Universidade Fernando Pessoa - CIAGEB, Praça de 9 de Abril 349, Porto, Portugal 2

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1 1 Universidade Fernando Pessoa - CIAGEB, Praça de 9 de Abril 349, Porto, Portugal 2 Academia das Ciências de Lisboa, Rua da Academia das Ciências 19, Lisboa, Portugal Sept 2009

2 The Energy Sector has been facing tremendous challenges during the last decade?! Related to: The growing insufficiency in oil supply and, even, in the associate natural gas The increase in energy demand The rise in the world global population The rise of living standards

3 HOW TO SOLVE THIS REAL ENERGETIC PROBLEM SOLUTIONS MUST BE TECHNICALLY FEASIBLE ECONOMICALLY FEASIBLE and GHG BLE TO REDUCE EMISSIONS

4 RENEWABLE ENERGIES NUCLEAR ENERGY Inherent restrictions to its implementation SOCIO-ECONOMIC-POLITICAL REASONS NERGETIC CAPACITY REASONS

5 In this perspective COAL EARNS AGAIN AN IMPORTANT ROLE in the New Global Energy Supply Yet, the New COAL Scenario implies Innovative

6 Zero Emissions Technologies - ZETs Coal Combustion and Gasification (PF, PCC, CFBC, PFBC, IGCC) (pre-c, pos-c, oxifuel) Coal To Liquids (CTL) Underground Coal Gasification Carbon Capture and Sequestration - CCS CBM Enhanced Production (ECBM) CO 2 Pure Sequestration Nomenclature from International Conferences on Clean Coal Technologies for our Future

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8 In the scope of CCS technologies the main technological and economic currently feasible issues are CBM production vs CO2 geological sequestration, as follows: Coal is a natural gas source Coal acts as one of the most suitable CO 2 geological sequestration sites, and CO 2 injection will increase the natural gas production from coal, allowing to obtain the Enhanced Coalbed Methane (ECBM)

9 NORTH- ATLANTIC COAL TYPE Genetic conditions GONDWANA COAL TYPE Chemical and Physical Properties GAS STORAGE Behaviour GAS DIFFUSION Behaviour

10 HOW TO SOLVE THE PROBLEM

11 SAMPLES A B C ( Bituminous A coal) 2 ( Bituminous C coal) 2 (Anthracite A) 2 (Per-bituminous coal) 1 (Ortho-bituminous coal) 1 (Meta-anthracite) 1 D (Ortho-bituminous coal) 1 (Bituminous C coal) 2 Gondwana coal types North-Atlantic coal types V (%) L (%) I (%) MM (%) Ro (%) V = vitrinite content (vol. %); L = liptinite content (vol. %); I = inertinite content (vol. %); MM = mineral matter (vol. %), ISO ; Ro = vitrinite mean random reflectance (%), ISO UN EC ISO 11760

12 EXPERIMENTAL CONDITIONS Gas storage capacity and diffusion determinations were calculated using sorption isotherm techniques The volumetric isotherm apparatus was idealized taking into account the Boyle- Mariotte Law

13 EXPERIMENTAL CONDITIONS (cont.) M (%) SM (g) BT (ºC) PS (µm) GS (%) Sample A CH 4 Sample B CH 4 Sample C CH 4 Sample D CH 4 M = moisture in the analysis sample (%) (ISO 11722); SM = sample mass (g); BT = bath temperature (ºC); PS = particle size (µm), GS = gas sorption (%).

14 METHODOLOGY Gas Storage Capacity Langmuir Model was used to fit individual gas sorption isotherm data V V P V = gas volume (scf/ton); P = equilibrium pressure (psi); V L = Langmuir Volume (scf/ton); P L = Langmuir Pressure (psi) L P P L Gas Diffusion Coefficient Diffusion coefficients were calculated from the slope of the first linear part of sorption data D brs Vi Vi D = diffusion coefficient (cm 2 /sec); b = tangent slope ; r s = spherical particle radius (cm); V i = gas content at the end of step I (scf/ton); V i-1 = gas content at the end of step I-1 (scf/ton) 1 2

15 RESULTS Gas Storage Capacity Gas Diffusion Coefficient

16 Gas Storage Capacity Higher gas storage capacities for North-Atlantic coal type (NAC) than for Gondwana coal type (GC), independently of temperature, rank and maceral composition. Sample A (GC) (V=82%, L=0%, I=18, MM=22%, Ro=1.48%) Sample C (NAC) (V= 83%, L=0%, I=17, MM=28%, Ro=2.10%) Sample A (sorption isotherm experiment performed at 30ºC) presents lower gas storage capacity than sample C (experiment at 35ºC)

17 Gas Storage Capacity (cont.) Sample A (GC) (V= 82%, L=0%, I=18, MM=22%, Ro=1.48%) Sample D (NAC) (V= 69%, L=10%, I=21, Ro=0.86%) Sorption isotherm in samples A and D carried out at 30ºC. Sample D (lower rank and vitrinite content values) presents higher gas storage capacity than sample A

18 Gas content (scf/ton) Gas Storage Capacity (cont.) Sample C Langmuir equation: V=(P x )/(P ) Sample A Langmuir equation: V=(P x )/(P ) North Atlantic Coals Sample D Langmuir equation: V=(P x )/(P ) Gondwana Coals Sample B Langmuir equation: V=(P x )/(P ) Pressure (bar) A B C D

19 Gas content (scf/ton) Gas Storage Capacity (cont.) North Atlantic Coal (V=82%, L=0%, I=18, MM=22%, Ro=1.48%) (T = 35ºC) Sample C Langmuir equation: V=(P x )/(P ) Sample A Langmuir equation: V=(P x )/(P ) Gondwana Coal (V= 83%, L=0%, I=17, MM=28%, Ro=2.10%) (T = 30ºC) Pressure (bar) A C

20 Gas content (scf/ton) Gas Storage Capacity (cont.) Sample D Langmuir equation: V=(P x )/(P ) Sample A Langmuir equation: V=(P x )/(P ) North-Atlantic Coal (V= 69%, L=10%, I=21, Ro=0.86%) (T = 30ºC) Gondwana Coal (V= 82%, L=0%, I=18, Ro=1.48%) (T = 30ºC) Pressure (bar) A D

21 Gas Storage Capacity (cont.) Gas storage capacity in all coals (both North-Atlantic or Gondwana types) is intimately related to coal seam underground conditions (pressure and temperature), nature of organic fragments, incarbonization process, and mainly to environmental settings of deposition (GC mostly aerobic conditions, NAC mostly anaerobic conditions). The vitrinite group of North Atlantic coal type is represented by macerals mainly characterized by: the production of secondary cell infillings induce an increase of the internal surface area in the vitrinite group induce an increase in gas storage capacity

22 Gas Diffusion Coefficients Diffusion coefficient values versus pressure in both North-Atlantic and Gondwana coal types Diffusion coefficient values dependency on temperature and petrographic characteristics, in Gondwana coal type (samples A and B) Diffusion coefficient values dependency on temperature and petrographic characteristics, in North-Atlantic coal type (samples C and D) Diffusion coefficient values dependency on temperature and genetic settings (including petrographic characteristics and environmental conditions of deposition)

23 Diffusion Coefficientsvs Pressure North-Atlantic and Gondwana coal types In both cases: during the adsorption process, diffusion coefficient values decrease with pressure increase during the desorption process, diffusion coefficient values increase with pressure decrease This general behaviour is intimately related to the increase and decrease of kinetic mechanisms induced by pressure increase and decrease, respectively.

24 Diffusion coefficient (cm 2 /sec) Diffusion coefficient (cm 2 /sec) Diffusion coefficient (cm 2 /sec) Diffusion coefficient (cm 2 /sec) Diffusion Coefficient vs Pressure (cont.) North- Atlantic Coal type Gondwana Coal type 1E-08 9E-09 8E-09 7E-09 6E-09 5E-09 4E-09 3E-09 2E-09 1E E E-08 3E E-08 2E E-08 1E-08 5E-09 0 Sample A Adsorption Desorption Pressure (bar) Sample C Adsorption Desorption Pressure (bar) 1.4E E-08 1E-08 8E-09 6E-09 4E-09 2E E E-08 1E-08 8E-09 6E-09 4E-09 2E-09 0 Sample B Adsorption Desorption Pressure (bar) Sample D Adsorption Desorption Pressure (bar)

25 Diffusion Coefficients vs temperature and petrographic characteristics Gondwana coal type Sample A (V= 82%, L=0%, I=18, MM=22%, Ro=1.48%) (T=30ºC) Sample B (V= 54%, L=13%, I=33, MM=9%, Ro=0.83%) (T=35ºC) Below c.20 bar Sample B presents higher diffusion coefficient values than sample A, suggesting an higher dependency on temperature than on petrographic characteristic. It means, the higher activation energy induced at higher temperatures (sample B) masks the effect of petrographic characteristics. Above c.20 bar Sample A presents higher diffusion coefficient values than sample B, suggesting an higher dependency on petrographic characteristic than on temperature. It means, the sample B, which is characterized by an higher vitrinite content and rank, presents an higher activation energy and, consequently, higher diffusion values than sample B.

26 Diffusion coefficient (cm 2 /sec) Diffusion coefficient (cm 2 /sec) Diffusion Coefficients vs temperature and petrographic characteristics (cont.) Gondwana coal type 1.2E-08 1E-08 8E-09 6E-09 4E-09 2E-09 0 Adsorption Sample A Sample B Pressure (bar) 1.4E E-08 1E-08 8E-09 6E-09 4E-09 2E-09 0 Desorption Sample A (V= 82%, L=0%, I=18, MM=22%, Ro=1.48%) (T=30ºC) Sample B (V= 54%, L=13%, I=33, MM=9%, Ro=0.83%) (T=35ºC) Sample A Sample B Pressure (bar)

27 Diffusion Coefficients vs temperature and petrographic characteristics North-Atlantic coal type Sample C (V= 83%, L=0%, I=17, MM=28%, Ro=2.10%) (T=35ºC) Sample D (V= 69%, L=10%, I=21, Ro=0.86%) (T=30ºC) Sample C presents, during the entire adsorption and desorption processes, higher diffusion coefficient values than sample D. In fact, both properties, temperature and petrographic characteristics, which contribute for higher activation energies for diffusion coefficients, present higher values in sample C than in sample D.

28 Diffusion coefficient (cm 2 /sec) Diffusion coefficient (cm 2 /sec) Diffusion coefficient (cm 2 /sec) Diffusion coefficient (cm 2 /sec) Diffusion Coefficients vs temperature and petrographic characteristics (cont.) North-Atlantic coal type Adsorption 1.8E-08 Sample C C 1.6E-08 Sample D D 1.4E E-08 1E-08 8E-09 6E-09 4E-09 2E Pressure (bar) Desorption 4E-08 Sample C C 3.5E-08 Sample D D 3E E-08 2E E-08 1E-08 5E Pressure (bar) Sample C (V= 83%, L=0%, I=17, MM=28%, Ro=2.10%) (T=35ºC) Sample D (V= 69%, L=10%, I=21, Ro=0.86%) (T=30ºC)

29 Diffusion Coefficients vs temperature and genetic settings North-Atlantic and Gondwana coal types Sample A (GC) (V=82%, L=0%, I=18, MM=22%, Ro=1.48%) (T=30ºC) Sample C (NAC) (V= 83%, L=0%, I=17, MM=28%, Ro=2.10%) (T=35ºC) Sample C presents, during the entire adsorption and desorption processes, higher diffusion coefficient values than sample A, due to the higher gas sorption temperature but, although in a smaller scale, also to different genetic conditions. Both samples have similar maceral compositions and slightly different ranks, but the vitrinite group in sample C is characterized by smaller micropores and, therefore, higher internal surface area than sample A, due to environmental genetic anaerobic conditions typical in North-Atlantic coal type, consequently inducing to higher diffusion coefficient values.

30 Diffusion coefficient (cm 2 /sec) Diffusion coefficient (cm 2 /sec) Diffusion Coefficients vs temperature and genetic settings (cont.) North-Atlantic and Gondwana coal types 1.8E E E E-08 1E-08 8E-09 6E-09 4E-09 2E-09 0 Adsorption Sample A Sample C Pressure (bar) 4E E-08 3E E-08 2E E-08 1E-08 5E-09 0 Desorption Sample A Sample C Pressure (bar) Sample A (GC) (V=82%, L=0%, I=18, MM=22%, Ro=1.48%) (T=30ºC) Sample C (NAC) (V= 83%, L=0%, I=17, MM=28%, Ro=2.10%) (T=35ºC)

31 Diffusion Coefficients vs temperature and genetic settings (cont.) North-Atlantic and Gondwana coal types Sample B (V= 54%, L=13%, I=33, MM=9%, Ro=0.83%) (T=35ºC) Sample D (V= 69%, L=10%, I=21, Ro=0.86%) (T=30ºC) Below c.30 bar Sample B presents higher diffusion coefficient values than sample D, suggesting that sample D (with higher vitrinite content and depositional environment mainly characterized by anaerobic conditions: two factors that increase the coal microstructure) have a lower gas kinetic mechanisms than sample B, consequently inducing an activation energy for diffusion coefficient values mainly controlled by temperature changes. Above c.30 bar Sample D presents higher diffusion coefficient values than sample B, i.e. the number of micropores in coal structure (strongly related to vitrinite content and anaerobic genetic conditions) is higher in sample D than in sample B, inducing an higher activation energy for diffusion in sample D. At higher pressures, diffusion values show an higher dependency on the maceral composition and genetic settings than on sorption test temperature.

32 Diffusion coefficient (cm 2 /sec) Diffusion coefficient (cm 2 /sec) Diffusion Coefficients vs temperature and genetic settings (cont.) North-Atlantic and Gondwana coal types 1.2E-08 1E-08 8E-09 6E-09 4E-09 2E-09 Adsorption Sample B Sample D 1.4E E-08 1E-08 8E-09 6E-09 4E-09 2E-09 Desorption Sample B Sample D Pressure (bar) Pressure (bar) Sample B (V= 54%, L=13%, I=33, MM=9%, Ro=0.83%) (T=35ºC) Sample D (V= 69%, L=10%, I=21, Ro=0.86%) (T=30ºC)

33 CONCLUSIONS Gas storage capacity and diffusion coefficient have a strong dependency on both experimental sorption conditions (simulating, in the laboratory, the reservoir pressure and temperature conditions) and petrographic characteristics (genetic conditions). All the four samples studied present an increase of gas storage capacity and a decrease of diffusion coefficient with pressure increase.

34 CONCLUSIONS (cont.) Gas Storage Capacity Gas storage capacity shows an higher dependency on the vitrinite content, rank (until the anthracite range) and anaerobic genetic environmental conditions (North-Atlantic coal type), rather than on temperature, due to an increased development of vitrinite microporous structures.

35 CONCLUSIONS (cont.) Gas Diffusion Coefficient Diffusion coefficient shows a more complex behaviour than the one reported in gas storage capacity. Diffusion coefficient values present a slightly higher dependency on temperature than on petrographic characteristics, i.e. depending on pressure steps temperature changes are able to mask petrographic characteristic effects, implying that the activation energy for the diffusion process is mainly controlled by temperature, and vice-versa.

36 CONCLUSIONS (cont.) As an example: At low pressures (below c. 20 bar), sample B (Gondwana coal type) presents higher diffusion values than sample A (also Gondwana coal type), and At high pressures (above c. 20 bar) samples A and B show an opposite behaviour. In fact, at low pressures, inducing low gas kinetic mechanisms, the activation energy for the diffusion is mainly controlled by temperature; on the contrary, at high pressures, the activation energy for the diffusion is mostly controlled by vitrinite content and rank.

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