Air pollution control equipment comes in a variety of problematic forms, a wide variety of which are called either hazardous air pollutants (HAPs) or volatile organic compounds (VOCs). Such pollutants, which include atmospheric vapors, sulphuric fumes, odors and gases, hydrocarbons and other byproducts, can cause or aggravate serious health and environmental issues. They may cause mild respiratory irritations, asthma symptoms or even severe allergic reactions, and they may create smog, acid rain, climate change carbon emissions and the like. These risks are why organizations like the EPA encourage or require the use of pollution control equipment, also called emission control systems, in industrial and commercial settings. Popular pollution control equipment include wet scrubbers, air scrubbers and electrostatic precipitators. Electrostatic precipitators, or ESPs for short, remove particulates from an air/gas stream via an electrostatic charge. Particulates include pollutants both visible and invisible to the naked eye, such as debris, smoke, dust, powder and ash. ESPs can remove up to 99.9% of contaminants from the air without majorly disrupting regular airflow and they widely display high performance; for these reasons, they are popular with the commercial and industrial emissions control systems of many different industries. Specifically, ESPs are used heavily in industries like petroleum processing, chemical processing, materials handling, textile, machining, electronics and general manufacturing.
So, how does an electrostatic precipitator work, exactly? It centers around ionization, the process by which an atom or molecule gains or loses electrons while acquiring a positive or negative charge, in order to form ions. Ionization within an ESP requires that the particles in its air supply be charged inductively with an electric field as the ESP’s metal tubes or plates, called collection tubes or plates, respectively, are charged with a negative voltage. The opposing charges will attract, causing the particulates to stick to the collection tubes or plates. Once the particulates have adhered to them, they may be transferred into a bin for disposal or recycling. ESP systems are divided into two main categories, based on the method by which the built-up particulates, or cake, are removed. These categories are wet and dry. Simply put, dry machines remove particulates by shaking, tapping or rapping the collector, while wet systems remove particulates by conditioning and rinsing them away with water or washing solutions. Whether one uses a dry ESP system or a wet ESP system depends mainly on resources at hand, the operating space and the type of pollutants within the targeted air stream.
Electrostatic precipitators offer a great many benefits to users. For one, they allow for the easy and hassle-free collection of trapped dust and particles, some of which may be reused, leading to significant material savings and a nod to the environment. In addition, since their very high cleaning success rate (99.9%) does not impede airflow, they offer incredibly efficiency. ESPs are also fantastically versatile; they work at high performance levels for applications across the board. Potential users will select the best precipitator for their application by considering the size of the system to be controlled, the type and electrical properties of the particles to be collected, the volume and velocity of the process gas and the available power supply. These factors inform what precipitator will offer optimal efficiency and operational abilities. In addition, given the numerous options before them, potential users should make sure to consult air pollution control equipment professionals prior to making their final decision.
To make sure an electrostatic precipitator works as well as it can with the highest level of efficiency that it can, an operator must make sure that it is assembled and installed properly and that it is sees routine maintenance. For example, when installing, one must make sure that the ESP’s potential maintenance areas, like motors, dampers, discharge devices, fans, insulators, hoppers, T-R sets and rappers, are readily accessible. Test and inspection areas, such as stack testing ports and continuous emission monitors, should be likewise accessible. Also, operators need to keep in mind any natural elements the ESP may encounter; if it will be exposed to snow or rain, for example, closer monitoring will likely be required. The regular performance of and diligent recording of monitoring procedures lay the groundwork for successful, long-lasting pollution control. System elements to monitor include: voltage/current, gas temperature, gas moisture and composition, gas distribution and flow rate, opacity and how your ESP functions on a daily basis. Such procedures help operators identify and remedy performance issues or systemic flaws by creating a reference point and exposing patterns.
Wet Electrostatic Precipitator System – B&W MEGTEC Systems, Inc.
Wet Electrostatic Precipitator Collection Tubes – B&W MEGTEC Systems, Inc.
Different Types of Electrostatic Precipitators
An electrostatic precipitator is an air filtration device used primarily in the manufacturing, metal, and mining industries. The device deploys an induced electrostatic charge to remove dust, smog, and particulate matters from exhaust air/gas streams. Also known as an electrostatic smoke precipitator (ESP), this is an essential utility for a manufacturing business that wants to keep its carbon and sulfur footprint under control.
Using electrostatic charge to remove dust is not a new concept. The technique is more than a century old. In 1824, Dr. M. Hohlfeld first used the technique to remove particles from a certain type of aerosol. However, the technology, in the present time, has significantly advanced. We now have smart air filters and air pollution control systems that can control even a consistently strong exhaust stream.
Different Types of Electrostatic Precipitators
Plate Precipitator – This simplest version of an ESP includes thin wires assembled vertically and placed just before a selection of large metal plates. These plates are also set vertically. The spacing between two plates could be any value between 1 and 18 centimeters. The mechanism is programmed in a way that the air flow passes through it horizontally. While the flow runs across the machine, dust particles are collected and processed. The plate precipitator supplies extreme voltage from the wires to the plates to order to ionize the air and the particles.
Industrial Precipitator – For industries, electrostatic smoke precipitators work as a pollution control mechanism, air filtration system, and as gas emission control systems and dust collectors. The purpose of an industrial precipitator is to ensure that a manufacturing business is abiding by governmental pollution control standards. A robust ESP can remove a number of particulate exhaust elements such as coal or oil smoke, salt cake, chemical pulp extracts, and gaseous elements. Industrial precipitators can treat substantial gas volumes under extreme high temperature. These devices include a parallel plate and wire design system and modern industrial ESPs leverage electrode designs that increase the corona production. Further, these machines can handle high electric current densities due to a powerful automatic voltage control unit.
Wet Precipitator – These are also branded as wet electrostatic smoke precipitators. As their name signifies, wet precipitators are suitable for liquid exhaust streams. They can remove particulate matter such as the dewdrops of sulfuric acid and other acidic elements from an industrial exhaust outlet. In addition to this purpose, wet precipitator systems can also be used for gas or air streams that are rich in moisture content. Such streams are labeled water vapor saturated air streams, and have almost zero percent humidity.
Apart from these types, a range of consumer focused precipitators, which are actually air purifier devices for residential use, are also available. These devices are smaller utilities which home and small office users can install as replacements for traditional furnace air filters.