How dry cement is made: wet and dry methods of cement production, technology

Since cement is the foundation of concrete, it is an essential component in construction. Knowing the manufacturing process for dry cement can help you understand its quality and functionality. The wet and dry processes are the two main ways that dry cement is made. Every one has a different technological impact on the finished product.

In the wet process, raw materials are combined with water to create a slurry, which is then heated in a kiln. Although this process can use a lot of energy, the product is frequently more consistent. As opposed to this, the dry process entails combining the raw materials while they are still dry and heating them in a kiln. This approach uses less energy and produces less waste, making it more ecologically friendly.

We’ll go into great detail about both approaches in this post, looking at the technology underlying each procedure and how it affects cement quality. Knowing these techniques will provide you important insight into the cement manufacturing industry, whether you’re a professional in the building industry or just interested in learning more about the creation of this necessary material.

Wet cement production technology

The wet method of producing cement starts with the same steps as any other method: solid limestone is extracted from quarries and crushed into various-sized pieces. After that, the pieces are crushed in specialized crushing units to a maximum of 8–10 millimeters of limestone fraction.

After that, clay is transported from the quarry to the plant, where it is crushed by rollers to a maximum particle size of 100 millimeters. The mixture of crushed clay is soaked in mash to produce a 70% moisture content clay slurry. After that, the slurry is transported to a mill where limestone is combined and ground with it.

After that, the slurry—whose moisture content is already 40%—is transferred to a vertical pool for the last stage of adjustment. Because the proper chemical formula for the slurry composition is formed and guaranteed here, this operation is crucial.

Following an inspection of the slurry’s quality, it is moved to carry out the next steps: the cement mass is moved from the vertical pool to the horizontal one, where it is stored until it is sent to the kiln for firing. Using compressed air, the raw materials in the horizontal pool are continuously mixed mechanically. This keeps the slurry from settling and allows for total homogenization.

The composition of the sludge is changed in a horizontal pool when raw materials with an unaltered chemical composition are used in the production of cement.

Subsequently, the sludge is fired in a kiln to produce clinker. After that, the clinker base is transferred to an industrial refrigerator for cooling. Following that, the clinker is broken down into a powder and fed back into the mill tanks.

The construction of an additional room is required in the event that the sludge firing process calls for the use of solid fuel (where the coal will be stored and prepared). The clinker firing process is streamlined if the technological scheme of cement production necessitates the use of gaseous or liquid fuel.

Cement is transported from the mill bunkers to designated rooms for storage at the end of production. Here, lab assistants check the product’s quality and identify its brand. The cement cannot be sent to the packaging machines until the test is finished.

Advantages

It is important to weigh the benefits and drawbacks of the wet method of producing cement. This process has unique characteristics, just like any other technological process.

• Reduction of technological costs for grinding raw materials – clay and chalk are perfectly wetted in water in the pool during primary processing, due to which they are ground easier and simpler.
• Transportation, averaging, adjustment of sludge are carried out more easily, more safely from an environmental point of view, especially in comparison with similar processes in the production of cement by the dry method.
• Much less dust is generated.
• Kilns are simple in design, reliable, have a high space utilization factor (varies within 0.89-0.91).
• It is possible to use components with a fairly "variegated" (different) chemical composition in production, and good homogenization of sludge is also ensured.

Disadvantages

The wet method of producing cement has a few drawbacks, but they are real and cannot be disregarded.

1. High specific consumption of thermal energy during the roasting process of raw materials. The raw materials supplied for firing have an average moisture content of up to 45%. And for the evaporation of moisture and proper heating of the components, up to 6800 kJ/kg of thermal energy or 35% of the thermal power of the furnace is required. Due to such calculations, part of the kiln functions as a drying unit with subsequent complications.
2. High level of material consumption of firing furnaces along with not very high productivity.

These flaws result in comparatively low labor productivity, high operating and technology expenses, and ultimately high production costs.

Wet and dry processes are the two basic techniques used in the production of dry cement. The wet method involves combining raw materials with water to create a slurry, which is then heated to create cement. Before being heated, materials are combined and ground into a fine powder in the dry method. Every method has a different technology and efficiency that affects the final product’s cost and quality. It is easier to select the optimal technique for making cement of superior quality when one is aware of these processes.

Dry production technology

A different technological scheme is used in the production of cement by the dry method. After being extracted from the quarry, limestone and clay are crushed and delivered to the separator mill. They are mixed, ground, and dried here. After being transferred to mixing equipment, the final mixture is combined with compressed air. Currently, the cement’s chemical composition has also been modified.

When using a clay component, the raw material is mixed by feeding it into augers and wetting it down with a small amount of water. Strong granules are produced, fed into the kiln to be fired, and their maximum moisture content is 14%.

Dry method raw material firing can be done in a variety of kilns; in this instance, raw material preparation is given extra consideration. Furthermore, the later phases of production resemble the wet method.

Advantages of the technology

The dry method has certain advantages over the wet method that need to be considered in calculations (for example, when organizing a cement production business).

• Relatively low specific energy consumption of heat for clinker firing – within 2900-3700 kJ / kg.
• The volume of furnace gases is 30-40% less, they can be reused for drying raw materials and significantly reduce energy costs for clinker production, reduce dust removal costs.
• Significantly lower metal consumption of kilns with increased productivity compared to wet technology. The capacity of kilns with the "dry" method is 3000-5000 tons per day, which is 1-2 times more than similar equipment of the wet method.
• No need for powerful water sources.

Disadvantages of the technology

The technology has drawbacks in addition to its clear benefits.

• Significantly more dust is emitted, which complicates compliance with sanitary standards, environmental protection rules.
• Complexity of the design of kilns and their exactingness in terms of fluctuations in the chemical composition of raw materials, its degree of humidity, dispersion.
• Relatively low utilization rate of furnaces – somewhere around 0.7-0.8.

Differences between wet and dry production technology

Each method of producing cement has its own subtleties, advantages, and disadvantages. However, there are some important factors that have to be considered first when organizing a business and figuring out costs and profits. The primary drawback of the wet method of producing cement is the extremely high energy intensity of the entire process, which causes the final product’s price to rise.

Since dry technology is less safe for the environment and more hazardous, it will cost a lot of money to remove this factor. In addition, the production process itself is more affordable overall, enabling you to reduce the cost of the finished good.

Features of the semi-dry method

With a few exceptions, the semi-dry method of producing cement is fairly similar to the dry method. There are roughly 10–20 millimeters of raw materials that go through the granulation stage, and the humidity range is 11–16%. The final product, the granules, are fed to a conveyor calciner after the raw materials are first burned in Lepol kilns.

After going through the granules on the grate, gases leave the kiln. As a result, the raw materials are heated to 900 degrees, which causes them to dry completely. This type of heat treatment helps the mixture decarbonize by 25–30%, which is essential for production. The last step in the process of making cement is sending the raw materials to the kiln.

Shaft kilns are another method for firing granulated cement; in this instance, coal particles are used for granulation, and the cement is then stored.

We can gain insight into the fundamental procedures behind a material that serves as the foundation for contemporary construction by knowing how dry cement is made. Every method, wet or dry, has specific benefits and uses. The wet method uses a lot of water and energy but yields a more homogenous product because of its thorough mixing and processing. The dry method, on the other hand, is more sustainable because it uses less energy and water, making it more environmentally friendly.

The quality and functionality of the finished product are affected by each method, so it’s critical to select the best one for your particular construction requirements. Understanding how these processes operate helps us to better understand the intricacy and skill required in the manufacture of cement.

Technology will continue to advance and enhance cement production as the construction industry develops. Accepting these innovations contributes to ensuring that we maintain high standards for building materials and make efficient use of our resources.

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