CHEVRONTEXACO PETROLEUM COMPANY
GENERAL DESCRIPTION OF THE KEROSENE HYDROTREATER UNIT
DESCRIPTION OF PROCESS
Kerosene
Hydrotreater (Diesel Hydrotreater) – Section 300
This unit was designed to hydrotreat kerosene but it
can be used to hydrotreat Diesel as well.
The high operating pressure favors the aromatics reduction from the
Diesel stream.
The Kerosene Hydrotreater is designed to upgrade a
sour kerosene cut by catalytic treating in the presence of hydrogen to convert
sulfur to H2S, remove nitrogen and heavy metals and saturate mono-cyclic and
poly-cyclic aromatics.
The kerosene charge pumps, located in the northwest
corner of the Crude Unit (Section 100) take suction from the kerosene surge
tank, FA-102, and pump to the unit under flow control (FRCA-104). The hydrogen-rich make-up gas flows to this
Unit from the separator drum, FA-201, in the Naphtha Hydrotreater area. This gas stream is compressed from
approximately 400 psig to approximately 1485 psig in GB-301. At the discharge side of GB-301 the H2
recycle gas from FA-.301 flash drum joins with the compressed H2 rich make-up
gas from the Naphtha Hydrotreater and is compressed further to 1616 psig. The total H2 gas from the second stage
compressor, GB-302, then joins with the kerosene liquid feed stock and enters
feed heater, BA-301, where it is heated to the desired temperature of
approximately 600-625°F, prior to entering the reactor DC-301. The aromatic hydrogenation reaction is highly
exothermic. The temperature rise in the
reactor is expected to be approximately 100°F.
As the average reaction temperature is sensitive to optimum aromatic
saturation, care should be exercised so that the outlet temperature does not
exceed 725°F.
The reactor effluent flows to the tube side of EA-301
where it gives up some of its heat to the incoming charge stream which flows
through the shellside of EA-301. The
effluent then flows from the tube side of EA-301 to the tube side of EA-303
where it preheats the flash drum, FA-301, liquid to approximately 340°F. The reactor effluent is then chilled to 100°F
in EA-302A and B by cooling water, and flows to the flash drum, FA-301, where
the liquid and recycle hydrogen gas separate.
This recycled gas flows form the top of the flash
drum to the suction of GB-302. The gas
is compressed, combined with sour kerosene feed, and recycled through the
exchanger EA-301, feed heater BA-301 and the reactor DC-301. Excess gas from FA-301 flows under back
pressure control to the Fuel Gas System (Drawing: D-T5277-016A).
Liquid kerosene from the bottom of the flash drum
FA-.301 is preheated in exchanger EA-303 to approximately 340°F and is fed to
the kerosene stripper, DA-301, on tray #9.
The flow of kerosene to this tower is under level control (LC-301). This kerosene stream contains a slight trace
of H2S, H2, and trace quantities of C1 through C8 which are separated out in
the kerosene stripper.
The overhead gas from the kerosene stripper, DA-301,
then flows to the overhead condenser, EA-304, where it is partially condensed
at 100°F and approximately 11 psig. Two
streams leave this drum; 1) reflux
liquid is pumped by GA-301 and re-enters the top of the kerosene stripper 2) fuel gas leaves the top of FA-302 and flows
under pressure control (PRC-303) to the low pressure Fuel Gas System. This fuel gas normally contains all the H2S
and light ends carried over from the flash drum, FA-301. Water collected in the boot of FA-301 is drawn
off under level control (LC-304) to the Sour Water System (Drawing: D-T5277-016B).
The liquid from the bottom of the kerosene stripper
DA-301 is pumped by GA-302 and cooled to 130°F by cooling water in exchanger
EA-305. The product, kerosene, then
flows to the kerosene storage tank FB-504A and B under level control (LC-302).
Water injection equivalent to 2 ½ weight percent of
the charge is provided for washing the reactor effluent condenser and kerosene
stripper condenser using pump GA-303.
Ammonia vapor from cylinders is provided for
injection into wash water at GA-303 for use in maintaining a Ph of 7 on the
water withdrawn from the drums FA-301 and FA-302.
Corrosion inhibitor solution of 50% Kontol in
kerosene is made up in the inhibitor mix drum HA-301. Nitrogen is used for agitation to mix the
solution. Normally this solution is
injected at a rate of 0.25 to 0.50 gallons of inhibitor per 1,000 barrels of
stream flow to each point, reactor effluent and stripper condensers,
simultaneously. Nitrogen is used to
pressure the solution into the stripper overhead, and pump, GA-303 is used for
injection into the reactor effluent.
Tertiary-Butyl mercaptan is used for sulfiding the
reactor catalyst (Ni-4303-E) at initial start-up and following each
regeneration, in order to prevent oxidation of the nickel catalyst with
otherwise would become inactive. This
material is pumped into the reactor using GA-303.