Delayed coker revamp for a capacity increase

Revamping to a three-drum coker arrangement delivered improved product yields,

higher throughput, and greater feedstock flexibility

KEITH MAGDOZA and VIRENDRA MANRAL

Chevron Lummus Global

C
rude price volatility and cur- plot space and maximising the use of operation, modelling the test run
rent over-capacity in the existing equipment. data, determining key revamp oper-
global refining sector have The feasibility study’s results were ating parameters and product yield
made refiners wary of taking up encouraging, and further economic structure, identifying bottlenecks
new greenfield projects. However, analysis enabled the project to pro- and potential modifications, and
refiners in emerging economies gress to the next phase: the develop- preparing a preliminary equipment
continue to seek the ability to scale ment of a basic engineering design layout and budgetary revamp capital
up capacity and to switch their package (BEDP) by CLG. Innovative estimate.
feed slate to heavier crudes based design solutions, such as adding a During this phase of the project,
on economics. A delayed coking third coke drum, a parallel wet gas the existing equipment was eval-
unit (DCU) revamp in such scenar- compressor, a steam feed preheater, uated to determine its adequacy
ios can enable refiners to process and a water ring compressor were for the revamp conditions. For the
higher bottom-of-the-barrel capac- all implemented to overcome the equipment found inadequate, poten-
ity, improve the ability to shift challenges faced during this revamp. tial modifications, replacements and,
the product slate, or even change These design improvements helped in some cases, altogether new equip-
the coke type in line with market further optimise cost and supported ment was proposed. Plot availability
demand. Moreover, revamp pro- the project to be approved for execu- for all changes was validated, and
jects are more likely to be funded tion with full funding. all major changes were marked on a
because of relatively low capital The third and final phase of the preliminary revamp plot plan indi-
expenditure with a desirable inter- project was detailed engineering cating approximate locations for new
nal rate of return (IRR). This article and execution. The original detailed and modified equipment with high-
describes the recent revamp of an engineering contractor (DEC), which level constructability considerations.
existing DCU aimed at achieving performed the detailed engineer- For the feasibility study, the unit’s
capacity expansion, feedstock flex- ing design of the original unit, was operating parameters were opti-
ibility, and energy efficiency. It dis- selected as the DEC for this phase. mised to achieve increased revamp
cusses the meticulous planning and This phase was carefully planned to throughput. The coke drum pressure
importance of innovative design for achieve the goal of completing the was increased, and the cycle time
the successful execution of the pro- revamp during the refinery turna- was lowered in order to mitigate
ject in a limited timeframe. round period. the increase in coke drum superfi-
The unit’s revamp modifications cial vapour velocity associated with
Background were completed in November 2018, the higher revamp throughput.
The subject DCU is located in cen- with the third coke drum installed The pumparound duties and heat
tral India and was initially designed but not yet tied into the existing recovery of the unit were optimised
to process vacuum residue from coke drum structure package. In to ensure maximum energy effi-
high sulphur crude using a two- September 2019, the third coke drum ciency. The revamp conditions were
drum configuration. After successful was successfully commissioned, designed such that no change would
operation at design conditions, the and the unit operated at its revamp be required for the two existing coke
refiner wanted to increase the DCU’s capacity. drums.
capacity by 33.8% in line with refin- CLG’s in-house coking yield corre-
ery expansion plans. As a result, a Revamp phase 1: feasibility study lations were fine-tuned by the results
revamp project was implemented in The first step of any revamp project of a benchmark test run in order to
three phases. is the feasibility study. The feasibility match plant performance closely.
The first phase of the project was a study is crucial as it helps determine Various parameters in the simulation
detailed feasibility study performed whether the project is economically model were adjusted to represent the
by Chevron Lummus Global (CLG). feasible before further capital is benchmark operation of the DCU.
During this phase, CLG validated invested in the project. A feasibility Based on this model, the product
the feasibility of capacity expansion study typically involves benchmark- yields for the high pressure operat-
while considering the constraints on ing the unit’s yields and current ing cases were estimated and pro-

www.digitalrefining.com/article/1002589 PTQ Q1 2021 87

 to the unit. The third coke drum was
To blowdown located away from the existing pair
of coke drums, and a new coke drum
To fractionator switch valve was added to service
the third coke drum. The detailed
engineering for the coke drum struc-
ture package was prepared by CLG.
The design required an extension
of the coke pit and the coker bridge

Decoking

Decoking
Coking

New Coke Drum Existing pair crane rail, and these extensions
Coke Drum C Coke Drums
A and B
and modifications were marked on
the revamp plot plan provided as
part of the BEDP. Figure 2 shows
the full plot model isometric of the
revamped coke drum structure
developed during the BEDP phase.
Heater outlet The existing coker heater was a
proprietary design by Lummus Heat
Figure 1 Three coke drum configuration Transfer. As such, for the revamp
Lummus Heat Transfer performed
Three coke drum coking/decoking schedule the re-rating of the coker heater. The
coker heater required several modifi-
Time 15 hours 15 hours 15 hours cations to achieve increased capacity
Coke Drum A Coking Decoking Decoking while maintaining heater efficiency,
Coke Drum B Decoking Coking Decoking
Coke Drum C Decoking Decoking Coking including the addition of radiant
roof tubes, upgrade of radiant coil
Table 1 metallurgy, the addition of convec-
tion coil tube rows, the replacement
vided as part of the feasibility study. required no change to the blow- of radiant intermediate tube sup-
After a review of the feasibility down tower due to the increase in ports, and the replacement of forced
study, it was noted that the higher decoking times for each drum. Feed draft and induced draft fans.
pressure operation resulted in an flexibility would also increase as It was determined that the existing
increase in coke yield. To reduce the this configuration can handle higher wet gas compressor was unable to
coke yield, two options were investi- CCR by further lowering coking handle the increased revamp capac-
gated. The first option was the instal- cycle times. With this encouraging ity, so a new wet gas compressor
lation of an additional pair of coke proposal, the three coke drum con- was added in parallel to the existing
drums and heater operating at the figuration was determined as cost-vi- wet gas compressor.
original design pressure. However, able, and the project moved forward Another new piece of equipment
this option would be capital inten- to the next phase of the revamp, installed for the revamp was a feed/
sive and would require plot space preparation of the BEDP. HP steam exchanger which uses
greater than was available. The sec- high pressure steam to preheat the
ond option was a three coke drum Revamp phase 2: basic engineering incoming fresh feed and therefore
configuration operating at a slightly design package lessens the duty required from the
higher pressure than the original Using the results of the feasibil- existing coker heater. This exchanger
design. This configuration would ity study and the three coke drum would also help lessen the impact of
eliminate concerns about coke drum configuration as a basis, a BEDP any fresh feed temperature fluctua-
ullage by further lowering the cok- was prepared for the DCU revamp. tions on the coker heater firing duty,
ing cycle time. Such a configuration A typical revamp BEDP includes which was successfully validated
would be the first of its kind in India, equipment datasheets for all exist- in the actual operation of the unit
and the feasibility of its design was ing, new, and modified equipment. post-revamp.
carefully studied by CLG and the Marked-up PFDs and P&IDs are A water ring compressor was
refiner. Figure 1 and Table 1 show a provided as well with their respec- added to the blowdown overhead
diagram of the three coke drum con- tive demolishing drawings. The receiver vent line to allow for recy-
figuration and its coking and decok- BEDP contains all information nec- cling of the blowdown overhead
ing schedule, respectively. essary for the selected detailed receiver vent gas to the fractionator
The configuration was designed engineering contractor to proceed overhead system, thus recovering
such that one coke drum would be with the detailed engineering of the more hydrocarbons. This compres-
in coking mode while the other two project. sor also allows the coke drum vent
coke drums would be in decoking A new vertical plate coke drum silencer to be opened at a lower pres-
mode. Along with saving on both (VPCD) with the same dimensions as sure, resulting in safer operation.
plot space and cost, this option the existing coke drums was added All equipment was re-evaluated

88 PTQ Q1 2021 www.digitalrefining.com/article/1002589

for the revamp conditions using the two coke drum config-
with information obtained uration near the desired revamp
from as-built datasheets. The capacity for several months to
diameters for the existing ensure a safe and successful
columns were all found to transition to the three coke drum
be adequate for the revamp configuration. In September
conditions. However, several 2019, the third coke drum was
modifications were required successfully taken in line, and
for the column internals. The the unit operated at the revamp
existing heat exchangers and capacity.
air coolers were evaluated
based on UA analysis, and Conclusion
modifications or replacements The revamp project proved a
for the exchangers were rec- success, achieving all desired
ommended accordingly. The results including desired IRR,
existing drums were evalu- improved product yields, higher
ated, and a few new drums revamp throughput, and a
were required. The hydraulics smooth commissioning phase
of all critical lines were per- for the first such configuration
formed for the revamp con- for any Indian plant. Its success
ditions. The existing pumps can be attributed principally to
were evaluated based on the the meticulous planning and
manufacturer pump curves, systematic execution of each
and any required changes phase, with no recourse to short-
such as impeller size or pump cuts or half measures. Each of
replacement were recom- the key project steps, such as
mended in the BEDP. optimisation (operating con-
To ensure meticulous exe- Figure Figure 2 plot
2 Full Fullmodel
plot model isometric
isometric of revampedof revamped
coke coke drum
ditions, plotstructure
plan, equipment
cution, a preliminary con- drum structure design changes, coker valve con-
structability evaluation was figurations, sequencing, and so
The existing coker heater was a proprietary design by Lummus Heat Transfer. As
conducted as part of the BEDP, including the P&ID, plot plan, and on), management of changes with
which outlined general constructa- such, HAZOP reviews.Lummus Heat Transferattention
for the revamp performed to detail (technical
the rerating reviews,
of the coker
bility issues of the revamp, including Several challenges were faced dur- detailed HAZOP of all designs),
heater. The coker heater required several modifications to achieve increased
accessibility, equipment transport, ing the detailed engineering phase. and well-planned execution strat-
heavy lifts, and installation. To com- Thewhile
capacity design and engineering
maintaining of pip- egy
heater efficiency, (revamp
including theconstruction and com-
addition of radiant roof
plete the revamp within an allo- tubes,ing, valves,
upgrade and structure
of radiant for the themissioning
coil metallurgy, addition ofplanning)
convection allcoil
helped in
tube rows,
cated time frame of a single unit integration of the new coke drum making this revamp successful. This
shutdown, extensive planning and the replacement
with the of radiant facilities
existing intermediateweretubeexecution
supports,template
and the replacement
can be utilised of
scheduling would be required on the forcedcarefully
draft andexecuted. To make
induced draft fans. room for all subsequent revamp projects to
part of the detailed engineering con- for the new coke drum, the blow- ensure optimum results.
tractor, along with close collabora-It wasdown
determined
tower that the existing
overhead vesselwet gas compressor was unable to handle the
and Keith Magdoza is a Senior Process Engineer for
tion with the refiner and CLG. With otherrevamp
increased equipment had toso
capacity, be arelocated.
new wet gas compressor
Lummus Technology,was added
located in parallel
in Houston, USA. to
this in mind, the project proceeded Controls and logics were designed He has over seven years’ experience in process
to the final phase of the revamp, the existing
for safewet
andgas compressor.
flexible operation of the engineering and design, and holds a degree in
detailed engineering and execution. unit. The major columns of the coke chemical engineering from the University of
pit/pad were retained while main- Texas at Austin, USA.
Revamp phase 3: detailed taining the integrity of the existing Email: keith.magdoza@lummustech.com
Virendra Manral is the Delayed Coking
engineering and execution structure for crane movement.
Technology Manager for Lummus Technology,
For this project, the DEC that pro- In this phase, the re-rating of all
Houston. He has over 30 years’ experience in
vided the detailed engineering for heat exchangers was carried out process design and technology development.
the original DCU was selected to based on UA analysis of the BEDP. He holds a degree in chemical engineering
perform the detailed engineering for Detailed hydraulics for all lines from Panjab University, India and is a registered
the revamp as well. were also performed. Equipment Professional Engineer in Texas.
This phase was carefully planned was replaced piecemeal and operat- Email: virendra.manral@lummustech.com
in order to achieve the goal of com- ing conditions were adjusted slowly
pleting the revamp during a refin- over time to ensure efficient transi- LINKS
ery turnaround. It required close tion to a higher capacity.
collaboration between the licensor, In November 2018, the revamp More articles from the following
licensee, and DEC. Throughout this of the unit was completed with the categories:
phase, several review meetings were third coke drum installed but not yet Heavy and Sour Feedstocks
conducted involving all parties, in operation. The unit was operated Instrumentation, Automation and
Process Control
Revamps and Turnarounds

www.digitalrefining.com/article/1002589 PTQ Q1 2021 89