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Recycling Plant Crushes Energy Concerns
Posted By Contributed On January 3, 2014 @ 2:47 pm In Aggbeat Online,News | No Comments
Melbourne, Australia-based Alex Fraser Group processes millions of metric tons of waste construction material – such as concrete, asphalt, rock and glass that would traditionally end up as landfill – and turns it into products suitable for reuse as roadbase and other similar applications.
An RMIT Centre for Design study found recycled concrete products had a carbon footprint 65 percent smaller than the equivalent quarried products. And, as it built a state-of-the-art plant, Alex Fraser was able to cut its processing costs nearly in half.
Raising productivity without increased costs
Opened by the then-Victorian premier John Brumby on Nov. 18, 2009, the plant includes a number of state-of-the art features. Not only is its throughput up to four times greater than its previous line, its location – dug in to sit below ground level – suppresses noise, reduces dust levels and saves fuels, with loaders no longer having to haul material up to the hoppers, which are now at the same level as the road.
Gordyn & Palmer, an electrical engineering and contract company trained in the EcoSmart Electricians program (which certifies and accredits contractors in energy efficiency), designed a system that demonstrates how an innovative approach to sustainability can also give an organization the competitive edge.
“Crushing plants are traditionally heavy users of electricity,” explains Alex Fraser Plant Projects Manager Brent Alford. “We were determined to run the new plant as efficiently as possible and called in the experts. It’s no good having extremely effective crushing capabilities that consume so much power that they defeat any throughput gains. We’re extremely happy with the results all round from the new plant.”
The facility crushes an average of 3,500 to 4,000 metric tons per day, as opposed to the old plant, which struggled to deliver more than 1,000 metric tons per day. But the big news for this plant is it has reduced the cost of producing a ton of material by nearly half.
To achieve an increase in throughput, it’s not just a matter of turning up the speed of the conveyors to transport more material from one crusher to the next, or getting more raw feed dumped into the hoppers. A holistic approach must be taken to ensure the entire plant is running at its optimum and coping adequately with the demand.
“We need to keep all the components of the plant operating efficiently,” Alford explains. “To do that, we have variable speed drives throughout the plant controlling feed to the conveyors and crushers, to ensure we don’t suffer from bottlenecks or have a shortfall of material going through the plant at any one time.
“We also need to see what’s going on with each part of the operation – is one machine running slower than the others, is another drawing too much current? Is everything moving along nicely? And how much is all this costing us in power?
“We tendered the huge electrical component of the works to Gordyn & Palmer. Since winning the contract, they’ve been much more than just electrical contractors. Originally, that is what we set out to get, but the management team at Gordyn & Palmer helped with developing the programming to suit our specific needs. Often, we’d come up with new and intuitive ideas, and they were great with letting us know about new electrical equipment to enable us to implement the idea.”
Terry Hickey, joint managing director at Gordyn & Palmer, and the project team headed by Michael Steinfort were involved with the electrical installation at the plant.
“We were involved after the project was initiated and, due to our background in quarrying, we became part of the project team to help bring the ideas together,” Hickey explains. “We endeavoured to get up to speed with the plant’s objectives and machinery requirements. We started by estimating the loadings right through the plant where the segregation would suit and allocated suitable transformers. Then, we produced the drawings and worked with Alex Fraser to create a control philosophy for the software to control the plant. It was incredibly thorough.
“We helped design a system that visually represents what the plant is doing, so all the operators can see at a glance how well each section of the plant is operating, which was a requirement Alex Fraser asked us to fulfil. It shows how much power each piece of equipment is using and how much material it is processing. This way, the operators can tell at what level of efficiency the entire plant is operating section by section. Our job is to help the plant produce the most throughput for the least amount of energy and we believe we’ve been able to achieve that with this system.”
They designed from the ground up a fully automated energy efficient system that maximizes production with minimum energy usage and wastage. The project included all electrical engineering requirements and the placement of critical items including switchrooms, control rooms, and high-voltage switchyards. All equipment, including motors, was chosen with a high efficiency rating, in line with minimum energy performance (MEPs) requirements.
“We undertook the EcoSmart Electricians training with a focus on motors, namely the variable speed drives,” Hickey says. “We’ve been installing them for about 25 years, but wanted to make sure we knew all the latest developments. We were also interested in other methods to help clients save energy. I’ve undertaken my course and, like my other staff who have done the training, have come back to the office with lots of good ideas.”
Power factor correction
In a plant this size, often there is a lot of wasted power because of the amount of energy needed to run all the motors and equipment. Typically, these types of operations with large loads suffer from a poor power factor, which can reduce the amount of usable energy that can be extracted. The team installed a very large automatic power factor correction (PFC) bank to counter the problem.
“A lot of inductive motors, such as those found in the crushing plant, can distort the power and this affects the efficiency of the power,” Hickey explains. “By installing the power factor correction units it returns the power to unity and makes it efficient in the way it behaves, such as more electrical current for less cost.
“It’s a hardware solution, comprising a large bank of capacitors in a switchboard with its own controller, which analyzes the power. As the power factor deteriorates, it switches on the appropriate number of capacitors to correct the problem and restore it as close as possible to unity.
“The return on investment (ROI) for this sort of equipment is usually about two and a half years. It’s a fairly expensive exercise to undertake to begin with but as electricity costs begin to rise, it’s well worth the investment. The project team was mindful of this and they were very pleased with our solution. They were able to reduce the size of their transformers because they could access more electrical current from less power gained through better power efficiencies.”
Hickey says many big buildings and industries in Melbourne had undertaken the same power factor corrections, because of the relatively short ROI. He added that all new fluorescent tube fittings have built-in capacitors so their power factor is usually very good. This makes a great difference in large retail environments and office blocks that may have 1000s of tubes operating constantly. Where poor power factor is an issue, PFC units are an excellent way of creating efficient power.
“Efficient power usage equals monetary savings, not only for consumers but also for power providers,” Hickey says.
Alford says the Alex Fraser site had an important safety isolation procedure that had to be incorporated into the electrical system. This allows sections of the plant to be safely isolated for maintenance. It gives operators and maintenance staff confidence that all sources of energy have been locked out in that section. This effective mechanism significantly simplifies this important operation.
The software control monitors a vast array of equipment, including a number of variable speed drives, radar level sensors, belt weighers and pressure sensors that have been positioned around the plant to allow the automation and SCADA (supervisory control and data acquisition) systems to be optimized. As the plant is fully automated, the system is constantly updating its speed and loading to ensure the energy coming into the plant is used efficiently. Rock crushers are constantly monitored for current, pressure and position, and they are adjusted to ensure peak performance and optimisation.
“The operator interface is critical to the operation,” Hickey says. “The operators have to be comfortable with each of the pages we’ve created, and they have to be an accurate representation of what’s happening in the plant. With this interface, the operators can increase and back off equipment to suit the product.
“Operators can see at a glance what rate machines are running at and what power they are drawing. They can also look out of the window and see the conveyors as a visual ‘double-check’. If there’s a problem, it’s quickly and easily detected, which saves on downtime and the expense of replacing equipment that may have burnt out because of a jam or a belt ripping due to a stray piece of steel getting through.
“And just having all that information feeding into one big system makes it so much easier to control the energy utilization of the plant, therefore saving costs and the environment. All electrical switch rooms and cabinets are sealed to IP54 (this international protection rating denotes protection from dust interfering with equipment as well as protection from splashing water) and by creating those rooms, we are keeping more than $1 million worth of electrical equipment in an ideal environment to extract the longevity required from it.”
Alford adds, “That’s why it’s the most advanced recycling plant in Australia. No one [else] has invested the time, money, or the sheer manpower in a project like this.
“The whole investment has cost about $44 million. We made it because recycling is the future. A lot of government tenders for this type of product are asking for a percentage of recycled materials, and we think it won’t be long before contracts are asking for 50 to 100 percent of recycled product.
“It’s an investment towards the future for our company and has proved to be a good business decision. We want to maintain our market leadership position in this industry and believe we have secured that now.”
Alford also says that, in Europe, the construction industry had to recycle everything, even its rubbish.
The whole site is designed around a sustainable future focus. Alford says the company tried to capture all water used on the site; rainwater and storm water is harvested, and there is even a back-up bore.
“This nearly eliminates the need for us to use mains water and ensures we have a ready supply to control important environmental factors such as dust,” Alford says.
Hickey says a weight sensor on the conveyor belts detects if there is product passing through, which activates a water sprayer to reduce localized dust.
“Before the changes, this type of water sprayer may have run whenever the belt was running, whether it needed water or not. Now, we are saving water and the embodied energy used to operate it,” Hickey says.
“There are also daylight sensors for all our lighting,” Alford adds. He says recycled steel from the concrete was also big business. “In the past, this would have gone into landfill, now new items can be made from the recycled steel.”
Alford says there are now a few more concrete recyclers entering the market, as pressure mounts on developers to recycle older building materials that are destroyed to make way for new constructions. He predicts Australia will go through a rebuilding phase soon in which older structures will be reduced to rubble to make way for greener, more sustainable office and manufacturing environments.
At present, the plant runs for 10 hours a day Monday to Friday and eight hours on Saturday, for about 48 weeks a year. It aims for 4,000 metric tons a day, but this depends on how much processing of materials is required; the smaller the finished product, the more it must be processed.
Alford says Alex Fraser had stockpiled about 1.1 million metric tons.
“And with new materials coming in every day, there’s certainly no shortage of supply,” Alford continues. “We’re totally confident that every product we sell is comparable on a quality basis with virgin quarried product. But our carbon footprint is about 65 percent less than that of a quarry.”
“Our involvement at the plant is to ensure that it is producing the optimum amount of material at the lowest cost per kilowatt, and the team has done a top job here,” Hickey adds. “If you’ve got a company behind you like Alex Fraser that’s committed to the same results, it’s so much easier to create something really intelligent that ticks all the boxes.”
This article is reprinted with the permission of EcoSmart Electricians and Sustainability Victoria.
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