An activated coke denitrification system for ultra-low nitrogen oxide emissions

Abstract

This invention discloses an activated coke denitrification system for ultra-low nitrogen oxide emissions, comprising a flue gas header, a distribution mechanism, several denitrification towers, an ammonia supply mechanism, and a main flue gas outlet pipe. A first NOx measuring device is installed on the flue gas header. The distribution mechanism includes a distribution tank. Activated coke is installed in each denitrification tower, and a second NOx measuring device is installed at the outlet of each denitrification tower. The ammonia supply mechanism includes an ammonia supply main pipe and several ammonia injection units with adjustable injection rates. The beneficial effects of this invention are: in-situ rapid NOx measurement is performed at the outlet of each denitrification tower; the ammonia injection rate of the injection units is controlled based on the measured NOx results, achieving precise ammonia injection, low ammonia slip, and eliminating the influence of ammonium bisulfate on subsequent equipment; the NOx content in the flue gas header is detected by the first NOx measuring device, allowing the ammonia injection rate to be adaptively adjusted according to changes in NOx content, resulting in stable and minimally fluctuating NOx concentration control at the denitrification outlet.

Description

Technical Field

[0001] This invention relates to the field of activated coke denitrification technology, and in particular to an activated coke denitrification system for ultra-low nitrogen oxide emissions. Background Technology

[0002] The activated carbon coke desulfurization and denitrification process utilizes the adsorption and catalytic properties of activated carbon / coke to adsorb SO2, O2 and water vapor in flue gas onto the surface of activated coke, and then react to generate H2SO4 which is adsorbed in the micropores of activated coke, thereby achieving the desulfurization effect.

[0003] 2SO2 + O2 + 2H2O → 2H2SO4

[0004] Activated coke denitrification mainly utilizes the catalytic properties of activated coke to carry out selective catalytic reduction (SCR) reaction, reducing NO to N2 under the action of reducing agent NH3.

[0005] The activated coke denitrification process is large in scale. Generally speaking, depending on the flue gas volume, the denitrification tower is divided into 4-5 compartments. The ammonia injection point is located at the inlet of each denitrification tower compartment. Because the source airflow of each compartment is unevenly distributed and the flue gas volume of each compartment is different, in order to ensure overall compliance, the number of locations where the ammonia-nitrogen molar ratio at a certain compartment cross-section exceeds 1 will increase significantly. Ammonia will escape in large quantities at these locations, causing subsequent equipment to be easily blocked. Conversely, at locations where the ammonia-nitrogen molar ratio is lower than the average value, the denitrification efficiency cannot meet the standard. Summary of the Invention

[0006] In view of this, it is necessary to provide an activated coke denitrification system for ultra-low nitrogen oxide emissions to solve the problem of uneven flue gas volume in each compartment. Existing ultra-low emission nitrogen oxide emission measurement is lagging, and it is impossible to control ammonia injection by the nitrogen oxide emission of each parallel compartment. Excessive ammonia injection in some compartments will lead to the problem of ammonium bisulfate blockage.

[0007] To achieve the above objectives, the present invention provides an activated coke denitrification system for ultra-low nitrogen oxide emissions, comprising a flue gas header, a distribution mechanism, several denitrification towers, an ammonia supply mechanism, and a flue gas outlet header.

[0008] A first NOx measuring device is installed on the flue gas header, and the first NOx measuring device is used to detect the NOx content in the flue gas header.

[0009] The distribution mechanism includes a distribution tank with a cylindrical distribution cavity. An air inlet is provided at the center of the lower end face of the distribution tank, which is connected to the flue gas header. Several air outlets are provided on the upper end face of the distribution tank, and each air outlet is equidistant from the center of the upper end face of the distribution tank.

[0010] Each of the denitrification towers is equipped with activated coke, the inlet of each of the denitrification towers is connected to each of the gas outlets, the outlet of each of the denitrification towers is connected to the main flue gas pipe, and a second NOx measuring device is installed at the outlet of each of the denitrification towers.

[0011] The ammonia supply mechanism includes a main ammonia supply pipe and several ammonia injection units with adjustable injection volume. The inlet of each ammonia injection unit is connected to the main ammonia supply pipe, and the outlet of each ammonia injection unit is connected to the inner cavity of each denitrification tower.

[0012] In some embodiments, the specific method for determining the optimal ammonia injection rate is as follows: Let the NOx content in the flue gas header obtained at time t1-Δt be c1, the NOx content in the flue gas header obtained at time t1 be c2, the NOx content in the flue gas discharged from the denitrification tower outlet obtained at time t1 be d1, the ammonia injection rate at time t1 be k1, and the NOx standard emission level be a. Then, the optimal ammonia injection rate k2 at time t1+Δt is:

[0013]

[0014] Where N is the number of denitrification towers, and Δt is the time it takes for flue gas to flow from the location of the first NOx measuring device into the denitrification tower.

[0015] In some embodiments, a flow rate detection element is also provided inside the flue gas header.

[0016] In some embodiments, the dispensing mechanism further includes a sieve cylinder, which is fixed inside the dispensing tank and divides the dispensing chamber into an inner dispensing chamber and an outer dispensing chamber. The air inlet is connected to the inner dispensing chamber, and each of the air outlets is connected to the outer dispensing chamber.

[0017] In some embodiments, the ammonia injection component includes an ammonia injection pipe, an ammonia injection head, and an ammonia injection valve. One end of the ammonia injection pipe is connected to the main ammonia supply pipe, and the other end of the ammonia injection pipe is connected to the ammonia injection head. The ammonia injection head is disposed in the corresponding denitrification tower.

[0018] In some embodiments, the ammonia supply mechanism further includes an annular pipe, one end of which is connected to the main ammonia supply pipe, and one end of each of the ammonia injection pipes is connected to the annular pipe.

[0019] In some embodiments, each of the denitrification towers is connected to a tee at its outlet. The first port of the tee is connected to the outlet of the denitrification tower, the second port of the tee is connected to one end of a first gas valve, and the other end of the first gas valve is connected to the main flue gas pipe.

[0020] The activated coke denitrification system for ultra-low nitrogen oxide emissions also includes a backflow device, which includes a second air valve and a backflow pump. One end of the second air valve is connected to the third port of the three-way valve, and the other end of the second air valve is connected to the inlet of the backflow pump. The outlet of the backflow pump is connected to the distribution tank.

[0021] In some embodiments, the backflow device further includes a one-way valve, the inlet of which is connected to the outlet of the backflow pump, and the outlet of which is connected to the distribution tank.

[0022] In some embodiments, the backflow device further includes a plurality of branch pipes and a first main pipe, one end of each branch pipe is connected to the third interface of the corresponding tee, the other end of each branch pipe is connected to one end of the first main pipe, and the other end of the first main pipe is connected to the inlet of the backflow pump.

[0023] In some embodiments, the backflow device further includes a second main pipe, one end of which is connected to the outlet of the backflow pump, and the other end of which is connected to the distribution chamber.

[0024] Compared with existing technologies, the beneficial effects of the technical solution proposed in this invention are as follows: During control, NOx is rapidly measured in situ at the outlet of each denitrification tower. Based on the measured NOx results, the ammonia injection rate is controlled to ensure precise ammonia injection, achieving appropriate ammonia injection, low ammonia slip, and eliminating the impact of ammonium bisulfate on subsequent equipment. Simultaneously, the NOx content in the flue gas header is detected by the first NOx measuring device, allowing the ammonia injection rate to be adaptively adjusted according to changes in NOx content. This ensures stable and minimally fluctuating NOx concentration control at the denitrification outlet, meeting the requirements for ultra-low emissions and higher precision denitrification control, thereby reducing ammonia slip and mitigating or preventing blockages in subsequent equipment. Attached Figure Description

[0025] Figure 1 This is a three-dimensional structural schematic diagram of an embodiment of the activated coke denitrification system for ultra-low nitrogen oxide emissions provided by the present invention;

[0026] Figure 2 yes Figure 1 A schematic diagram of an embodiment of an activated coke denitrification system for ultra-low nitrogen oxide emissions;

[0027] Figure 3 yes Figure 2 A magnified view of a portion of region A in the middle;

[0028] In the diagram: 1-Flue gas main pipe, 11-First NOx measuring device, 12-Flow rate detection device, 2-Distribution mechanism, 21-Distribution tank, 211-Inlet, 212-Outlet, 22-Sieve cylinder, 3-Denitrification tower, 31-Second NOx measuring device, 32-First gas valve, 33-T-way valve, 4-Ammonia supply mechanism, 41-Ammonia supply main pipe, 42-Ammonia injection device, 421-Ammonia injection pipe, 422-Ammonia injection head, 423-Ammonia injection valve, 43-Ring pipe, 5-Flue gas main pipe, 6-Return device, 61-Second gas valve, 62-Return pump, 63-Check valve, 64-Branch pipe, 65-First main pipe, 66-Second main pipe. Detailed Implementation

[0029] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0030] Please refer to Figure 1 and Figure 2 The present invention provides an activated coke denitrification system for ultra-low nitrogen oxide emissions, comprising a flue gas header 1, a distribution mechanism 2, several denitrification towers 3, an ammonia supply mechanism 4, and a flue gas outlet main pipe 5;

[0031] A first NOx measuring device 11 is installed on the flue gas header 1, and the first NOx measuring device 11 is used to detect the NOx content in the flue gas header 1.

[0032] The distribution mechanism 2 includes a distribution tank 21, which has a cylindrical distribution cavity. An air inlet 211 is provided at the center of the lower end face of the distribution tank 21, and the air inlet 211 is connected to the flue gas header 1. A plurality of air outlets 212 are provided on the upper end face of the distribution tank 21, and each air outlet 212 is equidistant from the center of the upper end face of the distribution tank 21.

[0033] Each of the denitrification towers 3 is equipped with activated coke, the inlet of each of the denitrification towers 3 is connected to each of the gas outlets 212, the outlet of each of the denitrification towers 3 is connected to the main flue gas pipe 5, and a second NOx measuring device 31 is installed on the outlet of each of the denitrification towers 3.

[0034] The ammonia supply mechanism 4 includes an ammonia supply main pipe 41 and several ammonia injection elements 42 with adjustable jet volume. The inlet of each ammonia injection element 42 is connected to the ammonia supply main pipe 41, and the outlet of each ammonia injection element 42 is connected to the inner cavity of each denitrification tower 3.

[0035] In operation, the flue gas to be denitrated enters the flue gas header 1, then enters the distribution tank 21 from the inlet 211, and is discharged into each denitrification tower 3 from the outlets 212. Since the distance between each outlet 212 and the center of the upper surface of the distribution tank 21 is equal, the amount of flue gas entering each denitrification tower 3 is approximately equal, thus ensuring that each denitrification tower 3 bears the denitrification pressure as evenly as possible. Afterwards, the ammonia injection unit 42 injects ammonia gas into the corresponding denitrification tower 3. The ammonia gas reacts with the NOx in the flue gas, thereby denitrifying the flue gas. The denitrated flue gas then exits from... The flue gas is discharged from the main exhaust pipe 5. During this process, the NOx content in the flue gas discharged from the outlet of the corresponding denitrification tower 3 is continuously detected by each second NOx measuring device 31, and the NOx content in the flue gas header 1 is continuously detected by the first NOx measuring device 11. Based on the NOx content in the flue gas header 1 and the NOx content in the flue gas discharged from the outlet of the denitrification tower 3, the optimal ammonia injection amount of the ammonia injection component 42 is determined, and ammonia is injected according to the optimal ammonia injection amount. This ensures that the flue gas denitrification is not incomplete due to insufficient ammonia injection, nor that subsequent equipment is easily blocked due to excessive ammonia injection.

[0036] Preferably, the specific method for determining the optimal ammonia injection rate of the ammonia injection unit 42 is as follows: Let the NOx content in the flue gas header 1 obtained at time t1-Δt be c1, the NOx content in the flue gas header 1 obtained at time t1 be c2, the NOx content in the flue gas discharged from the outlet of the denitrification tower 3 obtained at time t1 be d1, the ammonia injection rate at time t1 be k1, and the standard NOx emission level be a. Then, the optimal ammonia injection rate k2 at time t1+Δt is:

[0037]

[0038] Wherein, N is the number of denitrification towers 3, and in this embodiment, N is 4.

[0039] In formula (1), Δt is the time it takes for the flue gas to flow from the location of the first NOx measuring device 11 into the denitrification tower 3.

[0040] The derivation of the above formula is as follows:

[0041] The NOx reduction caused by the ammonia content of k1 injected at time t1 is: c1 / N–d1. The NOx reduction required by the optimal ammonia injection rate k2 at time t1+Δt is: c2 / N–a. Therefore, we have:

[0042]

[0043] Simplifying equation (2) yields equation (1).

[0044] Preferably, please refer to Figure 2The distribution mechanism 2 also includes a screen cylinder 22, which is fixed inside the distribution tank 21 and divides the distribution chamber into an inner distribution chamber and an outer distribution chamber. The air inlet 211 communicates with the inner distribution chamber, and each of the air outlets 212 communicates with the outer distribution chamber. By setting the screen cylinder 22, the flow of flue gas can be slowed down, and the uniformity of flue gas discharge in all directions of the distribution chamber can be improved.

[0045] Preferably, to accurately calculate the time it takes for the flue gas to flow from the location of the first NOx measuring device 11 into the denitrification tower 3, please refer to... Figure 2 The flue gas header 1 is also equipped with a flow velocity detection device 12. The flue gas flow velocity is measured by the flow velocity detection device 12. Then, the time it takes for the flue gas to flow from the position of the first NOx measuring device 11 to the denitrification tower 3 can be obtained by dividing the length of the flue gas from the position of the first NOx measuring device 11 to the denitrification tower 3 by the flow velocity.

[0046] Specifically, please refer to Figure 2 and Figure 3 The ammonia injection component 42 includes an ammonia injection pipe 421, an ammonia injection head 422, and an ammonia injection valve 423. One end of the ammonia injection pipe 421 is connected to the main ammonia supply pipe 41, and the other end of the ammonia injection pipe 421 is connected to the ammonia injection head 422. The ammonia injection head 422 is installed in the corresponding denitrification tower 3. In use, the amount of ammonia injected by the ammonia injection component 42 can be adjusted by controlling the opening degree of the ammonia injection valve 423.

[0047] Preferably, please refer to Figure 1 and Figure 2 In order to specifically realize the connection between one end of the ammonia injection pipe 421 and the ammonia supply main pipe 41, the ammonia supply mechanism 4 also includes an annular pipe 43, one end of the annular pipe 43 is connected to the ammonia supply main pipe 41, and one end of each of the ammonia injection pipes 421 is connected to the annular pipe 43.

[0048] Preferably, please refer to Figure 1 and Figure 2To prevent the emission of excessive flue gas when the second NOx measuring device 31 detects excessive NOx content, each of the denitrification towers 3 is connected to a tee 33 at its outlet. The first port of the tee 33 is connected to the outlet of the denitrification tower 3, and the second port of the tee 33 is connected to one end of the first gas valve 32. The other end of the first gas valve 32 is connected to the main flue gas pipe 5. The activated coke denitrification system for ultra-low nitrogen oxide emissions also includes a return device 6. The return device 6 includes a second gas valve 61 and a return pump 62. One end of the second gas valve 61 is connected to the third port of the tee 33, and the other end of the second gas valve 61 is connected to the inlet of the return pump 62. The outlet of the return pump 62 is connected to the distribution tank 21. During use, when the second NOx measuring device 31 detects that the NOx content exceeds the standard, the first gas valve 32 is closed, and the second gas valve 61 and the return pump 62 are opened. The return pump 62 draws the unqualified flue gas into the distribution tank 21, and at the same time, the ammonia injection amount of the corresponding ammonia injection component 42 is appropriately increased. When the second NOx measuring device 31 detects that the NOx content meets the standard, the second gas valve 61 and the return pump 62 are closed, and the first gas valve 32 is opened to carry out the normal denitrification process.

[0049] Preferably, please refer to Figure 1 and Figure 2 The return discharge device 6 also includes a one-way valve 63. The inlet of the one-way valve 63 is connected to the outlet of the return discharge pump 62, and the outlet of the one-way valve 63 is connected to the distribution tank 21. By setting the one-way valve 63, the flue gas in the distribution tank 21 can be prevented from flowing back into the return discharge pump 62.

[0050] Preferably, please refer to Figure 1 and Figure 2 The backflow device 6 further includes several branch pipes 64 and a first main pipe 65. One end of each branch pipe 64 is connected to the third interface of the corresponding tee 33, and the other end of each branch pipe 64 is connected to one end of the first main pipe 65. Each second air valve 61 is installed on the corresponding branch pipe 64, and the other end of the first main pipe 65 is connected to the inlet of the backflow pump 62.

[0051] Preferably, please refer to Figure 1 and Figure 2 The return device 6 further includes a second main pipe 66, one end of which is connected to the outlet of the return pump 62, and the other end of which is connected to the distribution chamber.

[0052] The activated coke denitrification system for ultra-low nitrogen oxide emissions provided by this invention performs in-situ rapid NOx measurement at the outlet of each denitrification tower 3. Based on the measured NOx results, the opening of the ammonia injection valve 423 is controlled to precisely inject ammonia, achieving appropriate ammonia injection, low ammonia slip, and preventing downstream equipment from being affected by ammonium bisulfate. Simultaneously, the NOx content in the flue gas header 1 is detected by the first NOx measuring device 11, allowing the ammonia injection rate to be adaptively adjusted according to changes in NOx content. This ensures stable and minimally fluctuating NOx concentration control at the denitrification outlet, meeting the requirements for ultra-low emissions and higher precision denitrification control, thereby reducing ammonia slip and mitigating or preventing blockages in downstream equipment.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An activated coke denitrification system for ultra-low nitrogen oxide emissions, characterized in that, It includes a flue gas header, distribution system, several denitrification towers, ammonia supply system, and main flue gas outlet pipe; A first NOx measuring device is installed on the flue gas header, and the first NOx measuring device is used to detect the NOx content in the flue gas header. The distribution mechanism includes a distribution tank with a cylindrical distribution cavity. An air inlet is provided at the center of the lower end face of the distribution tank, which is connected to the flue gas header. Several air outlets are provided on the upper end face of the distribution tank, and each air outlet is equidistant from the center of the upper end face of the distribution tank. Each of the denitrification towers is equipped with activated coke, the inlet of each of the denitrification towers is connected to each of the gas outlets, the outlet of each of the denitrification towers is connected to the main flue gas pipe, and a second NOx measuring device is installed at the outlet of each of the denitrification towers. The ammonia supply mechanism includes a main ammonia supply pipe and several ammonia injection units with adjustable injection volume. The inlet of each ammonia injection unit is connected to the main ammonia supply pipe, and the outlet of each ammonia injection unit is connected to the inner cavity of each denitrification tower. The specific method for determining the optimal ammonia injection rate is as follows: Let the NOx content in the flue gas header obtained at time t1-Δt be c1, the NOx content in the flue gas header obtained at time t1 be c2, the NOx content in the flue gas discharged from the denitrification tower outlet obtained at time t1 be d1, the ammonia injection rate at time t1 be k1, and the standard NOx emission level be a. Then, the optimal ammonia injection rate k2 at time t1+Δt is: Where N is the number of denitrification towers, and Δt is the time it takes for flue gas to flow from the location of the first NOx measuring device into the denitrification tower.

2. The activated coke denitrification system for ultra-low nitrogen oxide emissions according to claim 1, characterized in that, A flow rate detection device is also installed inside the flue gas header.

3. The activated coke denitrification system for ultra-low nitrogen oxide emissions according to claim 1, characterized in that, The distribution mechanism also includes a sieve cylinder, which is fixed inside the distribution tank and divides the distribution chamber into an inner distribution chamber and an outer distribution chamber. The air inlet is connected to the inner distribution chamber, and each of the air outlets is connected to the outer distribution chamber.

4. The activated coke denitrification system for ultra-low nitrogen oxide emissions according to claim 1, characterized in that, The ammonia injection component includes an ammonia injection pipe, an ammonia injection head, and an ammonia injection valve. One end of the ammonia injection pipe is connected to the main ammonia supply pipe, and the other end of the ammonia injection pipe is connected to the ammonia injection head. The ammonia injection head is installed in the corresponding denitrification tower.

5. The activated coke denitrification system for ultra-low nitrogen oxide emissions according to claim 4, characterized in that, The ammonia supply mechanism also includes a ring pipe, one end of which is connected to the main ammonia supply pipe, and one end of each of the ammonia injection pipes is connected to the ring pipe.

6. The activated coke denitrification system for ultra-low nitrogen oxide emissions according to claim 1, characterized in that, Each of the denitrification towers is connected to a tee at its outlet. The first port of the tee is connected to the outlet of the denitrification tower, the second port of the tee is connected to one end of a first gas valve, and the other end of the first gas valve is connected to the main flue gas pipe. The activated coke denitrification system for ultra-low nitrogen oxide emissions also includes a backflow device, which includes a second air valve and a backflow pump. One end of the second air valve is connected to the third port of the three-way valve, and the other end of the second air valve is connected to the inlet of the backflow pump. The outlet of the backflow pump is connected to the distribution tank.

7. The activated coke denitrification system for ultra-low nitrogen oxide emissions according to claim 6, characterized in that, The backflow device also includes a one-way valve, the inlet of which is connected to the outlet of the backflow pump, and the outlet of which is connected to the distribution tank.

8. The activated coke denitrification system for ultra-low nitrogen oxide emissions according to claim 6, characterized in that, The backflow device also includes several branch pipes and a first main pipe. One end of each branch pipe is connected to the third interface of the corresponding tee, and the other end of each branch pipe is connected to one end of the first main pipe. The other end of the first main pipe is connected to the inlet of the backflow pump.

9. The activated coke denitrification system for ultra-low nitrogen oxide emissions according to claim 8, characterized in that, The return flow device also includes a second main pipe, one end of which is connected to the outlet of the return flow pump, and the other end of which is connected to the distribution chamber.

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