Investigations on methane hydrate formation,dissociation,and viscosity in gas-water-sand system

Understanding the kinetics and viscosity of hydrate slurry in gas-water-sand system is of great significance for the high-efficiency and high-safety development of natural gas hydrates.The effect of micronsized sands with various concentrations and particle sizes on the hydrate formation,dissociation,and viscosity in gas-water-sand system are investigated in this work.The experimental results show that the hydrate induction time in the sandy system is slightly prolonged compared to the pure gas-water system,and the inhibition effect first strengthens and then weakens as the sand concentration increases from0 wt%to 5 wt%.Besides,the difference of hydrate formation amount in various cases is not obvious.The concentration and particle size of sand have little effect on the kinetics of hydrate formation.Both promoting and inhibiting effects on hydrate formation have been found in the sandy multiphase fluid.For the viscosity characteristics,there are three variations of hydrate slurry viscosity during the formation process:Steep drop type,S-type and Fluctuation type.Moreover,appropriate sand size is helpful to reduce the randomness of slurry viscosity change.Meanwhile,even at the same hydrate volume fraction,the slurry viscosity in the formation process is significantly higher than that in dissociation process,which needs further research.This work provides further insights of hydrate formation,dissociation,and viscosity in gas-water-sand system,which is of great significance for safe and economic development of natural gas hydrates.

Characteristics of Hyaluronic Acid Derivative Cross-linked by Polyethylene Glycol

Characteristic and dynamic viscosities of Hyaluronic acid （ HA ） derivative modified by polyethylene glycol （PEG） were tested with different reaction times （6 h,12 h,18 h and 24 h ）, different molar ratio of HA/PEG （1/10,1/5,1/3 and 1/2）, different molecular weight of PEG（400,6 000 and 20 000） and mass fraction is 0. 4% by Wushi Viscosimeter and L-90 Rheometer at 25℃ . Characteristic viscosity of HA derivative had the largest value in 12 h, which decreased with increasing of PEG molecular weight, bat its aqueous dynamic viscosity increased with increment of PEG molecular weight. Meanwhile, we tested dynamic mechanic properties of HA derivative by 3ARES3 Rheometer at 25℃ to study viscoelastic changes and to compare change difference from viscosity to elasticity with the changes of vibration frequency between unmodified HA and HA derivative. Change from low vibrated freqnency to high one of solution resulted in change from viscosity to elasticity of solution. In conclusion, as to the rheological properties, structure- modified HA derivative meets the requirement of biomaterial .

Flow Properties of Entrained Flow Gasifier Fine Slag and Network Structure of its Molten Slag

The entrained flow gasification has been identified as the most promising gasification technology.Serious environmental pollution and waste of land resources are caused by the increasing amount of storage and production of coal gasification slag.The aim of this work is to explore the feasibility of high-temperature combustion and melting technology for treating coal gasification fine slag and determine the important parameters of system operation.The flow properties and molten slag structure characteristics of three fine slags from different entrained flow gasifiers were studied.Depending on the melting mechanism of melt-dissolution,the melting time of fine slags is short.Three fine slags all produce glassy slags,which is conducive to slag discharge.The degree of polymerization of silicate melt is proportionate to the amount of SiO_(2)in the slag.A part of Al^(3+)exist in the form of[AlO_(4)]^(5-)because of the effect of CaO and Na_(2)O,as the network former.Finally,the degree of polymerization of the three type molten slag was calculated by considering the role of Si and Al in molten slag and the property of each one.