Addressing your Waste Gas with Absorption and Chemistry
Utilizing scrubbing and quenching systems are a great addition to your existing pollutant destruction system and can keep your pollutants to a minimum. Scrubber and quench systems include a process by where waste gas pollutant temperatures are reduced so the pollutants can be diluted, re-formed, or altered by changing the chemical composition to meet the needs of either expulsion or recycling. CleanCap’s highly trained team of professionals are not only familiar with how to maintain or repair these types of systems, but our design team can help your facility create systems custom fit for your needs that can significantly improve your industrial emissions.
Quenching: Wet-Scrubbing Pretreatment
Quenching is a method of gas cooling often used when a hot gas stream is to be treated by a wet scrubber. This is necessary to prevent evaporative losses inside the scrubber that would otherwise reduce its removal efficiency. Quenching is achieved by spraying water into the hot gas stream until a point of adiabatic saturation is reached. At this point any heat that would be transferred through evaporation is immediately offset by an equal amount of condensation. This assures that none of the scrubbing liquid will evaporate as the gas stream heads into the scrubber.
Wet Scrubbers
Wet scrubbers are designed to remove pollutants from a gaseous stream with a scrubbing liquid. Contaminants are absorbed out of the air stream and dissolved in the liquid. In certain cases, contaminants which are low in solubility require the addition of chemical additives to improve absorption.
In a single-stage, vertical packed scrubber, the tower contains randomly dispersed packing to improve contact between the gas and liquid phases. The polluted air stream flows upwards through the bottom of the packed tower counter-currently to the flow of a scrubbing liquid. The cleaned gas then passes through a mist eliminator to remove any entrained liquids. As the scrubbing liquid is re-circulated, the addition of fresh water and removal of old liquid is necessary to purge contaminants that accumulate. Fresh water may be added to the recycle reservoir either continuously or on a periodic basis.
Multiple scrubber stages may be employed for the removal of different compounds. For example, use of a caustic solution may be used in one stage to neutralize and absorb acids, and a sulfuric acid solution in the other to remove ammonia.
Dry Scrubbers
Dry scrubbers are primarily used to abate acidic gases, like those associated with acid rain. This is one of the most common pieces of equipment found in manufacturing plants because of its ability to handle high temperatures, and highly acidic exhaust streams. A dry scrubber works by combining carefully chosen chemical reagents with the exhaust stream at incredibly high speeds, that react with or absorb the compounds in the stream. These chemicals react differently, depending on which compounds are being targeted; reactions either neutralize the dangerous VOCs, or absorb them into a different compound all-together. Once converted, the substance left over can then be disposed of or transported easily. Each type of scrubber media removes particles and compounds in a different way; some chemical reactions, while others use electrostatic adhesion.
Scrubbers in general have many advantages as a form of air pollution control: