Page 201 - Elements of Chemical Reaction Engineering 3rd Edition

Sec. 4.4 Pressure Drop in Reactors 173

1.000
__
IKEY:
-Xl 0.800
-. x2
.-y1
-- y2
11.600
0.400

n. 200

ci. oao
0.000 0. so0 o.ao0 1.200 1.600 :!.ooo
u-10-5
Figure 64-8.2 Pressure and conversion for: 1, tubular PBR; 2, spherical PBR.

and )? represent the sphencal reactor In addition to the higher conversiori, the
spherical reactor has the economic benefit of reducing the pumpmg and compres-
sion cost because of higher preswre at the exit

Because the pressure drop in the spherical reactor is very small, one
could increase the reactant flow rate significantly and still maintain adequate
pressure at the exit. In fact, Amoco uses a reactor with similar specifications to
process 60,000 barrels of petroleum naphtha per day.
4.4.4 Pressure Drop in Pipes

Wormally, the pressure drop for gases flowing through pipes without
packing can be neglected. For flow in pipes, the pressure drop along the length
of the pipe is given by

sip 2fG2 (4-40)
-=-G--- du
dt dL pD

where D = pipe diameter, cm
11 = average velocity of gas, cmk
f = Fanning friction factor
4 G = pit, g/cm2. s
The friction factor is a function of the Reynolds number and pipe roughness.
The mass velocity G is constant along the length of the pipe. Replacing u with
G/p, and combining with Equation (4-23) for the case of constant T and FT,
Equation (4-40) becomes

P dP dP 2fG2 -o
Pop, PdL+ 7-