New Tech, Services Keep up with Asphalt Production Trends
BY Sandy Lender
It feels as though this year’s World of Asphalt and AGG1 conferences and trade shows in Nashville were a lifetime ago, when in fact they were March 22 through 24. A mere five months ago, asphalt and aggregate professionals from around the globe gathered at the Music City Center to share knowledge and learn what’s new in the industry. While the business of construction has moved right along since then, the technology and equipment launched there continues to advance the way producers can think about the bottom line.
For example, asphalt producers know there are sectors of North America where air pollution mitigation has become a war cry. Our desire is great to assist the global community in reducing carbon emissions from all sources, but asphalt plants are already low “emitters,” as it were. Even with low combustion in today’s modern asphalt plants, companies offer lo-NOx burners to drive scant emissions down further. Even though those burners aren’t mandatory in all areas, thus lo-NOx burners are usually an option when you’re looking at new equipment, OEMs make them available to anyone who is interested.
Mike Devine, the president of Asphalt Drum Mixers, Huntertown, Ind., shared, “There is a lot of misleading information about asphalt plants that make people tend to look at the asphalt industry as one that pollutes the earth. The truth is that asphalt pavement plants are well regulated by federal and state environmental agencies. At ADM, we know that clean air is in everyone’s best interest, which is why we make our lo-NOx burners available to all of our customers, not just those in difficult-attainment areas. We typically offer the NovaStar Lo-NOx burner from Hauck Manufacturing Co., which uses the latest lean burn premix technologies to reduce pollutant formation without sacrificing overall quality or efficiency. Through the steps we’ve taken to reduce emissions, we’ve dramatically reduced our carbon footprint while making a positive impact in our customers’ bottom line.
“ADM is constantly seeking innovative solutions to provide the lowest available combustion emissions,” Devine continued. “By taking advantage of the latest asphalt mixing technologies, we’ve produced some of the cleanest stack tests in the industry. All of our portable, relocatable and stationary asphalt plants are available with lo-NOx burner options and can be customized to satisfy each of our customers’ unique requirements and meet their specific needs. Additionally, we have designed our new EX Series to virtually eliminate unsafe hydrocarbon emissions and reintroduce residual gases back to the drum’s combustion zone.”
Another way to reduce emissions is to reduce temperatures and get a firm handle on controls. Plant OEMs are eager to show the industry that they’re on top of this need.
While the plant itself isn’t new to the marketplace (Tarmac introduced its rotary dryer to its customers in 1998), the rotary dryer from Tarmac International Inc., Lee’s Summit, Mo., has a new feature available. Ron Heap shared, “We have an adjustable flight with a build-in liner that bolts in place when you bolt the flight in. Previously, the dryer shell liners had to be welded or bolted in separately, which is a costly venture. What a fantastic savings both in original cost of installed shell liners and the replacement of dryer shell liners to be able to bolt them in when you put the flight in.”
The additions to plants don’t have to be internal to make efficiency fabulous. Take a look at what Stansteel/Hotmix Parts, Lexington, Ky., had to share concerning pumping, metering and liquid systems for blending additives and asphalt cements (ACs). As of press time, the company had more than 17 different chemical liquid configurations.
“Over the last five years, there has been a dramatic development of many liquid chemical and other liquids to provide anti-strip, rejuvenators, liquid AC conditioners and even modifying liquid AC to create a new PG grade AC. Stansteel/Hotmix Parts has met one of the most critical parts, which is to custom design all types of systems in order to correctly handle these liquids, combine them with different ACs so there is a colloidal blend of ingredients and, of course, deliver them into the hot-mix plant process for proper combination, mixing, blending, coating and more.”
A spokesperson for the company explained that it takes precision to get all the conditions right for blending, metering, calibrating, etc. “To just randomly pump a liquid without being able to verify that the device is working correctly and delivering the exact amount of liquid called for in the design specifications could be catastrophic. Too little of liquid additive does not result in either the proper conditioning, chemical warm mix or fully treated AC to meet the proper grade of asphalt. Naturally, too much of the liquid is wasteful and it also can throw the final mix out of tolerance…Stansteel/Hotmix Parts has also found that there may be a whole assortment and types of devices and apparatuses that are needed to accomplish the end result specification and affect quality control conditions that are mandatory to achieve bonus pay on projects. The components required to build a liquid additive skid are very similar to that of an AC skid. Besides a pump and motor, a meter is needed to accurately convey the proper additive flow rate. An electrically actuated divert valve is necessary to ensure the additive is pumping correctly by circulating it back to the tote or tank before being injected into the AC line. Also, a strainer is helpful with this process to prevent damage to the system and a pressure gauge can help to diagnose problems in real time.”
Readers have seen the Accu-Shear® multi-purpose dynamic mixing and blending system from Stansteel in the magazine before, but the system has been updated.
“In a large number of plants, the liquid additives are also combined with the Accu-Shear multi-purpose dynamic mixing and blending system and can be combined in individual combinations of the AC and the liquid product or, in some cases, multiple liquids combined simultaneously. In many of these situations, it’s important to have the electronic controls know-how to provide proper signals to the existing plant control or provide an entire new multi-purpose blending control to meter and properly combine the ingredients.”
A number of OEMs with mechanical WMA systems have made updates and upgrades to their products since AsphaltPro highlighted the systems several years ago in our popular Here’s How it Works department. Starting in the May/June issue this year, we’ve given you a look at those enhanced WMA systems, and invite you to check out the four included in this month’s issue, starting on page xx.
No article about innovations and trends in asphalt production would be complete with a look at what OEMs are doing to make increased recycle percentages easier for producers.
Rock Systems rolled out a new feeder system about a year ago called the portable 2 bin RAP feeder. It’s designed to introduce fractionated RAP to the asphalt plant and can be built portable or stationary. Despite its name, it can come with two or three bin configurations.
Increasing the production of recycled asphalt pavement (RAP) remains a priority around North America, and OEMs have myriad ways to help producers do it. Take a look at how you’re transferring material to the dryer. Mike Bruce of Rock Systems Inc., Sacramento, reminded us: “Fractionated RAP enables a mix designer to have control over the fine and coarse RAP gradations in the mix.” The team at KPI-JCI and Astec Mobile Screen still offers fractionating screens and systems to ensure you have appropriate sizes of RAP. It’s a vital part of increasing your percentage of RAP; you need to have the same quality control of your recycle material as you do virgin material.
Once you get material sized, what will you feed it to? Rock Systems rolled out a new feeder system in May 2015 called the portable 2 bin RAP feeder. It’s designed to introduce fractionated RAP to the asphalt plant and can be built portable or stationary. Despite its name, it can come with two or three bin configurations. Each hopper measures 13 feet by 7 feet, 8 inches with 13 cubic yards struck storage capacity. Vertical front walls and steep side walls with self-relieving openings are designed to keep the RAP flowing through the hopper. 30-inch-wide roller belt feeders with variable speed drive motors provide precise measuring. A 36-inch-wide collecting conveyor mounted under the feeders and hoppers delivers the blended, fractionated RAP. All equipment is mounted on a portable chassis with brakes, lights, mud flaps and fifth wheel pin. Options such as reject oversize grizzlies, bulkheads and air cannons can be installed.
The team at ADM offers a specialized bin and conveyance system for recycled materials also. The steeply sloped sidewalls of ADM’s recycle systems are designed to prevent material plugging and bridging, but they come standard with air cannons to make it all efficient. Devine shared: “ADM’s RAP systems include air cannons and reduce costs by allowing plants to produce hot mix containing up to 50 percent recycled material.”
Producers may equate the Double Barrel plant from Astec, Chattanooga, with WMA production, but the company has introduced the new, compact Double Barrel® Express plant designed to produce mix with up to 50 percent RAP content. Of course the plant includes the Astec Double Barrel drum with the insulated outer chamber where the RAP is heated and mixed with virgin aggregate, baghouse fines and liquid asphalt. The drum’s V-flights are designed to provide uniformity of the aggregate veil during drying for best heat transfer, thus reduced fuel use. The cold feed bins for the plant are vibrated with dancing plate to minimize segregation of virgin material. It’s a 5-foot by 30-foot plant rated at 140 tons per hour.
Keep in mind, the product galleries in AsphaltPro are set up to feature the new elements and new equipment from OEMs. As you review the galleries each month, you’ll find the latest innovations in technology and service that manufacturers are using to keep you current with trends in the industry. You don’t have to wait for an international tradeshow to get new information if you’re reading this publication each month.