JPH0558764B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an apparatus for recovering alkali from gas, and more particularly to an alkali recovery apparatus suitable for application to a low-alkali cement manufacturing apparatus.

[Prior Art] For example, when producing low-alkali cement using a cement clinker firing kiln system with a suspension preheater, in the past, as shown in FIG. 1000℃
By extracting a part of the kiln exhaust gas of about 100°C, introducing it into the spray tower 16, and spraying water on this gas to cool the gas temperature to about 100°C,
This is carried out using an alkali bypass method and device in which alkali is adsorbed using cement powder raw material as an adsorption medium, and then the powder is collected by a dust collector (bag filter) 18. In addition, in Fig. 5, the symbol 2
0 and 24 are attraction fans, and 22 is a clinker cooler.

[Problems to be Solved by the Invention] However, the above-mentioned alkaline bypass system has the following problems.

Since the temperature of the extracted kiln exhaust gas is lowered to about 100°C below the preheater exhaust gas temperature, all of the sensible heat that should originally be used to preheat the cement powder raw material is wasted.

The sensible heat of the cement powder raw material in the extracted kiln exhaust gas is discarded for the same reason as above.
In addition, since alkali is adsorbed to the cement powder raw material, the recovered cement powder raw material cannot be reused, resulting in a large loss of crushing power.

The cement raw material powder recovered by the alkali bypass method cannot be reused because it has adsorbed alkali as described above, and must be discarded, which results in wasted cement raw material powder. In addition, it is difficult to secure land for disposal within Japan.

Managing the nozzle for spraying water onto dust-containing gas in a spray tower is complicated. Further, troubles tend to occur when the cement powder raw material with moisture attached is discharged from the spray tower, which poses problems in operational management.

[Means for Solving the Problems] The apparatus for recovering alkali from gas according to the present invention includes a powder separator for separating powder from dust-containing gas and extracting the gas, and a gas separated by the powder separator. It is equipped with an alkali separation device to be introduced.

This alkali separation device includes a ventilation chamber through which gas is circulated, a casing installed in the ventilation chamber, balls loaded in the casing, and balls that are received from inside the casing and are absorbed by the balls. a rotating hollow cylinder for removing recovered alkali from the balls; a separator between the recovered alkali and the balls connected to the rotating hollow cylinder to receive the balls; and a transfer means for returning the balls from the separator to the casing. and a ball cooling means provided in the middle of the ball circulation path from the ball outlet to the ball inlet of the casing. Note that the casing has ventilation holes formed on its circumferential surface, and gas flowing through the ventilation chamber flows into the casing and comes into contact with the balls.

In addition, in the present invention, the powder separation device includes:
It is preferable to include a ceramic filter, means for injecting back-blowing air to the ceramic filter, and a heat exchanger for heating the back-blowing air.

[Function] In the present invention, dust-containing gas such as kiln exhaust gas taken out from a rotary kiln for firing cement is first separated into a gas component and a powder component in a powder separator, and this gas is introduced into an alkali separator to extract the gas. The alkali contained therein is recovered.

In the present invention, gas is introduced into the casing inside the ventilation chamber and comes into contact with the ball, and the alkali contained in the gas is cooled and condensed on the surface of the ball. The balls are introduced from the casing into a rotating hollow cylindrical body, and by rotating this cylindrical body, the balls rub against each other, and the alkali component adhering to the surface of the balls is peeled off from the balls. Next, the balls and recovered alkali are introduced into a separator, and the balls and recovered alkali are separated. The balls are returned to the casing by the transfer means and adsorb alkali again. The separated recovered alkali can be taken out as a recovered product.

If the powder separator is equipped with a ceramic filter and a means for blowing heated air toward the ceramic filter, the filter can be easily removed from clogging. Furthermore, if this back-blowing air is heated, cooling of the filter due to back-blowing is prevented.

In addition, in the present invention, compounds such as sulfites, sulfates, chlorides, nitrates, carbonates, and oxides of alkali metals such as sodium and potassium adhere to the surface of the ball. are collectively called alkalis.

[Examples] The present invention will be described in more detail below with reference to examples shown in the drawings.

FIG. 1 is a system diagram of an alkali recovery apparatus according to an embodiment in which the present invention is applied to cement firing equipment.
In FIG. 1, a suspension preheater 12 is connected to a rotary kiln 10 via a housing 14, and an induction fan 24, a chute 26 for charging raw cement powder, and a burner 28 are installed. Alkali recovery device 30 of this embodiment
is a powder separator 32 and an alkali separator 34
The powder separation device 32
Exhaust gas from the kiln 10 is introduced from the housing 14 through the duct 32a. Reference numeral 32b indicates a chute for returning the powder separated by the powder separator to the housing 14. Powder separation device 32
The gas from which the powder components have been separated is introduced into the alkali separator 34 through the duct 34a, and the alkali is separated from the gas. The gas from which the alkaline content has been separated is returned to the upper stage side of the suspension preheater 12 through the duct 34b.

FIG. 2 shows the configuration of this alkali separation device 34. Reference numeral 36 is a ventilation chamber, and a casing 38 is installed inside the ventilation chamber. The casing 38 has a cylindrical shape with a large number of openings formed on its circumferential surface, and balls 40 for alkali adsorption are loaded inside the casing 38 . The upper end of the casing 38 communicates with the outside of the ventilation chamber 36, and is connected to a ball receiving hopper 44 via an airtight feeder 42 such as a rotary valve.
are installed in succession. Similarly, the lower end of the casing 38 is connected to a rotating hollow cylindrical body 50 via an airtight feeder 46 such as a rotary valve and a chute 48.

The rotating hollow cylindrical body 50 is driven by a drive device (not shown).
It is rotated around its axis by
This is for peeling off alkaline components adhering to the ball surface as the balls introduced inside roll within the cylindrical body 50. This cylindrical body 5
A separator 52 such as a sieve for separating the balls 40 and the alkali peeled from the balls 40 is installed on the discharge side of the In the example, it is possible to transfer the material to the hopper 44 by a bucket elevator (54).

In this embodiment, the powder separator 32 is a filter-type dust collector, but this filter has heat resistance of at least 800°C or higher and stability that does not react with gas or powder components at a temperature of 800°C. Made of material. This filter preferably has a high collection efficiency of, for example, 99% or more for collecting the powder raw material, and has pores with a pressure loss of, for example, 200 mmAq or less. Specifically, porous alumina or porous silicon carbide is suitable for such a filter.

In FIGS. 1 and 2, combustion gas generated by combustion of fuel in the burner 28 burns clinker in the rotary kiln 10 and is then introduced into the suspension preheater 12 from the housing 14 to preheat the raw material powder. . A portion of the combustion gas from the kiln 10 is extracted from the housing 14 through the duct 32a and introduced into the powder separator 32, where powder components are removed. The removed powder is returned to the housing 14 by the duct 14b. Further, the gas from which the powder has been removed passes through the duct 34a to the alkali separator 3.
4 will be introduced.

In this alkali separation device 34, the duct 3
The gas from 4a is first introduced into the ventilation chamber 36,
Further, it flows into the inside of the casing 38 and comes into contact with the ball 40. The balls 40 are circulated through the casing 38, the rotating hollow cylinder 50, the separator 52, the transfer means 54, and the hopper 44, and are kept at a temperature lower than the evaporation temperature of the alkali contained in the gas. Therefore, the alkali contained in the gas condenses on the surface of this ball 40 and is separated from the gas. The gas from which the alkaline content has been separated is returned to the suspension preheater 12 from the ventilation chamber 36 via the duct 34b. On the other hand, airtight type feeder 4
2, 46 are continuously driven, and the ball 40
is continuously moved downward within the casing 38. Therefore, the balls on which the alkali content has condensed and adhered are introduced from the casing 38 into the rotating hollow cylinder 50. This rotating hollow cylindrical body 5
At zero, the balls collide and rub against each other, and the alkali adhering to the ball surfaces is peeled off. The peeled off deposits are introduced into the separator 52 together with the balls, where they are separated from the balls and collected. The ball is returned to hopper 44 as described above.

In this embodiment, the transport means 54 consisting of a bucket elevator functions as the main cooling means for the balls 40. That is, the balls 40 discharged from the separator 52 are cooled while being transferred by the transfer means 54. Of course, shoot 48,
Although the ball 40 is also cooled in the rotating hollow cylinder 50, the separator 52, the hopper 44, etc., cooling is mainly performed in the bucket elevator 54 exposed to the atmosphere.

In this embodiment, a solvent supply device 56 may be connected to the chute 48. In this case, the alkali adhering to the surface of the ball 40 is dissolved in the solvent in the rotating hollow cylinder 50 and the separator 5
2 is recovered as a solution. Further, in this case, the ball 40 is efficiently cooled with liquid by contacting the solvent. That is, in this case, the chute 48,
The rotating hollow cylinder 50 and the solvent supply device 56 function as the main cooling means for the ball 40. In addition,
Water and dilute acids are suitable as this solvent.

As mentioned above, the powder separator 32 has a filter therein, but as the operating time elapses, powder accumulates on the filter and the pressure loss increases. Therefore, it is necessary to periodically remove this powder from the filter. This filter is usually made of porous ceramics, but when removing adhering powder from such a ceramic filter, it is undesirable to apply blows or vibrations to shake it off, so filtration is not recommended. It is preferred to blow air in the opposite direction. It is desirable to use high-temperature, clean air for this back-blowing, since it does not contain powder and the filter temperature does not drop below the alkali condensation temperature. Such high-temperature, clean back-blowing air is preferably heated by a heat exchanger installed in the housing, preheater, or alkali recovery device.

FIG. 3 is an overall system diagram showing the configuration when a heat exchanger 58 is provided in the alkali recovery device. Specifically, this heat exchanger 58 is preferably provided downstream of the casing 38 of the ventilation chamber 37. The air heated by the heat exchanger 58 is transferred to the duct 58
The powder is introduced into the powder separator 32 via the filter a, and the filter can be back-blown. The rest of the structure in FIG. 3 is the same as in FIG. 1, and the same members are given the same reference numerals.

FIG. 4 is a schematic side view showing an example of the configuration of the heat exchanger 58. The heat exchanger 58 includes a drum 60 installed in the ventilation chamber 36 and a compressor 62 for supplying air to the drum 60. The air passed through the drum 6
0 The structure allows the temperature to rise rapidly by receiving heat from external gas. Of course, various other types of heat exchangers can be used.

In each of the above-mentioned embodiments and the embodiment shown in FIG. 7 described later, gas is transferred to the powder separator 32 and the alkali separator 30 by the pressure difference between the housing 14 and the upper stage of the suspension preheater 12.
A special gas blowing fan for alkali separation is not installed. However, in the present invention, as shown in FIG. 6, a fan 79 may be provided in the middle of the duct 34b to forcefully circulate the alkali recovery gas.

FIG. 7 is an overall configuration diagram showing an embodiment in which the powder separation device 32 is provided integrally with the housing 14.
FIG. 8 is a longitudinal cross-sectional view showing the structure of the powder separation device 32 provided integrally with the housing 14. As shown in FIG. Reference numeral 80 is the casing of the powder separator, and the opening 14 provided in the side of the housing 14
It is installed so as to communicate with the inside of the housing 14 via a. A cylindrical filter 82 is inserted into the housing 80 from its upper surface, and the inside of the filter 82 communicates with a gas extraction chamber 84 . This extraction chamber 84 is communicated with the alkali recovery device 34 via the duct 34a.
A nozzle 86 is installed facing the upper opening of the cylindrical filter 82 to blow out clean air for reverse blowing. By being ejected into the filter 82, the powder adhering to the filter 82 is brushed off.

FIG. 9 shows still another embodiment of the present invention, and shows the entire embodiment in which the gas from which the alkali content has been removed in the alkali recovery device is used as the primary air or secondary air of the boiler 92. FIG. 2 is a system diagram showing the configuration. In the embodiment shown in FIG. 9, the powder separation device 32 is provided integrally with the housing 14, but the powder separation device 32 may be provided separately from the housing as in the embodiments shown in FIGS. 1, 3, etc. is clear.

In the embodiments shown in FIGS. 6, 7, and 9, other configurations are the same as in FIG. 1, so the same members are given the same reference numerals and their explanations will be omitted.

All of the above embodiments relate to embodiments in which the device of the present invention is applied to a cement manufacturing device.
The alkali recovery device of the present invention can recover alkali from various other gases, for example, for producing high-value products such as potassium from the exhaust gas of a furnace that burns materials containing a large amount of alkali such as clay. It can also be applied as a device.

[Effects of the Invention] As is clear from the above examples, the alkali recovery device of the present invention can perform alkali recovery without significantly lowering the gas temperature, and there is extremely little wastage of thermal energy held by the gas stove. . Further, there is no need to use product raw material powder (for example, cement powder) for alkali recovery, and the recovery cost is low. Also, no unnecessary waste is generated. In addition, the apparatus of the present invention does not require complicated equipment for operation management such as a spray tower, can be operated continuously with simple maintenance management, and is extremely easy to operate.

[Brief explanation of the drawing]

1, 3, 6, 7, and 9 are overall configuration diagrams of a cement manufacturing apparatus incorporating an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of an alkali separation apparatus. FIG. 4 is a side view showing an air heating device for reverse blowing, FIG. 5 is a system diagram showing a conventional example, and FIG. 8 is a longitudinal sectional view of a powder separation device used in a different embodiment. 10... Rotary kiln, 12... Suspension preheater, 32... Powder separation device, 34
...Alkali separation device, 38...Casing, 4
0...ball, 50...rotating hollow cylinder, 54...
...bucket elevator (transportation means).

Claims (1)

[Scope of Claims] 1. A method for separating alkali from a gas, which has a powder separator that separates powder from a dust-containing gas and extracts the gas, and an alkali separator into which the gas from which the powder has been separated by the powder separator is introduced. In the recovery device, the alkali separation device includes: a ventilation chamber through which gas is passed; a casing provided within the ventilation chamber, in which balls for alkali adsorption are loaded; and a peripheral surface of the casing. a ventilation hole opened in the casing, a ball introduction port provided in the upper part of the casing, a ball discharge port provided in the lower part of the casing, and a rotating hollow cylindrical body connected to the ball discharge port so as to be able to receive the balls. a recovered alkali-ball separator connected to the rotating hollow cylindrical body so as to be able to receive the balls; a transfer means for transferring the balls from the separator to the ball input port of the casing; and a ball discharger of the casing. A device for recovering alkali from gas, comprising: a ball cooling means provided in the middle of a ball circulation path from an outlet to a ball inlet. 2. In an apparatus for recovering alkali from gas, which has a powder separator that separates powder from dust-containing gas to extract the gas, and an alkali separator into which the gas from which the powder has been separated by the powder separator is introduced. The separation device includes a ventilation chamber through which the gas passes, a casing provided within the ventilation chamber in which balls for alkali adsorption are loaded, and ventilation holes provided on the circumference of the casing. , a ball inlet provided at the top of the casing and a ball discharge port provided at the bottom of the casing; a rotating hollow cylindrical body connected to the ball discharge port so as to be able to receive balls; and the rotating hollow cylinder. a separator between recovered alkali and the balls connected to the body so as to be able to receive the balls; a transfer means for transferring the balls from the separator to the ball input port of the casing; and a transfer means for transferring the balls from the ball discharge port of the casing to the ball introduction port. a ball cooling means provided in the middle of the ball circulation path; a heat exchanger for heating the air; and an alkali recovery device from gas. 3. The gas alkali recovery apparatus according to claim 2, wherein the heat exchanger uses the dust-containing gas or the gas after alkali separation as a heat source fluid.