module 2c - casindo · module 2c anaerobic digestion ... opbrengst p y dm om m (in m3gas) m: ......
TRANSCRIPT
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Module 2c
Anaerobic digestion
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Outline
Process
Conditions
Biogas yield
Upgrading to Green Gas
Examples
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Anaerobic digestion
Proven technology from a very small scale (some m3reactor volume), to a very large scale (1000+ m3reactor volume)
Anaerobic digestion is– biological– degradation– of organic material– without oxygen present
resulting in a combustible gas, containing ca. 60%methane
Technology is suitable for “wet” biomass, such asmanure. Products are generally energy, heat andfertilisers
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The process
Biological steps– Hydrolysis: Break-down to smaller molecules– Acidogenesis: further break-down to e.g. acids– Acetagenesis: production of acetates, carbondioxide and hydrogen.– Methanogenesis: methane, carbondioxide and water are produced– There are several groups of bacteria that perform each step
Process conditionsRegimes Typical temperatures Typical residence timesPsychrofilic 15 – 22°C monthsMesophilic 25 – 38°C 25 – 50 daysThermophilic 50 – 70°C 10 – 30 days
The mesophilic regime is mostly used, because it is a stableprocess, producing a reasonable amount of biogas, in anacceptable time frame
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The process: no oxygen
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The process
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Flowsheet
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Larger scale Anaerobic Digestion
Silo
Insulation
Biogasstorage
Heating
Mixing
Covering
Manure input
Biogas to CHP unit
Regime: MesophilicResidence time: ca. 40 daysWorld-wide implementations: Several thousands (e.g. 1500 in Germany)
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Small scale digestor
Used for cooking or heating
Fed with manure (e.g. from cows,pigs, etc). Amount needed:>22 kg/day, which is 1 cow or 6pigs
Total costs ca. 100 - 150 USD
Applied in:• Costa Rica• Equador• Nepal (other design for cold climate)
>65,000 units implemented today
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Process conditions
Anaerobic conditions
>50 % moisture
Temperature (dependent on the type of bacteria)
Residence time
pH-value 7,5
Organic load ( OM/m3/day)
Additives (nitrogen, minerals)
Particle size substrate
Ammoniak formation (NH3)
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Biogas composition
<< 1Hydrogensulfide [H2S]
<< 1Oxygen [O2]
<< 1Hydrogen [H2]
<< 1Nitrogen [N2]
24 – 45Carbondioxide [CO2]
45 – 75Methane [CH4]
Volume percentage [%]Compound
HHVbiogas: 20 – 25 MJ/m3
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Energy production
Manure
Organics
Organics to biogas
Biogas
CHP (purpose build gas
engine)
Contains e.g. 10% solids (cow manure)Other components are water, dissolvedorganics and minerals
2/3 of solids material
0.4 m3/kg Organics (ca. 50% conversion)
60% methane, 40% CO2/ 21 MJ/m3
biogas
30% electrical energy and 50% thermalenergy (for example)
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Parameters:
DM [%]: percentage droge stof in substraat
OM [%]: percentage organische materie in substraat
ODM [%]: percentage organische droge stof (= DM . OM)
Y: Maximaal mogelijke productie biogas ( m3/(t ODM))
)gasm3(inmOMDMYPOpbrengst
m: massa substraat(t)
Source: bioenergy systems
Biogas yield
5124 – 88350 – 55070 – 8010 – 20Chicken
277 – 61350 – 55065 – 853 – 13Pig manure
259 – 51200 – 40065 – 857 – 15Cow manure
PgemPYOM(% van DM)DMSubstrate
5124 – 88350 – 55070 – 8010 – 20Chicken
277 – 61350 – 55065 – 853 – 13Pig manure
259 – 51200 – 40065 – 857 – 15Cow manure
PgemPYOM(% van DM)DMSubstrate
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Biogas yield
Manure type DS % m3/ton kWhel/ton
Pigs 9% 27 48
Cows 10% 14 26
Chickens 25% 82 147
Verge grass 30% 120 216
Maize 30% 150 270
Fats 100% 560 1000
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Application
Manure
Sludge (volume reduction)
Co-digestion (increasing gas yield
No woody materials:
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Upgrading to Green Gas orSynthetic natural gas
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History 1980’s: several initiatives (technical problems)
June 2004: co-digestion acceptance gave a boost in new projects
Biogas upgrading Pressure increase
H2S removal
CFK’s removal
CO2 removal
Drying
Smell
Quality and quantity control
Upgrading to Green Gas orSynthetic natural gas
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Biogas upgrading systems Membranes
Waster washing (absorption under pressure)
VPSA (adsorption with molecular sieves)
LP Cooab (chemical absorption)
Advantages/disadvantages of upgradingsystems Well-known and documented
Can be supplied if of interest
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Biogas upgrading VPSA, landfil gas, 1989(example)
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Active players in Netherlands Cirmac International
GTS, Gastreatment Services BV
BioGast Sustainable Energy
ENECO, Ecogas project
Sweden 30 biogas upgrading systems of which:
4 are delivering to the gasnet
26 are used for transportation fuel
Switzerland 6 upgrading plants delivering to the grid
2 more are under construction
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Constraints (according to Cirmac) No national quality requirements and analyses
prescription
No obligation for the distributor to accept Green Gas
Investment costs for piping, measures to be taken
No incentive for increased efficiency or lower emission
No consistent government policy
More chances by (according to BioGast) Introducing certificate system
Obliged percentage Green Gas in f.i. 2010
Level playing field for gas and electricity
No government interference with technology
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GPP® system (Gastreatment Power Package) Compression to 10 barg
TCR technology for gascleaning and cooling to minus 25oC
SOXSIA catalyst for H2S, siloxans and water removal
Cooling to minus 80 oC to condens the CO2
Results in wobbe index of 43,7 MJ/Nm3
Pilot plant of 30 Nm3/hr biogas Max. 16 Nm3/hr SNG
Liquid CO2 amounts to 18 kg/h
Electricity consumption is 12 kWe
Four test locations
Results so far are very promising
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BioGast Operational since September 2006
Private company producing Green Gas
Stand-alone units at biogas production location
Network of small units
Many advantages to CHP
“Gas is a fuel, electricity is energy”
Potential Now: Sewage sludge and landfills: 50-100 million m3 SNG
Within 10 years: >> 1000 million m3 SNG
Natural gas supply is limited and uncertain
Can be applied at each location
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Ecogas project (ENECO) Requirements to the biogas feed
Need for second Wobbe Index meter?
Reliability Sulphur measurement?
Allowable fluctuation of the Wobbe Index?
Whole list of paramaters and values
Injection of 75 m3/h biogas on the 100 mbar distributionnetwork
Safety requirements are slightly increased
Adjustments took much more time and more money!
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Situation is crucial (heat demand or not?)
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Potential study of biogas in the Netherlands, (report ofJanuary 2007, SenterNovem) 11% of natural gas can be replaced by SNG
Certification is needed like green electricity
Quality ensurance is needed
Arrangements of green gas injection to low pressure grid is needed
Financial support or fiscal measures is needed
Netherlands Platform New gas (PNG)
Within PNG: working group “Green Gas”
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Letter by Minister of Economic Affairs to theparliamant (26 March 2007): Green gas can contribute to sustainable development and
solving the manure disposal problems
The technology need to be further improved (digestion,gasification and upgrading to SNG)
The question: is Green Gas sustainable need to be answered
UKR (Unieke Kansen Regeling) can be applied, not the MEP(meant for green electricity only)
Before summer 2007 (to be expected)
Document “Visions on Green Gas” by SenterNovem
Respons from the parliament (priority statements by 2020)
Meeting of Dutch partners within Redubar with SenterNovem
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Examples in the Netherlands