JPH08168645A - Ammonia adsorption device - Google Patents

Abstract

PURPOSE: To effectively desorb ammonia in an ammonia adsorption device installed downstream of a denitrifying device for reduction and decomposition of NOx contained in exhaust gas using ammonia. CONSTITUTION: Ammonia adsorption columns 5A, 5B, in at least two series, which are installed downstream of a denitrifying device 4 for reducing and decomposing NOx contained in exhaust gas using ammonia are formed into a vertical type, and at the time of regeneration, high temperature gas is caused to flow from the top of each of the columns 5A, 5B downwardly, while cooling gas is caused to flow from the bottom of each of the columns 5A, 5B upwardly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ammonia adsorption facility installed downstream of a denitration device using ammonia as a reducing agent.

[0002]

2. Description of the Related Art FIG. 4 is a system diagram of a conventional denitration device equipped with an ammonia adsorption facility. In this conventional device, the exhaust gas generated from the gas turbine 1 is introduced into the exhaust heat recovery boiler 2 from the flue, mixed with the ammonia injected by the ammonia injection device 3 provided inside, and provided in the downstream. The nitrogen oxide (NO _x ) in the exhaust gas is decomposed into harmless nitrogen and water. The exhaust gas is then introduced into one of the two horizontal adsorption towers 5 and 5 arranged in parallel from the exhaust gas ducts 7A and 7B,
After the residual ammonia is adsorbed, it is discharged from the exhaust gas duct 8 to the atmosphere through the chimney 6. The inside of the adsorption tower 5 is filled with an ammonia adsorbent, but after adsorption of a certain amount or more of ammonia, the adsorption is not performed. Therefore, the dampers before and after the adsorption tower 5 are closed, and the high-temperature exhaust gas generated in the gas turbine 1 is introduced as the desorption gas into the adsorption tower 5 through the desorption gas duct 9 to raise the temperature of the ammonia adsorbent to desorb ammonia and to remove the chimney. It is released to 6.

After the ammonia in one of the adsorption towers 5 is sufficiently desorbed, a low-temperature gas is made to flow from the upper part to the lower part through a cooling gas duct (not shown) in the adsorption tower 5 in preparation for the next adsorption, or a fan (not shown). Thus, the air is sent to the top of the adsorption tower 5 to cool the adsorption tower 5. The above steps are repeated in each adsorption tower. In addition, in FIG.
When one adsorption tower 5 is in the adsorption step, the other adsorption tower 5 is in the desorption step, and these steps are alternately repeated in the two adsorption towers 5.

[0004]

When the adsorption tower is of a horizontal type as in the conventional ammonia adsorption equipment described above, in order to desorb ammonia, 1/50 of the main gas is directed in the same direction as when adsorbing. Although the flow is for temperature raising, a small amount of gas causes a non-uniform flow, resulting in uneven temperature rise in the adsorption tower. Therefore, the ammonia adsorbed by the adsorbent cannot be sufficiently desorbed within the temperature programmed desorption time, and the amount of adsorption next time decreases. Further, since the low-temperature gas is introduced from the upper part to the lower part during cooling, the low-temperature gas unevenly passes through the adsorption tower, so that the whole tower is not cooled and the cooling time is long.
Therefore, the adsorption / desorption time schedule was reviewed, the number of adsorption towers was revised, and adsorption / desorption control became complicated, which was a problem in facility operation.

The present invention is intended to provide an ammonia adsorption equipment which can solve the above problems in the conventional ammonia adsorption equipment.

[0006]

According to the present invention, in an ammonia adsorption facility installed downstream of a denitration device for decomposing nitrogen oxides contained in exhaust gas with ammonia as a reducing agent, exhaust gas containing ammonia is vertically directed. At least two ammonia adsorption towers are installed to adsorb and desorb ammonia.
It is characterized in that the high temperature gas for desorption is caused to flow from the upper portion to the lower portion of the adsorption tower and the cooling gas is caused to flow from the lower portion to the upper portion of the adsorption tower when the adsorption tower is regenerated.

[0007] Desorption high-temperature gas (usually 1/5 of the main gas amount) in the adsorption tower that has sufficiently adsorbed ammonia during the adsorption time.
By causing (0) to flow downward from the upper part of the adsorption tower, even a gas having a small differential pressure is stratified by the adsorbent layer, the temperature inside the adsorption tower becomes uniform, and desorption proceeds smoothly. Further, by flowing the cooling gas upward from the lower part of the adsorption tower, the cooling gas of low temperature passes through the entire adsorption tower, so that the entire tower can be cooled in a short time, the adsorption / desorption cycle is smoothed, and the control is simple. Be converted.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIG. In FIG. 1, 1 is a gas turbine, 2
Is an exhaust heat recovery boiler into which the exhaust gas of the gas turbine is introduced,
Reference numeral 3 is an ammonia injection device provided in the exhaust heat recovery boiler 2, 4 is a denitration device provided on the downstream side of the ammonia injection device, and 5A and 5B are arranged in parallel on the downstream side of the denitration device 4 to adsorb ammonia. Two adsorption towers filled with the agent, and 6 are chimneys provided on the downstream side of the adsorption towers 5A and 5B. The adsorption towers 5A and 5B are of a vertical type, and as will be described later, the exhaust gas containing ammonia flows in the adsorption tower 5 as a vertical downward flow.

The two branched exhaust gas ducts 7A and 7B through which the exhaust gas from the denitration device 4 flows are respectively provided in the adsorption tower 5.
The exhaust gas ducts 7A, 7B are connected to the tops of A, 5B
Are provided with dampers D ₁ and D ₆ , respectively. Further, the bottoms of the adsorption towers 5A and 5B have dampers D ₂ and
Exhaust gas ducts 8A, 8B having D ₇ and the same duct 8
It is connected to the chimney 6 by an exhaust gas duct 8C where A and 8B merge.

Reference numeral 12 is a damper D of the exhaust gas duct 7A.₁
On the downstream side of the exhaust gas and the damper D of the exhaust gas duct 7B₆of
It is a duct that connects the downstream side part and damper D₃,
D₈Is provided. Gas turbine 1 and exhaust heat recovery boiler
Desorption by branching the exhaust gas of the gas turbine 1 from between
Damper D in gas duct 9₁₃Is provided. Exhaust gas
Duct 1 divided from the upstream side of the stack of duct 8C
Damper D for 1₁₄, D _FifteenInstalled, desorption gas duct 9
And duct 11 are dampers D₁₃And damper D_FifteenMerges downstream of
Becomes duct 18 and the gas flowing in the duct 18 becomes
Damper D₁₃, D _FifteenThe flow rate is adjusted by the specified temperature
It is supposed to be. The duct 18 is a damper D.₃,
D₈It is connected to the duct 12 between.

The portion of the exhaust gas duct 8A on the upstream side of the damper D ₂ and the portion of the gas duct 8B on the upstream side of the damper D ₇ are connected by a duct 14 having dampers D ₄ and D _9. The duct 10 is branched from the portion between the dampers D ₄ and D ₉ of the exhaust heat recovery boiler 2, and the duct 10 is connected to the portion between the ammonia injection device 3 and the denitration device 4 of the exhaust heat recovery boiler 2.

The portion of the exhaust gas duct 7A on the downstream side of the damper D ₁ and the portion of the exhaust gas duct 7B on the downstream side of the damper D ₆ are connected by a duct 15 having dampers D ₁₁ and D _12. A duct 16 branches from a portion between the dampers D ₁₁ and D ₁₂ of 15, and the duct 16 is connected to the chimney 6. Moreover, the the upstream portion of the damper D ₇ of the upstream-side portion of the damper D ₂ of the duct 8A and the duct 8B are connected by a duct 17 with a damper D _5, D _10, the damper of the duct 11 The cooling gas duct 13 branched from between D ₁₅ and the damper D ₁₄ is connected to a portion of the duct 17 between the damper D ₅ and the damper D ₁₀ .

In the present embodiment, the exhaust gas containing NO _x at a high temperature generated in the gas turbine 1 is introduced into the exhaust heat recovery boiler 2 provided on the downstream side and heat-exchanged by a heat exchanger (not shown). It became a low temperature and ammonia injection device 3
The NO _x is decomposed into harmless nitrogen and water in the denitration device 4 by mixing with the ammonia injected in the above. At this time, the injection amount of ammonia is set to be higher than that which reacts with NO _x to achieve a high denitration rate. Therefore, the residual ammonia that has not been used in the reaction in the denitration device 4 remains in the exhaust gas downstream of the denitration device.

By opening the dampers D ₁ and D ₂ on _one side of the adsorption tower 5A, the above-mentioned exhaust gas containing ammonia excessively injected by the ammonia injection device 3 becomes one of the adsorption towers on the downstream side of the denitration device 4. Introduced on top of 5A.

In this way, the exhaust gas containing ammonia introduced into one of the adsorption towers 5A flows in the adsorption tower 5A as a vertical downward flow, and the ammonia in the exhaust gas is adsorbed in the adsorbent filled in the adsorption tower 5A. After being adsorbed, it is discharged to the atmosphere from the chimney 6 through the exhaust gas duct 8A.

At this time, the dampers D ₁₃ , D ₁₄ and D ₁₅ are opened. As a result, a part of the high temperature exhaust gas of the gas turbine 1 from the desorption gas duct 9 and a part of the low temperature exhaust gas of the chimney inlet from the duct 11 are mixed in the duct 18 and are desorbed as desorption gas through the opened damper D _8. The other adsorption tower 5
It is introduced at the top of B and flows in the adsorption tower 5B as a downward flow in the vertical direction to raise the temperature of the adsorbent filled in the adsorption tower 5B to desorb the ammonia adsorbed by the adsorbent. This desorbed desorbed gas containing ammonia is introduced into the exhaust heat recovery boiler 2 from the bottom of the adsorption tower 5B through the exhaust gas duct 8B, the duct 14 in which the damper D ₉ is opened, and the duct 10, and the desorbed ammonia is recycled. Be used effectively. As the desorption gas, the exhaust gas of the gas turbine 1 which is about 1/50 of the main exhaust gas introduced into the exhaust heat recovery boiler 2 is used.

When the ammonia is sufficiently desorbed in the adsorption tower 5B as described above, the dampers D ₁₃ and D ₁₅ are closed, the dampers D ₁₄ and D ₁₀ are opened, and the other dampers are operated to adsorb Low-temperature gas is introduced into the tower 5B through the duct 11, the cooling gas duct 13, the duct 17 and the exhaust gas duct 8B as a cooling gas at the bottom of the adsorption tower 5B, and the cooling gas rises in the adsorption tower 5B and rises in the tower. After cooling the adsorbent therein, the adsorbent is discharged from the top to the chimney 6 through the exhaust gas duct 7B, the duct 15 and the duct 16.

Adsorption in the adsorption tower 5A and adsorption tower 5
When the desorption including the cooling by the cooling gas in B progresses, the dampers are operated so that the desorption step is performed in the adsorption tower 5A and the adsorption step is performed in the adsorption tower 5B. The adsorption step and the desorption step are sequentially repeated alternately. Although the opening and closing of the main damper has been described in the above description of the steps, other dampers are opened and closed as appropriate so that the above steps are performed.

2A, 2B, and 2C, the time-dependent change of the desorption gas flow in the vertically arranged adsorption towers 5A and 5B will be described. A small amount of desorbed gas at high temperature is desorbed in the desorbed gas duct 9, ducts 18 and 12 and exhaust gas duct 7A,
It is introduced into the top of the adsorption towers 5A and 5B via 7B and flows as a downward flow downward in the adsorption towers 5A and 5B. On this occasion,
Since the desorption gas is small and the differential pressure is small, it does not flow directly downward, but descends in the tower while stratifying from above (Fig. 2 (a) → Fig. 2).
(B)) The temperature inside the adsorption towers 5A, 5B is sequentially and uniformly raised to reach the ammonia desorption temperature, and then the desorbed ammonia is discharged through the lower exhaust gas ducts 8A, 8B, the duct 14 and the duct 10. In this way, by uniformly heating the adsorption towers 5A and 5B from the upper portion to the lower portion while the high-temperature desorption gas is stratified, the inside of the adsorption towers 5A and 5B is sufficiently heated by a small amount of the desorption gas. In addition, ammonia can be desorbed uniformly in a short time.

FIG. 3 illustrates the change over time in the exhaust gas temperature in the upper and lower portions of the adsorption tower during operation of the ammonia adsorption tower. Shows the case where the cooling gas flow of the present embodiment is below the adsorption tower → above (cooling gas rising method), and conversely shows the case where the cooling gas flow is above the adsorption tower → below (cooling gas descending method). The broken lines indicate the upper temperature of the adsorption tower and the lower temperature of the adsorption tower,
The one-dot chain line and the two-dot chain line are the adsorption tower upper temperature and the adsorption tower lower temperature, respectively. Ammonia is sufficiently adsorbed from the adsorption start point to end the adsorption step, and high-temperature exhaust gas is introduced from the upper part of the adsorption tower to raise the temperature of the adsorption tower for the temperature rise desorption step. At this time, the temperature rises from the upper part of the adsorption tower, and the temperature of the lower part of the adsorption tower rises with a delay. The desorption process is continued until the ammonia in the adsorption column is sufficiently desorbed (desorption lower concentration to 0 ppm), and then the inside of the adsorption column is cooled in preparation for the next adsorption process. In the cooling gas rising method, the temperature is lowered from the lower part of the adsorption tower, the whole adsorption / desorption process is completed at one cycle point of adsorption / desorption, and the next cycle is smoothly started. On the other hand, in the cooling gas descending system, the temperature is lowered from the upper part of the adsorption tower and the temperature in the tower is gradually lowered.
A temperature distribution was generated in the adsorption tower, and it took about 1.5 times as long as the time required for the cooling gas to flow through the entire tower to reach the temperature at which adsorption can be performed next time. Therefore, the adsorption / desorption cycle changes every cycle, which is not practical.

Although the exhaust gas from the gas turbine is used as the desorption gas in the above embodiment, other high temperature gas may be used.

[0022]

According to the present invention, the following effects can be obtained. (1) By making the adsorption tower a vertical type and flowing a high-temperature gas for desorption downward from the upper part of the adsorption tower, the inside of the adsorption tower is sufficiently heated even with a small amount of gas, and the gas is formed while stratifying inside the adsorption tower. Since it descends, the desorption of ammonia is uniformly performed, and the desorption of ammonia is completed in a short time. (2) By flowing the cooling gas upward from the lower portion of the vertical adsorption tower, the cooling gas rises in the tower without being biased and the cooling process can be completed in a short time. (3) Since the desorption cooling step has a margin as described above, the adsorption / desorption cycle is stable. Furthermore, the gas adsorption / desorption system can be operated in two series with the highest operation efficiency, and the system can be efficiently operated with a small amount of catalyst and a small number of adsorption towers.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a gas flow in the ammonia adsorption tower of the above embodiment.

FIG. 3 is an explanatory diagram of changes with time in the upper and lower temperatures of the adsorption tower.

FIG. 4 is an explanatory diagram of a conventional ammonia adsorption facility.

[Explanation of symbols]

1 Gas Turbine 2 Exhaust Heat Recovery Boiler 3 Ammonia Injector 4 Denitration Device 5A, 5B Adsorption Tower 6 Chimney 7A, 7B, 8A, 8B, 8C Exhaust Gas Duct 9 Desorption Gas Duct 10, 11, 12, 14, 15, 16, 17, 18 Duct 13 Cooling duct D ₁ ~ D ₁₅ Damper

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B01D 53/58 B01D 53/34 131 (72) Inventor Jun Morii No. 1 Atsunoura-cho, Nagasaki-shi Mitsubishi Heavy Industry Co., Ltd. Nagasaki Shipyard (72) Inventor Osamu Naito 1-1 1-1 Atsunoura-machi, Nagasaki City Mitsubishi Heavy Industries Ltd. Nagasaki Shipyard (72) Inventor Shigeyuki Nishijima 5-717-1, Fukahori-cho, Nagasaki City Mitsubishi Heavy Industries, Ltd. Nagasaki Institute

Claims (1)

[Claims] 1. In an ammonia adsorbing facility installed downstream of a denitration device for decomposing nitrogen oxides contained in exhaust gas with ammonia as a reducing agent, the exhaust gas containing ammonia is introduced vertically to adsorb and desorb ammonia. At least two series of adsorption towers are provided, and when the adsorption tower is regenerated, the high temperature gas for desorption is made to flow downward from the upper portion of the adsorption tower and the cooling gas is made to flow upward from the lower portion of the adsorption tower. Ammonia adsorption equipment.