Upload
trinhnhan
View
255
Download
5
Embed Size (px)
Citation preview
Page 1 of 37
THE DELAYED COKING PROCESS - Thomas E. Wolf
© 2013 by Thomas E. Wolf. All rights reserved. No part of this document may be
reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval system without written permission of the copyright holder, except for the inclusion of brief quotations in a review.
Products –
o Gasoline (Naphtha)
o Diesel (Light and Heavy Coker Gas Oil)
o LPG (Propane and Butane)
o Fuel gas
o Petroleum Coke (predominantly carbon)
Heavier, less expensive crude oil produces more residue to process (thus more
coke) compared with lighter, more expensive crude oil.
Process Description – Basic Process Flow Diagram
In this section the delayed coking process will be described by walking
through the individual pieces of equipment with a brief description of the various
process steps within the equipment. Two diagrams are essential in this effort, Figure
1, the process flow diagram (PFD), and Figure 2, coke drum schematic. The PFD
depicts a very simplified two drum delayed coker, showing the major equipment, flow
lines, and valves and the coke drum schematic illustrates a few vital parts of the coke
drums/table top/drill derrick. In the next section Figure 3 and Figure 4, the
temperature-pressure profile, will then be utilized to describe the basic process in an
alternate manner. Each of these basic description methods provide the same
information but in a slightly different format. Then in a later section, both of these
methods will be combined to describe the process in the context of a two drum
concurrent, integrated operation with the aid of Figures 5 through 16.
Page 2 of 37
The heavy feed, typically from the refinery’s atmospheric and/or vacuum unit,
is introduced into the bottom of the fractionator vessel, T-1. The fractionator tower
(also known as the main fractionator or combination tower) receives the unit feed and
the overhead hot vapors from the coking drum in the bottom tower section. In this
bottom tower section the unit feed is both preheated by hot coke drum overhead
vapors and provided necessary recycle. As the hot vapors travel vertically through
the fractionator, the vapors cool at different rates and the various products are taken
as side cuts from the fractionator. These products can be, from tower bottom to top,
heavy coker gas oil, diesel, kerosene, and naphtha. Note the side cuts are not shown
in the simplified PFD, but only shown as products going overhead from the
fractionator. The preheated heavy feed is then pumped to the coker furnace.
Page 3 of 37
stm
stm
D-2
prod
ucts
was
te
prod
ucts
wa
ter
T-2
Cut
ting
Wat
er
Fee
d
Cok
e +
W
ater
wat
er
switc
hin
g va
lve
D-1
H-1
T-1
Figure 1 – Process Flow Diagram
Page 4 of 37
The coker furnace or heater, H-1, heats the feed to the temperature at which
thermal cracking occurs, typically between 900 OF and 950 OF. To delay the coking
process and subsequent fouling of the furnace tubes with solid coke, the hot feed
velocity through the tubes is controlled, typically between six to ten feet per second.
Upon exiting the furnace, the hot feed is piped to the switching valve which routes the
feed one of the drums to initiate the coking process.
The PFD shows coke drum D-1 as the coking drum. As the hot feed enters the
empty drum, the coking process begins, with the large drum providing the necessary
residence time to complete the cracking process. Within the drum, the hot liquid feed
is first thermally cracked to coke and vapor, and then the vapor is thermally cracked
as it passes upward through the drum. The solid coke collects in the bottom, the hot
feed passed through the collected solid coke in random channels, the hot cracked
vapor exits the top of the drum and routed to the fractionator bottom. Over time the
drum is filled to a predetermined level at which time that drum is considered filled
and ready to be emptied. This predetermined level is generally called outage and is
measured as the distance from the top nozzle and when this level is reached, time to
switch drums.
As can well be imagined with the quantity of solid coke being produced and
with hot feed channeling upward through the solid coke, tremendous turbulence and
internally applied forces are transmitted to the drum and supporting structures. Also
as the coking process continues a froth or foam forms which can be a problem if
allowed to exit the drum. To counter this, antifoam chemical is injected reduce
carryover of tars and fines from the coke drums to the fractionator.
While coke drum D-1 is coking, drum D-2 is decoking, that is, the solid coke is
first prepared for removal then emptied from the drum bottom. At the beginning of
the decoking sequence drum D-2 contains both hot solid coke and residual hot vapor,
and the vessel shell is also at its maximum temperature. Steam is introduced to
initiate the cooling process. As the drum cooling process progresses the mixture of
residual hot vapor and steam are routed to the quench tower, T-2 (sometimes called
the blowdown tower). The quench tower separates the various products from the
Page 5 of 37
contaminated steam (waste) which then is further treated.
Then water is added to complete the cooling sequence. Upon completing the
cooling phase, the drum is deheaded (sometimes described as unheaded), that is, first
the top is removed, then the bottom head; the top head being removed first prevents
the drum shell from collapsing due the vacuum caused by the water exiting the
bottom head. The water is dumped to the coke pad, collected, and processed for
reuse. The solid coke remains in the vessel and must be cut into smaller pieces to
allow it to empty onto the coke pad. To cut the solid coke, high-pressure water is
used.
Figure 2 is a simplified two drum arrangement consisting of two coke drums, a
concrete supporting table top with unloading chutes to direct the dumped water and
the cut solid coke to the concrete temporary storage pad. The water is gravity drained
to a collection point to remove coke fines and process the water for subsequent coke
cutting. The solid coke is removed from the pad by mechanical means such as
overhead cranes or dozers. A steel structure is also supported by the concrete table
top which in turn supports the drill derrick structure. The derrick is utilized to insert
and withdraw the drill stem, a steel pipe rated for the high water pressure, with a
cutting tool on the bottom and connected at the top to the high-pressure water source
via a flexible high-pressure hose. The drill stem is raised and lowered by a motor
driven hoist and the stem is rotated by another motor.
The top of the stem is connected to the crosshead, which facilitates the stem
hoisting and rotating, and a free fall arrestor is installed to protect the installation from
a hoist failure. The cutting tool is designed to direct the high-pressure water both
vertically down and horizontally as the stem is raised and lowered. The cutting tool is
also designed to automatically switch between vertical and horizontal cutting while
the tool remains inside the drum.
Page 6 of 37
When the drum is ready for decoking and the top and bottom nozzles opened,
the cutting process begins. The drill stem is lowered into the coke drum with the
cutting tool directing the high pressure water vertically down to cut a pilot hole in the
solid coke the full length of the stem. Once pilot hole is cut the stem is raised, the tool
reoriented to cut horizontally, and the stem both lowered and rotated to cut the coke,
which falls out the drum bottom nozzle to the chute and onto the pad.
RULES OF THUMB
Coking Temperature and Pressure
Typical thermal cracking temperature at coke furnace is in the range of 900 to
950 F.
Typical coking pressures in coke drums are about 15 psig to 20 psig.
Page 7 of 37
Pad
Chute
Table Top
CokingDrum
Structure
Cutting Deck
Cutting Tool
Drill Stem DriveDrill Stem Withdrawn
DerrickCrosshead and Free Fall Arrestor
High Pressure Water Hose
Decoking Drum
Drill Stem Inserted
Figure 2 – Coke Drum Schematic
Page 8 of 37
Process Description – Basic Pressure Temperature Profile
In the previous section, the delayed coking process was described by using the
process flow diagram (PFD) and coke drum schematic. Another way to illustrate the
basic coke drum operation will be employed in this section, the pressure-temperature
profile for one complete cycle. In the next section, both of these methods will be
combined to describe the process in the context of a two drum concurrent, integrated
operation with the aid of Figures 3 through 16.
Below are two simplified pressure-temperature profiles for one complete coke
drum cycle, the first depicts the temperature and pressure over time as an individual
drum progresses through an entire coking cycle. The second profile overlays a
description of what is causing the pressure and temperature to change. A brief
explanation of each sequence segment is also provided.
Page 9 of 37
Simplified Pressure - Temperature Profile
(Single Drum, One Complete Cycle)
Not To Scale
Cycle Duration (hours)
Tem
per
atu
re (
deg
F)
Pre
ssu
re (
psi
g)
Temperature Profile
Pressure Profile
Figure 3 – Simplified Pressure-Temperature Profile
Cycle Duration (hours)Not To Scale
Simplified Pressure - Temperature Profile
Tem
per
atu
re (
deg
F)
Pre
ssu
re (
psi
g)
Temperature Profile
Pressure Profile
Steam Preheat, then
Hot Vapor Preheat
Steam Strip
Water Quench
Coking
Drill and Decoke
Rehead, Purge, Test
Unhead, Drain
Figure 4 - Simplified Pressure-Temperature Profile
Page 10 of 37
Preheat (or warm up) period – Preheat is the coke drum warm-up period prior
to introducing hot feed from the furnace. With the drum having been previously
emptied of coke, re-headed, purged of oxygen with steam, and tested for gasket leaks,
the vessel temperature is relatively cold, but not ambient. The preheat period is a
controlled temperature and pressure increase to bring the vessel closer to the hot feed
temperature; first with steam preheat, then hot vapor preheat from the coking drum.
This controlled temperature increase is necessary to minimize adverse thermal stress
and strain on the drum, primarily the skirt/cone/shell junction.
Coking segment (feed fill portion of cycle) – After the drum has been
preheated, feed is introduced into the drum from the furnace and the thermal cracking
process begins. Hot feed entering the bottom of the drum forms coke and releases
light ends (hydrocarbon vapors) overhead to the fractionator tower. This is the
longest segment in the sequence and is half (50%) of the total cycle duration.
Steam stripping (also referred to as steam out and steam to blowdown) – High
pressure steam is introduced initially to the overhead vapors en route to the
fractionator tower to remove additional light ends remaining on coke. Then the
balance of steam and hydrocarbon vapors are sent to the quench tower for separation
of sour water (waste) and additional light ends recovery. Steam stripping also acts as
the first stage in the cooling down process prior to decoking the drum.
Quench water segment – Water is introduced into drum to cool or quench the
coke, at first at a slow rate, until the water has cooled the drum level at least above the
skirt/cone/shell junction. Then after this level is achieved, the quench water rate can
be accelerated to speed this portion of the cycle. The initial slower rate is necessary to
reduce the thermal shock of cooling on the crack susceptible skirt/cone/shell junction
and bulge creation in the lower portion of the cylindrical portion of the shell.
Unhead, Drain segment – the top and bottom heads are removed, and the
quench water is drained from drum to pad.
Page 11 of 37
Drill portion – The drill stem is first lowered from the derrick and inserted
through the top manway nozzle with the cutting tool set to blast high-pressure water
vertically down to drill a pilot hole the full length of the coke.
Decoking period (or coke cutting) – After the pilot hole is completed, the drill
stem is raised and the cutting tool hydroblasting nozzle is reoriented to blast
horizontally. The drill stem is then both rotated and reinserted, cutting the coke, and
allowing coke and cutting water to exit bottom nozzle.
Re-heading, Purge, Test – The top and bottom heads are then reinstalled (re-
headed), the drum purged with steam to remove air, and the drum steam tested to
ensure top and bottom gaskets are sealed. The cycle is then repeated.
RULES OF THUMB
Coking cycle time
Typical cycle range 30 to 40 hours TOTAL, but could be lower or higher, and
the cycle segments are approximately:
o Preheat 10% to 12%
o Coking 50%
o Steam Stripping 4% to 5%
o Quench 14% to 15%
o Drain 5% to 6%
o Drill and Decoking 10%
o Rehead, Purge, Test 4% to 5%
o TOTAL CYCLE 100%
Caution – sometimes in the literature ‘coking cycle’ is described as being in the
15 to 20 hour range, when described this way, only the Coking portion (50%) of
the Total Cycle is being expressed. This can be misleading at times, and in this
document, ‘coking cycle’ is defined to mean the Total Cycle.
Page 12 of 37
Process Description – Two Drum Operation
In the previous two sections, the delayed coking process was described by
using two different methods to explain the steps in the process. The first utilized the
process flow diagram (PFD), and coke drum schematic. The next section used the
pressure-temperature profile. The following pages combine the process flow diagram
and the pressure temperature profile to follow the many steps of a complete two drum
operation.
Page 13 of 37
Cyc
le S
tep
On
e
Dru
m D
-1 h
as p
revi
ousl
y be
en p
ress
ure
test
ed w
ith
stea
m to
ens
ure
ther
e ar
e no
leak
s pr
ior
to c
onti
nuin
g th
e cy
cle.
Ste
am is
app
lied
to d
rum
D-1
as
the
firs
t ste
p (s
team
pre-
heat
) in
the
war
m-u
p pr
oces
s an
d th
e te
mpe
ratu
re b
egin
s to
incr
ease
. T
he v
apor
s
are
rout
ed to
the
quen
ch to
wer
T-2
.
At t
his
poin
t, d
rum
D-2
is e
ndin
g th
e co
king
por
tion
of t
he c
ycle
and
the
drum
tem
pera
ture
is r
elat
ivel
y co
nsta
nt a
t the
cok
ing
tem
pera
ture
. O
verh
ead
gas
from
D-2
cont
inue
s to
be
sent
to th
e fr
acti
onat
or T
-1 fo
r th
e fe
ed p
rehe
at a
nd s
ubse
quen
t pro
duc
t
sepa
rati
on.
Feed
ent
ers
the
low
er s
ecti
on o
f the
frac
tion
ator
T-1
to b
e pr
ehea
ted
by
the
hot o
verh
ead
vap
ors
from
the
on-l
ine
dru
m’s
(D-2
) cok
ing
cycl
e. T
he p
rehe
ated
feed
is
pum
ped
to th
e fu
rnac
e H
-1 w
here
the
feed
is h
eate
d to
cok
ing
tem
pera
ture
and
rou
ted
via
the
swit
chin
g va
lve
(sho
wn
as th
e th
ree
way
val
ve) t
o th
e co
king
dru
m D
-2.
Whe
n
dru
m D
-2 is
full,
it is
sw
itch
ed o
ff li
ne to
beg
in th
e d
ecok
ing
sequ
ence
s.
Page 14 of 37
prod
ucts
was
te
T-2
T-1
stm
D-2
tem
p
Fee
dw
ater
D-1
H-1
thre
e w
ay v
alve
time
D-2
D-1O
pen
Clo
sed
LE
GE
ND
stm
wat
er
prod
uct
Figure 5 – Cycle Step 1
Page 15 of 37
Cyc
le S
tep
Tw
o
Dru
m D
-1’s
war
m-u
p (p
re-h
eat)
con
tinue
s w
ith th
e ho
t ove
rhea
d v
apor
rer
oute
d
from
dru
m D
-2.
The
war
min
g ga
s is
firs
t rou
ted
to th
e qu
ench
tow
er T
-2, b
ut d
urin
g St
ep
Two
the
vapo
r is
div
erte
d to
the
frac
tiona
tor
T-1.
The
war
m-u
p st
eps,
bot
h st
eam
pre
-hea
t and
hot
ove
rhea
d va
por,
are
mea
sure
s
take
n to
red
uce
the
ther
mal
sho
ck o
f int
rodu
cing
hot
feed
from
the
furn
ace
H-1
to th
e
rela
tivel
y co
ld d
rum
D-1
.
With
the
feed
no
long
er b
eing
sen
t to
drum
D-2
and
the
over
head
vap
ors
bein
g ro
uted
to
D-1
, D-2
tem
pera
ture
beg
ins
to d
ecre
ase.
Page 16 of 37
prod
ucts
was
te
T-2
T-1
stm
D-2
tem
p
Fee
dw
ater
D-1
H-1
thre
e w
ay v
alve
time
D-2
D-1O
pen
Clo
sed
LE
GE
ND
stm
wat
er
prod
uct
Figure 6 - Cycle Step 2
Page 17 of 37
Cyc
le S
tep
Th
ree
D
-2 is
then
ste
amed
out
(pur
ged
with
ste
am) t
o re
cove
r th
e ba
lanc
e of
the
prod
uct
oils
rem
aini
ng o
n th
e co
ke, t
he te
mpe
ratu
re o
f D-2
con
tinue
s to
dec
reas
e. T
he s
team
and
oil v
apor
are
rou
ted
initi
ally
to th
e fr
actio
nato
r T-
1 be
fore
sw
itchi
ng to
the
quen
ch to
wer
T-
2 w
hen
mos
t of t
he r
ecov
erab
le h
ydro
carb
ons
have
bee
n st
ripp
ed fr
om th
e co
ke.
As
the
vapo
r ri
ses
thro
ugh
T-2,
res
idua
l pro
duct
s ar
e se
para
ted
and
the
sour
wat
er v
apor
is
reco
vere
d fo
r fu
rthe
r pr
oces
sing
.
D
-1 h
as b
een
preh
eate
d an
d th
e ho
t fee
d a
t cok
ing
tem
pera
ture
from
the
furn
ace
H-1
is s
wit
ched
into
dru
m D
-1 to
sta
rt th
e co
king
por
tion
of i
t’s
cycl
e.
Page 18 of 37
pr
oduc
ts
was
te
T-2
T-1
stm
D-2
tem
p
Fee
dw
ater
D-1
H-1
thre
e w
ay v
alve
time
D-2
D-1O
pen
Clo
sed
LE
GE
ND
stm
wat
er
prod
uct
Figure 7 - Cycle Step 3
Page 19 of 37
Cyc
le S
tep
Fou
r
Dru
m D
-1 c
onti
nues
the
coki
ng p
orti
on o
f the
cyc
le a
nd r
emai
ns a
t cok
ing
tem
per
atu
re.
Qu
ench
wat
er is
then
add
ed to
dru
m D
-2 to
coo
l the
cok
e in
pre
para
tion
of
cutt
ing
and
du
mpi
ng fr
om th
e d
rum
. T
he q
uenc
h w
ater
is a
dded
slo
wly
unt
il th
e dr
um
is c
oole
d ab
ove
the
skir
t/co
ne/s
hell
junc
tion
area
. A
fter
this
poi
nt is
rea
ched
, the
que
nch
wat
er r
ate
is in
crea
sed
to s
peed
the
coke
coo
l dow
n tim
e w
ith th
e w
ater
flow
con
trol
led
to
ensu
re th
e pr
essu
re g
ener
ated
by
the
vapo
riza
tion
of w
ater
doe
s no
t exc
eed
the
relie
f val
ve
set p
ress
ure.
Th
e st
eam
and
oil
vapo
rs fo
rmed
dur
ing
the
wat
er q
uenc
h ar
e ro
ute
d to
the
quen
ch to
wer
T-2
.
Aft
er d
rum
D-2
has
coo
led
, the
wat
er is
dra
ined
to th
e co
ke p
ad, a
nd th
e dr
um
unh
ead
ed, b
oth
top
and
bot
tom
.
Page 20 of 37
LE
GE
ND
stm
wat
er
prod
uct
time
D-2
D-1O
pen
Clo
sed
stm
D-2
tem
p
Fee
dw
ater
D-1
H-1
thre
e w
ay v
alve
prod
ucts
was
te
T-2
T-1
Figure 8 - Cycle Step 4
Page 21 of 37
Cyc
le S
tep
Five
D
rum
D-1
con
tinu
es th
e co
king
por
tion
of t
he c
ycle
at c
okin
g te
mp
erat
ure
.
Aft
er d
rum
D-2
has
bee
n d
ehea
ded
, the
dri
ll st
em is
low
ered
into
the
top
of th
e dr
um w
ith th
e cu
ttin
g he
ad p
ositi
oned
for
vert
ical
dow
n cu
ttin
g, th
e hi
gh p
ress
ure
wat
er
pum
p st
arte
d, a
nd th
e pi
lot h
ole
is d
rille
d th
roug
h th
e en
tire
leng
th o
f the
cok
e be
d.
Page 22 of 37
prod
ucts
was
te
T-2
T-1
Cu
ttin
g W
ate
r
stm
D-2
tem
p
Fee
dw
ater
D-1
H-1
thre
e w
ay v
alve
time
D-2
D-1O
pen
Clo
sed
LE
GE
ND
stm
wat
er
prod
uct
Figure 9 - Cycle Step 5
Page 23 of 37
Cyc
le S
tep
Six
D
rum
D-1
con
tinu
es th
e co
king
por
tion
of t
he c
ycle
at c
okin
g te
mpe
ratu
re.
In d
rum
D-2
, the
dri
ll st
em is
rai
sed
, the
cut
ting
head
rep
ositi
oned
for
hori
zont
al
cutt
ing,
and
the
coke
is th
en c
ut fr
om th
e to
p do
wn.
The
cok
e an
d cu
ttin
g w
ater
em
pty
onto
the
coke
pad
via
the
chut
e at
the
bott
om o
f the
cok
e dr
um ta
ble
top.
Dru
m D
-2’s
tem
pera
ture
is s
igni
fican
tly lo
wer
, but
doe
s no
t rea
ch a
mbi
ent t
empe
ratu
re d
urin
g th
is
deco
king
pro
cess
.
A
fter
the
coke
is r
emov
ed fr
om d
rum
D-2
, the
dru
m is
reh
eade
d, p
urge
d of
air
, an
d pr
essu
re te
sted
with
ste
am.
Page 24 of 37
prod
ucts
was
te
T-2
T-1
stm
D-2
tem
p
Fee
dw
ater
D-1
H-1
thre
e w
ay v
alve
Co
ke
+ W
ater
time
D-2
D-1O
pen
Clo
sed
LE
GE
ND
stm
wat
er
prod
uct
Figure 10 - Cycle Step 6
Page 25 of 37
Cyc
le S
tep
Sev
en
At t
his
poin
t, d
rum
D-1
is e
ndin
g th
e co
king
por
tion
of t
he c
ycle
and
rem
ains
at c
okin
g te
mp
erat
ure.
Whe
n d
rum
D-1
is fu
ll, it
is s
wit
ched
off
line
to b
egin
the
dec
okin
g p
orti
on o
f the
cyc
le.
Dru
m D
-2 h
as b
een
pres
sure
test
ed w
ith
stea
m a
nd s
team
is th
en c
onti
nued
to
be a
pp
lied
to d
rum
D-2
as
the
firs
t ste
p (s
team
pre
-hea
t) in
the
war
m-u
p pr
oces
s w
ith
the
vapo
r ro
ute
d to
the
quen
ch to
wer
T-2
.
Page 26 of 37
prod
ucts
was
te
T-2
T-1
stm
D-2
tem
p
Fee
dw
ater
D-1
H-1
thre
e w
ay v
alve
time
D-2
D-1O
pen
Clo
sed
LE
GE
ND
stm
wat
er
prod
uct
Figure 11 - Cycle Step 7
Page 27 of 37
Cyc
le S
tep
Eig
ht
Dru
m D
-2’s
war
m-u
p (p
re-h
eat)
con
tinue
s w
ith th
e ho
t ove
rhea
d va
por
rero
uted
from
dru
m D
-1 w
hich
als
o in
itiat
es D
-1 c
oolin
g. T
he w
arm
ing
gas
is fi
rst r
oute
d to
the
quen
ch to
wer
T-2
, but
dur
ing
Step
Eig
ht th
e va
por i
s di
vert
ed to
the
frac
tiona
tor
T-1.
Page 28 of 37
LE
GE
ND
stm
wat
er
prod
uct
time
D-2
D-1O
pen
Clo
sed
stm
D-2
tem
p
Fee
dw
ater
D-1
H-1
thre
e w
ay v
alve
prod
ucts
was
te
T-2
T-1
Figure 12 - Cycle Step 8
Page 29 of 37
Cyc
le S
tep
Nin
e
D
-1 is
then
ste
amed
out
(pur
ged
with
ste
am) t
o re
cove
r th
e ba
lanc
e of
the
prod
uct
oils
rem
aini
ng o
n th
e co
ke.
The
stea
m a
nd o
il va
por
are
rout
ed in
itial
ly to
the
frac
tiona
tor
T-1
befo
re s
witc
hing
to th
e qu
ench
tow
er T
-2 w
hen
mos
t of t
he r
ecov
erab
le h
ydro
carb
ons
have
bee
n st
ripp
ed fr
om th
e co
ke.
D-1
’s te
mpe
ratu
re c
ontin
ues
to c
ool.
H
ot fe
ed fr
om th
e fu
rnac
e H
-1 is
then
sw
itch
ed in
to d
rum
D-2
to s
tart
the
coki
ng
por
tion
of t
he c
ycle
.
Page 30 of 37
LE
GE
ND
stm
wat
er
prod
uct
time
D-2
D-1O
pen
Clo
sed
stm
D-2
tem
p
Fee
dw
ater
D-1
H-1
thre
e w
ay v
alve
prod
ucts
was
te
T-2
T-1
Figure 13 - Cycle Step 9
Page 31 of 37
Cyc
le S
tep
Ten
Dru
m D
-2 c
onti
nues
the
coki
ng p
orti
on o
f the
cyc
le a
t cok
ing
tem
pera
ture
.
Que
nch
wat
er is
then
add
ed to
dru
m D
-1 to
coo
l the
cok
e in
pre
para
tion
of
cutt
ing
and
dum
ping
from
the
dru
m.
The
ste
am a
nd o
il va
pors
form
ed d
urin
g th
e
wat
er q
uenc
h ar
e ro
uted
to th
e qu
ench
tow
er T
-2.
The
que
nch
wat
er is
add
ed s
low
ly
until
the
drum
is c
oole
d ab
ove
the
skir
t/co
ne/s
hell
junc
tion
area
. A
fter
this
leve
l is
reac
hed,
the
quen
ch w
ater
rat
e is
incr
ease
d to
spe
ed th
e co
ke c
ool d
own
time
with
the
wat
er fl
ow c
ontr
olle
d to
ens
ure
the
pres
sure
gen
erat
ed b
y th
e va
pori
zatio
n of
wat
er d
oes
not e
xcee
d th
e re
lief v
alve
set
pre
ssur
e.
Aft
er d
rum
D-1
has
coo
led
, the
wat
er is
dra
ined
to th
e co
ke p
ad, a
nd th
e dr
um
unhe
aded
, bot
h to
p an
d b
otto
m.
Page 32 of 37
prod
ucts
was
te
T-2
T-1
stm
D-2
tem
p
Fee
dw
ater
D-1
H-1
thre
e w
ay v
alve
time
D-2
D-1O
pen
Clo
sed
LE
GE
ND
stm
wat
er
prod
uct
Figure 14 - Cycle Step 10
Page 33 of 37
Cyc
le S
tep
Ele
ven
D
rum
D-2
con
tinu
es th
e co
king
por
tion
of t
he c
ycle
at c
okin
g te
mpe
ratu
re.
A
fter
dru
m D
-1 h
as b
een
deh
ead
ed, t
he d
rill
stem
is lo
wer
ed in
to th
e to
p of
the
dru
m w
ith th
e cu
ttin
g he
ad p
ositi
oned
for
vert
ical
dow
n cu
ttin
g, th
e hi
gh p
ress
ure
wat
er
pum
p st
arte
d, a
nd th
e pi
lot h
ole
is d
rille
d th
roug
h th
e en
tire
leng
th o
f the
cok
e be
d.
Page 34 of 37
prod
ucts
was
te
T-2
T-1
Cu
ttin
g W
ate
r
stm
D-2
tem
p
Fee
dw
ater
D-1
H-1
thre
e w
ay v
alve
time
D-2
D-1O
pen
Clo
sed
LE
GE
ND
stm
wat
er
prod
uct
Figure 15 - Cycle Step 11
Page 35 of 37
Cyc
le S
tep
Tw
elve
D
rum
D-2
con
tinu
es th
e co
king
por
tion
of t
he c
ycle
at c
okin
g te
mpe
ratu
re.
In d
rum
D-1
, the
dri
ll st
em is
rai
sed
, the
cut
ting
head
rep
ositi
oned
for
hori
zont
al
cutt
ing,
and
the
coke
is th
en c
ut fr
om th
e to
p do
wn.
The
cok
e an
d cu
ttin
g w
ater
em
pty
onto
the
coke
pad
via
the
chut
e at
the
bott
om o
f the
cok
e d
rum
tabl
e to
p. D
rum
D-1
’s
tem
pera
ture
is s
igni
fican
tly lo
wer
, but
aga
in d
oes
not r
each
am
bien
t tem
pera
ture
dur
ing
this
dec
okin
g pr
oces
s.
A
fter
the
coke
is r
emov
ed fr
om d
rum
D-1
, the
dru
m is
reh
eade
d, p
urge
d of
air
,
and
pres
sure
test
ed w
ith s
team
.
Page 36 of 37
pr
oduc
ts
was
te
T-2
T-1
stm
D-2
tem
p
Fee
dw
ater
D-1
H-1
thre
e w
ay v
alve
time
D-2
D-1O
pen
Clo
sed
Co
ke
+ W
ate
r
LE
GE
ND
stm
wat
er
prod
uct
Figure 16 - Cycle Step 12
Page 37 of 37
T.E. Wolf has over 40 years petroleum and petrochemical experience, including 25 years in project management. He holds a BS degree in Mechanical Engineering and is a registered Professional Engineer.
© 2013 by Thomas E. Wolf. All rights reserved. No part of this document may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval system without written permission of the copyright holder, except for the inclusion of brief quotations in a review.