Module 2c. Outline. Anaerobic digestion. Process Conditions Biogas yield Upgrading to Green Gas Examples. Training course on Renewable Energy

Transcription

1 Module 2c Anaerobic digestion Outline Process Conditions Biogas yield Upgrading to Green Gas Examples slide 2/30 1

2 Anaerobic digestion Proven technology from a very small scale (some m3 reactor volume), to a very large scale (1000+ m3 reactor volume) Anaerobic digestion is biological degradation of organic material without oxygen present slide 3/30 resulting in a combustible gas, containing ca. 60% methane Technology is suitable for wet biomass, such as manure. Products are generally energy, heat and fertilisers 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 conditions Regimes Typical temperatures Typical residence times Psychrofilic C months Mesophilic C days Thermophilic C days The mesophilic regime is mostly used, because it is a stable process, producing a reasonable amount of biogas, in an acceptable time frame slide 4/30 2

3 The process: no oxygen slide 5/30 The process slide 6/30 3

4 Flowsheet slide 7/30 Larger scale Anaerobic Digestion Biogas to CHP unit Covering Silo Insulation Biogas storage Mixing Heating Manure input Regime: Residence time: ca. World-wide implementations: Mesophilic 40 days Several thousands (e.g in Germany) slide 8/30 4

5 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 6 pigs Total costs ca USD Applied in: Costa Rica Equador Nepal (other design for cold climate) >65,000 units implemented today slide 9/30 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) slide 10/30 5

6 Biogas composition Compound Methane [CH 4 ] Carbondioxide [CO 2 ] Nitrogen [N 2 ] Hydrogen [H 2 ] Oxygen [O 2 ] Hydrogensulfide [H 2 S] Volume percentage [%] << 1 << 1 << 1 << 1 HHV biogas : MJ/m 3 slide 11/30 Energy production Manure Organics Organics to biogas Biogas CHP (purpose build gas engine) Contains e.g. 10% solids (cow manure) Other components are water, dissolved organics and minerals 2/3 of solids material 0.4 m 3 /kg Organics (ca. 50% conversion) 60% methane, 40% CO 2/ 21 MJ/m 3 biogas 30% electrical energy and 50% thermal energy (for example) slide 12/30 6 6

7 Biogas yield 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 ( m 3 /(t ODM)) m: massa substraat(t) Opbrengst P Y DM OM m (in m3 gas) Substrate DM OM(% van DM) Y P P gem Cow manure Pig manure Chicken slide 13/ Source: bioenergy systems Biogas yield Manure type DS % m 3 /ton kwh el /ton Pigs 9% Cows 10% Chickens 25% Verge grass 30% Maize 30% Fats 100% slide 14/30 7

8 Application Manure Sludge (volume reduction) Co-digestion (increasing gas yield No woody materials: slide 15/30 Upgrading to Green Gas or Synthetic natural gas slide 16/30 8

9 Upgrading to Green Gas or Synthetic natural gas History 1980 s: several initiatives (technical problems) June 2004: co-digestion acceptance gave a boost in new projects Biogas upgrading Pressure increase H 2 S removal CFK s removal CO 2 removal Drying Smell Quality and quantity control slide 17/30 Biogas upgrading systems Membranes Waster washing (absorption under pressure) VPSA (adsorption with molecular sieves) LP Cooab (chemical absorption) Advantages/disadvantages of upgrading systems Well-known and documented Can be supplied if of interest slide 18/30 9

10 Biogas upgrading VPSA, landfil gas, 1989 (example) slide 19/30 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 slide 20/30 10

11 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 Level playing field for gas and electricity No government interference with technology slide 21/30 GPP system (Gastreatment Power Package) Compression to 10 barg TCR technology for gascleaning and cooling to minus 25 o C SOXSIA catalyst for H 2 S, siloxans and water removal Cooling to minus 80 o C to condens the CO 2 Results in wobbe index of 43,7 MJ/Nm 3 Pilot plant of 30 Nm 3 /hr biogas Max. 16 Nm 3 /hr SNG Liquid CO 2 amounts to 18 kg/h Electricity consumption is 12 kw e Four test locations Results so far are very promising slide 22/30 11

12 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: million m 3 SNG Within 10 years: >> 1000 million m 3 SNG Natural gas supply is limited and uncertain Can be applied at each location slide 23/30 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 m 3 /h biogas on the 100 mbar distribution network Safety requirements are slightly increased Adjustments took much more time and more money! slide 24/30 12

13 Situation is crucial (heat demand or not?) slide 25/30 Potential study of biogas in the Netherlands, (report of January 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 slide 26/30 13

14 Letter by Minister of Economic Affairs to the parliamant (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 slide 27/30 Examples in the Netherlands slide 28/30 14

15 Example: Ukrain slide 29/30 THANKS FOR YOUR ATTENTION TERIMAH KASIH 15