BY William C. Peters
The latest news around the fire apparatus industry centers on the new Environmental Protection Agency (EPA) diesel exhaust regulations that are due to take effect in 2010. While the 2007 changes have just been fully implemented, a whole series of new changes are on the horizon.
You may wonder, What will this most recent regulation affect? The answer is, every new apparatus that is ordered and manufactured after this year. It will affect engine availability, in some cases the wheelbase of the apparatus, and additional maintenance concerns; also, it will increase the price.
DIESEL EMISSIONS
Over the years, the EPA has been steadily requiring reductions in diesel exhaust emissions. Figure 1 shows just how much reduction has taken place and what is expected in 2010.
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The two major components of diesel exhaust that cause air pollution are nitrous oxide gases, commonly referred to as NOx, and particulate matter or soot. Nitrogen oxide gases readily form nitrogen dioxide (NO2) in the environment, which is a major component of smog, acid rain, and ozone formation.
Some people feel that “we are the fire service and we should be exempt from these requirements!” No such exemption is offered or available. So for all intents and purposes, the engine in your pumper or aerial might just as well be powering an over-the-road truck or a transit bus.
EXHAUST MAKEUP AND EPA REGULATIONS
Diesel engines very effectively convert the chemical energy contained in the fuel into mechanical power. Diesel fuel is injected under pressure into the engine cylinder, where it mixes with air and where the combustion occurs, driving the pistons down on the power stroke. The exhaust gases, which are discharged from the engine after combustion, contain several compounds that are harmful to human health and to the environment.
Nitrogen oxides (NOx) are generated from nitrogen and oxygen combining under the high pressure and high temperature conditions in the engine cylinder. NOx (a generic term) consists mostly of nitric oxide (NO) and a small fraction of NO2. NO2 is very toxic. NOx emissions are also a serious environmental concern because of their role in the formation of smog.
Diesel particulate matter (DPM), as defined by the EPA regulations and sampling procedures, is a complex aggregate of solid and liquid material. Its origin is carbonaceous particles generated in the engine cylinder during combustion. The EPA reports that these fine particles of soot in the air are a serious public health problem because they easily pass through the nose and throat and lodge themselves in the lungs. They can cause lung damage and lung cancer and aggravate respiratory conditions such as asthma and bronchitis. The fine particles from diesel engines also contribute to haze, which restricts our ability to see long distances; ozone formation (or smog); acid rain; and global climate change.
Another pollutant, sulfur dioxide (SO2), is generated from the sulfur present in diesel fuel. The concentration of SO2 in the exhaust gas depends highly on the sulfur content of the fuel. This problem has been addressed and brought under control by the requirement in 2006 that almost all of the petroleum-based diesel fuel available in Europe and North America be of an Ultra Low Sulfur Diesel (ULSD) type, having no more than 15 parts per million (ppm) of sulfur content. Prior to 2006, it was set at 500 ppm. The move to lower sulfur content diesel fuel has allowed the application of newer emissions control technologies that substantially lowered emissions of particulate matter from diesel engines as well.
Venting crankcase emissions to the atmosphere (sometimes know as “blowby”) has been eliminated, and the fumes are now regulated as exhaust emissions.
NOx and diesel particulate matter are measured in grams per brake horsepower per hour (g/b hp-hr).
Diesel particulate matter was regulated to .10 g/b hp-hr in 1994 and remained at that level until 2007, when it was dropped to .01 g/b hp-hr. It remains at that level for the 2010 law as well.
The quantity of NOx allowed by the EPA has steadily decreased with each change of the standard. In 1994, it was at a high of 5.0 g/b hp-hr. In 1998, it dropped to 4.0; in 2004, it dropped again to 2.50; in 2007, it was set at 1.20; and in 2010, it will be required not to exceed .20 g/b hp-hr.
THE 2007 COMPLIANCE SOLUTIONS
NOx and diesel particulate matter must be addressed in different and distinct ways. One way that the engine manufacturers developed to reduce the NOx pollution was to recirculate the exhaust gas and reburn a portion of it. This involved the use of an exhaust gas recirculation (EGR) valve to direct a portion of the exhaust gases back to the air intake side of the engine for reintroduction into the combustion chamber. This was being done on most engines, but the degree of recirculation needed to be increased, which also increased the heat generated by the engine. The 2007 series of engines required larger radiators and more space under the cab for the pollution control devices.
Other control methods that were introduced or improved involved more efficient combustion controls including fuel injection and airflow into the cylinders. Some thought that this would have an adverse effect on the diesel engine’s acceleration performance, but for most users it went unnoticed.
A second way to address the NOx problem that had been used in Europe for several years is to chemically treat the exhaust with a compound known as diesel emissions fluid (DEF), which is made up of urea and deionized water. This system requires a separate storage tank on the apparatus, and the chemical has to be readily available for use. All of the engines in production that were used in fire apparatus met the 2007 requirements without this after-treatment.
Particulate matter was handled by a combination muffler/diesel particulate filter, with catalytic elements, installed in the exhaust system. As easy as this seems, there were some significant complications when it came to installing the diesel particulate filter (DPF) on some fire apparatus. Depending on the horsepower of the engine, the DPF could be as long as four feet in length and more than a foot in diameter. Another consideration is its location. The filter’s operation requires retention and generation of heat in the exhaust system to regenerate or burn out the particulate matter and soot that accumulates. The DPF needs to be located relatively close to the engine’s exhaust manifold. This results in higher exhaust temperatures, which leads to additional insulation and protection in the area of exhaust discharge. NFPA 1901, Standard for Automotive Fire Apparatus, has set the maximum exhaust temperature at 851ºF. To meet this requirement, most manufacturers have installed a device to entrain air at the end of the exhaust pipe, which results in a compliant exhaust temperature. All vehicles will be required to have an onboard diagnostic system to monitor and control the performance of the engine’s emission system.
Meeting the 2007 standards was a huge step forward in cleaning the air and increasing the health of firefighters and the general public by reducing the particulate matter, NOx, and sulfur dioxide.
2010 SOLUTIONS
The 2007 requirements of 1.2 g/b hp-hr NOx and .01 g/b hp-hr particulate were a bit challenging, but now, reducing NOx to .2 requires another step in the way we generate and treat our diesel exhaust. Since all manufacturers were able to comply with the previously required level of diesel particulate, the engineers now had to concentrate on reducing the NOx levels in the exhaust for 2010. There are two different approaches to addressing this problem: exhaust gas recirculation and selective catalytic reduction (SCR). A third approach some engine manufacturers took was to stop supplying diesel engines for the on-highway market starting in 2010.
I have attended several seminars on this subject, and each camp feels that it has the best approach to dealing with the problem. The following is a brief overview of how each will achieve the necessary levels.
EGR TECHNOLOGY
All diesel engines have some form of EGR system to reduce pollution and meet previous EPA standards. Navistar/International has developed an advanced EGR system on its Maxxforce compliant diesel engines. By engineering an advanced engine design, the company was able to reduce the NOx levels without additional external equipment using a four-step approach.
Step 1: advanced fuel injection technology. Typically, as the piston travels up in the cylinder, the air is tightly compressed, causing an increase in temperature. When the piston reaches the top of its travel, diesel fuel is sprayed into the heated air and it explosively ignites, driving the piston down on the power stroke. The Navistar next-generation fuel injection system delivers fuel into the cylinder at higher pressures than before and multiple times on the compression and power strokes. This creates pre- and post-injections, along with the main injection, causing combustion to take place over a longer period of time, which allows for more complete combustion and the creation of less NOx emissions.
Step 2: redesigned combustion bowl at the top of the cylinder that, when combined with the higher fuel injection pressures, causes the diesel fuel to break up into a finer mist and spread more evenly inside the cylinder. This helps create a more complete and cleaner burn.
Step 3: The Maxxforce engine uses two turbochargers to move air into the engine cylinders. The first provides additional boost at lower engine speeds, followed by an interstage cooler to allow more air to be packed into the large second stage turbo for maximum power at higher engine speeds. Combining these features with increased exhaust gas recirculation results in a slower burn at lower temperatures inside the cylinder.
Step 4: an advanced electronic engine controller that continuously calculates the optimum fuel mix to achieve maximum power and efficiency, depending on the situation.
The previously described diesel particulate filter that was required by the 2007 standard completes the package (photo 1).
 (1) The Navistar Maxxforce advanced EGR-compliant 2010 engine. (Photos by author.) |
SCR SYSTEMS
Cummins and Detroit Diesel have each opted to use the SCR method of dealing with reducing levels of NOx in the exhaust. As the exhaust exits the engine, it first enters the diesel particulate filter, as it presently does. This stage collects and oxidizes carbon particles, filtering the diesel particulate.
The exhaust then enters a decomposition reactor, which is shaped like an exhaust pipe between the particulate filter and the catalyst. A fluid dosing valve allows a fine mist of diesel exhaust fluid from a holding tank to be sprayed into the hot exhaust stream in the reactor. The DEF is a solution of 32.5 percent urea and deionized water, which breaks down into ammonia during a chemical reaction in the decomposition reactorknown as hydrolysis. The NOx and ammonia then pass into the SCR element where a catalytic reaction takes place, converting the NOx into harmless nitrogen gas and water vapor. It then passes over a second catalyst, which converts any leftover traces of ammonia before the exhaust exits the system. The result is near zero emissions (photo 2).
THE PROS AND CONS OF EACH SYSTEM
EGR. Obviously, each manufacturer feels it has the best method of removing exhaust pollution and meeting the EPA regulations.
EGR has been around for many years and is a part of the diesel engine equipment on both types. Navistar has enhanced the EGR system by adding an additional turbocharger and an EGR cooler, improved the design of the cylinder head, introduced multishot fuel injection, and improved computer control of the engine’s fuel system.
The outside of the engine is almost the same as the 2007 version, so no alterations to the chassis will be necessary. The company also states that the additional equipment necessary for the enhanced EGR system will add approximately 70 to 100 pounds of weight to the engine.
With the enhanced EGR system, there is no driver involvement in maintenance, upkeep, or operation of the system.
The EGR-equipped Navistar engine does not presently reach the .2 level of NOx required by the 2010 regulations. The current rate of NOx is approximately .5. To compensate for the difference, Navistar is using EPA “credits” that it has accumulated over the past several years by manufacturing engines that ran cleaner and exceeded EPA standards. It is able to use up to 80 percent of the credits toward its new engines. The use of credits will be discontinued by 2012, and Navistar stated that before that deadline it will have fine-tuned its product to fully meet the .2 level without after treatment.
SCR. The SCR system has been used in Europe for many years and is a proven technology. Cummins and Detroit Diesel will both employ SCR systems to meet the 2010 requirements.
A number of components in addition to the DPF will need to be installed on the chassis. They might come as a package, like the Cummins unit shown at the FDIC, or the apparatus manufacturer might have to locate the components. In either case, the mounting might be a challenge, especially on a pumper or an aerial apparatus with a pump that takes up a lot of space under the center of the chassis. Finally, the clean exhaust will have to be routed to the outside edge of the apparatus.
In addition, a DEF tank and pump will have to be located somewhere accessible on the chassis. The tank and lines will need to be insulated and heated to prevent the DEF from freezing (at 12ºF). The additional equipment is estimated to weigh between 300 and 400 pounds, including the full tank of DEF.
Since many of the over-the-road trucks will require DEF, it will likely be readily available when the 2010 engines make their entrance. It is estimated that DEF consumption will be approximately 2 percent of your fuel consumption, so for every 50 gallons of diesel fuel used, one gallon of DEF will be consumed. A “low fluid” lamp will be in the cab to warn that the DEF tank is low. The final DEF controls have not been determined at this time, but if the truck runs out of DEF it will not shut down. If an empty tank or the wrong fluid is detected in the tank (such as diesel fuel), the engine might automatically have a power reduction. Eventually, if the unit is shut down, it will not restart. The control restrictions have not been fully determined as of yet.
COST
Navistar estimates a $2,000 to $4,000 charge for the new technology on its engines. One of the major fire apparatus manufacturers estimated that the SCR system could add $5,000 to $15,000 to a chassis equipped with that system.
The cost of DEF is another controversial estimation. Currently, small quantities, such as a one-gallon container, have been quoted at around $12 per gallon. Obviously, as it becomes more readily available and truck stops install dispensers, the price should drop dramatically. One engine manufacturer estimated that it will eventually come down to the $2 to $3 range. Most agree that it will probably sell for approximately $5 per gallon.
One source was quoted as saying that SCR increases fuel mileage, which reduces fuel costs.
AVAILABLE ENGINES
As stated earlier, the engine selection for your next apparatus will be limited, depending on the apparatus manufacturer.
Caterpillar and Mercedes Benz decided to stop supplying diesel engines for the trucking industry when the 2010 regulations take effect.
Detroit Diesel announced an exclusive agreement to supply 2010-compliant Detroit Diesel DD13 engines to Pierce Manufacturing. Pierce and Detroit Diesel will be sharing engineering resources to package the DD13 and its BlueTec SCR emission technology in their fire trucks (photo 3).
 (3) Pierce and Detroit Diesel entered into an exclusive agreement to install the Detroit Diesel model DD13 engine in Pierce apparatus. |
Navistar/International will obviously equip its trucks with the Maxxforce line of EGR-compliant engines.
It appears that most other manufacturers will be turning to Cummins with its ISX 11.9 and ISL 9 engines that use SCR technology. Those engine selections will also be available to Pierce customers.
THE BENEFITS
Although the fire service is only a small part of the pollution problem, the EPA is taking these steps, which it predicts will result in substantial benefits to the public health and welfare by reducing diesel emissions.
The 2007 regulations resulted in each new truck and bus operating more than 90 percent cleaner than the 2002 models. Visible diesel smoke became a thing of the past (no more wiping off the TV screen after a run!). Now we are eliminating the invisible NOx, one of the most potent polluters that causes smog in our cities. One manufacturer said the diesel exhaust will most likely be cleaner than the ambient air!
The clean air impact of this program will be dramatically noticeable when fully implemented. These emission reductions are estimated to prevent premature deaths, hospitalizations, and lost workdays. That has to be good for all of us!
WILLIAM C. PETERS retired after 28 years with the Jersey City (NJ) Fire Department, having served the past 17 years as battalion chief/supervisor of apparatus. He served as a voting member of the NFPA 1901 apparatus committee for several years and is the author of Fire Apparatus Purchasing Handbook (Fire Engineering, 1994), the apparatus chapters in The Fire Chief’s Handbook, and numerous apparatus-related articles. He is a member of the Fire Engineering editorial advisory board and of the FDIC executive advisory board.
