Recently, the key technology of the mixed-material mechanized lime shaft kiln has been continuously improved. Based on different needs, the improvement of key technologies of the lime shaft kiln can promote customers to trust and use our lime shaft kiln more. In this article, we will explain the key technological changes of the mixed-material mechanized lime shaft kiln from the aspects of improving the quality and reducing the consumption of the kiln, the large-volume and low utilization coefficient of the kiln, the kiln lining structure, the flue gas treatment system, and the combustion-supporting blower.
Improve Lime Kiln Quality and Reduce Consumption
One of the key technologies of the mixed-material mechanized lime shaft kiln is the improvement of kiln quality and the reduction of consumption. For production enterprises, reducing costs is an eternal theme of enterprise management. Keeping the long-term stable operation of the lime kiln is the best way to reduce costs and increase efficiency. Stable quality and reduced consumption are the ultimate goals of lime kiln operation. It is meaningful and an effective way to reduce carbon emissions by using the characteristics of thermal system and optimizing the thermal process operation to improve calcination quality and reduce calcination energy consumption for mixed-material lime shaft kiln.
There are two important responsibilities for the operation management of the mixed-firing shaft kiln:
- 1) fuel management is the most basic work for reducing fuel consumption in the mixed-material lime shaft kiln
- 2) combustion-supporting air management is the key link to improve quality and reduce consumption in the mixed-firing shaft kiln. In addition to the fan selection, air supply mode, and internal blower, the excess coefficient of combustion-supporting air, that is, the rationality of air ratio, plays an immeasurable role in improving fuel combustion rate.
The automatic compensation function of fuel weighing error and online analysis of flue gas at the top of the kiln are the monitoring means to ensure the accuracy of fuel addition and full combustion of fuel for mixed-material lime shaft kiln. Taking the kiln gas as a guide to dynamically manage the thermal state of the kiln is an effective way to improve the smooth production and reduce calcination heat consumption of mixed-material lime shaft kiln. These two measures must be given great attention by the shaft kiln operators.
Large Volume and Low Utilization Coefficient of Lime Shaft Kiln
Another key technology of the mixed-material mechanized lime shaft kiln is the large volume and low utilization coefficient of the kiln. In recent years, there has been a misconception in the industry that the larger the volume of the mixed-material shaft kiln, the more advanced and fashionable it is. Shaft kilns with a capacity of more than 700m3 are not uncommon, but many kiln utilization coefficients have remained at around 0.4 for a long time, resulting in low production efficiency and poor economic benefits. This problem should be given attention by the industry.
Due to the “wall effect” of the kiln structure itself, the utilization and control of the “wall effect” are the core work of the design and operation of the shaft kiln. To adapt to the material distribution at the top and material discharge at the bottom of the kiln, the upper and lower openings of the shaft kiln maintain a small volume, and only the diameter of the kiln belly is increased to form a “big belly” shape. This shape is prone to the suspension of mixed materials, accumulation of dead materials, and increased possibility of lateral movement of mixed materials in the kiln, which is prone to produce “raw” material columns.
To achieve large-scale vertical kilns, research and development must be conducted in large-scale kiln structure forms, large-scale feeding equipment, large-scale ash unloading equipment, and large-scale kiln ventilation devices. Otherwise, blindly pursuing large capacity to ensure production targets may lead to entering the wrong path, increasing engineering investment, and running vertical kilns at a low utilization coefficient for a long time. This will make the quality highly fluctuating and production costs inevitably high.
Vertical Kiln Lining Structure
Another key technology of the mixed material mechanized lime vertical kiln is the vertical kiln lining structure. According to the process characteristics of the mixed material mechanized lime vertical kiln, a scientifically and reasonably designed lining structure form, refractory materials that meet performance requirements, and standard and design-compliant masonry construction, with supporting scientific and standardized operation and maintenance, can make the vertical kiln lining stable for a long time and reduce kiln heat loss, enabling low-cost operation for the enterprise.
In some vertical kiln projects, in order to reduce construction investment costs or increase insulation coefficient, the lining thickness is blindly increased, and a large amount of low-grade refractory waste material or even soil is used to fill it. This neglects the scientific rationality of the lining structure and refractory material performance, which is not only useless for kiln body stability and insulation but also increases the kiln body load, making the kiln foundation inevitably need to be reinforced, resulting in an invisible increase in construction investment. This phenomenon must be taken seriously.
Flue Gas Treatment System of Lime Vertical Kiln
Another key technology of the mixed material mechanized lime vertical kiln is the flue gas treatment system. The top flue gas treatment system of the vertical kiln has become a focus of enterprise attention and investment. The cyclone+bag filter+spray desulfurization process path for top flue gas treatment has been basically formed but has some unreasonable problems: first, the top sealing is not tight, causing changes in the amount of flue gas; second, the flue gas treatment system does not match the vertical kiln capacity, leading to poor operation of the flue gas treatment system; third, the one-to-two or one-to-many process configuration is unreasonable.
Combustion-supporting Drum Wind of Vertical Lime Kiln
The last key technology of the mixed material mechanized lime vertical kiln is the combustion-supporting drum wind. The flow rate and velocity of the wind for calcining are directly related to the production capacity of the kiln. The operation and management of vertical kiln ventilation play an important role in ensuring the reasonable supply of air volume required for the combustion of calcining fuel, the reasonable distribution of air flow on the cross-section of the kiln, and ensuring the production capacity and quality of the vertical kiln. The importance of combustion-supporting drum wind has been widely recognized in the industry, but there are still problems, such as unreasonable fan selection, mismatch between air volume and pressure, mismatch between air duct size and fan, arbitrary vertical kiln wind device, and unreasonable ash sealing.
