A novel hydrophobic shell of bio-based polyurethane coated on zeolite 13X: For designing a high-efficiency adsorption heat pump
Adsorption heat pump is a promising technology to generate steam from the recovery of low-grade waste heat. Although the direct contact heat exchange method has been proposed in the adsorption heat pump, the presence of free water within the adsorbents limits the improvement of system performance. In this work, a shell-core structure was prepared using a hydrothermally stable zeolite 13X as the core and a hydrophobic bio-based polyurethane as the shell through a drum coating method. The Scanning Electron Microscopy results proved the successful preparation of shell-core zeolites with a shell layer thickness ranging from 7.5 to 9.0 μm. Thermogravimetric analysis results showed that the shell-core zeolite exhibited good thermal stability up to 300 °C. The water content is reduced by 69 % compared to unmodified zeolite 13X. Cyclic operation based on a packed bed of the shell-core zeolite showed 218 ∼ 233 °C steam generated from hot water at 72 °C, while 140 °C hot dry gas was used for regeneration. The steam temperature and generation rate of the shell-core zeolite were increased by 22.7 % and 21.6 %, respectively. The mass of free water within the packed bed was greatly reduced by 49.3 %, which resulted in a 49.4 % reduction in regeneration consumption. The Coefficient of Performance for Heating and Specific Heating Power of the shell-core zeolite were maximized by 91 % and 12.3 %, respectively. The tiny protrusions on the surface of the silicon dioxide-modified shell and the air within the pores created an air film that effectively prevented liquid water. Consequently, water could only enter the adsorbent in the form of water vapor. Overall, shell-core zeolite is a suitable adsorbent that can greatly reduce regeneration energy consumption and effectively improve system efficiency. It is foreseeable that the adsorbent preparation method presented in this work will provide a means for advancing the fields of coated slow-release fertilizers and gas separation.
危险品化学品经营许可证（带存储）