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What is a scrubber and what does it do ?

Scrubber is an air pollution control device which uses either liquid spray to remove solid or liquid particulate matter and gaseous pollutants which are either absorbed or chemically neutralized.

Why scrubbers should be used ?

Scrubbers are devices that are used in controlling air pollution. It uses liquid to remove particulate matter or gases from an industrial exhaust or flue gas stream. This liquid en-trains the particles and pollutants to wash them out of the gas flow.

How does a venturi scrubber work?

Venturi scrubber works on the principle of absorption technology and venturi effect, where the pollutants gas and scrubbing liquid / water is made to pass through a confined throat where both comes in contact so closely at high velocity forming large number of droplets, there by creating large area for the particles to get absorbed to liquid droplets. The sizing of scrubber, Throat design, selection of scrubber solution, Material and inner lining is critical in designing Venturi scrubber for a particular application.

How is sulfur dioxide removed from flue gases?

Once sulfur is burned and produces SO2, the exhaust gas passes through the scrubber where a spray mixture of limestone (or other chemical reagent) and water reacts with the SO2. The reaction enables the SO2 to be removed before it’s released into the atmosphere. Scrubbers are typically designed to remove 95% or more of the SO2from the exhaust gas. The white plume that comes out of the stack is water vapor.

Why is an wet air gas scrubber used for in manufacturing industries ?

Scrubbers are air pollution control devices that use liquid to remove particulate matter or gases from an industrial exhaust or flue gas stream. This atomized liquid (typically water) entrains particles and pollutant gases in order to effectively wash them out of the gas flow. In comparison to other air pollution control devices, scrubbers are very multidisciplinary, with the ability to remove solids, mists, and gases simultaneously while also providing cooling. They are also capable of handling explosive and flammable gases safely. However, scrubbers suffer from high levels of corrosion and produce slurry waste streams which are less convenient for recycling and disposal.

What is wet scrubbing  &  working principle of scrubber ?

Wet scrubbers relay on the liquid spray to remove dust particles from the gas stream. It is also for the fume absorption and so very useful in fume extraction systems. It removes air pollutants by inertia of diffusional impaction, reaction with absorbent or reagent slurry or absorption into a liquid solvent. The inlet gas stream usually enters the bottom of the tower and moves upward, while liquid is sprayed downward from one or more levels.

How to calculate the efficiency of a scrubber ?

The factors influencing the scrubber efficiency  can be  determined from the DOE requirements. These factors includes irrigation area, scrubbing liquid, bed depth, liquid flow rate, temperature, material of construction, packing, maintenance, liquid to gas ratio and heat effect.

What is scrubber in chemical engineering ?

How scrubbers work to exhaust  industrial dust ladden air ?

The design of wet scrubbers depends on the industrial process conditions and the nature of the air pollutants involved. Inlet gas characteristics and dust properties of primary importance. Dust particles are removed by wet scrubbers by capturing them in liquid droplets. The droplets are then collected . Any droplets that remain in the scrubber inlet gas must be separated from the outlet gas stream by means of  to as a mist eliminator or entrainment separator.

What is the working principle of mist eliminator ?

Mist eliminators work on the principle of direct impaction. The liquid droplets are collected in a direct impact with a portion of the packed bed media.

How to choose right scrubber for your industry ?

What is the difference between scrubber and absorber ?

Absorber is used mostly for removal of only gaseous component from gaseous stream using suitable solvent which then is regenerated while scrubber is used to remove pollutant from outgoing gases mostly pollutants are gases (acid gases), particulate, dust etc. while there is no necessary regeneration of solvent in scrubber other assembly is similar in both absorber and scrubber.

What is liquid to gas ratio ?

An important parameter in wet scrubbing systems is the rate of liquid flow. It is common in wet scrubber terminology to express the liquid flow as a function of the gas flow rate that is being treated. This is commonly called the liquid-to-gas ratio (L/G ratio) and uses the units of gallons per 1,000 actual cubic feet or liters/cubic meter (l/m³).

Expressing the amount of liquid used as a ratio enables systems of different sizes to be readily compared. For particulate removal, the liquid-to-gas ratio is a function of the mechanical design of the system; while for gas absorption this ratio gives an indication of the difficulty of removing a pollutant. Most wet scrubbers used for particulate control operate with liquid-to-gas ratios in the range of 4 to 20 gallons per 1,000 actual ft³ (0.5 to 3 liters per actual m³).

Depending on scrubber design, a minimum volume of liquid is required to “wet” the scrubber internals and create sufficient collection targets. After a certain optimum point, adding excess liquid to a particulate wet scrubber does not increase efficiency and in fact, could be counter-productive by causing excessive pressure loss. Liquid-to-gas ratios for gas absorption are often higher, in the range of 20 to 40 gallons per 1,000 actual ft³ (3 to 6 litres per actual m³).

L/G ratio illustrates a number of points about the choice of wet scrubbers used for gas absorption. For example, because flue-gas desulfurization systems must deal with heavy particulate loadings, open, simple designs (such as venturi, spray chamber and moving bed) are used. Also, the liquid-to-gas ratio for the absorption process is higher than for particle removal and gas velocities are kept low to enhance the absorption process.

How does wet scrubber work in controlling emission of pollutants?

Wet scrubbers are compatible and effective air pollution control devices to arrest particulate matters and polluting gases coming out of industrial processes as air polluting emissions. There are various types of wet scrubbers that are used for the removal of harmful pollutant from the dust ladden gas. The scrubbing efficiency of the perfectly designed  wet scrubber can be around 99.99 percent.

What is the working principle of dry scrubber ?

Dry Scrubber system utilizes dry adsorption techniques to separate pollutant acid gases from exhaust air stream. These scrubbers are mainly used to remove acid gases from combustion sources. This removal of acid gases is done by using a series of dry reactants that on reaction exhausts gas at high speeds and thus neutralizing the pollutants in the gas.

What is wet scrubbing gcse ?

What is a scrubber in a chimney for?

Chimney or Stack in a scrubber is used to send out the exhaust gas that is free from pollutants after the scrubbing process.  The stack must be designed for the process, and then designed mechanically and for accessories requirements. The process will dictate location and size. The mechanical analysis will take into account loads contributed by the stack dead weight, seismic and wind loads, buckling and bending moments, guy wire compression and temperature gradients to name a few.