environmentally responsible methods to mitigate the use ...€¦ · boiler thermal efficiency, ......

Professor Rosemary Falcon and Dr Samson Bada

DST-NRF SARChI Clean Coal Technology Research group

University of the Witwatersrand

ENVIRONMENTALLY RESPONSIBLE METHODS TO MITIGATE THE USE OF COAL IN THE

SUSTAINABLE ENERGY MIX.

1

CONTENTS

1. STRATEGIC CONTEXT OF COAL

2. CHALLENGES TO THE USE OF COAL

3. OPTIONS FOR THE ENVIRONMENTALLY RESPONSIBLE USE OF COAL

4. CASE STUDIES IN SOUTH AFRICA

5. COMPARATIVE COSTS AND EMISSIONS

6. CONCLUSIONS

2

1. GLOBAL AND NATIONAL STRATEGIC CONTEXT OF COAL

GLOBAL CONTEXTCFBC Project

addresses the UN’S SDGs for a low

carbon economy

SOCIO-ECONOMIC CONTEXT

Modern Coal Developments • Will improve environmental, economic and social benefits and

quality of life for people• will create a high level skills and expertise required for the technology

TECHNOLOGICAL CONTEXT

Modern Coal Developments provide • Cleaner utilisation technologies• Have numerous benefits over old• Are commercially proven abroad• Can be applied to RSA coals and

alternative fuels

DST CONTEXTaligns with the DST’s

Programme 2+ Programme 3+ Programme 4

NATIONAL CONTEXTaligns with NDP’s

3 Phases of Innovation

REGIONAL CONTEXTaligns with projects

in Botswana, Zimbabwe and Mozambique

3

Ref: POLICY ADJUSTED IRP 2010

4

The size and mix of the South African power generation capacity pie – 2010 to 2030

1. NATIONAL CONTEXT OF COAL – 1 – IRP 2010

Hydrocarbons

57%

Hydrocarbons 86%

2010 2030

Discards51.8 Mt

Electricity120.8 Mt

Exports64.0 Mt

5

LOW CARBON ECONOMY IN SA - 1IRP2010 - SA’S Integrated Resource Plan 2010

The Role of Coal going forward....

The role of coal (% in mix)

86%.......57%


6

LOW CARBON ECONOMY IN SA - 2IRP2010 - SA’S Integrated Resource Plan 2010

The Role of Coal going forward....

The role of coal (MW)

86%.................57%


South Africa is the 7th largest producer of coal in the world

7th largest exporter of coal

Major supplier to the Middle East, India and Far East, with some to EU and Africa

Coal in SA accounts for Highest foreign exchange earnings in the country each year from 2011 (R50

Billion in 2017)

Total coal sales local and export generated R120 billion 2017.

Largest mining income earner, beating gold, platinum, diamonds

>91% of SA energy production, 81% of the regions’ energy

>100% of carbon reductants in the metallurgical industry

>33% of liquid fuels - petrol, diesel and other requirements

>200 major chemicals for 1000s of carbon-based products

Socio-economic factors related to coal Over 255 000 direct employees in coal mining, power generation, Sasol, metallurgical and over 6 000

coal-fired manufacturing industries. More than 4 times employed in related service industries or are dependents. Supports most major towns in Mpumalanga and Limpopo, and some in KwaZulu Natal

1. ECONOMIC CONTEXT OF COAL – 4

7

CONTENTS






6. CONCLUSIONS

8

0 1 000 2 000 3 000 4 000 5 000 6 000 7 000

China

USA

Russia

India

Japan

Germany

Canada

UK

Iran

Korea

Italy

Mexico

Australia

Saudi Arabia

Indonesia

France

Brazil

South Africa

Spain

Ukraine

Million tons CO2

SA is responsible for 1.1% of total global CO2 emissions,

but South Africa has committed to reducing its emissions

by 35% and 42% within the next 8 years (2025)

CO2 EMISSIONS FROM SOUTH AFRICA

Source IEA - Top 20 CO2 Country emitters, 2008

9

MULTIPLE TYPES OF COAL-FIRED BOILERS

6 000 INDUSTRIAL BOILERS for heat and power - Travelling grate, Shell, Water tube, Fluidised bed, Kilns, etc.

14 ESKOM POWER STATIONS for power generation –pulverised coal.

10

CO2 EMISSIONS IN SA

Total of Point Source Emissions of CO2 >1 Mt/A Plant

313 Mt/a

CO2 concentration Mt CO2/a

Coal to Liquids 85% 21,7

Power Generation 8-12% 224,6

Other industries 8-30% 31,8

11

2. CHALLENGES TO THE USE OF COAL IN SOUTH AFRICAFOR ELECRICITY PRODUCTION - 1

AIR QUALITY AND GREENHOUSE GAS EMISSIONS

12

➢ At the 2009 UN Climate Change talks, South Africa undertook to reduce the country’s CO2 emissions trajectory by 34% by 2020, and 42% by 2025, subject to adequate financial and technical support.

➢ Challenges to meet this level of reduction: ➢ High relative costs of abatement (technology +/-equal to new boilers)

➢ Considerable water requirements

➢ South Africa has little or no suitable geology to store CO2 - less that 1,5% on land; in excess of 1 000 kms to transport CO2 the nearest off-shore gas fields.

➢ South Africa plans to introduce Carbon Tax in 2018 to ensure compliance in CO2 reduction, with the following further challenges: ➢ Carbon Tax may lead to the demise of many major, minor and

potential industrial developments in the country

CONTENTS



3. OPTIONS FOR THE ENVIRONMENTALLY RESPONSIBLEUSE OF COAL



6. CONCLUSIONS

13

HIGH EFFICIENCY AND LOW EMISSIONSHELE PROGRAMME

14Source IEA CCC

Efficiency gains using

today’s technology can cut

CO2

emissions by 33%

CCS technology can produce 50% loss

but leads to efficiency loss of

7-12% points

1. INCREASED EFFICIENCY of coal combustion

2. CO-FIRING (burning coal with Carbon-neutral renewables -biomass)

3. CO-GENERATION (use of unused excess heat for additional power)

4. CARBON CAPTURE AND STORAGE (CCS)

5. CARBON CAPTURE AND UTILISATION OF CO2 (CCU)

METHODS TO MITIGATE CO2 – 1

15

1. INCREASED EFFICIENCY OF COAL COMBUSTION through:(i) BENEFICIATION AND USE OF HIGHER GRADE COALS

Coal Mines do beneficiate in South Africa (beneficiated products for export) Less coal per unit heat produced = less CO2 per unit coal produced

(ii) ADAPTATION OF BOILER PLANT TO MATCH THE GRADES OF COAL/VVSubcritical Pulverised Coal PC boilers e.g. Lethabo, Duvha, etc

(iii) ADVANCED HIGHER PRESSURE - HIGH TEMPERATURE PLANT➢ Supercritical PC Boilers – None in SA

➢ Ultra Supercritical Boilers – None in SA

➢ Advanced Supercritical Boilers – Medupi and Kusile PSs

➢ Integrated Gasification Combined Cycle - None in SA, only demonstration abroad

➢ Use of Fluidised bed power generating technologies - None in SA

2. CO-FIRING*

Burning Carbon-neutral renewables (biomass)with coal in

Pulverised and Fluidised Bed power generating technologies


* Case studies in South Africa to follow 16

3. CO-GENERATION

Use of excess heat from existing processes to supplement power production. Implementation is on-going in South Africa

4. CARBON CAPTURE AND STORAGE (CCS)Numerous capture mechanisms and storage sites are under reviewSouth Africa has limited to negligible on land geological storage capacity

5. CARBON CAPTURE AND UTILISATION OF CO2 (CCU)Use of CO2 streams / flue gases from coal-fired stacks for:

• Enhanced oil, natural gas and mine methane recovery

• Manufacture of advanced carbon materials e.g. carbon nanotube manufacture,

• Heating and advanced power generation

Research is on-going in South Africa


17

CONTENTS

1. STRATEGIC CONTECT OF COAL


3. OPTIONS FOR THE ENVIRONMENTALLY RESPONSIBLE USEOF COAL


4.1 - TECHNOLOGY – CIRCULATING FLUIDISED BED COMBUSTION (CFBC)

4.2 - FEEDSTOCK – COAL CO-FIRED WITH BIOMASS


6. CONCLUSIONS

18

Size of FB power plants:

➢ Bubbling Fluidised bed (BFB) boilers – <60 MWe

➢ Circulating Fluidised bed (CFB) boilers – 60-550 MWe

❖CFB is the preferred technology for larger scale power

production.

❖CFBC is highly successful internationally - EU, USA, India, China and

many Far Eastern countries.

❖CFBC is considered to be one of the most sustainable Clean

Coal Technology solutions for the following reasons:

❖Most efficient method to address escalating environmental constraints

❖Tolerates wide fuel flexibility and quality variation

4.1 – TECHNOLOGY:FLUIDISED BED (FB) BOILER TECHNOLOGY

19

Pulverised coal (PC) technology versus Circulating Fluidised Bed technology

PC

20

Pilot PlantOriental Chem

General Motors

Tri State

Vaskalouden

Nova Scotia

Turow 1

JEA

0

100

200

300

400

500

600

700

800

1979 1981 1984 1986 1987 1990 1993 1998 2001 2009 2015

MWe

Unit Start-up Year

CFB Technology Evolution

Lagisza

Samcheok

Longest Running Largest Petcoke CFB

2 x 300 MWe

Longest Running Supercritical CFB

1 x 460 MWe

1st Ultra Supercritical CFB

4 x 550 MWe

World CFB MarketOrders Over 2005-2014 Period

21

70%

30%

Amec FW Others

CFB over 200 MW All CFB

46%54%

100s of CFBC installations in OECD and NON-OECD countries

EXPANSION OF CFBC TECHNOLOGY STATUS WORLDWIDE

Ref: R Giglio, Amec FW, PCC 2016

Łagisza, Poland 460 MWe

supercritical CFB power plant

Fuel Coal Steam flow (SH/RH), kg/s 360/313Steam pressure (SH/RH), MPa 27.5/5.0Steam temperature (SH/RH), ºC 565/580Feed water temperature, ºC 290Boiler thermal efficiency, % 94.5Electrical output, MW

gross 460.0net 438.9

Plant thermal efficiency, %gross 45.3net 43.3

Połaniec, Poland 205 MWe

supercritical CFB power plant

Fuel: Wood residue, agro biomassLHV: 10.5 MJ/kgMoisture (AR): 35.9%Ash yield (DB) 2.8%Boiler efficiency (LHV): 91.0%Steam flow (SH/RH): 158.3/135.1 kg/sSteam pressure (SH/RH): 127.5/19.5 bar(a)Steam temperature (SH/RH): 535/535°CFeed water temperature: 242°C

Reported Performance data (dry 6% O2 /50% MCR)NOx <150 mg/m3

n

SO2 <150 mg/m3n

CO <50 mg/m3n

Particulate matter <20 mg/m3n

The power station meets the EU emission requirements

Emissions mg/m3n(6%)2 dry

SO2 200NOx 200Particulates 30

22

Samcheok Green 550 MWe Power plant, South Korea

The world most advance ultra-supercritical CFB Commercial operation 2015

The power station meets the stringent emission values stated below

Fuel: Indonesian coal and biomassBoilers: 4 × 550 MWe CFBNet plant efficiency (LHV): 42.4%Steam flow (SH/RH): 1573/1282 t/hSteam pressure (SH/RH): 257/53 bar(g)Steam temperature (SH/RH): 603/603°CFeed water temperature: 297°C

23

FBC

Particle Size 1-5cm

Operating

temperatures

<900oC

Burnout time As long as needed

SOx sorbentDolomite+ & Limestone*

Combustion In-bed

Fuel Coal / flexible fuels

Variable qualities

REASONS FOR REDUCED GHG EMISSIONS (SOx AND NOx)

<900oC - Prevents NOx formation

Prevents ash slagging

* Limestone and +Dolomite -

Capture SOx in combustion bedNB: This precludes the need for Flu Gas Desulphurisation (FGD)

24

EXAMPLES OF SELF-SCRUBBED / SELF SOx-REDUCING COALS IN FBC TEST FACILITIES – SOUTH AFRICAN EXPERIENCE

0

10

20

30

40

50

60

70

80

1 2 3 4 5 6 7 8 9 10 11 12 13

% S

elf

scru

bb

ed b

lue

+ A

sh%

bro

wn

Coal samples with increasing percentages of self scrubbed SOx

% SELF SCRUBBED ASH % TOTAL S %

Source: R Taole PhD - 2018

Ash % – 24% to 63% adSOx % self-removed – 37% to 75%

25

CONTENTS



3. OPTIONS FOR THE ENVIRONMENTALLY RESPONSIBLE USEOF COAL


4.1 - TECHNOLOGY – CIRCULATING FLUIDISED BED COMBUSTION (CFBC)

4.2 - FEEDSTOCK – COAL CO-FIRED WITH BIOMASS


6. CONCLUSIONS

26

PEAT

- PLY -

WOOD

SEWAGE

SLUDGE

BIO &

FIBER

SLUDGE

&

S

ANTRACITE

WOOD BIOMASS

DEMOLITIONWOOD

CHIP-BOARD-

POLYOLEFINPLASTICS

(PE, PP, PC..)

COLOREDOR

PRINTEDPLASTICS,

CLEAN

COLOREDOR

PRINTEDMIXED

PLASTICS

RDF

CONSUMER REF II - III

MIXEDPLASTICS

PAPER &WOOD

PETROLEUM COKE

DEINKINGSLUDGE

SEWAGESLUDGE

REFPELLETS

WOOD &PLASTICS

REF ICOMMERCIAL

&INDUSTRIAL

PEAT W/HIGH

Ca, Cl, Br

BITUMINOUSCOAL

ANTRACITECOAL

BIO &FIBER

SLUDGE

BROWN COAL,LIGNITE

PLY-WOOD

WASTECOAL

OILSHALE

PC Fuel

Combustion difficulty

BARK

CFB Fuel = all fuels

27

CFB provides the widest fuel flexibility in a single boiler design

Source: R Giglio, Amec FW, PCC 2016

He

atin

g V

alu

e in

MJ/

kg

35

20

10

5

0

COMPARISON OF FUEL FORMS FOR PC AND CFBC BOILERS

Renewable Fuels

COALGAE

CO-FIRING OF BIOMASS WITH COAL FOR CO2 REDUCTION

The biomass of choice is Bamboo for the following reasons:

• HIGH GROWTH RATE - 30.48 cm per day under ideal conditions

• RENEWABLE - produces new shoots annually (no replanting)

• FULLY MATURES - in 4-6 years (Pine trees take up to 20-25 years)

• HARVESTS - every 2/3 years,

• PRODUCES - 10-30% annual yield compared to 2-5% trees, shrubs, grasses• or

• Up to 60 tons/hectare of biomass annually compared to• - 20 tons/hectare from trees,• - 1-2 tons /hectare from cotton trees• - 4-6 tons /hectare Macadamia nuts

• CAN SEQUESTRATE UP TO 15 TONS OF CO2/HECTARE (NEW FOREST), AND

UP TO 62 TONS OF CO2/HECTARE (OLDER FOREST) –

i.e. it is a valuable CO2 sequestering plant 28

April 4, 2011

January 13, 2012

1st Harvest after 2 years = March 14, 2013

Source: Desa Harjobinangun, and Pakem Sleman, Yogyakarta 2014

EXAMPLE:

Growth Factors of

Bamboo

29

CURRENT RESEARCH ON BIOMASS (BAMBOO SPP suitable for the SA Highveld)

Ultimate analysis of different Bamboo Species and coal

Physicochemical properties of Bamboo Species and coalOBSERVATIONS: Compared to coal, Bamboo species have:

Calorific values (heat content)comparable or equal to coal.

Ash contents considerably lower than

coal

Volatile matter considerably higher

than coal

Nitrogen contents considerably lower

than that of coal

Sulphur contents lower than coal (B.

balcooa has the lowest sulpur content(0.017%ad).

The firing of the bamboo (aloneor co-fired with coal) can beexpected to generate lower NOxand SOx compared to coal - asproved by the UK’s Drax full scalebiomass burning power plantSource: Samson Bada, 2018

30

CO-FIRING COAL AND BAMBOO SPECIES - Case Study 1 Raw (Unheated) Bamboo with Coal (25% Ash)

Observations:(i) The coal combustion profile (solid black) shows peak burnout at the highest temperature (450oC )(ii) The DTG profile presents two different peaks for the bamboo(iii) The shoulders observed within 210 – 300 0C could be attributed to the decomposition of hemicellulose & some cellulose.(iv) At temperature >300 0C, lignin is being degraded.(v) The ignition of the bamboo occurs at the lower temp region(vi) The B. bambos has the highest peak/reactivity compared to all fuels in Fig 4b

DTG curves for coal, Dendrocalamus asper, Bambusa balcooa and Bambusa bambos

Peak combustion of Coal

Peak combustion of Three Bamboo spp

31

CO-FIRING COAL AND BAMBOO SPECIES - Case Study 2 Co-combustion of raw Bambusa balcooa with coal at different Wt% ratio

DTG curves for Raw BB, Coal and BB/coal at different Wt % ratios

Observations:(i) Both the raw BB and the 90%BB+10%coal samples have virtually identical burning profiles and mass loss rates (%/min)(ii) Raw 100% BB has the lowest burnout temperature while 100% coal has the highest burnout temperature.(iii) Two peaks were noted for all coal+raw BB blended samples; coal on its own had only one peak(iv) As the coal ratio (%) in the blends increases, the combustion peaks and reactivity rates decrease; this is due to the reducing

proportions of bamboo and, with that, the progressive reduction in VM and hemicellulose content in the bamboo.(v) The 75% coal/BB sample has the closest profile to coal, indicating increasing combustion compatibility between the products(vi) Varying proportions of the different fuels do affect the overall combustion behaviour of the sample

Peak combustion of Coal

Peak combustion of Increasing wt% of Bamboo balcooa

DTG curves for coal and Bambusa balcooa in different wt% proportions

32

CO-FIRING COAL AND BAMBOO SPECIES - Case Study 3 Co-combustion of heat-treated Bambusa balcooa with coal at different Wt% ratio

DTG curves for BB @ 280 C, Coal and BB/coal at different Wt % ratios

DTG curves for BB @ 380 C, Coal and BB/coal at different Wt % ratios

Observation:i. All samples are seen with one single main peaks ii. Peak combustion temperatures coincide for both heat-treated bamboo and coal iii. Close burning compatibility was noted

280oC 380oC

33

Conclusions of Current Research: 1Co-firing Biomass (bamboo) and Coal

With simple heat treatment, mature (4 year old) bamboo matched that of bituminous coal in the following aspects:

➢GRINDABILITY (important for pulverising)

➢HIGH DENSITY (compact, dense, fibrous material without pelletisation)

➢ENERGY YIELD (Heat Content or Calorific Value)

➢FUEL PROPERTIES (Fixed Carbon content)

➢COMBUSTION PROPERTIES (excellent Ignition, Peak Burning and Burnout temperatures)

➢ these results indicate that heat-treated bamboo exhibits highly compatible and synergistic combustion behaviour when co-fired with coal.

34

With regard to GHG emissions when burning bamboo:

• The BIOGENIC CO2 EMISSIONS during the combustion of biomass are eventually balanced by the uptake of CO2 in plantations and forests.

• Such biogenic CO2 emissions, therefore, do not contribute to atmospheric CO2 levels


35


Growth of bamboo plantations have the following additional

benefits:

➢PHYTOREMEDIATION (uptake of heavy metals)

➢REHABILITATION OF MINE LAND (high tolerance of disturbed land)

➢ALTERNATE USAGE BEYOND POWER GENERATION (furniture, building

materials, scaffolding, cloth materials, paper, ornaments, etc)

➢SOCIO-ECONOMIC BENEFITS THROUGH DEVELOPMENT OF MICRO-

INDUSTRIES (important factor for communities in locations of mine or

power plant closures)

36

CONTENTS






6. CONCLUSIONS

37

CO-FIRING BIOMASS AT DRAX POWER STATION, UKEMISSIONS

Drax Power Station (UK) results show that woody biomass can meet emission target even when shipped over a long distance

Current 2025 UK TARGETS

Bio NG US Canada EU UK Avge

DRAX

38

LEVELISED COST OF ELECTRICITY GENERATION

➢ LCOE from co-firing is greater than conventional 100% coal, as the coal ratio increases

➢ Co-firing is seen to be competitive with offshore wind and solar installation

➢ There is greater certainty in the estimation of the LCOE for co-firing compared to renewable technologies

Source:: IEA Clean Coal Centre, 2018

Solar P

V

Offsh

ore

win

d

Gas C

CG

T

10

0%

bio

mass

50

% b

iom

ass C

o-firin

g

10

% b

iom

assC

o-firin

g

Lignite

Sup

ercritical

Co

alSu

pe

rcritical

Co

al C

on

ven

tion

al

39

LEVELISED COST OF ELECTRICITY GENERATION (WITH $30 CARBON TAX)

• With an added carbon tax, wind and solar become cheaper than co-firing in some cases

• The range in LCOE estimation for wind and solar is significant compared to co-firing

Source: IEA Clean Coal Centre, 2018

Solar P

V

Offsh

ore

win

d

Gas C

CG

T

10

0%

bio

mass

50

% b

iom

ass C

o-firin

g

10

% b

iom

assC

o-firin

g

Lignite

Sup

ercritical

Co

alSu

pe

rcritical

Co

al C

on

ven

tion

al

40

CONTENTS






6. CONCLUSIONS

41

5. CONCLUSIONS

1. CONTRARY TO POPULAR BELIEF THAT “COAL IS DEAD”, SA’s coal resources are abundant and can provide low-emitting, cost effective, reliable and sustainable power well into the future with the correct technology

2. ENERGY: CFBC is proving to be the boiler technology of choice in many energy-intensive countries in the world (Spain, Poland, India, China, Vietnam, Korea and other countries in the Far East)

3. EFFICIENCY: CFBC is flexible, tolerant, efficient, water-constrained and can be applied to ensure optimal use of a wide range of low grade materials (coals, discards, waste).

4. EMISSIONS: GHG SOx and NOx emissions are significantly reduced in CFBC due to in-bed SOx capture (dolomite) and NOx is reduced due to low temperature operations.

CO2 emissions are significantly reduced when coal is co-fired with biomass.

42

5. CONCLUSIONS

In SUMMARY,

CFB BOILER TECHNOLOGY and CO-FIRING COAL WITH BIOMASS offers

a vital, practical, affordable, environmentally responsible

and innovative solution

to mitigate the future use of coal in South Africa

and to address the

ENERGY, WATER AND WASTE TRILEMMA

So prevalent in this country

43

THANK YOU

44

environmentally responsible methods to mitigate the use ...€¦ · boiler thermal efficiency, ......

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