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The Answer is Blowing in the Wind
At least that’s where Teichert Aggregates hopes to find a way to lower energy costs at one of its plants.
By Kerry Clines, Senior Editor
Editor’s Note: This article originally appeared in the May 2011 issue of Aggregates Manager.
California-based Teichert Aggregates began construction of its Vernalis Plant in 1999, completing it in 2000. “It was exciting,” says Paul Mercurio, production manager. “We started a new plant with new people. Fortunately, the economy was good at that time. We went up to double production shifts almost right away with the anticipation of growing the plant in the future. It worked out well.”
The new wind turbine towering over aggregate operations at Teichert’s Vernalis Plant is expected to supply 25 percent of the plant’s energy needs.
The Vernalis Plant replaced Teichert’s Tracy Plant located about 7 miles away, which was being depleted, and began supplying aggregate for the entire area. “Depending on the product, our sphere of influence could be as much as 60 to 80 miles,” says Jerry Hansen, plant manager.
“We go into the Bay area,” Mercurio adds. “Some products go as far as San Jose and some get into San Francisco, but it has to be a special product to get out that far. The majority of the products are centered in Stockton, Livermore, Modesto, Manteca, and all the surrounding area.”
Making adjustments
Since 2008, Teichert Aggregates, like every other aggregate operation in California and many aggregate operations nationwide, has been making adjustments to maintain business during the downturn in the economy. One such adjustment addressed not only lowering costs, but being environmentally friendly as well.
The plant was designed with distribution bins that allow material to be blended and sent in multiple directions.
“We had been talking about going forward, trying to figure out every way to keep our energy costs down,” Mercurio says. “We talked with Foundation Wind Power about the concept of installing a wind turbine on site. A group of investors put the money up for it, and we provided a site for them to place the turbine. We agreed to purchase the generated power favorable to our utility rate. The investors are responsible for everything else, including turbine maintenance.”
“The computer brain of the wind turbine is monitored in New York,” says Steve Grant, a former Vernalis Plant employee who now works for Foundation Wind Power. “Basically, electricity is generated at the top of the turbine and comes down cables. The blades turn, within reason, as fast as they can to generate as much power as they can. Another device senses what power is being sent and interacts with it to change it into 60 hertz, or 690 volts. That goes out to the transformer just outside the turbine where it is stepped up to plant voltage, which is 4,160 volts.”
There are sensors on top of the wind turbine that send wind speed and direction to the computer, which engages two yaw motors that turn the turbine into the wind. The pitch of the blades is adjustable as well. “The objective is to hold at a steady RPM,” Mercurio says. “They tune it to achieve that level.”
The wind turbine is expected to supply about 25 percent of the plant’s power needs, depending on wind speed and what’s running in the plant. “It’s an effort to have less of an impact [on the environment],” Mercurio says. “We have the land and the wind, and we consume the energy. The neat part is it’s locally provided energy. This is where you’re producing it, and this is where you’re using it.”
Twenty years is the average life span of this wind turbine. “By then, I’m sure there will be a better mousetrap, and we’ll probably want to replace it,” Mercurio says. “The challenging point is that it only produces energy when the wind blows, and usage depends on how much the plant is running. This is just dipping our toe in the water. We will see what it’s like and be sure it makes sense.”
Daily operations
The Vernalis Plant produces all sand and gravel. Larger stones are crushed, but there is no blasting. “We’re mining out of two different pits and blending the materials,” Hansen says. “We mine the pits and then fill them back in with the clay and silt that washes out of the material. The pit is composed of alternating layers of aggregates and clay, and we use scrapers to take the layers out in the reverse order they were put in. So we’re effectively harvesting — taking the good, relatively speaking.”
“That’s why we use scrapers,” Mercurio adds. “We skim horizontally to get the rock off, then remove the clay, then go back to the rock. You can’t be that selective with other types of equipment. We have self-elevating scrapers with paddle wheels, and they can take a relatively thin lift. The paddles rotate, pick up the material, and break up the clumps.”
The traffic patterns in the pits are all one way so the three or four scrapers that are usually working each day don’t cross paths, and the risk of a head-on collision is eliminated. The scrapers make the loop, then dump their loads into a grizzly feeder over an earthen hopper that feeds the material onto a conveyor belt, which carries it up to the processing plant.
Material goes through rotary scrubbers and vibrating screens. The three-eighths inch minus goes into a bucket wheel, which scoops it up and dewaters the material so it can be conveyed, then dumps onto a conveyor that carries the material to the concrete aggregate (CA) screens. “Bucket wheels are pretty uncommon,” Mercurio says. “You don’t see them around rock plants very often. You normally see a fine material washer.”
At the CA screens, the material is washed and sorted. “We make 1 by 4 pea gravel, bird’s eye, and concrete sand,” Hansen says. “The 1-inch plus goes out to feed our primary crusher. It then goes through a screen to get sized. The oversized goes back to our secondary crushers. The inch and a half goes to one stockpile, and the minus 1-inch goes to MA (mineral aggregate) screens where it is sized to make our three-quarter, half, three-eighths, and crusher dust.”
Tunnels beneath every stockpile contain a conveyor that transports the material to distribution bins. “The plant was originally designed with distribution bins because each one of the products can go so many different ways,” Mercurio says. “Underneath each of these distribution bins, there are feeders. You can run each one at a different rate to blend products. One belt returns material to the crusher if you want to recrush it, and another belt is a blending belt that goes out to the stacker where you can blend any proportion of any product that you want. Another belt goes to the asphalt plant so it doesn’t need a loader to feed it. We typically have two loaders servicing our customers.”
“The idea is not to touch the material again,” Hansen says. “We have the same thing on our concrete aggregate side where we wash it one more time before it goes up into silos to loadout into customer trucks.”
The plant is fully automated. Sensors detect when the level of material in a distribution bin or silo gets low and automatically turns on the conveyor to refill it. Even the asphalt plant will tell the feeder when it needs material and how fast to run.
Grant speaks fondly of his days with Teichert when the plant was being designed and built. “Teichert did it right,” he says. “All the conveyors have catwalks on them so it’s safer for a man to do repair work, such as changing a roller. Jerry [Hansen] could probably speak to the fact that the plant has a tremendous amount of flexibility and is extremely sophisticated. The plant is set up to blend product even when it’s not running. The plant’s rod mill is a piece of equipment that isn’t normally used in sand and gravel operations. It’s used more for mining and extracting ore. We bought it in northeastern Quebec, brought it here, and it’s being used to make sand.”
Hansen describes the rod mill as “a big cylinder similar to the super scrubber, only the inside is lined with cast liners and piled about waist deep with metal grinding rods that are 14 feet, 6 inches long and about 3½ inches in diameter when they’re new. The rods just lay inside the cylinder. We pump in water and aggregate and the cylinder spins. There are little lobes inside that lift the rods up, and then they roll back down. It gently grinds the rock into sand versus an impact crusher.”
“It’s more like what a river does,” Mercurio adds. “It grinds the rock on itself between the hard metal rods.”
Cost and community conscious
Teichert has adopted ways of being cost and community conscious at Vernalis Plant, as well as environmentally friendly. During the summer months, the plant operates in the mornings and ceases operation by noon. “From noon to 6 p.m., the peak time of power consumption on the grid, we take ourselves offline,” Hansen says. “Two reasons — it’s less expensive, and it leaves the power available for homes. It may not be as convenient for our guys as a traditional day shift, but they come in at 3:30 in the morning and are off by 11:30 a.m. or noon. They still have time to do other things, and it takes us offline during the peak. We do that every year — May through October.”
The repair shift comes on at 11:30 a.m. to get assignments for the day and handle repairs while the plant isn’t running. “That’s one thing we haven’t figured out,” Hansen says, “something that the rock doesn’t wear out. We just slow it with wear plates, rubber liners, urethane, and different alloys.”
EQUIPMENT LIST
McLanahan 8 x 25 super scrubbers (2)
SECO 6 x 14 single-deck inclined scalping screen
Simplicity 8 x 24 triple-deck inclined screens (5)
SECO 8 x 24 triple-deck inclined screens (3)
Svedala 5 x 14 single-deck horizontal screens (3)
Cedarapids 8 x 20 two-deck horizontal screen
Metso 6 x 10 single-deck dewatering screens (2)
Svedala 6 x 10 single-deck dewatering screen
Schenk 8 x 12 single-deck dewatering screens (2)
Metso HP500 cone crusher
Metso HP400 cone crusher
Metso HP300 cone crusher
Texas vertical shaft impact crusher
New Dominion rodmill-11 x 15.25
CFS density separator
Phoenix 80-foot clarifier
Weir slurry pumps (22)
Krebs cyclones (9)
Basic Technology FS400 bucket wheels (3)
Eagle Iron Works twin 44-inch coarse material washer
GreyStone twin 54-inch fine material washer
Kolberg twin 44-inch fine material washer
Trio single 44-inch fine material washer
Kolman 48-inch x 180-foot radial stacking conveyor
Plant conveyors (86)
Mobile Equipment
Caterpillar 633E elevating scrapers (5)
Caterpillar 633D elevating scrapers (2)
Caterpillar D10R dozer
Caterpillar D9R dozer
Caterpillar 14H motor grader
Caterpillar 623B water tanker
Komatsu WA600 wheel loaders (2)
Caterpillar 988F wheel loader
Komatsu WA500 wheel loader
John Deere 9320 tractor, w/18 cubic-yard scraper
Caterpillar 769C haul truck
Grove RT745 hydraulic crane
Kenworth 4,200-gallon water truck
John Deere 210 LE skip tractor
Caterpillar 246 skid steer