GBH Enterprises, Ltd.

Engineering Design Guide
Carbon Formation in Mixed Feed Preheat
Coils

Process Information Disclaim...
Carbon Formation in Mixed Feed Preheat Coils

Maximum Mixed Feed Pre-heat Temperature

What follows is a crude but effecti...
Example 1 (NG)
NG composition......
C1
86.0 mol %
C2
6.6 mol %
C3
3.6 mol %
C4
1.5 mol %
C5
0.4 mol %
H2
2.0 mol %
N2
1.0 ...
Note: This approach takes no account of pre-heat coil positioning, size,
counter/co-current etc. notwithstanding the other...
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Carbon Formation in Mixed Feed Preheat Coils

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Carbon Formation in Mixed Feed Preheat Coils:
Maximum Mixed Feed Pre-heat Temperature

What follows is a crude but effective routine, which evaluates the maximum possible temperature allowable to prevent excessive carbon laydown in the mixed feed pre-heat coils.

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Carbon Formation in Mixed Feed Preheat Coils

  1. 1. GBH Enterprises, Ltd. Engineering Design Guide Carbon Formation in Mixed Feed Preheat Coils Process Information Disclaimer Information contained in this publication or as otherwise supplied to Users is believed to be accurate and correct at time of going to press, and is given in good faith, but it is for the User to satisfy itself of the suitability of the Product for its own particular purpose. GBHE gives no warranty as to the fitness of the Product for any particular purpose and any implied warranty or condition (statutory or otherwise) is excluded except to the extent that exclusion is prevented by law. GBHE accepts no liability for loss, damage or personnel injury caused or resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  2. 2. Carbon Formation in Mixed Feed Preheat Coils Maximum Mixed Feed Pre-heat Temperature What follows is a crude but effective routine, which evaluates the maximum possible temperature allowable to prevent excessive carbon laydown in the mixed feed pre-heat coil. The method assumes that 100% CH4 mixed with steam (S/C =3) could in theory be heated-up with steam to 645oC. As heavier hydrocarbons are added, this temperature will fall. As hydrogen is added, or S/C increased, the temperature can increase. A table of indices for the calculation is as follows: Component C1 C2 C3 C4 C5 C6 C7 C8 H2 N2, CO, CO2 etc S/C (molar) Index [X] 0.05 1.2 1.5 1.7 1.55 1.65 1.75 1.8 -0.5 0 10 Each component composition in the feed (mol %) is then multiplied by the respective index number [X] and totalled. The S/C ratio correction is then calculated by subtracting the S/C ratio from 3 and multiplied by the index number [X = 10]. The total summation of these numbers is then subtracted from 650oC to yield the maximum allowable pre-heat temperature. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  3. 3. Example 1 (NG) NG composition...... C1 86.0 mol % C2 6.6 mol % C3 3.6 mol % C4 1.5 mol % C5 0.4 mol % H2 2.0 mol % N2 1.0 mol % S/C ratio 3.3 So maximum pre-heat temperature = 650 - [(86 x 0.05) + (5.5 x 1.2) + (3.6 x 1.5) + (1.5 x 1.7) + (0.4 x 1.55) + (2 x -0.5) + (3 - 3.3)x10] = 632oC Example 2 (LPG) LPG composition...... C3 0.47 mol % C4 83.52 mol % C5 0.35 mol % H2 15.66 mol % S/C ratio 3.3 So maximum pre-heat temperature = 650 - [(0.47 x 1.5) + (83.52 x 1.7) + (0.35 x 1.55) + (15.66 x -0.5) + (3 - 3.3)x10] = 518oC Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  4. 4. Note: This approach takes no account of pre-heat coil positioning, size, counter/co-current etc. notwithstanding the other approximations. However, even a crude approach may help in recommending maximum pre-heat temperatures. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com

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