Activated carbon low-temperature ammonia pre-spraying method

Abstract

The invention relates to an activated carbon low-temperature ammonia pre-injection method, which comprises the following steps of: 1) stopping a sintering machine and an activated carbon flue gas purification system for maintenance, and pumping cooling gas to cool an activated carbon bed layer in the activated carbon flue gas purification system; and 2) spraying ammonia gas into the denitration tower while cooling the activated carbon bed layer, so that the activated carbon is adsorbed on the activated carbon bed layer of the denitration tower, and providing an ammonia source for sintering startup denitration reaction. According to the low-temperature ammonia pre-spraying method for the activated carbon, the cooling gas doped with the ammonia gas is introduced in the cooling process of the activated carbon bed layer, an ammonia source is provided for a denitration reaction, the daily mean value of NOx in the starting process is effectively reduced, the ammonia spraying amount is calculated, and accurate control over the ammonia spraying amount is achieved.

Description

Technical Field

[0001] The invention relates to a pre-injection ammonia method, in particular to a low-temperature pre-injection ammonia method of activated carbon, and belongs to the technical field of flue gas purification. Background Art

[0002] Activated carbon flue gas purification technology has the advantage of efficient purification of multiple pollutants, and is suitable for sintering flue gas with complex components (SO2, NO x , dust, O2, water vapor, heavy metals), and large temperature fluctuations (110-180℃). It has been successfully applied to the sintering flue gas purification system and has also been promoted to many industries such as coking and electric power. In the current ultra-low emission context, it has a large application space.

[0003] Activated carbon flue gas purification technology process flow Figure 5 As shown in the figure, the flue gas first passes through the denitrification tower, then through the desulfurization tower, the activated carbon first goes to the desulfurization tower and then to the denitrification tower, and then to the analysis tower for regeneration and then sent to the desulfurization tower for recycling. Figure 6 As shown, the activated carbon fills the denitrification tower and the desulfurization tower from top to bottom. The upper part is connected to the tower feed bin, and the lower part is connected to the tower bottom hopper. The discharging device adopts a long-axis roller type discharging device. Under the action of gravity, the activated carbon is discharged by relying on the friction between the round roller and the activated carbon. According to the order of contact with the flue gas, multiple front, middle and rear channels are set, and the activated carbon discharge speed of each channel is controlled separately to achieve efficient and coordinated removal of different pollutants.

[0004] When the flue gas purification system is operating normally, the bed temperature is between 120 and 140 °C. Within this temperature range, the activated carbon has a high x High removal efficiency, capable of achieving NO x Stable emission standards. When the flue gas purification system is shut down for maintenance, it is necessary to enter the adsorption tower or the analysis tower to check the equipment status, and the bed temperature is required to drop to about 50°C. When the sintering machine is started, it takes more than 20 hours for the bed temperature to rise from 50°C to 120°C (such as Figure 7 ), during this period, the activated carbon exports NO x Concentration exceeds 50mg / Nm 3 , leading to NO x The daily average outlet concentration exceeded the standard for a long time.

[0005] If ammonia is added during the activated carbon heating process, the following problems will occur: in the initial stage, the bed temperature is low, the sintering flue gas volume is large, and the moisture content is as high as 10%. A large amount of water will dissolve into the bed. If ammonia is added during the heating stage, it will cause the ammonia to dissolve into the water, making it difficult to achieve the denitrification effect. Most importantly, ammonia water will corrode steel equipment. Therefore, the introduction of ammonia during the heating process will result in low ammonia utilization, affecting equipment safety. Summary of the invention

[0006] According to the characteristics of sintering start-up and shutdown, in order to solve the problem of NO x In order to solve the problem that the daily average outlet concentration exceeds the standard for a long time, the present invention develops a method for pre-spraying ammonia on activated carbon at low temperature. Ammonia is added to the cooling gas during the cooling process of the activated carbon, and the amount of ammonia sprayed is calculated to reduce NO x The daily average concentration can be calculated, and the trend of outlet denitrification changes at the initial startup can be further predicted to help meet environmental protection NOx daily average emission standards.

[0007] According to an embodiment of the present invention, a method for low-temperature pre-injection of ammonia with activated carbon is provided.

[0008] A method for pre-spraying ammonia on activated carbon at low temperature, the method comprising the following steps:

[0009] 1) The sintering machine and activated carbon flue gas purification system are shut down for maintenance, and cooling gas is drawn in to cool the activated carbon bed in the activated carbon flue gas purification system;

[0010] 2) While cooling the activated carbon bed, ammonia is sprayed into the denitrification tower so that the activated carbon is adsorbed on the activated carbon bed of the denitrification tower, providing an ammonia source for the denitrification reaction during sintering startup.

[0011] Preferably, the spraying of ammonia into the denitration tower is specifically: using a mixed gas composed of cold air and ammonia as a cooling gas for the activated carbon bed in the denitration tower, and controlling the introduction time of the mixed gas so that the adsorption amount of ammonia in the activated carbon bed after cooling reaches a target adsorption value. Preferably, the target adsorption value is not less than 80% of the saturated adsorption amount of ammonia by the activated carbon bed at the corresponding temperature.

[0012] Preferably, the saturated adsorption capacity of ammonia by the activated carbon bed is as follows: a penetration experiment of the activated carbon bed for NH3 is performed at different temperatures to obtain a penetration curve of the activated carbon bed for NH3, and the penetration curve is integrated and calculated to finally obtain the saturated adsorption capacity of NH3 by the activated carbon bed at different temperatures, and the relationship between the temperature and the saturated adsorption capacity of NH3 by the activated carbon bed is obtained by fitting.

[0013] Preferably, the relationship between the temperature and the saturated adsorption capacity of NH3 by the activated carbon bed obtained by the fitting is:

[0014] q=a·In(T)+6.8066……(Formula 1)

[0015] Wherein, q is the saturated adsorption capacity of NH3 per unit mass of activated carbon at temperature T, mg / g; T is the adsorption temperature, °C; a is the adsorption capacity adjustment coefficient, a=-1.329 mg / °C·g.

[0016] Preferably, the time for controlling the introduction of the mixed gas is specifically:

[0017] By testing the cooling flue gas volume Q introduced into the denitrification tower, the activated carbon bed temperature, the NH3 concentration in the cooling flue gas at the inlet and outlet of the denitrification tower, and the loading amount of activated carbon in the denitrification tower, we can obtain:

[0018]

[0019] Where Q is the amount of cooling flue gas introduced into the denitrification tower per unit time, Nm 3 / h; C0 is the concentration of NH3 in the mixed gas used for cooling flue gas, mg / Nm 3 ; C1 is the concentration of NH3 in the flue gas at the outlet of the denitrification tower, mg / Nm 3 ; t is the time for the mixed gas to be introduced into the denitration tower so that the activated carbon bed reaches the saturated adsorption capacity of NH3, h; m is the loading amount of activated carbon in the denitration tower, kg; q is the saturated adsorption capacity of NH3 per unit mass of activated carbon at temperature T, mg / g; b is the time adjustment coefficient, b=1000g / kg; control the actual introduction time of the mixed gas t s ≤t.

[0020] Preferably, the method further comprises:

[0021] 2a) When downtime t a When ≥t, ammonia is injected normally according to time t, and the activated carbon bed reaches the target adsorption value;

[0022] 2b) When downtime t a When t<t, adjust the amount of cooling flue gas introduced to control the cooling rate of the activated carbon bed so that a Within the range, the activated carbon bed reaches the target adsorption value; and / or, the concentration of NH3 in the cooling flue gas is controlled so that at t a Within this range, the activated carbon bed reaches the target adsorption value.

[0023] Preferably, the method further comprises: 3) estimating the denitration rate of the activated carbon bed within a certain time range based on the adsorption amount of NH3 by the activated carbon bed in the denitration tower.

[0024] Preferably, the denitration rate of the activated carbon bed is estimated as follows: after obtaining the saturated adsorption amount of NH3 by the activated carbon bed at different temperatures, the flue gas containing nitrogen oxides is adsorbed within a certain period of time, the adsorption rate is detected, and the corresponding relationship between the adsorption amount of NH3 by the activated carbon bed and the denitration rate is obtained by fitting, so that the denitration rate within the same period of time can be estimated according to the actual adsorption amount of NH3 by the activated carbon bed. Preferably, the certain period of time is 3 to 8 hours.

[0025] Preferably, the certain time is 4 hours, and the corresponding relationship between the adsorption amount of NH3 by the activated carbon bed and the denitrification rate is fitted as follows:

[0026] A=γ*x 2 +μ*x+θ……(Formula 3)

[0027]

[0028] In the formula, Y is the average denitration rate of the activated carbon bed, %; A is the adsorption of nitrogen oxides in flue gas by unit mass of activated carbon, mg / g-AC; M is the mass of activated carbon circulating in the denitration tower per hour, g / h; N is the concentration of nitrogen oxides in flue gas, mg / Nm 3 ; V is the flue gas flow rate to be purified into the denitrification tower per unit time, Nm 3 / h; x is the actual adsorption capacity of NH3 by activated carbon at different temperatures, mg / g-AC; γ, μ, and θ are the denitrification adjustment coefficients, the value of γ is -6.921 g / mg; the value of μ is 42.84; and the value of θ is 57.78 mg / g.

[0029] Among them, Formula 3 and Formula 4 are only the relationship between the amount of NH3 adsorbed in the activated carbon and the average denitrification rate between 50 and 100°C during the heating process of the flue gas purification system. When the temperature returns to the normal operating temperature of the flue gas purification system, the denitrification efficiency gradually increases with the increase of the reaction temperature. The average denitrification rate can be calculated by other methods.

[0030] Preferably, the method further comprises: 4) according to the actual adsorption amount of NH3 by the activated carbon bed, the denitrification efficiency is predicted by (Formula 3), and according to the emission requirements, it is determined whether the flue gas emitted after denitrification after pre-injection of ammonia needs further treatment.

[0031] Preferably, the temperature of the shutdown inspection in step 1) is not higher than 60°C, preferably not higher than 50°C.

[0032] Preferably, the cooling gas in step 1) is air.

[0033] Preferably, the temperature of the ammonia gas sprayed into the denitration tower in step 2) is 50-100°C.

[0034] In the present invention, during the cooling process of the activated carbon bed, cooling gas is introduced into the denitrification tower, and while the activated carbon bed is being cooled, ammonia is sprayed into the denitrification tower. The sprayed ammonia is adsorbed on the surface of the activated carbon bed in the denitrification tower, and when the sintering is started, it can provide an ammonia source for the denitrification reaction, which can effectively reduce NO during the startup process. xPreferably, this solution finds that the saturated adsorption capacity of NH3 by the activated carbon bed at different temperatures is different, and further calculates the saturated adsorption capacity of ammonia by the activated carbon bed at different target temperatures according to the cooling target temperature of the activated carbon, and then calculates the amount of ammonia sprayed in the actual application process according to the saturated adsorption capacity to ensure that the activated carbon bed absorbs enough ammonia when the sintering machine is started, which can provide enough ammonia source for the denitrification reaction and reduce NO x It reduces emissions while avoiding waste caused by excessive ammonia and achieves precise control of the amount of ammonia sprayed.

[0035] In the present invention, the penetration curves of activated carbon bed to NH3 at different temperatures (such as Figure 1 ), it can be found that the penetration ability of the activated carbon bed to NH3 gradually decreases with the increase of temperature, that is, the higher the temperature, the shorter the penetration time, and the lower the temperature, the longer the penetration time. After obtaining the penetration curve of the activated carbon bed to NH3 at different temperatures, the integral calculation is performed to obtain the saturated adsorption capacity of activated carbon to NH3 under different temperature conditions. The results are as follows Figure 2 As shown, it can be seen that: at 50°C, the saturated adsorption of NH3 is 1.76mg / g-AC; at 60°C, the saturated adsorption of NH3 is 1.4mg / g-AC; at 70°C, the saturated adsorption of NH3 is 1.16mg / g-AC; at 80°C, the saturated adsorption of NH3 is 0.91mg / g-AC; at 100°C, the saturated adsorption of NH3 is only 0.73mg / g-AC. Further, the present invention fits the relationship between the above temperature and the saturated adsorption of NH3 by the activated carbon bed to obtain formula 1, from which it can be inferred that when T=50-100°C, the saturated adsorption of NH3 by the activated carbon bed.

[0036] In the present invention, based on the properties of the sintering flue gas and the activated carbon bed, including the amount of cooling gas introduced into the denitrification tower, the concentration of NH3 in the cooling gas, the concentration of NH3 in the cooling gas at the outlet of the denitrification tower, the time for introducing ammonia into the denitrification tower, the filling amount of activated carbon in the denitrification tower, and the saturated adsorption amount of NH3 by the activated carbon, the time for doping NH3 into the cooling gas can be further calculated, thereby accurately controlling the amount of ammonia injection.

[0037] In the present invention, since the downtime for maintenance and the ammonia injection time will vary according to the actual situation, there will be two situations: the downtime is greater than or equal to the ammonia injection time and the downtime is less than the ammonia injection time. When the downtime is greater than or equal to the ammonia injection time, ammonia can be injected normally, and the ammonia injection is completed at the end of the downtime. When the downtime is less than the ammonia injection time, it is necessary to control the amount of cooling gas introduced to extend the cooling process time, or increase the ammonia concentration during the ammonia injection process and reduce the ammonia injection time, so that the activated carbon bed can adsorb enough ammonia at the end of the downtime.

[0038] In the present invention, the denitrification efficiency of activated carbon saturated with NH3 adsorption at different temperatures was tested. Figure 3 , for 300mg / Nm 3 NO x , at 80℃, within 4h, the denitrification rate of activated carbon saturated with NH3 adsorbed in advance under different temperature conditions was tested. The experiment shows that the denitrification rate of activated carbon saturated with NH3 adsorbed at 50℃ is the highest, followed by 60℃, 70℃, and finally 100℃, that is, the higher the amount of NH3 adsorbed, the higher the denitrification efficiency. Based on the above conclusions, the formula of the adsorption amount of nitrogen oxides in flue gas per unit mass of activated carbon and the actual adsorption amount of NH3 by activated carbon at different temperatures can be estimated, and the average denitrification rate (Formula 3 and Formula 4) can be further calculated by the concentration of nitrogen oxides in the flue gas to be purified. In addition, the denitrification rate of activated carbon saturated with NH3 adsorbed at different temperatures at different times such as 3h, 5h, and 6h can also be tested.

[0039] In the present invention, the denitrification rate can be estimated according to the actual adsorption amount of ammonia by the activated carbon bed, and the denitrification rate can be used to calculate whether the flue gas discharged after denitrification needs further adjustment, so as to control NO x emissions.

[0040] In the present invention, the direction of flue gas and activated carbon is as follows: the original flue gas is purified by the activated carbon bed in the desulfurization tower and the denitration tower in turn to obtain clean flue gas; during the purification process of the flue gas, ammonia needs to be sprayed into the denitration tower. Fresh activated carbon enters the denitration tower and the desulfurization tower in turn to purify the flue gas, and the activated carbon adsorbed with pollutants is transported to the analysis tower for regeneration to obtain regenerated fresh activated carbon, which is recycled.

[0041] In the present invention, the specific surface area of ​​the desulfurization and denitrification activated carbon used is generally 200 to 300 mg / Nm 3 The average pore size is 2.5 nm. Particle size distribution: generally a cylindrical structure with a diameter of 9 mm and a height of 5.6 to 11.2. Therefore, the present invention only considers the temperature factor when calculating the saturated adsorption capacity of activated carbon for NH3.

[0042] In the present invention, all formulas in the present invention are obtained by fitting by the inventors based on experiments and engineering applications, and all calculations are numerical values ​​converted according to prescribed units, which are obtained by substituting the converted numerical values ​​into the formulas for calculation (after converting the units of each parameter, only the numerical values ​​are substituted into the formulas for calculation without substituting the units, and the units are only used to adjust the size of the numerical values).

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. The present invention provides a method for pre-spraying ammonia on activated carbon at low temperature. During the cooling process of the activated carbon bed, cooling gas doped with ammonia is introduced to provide an ammonia source for the denitration reaction, effectively reducing NO during the startup process. x The daily average value is calculated and the ammonia injection amount is calculated to achieve accurate control of the ammonia injection amount.

[0045] 2. The present invention provides an activated carbon low-temperature ammonia pre-spraying method, which can estimate the relationship between the actual adsorption amount of NH3 and the average denitrification rate, and then make corresponding adjustments to the purification system according to the denitrification rate. It can effectively cope with changes in process conditions during the production process and has high practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is the breakthrough curve of NH3 in activated carbon bed at different temperatures.

[0047] Figure 2 is the saturated adsorption capacity of NH3 by the activated carbon bed at different temperatures.

[0048] Figure 3 The denitrification efficiency of activated carbon saturated with NH3 adsorption at different temperatures.

[0049] Figure 4 This is the process flow chart of activated carbon flue gas purification technology.

[0050] Figure 5 This is a schematic diagram of the structure of the denitrification tower and the desulfurization tower.

[0051] Figure 6 This is the temperature rise curve of the activated carbon bed.

[0052] Figure 7 Parameter diagram of the activated carbon used in the present invention. DETAILED DESCRIPTION

[0053] The technical solution of the present invention is illustrated below by way of example, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0054] According to an embodiment of the present invention, a method for low-temperature pre-injection of ammonia with activated carbon is provided.

[0055] A method for pre-spraying ammonia on activated carbon at low temperature, the method comprising the following steps:

[0056] 1) The sintering machine and activated carbon flue gas purification system are shut down for maintenance, and cooling gas is drawn in to cool the activated carbon bed in the activated carbon flue gas purification system;

[0057] 2) While cooling the activated carbon bed, ammonia is sprayed into the denitrification tower so that the activated carbon is adsorbed on the activated carbon bed of the denitrification tower, providing an ammonia source for the denitrification reaction during sintering startup.

[0058] Preferably, the spraying of ammonia into the denitration tower is specifically: using a mixed gas composed of cold air and ammonia as a cooling gas for the activated carbon bed in the denitration tower, and controlling the introduction time of the mixed gas so that the adsorption amount of ammonia in the activated carbon bed after cooling reaches a target adsorption value. Preferably, the target adsorption value is not less than 80% of the saturated adsorption amount of ammonia by the activated carbon bed at the corresponding temperature.

[0059] Preferably, the saturated adsorption capacity of ammonia by the activated carbon bed is as follows: a penetration experiment of the activated carbon bed for NH3 is performed at different temperatures to obtain a penetration curve of the activated carbon bed for NH3, and the penetration curve is integrated and calculated to finally obtain the saturated adsorption capacity of NH3 by the activated carbon bed at different temperatures, and the relationship between the temperature and the saturated adsorption capacity of NH3 by the activated carbon bed is obtained by fitting.

[0060] Preferably, the relationship between the temperature and the saturated adsorption capacity of NH3 by the activated carbon bed obtained by the fitting is:

[0061] q=a·In(T)+6.8066……(Formula 1)

[0062] Wherein, q is the saturated adsorption capacity of NH3 per unit mass of activated carbon at temperature T, mg / g; T is the adsorption temperature, °C; a is the adsorption capacity adjustment coefficient, a=-1.329 mg / °C·g.

[0063] Preferably, the time for controlling the introduction of the mixed gas is specifically:

[0064] By testing the cooling flue gas volume Q introduced into the denitrification tower, the activated carbon bed temperature, the NH3 concentration in the cooling flue gas at the inlet and outlet of the denitrification tower, and the loading amount of activated carbon in the denitrification tower, we can obtain:

[0065]

[0066] Where Q is the amount of cooling gas introduced into the denitrification tower per unit time, Nm 3 / h; C0 is the concentration of NH3 in the mixed gas used as cooling gas, mg / Nm 3 ; C1 is the concentration of NH3 in the gas at the outlet of the denitrification tower, mg / Nm 3 ; t is the time for the mixed gas to be introduced into the denitration tower so that the activated carbon bed reaches the saturated adsorption capacity of NH3, h; m is the loading amount of activated carbon in the denitration tower, kg; q is the saturated adsorption capacity of NH3 per unit mass of activated carbon at temperature T, mg / g; b is the time adjustment coefficient, b=1000g / kg; control the actual introduction time of the mixed gas t s ≤t.

[0067] Preferably, the method further comprises:

[0068] 2a) When downtime t a When ≥t, ammonia is injected normally according to time t, and the activated carbon bed reaches the target adsorption value;

[0069] 2b) When downtime t a When t<t, adjust the amount of cooling flue gas introduced to control the cooling rate of the activated carbon bed so that a Within the range, the activated carbon bed reaches the target adsorption value; and / or, the concentration of NH3 in the cooling flue gas is controlled so that at t a Within this range, the activated carbon bed reaches the target adsorption value.

[0070] Preferably, the method further comprises: 3) estimating the denitration rate of the activated carbon bed within a certain time range based on the adsorption amount of NH3 by the activated carbon bed in the denitration tower.

[0071] Preferably, the denitration rate of the activated carbon bed is estimated as follows: after obtaining the saturated adsorption amount of NH3 by the activated carbon bed at different temperatures, the flue gas containing nitrogen oxides is adsorbed within a certain period of time, the adsorption rate is detected, and the corresponding relationship between the adsorption amount of NH3 by the activated carbon bed and the denitration rate is obtained by fitting, so that the denitration rate within the same period of time can be estimated according to the actual adsorption amount of NH3 by the activated carbon bed. Preferably, the certain period of time is 3 to 8 hours.

[0072] Preferably, the certain time is 4 hours, and the corresponding relationship between the adsorption amount of NH3 by the activated carbon bed and the denitrification rate is fitted as follows:

[0073] A=γ*x 2 +μ*x+θ……(Formula 3)

[0074]

[0075] In the formula, Y is the average denitration rate of the activated carbon bed, %; A is the adsorption of nitrogen oxides in flue gas by unit mass of activated carbon, mg / g-AC; M is the mass of activated carbon circulating in the denitration tower per hour, g / h; N is the concentration of nitrogen oxides in flue gas, mg / Nm 3 ; V is the flue gas flow rate to be purified into the denitrification tower per unit time, Nm 3 / h; x is the actual adsorption capacity of NH3 by activated carbon at different temperatures, mg / g-AC; γ, μ, and θ are the denitrification adjustment coefficients, the value of γ is -6.921; the value of μ is 42.84; and the value of θ is 57.78.

[0076] Preferably, the method further comprises: 4) according to the actual adsorption amount of NH3 by the activated carbon bed, the denitrification efficiency is predicted by (Formula 3), and according to the emission requirements, it is determined whether the flue gas emitted after denitrification after pre-injection of ammonia needs further treatment.

[0077] Preferably, the temperature of the shutdown inspection in step 1) is not higher than 60°C, preferably not higher than 50°C.

[0078] Preferably, the cooling gas in step 1) is air.

[0079] Preferably, the temperature of the ammonia gas sprayed into the denitration tower in step 2) is 50-100°C.

[0080] Example 1

[0081] A method for pre-spraying ammonia on activated carbon at low temperature, the method comprising the following steps:

[0082] 1) The sintering machine and activated carbon flue gas purification system were shut down for maintenance, and cooling gas was pumped in to cool the activated carbon bed in the activated carbon flue gas purification system, gradually cooling the activated carbon bed to 50°C;

[0083] 2) When the temperature of the activated carbon bed drops to 60°C, a mixed gas consisting of cold air and ammonia is used as the cooling gas for the activated carbon bed in the denitrification tower. The time required for the activated carbon bed to drop from 60°C to 50°C is t a =15min; at 50℃, the saturated adsorption capacity of activated carbon bed for NH3 is:

[0084] q=-1.329In(T)+6.8066=1.61mg / g

[0085] Then control the introduction time of the mixed gas:

[0086]

[0087] In the formula, Q is the amount of cooling flue gas introduced into the denitrification tower per unit time, and its value is 200000Nm 3 / h; C0 is the concentration of NH3 in the mixed gas used for cooling the flue gas, and its value is 15000mg / Nm 3 ; C1 is the concentration of NH3 in the flue gas at the outlet of the denitrification tower, which is 5 mg / Nm 3 ; t is the time for the mixed gas to be introduced into the denitrification tower so that the activated carbon bed reaches the saturated adsorption capacity of NH3, h; m is the loading amount of activated carbon in the denitrification tower, which is 400000 kg; q is the saturated adsorption capacity of NH3 per unit mass of activated carbon at a temperature of 50°C, which is 1.61 mg / g. Control the actual introduction time t of the mixed gas s =t=0.21h.

[0088] Due to t a >t s , according to t sAmmonia is sprayed into the activated carbon bed at normal time to make the activated carbon bed reach saturated adsorption capacity.

[0089] 3) According to the corresponding relationship between the adsorption amount of NH3 by the activated carbon bed and the denitrification rate:

[0090] A=γ*x 2 +μ*x+θ=-6.921*1.61 2 +42.84*1.61+57.78=108.81mg / g

[0091]

[0092] Where, Y is the average denitration rate of the activated carbon bed, %; A is the adsorption of nitrogen oxides in flue gas by unit mass of activated carbon, 108.81 mg / g-AC; M is the mass of activated carbon circulating in the denitration tower per hour, which is 120000 g / h; N is the concentration of nitrogen oxides in flue gas, which is 60 mg / Nm 3 ; V is the flue gas flow rate to be purified into the denitrification tower per unit time, and its value is 400000Nm 3 / h; x is the actual adsorption capacity of NH3 by activated carbon at different temperatures, and its value is 1.61 mg / g-AC; γ, μ, and θ are the denitrification adjustment coefficients, and the value of γ is -6.921; the value of μ is 42.84; and the value of θ is 57.78.

[0093] It is estimated that under this condition, the average denitrification rate of the activated carbon bed is 54.41%.

[0094] 4) The nitrogen oxide concentration in the sintering flue gas during startup is 60 mg / Nm 3 The estimated nitrogen oxide concentration after denitrification is 27.364 mg / Nm 3 , not exceeding 50mg / Nm 3 , no further processing is required.

[0095] Example 2

[0096] A method for pre-spraying ammonia on activated carbon at low temperature, the method comprising the following steps:

[0097] 1) The sintering machine and activated carbon flue gas purification system were shut down for maintenance, and cooling gas was pumped in to cool the activated carbon bed in the activated carbon flue gas purification system, gradually cooling the activated carbon bed to 55°C;

[0098] 2) When the temperature of the activated carbon bed drops to 70°C, a mixed gas consisting of cold air and ammonia is used as the cooling gas for the activated carbon bed in the denitrification tower. The time required for the activated carbon bed to drop from 70°C to 55°C is t a=19min; at 55℃, the saturated adsorption capacity of activated carbon bed for NH3 is:

[0099] q=-1.329In(T)+6.8066=1.48mg / g

[0100] Then control the introduction time of the mixed gas:

[0101]

[0102] In the formula, Q is the amount of cooling flue gas introduced into the denitrification tower per unit time, and its value is 200000Nm 3 / h; C0 is the concentration of NH3 in the mixed gas used for cooling the flue gas, and its value is 15000mg / Nm 3 ; C1 is the concentration of NH3 in the flue gas at the outlet of the denitrification tower, which is 8 mg / Nm 3 ; t is the time for the mixed gas to be introduced into the denitrification tower so that the activated carbon bed reaches the saturated adsorption capacity of NH3, h; m is the loading amount of activated carbon in the denitrification tower, which is 400000 kg; q is the saturated adsorption capacity of NH3 per unit mass of activated carbon at a temperature of 55°C, which is 1.48 mg / g. Control the actual introduction time t of the mixed gas s =t=0.197h.

[0103] Due to t a >t s , according to t s Ammonia is sprayed into the activated carbon bed at normal time to make the activated carbon bed reach saturated adsorption capacity.

[0104] 3) According to the corresponding relationship between the adsorption amount of NH3 by the activated carbon bed and the denitrification rate:

[0105] A=γ*x 2 +μ*x+θ=-6.921*1.48 2 +42.84*1.48+57.78=106.02mg / g

[0106]

[0107] Where, Y is the average denitration rate of the activated carbon bed, %; A is the adsorption of nitrogen oxides in flue gas by unit mass of activated carbon, 106.02 mg / g-AC; M is the mass of activated carbon circulating in the denitration tower per hour, which is 120000 g / h; N is the concentration of nitrogen oxides in flue gas, which is 60 mg / Nm 3 ; V is the flue gas flow rate to be purified into the denitrification tower per unit time, and its value is 400000Nm 3 / h; x is the actual adsorption capacity of NH3 by activated carbon at different temperatures, and its value is 1.48mg / g-AC; γ, μ, and θ are the denitrification adjustment coefficients, and the value of γ is -6.921; the value of μ is 42.84; and the value of θ is 57.78.

[0108] It is estimated that under this condition, the average denitrification rate of the activated carbon bed is 53.01%.

[0109] 4) The nitrogen oxide concentration in the sintering flue gas during startup is 60 mg / Nm 3 The estimated nitrogen oxide concentration after denitrification is 28.2 mg / Nm 3 , not exceeding 50mg / Nm 3 , no further processing is required.

Claims

1. A method for pre-spraying ammonia on activated carbon at low temperature, characterized in that: The method comprises the following steps: 1) The sintering machine and activated carbon flue gas purification system are shut down for maintenance, and cooling gas is drawn in to cool the activated carbon bed in the activated carbon flue gas purification system; 2) While cooling the activated carbon bed, ammonia is sprayed into the denitrification tower so that the activated carbon is adsorbed on the activated carbon bed of the denitrification tower, providing an ammonia source for the denitrification reaction during sintering startup.

2. The method according to claim 1, characterized in that: The method of spraying ammonia into the denitrification tower specifically comprises: using a mixed gas composed of cold air and ammonia as a cooling gas for the activated carbon bed in the denitrification tower, and controlling the introduction time of the mixed gas so that the adsorption amount of ammonia in the activated carbon bed after cooling reaches a target adsorption value; preferably, the target adsorption value is not less than 80% of the saturated adsorption amount of ammonia by the activated carbon bed at the corresponding temperature.

3. The method according to claim 2, characterized in that: The saturated adsorption capacity of ammonia by the activated carbon bed is as follows: a penetration test of NH3 by the activated carbon bed is performed at different temperatures to obtain a penetration curve of NH3 by the activated carbon bed, and the penetration curve is integrated and calculated to finally obtain the saturated adsorption capacity of NH3 by the activated carbon bed at different temperatures, and the relationship between the temperature and the saturated adsorption capacity of NH3 by the activated carbon bed is obtained by fitting; Preferably, the relationship between the temperature and the saturated adsorption capacity of NH3 by the activated carbon bed obtained by the fitting is: q=a·In(T)+6.8066……(Formula 1) Wherein, q is the saturated adsorption capacity of NH3 per unit mass of activated carbon at temperature T, mg / g; T is the adsorption temperature, °C; a is the adsorption capacity adjustment coefficient, a=-1.329 mg / °C·g.

4. The method according to claim 3, characterized in that: The specific time of controlling the introduction of the mixed gas is: By detecting the amount of cooling gas Q introduced into the denitrification tower, the temperature of the activated carbon bed, the concentration of NH3 in the cooling gas at the inlet and outlet of the denitrification tower, and the amount of activated carbon loaded in the denitrification tower, we can obtain: Where Q is the amount of cooling gas introduced into the denitrification tower per unit time, Nm 3 / h; C0 is the concentration of NH3 in the mixed gas used as cooling gas, mg / Nm 3 ; C1 is the concentration of NH3 in the gas at the outlet of the denitrification tower, mg / Nm 3 ; t is the time for the mixed gas to be introduced into the denitration tower so that the activated carbon bed reaches the saturated adsorption capacity of NH3, h; m is the loading amount of activated carbon in the denitration tower, kg; q is the saturated adsorption capacity of NH3 per unit mass of activated carbon at temperature T, mg / g; b is the time adjustment coefficient, b=1000g / kg; control the actual introduction time of the mixed gas t s ≤t.

5. The method according to claim 4, characterized in that: The method further includes: 2a) When downtime t a When ≥t, ammonia is injected normally according to time t, and the activated carbon bed reaches the target adsorption value; 2b) When downtime t a When t<t, adjust the amount of cooling gas introduced to control the cooling rate of the activated carbon bed so that a Within the range, the activated carbon bed reaches the target adsorption value; and / or, controlling the concentration of NH3 in the cooling gas so that at t a Within this range, the activated carbon bed reaches the target adsorption value.

6. The method according to any one of claims 2 to 5, characterized in that: The method further includes: 3) estimating the denitration rate of the activated carbon bed within a certain time range according to the adsorption amount of NH3 by the activated carbon bed in the denitration tower; Preferably, the estimated denitrification rate of the activated carbon bed is as follows: after obtaining the saturated adsorption capacity of NH3 by the activated carbon bed at different temperatures, the flue gas containing nitrogen oxides is adsorbed within a certain period of time, the adsorption rate is detected, and the corresponding relationship between the adsorption capacity of NH3 by the activated carbon bed and the denitrification rate is obtained by fitting, so that the denitrification rate within the same period of time can be estimated according to the actual adsorption capacity of NH3 by the activated carbon bed; preferably, the certain period of time is 3 to 8 hours.

7. The method according to claim 6, characterized in that: The certain time is 4 hours, and the corresponding relationship between the adsorption amount of NH3 by the activated carbon bed and the denitrification rate is obtained by fitting: A=γ*x 2 +μ*x+θ……(equation 3) In the formula, Y is the average denitration rate of the activated carbon bed, %; A is the adsorption of nitrogen oxides in flue gas by unit mass of activated carbon, mg / g-AC; M is the mass of activated carbon circulating in the denitration tower per hour, g / h; N is the concentration of nitrogen oxides in flue gas, mg / Nm 3 ; V is the flue gas flow rate to be purified into the denitrification tower per unit time, Nm 3 / h; x is the actual adsorption capacity of NH3 by activated carbon at different temperatures, mg / g-AC; γ, μ, and θ are the denitrification adjustment coefficients, the value of γ is -6.921; the value of μ is 42.84; and the value of θ is 57.

78.

8. The method according to claim 7, characterized in that: The method also includes: 4) according to the actual adsorption amount of NH3 by the activated carbon bed, the denitrification efficiency is predicted by (Formula 3), and according to the emission requirements, it is determined whether the flue gas discharged after denitrification after pre-injection of ammonia needs further treatment.

9. The method according to any one of claims 1 to 8, characterized in that: Step 1) The temperature of the shutdown for maintenance is not higher than 60°C, preferably not higher than 50°C; and / or The cooling gas in step 1) is air.

10. The method according to any one of claims 1 to 9, characterized in that: In step 2), the temperature of ammonia gas sprayed into the denitration tower is 50-100°C.

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