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Why use an Exhaust Gas Scrubber? 

As of January 1, 2020, MARPOL Annex VI has imposed stringent fuel sulfur limits on all vessels while operating in global emission control areas (ECAs). Vessels that continue to use  Heavy Fuel Oil (HFO) and other fuels with high sulpher content must reduce pollutants such as NOx, SOx and PM emissions. Scrubbing units can be installed to meet emission requirements.

Scrubber ECA zone
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Maritime Training: Exhaust Gas Scrubbers & Caustic Soda Safety (closed loop)

How do wet scrubbers work?

Exhaust Gas Cleaning System (EGCS) or Wet exhaust gas scrubbers (EGS) commonly found on ships and marine vessels use the Principles of Absorption where by the soluble component of a gas is dissolved in liquid. Ships and marine vessels pump seawater or caustic soda into the scrubber vessels where it is sprayed into the gas path. The pollutants are absorbed by the seawater which travels to the bottom of the vessel under gravity, and then retained for further processing or discharge in open loop systems. The exhaust gas travels out of the scrubber into the atmosphere.

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What savings can scrubbers achieve?

The volume of fuel consumed by the vessel will have minimum impact. However the savings are realized when comparing the different cost of fuel between HFO and low sulpher fuel. 

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What are the problems?

Upon receiving clarity from the International Maritime Organization on requirements, and the availability of suitable technology, the marine scrubber industry has grown exponentially since 2018. The short regulatory compliance timescales, high vessels demand, and complexity of the installation has created quality issues throughout the industry. To increase corrosion resistance, scrubbers use materials that are generally uncommon in the shipping industry and require stringent quality controls to achieve the desired performance. The thermal changes across the system require an engineered thermal analysis to ensure stress remain within allowable limits, and sufficient inherent pipework flexibility is available to absorb thermal expansion. The steep learning curve has resulted in numerous cases of early failure and repairs as installers and ship owners battle to maintain availability.  

How can GreenTech Energy support?

We have the expertise and experience to support all aspects of the scrubber process, including: 

  • Project management and installation supervision.

  • Design reviews.

  • Post-installation inspections.

  • In-service condition assessments.

  • Written scheme of examination.

  • Warranty claims.

  • Repair and upgrades solutions.

  • Expert witness.

Carnival Splendor Scrubber Installation

  Scrubber  Section Installation

What is GreenTech Energy Tower upgrade?

GreenTech Energy has developed a patent pending vortex inlet generator which can be installed on inline spray tower scrubbers to control how the exhaust gas travels through the scrubber vessel. As the gas travels from the engine upwards through the exhaust duct, it enters the scrubber from the bottom of the vessel, reducing space and duct work. The gas enters the vortex generator and changes direction as it passes the stator blades before discharging tangentially, forcing the gas vertically through the scrubber in a helical gas flow.  

scrubber vortex generator

What are the benefits of the GreenTech Energy Tower Upgrade?

The efficiency of a spray tower scrubbing process improves the longer the exhaust gas remains in the scrubber vessel, allowing more time for pollutants to react with the liquid spray. The helical gas flow increases the gasses travel distance between the scrubber inlet and outlet, increasing absorption time and overall pollution removal when compared to existing designs.

A secondary advantage is how helical gas flow forces particulate matter and liquid carryover against the scrubber vessel shell where they are washed to the scrubber bottom and discharged from the process, rather than exiting as exhaust gas pollution into the atmosphere.   


  • Improved pollution removal.

  • Reduction in spray water.

  • Simple installation.

  • Reduced size.

  • Reduced power consumption.

  • Reduced cost. 

scrubber helical gas flow CFD
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