Acrolein Production

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Hesketh Chemical Reaction Engineering presentation

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Production of Acrolein by the Partial Oxidation of Propylene

Production of Acrolein from the Catalytic Oxidation of Propylene in a Fixed Bed ReactorTeam 1Michael GlasspoolSarah WilsonNicole CosgroveProduction GoalsProduce 30,000 Metric Tonnes / yearOperate for 350 days / yearProduce acrolein at 0.0177 kmol / s

Allowable Process Conditions1,2Process typically run between 320 390 CRun between atmospheric pressure and 303.975 kPa (3 atm)Use air as an oxygen sourceTypical Conversion between 65 90 %Propylene flammability range 2 11.1 %

Process OptimizationProcess was optimized in a series of reportsModeling started off simple and became more complexPressure drop calculations and energy balances were added over the course of the semester to accurately model the systemMaterial BalanceAssume an 80 % propylene conversionFlow enough air to stay below LFL of 2%C3H6 + O2C3H4O + H2O

Preliminary Energy BalanceThis model assumes a single reactionAdiabatic and Isothermal cases were modeled

Simple Kinetic Expression3 Rate expression was first order in propylene and half order in oxygen

Simple Kinetics ResultsAssuming steady-state, isothermal plug flow, the reactor was modeled in POLYMATH and Aspen Plus

Simple Kinetics Results

Major FindingsThe reactor volume was too largeIncreasing the temperature can drastically decrease the reactor volumeReactor temperature would be raised to 663.15 K, the maximum temperaturePressure Drop CalculationA pressure drop calculation was added using the Ergun Equation, assuming an isothermal plug flow reactor with a catalyst void fraction of 0.40 4

Pressure Drop ResultsBy increasing the inlet pressure to 3 atm, the reactor size was minimized and pressure drop was more easily modeled

Reaction KineticsReal reaction kinetics were found as modeled by Tan et al 5

Kinetic DevelopmentRate constants were given at different temperatures

Kinetic Development

Kinetic Modeling AssumptionsThe reaction was assumed to take place in a steady state, isothermal plug flow reactorThe catalyst void fraction was assumed to be 0.45 with a bulk density of 1565.5 kg/m3 6Kinetic Modeling ResultsThe new kinetics reduced the volume necessary to produce an 80 % conversionThis allowed the reaction to take place in only one reactorThe best acrolein selectivity was found at the higher end of the temperature range (390 C)Molar Flow Rate throughout Reactor

Acrolein Selectivity

Incorporation of an Energy BalanceAn energy balance was added to account for temperature changes throughout the reactorMolten salt (Ua = 227 W/m2-K) was used as a coolant to prevent a runaway reactor temperature7Energy Balance AssumptionsThe flow rate of coolant was kept high enough to maintain a constant coolant temperature of 658.15 KHeat capacities and heats of reaction were assumed to be constantEnergy Balance ResultsThe addition of the energy balance reduced the overall volume necessary to reach 80 % conversionThe pressure drop was also reduced from 10.64 % to 9.98 %

Reactor Temperature ProfileThe temperature throughout the reactor was modeled to determine the reactor hotspotThe effect of changes in the inlet and coolant temperatures were also exploredFor the base case, the reactor hotspot occurred at the beginning of the reactor and reached a temperature of 672.5 KReactor Temperature Profile

Reactor GainThe reactor gain was analyzed to determine the thermodynamic stability of the reactor 7

For a 1 C change in inlet temperature, the gain was found to be 0.0754

Reactor Gain Profile

Energy Balance ResultsThe coolant temperature effected the selectivity of the reactor

The highest selectivity was found when the coolant temperature and the inlet temperature were equal

Final Reactor Design

Temperature Profile in Final Reactor Design

Flow Rate Profile in Final Reactor Design

ReferencesGuest, H.R.. "Acrolein and Derivatives." Kirk-Othmer Encyclopedia of Chemical Technology. 4th ed.Machhammer, et al. Method for Producing Acrolein and/or Acrylic Acid. US Patent 7,321,058. January 2008.Dr. Concetta LaMarca. Memo 2: Simple Kinetics. 2008.Fogler, H. Scott. Elements of Chemical Reaction Engineering. 4th Ed. Prentice Hall. 2006.Tan, H. S., J. Downie, and D. W. Bacon. "The Reaction Network for the Oxidation of Propylene over a Bismuth Molybdate Catalyst." The Canadian Journal of Chemical Engineering 67(1989): 412-417."Bismuth molybdate, powder and pieces." CERAC Online Catalog Search. CERAC Incorporated. 05 Mar 2008 .Dr. Concetta LaMarca. Memo 5: Energy Balance. 2008.

Any Questions?

Species NameChemical FormulaInlet Molar Flow rate(kmol/s)Inlet Mass Flow rate(kg/s)Outlet Molar Flow rate(kmol/s)Outlet Mass Flow rate(kg/s)

PropyleneC3H60.02210.93080.00440.1862

OxygenO20.24337.78640.22567.2202

NitrogenN20.915425.63040.915425.6304

AcroleinC3H4O0.00000.00000.01770.9921

WaterH2O0.00000.00000.01770.3188

Total-1.180834.34761.180834.3476

VariableIsothermalAdiabatic

Inlet Temp (K)623.15623.15

Outlet Temp (K)623.15777.84

Hrxn (J/s)x10-6-6.020

Heat Duty (J/kmol reacted)x10-6-3400

Number of Tubes1

Tube Diameter (m)10

Tube Length (m)759.89

Reactor Volume (m3)59681.87

Catalyst Bulk Density (kg/m3rxtr) 1000

Catalyst Weight (kg)59681870

Catalyst Void Fraction0.4

Reactor Temperature (K)623.15

Reactor Pressure (kPa)101.325

Heat Duty (W)-6014660

Calculated Heat Duty (W)-6020000

Residence Time (s)395.3

Sheet1Temperature (K)Conversion623.1580633.1590.52804643.1596.69827653.1599.24229663.1599.90107673.1599.99391683.1599.99986693.15100703.15100713.15100723.15100

Volume vs Conversion

Sheet2623 K633 K643 K653 K663 K673 K683 K693 K703 K713 K723 KVolume (m3)ConversionVolume (m3)ConversionVolume (m3)ConversionVolume (m3)ConversionVolume (m3)ConversionVolume (m3)ConversionVolume (m3)ConversionVolume (m3)ConversionVolume (m3)ConversionVolume (m3)ConversionVolume (m3)Conversion1.00E-0501.00E-0501.00E-0501.00E-0501.00E-0501.00E-0501.00E-0501.00E-0501.00E-0501.00E-0501.00E-0501452.3183.9270041472.4195.8025311474.1028.3302521359.44110.881851351.01315.001441569.27723.268891200.72724.563931196.74532.045281403.17545.981281249.07952.293261258.76763.088461929.7735.1825711949.8747.6077521951.55710.870541836.89614.404561828.46819.725832046.73229.172662091.99638.693621891.55445.574651971.09557.767671892.11567.228141903.52777.662512407.2286.421032427.3299.3769442429.01213.337652791.80621.022782783.37828.375882524.18734.608362569.45145.111532665.28857.432942551.84967.123952541.45377.519122391.24784.69373362.1388.8476193382.23912.810313383.92218.061243269.26124.130643260.83332.333633001.64239.615123046.90650.841983060.7562.438863136.52174.424853195.38884.595213045.11290.763793839.59210.036243859.69414.475983861.37720.322013746.71627.112063738.28836.066163956.55148.480814001.81560.538083856.04770.770233724.29480.115123633.19888.031833701.60194.431274317.04711.208734337.14916.10864338.83222.518174224.17129.972514215.74339.586974434.00652.40164479.2764.630864255.55874.221014314.51684.545954291.92491.80824195.05796.191074794.50212.365324814.60417.708874816.28724.651695179.0835.351035170.65346.043114911.46156.017764956.72568.292685057.6579.956344906.66487.993514952.39594.395314853.91697.705235749.41214.631755769.51420.81515771.19728.738325656.53537.878775648.10849.001295388.91659.353865434.1871.570185460.00882.329045500.32590.674445393.40395.648945513.4498.617766226.86715.742036246.96922.322376248.65230.695056133.9940.304916125.56351.793586343.82665.27386389.0977.132966266.87286.268856095.16892.758246055.66397.024346008.35899.055016704.32216.837326724.42423.799946726.10732.596366611.44542.633736603.01854.429686821.28167.8976866.54579.487566671.2287.897386690.93694.377336718.56697.965286668.47799.43097181.77717.917837201.87925.248437203.56134.443917566.35547.015647557.92859.269047298.73670.3192734481.597537481.40990.59977287.42595.634987381.91198.608837163.6899.610968136.68720.035378156.78828.060598158.47137.984098043.8149.076368035.38361.488837776.19172.556227821.45583.48877887.13891.716057884.47596.611657824.31598.920357824.04599.765738614.14221.072828634.24329.425438635.92639.679798521.26551.055088512.83863.585528731.10176.531538776.36586.704298699.62993.567638481.96397.378488.10999.261918484.47899.858939091.59722.096329111.69830.763549113.38141.327838998.7252.955198990.29365.566179208.55678.295399253.8288.067589106.31394.332219079.79197.958749152.06399.495438979.83199.903579569.05223.106079589.15332.075489590.83642.929649953.6356.532459945.20369.205429686.01179.925379731.27589.290359920.39395.599939677.88398.415769594.76399.608449640.32599.941931.05E+0425.085131.05E+0434.622981.06E+0445.999951.04E+0458.215681.04E+0470.87611.02E+0481.431841.02E+0490.387211.03E+0496.123271.03E+0498.770511.03E+0499.732341.03E+0499.965031.10E+0426.054821.10E+0435.859591.10E+0447.471041.09E+0459.832471.09E+0472.454921.11E+0484.111531.12E+0492.254191.11E+0496.990811.09E+0499.045841.09E+0499.817031.08E+0499.97611.15E+0427.011531.15E+0437.072121.15E+0448.901081.14E+0461.385551.14E+0473.947081.16E+0485.301591.16E+0493.046461.16E+0497.348871.15E+0499.259531.14E+0499.858021.15E+0499.985611.20E+0427.955441.20E+0438.261061.20E+0450.291271.23E+0464.310821.23E+0476.690571.21E+0486.401911.21E+0493.757441.20E+0497.664371.21E+0499.425381.20E+0499.902941.20E+0499.990161.29E+0429.805621.29E+0440.570111.29E+0452.95671.28E+0465.687881.28E+0477.950811.26E+0487.419361.26E+0494.395531.28E+0498.187251.27E+0499.554081.27E+0499.933661.26E+0499.994081.34E+0430.712241.34E+0441.691151.34E+0454.234151.33E+0467.010971.33E+0479.142221.35E+0489.230381.36E+0495.482271.32E+0498.403031.33E+0499.653961.31E+0499.948521.33E+0499.996441.39E+0431.60