Maritime Environment Protection committee of International Maritime Organization has decided to lower the Sulphur cap from 3.5% to 0.5% worldwide, ECA are regulation will remain as it is. Therefore from 1st January 2020, all ship-owners will have to comply with low sulphur emission requirement for which there will be 4 choices;
- Use compliant fuel, i.e.0.5% Sulphur fuel
- or, use wet Exhaust gas cleaning system
- or, use dry exhaust gas cleaning system
- or, use LNG propelled engine.
to either switch to low sulphur fuel oil containing below 0.5% Sulphur or install exhaust gas cleaning system also called scrubber if they wish to burn fuel containing up to 3.5% Sulphur. Both choices will have detrimental effect on running cost of vessel. As an estimate, 3 million barrel heavy fuel bunker (up to 3.5% Sulphur) per day will be required to be switched to 0.5% Sulphur. This will cause significant rise in fuel cost resulting in rise of freight cost.
Use of compliant fuel – there are 2 methods to produce compliant fuel, either to blend fuel or to refine compliant low sulphur fuel. Blending is very common in industry now. Refineries can produce low sulphur fuel as required but there are two major concerns; firstly it will require huge investment and down time of refinery, secondly, the upgrade will cause destruction of residue causing loss of refining margin. Besides this there is no way to know the demand- supply of 0.5% low sulphur fuel in 2020 and hence no way to know the price of fuel. Refineries will not invest where market price of the product is not known.
There are new developments in marine fuel industry to test and provide required fuel, Shell has announced that they will be using same technology (they are using for present 0.1% S fuel) of blending Gas oil with high Sulphur fuel to achieve 0.5% Sulphur fuel. Read More on Shell about it. BP has their own technology to produce 0.1% Sulphur fuel and
Wet exhaust gas cleaning system – There are many companies in race and some are already installed on board as test unit or on new vessels as compliance requirement. Wartsila (Closed Loop, Open Loop and Hybrid system), Alfa Laval, Clean Marine ECGS system (hybrid type) and many more are there to grab the opportunity. Approximately 50m3/hr per KW sea water is required for washing the exhaust gas. This water is required to dilute the pH to 6.5 which is the limit set by IMO for discharge to sea.
- Open loop system uses Sea water which enters scrubber and is sprayed with seawater in different stages. The sulphur oxide in the exhaust reacts with water and forms sulphuric acid. No external chemical is required because of the natural alkalinity of seawater neutralises the acid. Wash water from the scrubber is treated and monitored to ensure compliance with MEPC 184(59) discharge criteria.
- Closed loop system – In a closed loop scrubber system, the exhaust gas enters the scrubber and is sprayed with Fresh water or sea water that has been mixed with caustic soda (NaOH). A small amount of chemical is always added to keep the alkalinity. The effluent can be stored in tanks and discharges ashore. Closed loop system is suitable for fresh water area like Great Lakes, long river passages etc.
- Hybrid system – Some systems are designed for both closed and open loop system, they can switch to either system depending upon the area of operation. During port and manoeuvring vessel can use closed loop system and in open sea open loop system because there is limited space to store effluents.
Dry Exhaust Gas cleaning system – It uses absorption mechanism to remove the Sulphur from exhaust, the process is called chemisorption and Ca(OH)2, Calcium Hydroxide is used as absorption material, fine chemical in powder form gives a large surface area to maximise absorption of SO2. As per Lloyds Register 2012, page 27, a20MW engine requires about 20tons of Ca(OH)2 in 24 hours operation. So it needs a large storage space on board for Ca(OH)2. The positive side of dry scrubber system is that the temperature drop is minimum across this scrubber.
Installing any type of scrubber system on existing ship will always be a challenge because of size of scrubber unit, space limitation , on board, installation of pipeline, pumps, other accessories and most difficult part is to have facility to store effluent.
Risk of Storage of acidic solution– There is always a risk of corrosion of storage of acidic residue. Usually ordinary ballast tanks are used as storage for effluent which is highly corrosive. Cases are there in recent past where due to pipeline leak there was flooding incident on board and this pipeline was in use in the scrubber system handling effluent.
Cost – A full set of exhaust gas cleaning system is retrofit would cost from $ 500,000 to $50,00,000, depending upon the size of engine. Retrofitting of scrubber unit and its accessories is huge modification of structure and technical part and takes long lay up, so installing it during docking is the most convenient and economical solution. Below is the estimated payback time calculation for 20000KW engine, at best practical estimation and excluding lay up time;
|Pay back time calculation for Exhaust gas cleaning system|
|Fuel price difference (estimated)||60||$/ton|
|Operation cost (power, chemical etc)||38||$/ton of fuel|
|Cost of installation of EGCS||1,500,000||$|
|Per day fuel consumption||80||Tons/day|
|Yearly running days||280||Days|
|Annual running cost||851200||$|
|Net Annual saving||492800||$|
|Pay back time||4.185||Years|
LNG propelled ship – As per Wartsila website information till July 2017, Wartsila has fitted 100 vessels with LNG fuelled engines which are either on order or in operation. MAN has introduced duel fuel engines in 2012, and since then various different engines are made for special fuel available. ME-LGIM, for methane and ME-LGIP, for propane has been developed. ME-LGIM are already in service on Methane carriers. MAN has also added programme to retrofit all existing 2stroke MAN engines to run on LGI concept. If this retrofit is cost effective then owners will have this option as an advantage.
MAN has now extended its dual-fuel engine programme with ME-LGI unit that can run on alternative low-flashpoint liquid fuel (distillate fuel), so owners will have another option to run vessel if LPG fuel are not available in any port or bunkering station.
Source – MAN, Wartsila wdebsite information, bulletins, Shell bulletin, Clean Marine
Categories: Eng & Tech