Since these aluminum residues still have considerable amounts of metallic aluminum, why not to use it to get hydrogen as an new resource of energy? The product of hydrolysis of aluminum is hydrogen and aluminum hydroxide, which should further increase the values of residue.
Article Can hazardous waste become a raw material? The case study of...
I know that the bottom ash from MSW incineration and the slag from an aluminium recycling furnace (black dross) can both contain plenty of aluminium. In some ways this is a problem as the fine aluminium powder can be a fire / explosion threat. If the black dross or the ash gets wet then hydrogen can form inside a waste storage site.
I think it is better to remove the aluminium from these wastes using a eddy current device to allow the aluminium to be then put into a secondary aluminium furnace. Aluminium is a very energy intensive material, a lot of electrical energy is required per kilo of aluminium metal (Hall cell production method) so it makes sense to recycle aluminium metal as the metal rather than converting it into low grade heat energy.
also bear in mind that a black dross is not a good fuel as it often contains plenty of other things like Al2S3, AlP, AlN and Al4C3. The carbide is not too bad but the nitride, sulfide and phosphide can form offensive fumes when it is wetted with water.
I have been worked for aluminum dross from secondary aluminum production in America. I have tested 39 salt cake and 44 baghouse dust. Most of them can release considerable amount of hydrogen, even just with water at the 50 C conditions. This is similar to the landfill environmental conditions, and the reactions can be enhanced with the processing which indicated that some catalysis can be generated and keep activited.
Just as Mark mentioed that the other aluminum mineral also reacted with water and the gas need to be treated for the hydrogen, but it is not a problem with the current technology. The hydrogen concentration can be as high as 50 to 80%, even without treatments.
I agree with you that getting hydrogen is a good options to increase the value of the waste. Several authors have studied it. In our process the hydrolisis was performed in acid medium to get Al solutions with the minimun content of other elements. In this conditions hydrogen and ammonia can also be get.
I am workong on this field. And, my group have prepared the red mud supported Ni catalysts for the decomposition of ammonia to hydrogen. Attachment you can find this article.
Thanks for your response. Dr. Cao. This might be a interesting approach to get the catalysis, however, either the waste from the secondary aluminum production, e.g. salt cake or the primary aluminum production, red mud, are huge. What I am concerning is the metallic aluminum in the wastes, minely SAP. How to use them before the waste to landfill?
- Badges
- Science topic