The Preparation Method For Brown Coal Of Liquid CO₂Slurry And The Research Of Coal Slurry’s Trait

Coal is the most important primary-energy in China. Coal gasification, which can transformthe coal into gaseous fuel, is considered to make efficient use of the limited coal resource andreduce unnecessary waste. Coal-water slurry gasification is a traditional way of coal gasification.High rank coal and high solid concentration in coal-water slurry are usually needed to ensure thehigh efficiency of coal water slurry gasification system. However, when using low rank coal, suchas lignite, the result shows a relative poor performance. The liquid CO2slurry technology issupposed using liquid CO2instead of water. The liquid CO2slurry technology not only improves thesolid concentration of coal slurry effectively, but also reduces energy consumption inthe gasification stage because of the low liquid-CO2-gasification latent heat.Based on the future application of lignite gasification, a liquid CO2-coal slurry preparationsystem with high pressure and low temperature was designed in this work. Three kinds of lignitefrom Inner Mongolia and Yunnan were adopted to investigate the properties of liquid CO2–coalslurry. The following research works were performed:(1) The design and the development of the liquid CO2-coal slurry preparation system. Thispart of work mainly focused on the design and installation of the process, structure and keycomponent of the preparation system. This system works under high-pressure and low-temperaturecondition. The results show that the device can realize the preparation of liquid CO2coal slurryalong with other functions, hence achieve the designing requirements.(2) The coal slurry viscosity measurement system was designed. In order to fit the conditionsof producing the liquid CO2-coal slurry in the high pressure and low temperature sealing device, avibration on-line viscosity measuring method was developed in this work. The viscositymeasurement system was designed to acquire the vibration frequency of the probe, and thusexchange the frequency into viscosity. The relationship of vibration frequency and dynamicviscosity of lignite coal slurry was calibrated and fitted by using a rotary viscometer.(3) The experimental research of properties of coal water slurry was performed. The resultsshow that the maximum solid concentration of coal water slurry was relatively low. This isconsidered to be related with the content of water and ash inside of coal.(4) Experimental study of liquid CO2coal slurry preparation was performed and the propertiesof slurry were analyzed. It turns out that the maximum concentration of liquid CO2coal slurry wassignificantly higher than coal water slurry.. The properties of the coal-CO2slurry were affected bycoal characteristics、thermal-modification and the amount of addictives Baiyinhua lignite liquid CO2 slurry shown the biggest slurry concentration Thermal modification can increase the solidconcentration of liquid CO2slurry by reducing the moisture and volatile inside of coal. Themaximum slurry concentration can be improved by adding additive with0.8%by weight of coal,while too much additive content cannot increase its maximum slurry concentration.