Page 311 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Mechanical Separations 281

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E

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Figure 4-81. Electrical precipitator principle of operation. Courtesy
Duo Stzlndard
of Sturtevant Div. Westinghouse Electric Corp.
Figure 4-78. Tubular in-line pressure filter with reusable elements.
The flow: unfiltered liquid enters the inlet port, flows upward,
around, and through the media, which is a stainless steel or fabric Operating temperatures can be as high as I 000°F and
screen reinforced by a perforated stainless steel backing. Filtered above [ 41].
liquid discharges through the outlet (top) port. Because of outside-
to-Inside flow path, solids collect on the outside of the element so To improve the efficiency of collection, several units
screens are easy to clean. By permission, Ronningen-Petter® Engi- can be installed in series. The plate type unit is the
neered Fiiter Systems, Bulletin RP-2. most common design for dry dust removal, while pipe
design is mainly for removal of liquid or sludge parti-
cles and volatilized fumes. The plates/pipes are the col-
lecting electrodes, with the discharge electrodes sus-
pended between the plates or suspended in the pipes
Call1ct1d
Parlicl11 [41,53,57].
In operation, the voltage difference between the dis-
charge and collecting electrodes sets up a strong electri-
(+I C�arg1d
Partlcl11 cal field between them [63]. The "dirty" gas with particles
passes through this field, and the gas ions from the dis-
Figure 4-79. Charging particles in electrostatic precipitator. By per-
mission, adapted after A. Nutting, American Air Filter Co. charge electrode attach to the suspended "dirty" particles,
giving them a negative charge. The charged particles are
_.....-Grounded Eltclro4e(-I then attracted to the positively charged collecting elec-
,#, � l+ICMrgld Parlicl11 trode, discharging their charge on contact, becoming
(+) Ian Path�\ I - -
i: 1'1 • ·� electrically inert.
I l II •
- - \1 ,I./ "" Gas Flaw Through Collected liquids flow down the pipes and drain to a
Positivt Electrode � , • • • CMrg1d Field
( ( \ I ! Su1ptnd1d Parlicln collection sump. Collected solids are washed off the
1 H , .. Charged (+I. plates with water or other liquid. Sometimes the
1
\ht_ .. ·- dust/solids can be removed by mechanically vibrating
Grounded E ltctrodtH
or knocking on the plates while the particles are dry.
Figure 4-80. Particle collection. By permission, Nutting, A., Ameri- The electrical power of the precipitator is applied only
can Air Fiiter Co. (text continued 011 paKP 281)