Mining Waste Can Carry Out Cleaner Combustion

Researchers from the Universidad del Valle (Univalle) are studying mining waste materials that may one day support the capture of carbon dioxide, one of the greenhouse gases.

Professor Carmen Rosa Forero Amórtegui, a member of the Carbon Science and Technology research group (GCTC), said that in the future, the combustion of residues from the cane harvest (RAC) can be an industrial energy solution for the Valle del Cauca region, but before that can happen more research is needed to optimize its combustion and explore the options to capture carbon dioxide.

“In conventional combustion processes, such as in a home stove and in industrial processes, the oxygen for the combustion reaction with the fuel (natural gas, coal, biomass, among others) comes from the air, which is a mixture of oxygen, nitrogen and other gases,”  Professor Forero said.

The professor explained that her current studies focus on a novel combustion process where oxygen does not come directly from the air.

The new process relies on a solid oxygen carrier, which is a metallic compound giving and receiving oxygen molecules while circulating between two pieces of equipment.

Professor Forero, who has more than 20 years of experience in the field of combustion, explained that the hope is that this configuration will reduce energy consumption and make it easier to capture combustion products such as carbon dioxide.

"The important thing is that we are advancing in studies on the use of this oxygen carrier in combustion with solid materials such as cane residues, which in the future may represent an alternative fuel for the Valle del Cauca region," Professor Forero said.

Photo: Crucibles to load the oxygen carrier in a thermobalance, a piece of equipment that allows combustion studies to be carried out. Credit: Andrew James/NCC-FI/Univalle

Towards a More Efficient Combustion

Within the Fuel Combustion Laboratory, Professor Forero and Sandra Peña Murillo, a doctoral researcher, demonstrated the experimental setup that uses natural gas as fuel and an oxygen carrier based on manganese.

"The manganese minerals that we use are mining residues, so we are finding a new use for this waste material," Professor Forero said.

The manganese ore is made into a powder, combined with a copper nitrate solution. Initially, 50 milligrams of the compound are loaded into a crucible (basket) within a thermogravimetric balance that allows researchers to identify whether the material has the ability to deliver and receive oxygen.

Then, approximately 200 grams are loaded into a pilot plant that allows the monitoring of combustion gases.

Using software, researchers can analyze the reaction: methane from natural gas is burned with oxygen from manganese. In another cycle, the carrier material is put in contact with air, to replenish the oxygen.

This combustion is more efficient than conventional combustion, because using pure oxygen instead of air ensures complete combustion.

Foto: La profesora Forero (izquierda) muestra un residuo de manganeso. Crédito: Andrew James/NCC-FI/Univalle

Towards a Better Energy Source from Sugarcane

In the Valle del Cauca region, around 241,205 hectares are planted with sugar cane. Therefore, looking for another use for waste such as RAC becomes important.

Together with researchers from Cenicaña, a sugarcane research center, Univalle researchers are also working on how they can convert RAC into a syngas (carbon monoxide and hydrogen) to be used in the combustion process with the transporter of oxygen.

In a pre-print paper “Gasification of Sugarcane Cutting Residues in the Capture of Carbon Dioxide by Simulation” in April 2022, Peña, the lead author, explained that one advantage of the gasification of solid cane waste is that it is easier to capture carbon dioxide than other forms of combustion. 

In addition, syngas can generate energy for industry in the Valle del Cauca region, reducing the amount of mineral coal imported from other parts of Colombia.

Also, the global syngas market reached a volume of 308.8 gigawatt hours (GWH) in 2021, with a predicted reach of 574.5 GWH by 2027, according to a market report in 2022.

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International view for a local impact

Peña, who came from the University of Guayaquil in Ecuador to work on the project in Colombia, said  that the work with the conveyor and gasification are very valuable due to their impact.

"I really like this work because if the industry can incorporate this technology it would be much better for the planet," Peña said, adding that scientific advances are key.

“If we can show that the technology works, industry can be encouraged to implement more environmentally friendly practices,” Peña said.

Another international facet of the project is the overseas collaborators.

Professor Forero said that within the project, they have links to the University of Nottingham in the UK and the Instituto Carboquímica in Zaragoza, Spain.

If you would like to contact the researchers or learn more about the projects, write to the Communications Office of the Faculty of Engineering: comunicaingenieria(at)correounivalle.edu.co

Banner photo: Doctoral researcher Sandra Peña (left) and Professor Forero. Credit: Andrew James/NCC-FI/Univalle