The Problem
The Cemex "Clinchfield 2000 Project" resulted in a 50% increase in plant production capability at this former Southdown/Medusa-Citadel plant. Providing a continuous, uniform feed of sticky bulk solids like 20% moisture content limestone and 25% moisture clay was a major challenge and anticipated to create a process bottleneck.
Jenike & Johanson were contracted to develop functional design recommendations for the storage bins and feeders required to handle various raw materials at the plant so that the production capacity increase could be met.
Jenike & Johanson's Solution
Using flow properties test results prevented the use of error prone guess-work commonly involved with hopper design. Based on the cohesive strength test results for the clay, gravity discharge from a mass flow bin was unlikely, especially after overnight storage at rest. Therefore, a special bin was designed to handle the clay without convergence. This unique clay bins are shown in the adjacent photo.
A mass flow transition hopper, pin gate, feeder interface, and apron feeder is used to feed limestone into the grinding process. The apron feeder interface is critical for maintaining mass flow in a bin.
The Result
As a result of the installed mass flow storage bins and apron feeders, Cemex has been able to provide reliable feed of the limestone and clay into the grinding process. Since the bins have been in operation, substantial savings have been realized because operators are not required to use brute force methods to initiate flow. Furthermore, product and process quality improvements have resulted because of the consistent mill feed with each raw material.
Antonio Deluca, the plant manager at Cemex Clinchfield, has recently confirmed that over the past decade, these bins and feeders have provided reliable discharge of the sticky limestone and clay, and additionally, similar mass flow bin and apron feeders designs have been implemented for other raw materials like raw mix, mill scale, and iron ore.
