Experimental and Kinetic Analysis of H₂O on Hg⁰ Removal by Sorbent Traps in Oxy-combustion Atmosphere

Abstract

Oxy-combustion technology is under development for CO2 capture. H2O could influence the Hg0 removal by sorbent traps in an oxy-combustion atmosphere. A study of the effects of H2O on Hg0 removal by biomass char under oxy-combustion conditions is presented in this paper. The kinetic model analysis was conducted to study the adsorption process of Hg0, which included a pseudo-first-order kinetic model, a pseudo-second-order kinetic model, and intraparticle diffusion kinetic model. Experimental results showed that a low-level of H2O had a promoting effect on the adsorption of Hg0, and high-level of H2O had an inhibiting effect. A high concentration of H2O would form a water film on the surface of sorbent traps to hinder the removal of external mass transfer on Hg0. Although the adsorption rate of Hg0 depended both on external mass transfer and intraparticle diffusion, external mass transfer was a more important controlling factor. It was found that physical adsorption was one of the main forms of Hg0 removal on the surface of sorbent traps, owing to the large specific surface area and good pore structure of the modified corn straw char. The removal of Hg0 was mainly attributed to capture by physical adsorption and the formation of HgO by chemisorption.

Interference Effect of H2O on Hg0 Removal by a Mercury Sorbent in an Oxyfuel-Combustion Atmosphere

“…TPD is a method of heating the desorption adsorbate according to a predetermined temperature program to obtain the relationship between the desorption amount and temperature. It is one of the most commonly used methods in our previous studies to explore the types of mercury compounds according to the different thermal stabilities of mercury compounds. − …”

The Effect of Acid Gases on Elemental Hg Removal and Experimental Studies Accompanied by Quantum Chemical Calculations (DFT)

“…Therefore, NH 4 Br and HNO 3 are used for joint modification in this work, and the mercury removal mechanism is further analyzed. Wu 28 only studied the effect of H 2 O on the removal of Hg 0 from biomass char under the condition of oxy-fuel combustion, and the analysis of the effect on acid gas was not enough. In addition, in the oxy-fuel combustion flue gas, a complex atmosphere of acid gases such as SO 2 , HCl, and NO generally exists at the same time.…”

Interference Effect of Experimental Parameters on the Mercury Removal Mechanism of Biomass Char under an Oxy-Fuel Atmosphere

“… 29 , 30 Biomass char is an ideal adsorbent for mercury removal due to its low price, abundant surface functional groups, simple raw materials, and environmental protection. 31 , 32 …”

“…29,30 Biomass char is an ideal adsorbent for mercury removal due to its low price, abundant surface functional groups, simple raw materials, and environmental protection. 31,32 The parameters in the experiment will also have a great impact on the experimental results. Zhao et al 33 showed that the change of Hg 0 removal efficiency with the increase of reaction temperature is non-monotonical.…”

“…At present, activated carbon injection (ACI) is the most mature and feasible technology for mercury removal in coal-fired power plants. , Scholars have carried out a lot of experiments and theoretical studies on mercury removal by activated carbon from coal-fired flue gas. − However, activated carbon is expensive and not suitable for large-scale commercial use. Nowadays, researchers have turned their attention to biomass. , Biomass char is an ideal adsorbent for mercury removal due to its low price, abundant surface functional groups, simple raw materials, and environmental protection. , …”