3/9/2013

UNIVERSITY OF KARACHI

Prepared by:

Sadia Urooj

Submitted to:

Sir Zeeshan Zaki

s-Zorb (Conophillips)

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S‐Zorb (ConocoPhillips)

Introduction:

ConocoPhillips Company breakthrough technology, S Zorb Sulfur Removal

Technology (SRT), substantially lowers the sulfur concentration in FCC gasoline

while still protecting octane-rich olefins and aromatics. In the S Zorb process

sulfur-containing molecules react with the novel S Zorb sorbent that retains the

sulfur atom from the molecule while the hydrocarbon portion of the molecule is

released back into the process stream. This unique reaction pathway does not

generate free H2S; therefore, preventing recombination of hydrogen sulfide and

olefins to form mercaptans. This technology was first demonstrated at the

ConocoPhillips’ refinery in Borger, Texas, USA in April 2001 and a second

commercial unit began operation in November 2003 and ConocoPhillips refinery

in Ferndale, Washington, USA.

Overview of S Zorb Sulfur Removal Chemistry:

Application:

ConocoPhillips’ S Zorb SRT process can economically reduce the sulfur content of

gasoline to less than 10 ppm with minimal octane loss, minimal hydrogen

consumption and near zero volume loss. Hydrogen consumption is kept low by

minimizing the extent of olefin saturation.

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Process Description:

Hydrocarbon is fed to a charge pump and is then mixed with the recycle hydrogen

stream containing a small amount of makeup hydrogen. After hydrogen addition, the

combined stream is passed through a feed effluent heat exchanger for vaporization

and then to a fired heater to achieve the desired feed temperature. The vaporized

feed is sent to the bottom of the reactor vessel containing a fluidized bed of the S

Zorb sorbent. After passing through the sorbent bed, the hydrocarbon stream exits

the top of the vessel through fines filters that remove any entrained sorbent. The

desulfurized hydrocarbon product exits the reactor and proceeds through a series of

heat recovery and cooling steps before entering the product separator for

vapor/liquid separation. The vapor from the product separator is sent to the recycle

compressor. Liquid from the product separator is passed through heat recovery and

then fed to the stabilizer where light material, mainly hydrogen, is stripped out of the

liquid product. The bottoms product from the stabilizer is cooled and sent to product

blending.

Regeneration:

The sorbent (catalyst) is continuously withdrawn from the reactor and transferred to

the regenerator section (2), where the sulphur is removed as SO2 and sent to a

sulfur-recovery unit. The cleansed sorbent is reconditioned and returned to the

reactor. The rate of sorbent circulation is controlled to help maintain the desired

sulfur concentration in the product.

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Constraint Analysis:

At the inlet of reactor (from charge heater): The reactor temperature is a

constraint that should be constant generally ranging from 750 to 825 oF.

At the inlet of regenerator: The oxygen content of the regenerator is another

constraint that needs to be limited to control the temperature rise in the

regenerator.

At the inlet of reactor (from regenerator): Since the regenerator

temperatures are near 1000oF to convert metal sulphides into metal oxides,

and SO2 is released, also carbon converts into CO2. So before the sorbent

returns into the reactor, it should spend a short time in a reducing atmosphere

near 750oF to reactivate the metals. This is another constraint.

At the outlet of Stabilizer: The treated gasoline should have sulphur content

less than 10 ppm is another constraint.

Operating Conditions:

Temperature, °F 750 – 825

Pressure, psig 100 – 500

Space velocity, whsv 4 – 8

Hydrogen purity, % 70 – 99

Total H2 usage, scf / bbl 40 – 60

Process Patents (EP 1 448 294 B1): EP 1 448 294 B1 is the patent for

the process.

Economics: