Amine Plant Energy Requirements & Items impacting the SRU 10 - PowerPoint PPT Presentation

Amine Plant Energy Requirements & Items impacting the SRU 10 October 2016 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

Agenda AGRU energy needs Amine energy requirements – Regeneration SRU energy supply – Processing effects Waste heat Leanness required – Reactor – Determine required – Incinerator leanness in excess of SRU/TGT needs, – Over stripping Is there more to save? Energy sources – In amine system Optimisation dependent on operating – Sulphur conversion waste conditions All quoted figures are indicative heat loss due to AGRU 2 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

Amine closed system – chemical reaction The amine solvent loading is set by temperature and partial pressure of H 2 S and CO 2 in a certain %wt amine solvent, determined by equilibrium, kinetics and the mass transfer between gas and liquid phase Regenerator temperature, typical 115 ° C < T < 140 ° C Regenerator pressure, typical 1.5 < p < 2.5 bara Equilibrium partial pressure of H 2 S Typical amine solvent Regeneration 2,000 Operation: High temp, low pressure High solvent equilibrium partial pressure at solvent inlet , mass transfer Pressure (mbara) 1,500 acid component from solvent to gas phase Absorption 1,000 Low temp, high - low pressure Low solvent equilibrium partial 500 pressure at solvent inlet, mass transfer of the acid components from gas to 0 solvent phase, kinetics role 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Absorber temperature, typical 30 ° C < T < 65 ° C Typical Solvent loading (mol/mol) Absorber pressure, typical 1.1 < p < 100 bara 3 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

Amine energy consumers Solvent regeneration heat Reboiler steam 75 – 95 % of energy consumption in amine system  Several components require energy (heat) o Desorption o Heating of solvent to regenerator bottom condition o Internal generation of steam in regenerator reboiler Heating medium: low pressure steam, also because of the constraint of thermal degradation of the amine at high temperature Solvent circulation pumps Remainder of total energy consumption depending on pressure differential and solvent properties Air cooling is a minor energy consumer compared to other energy consumers 4 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

Amine – energy generation Equilibrium partial pressure of H 2 S Typical amine solvent Amine type kJ/kmol H 2 S kJ/kmol CO 2 2,000 60%wt DGA 54 99 50%wt MDEA 40 70 1,500 Pressure (mbara) 1,000 500 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Solvent loading (mol/mol) 5 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

Absorber Heat (Enthalpy) Balance Heat of absorption (energy make) determined by: • Solvent type C p (for energy balance) o M sweet , Cp sweet , T sweet Amine type • Sweet gas • Solvent %wt amine • Type of treating M lean , Cp lean , T lean selectivity o other components removal o Lean solvent Feed gas pressure • heat of absorption • Feed gas composition - C p • Lean solvent temperature prevention HC condensation criteria o • Feed gas acid content Sweet gas specification • M feed , T feed , Cp feed In principle independent of type of internals unless heat distributions is hampered Feed gas The maximum temperature is usually above the bottom tray M rich , Cp rich , T rich Rich solvent Heat of absorption is larger when the loading is T rich > T sweet 6 smaller, thus not a constant! GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

Amine – energy consumption for regeneration Equilibrium partial pressure of H 2 S Typical amine solvent 2,000 Amine type kJ/kg H 2 S kJ/kg CO 2 60%wt DGA 1570 1972 1,500 50%wt MDEA 1045 1340 Pressure (mbara) 1,000 500 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Solvent loading (mol/mol) 7 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

Amine Regeneration (Heat) Enthalpy balance Heat for regeneration determined by: Acid gas/steam Solvent type • C p (for energy balance) o • Amine type Rich solvent loading and temperature Reflux o after flash and L/R HE Solvent %wt amine • Rich solvent Solvent boiling temperature reboiler o Two phase All streams: • Type of treating M stream , T stream , Cp stream selectivity o other components removal o H 2 S • Regenerator bottom pressure LP steam Downstream unit pressure drop o Generated steam Type of internals o Sweet gas specification o • Reflux temperature Condensate Hydraulic constraint at regenerator inlet due to Stripped solvent Lean solvent flashing and flow pattern may limit Lean solvent Overstripping causes corrosion/erosion 8 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

Steam requirements regenerator The required solvent leanness is Top steam ∆ H r reaction heat determined by the sweet gas C p specific heat specification T temperature P pressure Reflux S s = sensible heat S t heating solvent to bottom temperature Rich solvent Two phase S r = heat of reaction chemical desorption of H 2 S, CO 2, Steam other S r = (CO 2 ) ∆ H r,CO2 + (H 2 S) ∆ H r,H2S S s = C p ∆ T CO 2 , H 2 S LP steam S t = top steam S b Bottom steam for sufficiently low acid partial pressure in the lean solvent at feed tray, minimum applied by process Condensate vendors + Lean solvent S b = bottom steam (kg/m 3 ) = S t + S s + S r minimum applied by process vendors 9 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

Regenerator Bottom Temperature Acid gas/steam • The regenerator bottom temperature is determined by the amount of steam generated in the reboiler, which is a boiling Reflux aqueous amine at the bottom pressure: P 0 • The more steam is generated, the higher the Rich solvent pressure drop ( ∆ P) across the regenerator trays, more gas phase Two phase: Flashed H 2 S • The higher the pressure drop, the higher the regenerator bottom pressure (P 0 + ∆ P) and CO 2 Stripping stage H 2 S + separates at • The higher the bottom pressure, the higher LP steam CO 2 + feed inlet the bottom temperature steam • NB similar effect due to the stripping of acid gas in the reboiler is very small, because the P 0 + Δ P solvent leanness should be met at the Condensate stripping stage Lean solvent • Reboiler external steam regenerator steam 10 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

AGRU internal energy saving Inside AGRU Turbo expander High pressure absorber only SRU FEED SWEET GAS Not on one shaft with solvent pump Saving on pump power dependent on pressure difference FLASH GAS FEED GAS HEAT IN 11 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

AGRU internal energy saving Inside AGRU Lean/rich heat exchanger SRU FEED SWEET GAS Optimisation limited by: - Regeneration needs (see leanness) - Type of heat exchanger - Use of low pressure steam limitation FLASH GAS - Solvent loading (flashing in HE) - Fouling system FEED GAS - System configuration (vibration due HEAT IN to 2 phase flow in vertical regenerator inlet piping) 12 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

AGRU and SRU interfaces Outside AGRU affecting SRU TAIL GAS ANALYSER AIR SRU FEED SWEET GAS WASTE HEAT (Steam generation) FLASH GAS FEED GAS TO DEGASSER HEAT IN HYDROCARBON and CO 2 IN AMINE SOVENT HS - + R 3 NH + H 2 S + R 3 N H 2 S + ½O 2 S + H 2 O 13 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

Entrained and soluble hydrocarbon route Hydrocarbon in acid gas TAIL GAS ANALYSER AIR SRU FEED SWEET GAS WASTE HEAT (Steam generation) FLASH GAS FEED GAS TO DEGASSER HEAT IN HYDROCARBON Hydrocarbon IN AMINE SOVENT When the color is more intensive, there is more entrained combustion consumes than soluble rated hydrocarbon in the stream energy in the SRU 14 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

SRU affected by hydrocarbon from amine unit Hydrocarbon content in SRU feed gas – Preferably below 1%vol – Maximum 5% vol This can be handled • Air consumption increase thus by Tail gas analyser – Reduction maximum capacity when change is slow – Therefore the overall Sulphur conversion • Energy consumption increase However Hydrocarbon composition fluctuation Unburned liquid and heavy HC form soot on catalyst Black Sulphur Can even block Sulphur rundown 15 Fast composition changes cannot be controlled by analysers due to dead time GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)

Co-absorption of CO 2 – selective treating H 2 S Ratio CO 2 TAIL GAS ANALYSER AIR SRU FEED SWEET GAS WASTE HEAT (Steam generation) FLASH GAS FEED GAS TO DEGASSER HEAT IN HYDROCARBON IN AMINE SOVENT H 2 S + ½O 2 S + H 2 O HS - + R 3 NH + H 2 S + R 3 N 16 GASCO presentation MESPON 2016 ABU DHABI GAS INDUSTRIES (GASCO)