Hydrocarbon Processing - June 2022 - 72

Carbon Capture/CO2
* Calculate steam turbine
isentropic efficiency (steam
temperature in vs. temperature
out). Consider replacing small,
inefficient (30% efficiency) steam
turbines with motor drives.
* Minimize compressor recycling by
using suction throttling, inlet guide
vanes, variable frequency drive
motors, reciprocating compressor
variable pocket unloaders
and re-rotor compressors. In
addition, personnel should
check the inlet temperature to
the compressor stages and clean
interstage heat exchangers.
* Optimize the operation of parallel
compressors to avoid having
excess recycle-this can occur in
LNG and gas processing plants.
Utility system optimization. The
following recommendations can help optimize
a plant's utility system:
* Utilize a steam header ladder
diagram to obtain an overview of
steam demand at each pressure
level, which utility boilers and
turbines are operating, and
steam letdowns (high pressure to
medium pressure to low pressure).
In addition, optimize the use of
steam letdown turbines to recover
mechanical energy lost through
pressure control letdown valves.
1% Miscellaneous
19% Coal
20% Renewables
20% Nuclear
40% Natural gas
FIG. 4. U.S. power generation by source,
2020. Power generation totaled 4.12 T KWh.
Source: U.S. EIA.
2% Geothermal
7% Biomass
14% Solar
31% Hydro
46% Wind
FIG. 5. U.S. utility-scale electricity generation by
renewable sources, 2021. Total renewable power
generated was 826 B KWh. Source: U.S. EIA.
72 JUNE 2022 | HydrocarbonProcessing.com
Mitigation
* Eliminate low-pressure steam
venting by replacing pump
turbine drivers exhausting to
the low-pressure steam header
with motor drives. If a motor is
in critical service, keep a spare
turbine on hot standby with its
casing and inlet/outlet lines hot.
* Remember that a steam trap/
leak program can pay for itself
in less than 6 mos. Operators
should also fix air header/air
compressor leaks and shut down
rental diesel air compressors.
* Consider installing a cogeneration
unit if more steam is needed or if
old boilers need to be replaced.
Pathway 2: New technologies. When
it is time for a major maintenance turnaround
or debottlenecking project, plant
owners should consider using the latest
technologies. This can range from
re-rotoring compressors and upgrading
turbines to using higher-capacity trays in
columns or higher-efficiency heat transfer
equipment. The following is a partial
list of technology items to consider:
* For new grassroots projects,
seek new technologies that
provide higher yields and
reduced energy consumption,
instead of replicating an existing,
older, less-efficient design.
* For revamps or new units, use new
improved catalysts to increase yield
and reduce recycle, thus reducing
energy and GHG intensity.
* For the electrification of
compressor drivers on offshore
platforms, use offshore wind
or onshore green power.
* Install once-through steam
generators (OTSGs) on opencycle
gas turbines to recover gas
turbine exhaust heat. The light
weight and small footprint of
OTSGs allow for retrofitting.
* Use a divided wall column
(which uses one distillation
column instead of two columns)
for reduced capital and
operational expenditures.
* Install heat pumps on columns
separating close boiling
temperature components
(e.g., ethylene/ethane splitter,
propylene/propane splitter).
* Using a low-emissions cracking
furnace designed to shift more
fired duty into process heating
in the firebox and generate less
steam in the convection section,
can reduce fuel requirements by
30%. Reduced steam production
provides the opportunity to
replace condensing steam
turbines with efficient motors
using renewable power.
* Use new monoethylene glycol
(MEG) technology, such as a
proprietary MEG processb
reduces steam usage by 20%.
that
* Utilize new propylene oxide (PO)
processes, such as a proprietary
PO processc
that reduces energy
usage by 35% and wastewater by
70% vs. existing PO technologies.
* Use new ethylene processes
(e.g., methanol-to-olefins,
oxidative coupling methane).
* Utilize the Allam-Fetvedt cycle for
power generation (e.g., an oxyfired
gas turbine using a supercritical
CO2
cycle, where CO2
offtake is ready for CO2 pipelines).
This creates clean power with
no net carbon to atmosphere.
Pathway 3: Electrification with renewable
power. In 2020, electrical generation
in the U.S. accounted for 32% of
CO2
emissions from the burning of fossil
fuel. Electrification of process equipment
and transportation vehicles using renewable
power will be critical to reducing CO2
emissions. Renewable power has no CO2
footprint, and includes solar photovoltaic
(PV) systems, as well as concentrated
solar, onshore and offshore wind, hydroelectric
and geothermal systems. Nuclear
power also has no CO2
footprint. One
MWh of electricity will power approximately
200 homes on a hot summer day.
According to the Center for Climate
and Energy Solutions, approximately 29%
of global electricity generation was produced
via renewables in 2020. Also in that
year, electric power in the U.S. was generated
from natural gas (40%), renewables
(20%), nuclear (20%), coal (19%) and
miscellaneous (1%)-and that year was
also the first year in which renewable power
constituted a larger market share than
coal power (FIG. 4). In 2021, most of the
installed utility-scale power generation in
the U.S. from renewable sources was wind
(46%), followed by hydro (31%), solar
http://www.HydrocarbonProcessing.com
Hydrocarbon Processing - June 2022

Table of Contents for the Digital Edition of Hydrocarbon Processing - June 2022
