Ensuring Reliable Measurement of Feedstock and Preventing Clogging from Fly Ash

Ensuring Reliable Measurement of Feedstock and Preventing Clogging from Fly Ash

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The manufacturing process for cement requires raw materials like clay and limestone. Limestone rock is obtained from the quarry and transported by truck to a close by cement plant.

The rock acquired from the quarry is sent to a grinding plant where it is crushed prior to being reduced to a fine powder. The raw materials contain 20% clay and 80% limestone. They are subsequently kept in the pre-homogenization pile, which is known as the raw mix. Figure 1 shows a layout of cement production.

Cement production process

Figure 1. Cement production

Challenges

The raw materials are kept in piles in very large warehouses or silos, but these materials often settle in uneven shapes. This makes it complicated for end users to review inventory levels.

With its unique multi-point surface mapping capabilities, the 3DLevelScanner system from BinMaster can accurately and consistently measure the amount of raw mix stored in different types of silos, open bins, or warehouses.

Binmaster

Figure 2. BinMaster’s 3DLevelScanner

Blending and Storage Silos

As part of the raw material homogenization process, a uniform mixture is stored in silos.

Challenges

The raw materials are kept in large silos, often settling irregularly. This makes it difficult for operators to review the actual inventory levels.

BinMaster’s 3DLevelScanner has unique multi-point surface mapping capabilities to accurately and reliably determine the amount of mixture stored in the silos. The optional 3D visualization tool of the 3DLevelScanner also provides operators with real-time visualization of mixture distribution within the silos.

Filter (ESP)

Fly ash is collected and removed from the flue gas via electrostatic precipitators or fabric bag filters placed at the furnace outlet before the induced draft fan.

The fly ash is captured in hoppers under the bag filters or precipitators and removed from them on a periodic basis.

Challenges

Hot fly ash is continuously filled in ESP hoppers. The fly ash sticks to the walls of the hopper due to the collective effect of temperature and humidity. This can cause material buildup and may clog the hopper, which can break the ESP plates.

For end users, it is very important to continuously monitor and understand the distribution of fly ash in the hoppers. With access to real-time, accurate data, preventive action can be implemented to empty the hoppers quickly, and to clean and carry out the maintenance work if and when required.

This should be done to prevent the hoppers from clogging and the associated risk of damage to the ESP plates. Damaged ESP plates can also create health and environmental concerns.

At present, the only available technology is 3DLevelScanner, which enables continuous measurement of the volume level of fly ash within the ESP hopper.

With the optional 3D visualization tool, end users can view the exact allocation of material within the hopper and identify the material buildup as it occurs. This allows maintenance work to be scheduled in time, so that costly and spontaneous process interruptions as well as damage to the ESP plates can be prevented.

In cement plants that do not employ the 3DLevelScanner technology in their ESP process, emptying the hopper may not be linked to the filling process. There is no consistent method to determine the volume of fly ash in the hopper, so a timer is set to start emptying, irrespective of the amount of fly ash left in the hopper.

This renders the process inefficient and causes the air compressors to work needlessly. With the 3DLevel Scanner, users can coordinate and automate the emptying and filling of ESP hoppers in the most reliable way.

Coal Storage

Coal is usually kept in silos, which feed the coal to the kiln.

Challenges

The coal silos contain several hours supply of coal. This coal is fed into the coal handling system, which feeds the coal to the kiln. If a coal silo is fully emptied, then the kiln would need to be shut down.

End users look for optimal technology that can provide accurate and continuous readings regarding the amount of coal accommodated in a given silo. The 3DLevelScanner system from BinMaster provides accurate measurements even in very harsh and dusty conditions that are typical of a coal storage environment.

Clinker Storage

A pre-heating tower is fed with the raw mixture at a temperature of 800°C (1472°F) prior to returning to the upright rotary kiln, where it is heated to 1450°C (2642°F). Combustion promotes decarbonation, a chemical reaction that emits CO2 gas trapped in the limestone.

The fired materials assume the form of hard granules known as clinker, which is similar to pellets and measure the size of marbles. After re-cooling, the clinker is stored in silos and subsequently changed into cement based on the production needs.

Challenges

Normally, clinker silos have an extremely large diameter and can house a large volume of material. The material is quite dusty and fed into the silo at an extreme temperature of 100°C (212°F). However, a major challenge for end users is to discover the amount of clinker kept in the silo.

The 3DLevelScanner system from BinMaster is designed to give an accurate measurement of volume regardless of any size of clinker silo.

In addition, the optional 3D visualization tool of 3DLevelScanner enables the end user to observe material distribution within the silo and to constantly track inventory levels. The HT model of the 3DLevelScanner is suitable for clinker silos and can be used in adverse environments.

Additives Storage

Limestone is initially mixed with clay, crushed in a crusher, and subsequently fed into the additive silos. Following this, sand, fly ash, and slag are combined with the clay and limestone in carefully controlled volumes. This mixture is then transferred to in a roller mill, where it is ground to a fine powder.

Challenges

The main challenge encountered by end users is to vigilantly control the volume of additive introduced to the cement production process.

Fly ash and slag can be very dusty and susceptible to inconsistent topography as they are loaded and released from the silo, while sand may not be able to flow freely based on the size and shape of particles and the amount of moisture present.

The 3DLevelScanner uses dust-penetrating, multiple point measurement technology to accurately monitor the amount of additives in inventory. This allows the end user to produce efficiently, and to measure the cost-of-goods marketed with more confidence.

Cement Storage

Finished cement is a fine powder material kept in silos prior to being packaged into bags or supplied in bulk through tanker trucks.

Challenges

During the filling process, the finished cement generates a dusty environment. It is often kept in large silos, where material buildup can occur. However, this makes inventory control and management even more complicated.

BinMaster’s 3DLevelScanner determines various points in the silo and accurately measures the volume of stored cement. It performs consistently even in harsh, dusty environments.

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This information has been sourced, reviewed and adapted from materials provided by BinMaster.

For more information on this source, please visit BinMaster.

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