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Transcript of '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%
1. NATIONAL CONTEXT OF COAL – 2 – IRP 2010
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%
1. NATIONAL CONTEXT OF COAL – 3 – IRP 2010
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
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
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
1. STRATEGIC CONTEXT OF COAL
2. CHALLENGES TO THE USE OF COAL
3. OPTIONS FOR THE ENVIRONMENTALLY RESPONSIBLEUSE OF COAL
4. CASE STUDIES IN SOUTH AFRICA
5. COMPARATIVE COSTS AND EMISSIONS
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
METHODS TO MITIGATE CO2 – 2
* 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
METHODS TO MITIGATE CO2 – 3
17
CONTENTS
1. STRATEGIC CONTECT OF COAL
2. CHALLENGES TO THE USE OF COAL
3. OPTIONS FOR THE ENVIRONMENTALLY RESPONSIBLE USEOF COAL
4. CASE STUDIES IN SOUTH AFRICA
4.1 - TECHNOLOGY – CIRCULATING FLUIDISED BED COMBUSTION (CFBC)
4.2 - FEEDSTOCK – COAL CO-FIRED WITH BIOMASS
5. COMPARATIVE COSTS AND EMISSIONS
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
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
1. STRATEGIC CONTEXT OF COAL
2. CHALLENGES TO THE USE OF COAL
3. OPTIONS FOR THE ENVIRONMENTALLY RESPONSIBLE USEOF COAL
4. CASE STUDIES IN SOUTH AFRICA
4.1 - TECHNOLOGY – CIRCULATING FLUIDISED BED COMBUSTION (CFBC)
4.2 - FEEDSTOCK – COAL CO-FIRED WITH BIOMASS
5. COMPARATIVE COSTS AND EMISSIONS
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
Conclusions of Current Research: 2Co-firing Biomass (bamboo) and Coal
35
Conclusions of Current Research: 3Co-firing Biomass (bamboo) and Coal
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
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
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
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
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