Making Coal in the Laboratory by Simulating Natural Conditions

Making Coal in the Laboratory by Simulating Natural Conditions This project tests conditions for bituminous and anthracite coal formation. An apparatus was designed and fabricated that could simulate natural conditions within the earth including, 1) Water depths up to 701m (6.9 MPa, to prevent water from boiling), 2) Overburden of inorganic sediments, up to 20.7 MPa compression, and 3) Geothermal temperatures up to 260°C. Douglas fir, red oak, white pine wood, and black peat moss were tested at 224°C, 5.5 MPa water pressure, and compressed at zero, 10.3 MPa and 20.7 MPa for 1 to 3 weeks. The following observations were made, 1) Coal made from black peat moss contains many particles and agglomerations of sand and miscellaneous minerals where bituminous and anthracite do not, 2) At zero compression the result looked like charcoal and since it was formed within liquid water is also known as hydrochar. Density 0.24-0.32 gm/cc, very soft, 3) At 10.3 MPa compression the coal was much denser but still had the appearance of charred wood, 4) At 20.7 MPa compression the samples actually look like natural coal. The fractures were black and shiny, similar to obsidian glass. All subsequent tests were then performed at 20.7 MPa, 5) Average solid density was approximately 1.3gm/cc which is very similar to bituminous but not as high as anthracite which is about 1.5gm/cc, 6) Vickers hardness was similar to natural coal but difficult to measure due to the tendency of natural coal to fracture even at low indenter loads, 7) Laboratory ultimate analysis of one week samples indicated that carbon content was 68 to 73% and that hydrogen to carbon ratio of all samples were very close to bituminous, 0.06 to 0.07, 8) Lab analysis also indicated that oxygen content was high, 21 to 26%. Oxygen to carbon ratio was higher at 0.3 to 0.4 for the samples where bituminous is approximately 0.2 or less, 9) Ultimate analysis of the three-week sample indicated oxygen had come down to 20%. 10)Some of the extracted liquids were soluble in water, others were soluble in acetone, and still others were not soluble in water or acetone, 11) Original wood to coal compression ratio is about 5:1. Natural vegetation to coal compression ratios are estimated at 10:1 up to 30:1. In conclusion, 1) The test equipment and test methods appear to produce synthetic coal that has the same physical properties and appearance as natural coal as well as similar chemical properties. 2) Based on the estimated compression ratios of coal, a 30 m thick coal seam found in North America would have started out as a 300m to 900m thick bed of vegetation. 3) To achieve the appearance and density of natural bituminous coal, the samples had to be compressed to 20.7 MPa. This would suggest that natural coal was also compressed in a similar fashion by inorganic sedimentary overburden that was 900m to 2700m thick depending on density and buoyancy of the sediment if waterborne. 4) Assuming the black peat moss was formed in an ancient low-lying bog or swamp, observations using a microscope or even the naked eye would suggest that bituminous or anthracite coal could never have come from this or similar source. 5) If liquid water was present at 224°C, a water depth of approximately 250m of head pressure would be required to keep the water from boiling away.