Research on the maceral characteristics of Shenhua coal and efficient and directional direct coal liquefaction technology

In this research,molecular structure models were developed respectively for Shenhua coal vitrinite concentrates(SDV)and inertinite concentrates(SDI),on the basis of information on constitutional unit of Shenhau coal and elemental analysis results obtained from^(13)C-NMR analysis characterization,FTIR analysis characterization,X-ray diffraction XRD and XPS analysis characterization.It can be observed from characterization data and molecular structure models that the structure of SDV and SDI is dominated by aromatic hydrocarbon,with aromaticity of SDI higher than that of SDV;SDV mainly consists of small molecule basic structure unit,while SDI is largely made from macromolecular structure unit.Based on bond-level parameters of the molecular model,the research found through the autoclave experiment that vitrinite liquefaction process goes under thermodynamics control and inertinite liquefaction process under dynamics control.The research developed an efficient directional direct coal liquefaction technology based on the maceral characteristics of Shenhua coal,which can effectively improve oil yield and lower gas yield.

Discharge characteristics of coal and extraction residue from direct coal liquefaction in partial fluidization silo

Gasification of extraction residue(ER) from direct coal liquefaction with pulverized coal is an efficient way for the utilization of carbonaceous wastes, which improve the overall efficiency of direct coal liquefaction technology. The discharge characteristics of ER mixing with pulverized coal is important paraments for its gasification process, which is seldom studied in the literature. In this study, the discharge characteristics of the pulverized coal(M1) as well as its mixture with ER(M2) were systematically investigated in an atmospheric pressure partial fluidization silo with different fluidization apparent velocity. It was observed that although M2 is a viscous powder with lower flowability than M1, the mass flow rate of M2 is 65% higher than M1 at the 3.7 mm·s-1apparent gas velocity. M2 exhibits the properties of Geldart A type powder, which improves the mass flow rate and stability of the discharged material. The mass flow rate of both M1 and M2 first increases and then slowly decreases with the increase of apparent gas velocity of the fluidizing air, which means the discharge process of M1 and M2 can be optimized by the apparent gas velocity.

Regulation of radicals by hydrogen-donor solvent in direct coal liquefaction

Radicals are important intermediates in direct coal liquefaction.Certain radicals can cause the cleavage of chemical bonds.At high temperatures,radical fragments can be produced by the splitting of large organic molecules,which can break strong chemical bonds through the induction pyrolysis of radicals.The reaction between the formation and annihilation of coal radical fragments and the effect of hydrogen-donor solvents on the radical fragments are discussed in lignite hydrogenolysis.Using the hydroxyl and ether bonds as indicators,the effects of different radicals on the cleavage of chemical bond were investigated employing density functional theory calculations and lignite hydrogenolysis experiments.Results showed that the adjustment of the coal radical fragments could be made by the addition of hydrogendonor solvents.Results showed that the transition from coal radical fragment to H radical leads to the variation of product distribution.The synergistic mechanism of hydrogen supply and hydrogenolysis of hydrogen-donor solvent was proposed.

Micro Morphology of Soot Particles Sampled from High Pressure Jet Flames of Diesel from Direct Coal Liquefaction

Diesel from direct coal liquefaction(DDCL) is a new type of engine alternative energy. But its hydrocarbon composition and physicochemical properties are quite different from those of Petro diesel. In this study, a premixed constant volume combustion chamber(CVCC) system with soot particle sampling devices was built. The soot particles in the spray flame were sampled and photographed by thermophoresis probe and transmission electron microscope(TEM). An automatic processing code based on Matlab software was developed to process the TEM images and extract the micro morphology parameters of the soot particles. This study has systematically studied the effects of sampling location, injection pressure, ambient density and oxygen concentration on the micro morphology of soot particles. The ambient density refers to the initial gas density in the CVCC. The results showed that various morphologies and sizes of soot particles coexisted in the upstream of the spray flame. During the evolution of soot particles from upstream to downstream in the flame, the size of soot aggregates gradually decreased, while the maturity of soot aggregates increased. With the increase of injection pressure, ambient density and oxygen concentration, the average sizes of soot aggregates and primary soot particles decreased, but the fractal dimensions of soot aggregates increased gradually. Under the same combustion condition and in-flame sampling location, the average projection area, gyration radius and primary soot diameter of soot aggregates produced by DDCL were significantly lower than those of Petro diesel. The structure of soot particles from DDCL was more compact than that of Petro diesel.

Study on the corrosion of refractory materials by coal blended with the extraction residue of direct coal liquefaction in a simulated gasification atmosphere

Utilizing the extraction residue(ER)of direct coal liquefaction residue as a gasification feedstock has significant economic value.But the characteristic of high ash and iron in the ER would increase the risk of corrosion of the refractory materials and affect the long-term operation of the gasifier.In this work,corrosion experiments of molten slag derived from a mixture of 20 wt%ER and 80 wt%coal on a high-chromia refractory brick and SiC brick were carried out using a rotary-drum furnace in a simulated gasification atmosphere.The experimental results show that the viscosity of the poured slag is larger as compared to the initial ash sample at the same temperature,which suggests that the viscosity-temperature relationship of the poured slag should be used as the reference for the operation temperature of the gasifier to ensure that the slag can flow during operation.For a high-chromia refractory brick,iron oxides in molten slag could react with Cr_(2)O_(3) in the refractory matrix but,because the aggregate was not found to be damaged,the damage to the matrix structure was the key factor for causing the corrosion of the high-chromia refractory brick.Metallic iron was observed in the exposed SiC brick,which indicated that the reaction between the iron oxides in the slag and SiC occurred,forming metallic iron and SiO_(2).The corrosion of a SiC brick by molten slag depended mainly on the dissolution of Al_(2)O_(3) particles and the reaction between iron oxides in the molten slag and SiC particles.Therefore,the high iron content in coal ash had a serious influence on the corrosion of refractory materials.More efforts need to be made on coal blended with ER as a gasification feedstock in the future.