1 NEW DEVELOPMENTS NEW DEVELOPMENTS IN IN SULFURIC ACID SULFURIC ACID ALKYLATION ALKYLATION RHT-Alkylation RHT-Alkylation SM SM TECHNOLOGY TECHNOLOGY RHT D r. Amarjit Bakshi: Refining Hydrocarbon Technologies LLC Katy ( Houston Suburb), Texas 77450 , USA
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Paradigm Shifts No Major Complex Internals in the Reactor No Maintenance and Mechanical
Problems Isothermal Low Temperature
Operation Provides mixing with a simple
Eductor providing good interfacial area.
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RHT-AlkylateRHT-Alkylate ProcessProcess
Auto refrigeration vapor can be absorbed and Compressor can be deleted. A major
Paradigm shift and low cost option for grass root and revamps including HF units. Low maintenance option.
Hydrocarbon /Acid separation by low cost coalescers with optimized design.
No waste production. Standard Process industry
equipment Standard Reactor internals, no
proprietary internals.
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RHT-AlkylateRHT-Alkylate ProcessProcess Absorption is a low Capex option,
improves system reliability. Liquid from absorber is sent to reactor which saves utilities. Compression can still be used in the existing units if so desired.
Lower Capex by 33 to 45 %, due to economy of scale and other improvement.
Depending upon the option used for vapor recovery from auto refrigeration( Absorption or Compression) lower Opex by 35 to 45 %.
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RHT-Alkylate ProcessRHT-Alkylate Process
Better Octane Lower Acid Consumption Easier to revamp the unit with
Reactor and novel mixing Concept. Vapor absorption rather than
expense of compressor replacement or revamp.
No complex seals or proprietary internals which either require regular replacement or maintenance.
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RHT-Alkylate ProcessRHT-Alkylate Process Reactor can be sized to any size no
scale up issues. Multiple eductor systems to provide good mixing.
RHT-Alkylate process uses standard equipment used in Refining or Petrochemical industry.
Flexible operation. No internals so no undue risk of any mishap due to internals, maintenance or replacement of internals.
Propylene can be fed at the motive fluid pump discharge with inline mixer, higher OSV and acid concentration, provides better efficiency.
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Alkylation ChemistryAlkylation Chemistry• Reaction Chemistry is pretty
complex but same as conventional Alkylation Process chemistry though better yield observed at low temperature (US Pat. 5095068)
• Selective at low temperature hence less acid soluble oil produced
• Polymerization reaction•Cracking Reactions•Disproportionation reaction•Hydrogen Transfer reaction•Esterification reaction
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OPERATING VARIABLES• Hydrocarbon/ Acid mixing.
• Temperature.
• Isobutane concentration in reactor and in reactor effluent .
• Acid Concentration.
• Olefin Space Velocity,is olefin Volume fed to reactor per hour per volume of Acid Catalyst
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OPERATING VARIABLES• Hydrocarbon/ Acid mixing is major
variable in the alkylation reaction so that all the acid interfacial area is available to olefin and isobutane to react. The eductor device provides this function very efficiently.The OSV is kept in 0.2 to 0.4 1/hr range.
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OPERATING VARIABLES• Temperature is another variable which is
very important and present RHT configuration, provides the best results due to essentially isothermal conditions (25 -27 F) in the reactor. Higher reaction temperature favors polymerization reactions, which reduces the acid concentration, increases acid consumption, corrosion and reduces the Product Quality/Octane.
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OPERATING VARIABLES• Isobutane concentration is kept at the
optimum condition I/O ratio of 6 to 15 to provide good product quality and selectivity and still not increasing de-isobutanizer loads. Lower I/O ratio enhances the olefin polymerization, which is not good for quality and increases the acid consumption. Isobutane in Reactor effluent 53 to 75 % by Vol.
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OPERATING VARIABLES• Acid concentration is very important
for alkylation reaction. At lower acid concentration ASO make increases, product quality goes down. Normal acid concentrations are kept in the range of 89 to 95 %. Concentration below 86 % Acid concentration, activity is decreased, enhancing polymerization, this condition is known as close to acid run away as acid concentration is difficult to control.
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OPERATING VARIABLES• Olefin Space Velocity is a Measure of
Olefin Volume compared to Acid volume in the reactor. Higher Space velocity enhances the acid consumption and lower product quality. The Volume of acid is optimized in relation to olefin to provide optimum results.
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OPERATING VARIABLES• Acid hydrocarbon separation is very
important issue. RHT uses Coalescer, so as to remove traces of acid from hydrocarbon. RHT has patented the higher temperature separation/acid settling from the hydrocarbon, which favors the acid settling from the hydrocarbon. Vertical or horizontal coalescers can be used.
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OPERATING VARIABLES
RHT process reduces all the equipment which is used for neutralization and wash and produces Caustic waste stream. This provides major savings to Capex and also Opex for deleting the requirements for treating the waste stream.
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OPERATING VARIABLES
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The conventional processes use the settling together with neutralization (wet system), which dilutes the acid , produces caustic waste and corrosion problems. Conventional process have reduced acid carry over from settlers by using coalescers. RHT has enhanced that concept to the ultimate with patented temperature for coalescer operation.
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RHT-ARHT-Alkylate Revamplkylate Revamp Additional reactor and Pumps Absorption system if Compression bottleneck. Coalescers to handle the acid separation. Existing De-isobutanizer revamp Easy to convert HF alkylation Vertical equipment , plot area not major constraint. Easy to add on additional capacity.
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General Considerations• Inerts, components which do not
contribute in the reaction, take up the Reactor space, reduce the space velocity and Capex.
• Water in acid, lowers acid concentration produces low octane alkylate.
• Polymerization reaction form conjunct polymers (ASO) and dilute the acid concentration and acid consumption.
• Contaminants like diolefins, sulfur compounds and oxygenates consume more acid.
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Alkylate yields Etc
• Alkylate Yield C3= C4
= C5=
• Volume V/V O 1.67-1.78 1.70-1.76 1.67-1.83 • Mass M/M O 2.28- 2.39 2.05-2.09 1.85-2.07• Molar m/m O 0.91-1.1 0.96-1.04 1.02-1.22• RON C 89-92 94.5- 97.5 92.5-93.5 • MON C 88.5-90.5 92-95 91.4-92.4• Isobutane V/V O 1.02-1.22 1.17-1.2 1.32-1.55• Acid cons lb/g Alk 0.55/0.65 0.19/0.26 0.28/0.38
• O=Olefin,RHT
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Safety consideration• Spent acid could form mist and SO2 if
released under pressure.
• Monitor no acid goes to fractionation
• Spent Acid regeneration off-site
• Non volatile liquid
• Highly corrosive, causes burns on skin
• Adequate monitoring for acid so it is completely taken out before fractionation.
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Safety ConsiderationCaution and measures to Be taken• Monitor spent acid strength
during transfer to storage and transportation.
• To complete Hazop studies• No volatile hydrocarbon or low
strength acid to be sent to storage.
• Prevent acid run away by extensive education and training.
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Causes of Acid Runaway• Poor mixing• Low acid in the reactor• Low acid recycle rates• High content oxygenates• Low Acid strength• High Reactor temperature• Excessive contaminants• Loss of acid strength• Alkylate turns light reddish in color.
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Safety Measures• Monitor Alkylate color
• Reactor gets cold without Feed reduction
• Control Acid Strength
• Watch for Acid carry over for multiple reasons
• Check acid reactivity before sending to storage for non-reactivity of acid