Will Diesel Exhaust Fluid (DEF) technology be installed in boats?

" ... is this technology expected to be a permanent fixture or even a law enacted in that respect to be used in boats any time soon?"

https://community.metstrade.com/superyacht/b/challenge/posts/tiers-before-bedtime

https://www.dnvgl.com/news/imo-nox-tier-iii-requirements-to-take-effect-on-january-1st-2016-51970

http://britishmarine.co.uk/Home/What-We-Do/~/~/link.aspx?_id=729E2AA71CE54FBB8D0A7BF6D0AB8C36&_z=z

There are options for selective catalytic reduction (SCR) other than using urea (DEF) injection to meet NOx emissions standards. EnerYacht and DeAngelo Marine Exhaust are working on a retrofit solution for smaller yachts.

For EPA Tier 4 and IMO Tier III emission requirements, SCR After Treatment with Urea Injection are going to be the reality for all commercial vessels, as spelled out by those governing agencies. There are engine size and power requirements, and recreational rules will differ.

As this commercial population of SCR equipped fleets grow, we will begin to see better distribution of Urea for marine use and innovation in the size/style of Catalyst. These are basically honeycomb cartridges that are sized for the exhaust flow of the engine, as there is a calculation that shows the required amount of injected urea and the length/size of the honeycomb cartridges that allow the urea (ammonia) to react with the exhaust gases and remove the harmful NOx levels. The Urea can be in liquid form (aqueous) or in pellet form requiring an onboard mixer (and an onboard water source).

HUG is just one of the players in this field, although engine manufacturers are racing to come up with their own designs as well.

http://hug-engineering.com/en/technologies/scr-reduction

The purity of the water and quality control required for DEF that will not destroy the SCR catalyst or clog the injection nozzle or swirl devices in the decomposition section ahead of the catalyst is far beyond what is available on even the largest yachts. DIY DEF is not going to be an option in the foreseeable future.

DEF consumption is around 3 percent of fuel burn (can be less depending on engine NOx out but 3 percent is an accepted planning value). That means a single 99kW generator will consume around 50 gallons per week, think nearly 100 gallons required every couple of weeks or less just for a single generator. Almost double that for yacht on charter in the Caribbean with generators paralleled. If the yacht is large enough to be capable of an Atlantic crossing on its own bottom it will probably consume another 500 or 600 gallons of DEF in the mains.

This is not a trivial issue. Storage space is enough problem as is without having to provide for full and empty DEF containers.

Also to consider is the shelf life of aqueous urea. It loses its effectiveness over time and long term storage strategies should not be considered. Finally, all piping and systems that come in contact with Urea, including storage tanks, will need to be stainless steel.

CAT 3500 Series, MTU 4000 series and MAN product have working systems in the commercial industries.

Have you seen the size of these units? The 3500 one i saw was as big as the engine itself.

The boats will have to be designed and built to use these things on main propulsion not simply bolt them on as an afterthought.

Size is definitely a major problem. Most boats with a 3500 series engine or similar already use a very large muffler and the volume occupied by that unit can be repurposed for emissions controls but maintenance is going to be a barrier as large as urea reductant (DEF) storage.

The IMO was thinking ships, not yachts, when it developed Annex VI and the NOx code and ships usually have a very large volume in and above the machinery spaces to use for emissions control equipment, even to the point of installing scrubbers on deck next to the stack ... not something we will ever see on a yacht.

Much of what we see on exhaust treatment company websites is vaporware, few of them have systems for sale now or have ever installed one. Because of the widely varying ways that yachts operate, and their widely varying power requirements, systems that work on stationary industrial installations are poor candidates for yacht use. Looking at the full suite of emissions treatment requirements, SOx, NOx, and PM (soot) there is no one device cures all solution. There are systems under development that will combine some features with a blend of catalysts but again, while these may work on stationary sites where fuel standards and installation volume are easily managed, neither of those factors describe a yacht.

Passive particulate filters have proven to be "problematic" to put it kindly, and while the major players have begun to offer active systems which incorporate electrical exhaust heating to permit filter regeneration (burning off accumulated soot), they are generally very large, very expensive, and (with one notable exception) have not been proven to perform as advertised.

Fuel quality is and has been a factor in the success of emissions treatment systems on yachts. There are regions and ports visited by yachts where the bunker note doesn't necessarily reflect the composition of the fuel delivered. Sulfur in fuel is the death of emissions catalysts, it poisons them or buries them alive and the international limit for sulfur content of marine distillate fuel is almost 70 times higher than that of ULSD. Unfortunately, when a yacht orders and pays for ultra low sulfur diesel in some places, what goes on the receipt may not match what went in the tanks. When this happens, all emissions including SOx NOX and PM, increase drastically. This cripples system performance and may even kill it in very short order.

All the factors described above are what makes this an interesting as well as frustrating and expensive situation for everyone in the large yacht business. As K1W1 stated, the solution will have to start on the drawing board.

Absolutely spot on.

I certainly would prefer to see a combo muffler / SCR system. But the SCR Honeycombs need to be accessible / serviceable, so no more buried exhaust runs. I know purpose built commercial vessels like one of the San Francisco WETA Ferries currently has a designed for SCR system with MTU 4000s soon to be running daily. I have also see retrofits on CAT 35500 series for commercial use, but these had copious amounts of available machinery space to install the systems. I have not heard of any PF system being particularly effective and they become quite a nuisance for maintenance / replacement as well as disposal

Ah ha ... you have not been listening to the right voices or in the right places.

That very well could be, I have been living in a large power vacuum lately.

Gensets over 1250kW and main propulsion diesels over 7200kW.

A big technical challenge is the additional amount of restriction/backpressure the SCR System places on the Engines Exhaust run. Each engine varies in its tolerance for back pressure limits, but the length of the newly configured exhaust piping with mixers / diffusers and the effective length of the SCR Reactor that is filled with the Honeycomb catalyst will drive retrofit crews mad as they try to find the magic formula.

The magic formula is proper sizing of the exhaust to meet the backpressure requirements. Each item will add to the backpressure. The important point is to know what each component will add to the backpressure and design it so that at the initial sea trial, there are no surprises.

Certainly you have to do your upfront engineering and perform the calculations. But these will include assumptions and "calculated" values, maybe some backed up by testing. Now you get to the point where you ask "has the entire system been tested as it is configured for this particular / custom or one-off design? Do the honeycomb bricks perform as predicted, is it as efficient as advertised? Does the SCR Reactor need to be lengthened for more honeycomb bricks? Is the length of run prior to the SCR reactor sufficient or are the additional bends needed to make the system work to restrictive? Testing will be the only verifiable proof, how much does that cost, who is going to do it, and what are the ramifications for change?

And then you get to a final back pressure value, hopefully verified for testing, at a real ship's load and you may find that it is even designed / predicted to be within the limits of the engine manufacturer. Do the onboard tests verify this? And so ok, say it is now at 95% of the allowable back pressure limits - what are the long term running effects of this - more engine wear and tear, reduced maintenance cycles, reduced reliability?

The goal of any soot filtration system design is to be well below the maximum allowable backpressure. As anything else, to determine the proper sizing depends on the data given for the design of the system. What is the current backpressure of the generators as a baseline. If your starting point is already let's say at 75% of allowable, you know that the system will need to grow in size. Another way to determine the backpressure of the components is to "map" out the backpressure. The system can be designed to have ports throughout the run.

Backpressure monitoring will be necessary. As well as SCR Operating Temperatures. Another set of features for the Platform Management Systems to keep tabs on.

Most of the "questions" you asked are answered long before the hardware arrives in the engine room.

There is no "magic" involved. Jorge is speaking for his co workers who design and install those systems. They know what they are doing, what works and doesn't work, and why. You might call it magic but a successful installation is based on the kind of experience and knowledge that cannot be packed in a box of parts shipped to a yard for the pipe shop to figure out where to put it all.

Very often, commissioning of the completed installation shows a backpressure that is actually far lower than the original factory installed system. Many boats are operating at this moment with backpressure far above the maximum limit and may have been doing so for thousands of hours. They operate that way because the engines run OK, maybe a little dirty and have a lot of oil leaks but they work and besides, no one knows what the back pressure is because it is not monitored.

Like Jorge wrote, the highest priority in designing a system is to obtain the lowest possible backpressure at the highest test loading which is generally 110 percent of maximum rated output. If the backpressure at that point is 95 percent of maximum allowable it is not a failure, it is not the desired or even best result but the engine manufacturer rates the engine to operate for its lifetime at 5 percent above that pressure. It is not a problem for the engine but it may be a problem for whoever warrants exhaust system performance. That is not enough margin for normal catalyst fouling and service intervals may not match the boat's operating style. In real life the target for a competent and professional system designer is around 50 percent or less when the engine is operating at the load level imposed by normal operations. This assures long filter life and better fuel efficiency. A good installation will often function at 25 percent of maximum allowable at "normal" loads and continue to do so for thousands of hours.

You are aware that I am referencing SCR Systems which use DEF and not Soot / PM Filtration devices? I have no knock on Jorge and his colleagues at his fine company.

Maybe you have issue with the term "magic", I could substitute the "well proven in the field calculation". This topic is all about the infancy of the SCR solutions and the upcoming issues facing boat owners/engineers for EPA Tier 4 and IMO III emission requirements, not exclusive to gensets. There will be (and is going on now) a learning curve for these solutions, even for companies that have been in this field for years, as there are many issues to deal with.

As far as exhaust back pressure goes, good luck with "boats are operating at this moment with backpressure far above the maximum limit and may have been doing so for thousands of hours. They operate that way because the engines run OK, maybe a little dirty and have a lot of oil leaks but they work and besides, no one knows what the back pressure is because it is not monitored" approach, as it has been my experience that assessment does not fly with the engine manufacturers.

No big deal ... No magic involved, just good design, fabrication, and installation.

The standard SeaClean system for example, monitors, displays, and logs exhaust gas temperature, backpressure, heater power, heater element temperature, operating hours, and when required by class, catalyst outlet temperature and pressure. It provides for EGT setpoint control and display, and an alarm output to the yacht's alarm system when high backpressure is detected. These are part of the standalone controller package that maintains exhaust gas temperature at a level high enough to permit near constant regeneration across the entire generator operating load range. The system is fully automated and requires no operator input during normal operation.

Safety interlocks prevent the exhaust heaters from drawing power until the generator is online. Data display and logging is continuous during generator operation - online or offline - as is backpressure alarm status. Operational safety interlocks prevent heater operation in the event of temperature sensor failure, very low or very high exhaust temperature, or sensor open or short circuits.

It does not add any burden to a yacht's AMS or a guided missile cruiser's PMS. It does not add any burden on the engineers. All the heavy lifting was done before the system was installed.