Biomass GasificationJim Frederick

Table Mountain Consulting

Golden, CO

Overview

Gasification

• Definition: conversion of carbonaceous materials

into carbon monoxide (CO) and and hydrogen (H2)

by reaction at high temperatures with oxygen and/or

steam.

• Desired products: CO and H2 (synthesis gas)

• Co-products:

- CO2 and water vapor

- methane (CH4) and other light hydrocarbons

- tar

- inorganic vapors and ash

• Energy conversion efficiency: 65-70%

Utilization of Products

• Fuel gas

- Combustion for heat

and power

- Fuel for fuel cells

• Synthesis of fuels

and chemicals

1938 Adler Diplomat with biomass gasifier

Synthetic Products from Syngas

Key Aspects of Gasification

• Gasification is endothermic (needs heat to

drive it)

• Easy to accomplish with air or oxygen

• Requires external heat source with steam

• Some carbon residue with steam

• Tar residue at gasification temperatures below

1300oC

• Sulfur, alkali metals, ammonia, and chloride

are problematic for downstream processing

Syngas Requirements

• Fuel gas

- Transportable without condensation of tar

components

- Clean burning

• Fuel cells or chemical synthesis

- Free of tar

- Free of catalyst poisons: sulfur gases, halides,

NH3, NOX, HCN, alkali and other metals

- Shifted to product-specific H2/CO ratio

Characteristics of Biomass

for Gasification

Characteristics of Biomass

for Gasification

SourceHHV, MJ/kg

(daf)Ash, % Sulfur Alkali metals Silica

Alfalfa stems 19.7 5.3 1.9 29.2 5.8

Wheat straw 19.2 7.0 4.4 27.3 55.3

Rice straw 18.6 18.7 1.2 13.3 74.7

Switchgrass 19.9 9.0 0.4 12.2 65.2

Bagasse 19.5 2.4 2.1 0.9 46.6

Corn stover 19.8 5.2

Fir 20.5 0.4 2.9 30.5 15.2

Hybrid poplar 19.5 2.7 2.0 9.8 5.9

Willow 19.9 1.7 1.8 16.0 2.4Source: Jenkins et al., Fuel Processing Technology,

1998

Status of Technology

Biomass

gasifiers are

available

commercially

At least five

commercial

installations in

US and Europe

Commercially available

and under development:

•tar capture/destruction

•acid gas capture

•metals capture

•chloride capture

Water gas shift

technology is proven

and commercially

availableAvailable technology:

•F-T hydrocarbons

•Methanol

•Methanol-to-gasoline

Under development

•ethanol synthesis

Separations

technology

is proven

and

commerciall

y available

Status of Technology Components

Recycle

Gasificatio

n

Product

Synthesis

Gas

Conditioning

Gas

CleaningSeparation

Products

Biomass

Biomass

Gasifying agent

Cyclone

Return

leg

Gasifier

Raw

syngas

Ash

Stationary bed

gasifier

Recirculating

twin bed

gasifier

Externally heated

steam reformerBlack liquor

Circulating

bed gasifier

Oxygen

Biomass

Raw

Syngas

Slag

Biomass

Steam

Exhaust

gas

Raw

syngas

Entrained

flow

gasifier

Typical Component

Concentrations in Syngas

Heat provision Autothermal Allothermal

Gasifying agent Air O2/steam Steam

H2, vol-% 11-16 23-28% 35-40

CO, vol-% 13-18 45-55% 22-25

CO2, vol-% 12-16 10-15% 20-25

CH4, vol-% 2-6 <1 9-11

N2, vol-% 45-60 <5 <1%

LHV, MJ/Nm3 4-6 10-12 12-14

Bacovsky, D., et al.. IEA Bioenergy Task 39, Report T39-P1b (July 2010).

Tar Characteristics

OH

O

O CH3

CH3

Syngas Cleaning

• Cleaning requirements: - tar & light organic <300 ppmv absorption,

reforming

- sulfur gases <0.1 ppmv adsorption,

absorption

- halides <10 ppbv adsorption

- NH3 <10 ppmv absorption

- CO2 <100 ppmv absorption

• Industrial syngas cleaning systems are

available

• Areas for improvement- tar reforming catalysts

-

Gasification Plants in

Operation

Biomass gasifiers - U.S. and Europe

ProviderOperating plants Under construction Planned

Synthesis Power Synthesis Power Synthesis Power

Andritz/Carbona comm. comm.

Chemrec AB pilot demo

Conzepte Technik

Umweltdemo (2008)

Cutec pilot (1990)

ECN pilot demo

Enerkem pilot (2003) demo comm.

Foster Wheeler demo (2009)comm (6),

pilot (2)comm. comm.

Karlsruhe Inst. Tech. pilot

Nexterra comm. (3) comm. (4)

Rentech/Clear Fuels comm. (3)

Repotec comm. demo

Thermochem Recovery comm. demo (2)

Uhde GmbHcomm.

pilot

Biomass gasifiers - U.S. and Europe

Summary