Articles

Energy Efficiency and Cost Savings in Cement Production Using Refractory Material

by Sucheta S. Digital Marketing professional
Cement is an inorganic, non-metallic substance with hydraulic binding properties used in construction materials as a bonding agent. A fine, usually grey coloured powder made up of a blend of hydraulic cement minerals, which are supplemented by one or more forms of calcium sulphate. It is mixed with water and forms a paste that hardens due to the formation of mineral hydrates of cement. Cement is the concrete binding agent which combines cement, mineral aggregates, and water.  Concrete is the most important construction material in a variety of applications.

Why Refractory is Essential in a Rotary Kiln in the Cement Industry?

High temperatures are used in rotary kilns to produce a chemical reaction or a physical change in a substance. In most cases, an exposed carbon steel shell will be destroyed by these high operating temperatures. As a result, refractory is used.
Refractory is only used in direct-fired rotary kilns; heat is transferred mainly via the kiln shell wall in indirect-fired rotary kilns. Another barrier for heat to move through until it comes into contact with material will be refractory, lowering the efficiency of the process. As a result, indirect-fired kilns usually use a more heat-resistant shell rather than refractory.

Direct-fired kilns normally do not use combustion chambers, so the flame is in continuous direct contact with the internals, necessitating the use of refractory. The temperature of a flame will vary from 1600 to 3200°F (depending on the amount of air present) – a harsh manufacturing condition that carbon steel cannot endure.
Since the primary function of refractory is to protect the kiln shell, it also helps to minimize heat loss, saving both energy and costs. While a kiln with poor refractory protects the kiln shell, it also allows considerable heat loss, reducing overall process efficiency and increasing operating costs.

Energy Saving & Cost Reduction Process Using Appropriate Refractory Material:

In terms of cement plant operations, the cost of production can be broken down into the following main categories:

1.    Optimizing the cost of raw materials: The first step in reducing raw material costs is to benchmark and determine which of the existing raw materials is the most cost-effective and technically viable for use in cement manufacturing; are there any substitute or surplus raw materials that can be used in the cement manufacturing process? If suitable waste or substitute raw materials are available, they will usually be less expensive than the traditional raw materials used in the cement manufacturing process.In certain regions, the limestone contains variable MgO content, so the high MgO limestone is reserved for cement grinding instead of dumping/landfilling since it is not the combined MgO that causes expansion and is only a free Hard Burnt MgO produced for pyroprocessing which is not good from the quality standpoint. The total MgO content exists under different international standards, the total MgO must therefore be reasonably smaller than the maximum permitted level as defined by international standards.

2.    Optimizing the cost of fuel: The sulphur content is a critical aspect of fuel selection; it is also a limiting factor in fuel selection; the higher the sulphur in the fuel, the more alkalis are required to balance it out in order to avoid buildup/coatings in the pyroprocessing. Furthermore, in cement standards, there is a limit on total SO3 in cement, higher sulphur input from pyroprocessing means less gypsum can be added to reach that max level if gypsum is cheaper than clinker than high sulphur from fuel means less addition of gypsum which means the high cost of production not only due to materials price but also because gypsum is much soft in comparison to clinker. As a result, the cement mill produces a low output.For instance, pet coke can increase the clinker SO3 content with a high substitution percentage and thus increase the power consumed by the cement mill.

3.    Optimizing the cost of electricity:The key to lowering power costs is to use the right refractory raw materials and produce high-quality process materials like clinker, which requires the least amount of grinding energy. Grinding energy can be saved by removing, reducing, or replacing harder grind materials / abrasive materials with softer materials. Appropriate lab tests are needed to determine which materials need more energy to grind, which can then be compared to field results in real industrial usage.For example, when it comes to Siliceous or Argillaceous materials, Silica may be derived from a variety of raw materials such as Clay, Shale, Slate, Sand Stone, and Silica Sand. However, within the kiln, each has its own characteristics such as abrasiveness, hardness, and combinability behaviour, resulting in different raw mill performance, kiln operating parameters, and power consumption.Similarly, limestone may be of varying consistency and must be considered and used in conjunction with argillaceous materials. In contrast to moderate purity limestone, very high purity limestone will be difficult to grind and combine; marl will be much easier to grind and combine in the kiln.

Conclusion:
The cost of cement production can be reduced/minimized by carefully analyzing the available refractory materials and fuels, and then choosing and using the best among them.  Furthermore, refractory products should be purchased from a top refractory company to avoid wasting money on ineffective materials.


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About Sucheta S. Junior   Digital Marketing professional

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Joined APSense since, April 6th, 2021, From Delhi, India.

Created on Apr 8th 2021 10:14. Viewed 190 times.

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