Final Report Summary - ALUSALT (Efficient Aluminium Salt cake Recycling Technology)
Executive Summary:
This report summarises the work conducted by the project consortium during the 26 month period of the AluSalt project (1st November 2012 to 31st December 2014). Further reference to the work conducted can be found in the project deliverable reports and in the periodic reports submitted at M9 and M26.
AluSalt is funded under the Seventh Framework Programme (FP7) for EU research and is entitled “Efficient Aluminium Salt-cake Recycling Technology”. The overall industrial objective of the project is to develop an in situ salt cake recycling technology at aluminium recycling facilities. The system will be smaller than the existing technologies, more economically viable with lower capital and operating costs.
The natural starting point for the AluSalt technology is the global requirement for aluminium recycling. Recycling aluminium is estimated to use only 5% of the energy required to make aluminium when extracted from its ore, bauxite. This combined with its ever growing use in a variety of industry sectors and the ability of aluminium to be recycled infinite times means recycled aluminium growth will significantly increase for the foreseeable future.
Recycling aluminium does however have its drawbacks such as producing salt slag generated as a bi product of the Rotary Furnace Technology process that is used to recycle some aluminium scraps and also aluminium drosses. Depending on how clean or contaminated the aluminium scrap is will determine how much salt slag is produced; the dirtier the scrap the more salt flux is required and also the more slag is created. Due to the toxicity of salt slag, many countries are beginning to prohibit landfilling of the substance, forcing companies to send it to a small number of salt slag recycling facilities (mainly in the EU). These salt slag recycling facilities are very large, have high capital and operating costs and as a consequence salt slag producing recyclers have to pay high process fees to them. Transportation to and from these sites costs the industry a lot of money and produces huge amounts of CO2 in the process. As global environmental legislation tightens, salt slag recycling will most likely become more prominent requirement for recyclers around the world.
AluSalt is the solution to the issue of salt slag recycling, bringing the plant to the recycler. A multi-stage cooling, crushing, leaching, drying process separates aluminium, ferrous metals, NMPs and salts. This keeps the process in-house at the salt slag generator, improving operational flexibility and control and significantly reducing processing costs. The value elements of the salt slag is extracted and again, kept in-house only to the recyclers gain.
The AluSalt project has successfully developed and demonstrated that the multi-stage processes of the system performed as required. This resulted in successfully demonstrating the ‘proof of principle’ of the recycling and recovery of the salt from the aluminium industrial ‘saltcake’ waste. The trials have shown that the up-scale pilot system can handle ‘pilot’ quantities of industrial ‘salt slag’ waste.
Project Context and Objectives:
The overall industrial objective of the ALUSALT project is to develop an in situ salt cake recycling technology in the aluminium recycling facility. On average, the medium size aluminium recyclers produce around 10,000 tonnes of salt cake per year. The recycling system developed by ALUSALT will be 10-15 times smaller than the existing technologies. In order to be economically viable the capital and the operating cost of the system has to be very low.
The scientific objectives of the project were to:
• Characterization of the flue gas
• To create a validated multi physics model for gas injection to the evaporator
• Characterization of the salt cake off-gas
• To create a validated multi physics model for after gas combustion to produce combined heat and power (CHP)
The technological challenges of the project are to:
• Challenge of injecting the flue gas to the evaporator: To inject the flue gas from the rotary furnace into the evaporator. However, there are some technical barriers. The pressure of the flue gas may not be enough to produce forced circulation and evaporate the water at a faster rate.
• Challenge with the evaporation tank: A single-stage forced circulation evaporator in order to reduce the costs to be developed.
• Challenge with the synchronization of the system: In the aluminium recycling plant the furnace operates 24 hours a day with 6 cycles. After each cycle the molten aluminium and the salt cake is discharged and new scraps are charged, which takes about 20 minutes. Flue gases are generated all the time except for the charging and discharging period as they escape through the open door. Synchronize the whole recycling system needs to be considered.
The technical work during the project reporting period (1st November 2012 to 31st December 2014) has been spread over the tasks in the following Work Packages:-
• Work Package 1: Multi physics modelling
• Work Package 2: Development of novel gas injection evaporator system
• Work Package 3: Development of aluminium separation system, combined heat and power unit, super-heated steam dryer and control system
• Work Package 4: Integration and Validation
This work during the reporting period impacts on the following results:
• Validated multi physics model for gas injection
• Validated model for the after gas combustion model
• Prototype injector nozzles
• Prototype evaporator
• Prototype leaching tank
• Prototype crushing system
• Prototype magnetic metal separation unit
• Prototype CHP unit for after gas burning
• Recycling of heat & power
• Process control system
• Prototype salt cake recycling system
Project Results:
In the ALUSALT project, we have developed an in situ salt slag recycling technology in the aluminium recycling facility. Small aluminium recyclers may produce down to 5,000T of salt slag per year. Thus the recycling system developed by ALUSALT will be 10-15 times smaller than the existing technologies and will meet the needs of the small recycler. In order to be economically viable, the capital and the operating costs of the system have to be very low.
The initial concept was to develop an advanced flue gas transfer system, which injects the hot flue gas from the rotary furnace through specialized nozzles. The temperature and pressure of the flue gas injection through the nozzles is controlled by adding super-heated steam along with the flue gas. The flue gas - creates convection currents in the brine, which - increases the evaporation rate. The heat and the pressure of the flue gas eliminates the need to use a multi-stage evaporator, which - reduces the size and the initial capital expenditure costs compared to the current state-of-the-art salt slag recycling system. This solution is realised through the achievement of the following Technical Aims (Functionalities):-
• Gas Injection Nozzle
AluSalt’s aim is to optimise energy consumption by taking the rejected heat and the pressure of the flue gas from the rotary furnace. A novel design of gas injection nozzle is required to enable this to be done effectively and reliably. The injectors -utilises specialised nozzles to add the super-heated steam to the flue gas in order to control the pressure and the temperature for injection into the evaporator. The nozzle material is operating in a harsh environment both thermally and chemically so must be corrosion and abrasion resistant.
• Ultrasonic cleaning system for the nozzle
As the nozzles operate in a harsh environment with potentially high levels of particulate matter, a novel cleaning system is required to operate whilst the system is operational to minimise down time and maintenance costs. The ultrasonic cleaner - ensures that there is minimal build-up of dusts and particles on the nozzle such that performance is not and that salt deposits on the nozzle heads are minimised again to ensure effective performance and to minimise corrosion issues.
• Evaporator
A novel evaporator is required to enable reuse of energy in the flue gas to be combined with energy from the CHP system to evaporate the water by using a single stage forced circulation evaporator which - ensures maximum heat transfer from the gas to the brine and allow better circulation. ALUSALT process aims to maximise the reuse of the available energy that is conventionally lost during the aluminium recycling process. The aspiration is that there is no additional requirement of energy for the salt slag recycling.
• Combined Heat and Power
A novel CHP system is required which will enable variable quality fuels to be utilised to generate heat and power for use in the drying stage.
• Control System
A sophisticated control system is required for the real time control of mass and energy balance between the furnace and the evaporator. Furnace operation and the salt slag recycling must be synchronized in order to obtain continuous recycling of salt slag when waste heat is available.
• Prototype salt cake recycling system
The unique prototype integration of the crushing, separation, leaching, filtering and spray drying technologies along with the control system that manages these processes to carry out the recycling of the industrial ‘salt cake’ waste.
Potential Impact:
The basis of AluSalt is to develop a salt slag recycling unit that can reprocess salt slag economically and efficiently in small volumes. The process will be located in situ at the aluminium recycling facilities where the salt slag is generated originally. This will allow aluminium recyclers to reprocess the salt slag in their own facility, without the need for transportation to off-site reprocessing and transport of residues to landfill. This could remove the cost for transportation and the associated CO2 emissions. It will also impact of space required for storage of hazardous material and the associated risks that this holds. Reprocessing the salt slag in house has the immediate benefit of reusing the salt and the recovered aluminium in their processes, again avoiding further transport costs and emissions; in addition there is the potential to sell the residues such as NMP to the market. The net effect is that the aluminium recycling companies can achieve significant cost savings, which can be used to enhance a substantial profit and/or deliver cost reductions that in turn increase competitiveness.
One of the major benefits of on-site reprocessing is that the energy in the flue gas that is normally wasted. These savings are derived from use of waste heat on site, avoided costs for flue gas treatment and reduced operational cost for the treatment plant, reduced carbon emissions and potential associated costs, This will be a paradigm shift in aluminium recycling and will increase the competitiveness of the industry.
It is assumed that a centralised plant would recover an average of 50% of the salt slag as metal (5%) and salt (45%) and sends the balance of 50% to landfill. By having an in situ efficient salt slag recycling system, the average secondary aluminium recyclers with a recycling capacity of producing 10,000 tonnes p.a. of salt slag is calculated to save approximately €350,000 in landfill cost (based on landfill cost of €70/T), approximately €225,000 p.a. on transportation to landfill and reduce emissions of CO2 by approximately 1150 tonnes p.a. just from avoiding the transportation of the salt slag to the salt slag recycling plants. The recovered aluminium metal would be worth a minimum of €450,000 based on €900/T and the salt would be worth €180,000 based on €40/T. The process developed by ALUSALT will reuse the heat lost from the rotary furnace, which will decrease the operating cost by more than 75%. Aluminium recycling companies can establish a standalone or joint salt slag recycling system. The small scale and cost effectiveness affecting as a low barrier to entry are key advantages of this technology.
Main Dissemination activities
The main publications being:
• Aluminium Times 5 times per year MMC Publications UK
• Aluminium International Today 6 issues per year Quartz Business Media Ltd. UK
• International Aluminium Journal 10 times yearly Giesel VerlagGmbH Germany
• Aluminium Praxis 10 times yearly Giesel VerlagGmbH Germany
• Journal of Materials Processing Technology na Elsevier UK
Exhibitions / Conferences attended:
• Metals Bulletin Conference Dubai 2013
• OEA Recycling Conference 2014/15
• NORCAST, Norway June 2014
• Metals Bulletin Conference Berlin 2014
• Aluminium Dusseldorf 2014 Exhibition
Intellectual property
The AluSalt development is expected to develop intellectual property (IP) in several areas which supports the patent application which is directed at the full AluSalt process.
Commercialisation strategy to include post project funding subject to Horizon 2020 and other grant assistance, and partnering with industry, to design and develop an income generating full production demonstrator in Europe. This could be a standalone unit with its own source of industrial aluminium ‘saltcake’ waste or a parallel activity located on the same premises as other aluminium recyclers.
List of Websites:
http://www.alusalt.eu
This report summarises the work conducted by the project consortium during the 26 month period of the AluSalt project (1st November 2012 to 31st December 2014). Further reference to the work conducted can be found in the project deliverable reports and in the periodic reports submitted at M9 and M26.
AluSalt is funded under the Seventh Framework Programme (FP7) for EU research and is entitled “Efficient Aluminium Salt-cake Recycling Technology”. The overall industrial objective of the project is to develop an in situ salt cake recycling technology at aluminium recycling facilities. The system will be smaller than the existing technologies, more economically viable with lower capital and operating costs.
The natural starting point for the AluSalt technology is the global requirement for aluminium recycling. Recycling aluminium is estimated to use only 5% of the energy required to make aluminium when extracted from its ore, bauxite. This combined with its ever growing use in a variety of industry sectors and the ability of aluminium to be recycled infinite times means recycled aluminium growth will significantly increase for the foreseeable future.
Recycling aluminium does however have its drawbacks such as producing salt slag generated as a bi product of the Rotary Furnace Technology process that is used to recycle some aluminium scraps and also aluminium drosses. Depending on how clean or contaminated the aluminium scrap is will determine how much salt slag is produced; the dirtier the scrap the more salt flux is required and also the more slag is created. Due to the toxicity of salt slag, many countries are beginning to prohibit landfilling of the substance, forcing companies to send it to a small number of salt slag recycling facilities (mainly in the EU). These salt slag recycling facilities are very large, have high capital and operating costs and as a consequence salt slag producing recyclers have to pay high process fees to them. Transportation to and from these sites costs the industry a lot of money and produces huge amounts of CO2 in the process. As global environmental legislation tightens, salt slag recycling will most likely become more prominent requirement for recyclers around the world.
AluSalt is the solution to the issue of salt slag recycling, bringing the plant to the recycler. A multi-stage cooling, crushing, leaching, drying process separates aluminium, ferrous metals, NMPs and salts. This keeps the process in-house at the salt slag generator, improving operational flexibility and control and significantly reducing processing costs. The value elements of the salt slag is extracted and again, kept in-house only to the recyclers gain.
The AluSalt project has successfully developed and demonstrated that the multi-stage processes of the system performed as required. This resulted in successfully demonstrating the ‘proof of principle’ of the recycling and recovery of the salt from the aluminium industrial ‘saltcake’ waste. The trials have shown that the up-scale pilot system can handle ‘pilot’ quantities of industrial ‘salt slag’ waste.
Project Context and Objectives:
The overall industrial objective of the ALUSALT project is to develop an in situ salt cake recycling technology in the aluminium recycling facility. On average, the medium size aluminium recyclers produce around 10,000 tonnes of salt cake per year. The recycling system developed by ALUSALT will be 10-15 times smaller than the existing technologies. In order to be economically viable the capital and the operating cost of the system has to be very low.
The scientific objectives of the project were to:
• Characterization of the flue gas
• To create a validated multi physics model for gas injection to the evaporator
• Characterization of the salt cake off-gas
• To create a validated multi physics model for after gas combustion to produce combined heat and power (CHP)
The technological challenges of the project are to:
• Challenge of injecting the flue gas to the evaporator: To inject the flue gas from the rotary furnace into the evaporator. However, there are some technical barriers. The pressure of the flue gas may not be enough to produce forced circulation and evaporate the water at a faster rate.
• Challenge with the evaporation tank: A single-stage forced circulation evaporator in order to reduce the costs to be developed.
• Challenge with the synchronization of the system: In the aluminium recycling plant the furnace operates 24 hours a day with 6 cycles. After each cycle the molten aluminium and the salt cake is discharged and new scraps are charged, which takes about 20 minutes. Flue gases are generated all the time except for the charging and discharging period as they escape through the open door. Synchronize the whole recycling system needs to be considered.
The technical work during the project reporting period (1st November 2012 to 31st December 2014) has been spread over the tasks in the following Work Packages:-
• Work Package 1: Multi physics modelling
• Work Package 2: Development of novel gas injection evaporator system
• Work Package 3: Development of aluminium separation system, combined heat and power unit, super-heated steam dryer and control system
• Work Package 4: Integration and Validation
This work during the reporting period impacts on the following results:
• Validated multi physics model for gas injection
• Validated model for the after gas combustion model
• Prototype injector nozzles
• Prototype evaporator
• Prototype leaching tank
• Prototype crushing system
• Prototype magnetic metal separation unit
• Prototype CHP unit for after gas burning
• Recycling of heat & power
• Process control system
• Prototype salt cake recycling system
Project Results:
In the ALUSALT project, we have developed an in situ salt slag recycling technology in the aluminium recycling facility. Small aluminium recyclers may produce down to 5,000T of salt slag per year. Thus the recycling system developed by ALUSALT will be 10-15 times smaller than the existing technologies and will meet the needs of the small recycler. In order to be economically viable, the capital and the operating costs of the system have to be very low.
The initial concept was to develop an advanced flue gas transfer system, which injects the hot flue gas from the rotary furnace through specialized nozzles. The temperature and pressure of the flue gas injection through the nozzles is controlled by adding super-heated steam along with the flue gas. The flue gas - creates convection currents in the brine, which - increases the evaporation rate. The heat and the pressure of the flue gas eliminates the need to use a multi-stage evaporator, which - reduces the size and the initial capital expenditure costs compared to the current state-of-the-art salt slag recycling system. This solution is realised through the achievement of the following Technical Aims (Functionalities):-
• Gas Injection Nozzle
AluSalt’s aim is to optimise energy consumption by taking the rejected heat and the pressure of the flue gas from the rotary furnace. A novel design of gas injection nozzle is required to enable this to be done effectively and reliably. The injectors -utilises specialised nozzles to add the super-heated steam to the flue gas in order to control the pressure and the temperature for injection into the evaporator. The nozzle material is operating in a harsh environment both thermally and chemically so must be corrosion and abrasion resistant.
• Ultrasonic cleaning system for the nozzle
As the nozzles operate in a harsh environment with potentially high levels of particulate matter, a novel cleaning system is required to operate whilst the system is operational to minimise down time and maintenance costs. The ultrasonic cleaner - ensures that there is minimal build-up of dusts and particles on the nozzle such that performance is not and that salt deposits on the nozzle heads are minimised again to ensure effective performance and to minimise corrosion issues.
• Evaporator
A novel evaporator is required to enable reuse of energy in the flue gas to be combined with energy from the CHP system to evaporate the water by using a single stage forced circulation evaporator which - ensures maximum heat transfer from the gas to the brine and allow better circulation. ALUSALT process aims to maximise the reuse of the available energy that is conventionally lost during the aluminium recycling process. The aspiration is that there is no additional requirement of energy for the salt slag recycling.
• Combined Heat and Power
A novel CHP system is required which will enable variable quality fuels to be utilised to generate heat and power for use in the drying stage.
• Control System
A sophisticated control system is required for the real time control of mass and energy balance between the furnace and the evaporator. Furnace operation and the salt slag recycling must be synchronized in order to obtain continuous recycling of salt slag when waste heat is available.
• Prototype salt cake recycling system
The unique prototype integration of the crushing, separation, leaching, filtering and spray drying technologies along with the control system that manages these processes to carry out the recycling of the industrial ‘salt cake’ waste.
Potential Impact:
The basis of AluSalt is to develop a salt slag recycling unit that can reprocess salt slag economically and efficiently in small volumes. The process will be located in situ at the aluminium recycling facilities where the salt slag is generated originally. This will allow aluminium recyclers to reprocess the salt slag in their own facility, without the need for transportation to off-site reprocessing and transport of residues to landfill. This could remove the cost for transportation and the associated CO2 emissions. It will also impact of space required for storage of hazardous material and the associated risks that this holds. Reprocessing the salt slag in house has the immediate benefit of reusing the salt and the recovered aluminium in their processes, again avoiding further transport costs and emissions; in addition there is the potential to sell the residues such as NMP to the market. The net effect is that the aluminium recycling companies can achieve significant cost savings, which can be used to enhance a substantial profit and/or deliver cost reductions that in turn increase competitiveness.
One of the major benefits of on-site reprocessing is that the energy in the flue gas that is normally wasted. These savings are derived from use of waste heat on site, avoided costs for flue gas treatment and reduced operational cost for the treatment plant, reduced carbon emissions and potential associated costs, This will be a paradigm shift in aluminium recycling and will increase the competitiveness of the industry.
It is assumed that a centralised plant would recover an average of 50% of the salt slag as metal (5%) and salt (45%) and sends the balance of 50% to landfill. By having an in situ efficient salt slag recycling system, the average secondary aluminium recyclers with a recycling capacity of producing 10,000 tonnes p.a. of salt slag is calculated to save approximately €350,000 in landfill cost (based on landfill cost of €70/T), approximately €225,000 p.a. on transportation to landfill and reduce emissions of CO2 by approximately 1150 tonnes p.a. just from avoiding the transportation of the salt slag to the salt slag recycling plants. The recovered aluminium metal would be worth a minimum of €450,000 based on €900/T and the salt would be worth €180,000 based on €40/T. The process developed by ALUSALT will reuse the heat lost from the rotary furnace, which will decrease the operating cost by more than 75%. Aluminium recycling companies can establish a standalone or joint salt slag recycling system. The small scale and cost effectiveness affecting as a low barrier to entry are key advantages of this technology.
Main Dissemination activities
The main publications being:
• Aluminium Times 5 times per year MMC Publications UK
• Aluminium International Today 6 issues per year Quartz Business Media Ltd. UK
• International Aluminium Journal 10 times yearly Giesel VerlagGmbH Germany
• Aluminium Praxis 10 times yearly Giesel VerlagGmbH Germany
• Journal of Materials Processing Technology na Elsevier UK
Exhibitions / Conferences attended:
• Metals Bulletin Conference Dubai 2013
• OEA Recycling Conference 2014/15
• NORCAST, Norway June 2014
• Metals Bulletin Conference Berlin 2014
• Aluminium Dusseldorf 2014 Exhibition
Intellectual property
The AluSalt development is expected to develop intellectual property (IP) in several areas which supports the patent application which is directed at the full AluSalt process.
Commercialisation strategy to include post project funding subject to Horizon 2020 and other grant assistance, and partnering with industry, to design and develop an income generating full production demonstrator in Europe. This could be a standalone unit with its own source of industrial aluminium ‘saltcake’ waste or a parallel activity located on the same premises as other aluminium recyclers.
List of Websites:
http://www.alusalt.eu