Nitrogen Desorption in Molten Stainless Steel During Immersion Argon Blowing

The behavior of nitrogen desorption reaction in molten stainless steel for AISI 304 and 316 during immersion argon blowing through an immersed alumina nozzle with 3 mm in I. D. has been investigated by sampling method. Some kinetic parameters such as reaction order, rate constant and apparent activation energy of nitrogen desorption reaction for AISI 304 and 316 have been obtained. Results show that nitrogen desorption reaction from molten stainless steel for AISI 304 and 316 is the second order reaction. The rate constant at 1550 ℃ and 1 580 ℃ for AISI 316 is 0. 08407%-1 · min^-1 and 0. 82370%-1 · min^-1 , respectively. The rate constant at 1550 ℃ for AISI 304 is 0. 416 6%-1 · min^-1. The apparent activation energy Ea of nitrogen desorption reaction for AISI 316 is 2 136.47 kJ/ mol. This huge value of apparent activation energy verifies that the nitrogen desorption reaction has a complex and multistep reaction mechanism. The rate of nitrogen desorption reaction from molten stainless steel is mixed controlled by the desorption reaction of diatomic molecule nitrogen or of monatomic nitrogen from molten metal at the gas-metal interface and the mass transfer of nitrogen in molten metal. The rate equation of process for nitrogen desorption has been deduced.

Micro-pore Structure and Gas Accumulation Characteristics of Shale in the Longmaxi Formation, Northwest Guizhou

For further study on characteristics of micro-pores in the marine shale reservoirs in Northwest Guizhou,shale samples in the Lower Silurian Longmaxi Formation were selected to investigate effect of micro-pores on the characteristics of gas accumulation in shales,through methods of the argon broad ion beam-field emission scanning electron microscope and the nitrogen adsorption/desorption,analysis on the characteristics of micro-pores and related geochemical analysis.Results show that there are seven types of pores in the Longmaxi Formation shale,including interparticle pores,intraparticle pores,intercrystalline pores,dissolution pores,fossil pores,organic pores,and microfractures,among which the interparticle pores and organic pores are best developed.According to the nitrogen adsorption/desorption curves,the pore structures can be classified into three types,including the cylindrical pores with both opening ends,narrow parallel-plate pores and tapered parallel-plate pores with four opening sides.Diameter of micro-pores ranges from 2 to 64 nm,mainly at 2-6 nm.The diameter of micro-pores(less than 2 nm)ranges from 0.4 to 1.8 nm,The micro-pores with a diameter of 0.4-1.0 nm contribute most to the pore volume.Pore volume is dominated by meso-pores(2-50 nm)with a proportion of 83.1%.The micro-pores and meso-pores make major contribution to the specific surface area of pores with proportions of 20.1%and 79.3%,respectively.The total organic carbon(TOC)is the major factor controlling development of nanopores.Different pore types have different characteristics of gas occurrence and migration,indicating that nanopores provide favorable conditions for the occurrence and microscopic migration of gas in shales.