Reducing emissions and increasing the use of reclaimed asphalt pavement is among the key aims of plant manufacturers. Patrick Smith reports. Lower emissions and the use of recycled materials coupled with reduced costs are the aims of manufacturers of modern asphalt plants.
One of the 11 earthquake-resistant SIM-Ammann ashpalt mixing plants supplying Algeria's East-West Highway development
RSS
Technology now allows the production of asphalt at ever lower temperatures and the utilisation of even more reclaimed asphalt pavement (RAP) than previously with companies rising to the challenges.
One example comes from Germany where local contractor1249 Johann Bunte, a road specialist with three asphalt plants, aims to optimise production of hot asphalt and to reduce the consumption of energy: a "green approach for black asphalt." To meet this target, the rates of RAP in the mixture must be dramatically increased. The production process needs some optimisation and the electricity consumption of all major drives must be minimised using frequency converters.
The existing 2005 batch mix plant was retrofitted two years ago by an ATS/273 Marini (2779 Fayat Group) recycling ring on the existing dryer to increase recycling rates. The RAP cold feeding into the mixer was insufficient with only 20%, but by retrofitting the recycling ring the feed rates could be increased up to 40% and more.
However, for big production runs and higher RAP rates it was necessary to install a powerful parallel dryer with burner for lignite dust and gasoil.
The concept developed with Bunte proved itself during the first major productions with daily production of above 2,500tonnes and a recycling rate far above 60%.
ATS received the contract for the retrofit together with installation of frequency converters for both dryer drums and the big filter exhauster but the complex control task could not be handled with the existing controls so it was necessary to install the latest generation of ATS/Marini plant controls. Now by simply clicking the mouse all the processes can be started, changed and supervised, and the batch log registers all parameters, consumption and events.
The project required a parallel flow dryer drum for RAP with a nominal output of 180tonnes/hr with variable rotation speed to achieve a temperature of the RAP material at the dryer discharge of between 140-160°C. The exhaust fumes temperature could not be higher than 10-15 kW above product temperature, and to meet this target the drum was sized with a 2.5m diameter and a length of 14m. The drum and drives were designed by Marini and ATS in close cooperation.
A 32m high heavy steel structure included the elevated mixer with a buffer hopper of 26tonnes, a separate weighing hopper of 3tonnes, and a highly inclined chute into the mixer.
The hoppers for the hot RAP are insulated and electrically heated, and the chute into the mixture is highly inclined with special steel surfaces and is heated and insulated to avoid any sticking.
"The heat for drying the RAP is generated by a double fuel burner for coal dust/oil. The application of these burners in recycling parallel dryers is a new technology and needs special care when designing the combustion area. The problem is to transfer the heat into the sensitive RAP material by avoiding overheating and thus damaging the bitumen. RAP should never become too sticky, otherwise all the lifters will be blocked," says ATS/Marini.
"Special flights were designed and installed. So the drum performed in reality better than expected." For the parallel operation of the two dryer drums (virgin aggregates and RAP) the regulation of low-pressure at the burner front wall is quite complicated and needs two servo-controlled dampers for both fumes ducts and a constant under-pressure in the raw gas duct ahead of the bag filter. The existing exhauster is speed controlled with a new frequency converter to keep this constant low-pressure in the main duct. The reduced noise is an additional benefit.
The newly developed ATS/Marini burner control system receives additional input by belt weighing scales indicating material flow into the drum. It calculates any change in material flow for changing the burner capacity in time for a constant product temperature. This offers additional savings in energy and improvements of the asphalt quality.
Erection and commissioning took place within two months without major interruptions to production.
3764 Ammann Group also points to modern technology as being able to help significantly reduce the carbon monoxide emissions of a standard asphalt plant and save costs.
The company says model calculations on the future of the global climate are based on various scenarios: one of the more optimistic assumes an average warming rate of 1.8°C by the year 2100.
"As a reaction to these insights, the countries that have ratified the Kyoto Protocol have agreed to reduce the levels of CO2 and other greenhouse gases to 5% below the value of 1990, a goal it is hoped will be achieved between 2008 and 2012. The two decisive aspects of a greener asphalt industry are lower operating temperatures and the use of as much recycled asphalt as possible," says Ammann.
"According to studies, the production of new bitumen causes 13kg of indirect CO2 emissions per tonne of new asphalt. Increasing the proportion of recycled asphalt is therefore equivalent to a direct reduction in overall CO2 emissions of the road construction industry. Even today, large quantities of asphalt are simply placed into storage or used for insignificant applications. However, it would be more appropriate with regard to sparing our resources to use the available recycled asphalt gained from high quality bitumen and processed aggregate in high performance plants for the construction of new, long-lasting roads." The company says it recognised the importance of asphalt recycling at an early stage, introducing parallel drum technology more than 20 years ago, and in 2008 it introduced a drum with counterflow technology that allowed the utilisation of 100% recycled asphalt.
"An improved drying and heating process increases efficiency and enables fuel savings of around 10%, while the 100% recycled asphalt parallel drum works according to the counter-flow principle: the method is unusual for this type of drum and output temperatures correspond with those of processable asphalt," says Ammann.
The company now has 11 earthquake-resistant SIM-Ammann asphalt mixing plants with a total capacity of 2,450tonnes/hour currently producing asphalt surfacing for part of Algeria's US$11.2 billion East-West Highway development (World Highway, September 2009), which is scheduled for completion this year. It will run for 1,216km, ensuring the link between Annaba in the north-east and Tlemcen in the north-west, passing directly through 24 provinces and linking Algeria to Tunisia and Morocco.
The US$5 billion, six-lane, 400km Eastern section is being delivered by COJAAL which ordered the SIM asphalt plants.
1250 Astec is unveiling its new second-generation design for its lower temperature warm mix Double Barrel Green system.
The company will showcase a full-size display of the system at the World of Asphalt (Cincinnati, USA, 16-18 February) where it will exhibit alongside other Astec Industries' companies1252 Roadtec, 179 CEI Enterprises and 1251 Heatec.
Benefits of the new system include simpler control (all valves open at the same time); minimal hot oil jacket at one-third the size of the original; no AC foaming valves to maintain; the system does not retain pressure once AC flow stops, and self-cleaning water injection valves.
The new design is now standard for both the Double Barrel Green System and for the Green Pac warm mix systems. The Green Pac system can be retrofitted to continuous mix and batch plants from any manufacturer.
The Green Pac System expands the benefits of Astec's exclusive Double Barrel Green warm mix system to any asphalt plant owner or operator.
Astec says that the Double Barrel Green system saves energy and eliminates smoke and emissions without compromising mix quality. It uses water to produce a foamed warm mix asphalt that is odourless, smokeless and longer lasting.
The company says that with the Green Pac System an operator can decrease fuel consumption 14% by decreasing the mix temperature. Other benefits include the elimination of smoke and smell, an increase in production, and the ability to run higher percentages of recycled asphalt pavement (RAP).
Late in 2009, Astec completed the 300th burner it has manufactured since entering the burner market in 2003. Astec's Burner Group engineers the burners to the specifications of each customer and manufactures each in a new state-of-the-art manufacturing facility. Prior to shipment, each burner is tested on one of Astec's tri-fuel (oil, gas and coal) test stands to ensure fast and easy start-up at installation.
Meanwhile, German manufacturer1177 Lintec has developed a new asphalt mixing plant, the CSD1200, which is designed to fit in fewer container units. It can produce about 80tonnes/hour of high quality asphalt.
Details of the new plant will be unveiled at the up coming688 Bauma 2010 exhibition.
1253 Asphalt Drum Mixers) says its series of plants includes the MileMaker, which utilises separate drying and mixing zones to achieve the maximum level of heat transfer and fuel efficiency.
In the plant's counterflow system, aggregate and superheated air move in opposite directions: aggregate is dried and heated in one drum, while asphalt is later mixed in a second drum.
"The MileMaker handles large percentages of RAP without reducing the temperature. Counterflow technology is productive, efficient and environmentally friendly," says ADM.
The MileMaker produces between 160-425tonnes/hour, while the company's RoadBuilder series has a number of production sizes ranging from 110- 320 tonnes/hour.
The portable RoadBuilder features ADM's parallel flow system, which maximises heat transfer by moving moisture-laden asphalt in a rotating veiled pattern away from the burner.
Meanwhile, ADM's SPL Series is said to be ideally suited for asphalt producers in markets with more flexible government restrictions, producing between 55-145tonnes/hour.
"The SPL provides every component needed for asphalt production (drying/mixing drum, wetwash, cold feed bin and surge system) yet the entire plant can still travel on a single trailer," says ADM. Other options include multiple silos and surge systems, environmentally friendly baghouses, add-on cold feed bins, scalping screens and AC tanks.
Turkish manufacturer ÇESAN, founded in 1989, says its aim is to become a global brand.
The company, which operates from a modern production 24,000m² production facility with 130 staff on the Sincan industrial zone in Ankara, started to produce asphalt plants in 1995, and now offers both batch and drum-type stationary and mobile asphalt plants with capacities of between 60-300tonnes/hour (higher if requested). It also produces related products and components including thermal oil heaters, high pressure burners, dryers, screens, filters, bitumen and fuel tanks.
181 Cesan says it is about to complete a new production facility in the same industrial zone to expand production range with concrete batching plants, while research and development studies are continuing to manufacture batch and drum mix-type mobile asphalt plants on a single chassis.
It says its plants can mix a minimum 15% RAP into the asphalt mix while reducing energy consumption, greenhouse gas emissions and improving efficiencies by reducing fuel consumption at the asphalt plant with its self-designed dryer, which operates on the principle heat transfer to the aggregates. Using this technique, the company claims that for each tonne of asphalt a minimum of 1 litre of fuel can be saved.
In recent years ÇESAN has increased export volumes and added new countries such as Afghanistan, Albania, Nigeria to its portfolio along with Iraq, Algeria, Sudan, Kazakhistan and Bulgaria.
1222 Terex Roadbuilding says its new foamed asphalt system allows producers to take advantage of the benefits of running warm mix asphalt without the significant costs associated with additives. By simply mixing water and hot liquid asphalt (AC) in its "exclusive expansion chamber," the new system eliminates the need for additives.
Since its introduction in mid-2008, many Terex warm mix asphalt systems have been installed, The simple Terex system design, which "successfully reducing mix temperatures by 10-32˚C," consists of two main components: an expansion chamber and a programmable logic control (PLC) skid package. The single-mixing point expansion chamber is based on the proven foamed asphalt technology from Terex. Once the hot AC and water combine in the expansion chamber, the foamed asphalt is immediately injected into the drum. The injection pipe is sized to the drum with a variable number of spray nozzles to evenly and thoroughly coat the heated aggregate.
The Terex system is capable of producing up to 544tonnes/hr of asphalt at a 4% injection rate, and producers can quickly switch between running warm and traditional hot mix designs.RSS
Reducing emissions and increasing the use of reclaimed asphalt pavement is among the key aims of plant manufacturers. Patrick Smith reports
Lower emissions and the use of recycled materials coupled with reduced costs are the aims of manufacturers of modern asphalt plants.Technology now allows the production of asphalt at ever lower temperatures and the utilisation of even more reclaimed asphalt pavement (RAP) than previously with companies rising to the challenges.
One example comes from Germany where local contractor
The existing 2005 batch mix plant was retrofitted two years ago by an ATS/
However, for big production runs and higher RAP rates it was necessary to install a powerful parallel dryer with burner for lignite dust and gasoil.
The concept developed with Bunte proved itself during the first major productions with daily production of above 2,500tonnes and a recycling rate far above 60%.
ATS received the contract for the retrofit together with installation of frequency converters for both dryer drums and the big filter exhauster but the complex control task could not be handled with the existing controls so it was necessary to install the latest generation of ATS/Marini plant controls. Now by simply clicking the mouse all the processes can be started, changed and supervised, and the batch log registers all parameters, consumption and events.
The project required a parallel flow dryer drum for RAP with a nominal output of 180tonnes/hr with variable rotation speed to achieve a temperature of the RAP material at the dryer discharge of between 140-160°C. The exhaust fumes temperature could not be higher than 10-15 kW above product temperature, and to meet this target the drum was sized with a 2.5m diameter and a length of 14m. The drum and drives were designed by Marini and ATS in close cooperation.
A 32m high heavy steel structure included the elevated mixer with a buffer hopper of 26tonnes, a separate weighing hopper of 3tonnes, and a highly inclined chute into the mixer.
The hoppers for the hot RAP are insulated and electrically heated, and the chute into the mixture is highly inclined with special steel surfaces and is heated and insulated to avoid any sticking.
"The heat for drying the RAP is generated by a double fuel burner for coal dust/oil. The application of these burners in recycling parallel dryers is a new technology and needs special care when designing the combustion area. The problem is to transfer the heat into the sensitive RAP material by avoiding overheating and thus damaging the bitumen. RAP should never become too sticky, otherwise all the lifters will be blocked," says ATS/Marini.
"Special flights were designed and installed. So the drum performed in reality better than expected." For the parallel operation of the two dryer drums (virgin aggregates and RAP) the regulation of low-pressure at the burner front wall is quite complicated and needs two servo-controlled dampers for both fumes ducts and a constant under-pressure in the raw gas duct ahead of the bag filter. The existing exhauster is speed controlled with a new frequency converter to keep this constant low-pressure in the main duct. The reduced noise is an additional benefit.
The newly developed ATS/Marini burner control system receives additional input by belt weighing scales indicating material flow into the drum. It calculates any change in material flow for changing the burner capacity in time for a constant product temperature. This offers additional savings in energy and improvements of the asphalt quality.
Erection and commissioning took place within two months without major interruptions to production.
Model calculations
TheThe company says model calculations on the future of the global climate are based on various scenarios: one of the more optimistic assumes an average warming rate of 1.8°C by the year 2100.
"As a reaction to these insights, the countries that have ratified the Kyoto Protocol have agreed to reduce the levels of CO2 and other greenhouse gases to 5% below the value of 1990, a goal it is hoped will be achieved between 2008 and 2012. The two decisive aspects of a greener asphalt industry are lower operating temperatures and the use of as much recycled asphalt as possible," says Ammann.
"According to studies, the production of new bitumen causes 13kg of indirect CO2 emissions per tonne of new asphalt. Increasing the proportion of recycled asphalt is therefore equivalent to a direct reduction in overall CO2 emissions of the road construction industry. Even today, large quantities of asphalt are simply placed into storage or used for insignificant applications. However, it would be more appropriate with regard to sparing our resources to use the available recycled asphalt gained from high quality bitumen and processed aggregate in high performance plants for the construction of new, long-lasting roads." The company says it recognised the importance of asphalt recycling at an early stage, introducing parallel drum technology more than 20 years ago, and in 2008 it introduced a drum with counterflow technology that allowed the utilisation of 100% recycled asphalt.
"An improved drying and heating process increases efficiency and enables fuel savings of around 10%, while the 100% recycled asphalt parallel drum works according to the counter-flow principle: the method is unusual for this type of drum and output temperatures correspond with those of processable asphalt," says Ammann.
The company now has 11 earthquake-resistant SIM-Ammann asphalt mixing plants with a total capacity of 2,450tonnes/hour currently producing asphalt surfacing for part of Algeria's US$11.2 billion East-West Highway development (World Highway, September 2009), which is scheduled for completion this year. It will run for 1,216km, ensuring the link between Annaba in the north-east and Tlemcen in the north-west, passing directly through 24 provinces and linking Algeria to Tunisia and Morocco.
The US$5 billion, six-lane, 400km Eastern section is being delivered by COJAAL which ordered the SIM asphalt plants.
Green system
The company will showcase a full-size display of the system at the World of Asphalt (Cincinnati, USA, 16-18 February) where it will exhibit alongside other Astec Industries' companies
Benefits of the new system include simpler control (all valves open at the same time); minimal hot oil jacket at one-third the size of the original; no AC foaming valves to maintain; the system does not retain pressure once AC flow stops, and self-cleaning water injection valves.
The new design is now standard for both the Double Barrel Green System and for the Green Pac warm mix systems. The Green Pac system can be retrofitted to continuous mix and batch plants from any manufacturer.
The Green Pac System expands the benefits of Astec's exclusive Double Barrel Green warm mix system to any asphalt plant owner or operator.
Astec says that the Double Barrel Green system saves energy and eliminates smoke and emissions without compromising mix quality. It uses water to produce a foamed warm mix asphalt that is odourless, smokeless and longer lasting.
The company says that with the Green Pac System an operator can decrease fuel consumption 14% by decreasing the mix temperature. Other benefits include the elimination of smoke and smell, an increase in production, and the ability to run higher percentages of recycled asphalt pavement (RAP).
Late in 2009, Astec completed the 300th burner it has manufactured since entering the burner market in 2003. Astec's Burner Group engineers the burners to the specifications of each customer and manufactures each in a new state-of-the-art manufacturing facility. Prior to shipment, each burner is tested on one of Astec's tri-fuel (oil, gas and coal) test stands to ensure fast and easy start-up at installation.
Meanwhile, German manufacturer
Details of the new plant will be unveiled at the up coming
Separate mixing zones
ADM (In the plant's counterflow system, aggregate and superheated air move in opposite directions: aggregate is dried and heated in one drum, while asphalt is later mixed in a second drum.
"The MileMaker handles large percentages of RAP without reducing the temperature. Counterflow technology is productive, efficient and environmentally friendly," says ADM.
The MileMaker produces between 160-425tonnes/hour, while the company's RoadBuilder series has a number of production sizes ranging from 110- 320 tonnes/hour.
The portable RoadBuilder features ADM's parallel flow system, which maximises heat transfer by moving moisture-laden asphalt in a rotating veiled pattern away from the burner.
Meanwhile, ADM's SPL Series is said to be ideally suited for asphalt producers in markets with more flexible government restrictions, producing between 55-145tonnes/hour.
"The SPL provides every component needed for asphalt production (drying/mixing drum, wetwash, cold feed bin and surge system) yet the entire plant can still travel on a single trailer," says ADM. Other options include multiple silos and surge systems, environmentally friendly baghouses, add-on cold feed bins, scalping screens and AC tanks.
Turkish manufacturer ÇESAN, founded in 1989, says its aim is to become a global brand.
The company, which operates from a modern production 24,000m² production facility with 130 staff on the Sincan industrial zone in Ankara, started to produce asphalt plants in 1995, and now offers both batch and drum-type stationary and mobile asphalt plants with capacities of between 60-300tonnes/hour (higher if requested). It also produces related products and components including thermal oil heaters, high pressure burners, dryers, screens, filters, bitumen and fuel tanks.
It says its plants can mix a minimum 15% RAP into the asphalt mix while reducing energy consumption, greenhouse gas emissions and improving efficiencies by reducing fuel consumption at the asphalt plant with its self-designed dryer, which operates on the principle heat transfer to the aggregates. Using this technique, the company claims that for each tonne of asphalt a minimum of 1 litre of fuel can be saved.
In recent years ÇESAN has increased export volumes and added new countries such as Afghanistan, Albania, Nigeria to its portfolio along with Iraq, Algeria, Sudan, Kazakhistan and Bulgaria.
Since its introduction in mid-2008, many Terex warm mix asphalt systems have been installed, The simple Terex system design, which "successfully reducing mix temperatures by 10-32˚C," consists of two main components: an expansion chamber and a programmable logic control (PLC) skid package. The single-mixing point expansion chamber is based on the proven foamed asphalt technology from Terex. Once the hot AC and water combine in the expansion chamber, the foamed asphalt is immediately injected into the drum. The injection pipe is sized to the drum with a variable number of spray nozzles to evenly and thoroughly coat the heated aggregate.
The Terex system is capable of producing up to 544tonnes/hr of asphalt at a 4% injection rate, and producers can quickly switch between running warm and traditional hot mix designs.RSS
