The system provides the following functions: (1) assays for copper and iron from ten process streams on a continuous rotating basis, (2) directs hardware to automatically flush and start up cone units based on measured performance variables, (3) provides continuous plant operating data and calculates metallurgical averages as well as production figures for shift and daily summaries, and (4) provides data logging capabilities.
The process of making precipitate copper is often called the cementation process. Scrap iron is contacted with the dilute copper-bearing solution derived from the leaching of mine waste dumps with water. Copper is precipitated under the general substitution reaction CuSO4 + Fe → Cu + FeSO4. To optimize the solubility and recovery of CuSO4 at Chino Mines Division, varying techniques to wet as much dump surface and volume as possible have been investigated. Head solutions to the plant historically have declined as flow was increased to offset loss in production.
Water is distributed to the dumps through polyvinyl chloride lined steel pipe and asbestos-cement pipe in sizes ranging from 10 to 16 in. in diameter. The dumps vary in physical size, material and particle sizes, permeability, and mineral content.
Originally, at the Chino Precipitation Plant scrap iron was loaded into gravity launders. Recoveries from the launders were satisfactory; however, iron consumption was two to four times greater than that theoretically required. The plant has been expanded several times, through the years, and the precipitation cone was developed and employed effectively for primary recovery of precipitate copper. Gravity launders were retained for second stage scavenging of the cone tailing.
Shredded scrap iron is loaded into the top of the tank by rail-mounted crane and electromagnet. Pregnant copper solution is pumped into the cone base through a diffuser. Rapidly precipitating copper settles down through the screen to accumulate on the sloped false bottom. The copper concentrate is intermittently discharged from the cone into decant basins for dewatering.
A cone and plant sampling system, flowmeters, level and flow switches, X-ray spectrometer, mini-computer system, and cone flushing control hardware make up the, cone monitoring system installed at Chino Mines Division.
Mine water to the plant is measured at the head water dam by a Parshall flume and electronic level transmitter. Flowrate to each cone is monitored by a magnetic flowmeter. Pressure-type level switches indicate loss of solution level in the cones, and mercury-tilt switches determine when the scrap iron level in the cones has dropped.
Interfaced with the plant sensors and X-ray analyzer is a Digital Equipment Corporation PDP 8/I computer programmed for process monitoring and control. The computer is equipped with an 8K word core memory and a 96K word disc storage capacity. Analog and digital signals from the field interact with the INDAC 8/2 operating system software to produce raw data for the in-house written supervisory programs. On the basis of process information, the supervisory program calculates and prints assays for process sample streams every fifteen minutes, computes averages and material balances for shift and daily reports, provides trend analysis, data logging and alarm functions. The operational status of plant equipment is kept current. The computer controls the process sampling system, X-ray spectrometer and operator’s console.
