Exhaust scrubbers are a viable option for IMO 2020 (ADS)

With the goal to reduce airborne sulphur emissions, the International Maritime Organization (IMO) has mandated that international shippers use fuel with a sulphur content of less than 0.5 wt% starting on 1 January 2020.

Pat Quotson

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Article Summary

Those ships fitted with scrubbers will be able to use fuels with a current level of 3.5% sulphur. Alternatively, ships could convert to a cleaner burning fuel, such as liquified natural gas (LNG) or fuel oil with a reduced sulphur content. Each of these options has advantages and disadvantages.

Petroleum refiners will have to assess the viability of producing the compliant low sulphur fuel based on the complexity of their refineries, the type of crude they run, and the investment cost. Many have already made the necessary modifications and are making shipments of low sulphur fuel oil (LSFO), however demand is likely to exceed supply, at least in the short term. Disruption of fuel supplies could impact shipping schedules.

As the demand for high sulphur fuel oil (HSFO) decreases after 1 January 2020, the price spread between it and LSFO will increase. Even ahead of the deadline, the price of LSFO is at a premium of roughly $200 per metric ton compared to HSFO. Higher fuel prices are expected to increase the cost of ocean freight.

Using LNG as marine fuel has several benefits, such as lower emissions and reasonable operating cost, however it requires significant investment on the part of both shippers and port authorities. Ship owners must convert their vessel engines to run on LNG, and terminals would need to be added or expanded.

open or closed loop
With the exception of non-compliance, that leaves the installation of scrubbers that remove sulphur emissions from exhaust gases, to comply with the new regulations. Scrubbers are devices that contact seawater with the engine exhaust. The natural alkalinity of seawater makes it a good absorbent for sulphur oxides (SOx) formed by the combustion of hydrocarbons. There are two types of scrubbers: open loop and closed loop. Open-loop scrubbers send water used to clean the exhaust gas back into the sea while closed-loop scrubbers retain the sulphur laden water for disposal at port. A hybrid system may be employed that allows the use of HSFO in coastal waters, where the discharge of spent seawater is not allowed.

random packing
Scrubbers may be empty chambers, or they may be fitted with a bed of random packing. Spray scrubbers with no packing have the advantage of low pressure drop and are not subject to the adverse effects of wave motion, fouling, or corrosion.

Random packing provides additional area for mass transfer and therefore higher efficiency, however at the expense of slightly higher pressure drop. It is important to keep pressure drop low, as this will maximise engine efficiency. Modern random packing, such as the INTALOX ULTRA® random packing developed by Koch-Glitsch, are ideal for this application because they provide a large amount of effective surface area with very low pressure drop. These packings can be manufactured in a variety of metals, including high chromium duplex stainless that is resistant to the corrosive nature of seawater.

installation costs
The cost to install a scrubbing system is roughly $2-$10 million, depending on the size of the vessel, but it allows the ship to utilise the much cheaper fuel that is currently in use. Based on the price differential between HSFO and LSFO, scrubbers are expected to earn back their investment in about three years. Less than 1% of all seagoing vessels subject to the IMO 2020 regulations are currently fitted with scrubbers, but the International Energy Agency estimates that around 5200 vessels will have scrubbers installed by 2024, or around 10% of the worldwide merchant fleet.

With the IMO 2020 deadline only months away, shippers will have to quickly navigate the various options available to them for lowering their sulphur emissions. Scrubbers are an attractive option to avoid the higher cost of low sulphur fuel.

This short article originally appeared in the 2019 Asian Downstream Summit Newspaper, produced by PTQ / DigitalRefining.

You can view the digital issue here - http://www.eptq.com/digitalPTQ/2019-ads/html5/index.html?&locale=ENG

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