SRC SUPER RADIANT COIL

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1 SRC SUPER RADIANT COIL ETHYLENE FURNACES STEAM CRACKING TECHNOLOGY EVOLUTION Inventors : Dr.ing. Maurizio Spoto - Dr.ing. Benedetto Spoto

THE CRACKING FURNACE IS THE CORE OF ETHYLENE BUSINESS The reaction

radiant coil to improve the surface to volume ratio.

2 THE CRACKING FURNACE IS THE CORE OF ETHYLENE BUSINESS The reaction yield increases by reducing both the gas residence time and the hydrocarbon partial pressure. Furnace designers are continuously modifying the geometry of the radiant coil to improve the surface to volume ratio. The resulting higher heat flux and tube metal temperature force the radiant coil to operate close to its metallurgical limit.

3 Short residence time requires small diameter tubes which causes: Higher Tube Metal Temperature (TMT) Higher pressure drop Higher coking rate Higher carburization and creep rates Selectivity loss during the Run Length (RL) Tube plugging

4 SRC Technology Objectives: Short residence time with large bore tubes Increase the heat transfer area Enhance the radiant heat transfer Reduce the tube metal temperature Reduce the coking rate Avoid tube plugging

5 SRC Technology Achievements: High olefins selectivity Low coking rate - Extended furnace run length Lower Tube Metal Temperature Extended coil life (low carburization rate)

Temperature A Tube heat transfer surface U Overall tube heat transfer coefficient Stefan-Bolzmann constant

6 Heat transfer in cylindrical tube q rb q cb T wo T wi T f Firebox Radiative Heat Flow Firebox Convection Heat Flow Tube Wall Outside Temperature Tube Wall Inside Temperature Cracking gas Temperature T box Firebox Temperature A Tube heat transfer surface U Overall tube heat transfer coefficient Stefan-Bolzmann constant GS Overall exchange area q b =q rb+ q cb =GS* *(T box 4 - T wo4 )+A o *h o *(T box - T wo ) = U*A*(T wi -T f )

7 Typical commercial coils Geometry Name Run Length days Coil ID inches Residence time sec UDC > Split Coil U-tube Millisecond < 0.2

8 SUPER RADIANT COIL Heat Transfer Mechanism q C2 q C2 q C1 q r SRC q rb q cb q k Firebox Radiative Heat Flow Firebox Convection Heat Flow Conduction heat flow q c1 Convection heat flow 1 q c2 Convection heat flow 2 q r SRC Inner Radiative Heat Flow Heat Balance : q r = q rb + q cb = q C1 +q C2 q r SRC =q C2

9 SUPER RADIANT COIL Heat Balance T f T wi TSRC Fluid Temperature Tube Wall inside Temperature SRC Temperature SRC q C2 q C1 Convection Heat Transfer : q C =q C1 +q C2 = A wi *h C1 (T wi -T f ) +A SRC *h SRC *(T SRC -T f ) q r SRC q C2 = qr SRC h SRC > hc 1 hc 1 =Tube inner convection heat transfer coefficient h SRC = SRC outer convection heat transfer coefficient

10 Heat Transfer Over the Insert (SRC) RADIANT HEAT TRANSFER INSIDE THE TUBE: q r SRC = *(T wi4 -T SRC4 )*A SRC f(ε SRC, ε T, ε g,f SRC,T ) SRC q C1 HEAT BALANCE OVER THE CYLINDRICAL INSERT(SRC): q C2 q r SRC = q C2 q r SRC T SRC A SRC Insert temperature Insert surface F SRC,T View factor ε SRC, ε T, ε g Emissivity (SRC, tube and cracking gas)

SUPER RADIANT COIL Industrial Test Furnace Polimeri Europa Ethylene Plant- Gela (Sicily) Industrial test has been carried out by installing two SRC

have been kept unchanged to act as reference tubes Both couples of tubes receive the same heat flow from the fire-box.

11 SUPER RADIANT COIL Industrial Test Furnace Polimeri Europa Ethylene Plant- Gela (Sicily) Industrial test has been carried out by installing two SRC devices in an industrial Gela Ethylene plant An identical couple of tubes in the same furnace and operating under identical conditions have been kept unchanged to act as reference tubes Both couples of tubes receive the same heat flow from the fire-box. Tube wall temperatures have been collected by using a laser pyrometer. The tube wall temperature of the base coil has been on an average 40 C higher than the TMT of the SRC coils.

12 SUPER RADIANT COIL : Process Calculations Process yields Material, heat and momentum balance Coke formation Are calculated using our proprietary kinetic model PYCOS PYCOS PYROLYSIS COIL SIMULATOR

13 SUPER RADIANT COIL The following two case studies 1 & 2 show that using SRC technology it is possible to increase the furnace capacity of existing furnaces with a dramatic reduction of the tube wall temperature and coking rates. The third case study is the recoil of an existing Selas furnace. The use of the SRC technology allows a very good selectivity increase: Ethylene from to wt % Propylene from to wt % Butadiene from 3.57 to 5.26 wt % The calculate economic benefits of the selectivity increase is about /y The total cost of the recoil is about

14 Case study 1 : Capacity increase from 9.62 t/h to 10.5 t/h Feed:ethane % wt -ethylene 0.13 % wt Fixed firebox size -Tube design temperature:1030 C Coils type unit base LC base HC SRC (60%) SRC (65%) Ethane flow t /h 9,62 10, ,5 Steam dilution ratio Steam /Oil kg/kg 0,4 0,4 0,4 0,4 Fire duty GJ/h 82,54 92,6 90,2 102 Firebox efficiency % 40 38,34 39,28 37,1 Furnace inside radiant surface m Average inside heat flux Kw/m 2 76,8 82,6 74,6 80 Pressure drop at SOR Kg/cm 2 1,67 1,9 1,12 1,12 Pressure drop at EOR Kg/cm 3 2,24 2,57 1,47 1,69 Residence time s 0,58 0,54 0,58 0,58 Ethane conversion % Ethylene yield % 48, ,8 51,8 Max inner TMT at SOR C Max outer TMT at R.L C Coking rate mm/mth 2,93 2,98 1,86 2,73 Max velovcity at R.L. m/s Run length: R.L. days

15 Case study 2: Capacity increase from 23.0 t/h to 25.3 t/h Feed : Naphtha -Fixed firebox size -Tube design temperature:1100 C unit Case a Case -b Case c Hydrocarbon flow t /h Steam dilution Kg/kg Fired duty GJ/h Fire box efficiency % Heat absorbed GJ/h Furnace inside radiant surface m Average inside heat flux kw/m XOT: cross over temperature C COT: coil outlet temperature C Flue gas at cross-over C Severity: propylene/ethylene ratio Kg/kg COP: coil outlet pressure Bar, a Pressure drop Kg/cm Residence time s Coking rate (last tube) mm/mth MAX TMT SOR (last tube) C MAX TMT 30days (last tube) C Run length Days

16 Case study 3 : Selas recoil - Capacity : 24 t/h Feed : Naphtha -Fixed firebox size -Tube design temperature:1100 C Yields % wt Selas Selas-SRC Delta /kg /a /a H CH C2H C2H C2H C3H C3H C3H C4H C4H C4H C5 totali Benzolo Toluolo Xiloli+Etb Styrolo C6-C8 Na C Residuo Total feed [t/year] ( * ) Naphtha price [ /kg] Run length [days] Fuel gas [kg/h] Operating hours = 8000 hours/year ( * ) Selectivity economics naphtha flow rate 24 t/h Benefits /a

17 SUPER RADIANT COIL:Applications Ethane Main Purpose Large Diameter Tubes Low Tube Wall Temperature Low Coking Rate No Tube Plugging Increase Conversion Increase Capacity Increase Selectivity Low carburization Low Pressure Drop LPG/naphtha/GO Main Purpose Large Diameter Tubes Short Residence Time Low Tube Wall Temperature Low Coking Rate No Tube Plugging Long Operating Cycle High Severity High Selectivity Low Pressure Drop

SUPER RADIANT COIL Conclusions Objectives: Short residence time Increase heat transfer rate Enhance radiant heat transfer Reduce TMT Reduce coking rate Reduce tube

18 SUPER RADIANT COIL Conclusions Objectives: Short residence time Increase heat transfer rate Enhance radiant heat transfer Reduce TMT Reduce coking rate Reduce tube plugging SRC achievements: Reduced cross sectional area Higher film coefficient Internal radiant heat transfer Increased Heat Transfer Area Lower TMT Large diameter tube

19 SUPER RADIANT COIL PATENT GRANTED IN EUROPE USA & RUSSIA

Full Furnace Simulations and Optimization with COILSIM1D

Full Furnace Simulations and Optimization with COILSIM1D Kevin M. Van Geem 1 Alexander J. Vervust 1 Ismaël Amghizar 1 Andrés E. Muñoz G. 2 Guy B. Marin 1 1 Laboratory for Chemical Technology, Ghent University