12/10/2019 | Industrial Water Treatment | 9 MINUTE READ

Wet vs. Dry Industrial Scrubbers

Industrial scrubbers are devices that can control pollution by purifying the exhaust streams, which means that hardly any harmful gases or particulates will leave the building and enter the environment. Along with getting rid of toxic substances, industrial scrubbers are able to clean the atmosphere and eliminate any fumes in the vicinity. There are two basic types of industrial scrubbers that you can select from, which include a wet scrubber and a dry scrubber.

A wet industrial scrubber is able to remove harmful substances from exhaust gases by using a wet substance to do so. When flue gas is sent through the system, the wet industrial scrubber sprays this gas with a special fluid that reacts mainly with the heavier contaminants that are present in the gas. On the other hand, a dry industrial scrubber sprays numerous dry reagents onto the exhaust stream. This slurry can either neutralize pollutants or change them into a different substance altogether.

The main purpose of both of these industrial scrubbers is to make sure that the exhaust gases created in an industrial plant don’t cause undue amounts of pollution to enter into the environment. Both types of industrial scrubbers are able to eliminate acidic gases that are known to directly contribute to harmful acid rain. While both of these systems are effective at removing pollutants from industrial exhaust gases, they also have some notable differences between them.

It’s important that you know these differences if you want to invest in the right industrial scrubber for your business or plant. The following offers up a guide on the various differences between wet and dry industrial scrubbers as well as the use of these scrubbers within industrial applications.

Wet Industrial Scrubbers

smoke from industrial chimney

Wet industrial scrubbers are able to remove pollutants from flue gas and similar gas streams by spraying a liquid onto the gas and removing the contaminants before the gas is sent into the environment. The liquid can either absorb or dissolve the pollutants. When attempting to remove particulate matter and dust, the only liquid that needs to be used in a wet industrial scrubber is water. On the other hand, additional chemicals can be placed in the solution if you want to get rid of airborne contaminants like acidic gases. Keep in mind that high amounts of water vapor are added to the gas before it’s vented into the environment, which is why wet industrial scrubbers cause white smoke to be released from the vents.

Wet industrial scrubbers are useful for any industrial application or process where gas is created. For instance, these scrubbers are commonly used in manufacturing plants that directly process natural gases like propane. These scrubbers are able to remove any pollutants from the gas stream before it enters the environment, which can help your facility avoid significantly harming the environment. Wet industrial scrubbers can be used in almost all temperatures, which makes them beneficial for most industrial applications. When you use a wet scrubber, you’ll find that the system is highly effective and can get rid of over 99 percent of particulate matter in the air. If you are thinking about selecting a wet scrubber for your company, there are many advantages and disadvantages that you should first be aware of.

Advantages of Wet Industrial Scrubbers

  • They can effectively prevent most pollutants from entering directly entering the air via exhaust gases
  • These scrubbers don’t usually require much space
  • Wet scrubbers are able to get rid of corrosive gases
  • Nearly all fine particulates should be removed from the gas
  • Harmful gases can be collected alongside particulates
  • High-humidity and high-temperature gas streams can be properly handled without issue
  • Gas streams with explosive or flammable materials can readily be handled with a wet scrubber
  • Some of the dry dusts that can accumulate in gas streams are flammable, which isn’t an issue when using a wet scrubber
  • Initial costs are relatively low

Disadvantages of Wet Industrial Scrubbers

  • The collected product is wet, which can create problems with disposal of the water
  • Maintenance costs can be high
  • You will need to make sure that the collected substances don’t freeze
  • If the exit gas has a low temperature, the exhaust plume dispersion is significantly reduced
  • Horsepower requirements and pressure-drop requirements are relatively high unless you purchase a portable system, which likely won’t accommodate your needs
  • It’s possible for solids to build up around the wet-dry interface, which can create maintenance problems
  • The accumulation of collected water can make the system very heavy

How Is It Used?

water bottle pollutant

Wet scrubbers consist of a device that’s able to remove most pollutants from exhaust gas with the help of a scrubbing liquid. The exhaust gas is sent directly through the liquid within the scrubber, which is sprayed into the gas via a standard misting process. Since pollutants and contaminants are heavier than the pure gas, the gas will eventually move through the liquid while the contaminants remain behind. It’s at this point that the gas is vented into the outside air.

Because of the chemical composition of the liquid, the contaminants become attached to the spray solution. Another technique that can be used with wet industrial scrubbers involves the exhaust gas being forced to bubble through a sizable pool of the scrubbing liquid. When this occurs, the contaminants are left behind in the scrubbing fluid. Because of how similar these designs are, the structures of most wet industrial scrubbers are the same. A fan system will combine with basic ductwork to send the gas through the chambers and to the exhaust vents. A collection area is also included for the scrubbing liquid and any pollutants that have been caught. Because of the content of this liquid, you will be required to dispose of the waste via special methods.

Dry Industrial Scrubbers

modern plant

Dry scrubbing systems are used in the majority of modern plants and are notable for being able to get rid of pollutants and contaminants in exhaust gas without creating a wet sludge. Because of how these systems work, they typically don’t come with wastewater disposal or handling requirements. While dry scrubbers purify the gas with dry substances, these systems work almost exactly like wet scrubbers. The device that’s connected to the scrubber will spray a selection of dry reagents directly into the gas stream, which allows for the removal of any harmful pollutants or a complete changing of a contaminant into another substance.

Before the exhaust gas stream leaves the scrubber chamber, the weightier pollutants will fall down and be caught within a particle screen. These scrubbers are mainly used to eliminate acidic substances like hydrochloric acid from various combustion sources. You should use these scrubbers because they are highly advantageous to the environment. Even though these scrubbers are able to get rid of most pollutants from exhaust gas, they create very little waste material when compared to wet scrubbers, which also removes the hassle of needing to dispose of wet waste material.

Dry industrial scrubbers are highly effective. However, they aren’t able to remove as many pollutants from exhaust streams when compared to wet scrubbers. When you are considering all of your industrial scrubber options, keep in mind that there are advantages and disadvantages to using a dry industrial scrubber.

Advantages of Dry Industrial Scrubbers

  • Doesn’t produce any wet sludge
  • Is able to collect acid gases at relatively high efficiencies
  • Doesn’t have many space requirements
  • Can include a fabric filter to effectively control the particulates
  • Is able to handle gas streams at higher temperatures
  • Hardly any maintenance costs

Disadvantages of Dry Industrial Scrubbers

  • The control efficiency of acid gas isn’t as high as a wet scrubber
  • Any residual waste powder that isn’t burned off will still need to be disposed
  • Scrubbing is somewhat expensive with a dry industrial scrubber
  • This system isn’t able to remove all types of contaminants from the gas that you send through

How Is It Used?

white smoke from factory chimney

When you install a dry industrial scrubber, dry reactants will be introduced to the gas streams at very high speeds, which helps to neutralize any of the pollutants that are contained within the gas. Three steps occur during this process, the first of which involves cooling the gas. In order to effectively prepare the exhaust gases, the gas will need to be cooled with an evaporative cooler. This step helps make it simpler for the system to remove contaminants from the gas.

Once the cooling has occurred, the reagent injected will be applied to the gas, which is when the contaminants and pollutants are finally removed. Sodium bicarbonate is a very common dry reagent that’s used in this process. The various reagent powders are combined before being directed at the exhaust gas at a high pressure. The chemical reactions that take place at this point will lessen the acidity and get rid of harmful contaminants. A fabric filter at the bottom of the system will then collect the scrubbing powder while the clean gas is sent through the exhaust vents.

The Use of Wet and Dry Scrubbers in Industrial Applications

rainy city

If the industrial processes at your plant or wastewater treatment facility create any kind of harmful gas, wet and dry scrubbers can be used to help you get rid of the harmful pollutants and contaminants that are contained within this gas. Using one of these scrubbers will keep you from causing undue amounts of damage to the environment and any homeowners living nearby your facility. The types of gases that can be treated with a wet or dry scrubber include sulfur dioxide, chlorine, hydrogen sulfide, and hydrogen chloride.

When you shop at Sensorex, you’ll find that we offer many sensors that will allow you to monitor the concentration of your scrubbing solutions, which is necessary when you want to get rid of the harmful contaminants within a certain type of gas. For instance, hydrogen chloride gas requires a caustic scrubber solution at 10-15 percent, which can best be measured with one of our toroidal conductivity sensors like the TCSP series. On the other hand, sulfur dioxide gas requires a lime scrubber solution, which can most effectively be measured with a pH sensor like the S272CD process sensor.

At Sensorex, we provide different products for industrial use that will allow you to effectively monitor everything from the exact composition of your scrubber solution to the feed water in your boiler.

Posted by Sensorex on December 10, 2019

Sensorex is a global leader in the design and manufacture of quality sensors for water quality and process applications. The company offers more than 2000 sensor packages for pH, ORP, conductivity, dissolved oxygen, free chlorine, chlorine dioxide, UV transmittance and other specialty measurements, as well as a full line of sensor accessories and transmitters. Its expert technical support engineers solve analytical sensor challenges with custom designs and off the shelf products.

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