The Shell Deep Thermal Conversion process fills the gap between visbreaking and coking. It was developed based on many years of experience with the Shell Soaker Visbreaking process. The process yields a maximum of distillates by applying deep thermal conversion of the vacuum residue feed and by vacuum flashing of the cracked residue. High distillate yields are obtained while still producing a stable liquid residual product, referred to as liquid residue. This liquid residue stream, which is not suitable for blending to commercial fuel, is used for specialty applications, like gasification and/or combustion, e.g. to generate power and/or hydrogen.
When compared to Delayed Coking, Deep Thermal Conversion technology offers the following advantages:
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The investment costs are significantly (typically 50%) lower |
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The Deep Thermal Conversion process provides a pumpable product, instead of a (difficult to handle) solid product. |
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The Delayed Coking process yields a significant amount of (lower value) offgas, whereas the Deep Thermal Conversion technology yields less offgas and more valuable distillate and fuel products |
Preheated vacuum residue is charged to the heater and from there to the soaker, where the deep thermal conversion takes place. The conversion is maximized by controlling the operating temperature and pressure. The soaker effluent is routed to a cyclone and the cyclone overheads are charged to the flash zone of the atmospheric Fractionator to produce the desired products like gas, LPG, naphtha, kero and gasoil. The fractionator bottoms are routed to a vacuum flasher, which recovers additional gasoil and vacuum gasoil (VGO). Vacuum flashed cracked residue is routed to offsites for further processing depending on the end use.
Products yields are dependent on feed type and product specifications. Typical product yields for Middle East crude are given below.
Based on vacuum residue feed:
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Product |
Yield (wt%) |
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Gas |
4 % |
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Naphtha |
9 % |
Endpoint 165 °C |
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Light Gasoil |
20 % |
Endpoint 350 °C |
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Heavy Gasoil |
21 % |
Endpoint 520 °C |
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Liquid Residue |
46 % |
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The investment amounts to 1300 - 1600 US$/BPSD installed excluding treating facilities and depending on the capacity and configuration.
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Utilities, typical per bbl @ 180°C: |
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Fuel, Mcal |
|
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Electricity, kWh |
0.5 |
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Net steam production, kg |
20 |
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Cooling water, m3 |
0.15 |