UPGRADING OF BIOGAS IN DENMARK

Transcription

1 UPGRADING OF BIOGAS IN DENMARK ALASTAIR WARD DEPARTMENT OF ENGINEERING AARHUS UNIVERSITY DENMARK præsen TATION 1

2 BIOGAS INDUSTRY IN DENMARK Relatively large animal production in Denmark Slow growth in early 2000s Ca. 170 plants in 2010, less than half agricultural based, about 60 small scale farm based plants Subsidy based on electricity production ( 0.1 / kwh electricity produced) Small power stations (<2MW) decentralised Electrical conversion efficiency <40%, heat utilised where possible 2

3 NEW DEAL FOR BIOGAS 2012 Change in the subsidy to / MJ Biogas no longer tied to electricity production Have seen many new (large) plants constructed or planned since 2012 Example: Horsens Bioenergi (2014) Manure and waste products (slaughterhouse etc) 240,000 t/annum 10,000,000 m 3 biogas/annum Gas upgraded and grid injected 3

4 BIOGAS FOR GRID INJECTION Removal of CO 2 (ca. 40%), H 2 S, H 2 O etc Gas grid qualitative requirements vary from country to country, >97% methane End product can be used as natural gas; electricity production, domestic, vehicle fuel etc 4

5 Denmark has a fairly extensive natural gas grid Gas fields in the North Sea Connection to European network 5 Torben Kvist Jensen, IEA Bioenergy Task 37 seminar, 2010

6 UPGRADING TECHNOLOGIES 6

7 GROWTH OF BIOGAS UPGRADING 7

8 Madsen Bioenergi Skive, Denmark Ammongas chemical scrubber 8

9 INVESTMENT AND OPERATING COSTS 9

10 ENERGY DEMANDS 10

11 COMPRESSION IS ALSO EXPENSIVE 11

12 POWER TO GAS A growing industry: Conversion of CO 2 to CH 4 rather than CO 2 removal CO 2 + 4H 2 CH 4 + 2H 2 O Requires a large amount of hydrogen Hydrogen produced from other forms of renewable energy that are not so controllable Storage of electrical energy as gas 12

13 Wind energy is a growing source of renewable energy in Denmark Electrical consumption From wind power 13

14 Prevailing wind from south west 14

15 DKK / MWh AARHUS Supply and demand of electricity leads to vary variable sale prices for producers spot price data /01/16 00:00:00 01/03/16 00:00:00 20/04/16 00:00:00 09/06/16 00:00:00 29/07/16 00:00:00 17/09/16 00:00:00 06/11/16 00:00:00 26/12/16 00:00: Date

16 METHODS OF CO 2 CONVERSION Biological: Microorganisms (hydrogenotrophic methanogens) present in biogas reactors Produce CH 4 from H 2 +CO 2 naturally Chemical : Sabatier process Developed ca C Ni catalyst 16

17 BIOLOGICAL METHOD 1 H 2 addition to existing biogas reactors. Small experiments at Danish Technical University, full scale at Aarhus University Biogas with higher % methane Hydrogen added Hydrogen converted to methane by hydrogenotrophs using CO2 in the biogas 17

18 FULL SCALE H 2 ADDITION AT AARHUS UNIVERSITY Small amounts of H 2 added (a few hundred m 3 ) No problems with the process Up to 62% of H 2 was utilised Need to develop better H 2 injection method: Elektrogas project, also investigating direct electron addition 18

19 BIOLOGICAL METHOD 2 H2 addition to a smaller reactor in a loop from the main reactor using naturally occuring bacteria. German patent. Biogas Hydrogen added Biogas with higher % methane Hydrogen converted to methane by hydrogenotrophs using CO2 in the biogas The smaller reactor contains organsims that were put there by adding digested material from the main reactor but have assumed a new population profile under the special conditions 19

20 BIOLOGICAL METHOD 3 H2 addition to a pure culture of hydrogenotrophic methanogens. US company Electrochaea. Biogas Biogas with higher % methane Hydrogen The smaller reactor contains hydrogenotrophs that have been grown in a laboratory because they were found to be very efficient at converting CO2+H2 to CH4 Biocat plant, Copenhagen Denmark 20

21 CHEMICAL METHOD Pilot Sabatier process plant at Aarhus University 10m 3 /hour methane production Average 97.7% CH 4 21

22 COMPARING THE METHODS Biological Low solubility of H 2 is a problem Converting all CO 2 means ph >10+ Equipment is not usually expensive Chemical Sabatier process requires extensive removal of H 2 S etc to prevent damage to the catalyst Expensive equipment Both Production of H 2 by conventional electrolyser has poor efficiency (50-60%) 22

23 NEW ELECTROLYSER TECHNOLOGY Solid oxide electrolysis cell (SOEC) 50kW pilot unit by Danish company Haldor Topsøe Part of the Sabatier pilot plant at Aarhus University 10+ hour warm up but fast on/off once warm Experimental runs show almost 80% power to gas efficiency 23

24 FUTURE PROSPECTS Power to Gas is a new concept in biogas plants External reactor type biological methods require special new reactors (much smaller than the biogas reactor) Direct H 2 addition to a reactor cannot produce grid quality gas (ph problem) Sabatier process requires extensive equipment The additional expense favours large scale plants Perhaps direct H 2 addition at the biogas plant, then piping semi-upgraded gas to a centralised chemical (Sabatier) upgrading facility? 24

25 H2AD pilot Mini automated reactors THANK YOU 30m3 pilot reactors Solid substrate feeding and extrusion treatment Continuous flow pressure cooker Biogas scientific team: Lars Ottosen Henrik Møller Alastair Ward Veronica Moset Hernandez Sabatier process Ib Johanssen Christian Dannesboe PhD students: Mads Jensen Laura Agneesens Lu Feng Maja Nielsen Technician: Britt Amby Malthesen 25