Desulfurization of Liquid Fuels by Adsorption for Fuel Cell Applications

Desulfurization of Liquid Fuels byAdsorption for Fuel CellApplicationsAmbal Jayaraman, Gökhan O. Alptekin,Margarita Dubovik, Mathew Schaefer, John Monroeand Lauren BricknerFuel Cell Portable Power Systems I2008 AIChE Annual MeetingNovember 16 th -21 st , 2008Philadelphia, PATDA Research Inc. • Wheat Ridge, CO 80033 • www.tda.com

Portable Fuel Cell Applications• Defense Applications• Sensor Power (0 - 100 W)• Soldier Power (< 500 W)• APUs (0.5 – 10 kW)• Commercial applications• Recreational vehicles• Emergency power• Automobiles, refrigerated trucks• Currently for the < 500 W scale - fuel cells usestored hydrogen, LPG, and methanol/water mix asfuel• Preferred fuel for:Defense applications - Jet fuel (JP-8)Commercial applications - Diesel (ULSD)• High energy density• Longer missions/operation hours• No water needed• JP-8 and ULSD contain sulfur and needs to beremoved to produce desulfurized fuel that can beused in the portable PEM/SOFC system to producepower2TDAR e s e a r c h

Military Fuel Cell APUs• Supplying fuel to the battlefield is one ofArmy’s largest logistic burdens• Delivering JP-8 fuel to Afghanistan cost~$300 per gallon (Mills, 2003)• Even modest gains in fuel efficiency couldsignificantly impact this logistics cost• A fuel cell APU integrated with a BradleyM2A3 Diesel Infantry Fighting Vehiclecould reduce fuel consumption by 86% inthe “silent watch” mode• Logistic fuel powered fuel cells can deliverportable power for soldiers, squad batterychargers, silent watch “APUs” and powerto ships, UUVs, submersibles, UAVs etc• Fuel savings benefit is not the only tacticaladvantage to the military• Near silent operation, reduced heatsignature and reduced space are alsoimportant benefits3TDAR e s e a r c h

Diesel Fuel APUs• Commercial long haul truckscould benefit from a fuel cellAPU to increase efficiency andcomply with noise and emissionregulations• The potential fuel savingsprovided by improved fuelefficiency could exceed $2billion per year• The power need for the truckbasedAPUs are 1-2 kWe• The low sulfur concentration ofULSD (< 15 ppmw) makes itpossible to use an expendabledesulfurizer cartridge• The cartridge can beregenerated off-vehicle toreduce complexityAPU SizeFuel Flow RateSulfur ContentReplacement Freq.Sorbent SizeSulfur CapacityHeavy Duty TruckDiesel1kWe3.2 mL/min15 ppmw6months1.2 L350 mL/mL4TDAR e s e a r c h

Jet Fuel Desulfurization5TDAR e s e a r c h

Characteristics of JP8 and JP5 FuelsHydrocarbon Type JP-8 JP-5Paraffins 71.4 30.8Cycloparaffins 8.0 52.8PAH’s 3.5 No dataOlefins No data 0.5Total paraffins 79.4 83.6Total Aromatics 20.6 15.9• JP-8 and JP-5 are kerosene-likefuels• JP-5 contains more aliphatics toincrease the flash point• Both of fuels may contain up to3,000 ppmw sulfur• The sulfur components in the jetand diesel range are referred toas “refractory sulfur”• Benzothiophene• Alkyl-benzothiophene• DibenzothiopheneSulfur compounds in logistic fuelsSource: Song, 20036TDAR e s e a r c h

Sorbent Characteristics• TDA developed SulfaTrap TM -D1 sorbent, a regenerable,physical adsorbent for low temperature desulfurizationof logistics and transportation fuels• Sorbent characteristics:• High sulfur capacity• Regenerability– Small size and reduced replacement frequency• High removal efficiency– Reduce the sulfur concentration of the fuel to subppmlevels• Inertness– No undesirable side reactions– No change in fuel properties• Ease of handling and disposal– No toxicity, flammability, pyrophorocity7TDAR e s e a r c h

Bench-scale Test SetupSampling valveFuelPumpCeramic heater withReactor-1 insideReactor-2SulfurChemiluminescenceDetector (SCD)Liquid sampling8TDAR e s e a r c h

Jet Fuel Sulfur Removal Efficiency20000000T=120°C, JP-8 Sulfur Content= ~430 ppmw, LHSV= 1.6 h -1180000001600000014000000Response120000001000000080000006000000400000020000000Desulfurized fuel= 14 mL/gDesulfurized fuel= 9 mL/g0 5 10 15 20TimeSulfur = 430 ppmwSulfur < 1.5 ppmvSulfur < 40 ppbv• SulfaTrap TM -D1 sorbent could reduce the sulfur to sub ppmw levels9TDAR e s e a r c h

Performance with JP-8 and JP-5total sulfur (ppmw)12001000800600400200JP8JP5T ads= 120 o C, LHSV= 1.6 h -1JP-8 1194 ppmw SJP-51100 ppmw S00 2 4 6 8 10 12mL fuel desulfurized/g of sorbent• SulfaTrap TM -D1 achieves higher sulfur capacity for JP-5 desulfurization• JP-5 typically has lower aromatic and polyaromatic content than JP-8• JP-8 also has additives for static dissipation which contains toluene,naphthalene and nitrogen containing polymers10TDAR e s e a r c h

Effect of TemperatureSulfur Concn., ppmwJP-8, 1,450 ppmw sulfur, LHSV= 1.6 h -1140012001000800600400T = 65CT = 90C200T = 120CSulfur Breakthrough capacitiesas a function of temperatureAds.Temp.( o C)BreakthroughCapacity(mg S/g)SaturationCapacity(mg S/g)65 2.2 2.890 2.8 4.2120 3.0 4.100 1 2 3 4 5 6Fuel Desulfurized, mL/g• Sulfur capacity slightly increases with temperature• At higher temperatures the sorbent’s interactions with unsaturatedhydrocarbons are significantly weaker than those with sulfur• Higher operating temperature is desirable to reduce the ∆T neededsorbent regeneration11TDAR e s e a r c h

Options for Regeneration Gas201816Regens in 2%H 2 /HeCycle # 1 = 7.0 mL/gCycle # 2 = 3.6 mL/gCycle # 3 = 1.6 mL/gCycle #4-14 = 0.3-0.5 mL/gTDA SulfaTrap (1/16" pellets)Optimization of Regen Gas @ 400-450 o CCycling Data - JP-5 with 500 ppmw SSulfur concn. (ppmw S)141210864Regenerations inH2%H 2 Regens2 /HeCycle # 4-14Cycle# 4-14Air RegenerationsCycle# 27-67Regenerations in airCycle # 27-52Air RegenerationsRegenerationsfollowed byinH 2air Reduction& 2%H 2 /HeCycle# # 15- 15-26200 0.5 1 1.5 2 2.5 3mL Fuel Desulfurized/g of Sorbent• SulfaTrap TM -D1 sorbent can be regenerated by using hot air,reducing gas or an inert gas12TDAR e s e a r c h

Multiple Cycles with Air RegenerationSulfur concn. (ppmw S)252015105TDA SulfaTrap TM -D1 (1/16" pellets)Cycling Data with air regeneration @ 400 o CCycle #1 - Cycle #90#17#18#3#2#15#90#51#58#1900 0.5 1 1.5 2mL Fuel Desulfurized/g of Sorbent• SulfaTrap TM -D1 sorbent maintained its capacity for over 100 cycles13TDAR e s e a r c h

TDA’s Jet Fuel Desulfurizer21”26”26”• A stand alone prototype desulfurizer was built to remove sulfurcompounds directly from liquid fuels (e.g., JP-8, JP-5, diesel fuel)• The unit is sized to 3 kWe and treats up to 10 mL/min fuel with up to3,000 ppmv sulfur)14TDAR e s e a r c h

Manifolds and ConnectionsAir OutIn-line Electric GasHeaterFuel OutAir InThermocouple wellsValve &ActuatorMicro-switchindicatorReactorFuel In15TDAR e s e a r c h

Sorbent ReactorsRegenerationAir OutletRegenerationAir InletFuel Outlet3”φ 3”ØThermocouple14”SupportScreensSorbentSorbentFill PortThermocoupleFuel Inlet16TDAR e s e a r c h

Cycle SequenceCycle Time (Hours)BED 1012 3 4 5 6 7 8BED 2BED 3BED 4ADSORPTION (120 MIN)DRAIN (15 MIN)HEATING (70 MIN)REGENERATION (210 MIN)COOLING (30 MIN)Full-cycle time = 8 hrsFILL (35 MIN)• Four beds undergo six steps to achieve continuous desulfurization• 1) Adsorption, 2) Drain, 3) Heating, 4) Regeneration, 5) Cooling, 6) Fill• One bed always remains on-line, while other beds regenerate or undergoheating/cooling and fill/drain transitions171TDAR e s e a r c h

High Temperature Fuel Desulfurization• SulfaTrap TM -D1 sorbent works muchmore effectively at 200 o C and 75 psig• In order to maintain fuel in the liquidstate, the fuel is pressurized to 75 psig at200 o C during adsorptiontotal sulfur (ppmw)500400300200100TDA- SulfaTrap TM - D1JP-8 ~ 430 ppmw S200 o C & 75 psig200C, 75 psig120C, ambientTotal Sulfur Conc, ppmw350300250200150100500#5#6Cycle #1Cycle #2Cycle #3Cycle #4Cycle #5Cycle #6TDA SulfaTrap TM -D1JP8 ~ 430 ppmw S0 5 10 15 20 25mL Fuel Desulfurized/ g sorbent#100 4 8 12 16 20 24mL fuel desulfurized/g of sorbent• Higher adsorptiontemperature and reducedT swing betweenadsorption andregeneration also has afavorable impact onsystem18TDAR e s e a r c h

Next Generation Desulfurizer Design• The next generationdesulfurizer (3 kWe) isdesigned to fit into20”x12”x 16.5”• By eliminating redundantpieces and using custombuiltcomponents• Increased energy densityis expected for largersystems since the size ofthe auxiliary equipment(valves etc.) will notproportionally increasewith system size19TDAR e s e a r c h

Diesel Fuel Desulfurization20TDAR e s e a r c h

Desulfurization of Diesel FuelT ads= 120 o C LHSV = 1.6 h -1 MoSulfur Concn. inCollected Fuel (ppmw)108642Proprietary CarbonSelexsorbTDA-SulfaTrap-D1ULSD Desulfurization @ 120 o C4,6-dimethyldibenzothiopheneS00 20 40 60 80 100 120Fuel Desulfurized mL/g• SulfaTrap TM -D1 can desulfurize 100 mL of ULSD per g sorbent with 90+%removal efficiency reducing the sulfur content to less than 1 ppmw21TDAR e s e a r c h

Diesel Fuel – Removal Efficiency4,6-dimethyldibenzothiopheneT=120°C, Sulfur Content= ~10.5ppmw, LHSV= 1.6 h -1SMoSulfur < 0.4 ppmvDesulfurized fuel= 20 mL/g• SulfaTrap TM -D1 sorbent could effectively desulfurize the ultra low diesel fuelfor fuel cell applications• Recent formulations could desulfurize up to ~650 mL of fuel per g sorbent22TDAR e s e a r c h

Extended Testing1412ULSD - 14.1 ppmw S (inlet) onSulfaTrap TM -D1(P = 125 psig)350300ppmw sulfur10864cumulative average sulfur in effluentFuel Adsorption Temp.250200150100Temperature, o C25000 100 200 300 4000mL Fuel Desulfurized/mL of Sorbent• The extended testing of SulfaTrap TM -D1 provided ~ 400 mL of desulfurizedfuel per mL of Sorbent with < 3 ppmw S cumulative average sulfur leakage• SulfaTrap TM -D1 had increased capacity and removal efficiency at highertemperature and lower space velocityTDAR e s e a r c h

Straight-cut Diesel Desulfurizationtotal sulfur (ppmw)T=120°C, Sulfur Content = 120 ppmw, LHSV= 0.8 h -15040302010Cycle #1Cycle #2Cycle #3Cycle #4Cycle #6Cycle #7#6#1#7#3#4#20TDA- SulfaTrap TM - D10 1 2 3 4 5mL fuel desulfurized/g of sorbent• TDA SulfaTrap TM -D1 provided good performance for desulfurization ofstraight-cut dieselTDAR e s e a r c h

Conclusions• SulfaTrap TM -D1 sorbent is highly effective for deepdesulfurization of jet fuel• The sorbent is regenerable in air and/or reducing gasat 400 o C and maintains its performance over manycycles• TDA is demonstrating the concept in a practicalbreadboard prototype desulfurizer• The sorbent is successful for desulfurization of bothULSD and straight-cut diesel• TDA has successfully demonstrated SulfaTrap TM -Psorbent for desulfurization of LPG in-line with portablefuel cells25TDAR e s e a r c h