John Kaltenstein is Clean Vessels Program Manager for Friends of the Earth - U.S. Kaltenstein works predominately on ship air pollution issues and represents the organization at the IMO. He holds a law degree, with a certificate in Environmental and Natural Resources Law.
Amidst all the discussions and debate surrounding greenhouse gas (GhG) emission reductions, the US/Canada Emission Control Area, and increased Arctic shipping at MEPC 59, a 'new' issue could, hopefully, emerge and receive greater public attention: local and regional efforts to expand green shipping.
While modest progress has been made to reduce pollution from shipping, a recent submission from Friends of the Earth International (FoEI) notes that "additional measures beyond the MARPOL Convention and related IMO instruments have a high potential to help develop shipping into a more sustainable transport mode."
FoEI’s paper specifically highlights a Clean Shipping Project established in Sweden, by the Region of Västra Götaland and other local entities, which enables companies to select ships on the basis of environmental performance, in additional to conventional attributes.
Criteria include fuel quality consumption, chemical use, ballast water treatment, and sewage processing, among others. In addition, ports and other entities in some parts of the world have implemented or are contemplating the use of economic incentives and other inducements - such as differentiated port and fairway dues, and certification credentialing - to garner additional pollution reductions from the shipping sector.
In the United States, the West Coast ports of Los Angeles and Long Beach have been ahead of the green shipping curve in introducing new incentive-based programs.
While, some of their programs have proven quite successful, the incentive structure and design of these programs is extremely important for their success.
Whereas the ports’ vessel speed reduction programs, which essentially offer a 15 to 25 percent reduction in dockage fees to participants, have achieved compliance rates of over 90 percent, a low-sulphur fuel incentive program, in which the ports only paid the cost differential between bunker fuel and marine gas oil, did not attain 20 percent compliance.
Replicating and perhaps enhancing successful European and US West Coast green shipping programs in other US ports would pay big environmental dividends.
The US EPA can help lead this process, potentially even using its SmartWay program, which has attracted a number of land-based goods movement operators, to serve as a platform for integrating greater marine vessel participation.
I think that the debate of GHG and pollution in shipping are two entirely separate categories.
Shipping is by far the "greenest" form of transportation in existence today and if other forms of transportation would bring their CO2 emissions anywhere near the levels of shipping emissions per unit of cargo it would go a long way in solving GHG problem.
As far as other types of pollution are concerned, SOx NOx and particulate matter, we should be working towards emissions legislation not fuel based legislation such as MARPOL. It is much more important what comes out of the ship then what comes in.
Abatement solutions exists, ballast water treatments exist, biodegradable lubricants exist so how do we make shipping industry adopt these....?? I do not see many volunteers ....
PROPOSAL FOR EVALUATE THE REDUCTION OF NOx EMISSION WITH RETARDED INJECTION TIMING AND PACIFIC PETROLEUM FUEL OIL TREATMENT.
MECHANISM OF NOx FORMATION IN DIESEL ENGINES
Nitrogen is normally an inert gas. At the temperatures of the burning fuel spray, (about 2000K to 2500K) the nitrogen in the air is no longer inactive and some will combine with oxygen to form oxides of nitrogen. Initially mostly nitric oxide (NO) is formed. Later, during the expansion process and in the exhaust, some of this NO will convert to nitrogen dioxide (NO2) and nitrous oxide (N2O ), typically 5% and 1% , respectively, of the original NO. The mix of oxides of nitrogen is called NOx.
The reactions involving oxides of nitrogen are slower than the reactions involved in oxidation of the fuel, so oxides of nitrogen formation mainly takes place in the high temperature burnt gas which arises from the combustion process. The rate of reaction is controlled by the concentration of oxygen and the temperature. The temperature dependence is exponential. NO formation rate can increase by a factor of 10 for every 100K temperature rise.
Thus, NOx formation depends on the temperature of the burnt gas, the residence time of the burnt gas at high temperature and the amount of oxygen present. The burnt gas arising from the part of the combustion which occurs before peak pressure is compressed due to the rising pressure in the combustion chamber. This means it remains at high temperatures for a long time compared with the burnt gas from the later stages of combustion. This allows more time for NO to form. Slow speed engines produce more NOx than medium speed engines because the combustion process spans a longer time period so there is more time available for NO formation.
Three Phases of Combustion
Combustion in diesel engines can be divided into 3 different phases. The first phase involves evaporation and mixing of the early injected fuel with the air in the cylinder. During this phase, certain pre-reactions occur prior to actual combustion. During this delay period, fuel air mixture is forming continuously. As soon as the actual combustion starts, the fuel air mixture formed during the delay period ignites and burns rapidly, as it is already mixed and ready to burn. This is the second phase of combustion or premixed phase, which typically produces the highest pressure rise rates. After this pre-mix of fuel and air formed during the delay period is consumed, the combustion rate becomes controlled by the rate of evaporation and mixing of the fuel and air. This is the third phase or diffusion controlled phase.
The length of the delay period is a function of the fuel ignition characteristics and the temperature in the combustion chamber. Reducing the length of the delay period reduces the amount of fuel consumed in the second phase. The length of the delay period is basically independent of engine speed, so the proportion of total fuel injected during the delay period is greater in medium speed diesels than in slow speed diesels. The second phase of combustion involves high temperatures and pressures because the combustion rate is high. Also, because it happens early in the combustion process the burnt gas from this phase will remain at high temperatures for a relatively long time due to further compression by the rising cylinder pressure. This phase is likely to produce high NOx concentrations and is more important in medium speed engines.
Smoke and NOx
Smoke (soot) arises primarily from within the fuel spray during combustion. Fuel heated in the absence of oxygen partially reconstitutes into particles with high carbon content. It is the burning of these particles that leads to the high rate of visible and thermal radiation from diesel combustion. It is generally considered that
there are two main processes determining soot levels. The first is the rate of formation of particles in the flame and the second is the rate of oxidation of the particles.
Good atomisation and air entrainment reduce soot. If combustion temperatures are too low, oxidation of soot is inhibited. However, low combustion temperatures are used to reduce NOx. Increased compression ratio, injection timing retard, increased charge air cooling, exhaust gas recirculation, inlet air humidification and direct water injection all can increase soot. The problem is greatest at low loads where spray penetration and atomisation and air entrainment are least. Common rail injection systems improve the situation at part load by maintaining high injection pressures. Auxiliary blowers and Jet-Assist turbochargers help maintain charge air pressure at low loads and during load changes. The new low sac volume fuel injectors have also made a significant contribution to smoke reduction, as they avoid the problem of dribble after injection and subsequent inefficient burning of the leaked fuel. Higher injection intensities and good air motion are used in combination with retarded injection timing and increased compression ratio for NOx control. Higher injection intensities and air movement improve atomisation, penetration and air entrainment, thus tending to compensate for the negative effects on smoke of other changes.
NOX CONTROL MEASURES
Delayed injection timing is very effective in reducing NOx but increases fuel consumption and smoke. It is usually combined with increased compression pressure and decreased injection duration to minimise or avoid increase in fuel consumption.
NOx formation depends on temperature as well as residence time. The burnt gas arising from the part of the combustion which occurs before peak pressure is compressed due to the rising pressure in the combustion chamber. This means it remains at high temperatures for a long time compared with the burnt gas from the later stages of combustion. This allows more time for NOx to form. Delayed injection leads to lower pressure and temperature throughout most of the combustion. Delayed injection increases fuel consumption due to later burning, as less of the combustion energy release is subject to the full expansion process and gas temperatures remain high later into the expansion stroke, resulting in more heat losses to the walls. Smoke also increases due to reduced combustion temperatures and thus less oxidation of the soot produced earlier in the combustion.
EXPERIMENTAL MEASURE OF NOx, SOOT EMISSION AND SPECIFIC FUEL CONSUMPTION.
By using PP3-F Fuel oil treatment the combustion of the fuel become more intense and the heat release rate increases. This function will counteract the drawbacks from retarded injection timing.
One degree retarded injection timing will reduce the NOx formation with about 7%. We propose that the test is made step by step with measurement of the NOx and soot emission after each adjustment of injection timing. Theoretically it is possible to reach 30 to 35% reduced NOx emission by retarding the injection timing.
The additive is blended into the diesel fuel using the following doses: 1/1000 2/1000 3/1000. With higher dose of additive the more quick combustion and less soot formation.
When the NOx formation has reached the expected final level and the final soot (PM) emission are within accepted limits compare the specific fuel consumption with the base line values from before the adjustment of the injection timing. You may find that the normal fuel penalty has changed and become a small fuel saving.
ADDITIONAL SMOKE REDUCTION BY USING PP 2000 ENGINE PROTECTOR LUBE OIL ADDITIVE.
The National Technical University of Athens Greece has found that if the above mentioned lube oil additive is used at 6% volume blended in the crank case oil the smoke (PM) emission is reduced more than 25% in a medium speed 4-stroke diesel engine. Due to the primary function of the additive the internal friction in the engine is reduced providing increased mechanical efficiency and increased power up to 4,2% or reduced fuel consumption in the same order.
Source of information:
Dr Laurie Goldsworthy
Faculty of Maritime Transport and Engineering
Australian Maritime College
Prof. Dimitris Hountalas.
Internal Combustion Engine Laboratory
National Technical University of Athens Greece
For more information: firstname.lastname@example.org