That our roads, from local streets to interstates, are in sad shape is not news to anyone with a driver's license. How we got here is almost as obvious. With government budgets in trouble at every level, money for roads is hard to come by. At the same time, the price of materials, liquid asphalt and rock, continues to rise.
I think contractor opinions are better sources of wisdom concerning what we can do during this funding drought than anything I can offer. What several contractors have told me can be summed up by saying "we (the industry) need to do what we do better, especially when it comes to recycling and efficiencies at the plants." My first reaction was that would be tough. After all, how much better can plants get? We have already come a long way on both of those fronts. If that isn't enough, I have also been told that we need better control of the plant process. No pressure!
Answering The Call
Although plants today are considerably more sophisticated and efficient than they were just 10 or 15 years ago, the message is clear that they need to be better. We have responded to such needs before. For instance, when Astec was confronted with tighter NOX emissions limitations in California's South Coast Air Quality Management District around 1990, we responded by introducing the industry's first Flue Gas Recirculation System (FGR) system. It worked very well and became the standard solution to the California NOX requirements for several years. We were proud of the accomplishment. We have since replaced that technology with burners that don't need FGR to meet even tighter requirements. It's time to step up again. When I look at the technology in my car, I realize that it's so smart it's scary. So, yes, there are ways to do it still better.
One such opportunity is burner control. Ever since the introduction of counterflow drying technology (a long time ago) there has really been no effective automatic burner control. There may be a button on the screen that says "auto" but the burner will only run on automatic when it doesn't need active control. We need to do better than that; so we are. Feed-forward burner control, based on real-time data on moisture contents of aggregates and RAP, can be accomplished by calculating the heat demand and flowing the amount of fuel needed.
We could do a lot better on fuel efficiency, too. Why do we want to keep baghouse temperature at about 240 to 250 degrees F (116 to 121 degrees C) as a minimum? It's because we need to avoid mud and corrosion caused by condensation, right? Condensation in a baghouse is bad news. However, if we really look at the conditions under which condensation occurs, we realize that we could very often run the temperature down to 150 degrees F (66 degrees C) without a problem. So, it seems that we are often leaving about 100 degrees worth of fuel energy on the table—not a good thing. By changing our control from looking at temperature to looking at dew point, we can keep away from the mud while capturing all of the available energy.
Another place where we can be better is control of asphalt content. At US $600 per ton, precise control is pretty important. Real-time measurements of moisture and the AC content of the RAP enable us to be more precise with the amount of virgin AC we inject.
Astec Smart Plant
We have responded to our contractor friends with the Astec Smart Plant. The Smart Plant is the same highly reliable and durable Astec Double Barrel® that's been around for years, but much smarter. More information is collected by sensors and processed by the control system. This enables the Smart Plant to do more with less and save money, enabling the current reduced funding to pave more lane miles.
As we responded to the expressed need for the ability to use more RAP, we found that we can do better there, too. The capability of plants to make high-quality mixes with very high RAP percentages, up to 100 percent, has resulted. Combining the enhanced recycling capabilities with the Smart Plant technology is more than just a bridge to better times.
As is so often the case, the great insights of our contractor friends are leading to some big improvements in plant design that will make our industry more competitive and, therefore, better able to weather lean times. When the funding situation improves, the advances that have come about because of the struggle will still be here and we will all be better for it.BACK TO ISSUE