II3 GROUP l(b). TEERMAL PROCESSING TECHNOLOGIES

Main Participants:

Erik Rensfelt (S) Tony Bridgwater (UK)

(and as Group l(a)).

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STATUS AND OPPORTUNITIES FOR THERMOCHEMICAL PROCESSING OF REFUSE IN THE UK

A V Bridgwater Energy Research Group

Chemical Engineering Department Aston University

Birmingham B4 7ET

The realisation of energy from waste can be by thermochemical or bio-chemical processes. The range of thermochemical processes is summarised in Figure 1, in which the perceived advantage of gasification and pyrolysis is clear from the multiplicity of products derivable from gasification and pyrolysis compared to combustion from which the only direct product is heat which cannot be stored and must therefore be used immediately.

COMBUSTION vs GASIFICATION / PYROLYSIS

BIOMASS or WASTE

GO M B USTlO N I I Char Fuel aas Liauid

/ / BURNER I

\\ ENGINE / /

EXPORT

Figure 1 OVERVIEW O f THERMAL PROCESSING TECHNOLOGIES

- 112 -

Presentation to IEA Workshop on MSW Processing

Cambridge, UK, June 26128,1988

STATUS AND OPPORTUNITIES FOR

THERMOCHEMICAL PROCESSING OF REFUSE IN

THE UK

A V Bridgwater

Energy Research Group Chemical Engineering Department

Aston University Birmingham B4 7ET

UK

- 1 1 1 -

While this simplistic viewpoint is interesting, few actual gasification or pyrolysis processes have been sucessfully commercialised. Reasons are multiple and complex, but are mostly due to the more complex technology, poor track record of installations, and ready availability of combustion technology which is perceived to be more reliable, easier to operate, and more widely available.

This paper summarises the range of technologies for thermochemical conversion of refuse/MSW, and relates them to recent, current, and planned UK research activities, which are listed in Table 1 for reference. Most of the information is presented in tabular or diagrammatic form for conciseness, which should be self explanatory. The contents are as follows: -

INTRODUCTION Figure 1 OVERVIEW OF THERMAL PROCESSING TECHNOLOGIES Table 1 THERMOCHEMICAL REFUSE CONVERSION ACTIVITIES IN THE UK Table 2 CLASSIFICATION OF THERMOCHEMICAL PROCESSES Table 3 THERMOCHEMICAL TECHNOLOGIES CHARACTERISTICS Table 4 PRIMARY PRODUCTS OF THERMOCHEMICALCONVERSION Table 5 PRIMARY AND SECONDARY PRODUCTS Figure 2 OVERVIEW OF THERMOCHEMICAL CONVERSION TECHNOLOGIES AND

PRODUCTS Table 6 THERMOCHEMICAL REACTOR TYPES Table 7 ANALYSIS OF CONVERSION ACTIVITIES 1983-1987 - Research to Commercial

GASIFICATION Table 8 GASIFICATION TYPES Table 9 GASIFIER CHARACTERISTICS

PYROLYSIS Table 10 MODES OF PYROLYSIS Table 11 PYROLYSIS REACTORS

APPLICATIONS Table 12 Table 13 CONTAMINANTS IN GAS Figure 3 Table 14

APPLICATIONS - Known Gasifiers and Pyrolyses (1 983-1985)

QUALITY REQUIREMENTS OF FUEL GAS PRODUCT QUALITY 8, APPLICATIONS

ECONOMICS Figure 4

Table 15 Figure 5

CAPITAL COST OF GASIFIERS AND PYROLYSERS COMPARED TO COMBUSTORS FUEL GAS PRODUCTION COSTS PYROLYSIS OIL PRODUCTION COST IN RELATION TO FUEL OIL PRICES NOW, AND PLUS 50%

CONCLUSIONS

- 113 -

INTRODUCTION

Table 1 THERMOCHEMICAL REFUSE CONVERSION ACTIVITIES IN THE UK

Institution Activity l&"du

U M IST/Manoil liquefaction of refuse 1978 ongoing components

Foster Wheeler Power Products fluid bed gasification of fluff 1981 in abeyance and pellets for gas and power

Aston University database of research and 1986 ongoing commercial activities worldwide

Warren Spring Laboratory pyrolysis of pellets 1986 completed Aston University technoeconomic 1987 ongoing

assessment of processes for liquid fuel production

Leeds University pyrolysis of components 1988 about to start and pellets for liquids

Table 2 CLASSIFICATION OF THERMOCHEMICAL PROCESSES

PYROLYSIS Energy provided indirectly or directly Moderate temperature (400 - 800°C) Low pressure (up to 5 bar) Relatively low gas yields (MHV gas) with high liquid yields and

carbonaceous residues Fast Pyrolysis ) As pyrolysis, but very short residence time, Flash Pyrolysis ) high reaction rates and high yields of liquid

GASIFICATION Energy provided internally by exothermic reaction of part of the feed High temperature (800 - 1400°C) Low to moderate pressure (up to 30 bar) All carbon converted to gas (LHV or MHV), leaving only an inert

Low temperatures (250 - 400°C) High pressures (up to 500 bar) High yields of "oil"

residue (ash) LIQUEFACTION Energy provided indirectly

Table 3 THERMOCHEMICAL TECHNOLOGIES CHARACTERISTICS

FEEDSTOCK Feed size Moisture PARAMETERS Temperature, "C Pressure, bar Max. throughput, t/h PRODUCTS Gas yield

Liquid yield

Solid yield

HV, M J " 3

HV, MJ/kg

HV, MJ/kg

mixed 50%

1000-1 400 < 20 20

100-250 5-1 5 c3 20 nil

Slow Flash

any Small low very low

500-700 500-900 0.1 -1 1 5 0.05

c 40 c 70 5-1 0 10-20 c 30 < 70 20 20 30 c 20 30 30

Liauefact ion

small very low

250-350 100-200

0.1

20 2-6 c 50

25 c 25

30

- 114 -

Table 4 PRIMARY PRODUCTS OF THERMOCHEMICALCONVERSION

Product Content S Q u e

GAS fuel gas, CO, H2, C02, CH4, gasification, synthesis gas N2 (from air), C2+ pyrolysis

LIQUID tar or "oil" insoluble oxygenates pyrolysis, (high boiling point) liquefaction

WATER waste water soluble oxygenates gasification, (low boiling point) pyrolysis,

& liquefaction

CHAR charcoal pyrolysis, liquefaction

Table 5

LHV gas

MHV gas

Liquid

Char

"Oil"

PRIMARY AND SECONDARY PRODUCTS

Fuel gas 0.1-5 Engine Power Electricity 0.1-5 Turbine Power CHP 1 -10 Conversion Ammonia Conversion Fertilisers 2 -20+

Fuel gas 1-5 Engine Power Electricity 1-5 Turbine Power CHP 1-10 Conversion Methane SNG 1 o+ Conversion Methanol Refine Methanol 1 o+ Conversion Methanol Conversion Gasoline 1 o+ Conversion Hydrocarbons Refine Gasoline etc 1 o+ Hydrotreat Intermediate Refine Gasoline etc 5-20+ Zeolites Hydrocarbons Refine Gasoline etc 5-20+

(briquetting) Solid fuel 0.2-5

Hydrotreat Hydrocarbons Refine Gasoline etc 2-20+

- 115 -

I THERMOCHEMICAL CONVERSION TECHNOLOGIES and PRODUCTS

Y nderlined materials are useful products m

Figure 2 OVERVIEW OF THERMOCHEMICAL CONVERSION TECHNOLOGIES AND PRODUCTS

Table 6 THERMOCHEMICAL REACTOR TYPES

Fixed bed Gas mot ion Solid motion Alternative desc riotion Downdraft down down co-cu rre nt Updraft down UP counter-current Cross current horizontally down cross draft Stirred bed downdraft or updraft Two stage as Updraft

Fluid bed Gas velocity Fluid medium Single low stays in reactor Fast medium elutriated and recycled Circulating high elutriated and recycled. Also twin Entrained very high usually none Twin low - medium recirculated

Other Moving bed Multiple hearth Horizontal moving bed Sloping hearth Screw / auger kiln. Rotary kiln Cyclonic reactor Vortex reactor

- 116 -

Table 7 ANALYSIS OF CONVERSION ACTIVITIES WORLDWIDE 1983-1987 - Research to Commercial

BY ACTIVITY

AREA OF ACTIVITY Number Gasification 239 Pyrolysis 159 Liquefaction 56 Zeolites and hydrotreating 33 MSW 20 System studies 51 TOTAL 558

(Some activities are duplicated)

BY REGION

North America Europe Rest of the World

USA Canada France West Germany UK bry Japan Belgium Finland Sweden India Brazil Netherlands Austria New Zealand Spain South Africa Australia Greece Chile

BY COUNTRY

160 53 48 43 32 31 28 20 17 16 12 11 10 7 5 5 4 3 3 2

Korea Denmark

Indonesia Po rtu g a I USSR Algeria China East Germany French West lndies Ghana Iraq Malaysia Romania Switzerland Taiwan Thailand Turkey Venezuela Others

Egypt

213 237

82 499

2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 ?

- 117 -

GASIFICATION

Table 8 GASIFICATION MODES

Air gasification

Oxygen gasification

Steam gasification

Hydrogasification

Reagents

Catalysts

Energy efficiencies

air oxidises part of feed to generate heat to gasify the rest product is LHV fuel gas with up to 60% nitrogen, 4-6 MJ/Nm3 temperature 800-1 000°C Usually 1 bar pressure air separation required gives a nitrogen free MHV product higher temperatures and oxygen require better control, and

temperature 1200-1400OC Up to 20 bar pressure Better quality gas, 10-1 5 MJ/"3, lower tars energy supplied by steam reforming reaction which is only

steam also added as thermal moderator in oxygen gasification. ocurs to a certain extent in all thermal processing. twin bed: i pyrolysis ii char combustion temperature 700-9OO0C up to 20 bar pressure better quality gas, 15-20 MJ/Nm3 (400-600 Btu/scf) higher tars from pyrolysis gasification or pyrolysis in a high hydrogen or carbon monoxide environment discourages formation of oxygen rich compounds may be added such as carbon dioxide to improve carbon

conversion efficiency; or methane which suppresses methane formation and/or gives high yields of hydrocarbons.

added to non-equilibrium systems to encourage advantageous reactions eg nickel for methane formation and calciunzlmagnesium for tar cracking.

70-75% to clean cold fuel gas, up to 90% to hot raw gas

safety

exothermic at high pressures, typically above 7 bars

Table 9 GASIFIER CHARACTERISTICS

Gasification Downdraft, air Downdraft, oxygen Updraft, air Updraft, oxygen Single fluid bed, air Single fluid bed, oxygen Fast fluid bed, air Fast fluid bed, oxygen Twin fluid bed Cross flow, air Horizontal moving bed, air Rotary kiln, air Multiple hearth Single fluid bed, steam

Secondary processing Pyrolysis (all types)

0.1-0.7 0.1-0.7 0.2-10 0.2-10 0.3-1 5 2-1 0 2-3

0.3-10 1-10 0.5-2 0.5-5 1-20 2-20 1-10

1-8

Number

20 2 17 1

16 5 2 1 6 1 1 1 2 1 5 13

good good poor poor

fair fair

poor poor poor

very poor poor

fair fair

poor very good very poor

Table 10

Carbonisat ion Conventional Fast Flash - liquid Flash-- Uhra

Vacuum Hydropyrolysis Methanolysis

MODES OF PYROLYSIS

Residence Jieatinq m m

hours very low 5-30 mins low

0.5-5 secs fairly high <1 secs high <1 secs high

~ 0 . 5 secs very high

2-30 secs medium 4 0 secs high 4 . 5 secs high

TemDe ratu re. Maior F x Droduct

400 Solid 600 Gas, liquid & solid 65 0 Liquid

e650 Liquid >650 Gas 1000 Gas, chemicals

400 Liquid 4 0 0 Liquid 1050 Chemicals

Table 11 PYROLYSIS REACTORS

PILOT cyclonic reactor cyclonic reactor entrained bed multiple hearth DEMONSTRATION fluid bed fluid bed rotary kiln COMMERCIAL vertical retort horizontal moving bed horizontal moving bed cyclonic reactor vertical retort, batch reactor

Heatina metha

hot sand hot wall

combustion products combustion products

burning product gas partial gasification

burning product gas

burning product gas burning product gas combustion products burning product gas burning product gas

partial gasification

Ensyn SERl

GIT Lava1

Waterloo Alten

Kiener

American Carbon Pyrosol, AEI

Shirley Pyrotech

Shirley (current 3rd world)

APPLICATIONS

Table 12 APPLICATIONS OF KNOWN GASIFIERS AND PYROLYSERS (1 983-1 985) Oemonstrationand Commercial

Abblicatibn

Kiln Boiler Drying Metal processing Fuel gas Power Chemicals Otherlu nspecif ied TOTAL

11 3.2 40 11.7 17 4.9 3 0.9

81 23.6 110 32.1

4 1.2 77 22.4

343 1 OQ.0

1 033.3 730.5 51 1 .O 250.7

4 895.0 196.5 450.0

2 052.0 10 119.6

10.2 32.6 7.2 23.0 5.1 16.3 2.5 8.0

1.9 6.1 4.4 14.0

100.0 100.0

48.4

20.3

- 119 -

Table 13 CONTAMINANTS IN GAS

Water < 50% < 50%

Condensible organics acetic acid < 1% C 5% Immiscible organics tars < 5% < 25%

Non condensibles H2S, HCI < 1% c 1%

c 1000 ppm Ash 1000 ppm

Sand from fluid beds 1000 ppm 1000 ppm - Char 1000 ppm < 2”/0

~

CONTAMINANTS

TARS I None Very low Low Moderate High

PARTlCULATES I None Very low Low Moderate High

Figure 3 QUALITY REQUIREMENTS OF FUEL GAS

Table 14 PRODUCT QUALITY 81 APPLICATIONS

High High Updraft, crossflow

High Low Fast fluid bed,

Low High Pyrolysis Moderate Moderate Fluid bed

Low Low Downdraft,

Very low Very low Cleaning needed or cleaning needed

None None Cleaning needed

Direct firing when product contamination acceptable Direct firing when product contamination acceptable Direct firing, retrofitting Direct firing when product contamination acceptable Engine, CHP, retrofitting, boilers, drying

Direct firing when product contamination not acceptable Turbine, CHP, syngas

- 120 -

ECONOMICS

I

CAPITAL COSTS OF GASIFIERS AND COMPETING TECHNOLOGIES

10

Capita I cost

$1987 million

1

0.1

0.01 0.1

Combustion

Low- cost gasification

1 10 Biomass feedrate, daf t/h

Figure 4 CAPITAL COST OF GASIFIERS AND PYROLYSERS COMPARED TO COMBUSTORS

- 121 -

Table 15 FUEL GAS PRODUCTION COSTS

SCOPE Delivered prepared feed to cold clean gas including water wash 6000 h/y operation (i.e. 70% load factor) Simple fluid bed technology Gas costs are on a real basis, and averaged over the 10 y plant life Current interruptible natural gas price is f3.3/GJ. 75% gives a fuel gas priceof f2.4IGJ. costs underlined ' are those below the current market value of f2.4/GJ, and those marked

are not likely to be available on-site in sufficient quantities

COLD CLEAN GAS

FEEDSTOCK STRAW (78% conversion efficiency at 17% water) f22/t delivered ( f 2 M daf) f17R on-farm (f2011 daf)

3.2 2.7 24 23 2.8 G 3 z p T l . s

REFUSE-WET (71% conversion efficiency at 35% water: f 1 Ott raw refuse disposal credit zp 19

f5A raw refuse disposal credit 2.7 21 (Stt daf, shredded, screened, classified)

( f 1511 daf, shredded, screened, classified) REFUSE-DRY (78% conversion efficiency at 17% water) f 1 Oh raw refuse disposal credit 2.5 ZQ

( f 15lt daf shredded, screened, classified, dried)

WOOD (62% efficiency due to water at 50%) f 17tt delivered (f34/t daf) f13tt on-site (f26lt daf) f7.5n ( f is / t daf)

HOT RAW GAS

4.6 3.9 3.6 3.4 4.0 3.3 3.0* 2.8' 3.1 24 21 L.9

STRAW (90% conversion efficiency at 17% water) f2Bt delivered (f26lt daf) 2.7 23 f 1711 on-farm (f20/t daf) 24 lt9

REFUSE-WET (83% conversion efficiency at 35% water) f 1 OR raw refuse disposal credit Lz I 2 f S R raw refuse disposal credit

( f S R daf, shredded, screened, classified)

(f 15tt daf, shredded, screened, classified) iL3

REFUSE-DRY (90% conversion efficiency at 17% water) f 1 OR raw refuse disposal credit 21

( f l5t t daf, shredded, screened, classified, dried)

WOOD (72% efficiency due to water at 50%) f 17tt delivered ( f 34/t daf) f13tt on-site (f26/t daf) f7Sn ( f 1 M daf)

3.8 3.4 3.3 2.7 2.5 ZQ

21 u

3.1 2 x -tB

ea 13

14

2.9 231 Id&

- 122 -

Pyrolysis Liquid Production Cost v Feed Cost

Product I I I I

300

200

1 00

0 0 10 20 30 40 50 60

Feed cost, ECUh

Capacity

1 t h

2th 3th 5 t h

20 th 100th

Figure 5 PYROLYSIS OIL PRODUCTION COST IN RELATION TO FUEL OIL PRICES NOW, AND PLUS 50% Current fuel oil prices are believed to be around 125 ECU/t, which is equivalent to 80 ECU/t of pyrolysis oil on an equivalent heating value basis of 25 MJ/kg. This is shown as the lighter shaded part of Figure 5 which identifies the plant capacities and feed costs that can be justified at this price level. The larger darker shaded area represents an oil price 50% higher, showing the sensitivity of production costs to scale ofoperation and feed cost.

CONCLUSIONS Technology

Short term opportunities

Long term opportunities Limitations Resources

Demand Problems

OUTLOOK

established, versati le, some unresolved problems wastes and residues as feeds, fuel gas product in direct firing and retrofitting liquid fuel product (crude oxygenates), power transport fuels & chemicals in developing countries current low energy prices no shortage of wastes and residues, energy crops in longer term assured for all products except heat poor match between market and technology, current energy price levels, financing implementation for developing countries, training needs must be met in developing countries, substantial worldwide market opportunity, technology needs matching to market needs.

- 123 -

l ( b ) . DISCUSSXON

Two projects were recomended by Working Group l(b) as having potential for international co-operation:

(a) 1 (high priority)

A number of potential processes exist for thermochemical conversion of MSW but these are currently at varying degrees of development. The aims ~~

of this project would be to provide a critical assessment of the technical and economic performance of projects undertaken to date.

would involve an initial literature review followed by visits to key sites. A comprehensive report would be compiled for each technology,

with emphasis being placed on the problems which have arisen, the responses made to these problems (and where appropriate either the solutions found or reasons given for abandonment) and the criteria used to judge success or failure.

This

The project could be organised by co-ordinating national activities in

each participating country or having a single co-funded activity. Costs

were estimated at US $80,000 spread over two years, although the contribution from IEA funds would be limited to costs of organisation and

co-ordination.

Principal Contacts: Tony Bridgwater (UK) , Erik Rensfelt (S) .

(b) ASSESSMENT OF THE FUNDAMENTAL PROBLEMS OF THERMOCHEMICAL PROCESSING OF MSW WITH RESPECT TO THE ENVIRONMENT (high priority)

Thermochemical processing of MSW can lead to special problems with both gaseous and aqueous emissions together with problems associated with the need to dispose of solid residues. It was considered important that such problems be clearly identified and communicated during the early stages

of R&D.

establishment of a working group comprising one member from each It was suggested that this proposal could best be handled by the

participating country. identified and tasks allocated to each member. held to update and exchange information and report on RCD requirements.

Specific areas of concern and interest would be

Regular meetings would be

A budget of US $7,000 per participating country, plus US $10,000 for reporting, spread over a period of two years, was considered adequate.

Principal Contacts: Tony Bridgwater (UK) , Erik Rensfelt (S) . - 124 -

II.3 GROUP 2. BASIC COMBUSTION AND RELATED RESEARCH

Main Participants:

Christopher Rappe (S) ‘Mike Woodfield (UK) David Hay (C) Frank Karasek (C) Bill Livingstone (UK) Terry Rampling (UK) Mark Kibblewhite (UK)

- 125 -