| Thermal plasma technology is widely used in the industries due to its unique merits such as high temperature, high enthalpy and rich reactive species. Lots of gaseous low-chain hydrocarbon such as acetylene, ethylene and methane are produced instantaneously after coal particles are flowed into plasma reactor. While gaseous products are being produced, some coke is also produced and attached to the inner surface of plasma reactor and large scale of pyrolysis residue (nearly60wt%of the input coal particles) was discharged from the process. Such residue is called solid product in this work and treated as research object. Making good use of solid product is significant in improving the economy of coal pyrolysis process. In this article, preparation of coal-water slurry (CWS) from this solid product according to its characters like high carbon content, small particle size, and low sulfur content is discussed. The effect of particle size, solid concentration, pH and temperature on the rheological properties of CWS is investigated. One part of such discussion is about the rheology of the CWS without any additive involved and the other part is focused on the effection of different kind of additives on the flow properties of such special CWS prepared from the solid residue.At first chemical and physical properties of the solid residue are measured thoroughly. The particle size distribution result shows that90wt%of the whole particles are69.430μm. The other tests such as bulk density, angle of repose, hydrophilic contact angle, specific surface area and proximate and ultimate analysis indicate that such solid residue has the characters of high ash and fixed carbon content and low content of sulfur.Then the rheology of CWS made from such solid residue without any additive involved is studied and lots of interesting and meaningful results have been got.(1) Newtonian and shear-thinning behavior of suspension has been observed depending on component content and operating conditions.(2) The apparent viscosity of CWS increases with decreasing particle size.(3) Alkaline suspension gives better flow property and is favored for storage and transport.(4) Relation between viscosity and temperature is not simply linear and a more suitable cubic model proposed.(5) After sedimentation for12days, the volume ratio of the clear liquid to the initial volume of55%wt%suspension is nearly2%.Finally, three different kinds of ionic dispersant (sodium naphthalene sulfonate formaldehyde, Sodium lignosulfonate and maleic anhydride-sodium acrylate copolymer) and one non-ionic dispersant (Polyoxyethylene lauryl ether) are used for evaluating the effection of additives on the rheology of such special CWS prepared from the solid residue of pyrolysis of coal. The rheological data and the flow pattern of the suspension are not only different from the one without any additives, but also different from the general CWS made from the lignite.(1) With different additives involved, the CWS present a very special flow property. When solid concentration is50%, there exists a peak value of viscosity with increasing shear rate. But when solid concentration becomes55%, such peak value disappears and so is the positive effect. Such different additives show a negative effect on decreasing the viscosity of such CWS, which means making the flow property even worse than the system without any additive.(2) The apparent viscosity increases with increasing solid concentration under the same shear rate for the CWS with1#additive. When solid concentration is bigger than55%, such increasing rate of viscosity becomes incredibly high.(3) It is very unusual that the apparent viscosity does not keep decreasing or to a stable valve with increasing amount of additive. On the opposite apparent viscosity will increase when the amount of additive becomes bigger than a certain value.(4) The relation between viscosity and temperature of CWS with different additives is almost the same. The apparent viscosity decrease with temperature increasing, but such decreasing rate is different. Some system is suitable for the quadratic model.(5) The stability of CWS prepared from such solid is improved with the help of additives. After sedimentation for12days, the volume ratio of the clear liquid to the initial volume of55%wt%suspension is decreased to0.5%. The change of the apparent viscosity before and after sedimentation test is decreased.In this work, lots of special rheological behavior and data are observed and recorded by designing and doing different experiments. At the same time, detailed analysis for the unusual flow property of such CWS prepared from the solid residue has been carried out. These basic data, analysis and theory could be a theoretical support for the scaled utilization of such solid residue in the future. |
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