ERTC 2023
Reduce, reuse, and repurpose: Minor changes for major results
Matthew Clingerman Sulzer Chemtech
An industry evolution Transformational change within a refinery can be challenging to navigate. New policies that incentivise sustainability also require significant investment. Concurrently, high asset utilisation in a challenged process environment leads to a question of ongoing profitability. Greenfield investments can yield sizeable returns, but a focus solely on grassroots units ignores the possibilities found in revamping existing assets. The right decarbonisation-related revamps can also increase profitabil- ity. However, revamps often come with challenges such as feedstock compat- ibility, safety, and operational efficiency. For example, waste plastics pyrolysis oils or biomass-based feeds raise concerns about mechanical reliability and long-term operability of the redesigned unit. Successfully navigating these chal- lenges requires enhancing margins and improving unit and operational flexibility to shift as markets change. Reconsider core assets Some process units, such as off-gas treat- ing and hydrotreaters, have become core operations that ensure refineries meet modern clean air and clean fuel regu- lations. Other units, such as aromatic extraction, improve margins and produce valuable petrochemicals. Revamps of these units have been viewed through the lens of optimisation and profitability. The goal has been to extract maximum value from a barrel of oil. However, taking a sec- ond look at all units throughout the refin- ery can uncover revamp opportunities that also offer another step towards achieving decarbonisation goals. With these objectives in mind, Sulzer Chemtech partnered with refineries to dis- cover new ways to reduce carbon emis- sions, increase production of high octane gasoline, and enable the switch to renew- able fuels. Mitigate carbon emissions in gas processing Inefficient gas treating operations are a significant source of CO₂ emissions. LPG from mixed fuel gas streams is difficult to recover and typically requires a multi-col- umn approach. This high Capex arrange- ment also has higher utility consumption. Alternatively, GT-LPG Max TM (see Figure 1 ) provides a cost-effective solution for recovering the LPG product using the con- cept of absorption plus distillation within the same fractionating vessel. This pro- cess separates lights, intermediates, and heavies in a single column with the top dividing wall, which divides the top of the column into absorption and frac- tionation sections. Feed is supplied to the absorption section, where a heavy liquid recovers the C₃ and C₄ components, and non-condensables are sent overhead. The fractionation side concentrates and col- lects the C₃.
Produce high-octane gasoline GT-BTX PluS™ is an extractive distillation process that enhances the volatility of non-aromatic compounds in a mixture also containing aromatics. The process con- sists of only two major columns: an extrac- tive distillation column (EDC) and a solvent recovery column (SRC) (see Figure 2 ). The solvent, a proprietary blend from Sulzer called TECHTIV TM , recirculates between the two columns to extract the aromatics and sulphur components while rejecting the non-aromatics, including olefins, to be the raffinate. GT-BTX PluS is especially helpful in an FCC gasoline hydrotreater. Mercaptans and olefins are the dominant species in the lighter fraction, and thiophenes and aro- matics are dominant in the heavier cuts. The heaviest fraction has few olefins spe- cies to impact the desulphurisation (HDS) unit. However, the heavy naphtha stream in a gasoline hydrotreater also contains mid- dle-boiling components that are primarily olefins and thiophenic hydrocarbons. This mid-cut naphtha is most susceptible to olefin saturation in the HDS units and, con- sequently, octane loss. An example of a revamp with GT-BTX PluS is highlighted in Figure 3 . Here, heavy naphtha is routed to a new splitter, from which the olefin-rich mid-cut is sent to a new GT-BTX PluS unit. A benzene concentrate stream will be co-processed in the new unit as well. The raffinate from GT-BTX PluS, containing the olefins, goes directly to the gasoline product. The extract, containing the sulphur and aro- matic molecules, is mixed with the heavy naphtha and then treated in the existing HDS unit. A second new column is added to recover high-purity benzene. With GT-BTX PluS, the final treated gas- oline product has retained most of the ole- fins, which leads to a reduction in RON of only 0.4 instead of 3.0. Hydrogen consump- tion is reduced by more than half, as the HDS unit now operates more efficiently and at lower capacity with the MCN removed. In this example, additional revenue is gained from the new benzene stream and expan- sion of the gasoline pool. In a revamped unit using GT-BTX PluS, the gasoline hydro- treater could produce cleaner-burning gas- oline while at the same time reducing utility consumption and, ultimately, a reduction in Scope 1, 2, and 3 emissions. Switch to sustainable Aviation Fuel SAF produced via hydrotreating of fats, oils, and greases can reduce lifecycle CO₂ emissions from the aviation sec- tor compared to petroleum fuels. BioFlux technology, developed to offer superior hydrotreating performance, is a versa- tile process to maximise the yield of SAF from biomass-based feeds. The process operates with a liquid full reactor, where all hydrogen necessary for the reactions is dissolved into the feed at the reactor inlet.
O - gas
taking a second look at units throughout the refinery can uncover revamp opportunities that offer another step towards achieving decarbonisation goals
Top liquid product
Feed
Bottom product is the absorbing medium
Figure 1 A GT-LPG Max top dividing wall column
Extract
Ra nate
EDC
SRC
HC feed
Rich solvent
Lean TECHTIV solvent
Figure 2 Schematic of the GT-BTX PluS extractive distillation and solvent recovery columns unit
a portion of the off-gases which had been fed to one of two fuel gas treating units. The unit was severely bottlenecked, so C₃ and C₄ were being sent to the flare, which reduced product revenue and increased CO₂ emissions. Using GT-LPG Max technology, this plant accomplished three goals: reduce carbon emissions, debottleneck the unit, and produce a C₃ stream suitable as steam cracker feedstock.
In addition to reduced capital and oper- ating expenses, benefits of using a single dividing wall column include higher recov- ery of valuable components, lower emis- sions through reduced energy usage, and the potential to debottleneck downstream units or shift to increased petrochemical production. A major petrochemical plant in Asia recently commissioned and now oper- ates a GT-LPG Max unit. The unit treats
Benzene concentrate from reformate
Of f- gas
Naphtha splitter
LCN
SHU
Ra nate
New GT- BTX Plus
FCC naphtha
Benzene
Stabiliser
H
Extract
HCN
BZ column
HDS
MCN splitter
H
Treated FCC gasoline
Figure 3 Existing gasoline hydrotreater (grey) that has been retrofitted with GT-BTX
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