JPS6116743B2 - - Google Patents

Description

[Detailed Description of the Invention] In addition to the small-scale underground kiln type (also called sake bottle kiln) that has been used since ancient times, there are also large-scale vertical shaft kiln type and rotary kiln type lime kilns. be. Among these, although underground is primitive, it uses cheap solid fuel, saves power due to natural ventilation, has a simple structure, has few breakdowns, and can be operated unmanned at night. Because of these advantages, it is still widely used as a small kiln in large numbers.

The sake-bottle-shaped body of the earthen kiln is buried in the earth cut out of a cliff, and its upper and lower ends are open to the atmosphere to allow natural ventilation. Coarse-grained limestone and coarse coke (anthracite can also be used) are injected intermittently through the upper opening, filling the furnace body in a mixed state or in layers. constitutes the firing zone, and the lower portion constitutes the cooling zone. An ore scavenger is attached to the opening at the lower end of the furnace body, and combustion air rises within the furnace body through a gap between the two by natural ventilation. Then, in the cooling zone, the calcined lime that descends from the top is cooled by cold air, and the moist air rises to the calcining zone and burns the fuel, and this combustion heat decarboxylates and decomposes the limestone. It can be done. The carbon dioxide gas and calcination gas generated in the calcination zone are combined and enter the preheating zone above the calcination zone, where the raw material that is introduced through the top opening and falls is preheated by the sensible heat of the gas, and then discharged into the atmosphere from the top opening. be done.

The temperature of the exhaust gas from the upper opening is approximately 300℃, the temperature of the firing zone is 1000℃ to 1200℃, the temperature of the calcined quicklime discharged from the lower opening is approximately 100℃, and the daily production capacity of the kiln is 10 to 15 tons of quicklime. . The size of the furnace body is approximately 2.5 meters in inner diameter and 8 meters in height.

The drawback of this underground kiln is that homogeneous firing cannot be achieved and a mixture of hard quicklime, soft quicklime and unburned coke is taken out from the bottom of the kiln. This mixed product must then be sorted separately at different locations.

The reason for non-uniform firing is that the limestone and calcined lime in the furnace body are not filled uniformly, and the filling tends to be coarse along the furnace walls and dense in the furnace core. be. In other words, large gaps are formed between the particles near the wall of the furnace body, and the gas passage rate and amount are large, and combustion occurs completely, resulting in a high temperature and the production of hard quicklime. In the core, this gap becomes smaller, reducing the rate and amount of gas passing through the core, resulting in incomplete combustion, resulting in lower temperatures and the production of soft and unburned quicklime mixed with end-burning coke. .

In order to eliminate this drawback, the present inventor previously filed a patent application
In No. 55-132406 (Japanese Unexamined Patent Publication No. 57-58069),
By providing the furnace core with a furnace core column that extends upward from the furnace bottom and is sealed at its tip, it is possible to eliminate the passage of raw materials and gas into the furnace core, and to prevent the outer surface of the furnace core column from passing through the furnace core. By creating large interparticle gaps in the raw material and calcined lime in contact with the furnace, uniform ventilation is possible throughout the furnace body, and a homogeneous product can be obtained with almost no unburned coke.

The upper end of the furnace core column in the above-mentioned previous invention is closed. The reason for this is that the core column of the previous invention was not suitable for large-scale applications that provide continuous mechanical throwing, as seen in Japanese Patent Application No. 55-132405 (Japanese Unexamined Patent Publication No. 57-61629) by the present inventor. This is because the target was a lime kiln. In other words, in this case, the upper end of the main body of the kiln is closed except for the raw material inlet, and the exhaust gas is removed by forced ventilation using a blower rather than natural dissipation, so the upper end of the furnace core column must be closed off. It is inevitable. Since this furnace core column is fixed inside the high-temperature furnace body, there is a risk that the iron core tube lining the furnace core column may be deformed by heat. Patent Application No. 132406 (1982)
Although it is not described in the specification or drawings of Publication No. 58069, it is actually necessary to force cooling air into the core column to cool it.

The present invention applies the above-mentioned furnace core column installation to a small-scale underground kiln type lime kiln.
However, in this case, the upper end of the furnace core column is
As shown in the example in Japanese Patent No. 82-1717, the opening reaches the upper end of the furnace body or extends upward beyond that point. The opening is covered with a cap to allow ventilation. The lower end of the furnace core column, like the lower end of the cooling zone of the furnace body, is open to the outside air, and some of the air due to natural ventilation naturally rises inside this furnace core column and is dissipated into the outside air from the upper end opening. Since the iron core tube on the inner wall of the furnace core column is protected by cooling, there is no need for forced cooling as described above.

The structure and effects of the lime kiln according to the present invention will be explained with reference to the drawings. As is well known, the main body 2 of the kiln, which is constructed by being buried in a layer of rocky soil 1, has a preheating zone A, a firing zone B, and a cooling zone C for raw materials, combustion, and fired products formed in this order from the top. Ru.
The upper and lower ends of the furnace body are open to allow ventilation. A hoist 4 attached to a pedestal 3 in the shed that covers the upper end of the furnace body 2 moves a basket 5 for transporting raw materials and fuel, and the mixed raw ore and fuel coke contained in the basket 5 are moved. Others are injected into the furnace body intermittently. The fired products are taken out from the furnace body intermittently through the opening at the lower end of the furnace body 2 by appropriate means and collected in the ore removal machine 7 supported by the pedestal 6, and the products exiting this are transferred to the belt conveyor 8. be transported to another location by

An iron core pipe 9 is erected in the core of the furnace body 2, its lower end is fixed to a suspension 11 fixed to a pedestal 10, and its upper end is fixed to a pedestal 12 suspended above the furnace top.
Fixed. The outer surface of the core tube 9 is lined with a double layer of refractory bricks 13 for heat protection. The upper and lower ends of the core tube 9 are open to allow ventilation. Above the upper end of the core tube 9 is a cap 14 that can be freely ventilated.
is placed thereon to prevent the raw materials dropped from the basket 5 from falling into the core tube 9.

Core pipe 9 whose outer surface is lined with firebrick
(They will be collectively referred to as the furnace core column 15.)
As a result, raw ore, fuel coke, and fired products enter the furnace core while the core tube 9 is cooled and heat-insulated by some of the air flowing from the furnace bottom into the furnace as described above. is eliminated, and the combustion air and exhaust gas rise uniformly through the large gaps of the particles uniformly distributed only on the outside of the furnace core column 15. Combustion is completed and unburned coke is produced as a product. It is possible to efficiently obtain a homogeneous product. Furthermore, by appropriately adjusting the firing temperature and time, hard quicklime or soft quicklime can be produced freely, eliminating the need for sorting.

Furthermore, in conventional underground kilns, complete combustion is possible in the furnace walls, but due to lack of air in the furnace core, CO gas is generated during the combustion process, and CO gas in the exhaust gas is generated.
The concentration reaches 1 to 2%, which causes a loss of dissipated heat and is harmful to the hygiene of the mirror, but the furnace of the present invention has the advantage of eliminating the production of CO. In addition, the production efficiency is good, so it is possible to produce approximately 20 tons per day using a conventional 12 tons daily lime furnace. Furthermore, since the condition of the firing zone is stabilized, it also has the advantage of extending the life of the brick.

Next, the fuel coke lump may be mixed with fine powder that has been pulverized by impact during transportation. If this lump coke mixed with fine powder is put into the furnace as it is, the fine coke will immediately burn on the furnace surface, and the heat will be dissipated into the exhaust gas without being used for calcination of lime. In order to make effective use of this pulverized coke, compressed air is used to blow pulverized coke into the center of the firing zone of the furnace through a jet pipe inserted inside the furnace core column, and it is used as fuel. I found out what can be done.

To explain the drawings, pulverized coke separated from lump coke in advance or inexpensive pulverized coke produced as a by-product from a coke factory or the like is stored in a storage tank 21 fixed to a pedestal 3 on the roof of the furnace. A delivery pipe 23 connected to the lower end of the storage tank 21 via an automatic delivery rotary valve 22 is extended,
It is inserted and fixed into the core tube 9 of the furnace core column 15, and its tip is projected into the opening 24 provided in the furnace core column wall at the central position of the firing zone. While continuously dropping fine coke powder from the storage tank 21, the pneumatic feeder 25
When compressed air with a pressure of 2 to 10 kg/cm ² is fed into the delivery pipe 23, the fine coke is blown into the firing zone of the furnace body from the nozzle at the lower end of the delivery pipe. It burns completely.

Although the above-mentioned delivery pipe 23 is simplified to be one in the drawing, in reality, a plurality of pipes are inserted into the core pipe 9 and solidified in order to uniformly blow into the firing zone. In a conventional underground kiln, it is practically impossible to insert and fix such a delivery pipe into the furnace body, but fortunately in the furnace of the present invention, there is a furnace core column, so it is possible to utilize this. The delivery tube as described above can be inserted and fixed into the furnace body very easily.

Furthermore, recently, when blowing a small amount of steam into the firing zone of a general lime kiln,
It has been reported that soft quicklime with high activity can be obtained even at high firing temperatures. (Japan Lime Association, “Lime Manufacturing Technology Handbag” 1979 edition, 37
See pages ~40. ) If it is desired to put this into practice, there is an advantage in that it can be easily carried out by mixing the water vapor from the water vapor supply means 26 into the air blown into the delivery pipe 23. Alternatively, it is also conceivable to press only water vapor into the delivery pipe instead of air.

Although it is not an underground lime kiln, in the aforementioned Japanese Patent Publication No. 32-1717, in order to eliminate the incomplete firing of raw materials in the center of the furnace, an exhaust fan was introduced to the furnace core. Lime kilns with heavy oil burners equipped with tubes (i.e. core columns) are described.

[Brief explanation of the drawing]

The figure is a longitudinal sectional view of the lime furnace of the present invention. 2... Furnace body, A... Pre-heating zone, B... Firing zone,
C... Cooling zone, 5... Basket, 7... Mine removal machine, 8... Belt conveyor, 9... Core pipe, 13...
... Refractory brick layer, 14 ... Cap, 15 ... Core column, 21 ... Fine powder coke storage tank, 22 ... Automatic delivery valve, 23 ... Delivery pipe, 24 ... Opening of furnace core column, 25 ... ...Pneumatic feeder.

Claims (1)

[Scope of Claims] 1. The core of the furnace body, which is embedded in the cliff soil and is composed of a pre-heating zone, a firing zone, and a cooling zone, has an upper end and a lower end opened at each end of the furnace body to allow air to freely circulate. In a lime calcining furnace equipped with a hollow core column, a plurality of delivery pipes for pneumatically transporting pulverized coke are installed inside the furnace core column, and the lower end nozzle of the delivery pipe is connected to the center of the baking zone. An underground kiln type lime kiln with a furnace core protruding into respective openings penetrating the column wall at a height. 2. The underground kiln type lime kiln according to claim 1, characterized in that the upper end of the furnace core column is covered with a cap through which air can freely circulate to prevent the raw materials from falling. 3. The underground kiln type lime kiln according to claim 1, characterized in that it has means for mixing water vapor into the delivery pipe.