JP2546092Y2 - Lime firing kiln exhaust 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 device for treating lime-fired kiln exhaust gas, and more particularly, to a lime-fired kiln used in producing light calcium carbonate using exhaust gas from a lime-fired kiln of a pulp manufacturing plant. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for treating exhaust gas from a kiln, which is capable of improving the heat exchange efficiency of a heat exchanger without fixing dust in the exhaust gas.

[0002]

2. Description of the Related Art Calcium carbonate is widely used as a white filler such as pigments and paints, and a filler for composite plastics. In particular, recently, neutral paper is increasingly produced using calcium carbonate instead of talc, which has been used as a filler for papermaking.

Conventionally, calcium carbonate used as a filler for neutral paper has been heavy calcium carbonate. However, light calcium carbonate has been increasingly used because of the large wear of paper machine wires, especially plastic wires. I have. This light calcium carbonate is generally spindle-shaped, columnar,
Cubic particles and the like are known, and various particle sizes are obtained by changing the reaction conditions.

[0004] A typical industrial production method of this light calcium carbonate is to bubble the carbon dioxide gas by bubbling the suspension with carbon dioxide gas from a nozzle or a straight pipe or the like from the bottom of the carbonation reaction tank. While floating, it is brought into contact with calcium hydroxide in the suspension to cause a reaction.

Conventionally, when producing light calcium carbonate
Is a lime-fired kiln (hereinafter referred to as a gas containing carbon dioxide)
Exhaust gas from lime kiln) is used, but the exhaust gas from this lime kiln is sent to a scrubber by a blower, primary cooling and dust removal are performed, then sent to a packed tower, and further finely mist filtered. , And then sent to a carbonation reactor through a secondary cooler via a blower.

[0006]

Conventionally, the light calcium carbonate production system has been provided with various facilities for removing dust contained in the kiln exhaust gas. Many. First, since dust adheres to a blower that sends exhaust gas to a carbonation reaction tank, a positive displacement blower having a small clearance, such as a roots blower, having a narrow clearance cannot be used, and power consumption is large.

Second, the mist filter for removing fine dust is frequently clogged and has a large pressure loss, which is not only against power saving but also causes operational problems.

Third, a heat exchanger for cooling the exhaust gas is used. When a heat exchanger of a shell-and-tube type is used for the heat exchanger, the heat exchanger is contained in the exhaust gas. It is necessary to pass dust and dust through a cleanable tube to remove the dust, which inevitably results in poor thermal efficiency and an overall heat transfer coefficient of 10 to 50 Kcal / m ² · hr.
There was a disadvantage that the temperature was as low as ° C.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a processing apparatus which solves the above-mentioned drawbacks of the prior art, reduces the adhesion of dust in exhaust gas, and improves the heat efficiency of a heat exchanger.

[0010]

SUMMARY OF THE INVENTION The present invention provides a lime burning killer.
Equipment for producing light calcium carbonate using
The lime-fired kiln kiln flue gas treatment system consists of a combination of a wet scrubber and a shell and tube heat exchanger, and the exhaust gas treated by the wet scrubber is converted to a shell and tube heat exchanger. And the cooling medium is conducted through a number of tubes inside the shell-and-tube heat exchanger.

[0011]

[Action] The lime kiln exhaust gas has a carbon dioxide gas concentration of about 19.6%
From about 210 ° C. to about 60 ° C. with a wet scrubber.
Primary cooling to ° C. and removal of dust contained in the exhaust gas (when discharging the exhaust gas to the atmosphere, the dust is removed by an electric dust collector). Since the exhaust gas is treated by a wet scrubber, the relative humidity is about 100%, and the dust is not completely removed.

The present invention treats exhaust gas with an apparatus combining a wet scrubber and a shell-and-tube heat exchanger, and uses a shell-and-tube heat exchanger of about 60 ° C. to about 40 ° C. Cool down to However, the cooling temperature at this time may be appropriately changed according to the quality design because of one requirement of the quality design of calcium carbonate.

In the shell and tube heat exchanger of the present invention, the lime kiln exhaust gas is conducted to the shell side, while the cooling medium is conducted to a large number of tubes mounted inside the heat exchanger.

That is, the exhaust gas introduced into the heat exchanger of the present invention is cooled by contacting the outer surfaces of many tubes through which the cooling medium is conducted. However, since the relative humidity is about 100%, the exhaust gas is exhausted. The moisture in the inside comes into contact with the tube and condenses and forms dew. With the progress of the dew, the entire outer surface of the tube becomes wet and eventually drops and falls. At this time, the dust contained in the lime kiln exhaust gas is captured by moisture condensed on the outer surface of the tube, and the dust is removed.

[0015] The behavior of dew condensation, formation of drops and dropping of water on the outer surface of the tube is continuously performed, so that dust does not adhere to the outer surface of the tube, and the outer surface of the tube is always kept clean. It has excellent cleaning action. Furthermore, since the outer surfaces of a large number of tubes through which the cooling medium is conducted are kept clean without the adhesion of dust and are always kept in a wet state, the overall heat transfer coefficient is 400 Kcal / m ^2. -Since the temperature can be maintained at about hr · ° C., the heat exchange rate is extremely high, and continuous operation is possible.

On the other hand, the lime kiln exhaust gas is sent to a carbonation reaction tank by a blower.
A turbo blower with a large clearance and large shaft power is used. Is achieved.

[0017]

FIG. 1 shows an embodiment of the present invention. Next, the structure and operation of the present invention will be described in detail with reference to the drawings. The exhaust gas from the lime kiln 1 is sent to the wet scrubber 3 by the blower 2, and the exhaust gas is sent to a shell and tube heat exchanger 4 (hereinafter abbreviated as a heat exchanger) combined with the wet scrubber 3. Is supplied to the carbonation reaction tank 6 by the blower 5.

As shown in FIG. 2, the shell-and-tube type heat exchanger 4 of the present invention is a quadrangular prism-shaped heat exchanger.
Inside, a large number of small-diameter tubes 8 connected in parallel in the horizontal direction are mounted. As an example, the cross-sectional area of the shell is about 2.2 m ² , and the diameter of the tube in this case is about 15.9 mm in outer diameter, and the number of tubes is 3120. Further, the capacity of the carbonation reaction tank 6 is 30
At m ^3, the exhaust gas sent to the reaction tank 6 is 1600
At m ³ / hr, the exhaust gas supplied to the heat exchanger 4 in this case is about 220 m ³ / min. However, the present invention is not limited to the above specification, and it is needless to say that the present invention can be appropriately changed depending on the capacity of the carbonation reaction tank.

An exhaust gas inlet 9 is formed below the shell 7, and an exhaust gas outlet 10 is formed at the top of the shell 7, and the exhaust gas is introduced into the heat exchanger 4 on the shell 7 side. The small-diameter tube 8 is configured such that cooling water is introduced from a cooling water inlet 11 and is discharged from a cooling water outlet 12 while being sequentially sent to a large number of tubes 8 connected and arranged. Reference numeral 13 in FIG. 2 denotes a shower for cleaning the outer surface of the tube 8 when the heat exchanger 4 is stopped.

As shown in FIG. 1, the exhaust gas of the wet scrubber 3 is supplied from the exhaust gas inlet 9 of the heat exchanger 4 combined with the scrubber 3 to the inside of the shell 7, and is supplied to the interior of the tube 8 of the heat exchanger 4. Is cooled by cooling water. Since the exhaust gas supplied from the wet scrubber 3 has a relative humidity of 100%, the moisture in the exhaust gas is reduced by a tube 8.
When it comes into contact with water, it forms condensation, which drops and falls. Therefore, the dust contained in the exhaust gas is trapped and removed by the condensed moisture, the dust is remarkably reduced, and sent to the carbonation reaction tank 6 by the blower 5.

Since the exhaust gas is made lower by removing the dust in the heat exchanger 4 of the present invention, the blower 5 for sending the exhaust gas to the carbonation reaction tank 6 is a volume type with a small shaft power. Roots blower can be used and power saving is achieved.

Incidentally, when calcium carbonate was produced in a plant using the combination of the wet scrubber and the heat exchanger of the present invention (calcium hydroxide concentration 15%, reaction time 4.5 hours, reaction temperature 45 ° C.) The whiteness of calcium carbonate (according to the test method of JISP.8123) is
97.5%, whereas the whiteness of calcium carbonate when only the wet scrubber was used without using the cooler of the present invention was as poor as 90.0% due to the contamination of dust.

[0023]

As described above, according to the present invention, when a carbonation reaction is performed using the exhaust gas of a lime kiln, the exhaust gas is used by combining a wet scrubber with a shell-and-tube heat exchanger. By introducing the exhaust gas to the shell side of the heat exchanger, the overall heat transfer coefficient can be greatly improved, and the dust in the exhaust gas can be significantly reduced.

Further, according to the present invention, since the dust in the exhaust gas sent to the carbonation reaction tank is significantly reduced, a volume-type roots blower having a small shaft power can be used as the blower for sending the exhaust gas to the carbonation reaction tank. Electricity is achieved.

[Brief description of the drawings]

FIG. 1 is an embodiment of a flow of a carbonation reaction according to the present invention using lime kiln exhaust gas.

FIG. 2 is a side view of an example of a shell and tube heat exchanger.

[Explanation of symbols]

 1: Lime kiln 2, 5: Blower 3: Wet scrubber 4: Heat exchanger 6: Carbonation reaction tank 7: Shell 8: Tube 9: Exhaust gas inlet 10: Exhaust gas outlet 11: Cooling water inlet 12: Cooling water outlet 13: shower

Claims (1)

(57) [Scope of request for utility model registration] Claims: 1. Use of the waste gas from a lime burning kiln
In a lime-burning kiln exhaust gas treatment unit for a facility that produces calcium carbonate , a wet scrubber and a shell and
Combined with a tube heat exchanger,
The exhaust gas treated by the wet scrubber is configured to be introduced into the shell side of the shell-and-tube heat exchanger, and a large number of tubes inside the shell-and-tube heat exchanger. A lime-burning kiln exhaust gas treatment apparatus, wherein a cooling medium is conducted in the inside.