Location: Penticton, British Columbia
Year Completed: 1996
Deliverables: 4MMBtu/h Tailing Pond Water Heating System
In late 1996, Inproheat supplied a 4 MM Btu/h pond water heating system for Homestake Canada (since acquired by Barrick Gold) Nickel Plate Mine. This old gold mine is located near the top of Nickel Plate Mountain near the town of Hedley, approximately 45 minutes by car from Penticton, BC.
Nickel Plate mine was exhausted in 1996 and was undergoing the reclamation process. Part of the process involves the elimination of existing large process water ponds and deep wells.
Water in these ponds contains various minerals and chemicals used in the gold extraction process. Before water was permitted to be discharged to the local river it had to be treated to remove dissolved chemicals and metals. A new treatment plant was built to facilitate this process.
The chemical treatment process requires that the pond water be heated to 68º F. The inlet temperature is relatively consistent throughout the year at between 38° and 42º F. A continuous flow of 120 USgpm has to be maintained to lower the pond level. Rainfall and groundwater continuously seep into the pond and becomes contaminated with the resident chemicals.
The addition of nitrates being leached from surrounding mounds of tailings complicates the process even further. The resulting pond water is chemically hard and easily deposits mineral scale inside pipes, tanks and heat exchangers.
The requirement for high efficiency is dictated not only by economics but also by logistics of trucking propane to the remote mine location on the top of the mountain. Consideration had to be given to reduced staff levels at the mine. The heater had to operate with minimal operator attention and without a certified boiler operator on site.
Inproheat designed and manufactured a 4 MM Btu/h submerged combustion system. The unit was skid-mounted, prepackaged and prewired including the heating tank, submerged combustion burner, combustion air blower, propane fuel train, inlet water shutoff and control valves, discharge pump, and control panel. The fabricated steel vent stack was shipped in two sections. Homestake provided the water inlet and outlet connection and propane supply. Water is pumped from the ponds into a storage tank adjacent to the heating system and then fed into the heater by gravity. An inlet control valve maintains the water level inside the heater.
On the discharge side, a stainless steel centrifugal pump with variable frequency drive control removes heated water from the heater. The pumping rate is controlled by the plant DCS based on the load index. The heater is connected to a 15 psig propane supply. It can operate automatically without supervision, using a remote start/stop signal from the plant DCS.
Inproheat commissioned and started the system up in November 1996. A number of combustion tests were conducted. The water discharge temperature was set at 68º F, with stack temperature between 67 and 69º F. The resulting overall system efficiency was calculated at 98% of the propane higher heating value, compared to a typical maximum of 82% efficiency of other heating methods.