Why Use a Closed-Loop Scrubber?

At the top of the scrubber tower, a continuous emission monitoring system (CEMS) is placed to monitor the emission outlet concerning the IMO 2020 sulfur limit to ensure constant compliance. The cleaned exhaust gas stream can pass through an inlet at the top of the closed-loop scrubber. The wash water will move downstream to the process tank. Through automatic monitoring and control, alkali is automatically dosed directly into the process tank to maintain the process pH and, thereby, the SOx removal efficiency. Dosage can also be inline before the scrubber. The alkaline and the specific amount depend highly on where and how the vessel operates. The pH adjustment is the primary environmental advantage as it ensures to neutralize the sulfuric wash water. Additionally, the water quality is reached by maintaining a low temperature by cooling the scrubber water with fresh seawater in a heat exchanger. A small amount of the wash water is bled off from the process tank to a water treatment unit (WTU) to remove the accumulated impurities from the scrubber wash water. The WTU removes suspended solids, polycyclic aromatic hydrocarbons (PAH=, particulate matter (PM), and harmful elements stemming from the combustion process, such as oil, ash, and soot. A water monitoring unit (WMU) is attached to continuously monitor and control pH, temperature, turbidity, and PAHs concerning IMO regulations on scrubber water discharge. The scrubber sludge is led to a holding tank, where it is stored until land-based disposal is possible, against fee payment. The sludge can be dewatered with a filter press for further solid and liquid separation to reduce the weight of the sludge. Reduced sludge weight causes reduced sludge handling costs. The rejected water is then recirculated back into the scrubbing process.

There are multiple reasons why treating marine exhaust gas streams with a closed-loop scrubber is advantageous, but three significant reasons are worth highlighting.

1) Compliance

More and more environmental regulations are adopted to obtain a cleaner shipping industry, including the sulfur cap limit of 0.1% for the Emission Control Areas (ECA) and the IMO 2020 sulfur cap of 0.5%. And with the tremendous current emphasis on sustainability, more regulations are expected to enter into force.

See the below video to grasp the timeline of the international mandates in the marine industry.

The marine industry is an industry moving towards zero emissions. Currently, there is a massive focus on reducing sulfur oxide (SOx) emissions, which scrubbers can ultimately do. All current regulations on SOx reduction are vital to comply with as the local authorities monitor all vessels’ operations. Violations of the IMO 2020 involve severe punishments, which can be costly and cause delays, obstructing your operation.

The shipping industry has two options to comply with current SOx regulations:

  • Option 1: Switch to a compliant fuel containing a lower amount of sulfur, such as low sulfur fuel oil (VLSFO), or an alternative non-sulfur fuel such as methanol, liquified biogas (LBG), or liquified natural gases (LNG).
  • Option 2: Implement a scrubber technology to lower the SOx output and continue to operate on heavy fuel oil (HFO).

It is essential to comply with environmental regulations, which both methods can ultimately do. Yet, by retrofitting a vessel’s machinery with a closed-loop scrubber, you can reduce its SOx emission from the previously allowed 3.5% to the currently allowed 0.1% m/m (mass by mass), ensuring that your vessel can also operate within the ECA.

Open Loop Scrubber Ban World Map Liqtech (1)

Over +120 Ports Have Banned Open-Loop Scrubbers Discharge

Over 120 ports worldwide have banned open-loop scrubber discharge, and we are soon facing a global ban for open-loop scrubbers, stressing that closed-loop scrubbers are the future. IMO, the EU, and other regulatory institutions are tightening regulations for open-loop discharge.

Moreover, closed-loop scrubbers bring about financial gains and a sustainable outlook, which gives us the following reasons for using a closed-loop scrubber.

2) Financial Gains

Installing or retrofitting to a closed-loop scrubber is a cost-intensive solution. Still, it brings a significant market advantage by providing fuel cost savings returns. You can continue to operate on cheaper HFO rather than more expensive low-sulfur fuel with a scrubber. Thus, a closed-loop scrubber ensures low OPEX, condoning the CAPEX and making it the most competitive solution long-term.

Whether a closed-loop scrubber is a profitable solution highly depends on the fuel price spread, which constantly changes. The fuel price spread has increased over the past years, making the installation of a closed-loop scrubber even more advantageous. Get an overview of the fuel price spread in real-time here. Still, a conservative return on investment is typically 1-3 years, which still secures a promising financial outlook for scrubbers.

Return on investment depends on:

  1. CAPEX: The capital expenditure and the installation cost of the closed-loop scrubber
  2. Fuel consumption on the ECA per year
  3. The price spread between HFO and alternative low-sulfur fuels.

3) A Sustainable Outlook

Closed-loop scrubber technology is a market-proven and environmentally sound solution. The research and analyst firm CE Delft, specializing in assessing innovative solutions for environmental problems, has conducted a study comparing CO2 emissions from producing and installing scrubbers with CO2 emissions from producing and using refined marine fuel. To this comparison, CE Delft could conclude that scrubbers result in a 1.5-3% rise in CO2 emissions for various relevant ships. Concurrently, using low sulfur fuel results in a 1-25% rise in CO2 emissions. Consequently, scrubbers have a significantly lower carbon footprint than alternative fuel options

On that account, you obtain a long-term sustainable solution that is always compliant, cost-effective, and durable. Read more about the differences between open-loop scrubbers, closed-loop scrubbers, and hybrid scrubbers.

By implementing a closed-loop scrubber, you embark on an improved future and take an active role in reducing world pollution. Lowering SOX emissions will benefit the environment and all people and wildlife. This will primarily help the people living in port cities and coastal areas of Asia-Pacific, Africa, and Latin America. The IMO 2020 sulfur cap will deliver a 77% decrease in overall sulfur oxide emissions from ships, corresponding to a yearly drop of approximately 8.5 million metric tons of SOx emissions. Moreover, particulate matter (PM) is also redused. PM are small harmful particles formed once the fuel is burned. As a result, the cases of several severe diseases, such as strokes, asthma, lung cancer, and cardiovascular and pulmonary diseases, are expected to decrease significantly. Lastly, reducing SOx emissions is also expected to prevent acid rain and ocean acidification and improve the conditions for crops, forests, and aquatic species.

A closed-loop scrubber can be installed as a new system or by retrofitting open-loop scrubbers to closed-loop scrubbers. Learn more about open-loop to closed-loop conversion here.

See our Marine Scrubber Water Treatment System
Marine Knowlegde Ebook Download

Marine Knowledge E-book

If you want to learn more about the marine industry, you can download our Marine Industry Knowledge e-book.

Learn everything worth knowing about marine scrubbers, wash water treatment, and how to comply with the IMO 2020 sulfur cap.

Read about emerging trends affecting the maritime industry, marine regulations, and how to stay compliant now and in the future. 

At LiqTech, our goal is to minimize the negative impacts of living an improved lifestyle. With innovative clean technology, we reduce the harmful effects caused by various polluting industries, including the marine industry, in line with current and emerging environmental regulations. We want to share our knowledge with you; therefore, we have created a universe full of marine knowledge.

Download E-Book

Get in Touch With an Expert