Importance

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Abstract

A method of reblending sand in a classification tank having multiples stations and discharge valves within each station includes the steps of delivering sand to the tank; calibrating the tank to analyze the raw feed material and develop discharge rates, flow multipliers, and a mathematical model of the tank; and inputting a specification or quantity and sieve size distribution for a reblended sand product into a computer for controlling the tank. Then the tank is operated in a production mode and the discharge valves at each station of the tank are adjusted by the computer for percent open time and discharge rate. With one algorithm, the computer identifies which station has the most of a sieve size that is out of specification and diverts material at that station by closing the appropriate discharge valve(s). In another algorithm especially adapted to minimize fines, the computer begins with the station most remote from the inlet and diverts material by repeatedly reducing the valve open percentage of the appropriate valve at that station by a given amount until the specification is met or the valve is always closed. Once the valve is always closed, the computer moves a station closer to the inlet and repeats the process. Once a primary product is being produced to specification, the same algorithm can be used to control the production of a secondary product.

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First Claim