During his presentation at the last GREEN4SEA Conference, Mr. Ole Johan Øby Svendsen, Senior Sales Manager, Exhaust Gas Cleaning, Wärtsilä, argued on how to customize a scrubber system to fit the operators’ need for new builds and retrofits as well as to make a feasible installation process for retrofit installations. Customizing the scrubber system is mainly done by choosing the most feasible system for the vessels trading route and optimizing the system for the operational profile of the vessel. Making a smooth retrofit process is all about controlling the value chain as well as applying a feasible installation concept, he further said.
Many people say that there will be more CO2 with the use of scrubber; that is actually true, however, it is important to view the whole picture. For instance, the increase of CO2 from the use of scrubbers amounts approximately 1-2% per vessel. Therefore, it is important to consider the added CO2 amount of producing Marine Gasoil(MGO) which is one alternative or LNG which is a different alternative.
When it comes to scrubber systems, there are a lot of different options and there is always an option to tailor-make the system for each vessel.Talking about scrubbing efficiency, we believe tha the Venturi scrubber option is the best, however, if there is not possibility to install a Venturi scrubber, the Inline scrubbers offer one benefit; the overall footprint.
Another option are the system configurations including hybrid systems, open loop and close loop systems The closed loop was always a solution for special vessels (ex. Vessels sailing the Great Lakes). But, in case of sailing to certain ports of Europe or to Connecticut, the operator might want to invest in hybrid rather than in Open Loop. This should be carefully considered based on the initial cost of the system and also the cost of operating the system as well as the footprint.
2020 sulphur cap
For the 2020 sulphur cap, according to which the sulphur emissions to atmosphere should be 0,5% and 0,1% in emission control areas(ECAs), some makers have a specialized system for each option (0,5% or 0,1%). However, it may be better to make one system that fits all giving the operator the possibility to choose between 0,5 and 0.1 because the saving from making a 0.5 system than a 0,1 system is very small.
This, basically for Open Loop system, means less water from 0,5 while the scrubber size will remain the same. Further customization can be done using special concepts for special vessels (Cruise, Ferry, VLCC), while there are also possibilities to customize redundancy for added reliability, extraction fan for eliminating scrubber back pressure; booster fan for boilers; Open Loop water cleaning; sludge de-watering system; booster pump and specialized Venturi for added PM removal or Open Loop VGP.
Dimensioning your scrubber system: VLCC Case Study
A lot of VLCC operators tend to step in the wrong direction. For an operational profile for VLCC, scrubber dimensioning would be quite typical. Operators are initially thinking: “Well, I want the scrubber to cover everything that the vessel might need to do and to cover the normal operation of the vessel”. That is basically a good idea, but small adjustments can have a large impact. So, if you are in a port commission area where you have two auxiliary boilers at 100% load, this adds up to a scrubber size of 40MW; a quite large power consumption of 430 kilowatts and an overcapacity in seagoing of 17,5MW. All in all, the system is dimensional for port mode but in seagoing operators will have an over-dimension system; use more power than necessary and in general they will have a much larger system than needed.
To do one adjustment to this, operators can remove one of the auxiliary boilers from the scrubbing in port and still choose which one will be scrubbed. The boiler that is not scrubbed will need to burn MGO. Just by doing this, operators may reduce the scrubber size to 22, 5MW and the overcapacity in seagoing is 0 MW. Thus, operators will have tailored the system to seagoing rather than to port mode.
Operators choosing Case 2 over Case 1 will reduce the scrubber size to 44%, scrubber footprint to 43 %, scrubber height to 11%, water requirement to 44%, power consumption to 40% and scrubber price to 27%. In other words, operators will never make back the difference, if they scrub that other boiler and they will lose money doing it.
Scrubber Retrofitting
Color Line SuperSpeed 2 was a vessel that Wartsila retrofitted with an inline scrubber system in less than two weeks; a quite demanding project with such an installation size. The inline scrubber system operates as a conventional Wärtsilä open loop scrubber system. The exhaust flows enter from the bottom and exits at the top, with water being sprayed in three stages in a counter flow to the exhaust. A Wärtsilä designed water trap prevents the scrubbing water from entering the engine. The inline configuration can be offered on the hybrid scrubber system as well.
Traditional Installation or Fast Installation?
Traditionally you would have to modify the ship to fit the installation. With the fast installation concept you would fit most of the equipment inside a scrubber module that would be added to the ship.
A better solution is to prefabricate a module that contains everything they need for the scrubbing system including the scrubber inside this module that they lift and fit onboard the vessel. Certainly, all that an operator would need to modify inside the vessel is piping and the co-ops; this makes the whole process a lot quicker and hopefully a lot less painful.
The views expressed in this article are solely those of the author and do not necessarily represent those of SAFETY4SEA and are for information sharing and discussion purposes only.
Above text is an edited article of Ole Johan Øby Svendsen’s presentation during the 2018 GREEN4SEA Conference
View Ole-Johan Øby Svendsen’s presentation on Exhaust Gas Cleaning Systems during the last GREEN4SEA Conference herebelow
Ole-Johan Øby Svendsen is a Senior Sales Manager for Wärtsilä Exhaust Gas Cleaning. He has a Masters degree in mechanical engineering and has handled new build and retrofit projects for scrubbers world wide. He has been involved in the scrubber business since the first commercial scrubber project in shipping and his main focus area is currently new builds in Korea as well as the Greek market.
