Page 314 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

284 Applied Process Design for Chemical and Petrochemical Plants

(text continuedfrom page 281) F, = Total flow rate of both phases, GPM
to the particles collected, thereby allowing for large vol- g = g, = 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 a ves-
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- h, = 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 eff- the top of the vessel, in.
ciency of removal. Some particle materials of high electri- h~ = Cyclone inlet velocity head, in. water
H = Height of a segment of a circle, ft
cal resistivity prevent proper electrical operation. H, = Height of rectangular cyclone inlet duct, ft
Table 415 illustrates some industrial application of HD = 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
K, = Stokes-Cunningham correction factor, dimen-
a = Specific surface area, sq ft/cu ft sionless
a, = Acceleration due to gravity, 32.2 ft/s2 or 9.8 m/s2 he = Proportionality factor in Stokes-Cunningham
A = Area of segment of a circle, sq ft correction factor, dimensionless
or, A = Cross-sectional flow area, sq ft k = Constant for wire mesh separators
Ab = Cross-sectional area at bottom of vessel occu- 1 = Wire mesh thickness, ft
pied by continuous aqueous phase, sq ft
A, = Cyclone inlet area = WiH, for cyclone with L = Length of vessel from hydrocarbon inlet to
hydrocarbon outlet, or length of decanter, ft
rectangular inlet, sq ft
AI = Area of interface, assumes flat horizontal, sq ft L1 = Liquid entering Webre separator, lbs per minute
AH = 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 = Crosssectional area allocated to light phase, sq ft minute per square foot of inlet pipe cross
section
A, = Area of particle projected on plane normal to
direction of flow or motion, sq ft m = Exponent given by equations
At = 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 NR, = Reynolds number, dimensionless (use
bl = Constant given in table or (R,J 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 AP = Pressure drop, lbs/sq in.
Db = See D,, min Ap = Pressure drop, in. water
= Pressure drop, no entrainment, in. water
D, = Cyclone diameter, ft dp~
D, = Cyclone gas exit duct diameter, ft APL = Pressure drop due to liquid load, in. water
DH = Hydraulic diameter, ft = 4 (flow area for phase APT = Pressure drop, total across wet pad, in. water
in question/wetted perimeter); also, DH in Q = Dispensed phase volumetric flow rate, cu
decanter design represents diameter for heavy ft/sec
phase, ft = Volumetric flow rate, heavy phase, cu ft/sec
D, = Diameter for light phase, ft QL = Volumetric flow rate, light phase, cu ft/sec
D, = 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, = Specific gravity of settling particle at flow con-
D’, = Diameter of particle, in. or mm ditions
d = Droplet diameter, ft ASpGr = Difference in specific gravity of the particle
f = Factor relating average velocity to maximum and the surrounding fluid
velocity a,, = Average residence time based on liquid flow
f, = Friction factor, dimensionless rate and vessel volume, min
F = Flow rate of one phase, GPM bin = Minimum residence time to allow particles to
Fa, = Aqueous phase flow rate, GPM settle based on Stokes Law, min
F,, = Cyclone friction loss, expressed as number of u = Relative velocity between particle and main
cyclone inlet velocity heads, based on A, body of fluid, ft/sec
Fd = Drag or resistance to motion of body in fluid, ut = Terminal settling velocity determined by
poundals Stokes Law, of particle under action of gravity,
Fh, = Hydrocarbon phase flow rate, GPM ft/sec