Chemical Process Design / Diseño de Procesos Químicos

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Viguri Fuente Eva Cifrian Bemposta Department of

Green Engineering and Resources Research Group This

1 Chemical Process Design / Diseño de Procesos Químicos Topic 5.3. Heat transfer equipment Javier R. Viguri Fuente Eva Cifrian Bemposta Department of Chemistry and Process & Resource Engineering GER Green Engineering and Resources Research Group This work is published under a License: Crea>ve Commons BY- NC- SA 4.0

2 Heat Transfer Equipment Sizing Heat exchanger types used in chemical processes: By function: - Refrigerants (air or water). - Condensers (v, v + l l). - Reboilers, vaporizers (l v). - Exchangers in general. By constructive shape: - Double pipe exchanger: the simplest one. - Shell and tube exchangers: used for all applications. - Plate and frame exchangers. - Air cooled: used for coolers and condensers. - Direct contact: used for cooling and quenching (enfriamiento brusco). - Jacketed vessels, agitated vessels and internal coils (serpentines). - Fired heaters: furnaces and boilers.

3 Heat Transfer Equipment Sizing Heat exchanger types used in chemical processes: By constructive shape: Double pipe exchanger: the simplest one Fired heaters: furnaces and boilers Jacketed vessels, agitated vessels and internal coils. Convection section - Koch Heat Transfer Company: Plate and frame exchangers - Thermax, Ltd. - Lenox Instrument Co. Shell and tube exchangers: used for all applications - Tranter - The Heat Transfer People: - APL Apparatebau GMBH. Direct contact: used for cooling and quenching Air cooled: used for coolers and condensers Air OUT Water IN 50º C Air IN Water OUT 45º C

4 HEAT EXCHANGERS

5 HEAT EXCHANGERS

6 Heat Transfer Equipment Sizing Shell and tube countercurrent exchanger, steady state: Q = U A DT lm T1 T2 Q: from the energy balance. U: estimation of heat transfer coefficient. Depending on configuration and media used in the Shell and Tube side: L-L, Condensing vapor-l, Gas-L, Vaporizers). (Perry's Handbook (2008): A: area. DT lm : logarithmic Mean DT = (T1 t2) (T2 t1) / ln (T1 t2 / T2 t1). t2 t1 - If phase changes Approximation of 2 heat exchangers (A = A1 + A2). - Maximum area A 1000 m 2, else Parallel HX. MPF = Fm (F p + F d )

7 Heat exchanger: Countercurrent, steady state Guthrie Material and pressure factors for Heat Exchangers: MPF = F m (F p + F d ) Design Type, F d Vessel Pressure (psig) Kettle Reboiler 1.35 Floating Head 1.00 Up to U Tube 0.85 F p Fixed tube sheet 0.80 Shell/Tube Materials, F m Surface Area (ft 2 ) CS/ CS/ CS/ SS/ CS/ Monel CS/ Ti/ CS Brass SS SS Monel Monel Ti Ti Up to to to to

8 Heat exchanger: Countercurrent, steady state Equipment Type C 0 ($10 3 ) S 0 Range (S) MF2 / MF4 / MF6 / MF8 / MF10 Heat exchanger / 3.18 / 3.14 / 3.12 / 3.09 Shell and tube, S = Area (ft 2 ) Heat exchanger / 1.83 / 1.83 / 1.83 / 1.83 Shell and tube, S = Area (ft 2 ) Air Coolers / 2.21 / 2.18 / 2.16 / 2.15 S = [calculated area (ft 2 ) / 15.5] S Area from sizing calculations C = BC = C 0 (S / S 0 ) MF (Module Factor) MF 2: If C < $ MF 4: If C = $ MF 6: If C = $ MF 8: If C = $ MF 10: If C = $ Materials and Pressure correction Factor: MPF = F m (F p + F d ) Update Factor UF = Present Cost Index (CI actual ) / Base Cost Index (CI base ) Updated bare (simple) module cost: BMC = UF(BC) (MPF + MF 1)

9 Furnaces and Direct Fired Heaters Boilers, reboilers, pyrolysis, reformers: Q = Absorbed duty from heat balance Radiant section (q rad = 37.6 kw/m 2 heat flux) + + Convection section (q conv = 12.5 kw/m 2 heat flux). Equal heat transmission (kw) A conv A rad Convection section Radiation section A rad = 0.5 Q kw/q rad ; A conv = 0.5 Q kw/q conv Sectional view of a heater. Basic configuration for furnaces is given by a process heater with a box or A-frame construction, carbon steel tubes, and a 500 psig design Pressure. This includes complete field erection. Direct fired heaters is given by a process heater with cylindrical construction, carbon steel tubes, and a 500 psig design pressure.

10 Furnaces and Direct Fired Heaters Boilers, reboilers, pyrolysis, reformers:

11 Furnaces and Direct Fired Heaters Boilers, reboilers, pyrolysis, reformers: Equipment Type C 0 ($10 3 ) S 0 Range (S) MF2 / MF4 / MF6 / MF8 / MF10 Process furnaces / 2.19 / 2.16 / 2.15 / 2.13 S = Absorbed duty (10 6 Btu/h) Direct fired heaters / 2.15 / 2.13 / 2.12 / 2.10 S = Absorbed duty (10 6 Btu/h) S Absorbed duty, Q C = BC = C 0 (S / S 0 ) MF (Module Factor) MF 2: If C < $ MF 4: If C = $ MF 6: If C = $ MF 8: If C = $ MF 10: If C = $ Materials and Pressure correction Factor: MPF = F m (F p + F d ) Update Factor UF = Present Cost Index (CI actual ) / Base Cost Index (CI base ) Updated bare (simple) module cost: BMC = UF(BC) (MPF + MF 1)

12 Furnaces and Direct Fired Heaters Boilers, reboilers, pyrolysis, reformers: Indaver, Belgium. Fired Reboiler (CC BY-SA 3.0).

How is the heat transfer?

How is the heat transfer? As we discussed early in the first chapter that heat can transfer through materials and the surrounding medium whenever temperature gradient exists until thermal equilibrium is