JPS60112652A - Treatment of dust generated from lime calciner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating dust in exhaust gas generated when limestone is fired in a lime kiln.

A lime kiln for firing limestone is composed of a plurality of shafts, and each shaft repeats combustion and heat storage in a constant cycle, thereby firing the limestone supplied into the shaft. ing. 1st
The figure is an explanatory diagram showing the gas flow of the lime kiln. Reference numeral 1 denotes a kiln which is composed of a plurality of shafts 2 and 3, in which a limestone supplying hole 4 and an exhaust gas outlet 5 are provided in the upper part, and a product discharge feeder 6 and a product hopper 7 are provided in the lower part. lances 8 and 9 are provided inside the shaft 2°3, respectively.

10 is a cyclone, 11 is a bag filter, and 12 is a dust hopper.

Assuming that 2 is a combustion side shaft and 3 is a heat storage side shaft, inside the combustion side shaft 2, the limestone is heated by the fuel 13 blown from the lance 8 and the combustion air 14 heated by the heat storage side shaft 3. Calcining is performed, and the calcined quicklime is discharged from the feeder 6 to the conch 7.

The high-temperature gas after calcining the limestone in the combustion-side shaft 2 is guided into the heat-storage-side shaft 3 through the channel portion 15, stores heat in the heat-storage-side shaft 3, and is then discharged from the exhaust gas outlet 5, forming a cyclone]0 and a bug. After the dust is collected by the filter 11, it is released into the atmosphere.

The combustion and heat storage by the shafts 2 and 3 are switched in a constant cycle according to the optimum firing time of the limestone.

In the above-described operation, the fuel injected into the combustion side shaft 2 just before the end of the combustion time remains unburned in the shaft 2 because the supply of combustion air 14 is stopped before the combustion is completely completed. It may remain inside. Furthermore, free carbon generated during combustion of the fuel 13 is present within the shaft 2 .

The unburned portion of the fuel, that is, the unburned carbon and free carbon, mixes with dust mainly consisting of limestone grains floating in the furnace, and is discharged from the furnace through the exhaust port 5 together with the exhaust gas. On the other hand, in the heat storage side shaft 3, the lance 9 and the fuel supply pipe are cleaned by blowing steam into the lance 9, and the steam after cleaning is jetted from the lance 9 into the heat storage side shaft 3. .

Therefore, the exhaust gas discharged from the exhaust gas outlet 5 to the outside of the furnace contains unburned carbon and free carbon attached to the surface.
Dust consisting mainly of limestone grains is present. This dust is collected by a cyclone 10 and a bag filter 11 and stored in a dust trap 2. The amount of dust generated is large, reaching 2 to 5 tons per day, but since the limestone grains, which are the main component of the dust, are not sufficiently calcined, the quality is low and has no commercial value. For example, if there is a firing furnace such as a rotary kiln, the dust can be fired in the rotary kiln, unburned carbon can be burned, and the product can be recovered as a product. However, it is economically impossible to install a rotary kiln for this purpose because it requires a large amount of equipment cost. Therefore, the above-mentioned dust has conventionally had to be disposed of as industrial waste.

From the above-mentioned viewpoint, the present invention aims to burn limestone grains, which are the main component of dust in exhaust gas generated during limestone firing in a lime kiln, without requiring a special heat source and recover them as quicklime grains. The present invention provides a method for treating dust generated from a lime kiln, in which the dust contained in the exhaust gas is collected from the exhaust gas generated when limestone is fired in the lime kiln, and the dust is supplied into the high-temperature gas extracted from the inside of the lime kiln to burn the unburned carbon adhering to the dust, and thermally decompose the limestone grains that are the main component of the dust, thus , the dust is burned with the high-temperature gas and recovered as quicklime particles.

Next, the present invention will be explained with reference to the drawings.

FIG. 2 is an explanatory diagram showing one embodiment of the method of this invention. In the method of this invention, as shown in FIG. 2, a small amount of gas at a temperature of 900°C or higher is extracted from a high-temperature part in the firing furnace l, such as a channel part 15, by a pipe 16, about 1 ton of the total amount of gas. and leads to the bag filter 17. Then, the dust in the exhaust gas stored in the dust tube 12 is supplied into the pipe 16, and while the dust is being air-fed to the bag filter 17 by the high-temperature gas passing through the pipe 16, the high-temperature gas is The limestone particles in the dust are thermally decomposed and fired, and the unburned carbon adhering to the dust is burned to form quicklime particles, which are collected by a bag filter 17. At this time, the combustion heat of unburned carbon is used to burn the limestone grains. In Figure 2, 1
8 is a combustion air supply pipe for supplying combustion air into the pipe 16, 19 is a cooling air supply pipe for supplying cooling air into the pipe 16 near the bag filter 17, and 2o is a Haku filter 17. This is a product hopper located below.

FIG. 3i is an explanatory diagram showing another embodiment of the method of the present invention. In this embodiment, the dust stored in the dust hopper 12 is supplied from the upper part, and the dust is supplied from the lower part to the pipe 1.
6 provides a vertical firing chamber 21 into which the hot gas extracted from the channel portion 15 is blown, for firing the dust with the hot gas.

Therefore, the dust supplied into the firing chamber 21 from the upper part descends inside the firing chamber 21 and is discharged from the lower end of the trench, while the dust is blown from the lower part of the firing chamber 21 and rises inside the firing chamber 21. The counterflow of high-temperature gas discharged from the top causes thermal decomposition of limestone grains in the dust and combustion of unburned carbon adhering to the dust. The quicklime particles are calcined in the firing chamber 21 and discharged from the firing chamber 21 through a pipe 22 to the bag filter 1.
7, and is collected by a bag filter 17.

Next, the present invention will be explained using examples. By the method shown in FIG. 2, from the channel part 15 of the firing furnace 1,
High-temperature gas at a temperature of 0°C is passed through tube 1 at a flow rate of 10105N/H.
Extracted within 6 days. Inside the pipe 16, there is a dust hole zf l
2f) Dust at a temperature of 15°C at 200 kv/
The dust was heated at a temperature of 15° C. supplied from the high temperature gas and the combustion air supply pipe 18 for 60°C.
Calcining was carried out in tube 16 with combustion air at a flow rate of Nm3/H.

Cooling air at a temperature of 15° C. and a flow rate of 1500 Nm37H was supplied from a cooling air supply pipe 19 into the tube 16 near the bag filter F, and the baked dust was collected in the bag filter 17. As a result, it was possible to recover calcined dust or quicklime particles at a temperature of 150° C. in an amount of 130 ky/h. The flow rate of the exhaust gas after dust was collected by the bag filter 17 was 1710 Nm3/H. As is clear from the above, the amount of dust generated is 4.8
．． The amount of quicklime particles recovered from the dust in the case of T/D is 3. I2T/D, and this amount corresponds to about 2% of the amount of quicklime produced by the kiln.

As described above, according to the method of the present invention, the dust generated during limestone firing in a lime kiln, which was conventionally treated as waste, is treated by using high-temperature gas extracted from inside the lime kiln. Combustion of unburned carbon adhering to the dust and thermal decomposition of the limestone grains, which are the main components of the dust, are carried out, and the combustion heat of the unburned carbon can be used to sinter the limestone grains. , thus,
This provides an industrially excellent effect in that quicklime particles can be efficiently recovered from dust without requiring a special heat source.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the gas 70- of the lime kiln, FIG. 2 is an explanatory diagram showing one embodiment of the method of this invention, and FIG. 3 is an explanatory diagram showing another embodiment of the method of this invention. . In the drawings, 1...Kilning furnace, 2, 3...Shaft, 4...Hosogu, 5...Exhaust gas outlet, 6...Feeder for product discharge, 7...Product outlet , 8.9... Lance, 10... Cyclone, 11... Bag filter,
12...Amount of dust generated, 13...Fuel, 14...
・Combustion air, 15...Channel part, 16...Pipe, 17...Bag filter 18...Combustion air supply pipe, 19...Cooling air supply pipe, 20...Product Hollow 21... firing chamber, 22...
··tube. Applicant Nippon Kokan Co., Ltd. Agent Natsuo Shioya (and 2 others) Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] Collecting dust contained in the exhaust gas from the exhaust gas generated when calcining limestone in the lime calcining furnace, and supplying the dust to the high temperature gas extracted from the inside of the lime calcining furnace, The unburnt carbon adhering to the dust is burned, and the limestone grains, which are the main component of the dust, are pyrolyzed, and the dust is then calcined by the high-temperature gas to form quicklime grains. % to recover
A method for treating dust generated from a lime kiln.