Page 189 - Applied Process Design For Chemical And Petrochemical Plants Volume III
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66131_Ludwig_CH10E  5/30/2001 4:33 PM  Page 152










                       152                       Applied Process Design for Chemical and Petrochemical Plants

                           Because this rate is so close to the previous G s of 24,000,  p c   0.867 psia at 97°F
                           it is reasonable to assume that the h o value will be close  p g     32.0   0.867   31.133 psia
                           also. Use h o   70.0.
                                                                                  31.133   30.058
                       Latent heat,  , at 130°F   1,020.0 Btu/lb             p gf                 30.2 psia
                                                                                         31.133
                       Assume condensate temperature, t c   98.5°F                 2.3 log
                                                                                         30.058
                       P c at 98.5°F   0.907 psia
                       P g   32.5   0.907   31.593                                              5.41              1.942   0.867
                                                                                 701125   972         118211,022.92a         b
                                                                                              £  30.2 §               14.7
                                                                                               a    b
                            31.593   30.27                                                      14.7
                       P gf                31.6
                                  31.593                                                   1,140197   92.32
                             2.3 log
                                   30.27
                                                                             1,960   3,540   5,350
                       h o   (t g   t c )   K G M V   (p v   p c )   h io   (t c   t w  )  5,500   5,350
                           (See the previous note regarding h io  .)             Close enough check.
                           701130   98.52                                           5,500     5,350
                                                                             U t                     5425
                                                                                          2
                         5.41          12.223   0.9072                              5,425
                              118211,0202             1,140198.5   932       U               166 Btu>hr 1ft 21°F2
                                                                                                        2
                        £ 31.6 §            14.7                                 125   92.3
                         14.7
                                                                             Interval 115°F—104°F
                       2,210   4,140   6,270                                   Point at 104°F
                             6,350   6,270                                     t g   104°F
                                                                               p v   1.069 psi at 104°F
                           Close enough check (slightly   1%).                 p g   31.0   1.069   29.931 psia


                             6,350   6,270                                               314,730
                       U t                 6,310                             t¿ w   91.1          90.05°F, close enough check to 90°F
                                  2                                                     299,00112
                             6,310
                       U             170 Btu>hr 1ft 21°F2                    New gas rate   970(14)   34.6(18)   14,223 lb/hr
                                                2
                           130   93
                                                                                 Note that this is the same as the previous interval; the
                       Interval 125°F—115°F
                                                                                 difference is discussed there. Using Kern’s outline, this
                             t g   125
                                                                                 effect is as discussed and not as demonstrated here. In
                            p v   1.942 psia at 125°F
                            p s   32.0   1.942   30.058 psia                     this case, the difference is negligible.
                                                      213,940
                       t w   93.0 1from previous interval2       92.3°F      Use h o   65
                                                    1299,0002112
                                                                             Latent heat at 104°F   1034.9 Btu/lb
                                                                             Assume condensate temperature, t c , of 91.7°F
                       New gas rate   (970)(14)   (46.8)(18) - 14,442        p c   0.736 psia at 92°F
                            14,442                                           p’ g   3.10   0.736   30.264 psia
                                                2
                       G s          23,100 lb>hr 1ft 2
                            0.624
                                                                                  30.264   29.931
                                                                             p gf                 30.0
                           This is still not enough change in G s from 24,000 to         30.264
                                                                                   2.3 log
                           justify a calculation of a new h o . Use of the water vapor   29.931
                           flow leaving the assumed interval means the actual G s          5.41            1.069   0.736
                           through that interval will be equal to or greater than  65(104 92)      118211,034.92
                                                                                          £ 30.0 §             14.7
                           the value for conditions at 115°F. This value is on the
                                                                                           14.7
                           safe side for h o .
                                                                                        1,140(91.7   90)
                       Latent heat at 125°F,    1022.9 Btu/lb                800   1120   1940
                       Assume condensate temperature of t c   97.0°F              1920   1940
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