Mountain high, ocean deep: part three

Read part two of this article here.

Removing sulfur on board

DeNOx technology can be retrofitted to the system to reduce NO_X, while an interesting method of removing SO_X emissions is the use of seawater for wet gas scrubbing. No additives are required in this method, as the inherent alkalinity of the seawater is used as the sorbent, and no byproducts are produced beyond a slight increase in the natural concentration of sulfate in seawater, the emissions must be monitored and the scrubber must catch a ratio of 4.3 (equitable to 0.1% sulfur content) to be compliant with legislation within ECA zones as of 2015.

In order to comply with the ever tightening emission regulations, shipping operators might choose to adopt an integrated approach that considers the use of lower sulfur content fuel, the use of wet gas scrubbing for SO₂ removal, the use of SCR for NO_X reduction or a conversion to LNG. However, this last option would require technology adjustments, similar to the engine modifications currently being applied in the automotive industry.

The notion of running a parallel two fuel operation has in itself significant challenges and costs for refineries. The required segregation of fuel storage tanks at the terminal would result in a spiralling of costs through not only increased CAPEX facilities but through the higher value locked up when storing different types of fuel.

Without doubt the most elegant solution is to operate with a single grade of low sulfur fuel (0.5%) and it is expected that within time, this will be the adopted standard.

Monitoring and detection

Other emission management measures called for by the legislation include implementing a far higher level of measurement, analysis and reporting during voyages. Emissions such as oxygen and carbon monoxide levels in the combustion process can be monitored to ensure that the process is functioning optimally. It is also possible to measure different hydrocarbons such as methane, propane, butane, isobutane and pentane to determine if fuel is escaping from the engine. Hydrogen sulfide can also be measured and controlled at various different points in the reaction pathway. Urea and ammonia levels also require monitoring to make sure the DeNOx equipment is working well and that the ammonia or urea is not being overdosed, which would result in the undesirable, so called, ammonia ‘slip’.

The tightening legislation also impacts players beyond the shipping operators, notably the designers and manufacturers of marine diesel engines, and the associated emission reduction technologies, as well as the refineries implementing sulfur reduction technology to produce lower sulfur bunker fuels for shipping. This low sulfur fuel introduction also impacts the bunker fuel oil stocking locations in the supply chain that are holding inventory for ships. As part of this ‘shore to ship’ emissions reduction scenario, Linde also works closely with refineries to supply gases such as oxygen and hydrogen and implement technology to reduce sulfur levels at these refineries.

Linde Gases supports the global shipping industry and its associated supply industries with state of the art emissions management and mitigation technologies. A key area is the supply of high precision specialty gases calibration gas mixtures to the facilities where emissions testing of heavy marine engines is carried out during their development or production, to ensure compliance with emissions regulations. This sector requires accurate calibration of the test instrumentation that detects and monitors emissions volume and type. Under the brand name HiQ^®, Linde offers a number of high precision, traceable calibration gas mixtures and pure specialty gas grades up to 99.99999% purity to ensure consistently accurate analytical measurement. This portfolio of products is continually evolving to remain relevant to the needs of the industry, for example, as the MARPOL legislation evolves.

The future with LNG?

With LNG now being seriously evaluated as an alternative marine fuel, Linde has already developed the necessary technology to supply the maritime industry with this efficient and environmentally friendly replacement for bunker oil. The use of LNG allows for a significant reduction in SO_X, NO_X, PM and CO₂ emissions, offering ship owners and operators a sustainable solution to meet existing and future emission standards. Other significant advantages are a very low safety risk and the possibility of combining LNG with other fuels in a dual fuel engine. Linde is one of the few companies in the world able to deliver a complete solution for LNG. From liquefaction and the safe and reliable delivery, handling and storage of cryogenic liquids to bunkering, vapourising and dispensing, Linde provides an end to end solution for customers looking to reduce fuel costs and environmental impacts.

In a landmark agreement, the shipping company EMS AG and Bomin Linde LNG recently signed the first contract for the delivery of LNG to Germany. The agreement is seeing the supply of LNG as fuel for the MS Ostfriesland passenger ferry operated by AG EMS, following a retrofit, making it the first user of LNG for German passenger ferry services. Regarded as an important step towards using LNG as a marine fuel in Germany, the agreement sends a clear signal that this low emission propulsion system will play an increasingly important role in the marine sector in future years.

The technical process for storage of LNG is comparable to bunkering operations for traditional fuels, but since the LNG is cooled down to approximately -163°C, appropriate personnel training is required. Deliveries to the port of Emden are currently covering initial supply requirements, while two LNG bunker terminals are being constructed in the ports of Hamburg and Bremerhaven. Once operational in 2015, these terminals will be able to supply LNG to ships operating in German ports along the North and Baltic Seas.

Written by Stephen Harrison and Ismail Erilhan, Linde Gases. This is an abridged version of an article taken from Hydrocarbon Engineering’s August 2015 issue.

Read the article online at: https://www.hydrocarbonengineering.com/special-reports/04082015/mountain-high-ocean-deep-part-three-1207/