Sorbents for the oxidation and removal of mercury

What is this patent about?

’114 is related to the field of emission control and pollutant removal from industrial gas streams. Specifically, it addresses the technical challenge of capturing elemental and oxidized mercury from flue gases generated by coal combustion or gasification systems, where traditional untreated sorbents often lack the necessary reactivity and kinetic speed to meet stringent environmental standards.

The underlying idea behind ’114 is the creation of a highly reactive promoted sorbent by facilitating a surface-level chemical reaction between a base material and a halogen promoter. Rather than relying on simple physical adsorption, the invention utilizes the formation of metastable complexes—such as Lewis acid or basic sites—on the sorbent surface to actively oxidize elemental mercury upon contact, significantly accelerating the capture process even within the very short residence times available in a flue gas duct.

The claims of ’114 focus on a method for separating mercury by introducing a bromine-based promoter—such as HBr or Br2—directly into the combustion process or onto the coal itself, followed by the downstream injection of an activated carbon sorbent. The independent claims specifically protect the process of allowing the sorbent to react with the gas-phase promoter to form a promoted sorbent in-flight, which then binds with mercury to be collected by a particulate control device.

In practice, the system functions as a dynamic, feedback-controlled loop where the mercury content of the cleaned gas is continuously monitored to adjust the injection rates of either the sorbent or the bromine promoter. This in-flight preparation allows the sorbent to be activated at the moment of use, ensuring maximum reactivity and allowing for real-time optimization based on the specific chemistry of the coal being burned. The invention also contemplates the use of non-carbon bases, such as vesicular felsic materials, which can be physically separated from fly ash for regeneration.

This approach differentiates itself from prior art by moving away from expensive, pre-treated sorbents that may lose potency during storage or transport. By utilizing the synergistic effect of gas-phase bromine species and injected particulates, the method overcomes the kinetic barriers that typically hinder mercury oxidation in low-chlorine environments. Furthermore, the ability to use larger sorbent particles that are physically separable from ash allows for the recovery of both the sorbent and high-quality ash for use in cement, improving the overall economic and environmental footprint of the facility.