Deamination device for trapping ammonia escape based on absorbent

Abstract

The utility model discloses a deamination device for trapping ammonia escape based on an absorbent, which comprises an absorption tower with the lower section being a first circulation section and the upper section being a second circulation section; the first upper end of the ammonia recovery tower is connected with a rich liquid outlet of the first circulation section of the absorption tower through a first guide pipe; a barren liquor discharge port of the ammonia recovery tower is connected with the second circulation section of the absorption tower through a second guide pipe and a barren liquor discharge pump; the electric heater is arranged in the first guide pipe; the upper end of the reboiler is connected with the top end of the ammonia recovery tower through a third guide pipe and a compressor; the top of the reboiler is connected with the middle part of the ammonia recovery tower through a fourth guide pipe; the bottom end of the reboiler is connected with the bottom end of the ammonia recovery tower through a fifth guide pipe and a reboiler circulating pump; the lower end of the flash tank is connected with the lower end of the reboiler through a sixth guide pipe, the bottom end of the flash tank is connected with the second upper end of the ammonia recovery tower through a reflux pump, and the top end of the flash tank is connected with the first heat exchanger and the ammonia water storage tank through a seventh guide pipe.

Description

Technical Field

[0001] The utility model relates to the technical field of ammonia escape control, in particular to a deammonification device based on an absorbent to capture ammonia escape. Background Art

[0002] Nitrogen oxides (NO, NO2, and N2O) are considered major air pollutants that contribute to acid rain, the greenhouse effect, photochemical smog, and human lung diseases. The combustion of fossil fuels for transportation and industry is the primary source of these oxides. Selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) of NOx with ammonia are currently considered the most effective technologies for removing NOx, with VW(Mo)-Ti catalysts being the most widely used catalysts in SCR technology.

[0003] With the introduction of ultra-low emission standards in China in 2014, the requirements for nitrogen oxide emission concentrations have become more stringent (less than 50mg / Nm 3 ), to improve denitrification efficiency, more ammonia needs to be injected into the flue gas to provide sufficient reducing agent to remove nitrogen oxides. However, excess ammonia cannot be completely consumed by nitrogen oxides. Deactivation of commercial SCR catalysts or uneven mixing of ammonia and nitrogen oxide gases can easily exacerbate this situation, leading to ammonia slip. Ammonia slip is undoubtedly a waste of resources and inconsistent with the concept of green development. More importantly, ammonia slip is harmful to both the environment and the SCR system. Commercial SCR catalysts can oxidize SO2 in the flue gas to SO3, which then reacts with ammonia slip to form sticky NH4HSO4, leading to catalyst poisoning and air preheater corrosion, shortening the service life of the SCR system. Ammonia slip is a key indicator of denitrification performance.

[0004] The main measures to control ammonia escape include developing an injection system to make the flue gas mix evenly, or to mix NH3 / NO x The ratio is limited to around 0.9-0.95, but the current solution is not effective and difficult to achieve. The method of reducing ammonia content will reduce the conversion efficiency of nitrogen oxides, making it difficult to meet the strict ultra-low emission standards. PID control and manual ammonia injection adjustment are currently commonly used to control ammonia slip. Operators often increase the amount of ammonia to quickly reduce the concentration of nitrogen oxides, but this will cause excess ammonia to escape into the environment, wasting energy and causing secondary pollution. In addition, the existing PID input and output structure is simple, and the closed-loop dynamic quality is very sensitive to changes in PID gain. Under complex denitrification settings, PID can only control one denitrification indicator at a time. In addition, since the system needs to constantly modify the control parameters, the system operation is still unstable, making it difficult to meet the strict current ultra-low emission standards for nitrogen oxides. Therefore, ammonia cannot be effectively absorbed and the treatment efficiency is low. Utility Model Content

[0005] In view of this, an embodiment of the present invention provides a deammonification device based on capturing ammonia escape with an absorbent, so as to solve the problem that the solutions for controlling ammonia escape in the prior art are not effective.

[0006] The present invention provides a deammonification device based on an absorbent to capture ammonia escape, comprising:

[0007] The lower section of the absorption tower is the first circulation section, and the upper section of the absorption tower is the second circulation section. The flue gas inlet is set between the spray port of the first circulation section of the absorption tower and the absorbent liquid level. The flue gas after ammonia removal is sent to the chimney from the top of the absorption tower. The bottom end of the absorption tower is the rich liquid discharge outlet.

[0008] an ammonia recovery tower, wherein a first upper end thereof is connected to the rich liquid outlet of the first circulation section of the absorption tower via a first conduit; and a lean liquid outlet of the ammonia recovery tower is connected to the second circulation section of the absorption tower via a second conduit and a lean liquid discharge pump;

[0009] an electric heater, disposed in the first conduit, for heating the rich liquid discharged from the first circulation section of the absorption tower to a boiling state, thereby decomposing ammonia;

[0010] A reboiler, the upper end of which is connected to the top of the ammonia recovery tower via a third conduit and a compressor; the top of the reboiler is connected to the middle of the ammonia recovery tower via a fourth conduit; the bottom end of the reboiler is connected to the bottom end of the ammonia recovery tower via a fifth conduit and a reboiler circulation pump, the reboiler circulation pump being used to transport lean liquid from the bottom of the ammonia recovery tower to the reboiler;

[0011] The lower end of the flash tank is connected to the lower end of the reboiler through the sixth conduit, the bottom end of the flash tank is connected to the second upper end of the ammonia recovery tower through a reflux pump, and the top end of the flash tank is connected to the ammonia water storage tank through the seventh conduit and the first heat exchanger.

[0012] Optionally, it also includes:

[0013] One end of the eighth conduit is connected to the lean liquid outlet of the second circulation section of the absorption tower, and the other end of the eighth conduit is connected to the lean liquid inlet of the first circulation section of the absorption tower.

[0014] Optionally, it also includes:

[0015] The upper end of the circulation box is connected to the other end of the eighth conduit, and the lower end of the circulation box is connected to the lean liquid input port of the first circulation section of the absorption tower through the ninth conduit; an absorbent dosing port is provided at the top of the circulation box, and the absorbent dosing port is connected to the absorbent storage tank.

[0016] Optionally, it also includes:

[0017] The second heat exchanger is arranged at the second conduit and is used to cool the lean liquid discharged from the ammonia recovery tower.

[0018] Optionally, the first heat exchanger and the second heat exchanger are circulating water heat exchangers.

[0019] Optionally, the cold end inlet of the second heat exchanger is connected to the rich liquid discharge outlet of the first circulation section of the absorption tower through the rich liquid discharge pump and the first conduit, and the cold end outlet of the second heat exchanger is connected to the ammonia recovery tower through the electric heater and the second conduit; the hot end inlet of the second heat exchanger is connected to the outlet of the lean liquid discharge pump; and the hot end outlet of the second heat exchanger is connected to the second circulation section of the absorption tower.

[0020] Optionally, the spray device of the first circulation section of the absorption tower is connected to the absorbent solution at the lower end of the first circulation section through a tenth conduit and the first circulation pump.

[0021] Optionally, the spraying device of the first circulation section of the absorption tower is connected to the circulation box through the eleventh conduit and the second circulation pump.

[0022] Optionally, it also includes:

[0023] The dust collector and kiln tail fan are installed in front of the flue gas inlet.

[0024] Beneficial effects of the utility model:

[0025] This embodiment of the utility model provides a denitrification device that uses an absorbent to capture ammonia escape, suitable for energy-intensive industries such as cement, steel, thermal power, and chemical industries. SCR flue gas denitrification technology achieves a denitrification efficiency exceeding 85%, while SNCR flue gas denitrification technology generally has a denitrification efficiency of 40%-60%, but still results in significant ammonia escape. The denitrification device provided in this embodiment can be directly installed at the back end of an SCR, SNCR, or SCR-SNCR system, significantly reducing the concentration of escaped ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the present invention in any way. In the accompanying drawings:

[0027] Figure 1 The following is a structural block diagram of a deammonification device based on an absorbent to capture ammonia escape in an embodiment of the present invention;

[0028] Figure 2 Shows the cycle process diagram. DETAILED DESCRIPTION

[0029] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0030] The present invention provides a deamination device based on an absorbent to capture ammonia escape, such as Figure 1 As shown, including:

[0031] The lower section of the absorption tower is the first circulation section (marked as circulation section A in the figure), and the upper section of the absorption tower is the second circulation section (marked as circulation section B in the figure). The flue gas inlet 1 is located between the spray port of the first circulation section of the absorption tower and the absorbent liquid level. The flue gas after ammonia removal is sent from the top of the absorption tower to the chimney 2; the bottom of the absorption tower is the rich liquid discharge outlet.

[0032] The first upper end of the ammonia recovery tower 3 is connected to the rich liquid outlet of the first circulation section of the absorption tower through a first conduit; the lean liquid outlet of the ammonia recovery tower 3 is connected to the second circulation section of the absorption tower through a second conduit and a lean liquid discharge pump 4.

[0033] The electric heater 5 is provided in the first conduit and is used to heat the rich liquid discharged from the first circulation section of the absorption tower to a boiling state, thereby decomposing ammonia.

[0034] The upper end of the reboiler 6 is connected to the top of the ammonia recovery tower through the third conduit and the compressor 7; the top of the reboiler 6 is connected to the middle of the ammonia recovery tower 3 through the fourth conduit; the bottom end of the reboiler 6 is connected to the bottom end of the ammonia recovery tower through the fifth conduit and the reboiler circulation pump 8. The reboiler circulation pump 8 is used to transport the lean liquid at the bottom of the ammonia recovery tower 3 to the reboiler 6.

[0035] The lower end of the flash tank 9 is connected to the lower end of the reboiler 6 through the sixth conduit, the bottom end of the flash tank is connected to the second upper end of the ammonia recovery tower 3 through the reflux pump 10, and the top end of the flash tank 9 is connected to the ammonia solution storage tank through the seventh conduit and the first heat exchanger 11.

[0036] As an optional embodiment, an eighth conduit is further included, one end of which is connected to the lean liquid outlet 12 of the second circulation section of the absorption tower, and the other end of the eighth conduit is connected to the lean liquid inlet of the first circulation section of the absorption tower.

[0037] As an optional embodiment, a circulation box 13 is further included, the upper end of which is connected to the other end of the eighth conduit. The lower end of the circulation box 13 is connected to the lean liquid inlet of the first circulation stage of the absorption tower via a ninth conduit. An absorbent dosing port is provided at the top of the circulation box, which is connected to the absorbent storage tank 14. In this embodiment, the absorbent is a phosphoric acid solution.

[0038] As an optional embodiment, a second heat exchanger 15 is further included, which is arranged at the second conduit and is used to cool the lean liquid discharged from the ammonia recovery tower.

[0039] As an optional embodiment, the first heat exchanger 11 and the second heat exchanger 15 are circulating water heat exchangers.

[0040] As an optional embodiment, the cold-end inlet of the second heat exchanger 15 is connected to the rich-liquid outlet of the first circulation section of the absorber via a rich-liquid discharge pump 16 and a first conduit. The cold-end outlet of the second heat exchanger 15 is connected to the ammonia recovery tower 3 via an electric heater 5 and a second conduit. The hot-end inlet of the second heat exchanger 15 is connected to the outlet of the lean-liquid discharge pump 4; and the hot-end outlet of the second heat exchanger 15 is connected to the second circulation section of the absorber. In this embodiment, the rich liquid is initially heated by the hot lean liquid, which then dissipates heat through the rich liquid, thereby restoring ammonia absorption capacity and eliminating an additional cooling water cycle for heat exchange.

[0041] As an optional embodiment, the spraying device of the first circulation section of the absorption tower is connected to the absorbent solution at the lower end of the first circulation section through the tenth conduit and the first circulation pump 17.

[0042] As an optional embodiment, the spraying device of the second circulation section of the absorption tower is connected to the circulation box 13 through the eleventh conduit and the second circulation pump 18.

[0043] As an optional embodiment, a dust collector 19 and a kiln tail fan 20 are further included, which are arranged at the front end of the flue gas inlet 1 to remove dust from the flue gas 21.

[0044] The workflow of the deamination device based on the capture of ammonia escape by an absorbent provided in this embodiment is mainly divided into three parts:

[0045] Flue gas flow: Flue gas enters the absorption tower, cools in the A circulation section, and then enters the B circulation section, where it comes into countercurrent contact with an absorbent, such as phosphoric acid solution. Over 95% of the ammonia in the flue gas is absorbed in the B circulation section. The ammonia-free flue gas is then sent from the top of the absorption tower to the chimney.

[0046] Mother liquor process: The phosphoric acid solution in the absorption tower A cycle and B cycle is supplied by two circulating pumps (one for standby). Figure 2As shown, the circulating pump in section A delivers a portion of the rich liquid (phosphoric acid solution after ammonia absorption) to the solution heat exchanger (lean-rich liquid heat exchanger). The rich liquid undergoes heat exchange with the hot lean liquid (desorbed phosphoric acid solution) from the bottom of the ammonia recovery tower. The rich liquid is heated to a boiling state and then enters the ammonia recovery tower, where a small amount of acidic gas in the rich liquid is blown out and returned to the ammonia absorption tower. The rich liquid then countercurrently contacts the saturated steam from the bottom of the desorption tower, desorbing ammonia from the rich liquid. The lean liquid at the bottom of the tower enters the lean-rich liquid heat exchanger, where it is cooled and then enters the circulation section B of the absorption tower for recycling.

[0047] Ammonia water process: After the ammonia vapor coming out of the top of the ammonia recovery tower passes through the compressor and reboiler and exchanges heat with the lean liquid from the bottom of the ammonia recovery tower, the ammonia vapor then passes through the circulating water heat exchanger and is completely condensed by cooling water into ≥20% ammonia water. It flows to the ammonia water intermediate tank and then enters the owner's SNCR or SCR ammonia water storage tank.

[0048] The reaction principle of the deamination device based on the absorbent capturing ammonia escape provided in this embodiment is as follows:

[0049] Absorption principle: The flue gas is washed by phosphoric acid mother liquor, and the ammonia in the flue gas reacts with phosphoric acid in the mother liquor to produce three ammonium salts with different thermal stability: diammonium dihydrogen phosphate (NH4H2PO4), diammonium hydrogen phosphate ((NH4)2HPO4), and ammonium phosphate ((NH4)3PO4), which are then absorbed by the phosphoric acid mother liquor.

[0050] Desorption principle: The three ammonium salts produced in the ammonia absorption tower have different thermal stabilities. Ammonium phosphate is very unstable and decomposes to produce diammonium hydrogen phosphate and ammonia at room temperature; diammonium hydrogen phosphate is relatively unstable and begins to decompose to produce ammonium dihydrogen phosphate and ammonia at 70°C; diammonium dihydrogen phosphate is very unstable and begins to decompose to produce phosphoric acid and ammonia at temperatures above 130°C. Taking advantage of the different thermal stabilities of these three ammonium salts, they are heated with steam in the ammonia recovery tower to decompose them to produce ammonia, which is then made into concentrated ammonia water.

[0051] In normal production, the ammonium salt in the solution exists in two forms: diammonium dihydrogen phosphate and diammonium hydrogen phosphate. The principle reaction formula is as follows:

[0052]

[0053] This embodiment of the utility model provides a denitrification device that uses an absorbent to capture ammonia escape, suitable for energy-intensive industries such as cement, steel, thermal power, and chemical industries. SCR flue gas denitrification technology achieves a denitrification efficiency exceeding 85%, while SNCR flue gas denitrification technology generally has a denitrification efficiency of 40%-60%, but still results in significant ammonia escape. The denitrification device provided in this embodiment can be directly installed at the back end of an SCR, SNCR, or SCR-SNCR system, significantly reducing the concentration of escaped ammonia.

[0054] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations shall fall within the scope defined by the appended claims.

Claims

1. A deamination device based on an absorbent to capture ammonia escape, characterized in that: include: An absorption tower, wherein the lower section is the first circulation section, and the upper section of the absorption tower is the second circulation section; wherein the flue gas inlet is arranged between the spray port of the first circulation section of the absorption tower and the absorbent liquid level, and the flue gas after ammonia removal is sent into the chimney from the top of the absorption tower; the bottom end of the absorption tower is the rich liquid discharge outlet; an ammonia recovery tower, wherein a first upper end thereof is connected to the rich liquid outlet of the first circulation section of the absorber tower via a first conduit; and a lean liquid outlet of the ammonia recovery tower is connected to the second circulation section of the absorber tower via a second conduit and a lean liquid discharge pump; an electric heater, disposed in the first conduit, for heating the rich liquid discharged from the first circulation section of the absorption tower to a boiling state, thereby decomposing ammonia; a reboiler, the upper end of which is connected to the top of the ammonia recovery tower via a third conduit and a compressor; the top of the reboiler is connected to the middle of the ammonia recovery tower via a fourth conduit; the bottom end of the reboiler is connected to the bottom end of the ammonia recovery tower via a fifth conduit and a reboiler circulation pump, the reboiler circulation pump being used to transport the lean liquid at the bottom of the ammonia recovery tower to the reboiler; The lower end of the flash tank is connected to the lower end of the reboiler through the sixth conduit, the bottom end of the flash tank is connected to the second upper end of the ammonia recovery tower through a reflux pump, and the top end of the flash tank is connected to the first heat exchanger and the ammonia water storage tank through the seventh conduit.

2. The deamination device based on the absorbent to capture ammonia escape according to claim 1, characterized in that: Also includes: An eighth conduit has one end connected to the lean liquid outlet of the second circulation section of the absorption tower, and the other end connected to the lean liquid inlet of the first circulation section of the absorption tower.

3. The deamination device based on the absorbent to capture ammonia escape according to claim 2, characterized in that: Also includes: A circulation box, the upper end of which is connected to the other end of the eighth conduit, and the lower end of which is connected to the lean liquid inlet of the first circulation section of the absorption tower through the ninth conduit; an absorbent dosing port is provided at the top of the circulation box, and the absorbent dosing port is connected to the absorbent storage tank.

4. The deamination device based on capturing ammonia escape by an absorbent according to claim 1, characterized in that: Also includes: The second heat exchanger is arranged at the second conduit and is used to cool the lean liquid discharged from the ammonia recovery tower.

5. The deamination device based on capturing ammonia escape with an absorbent according to claim 4, characterized in that: The first heat exchanger and the second heat exchanger are circulating water heat exchangers.

6. The deamination device based on capturing ammonia escape by an absorbent according to claim 4, characterized in that: The cold end inlet of the second heat exchanger is connected to the rich liquid discharge outlet of the first circulation section of the absorption tower through a rich liquid discharge pump and a first conduit, and the cold end outlet of the second heat exchanger is connected to the ammonia recovery tower through an electric heater and a second conduit; the hot end inlet of the second heat exchanger is connected to the outlet of the lean liquid discharge pump; and the hot end outlet of the second heat exchanger is connected to the second circulation section of the absorption tower.

7. The deamination device based on capturing ammonia escape by an absorbent according to claim 1, characterized in that: The spray device of the first circulation section of the absorption tower is connected to the absorbent solution at the lower end of the first circulation section through the tenth conduit and the first circulation pump.

8. The deamination device based on capturing ammonia escape with an absorbent according to claim 3, characterized in that: The spray device of the second circulation section of the absorption tower is connected to the circulation box through the eleventh conduit and the second circulation pump.

9. The deamination device based on capturing ammonia escape with an absorbent according to claim 1, characterized in that: Also includes: The dust collector and the kiln tail fan are arranged at the front end of the flue gas inlet.

Images