Aspen Plus Process Model for Production of Gaseous Hydrogen via Steam Gasification of Bagasse

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Derrick McGee
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1 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

2 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

3 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

4 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

5 Rationale Biomass gasification is a well-developed & old technology (see examples below) Syngas (H 2 +CO X ) so generated is a renewable energy source

6 Hydrogen via Biomass Gasification Simple Capital Equipment Layout Brazil McNeil Station, VT Maui, HI

7 Biomass Resources in Florida: Flexible, Available, and Inexpensive Orange Peels Fast Growing Grasses Bagasse

8 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

9 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)

10 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

11 Process Flow Diagram Bagasse to Gaseous H 2 11 Dryer Section HEAT-HX DRYER H2O-FLH1 PSA-CO2 PSA-N2 PSA-H2 10 TH ERMO H2-MX MIXER HX1 COMBUST BAG-SP BAG-SP2 13 GASIFIER 4 PSA Section 55 H2-SP COOL-HX 18 COMBUST Clean Up Section 28 HX REFORMER H2O-FLH2 19 HX3 26 HX4 W W COMP 40 ASH-SP 27 SHIFT HX2 32 Gas./Comb Section H2O-MX MIXER HX5 56 HX H2O-RECY 38 34

12 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 o C 1550 o C 1150 o C 159 kg.hr

13 Simulation Results Ultimate Analysis of Bagasse (dry basis) Ultimate Analysis Wt% Ash 8.61 C 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 Cl CO 219 NH H 2 S 481 None 0.3 O 38.9

14 Hydrogen Flow Rate in Aspen Plus TM CPS Results H2 (kg / hr) gasifier reformer shift PSA off-gas

15 Biomass Feedstock Requirements for Multiple Shuttle Launches Ba g a sse Hy d ro g e n 200 Bagasse (kg/hr) Hydrogen (kg/hr) Number Launches

16 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

17 Acknowledgements Support for this work was provided by the National Aeronautics and Space Administration (NASA) through Glenn Research Center.

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