Study On Slurryability Of Liquid CO₂ Slurry For Low Rank Coal

The reserve of low rank coal?LRC?reaches more than 50 percent of the gross in China.It is featured with low caloricity degree,low heat value,high content of moisture,volatiles and ash.Therefore it is hard to produce coal water slurry?CWS?with LRC and the combustion efficiency is also low when it is used as fuel for steam-electric power generation.However it is easier to convert LRC into synthesis gas by gasification due to its high content of volatiles.Gasification is considered to be an effective way for clean utilization of LRC.Three kinds of low rank coal from major coal mining areas in China,Zhaotong?ZT?in Yunnan,Baiyinhua?BYH?and Wulagai?WLG?in Inner Mongolia,were adopted in this work.Based on the coal quality and structure analysis of three LRCs,this work mainly focus on the factors that influence the slurryability of liquid CO₂-coal slurry?LCCS?.The results of this research could further contribute to application and development of LRC gasification technology.A series of work and analysis were performed:?1?Analysis of LRC characteristics,such as proximate and ultimate analysis,ash analysis,nitrogen adsorption method based pore property analysis and the surface functional group analysis with Fourier transform infrared spectrum?FT-IR?.It is shown that raw LRC had high content of moisture,oxygen and low caloricity.The BET specific surface area was low due to plenty of mesopore.FT-IR analysis showed obvious adsorption peaks of surface oxygenic groups.?2?Analysis of thermal-modified LRC under 150? and 200?.It was found that the moisture and oxygen content decreased,while caloricity increased through thermal-modification.Volatiles,ash and sulfur content kept almost unchanged.The BET specific surface area decreased and the average pore diameter increased as the results of more macropore.?3?Comparison of slurryability between CWS and LCCS.The maximum solid concentration of CWS was low,43.5%,38% and 30%,respectively for ZT,BYH and WLG coal.However the maximum solid concentration of LCCS improved to 50.3%,53% and 41.5%,respectively.?4?Analysis of factors influenced the slurryability of LCCS,such as coal characteristics,thermal-modification,additive,shear rate and so on.The effects of coal characteristics was analyzed,including O/C,H/C,moisture and fixed carbon content,specific surface area and porosity.The maximum solid concentration of LCCS decreased with higher H/C and fixed carbon content.However the effect of O/C was just the opposite.Thermal-modification process could improve the slurryability of LCCS.Sodium ligninsulfonate also enhanced the maximum solid concentration for LCCS as an additive under 1% of weight.Shear rate had certain influence on liquid CO₂ coal slurry.Low shear ratecould decrease the slurry viscosity.?5?Development of prediction model for temperature-viscosity of liquid CO₂ coal slurry and CWS.The results showed that the slurry viscosity decreased when the temperature rose.