Ammann Asphalt-Mixing Plants remove dust through a highly efficient baghouse filter
It actually lowers exhaust dust to less than 10 mg/m3 , which is an exemplary benchmark. We are currently working on reducing this value significantly again, to < 5mg/m³, says Dr. HansFriedrich Peters, Executive Vice President – Asphalt and Concrete Plants, Ammann Group.
The placement of asphalt plants in residential and commercial areas also raises noise issues. Why plants located in these areas and what are can be done to limit the noise?
A shortage of industrial land means that asphalt plants increasingly must be located closer to residential areas. Local governments can have very strict standards when it comes to noise, so we have to make the plants as quiet as possible.
Ammann has been very proactive on this front. We offer varied sound-suppression packages to meet our customers’ specific needs. Some customers need to lower sound a bit, while others have to take more substantial measures. The efforts start with equipping burners with variable speed motor drives, which are much quieter, and stack silencers, which control exhaust noise. We offer more and more sound-suppression options, all the way to cladding the entire plant.
That cladding makes the plants look like commercial buildings. They are beautiful facilities that fit nicely in urban office parks. Passersby would never guess there is an asphalt-mixing plant inside.
Dust emission is becoming a bigger issue as plants must often be located in sensitive areas. Can anything further be done to limit the dust that results from these plants?
The conversation about dust emissions starts with the baghouse. Ammann Asphalt-Mixing Plants remove dust through a highly efficient baghouse filter. It actually lowers exhaust dust to less than 10 mg/m3 , which is an exemplary benchmark. We are currently working on reducing this value significantly again, to < 5mg/m³.
People often focus solely on the dust resulting from the mix-making process, and what comes out of the chimney. They forget that all the logistical operations around an asphalt-mixing plant, and around equipment like trucks and wheel loaders, are creating much more dust than the plant itself. Fortunately, countries like China, and also some areas in Europe, are increasingly considering these other sources.
Ammann and our customers have together developed solutions to further limit dust. We focus on dust reduction points for further improvement. Taking measures at the cold feeder, load-out, skip hood, overflow silo, filler loading area, screen, belts and transfer points makes a big difference. That’s in addition to the efforts provided through the baghouse.
To summarise the current state of emissions, I would say the main focus is on trimming CO2 , VOCs and NOx in the combustion process and on reducing the residual dust content after the baghouse. There are also markets in which, for example, the integration of pre-dosing into the dedusting process is also being promoted.
Are local governmental requirements becoming stricter in general? We discussed CO2 , sound and dust emissions, but what about odour – particularly given that the plants are increasingly placed in residential or commercial areas?
Yes, the requirements are becoming stricter – but they are extremely different from one country to the next. We are eager to comply with all the regulations because it’s the law and because we want to be good neighbours, too. That means a lot more than shrinking carbon and VOC emissions. It also includes muffling sound, which we just discussed, as well as dust and odour. Bitumen fumes are the primary source of odour.
Ammann offers different solutions to contain the fumes and the odour that can result. As with dust, we have reduction points – in this case the bitumen tanks, the skip and load-out levels and the stack. There is a great deal of talk about alternative energy sources, including biofuels. But some mix producers who are contemplating a plant purchase might be hesitant to commit to such fuels, as they are somewhat unproven and their availability might not be as consistent as traditional sources.
Ammann biofuel burners can also utilise more traditional fuels such as natural gas, LPG, light and heavy oil and kerosene. This alleviates the concerns of customers who are hesitant to rely solely on newer fuels. The use of these new fuels is another meaningful win on the green front. We are taking renewable energy sources or, in some cases, converting a waste product into fuel. This conserves natural resources and puts less pressure on landfills.
On the renewable front, we are very high on the wood dust burner. The burner transforms wood dust, a material that is available from local sources, into a renewable fuel. What makes this dust burner even more exceptional is its carbon neutrality. The carbon dioxide released when burning wood is offset by the fact the tree consumed that amount of carbon dioxide during its life. Therefore, this part of the emissions is carbon-neutral. The burner has proven effective and is utilised on a number of Ammann Asphalt Mixing Plants. It can be retrofitted on existing plants as well.
Biofuels are another initiative. They support climate protection and reduce dependency on mineral oil. Examples of these fuels are rapeseed and sugar cane. Tall oil, which is a waste product of cellulose sulphate production, can be used, too. We expect that in the near future other fuel types such as hydrogen will significantly reduce gas emission values. These fuels will also be much more important in our industry. Ammann is already working on solutions to be prepared for this.
How can an asphalt producer begin to make the change to a more green operation while utilising their existing plant?
Asphalt producers might be surprised by how much they can accomplish with their existing plant. A very easy first step is to upgrade the control system. A modern control system can have a significant impact on efficiency and that cuts across many parts of the process. Improved efficiency will lessen fuel usage, emissions and material waste. And the as1 is the best in the business at doing exactly that.
Training is another immediate step that can be taken. The best plant and control system in the world will underperform if the operator is unable to leverage the built-in value. Another option is a more comprehensive retrofit. It still costs a fraction of the price of a new plant and is compatible with products made by Ammann and other manufacturers. A retrofit has a host of options you can choose from, including recycling solutions. A retrofit enables the use of foam bitumen, waxes and other additives. Special bitumen and alternative mixing cycles can be utilised as well.
Again, the plant owner can determine the level of the commitment. Many retrofit customers incorporate a new dryer, which optimises heat transfer – and of course reduces emissions – and enables the employment of an expanded range of materials, including RAP. A retrofit can include environmental upgrades to the bitumen tank and baghouse. It can incorporate noise reduction solutions, too. A host of technological improvements can be made – including revamped burners, mixers and the control system.
What is the next step for a business that wants to explore some of the solutions you referenced?
They should get in touch with Ammann sales or support teams. If they don’t have a specific contact, they can visit Ammann.com. There is a “Find A Dealer” link prominently displayed on the home page. The website also has a host of information on all Ammann products, including asphalt-mixing plants