JP3029936B2 - Ammonia adsorption equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ammonia adsorbing apparatus installed downstream of a gas flow of a denitration apparatus using ammonia as a reducing agent.

[0002]

2. Description of the Related Art FIG. 4 shows a system diagram of a conventional denitration apparatus provided with ammonia adsorption equipment, and the prior art will be described. Exhaust gas generated from the gas turbine 1 is introduced into the exhaust heat recovery boiler 2 from a flue, mixed with ammonia injected by an ammonia injection device 3 provided inside, and NOx is removed by a denitration device 4 provided downstream. Decomposes into harmless nitrogen and moisture. The exhaust gas is then passed from the exhaust gas duct 7 to the adsorption towers A and B.
After being introduced into one of the adsorption towers 5 and adsorbing residual ammonia, the residual ammonia is discharged from the exhaust gas duct 8 through the chimney 6 to the atmosphere. Although the inside of the adsorption tower 5 is filled with an ammonia adsorbent, it does not adsorb after adsorbing a certain amount or more of ammonia. The dampers before and after the adsorption tower 5 are closed, high-temperature gas is introduced into the adsorption tower 5 from the desorption gas duct 9 to desorb ammonia, and is returned to the exhaust heat recovery boiler 2 again from the desorption gas duct 10. In FIG. 4, when one of the adsorption towers A of the adsorption towers 5 is in the adsorption step, the adsorption tower B is in the desorption step. The conventional apparatus shown in FIG. 4 is a dry type denitration apparatus using ammonia as a reducing agent, in which residual ammonia not denitrated is adsorbed and the desorbed gas is recycled as denitration ammonia.

[0003]

When the ammonia adsorption equipment is of the horizontal flow type, the distribution of ammonia adsorbed on the adsorption tower is biased. To desorb ammonia, 1
Although a / 50 amount of gas was flowing in the same direction as that for adsorption for increasing the temperature, the flow was disturbed due to the small amount of gas, and the ammonia distribution was uneven, resulting in a variation in temperature rise. As a result, the ammonia adsorbed by the adsorbent could not be sufficiently desorbed within the heating / desorption time, and the next adsorption capacity decreased. Accordingly, the review of the adsorption / desorption time schedule, the number of adsorption towers, and the control of the adsorption / desorption cycle were complicated.
In addition, since the gas flow direction at the time of adsorption and the gas flow direction at the time of desorption are the same, all of the adsorbed ammonia passes through the adsorbent, so that the desorption time is long. In addition, it is difficult to regenerate the adsorbent and recover the ammonia, and it is not possible to determine the amount of the recycle. Therefore, the control of the amount of ammonia injected into the denitration apparatus has not been successful.

The present invention has been made in view of the above-mentioned state of the art, and aims to provide an ammonia adsorption apparatus free from the problems as in the conventional method.

[0005]

SUMMARY OF THE INVENTION The present invention relates to an ammonia adsorbing facility installed downstream of a denitration apparatus using nitrogen oxides contained in exhaust gas as a reducing agent for reducing the flow of exhaust gas during ammonia adsorption. At least two lines of ammonia adsorption towers equipped with ducts and dampers are provided so that the upward flow and the high-temperature gas flow at the time of ammonia desorption become a downward flow, and the ammonia-containing gas discharged at the time of desorption is placed upstream of the denitration device. Ammonia adsorption equipment, characterized in that a desorption gas duct is provided to lead to the ammonia adsorption equipment.

[0006]

When the ammonia is flowed at a constant temperature during the adsorption time, the concentration distribution of the adsorbed ammonia increases near the inlet of the adsorbent and decreases toward the outlet. In order to prevent re-adsorption of ammonia in the adsorbent at the time of desorption and to efficiently desorb ammonia within the desorption time, the gas flow at the time of adsorption and desorption is reversed so that the next adsorption capacity can be secured. In addition, a 1/50 volume of exhaust gas is passed as a gas for heating and desorption, but in the conventional method, the flow was disturbed due to a small differential pressure. When the gas for adsorption was set to the upward flow, the adsorption / desorption cycle was smoothed and the control was simplified.

[0007]

FIG. 1 shows an embodiment of the present invention.
In FIG. 1, 1 is a gas turbine, 2 is an exhaust heat recovery boiler, 3 is an ammonia injection device, 4 is a denitration device, 5 is an ammonia adsorption tower indicated by adsorption towers A and B, 6 is a chimney, 7,
8 is an exhaust gas duct, 11, 12, 13, 14, 16, 1
7, 18, 19 are dampers, 15 is a desorption gas duct, 20
Is a desorption gas duct.

Exhaust gas containing ammonia excessively injected by the ammonia injection device 3 in FIG. 1 is pushed into the ammonia adsorption tower A5 on the downstream side of the denitration device 4 as an upward flow with the dampers 11, 12 opened. After the adsorption tower A5 has sufficiently adsorbed ammonia, the dampers 11 and 12 are closed, and the dampers 13 and
14 is opened to switch the adsorption operation to the adsorption tower B5. The temperature of the adsorption tower A5 that has sufficiently adsorbed ammonia is raised, and the desorbed gas is allowed to flow downward from above via the desorption gas / desorption gas duct 20 and the damper 18, and the damper 16 is opened to return the desorbed ammonia to the upstream side of the denitration device 4.

The operation of FIG. 1 will be described more specifically. Exhaust gas containing NOx at a high temperature generated in the gas turbine 1 is introduced into an exhaust heat recovery boiler 2 provided in the downstream, and is subjected to heat exchange in a heat exchanger (not shown) to have a low temperature. Since the exhaust heat recovery boiler 2 is provided with an ammonia injection device 3 and a denitration device 4 downstream thereof, the ammonia injected by the ammonia injection device 3 is mixed with the exhaust gas to be discharged by the downstream denitration device 4. NOx is broken down into harmless nitrogen and moisture. At this time, the injection amount of ammonia is N
Injection in excess of the amount that reacts with Ox increases the denitration rate, so that residual ammonia not subjected to the reaction remains in the exhaust gas.

The exhaust gas containing ammonia is arranged in a vertical flow from an exhaust gas duct 7 and sent to one of two adsorption towers 5 comprising ammonia adsorption towers A and B arranged in parallel, and the ammonia is adsorbed by the adsorbent. Then, the gas is discharged from the exhaust gas duct 8 through the chimney 6 to the atmosphere. The upper exhaust gas duct 8 of the above-mentioned adsorption tower 5 is provided with dampers 12 and 14, and the lower exhaust gas duct 7 is provided with dampers 11 and 13, and both the adsorption towers A and B adsorb ammonia. At this time, these dampers are fully opened, and when one adsorption tower A is in the adsorption step and the other adsorption tower B is in the desorption step, the dampers 11 and 12 are opened and the dampers 13 and 14 are closed. It is configured.

A desorption gas duct 20 is connected to the exhaust gas duct 8 above the adsorption tower 5, and dampers 18 and 19 are provided at their inlets. A desorption gas duct 15 is connected to the lower exhaust gas duct 7, one of which is connected to the exhaust gas boiler 2 on the upstream side of the denitration device 4, and dampers 16 and 17 are provided at their outlets. I have.

A high-temperature, ammonia-free gas is introduced into the desorption gas duct 20 by using high-temperature exhaust gas extracted from a section downstream of the gas turbine 1 and up to the ammonia injection device 3 of the exhaust gas boiler 2. Or a different system of gas may be used.

2 (a), 2 (b) and 2 (c), the change over time of the flow of the desorbed gas in the adsorption tower 5 will be described. At a high temperature, a small amount of desorbed gas is introduced from the desorbed gas duct 20 connected to the upper side of the adsorption tower 5, but since the amount is small, the gas does not directly flow downward but stays at the upper side and fills up. ((A) → (b)) After the entirety of the adsorption tower 5 is filled with the high-temperature gas, the gas is discharged from the lower desorption gas duct 15. (C)

At this time, the adsorbed ammonia is desorbed and discharged at the same time as the desorbed gas. However, since the desorbed gas to the adsorption tower 5 is filled from the upper part, the temperature rise of the adsorbent and the desorption of ammonia are slightly increased. FIG. 3 shows that the desorption is completed in a short time because it takes time, but the entire adsorbent is desorbed because it is completely filled and flows out. FIG. 3 is a table showing the relationship between desorbed ammonia and the time taken to start and end the desorption of ammonia from the start of temperature rise. The case in the opposite direction is shown.

[0015]

According to the present invention, the following effects can be obtained. The concentration distribution of adsorbed ammonia is indicated by the adsorption inlet (desorption outlet)
When the temperature rises, the temperature rises from the lower concentration distribution and ammonia is desorbed.The ammonia concentration distribution is high at the desorption outlet, and the desorbed ammonia does not re-adsorb to the adsorbent. -Although it takes time until the start of desorption, ammonia can be completely desorbed from the adsorbent in a short time, so that the adsorbent can be sufficiently cooled for the next adsorption. The remaining NH ₃ in the adsorbent is less than 1%, the next adsorption capacity is sufficiently secured, the desorption system can be controlled in a long time, the time schedule is simple, a small amount of catalyst and a small amount of adsorption tower are sufficient Can operate.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a gas flow in an ammonia adsorption tower at the time of desorption according to the present invention.

FIG. 3 is a chart showing the relationship between the time required to start and end ammonia desorption from the start of temperature rise and desorbed ammonia.

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

Continued on the front page (72) Inventor Toshihiko Imamoto 1-1, Akunoura-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (72) Inventor Osamu Naito 1-1, Akunoura-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries Inside Nagasaki Shipyard Co., Ltd. (72) Akira Serizawa, Inventor 1-1 1-1 Akunouramachi, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard Co., Ltd. (56) References JP-A-4-281819 (JP, A) JP-A-4 -250822 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 53/58 B01D 53/34 B01D 53/56

Claims (1)

(57) [Claims] 1. An ammonia adsorbing facility installed downstream of a denitration apparatus using nitrogen oxides contained in exhaust gas as a reducing agent with ammonia as a reducing agent. At least two lines of ammonia adsorption towers provided with a duct and a damper are provided so that the hot gas flow becomes a downward flow, and a desorption gas duct is provided to guide the ammonia-containing gas discharged at the time of desorption to the upstream side of the denitration device. Ammonia adsorption equipment, characterized in that: