Fluid Mechanics, Heat Transfer, Thermodynamics Design Project Production of Styrene The feasibility of constructing a new, grass-roots, 100,000 tonne/y, styrene plant is being investigated. As part of the feasibility study, some of the details of the proposed plant must be analyzed. Styrene Production Reaction For this analysis, it may be assumed that the only reaction is given in Equation 1. styrene eehylbenzen 22563256HCHCHHCCHCHHC +=↔ (1) For the purposes of this preliminary evaluation, it is assumed that the reaction occurs in an adiabatic packed bed of catalyst particles. Equilibrium limitations and equipment limitations make the maximum possible conversion 40%. Feed and Reaction Sections The PFD for the feed and reaction sections is given in Figure 1. The feed to the process is liquid ethylbenzene. The pressure drop at all mixing points is 10 kPa. The reaction is endothermic, and the reactor is adiabatic. The only constraint is a maximum temperature of 600°C. Following the reactor, the reaction products are cooled to the three-phase flash conditions. In the three-phase flash, hydrogen and wastewater are separated from the organics. Ethylbenzene and styrene are separated in a distillation column, which may be assumed to be a perfect separator for this semester’s project only. The wastewater stream must be at 200 kPa and the hydrogen stream at 300 kPa for further treatment.23Process Details Feed Streams Stream 1: ethylbenzene liquid at 210 kPa, 136°C Stream 4: low-pressure steam at 3000 kmol/h Stream 17: recycle ethylbenzene, at 210 kPa – temperature is that of saturated liquid at pressure of distillation column, which is 60 kPa Effluent Streams Stream 12: Hydrogen by-product – must be at 300 kPa – purification and sale should not be considered – it can be burned for credit at its LHV Stream 13: Wastewater stream to treatment – must be at 200 kPa Stream 16: Styrene product – must be at 200 kPa Equipment Summary H-401: Fired Heater – a furnace that can heat to temperatures above high-pressure steam using an open flame – outlet temperature to be determined E-401: Heat Exchanger – to preheat and vaporize ethylbenzene feed to 240°C R-401: Reactor – adiabatic – inlet temperature must be 550°C and the inlet pressure must be 155 kPa – assume to have a pressure drop of 45 kPa E-402: Product cooler – cools reactor outlet stream to 65°C – assume to have a pressure drop of 35 kPa V-401: Three-phase separator operating at 75 kPa – produces an oil-water-gas three-phase mixture that is assumed to separate easily into three distinct streams – can be simulated on Chemcad using a perfect component separator C-401: Compressor – to compress hydrogen to the required pressure – the compressor has an isentropic efficiency of 75% and a maximum operating temperature of 200°C P-401: Pump – to pump waste water to required pressure – A/B means two in parallel with only one operating P-402: Pump – to pump styrene product to required pressure – A/B means two in parallel with only one operating4 P-403: Pump – to pump ethylbenzene recycle to required pressure – A/B means two in parallel with only one operating T-401: Distillation column – to produce styrene product and ethylbenzene for recycle –the component separator in Chemcad should be used – a perfect separator may be assumed (which is physically impossible) for this semester only, i.e., all ethylbenzene to the recycle and all styrene to the product Assignment The first task is to obtain base-case stream flows for the process using Chemcad. The remainder of the assignment consists of five “mini-designs.” 1. Fluid Mechanics (ChE 310) – Optimization of the Feed Section and Wastewater Pump. Pump P-401 A/B should be sized. The optimum pipe size for Streams 11 and 13 should be determined. The objective function for the optimization is the Equivalent Annual Operating Cost (EAOC) of the pipe in Streams 11 and 13 and of P-401 A/B ($/y). The EAOC is defined as: A/B 401-Pfor costsoperatingannual,, +⎟⎠⎞⎜⎝⎛= niPACAPEAOC (2) where CAP = the installed cost of P-401 A/B and the pipe in Streams 11 and 13, and ()()[]APiniiinn,,⎛⎝⎜⎞⎠⎟=++−111 (3) where i = 0.15 (15% rate of return) and n = 10 (ten-year plant life). Raw-material costs or wastewater-treatment costs should not be included, so CAP only includes the installed cost of pipes and pumps, and operating costs include the electricity to run the pump. The liquid level to be maintained in V-401 to avoid cavitation of P-401 A/B should be specified. Pump P-401 A/B is 5 m horizontally distant from the V-401 draw, the tank bottom is 3 m above the pump suction line, and this piping contains two 90° elbows. Stream 13 has an equivalent length of 100 m. There is a supply of centrifugal pumps used in other plants. Their pump curves and their NPSH curves are attached (Figures 2 and 3). The data for these figures are shown in Table 1. The design should include flexibility for 30% scale-up in the future.5Figure 2: Pump Curve for P-401 A/BWater Flowrate (m3/s)0.00 0.01 0.02 0.03Differential Head (kPa)050100150200250Figure 3: NPSH Curve for P-401 A/BWater Flowrate (m3/s)0.00 0.01 0.02 0.03NPSH (m liquid)0123456Table 1: Data for Figures 2 and 3 water flowrate (m3/s) differential head (kPa) NPSH (m liquid)0.0000 225 3.000 0.0025 224 3.025 0.0050 223 3.050 0.0075 222 3.080 0.0100 220 3.120 0.0125 218 3.150 0.0150 216 3.230 0.0175 212 3.360 0.0200 205 3.500 0.0225 192 3.700 0.0250 168 3.900 0.0275 130 4.100 0.0300 72 4.300 The pressure drop from V-401 to the compressor inlet is 10 kPa, which is applicable to the thermodynamics design section. 2. Heat Transfer (ChE 311) – Design of E-401. The heat exchanger, E-401, must be designed in detail for the base case. Assume the inlet pressure is the same as Stream 1. The outlet pressure must be as specified based on the heat-exchanger design and the required inlet pressure to the reactor. It should be assumed that utilities are available at the conditions specified in the Appendix of this problem statement. For this heat exchanger design, the following information should be provided: • Diameter of shell • Thickness of shell wall • Number of tube and shell passes (where applicable) • Number of tubes per pass • Tube pitch