Abstract
In order to obtain the adsorption mechanism and failure characteristics of CO2 adsorption by potassium-based adsorbents with different supports, five types of supports (circulating fluidized bed boiler fly ash, pulverized coal boiler fly ash, activated carbon, molecular sieve, and alumina) and three kinds of adsorbents under the modified conditions of K2CO3 theoretical loading (10%, 30%, and 50%) were studied. The effect of the reaction temperature (50 °C, 60 °C, 70 °C, 80 °C, and 90 °C) and CO2 concentration (5%, 7.5%, 10%, 12.5%, and 15%) on the adsorption of CO2 by the adsorbent after loading and the effect of flue gas composition on the failure characteristics of adsorbents were obtained. At the same time, the microscopic characteristics of the adsorbents before and after loading and the reaction were studied by using a specific surface area and porosity analyzer as well as a scanning electron microscope and X-ray diffractometer. Combining its reaction and adsorption kinetics process, the mechanism of influence was explored. The results show that the optimal theoretical loading of the five adsorbents is 30% and the reaction temperature of 70 °C and the concentration of 12.5% CO2 are the best reaction conditions. The actual loading and CO2 adsorption performance of the K2CO3/AC adsorbent are the best while the K2CO3/Al2O3 adsorbent is the worst. During the carbonation reaction of the adsorbent, the cumulative pore volume plays a more important role in the adsorption process than the specific surface area. As the reaction temperature increases, the internal diffusion resistance increases remarkably. K2CO3/AC has the lowest activation energy and the carbonation reaction is the easiest to carry out. SO2 and HCl react with K2CO3 to produce new substances, which leads to the gradual failure of the adsorbents and K2CO3/AC has the best cycle failure performance.
Highlights
Global climate change caused by greenhouse gas emissions is a hot issue in our modern society, which is related to the development and survival of the whole mankind
Some researchers have modified the potassium-based adsorbent by using activated carbon (AC), MgO, TiO2 [21], and a 5A molecular sieves [22] and studied the carbonation reaction by thermogravimetric analyzer. They found that the CO2 adsorption rate of K2 CO3 /AC adsorbent increased by 73% as the AC loading increased from 9% to 33% under the conditions of 60 ◦ C and
The surface morphology of the adsorbent was obtained by the Nova Nano SEM 50 scanning electron microscopy (Thermo Fisher Scientific, Hillsboro, OR, USA) and the crystal structure of the adsorbent was obtained by the X/max-2500 X-ray diffractometer (XRD) (Rigaku, Tokyo, Japan)
Summary
Global climate change caused by greenhouse gas emissions is a hot issue in our modern society, which is related to the development and survival of the whole mankind. Some researchers have modified the potassium-based adsorbent by using activated carbon (AC), MgO, TiO2 [21], and a 5A molecular sieves [22] and studied the carbonation reaction by thermogravimetric analyzer They found that the CO2 adsorption rate of K2 CO3 /AC adsorbent increased by 73% as the AC loading increased from 9% to 33% under the conditions of 60 ◦ C and. The reaction and adsorption kinetics studies have become an important method for predicting the adsorption rate-determining step and analyzing the adsorption mechanism It is widely used in the adsorption of heavy metals from the liquid phase and the adsorption of SO2 and NO on the surface of solid adsorbents. On the basis of different supports’ effects on the CO2 adsorption characteristics of potassium-based adsorbents combined with the microscopic properties of the adsorbent, the mechanism of carbonation is studied using reaction and adsorption kinetics. The effect of flue gas composition on the failure characteristics of the adsorbent is studied, which will provide a theoretical basis for future CO2 removal methods
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