Page 316 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

284 Applied Process Design for Chemical and Petrochemical Plants

(lex/ continued from page 281) F, = Total flow rate of both phases, GPM
to the particles collected, thereby allowing for large vol- g = gc = gL = Acceleration due to gravity, 32.2 ft/ (sec) (sec)
umes of gas to be handled with very low pressure drop. h = Distance from center to given chord of aves-
For corrosive gases/liquid particles, corrosion resistant sel, ft
metals can be used for construction. hb = Height of continuous aqueous phase in the
bottom of the vessel, in.
The performance of the unit involves the gas charac- he = Height of a segment of a circle, in.
teristics, analysis, velocity, flow rate, dust or liquid particle h, = Height of continuous hydrocarbon phase in
size and analysis, resistivity and required final particle effi- the top of the vessel, in.
ciency of removal. Some particle materials of high electri- hvi = Cyclone inlet velocity head, in. water
H = Height of a segment of a circle, ft
cal resistivity prevent proper electrical operation. He = Height of rectangular cyclone inlet duct, ft
Table 4-15 illustrates some industrial application of H 0 = Height of dispersion band, ft
electrostatic precipitators; however, it is not intended to I = Width of interface, ft
be all inclusive. k = K = Empirical proportionally constant for cyclone
pressure drop or friction loss, dimensionless
Nomenclature K' = Constant for stationary vane separators, based
on design
Km = Stokes-Cunningham correction factor, dimen-
a = Specific surface area, sq ft/cu ft sionless
a, = Acceleration due to gravity, 32.2 ft/s or 9.8 m/s 2 Kme = Proportionality factor in Stokes-Cunningham
2
A = Area of segment of a circle, sq ft correction factor, dimensionless
or, A = Cross-sectional flow area, sq ft
Ab = Cross-sectional area at bottom of vessel occu- k = Constant for wire mesh separators
1 = Wire mesh thickness, ft
pied by continuous aqueous phase, sq ft
A,, = Cyclone inlet area = WiHc for cyclone with L = Length of vessel from hydrocarbon inlet to
hydrocarbon outlet, or length of decanter, ft
rectangular inlet, sq ft
A 1 = Area of interface, assumes flat horizontal, sq ft L 1 = Liquid entering Webre separator, lbs per minute
A1-1 = Cross-sectional area allocated to heavy phase, per square foot of inlet pipe cross-section
sq ft L,. = Entrainment from Webre unit, lb liquid per
AL = Cross-sectional area allocated to light phase, sq ft minute per square foot of inlet pipe cross
AP = Area of particle projected on plane normal to section
direction of flow or motion, sq ft m = Exponent given by equations
A, = Cross-sectional area at top of vessel occupied mp = Mass of particle, lb mass
by continuous hydrocarbon phase, sq ft n = Constant given in table
ACFS = Actual flow at conditions, cu ft/sec NRc = Reynolds number, dimensionless (use
h, = Constant given in table or (Re) consistent units)
c = Volume fraction solids N, = Number of turns made by gas stream in a
C = Overall drag coefficient, dimensionless cyclone separator
D = Diameter of vessel, ft 6P = Pressure drop, lbs/sq in.
Db = See Dp, min 6p = Pressure drop, in. water
De = Cyclone diameter, ft 6p 0 = Pressure drop, no entrainment, in. water
De = Cyclone gas exit duct diameter, ft 6pL = Pressure drop due to liquid load, in. water
DH = Hydraulic diameter, ft = 4 (flow area for phase 6pT = Pressure drop, total across wet pad, in. water
in question/wetted perimeter); also, D1-1 in Qo = Dispensed phase volumetric flow rate, cu
decanter design represents diameter for heavy ft/sec
phase, ft Qi, = Volumetric flow rate, heavy phase, cu ft/sec
DL = Diameter for light phase, ft Qi. = Volumetric flow rate, light phase, cu ft/sec
DP = Diameter of particle, ft or equivalent diameter r = Vessel radius, ft
of spherical particle, ft SpGr = Specific gravity of continuous phase at flow
Dp-min = Minimum diameter of particle that is com- conditions
pletely collected, ft SpGr P = Specific gravity of settling particle at flow con-
D' P = Diameter of particle, in. or mm ditions
d = Droplet diameter, ft 6SpGr = Difference in specific gravity of the particle
f = Factor relating average velocity to maximum and the surrounding fluid
velocity lavg = Average residence time based on liquid flow
fc = Friction factor, dimensionless race and vessel volume, min
F = Flow rate of one phase, GPM l:n,in = Minimum residence time to allow particles to
Faq = Aqueous phase flow rate, GPM settle based on Stokes Law, min
Fcv = Cyclone friction loss, expressed as number of u = Relative velocity between particle and main
cyclone inlet velocity beads, based on 1\: body of fluid, ft/sec
Fd = Drag or resistance to motion of body in fluid, u. = Terminal settling velocity determined by
poundals Stokes Law, of particle under action of gravity,
Fhc = Hydrocarbon phase flow rate, GPM ft/sec