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Mining operations generate waste, some that is obvious and some that is less easy to see. Most mining operations have to deal with overburden, fines, soil, and other debris. Process wastewater and storm water are also common concerns in mining. Disposal of packaging materials, conveyor belts, truck tires, and machinery components can also be an expensive problem. Some of the less obvious wastes are leaking oil from hydraulic systems on trucks, excessive energy use for pumping water, excessive fuel use in heavy trucks, and premature wear or failure of tires, hydraulic cylinders, and conveyor belts. Below are some general methods to reduce waste in the mining industry.

Reducing Electricity Costs

• Use high efficiency electric motors. Replacing standard efficiency motors with high efficiency motors can save money. If a standard efficiency 100 HP motor (90% efficient) operates 7,000 hours per year, it will use 580,220 kilowatt-hours of electricity. A high efficiency 100 HP motor (95% efficient) will use 549,680 kW-hrs and will save $1,526 in usage cost at $0.05 per kW-hr. It will also lower the amperage demand which can save additional cost. A software package called MotorMaster™ is available from the Department of Energy, and it can help determine which motor is best suited for a particular application.

• Use cogged V-belts instead of standard V-belts. Cogged V-belts are 1 to 2% more efficient than standard belts and cost no more to purchase.

• Turn pump motors off when they are not needed. Often pumps are left running and moving water even when the mine is not running. Installing float switches on pumps to control when the pump runs is one way to save energy and avoid damage due to air induced pump cavitation.

• Tension and align V-belts and flat belts properly.

• Reduce peak demand by avoiding running several large motors at the same time. For example, running two 100 HP motors will have a demand of approximately 150 kW if they are run simultaneously. Running the motors separately will reduce the demand to 75 kW. Since electrical demand costs amount to one-half of industrial power bills, reducing demand can result in substantial savings.

• Replace low efficiency lighting with higher efficiency lights.

• Repair leaks in compressed air systems. A single small leak can cost $350 per year in electric costs.

• Combine electric power meters. Two meters are typically billed at a higher rate than one meter.

Water Use and Pumping Costs

• Reuse cooling water. For example, a crusher can be fitted with a cooling water system and a dust suppression system, both of which use 5 gallons of water per minute. Repiping so that the cooling water is diverted after use to the dust suppression system will reduce water use and pumping costs. At 5 gallons per minute operating 24 hours per day, this modification can save 2.5 million gallons per year and 1,200 kW-hrs in power use for pumping.

• Fit water hoses with self-closing spring loaded nozzles.

• Avoid cleaning spills with water hoses. Use a broom or floor sweeper.

Reducing Oil Use

• Fit hydraulic cylinders with dust boots. Oil change frequency, damage to hydraulic cylinders, and leaks can all be reduced by preventing dust from entering into hydraulic systems. Dust enters the system through hydraulic cylinder seals. When the cylinder is extended, dust adheres to the cylinder rod surface. When it retracts, the dust damages the seal and rod, and contaminates the oil. A simple solution to this problem is to fit all cylinders with rubber accordion style boots that cover the rods fully. Accordion style boots can be purchased from cylinder manufacturers and independent manufacturers. Boots are available for all types of cylinders from several inches to five feet or more in length.

• Fit truck engines with high quality air and oil filters. Oil change frequency and engine damage can be reduced.

• Test engine and hydraulic oil. Most oil suppliers can provide lab testing to determine optimum changing schedules to avoid equipment damage and maximize the life of the oil.

• Clean cooling coils and radiators on hydraulic units. Overheating is a common cause of oil leaks and oil failure.

Increase Truck Tire Life

• Maintain mining roads to have no more than an 8% grade. Tire life will increase.

• Maintain roads and remove large rocks to avoid tire damage.

• Maintain proper air pressure in truck tires. Check at least once per day.

• Do not overload truck. Filling the trucks to maximum capacity is desirable; overloading can cause tire damage.

Increase Truck Fuel Economy

• Decrease idling time. Often trucks are left idling for extended periods while filling or waiting to dump loads. Modern diesel engines are easy to start if properly maintained and do not require idling. Sometimes this is done in order to maintain air conditioning and heat to the driver. Separate heating and cooling units that operate off of a small motor or batteries can be fitted to trucks to maintain driver comfort even when the engine is off.

• Maintain engines properly, including replacement of air and oil filters. Clean cooling coils and radiators to prevent overheating.

• Load trucks to their rated capacity — don't overfill or underfill.

• Spent lubricating oils can be mixed with diesel fuel at the ratio of 1 gallon of oil with 99 gallons of diesel fuel. With proper filtration, the mixture can be used to power diesel truck engines.

Recycle Wastes

• Paper, cardboard, plastic, pallets, oil, glass, tires, batteries and many other materials can be economically recycled.

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