1. Classification, advantages and disadvantages of shaft kiln
Shaft kiln (also known as shaft kiln, bottle kiln) is used to forge refractory raw materials and lime kiln.
(1) Classification method of shaft kiln:
Generally, it can be classified according to the type of forging materials and the use of fuel, and it can also be classified according to the different air supply methods and mechanization levels.
1) According to different types of forging materials can be divided into:
Clay shaft kiln (calcination temperature 1300 ~ 1400℃), dolomite shaft kiln (calcination temperature 1600 ~ 1650℃), lime shaft kiln (calcination temperature 1200 ~ 1300℃), magnesite shaft kiln (calcination temperature 1600 ~ 1650℃), high aluminum shaft kiln (calcination temperature 1450 ~ 1650℃);
2) According to the type of fuel can be divided into:
Solid fuel shaft kiln (coke, anthracite as fuel), liquid fuel shaft kiln (heavy oil as fuel), gas fuel shaft kiln (coke oven gas, mixed gas, natural gas);
3) According to different air supply methods can be divided into:
Forced ventilation shaft kiln: air is pumped into the kiln by a blower to strengthen the forging process.
Natural ventilation shaft kiln: the gas flow in the kiln is mainly operated by the natural pumping force of the shaft itself.
· According to different degrees of mechanization, it can be divided into: manual feeding shaft kiln and mechanized shaft kiln, which are completely mechanized from feeding to discharging.
(2) Advantages of shaft kiln:
The equipment is simple, the investment is less, the fuel consumed per unit of finished products is less, the cost is low, the unit volume utilization coefficient is large, and the equipment itself occupies a small area. Disadvantages: the temperature distribution in the kiln is not uniform, so it is easy to produce under-burned and over-burned products; When coke or anthracite is used as fuel, ash pollution products; There are certain restrictions on the lumpiness of raw materials into the kiln, and the crushed materials (<30mm) can not be used in the shaft kiln forging, resulting in a waste of resources, and the production capacity of the shaft kiln is also small, and the working conditions are poor.
From the development of shaft kiln, it was originally manual operation, natural ventilation, and regular feeding and discharging. With the development of production technology, in order to improve output, quality, improve working conditions, improve production efficiency, and reduce fuel consumption, mechanized shaft kilns such as mechanized ventilation, mechanized feeding and discharging, water-cooled furnace walls, and sealed devices have been gradually realized, so that the shaft kilns have been continuously improved to adapt to the modernization of production.
2. Structure and shape of shaft kiln
(1) Structure of shaft kiln
Kiln body, charging device, sealing device, vaporizing cooling device, discharging device and ventilation device, etc.
(2) Shape of kiln body:
There is no doubt that the movement of materials in the kiln and the distribution of air flow in the kiln have important effects. To ensure the uniform subsidence and alignment of the materials in the kiln, and make the air flow evenly distributed along the kiln section, is the basic requirement for the shape of the shaft kiln body, and its shape is roughly as follows:
1) Straight cylindrical shape: that is, the upper and lower inner diameter of the same cylindrical shape, this type is suitable for calcining various refractory raw materials. This kind of shaft kiln is simple and strong in structure, which is conducive to the material going straight and sinking evenly, and the masonry is convenient. However, when the material moves from top to bottom in the kiln, once it is sintered, the volume will shrink, forming a ring gap between it and the kiln wall, resulting in less resistance around the kiln than in the middle of the kiln; At the same time, the packing density of the material near the kiln lining is also looser than that in the middle, so that the ventilation of the same section of the shaft kiln is uneven, resulting in uneven calcination of the material.
2) cylinder-shaped shaft kiln with inner diameter shrinkage: In order to overcome the above shortcomings, the inner diameter of the calcined belt can be slightly shrunk, which can reduce the gap between the material and the kiln wall, so that the gas is more evenly distributed along the kiln section. For shaft kilns that use vaporization to cool the furnace wall, the surrounding materials can also be turned inward during the sinking process, so as to improve the calcining conditions of the materials and reduce under-fired products.