Page 508 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

474 Applied Process Design for Chemical and Petrochemical Plants

Table 7-16
Gravity and Temperature Correction Factors for Low Pressure Venting Calculations for Vapors
Sp. C:r. of Gas. Sp. Gr. Sp. Gr. of GH Sp. Gr. Temp. Factor Temp. F1ctor Temp. F1ctor
AIR= 1.00 Factors AIR= 1.00 Factors 1•r1 (•F) (0 f)
.20 .447 1.10 1.050 5 1.0575 70 .9905 200 .8932
--- ------- - --- - - - ·- --- ·- -- ---- ,. - ----1---- -· ---·
--
.30 .548 1 .20 1.095 10 1.0518 80 .9813 220
--------·- - ·---·- -··
.40 .632 1.30 1.141 15 1.0463 90 .9723 2.«I .8619
- -· -·-·--·-- -- - -· -·--- - -· ---· - -------
.50 .707 1.40 1.185 20 1.0408 100 .9638 260 .8498
-�-----·---·-- f- ------- . - -------- - - --- -·-
.60 .775 1.50 1.223 25 1.0355 110 .9551 280 .8383
---·------- - --------- -- --- ·- ---- -- -··
-·
.65 .806 1 .60 1.265 30 1.0302 120 .9469 300 .8272
---------· ------ ----- -- ·-- ·---
.70 .837 1.70 1.305 35 1.0249 130 .9388 .8165
----- ··------- ,--- ··--·----
.75 .866 1.80 1.340 40 1.0198 140 .9309 340 .8063
-··-------- .. - --- ------ ---··· - ·- -
.80
.894
-----· ----------- 1 . 90 1.380 45 1.0147 150 .9233 360 .7963
.9158
2.00
160
.85
.922
1.0098
1.412
50
--------- -·--- ---- ·-------- ----·---------- -- - --- - ···-···----···-- 380 .7868
.90 .949 2.50 1.581 55 1.0048 170 .9084 400 .7776
---------· -- --- - - ---- -··. ---- - -- - ----- ·- -· -- ·- ------.
--- -- - -
.95 .975 3.00 1 .731 60 1 .0000 180 . 9014 420 .7687
---------- ·----·---·------· - ······---·-
1.00 1.000 3.50 1.870
-- ----- - ·---· ··---
1.05 1.025 4.00 2.000
By permission, Groth Equipment Corp., Tank Equipment Division.
(text continued from page 470) SpGr correction = (2.69) 1 = 1.64
1 2
Free gas capacity of valve (at 14.7 psia and 60° F = Temperature correction = 0.9551 from Table 7-16
(free air capacity) (temp. corr. factor) The volume at standard conditions of 14. 7 psia and 60°F:
(7 - 52)
(SpGr correction factor)
_ ( 460 + 60 ) ( 15. 7)
-- = 48,717 cu ft/hr
Free air capacity of valve = = (.'.>0,000) ( 460 + 11 0 ) (14. 7 )
(free gas capacity) (SpGr co1T factor)
(7-53)
temperature corr. factor Free air capacity of valve at same setting:
. (45,000) (1.0)
Free gas capacity of valve =
1.0518 ( 48, 717) ( 1.64) 83,651 SCFH
0.9551
= 42, 783 SCFH at 60° F
and 14. 7 psia Example 7-11: Storing Benzene in Cone Roof Tank
If this volume were needed to be expressed at 55°F and A 26,000 gallon outdoor vertical storage tank contains
1.5 psig, then using the gas laws: benzene. The tank is not insulated, but has a dike around
it with a volume equal to one-and-a-half times the volume
Actual flowing volume at 55°F and 1.5 psig of the tank. Size 15' diameter X 20'. Tank does not have
weak roof. Temp. = 60°F, pressure = 14.7 psia.
460 55 7
= 42, 783 SCFH ( + ) 0 4- ) Data: Flash point of benzene: < 100°F
( ) ( 460 + 60) (14.7 + 1.5)
Latent heat of vaporization: 169 BTU/lb
Tank size (nominal): 15' diameter and 20' high
= 38,448 cu ft/hr
Operating pressure: 1.5 oz/in. 2
Maximum allowable tank pressure: 3.5 oz/in. 2
Example 7-10: Converting Required Free Air Capacity
Maximum allowable vacuum: 1.0 oz/in. 2
The capacity of a relief valve for a tank has been calcu- Relief valve settings:
lated to be 50,000 cu ft/hr at l l0°F and 1.0 psig, with a (1) For pressure: 2.0 oz/in. 2 2
(2) For vacuum: 0.5 oz/in.
benzene vapor. Determine the required free air capacity. Filling rate: 350 gpm (max)
For benzene: MW = 78.11
Draw-out rate (emptying): 250 gpm
A. Normal venting requirements
78.11
SpGr = -- = 2.69 1. Pressure: filling
29
Rate = (350 gpm) (60) = 21,000 gal/hr