Efficient thermal management of high-temperature synthesis gas generated during underground coal gasification (UCG) is essential for improving energy efficiency and ensuring safe gas handling operations. Advanced heat exchanger designs such as membrane helical coil heat exchangers have demonstrated superior heat transfer performance compared with conventional designs. However, the large-scale implementation of such technologies requires comprehensive evaluation of economic feasibility and environmental sustainability.

The present study performs a thermo-economic and sustainability assessment of membrane helical coil heat exchangers used for high pressure syngas cooling in underground coal gasification systems. A combined analytical and computational approach was adopted to evaluate heat transfer performance, energy savings, operational cost, and environmental impact. The analysis incorporates parameters such as capital investment, operational cost, pressure drop penalties, energy recovery potential, and carbon emission reduction.

The results indicate that the enhanced heat transfer capability of membrane helical coil heat exchangers significantly improves overall system efficiency. Compared with conventional serpentine tube heat exchangers, the proposed configuration reduces energy consumption by approximately 18% and increases heat recovery efficiency by nearly 25%. The economic analysis demonstrates that although the initial investment cost of the advanced heat exchanger is slightly higher, the payback period is less than 3.5 years due to improved energy efficiency and reduced operational costs.

Furthermore, sustainability assessment indicates that improved thermal efficiency results in lower greenhouse gas emissions and better resource utilization in underground coal gasification systems. The findings of this study highlight the potential of membrane helical coil heat exchangers as a sustainable solution for high temperature gas cooling in advanced energy conversion technologies.