Preliminary Study On The Mechanism Of Water-oil Separatation By Chemical Demulsification Of Low-temperature Coal Tar

The physical characteristics and chemical composition of low-temperature coal tar decides that the pressurization-quiescence and tube furnace flash dehydration method which is commonly used in high-temperature coal tar cannot satisfy the dehydration of the low-temperature coal tar. So oil-water separation becomes the key technique and also the most difficult part in the whole low-temperature coal tar development and comprehensive utilization. This article makes a deep research on the key factors that effects the low-temperature coal tar emulsion stability and the demulsification as well, which takes the chemical demulsification and dehydration of crude as the theoretical basis, combines the high-temperature coal tar dehydration method and starts from the research on the low-temperature coal tar emulsion.Firstly, a lot of research work of low-temperature coal tar has been done on the physical characteristics, the elemental composition and SD (simulated distillation), from which a lot of information has been obtained that includes:its density is close to water; a big viscosity, a low H/C, a high content of oxygen, a low content of sulfur and a high heavy component, etc. Those factors have some direct and indirect influences on the emulsion stability and the demulsification mechanism.Secondly, through the separation of the group composition by column chromatography and the analysis of GC/MS method, the low-temperature coal tar has been divided into aliphatic, aromatic, esters and polar fraction. To have a panorama of the emulsion continuous phase of the low-temperature coal tar, a further study has been made on the classification and the relative content of aliphatic hydrocarbon (chain alkanes, Cyclanes, Alkenes, etc.),aromatic group (Naphthalenes,Anthracenes, Phenanthrenes, etc.), oxygenated chemicals and nitrogen compounds.Thirdly, there are the separation and the charaterization of asphaltene and resin what is called the natural surfactant of the low-temperature coal tar. First, extract the asphaltene and resin taking oil separation method as a reference. Then, take an elemental analysis separately on the obtained asphaltene and resin and mesure the average molecular weight and the molecular weight distribution with GPC. Calculate and analyse the charaterization of aromaticity and the structural parameter with the help of1H NMR spectrum information. Make the qualitativeanalysis on the functional group of it according to FTIR spectra. Finaly, a scitific and effective structure simulation of the asphaltene and resin average molecular structure unit has been perfectly made.Compared with the crude demulsification mechanism, the emulsion stability and the demulsification mechanism of the low-temperature coal tar have the decisive factor of the interfacial tension, instead of the interfacial film strength, which is the main principle of selecting the low temperature coal tar demulsifier. The difficulty of breaking process of emulsion is the oil-water layer of the dispersed phase, instead of the flocculation of droplets.