Kinetics of quartz sand and its mixtures drying by microwave radiation
Authors: Solonenko L. I. , Repiakh S. I. , Uzlov K. I. , Mamuzich I. , Kimstach T. V. , Bilyi O. P. 
Published: March 2021

Purpose. Kinetics research and description of drying by microwave radiation mechanism development of quartz sand and its mixes with sodium silicate in limited quantity of water steam medium. Methodology. Distilled water, sodium silicate solute and quartz sand have been used in this research. Study has been performed on sand samples weighing 200 g. Mixtures drying and structuring have been performed by microwave radiation with power of 700W with frequency of 2.45 GHz in air and in saturated water weighing 1 g steam medium. Accuracy of temperature measurement is 1, mass is 0.02 g. Realized in this investigation drying kinetics has been specified as specimen weight change dependence and moisture evaporation from this mixture rate vs. drying duration. Dependencies have been built on the results of video recording and corresponding chrono-gravimetric measurements data digitalization. Mixtures during heating by microwave radiation temperature changes registration has been performed with an interval of 1560 s. Samples average heating rate has been estimated by calculation based on results in their temperature change determination during first 2 minutes of heating with microwave radiation. Findings. For the first time, microwave drying kinetics of quartz sand and its mixtures with sodium silicate in limited water medium (structured by SMS-process) has been studied. For the first time, based on SMS-process material balance, analytical dependence has been developed. This dependence application allows sand-sodium-silicate mixture structured by SMS-process maximum mass to calculate when using sodium silicate solute (silicate module 2.83.0) for quartz sand cladding and 1 g of saturated water steam for mixture structuring. It has been established that when mixtures structuring according to SMS-process water extraction from them takes place in three stages at ~100, 100108 and at 125138 . Maximum appropriate heating temperature of sand-sodium-silicate mixture during structuring by SMS-process has been recommended as ~125 . Exceeding of specified temperature leads to hydrated water from mixture releasing in steam form and its condensation on colder working surface of model-rod rigging. Resulting condensate leads to mixture restructuring in contact with equipment places and, accordingly, sharp quality deterioration in prepared molds and rods. For manufactured molds and rods quality stabilization, it has been recommended to pre-dry the quartz sand cladded with sodium silicate solute in microwave field for at least 3 minutes before structuring according to SMS-process. Originality. For the first time, data on drying kinetics has been obtained and quartz sand and its mixtures with sodium silicate in limited water steam medium microwave drying mechanism description has been developed. Influence of number of SMS-process basic parameters on structured quartz sand weight regularities has been established. Practical value. Research results will be useful in terms of ideas expanding about the processes that accompany granular materials drying, as well as in technologies and equipment for drying and structuring fine-grained dielectric materials and their mixtures development, creating new capillary-porous media, etc. under microwave radiation influence.