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Environmental Engineering SystemsDiesel Particulate TrapUV Disinfection Systems Diesel Particulate Trap
At the present time a device that is robust,
efficient, durable, packagable, and maintenance-free
is not available for elimination of particulate
matter (PM). For diesel engines in particular,
several devices have been designed to combat the
problem of particulate emissions. Most of these
devices use different filtration technologies
with either thermal regeneration capabilities
or manually replaceable filtration media.
The problem with these filtration devices
is that they quickly clog and increase the
exhaust backpressure thus negatively affecting engine
efficiency and performance. In addition thermal
regeneration requires vast amounts of energy and
produces very high temperatures. There are several
other technologies available for separating PM
from a gas stream. These include thermophoresis,
ultrasonic methods, and cyclone and wet scrubbers.
Many of these however have costly energy usage and
lower efficiencies.
EET's solution for control of PM is to adapt an integrated solution combining non-thermal plasma, electrostatic precipitation (EP) and diesel oxidation catalyst (DOC) technologies. The prototype trap that is being tested is particularly innovative because it continuously oxidizes carbon particulates and self regenerates. Since it works with non-thermal plasma, it is very efficient in terms of power consumption when compared to other particle separation and trapping technologies. The unique feature of the proposed product is simplicity of design, associated low cost, passive self regeneration, lower weight, and lower system pressure drop-less fuel penalty. While the non-thermal plasma and EP sections reduces PM, and NOx, DOC will reduce NMHCs.
This self-regenerating trap works by charging
particles in an exhaust stream with ions repelled
by corona discharge created by a high voltage
electrode. In the particle-charging zone the
collision between electrons and gas molecules of
electronegative gases such as oxygen, carbon
dioxide, and sulfur dioxide result in capture of
electrons to produce negative ions such as O-,
O2-, O3-, OH and NO2 (from conversion of NO).
These highly reactive radicals continuously
oxidize particulates into gases such as N2, CO,
CO2 and H2O, while the trap maintains
self-regeneration.
UV technology is recognized by the EPA as one of four approved methods of sterilizing water, and is preferable over the other tree methods (chlorine, iodine, and distillation) due to the cost of treatment and effectiveness of UV. UV irradiation is now accepted by both the EPA and FDA as a safe, effective method of water disinfection. It is fast, it does not alter pH, taste, and carries no risk of overdose. It is a non-chemical approach for microbial control and produces no toxic by-products. UV light is also a "World Health Organization" approved method of disinfecting water. A UV or germicidal bulb is similar to a fluorescent bulb, except that it lacks the internal phosphor coating and is housed in fused quartz rather than glass.
EET is developing UV systems that use less energy
while delivering the necessary dose for
inactivation of pathogens. Tools, including CFD,
are being used to design UV reactor geometries
that enable higher exposure times which in turn
allow the use of lower intensity light to result
in lower energy consumption during treatment.
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UV light is capable of destroying pathogens such
as bacteria, viruses, and protozoa that can cause
a variety of illnesses such as amoebic dysentery,
cholera, polio, and typhoid fever. UV radiation
works by causing the formation of chemical bonds
in cellular DNA. The exposure thus interrupts
normal DNA replication and organisms are killed
or rendered inactive. UV disinfection of water is
currently used in drinking water, wastewater, and
aquaculture industries. The development of UV
technology for use in these industries has
defined the operational parameters that influence
the effectiveness of UV in water disinfection
systems.