Aspen Plus Process Model for Production of Gaseous Hydrogen via Steam Gasification of Bagasse Mohamed Elbaccouch and Ali T-Raissi Florida Solar Energy Center University of Central Florida Cocoa, FL, USA
Objectives Determine the potential of producing hydrogen gas from an air-fired biomass gasifier utilizing local resources for use in the NASA Shuttle program Use Aspen Plus chemical process simulator (CPS) platform to model the process
Simulation Criteria Thermo-neutral plant design for production of H 2 from bagasse Aspen Plus Chemical Process Simulator: no heat generation Flowsheet consisted of four sections: 1) Dryer section to partially dry the bagasse 2) Gasifier consisting of bagasse combustion zone and gasification zone 3) Gas clean up section to purify the H 2 product 4) Pressure swing adsorption unit to recover H 2 at desired purity levels
Methodology Part of the bagasse was used as fuel to supply heat to the plant Temperature of the combustor was set at 1550 o C Heat generated was inputted to the plant s reactors and flow streams All other process units operate adiabatically 900 kg/hr of bagasse was used to produce 17.4 kg/hr of ultra pure hydrogen gas
Rationale Biomass gasification is a well-developed & old technology (see examples below) Syngas (H 2 +CO X ) so generated is a renewable energy source
Hydrogen via Biomass Gasification Simple Capital Equipment Layout Brazil McNeil Station, VT Maui, HI
Biomass Resources in Florida: Flexible, Available, and Inexpensive Orange Peels Fast Growing Grasses Bagasse
Why Aspen Plus TM CPS? Process design oriented language facilitates complex chemical process calculations Applies mass and energy balances and chemical equilibrium relationships to predict design performance Small sections of a complex integrated system can be generated and tested as separate modules before integration Contains large property data bank and thermodynamic models
Simulation Assumptions Linear plant capacity Ultimate analysis of bagasse used as the feedstock composition input to the plant Process yields no tar Residence time in the gasification zone is long enough to allow approach to chemical equilibrium (Gibbs reactor model)
Modeling Approach Biomass feed Producer gas out Dryer Fuel to Clean-up Biomass Section Combustor-1 Biomass Feed Drying Zone Gasification Zone HEAT Air in Heat Biomass Combustor-2 Unreacted Biomass Biomass Biomass Unreacted Biomass + Ash Gasifier Producer gas out Air Grate Comb. Zone Ash Ash bin Ash out CO 2 + H 2 O + NO x + Unreacted Biomass
Process Flow Diagram Bagasse to Gaseous H 2 11 Dryer Section HEAT-HX DRYER 1 2 3 H2O-FLH1 PSA-CO2 PSA-N2 PSA-H2 10 TH ERMO 5 48 50 H2-MX MIXER 51 52 HX1 COMBUST1 6 46 8 BAG-SP1 47 53 49 54 9 12 14 7 BAG-SP2 13 GASIFIER 4 PSA Section 55 H2-SP COOL-HX 18 COMBUST2 15 17 16 21 36 Clean Up Section 28 HX7 44 45 20 REFORMER H2O-FLH2 19 HX3 26 HX4 W W 43 30 COMP 40 ASH-SP 27 SHIFT 22 25 29 31 41 HX2 32 Gas./Comb Section 23 24 37 H2O-MX MIXER 35 33 HX5 56 HX6 42 39 H2O-RECY 38 34
Aspen Optimized Gasification Conditions (17 kg/hr H 2 gas) Biomass feed Combustor-1 temp Combustor-2 temp Gasifier output temp Water removed from Dryer Split ratio: biomass to combustors 1&2 900 kg.hr -1 1550 o C 1550 o C 1150 o C 159 kg.hr -1 0.47
Simulation Results Ultimate Analysis of Bagasse (dry basis) Ultimate Analysis Wt% Ash 8.61 C 46.38 H 5.86 N 0.19 Cl 0.01 S 0.05 Gasifier Output kg.hr -1 H 2 O C H 2 12 N 2 1919 Cl 2 0.06 CO 219 NH 3 0.001 H 2 S 481 None 0.3 O 38.9
Hydrogen Flow Rate in Aspen Plus TM CPS Results 30 25 H2 (kg / hr) 20 15 10 5 0 gasifier reformer shift PSA off-gas
Biomass Feedstock Requirements for Multiple Shuttle Launches 12000 250 10000 Ba g a sse Hy d ro g e n 200 Bagasse (kg/hr) 8000 6000 4000 150 100 Hydrogen (kg/hr) 2000 50 0 0 1 2 3 4 5 6 7 8 0 Number Launches
Summary Hydrogen production from bagasse gasification process for Shuttle program at the NASA-KSC was analyzed using Aspen Plus CPS Plant consisted of dryer, gasifier, clean-up, & PSA sections Gasifier operates with no carbon formation nor heat production Plant functions within the typical range of industrial processes
Acknowledgements Support for this work was provided by the National Aeronautics and Space Administration (NASA) through Glenn Research Center.