JP2001179042A - Intermittent operation method for exhaust gas treatment facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermittent operation method for an exhaust gas treatment facility capable of treating suitably an exhaust gas in a simply constituted exhaust gas treatment facility. SOLUTION: In each operation time of intermittent operation, when the operation is started, after raising the temperatures of a desorption and regeneration tower to specific temperatures, transfer of a carbonaceous adsorbent from an adsorption tower to a desorption and regeneration tower is started. When the operation is stopped, transfer of the carbonaceous adsorbent to the desorption and regeneration tower and transfer of the carbonaceous adsorbent in the desorption and regeneration tower are stopped. Thereafter, the desorption and regeneration tower is continuously heated at a specific temperature or higher for at least a specific time. After completing the desorption and regeneration of the carbonaceous adsorbent, operation of the exhaust gas treatment facility is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation method of an exhaust gas treatment apparatus, and more particularly to an intermittent operation method of an exhaust gas treatment apparatus which can be suitably applied to an exhaust gas treatment apparatus which is not a continuous operation type.

[0002]

2. Description of the Related Art As a method for removing harmful substances from exhaust gas, there is known a method for removing harmful substances by using a moving bed type adsorption tower filled with a carbonaceous adsorbent such as activated carbon. Then, by heating the carbonaceous adsorbent that has adsorbed the harmful substance, the harmful substance is desorbed from the carbonaceous adsorbent.
Decomposed and regenerated carbonaceous adsorbents are reused.

[0003] When desorption / regeneration is performed by heating with the carbonaceous adsorbent fixed and filled, a bridging phenomenon occurs in which the particles of the carbonaceous adsorbent are welded to each other in the heating step of the carbonaceous adsorbent. It is known that desorption / regeneration becomes difficult. For this reason, in desorption / regeneration, a moving bed type desorption / regeneration tower that heats while moving a carbonaceous adsorbent is generally used.

[0004]

In small-scale refuse treatment facilities and the like, intermittent operation is performed in which incineration facilities are not operated continuously but are operated only during the daytime. When treating exhaust gas from such an incineration facility, the exhaust gas treatment device also needs to perform intermittent operation. FIG. 3 is a schematic diagram showing a configuration of a general exhaust gas treatment device for intermittent operation.

As shown in FIG. 3, in an exhaust gas treatment apparatus used for intermittent operation, a service tank 50 and a service tank 50 are provided in the adsorption tower 10 and the desorption / regeneration tower 20, respectively, on the downstream side in the flow direction of the carbonaceous adsorbent. 51 are provided. Then, both the adsorption tower 10 and the desorption / regeneration tower 20 are operated in a moving bed system, and the entire processed amount is stored in the service tanks 50 and 51 until the next operation. By doing so, there has been adopted a method of avoiding the temperature rise in the state of fixed filling and preventing the above-mentioned bridging phenomenon. Since this method requires a service tank, there is a disadvantage that the apparatus itself becomes large.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an intermittent operation method of an exhaust gas treatment apparatus capable of performing preferable exhaust gas treatment with an exhaust gas treatment apparatus having a simple configuration.

[0007]

In order to solve the above-mentioned problems, an operation method of an exhaust gas treatment apparatus according to the present invention comprises the steps of: bringing a charged carbonaceous adsorbent into contact with an exhaust gas to be treated while moving the carbonaceous adsorbent; A moving bed type adsorption tower that adsorbs and removes harmful substances, and a moving bed type that desorbs and regenerates by heating the carbonaceous adsorbent after removal of harmful substances taken out of the adsorption tower in an inert gas atmosphere In an intermittent operation method of an exhaust gas treatment device including a desorption / regeneration tower and a circulating means for circulating a carbonaceous adsorbent between the adsorption tower and the desorption / regeneration tower, (1) at the start of operation, After the temperature of the regeneration tower is raised to a predetermined temperature, the transfer of the carbonaceous adsorbent from the adsorption tower to the desorption / regeneration tower is started.
After stopping the transfer of the carbonaceous adsorbent to the regeneration tower and the movement of the carbonaceous adsorbent in the desorption / regeneration tower, the desorption / regeneration tower is continuously heated at a predetermined temperature or higher for a predetermined time or longer to adsorb the carbonaceous substance. The operation of the exhaust gas treatment device is stopped after the desorption / regeneration of the agent is completed.

According to the present invention, after the transfer of the carbonaceous adsorbent to the desorption / regeneration tower is stopped, the movement of the carbonaceous adsorbent present in the desorption / regeneration tower in the tower is stopped. The desorption / regeneration is completed by the fixed layer method. At this time, since the carbonaceous adsorbent present in the desorption / regeneration tower has already been heated to a predetermined temperature or higher, the occurrence of the bridging phenomenon that occurs in the above-described temperature raising step is avoided. By stopping the operation of the entire plant after the completion of the desorption / regeneration, the adsorption tower and the desorption / regeneration tower also have the function of the service tank, and a large service tank is not required.

At the start of operation, the temperature of the desorption / regeneration tower is raised to a predetermined temperature, and then the transfer of the carbonaceous adsorbent to the desorption / regeneration tower is restarted. This heating is performed in a fixed bed state in which the carbonaceous adsorbent in the desorption / regeneration tower is not moved, but the above-mentioned bridging phenomenon is a phenomenon seen when an adsorbate is present in the carbonaceous adsorbent, In the present invention, since the desorption of the adsorbate has been completed at the time of the previous operation stop, the occurrence of the bridge phenomenon at this stage is also avoided. Furthermore, mixing of undecomposed dioxins in the desorbed gas at this heating stage is also avoided.

The predetermined temperature is preferably 350 ° C. or more, and the predetermined time is preferably one hour or more. By heating the carbonaceous adsorbent at a temperature of 350 ° C. or more for one hour or more, the dioxins adsorbed on the carbonaceous adsorbent are efficiently decomposed.

[0011]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an exhaust gas treatment apparatus to which the intermittent operation system according to the present invention can be suitably applied.

This exhaust gas treatment apparatus has an adsorption tower 10 in which activated carbon is filled, and a desorption / regeneration tower 20 for regenerating activated carbon after adsorbing harmful substances by heat treatment.
Both are connected by conveying devices 31 and 32 including a belt conveyor or the like for circulating activated carbon between them.

The adsorption tower 10 forms a moving bed by moving the activated carbon vertically downward, and brings the activated carbon in the moving bed into contact with the exhaust gas introduced in the horizontal direction, thereby converting harmful substances in the exhaust gas into the activated carbon. This is a cross-flow type adsorption tower that treats exhaust gas by adsorption. Exhaust gas inlet 11 and Exhaust gas outlet 14
The screens 12 and 13 are disposed between the screens 12 and 13 to prevent the activated carbon filled between the screens 12 and 13 from scattering. Valves 15 and 17 for adjusting the amount of activated carbon introduced and withdrawn into the adsorption tower 10 are provided at the top and bottom of the adsorption tower 10, respectively. A plurality of roll feeders 16 are provided in the tower. Are located.

The desorption / regeneration tower 20 moves the adsorbed activated carbon vertically downward to form a moving bed, and performs desorption / regeneration by heating the activated carbon in the moving bed in an inert gas. . The desorption / regeneration tower 20 is, from top to bottom, 20a to 20a.
The pipes 21a to 21c are divided into six regions f and transfer the introduced activated carbon between the regions.

A seal valve 22 is provided above the region 20a.
Are arranged, and are connected to the region 20b by a pipe 21a. The region 20b is provided with an inlet 24 for introducing an inert gas, and the region 20d is provided with an outlet 25 for discharging a desorbed gas. Both are pipe 2
1b. In an area 20c between the two areas 20b and 20d, an inlet 26 and an outlet 27 for introducing and discharging hot air are disposed at a lower portion and an upper portion, respectively, and a region surrounding the pipe 21b extends around the pipe 21b. Partitioned to circulate hot air. A hot air circulation path is connected to the outside of the inlet 26 and the outlet 27, and a blower 40 and a hot stove 41 are arranged on the path. The region 20d is further connected to the region 20f by a pipe 21c. In an area 20e existing between the two areas 20d and 20f, an inlet 28 and an outlet 29 for the cooling water are provided, respectively. On the other hand, a seal valve 23 is disposed at the lower end of the region 20f.

A screen 33 for sieving the regenerated activated carbon is disposed between the desorption / regeneration tower 20 and the transport device 32 for returning the activated carbon to the adsorption tower 10.

Next, the operation of the present apparatus when the intermittent operation method according to the present invention is performed will be described. FIG. 2 is a timing chart illustrating the intermittent operation method according to the present invention. Here, the incinerator is operated from 8:00 to 14:00 every day,
An example in which the intermittent operation for terminating the operation of the whole plant is sometimes repeated will be described as an example. Then, in order to make it easier to understand the features of the intermittent operation method according to the present invention, the description will be made not from the time when the device restarts operation (8:00) but from the time when the entire plant is in operation (after 8:30).

At this time, valves 15 to 17,
Reference numerals 22 and 23 are set to an open state, and the opening degree is adjusted to adjust the moving speed of the activated carbon in each of the adsorption tower 10 and the desorption / regeneration tower 20.

Exhaust gas introduced from the exhaust gas inlet 11 into the adsorption tower 10 comes into contact with activated carbon moving vertically downward between the screens 12 and 13, and harmful substances such as dioxins contained therein are adsorbed on the activated carbon surface. Is removed. The exhaust gas thus purified is discharged from the exhaust gas outlet 14.

On the other hand, the activated carbon to which the harmful substances have been adsorbed is sent to the transfer device 31 via the roll feeder 16 and the valve 17 and transferred to the desorption / regeneration tower 31. At this time, A
It is preferable to supply activated carbon by the line indicated by.

The activated carbon introduced into the desorption / regeneration tower 20 via the valve 22 is sent from the area 20a to the area 20b via the pipe 21a, where the inert gas introduced from the introduction port 24 is introduced. For example, it is mixed with nitrogen gas and sent to the region 20d via the pipe 21b. And
When passing through the region 20c, the pipe 2 introduced through the inlet 26 through the blower 40 and the hot stove 41
Heated by hot air circulating outside 1b. As a result, the adsorbed harmful substances are desorbed and decomposed, and the activated carbon is regenerated. The generated desorbed gas is discharged from the discharge port 25 and is separately processed. On the other hand, the hot air whose temperature has decreased by heating the activated carbon is discharged from the outlet 27, sent to the hot blast stove 41 by the blower 40, heated again, and circulated and reused.

Here, in the area 20c, see JP-A-5-301.
No. 322, as disclosed in Japanese Patent Publication No. 022
By adjusting the moving speed of the activated carbon, the temperature and the flow rate of the hot air so that the activated carbon stays for one hour or more, the harmful components adsorbed by the activated carbon can be efficiently removed and decomposed.

The activated carbon that has reached the region 20d further passes through the region 20e via the pipe 21c, and then enters the region 20f.
And discharged from the valve 23 to the outside of the desorption / regeneration tower 20. When passing through the region 20e, the activated carbon is introduced through the inlet 28 and cooled by cooling water circulating outside the pipe 21c. The cooling water is discharged from the discharge port 29.

The activated carbon discharged from the desorption / regeneration tower 20 is sieved by a screen 33, and the deteriorated powdery components are separated into a line indicated by B in the figure and returned to, for example, an incinerator to be processed. You. On the other hand, the regenerated activated carbon having a large particle size is separated into a line indicated by C in the figure, returned to the adsorption tower 15 by the transport device 32, and circulated.

Next, the operation before the plant stops will be described. Before stopping the incinerator, here, at 14:00, the transfer of the activated carbon to the desorption / regeneration tower 20 is stopped, and then the movement of the activated carbon in the desorption / regeneration tower 20 is stopped. In this state, the activated carbon is heated and regenerated in a state where the movement of the activated carbon is stopped, that is, in a fixed bed state. Since the transfer of the activated carbon is stopped after the temperature of the activated carbon in the tower is raised, the above-mentioned bridging phenomenon does not occur.

On the other hand, the transfer of the activated carbon in the adsorption tower 10 is continued until 14:00 when the operation of the incinerator is stopped. This makes it possible to reliably treat the exhaust gas generated in the incinerator in the adsorption tower 10.

The heating in the desorption / regeneration tower 20 is continued for about 2 hours after stopping the transfer of the activated carbon. After stopping the transfer of the activated carbon by closing the valve 23, it is preferable that the top of the activated carbon in the tower descends to the region 20c. This is because all the activated carbon in the tower can be heated. And, even in the fixed layer state, 1
By performing the heat treatment for more than an hour, the harmful components adsorbed by the activated carbon can be efficiently removed and decomposed. After almost completely removing the harmful components, the desorption / regeneration tower 20
Is stopped, and the operation of the plant is terminated (at 16:00).

On the next day, the operation of the incinerator at 8:00 and the adsorption tower 1
Injection of the exhaust gas to zero and transfer of the activated carbon in the adsorption tower 10 are started. At this point, the roll feeder 1 of the adsorption tower 10
The activated carbon discharged from 6 passes through the valve 17, is conveyed by the conveyor 31, is supplied from the valve 22 to the desorption / regeneration tower 20, and is stored in the space 20 a. Then, the supply of hot air from the blower 40 and the hot blast stove 41 to the region 20c of the desorption / regeneration tower 20 is started to raise the temperature of the activated carbon inside. Since the harmful components of the filled activated carbon have been almost completely removed by the desorption / regeneration treatment on the previous day, the above-mentioned bridging phenomenon does not occur. Further, since no desorbed gas is generated at the time of this temperature rise, the inlet 24 and the outlet 2
If the operation is performed in a closed state with 5 closed, heat does not escape to the outside, and the temperature can be raised in a short time.

When the heating area 20c reaches a temperature sufficient for the regeneration of the activated carbon by heating for 30 minutes, the valve 23 is opened and the roll feeder 23a is operated to operate the desorption / regeneration tower 2c.
The transfer of the activated carbon to zero and the transfer of the activated carbon in the tower are started.
Thereafter, the operation returns to the normal operation described above.

By adopting such an operation system, there is no need to provide a large service tank as in the prior art, and the apparatus can be made compact and the equipment cost can be reduced.

In the above description, the embodiment using activated carbon as an adsorbent has been described. However, the adsorbent is not limited to activated carbon, and after adding a binder to a carbon-containing substance such as coal and forming, a heat treatment is performed. Alternatively, activated carbon, activated coke, activated char obtained by activation with steam, air, or the like, or a carbonaceous adsorbent obtained by supporting a compound such as vanadium, iron, or copper on these can be suitably used.

At the time of heating and regeneration in the desorption / regeneration tower,
It is preferable to add an alkali component such as urea and ammonia since the decomposition efficiency of dioxins can be further increased. Here, the parallel flow type apparatus in which the inert gas and the carbonaceous adsorbent flow in the same direction in the desorption / regeneration tower has been described as an example, but the inert gas and the carbonaceous adsorbent flow in the opposite directions. -Flow type, which flows into and comes into contact with each other,
Even in the case of a regeneration tower, the intermittent operation method according to the present invention can be suitably applied.

[0033]

The intermittent operation method of the exhaust gas treatment apparatus according to the present invention completes the desorption / regeneration of the carbonaceous adsorbent in the desorption / regeneration tower in a fixed bed system before the end of each intermittent operation. Therefore, there is no possibility that a bridge phenomenon occurs when the temperature of the carbonaceous adsorbent in the desorption / regeneration tower is raised at the start of the next operation, and a service tank is not required, and the apparatus can be compact.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of an apparatus to which an intermittent operation method of an exhaust gas treatment apparatus according to the present invention is applied.

FIG. 2 is a time chart illustrating an intermittent operation method of the exhaust gas treatment apparatus according to the present invention.

FIG. 3 is an overall schematic view showing a conventional exhaust gas treatment device for intermittent operation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Adsorption tower, 20 ... Desorption / regeneration tower, 31 and 32 ... Circulation means, 40 ... Blower, 41 ... Hot-blast furnace, 50, 51 ... Service tank.

Claims (2)

[Claims] 1. A moving bed type adsorption tower for adsorbing and removing harmful substances in exhaust gas by bringing a filled carbonaceous adsorbent into contact with an exhaust gas to be treated while moving, and adsorbing harmful substances taken out of the adsorption tower. A moving bed type desorption / regeneration tower for desorption / regeneration by heating the carbonaceous adsorbent afterwards in an inert gas atmosphere, and carbonaceous adsorption between the adsorption tower and the desorption / regeneration tower Intermittently operating the exhaust gas treatment device comprising a circulating means for circulating the agent, wherein at the start of operation, after the desorption / regeneration tower is heated to a predetermined temperature, The transfer of the adsorbent is started, and when the operation is stopped, the transfer of the carbonaceous adsorbent to the desorption / regeneration tower and the movement of the carbonaceous adsorbent in the desorption / regeneration tower are stopped, and then the desorption is performed.・ Continue heating the regeneration tower at a specified temperature or more for a specified time Said must complete the desorption-regeneration of the carbonaceous adsorbent stops the operation of the exhaust gas treatment apparatus, intermittent operation method of the exhaust gas treatment apparatus characterized by Te. 2. The method according to claim 1, wherein the predetermined temperature is 350 ° C. or more, and the predetermined time is one hour or more.