Abstract
To recover energy from the waste heat of aluminum reduction cells, a waste heat power generation system (WHPGS) with low boiling point working fluid based on Organic Rankine Cycle was proposed. A simplified model for the heat transfer around the walls of aluminum reduction cells and thermodynamic cycle was established. By using the model developed and coded in Matlab, thermal performance analysis of the system was conducted. Results show that the electrolyte temperature and the freeze ledge thickness in the cell can significantly affect the heat absorption of the working fluid in the heat exchange system on the walls. Besides, both the output power and the thermal efficiency of the power generation system increase with the system pressure. The output power and thermal efficiency of the system can also be affected by the type of working fluid used in the system. Working fluids for the best system performance under different output pressures were determined, based on the performance analysis. This WHPGS would be a good solution of energy-saving in aluminum electrolysis enterprises.
Highlights
The electrolytic aluminum industry is the industry of high energy consumption
In order to improve the accuracy of calculation, the heat aluminum reduction cell, and the entire heat exchange system was simplified to a heat transfer transfer system was divided into several layers for successive iteration calculation, which is shown in process with one-dimensional steady state
M4 where h5 and h6 are the enthalpy of working fluid at the expander inlet and outlet, and h6s is the calculated enthalpy at the expander outlet based on the hypothesis that the gas is expanded at a constant entropy process
Summary
The electrolytic aluminum industry is the industry of high energy consumption. Nowadays, the annual production of electrolytic aluminum is close to 40 million tons in China. The power generation system based on Organic Rankine Cycle with low boiling point refrigerant can effectively recover energy from low-temperature waste heat. With other advantages such as simple equipment requirement, no pollution, etc., it has gained the interest of some research groups. Wang et al [13] studied the working fluid and performance of a power generation system applied to low-temperature waste heat by using the simulated annealing algorithm. Analyzed the performance of ORC to recover low-temperature gas waste from an reduction cell. For a heat source temperature range of 80~140 the working fluids given the biggest net power are R227ea and R236fa, respectively. The cell’s wall were established and used to analyze the thermal performance of the system
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