Effective FAQs Guideline – Scrubber System

Welcome to the ultimate FAQs page of Scrubber System. In this article, you’ll find a complete guideline about the scrubbing system, its pros and cons, types, and how they are useful in the marine world.

With the advancement of technology, various harmful materials are causing damage to our environment. For this reason, authorities are taking measures to protect the environment.

Let’s begin the article to understand the Scrubber System:

1. What is Scrubber System?

A Scrubber System is used to remove hazardous substances from the (ships or industrial) exhaust gases before their release into the environment.

The acidic gases produced as a result of fuel combustion are harmful to our environment. Devices like Scrubbers are meant to control these acidic gaseous emissions.

According to the regulations given by IMO (International Maritime Organization), it is directed that the fuel consumed in commercial vessels must have 0.50% sulphur content in it globally.

IMO regulation has also instructed that this amount in ECAS (Emission Control Areas) has to be limited to 0.10% m/m.

The maximum amount of sulphur content, before the IMO regulation, was kept at 3.5% m/m. By the IMO’s new rule, vessels have two options, consume the fuel containing low sulphur (that’s expensive) or use exhaust scrubbing system to clean the gases emitted by exhausts (that’s economical).

Hence, many vessels, scrubber systems are installed to fulfil the international standards and regulations by IMO.

scrubber system

Scrubber System

2. How do Scrubber Systems Work?

Scrubbers are devices that remove hazardous material from gases that are exhausted through fuel gas stream. It uses liquid (usually water) to catch and wash off the pollutants from the gases. This liquid acts as an alkaline material to neutralize the acidic nature of the exhausted gases.

Earlier, the exhaust from the ship was released directly into the air, causing air pollution. With the invention of these air pollution control devices, the impurities are controlled by eliminating sulphur-oxide from the exhaust before letting it go into the air.

Here’s a video to understand how scrubbers use water to remove pollutants from gases.


The purified gases after being scrubbed are then released into the atmosphere. Scrubbing material used in the scrubbing process is either discharged immediately or may be stored. The scrubbing material is usually a kind of material that quickly gets rid of impurities by certain chemical treatments.

Marine scrubbers usually use lime or caustic soda to remove sulphur from gases. After the scrubbing treatment, salts are produced that are sulphur based. These salts are not threatening to the environment. Therefore, they are discharged quickly.

Packed beds are present inside the scrubbers to maximize the exposure time between scrubbing material and gas. Inside these packed beds are present reactants to remove gaseous pollutants. The purpose of packed beds is to slow down the scrubbing liquids vertical flow and escalate the neutralization process.

how do scrubber system work

How do Scrubber Systems Work?

3. What are the Pros and Cons of Scrubber System?

Although the scrubber systems are made to benefit the environment, it certainly has its drawbacks too. Let’s look at its pros and cons.

Pros of Scrubber System:

  • The atmosphere becomes cleaner with the reduction of sulphur oxide.
  • Specific hazards to human health due to air pollution become less.
  • To meet the IMO 2020 regulation, vessels must use high-quality fuel.
  • Authorities will monitor the ships for compliance.
  • Installing a scrubber system is not cost-friendly but using low sulphur fuel regularly is more expensive than installing a scrubber system.

For details watch this: https://youtu.be/Cr4Kw0oLwzU

Cons of Scrubber System:

  • It is not cost-friendly to install.
  • During the installation or retrofitting period of scrubber system, the ships could be inactive for several weeks.
  • Scrubbers are designed to remove sulphur oxide and not nitrogen oxide or carbon dioxide.
  • Certain marine life safety issues are coming up regarding the disposal of used scrubbing material into the sea. Therefore this is recommended not to use scrubber fitted vessels near conservation areas.
  • Corrosion is another disadvantage of scrubbers.
  • The treatment of used scrubbing liquid adds more cost.

pros and cons of scrubber system

Pros and Cons of Scrubber System

4. How to maintain Scrubber System?

We can’t neglect the importance of scrubbers. They help to prevent our atmosphere from impurities. We must adequately maintain them with regular monitoring. Following are the measures that shall be checked on daily, weekly, monthly, and annually.

  • The fresh water in the scrubber tank
  • Checking duct system for airflow
  • Mist eliminator
  • The temperature of water storage
  • Pressure of pump
  • The flow rate of the pump
  • The water level in the storage tank
  • The pressure drop across the scrubber
  • Erosion and plugging of the nozzle
  • Draining and refilling water storage tank
  • Leakages
  • Signs of corrosion

how to maintain scrubber system

How to maintain Scrubber System?

5. What is Scrubber System in Ships?

Fuel used by the ships, when combust, produce sulphur oxide. Scrubbers are used to eliminate harmful elements from this exhausted gas. It is also known as EGCS (Exhaust Gas Cleaning System). According to IMO regulation scrubbers are a must-to-install device in ships to protect our environment from sulphur.

The marine boilers and engines of vessels use diesel. The exhaust gases from these engines contain pollutants as well as climate-changing agents. Along with gas certain vapours are also produced by the fuel and lubricants. According to surveys, it is concluded that 10% of sulphur oxide that is emitted into the air, through human activities, are from marine transportation.

scrubber system in ships

Scrubber System in Ships

6. How many types of Scrubbers are there?

After the strict rules of IMO 2020 ship operators have got two options. Either to use low sulphur content fuel or to use less expensive high sulphur content fuel. They must install scrubber systems in their vessels with the use of high sulphur fuel. These exhaust gas scrubbers come in many designs with two main types:

  • Wet Scrubber

These scrubbers remove the pollutants from the exhaust gases by using water as an eliminating agent. About 90 % of the acid rain and smog can be controlled with the use of these scrubbers.

  • Dry Scrubber

The wet scrubbers are further categorized into three types:

  • Open-loop Scrubber

This exhaust gas cleaning system uses seawater as a cleaning agent. The water is usually discharged back into the sea without being treated, containing hazardous materials in it.

  • Closed-loop Scrubber

This exhaust gas cleaning system uses freshwater for cleaning purpose. After the scrubbing procedure, the used water is then treated to remove solid particles from it. A minimal amount of water is discharged into the sea in this system. The filtered water is ready to be circulated again.

  • Hybrid Scrubber

These scrubbers have both options either to use seawater or freshwater as a cleaning agent.

marine scrubbers

Types of Scrubbers

7. What are the Basic Components of a Wet Scrubbing System?

There are three essential components of a wet scrubbing system:

  • Vessel

Here, either freshwater or seawater is combined with the dirty gas.

  • Treatment plant

Here, the scrubbing liquid is treated, and pollutants are removed from it.

  • Facilities to handle sludge

Excessive sulphur is collected here. It is to be disposed off later.

Dirty gas is treated with scrubbing liquid. In this process, the pollutants (water droplets or solids) are separated from threat-free gases.

The wet scrubbing system is operating successfully with an efficiency rate of over 95%. The efficiency of a wet scrubber increases if a pre-filter is used as a dust collector. The dust, when captured in water droplets, increase in size. This increase results in easy removal of the dust.

As the wet scrubbers have three energy usage levels, they can also remove acid gases.

components of a wet scrubbing system

Components of a Wet Scrubbing System

8. Is Scrubber System Expensive?

As there are two options to follow, one is to use low sulphur fuel. The second option is to install a scrubber system if you are using high sulphur fuel.

Scrubber system is not a well-accepted choice so far. As the ship owners complaint, it takes several weeks to install causing an interruption in their transportation. Moreover, $5 to $10 million is required to install the system.

The cost of the scrubbing system depends on various factors:

  • Size
  • Material used
  • Features
  • Manufacturers

Installation of a scrubbing system is a one-time payment. Whereas, using low sulphur content fuel will continuously cost you. If we can save our environment, marine life, and human life with just installing a scrubber system, it is worth it.

is scrubber system expensive

Is Scrubber System Expensive?

9. What is the Effect of Scrubber System on Environment?

Scrubber systems are well-planned devices to control air pollution. They have declined the emission of sulphur dioxide into the atmosphere by 88% and emission of nitrogen oxide by 20%.  Scrubbers with advance technologies are attaining their goals up to 95%.

Prevention from the formation of acid rains has also become possible due to the acidic gas removing scrubbers.

The control of sulphur emissions into the environment will prevent asthma cases since childhood and premature deaths up to 150,000 per annum.

Bloomberg NEF’s survey states that by 2025, scrubber systems will be installed in almost 4,800 vessels.

However, the adverse effects on the environment caused by the scrubber system are, increase in temperature and the discharge of untreated scrubbing liquid in water.

Watch: https://youtu.be/x7KjSLYmvJM

effect of scrubber system on environment

Effect of Scrubber System on Environment

10. What is the Difference between Dry and Wet Scrubbers?

When choosing a scrubbing system for your ship, various factors shall be considered, such as availability of space on the vessel, engine power, operating area, availability of freshwater, and many others.

Here are certain differences between wet and dry scrubber systems mentioned to make a choice easier.

Wet ScrubberDry Scrubber
More commonly used and acknowledged for their efficiency.Comparatively less acknowledged
Uses scrubbing liquid (fresh or seawater) to filter the gasUses dry reactants (solid lime) to filter the gas
Controls less than 10-micrometre particulate materialUnder the right conditions, it can effectively remove 90% sulphur dioxide.
Removes SO2, H2S, NH3 and some fluorides and chloridesRemoves HF, HCL and heavy metals
VOCs (Volatile organic compounds) can also be controlledPAHs (Polycyclic Aromatic Hydrocarbons) can be controlled.
Condensed pollutants are easy to removeCosts low for its waste disposal
More water is needed for the treatment.Water consumption is less.
Useful for marine vesselsEffective for small to medium-sized power plants
Works on low temperatureHigher temperature
More power consumptionLess power consumption
Pollutants do not require storage as they are discharged onboard.Pollutants need to be stored and discharged at ports.
Lighter in weightHeavier in weight

difference between dry and wet scrubbers

Difference between Dry and Wet Scrubbers

11. Which Cables are used to Support Scrubber System?

We, Honest Cables, the manufacturers and suppliers of water-resistant onshore and offshore power cables, proudly support the scrubber systems.

Our concern is to protect the environment and create eco-friendly content, bringing us to facilitate the vessels with our best cables. Installation of the scrubber system in ships is more reliable and durable with our tinned copper cables.

We provide fire-resistant, flame-retardant, and low-halogen cables to deal with any disaster.

Our tinned copper wires are corrosion-resistant to last longer. For the harsh marine environment, we insulate the cables with PVC to remain protected.

High current carrying capacity makes the working of the scrubbers even better without threatening damage to scrubbers or cables.

Our ductile and flexible cables can easily be installed even in tight spaces. We offer a large variety of wires, depending on the current-carrying capacity.

Saving marine life is our ultimate wish!!

Deep sea maintenance
Deep sea repair work on a corroded metal pipe

Honest Cables

12. What Happens if a Scrubber System Malfunctions?

Scrubber systems are designed to clean the exhaust gas from the vessels. If it malfunctions, it will not filter the gas, resulting in the emission of hazardous materials into the air. This can be very dangerous.

To avoid malfunctioning, the approval of a scrubber system is defined under two schemes as per EGCS guideline:

  • Scheme A: Attaining a certificate for scrubber system performance. After that, continuous monitoring of operations and a check on emissions on daily basis will confirm the system’s performance.
  • Scheme B: By using an approved system, regular monitoring of emissions from exhaust and checks on operations on daily basis will confirm the system’s performance.

So, the scrubber systems require a continuous check on system operating parameters and exhaust emissions. In case CEMS (Continuous Emission Monitoring System) malfunctions, it is advised, by the industry legal advisors, to EGCSA to report to their Port State Control about the fault immediately. Ask them to take action and provide a remedy.

scrubber system malfunctioning

Scrubber System Malfunctioning

13. What are Scrubbers made up of?

The selection of material for wet scrubber shall be made intelligently, to avoid hazards of corrosion and temperature issues. The material used shall also be cost-friendly. There are a lot of materials used for scrubber construction. Such as:


  • Carbon steel
  • Cast iron
  • Ni resist cast iron alloys
  • Stainless steel
  • Medium alloys


  • FRP Fibreglass Reinforced Plastic
  • PVC Polyvinyl Chloride
  • Furfuryl Alcohol Resin
  • Resins


  • Carbon Graphite
  • Teflon Linings
  • Kynar

what are scrubbers made up of

What are Scrubbers made up of?

14. How do Scrubber Systems reduce Pollution?

Dry Scrubbers use static electricity to purify the exhaust gas from ash and soot. This scrubber system is commonly used in power stations that burn coal or oil to produce electricity. Industrial exhaust gases contain a lot of hazardous gases and pollutants in them. Scrubber system filters and purifies those gases before they are emitted to air.

Wet scrubbers, on the other hand, are most commonly used in marine vessels. The fuel combustion in ships causes sulphur and other insecure gases to emit from the exhaust. To protect the emission directly into the environment wet scrubbers are installed in the vessels. These scrubbers use scrubbing liquid to filter and purify the gases from harmful materials.

Thus, they are preventing our environment from sulphur oxide, nitrogen oxide, and many other dangerous chemicals that are injurious to health. They are saving our world from air pollution.

how do scrubber systems reduce pollution

How do Scrubber Systems reduce Pollution?

15. How is Scrubber efficiency calculated?

We can calculate the efficiency of a scrubber system in a below-mentioned way:

  • The velocity of air through the washer must be 2 – 3 meters per second (m/s).
  • Pressure drop resistance of airflow must range between 50 – 140 Newton per square meter (N/m2).
  • Before the nozzle, water pressure must be 100 – 170 kilo Newton per square meter (kN/m2).
  • Consumption of water must range between 0.45 – 0.55 litres per cubic meter air (l/m3). (it may vary depending on the process air temperature)
  • The scrubber’s cleaning efficiency must be 80% of coarse dirt and 70% of fine dust.

how is scrubber efficiency calculated

How is Scrubber efficiency calculated?

16. What is Scrubbing Liquid?

In wet scrubbers liquid is used to treat the exhaust gas. Usually, this liquid is fresh or seawater. Other liquids that are used to treat the exhaust gas are:

  • Amines or Dimethylaniline (CH3)2NH – used for low water-soluble gases
  • Caustic solution (NaOH) – used for controlling acid-gas
  • Sodium carbonate (Na2CO3)
  • Calcium hydroxide (Ca[OH]2)

what is scrubbing liquid

What is Scrubbing Liquid?

17. Do Scrubbers remove CO2?

For the removal of carbon dioxide from industrial exhaust gases, carbon dioxide scrubbers are used. Dry scrubbers are usually used to remove CO2. The power plants that combust coal needs scrubbers to treat CO2.

Air scrubbers can also remove carbon dioxide.

do scrubbers remove CO2

Do Scrubbers remove CO2?

18. What can a Scrubber System remove?

A scrubber system can remove many dangerous gasses. However, the percentage of removal may vary due to the type of chemical scrubber used.

Wet scrubbers can remove:

these gases less than 90%

  • Acetic acid (CH3COOH)
  • Hydrochloric acid (HCL)
  • Hydrofluoric acid (HF)
  • Sulphuric acid (H2SO4)
  • Sulphur dioxide (SO2)

Removal rate varies in the following gases:

  • Chlorine (Cl2) less than 80%
  • Ammonia (NH3) less than 60%
  • Hydrogen sulphide (H2S) less than 50%

Dry scrubbers are mainly used to remove acidic gases from the industrial exhaust gas.  SO2 sulphur dioxide tends to be removed up to 98%. Certain metallic compounds, HF, and HCL, are also removed through dry scrubbers.

what can a scrubber remove

What can a Scrubber remove?

19. How many Ships have Scrubber Systems installed?

It usually takes 15 – 30 days for the installation of the scrubber system on ships. Large cruise ships can take even longer. However, more than 4000 vessels have already installed or preparing to install to avoid using expensive low sulphur content fuel.

This number could have increased rapidly, but the only point of concern is that the used scrubbing liquid is discharged directly into the water. So, is it safe to use a scrubber system?

These systems are already banned in areas with more traffic and near coastal areas. However, measures can be taken to discharge the polluted scrubbing liquid properly.

ships with scrubber system

Ships with Scrubber Systems

20. What is an Open-Loop Scrubber System?

An open-loop scrubber system is a type of wet scrubber. This scrubber system uses seawater as a scrubbing liquid. The seawater treats the exhaust gases, and then the contaminated fluid is excreted into the water without being treated.

These scrubbers are the most popular as they cost low to install and use. Among all the scrubbers installed on vessels, 80% are open-loop scrubbers.

To avoid collection and storage of scrubber sludge, mostly vessels use open-loop mode in hybrid scrubbers.

Open-loop scrubbers or hybrid scrubber used in open-loop mode are very hazardous for our environment. They pour polluted water directly into the sea, making the seas acidic. This is increasing water pollution resulting in low pH water.

open loop scrubber system

Open-loop Scrubber System

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