Optimising the efficiency of processes for the …...Process integration for SNG production •...
Transcript of Optimising the efficiency of processes for the …...Process integration for SNG production •...
Department of Energy and Environment – Heat and Power Technology
Optimising the efficiency of
processes for the production
of Bio-SNG Process integration’s role in
achieving high efficiency production
Stefan HeyneChalmers Energy Conference
2011-01-26
Department of Energy and Environment – Heat and Power Technology
Outline
• Synthetic Natural Gas (SNG)– some definitions and numbers
• Identifying efficient production pathways– process integration a key methodology
• Integration of SNG production with existing CHP plants
• Conclusions• Outlook
Department of Energy and Environment – Heat and Power Technology
Potential in Sweden• biogas (waste, manure, sewage sludge)
– production (2005)1 1.3 TWh– near future potential2 14-17 TWh
• bio-SNG (forest residues)– conservative estimate2 59 TWh– optimistic long term estimate2 up to 200 TWh
• Primary energy supply in 20083 612 TWh
• Transport sector energy consumption (2008)3 129 TWh
50%
1 Clementsson, Biogas – basic data on biogas – Sweden, 20072 Svensson et al., Renewable Methane – An Important Aspect when Establishing a More Diversified Sourcing and Distribution of Energy Gas in Sweden, 20093 Swedish Energy Agency, Energiläget 2009
Department of Energy and Environment – Heat and Power Technology
Process integration for SNG production
• Identification of efficient pathways for SNG production using process integration tools
– conversion efficiency of biomass into SNG– use of recoverable heat for cogeneration of power and heat
• Economic performance of optimized SNG production alternatives against future energy market scenarios
• CO2 emission consequences related to production and use of SNG
Department of Energy and Environment – Heat and Power Technology
SNG production process
Drying
Gasification
Gascleaning
Methanation
Gas upgrade
Biomass
SNG
recoverable by-products
heat
electricityexcess heat
heat
electricity
heat demand
power demand
CO2
sulphur
Department of Energy and Environment – Heat and Power Technology
Base case SNG processHeatWorkFuel
el
DH
Department of Energy and Environment – Heat and Power Technology
Pinch analysis
Evaluation(Thermodynamics,
Economics &CO2 emission
balances)
Process modifications
Process modelling & validation (Aspen Plus)
Process integration
study
2
3
1
4
Methodology
Department of Energy and Environment – Heat and Power Technology
Pinch theory - Grand Composite Curves
Q (kW)0
0
Tin
terv
al (
ºC)
minimumexternalheatingdemand
“heat pockets”potential for internal
heat exchange
mimimum external cooling demand
Department of Energy and Environment – Heat and Power Technology
Heat stream representation
externalcooling
(high temp)
internal heat exchange potential
external cooling (low temp)
Department of Energy and Environment – Heat and Power Technology
Indirect gasification
Gasificationfluidised
bed combustion
hot bed material
bed material, ash & char
fuel gasificationmedium
product gas
fuel
flue gas
air
heatfuel
Department of Energy and Environment – Heat and Power Technology
Chalmers gasifier
Hot
bed
mat
eria
l
Heat, Electricity, Steam
Air
Flue gas
Biomass
Fluidization gas(Steam or Bio Producer Gas or …)
Bio Product Gas
Fuel
Hot
bed
mat
eria
l
Heat, Electricity, Steam
Air
Flue gas
New concept
Fuel
Source: H.Thunman
Department of Energy and Environment – Heat and Power Technology
Biomass SNG(extension)
Integration with existing infrastructure
boile
r
gasi
fierpower
heat
fuel fuel
heatchar
gas processing SNG
excess heat
steam
Biomass CHP(existing)
Thermalintegration
Department of Energy and Environment – Heat and Power Technology
Integration with steam cycle
00
T(°
C)
Q (kW)
Internal heat recovery
heatto
steamcycle
external cooling
Department of Energy and Environment – Heat and Power Technology
Increased integration
00
T(°
C)
Q (kW)
steam
heatto
cycle
heat recovered from steam cycleexternal cooling
Department of Energy and Environment – Heat and Power Technology
Integration cases studied
• Integrated feedstock drying applied for the SNG process• Both boiler and gasifier sized for a thermal load input of 100 MW
1Abalancing integration
1Bincreased integration
Case 1steam drying 2A
balancing integration
2Bincreased integration
Case 2low
temperature air drying
Department of Energy and Environment – Heat and Power Technology
Process performance indicators
• Overall SNG, power and heat production & efficiency
• Heat and power production associated to SNG process
SNGfuelCHPfuel
DHelSNGtot QQ
QPQ
,,
+++
=η
CHPelCHPfuelelSNGel QPP ,,, η⋅−=
CHPqCHPfuelDHSNGDH QQQ ,,, η⋅−=
all indicators based on lower heating value (LHV) of wet fuel
Department of Energy and Environment – Heat and Power Technology
Results integration SNG & CHP
0
10
20
30
40
50
60
70
80
90
100
MW
CHP 1A 1B 2A 2B
PelCHP SNG
Qfuel,LHV QDH QSNG,LHV
CHPref
Department of Energy and Environment – Heat and Power Technology
Results integration SNG & CHPCHP Case
1ACase
1BCase
2ACase
2B
[MWLHV] 100 71.5 (all four cases)
[MWLHV] - 90.3 (all four cases)
Pel [MW] 31.7 24.7 27.6 23.2 28.3
[MW] 76.8 68.4 64.1 60.1 54.9
[MWLHV] - 62.7 (all four cases)
ηtot [%] 108.6 96.3 95.4 90.2 90.1
Pel,SNG [MW] - 2.0 4.9 0.5 5.6
[MW] - 13.5 9.1 5.2 0.0
SNGfuelQ ,
SNGDHQ ,
SNGQ
CHPfuelQ ,
DHQ
• SNG process net power producer for all cases
• SNG production unaffected by choice of drying technology and level of thermal integration
• Increased level of thermal integration leads to substantial increase in power production
• Overall efficiency decrease misleading performance indicator
Department of Energy and Environment – Heat and Power Technology
Conclusions• Bio-SNG via gasification can be produced at high thermal
efficiency with cold gas efficiencies at around 70%
• Efficient use of the excess heat from the SNG process is essential for good overall efficiencies
• Electricity production can be efficiently realised when integrating SNG production with existing CHP steam power plants
• Pinch analysis is a very useful tool for a systematic analysis of the heat recovery system of the SNG process (and biorefinery concepts in general)
Department of Energy and Environment – Heat and Power Technology
Conclusions• Thermal integration can help substantially to increase the
electricity produced from the available excess heat of the SNG process
• Integrated feedstock drying improves the process efficiency considerably, low temperature air-drying being the most favourable option
• Integrating gasification in general and SNG production in particular with existing infrastructure can result in a faster introduction of gasification technology
Department of Energy and Environment – Heat and Power Technology
Outlook• Definition of appropriate performance indicators for just
comparison to other biofuel process alternatives
• Economic evaluation against possible future energy market scenarios– identification of economically robust process alternatives
• Assessment of CO2 consequences
• Improved modelling of key conversion steps– Gasification– Tar reforming collaboration with Energy Technology
Department of Energy and Environment – Heat and Power Technology
Thank you for you attention!!