Looks like "pissing in the pot" will be taken literally now ;-)
The good side of this, no longer need pee breaks on a long road trip to save
Starting in 2010, owners of diesel-powered cars and trucks may have to fill
a supplementary tank with urea, an organic compound that fights nitrogen
oxide emissions when it's injected into a vehicle's exhaust system, The
Washington Post reports.
In anticipation of vehicle makers adopting an emissions-reduction system
that depends on urea to meet tight diesel pollution-control rules, the
Environmental Protection Agency issued guidelines on March 27 telling
manufacturers how to earn certification for the new engines. The agency
wants to ensure that urea is easily available and that systems will be
designed to force owners to keep tanks full.
Companies must design a system that would meet Clean Air Act rules by 2010
calling for the virtual elimination of nitrogen oxides and compel owners to
maintain emission-control systems.
According to The Washington Post, the EPA cautioned that the systems must be
designed so they can't be disabled, tampered with or filled with something
other than the proper concentration of urea.
They have been talking about this for a few years and it applies to
diesel owners Diesels are very big NOx generators as one diesel SUV
makes as much or more NOx as about 10 gas powered ones. When the urea
solution is injected into exhaust flow it converts to ammonia (NH3)
and then via a SCR "CAT" it breaks down the NOx into water vapor and
plain nitrogen (Nx) There are few other methods out there but this
seems to be most popular. You are only becoming aware of this problem
now because diesel have had a free "lead" in this area for many years
and now are being brought into compliance. Gas motors have been
complying for over 30 years now.
SCR for NOx control is currently used on stationary
diesel engines, and has been proposed for mobile applications. SCR
uses ammonia as a NOx reducing agent. The ammonia is typically
supplied by introducing a urea/water mixture into the exhaust upstream
of the catalyst. The urea/water mixture is stored in a separate tank
that must be periodically replenished. These systems can be very
effective, with NOx reductions of 70 to 90%, and appear to be tolerant
of current U.S. on-highway diesel fuel sulfur levels.
However, there is concern that applying current SCR technology to
highway vehicles will require use of catalyst formulations that are
sensitive to sulfur, such as those employing platinum, to deal with
the broad range of operating temperatures typical of highway diesel
engines in use. There is also potential for formation of ammonia
sulfate, which is undesirable because it is a component of fine PM28
In addition, SCR systems bring some unique concerns. First, precise
control of the quantity of urea injection into the exhaust,
particularly during transient operation, is very critical. Injection
of too large of a quantity of urea leads to a condition of ``ammonia
slip'', whereby excess ammonia formation can lead to both direct
ammonia emissions (with accompanying health and odor concerns) and
oxidation of ammonia to produce (rather than reduce) NOx.
Second, there are potential hurdles to overcome with respect to the
need for frequent replenishment of the urea supply. This raises issues
related to supply infrastructure, tampering, and the possibility of
operating with the urea tank dry.
Third, there may be modes of engine operation with substantial NOX
generation in which SCR does not function well. Finally, there is
concern that SCR systems may produce N2O, a gas that has been
associated with greenhouse-effect emissions.
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