Is Kalina cycle or organic Rankine cycle for industrial waste heat recovery applications? A detailed performance, economic and environment based comprehensive analysis

Abstract

Contrary to the increase in energy demand throughout the world, fossil fuels, which are the main energy source, is now more difficult to reach because of the pandemic, transport or bilateral relations, etc. These obstacles in obtaining fossil fuels reveal the need to minimize energy wastage by utilizing low-temperature waste heat sources releasing the atmosphere without use. Especially for the industrial fields usage of advanced heat recovery systems is necessary. In addition, it is a remarkable point that the evaluation of low-temperature thermal energy potential will contribute significantly to the reduction of carbon emissions, which is one of the most important goals in developed and developing countries. In this study, Kalina and Organic Rankine cycles, which are the most important low-temperature energy conversion systems in the utilization of low-temperature industrial waste heat with a temperature of 250 ºC and a mass flow of 10 m/s, were examined and compared to each other in terms of energy, exergy efficiency, economic outlook, and environmental effects. During the study, the turbine inlet pressure of the Kalina cycle was selected as 60, 90 and 120 bar, while the turbine inlet pressure of the organic Rankine cycle increased from 10 bar to the critical pressure of the fluid. For all selected pressure levels, the turbine inlet temperature was increased from the saturated vapor temperature of the fluid to 240 ºC. As a result, although the Kalina cycle was found economically better than the organic Rankine cycle (3.93 years), the organic Rankine cycle using n-Pentane showed a better performance than the Kalina cycle in terms of energy, exergy, and CO2 emission reduction. The thermal efficiency, exergy efficiency, payback period, and CO2 emission reduction value of the organic Rankine cycle with n-Pentane were calculated as 25.95%, 71.77%, 4.03 years, and 207.17 kg-CO2/h, respectively.