The Problem
At Lone Star Industry's Cape Girardeau, Missouri cement plant (now owned by Buzzi Unicem), reliable coal feed to the kiln is crucial for keeping the entire clinker production process on-line. When their coal supply was interrupted, plant personnel had only 15 minutes to restore feed before the pre-calciner and rotary kiln shut down.
Coal was transferred from outdoor stockpiles to a pulverizing roller mill via a belt conveyor and a triple-gate dump valve located at the mill inlet. When air leaked into the mill, the pulverized coal was not conveyed away efficiently. Coal accumulated in the mill and clogged the unit requiring costly downtime.
Jenike & Johanson's Solution
Jenike & Johanson recommended a Solids Pump® pressure-sealing unit to feed the coal with minimal gas leakage between the conveyor belt and roller mill which are at different air pressures. The Solids Pump® can operate with almost any solid that can be conveyed in a screw conveyor. It consists of three primary functional components: the inlet/conveying section; the sealing section; and the discharge section. The sealing section is designed so that the bulk solid being conveyed through the screw forms a plug of sufficient length and density to provide the necessary gas seal without high solids pressures.
The Result
Lone Star installed the Solids Pump® during an annual plant shutdown without any problems. Savings in reduced maintenance costs alone paid for the installation of the Solids Pump® within 8 months (return on investment was 115%)! After one year of operation, Lone Star decided to install a second Solids Pump® to supply coal to another mill.
