With the development of technology and increasing the level of air pollution, people have naturally moved towards the creation of efficient air treatment devices, one of which is a scrubber — a system of dust and gas collecting, applied in a wide range of industrial and processing enterprises.
Scrubbing systems are industrial devices designed for cleaning gaseous matters from pollutants. The application of scrubbers includes technological and chemical processes, various fields of industry. The principle of the wet scrubber operation was developed in the early to the mid-19th century.
Scrubbing systems are devices of various designs, which are used for cleaning gases with special liquids in order to clear up them and to extract one or several components, as well as drum engines for cleaning mineral resources. Such air treatment devices are widely used for capturing products of coal carbonizing process and cleaning industrial gases from dust, for moistening and cooling gases, in various chemical-technological processes.
The principle of the scrubbing system is that the scrubber picks up suspended particulate matters from the exhaust gases. After that, the gas is cleaned with water or a special solution. The process is based on the intensive mixing of gas and liquid. This cleaning technique is called wet air scrubbing. The size of air pollutants increases due to condensation of water vapor on them resulting in efficient air treatment.
For example, a hollow nozzle Venturi scrubber is designed to create a high gas flow rate. The gas enters, accelerates in the narrowing part of the scrubbing system, and then mixes with a cleaning solution at high speed. It is widely used for gas moistening and cooling, for air treatment from dust pollutants.
The wet air scrubbers treat the incoming gas-air stream with the help of water or a special deactivating solution. Based on application parameters, wet scrubbers can be divided conditionally into air treatment devices and drum engines for cleaning mineral resources.
Scrubbing systems are employed in the mining industry for catching coking pollutants. In this industry, wet air scrubbers of conical or cylindrical shape are used predominantly, resembling a drum, in the center of which there is a rotating paddle. Fossils that require cleaning procedure are placed in a scrubbing system, where they, mixing with the cleaning solution, are moved in a spiral by the paddles. Pollutants containing clay and limestone are diluted by water and then removed from the drum with it, leaving the purified material. When it comes to air pollution treatment, the purified gas is transported to the atmosphere after the air treatment process, and the liquid with sludge enters the scrubbing system‘s tank through the drain pipe.
The store of cleaning solution is replenished through the tank with the reserve content, and the process can be carried out again. The capacity of wet scrubbers used in the mining industry is pretty high and amounts to 200 tons, with insignificant water consumption of 3-6 m3 / ton. and with minimal time intervals.
Types of scrubbers used in the mining industry are divided into reverse-flow and straight-flow depending on the water movement relative to the material. If the direction of material flow coincides with the direction of the water flow, then the scrubber is called direct-flow, if it is not the same, then the scrubber is reverse-flow.
Thus, it is possible to clean the gas from particles of any size.
The disadvantage of wet scrubbing technology for air treatment can include the formation of a large amount of sludge. The advantages include the relatively low cost of wet scrubbing device. This method is applied in the chemical industry, foundry, leather, ceramic production, oil refining, and mining industry during working with various types of bitumen, as well as the combustion of industrial gases and waste.
Scrubbing systems are installed in large enterprises in treatment facilities. The main requirement for the wet scrubbers is the most developed surface of the contact phase. This is necessary for more complete extraction of a given component from the gas phase. The scrubbers with a movable nozzle most fully meet the conditions.
These scrubbing systems can operate at high loads in terms of gas temperature and volume, as well as concentrations of extracted components, they are characterized by high efficiency, and also have an important property – the mobility of the nozzle that eliminates the formation of suspended particles sediment and clogging the effective section of the wet scrubbing device. The high speed of the gas (3-8 m/s) makes it possible to manufacture the devices rather compact.
Modern scrubbers with a movable nozzle have different shapes and design features depending on their purpose, such as mass transfer, heat transfer, or heat-mass transfer. Herewith, the heat and mass transfer processes can take place in the device selectively at different mass transfer elements for different substances, and even during the use of absorbers differing in their characteristics.
Such properties and capabilities of scrubbers with a movable nozzle predetermined their wide distribution and application in various industries. Generally, the scrubber consists of the following parts (they may vary slightly depending on the purpose and features of operation):
- air circulation and gas circuit systems;
- carbonation chamber (optional);
- in fact, an operational body (cleaning room);
- trapping separator, (otherwise – a drop or mist separator);
- self-cleaning system and/or recycling system (optional);
- outlet pipe.
In addition to washing application, scrubbing systems are used for separation (sizing) material. In order to perform the separation procedure, a conical perforated part is connected to the drum of the wet scrubber. An important feature of the wet scrubber operation is that, in fact, undesirable pollutants do not disappear anywhere during the cleaning process, but they are only “removed” from the passing polluted stream and are concentrated on a liquid solution, paste or dry powder.
It often happens that waste products from wet scrubbing systems also need to be carefully disposed of: for example, the contents of the collectors after the treatment of mercury ores should be safely buried in special mercury storage.
Nevertheless, it is impossible not to take into account the positive aspects. For example, wet air scrubbers, cleaning emissions of power plants, form synthetic gypsum of high quality as output waste that is successfully used for the manufacture of gypsum board and other building materials. And this is not the only example of rational disposal of sludge.
The following advantages should be mentioned among others:
- compact size, and consequently, easy installation in the industry: the small size of the wet scrubbing devices results in less capital investment with high mobility of the structures compared with units of the same productivity, but of a different type of action;
- no secondary sources of dust and air pollution: once packed in the collector, waste is easily transported without any leaks;
- the ability to operate with highly saturated and high-temperature flows: no problems with condensation and temperature limitations (as, for example, in electrostatic separators or bag filters);
- maximum fire and explosion safety: the presence of a liquid medium minimizes the possibility of detonation or fire in the scrubber;
- universality: the ability to operate with both gaseous chemical and mechanical air pollutants of various fractions.
Such properties of dust particles as particle density, adhesion (the ability of strong adhesion), flowability, wettability, solubility of particles, electrical and electromagnetic properties of particles, ability of spontaneous combustion and formation of explosive mixtures with air have a great influence on the choice of methods and techniques of dust collection and dust suppression.
Wet scrubbing devices are characterized by high cleaning efficiency from fine dust (0.3-1.0 microns), as well as the possibility of cleaning hot and explosive gases from dust. Therefore, you should keep in mind the following during choosing means for cleaning emissions into the atmosphere:
- dry mechanical methods and scrubbing devices are not effective at removing fine and sticking dust.
- wet scrubbing techniques are not effective in cleaning up emissions that contain poorly cohesive and lumpy substances (for example, cement).
- electric separators are not effective in removing contaminants that are poorly charged with electricity.
- bag filters are not effective in cleaning the emissions from the adhesive and wetted contaminants.
- wet scrubbers are not suitable for outdoor use in winter conditions.
For scrubbing of non-explosive dust, like iron ore dust, it is more beneficial to use wet scrubbers rather than dry ones. Firstly, such productions in most cases already utilize water in their manufacturing cycle. Secondly, dry scrubbers, such as tubular cloth filters or electrofilters, usually operate at average gas flow speeds of not more than 1.5 m/s, while most wet scrubbers operate at flow speeds of 4 m/s and more.
Redwood technology is a fast-growing vendor of wet air scrubbers. The multi-vortex scrubber can remove gas emissions, dust, vapors, and other pollutants from a gas stream. It is an innovative technology created to save water that makes it more cost-efficient and differs from other types of scrubbers. If you have any questions or would like to purchase a multi-vortex wet air scrubber, please contact us at email@example.com