Molten salt-enhanced production of hydrogen by using skimmed hot dross from aluminum re-melting

Significance 

The unprecedented global rise in temperature and climatic change has triggered the need for a clean and regenerative energy. This in return has created an urgent need for hydrogen and alternative means of producing it. Presently, 95% of hydrogen is produced by steam/partial oxidation reforming of natural gas and coal gasification. Recent technological advances have seen the development of a variety of alternative techniques and materials that can be used for hydrogen generation. Amongst them, aluminum and its alloys is the most promising material. Unfortunately, its application has been limited due to the absence of a technique that can minimize the formation of a passive oxide layer. As a partial remedy, several pretreatments have been established so as to accelerate hydrogen generation by activating metallic aluminum. Previous studies have already shown that production of hydrogen by use of secondary aluminum, aluminum scrap and waste or aluminum dross is economical and environmentally friendly. Surprisingly, little has been done on hydrogen production using water steam at high temperature from skimmed hot dross as an alternative technique.

Peng Li and colleagues developed an innovative process for hydrogen generation using skimmed hot dross from aluminum remelting industry. The team hoped to put into use the skimmed hot dross generated during the secondary production of aluminum which contains both high amount of metallic aluminum and potential heat. They aimed at carrying out studies on the reaction behavior between the skimmed dross and water steam in terms of hydrogen evolution variation at high temperature. Their research work is currently published in the research journal, International journal of hydrogen energy.

The procedure used involved, first, the preparation of the samples to be used in the experiments which was achieved by air drying crushed salt cake at 150 °C and splitting them into various concentrations. The team then proceeded to hydrogen production where isothermal studies were carried out at the temperature range of between 600 – 900 °C for a specified duration. Eventually, the team employed various techniques to analyze and characterize the contents of specific elements of the prepared skimmed dross.

The authors observed that the inherent salts in the dross accelerated hydrogen generation at temperature region of between 600 – 850 °C by dissolving the amorphous and γ-alumina product layer in water steam atmosphere. They also noted that the maximum aluminum conversion degree was more than 60%, and the hydrogen evolution rate was over 60 cubic centimeter/gram/minute when skimmed dross with 30 wt% aluminum was used in non-isothermal mode. More so, the presence of the salt flux was seen to alter the water/aluminum interaction mechanism by altering the polymorphic alumina transitions.

Here-in, a study on the reaction behavior between skimmed dross and water steam in terms of hydrogen evolution variation at high temperature and the influences of impurities existing in the skimmed dross on the aluminum/water reaction has been presented. The results obtained have confirmed that the inherent salt flux in the dross could be used as catalyst to enhance the hydrogen production in a relatively lower temperature region of 600 – 850 °C, by dissolving the product layer containing amorphous and γ-alumina. The advanced technique here enables economical hydrogen production by skimmed hot dross. Also, the inherent salt flux impurities in the dross enhances hydrogen production from aluminum/water high-temperature reaction without any pre-activation process.

Molten salt-enhanced production of hydrogen by using skimmed hot dross from aluminum re-melting at high temperature. Renewable Energy Global Innovations

About the author

Dr. Peng Li is currently a lecturer at School of Iron and Steel, Soochow University, Suzhou, PR. China. He received his Ph.D degree in Department of Materials Science and Engineering, the Royal Institute of Technology, Sweden in 2012. His research interest mainly focuses on thermodynamics and kinetics behavior of high temperature reactions, which are involved in the extraction of valuable elements, recovery of waste heat, and energy production from metallurgical wastes.

About the author

Dr. Hong Wei Guo works in School of Iron and Steel, Soochow University since 2014, after 7 years’ work experience in University of Science and Technology Beijing from 2007 to 2014, owning Metallurgical Engineering master degree, and Management Science and Engineering Ph. D degree. He has done many work with the cross of the two subjects, such as development of Blast Furnace Expert System and Hot Blast Stove Combustion Optimization System.

Besides, as the director of the Department of Resource Recycling Science and Engineering, resources recycling of metallurgical slag is also his main research direction, especially on the efficient utilization of metallurgical slag.

About the author

Dr. Bing Ji Yan works in School of Iron and Steel, Soochow University since 2015, and got doctorate from University of Science and Technology Beijing majored in Metallurgical Engineering in the same year. The main research directions focus on reuse of metallurgical solid wastes to prepare building material or reuse the energy, and the efficient utilization of ferrous materials in the process of ironmaking.

Reference

Peng Li, Jun Wang, Xiuxia Zhang, Xinmei Hou, Bingji Yan, Hongwei Guo, Seshadri Seetharaman. Molten salt-enhanced production of hydrogen by using skimmed hot dross from aluminum re-melting at high temperature. International journal of hydrogen energy volume 42(2017) pages 12956-12966.

 

Go To International journal of hydrogen energy

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