pilot plant experiences with fluidised bed gasification of orujillo...

University of Seville. 19th FBC Conference

Pilot plant experiences with fluidised bed gasification of orujillo and MBM

19th FBC Conference, Session B323 May 2006

Vienna, Austria

Gómez-Barea A., Campoy M., Ollero P., Fernández-Pereira C.Chemical and Environmental Department

University of Seville Spain

19th FBC ConferenceThe International Conference on Fluidized Bed Combustion

May 21 – 24, 2006, Vienna, Austria


Content

1. Introduction2. Objectives3. Experimental4. Analysis of pilot plant performance 5. Ash characterisation6. Methods for fly-ash utilisation 7. Utilisation options for the produced fly ash8. Conclusions


1. Introduction

• Atmospheric air gasification of biomass and waste in a BFB reactor is a simple and cheap process

• Classical analysis is focussed on the LHV and quality of the producer gas.

• A key factor limiting gasification is fly ash quality, especially the carbon content of the ash.

• Fly ash from the gasification of biomass differs considerable from conventional combustion ash1. unburned carbon is much higher, typically 10–60% w.w.2. It contains PAH and in case of waste gasification

chlorine and heavy metals. • Issues 1 and 2 make the management of gasification fly ash

a challenging task – Difficult recycle or utilisation

1. Introduction


Introduction (cont.)

• An increase in carbon conversion results in:– higher efficiency direct positive influence on power

production efficiency– higher possibility to recycle or use of ashes as raw

material in other processes. • An essential part of BFB gasification is to optimise

operation to improve ash quality (especially to reduce carbon content)

• This will facilitate the development of sustainable economical methods for ash management

1. Introduction


Objectives of this work

• Assess the impact of:– operating conditions – bed material and additives

on the gas quality and the ash quality. • Discuss the impact of the ash quality on:

– potential utilisation options of the ashes– economics of their future utilisation

• Present experience acquired by gasifying – two fuels: orujillo and MBM – in a 150 kWth BFB pilot plant

2. Objectives


3. Experimental. Materials

• Fuels– orujillo – MBM

• Bed materials and additives– silica sand – ofite – Lime– Limestone

3. Experimental


Test facility

3. Experimental

Gasifier

Screw feederHigh-speed screw

Hoppers

Flexible

27 kWe Oven

After Burner

Ashtray

Preheater

Outlet gas

Scrubber

Cyclones

Filters

To Water Treatment

Water

To Stack

Propane

Isolation Blanket

Preheater

Water

Steam generator

Overflow


Technical and operating data of pilot plant facility

3. Experimental

Inside bed diameter 0.15 m Bed height 1.7 m Inside freeboard diameter 0.25 m Freeboard height 2.5 m Fluidisation velocity 0.8 – 1.4 m/s Bed material Ofite, limestone Fuel Orujillo, MBM Fuel feed rate 6 – 35 kg/h Gasification agent Air Operating temperature 700 – 850ºC Operating pressure Atmospheric Fluidisation regime Bubbling Maximum thermal capacity 150 kWth


4. Analysis of pilot plant performance


• Orujillo tests: – Severe sintering using silica sand > 750ºC No valid

data– Ofite solved sintering up to 830 ºC– Good quality of producer gas (LHV=5 MJ/Nm3)– Optimum for gasification efficiency at ER=0.25 (0.17 ,

0.31)– Carbon conversion 90% – High carbon content and Chlorine in ash (also

Chromium)


Optimisation with orujillo

70.0

72.0

74.0

76.0

78.0

80.0

82.0

84.0

86.0

88.0

0.16 0.18 0.20 0.22 0.24 0.26 0.28 0.30 0.32ER

Car

bon

conv

ersi

on (%

)

45.0

50.0

55.0

60.0

65.0

70.0

0.16 0.18 0.20 0.22 0.24 0.26 0.28 0.30 0.32

ER

Gas

ifica

tion

effic

ienc

y

– Optimisation:• Constrained by sintering• Aceptable carbon conversion with maximun

efficiency4. Analysis of pilot plant performance




• MBM tests: – Pelletisation was necessary (feeding problems)– Poor gas quality (LHV<3 MJ/Nm3)– Very high carbon conversion (~98%)– Low carbon content and volume of ash– Additives improve gas quality but little effect

upon ash quality


Synergy of the fuels

• Poor gas quality for MBM due to diluting effect (very low O/C content)

• Good synergy of the two fuels: Blends of orujillo + MBM – acceptable O/C– acceptable flowing properties without pelletisation

0.50

1.00

1.50

2.00

2.50

3.00

0.15 0.2 0.25 0.3 0.35

ER

AR (N

m3/

kg)

Tyre Coal MBMWood

Straw

Rice huskOrujillo

0.50

1.00

1.50

2.00

2.50

3.00

0.15 0.2 0.25 0.3 0.35

ER

AR (N

m3/

kg)

Tyre Coal MBMWood

Straw

Rice huskOrujillo



5. Ash characterisation


Basic ash characterisation– Physical analysis: density and PSD– Elemental and ultimate analysis

Test T bed (ºC) ER %C Overflow %C Cyclone 1 %C Cyclone 2 1 700 0.17 37.54 20.18 22.08 2 740 0.20 20.77 12.00 15.24 3 750 0.22 37.44 15.78 18.08 4 760 0.23 29.85 14.51 19.51 5 785 0.24 19.85 14.03 15.86 6 780 0.29 8.24 11.58 9.66 7 820 0.31 5.33 9.09 12.04

5

7

9

11

13

15

17

19

21

650 700 750 800 850

T (ºC)

% C

in a

shes

Cyclone 1


Further characterisation of ashes

• Further characterisation (necessary for the screening of existing utilisation options )– Trace elements (ASTM D-3683)– Ashes leachability

• DIN 38414 • TCLP (USEPA 1311)• compliance batch leaching test EN 12457/1-4 • Up-flow percolation test EN 14405 (colum test)

– Analysis of Eluates (metals) – Thermal analysis (TGA, DSC, DTA)– Other: PAH, and specific for a given route being tested



6. Methods for fly-ash utilisation

Three main utilisation categories can be identified 1. Use as fuel:

– co-firing in coal/biomass-fired power plants; – firing in a dedicated boiler; – replacement fuel in smelters/incinerators – firing in cement kiln;

2. Use in construction: • Fine applications: cement replacement in concrete. • Less stringent applications:

– soil stabilization– road base – structural fill (filler in asphalt, asphalt-like products)– lightweight bricks

3. Use in agriculture: directly as fertilizer or as soil improver.

6. Methods for fly-ash utilisation


7. Utilisation options for the produced fly ash

• High carbon content of ashes (especially orujillo) limits applications

• Construction– Fine applications in fully violated (carbon content and Cl)– Other: plausible

• Fertiliser: – MBM: ash often considered attractive for fertilisers

• the high PAH content found in this work make difficult this application.

• low solubility of P and Ca make the attractiveness of this routedoubtful (for common soils).

• TCLP tests showed acceptable solubility for P and Ca acid soils – Orujillo: soil amendment (PAH limit)– Most probably pretreatment necessary



Utilisation options for the produced fly ash

• Application as fuel– Cl, TOC and PSD limits– Co-combustion in existing boilers reasonable but plant

owner refused these ashes– Fuel in cement kilns

• Mixed with the fuel (in the burners). • Other options are limited by:

– TOC (with the raw material) – PSD (in the combustion chamber)

– Pelletisation of ash (depends of the actual LHV). • Non feasible for this ash but acceptable for full-scale ashes like

Ammer and Lahti full-scale gasifies (15-20 MJ/kg)



Further options for the produced fly ash

• We have investigated more advanced options with promising results– Stabilisation/Solidification (S/S)– Use in lightweight construction boards

• low-cost moulding and curing methods• ash percentages up to 60%w/w• Gypsum and additives (vermiculite and fibre)

– Use in bricks manufacture• Ash content in bricks up to 20%• Bricks with special insulating thermal and acoustic properties



8. Conclusions

• We made a technical assessment of MBM and orujillo by long-term test trials in FB at pilot scale

• Orujillo is a good feedstock for FB gasification while MBM produces poor gas

• High carbon conversion achieved with MBM while orujillo is severe limited by sintering

• Optimisation of orujillo was optimised to achivelong enough tests

• Synergy of fuels seems rather attractive: under current investigation

8. Conclusions


8. Conclusions (cont.)

• Ash limited by chlorine (orujillo) and carbon content (both)

• In general, direct ash utilisation is difficult• Fertiliser seems reasonable option with pretreatment

(oxidation and/or leaching) • Fuel in cement kilns mixed with the fuel (in the

burners) very promising without pretreatment (prices have to compete with other fuels)

• New utilisation routes have been investigated: bricks with thermal and acoustic properties and lightweight construction boards. Promising results but they are still under further testing

8. Conclusions


Thank you for your attention

Questions are most welcome


Pilot plant experiences with fluidised bed gasification of orujillo and MBM

19th FBC Conference, Session B323 May 2006

Vienna, Austria

Gómez-Barea A., Campoy M., Ollero P., Fernández-Pereira C.Chemical and Environmental Department

University of Seville Spain

19th FBC ConferenceThe International Conference on Fluidized Bed Combustion

May 21 – 24, 2006, Vienna, Austria

pilot plant experiences with fluidised bed gasification of orujillo...

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