JP3202469B2 - Gas treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas treatment apparatus having an ammonia recovery apparatus for recovering ammonia from exhaust gas denitrated by adding ammonia by a temperature swing method using an adsorption tower.

[0002]

2. Description of the Related Art In order to denitrate flue gas, ammonia is injected into the flue gas in a denitration apparatus.
Since ammonia is excessively injected, it is necessary to recover unreacted ammonia (NH ₃ ) from exhaust gas discharged from the denitration device. The recovery of NH ₃ adsorbed NH ₃ with an adsorption tower, the NH ₃ by heating the adsorbent already adsorbent to desorb the NH _3, the temperature swing method using a so-called adsorption column is used. FIG. 4 shows a basic configuration of a conventional apparatus for recovering NH ₃ from a gas flowing from a denitration apparatus using an adsorption tower.

[0003] As shown in FIG. 4, an adsorption tower 1 filled with an adsorbent 30 is connected to a flue gas 9 from a flue gas from a denitration apparatus, and a valve is provided when a high concentration of NH ₃ flows through the flue 9. The exhaust gas is led to the adsorption tower 1 by the operation of V1 and V2,
Adsorb H ₃ . The adsorbed NH ₃ is treated gas flue 10
A high-temperature gas flows into the adsorption tower 1 from the side, is desorbed, and flows to the flue 24 side.

FIG. 5 is a system diagram of an entire conventional gas processing apparatus in which NH ₃ gas adsorption towers 1 and 2 are installed downstream of a denitration apparatus of a flue gas of a flue gas, and this will be described. The gas adsorbers 1 and 2 are filled with an adsorbent, and adsorb unreacted NH ₃ contained in exhaust gas discharged from the denitration device. Since the adsorption towers 1 and 2 alternately perform adsorption and desorption and have the same operation, the adsorption tower 1 will be described first. FIG. 4 shows only the adsorption tower 1.

In FIG. 5, first, valves V1 and V6 are opened, and V2 and V5 are closed to exit the denitration apparatus, and 20 ppm of N
100 ° C. low-temperature exhaust gas containing H ₃ is passed through the adsorption tower 1 to adsorb NH ₃ in the exhaust gas. When the adsorbent 30 is saturated with NH ₃ , the valves V1 and V6 are closed, and the valves V2 and V6 are closed.
5, V7 is opened, and the adsorption tower 1 enters the step of desorbing NH ₃ .
The desorption is performed by introducing the high-temperature exhaust gas before entering the denitration apparatus through the valve V7 into the adsorption tower 1 to raise the temperature of the interior of the adsorption tower 1 by a heating device. The desorbed NH ₃ is discharged from the chimney inlet through the valve V2 or denitration apparatus. It shall be reused at the entrance.

Gas adsorption / desorption equipment using this temperature swing method
The device is NH at low temperature _ThreeIs adsorbed on adsorbent 3
Thereafter, the temperature of the adsorbent 30 and / or its container is raised.
Adsorbed by_ThreeFor desorbing and collecting gas
You. Adsorbed NH_ThreeAs the temperature in the adsorption tower rises, the gas
Desorbed gradually, but after a certain time, a large excess of NH
_ThreeGas was detected at the container outlet.

[0007] NH ₃ of the adsorption tower outlet the desorbed NH ₃ concentration
FIG. 6 shows the result measured by the total M1. Desorption start time is 0
Result of observation of the time course of the desorption NH ₃ as a frequency, NH ₃ concentration adsorption tower internal temperature as indicated by a broken line, are discharged from the adsorption tower as it rises rapidly increase after 3 hours 4000
ppm NH ₃ was observed at the outlet of the adsorption tower.

[0008]

When the adsorbed NH ₃ gas is desorbed from the adsorption tower, the NH ₃ gas is desorbed as the temperature rises.
It reaches its peak after a certain time. This large excess of NH ₃ gas is 10 ² ppm to 10 by volume conversion with respect to the exhaust gas at the inlet of the adsorption device.
^It was equivalent to ⁴ ppm. In order to discharge this NH ₃ gas directly from the chimney or to use it for other purposes, it was necessary to adjust the desorbed NH ₃ gas to a certain concentration or less.

Further, since the NH ₃ concentration which can be discharged normally is 10 ppm or less at the chimney outlet, 400 times the amount of exhaust gas is required to satisfy the discharge standard. Separately, when the recovered NH ₃ is reused for denitration, it is necessary to dilute the exhaust gas by a factor of 80. For this reason, the pipe diameter increases and the fans also increase in size. Lower NH ₃ peak value to make NH
It was necessary to discharge ₃ . An object of the present invention is to provide a gas processing apparatus provided with a temperature swing type ammonia recovery apparatus capable of recovering ammonia having a stable concentration.

[0010]

SUMMARY OF THE INVENTION The present invention has an ammonia recovery apparatus for adsorbing ammonia from an exhaust gas denitrified by adding ammonia with an adsorption tower and desorbing and recovering the adsorbed ammonia from the adsorption tower. In order to prevent the temporary release of excessive desorbed NH ₃ gas in the gas treatment apparatus, a desorption gas is provided in the desorption gas flue of the adsorption tower, which is provided with a bypass device filled with an adsorbent to selectively flow the desorption gas. A configuration with a bypass line is adopted.

By installing a desorption gas bypass line having a bypass device filled with an adsorbent in this way, for example, NH ₃ gas having a discharge reference value or more can be stored in the bypass device. ₃ Prevent gas release. Further, for a system that reuses the desorbed gas, a desorbed NH ₃ gas having a required concentration equal to or lower than the desorbed concentration is supplied, so that the release of surplus gas can be prevented. The NH ₃ gas adsorbed by the bypass device is gradually desorbed, and the discharged NH ₃ concentration is maintained in a stable state.

[0012] In the gas treatment apparatus according to the present invention, at least two adsorption towers constituting the ammonia recovery apparatus are provided so that each can be switched by a valve, and a switching valve is provided in front of and behind the desorption gas flue of each adsorption tower. In addition, the desorption gas bypass line provided with the bypass device having the above-described configuration is connected to prevent the high concentration desorption NH ₃ gas from being released using the desorption gas bypass line while continuously performing adsorption and desorption. can do.

In the gas treatment apparatus according to another aspect of the present invention, in addition to the above-described structure, a low-temperature gas discharged from the adsorption tower and an exhaust gas before denitration are mixed, and a gas at an appropriate temperature is supplied to the adsorption tower as a desorption gas. Configure to guide. As a result, the temperature of the desorption gas can be selected to a desired value, so that the temperature change of the adsorbent to be desorbed is made gentle and the desorption NH ₃ gas concentration can be kept in a stable state.

In the gas treatment apparatus according to the present invention, at least one of the ammonia gas desorbed from the adsorbent of the adsorption tower and the bypass device can be reused for denitration. As a result, the release of NH ₃ gas exceeding the emission standard can be prevented, and NH ₃ can be used effectively for denitration.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a gas processing apparatus according to the present invention will be described in detail with reference to one embodiment shown in FIGS. FIG. 1 shows a basic configuration of a gas treatment apparatus according to the present invention having an ammonia recovery apparatus installed downstream of a denitration apparatus of a flue gas of a flue gas. First, this will be described.

A flue gas flue 9 downstream of a denitration device (not shown) is provided with an adsorption tower 1 filled with an NH ₃ adsorbent 30.
Valves V1 and V6 are provided before and after that. On the inlet side of the adsorption tower 1, after the valve V1, the desorption gas flue provided with the valve V2 is designated as 24. In the desorption gas flue 24, the bypass line 21 which is branched upstream from the valve V2 Is added to the bypass line 21 and N
A bypass device 3 for desorbed NH ₃ filled with an H ₃ adsorbent 30 is provided. A valve V3 and a valve V4 are provided before and after the bypass device 3. Reference numeral 10 denotes a processing gas flue connected to a chimney (not shown) or the like.

In FIG. 1, a low-temperature exhaust gas containing about 20 ppm of NH ₃ flows from the denitration apparatus into the adsorption tower 1.
Valves V1 and V6, opens, the valve V2, V3 and V4 and closed, after the NH ₃ adsorbed in the NH ₃ adsorbing agent 30 in the adsorption tower 1, is discharged from a chimney (not shown) to the atmosphere. When the NH ₃ adsorbent 30 in the adsorption tower 1 is saturated with NH ₃ , the valves V1 and V6 are closed, and high-temperature gas is flown into the adsorption tower 1 from the processing gas flue 10 side for desorption.

After the start of desorption, as the internal temperature of the adsorption tower 1 increases, the concentration of NH ₃ discharged from the adsorption tower 1 sharply increases. Leave measuring the concentration NH ₃ meter M2, when it exceeds a certain concentration, closing the valve V2, and the valves V3 and V4 is opened, flow desorption gas to the bypass device 3.

The high concentration desorption of NH ₃ is once adsorbed on NH ₃ adsorbent 30 of the cold bypass device 3, NH ₃ desorption gas flue 24 is fed to a chimney or the like becomes low concentrations. Further, when the desorbed gas flows into the bypass device 3, the temperature inside the device 3 gradually rises due to the flow of the high-temperature exhaust gas, so that the temporarily adsorbed NH ₃ is desorbed again and the valve V4
And discharged from the chimney to the upstream side of the desorption device and reused for denitration. Thereby, the high concentration of NH ₃ desorbed from the NH ₃ adsorption tower 1 is suppressed by the bypass device 3,
The concentration is almost constant and the gas is discharged, which can be released to the atmosphere and the control when the desorption device is reused becomes simple.

A preferred embodiment of the present invention is shown in FIG. 2 as an overall system diagram, which will be described next. In the case of this drawing, the denitration of the combustion exhaust gas from a gas turbine or the like is efficiently performed by injecting excessive ammonia, and the exhaust gas boiler 5 provided in the flue gas flue 8 of the gas turbine 4 is used.
It is an application of the present invention to those installed ammonia recovery device with two systems of NH ₃ adsorption column filled with the NH ₃ adsorbent for adsorbing the leak ammonia stream after.

First, an exhaust gas boiler 5 equipped with a denitration device 6 and an NH ₃ injection nozzle 7 is provided in a flue downstream of the gas turbine 4, and the subsequent flue gas flue 8 is divided into two systems. Are flue gas inlet flues 9 and 12,
This NH ₃ provided NH ₃ adsorption towers 1 and 2 packed with an adsorbent, after which connects the process gas flue 10 and 13,
These merge and are connected to the chimney 11. This NH ₃
Valves V1, V6 and V9 and V14 are provided before and after the adsorption towers 1 and 2, respectively.

The high-temperature gas for desorption is supplied to the exhaust gas boiler 5.
Of branches in the preceding, the feed to the mixer 15 and hot gas flue 14, after the appropriate temperature is combined with the cold gas of the low-temperature gas flue 16 which branches from the previous chimney 11, NH ₃ adsorbed as hot gas flue 18 It is connected to the downstream of columns 1 and 2. The high-temperature gas flue 18 is provided with valves V5 and V13, respectively, so that the high-temperature gas is guided through the circulation fan 17 as needed (during the desorption step).

The novel part of the gas treatment apparatus shown in FIG. 2 is provided with a bypass flue 19 connecting the flue gas inlet flues 9 and 12 at the inlets of the NH ₃ adsorption towers 1 and 2, and the N 2 is provided with a bypass flue 19.
The bypass device 3 filled with the H ₃ adsorbent and valves V3 and V11 before and after are provided. Further, between the bypass device 3 and the valves V3 and V11, desorbed gas flues 21 and 20 connected to the desorbed NH ₃ flues 24 and 25 are additionally provided. The desorption gas flues 21 and 20 are provided with valves V4 and V12, respectively.

The desorbed NH ₃ flues 24 and 25 merge to form a circulating NH ₃ flue 22 provided with a circulating fan 23, which is connected to the NH ₃ injection nozzle 7 in the exhaust gas boiler 5. Although not shown separately, the circulating NH ₃ flue 2
2 and the desorbed NH ₃ flues 24 and 25
May be connected to the processing gas flue 10 and 13 before the above.

The operation of the gas processing apparatus shown in FIG. 2 will be described. Adsorption towers 1 and 2 filled with NH ₃ adsorbent
Has a bypass flue 19 equipped with a bypass device 3 for desorbed NH ₃ , which is delimited by valves V3 and V11. Adsorption of leak ammonia after denitration of the combustion exhaust gas generated from the gas turbine 4 is performed by first opening the valves V1 and V6 and opening the valves V2 and V3.
V11, V5 and V7 are closed, and a low-temperature exhaust gas containing 20 ppm of NH ₃ at 100 ° C. is flowed into the system A of the NH ₃ adsorption tower 1 to adsorb NH ₃ . Valves V1, V6 at which the adsorbent is saturated with NH ₃ closed, it enters the desorption step of the NH ₃ in the adsorption tower 1 by opening the valves V2, V5, V7 flow hot gas to NH ₃ adsorption tower 1.

The desorption is performed by raising the temperature of the interior of the adsorption tower 1 with a heating device, and the desorbed NH ₃ is sent to the NH ₃ injection nozzle 7 at the inlet of the denitration device 6 through the valve V2 for reuse. FIG. 6 shows the desorption NH ₃ concentration measured by the NH ₃ meter M1 at the outlet of the adsorption tower 1. Desorption NH with the desorption start time set to 0 minutes
As a result of observing the change with time in ( _{3), as} the internal temperature of the adsorption tower indicated by the broken line increases, the NH ₃ concentration discharged from the adsorption tower sharply increases, and two hours later, 2000 ppm of NH ₃ is observed at the exit of the adsorption tower. Was. When the desorbed NH ₃ observed by the NH ₃ meter M1 exceeds 2000 ppm, the valve V2 is closed and the valves V3 and V4 are opened to pass the desorbed NH ₃ to the bypass device 3.
Flows into.

High concentration of NH_ThreeOnce the cold viper
Adsorbed on the adsorption device 3, but desorbed NH _ThreeHigh temperature exhaust containing
As the gas flows in, the temperature inside the bypass device 3 gradually increases.
Ascended and temporarily adsorbed NH_ThreeAgain take off the bal
Re-used for denitration on the upstream side of the denitration device 6
You. NH at this time_ThreeNH concentration_ThreeObserved by total
The results are shown in FIG. On the other hand, NH_ThreeB system including adsorption tower 2
Is a gas turbine by performing the reverse process of the A system.
The flue gas from step 4 can be continuously denitrated,
Adsorption and desorption of ammonia can be performed. Note that
In the above description, the desorbed NH_ThreeShall be reused for denitration
As described above, let it be discharged from the chimney 11
You may.

[0028]

As described above, according to the gas treatment apparatus of the present invention, it is possible to satisfy the NH ₃ emission standard at the smoke outlet. In addition, excess NH ₃ can be used in the denitration device installed upstream of the ammonia recovery device, and the denitration efficiency is improved. Even if high concentration NH ₃ is discharged by desorption from the adsorption tower, the desorption N
Since the H ₃ concentration can be leveled, it is not necessary to adjust the flow rate and temperature of the desorbed gas, and the control is simple.

Furthermore, in the gas treatment apparatus of the present invention, since the bypass device has the ability to adjust the desorbed NH ₃ , the temperature in the adsorption tower can be increased quickly. Therefore, the time required for NH ₃ desorption is reduced. In addition, since the concentration of NH ₃ desorbed from the adsorption tower is made substantially constant by the bypass device, control at the time of discharging NH ₃ or reusing the denitration is simple.

[Brief description of the drawings]

FIG. 1 is a device layout diagram showing a basic configuration of an ammonia recovery device provided with a desorption gas bypass line provided with a bypass device according to the present invention.

FIG. 2 is an equipment layout diagram of a gas processing apparatus according to one embodiment of the present invention.

FIG. 3 shows desorbed NH ₃ in a gas treatment apparatus according to the present invention.
5 is a graph showing the change over time in the concentration.

FIG. 4 is a device layout diagram showing a basic configuration of an ammonia recovery device in a conventional gas processing device.

FIG. 5 is a device layout diagram of a conventional gas processing apparatus.

FIG. 6 is a graph showing a change over time of a desorbed NH ₃ concentration in a conventional gas processing apparatus.

[Explanation of symbols]

1 NH ₃ adsorption columns 2 NH ₃ adsorption towers 3 bypass device 4 gas turbine 5 exhaust gas boiler 6 denitrator 7 NH ₃ injection nozzle 8 a combustion exhaust gas flue 9 flue gas inlet flue 10 process gas flue 11 chimney 12 the flue gas inlet smoke Road 13 Process gas flue 14 Hot gas flue 15 Mixer 16 Low temperature gas flue 17 Circulation fan 18 Hot gas flue 19 Bypass flue 20 Desorption gas flue 21 Desorption gas flue 22 Circulation NH ₃ flue 23 Circulation fan 24 Desorption NH ₃ flue 25 Desorption NH ₃ flue V1 to V14 Valve

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsushi Morii 1-1, Akunouracho, Nagasaki-shi Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (72) Inventor Osamu Naito 1-1, Akunouracho, Nagasaki-shi Mitsubishi Heavy Industries, Ltd. Inside Nagasaki Shipyard (72) Inventor Keiko Kobayashi 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Heavy Industries, Ltd. (72) Inventor Kozo Iida 4-622 Kannonshinmachi, Nishi-ku, Hiroshima-shi Sanishi Heavy Industries, Ltd. Hiroshima Research Institute (72) Inventor Kazuto Kobayashi Hiroshima City, Hiroshima City 4-72 Kanon Shinmachi Hiroshima Research Institute (72) Inventor Hiroyuki Ozora Hiroshima City Nishi-ku 4-6-1 Kanon Shinmachi, Hiroshima City (56) References JP-A-7-213845 (JP, A) JP-A-7-204461 (JP, A) JP-A-7-31849 JP, A) JP flat 6-226044 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) B01D 53/34 - 53/96 B01D 53/04

Claims (4)

(57) [Claims] 1. A gas treatment apparatus having an ammonia recovery device for adsorbing ammonia from an exhaust gas denitrated by adding ammonia by an adsorption tower and desorbing and recovering the adsorbed ammonia from the adsorption tower, A gas processing apparatus, comprising: a desorption gas flue, a bypass device filled with an adsorbent, and a desorption gas bypass line for selectively flowing desorption gas. 2. A desorption gas comprising at least two systems of said adsorption towers, each of which can be switched by a valve, and wherein said desorption gas flue of each adsorption tower is provided with a switching valve at the front and rear thereof and said bypass device. The gas processing apparatus according to claim 1, wherein a bypass line is connected. 3. The gas processing apparatus according to claim 1, wherein the low-temperature gas discharged from the adsorption tower and the exhaust gas before denitration are mixed and a gas adjusted to an appropriate temperature is led to the adsorption tower as a desorption gas. 4. The apparatus according to claim 1, wherein at least one of ammonia gas desorbed from the adsorbed substance in the adsorption tower and the bypass device is reused for denitration.
The gas processing apparatus according to any one of the three items.