Research On Pyrolysis Characteristics Of Oil Shale With Terahertz Spectrum

The pyrolysis characteristics of Huadian oil shale in the wide temperature range of 100-800? was studied and the general rules of oil shale pyrolysis in the wide temperature range was obtained in this paper.The terahertz(THz)time-domain spectroscopy technique was used to study the pyrolysis reaction of kerogen and different minerals in oil shale.By testing the oil shale samples prepared under different conditions,the optical parameters in the THz band were extracted,and the changing rules and influencing factors of the THz parameters were discussed.The results showed that the evaporation of free and combined water in the oil shale at the initial heating stage(<200?)caused a slight weight loss and an increase in THz signal peak.The pyrolysis temperature of the organic matter is mainly concentrated between 375-525?,and the amount of volatile oil and gas reaches a maximum at about 470?.The main component of volatile gas is C₁-C₅hydrocarbon.In addition,there are inorganic gas generation,such as H₂,CO₂,SO₂,H₂O.There are three main reasons for the decrease in the absorption intensity of THz waves in samples during the pyrolysis of organic matter.The first reason is the removal of polar functional groups in the kerogen molecule.The second reason is that various intramolecular hydrogen bonds in the macromolecular system are blocked.The third reason is the reduction of side chain branches.At the decomposition stage of inorganic minerals,the peak intensity of the THz signal decreases with the increase of temperature,especially the absorption of THz wave increases rapidly after 700?.The formation of decomposition products such as Ca O,Ca SO₄,hematite,and elemental iron is the main cause of the reduction in terahertz signal strength.Calcite quickly decomposes between500-600? to produce calcium oxide particles,which continues to react to form Ca S.While calcite decomposes,it also reacts with sulfur dioxide and oxygen in the atmosphere to form Ca SO4.These three reactions proceed at the same time,but the three reactions proceed differently at different temperatures.The decomposition temperature range of pyrite is about 300-700?,and 540? is the rapid decomposition temperature.Between500-600?,the decomposition products of pyrite are composed of monoclinic pyrite and a small amount of hexagonal pyrite.At 650?,pyrite undergoes oxidation and decomposition reactions simultaneously,and forms a multilayer core-shell structure with complex components.Different from that at low temperature,pyrite undergoes rapid oxidation at 700?.The oxidation products are mainly pyrrhotite and contain a small amount of hematite.At a high temperature of 800? pyrite undergoes a large-scale melting and recrystallization process,and large pieces of molten iron oxide and iron element appears.