| Air humidity not only affect people’s perception of temperature and thermal comfort, but also have a significant impact on modern industrial and agricultural production, so the control humidity attracted widespread attention. At present, The most commonly used desiccant materials are silica gel, alumina, molecular sieves, etc., Molecular sieve is widely used in the place where required depth dehumidification for the excellent adsorptive performance under high temperature and low humidity condition. It will bring greater energy consumption in the use of molecular sieve as the desiccant material,because the desorption temperature molecular sieve is relatively high and the desorption energy consumption is relatively large, in addition, dehumidification is a work with high-energy consumption itself, which accounts for 20%~40% of the total energy consumption of the air conditioning,so try to improve the desorption performance of the desiccant material will be of great significance to the whole social energy and the environment.In this paper, two kinds of modified molecular sieve 13X/NAY were prepared with cerium nitrate as modifier,the influence on the adsorptive performance of calcinations temperature, impregnation time, impregnation concentration, impregnation solution p H, impregnation temperature in the preparation process of modified molecular sieve was investigated by static adsorption experiments in order to optimize the preparation conditions, the results showed that the excellent adsorption performance of molecular sieves could be kept when choose appropriate preparation conditions and optimum conditions of two different molecular sieves were different, which may be due to the silica alumina ratio of two kinds of molecular sieves were different,the different aperture size or the concentration and distribution of metal ions in molecular sieve skeleton were different.The adsorption isotherms of two kinds of molecular sieves were determined and adsorption heat was calculated with an adsorption isotherm respectively,the result showed that adsorption isotherms of two kinds of molecular sieves were all belong to type I, the adsorption heat decreased and adsorption weakened after modified.The structure of molecular sieves were characterized by X-ray diffraction( XRD), Fourier infrared spectroscopy(FTIR)analysis, XRD analysis showed that the diffraction peak intensities of two kinds of molecular sieves weakened significantly and crystallinity reduced,but the characteristic peak position did not change after modified; FTIR analysis showed that the infrared spectra absorption peaks of the two kinds of molecular sieves were similar before and after modified which indicated the presence of the original molecular sieve framework structure and microstructure of the molecular sieve had no fundamental change.The desorption performance of molecular sieve adsorbent was evaluated by thermogravimetry(TG),activation energy of water vapor desorption on molecular sieve was calculated using the W.J.Wang Method, the most probable mechanism functions to characterize the kinetics of water vapor desorption on molecular sieves were determined using the principal curve method, also the pre-exponential factor was calculated in order to complete a comprehensive study of “kinetic triplet” in the desorption reaction. The results showed that the desorption temperature and activation energy were decreased, the desorption performance was improved, and the threedimensional diffusion function was determined as the most probable mechanism function.The prepared adsorbents were used in solar staged-regeneration desiccant wheel air conditioning system, and the performance of air conditioning system was computed. The result showed that the system thermal performance coefficient increased 11.22%, 7.73% respectively when 13X/NAY molecular sieve desiccant after modified by cerium nitrate, thus improved energy efficiency.In the modification study of two kinds of molecular sieve 13X/NAY, the 13 X modification effect was more ideal than NAY molecular sieve,the reason may be that 13 x molecular sieve pore size is larger than NAY molecular sieve,so 3Ce+ can be more easily into the 13 x molecular sieve hole, the distribution of metal ions in molecular sieve skeleton of two kinds of molecular sieves were different, it was easier to exchange the metal ions in 13 x molecular sieve skeleton; in addition, there were more Na+、3Al+ in the 13 x molecular sieve skeleton,so those two metal ions had a more replacement in 13 x molecular sieve, then had a better modification effect. |
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