Hydroxyl Radical Eliminates H2S in Wet Scrubbers & Flue Gases
In a recent study in Houston, TX, H2S was removed from a natural gas stream containing 2,000 mg/l of H2S and 5% CO2 using JC 9450 ROS. JC 9450 ROS is a new mineral oxychloride compound that generates Reactive Oxygen Species (ROS) like hydroxyl radical ions and others in a highly soluble form that is easy to use. The study, which simulated operating conditions of a wet scrubber, found that the high concentration of soluble hydroxyl radical ions quickly took the ORP (oxidation-reduction potential as measured by mV) from -150 mV to +100 mV, completely eliminating the H2S. The residual materials left in solution were inert sulfate compounds.
Sour gas and sour water are terms used to describe gas and water containing significant amounts of hydrogen sulfide (H2S). Sour water and sour gas applications are abundant at oil refineries and natural gas plants. The “sweetening” of gas and water refers to the processes used to remove H2S and organosulfide compounds. Hydrodesulfurization is a method used to remove sulfur in these applications. It is a catalytic chemical process used to capture the sulfides in natural gas and refined petroleum products including gasoline, jet fuel, kerosene, fuel oils and diesel fuel. The H2S gas is subsequently converted into elemental sulfur with the Claus Process.
One of the reasons that it is important to remove sulfides from natural gas and refined petroleum products is to reduce the sulfur dioxide emitted when the fuel is combusted in automobile engines, power plants and furnaces. The U.S. Environmental Protection Agency (EPA) has focused on SO2 as a pollutant for decades. The largest sources of SO2 emissions are from fossil fuel combustion at power plants (73%) and other industrial facilities (20%). In 2010, the U.S. EPA revised the primary SO2 National Ambient Air Quality Standards (NAAQS) by establishing a new one-hour standard at a level of 75 ppb. The EPA revoked the two existing primary standards because they would not provide additional public health protection given a one-hour standard at 75 ppb.
According to the U.S. EPA, current scientific evidence links short-term SO2 exposures, ranging from 5 minutes to 24 hours, with an array of adverse respiratory effects, including bronchial constriction and increased asthma symptoms. These effects are particularly important for asthmatics at elevated ventilation rates (e.g. while exercising or playing). Studies also show a connection between short-term SO2 exposure and increased visits to emergency departments and hospital admissions for respiratory illnesses, particularly in at-risk populations such as children, the elderly, and asthmatics.
Wet scrubbing is one of the processes used to remove Nitrogen compounds (NOx) and Sulfur compounds (SOx). During this process, particulates and pollutants are removed from a gas or liquid stream through contact with a scrubbing liquid. The scrubbing liquid is typically a water-based solution that is recirculated through a sprayer at the top of a tower, with the gas stream moving up the tower from the bottom. This countercurrent flow is used to efficiently capture particulate matter and absorb specific chemicals from the gas. Acidic solutions (sulfuric acid solutions) absorb alkaline gases such as ammonia, and alkaline solutions (caustic soda, sodium hypochlorite, lime slurry) absorb acidic gases such as sulfur dioxide, carbon dioxide and hydrogen sulfide. The goal of this treatment is to keep hydrogen sulfide below 4 mg/l. In the area of non-regenerative systems there are four types of chemical scavengers: aldehyde-based, metallic oxide-based, caustic-based and other processes (oxidants).