Particulate filter

The purity of oxygen from chlorate candles before and after gas filtration is indicated in Table 2. A particulate filter is always used. Filter chemicals are HopcaUte, which oxidizes CO to CO2 molecular sieves (qv), which remove chlorine compounds and basic materials, eg, soda lime, which removes CO2 and chlorine compounds. Other than H2O and N2, impurity levels of <1 ppm can be attained. Moisture can be reduced by using a desiccant (see Desiccants). Gas purity is a function of candle packaging as well as composition. A hotter burning unit, eg, one in which steel wool is the binder, generates more impurities. 

Evaporation of medium provides a little cooling. The inlet air to particulate filters must not be near saturation because condensation of moisture on the filter medium mobihzes contaminating microorganisms so that their chances of penetration are greatly increased. Sometimes humidified air is used, and the filter unit is heated to prevent condensation. However, this is common only for small equipment where the extra operations are relatively easy to install and maintain. 

Fibrous or particulate filters are not important anymore because membrane filters are relatively compac t and perform veiy well. For filtration by straining, there is an intermediate air velocity at which filtration efficiency is a minimum because different collec tion mechanisms predominate at different ranges of velocity. At low velocities, diffusional and elec trostatic forces on the particle are important, and increased velocity shortens the time for them to operate. At high velocities, inertial forces that increase with air velocity come into play below a certain air velocity, their effect on collection is zero. Surges or brief power failures could change velocity and collection efficiency. 

Method 25 applies to the measurement of volatile organic compounds (VOC) as nonmethane organics (TGNMO), reported as carbon. Organic particulate matter will interfere with the analysis, and, therefore, in some cases, an in-stack particulate filter will be required. The method requires an emission sample to be withdrawn at a con-... 

Filter life Measure of the duration of a filter s useful service. This is based on the amount of standard contaminant required to cause differential pressure to increase to an unacceptable level-typically 2-4 times the initial differential pressure, a 50-80% drop in initial flow, or a downstream measure of unacceptable particulate. Filter media A porous material for separating suspended particulate matter from fluid. 

Deep-bed condensate polishers are commonly used for nuclear reactor power plants. Due to the extreme operating conditions, the resin is sometimes taken out of service as frequently as every 3 weeks for ultrasonic cleaning. This process removes the iron oxides and other particulates filtered out by the resin media. 

J. Dinesen, S.S. Nissen, and H. Christensen, Electrochemical Diesel Particulate Filter, SAE paper 980547, Diesel Exhaust Aftertreatment (SP-1313) 197-201 (1998). 

If the composite is left only partially densified, it can be used as a filter for high temperature filtering systems with high collection efficiency as required in direct coal-fired gas and steam turbines. Similar systems are considered for particulate filtering in diesel engines by a carbon foam or felt coated with silicon carbide by CVI. 

The small particles are reported to be very harmful for human health [98]. To remove particulate emissions from diesel engines, diesel particulate filters (DPF) are used. Filter systems can be metallic and ceramic with a large number of parallel channels. In applications to passenger cars, only ceramic filters are used. The channels in the filter are alternatively open and closed. Consequently, the exhaust gas is forced to flow through the porous walls of the honeycomb structure. The solid particles are deposited in the pores. Depending on the porosity of the filter material, these filters can attain filtration efficiencies up to 97%. The soot deposits in the particulate filter induce a steady rise in flow resistance. For this reason, the particulate filter must be regenerated at certain intervals, which can be achieved in the passive or active process [46]. 

Air line breathing apparatus Canister respirator Self-contained breathing apparatus Canister respirators with particulate filters Cartridge respirator General purpose dust respirators High efficiency dust respirators... 

A recent area of development is to use these NRS catalysts for the combined treatment of NOx and particulates. The combination of the NOx trap and of a particulate filter depends on various factors (1) the selection of the best suited filter technology... 

Catalyst activities, specific, 10 47t Catalyst additives, nitrogen oxide emissions and, 11 719 Catalyst-based diesel particulate filter (CB-DPF) technology, 10 61-62 Catalyst bed(s)... 

DCL DDGS DEFC DICI DISI DME DMFC DOE DP DPF Direct coal liquefaction Distillers dried grains with solubles Direct ethanol fuel cell Direct-injection compression ignition Direct-injection spark ignition Dimethylether Direct methanol fuel cell Department of Energy (USA) Dynamic programming Diesel particulate filter... 

Ai r Collection on particulate filter and polyurethane foam Soxhlet extraction alumina column clean-up GC/ECD 0.1 ng/m3 >95... 

FIG. 17-56 Typical porous wall tube array diesel particulate filter. 

The negative-draft pollution-abatement system with condensing scrubber and mist and particulate filters effectively captured nitrosodiphenyl-amine and other fugitive emissions. 

Dust masks, or particulate filter respirators, protect the respiratory system against any kind of inhaled particles. The simplest type, in the form of a cone-shaped fibrous filter that fits over the nose and mouth, is held in place by an elastic band around the back of the head. It is disposable, relatively comfortable to wear, and is useful when the dust is neither excessive nor toxic. It becomes readily clogged and should be discarded and replaced whenever breathing becomes restricted. Its use should not be carried over from day to day. 

Results(79) from a Round Robin analyses for the lead content of air particulate filters were given along with the average values obtained from 65 laboratories participating in the study. The procedures used by the other laboratories included x-ray, FAA, flameless atomic absorption, emission spectrometric, and dithizone-spectropho-tometric. The overall analytical agreement was very good. 

The extended SCR model has been integrated with other catalyst and diesel particulate filter (DPF) models in the Daimler exhaust gas after-treatment systems simulation environment ExACT. The model was also extended to other SCR catalytic materials [79]. 

Anke Giithenke, Daniel Chatterjee, Michel Weibel, Bernd Krutzsch, Petr Koci, Milos Marek, Isabella Nova and Enrico Tronconi, Current Status of Modeling Lean Exhaust Gas Aftertreatment Catalysts Athanasios G. Konstandopoulos, Margaritis Kostoglou, Nickolas Vlachos and Evdoxia Kladopoulou, Advances in the Science and Technology of Diesel Particulate Filter Simulation... 

High Efficiency Particulate Air (HEPA) Filter A HEPA filter is a particulate filter that has a... 

This chapter discusses both the development of models and their application. One way of organising this chapter would be to discuss model development first and then go on to consider the applications. However, as the entire reason for developing these models is to have a practical tool for system design, it was decided to start with the application of the models. The next section discusses the physical model for a monolith reactor, which is common to all technologies (except diesel particulate filters) discussed later. Our approach to model development will then be covered in detail, using TWCs as an example. The final section will outline work done on the various technologies used for diesel exhaust aftertreatment. 

Diesel particulate filters (DPF), which remove particulate from the exhaust stream. They can also be coated with catalyst, e.g. DOC, LNT or SCR, to enable removal of gaseous pollutants in the same system component. 

Regeneration using nitrogen dioxide is the basis for the operation of the CRT diesel particulate filter system (Allansson et al., 2002 Cooper et al., 1990). 

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