the overhead product from flash(S-112) is rich in nitrogen and will be used as fuel to power the fuel gas turbine. this stream has a flow rate of 2.201 lbmol/h and consists of 19.7% nitrogen, 80.2% methane, and 0.1% C2. Stream S-112 emerges from the flash vessel at 259F and 18 psia. It is then sent to the main heat exchanger as a cold stream, as it must be heated before it is compressed and fed to the turbine reaction chamber. This stream(S-113) emerges from the main exchanger at 61.2F and 18 psia. It then exits section 1 and proceeds to section 3(power generation), which is shown in Figure 6 on page 21.

Stream S-114 is the cold nitrogen stream that provides the bulk of the cooling power for the main heat exchanger. This stream enters the heat exchanger at 222F and 130 psia, with a flow rate of 69.012 lbmol/h of pure nitrogen. It emerges at the other end of the exchanger as stream S-115, with a temperature of 61.2F and a pressure of 130 psia. It then proceeds to section 4 (Nitrogen Cycle), where it will be re-compressed, cooled, and expanded so that it is again at 222F.

Stream S-116 is the re-compressed nitrogen stream that must be pre-cooled before it can be expanded to provide the necessary cooling for the main heat exchanger. It enters HX-101 at 90F and 995 psia, with a flow rate of 69.012 lbmol/h. It is cooled by streams S-112 and S-114 to 50F at 995 psia, when it emerges as stream S-117. stream S-117 then proceeds from section 1 to section 4, where it will be expanded to provide cooling power.

FRACTIONATION TRAINSection 2 of the process is the fractionation train. The main purpose of this section is to further separate the heavy components(C2+) present in the bottoms product of D-101, stream S-110, so they can be sold for additional revenue. Figure 5, on page 19 above, shows the process flow diagram for this process section. Additionally, table 2, on page 20 above, provides detailed information on the streams introduced in figure 5.

The liquid stream (S-110 from figure 4 or S-200 on figure 5) coming from the bottom of the scrub column (D-101) contains 0.8% methane, 53.5% ethane, 22.9% propane, 11.4% butane, and 11.4% C5+, at 66.1F and 300 psia. This stream is then throttled in a valve (V-201) to a temperature of 41.2F and a pressure of 200 psia (S-201). Decreasing the pressure of the stream increases the relative volatilities of the components, and thus makes separation easier.

Stream S-201 then proceeds to the first distillation column in the train (D-201). This column separates the components of S-201 into light (methane, ethane and propane) components and heavy (butane and higher) components. These streams are then further separated by other columns further along the train. The vapor product (S-202) of column D-201 has a flow rate of 910 lb mol/h at 41.8F and 190 psia, and contains 1.2% methane, 69.2% ethane, 28.8% propane, 0.7% butane, and the balance C5+. This steam (S-202) is then sent to the light distillation column (D-202), where it will be separated further. The liquid bottoms product (S-205) from column D-201 has a flow rate of 270 lbmol/h at 228F and 190 psia. It contains