JPS6026060B2 - Method for preheating raw materials and collecting dust from lime kiln - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to how to preheat raw materials and collect dust from exhaust gas in a lime kiln.

The exhaust gas discharged from the lime kiln is introduced into a subheater before being released into the atmosphere.

In this preheater, the heat of the exhaust gas is used for drying, ripening, and calcining of the lime raw material input into the subheater. Through this use, the temperature of the exhaust gas discharged from the lime kiln at about 1200°C is reduced to about 350 qo. A so-called preheater is used for drying, heating and pre-firing the raw material, and there are two types of preheaters: one of a subordinate grate type and one of a packed bed type.

Each of these two types has its advantages and disadvantages; the grate type has a pressure drop of 4.5 mm, but the heat exchange rate is poor;
On the other hand, the packed bed type has a good heat exchange rate but a large pressure loss. Furthermore, in the past, a dust collector had to be provided separately from the preheater, which was disadvantageous in terms of recovering residual heat.

In view of the above, the present invention provides a raw material heating method in which exhaust gas discharged from a kiln is discharged into the atmosphere through a preheater for preheating the raw material. The raw materials sorted by particle size are put into each of the plurality of filling sheets of the fluidized descent type, and the exhaust gas is passed through the packed bed for raw materials with large particle size before the packed bed for raw materials with small particle size. is introduced into a subheater, and the exhaust gas coming out of the subheater recovers its residual heat before releasing it into the atmosphere.
It is an object of the present invention to provide a method for collecting dust from exhaust gas, thereby realizing an integrated configuration of a subheater and a dust collector while making heat recovery advantageous.

The present invention will be specifically explained in detail below with reference to Examples. Exhaust gas discharged from a lime kiln, for example a kiln 1, is introduced into a preheater 2, as shown in FIG.

The raw lime 3 fed into the preheater 2 is sorted by particle size using a shark 4. For example, large particle size and small particle size are used as fine powder. The separated particles are separated separately, with large particles passing through path 4A and small particles passing through path 4A.
B, and is sent to the child heater. Inside the subheater 2,
A plurality of fluidized descending packed beds 6A and 6B are provided separately. Raw materials sorted by particle size as described above are introduced into each of the plurality of layers. The powder may be directly fed into the kiln 1 through the arrow path 7. The exhaust gas introduced into the subheater first passes through the packed bed 6A with larger particle size, and after leaving this layer, passes through the packed bed 6B with smaller particle size.
and exits preheater 2.

The packed bed is of a granular type so that it has a dust collection function. The number of layers is not limited to two. The raw materials of each particle size are discharged from the bottom of the packed bed by flowing downward.
Mixed and fed to kiln. The exhaust gas leaving the subheater 2 is input into a heat recovery device 8 and then discharged from a chimney 10 by a suction fan 9.

As the heat recovery device 8, for example, a low pressure boiler (an inorganic or organic solvent is used in addition to water as the heat exchange medium) is used, and the recovered heat may be in any form such as hot water, steam, or electric power. The drawing shows a turbine 11 connected to a heat recovery device.
The case where it can be converted into a box force is shown. In this case, by coaxially coupling the turbine with the suction fan 9, heat can be efficiently recovered for powering the fan. Exhaust gas after being burned in the burner 12 leaves the kiln 1 and is introduced into the subheater 2.

The exhaust gas that has entered the preheater 2 first passes through the packed bed 6A, which has a larger particle size. While passing through this layer, dust in the exhaust gas is captured in this layer, and the dust removal in this step is mainly a rough removal. Next, sufficient dust is removed while passing through the packed bed 6B with a particle size of 4 mm. On the other hand, the exhaust gas at a temperature of about 1200 oo passes through the first packed bed and drops to about 600 qo, then passes through the second packed bed and drops to about 350 qo, while the raw materials in each layer become fluid. Drying, preheating, and firing are performed as they descend.

The raw material is taken out from the bottom of the heating element and fed into the kiln together with the powder. Approximately 350qo from preheater 2
The exhaust gas further gives heat to the boiler 8 and is then discharged from the chimney via a suction fan.

Dust has been sufficiently removed from the exhaust gas after passing through the layer 6B, which has a small particle size, to the extent that it can be released into the atmosphere. The heat recovered by the boiler 8 is converted into electric power by, for example, a turbine 11. In this case, the shaft of the turbine is directly connected to the suction fan 9, and the efficiency of heat recovery is particularly high. According to [11] Since it is a preheating device rule dust collector, the equipment system is contracted, and therefore the equipment is simple and compact.
The process of drying, preheating, and pre-calcining the raw material limestone itself becomes the dust collection process of the exhaust gas, and is the same process in an intersecting manner. is smaller than that of the conventional (packed bed preheater and dust collector), and the thermal efficiency of the '41 subheater is greater than that of the conventional grate preheater;
Heat recovery from qo to 150oo is extremely effective (it can be recovered to lower temperatures using organic solvents).
In other words, from 1200℃ to 350qo, for drying, preheating, and pre-calcining the raw materials, 35pi0 to 150qo (even in the case of steam, if the exhaust gas does not contain corrosive gases, it is necessary to use a lower temperature) 50qo~60℃) with hot water,
It can be effectively recovered as electric power, etc., and the heat recovery rate is further increased by direct connection between the turbine and the fan.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a conventional device system, and FIG. 2 is a system diagram of a device system according to the present invention. 1...Kiln, 2...Subheater, 3...Raw material, 4A, 4B
... Supply channel, 6A, 6B... Filled bed, 7... Supply channel, 8
... Boiler (W. 日・B), 9.. Suction fan, 10.. Chimney, 11..
turbine. Garden map N

Claims (1)

[Claims] 1 In a raw material preheating method in which exhaust gas discharged from a kiln is discharged into the atmosphere through a preheater for preheating the raw material, a plurality of packed beds of a fluidized descent type provided in the preheater are used. Raw materials separated by particle size are input into each of the above, and the exhaust gas is introduced into a preheater so that it exits through the packed bed for raw materials with large particle size before the packed bed for raw materials with small particle size, and preheats. This is a method for preheating raw materials and collecting dust from lime kilns, in which the exhaust gas that comes out of the vessel is discharged into the atmosphere after recovering residual heat.