Improvement of selenium adsorption performance at high temperature by CaO/ZSM-5 composite sorbents

Selenium in flue gas from coal combustion, released into the atmosphere, will affect the environment and human health greatly. The adsorption method can achieve good control of selenium emission, by using CaO as adsorbent, but CaO is easy to sinter at high temperature, resulting in the decrease of adsorption capacity. Therefore, thermostability ZSM-5 molecular sieve was added to prepare composite adsorbent to improve the adsorption performance for selenium at high temperature. CaO/ZSM-5 composite adsorbent was prepared by impregnation method, and its adsorption performance and mechanism were studied. The results show that the composite adsorbent shows stronger adsorption capacity at high temperatures. The mixing ratio has a great influence on the microstructure of the composite adsorbent influencing the adsorption capacity. When the ratio is 1:1, the adsorption efficiency of the composite adsorbent shows a good performance. At 900°C, the adsorption efficiency of Z1C1(ZSM-5/CaO = 1:1 wt%) can still maintain 67%, which is 32% higher than that of CaO. Si and Al in the composite adsorbent have different effects on the improvement of microstructure. The existence of Si is conducive to maintaining the stable skeleton of the composite adsorbent, improving anti-sintering, while the addition of Al tends to improve the porosity, furtherly ameliorating the structure of the composite adsorbent for high-temperature adsorption.