Oil-to-chemicals is an important trend in the oil and gas industry. A recent
article in PTQ-Petroleum Technology Quarterly (www.eptq.com)
offers an excellent review of major projects in this area.
It is available from PTQ in pdf format at no charge. You do need to register
with the site, but that, too, is free.
Here are excerpts from the article …
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PTQ-Petroleum Technology Quarterly,
Quarter 2 (2020)
Oil-to-chemicals:
new approaches
[ EXCERPTS ]
Crude oil-to-chemicals (COTC) continues to be a powerful industry driver and a
strong trend of high interest to all integrated refineries and chemicals
producers in Asia/Pacific, China, the Middle East, and Eastern Europe. This is
reinforced by many factors, most notably the forecasts which predict a slowing
of transportation fuels growth approaching 2040 (with hybrids and electric
vehicles), while growth in chemicals is expected to increase as populations and
middle class wealth continue to rise, leading to increasing demand for
packaging, consumer goods, and automobiles. [M]ore than 12 corporations have
committed over $315 billion to date to reconfigure their assets to produce more
petrochemicals than transportation fuels, as revamps as well as building new grassroots
refineries during the next 5-6 years. Based on announcements to date, we anticipate
in the next five years that another $300+ billion, or more, will be announced as
refiners and chemical companies all reassess their positions, knowing that the
longer term outlook for transportation fuels from crude oil is expected to
plateau and then decline. All players are taking this trend seriously ...
Advances in heavy oil processes
In focusing on the processes by which the higher molecular weight constituents
of petroleum (the heavy ends) can be converted to products that are suitable
for use as feedstocks for the petrochemical section of the refinery, our
assessments include carbon rejection and hydrogen addition approaches, along
with process combinations and new configurations:
1. Carbon rejection
2. Hydrogen addition
3. Combining processes and treatment of intermediates
4. Configuration issues and advances
5. New processes likely to be deployed during the next five years
For decades, propane has been the mainstay in deasphalting heavy feedstocks,
especially in the preparation of high quality lubricating oils and feedstocks
for catalytic cracking units. Future units, which may well be derived from
KBR’s ROSE process, will use solvent systems that will allow operation at
elevated temperatures relative to conventional propane deasphalting
temperatures, thereby permitting easy heat exchange. This will require changes to
the solvent composition and the inclusion of solvents not usually considered to
be deasphalting solvents. Other areas of future process modification will be in
extractor tower internals, studies with higher molecular weight solvent,
accurate estimation of physical properties of mix stream, studies in
combination with other processes, and firming up design tools for supercritical
solvent recovery configurations. For heavy feedstocks, which will increase in
amounts as hydrocracking feedstocks, reactor designs will continue to focus on
online catalyst addition and withdrawal. Fixed bed designs have suffered from
mechanical inadequacy when used for the heavier feedstocks, as well as short catalyst
lives – six months or less – even though large catalyst volumes are used (LHSV
typically of 0.5- 1.5). Refiners will attempt to overcome these shortcomings
through innovative designs, allowing better feedstock flow and catalyst
utilisation, or online catalyst removal. For example, the OCR process, in which
a lead moving bed reactor is used to demetallise the heavy feedstock ahead of
the fixed bed hydrocracking reactors, has seen some success. But whether this
will be adequate for continuous hydrocracking of heavy feedstocks remains a
question. Catalyst development will be key in the modification of processes and
the development of new ones to make environmentally acceptable distillable
liquids.
From a comprehensive or holistic perspective, the following approaches have
been assessed as commercially viable or considered to become commercially
viable in specific situations:
• New pipeline technology
• Advances in new configurations
• New catalyst approaches
• Economics of different catalysts and process improvements
Competitive and strategic implications
In reviewing some of the key findings from
our report (The Catalyst Group Resources 2019), as well as the limits of
current state-of-the art based on the basket of crudes defined in the report,
here are some key considerations:
• No study can take into account all possible site-specific issues and questions,
as they may relate to existing configurations for revamp vs greenfield choices
because they are highly dependent on each refinery’s crude slates,
availability/pricing, and the local/regional products desired. Given this
situation, the study takes a 10 000ft view, looking into the hypothesis of a
50/50 fuels/ petrochemicals refinery, and then discusses future technology
options/ changes in the pipeline in the direction for 40/60
fuels/petrochemicals.
• Today’s resid FCCs (RFCC) can process feeds with up to 8 Concarbon, though
6-7 is more comfortable. Today’s RFCCs are designed for catalyst metals levels of
10 000 wtppm. However, it is cheaper to take the metals out on an HDM
pretreater catalyst which holds up to 50% of their weight in metals. A standard
design is to include an extra riser for making olefins. A 100 000 b/d RFCC can
make over 500 000 t/y of propylene, assuming a 10 wt% yield. Additional
technologies can increase this to 30-40 wt%. For instance, VGO processing with an
HDM/HDS unit can give around 29 wt% propylene. The FCC gasoline, which is about
50 wt% BTX, can also be partially processed in the aromatics plant. Fine tuning
in the RFCC for propylene is a lot less costly than propane dehydrogenation.
• When processing heavier feedstocks, the consensus is to have hydrogen-in
revamps or greenfield designs.
• Increasing the severity of RDS/ RFCC to produce more propylene decreases both
gasoline and diesel yield. Forwarding heavy naphtha is required for reformate
feed to aromatics. Improving liquid yields can be done to different degrees by upping
VGO+DAO, while reducing coke to almost zero.
• Smaller (100 000 b/d) refineries will not be as likely to have the capital to
integrate like >250 000 b/d and larger sites.
• All licensors, by their remits, will try to sell complex greenfield site configurations
based on their competitive advantages. Others have different levels of revamp
expertise.
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TIP:
Read the article for its information, but remember this. As well written as it
is, the article is intended to promote the purchase of the full report.
Having said that, after reading the article, you may well decide that the
purchase price is money well spent.
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Jean Steinhardt served as Librarian,
Aramco Services, Engineering Division, for 13 years. He now heads Jean
Steinhardt Consulting LLC, producing the same high quality research that he
performed for Aramco.
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