Investigation on the reaction of iron powder mixture as a portable heat source for thermoelectric power generators

Dale H Huang,Thanh N Tran,Bao Yang

doi:10.1007/s10973-013-3619-9

Abstract

This paper reports our investigation on the thermal behavior and ignition characteristics of iron powder and mixtures of iron with other materials such as activated carbon and sodium chloride in which iron is the main ingredient used as fuel. Thermal analysis techniques such as differential scanning calorimetry (DSC) and thermogravimetric analysis were used to characterize the materials and for further understanding of reaction kinetics of the pyrophoric iron mixtures. The experimental results demonstrated that iron micron particles react exothermically to the oxygen in atmosphere and produced iron oxide with ignition temperature of 427.87 °C and heat generation of 4,844 J g−1. However, in this study, the pyrophoric iron mixture acts as a heat source for the thermoelectric power generators, the final mixture composition is determined to compose of iron powder, activated carbon, and sodium chloride with the mass ratio of approximately 5/1/1. The mixture generated two exothermic peaks DSC curves that showed ignition temperature of 431.53 and 554.85 °C and with a higher heat generation of 9,366 J g−1 at higher temperature. The effects of test pan materials and heating rate on the ignition were also examined by DSC method. Kinetic data such as the activation energy (Ea), the entropy of activation (ΔS#), enthalpy of activation (ΔH#), and Gibbs energy of activation (ΔG#) on the ignition processes was also derived from the DSC analysis. From the ignition temperature, heat generation, and kinetics test data, the mass ratio of 5/1/1 proved to generate the most amount of heat with high temperatures for the standalone thermoelectric power generators.

Highlights

The idea of small size, light mass, robust, scalable, and standalone power generators has always been of great interest in personal and commercial transportation systems
This paper reports our investigation on the thermal behavior and ignition characteristics of iron powder and mixtures of iron with other materials such as activated carbon and sodium chloride in which iron is the main ingredient used as fuel
In this study, the pyrophoric iron mixture acts as a heat source for the thermoelectric power generators, the final mixture composition is determined to compose of iron powder, activated carbon, and sodium chloride with the mass ratio of approximately 5/1/1

Summary

Introduction

The idea of small size, light mass, robust, scalable, and standalone power generators has always been of great interest in personal and commercial transportation systems. One potential source of portable power is electricity produced from heat sources through the use of thermoelectric materials [1,2,3,4]. The heat can come from the combustion of fossil fuels, from sunlight, or as a byproduct of various processes (e.g. combustion, chemical reactions, and nuclear decay). A pyrophoric iron mixture provides spontaneous heat as soon as it reacts with air. The final mixture of the pyrophoric materials composition was determined to be iron powder, activated carbon, and salt. Thermal analysis study of heterogeneous oxidation of Fe powder leading to ignition was recently developed and quantified for reaction of iron in environments containing oxygen as the only oxidizer [5]

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