop, the blast furnace hot blast stove itself PLC can be used to operate the flue gas system, so that the valve k01-02 can be remotely operated.

[0074] The application discloses a method for realizing ultra-low emission by using a dry calcium-based fixed bed for flue gas desulfurization and denitrification of a blast furnace hot blast stove.

[0075] The quality performance requirements of the hot blast stove flue gas desulfurization and denitrification agent are as follows:

[0076]

[0077] Effects of the application:

[0078] 1) Safe and reliable. The fixed bed absorbent is inorganic material, safe and non-flammable, can adapt to the temperature range of 80-350℃ of flue gas, the system has wide temperature range, ensures the safety of hot blast stove gas system, and does not produce waste water and secondary pollution.

[0079] 2) Wide range of adaptation. First, the temperature adaptation range of flue gas pollutant treatment material is wide: all the flue gas generated by the blast furnace hot blast stove and power plant is mainly burned blast furnace gas, the composition and temperature are within the adaptation range of the present application, i.e. temperature≯350℃, SO2 content≯150mg / m 3 , Nox≯200mg / m 3 . Second, the process itself has good adaptability to the fluctuation of flue gas volume: the fixed bed process can better adapt to the large fluctuation of flue gas volume when the blast furnace hot blast stove is replaced and the number of burning furnace seats is changed.

[0080] 3) High efficiency of flue gas treatment. A set of system can treat flue gas for desulfurization or denitrification alone, or for desulfurization and denitrification at the same time, the system is more simple and efficient, and under the condition of strict emission indicators, the blast furnace hot blast stove flue gas has the characteristics of high flow, non-constant, large temperature fluctuation, the conventional working temperature is about 120-200℃, and there is high temperature of 300-350℃ in some time periods, and the concentration of flue gas pollutants is much lower than that of sintering and coking flue gas.

[0081] NOX ultra-low emission can be realized; if the NOX emission requirement is strict, i.e. desulfurizer and denitrifier are installed in the reaction tower at the same time, or material with the ability of simultaneous desulfurization and denitrification is added, the integrated treatment of desulfurization and denitrification is realized.

[0082] Desulfurization operation effect: the system is currently running stably, and SO2 is controlled at 40mg / Nm 3 Below, the replacement is carried out periodically at 2 bins / month, and the replacement is implemented periodically.

[0083] 4) Simple process, small footprint. The fixed bed is modularized, flexible in layout, suitable for existing site conditions, simple in system operation and maintenance, stable in running, and can realize fully automatic control.

[0084] 5) Small energy loss. The system does not need to spray water, the flue gas is not cooled down, and the use of treated flue gas in coal powder production is not affected. BRIEF DESCRIPTION OF DRAWINGS

[0085] Figure 1 It is a schematic diagram of the dry fixed bed process for flue gas desulfurization and denitrification of blast furnace hot blast stove.

[0086] Figure 2 It is a layout diagram of desulfurization and denitrification bin.

[0087] Figure 3 It is a schematic diagram of the reaction tower plan.

[0088] In the figure, 1 is the hot blast furnace original flue gas, 2 is the original flue gas heat exchanger, 3 is the chimney, 4 is the chimney CEMS, 5 is the coal pulverizing mill, 6 is the k01-06 into the coal pulverizing pipeline damper valve, 7 is the induced draft fan, 8 is the desulfurization bin outlet damper valve, 9 is the desulfurization bin import damper valve, 10 is the desulfurization system pipeline temperature gauge, 11 is the desulfurization system pipeline pressure gauge, 10 is the waste desulfurizer discharge system, 13 is the desulfurization bin discharge system, 14 is the desulfurization bin pressure gauge, 15 is the desulfurization bin level gauge, 16 is the new desulfurizer feeding system, 17 is the desulfurization bin feeding system. DETAILED DESCRIPTION

[0089] EMBODIMENT

[0090] First, a dry method calcium-based fixed bed for flue gas desulfurization and denitrification of blast furnace hot blast furnace is provided, which comprises: a flue gas induced draft system, which uses the flue gas of the blast furnace hot blast furnace to be introduced into the desulfurization and denitrification system while controlling the flue gas flow;

[0091] A desulfurization and denitrification body system, which comprises: a desulfurization and denitrification reaction tower, which mainly uses chemical reaction or adsorption of the desulfurizer with SO2 and NOx in the flue gas to ensure that the content of SO2 and NOx in the flue gas meets the ultra-low emission requirement; a tower top feeding system;

[0092] A tower bottom discharge system, which uses to discharge the desulfurization and denitrification agent 12 that has reached saturation and lost efficacy,

[0093] A flue gas pollutant on-line detection system, which uses to detect the composition, temperature, pressure and flow of the original flue gas and the treated flue gas; and

[0094] A control system, which uses to collect data, monitor and operate control of each link of the process, including interlocking control with the blast furnace hot blast furnace and the pulverizing system.

[0095] According to the dry method calcium-based fixed bed for flue gas desulfurization and denitrification of blast furnace hot blast furnace, the flue gas induced draft fan uses a variable frequency fan, which can adjust the frequency according to the content of the original pollutants in the flue gas and the content of the pollutants in the discharged flue gas, so as to control the amount of flue gas entering the desulfurization and denitrification system; the induced draft fan 7 can also use feedback control of the concentration of the discharged flue gas pollutants.

[0096] According to the embodiment, before the flue gas purification system starts:

[0097] The total valve (K01-01) of the purification system flue gas inlet is fully closed;

[0098] The valve (K01-02) of the original flue gas directly into the chimney flow is fully opened;

[0099] The valve (K01-03) of the original flue gas to the pulverizing system flow is fully opened;

[0100] K01-04 is fully closed;

[0101] K01-05 is fully closed;

[0102] K01-06 is fully closed;

[0103] Start of the flue gas purification system: the start of the flue gas purification system refers to the start of the induced draft fan.

[0104] First, K01-05 is fully opened, then K01-01 is fully opened, and then the induced draft fan is started.

[0105] After the induced draft fan is started, K01-04 is gradually opened from 0 to 100%.

[0106] The flue gas flows from the original flue gas pipeline through K01-01 to the purification tower, and then flows from K01-04 to the induced draft fan, and then flows from K01-05 to the chimney, and finally flows to the atmosphere.

[0107] According to the present embodiment, the fixed bed process parameters are designed as follows: Table 1

[0108]

[0109] After the flue gas from the hot blast stove, there are two paths: one is through the waste heat recovery system (flue gas heat exchanger in the figure) to recover the waste heat of the flue gas, and the other is not through the waste heat recovery system, mainly the flue gas path during the maintenance of the waste heat recovery system. The flue gas of the two paths is finally collected into one pipeline. There are three paths after that, one is directly to the coal mill, two is directly to the chimney, and three is to enter the flue gas treatment system (desulfurization and denitrification). Under normal circumstances, the third path is taken, and the flue gas is introduced by the system induced draft fan. The flue gas treatment system is provided with multiple desulfurization and denitrification reaction towers in parallel, and the reaction towers are filled with removal agents. The flue gas enters from the bottom of the tower and flows upward, and SO2 and NOx in the flue gas react with the removal agents in the reaction tower to remove them, so that the content of SO2 and NOx in the flue gas meets the ultra-low emission requirement, and is discharged from the upper part of the reaction tower. Finally, the flue gas after desulfurization and denitrification is collected into one pipeline, and the flue gas after desulfurization and denitrification can be used as drying gas for the blast furnace pulverizing system, or can be directly discharged through the chimney.

[0110] According to the embodiment, the reaction tower adopts a modular design, and the number of the reaction towers can be configured according to the flue gas amount and the pollutant concentration, and multiple reaction towers are closely arranged in parallel; a single reaction tower is composed of a metal shell, a stock bin, a material bed, a gas isolation and discharge valve, a flue gas inlet, a flue gas outlet and the like. The reactor unit is designed according to 5.7*5.7m*high 8m, and the bed layer is 5m high; the integrated calcium-based desulfurization device has three layers, and each layer has six reactor units, and a total of 18 reactor units. The desulfurization device of each project can be modularly combined according to the size of the site and the flue gas condition. Figure 3 .

[0111] According to the embodiment:

[0112] The valve opening degree of the induced draft fan inlet baffle valve K01-04, the valve opening degree of the raw flue gas to the pulverizing baffle valve K01-03, and the valve opening degree of the clean flue gas to the pulverizing baffle valve K01-06 are adjusted, the action opening degree of each valve is reasonably adjusted according to the data of the chimney CEMS (flue gas automatic monitoring system), and it is ensured that the emission data is up to standard <= 50mg / m 3 per hour on average. Table 2

[0113]

[0114] After the flue gas desulfurization and denitrification of the high-temperature blast furnace flue gas by the dry-process calcium-based fixed-bed flue gas treatment system of the application, the SO2 concentration in the discharged flue gas can be controlled within 35mg / m 3 , which meets the current ultra-low emission requirement. At present, when the flue gas of the hot blast furnace is directly discharged without flue gas treatment, the SO2 concentration is 70-90mg / m 3 , and the NOx concentration is 90-120mg / m 3 .

[0115] It should be noted that the application limits the blast furnace hot blast furnace flue gas treatment process technology, and the flue gas generated in other industries and smelting processes is not within the scope of the application.

Claims

1. A dry calcium-based fixed bed for desulfurization and denitrification of flue gas from a blast furnace hot blast stove, characterized in that, The dry calcium-based immobilized bed includes: The flue gas induced draft system is equipped with an induced draft fan and a pressure gauge to introduce the flue gas from the blast furnace hot blast stove into the desulfurization and denitrification system, while controlling the flue gas flow rate. The desulfurization and denitrification system includes: The desulfurization and denitrification reaction tower is mainly used for the chemical reaction or adsorption of SO2 and NOx in flue gas by the removal agent, so as to ensure that the SO2 and NOx content in the flue gas meets the ultra-low emission requirements. Top feeding system; The bottom unloading system is used to discharge desulfurization and denitrification agents that have reached saturation and lost their effectiveness. An online flue gas pollutant detection system is used to detect the composition, temperature, pressure, and flow rate of raw and treated flue gas; and The control system is used to collect data, monitor and control operations at each stage of the process, including interlocking with the blast furnace hot blast stove and the pulverizing system.

2. A method for achieving ultra-low emissions using a dry calcium-based fixed bed for desulfurization and denitrification of blast furnace hot blast stove flue gas as described in claim 1, characterized in that: Step 1) Control the stability of pollutant content in the flue gas emitted from the hot blast stove to ensure that the pollutant emission concentration does not exceed the standard: Based on the pollutant content of the inlet and outlet flue gas, the amount of inlet flue gas is controlled and adjusted according to feedback. Based on the component data detected by the inlet CEMS and the outlet chimney CEMS, the intake and exhaust volumes of flue gas are adjusted. Step 2) Combining the saturation state of desulfurization and denitrification agents, alternately use silos and replace saturated adsorption materials to control the concentration of pollutants emitted from flue gas to ensure it does not exceed the standard: That is, the material replacement sequence of the desulfurization and denitrification reaction towers is designed in advance, the air intake of different desulfurization and denitrification reaction towers is set respectively, and the saturation time of the desulfurization and denitrification agents in different desulfurization and denitrification reaction towers is controlled. Feeding and unloading are carried out in an orderly manner according to the saturation level of different silos to ensure that the exhaust gas is stably controlled below the ultra-low emission target.

3. The method for achieving ultra-low emissions using a dry calcium-based fixed bed for desulfurization and denitrification of blast furnace hot blast stove flue gas as described in claim 2, characterized in that: In step 1): Adjust the valve opening of the induced draft fan inlet damper valve K01-04, the valve opening of the raw flue gas to pulverizing damper valve K01-03, and the valve opening of the clean flue gas to pulverizing damper valve K01-06 to ensure that the SO2 concentration emission data meets the standard of ≤50mg / m³. 3 Average per hour.

4. The method for achieving ultra-low emissions using a dry calcium-based fixed bed for desulfurization and denitrification of blast furnace hot blast stove flue gas as described in claim 3. After the system is running stably, gradually open the valve (K01-06) for the flow of purified flue gas to the pulverizing system from 0 to 100%, and then gradually close the valve (K01-03) for the flow of raw flue gas to the pulverizing system from 100% to 0. Gradually close the valve (K01-02) controlling the flow rate of raw flue gas directly into the chimney, and maintain the valve opening between 20-60% to ensure that SO2 concentration emission data meets the standard of ≤50mg / m³. 3 Average per hour.

5. A method for achieving ultra-low emissions using a dry calcium-based fixed bed for desulfurization and denitrification of blast furnace hot blast stove flue gas as described in any one of claims 2-4, characterized in that: When the SO2 at the outlet of the desulfurization and denitrification reaction tower is ≥40 mg / Nm 3 If the system operates for more than 3 months, or if any of these conditions are met, the system will perform unloading and feeding operations based on the emission concentration of pollutants in the flue gas at the outlet and the time and level of the desulfurizing agent replacement in each silo.

6. A method for achieving ultra-low emissions using a dry calcium-based fixed bed for desulfurization and denitrification of blast furnace hot blast stove flue gas as described in any one of claims 2-4, characterized in that: The dry calcium-based fixed bed is connected in series with the pulverizing system, and the following safety interlocks are set up between the hot blast stove system, the desulfurization flue gas system, and the pulverizing system: When the flue gas purification fails, the hot blast stove will be shut down by interlock control to prevent the positive pressure in the flue from backflowing into the gas pipeline. When the hot blast stove is shut down, an "emergency shutdown" safety interlock control is set up with the pulverizing system to prevent a coal powder explosion accident caused by the pulverizing induced draft fan drawing air back from the chimney after the hot blast stove stops burning, which would increase the oxygen concentration.

7. A method for achieving ultra-low emissions using a dry calcium-based fixed bed for desulfurization and denitrification of blast furnace hot blast stove flue gas as described in any one of claims 2-4, characterized in that: Interlocking is achieved between the induced draft fan and the pressure gauge. The pressure in the main flue is between -500 and 100 Pa, the induced draft fan operates normally, and the motor frequency remains unchanged; When the pressure of the main flue is less than -200Pa, the frequency of the induced draft fan motor is reduced, and the opening of the induced draft fan inlet regulating valve (k01-04) is reduced accordingly. When the pressure in the main flue is greater than 0 Pa, the frequency of the induced draft fan motor increases. Therefore, the opening of the induced draft fan inlet regulating valve (k01-04) should be increased accordingly. When the pressure in the main flue continues to rise and reaches >100Pa, immediately open the original electric regulating valve (k01-02) at the chimney inlet and the original electric regulating valve (k01-03) in the coal mill flue to ensure that the pressure difference between the two is within a safe range.

8. A method for achieving ultra-low emissions using a dry calcium-based fixed bed for desulfurization and denitrification of blast furnace hot blast stove flue gas as described in any one of claims 2-4, characterized in that: The oxygen content in the chimney exhaust gas should be controlled between 1% and 5%. If the oxygen content is greater than 5%, the frequency of the induced draft fan motor should be reduced, and the opening of the induced draft fan inlet regulating valve (k01-04) should be reduced accordingly. When the oxygen content continues to rise and reaches a certain high value, immediately open the original chimney inlet electric regulating valve (k01-02) and the original coal mill flue electric regulating valve (k01-03), and confirm whether the oxygen content control range of the hot blast stove exhaust gas exceeds the standard; or If the oxygen content exceeds the standard, the air-fuel ratio should be appropriately reduced to ensure that the oxygen content of the system does not exceed the safe value, and the oxygen content should be controlled within the range of 5%-8%.

9. A method for achieving ultra-low emissions using a dry calcium-based fixed bed for desulfurization and denitrification of blast furnace hot blast stove flue gas as described in any one of claims 2-4, characterized in that: During the operation of the hot blast stove, before entering the furnace replacement sequence, the hot blast stove sends a feedback signal in advance. When the furnace replacement feedback signal is received, that is, when the combustion signal disappears, the frequency of the induced draft fan motor begins to decrease accordingly to control the negative pressure to stabilize between -500 and 100 Pa.

10. The method for achieving ultra-low emissions using a dry calcium-based fixed bed for desulfurization and denitrification of blast furnace hot blast stove flue gas as described in claim 9, characterized in that: During the operation of the hot blast stove, 15 minutes before entering the furnace replacement sequence, the hot blast stove sends a feedback signal in advance; it receives the combustion signal of the blast furnace hot blast stove + the blast furnace gas shut-off valve opening command + the blast furnace gas shut-off closing command signal, and the coke oven gas shut-off valve opening and closing signal.

11. A method for achieving ultra-low emissions using a dry calcium-based fixed bed for desulfurization and denitrification of blast furnace hot blast stove flue gas as described in any one of claims 2-4, characterized in that: After the hot blast furnace is operating normally, when the flue gas is cut into the desulfurization unit, the original chimney inlet electric regulating valve (k01-02) should be kept at a certain opening, with the opening range being 20% ​​to 60%; so that the original chimney inlet electric regulating valve (k01-02) can be remotely opened in any state, including in an emergency situation where the PLC stops working.

12. A method for achieving ultra-low emissions using a dry calcium-based fixed bed for desulfurization and denitrification of blast furnace hot blast stove flue gas as described in any one of claims 2-4, characterized in that: The quality performance requirements for desulfurization and denitrification agents for hot blast stove flue gas are as follows:

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