Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6609928 | Electrochimica Acta | 2015 | 9 Pages |
Abstract
We report Seebeck coefficients of electrochemical cells with molten carbonate mixtures as electrolytes and carbon dioxide|oxygen electrodes. The system is relevant for use of waste heat and off-gases with concentration of carbon dioxide different from air, as for example in the metallurgical industry. The coefficient is â1.25 mV Kâ1 for a nearly equimolar mixture of lithium and sodium carbonate with dispersed magnesium oxide at 750 °C, one bar total pressure and a pressure ratio of carbon dioxide to oxygen of 2:1. The value is slightly lower when sodium is replaced by potassium. The theoretical expression of the Seebeck coefficient was established using the theory of non-equilibrium thermodynamics. We used this expression to predict an increase to â1.4 mV Kâ1 when lowering the gas partial pressures to 0.015 and 0.2 bar, respectively, for carbon dioxide and oxygen, a gas composition that can represent that of the off-gases from a silicon furnace which we are concerned with. The absolute value of the Seebeck coefficient increases by 0.2 mV Kâ1 when the cell average temperature increases from 550 to 850 °C. The presence of a second component in the electrolyte increases the coefficient significantly above the values obtained with one component, compatible with a lowering of the transported entropy of the carbonate ion. A concentration cell, using the off-gas from the silicon furnace as anode gas and air as cathode gas, will add 0.14 V at 550°C to the absolute value of the potential. The series construction has the potential to offer a power density at matched load conditions in the order of 0.5 kW mâ2.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Chemical Engineering (General)
Authors
X. Kang, M.T. Børset, O.S. Burheim, G.M. Haarberg, Q. Xu, S. Kjelstrup,