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Exhaust Scrubbers

As we gear up for the nearing Sulphur Cap of 2020, understanding Sulphur Oxide (SOx) scrubbers as a way of complying is certainly important. Scrubbers are becoming a popular choice in the marine industry as they provide an excellent balance of compliance security and operating economy. Are scrubbers the right solution for your vessel? We’ve put together 10 Frequently Asked Questions about scrubbers in this blog. Learn the facts here before you decide.

1. How does a scrubber reduce Sulphur Oxide (SOx) emissions?

Marine exhaust gas scrubbers are atmospheric emission purification systems that capture and neutralize harmful particulates and pollutants using water. Scrubbers spray alkaline water (either pure seawater or water mixed with alkali) into the vessel’s exhaust thus removing SOx from the ship’s engine and boiler exhaust gases. The sulfates resulting from the SOX removal are discharged in the wash-water to the sea.

2. Is the sulfur included in the wash-water from the scrubbing process harmful to the sea/environment?

SOx becomes sulfate after going through the scrubbing process. Sulfates are natural components of seawater. The number of sulfates formed in the scrubbing process is far less than already exist naturally in oceans and therefore they are not harmful to the sea.1 Sulfur removal through the exhaust gas scrubbing process contributes an important environmental benefit of reducing the negative impact of emissions to air, as air emissions in the form of SOX can add to the formation of aerosols and particulate matter which cause heart and respiratory issues.2

3. How is it ensured that the water discharged into the sea does not harm the environment?

The resulting wastewater needs to contain elements as per the IMO and MARPOL requirements before being discharged. Scrubber systems continuously monitor discharge water parameters through water analysis instruments. The following discharge water parameters are continuously monitored:

  • pH (with temperature compensation)
  • Polycyclic Aromatic Hydrocarbons (PAH)
  • Turbidity
  • Nitrates

4. Do scrubbers on ships using heavy fuel oil (HFO) reduce SOx emissions as efficiently as the use of compliant fuel?

Studies reveal that scrubbers on ships using heavy fuel oil (HFO) remove more than 98% of the SOx from the ship exhaust. This result is considerably lower than the emissions from ships using marine gas oil (MGO). As a result, scrubbers are approved as a tractable method to use over-compliant fuels by the IMO, European Union, and the US Environmental Protection Agency.

5. What other environmental benefits do scrubbers have?

Further refining of HFO would require investing heavily in upgrading facilities and takes years to materialize. Less refining means less greenhouse gas emissions – with scrubbers, ships continue to operate using HFO.

6. How do suppliers identify the best type of scrubbers for a vessel?

Choosing the right scrubber which balances space requirements and operational efficiency is critical. One should be aware of the operational profile and routes of the vessel when identifying the scrubber type best for their ship. Each scrubber type serves a different purpose as follows:

Open-loop scrubbers are used for seawater to neutralize and balance the Sulfuric acid formed during the exhaust gas cleaning process. A hybrid scrubber system is used if a vessel occasionally deals in waters with low alkalinities, such as rivers or brackish waters, by switching from open to closed mode, eliminating the risk of compliance violations.

Closed-loop scrubbers mainly use freshwater mixed with chemicals such as caustic soda to boost the alkalinity of the wash water. Most ship-owners opt for open-loop scrubbers because they are less complex and then later switch for hybrid systems followed by the closed-loop.

7. How long should I wait for the Return on Investment of scrubbers?

A typical payback period for an installed scrubber is within 0.5-3 years depending on the engine size, routing and operation profile.

8. Do scrubbers reduce other types of emissions as well?

Exhaust scrubbers for marine diesel engines can remove more than 99 percent of the chemical families related to acids, alcohols, and ketones found in the exhaust gases. Some research and studies state that exhaust scrubbers for diesel engines bring down particulate matter (PM) by 60% to 90% depending on the type of scrubbing. The wet-type scrubber removes particles from 1 µm to 100 µm at very high efficiencies. Certain SO2 scrubber types are also effective in withdrawing black carbon (BC).3

9. What to look for in choosing an exhaust scrubber supplier?

Scrubber supplier selection depends on wide factors such as value for money, quality, reliability, and service. Furthermore, the extent of focus on these factors depends on your business’ priorities and strategies. The best scrubber supplier is the one who offers the best services along with a fast-reacting service network for your system. You need not only the most suitable SO2 scrubber system but also the right supplier that can take you through a smooth installation and reliable complaint operation.

Kamelia Cleantech is the Answer

If you have a question about exhaust scrubbers, Kamelia Cleantech can give you an answer. With combined experience in the Oil & Gas and Marine industries spanning the last 35 years, our experts have developed best in class scrubbers and control systems. The confidence of our clients relies on our ability to take care of the complete process from the first contact until the commissioning and post-installation services of the scrubber. Prior to giving a quote, we determine the most economical solution based on the vessel machinery, layout, and operation route to provide the appropriate type of SO2 scrubber system.

Have a question? Send us an email and our Scrubber Experts will be more than happy to assist you.

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1 Andreasen and Mayer 2007, Use of Seawater: Scrubbing for SOX Removal from Marine Engine Exhaust Gas, Energy Fuels 21 (2007) 3274-3279

2 Tokumura et al 2006; Andreasen and Mayer 2007 (Tokumura: Neutralization of the Acified Sea Water: Effluent from the Flue Gas Desulfurization Process: Experimental Investigation; Dynamic Modelling and Simulation; Ind Eng. Chem Res 45 (2006) 6339-6348

3 VTT, Control measures of Black Carbon (BC) emissions from marine diesel engines

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