Stacker and Reclaimer Systems For Cement Plants

Key Benefits

All stacker and reclaimer systems are:

• Ideal for both prehomogenisation and buffer storage
• Designed for heavy-duty operation
• Compatible with products from all types of crushing installations

Heavy-duty performance

Ideal for both prehomogenisation and buffer storage of raw materials, FLSmidth stacker and reclaimer systems have an impressive track record of performance. FLSmidth has commissioned some of the largest stackers and reclaimers in the cement industry, matching kiln throughputs of up to 12,000-13,000 tpd. We offer an extensive selection of stacker and reclaimer systems to meet precisely your needs. Selection criteria When planning which stacker and reclaimer system to use, you will need to consider various questions before selecting type and size:

• Homogenising effect required
• Future uprating of the store
• Open or roofed store
• Mill feed system
• Chemical characteristics of the materials to be handled

Prehomogenisation

Prehomogenisation is often necessary in the cement industry, in cases where the raw material chemical composition varies greatly. Prehomogenisation is used primarily for the main components in cement production, i.e. limestone and clay. With the increasing variation in the grades of coal used for coal firing installations, there is a growing need for prehomogenisation and storage of coal. Depending on the properties of the coal used, a prehomogenising or buffer store is used. 

Methods

Blending Effect

The blending effect [ H=Sin/Sout] of a homogenising stacker/reclaimer system is generally determined as the ratio between the standard deviation Sin of one leading chemical parameter of the store input and the standard deviation of the same chemical parameter Sout of the store output. In principle, the standard deviation is reduced by stacking the material in a large number of layers and subsequently reclaiming these layers. Theoretically – without taking the particulate nature of the material into account – the blending effect is closely linked to the square root of the number of layers reclaimed simultaneously with stacking. However, almost every reclaimer operates with some kind of scraper or bucket chain arrangement, and especially with coarse particles the actual blending effect is lower than the theoretical value because it is limited by the number of particles between one pair of scraper blades or within a bucket.

Stacking methods

Longitudinal stores: The most commonly used stacking methods are Chevron, Windrow and Cone Shell. Basically these methods consist of stacking a large number of layers on top of each other in the longitudinal direction of the pile. According to the Chevron method material is deposited by the stacker moving to and fro over the centre line of the pile. The Chevron stacking method causes segregation of the material with fine particles in the central part of the pile and coarse particles on the surface and at the bottom of the pile. To ensure proper blending a Chevron pile must therefore be reclaimed from the face of the pile, working across the entire cross section. According to the Windrow method material is deposited from a number of positions across the full width of the pile. The Windrow method prevents regregation and ensures more even distribution of fine and coarse particles across the pile. The Windrow method is preferred in cases where the reclaimer is only operating in one part of the pile cross section at a time or in cases where segregation would make an open pile base unacceptable – typically in coal stores. The Cone Shell method is often used in cases where homogenisation is not necessary. The pile is formed by depositing material in a single cone from a fixed position. When this conical pile is full, the depositing of material moves to a new position and a new cone is formed against the shell of the first one. This process continues in the longitudinal direction of the store until the stockpile is complete. Circular stores: Continuous Chevron stacking is the most commonly used method. The circular store has a round base with aring-shaped pile being continuously stacked at one end and reclaimed at the other. Stacking takes Chevron Windrow Windrow – open pile Continuous Chevron