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Use of neutron radiography to improve the design of a salt separator in supercritical-water biomass gasification

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Neutron transmission radiography is an imaging technique that allows cross-sectional visualization of objects. Neutrons are passed through a sample;

different materials interact with the neutrons with different attenuations. The neutrons that are transmitted through a sample are detected and produce a grayscale

image. By the proper choice of materials, phenomena occurring inside of thick-walled vessels can be observed.

See the project homepage at:

http://cpe.web.psi.ch

Waldner, M.H., Vogel, F. Renewable Production of Methane from Woody Biomass by Catalytic Hydrothermal Gasification Ind.

Eng. Chem. Res., 2005 (in press).

http://dx.doi.org/10.1021/ie050161h

Fuels from biomass:

Use of neutron radiography to improve the design of a salt separator in supercritical-water biomass gasification

Andrew A. Peterson

a,b

, Maurice H. Waldner

b

, Frédéric Vogel

b,#

, Jefferson W. Tester

a

b Paul Scherrer Institut, Villigen, Switzerland.

a Massachusetts Institute of Technology, Cambridge, MA, USA.

Abstract

Wet biomass, such as manureor wood waste, can be converted into methanevia catalyticconversion in supercritical water. However, salts that are present in the biomass may precipitate out and lead to catalyst deactivation. If these saltscan be separated and recovered, they may be used as afertilizer.

The neutron radiography facilities at PSI provide a unique means to optimize the design of a supercritical-water salt separator for this process.

Neutron transmission radiographywill be used to visualizethe interior of prototype salt separators.

# Corresponding author. Frédéric Vogel, OVGA/104, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland. +41(0)56 310 2135. frederic.vogel@psi.ch

Salts in Biomass

Biomass Gasification Process

Current results

Desired process

ƒBatchprocess which con- verts woody biomass to near-equilibrium yields of methane, hydrogen, and carbon dioxide.

ƒCatalytic conversionpro- cess in supercritical water.

(400°C, 30 MPa).

ƒThe process can handle wet streamsthat needed to be dried before conventional gasification.

ƒProduces up to 0.33 grams CH4 per gram dry biomass. This is a sub- stantially higher yield than by biol. methods.

ƒDevelopment of a continuous process, capable of converting a wide range of biomass materials into methane, hydrogen, and carbon dioxide.

ƒRecoveryof inorganicconstitutents for use as fertilizers.

ƒBiomass can contain a large amount ofinorganicconstitutents which cannotbe convertedinto fuels.

ƒThese saltscan complicate the conversion process, since salts are only slightly solublein supercritical water.

ƒThe recoveryof these salts may lead to the production of a useful fertilizerfrom the biomass conversion process.

Salt Separator Design

ƒNeutron radiographywill be used to aid in the design of a separator.

ƒNeutron radiography allows in-situ visualization of a separation process occurring in this high- pressure, high-temperature vessel.

ƒComputational fluid mechanics (CFD) are being used to predict the behavior of proposed vessel designs; neutron radiography is being used to confirm actual vessel behavior.

About Neutron Radiography

Image from http://neutra.web.psi.ch/

Scoping Image

1-cm thick zircaloy panel

heavy water (D2O)

aluminum cylinder borax salt

Further Information

CFD simulation of a reverse-flow salt separation vessel.

Woody biomass is gasified into CH4, H2, and CO2. The remaining water contains <2% of the feed carbon.

CH1.49O0.68+ 0.29 H2O → 0.52 CH4+ 0.48 CO2

wood water methane carbon

dioxide

0 10 20 30 40 90 100

0 5 10 15 20 25 30 35 40 45 50 55

CH4 / vol%

time (T > 374 °C) / min.

HB400R05 HB400R04 HB400R06 HB400R07 HB400NC1

nickel catalyst

no catalyst thermodynamic equilibrium

Methane yields approach the maximum governed by thermo- dynamics.

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