Once in a while the question is asked about the need of heating bilge water for processing. The question is asked, because some makers offer heaters in their bilge separators.
Anyone who cooks pasta knows that it takes quite a while to heat a pot of water on the electric stove. Let me demonstrate on hand the old British system how much heat is required to heat bilge water while processing. By definition 1 British Thermal Unit (BTU) is the energy required to raise the temperature of 1 lb of water by 1 degree Farenheit. Applying this to a small 1 ton/hr bilge separator, the size of the heater can be determined as follows:
To raise the temperature of the 1,000 liters (2,200 lbs) process water by 1 degree Centigrade (1.8 deg.F), we need to apply 1.8 x 2.2 x 1000 = 3,960 BTU/hr; which factors out to a heater capacity of 1.16kW. - To get a meaningful 10 deg C (18 deg F) temperature rise in a 1 ton/hr unit we'd need to install an 11.6kW (15HP) heater, with a 2.5 ton/hr separator a 29kW heater is required!
The other side of the coin in bilge water heating is heat density of the heating element. Oil has roughly half the heat value of water, therefore when heating the oily water mixture the oil will "bake" to the high density heating surface of the element, causing the electric heater to burn out.
All this to say that in my personal opinion, whether the ship is burning HFO or distillate, it is not really possible to heat the bilge water significantly while processing. A heating element in the bilge separator may very well be practical as a freeze protection.
Monday, June 28, 2010
Wednesday, June 23, 2010
Why not LNG?
If I read the IEA's medium-term Oil & Gas Markets 2010 correctly, we are moving towards tighter oil, while we have ample natural gas available from North American sources.
The medium-term looks forward to 2015 only. The oil supply down the road relies on an OPEC capacity increase by 2014 and increased reliance, also from 2014 onward on the Canadian oil sands and biofuels.
Another concern might be the shift of refining capacity; China, Asia and the Mid-East are adding refining capacity of 9 mb/d whereas the OECD cuts capacity by at least 1.4 mb/d by 2015.
With the ECA requirements tightening by 2015 and being fully implemented by 2020 (for which we have no projections), we will rely more on foreign finished product than we do today, especially for marine fuel as domestic refiners will cater to the higher volume land based transport sector. Therefore, it would almost seem logical to consider LNG as THE alternative fuel for marine transport for the medium to the long term; this would reduce GHG and harmful emissions from ships while providing secure, long-term low cost fuel.
The medium-term looks forward to 2015 only. The oil supply down the road relies on an OPEC capacity increase by 2014 and increased reliance, also from 2014 onward on the Canadian oil sands and biofuels.
Another concern might be the shift of refining capacity; China, Asia and the Mid-East are adding refining capacity of 9 mb/d whereas the OECD cuts capacity by at least 1.4 mb/d by 2015.
With the ECA requirements tightening by 2015 and being fully implemented by 2020 (for which we have no projections), we will rely more on foreign finished product than we do today, especially for marine fuel as domestic refiners will cater to the higher volume land based transport sector. Therefore, it would almost seem logical to consider LNG as THE alternative fuel for marine transport for the medium to the long term; this would reduce GHG and harmful emissions from ships while providing secure, long-term low cost fuel.
Tuesday, June 15, 2010
Bilge Water Discharge
The 5-ppm bilge water limit for the Great Lakes (Canadian inland waters) is in essence a 0-ppm limit with the +5ppm deviation permitted in the MARPOL regulations.
Back, when the effluent limit was debated the regulator made a distinction between oily water entering the bilge separator and oil free effluent leaving the bilge separator. It took me a while to understand that the discharge, which satisfies the regulations, is (by rule) an oil free discharge. Therefore, bilge water effluent quality below the alarm point setting is oil free water that can be discharged, effluent exceeding the alarm point setting is an oily water mixture and therefore a pollutant
Like I said, it took me a while to grasp that concept. Looking at it from the practical side, it does make sense to me too. Here is why:
Oil separates from water by gravity. Large oil droplets rise fast, small ones slow. That means the discharge from the bilge separator contains only oil droplets that are too small to be separated and removed from the water. Therefore the discharge water contains only fine oil droplets, evenly dispersed in the effluent stream.
At 15ppm, the international limit, the total oil dispersed represents a volume equal to a 2.5 x 2.5 x 2.5mm oil quantity in one liter of water; 5ppm is a volume of 1.7 x 1.7 x 1.7mm in one liter of water. This oil is not present in a single oil drop , but evenly distributed in tiny oil droplets throughout the water column, in a stable mixture.
How big a threat of pollution is then the compliant bilge water discharge? Is there a chance of visible oil pollution? Compliant bilge water discharges do not pose an environmental threat. Here is how I look at it. The ship needs to be moving to be allowed to discharge. Let's say the ship moves at 2 knots, which is about 3.6km/hr, roughly 1 meter/second. With a 3.5t/hr bilge separator, the ship discharges 3500 liters/hr, roughly 1 liter per second. Therefore, the oil drop I mentioned above, evenly dispersed in the 1 liter of water is discharged over the 1 meter of distance traveled.
Back, when the effluent limit was debated the regulator made a distinction between oily water entering the bilge separator and oil free effluent leaving the bilge separator. It took me a while to understand that the discharge, which satisfies the regulations, is (by rule) an oil free discharge. Therefore, bilge water effluent quality below the alarm point setting is oil free water that can be discharged, effluent exceeding the alarm point setting is an oily water mixture and therefore a pollutant
Like I said, it took me a while to grasp that concept. Looking at it from the practical side, it does make sense to me too. Here is why:
Oil separates from water by gravity. Large oil droplets rise fast, small ones slow. That means the discharge from the bilge separator contains only oil droplets that are too small to be separated and removed from the water. Therefore the discharge water contains only fine oil droplets, evenly dispersed in the effluent stream.
At 15ppm, the international limit, the total oil dispersed represents a volume equal to a 2.5 x 2.5 x 2.5mm oil quantity in one liter of water; 5ppm is a volume of 1.7 x 1.7 x 1.7mm in one liter of water. This oil is not present in a single oil drop , but evenly distributed in tiny oil droplets throughout the water column, in a stable mixture.
How big a threat of pollution is then the compliant bilge water discharge? Is there a chance of visible oil pollution? Compliant bilge water discharges do not pose an environmental threat. Here is how I look at it. The ship needs to be moving to be allowed to discharge. Let's say the ship moves at 2 knots, which is about 3.6km/hr, roughly 1 meter/second. With a 3.5t/hr bilge separator, the ship discharges 3500 liters/hr, roughly 1 liter per second. Therefore, the oil drop I mentioned above, evenly dispersed in the 1 liter of water is discharged over the 1 meter of distance traveled.
Tuesday, June 1, 2010
From Truck to Rail to Ship
It seems to me that the environmental agenda evolves from what is closest to us then moves to the more remote. In the case of diesel engines, it started with truck engines, then progressed to locomotive engines and now marine engines come under scrutiny.
Automotive diesel engines burn very clean fuel today, with S-content of not more than 50ppm, or 0.005% S-content by mass; therefore emit only small amounts of SOx and particulate matter. Regulations now require also the installation of secondary exhaust gas treatment (SCRs) and particulate filters on trucks and cars; to eliminate NOx and PM.
Locomotive engines are somewhat bigger than truck engines and with size some basic mechanical requirements need to be satisfied. The fuel pumps and the diesel injectors are bigger than what we see in trucks, therefore sliding surfaces become bigger and the lubricating oil film the fuel provides becomes more difficult to maintain as the fuel becomes lighter and less viscous. Installation of exhaust gas after treatment on locomotives becomes an issue because of size and suitability for the fuel used. The question is, can locomotives be made as clean as trucks, when it comes to exhaust emissions?
Stepping then up in size again to the large bore marine engines the problem gets bigger. The lubrication provided by the fuel in the injection equipment increases in importance because these components are massive.
What I hear from the experts is that diesel engines up to 250mm bore should operate with a fuel viscosity of at least 1.8cSt at the fuel injection pump, above that bore 2.0cSt or higher is recommended. These viscosity values mean that for the safe operation on a ship fuel temperature needs to be maintained and cooling or chilling of the distillate fuel may become necessary to maintain the lubricating properties of the fuel. As it stands now, it seems that ULS road diesel can not be safely burnt in the large bore marine engines.
Automotive diesel engines burn very clean fuel today, with S-content of not more than 50ppm, or 0.005% S-content by mass; therefore emit only small amounts of SOx and particulate matter. Regulations now require also the installation of secondary exhaust gas treatment (SCRs) and particulate filters on trucks and cars; to eliminate NOx and PM.
Locomotive engines are somewhat bigger than truck engines and with size some basic mechanical requirements need to be satisfied. The fuel pumps and the diesel injectors are bigger than what we see in trucks, therefore sliding surfaces become bigger and the lubricating oil film the fuel provides becomes more difficult to maintain as the fuel becomes lighter and less viscous. Installation of exhaust gas after treatment on locomotives becomes an issue because of size and suitability for the fuel used. The question is, can locomotives be made as clean as trucks, when it comes to exhaust emissions?
Stepping then up in size again to the large bore marine engines the problem gets bigger. The lubrication provided by the fuel in the injection equipment increases in importance because these components are massive.
What I hear from the experts is that diesel engines up to 250mm bore should operate with a fuel viscosity of at least 1.8cSt at the fuel injection pump, above that bore 2.0cSt or higher is recommended. These viscosity values mean that for the safe operation on a ship fuel temperature needs to be maintained and cooling or chilling of the distillate fuel may become necessary to maintain the lubricating properties of the fuel. As it stands now, it seems that ULS road diesel can not be safely burnt in the large bore marine engines.
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