Dosing and mixing specialist Ecochem Pumps has completed the design and fabrication of two identical chemical reagent dosing systems for the platinum mines.The systems will effect round-the-clock dosing within customer concentrator plants, automatically maintaining a flow rate proportional to the rate of ore feed. Over or under-dosing is not possible. Ecochem Pumps successfully installed and commissioned several other similar systems over the past two years, each one guaranteed to achieve a full 12-month maintenance-free operation interval across a 24/7 duty cycle. Results on-site have to date achieved an 18-month operational interval without a single breakdown on any of the dosing pumps. Accurate reagent dosing is a vital component of optimum platinum recovery. If any of the four key reagents is under-dosed, valuable platinum is lost to the tailings and dumped in the slimes dam. Conversely, over-dosing to ensure full mineral recovery needs to be avoided because of the very high cost of reagents, and potential environmental damage caused by excessive use. At the heart of the two dosing systems are a number of API 675 and ATEX-compliant Maxroy industrial dosing pumps from Milton Roy. During design, Ecochem’s projects division provided for very close monitoring of pump dosing rates by including magflow meters on the chemical dosing lines. After delivery, these will be integrated with the customer’s PLC and SCADA control systems to allow measurement and monitoring of the actual chemical dosing flow rate of each pump, and comparison with a control set-point.
Dosing rates will be automatically adjusted either by variable speed drives that change the motor speed or in some cases by electric actuators varying stroke lengths.Pumps throughout the two systems are equipped with calibration run pots on the suction side. These pots allow operating and engineering staff to perform online calibration run tests to independently verify actual flow rates without any risk of contact with the chemicals. Without the pots, these tests are usually carried out by hand, under conditions of risk, using a bucket and stopwatch. The Maxroy pumps utilised in Ecochem’s two dosing systems feature 316 stainless steel. All pumps have been fitted with double diaphragms and rupture detection warning to enable continued operation even after diaphragm rupture. Continued operation is further ensured by integrated pressure relief valves inside the liquid ends to protect the diaphragms and dosing lines. Should any pump be inadvertently started against a closed valve or blocked dosing line, the very rapid rise of pressure in the liquid end would be safely bled away internally. In the event of diaphragm rupture, replacement is enabled by the inclusion of a standby pump in each system. Integration with the PLC and SCADA systems facilitates automatic pump changeover so that plant production is not impacted. In South Africa, Ecochem Pumps is the sole authorised agent for the Milton Roy dosing pump range commonly used in processing industries.