Vapor Carbon Adsorbers & Carbon Vessels
ProAct uses carbon vessels to remove organic contaminants from a waste vapor stream. Carbon adsorbers take advantage of molecular forces to treat vapors contaminated with organic compounds. It is the same chemistry that occurs in a charcoal “filter” cartridge for an organic vapor respirator.
When molecules or ions do not have all their molecular forces satisfied, they are “unsaturated.” Carbon particles can satisfy their molecular forces by attracting and holding compounds from a vapor stream. This concentration of molecules on a solid surface is called adsorption.
Carbon adsorption occurs when organic compounds are selectively adsorbed onto the surface of carbon. When carbon is “activated,” usually by heating it with oxygen or steam, the carbon becomes more porous. The available surface area within an activated carbon particle is hundreds of square meters per gram. Inter-molecular attraction draws organic molecules to the porous surface of the carbon particles.
The purpose of a vapor carbon vessel is to provide a place where a contaminated vapor stream can come into contact with activated carbon, and allow enough contact time for the contaminants to transfer from the vapor stream to the carbon. The contaminants are then destroyed when the carbon is regenerated. Alternatively, the carbon, with the contaminants, can be sent to a landfill for disposal.
ProAct carbon vessels range from 200 lb. (55-gal. drum size) to 20,000 lb. (large 10-ft. diameter tanks). Vapor enters the vessel through an influent connection at the bottom and escapes at the top. Large carbon vessels have manways for carbon addition and removal.
To protect the vapor carbon from becoming fouled by liquid or product, the vapor usually flows through a “knock-out” tank before entering the carbon vessels. The liquids are retained in the knock-out tank and the vapor passes through. The retained liquids are then disposed of safely.
The vapors then enter the carbon vessels. There are usually at least two vapor vessels in a carbon vapor treatment system, and sometimes many more. The vessels can be connected in various configurations. A common configuration is to have sets of two vapor carbon vessels connected in series. Several such sets can be arranged in parallel to allow for high flow rates.
Vapor flows from the knock-out tank to the influent at the bottom of the first vapor carbon vessel. It flows up through the carbon to the effluent discharge point at the top. The effluent from the top of the first vessel then flows into the bottom of the next vessel. After treatment through the last vapor carbon vessel, the vapor treatment stream may be discharged to the atmosphere, or captured for further treatment, depending on project needs.
Carbon becomes spent when it is unable to adsorb any more contaminants. The spent carbon must then be replaced with fresh carbon. The spent carbon may be disposed of, or sent to a facility where the adsorbed molecules may be removed from the spent carbon. This process is called regeneration, and is usually done offsite at a regeneration facility, by applying heat.
Vapor carbon systems are often used when a high flow rate (>3000 cfm) is needed. They are also a great option when the waste vapor’s burn value is not high enough to support thermal oxidation. While carbon effectively removes most organics from a vapor stream, some contaminants are not readily captured. ProAct’s vapor vessels may be filled with different media that operate by different chemical means to remove these contaminants.
ProAct has many vapor vessels in different sizes and flow rates. ProAct has alternative treatment methods, if vapor vessels are not perfect for your application. ProAct can design and build the most effective system to meet your vapor treatment needs. ProAct’s experienced technicians can operate your system to maximize the treatment effectiveness. Call a ProAct specialist today to discuss how best to meet your vapor treatment needs.